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<p style="max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", " ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 17px;letter-spacing: 0.544px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><img data-type="gif" class="__bg_gif " data-ratio="0.10555555555555556" data-w="720" src="http://mmbiz.qpic.cn/mmbiz/M2H0aGBjWUTRia7nqkArYeKZUqEfdmpNibMPiaZk4gvlWk5v5lUKyXhjJP4CENKQeQt5HI8zwcTCWJOkicfWJiatdJQ/640?wx_fmt=gif" style="box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;width: auto !important;" /></p><p style="max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 17px;letter-spacing: 0.544px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 12px;color: rgb(136, 136, 136);box-sizing: border-box !important;word-wrap: break-word !important;">来源：医疗维修帮</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;color: rgb(61, 167, 66);box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">一、压电换能器 </span></strong></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 超声诊断仪是通过探头产生入射超声波(发射波)和接收反射超声波(回波)的，它是诊断设备的重要部件。高频电能激励探头中的晶体产生机械振动，反射超声波的机械振动又可以通过探头转换为电脉冲。<span style="max-width: 100%;color: rgb(255, 41, 65);box-sizing: border-box !important;word-wrap: break-word !important;">也就是说探头能将电能转换成声能，又能够将声能转换成电能，所以探头又称做超声换能器。</span>其原理来自于晶体的压电效应。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 1.压电效应</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 压电效应泛指晶体处于弹性介质中所具有的一种声-电可逆特性，此现象为法国物理学者居里兄弟于1880年所发现，故也称居里效应（图7-4）。<br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> </span></p><p><img data-s="300,640" data-type="jpeg" data-ratio="0.7026476578411406" data-w="491" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQSe1mmgwuNp3Wrgx6j0awRqrexaaTmIaJoa84MblTbmpLehr7BGYngZA/640?wx_fmt=jpeg" style="color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;line-height: 22.4px;text-align: justify;white-space: normal;widows: 1;width: 677px;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;" /><br style="max-width: 100%;color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;line-height: 22.4px;text-align: justify;white-space: normal;widows: 1;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;" /></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-4 晶体的压电效应</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"> 具有压电效应性质的晶体,称为压电晶体。目前常用于超声探头的晶体片有锆酸铅、钛酸钡、石英、硫酸锂等人工或天然晶体。钛酸钡及锆酸铅是在高温下烧结的多晶陶瓷体，把毛坯烧结成陶瓷体后，经过适当的研磨修整，得到所需的几何尺寸，再用高压直流电场极化后,就具有压电性质，成为换能器件。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (1)正压电效应 在晶体或陶瓷的一定方向上，加上机械力使其发生形变，晶体或陶瓷的两个受力面上，产生符号相反的电荷;<span style="max-width: 100%;color: rgb(255, 41, 65);box-sizing: border-box !important;word-wrap: break-word !important;">形变方向相反，电荷的极性随之变换，电荷密度同外施机械力成正比，</span>这种因机械力作用而激起表面电荷的效应，称为正压电效应，如图7-4（a）。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (2)逆压电效应 在晶体或陶瓷表面沿着电场方向施加电压，在电场作用下引起晶体或陶瓷几何形状应变，<span style="max-width: 100%;color: rgb(255, 41, 65);box-sizing: border-box !important;word-wrap: break-word !important;">电压方向改变，应变方向亦随之改变，形变与电场电压成比例</span>，这种因电场作用而诱发的形变效应，称为逆压电效应，如图7-4（b）。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 一般情况下，压电效应是线性的，然而，当电场过强或压力很大时，就会出现非线性关系。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 2.压电换能器的特性</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 压电换能器的特性参量很多，现只简单介绍以下3种。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (1)频率特性 压电换能器的晶体本身是一个弹性体，因此有其固有的谐振频率，当所施力的频率等于其固有频率时，它将产生机械谐振，由于正压电效应而产生最大电信号。另一方面，当所施加电的频率和压电晶体固有频率一致时，由于逆压电效应则应发生机械谐振，谐振时振幅最大，弹性能量也最大，这时，压电体获得最大形变振动,通过介质产生超声波输出。实验证明，当所施加力或电的频率不与晶体固有频率一致时，压电换能器晶体产生的电信号幅度和变形振动幅度都将变小，可见，它们都是频率的函数。<br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> </span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><img data-s="300,640" data-type="jpeg" data-ratio="0.5365344467640919" data-w="479" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQSRD755nTUAk56JBzBhgTNICzYucicLhCLSsJ8e9HskKO5FOqGH5LibFnQ/640?wx_fmt=jpeg" style="width: 677px;box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;" /><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-5 压电晶体的电流-频率特性</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"> 如果对压电晶体施加一定值的电压，改变所加电压的频率，回路电流或阻抗将随其变化，当电压频率为某一频率fm时，电流出现最大值 Imax，当电压频率为另一频率fn时，电流出现最小值 Imin。压电晶体的电流随频率而变化的现象（见图7-5），说明了压电换能器晶体的等效阻抗是一个随频率而变化的量。如果继续增加电压的频率，还可以发现有规律地出现一系列电流的波动，且波动的最大值(对应fm1、fm2…)是依次减小的，而波动最小值(对应fn1、fn2…则是依次增大的，fm称为压电振子的最小阻抗频率(又可称为最大传输频率);fn称为最大阻抗频率(又可称为最小传输频率)。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (2)换能特性 换能器的换能特性包括两个方面 ：<span style="max-width: 100%;color: rgb(255, 41, 65);box-sizing: border-box !important;word-wrap: break-word !important;"><span class="Apple-converted-space"> </span>电能－机械能－超声能，超声能－机械能－电能。</span>前者属于发射过程，后者属于接收过程。能量间转换必然产生损失(产生了无益的能耗)，以转换效率来表征换能器这一性能：</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" />电机转换效率=输出的机械功率／输入的电功率</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 机声转换效率=辐射的超声功率／输入的机械功率</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" />因此： 电声转换效率=辐射的超声功率／输入的电功率</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (3)暂态特性 超声诊断仪的换能器大多工作于脉冲状态，换能器对脉冲的响应速率称为暂态特性，这也是一项重要指标。换能器的暂态特性与其频率特性是有关系的，简言之，换能器的频谱越宽，它的暂态特性也越好，可允许的超声脉冲的宽度越窄。在这里，所描述的脉冲宽度是指断续发射出超声的时间长度，单位是秒(s），它与频率（超声波每秒振动的次数）是不同的。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> <span class="Apple-converted-space"> </span><strong style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;color: rgb(61, 167, 66);box-sizing: border-box !important;word-wrap: break-word !important;">二、超声探头的类别</span></strong></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 超声探头可以从以下不同方面来分类，它们是:</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">①按诊断部位分类，有眼科探头、心脏探头、腹部探头、颅脑探头、腔内探头和儿童探头等之分（图7-6）；</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">②按应用方式分类，有体外探头、体内探头、穿刺活检探头之分;</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">③按探头中换能器所用振元数目分类，又有单元探头和多元探头之说; <br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><img data-s="300,640" data-type="jpeg" data-ratio="1.3567961165048543" data-w="412" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQSHMA9eLSno2qQdOYmyLicFwRmASbicvOAfPAqDgdE7FD8BSibeRJfNvJQQ/640?wx_fmt=jpeg" style="box-sizing: border-box !important;word-wrap: break-word !important;width: auto !important;visibility: visible !important;" /><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-6 应用在不同诊断部位的各类超声探头</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">④按波束控制方式分类，则有线扫探头、相控阵探头、机械扇扫探头和方阵探头等;</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">⑤按探头的几何形状分类(这是一种惯用的分类方法)，则有矩形探头、柱形探头、弧形探头(又称凸形)、圆形探头等。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">以下仅就最常见典型探头加以介绍。<br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> </span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><img data-s="300,640" data-type="jpeg" data-ratio="1.316425120772947" data-w="414" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQSsOEiciaibRPKMl5J4XvQQNkrkmlA79P7TMI7UAPMicrYXq9QojE83mppnQ/640?wx_fmt=jpeg" style="box-sizing: border-box !important;word-wrap: break-word !important;width: 414px !important;visibility: visible !important;" /><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-7 柱形单振元探头结构剖面图</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"> </span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;line-height: 1.75em;box-sizing: border-box !important;word-wrap: break-word !important;">1.柱形单振元探头</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;line-height: 1.75em;box-sizing: border-box !important;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"> 柱形单振元探头主要用于A超和M超，又称笔杆式探头。目前在经颅多普勒（TCD)及胎心监护仪器中亦用此探头。由于它是各型超声成像仪用探头的结构基础，特此作一介绍。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (1)结构 柱形单振元探头的基本结构如图7-7所示。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 它主要由5部分组成:</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">①压电晶体，用于接收电脉冲产生机械超声振动，完成声-电和电-声转换工作。其几何形状和尺寸是根据诊断要求来设计的，上、下电极分别焊有一根引线，用来传输电信号;</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">②垫衬吸声材料，用于衰减并吸收压电振子背向辐射的超声能量，使之不在探头中来回反射而使振子的振铃时间加长，因此要求垫衬具有较大的衰减能力，并具有与压电材料接近的声阻抗，以使来自压电振子背向辐射的声波全部进入垫衬中并不再反射回到振子中去，吸声材料一般为环氧树脂加钨粉，或铁氧体粉加橡胶粉配合而成;</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">③声学绝缘层，防止超声能量传至探头外壳引起反射，造成对信号的干扰;</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">④外壳，作为探头内部材料的支承体，并固定电缆引线，壳体上通常标明该探头的型号、标称频率;</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">⑤保护层，用以保护振子不被磨损。保护层应该选择衰减系数低并耐磨的材料，由于保护层与振子和人体组织同时接触，其声阻抗应接近人体组织的声阻，并将保护层兼做为层间插入的声阻抗渐变层，其厚度应为λ/4。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (2)基本特性 超声探头作为一种传感器，其最重要的性能有:特征频率、受电激励后振动时间的长短以及其体积的大小。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 探头的特征频率决定于压电晶体的厚度。给压电晶体施加电激励后，其前面和后面都会发出声能，只要周围介质的声阻抗与压电晶体不一样，部分声能就会在前后界面处反射回晶体，并以声波形式在晶体内以同一速度传播。声波传至对面所需要的时间与晶体的厚度成正比，当晶体厚度恰为波长的一半时，反射应力和发射应力在每一面相互加强，压电晶体产生共振，呈现最大的位移幅度。相当于半波长厚度的频率叫压电晶体的基础共振频率。当晶体厚度与波长相等时，每一面的应力正好相反，位移幅度最小。由于任何频率下的半波长晶体的厚度决定于声波在该晶体材料中的传播速度，因此，对每一种压电材料都必须特别计算出它的半波长厚度，也就是说，不同的压电材料的半波长厚度并不相同。由于波长与频度成反比，所以压电元件的厚度与产生的频率成反比。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 传感器受电激励后振动时间的长短影响超声系统的纵向分辨力。为了追求好的纵向分辨力，通常使激励电脉冲宽度尽量窄，然而由于超声探头的压电材料对电激励常呈较长时间的反应(即电脉冲结束后声振荡仍以衰减振荡方式维持一段时间),此种振铃反应会产生长超声脉冲，如不予以阻尼，就会导致分辨力减弱。为此必须在压电体后面放置特别的垫衬材料，利用其吸音特性产生阻尼，使振铃反应减弱,从而缩短脉冲总长度。同时，此阻尼材料还可以吸收压电晶体后面发出的声能，否则这种能量就会在晶体中产生反射，干扰来自被检介质中的回声。阻尼强的垫衬使换能器的声脉冲时间缩短，但也使灵敏度降低;阻尼弱则有损于分辨力，却使换能器有较佳的灵敏度。<br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> </span></p><p><img data-s="300,640" data-type="jpeg" data-ratio="0.6258503401360545" data-w="441" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQSRAzNbiczQ0RCHZKR6aZxXRzTWBogChkSAgz9BlkYo5dib64wenPUxTtA/640?wx_fmt=jpeg" style="color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;line-height: 22.4px;text-align: justify;white-space: normal;widows: 1;width: 677px;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;" /><br style="max-width: 100%;color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;line-height: 22.4px;text-align: justify;white-space: normal;widows: 1;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;" /><br style="max-width: 100%;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: normal;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;" /></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-8 机械扇形扫描探头工作原理示意</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"> 对于柱形单振元探头，振元直径的大小主要影响超声场的形状。一般来说，振元直径大，声束的指向性好，并易于聚焦。当然，当声窗受限制时，只能使用较小的振元。通常振元直径在5～30mm范围内选定。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 2.机械扇扫超声探头</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 机械扇形扫描超声探头配用于扇扫式B型超声诊断仪，它是依靠机械传动方式带动传感器往复摇摆或连续旋转来实现扇形扫描的（图7-8）。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 利用机械扫描实现超声影像的实时动态显示，是70年代后期才趋于成熟的一项技术。开始时扫描线数较少，扫描角度也不大，扫描线的间隔角度的均匀性亦差,而且探头的体积和重量都较大，操作使用十分不便。比如早期的机械扇扫探头的重量达0.6kg以上，且扫描角度仅30°。随着技术的进步，到80年代中期，机械扇扫超声换能器的产品性能日趋改善，重量可以做到0.2kg以下，扫描帧频约30帧/s,扫描角度达85°，而且扫描线的均匀性也大大改善。这不仅给操作使用带来了方便,而且使机械扇扫超声影像的质量获得明显的提高。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 机械扇扫探头除换能器声学特性的基本要求之外，还应满足以下要求:①保证探头中的压电振子作30次/s左右的高速摆动，摆动幅度应足够大；②摆动速度应均匀稳定；③整体体积小、重量轻，便于手持操作;④外形应适合探查的需要，并能灵活改变扫查方向;⑤机械振动及噪声应小到不致引起病人的紧张和烦躁。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 目前来看，机械扇扫探头主要存在的不足之处，是噪声大和探头寿命短。多数的机械扇扫探头寿命仅有数千小时，对于这种结构而言，无论是技术、工艺、或者材料都是十分难以解决的问题。目前，机械扇扫探头的生产已越来越少，大有被电子凸阵及相控阵扇扫探头所取代的趋势。 <br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><img data-s="300,640" data-type="jpeg" data-ratio="0.5831533477321814" data-w="463" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQStRdR1IWCZoUabQugopUxkyhNGEVib3lsBiaokOVjFGCuPgwWqhTaw4ww/640?wx_fmt=jpeg" style="width: 677px;box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;" /><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-9 电子线阵探头剖面示意</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"> </span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">3.电子线阵超声探头</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 电子线阵超声探头配用于电子式线性扫描超声诊断仪。其结构如图7-9所示，它主要由6部分组成:开关控制器、阻尼垫衬、换能器阵列、匹配层、声透镜和外壳。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (1)开关控制器 用于控制探头中各振元按一定组合方式工作，若采用直接激励，则每一个振元需要一条信号线连接到主机，目前换能器振元数已普遍增加到数百个，则与主机的连线需要数百根，这不仅使工艺复杂，因此而增加的探头和电缆的重量也是不堪设想的。采用开关控制器就可以使探头与主机的连线数大大减小。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (2)阻尼垫衬 其作用与柱形单振元探头中的垫衬作用相同，用于产生阻尼,抑制振铃并消除反射干扰。阻尼垫衬材料的构成要求亦和柱形单振元探头相似。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (3)换能器阵列 换能器的晶体振元通常是采用切割法制造工艺，即对一宽约10mm，一定厚度的矩形压电晶体，通过计算机程控顺序开槽。开槽宽度应小于0.1mm，开槽深度则不能一概而论，这是因为所用晶片的厚度取决于探头的工作频率，相当于半波长厚度的频率叫做压电晶体的基础共振频率。晶体材料的半波长厚度σ可由下式给出。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" />σ=Cp·T·1／2</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" />式中:Cp为超声波在该材料中的传播速度，T为工作频率超声波的周期。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 当换能器的工作频率确定后，根据所用晶片材料的半波长厚度，即可确定所用晶片的厚度。显然，探头的工作频率越高，所用晶片的厚度则越薄。开槽的深度主要影响振元间互相耦合的大小，振元间互耦大则相互干扰大，使收发分辨力降低。一般来说，开槽深则互耦小。至于每个振元的宽度，一是考虑辐射强度，宽度窄则振元的有效面积小，辐射强度小，影响探测灵敏度。二是波束和扩散角，宽度窄则近场区域以外扩散角大,声束主瓣宽,副瓣大,横向分辨力下降，要使副瓣小,则应满足振元中心间距d<1/2λ。考虑以上因素，通常取单个振元宽度与厚度之比小于0.6。因此，工作频率越高,换能器的制作困难越大。例如，对某种已选定的晶体材料而言，当工作频率为2.5MHz时，假设其半波长厚度为0.8mm，则单个振元的宽度小于0.48mm。当工作频率上升到5MHz时，晶体的半波长厚度仅为0.4mm，则单个振元的宽度小于0.24mm。当工作频率为7.5MHz时，晶体半波长厚度仅有0.26mm，则单个振元的宽度应小于0.16mm。可见，高频率的探头、换能器制作工艺难度大。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 为了进一步减小互耦，线阵探头应满足d<λ/2的条件。但前已述及，对于高频探头，晶片切割难度大，再考虑单片辐射面积的需要，只好折中考虑，取振元的宽、厚比为0.6，这往往并不满足d<λ/2的条件。更新的设计是采用组合振元方式，即每一组激励振元由几个晶片组成(这样的一个组合称作一群)，则可以较好地解决互耦与工艺的矛盾。比如将100mm×10mm×0.8mm的压电晶体均匀刻划成64个窄条，刻缝宽为0.05mm，每一个窄条作为一个振元，并设工作波长λ=1.60，那么这种尺寸结构d/λ=1.55/1.60≈1，远不能满足d<λ/2的条件。而如果将此压电晶体刻划成256个窄条，每4个窄条作为一个振元(发射时给予同相激励)，探头总共仍为64个振元(或称作64群)，但尺寸结构d/λ=0.40/1.60=1/4，则可以满足以上条件。所以采用新设计的优点是显而易见的，它既保证了探头的辐射功率，又使副瓣得到压缩。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> (4)匹配层 由于声透镜同时与晶体振元和人体接触，两者的声阻抗差别甚大［压电晶体振元的阻抗Zf≈(20～35)×106kg·s－１·m－2，人体组织的阻抗Ze≈(1.58～1.7)×106kg·s－１·m－2］，难于使声透镜的特性阻抗同时与两者匹配。超声经不同阻抗界面传播，将产生反射，会增加能量损耗并影响分辨力，因此，往往需要采用匹配层来实现探头与负载之间的匹配。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 对匹配层除厚度与声阻抗的要求外，还要求其声阻尼要小，以减小对超声能量的损耗。在工艺上应保证其同时与晶体振元和声透镜接触良好。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;text-indent: 2em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> <img data-s="300,640" data-type="jpeg" data-ratio="1.087557603686636" data-w="434" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQSUuu7LY8dfT7Xa8Ndeeg52eUhIwJW1CyTen9u2EshORLBics8ZnIUGug/640?wx_fmt=jpeg" style="box-sizing: border-box !important;word-wrap: break-word !important;width: 434px !important;visibility: visible !important;" /><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-10 电子凸阵探头示意</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">匹配层材料通常也采用环氧加钨粉配制。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 4.电子凸阵超声探头</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 凸阵探头的结构原理与线阵探头相类似，只是振元排列成凸形（图7-10）。但相同振元结构凸形探头的视野要比线阵探头大。由于其探查视场为扇形，故对某些声窗较小的脏器的探查比线阵探头更为优越，比如检测骨下脏器，有二氧化碳和空气障碍的部位更能显现其特点。但凸形探头波束扫描远程扩散，必须给予线插补，否则因线密度低将使影像清晰度变差。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 最后要特别提一下的是探头的工作情况，不论是线阵探头还是凸形探头，探头中的振元都不是同时被激励的，它们总是被分组分时受激励，而且分配的方法有多样。</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /> 5.相控阵超声探头 <br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><img data-s="300,640" data-type="jpeg" data-ratio="0.4547325102880658" data-w="486" class="" src="http://mmbiz.qpic.cn/mmbiz_jpg/qbiclCHl7mOEVIKKLIBicJC4YmEKJGUkQSz0szico6MEO2Hsic6MEtLpaIJOC4ibAPQljcNUOT1TA19wfXZKAqibOh4g/640?wx_fmt=jpeg" style="width: 677px;box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;" /><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;text-align: center;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">图7-11 相控阵探头结构示意</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"> 相探阵超声探头可以实现波束扇形扫描，因此又称为相控电子扇扫探头，它配用于相控阵扇形扫描超声诊断仪。相控阵超声探头外形及内部结构与线阵探头颇有相似之处。其一是所用换能器也是多元换能器阵列;其二是探头的结构、材料和工艺亦相近，主要由换能器、阻尼垫衬、声透镜以及匹配层几部分组成；</span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;"><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></span></p><p style="margin-top: 5px;margin-bottom: 5px;max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-size: 14px;font-variant-numeric: normal;font-variant-east-asian: normal;letter-spacing: 0.544px;text-align: justify;white-space: normal;widows: 1;font-family: "Helvitica Neue", Helvitica, Arial, "Hiragino Sans GB", "Microsoft YaHei", "Arial Regular", "Microsoft JhengHei", sans-serif;line-height: 1.75em;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;word-wrap: break-word !important;">但它们的不同之处也主要有两点：第一是在探头中没有开关控制器，这是因为相控阵探头换能器中，各振元基本上是同时被激励的，而不是像线阵探头换能器那样分组、分时工作的，因此，不需要用控制器来选择参与工作的振元。第二是相控阵探头的体积和声窗面积都较小（图7-11），这是因为相控阵探头是以扇形扫描方式工作的，其近场波束尺寸小，也正因为此，它具有机械扇形扫描探头的优点，可以通过一个小的“窗口”，对一个较大的扇形视野进行探查。</span></p><p style="max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 17px;letter-spacing: 0.544px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 12px;color: rgb(136, 136, 136);box-sizing: border-box !important;word-wrap: break-word !important;"><br /></span></p><p style="max-width: 100%;min-height: 1em;color: rgb(51, 51, 51);font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "ingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif;font-size: 17px;letter-spacing: 0.544px;text-align: justify;white-space: normal;background-color: rgb(255, 255, 255);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 12px;color: rgb(136, 136, 136);box-sizing: border-box !important;word-wrap: break-word !important;"><br /></span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;white-space: normal;font-size: 16px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);text-align: center;font-family: 微软雅黑;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;">赞<span style="max-width: 100%;line-height: 25px;box-sizing: border-box !important;word-wrap: break-word !important;">是一种友谊 | </span><span style="max-width: 100%;line-height: 25px;color: rgb(192, 0, 0);box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;">分享</strong></span><span style="max-width: 100%;line-height: 25px;box-sizing: border-box !important;word-wrap: break-word !important;">传递智慧</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;white-space: normal;font-size: 16px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);text-align: center;font-family: 微软雅黑;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;letter-spacing: 0.5px;line-height: 28px;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;letter-spacing: 1px;line-height: 25.6px;white-space: pre;color: rgb(68, 68, 68);font-family: 宋体;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;color: rgb(95, 73, 122);font-size: 14px;line-height: 24.381px;text-align: justify;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 18px;color: rgb(62, 62, 62);line-height: 25px;text-align: center;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;white-space: normal;font-family: 微软雅黑;color: rgb(171, 25, 66);box-sizing: border-box !important;word-wrap: break-word !important;">，您身边专业超声维修专家</strong></span></strong></strong></strong></span></strong></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;white-space: normal;font-size: 16px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);text-align: center;font-family: 微软雅黑;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;letter-spacing: 0.5px;line-height: 28px;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 15px;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;letter-spacing: 1px;line-height: 25.6px;white-space: pre;color: rgb(68, 68, 68);font-family: 宋体;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;color: rgb(95, 73, 122);font-size: 14px;line-height: 24.381px;text-align: justify;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 18px;color: rgb(62, 62, 62);line-height: 25px;text-align: center;box-sizing: border-box !important;word-wrap: break-word !important;"><strong style="max-width: 100%;white-space: normal;font-family: 微软雅黑;color: rgb(171, 25, 66);box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;color: rgb(62, 62, 62);font-size: 15px;line-height: 24px;box-sizing: border-box !important;word-wrap: break-word !important;">超声一站式服务商</span></strong></span></strong></strong></strong></span></strong></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;white-space: normal;font-size: 16px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: 微软雅黑;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;text-indent: 0em;font-family: Arial, Verdana, sans-serif;line-height: 1.75em;box-sizing: border-box !important;word-wrap: break-word !important;">地址：广州市天河区银利街银利茶叶博览中心E栋4楼E4030室 </span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;line-height: 1.75em;box-sizing: border-box !important;word-wrap: break-word !important;">邮编：510507</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">电话：(+86)020-8722 8723 8764 5360 </span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">传真：020-8722 8623</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">全国统一免费服务热线：400-020-6788</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;line-height: 24.381px;box-sizing: border-box !important;word-wrap: break-word !important;">公司官网：http://www.parts-ultrasound.com/</span><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;"></span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;white-space: normal;font-size: 16px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: 微软雅黑;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;line-height: 1.75em;text-indent: 0em;font-size: 14px;font-family: Arial, Verdana, sans-serif;box-sizing: border-box !important;word-wrap: break-word !important;">微信公众帐号：</span></p><p style="max-width: 100%;min-height: 1em;letter-spacing: 0.544px;white-space: normal;font-size: 16px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);line-height: 25.6px;text-align: center;font-family: 微软雅黑;box-sizing: border-box !important;word-wrap: break-word !important;"><img class="" data-ratio="1" data-s="300,640" data-type="jpeg" data-w="258" width="auto" src="http://mmbiz.qpic.cn/mmbiz_jpg/dx3KibwtDhvfh2wVX4NftfnfjcZWIKK6EQDWtTTsYwjfQBnsqkThAZP5OlDmg5S3g22gSqMWhAxr2O4MydSJHnQ/640?wx_fmt=jpeg" style="float: left;box-sizing: border-box !important;word-wrap: break-word !important;visibility: visible !important;width: auto !important;" /></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">维修咨询：QQ: 712638 404</span><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">设备咨询: QQ: 712638 405</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;white-space: normal;font-size: 16px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: 微软雅黑;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;font-family: Arial, Verdana, sans-serif;line-height: 1.75em;text-indent: 0em;box-sizing: border-box !important;word-wrap: break-word !important;">软件咨询：QQ: 712638 406</span><br style="max-width: 100%;box-sizing: border-box !important;word-wrap: break-word !important;" /></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">配件咨询：QQ: 712638 407</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">交流Q群：1106 11074</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">阿里店铺网址：https://renchengyiliao.1688.com</span></p><p style="margin-bottom: 5px;max-width: 100%;min-height: 1em;letter-spacing: 0.544px;text-align: justify;text-indent: 0em;white-space: normal;font-size: 12px;background-color: rgb(255, 255, 255);color: rgb(62, 62, 62);font-family: Arial, Verdana, sans-serif;line-height: 2em;box-sizing: border-box !important;word-wrap: break-word !important;"><span style="max-width: 100%;font-size: 14px;box-sizing: border-box !important;word-wrap: break-word !important;">电子邮箱：sales@parts-ultrasound.com</span></p>
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发表于 2020-10-19 22:49:33