锁相放大器在TDLAS技术中的应用
<p>可调谐二极管激光吸收光谱分析(TDLAS)技术是一种能够在工业应用中实现对气体组分浓度和温度场甚至速度场测量的检测技术。TDLAS依据Beer-Lambert定律，当激光通过气体分子介质时，只要激光的波长与任何一种分子的能级跃迁相等，一部分的光会被吸收。出射光强与入射光强的关系如下：</p><p><br />
<img alt="" border="0" file="https://www.zhihu.com/equation?tex=I+%3D+I_0e%5E%7B-%5Calpha%28v%29%5Ctimes+L%7D+%3DI_0e%5E%7B-N%5Ctimes+%5Csigma%28v%29%5Ctimes+L%7D" height="29" id="aimg_au64Z" lazyloaded="true" lazyloadthumb="1" onclick="zoom(this, this.src, 0, 0, 0)" onmouseover="img_onmouseoverfunc(this)" src="https://www.zhihu.com/equation?tex=I+%3D+I_0e%5E%7B-%5Calpha%28v%29%5Ctimes+L%7D+%3DI_0e%5E%7B-N%5Ctimes+%5Csigma%28v%29%5Ctimes+L%7D" width="273" /></p>
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其中 <img alt="" border="0" file="https://www.zhihu.com/equation?tex=-%5Calpha%28cm%5E%7B-1%7D%29" height="28" id="aimg_KL4F6" lazyloaded="true" lazyloadthumb="1" onclick="zoom(this, this.src, 0, 0, 0)" onmouseover="img_onmouseoverfunc(this)" src="https://www.zhihu.com/equation?tex=-%5Calpha%28cm%5E%7B-1%7D%29" width="94" /> 为介质单位长度的吸收系数； <img alt="" border="0" file="https://www.zhihu.com/equation?tex=L%28cm%29" height="26" id="aimg_IN4NT" lazyloaded="true" lazyloadthumb="1" onclick="zoom(this, this.src, 0, 0, 0)" onmouseover="img_onmouseoverfunc(this)" src="https://www.zhihu.com/equation?tex=L%28cm%29" width="58" /> 为有效吸收长度； <img alt="" border="0" file="https://www.zhihu.com/equation?tex=N%28cm%5E%7B-3%7D%29" height="29" id="aimg_P3zvY" lazyloaded="true" lazyloadthumb="1" onclick="zoom(this, this.src, 0, 0, 0)" onmouseover="img_onmouseoverfunc(this)" src="https://www.zhihu.com/equation?tex=N%28cm%5E%7B-3%7D%29" width="83" /> 为单位体积内的分子数（即浓度）； <img alt="" border="0" file="https://www.zhihu.com/equation?tex=%5Csigma%28cm%5E%7B-2%7D%29" height="28" id="aimg_PKG80" lazyloaded="true" lazyloadthumb="1" onclick="zoom(this, this.src, 0, 0, 0)" onmouseover="img_onmouseoverfunc(this)" src="https://www.zhihu.com/equation?tex=%5Csigma%28cm%5E%7B-2%7D%29" width="76" /> 为分子的吸收截面，是波长的高斯函数。经过频率调制后，且 <img alt="" border="0" file="https://www.zhihu.com/equation?tex=v_a%2Fv_0%5Cll1" height="26" id="aimg_UZJrn" lazyloaded="true" lazyloadthumb="1" onclick="zoom(this, this.src, 0, 0, 0)" onmouseover="img_onmouseoverfunc(this)" src="https://www.zhihu.com/equation?tex=v_a%2Fv_0%5Cll1" width="93" /> 时，上式写成：</p>
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<img alt="" border="0" file="https://pic4.zhimg.com/80/v2-6e5e029487440f528c43028a4ca1c93f_720w.jpg" height="104" id="aimg_RKc59" lazyloaded="true" onclick="zoom(this, this.src, 0, 0, 0)" src="https://pic4.zhimg.com/80/v2-6e5e029487440f528c43028a4ca1c93f_720w.jpg" width="606" /></p>
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<p>由上式可看出分子对激光的吸收出现高阶吸收成分，在信号检测通路中采用锁相放大技术来实现调制信号的二次谐波检测，分别在1f、2f或3f频率处检相得到高斯函数的一阶、二阶或三阶导数。<br />
在这个激光锁相系统中，最关键的部分是利用锁相放大器同时实现被测气体、参考气体的两路检测，甚至需要实现被测气体、参考气体以及激光背景的三路检测，对此，我司的数字锁相放大器OE1022具备的多路谐波测量功能可顺利解决此问题。</p>
<p>详情请查看链接，转载于：https://zhuanlan.zhihu.com/p/3427248</p>
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