工业生产中经常需要测量微米级圆孔孔径的大小.基于圆孔的夫朗禾费衍射原理，激光经过圆孔衍射在接收屏上形成圆环型条纹分布，孔径改变时，艾里斑区域的激光能量密度随之改变，利用光电池作为光电探测器，只接收大部分艾里斑中心光强信号而屏蔽其它高级次的衍射亮环，光电池输出的电压值反应了孔径直径大小.单片机作为控制系统，采用双光路的光电检测方法，搭建了检测系统.利用已知孔径的圆孔标定系统后，获得电压信号与孔径大小的对应关系，通过拟合可以得到检测系统的函数关系式.实验表明，可以实现50-300 μm孔径大小的检测.

It is important to measure micron grade of the aperture size in the field of industrial production. Based on the Fraunhofer diffraction principle of circular hole，there is a circular diffraction pattern on the receiving screen when laser passes through a small hole，the laser fluency in the area of the airy disk changes with the aperture size. Photovoltaic cell as the photoelectric detector only receives the laser intensity signal at the center of airy disk but not the higher order diffraction rings. The voltage value transformed from the photovoltaic cell includes the aperture size. The detection system is built with single - chip microcomputer and dual optical path. After calibration test using known aperture size，the relation between the output voltage signal and aperture size can be acquired. The functional relation of the detection system can be obtained by linear fitting the experimental results.Experimental result shows that this system can test the aperture sizes varied from 50 to 300 μm.