基于光电传感技术和平行光扫描检测原理，设计了一种透射式激光扫描直径检测系统。该系统利用平行平晶构成透射式激光扫描发射器，在不包含扫描物镜的条件下就能产生高度平行的扫描光束。以FPGA 为核心的测控平台包含前端数据处理模块和通讯模块；根据外围计时电路测得的时间参数求出入射光在平晶表面的入射角度，从而得到透射光相对入射光的偏移距离，再经过简单的代数运算得到被测工件的直径。详细论述了系统的检测原理和相关特性，搭建了试验平台，分析和试验结果表明该方法对扫描转台的装配精度要求不高，容易将测量误差限制在±0.008 mm 以内。

Based on the optoelectronic transformation technology and the parallel-laser-scanning inspection principle, a transmission laser scanning inspection system for diameter measurement was designed. A parallel-flat-crystal was used to make up the transmission laser scanning transmitter so that highly paralleled scanning beam can be acquired in the absence of scanning objective lens. The front data processing module and the communication module were included in the measurement and control platform based on FPGA. The incident angle was determined by the time parameter which was measured by the peripheral timing circuit. The offset between transmission beam and incident beam was calculated through the incident angle. The diameter of work-piece was then derived by simple algebraic operation. The measuring principle and characteristics of the system were discussed in details. The experimental platform was established and results show that precision requirement on assembly of the transmitter is not so higher than other systems and measurement error can be easily limited in ±0.008 mm.