位置检测装置作为数控机床的重要组成部分，其作用就是检测位移量，并发出反馈信号与数控装置发出的指令信号相比较。光电编码器就是一种旋转式位置传感器，在现代数控伺服系统中广泛应用于角位移或角速率的测量。目前生产和使用的数控机床大多采用的是半闭环控制方式，大多数的系统生产厂家均将位置编码器内置于驱动电机端部，间接测量执行部件的实际位置或位移。(The position detection device is an important part of the CNC machine tool, its function is to detect the displacement and send the feedback signal to compare with the command signal produced by the numerical control device. Photoelectric encoder is a rotary position sensor, widely used in modern CNC servo system for angular displacement or angular rate measurement. At present, most of the CNC machine tools used in production and use are semi closed loop control. Most of the system manufacturers have put the position encoder in the end of the drive motor to indirectly measure the actual position or displacement of the executing parts.)