在红外热像仪调焦系统设计中，通过电机带动调焦镜组沿直线导轨往复运动，从而对调焦镜组的位置精确变化实现焦距的变化。为了精确控制调焦镜组的位置，调焦控制系统需要高分辨率的编码器实时反馈调焦镜组的位置，以实现对调焦镜组的闭环控制。红外热像仪调焦控制系统中采用增量式光电编码器作为调焦镜组位置的反馈测量元件。针对增量式编码器的特点，利用 CPLD（complex programmable logic device）丰富的逻辑资源和可编程的灵活性，设计了一种读出电路，可以实时精确反馈调焦镜组的位置。经实际项目验证，该方案可以实时并精确地读出增量式光电编码器的位置信息，具有一定的抗干扰能力，可以实现高精度的位置伺服控制，满足系统要求。

In the focusing system design of an infrared(IR) imager, the motor drives the focusing lens group to reciprocate along the linear guide rail to change the position of the focusing lens group accurately and to change the focal length. To control the position of the focus lens group accurately, the focus control system requires a high-resolution encoder to reflect the position of the focus lens group to realize closed-loop control of the group. In the focusing control system of the IR imager, an incremental encoder is used to feedback the position of the focusing lens group. According to the characteristics of the incremental encoder, because of the rich logic resources and programmable flexibility of the complex programmable logic device, a readout circuit is designed that can accurately feedback the position of the focusing lens group in real time. Verification in an actual project demonstrated that this scheme can read out the position of the incremental encoder accurately in real time, has reliable anti-interference ability, and meets the system requirements of high-precision position control.