为了提高联合变换相关器跟踪和识别目标的能力，且满足坦克瞄准镜的工作要求，针对1英寸红外CCD探测器，设计了8 ~12 μm波段折射式长波红外连续变焦系统.该系统采用机械补偿的方式，变焦过程中相对孔径不变，F数为2，变倍比为4∶1，在50~200 mm范围内可实现连续变焦，且变倍曲线和补偿曲线平滑，扩大了坦克瞄准镜的搜索范围.用ZEMAX光学设计软件对设计结果进行像质评价，结果表明，在17 lp/mm空间频率处，全焦距范围内调制传递函数均在0.53以上，接近衍射极限，像面稳定性良好，满足光学系统的设计要求.

In order to meet the requirement of tank sight and improve the ability of joint transform correlator in target tracking and recognition, an infrared continuous refractive zoom optical system for 8~12 μm wave-band is designed for 1 inch infrared CCD detector. The zoom system uses mechanical compensation. The relative aperture is invariant during the zoom process. The F number of the system is 2, and the zoom ratio is 4∶1.The focal length from 50 mm to 200 mm could be changed continuously. Variable magnification curve and compensation curve are smooth. The range of tank sight searching targets was expanded. The optical system image quality is evaluated with ZEMAX optical design software. The results have shown when spatial frequency is 17lp/mm, the MTF curve in the whole range of focal length are all above 0.55 which is closed to the diffraction limited curve. The stability of the image plane is well. The result of this system meets the requirement of technical specification.