为解决光学消热差技术镜片多且结构复杂的问题，提出了一种两片式远距结构消热差光学设计方法。该光学系统由前折衍混合正透镜和后负透镜组成，衍射面补偿系统的大部分色差和小部分热差，剩余色差和热差由负透镜平衡。设计了用于非制冷红外探测器的长波红外物镜，焦距为120 mm，F数为1.2，远距比为0.9。调制传递函数（MTF）的设计值接近衍射极限，轴上30 lp/mm处MTF的实测结果优于0.45，成像质量优良。环境温度实验测试结果表明，-40 ℃~60 ℃温度范围内，靶标边缘锐利，无温度离焦。两片式远距结构消热差红外物镜适用于机载或弹载的轻量化光电系统。

A method to design athermalized infrared two-lens telephoto objectives is proposed to reduce the number of lenses and simply the structure of an athermal optical system. The telephoto structure is composed of a front refractive-diffractive positive single lens and a rear negative single lens. A diffractive surface is used to compensate most of chromatic aberration and a small amount of thermal aberration, and residual aberrations are balanced by the rear negative lens. A long-wavelength infrared objective used for uncooled focal plane arrays is designed, whose focal length is 120 mm, F number is 1.2 and telephoto ratio is 0.9. The designed modulation transfer function (MTF) is close to the diffraction limit and the measured result of MTF is greater than 0.45 at the spatial frequency of 30 lp/mm. The results of temperature tests show that the target image remained sharp in the temperature range from -40 ℃ to 60 ℃. The proposed two-lens structure can be applied in airborne and missile-borne electro-optical equipments.