针对近红外InGaAs焦平面(FPA)调制传递函数（MTF）的测量要求，设计了一种全反射式Offner光学系统，由两块共轴的球面反射镜构成，11成像，F数为4。在焦平面工作波长1.7 μm下对光学系统进行优化，设计结果显示，在8 mm×30 mm的宽视场(FOV)内任一点，空间频率20 lp/mm处（对应光敏元尺寸25 μm×25 μm的焦平面的Nyquist频率），光学系统的MTF在1.7 \mm达到0.82，接近衍射限。Zygo激光干涉仪在0.6328 μm波长下的测量结果显示，系统的波前差均方根（RMS）值在0.6328 \mm约为1/20 λ，20 lp/mm处MTF在0.6328 \mm达到0.93。将测量得到的波前差数据代入CODEV中计算，结果表明波长1.7 μm下系统在8 mm×30 mm的视场内任一点，空间频率20 lp/mm处的MTF实验值仍高于0.8，满足要求。

To measure the modulation transfer function (MTF) of near-infrared InGaAs focal plane arrays (FPA), an all-reflective Offner optical system is designed and fabricated, which consists of two co-axial spherical mirrors, operating as a 11 imager with F/#=4. After optimization at the FPA working wavelength 1.7 μm, a nearly diffraction limited field of view (FOV) up to 8 mm×30 mm is obtained. The MTF at a space frequency of 20 lp/mm (referring to the 25 μm×25 μm device′s Nyquist frequency) is above 0.8 in the FOV. After fabrication and calibration of the optical system, a Zygo interferometer is used to check its performance, finding that the root mean square (RMS) of wavefront error is about 1/20 wave at 0.6328 μm, and the MTF@20 lp/mm (0.6328 μm), is above 0.93. Then the measured wavefront data is inputted into CODEV to calculate the MTF at 1.7 μm. The result shows that, the value of MTF @1.7 μm,20 lp/mm is still above 0.8.