为满足微光夜视光学系统的轻小化要求,利用塑料双层衍射元件研制了一款折衍混合微光夜视物镜系统.系统在整个设计波段任意波长的衍射效率均大于90％,有效地提高了光能利用率和成像对比度.系统的视场角为32°,有效焦距为32 mm,直径为26 mm,长度为49 mm,重量为28 g;调制传递函数(MTF)在35 lp/mm时,边缘视场达到0.4以上,中心视场达到0.7;满足超二代微光探测器的成像要求.同时给出了双层衍射元件的二元面特征曲线,当每周期刻蚀8个台阶时,最小特征尺寸为15.63 μm,易于塑料光学元件的挤压成型.%A night vision object optical system with double-layer Diffractive Optical Element (DOE) was designed and the detail design procedure was given. The diffraction efficiency of the system at each wavelength in designed band was larger than 90% , which improved the image contrast and the energy utilization ratio. The Field of View (FOV) was 32° while the effective focal length was 32 mm. The features of 49 mm system size and 28 g overall weight guaranteed the lightness and compactness of the optical system. The modulation transfer function (MTF) value at 0° FOV was 0. 7 for 35 1p/mm spatial frequency, and more than 0. 4 for all FOV, which satisfied the requirement of high performance low-light-level imaging system. The phase and line frequency versus aperture of the two binary surfaces were also given. When the number of etching levels was 8, the minimum feature sizes of both the diffractive surfaces were 15. 63 μm, which was not a very high demand for technique.
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