LWIR Optical System Design by Passive Athermalization
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摘要: 结合光学被动无热化和机械被动无热化各自优势,提出一种低成本、高质量混合被动无热化方法。针对焦距75 mm,F/1的无热化镜头研制要求,分别利用光学被动无热化和混合被动无热化设计实现。对比发现,相较于传统的机械被动式无热化,混合无热化可减小补偿结构的体积和复杂性,从而有助于系统的小型化、轻量化;相较于光学被动无热化,在保证成像质量相当的情况下,可减小系统的体积和加工难度。从而证实,利用混合被动无热化技术可实现低成本、高质量的长波无热化镜头设计。Abstract: A low-cost and high-quality hybrid passive athermalization method for LWIR was proposed by combining passive optical and passive mechanical athermalization. An athermalization optical system with a focal length of 75 mm and F/1 was designed using passive optical and hybrid passive athermalization. Compared with traditional passive mechanical athermalization, the volume and complexity of the thermal compensation structure can be reduced using hybrid passive athermalization. In addition, the proposed method decreases the volume and weight of the system. Compared with passive optical athermalization, hybrid passive athermalization can reduce the volume and processing difficulty when the imaging quality is the same. Thus, the propose method can be used to achieve a low-cost, high-quality, long-wave athermalization system.
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表 1 设计指标要求
Table 1. Requirements of design parameters
Parameters Value Focal length 75 mm Wavelength 8μm~12 μm Temperature -40℃~+60℃ F/# 1 Field of view 5.86°×4.69° MTF@42 lp/mm On axis>0.4 Out axis>0.3 Detector 640×512,12 μm 表 2 不同温度下透镜3的相对位移
Table 2. Shift of the lens 3 under different temperature
Temperature /℃ -40 20 60 Displacement/mm -0.052 0 0.034 表 3 仿真分析不同温度下透镜3的位移
Table 3. Shift of lens 3 under different temperature by simulation
Temperature /℃ -40 20 60 Displacement /mm -0.053 0 0.032 表 4 两种无热化方案对比
Table 4. Comparison of different athermalization methods
Passive optical athermalization Passive optical and mechanical athermalization Weight 356 g 354 g Volume φ75 mm×80 mm φ75 mm×75 mm MTF On axis≥0.42 On axis≥0.46 Out axis≥0.38 Out axis≥0.37 Distortion ≤0.7% ≤1.3% Complexity 3 aspheric surface
1 diffractive surface3 aspheric surface -
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