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1、中国科学技术大学博士学位论文光-机械式非制冷红外成像研究光机械式非制冷红外成像研究姓名：史海涛申请学位级别：博士专业：固体力学指导教师：伍小平;张青川20100501摘 要 ii 性和扩展宽度对光学读出响应率的影响。分析表明，LED 光源非单色性的影响可以忽略； 光学读出响应率随光源的增宽迅速减小， 对长度为 L 的反光板定义了相应的临界半高宽 Hc，当光源半高宽 HHc时，分析时可近似认为光源为单色点光源。 在光强不超过 CCD 满量程的约束条件下，研究了刀口滤波位置对光学读出响应率的影响，建立了无量纲形式的理论模型。理论分析指出，对于完全平整的反光板刀口挡住 3/4 衍射谱时光学读出响应率
2、达到最大；对于变形反光板，刀口的最佳滤波位置与变形曲率半径有关。与刀口衍射谱中心滤波法相比，通过改进刀口的滤波位置，对于平整反光板，光学读出响应率可以提高 80%；而对于长55m、 曲率半径为 6mm 的反光板， 理论和实验证明光学读出响应率可提高 33%。 对光学滤波读出技术首次建立了统一的读出响应率理论模型， 该模型为以后优化设计性能更高的光学滤波器提供了理论基础。具体分析了刀口、狭缝、方孔和圆孔滤波法，并对这四种滤波方法的光源能量利用率、空间分辨率、动态响应范围进行了具体的讨论。结果表明：狭缝滤波法优于圆孔、方孔滤波法；狭缝滤波法与刀口滤波法相比，狭缝滤波法具有高的探测灵敏度，刀口中心滤
3、波法具有高光源能量利用率、高分辨率、高动态响应范围，刀口最佳位置滤波法的性能处于这两者之间。 最后，实验测定了不同滤波方法和不同 CCD 背景光强下的系统噪声，证明了增大 CCD 背景光强和改进滤波方法不仅能提系统的高光学读出响应率，而且能够有效降低系统的 NETD。 关键词关键词：微悬臂梁，光学滤波读出，非制冷，红外成像，无基底，焦平面阵列 Abstract iii Abstract Infrared (IR) imaging technique plays a critical role in military, medical, meteoro-logic, agricultural,
4、and industrial applications. Opto-mechanical uncooled infrared imging technique becomes a hotspot of research because of its attractive features like low cost and high theoretical temperature resolution. However, the traditional theo-retical models of IR energy conversion efficiency H and thermo-mec
5、hanical sensitiv-ity ST are not suitable for substarte-free FPA, and the traditional theory of the optical responsivity does not agree with experiments. To solve these problems, new and absolutely suitable theoretical models are established in this dissertation. Based on the models, substrate-free F
6、PA and optical filtering readout technique are optimized and improved. When substrate-free FPA is radiated by IR radiation, the accurate temperature dis-tribution of substrate-free FPA can be calculated by finite element method (FEM). However, FPA usually contains more than 100,000 pixels, so the ca
7、lculation will be very large and the calculation time will be very long. Apparently FEM is unsuitable for optimization design of substrate-free FPA. So a theoretical approximate formula is needed. A thermal resistance model of substrate-free FPA is established in this dis-sertation considering the s
8、upporting frameworks thermal resisitance. After reasona-bly simplifying the model, the theoretical expressions of H and ST are derived. Com-pared to FEM results, the error of the model is less than 10%. The theoretical expres-sion of the thermal response time of substrate-free FPA is also obtained.
9、To validate the expression, a substrate-free FPA contained four imaging areas (the design pa-rameters of the areas are different) is fabricated. The experimental results of the ther-mal response time well match the theoretical results. The imaging performance of the substate-free FPA situated in atm
10、osphere is deeply analyzed. Analysis shows that the traditional theory can not explain the phenomenon that substrate-free FPA can obtain the thermal image at room temperature even satiated in atmosphere. To explain this phenomenon, a thermal resistance model of the substrate-free FPA situated in atm
11、os-phere is established. The error of the traditional optical responsivity theory results from not considering the morrors undesired deformation. In this dissertation, a theoretical optical respon-sivity model related to deformed mirror is established. Theoretical analysis and ex-periment both show
12、that the bending deformation will seriously degrade the optical Abstract iv responsivity. To reduce the deformation of mirror, three kinds of structures, namely thin-metal-film structure, enhanced-beams structure and two-layers structure, are de-signed and fabricated. Experiments demonstrate that: F
13、or 180-m mirror, thin-metal-film structure increases its deformation radius from 5.3mm to 25mm, the optical responsivity correspondingly increases 5.2 times. Enhanced-beams structure makes the deformation radius of the mirror increase 4 times, the optical responsivity increases 15%. The two-layers s
14、tructure makes the mirror like an I beam, so the de-formation of the mirror will be very little. To reduce blindness of production process and avoid unnecessary loses, for the mirror with length L, a critical deformation ra-dius cR is given. If its deformation radius is bigger thancR , the deformati
15、on of the mirror doesnt need reducing. Theoretical analysis shows that there exists an optimal mirror length which makes the optical responsivity achieve its maximum under a cer-tain mirror deformation. Based on the results, a substrate-free FPA with optimal mir-ror length is designed and fabricated
16、. The experimental results of the performance of the FPA agree with the theoretical results. The visible light source usually is not an ideal point, and is nonmonochromatic. The influences of the spectral width and the spatial width of the light source on the optical responsivity are discussed. Analysis shows that the influence of the spectral width of LED can be ignored. The optical responsivity rapidly decreases with increasing the spatial width of the light source. However, for t
