20 November 2014 Infrared lens thermal effect: equivalent focal shift and calculating model
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Proceedings Volume 9300, International Symposium on Optoelectronic Technology and Application 2014: Infrared Technology and Applications; 93001U (2014) https://doi.org/10.1117/12.2072597
Event: International Symposium on Optoelectronic Technology and Application 2014, 2014, Beijing, China
Abstract
It's well-know that the focal shift of infrared lens is the major factor in degeneration of imaging quality when temperature change. In order to figure out the connection between temperature change and focal shift, partial differential equations of thermal effect on light path are obtained by raytrace method, to begin with. The approximately solution of the PDEs show that focal shift is proportional to temperature change. And a formula to compute the proportional factor is given. In order to understand infrared lens thermal effect deeply, we use defocus by image plane shift at constant temperature to equivalently represent thermal effect on infrared lens. So equivalent focal shift (EFS) is defined and its calculating model is proposed at last. In order to verify EFS and its calculating model, Physical experimental platform including a motorized linear stage with built-in controller, blackbody, target, collimator, IR detector, computer and other devices is developed. The experimental results indicate that EFS make the image plane shift at constant temperature have the same influence on infrared lens as thermal effect and its calculating model is correct.
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Cheng-shuo Zhang, Zelin Shi, Bin Feng, Bao-shu Xu, "Infrared lens thermal effect: equivalent focal shift and calculating model ", Proc. SPIE 9300, International Symposium on Optoelectronic Technology and Application 2014: Infrared Technology and Applications, 93001U (20 November 2014); doi: 10.1117/12.2072597; https://doi.org/10.1117/12.2072597
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