Multiple lens athermalization and achromatization by the Cartesian-product free combination method based on the
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We proposed a thermally-induced defocus model that simultaneously considers the effects of optics and lens mounting, addressing the shortcoming of the traditional athermalization model that does not account for the impact of lens displacement on imaging in a thermal environment. This model is suitable for considering both thermal defocus and focal length stability in multi-lens systems. Based on this model, we propose a new method for athermalization and achromatization design. By establishing combinations of candidate optical and mounting materials during the design process, the combined effects of different material combinations on thermal defocus and effective focal length ratio are compared, and suitable material combinations are selected to achieve the simultaneous replacement of optical and mounting materials. To verify the accuracy of the system model, we conducted a passive athermalization design for an F/2 seven-element optical system using different lens mounting materials. Ultimately, the system maintained an MTF > 0.4 at 100 cycles/mm across a wide temperature range from -50°C to +90°C. The results demonstrate that this method expands the optimization variables and improves the accuracy of athermalization for the transmissive system.
