Current Optics and Photonics

Optical Society of Korea (한국광학회)
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Athermal Design and Performance Verification of an LWIR Zoom Lens for Drones

  • Kwang-Woo Park (Agency for Defense Development) ;
  • Sung-Chan Park (Department of Physics, Dankook University)
  • Received : 2024.05.08
  • Accepted : 2024.06.17
  • Published : 2024.08.25
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Abstract

This paper presents an optimum method for determining the parameters to athermalize a long-wavelength infrared (LWIR) zoom camera by introducing the defocus sensitivity analysis. To effectively find parameters that significantly affect thermal defocus, we simulated athermal analysis with temperature changes for all variables. Consequently, we found that the optimum parameter to correct thermal defocus is the compensation lens, and its movements with temperature at each zoom position are obtained from the simulated athermal analysis. To verify the efficiency of our athermal approach, we performed actual athermal tests in a broad temperature range at each zoom position. The simulated athermal analysis provides the initial position of the compensation lens at the corresponding temperature and zoom position. Then the compensation lens is elaboratively moved to serve the highest live contrast ratio (LCR) for the target. This experiment shows that the compensation lens locations in the actual test are closely matched to those in the simulated athermal analysis. In addition, two outdoor tests conducted in two different environments confirm that the autofocus system suggested in this study performs well at all zoom positions. Using the proposed athermal analysis approach in this paper, we efficiently realize an athermal system over the specified temperature and zoom ranges.

Keywords

Acknowledgement

We would like to express our thanks to Siyoun Choi of LIG Nex1 for support in manufacturing and measurement.

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