Minimizing thermal defocus effects in liquid lens based autofocus imaging systems using partial passive optical athermalization (PPOA)

Optical imaging systems that use liquid lens modules for autofocus are subject to thermally induced focus variation due to the impact of temperature on the fluid components. This white paper illustrates how to minimize such effects through the application of basic optical imaging principles. In particular, it is shown that, in an arrangement where the liquid lens module is mounted in front of a fixed focus lens, thermal defocus of the final image is minimized when the liquid lens’s focal length is set to infinity, and the fixed focus lens is set to focus at some distance other than infinity. In this paper, we refer to such a condition as “partial passive optical athermalization”