Athermal research on high resolution imaging for visible optical system on airborne CCD camera

Abstract

Thermal effect of optical system is the key factor influencing high resolution image quality for airborne CCD camera, athermalization is the key technology and leading topic in optical engineering field. The researh field focus on infrared system, however, the visible system is quite few considered. Based on optical compensation method, the conception of general zoom system was proposed to realize athermal design for complex visible refractive system. Three steps of the athermalization was considered as three status of zoom system design, correspondence between the athermal design and zoom system design was established. Firstly a good optical system was designed to satisfy image quality in normal temperature, and then multiple zooming positions were established in actual temperature range from -40&deg;<i>C</i> to +60&deg;<i>C</i> , the excellent imaging quality was obtained by replacing partial materials properly. An optical system in the 0.43um, 0.75um waveband was designed with 650mm focal length, F/5.6 F-number, 5.5&deg; field-of-view by the general zoom method. The results showed the image quality had a reliable performance with -40&deg;<i>C</i> +60&deg;<i>C</i>, and the MTF is higher than 0.5 at the spatial frequency of 70lp/mm, image quality reached the diffraction limit. The MTF decreased only with 5%, the athermal design can meet high resolution requirement for airborne CCD camera in wide temperature range. The atheraml research for visible optical system will further complete athermal theories and technologies, and its study and applications will produce important value for military airborne optical system and space optical system.