Athermalization Of Infrared Optical Sysem Based On Wavefrant Coding

Currently, application field of infrared optical system is increasingly wide, which requires optical system more adaptable to the external environment. The influence of temperature to the infrared optical system is quite obvious of many external factors. When temperature is out of operateing range, image quality of optical system decline seriously and system overall performance also become no longer stable. So it is necessary to athermalize the infrared optical systems.Wavefront coding combines both optical image and digital image processing. A phase mask specially designed is added to the pupil of optical system to re-modulate the wave front, making the system not sensitive to defocus. This is same as the athermalization theory of infrared optical system. Applying the theory of wavefront coding technology to infrared optical system can make the system not sensitive to thermal defocus, athermalizing the optical system.1 The theories of wavefront coding and decoding are introduced, the analytical expression of three phase plate is derived and the traditional optical system and wavefront coding system are compared in spatial frequency and light position.2 Influence of temperature is analyzed on optical element, refractive index of air, element spacing, thickness and surface figure, and also thermal focal shift of the optical system caused by temperature change; The theory of athermal design to optical systems with wavefront coding theory is deducted, working temperature range of the wavefront coding athermal system is analyaed based on the theory.3 Optimization functiones of phase plate based on different criteria are analyzed, optimization functiones based on transfer function consistency and image recoverability are established, wavefront coding system using different optimization functiones is contrasted in both in spatial and frequent field.4 Typical athermal infrared optical system is athermalized applying wavefront coding technology, the intermediate image is restored with several commonly used filters. The image restoration capabilities of the filters with noise are contrasted. Then the impact of phase plate self-heating effect to the system is also analyzed.