Shape distortions of infrared focal plane array and optical readout

Abstract

The optical readout principle of focal plane array (FPA) infrared image system based on bi-material cantilever and micro mirror structure is introduced briefly. And the ideal angular sensitivity of the optical readout is about 1.5e-6 radian. While there are two kinds of unexpected shape distortion of FPA, reflecting direction dispersion and reflecting surface bending. With that the distortion limits for perfect detection are calculated. Then the reflecting surface bending effect is analyzed in detail. It shows that the sensitivity may lie on not only the cliff-edge optical filtering effect, which is well known already, but also the light spot moving effect, if the reflecting surface is bended. This effect means that each micro mirror's imaging area on the image plane may not be illuminated equivalently but have a light spot within its boundary if it is bended. And the spot's position changes along with the reflect angle of the mirror. Then the experiment results are given to support this thought. Though there are still obvious shape distortions exist, we obtained IR images of objects about 500K.