Study On Denoising Methods For Infrared Star Point Target Imaging System

Daytime star sensor technology is an important development direction of starsensor technology. The research on daytime star sensor technology is the premise andfoundation of extending the application platform of present star sensor to airborne,shipborne, missileborne and other platforms. Using the stars as the detecting targets,researching infrared imaging systems and launching daytime star observationexperiments is one effective scheme and technical approach of daytime star sensortechnology research.The thesis did research around the denoising methods, which was one keytechnology of infrared star point target imaging system. The thesis made intensive studyon denoising methods in two sections: before and after star point target imaging, whichwas of great significance in resolving the key problems of daytime star sensor.Before the star point target imaging, the technology of designing low noise infraredimaging circuits was researched. On the basis of theoretical analysis, a low noise CCDdriving circuit and a denoising circuit were designed, a CCD star camera was designedand an inroom imaging experiment was accomplished. Denoising methods for infraredstar camera were researched, which contain the design technique of low noise drivingcircuit, signal acquisition circuit, cooling circuit, two-piont nonuniformity correctionmethod integrated in infrared camera and etc. Then the scheme of daytime starobservation was designed, the experimental system was set up, the experiment wasaccomplished and sevral infrared star maps were collected. Through the experiment, theeffectiveness of scheme and denoising methods were confirmed.After star point target imaging, for the single-point-noise, the denoising algorithmsbased on4neighborhood and column direction scanning were proposed. For the stripe- noise, the algorithms based on column histogram offset correction (CHOC) and colummean offset correction (CMOC) were proposed. When the algorithms were used to thestar maps collected in out-field experiment, the results showed that the quality of starmaps was improved largely and the star point target peak signal-noise-ratio (PSNR) wasraised to nearly2times after denoising single-point-noise and stripe-noise.To increase the star and background contrast ratio furtherly, sevral backgroundfiltering algorithms were analyzed. On the basis of experimental analysis, a composedfiltering algorithm wiener2_top-hat, which was suitable for infrared star map, wasproposed. We added the simulated ideal star map to the observed star map to make up acomposed star map, and use the composed star map to confirm the effectiveness ofdenoising algorithms, the star-point target PSNR and offset error of star-point centroidwere analyzed. The result showed that, after the serial denosing processing, the Psnrwas raised to3~4times of the raw star map, and the offset error of star-point centroid isonly1/30pixel, the accuracy of the algorithms in the paper is high.The thesis did an in-depth study on the denoising methods for infrared star pointtarget imaging system. The characteristics and denosing methods were analyzed, andspecific ideas and schematics were put forward, the result of out-field experiment andexperiment of processing to star map showed good results, which laid a foundation forinfrared daytime star observation.