CMOS imager non-uniformity response correction-based high-accuracy spot target localization

High-accuracy spot target detection based on a complementary metal-oxide semiconductor (CMOS) image sensor, such as astronomy magnitude, medicine, and astronomy photometrics, needs accurate pixel response. Because pixels have different silicon structures and read outputting, each pixel has non-uniformity response with specific illumination. The flat-field correction of a CMOS image sensor is crucial before image processing. In this work, a flat-field model and correction method based on spot scale areas of CMOS image sensor pixel response are proposed. Compared with traditional full-plane calibration, this method aims at spot areas to fit most selected normal pixels’ mean response curve with different light intensities and exposure times, which can guarantee spot imaging areas with higher accurate pixel response. Finally, the accuracy of this flat-field correction method is evaluated by the influence on spot target extraction accuracy. The experimental results indicate that using this flat-field correction method can decrease the non-uniform variance from 7.34 (LSB/10 bit) to 1.91 (LSB/10 bit) (improved by 74.1%) and reduce the noise effect on spot extraction accuracy, which improves it from 0.3453 pixel to 0.0116 pixel ($1\sigma$). The proposed approach solves the problem of non-uniform pixel response and improves imaging SNR for high-accuracy spot target localization.