Realization of the FPGA based TDI Algorithm in Digital Domain for CMOS Cameras

In order to make the CMOS image sensors suitable for space high resolution imaging applications, a new method realizing TDI in digital domain by FPGA is proposed in this paper, which improves the imaging mode for area array CMOS sensors. The TDI algorithm accumulates the corresponding pixels of adjoining frames in digital domain, so the gray values increase by M times, where M is for the integration number, and the image's quality in signal-to-noise ratio can be improved. In addition, the TDI optimization algorithm is discussed. Firstly, the signal storage is optimized by 2 slices of external RAM, where memory depth expanding and the table tennis operation mechanism are used. Secondly, the FIFO operation mechanism reduces the reading and writing operation on memory by Mx(M-1) times, It saves so much signal transfer time as is proportional to the square of integration number M-2, that the frame frequency is able to increase greatly. At last, the CMOS camera based on TDI in digital domain is developed, and the algorithm is validated by experiments on it.