Design of Parallel Image Compression Circuits for High-speed CMOS Image Sensors

Abstract

We investigated parallel image compression circuits suitable for integration in high-speed CMOS image sensors.We compared the coding efficiency and hardware complexity of several image compression algorithms that use 2-D DCTs using simulation and logic synthesis,and found that using 4$\ imes$4 point 2-D DCT-based coding methods reduced hardware complexity and improved coding efficiency.We developed a parallel processing architecture for on-sensor image compression that use a processing element array and a data-buffering scheme for parallel data-output.We constructed a prototype 256 $\ imes$ 256 pixel high-speed CMOS image sensor chip that integrates 16 image compression-processing elements and uses 0.25-$\mu$m CMOS technology.The area of the image compression circuits is 80\% of the image array with 15 $\mu$m square pixels.The entire chip could be operated at a clock frequency of 53.6 MHz,and high-speed images compressed by a factor of four could be read out at 10,000 fps using a 32-bit parallel bus.