Abstract: Compression is one of the most demanding of the processing steps. Still, image compression is achieved by removing spatial redundancy, while in video devices, temporal redundancy can be used to further improve the compression performance. Various image compression algorithms and coding schemes have been proposed, such as predictive coding, Discrete Cosine Transform (DCT) based compression algorithms and wavelet-based compression, Joint Photographic Experts Group (JPEG) algorithms, moving Picture Experts Group (MPEG) standards. VLSI circuit implemented image/video compression standards have been reported in the early literature Improvement in CMOS technology results in CMOS image sensor competitive to CCD image sensor in many applications. In this article, we provide a basic introduction to CMOS and CCD image-sensor technology, design and performance limits and present recent developments and future directions in this area correspondingly. CMOS technology enables the integration of image sensing and image processing, making the CMOS image sensor the optimum solution to improve the performance of the overall system. In the last several decades, image sensors integrating different on-chip compression algorithms, such as predictive coding. One of the most important advantages of CMOS image sensors over CCDs is the ability to integrate sensing with analog and digital processing down to the pixel level.

Keywords: CMOS, CCD, image sensor.