Combined image signal processing for CMOS image sensors

Abstract

This paper presents an efficient image signal processing structure for CMOS image sensors to achieve low area and power consumption. Although CMOS image sensors (CISs) have various benefits compared with charge-coupled devices (CCDs), the images obtained from CISs have much lower quality than those from CCDs. To improve the quality of CIS images, it is required to do reproducing and enhancing processings such as color interpolation, white balancing, color correction, gamma correction and color conversion. They are implemented individually in most conventional designs though they have similar functional characteristics. In this proposed structure, the gamma correction block is moved to the front in order to combine several image signal processings into one block. An efficient compensation scheme is also proposed to reduce the errors caused by the moving of the non-linear gamma correction. A prototype CIS image signal processor is implemented in Verilog-HDL and synthesized with 0.18um standard cell library. Experimental results show that the proposed structure reduces area and power consumption by 23.8% and 31.1%, respectively.