イメージセンシング技術とその応用 画素容量・列容量電荷電圧変換を組合せた多重露光線形応答広ダイナミックレンジＣＭＯＳイメージセンサ

Abstract

We discuss the operation methods for keeping a high S/N ratio at all switching points in multiple exposures and for shorting the total integration time of a wide dynamic range (DR) lateral overflow integration capacitor (LOFIC) CMOS image sensor that combines electric-charge voltage conversions in a pixel and a column capacitor. We have used these methods on a color LOFIC CMOS image sensor. This sensor had a pixel pitch of 5.6-um and the number of effective pixels was 800 (H) x 600 (V). It was made by using 0.18-um 2P3M CMOS technology. Fully linear responses were obtained, as well as a DR of 207 dB. Furthermore, the S/N ratio was 26-dB for the image of 18% gray card at all the switching points between the multiple exposures. The total exposure time was1/13-sec and was obtained by three photoelectric conversion operations at FD and LOFIC capacitors and one photoelectric conversion operation in the column capacitor.