一种实时CIS暗电流校正方法及系统实现  

Real-time calibration and implementation of dark current in CIS

作　　者：孙权[1] 姚素英[1] 郑炜[1] 

机构地区：[1]天津大学电子信息工程学院,天津300072

出　　处：《光电子．激光》2013年第1期21-27,共7页Journal of Optoelectronics·Laser

基　　金：国家自然科学基金(61076024)资助项目

摘　　要：为了减弱暗电流对互补型金属氧化物半导体(CMOS)图像传感器(简称CIS)图像质量的影响,本文基于图像处理的方式提出了一种实时校正CMOS图像传感器暗电流的方法,并在一个最高帧频(50f/s)的4晶体管像素结构CMOS图像传感器内集成了该方法的电路。测试结果表明,该方法获得了准确的暗电平,并且实时消除了75%以上暗电流引入的固定模式噪声(FPN,fixed pat-tern noise),大大改善了图像质量。In order to reduce the fixed pattern nise （FPN） induced by dark current in CMOS image sensor, this paper presents a real-time dark current calibration method based on image processing technolo- gy. This method is implemented and integrated into a 4T CMOS image sensor which is serving as a 50 f/ s video camera. In this paper,the composition of the 4T CMOS image sensor＇s ADC output is analyzed. According to the analysis, the dependences of the dark current induced FPN on exposure time and temperature are modeled. After the black level is obtained and subtracted from the sensor＇s AI）C output, the dark current factor matrix is calculated by subtracting reference pixels＇ （exposure time of 0） outputs from active pixels outputs. The dark current factor matrix is calculated every 10° centigrade and saved in a flash memory. By interpolation, the dark current factor matirx can cover the 4T COMS image sensor＇s working temperature range. Finally, based on the 4T CMOS image sensor＇s exposure time and gain settings, the proper dark current matrix is selected and read in via SPI. Then the dark current induced FPN is evaluated and reduced proportionally. The experimental results reveal that by using this method the dark current FPN is reduced by more than 75 % with the CMOS image sensor＇s working temperature range,and the accurate black level is also obtained.

关 键 词：互补型金属氧化物半导体(CMOS)图像传感器(CIS) 图像处理 暗电流校正 固定模式噪声(FPN) 暗电平校准 

分 类 号：TN492[电子电信—微电子学与固体电子学]