Bae Jaeyoung, Kim Daeyun, Ham Seokheon, Chae Youngcheol, Song Minkyu
Department Semiconductor Science, Dongguk University, Seoul 100-715, Korea.
Samsung Electronics Co.Ltd, Kiheung 446-711, Korea.
Sensors (Basel). 2014 Jul 4;14(7):11825-43. doi: 10.3390/s140711825.
In this paper, a 120 frames per second (fps) low noise CMOS Image Sensor (CIS) based on a Two-Step Single Slope ADC (TS SS ADC) and column self-calibration technique is proposed. The TS SS ADC is suitable for high speed video systems because its conversion speed is much faster (by more than 10 times) than that of the Single Slope ADC (SS ADC). However, there exist some mismatching errors between the coarse block and the fine block due to the 2-step operation of the TS SS ADC. In general, this makes it difficult to implement the TS SS ADC beyond a 10-bit resolution. In order to improve such errors, a new 4-input comparator is discussed and a high resolution TS SS ADC is proposed. Further, a feedback circuit that enables column self-calibration to reduce the Fixed Pattern Noise (FPN) is also described. The proposed chip has been fabricated with 0.13 μm Samsung CIS technology and the chip satisfies the VGA resolution. The pixel is based on the 4-TR Active Pixel Sensor (APS). The high frame rate of 120 fps is achieved at the VGA resolution. The measured FPN is 0.38 LSB, and measured dynamic range is about 64.6 dB.
本文提出了一种基于两步单斜率模数转换器（TS SS ADC）和列自校准技术的120帧每秒（fps）低噪声互补金属氧化物半导体图像传感器（CIS）。TS SS ADC适用于高速视频系统，因为其转换速度比单斜率模数转换器（SS ADC）快得多（超过10倍）。然而，由于TS SS ADC的两步操作，粗调块和微调块之间存在一些失配误差。一般来说，这使得TS SS ADC难以实现超过10位的分辨率。为了改善此类误差，本文讨论了一种新型四输入比较器，并提出了一种高分辨率TS SS ADC。此外，还描述了一种能够实现列自校准以降低固定模式噪声（FPN）的反馈电路。所提出的芯片采用0.13μm三星CIS技术制造，该芯片满足VGA分辨率。像素基于4晶体管有源像素传感器（APS）。在VGA分辨率下实现了120 fps的高帧率。测得的FPN为0.38 LSB，测得的动态范围约为64.6 dB。
