A High Dynamic Range Pixel with Inverse Proportional Response

Abstract

This paper proposes a high dynamic range (HDR) pixel that combines linear response and inverse proportional response. This pixel achieves nonlinear compression of light intensity under inverse proportional response to improve dynamic range (DR), suitable for CMOS image sensors (CIS) with rolling shutter operation. The proposed pixel is composed of only 4 MOSFET. In HDR mode, it loads the output signal with brightness information dynamically onto the column signal bus. This pixel does not rely on the I-V characteristics of the CMOS subthreshold region and adopts a hard reset structure, overcoming the problems of poor low light SNR performance and image lagging in the traditional logarithmic pixels. The use of low threshold NMOS transistors in the pixel circuit results in the swing of the pixel output close to the power supply voltage, improving the low-voltage performance of the pixel circuit and bringing higher DR. Under a standard CMOS process, the pixel pitch is 6.6μm with a fill factor of 37.6%. The post simulation results indicate that the proposed pixel has good linear and inverse proportional responses to photocurrent. Compared to the linear mode, this pixel has a DR improvement of at least 31.9dB in the HDR mode.

Yuchen Wang

Master’s Student

My research interests include the design of high dynamic range and multi-mode image sensors.

Wenji Mo

Master’s Student

My research interests include circuit design of low-power RISC-V processors and self-powered SoCs.

Haoning Sun

Master’s Student

My research interests include circuit design of analog to digital converter for biomedical applications and noise shaping SAR ADC.

Jingjing Liu

Associate Professor

My research interests include low-power smart micro-sensor integrated circuit design, image sensors, biomedical sensors, and energy harvesting circuits.