Design and Simulation of an HDR CMOS Image Sensor Employing Programmable Linear–Logarithmic Counter With Nonlinear Response Pixel

Abstract

This article presents a high dynamic range (HDR) CMOS image sensor, which is designed using a 0.18-$\mu$m technology, resulting from integrating two previously studied HDR sensor architectures. In this image sensor, we use the readout circuit from a previous design about an HDR CMOS image sensor employing programmable linear–logarithmic counter for low-light imaging applications, combined with the pixel, which is slightly modified, from a previous work about a pixel for asynchronous HDR acquisition through adaptive tone mapping. The pixel resembles the design of a 3T pixel, but includes two more transistors (five in total) in order to allow for the use of the average photocurrent information from the entire pixel array. It is thus possible to obtain an image sensor with programmable sensitivity and HDR. The proposed pixel holds (considering a 10 $\mu$m × 10 $\mu$m photodiode) a fill factor of 65%, a pixel pitch of 16.93 $\mu$m, and a pixel area of 15.12 $\mu$m × 10.16 $\mu$m. By configuring sensor parameters, it is possible to perform tone mapping and to control the image brightness, contrast, detail levels, and the number of bits used in the image. As a consequence, the resulting image may include either more or less detail, as defined by application-specific (or user-selected) parameters. The simulated dynamic range of the proposed image sensor is equal to 95.72 dB.