A Sensitivity and Linearity Improvement of a 100-dB Dynamic Range CMOS Image Sensor Using a Lateral Overflow Integration Capacitor

摘要

In a CMOS image sensor featuring a lateral overflow integration capacitor in a pixel, which integrates the overflowed charges from a fully depleted photodiode during the same exposure, the sensitivity in nonsaturated signal and the linearity in saturated overflow signal have been improved by introducing a new pixel circuit and its operation. The floating diffusion capacitance of the CMOS image sensor is as small as that of a four transistors type CMOS image sensor because the lateral overflow integration capacitor is located next to the reset switch. A 1/3-inch VGA format (640{sup}H × 480{sup}V pixels), 7.5 × 7.5 μm{sup}2 pixel color CMOS image sensor fabricated through 0.35-μm two-poly three-metal CMOS process results in a 100 dB dynamic range characteristic, with improved sensitivity and linearity.