A 1280×1920 Global Shutter CMOS Image Sensor with On-Chip Background Light Cancellation

Interference from background illumination is one of the most critical factors affecting the performance of 3D image sensors. Background light cancellation (BLC) techniques can be used to reduce the effects of ambient light, but often result in increased pixel area or processing power. In this work, we propose a hybrid shutter scheme that combines the benefits of a Global Shutter and Rolling Shutter for both laser signal and background light, resulting in a low-cost, high-precision BLC scheme without the need for external memories or excessive power. A 2.3-megapixel 2.5μm-pixel-pitch 3D CMOS image sensor (CIS) has been designed in a 65-nm front-side-illuminated (FSI) CIS technology. The sensor achieves a 2.6 e- readout noise and 180 fps frame rate while consuming only 301 mW of power, leading to a FoM of only 1.77 e-nJ. The embedded BLC feature effectively suppresses the depth error caused by strong background light and greatly improves the imaging quality.