Low-light CMOS Image Sensors ‒ ICLAB ‐ EPFL

Low-light CMOS image sensor
Chip micrograph of the realized VGA CMOS image sensor.

Low-light images

Images of the same scene taken with the presented chip for different amounts of input light. The left picture shows the image obtained at 0.005lux with a column-level gain set to 64 and an average of 3 photogenerated electrons per pixel. The left picture shows it at 0.5lux with the column-level gain set to 1 and an average of 320 photo-generated electrons.

Background

The continuous improvements of CMOS image sensors (CIS) in terms of quantum efficiency, speed, and resolution brought this low-cost device into high-performance applications, replacing progressively the charge coupled devices (CCDs). Photoelectron counting capability is the next step for CIS for ultimate low-light performance and new imaging paradigms. With recent improvements of CIS sensitivity, the sub-electron read-noise limit has been reached. But this low-noise level is still a bottleneck, and further reduction towards deep sub-electron noise is required.

Objective

In the Ultra-Low-Noise CMOS Image Sensors project, we aim at demonstrating that a detailed analytical noise calculation of the read noise (thermal noise, 1/f noise, RTS noise and leakage-current shot noise) allows a noise reduction to deep subelectron levels, enabling photoelectron counting by using exclusively design optimization in standard technology without any process refinements.

Recent publications

A. Boukhayma, A. Peizerat, and C. Enz, “A Sub-0.5 Electron Read Noise VGA Image Sensor in a Standard CMOS Process,” Solid-State Circuits, IEEE Journal of, vol. 51, no. 9, pp. 2180-2191, 2016.

A. Boukhayma, A. Peizerat, and C. Enz, “Temporal Readout Noise Analysis and Reduction Techniques for Low-Light CMOS Image Sensors,” Electron Devices, IEEE Transactions on, pp. 72-78, 2016.

A. Boukhayma, A. Peizerat, and C. Enz, “Noise Reduction Techniques and Scaling Effects Towards Photon Counting CMOS Image Sensors,” Sensors, vol. 16, no. 4, 2016.