A high performance integrated readout circuit for wavefront sensors

Abstract

This work presents an integrated pixel topology that promises to offer superior performance in a Hartmann-Shack Wavefront Sensor (WFS) with an orthogonal array of Quad Cells serving as Position-Sensitive Detectors. The readout integrated circuit for each photodiode is fully compliant to any standard CMOS microelectronics technology and is advantageously tolerant to high background illumination levels whereas maintaining both high linearity and high sensitivity. To assess the operation of this pixel on the focal-plane array of the WFS, we developed a computational platform encompassing a full detection chain comprising wavefront sampling, photodetection, electronic circuitry and wavefront reconstruction. It couples an algorithm written in C to SPICE (Simulated Program with Integrated Circuits Emphasis). The platform is technology agnostic and flexible, enabling easy modification to represent different detection or reconstruction methods. The results obtained with the proposed pixel have been compared to those obtained with a conventional pixel in CMOS image sensor.

A Review of Optical Sensors in CMOS

“…Figure 11b illustrates the second type of pixel, i.e., the active pixel sensor (APS) [65,[81][82][83][84][85][86][87], which consists of a matrix of pixels in the same way as the PPS, but with the difference of containing three MOSFETs, where M 1 is the reset transistor, M 2 is the amplifying transistor, and M 3 is the pixel address transistor. The APS has three modes of operation: the reset mode, the integration mode, and the readout mode [12,22,35,[88][89][90]. The reset signal closes the reset transistor M 1 during the first mode and directly connects the N-type region of the photodetector to the supply voltage V dd .…”