A fully integrated CMOS sensor for optical tracking

摘要

A fast, low power CMOS sensor for optical tracking is presented. The tracking function is carried out by pointing at the target with a collimated light beam and estimating the position of the back-reflected beam portion impinging on the device. An example of optical tracking sensor is represented by a Position Sensitive Detector (PSD). This work presents a novel architecture of a 2D pixel array for single spot detection and tracking, based on image outline extraction. The prototype device, designed in standard 0.8 μm CMOS technology, consists of an array of 20x20 pixels with a pitch of 70.25 μm and a fill factor of 12%. The photosensitive detector is provided with analogue processing circuitry and digital blocks which allow to extract the spot centroid. Two different multiple threshold working modes are adopted in order to improve the sensor accuracy and frame rate. The light spot position can be estimated in 120μsec with an accuracy of 0.9 μm, when the sensor is operated with the first mode. The second mode is adopted to improve the frame rate. The chip exhibits a worst case power consumption of 15 mW @ 5 V and a frame rate up to 3000 frames/s.