Eye Tracker with In-pixel Signal Processing for Fast Eye Tracking

Abstract

This study proposed an eye tracker with in-pixel signal processing. The eye tracker achieved low power consumption and latency by realizing a detection unit within a pixel, eliminating the need for image storage memory and interface circuit for image transmission. The detection unit utilized morphological operations - shrinkage and expansion - to detect a pupil or glint center and was implemented with all digital circuits, further improving the power efficiency. Additionally, an adaptive thresholding method was proposed to optimize latency for a given illumination condition. A threshold voltage for image binarization and integration time for a photodiode was adjusted to minimize the latency without compromising detection accuracy. The eye tracker comprising a 176 × 120-pixel array was fabricated using a 180 nm standard CMOS process and validated through appropriate experiments. It achieved a √2 pixel error with a latency of 80 μs and dissipated 5 mW from a 3.3 V supply voltage. © 2001-2012 IEEE.