A New Active 3D Optical Proximity Sensor Array and its Readout Circuit

Abstract

A new 3-D proximity sensor panel (3-D touch panel) for a single object is proposed in this paper. The sensor panel consists of a photo detector (PD) array as active pixels, along with its optics design, a computation algorithm, and sensing circuitry to eliminate background lighting. This sensing panel system acts as a noncontact 3-D positioning sensor, which is able to sense spatial positions of the object without realistic touching to the panel. New active readout pixel circuits for the PDs are designed to efficiently convert PD-received light intensities to voltage signals. It offers high readout resolutions, larger output ranges, and lower noises, as compared with the conventional active pixel sensor (APS) with a 3T-structure (called 3T-APS). Toward success of the sensor, background light is eliminated by a specially designed sample and hold circuitry, whereas a computation algorithm for 3-D object detection is developed based on photometry. The circuit is fabricated by Taiwan Semiconductor Manufacturing Company 0.35- $\mu{\rm m}$ 2P4M 3.3 V mixed signal CMOS process. Sensing trials for a moving object are finally conducted. The sensor performance is validated and further illustrated by a Labview program. The sensing errors of a sphere object are successfully limited to 5% in percentages.