Integrated Circuit Angular Displacement Sensor with On-chip Pinhole Aperture.

Udumbara Wijesinghe,Andrew Marshall,William Krenik,Mark Lee,Can Duan,Akash Neel Dey,Hal Edwards

doi:10.3390/s20061794

Udumbara Wijesinghe, Andrew Marshall + Show 5 more

Open Access

https://doi.org/10.3390/s20061794

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Abstract

Sensors that remotely track the displacement of a moving object have a wide range of applications from robotic control to motion capture. In this paper, we introduce a simple, small silicon integrated circuit sensor that tracks the angular displacement of an object tagged with a small light source, such as a light-emitting diode (LED). This sensor uses a new angular transduction mechanism, differential diffusion of photoelectrons generated from the light spot cast by the light tag onto a Si anode, that is described by a simple physics model using pinhole optics and carrier diffusion. Because the light spot is formed by a pinhole aperture integrated on the sensor chip, no external focusing optics are needed, reducing system complexity, size, and weight. Prototype sensors based on this model were fabricated and their basic characteristics are presented. These sensors transduce angular displacement of an LED across orthogonal latitudinal and longitudinal arcs into normalized differential photocathode currents with signal linearly proportional to LED angular position across a ± 40° field-of-view. These sensors offer potential performance and ease-of-use benefits compared to existing displacement sensor technologies.

Highlights

Electronic sensors that can remotely track an object’s displacement in space have numerous applications including feedback control of robotic motion, logging motion of celestial bodies, automated tool alignment, and motion capture [1,2,3,4,5]
We introduce a new type of position-sensitive detectors (PSD) based on an angular transduction mechanism fundamentally different from quadrant photodiodes (QPD) and lateral effect photosensors (LEP)
Each was mounted in an uncovered 8-pin ceramic dual inline package (DIP) and Au wire bonds were made from the four cathodes and one anode contact pads on the chip to the pin leads on the DIP

Summary

Introduction

Electronic sensors that can remotely track an object’s displacement in space have numerous applications including feedback control of robotic motion, logging motion of celestial bodies, automated tool alignment, and motion capture [1,2,3,4,5]. APS tracking systems are powerful and flexible but require high-quality optical lenses, large area (several cm2 ) megapixel image sensors, and dedicated high-speed image processors This is often prohibitively expensive or complicated for simple displacement sensing tasks where the object being tracked can be tagged by a small light source, so that forming an image is unnecessary. The IC astrolabe uses an on-chip integrated pinhole aperture to focus light from the light tag onto the sensor surface [19], eliminating the need for front-end optical components This reduces system size, weight, and cost compared to all existing APS and PSD based displacement sensing systems. LEPs are strongly affected by surface recombination and the material quality of a thin heavily doped layer [20], problems avoided in the IC astrolabe

IC Astrolabe Concept and Angular Transduction Model

Prototype

Measurement Methods

Potential Future Improvements to the Prototype IC Astrolabe

Findings

Summary