Microelectronic Angular Displacement Sensor With Near Hemispherical Linear Field-of-View

Small, low-cost solid-state sensors capable of tracking an object's displacement have many potential applications ranging from guidance of robotic tools to solar tracking. We describe a simple, compact (~1 mm \times1 mm) microelectronic sensor that can track the angular displacement of an object tagged by a point source of light across a nearly hemispherical field-of-view (FoV) with highly linear angular response. These sensors were fabricated using an industrial silicon integrated circuit process technology. They transduce angular displacement as an imbalance in photoelectron diffusion to photocathodes placed at the perimeters of a light absorbing anode. The sensing area is enclosed within an on-chip integrated metal box with a pinhole aperture. Use of pinhole optics makes optical lenses or mirrors unnecessary, reducing system size, weight, and cost. The sensor signal is linearly proportional to a light tag's angular position across a 160° FoV in both latitudinal and longitudinal arcs, with horizons limited by packaging considerations. A single sensor chip can thus track angular displacement of an object across > 1.7\pi steradians of solid angle with highly linear response. By monolithically integrating an on-chip amplifier with the sensor and using lock-in detection to a modulated light tag, signal-to-noise is found to improve significantly with modulation frequency up to 500 Hz. These sensors are small, lightweight, operate with very low power, and can be easily integrated with silicon signal processing circuits and manufactured in high volume.