Developing a vector light sensor

Over the past few decades, numerous sensors have been invented for the measurement of light intensity. In most cases, a setup external to the sensor is required to detect the direction of an incoming beam of light. In this work, the design, fabrication, and characterization of a novel light sensor is described. The three-dimensional structure of the sensor allows it to detect both the intensity as well as the direction of the incident light beam, hence becoming a vector light sensor (VLS). The sensor structure is based on creating photodiodes on sidewalls of miniaturized raised or inverted pyramids etched in silicon. Each photodiode was formed by selective doping of the material on each facet of the pyramid, forming a photodiode with the P-type substrate. A set of signal processing algorithms was developed to estimate the direction and the distance of a light source from the sensors. The light sensing devices with both raised and inverted pyramid structures were then fabricated in a cleanroom based on silicon microfabrication technologies. Throughout the process, the lithography step for the textured surface needed to be optimized. An interface circuit was designed and used to amplify and process the signals from the devices. The device operation was verified experimentally to estimate the direction of a light beam. The small size and low power consumption of the individual sensors make them suitable for applications were simple distance and direction estimation is required. The sensors can be arrayed to provide light-field information in the plane of sensor.