Angle Sensitive Optical Sensor for Light Source Tracker Miniaturization

An angle sensitive optical sensor without conventional optics is presented in this article. The reported device omits the need for adding 3-D optics in postprocessing by monolithic integration of complimentary metal-oxide semiconductor compatible diffraction grating layers, which cuts down the fabrication costs and allows for miniaturization of these types of sensors. The sensor resolves angular information from a monochromatic light source over a single axis with a mean absolute accuracy of 0.6° in an investigated $\pm 26$° field-of-view using four unique pixels. This letter facilitates miniaturization of light source trackers, such as sun position sensors on small satellites of the future.

I. Introduction

Light source trackers are a sensor family that is not often seen in daily life. Still, this type of sensor is vital in aerospace applications where the movement of the spacecraft needs control. This activity is called attitude control and relies on the direction toward a known reference. Typically, this reference is the sun, and the spacecraft relies on a sun position sensor for the determination of its direction. The sun position sensor has different implementations, classified by the collimating, sun-pointing, tilted mount, and hybrid sensors [1]. The collimating sensor is adopted in most of the state-of-the-art and commercial devices. Reports of miniaturized examples include an active pixel sensor (APS) array [2] and pixel line sensor [3], which contain hundreds of individual photodetectors on a chip of few tens of mm.