A Cost-Effective Micro Sun Sensor Based on Black Sun Effect

A cost-effective micro sun sensor is presented for extracting the sun vector from image sensors based on a phenomenon called the black sun. The black sun, appearing as the result of electron overspill at an oversaturated CMOS image pixel when capturing a bright spot such as the sun, allows extracting the sun centroid accurately and robustly even when the sun image appears irregular and noisy due to glare. This greatly enhances the accuracy and robustness of sun vector extraction, while taking advantage of image sensors in terms of their field-of-view and cost-effectiveness. With the micro sun sensor implemented, we demonstrate its performance based on the two types of applications: 1) a stationary application targeted for heliostats or solar panels with a single image sensor configuration and 2) a non-stationary application targeted for space rovers with the multiple image sensors configured in the icosahedron geometry. The experiments indicate that an accuracy of 0.1 degrees and 0.3 degrees are achievable for the stationary and non-stationary applications, respectively, using as small as 1x1mm size and as low as 250 x 250 pixel resolution of micro cameras.