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Preliminary Characterization of Robust Detection Method of Solar Cell Array for Optical Wireless Power Transmission with Differential Absorption Image Sensing

In an optical wireless power transmission (OWPT) system, position and size of the photovoltaic device (PV) should be accurately determined from the light source position. Even though the detection of PV for OWPT has been studied and reported in some literature, the methods reported thus far are not so robust against varying background illumination. This study aims to solve such problems utilizing an image sensor which generates a differential absorption image from two wavelength images. Unnecessary background illumination presented in the two images is subtracted in the differential image. The differential image of the Si substrate target, which simulates PV, was detected by this sensor from a 104.5 cm distance. Signal illumination intensity was less than 1 μW/cm2 on the target, and detection accuracy was 3.1% for the diameter of the substrate and about 6.3% for the area. The system level requirement is derived, and they were verified by these results. The detection range of this sensor is shown to be expandable at the cost of, for example, increasing the receiver diameter of the image sensor or controlling the transmitter beam’s divergence. With the simple experiment apparatus, preliminary results of performance assessment were obtained and issues for performance improvement and potential of this image sensor were recognized.