Solar Cell Detection and Position, Attitude Determination by Differential Absorption Imaging in Optical Wireless Power Transmission

In optical wireless power transmission, position, size, and attitude of photovoltaic device (PV) must be determined from light source. A method proposed in the previous report is based on selective absorption characteristics of PV, and it is detected by differentiating images of strongly absorbable wavelength and one not. In this study, using two infrared wavelengths, two kinds of targets were detected by differential absorption imaging. One was a GaAs substrate which simulates diffuse rear surface, and the other was a real GaAs PV. It was found that the substrate's reflective characteristic was diffuse, and the solar cell's was mainly non-diffuse and accompanied by small diffuse component supporting wide-angle reflection. Using this feature, the position of the GaAs solar cell could be determined within a wide range of angle. Its attitude could also be determined with an accuracy of +/- 10 degrees to its normal. The position of diffuse GaAs substrate could be determined within a wide range of angles, and its attitude determination was proposed by exploiting its varying apparent size with tilt angle. Broad reflection characteristics of the GaAs substrate enabled attitude determination for a wide-angle range, and determination around normal would be erroneous.