Visible Light Positioning Using an Aperture and a Quadrant Photodiode

This paper describes a new form of angle of arrival (AOA) detector which can be applied in an indoor visible light positioning system using LED luminaires. In this new detector, a quadrant photodiode (PD) is placed below a transparent aperture in an opaque screen. Light passing through the aperture creates an illuminated area on the quadrant PD. This light spot has the same shape and size as the aperture. The position of the light spot on the PD depends on the AOA of the light. It is shown that this position can be determined by measuring the relative optical power of the light reaching each of the four quadrants of the PD. For the case of a square aperture and a square photodetector, a simple algorithm can be used to determine the x and y coordinates of the center of the light spot on the PD. From this, the AOA can be calculated. Simulations for an indoor visible light positioning system using LED luminaires and realistic parameters show that accurate AOA estimation is possible. If different luminaires transmit different orthogonal signals, digital signal processing can be used to separately estimate the received signal powers from each of the transmitting luminaires. Thus, this new detector has the potential to provide accurate three-dimensional positioning using a single quadrant PD.