Indoor Positioning Using Reflected Light and a Video Camera

This paper describes an indoor positioning technique using a video camera that captures LED light reflected by the floor. Indoor positioning for mobile devices can be very useful. In particular, localization techniques using LEDs and cameras, so-called visible light positioning, are known to be effective and have high accuracy. However, existing methods have the constraint that they must capture the light source directly. This requires a high-performance processor and a high-resolution image. However, light sources cannot always be detected directly (loss of signal: LOS). Our proposal aims to solve these problems by estimating the position of a camera that does not face the light directly but monitors light reflected by the floor. Specifically, individual LED ceiling lights emit sinusoidal waves modulated with different frequencies, and the camera captures the overlapped light from the LEDs reflected by the floor then demodulates the signal. The camera need not seek the ceiling lights directly from an image, unlike existing methods. The position can be estimated using any part of the image because usually the ceiling light is reflected by the whole floor. Experimental results show that the proposal requires less than 1/100 as many pixels for localization as existing methods and the position can be estimated within 0.4 m at the 90th percentile in a 2.5 m square room. We show that the cause of errors is mainly the difference between the LED diffusion model and the actual light diffusion, the occlusion and the noise and movement of the camera. Overcoming these problems remains as our future work.