Optical Design and Receiving Characteristics of Two Lens Type Visible Light Communication System

Abstract

This paper describes the optical design for two lens type visible light communication system to reduce back ground noise. The system is composed of image sensor, receiving element and control software. The selected area for the receiving element was calculated by considering the chip size, focal length of lens and the pitch between image sensor and receiving element on the PCB board. The communication length is expected in proportional to the focal length of lens. LED sources were modulated with sub-carrier 4bit pulse position modulation of visible light ID at the carrier frequency of 28.8kHz. The communicational length of the system by using commercialized high sensitive photo transistor was measured up to 16.5m for the focal length of 12mm. In the photo-transistor array system, the brightness and illuminant size from the image sensor is used to identify the signal source. The system separates the data from multi signal sources by selecting the arbitrary receiving element.