A Study on On-vehicle High-speed Camera Image Processing for Parallel Visible Light Communication

Intelligent Transportation Systems(ITS) have been introduced to give solutions for traffic problems such as traffic accidents and congestions. Assistance of safe driving is one of the major significant area in ITS. On-vehicle and Infrastructure cameras play an important role in many ITS deployments related to assistance for safe driving. Those systems detect vehicle local information by cameras and driver is assisted regarding that information. Recently, high-speed cameras are also used in ITS as well as in other scientific research, military test, and industry. High-speed cameras can capture more information of fast moving objects and changing objects in high frequency compared to the normal cameras. Our research group introduces a road-to-vehicle Visible Light Communication(VLC) system using an on-vehicle high-speed camera as a receiver and an LED traffic light as a transmitter. Driver can be assisted at signalized intersection by sending traffic information to vehicles through this system. VLC is a wireless communication method using luminance, transmitting data by modulating blinking light. Many of conventional VLC systems use Photo Diode(PD) as receiver. However, the proposed system uses a high-speed camera as a receiver. Here, the data is sent by blinking LEDs at high frequency. Those lighting patterns are captured for demodulation by processing the images from the high-speed camera at high frame rate. This image processing includes finding the transmitter, tracking the found transmitter consecutively, and capturing the lighting patterns of transmitter at each consecutive frame. This thesis presents algorithms for those image processing steps considering the features of high-speed image capturing, and available literature on these kind of studies is limited. In addition, all of those image processing steps should be conducted in real time. However, it might be difficult to realize this in software, since the images are taken at high frame rate. Even, to conduct it in real time on hardware, image processing algorithms should include approaches for processing time reduction. For this reason, all algorithms are presented considering the processing time reduction approaches as well. Outdoor experiments were conducted to confirm the effectiveness of each proposed algorithm separately. Then the communication possibility of proposed VLC system was also evaluated using the new algorithms. It showed that finding, tracking and lighting pattern capturing can be effectively conducted with the proposed algorithms. By applying them, data communication can be conducted through the proposed VLC system at a distance between 20m and 40m far from the transmitter in a driving environment.