Michinori Andoh

Image-sensor-based visible light communication for automotive applications

The present article introduces VLC for automotive applications using an image sensor. In particular, V2I-VLC and V2V-VLC are presented. While previous studies have documented the effectiveness of V2I and V2V communication using radio technology in terms of improving automotive safety, in the present article, we identify characteristics unique to image-sensor-based VLC as compared to radio wave technology. The two primary advantages of a VLC system are its line-of-sight feature and an image sensor that not only provides VLC functions, but also the potential vehicle safety applications made possible by image and video processing. Herein, we present two ongoing image-sensor-based V2I-VLC and V2VVLC projects. In the first, a transmitter using an LED array (which is assumed to be an LED traffic light) and a receiver using a high-framerate CMOS image sensor camera is introduced as a potential V2I-VLC system. For this system, real-time transmission of the audio signal has been confirmed through a field trial. In the second project, we introduce a newly developed CMOS image sensor capable of receiving highspeed optical signals and demonstrate its effectiveness through a V2V communication field trial. In experiments, due to the high-speed signal reception capability of the camera receiver using the developed image sensor, a data transmission rate of 10 Mb/s has been achieved, and image (320 × 240, color) reception has been confirmed together with simultaneous reception of various internal vehicle data, such as vehicle ID and speed.

LED and CMOS Image Sensor Based Optical Wireless Communication System for Automotive Applications

An optical wireless communication (OWC) system based on a light-emitting-diode (LED) transmitter and a camera receiver has been developed for use in the automotive area. The automotive OWC system will require Mb/s-class data rates and the ability to quickly detect LEDs from an image. The key to achieving this is improvements to the capabilities of the image sensor mounted on the camera receiver. In this paper, we report on a novel OWC system equipped with an optical communication image sensor (OCI), which is newly developed using CMOS technology. To obtain higher transmission rates, the OCI employs a specialized “communication pixel (CPx)” capable of responding promptly to optical intensity variations. Furthermore, a new quick LED detection technique, based on a 1-bit flag image which only reacts to high-intensity objects, is formulated. The communication pixels, ordinary image pixels, and associated circuits (including 1-bit flag image output circuits) are then integrated into the OCI. This paper describes the design, fabrication, and capabilities of the OCI, as well as the development of the LED and image sensor based OWC system, which boasts a 20-Mb/s/pixel data rate without LED detection and a 15-Mb/s/pixel data rate with a 16.6-ms real-time LED detection.

Optical Vehicle-to-Vehicle Communication System Using LED Transmitter and Camera Receiver

This paper introduces an optical vehicle-to-vehicle (V2V) communication system based on an optical wireless communication technology using an LED transmitter and a camera receiver, which employs a special CMOS image sensor, i.e, an optical communication image sensor (OCI). The OCI has a “communication pixel (CPx)” that can promptly respond to light intensity variations and an output circuit of a “flag image” in which only high-intensity light sources, such as LEDs, have emerged. The OCI that employs these two technologies provides capabilities for a 10-Mb/s optical signal reception and real-time LED detection to the camera receiver. The optical V2V communication system consisting of the LED transmitters mounted on a leading vehicle and the camera receiver mounted on a following vehicle is constructed, and various experiments are conducted under real driving and outdoor lighting conditions. Due to the LED detection method using the flag image, the camera receiver correctly detects LEDs, in real time, in challenging outdoor conditions. Furthermore, between two vehicles, various vehicle internal data (such as speed) and image data (320 × 240, color) are transmitted successfully, and the 13.0-fps image data reception is achieved while driving outside.

A CMOS image sensor for 10Mb/s 70m-range LED-based spatial optical communication

Spatial optical communication has recently been of interest in the mobile local-area communication systems, especially in the automotive applications. It has many advantages over the radio communication such as robustness to jamming, human safety due to lack of electromagnetic waves and sender finding function. The image sensor communication (ISC) technology is useful for the spatial optical communication because to find the light source and to intensify the light energy density at the receiver, the optical receiver has to have signal light source finding and tracking functions. A few approaches for the ISC have been reported. CMOS ISC chips have been used for ID beacon detection [1] [2], where very low data rate is required. In an ISC chip for optical wireless LAN application [3], the data rate of several hundreds of MHz has been demonstrated. In this approach, however, photo-diode current of a 2-D detector array directly flows into external receiver circuits, and because of this, extremely large optical power using laser lights is required. The authors have reported an ISC chip for LED-light communications [4]. In this chip, the bit rate of 1Mb/s and the communication range of a few meters only have been demonstrated. Though the chip claims the function of signal light source tracking, no experimental results have been shown. This paper presents a CMOS ISC chip which demonstrates that the high-speed long-distance spatial optical communication over 10Mb/s and 50meters are realized for the system using LED light sources while attaining signal-light finding and tracking functions. The key techniques to improve the data rate and tracking performance are a new pixel structure using depleted diode, pulse equalizing, and binary flag image readout to find the exact area of light source.

A CMOS imager and 2-D light pulse receiver array for spatial optical communication

This paper presents a CMOS imager and 2-D Light Pulse Receiver (LPR) array for car-to-car and road-to-car spatial optical communication. Using the prototype sensor with 640×240 image pixels and 640×240 LPR cells implemented with 0.18μm CMOS technology. Both imaging and 60fps optical communication at the carrier frequency of 1MHz are successfully performed. The measured signal amplitude and the calculation results of photocurrent shows that the spatial optical communication up to 100m is possible.

Design and Implementation of A CMOS Light Pulse Receiver Cell Array for Spatial Optical Communications

A CMOS light pulse receiver (LPR) cell for spatial optical communications is designed and evaluated by device simulations and a prototype chip implementation. The LPR cell consists of a pinned photodiode and four transistors. It works under sub-threshold region of a MOS transistor and the source terminal voltage which responds to the logarithm of the photo current are read out with a source follower circuit. For finding the position of the light spot on the focal plane, an image pixel array is embedded on the same plane of the LPR cell array. A prototype chip with 640 × 240 image pixels and 640 × 240 LPR cells is implemented with 0.18 μm CMOS technology. A proposed model of the transient response of the LPR cell agrees with the result of the device simulations and measurements. Both imaging at 60 fps and optical communication at the carrier frequency of 1 MHz are successfully performed. The measured signal amplitude and the calculation results of photocurrents show that the spatial optical communication up to 100 m is feasible using a 10 × 10 LED array.

Skin detection by near infrared multi-band for driver support system

Many active safety technologies for the driver support system are developed. Most of the traffic accidents are caused by driver’s inattentive or drowsy. We are developing a driver support system that protects from traffic accidents by these causes. Our purpose is to detect the driver’s face region. A lot of face detection methods are proposed, but there is not a technique addressing every environment inside the car. In this paper, we propose a skin detection method by the unique reflection characteristics of the materials. We developed the skin detection system, and confirmed the effectiveness by the evaluation experiment.

Neocognitron capable of position detection and vehicle recognition

We propose a vehicle recognition system using Neocognitron that is tolerant of deformations and shifts in position. For this system, we have developed a function of position detection and a method of supplementing partial features to occluded areas. The system recognizes multiple vehicles independently, even if vehicles are overlapped by other ones. Furthermore, it obtains positions of recognized vehicles in input images.