Since LEDs are widely used for the traffic lights or tail lights, the spatial optical communication using LEDs is expected for applications to car-to-car and road-to-car communication. We have been investigating CMOS image sensors for the spatial optical communication. The sensor has functions of the image acquisition and the searching for the communication source. To realize there functions this image sensor has an array of pixels for imaging and communication alternatively arranged. The pixel structure for the communication signal has a structure as shown in the figure below. Parasitic capacitance of the photo diode is reduced by the fringing electric field, and the generated charge instantly moves to the charge detection part. Using this technology, a long distance (>100m) and high career frequency (>10Mbps) in the spatial optical communication has been achieved. This CMOS sensor chip has been presented at ISSCC 2010.
|Spatial optical communication image sensor
|Pixel structure for communication signal
|Block diagram chart of image sensor
|Taking picture image (a&b), Signal reproduction image (c&d)