Next Generation Image Sensor

Toshihisa Watabe, Principal Research Engineer, NHK Science and Technical Research Laboratories, Tokyo, Japan

Abstract: In current professional-use cameras, such as broadcast television (TV) cameras, incident light through a lens is separated into three primary color components (blue, green and red) by a dichroic prism, and each color is then detected individually by one of three imaging devices, such as CCD. As the number of the pixel of the sensor is increasing to achieve a high-resolution, sensitivity is reduced due to shrinking the pixel area of the sensor. This low sensitivity is compensated by amplifying the signal output electrically especially when the camera is used to shoot pictures under low light conditions, so the picture quality (Signal-to-noise ratio) is degraded. Moreover, the dichroic prism makes a size of the camera large, so that the feature of handiness is reduced. To solve these problems, we have been researching a super-high sensitivity imaging devices with HARP (High-gain Avalanche Rushing amorphous Photoconductor) and a new type of solid-state image sensor overlaid with three kinds of organic photoconductive films which are sensitive to only blue, green, and red light to achieve compact, lightweight and high-resolution color camera without dichroic prism. These technologies also improve the potential of the imaging devices used in consumer products, such as digital cameras and cell phones, that is, improve the low sensitivity due to the decreasing pixel size which reaches 2 microns, and reduction of picture quality due to single sensor with mosaic color filters installed in the cameras. We discuss the developing techniques and issues for a next generation image sensor based on a new concept to achieve the highest sensitivity and picture quality.

About the speaker: Toshihisa Watabe received his B.E. and M.E. degrees in electronic engineering from Keio University, Yokohama, Japan, in 1989 and 1991, respectively. In 1991, he joined the Japan Broadcasting Corporation NHK, Tokyo, Japan. From 1991 to 1994, he worked at the Niigata regional broadcasting station of NHK as a television engineer. Since 1994, he has been engaged in the research and development of the highly sensitive CMOS image sensor, CMOS image sensor with organic photoconductive films, and highly sensitive field-emitter-array image sensor in the Advanced Boadcasting Devices Department of the NHK Science and Technical Research Laboratories where he currently is a principal research engineer.


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