NHK Develops Organic Image Sensor w/ Transparent TFT

May 26, 2008 19:47 Tetsuo Nozawa, Nikkei Electronics

Japan Broadcasting Corp (NHK) Science & Technical Research Laboratories exhibited an organic single-plate color image sensor along with images recorded by the sensor at Open House 2008.

NHK Research Laboratories regards the image sensor as the technology to reduce the size of 3CCD camcorders with a resolution of 7680 x 4320, which the Laboratories calls "Super High-vision," or 3840 x 2160.

The image sensor is composed of three image pickup devices stacked on one another. Each of the pickup devices includes a colored organic semiconductor and a transparent zinc oxide (ZnO) TFT. By using different organic semiconductors for three image pickup devices, each of them is designed to absorb one of red (R), green (G) and blue (B) colors. The semiconductors absorb light in B, G and R colors in this order.

The 3CCD system divides light from the camera into RGB colors with a prism, and uses image sensors corresponding to these colors. While it provides a high resolution, the system involves a problem of increased camera size due to three image sensors required. The adoption of organic image sensor leads to a reduction of camera size because it eliminates the need for the prism and requires footprint for just one image sensor.

At the moment, the latest organic image sensor only has a low resolution, approximately 47 × 30, which is far from Super High-vision.

"We do not see any problem in this regard because the latest ZnO TFT is the first prototype that was made only a week ago and we are planning to further increase its resolution," the demonstrator said.

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