May 22, 2007

NHK demos image sensor for full HDTV

By Yoshiko Hara

TOKYO — Japan Broadcasting Corp. (NHK) has developed a 33-million pixel CMOS image sensor to deliver "8K by 4K" video resolution, which Japan's largest broadcaster is promoting as Super Hi-Vision for future broadcast services.

NHK demonstrated on Tuesday (May 22) a 2.5-inch image sensor before an open house at its Science & Technical Research Laboratories.

"With the full coverage of terrestrial digital TV broadcasting nationwide since last December, high-definition broadcasting" is available throughout Japan, said Kenkichi Tanioka, the lab's director general. NHK is developing the 8K by 4K system as a proposed next-generation broadcast technology that would be fielded in the next 20 years.

Super Hi-Vision images consists of about 33 million (7,680 by 4,320) pixels. NHK currently uses Super Hi-Vision cameras that employ four 8-megapixel CMOS sensors jointly developed with Micron Technology Inc. to produce 8K by 4K video, but a full 33-million pixel resolution resolution image sensor was the first priority.

NHK researchers worked with a U.S. joint venture company to develop the image sensor and fabricate a prototype. During the demonstration, they used the image sensor to capture monochrome moving images with a 12-bit gray scale and progressive scanning.

"Pixel size was kept as large as possible for requirements such as sensitivity and dynamic range," a laboratory spokesman said, adding that the 3.8 by 3.8 micron pixel was almost the same size as the 8-megapixel image sensor.

Twelve-bit image data was divided into 16 fragments for read out. The prototype currently operates at 30 frames/second at 125 MHz. "If the image sensor operates fast enough, we will not need to use 16-channel parallel reading out," the spokesman added.

Next, the NHK researchers will build a Super Hi-Vision color camera using multiple image sensors. The camera will be used to study full-specification Super Hi-Vision picture quality.