The 133-Mpixel CMOS image sensor exhibited by NHK
The 133-Mpixel CMOS image sensor exhibited by NHK
[Click to enlarge image]

Japan Broadcasting Corp (NHK) developed a 133-Mpixel CMOS image sensor for shooting so-called "8k4k" video.

NHK exhibited a prototype of the sensor at a private show of Open House 2014, which NHK Science & Technology Research Laboratories organized for the press May 27, 2014.

In general, to shoot an 8k video, an image sensor with a pixel count of about 33 million (7,680 x 4,320) is necessary. Because 33 Mpixels of data is collected for each of red, blue and green colors, three 33-Mpixel image sensors are conventionally used. However, this method requires a prism that separates light into three colors, making it difficult to reduce camera size.

To reduce camera size without using a prism, the "single-plate color imaging method," which collects data of three colors with a single image sensor, can be used. But with this method, it is difficult to ensure an image quality equivalent to that with the method using three image sensors. This is because the single-plate color imaging method collects data of only one color per pixel.

In the case of a 33-Mpixel image sensor using an RBGG (Bayer array) color filter and the single-plate color imaging method, the amounts of data of G signals and R/B signals are about 16.6 Mpixels and 8.3 Mpixels, respectively. Those data are used to make 33-Mpixel color video with pixel interpolation technology.

The pixel count of the newly-developed CMOS image sensor is 133 million, which is about four times that of the conventional 33-Mpixel image sensor. With an RBGG color filter, the new sensor can collect about 66 Mpixels of G signal data and about 33 Mpixels of R/B signal data, enabling to use the single-plate color imaging method to make an 8k video without pixel interpolation.

It is a so-called "35mm full-size" sensor. Its imaging area measures 37.6mm (horizontal) x 21.2mm (vertical). Its pixel count and pitch are 15,360 (horizontal) x 8,640 (vertical) and 2.45μm, respectively. The frame frequency and gradation of the sensor are 60Hz and 12 bit. It uses a μ-PGA package with 1,125 pins.