NHK Science and Technical Research Laboratories is developing a single-plate color image sensor using organic films, with the aim of achieving an ultra-compact, high-definition camera. Now, the company has fabricated a prototype with higher resolution, by using even smaller pixels and increasing their number.
The organic image sensor use three organic films, each sensitive to one of the three primary colors of light. This single-plate color imaging device has a structure where the three films are inter-layered with three transmissive TFT circuits for reading the signals.
"Conventional broadcast cameras use a color-resolving prism to separate the light coming in through the lens into the three primary colors, and they use three imaging devices. This gives a camera that's very sensitive and has high resolution. But because the camera has a prism, it's inevitably large. If you create a structure where the colors are each separated in turn in the depth direction, that's the sort of structure which is used in photographic film. An image sensor, or imaging device, with a structure like photographic film doesn't need a prism. Another advantage is that you only need one device, so the camera can be made very small."
"This is a prototype device. From the left are the elements sensitive to blue only, green only, and red only. The colors you see are complementary to the colors absorbed; in other words, they're yellow, magenta, and cyan. These colored parts are called organic photoelectric conversion films. For example, in the leftmost element, blue light only is absorbed, and an electric charge is generated in proportion to the amount of light. The green and red light pass through to the bottom. Next, the green component alone is converted using the next element, and the red passes through. By using this structure, the colors can be separated in the depth direction. Here, we're showing color images actually taken with these three elements superimposed."
In this prototype, the pixel pitch has been reduced to 100 microns, which is one-sixth the previous pitch, as the transmissive TFR circuit performance has been improved. The device also has over eight times as many pixels as before, with 128 horizontally and 96 vertically to give 12,200.
From now on, NHK aims to develop organic imaging devices with even higher resolution by further increasing the TFT integration density.
Related Links :
- YouTube
- Organic Image Sensor
- NHK OPEN HOUSE 2010
