Hitachi's 3D Display Requires No Glasses but Has High Resolution

Hitachi Ltd exhibited its 10-inch "Full Parallax 3D TV" at CEATEC 2009. It does not require special glasses, can be watched from any direction and has a resolution of 3D image as high as VGA (640 x 480 pixels), according to the company. The Full Parallax 3D TV is based on a method called "Integral Photography with Overlaid Projection." Specifically, it consists of 16 projectors and a lens array sheet to cover them. The lens array sheet ensures parallax in any direction (not only in the horizontal direction). Because of parallax, the 3D image seen by the user differs in accordance with the angle from which the screen is viewed.

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In general, the total pixel count of a 3D display that does not require special glasses is equal to the pixel count of 3D image multiplied by the number of viewpoints that show different images. In other words, there is a trade-off between the number of viewpoints and the resolution of 3D image. If the number of viewpoints is focused too much, the resolution of 3D image deteriorates. But it is not easy to increase the total pixel count of a display. For example, the Science & Technical Research Laboratories (STRL) of Japan Broadcasting Corp (NHK) is now developing a 3D display using the "Ultra-high Definition TV" with a resolution of 7,680 x 4,320 (approximately 33 Mpixels) but seems having a hard time to achieve a high resolution.

Hitachi aims to go over the limit of total pixel count by using multiple projectors, each of which has a resolution of 800 x 600 pixels (SVGA). So, a display using 16 projectors has a resolution of 7.68 Mpixels, which is equivalent to 4K x 2K resolution. Considering its small size (10 inches), the new 3D display is much finer than a normal 4K x 2K display.

"We will be able to arrange projectors in a higher density by employing laser-based micro-projectors and increase the number of projectors by more than 10 times," Hitachi said.

Japan's National Institute of Information and Communications Technology (NICT) also employed the method of increasing the total pixel count by using projectors and exhibited a 3D display that does not require special glasses at CEATEC in two consecutive years. But NICT utilizes projectors to increase the pixel count only in the horizontal direction.

By Tetsuo Nozawa, Nikkei Electronics