A finer production process has also been employed to manufacture the displays. As a result, the driver wiring is narrower, and the redesigned transistor elements used to switch the pixels on and off are smaller.
The benefits of this are threefold, says Chino. First, there is an increase in the aperture ratio of the color filters. This allows more light to be transmitted from the backlight unit, boosting picture resolution. The second improvement is an increase in pixel density. Whereas a typical mobile phone display uses around 200 pixels per inch, Photo Fine Chromarich displays produce 280 ppi. And third, power consumption has hardly changed, an important factor for mobile products, with depend on battery power.
"One of our competitors has exhibited its own color gamut display, but it has done this in part by using a three-color light-emitting diode backlighting system," says Chino. "This not only raises the power consumption, it also increase the panel's thickness. From the beginning we designed our Photo Fine Chromarich displays to meet the needs of mobile market."
Another key technology is the color management system. "Just using a new full-color filter set would be of no help at all," says Kiyoaki Murai, a manager in the Imaging Technology Laboratory, Corporate R&D Division, at Seiko Epson. "So Epson has developed a color management system for new four-color filter set - a new transistor driver chip that incorporates a color-conversion algorithm needed to change the RGB input signals to a RG1G2B four-color output signal," he explains.
Employing the color-conversation algorithm in the driver ship in this way allows the new LCD modules to maintain the same interface specifications as a standard LCD, Murai points out. This makes the display attractive for designers of end products, who can easily substitute a standard panel with the superior Photo Fine Chromarich panel, "without the headache of having to change their own interface specifications," he adds.
The final technology that had to be improved in order to optimize the images on the displays was the white light-emitting diode (LED) backlighting unit. This has been changed to meet the requirements of and get the best out of the new four-color filter system.

Integrating the color-conversion algorithm into the driver chip allows the new LCD modules to reproduce colors accurately even with standard RGB input signals.

The Photo Fine Chromarich display took about two years of research and development to perfect. In order to reproduce the most natural colors possible, one engineer went so far as to visit Okinawa, a chain of islands in south-western Japan, just to take pictures of he vivid emerald green waters for which the region is famous. These pictures were then used to help produce the optimum color pigment for the two new green filters.
Volume production of the new displays is set to begin in spring 2006. Epson Imaging Devices will target manufactures of mobile phones and digital cameras with the 2.2-inch and 2.8-inch displays, while the 4.5-inch product will be marketed to makers of PDAs, digital picture viewers, and handheld video game consoles, as well as manufacturers of in-car equipment and the emerging market for mobile satellite TV viewers.

* NTSC refers to the standard format for terrestrial analog television broadcasting in the United States set out by the National Television System Committee in 1953. The NTSC format is the basis for TV color reproduction in Japan, the United States, Canada, and Latin America.

John Boyd is a freelance writer based in Yokohama. He writes for a number of publications and covers technology and business news and issues in Japan and Asia.

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