Mitsubishi Electric Corp. has developed an LCD monitor using light-emitting diodes (LED) of six different colors as a backlight. The range of color reproduction expands to 119% compared to the company's prototype with a 3 color LED backlight, and to 181% compared to the sRGB standard. The LCD monitor can display 95.58% of the Munsell Color Cascade, a series of natural object color samples. The conventional product using a 3 color LED backlight could only display 80.62% of the Munsell Color Cascade and 52.67% of the sRGB standard.
The peak wavelength of each LED is 410 nm (B2), 430 nm (B1), 510 nm (G1), 540 nm (G2), 615 nm (R2) and 625 nm (R1). These LEDs are divided into two groups, and frames consisting of R1, G1 and B1 LEDs and those containing R2, G2 and B2 LEDs are lit in sequence. This technology is called field sequential. The LCD panel's subpixels and 3 color filters respond to these 3 color LEDs lit in each field. Mitsubishi employed the technology, because "It allows us to expand the color reproduction range using a conventional LCD panel, without modifying the resolution structure and the color filter." The LEDs are manufactured by Lumileds Lighting, LLC, and 26 R1, R2, B1 and B2 LEDs, as well as 56 G1 and G2 LEDs are used. The backlight's power consumption is 60 W.
The prototype LCD is a 23-inch monitor with a resolution of 1280 x 768 pixels. The luminance is 80 cd/m2. It features a proprietary circuit that converts RGB signals into those compliant with the 6 primary colors. The LCD panel also features another circuit that adjusts to the LEDs' color change due to factors such as temperature and time.
Takuya Otani, Nikkei Electronics
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