Grating arrays display photo-like colors

Aug. 1, 2001
TOKYO—Researchers at Toppan Printing have developed a hologram that reproduces color with a brilliance twice that of conventional holograms. Because three primary colors are used, photo-like figures and scenes can be reproduced.
HOLOGRAPHY

Incorporating news from O plus E magazine, Tokyo

TOKYO—Researchers at Toppan Printing have developed a hologram that reproduces color with a brilliance twice that of conventional holograms. Because three primary colors are used, photo-like figures and scenes can be reproduced.

Full-color hologram derives its hues from bit-mapped arrays of red, blue, and green-diffracting gratings. (Photo courtesy of Toppan Printing)
Click here to enlarge image

The hologram uses a so-called "grating image" technology in which photographic images are transformed into data via bit-mapping and then recorded as a holographic image using arrays of gratings as the image elements. By manipulating the diffraction angles, various images can be constructed. The images are recorded by the usual holographic technique of shining a laser beam onto a light-sensitive surface and creating interference patterns.

In the hologram gratings, three rectangular (longer in the vertical direction) image elements—red, green, and blue—are arranged adjacent to each other. The images become apparent via additive color mixing of three primary colors. The three colors are produced using optically designed gratings; the individual pixels are so small that they cannot be distinguished by the naked eye (see figure). Because this method can produce conventionally difficult images such as portraits, the company will expand applications to include the security market.

Courtesy O plus E magazine, Tokyo

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