EE Times:
Optical device could help read most disk formats
Yoshiko Hara
(07/07/2006 10:07 AM EDT)
URL:
http://www.eetimes.com/showArticle.jhtml?articleID=190300953
TOKYO — Trying to bridge the gap between next-generation optical disk formats, Ricoh said it has developed an optical component that reads and writes all disk formats—Blu-ray Disc and HD-DVD, as well as DVD and CD—with one pickup and one objective lens.
Ricoh will show the optical device at the International Optoelectronics Exhibition '06 outside Tokyo on July 12-14. The company intends to offer the device to OEMs by year's end.
The component is a 3.5-mm diameter, 1-mm thick round diffraction plate with minute concentric groves on both sides which function as a diffraction grating.
The diffraction plate is placed between lasers and an objective lens. The diffraction grating is designed to adjust a light beam to an optimum incident ray relative to the objective lens so that light focuses on the proper position for each disk format.
The data layer of the Blu-ray Disc resides 0.1 mm from the disk's surface, while the HD-DVD data layer is 0.6-mm deep from the disk's surface, the same as DVD disks. CDs have a data layer depth of 1.1 mm from the disk surface.
Multiformat players and recorders can identify which format disk is loaded. Based on the disc information, Ricoh's optical diffraction component adjusts the laser beam with its diffraction grating for each format and passes it to the objective lens. The lens then forms a beam spot at the appropriate depth for each disk format.
"This diffraction device is the first one that is ready for four formats, including BD and HD-DVD," claimed a Ricoh spokesman. "It will make it possible to build players and recorders ready for all formats, which will benefit consumers," he added.
Although the diffraction device works for both reading and writing modes, Ricoh will initially offer the device for disk players only. Because some laser beam energy is lost at the grating, using the diffraction device for recording will require a blue laser with higher power than those used in conventional recorders.
