Ricoh has reportedly
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
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.
In various optical disk formats, the data layer is positioned at different distances
from the surface of the disk, a factor that contributes to the difficulty of supporting
multiple formats in a single drive. 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. For this reason, Ricoh, placed the diffraction plate 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.
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.
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.