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.