Patent ID: 7190657

Claim:
An optical pickup device comprising: a dual wavelength light source module for emitting a selected one of two light beams having different wavelengths; a wavelength selective dual grating having a predetermined thickness while being formed at an upper surface thereof with a plurality of upper diffraction grating patterns adapted to split said selected light beam, received from said dual wavelength light source, into at least three beams of zero, +1st, and −1st orders, when said selected light beam is one of said two light beams, and at a lower surface thereof with a plurality of lower diffraction grating patterns adapted to split said selected light beam into at least three beams of zero, +1st, and −1st orders, when said selected light beam is the other light beam; a beam splitter for receiving said selected light beam emerging from said dual grating, and reflecting said selected light beam toward an optical disc; an objective lens for receiving said selected light beam from said beam splitter, and focusing said selected light beam onto a spot on an optical disc; a hologram for receiving said three beams of said selected light beam reflected from said optical disc after striking a signal track of said optical disc, said hologram maximizing a diffraction efficiency of the zero-order one of said three beams, included in said selected light beam, traveling in a straight direction, when said selected light beam is said one light beam, while maximizing a diffraction efficiency of the +1st or −1st-order one of said three beams, included in said selected light beam, traveling in a refracted direction, when said selected light beam is said other light beam, said hologram being adjustable in position to focus said zero-order beam and said +1st or −1st-order beam on the same spot; and a photodetector for detecting said three beams of said selected light beam emerging from said hologram, and generating electrical signals, based on said detected beams, respectively.