Optical pick-up apparatus

DETAILED DESCRIPTION Accordingly, the present invention has a purpose, in view of above-described problems or disadvantages encountered in the prior art, to provide an optical pick-up apparatus capable of realizing both the conversion of a laser beam to the optical disk and/or the photo detector and the differentiation of going and returning laser beam paths, by use of only one holographic optical element, thereby providing cheaper optical pick-up apparatus.
In order to accomplish above purposes, the present invention provides not more than one compound holographic optical element on an optical path starting from a semiconductor laser chip and arriving at a photo detector via an optical disk.
A hologram pattern of this compound holographic optical element is the superposition of a first hologram pattern, converging a laser beam emitted from the semiconductor laser chip onto the optical disk, and a second hologram pattern, diffracting the laser beam reflected at the optical disk toward the photo detector and changing it into a focusing beam.
This single holographic optical element not only realizes the convergence of the laser beam onto the optical disk and/or the photo detector and the differentiation of going and returning optical paths but reduces the size and production cost of the optical pick-up apparatus.
Furthermore, another aspect of the present invention provides a single holographic optical element having at least one hologram pattern.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description which is to be read in conjunction with the accompanying drawings.