Optical pickup system with five longitudinal splitted detection areas to prevent information reproducing error by wavelength variations

摘要

An optical pickup system capable of improving productivity by facilitating the arrangement and assembly of components thereof and preventing an error caused by wavelength variation of a laser beam includes a laser diode used as a light source, a grating for classifying a beam from the laser diode into three diffracted lights of zero, +first and -first orders, an objective lens placed the grating and an optical disc for focusing the three diffracted lights passed through the grating on the optical disc while receiving the lights reflected from the optical disc, a photodetector divided-by-five formed of five split areas partitioned in the longitudinal direction to be arranged side by side in the sequence of fourth, first, second, third and fifth split areas to receive the lights reflected from the optical disc focusing on the respective split areas for detecting a focus error and a tracking error and reading out information recorded on the optical disc, and a hologram element divided-by-two formed of a first hologram of which reference light position is a light-emitting point of the laser diode and an object light position is set before passing the photodetector divided-by-five and a second hologram of which reference light position is the light- emitting point of the laser diode and an object light position is set after passing the photodetector divided-by-five, for diffracting the reflected lights from the optical disc prior to passing the photodetector divided-by-five, thereby being applicable to optical apparatuses such as CDPs, VDPs, ODPs and MDPs.