Patent ID: 8923105
Filing Date: 2014-12-30
Classification: G11B

Abstract:
1. An optical information device comprising: a laser light source that emits a light flux; an objective lens that converges the light flux emitted from the laser light source on an optical information medium having an information track on which information is recorded in a row; a split element that includes a center region including the center of an optical axis, a first end region disposed adjacent to one side of the center region in a direction perpendicular to a tangent to the information track, and a second end region disposed adjacent to the other side of the center region in the direction perpendicular to the tangent to the information track, and splits the light flux reflected and diffracted on the optical information medium into a first light flux passing through the center region, a second light flux passing through the first end region, and a third light flux passing through the second end region; a photodetector that receives the first light flux, the second light flux, and the third light flux obtained by splitting by the split element, and outputs a first signal, a second signal, and a third signal corresponding to light amounts of the received first light flux, the received second light flux, and the received third light flux; a first waveform equalizer that gives a gain corresponding to a frequency component of the first signal to the first signal outputted from the photodetector; a second waveform equalizer that gives a gain different from the gain of the first signal corresponding to a frequency component of the second signal to the second signal outputted from the photodetector; a third waveform equalizer that gives a gain different from the gains of the first signal and the second signal corresponding to a frequency component of the third signal to the third signal outputted from the photodetector; an adder that adds up output signals from the first waveform equalizer, the second waveform equalizer, and the third waveform equalizer; and a reproduction signal processing section that outputs a signal obtained by the addition by the adder as an information reproduction signal, wherein the information track scanned with the light flux converged by the objective lens is assumed to be a main track, and the information track adjacent to the main track is assumed to be an adjacent track, the first signal, the second signal, and the third signal outputted from the photodetector include both of information recorded on the main track and information recorded on the adjacent track, a ratio Xm of the information recorded on the adjacent track relative to the information recorded on the main track included in the first signal obtained from the first light flux having passed through the center region is different from a ratio Xs1 of the information recorded on the adjacent track relative to the information recorded on the main track included in the second signal obtained from the second light flux having passed through the first end region and also different from a ratio Xs2 of the information recorded on the adjacent track relative to the information recorded on the main track included in the third signal obtained from the third light flux having passed through the second end region, and a ratio among the respective gains of the first waveform equalizer, the second waveform equalizer, and the third waveform equalizer is determined so as to cancel the information recorded on the adjacent track in each of the frequency components of the first signal, the second signal, and the third signal.