Patent ID: 8867324
Filing Date: 2014-10-21
Classification: G11B

Abstract:
1. A reproducing device, comprising: a light generation and emission unit that obtains signal light as reflection light, the reflection light reflecting both of recording signals of a land and a groove, by irradiating an optical recording medium, in which a signal is recorded in both of the land and the groove and a level difference between the land and the groove is set so as to provide a phase difference of approximately 90° to reflection light from the land and reflection light from the groove, with light emitted from a light source, and generates reference light as coherent light by making the light emitted from the light source be reflected by a mirror, so as to emit the signal light and the reference light in a superposed manner; a detection optical system configured to generate a first combination of signal light and reference light, the first combination being obtained by providing a phase difference of approximately 0° to superposed light of the signal light and the reference light, the superposed light being emitted by the light generation and emission unit, a second combination of signal light and reference light, the second combination being obtained by providing a phase difference of approximately 180° to the superposed light, a third combination of signal light and reference light, the third combination being obtained by providing a phase difference of approximately 90° to the superposed light, and a fourth combination of signal light and reference light, the fourth combination being obtained by providing a phase difference of approximately 270° to the superposed light, respectively; a light receiving unit in which the first combination of signal light and reference light, the second combination of signal light and reference light, the third combination of signal light and reference light, and the fourth combination of signal light and reference light are respectively received by a first light receiving element, a second light receiving element, a third light receiving element, and a fourth light receiving element; and a reproduction unit configured to reproduce the recording signal of the land and the recording signal of the groove on the basis of a first light receiving signal that is obtained by the first light receiving element, a second light receiving signal that is obtained by the second light receiving element, a third light receiving signal that is obtained by the third light receiving element, and a fourth light receiving signal that is obtained by the fourth light receiving element, wherein the reproduction unit calculates a first differential signal that is a difference between the first light receiving signal and the second light receiving signal and a second differential signal that is a difference between the third light receiving signal and the fourth light receiving signal and reproduces the recording signal of the land and the recording signal of the groove on the basis of the first differential signal and the second differential signal; wherein a phase difference of the signal light and the reference light, the signal light and the reference light being emitted by the light generation and emission unit, is cancelled by calculation or control of a position of the mirror; and wherein when a first low frequency signal that is a signal obtained by extracting a low frequency component of the first differential signal is denoted as I1_lpf and a second low frequency signal that is a signal obtained by extracting a low frequency component of the second differential signal is denoted as I2_lpf, the reproduction unit calculates so as to obtain a value of the phase difference of the signal light and the reference light, the signal light and the reference light being emitted by the light generation and emission unit, and perform calculation for cancelling the phase difference by using the value.