Optical pickup head device, information recording/reproducing apparatus, and method for recording information
a technology of information recording/reproducing apparatus and optical pickup head, which is applied in the direction of data recording, disposition/mounting of head, instruments, etc., can solve the problems of beam not being cancelled completely by the dpp method, uncorrectable offset fluctuations, and inability to detect tracking error signals with the phase-difference method, so as to reduce offset fluctuations in tracking error signals and ensure the reading of information
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embodiment 1
[0045]FIG. 1 shows an example of the configuration of an optical pickup head device of the present invention. A semiconductor laser source 1, i.e., a light source, emits a linearly polarized divergent beam 70 having a wavelength λ of 650 nm. The beam 70 emitted from the semiconductor laser 1 enters a diffraction grating 61. The diffraction grating 61 divides the beam 70 into three beams: a zero-order diffracted light beam and ±first-order diffracted light beams. The zero-order diffracted light beam is a main beam 70a for recording / reproducing information. The ±first-order diffracted light beams are two sub-beams 70b, 70c used for DPP, with which a tracking error signal can be detected stably. To avoid unnecessary recording by the sub-beams 70b, 70c, the ratio of diffraction efficiency of the zero-order diffracted light beam 70a to each of the first-order diffracted light beams 70b, 70c is generally about 20:1. In this embodiment, however, the ratio is 10:1. The three beams 70a to 70...
embodiment 2
[0061]FIG. 5A is a front view schematically showing a diffraction grating 62 used in another example of an optical pickup head device of the present invention, and FIG. 5B is a cross-sectional side view of the diffraction grating 62. The optical pickup head device can be formed by using the diffraction grating 62 instead of the diffraction grating 61 in Embodiment 1.
[0062]The diffraction grating 62 includes two pattern regions 62a and 62b. Both grating patterns formed in the pattern regions 62a, 62b are straight patterns and have a constant period of Pt. However, the phase is reversed at an imaginary boundary line 62c in the center of the diffraction grating 62 by 180 degrees. The diffraction grating 62 receives a beam 70 emitted from a semiconductor laser source 1 and generates a zero-order diffracted light beam 71a and first-order diffracted light beams 71b, 71c.
[0063]FIG. 6 schematically shows the beams 71a to 71c on an information recording plane 41b of an optical recording medi...
embodiment 3
[0066]FIG. 7A is a front view schematically showing a diffraction grating 63 used in another example of an optical pickup head device of the present invention, and FIG. 7B is a cross-sectional side view of the diffraction grating 63. The optical pickup head device can be formed by using the diffraction grating 63 instead of the diffraction grating 62 in Embodiment 2.
[0067]Like the diffraction grating 62, the diffraction grating 63 includes two pattern regions63a and 63b. Both grating patterns formed in the pattern regions 63a, 636 are straight patterns and have a constant period of Pt. However, the phase is reversed at an imaginary boundary line 63c in the center of the diffraction grating 63 by 180 degrees. The diffraction grating 63 differs from the diffraction grating 62 in that a pattern 63d is provided at the boundary between the pattern regions 63a and 63b. The formation of the pattern 63d can reduce unnecessary light that is present between a zero-order diffracted light beam ...
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Abstract
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