Optical pickup and optical disc apparatus
A technology for optical pickups and optical discs, applied in instruments, optical recording heads, recording/reproducing with optical methods, etc., can solve problems such as interlayer crosstalk, difficult to track control signals, etc., and achieve high-precision effects
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Embodiment 1
[0040] Briefly explain the DPP method.
[0041] FIG. 2 is a schematic diagram of the main optical system of an optical pickup using a tracking control signal detection module of the DPP method.
[0042] The laser beam emitted from the semiconductor laser 1 is split by a beam splitting element such as a diffraction grating 2 into a main beam 50 (zero-order light) that actually performs reproduction or recording of an information signal, and two sub-beams 51 and 2 for generating a tracking control signal. 52 (±1 diffracted light). Afterwards, these light beams pass through the one-way see-through glass 3 , the collimating lens 4 , and the objective lens 5 to focus independently on the specified recording layer in the optical disc 10 . At this time, the irradiation position interval in the radial direction of the optical disc 10 coincides with approximately half of the recording track interval of the optical disc 10. Spots of light (not shown). The reflected light beams from t...
Embodiment 2
[0067] Next, the second embodiment will be described with reference to FIG. 6 .
[0068] Fig. 6 shows the main part of the second embodiment. In this figure, the same reference numerals are assigned to the same constituent elements as those shown in FIGS. 1 and 3 .
[0069] In this embodiment, instead of setting the light-shielding band or the insensitive band of the first embodiment shown in FIG. The dividing lines 85 and 86 and 87 and 88, which are roughly parallel to 84, divide the light receiving area 81 into 4 light receiving surfaces 81a to 81d by each 3 dividing lines, and divide the light receiving area 82 into 4 light receiving surfaces 82a to 82d. . At this time, the interval between the dividing lines 85 and 86 and the interval W between the dividing lines 87 and 88 constitute the same dimension as the width W of the short side of the light-shielding band or insensitive band in the first embodiment shown in FIG. 1 .
[0070] From the light-receiving surface thus ...
Embodiment 3
[0074] Next, a third embodiment will be described using FIG. 7 and FIG. 8 . In this embodiment, the configuration of the optical system of the optical pickup and the configuration of the photodetector 8 may be the same as those shown in FIGS. 2 and 3, respectively. Instead, the diffraction grating 2 used as a beam splitting element has a different structure from conventional gratings. FIG. 7 is a schematic plan view showing the structure of the diffraction grating 2 used in this embodiment. In this embodiment, two divisions extending in a direction (ie, a direction corresponding to a tangential direction of the disc on the diffraction grating 2) approximately perpendicular to the direction of the grating groove (ie, a direction corresponding to the radial direction of the disc on the diffraction grating 2) are used. line, the diffraction grating 2 is divided into three regions such as regions 21, 22 and 23, wherein grating grooves are engraved in the two regions 21 and 23 san...
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Abstract
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