OPTICAL INFORMATION RECORDING/REPRODUCING APPARATUS

Abstract

There is provided an optical information recording/reproducing apparatus including a unit for detecting the focus error signal from the reflected light flux from a recording layer of an optical recording medium, and a unit for focusing the light flux on the recording layer of the optical disk on the basis of the focus error signal. In the case of detecting the focus error signal, the light flux of the effective numeric aperture NAeff<1 due to an objective lens and the SIL within a pupil is obtained by a splitting device as the focus error signal, whereby it is possible to suppress the reflected light from the bottom surface of the SIL from being mixed into the focus error signal as a noise.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram illustrating an optical information recording/reproducing apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating optical means for detecting a focus error signal according to the embodiment shown in FIG. 1 in detail.

FIG. 3 is a diagram schematically illustrating the light quantity distribution within a pupil according to the embodiment shown in FIG. 1.

FIG. 4 is a structural diagram illustrating Embodiment 2 of the present invention.

FIG. 5 is a diagram for explaining Embodiment 3 of the present invention.

FIG. 6 is a diagram for explaining a focus error that is obtained by a dual-layer disc according to the present invention.

FIG. 7 is a diagram for explaining spherical aberration correction of a liquid crystal device according to the present invention.

FIGS. 8A and 8B are diagrams for explaining an electrode of the liquid crystal device according to the present invention.

FIG. 9 is a diagram for explaining an optical information recording/reproducing apparatus for near field recording according to Embodiment 4 of the present invention.

FIG. 10 is a diagram illustrating a focus error signal that is obtained by a dual-layer disc shown in FIG. 1.

FIG. 11 is a diagram illustrating Embodiment 6 of the present invention.

FIG. 12 is a diagram illustrating Embodiment 7 of the present invention.

FIG. 13 is a diagram for explaining the pattern of a hologram according to Embodiment 7 of the present invention.

FIG. 14 is a diagram illustrating Embodiment 8 of the present invention.

FIG. 15 is a diagram for explaining the arrangement of GEPD according to the Embodiment 8 of the present invention.

FIG. 16 is a diagram illustrating Embodiment 9 of the present invention.

FIG. 17 is a diagram illustrating a configuration of an S curve that is obtained by a focus error detecting optical system according to Embodiment 10 of the present invention.

FIG. 18 is a diagram illustrating a configuration of the S curve in the vicinity of focusing on a first layer and a second layer.

FIG. 19 is a structural diagram illustrating an optical information recording/reproducing apparatus for near field recording in a conventional example.

FIG. 20 is a diagram for explaining a hemispherical SIL in a conventional example.

FIG. 21 is a diagram for explaining an super-hemispherical SIL in the conventional example.

FIG. 22 is a diagram illustrating a case in which a light flux is focused on an L0 recording layer of a dual-layer disc in the conventional example.

FIG. 23 is a diagram illustrating a case in which a light flux is focused on an L1 recording layer of the dual-layer disc in the conventional example.

FIG. 24 is a structural diagram illustrating an optical information recording/reproducing apparatus according to Embodiment 5 of the present invention.

Claims

1. An optical information recording/reproducing apparatus that records or reproduces information using a light spot due to near field effect, the apparatus comprising: a laser beam source;an objective lens that collects a light flux from the laser beam source;an SIL that is disposed between the objective lens and an optical recording medium;a light receiving device that receives a reflected light flux from the optical recording medium;a splitting device that guides the light flux of an effective numerical aperture NAeff<1 due to the objective lens and the SIL within a pupil among the reflected light fluxes to the light receiving device; anda control circuit that focuses the light flux on a recording layer of the optical recording medium on the basis of a focus error signal obtained by the light receiving device.

2. The optical information recording/reproducing apparatus according to claim 1, wherein the splitting device is a hologram or an aperture.

3. The optical information recording/reproducing apparatus according to claim 1, further comprising an expander lens, a ¼ wavelength plate, and a polarization beam splitter which are disposed between the objective lens and the light receiving device.

4. The optical information recording/reproducing apparatus according to claim 1, further comprising an expander lens, a polarization beam splitter, and an non-polarization beam splitter which are disposed between the objective lens and the light receiving device.

5. The optical information recording/reproducing apparatus according to claim 1, wherein the effective numerical aperture NAeff is in a range of from 0.75 to 0.95.

6. The optical information recording/reproducing apparatus according to claim 1, wherein one of the objective lens and an expander lens that is disposed between the objective lens and the laser beam source is driven to control it by the control circuit.

7. The optical information recording/reproducing apparatus according to claim 1, further comprising a spherical aberration correcting device that corrects spherical aberration.

8. The optical information recording/reproducing apparatus according to claim 7, wherein the spherical aberration correcting device comprises one of a liquid crystal device and an expander lens which is disposed between the objective lens and the laser beam source.

9. The optical information recording/reproducing apparatus according to claim 6, wherein the optical recording medium includes plural recording layers, and one of the objective lens and the expander lens conducts interlayer jump between the recording layers on the basis of the focus error signal.

10. The optical information recording/reproducing apparatus according to claim 6, wherein the expander lens has a collimator function.

11. The optical information recording/reproducing apparatus according to claim 10, wherein the expander lens having the collimator function comprises one lens or two lenses, andwherein the lens is movable in a focus direction.

12. The optical information recording/reproducing apparatus according to claim 11, further comprising a λ/4 plate, a polarization beam splitter, and a non-polarization beam splitter which are disposed between the laser beam source and the expander lens having the collimator function, wherein the non-polarization beam splitter splits a reflected light flux from the bottom of the SIL, and a gap error signal used for controlling gap interval between the SIL and the optical recording medium is generated according to the reflected light flux,wherein the polarization beam splitter splits the reflected light flux from the optical recording medium and a focus error signal is generated according to the reflected light flux from the optical recording medium, andwherein the λ/4 plate is disposed between the objective lens and the polarization beam splitter.

13. The optical information recording/reproducing apparatus according to claim 11, further comprising a polarization beam splitter and an non-polarization beam splitter which are disposed between the laser beam source and the expander lens having the collimator function, wherein the polarization beam splitter splits a reflected light flux from the bottom of the SIL, and a gap error signal used for controlling gap interval between the SIL and the optical recording medium is generated according to the reflected light flux, andwherein the non-polarization beam splitter splits the reflected light flux from the optical recording medium, and a focus error signal is generated according to the reflected light flux from the optical recording medium.

14. The optical information recording/reproducing apparatus according to claim 13, further comprising: a first photodetector that receives the light flux split by the polarization beam splitter; anda second photodetector that receives the light flux split by the non-polarization beam splitter,wherein a distance of the first photodetector from the center of the polarization beam splitter is shorter than a distance between the second photodetector and the center of the non-polarization beam splitter.

15. The optical information recording/reproducing apparatus according to claim 1, wherein the optical recording medium includes plural recording layers, and satisfies the following relational expression: d/n>L1/β2 where d is an interval between the recording layers, n is a refractive index between the recording layers, L1 is a positional interval between a maximum value and a minimum value of the S curve of the focus error signal, and β is a mean imaging magnification from the recording layer to the light receiving device.

16. The optical information recording/reproducing apparatus according to claim 15, wherein the effective numerical aperture (NAeff) of the objective lens satisfies the following relational expression: d>2500·T2/(tan(sin−1(NAeff/n))2·π)where d is an interval between the recording layers, T is a mean run length, and n is a refractive index between the recording layers.

17. The optical information recording/reproducing apparatus according to claim 1, wherein the optical recording medium includes an optical device that has plural recording layers and generates astigmatism, and satisfies the following relational expression: d/n>L2/β2 where d is an interval between the recording layers, n is a refractive index between the recording layers, L2 is a distance between a first focal line and a second focal line due to astigmatism generated by the optical device, and β is a mean imaging magnification from the recording layer to the light receiving device.