Optical pickup and optical information reproducing apparatus using same

Abstract

An optical pickup module with enhanced aberration correctability is disclosed. This pickup includes more than two different types of laser light sources, an objective lens for collecting and focusing any one of the laser beams leaving the light sources onto an optical disc, and an aberration correction device of the liquid crystal (LC) type, which is disposed between the light sources and the objective lens. The aberration corrector has a surface on which multiple spaced-apart electrodes are patterned for enabling aberration correction relative to incident beams. The corrector controls the potential of a voltage being applied to each electrode in deference to incident beam properties and variations occurrable thereto, e.g., wavelength, effective beam diameter and relative incidence position offsets, thereby to optimally correct beam aberrations, such as coma aberration or wavefront aberration. An optical information reproduction apparatus using the pickup is also disclosed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically showing a plan view of an exemplary electrode pattern of a coma aberration correction device embodying the invention.

FIG. 2 is a diagram showing a schematical plan view of an electrode pattern example of one prior art coma aberration correction device.

FIG. 3 is a diagram graphically showing the relationship of an incident light beam's relative position deviation and aberration correction factor in the prior art coma aberration correction device.

FIG. 4 is a graph showing an exemplary relation of a relative position deviation of an incident light beam in the coma aberration correction device of the illustrative embodiment and a relative phase difference to be added to each electrode portion penetration light beam in order to perform optimum aberration correction of a coma aberration amount, 0.01 λrms, in each case.

FIG. 5 is a graph showing a relation between relative position deviation of an incident light beam in the coma aberration correction device of this embodiment and an aberration correction factor with the optimum aberration correction applied thereto in each case.

FIG. 6 is a diagram schematically showing a configuration of one embodiment of an optical pickup with the coma aberration correction device of the embodiment being built therein.

Claims

1. An optical pickup comprising: a plurality of laser light sources;an objective lens for collecting light of said plurality of laser light sources onto a disc-like record carrier body;aberration correction means disposed between said laser light sources and said objective lens for correcting laser light source aberration; andmore than one electrode being disposed on a plane of said aberration correction means, for enabling aberration correction relative to the light from said plurality of laser light sources.

2. The optical pickup according to claim 1, wherein said aberration correction means corrects coma aberration, and wherein at least six electrodes are disposed on the plane of said aberration correction means.

3. An optical pickup comprising: a first laser light source;a second laser light source less in light flux diameter than said first laser light source;an objective lens for correcting light of the first and second laser light sources onto a disc;coma aberration correction means for correcting coma aberration of said first and second laser light sources; andsaid coma aberration correction means having a plane on which are disposed a first electrode for enabling correction of coma aberration relative to light from said first laser light source and a second electrode for enabling coma aberration correction for light from said second laser light source.

4. An aberration correction device comprising: aberration correction means disposed between a laser light source and an objective lens for correction of a light beam emitted from the laser light source onto a certain optical information recording medium, for correcting a wavefront difference of the light beam occurring due to giving a prespecified phase difference to said light beam;a plurality of electrodes provided to apply a potential difference at each of prespecified positions on a predefined plane for pass-through of said light beam within said aberration correction means; andmeans for controlling, with respect to more than two light rays passing through said aberration correction device and being different in light flux diameter from each other, a potential difference being applied to each said electrode in units of said light rays in such a way as to correct a wavefront aberration of each said light ray.

5. An aberration correction device comprising: aberration correction means disposed between a laser light source and an objective lens for correction of a light beam emitted from the laser light source onto a certain optical information recording medium, for correcting a wavefront difference of the light beam occurring due to giving a prespecified phase difference to said light beam;a plurality of electrodes provided to apply a potential difference at each of prespecified positions on a predefined plane for pass-through of said light beam within said aberration correction means; andmeans for performing voltage application to each said electrode while independently controlling a potential difference being applied to each said electrode in accordance with an amount of wavefront aberration at least occurring at each light ray passing through the aberration correction means within said aberration correction device and an amount of relative position deviation between an incidence position of optical axis and a center point upon entry of each said light ray onto the electrode layout plane.

6. The aberration correction device according to claim 4, further comprising: means for mainly correcting at least coma aberration among wavefront aberrations of each said light ray.

7. The aberration correction device according to claim 4, wherein at least more than six independent electrodes are disposed in a way substantially axial symmetrical to a predetermined axis almost extending through a center point in the plane on which these electrodes are disposed.

8. The aberration correction device according to claim 4, wherein said aberration correction means includes a liquid crystal element for changing refractivity in response to a voltage as applied to each said electrode and for giving, due to the refractivity change, a local phase difference to a light beam passing through said aberration correction means to thereby correct a prespecified wavefront aberration.

9. An optical pickup comprising: more than one laser light source;an objective lens for collecting light leaving said light source onto a disc-like optical information recording medium; andan aberration correction device including,aberration correction means disposed between a laser light source and an objective lens for correction of a light beam emitted from the laser light source onto a certain optical information recording medium, for correcting a wavefront difference of the light beam occurring due to giving a prespecified phase difference to said light beam,a plurality of electrodes provided to apply a potential difference at each of prespecified positions on a predefined plane for pass-through of said light beam within said aberration correction means, andmeans for controlling, with respect to more than two light rays passing through said aberration correction device and being different in light flux diameter from each other, a potential difference being applied to each said electrode in units of said light rays in such a way as to appropriately correct a wavefront aberration of each said light ray.

10. An optical information reproduction apparatus comprising control means for controlling the optical pickup as recited in claim 2.

11. The aberration correction device according to claim 5, further comprising: means for mainly correcting at least coma aberration among wavefront aberrations of each said light ray.

12. The aberration correction device according to claim 5, wherein at least more than six independent electrodes are disposed in a way substantially axial symmetrical to a predetermined axis almost extending through a center point in the plane on which these electrodes are disposed.

13. The aberration correction device according to claim 6, wherein at least more than six independent electrodes are disposed in a way substantially axial symmetrical to a predetermined axis almost extending through a center point in the plane on which these electrodes are disposed.

14. The aberration correction device according to claim 5, wherein said aberration correction means includes a liquid crystal element for changing refractivity in response to a voltage as applied to each said electrode and for giving, due to the refractivity change, a local phase difference to a light beam passing through said aberration correction means to thereby correct a prespecified wavefront aberration.

15. The aberration correction device according to claim 6, wherein said aberration correction means includes a liquid crystal element for changing refractivity in response to a voltage as applied to each said electrode and for giving, due to the refractivity change, a local phase difference to a light beam passing through said aberration correction means to thereby correct a prespecified wavefront aberration.

16. The aberration correction device according to claim 7, wherein said aberration correction means includes a liquid crystal element for changing refractivity in response to a voltage as applied to each said electrode and for giving, due to the refractivity change, a local phase difference to a light beam passing through said aberration correction means to thereby correct a prespecified wavefront aberration.

17. An optical pickup comprising: more than one laser light source;an objective lens for collecting light leaving said light source onto a disc-like optical information recording medium; andan aberration correction device including,aberration correction means disposed between a laser light source and an objective lens for correction of a light beam emitted from the laser light source onto a certain optical information recording medium, for correcting a wavefront difference of the light beam occurring due to giving a prespecified phase difference to said light beam,a plurality of electrodes provided to apply a potential difference at each of prespecified positions on a predefined plane for pass-through of said light beam within said aberration correction means, andmeans for performing voltage application to each said electrode while independently controlling a potential difference being applied to each said electrode in accordance with an amount of wavefront aberration at least occurring at each light ray passing through the aberration correction means within said aberration correction device and an amount of relative position deviation between an incidence position of optical axis and said center point upon entry of each said light ray onto the electrode layout plane.

18. An optical pickup comprising: more than one laser light source;an objective lens for collecting light leaving said light source onto a disc-like optical information recording medium; andan aberration correction device including,aberration correction means disposed between a laser light source and an objective lens for correction of a light beam emitted from the laser light source onto a certain optical information recording medium, for correcting a wavefront difference of the light beam occurring due to giving a prespecified phase difference to said light beam,a plurality of electrodes provided to apply a potential difference at each of prespecified positions on a predefined plane for pass-through of said light beam within said aberration correction means,means for performing voltage application to each said electrode while independently controlling a potential difference being applied to each said electrode in accordance with an amount of wavefront aberration at least occurring at each light ray passing through the aberration correction means within said aberration correction device and an amount of relative position deviation between an incidence position of optical axis and said center point upon entry of each said light ray onto the electrode layout plane, andmeans for mainly correcting at least coma aberration among wavefront aberrations of each said light ray.

19. An optical pickup comprising: more than one laser light source;an objective lens for collecting light leaving said light source onto a disc-like optical information recording medium; andan aberration correction device including,aberration correction means disposed between a laser light source and an objective lens for correction of a light beam emitted from the laser light source onto a certain optical information recording medium, for correcting a wavefront difference of the light beam occurring due to giving a prespecified phase difference to said light beam,a plurality of electrodes provided to apply a potential difference at each of prespecified positions on a predefined plane for pass-through of said light beam within said aberration correction means,means for performing voltage application to each said electrode while independently controlling a potential difference being applied to each said electrode in accordance with an amount of wavefront aberration at least occurring at each light ray passing through the aberration correction means within said aberration correction device and an amount of relative position deviation between an incidence position of optical axis and said center point upon entry of each said light ray onto the electrode layout plane,means for mainly correcting at least coma aberration among wavefront aberrations of each said light ray, andsaid aberration correction device being arranged so that at least more than six independent electrodes are disposed in a way substantially axial symmetrical to a predetermined axis almost extending through a center point in the plane on which these electrodes are disposed.

20. An optical pickup comprising: more than one laser light source;an objective lens for collecting light leaving said light source onto a disc-like optical information recording medium; andan aberration correction device including,aberration correction means disposed between a laser light source and an objective lens for correction of a light beam emitted from the laser light source onto a certain optical information recording medium, for correcting a wavefront difference of the light beam occurring due to giving a prespecified phase difference to said light beam,a plurality of electrodes provided to apply a potential difference at each of prespecified positions on a predefined plane for pass-through of said light beam within said aberration correction means,means for performing voltage application to each said electrode while independently controlling a potential difference being applied to each said electrode in accordance with an amount of wavefront aberration at least occurring at each light ray passing through the aberration correction means within said aberration correction device and an amount of relative position deviation between an incidence position of optical axis and said center point upon entry of each said light ray onto the electrode layout plane,means for mainly correcting at least coma aberration among wavefront aberrations of each said light ray,said aberration correction device being arranged so that at least more than six independent electrodes are disposed in a way substantially axial symmetrical to a predetermined axis almost extending through a center point in the plane on which these electrodes are disposed, andsaid aberration correction means including a liquid crystal element for changing refractivity in response to a voltage as applied to each said electrode and for giving, due to the refractivity change, a local phase difference to a light beam passing through said aberration correction means to thereby correct a prespecified wavefront aberration.