Method and apparatus for multiplexing optical information for recording and reproducing optical information over optical storage medium

1. An optical multiplexer comprising:

a substrate having a first surface to a second surface; and

a plurality of beam transmitting portions formed in and extending through holes in the substrate from the first surface to the second surface, each of the plurality of beam transmitting portions having a diffraction grating, said diffraction grating formed by irradiating a spherical wave beam and a plane wave beam respectively to the each of the plurality of beam transmitting portions, wherein each irradiation angle formed by the spherical beam and the plane wave beam onto each of the beam transmitting portions is different, and the diffraction grating diffracts a beam irradiated to the each of the plurality of beam transmitting portions at different angle, and the diffracted beam is multiplexed, wherein the multiplexed beam is incident on an optical information storage medium to record and reproduce data.

2. The optical multiplexer according to claim 1 , wherein the diffraction grating is a holographic interference fringe formed in photo-polymer filled in the each of the plurality of beam transmitting portions.

3. The optical multiplexer according to claim 1 , wherein the substrate is made of a material that reflects and/or absorbs light.

4. The optical multiplexer according to claim 3 , wherein the each of the plurality of beam transmitting portions forms in and extending through each of the hole in the substrate.

5. The optical multiplexer according to claim 1 , wherein the substrate has a disc shape and the beam transmitting portions are spaced from each other along the circumference of the substrate.

6. The optical multiplexer according to claim 1 , wherein the substrate has a bar shape and the beam transmitting portions are spaced from each other in the longitudinal direction of the substrate.

7. The optical multiplexer according to claim 1 , wherein the substrate has a belt shape and the beam transmitting portions are spaced from each other in the traveling direction of the belt.

8. An optical information reproducing apparatus comprising:

a light source;

an optical multiplexer including a plurality of beam transmitting portions formed in and extending through holes in a substrate, each of the plurality of beam transmitting portions having a diffraction grating, the diffraction grating formed by irradiating a spherical wave beam having same irradiation angle onto each of the beam transmitting portion and a plane wave beam having different irradiation angle onto each of the plurality of beam transmitting portions, wherein the irradiation angle is determined based on an angle formed by the spherical wave and the plane wave irradiated on the substrate;

an optical system configured to guide a beam emitted from the light source to the optical multiplexer, wherein the diffraction grating diffracts the beam irradiated to the each of the plurality of beam transmitting portions at a different angle, the diffracted beam is multiplexed, and the optical multiplexer is configured to guide the multiplexed beam to an optical information storage medium which stores multiplexed optical information; and

an optical information detector configured to detect the multiplexed optical information reproduced from the optical information storage medium by the multiplexed beam.

9. The optical information reproducing apparatus according to claim 8 , wherein the substrate revolves for the beam to be irradiated to the each of the plurality of beam transmitting portions.

10. The optical information reproducing apparatus according to claim 9 , wherein the beam irradiated to the optical multiplexer is a spherical-wave beam and the multiplexed beam emitted from the optical multiplexer is a plane-wave beam.

11. The optical information reproducing apparatus according to claim 10 , wherein the each of the plurality of beam transmitting portion generates the plane-wave beam with a different out-of-plane angle when the substrate is moved at an out-of-plane position.

12. A method for making an optical multiplexer, the method comprising:

configuring a plurality of transmitting portions formed in and extending through a first hole in a substrate;

irradiating a first spherical wave beam at a predetermined irradiation angle and a first plane wave beam at different angle from the predetermined irradiation angle respectively to a first beam transmitting portion for forming a first diffraction grating;

irradiating a second spherical wave beam at the predetermined angle and a second plane wave beam at different from the first irradiation angle of the first plane wave beam to a second beam transmitting portion for forming a second diffraction grating, wherein each of the first diffraction grating and the second diffraction grating diffracts a beam irradiated thereon; and

irradiating a third spherical wave beam at the predetermined angle and a third plane wave beam at different from the irradiation angle of each of the first and second plane wave beam to a third beam transmitting portion for forming a third diffraction grating;

wherein each of the first, second and third diffraction grating diffracts a beam irradiated thereon and is multiplexed, wherein the multiplexed beam is incident on an optical information storage medium to record and reproduce data.

13. The method according to claim 12 , wherein the second angle and the third angle are different each other, and the each of the first diffraction grating and the second diffraction grating diffracts the beam at a different angle.

14. An optical information recording apparatus comprising:

a light source;

a beam splitter configured to split a beam emitted from the light source;

a signal beam optical system configured to produce a signal beam by loading data to the split beam from the beam splitter;

an optical multiplexer including a plurality of beam transmitting portions formed in and extending through holes in a substrate having a first surface to a second surface, each of the plurality of beam transmitting portions having a diffraction grating, the diffraction grating formed by irradiating a spherical wave beam having a same irradiation angle and a plane wave beam having a different irradiation angle, irradiated to the each of the plurality of beam transmitting portions, respectively, wherein each of the irradiation angle is determined based on an angle formed by the spherical wave and the plane wave irradiated to the substrate; and

a reference beam optical system configured to guide the another split beam from the beam splitter as a reference beam to the optical multiplexer, wherein the diffraction grating diffracts the reference beam irradiated to the each of the plurality of beam transmitting portions at a different angle, and the diffracted reference beam is multiplexed, and the optical multiplexer is configured to guide the multiplexed beam to an optical information storage medium.

15. The optical multiplexer according to claim 1 , further comprising:

each of the spherical beam is irradiated onto each of the beam transmitting portions with same irradiation angle one another and each of the plane wave beam is irradiated onto each of the beam transmitting with different irradiation angle one another and the each irradiation angle is determined based on an angle incident onto substrate of each of the beam transmitting portion.