Claims
- 1. An apparatus for creating a reduced effective spot size, comprising:
an objective lens; a light beam incident at the entrance to said objective lens comprising a polarization pattern comprising first regions; and a storage medium configured so that said objective lens brings said light beam to a focus to form a spot comprising second regions at said storage medium.
- 2. The apparatus of claim 1, wherein said first regions have different modes of polarization.
- 3. The apparatus of claim 1, wherein said second regions have different modes of polarization.
- 4. The apparatus of claim 1, further comprising an optical element configured to create said polarization pattern.
- 5. The apparatus of claim 4, wherein said optical element comprises a polarizer.
- 6. The apparatus of claim 4, wherein said optical element comprises a quarter-wave plate.
- 7. The apparatus of claim 4, wherein said optical element comprises a half-wave plate.
- 8. The apparatus of claim 4, wherein said optical element comprises liquid-crystal cells.
- 9. The apparatus of claim 1, wherein said spot comprises a linearly polarized center region as one of said second regions.
- 10. The apparatus of claim 1, wherein said spot comprises a linearly polarized center region of said second regions and an outer region comprises a left circular polarized region of said second regions and a right circular polarized region of said second regions.
- 11. The apparatus of claim 1 wherein said second regions include a substantially “D” shaped side region having substantially clockwise polarization, a backwards substantially “D” shaped side region having substantially counterclockwise polarization and a substantially circular central region having substantially linear polarization.
- 12. The apparatus of claim 1 wherein said second regions include a substantially “D” shaped side region having substantially clockwise polarization. a backwards substantially “D” shaped side region having substantially counterclockwise polarization and a substantially rectangular central region having substantially linear polarization.
- 13. The apparatus of claim 1, wherein said polarization pattern comprises said first regions comprising a right-hand side region polarized at about +45 degrees to an X-axis and a left-hand side region polarized at about 45 degrees to said X-axis.
- 14. The apparatus of claim 1, wherein said polarization pattern comprises said first regions comprising an incident light beam at the entrance pupil to said objective lens comprising a polarization state comprising a region which is right-hand side polarized at +45 degrees to an X-axis and a region which is left-hand side at −135 degrees to said X-axis
- 15. The apparatus of claim 1, wherein an incident light beam at the entrance pupil to said objective lens comprises said first regions comprising a first quadrant, a second quadrant, a third quadrant, and a fourth quadrant with opposite quadrants having mutually orthogonal polarizations.
- 16. The apparatus of claim 1 is a magneto-optical readout system.
- 17. The apparatus of claim 1 wherein said storage medium comprises a magneto-optical disk.
- 18. The apparatus of claim 1, further comprises a differential detector for receiving a reflected component of said spot.
- 19. The apparatus of claim 18, wherein said differential detector further comprises:
a split photodetector configured to receive said reflected component of said spot and convert said reflected component to a first electrical signal and a second electrical signal; and a differential amplifier configured to generate from said first and-second electrical signals a readout signal indicating the binary state of said storage medium under said light beam.
- 20. The apparatus of claim 1, wherein said light beam is a coherent, quasi-monochromatic beam of light from a semiconductor laser diode.
- 21. A method for creating a reduced spot size, comprising the steps of focusing a light beam comprising a polarization pattern comprising first regions to a storage medium to form a spot comprising second regions at said storage medium.
- 22. The method of claim 21, further comprising the step of polarizing said light beam to create said polarization pattern comprising said first regions.
- 23. The method of claim 21, wherein said first regions have different modes of polarization.
- 24. The method of claim 21, wherein said second regions have different modes of polarization.
- 25. The method of claim 21, further comprising an optical element configured to create said polarization pattern.
- 26. The method of claim 25, wherein said optical element comprises a polarizer.
- 27. The method of claim 25, wherein said optical element comprises a quarter-wave plate.
- 28. The method of claim 25, wherein said optical element comprises a half-wave plate.
- 29. The method of claim 25, wherein said optical element comprises liquid-crystal cells.
- 30. The method of claim 21, wherein said spot comprises a linearly polarized center region as one of said second regions.
- 31. The method of claim 21, wherein said spot comprises a linearly polarized center region of said second regions and an outer region comprises a left circular polarized region of said second regions and a right circular polarized region of said second regions.
- 32. The method of claim 21 wherein said second regions include a substantially “D” shaped side region having substantially clockwise polarization, a backwards substantially “D” shaped side region having substantially counterclockwise polarization and a substantially circular central region having substantially linear polarization.
- 33. The method of claim 21 wherein said second regions include a substantially “D” shaped side region having substantially clockwise polarization. a backwards substantially “D” shaped side region having substantially counterclockwise polarization and a substantially rectangular central region having substantially linear polarization.
- 34. The method of claim 21, wherein said polarization pattern comprises said first regions comprising a right-hand side region polarized at about +45 degrees to an X-axis and a left-hand side region polarized at about 45 degrees to said X-axis.
- 35. The method of claim 21, wherein said polarization pattern comprises said first regions comprising an incident light beam at the entrance pupil to said objective lens comprising a polarization state comprising a region which is right-hand side polarized at about +45 degrees to an X-axis and a region which is left-hand side at about −135 degrees to said X-axis
- 36. The method of claim 21, wherein an incident light beam at the entrance pupil to said objective lens comprises said first regions comprising a first quadrant, a second quadrant, a third quadrant, and a fourth quadrant with opposite quadrants having mutually orthogonal polarizations.
- 37. The method of claim 21 is a magneto-optical readout system.
- 38. The method of claim 21 wherein said storage medium comprises a magneto-optical disk.
- 39. The method of claim 21, further comprising the step of differential detecting a reflected component of said spot.
- 40. The method of claim 21, further comprising the step of:
differentially converting a reflected component of said spot to a first electrical signal and a second electrical signal; and generating from said first and second electrical signals a readout signal indicating the binary state of said storage medium under said light beam.
- 41. The method of claim 21, wherein said light beam is a coherent, quasi-monochromatic beam of light from a semiconductor laser diode.
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Serial No. 60/425,123, filed on Nov. 8, 2002, for AN APPARATUS AND METHOD FOR EFFECTIVE REDUCTION OF A LASER BEAM SPOT SIZE, the entirety of which is hereby incorporated by reference.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60425123 |
Nov 2002 |
US |