High efficiency homogeneous polarization converter

• US 6,081,378 A
• Filed: 07/23/1998
• Issued: 06/27/2000
• Est. Priority Date: 04/24/1995
• Status: Expired due to Term

• Current Assignee: Polycom Incorporated (HP Inc.)
• Original Assignee: Polycom Incorporated (HP Inc.)
• Inventors: Hinman, Brian L., Romano, Pasquale
• Primary Examiner(s): Schuberg, Darren E.
• Application Number:
  US09/121,777
• Time in Patent Office: 705 Days
• Field of Search: 359/483, 359/485, 359/487, 359/495, 359/497, 349/9, 349/95, 349/96
• US Class Current: 359/485.07
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 27/285 comprising arrays of elements, e.g. microprisms
• CPC Class Codes: G02B 5/3025 Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state G02B5/3008, G02B5/3016 take precedence
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/13355 Polarising beam splitters [PBS]
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n

Abstract

A polarization converter polarizes an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane. The polarization converter comprises a planar matrix for concentrating and collimating the incident light beam; a polarizer parallel to the planar matrix for refracting the first component and reflecting the second component; quarter-wave retarding means, parallel to the planar matrix and disposed between the planar matrix and the polarizer, for delaying the second component one-quarter wavelength relative to that of the first component; and reflection means, between the quarter-wave retarding means and the planar matrix, for reflecting the second component back through the quarter-wave retarder. The planar matrix may include on a top surface an array of first lenses and on a bottom surface an array of second lenses. The first and second lenses operate jointly to concentrate and collimate the incident light beam. The polarizer divides the concentrated light beam based on their planes of polarization into the first and second components, thereby enabling the quarter-wave retarder and the reflection means to orient only the second component to match the orientation of the first component.

Claims

1. A system for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising:

concentrating means for concentrating the incident light beam;

collimating means parallel to the concentrating means for collimating the concentrated light beam;

polarization means parallel to the concentrating means for refracting the first component and reflecting the second component; and

orienting means parallel to the concentrating means for orienting the polarization of the second component to that of the first component;

wherein the concentrating means includes a first lens array defining a plane oriented perpendicular to the incident light beam with lenses adjacently disposed in a row for dividing the incident light beam into a plurality of light beams.

2. The system of claim 1 wherein each lens of the first lens array concentrates one of the plurality of light beams to create a light beam which has a first diameter proximate to the lens and a second diameter less than the first diameter distal to the lens.

3. The system of claim 2 wherein the first lens array comprises convex lenses.

4. The system of claim 2 wherein the collimating means includes a second lens array disposed to intercept the plurality of light beams from the first lens array.

5. The system of claim 4 wherein the second lens array comprises concave lenses.

6. The system of claim 5 wherein flat surfaces comprising reflective means with a reflective side facing away from the concentrating means are disposed adjacent to and between the concave lenses.

7. The system of claim 4 wherein the second diameter is the diameter of the light beam at the second lens array and the second diameter is half that of the first diameter.

8. The system of claim 4 wherein the distance between the first lens array and the second lens array is such that the concentration ratio of the incident light beam is 2:

1.

9. The system of claim 4 wherein each lens of the second lens array is approximately one-half the size of each lens of the first lens array.

10. The system of claim 4 wherein each lens of the second lens array is disposed to receive light beams from a corresponding lens of the first lens array.

11. The system of claim 1 wherein the polarization means includes polarization film.

12. The system of claim 1 wherein the orienting means includes a mirror having a reflective side parallel to the collimating means and between the polarization means and the collimating means.

13. The system of claim 12 wherein the orienting means includes a quarter-wave retarder between the mirror and the polarization means, thereby enabling the second component to reflect off the polarization means, through the quarter-wave retarder a first time, off the mirror and back through the quarter-wave retarder a second time.

14. The system of claim 12 further comprising redirection means for redirecting the concentrating light beams to shift laterally so that the second component reflects off the mirror.

15. The system of claim 1 further comprising a beam-collimating means for redirecting the polarized light beams to travel in the same direction as the incident light beam.

16. A system for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising:

concentrating means for concentrating the incident light beam;

collimating means parallel to the concentrating means for collimating the concentrated light beam;

polarization means parallel to the concentrating means for refracting the first component and reflecting the second component; and

orienting means parallel to the concentrating means for orienting the polarization of the second component to that of the first component;

wherein the polarization means further includes clean-up polarization means for performing absorptive polarization on the collimated light beams.

17. A polarization converter for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising:

a first planar matrix for refracting the incident light beam in an ever-narrowing diameter;

a second planar matrix parallel to the first planar matrix for collimating the refracted light beam;

a polarizer parallel to the first planar matrix for refracting the first component and reflecting the second component;

quarter-wave retarding means, parallel to the first planar matrix and disposed between the second planar matrix and the polarizer, for delaying the second component one-quarter relative to that of the first component; and

reflection means, between the quarter-wave retarding means and the second planar matrix, for reflecting the second component back through the quarter-wave retarder;

wherein the first planar matrix is oriented perpendicular to the incident light beam and includes convex lenses adjacently disposed in a row.

18. The polarization converter of claim 17 wherein the second planar matrix includes concave lenses.

19. The polarization converter of claim 18 wherein the first planar matrix includes convex lenses for dividing the incident light beam into a plurality of light beams.

20. The polarization converter of claim 19 wherein each convex lens concentrates one of the plurality of light beams to create a light beam which has a first diameter proximate to the convex lens and a second diameter less than the first diameter distal to the convex lens.

21. The polarization converter of claim 20 wherein the second diameter is the diameter of the light beam at the second lenses and the second diameter is half that of the first diameter.

22. The polarization converter of claim 20 wherein the distance between the convex lenses and the concave lenses is such that the concentration ratio of the incident light beam is 2:

1.

23. The polarization converter of claim 19 wherein each concave lens is approximately one-half the size of each convex lens.

24. The polarization converter of claim 19 wherein each concave lens is disposed to receive one of the plurality of light beams from a corresponding convex lens.

25. The polarization converter of claim 19 wherein the polarizer includes polarization film.

26. The polarization converter of claim 19 wherein the reflection means includes a mirror which is substantially coplanar to the concave lenses.

27. The polarization converter of claim 19 further comprising a beam-collimating means for redirecting the polarized light beams to travel in the same direction as the incident light beam.

28. The polarization converter of claim 17 wherein the reflection means includes a mirror.

29. The polarization converter of claim 28 further comprising redirection means for redirecting the concentrated light beams to shift laterally so that the second component reflects off the mirror.

30. A polarization converter for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising:

a first planar matrix for refracting the incident light beam in an ever-narrowing diameter;

a second planar matrix parallel to the first planar matrix for collimating the refracted light beam;

a polarizer parallel to the first planar matrix for refracting the first component and reflecting the second component;

quarter-wave retarding means, parallel to the first planar matrix and disposed between the second planar matrix and the polarizer, for delaying the second component one-quarter relative to that of the first component;

reflection means, between the quarter-wave retarding means and the second planar matrix, for reflecting the second component back through the quarter-wave retarder; and

a clean-up polarizer for performing absorptive polarization on the collimated light beams;

wherein the second planar matrix includes concave lenses and the first planar matrix includes convex lenses for dividing the incident light beam into a plurality of light beams.

31. A method for manufacturing a polarizing converter for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising the steps of:

forming a beam-concentrating element which includes an upper surface, a lower surface, a first lens array on the upper surface and a second lens array on the lower surface, the first and second lens array jointly having a prescription to concentrate and collimate the incident light beam, and the first lens array defining a plane oriented perpendicular to the incident light beam and comprising lenses adjacently disposed in a row;

placing a polarizer parallel to and at a predetermined distance from the second lens array for refracting the first component and reflecting the second component;

placing a mirror parallel to the beam-concentrating element and between the polarizer and the beam-concentrating element such that the reflective side of the mirror film faces away from the beam-concentrating element; and

placing a quarter-wave retarder parallel to the beam-concentrating element and between the mirror and the polarizer.

32. A method for manufacturing a polarizing converter for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising the steps of:

forming a beam-concentrating element which includes an upper surface, a lower surface, a first array of adjacently disposed first lenses on the upper surface, a second array of second lenses on the lower surface, and flat surfaces between the second lenses, the first and second array for concentrating and collimating the incident light beam;

depositing mirror film on the flat surfaces such that the reflective side of the mirror film faces away from the beam-concentrating element;

placing a polarizer for refracting the first component and reflecting the second component parallel to the beam-concentrating element and at a predetermined distance from the mirror film; and

placing a quarter-wave retarder parallel to the beam-concentrating element and between the mirror film and the polarizer.

33. A method for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising the steps of:

concentrating the incident light beam to an ever-narrowing diameter through a concentrating means comprising an array of lenses adjacently disposed in a row, wherein the array defines a plane oriented perpendicular to the incident light beam;

collimating the concentrating light beam with a collimating means parallel to the concentrating means;

refracting the first component of the collimated light beam with a polarizer parallel to the concentrating means;

reflecting the second component of the collimated light beam with the polarizer;

orienting the polarization of the second component to that of the first component with an orienting means parallel to the concentrating means; and

refracting the oriented second component.

34. The method of claim 33 wherein the step of concentrating includes the step of dividing the incident light beam into a plurality of light beams.

35. The method of claim 33 wherein the step of concentrating includes before the step of collimating the step of concentrating the light beam until each reaches half its diameter.

36. The method of claim 33 wherein the step of orienting includes the step of passing the second component through a quarter-wave retarder twice.

37. The method of claim 33 further comprising the step of redirecting the concentrating light beams to shift laterally so that the second component reflects off a mirror.

38. The method of claim 33 further comprising the step of redirecting the oriented second component to travel in the same direction as the incident light beam.

39. A method for manufacturing a polarizing converter for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising the steps of:

forming a beam-concentrating element which includes an upper surface, a lower surface, a first lens array on the upper surface and a second lens array on the lower surface, the first and second lens array jointly having a prescription to concentrate and collimate the incident light beam;

placing a polarizing film parallel to and at a predetermined distance from the second lens array for refracting the first component and reflecting the second component;

placing a mirror parallel to the beam-concentrating element and between the polarizing film and the beam-concentrating element such that the reflective side of the mirror film faces away from the beam-concentrating element;

placing a quarter-wave retarder parallel to the beam-concentrating element and between the mirror and the polarizing film; and

placing a clean-up polarizer parallel to the beam-concentrating element and between the polarizing film and a series of adjacently disposed inclined steps.

40. A method for polarizing an incident light beam having a first component with a first plane of polarization and a second component with a second plane of polarization orthogonal to the first plane, comprising the steps of:

concentrating the incident light beam to an ever-narrowing diameter;

collimating the concentrating light beam;

refracting the first component of the collimated light beam;

reflecting the second component of the collimated light beam;

orienting the polarization of the second component to that of the first component;

refracting the oriented second component; and

absorptively polarizing the collimated light beam to filter out any leaked light of unwanted polarization.