Method and apparatus for modulating a light beam

• US 5,311,360 A
• Filed: 04/28/1992
• Issued: 05/10/1994
• Est. Priority Date: 04/28/1992
• Status: Expired due to Term

• Current Assignee: Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Bloom, David M., Solgaard, Olav, Sandejas, Francisco S. A.
• Primary Examiner(s): Ben, Loha
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US07/876,078
• Time in Patent Office: 742 Days
• Field of Search: 359/231, 359/298, 359/299, 359/302, 359/558, 359/566, 359/569, 359/572, 359/573, 359/291, 359/295, 359/213, 359/224, 359/226, 359/230, 359/290, 359/292, 359/846, 359/855, 358/206, 358/208, 345/85, 345/108
• US Class Current: 359/572
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81C 2201/115 Roughening a surface
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 5/1828 having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A modulator for modulating an incident beam of light, the modulator comprising a plurality of equally spaced-apart elements, each of which includes a light-reflective planar surface. The elements are arranged parallel to each other with their light-reflective surfaces parallel to each other. The modulator includes means for supporting the elements in relation to one another and means for moving particular ones of the elements relative to others so that the moved elements transit between a first configuration wherein the modulator acts to reflect the incident beam of light as a plane mirror, and a second configuration wherein the modulator diffracts the light reflected therefrom. In operation the light-reflective surfaces of the elements remain parallel to each other in both the first and second configurations. The perpendicular spacing between the reflective surfaces of the respective elements is equal to m/4 × the wavelength of the incident beam of light, wherein m equals an even whole number or zero when the elements are in the first configuration and m equals an odd whole number when the elements are in the second configuration.

Claims

1. A modulator for modulating an incident beam of light, comprising:

a plurality of elongated elements, each including a light reflective planar surface, the elements being arranged parallel to each other and with the light reflective surfaces of the elements lying in one or more parallel planes;

means for supporting the elements in relation to one another; and

means for moving a first set of the elements in a direction normal to said planes and relative to a second set of the elements, and between a first modulator configuration wherein said first and second sets act to reflect the incident beam of light as a plane mirror, and a second modulator configuration wherein said first and second sets diffract the incident beam of light as it is reflected from the surfaces of the elements.

2. A modulator as recited in claim 1, wherein the reflective surfaces of adjacent elements lie within planes separated by a distance equal to m/4 times a particular wavelength of the incident beam of light, wherein m=an even whole number or zero when the elements are in the first configuration and m =an odd whole number when the elements are in the second configuration.

3. A modulator as recited in claim 2, wherein the reflective surfaces of the plurality of elements are equal in dimensions and are substantially rectangular in plan.

4. A modulator as recited in claim 2, wherein alternate elements are fixed relative to the supporting means.

5. A modulator as recited in claim 2, wherein the means for moving the elements operates to rotate the elements about axes extending generally parallel to their longitudinal dimensions when moving them relative to one another.

6. A modulator as recited in claim 5, wherein the elements are resilient.

7. A modulator as recited in claim 1, wherein the means for moving the first set of elements comprises means for applying an electrostatic force to the first set of elements.

8. A modulator as recited in claim 7, wherein the reflective surfaces are formed by metallic layers deposited on the upper surfaces of said elements.

9. A modulator as recited in claim 8, wherein the means for applying electrostatic force includes a voltage supply coupled to the metallic layers.

10. A modulator as recited in claim 1, wherein the means for moving said first set of elements comprises means for applying an electrostatic force thereto.

11. A modulator as recited in claim 10 wherein said first set of elements has a hysteretic characteristic such that following application of a first electrostatic force thereto to move it into said second configuration, a second electrostatic force of lesser magnitude than that of said first electrostatic force can be used to hold said first set of elements in said second configuration.

12. A modulator as recited in claim 10 wherein the first set of elements are formed of a deformable resilient material.

13. A modulator as recited in claim 1 and further comprising means for moving a third set of the elements relative to a fourth set of the elements and between

a third modulator configuration wherein said third and fourth sets act to reflect the incident beam of light as a plane mirror, and

a fourth modulator configuration wherein said third and fourth sets diffract the incident beam of light as it is reflected from the surfaces thereof, wherein said means for moving includes means for selectively applying electrostatic forces to particular groups of said first set of elements.

14. A modulator for modulating a beam of incident light, comprising;

means forming a first planar light reflective surface;

a grating having means forming a plurality of second planar light reflective surfaces, the grating being arranged with its second reflective surfaces lying in a plane parallel to and spaced from the first planar reflective surface in a direction normal thereto; and

means for moving the grating in a direction normal to said first planar reflective surface and into a position closer thereto while maintaining the second reflective surfaces of the grating substantially parallel to the first planar reflective surface;

whereby, when the spacing between the respective first and second light reflective surfaces is equal to m/4 times a particular wavelength of the incident light and m=an even whole number or zero, the modulator acts to reflect the incident light as a plane mirror, and when m=an odd whole number the modulator diffracts the incident light as it reflects it, thereby providing modulation of the beam.

15. A modulator as recited in claim 14 wherein said means for moving includes means for selectively applying particular electrostatic forces to discrete groups of said means forming said second reflective surfaces.

16. A modulator as recited in claim 14 wherein the grating is comprised of a plurality of equally sized rectangular elements configured such that an incident beam of light directed normal to said light reflective surfaces is reflected back along the incident ray path when said first set of elements are in said first configuration, and the incident beam is angularly diffracted relative to said incident ray path when said first set of elements are in said second configuration, the angularly diffracted beam lying in a plane including said incident ray path and transversely intersecting said elements.

17. A modulator as recited in claim 14 wherein an incident beam of light directed normal to said light reflective surfaces is reflected back along the incident beam path when said grating is in one position, and said incident beam of light is angularly diffracted relative to said incident beam path when said grating is moved to another position.

18. A modulator as recited in claim 14, wherein the grating is comprised of a plurality of equally sized and equally spaced apart elongated rectangular elements disposed parallel to each other.

19. A modulator as recited in claim 18 wherein each said element of the grating is comprised of a deformable resilient material.

20. A modulator as recited in claim 18, wherein the spacing between each of the elements is substantially equal to the transverse width of each of the elements.

21. A modulator as recited in claim 20, wherein the spacing between the first planar reflective surface and the second planar reflective surfaces of the unmoved grating is equal to one-half the wavelength of the beam of incident light.

22. A modulator as recited in claim 21, wherein the means for moving the grating towards the first planar reflective surface and into the position closer thereto comprises means for applying an electrostatic force between the first planar reflective surface and the second planar reflective surfaces of the grating.

23. A modulator as recited in claim 22 wherein said grating has a hysteretic characteristic such that following application of said electrostatic force said grating can be held in the closer position by a reduced electrostatic force.

24. A modulator as recited in claim 22, wherein the thickness of each element is equal to one-half the spacing between the first planar reflective surface and second reflective surfaces of the grating.

25. A modulator for modulating an incident beam of light, comprising:

a plurality of equally spaced apart elements, each including a light reflective planar surface, the elements being arranged parallel to each other and with the light reflective surfaces of the elements lying in a first plane;

means for supporting the elements in relation to one another; and

means for moving alternate ones of the elements relative to the other elements and between a first configuration wherein all elements lie in the first plane and the modulator acts to reflect the incident beam of light as a plane mirror, and a second configuration wherein alternate elements lie in a second plane parallel to the first plane and the modulator diffracts the incident beam of light as it is reflected from the planar surfaces of the elements.

26. A modulator as recited in claim 25 wherein an incident beam of light directed normal to said light reflective surfaces is reflected back along the incident beam path when said alternate ones of said elements are in said first configuration, and said incident beam is diffracted at an angle to said incident beam path when said alternate ones of said elements are in said second configuration.

27. A modulator as recited in claim 25 wherein said means for moving includes means for selectively moving particular groups of said alternate ones of said beam elements such that a detector placed in the path of the diffracted beam will detect a beam intensity proportional to certain characteristics of the particular groups moved.

28. A modulator as recited in claim 25, wherein said means for moving includes means for selectively applying electrostatic forces to said alternate ones of said elements.

29. A modulator as recited in claim 28 wherein following application of a first electrostatic force to said alternate ones of said elements, application of a second electrostatic force less than said first electrostatic force can be used to hold said alternate ones in said second configuration.

30. A modulator as recited in claim 28, wherein the spacing between the first plane and the second plane is equal to m/4 times a particular wavelength of the incident beam of light, wherein m=an even whole number or zero when the elements are in the first configuration and m=an odd whole number when the elements are in the second configuration.

31. A modulator as recited in claim 30, wherein the means for moving the alternate elements operates to rotate the alternate elements when moving them relative to one another.

32. A modulator as recited in claim 31, wherein said other elements are fixed relative to the support means.

33. A method of modulating a beam of light, comprising the steps of:

causing the beam to impinge upon a plurality of equally spaced apart elements, each including an elongated, light reflective planar surface, the elements being arranged parallel to each other and with the light reflective surfaces of the elements being parallel to each other; and

moving some of the elements relative to others between a first configuration wherein the the incident beam of light is reflected as by a plane mirror, and a second configuration wherein the the incident beam of light is diffracted as it is reflected from the elements.

34. A method as recited in claim 33, wherein in the second configuration the said some of the elements are moved to positions wherein the spacing between the planes of the reflective surfaces of adjacent elements is equal to m/4 times a particular wavelength of the incident beam of light, wherein m=an even whole number or zero when the elements are in the first configuration and m=an odd whole number when the elements are in the second configuration.

35. A method as recited in claim 34, wherein the thickness of each element is equal to one-half the spacing between the planes of the adjacent reflective surfaces when in said first configuration.

36. A method as recited in claim 35, wherein the said some of the elements are caused to move relative to the other elements by applying electrostatic forces to said some of the elements.

37. In a light modulating device including an array of individual light modulators for modulating an incident beam of light to generate an image, each pixel of which has a chromatic and/or luminous characteristic corresponding to a physical characteristic of a corresponding modulator in the array, an improved modulator comprising:

a plurality of elongated elements, each including a light reflective planar surface, the elements being arranged parallel to each other and with the light reflective surfaces of the elements lying in one or more parallel planes;

means for supporting the elements in relation to one another; and

means for moving a first set of the elements in a direction normal to said planes and relative to a second set of the elements and between a first modulator configuration wherein said first and second sets act to reflect the incident beam of light as a plane mirror, and a second modulator configuration wherein said first and second sets diffract the incident beam of light as it is reflected from the surfaces of the elements.

38. In a light modulating device including an array of individual light modulators for modulating an incident beam of light to generate an image, each pixel of which has a chromatic and/or luminous characteristic corresponding to a physical characteristic of a corresponding modulator in the array, an improved modulator comprising:

means forming a first planar light reflective surface;

a grating having means forming a plurality of second planar light reflective surfaces, the grating being arranged with its second reflective surfaces lying in a plane parallel to and spaced from the first planar reflective surface in a direction normal thereto; and

means for moving the grating in a direction normal to said first planar reflective surface while maintaining the second reflective surfaces of the grating substantially parallel to the first planar reflective surface;

whereby, when the spacing between the respective first and second light reflective surfaces is equal to m/4 times a particular wavelength of the incident light and m=an even whole number or zero, the modulator acts to reflect the particular wavelength of the incident light as a plane mirror, and when m=an odd whole number the modulator diffracts the particular wavelength of the beam of incident light as it reflects it, thereby providing modulation of the beam.

39. In a light modulating device including an array of individual light modulators for modulating an incident beam of light to generate an image, each pixel of which has a chromatic and/or luminous characteristic corresponding to a physical characteristic of a corresponding modulator in the array, an improved modulator comprising:

a plurality of equally spaced apart elements, each including a light reflective planar surface, the elements being arranged parallel to each other and with the light reflective surfaces of the elements lying in a first plane;

means for supporting the elements in relation to one another; and

means for moving alternate ones of the elements relative to the other elements and between a first configuration wherein all elements lie in the first plane and the modulator acts to reflect the incident beam of light as a plane mirror, and a second configuration wherein alternate elements lie in a second plane parallel to the first plane and the modulator diffracts the incident beam of light as it is reflected from the planar surfaces of the elements.

40. In a light modulating device including an array of individual light modulators for modulating an incident beam of light to generate an image, each pixel of which has a chromatic and/or luminous characteristic corresponding to a physical characteristic of a corresponding modulator in the array, an improved modulator including at least three modulation components each of which is comprised of:

a plurality of elongated elements, each including a light reflective planar surface, the elements being arranged parallel to each other and with the light reflective surfaces of the elements lying in one or more parallel planes;

means for supporting the elements in relation to one another; and

means for moving a first set of the elements in a direction normal to said planes and relative to a second set of the elements and between a first modulator configuration wherein said first and second sets act to reflect the incident beam of light as a plane mirror, and a second modulator configuration wherein said first and second sets diffract the incident beam of light as it is reflected from the surfaces of the several elements,

each said modulation component being designed to diffract a different color into an optical system when illuminated with a beam of white light.

41. In a light modulating device including an array of individual light modulators for modulating an incident beam of light to generate an image, each pixel of which has a chromatic and/or luminous characteristic corresponding to a physical characteristic of a corresponding modulator in the array, an improved modulator including at least three modulation components each of which is comprised of:

means forming a first planar light reflective surface;

a grating having means forming a plurality of second planar light reflective surfaces, the grating being arranged with its second reflective surfaces lying in a plane parallel to and spaced from the first planar reflective surface in a direction normal thereto; and

means for moving the grating in a direction normal to said first planar reflective surface while maintaining the second reflective surfaces of the grating substantially parallel to the first planar reflective surface;

whereby, when the spacing between the respective first and second light reflective surfaces is equal to m/4 times a particular wavelength of the incident light and m=an even whole number or zero, the modulator acts to reflect the particular wavelength of the incident light as a plane mirror, and when m=an odd whole number the modulator diffracts the particular wavelength of the beam of incident light as it reflects it, thereby providing modulation of the beam,

each said modulation component being designed to diffract a different color into an optical system when illuminated with a beam of white light.

42. In a light modulating device including an array of individual light modulators for modulating an incident beam of light to generate an image, each pixel of which has a chromatic and/or luminous characteristic corresponding to a physical characteristic of a corresponding modulator in the array, an improved modulator including at least three modulation components each of which is comprised of:

a plurality of equally spaced apart elements, each including a light reflective planar surface, the elements being arranged parallel to each other and with the light reflective surfaces of the elements lying in a first plane;

means for supporting the elements in relation to one another; and

means for moving alternate ones of the elements relative to the other elements and between a first configuration wherein all elements lie in the first plane and the modulator acts to reflect the incident beam of light as a plane mirror, and a second configuration wherein alternate elements lie in a second plane parallel to the first plane and the modulator diffracts the incident beam of light as it is reflected from the planar surfaces of the elements,

each said modulation component being designed to diffract a different color into an optical system when illuminated with a beam of white light.