Beam deflector and scanner

• US 6,169,594 B1
• Filed: 08/24/1998
• Issued: 01/02/2001
• Est. Priority Date: 08/24/1998
• Status: Expired due to Term

• Current Assignee: Intellisense Systems, Inc.
• Original Assignee: Physical Optics Corporation
• Inventors: Savant, Gajendra D., Aye, Tin M.
• Primary Examiner(s): Dudek, James A.
• Application Number:
  US09/139,152
• Time in Patent Office: 862 Days
• Field of Search: 349/1, 349/196, 359/245, 359/253, 359/259, 359/262, 359/832, 359/246, 359/251, 359/252, 359/261, 359/831, 359/290
• US Class Current: 349/196
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 5/06 Fluid-filled or evacuated prisms
• CPC Class Codes: G02F 1/13 based on liquid crystals, e.g. single liquid crystal display cells
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 1/29 for the control of the position or the direction of light beams, i.e. deflection

Abstract

A beam deflector comprising a pair of mated microprism arrays with one of the arrays comprised of a variable refractive index material capable of being selectively changed in response to a field whose magnitude or intensity is regulated by regulating voltage applied. The other array preferably is comprised of a material having a constant refractive index. A conductive layer is disposed on both sides of the variable refractive index array. A pane preferably is disposed in front and behind the arrays. Two pairs of the arrays can be arranged parallel to each other with their microprisms generally perpendicular forming a two-dimensional deflector. To achieve a deflection response time faster than 100 μs, each prism has a height no larger than about 20 μm and a width preferably no greater than about 100 μm. Preferably, each prism height is less than about 15 to about 10 μm to achieve a response time 30 μs or faster. A method of making the deflector includes using direct-write electron beam lithography to make a master for replicating arrays having a height of 10 μm or less. A pair of deflectors can be used to deflect a beam in two dimensions and can be used in a scanner. Where the beam is a laser, the deflector can be used in a laser imaging radar assembly. Such a scanner and laser imaging radar assembly provide fast scanning of an object or region advantageously without requiring the deflector to move during scanning.

Claims

1. A beam deflector for deflecting a beam of electromagnetic energy comprising:

a plurality of first prisms having a pitch of between 20 μ

m and 100 μ

m and (1) a refractive index capable of varying in the presence of an electric or magnetic field, (2) a first face through which the beam enters the plurality of first prisms, and (3) a second face through which the beam exits the plurality of first prisms;

a plurality of second prisms having (1) a refractive index that remains substantially constant, (2) a first face through which the beam enters the plurality of second prisms, and (3) a second face through which the beam exits the plurality of second prisms;

wherein the plurality of first prisms and plurality of second prisms are mated such that the second face of the plurality of first prisms is disposed adjacent the first face of the plurality of second prisms;

a source of an electric or magnetic field constructed and arranged such that the field extends at least through the plurality of first prisms; and

a first conductive layer disposed adjacent the first face of the plurality of first prisms and a second conductive layer disposed adjacent the second face of the plurality of second prisms and a voltage source electrically connected to the first conductive layer and the second conductive layer for providing the electric field or the magnetic field through the plurality of first prisms when a voltage from the voltage source is applied to the first conductive layer and the second conductive layer;

wherein changes in the flux of the electric field or the magnetic field change the refractive index of the plurality of first prisms thereby changing the angle at which the beam is deflected when passing through the plurality of first prisms and plurality of second prisms.

2. The beam deflector of claim 1 wherein the plurality of first prisms and the plurality of second prisms both respond to a change in the electric field or the magnetic field no slower than about 100 μ

m.

3. The beam deflector of claim 2 wherein the pitch comprises the thickness of at least one of the plurality of first prisms and the plurality of second prisms in a direction generally parallel to the direction of the beam.

4. The beam deflector of claim 2 wherein the beam has a diameter less than about 100 μ

m.

5. The beam deflector of claim 2 wherein the plurality of first prisms and the plurality of second prisms each have a width no greater than about 30 μ

m.

6. The beam deflector of claim 2 wherein the plurality of first prisms changes its refractive index when responding to the change in the electric field or the magnetic field.

7. The beam deflector of claim 1 wherein the plurality of first prisms changes its refractive index in response to a change in the electric field or the magnetic in no more than about 30 μ

s.

8. The beam deflector of claim 1 wherein the first conductive layer and the second conductive layer are comprised of indium tin oxide.

9. The beam deflector of claim 1 wherein the plurality of first prisms and the plurality of second prisms both have a generally triangular cross section and an apex angle between about 45°

and about 60°

.

10. The beam deflector of claim 9 wherein the pitch comprises the maximum cross-sectional thickness in a direction generally parallel to the direction of the beam, the apex angle of the plurality of first prisms comprises the angle between the first face and the second face of the plurality of first prisms, and the apex angle of the plurality of second prisms comprises the angle between the first face and the second face of the plurality of second prisms.

11. The beam deflector of claim 9 wherein the plurality of first prisms and the plurality of second prisms are both at least one centimeter long.

12. The beam deflector of claim 3 wherein the plurality of first prisms is comprised of a variable refractive index material whose refractive index can change as much as 0.2 depending upon the flux or magnitude of the electric or magnetic field applied.

13. The beam deflector of claim 7 comprises a plurality of pairs of the first prism arranged in a first array and a plurality of pairs of the second prism arranged in a second array wherein (1) the first array of the first prisms and the second array of the second prisms are mated together and (2) the first array and the second array are oriented generally perpendicular to the direction of the beam.

14. The beam deflector of claim 13 further comprising (1) a first pane disposed on one side of the first and second arrays and (2) a second pane disposed on another side of the first and second arrays, wherein (1) the first pane and the second pane are oriented generally perpendicular to the direction of the beam and (2) the first pane, the first array, the second array and the second pane define a panel assembly.

15. The beam deflector of claim 14 further comprising a beam polarizer disposed in front of the panel assembly such that the beam passes through the polarizer before the beam passes through the panel assembly.

16. The beam deflector of claim 14 further comprising (1) a first conductive layer disposed between one of the panes and one of the arrays, (2) a second conductive layer disposed between the other of the panes and the other of the arrays, (3) a voltage source electrically connected to (i) the first conductive layer and (ii) the second conductive layer such that the magnitude of the electric field applied to each of the first prisms is substantially the same.

17. The beam deflector of claim 16 wherein the first conductive layer is disposed between the first pane and the first array and the second conductive layer is disposed between the second pane and the second array.

18. The beam deflector of claim 16 wherein one of the conductive layers is disposed between the first array and the second array for creating a non-uniform electric or magnetic field in each of the first prisms.

19. The beam deflector of claim 14 further comprising means for compensating for the temperature of the panel assembly in operable communication with the panel assembly.

20. The beam deflector of claim 19 wherein the temperature compensating means comprises a temperature sensor and a heater in contact with the panel assembly.

21. The beam deflector of claim 20 wherein the temperature sensor is not in contact with the panel assembly and the heater comprises an electrically heated thermal blanket in contact with the panel assembly that selectively heats the panel assembly in response to the temperature sensed by the temperature sensor.

22. The beam deflector of claim 14 comprising a plurality of the beams such that one of the beams passes through and is deflected by each one of the first and second prisms.

23. The beam deflector of claim 14 further comprising (1) a positive microlens array disposed in front of the panel assembly such that the beam first passes through the positive microlens array before passing through the panel assembly and (2) a negative microlens array disposed behind the panel assembly such that the beam first passes through the panel assembly before passing through the negative microlens array.

24. The beam deflector of claim 14 further comprising (1) a positive microlens array disposed in front of the panel assembly such that the beam first passes through the positive microlens array before passing through the panel assembly and (2) a negative microlens array disposed between the positive microlens array and the panel assembly.

25. The beam deflector of claim 14 where in (1) the first array and the second array both comprise at least five prisms, (2) a first of the second prisms has a first width, a second of the second prisms has a second width, a third of the second prisms has a third width, a fourth of the second prisms has a fourth width, and a fifth of the second prisms has a fifth width, (3) none of the widths are the same, and (4) the sum of the first width, the second width, the third width, the fourth width, and the fifth width is greater than about one hundred times the wavelength of the beam for reducing diffraction noise.

26. The beam deflector of claim 14 wherein the panel assembly comprises at least about one inch in length and at least about one inch in height.

27. The beam deflector of claim 26 wherein the panel assembly is at least about 3.5 inches in length and at least about 3.5 inches in height.

28. The beam deflector of claim 27 wherein the panel assembly is no more than ten millimeters thick.

29. The beam deflector of claim 14 wherein the beam has a diameter of less than 100 μ

m and can be selectively deflected at an angle at least as much as about 30°

as it passes through the panel assembly.

30. The beam deflector of claim 29 wherein the beam can be selectively deflected between about 0°

and about 30°

.

31. The beam deflector of claim 29 wherein the beam can be selectively deflected within about 0.5 milliradians of a desired angle of deflection.

32. The beam deflector of claim 29 wherein the beam is comprised of light having a wavelength between about 0.3 μ

m and about 30 μ

m.

33. The beam deflector of claim 29 wherein the beam is comprised of collimated light.

34. The beam deflector of claim 33 wherein the collimated light is produced by a laser.

35. The beam deflector of claim 34 wherein the beam is comprised of infrared light.

36. The beam deflector of claim 35 wherein the infrared light has a wavelength of between about 1.2 μ

m and about 1.5 μ

m.

37. The beam deflector of claim 14 comprising a pair of the panel assemblies such that one of the panel assemblies is disposed adjacent the other of the panel assemblies wherein the prisms of the first array of one of the panel assemblies are orthogonal to the prisms of the first array of the other of the panel assemblies and the prisms of the second array of the one of the panel assemblies are orthogonal to the prisms of the second array of the other of the panel assemblies such that one of the panel assemblies deflects the beam in one direction and the other of the panel assemblies deflects the beam in another direction.

38. The beam deflector of claim 37 wherein one of the panel assemblies deflects the beam in one dimension and the other of the panel assemblies deflects the beam in another dimension.

39. The beam deflector of claim 38 wherein one of the panel assemblies deflects the beam horizontally and the other of the panel assemblies deflects the beam vertically.

40. The beam deflector of claim 35 further comprising a polarizer plate disposed between the panel assemblies.

41. The beam deflector of claim 12 wherein the variable refractive index material is comprised of a liquid crystal.

42. The beam deflector of claim 41 wherein each of the plurality of first prisms is comprised of a ferroelectric liquid crystal.

43. The beam deflector of claim 41 wherein each of the plurality of first prisms is comprised of a nematic liquid crystal.