Device for Homogenizing Radiation by Means of Irregular Microlens Arrays

• US 20100033829A1
• Filed: 10/05/2007
• Published: 02/11/2010
• Est. Priority Date: 10/10/2006
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Wippermann, Frank, Bräuer, Andreas, Schreiber, Peter
• Granted Patent: US 7,839,573 B2
• Time in Patent Office: Days
• US Class Current: 359/623
• CPC Class Codes: G02B 27/01 Head-up displays
• CPC Class Codes: G02B 27/0961 Lens arrays lens arrays per se G02B3/0006

Abstract

A device for the homogenization of radiation, preferably light, using chirped microlens arrays (cMLA) from the established regular microlens arrays (rMLA), chirped microlens arrays are an arrangement of non-identical lenses in one array. Non-identical means that the lens parameters of the lenses of the array, such as e.g. the radius of curvature, the free diameter, vertex position, and others, can vary from lens to lens or cell to cell. The parameters of each lens or cell can be determined by functions (analytically, numerically), the functions preferably being dependent upon the position of the cell or the lens in the array.

Claims

1. A device for the homogenisation of radiation or light, comprising at least one lens arrangement which has a large number of lens systems disposed with parallel optical axes, the lens systems being at least partially non-identical and the non-identical lens systems having respectively a same numerical aperture in a first direction parallel to main plane of the lens systems.

2. The device according to claim 1, wherein the non-identical lens systems have the same numerical aperture in a second direction perpendicular to the first direction and/or in that the numerical aperture of the non-identical lens systems is the same in the second direction as in the first direction.

3. The device according to claim 1, wherein a focal distance and/or dimensions and/or a radius of curvature and/or a free diameter and/or a vertex position of the lens systems is determined by a function which is dependent upon a position of the lens system in the lens arrangement.

4. The device according to claim 1, wherein the at least one lens arrangement is a first microlens array, the lens systems are microlenses, and the microlenses are disposed on one surface.

5. The device according to claim 4, wherein, in addition to a first microlens array, a second microlens array which has a large number of microlenses disposed with parallel optical axes is disposed such that the optical axes of the microlenses of the first microlens array pass through the microlenses of the second microlens array.

6. The device according to claim 5, wherein the microlenses of the second microlens array are disposed on one surface.

7. The device according to claim 4, wherein the surface of the first and/or the second microlens array is planar, spherical, aspherical, toroidal or a freely-formed surface.

8. The device according to claim 5, wherein, on an optical axis of each microlens of the first microlens array, a microlens of the same focal length of the second microlens array is disposed such that the optical axis of the respective microlens of the second microlens array is situated parallel to the optical axis of the corresponding microlens of the first microlens array and spacing between the corresponding microlenses is equal to their focal distance.

9. The device according to claim 8, wherein the optical axes of the microlenses of the second microlens array coincide with the optical axes of the corresponding microlens of the first microlens array.

10. The device according to claim 8, wherein the microlenses of the second microlens array are displaced relative to the corresponding microlenses of the first microlens array in a lens plane of the microlens of the second microlens array such that light which impinges parallel to the optical axis on a microlens of the first microlens array is deflected by a corresponding microlens of the second microlens array such that it illuminates the same region for all microlenses of the first microlens array at a specific spacing from the second microlens array.

11. The device according to claim 1, wherein the lens systems, respectively disposed in succession in a beam path, have a first and a second microlens, the optical axes of which coincide, the first lenses forming a first microlens array and the second lenses forming a second microlens array and a third microlens array having a large number of microlenses being disposed on a side of the second microlens array orientated away from the first microlens array, such that optical axes of the lens systems pass through the third microlens array.

12. The device according to claim 11, wherein a microlens of the third microlens array is disposed on the optical axis of each lens system such that the optical axis of the respective microlens of the third microlens array is situated parallel to the optical axis of the corresponding lens system, the microlens of the third microlens system being disposed with the main plane thereof in a focus of the corresponding lens system.

13. The device according to claim 12, wherein the optical axes of the microlenses of the third microlens array coincide with the optical axes of the corresponding lens systems.

14. The device according to claim 12, wherein the optical axes of the microlenses of the third microlens array are displaced relative to the optical axes of the corresponding lens systems such that light beams which impinge along the optical axis of a lens system on the respective lens system are deflected by the corresponding microlens of the third microlens array to a point common to all lens systems.

15. The device according to claim 5, wherein the microlenses of adjacent microlens arrays are accommodated respectively on one side on a substrate comprising a transparent material, a glass material, or a polymer material.

16. The device according to claim 15, wherein the substrates are at a spacing relative to each other, and an intermediate space is filled with air or a transparent material.

17. The device according to claim 1, wherein the microlenses of two adjacent microlens arrays are accommodated on surfaces of a body which are situated in succession in a beam path, said body comprising a transparent material, in particular glass or a transparent polymer.

18. The device according to claim 17, wherein the body is a prism or a body with a rectangular cross-section.

19. The device according to claim 5, wherein the microlenses of a last microlens array in a direction of a beam path are disposed in the vicinity of, but not exactly in the focus of, the microlenses or lens systems situated in front thereof.

20. The device according to claim 5, wherein a Fourier lens is disposed in a direction of the beam path behind the lens arrangement with a lens plane parallel to the main planes of the lens systems such that the optical axes of the lens systems pass through the Fourier lens.

21. The device according to claim 5, wherein a Fourier lens is disposed behind the second microlens array on the side thereof orientated away from the first microlens array with the lens plane parallel to the lens planes of the microlenses of the first microlens array such that the optical axes of the microlenses of the second microlens array pass through the Fourier lens.

22. The device according to claim 11, wherein a Fourier lens is disposed in the direction of the beam path behind the third microlens array on the side orientated away from the lens arrangement with the lens plane parallel to the lens planes of the microlenses of the first microlens array such that the optical axes of the microlenses of the third microlens array pass through the Fourier lens.

23. The device according to claim 22, wherein the microlens arrays in a plane parallel to the lens plane of the Fourier lens can be displaced together and the Fourier lens is stationary.

24. The device according to claim 1, wherein the device can be displaced in a direction parallel to the plane of the first microlens array relative to incident radiation.

25. The device according to claim 1, wherein at least a part of the microlenses at least of one microlens array are axially symmetrical about their optical axis and/or have a circular circumference in the plane of the microlens array.

26. The device according to claim 1, wherein at least a part of the microlenses at least of one microlens array are lenses which are axially symmetrical about their optical axis, and have a rectangular edge in the plane of the microlens array.

27. The device according to claim 26, wherein at least a part of the lenses which are axially symmetrical about their optical axis have a square edge in the plane of the microlens array.

28. The device according to claim 1, wherein at least a part of the microlenses are anamorphic and/or elliptical lenses.

29. The device according to claim 28, wherein at least a part of the anamorphic or elliptical microlenses at least of one microlens array have rectangular edges in the plane of the microlens array.

30. The device according to claim 29, wherein at least a part of the anamorphic or elliptical microlenses at least of one microlens array have square edges in the plane of the microlens array.

31. The device according to claim 1, wherein at least a part of the microlenses at least of one microlens array are cylindrical lenses.

32. The device according to claim 31, wherein at least a part of the cylindrical lenses at least of one microlens array has a constant focal distance along a cylinder axis.

33. The device according to claim 31, wherein a focal distance at least of one cylindrical lens is not constant along a cylinder axis and/or changes continuously along the cylinder axis.

34. The device according to claim 31, wherein the edges of the cylindrical lenses extend parallel to each other.

35. The device according to claim 31, wherein a length of the cylindrical lenses is equal to the extension of the microlens array in the direction of the cylinder axes.

36. The device according to claim 11, wherein the second and the third microlens array respectively have at least one cylindrical lens, the cylindrical lens of the second and/or third microlens array being disposed on the optical axis of the cylindrical lens of the first microlens array with a parallel optical axis and being rotated in the lens plane thereof by an angle relative to the cylindrical lens of the first microlens array.

37. The device according to claim 31, wherein a similarly constructed device is disposed in a beam path behind the device such that the optical axes of the microlenses of a rearmost microlens array, in a direction of the beam path, of a front device pass through a foremost microlens array, in the direction of the beam path, of a rear device and extend parallel to the optical axes of the microlenses of a foremost microlens array of the rear device, the rear device being rotated relative to the front device by 90°

about the direction of the optical axes.

38. The device according to claim 1, wherein the microlenses of the same microlens array have at least partially different focal distances.

39. The device according to claim 1, wherein the microlenses at least of one microlens array are disposed such that all the microlenses or lens systems in one direction have the same focal distance and, in a direction perpendicular thereto, their focal distance increases or reduces monotonically from one edge of the microlens array or lens arrangement to the other edge.

40. The device according to claim 1, wherein the ratio of the surface, covered by microlenses, at least of one microlens array to the total surface of the corresponding microlens array is maximum for given microlenses.

42. A method, comprising homogenising radiation using the device according to claim 1.

41. A method for the homogenisation of radiation, characterised in that the radiation is deflected to a microlens array with a large number of microlenses disposed with parallel optical axes, the microlenses being at least partially non-identical and the non-identical microlenses having a same numerical aperture.