METHOD FOR THE CALCULATION OF, STORAGE MEDIUM FOR AND DEVICE FOR THE READ-OUT OF COMPUTER-GENERATED HOLOGRAMS ON A NON-PLANAR SURFACE

Abstract

The invention relates to a method for calculating a light field which propagates between a non planar surface of a computer-generated hologram and a planar reconstruction surface, in which an intermediate plane arranged in front of the hologram is defined, in which the propagation of the light field between the reconstruction plane and the intermediate plane is calculated by means of a transformation, and in which the propagation of the light field between the non-planar hologram surface and the intermediate plane is estimated. This method solves the technical problem of taking account of the geometrical distance differences that arise on account of unevennesses of the storage medium ill the calculation of the hologram function and the reconstruction or read-out and at the same time of specifying a fast algorithm. The invention also relates to a method for producing a hologram, storage medium and a device for reading out a hologram.

Description

The invention is explained in more detail below on the basis of exemplary embodiments, in respect of which reference is made to the accompanying drawing, in which:

FIG. 1 shows a reconstruction of an amplitude hologram calculated for a planar hologram surface and a reconstruction for the same hologram if it assumes a cylindrical surface form,

FIG. 2 shows a schematic illustration for elucidating the terms used in the description of the method for the calculation of a computer-generated hologram and for calculating the reconstruction arising therefrom,

FIG. 3 shows an illustration of a phase difference field for a cylindrical hologram surface,

FIG. 4 shows an illustration of the inverse transformation proceeding from the reconstruction to the non-planar hologram surface,

FIG. 5 shows an illustration of the transformation proceeding from the non-planar hologram surface to the reconstruction,

FIG. 6 shows an illustration of the inverse transformation of a plane wave in the intermediate plane into the non-planar hologram surface,

FIG. 7 shows an amplitude hologram calculated for a cylindrical hologram surface and the calculated reconstruction of said hologram,

FIG. 8 shows a binary phase hologram calculated for a cylindrical hologram surface and the calculated reconstruction of said hologram,

FIG. 9 shows an optimized binary phase hologram calculated for a cylindrical hologram surface and the calculated reconstruction of said hologram,

FIG. 10 shows a Fresnel amplitude hologram calculated for a cylindrical hologram surface and the calculated reconstruction of said hologram,

FIG. 11 shows an illustration of a phase difference field for a spherical hologram surface,

FIG. 12 shows an amplitude hologram calculated for a spherical hologram surface and the calculated reconstruction of said hologram,

FIG. 13 shows a first exemplary embodiment of a reading device according to the invention for holograms arranged on a non-planar surface of a storage medium,

FIG. 14 shows a second exemplary embodiment of a reading device according to the invention for holograms arranged on a non-planar surface of a storage medium,

FIG. 15 shows a third exemplary embodiment of a reading device according to the invention for holograms arranged on a non-planar surface of a storage medium.

Claims

1-27. (canceled)

28. A method for calculating a light field which propagates between a non-planar surface of a computer-generated hologram and a planar reconstruction surface, comprising the steps of (a) defining an intermediate plane arranged in front of the hologram,(b) calculating the propagation of the light field between the reconstruction plane and the intermediate plane by means of a transformation, and(c) estimating the propagation of the light field between the non-planar hologram surface and the intermediate plane is estimated.

29. The method according to claim 28, further comprising the steps of (d) determining, on the basis of the information to be reconstructed, the light field in the reconstruction plane, and determining the light field of a read beam in the non-planar surface of the computer-generated hologram,(e) calculating the light field in the intermediate plane arranged in front of the hologram from the propagation of the light field between the reconstruction plane and the intermediate plane, and(f) estimating the light field in the non-planar surface of the computer-generated hologram proceeding from the intermediate plane and superimposing the estimated light field with the light field of the read beam in order to calculate the phase and/or amplitude information of the hologram.

30. The method according to claim 29, (g) calculating the light field of an incident light wave in the non-planar surface of the hologram by a superimposition of the impinging light field and the phase and/or amplitude information of the hologram,(h) estimating the light field in the intermediate plane in front of the hologram, proceeding from the non-planar surface of the hologram, and(i) calculating the light field in the reconstruction plane from the propagation of the light field between the intermediate plane and the reconstruction plane.

31. The method according to claim 30, further comprising the steps of (j) calculating or defining the light field of a read beam in the intermediate plane, and(k) estimating the light field impinging in the non-planar surface of the hologram is estimated proceeding from the intermediate plane.

32. The method according to claim 29, further comprising the steps of calculating a reflection hologram or the reconstruction thereof.

33. The method according to claims 29, further comprising the steps of calculating a phase difference field from the wavelength of the light and the distribution of the propagation time differences of the light between the intermediate plane and the hologram on the non-planar surface.

34. The method according to claim 30, wherein in step (f) the light field in the non-planar surface of the hologram is estimated by a superimposition of the light field in the intermediate plane with the phase difference field.

35. The method according to claim 33, wherein in step (h), the light field in the intermediate plane is estimated by a superimposition of the light field in the non-planar surface of the hologram with the phase difference field.

36. The method according to one of claims 31, wherein in step (k), the light field in the non-planar surface of the hologram is estimated by a superimposition of the light field in the intermediate plane with the phase difference field.

37. The method according to claim 36, wherein the light field of the read beam is defined in the intermediate plane as a plane wave, and wherein the read beam is taken into account in the calculation by a doubling of the phase difference field between the intermediate plane and the hologram surface and the light field of the read beam is ignored afterwards.

38. The method according to claim 28, wherein an optimization algorithm is used for the calculation of the hologram.

39. The method according to claim 28, wherein the non-planar surface is calculated or approximated by means of a mathematical and/or numerical function.

40. The method according to claim 39, wherein one of a cylindrical surface, a spherical surface, a parabolic surface or a sinusoidal surface is used.

41. The method according to claim 28, wherein the phase shift caused by an optical element arranged in the beam path is taken into account.

42. The method for producing a computer-generated hologram on a non-planar surface, comprising the steps of calculating the hologram with the aid of a method according to claim 28,writing the hologram to a storage medium arranged in planar fashion with the aid of a writing device, andfixing the planar storage medium on a non-planar surface, whereby the material layer of the storage medium that carries the hologram assumes the non-planar form.

43. The method according to claim 42, further comprising the step of selecting the hologram from the planar storage medium and reconstructing the hologram for quality control, with the aid of a device according to claim 47.

44. A storage medium for a computer-generated hologram, comprising at least one optically variable non-planar material layer in which the hologram is written,wherein reconstructing of the hologram leads to reconstructing of the information in an order which has a better resolution in comparison with the reconstructing in the same order with an opposite sign.

45. The storage medium according to claim 44, wherein the non-planar surface is calculated or approximated by means of a mathematical and/or numerical function.

46. The Storage medium according to claim 45, wherein the non-planar surface is one of a cylindrical surface, a spherical surface, a parabolic surface or a sinusoidal surface.

47. A device for reconstructing a computer-generated hologram arranged on a non-planar surface of a storage medium, comprising a light source,recording means for recording the reconstruction,an optical element for at least partly compensating for a non-planar surface disposed ill a beam path between a light source and a recording means.

48. A device according to claim 47, wherein a beam splitter (10) is provided in the beam path.

49. The device according to claim 48, wherein the optical element is arranged in the beam path between the storage medium and the beam splitter.

50. The device according to claim 48, wherein the optical element is arranged in the beam path between the light source and the beam splitter.

51. The device according to claim 48, wherein the optical element is arranged in the beam path between the beam splitter and the recording means.

52. The device according to claim 47, wherein the optical element is arranged such that it can be pivoted into the beam path.

53. The device according to claim 47, wherein the optical element completely compensates for the non-planar surface.

54. The device according to claim 47, wherein the hologram arranged on the storage medium has been calculated according to claim 37, and the optical element partly compensates for the non-planar surface.