ILLUMINATION DEVICE

• US 20150268399A1
• Filed: 10/24/2013
• Published: 09/24/2015
• Est. Priority Date: 10/24/2012
• Status: Active Grant

• Current Assignee: SeeReal Technologies S.A.
• Original Assignee: SeeReal Technologies S.A.
• Inventors: Futterer, Gerald
• Granted Patent: US 9,927,571 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 30/33 involving directional light or back-light sources
• CPC Class Codes: G02B 6/0023 provided by one optical element, or plurality thereof, placed between the light guide and the light source, or around the light source
• CPC Class Codes: G02B 6/0025 Diffusing sheet or layer; Prismatic sheet or layer
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/02057 comprising gratings
• CPC Class Codes: G09G 3/003 to produce spatial visual effects
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3473 based on light coupled out of a light guide, e.g. due to scattering, by contracting the light guide with external means
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

An illumination device for illuminating at least one spatial light modulator device. At least one light source device with at least one light source illuminates the at least one spatial light modulator device; a light guiding element through which light emanating from the light source propagates; and at least one light decoupling element arranged on top or inside of the light guiding element. The at least one light decoupling element decouples of a wave field of the light which propagating in the light guiding element into the direction of the spatial light modulator device. The light guiding element has a refractive index which is lower than or at least equal to the refractive index of the at least one light decoupling element. The entrance angle of the wave field entering the light decoupling element is determined by the difference between the refractive indices according to a particular equation.

Claims

1. An illumination device for illuminating at least one spatial light modulator device being used preferably for displaying two-dimensional and/or three-dimensional images comprising:

at least one light source device with at least one light source illuminating the at least one spatial light modulator device;

a preferably substantially planar light guiding element comprising at least one light conducting core, where the at least one light source device is arranged on a side of the light guiding element and where the light emanating from at least one light source of the at least one light source device propagates areally through the light guiding element;

at least one light decoupling element arranged on top or inside of the light guiding element, the at least one light decoupling element is provided for decoupling of a wave field of the light which propagates in the light guiding element into the direction of the at least one spatial light modulator device;

wherein;

the light guiding element has a refractive index lower than or at least equal to the refractive index of the at least one light decoupling element, where the entrance angle of the wave field entering the at least one light decoupling element is determined by the difference between the said refractive indices in such a way that an angular spectrum of plane waves decoupled from the at least one light decoupling element has a predefined value which depends on the required use of the illumination device.

2. The illumination device according to claim 1, wherein for holographic applications the angular spectrum of plane waves decoupling from the at least one light decoupling element is not greater than 1/60°

deg in at least one lateral direction.

3. The illumination device according to claim 2, wherein the angular spectrum of plane waves is not greater than 1/60 °

deg in the direction of the holographic encoding and has a value of approximately 0.5°

deg to 3°

deg, preferably 1°

deg, in a direction perpendicular to the direction of holographic encoding.

4. The illumination device according to claim 1, wherein the at least one light decoupling element is arranged parallel to the propagation direction of the light in the light guiding element, where the light within the light guiding element propagates at an angle close to 90°

deg to the surface normal of the light decoupling element.

5. The illumination device according to claim 1, wherein a cladding layer is provided between the light guiding element and the at least one light decoupling element.

6. The illumination device according to claim 5, wherein the cladding layer is formed as an antireflection coating, preferably a dielectric coating, for providing a gradientlike transition of the refractive index of the light guiding element to the at least one light decoupling element and wherein the antireflection coating comprises a stack of dielectric layers.

8. The illumination device according to claim 6, wherein an apodization profile is implemented into the reflective planes of the dielectric layers.

9. The illumination device according to claim 1, wherein an absorber layer is provided which is arranged on the light guiding element on the opposite side of the cladding layer.

10. The illumination device according to claim 1, wherein a collimation device is provided for collinnating the light emanating from at least one light source of the at least one light source device.

11. The illumination device according to claim 10, wherein the collimation device is designed in such a way that a reasonable collimated and tailored wave field which has the required angular spectrum of plane waves of preferably not greater than 1/60°

deg is available.

12. The illumination device according to claim 10, wherein the collimation device comprises an aperture for limiting the initial diameter of the light path, where the aperture comprises an amplitude apodization profile and/or a phase apodization profile.

13. The illumination device according to claim 1, wherein the light-conducting core of the light guiding element is made in the form of a holographic volume grating.

14. The illumination device according to claim 1, wherein the light guiding element comprises inside a light decoupling element, preferably a volume grating, comprising a plurality of light decoupling segment elements preferably for reshaping the wave field which has to be coupled out and to implement a plurality of optical path differences which are present between parts of the wave field.

15. The illumination device according to claim 14, wherein the light decoupling segment elements are exposed into the light guiding element and have lateral extensions which are much smaller than the thickness of the light guiding element.

16. The illumination device according to claim 1, wherein the divergence of the wave field propagating in the light guiding element is used for coupling out the light of the light decoupling element or of the light decoupling segment elements.

17. The illumination device according to claim 1, wherein the diameter of the light propagating in the light guiding element has a value in the range of millimetres in one direction, where in the direction perpendicular to this direction the value of the diameter can be greater.

18. The illumination device according to claim 1, wherein the at least one light source device has a static complex valued amplitude distribution and comprises in case of using a substantially coherent light source device additionally a dynamic scatter plate.

19. The illumination device according to claim 1, wherein the at least one light source device comprises an amplitude mask, which is preferably spatially structured, to achieve a fixed amplitude distribution within an exit plane of the light source device.

20. The illumination device according to claim 1, wherein the at least one light source device comprises a continuous phase function mask or a surface relief grating or a computer-generated hologram to provide a phase distribution to modify the light source plane.

21. The illumination device according to claim 1, wherein the at least one light source device comprises light sources for the primary colours red, green and blue, which are optimized separately regarding the intensity distribution of an exit plane of the light source device, where the optimized light paths of the single light sources are combined before entering in the light guiding element.

22. The illumination device according to claim 21, wherein colour filters or colour film-like amplitude distribution profiles are provided to optimize the amplitude distributions for the primary colours separately.

23. The illumination device according to claim 22, wherein the optimized amplitude distributions of the filters for the primary colours are exposed into a fine grain red-green-blue type microfiche material.

24. The illumination device according to claim 1, wherein a refractive spatial sampled prism matrix is provided at an exit plane of the light guiding and light decoupling structure.

25. The illumination device according to claim 1, wherein the light emanating from the light source device is at least partially coherent in one direction, or incoherent in either direction.

26. The illumination device according to claim 1, wherein the light decoupling element is a volume grating or other types of gratings.

27. The illumination device according to claim 1, wherein the light propagates in the light guiding element in a collimated manner in at least one direction.

28. The illumination device according to claim 1, wherein a reflective or light-transmissive spatial light modulator device is arranged downstream of the output coupling side of the illumination device in the direction of light propagation.

29. The illumination device according to claim 1, further comprising a photo detector array for measuring varying intensity distributions provided by the illumination device and/or an incidence angle of light onto a light decoupling element inside the illumination device.

30. A spatial light modulator device, which is illuminated by an illumination device according to claim 1.

31. The spatial light modulator device according to claim 30, comprising a photo detector array for measuring varying intensity distributions provided by the illumination device and/or an incidence angle of light onto a light decoupling element inside the illumination device.

32. The spatial light modulator device according to claim 31, wherein the photo detector array is formed as a grid and is arranged onto an absorptive area of the spatial light modulator device.

33. A display device comprising an illumination device according claim 1, where a spatial light modulator device is arranged downstream of the illumination device seen in the direction of light propagation.

7. (canceled)

34. A method for measuring and compensating local and/or temporal intensity distribution variations of light existing at an entrance plane of a spatial light modulator device and provided by an illumination device by:

Measuring of varying intensity distributions by means of a detector device as a part of the spatial light modulator device or of the illumination device, or arranged near the spatial light modulator device or the illumination device, whereby measured values for compensating of the varying intensity distributions are received;

Compensating of the varying intensity distributions by modifying the local transmission, which is the amplitude value, of the spatial light modulator device; and

Writing the compensated transparency values into the spatial light modulator device.

35. A method according to claim 34, wherein intensity distribution variations are measured indirectly by using the light which is not decoupled from the illumination device into the direction to the spatial light modulator.

36. A method according to claim 34, wherein additionally the angular distribution of the incident light is measured at the same time with the intensity distribution by using four quadrant photo detectors and arranging a grid of microlenses in front of the photo detectors.

37. A detector device for measuring local and/or temporal intensity distribution variations of light existing at an entrance plane of a spatial light modulator device and providing by an illumination device for applying a method according to claim 34.

38. A detector device according to claim 37, comprising a detector grid which is arranged onto absorptive areas of the spatial light modulator device or onto an exit plane of the illumination device.

39. A detector device according to claim 38, wherein the detector grid comprises semi-transparent or highly transparent photo detectors.

40. A detector device according to claim 38, wherein the detector grid comprises a light guiding grid or light guiding lines with defined “

couple in”

points.