Beam divergence and various collimators for holographic or stereoscopic displays

Patent metadata

Field	Value
Publication number	US-10295959-B2
Application number	US-201615191596-A
Country	US
Kind code	B2
Filing date	Jun 24, 2016
Priority date	Jul 6, 2010
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A holographic display with an illumination device, an enlarging unit and a light modulator. The illumination device includes at least one light source and a light collimation unit, the light collimation unit collimates the light of the at least one light source and generates a light wave field of the light that is emitted by the light source with a specifiable angular spectrum of plane waves, the enlarging unit is disposed downstream of the light collimation unit, seen in the direction of light propagation, where the enlarging unit includes a transmissive volume hologram realizing an anamorphic broadening of the light wave field due to a transmissive interaction of the light wave field with the volume hologram, and the light modulator is disposed upstream or downstream of the anamorphic enlarging unit, seen in the direction of light propagation.

First claim

The invention claimed is:

1. A holographic display comprising an illumination device, an enlarging unit and a light modulator, wherein:
the illumination device comprises at least one light source and a light collimation unit, the light collimation unit collimating the light of the at least one light source and generating a light wave field of the light that is emitted by the light source with a specifiable angular spectrum of plane waves, where the illumination device is designed as a line-shaped illumination device which generates a statistic, temporally variable spatial variation of the phase of the light;
the enlarging unit is disposed downstream of the light collimation unit, seen in the direction of light propagation, the enlarging unit comprising at least one volume hologram realizing a broadening of the light wave field due to an interaction of the light wave field with the volume hologram; and
the light modulator is disposed upstream or downstream of the enlarging unit, seen in the direction of light propagation.

2. The holographic display according to claim 1 , wherein the volume hologram is designed as a transmissive volume hologram.

3. The holographic display according to claim 1 , wherein an anamorphic broadening of the light wave field is realized by the enlarging unit.

4. The holographic display according to claim 1 , wherein the light wave field coming from the light collimation unit hits the volume hologram at a specifiable angle of incidence, which is not smaller than 70°.

5. The holographic display according to claim 1 , wherein a thickness of the volume hologram is chosen such that the light wave field comprises an angular distribution of wave vectors and that the maximum deviation of the angle distribution of wave vectors of the light wave field does not exceed a value of 1/20° in at least one direction.

6. The holographic display according to claim 1 , wherein a difference in optical path length z(x, y) of the light beams of the enlarged light wave field between two defined points on the light modulator does not exceed a predetermined value on the encoding surface of the light modulator at a given coherence length of the light so that the difference in optical path length is small enough that said light beams of the enlarged light wave field are still capable of generating interference.

7. The holographic display according to claim 1 , wherein the enlarging unit comprises a further volume hologram, which is disposed downstream of the volume hologram, seen in the direction of light propagation, and where the volume holograms of the enlarging unit are designed and disposed such that the light is deflected into two different directions, where the light modulator is disposed upstream or downstream of the further volume hologram, seen in the direction of light propagation.

8. The holographic display according to claim 7 , wherein the light collimation unit is followed in the direction of light propagation by two volume holograms such that they anamorphically broaden the light wave field with the defined angular spectrum of plane waves in two substantially perpendicular directions.

9. The holographic display according to claim 7 , wherein the volume holograms are off-axis volume holograms.

10. The holographic display according to claim 7 , wherein one of the volume holograms is designed such that it has a field lens function, in addition to its function as an enlarging element.

11. The holographic display according to claim 1 , wherein the light source comprises a laser, laser diode, LED or OLED.

12. The holographic display according to claim 1 , wherein a beam combiner is provided for combining the light of the at least one light source into a common optical fibre.

13. The holographic display according to claim 1 , wherein the light collimation unit comprises a primary collimation lens.

14. The holographic display according to claim 13 , wherein the primary collimation lens is followed in the direction of light propagation by an angular filter in the form of a volume hologram whose thickness is chosen such that the light wave field comprises an angular distribution of wave vectors and that a maximum deviation of the angle distribution of wave vectors of the light wave field does not exceed a value of 1/20° in at least one direction.

15. The holographic display according to claim 13 , wherein the light collimation unit comprises a first micro-lens array which is illuminated by a collimated light wave field.

16. The holographic display according to claim 15 , wherein a scattering device is disposed in a focal plane of the first micro-lens array, from which the light propagates to a first aperture stop which is situated immediately downstream of it.

17. The holographic display according to claim 16 , wherein apertures of the first aperture stop have asymmetric lateral extents in order to generate an angular spectrum of plane waves of the light wave field with specifiable coherence properties with regard to the respective lateral extent.

18. The holographic display according to claim 17 , wherein the apertures of the first aperture stop of the light collimation unit are dimensioned such that the coherence properties of the light wave field differ in two different directions such that the radiation is incoherent in the one direction, whereas it is sufficiently coherent in the other.

19. The holographic display according to claim 16 , wherein a second micro-lens array is disposed downstream of the first aperture stop in the direction of light propagation such that the apertures of the first aperture stop coincide with rear focal points of the corresponding micro-lenses of the second micro-lens array.

20. The holographic display according to claim 19 , wherein two further aperture stops are disposed between the first aperture stop and the second micro-lens array.

21. The holographic display according to claim 19 , wherein the second micro-lens array generates a segmented light wave field with an angular spectrum of plane waves with which a following light modulator which carries a holographic code is illuminated either directly or after lateral enlargement of the light wave field.

22. The holographic display according to claim 15 , wherein a shutter is disposed upstream of the first micro-lens array of the light collimation unit, seen in the direction of light propagation, where a transparency of multiple strip-shaped segments which run in the vertical or horizontal direction is controllable.

23. The holographic display according to claim 22 , wherein two strip-shaped segments of an illuminating light are switched on, respectively, which run vertically in the plane of the light modulator and which are movable time-sequentially in the horizontal or vertical direction between the edge of the light modulator and its centre.

24. The holographic display according to claim 15 , wherein selected lenses of a primary collimation lens array which is disposed upstream of the first micro-lens array of the light collimation unit are illuminated by a cascade of fibre-optic light sources which are switchable by fibre-optic switches.

25. The holographic display according to claim 24 , wherein passive light exits are provided at the ends of optical multi-mode fibres for illuminating selectable lenses of a primary collimation lens array which is disposed upstream of the first micro-lens array of the light collimation unit.

Assignees

• Seereal Tech S A

Inventors

• Futterer Gerald

Classifications

• G03H1/30

  discrete holograms only · CPC title

• G02F1/133621

  providing coloured light (G02F1/133617, G02F1/133533 take precedence) · CPC title

• G03H1/2286

  Particular reconstruction light (G03H1/24 takes precedence); Beam properties · CPC title

• G03H2001/2242

  Multiple viewing windows · CPC title

• G03H1/2294

  Addressing the hologram to an active spatial light modulator · CPC title