Illumination device for synthesizing light from an object at virtually infinite distance

Patent metadata

Field	Value
Publication number	US-10267492-B2
Application number	US-201514711586-A
Country	US
Kind code	B2
Filing date	May 13, 2015
Priority date	Nov 14, 2012
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

An illumination device for synthesizing light from an object at virtually infinite distance comprises a primary light source configured to emit a primary light, a concentrator positioned downstream the primary light source and configured to reduce the divergence of the primary light, an emitting surface positioned downstream the concentrator, and an absorber made of light-absorbing material positioned upstream the emitting surface and configured to absorb light rays which cross the emitting surface in an upstream direction and which, in the absence of the absorber would not be directed toward the primary light source, wherein the primary light source, the concentrator, the emitting surface and the absorber are configured so that they produces from the primary light an output light that exits the emitting surface with a luminance profile which is spatially uniform across the emitting surface, and has a narrow peak in the polar-angle distribution around an output-light direction.

First claim

The invention claimed is:

1. An apparatus comprising:
an array of light sources configured to produce a plurality of primary diverging light beams extending generally along a light emitting direction, each light source having an extent in a direction perpendicular to the light emitting direction;
an array of collimators, with each collimator positioned downstream of a light source, wherein the array of collimators is configured to reduce a divergence of the primary diverging light beam to thereby form an array of collimated light beams configured to have a luminance with a peak in the polar-angle distribution along the light-emitting direction, the peak having an average half width at half maximum less than 10°;
an emitting surface that extends along x and y directions and is defined by the collimated light beams being uniformly and adjacently packed across the emitting surface, wherein an output beam is formed from the collimated light beams at the emitting surface that exits the emitting surface along an output-light direction, the emitting surface providing an output light that forms a virtual image at infinite distance; and
an array of absorbers between the emitting surface and the light source array, each of the absorbers including a light absorbing material and being configured to absorb ambient light that crosses the emitting surface apart from ambient light that returns to the respective light source.

2. The apparatus according to claim 1 , wherein:
a peak of a luminance of the output light at the emitting surface comprises an average half-width at half maximum value less than 5° ; and
the luminance outside the peak is lower than 10% of a maximum value L max for any polar angle greater than 3 times the average half-width at half maximum value.

3. The apparatus according to claim 1 , wherein the emitting surface comprises a total reflectance factor η r ≤0.4.

4. The apparatus according to claim 1 , wherein each collimator is positioned at its focal length from a respective primary light source along an optical axis which coincides with the output-light direction.

5. The apparatus according to claim 4 , wherein
each absorber includes a dark box, the dark box comprising an aperture where the respective collimator is positioned.

6. The apparatus according to claim 5 , wherein the internal surface of each dark box is formed by a light-absorbing material and the light-absorbing material comprises an absorption coefficient for visible light greater than 90%.

7. The apparatus according to claim 4 , further comprising a plurality of freeform optical elements, each freeform optical element associated with a primary light source and configured to flatten an illuminance distribution of the primary light onto the collimator, wherein the freeform optical element includes a lens or a reflective collimator.

8. The apparatus according to claim 4 , wherein each light source comprises a circular aperture.

9. The apparatus according to claim 1 , wherein:
the collimators are positioned so that they abut each other so that the array of collimators form a joint surface.

10. An artificial illumination device comprising an apparatus according to claim 1 and a Rayleigh scattering panel which is configured to scatter short-wavelength components of the impinging radiation with respect to the long-wavelength components, wherein said Rayleigh scattering panel is positioned downstream the apparatus.

11. A system made-up of a plurality of the apparatuses according to claim 1 , wherein the apparatuses are arranged relative to each other so that the directions of the output light from the apparatuses are the same.

12. The apparatus of claim 1 , wherein the light sources in the light source array are identical to each other and the collimators in the collimator array are identical to each other such that the array of collimated light beams is an array of substantially identical collimated light beams.

13. The apparatus of claim 1 , wherein the array of light sources includes a two-dimensional array of light sources that extends along a plane that is parallel with the x and y directions, the array of collimators is a two-dimensional array that extends along a plane that is parallel with the x and y directions, with each collimator aligning with a respective light source and offset in the z direction from the respective light source.

14. The apparatus of claim 1 , wherein each light source includes a light emitting diode having an extent in a direction perpendicular to the light emitting direction that is less than or equal to 3 millimeters (mm).

15. The apparatus of claim 1 , wherein a pitch of the array of light sources is less than or equal to 3 mm.

16. The apparatus of claim 1 , wherein each collimator includes a lens or a Fresnel lens.

17. The apparatus of claim 1 , wherein each collimator is antireflection coated.

18. An artificial illumination device comprising:
an apparatus according to claim 1 , and
an edge-lit diffusing panel lit by a secondary light source having a correlated color temperature (CCT) that is at least 1.2 times larger than a CCT of the light sources,
wherein the edge-lit diffusing panel is positioned downstream the apparatus.

19. The apparatus of claim 1 , wherein each collimator has a focal length that is at least ten times as large as the extent of the respective light source.

20. The apparatus of claim 1 , wherein the array of absorbers comprises a black sheet having an array of pin holes.

21. The apparatus of claim 1 , wherein the output light from the emitting surface has a luminance that:
varies in a portion of the emitting surface by less than 50% of an average value calculated over the portion of the emitting surface with respect to the output-light direction,
is substantially independent of an azimuthal direction measured relative to the output-light direction, and
has a dark background for observation directions corresponding to a polar angle outside the peak.

22. An illumination device for synthesizing light, the illumination device comprising:
a collimated light source comprising:
a plurality of primary light sources configured to emit primary light; and
a plurality of collimators, each collimator being associated with a primary light source, each collimator comprising a collimating lens and a concave reflector;
wherein each primary light source is positioned between a collimating lens and a concave reflector;
wherein the concave reflector is configured to focus the primary light from the primary light source in order to create a beam waist upstream of the collimating lens;

an absorbing layer comprising a plurality of pin holes, each pin hole positioned at the beam waist of primary light;
an emitting surface positioned downstream the collimated light source; and
wherein the plurality of the primary light sources and the collimators, the emitting surface, and the absorbing layer are configured so that they produce from the primary light an output light that exits the emitting surface along the output-light direction so that a bright spot is visible when viewing the output light exiting the emitting surface, and the bright spot moves relative to the emitting surface when the output light is viewed at different locations as if the bright spot stemmed from an object positioned at infinity.

23. The illumination device according to claim 22 , wherein:
each pin hole exhibits a circular shape.

24. The illum

Assignees

• Coelux Srl

Inventors

• Di Trapani Paolo

Classifications

• G02B6/0046

  Tapered light guide, e.g. wedge-shaped light guide · CPC title

• G02B19/0066

  in the form of an LED array · CPC title

• G02B6/0055

  Reflecting element, sheet or layer · CPC title

• G02B19/0014

  at least one surface having optical power · CPC title

• F21Y2115/10

  Light-emitting diodes [LED] · CPC title