Directional backlights with light emitting element packages

• US 20150177447A1
• Filed: 11/11/2014
• Published: 06/25/2015
• Est. Priority Date: 11/15/2013
• Status: Active Grant

• Current Assignee: Reald Spark, LLC
• Original Assignee: RealD Incorporated
• Inventors: Woodgate, Graham J., Robinson, Michael G., Harrold, Jonathan
• Granted Patent: US 9,551,825 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 30/27 involving lenticular arrays
• CPC Class Codes: G02B 30/33 involving directional light or back-light sources
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0048 with stepwise taper
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0063 for extracting light out both the major surfaces of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/49113 the connectors connecting different bonding areas on the semiconductor or solid-state body to a common bonding area outside the body, e.g. converging wires
• CPC Class Codes: H01L 2224/85399 Material
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/49 of a plurality of wire connectors
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 25/167 : comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 27/15 : including semiconductor components having potential barriers, specially adapted for light emission
• CPC Class Codes: H01L 29/866 : Zener diodes
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2933/0066 : relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 2933/0075 : relating to heat extraction or cooling elements
• CPC Class Codes: H01L 33/486 : adapted for surface mounting
• CPC Class Codes: H01L 33/505 : characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/62 : Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H01L 33/642 : characterized by the shape
• CPC Class Codes: H01L 33/647 : the elements conducting electric current to or from the semiconductor body

Abstract

A light emitting diode package for a directional display may comprise light emitting diodes and a protection diode. The protection diode may be arranged in a well that is at a different location to the well that the light emitting diodes are arranged. The directional display may include a waveguide. The waveguide may include light extraction features arranged to direct light from an array of light sources by total internal reflection to an array of viewing windows and a reflector arranged to direct light from the waveguide by transmission through extraction features of the waveguide to the same array of viewing windows. The brightness of the directional display can be increased. An efficient and bright directional display system can be achieved. Efficient light baffling for light escaping from the edge of the waveguide is achieved through light deflecting extraction films.

Claims

1. A light emitting diode package for a directional display apparatus comprising:

a body of packaging material;

at least one light generation element arranged to generate light in an emission band; and

a protection diode;

wherein the at least one light generation element is arranged in a first well in said body, and the protection diode is not arranged in the first well.

2. A light emitting diode package according to claim 1, wherein the protection diode is arranged in a second well in said body.

3. A light emitting diode package according to claim 2, wherein the second well contains a protective material covering the protection diode.

4. A light emitting diode package according to claim 2, wherein the first well has lateral extents in first and second directions that are orthogonal to each other, the lateral extent in the first direction being greater than the lateral extent in the second direction, and the second well being displaced from the first well in the second direction.

5. A light emitting diode package according to claim 4, wherein the lateral extent of the first well in the second direction is less than 150% of the lateral extent of the light generation element in the second direction.

6. A light emitting diode package according to claim 4, comprising at least two light generation elements arranged as an array in the first direction.

7. A light emitting diode package according to claim 6, wherein the at least two light generation elements have the same lateral extent and position in the second direction.

8. A light emitting diode package according to claim 1, wherein the first well contains a material covering the at least one light generation element, which material is a transparent material or a wavelength conversion material arranged to convert at least some of the light in the emission band generated by the light generation element into light in a conversion band.

9. A light emitting diode package according to claim 8, wherein the material contained in the first well is said wavelength conversion material, the emission band being blue light and the conversion band being yellow light.

10. A light emitting diode package according to claim 8, wherein the material contained in the first well is said wavelength conversion material and is a phosphor or a quantum dot material.

11. A light emitting diode package according to claim 1, wherein the light emitting diode package further comprises:

at least two conductive heat slugs, the at least one light generation element being located on a first one of the heat slugs, the protection diode being located on a second one of the heat slugs, and the first and second heat slugs extending underneath the first well;

wire bonds connecting the at least one light generation element and the protection diode to the first and second heat slugs, the wire bonds that connect the at least one light generation element to the first and second heat slugs being located in the first well.

12. A light emitting diode package according to claim 1, wherein the light generation element is a semiconductor diode.

13. A light emitting diode package according to claim 1, further comprising a pair of walls extending outwardly from the body on opposite sides of the well, the walls forming a slot for receiving an input end of a waveguide, the protection diode being displaced from the first well laterally of the slot.

14. A light emitting diode array for a directional display apparatus, comprising:

a first array of light emitting diode packages, each being a light emitting diode package being arrayed linearly, the light emitting diode package comprising;

a body of packaging material;

at least one light generation element arranged to generate light in an emission band; and

a protection diode;

wherein the at least one light generation element is arranged in a first well in said body, and the protection diode is not arranged in the first well.

15. A light emitting diode array according to claim 14, wherein the ratio of the luminous emittance per unit length of the first array of light emitting diode packages to the lateral extent of the first wells orthogonal to the direction in which the light emitting diode packages are arrayed is greater than 15 lumens per mm².

16. A light emitting diode array according to claim 14, further comprising a second array of light emitting diode packages, the first and second arrays of light emitting diodes having luminous emittances per unit length that are different from each other.

17. A directional backlight for a directional display apparatus,

comprising:

a light emitting diode array, comprising;

a first array of light emitting diode packages, each being a light emitting diode package being arrayed linearly, the light emitting diode package comprising;

a body of packaging material;

at least one light generation element arranged to generate light in an emission band; and

a protection diode;

wherein the at least one light generation element is arranged in a first well in said body, and the protection diode is not arranged in the first well; and

a waveguide comprising an input end arranged to receive input light from the light emitting diode array at respective input positions, first and second, opposed guide surfaces for guiding input light along the waveguide, and a reflective end for reflecting input light back through the waveguide, the second guide surface being arranged to deflect light after reflection from the reflective end as output light through the first guide surface, and the waveguide being arranged to direct the output light into optical windows in output directions that are distributed in a lateral direction in dependence on the input position of the input light.

18. A directional backlight according to claim 17, wherein the first guide surface is arranged to guide light by total internal reflection and the second guide surface comprises a plurality of light extraction features oriented to direct light guided through the waveguide in directions allowing exit through the first guide surface as the output light and intermediate regions between the light extraction features that are arranged to guide light through the waveguide.

19. A directional backlight according to claim 18, wherein the first guide surface is arranged to guide light by total internal reflection and the second guide surface is substantially planar and inclined at an angle to direct light in directions that break that total internal reflection for outputting light through the first guide surface, and the display device further comprises a deflection element extending across the first guide surface of the waveguide for deflecting light towards the normal to the first guide surface.

20. A directional display apparatus comprising:

a directional backlight, comprising;

a light emitting diode array, comprising;

a first array of light emitting diode packages, each being a light emitting diode package being arrayed linearly, the light emitting diode package comprising;

a body of packaging material;

at least one light generation element arranged to generate light in an emission band; and

a protection diode;

wherein the at least one light generation element is arranged in a first well in said body, and the protection diode is not arranged in the first well; and

a waveguide comprising an input end arranged to receive input light from the light emitting diode array at respective input positions, first and second, opposed guide surfaces for guiding input light along the waveguide, and a reflective end for reflecting input light back through the waveguide, the second guide surface being arranged to deflect light after reflection from the reflective end as output light through the first guide surface, and the waveguide being arranged to direct the output light into optical windows in output directions that are distributed in a lateral direction in dependence on the input position of the input light; and

a transmissive spatial light modulator arranged to receive the output light from the first guide surface of the waveguide and to modulate it to display an image.

21. A method of forming an array of light emitting diode packages, the method using a linear holder comprising a slot capable of receiving a line of light emitting diode packages, the method comprising:

disposing the light emitting diode packages in the slot of the holder;

aligning the linear holder with an array substrate;

providing solder and thermal connection between the array of light emitting diode packages and the array substrate; and

removing the linear holder.

22. A method of forming an array of light emitting diode packages according to claim 21, wherein the light emitting diode packages have lugs arranged to provide a controlled spacing in the linear holder.

23. A directional backlight for a directional display apparatus, comprising:

an array of light sources;

a waveguide comprising an input end arranged to receive input light from the light emitting diode array at respective input positions, and first and second, opposed guide surfaces for guiding input light along the waveguide, the second guide surface being arranged to deflect light as output light through the first guide surface, and the waveguide being arranged to direct the output light into optical windows in output directions that are distributed in a lateral direction in dependence on the input position of the input light; and

an input end, front light shielding arrangement for shielding the light sources, comprising;

an extraction film strip extending across the first guide surface adjacent the input end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive light that leaks from the first guide surface while being guided along the waveguide, and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and

a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets.

24. A directional backlight according to claim 23, wherein the extraction film strip is absorptive for absorbing at least part of the received light.

25. A directional backlight according to claim 23, further comprising an input end, rear light shielding arrangement for shielding the light sources, comprising:

an extraction film strip extending across the second guide surface adjacent the input end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive light that leaks from the second guide surface while being guided along the waveguide and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and

a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets.

26. A directional backlight according to claim 23, wherein the waveguide further comprises a reflective end for reflecting input light back through the waveguide, the second guide surface being arranged to deflect light after reflection from the reflective end as said output light.

27. A directional backlight according to claim 26, further comprising a reflective end, front light shielding arrangement for shielding the light sources, comprising:

an extraction film strip extending across the first guide surface adjacent the reflective end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive light that leaks from the first guide surface while being guided along the waveguide, and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and

a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets.

28. A directional backlight according to claim 27, further comprising a reflective end, rear light shielding arrangement for shielding the light sources, comprising:

an extraction film strip extending across the second guide surface adjacent the input end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive light that leaks from the second guide surface while being guided along the waveguide and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and

a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets.

29. A directional backlight according to claim 23, wherein the mask of the or each light shielding arrangement is a layer formed on the outside surface of the extraction film strip.

30. A directional backlight according to claim 23, wherein the first guide surface is arranged to guide light by total internal reflection and the second guide surface comprises a plurality of light extraction features oriented to direct light guided through the waveguide in directions allowing exit through the first guide surface as the output light and intermediate regions between the light extraction features that are arranged to guide light through the waveguide.

31. A directional backlight according to claim 23, wherein

the first guide surface is arranged to guide light by total internal reflection and the second guide surface is substantially planar and inclined at an angle to direct light in directions that break that total internal reflection for outputting light through the first guide surface, and

the display device further comprises a deflection element extending across the first guide surface of the waveguide for deflecting light towards the normal to the first guide surface.

32. A directional display apparatus comprising:

a directional backlight, comprising;

a waveguide comprising an input end arranged to receive input light from the light emitting diode array at respective input positions, and first and second, opposed guide surfaces for guiding input light along the waveguide, the second guide surface being arranged to deflect light as output light through the first guide surface, and the waveguide being arranged to direct the output light into optical windows in output directions that are distributed in a lateral direction in dependence on the input position of the input light; and

an input end, front light shielding arrangement for shielding the light sources, comprising;

an extraction film strip extending across the first guide surface adjacent the input end, the extraction film strip comprising an array of alternating first and second facets, the first facets being oriented to receive light that leaks from the first guide surface while being guided along the waveguide, and the second facets being arranged to deflect the received light towards the normal to the first guide surface; and

a mask arranged outside the extraction film strip arranged to absorb the received light after deflection by the second facets; and

a transmissive spatial light modulator arranged to receive the output light from the first guide surface of the waveguide and to modulate it to display an image.

33. A directional display apparatus according to claim 32, wherein the mask of the input end, front light shielding arrangement is a portion of the spatial light modulator.