High-uniformity limited-spread point spread function light emitter

• US 9,534,746 B2
• Filed: 06/04/2013
• Issued: 01/03/2017
• Est. Priority Date: 06/04/2012
• Status: Expired due to Fees

• Current Assignee: A.L. Whitehead Ltd.
• Original Assignee: A.L. Whitehead Ltd.
• Inventors: Whitehead, Lorne A.
• Primary Examiner(s): Neils, Peggy
• Assistant Examiner(s): GARLEN, ALEXANDER K
• Application Number:
  US14/404,249
• Publication Number:
  US 20150167904A1
• Time in Patent Office: 1,309 Days
• US Class Current: 1/1
• CPC Class Codes: F21K 9/62 using mixing chambers, e.g. housings with reflective walls
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133605 including specially adapted reflectors
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity
• CPC Class Codes: G09F 13/04 Signs, boards or panels, illuminated from behind the insignia
• CPC Class Codes: G09F 2013/222 with LEDs

Abstract

Simple yet powerful mathematical solutions are provided for producing a minimally-spreading de-pixelization light spread function with four-fold bilateral symmetry to create a High Dynamic Range LED-LCD display where the point spread functions of each LED regardless of intensity can be designed such that adjacent rows and columns of LEDs within an array blend smoothly and uniformly to create a non-pixelated continuous image in two dimensions on the diffuser screen and with minimal luminance overlap to minimize the computational demands required at video rate of an HDR display. The resulting image has substantially visually perfect uniform luminance, linear luminance and quadratic luminance gradient. Additionally a new display architecture is unveiled and described that emulates the mathematically developed light spread functions mentioned. This new architecture comprises several sub-aspects to tune the display device to the desired design requirements.

Claims

1. A light distribution system to produce a smoothly varying Lambertian luminance output on an output surface that emits light in a frontward direction towards the viewer, in one or more directions perpendicular to the frontward direction to form a two dimensional array of unit cells, each unit cell comprising:

a. a rear optical cavity further comprising;

i. one or more electric light sources,

ii. a rear surface with transmission less than about 5% and reflectance greater than about 70%,

iii. a plurality of side surfaces with transmission less than about 5% and reflectance greater than about 70%,

iv. a front Lambertian transmission surface having absorption less than about 20% and a Lambertian angular distribution for the transmitted light, wherein the front Lambertian transmission varies according to a predetermined transmission function T(x,y) having a four-fold bilateral symmetry in a square unit cell array or a six-fold bilateral symmetry in a hexagonal unit cell array to substantially match the symmetry of the unit cell array and wherein x and y) are measured from the center of the front Lambertian transmission surface;

b. a baffled diffusion cavity adjacent the rear optical cavity, the baffled diffusion cavity further comprising;

i. an optically clear medium in an interior region of the baffled diffusion cavity, the interior region of the baffled diffusion cavity defining a space having a thickness of about 30% of the width thereof, and

ii. a baffle with an optical transmission rate of less than about 5% located on each of the four sides of the baffled diffusion cavity, with at least one baffle having a thickness of about less than about 10% of the width of the cavity; and

c. a non-baffled diffusion cavity adjacent to the baffled diffusion cavity, the non-baffled diffusion cavity further comprising;

i. an optically clear medium, with a thickness of about 30% of the width of the cavity

ii. a front Lambertian light output surface having absorption less than about 20% and which by means of diffusion within the front Lambertian light output surface achieves a Lambertian angular distribution for the transmitted light and wherein the transmission percentage exceeds at least about 30%

wherein the transmission function T(x,y) is predetermined by a deterministic ray trace or an experimental optimization to minimize the visual perception of dis-uniformity arising from the combination of dis-uniform light output, dis-uniform linear gradient light output variation, and dis-uniform quadratic gradient light output variation; and

wherein the baffled diffusion cavity includes baffles with a first inner diffuse reflector layer and a second outer retro-reflective layer.

2. The light distribution system according to claim 1, wherein the one or more electric light sources are multi-colored.

3. The light distribution system according to claim 2, wherein the multi-colored electric light sources of said rear optical cavity include red, green and blue light emitting diodes.

4. The light distribution system according to claim 1, wherein the rear and side surfaces of said rear optical cavity are substantially inter-reflective such that the one or more electric light sources produce substantially similar spatial variation of output light.

5. The light distribution system according to claim 1, wherein the Lambertian transmission surface of the rear optical cavity further comprise titania or particles dispersed within a continuous polymer matrix, wherein the particles have a higher reflective index relative to the polymer matrix.

6. The light distribution system according to claim 1, wherein the unit cells are arranged in a square-like or hexagonal-like array.

7. The light distribution system according to claim 1, wherein the baffled diffusion cavity comprises baffles with a reflective or a retro-reflective surface.

8. The light distribution system according to claim 1, wherein components of the unit cell interact to produce a point spread function to substantially minimize de-pixelization light spread function for the two dimensional array.

9. The light distribution system according to claim 8, that achieves a point spread function that is a minimally-spreading de-pixelization light spread function for a two dimensional light emitting array further comprising a plurality of light emitting diodes within the rear cavity.

10. The light distribution system according to claim 1, further comprising a light modulating LCD panel adjacent to the front Lambertian light output surface disposed between a viewer and the front Lambertian light output surface.

11. The light distribution system according to claim 10, that further comprising light emitting diodes as the electric light sources in the rear cavity.

12. The light distribution system according to claim 11, wherein the light emitting diodes and LCD panel are produce a high dynamic range.

13. The light distribution system according to claim 1, wherein each unit cell is configured to provide a point spread function emitting more than about 30% light from the cell, more than about 60% light from a combination of the cell and one or more immediate neighbors, and more than about 90% light from a combination of the cell and adjacent neighbors.

14. The light distribution system according to claim 1, wherein each unit cell is configured to produce a point spread function that is a minimally-spreading de-pixelization light spread function for the two dimensional light emitting array.