METHOD AND APPARATUS FOR BACKLIGHT SIMULATION

• US 20070124122A1
• Filed: 11/30/2006
• Published: 05/31/2007
• Est. Priority Date: 11/30/2005
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Freier, David
• Granted Patent: US 7,898,520 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: G06T 15/06 Ray-tracing
• CPC Class Codes: G06T 15/50 Lighting effects
• CPC Class Codes: G06T 15/506 Illumination models

Abstract

Computer-implemented methods of simulating backlights, and machine-readable media for carrying out such methods, are disclosed. The backlight may include a plurality of components, each component having at least one element. Some methods can include: tracing rays to an output plane of the backlight; collecting information from the traced rays to produce a first database containing spatial and directional information of the rays incident on the output plane; associating a probability function with the output plane; and calculating a second database containing spatial and directional information for rays exiting the output plane as a function of the probability function and the database. The output plane can if desired correspond to a stack of optical films, e.g., diffusing films, prismatic films, reflective polarizing films, turning films, and the like. Preferably, the probability function is a bi-directional scattering distribution function (BSDF) of the output plane.

Claims

1. A computer-implemented method of simulating a backlight, comprising:

tracing rays to an output plane of the backlight;

collecting information from the traced rays to produce a first database containing spatial and directional information of the rays incident on the output plane;

associating a probability function with the output plane; and

calculating a second database containing spatial and directional information for rays exiting the output plane as a function of the probability function and the first database.

2. The method of claim 1, wherein the probability function is a bi-directional scattering distribution function (BSDF) associated with at least one element of the backlight.

3. The method of claim 2, wherein the at least one element is selected from the group of a scattering element, a structured surface element, and a Lambertian element.

4. The method of claim 2, wherein the BSDF is associated with a plurality of elements.

5. The method of claim 4, wherein the BSDF is associated with a film stack.

6. The method of claim 1, wherein the tracing step includes tracing rays using at least one bi-directional scattering distribution function (BSDF) for at least one element of the backlight.

7. The method of claim 1, wherein the backlight has a film stack at the output plane and a light source, the method further comprising:

identifying a plurality of components of an optical path in the film stack that are suitable for representation by respective bi-directional scattering distribution functions (BSDFs);

acquiring the BSDFs of the components;

calculating a BSDF of the film stack from the component BSDFs, the film stack BSDF being the probability function associated with the output plane; and

acquiring a mathematical description of the light source;

wherein the tracing step traces rays from the light source according to the mathematical description thereof to the output plane; and

wherein the second database represents radiance as a function of location on the output plane.

8. The method of claim 7,

wherein the BSDF acquiring step comprises selecting the BSDFs of at least one component from a library of BSDFs.

9. The method of claim 8,

wherein the light source mathematical description acquiring step comprises selecting the light source mathematical description from a light source description library.

10. The method of claim 8, wherein:

the film stack BSDF calculating step comprises calculating the film stack BSDF from matrix representations of the component BSDFs, the calculating step also exploiting physical and/or electromagnetic reciprocal symmetries in at least some of the matrix representations being enforced and exploited.

11. The method of claim 7, wherein the BSDFs of the components and the BSDF of the film stack are each represented mathematically by a first matrix representing a reflection from above, a second matrix representing a transmission from above, a third matrix representing a reflection from below, and a fourth matrix representing a transmission from below.

12. The method of claim 11, wherein:

the first, second, third and fourth matrices all have a first dimension representing an incident direction, and a second dimension perpendicular to the first dimension representing an exiting direction; and

each entry in the four matrices represents a probability density that a ray incident with the incident direction will exit with the exiting direction.

13. The method of claim 7, wherein the BSDFs of the components and the BSDF of the film stack are location dependent.

14. The method of claim 1, wherein the second database represents brightness of the backlight at the output plane, the method further comprising displaying the calculated brightness on an output device.

15. A machine-readable media containing instructions to carry out the method of claim 1 on a computer system.

16. A computer-implemented method of simulating a backlight including a plurality of optical elements, the method comprising:

acquiring a first probability function of a first element of the backlight;

acquiring a second probability function of a second element of the backlight, the second probability function being different from the first probability function;

calculating a combined probability function using at least the first and second probability functions; and

tracing rays through the backlight using the combined probability function.

17. The method of claim 16, wherein the first probability function, the second probability function, and the combined probability function are all bi-directional scattering distribution functions (BSDFs).

18. The method of claim 16, wherein the first probability function, the second probability function, and the combined probability function are each represented mathematically by at least one matrix, and wherein a cell location within the at least one matrix represents an incident direction and an exiting direction.

19. The method of claim 18, wherein a cell value at the cell location is proportional to a probability that an incident ray having the incident direction is converted to an exiting ray having the exiting direction.

20. The method of claim 16, further comprising:

calculating brightness of the backlight from the rays traced in the tracing step; and

displaying the calculated brightness on an output device.

21. A machine-readable media containing instructions to carry out the method of claim 16 on a computer system.