Rendering luminance levels of a high dynamic range display

• US 7,821,474 B2
• Filed: 10/13/2006
• Issued: 10/26/2010
• Est. Priority Date: 10/13/2006
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Wei, Marcu, Gabriel G.
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): HARRIS, DOROTHY H
• Application Number:
  US11/549,544
• Publication Number:
  US 20080088647A1
• Time in Patent Office: 1,474 Days
• Field of Search: 345/690
• US Class Current: 345/4
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters

Abstract

Systems, methods, and computer software for use in driving a high dynamic range display involve generating table entries of luminance levels for a high dynamic range display and ordering the table according to the luminance levels. If the table includes multiple entries with equal values for a particular luminance level, one of the multiple entries is designated as corresponding to the luminance level.

Claims

1. A computer-implemented method comprising:

generating, by operation of a computer, entries of a table of luminance levels of a high dynamic range display, wherein the high dynamic range display includes a plurality of panels, with each panel having independently adjustable transmission levels, and each luminance level in the table corresponds to a particular combination of transmission levels for the panels of the high dynamic range display; and

ordering, by operation of a computer, the table according to the luminance levels, wherein the table includes multiple entries with substantially equal values for a luminance level;

designating one of the multiple entries to correspond to the luminance level according to a set of predetermined criteria; and

storing the table in a computer-readable storage medium for use in controlling a high dynamic range display.

2. The method of claim 1 wherein after designating one of the multiple entries, the method further comprises:

deleting the other multiple entries.

3. The method of claim 1 wherein the method further comprises:

indexing the table monotonically according to an index 0 to M, wherein M is a number of rows of entries in the table and corresponds to M possible luminance levels of the display.

4. The method of claim 1 wherein:

the display includes first and second panels;

the first panel has Na possible transmission levels; and

the second panel has Nb possible transmission levels.

5. The method of claim 4 wherein generating the entries of the table comprises:

measuring the luminance level of the display resulting from each combination of the transmission levels.

6. The method of claim 4 wherein generating the entries of the table comprises:

computing the luminance level of the display from each combination of the transmission levels;

wherein computing comprises using a luminance transfer function.

7. The method of claim 6 wherein the luminance transfer function is G(i,j)=Y(0)*Ta(i)*Tb(j)*C, wherein:

Y(0) is a luminance level of a backlight of the display;

C is a constant; and

G(i,j) is the luminance level corresponding to transmission levels Ta and Tb of the first and second panels, respectively, wherein;

Ta is denoted from Ta(0) to Ta(Na−

1) and indexed Ta(i), wherein 0≦

i≦

Na−

1; and

Tb is denoted from Tb(0) to Tb(Nb−

1) and indexed T(j), wherein 0≦

j≦

Nb−

1.

8. The method of claim 1 further comprising rendering the display to a luminance level according to a corresponding entry in the table.

9. The method of claim 1 further comprising generating a tone mapping correction between the ordered table and an output target function for the high dynamic range display.

10. The method of claim 9 wherein the tone mapping correction comprises gamma correction.

11. A computer program product, tangibly stored on a non-transitory computer-readable storage medium, to drive a high dynamic range display, comprising instructions operable to cause a programmable processor to:

generate entries of a table of luminance levels of a high dynamic range display, wherein the high dynamic range display includes a plurality of panels, with each panel having independently adjustable transmission levels, and each luminance level in the table corresponds to a particular combination of transmission levels for the panels of the high dynamic range display; and

order the table according to the luminance levels, wherein the table includes multiple entries with substantially equal values for a luminance level;

designate one of the multiple entries to correspond to the luminance level according to a set of predetermined criteria; and

store the table in a computer-readable storage medium for use in controlling a high dynamic range display.

12. The computer program product of claim 11 wherein after designating one of the multiple entries, the computer program product further comprises instructions operable to cause a programmable processor to:

delete the other multiple entries.

13. The computer program product of claim 11 further comprising instructions operable to cause a programmable processor to:

index the table monotonically according to an index 0 to M, wherein M is a number of rows of entries in the table and corresponds to M possible luminance levels of the display.

14. The computer program product of claim 11 wherein:

the display includes first and second panels;

the first panel has Na possible transmission levels; and

the second panel has Nb possible transmission levels.

15. The computer program product of claim 14 wherein generating the entries of the table comprises:

measuring the luminance level of the display resulting from each combination of the transmission levels.

16. The computer program product of claim 14 wherein generating the entries of the table comprises:

computing the luminance level of the display from each combination of the transmission levels;

wherein computing comprises using a luminance transfer function.

17. The computer program product of claim 16 wherein the luminance transfer function is G(i,j)=Y(0)*Ta(i)*Tb(j)*C, wherein:

Y(0) is a luminance level of a backlight of the display;

C is a constant; and

G(i,j) is the luminance level corresponding to transmission levels Ta and Tb of the first and second panels, respectively, wherein;

Ta is denoted from Ta(0) to Ta(Na−

1) and indexed Ta(i), wherein 0≦

i≦

Na−

1; and

Tb is denoted from Tb(0) to Tb(Nb−

1) and indexed T(j), wherein 0≦

j≦

Nb−

1.

18. The computer program product of claim 11 further comprising instructions operable to cause a programmable processor to:

render the display to a luminance level according to a corresponding entry in the table.

19. The computer program product of claim 11 further comprising instructions operable to cause a programmable processor to map the ordered table to an output target function.

20. A display comprising:

a light source;

first and second panels arranged such that light from the light source passes through the first and second panels in series, wherein;

the first panel includes Na possible transmission levels for a first color channel; and

the second panel includes Nb possible transmission levels for the first color channel;

a driver coupled to the first and second panels to drive the first and second panels to respective transmission levels according to entries of a table of luminance levels, with each entry in the table corresponding to a combination of respective transmission levels for the first and second panels, wherein a plurality of different possible combinations of transmission levels for the first and second panels produce luminance values that are substantially equal for the first color channel, and wherein, for the plurality of different possible combinations of transmission levels that produce luminance values that are substantially equal, the table of luminance values includes one combination of the plurality of different possible combinations of transmission levels for the first and second panels that is designated for the driver to use to produce the substantially equal luminance value for the first color channel.

21. The display of claim 20, wherein values of the transmission levels are stored as retrievable entries in a table on one or more machine-readable media.

22. The display of claim 20, wherein the driver comprises a luminance transfer function.

23. The display of claim 22, wherein the luminance transfer function is mapped to a gamma correction function.

24. The display of claim 22, wherein the luminance transfer function is G(i,j)=Y(0)*Ta(i)*Tb(j)*C, wherein:

Y(0) is a luminance level of a backlight of the display;

C is a constant; and

G(i,j) is the luminance level corresponding to transmission levels Ta and Tb of the first and second panels, respectively, wherein;

Ta is denoted from Ta(0) to Ta(Na−

1) and indexed Ta(i), wherein 0≦

i≦

Na−

1; and

Tb is denoted from Tb(0) to Tb(Nb−

1) and indexed T(j), wherein 0≦

j≦

Nb−

1.

25. A system comprising:

means for controlling a transmissivity level for each pixel location of a plurality of pixel locations on two or more display panels, with each display panel operable to realize a transmissivity level for each pixel location independently of a corresponding pixel location on the other display panel(s), wherein a set of corresponding pixel locations on the two or more display panels are operable to produce a combined luminance level for a pixel; and

means for storing a table of luminance level entries, each luminance level entry identifying a particular transmissivity level for each of the two or more display panels usable to produce a particular luminance for a particular color, wherein at least a portion of the luminance level entries are substantially equal to at least one other combination of transmissivity levels for the two or more display panels capable of producing the particular color at the same combined luminance level.

26. The system of claim 25 further comprising means for generating the table of luminance levels entries.

27. The system of claim 26 further comprising:

means for ordering the table by the luminance levels; and

means for designating one of multiple entries to correspond to a specific luminance level in cases where the table includes multiple entries with equal values for the specific luminance level.