Wide gamut display driver

• US 6,262,744 B1
• Filed: 10/30/1998
• Issued: 07/17/2001
• Est. Priority Date: 05/07/1996
• Status: Expired due to Term

• Current Assignee: Barco NV
• Original Assignee: Barco NV
• Inventors: Carrein, Geert
• Primary Examiner(s): Luu, Matthew
• Assistant Examiner(s): Sajous, Wesner
• Application Number:
  US09/182,523
• Time in Patent Office: 991 Days
• Field of Search: G09/G.502, G03/F.300, 345/431, 345/199, 345/153, 345/154, 345/150, 345/22, 345/156, 345/204, 345/205, 358/520, 358/518, 358/515, 358/519, 358/517, 382/167, 382/1.2, 349/57, 349/62, 349/95
• US Class Current: 345/604
• CPC Class Codes: H04N 11/00 Colour television systems details H04N9/00

Abstract

The present invention relates to a method for coding a signal which describes a picture as a function of three tristimulus values (X, Y, Z), to produce a signal which describes the picture as a function of n independent display primaries (R, G, B, D1, . . . , Dn−3), with n>3. In this method, for each color to be represented, drive signals for the display primaries (R, G, B, D1, . . . , Dn−3) are calculated via a comparison of the location of that color with respect to a straight line in the chromaticity diagram. A number of the drive signals are mutually exclusive.

The invention also relates to a display system comprising n display primaries, where n>3.

Claims

1. Method for coding a signal which describes a picture as a function of three tristimulus values (X, Y, Z) to produce a signal which describes the picture as a function of n independent display primaries (R, G, B, D1, . . . , Dn−

3), with n>

3, the method comprising;

dividing the display primaries in a group of principal primaries and a group of auxiliary primaries, the group of principal primaries and the group of auxiliary primaries being distinguished in that the group of principal primaries includes primaries chosen out of n display primaries (R, G, B, D1, . . . , Dn−

3), with n>

3;

defining a principal straight line for each set of two principal primaries;

calculating drive signals for the n display primaries via a comparison of a location of a colour to be represented with respect to a principal straight line in a chromaticity diagram; and

deciding which display primaries are to be driven for representing the colour based on the location of the colour with respect to the principal straight line, a plurality of the drive signals being mutually exclusive.

2. The method according to claim 1, including transmitting via k channels the picture as a function of the n display primaries to a display system, where k≦

n.

3. The method according to claim 2, including splitting the drive signals describing the picture to drive each of the n display primaries.

4. The method according to claim 2, including combining in at least one of the k channels the mutually exclusive drive signals by multiplexing in the time domain, wherein k<

n, and the mutually exclusive drive signals drive different display primaries.

5. The method according to claim 4, wherein the drive signals for the n display primaries comprise at least two rasters generated at a higher vertical frequency.

6. The method according to claim 4, wherein the multiplexing in the time domain comprises multiplexing successive mutually exclusive drive signals during successive vertical syncs.

7. The method according to claim 2, including combining in at least one of the k channels the mutually exclusive drive signals by multiplexing in the amplitude domain, wherein k<

n, and the mutually exclusive drive signals drive different display primaries.

8. The method according to claim 7, wherein the number of display primaries coded per channel comprises n/k, and the number of channels carrying more than n/k display primaries comprises (n mod k) channels.

9. The method according to claim 7, wherein the multiplexing in the amplitude domain comprises splitting the range of a signal on the at least one of the k channels into p parts by introducing p−

1 drive thresholds (TH1, TH2 ), each of the parts being allocated to one of the mutually exclusive drive signals.

10. The method according to claim 7, wherein the multiplexing in the amplitude domain comprises causing at least one of two maximum and two minimum drive signals of two display primaries to coincide at a drive threshold.

11. The method according to claim 7, wherein the multiplexing in the amplitude domain comprises digital coding.

12. The method according to claim 11, wherein the digital coding comprises coding to identify at least one of the mutually exclusive drive signals.

13. The method according to claim 1, including:

comparing a position to be represented and a position of an auxiliary primary with respect to a principal straight line associated with the auxiliary primary;

representing the position to be represented by three principal primaries if the positions are located on different sides of the principal straight line and if the auxiliary primary comprises an (n−

3)th auxiliary primary, or if the position to be represented is located on the principal straight line;

representing the position to be represented by the auxiliary primary and two principal primaries if the positions are located on the same side of the principal straight line and if one of a plurality of auxiliary primaries is associated with the principal straight line, the two principal primaries defining the principal straight line; and

multiplexing mutually exclusive drive signals if the number of display primaries exceed the number of channels for transmitting the picture as a function of the display primaries.

14. The method according to claim 13, wherein the multiplexing comprises multiplexing in the time domain.

15. The method according to claim 14, wherein the drive signals for the n display primaries comprise at least two rasters generated at a higher vertical frequency.

16. The method according to claim 14, wherein the multiplexing in the time domain comprises multiplexing successive mutually exclusive drive signals during successive vertical syncs.

17. The method according to claim 13, wherein the multiplexing comprises multiplexing in the amplitude domain.

18. The method according to claim 17, wherein the number of display primaries coded per channel comprises n/k, n being the number of display primaries and k being the number of channels for transmitting the picture as a function of the n display primaries, and the number of channels carrying more than n/k display primaries comprises (n mod k) channels.

19. The method according to claim 17, wherein the multiplexing in the amplitude domain comprises splitting the range of a signal on at least one of k channels into p parts by introducing p-1 drive thresholds (TH1, TH2), each of the parts being allocated to one of the mutually exclusive drive signals.

20. The method according to claim 18, wherein the multiplexing in the amplitude domain comprises causing at least one of two maximum and two minimum drive signals of two display primaries to coincide at a drive threshold.

21. The method according to claim 13, including choosing the principal primaries to distribute the auxiliary primaries as evenly as possible between the principal primaries.

22. The method according to claim 13, including mapping “

out-of-gamut”

colours onto an edge of a convex polygon formed by the n display primaries.

23. The method according to claim 13, including splitting the drive signals describing the picture to drive each of the n display primaries if the number of display primaries exceeds the number of channels.

42. The method according to claim 1, wherein the primaries chosen out of the n display primaries comprise primaries arbitrarily chosen out of the n display primaries.

24. A coding device for coding a signal which describes a picture as a function of three tristimulus values (X, Y, Z) to produce a signal which describes the picture as a function of n independent display primaries (R, G, B, D1, . . . , Dn−

3), with n>

3, the device comprising;

calculating means to calculate, for each colour to be represented as a function of three tristimulus values (X, Y, Z), drive signals for n display primaries (R, G, B, D1, . . . , Dn−

3), the display primaries being divided in a group of principal primaries and a group of auxiliary primaries, the group of principal primaries and the group of auxiliary primaries being distinguished in that the group of principal primaries includes primaries chosen out of the n display primaries, each set of two principal primaries to define a principal straight line, a chromaticity diagram to compare a location of a colour with respect to a principal straight line, a plurality of the drive signals being mutually exclusive, and

k channels to transmit the picture as a function of the n display primaries to a display system.

25. The coding device according to claim 24, wherein the number of k channels does not exceed the number of n display primaries.

26. The coding device according to claim 25, including at least one multiplexer to combine in the time domain mutually exclusive signals to drive different display primaries.

27. The coding device according to claim 26, wherein the at least one multiplexer is driven by control signals having a frequency higher than a repetition rate of the picture.

28. The coding device according to claim 26, wherein the at least one multiplexer combines mutually exclusive signals, the at least one multiplexer being driven by successive vertical syncs.

29. The coding device according to claim 25, including at least one multiplexer to combine in the amplitude domain mutually exclusive signals to drive different display primaries.

30. The coding device according to claim 29, wherein the at least one multiplexer is arranged and constructed to combine p mutually exclusive signals on at least one of the k channels, the coding device including:

splitting means to split the range of a signal on the at least one of the k channels into p parts by introducing p-1 drive thresholds, and

allocating means to allocate each of the parts of the channel to one of the mutually exclusive signals.

31. The coding device according to claim 29, including inverting means to cause at least one of two maximum and two minimum drive signals of two display primaries to coincide at a drive threshold.

32. The coding device according to claim 29, wherein the multiplexer comprises a digital multiplexer.

33. The coding device according to claim 32, including identification means to identify the mutually exclusive signals by identifying codes, the identifying codes being multiplexed into the drive signals.

34. The coding device according to claim 24, wherein the calculating means comprises:

conversion means to convert the coordinates of a colour point represented as a function of the three tristimulus values (X, Y, Z) into coordinates (x_i, y_i) in the chromaticity diagram,

selection means to select for each point in the chromaticity diagram the display primaries to represent the colour point, the selection being based on a comparison of the location of the colour point with respect to a principal straight line in the chromaticity diagram, the comparison to be used at least one of to calculate the drive signals for the display primaries and to calculate the display primaries to be driven for representing the colour, and

drive-calculating means to calculate the drive signals for each display primary, the drive-calculating means to receive at least one of the coordinates (x_i, y_i) of the colour point in the chromaticity diagram and an output of the selection means.

35. The coding device according to claim 34, including mapping means to map “

out-of-gamut”

colours onto an edge of an convex polygon formed by the n display primaries in the chromaticity diagram.

43. The coding device according to claim 24, wherein the primaries chosen out of the n display primaries comprise primaries arbitrarily chosen out of the n display primaries.

36. Display device comprising n display primaries, n>

3, suitable for receiving signals which are combined on one channel, the device comprising;

an input circuit to receive input signals, coded in a form of combined signals to drive n display primaries,

at least one splitter circuit to split the combined input signals into components to form n drive signals to drive the n display primaries, the at least one splitter circuit comprising means to invert at least one of the components of the combined input signals,

a display screen to display a picture, the display screen to use the n drive signals to drive the n display primaries.

37. The display device according to claim 36, wherein the at least one splitter circuit comprises a circuit arranged and constructed to clip the combined signals to a drive threshold.

38. The display device according to claim 36, including a wide gamut switch to switch between one of a standard colour display constructed and arranged to use three display primaries and a display system constructed and arranged to use n display primaries.

39. Display device comprising n primaries, n>

3, for receiving time-multiplexed signals, the device comprising;

an input circuit to receive input signals coded in a form of time-multiplexed signals to drive n display primaries,

a demultiplexing system to split information into drive signals for each of the display primaries, the demultiplexing system comprising means to invert at least one of the components of the time-multiplexed input signals,

a display screen to display a picture, the display screen to use the drive signals for each of the display primaries.

40. The display device according to claim 39, wherein the demultiplexing system is arranged and constructed to demultiplex mutually exclusive successive signals during successive vertical syncs.

41. The display device according to claim 39, including a wide gamut switch to switch between one of a standard colour display constructed and arranged to use three display primaries and a display system constructed and arranged to use n display primaries.