Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1998-10-30
2001-07-17
Luu, Matthew (Department: 2672)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C345S022000, C345S204000, C358S515000, C358S518000, C358S519000
Reexamination Certificate
active
06262744
ABSTRACT:
The present invention is in the field of driving a display system comprising four or more primary colours (also referred to as primaries), based on a signal from a display generator comprising a smaller number of primaries. Thus a wider gamut is obtained for the colour representation on such a display system.
Classic cathode-ray tube technology allows us to reproduce colours on a display system with the aid of three primary colours, usually red (R), green (G) and blue (B). The maximum colour gamut of such a display system is defined by a triangle which is spanned in a CIE chromaticity diagram by the location of the colour coordinates of its three cathode ray tube phosphors R, G and B. This colour gamut, however, is always quite considerably smaller than the total visible colour space, and many colours occurring in nature can therefore not be represented on a classic display system. These colours are referred to as “out-of-gamut” colours.
This limited colour representation by means of a classic colour display system is one of the problems which, inter alia, only permits partial softproofing, i.e. the representation on a display system of what is to be printed. The aim, after all, is for the picture visible on the display system to correspond as closely as possible to the printed picture.
Other fields where a wider gamut is of interest for a display system are all those applications where the aim is to obtain as natural as possible a representation of an original as, for example, in the case of digital cinema, digital photography, printing systems for textiles etc.
These issues will become even more critical in future as a result of the increasing popularity of the wide gamut colours such as, for example, the so-called HIFI® colours. These employ colorants which are able to generate very highly saturated colours. These colours are always outside the colour gamut of a classic display system, and pictures with such a colour will consequently be represented very poorly on such a system.
Choosing a type of phosphor other than red, green or blue as the third primary colour for a classic display system permits some improvement of the colour representation in a particular region of the colour spectrum, but has the drawback that the colour representation in another region will become poorer. In fact, the result of this method is that the colour triangle, which represents the colour gamut of the display system, is simply shifted in the CIE chromaticity diagram.
Classic cathode-ray tubes comprising more than three primary colours might be able to provide a solution, but because of the low efficiency of an additional phosphor, as well as the more difficult deflection problems (four beams have to converge) this approach is not really feasible.
Existing application software mostly works with three primary colours, certainly as far as the display section is concerned. For high-end page layout systems, there are a number of solutions which are able to perform a separation in terms of four (CMYK, i.e. cyan, magenta, yellow and black) or more primaries as regards printing, for example as described in EP-A-0 586 139. With these systems the multidimensional conversions are very slow, and use has to be made of special hardware so as to considerably accelerate the algorithms. Such methods are not suitable for driving a display system comprising four or more primary colours, since they are too slow to allow the user to see an immediate result.
The international patent application WO 95/10160 describes a method for decoding a signal which describes a video picture as a function of a number of independent system primaries to produce a signal which describes the same video picture as a function of more independent display primaries.
A first step in the method described there consists in the various display primaries being selected in such a way that an improved colour gamut is obtained. Then, the signals entering the display need to be converted into signals for driving each of the selected display primaries. This is tantamount to solving a system with more unknowns than equations, which generally provides an infinite number of possible solutions for depicting a particular colour within the new gamut. So as to generate a unique set of drive voltages in accordance with the incoming signals, somewhat arbitrary additional conditions are imposed.
To this end, the colour polygon which specifies the colour gamut of the display comprising a plurality of primaries is split into overlapping and non-overlapping triangles which are formed by groups of three primaries at a time.
The use of non-overlapping triangles may cause problems if the implementation of the arithmetic units has not been carried out with sufficient accuracy. Noise may then cause rapid jumping between adjoining triangles.
To prevent this it is possible, according to said patent application, to employ overlapping triangles. Hysteresis is relied upon to ensure that jumping between different triangles (i.e. the driving of display primaries different from the original one, even if that is not strictly necessary) is prevented as far as possible.
The received video signal is converted, via matrix computations which are carried out in matrix units, into drive signals for each of the primaries which form a triangle, this being done for each of the triangles which make up the system. A logical unit is linked to each matrix unit and examines the output signals of each of them and selects a particular set which contains only positive drive signals. These drive signals are then used to drive the display primaries.
The matrix computations described in the above invention are very complex.
In BE-A-532363 is disclosed a method for realising a coloured picture by juxtaposition of different coloured images, which are each represented by different groups of display primaries, each group of display primaries being sufficient for representing almost each of the colours to be reproduced. In an example a signal has been coded which describes a picture as a function of three tristimulus values to produce a signal which describes the picture as a function of 9 independent display primaries. The 9 independent display primaries are divided into 3 trichromatic systems, each comprising three primary colours. Each primary colour for one trichromatic system is a secondary colour for each of the other trichromatic systems. For reproducing a colour by means of three trichromatic systems, three different reproductions are obtained, which are combined afterwards. This means that it may be possible that an “out-of-gamut” colour is not reproduced as accurately as it should, but that it is reproduced as an additive composition of different colours. Furthermore, for a system comprising 9 independent display primaries, 9 channels need be provided for transmitting the drive signals to a display. This means that the method described cannot be used on existing systems presenting only three channels for transmitting the drive signals.
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), or some other representation associated therewith, to produce a signal which describes the same picture as a function of four or more independent display primaries. The use of more than three display primaries has the advantage that a wider colour gamut is possible.
The present invention also relates to the coding device for applying the method for coding a signal as described hereinabove.
The coding device comprises calculating means for calculating drive signals for the display primaries thereby using a comparison of the location of each colour to be represented with respect to a straight line in the chromaticity diagram, each colour to be represented being given as a function of three tristimulus values. The calculating means deliver the drive signals, a number of which are mutually exclusive.
The coding device furthermore comprises k channels for transmitting the picture as a function of the n display primaries to
Barco N.V.
Luu Matthew
Pillsbury & Winthrop LLP
Sajous Wesner
LandOfFree
Wide gamut display driver does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wide gamut display driver, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wide gamut display driver will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2544186