# US 2008/0186323 A1 · Converting a Three-Primary Input Color Signal into an N-Primary Color Drive Signal

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- Number: US 2008/0186323 A1
- Document ID: US20080186323A1
- Status: Published application
- Kind: A1
- Application number: 11/911,584
- Filed: 2006-04-19
- Published: 2008-08-07
- Earliest claimed: 2005-04-21
- Assignees: Koninklijke Philips Electronics N.V.
- Inventors: Oleg Belik; Gerben Johan Hekstra; Michiel Adriaanszoon Klompenhouwer; Erno Hermanus Antonius Langendijk
- Web page: https://patentgrep.com/patent/US20080186323A1

## CPC

- G09G 5/02: characterised by the way in which colour is displayed {(details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607)}
- G09G 2300/0452: Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
- G09G 2310/0235: Field-sequential colour display
- G09G 2340/06: Colour space transformation
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

A method of converting a three-primary input color signal (IS) comprising three input components (R, G, B) per input sample into an N-primary color drive signal (DS) comprising N≧4 drive components (D1, . . . , DN) per output sample for driving N sub-pixels (SP1, . . . , SPN) of a color additive display. The N sub-pixels (SP1, . . . , SPN) have N primary colors. The method comprises adding (10), to three equations defining a relation between the N drive components (D1, . . . , DN) and the three input components (R, G, B), at least one linear equation defining a value for a combination of a first subset of the N drive components (D1, . . . , DN) and a second subset of the N-drive components (D1, . . . , DN) to obtain an extended set of equations. The first subset comprises a first linear combination (LC1) of 1≦M1<N of the N drive components (D1, . . . , DN), and the second subset comprises a second linear combination (LC2) of 1≦M2<N of the N drive components (D1, . . . , DN). The first and the second linear combination are different. The method further comprises determining (10) a solution for the N drive components (D1, . . . , DN) from the extended set of equations.

## Claims

### Claim 1

A method of converting a three-primary input color signal (IS) comprising three input components (R, G, B) per input sample into an N-primary color drive signal (DS) comprising N≧4 drive components (D1, . . . , DN) per output sample for driving N sub-pixels (SP1, . . . , SPN) of a color additive display, the N sub-pixels (SP1, . . . , SPN) having N primary colors, the method comprises:
adding (10), to three equations defining a relation between the N drive components (D1, . . . , DN) and the three input components (R, G, B), at least one linear equation defining a value for a combination of a first subset of the N drive components (D1, . . . , DN) and a second subset of the N-drive components (D1, . . . , DN) to obtain an extended set of equations, and
determining (10) a solution for the N drive components (D1, . . . , DN) from the extended set of equations.

### Claim 2 (depends on 1)

A method as claimed in claim 1, wherein the first subset comprises a first linear combination (LC1) of 1≦M1<N of the N drive components (D1, . . . , DN), and the second subset comprises a second linear combination (LC2) of 1≦M2<N of the N drive components (D1, . . . , DN), wherein the first linear combination (LC1) for M1=1, and/or the second linear combination (LC2) for M2=1 comprises a single one of the N drive components (D1, . . . , DN) only, the first linear combination (LC1) defines a first value of the first subset, the second linear combination (LC2) defines a second value of the second subset, and wherein drive components (D1, . . . , DN) contributing to the second linear combination (LC2) do not contribute to the first linear combination (LC1) and the other way around.

### Claim 3 (depends on 2)

A method as claimed in claim 2, wherein M1 is equal to M and M2 is equal to N-M, and wherein the second linear combination (LC2) is subtracted from the first linear combination (LC1), and the value is substantially zero to obtain a substantially identical first and second linear combination.

### Claim 4 (depends on 3)

A method as claimed in claim 3, wherein a first set of the sub-pixels (SP1, . . . , SPN) associated with the first subset of the M drive components (D1, . . . , DM) and a second set of the sub-pixels (SP1, . . . , SPN) associated with the second subset of the N-M drive components (DM+1, . . . , DN) are adjacently positioned.

### Claim 5 (depends on 4)

A method as claimed in claim 4, wherein the first subset comprises a first drive component (D1), a second drive component (D2), and a third drive component (D3) for driving three non-white sub-pixels (SP1, SP2, SP3), and the second subset comprises a fourth drive component (D4) for driving a white sub-pixel (SP4).

### Claim 6 (depends on 5)

A method as claimed in claim 5, wherein the first input component (R), the second input component (G), and the third input component (B) of a same input sample of the three-primary input color signal (IS) are mapped to the adjacently positioned three non-white sub-pixels (SP1, SP2, SP3) and the white sub-pixel (SP4).

### Claim 7 (depends on 5)

A method as claimed in claim 5, wherein a particular input sample of a particular line of an input image defined by the three-primary input color signal (IS) is mapped to the three non-white sub-pixels (SP1, SP2, SP3), and wherein a further input sample adjacent to the particular input sample is mapped to the white sub-pixel (SP4).

### Claim 8 (depends on 5)

A method as claimed in claim 5, wherein a color point of the white sub-pixel (SP4) coincides with a white point of the three non-white sub-pixels (SP1, SP2, SP3).

### Claim 9 (depends on 4)

A method as claimed in claim 4, wherein the display (3) is a spectral sequential display wherein the first subset is displayed in a first frame and the second subset is displayed in a second frame succeeding the first frame.

### Claim 10 (depends on 9)

A method as claimed in claim 9, wherein the first subset comprises a first set of drive components (D1, . . . , DN) for driving a first set of sub-pixels (SP1, . . . , SPN), and wherein the second subset comprises a second set of drive components (D1, . . . , DN) for driving a second set of sub-pixels (SP1, . . . , SPN), the sub-pixels (SP1, . . . , SPN) of the second set having other primary colors than the sub-pixels (SP1, . . . , SPN) of the first set.

### Claim 11 (depends on 1)

A method as claimed in claim 1, wherein the N drive components (D1, . . . , DN) have valid ranges wherein their values are valid, and wherein the method further comprises:
determining (10) whether the determining (10) a solution of the extended set of equations provides a solution for values of the N drive components (D1, . . . , DN) which are valid, and if not,
clipping (10) at least one of the values of the N drive components (D1, . . . , DN) to the nearest border of the valid ranges.

### Claim 12 (depends on 11)

A method is claimed in claim 11, wherein N=4, the method further comprises:
defining (10) three functions (F1, F2, F3) representing three (D1, D2, D3) of the N drive components as a function of the remaining fourth one (D4) of the N drive components,
determining (10) a valid range (VR) of the fourth drive component (D4) wherein all the four of the N drive components (D1, D2, D3, D4) have valid values, and
clipping (10) the value of the fourth drive component (D4) to the nearest border (D4min, D4max) of the valid range (VR) of the fourth drive component (D4) if the solution provides a value of the fourth drive component (D4) outside the valid range (VR) of the fourth drive component (D4).

### Claim 13 (depends on 1)

A computer program product comprising a processor readable code to enable a processor (10) to execute the method of claim 1, the processor readable code comprising:
code for adding (10), to three equations defining a relation between the N drive components (D1, . . . , DN) and the three input components (R, G, B), at least one linear equation defining a value for a combination of a first subset of the N drive components (D1, . . . , DN) and a second subset of the N-drive components (D1, . . . , DN) to obtain an extended set of equations, and
code for determining (10) a solution for the N drive components (D1, . . . , DN) from the extended set of equations.

### Claim 14 (depends on 13)

A computer program product as claimed in claim 13, wherein the computer program product is a software plug-in in an image processing application.

### Claim 15

A system for converting a three-primary input color signal (IS) comprising three input components (R, G, B) per input sample into an N-primary color drive signal (DS) comprising N=4 drive components (D1, . . . , DN) per output sample for driving N sub-pixels (SP1, . . . , SPN) of a color additive display, the N sub-pixels (SP1, . . . , SPN) having N primary colors, the system comprising:
means for adding (10), to three equations defining a relation between the N drive components (D1, . . . , DN) and the three input components (R, G, B), at least one linear equation defining a value for a combination of a first subset of the N drive components (D1, . . . , DN) and a second subset of the N-drive components (D1, . . . , DN) to obtain an extended set of equations, and
means for determining (10) a solution for the N drive components (D1, . . . , DN) from the extended set of equations.

### Claim 16 (depends on 15)

A display apparatus comprising the system of claim 15, a signal processor (4) for receiving an input signal (IV) representing an image to be displayed to supply the three input components (R, G, B) to the system, and a display device (3) for supplying the N drive components (D1, . . . , DN) to sub-pixels (SP1, . . . , SPN) of the display device (3).

### Claim 17 (depends on 15)

A camera comprising the system of claim 15, and an image sensor supplying the three-primary color input signal (IS).

### Claim 18 (depends on 16)

A portable device comprising the display apparatus of claim 16.