JP2000305507A - Adjusting method and device for white point in digital color display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently adjust a white point in the maximum gradation and correct a blue shift of the white point in low gradation by a simple circuit in a digital color display system. SOLUTION: In the adjustment of a white point in the maximum gradation (namely white level), (1) inputted colors whose R, G and B have the maximum gradation value respectively are converted into a different tone of the color based on each conversion value of R, G and B set up by a user. (2) Other inputted colors are gradually decreased in their conversion values, the conversion value of the color whose values of R, G and B by a conversion A are zero, is made to zero, or the conversion value of the color whose values of R or G or B by a conversion B is zero, and is made to zero. In the adjustment of the white point in low gradation, (1) the inputted color whose values of R, G and B are zero, is converted into the different tone of the color based on each conversion value set up by the user. (2) The other inputted colors are gradually decreased in their conversion values, the conversion value of the color whose values of R, G and B are the maximum gradation value, is made to zero, or the conversion value of the color whose values of R or G or B is the maximum gradation value, is made to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for adjusting a white point in a digital color display system, and more particularly, to adjusting a white point (or white level) at a maximum gradation and a low gradation. The present invention relates to a method and apparatus for adjusting a white point in a digital color display system for adjusting a white point (that is, a black level).

[0002]

2. Description of the Related Art In a color display system such as an LCD or a CRT, it is ideal that colors that can be expressed are as close as possible to natural colors (color fidelity). In addition, the device can be adjusted automatically or manually by the user according to the environment such as the lighting where the device is placed, so that the optimum color can be displayed according to each environment (color calibration). It is also strongly desired that the same color can be output regardless of the output color device (color matching). These themes are collectively called color management, and are indispensable items for the next-generation and subsequent color display systems (especially high-performance models) in important fields where various research and development are being conducted. is there. Among them, the adjustment of the white point in display is an item that has been recognized as being important and has been actually realized on a color monitor or the like.

In general, there is a well-known xy chromaticity diagram for quantitatively treating all colors in the natural world. FIG. 1 shows an example of the xy chromaticity diagram. This is a coordinate point (chromaticity point)
The hue and the color saturation of the color are represented by the position of, and the entire range of the color perceived by the human eye is shown on and inside the horseshoe-shaped closed curve c in the figure. If points R, G, and B in the figure are points representing colors displayed only by the red, green, and blue primaries of a color display system, the coordinates of the colors obtained by mixing these three primaries. The point (X, Y) is as follows.

(Equation 1)

That is, in this color display, 3
All colors on and inside the sides of the square RGB can be represented by an appropriate mixture of R, G, and B. The maximum brightness white is usually a mixed color W when each R, G, B is set to the maximum brightness.
And is usually near the intersection of each midline of the triangle RGB. This W is the so-called white point at the maximum gradation, and each color display is designed so that this position is optimized. As an example, the white point at which white looks like white varies depending on the environmental illumination to be observed. White having a color temperature 3000 K to 4000 K higher than the color temperature of the illumination appears to be the most white. (Color temperature about 3000K) or white fluorescent lamp (color temperature about 4000K)
A report is known that recommends using a point at which a color temperature of 6500K does not cause redness or greenness as an optimal white point of a T-LCD. Based on these recommendations, adjust the values of the maximum luminance at points R, G, and B in FIG.
By changing the positions of the R, G, and B points, a more optimal white point is designed. For example, in the case of an LCD module, the spectral emission characteristics of the backlight and the transmission characteristics of the color filter are mainly used. Will be determined by

[0005] Although the white point is designed as an optimal value as described above, since this value is a fixed value, it still has the following problems. 1) The problem that the color of white differs depending on the environmental lighting: For example, if the white point is designed to have a color temperature of 7000K, it feels bluish under bulb light illumination of about 2800K and yellowish under daylight of 6500K. I will. 2) The problem that the preferred white point changes depending on the content of the display image (image): The desired white color differs between an application on MS-Windows and a photo or moving image. Photos are also affected by the circumstances in which they were created. 3) There are individual differences among users regarding the preference of white:
It is generally said that Japanese like bluish colors. It is also affected by visual disorders and differences in visual function. 4) There are manufacturing variations. Therefore, as a characteristic of the color display system, it is extremely significant that the user can adjust the white point (that is, white balance) of the maximum gradation in some way.

Another problem is that TFT / LC
Intermediate gradation (especially low gradation)
There is a so-called blue shift of the white point (blue shift). This is because when an achromatic color (R, G, and B have the same gradation value) is displayed on a TFT / LCD display device,
As the gradation value is lowered, the color becomes bluish (that is, the coordinates of the white point shift in the blue direction). This may be quite noticeable depending on the type of panel, and may be noticeable depending on the angle at which the user views the display (viewing angle). Therefore, it can be said that the adjustment of the white point of the intermediate gradation (low gradation) is meaningful if the user can perform the adjustment interactively.

[0007] Against this background, analog and analog
In LCDs and CRT color monitors having a video interface, a mechanism for allowing a user to adjust the white point of the maximum gradation has been adopted. That is, the level of any or all of the red, green, and blue analog signals sent from the host system is intentionally attenuated at a certain ratio to balance the mixing of the three. In other words, the color tone of white is adjusted. Although there is some difference in the execution method depending on the type of the monitor, the following method is adopted in a general analog video interface LCD monitor using an A / D converter.

FIG. 2 is a block diagram showing an example of an analog video interface LCD color monitor in which the digital processing unit is n bits / color.
Here, the A / D conversion rate of each A / D converter is shown in FIG.
As shown in (1), adjustment can be made separately for each A / D converter. That is, it is possible to set how much each of the maximum input voltage values of the analog R, G, and B (in this case, 0.7 V) correspond to the gradation values of the digital R, G, and B, respectively. This allows the host system to display Ra = Ga = Ba = 0.7, for example, to display white with maximum brightness.
When V (maximum voltage) is input to the monitor,
The conversion rate of green is 0.7V → L ′, and the conversion rate of blue is 0.7V → L (where L = 2 ⁿ −1, 0 <L ′ <
L), the LCD module has Rd
= Gd = L ', Bd = L digital R, G, B data will be input, and a bluish (higher color temperature) white is displayed on the LCD panel than the white value intended by the host system. Will be done.

[0009] Now, a digital / n-bit / color digital
Red, green, and blue values R of color data
d, Gd, Bd (where 0 ≦ Rd, Gd, Bd ≦ L = 2 ⁿ
-1, Rd, Gd, Bd: integers) are respectively R, G, B in a three-dimensional space formed by the RGB orthogonal coordinate axes shown in FIG.
Considering a point having each coordinate value (hereinafter also referred to as an “integer grid point” in some cases), an arbitrary color is represented by the cube O in FIG.
It can be made to correspond to any one of all the integer lattice points ( ³ (L + 1) in total) on and inside the surface of BMR-GCWY. The point W represents the color when the red, green, and blue have the maximum gradation value L, that is, the white with the maximum luminance. Each integer lattice point on the line segment OW is changed from black (point O) to white (point W). L + 1 stages up to the achromatic color (gray).
The meaning of the white point adjustment method described above is that A / D
Of the cube OB'M'R'-G'C'W'Y ', using the transformation time of the cube OBMR-GCWY, the color originally expressed using all the integer lattice points on and in the plane of the cube OBMR-GCWY. That is, the color conversion is performed so that the color is expressed only in the range of the surface and the inside.

[0010]

In the method described above, A
Naturally, it cannot be applied to an LCD monitor or the like of a digital video interface having no / D converter block. In fact, the video signal originally output as digital data from the graphics controller of the system unit is converted to analog and then converted again to digital for data handling by the LCD module (or a CRT monitor for digital processing). This is very inefficient in terms of parts cost and data error. Therefore, LVDS and TMDS (PanelLin
L) of a digital video interface using a low-voltage operation type digital data transmission system such as k).
CD monitors are becoming mainstream. Inside these, the video signals are all digital data until they are output from the graphics controller and input to the source driver of the LCD module. Notebook PCs are also all digital data.

If the above-mentioned white point adjustment is performed in such a digital color display system, conversion of R, G, and B digital data must be performed. The tone conversion method itself by converting digital color data is an expected converted value for a combination of input color values of many samples in order to bring the tone of the output color closer to the original color in a color printer or the like. Is given in advance as a table, and a conversion is performed based on the information (for example, Japanese Patent Application Laid-Open Nos. 7-99586 and 7-99586).
-99587). However, these conversion methods are generally very complicated and the circuit scale is extremely enormous, and the conversion is complicated, which may cause a conversion error. Furthermore, such a table system itself is inappropriate for the purpose of allowing the user to interactively and easily adjust the white point on a color display.

In the above-described method, it is expected that the color originally indicated by the point W is converted to the color indicated by the bluish point W ', as expected. All colors represented by points outside the rectangular parallelepiped, such as → R ′, G → G ′, and Y → Y ′, are all converted to colors on or inside the surface of the rectangular parallelepiped. In some applications, such as those that make extensive use of dither-like color expression, the conversion to this rectangular parallelepiped may be unavoidable.
In applications such as A-pictures that express colors in exactly n bits / color, this method reduces the maximum brightness of pure three primary colors (red, green, blue), yellow, cyan, magenta, etc. The number of colors that can be reduced is reduced, and it is impossible to make use of the prevailing n-bit / color multi-gradation.

Further, in the method described above, the TFT / LC
It has not been considered to correct the blue shift of the white point at a low gradation seen in a D monitor or the like.

A first object of the present invention is to solve the above-mentioned problems, and to adjust a white point of a maximum gradation and a white point of a low gradation (mainly a blue color point) in a digital color display system. It is an object of the present invention to provide a method and an apparatus for adjusting a white point in a digital color display system which can efficiently perform (correction of shift) with a simple circuit.

Further, a second object of the present invention is to solve the above-mentioned problem and to adjust the white point of the maximum gradation and the white point of the low gradation (mainly, the blue point adjustment) in the digital color display system. In the shift correction), a digital color system that can perform this adjustment with a simple circuit configuration without reducing the maximum luminance of pure three primary colors (red, green, and blue), yellow, cyan, and magenta. It is an object of the present invention to provide a method and apparatus for adjusting a white point in a display system.

[0016]

According to a first aspect of the present invention, there is provided a method for adjusting a white point in a digital color display system, comprising the steps of:
(1) An input color having a maximum gradation value for each of R, G, and B is converted into a color having a different color tone based on a conversion amount of each value of R, G, and B set by a user; For other input colors, the conversion amount is gradually reduced, and the conversion amount of a color in which the values of [Conversion A] R, G, and B are all 0 is 0.
Alternatively, [conversion B] is characterized in that the conversion amount of a color having a value of R, G, or B of 0 is zero.

Further, the second invention of the white point adjusting method in the digital color display system according to the present invention includes the following steps.
An input color having both G and B values of 0 is converted into a color having a different tone based on the conversion amount of each of the R, G, and B values set by the user. (2) For other input colors, The conversion amount is gradually reduced. [Conversion A] The conversion amount of a color in which the values of R, G, and B all have the maximum gradation value is set to 0, or [Conversion B] of R, G, or B The conversion amount of a color whose value is the maximum gradation value is set to 0.

Further, a white point adjusting apparatus in a digital color display system according to the present invention is an apparatus for executing the white point adjusting method in the digital color display system described above, wherein the core calc function is adjusted. : Conversion of line segments into integer values using Z = f (X, Y) is configured so that Z is output in a pipeline manner for inputs X and Y by hardware. It is.

According to the present invention, in adjusting the white point at the maximum gradation, (1) the input color having the maximum gradation value for each of R, G, and B is the value of each of the R, G, and B set by the user. (2) The conversion amounts are gradually reduced for the other input colors, and the values of [Conversion A] R, G, and B are all 0. In the principle that the amount of color conversion is 0, or that [Conversion B] the amount of conversion of a color having a value of R, G, or B of 0 is 0, or that a white point is adjusted at a low gradation, (1) An input color whose R, G, and B values are all 0 is converted to a color having a different color tone based on the conversion amount of each of the R, G, and B values set by the user; (2) Others For the input color of, the conversion amount is gradually reduced, and the value of [Conversion A] R, G, B is the color having the maximum gradation value. The conversion amount is 0, or [conversion B] is based on the principle that the conversion amount of a color whose R, G, or B value is the maximum gradation value is 0. By using a circuit block that uses an algorithm that approximates with an efficient amount of computation in terms of integer coordinates as the core, the digital color data that is input one after another in synchronization with the pixel clock is fixed. FIG. 3 shows a conversion formula and an example of a circuit configuration for converting the data through a number of clock cycles and outputting the data in a pipelined manner with a relatively simple circuit.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a description will be given of digital data conversion for realizing only white point adjustment of the maximum gradation. A digital value indicating an arbitrary color to be input is Rdi,
Gdi and Bdi, and the digital values of Rdo, Gdo and Bdo obtained by converting them by the conversion of the present invention are shown in FIG.
Is represented by the movement of an integer lattice point in the same RGB coordinate system. Rwm, Gwm and Bwm are respectively R
When di = Gdi = Bdi = L (= 2 ⁿ -1), the values are designated by the user of red, green, and blue, which are reduced by this conversion. That is, if Rdi = Gdi = Bdi = L (=
If 2 ⁿ −1), then Rdo = Rdi−Rwm = L−Rwm (0 ≦ Rwm ≦ L) Gdo = Gdi−Gwm = L−Gwm (0 ≦ Gwm ≦ L) Bdo = Bdi−Bwm = L−Bwm (0 ≤ Bwm ≤ L). After that, the following conversion A and conversion B are used as adjustment methods.
Divided into

Conversion A Conversion A in the white point adjustment of the maximum gradation is performed by the cubic OBMR-GCWY shown in FIG.
The integer lattice points on and in the plane of the rectangular parallelepiped OB'M'R'-G '
It is moved to an integer lattice point on and inside the plane of C'W'Y '. That is, if the values of Rdi are the same, the values are uniformly reduced and converted to Rdo regardless of the values of Gdi and Bdi, and the amount of reduction decreases as the value of Rdi decreases. Gd
The same applies to i and Bdi. This conversion is performed based on the following conversion formula. That is, first, based on Rwm, Gwm, and Bwm specified by the user, digital values Rw, Gw, and Rn that approximate the conversion amounts of R, G, and B for Rdi, Gdi, and Bdi.
Bw is obtained as follows using the core calc function f (X, Y). Rw = f (Rdi, Rwm) Gw = f (Gdi, Gwm) (3) Bw = f (Bdi, Bwm)

Next, from the obtained Rw, Gw, and Bw, Rdo, Gdo, and Bdo are obtained by adjusting the white point to be output according to the following equation.
Ask for do. Rdo = Rdi−Rw (0 ≦ Rw ≦ Rwm) Gdo = Gdi−Gw (0 ≦ Gw ≦ Gwm) (4) Bdo = Bdi−Bw (0 ≦ Bw ≦ Bwm) where the core / calc function f (X , Y), Z = f
When expressed as (X, Y), a triangle OA as shown in FIG.
Considering B, it is a function for obtaining a y-coordinate value Z of a point P whose x-coordinate value is X among integer lattice points located near the side OA. The core-calc function will be described later in detail.

Conversion B In the conversion B in the white point adjustment of the maximum gradation, in FIG. 8, the integer lattice points on and inside the cube OBMR-GCWY are converted into triangles W'BM, W'BC, W'GC, W'GY,
W'RY, W'RM, square OBMR, OBCG, ORY
It is moved to an integer lattice point substantially on and inside the irregular nine-sided object surrounded by G. Since the conversion of the integer lattice points is considered, it is not necessarily completely moved on and inside the surface of the nine-sided object, but the distance protruding from the surface is within one. That is, in FIG. 8, the point W is moved to W ′,
The movement amount gradually decreases as the value of Rdi, Gdi, or Bdi decreases, and the surface ORMB, OBCG, OGY
Points on R are not transformed at all. That is, the maximum luminance of pure three primary colors (red, green, and blue), yellow, cyan, magenta, and the like cannot be reduced.

This conversion is performed based on the following conversion formula. That is, first, based on Rwm, Gwm, and Bwm specified by the user, the digital values Rw, Gw, and Bw that approximate the conversion amounts of R, G, and B for Rdi, Gdi, and Bdi are converted to the core calc function f (X, Using Y), it is obtained as follows. Cmin = min (Rdi, Gdi, Bdi) (5) Rw = f (Cmin, Rwm) Gw = f (Cmin, Gwm) (6) Bw = f (Cmin, Bwm) where f (X, Y) ) Is the core calc function, the calculated Rw,
From Gw and Bw, Rdo, Gdo and Bdo are obtained by adjusting the white point to be output by the following equation. Rdo = Rdi−Rw (0 ≦ Rw ≦ Rwm) Gdo = Gdi−Gw (0 ≦ Rw ≦ Rwm) Bdo = Bdi−Bw (0 ≦ Bw ≦ Bwm)

This conversion formula means that in FIG. 9, a point X (Rdi, Gdi, Bd
When i) is on or in the plane of the quadrangular pyramid W-OGCB, it is Gdi when it is on or in the plane of the quadrangular pyramid W-ORYG, and when it is on or in the plane of the quadrangular pyramid W-OGCB. The conversion amount (decrease amount of each coordinate value) is determined based on each value of Rdi. FIG. 10 is an enlarged view of a grid point near point W of the cube.
The magnitude relation of the conversion amount Rw of the r coordinate value based on the above equations (5), (6), and (4) is represented by the number of circles attached to each grid point. From the nature of the core-calc function in equation (6), the Rt value of the adjacent grid point whose r coordinate value is smaller by 1 is the same or -1 with respect to a certain grid point. Larger grid points never overtake smaller grid points (although they may be in the same position). The same can be said for Gw and Bw. That is, the magnitude relationship between the color coordinate values before the conversion does not reverse in the conversion by the conversion B.

Next, a description will be given of digital data conversion for realizing only adjustment of a white point of low gradation. Similarly to the adjustment of the white point of the maximum gradation, the digital values indicating an arbitrary input color are Rdi, Gdi, and Bdi, and Rdo, Rdo,
The digital values of Gdo and Bdo are represented by the movement of integer grid points in the same RGB orthogonal coordinate system as in FIG.
Rbm, Gbm and Bbm are respectively Rdi = Gdi = Bdi = 0.
At this time, the value is increased by the conversion, and is a value specified by the user of red, green, and blue. That is, if Rdi = Gdi = Bdi = 0, then Rdo = Rdi + Rbm = Rbm (0 ≦ Rbm ≦ L) Gdo = Gdi + Gbm = Gbm (0 ≦ Gbm ≦ L) Bdo = Bdi + Bbm = Bbm (0 ≦ Bbm ≦ L) . After that, the following conversion A and conversion B are used as adjustment methods.
Divided into

Conversion A In the conversion A in the adjustment of the white point of the low gradation, in FIG. 11, the integer lattice points on and in the plane of the cube OBMR-GCWY are converted into the rectangular parallelepiped O "B" M "R" -G "C". WY "is converted into an integer lattice point on the surface and inside. If the values of Rdi are the same, they are uniformly increased and converted to Rdo regardless of the values of Gdi and Bdi. This conversion is performed based on the following conversion formula, that is, first, Rdi, Rbm, Gbm, and Bbm specified by the user. The digital values Rb, Gb, Bb approximated to the conversion amounts of R, G, B for Gdi, Bdi are converted to the core-calc function f
It is obtained as follows using (X, Y). Rb = f (L−Rdi, Rbm) Gb = f (L−Gdi, Gbm) (7) Bb = f (L−Bdi, Bbm) where L = 2 ⁿ −1

Next, from the obtained Rb, Gb, and Bb, Rdo, Gdo, and Bdo obtained by adjusting the blue shift of the white point to be output are obtained by the following equation. Rdo = Rdi + Rb (0 ≦ Rb ≦ Rbm) Gdo = Gdi + Gb (0 ≦ Gb ≦ Gbm) (8) Bdo = Bdi + Bb (0 ≦ Bb ≦ Bbm) Here, the core-calc function f (X, Y) is described above. Same as the example.

Conversion B In the conversion B in the adjustment of the white point of the low gradation, in FIG. 12, the integer lattice points on the surface and inside of the cube OBMR-GCWY are converted into triangles O "BM, O" BC, O "GC. , O "GY,
O "RY, O" RM, square WCBM, WCGY, WYR
It is moved to an integer lattice point substantially on and inside the irregular nine-sided object surrounded by M. In addition, since the conversion between the integer lattice points is considered, it is not necessarily moved completely on and inside the surface of the nine-sided object, but the distance protruding from the surface is one.
Within. That is, in FIG. 12, the point O is moved to O ", but the moving amount gradually decreases as the value of Rdi, Gdi, or Bdi increases, and the surfaces WCBM, WCGY, W
Points on the YRM are not moved at all.

This conversion is performed based on the following conversion formula. That is, first, based on Rbm, Gbm, and Bbm specified by the user, digital values Rb, Gb, and Bb that approximate the conversion amounts of R, G, and B for Rdi, Gdi, and Bdi are converted to the core calc function f (X, Using Y), it is obtained as follows. Cmax = max (Rdi, Gdi, Bdi) (9) Rb = f (LCmax, Rbm) Gb = f (LCmax, Gbm) (10) Bb = f (LCmax, Bbm) where , F (X, Y) are core calc functions, and L = 2 ⁿ −1. Rb, Gb, and Bb obtained by adjusting the white point to be output are obtained by the following equations from Rb, Gb, and Bb. Rdo = Rdi + Rb (0 ≦ Rb ≦ Rbm) Gdo = Gdi + Gb (0 ≦ Rb ≦ Rbm) Bdo = Bdi + Bb (0 ≦ Bb ≦ Bbm) This conversion formula is also based on the same concept as in the case of white point adjustment of maximum gradation. This conversion does not reverse the magnitude relationship of the color coordinate values before the conversion.

Next, a conversion formula for realizing both the adjustment of the white point of the maximum gradation and the adjustment of the white point of the low gradation will be described. As in the example described above, Rwm, Gwm, and Bwm are each Rdi.
When = Gdi = Bdi = L (= 2 ⁿ -1), the red, green, and blue values to be reduced by the conversion for adjusting the white point of the maximum gradation are designated. Also, Rbm, G
bm and Bbm specify red, green, and blue values that are increased by conversion for adjusting a low-gradation white point when Rdi = Gdi = Bdi = 0.
That is, if Rdi = Gdi = Bdi = L (= 2 ⁿ -1) Rdo = Rdi-Rwm = L-Rwm Gdo = Gdi-Gwm = L-Gwm Bdo = Bdi-Bwm = L-Bwm If Rdi = Gdi = If Bdi = 0, Rdo = Rdi + Rbm = Rbm Gdo = Gdi + Gbm = Gbm Bdo = Bdi + Bbm = Bbm (0 ≦ Rwm + Rbm ≦ L) (0 ≦ Gwm + Gbm ≦ L) (0 ≦ Bwm + Bbm ≦ L) After that, the following conversion A and conversion B are used as adjustment methods.
Divided into

Conversion A This is obtained by using the above equations (3) and (4) and equations (7) and (8)
Are obtained by combining Rw = f (Rdi, Rwm) Gw = f (Gdi, Gwm) Bw = f (Bdi, Bwm) and Rb = f (L-Rdi, Rbm) Gb = f (L-Gdi, Gbm) Bb = f (L−Bdi, Bbm) Here, the following Rdo, Gdo, and Bdo are obtained from L = 2 ⁿ −1. Rdo = Rdi−Rw + Rb (0 ≦ Rw ≦ Rwm, 0 ≦ Rb ≦ Rbm) Gdo = Gdi−Gw + Gb (0 ≦ Gw ≦ Gwm, 0 ≦ Gb ≦ Gbm) (11) Bdo = Bdi−Bw + Bb (0 ≦ Bw ≦ Bwm, 0 ≦ Bb ≦ Bbm) where f (X, Y) is a core calc function.

Conversion B This is obtained by using the above equations (5) and (6) and equations (9) and (1)
0). That is, Cmin = min (Rdi, Gdi, Bdi) Cmax = max (Rdi, Gdi, Bdi) and Rw = f (Cmin, Rwm) Gw = f (Cmin, Gwm) Bw = f (Cmin, Bwm) and Rb = f (LCmax, Rbm) Gb = f (LCmax, Gbm) Bb = f (LCmax, Bbm) However, the following Rdo, Gdo, Bdo are obtained from L = 2 ⁿ -1. Rdo = Rdi−Rw + Rb (0 ≦ Rw ≦ Rwm, 0 ≦ Rb ≦ Rbm) Gdo = Gdi−Gw + Gb (0 ≦ Gw ≦ Gwm, 0 ≦ Gb ≦ Gbm) Bdo = Bdi−Bw + Bb (0 ≦ Bw ≦ Bwm, 0 ≦ Bb ≦ Bbm) where f (X, Y) is a core calc function.

This is, as shown in FIG.
The integer lattice points on the surface and inside of MR-GCWY are defined as triangles W'BM, W'BC, W'GC, W'GY, W'RY, W'R.
M, O "BM, O" BC, O "GC, O" GY, O "RY,
It is moved to an integer lattice point almost on and inside the irregular dodecahedron surrounded by O "RM. Since conversion between integer lattice points is considered, it is not always necessary to move the lattice on and inside the dodecahedron. Although not completely moved, the distance protruding from the surface is within 1. That is, in FIG.
The point O is moved to O ", but the line segments BM, MR, R
Points on Y, YG, GC, CB are not moved at all. An achromatic input color (black / gray / white) is a line segment O
The integer lattice points on W are converted into colors represented by integer lattice points near the line segment O "W '.

Next, an example of the core calc function f (X, Y) used in the above-described method of adjusting the white point in the digital color display system of the present invention will be described. That is, in the present invention, when a straight line in the orthogonal two-dimensional coordinate system is approximated to a point having integer coordinates, it is composed of the origin O (0, 0), point A (L, Y), and point B (L, 0). Considering a triangle OAB, a point located near the side OA such that each coordinate value is an integer (hereinafter referred to as an “integer grid point”)
), The y coordinate value Z of the point P whose x coordinate value is X
From the following core calc function: f (X, Y). Z = f (X, Y) where 0 ≦ X ≦ L, 0 ≦ Y ≦ L, X, Y: integer L = 2 ⁿ −1, n ≧ 1, n: integer where the following conditions are satisfied: I) f (0,0) = 0 and for any Y, f (L,
Y) = Y, ii) for any 0 ≦ X <L, for any Y, f (X + 1, Y) = f (X, Y) +0 or f (X + 1, Y) = f (X, Y) +1 Iii) f (X, Y + 1) = f (X, Y) +0 or f (X, Y + 1) = f (X, Y) +1 for any 0 ≦ Y <L and for any X, and iv ) An output Z is always obtained after a certain calculation step for any input X, Y. The applicant has filed another application for details of the core-calc function.

Next, an example of a circuit for realizing the white point adjusting method in the above-described digital color display system of the present invention will be described. FIG. 5 is a diagram showing a digital color data conversion block according to the present invention in an n-bit / color digital color display system. In the example shown in FIG. 5, the input bus signals Rdi, G to the Block-CA
di and Bdi are the pixel clock (PIX_CLK), respectively.
The color data of the red, green, and blue sub-pixels successively sent from the host system in synchronization with the sub-pixels is transmitted. Similarly, VSYdi, HSYdi, and DISPdi are the horizontal sync (Horizontal Synch) and vertical sync (Vertical Sync) sent from the host system, respectively.
h) and display timing (Display Timing). The input bus signals Rwm, Gwm, and Bwm are setting inputs for adjusting the white point of the maximum gradation, and Rbm, Gbm, and Bbm are setting inputs for adjusting the white point of the low gradation. These are all outputs of n-bit latches, and the values of these latches are set by the user from outside the system. Further, CONV_A is a setting input for designating which of the above-described conversion A and conversion B is to be selected.
When NV_A = "High", conversion A is selected.

The Block-CA calculates the values of these Rdi, Gdi, and Bdi for each pixel clock period as Rwm, Gwm, and Bw.
With reference to the values of m, Rbm, Gbm, and Bbm, conversion is performed according to the above-described conversion formula for white point adjustment, and signals Rdo, Gdo, and Bdo that are also synchronized with the pixel clock after a delay corresponding to the Dca clock cycle. As a pipeline output. VSYdi, HSYdi, and DISPdi are simply delayed by the Dca clock, and VSYdo, HSYdo, and DISPdi, respectively.
Output as do. FIG. 17 is a timing chart showing the relationship between these input / output signals.

For example, when assuming an LCD module of an LVDS video interface as a digital color display system, the Block-CA is shown in FIG.
As shown in FIG.
It will be located between the DS receiver macro and the conventional LCD control logic.

Next, a block diagram of logic constituting the Block-CA shown in FIG. 5 is shown. First, FIG. 14 shows an example of a circuit configuration that realizes only the white point adjustment at the maximum gradation described above. In this circuit, whether to use conversion A or conversion B is input
Select with CONV_A. Block-CC is a circuit block that realizes the core calc function (Core Calculation Functio
n Block), and the pipeline stage number of this block is D
ccf. Next, FIGS. 15 and 16 show circuit configuration examples for realizing both the white point adjustment at the maximum gradation and the white point adjustment at the low gradation. In this circuit, CONV_A selects whether to use the conversion A or the conversion B for both the white point adjustment at the maximum gradation and the white point adjustment at the low gradation. FIG.
Is a breakdown of Block-MAX & MIN represented as Black Box in FIG. In FIG. 15, the Core Calculation F
Since the number of pipeline stages of the unction block is Dccf, the number of pipeline stages of the entire Block-WA is Dccf from the figure.
+3 stages.

[0040]

As is apparent from the above description, according to the present invention, in the digital color display system, the adjustment of the white point at the maximum gradation and the adjustment of the white point at the low gradation are performed. The adjustment (mainly for the correction of the blue shift) can be performed as digital data by using the core calc function, and the method can be performed in real time by a simple circuit ( Conversion A and conversion B). Also, in a digital color display system, the adjustment of the white point at the maximum gradation and the adjustment of the white point at the low gradation (mainly for correction of the blue shift) are performed by a pure 3 point. This can be performed without reducing the maximum luminance of primary colors (red, green, blue), yellow, cyan, magenta, and the like (conversion B).
When the conversion A and the conversion B are compared, the conversion B can express a color closer to the actual color. However, for example, when an image is displayed dithering, the conversion A is more realistic. It becomes a color close to.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an xy chromaticity diagram.

FIG. 2 is a diagram showing an example of an analog video interface LCD color monitor in which the digital processing unit is n bits / color.

FIG. 3 is a diagram illustrating an example of adjustment of an A / D conversion rate in an A / D converter.

FIG. 4 is a diagram for explaining adjustment (conversion A) of a white point of the maximum gradation on the RGB orthogonal coordinate axis.

FIG. 5 is a diagram showing an example of a digital color data conversion block in a digital color display system.

FIG. 6 is a diagram showing an example of an LCD module of an LVDS video interface.

FIG. 7 is a diagram for explaining the concept of a core-calc function.

FIG. 8 is a diagram for explaining adjustment (conversion B) of a white point of the maximum gradation on the RGB orthogonal coordinate axis.

FIG. 9 shows an input color X on an RGB orthogonal coordinate axis.
(Rdi, Gdi, Bdi).

FIG. 10 is an enlarged view of a lattice point near a point W of the cube shown in FIG. 9;

FIG. 11 is a diagram for explaining adjustment (conversion A) of a white point at a low gradation on an RGB orthogonal coordinate axis.

FIG. 12 is a diagram for explaining adjustment (conversion B) of a white point at a low gradation on an RGB orthogonal coordinate axis.

FIG. 13 is a diagram for explaining an example of performing both white point adjustment (conversion B) at the maximum gradation and white point adjustment at the low gradation on the RGB orthogonal coordinate axes.

FIG. 14 is a diagram illustrating an example of a configuration of a circuit that realizes only white point adjustment at the maximum gradation.

FIG. 15 is a diagram illustrating an example of a circuit that realizes both white point adjustment at the maximum gradation and white point adjustment at the low gradation.

16 is a diagram illustrating a configuration of an example of Block-MAX & MIN illustrated in FIG. 15;

FIG. 17 is a diagram showing an example of a timing chart showing a relationship between input and output signals.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 2, 2000 (200.2.2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 3

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 7

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

This conversion is performed based on the following conversion formula. That is, first, based on Rwm, Gwm, and Bwm specified by the user, the digital values Rw, Gw, and Bw that approximate the conversion amounts of R, G, and B for Rdi, Gdi, and Bdi are converted to the core calc function f (X, Using Y), it is obtained as follows. Cmin = min (Rdi, Gdi, Bdi) (5) Rw = f (Cmin, Rwm) Gw = f (Cmin, Gwm) (6) Bw = f (Cmin, Bwm) where f (X, Y) ) Is the core calc function, the calculated Rw,
From Gw and Bw, Rdo, Gdo and Bdo are obtained by adjusting the white point to be output by the following equation. Rdo = Rdi−Rw (0 ≦ Rw ≦ Rwm) Gdo = Gdi−Gw (0 ≦ Gw ≦ Gwm) Bdo = Bdi−Bw (0 ≦ Bw ≦ Bwm)

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

This conversion formula means that in FIG. 9, a point X (Rdi, Gdi, Bd
When i) is on or in the plane of the four-sided pyramid W-ORMB, Gdi is when it is on or in the plane of the four-sided pyramid W-ORYG, and when it is on or in the plane of the four-sided pyramid W-OGCB. The conversion amount (decrease amount of each coordinate value) is determined based on each value of Rdi. FIG. 10 is an enlarged view of a grid point near point W of the cube.
The magnitude relation of the conversion amount Rw of the R coordinate value based on the above equations (5), (6), and (4) is represented by the number of circles attached to each grid point. According to the nature of the core-calc function in the equation (6), the Rw value of the adjacent grid point whose R coordinate value is smaller by 1 is the same or -1 with respect to a certain grid point. Larger grid points never overtake smaller grid points (although they may be in the same position). The same can be said for Gw and Bw. That is, the magnitude relationship between the color coordinate values before the conversion does not reverse in the conversion by the conversion B.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0030

[Correction method] Change

[Correction contents]

This conversion is performed based on the following conversion formula. That is, first, based on Rbm, Gbm, and Bbm specified by the user, digital values Rb, Gb, and Bb that approximate the conversion amounts of R, G, and B for Rdi, Gdi, and Bdi are converted to the core calc function f (X, Using Y), it is obtained as follows. Cmax = max (Rdi, Gdi, Bdi) (9) Rb = f (LCmax, Rbm) Gb = f (LCmax, Gbm) (10) Bb = f (LCmax, Bbm) where , F (X, Y) are core calc functions, and L = 2 ⁿ −1. Rb, Gb, and Bb obtained by adjusting the white point to be output are obtained by the following equations from Rb, Gb, and Bb. Rdo = Rdi + Rb (0 ≦ Rb ≦ Rbm) Gdo = Gdi + Gb (0 ≦ Gb ≦ Gbm) Bdo = Bdi + Bb (0 ≦ Bb ≦ Bbm) This conversion formula is also based on the same concept as the case of the white point adjustment of the maximum gradation. This conversion does not reverse the magnitude relationship of the color coordinate values before the conversion.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

Next, an example of the core calc function f (X, Y) used in the above-described method of adjusting the white point in the digital color display system of the present invention will be described. That is, in the present invention, when a straight line in the orthogonal two-dimensional coordinate system is approximated to a point having integer coordinates, it is composed of the origin O (0, 0), point A (L, Y), and point B (L, 0). Considering a triangle OAB, a point located near the side OA such that each coordinate value is an integer (hereinafter referred to as an “integer grid point”)
), The y coordinate value Z of the point P whose x coordinate value is X
From the following core calc function: f (X, Y). Z = f (X, Y) where 0 ≦ X ≦ L, 0 ≦ Y ≦ L, X, Y: integer L = 2 ⁿ −1, n ≧ 1, n: integer where the following conditions are satisfied: I) For any Y, f (0, Y) = 0 and f (L,
Y) = Y, ii) for any 0 ≦ X <L, for any Y, f (X + 1, Y) = f (X, Y) +0 or f (X + 1, Y) = f (X, Y) +1 Iii) f (X, Y + 1) = f (X, Y) +0 or f (X, Y + 1) = f (X, Y) +1 for any 0 ≦ Y <L and for any X, and iv ) An output Z is always obtained after a certain calculation step for any input X, Y. The applicant has filed another application for details of the core-calc function.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction contents]

Next, a block diagram of logic constituting the Block-CA shown in FIG. 5 is shown. First, FIG. 14 shows an example of a circuit configuration that realizes only the white point adjustment at the maximum gradation described above. In this circuit, whether to use conversion A or conversion B is input
Select with CONV_A. Block-CC is a circuit block that realizes the core calc function (Core Calculation Functio
n Block), and the pipeline stage number of this block is D
ccf. Next, FIGS. 15 and 16 show circuit configuration examples for realizing both the white point adjustment at the maximum gradation and the white point adjustment at the low gradation. In this circuit, CONV_A selects whether to use the conversion A or the conversion B for both the white point adjustment at the maximum gradation and the white point adjustment at the low gradation. FIG.
Is Block-MAX & MI shown as a black box in Fig.15
N breakdown. In FIG. 15, Core Calcul
Since the number of pipeline stages of the ation Function Block is Dccf, the number of pipeline stages of the entire Block-CA is Dccf + 3 from the figure.

[Procedure amendment 8]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 9]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

[Procedure amendment 10]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

[Procedure amendment 11]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

[Procedure amendment 12]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 14

[Procedure amendment 13]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Karube 1623-14 Shimotsuruma, Yamato-shi, Kanagawa Japan F-term in the Yamato Office of IBM Japan, Ltd. HA02 KE16 KE19 KM13 5C080 AA10 BB05 BB10 CC03 DD03 DD30 EE28 FF09 JJ02 JJ04 JJ05 5C082 AA01 AA02 AA13 BA34 BA35 BD01 BD02 CA12 CA85 CB08 DA51 EA20 MM09 MM10

Claims (8)

[Claims] In the adjustment of a white point (that is, a white level) at a maximum gradation, (1) an input color having a maximum gradation value for each of R, G, and B is set to R, G, and B set by a user. Based on the conversion amount of each value, convert to different shades of color,
(2) For other input colors, the conversion amount is gradually reduced, and [Conversion A] The conversion amount of a color in which the values of R, G, and B are all 0 is set to 0, or [Conversion B] A method for adjusting a white point in a digital color display system, wherein a conversion amount of a color having a value of R, G, or B of 0 is set to 0. 2. A method for adjusting a white point (that is, a white level) at a maximum gradation according to claim 1, wherein the white point is set by a user. Assuming that the amounts are Rwm, Gwm, and Bwm, Rd, Gdo, and Bdo that indicate the color whose white point has been adjusted are output from Rdi, Gdi, and Bdi that indicate the input arbitrary color.
R, Gdi, Bdi R, G, B based on m, Gwm, Bwm
Digital values Rw, Gw, B approximating each conversion amount
w is calculated based on the following conversion formula: Rw = f (Rdi, Rwm) Gw = f (Gdi, Gwm) Bw = f (Bdi, Bwm) where f (X, Y) is a core-calc function. Rw,
Rdo = Rdi−Rw (0 ≦ Rw ≦ Rwm) Gdo = Gdi−Gw (0 ≦ Gw ≦ Gwm) Bdo = Bdi−Bw (0 ≦ Bw ≦ Bwm) from Gw and Bw to output Rdo, Gdo and Bdo A method for adjusting a white point in a digital color display system. 3. A method of adjusting a white point (ie, white level) at the maximum gradation according to claim 1, wherein the white point is adjusted by using a conversion B, wherein the white point set by a user is reduced. Assuming that the amounts are Rwm, Gwm, and Bwm, Rd, Gdo, and Bdo that indicate the color whose white point has been adjusted are output from Rdi, Gdi, and Bdi that indicate the input arbitrary color.
R, Gdi, Bdi R, G, B based on m, Gwm, Bwm
Digital values Rw, Gw, B approximating each conversion amount
w is obtained based on the following conversion formula: Cmin = min (Rdi, Gdi, Bdi) Rw = f (Cmin, Rwm) Gw = f (Cmin, Gwm) Bw = f (Cmin, Bwm) where f ( X, Y) are the core calc function, the obtained Rw,
Rdo = Rdi−Rw (0 ≦ Rw ≦ Rwm) Gdo = Gdi−Gw (0 ≦ Rw ≦ Rwm) Bdo = Bdi−Bw (0 ≦ Bw ≦ Bwm) from Gw and Bw to output Rdo, Gdo and Bdo A method for adjusting a white point in a digital color display system. 4. In adjusting a white point (that is, a black level) in a low gradation, (1) an input color in which the values of R, G, and B are all 0 is set for each of R, G, and B set by the user. Based on the conversion amount of the value, the color is converted into a different color tone, and (2) the conversion amount is gradually reduced for the other input colors.
[Conversion A] The conversion amount of a color whose R, G, and B values have the maximum gradation value is set to 0, or [Conversion B] of a color whose R, G, or B value is the maximum gradation value. A method for adjusting a white point in a digital color display system, wherein the conversion amount is zero. 5. A method for adjusting a white point (ie, a black level) at a low gradation using a conversion A according to claim 4, wherein the white point set by a user is increased. Assuming that the amounts are Rbm, Gbm, and Bbm, Rdo, Gdo, and Bdo that indicate the color for which the white point (that is, the black level) at a low gradation has been adjusted from Rdi, Gdi, and Bdi that indicate an input arbitrary color.
Is output based on Rbm, Gbm, and Bbm.
Digital values Rb, Gb, and Bb approximating the respective conversion amounts of R, G, and B of Gdi and Bdi are obtained based on the following conversion formula. Rb = f (L−Rdi, Rbm) Gb = f (L−Gdi , Gbm) Bb = f (L−Bdi, Bbm) where f (X, Y) is a core calc function, and L = 2 ⁿ −1 from Rb, Gb, Bb obtained, Rdo = Rdi + Rb (0 ≦ Rb ≦ Rbm) Gdo = Gdi + Gb (0 ≦ Gb ≦ Gbm) Bdo = Bdi + Bb (0 ≦ Bb ≦ Bbm) and outputs Rdo, Gdo, Bdo, and a white point adjustment method in a digital color display system. 6. A method for adjusting a white point (ie, black level) at a low gradation using a conversion B according to claim 4, wherein the white point set by a user is increased. Assuming that the amounts are Rbm, Gbm, and Bbm, Rdo, Gdo, and Bdo that indicate the color for which the white point (that is, the black level) at a low gradation has been adjusted from Rdi, Gdi, and Bdi that indicate an input arbitrary color.
Is output based on Rbm, Gbm, and Bbm.
Digital values Rb, Gb, Bb approximated to the respective conversion amounts of R, G, B of Gdi, Bdi are obtained based on the following conversion formula, and Cmax = max (Rdi, Gdi, Bdi) Rb = f (LCmax) , Rbm) Gb = f (LCmax, Gbm) Bb = f (LCmax, Bbm) where f (X, Y) is a core calc function, and L = 2 ⁿ -1 from the calculated Rb, Gb, Bb. Rdo = Rdi + Rb (0 ≦ Rb ≦ Rbm) Gdo = Gdi + Gb (0 ≦ Gb ≦ Gbm) Bdo = Bdi + Bb (0 ≦ Bb ≦ Bbm) and output Rdo, Gdo, Bdo. How to adjust the white point in a display system. 7. When obtaining each conversion amount, when approximating a straight line in an orthogonal two-dimensional coordinate system to a point having integer coordinates, the origin O (0, 0), the point A (L, Y), and the point B ( L,
Considering a triangle OAB composed of 0), among the points located near the side OA where the coordinate values are integer values (hereinafter referred to as “integer grid points”), the x coordinate value is X. The y coordinate value Z of the point P is calculated by the following core calc function: f (X, Y)
7. The method according to claim 1, wherein the value is obtained from
Z = f (X, Y) where 0 ≦ X ≦ L, 0 ≦ Y ≦ L, X, Y: integer L = 2 ⁿ -1, n ≧ 1, n: an integer that satisfies all of the following conditions: i) f (0, 0) = 0 and f (L,
Y) = Y, ii) for any 0 ≦ X <L, for any Y, f (X + 1, Y) = f (X, Y) +0 or f (X + 1, Y) = f (X, Y) +1 Iii) f (X, Y + 1) = f (X, Y) +0 or f (X, Y + 1) = f (X, Y) +1 for any 0 ≦ Y <L and for any X, and iv ) An output Z is always obtained after a certain calculation step for any input X, Y. 8. An apparatus for executing a white point adjustment method in a digital color display system according to claim 1, wherein said core calc function: Z = f (X, An apparatus characterized in that the conversion of a line segment into an integer value using Y) is configured such that Z is output in a pipeline manner for inputs X and Y by hardware.