JP2000333194A - Color correction device for liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a color correction device of a liquid crystal panel that corrects a characteristic of a color filter of the liquid crystal panel so as to enhance the color reproducibility. SOLUTION: The color correction device includes a color rotation section 2 that rotates a phase of a received color difference signal by a prescribed angle to correct in advance the color difference signal in response to a characteristic of a color filter in a liquid crystal panel receiving a luminance signal and the color difference signal, an (R-Y) amplifier section 3 and a (B-Y) amplifier section 4 that respectively amplify (R-Y) and (B-Y) signals being the color difference signals outputted from the color rotation section 2, a color inverse rotation section 5 that rotates the color difference signals outputted from the (R-Y) amplifier section 3 and the (B-Y) amplifier section 4 by the prescribed angle in a direction reverse to the rotating direction of the color rotation section 2, and a decode section 6 that generates an RGB signal on the basis of the color difference signals outputted finally from the color inverse rotation section 5 and the luminance signal received at first so as to freely set an optional color gain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color correction device for correcting the characteristics of a color filter of a liquid crystal panel in consideration of the characteristics of the color filter and improving color reproducibility.

[0002]

2. Description of the Related Art In recent years, liquid crystal panels have rapidly become widespread, mainly in portable devices and the like, because they consume less space and consume less power than CRTs. However, the liquid crystal panel is inferior to the CRT in contrast, brightness, color vividness, and the like, and attempts have been made on both the liquid crystal panel side and the drive circuit side to improve these.

FIG. 31 is a block diagram of general video signal processing for displaying a video on a liquid crystal panel. In FIG. 31, 1 is a liquid crystal panel, and 6 is an input luminance signal Y and color difference signals (RY) and (BY).
And a decoding circuit for converting the data into RGB.

[0004] Reference numeral 7 denotes a contrast and bright circuit, which can adjust contrast and the like according to the characteristics of the liquid crystal panel. Further, reference numeral 8 denotes a gamma correction circuit for correcting the γ characteristic of the liquid crystal panel, which can also be adjusted according to the liquid crystal panel. It should be noted that a circuit for adjusting the color gain, a circuit for adjusting the hue, a circuit for emphasizing the details of the video, and the like are often added in addition to those shown in FIG.

Further, in order to improve the image quality of the liquid crystal panel, as disclosed in Japanese Patent Application Laid-Open No. 5-183921, the luminance level of an input signal is detected, and the contrast and brightness are adjusted according to the detected luminance level. A device such as setting is devised.

[0006]

Recently, in order to greatly reduce the power of a liquid crystal panel, a reflective liquid crystal panel that does not use a backlight has been put to practical use. Reflective liquid crystal panels tend to increase the light reflectance, that is, the brightness, by reducing the color purity of the color filters to the minimum necessary in order to increase the visibility particularly in dark places such as indoors. FIG. 32 shows typical characteristics of a color filter used in a reflection type liquid crystal panel.
3 shows typical characteristics of a color filter used in a transmission type liquid crystal panel.

As shown in FIG. 32, the cutoff characteristic of a color filter used in a reflection type liquid crystal panel is gentler than that of a transmission type. For example, the characteristics of a G color filter are not limited to G wavelength. 50% of light of R and B wavelengths
It can be seen that the light is transmitted to some extent. For this reason, it transmits more light as a whole compared to a transmission type color filter,
It has the property that the color purity tends to be insufficient. Therefore, there has been a problem that the color density is extremely deteriorated when displaying an image.

In order to cope with such a problem, in the conventional liquid crystal signal processing as shown in FIG. 31, a method of increasing the color gain in advance and correcting the color density has been considered. If the cutoff characteristics of the filters are not uniform, the degree of deterioration of the color density varies depending on the color, so that the color gain of a specific color becomes insufficient or an excessive color gain is obtained. Is secondary. FIG. 34 shows a change in the color of the input signal due to the characteristics of the color filter shown in FIG.
In FIG. 34, the vertical axis is (RY) and the horizontal axis is (BY).
Where ● represents the color vector position of the input signal, and x represents the color vector displayed on the liquid crystal panel. FIG.
As shown in FIG. 7, it can be seen that the degree of deterioration of the color density differs depending on the color depending on the characteristics of the color filter, and that the color phase also deviates from the original phase.

Further, as disclosed in Japanese Patent Application Laid-Open No. Hei 9-138675, a method of converting an image displayed on a display into a human color sensation using a 3 × 3 primary conversion matrix has been considered. In such a method, conversion is performed according to (Equation 2).

[0010]

(Equation 2)

Here, if each coefficient of the 3 × 3 conversion matrix is set so as to correct the characteristics of the color filter, accurate correction can be performed.

However, R ′ obtained by (Equation 2)
The values of B 'and G' are not always positive values, and there may be negative values in some cases. In this case, since there is no negative concept for the RGB signals, it is necessary to take measures such as clipping to 0 (zero) and outputting. However, clipping to 0 (zero) causes a new problem such as a change in color phase.

The present invention has been made in order to solve the above problems.
It is an object of the present invention to provide a color correction device for a liquid crystal panel that can relatively accurately correct the characteristics of a color filter without using a complicated circuit or device.

[0014]

In order to achieve the above object, a color correcting apparatus for a liquid crystal panel according to the present invention comprises: a liquid crystal panel to which a luminance signal and a color difference signal are inputted; In order to correct the signal in advance, a color rotator that rotates the phase of the input color difference signal by a predetermined angle, and a (RY) signal and a (BY) signal, which are color difference signals output from the color rotator. (R−Y) amplification unit and (B−Y) amplification unit for amplifying
-Y) a color reverse rotation unit that rotates the color difference signal output from the amplification unit and (BY) the amplification unit by a predetermined angle in a direction opposite to the rotation direction of the color rotation unit; And a decoding unit that generates an RGB signal based on the color difference signal output from the first and the first input luminance signals.

With such a configuration, by correcting the color vector before display according to the characteristics of the color filter, a display image similar to the color vector of the original input image can be obtained. .

Further, in the color correcting apparatus for a liquid crystal panel according to the present invention, the color gains in the (RY) amplifying section and the (BY) amplifying section are obtained by inputting the (RY) signal and the (B−Y) signal.
Y) Preferably, it can be switched by the sign of the signal. This is because proper correction can be performed even when the color vector is an asymmetric vector.

Next, in order to achieve the above object, a color correcting apparatus for a liquid crystal panel according to the present invention provides a liquid crystal panel to which a luminance signal and a color difference signal are inputted, the color of which rotates the phase of the color difference signal by a predetermined angle. A rotator and a (RY) signal and a (BY) signal, which are color difference signals output from the color rotator, are given. (RY) is a vertical axis, and (BY) is a horizontal axis. The first straight line (RY) =-(B-
Y) and the four regions divided by the second straight line (RY) = (BY), (RY) <(BY) and (RY)
-Y)> the first region given by-(BY) or
(RY)> (BY) and (RY) <-(B-
In the second area given by Y), 0 (zero) is output, and (RY)> (BY) and (RY)>-
In the third region given by (BY), (RY)-|
BY | is output, and (RY) <(BY) and (R
−Y) <− (B−Y) In the fourth region given by (R
−Y) + │BY│ output, and either the (RY) signal or the (BY) signal which is a color difference signal output from the nonlinear operation unit and the color rotator, An (RY) signal and a (BY) signal, which are color difference signals output from the color rotator, are input through the adder, and are added in the opposite direction to the rotation direction of the color rotator. A color reverse rotation unit that rotates by a predetermined angle, a color difference signal finally output from the color reverse rotation unit, and a decoding unit that generates an RGB signal based on a luminance signal input first. It is characterized by.

With this configuration, it is possible to increase the color gain only for the color around the color vector of interest and its surroundings, and it is possible to correct the color gain without causing a large change in the color phase. .

Further, in the color correcting apparatus for a liquid crystal panel according to the present invention, the first straight line of the non-linear operation section is (RY) =-a
× (BY) (a is an arbitrary positive real number), and the second
Is given by (R−Y) = b × (B−Y) (b is an arbitrary positive real number), and among the four regions divided by the first straight line and the second straight line, 0 in the area and the second area
(Zero), and in the third area, c × ((R−Y) −
| B−Y |) (c is an arbitrary real number), and d × ((R−Y) + | B−Y |) (d is an arbitrary real number) is preferably output in the fourth region. . This is because the division angle of the region can be freely set.

Further, in the color correcting apparatus for a liquid crystal panel according to the present invention, the non-linear operation section determines the absolute values of the (RY) signal and the (BY) signal which are the color difference signals output from the color rotating section. An (RY) absolute value circuit and a (BY) absolute value circuit, and an adder circuit for calculating a difference between an output of the (RY) absolute value circuit and an output of the (BY) absolute value circuit. , A clipping circuit that clips to 0 (zero) when the output of the adding circuit is negative, a sign inverting circuit that inverts the sign of the output of the clipping circuit, and outputs the signal (RY). It is preferable to include a selector that selects the output of the clipping circuit when the signal is positive and selects the output of the sign inverting circuit when the signal is negative. This is because appropriate correction can be performed even when the characteristics of the color filter are asymmetric vectors.

Further, in the color correcting apparatus for a liquid crystal panel according to the present invention, the non-linear operation unit outputs from the color rotation unit (R
-Y) and (B-Y) output the absolute value of the signal (R
-Y) an absolute value circuit and (BY) an absolute value circuit;
Y) Multiply the output of the absolute value circuit by the coefficient Kry (RY)
The coefficient Kby is applied to the output of the multiplication circuit and the (BY) absolute value circuit.
(BY) multiplication circuit, an addition circuit for calculating the difference between the output of the (RY) multiplication circuit and the output of the (BY) multiplication circuit, and 0 (zero) when the output of the addition circuit is negative. ), A sign inverting circuit for inverting the sign of the output of the clipping circuit and outputting the same, a first multiplying circuit for multiplying the output of the clipping circuit by a coefficient K1, and a coefficient K2 for the output of the sign inverting circuit. The second multiplication circuit to be multiplied, and the output of the first multiplication circuit is selected when the (R-Y) signal output from the color rotator is positive, and the output of the second multiplication circuit is selected when the (R-Y) signal is negative. It is preferable to include a selector that performs the selection. Similarly, even when the characteristics of the color filter are asymmetric vectors, appropriate correction can be performed.

Next, in order to achieve the above object, a color correction apparatus for a liquid crystal panel according to the present invention comprises: a liquid crystal panel to which a luminance signal and a color difference signal are inputted; A decoding unit for generating an RGB signal based on a (RY) signal and a (BY) signal, which are color difference signals output from the gain unit, and a luminance signal, and a color gain adapted to a color filter characteristic of a liquid crystal panel The output of the 3 × 3 matrix color gain correction conversion unit for performing the correction, the 3 × 3 matrix color filter correction conversion unit having the inverse characteristic of the color filter characteristic of the liquid crystal panel, and the output of the color filter correction conversion unit exceeded 1. In this case, a clip circuit for normalizing to 1 and outputting the result is included.

With this configuration, it is possible to perform appropriate correction even when the characteristics of the color filter do not exhibit an ideal vector graphic.

Further, in the color correction device for a liquid crystal panel according to the present invention, it is preferable that the conversion matrix of the color gain correction conversion unit is (Equation 3).

[0025]

(Equation 3)

[0026]

(Embodiment 1) Hereinafter, a color correction apparatus for a liquid crystal panel according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a color correction device for a liquid crystal panel according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a liquid crystal panel, and 2 denotes an input color difference signal (RY) signal and (BY).
A color rotation circuit that rotates the color phase of the signal by a predetermined angle θ based on (Equation 4) and outputs (R−Y) r and (B−Y) r is shown.

[0028]

(Equation 4)

Reference numeral 3 denotes (RY) g which is obtained by multiplying (RY) r output from the color rotation circuit 2 by a predetermined value (R).
Similarly, 4 is a (BY) amplifier circuit that outputs (BY) g by multiplying (BY) r output from the color rotation circuit 2 by a predetermined number, and 5 is an amplifier circuit. The color phases of the color difference signals output from the (RY) amplifier circuit 3 and the (BY) amplifier circuit 4 are inversely rotated by a predetermined angle θ based on (Equation 5),
A color reversal circuit for outputting (RY) c and (BY) c is shown, respectively.

[0030]

(Equation 5)

In the first embodiment, for the sake of convenience, the color reverse rotation circuit 5 rotates the color rotation circuit 2 by the same angle in the direction opposite to the rotation angle θ.

In a general color filter of a reflection type liquid crystal panel as shown in FIG. 1, there is a tendency that the cutoff characteristic of a G color filter, which is highly dependent on luminance, is made gentler with respect to R and B. is there. For this reason, especially, the color purity of G is deteriorated with respect to other colors, and tends to have characteristics as shown in FIG. In FIG. 34, green, yellow,
Insufficient gain for blue and magenta colors.

FIG. 2 schematically shows this characteristic. The ideal color vector 2A on the circumference is actually distorted on an ellipse as shown by the color vector 2B due to the characteristics of the color filter. Is shown. To correct this, a color gain corresponding to the actually obtained color vector 2B is set, and as shown in FIG. 3, the color vector 3A on the circumference is previously set in the direction opposite to the color gain characteristic of the color filter. What is necessary is just to correct and to set it as the color vector 3B.

In the first embodiment, the means for performing the correction shown in FIG. 3 is shown. Here, in order to make the explanation easy to understand, the input image data is represented by a color vector on the circumference shown in FIG. It will be described as if.

First, the color rotation circuit 2 rotates the color vector of the input image about the origin, as shown in FIG. Next, in the (RY) amplifier circuit 3 and the (BY) amplifier circuit 4, the (RY) signal and the (BY) signal are amplified as shown in FIG. Color vector 5
A is corrected so that A becomes an elliptical color vector 5B.

Next, as shown in FIG. 6, in the color reverse rotation circuit 5, reverse rotation is performed by the angle rotated by the color rotation circuit 2 so that the color phase returns to the original phase. That is,
By rotating the color vector 6A, which is the output of the (RY) amplifier circuit 3 and the (BY) amplifier circuit 4, in the direction opposite to that of the color rotation circuit 2, the color vector 6B is output.

The color vector 6B output from the color reverse rotation circuit 5 is converted by the color filter of the liquid crystal panel, and is finally restored as the original input image data as shown in FIG. That is, by inputting the color vector 7A, which has been corrected in advance in accordance with the characteristics of the color filters, to the liquid crystal panel, it is possible to obtain the color vector 7B equivalent to the color vector on the circumference, which is the desired image data. it can.

Taking the color filter characteristics shown in FIG. 34 as an example, FIG. 8 shows the result corrected in the first embodiment. FIG.
In the figure, ● indicates input image data, X indicates liquid crystal display data before correction, and □ indicates liquid crystal display data after correction according to the present embodiment. In FIG. 8, the color rotation angle is 45 degrees, the (R-Y) gain is 1.6, and the (B-
Y) The gain is set to 1.1. As described above, it can be seen that the color vector after correction is much closer to the color vector of the original input image than the color vector before correction.

As described above, according to the first embodiment, the characteristics of the color filter can be easily corrected, and a color correction device for a liquid crystal panel having excellent color reproducibility can be obtained.

In the first embodiment, the color gains of the (RY) amplifier circuit 3 and the (BY) amplifier circuit 4 are fixed irrespective of the sign of the signal. As shown in FIG. 9, when the color vector is asymmetrical about the origin on the color vector, that is, when the actually obtained color vector is a color vector as shown in 9B,
The color gain of the (RY) amplifier circuit 3 and the color gain of the (BY) amplifier circuit 4 may be switched by the sign of the signal.

FIG. 10 shows a block diagram of a color correcting device for a liquid crystal panel in this case. In FIG. 10, reference numeral 3a denotes a first code detection circuit for detecting the sign of (RY) r output from the color rotation circuit 2, and 4a denotes a second code for detecting the sign of (BY) r. 3 shows a code detection circuit. 11 to 14 show the outline of the color correction operation as in the first embodiment.

The difference from the first embodiment is that (R
-Y) The color gain of the amplifier circuit 3 is such that the color gain when (RY) is negative is larger than the color gain when (RY) is positive. That is, in FIG. 12, the amplified color vector 12B is converted so as to have a vector shape extending in the negative direction of the (RY) axis. By performing such correction processing, the color vector input to the liquid crystal panel has an asymmetric shape as shown in FIG. 14A, and proper correction can be performed even when the characteristics of the color filters are asymmetric. Becomes possible.

In the first embodiment, the (RY) axis,
Since the color gain of an arbitrary color phase can be adjusted in four directions of the (BY) axis and by color rotation, it is effective not only for correction of a color filter of a transmission type liquid crystal panel but also of a reflection type liquid crystal panel. is there.

(Embodiment 2) Hereinafter, a color correction apparatus for a liquid crystal panel according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 15 is a block diagram of a color correction device for a liquid crystal panel according to the second embodiment of the present invention. In FIG. 15, reference numeral 10 denotes (R−Y) r and (B−Y) r output from the color rotation circuit 2, as shown in FIG. 16, where (R−Y) r = − (B−Y) r And (R-
Y) Of the four areas divided by the straight line of r = (BY) r, 0 (zero) is output when the area is in areas A and C,
In the case of the region B, (RY) r- | (BY) r |
Is output, and when it is in the area D, (R−Y) r + | (B
−Y) shows a non-linear operation circuit that outputs r |. 11 is
4 shows an addition circuit that adds (R−Y) r output from the color rotation circuit 2 and a signal output from the nonlinear operation circuit 10. Reference numeral 12 denotes a color amplifying circuit for amplifying the color signal output from the color reverse rotation circuit 5. Other configurations are the same as those of the first embodiment.

In FIG. 15, also in the second embodiment, the basic concept of correction, that is, the input color difference signal is rotated, and individual gains are set on the (RY) axis and the (BY) axis. The concept of performing reverse rotation of colors to amplify and return to the original color phase is substantially the same as in the first embodiment. The difference is that the method of color gain correction after rotating the input color difference signal is different. Here, in order to simplify the description, the operations of the nonlinear operation circuit 10, the addition circuit 11, and the color amplification circuit 12, which are features of the second embodiment, will be mainly described.

FIG. 1 shows a specific configuration of the nonlinear arithmetic circuit 10.
FIG. In FIG. 17, 10a is (RY) r,
(B−Y) An absolute value circuit that outputs the absolute value of r
Is an addition circuit for performing the difference operation shown in (Equation 6), 10c is a clipping circuit for clipping and outputting 0 (zero) when the value of the difference signal Sa output from the addition circuit 10b is negative, and 10d. Is a sign inverting circuit that inverts the sign of the output data of the clipping circuit (that is, makes a negative value), and 10e is the sign inverting circuit of the clipping circuit 10c when the input (RY) r signal is positive. The selectors that output the data as it is and output the output data of the sign inverting circuit 10d when the output is negative indicate the respective selectors.

[0047]

(Equation 6)

In FIG. 17, first, the operation shown in (Equation 6) is performed by the absolute value circuit 10a and the adder circuit 10b. The clip circuit 10c outputs Sa as it is when Sa ≧ 0, and outputs 0 (zero) when Sa <0. Here, Sa <0 is (RY) r, (BY)
This means that r is in the region A or the region C in FIG.

Next, the sign inversion circuit 10d and the selector 10
In e, the signal output from the clip circuit 10c is S
a ′, first, when (R−Y) r ≧ 0, Sa ′
Is output as it is, and conversely, when (RY) r <0,-
Sa ′ is output. Sa 'means that the area is in the area B, and -Sa' means that it is in the area D.

This data is output to the adder circuit 11 by (R−
Y) Since it is added to r, in the area B, the value of (R−Y) output from the adding circuit 12 increases in proportion to the value of Sa ′. On the other hand, in the area D, the value becomes smaller in proportion to the value of Sa ′. Hereinafter, the color amplifying circuit 12 amplifies and outputs the color difference signal returned to the original input phase by the color reverse rotation circuit 5.

FIGS. 18 to 20 are explanatory diagrams of the operation of the liquid crystal panel color correction device according to the second embodiment. First, FIG. 18 shows the correction in the non-linear operation circuit 10 and the addition circuit 11, and the point a in the area A and the area C
The point c is output as it is, the point b in the area B is converted to the point b ', and the point d in the area D is converted to the point d'. As a result of this correction, the color vector 19A output from the color rotation circuit 2 becomes 1 as shown in FIG.
It is converted as shown by 9B. Finally, the color phase is returned to the original color phase by the color reverse rotation circuit 5 and output as a color vector such as 20B in FIG. The color amplification circuit 12 is used for adjusting the overall color gain.

As described above, the second embodiment is different from the first embodiment in that the color gain is increased only for the color around the color vector of interest and the surrounding colors. As an effect unique to this method, a change in color phase can be minimized, and the gain of only a specific color vector can be increased. 21 and 22 are diagrams for explaining this effect. FIG. 21 shows a change in color phase according to the first embodiment, and FIG. 22 shows a change in color phase according to the second embodiment.

First, as shown in FIG.
In the color correction by, since the gain of all colors is increased along the (RY) axis, the color phase greatly changes at a position away from the (RY) axis as shown by a point a. Therefore, considering the color phase, the gain of (RY) and the gain of (BY)
The gain difference cannot be made too large.

On the other hand, as shown in FIG. 22, in the color correction according to the second embodiment, a color away from the (RY) axis is output as it is, and the color near the (RY) axis (In the vicinity of the color vector to be corrected), the color gain is corrected, so that even if the gain is increased, the change in the color phase can be minimized.

Further, in the second embodiment, the color gain of the (R-Y) signal after the color rotation is set to double on the (R-Y) axis as shown in FIG. I have. The range in which the color gain correction is performed is also fixed to the regions B and D as shown in FIG. 20, but the adjustment of the color gain and the color correction range can be easily performed.

FIG. 23 is a block diagram of the nonlinear arithmetic circuit 10 according to the embodiment, which can easily adjust the color gain and the color correction range. In FIG. 23, 10f is output from the absolute value circuit 10a | (R
−Y) A first multiplication circuit that performs multiplication of r | by the coefficient Kry, and 10g is a | (B−) output from the absolute value circuit 10a.
Y) A second multiplication circuit for multiplying r | by the coefficient Kby, 10h a third multiplication circuit for multiplying the output data of the clipping circuit 10c by the coefficient K1, and 10i for a sign inversion circuit 10d. A fourth multiplication circuit for multiplying the output data by the coefficient K2 is shown.

In FIG. 23, a first multiplication circuit 10f,
The division form of the region shown in FIG. 16 by the second multiplication circuit 10g is as shown in FIG. That is, the setting of the division angle of the region can be freely adjusted by the coefficients Kry and Kby given to these multiplication circuits.

The gain of the data to be added to the (RY) r signal can be arbitrarily set by the third multiplication circuit 10h and the fourth multiplication circuit 10i when the correction data is negative or positive. Becomes That is, when (RY) is positive, the correction 25A using the coefficient K1 is performed, and when (RY) is negative, the correction 25B using the coefficient K2 is performed. Even if the characteristic is asymmetric, appropriate characteristic correction can be performed.

In the second embodiment, the color gain correction is performed on the (RY) r signal. However, this is a method of adding the color gain correction to the (BY) r signal. Also, by reversing the rotation directions of the color rotation circuit 2 and the color reverse rotation circuit 5, the same effect can be expected.

As described above, according to the second embodiment, the characteristics of the color filters can be corrected with a simple configuration, and the change in the color phase due to the color correction is minimized, and the color reproducibility is excellent. A color correction device for a liquid crystal panel can be obtained.

(Embodiment 3) Hereinafter, a color correction apparatus for a liquid crystal panel according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 26 is a block diagram of a liquid crystal panel color correction device according to the third embodiment of the present invention. In FIG. 26, reference numeral 20 denotes a color gain correction circuit;
It is composed of a 3 × 3 color gain correction matrix H as shown in (Equation 7). Here, for convenience, h in Equation 7 is set to 1.5 and p is set to 1.0.

[0062]

(Equation 7)

Reference numeral 21 denotes a color filter color correction circuit.
When the characteristic of the color filter is a 3 × 3 conversion matrix B, the color filter color correction matrix A is
Is to give.

Reference numeral 22 denotes a clipping circuit for normalizing the maximum value to 1 when any of the Rc, Gc, and Bc signals output from the color filter color correction circuit exceeds 1.

An example of the color filter characteristic matrix B in FIG. 26 is shown in (Equation 8).

[0066]

(Equation 8)

(Equation 8) indicates that the R transmittance of the R color filter is 95%, the G transmittance is 20%, and the B transmittance is 50%.
The R transmittance of the G color filter is 50%, and the G transmittance is 90
%, The B transmittance is 60%, the R transmittance of the B color filter is 20%, the G transmittance is 50%, and the B transmittance is 90%. However, in the reflection type liquid crystal, since the incident light passes through the color filter twice at the time of incidence and at the time of emission, the transmittance is squared to obtain a color filter characteristic matrix. (Equation 8) indicates that, for example, the red level Rdp displayed on the liquid crystal panel is equal to Rlc input to the liquid crystal panel.
Rd based on the d signal, the Glcd signal, and the Blcd signal.
p = 0.925 × Rlcd + 0.04 × Glcd +
It means that it is represented by 0.25 × Blcd.

The inverse matrix of the color filter characteristic matrix B shown in (Equation 8) is shown in (Equation 9). This (Equation 9) becomes the color filter color correction matrix A in the color filter color correction circuit 21.

[0069]

(Equation 9)

The basic principle of the present invention is to perform conversion using the inverse matrix of the color filter characteristic matrix in order to correct the characteristics of the color filter. That is, the signal RGB output from the decoding circuit is multiplied by the matrix A to obtain Rlcd, Gl
When cd and Blcd are used, the image displayed on the liquid crystal panel is further multiplied by a color filter characteristic matrix, as shown in (Equation 10). That is, it means that the original RGB signals are restored on the liquid crystal panel.

[0071]

(Equation 10)

However, if the characteristics of the color filter are not ideal, there are colors that cannot be physically represented. Therefore, Rlcd, which is obtained by multiplying the color filter color correction matrix A,
The Glcd and Blcd signals may include negative values that cannot be represented in practice. (Table 1) shows a 50% level color bar signal (yellow, cyan, green,
Magenta, red, blue signals) (Equation 10)
Rlcd, Glcd, Blcd and Rdp, Gdp, Bdp displayed on the liquid crystal. A is an input signal, B is an output signal, and C is an ideal output signal. D indicates the liquid crystal display when D is obtained, and D indicates the liquid crystal display when the value of the output signal B is negative and clipped to 0 (zero) and output.

[0073]

[Table 1]

As shown by C in Table 1, if a negative value can be expressed in the output signal, the original input signal is reproduced on the liquid crystal display, but actually, as shown in D in Table 1, The liquid crystal display differs from the original input signal. Based on the data of (Table 1), the color vector input in FIG. 27 was compared with the color vector displayed on the liquid crystal. As shown in FIG. 27, it can be seen that there is a large difference between the input color vector and the color vector displayed on the liquid crystal. In particular, as described above, when the characteristics of the color filter are not ideal, there are colors that cannot be physically represented, and there is a limit to complete correction in both the color level and the hue. However, it is possible to correct only the hue. Particularly in an actual image display, a change in the hue causes a clear sense of incongruity to human eyes. Therefore, it is necessary to avoid the change in the hue as much as possible.

The color gain correction matrix H is configured to prevent the output signal from having a negative value. The correction of the color filter color correction matrix A is performed by multiplying the characteristic matrix of the color filter by multiplication to convert the unit matrix, that is, the color filter to have ideal characteristics. . Therefore, the color gain correction matrix H allows the color filter to be corrected not by a color filter having an ideal cutoff characteristic but by a characteristic of an RGB cutoff filter while taking the actual cutoff characteristic into consideration. The correction is performed, and the lack of color gain due to the correction is corrected by the color amplifier circuit 12. In some cases, the output is 1 or more. This is to avoid a change in hue by normalizing the maximum value to 1 by the clipping circuit 22 and outputting the normalized value.

In the third embodiment, the color gain correction matrix H
Is a 3 × 3 matrix (h = 1.5, p = 1.
0). Again, a 50% level color bar signal is used as an input signal. Table 2 shows the calculation results according to the third embodiment, where A is the input luminance signal Y, color difference signals (RY) and (BY), and B is the color gain correction matrix 21. , The color gain is halved, so that the result of doubling in the color amplifying circuit 12 in advance, C is the output of the decoding circuit 6, and D is the color filter color correcting circuit 2
1 indicates the output signal (Rc, Gc, Bc), E indicates the output of the clipping circuit 22, and F indicates the liquid crystal display.

[0077]

[Table 2]

FIG. 28 shows the color vectors displayed on the liquid crystal calculated based on F in (Table 2). (Table 2)
As shown in (1), all the outputs of the color filter color correction circuit 21 are corrected to positive values except for green. For this reason, as shown in FIG. 28, the hue displayed on the liquid crystal maintains the hue at the time of input except for green. Further, it can be seen that red and yellow, which could not be expressed by the correction of only the color filter color correction circuit 21 in FIG. 27, are completely corrected.

In the third embodiment, the color amplifying circuit 1
The gain of 2 is doubled and the color level is also being corrected at the same time. If this is suppressed to, for example, 1.5 times,
Hue correction is also possible for green. The calculation results at this time are shown in (Table 3), and FIG. 29 shows the color vectors displayed on the liquid crystal calculated based on F in (Table 3).

[0080]

[Table 3]

As shown in Table 3 and FIG. 29, when the color gain of the color amplifying circuit 12 is twice, the hue is corrected for all colors including green which could not be corrected.

As described above, in the third embodiment, color correction using the inverse matrix of the color filter characteristic matrix
By using a color gain correction matrix for preventing the output value after correction from becoming negative, the characteristics of the color filters can be corrected with a simple configuration, and a color correction device having excellent color reproducibility can be obtained.

In the third embodiment, as shown in FIG. 26, the conversion of the decoding circuit 6 and the color gain correction circuit 2
Although the conversion of 0 and the conversion by the color filter color correction matrix are explicitly divided, when actually configuring a circuit, the product of these matrices should be configured as one matrix as shown in FIG. Is also possible. In this case, it is apparent that the same effect as that of the embodiment of FIG. 26 can be obtained.

Further, in the first to third embodiments, the correction of the characteristics of the color filters has been particularly described. However, not only the color filters but also the components of the liquid crystal such as a retardation film change the color. It goes without saying that the method of the present invention can correct not only the characteristics of the color filters but also the color change of the entire liquid crystal by considering the characteristics of the entire liquid crystal as one characteristic.

[0085]

As described above, according to the color correcting apparatus for a liquid crystal panel according to the present invention, the input color phase is rotated and (R
Since the color gains of the (−Y) axis and the (BY) axis are individually changed, and the colors are reversely rotated so as to return to the original input phase, the color gain of a specific color at an arbitrary angle is changed. The color correction of the liquid crystal panel can be realized with a simple configuration that can be set freely.

Further, according to the color correcting apparatus for a liquid crystal panel of the present invention, the input color phase is rotated to minimize the change of the color hue while keeping the (RY) axis and the (BY) axis. Since the color gain is changed individually and the color is reversely rotated to return to the original input phase, the color gain can be set freely for a specific color at an arbitrary angle, with a simple configuration,
Further, even if the ratio of the color gain between the (RY) axis and the (BY) axis is increased, the color correction of the liquid crystal panel that minimizes the change in hue can be realized.

Further, according to the color correcting apparatus for a liquid crystal panel of the present invention, the color correction by the inverse matrix of the color filter characteristic matrix and the color gain correction matrix for preventing the output value after correction from becoming negative. Accordingly, the characteristics of a liquid crystal panel having arbitrary characteristics can be corrected, and a color correction device having excellent color reproducibility can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color correction device for a liquid crystal panel according to a first embodiment of the present invention;

FIG. 2 is a diagram illustrating the principle of a color correction device for a liquid crystal panel according to the first embodiment of the present invention;

FIG. 3 is a diagram illustrating the principle of a color correction device for a liquid crystal panel according to the first embodiment of the present invention;

FIG. 4 is an operation explanatory diagram of the liquid crystal panel color correction device according to the first embodiment of the present invention;

FIG. 5 is an operation explanatory diagram of the color correction device for a liquid crystal panel according to the first embodiment of the present invention;

FIG. 6 is an operation explanatory diagram of the liquid crystal panel color correction device according to the first embodiment of the present invention;

FIG. 7 is an operation explanatory diagram of the liquid crystal panel color correction device according to the first embodiment of the present invention;

FIG. 8 is a color vector diagram showing a correction result using the color correction device for a liquid crystal panel according to the first embodiment of the present invention.

FIG. 9 is a color vector diagram showing characteristics of a color filter.

FIG. 10 is a block diagram of a color correction device for a liquid crystal panel according to an embodiment of the present invention.

FIG. 11 is a diagram illustrating the operation of the color correction device for a liquid crystal panel according to one embodiment of the present invention.

FIG. 12 is a diagram illustrating the operation of the color correction device for a liquid crystal panel according to one embodiment of the present invention.

FIG. 13 is a diagram illustrating the operation of the color correction device for a liquid crystal panel according to one embodiment of the present invention.

FIG. 14 is a diagram illustrating the operation of the color correction device for a liquid crystal panel according to one embodiment of the present invention.

FIG. 15 is a block diagram of a color correction device for a liquid crystal panel according to a second embodiment of the present invention;

FIG. 16 is an explanatory diagram of a color difference plane region in the liquid crystal panel color correction device according to the second embodiment of the present invention;

FIG. 17 is a block diagram of a non-linear operation circuit in the liquid crystal panel color correction apparatus according to the second embodiment of the present invention;

FIG. 18 is an operation explanatory diagram of the color correction device for a liquid crystal panel according to the second embodiment of the present invention;

FIG. 19 is an operation explanatory diagram of the color correction device for a liquid crystal panel according to the second embodiment of the present invention;

FIG. 20 is an explanatory diagram of an operation of the color correction device for a liquid crystal panel according to the second embodiment of the present invention;

FIG. 21 is a diagram showing a color phase change by the liquid crystal panel color correction device according to the first embodiment of the present invention;

FIG. 22 is a diagram showing a color phase change by the liquid crystal panel color correction device according to the second embodiment of the present invention;

FIG. 23 is a block diagram of a non-linear operation circuit in a liquid crystal panel color correction apparatus according to another embodiment of the present invention.

FIG. 24 is an explanatory diagram of a color difference plane region in a color correction device for a liquid crystal panel according to another embodiment of the present invention.

FIG. 25 is an explanatory diagram of an operation of a non-linear operation circuit in a color correction device for a liquid crystal panel according to another embodiment of the present invention.

FIG. 26 is a block diagram of a color correction device for a liquid crystal panel according to a third embodiment of the present invention;

FIG. 27 is a comparison diagram of an input color vector and a displayed color vector.

FIG. 28 is a color vector diagram showing a correction result using the liquid crystal panel color correction device according to the third embodiment of the present invention.

FIG. 29 is a color vector diagram showing a correction result using the liquid crystal panel color correction device according to the third embodiment of the present invention.

FIG. 30 is a block diagram of a color correction device for a liquid crystal panel according to another embodiment of the present invention.

FIG. 31 is a block diagram of a conventional liquid crystal panel color correction device.

FIG. 32 is a view showing an example of the characteristics of a color filter used in a reflective liquid crystal panel.

FIG. 33 is a view showing an example of characteristics of a color filter used in a transmission type liquid crystal panel.

FIG. 34 is a color vector diagram showing a color change by a color filter used in a reflective liquid crystal panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Color rotation circuit 3 (R-Y) amplification circuit 4 (B-Y) amplification circuit 5 Color reverse rotation circuit 6 Decoding circuit 7 Contrast and bright circuit 8 Gamma correction circuit 10 Non-linear operation circuit 11 Addition circuit 12 Color amplification circuit 20 Color gain correction circuit 21 Color filter color correction circuit 22 Clip circuit 30 Conversion matrix circuit 2A, 9A Ideal color vector 2B, 9B Actual color vector 3A Input color vector 3B Color vector after correction 5A, 12A Color vector before amplification 5B, 12B Color vector after amplification 6A, 13A Color vector before reverse rotation 6B, 13B, 20B Color vector after reverse rotation 7A, 14A Color vector input to liquid crystal panel 7B, 14B Color filter conversion Color vector after 19A Color vector after color rotation 19B Non-linear Correction by the correction 25B coefficient K2 by the color vectors 25A coefficients K1 outputted from the arithmetic circuit

Continued on front page F-term (reference) 2H093 NC66 ND17 ND58 5C006 AA01 AA22 AF13 AF46 AF51 AF52 AF53 AF85 BB11 BB28 BF14 BF24 BF25 BF26 BF28 FA18 FA56 5C060 BA03 BA09 BB01 BC05 BE05 BE10 DB00 HB00 HB16 HC01 GA20 KA08 KA12 KA13 KD08 KE04 KL13 KM05 KM13 KP05 5C080 AA10 BB05 CC03 DD03 EE30 JJ02 JJ05

Claims (8)

[Claims] In a liquid crystal panel to which a luminance signal and a color difference signal are input, a color in which the phase of the input color difference signal is rotated by a predetermined angle in order to correct the color difference signal in advance according to the characteristics of a color filter. A rotator, and a color difference signal output from the color rotator (RY)
The signal and the (BY) signal are amplified (R-
Y) amplifying section and (BY) amplifying section, and a color difference signal output from the (RY) amplifying section and (BY) amplifying section are determined in a direction opposite to a rotating direction of the color rotating section. And a decoding unit that generates an RGB signal based on the color difference signal finally output from the color reverse rotation unit and the luminance signal input first. Characteristic liquid crystal panel color correction device. 2. The (RY) amplifier and the (B-A)
Y) The color gain in the amplifying unit is determined by the input (R−
2. The color correcting device for a liquid crystal panel according to claim 1, wherein the color correction can be switched by the sign of the (Y) signal and the (BY) signal. 3. A liquid crystal panel to which a luminance signal and a chrominance signal are input, a color rotator for rotating the phase of the chrominance signal by a predetermined angle, and a chrominance signal output from the color rotator. Y)
Signal and the (BY) signal are given, (RY) is the vertical axis,
On a color difference plane with (BY) as the horizontal axis, the first straight line (RY) =-(BY) and the second straight line (RY) =
Of the four regions divided by (BY), (RY)
The first region given by <(BY) and (RY)>-(BY) or (RY)> (BY) and (RY) <-( In the second area given by (BY), 0 (zero) is output, and (RY)>(BY);
In the third region given by (RY)>-(BY), (RY)-| BY- | is output, and (RY) <
A non-linear operation unit that outputs (R−Y) + | B−Y | in a fourth area given by (B−Y) and (R−Y) <− (B−Y); And an adder for adding either the (RY) signal or the (BY) signal which is a color difference signal output from the color rotator, and a color difference signal output from the color rotator. Yes (RY)
A signal and a (BY) signal are input through the adder, and a color reverse rotator for rotating the color rotator by a predetermined angle in a direction opposite to the rotation direction of the color rotator; A color correction device for a liquid crystal panel, comprising: a color difference signal to be output; and a decoding unit that generates an RGB signal based on the luminance signal input first. 4. The first straight line of the non-linear operation unit is (RY)
= −a × (B−Y) (a is any positive real number), and the second straight line is (RY) = b × (BY) (b is any positive real number). Given, among the four regions divided by the first straight line and the second straight line, 0 in the first region and the second region.
(Zero), and in the third region, c × ((R−
Y) -│BY│) (c is an arbitrary real number), and d × ((RY) + │BY│) (d is an arbitrary real number) in the fourth area. The color correction device for a liquid crystal panel according to claim 3. 5. An (RY) absolute value circuit, wherein the non-linear operation section outputs absolute values of a (RY) signal and a (BY) signal, which are color difference signals output from a color rotation section. (B-
Y) an absolute value circuit; an adder circuit for calculating a difference between an output of the (RY) absolute value circuit and an output of the (BY) absolute value circuit; 0 when the output of the adder circuit is negative. A clipping circuit for clipping to (zero), a sign inverting circuit for inverting the sign of the output of the clipping circuit and outputting the same, and a clipping when the (RY) signal output from the color rotator is positive. 4. The color correction device for a liquid crystal panel according to claim 3, further comprising a selector for selecting an output of the circuit and, when negative, selecting an output of the sign inversion circuit. 6. The (RY) absolute value circuit for outputting the absolute values of the (RY) signal and the (BY) signal output from the color rotator, and the (BY) ) An absolute value circuit, a (RY) multiplication circuit for multiplying the output of the (RY) absolute value circuit by a coefficient Kry, and a multiplication circuit for multiplying the output of the (BY) absolute value circuit by a coefficient Kby (B− Y) a multiplying circuit, an adding circuit for calculating a difference between an output of the (RY) multiplying circuit and an output of the (BY) multiplying circuit, and 0 (zero) when the output of the adding circuit is negative. A clipping circuit for clipping, a sign inversion circuit for inverting the sign of the output of the clipping circuit and outputting the same, a first multiplication circuit for multiplying the output of the clipping circuit by a coefficient K1, and a coefficient K for the output of the sign inversion circuit.
A second multiplying circuit for multiplying by 2 and an output of the first multiplying circuit when the (R-Y) signal output from the color rotator is positive; 4. The liquid crystal panel color correction device according to claim 3, further comprising a selector for selecting an output of the circuit. 7. A liquid crystal panel to which a luminance signal and a color difference signal are input, wherein: a color gain unit for multiplying the color difference signal by a predetermined value; and a color difference signal output from the color gain unit.
A decoding section for generating an RGB signal based on the Y) signal and the (BY) signal and the luminance signal; and a color gain correction conversion of a 3 × 3 matrix for performing a color gain correction in accordance with a color filter characteristic of a liquid crystal panel. Having a reverse characteristic of the color filter characteristic of the liquid crystal panel
A color correction device for a liquid crystal panel, comprising: a color filter correction conversion unit of three matrices; and a clipping circuit for normalizing the output to one when the output of the color filter correction conversion unit exceeds one. 8. A conversion matrix of the color gain correction conversion unit,
8. The color correcting device for a liquid crystal panel according to claim 7, wherein (1). (Equation 1)