JP2003304559A - Rgb conversion circuit and video apparatus mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RGB conversion circuit capable of implementing color correction conversion in details. <P>SOLUTION: The RGB conversion circuit 10 is provided with LUTs 3, 4 for storing color difference coefficient correction values, whereby correction coefficients of color difference coefficient units 1, 2 for setting correction coefficients used to apply color difference correction to color difference signals can furthermore be corrected in response to a level of any of a received luminance signal Y or the color difference signals Cr, Cb, arithmetic units 7, 8 correct the levels of the received color difference signals Cr, Cb according to outputs of adders 5, 6 for summing the color difference coefficient correction values read from the LUTs 3, 4 and the correction coefficients of the color difference coefficient units 1, 2 and allow a matrix circuit 9 to perform matrix arithmetic operations and to produce R, G, B color signals. Further, the color difference coefficient correction value is a real number the absolute value of which is smaller than the unity. Moreover, each of the LUTs 3, 4 is configured with a high speed RAM or a high speed ROM which can be accessed at a high speed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RGB conversion circuit and a video device equipped with the RGB conversion circuit, and in particular,
The present invention relates to an RGB conversion circuit including a color difference coefficient correction unit that corrects a color difference coefficient in image processing, and a video device equipped with the RGB conversion circuit. As the video equipment according to the present invention,
For example, it can be applied to an image pickup device such as a digital video camera and a video reproducing device such as a VTR.

[0002]

2. Description of the Related Art When performing digital signal processing on color difference signals, general color adjustment (color density adjustment) is performed by A
Before the A / D conversion, the amplitudes of the color difference signals RY and BY are adjusted at the stage of the analog gain adjustment, but various proposals have been made as the color adjustment after the A / D conversion. There is.

Normally, in order to increase the color density, the color difference signal R
Amplification processing is performed to increase both -Y and BY amplitudes at the same ratio. For example, in the A / D input stage, when it is attempted to secure the brightness (Y) up to the maximum level value of the A / D dynamic range according to the standard, the color difference signals R-Y and B-Y each have 8 bits. In some cases, center 12
8 requires 0 to 255 steps. This shows the maximum color level (color saturated color) that the signal can express, but it is necessary for the image display device to reproduce the color up to this level.

FIG. 3 shows a circuit block of an RGB conversion circuit in the prior art. In the conventional RGB conversion circuit 20 shown in FIG. 3, reference numerals 21 and 22 denote color difference coefficient units, and reference numeral 2
3, 24 are arithmetic units, reference numeral 25 is a matrix circuit, reference numeral Y is a luminance signal which is one input signal, reference numerals Cr and Cb are color difference signals which are the other input signals, and reference numerals R,
G and B are output signals, which are red, green, and blue color signals, respectively.

First, 8-bit color difference signals Cr, C
Regarding the color difference data value of b, a value of “80H” indicating an 8-bit center in hexadecimal notation (in the following description,
The symbol "H" is added as hexadecimal notation to describe as "80H". ) Centered around 1. When Cr and Cb ≧ 80H, the data values of the color difference signals Cr and Cb are respectively 80
As Cr1 and Cb1 obtained by subtracting H, computing units 23 and 24
Respectively, and 2. On the other hand, when Cr and Cb <80H, the shift operation is performed in which the original data of the color difference signals Cr and Cb are directly input to the arithmetic units 23 and 24 as Cr2 and Cb2, respectively. The color difference data Cr1, Cb1 or Cr2, Cb2 as the result of the shift calculation will be represented by the symbols Crn, Cbn (n = 1 or 2), respectively.

The color difference data indicated by the symbols Crn and Cbn are uniformly calculated in the calculators 22 and 23 by a predetermined coefficient (Kr, Kb) preset in the color difference coefficient units 21 and 22. Apply and correct color difference data C
Find r'and Cb '. Cr '= Kr * Crn Cb' = Kb * Cbn Corrected color difference data C output from the computing units 23 and 24
r ′ and Cb ′ together with the luminance signal Y of the input signal are subjected to a matrix operation in the matrix circuit 25, for example, as shown in equation (1), and red, green and blue color signals R, G and B, respectively. Convert data to.

[0007]

[Formula 1]

In Japanese Patent Laid-Open No. 2001-103505, "Color correction circuit for color difference input signal", when a color difference signal with a high color saturation level is input, color collapse occurs due to over-dynamic range of A / D converter. A proposal to prevent this is disclosed.

That is, Japanese Unexamined Patent Application Publication No. 2001-103505 discloses an A / D converter that converts each of two types of input analog color difference signals into a digital color difference signal, and each color difference converted by the A / D converter. A polarity determination unit for a color difference signal that determines whether the polarity of the color difference data of the signal is positive or negative, and outputs the determined color difference data of either polarity as the amplitude level of the input color difference signal, and the polarity for the color difference signal. Based on the color difference data output from the determination unit,
A color level detection circuit that calculates a color level and outputs it as color level data, and the color level data of the color level detection circuit and the color difference data of the input color difference signal are indexed as addresses to select a correction curve. A correction curve data memory unit LUT (Lookup Tab) in which a plurality of correction curves are preset and stored.
le).

Thus, it is possible to digitally control the amplification degree of the amplitude of the input color difference signal based on the correction curve selected from the correction curve data memory unit, and perform digital correction for each pixel. This prevents the occurrence of color collapse in a color difference signal having a high color saturation level.

[0011]

However, in the conventional method as shown in FIG. 3, regardless of the input color difference signal, the constant coefficient (Kr, Since only the calculation based on Kb) is performed, there is a problem that fine color correction conversion cannot be performed. In Japanese Patent Laid-Open No. 2001-103505, similarly, a correction curve for correcting the color difference signal is selected from the correction curves preset in the correction curve data memory unit, so that the correction value is fixed. Therefore, there remains a problem that fine color correction conversion cannot be performed. Furthermore, the memory capacity of the correction curve data memory unit is (16+
n) Bit address * About 2 bytes (about 200,000 bytes)
Therefore, there are problems that the capacity becomes large and the circuit scale becomes large.

The present invention has been made in view of such circumstances, and color correction conversion is performed by freely setting color difference coefficients used for conversion of color difference signals to further enhance or attenuate color saturation. It is an object of the present invention to provide an RGB conversion circuit and a video device equipped with the RGB conversion circuit, which enables a detailed operation and a circuit scale to be reduced.

[0013]

An RGB conversion circuit according to the present invention and a video device equipped with the RGB conversion circuit are composed of the following technical means. A first technical means is a correction coefficient setting means for setting a correction coefficient for performing color difference correction of the color difference signal in an RGB conversion circuit which outputs RGB color signals using a luminance signal and a color difference signal as input signals. And, depending on the brightness level of the brightness signal,
The RGB conversion circuit is provided with a color difference coefficient correction means capable of further correcting the correction coefficient set in the correction coefficient setting means.

A second technical means is an RGB conversion circuit which outputs RGB color signals using a luminance signal and a color difference signal as input signals, and sets a correction coefficient for performing color difference correction of the color difference signal. An RGB conversion circuit having a coefficient setting unit and a color difference coefficient correcting unit capable of further correcting the correction coefficient set in the correction coefficient setting unit according to the color difference level of the color difference signal. It is characterized by

In a third technical means, in the RGB conversion circuit according to the first or second technical means, a dye coefficient correction value for further correcting the correction coefficient in the color difference coefficient correction means is an absolute value. Is an RGB conversion circuit having a real number smaller than 1.

A fourth technical means is the RGB conversion circuit according to any one of the first to third technical means, wherein a color difference coefficient correction value for further correcting the correction coefficient by the color difference coefficient correction means is provided. The RGB conversion circuit is stored in a lookup table accessible by either the brightness level or the color difference level.

A fifth technical means is the RGB conversion circuit according to the fourth technical means, wherein the lookup table is a high-speed RAM (Random) capable of high-speed access.
Access Memory) or high-speed ROM (Rea)
d Only Memory), which is an RGB conversion circuit.

A sixth technical means is a video device for picking up an image or reproducing an image, and the sixth to fifth means are provided.
The video equipment is equipped with the RGB conversion circuit according to any one of the above technical means.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an RGB conversion circuit according to the present invention and a video device equipped with the RGB conversion circuit will be described below with reference to the drawings. here,
The RGB conversion circuit can be applied to various video devices such as an image pickup device such as a digital video camera and a video playback device such as a VTR. First, a first embodiment of an RGB conversion circuit according to the present invention will be described with reference to FIG. FIG. 1 is a block configuration diagram showing a configuration example of a circuit block of an RGB conversion circuit according to the present invention.

In the RGB conversion circuit 10 shown in FIG.
Reference numerals 1 and 2 denote color difference signals Cr and Cr, which are input signals, respectively.
Color difference coefficient units providing correction coefficient setting means for setting correction coefficients Ksr and Ksb used for Cb color difference correction, and reference numerals 3 and 4 are the correction coefficients set in the color difference coefficient units 1 and 2, respectively. , A look-up table LUT (Lookup Table) for storing color difference coefficient correction values, that is, Cr and Cb correction values, for correcting the color difference coefficient correction coefficients Ks of the color difference coefficient units 1 and 2, respectively.
r, Ksb and the color difference coefficient correction values output from the LUTs 3, 4, that is, the Cr, Cb correction values, and an adder that adds the color difference coefficient correction values. , 2 are provided to provide a color difference coefficient correction unit that can further correct the correction coefficient set to the color correction coefficient setting unit 2.

Reference numerals 7 and 8 are arithmetic units for performing arithmetic operations between the color difference signals Cr and Cb which are input signals and the addition results of the adders 5 and 6, respectively. Reference symbol Y is a luminance signal that is one input signal, reference symbols Cr and Cb are color difference signals that are the other input signals, and reference symbols R, G, and B are output signals, and the colors are red, green, and blue, respectively. It is a signal.

Digital data of an imaged video signal transmitted from an image pickup device or a reading / reproducing circuit of a video device (not shown) includes a luminance signal Y having luminance data and RY, BY.
The color difference signals Cr and Cb having the color difference data are input in parallel to the RGB conversion circuit 10 according to the present invention. Here, the luminance signal Y which is one of the input signals
On the basis of the value of the luminance data indicated by
In order to correct the color difference coefficients Ksr and Ksb used for the color difference correction, the LUTs 3 and 4 are indexed by the brightness data value (that is, the brightness level) of the brightness signal Y to obtain the corresponding color difference coefficient correction value, and the addition is performed. It is output as an input signal to the devices 5 and 6.

That is, the color difference coefficient correction value is stored in the high-speed memory R
AM (Random Access Memory) or high-speed memory ROM (Read Only Memory)
The lookup table LUT3 configured by
4 are set as the Cr correction value and the Cb correction value for correcting the color difference coefficients Ksr and Ksb with respect to the color difference signals Cr and Cb, respectively, and the brightness data of the brightness signal Y, which is one of the input signals, Each is set according to the value. Thus, by indexing the value of the brightness data indicated by the brightness signal Y, which is one of the input signals, as the address of each of the LUTs 3 and 4, the color difference coefficient correction value stored and set in each of the addresses of the LUTs 3 and 4. That is, Cr
The correction value and the Cb correction value are the color difference signal Cr, which is the input signal,
CP (not shown) is used as color difference coefficient correction values ΔKr and ΔKb for correcting the color difference coefficients Cr and Cb with respect to Cb.
It is read by U and output to the adders 5 and 6.

In the adders 5 and 6, the input color difference signals Cr and C are used for correcting the color difference coefficient based on the brightness data value (that is, the brightness level) of the brightness signal Y of the input signal.
The color difference coefficient correction values ΔKr and ΔKb for b are added to the color difference coefficient units 1 and 2 and the correction coefficients Ksr and Ksb set for color difference correction of the color difference signals Cr and Cb, respectively. (Ksr + ΔK
r) and (Ksb + ΔKb) are output to the computing units 7 and 8.

On the other hand, 8-bit color difference signals Cr, C
As for the color difference data value of b, as described in the description of the prior art, centering on the value of “80H” indicating the center of 8 bits in hexadecimal notation, 1. Cr, Cb ≧
When the value is 80H, Cr1 and Cb1 obtained by subtracting 80H from the data values of the color difference signals Cr and Cb are input to the calculators 7 and 8, respectively. On the other hand, Cr, Cb <80
When it is H, the original data of the color difference signals Cr and Cb is set to Cr2 and C.
Input as b2 into the arithmetic units 7 and 8 as they are,
Shift calculation is performed. The color difference data Cr1, Cb1 or Cr2, Cb2 as the result of the shift calculation will be represented by the symbols Crn, Cbn (n = 1 or 2), respectively.

In the arithmetic units 7 and 8, the code Cr
For the color difference data indicated by n and Cbn, the adder 5,
Data for color difference correction (Ks
r + ΔKr) and (Ksb + ΔKb) are calculated to obtain the corrected color difference data Cr ′, Cb ′ for conversion. Cr ′ = (Ksr + ΔKr) * Crn Cb ′ = (Ksb + ΔKb) * Cbn

The corrected color difference data Cr 'and Cb' output from the arithmetic units 7 and 8 together with the luminance signal Y of the input signal are calculated in the matrix circuit 9 by, for example, matrix calculation as shown in the above-mentioned formula (1). , Red, green,
Data conversion into blue color signals R, G, B.

Here, for correction of the correction coefficients Ksr and Ksb used for color difference correction of the color difference signals Cr and Cb,
Color difference coefficient correction values ΔKr stored in LUTs 3 and 4,
The data value of ΔKb is composed of 4-bit data as shown in Table 1 in correlation with the brightness data value of the brightness signal Y, and is a positive value consisting of a real number whose absolute value is smaller than 1. Either negative value is set. Thus, the color difference data values (color difference levels) of the color difference signals Cr and Cb of the input signal can be amplified or, conversely, attenuated.

[0029]

[Table 1]

That is, of the 4-bit structure, the MSD (Mo
The third bit on the st Significant Digit side is a sign bit indicating the polarity (positive / negative), and the second bit
The bit number is the first decimal place (that is, the digit of (1/2)), the second bit is the second decimal place (that is, the digit of (1/4)),
The third bit is the first decimal place (that is, the digit of (1/8))
Is shown. For example, as the brightness data value of the brightness signal Y, when the center value is “80H” in hexadecimal display,
If “6H” (that is, “0110B”) is stored as the data value of the color difference coefficient correction values ΔKr and ΔKb stored in each of the LUTs 3 and 4, the color difference coefficient correction values ΔKr and ΔKb are Both ΔKr (, ΔKb) = (1/2) + (1/4) =
When 0.75 is set and the brightness level of the brightness signal Y is at the center, the color saturation is further increased by "0.75" for each of the correction coefficients Ksr and Ksb of the color difference signals Cr and Cb. It will be emphasized.

Then, using the data values of the color difference coefficient correction values ΔKr and ΔKb stored in the LUTs 3 and 4 in accordance with the brightness level of the brightness signal Y, the color difference coefficient units 1 and 1 are used.
2 The correction coefficients Ksr and Ks preset for each
By further correcting b, it becomes possible to perform fine color correction conversion based on the intensity of the luminance signal Y. For example, even when a color difference signal with a high color saturation level is input, color collapse occurs. Can be prevented, and the fidelity of color reproduction can be improved.

The correction coefficients Ksr and Ksb are set according to the magnitude of the luminance data value (luminance level) indicated by the luminance signal Y.
Lookup table LUT capable of looking up the values of the color difference coefficient correction values ΔKr and ΔKb based on the magnitude of the luminance data value when further correcting the magnitude of
3, 4 and the lookup table L
RAM (Random) that enables high-speed access to UTs 3 and 4
m Access Memory) or ROM (Read
By configuring with Only Memory,
High-speed color difference correction is possible, and high-speed processing in real time can be realized.

Further, even when it is not applied to a display system having different color reproducibility, the look-up table in which the color difference coefficient correction values ΔKr and ΔKb are set according to the display system is set. It is possible to easily deal with the problem by changing only the stored contents. Furthermore, by adjusting and changing the stored contents of the look-up table, it is possible to easily realize a special effect (special hue) for the expression color.

Further, the look-up table LUT is not based on the correction coefficients Ksr and Ksb itself, but only on the color difference coefficient correction values ΔKr and ΔKb for further finely correcting the correction coefficient.
By configuring 3 and 4, the color difference coefficient correction value ΔKr,
Even if ΔKb is prepared corresponding to each gradation of the luminance signal Y, for example, the color difference coefficient correction values ΔKr, Δ
Even if the bit length of Kb is 4 bits and the number of gradations is 256, the storage capacity of 128 bytes is sufficient, and the storage capacity of the lookup tables LUT3, 4 can be made a small amount. The circuit scale can be reduced, and the cost can be reduced.

Next, a second embodiment of the RGB conversion circuit according to the present invention will be described with reference to FIG. FIG. 2 is a block configuration diagram showing another configuration example of the circuit block of the RGB conversion circuit according to the present invention. RG shown in FIG.
In the B conversion circuit 10 ', the circuit blocks having the same functions as those of the circuit block shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, the color difference coefficient units 1 and 1,
A look-up table LUT (Lookup Table) that stores color difference coefficient correction values, that is, Cr and Cb correction values for further correcting the correction coefficient set to 2.
e) Although each of 3 and 4 is indexed based on the luminance data value of the luminance signal Y, in FIG. 2 in the present embodiment, such a lookup table LUT (Look) is used.
Up Table) 13 and 14 respectively, instead of the luminance data value (luminance level) of the luminance signal Y, color difference data values (color difference levels) indicated by the color difference signals Cr and Cb, respectively.
I try to index based on.

The digital data of the picked-up image signal transmitted from the image pickup device or the reading / reproducing circuit of the image device (not shown) includes a luminance signal Y having luminance data and RY, BY.
The color difference signals Cr and Cb having the color difference data are input in parallel to the RGB conversion circuit 10 'according to the present invention. Here, the color difference signals Cr and Cb of the input signal
, The color difference coefficients Ksr, Ks used for correcting the color difference of the color difference signals Cr, Cb, respectively.
In order to correct b, the respective color difference signals Cr, C
LUT1 according to the color difference data value of b (that is, the color difference level)
3 and 14 are indexed to obtain corresponding color difference coefficient correction values, which are output as input signals to the adders 5 and 6.

That is, the color difference coefficient correction value is stored in the memory RAM.
Lookup table LUT1 configured by
3 and 14, Cr correction values and Cb for correcting the color difference coefficients Ksr and Ksb for the color difference signals Cr and Cb, respectively.
It is set as a correction value, and is set corresponding to each color difference data value indicated by the color difference signals Cr and Cb which are input signals. Then, the values of the color difference data indicated by the color difference signals Cr and Cb, which are the input signals, are indexed as the addresses of the LUTs 13 and 14, respectively, so that the color difference coefficients stored in the addresses of the LUTs 13 and 14 are set. Correction value, that is, Cr correction value,
The Cb correction value is read out by a CPU (not shown) as color difference coefficient correction values ΔKr ′, ΔKb ′ for correcting the color difference coefficients Cr, Cb with respect to the color difference signals Cr, Cb which are input signals, and the adder 5, 6 is output.

In the adders 5 and 6, for the color difference coefficient correction based on the color difference data values (that is, the color difference levels) of the color difference signals Cr and Cb of the input signals, the color difference coefficient correction for the input color difference signals Cr and Cb is performed. Value ΔKr ′, ΔKb ′
And color difference signals Cr and Cb to color difference coefficient units 1 and 2, respectively.
Correction coefficients Ksr, K set for the color difference correction of
sb and color difference correction data (K
sr + ΔKr ′) and (Ksb + ΔKb ′) are output to the computing units 7 and 8.

On the other hand, 8-bit color difference signals Cr, C
As for the color difference data value of b, as described in the description of the prior art, centering on the value of “80H” indicating the center of 8 bits in hexadecimal notation, 1. Cr, Cb ≧
When the value is 80H, Cr1 and Cb1 obtained by subtracting 80H from the data values of the color difference signals Cr and Cb are input to the calculators 7 and 8, respectively. On the other hand, Cr, Cb <80
When it is H, the original data of the color difference signals Cr and Cb is set to Cr2 and C.
Input as b2 into the arithmetic units 7 and 8 as they are,
Shift calculation is performed. The color difference data Cr1, Cb1 or Cr2, Cb2 as the result of the shift calculation will be represented by the symbols Crn, Cbn (n = 1 or 2), respectively.

In the arithmetic units 7 and 8, the code Cr
For the color difference data indicated by n and Cbn, the adder 5,
Data for color difference correction (Ks
r + ΔKr ′) and (Ksb + ΔKb ′) to obtain corrected color difference data Cr ′ and Cb ′ for conversion. Cr ′ = (Ksr + ΔKr ′) * Crn Cb ′ = (Ksb + ΔKb ′) * Cbn

The corrected chrominance data Cr 'and Cb' output from the arithmetic units 7 and 8 together with the luminance signal Y of the input signal are calculated by the matrix circuit 9 in a matrix operation as shown in the above-mentioned equation (1). , Red, green,
Data conversion into blue color signals R, G, B.

Here, for correction of the correction coefficients Ksr and Ksb used for color difference correction of the color difference signals Cr and Cb,
Color difference coefficient correction value ΔK stored in LUTs 3 and 4
The data values of r ′ and ΔKb ′ are the color difference signals Cr and C.
Correlated with the size of the color difference data of b, it is composed of, for example, 4-bit data, and is set to any desired value of positive or negative consisting of a real number whose absolute value is smaller than 1. Further, for example, when the color difference data values of the color difference signals Cr and Cb are near “80H”, the LUTs 13 and 14 are provided.
The color difference coefficient correction values .DELTA.Kr 'and .DELTA.Kb' output from are reduced, and the color difference coefficient correction values .DELTA.Kr 'and .DELTA.Kb' are increased as the color difference data of the color difference signals Cr and Cb move away from "80H". It is supposed to be set.

Then, using the data values of the color difference coefficient correction values ΔKr ′ and ΔKb ′ stored in the LUTs 3 and 4, respectively, the correction coefficients Ksr and By further correcting Ksb, it becomes possible to perform fine color correction conversion based on the size of the color difference data values of the color difference signals Cr and Cb. For example, when a color difference signal close to the color saturation level is input. However, even if the color saturation level is close to the color saturation level, the color difference correction values ΔKr ′ and ΔKb ′ with respect to the correction coefficients Ksr and Ksb for performing the color difference correction are gradually increased, so that the color collapse occurs. It is possible to generate a color signal having a natural color tone that is prevented from occurring.

[0045]

As described above, the R according to the present invention
According to the video equipment equipped with the GB conversion circuit and the RGB conversion circuit, the following operational effects can be brought about. First, the magnitude of the luminance data value (luminance level) indicated by the input luminance signal Y or the color difference signals Cr, C.
According to the magnitude of the color difference data value (color difference level) of b, the magnitude of the correction coefficient for correcting the color difference signals Cr and Cb, respectively, can be further finely corrected, and the degree of emphasis of the color can be finely corrected. Therefore, it is possible to generate a color signal having a natural color tone in which color collapse is prevented.

Secondly, when the magnitude of the correction coefficient is further corrected according to the magnitude of the luminance data value indicated by the luminance signal Y or the magnitude of the color difference data values of the color difference signals Cr and Cb,
The value of the color difference coefficient correction value that further corrects the correction coefficient is configured as a lookup table that can be looked up according to the size of the luminance data value or the size of the color difference data value, and high-speed access is possible. RAM or R
Since the lookup table is composed of OM, high-speed color difference correction can be performed, and high-speed processing in real time can be realized.

Thirdly, even when it is applied to a display system having different color reproducibility, the look-up table storing the color difference coefficient correction value is set according to the display system. It is possible to easily deal with this by changing only the content. Further, it is possible to easily realize a special effect for the expression color by adjusting and changing the stored contents of the look-up table.

Fourth, since the look-up table is configured not by the correction coefficient itself but only by the color difference coefficient correction value for further correcting the correction coefficient, for example, the color difference coefficient correction value is set for each gradation of the luminance signal. Even if each is prepared, the storage capacity of the look-up table can be made small, the circuit scale can be reduced, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a configuration example of a circuit block of an RGB conversion circuit according to the present invention.

FIG. 2 is a block configuration diagram showing another configuration example of the circuit block of the RGB conversion circuit according to the present invention.

FIG. 3 is a block configuration diagram showing a circuit block of an RGB conversion circuit in a conventional technique.

[Explanation of symbols]

1, 2 ... Color difference coefficient unit, 3, 4 ... Look-up table L
UT, 5, 6 ... Adder, 7, 8 ... Arithmetic unit, 10 ... RGB
Conversion circuit, 13, 14 ... Look-up table LUT,
20 ... RGB conversion circuit, 21, 22 ... Color difference coefficient unit, 2
3, 24 ... Operation unit, 25 ... Matrix circuit, Cr, C
b ... Color difference signal, R, G, B ... Color signal, Y ... Luminance signal.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 9/67 H04N 1/40 D 5C079 9/79 1/46 Z F term (reference) 5B057 CA01 CA08 CB01 CB08 CE17 CE18 CH07 5C055 BA01 BA05 EA02 EA04 HA14 HA37 5C065 AA01 BB01 CC02 CC03 GG15 GG21 5C066 AA01 AA06 AA11 CA17 EA03 EA13 EE03 GA02 GA05 GB01 JA01 KE02 KE04 KE07 5C077 MP08 PP32 PP34 PP37 PQ23 5C079 HB01 HB04 HB12 LB02 MA04 NA03

Claims (6)

[Claims] 1. An RGB conversion circuit that outputs a RGB color signal using a luminance signal and a color difference signal as input signals, and a correction coefficient setting unit that sets a correction coefficient for performing color difference correction of the color difference signal, An RGB conversion circuit, comprising: a color difference coefficient correction unit capable of further correcting the correction coefficient set in the correction coefficient setting unit according to the brightness level of the brightness signal. . 2. A correction coefficient setting means for setting a correction coefficient for performing color difference correction of the color difference signal in an RGB conversion circuit which outputs RGB color signals using a luminance signal and a color difference signal as input signals, An RGB conversion circuit comprising: a color difference coefficient correction unit capable of further correcting the correction coefficient set in the correction coefficient setting unit according to the color difference level of the color difference signal. . 3. The RGB conversion circuit according to claim 1, wherein the color difference coefficient correction value for further correcting the correction coefficient in the color difference coefficient correction means is a real number whose absolute value is smaller than 1. RGB characterized in that
Conversion circuit. 4. The RG according to any one of claims 1 to 3.
In the B conversion circuit, a color difference coefficient correction value for further correcting the correction coefficient by the color difference coefficient correction means is stored in a look-up table accessible by either the luminance level or the color difference level. An RGB conversion circuit characterized by: 5. The RGB conversion circuit according to claim 4, wherein the lookup table is a high-speed RAM (Random Access Memory) capable of high-speed access.
y) or high-speed ROM (Read Only Memory)
An RGB conversion circuit characterized by comprising y). 6. A video device for picking up an image and reproducing the image, comprising the RGB conversion circuit according to any one of claims 1 to 5.