JP2006005961A - Video display device and color temperature correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a visually preferable white color by highly accurately performing color temperature correction on a white color signal having high luminance and low saturation. <P>SOLUTION: A signal processing circuit relating to the present invention comprises an A/D converter 14 for converting an input video signal into a digital signal; a matrix circuit 15 for converting the digital signal outputted from the A/D converter into a luminance signal and at least two color difference signals; a hue conversion circuit 18 for obtaining a hue signal from the color difference signals outputted from the matrix circuit; a hue correction circuit 20 for correcting this hue signal; a saturation conversion circuit 21 for obtaining a saturation signal from said color difference signals; a saturation correction circuit 22 for correcting this saturation signal; and a color temperature correction circuit 23 for performing color temperature correction on the corrected hue signal and the corrected saturation signal, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for correcting the color temperature of a video signal, and a video display device such as a color television receiver or a liquid crystal projector provided with such a color temperature correction circuit.

  In display devices such as color television receivers, especially when bright white is displayed on the display device, if the color temperature is raised to a slightly bluish white and displayed on the display device, the image will appear visually beautiful. Is generally known.

  As such a conventional technique, for example, one described in Patent Document 1 is known. This is because the achromatic portion is detected by detecting an achromatic portion such as white or gray from the maximum values of the three color difference signals RY, GY, and BY and controlling the level of BY high. The blue temperature component is strengthened to increase the color temperature.

Japanese Patent Laid-Open No. 7-23414

  By the way, the actual image is not only pure white but also a color close to white that is slightly mixed with pure white (hereinafter such color is called approximate white, and this approximate white and pure white are In general). In natural images such as landscapes and portrait images, the portion that appears white is actually a proportion of approximate white rather than pure white, and pure white is often slight. In the above prior art, only the achromatic color part operates so as to increase the color temperature. Only done. Therefore, there arises a problem that the visual effect due to the color temperature rise when the entire image is viewed is reduced.

  Further, even if the color temperature is originally a light yellowish approximate white with a low color temperature, it may appear more beautiful when it is made a light blueish approximate white with a high color temperature. Furthermore, when using a display device with a color reproduction characteristic such as displaying a white system at a color temperature lower than the color temperature of the video signal (for example, displaying pure white as an approximate white with yellowing), only pure white is used. In addition, it is visually preferable to increase the color temperature even for an approximate white color having a low color temperature. However, the above prior art is not designed to increase the color temperature of the approximate white, and cannot meet such a requirement.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a video display device capable of displaying a video having a visually preferable color by correcting the color temperature more suitably. And a color temperature correction method therefor.

  In order to achieve the above object, an image display device according to the present invention is a white display system including an approximate white color having a luminance of a predetermined level or higher and having a saturation level of a predetermined level or less. A signal processing circuit including a color temperature correction circuit for correcting the color temperature of the signal is provided.

  Specifically, the signal processing circuit converts an input video signal into a digital signal, and converts the digital signal output from the A / D converter into a luminance signal and at least two color difference signals. A matrix circuit, a hue processing circuit for obtaining a hue signal from the color difference signal output from the matrix circuit, a saturation processing circuit for obtaining a saturation signal from the color difference signal, and a microcomputer, The color temperature correction circuit includes a hue signal output from the hue processing circuit and a saturation output from the saturation processing circuit based on a set value of a predetermined luminance level and a predetermined saturation level supplied from the microcomputer. Among the signals, color temperature correction processing is performed to increase the color temperature of the signal belonging to the white color system (close to blue).

  The color temperature correction circuit includes: a first color temperature correction unit that performs color temperature correction on a hue signal belonging to the white color system out of the hue signals output from the hue processing circuit; and the saturation processing circuit. Among the output saturation signals, a second color temperature correction unit that performs color temperature correction on the saturation signal belonging to the white system, an output signal from the first color temperature correction unit, and the hue processing A first selection circuit that selects and outputs one of the hue signals output from the circuit, an output signal from the second color temperature correction unit, and a saturation signal output from the saturation processing circuit. And a second selection circuit that selects and outputs one of them. The first and second selection circuits may detect the first and second color temperatures when an area of a signal belonging to a white system having a predetermined luminance or higher and a predetermined saturation or lower is detected in the input video signal. The output signal of the correction unit is selected.

  The color temperature correction method according to the present invention includes a step of converting an input video signal into a digital signal, a step of separating the digital signal into a luminance signal and a color difference signal, and converting the color difference signal into a hue signal and a saturation signal. And a step of performing a color temperature correction process for increasing a color temperature for a signal belonging to a white system that is equal to or higher than a predetermined luminance and equal to or lower than a predetermined saturation among the hue signal and the saturation signal. It is characterized by this. The step of performing the color temperature correction processing may include a step of bringing the hue of the signal belonging to the white system close to blue and a step of increasing the saturation of the signal belonging to the white system.

  According to the configuration of the present invention, the color temperature correction is performed on a white signal having a predetermined luminance or higher and a predetermined saturation or lower. Therefore, not only pure white but also slightly white The color temperature can also be corrected for an approximate white signal that is mixed. For this reason, even if the image contains a lot of approximate white, such as a natural image, the approximate white color temperature is corrected, for example, to be higher (closer to blue) to obtain a visually desirable white It is possible to provide more beautiful images.

  As described above, according to the present invention, it is possible to suitably correct the hue and saturation of a video signal within a predetermined range. In particular, more accurate color temperature correction can be performed for a white signal having a predetermined luminance or higher and a predetermined saturation or lower. Further, since the color temperature correction is not performed for a signal of a color other than the designated white color, it is possible to reduce image quality deterioration for an image having a color other than the white color.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a signal processing circuit used in a video display device according to the present invention. The R primary color signal input to the R input terminal 11, the B primary color signal input to the G input terminal 12, and the B primary color signal input to the B input terminal 13 are respectively supplied to the A / D conversion circuit 14. Converted to a digital signal. The matrix conversion circuit 15 performs matrix conversion processing on the digital primary color signals (R, G, B) output from the A / D conversion circuit 14, and converts the digital three primary color signals into luminance signals Y and color difference signals. A certain (R−Y) signal and (B−Y) signal are converted and output. The luminance signal Y is input to the detection circuit 17 and the inverse matrix conversion circuit 27, respectively. Further, the (R−Y) signal and the (B−Y) signal, which are color difference signals, are respectively input to the hue conversion circuit 18 and the saturation conversion circuit 21. The hue conversion circuit 18 uses the input (R−Y) signal and (B−Y) signal, for example, performs an attribute conversion calculation as shown in Equation 1, and outputs a digital hue signal (θ). .

一方、彩度変換回路２１は、この入力された（Ｒ−Ｙ）信号と(Ｂ−Ｙ)信号を用いて、例えば数２に示すような属性変換演算をしてデジタル形式の彩度信号(Ｓ)を出力する。

On the other hand, the saturation conversion circuit 21 uses the input (R−Y) signal and (B−Y) signal to perform an attribute conversion operation as shown in, for example, Equation 2 to obtain a digital saturation signal ( S) is output.

ここで、色相信号と彩度信号について以下に説明する。図２に示すように、横軸に(Ｂ−Ｙ)信号をとり、縦軸に(Ｒ−Ｙ)信号をとったとき、色はベクトルで表される。そのベクトルの方向(横軸である(Ｂ−Ｙ)軸とそのベクトルとが為す角度)が色合いである色相(θ)を示し、ベクトルの大きさが色の濃淡である彩度(Ｓ)を示す。このように、色をベクトル表示したものは色相環と呼ばれ、一般的に知られている。この色相環において、例えばマゼンタは、図２に示すように、(Ｂ−Ｙ)軸から４５°の角度に位置するベクトルで表される。すなわち、マゼンタの色相(θ)は４５°である。彩度(Ｓ)は、そのベクトルの大きさにより決定され、ベクトルの大きさが大きいほど色が濃く、小さければ色が淡い。またベクトルの大きさが０であればその色が無いことを示している。また、赤色、黄色、緑色、シアン色、青色の色相は、それぞれ１１３．２°、１７３．０°、２２５．０°、２９３．２°、３５３．０°である。色相変換回路１８は、デジタル形式の色相信号を出力しており、デジタル信号のビット精度を１０ビットとすると、色相０°〜３５９．９°を０〜１０２３のデジタル信号として出力する。すなわち、色相３６０°を２の１０乗である１０２４で分割した精度となり、色相デジタル信号の１LSBは約０．３５°となる。

Here, the hue signal and the saturation signal will be described below. As shown in FIG. 2, when the (BY) signal is taken on the horizontal axis and the (RY) signal is taken on the vertical axis, the color is represented by a vector. The direction of the vector (the angle formed by the (BY) axis which is the horizontal axis and the vector) indicates hue (θ) which is a hue, and the saturation (S) where the magnitude of the vector is shade of color. Show. In this way, a color vector display is called a hue circle and is generally known. In this hue circle, for example, magenta is represented by a vector located at an angle of 45 ° from the (BY) axis, as shown in FIG. That is, the hue (θ) of magenta is 45 °. The saturation (S) is determined by the size of the vector. The larger the vector size, the darker the color, and the smaller the color, the lighter the color. If the vector size is 0, it indicates that there is no color. The hues of red, yellow, green, cyan, and blue are 113.2 °, 173.0 °, 225.0 °, 293.2 °, and 353.0 °, respectively. The hue conversion circuit 18 outputs a hue signal in a digital format. If the bit accuracy of the digital signal is 10 bits, the hue conversion circuit 18 outputs a hue of 0 ° to 359.9 ° as a digital signal of 0 to 1023. That is, the hue 360 ° is divided by 1024 which is the power of 2, and 1 LSB of the hue digital signal is about 0.35 °.

  FIG. 3 is a diagram supplementing the contents described above, and an example of the relationship between the hue signal and the saturation signal is shown by a waveform 301. In FIG. 3, the horizontal axis represents the hue signal θ (10-bit accuracy), and the vertical axis represents the saturation signal S (8-bit accuracy). Further, representative hues (BY) are shown as 0, (RY) as 256,-(BY) as 512, and-(RY) as 768.

  On the other hand, the saturation conversion circuit 21 outputs a saturation signal having a color vector size corresponding to the hue signals 0 to 1023 as a digital signal. When the bit accuracy of the digital saturation signal is 8 bits, the saturation conversion circuit 21 outputs a digital signal of 0 to 255.

  The digital hue signal output from the hue conversion circuit 18 is input to the hue correction circuit 20. The hue correction circuit 20 includes a local hue correction circuit 203 and adders 201 and 202, and corrects and outputs a signal having a specific range of hues among the input digital hue signals. The hue range and correction amount of the hue signal corrected by the hue correction circuit 20 are determined by various setting values output from a microcomputer (hereinafter referred to as a microcomputer) 40. The digital saturation signal output from the saturation conversion circuit 21 is input to the saturation correction circuit 22. The saturation correction circuit 22 includes a saturation correction coefficient generation circuit 222, a multiplier 221 and an adder 223, and corrects a signal having a specific range of saturation from the input digital saturation signal. Output. The saturation range and the correction amount of the saturation signal corrected by the saturation correction circuit are determined by various setting values output from the microcomputer 40.

  A digital hue signal (hereinafter referred to as a corrected hue signal) corrected by the hue correction circuit 20 and a digital saturation signal (hereinafter referred to as a corrected saturation signal) corrected by the saturation correction circuit are referred to as a color temperature correction circuit. 23. The color temperature correction circuit 23 is a main characteristic part of the present invention, and is determined by the saturation upper limit setting value ST and the luminance lower limit setting value YB supplied from the microcomputer 40 among the input correction hue signal and correction saturation signal. The color temperature correction is performed so as to increase the color temperature of a white signal having a predetermined luminance or higher and a predetermined saturation or lower. The color temperature correction circuit 23 also includes a first color temperature correction unit 231 that performs color temperature correction on the correction hue signal, an output signal from the first color temperature correction unit 231 and a correction hue signal (of the hue correction circuit 20). A first selection circuit that selects and outputs one of the output signals), a second color temperature correction unit 235 that performs color temperature correction on the corrected saturation signal, and an output from the first color temperature correction unit 235 A second selection circuit 236 that selects and outputs either the signal or the corrected saturation signal (the output signal from the saturation correction circuit 22). The first selection circuit 232 and the second selection circuit 236 respectively output the first color correction unit 231 and the second color correction unit 235 when the input video signal is equal to or higher than a predetermined luminance and equal to or lower than a predetermined saturation. A signal is selected and output. In other cases, a corrected hue signal and a corrected saturation signal are selected and output. The signal selection operation in the first selection circuit 232 and the second selection circuit 236 is performed based on a control signal output from the detection circuit 17.

  The detection circuit 17 detects whether the input video signal is a white signal having a predetermined luminance or higher and a predetermined saturation or lower. Specifically, the detection circuit 17 compares the luminance signal output from the matrix conversion circuit 15 with the luminance lower limit setting value YB set by the microcomputer 40, and the microcomputer similarly to the correction saturation signal. A saturation comparison circuit 172 that compares the set saturation upper limit setting value ST, an output signal from the luminance comparison circuit 171 and an output signal from the saturation comparison circuit 172 are input, and the input video is based on these signals. It is determined whether or not the signal satisfies a condition that is greater than or equal to a predetermined luminance and less than or equal to a predetermined saturation, and if the condition is satisfied, a control signal is sent to the first selection circuit 232 and the second selection circuit 236. Has a switching control circuit 173 that outputs. That is, the switching control circuit 173 selects the output signals of the first color correction unit 231 and the second color correction unit 235 when the first selection circuit 232 and the second selection circuit 236 satisfy the above condition. The output is controlled.

  Output signals from the first selection circuit 232 and the second selection circuit 236 are input to the color difference conversion circuit 26. The color difference conversion circuit 26 generates and outputs (R−Y) and (B−Y) signals as color difference signals from these output signals. The color difference signal output from the color difference conversion circuit 26 is input to the inverse matrix conversion circuit 27, and converted into the R, G, and B primary color signals by the inverse matrix conversion process together with the luminance signal output from the matrix conversion circuit 15. The The three primary color signals output from the inverse matrix conversion circuit 27 are supplied to the display device 28, and the display device 28 displays an image based on the three primary color signals.

  Next, the detail of each part is demonstrated below. First, details of the hue correction circuit 20 will be described with reference to FIGS. The hue correction circuit 20 has linear input / output characteristics as indicated by a straight line 401 in FIG. 4A when the adders 201 and 202 do not add anything to the digital hue signal. The digital hue signal output from the hue conversion circuit 18 is input to the adder 201 and the local hue correction circuit 203, respectively. In the local hue correction circuit 203, the center value (HP shown in FIG. 4B), the level (H shown in FIG. 4B), the hue width (shown in FIG. 4B) output from the microcomputer 40. W) is input, the hue within this range is decoded based on these values, and a signal having a waveform as indicated by 402 in FIG. 4B is output. The adder 201 adds the digital hue signal and the output signal of the local hue correction circuit 203 having the trapezoidal waveform 402. As a result, as shown in FIG. 5A, the output of the adder 201 outputs a signal having a waveform 501 shifted by H upward in the W section centered on HP. This shift (control) amount is determined by the level H input from the microcomputer 40. As described above, since the local hue correction circuit 203 and the adder 201 variably control the hue within the range specified by the microcomputer 40 at the level specified by the microcomputer, the local hue can be controlled. It becomes.

  Further, the signal (waveform 501) output from the adder 201 is input to one input terminal of the adder 202. The offset value output from the microcomputer 40 is input to the other input terminal of the adder 202. This offset value has a constant level a over the entire hue, as shown by a straight line 502 in FIG. The adder 202 adds the signal output from the adder 201 and the offset value output from the microcomputer 40. As a result, the adder 202 outputs a signal obtained by shifting (offset) the entire signal shown in FIG. 5A upward by the offset value level a as shown by the waveform 503 in FIG. 5C. In this way, the adder 202 can control the overall hue (over all hues). This is a function corresponding to so-called tint adjustment, and is used when it is desired to adjust the overall hue. In the present embodiment, a 10-bit adder is used for both the input and output as the adder 202. Therefore, when the addition result exceeds 1023, it overflows and returns to 0. Accordingly, when the addition result exceeds 1023, the adder 202 outputs a value obtained by subtracting 1023 from the addition result.

  As described above, the hue correction circuit 20 changes the hue signal in the hue range designated by the microcomputer 40 to another hue, and outputs a signal in which the entire hue is offset by a predetermined value by setting an offset. can do. Further, since a 10-bit digital signal is used as the hue signal, highly accurate hue shift control and hue offset control in units of about 0.35 degrees can be performed. Further, since parameters related to hue correction such as hue shift amount, shift range, and offset amount are set by the microcomputer 40, these parameters can be arbitrarily changed and adjusted. In the present embodiment, the hue shift range is set to one, but a plurality of local hue correction circuits 203 are prepared, and these output signals are added and input to the adder 201, whereby a plurality of hue ranges are obtained. It is also possible to shift (control) independently.

  Next, details of the saturation correction circuit 22 will be described with reference to FIG. When nothing is added to the digital saturation signal by the adder 223 and nothing is multiplied by the multiplier 221, the saturation correction circuit 22 is linear as shown by a straight line 1201A in FIG. Suppose that it has an input / output characteristic. The digital saturation signal output from the saturation conversion circuit 21 is input to the multiplier 221 of the saturation correction circuit 22. On the other hand, the digital hue signal output from the hue conversion circuit 18 is input to the local saturation correction circuit 222. The local saturation correction circuit 222 determines the center value (HP shown in FIG. 13B), the level (H shown in FIG. 13B), the hue width (FIG. 13B) designated by the microcomputer 40. W) is input, the hue within this range is decoded based on these values, and the saturation of the hue in the specific range as shown in the waveform 1202A of FIG. 13B is locally corrected. Output a correction signal. The adder 223 adds the offset value output from the microcomputer 40 and the output signal of the local saturation signal correction circuit 222. As a result, the adder 223 outputs a saturation amplification coefficient having a characteristic as shown by the waveform 1203A in FIG. Therefore, it is the height H that determines the amplification degree of the saturation signal in the specific hue range, and the amplification degree of the entire saturation signal (saturation signal in all hues) is determined by the offset value from the microcomputer 40. . This offset value is constant over the entire hue, and in this embodiment, the level is set to 128, which is intermediate between the minimum value (0) and the maximum value (255) of the saturation signal. The output signal (saturation amplification coefficient) of the adder 223 is input to one input terminal of the multiplier 221, and the digital saturation signal from the saturation conversion circuit 21 is input to the other input terminal. The multiplier 221 shifts (corrects) the saturation level of the specific hue range by multiplying the digital saturation signal and the saturation amplification coefficient.

  In this way, the saturation correction circuit 22 can locally correct the saturation signal in the specified hue range to variably control the color shading in a specific hue, and control the saturation signal of all hues. Thus, it is also possible to variably control the color shade in all hues. This is a function corresponding to so-called color adjustment. In addition, since parameters related to saturation correction such as a saturation correction amount, a correction range, and an offset amount are set by the microcomputer 40, these parameters can be arbitrarily changed and adjusted. In this embodiment, one saturation correction range is provided. However, a plurality of local saturation correction circuits are prepared, and these outputs are added and input to the multiplier 221, so that a plurality of hue ranges can be obtained. It is also possible to correct the saturation independently.

  Next, details of the detection circuit 17 will be described with reference to FIG. The luminance signal Y output from the matrix conversion circuit 15 is input to the luminance level comparison circuit 171. The luminance level comparison circuit 171 compares the luminance signal Y with the luminance lower limit setting value YB (601) shown in FIG. 6, and when the luminance signal Y is larger than the luminance lower limit setting value YB, a high luminance level of “1”. A detection signal is output. On the contrary, when the luminance signal Y is smaller than the luminance lower limit setting value YB, “0” is output. In the present embodiment, the luminance lower limit set value YB is 210. On the other hand, the saturation signal output from the multiplier 22 of the saturation correction circuit 22 is input to the saturation level comparison circuit 172. The saturation level comparison circuit 172 compares the saturation signal with the saturation upper limit setting value ST (602) shown in FIG. 6, and when the saturation signal is smaller than the saturation upper limit setting value ST, “1”. Output a low saturation level detection signal. On the contrary, when the saturation signal is larger than the saturation upper limit set value ST, “0” is output. In the present embodiment, the saturation upper limit set value ST is set to 10.

  Both the high luminance level detection signal and the low saturation level detection signal are input to the switching control circuit 173. The switching control circuit 173 performs an AND operation on the two detection signals, so that the input video signal is a white signal that is equal to or higher than a predetermined luminance and equal to or lower than a predetermined saturation (that is, a white signal that is very bright and has a very light color). It is determined whether or not there is. That is, the switching control circuit 173 determines whether or not the input video signal is present in the shaded cylindrical area (white signal region) shown in FIG. When the input video signal is within the shaded cylindrical area (that is, when the two detection signals are both “1”), “1” is indicated, and when the input video signal is outside the shaded cylindrical area (ie, the two detection signals are A flag signal of “0” is output when one or both of them are 0). This flag signal is supplied to the first and second selection circuits as a control signal for controlling the first selection circuit 232 and the second selection circuit 236 of the color temperature correction circuit 23.

  As described above, the detection circuit 17 according to the present embodiment detects a video signal having a saturation equal to or lower than the saturation upper limit setting value ST and a luminance equal to or higher than the luminance lower limit setting value YB. It is possible to detect not only white but also white signals in which colors are slightly mixed and white signals having low luminance (slightly mixed in gray). Further, since the luminance lower limit setting value YB and the saturation upper limit setting value ST, which are the reference for detection of the white signal, are set by the microcomputer 40, the range of the white signal to be detected is arbitrarily and accurately set. it can. Further, for example, in an image area where the color is sufficiently colored such as human skin, the amplitude level of the saturation signal is large and the luminance signal is not extremely large. Therefore, depending on the set values of ST and YB, the white signal It can be excluded from the detection range.

  Next, details of the color temperature correction circuit 23 will be described with reference to FIGS. First, the first color temperature correction unit 231 that performs color temperature correction on the hue signal will be described with reference to FIGS. The first color temperature correction unit 231 uses the hue (blue hue here) shown in the vector 801 in FIG. 8A as a reference hue, and generates a hue shift coefficient that gathers the surrounding hues together with this reference hue. To do. A specific example of the circuit configuration is shown in FIG.

  In FIG. 7, the corrected color signal output from the adder 202 of the hue correction circuit 20 is input to the hue input terminal 2312 of the first color temperature correction unit 231. The corrected hue signal input to the hue input terminal 2312 is supplied to one input terminal of the adder 2322. Further, the hue offset value (HUEOFFSET) set by the microcomputer 40 is supplied to the other input terminal of the adder 2322 via the hue offset input terminal 2311. The hue offset value (HUEOFFSET) is also supplied to one input terminal of the subtracter 2336. The adder 2322 adds the correction hue signal and the hue offset value (HUEOFFSET). Here, the hue offset value (HUEOFFSET) set by the microcomputer 40 is equal to the difference T between the digital value “1024” and the hue value θ of the reference vector 801 shown in FIG. It is determined by the following formula.

        HUEOFFSET = 1024− (353/360) · 1024 = 20 Therefore, the adder 2322 receives a signal having a hue value of the vector 801 as shown by the vector 802 in FIG. Outputs “0”. This indicates that the vector 801 is rotationally shifted counterclockwise by the hue offset value T to the position of the vector 802 which is the (BY) axis. The hue signal that is rotated (shifted) as a whole by the hue offset value (HUEOFFSET) by the adder 2322 is input to a subtracter 2323 that is a component of the first hue shift coefficient generation circuit 2340.

  Hereinafter, the operation of the first hue shift coefficient generation circuit 2340 will be described. The subtracter 2323 outputs a hue signal obtained by subtracting 512 from the hue signal output from the adder 2322. At the same time, the subtracter 2323 outputs a digital value “1” if the subtraction result is positive, and outputs a sign signal of the digital value “0” if it is negative. The hue signal and the sign signal that are subtracted and output are input to the absolute value circuit 2324. The absolute value circuit 2324 outputs the input signal as it is when the sign signal is “1”, and performs the absolute value calculation and outputs it because the input signal is negative when the sign signal is “0”. The hue component converted into an absolute value by the absolute value circuit 2324 is input to the multiplier 2325 and is multiplied by the hue multiplication coefficient input from the microcomputer 40 via the input terminal 2313 to adjust the gain. The multiplier 2325 outputs the gain-adjusted hue component to the first input terminal of the selection circuit 2332. In this way, the first hue shift coefficient generation circuit 2340 has a hue (digital value shifted by 512) that is shifted by 180 ° from the hue value near blue (the vector 801 shown in FIG. 8A) set by the microcomputer 40. (Hue) is set to the smallest shift amount, and a hue shift coefficient that gradually increases as the hue value shifted by 180 ° is generated. This hue shift coefficient is gain-adjusted by a multiplier 2325. The hue multiplication coefficient for gain adjustment can be adjusted by the microcomputer 40.

  The second hue shift coefficient generation circuit 2341 outputs a difference signal from the luminance signal Y larger than the luminance lower limit setting value YB used for detection of the white signal in the detection circuit 17 described above. When the luminance signal is smaller than the luminance lower limit set value YB, the level of the difference signal is set to zero. Then, a hue shift coefficient proportional to the magnitude of the difference signal is generated. The gain adjustment of the hue shift coefficient can also be set by the microcomputer 40. Details of the second hue shift coefficient generation circuit 2341 will be described below. The luminance signal Y output from the matrix conversion circuit 15 described above is supplied to the subtracter 2326 via the luminance input terminal 2314. The other input terminal 2315 of the subtracter 2326 is supplied with the luminance lower limit set value YB. The subtracter 2326 subtracts the luminance lower limit set value YB from the luminance signal Y and outputs a signal indicating the difference. This luminance difference signal is supplied to the clip circuit 2327. The clip circuit 2327 clips the negative value of the input luminance difference signal to “0” and outputs a positive luminance difference signal. The output signal of the clip circuit 2327 is input to the multiplier 2328 and is multiplied by the luminance multiplication coefficient input via the microcomputer 40 to adjust the gain. The multiplier 2328 outputs the gain-adjusted luminance component to the second input terminal of the selection circuit 2332 as a hue shift coefficient. A straight line 1001 in FIG. 10A indicates the input / output characteristics of the second hue shift coefficient generation circuit 2341. It is the luminance multiplication coefficient that adjusts the slope of the straight line 1001. In this way, the second hue shift coefficient generation circuit 2341 outputs a hue shift coefficient whose value increases as the luminance signal level increases when the level of the luminance signal is equal to or higher than the luminance lower limit setting value YB. When the luminance signal level is equal to or lower than the luminance lower limit setting value YB, 0 is output (that is, the hue shift amount is also 0).

  The third hue shift coefficient generation circuit 2342 uses the hue upper limit set value ST used for the detection of the white signal in the detection circuit 17 as a reference, and shifts the hue based on a difference signal with a smaller saturation signal. Generate coefficients. When the saturation signal is larger than the saturation upper limit setting value ST, the difference signal is 0 and the hue shift amount is also 0. Details of the third hue shift coefficient generation circuit 2342 will be described below. The corrected saturation signal output from the multiplier 221 of the saturation correction circuit described above is supplied to one input terminal of the subtractor 2329 via the saturation input terminal 2318. The saturation input upper limit value ST is supplied to the other input terminal of the subtracter 2326 via the input terminal 2317. Then, the subtracter 2329 subtracts the saturation upper limit set value ST from the corrected saturation signal, and outputs the difference signal to the clip circuit 2330. The clip circuit 2330 clips the negative value of the input difference signal to “0” and outputs only the positive difference signal. The difference signal output from the clip circuit 2330 is input to the multiplier 2331. The multiplier 2331 multiplies the difference signal by the saturation multiplication coefficient supplied from the microcomputer 40 via the input terminal 2319 to perform gain adjustment. The saturation component whose gain has been adjusted by the multiplier 2331 is supplied to the third input terminal of the selection circuit 2332. A straight line 1002 in FIG. 10B shows input / output characteristics of the third hue shift coefficient generation circuit 2342. The slope of the straight line 1002 is adjusted by the saturation multiplication coefficient. As described above, the third hue shift coefficient generation circuit 2342 generates a hue shift coefficient whose value increases as the saturation signal level decreases when the level of the saturation signal is lower than the saturation upper limit setting value ST. . When the level of the saturation signal is higher than the saturation upper limit setting value ST, 0 is output (the hue shift amount is also 0).

  The selection circuit 2332 has a signal input to the first input terminal (output signal from the first hue shift coefficient generation circuit 2340) and a signal input to the second input terminal (second hue shift coefficient generation). The output signal from the circuit 2341) and the signal input to the third input terminal (the output signal from the third hue shift coefficient generation circuit 2342) are selected as the minimum or maximum signal of the hue shift amount. Output. The signal selection operation in the selection circuit 2332 is controlled in accordance with a switching control signal from the microcomputer 40 input via the input terminal 2321. The processing contents of the signal selected by the selection circuit 2332 will be described below with reference to FIG. 9 by taking as an example the case where the selection circuit 2332 selects the signal input to the first input terminal for easy explanation. FIG. 9 to be described shows input / output characteristics of each unit in the first color temperature correction unit 231. FIG. 9A shows the input / output characteristics of the adder 2322 and the hue offset value (HUEOFFSET) is zero. FIG. 9B shows the input / output characteristics of the first hue shift coefficient generation circuit 2340, and FIG. 9C shows the input / output characteristics of the switching circuit 2335.

  The hue component output from the multiplier 2325 is input to the subtracter 2333 and the adder 2334 via the selection circuit 2332. The hue signal output from the adder 2322 is input to the subtracter 2323 and also input to the subtracter 2333 and the adder 2334. First, the subtracter 2333 subtracts the output signal of the selection circuit 2332 from the hue signal output from the adder 2322. If the subtraction result is negative, it is clipped to 0 by a built-in clip circuit (not shown). And output to the input terminal A of the switching circuit 2335. The adder 2334 adds the hue signal output from the adder 2322 and the output signal from the selection circuit 2332, and if the addition result exceeds 1023, the built-in clip circuit (not shown) sets an upper limit value. Clip to 1023 and output to the input terminal B of the switching circuit 2335. When the value of the sign signal output from the subtracter 2323 is “1” (that is, the subtraction result of the subtracter 2323 is positive), the switching circuit 2335 selects and outputs the signal input to the input terminal B. . When the value of the sign signal is “0” (that is, the subtraction result of the subtracter 2323 is negative), the switching circuit 2335 selects and outputs the signal input to the input terminal A.

  That is, the subtracter 2333 performs the subtraction of the waveform 901 of FIG. 9A and the subtraction of FIG. 9B during the subtraction period of FIG. 9B (that is, the output of the adder 2322 is in the range of 0 to 512). The signal of the waveform 902 in the period is subtracted and output to the input terminal A of the switching circuit 2335. The adder 2334 adds the signal of the waveform 901 in FIG. 9A and the addition in FIG. 9B during the addition period of FIG. 9B (that is, the output of the adder 2322 is in the range of 513 to 1023). The signal of the waveform 902 in the period is added and output to the input terminal B of the switching circuit 2335. In response to the sign signal output from the subtracter 2323, the switching circuit 2335 receives the signal input to the input terminal A (the output signal of the subtracter 2333) and the signal input to the input terminal B (the output of the adder 2334. Signal) and output one of them. That is, the signal of the input terminal A is selected when the output of the adder 2322 is in the range of 0 to 512, and the signal of the input terminal B is selected when the output of the adder 2322 is in the range of 513 to 1023. As a result, the selection circuit 2335 outputs a signal whose hue is rotated and moved in the direction of 0 as shown by the waveform 903 in FIG. FIGS. 8C and 8D schematically show the state of the rotational movement of the hue. A waveform 803 in FIG. 8C shows that the rotational movement increases as the hue approaches 0 on the (BY) axis.

  The state of the rotational movement of the hue will be described using specific numerical values as an example. Hereinafter, for simplification of description, the hue offset value (HUEOFFSET) is assumed to be 0, and the multiplication coefficient multiplied by the multiplier 2325 is assumed to be 1.

  When the value of the correction hue signal is 10 and the hue is close to blue, the subtracter 2323 performs the calculation 10-512, and outputs “−502” as the calculation result and “0” as the code signal. The absolute value circuit converts −502 into 502 and outputs the result to the subtracter 2333 and the adder 2334. The subtracter 2333 performs an operation of 10-502, and since the operation result is negative (−492), “0” is output to the input terminal A of the selection circuit 2335 as the operation result. On the other hand, the adder 2334 performs an operation of 10 + 502 and outputs “512” as the operation result to the input terminal B of the selection circuit 2335. Since the sign signal from the subtracter 2323 is “0”, the selection circuit 2335 selects and outputs the signal at the input terminal A, that is, 0.

  If the value of the correction hue signal is 600 and the hue is relatively close to yellow, the subtracter 2323 performs a calculation of 600-512 and outputs “88” as the calculation result and “1” as the code signal. . The absolute value circuit outputs 88 as it is and supplies it to the subtracter 2333 and the adder 2334. The subtracter 2333 calculates 600-88 and outputs “512” as the calculation result to the input terminal A of the selection circuit 2335. On the other hand, the adder 2334 calculates 600 + 88 and outputs “688” as the calculation result to the input terminal B of the selection circuit 2335. Since the sign signal from the subtracter 2323 is “1”, the selection circuit 2335 selects and outputs the signal at the input terminal B, that is, 688.

  As described above, in the circuit configuration of the present embodiment, the hue shift from the blue is made smaller and the color temperature is raised without changing the hue much. On the other hand, for hues close to blue, the hue shift amount is increased so that the hue is closer to blue.

  FIG. 8D shows the hue rotational movement performed by the subtracter 2336. That is, the subtracter 2336 rotates the waveform 803 in FIG. 8C in the clockwise direction by the hue offset value (HUEOFFSET).

  As described above, the first color temperature correction unit 231 determines the color temperature of a color difference signal that is equal to or higher than a predetermined luminance (luminance lower limit setting value YB) and equal to or lower than a predetermined saturation (saturation upper limit setting value ST) among the color difference signals. The hue is rotated and moved (in the blue direction) so as to increase the brightness.

  In the above description regarding the first color temperature correction unit 231, the selection circuit 2332 has been described with reference to the case where the output signal of the first hue shift coefficient generation circuit 2340 is selected as an example. The output signal of the hue shift coefficient generation circuit 2341 or the third hue shift coefficient generation circuit 2342 may be selected. The selection of the signal in the selection circuit 2332 may be set in advance so as to select any one of the three hue shift coefficient generation circuits (in this case, the magnitude of the input signal of the selection circuit 2332 and the like) Regardless of the state, the selected signal is fixed to one type). Alternatively, the selection circuit 2332 may be a maximum value selection circuit, and the signal having the maximum level may be selected from the signals output from three or arbitrarily selected two hue shift coefficient generation circuits. Further, the selection circuit 2332 may be a minimum value selection circuit, and a signal having the minimum level may be selected from signals output from three or arbitrarily selected two hue shift coefficient generation circuits.

  Next, details of the second color temperature correction unit 235 will be described with reference to FIGS. 11 and 12 showing a specific example of the circuit configuration. The corrected saturation signal output from the multiplier 221 in the above-described saturation correction circuit 22 is input to one input terminal of the adder 2356 via the saturation input terminal 2351. A saturation difference signal is output from the output terminal 2320 of the first color temperature correction unit 231, and is input to one input terminal of the multiplier 2355 via the input terminal 2352. The multiplication coefficient output from the microcomputer 40 is input to the other input terminal of the multiplier 2355 via the input terminal 2353. Multiplier 2355 multiplies the saturation difference signal and the multiplication coefficient to adjust the gain of the saturation difference signal. The saturation difference signal whose gain has been adjusted by the multiplier 2355 is input to the other input terminal of the adder 2356. The adder 2356 adds the corrected saturation signal and the gain-adjusted saturation difference signal, and outputs the result to the clipping circuit 2357. When the addition result of the adder 2356 overflows, the clipping circuit 2357 clips the addition result with a predetermined upper limit value. The output signal of the clip circuit 2356 is supplied to the other input terminal of the switching circuit 236 via the saturation coefficient output terminal 2354. FIG. 12 shows the input / output characteristics of each part in the second color temperature correction unit 235. FIG. 12A shows the input / output characteristics of the second color temperature correction unit 235 when the saturation difference signal is 0 as a straight line 1201, and the case where nothing is added to the corrected saturation signal by the adder 2356. The characteristics are shown. In this case, the second color temperature correction unit outputs the corrected saturation signal from the saturation input terminal 2351 as it is. FIG. 12B shows the input / output characteristics of the multiplier 2355 by a straight line 1202. As can be understood from this figure, the multiplier 2355 outputs a signal of the maximum level (ST1) when the saturation signal is 0, and outputs a signal whose level decreases as the saturation signal increases. FIG. 12C shows input / output characteristics of the second color temperature correction unit, and a characteristic when the output signal of the multiplier 2355 is added to the corrected saturation signal by the adder 2356 is indicated by a broken line 1203. ing.

  In this manner, the second color temperature correction unit 235 performs color temperature correction on the saturation signal. That is, among the saturation signals, a signal of a predetermined saturation (saturation upper limit set value ST) or less is increased in saturation, and the white system shifted in the blue direction by the first color temperature correction unit 231. The signal is made darker blue and a beautiful (brilliant) white is obtained. This color temperature correction is effective when the blue saturation level is originally small. For white that has a high blue saturation level (a sufficiently blue color can be confirmed) and / or white that has a strong warm color, it is not necessary to perform such correction for increasing the saturation.

  When the flag signal output from the detection circuit 17 is “1”, that is, when an input signal with high luminance and low saturation is detected, the first selection circuit 232 includes the first color temperature correction unit 231. Output signal is selected and output. When the flag signal is “0”, that is, outside the high luminance and low saturation area, the first selection circuit 232 selects and outputs the output signal of the hue correction circuit 20. In conjunction with this selection control, when the value of the flag signal is “1”, the second selection circuit 236 outputs the output signal of the second color temperature correction unit 235 as an output signal. When the flag signal is “0”, the second selection circuit 236 selects and outputs the output signal of the saturation correction circuit 22. As described above, only a signal included in the range of the color temperature correction area (white signal range) is output as a hue signal with a shifted hue and a saturation signal with corrected saturation.

  As described above, the output signals of the first and second selection circuits 232 and 236 are converted into color difference signals by the color difference conversion circuit 26 and then converted into R, G, and B primary color signals by the inverse matrix circuit 27. And supplied to the display device 28. The display device 28 displays an image that has been optimally corrected for color temperature in accordance with the input signal.

  As described above, in the present embodiment, color temperature correction can be performed on a white signal that is equal to or higher than a predetermined luminance and equal to or lower than a predetermined saturation. Since the color temperature correction is digitally performed on each of the hue signal and the saturation signal, more accurate color temperature correction can be realized. Further, since the correction range and correction amount of the color temperature are set by the microcomputer, the correction range and correction amount can be adjusted arbitrarily.

  FIG. 14 is a block diagram showing another embodiment according to the present invention. In the figure, blocks having the same functions as those in FIG. FIG. 15 is a diagram for supplementarily explaining FIG. A difference from the embodiment shown in FIG. 1 in FIG. 14 is that a hue comparison circuit 131 is added to the components of the color temperature correction level detection circuit 17. The detection circuit to which the hue comparison circuit 131 is added is referred to as a new detection circuit 17 ′. The hue comparison circuit 131 performs a detection operation for excluding a signal having a predetermined hue from white signals having a predetermined luminance or higher and a predetermined saturation or lower from the target of color temperature correction. Details will be described below.

  The hue comparison circuit 131 receives the corrected hue signal output from the hue correction circuit 20 at one input terminal thereof. Further, the hue setting value in the range indicated by the hue 141 in FIG. 15, for example, output from the microcomputer 40 is input to the other input terminal. This hue setting value specifies a range of hues to be excluded from the color temperature correction target, and has two values representing the start and end of the range. The hue comparison circuit 131 compares the corrected hue signal with the hue setting value, and outputs “0” if the value of the correction hue signal is between the two hue setting values, and the value of the correction hue signal is two hues. If it is other than the set value (that is, the range shown by the hatching in FIG. 15), “1” is output. The switching control circuit 173 receives the output signals of the luminance comparison circuit 171, the saturation comparison circuit 172, and the hue comparison circuit 131. Then, an AND operation of these three signals is performed to output a flag signal for controlling the selection circuits 232 and 236 as described above. That is, in the switching control circuit 173, the luminance comparison circuit 171 detects a high luminance signal and outputs "1", the saturation comparison circuit 172 detects a low saturation signal and outputs "1", and the hue When the comparison circuit 131 detects a signal outside the range of the hue setting value and outputs “1”, the flag signal of “1” is output to the selection circuits 232 and 236, and the first color temperature correction unit 231 and Control is performed to select an output signal of the second color temperature correction unit 235. On the other hand, when both the luminance comparison circuit 171 and the saturation comparison circuit 172 output “1” and the hue comparison circuit 131 detects a signal within the range of the hue setting value and outputs “0”, the switching control circuit 173 outputs a flag signal of “0”. Therefore, in this case, although the input signal is a white signal with high luminance and low saturation, the selection circuits 232 and 236 have hues that are not subject to color temperature correction, so that the selection circuits 232 and 236 do not perform color temperature correction. Output signals from the correction circuit 20 and the saturation correction circuit 22 are selected.

  As described above, according to the present embodiment, it is possible to prevent color temperature correction from being performed in the hue range designated even in the white signal. Therefore, the correction range of the color temperature can be limited, and the correction of the hue can be prevented for a signal of a hue that is not preferable to be changed. In addition, since the target range of color temperature correction is specified by the microcomputer 40, an arbitrary range can be set.

  FIG. 16 is a block diagram showing still another embodiment according to the present invention. The difference from the embodiment shown in FIG. 1 is that a brightness correction circuit 151 is newly provided. In the following description, blocks having the same functions as those in FIG.

  The luminance correction circuit 151 variably controls the amplitude level and DC level of the luminance signal separated from the input video signal by the matrix conversion circuit 15, and FIG. 17 shows a detailed circuit diagram thereof. The luminance signal Y output from the matrix conversion circuit 15 is supplied to one input terminal of the black expansion circuit 1606. The other input terminal of the black extension circuit 1606 is supplied with the black extension upper limit set value (YBK) and gain coefficient set by the microcomputer 40 via the input terminal 1602. The black expansion circuit 1606 variably controls the luminance amplitude of the luminance signal equal to or lower than the black expansion upper limit setting value (YBK), and supplies it to one input terminal of the white expansion circuit 1607. A white expansion lower limit setting value (YWT) and a gain coefficient set by the microcomputer 40 are supplied to the other input terminal of the white expansion circuit 1607 via the input terminal 1603. The white expansion circuit 1607 variably controls the luminance amplitude of the luminance signal equal to or greater than the white expansion lower limit setting value (YWT) and outputs the luminance signal. The luminance signal whose amplitude is controlled by the white expansion circuit 1607 is supplied to the multiplication circuit 1608. The multiplication circuit 1608 multiplies this luminance signal by the contrast control coefficient input from the microcomputer 40 via the input terminal 1604 and variably controls the amplitude (contrast control). When an overflow occurs in the output signal from the multiplication circuit 1608, the clip circuit 1609 clips the overflow with an upper limit value (maximum value 255 with 8-bit accuracy) and outputs the result. This output signal is input to the adder circuit 1610. The adder circuit 1610 performs brightness control by adding the output signal and the direct current (DC) value input from the microcomputer 40 via the input terminal 1605. When an overflow occurs in the output signal from the adder circuit 1610, the clip circuit 1611 clips the overflow amount with an upper limit value (maximum value 255 with 8-bit accuracy). The output signal of the clip circuit 1611 is output to the inverse matrix conversion circuit 27, the detection circuit 17, and the color temperature correction circuit 23 via the luminance output terminal 1614. In addition, the maximum value / minimum value detection circuit 1612 detects the maximum level and the minimum level of the luminance signal before the luminance correction input via the input terminal 1601 and outputs the detected luminance level to the microcomputer 40. Based on the detected maximum level and minimum level, the microcomputer 40 sets the black expansion upper limit setting value (YBK) and gain coefficient input to the black expansion circuit 1606 and the white expansion lower limit setting input to the white expansion circuit 1607. The value (YWT) and the gain coefficient, the contrast control coefficient input to the multiplier circuit 1608, and the direct current value input to the adder circuit 1610 are calculated and determined.

  FIG. 18 is for supplementary explanation of the operation of the luminance correction circuit 151 described above, and shows input / output characteristics of each part of the luminance correction circuit 151. A waveform 1701 in FIG. 18A shows output characteristics when nothing is corrected by the luminance correction circuit 151, and shows a case where the luminance signal input from the luminance input terminal 1601 is output as it is. A waveform 1702 in FIG. 18B shows an output signal in which the black portion and the white portion are expanded by the black expansion circuit 1606 and the white expansion circuit 1607. In the waveform 1702, a portion processed by the black expansion circuit 1606 is a solid line portion whose gain is adjusted below the set value YBK level, and a portion processed by the white expansion circuit 1607 is a gain adjustment above the set value YWT level. It is the part of the solid line made. A waveform 1703 in FIG. 18C shows a signal when the luminance input signal is subjected to contrast control processing by the multiplier 1608 and the clip circuit 1609 (in FIG. 18C, for simplicity of illustration). The black and white stretches are shown as not being done). A waveform 1704 in FIG. 18D shows a signal when the waveform 1701 is subjected to brightness control processing by the adder 1610 and the clip circuit 1611 (in FIG. 18D, for simplicity of illustration). Black stretch, white stretch, and contrast control are shown as not being performed).

  Thus, in this embodiment, brightness signal brightness control (contrast control) and DC level control (brightness control) are performed, and gradation of high-level brightness signals is emphasized (white expansion control), and low level control is performed. Emphasis control (black expansion control) is performed on the gradation of the luminance signal of the level. As a result, a sharp tone-rich luminance signal (hereinafter referred to as a corrected luminance signal) can be obtained. The corrected luminance signal is simultaneously supplied to the detection circuit 17 and the color temperature correction circuit 23. Therefore, there is a correlation between the detection of the color temperature correction area (white signal region) in the detection circuit 17 or 17 ′ using the corrected luminance signal and the color temperature correction in the color temperature correction circuit 23 using the corrected luminance signal. You can have it. Therefore, there is an effect that color temperature correction can be performed more optimally even for a display device in which image quality is better when luminance correction is performed.

  Although the details of the signal processing circuit including the color temperature correction according to the present invention have been described above, this signal processing circuit is used in a direct-view television receiver or a rear projection television receiver. The present invention can also be applied to a display device for a computer monitor. Furthermore, as a display device of a display device provided with this signal processing circuit, not only a cathode ray tube but also a liquid crystal panel, a plasma display panel (PDP) or the like can be used. That is, according to the present invention, the above-described effects can be obtained using any display device. Depending on the type of display device (various characteristics such as color reproduction and luminance saturation), various parameters relating to hue correction, saturation correction, white signal region detection, and color temperature correction (for example, the lower limit luminance setting value YB, It is also preferable to appropriately change the saturation upper limit setting ST and the like by the microcomputer 40. It goes without saying that such embodiments are also included in the present invention. In the above-described three embodiments, the color temperature correction is performed after the hue correction and the saturation correction are performed, but the processing order may be reversed. Furthermore, color temperature correction may be performed without performing hue correction and saturation correction.

The block diagram which shows one Embodiment of the signal processing circuit used for the video display apparatus which concerns on this invention. The figure which shows the hue ring which represented the color with the vector. The figure which shows an example of the relationship between a hue signal and a saturation signal. FIG. 4 is a diagram showing input / output characteristics of each part of the hue correction circuit 20. FIG. 4 is a diagram showing input / output characteristics of each part of the hue correction circuit 20. The figure which shows the range of the white-type signal detected by the detection circuit. FIG. 3 is a block diagram showing details of a first color temperature correction unit 231. FIG. 6 is a diagram for explaining the operation of a first color temperature correction unit 231. FIG. 10 is a diagram illustrating input / output characteristics of each unit of the first color temperature correction unit 231. The figure which shows the input-output characteristic of the 2nd hue shift coefficient generation circuit 2341 and the 3rd hue shift coefficient generation circuit 2342. The block diagram which shows the detail of 2nd color temperature correction | amendment FIG. FIG. 237 is a diagram illustrating input / output characteristics of each unit in the second color temperature correction FIG. Input / output characteristics of each part of the saturation correction circuit 22. The block diagram which shows another embodiment of this invention. The figure which shows the range of the white-type signal detected by detection circuit 17 '. The block diagram which shows another embodiment of this invention. 3 is a block diagram showing details of a luminance correction circuit 151. FIG. The figure which shows the input-output characteristic of each part of the brightness correction circuit 151.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... R primary color signal input terminal, 12 ... G primary color signal input terminal, 13 ... B primary color signal input terminal, 14 ... A / D conversion circuit, 15 ... Matrix conversion circuit, 17, 17 '... Detection circuit, 18 ... Hue conversion Circuit: 20 ... Hue correction circuit, 21 ... Saturation conversion circuit, 22 ... Saturation correction circuit, 23 ... Color temperature correction circuit, 26 ... Color difference conversion circuit, 27 ... Inverse matrix conversion circuit, 28 ... Display device, 40 ... Microcomputer 231 ... first color temperature correction unit, 232 ... first selection circuit, 235 ... second color temperature correction unit, 236 ... second selection circuit.

Claims (20)

  A video display apparatus comprising means for correcting a color temperature of a white video signal having a luminance higher than a predetermined value and a saturation lower than a predetermined value among input video signals. A signal processing circuit including a color temperature correction circuit that performs color temperature correction on the input video signal, and a display that performs display based on the video signal that has been supplied with the color temperature corrected by the color temperature correction circuit In a configured video display device comprising a device,
The color temperature correction circuit includes means for correcting a color temperature of a signal belonging to a white system having a predetermined luminance or higher and a predetermined saturation or lower among the input video signal. apparatus. The signal processing circuit includes: an A / D converter that converts the input video signal into a digital signal; a matrix circuit that converts the digital signal output from the A / D converter into a luminance signal and at least two color difference signals; A hue processing circuit for obtaining a hue signal from the color difference signal output from the matrix circuit, a saturation processing circuit for obtaining a saturation signal from the color difference signal, and a control circuit,
The color temperature correction circuit is output from the hue signal output from the hue processing circuit and the saturation processing circuit based on the set values of the predetermined luminance level and the predetermined saturation level supplied from the control circuit. The video display device according to claim 2, wherein color temperature correction processing is performed to correct a color temperature of a signal belonging to the white color system in a higher direction among the saturation signals.   The color temperature correction circuit includes: a first color temperature correction unit that performs color temperature correction on a hue signal belonging to the white color system out of the hue signals output from the hue processing circuit; and the saturation processing circuit. Among the output saturation signals, a second color temperature correction unit that performs color temperature correction on the saturation signal belonging to the white system, an output signal from the first color temperature correction unit, and the hue processing A first selection circuit that selects and outputs one of the hue signals output from the circuit, an output signal from the second color temperature correction unit, and a saturation signal output from the saturation processing circuit. The video display device according to claim 3, further comprising: a second selection circuit that selects and outputs one of them.   The signal processing circuit further includes a detection circuit that detects a region of a signal belonging to a white system having a predetermined luminance or more and a predetermined saturation or less in the input video signal, and the detection circuit detects the region 5. The video according to claim 4, wherein a control signal for selecting an output signal of the first and second color temperature correction units is output to the first and second selection circuits. Display device.   The video display device according to claim 5, wherein the control circuit supplies set values of the predetermined luminance level and predetermined saturation level to the detection circuit as a reference for detecting the region.   7. The video display device according to claim 6, wherein the detection circuit further includes means for detecting a signal of a hue within a predetermined range in the signal region belonging to the white system.   The signal processing circuit further outputs a color difference signal conversion circuit that converts the signals output from the first and second selection circuits into color difference signals, a color difference signal output from the color difference signal conversion circuit, and the matrix circuit. The video display device according to claim 4, further comprising: an inverse matrix conversion circuit that converts the luminance signal into R, G, B signals and supplies the converted signals to the display device. The hue processing circuit converts a color difference signal output from the matrix circuit into a hue signal, and corrects a predetermined range of hue signals from the hue signal output from the hue conversion circuit to correct the color temperature. A hue correction circuit that outputs to the correction circuit;
The saturation processing circuit corrects the saturation of a predetermined range among the hue conversion circuit that converts the color difference signal output from the matrix circuit into a saturation signal, and the saturation signal output from the hue conversion circuit. And a saturation correction circuit that outputs to the color temperature correction circuit,
The video display device according to claim 3, wherein the control circuit sets a hue correction range and a correction amount by the hue correction circuit and a saturation correction range and a correction amount by the saturation correction circuit. .   The video display apparatus according to claim 4, wherein the signal processing circuit further includes a luminance correction circuit that corrects the luminance signal output from the matrix circuit.   The luminance correction circuit includes a black expansion circuit that controls the amplitude of a black signal that is equal to or lower than a predetermined black luminance, a white expansion circuit that controls the amplitude of a white signal that is equal to or higher than a predetermined white luminance, and the amplitude of an output signal of the white expansion circuit. 11. The video display device according to claim 10, further comprising a contrast control circuit for controlling, and a brightness control circuit for controlling a direct current level of an output signal of the contrast control circuit.   The control circuit determines each set value of the predetermined black luminance and the predetermined white luminance based on the maximum value and the minimum value of the luminance signal output from the matrix circuit, and sets the set values for the black expansion circuit and the white expansion circuit. And setting each of the black signal amplitude control amount in the black extension circuit, the amplitude control amount in the white extension circuit, the amplitude control amount in the contrast control circuit, and the DC level control amount in the brightness control circuit, The video display device according to claim 11, wherein the video display device is supplied to each circuit.   13. The video display apparatus according to claim 3, 6, 9, or 12, wherein the control circuit is a microcomputer. A signal processing circuit including a color temperature correction circuit that performs color temperature correction on the input video signal, and a display that performs display based on the video signal that has been supplied with the color temperature corrected by the color temperature correction circuit In a configured video display device comprising a device,
The signal processing circuit has conversion means for converting the input video signal into a hue signal and a saturation signal in a digital format,
The color temperature correction circuit performs color temperature correction on each of the hue signal and the saturation signal converted by the conversion unit, and the luminance of the hue signal and the saturation signal is equal to or higher than a predetermined value. An image display apparatus comprising: a correcting unit that corrects a white signal having a saturation equal to or lower than a predetermined value so as to increase a color temperature thereof.   15. The video display device according to claim 14, wherein the correction means includes means for bringing the hue of the white signal close to a blue hue, and means for increasing the saturation of the white signal. .   A method for performing color temperature correction on an input video signal, wherein color temperature correction is performed on a white signal having luminance and saturation within a predetermined range of the input video signal. Color temperature correction method.   A method for performing color temperature correction on an input video signal, and for each of a hue component and a saturation component of a white signal that is equal to or higher than a predetermined luminance and equal to or lower than a predetermined saturation of the input video signal. A color temperature correction method characterized by performing processing for correcting the color temperature of the white signal.   The color temperature correction method according to claim 17, wherein the color temperature correction for the white signal is performed independently of a video signal other than the white signal.   A method for performing color temperature correction on an input video signal, the step of converting the input video signal into a digital signal, the step of separating the digital signal into a luminance signal and a color difference signal, and the color difference signal as a hue signal. A step of separating the signal into a saturation signal, and a color temperature correction process for increasing a color temperature of a signal belonging to a white system having a predetermined luminance or higher and a predetermined saturation or lower among the hue signal and the saturation signal. And a color temperature correction method characterized by comprising: The step of performing the color temperature correction processing includes a step of bringing the hue of the signal belonging to the white color system close to blue, and a step of increasing the saturation of the signal belonging to the white color system. The color temperature correction method described in 1.

Images