JP4011743B2 - Image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image display device such as a liquid crystal display, and relates to a saturation compensation technique in a state of displaying with low luminance.
[0002]
[Prior art]
In recent years, liquid crystal display devices such as front-projection LCD front projectors and rear-projection liquid crystal rear projectors that project images by enlarging and projecting PC screens to screens, and direct-view LCD monitors that are used as PC screen monitors on desktops It is rapidly spreading and is establishing its position as a display device after CRT.
[0003]
In general, a liquid crystal display device is said to have a wider color reproduction range and a better color reproducibility than a cathode ray tube compared to a cathode ray tube display device. Certainly, the high-intensity display on a liquid crystal projector has a colorful impression, and many presentations on a personal computer have a high impression. However, when a natural image such as a TV image is displayed, it may be dull and may not appear in the image.
[0004]
FIG. 19 is an example in which the maximum light emission luminance and the minimum light emission luminance of the RGB primary colors of the liquid crystal display device are equally divided and displayed on the chromaticity diagram. The gradation level at the maximum luminance is 1, and the minimum luminance is obtained. The gradation level is indicated by 0. As can be seen from the figure, in the liquid crystal display device, the RGB triangle becomes narrower as the gradation level decreases from 1 to 0.1.
On the other hand, FIG. 20 is an example of a chromaticity diagram of a cathode ray tube display device. As is clear from the figure, the RGB triangle of the CRT display device is hardly narrowed even when the gradation level is changed, as compared with the liquid crystal display device shown in FIG.
[0005]
As described above, the liquid crystal display device may have a wider RGB color reproduction range than the cathode ray tube display device at high luminance, but the range is reduced as the gradation level is reduced. This reduction of the color reproduction range lowers the pure color values of RGB, resulting in a decrease in saturation. That is, there is a problem in that the saturation is low at the low luminance level and the video is no longer visible.
[0006]
Usually, a television receiver or the like is equipped with a function for adjusting the saturation, referred to as color contrast for image adjustment, but the above problem is caused by the RGB color reproduction range changing according to the gradation level. Therefore, this adjustment function cannot solve this problem. In a liquid crystal display device, if the saturation is simply increased in order to cope with the decrease in saturation, the saturation of all gradation levels will increase, and the image will be glaring at high luminance. In a liquid crystal display device, it is necessary to increase the saturation only for the low luminance level in order to eliminate the deterioration of the image quality at the low luminance level.
[0007]
Japanese Patent Application Laid-Open No. 6-22174 discloses a video control circuit for reducing the noise feeling of a video in a region where the average picture level (APL) is low and increasing the effect of a selected video menu. Proposed. Since this circuit lowers the color level (color density) to some extent in an image with a low APL, the saturation of only the low luminance level cannot be increased.
[0008]
Japanese Patent Application Laid-Open No. 6-311396 discloses a method for compensating for the loss of details of a low-brightness signal when a high-brightness signal and a low-brightness signal are mixed in a video signal shot by a television camera or the like. It has been proposed to detect an average luminance level of a luminance video signal and control brightness and saturation by average luminance data obtained by correcting the average luminance level. This method can reproduce details of a low-luminance signal portion in a high-luminance signal image and has no effect on saturation. However, the low-luminance video signal lacks saturation. It is not considered to make up.
[0009]
Furthermore, in Japanese Patent Laid-Open No. Hei 8-2922752, as a brightness automatic adjustment device that performs appropriate screen adjustment according to the user's preference, the brightness value of the video signal is detected and the screen brightness of the display device is determined. It has been proposed to control the screen brightness to be high when the brightness of the video signal is too low. This method does not show increasing the saturation when the average video level is low.
[0010]
In addition, these proposals do not show increasing the saturation of a specific hue in a region where the average video level is low.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to eliminate a reduction in saturation at a low luminance level in the above image display device and to reproduce a dull image with respect to a natural image such as a television image signal.
It is another object of the present invention to provide an image display device that increases the saturation of a specific hue and reproduces a sharp image when the average video level in the specific hue is low.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention detects an average picture level (hereinafter referred to as APL) in a liquid crystal display device and increases the saturation of a video signal when the APL is low.
As a result, even when the screen is dark as a whole, the color saturation is increased and the image becomes more vivid and a sharp image display comparable to a CRT image can be realized.
[0013]
According to the present invention, in the image display device, the saturation of the video signal is changed according to the average video level of the input video signal.
[0014]
The present invention provides an image display apparatus comprising at least an average video level detection means for detecting an average video level of an input video signal and a video signal gain variable means for changing a gain of the input video signal. According to the average video level of the input video signal detected by the means, the gain of the video signal is controlled by the video signal gain varying means to change the saturation of the video signal.
[0015]
According to the present invention, in the above image display device, the video signal whose gain is controlled by the video signal gain varying means is a color difference signal.
[0016]
Further, according to the present invention, in the image display device, the saturation of the desired hue of the video signal is changed according to the average video level of the input video signal.
[0017]
The present invention includes at least an average video level detection unit that detects an average video level of an input video signal, a video signal gain variable unit that changes a gain of the input video signal, and a hue detection unit that detects a signal of a specific hue. In the image display apparatus, the gain of the video signal is adjusted with respect to the hue detected by the hue detection means by the video signal gain varying means according to the average video level of the input video signal detected by the average video level detection means. In addition to changing the saturation of the desired hue of the video signal, the video signal whose gain is controlled by the video signal gain varying means is used as the color difference signal.
[0018]
The present invention is characterized in that the image display device is a liquid crystal display device.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of an image display device according to the present invention will be described with reference to FIG. 1 as an example of a liquid crystal display device. The liquid crystal display device includes a decoder (hereinafter referred to as DEC) 1, a variable gain amplifier (hereinafter referred to as AMP) 2 and 3, DEC4, An APL detection circuit 5, an input / output conversion circuit 6, a control circuit 7, and a liquid crystal display device (hereinafter referred to as LCD) 8 are configured.
[0020]
DEC1 is a terminal T 11 Luminance signal Y input from the terminal T and the terminal T 12 The color difference signal BY and the color difference signal RY are generated from the color signal C input from. The AMPs 2 and 3 variably amplify the amplitudes of the color difference signal BY and the color difference signal RY based on the output signals of the input / output conversion circuit 6, respectively. The DEC 4 generates an RGB primary color signal by using the color difference signal BY color difference signal RY and the luminance signal Y that have been subjected to variable gain amplification. The APL detection circuit 5 detects the average video level of the video signal input from the input video signal using the luminance signal Y. Based on the average video level from the APL detection circuit 5, the input / output conversion circuit 6 calculates the amplification factor of AMP2 for amplifying the color difference signal BY and AMP3 for amplifying the color difference signal RY. The control circuit 7 has a terminal T 13 Input from the horizontal synchronizing signal H and terminal T 14 The LCD 8 is driven using the vertical synchronization signal V input from the above.
[0021]
An example of the configuration of the APL detection circuit 5 that detects the average video level (APL) of the input video signal will be described with reference to FIG.
The APL detection circuit 5 includes buffers (Buf) 51 and 52, a resistor 53, and a capacitor 54, and is configured as an integrator, and detects an average video level of the input video signal.
[0022]
An example of the configuration of the input / output conversion circuit 6 will be described with reference to FIG. The input / output conversion circuit 6 includes a constant voltage diode 61, a variable voltage source 62, resistors 63, 64, 65, and an operational amplifier 66. The output level of the terminal T6 increases at a voltage level that is equal to or lower than the voltage determined by the constant voltage diode 61.
The characteristic is similar to the characteristic shown in FIG. 4 showing the relationship between the average video level (APL) and the gain of AMPs 2 and 3. The vertical axis represents the output voltage at the terminal T6 instead of the AMP gain.
[0023]
The operation of the liquid crystal display device shown in FIG. 1 will be described below. DEC1 is a terminal T 11 Luminance signal Y and terminal T applied to 12 The color signal C applied to is decoded and a color difference signal BY and a color difference signal RY are output. The color difference signals BY and RY are input to the AMPs 2 and 3, respectively, are variably amplified, and then input to the DEC4. Further, the luminance signal Y is also input to the DEC 4, and the color difference signals BY, RY and the luminance signal Y are subjected to matrix calculation, and an RGB primary color signal is output. The RGB primary color signals are input to the LCD 8 to display a desired image. The control circuit 7 has a terminal T 13 The horizontal synchronizing signal H applied to the terminal T and the terminal T 14 A timing signal necessary for driving the LCD 8 is generated on the basis of the vertical synchronizing signal V applied to.
[0024]
On the other hand, the APL detection means 5 obtains the average video level by obtaining the average level of the luminance signal Y, converts the input / output characteristics by the input / output conversion circuit 6 and controls the gains of the AMPs 2 and 3.
[0025]
FIG. 4 shows the relationship between the average video level (APL) and the gain of AMPs 2 and 3. The input / output conversion circuit 6 operates to increase the gains of the AMPs 2 and 3 when the APL is low and to decrease the gains of the AMPs 2 and 3 when the APL is high. As a result, the amplitudes of the color difference signals BY and RY are controlled in accordance with APL.
[0026]
Here, the relationship between the color difference signals BY, RY, hue, and saturation will be described with reference to FIG. In FIG. 5, the horizontal axis indicates the amplitude of the color difference signal BY, and the vertical axis indicates the amplitude of the color difference signal RY signal. According to the figure, it can be seen that the hue and saturation are uniquely determined from the amplitudes of the BY axis and the RY axis. Accordingly, if the amplitude level is increased while the amplitude ratio between the color difference signals BY and RY is kept constant, the saturation can be increased while keeping the hue constant. Therefore, it is possible to change the saturation while keeping the hue constant by simultaneously changing the gain by the same amount in the AMPs 2 and 3 shown in FIG.
[0027]
Further, DEC1 and DEC4 can be easily configured by, for example, Toshiba color TV video, chroma, synchronous deflection circuit system LSI (TA1222AN), and the like. In the LSI, I and Q signals are output as color difference signals. The I and Q signals are obtained by correcting the color difference signals RY and BY in accordance with the characteristics of the human eye. Instead of the color difference signals RY and BY in FIG. It goes without saying that it may be used.
[0028]
As described above, the saturation can be varied according to the APL, and when the APL is low, the saturation can be increased to obtain a video display image that is brilliant even at a low luminance level. The image display with sharpness comparable to can be realized.
[0029]
A second embodiment of the image display apparatus according to the present invention will be described with reference to FIG. The liquid crystal display device according to this embodiment shows a case in which the input signal is an RGB primary color signal, and the first embodiment shown in FIG. 1 has an encoder (hereinafter referred to as ENC) 40 and a DEC 41. This is different from the embodiment. The same functional blocks as those in FIG.
[0030]
An example of the configuration of the ENC 40 will be described with reference to FIG. The ENC 40 includes multipliers 401R, 401G, 401B, and 402, adders 405, 406, 407, and 408, and coefficient units 403R, 403G, 403B, and 404.
The RGB signals applied to the terminals T40R, T40G, and T40B are multiplied by coefficients 403R to 403B by multipliers 401R, 401G, and 401B. The RGB signals multiplied by these coefficients are added by adders 405 and 406 to generate a luminance signal Y.
Further, the color difference signal RY is generated by subtracting the luminance signal Y from the R signal applied to the terminal T40R by the adder 407, and the color difference signal BY is luminance from the B signal applied to the terminal T40B by the adder 408. It can be generated by reducing the signal Y. -Y may be generated by multiplying the luminance signal Y by a -1 coefficient by the multiplier 402.
[0031]
The configuration of the DEC 41 will be described with reference to FIG. The DEC 41 includes multipliers 411Y, 411R, and 411B, coefficient units 412Y, 412R, and 412B, and adders 413, 414, 415, and 416.
[0032]
The luminance signal Y, the color difference signal RY, and the color difference signal BY applied to the terminals T41Y, T41R, and T41B are multiplied by coefficients 411Y, 412R, and 412B by multipliers 411Y, 411R, and 411B, and adders 413 and 414. To generate a G signal.
The R signal is generated by adding the luminance signal Y to the color difference signal RY applied to the terminal T41R by the adder 415, and the B signal is generated by adding the luminance signal Y to the color difference signal BY applied to the terminal T41B by the adder 416. The luminance signal Y can be added and generated.
Since the circuit operations of the APL detection circuit 5, the input / output conversion circuit 6, and the AMPs 2 and 3 are the same as those in the first embodiment shown in FIG.
[0033]
Even if the input signal form is an RGB primary color signal, the configuration according to this embodiment can detect the APL and control the gains of the color difference signals RY and BY. Similar to the form, the saturation can be made variable according to the APL. As a result, when the APL is low, it is possible to increase the saturation and display a vivid image even at a low luminance level, and to realize a sharp image display comparable to a CRT image.
[0034]
A third embodiment of the image display apparatus according to the present invention will be described with reference to FIG. The liquid crystal display device according to this embodiment includes a hue detection circuit 90, a switch 92, and a variable power source 91. In addition, blocks having the same functions as those of the first embodiment shown in FIG.
[0035]
A feature of the present embodiment is that a hue detection circuit 90 detects a specific hue, and based on the output, a switch 92 outputs a signal to the input / output conversion circuit 6 and the output of the APL detection circuit 5 and the variable power source 91. By switching, the saturation is raised for the color of a specific hue.
[0036]
Since the operations other than the hue detection circuit 90 and the switch 92 are the same as those in the first embodiment shown in FIG. 1, the description thereof will be omitted, and the operation of the hue detection circuit 90 will be mainly described.
[0037]
An example of the configuration of the hue detection circuit 90 will be described with reference to FIG. The hue detection circuit 90 includes comparators 901-1, 901-2, 901-3, 901-4, comparison reference power supplies 902-1, 902-2, 902-3, 902-4, and a multiplier 903. 904, 905.
[0038]
The output of the comparator 901-1 becomes “0” when the color difference signal BY applied to the terminal T901 is “1” smaller than the set voltage of the comparison reference power supply 902-1.
The output of the comparator 901-2 is “1” when the color difference signal BY applied to the terminal T901 is smaller than the set voltage of the comparison reference power supply 901-2, and becomes “0” when larger.
The outputs of the comparators 901-1 and 901-2 are multiplied by the multiplier 903. When both the comparators 901-1 and 901-2 are “1”, the output of the multiplier 903 becomes “1”. That is, when the comparison reference power supply 902-1 <comparison reference power supply 902-2, the comparators 901-1, 901-2, and the multiplier 903 are within the above voltage range with respect to the color difference signal BY applied to the terminal T901. Acts as a sensitive wind comparator.
[0039]
The comparators 901-3 and 901-4 and the multiplier 904 perform the same operation for the color difference signal RY signal applied to the terminal T902. The outputs of the multipliers 903 and 904 are further multiplied by a multiplier 905. As a result, “1” is output from the multiplier 905 when the signal levels of the color difference signals BY and RY applied to the terminals T901 and T902 are within a specific range, that is, a specific hue.
[0040]
This will be described with reference to FIG. In FIG. 11, the color difference signals BY and RY are plotted with the hue on the horizontal axis and the amplitude level on the vertical axis. The amplitude level is normalized.
[0041]
Here, the comparison power source 901-2 shown in FIG. 10 corresponds to an amplitude of -0.5 level, the comparison power source 902-1 corresponds to an amplitude of -0.86 level, and the comparison power source 902-4 has an amplitude of .0. When the comparison power source 902-3 is set to have an amplitude of 0.5 level corresponding to 86 levels, the output from the multiplier 905 in FIG. 10 is output when the hue is in the range of 120 ° to 150 ° indicated by hatching in FIG. Obtainable. The output of the multiplier 905 is the output of the hue detection circuit 90.
[0042]
The switch 92 shown in FIG. 9 selects the output of the APL detection circuit 5 when the output of the input hue detection circuit 90 is “1”, and outputs the variable power supply 91 when the output of the hue detection circuit 90 is “0”. Select.
The voltage of the variable power supply 91 is set to a voltage level such that the gain of the AMPs 2 and 3 is “1”, and is set so as not to increase the saturation.
[0043]
As a result, when a specific hue is detected by the hue detection circuit 90, the output of the APL detection circuit 5 is input to the input / output conversion circuit 6. If the APL is low at this time, the image saturation is increased. As shown in FIG. 19, since the reduction of the RGB reproduction range is not equal to RGB and is biased, this embodiment is effective in increasing the saturation of a specific hue.
[0044]
In this way, the saturation of the specific hue can be varied according to the APL, and when the APL of the specific hue is low, the saturation can be increased and a video display image can be displayed even at a low luminance level. A sharp image display comparable to the video can be realized.
[0045]
A fourth embodiment of the image display apparatus according to the present invention will be described with reference to FIG. The liquid crystal display device according to this embodiment is a combination of the second embodiment described with reference to FIG. 6 and the hue detection circuit 90 and the switch 92 according to the third embodiment described with reference to FIG. A configuration when a signal is input is shown. Since the details of each functional block have already been described, they are omitted here.
[0046]
According to the configuration of the present embodiment, even for RGB primary color signal input, the saturation of a specific hue can be varied according to the APL, and when the APL of the specific hue is low, the saturation is increased and a low luminance level is obtained. However, a vivid video display image becomes possible, and a sharp video display comparable to a CRT video can be realized.
[0047]
A fifth embodiment of the image display apparatus according to the present invention will be described with reference to FIG. In this embodiment, the liquid crystal display device according to the first embodiment is digitized.
A liquid crystal display device according to this embodiment includes a digital decoder (denoted as DEC) 1D, a digital decoder (DEC) 4D, an APL detection circuit 5D, an input / output conversion circuit 6D, a control circuit 7D, and a liquid crystal display device. (Referred to as LCD) 8, AD converters 96Y and 96C, DA converters 96R, 96G, and 96B, and digital multipliers 21 and 31.
[0048]
The luminance signal Y input from the terminal T11 is AD-converted by the AD converter 96Y, and the color signal C input from the terminal T12 is AD-converted by the AD converter 96C and processed by the subsequent circuits.
Further, the digital RGB primary color signal output of DEC4D is converted into an analog signal by the DA converters 96R to 96B and input to the LCD 8.
[0049]
An example of the configuration of the APL detection circuit 5D that detects APL (average video level) will be described with reference to FIG. The APL detection circuit 5D includes a multiplier 5D1, a coefficient circuit 5D2, an adder 5D3, a register 5D4, and a latch 5D5. The digital luminance signal Y applied to the terminal T5D1 is input to the adder 5D3 which multiplies the coefficient set in the coefficient circuit 5D2 by the multiplier 5D1.
The adder 5D3 adds the output of the multiplier 5D1 and the output of the register 5D4. The addition result is returned to the register 5D4 again. The operation of returning to this register is nothing but the accumulation operation. For example, when obtaining the average of 1000 times, the coefficient value of the coefficient circuit 5D2 is set to 1/1000, and the adder 5D3 and the register 5D4 accumulate 1000 times. . By latching by the latch 5D5 after accumulating 1000 times, the average luminance level is output to the terminal T5D2.
[0050]
The input / output conversion circuit 6D may be configured by a LUT (Look Up Table), for example (not shown). 1 may be the multipliers 21 and 31, and the characteristics including the APL detection circuit 5D, the input / output conversion circuit 6D, and the multipliers 21 and 31 are the same as those in FIG. Good.
[0051]
Further, DEC1D and DEC4D can be easily configured by, for example, a TV signal processing LSI (TC90A06F, TA8884AN) manufactured by Toshiba. In the LSI, I and Q signals are output as color difference signals. It goes without saying that I and Q signals may be used instead of the RY and BY signals as in the first embodiment.
[0052]
In the present embodiment, since the APL detection circuit 5D, the input / output conversion circuit 6D, and the multipliers 21 and 31 are configured by digital circuits, the LSI can be easily realized, and the cost merit by the LSI can be enjoyed to keep the production cost low. It becomes possible.
[0053]
In this way, the saturation can be varied according to the APL, and when the APL is low, the saturation is increased and a vivid video display image is possible even at a low luminance level. A certain video display device can be realized at low cost.
[0054]
A sixth embodiment of the image display apparatus according to the present invention will be described with reference to FIG. The liquid crystal display device of this embodiment is a digitized version of the liquid crystal display device of the second embodiment shown in FIG. The liquid crystal display device of this embodiment is configured to include AD converters 95R, 95G, and 95B, a digital encoder (denoted as ENC) 40D, and a digital decoder (denoted as DEC) 41D. Blocks having the same functions as those in FIG. 13 are denoted by the same reference numerals.
[0055]
The ENC 40D is digitized from the ENC 40 shown in FIG. 7, and the DEC 41D is digitized from the DEC 41 shown in FIG. For example, the multiplier may be replaced with a digital multiplier, the adder may be replaced with a digital adder, and the coefficient unit may be replaced with a register.
In the present embodiment, a configuration in which an input signal corresponds to a digitized RGB primary color signal is shown. Of course, it is possible to enjoy the cost merit of using LSI and to keep the production cost low.
Details of the operation have been described with reference to FIGS.
[0056]
Thus, even if the input signal form is an RGB primary color signal, the APL can be detected and the gains of the color difference signals RY and BY can be controlled with the configuration of the present embodiment. Saturation can be varied, and when APL is low, it is possible to increase the saturation and display a vivid image even at low luminance levels, realizing a sharp image display device comparable to a CRT image at a low cost. it can.
[0057]
A seventh embodiment of the image display apparatus according to the present invention will be described with reference to FIG. The liquid crystal display device according to this embodiment is a digitized version of the liquid crystal display device according to the third embodiment shown in FIG. The liquid crystal display device according to this embodiment includes a hue detection circuit 90D, a switch 92, and a setting register 91D. In addition, functional blocks having the same functions as those in FIG. Yes.
[0058]
The feature of the present embodiment is that the hue detection circuit 90D detects a specific hue, and the switch 92 switches the output of the APL detection circuit 5D and the setting register 91D by the output, thereby saturation with respect to the color of the specific hue. There is in being to raise.
[0059]
An example of the configuration of the hue detection circuit 90D will be described with reference to FIG. The hue detection circuit 90D shown in FIG. 17 is a digitized version of the hue detection circuit 90 shown in FIG. 10, and setting registers 9D2-1 to 9D2-4 are provided instead of the reference power supplies 902-1 to 902-4 for comparison. Used. Of course, the comparators 9D1-1 to 9D1-4 and the multipliers 9D3, 9D4, and 9D5 are configured as digital types.
[0060]
Since this operation is the same as that of the hue detection circuit 90 shown in FIGS. 10 and 12, detailed description thereof is omitted.
According to this embodiment, as in the embodiment shown in FIG. 13, it is possible to enjoy the cost merit of using LSI and to keep the production cost low.
[0061]
In this way, the saturation of a specific hue can be varied according to the APL, the saturation is increased when the APL is low at a specific hue, and a vivid video display image is possible even at a low luminance level. A sharp video display device comparable to video can be realized at low cost.
[0062]
The eighth embodiment of the image display apparatus according to the present invention will be described with reference to FIG. The liquid crystal display device according to this embodiment is a digitized version of the liquid crystal display device according to the fourth embodiment shown in FIG. The description of the hue detection circuit 90D and the like has already been described with reference to FIG. 16 of the third embodiment, and is omitted here.
[0063]
Also in this embodiment, the cost merit by using LSI can be enjoyed, and the production cost can be kept low.
[0064]
According to the configuration of this embodiment, even for RGB primary color signal input, the saturation of a specific hue can be varied according to the APL, and when the APL of the specific hue is low, the saturation is increased and the luminance is low. This makes it possible to display video images that are brilliant even at the level, and realize a sharp video display device comparable to a CRT video at a low cost.
[0065]
In the embodiments of FIGS. 13, 15, 16, and 18, the DA converters 96R to 96B convert the analog signals to the LCD 8 and apply them to the LCD 8. However, if the LCD 8 is a type that can be digitally input, the digital RGB It goes without saying that primary color signals may be input.
[0066]
In the above embodiments, an example in which an LCD is used as an image display device has been described. However, the image display device is not limited to an LCD, and the saturation of an image to be reproduced changes when the level of an input video signal changes. The present invention can be applied to an image display device having a fear. According to this, even if the level of the input video signal changes, an optimal image can be reproduced.
[0067]
【The invention's effect】
As described above, according to the present invention, the saturation can be varied according to the APL, so that the reduction phenomenon of the RGB color reproduction range at the low luminance level is compensated, and the saturation is reduced when the APL is low. It is possible to realize a video display comparable to a CRT picture, which can be raised and shine even at low luminance levels.
[0068]
Although the liquid crystal display device has been mainly described in the form of the present embodiment, there are various display devices such as PDP and EL that can be used instead of the cathode ray tube. It goes without saying that can be applied and enjoy its effects.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of an image display apparatus according to the present invention.
FIG. 2 is a diagram showing a specific configuration example of an APL detection circuit shown in FIG. 1;
FIG. 3 is a diagram showing a specific configuration example of the input / output conversion circuit shown in FIG. 1;
FIG. 4 is a diagram showing characteristics of APL vs. AMP gain.
FIG. 5 is a diagram illustrating a relationship between hue and saturation.
FIG. 6 is a block diagram showing a second embodiment of an image display device according to the present invention.
7 is a block diagram illustrating a specific configuration example of an ENC circuit illustrated in FIG. 6;
8 is a block diagram illustrating a specific configuration example of the DEC circuit illustrated in FIG. 6;
FIG. 9 is a block diagram showing a third embodiment of an image display apparatus according to the present invention.
10 is a block diagram illustrating a specific configuration example of a hue detection circuit illustrated in FIG. 9;
FIG. 11 is a diagram illustrating a relationship between a color difference signal and a hue.
FIG. 12 is a block diagram showing a fourth embodiment of an image display apparatus according to the present invention.
FIG. 13 is a block diagram showing a fifth embodiment of an image display apparatus according to the present invention.
14 is a block diagram showing a specific configuration example of the APL detection circuit shown in FIG. 13;
FIG. 15 is a block diagram showing a sixth embodiment of an image display apparatus according to the present invention.
FIG. 16 is a block diagram showing a seventh embodiment of an image display apparatus according to the present invention.
FIG. 17 is a block diagram showing a specific configuration example of the hue detection circuit shown in FIG. 16;
FIG. 18 is a block diagram showing an eighth embodiment of an image display apparatus according to the present invention.
FIG. 19 is a diagram showing a change in the RGB color reproduction range of the liquid crystal display device.
FIG. 20 is a diagram showing a change in RGB color reproduction range of a CRT display device.
[Explanation of symbols]
1,1D decoder (DEC)
2,3 Variable gain amplifier (AMP)
4,4D decoder (DEC)
5,5D APL (average video level) detection circuit
6,6D input / output conversion circuit
7,7D control circuit
8 Liquid crystal display (LCD)
21,31 multiplier
40D digital encoder (ENC)
41D digital decoder (DEC)
90,90D hue detection circuit
91, 91D Variable voltage source
92 switcher
95 AD converter
96 DA converter

Claims (9)

In an image display device,
A display device having a characteristic that the color reproduction range changes according to the average luminance level of the input video signal;
And means for obtaining an average luminance level of the video signal,
When the average luminance level of the obtained video signal is lower than a predetermined value, and means for increasing the saturation of the video signal sequentially in response to a decrease of the average luminance level of the video signal,
The image display device, wherein the display device displays an image in which a change in the color reproduction range is suppressed based on the signal with increased saturation. In an image display device,
A display device having a characteristic that the color reproduction range is reduced as the average luminance level of the input video signal is reduced;
And means for obtaining an average luminance level of the video signal,
And means for increasing the saturation of the lower the average luminance level of the video signal the video signal when less than the average luminance level is a predetermined value of the obtained video signal,
The image display apparatus, wherein the display device displays an image in which a change in the color reproduction range is suppressed based on the signal whose saturation is controlled.   The image display device according to claim 1, wherein the display device is a liquid crystal display element. 4. The image display device according to claim 3, wherein the average luminance level is obtained from a luminance signal obtained from an input video signal . 5. The image display device according to claim 1, further comprising signal generation means for generating color difference signals BY and RY and a luminance signal Y from the input video signal,
The means for detecting information relating to the brightness obtains an average brightness level of the video signal using the brightness signal Y generated by the signal generation means,
The means for controlling the saturation controls the saturation of the video signal by controlling the amplitude of the color difference signals BY and RY generated by the signal generation means. apparatus. 6. The image display device according to claim 5, wherein a color signal C and a luminance signal Y are input as the input video signal , and the signal generation means receives the color difference signals BY and R- from the color signal C and the luminance signal Y. An image display device that generates Y and a luminance signal Y. 6. The image display apparatus according to claim 5 , wherein RGB three primary color signals are input as the input video signal, and the signal generation means is configured to output the color difference signals BY and RY from the three primary color signals and a luminance signal. an image display device comprising a benzalkonium generate a Y. The image display device according to any one of claims 1 to 7 , wherein the means for controlling the saturation is a video signal having a desired hue, when information on the luminance of the video signal is lower than a predetermined value. An image display device characterized by controlling the saturation of the video signal . The image display device according to any one of claims 1 to 7 , wherein the means for controlling the saturation is a video signal having a desired hue, when information on the luminance of the video signal is lower than a predetermined value. An image display device, wherein the saturation of the video signal is controlled independently of the saturation of a video signal having another hue .

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