JPH06178310A - Amplifier for video signal - Google Patents

Abstract

PURPOSE:To execute correction fluctuating the rate of a color difference signal for video in parallel to a detection axis and to improve the color purity of an intermediate hue by obtaining a prescribed non-linear amplifier characteristic through the use of a multiplier squaring an input signal, a differentiator and an amplifier. CONSTITUTION:When the input signal X squared by the multiplier 13 and a signal X are processed in the differentiator 12, is amplified in the amplifier 14 with a constant gain K and the signal X is added by an adder 15, an output signal (y) becomes a value shown by an expression I based on the prescribed non-linear amplifier characteristic. When the signal X is set to be a color difference signal by the amplifier by using a TV video, the rate of the color difference signal can be fluctuated in parallel to the detection axis and the color purity of the intermediate hue can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal amplifier for amplifying a color difference signal which is a video signal in a television device or the like.

[0002]

2. Description of the Related Art Conventionally, in a television apparatus having a CRT (cathode ray tube), color images are displayed by using phosphors which emit red, green and blue light. In this television device, the color reproducibility of the image to be displayed is determined by the color purity of the emitted light of each phosphor.

Then, in the display image on the CRT, as shown in FIG. 8, in particular for red and green, rather than those specified in the so-called NTSC standard,
Color purity tends to be low. Therefore, in a television device, as shown in FIG. 9, a weighting (Wei) of a detection axis in a color difference signal is used by using an amplifier or the like.
The color purity is corrected by increasing the ratio of other color difference signals to the BY signal. In the example shown in FIG. 9, before correction, R
The -Y signal is 0.56 with respect to the BY signal, and the correction increases the RY signal to 0.80 with respect to the BY signal.

In such color purity correction, 10
Although it is not possible to improve the color purity at 0% saturation, a color having an intermediate saturation level is set so that the color indicated by a ′ on the chromaticity diagram shown in FIG. 10 is corrected to the color indicated by a on this chromaticity diagram. The intensity of
The color purity of the central saturation is corrected.

[0005]

By the way, in the correction of the color purity as described above, since only the correction of the saturation is performed, the correction in the monochromatic direction as shown by a in FIG. However, as shown by b and c in FIG.
The color of the intermediate hue cannot be corrected well.

That is, the colors of the intermediate hues indicated by b and c in FIG. 10 are b ′, c in FIG. 10 on the CRT.
As shown by c ', the color is reproduced in a color with reduced purity. Then, when the above-described color purity correction is performed on the colors of these intermediate hues, the hues are reproduced with deviation, as indicated by b ″ and c ″ in FIG. 10.

Therefore, the present invention has been proposed in view of the above circumstances, and in correcting the color purity of the intermediate saturation of reproduced colors in a television apparatus, not only the correction of the saturation of a single color but also It is an object of the present invention to provide a video signal amplifier capable of excellently correcting an intermediate hue.

[0008]

In order to solve the above problems and achieve the above objects, the video signal amplifier according to the present invention amplifies an input video signal by a non-linear characteristic. .

According to the present invention, the above-mentioned video signal amplifier is inputted with a multiplier to which a video signal is input and which squares and outputs the video signal, and to which the video signal and the output signal of the multiplier are input. A differential device that outputs a difference signal of the signals, an amplifier that amplifies the output signal of the differential device with a constant gain, the video signal and the output signal of the amplifier are input, and a sum signal of these signals is output. And an adder that does this.

Further, according to the present invention, the above-mentioned video signal amplifier is connected to an amplifier to which a video signal is input and which amplifies and outputs the input signal with a constant gain, and an input terminal side of the input terminal of the amplifier. And a power supply unit for applying a voltage to the output terminal side of the rectifying element.

[0011]

In the video signal amplifier according to the present invention, since the input video signal is amplified by the non-linear characteristic,
When used for correcting the color purity of the intermediate saturation of reproduced colors in a television device, the correction of changing the ratio of the color difference signals in parallel with the detection axis can be performed, and the color purity of the intermediate hue can be improved.

A multiplier for inputting the video signal to the above video signal amplifier and squaring the video signal and outputting the video signal, and a difference signal between the video signal and the output signal of the multiplier are input to the amplifier for the video signal. , An amplifier for amplifying the output signal of the differential device with a constant gain, and an adder for receiving the video signal and the output signal of the amplifier and outputting a sum signal of these signals. With this configuration, it is possible to change the linearity of the amplification characteristic according to the setting of the gain of the amplifier.

An amplifier for inputting a video signal, which amplifies the input signal with a constant gain, and outputs the amplifier, and a rectifying element whose input terminal is connected to an input terminal of the amplifier. And a power supply means for applying a voltage to the output terminal side of the rectifying element, an amplification characteristic having an inflection point can be obtained when the video signal is at a level corresponding to the voltage applied by the power supply means. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. This example is an example in which the video signal amplifier according to the present invention is used for correcting the color purity of the intermediate saturation of reproduced color in a television device.

As shown in FIG. 1, the television device has a tuner 2 for receiving broadcast radio waves such as so-called VHF broadcast, UHF broadcast, FM broadcast, BS broadcast and CS broadcast via an antenna 1. . The broadcast radio wave received by the tuner 2 is converted to an intermediate frequency by the tuner 2, sent to the video detection circuit 3, and demodulated into a composite video signal by the video detection circuit 3.
This composite video signal is the video switch 4
Sent to. In addition to the composite video signal, a video signal (EXT VIDEO) sent from a recording / reproducing device such as a video tape recorder or a video disc player is input to the video switch 4 via a video input terminal. .

Each video signal input to the video switch 4 is selected by the video switch 4, and the selected video signal is sent to the Y / C separation circuit 5. The Y / C separation circuit 5 separates the sent video signal into a luminance signal Y and a chroma signal C, and sends the luminance signal Y to the sharpness circuit 6. In addition, the Y / C separation circuit 5
Sends the chroma signal C to the color difference demodulation circuit 7.

The brightness signal Y is sharpened by the sharpness circuit 6 and sent to the Y color difference matrix circuit 9. On the other hand, the chroma signal C is converted into BY, RY color difference signals by the color difference demodulation circuit 7 and sent to the color difference matrix circuit 8. The color difference matrix circuit 8 converts the sent color difference signals BY, RY into color difference signals BY, GY, RY and sends them to the Y color difference matrix circuit 9. The Y color difference matrix circuit 9
Is the transmitted luminance signal Y and each color difference signal BY, G-
The three primary color signals R, G, B are generated from Y, RY and sent to the amplifier 10.

The amplifier 10 is provided with the respective primary color signals R,
G and B are amplified and sent to a CRT (cathode ray tube) 11. The CRT 11 displays an image based on the transmitted primary color signals R, G and B.

The video signal amplifier according to the present invention is interveningly connected after the color difference demodulation circuit 7 or the color difference matrix circuit 8, and the color difference signals BY, R- which are output signals of the color difference demodulation circuit 7. Y, or color difference signals BY, GY, R which are output signals of the color difference matrix circuit 8.
-Y is amplified to correct the color purity of the intermediate saturation of reproduced color.

The video signal amplifier according to the present invention, as shown in FIG. 2, is a multiplier 13 for inputting the color difference signal as a video signal from two terminals and squaring the color difference signal for output.
, The color difference signal and the output signal of the multiplier 13 are input to output the difference signal of these signals, and the amplifier 14 that amplifies the output signal of the differential device with a constant gain k.
And the adder 15 which receives the color difference signal and the output signal of the amplifier 14 and outputs a sum signal of these signals.

In this video signal amplifier, the input signal is x and the output signal is y. However, the input signal x is 1
The level of 00% is normalized to 1. Then,
The output signal y is y = x + k (1-x) * x (?-1 <x <0) y = x + k (-1-x) * x (? 0 <x <1). That is, the amplification characteristic of this video signal amplifier can change its linearity depending on the gain k of the amplifier 14 as shown by the dotted line in FIG. The amplification characteristic of this video signal amplifier is represented by a quadratic function when k is not 0, and is non-linear.

With this video signal amplifier, the color difference signal R
When -Y is amplified, when the input signal x is between 0 and 1, as shown in FIG. 4, the variation due to the correction of the reproduced color on the detection axis is different from the variation in the direction parallel to the RY axis. Become. It should be noted that, in the case of correction in which the saturation is simply increased, the variation of the reproduced color is such that the zero point becomes the center and spreads in a direction away from the zero point.

FIG. 5 is a chromaticity diagram showing variations in reproduced color due to correction of color purity using this video signal amplifier.
As shown in FIG. 5, the reproduction colors a ′, b ′, and c ′ before correction are shifted to the R (red) side substantially in parallel by the correction to become the reproduction colors a, b, and c after correction. . That is, in the correction of the color purity of the reproduced color using this video signal amplifier, the color purity of the intermediate hue is improved.

Further, in this video signal amplifier,
It is also possible to correct the reproduced color by amplifying the color difference signals B-Y and G-Y. Further, even when the input signal x is between -1 and 0, the same correction as described above can be performed.

The video signal amplifier according to the present invention, as shown in FIG. 6, includes an amplifier 20 for amplifying and outputting an input signal with a constant gain, a diode 18 serving as a rectifying element, and a power supply means. It can be configured by having a power source 19 which is In this video signal amplifier, the color difference signal, which is a video signal, is input to the input terminal of the amplifier 20 via the limiting resistor 16. The diode 18 is connected to the input terminal of the amplifier 20 via the limiting resistor 17 on the input end side. The anode of the power supply 19 is connected to the output terminal side of the diode 18. The cathode of this power supply 19 is grounded,
A constant voltage is applied to the output side of the diode 18.

In this video signal amplifier, the level of the color difference signal is controlled by the power source 19 by the diode 18
When the voltage is lower than the applied voltage, no current flows through the diode 18, and the color difference signals are all amplified by the amplifier 20 with a constant gain. When the level of the color difference signal becomes higher than the voltage applied to the diode 18 by the power supply 19, a forward current flows through the diode 18, and the color difference signal is partially converted to the diode. It escapes to the ground side via 18 and a part of it is amplified by the amplifier 20 with a constant gain. Therefore, the amplification characteristic of this video signal amplifier is a non-linear characteristic having an inflection point at a level corresponding to the electromotive voltage of the power source 19, as shown by the dotted line in FIG.

Also in the video signal amplifier thus constructed, when the electromotive voltage of the power source 19 and the gain of the amplifier 20 are appropriately set, when the color signal is used to correct the color purity of the reproduced color in the television apparatus. It is also possible to satisfactorily correct the color of the intermediate hue.

The video signal amplifier according to the present invention is
As described above, it can be used not only for correcting the color purity of the reproduced color but also for intentionally changing the reproduced color.

[0029]

As described above, in the video signal amplifier according to the present invention, since the input video signal is amplified by the non-linear characteristic, the color purity of the intermediate saturation degree of the reproduced color in the television device can be improved. When used for the correction, the ratio of the color difference signals can be corrected in parallel with the detection axis, and the color purity of the intermediate hue can be improved.

Therefore, in the video signal amplifier according to the present invention, when correcting the color purity of the intermediate saturation of the reproduced color in the television apparatus, not only the saturation of the single color but also the hue of the intermediate hue is corrected. It can be corrected well.

The video signal amplifier is supplied with a multiplier which receives the video signal and squares and outputs the video signal, and with the video signal and the output signal of the multiplier, the difference signal between these signals is inputted. A differential device for outputting, an amplifier for amplifying the output signal of the differential device with a constant gain, and an adder for receiving the video signal and the output signal of the amplifier and outputting a sum signal of these signals Can be configured. In this case, depending on the gain setting of the amplifier,
The linearity of the amplification characteristic can be changed.

The video signal amplifier includes an amplifier that receives a video signal and amplifies and outputs the input signal at a constant gain, and a rectifying element whose input terminal is connected to the input terminal of the amplifier. , A power supply means for applying a voltage to the output end side of the rectifying element. In this case, an amplification characteristic having an inflection point is obtained when the video signal is at a level corresponding to the voltage applied by the power supply means.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a television apparatus to which a video signal amplifier according to the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a video signal amplifier according to the present invention.

FIG. 3 is a graph showing an amplification characteristic of the video signal amplifier.

FIG. 4 is a graph showing how color purity correction is performed using the video signal amplifier.

FIG. 5 is a chromaticity diagram showing a state of color purity correction performed by using the video signal amplifier.

FIG. 6 is a circuit diagram showing another example of the configuration of the video signal amplifier according to the present invention.

7 is a graph showing amplification characteristics of the video signal amplifier shown in FIG. 6;

FIG. 8 is a chromaticity diagram illustrating color reproducibility in a television device.

FIG. 9 is a graph showing a state of color purity correction performed using a conventional video signal amplifier.

FIG. 10 is a chromaticity diagram showing a state of color purity correction performed using a conventional video signal amplifier.

[Explanation of symbols]

 12 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Differential device 13 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Multiplier 14 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Amplifier 15 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・Adder 18 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Diode 19 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Power Supply 20 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Amplifier

Claims (3)

[Claims] 1. A video signal amplifier obtained by amplifying an input video signal by a non-linear characteristic. 2. A multiplier which receives a video signal and squares and outputs the video signal, and a differential device which receives the video signal and an output signal of the multiplier and outputs a difference signal between these signals. And an amplifier that amplifies the output signal of the differential device with a constant gain, and an adder that receives the video signal and the output signal of the amplifier and outputs a sum signal of these signals. 1. The video signal amplifier according to 1. 3. An amplifier for inputting a video signal and amplifying and outputting the input signal with a constant gain, a rectifying element having an input terminal connected to an input terminal of the amplifier, and an output terminal of the rectifying element. The video signal amplifier according to claim 1, further comprising a power supply means for applying a voltage to the side.