JPH10271525A - Color television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color television receiver by which the color temperature of a white character is kept constant even when an average video level of a video signal is changed differently from an average video image level of the other video signal in the case of displaying a two-screen video image. SOLUTION: Inverters 21, 22 invert a luminance signal Y of 1st and 2nd video signals before the 1st and 2nd video signals are synthesized by a video synthesis circuit 3. Slice circuits 23, 24 slice outputs of the inverters 21, 22. An adder 25 adds outputs of the slice circuits 23, 24. A slice level generating circuit 14 decides a slice level in the slice circuits 23, 24. The output of the adder 25 is added to a color signal B by an adder 17 to correct the color temperature of a white character.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television receiver, and more particularly to a color television receiver having a two-screen display function and capable of favorably correcting the color temperature of white characters. About.

[0002]

2. Description of the Related Art Since the reference white on the image transmission side in the NTSC system is the average white of sunlight (color temperature of about 6500 K), the reference white of the white balance in a color television receiver is basically the same. , Should be the above color temperature. However, in actuality, the reference white in the color television receiver is a white (bluish) white having a slightly higher color temperature, and the color temperature is around 9300K in consideration of the tendency of the viewer's preference.

On the other hand, in recent years, with the increase in the size of color television receivers, the value added has been increased, and a high-quality color television receiver has been desired. For this reason, a color television receiver equipped with a white character correction circuit has also appeared as a circuit for correcting the color temperature. As one of the added values, there is a two-screen display function of displaying two images side by side on the left and right sides of the screen.

FIG. 4 is a block diagram showing an example of a conventional color television receiver having a two-screen display function and a white character correction circuit. In FIG. 4, a first video signal is input to a signal processing circuit 1, and a second video signal is input to a signal processing circuit 2. The signal processing circuits 1 and 2 respectively output a luminance signal Y and a color difference signal R- based on the first and second video signals.
Separate Y and BY. The luminance signal Y and the chrominance signals RY and BY output from the signal processing circuits 1 and 2 are input to the video synthesizing circuit 3, where the luminance signal Y and the chrominance signals RY and B- Y is set.

[0005] The color difference signal R-
Y and BY are used to generate a color difference signal GY.
It is input to the Y matrix circuit 4. The luminance signal Y, which is a two-screen image, is input to a contrast adjustment circuit 5 where the contrast is adjusted, and the luminance signal Y is inverted so that the luminance signal (−
Y) and is input to the matrix circuit 6. The matrix circuit 6 also receives the color difference signals RY and BY output from the video composition circuit 3 and the color difference signal GY output from the GY matrix circuit 4. The matrix circuit 6 outputs primary color signals R, G, and B by performing a matrix operation on the input signals.

Of the primary color signals R, G, B, signals R, G
Is input to the gain control circuit 7 as it is, and the signal B is input to the gain control circuit 7 via an adder 17 described later. The output of the gain control circuit 7 is input to a cathode ray tube (hereinafter abbreviated as CRT) 8, and a two-screen image is displayed.

On the other hand, the luminance signal Y output from the signal processing circuit 1 is input to a synchronization separation circuit 9, where the synchronization signal is separated. This synchronization signal is input to the deflection circuit 10, and the output of the deflection circuit 10 is input to the high voltage circuit 11. High voltage circuit 1
1 supplies a high pressure to the CRT 8. The anode current of the CRT 8 generated by the high voltage circuit 11 is ABL (automatic brightness limit).
Input to the circuit 12, the ABL circuit 12 generates a detection voltage corresponding to the anode current, and inputs the detection voltage to the contrast adjustment circuit 5. The contrast adjustment circuit 5 adjusts the contrast of the luminance signal Y, which is a two-screen video signal, according to the input detection voltage.

The color difference signals RY, BY, and GY input to the matrix circuit 6 are input to the color detection circuit 13 where the maximum value of the color difference signals is obtained. The output of the color detection circuit 13 is input to one terminal of the slice level generation circuit 14. The slice control voltage V1 is input to the other terminal of the slice level generation circuit 14. The slice level generation circuit 14 generates and outputs a slice voltage Vs.

The luminance signal (-Y) output from the contrast adjustment circuit 5 is input to the slice circuit 15 as one input a, and the slice voltage output from the slice level generation circuit 14 is input as the other input b. Vs,
The voltage divided by the resistors R1 and R2 is input. The slicing circuit 15 slices the luminance signal (-Y) as the input a with reference to the voltage of the input b to obtain an output c, which is input to the gain control circuit 16. As described above, by taking the maximum value of the color difference signal by the color detection circuit 13,
Where there is a color, the slice voltage Vs is lowered so that the slice circuit 15 does not slice the luminance signal (-Y).

The gain control voltage V2 is input to the gain control circuit 16, and the gain of the output c of the slice circuit 15 is controlled according to the gain control voltage V2. The output of the gain control circuit 16 is input to the adder 17 and is added to the signal B.

The above operation will be further described with reference to a waveform diagram shown in FIG. In FIG. 5A, the luminance signal (-Y) which is the input a of the slice circuit 15 is indicated by a solid line, and the slice level which is the input b of the slice circuit 15 is indicated by a broken line. Note that since the input a is obtained by inverting the luminance signal Y, the upper side in FIG. 5A is black and the lower side is white. Screen A is the left side of the two screens, and screen B is the right side
And Since the white character portion on the screen A is sliced at the slice level indicated by the broken line, the output c of the slice circuit 15 has the waveform shown in FIG. The output c is gain-adjusted by the gain control circuit 16 and added to the signal B by the adder 17, so that the output d of the adder 17 has a waveform shown in FIG. by this,
White characters are corrected.

[0012]

However, when a two-screen image is displayed on the CRT 8, the average image level of one image signal is different from the average image level of the other image signal with respect to the average image level of the two image signals. If the level changes by an amount different from the level, in an image based on the image signal having a smaller average image level change, the contrast and the brightness change more than necessary, which changes the peak of white characters.

This will be described with reference to FIG. FIG.
3A, the luminance signal (-Y) which is the input a of the slice circuit 15 is indicated by a solid line, and the slice level which is the input b of the slice circuit 15 is indicated by a broken line. Also in this case, the left side of the two screens is screen A, and the right side is screen B. In FIG. 6A, the contrast of the luminance signal (-Y), which is the input a, is smaller than that in FIG. In this case, the white character portion on the screen A is higher than the slice level indicated by the broken line.
5 is not sliced. Therefore, the slice circuit 1
The output c of No. 5 becomes no signal as shown in FIG. Therefore, the output d of the adder 17 has the waveform shown in FIG. 5C, and white characters are not corrected.

As described above, in the conventional color television receiver shown in FIG. 4, if the average video level of one video signal in a two-screen video changes by an amount different from the average video level of the other video signal. Since the amount of addition of the output of the gain control circuit 16 (that is, the luminance signal Y) to the signal B by the adder 17 changes, the color temperature (the degree of bluish tint) of the white character can be kept constant. There was a problem that it was not possible.

The present invention has been made in view of such a problem, and when displaying a two-screen video, the average video level of one video signal is different from the average video level of the other video signal. It is an object of the present invention to provide a color television receiver that can keep the color temperature of white characters constant even if the color temperature changes.

[0016]

According to the present invention, there is provided a video synthesizing circuit for synthesizing a first video signal and a second video signal. A contrast adjustment circuit (5) for adjusting the contrast of the video signal synthesized by the video synthesis circuit,
In a color television receiver for displaying a two-screen image on the display unit (8), a white character extraction circuit (15 or 23, 24) for extracting a portion corresponding to white characters from a luminance signal before contrast adjustment by the contrast adjustment circuit. )
And a white character extraction level generation circuit (14) for determining a level of white character extraction in the white character extraction circuit, and an output of the white character extraction circuit is obtained from a video signal after contrast adjustment by the contrast adjustment circuit. Provided is a color television receiver characterized by comprising an adder (17) for adding to a color signal, and (2) video synthesis for synthesizing a first video signal and a second video signal. In a color television receiver including a circuit (3) and displaying a two-screen image on a display unit (8), a portion corresponding to white characters from a luminance signal of the first video signal before being synthesized by the video synthesis circuit. The first white character extraction circuit (2
3) a second white character extraction circuit (24) for extracting a portion corresponding to a white character from the luminance signal of the second video signal before being synthesized by the video synthesis circuit; and the first and second white character extraction circuits. A white character extraction level generation circuit (14) for determining the level of white character extraction in the white character extraction circuit; and a first adder (2) for adding the outputs of the first and second white character extraction circuits.
And 5) adding the output of the first adder to the color signal obtained from the video signal synthesized by the video synthesis circuit.
And a color television receiver provided with the adder (17).

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color television receiver according to the present invention will be described below with reference to the accompanying drawings. FIG.
FIG. 2 is a block diagram showing a first embodiment of the color television receiver of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the color television receiver of the present invention, and FIG. 3 is a color television receiver of the present invention. FIG. 6 is a block diagram showing a second embodiment of the machine. 1 and 3, the same parts as those in FIG. 4 are denoted by the same reference numerals.

First, a first embodiment of the color television receiver of the present invention will be described. In FIG. 1, a first video signal is input to a signal processing circuit 1, and a second video signal is input to a signal processing circuit 2. Signal processing circuit 1,
2 separates a luminance signal Y and color difference signals RY and BY from the first and second video signals, respectively. Signal processing circuit 1,
2, the luminance signal Y and the color difference signals RY, B-
Y is input to the video synthesizing circuit 3 and becomes a luminance signal Y and color difference signals RY and BY synthesized on two screens.

The color difference signal R-
Y and BY are used to generate a color difference signal GY.
It is input to the Y matrix circuit 4. The luminance signal Y, which is a two-screen image, is input to a contrast adjustment circuit 5 where the contrast is adjusted, and the luminance signal Y is inverted so that the luminance signal (−
Y) and is input to the matrix circuit 6. The matrix circuit 6 also receives the color difference signals RY and BY output from the video composition circuit 3 and the color difference signal GY output from the GY matrix circuit 4. The matrix circuit 6 outputs primary color signals R, G, and B by performing a matrix operation on the input signals.

Of the primary color signals R, G, B, signals R, G
Is input to the gain control circuit 7 as it is, and the signal B is input to the gain control circuit 7 via an adder 17 described later. The output of the gain control circuit 7 is input to a cathode ray tube (hereinafter abbreviated as CRT) 8 as an example of a display unit, and a two-screen image is displayed.

On the other hand, the luminance signal Y output from the signal processing circuit 1 is input to a synchronization separation circuit 9 where the synchronization signal is separated. This synchronization signal is input to the deflection circuit 10, and the output of the deflection circuit 10 is input to the high voltage circuit 11. High voltage circuit 1
1 supplies a high pressure to the CRT 8. The anode current of the CRT 8 generated by the high voltage circuit 11 is ABL (automatic brightness limit).
Input to the circuit 12, the ABL circuit 12 generates a detection voltage corresponding to the anode current, and inputs the detection voltage to the contrast adjustment circuit 5. The contrast adjustment circuit 5 adjusts the contrast of the luminance signal Y, which is a two-screen video signal, according to the input detection voltage.

Further, the first video signal input to the video
The luminance signal Y of the video signal is input to the inverter 21 and inverted to be a luminance signal (-Y). The luminance signal Y of the second video signal input to the video synthesizing circuit 3 is input to the inverter 22 and inverted to be a luminance signal (-Y). The output of the inverter 21 is input as one input a to a slice circuit 23 which is a white character extraction circuit, and the output of the inverter 22 is input as one input b to a slice circuit 24 which is a white character extraction circuit. Is done. These slice circuits 23,
The slice level (white character extraction level) obtained as described below is input to input 24 as input c.

That is, the color difference signals RY, BY, and GY input to the matrix circuit 6 are input to the color detection circuit 13 and the maximum value of the color difference signals is obtained. The output of the color detection circuit 13 is input to one terminal of a slice level generation circuit 14 which is a white character extraction level generation circuit. The slice control voltage V1 is input to the other terminal of the slice level generation circuit 14. The slice level generation circuit 14 generates and outputs a slice voltage Vs. This slice voltage V
A voltage obtained by dividing s by the resistors R1 and R2 is input to the slice circuits 23 and 24 as an input c which is a slice level. As described above, by taking the maximum value of the color difference signal by the color detection circuit 13, the slice voltage Vs is lowered where there is a color, and the slice circuits 23 and 2 are set.
4 prevents the luminance signal (-Y) from being sliced.

The outputs d and e of the slice circuits 23 and 24 are input to an adder 25 and added. Adder 2
5 is input to the gain control circuit 16. The gain control voltage V2 is input to the gain control circuit 16, and the gain of the output f of the adder 25 is controlled in accordance with the gain control voltage V2. The output of the gain control circuit 16 is the adder 1
7 and is added to the signal B.

The operation of the present invention will be further described with reference to the waveform diagram shown in FIG. FIG. 2 shows a case where the average video level of one video signal in a two-screen video changes by an amount different from the average video level of the other video signal, similarly to FIG. In FIG. 2A, the luminance signal (-Y) of the first video signal which is the input a of the slice circuit 23 is indicated by a solid line, and the slice level which is the input c of the slice circuit 23 is indicated by a broken line. FIG. 2B shows the slice circuit 24.
The luminance signal (-Y) of the second video signal, which is the input b, is shown by a solid line, and the slice level, which is the input c of the slice circuit 24, is shown by a broken line. Again, the upper side is black,
The lower side is white.

Since the white character portion in the luminance signal (-Y) shown in FIG. 2A is sliced by the slice level shown by the broken line, the output d of the slice circuit 23 is shown in FIG.
The waveform shown in FIG. On the other hand, in the luminance signal (-Y) shown in FIG. 2B, since there is no white character exceeding the slice level shown by the broken line, the output e of the slice circuit 24 is output.
Becomes no signal as shown in FIG. The output f of the adder 25, which is the result of adding these outputs d and e, is shown in FIG.
The waveform shown in FIG. The output f is gain-adjusted by the gain control circuit 16 and added to the signal B by the adder 17, so that the output g of the adder 17 is as shown in FIG.
The waveform shown in FIG. As a result, white characters are corrected.

In the first embodiment, even if the average video level of one video signal in a two-screen video changes by an amount different from the average video level of the other video signal, the color temperature of white characters is always satisfactory. In addition to the characteristic that the slice circuit 2 can be kept constant.
Since 3 and 24 are provided, there is a feature that the slice level of white characters can be set separately for two screens.

Next, a second embodiment of the color television receiver of the present invention will be described. In the second embodiment shown in FIG. 3, the slice level of white characters cannot be set separately for two screens, but the average video level of one video signal in a two-screen video is the average video level of the other video signal. Even if it changes by an amount different from the level, the color temperature of the white character can always be kept satisfactorily constant. In FIG. 3, the description of the same parts as those in FIG. 4 will be omitted.

In FIG. 3, the luminance signal Y input to the contrast adjustment circuit 5 is inverted by an inverter 18 to be a luminance signal (−Y), and input to the slice circuit 15. Thus, in the second embodiment, unlike the conventional example shown in FIG. 4, instead of the luminance signal (-Y) output from the contrast adjustment circuit 5, the luminance signal Y before the contrast adjustment by the contrast adjustment circuit 5 is performed. Slice circuit 1
5 is input. Therefore, also in the second embodiment, 2
The average video level of one video signal in the screen video is
Even if the average video level of the other video signal changes by an amount different from the average video level, the color temperature of the white character can always be kept good and constant.

As described above, in the color television receiver of the present invention shown in FIG. 1 and FIG.
White characters are extracted from the luminance signal Y of the video signal before contrast adjustment by the contrast adjustment circuit 5 in response to the average video level of one video signal in the two-screen video and the average video level of the other video signal. Even if it changes by an amount different from the level, the color temperature of the white character can always be kept satisfactorily constant, and the above-mentioned problem of the conventional technique can be solved well. Although the present embodiment has been described with a focus on solving the problem of white character correction accompanying the contrast adjustment, the problem of white character correction accompanying the brightness adjustment can be completely solved in the same manner.

[0031]

As described above in detail, the color television receiver of the present invention comprises a white character extracting circuit for extracting a portion corresponding to a white character from a luminance signal before the contrast adjustment by the contrast adjusting circuit, and A white character extraction level generation circuit that determines the level of white character extraction in the white character extraction circuit; and an adder that adds the output of the white character extraction circuit to a color signal obtained from the video signal after the contrast adjustment by the contrast adjustment circuit. When displaying two-screen video on the display unit, even if the average video level of one video signal changes by a different amount from the average video level of the other video signal, The color temperature can be kept constant.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the first embodiment of the present invention.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional example.

FIG. 5 is a waveform chart for explaining the operation of the conventional example.

FIG. 6 is a waveform chart for explaining a problem of the conventional example.

[Explanation of symbols]

1, 2 signal processing circuit 3 video composition circuit 5 contrast adjustment circuit 8 cathode ray tube (display unit) 12 ABL circuit 13 color detection circuit 14 slice level generation circuit (white character extraction level generation circuit) 15 23, 24 slice circuit (white character) Extraction circuit) 16 Gain control circuit 17, 25 Adder 18, 21, 22, Inverter

Claims (2)

[Claims] An image synthesizing circuit for synthesizing a first image signal and a second image signal; and a contrast adjusting circuit for adjusting the contrast of the image signal synthesized by the image synthesizing circuit. In a color television receiver displaying a two-screen image, a white character extraction circuit for extracting a portion corresponding to a white character from a luminance signal before contrast adjustment by the contrast adjustment circuit; A white character extraction level generation circuit for determining a level; and an adder for adding an output of the white character extraction circuit to a color signal obtained from a video signal after contrast adjustment by the contrast adjustment circuit. Characteristic color television receiver. 2. A color television receiver comprising a video synthesizing circuit for synthesizing a first video signal and a second video signal and displaying a two-screen video on a display unit, wherein A first white character extraction circuit for extracting a portion corresponding to a white character from the luminance signal of the first video signal; and a white character than the luminance signal of the second video signal before being synthesized by the video synthesis circuit. A white character extraction circuit for extracting a portion to be extracted; a white character extraction level generation circuit for determining a level of white character extraction in the first and second white character extraction circuits; and a first and second white character extraction circuit. A first adder for adding the output of the character extraction circuit; and a second adder for adding the output of the first adder to a color signal obtained from the video signal synthesized by the video synthesis circuit. It is characterized by being provided and configured Color television receiver.