JPS625390B2 - - Google Patents

Description

[Detailed Description of the Invention] A still image such as a character is decomposed into a predetermined number of horizontal scanning lines, and the decomposed signal (character signal = still image information signal) Sw is sent to a predetermined area outside the effective screen of the composite television signal St. There is a multiplexing system for television broadcasting in which one horizontal period is sequentially inserted into each horizontal scanning period for transmission.

FIG. 1 shows the form of the character signal Sw transmitted in that case. In the figure, h is a horizontal synchronizing pulse, b
is a color burst signal. For example, the period between this horizontal synchronizing pulse h is a unit period of 364 digital signals.
Equally divided into Tc. Then, an information signal consisting of a synchronization period of 48Tc and an information period of 248Tc is superimposed on the period excluding the horizontal synchronization pulse h and the color burst signal b. Furthermore, an alternating signal Sf for performing frequency synchronization and a step signal Ss for performing phase synchronization as shown in the figure are inserted into the first 16Tc period and the following 16Tc period in the synchronization period, respectively.

Information signals include control signals and pattern signals. Here, the pattern signal is a signal obtained by decomposing one line of characters into a predetermined number of horizontal scanning lines. In addition, the control signal is a signal that is transmitted during the transmission period before one line of pattern signals is transmitted, and controls the display format of the pattern signals that are transmitted subsequently, such as full-screen display or scroll display. Distinguishing display formats and color information when coloring displayed characters are transmitted as digital signals.

When receiving such broadcasts, the character signals Sw in the television signal St are separated in a time division manner, and the separated character signals Sw are sequentially stored in a storage device, so that a series of character signals Sw is stored. After that,
This stored content is read out using a signal related to the synchronization signal of the television signal St and displayed on the picture tube.

Various methods can be considered for this display, but one example is a method in which characters are superimposed and displayed on the original television image. When performing such a display, if there is a difference in contrast or brightness between the image and the characters, the characters become extremely difficult to read. For example, if the contrast of the image is high and the contrast of the text is low, the text becomes difficult to read. Furthermore, if the contrast of the text is high and the contrast of the image is low, the screen will become dirty and difficult to see. The same can be said about screen brightness.

The present invention seeks to eliminate these drawbacks. Therefore, in the present invention, depending on the adjustment of the contrast and brightness of the television image,
The contrast and brightness of the characters are adjusted so that the contrast and brightness between the television image and the characters are always similar. An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall configuration diagram, in which the signal received by the tuner 1 is supplied to the video demodulation circuit 2, and the television signal St is demodulated. This signal St is supplied to the synchronization separation circuit 3 and the synchronization signal is separated.

The signal St is also supplied to the color signal separation circuit 11, and the separated color signal is sent to the muting circuit 12.
is supplied to the amplifier 13 through the amplifier 13.
The signals from the 3-axis color demodulation circuit 14 are supplied to the 3-axis color demodulation circuit 14. Also, a part of the signal from the amplifier 13 is supplied to the burst gate circuit 15 to separate the burst signal, this burst signal is supplied to the CW oscillator 16 to be made into a continuous signal, and this continuous signal is supplied to the color demodulation circuit 14. 3 of R-Y, B-Y, G-Y
Two color difference signals are demodulated. A part of the burst signal is also supplied to the ACC detection circuit 17, and the detected output is supplied to the amplifier 13 to perform ACC. The signal from the color demodulation circuit 14 is then supplied to the matrix circuit 19 through the clamp circuit 18.

Further, the signal St is supplied to an amplifier 23 through a delay circuit 21 and a muting circuit 22, and a signal from this amplifier 23 is sent to a pedestal clamp circuit 24.
The signal is supplied to the matrix circuit 19 through. And R, G, B from this matrix circuit 19
The three primary color signals are supplied to horizontal and vertical blanking circuits 25.

Furthermore, the signal St is supplied to a character signal decoding circuit 31 to separate the character signal Sw, and the pattern signal is stored in accordance with the control signal. Note that if the control signal has color information, the storage is distributed to three storage devices of R, G, and B according to the color information.

This stored content is read out in synchronization with the synchronizing signal from the separation circuit 3, and this signal is supplied to the mixing circuits 33R, 33G, 33B through the amplitude control circuits 32R, 32G, 32B for each color, and then from the blanking circuit 25. signal.

This mixed signal is supplied to the picture tube 5 through the output circuit 4. Further, the synchronizing signal from the separation circuit 3 is supplied to the oblate coil of the picture tube 5 through the oblate circuit 6, and the signal from the output circuit 4 is displayed.

Further, the signal from the contrast volume 41 is transmitted to the amplifiers 13, 23 and the amplitude control circuits 32R, 3.
2G and 32B, and the amplitude of each signal is controlled. Further, a signal from the brightness volume 42 is supplied to the pedestal clamp circuit 24 to control the pedestal level of the brightness signal.

Further, a control signal for full screen display in the decoder 31 is taken out, and this control signal is supplied to the muting circuits 12 and 22 to mute the respective signals.

According to this circuit, the contrast volume is 4
1 is adjusted, the amplitude of the luminance signal and color signal is controlled to change the contrast of the image, and the amplitude of the character signal is controlled to change the contrast of the character. Furthermore, when the brightness volume 42 is adjusted, the pedestal level of the brightness signal is controlled to change the brightness of the image, and since the character signal is superimposed on this brightness signal, the pedestal level of the brightness signal is controlled. Then, the level of the character signal is also controlled at the same time, changing the brightness of the character. Furthermore, when full-screen display is performed, the luminance signal is muted, but even in this case, the pedestal level is output to the output side of the amplifier 13, and this pedestal level is controlled by the clamp circuit 24. Therefore, the brightness of the characters is changed.

In this way, the contrast and brightness of images and characters are changed, and according to the present invention, by moving the contrast volume or brightness volume, the contrast or brightness of both images and characters are changed in conjunction, Since there is no difference in contrast or brightness between images and characters, there is no risk that the characters will become difficult to read or the screen will become dirty.

Furthermore, even when an image is displayed in full-screen mode, the contrast or brightness of the characters can be changed by adjusting the contrast volume or brightness volume.

Furthermore, FIG. 3 shows a character signal amplitude control circuit 32R.
~32B and character signal and image signal mixing circuit 3
An example of a specific connection diagram of 3R to 33B is shown.

In the figure, character signals separated into three primary colors from the decoding circuit 31 are input to input terminals 51 and 51 respectively.
It is supplied to R, 51G, and 51B. In addition, in the decoding circuit 31, a background signal for applying an arbitrary color to a background part other than characters when an image such as a full-screen display is muted is also separated into three primary colors, and these background signals are separated into three primary colors. Signals are supplied to input terminals 52R, 52G, and 52B, respectively.

These input terminals 51R~51B, 52R~5
The character signal and background signal from 2B are sent to attenuators 53R, 53G, 53B, 54R, 54G, 5
4B and diode 55R, 55G, 55B, 5
Items of the same color are mixed through 6R, 56G, and 56B.

These mixed signals are connected to the diodes 59R, 59
G, 59B and a clamp circuit consisting of a capacitor 60. Note that the capacitor 60 is common to the three systems. and diode 59R~59
The midpoint of the connection between B and the capacitor 60 is connected to the power supply terminal 63 through the transistor 61, and
The signal from contrast volume 41 is sent to terminal 6.
2 to the transistor 61.

The signals from these clamp circuits are differentially connected to one of the transistors 64R, 64G, and 64B.
Capacitors 66R, 6 are connected to the other transistors 65R, 65G, 65B which are connected differentially.
Reference voltages from 6G and 66B are supplied.

In the circuit so far, input terminals 51R to 5
1B, 52R to 52B are supplied with a signal in which a portion to be displayed is set at a high potential, as shown in FIG. 4A, for example. This signal is the transistor 57R~57
It is supplied to the clamp circuit through B. At the same time, the clamp level of this clamp circuit is controlled by the contrast volume 41 through the transistor 61. That is, as shown in FIG. 4, when the signal (voltage) from the contrast volume 41 changes, the transistors 57R to 57B
The signals from are generally moved up and down. Then, the portions higher than the reference voltage v from the capacitors 66R to 66B are amplified to form a signal whose amplitude is controlled as shown in FIG. 4C.

The signals thus formed are supplied to the transistors 67R, 67G, and 67B, respectively, and the attenuators 68R, 68G, and 68B and the transistor 67
A current corresponding to the amplitude-controlled signal is taken out through R to 67B.

On the other hand, the video signals separated into three primary colors from the blanking circuit 25 are input to the input terminals 69R and 69R, respectively.
It is supplied to 69G and 69B. Signals from these input terminals 69R to 69B are supplied to transistors 71R, 71G, and 71B through clamp circuits 70R, 70G, and 70B, respectively.

The signals from these transistors 71R to 71B and the signals from transistors 68R to 68B are mixed, and the signals from transistors 72R to 68B are mixed.
Output terminals 73R, 7 through R, 72G, 72B
3G, taken out at 73B. In addition, attenuators 53R~53B, 54R~54B, 68R~68
B etc., adjust the white balance of the text and background signals, the contrast with the image, and the balance of brightness.

In this case, transistors 67R to 67
B and attenuators 68R to 68B are in constant current operation, and even if the video signals from the input terminals 69R to 69B are mixed therewith, the DC level of the video signal will not fluctuate, and the character signal will not be mixed with the video signal. can be superimposed.

Furthermore, in the above-described apparatus, when superimposing text on an image, lowering the contrast of the image to some extent makes the text easier to read. Therefore, in FIG. 5, the signal from the contrast volume 41 is supplied to the gain control terminal of the amplifier 23, and
A transistor 81 is provided between this signal path and the power supply. At the same time, the decoding circuit 31 generates signals corresponding to the characters and their surroundings.
This signal is supplied to transistor 81 through transistor 82.

Therefore, in this circuit, the transistor 81 is turned on through the transistor 82 during the period when the character and its surrounding area are being scanned, and the voltage supplied to the amplifier 23 is increased by a predetermined amount. Furthermore, amplifier 2
The gain control characteristic of No. 3 is such that the gain decreases as the control voltage increases.

In this way, this circuit can lower the contrast around the characters to make them easier to read.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram of a character signal, FIG. 2 is a configuration diagram of an example of the present invention, and FIGS. 3 to 5 are diagrams for explaining the same. 31 is a decoding circuit, 32 is an amplitude control circuit, 3
3 is a mixing circuit, 41 is a contrast volume,
42 is a brightness volume.

Claims (1)

[Claims] 1. Receive a television signal in which a still image information signal is superimposed on a predetermined section within a vertical period for a fixed period of time, extract the above-mentioned still image information signal from this received signal, and store this extracted signal in a storage circuit. In a television multiplex broadcast receiving device which sequentially reads out the stored signals to obtain the still picture information signal, an amplitude control circuit for the still picture information signal is provided, and the output of the contrast volume is adjusted to adjust the brightness. Television multiplexing, which is supplied to a signal amplification circuit, a chrominance signal amplification circuit, and the amplitude control circuit, and controls the amplitude of the luminance signal and the chrominance signal by adjusting the contrast volume, and also controls the amplitude of the still picture information signal. Broadcast receiving device.