JPH0441868B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a television receiver that combines a plurality of video signals and displays the same on the same screen.

2. Description of the Related Art Recently, as a memory application for television receivers, a plurality of video signals have been combined and displayed on the same screen. Furthermore, in order to make it easier to use memory, each video signal handled in such a case is increasingly handled as a luminance signal and two color difference signals. In this way, 3
This is because the memory capacity can be halved due to the band compression effect compared to when handling primary color (R, G, B) signals.

An example of a conventional television receiver as described above will be described below with reference to the drawings. FIG. 3 shows a block diagram of a conventional television receiver. 301-303 and 3
04 to 306 are input terminals for video signals expressed by a luminance signal and two color difference signals, respectively. 307,
A matrix circuit 308 synthesizes the luminance signal and two color scan signals and outputs three primary color signals R, G, and B. Reference numeral 309 denotes a switching signal input terminal, and this signal switches switches 310 to 312 to combine two video signals and output the image to a cathode ray tube (CRT) 313. This type of circuit is used to switch between a main screen and a sub-screen in a two-screen television receiver or the like. (Television Society Technical Report “Monitor in Television” TEBS99-2
S.55.9.20) Problems to be Solved by the Invention However, the above configuration has a drawback in that it is difficult to match the white balance of the two images. This is because each system has separate matrix circuits 307 and 308, and the matrix ratio between the two will deviate due to errors in resistance values, etc. In addition, the center potential of the color difference signal is used in the signal processing process, such as A/D conversion process or D/A conversion process.
Another reason is that the value deviates from the original value.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a television receiver that facilitates white balance between a plurality of images displayed on the same screen.

Means for Solving the Problems In order to solve the above problems, the television receiver of the present invention clamps a plurality of sets of video signals expressed by a luminance signal and two color difference signals with a horizontal synchronizing pulse, and The clamp potential of the video signals except for one set can be adjusted independently for each of the luminance signal and two color difference signals, and the clamped video signals are switched using a switch to synthesize one video signal. The combined video signal is matrixed and converted into a luminance signal and three color difference signals or three primary color signals of R, G, and B.

According to the above-described configuration, the present invention first adjusts the center potential of the color difference signal to a normal potential by adjusting the clamp potential adjustment circuit, and then synthesizes the signals and uses the same matrix circuit. By doing so, it is possible to reduce deviations in white balance between a plurality of images on the same screen.

Embodiment Hereinafter, a television receiver according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a television receiver according to an embodiment of the present invention. In FIG. 1, 101 is a first luminance signal input terminal;
2,103 are two first color scan signal input terminals;
104 is a second luminance signal input terminal; 105, 1
06 is an input terminal for two second color difference signals.
107 is a clamp circuit section, 108 to 113 are capacitors, 114 to 119 are switches, 120 is a voltage source that determines a fixed clamp potential, and 121 to 1
23 is an input terminal, a variable voltage source for adjusting the clamp potential of the video signals of the systems 104 to 106;
124-129 are buffer amplifiers, and 130 is an input terminal for a clamp pulse signal for switching the switches 114-119. Furthermore, 131 is a switch 132 to 13 for switching between two signal systems.
135 is a matrix circuit, and 136 is a cathode ray tube (CRT).

The operation of the television receiver configured as described above will be explained below with reference to FIGS. 1 and 2.

First, FIG. 2 shows an operation waveform diagram of each part in FIG.
Pay attention to the switching. Waveform a is the waveform of the first color difference signal input terminal 102, and waveform b is the waveform of the second color difference signal input terminal 105.
09,112 to remove the DC component. Waveform c is the waveform of the clamp signal input terminal 130, and when the signal is at a high level, the switches 115 and 118 are closed to apply a clamp. At this time, buffer amplifier 12
The input potential of 5 is the potential of the constant voltage source 120, and the input potential of the buffer amplifier 128 is the potential of the constant voltage source 120.
is the sum of the potential of the variable voltage source 112 and the potential of the variable voltage source 112. Here, first, the potential of the variable voltage source 112 is set to 0. The outputs of the buffer amplifiers 125 and 128 are switched by a switching signal 131 having a waveform d. During the high level period, the switch 133 outputs the second color difference signal 10.
Connected to the 5 side. Therefore, switch 13
The output of No. 3 is as shown by the solid line of waveform e. The signals thus synthesized are input to the matrix circuit 135, and the output RGB signals are transmitted to the CRT 136.

As described above, according to this embodiment, since the signals are synthesized using the luminance signal and two color difference signals as they are, the matrix circuit can be reduced to one, and the mutual error in matrix ratio due to the provision of multiple matrix circuits can be reduced. Does not occur.

Furthermore, if there is an error in the center potential of the second color difference signal applied to the input terminal 105, for example, when the variable voltage source 122 is adjusted to △V, as shown by the dotted line of the waveform e in FIG. The color difference signal portion of No. 2 is raised by ΔV, and the error in the input signal can be absorbed.

Furthermore, this function can be used for brightness adjustment for brightness signals.

Note that although two systems of signal switching have been described here, it can be expanded to signal switching of a plurality of systems in the same manner.

Effects of the Invention As described above, by using a common power source as a constant voltage power source for a plurality of clamp circuits, the present invention can make the clamp voltage of each video signal constant, and eliminate the white balance deviation between each video signal. You can do less. At the same time, since the number of constant voltage sources can be reduced compared to the conventional method, the number of parts can be reduced, and the device can be made smaller. In addition, all clamp circuits except for one set of clamp circuits are provided with clamp potential adjustment circuits that independently adjust the clamp potential for each of the luminance signal and two color difference signals of the input video signal. By making fine adjustments, it is possible to reduce or eliminate white balance deviations between images with even higher precision.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining its operation, and FIG. 3 is a block diagram of a conventional television receiver. 101...first luminance signal input terminal, 102
~103... Input terminal for first color scan signal, 104
...Second luminance signal input terminal, 105-106
...Second color difference signal input terminal, 107...Clamp circuit section, 121-123...Variable voltage source, 1
14-119, 132-134...Switch, 1
35...Matrix circuit.

Claims (1)

[Claims] 1. A television receiver that receives as input a plurality of sets of video signals, one set of a luminance signal and two color difference signals, and can synthesize them and output them on the same screen as a main screen and a sub-screen. The machine has multiple sets of clamp circuits that clamp each of the multiple sets of video signals using horizontal synchronization pulses, and switches the video signals clamped by the clamp circuits to combine them into a single video signal. The multiple sets of clamp circuits are equipped with a synthesis circuit for outputting, and one matrix circuit for converting the video signals synthesized by this synthesis circuit into a luminance signal and three color difference signals or three primary color signals for output. In addition to having a common constant voltage source, the other clamp circuits except for one set include a clamp potential adjustment circuit that independently adjusts the clamp potential for each of the luminance signal and two color difference signals of the input video signal. A television receiver comprising: