JPH04207278A - Two-picture display television receiver - Google Patents

Abstract

PURPOSE:To obtain satisfactory images on master and slave screens by provid ing a bias circuit for contrast adjustment and a bias circuit for black level adjustment independently at first and second video signal processing circuits. CONSTITUTION:A switch control signal C from a two-plane processing circuit 9 goes to an L level in a master screen display period, and the terminals 16, 17 of a switch circuit 15 are connected to terminals 18, 19. respectively, and are controlled by the bias circuits 7a, 8a for contrast adjustment and black level adjustment included in an RGB interface circuit 10. Meanwhile, the switch control signal C goes to an H level in a slave screen display period, and the terminals 16, 17 of the circuit 15 are connected to terminals 20, 21, respectively, and control circuits for contrast and black level in the circuit 10 are controlled by the bias circuits 7b, 8b for contrast adjustment and black level adjustment. Therefore, it is possible to share the adjustment of contrast and black level on both master and slave screens by one control circuit, and the independent adjustment of the master and slave screens can be performed respectively.

Description

[Detailed Description of the Invention] No. 1 The present invention relates to a dual-screen television receiver that can simultaneously display a main screen and a sub-screen inserted into the main screen on one screen, and in particular, The present invention relates to a dual-screen display television receiver in which the contrast and black level of the sub-screen and the sub-screen can be adjusted independently.

Figure 3 is a block diagram of a conventional dual-screen television receiver. In FIG. 3, 1 and 2 are video input terminals into which first and second video signals are input. 3 is the first
and a change-over switch circuit that controls switching between the main screen and the sub-screen by controlling the switching of the second video signal, respectively, and is mainly used to provide a parent-child reversal function. Here, the switch circuit 3 shown in FIG. 3 mainly uses the video signal input from the first video input terminal for the main screen, and the video signal input from the second video input terminal 2 for the child screen. It is controlled as follows.

In FIG. 3, the video signal inputted from the first video input terminal 1 is inputted as the main screen signal S1 via the switch circuit 3 to the processing circuit 4a that performs processing such as video, chroma, synchronization, etc. After the processing, the data is input to the RGB interface circuit 10.

The hue and color density of the parent screen are adjusted by bias circuits 5a and 6a provided in the processing circuit 4a, respectively.

On the other hand, the video signal input from the second video input terminal 2 is input as a sub-screen signal S2 via the changeover switch circuit 3 to a processing circuit 4b that performs video, chroma, synchronization, etc. processing, and various processing is performed. After being applied, it is input to the two-sided processing circuit 9. Note that the hue and color density of the child screen are adjusted by bias circuits 5b and 6b provided in the processing circuit 4b, respectively.

The signal of the child screen processed by the processing circuit 4b is subjected to timing adjustment in the two-sided processing circuit 9 using the horizontal and vertical synchronization signals of the main screen obtained from the processing circuit 4a, and is subjected to time compression, scanning line thinning, etc. After being processed, the signal is input to the RGB interface circuit 10 as signal B of the child screen. Further, the dual-screen processing circuit 9 outputs a control signal C to the RGB interface circuit 10 for switching the screen in synchronization with the child screen signal in order to insert the child screen into the main screen. Note that since the two-sided processing circuit 9 is a conventionally well-known circuit, a detailed explanation of its operation will be omitted here.

The parent and child video signals processed as described above are R
In the GB interface circuit 10, first, the switching control signal C
As a result, the child screen signal is inserted into the main screen signal, and the contrast and black level are further adjusted with signals E and D from the contrast adjustment bias circuit 7 and the black level adjustment bias circuit 8, and the result is output as an image signal F. Ru. 11 is a beam suppression circuit (which detects the beam current of the cathode ray tube by the current flowing through the flyback transformer (FBT) of the cathode ray tube and suppresses overcurrent from flowing into the cathode ray tube.
This ABL circuit (hereinafter referred to as an ABL circuit) is connected to the contrast adjustment and black level adjustment bias circuits and prevents overcurrent from flowing into the cathode ray tube.

The image signal F is amplified by a video output circuit 12 and guided to a cathode ray tube 13 to display a video with a sub-screen inserted into the main screen. In this case, the contrast and black level are adjusted by the contrast adjustment bias circuit 7 and the black level adjustment bias circuit 8, but the main screen and sub screen are adjusted in conjunction with each other, and the user can and the contrast and black level of the sub screen cannot be adjusted independently.

This will be explained using FIG. 4. FIG. 4 is an operational waveform diagram of each part of the two-screen display television receiver configured as shown in the block diagram shown in FIG.

Now, the main screen is the above ABL circuit 11 as shown in Figure 4A.
It is assumed that the image is a bright image, and the sub-screen is a relatively dark image as shown in FIG. 4B. C shown in FIG. 4 is a switching control signal of a switching circuit used to insert a child screen into a main screen, and during the period of high level, the video screen is switched to the child screen.

D in FIG. 4 is the bias waveform of the control terminal provided in the RGB interface circuit 10 to adjust the contrast, and E shown in FIG. 4 is the bias waveform of the control terminal provided in the RGB interface circuit 10 to adjust the black level. These are bias waveforms, and these waveforms are normally set to potentials (7) and (8) by the contrast adjustment bias circuit 7 and the black level adjustment bias circuit 8. However, when the image on the main screen becomes brighter, the APL circuit 11 acts and the potentials v7 and 18 are respectively lowered to the potential V7'V@''.

Therefore, as shown at F in Figure 4, the main screen is the above ABL.
Due to the action of the circuit 11, the level shown by the broken line is set to the desired level shown by the solid line, but at the same time, the video level of the sub-screen which is at the dark level shown by the broken line is also lowered to the level shown by the solid line, degrading the image quality of the sub-screen. I'm letting you do it.

As mentioned above, in conventional dual-screen television receivers, it is not possible to adjust the contrast and black level independently for both the parent and child screens, and the image on the main screen cannot be adjusted independently. When the ABL circuit operates accordingly, the child screen is also adjusted to the same state as the main screen, deteriorating the image quality of the child screen.

In order to solve the above-mentioned problems, the present invention includes a contrast adjustment bias circuit and a black level adjustment bias circuit that are switched by a switching signal for both the parent and child screens, respectively, in the video signal processing circuit for the main screen and the sub screen. In addition to having a configuration with a circuit, a bias circuit for adjusting the contrast and black level of the main screen has a first circuit that suppresses overcurrent of the cathode ray tube.
A second beam suppression circuit is installed in the beam suppression circuit and the bias circuit for adjusting the contrast and black level of the subscreen, which detects the video average level of the subscreen and suppresses the beam current in the subscreen portion of the cathode ray tube using this detection signal. Make the configuration you have set.

1-The contrast and black level adjustment bias circuits provided independently for both the parent and child screens are selectively switched by a switching signal for synchronizing with the child screen and inserting the child screen into the parent screen. Since the contrast and black level can be adjusted independently for both the parent and child screens, and the first and second ABL circuits are provided that act separately on the video signals of both the parent and child screens,
The image quality of the child screen is not affected by the action of the ABL circuit of the main screen, and both the parent and child screens can be set in the best condition.

Example 1 - FIG. 1 is a block diagram of an embodiment of the present invention, and portions corresponding to those in the conventional example of FIG. 3 are designated by the same reference numerals, and their explanation will be omitted.

In FIG. 1, reference numeral 15 denotes a switch circuit that switches the contrast and black level adjustment of the video screen using control signals from the dual-screen processing circuit 9. When the main screen is selected, switching terminals 16 and 17 are connected to terminals 18 and 19, respectively. Furthermore, when the screen is a child screen, switching terminals 16 and 17 are connected to terminals 20 and 21, respectively. 7a and 8a are bias circuits for contrast adjustment and black level adjustment for the main screen, respectively, and the contrast adjustment bias circuit 7a is connected between the terminal 19 of the switch circuit 15 and the APL circuit 11a for the main screen, and also for black level adjustment. The bias circuit 8a for the main screen is connected to the terminal 18 of the switch circuit 15 and the ABL circuit 11a for the main screen.
provided in between. Similarly, 7b and 8b are bias circuits for contrast adjustment and black level adjustment for the sub-screen, respectively, and the contrast adjustment bias circuit 7b connects the terminal 20 of the switch circuit 15 to the APL circuit 11 for the sub-screen.
A bias circuit 8b for black level adjustment is provided between the terminal 21 of the switch circuit 15 and the ABL circuit 11b for the small screen. Reference numeral 14 denotes a video average level detection circuit (hereinafter referred to as rAPL detection circuit) that detects the video average level of the child screen.
Connected to circuit 11b.

That is, the difference from the conventional example shown in FIG. 3 is that the bias circuit for contrast adjustment is 7a for the main screen, 7b is for the sub screen, and the bias circuit for black level adjustment is 8a for the main screen. Bias circuits 8b for adjusting the contrast and black level of both the parent and child screens are individually provided for the child screen, and each of these bias circuits is connected to the switch circuit 15, respectively.

The switch circuit 15 is controlled by a control signal C1 outputted from the dual-screen processing circuit 9, that is, a switching signal for inserting the child screen into the main screen. This switching signal C connects the switch circuit 15 to the terminal 20 on the small screen side during the "H" level period.
21, and during the "L" level period, it is connected to the terminals 18 and 19 on the side of the bias circuit 7a18a for the main screen.

Furthermore, the difference from the above conventional example is that, whereas in the conventional example, the ABL circuit 11 was provided only in the bias circuit for contrast and black level adjustment for the main screen, in the present invention, the ABL circuit 11 is provided for both the parent screen and the sub-screen, respectively. ABL circuit 11a1
11b is provided, and the APL circuit 11b for the child screen
is provided with an APL detection circuit 14 that detects the APL of the child screen signal and controls the ABL circuit 11b.

Since the embodiment of the present invention has the above-described configuration, during the main screen display period, the switching control signal C from the two-sided processing circuit 9 is at the "L" level, and the terminal 16.1 of the switch circuit 15 is
7 are respectively connected to terminals 18 and 19, and the contrast and black level control circuits included in the RGB interface circuit 10 are controlled by bias circuits 7a and 8a for contrast and black level adjustment. On the other hand, during the child screen display period, the switching control signal C goes to the "H" level, and the terminals 16 and 17 of the switch circuit 15 are connected to the terminals 20 and 20, respectively.
The contrast and black level control circuit connected to 21 and located in the RGB interface circuit 10 is controlled by bias circuits 7b and 8b for contrast and black level adjustment. Therefore, the contrast and black level adjustment of both the parent and child screens can be shared by one contrast and black level control circuit provided in the RGB interface circuit 10, and the contrast and black level control circuit for the child screen can be used in common with the RGB interface circuit 10.
Independent adjustment of each parent and child is possible without adding the GB interface circuit IO.

Next, how the ABL circuit 11b of the main screen is prevented from affecting the child screen will be explained using FIG. 2.

In FIG. 2, similarly to the case shown in FIG. 4, the main screen is a bright image on which the APL circuit 11a acts, and the child screen is a relatively dark image, which are shown in A and B, respectively. C shown in FIG. 2 is a bias circuit 7a that switches between the main screen and the sub-screen and at the same time maintains the contrast and black level of both the main and sub-screens.
, 7b and 8a, 8b in a timely manner.

First, the period when the switching control signal C is at the "L" level, that is, the period during which the main screen is displayed will be explained.

D and E in FIG. 2 indicate the bias levels of the respective signals corresponding to the contrast and black level,
During the period when the switching control signal C is at the "L" level, the bias circuits 7a and 8a for adjusting the contrast and black level of the main screen are connected to the RGB interface circuit 10, and normally
The bias potential is set to 7 ve. However, if the main screen is a bright image as shown in A of FIG. 2, the bias potential V's, 8. are respectively■7. °, Veo °
The bias voltage has decreased to the bias potential shown by . Therefore, during the period when the switching control signal C is at the "L" level, that is, during the display period of the main screen, the video signal drops to the level shown by the solid line as shown at F in FIG.

Next, the period when the switching control signal C is at the "H" level, that is, the period during which the child screen is displayed will be explained. When the switching control signal C becomes 'H' level, the switch circuit 15 selects the contrast and black level bias circuit 7b18b of the sub-screen, and the contrast and black level control terminals of the RGB interface circuit 10 are connected to both bias circuits 7b18b.
and its bias potential is V71. , VH.

Here, since the child screen is relatively dark, the level detected by the APL detection circuit 14 is such that the child screen ABL circuit 11b does not operate.

Therefore, the bias potential of the bias circuit V 7bz V@b for adjusting the contrast and black level for the child screen is supplied to the RGB interface circuit 10 as it is as a control voltage for the contrast and black level. Therefore, during the period when the switching control signal C is at the "H" level, that is, during the display period of the sub-screen, as shown in F in FIG. Output in the state.

Also, when the sub-screen is a bright image, the APL detection circuit 14
operates to activate the second ABL circuit 11b, and lowers the video level of the sub-screen to prevent excessive current from flowing to the cathode ray tube.

In this way, since the ABL circuit 11a111b acts independently on each of the parent and child screens, the child screen is not affected by the parent screen as in the conventional case, and good images can be obtained on both the parent and child screens.

Since the present invention has the above-described configuration, it is possible to independently adjust the contrast and black level for both the parent and child screens with an extremely simple circuit configuration, and to adjust the ABL on the parent screen. Due to the action of the circuit, good image quality can be obtained on both the parent and child screens without adversely affecting the image quality of the child screen.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of Fig. 1, Fig. 3 is a block diagram of the conventional example, and Fig. 4 is an explanatory diagram of the operation of Fig. 3. It is. 1... First video input terminal 2... Second video input terminal 7a... Main screen contrast adjustment bias circuit 8a... Main screen black level adjustment bias circuit 7b...・Bias circuit 8b for contrast adjustment for the sub screen...Bias circuit 9 for adjusting the black level for the sub screen...
・Two-sided processing circuit 10...RGB interface circuit 11a...ABL circuit for main screen 11b...ABL circuit for sub-screen 13...CRT 14...APL detection circuit for sub-screen 15...・Switch circuit

Claims (4)

[Claims] (1) In a dual-screen television receiver in which a sub-screen based on a second video signal is displayed in a main screen based on a first video signal, the processing circuits for the first and second video signals are connected to each other. A two-screen display television receiver characterized by independently providing a bias circuit for contrast adjustment and a bias circuit for black level adjustment. (2) In a dual-screen television receiver that displays a sub-screen based on a second video signal within a main screen based on a first video signal, a switching control signal for switching between the first and second video signals. A switching control signal generating means for generating a switching control signal, a switching means controlled by a switching control signal from the switching control signal generating means, and a contrast and black level of both parent and child screens connected to the switching means can be adjusted independently. What is claimed is: 1. A dual-screen display television receiver comprising bias circuit means as described above, and a contrast and black level control circuit controlled by the output of the switching means. (3) In a dual-screen television receiver that displays a sub-screen based on a second video signal in a main screen based on a first video signal, a switching control signal for switching between the first and second video signals. A switching control signal generating means for generating a switching control signal, a switching means controlled by a switching control signal from the switching control signal generating means, and a contrast and black level of both parent and child screens connected to the switching means can be adjusted independently. a beam suppressing means connected to the bias circuit for adjusting the contrast and black level of the main screen and suppressing beam overcurrent of the cathode ray tube; and a contrast and black level controlled by the output of the switching means. A two-screen display television receiver characterized by comprising a control circuit. (4) In a dual-screen television receiver that displays a sub-screen based on a second video signal in a main screen based on a first video signal, a switching control signal for switching between the first and second video signals. A switching control signal generating means for generating a switching control signal, a switching means controlled by a switching control signal from the switching control signal generating means, and a contrast and black level of both parent and child screens connected to the switching means can be adjusted independently. The bias circuit means is connected to the bias circuit for adjusting the contrast and black level of the main screen, and the beam current of the cathode ray tube is detected by the current of the flyback transformer to prevent overcurrent from flowing to the cathode ray tube. The first method to suppress the beam current of the cathode ray tube
the beam suppression circuit means, the video average level detection means for detecting the average video level of the sub-screen, and the bias circuit for adjusting the contrast and black level of the sub-screen, and is connected to the output from the video average level detection means. Accordingly, the present invention is characterized by comprising second beam suppression circuit means for suppressing the beam current in the small screen portion of the cathode ray tube from flowing too much, and a contrast and black level control circuit controlled by the output of the switching means. A dual-screen television receiver.