JPH0267086A - Television receiver with two pictures - Google Patents

Abstract

PURPOSE:To obtain a stable picture by preventing a slave picture from generating dark sinking or doming by providing a slave picture video signal amplitude adjusting circuit to adjust the amplitude of a video signal on the slave picture by comparing the output of a detection circuit, respectively. CONSTITUTION:APL detection circuits 4 and 5 to detect the average picture levels(APL) of a master picture and the slave picture, a comparator 6 to compare the output of the APL detection circuits 4 and 5, respectively, the slave picture video signal amplitude adjusting circuit 7 to adjust the amplitude of the video signal on the slave picture in three stages corresponding to the output of the comparator 6, and a slave picture clamping circuit 8 to fit the pedestal level of the slave picture in the master picture are provided. Thereby, it is possible to obtain the stable picture by eliminating the floating and sinking of black on the slave picture of a television set with two screens, preventing the slave picture of the television with two pictures from generating the dark sinking by increasing the amplitude of the video signal on the slave picture when the APL of the master screen is high and that of the slave picture is low, and adversely, preventing the slave picture of the television with two screens from generating the doming by decreasing the amplitude of the video signal on the slave picture when the APL of the master picture is low and that of the slave picture is high.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal amplitude control circuit for a two-screen television receiver, particularly a sub-screen, such as a television receiver having a digital video processing device.

2. Description of the Related Art In recent years, there has been a remarkable introduction of digital technology into television receivers, and in particular, digital image processing for dual-screen televisions and the like has been attracting attention.

Hereinafter, an example of a video signal amplitude control circuit for a small screen in the conventional two-screen television described above will be described with reference to the drawings.

FIG. 2 shows a block diagram of a conventional amplitude control circuit. In FIG. 2, reference numeral 1 denotes a sub-screen video signal amplitude adjustment circuit that adjusts the amplitude of the video signal of the sub-screen to that of the main screen.

2 is a sub-screen soft clamp circuit that matches the average DC level of the sub-screen luminance signal with the average DC level of the main-screen luminance signal. 3 is a screen switching circuit that fits the child screen into the main screen.

The operation of the sub-screen video signal amplitude control circuit for a dual-screen television configured as described above will be described.

First, when the child screen receives the same video signal as the parent screen, the gain of the child screen video signal amplitude adjustment circuit 1 is adjusted and fixed so that the video signal amplitude of the child screen is equal to that of the parent screen. Then, the sub-screen video signal that has passed through the sub-screen video amplitude adjustment circuit 1 is passed through the sub-screen soft clamp circuit 2 to adjust the average DC level of the sub-screen video signal to the average DC level of the main screen video signal, and finally the screen is switched. Insert the child screen into the main screen using circuit 3.

Here, Figure 3 shows the sub-screen soft clamp circuit 2 in Figure 2.
This shows the video signals of the main screen and child screen. In Figure 2, the average brightness level of the main screen /L/(hereinafter referred to as A
When the AFL of the child screen is high and the AFL of the child screen is low, the (IL
), the pedestal level of the child screen rises relative to the parent screen, preventing the child screen of a dual-screen TV from becoming dark and sinking.
When L is high, as shown in (b), the pedestal level of the sub screen is lowered relative to the main screen to prevent the sub screen of the two-screen TV from shining too brightly.

Problems to be Solved by the Invention However, with the above configuration, there is a limit to changing the pedestal level of the child screen with respect to the pedestal level of the parent screen. When this is high, the APL of the video signal synthesized by the screen switching circuit is low, so automatic brightness limit (ABL) and automatic color limit (ACL) are not applied much, which may cause doming of the sub-screen.

In addition, since the sub-screen pedestal level is changed relative to the main screen, when the APL of the main screen is high and the APL of the sub-screen is low, the black on the sub-screen of a dual-screen TV will appear floating, and conversely, the AFL of the main screen will be low. When the APL of the sub-screen is low and the APL of the sub-screen is high, there is a problem that the black of the two-screen TV becomes dull.

In view of the above-mentioned problems, the present invention eliminates the rise and fall of the black of the sub-screen relative to the main screen, and at the same time prevents doming of the sub-screen of a dual-screen TV when the AFL of the main screen is low and the AFL of the sub-screen is high. The present invention provides a two-screen television receiver that can provide a stable screen using a video signal amplitude control circuit.

Means for Solving the Problems In order to solve the above problems, the video signal amplitude control circuit used in the dual-screen television receiver of the present invention includes an APL detection circuit that detects the APL of each of the main screen and the child screen. , a sub-screen video signal amplitude adjustment circuit that adjusts the video signal amplitude of the sub-screen by comparing the outputs of each of the APLs of the APL detection circuit, and a sub-screen clamp circuit that adjusts the pedestal level of the sub-screen to the parent screen. It is something.

Effects of the present invention With the above-described configuration, the pedestal level of the child screen is made equal to that of the parent screen, and when the AFL of the parent screen is high and the APL of the child screen is low, the gain of the child screen video signal amplitude adjustment circuit is increased. APL of the screen is low and AFL of the sub screen
When the APL of the main screen is low, the gain of the sub-screen video signal amplitude adjustment circuit is lowered to eliminate the fluctuations in black on the sub-screen of a dual-screen TV, and the
This prevents the sub-screens of a dual-screen TV from doming when the PL is high.

Embodiment Hereinafter, a small screen video signal amplitude control circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a small screen video signal amplitude control circuit. In FIG. 1, 4 is an APL detection circuit that detects the APL of the main screen, 5 is an APL detection circuit that detects the APL of the child screen, 6 is a comparison circuit that compares the outputs of each of the APL detection circuits 4 and 6; 7 is a sub-screen video signal amplitude adjustment circuit that adjusts the video signal amplitude of the sub-screen using the output of the comparison circuit; 8 is a sub-screen clamp circuit that adjusts the pedestal level of the sub-screen to the pedestal level of the main screen;
Reference numeral 9 denotes a screen switching circuit that fits the child screen into the main screen.

The operation of the two-screen television sub-screen video signal amplitude control circuit configured as described above will be described below with reference to FIG.

First, when the APL of the main screen and the sub-screen are almost equal, no output is generated from the comparator circuit 6, and the gain of the sub-screen video signal amplitude adjustment circuit remains unchanged. When the APL of the main screen is high and the APL of the sub-screen is low, the gain of the sub-screen video signal amplitude adjustment circuit is increased by the control signal from the comparison circuit 6, and conversely, the AFL of the main screen is low and the PL of the sub-screen is high. In this case, the gain of the small screen video signal amplitude adjustment circuit 7 is lowered.

The video signal of the sub-screen thus obtained is adjusted to the vedestal repé μ of the main screen by a sub-screen clamp circuit 8, and fitted into the main screen by a screen switching circuit 9.

As described above, according to this embodiment, the AP of the parent screen and the child screen
An APL detection circuit 4.5 that detects L, a comparison circuit 6 that compares the output of each of the APL detection circuits 4 and 5, and adjusts the video signal amplitude of the sub-screen in three stages according to the output of the comparison circuit 6. By providing the sub-screen video signal amplitude adjustment circuit 7 and the sub-screen clamp circuit 8 that adjusts the pedestal level of the sub-screen to the main screen, the black of the sub-screen of a dual-screen TV can be prevented from rising and falling, and the APL of the main screen can be high. When the APL of the sub screen is low, the amplitude of the video signal of the sub screen is increased to prevent the sub screen of a dual-screen TV from becoming dark. Conversely, when the APL of the main screen is low and the APL of the sub screen is high, the amplitude of the sub screen's video signal is increased. It is possible to provide a two-screen television set i that can obtain a stable screen by reducing the amplitude of the video signal and preventing the sub-screens of the two-screen television from doming.

Effects of the Invention As described above, the present invention provides an APL detection circuit that detects the APL of each of the main screen and sub screen of a dual screen television, and
By providing a sub-screen video signal amplitude adjustment circuit that compares the outputs of each of the L circuits and adjusts the video signal amplitude of the sub-screen, and a sub-screen flag circuit that adjusts the pedestal level of the sub-screen to the main screen. To provide a bivalent screen television receiver capable of eliminating fluctuations in black on a sub-screen of a television screen and at the same time preventing the sub-screen from darkening or doming to obtain a stable screen.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a dual-screen television receiver according to an embodiment of the present invention, FIG. 2 is a block diagram of a small-screen video signal amplitude control circuit of a conventional dual-screen television, and FIGS. FIG. 3 is a waveform diagram of video signals of the main screen and the child screen in the child screen soft clamp circuit of FIG. 2; 4.6... APL detection circuit, 6... Comparison circuit, End... Sub-screen video signal amplitude adjustment circuit,
8...Small screen clamp circuit, 9...Screen switching circuit.

Claims (1)

[Claims] a detection circuit that detects the average brightness level of each of the main screen and the sub-screen of a two-screen TV; and a sub-screen video signal amplitude adjustment circuit that compares the outputs of each of the detection circuits and adjusts the video signal amplitude of the sub-screen. , a sub-screen clamp circuit that adjusts the pedestal level of the sub-screen to the main screen, and increases the gain of the sub-screen video signal amplitude circuit when the average brightness level of the main screen is high and the average brightness level of the sub-screen is low; A two-screen television receiver characterized in that the gain of the child screen video signal amplitude adjustment circuit is lowered when the average brightness level of the main screen is low and the average brightness level of the child screen is high.