JPH03263984A - Video processor - Google Patents

Abstract

PURPOSE:To display a video image for a stable slave screen by using an automatic brightness limit (ABL) detection voltage so as to control the brightness and the contrast of the slave screen independently of those of a master screen thereby bringing the luminance and a black level of the slave pattern to a prescribed level. CONSTITUTION:When the brightness of a main screen is high, since the brightness of the main screen is eminent in the brightness of the screen synthesized with the slave screen, an ABL circuit 4 detects it that the entire brightness is high. Then a video processing circuit 2 decreases the brightness and the contrast of the synthesized video signal. In this case, since the brightness and the contrast of the slave screen is decreased simultaneously, an ABL detection voltage of the ABL circuit 4 is inputted to a microcomputer 7. Then the brightness and the contrast of only the slave screen is increased by a video processing circuit 8 for exclusive use of the slave screen to make the brightness and the black level of the slave screen constant independently of the brightness of the main pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video processing device for a television receiver that is capable of displaying two types of signals on a screen simultaneously.

2. Description of the Related Art In recent years, there has been an increase in the number of television receivers that have multiple video signal input terminals and are capable of displaying two types of video signals simultaneously on one screen.

FIG. 3 is a circuit diagram of a video processing circuit of a conventional television receiver. In Fig. 3, 1 is a signal synthesis circuit for the main screen signal and the sub-screen signal, 2 is a video processing circuit that receives the composite video signal as input and controls its brightness and contrast, and 3 displays a surface image on the display. The display circuit 4 is a well-known automatic brightness limit (ABL) circuit. 5
is a bright/contrast circuit which is a control circuit that creates control signals for controlling brightness and contrast based on the output of the ABL circuit 4.

In the above configuration, when the screen brightness increases, the ABL detects a current change in the flyback transformer (not shown).
Circuit 4 operates to prevent large anode current from flowing into the picture tube. Furthermore, in accordance with the output detection voltage of the ABL circuit 4, the brightness/contrast circuit 6 controls the video processing circuit 2 to control the brightness and contrast of the video (main screen video signal and subscreen video signal). The operation is controlled so as to reduce the blackness of the signal displayed on the picture tube.

Problems to be Solved by the Invention In the conventional configuration as described above, when the signals of the main screen and the sub-screen are different (for example, the main screen is a signal obtained by detecting an RF multiplied signal, and the sub-screen is a signal input from a VTR). case),
When the brightness of the signal displayed on the picture tube is high, the brightness of both the main screen video signal and the sub-screen video signal is controlled by the ABL circuit so that the brightness and contrast are reduced. That is, the brightness and black level of the child screen change depending on the brightness of the main screen. Now, when the brightness of the main screen is high and the brightness of the sub-screen is low, the main screen video signal and the ABL circuit work, reducing the brightness and contrast of both the main screen video signal and the sub-screen video signal. At this time, the brightness and contrast of the sub-screen with low brightness decreases, the brightness decreases, and the blacks become crushed.

The present invention is based on the above-mentioned problems, and an object of the present invention is to provide an image processing device having good luminance reproducibility.

Means for Solving the Problems The present invention provides a new video processing circuit that uses the ABL detection voltage to control the brightness and contrast of the sub-screen separately from the main screen, and integrates this new video processing circuit with the main screen. It is configured to be added to the small screen signal input side at a stage before the signal synthesis circuit for the small screen.

Function: The circuit configuration of the present invention uses the ABL detection voltage based on the brightness of the synthesized video signal to control the brightness and contrast of the child screen separately from the main screen, so that the child screen can be controlled independently of the brightness of the main screen. The brightness and black level of the screen can be set to a predetermined level.

Embodiment A video processing apparatus according to a first embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a main screen and sub screen signal synthesis circuit, 2 is a video processing circuit, 3 is a display circuit, and 4 is an ABL circuit. Reference numeral 5 denotes a bright contrast circuit, each of which has the same function as the configuration shown in FIG. Now, in Figure 1, 6
7 is a voltage conversion circuit for inputting the ABL detection voltage from ABL circuit 4 to the microcomputer, and 7 is a voltage conversion circuit for inputting the ABL detection voltage from ABL circuit 4 to the microcontroller.
A microcomputer (microcomputer) 8 having a function of controlling according to the detected voltage is a video processing circuit that controls the brightness and contrast of the sub-screen video signal based on the control signal from the microcomputer 7.

Now, when the brightness of the main screen part is high, the brightness of the screen combined with the child screen is also high due to the main screen, so the AEL circuit 4 detects that the brightness as a whole is high, and the video processing circuit 2 detects that the brightness of the combined screen is high. The brightness and contrast of the video signal are lowered. At this time, the brightness and contrast of the sub-screen area are also lowered at the same time, but the ABL detection voltage of the ABL circuit 4 is input to the microcomputer 7, and the brightness and contrast of only the sub-screen is reduced by the video processing circuit 8 dedicated to the sub-screen. By increasing the brightness, the brightness and black level of the sub screen will be constant regardless of the brightness of the main screen.

FIG. 2 shows a second embodiment of the invention. In this circuit configuration, the video processing circuit 8 is directly controlled by the output of the voltage conversion circuit 6 without using a microcontroller.

Effects of the Invention According to the circuit configuration of the present invention, when the signals of the main screen and the sub-screen are different, there is no change in the brightness or black level of the sub-screen due to the brightness of the main screen, and a stable image of the sub-screen can be output. This makes it possible to play back high-quality video.

[Brief explanation of drawings]

1 and 2 are circuit diagrams of a video processing circuit according to an embodiment of the present invention, and FIG. 3 is a circuit diagram of a conventional video processing circuit. 1...Signal synthesis circuit, 2-...Video processing circuit, 3...Display circuit, 4...ABL
Circuit, 6...Bright contrast circuit, 6
...Voltage conversion circuit, 7...Microcomputer,
8...Small screen video processing circuit.

Claims (1)

[Claims] A video processing device used in a television receiver that can process multiple input video signals and simultaneously display two types of video on one screen: a main screen in a screen display and a secondary screen in a screen display. a video processing circuit for controlling brightness and contrast of a video signal for a sub-screen;
A video processing device that includes a brightness detection circuit that detects the brightness of the entire screen, and a control circuit that supplies a control signal to the video processing circuit to control the brightness and contrast of a sub-screen according to the output of the brightness detection circuit.