JPH05167946A - Abl or acl circuit - Google Patents

Abstract

PURPOSE:To prevent a slave screen from being changed in its brightness by connecting an inverter circuit for applying reverse ABL or reverse ACL operation to the slave screen. CONSTITUTION:A bright or contrast control terminal 4 for a slave screen is connected to the terminal of an ABL or ACL device 6 for a master screen through an inverter circuit 5. The device 6 detects a voltage of ABL or ACL operation to be changed in accordance with the brightness of the whole screen and impresses the reverse voltage of the detected voltage to the terminal 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for displaying an image on a television or the like without a feeling of strangeness.

[0002]

2. Description of the Related Art Recently, television receivers are BS receivers, VTs.
A product having a so-called PinP function of connecting R, etc. to simultaneously see two screens has been put on the market.
In this PinP television, an ABL (automatic brightness limiter) or an ACL (automatic contrast limiter) is operated according to the brightness of the entire screen so as not to be too bright.

[0003]

Here, ABL or A is used.
CL operates according to the brightness of the entire screen.

However, since the area ratio of the child screen to the entire screen is extremely small, even if the child screen is dark, if the parent screen is bright, the ABL or ACL operates and the child screen becomes darker.

In view of the above problems, the present invention does not affect the child screen even if the parent screen becomes brighter. ABL or A
It is a CL device.

[0006]

In order to achieve this object, an ABL or ACL device of the present invention detects a voltage of an ABL or ACL operation which changes according to the brightness of the entire screen, and reverses this operation. The reverse ABL or ACL voltage is connected to the bright or contrast control terminal of the sub-picture video circuit.

The entire screen becomes brighter and ABL or ACL
When you operate it to darken with, only the sub-screen part is reverse ABL
Alternatively, it is characterized in that it is brightened in reverse by ACL.

[0008]

[Function] Even if the entire screen becomes brighter and becomes darker by ABL or ACL, only the sub-screen part is reverse ABL
Alternatively, ACL is applied so that the brightness of the small screen does not change.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a video circuit including a child screen ABL or ACL circuit according to an embodiment of the present invention. Reference numeral 1 is an input of a video signal of the main screen. 2 is a video input for a small screen. A sub-screen video circuit 3 has a contrast or bright control terminal 4. Reference numeral 5 is an inverter circuit that reverses the voltage of ABL or ACL. 6 is AB which operates when the entire screen becomes bright and the beam current of the CRT increases.
L or ACL circuit. Reference numeral 7 is an M1X circuit that mixes a parent screen and a child screen. Reference numeral 8 is a circuit for controlling the contrast or the brightness of the video signal in which the parent and child signals are mixed, and is controlled by the terminal 9. The circuit of 6 ABL or ACL is connected to this 9 terminal.

[0010]

As described above, according to the present invention, by adding a simple circuit, it is possible to maintain the most legible state without being affected by the whole screen being too bright or too dark. Effect is great.

[Brief description of drawings]

FIG. 1 is an ABL or ACL according to an embodiment of the present invention.
Schematic block diagram of circuit device

[Explanation of symbols]

 1 Parent screen video input section 2 Child screen video input section 3 Child screen video circuit 4 Child screen video control section 5 ABL or ACL inverter circuit 6 ABL, ACL circuit 7 Parent screen, Child screen mixing circuit 8 Contrast, Bright control circuit 9 Contrast Bright control terminal 10 Video output circuit

Claims (1)

[Claims] 1. An apparatus for displaying a parent screen and a child screen on the same screen, wherein an image processing circuit that automatically performs contrast or brightness lowering or ABL or ACL operation when the screen becomes bright is displayed on the child screen. Is an ABL or ACL circuit characterized by operating an ABL or ACL in the opposite direction to the entire screen.