JPH07264554A - Auto-zooming device - Google Patents

Abstract

PURPOSE:To prevent the generation of malfunction in auto-zooming in accordance with the contents of a video in a wide TV by holding a letter box detecting signal once detected from an input video signal until it is turned off from the external and fixing the held signal on a zoomed image to display the signal. CONSTITUTION:An input video signal (a) is inputted to a letter box signal detecting circuit 1, a black part having no video and a video part are judged by successively detecting a luminance level in the vertical direction and a letter box detection signal (b) is outputted. The signal (b) is inputted to a detection signal holding circuit 3, and once inputting the signal (b), the circuit 3 outputs a signal (c) for continuously holding the signal (b) until an off signal (e) is inputted from the external. When the output (c) is inputted to a zooming circuit 2, a zoomed video output (d) is always obtained and stable display can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention has an aspect ratio of 16: 9.
Wide-screen TV auto zoom device.

[0002]

2. Description of the Related Art Generally, in a wide television, zoom display is automatically performed when displaying a letterbox signal image on a laser disk or the like. The auto zoom function will be described below with reference to FIGS. 4 and 5.

FIG. 4 shows a basic structure of auto zoom. As shown in the figure, the auto-zoom device zooms the input video signal by a letterbox signal detection circuit 1 for detecting whether the input video signal a is a letterbox signal or not, and an output signal b of the letterbox signal detection circuit 1. It is composed of the circuit 2. The operation will be described with reference to FIG.

As shown in FIG. 5, the letterbox signal detection circuit 1 detects a black portion without a video and a portion with a video in the upper and lower parts of the screen in the vertical direction by the luminance signal level of the video signal to detect the letterbox signal. Determine whether And
By inputting the letterbox detection signal b to the zoom circuit 2 and controlling whether the input video signal is zoom display or normal display, an automatically zoomed video signal c can be obtained.

[0005]

However, even in the case of a video of a dark scene or the like even with a letterbox signal, as shown in FIG.
When the luminance level of the video signal is low as shown in (a),
It becomes impossible to detect whether it is a letter box signal,
There is a possibility that the zoom may or may not work depending on the scene as shown in FIG. Also,
When displaying an image with a normal aspect ratio of 4: 3 as shown in FIG. 7, in a scene where the upper and lower parts of the image are dark as shown in FIG. 7A, it is erroneously determined to be a letterbox signal, There is a possibility that the zoom function will work as shown in FIG. 7B, which is a visual problem.

The present invention has been made in consideration of the above-mentioned conventional problems, and an object of the present invention is to provide an auto-zoom device which prevents the auto-zoom from malfunctioning due to image contents in a wide television.

[0007]

In order to achieve the above-mentioned object, the present invention provides a detection circuit for detecting a letterbox signal, and a letterbox detection signal output from the detection circuit to an external OFF signal. The automatic zoom device is configured by a detection signal holding circuit that holds the signal until that time, a zoom circuit that zooms the video signal by the output of the detection signal holding circuit, and a clear switch that forcibly cancels the auto zoom.

[0008]

With the above-described structure, the auto-zoom device of the present invention holds the letterbox detection signal once detected from the input video signal until it is turned off from the outside, and displays the zoomed image in a fixed manner. Also, by mistake, the aspect ratio is 4: 3.
When the image is zoomed, the image can be displayed without any visual problem by turning off the zoom function from the outside with the clear switch.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An auto zoom device according to a first embodiment of the present invention will be described below. In FIG. 1, 1 is a component
Is a letterbox signal detection circuit, 2 is a zoom circuit, 3 is a detection signal holding circuit, and 4 is a clear switch. In the zoom device including the above-mentioned components, the input video signal a
Is input to the letterbox signal detection circuit 1 to detect the brightness level in the vertical direction, and to determine the black portion and the image portion where there is no image and output the letterbox detection signal b. The letterbox detection signal b is input to the detection signal holding circuit 3. Once the letterbox signal is input, the detection signal holding circuit 3 outputs a signal c that keeps the state until an off signal e is input from the outside.
The OFF signal mentioned here is automatically generated, for example, when the channel is switched or when the input is switched to video or the like. By inputting the output c into the zoom circuit 2, a zoomed image output d is always obtained, and as shown in FIG. 2B, zoom display and normal display can be performed depending on the scene. Stable display without switching. That is, according to this embodiment, a signal once determined to be letterbox is always displayed in a zoomed state, so that a malfunction due to a change in an image can be prevented.

However, in the first embodiment, if a normal signal is judged to be letterbox, there is a problem that zoom display is always performed unless the input is switched.

Therefore, the second embodiment will be described below. The difference from the first embodiment is that even if the zoom circuit 2 is erroneously zoom-displayed with an image having an aspect ratio of 4: 3 by inputting a signal f to the zoom circuit 2 by an external clear switch 4, That is to make it possible to turn off forcibly. The clear switch signal f is different from the off signal of the first embodiment and is generated when the television operator judges that the operation is a malfunction and presses the clear switch 4. As a result, when the normal display of FIG. 3A is changed to the zoom display of FIG. 3B, the zoom circuit is turned off by the clear switch 4 so that the normal display can be performed as shown in FIG. Can be returned to the state of detecting.

[0012]

As is apparent from the above description of the embodiment, the auto-zoom device of the present invention detects the letterbox signal from the detection circuit and the letterbox detection signal output from the detection circuit from the outside as an off signal. By using a detection signal holding circuit that holds until input, a zoom circuit that zooms the video signal by the output of the detection signal holding circuit, and a clear switch that forcibly cancels the auto zoom, the malfunction of the auto zoom function is prevented. Can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of an auto zoom device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a screen display state by the auto zoom device.

FIG. 3 is a diagram showing a screen display state by the auto zoom device.

FIG. 4 is a block diagram showing a configuration of a conventional auto zoom device.

FIG. 5 is an operation explanatory diagram of the auto zoom device.

FIG. 6 is an explanatory diagram of a problem of the auto zoom device.

FIG. 7 is a diagram for explaining another problem of the auto zoom device.

[Explanation of symbols]

 1 Letterbox detection circuit 2 Zoom circuit 3 Detection signal holding circuit 4 Clear switch

Claims (2)

[Claims] 1. A detection circuit for detecting a letterbox signal, a detection signal holding circuit for holding a letterbox detection signal output from the detection circuit until an off signal is input from the outside, and the detection signal holding circuit. An auto-zoom device comprising a zoom circuit for zooming a video signal according to the output of. 2. A detection circuit for detecting a letterbox signal, a detection signal holding circuit for holding a letterbox detection signal output from the detection circuit until an off signal is input from the outside, and the detection signal holding circuit. An auto-zoom device comprising a zoom circuit for zooming a video signal by the output of and a clear switch for forcibly canceling the auto-zoom.