JPS5940350B2 - Video signal contour correction device - Google Patents

Description

Detailed Description of the Invention When a video signal is supplied to a television receiver and displayed on its screen, the contour of the image in the vertical direction is, for example, above and below the shaded area in FIG. A device has been proposed that performs certain processing on the video signal so that the outline of the image becomes clear.

This contour correction device is constructed using two delay circuits, and has conventionally been constructed as shown in FIG.

That is, the input video signal SE (FIG. 3A - however, the horizontal synchronizing signal is omitted) is supplied to the first delay circuit 1 and
This delayed video signal S is delayed by a horizontal period TH.
D (FIG. 3B) is supplied to the second delay circuit 2 and further delayed by one horizontal period TH, and the video signal SDD (FIG. 3C) is delayed by two horizontal periods with respect to the input video signal 51. can get.

The video signal SD obtained from the first delay circuit 1 is the source of the output video signal and is supplied to the adder 3. Then, in the subtracter 4, the input video signal SE is subtracted from the video signal SD delayed by one horizontal period from the first delay circuit 1 to obtain a first subtracted signal SA (FIG. 3D), and In the subtracter 5, the video signal SDD delayed by 2 horizontal periods from the second delay circuit 2 is subtracted from the video signal SD delayed by 1 horizontal period to obtain a second subtracted signal SB (FIG. 3E).
is obtained, the first and second subtraction signals SA and SB are added in the adder 6, and the added signal is supplied to the low-pass filter T to obtain the correction signal Sc (FIG. 3F).

This correction signal Sc is then supplied to a level adjuster 8 to be at an appropriate level, and then supplied to an adder 3 where it is added to the video signal SD delayed by one horizontal period, and the adder 3 produces a corrected output. A video signal So (FIG. 3G) is obtained.

Therefore, in the output video signal 50, when the shaded area in FIG. 1 is displayed as a high-luminance area, the level in the horizontal section where the upper edge 9 is projected is closer to the white level, and the level immediately before it is closer to the white level. In the horizontal section, the level is lowered, and even in the horizontal section that reflects the lower edge 10 of the diagonal line, the level is closer to the white level, and in the horizontal section immediately after that, the level is lowered, and the contrast is emphasized to enhance the upper and lower contours. is clearly displayed.

However, in this conventional device, firstly, the subtracter 4
In addition to finding the difference between the video signal SD that has passed through the first delay circuit 1 and the video signal SE that has not passed, the subtracter 5 also calculates the difference between the video signal SDD that has passed through the second delay circuit 2 and the video signal that has not passed. Since the difference in SD is to be determined, the video signal S is a correction signal Sc obtained by adding the two subtraction signals SA and SB and is delayed by one horizontal period.

In order to prevent fluctuations in the DC level when added to It is necessary to prevent fluctuations due to external conditions such as Second, the first and second delay circuits 1 and 2
Since both delay the video signal itself, a wide band of about 4 MHz is required for both.

The first delay circuit 1 has an output signal SD as an output video signal S.
Although it is natural that a wide band is required since it is the source of O, the second delay circuit 2 forms a difference signal SB, and this difference signal SB is also Since it is added to one of the difference signals SA and supplied to the low-pass filter 7, it is thought that the second delay circuit 2 may have a narrow band. However, if the second delay circuit 2 is of a narrow band type, the subtracter 5 uses a combination of the wide band signal SD from the first delay circuit 1 and the narrow band signal from the second delay circuit 2. A difference signal is formed, and due to the influence of the phase rotation of the narrowband signal, an unnecessary component is generated in the correction signal obtained from the adder 6 according to the difference signal, which is undesirable. Therefore, the first
Both of the second delay circuits 1 and 2 need to have a wide band. However, a broadband delay circuit that delays one horizontal period is extremely expensive and occupies a large amount of space. Therefore, it is extremely inconvenient to require two of these. In consideration of these points, the present invention is devised so that although two delay circuits are required, the level setting of only one of them only needs to be set strictly, and only one of them needs to have a wide band. It is something. Hereinafter, the contour correction device according to the present invention will be explained with reference to FIG. 4 and subsequent figures. FIG. 4 shows an example of the contour correction device according to the present invention, which has two delay circuits 11 and 12, and input video signal SI (FIG. 5A - horizontal synchronization signal is omitted). 1 horizontal period TH
This delayed video signal SD (Fig. 5B
) is supplied to the adder 13. Then, in the subtracter 14, the input video signal SI is subtracted from the video signal SD delayed by one horizontal period from the first delay circuit 1, and the subtracted signal is sent to the low-pass filter 17. A difference signal SE (FIG. 5C) is formed.

This difference signal SE is then supplied to the second delay circuit 12 and delayed by one horizontal period TH, and the subtracter 15 converts the original difference signal SE to the delayed difference signal SF from the second delay circuit 12. (D in Figure 5) is subtracted and the correction signal S
c (Fig. 5E) is formed. This correction signal Sc is
This is similar to the filter obtained from the low-pass filter 7 of the conventional device shown in FIG. is added to the signal SD, and the adder 13
A video signal S that has been further corrected.

(FIG. 5F) is obtained. According to the device of the present invention, it is necessary for the first delay circuit 11 to strictly set the level and to prevent this level from changing due to external conditions such as temperature. In this way, only the difference signal SE is taken out from the low-pass filter 17 and therefore supplied to the second delay circuit 12, and the level of the second delay circuit 12 is strictly set. Even if the correction signal Sc is not used and its level fluctuates due to external conditions such as temperature, when the correction signal Sc is added to the video signal SD delayed by one horizontal period, the DC level will fluctuate. Instead, it simply creates an imbalance in the level of correction corresponding to the upper and lower edges 9 and 10 mentioned above.

Furthermore, since the first delay circuit 11 delays the video signal itself, it is required to have a wide band; however, the second delay circuit 2 delays the difference signal SE obtained from the low-pass filter 17. Therefore, it is not necessary to have a wide band, but a narrow band of about 1.5 MHz may be sufficient.

Therefore, the cost is significantly lower, the delay circuit occupies less space and is easier to handle. Note that an adder may be used instead of the subtracter 15, and a polarity inversion circuit may be inserted before or after the second delay circuit 12, or the difference signal SE from the low-pass filter 17 and the second A video signal S in which the difference signal SF from the second delay circuit 12 is separately level-adjusted and delayed by one horizontal period.

may be synthesized with a predetermined polarity.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining contour correction, FIG. 2 is a system diagram of a conventional contour correction device, FIG. 3 is a waveform diagram for explaining it, and FIG. 4 is an example of a contour correction device according to the present invention. phylogenetic diagram,
FIG. 5 is a waveform diagram for explaining this. 11 is a first delay circuit, 12 is a second delay circuit, 17 is a low-pass filter, and 18 is a level adjuster.

Claims (1)

[Claims] 1 has first and second delay circuits, and forms a difference signal between an input video signal and a signal obtained by delaying the input video signal by one horizontal period in the first delay circuit, and this difference signal is The second delay circuit delays the video signal by one horizontal period, and the difference signal and the output signal of the second delay circuit are combined with a predetermined polarity with respect to the video signal obtained from the first delay circuit, A video signal contour correction device configured to take out the composite video signal as an output video signal.