JPH03128577A - Contour emphasis system in video equipment - Google Patents

Abstract

PURPOSE:To prevent production of disturbance in synchronization on a display screen by cutting off a waveform of a prescribed under-cut level or below from a sum signal between contour component signal and an input luminance signal. CONSTITUTION:A gain of a variable gain amplifier circuit 10 is varied by the adjustment of a voltage of a contour emphasis control signal 12 and a pulse width of a contour component signal 23 is amplified based on the gain to obtain a contour component signal 24. An adder circuit 11 adds a delay clamp signal 22 inputted directly from a clamp circuit 3 and the contour component signal 24 after amplification inputted from the variable gain amplifier circuit 10 and an addition signal 25 with a waveform whose contour is emphasized is outputted to an under-cut circuit 6. The under-cut circuit 6 acts like under-cutting the addition signal 25 for a period To when an effective picture period signal 27 is at an L level, that is, for a period when the picture signal 30 exists so as to under-cut the waveform 25a lower than the under-cut level 34 in the adder signal 25.

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention is applicable to video equipment such as television receivers and video tape recorders, where the brightness of images displayed on a display such as a CRT or liquid crystal panel changes ( The present invention relates to an outline enhancement method for making the outline (outline) stand out sharply.

<Prior Art> FIG. 3 is a block diagram showing the electrical configuration of a conventional edge enhancement method.

In FIG. 3, 41 is a luminance signal input terminal, 42 is a contour component extraction circuit, 43 is a variable gain amplification circuit, 44 is an addition circuit, 45 is a luminance signal output terminal, and 46 is a contour emphasis m signal.

The luminance signal input terminal 41 is connected to an input terminal of the contour component extraction circuit 42 and one input terminal of the addition circuit 44.
The output terminal of the contour intensity extraction circuit 42 is connected to the variable gain amplifier circuit 4.
The output terminal of the variable gain amplifier circuit 43 is connected to the other input terminal of the adder circuit 44. The output terminal of the adder circuit 44 is connected to the luminance signal output terminal 45 , and the 0 edge enhancement amount control signal 46 is configured to be input to the control input terminal of the variable gain amplifier circuit 43 .

Next, the operation of the contour enhancement method in the above-mentioned conventional video equipment will be explained.

FIG. 4(a) is a waveform diagram of the input luminance signal 51, and FIG. 4(b) is a waveform diagram of the input luminance signal 51.
is a waveform diagram of the contour component signal 52 after amplification when the gain is small, (C) is a waveform diagram of the contour emphasis luminance signal 53 when the gain is small, and (d) is a waveform diagram after amplification when the gain is large (e) is a waveform diagram of the contour-enhanced luminance signal 53 when the gain is large.

In these figures, 60 is an image signal portion, 61 is a pedestal level which is a reference level of a blanking signal, and 62 is a synchronization signal portion.

The input luminance signal 51 led to the contour component extraction circuit 42 via the luminance signal input terminal 41 has its contour component extracted in the contour component extraction circuit 42, and is then sent to the variable gain amplification circuit 4.
3 is output.

Regarding the circuit configuration of the contour component extraction circuit 42, various methods have been proposed and implemented in the past, but since they do not directly relate to the gist of the present invention, which will be described later, they will not be discussed here. For the input luminance signal 51 as shown in FIG. 4(a), a waveform is created in which the boundary of luminance change is expressed by a set of "H" and "L" pulse signals, in which the pulse width increases as the luminance variation increases. The contour component signal of the image is extracted.

The contour component signal from the contour component extraction circuit 42 is input to a variable gain amplifier circuit 43 and amplified, and outputs a contour component signal 52 as shown in FIG. 4(b) to an addition circuit 44. The adder circuit 44 superimposes the input luminance signal 51 directly input from the luminance signal input terminal 41 and the amplified contour component signal 52 input from the variable gain amplification circuit 43, as shown in FIG. 4(C).
An edge-enhanced luminance signal 53 having a waveform with an enhanced edge as shown in FIG.

Contourability 11i1! By varying the gain of the variable gain amplifier circuit 43 by adjusting the voltage of the control signal 46, the fourth
By increasing or decreasing the pulse width of the amplified contour component signal 52 shown in FIG. 5B, the contour enhancement method (partial protrusion width at the brightness change boundary) of the contour emphasized luminance signal 53 can be adjusted. That is, by increasing the gain, the amount of contour enhancement can be increased, by decreasing the gain, the contour property 11111 can be decreased, and by setting the gain to zero, contour enhancement can be prevented. Can be done.

Note that FIGS. 4(b) and 4(c) show waveforms when the gain is small.

<Problems to be Solved by the Invention> Since the conventional contour enhancement method is configured as described above, it has had the following problems.

That is, when the voltage of the contour enhancement amount control signal 46 is increased to increase the gain of the variable gain amplifier circuit 43 in order to increase the amount of edge enhancement, the amplification by the variable gain amplifier circuit 43 is increased as shown in FIG. 4(d). “H” of the subsequent contour component signal 52
, the "L" pulse width increases.

Then, this is input to the input luminance signal 51 in the adder circuit 44.
The contour-enhanced luminance signal 53 shown in FIG. 4 <e> superimposed with
Among the waveforms, it is the falling waveform part where the luminance change is particularly large in the image signal part 60, and the waveform part 53a which protrudes significantly below the pedestal level 61 due to the superposition of the L'' pulse l,+ The level may drop to or near the level of the synchronization signal portion 62. In this case, the edge-enhancing luminance signal 53 may be mistakenly detected as a synchronization signal, and the image displayed on a display such as a CRT or liquid crystal panel may be synchronized. Disturbances occur, and the attempt to make the screen easier to see through edge enhancement ends up producing worse results.

Therefore, in conventional contour enhancement methods, contour quality! It was not possible to set III too large.

The present invention was devised to solve the above-mentioned disadvantages, and it is possible to obtain an edge-enhanced luminance signal that does not cause synchronization disturbance on the display screen even if the amount of edge enhancement is set to a large value. The purpose is to provide an emphasis method.

<Means for Solving the Problems> An edge enhancement method in a video device according to the present invention adds an edge component signal extracted from an input luminance signal and the input luminance signal to output an edge-enhanced added signal. In an edge enhancement method for video equipment configured as described above, an effective image period signal excluding the synchronization signal is created based on a synchronization signal separated from the input luminance signal, and while this effective image period signal exists, the addition signal is It is characterized in that the waveform portion below the pedestal level or an undercut level set slightly lower than the pedestal level is canted.

Effects> The effects of the above configuration of the contour enhancement method in the video equipment according to the present invention are as follows.

In other words, since the waveform portion below a predetermined undercut level is canted from the sum signal of the contour component signal and the input luminance signal, the lowest level of the contour-enhanced luminance signal after the undercut is sufficiently higher than the level of the synchronization signal. Therefore, no synchronization disturbance occurs on the display screen.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic diagram showing the electrical configuration of an edge enhancement method in a video device according to an embodiment of the present invention.

In FIG. 1, 1 is a luminance signal input terminal, 2 is a luminance signal delay circuit that delays the entire input luminance signal 21, including its leading and trailing edges, by a delay time (tl), and 3 is a delayed luminance signal. pedestal level 31 (see Figure 2)
a clamp circuit that adjusts the voltage to a predetermined clamp level 33;
4 is a synchronization signal separation circuit; 5 is a trailing edge delay circuit that delays only the trailing edge of the synchronization signal 26 by a delay time (t2) to create a row active effective image period signal 27 (described later); 6 is an effective image An undercut circuit 7 undercuts (base clips) the addition signal 25 by the addition circuit 11 at a predetermined undercut level 34 only during the period when the period signal 27 is input. A reference voltage source outputs a voltage for setting an undercut level 34, and 8 is a luminance signal output terminal.

The delay time (lg) of the trailing edge delay circuit 5 is approximately twice as long as the delay time (tl) of the luminance signal delay circuit 2 (h'2·h>), and the undercut level 34 is as follows.
Clamp level 33 (that is, pedestal level 31)
The level of the synchronizing signal 26 is set to be slightly lower than that of the synchronizing signal 26, and sufficiently higher than the level of the synchronizing signal 26.

Reference numeral 13 denotes an edge enhancement circuit having the same circuit configuration as the edge enhancement circuit shown in FIG. 3 as a conventional example. It is composed of a variable gain amplifier circuit lO and an adder circuit 11.

The luminance signal input terminal 1 is connected to the input terminal of the luminance signal delay circuit 2 and the input terminal of the synchronization signal separation circuit 4.

The output terminal of the luminance signal delay circuit 2 is connected to the input terminal of the clamp circuit 3. The output terminal of the synchronizing signal separation circuit 4 is connected to the input terminal of the trailing edge delay circuit 5, and the output terminal of the trailing edge delay circuit 5 is connected to the control input terminal of the undercut circuit 6.

Each output terminal of the reference voltage source 7 is connected to a voltage control input terminal of the clamp circuit 3 and a voltage control input terminal of the undercut circuit 6. The output terminal of clamp circuit 3 is
It is connected to the input terminal of the ring n precept extraction circuit 9 and one input terminal of the addition circuit 11 in the contour emphasizing circuit 13 .

In the contour enhancement circuit 13, as in the conventional example, the output terminal of the contour component extraction circuit 9 is connected to the input terminal of the variable gain amplifier circuit 10, and the output terminal of the variable gain amplifier circuit 10 is connected to the other one of the adder circuits 11. The zero edge enhancement amount control signal 12 connected to the input terminal is configured to be input to the control input terminal of the variable gain amplifier circuit 10.

The output terminal of the adder circuit 11 is connected to the input terminal of the undercut circuit 6, and the output terminal of the undercut circuit 6 is connected to the luminance signal output terminal 8.

Next, the operation of the edge enhancement method in the video equipment according to this embodiment will be explained based on the time chart of FIG. 2.

FIG. 2(a) is a waveform diagram of the input luminance signal 21, and FIG. 2(b) is a waveform diagram of the input luminance signal 21.
is a waveform diagram of the delayed clamp signal 22, (C) is a waveform diagram of the contour component signal 23, (d) is a waveform diagram of the amplified contour component signal 24, and (8) is a waveform diagram of the delayed clamp signal 22.
and the amplified contour component signal 24, Cf') is a waveform diagram of the synchronization signal 26, (g) is a waveform diagram of the effective image period signal 27, (h) is a waveform diagram of the undercut edge-enhanced luminance signal 28.

In these figures, 30 is an image signal portion, 31 is a pedestal level which is a reference level of a blanking signal, and 32 is a synchronization signal portion.

The input luminance signal 21 shown in FIG. 2(a) input to the luminance signal delay circuit 2 via the luminance signal input terminal 1 is processed by the luminance signal delay circuit 2 as a whole, including its leading and trailing edges.
The signal is delayed by the delay time (tl) and output to the clamp circuit 3.

The clamp circuit 3 is set in advance to have a predetermined clamp level 33 based on the output voltage from the reference voltage source 7. The clamp circuit 3 fixes the pedestal level 31 of the delayed luminance signal inputted from the luminance signal delay circuit 2 to a clamp level 33, and outputs the delayed clamp signal 22 as shown in FIG. 2(b) to the contour component extraction circuit in the contour enhancement circuit 13. 9 and an adder circuit 11. The delayed clamp signal 22 is delayed by a delay time (t,) compared to the input luminance signal 21 shown in FIG. 2(a).

Delayed clamp signal 22 input to contour component extraction circuit 9
is extracted by the contour component extraction circuit 9, and outputted to the variable gain amplifier circuit 10 as a contour component signal 23 shown in FIG. 2(C).

This contour component signal 23 has a waveform such that the boundary of the luminance change of the input luminance signal 21 is represented by a set of "H" and "L" pulse signals in which the pulse width increases as the luminance change increases.

The contour component signal 23 is input to the variable gain amplifier circuit 10. The gain of the variable gain amplifier circuit 10 is determined by the contour enhancement amount control signal 1.
2, and the pulse width of the contour component signal 23 is amplified based on the gain to obtain the amplified contour component signal 24 shown in FIG. 2(d). The adder circuit 11 receives the delayed clamp signal 2 directly input from the clamp circuit 3.
2 and the amplified contour component signal 24 inputted from the variable gain amplifier circuit 10, and outputs an added signal 25 having a waveform with an enhanced contour as shown in FIG. 2(e) to the undercut circuit 6. do.

Enhance contours to increase the amount of contour enhancement! When the voltage of the PI amount control signal 12 is increased to increase the gain of the variable gain amplifier circuit IO, the "H" and "L" pulses of the amplified contour component signal 24 are The width also increases, and as shown in FIG. 2(e), among the waveforms of the addition signal 25, the falling waveform part where the luminance change is particularly large in the image signal part 30, and the contour component signal 24 after amplification is “L”
The superposition of the pulses `` generates a waveform portion 25a that protrudes significantly below the pedestal level 31.The level of this waveform portion 25a reaches the level of the synchronizing signal portion 32 or its vicinity.

However, the waveform portion 25a that protrudes significantly below the pedestal level 31 can be undercut at the undercut level 34 by the undercut circuit 6. Its operation will be explained next.

The input luminance signal 21 shown in FIG. 2(a) is also input to the synchronizing signal separation circuit 4, and the synchronizing signal separating circuit 4 separates the synchronizing signal 26 shown in FIG. 2(f). This synchronization signal 26 is led to the trailing edge delay circuit 5, which delays only the trailing edge by a delay time (11) while leaving the leading edge as it is, and outputs the effective image period signal 27 as shown in FIG. 2(g) to an undercut circuit. Output to 6.

Since the delay time (t2) of the trailing edge delay circuit 5 is approximately twice as long as the delay time (tl) of the luminance signal delay circuit 2, the “H” level portion of the effective image period signal 27 is This is a signal that sandwiches the synchronization signal portion 32 of the signal 25 from the front and back, and the undercut circuit 6 does not have the function of undercutting (base clipping) the addition signal 25 during the period when the row active effective image period signal 27 is at the "H" level. do not have.

However, the undercant circuit 6 uses the effective image period signal 2
7 “L” level period T, that is, the image signal portion 30
During the existence period of , it functions as an undercant for the addition signal 25 and undercuts the waveform portion 25 a of the addition signal 25 that is lower than the undercut level 34 . The undercut circuit 6 is set in advance to have a predetermined undercut level 34 based on the output voltage from the reference voltage source 7.

As a result, the contour-enhanced luminance signal 28 output from the undercut circuit 6 to the luminance signal output terminal 8 is as shown in FIG. 2(h).
As shown in FIG. 2, at an undercut level 34 that is slightly lower than the pedestal level 31 and sufficiently higher than the level of the synchronizing signal portion 32, the waveform becomes a waveform in which the waveform portion 25a below the undercut level is undercut.

That is, even if the gain of the variable gain amplifier circuit 10 is increased to sufficiently increase the amount of edge enhancement, the lowest level of the image signal portion 30 will not become lower than the undercut level 34, and the protruding waveform portion 25a will not be lowered. Synchronization signal part 32
will not be falsely detected.

Therefore, synchronization errors do not occur in images displayed on a display such as a CRT or liquid crystal panel.

Since the protruding waveform portion 25a becomes a waveform portion 28a lower than the pedestal level 31 due to the undercut, the function of contour enhancement remains, although to a lesser extent. The other parts are contour-enhanced with a sufficiently large amount of contour-enhancement,
The image becomes sharp.

Note that in the above explanation, the protruding waveform portion 25a is shown at the final position of the image signal portion 30 in the horizontal line direction, but the same effect is obtained no matter where such a protruding waveform portion 25a is located in the image signal portion 30. Needless to say, the function is demonstrated.

As described above, according to this embodiment, synchronization errors are prevented even if the amount of edge enhancement is set to a sufficiently large value, so that a sharp image with distinct edges can be displayed on the display.

Note that the present invention is not limited to the above embodiment, and the same effect can be obtained even if a fixed gain amplifier circuit is used in place of the variable gain amplifier circuit 10.

Furthermore, the overall electrical configuration of the contour enhancement method in video equipment is not limited to the configuration shown in FIG. , any configuration may be used as long as it cant the waveform portion 25a below the undercut level 34 while the effective image period signal 27 exists.For example, the luminance signal delay circuit 2, the clamp circuit. 3
, it is also possible to omit the trailing edge delay circuit 5.

Furthermore, the waveform portion 25 below the undercut level 34
A occurs in the falling portion where the brightness changes are large, and since this portion already has a clear outline, the undercut level 34 may be set to the same level as the pedestal level 31.

<Effects of the Invention> As described above, according to the present invention, a synchronization signal is separated from an input luminance signal, an effective image period signal excluding the synchronization signal is created based on the same U signal, and the effective image period signal is It is configured to cut the waveform portion below the pedestal level or a predetermined undercut level slightly lower than the pedestal level of the sum signal of the contour component signal extracted from the input luminance signal and the input luminance signal during the presence of the input luminance signal. Therefore, the contour strength after undercanting [1 degree] The lowest level of the signal can always be sufficiently higher than the level of the synchronization signal, and therefore synchronization holes will occur on the display screen even if the contour enhancement amount is set large. This has the effect that it is possible to obtain an edge-enhanced luminance signal that does not cause any distortion.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 relate to one embodiment of the present invention.
The figure is a block diagram showing the electrical configuration of the edge enhancement method in the video equipment, and FIG. 2 is a time chart for explaining the operation. Further, FIGS. 3 and 4 relate to a conventional example, with FIG. 3 being a block diagram showing the electrical configuration of the edge enhancement method, and FIG. 4 being a time chart for explaining the operation. In the figure, 1 is a luminance signal input terminal, 4 is a synchronization signal separation circuit, 6 is an undercut circuit, 8 is a luminance signal output terminal, 9 is a contour component extraction circuit, and 10 is a variable gain increase I! circuit, 11 is an addition circuit, 12 is a contour + 1 metering control signal, 13
21 is an input luminance signal, 23 is a contour component signal, 24 is an amplified contour component signal, 25 is an addition signal,
25a is a waveform portion below the undercut level, 26 is a synchronization signal, 27 is an effective image period signal, 28 is an edge emphasis luminance signal, 28a is a waveform portion after undercut, 3o is an image signal portion, 31 is a pedestal level, 32 For example, the sync signal portion 34 is an undercut level. In addition, the same reference numerals indicate the same parts in the figures.

Claims (1)

[Claims] (1) In an edge enhancement method in a video device configured to add an edge component signal extracted from an input luminance signal and the input luminance signal to output an edge-enhanced added signal, separating the input luminance signal from the input luminance signal. An effective image period signal excluding the synchronous signal is created based on the synchronous signal, and during the presence of this effective image period signal, a waveform of the added signal that is equal to or lower than the pedestal level or an undercut level set slightly lower than the pedestal level is generated. An outline enhancement method for video equipment characterized by being configured to cut out a portion.