JPS5851672A - Sharpness improving circuit - Google Patents

Abstract

PURPOSE:To improve the sharpness of a TV picture, by modifying a signal into a pattern space, modifying a specific pattern in this pattern space and emphasizing the pattern. CONSTITUTION:A signal supplied to an input terminal is applied to a series circuit of delay circuits 2, 3 and the signal from the terminal 1 and the circuits 2, 3 is picked up through LPFs 4-6. The signals from the LPFs 4, 5 and 5, 6 are applied to logical operation (MIN) circuits 7, 8 which pick up the minimum signal out of the supplied signals. The signals from the circuits 7, 8 are applied to a logical operation (MAX) circuit 9 which picks up the maximum signal out of the supplied signal and to a MIN circuit 10 to obtain output signals E1 and E2. Further, output signals E3, E4 are obtained from the output signals of the LPFs 4-6 via MAX circuits 11, 12 and 14, and a MIN circuit 13. Subtractions 15, 16 of E1-E2 and E3-E4 are performed to form positive and negative emphasizing signals E5, E6, which are summed 19 to form an emphasis signal E7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to improve the sharpness of television screen images and the like.

In conventional so-called sharpness improvement devices, a method is often used in which high frequency components of an image are separated and extracted and added to the original signal to enhance it.

That is, FIGS. 1 and 2 are examples of each of these, and in FIG.
), this second-order differential output and the original signal are added in an adder circuit (104), and taken out to an output terminal (105). In Fig. 2, the signal from the input terminal (101) is supplied to arbitrary delay circuits (i06) and (107), and the original signal and the delay circuits (106) and (107) or the sum circuit (108) are connected to each other. This mixed output and the delay circuit (1
06) in an adder circuit (109) and output to an output terminal (105).

In these circuits, the frequency characteristics are B in each figure.
The high frequency components are emphasized. It is said that it is visually best to set the beater value of the frequency emphasized here to 1.5 to 2.0 MHz.

However, in the case of these methods, although sharpness is improved by emphasizing high frequency components, noise increases, and images with repeating patterns at frequencies close to the beater frequency are overemphasized. The image becomes unnatural.

In other words, Figure 3 shows specific waveform examples to explain the latter reason.Here, let's consider cases where the original signal is a step-like waveform, B when the original signal is a pulse-like waveform, and C when the original signal is a repetitive signal. And the high frequency components of these signals are human → C
The number increases in this order. Therefore, as shown in the figure, the amount of emphasis signals also increases in the order of person→C, and is approximately twice as large in the case of a person as in the case of a BSC.

Therefore, for example, if the amount of emphasis signals for a person is set to be the best, there will be too many emphasis signals for a BIC corresponding to a fine image such as text, resulting in an extremely unnatural image.

Furthermore, when improving the sharpness like this in the vertical direction of the image, conventionally a delay circuit (106
) and (107) are set to one horizontal period.

However, in that case, generally broadcast waves, camera output,
In the video signal such as B-output, a so-called line roll occurs in which the pedestal level fluctuates during each horizontal period due to the signal processing process of the video signal source. This fluctuation is extremely small (5% or less Usually this is not a problem, but
When such a signal is supplied to the sharpness improvement device described above, since this fluctuation corresponds to the repeated signal in the case of C in FIG.

In other words, in Fig. 4, in a signal in which the luminance signal changes stepwise in the vertical direction, when there is no line roll, as in the case of humans, the emphasized signal becomes as shown in B, and the sharpness is improved as shown in C. be done. On the other hand, if line tallow occurs as shown in D, a signal equivalent to the line tallow as shown in E is superimposed on the emphasized signal, and the line crawling is emphasized as shown in F. .

Therefore, in order to eliminate the influence of such a line roll component, it has been proposed to install a limiter circuit to remove the low-level portion of the emphasized signal, but this method also removes the emphasized signal itself, resulting in improved sharpness. This is particularly problematic because the lower the level of the signal, the greater the falsification effect.

In view of these points, the present invention provides a novel sharpness improvement device that does not cause the above-mentioned problems.

By the way, conventional sharpness improvement devices consider an image to be a combination of frequency components and try to improve sharpness by emphasizing a specific band (high frequency component), which is a type of frequency filter. . In response to this problem, the inventor of the present invention first proposed a filter device that converts a signal into a pattern space and performs filtering by deforming this pattern space. The present invention is an application of such a filter device.

That is, in the present invention, an image is considered to be a composite of pattern components distributed on a pattern space, and the sharpness is improved by emphasizing a specific pattern component.

An example of a filter device previously proposed by the inventor of the present application will be described below.

First, we will explain the pattern space.For example, consider that one frame of a television signal is composed of mln pixels vertically and horizontally, and the amplitude of each pixel is expressed as f(
x and yj) However, if tku4(m, 1≦j(n), then the above television signal is f (Xi e yj)
can be considered to be arranged in mxn order.

For example, ILi'-(fil f2 -----fk), where f4
By expressing mf(xx, yt) fkM-f(xrrl, ytl), this 17-frame television signal can be considered as a dimensional vector y.

In this way, the multidimensional space created when the signal levels at a plurality of time points are applied to each dimension and expressed in a petator is called a pattern space.

Similarly, the experimental level of signals at three adjacent points is 't-11f
A three-dimensional pattern space can be constructed using t and fl+1 (2<t<k-1).

FIG. 5 is a perspective view of such a three-dimensional pattern space, with each vector represented at any point in the space encompassed by the maximum level of the signal.

In this three-dimensional pattern space, the line segment connecting the origin 0 and the point P with the maximum vexile is ft-1""'t:
! ft+1.

Also, the plane shown in Figure 6 shows that ft-1=f and arrow 't+1. Furthermore, the plane shown in FIG. 6B shows f t-1 to 't-'t+1, which indicates that the signal changes in a stepwise manner.

On the other hand, the plane shown in Figure 6C is ft-1='t+1~f.

This shows that the signal is changing rapidly.

When this three-dimensional pattern space is viewed from an extension of the 0-P line, it becomes as shown in FIG. Here, the signals in each range change around the outer periphery as shown. In the figure, the fifth
The 0-P line in the figure is the origin, the human plane in Figure 6 is the λ axis, the B plane is the B axis, and the C plane is the C axis.

In this case, since the original and previous signals have an extremely strong correlation between adjacent signals, as shown in Figure 8, human - X-ray ~
It is concentrated and distributed in the B-X-ray range 5 and does not exist near the C-dye.On the other hand, noise etc. has no correlation between adjacent signals, so it is shown in Figure 8B. Evenly distributed throughout.

That is, for example, the 9th v! In the case of a signal as shown in J, when this is converted into the pattern space described above, it becomes as shown in FIG. 1O. Note that in FIG. 9, . indicates the position of the signal.

In this case, the signal outside the diagonally shaded range in Fig. 10 is
For example, by deforming as shown in the arrow, the noise N1~
N3 can be removed.

This transformation can be performed, for example, by the following logical operation.

That is, ftwMAX(MIN (ft, -1, ft), MIN
(f,, ft+□).

MIN (f, -□, ft+1))006. (1),,
, MIN(MAX (f, 1.ft), MAX(ft,
ft+□).

MAX(fl-1-'t+1))...Transformation is performed using the logical operation (2). Here, MAX indicates that the maximum item within the following parentheses is extracted, and MIN indicates that the minimum item within the following parentheses is extracted.

By performing this logical operation, for example, in the noise N1 part of FIG.
MIN (f8. f,).

MIN (fl, f9) ) w=MAX (f8. f8. fl)= fl. In addition, in the noise N2 part, f1□; MAX (MIN (flo - fl,)
-M I N ('11-'12) vMIN(f□
. , f□2)) 1===, MAX (flo, fl2. flo);
The fl2 noise N3 is also removed in the same way as the noise Nl.

On the other hand, for example, in the f5 signal, f5. ,
MAX(MIN (f4. f5), MIN (f5
．． f6).

MIN (f4. f6>) Kick MAX (f4. f5. f4) f5. Also, in the f6 signal, f6 proverb MAX (MIN (f 5v f 6), MIN
(f6. fl).

MIN(f5.fl)) -MAX (f5.f6.’s) ″f6 As a result, the original signal is extracted as is.

In this manner, in this filter device, filtering can be performed without degrading the original signal.

The present invention improves sharpness by applying such a filter device. An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 11, the original signals of persons B and C are the same as those in FIG. 3, and as in FIG. 9 described above, the * indicates the position of the signal. When this signal is converted into pattern space in the same manner as in FIG. 10, it becomes as shown in FIG. 12.

In the figure, sl, s2, . In this pattern space, by transforming a specific pattern such as a step pattern, it is possible to emphasize the pattern and improve sharpness.

Therefore, in Figure 1Ilk13, a fit circuit (2) in which the signal supplied to the input terminal (1) corresponds to 11 horizontal periods or one revolution of the upper limit frequency (1,5-2,0 MHsa) for desired sharpness improvement; (Supplied to 31 series circuits, deviation amount from this input terminal (1) and delay circuit (2)
, (3) output signals are respectively passed through the bus filter (4).
), (5), (6) I street.

It is taken out.

The signals from these filters (4) and (5) perform a logical operation (MIN) that extracts the minimum signal among the supplied signals.
The signals from the filters (5) and (6) are fed to the same <MIN circuit (8). The output signals of these MIN circuits (7) and (8) are supplied to a logic operation (MAX) circuit (9) which takes out the maximum signal among the supplied signals.

Therefore, the logical formulas of the circuit using these logic operation circuits (7) to (9) are: MAX(MIN(ft-1,f,), MIN(f,,f
, +□)), and this circuit performs transformations such as the 14th vlJA,B in the pattern space. As a result, the positive direction pulse pattern is removed, and the output signal E0 of the MAX circuit (9) becomes as shown in FIG.

Further, the output signals of the MXN circuits (8) and (7) are supplied to the MIN circuit Ql. Therefore, these logic operation circuits (8)
, i.

The logical formula of the circuit using α-mill is: MIN(MIN(f, 0.f,), MIN(ft, ft
+, )), and in the pattern space, Figure 15 Person, B
The following transformations are performed. As a result, the MIN circuit (1
(The output signal E2 of I becomes as shown in FIG. 11.

Further, the signals from the filters (4), <5) are supplied to the MAX circuit Uυ, and the signals from the filters (5), (6) are also supplied to the MAX circuit Q2. Furthermore, the output signals of these MAX circuits (11) and H are supplied to the MIN circuit α.

Therefore, the logical formulas of the circuit using these logic operation circuits αυ~0 are: MIN(MAX(f, 1.f,), MAX(f,,f,
, )), and the transformation as shown in Figure 16, B is performed in the pattern space. As a result, the output signal E3 of the MIN circuit Q3 becomes as shown in FIG.

Further, the output signals of the MAX circuits I and @ are supplied to the MAX circuit I. Therefore, these logic operation circuits aυ, aυ, (
The logical formulas of the circuit according to No. 141 are: MAX(MAX(fl,,f,), MAX(f,,f,
+, )), and in the pattern space, Fig. 17 A, B
The following transformations are performed. This allows the MAX circuit (
The output signal E4 of No. 14 is as shown in FIG.

Further, the output signal E0 of the MAX circuit (9) and the output signal 'B2 of the MIN circuit (I@) are supplied to the subtraction circuit a5,
-E2 is subtracted, a positive emphasis signal E5 as shown in FIG. 11 is formed, and the output signal 'f! 13 and the output signal E4 of the MAX circuit a is supplied to the subtraction circuit αQ, and subtraction of E, .-':+''4 is performed, thereby producing the negative emphasis signal E6 as shown in FIG. These emphasized signals E5 and B6 in the positive and negative directions are supplied to the adder circuit 0 through the 7th f*-1 (17), Q8), and an emphasized signal E7 as shown in the 11th m is formed and output. By adding this emphasized signal E7 to the terminal - and adding it to the original signal, the sharpness is improved as shown in FIG.

In this way, the sharpness is improved.According to the present invention, the signal is converted into a pattern space, and a specific pattern is transformed in this pattern space to emphasize that pattern. As shown in FIG. 11, it is possible to emphasize only a step pattern such as a person and not to emphasize a repeating pattern such as C. Note that in this figure, the amount of emphasized signals decreases in the order of A- and C.

Therefore, even if there are characters, lines, p-rings, etc., for example, an unnatural image or deterioration in image quality does not occur, and the sharpness can always be optimally improved.

Furthermore, FIG. 18 shows the circuit of FIG. 13 using specific circuit elements, and as shown in the figure, MINlff
l path (7), (8), Q., (13 is a pnp transistor "ic" formation L, MAXlli path (9),
<11), (IL (141) can be formed with an npn type transistor, and the present invention can be realized with an extremely simple circuit configuration.

Further, FIG. w shows another example of the present invention. That is, the entire logical formula of the circuit shown in FIG. 8 described above is MAX(MIN(ft-
0, f, ), MIN (ft, f, +, )) - MIN (M
IN (f, f), MIN (f, ,
ft+,))-1t +MIN(MAX (f,-0,ft),MAX (
f, , ft+□)) MAX(MAX (fl 1
*ft) *MAX (fl*fl4-1
)), but this can be transformed and expressed as follows.

MIN(f, MAX(f,-0,ft+,))-M
IN(f, f, f) t-1tt+1 +MAX(f,,MIN(ft-1,f,+□))-M
AX (f, 0.ft, f, 1) Therefore, in the 19th IiJ, filter (4), (6
) to the MAX circuit (2υ) and the MIN circuit (24
and the output signal of the MAX circuit υ and the filter (5
) is supplied to the MIN circuit (c), and the output signal of the MIN circuit (221) and the signal from the filter (5) are supplied to the MIN circuit (c).
Supplied to AX circuit @.

Furthermore, the signals from the filters (4), (5), and (6) are supplied to the MIN circuit (c) and the MAX circuit (a).

The output signals of the MIN circuits (c) and (c) are supplied to the subtraction circuit (19), and the output signals of the MAX circuits @ and 2 are supplied to the subtraction circuit section.

In this circuit as well, it is possible to obtain an emphasis signal similar to that described above and improve the sharpness.

In addition, in the above-described embodiment, the level of the kyokakubutsugo between the squares cannot be increased too much due to problems such as pluming. Furthermore, considerable improvement can be achieved using only the negative emphasis signal. Therefore, in FIG. 13 and FIG.
The circuits (c), (c), etc. may not be provided.

Furthermore, the present invention can also filter in multidimensional pattern space, including two dimensions.

Further, the present invention provides 1. The present invention can be applied to processing signals as either analog or digital signals.

[Brief explanation of the drawing]

Figures 1 to #I4 are diagrams for explaining the conventional device, and Figure 5
Figures 1 to n are diagrams for explaining the present invention, Figure 13 is a configuration diagram of an example of the present invention, Figures 14 to 17 are diagrams for explaining the same, Figure #118, and Figure 19 are diagrams for explaining the present invention. It is a block diagram of another example. (1) is an input terminal, (2), , (3) is a delay circuit, (
8) to 0 are logic operation circuits, and @ is an output terminal. Figure 8 R 1U C lt Figure 14 Figure 1B Figure 15 Figure 17 Figure 18

Claims (1)

[Claims] A sharpness improvement device that arranges video signals in a multidimensional pattern space based on the amplitudes of a plurality of adjacent pixels, and increases or decreases signals distributed in a desired space of the pattern space by logical operations.