JPS62264771A - Contour correcting device - Google Patents

Abstract

PURPOSE:To obtain a visually stable picture with high resolution without color blinking by using a 2-dimensional band pass filter so as to extract a 2-dimensional frequency band being a cause to cross color and applying contour correction to a signal subjected to cross color elimination. CONSTITUTION:Signals same as an original signal fOH(t), a 1H delay signal f1H(t) and a 2H delay signal f2H(t) to from a contour signal are used and a signal near the frequency band (525/4 lines for vertical and 3.58MHz for horizontal) being a cause to the cross color is extracted by using the 2-dimensional band pass filter 16 in terms of 2-dimension. The signal is subtracted from the 1H delay signal f1H(t) subjected to contour emphasis by a subtractor 18, and a contour signal obtained by an enhancer circuit 11 is added (14) to the signal subjected to the cross color elimination to obtain a picture with high resolution while no color blinking is observed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a contour corrector for improving the image quality of television signals and the like.

2. Description of the Related Art A conventional camera configuration including a contour corrector includes, for example, the configuration shown in FIG. In FIG. 6, 1 is a process circuit including a clamp circuit, a γ circuit, etc., 2 and 3 are matrix circuits that generate the Q signal and ■ signal, respectively, and 4 is a matrix circuit that generates the luminance signal Y. Further, 5 and 6 are low-pass filters. 7, 8, 9.10 are 1H (1 horizontal scanning time) delay circuits (IHDL), 11 is the original signal, 1
12 is an enhancer circuit that creates horizontal and vertical contour signals from the H delay signal and 2H delay signal; 12 is a coring circuit that reduces the noise component of the contour signal; and 13 is an enhancer circuit for synthesizing the 1H delayed bone and contour signals. This is a delay circuit that compensates for the delay time of the signal, 14 is an enhancer, and 15 is an encoder. The operation of the contour corrector included in this camera configuration will be explained using FIGS. 7 and 8.

FIGS. 7a to 7e are waveforms at various parts in FIGS. 6a to 6e. However, there is no delay time for the contour signal, and the coring circuit 12 also sets the coring level to zero.

The waveforms in Fig. 7 a, b, and c are the original signal '0H (t
), 1H delayed signal i1H(t), 2H delayed delayed bone f2H(
t) shows the vertical luminance signal level change. By operating the three signals in the enhancer circuit 11, a contour signal as shown in FIG. 7d is obtained. (In this example, 2f1H(t) - (f(1H(t) + f2
H(t) ) O performance N Casa FL tail. ) Furthermore, the contour signal passes through a coring circuit 12 and is inputted by an adder 14.
This signal is added to the delay time compensated signal of the H-delayed signal f1H(t) (in this example, the delay time compensation is set to zero), and the contour-corrected luminance signal shown in FIG. 7e is obtained. The contour-corrected luminance signal and the Q signal and I signal from the low-pass filter 6.6 are input to the encoder 15 to obtain an NTSC signal with improved frequency characteristics.

This shows that the frequency characteristics of the circuit that generates the contour signal are as shown in Figure 8a.
This is because it shows the characteristics of a bypass filter as shown in . Since the actual television system uses 2:1 interlaced scanning, the frequency is boosted to a peak at half the scanning line frequency. Horizontal contour correction is also performed on the same principle. If a THH delay circuit is used instead of each 1H delay circuit in FIG. 6, the frequency to be boosted will be as shown in FIG. 8. To boost both horizontal and vertical frequencies, three signal quantities are input to the enhancer circuit 11 of FIG. H(t), f1H(t), f2H(
t) is divided into several parts, and calculations are performed so that the desired frequency is boosted. In this way, contour correction is performed two-dimensionally.

The contour signal may not be extracted from the luminance signal, but may be extracted only from the green signal (for example, as described in Kiyotaka Okada's
"Digital contour corrector for high-quality television cameras." (Sho 5
9.2), NHK monthly report P60).

Problems to be Solved by the Invention However, in the above configuration, the contour signal depends only on changes in the brightness signal or the green signal, so even if the sharpness increases and the resolution improves by contour correction, the combing cannot be performed on the monitor side. When the luminance signal and color signal are separated using a filter etc., the high frequency (vertical - line, horizontal 3.58
Also, so-called cross color, in which the luminance signal of the frequency band near the &) is mixed into the color signal, was also emphasized, deteriorating the image quality.

For example, depending on the hue with high visibility, such as red in particular, when a cross color is mixed, the flicker of the color becomes noticeable, which is a problem in that the user feels visually uncomfortable.

In view of this, an object of the present invention is to provide a contour corrector that can reduce color flickering caused by cross colors and reproduce calm colors with high resolution.

Means for Solving the Problems In order to solve the above problems, the present invention uses an original signal fOH (t
) is delayed by 1H (1 horizontal scanning time) to generate a 1H delayed signal f1.
A first 1H delay circuit that obtains H(t), and further delays the 1H delay bone f1H(t) by 1H to obtain a 2H delay bone f2.
A second 1H delay circuit that obtains H(t) and the original signal fO
H(t), an enhancer circuit that obtains horizontal and vertical contour signals from the 1H delayed signal '11 ((1) and the 2H delayed bone f2H(t), and an enhancer circuit that obtains horizontal and vertical contour signals from the original signal (. 1H delay signal f1H(t) and 2H delay signal f2H(t) obtained from the shared first and second 1H delay circuits
a two-dimensional band-pass filter that extracts a signal in a desired frequency band more two-dimensionally; a variable gain circuit that varies the output gain of the two-dimensional band-pass filter; and a variable gain circuit that varies the output gain of the two-dimensional band-pass filter; The configuration includes a subtracter that subtracts the output of the two-dimensional bandpass filter, and an adder circuit that adds the output signal of the subtracter and the contour signal obtained from the enhancer circuit.

Operation The present invention has the above-described configuration, and the original signal fOH(t) for creating the contour signal, the 1H delay bone f 1H(t )
.

Using the same signal as the 2H slow-delay bone f2H(t), a two-dimensional bandpass filter extracts the signal near the frequency band (vertical-line, horizontal 3.58Vh) that causes cross color two-dimensionally, and then filters the signal with a subtracter. By subtracting from the 1H delayed bone f 1H(t) whose contour is emphasized and adding the contour signal obtained from the enhancer circuit to this signal from which cross color has been removed, it is possible to obtain a high-resolution signal with no color flickering. You can get a calm image.

Embodiment FIG. 1 shows a configuration diagram of a camera including a contour corrector according to a first embodiment of the present invention. In FIG. 1, 16 is the original signal fO
H(t), 1H delayed signal 'IH(t), 2H delayed signal'
Extracting the required frequency band two-dimensionally from 2H(t)2
2-dimensional band-pass filter; 17 is a variable gain circuit for varying the output gain of the 2-dimensional band-pass filter 16; 18 is a subtracter; 19 and 20 are delay circuits for delay time compensation (
DL). In FIG. 1, the same parts as in the conventional example shown in FIG. 5 are given the same numbers.

The operation of the contour corrector configured as above is shown in Figure 2a-
This will be explained using d.

FIG. 2 ayd shows the two-dimensional same-wavenumber characteristics of the respective signals of FIG. 1 a to d. Original signal 1°H(t).

1H delayed signal f1H(t), 2H delayed signal f2H(t
) is input to the two-dimensional bandpass filter 16,
As shown in FIG. 2a, frequencies centered on the horizontal 3.58vt& and vertical lines are extracted. The gain of this signal is set to an appropriate value by the variable gain circuit 17. 1H delayed delay bone f[((t) is compensated for the delay time by the delay circuit 19, and the signal with the gain set is subtracted by the subtracter 18, and shows the frequency characteristic as shown in FIG. The luminance signal of the signal fOH(t) has a nearly flat characteristic up to frequencies above the horizontal line (6.0% l11.vertical line).

On the other hand, the contour signal is converted into the original signal fOH by the enhancer circuit 11.
(t), 1H delayed signal f1H (t), 2H delayed delayed bone f2
The signal is obtained by calculating H(t), passes through the coring circuit 12 and the delay circuit 2o, and is added to the 1H delayed signal f1H(t) having frequency characteristics as shown in FIG. 2 in the adder 14.

For example, as shown in Fig. 2C, the contour signal boosts the horizontal wave number (both horizontally and vertically are boosted according to the 5i2f (f frequency) curve), and then has the characteristic of having the amount of boost shown in the diagonal direction and the arrow in C. Then, the output of the adder 14 is the second
The result will be as shown in Figure d. The brightness signal of this contour-corrected 1H delayed signal '1H(t) is not horizontally 3.68, although the high range is emphasized by the contour signal. For this reason, when the luminance signal and color signal are separated using a comb filter or the like on the monitor side, the luminance signal is almost never mixed into the color signal, so cross color does not occur, and high-resolution luminance signals is obtained.

As described above, according to this embodiment, the two-dimensional bandpass filter 16 extracts the frequency band that causes cross color, and the variable gain circuit 17 sets the frequency band to an appropriate value and subtracts it from the signal to be contour corrected. By doing so, color flickering due to cross color can be reduced.

FIG. 3 is a configuration diagram of a camera including a contour corrector showing a second embodiment of the present invention. In the figure, 16 is a two-dimensional band pass filter, 17 is a variable gain circuit, 18 is a subtracter,
Reference numerals 19 and 20 designate delay circuits, which have the same configuration as that shown in FIG. 1, but the variable gain circuit 17 uses a multiplier. Note that the variable gain circuit 17 also includes a delay circuit for adjusting the timing of the two inputs. The difference from the configuration shown in FIG. 1 is that a color signal level difference detection circuit 30 is provided, and its output is input to the multiplier of the variable gain circuit 17. The color signal level difference detection circuit 3° includes a one-pixel scanning time delay circuit (IHDL) 21°, a subtracter 22. It is composed of an absolute value circuit 23.

The operation of the contour corrector of the second embodiment configured as described above will be explained below with reference to FIGS. 4a-d and 6a/%-.
This will be explained using d.

FIGS. 4a to 4d show signal waveforms at each part of FIG. 3, 6 to d. If the I signal changes as shown in Figure 4a, the output of the delay circuit 21 will be as shown in Figure 4, and the difference between the two signals will be output from the subtracter 22, as shown in Figure 4C. Become. Further, the absolute value circuit 23 obtains the output shown in FIG. 4d. This output is input to the multiplier of the variable gain circuit 17 and multiplied by the output of the two-dimensional band pass filter 16. As a result, the output of the two-dimensional bandpass filter 16, that is, the horizontal 3.581
41! .

The gain of the signal in the vertical-line frequency band is varied according to the level change of the I signal. In this case, it is made proportional to the level change of the engineering signal. Similarly to the first embodiment,
The 1H delayed signal f 1H (t) is compensated for the delay time by a delay circuit 19, and a subtracter 18 subtracts the output signal of a two-dimensional bandpass filter 1e whose gain is varied in proportion to the level change of the signal, The adder 14 adds the signal to the contour signal and performs contour correction. The two-dimensional frequency characteristic of this contour-corrected signal e is shown in FIG. 6 ayd.

Figure 5B-d is the time 11.12.13°t of Figure 4d.
4 shows the characteristics.

As can be seen from FIG. 6, the removal ratio of the horizontal 3rd, 581st, and vertical line frequency bands changes with the change in the level of the signal, and the greater the change in the level of the signal, the greater the removal.

Therefore, at boundaries where there is a large level difference between visually sensitive colors, the characteristics of the frequency band of the luminance signal are somewhat reduced to reduce cross color caused by mixing of the high-frequency luminance signal into the color signal. Flickering in noticeable colors, especially red, can be reduced, and images with visually calmer color reproduction can be obtained.

In the second embodiment, the delay circuit 21 of the color signal level difference detection circuit 3o is a delay circuit of one pixel scanning time.
Needless to say, it is suitable as a delay circuit with any delay time that does not interfere with detection.

Furthermore, we used the I-axis color signal as the color signal (R, -
Y ) axis signals may also be used. It goes without saying that similar processing can also be performed in the vertical direction by detecting level differences in color signals.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, two 1H delay circuits for obtaining horizontal and vertical contour signals are shared with a two-dimensional bandpass filter for extracting a required frequency band, thereby reducing the circuit scale. We are trying not to increase the amount significantly.

Then, by extracting the two-dimensional frequency band that causes cross color using this two-dimensional bandpass filter, and removing this signal or contour-correcting the reduced signal, it is possible to create a visual image with high resolution and no color flickering. This has a great practical effect because it allows you to obtain a calm image.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a camera including a contour corrector according to a first embodiment of the present invention, FIG. 2 is a characteristic diagram showing two-dimensional frequency characteristics of signals of each part, and FIG. FIG. 4 is a waveform diagram showing the signals of each part of the second embodiment; FIG. 6 is a two-dimensional frequency characteristic diagram of the output signal of the adder; FIG. 7 is a diagram of the configuration of a camera including a conventional contour corrector, FIG. 7 is a waveform diagram of signals at each part, and FIG.
The figure is a frequency characteristic diagram of a circuit that generates a contour signal. 9.10... Delay circuit, 11... Enhancer circuit, 12... Coring circuit, 14...
... Adder, 16 ... Two-dimensional band pass filter, 17 ... Variable gain circuit, 18.22
・River...Subtractor, 19, 20゜21...Delay circuit, 23...Absolute value circuit, 3o...
Color signal level difference detection circuit. Name of agent: Patent attorney Toshio Nakao and one other person C<
X5 to Fig. 2 (0L) Fig. 2 (C) Fig. 4 1=142 Spider Agony Σ Figure 7

Claims (2)

[Claims] (1) a first 1H delay circuit that obtains a 1H delayed signal f_1_H(t) by delaying the original signal f_O_H(t) consisting of a luminance signal or a signal having a large contribution to the luminance signal by 1H (one horizontal scanning time); 1H delayed signal f_1_H(t
) is further delayed by 1H to obtain a 2H delayed signal f_2_H(t)
a second 1H delay circuit that obtains the original signal f_O_H(
t) and 1H delayed signal f_1_H(t) and 2H delayed signal f
An enhancer circuit that obtains horizontal and vertical contour signals from _2_H(t), the original signal f_O_H(t), a 1H delayed signal f_1_H(t), and a 2H delayed signal f_2_H(t).
a two-dimensional band-pass filter that extracts a signal in a desired frequency band more two-dimensionally; a variable gain circuit that varies the output gain of the two-dimensional band-pass filter; and a variable gain circuit that varies the output gain of the two-dimensional band-pass filter; A contour corrector comprising: a subtracter that subtracts the output of a two-dimensional bandpass filter; and an adder circuit that adds the output signal of the subtracter and the contour signal obtained from the enhancer circuit. (2) The variable gain circuit is controlled in accordance with the output of a color signal level difference detection circuit that detects level differences at color boundaries for color signals of arbitrary axes.
Contour corrector described in section.