JPH01202071A - Vertical aperture correcting device - Google Patents

Abstract

PURPOSE:To execute highly accurate contour correction generating no ringing by converting a video signal inputted by skip scanning into a sequential signal and then executing vertical aperture correction. CONSTITUTION:An input video signal is converted into a digital signal by an ADC 12 and supplied to a vertical aperture correcting circuit 15 in a digital bringhtness signal processing circuit. A contour extraction signal from an adder 26 and a signal from a 1H delay circuit are respectively inputted to an adder 27 and an output signal emphasized at its vertical outline is obtained from the adder 27. Since a scanning direction converter 13 is provided to the prestage of the circuit 15, a contour extraction signal component outputted from the adder 26 has twice frequency as compared to ordinary constitution arranged on the post stage. Consequently, accurate contour emphasis can be attained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a vertical aperture correction device used in image display devices such as television receivers, VTRs with a built-in video enhancer, etc. .

(Prior Art) The principle of aperture correction is explained in the spatial frequency domain, where boundaries of a plane image are treated as frequencies.

That is, in the spatial frequency domain, the contour portion of the image is composed of middle and high frequency components of the spatial frequency, and the image is sharpened by raising the middle and high frequency components. To extract the middle and high spatial frequencies, it is sufficient to perform differential processing on the video signal.

The signal extracted by this differential processing is called a contour extraction signal.

Now, if the input video signal is f (x, y) and the contour extraction signal is h (x, y), then the output video signal @ g (x, y)
is g(X, V) = h (X, V) * f (X
, V) can be obtained by performing the convolution operation (1).

FIG. 3 is a waveform diagram for briefly explaining an example of the above calculation process. FIG. 3a shows an input video signal, where f (x, y) is a step function that changes from high level to low level. The contour extraction signal is subjected to differential processing at the level change point (contour portion) to become a signal having a second-order differential waveform as shown in FIG. Then, an output video signal is obtained by adding this contour extraction signal to the original signal (input video signal).

By the way, current television broadcast signals are transmitted using an interlaced scanning method, but recently.

In order to eliminate line flicker when displaying characters, etc. and image quality deterioration when displaying moving images, a television display system was proposed in which interlaced scanning signals are converted to progressive scanning signals for display.

FIG. 4 is a block diagram showing an example of the configuration of this type of television receiver. In FIG. 4, 1 is a high-frequency receiving circuit that receives and selects high-frequency signals induced in the antenna 2;
is an analog-digital conversion circuit (AD) that digitizes the analog video signal detected by the high-frequency receiving circuit 2.
C).

In the following, the color signal processing system is omitted and only the o+maro signal circuit system is shown. The digital signal from the ADC 3 is processed by a digital luminance signal processing circuit 4. Vertical aperture correction circuit 5
is provided in this luminance signal processing circuit 4, and performs the trick shown in equation (1).

The signal from the luminance signal processing circuit 4 is sent to the scanning method conversion circuit 6.
The interlaced scanning signal is converted into a progressive scanning signal. This conversion uses, for example, two field memories,
It is sufficient to read each signal of one line alternately. The digital video signal whose scanning method has been sequentially converted is supplied to the CRT 9 via an analog-to-digital conversion circuit (DAC) and further via the video output circuit 8, and is displayed on the screen.

However, in the television receiver having the configuration shown in FIG.
Since it is provided at a subsequent stage, the vertical aperture correction circuit 5 extracts contour extraction signals between signals every other scanning line (adjacent scanning lines in the same field) on the screen. For this reason, the spatial frequency component of the contour extraction signal becomes a component lower than the J spatial frequency representing the image boundary due to sequential scanning, and there is a problem in that ringing occurs in the output image.

The occurrence of the ringing described above can be explained in terms of the relationship between the scanning beam spot and the scanning line as shown in FIG. Fifth
The figure shows the operation when correcting a beam spot by sequential scanning, and each vertical axis represents the brightness level, and the horizontal axis represents the spatial frequency ν in the vertical direction. In addition, LO, Ll, and L2 indicate the positions of scanning lines in the spatial frequency domain, LO is the scanning line on which the beam spot to be corrected hits, Ll is the scanning line that constitutes a field different from LO when interlaced scanning is performed, and L2 is a scanning line constituting the same field as LO.

As shown in FIG. 5a, the beam spot that hits one scanning line LO has a brightness distribution that spreads in a Gaussian distribution, and bright spots appear to spread to the adjacent scanning lines L1 and Ll. When vertical contour correction is performed on spots obtained by such sequential scanning, the contour extraction signal first obtains a spatial frequency component corresponding to the field scanning line pitch, as shown in FIG. Therefore, the output image is shown in Figure 5C.
As shown in FIG. 2, the LO is raised in the center, but at the same time, the 12th and 12th scanning lines are also affected, resulting in ringing, which is correction distortion. In this case, when the number of frame scanning lines is 525, the image evaluation is 525/
4 (cph).

(Problem to be Solved by the Invention) The correction output by the conventional vertical aperture correction device is
The beam spot will be accompanied by ringing as shown in Figure C.
There was a problem in that the image quality was significantly degraded.

An object of the present invention is to provide a vertical aperture correction device that eliminates the above-mentioned problems, accurately corrects a beam spot, and reduces ringing.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a scanning method converting means for converting a video signal assembled by an interlaced scanning method into a progressive scanning method signal, and a method for processing the video signal from the converting means. The image forming apparatus includes a contour correction means for performing vertical contour correction by generating a differential component at the image boundary, and is adapted to perform vertical aperture correction compatible with the progressive scanning method.

(Function) According to the present invention, vertical aperture correction is performed after converting a video signal inputted by interlaced scanning into a sequential signal, so that the contour extraction signal for contour correction has a space corresponding to the scanning line pitch of the sequential method. It becomes a frequency signal, and it is possible to perform highly accurate contour correction without causing ringing.

(Example) Hereinafter, an example will be described in which the present invention is applied to a television receiver that receives an interlaced scanning signal.

FIG. 1 is a circuit diagram showing an embodiment of a vertical aperture correction device according to the present invention.

In FIG. 1, an analog video signal (input video signal) transmitted and received using an interlaced scanning method is led to an input terminal 11. This input video signal is
The signal is converted into a digital signal and supplied to the vertical aperture correction circuit 15 in the digital luminance signal processing circuit.

The vertical aperture correction circuit 15 includes a one-day delay circuit 21.2 that determines the delay time of a -horizontal scanning period (hereinafter referred to as one day).
2 in series, coefficient multipliers 23, 24, 25, and two adder circuits 26, 27, and 1[1 delay circuits 21.
22, coefficient units 23, 24, and 25, and the addition circuit 26 constitute a digital filter (differential processing circuit) that extracts the differential component at the video boundary of the original signal. Specifically, the video signal whose scanning format has been converted is input to the first IHil extension circuit 21 as an original signal. Then, the above original signal and each first . The three signals output from the second delay circuits 21, 22 are weighted by predetermined digital weights using coefficients 323, 24, and 25, respectively, and then supplied to the adder circuit 26, respectively. In this way, the addition ( ) circuit 26 outputs the contour extraction signal described in equation (1).

Therefore, the contour extraction signal from the adder circuit 26 and the signal from the one-day delay circuit 21 are respectively guided to the adder circuit 21, and the adder circuit 27 obtains an output signal in which the contour in the vertical direction is emphasized. . This signal is a (x, y
) and is led out to the output terminal 17 via D A 01B.

Based on the above circuit configuration, scanning method conversion circuit 1
3 is provided at the front stage of the vertical aperture correction circuit 15, the component of the contour extraction signal outputted from the adder circuit 26 has twice the frequency as compared to the conventional configuration arranged at the rear stage. From this, the output signal a (x, y) is
Since correction is performed using higher spatial frequency components than in the past, more precise contour enhancement can be achieved.

FIG. 2 is an explanatory diagram showing the operation of the present invention when contour-correcting a beam spot.

b and c correspond to a, b and c in FIG.

FIG. 5a shows the brightness distribution of the beam spot, which, as in the conventional case, extends from the scanning line LO to the adjacent scanning line L1. However, the contour extraction signal shown in FIG. 2 is a signal with a frequency corresponding to the scanning line pitch of the frame, that is, a signal with a period of two scanning lines, and emphasizes the spot of the scanning line LO. The resulting output signal @q(x,y) is as shown in Figure 2C.
If the number of frame scanning lines is 525, then 52-5! -(C
ph) becomes a signal in which the spatial frequency component is emphasized.

In this case, since the contour extraction signal is not a signal with a period spanning four scanning lines, the occurrence of ringing is extremely reduced. As described above, since the present invention hardly causes ringing, vertical contour correction is ideal, and it is suitable for television reception and reception that employs a progressive scanning method.

[Effects of the Invention] As explained above, according to the present invention, it becomes possible to circulate in space, contributing to improvement in image quality.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the vertical aperture correction device according to the present invention, FIG. 2 is an explanatory diagram for explaining the operation of FIG. 1, and FIG. 3 is an explanation of the principle of vertical aperture correction. FIG. 4 is a block diagram showing a conventional circuit, and FIG. 5 is an explanatory diagram explaining the operation of the conventional circuit corresponding to FIG. 11... Input terminal, 12... ADC, 13... Scanning method conversion circuit, 15... Vertical aperture correction circuit,
16...DAC. 17... Output terminal, 21.22... 1 day delay circuit,
23.24゜25...Coefficient unit, 26.27...Addition circuit. Figure 2

Claims (1)

[Claims] Scanning method converting means for converting a video signal assembled by an interlaced scanning method into a progressive scanning method signal; 1. A vertical aperture correction device comprising: contour correction means for generating a certain contour extraction signal to perform vertical contour correction; and video output means for supplying a video signal from the contour correction means to image display means.