JPH03212069A - Contour correction circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in equipment such as television receivers and VCRs that process video signals into digital signals. This invention relates to a contour correction circuit that improves horizontal resolution by reproducing images.

2. Description of the Related Art In recent years, equipment that handles video signals has been increasingly digitized. This movement is also extending to consumer equipment such as television receivers and vCRs.

This is not only due to a reduction in the number of parts and improved reliability, but also due to digitalization of video signal processing circuits.
This is because it is expected that it will be easier to expand to D'TV.

By the way, when the image 1ψ signal processing circuit is digitized, the frequency characteristics of the luminance signal can be changed to A/D according to the sampling theorem.
Limited to one half of the converter sampling frequency. The frequency often used as a sampling frequency in Japan is 14.3181, which is four times the subcarrier frequency.
8M) lz. In this case, the maximum frequency that passes is approximately 1M1-1.

This is approximately 570 lines when converted to horizontal resolution.

On the other hand, in the domestic market, the performance required for high-end AV television receivers is 700 to 800 lines.

Therefore, in the past, the sampling frequency was 14.31
If video signal processing was performed digitally using 818M)lz, it would not be possible to reproduce the horizontal resolution required in the high-end AV television market for boat fishing.

An example of video signal processing by the conventional digital circuit described above will be described below with reference to the drawings.

FIG. 3 shows a schematic block diagram of signal processing by a conventional digital circuit. In FIG. 3, 4 is an A/D converter that converts the video signal into a digital signal in synchronization with the sampling frequency. Reference numeral 5 denotes a digital signal processing circuit that uses the sampling frequency as the input clock 7 and extracts a luminance signal in synchronization with the sampling frequency. 6 is a D/A converter that converts the digitized luminance signal into an analog signal in synchronization with the sampling frequency.

The operation of the signal processing circuit using the digital circuit configured as described above will be described below.

A video signal A/D converter 4 converts a band signal up to one-half of the sampling frequency into a digital signal. A digital signal processing circuit 6 reproduces a digital luminance signal from the converted digital signal. The reproduced digital luminance signal -t is converted into an analog luminance signal by the D/A converter 6.

Problems to be Solved by the Invention However, with the above configuration, if the sampling frequency is 14.31818M1-17, which is commonly used in Japan, the band of the luminance signal is limited to about 7.1M14z according to the sampling theorem. This translates to approximately 570 trees in horizontal resolution. In order to obtain a higher bandwidth, it is possible to increase the sampling frequency, but in reality, it is difficult and costly to create highly accurate A/D converters, digital signal processing circuits, and D/A converters that can support that clock speed. There is also the issue of higher prices.

In view of the above-mentioned problems, the present invention relates to a contour correction circuit that improves horizontal resolution by operating a signal processing circuit using a digital circuit at the same sampling frequency as the conventional circuit.

Means for Solving the Problems In order to solve the above problems, the contour correction circuit of the present invention includes a low-pass filter for extracting the low frequency range of a video signal, a bandpass filter for extracting the high frequency range of the video signal, and the low-pass filter I filter for extracting the high frequency range of the video signal. a signal processing circuit using a conventional digital circuit that inputs a low-frequency signal from the bandpass filter, a buried line that inputs a high-frequency signal from the bandpass filter, and a signal from the delay line and a signal generated by the conventional digital circuit. It is equipped with an adder circuit that combines signals from the processing circuits.

According to the above-described configuration, the present invention supplements the luminance signal reproduced by the digital signal processing circuit with the high-frequency luminance signal that is not reproduced by the digital signal circuit by bandpass filter, thereby improving the conventional digital signal. A luminance signal with a wider band than the processing circuit can be obtained. Since the horizontal resolution is proportional to the band of the luminance signal, the horizontal resolution is improved by the present invention. In the uninvention, a delay line is used to synchronize the time of the luminance signal reproduced by a digital signal processing circuit and the high-frequency luminance signal obtained by a bandpass filter.

Example Below is a ring of an example of the present invention! 11S correction circuit 1 Please refer to the drawing! ! ] I will explain while talking. FIG. 1 shows a ring in a first embodiment of the invention, '/Is? 11i shows a schematic block diagram of a positive circuit.

In Fig. 1, the high-frequency luminance signal 4+(y
2 is a delay line that stores high-frequency luminance signals, 3 is a low-pass filter that extracts low-frequency video signals, 4 is often used in Japan 1 4,318
18 Ml-17, A/D with sampling frequency i
Converter, 57d Digital signal processing circuit that extracts a luminance signal using the same clock as 4/D converter 4, 6
7 is a D/A converter that uses the same sampling frequency as the A/D converter 4, and 7 is an adder circuit that combines the high band luminance signal from the delay line 2 and the low band brightness signal from the D/A converter 6.

The operation of the contour correction circuit configured as described above will be explained below with reference to FIG. The video signal fH is separated into a low-frequency video signal by the low-pass filter 3 and a high-frequency video signal by the bandpass filter 1. The function of the low-pass filter 3 is that an aliasing phenomenon occurs when a video signal higher than half the sampling frequency of the A/D converter 4 is input. A video signal lower than
By inputting the signal to the /D converter 4, aliasing phenomenon does not occur in the M/D converter 4. &/
The sampling frequency of D converter 4 is 14.3181
The low-pass filter 3, which is an 8M filter, extracts a low-frequency video signal having a frequency characteristic of up to about 7.1M, which is half the sampling frequency. The low frequency video signal is A
/I) Converted into a digital video signal by the converter 4. A digital signal processing circuit 5 obtains a digitized luminance signal from the converted digital signal. The obtained digital luminance signal is converted into an analog luminance signal by the D/A converter 6. This luminance signal corresponds to approximately 570 lines when converted to horizontal resolution.

On the other hand, in order to extract the high-frequency signals removed by the low-pass filter 3, the bandpass filter 1 filters the video at a frequency of more than half the sampling frequency of the &/D converter 4, that is, about 7.1 MHz or more. Pass the signal. Since the video signal in this band is a luminance signal as it is, a high-frequency luminance signal can be obtained simply by passing it through the bandpass filter 1. Since the luminance signal from the D/l converter 6 has a larger delay than the high-frequency luminance signal from the bandpass filter 1, a delay line 2 is inserted after the output of the bandpass filter 1 to cancel out the delay. A time will be arranged. A high-frequency luminance signal from the delay line 2 is added to the luminance signal from the D/A converter 6 by an adder circuit 7 to obtain a luminance signal with a wider band.

As described above, according to this embodiment, by adding the high-frequency luminance signal extracted by the bandpass filter 1 to the luminance signal obtained by the digital signal processing circuit 5, the band can be improved without depending on the sampling frequency. A wide luminance signal can be obtained,
Get a horizontal resolution of over 670 trees.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a schematic block diagram of a contour correction circuit showing a second embodiment of the present invention.

As shown in FIG. 2, the difference from the configuration shown in FIG. 1 is that the hand-pass filter 1 is removed and a high-pass filter 8 is provided. High pass filter 8 is band pass filter 1
Similarly, extract the high frequency components of the video signal.

The contour correction circuit configured as described above operates in the same manner as the contour correction circuit shown in FIG. 1, and has the same effect.

In addition to the first or second embodiment described above, there is also an embodiment in which the connection order of the bandpass filter 1 and delay a2 of the first embodiment is switched, or a high-pass filter 8 of the second embodiment. An arrangement in which the order of connection of the delay lines 2 is changed has the same operation and effect as the first embodiment.

In the first embodiment, in place of the bandpass filter 1 and delay line 2 of the first embodiment, extended wires having the same filter characteristics as the bandpass filter 1 are used, or Even when a bandpass filter with time is used, the same operation and effect as in the first embodiment can be obtained.

In addition, in the second embodiment, instead of the high-pass filter 8 and delay line 2 of the second embodiment, a delay line having the same filter characteristics as the high-pass filter 8 is used, or the same delay as the delay line 2 is used. Even when a high-pass filter with time is used, the same operation and effect as in the first embodiment can be obtained.

Furthermore, in the first or second embodiment, a second low-pass filter is inserted between the D/A converter 6 and the adder circuit 7 in order to make the output signal from the D/A converter 6 continuous and smooth. This embodiment also has the same operation and effect as the first embodiment.

Effects of the Invention According to the present invention, by simply adding a simple circuit, A/D
It is possible to obtain a luminance signal with a wide frequency band that exceeds the limit of the sampling frequency of the converter, and thereby the reproduced horizontal line resolution is improved, so its practical effects are great.

[Brief explanation of drawings]

1 and 2 are schematic block diagrams of a contour correction circuit according to an embodiment of the present invention, and FIG. 3 is a schematic block diagram showing a conventional example of a digital image 1ψ processing circuit. 1... Punt pass filter, 2... Delay line, 3... Low pass filter, 4...
・A/D converter. 5...Digital signal processing circuit, 6...
D/A converter, 7..au.JXIJ8, a.
...High pass filter.

Claims (6)

[Claims] (1) A low-pass filter that extracts the low-frequency portion of the analog video signal, a band-pass filter that extracts the high-frequency luminance signal of the analog video signal, and an A/D that digitally converts the low-frequency video signal that has passed through the low-pass filter. a converter; a digital signal processing circuit that reproduces a luminance signal from the digital signal output from the A/D converter;
A D/A converter that converts the digital luminance signal output from the digital signal processing circuit into analog; a delay line that delays the high-frequency luminance signal extracted by the bandpass filter; and a high-frequency luminance signal from the delay line. Said D
A contour correction circuit including an addition circuit for synthesizing low-range luminance signals from the /A converter. (2) The contour correction circuit according to claim 1, wherein the connection order of the bandpass filter and the delay line is changed. (3) The contour correction circuit according to claim 1 or 2, wherein the band-pass filter is replaced with a high-pass filter. (4) The outline according to claim 1 or 3, wherein the delay line and bandpass filter, or the delay line and highpass filter, are replaced with a delay line having the same filter characteristics as the bandpass filter or highpass filter. correction circuit. (5) Contour correction according to claim 1 or 3, wherein the delay line and bandpass filter or the delay line and highpass filter are replaced with a bandpass filter or highpass filter having the same delay time as the delay line. circuit. (6) Claims 1 and 2, wherein a second low-pass filter is added between the D/A converter and the adding circuit in order to make the output signal from the D/A converter continuous and smooth.
The contour correction circuit according to any one of Item 3, Item 4, and Item 5.