KR950007309B1 - Image noise removing circuit of image recording & reproducing system - Google Patents

Abstract

means for dividing the input image signal into a luminance signal and a colour signal; a circuit for processing the divided luminance signal; means for frequency-modulating the processed luminance signal; means for band- filtering the frequency-modulated luminance signal; means for converting the divided colour signal to 629 KHz band width frequency; and means for mixing the band-pass filtered luminance signal, the converted low band-width colour signal and the frequency-modulated colour signal in a magnetic tape through an amplifier (70) and a head (75). The reproducing circuit comprises: an amplifier (95) for amplifying the pick-up image signal from the head (75); means for low-band filtering the amplified image signal; means for extracting the luminance signal by filtering the low-band filtered image signal; and means for mixing the demodulated luminance signal and the low band converted or frequency- demodulated colour signal.

Description

Video Noise Reduction Circuit in Video Recording Player

1 is a block diagram of a recording circuit of a conventional video recording and reproducing apparatus.

2 is a block diagram of a reproducing circuit of a conventional video recording and reproducing apparatus.

3 is an operation waveform diagram according to the conventional method.

4 is a block diagram of a recording circuit of a video recording and reproducing apparatus according to the present invention.

5 is a block diagram of a playback circuit of a video recording and playback player according to the present invention.

6 is an operating waveform diagram according to FIG.

7 is an operating waveform diagram according to FIG.

* Explanation of symbols for main parts of the drawings

30: luminance and color signal separation unit 35: luminance signal processor circuit unit

40: frequency modulator 45: band pass filter

50: first low pass converter 55: second low pass converter

60: frequency modulator 65, 115: signal mixer

70: Amp 75: Head

95: amplifier 100: first low pass filter

105: first high pass filter 110: luminance signal demodulation unit

120: second low pass filter 125: low-pass conversion color reproduction unit

130: switch 135: second high-pass filter

140: color frequency demodulation demodulator 145: 3.58 MHz playback unit

The present invention relates to a circuit for removing video signal noise of a video recording and reproducing apparatus, and more particularly, to a video signal noise removing circuit in a video signal processing system for frequency-modulating and transmitting a color signal.

FIG. 1 is a conventional video recording / player recording circuit diagram, which shows a block of a recording circuit used in a home video system (VHS), which is currently widely used.

Now, when the composite video signal is input to the input terminal 1, the input composite video signal is input to the luminance and color signal separation unit 10. The luminance signal separated by the luminance and color signal separator 10 is processed by the luminance signal processor circuit 11 and then input to the frequency modulator 12. The frequency modulator 12 modulates the input luminance signal by frequency modulation (FM modulation) to reduce noise and outputs the noise to the high pass filter unit 13. The high pass filter 13 performs high pass filtering on the luminance signal frequency modulated by the frequency modulator 12 and outputs the result to the signal mixing unit 15. The reason why the high frequency filtering of the luminance signal is performed is because a band of the luminance signal of the standard television is in a relatively wide band of about 1 megahealth to 4.5 megahealth (MHz).

On the other hand, the color signal low-pass converter 14 converts the color signal separated by the luminance and color signal separator 10 into a signal band of about 629 kilohealth (KHz) and then to the signal mixer 15. Output At this time, the signal mixing unit 15 mixes the frequency-modulated luminance signal and the low-pass converted color signal and records them on a predetermined tape through the amplifier 16 and the head 17.

2 is a block diagram of a recording circuit used in a conventional home video system (VHS), which relates to a conventional video recording / playback circuit. The operation of the video recording player is as follows.

When the video recording and playback player is operated in the playback mode, the amplifier 21 amplifies the video signal picked up and reproduced by the head 20 and outputs it to the high pass filter 22 and the low pass filter 23. The high pass filter 22 performs a high pass filtering on the reproduced video signal, extracts only the high luminance component luminance signal from the low frequency converted color signal and the frequency modulated signal, and outputs the luminance signal to the luminance signal demodulator 23. At this time, the luminance signal demodulator 23 frequency demodulates (FM demodulates) the luminance signal output from the high pass filter unit 22 and outputs the demodulated luminance signal to the signal mixing unit 26.

Meanwhile, the low pass filter 24 shown in FIG. 2 performs low pass filtering on the signal amplified by the amplifier 21, extracts the low frequency converted color signal, and outputs the low frequency converted color signal to the color reproduction unit 25. . The low frequency conversion color regeneration unit 25 demodulates the low frequency conversion color signal extracted by low frequency filtering of the sound field low frequency filter unit 24 and inputs the reproduced color signal to the signal mixing unit 26. Accordingly, the signal mixing unit 26 mixes the frequency demodulated luminance signal and the color signal and outputs them to a system such as a video player, for example, a television, through the output line 27.

3 is a waveform diagram of a spectral distribution diagram according to a conventional method, wherein (A) is a low frequency conversion (3.58 MHz to 629 KHz) of an image signal having a center frequency of 3.58 MHz and having a band of 629 KHz or less; In this case, the color signal is frequency-modulated by the luminance signal, and the color signal which is low-transformed is mixed with the frequency-modulated luminance signal and recorded on a predetermined tape.

(B) is a frequency modulation method of the luminance signal (Y) and the color signal (C) of the NTSC color signal as it is, the frequency carrier should be approximately 4MHz or more. Therefore, since the frequency carrier must be high, it is rarely used in a small video recording player.

(C) is a low frequency conversion of the color signal from 3.58 MHz to 2.15 MHz, mixed with the luminance signal, and then frequency modulated.

However, in the recording and reproducing method of a conventional video recording player having the same frequency distribution as that of FIG. 3, the low frequency conversion of the color signal uses amplitude modulation (AM modulation) to speed up the drum motor or the capstan motor. The frequency of the color signal recorded in association with the variation is changed. Therefore, when demodulating the recorded color signal, the signal / noise ratio of phase modulation and amplitude modulation becomes worse, resulting in deterioration of image quality.

Accordingly, an object of the present invention is to provide a video signal noise canceling circuit in a video recording / reproducing apparatus capable of removing noise generated in the process of reproducing and recording a video signal since the color signal of the video signal is modulated and reproduced.

Hereinafter, the present invention will be described in detail with reference to FIGS. 4, 5, 6, and 7.

4 is a block diagram of a recording circuit of an image recording and reproducing apparatus according to the present invention, wherein the luminance and color signal separation unit 30 separating the luminance signal and the color signal from the image signal input from the input terminal 80, and the luminance; And a luminance signal processor circuit 35 for processing and outputting the luminance signal separated by the color signal separator 30, and a frequency modulator 40 for frequency modulating the luminance signal output from the luminance signal processor circuit 35. And a band filter 45 for band-filtering the luminance signal frequency-modulated by the frequency modulator 40, and the color signal separated by the luminance and color signal separator 30 at a frequency of about 629 KHz. A first low pass converting unit 50 for converting, a second low pass converting unit 55 for low-converting the color signal separated by the luminance and color signal separating unit 30, and the second low pass converting unit 55 The low-converted color signal at A frequency modulator 60 to modulate, a luminance signal bandpass filtered from the bandpass filter 45, a low-pass color signal output from the first lowpass converter 50, and the frequency modulator 60. Mixing the frequency-modulated color signal from the mixer 70 is composed of a signal mixer 65 on a magnetic recording tape through the amplifier 70 and the head 75.

A characteristic of the recording circuit of the present invention configured as described above is that the bandpass filtering is performed by frequency modulation of the luminance signal, the low frequency conversion (AM modulation) of the color signal as well as the color signal is converted to the frequency of the low band and the frequency modulation. (FM modulation) by mixing the frequency-modulated luminance signal, the low-pass converted color signal, and the frequency-modulated color signal to record the luminance signal around the band, thereby extending the frequency band of the color signal.

FIG. 5 is a block diagram of a playback circuit of the video recording and playback apparatus according to the present invention, which is a circuit for playing back video signals recorded by the recording circuit of FIG. This configuration includes an amplifier 95 for amplifying the video signal picked up from the head 75, a first low pass filter 100 for low-pass filtering the video signal amplified and output from the amplifier 95, and the first filter. The first high pass filter 105 extracts the luminance signal by high pass filtering the image signal filtered by the first filter 100, and the frequency signal demodulates the luminance signal extracted by the first high pass filter 105. The low-pass conversion is performed by low-pass filtering the image signal through the luminance signal demodulator 110 and the first low pass filter 100 to a frequency of a passband lower than the low pass frequency of the first low pass filter 100. A second low-pass filter unit 120 for extracting a color signal, a low-pass color reproducing unit 125 for demodulating the low-pass color signal extracted by the second low-pass filter unit 120, and the amplifier 95 A second high pass filter which extracts the frequency modulated color signal by high pass filtering the video signal And a color frequency demodulator 140 for frequency demodulating and outputting the frequency modulated color signal output from the second high pass filter unit 135 and a color signal output from the color signal demodulation unit 140. A band pass filter 145 for band-pass filtering at a predetermined bandwidth, a low-pass demodulated color signal and a frequency demodulated color signal respectively output from the low-pass conversion color regeneration unit 125 and the band pass filter 145. Switching switching circuit section 130 for switching the low-frequency conversion color reproduction signal and the frequency-modulated color signal filtered by a predetermined bandwidth, the luminance signal output from the luminance signal demodulation section 110 and the switching connection circuit section ( The output terminal 150 may be mixed by mixing the low frequency conversion color reproduction signal output from the 130 or by mixing the luminance signal and the frequency demodulated color signal through the luminance signal demodulator 110. It comprises a signal mixing unit 115 to output a predetermined system.

6 is an operating waveform diagram according to FIG. 4, and FIG. 7 is an operating waveform diagram according to FIG.

Hereinafter, with reference to FIGS. 6 and 7 attached to the operation of FIGS. 5 and 6 according to the present invention will be described in detail.

Now, when the video signal is input to the recording circuit input terminal 80 of the predetermined video recording and reproducing apparatus, it is input to the luminance and color signal separation section 30. The luminance and color signal separator 30 separates the input image signal into a luminance signal as shown in FIG. 6 (a) and a color signal as shown in FIG. 6 (d). The separated luminance signal as shown in FIG. 6A is input to the luminance signal processor 35, and the luminance signal processor circuit 35 processes the input luminance signal and outputs the luminance signal to the frequency modulator 40. . The frequency modulator 40 frequency-modulates the input luminance signal as shown in FIG. At this time, the band pass filter 45 outputs the band luminance filtered through the input luminance signal. The filtering frequency of the band pass filter unit 45 has a filtering frequency of about 1 mega health centered on the 3.5 mega health as shown in FIG. 6 b), and the frequency of the band pass filter unit 45 from FIG. The filtered output signal is input to the signal mixer 65.

On the other hand, the separated color signal as shown in (d) of FIG. 6 separated by the luminance and color signal separation unit 30 is input to the first low-frequency conversion unit 50 is a low-pass conversion (e) of FIG. AM modulation) is input to the signal mixer 65. In addition, the color signal as shown in FIG. 6 (d) separated from the luminance and color signal separator 30 is low-converted by the second low-frequency converter 55 and input to the frequency modulator 60. The frequency modulator 60 supplies the color signal to the signal mixer 65 after frequency modulation as shown in FIG.

Therefore, the signal mixing section 65 mixes the input signal as shown in FIG. 6 (g) and records the predetermined signal in the head 75 through the amplifier 70. The reason for generating the video signal as shown in (g) of FIG. 6 is to be compatible with not only the video recording player according to the present invention but also an existing video recording player. The reason for low-converting the color signal of the 3.58 MHz band by using the second low frequency conversion unit 55 is that if the color signal of 3.58 MHz is directly frequency-modulated, the color frequency of the side band is widened so that the color signal is frequency-converted. This is because the frequency is so high that playback is impossible. Another example for the recording circuit of the predetermined video recording and reproducing apparatus is a business video recording and reproducing apparatus, when the low-conversion video signal is shifted by 90 ° and input to the signal mixer 65. Applicable to

The video signal recorded on the tape by the circuit of FIG. 4 is reproduced by the reproducing circuit configured as shown in FIG. 5. Looking at the reproducing circuit of the video recording and reproducing apparatus as follows.

When the head 75 shown in FIG. 5 picks up the video signal recorded on the magnetic recording tape, it is input to the amplifier 95 and amplified into a signal having a predetermined level as shown in FIG. After being amplified by the amplifier 95 as shown in FIG. 7A and then low-pass filtered as shown in FIG. 7B by the first low pass filter unit 100, the amplifier 95 is input to the first high pass filter 105. . The first high pass filter 105 performs high pass filtering on the low pass filtered image signal to extract luminance as shown in FIG. Thereafter, the luminance signal extracted by the first high pass filter 105 is input to the luminance signal demodulator 110, and the luminance signal demodulator 110 is frequency modulated to demodulate the input luminance signal. Output to the mixing unit 115.

Meanwhile, the low pass filtered image signal of the first low pass filter unit 100 is input to the second low pass filter unit 120 and then low pass filtered as shown in FIG. Is entered. In this case, the second low pass filter unit 120 is for extracting the low frequency converted color signal into a band of about 629 KHz. That is, to extract only the color signal converted by the second low-pass converter 50 of FIG. The low frequency conversion color reproduction unit 125 reproduces, i.e., demodulates, the color signal filtered out from the second low pass filter unit 120 and inputs the color signal to the signal mixing unit 115 through the switching connection circuit unit 130. Therefore, there is compatibility capable of reproducing the signal recorded by the existing video recording player.

The image signal through the amplifier 95 is input to the second high pass filter 135. The second high pass filter 135 detects the frequency-modulated color signal (the frequency-modulated signal by the second low-pass converter 55 and the frequency modulator 60 of FIG. 4 described above) among the image signals as shown in FIG. Filter only) and output as shown in FIG. The image signal filtered out from the second high pass filter 135 as in the seventh (e) is input to the color signal frequency demodulator 140. The color signal frequency demodulation demodulator 140 low-frequency transforms the frequency-modulated color signal and reproduces the frequency demodulation and low-band transform to the band pass filter 145. At this time, the band pass frequency of the band pass filter 145 has a frequency of 3.58MHz. Accordingly, it can be seen that the second high pass filter 135, the color frequency demodulator 140, and the band pass filter 145 extract and demodulate only the frequency-modulated color signal. The frequency demodulated color signal is input to the signal mixing unit 115 through the switching connection circuit 130. The signal mixing unit 115 mixes the input signals to generate an image signal to produce an output line 155. Enter into a given system through.

As described above, the video signal player according to the present invention has an advantage of eliminating noise generated when the color signal is reproduced since the color signal of the video signal is frequency-modulated and recorded on the tape.

Claims (1)

In the recording and reproducing circuit of the video recording and reproducing apparatus, a brightness and color signal separation section 30 for separating the brightness signal and the color signal from the video signal input from the input terminal 80, and the brightness and color signal separation section ( A luminance signal processor circuit 35 for processing and outputting the luminance signal separated at 30; a frequency modulator 40 for frequency modulating the luminance signal output from the luminance signal processor circuit 35; A band filter 45 for band-filtering the luminance signal frequency-modulated at 40 and the first low-pass transform for low-converting the color signal separated by the luminance and color signal separator 30 to a frequency of about 629 KHz. A second low frequency converter 55 for low-converting the color signal separated by the luminance and color signal separator 30, and a color signal low-converted by the second low frequency converter 55 Frequency modulating frequency Modulation section 60, the bandpass filtered luminance signal from the bandpass filter section 45, the low-pass color signal output from the first low-pass conversion section 50 and the frequency from the frequency modulator 60 A recording circuit comprising a signal mixing section 65 on a magnetic recording tape through the amplifier 70 and the head 75 by mixing the modulated color signals; An amplifier 95 for amplifying the video signal picked up from the head 75, a first low pass filter 100 for low-pass filtering the video signal amplified and output from the amplifier 95, and the first filter unit ( A first high pass filter 105 for extracting a luminance signal by high pass filtering the image signal filtered low by 100, and a luminance signal demodulator for frequency demodulating the luminance signal extracted by the first high pass filter 105 110 and low-pass filtering the image signal through the first low-pass filter unit 100 to a passband frequency lower than the low pass frequency of the first low-pass filter unit 100 to extract the low-pass color signal A second low pass filter unit 120, a low pass color reproduction unit 125 for demodulating the low pass color signal extracted by the second low pass filter unit 120, and an image signal through the amplifier 95. A second high pass filter 135 for extracting the frequency-modulated color signal by high pass filtering, and Band-pass the color frequency demodulator 140 for demodulating and outputting the frequency-modulated color signal output from the second high pass filter 135 and the color signal output from the color signal demodulator 140 with a predetermined bandwidth. The low pass conversion is performed by switching the low pass conversion demodulated color signal and the frequency demodulated color signal output from the band pass filter unit 145 for filtering, the low pass conversion color reproduction unit 125 and the band pass filter unit 145, respectively. A switching connection circuit unit 130 for switching a color reproduction signal and a frequency modulated color signal filtered with a predetermined bandwidth, and a luminance signal output from the luminance signal demodulation unit 110 and an output from the switching connection circuit unit 130. The low frequency conversion color reproduction signal is mixed or the luminance signal through the luminance signal demodulator 110 and the frequency demodulated color signal are mixed and output through the output terminal 150. In the video signal regenerator, it characterized in that the regenerator consists of a signal composed of the mixing portion 115 for outputting to the system video signal noise reduction circuit.

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