KR980009451U - Automatic Image Interference Cancellation Circuit by Audio Signal in Hi-Fi VCR - Google Patents

Abstract

The present invention relates to an automatic video interference elimination circuit by an audio signal in a hi-fi VCR, wherein an FM modulated audio signal is recorded between a color signal recording frequency band and a luminance signal recording frequency band of an image signal, thereby interfering with a color signal on a video screen during reproduction. This is to prevent it from appearing.

To this end, the present invention is an FM luminance signal detector and a color signal detector for separately detecting and detecting the FM luminance signal and the color signal from the pre-amplified signal read from the image head, and the FM luminance signal and the color signal detected above are respectively detected as original signals. It has a video signal processing flow consisting of a video signal processing unit which is demodulated, synthesized and finally output, and detects the presence or absence of a hi-fi audio signal by detecting a pre-amplified voice signal read from a hi-fi audio head and determining the presence or absence of a hi-fi audio signal. A hi-fi VCR having a hi-fi / mono detector for switching and controlling a voice signal output line, wherein the hi-fi / mono detector is switched to an output of the hi-fi / mono detector to selectively remove a hi-fi voice signal portion mixed with a color signal when a hi-fi voice signal is detected. FM signal removal means can be a color signal detection unit It is characterized in that configuration to connect the ryeokdan.

Description

Automatic Image Interference Cancellation Circuit by Audio Signal in Hi-Fi VCR

The present invention relates to a high fidelity video cassette recorder (hereinafter, referred to as a hi-fi VCR), which improves fidelity of an audio signal, and in particular, between a color signal recording frequency band and a luminance signal recording frequency band of a video signal in a hi-fi VCR. Automatically removes video interference caused by audio signals in a hi-fi VCR, which allows frequency signals (Frequency Modulation, or FM modulation) to be recorded to automatically remove color signal interference on the video screen during playback. It is about.

In general, a hi-fi VCR is a VCR capable of processing other information on a normal audio track. The hi-fi VCR focuses on a rotating head used for recording or reproducing a video signal, and uses this for recording and reproducing an audio signal, thereby making the audio signal high-fidelity. To record or play back. In particular, the VHS type hi-fi VCR is provided with two audio heads on a rotating drum in addition to the two video heads, and the audio signal is FM-modulated and recorded.

Since the carrier of the audio signal has a lower frequency than the carrier of the luminance signal, the audio head gap is wider than the video head gap and can be magnetized to the deep magnetic layer of the tape.

In addition, the video signal is superimposed on the previously recorded audio signal, but when the video signal is recorded on the audio signal once recorded, the video signal is recorded on the tape surface, and the audio signal remains because the magnetic force is low in the deep part of the tape. As a result, two types of signals coexist.

Therefore, when the audio signal is reproduced, since the audio signal surface portion is erased, the reproduction output is reduced by about 12 dB, but since the FM modulation is used, the influence of noise and the like is not a problem.

In order to realize the above hi-fi scheme, the reproduction signal processing circuit in the hi-fi VCR is provided with an image head 1, a mono audio head 11 and a hi-fi audio head 12, respectively, as shown in FIG. Preamplifiers 2, 13 and 14 are provided for the image head and the audio head, respectively, for a predetermined level amplification of the signals read out from the heads.

And an FM luminance signal detector 3 and a color signal detector 4 for separately detecting the FM luminance signal and the color signal from the preamplified signal read from the image head 1, and the FM luminance signal and the color signal detected above. Have a video signal processing flow consisting of the video signal processing section 5 which demodulates and synthesizes each of the original signals and outputs the final result.

In addition, a hi-fi audio signal processor 15 and a mono audio signal processor 16, which are read from the hi-fi audio head 11 and the mono audio head 12, and are processed by a predetermined level pre-amplified signal, are output. And a hi-fi / mono detector 17 for detecting a signal read from the hi-fi voice head and determining whether or not a hi-fi signal is present, and switching between the two hi-fi / mono detectors 17 to output the hi-fi / mono detector 17. It has a voice signal processing flow composed of the voice output switching unit SW1 to select and output.

In the Hi-Fi VCR of this configuration, the recording frequency of each signal is 0.629 ± 0.5 [MHz] and 1.3 [MHz] of the right audio signal in the NTSC (National Television System Committee) method as shown in Table 1 below. The left audio signal is 1.7 [MHz], and the brightness signal of video signal is 1.1 ~ 7 [MHz] band. In case of PAL (Phase Alternation by Line) method, the color signal frequency of video signal is 0.627 ± 0.5 [MHz], The right audio signal is 1.4 [MHz], the left audio signal is 1.8 [MHz], and the luminance signal is 1.1 to 7 [MHz] band.

TABLE 1

Recording frequency bandwidth of video and audio signals by NTSC and PAL methods

As shown in the spectrum analysis result of FIG. 2, which is taken as an example of the NTSC method described above, in both the NTSC method and the PAL method, an audio signal is FM-modulated between the color signal recording frequency band and the luminance signal recording frequency band of the video signal. .

Therefore, the reproduction FM signal from the luminance signal detection unit 3 of the luminance FM reproduction equalizer and the color signal detection unit 4 of the low pass filter having a pass band of 1M are supplied with the reproduction color signal, and the image signal processing unit 5 receives the original image. In the case of restoring the signal, the signal read out from the image head 1 and amplified through the preamplifier 2 contains not only a luminance signal and a color signal but also a hi-fi audio signal due to the recording structure as described above. In the case of the NTSC system, the right audio signal (1.3MHz) interferes with the color signal most severely. Therefore, when the audio signal is reproduced after hi-fi recording, the interference occurs diagonally over the color signal.

Therefore, the present invention has been devised to improve the above problems, and the present invention provides an FM voice capable of selectively removing a portion of the hi-fi voice signal mixed with the color signal at the output of the color signal detector when the hi-fi voice signal is detected at the voice head. In the hi-fi VCR which can automatically eliminate the occurrence of color signal interference on the video screen during playback because the FM modulated audio signal is recorded between the color signal recording frequency band and the luminance signal recording frequency band of the video signal by providing the signal removing means. It is to provide an automatic image interference cancellation circuit by the audio signal of.

The present invention for achieving the above object is an FM luminance signal detector and a color signal detector for detecting and separately detecting the FM luminance signal and the color signal from the pre-amplified signal read from the image head, and the detected FM luminance signal and color signal It has a video signal processing flow consisting of a video signal processing unit which demodulates and synthesizes the original signal and outputs the final signal, and detects the presence or absence of a hi-fi audio signal by detecting a pre-amplified voice signal read from a hi-fi audio head. A hi-fi VCR having a hi-fi / mono detector for switching and controlling a voice signal output line as a result of the determination, wherein the hi-fi voice signal portion mixed with a color signal is switched when the hi-fi voice signal is detected by switching to an output of the hi-fi / mono detector. Color FM audio signal removal means that can be selectively removed No. provides an image interference automatic cancellation circuit according to the voice signal in the Hi-Fi VCR, characterized in that for configuring the connection to the output of the detector.

1 is a block diagram of a reproduction signal processing circuit in a conventional hi-fi VCR.

2 is a graph showing a spectrum analysis result of a typical NTSC recording frequency.

3 is a block diagram of a reproduction signal processing circuit in a hi-fi VCR according to the present invention.

4 is a detailed circuit diagram showing an embodiment of the FM audio signal removing means of FIG.

* Explanation of symbols for the main parts of the drawings

1: image head 2, 13, 14: preamplifier

3: FM luminance signal detection unit 4: Color signal detection unit

5: video signal processor 6: FM audio signal removing means

6A: voice trap 11, 12: voice head

15, 16: voice signal processing unit 17: hi-fi / mono detector

Hereinafter, an automatic video interference cancellation circuit by an audio signal in a hi-fi VCR according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram schematically illustrating a configuration of an automatic image interference cancellation circuit by an audio signal in a hi-fi VCR according to an embodiment of the present invention.

In the drawing, an image head 1, a mono audio head 12 and a hi-fi audio head 11 are provided, respectively, and a preamplifier 2 for a predetermined level amplification of the signals read from the respective heads. (13) (14) are provided for each of the video head and the audio head.

And an FM luminance signal detector 3 and a color signal detector 4 for separately detecting the FM luminance signal and the color signal from the preamplified signal read from the image head 1, and the FM luminance signal and the color signal detected above. Are demodulated and synthesized as if they were original signals, and have a video signal processing flow composed of a video signal processor 5 for final output.

In addition, a hi-fi audio signal processor 15 and a mono audio signal processor 16, which are read from the hi-fi audio head 11 and the mono audio head 12, and are processed by a predetermined level pre-amplified signal, are output. And a hi-fi / mono detector 17 for detecting a signal read from the hi-fi voice head and determining whether or not a hi-fi signal is present, and switching between the two hi-fi / mono detectors 17 to output the hi-fi / mono detector 17. It has a voice signal processing flow composed of a voice output switching unit SW1 for selecting and outputting.

The output terminal of the color signal detection unit 16 includes an FM audio signal removal unit 6 which is switched to the output of the hi-fi / mono detection unit 17 and selectively removes a portion of the hi-fi audio signal mixed with the color signal when the hi-fi audio signal is detected. It is connected to the configuration.

The FM audio signal removing means 6 is controlled by an audio trap 6A for trapping a voice signal of a specific frequency band from the output of the color signal detector 4 and an output of the hi-fi / mono detector 17 to control the voice trap. It is preferable to comprise the switch SW2 which selectively controls the operation of 6A.

FIG. 4 is a detailed circuit diagram showing an embodiment of the FM audio signal removing means of FIG. 3, wherein the voice trap 6A comprises a series resonant circuit of an inductor L and a capacitor C. It is preferable to set it to be 1.4MHz, and the switch SW2 is turned on by the hi-fi detection signal of the hi-fi / mono detecting unit to turn on the voice trap, and is turned off by the mono detection signal to turn off the voice trap ( Q1) can be configured.

Referring to the automatic video interference elimination circuit by the audio signal in the hi-fi VCR according to the present invention configured as described above are as follows.

First, during reproduction, an image signal is detected from the image head 1 and amplified by 60 에서 by the preamplifier 2, and one extracts only the luminance FM signal from the luminance signal detector 3 through the luminance-FM reproduction equalizer. And is supplied to the image signal processing section 5, and the color signal detection section 4 detects only the color signal components of 627KHz ± 500KHz through the 1MHz low pass filter and supplies them to the video signal processing section 5. The signal processor 5 demodulates and combines each of the original signals and outputs the final signals.

On the other hand, since the audio signal is recorded in hi-fi and in mono, the hi-fi / mono detecting section 17 checks whether there is a signal from the head for hi-fi and determines whether it is hi-fi or mono.

That is, the hi-fi / mono detecting section 17 integrates and directs the envelope of the signal from the hi-fi audio head 11, and if the DC voltage value is higher than or equal to the predetermined voltage, determines that there is a hi-fi signal and determines the "H" voltage. If it is below a predetermined voltage, it determines that there is no hi-fi signal and outputs an "L" voltage.

This determination may be performed by a microprocessor or by a hi-fi IC.

However, in the video signal processing flow as described above, in principle, the luminance FM + color signal (mixed signal) component detected from the video head 1 passes through the 1 MHz LPF of the color signal detector 4 only 629 ± 500 KHz. It should be extracted, but in reality, 1.4MHz voice FM signal is mixed and interference occurs in the final playback screen.

Therefore, in order to further attenuate this mixed component, the FM audio signal removing means 6 receives the output from the hi-fi / mono detecting section 17 and supplies it to the base of the switching transistor Q1, and the collector of this transistor Q1. A voice trap 6A composed of an inductor L and a capacitor C is inserted between the output of the color signal detection unit 4 and the output of the 1 MHz LPF to remove the 1.4 MHz component.

Of course, the resonance frequency fo by the inductor L and the capacitor C is set to be 1.4 MHz.

That is, for example, when the inductance value is L = 180 μH and the capacitance value is C = 68 kHz, the resonance frequency fo is By fo ≒ 1.43MHz.

In order to prevent attenuation of the color signal from the upper band, it is necessary to set a high selectivity (this circuit is a series resonant circuit, so that L is set large and C is set small).

Accordingly, in the FM audio signal removing means 6, the switching transistor Q1 is turned on by the logic high ("H") signal of the hi-fi / mono detecting section 17 at the time of high-fidelity to generate the voice trap 6A of 1.4 MHz. The audio FM signal is further removed by turning it on, and since there is no audio FM signal at the time of mono, it is turned off by the logic low (“L”) signal of the hi-fi / mono detecting unit 17 to turn off the voice trap 6A, thereby providing a 1.4 MHz portion. By preventing the high frequency components of the reproduction luminance signal contained in the trap from being trapped, the frequency characteristic can be improved.

According to the automatic image interference elimination circuit by the audio signal in the Hi-Fi VCR according to the present invention as described above, there is a useful that can automatically remove the color signal screen interference by the audio FM signal originally possessed by the Hi-Fi VCR.

Claims (4)

The FM luminance signal detecting unit 3 and the color signal detecting unit 4 separately detecting and detecting the FM luminance signal and the color signal from the preamplified signal read out from the image head, and the FM luminance signal and the color signal detected above are the same as the original signals. After demodulating and synthesizing each of them, the video signal processing flow is composed of the video signal processing unit 5 which is finally outputted, and detects the presence or absence of the hi-fi audio signal by detecting the audio signal read by the hi-fi audio head and pre-amplified by a predetermined level. In the hi-fi VCR having the hi-fi / mono detecting section 17 for switching and controlling the voice signal output line as a result of the determination, the hi-fi voice signal mixed with the color signal when the hi-fi voice signal is detected by switching to the output of the hi-fi / mono detecting section. An FM audio signal removing means 6 capable of selectively removing portions is provided at the output terminal of the color signal detection section 4. Configuring the connection characterized by image interference automatically removed by the audio signal in the Hi-Fi VCR circuit which. 2. The FM signal removing means according to claim 1, further comprising: a voice trap (6A) for trapping a voice signal of a specific frequency band from the output of the color signal detector; And a switch (SW2) that is controlled by an output of a hi-fi / mono detector to selectively control the operation of the voice trap. 3. The hi-fi method according to claim 2, wherein the voice trap 6A is constituted by a series resonant circuit of an inductor L and a capacitor C, and the respective capacitance values are set such that the resonant frequency is 1.4 MHz. Automatic image interference elimination circuit by audio signal in VCR. 3. The switch of claim 2, wherein the switch is configured by a transistor (Q1) which is turned on by the hi-fi detection signal of the hi-fi / mono detecting unit to turn on the voice trap and is turned off by the mono detection signal to turn off the voice trap. Automatic video interference elimination circuit by audio signal in hi-fi VCR. ※ Note: This is to be disclosed based on the first application.