JPH04137202A - Rotary head device - Google Patents

Abstract

PURPOSE:To prevent a disturbing noise due to intermodulation between a reproduced information signal and an erasure signal from being mixed as a noise with the reproduced information signal by providing a video signal recording circuit with a trap circuit. CONSTITUTION:While the erasure signal is applied from an erasure signal processing circuit F to an erasure head 3 through a transmission transformer 3Tr to erase a video signal and an audio signal which are already recorded on a magnetic tape, an audio signal to be recorded is recorded on the magnetic tape and a video signal to be recorded is recorded on the magnetic tape. An erasure signal leaking from the transmission transformer 3Tr is applied to the primary coil of a transmission transformer 1'Tr for the video signal to be recorded and the input terminal of an audio recording amplifier 2'. The erasure signal applied to the primary coil of the transmission transformer 1'Tr is removed by the trap circuit 1'T and almost none of the erasure signal applied to the input terminal of the audio recording amplifier 2'A is recorded on the magnetic tape. Consequently, the noise originating from the erasure signal is prevented from being mixed with the reproduced information signal like the video signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary head device for processing video signals and audio signals, and particularly to information signals such as video signals and audio signals recorded on magnetic tape. The present invention relates to a rotary head device for preventing signals leaked from an erasing head from being recorded.

[Conventional technology]

FIG. 3 is a diagram showing circuit connections of a conventional circuit-equipped rotary cylinder. In FIG. 3, ■ is a video head, 2 is an audio head, 3 is an erase head, IS and 2S are
Step-up transformer, IA is a video playback amplifier, 2A is an audio playback amplifier, 1'^ is a video recording amplifier, 2
'A is an audio recording amplifier;
It consists of ), S to S3 are slip rings, B1 to B are brushes (S, , B2 and B+, Bz
supplies power to amplifiers 18 to 2'A, S and B,
supplies a recording/playback switching signal. ), ■ is a video signal processing circuit, A is an audio signal processing circuit, and F is an erasure signal processing circuit. Here, the primary If! of the transmission transformers IT, . . . , 3T. (R) and slip ring SI
S to S are mounted on a rotating cylinder and rotate when starting and stopping.

The operation of the conventional circuit-mounted rotary head device shown in FIG. 3 will be explained. First, slip ring S
,,S! and brushes Br and Bz, power is supplied to the amplifiers IA to 2'A; , supplies a recording/reproduction switching signal for switching between the audio reproduction amplifier 2A and the audio recording amplifier 2'A. When playing video and audio signals recorded on magnetic tape,
The video reproduction amplifier IA and the audio reproduction amplifier 2A are put into operation by the recording/reproduction switching signal. The video playback signal from the video head I is boosted by a step-up transformer IS, amplified by a video playback amplifier IA, and then transferred to a transmission transformer IT.

The signal is then transmitted from the rotating cylinder to the fixed video signal processing circuit V. Similarly, audio head 2
The audio playback signal is boosted by a step-up transformer 2S, amplified by an audio playback amplifier 28, and transmitted from a rotating cylinder to a fixed audio signal processing circuit A via a transmission transformer 2T. When recording a video signal and an audio signal on a tape, the video recording amplifier 1'A and the audio recording amplifier 2'A are put into operation by a recording/reproduction switching signal. next,
An erasing signal having a frequency higher than the frequency band of the video signal is applied from the erasing signal processing circuit F to the erasing head 3 via the transmission transformer 3T, thereby erasing the video signal and audio signal previously recorded on the magnetic tape. First, the audio signal is recorded on the magnetic tape, and then the video signal is recorded on the magnetic tape. The audio signal to be recorded is transmitted as a frequency modulated signal from the audio signal processing circuit A to the fixed secondary winding (<s) of the transmission transformer 2T, , and then to the primary winding (R ), passes through an audio recording amplifier 2'8, is stepped down by a step-up transformer 2S, is transmitted to the audio head 2, and is recorded on a magnetic tape. Similarly,
The video signal to be recorded is transmitted as a frequency modulated signal from the video signal processing circuit V to the fixed secondary !T of the transmission transformer 1'T. ! (S), is transmitted to the primary winding (R) provided on the rotating cylinder, and is transmitted to the video recording amplifier 1.
'A, the voltage is stepped down by a step-up transformer IS, and the video signal is transmitted to the RAD1 and recorded on a magnetic tape. Furthermore, when splicing, following the old video signal and old audio signal recorded as diagonal tracks in the front area of the magnetic tape, the new video signal and new audio signal are recorded diagonally in the rear area of the magnetic tape. When recording as a track, if the old video signal and old audio signal recorded in the rear area are erased with a full-width erase head (not shown) having an erase gap extending in the tape width direction, the last part of the front area A triangular portion surrounded by the full length track and the erase start line by the full width erase head remains as an unerased portion. Erasing by the erasing head 3 starts from a complete track in the front area including this triangular part and a little before it, and from that track (following the erasing head 3, the audio head 2 and the video head 1)
New audio signals and new video signals are being recorded.
In this case, the erasing head 3 stops its operation after erasing the triangular portion, and only the audio head 2 and video head 1 continue operating, so that a new video is created in the rear region following the front region. The signal and the new audio signal are recorded.

In addition, in order to prevent leakage of the erasing signal in the transmission transformer 3Tr, a capacitor 3Ct was inserted at both ends of the erasing head 3, and the secondary side was viewed from the inductance of the coil of the erasing head 3 and the next side of the transmission transformer 3T. The inductance and the capacitance of the capacitor 3C constitute a parallel resonant circuit having a resonant frequency equal to the frequency of the cancellation signal, and a transmission transformer 3T.

The current of the erase signal flowing through the negative side and the secondary side is reduced. Note that this type of prior art is described in Japanese Patent Application Laid-open Nos. 56-163503 and 63-19.
There are publications such as Publication No. 5802.

[Problem to be solved by the invention]

In the conventional circuit-equipped rotary head device shown in FIG.
When trying to improve the image quality of TR, in order to erase the video signal whose frequency band has increased, the frequency of the erasing signal output from the erasing signal processing circuit F is also increased to the extent that it does not affect the video signal, and the frequency band is increased accordingly. Therefore, the resonant frequency of the parallel resonant circuit was also made to match the erasing frequency, but the erasing current flowing through the transmission transformer 3Tr also increased, and the erasing signal leaked from the transmission transformer 3Tr, causing the video recording amplifier 1'
A and the input end of the audio recording amplifier 2'A. At this time, since the frequency band of the frequency modulated audio signal to be recorded is sufficiently lower than the frequency of the erasure signal, the recording gap characteristics of the audio recording amplifier 2'A and the audio head 2 are such that almost no erasure signal passes through. Since the erase signal is almost never recorded by the audio head 2, only the erase signal applied to the input terminal of the video recording amplifier 1'A is recorded on the magnetic tape. recorded.

Then, due to the nonlinear characteristics of the magnetic tape, cross-modulation occurs between the carrier wave of the video signal and the erase signal. When this magnetic tape is reproduced, there is a problem in that a signal cross-modulated by the frequency-modulated carrier wave of the video signal and the erasure signal and a beat signal are generated within the frequency band of the video signal. For example, if the carrier frequency f of a frequency-modulated video signal is 7 MHz and the cancellation frequency f is 13 MH2, then 2f, -f.

A disturbance frequency of =1 MHz is generated. Also, when playing,
The cross-modulated signal leaks from the regenerative amplifier IA to the transmission transformer 2Tr through the transmission transformer ITr, and enters the audio signal processing circuit A. Since the frequency of this cross-modulated signal is within the frequency band of the frequency-modulated audio signal, there is a problem in that noise is generated in the reproduced audio signal.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a rotary head device of a magnetic recording/reproducing device equipped with an erase head, in which an information signal such as a video signal is recorded from an erase signal supply circuit system during recording. The purpose of this invention is to prevent noise based on the erasure signal from being mixed into a reproduced information signal such as a video signal by preventing the erasure signal leaked into the circuit system from being recorded on the magnetic tape.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a rotary head having a recording/reproducing head for recording and reproducing information signals such as video signals, and an erasing head that performs erasing using an erasing signal having an erasing frequency higher than the frequency band of the information signal. In the apparatus, a trap circuit having a center frequency equal to the erasing frequency is provided in a recording circuit that supplies the information signal to the recording/reproducing head.

[For production]

By providing a trap circuit in the information (video) signal recording circuit, the erase signal leaked from the erase signal supply circuit system, such as an erase signal transmission transformer, to the information (video) signal recording circuit is prevented by this trap circuit. The erase signal is removed and the erase signal is not recorded on the magnetic tape.

As a result, cross-modulation components between the reproduction information signal (video signal carrier wave) and the erasure signal frequency are prevented from being generated as noise, and an information signal (video signal) with an excellent S/N can be reproduced. . Further, during playback, cross-modulation components will not leak from the video playback circuit to the audio playback circuit through the transmission transformer.

Furthermore, since it becomes possible to sufficiently increase the erasing signal current, video signals and audio signals can be sufficiently erased.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The rotary head device of FIG. 1 has a transmission transformer 1'Tr in the video signal recording circuit of the rotary head device of FIG.
A trap circuit 1'T whose center frequency is equal to the frequency of the erasing signal is provided between the primary winding (R) of the video recording amplifier 1'A and the input end of the video recording amplifier 1'A. In FIG. 1, other circuit elements are the same as those in FIG. 3, and those with the same names are given the same reference numerals as in FIG. 3, and their explanation will be omitted. The trap circuit fil'T is configured, for example, by providing a parallel resonant circuit including a coil and a capacitor between the input and output terminals on the upper side of the two-terminal pair circuit network.

The coil is composed of a series circuit of an inductance L and a resistance T of the coil, and a capacitor is composed of a capacitance C.

Further, in FIG. 2, 4 is the video signal voltage appearing at both ends of the primary wire ring (R) of the transmission transformer 1'Tr, and only the vicinity of the frequency fo of the erasure signal is represented by a dotted line.
5 is the video signal voltage appearing between the trap circuit 1'T and the input side of the video recording amplifier 1'A, and 6 is the video signal voltage appearing at both ends of the primary wire ring (R) of the erasure signal transmission transformer 3Tr. This is the erase signal voltage.

The operation of the embodiment of the present invention shown in FIG. 1 is as follows. When recording video signals and audio signals on a magnetic tape, an erasing signal is applied from the erasing signal processing circuit F to the erasing head 3 via the transmission transformer 3Tr.
An audio signal to be recorded is recorded on the magnetic tape while erasing the video signal and audio signal previously recorded on the magnetic tape, and then a video signal to be recorded is recorded on the magnetic tape. The erasure signal leaked from the transmission transformer 3Tr is transmitted to the transmission transformer 1'T of the video signal to be recorded.
It is applied to the primary winding of r and the input terminal of the audio recording amplifier 2'A. The erasing signal applied to the primary winding of the transmission transformer 1'Tr is removed by the trap circuit 1'T, and the erasing signal applied to the input terminal of the audio recording amplifier 2'A is removed by the magnetic In the end, the erase signal leaked from the transmission transformer 3Tr is not recorded on the magnetic tape.

Note that in the embodiment shown in FIG. 1, the trap circuit 1
'T, transmission transformer 1'Tr and video recording amplifier 1
Although it is provided between the input side of the video recording amplifier 1'A, it is clear that it may be provided anywhere in the video signal recording circuit, such as on the output side of the video recording amplifier 1'A.

Note that a similar trap circuit 1'T is connected to a transmission transformer 2T.
It is conceivable to provide it between r and the input side of the audio recording amplifier 2'A, but as mentioned above, the frequency of the frequency-modulated audio signal is far from the erasure frequency,
This was not necessary in this example since intermodulation rarely occurs.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below. That is, by providing a trap circuit in the video signal recording circuit, the erase signal leaked from the erase signal processing circuit to the information signal recording circuit (via the transmission transformer) is attenuated by the trap circuit, and the erase signal is recorded on the magnetic tape. Since it is no longer recorded, it is possible to prevent interference components based on cross-modulation between the reproduced information signal and the erased signal from being mixed into the reproduced information signal as noise. Furthermore, since the erasure signal leaked from the erasure signal processing circuit (for example, via a transmission transformer) is attenuated by the trap circuit, the output from the erasure signal processing circuit is increased.
Already recorded video and audio signals can be completely erased.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram of a rotary head device equipped with a circuit according to an embodiment of the present invention, Fig. 2 is a diagram showing frequency characteristics of a video signal voltage and an erasing signal voltage, and Fig. 3 is a diagram showing a conventional rotary head device equipped with a circuit B. ) is a wiring diagram of the device. l...Video head, 2...Ode 1°O head,
3... Erasing head, IA... Video recirculation amplifier,
1'^...Video recording amplifier, 2^--Audio playback amplifier, 2'^...Audio recording amplifier, Is, 2S...B pressure L lance, 3C...Capacitor, l Tr, l' Tr, 2Tr,
3Tr - Transmission transformer, R...Primary winding of transmission transformer, S...Secondary winding of transmission transformer, A...
Auteio signal processing circuit, F... erasure signal processing circuit,
■...Video signal processing circuit, S+, Sz, Ss...
・Slimplink, B,,B. B Yu...Brun, l'T...Trap circuit, 4...
・Video signal voltage appearing at the west end of the primary wire ring (R) of transmission t,,'T', 5...Trap circuit 1'
T and the video signal voltage appearing between the input terminal of the video recording amplifier 1'A and 01, 6...transmission transformer 1'T. The erasing signal voltage appearing across the second wire (R). ] Figure Figure

Claims (1)

[Claims] 1. On a rotating drum, a recording/reproducing head, an erasing head, a recording circuit that supplies an information signal to be recorded to the recording/reproducing head, and an erasing signal having a frequency higher than the frequency band of the information signal to the erasing head. What is claimed is: 1. A rotary head device having an erasing circuit for supplying an erasing signal, characterized in that the recording circuit includes a trap circuit whose center frequency is equal to the frequency of the erasing signal.