JPH0618045B2 - Erasing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an erasing device capable of high-performance erasing with a simple circuit configuration in a magnetic recording or reproducing device.

(Prior Art) Information such as a video signal is recorded on a record carrier such as a magnetic sheet,
Or, roughly categorized as those conventionally proposed as erasing devices in magnetic recording or reproducing devices for reproducing recorded information, (a) erasing all tracks by a bulk erasing device (b) What is a recording or reproducing head? With a separate erase head,
There are those that are erased by an AC or DC erase signal. (C) There is one that erases by alternately applying a gradually decaying DC current to the recording or reproducing head in opposite polarity.

Of these, (a) cannot erase only the required track, and (b) requires an erase head in addition to the recording or playback head, which complicates the head mechanism, and (c) shows Since it gradually disappears and is erased alternately by a DC magnetic field of opposite polarity, it takes a considerable time to completely remove the residual strain.

In order to solve the above-mentioned problems, the present applicant has previously found that the magnetic head has a low-frequency vibration outside the frequency band of the recording or reproduction signal and a continuous vibration (period T _{E1 in} FIG. ₁ ) and Proposal of an erasing device that can perform erasing efficiently for each recording track and wider than the recording track by generating a magnetic field due to the erasing signal including the subsequent oscillation (period T _{E2 in} the figure) (Japanese Patent Application No. 57-2196
59).

By the way, in the erasing device according to the above-mentioned applicant's proposal, and more generally, in the AC erasing device, relative rotation is performed between the magnetic head and the record carrier, and a magnetic field due to an erasing signal is applied to the magnetic head. Considering the mode of generating and erasing, it is necessary to specially provide a high-precision oscillator as the erasing signal source, and when the erasing signal contains many harmonic components, the noise characteristics after erasing deteriorate. There is a drawback that Furthermore, depending on the relationship between the frequency of the relative rotation between the magnetic head and the record carrier and the frequency of the erasing signal, the relative rotation of the relative rotation can be achieved in any track of the record carrier such as a magnetic sheet. There are points that are nodes of the erasing magnetic field for all, and there is a drawback that erasing cannot be sufficiently performed at these points.

For example, FIG. 2 shows that, while rotating the disk-shaped magnetic sheet, an erasing magnetic field is generated by the erasing signal shown in FIG. 1 to erase the signal recorded in any one of the concentric tracks on the magnetic sheet. The horizontal axis in the figure shows the length of any one track in one rotation of the magnetic sheet, and H _E1 and H _E2 are the first
It shows arbitrary two of the erase magnetic fields by the erase signal shown in the figure. In FIG. 2, the frequency _E of the erase signal and the rotation frequency _{V of the} magnetic sheet are , Then in any one of the above tracks, P ₁ , P ₂ ,
, P ₃ and P ₄ are always nodes of the erasing magnetic field for each rotation of the magnetic sheet, and there is a drawback that erasing is not performed at these points.

(Object) Therefore, the present invention provides a simple circuit in an erasing device for performing relative rotation between a magnetic head and a record carrier and for erasing by generating a magnetic field by an erasing signal in the magnetic head. It is an object of the present invention to provide an erasing device having a configuration and capable of increasing the frequency accuracy of an erasing signal, thereby reducing residual noise and enabling high-performance erasing.

Further, the present invention achieves the above-mentioned object, and prevents any node due to the erasing magnetic field from occurring in any of the above relative rotations at any point on the recording track of the record carrier, efficiently and in a short time. An object of the present invention is to provide an erasing device capable of erasing.

(Explanation by Examples) With reference to the examples shown in FIG. 3, FIG. 4, etc., the means taken in the present invention for achieving the above-mentioned object will be exemplified and described below. The following description is given in the order of the embodiment using a disc-shaped record carrier and the embodiment using a tape-shaped record carrier.

(Embodiment using a disk-shaped record carrier) (FIGS. 3 and 4)
FIG. 3 shows an embodiment in which the present invention is applied to erasing a signal recorded on a disk-shaped record carrier, together with a recording system and a reproducing system. In the figure, reference numeral 1 denotes a disk-shaped magnetic record carrier, which may be either a magnetic sheet or a magnetic disk, but in the following description of the embodiments, it is assumed to be a magnetic sheet.
Reference numeral 2 is a sheet rotation motor, and 3 is a magnetic head. In the figure, an example in which the recording or reproducing head is also used for erasing is shown, but this may be a dedicated erasing head. The video signal to be recorded is inputted from the input terminal 4, converted into a signal suitable for recording by the recording signal processing circuit 5, amplified by the recording amplifier 6 through the d terminal of the switch S2, and passed through the a terminal of the switch S1. It is recorded on the magnetic sheet 1 by the magnetic head 3. In this case, it is assumed that the recording tracks are concentrically formed. At the time of reproduction, the signal recorded on the magnetic sheet 1 is read by the head 3, and the switch S1
It is processed by the reproduction amplifier 7 and the reproduction signal processing circuit 8 via the terminal b, and is visually displayed on the display device 9 or printed by a printer (not shown). The signal to be recorded may be an audio signal or another signal in addition to the above video signal.

Reference numeral 10 is an erasing signal source, which comprises a synchronizing signal oscillator 11, a frequency divider 12, a ramp wave generator 13, a multiplier 14 and a band filter (BPF) 15 having the erasing signal frequency _E as a pass band. The horizontal sync signal generated by the sync signal oscillator 11 controls the recording signal processing circuit 5 and the reproduction signal processing circuit 8, and is also divided by the frequency divider 12 into 1/2 (a positive integer). The generated output is generated by the ramp wave generator 13, for example, the ramp wave having the illustrated waveform and the multiplier 1
It is multiplied by 4 and the output is supplied to the c terminal of the switch S2 as an erase signal through the bandpass filter 15. The horizontal synchronizing signal which is the source of the erasing signal may be obtained from the synchronizing signal oscillator of another device, instead of the synchronizing signal oscillator 11 built in the recording or reproducing apparatus as shown in FIG.

Next, the relationship between the frequency _E of the erasing signal and the rotational frequency _V of the magnetic sheet 1 (generally, the relative rotational frequency between the magnetic head and the record carrier) _V will be described. In practicing the present invention, there is no erase field node for all rotations of sheet 1 at any point on the recording track of sheet 1, ie, It is possible to have a relationship of. _{If the} above relationship is established between _E and _V , all points on the recording track receive the erasing magnetic field, and erasing can be efficiently performed in a short time.

A numerical example of the erase signal frequency _E when the output of the synchronization signal oscillator 11 is divided to obtain the erase signal will be described. For example, the horizontal synchronization signal frequency _H = 15.7 for a color video signal.
If the frequency of 34 kHz is divided by 1/2, the frequency _E of the erase signal becomes as shown in the table below for this value.

The erase signal frequency _E is a value that satisfies the above expression (1) with respect to the rotation frequency _V 1 of the sheet 1 = 15.734 kHz / 262.5 = 59.939 Hz. According to the experiment, in the table above
_The best erasing characteristics are shown when _E = 1.96675 kHz. The optimum erase signal frequency _E differs depending on the rotation frequency of the sheet 1, the frequency band of the recording or reproducing signal, and the materials of the sheet 1 and the head 3.

Since the synchronization signal oscillator 11 has high frequency accuracy, if the oscillation output is frequency-divided to obtain an erase signal, residual noise is reduced and high-performance erase becomes possible. However, the band filter of FIG. By outputting an erasing signal through 15, it is possible to eliminate unnecessary harmonic components that are residual noise components and perform erasing with higher performance. FIG. 4 (A) shows the reproduced noise spectrum after erasure in the case of using the band filter 15 which passes the erasing signal frequency _E. Compared with the case of the same figure (B) in which the band filter 15 is not used, Indicates that the spectrum has been improved.

Next, a description will be given of numerical examples such as a continuous oscillation period (T _{E1 in} FIG. ₁ ) and a damping oscillation period (also T _E2 ) suitable for carrying out the present invention. T _E1 is 0.1 to 1 second and T _E2 is 1 ~
2 seconds is allowed, and the continuous oscillation in the period T _E1 is allowed to have a constant amplitude, and the amplitude is
Allow 30-40 mA when _E1 is 0.2-0.4 seconds.

The operation of erasing a signal recorded on a desired track of the magnetic sheet 1 in the erasing apparatus of FIG. 3 will be described. The S2 is switched to supply the erase signal to the magnetic head 3.
Since the erasing signal includes the continuous oscillation having a constant amplitude during the period T _E1 and the extinction oscillation during the period T _E2 , the above-mentioned erasing action is, in other words, the magnetic sheet during the continuous oscillation period T _E1. 1
The magnetization of the inside is saturated, the original recording signal of the track is overwritten and erased, and then the distortion is removed during the decay oscillation period T _E2 .

Further, if the frequency _E of the erasing signal is set to a low frequency outside the band of the recording or reproducing signal, the magnetic head 3 operates in a region where the magnetic permeability is high, so that the magnetic flux density is increased, the erasing efficiency is improved, and the erasing efficiency is shortened. Can be erased. Even if the erasing signal component remains, it is a negligible amount as a beat component that may occur during re-recording. Further, since the low-frequency vibration has a large amount of leakage magnetic flux leaked to the outside at the gear part of the magnetic head 3, even if there is some track deviation at the position of the head 3, it can be erased sufficiently wide. The above-mentioned effects are basically exhibited in the same manner whether the recording or reproducing head is also used as the erasing head or the dedicated erasing head is provided.

(Embodiment using a tape-shaped record carrier) As means for recording or reproducing a still image in a video tape recorder using a magnetic tape, in addition to a means for taking a photograph created using the film with the video tape recorder, a film It is also possible to use a video tape recorder to directly shoot without using, and for that purpose, (a) recording is done by a normal joint shot, and the tape is stopped during playback to make a still image.

(b) Record the same signal for several frames using a frame memory, etc., and stop the tape during playback to see a still image. Alternatively, repeat the section where the same signal is recorded.

Means such as The applicant of the present invention has previously proposed that in a device configured to run a record carrier obliquely wound around a guide body and scan the record carrier with a rotating record head to record a video signal, the scanning of the record head is performed. A means for applying a displacement force in a direction transverse to the scanning direction to the recording head so that the trajectory is effectively the same trajectory when the record carrier is running and when the carrier is stationary, thereby providing a normal reproduction having no special function. We have proposed a recording device capable of reproducing a still image of good image quality by the device (Japanese Patent Application No. 57-161645).

The present invention can be applied to erasing a recording signal in an apparatus for recording or reproducing by stopping the magnetic tape and rotating the head as described above,
By dividing the horizontal synchronizing signal to obtain the erased signal, the accuracy of the erased signal can be increased, as described above, and thus high-performance erase can be performed with less residual noise. Furthermore, if the relationship between the head rotation frequency (the rotation frequency considering the number of heads in the case of multiple heads) and the erase signal frequency is set so as to satisfy the above equation (1), the recording track on the magnetic tape will be recorded. It is possible to eliminate the erasure field node for any rotation of the head relative to the magnetic tape at any point in the.

(Effects) As described above, according to the present invention, in the erasing device for erasing by causing the magnetic head and the record carrier to rotate relative to each other to generate a magnetic field by the erasing signal in the magnetic head to erase the erasing signal. Since the horizontal synchronizing signal generated by the horizontal synchronizing signal source is divided and obtained, the erasing device can be configured with a simple circuit without separately providing an erasing signal oscillator, and the frequency of the erasing signal can be increased. The accuracy can be increased, and residual noise can be reduced and high-performance erasing can be performed.

Furthermore, the relationship between the frequency of the relative rotation between the magnetic head and the record carrier and the frequency of the erasing signal is defined by the erasing magnetic field for all of the above relative rotations at any point of the recording track of the record carrier. If the setting is made so that no node occurs, all points on the recording track of the record carrier receive the erasing magnetic field, and erasing can be performed efficiently and in a short time.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing an example of an erase signal in the erase apparatus of the present invention, and FIG. 2 is an explanatory diagram of a situation in which there is a node of an erase magnetic field depending on the setting of the erase signal frequency in the AC erase apparatus. , FIG. 3 is a block diagram of an embodiment of the erasing device of the present invention using a disc-shaped record carrier, and FIGS. 4 (A) and 4 (B) respectively show an erasing signal through a band filter in the erasing device of FIG. It is a diagram which shows the noise spectrum in the case where it outputs and the case where a bandpass filter is not used. DESCRIPTION OF SYMBOLS 1: Magnetic sheet which is an example of a record carrier, 2: Sheet rotation motor, 3: Magnetic head, 10: Erase signal source, 11: Synchronous signal oscillator, 12: Divider, 15: Band filter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Ogawa 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant (56) Reference JP-A-49-82312 (JP, A) JP-A-51 −8910 (JP, A)

Claims (5)

[Claims] 1. A means for relatively rotating a magnetic head and a record carrier, a horizontal synchronization signal source for generating a horizontal synchronization signal, and means for dividing a horizontal synchronization signal generated by the horizontal synchronization signal source. An erasing device comprising means for applying an output of the frequency dividing means to the magnetic head as an erasing signal and generating an erasing magnetic field in the magnetic head. 2. The relationship between the relative frequency of rotation of the magnetic head and the record carrier and the frequency of the output of the frequency dividing means is:
The erasing device according to claim 1, wherein the erasing magnetic field is set so as not to generate a node of the erasing magnetic field for all the relative rotations at any point on the recording track of the record carrier. 3. The means for generating an erasing magnetic field in the magnetic head is configured to apply the output of the frequency dividing means to the magnetic head after passing through a bandpass filter. ) The erasing device described in. 4. An erasing apparatus according to claim 1, further comprising means for rotating a disk-shaped record carrier with respect to the magnetic head. 5. The erasing device according to claim 1, further comprising means for rotating the magnetic head with respect to a tape-shaped record carrier.