JPH0690765B2 - Erasing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an erasing device capable of efficiently erasing in a magnetic recording or reproducing device in a short time.

(Prior Art) Information such as a video signal is recorded on a record carrier such as a magnetic sheet,
Or, roughly categorized into 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 is a method of erasing from an AC or DC erasing signal. (C) A method of erasing by applying a gradually decaying DC current to the recording or reproducing head alternately with opposite polarities.

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

In order to solve the above-mentioned problems, the applicant of the present invention has found that a low-frequency vibration outside the frequency band of a recording or reproducing signal, which is a continuous vibration (period T _{E1 in} FIG. ₁ ), is applied to the magnetic head. We have proposed an erasing device that can perform erasing efficiently for each recording track and wider than the recording track by generating a magnetic field by the erasing signal including the subsequent damping oscillation (period T _{E2 in} the figure). (Japanese patent application 57-21965
9).

The applicant further sets the frequency of the damped oscillation above the frequency of the sustained oscillation, or lowers the relative speed between the magnetic head and the record carrier in the period T _E2 above the period T _E1. Proposed an erasing device that can remove residual distortion in a short time (Japanese Patent Application No. 58-1582).
1).

By the way, in the erasing device according to the above-mentioned applicant's proposal, more generally, in the AC erasing device, relative rotation is performed between the magnetic head and the record carrier, and a magnetic field generated by the erasing signal is applied to the magnetic head. When the mode of generating and erasing is further examined, depending on the relationship between the frequency of the relative rotation and the frequency of the erasing signal, for example, in the arbitrary track of the record carrier such as a magnetic sheet, the above-mentioned relative rotation is performed. There are points that are nodes of the erasing field for all of the rotations, which gives rise to the disadvantage that the erasing cannot be fully done at these points.

For example, FIG. 2 shows that, while rotating the disc-shaped magnetic sheet, an erasing magnetic field is generated by the erasing signal shown in FIG. 1 to erase the signal recorded on any one of concentric tracks on the magnetic sheet. FIG. 3 shows the state of the erasing magnetic field in the case of carrying out, the horizontal axis in the figure is the length of one arbitrary track in one rotation of the magnetic sheet, and H _E1 and H _E2 are the erasing signals shown in FIG. Any two of the erasing fields
Shows one. In FIG. 2, the frequency _E of the erased signal
And the rotation frequency _{V of the} magnetic sheet, If there is a relationship of P ₁ , P ₂ in any one track above
, P ₃ and P ₄ are always nodes of the erasing magnetic field for each rotation of the magnetic sheet, and erasing is not performed at these points.

(Object) Therefore, the present invention provides 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 a magnetic head. It is an object of the present invention to provide an erasing device capable of efficiently performing erasing in a short time by preventing nodes of the erasing magnetic field from occurring in all of the above relative rotations at any point on the recording track.

(Explanation by Embodiments) Means taken in the present invention in order to achieve the above object will be illustrated and described with reference to the embodiments shown in FIGS. The following description will be given in the order of the first and second embodiments using a disk-shaped record carrier and the embodiments using a tape-shaped record carrier.

(First embodiment using disc-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 disc-shaped record carrier. It is shown together with the system and the regeneration 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 that it is 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 input from the input terminal 4, converted into a signal suitable for recording by the recording signal processing circuit 5, and d of the switch S2.
It is amplified by the recording amplifier 6 via the terminal and recorded on the magnetic sheet 1 by the magnetic head 3 via the terminal a of the switch S1. In this case, the recording tracks are formed in concentric circles. At the time of reproduction, the signal recorded on the magnetic sheet 1 is read by the head 3 and the switch S1 b
It is processed by the reproduction amplifier 7 and the reproduction signal processing circuit 8 via the terminal, and is visually displayed on the display device 9 or printed by a printer or the like (not shown). The signal to be recorded may be an audio signal or another signal in addition to the above video signal.

An erase signal source 10 generates an erase signal having a waveform shown in FIG. 1, for example. To do this, the erase signal source 10
1. The ramp wave generator 12 and the multiplier 13 are used, and the multiplier 13 may multiply the oscillation of the frequency _E oscillated by the oscillator 11 and the illustrated ramp wave generated by the ramp wave generator 12. This erasing signal is amplified by the recording amplifier 6 via the c terminal of the switch S2, is supplied to the recording or reproducing head 3 which is also used as the erasing head via the a terminal of the switch S1, and erases the signal recorded on the sheet 1. .

Here, the relationship between the erase signal frequency _E oscillated by the oscillator 11 and the rotation frequency _{V of the} sheet 1 will be described. First, the erase signal frequency _E varies depending on the rotation frequency of the sheet 1, the frequency band of the recording or reproduction signal, the material of the sheet 1 and the head 3, and the like, but the rotation frequency of the sheet 1 is 60 Hz, and one field is provided for each concentric track. The erase signal frequency _E is 0.5 when the video signal is recorded.
~ 5kHz is suitable. In the apparatus of FIG. 3 which is an embodiment of the present invention, within the above range, the relationship between _E and _V described above is satisfied by the erase magnetic field for all rotations of the sheet 1 at any point on the recording track of the sheet 1. Set so that the clause of does not occur. If you explain this quantitatively Is set to (Where k is a positive integer).

Next, explaining the numerical examples of the periods T _E1 and T _{E2 in} FIG. 1, it is possible that T _E1 is 0.1 to 1 second and T _E2 is 1 to 2 seconds, and the continuous vibration in the period T _E1 is The amplitude can be constant, and the amplitude can be 30 to 40 mA when the period T _E1 is 0.2 to 0.4 seconds.

FIG. 4 shows the erase signal frequency based on the above numerical example.
The erasing action when _E is set as described above will be described. In the figure, for simplicity of explanation, The horizontal axis of FIG. 5A shows the length of any one of the concentric tracks of the sheet 1, and (1) to (5) show the erasing magnetic field acting on the above tracks. Considering the magnetic field acting on one point P on the track when the sheet 1 makes five rotations, (1) at the first rotation is the period T in FIG.
_{Assuming that} the magnetic field is due to the erase signal of constant amplitude at _E1 , it receives a large magnetic field in the positive direction, and the second time
It becomes the node of the magnetic field of (2), the third rotation receives the magnetic field of (3) smaller than the first rotation in the negative direction, the fourth rotation becomes the node of the magnetic field of (4), and the fifth rotation becomes the first rotation. In the same phase, it receives a magnetic field of (5), which is smaller than the third rotation. Then, after the sixth rotation, the same operation as described above is repeated.

FIG. 4 (B) shows the magnetic sheet 1 for the erasing magnetic field H _E of FIG. 4 (A).
Of the residual magnetic flux B _r , and the initial magnetization is assumed to be in the state shown by (O). First, the residual magnetic flux when it is saturated with the erase magnetic field (1) is (i), and the residual magnetic flux when it is magnetized in the opposite direction with the erase magnetic field (3) is (iii). The residual magnetic flux when magnetized in the same direction as the magnetic field (1) by the magnetic field (5) is (V), and it is shown that the same action is repeated and the residual magnetic flux finally converges to zero. With respect to all the rotations of the sheet 1 at points other than the above-mentioned point P, no node of the erasing magnetic field is produced, and the sheet is always affected.

In the above explanation, for simplicity However, (Where r is a positive integer), the last 3 /
Since the same situation as that shown in FIG. 4 is obtained for four wavelengths, no erasing magnetic field node is generated for all rotations of the sheet 1 at any point on the arbitrary track of the sheet 1. Since it is inevitably affected by the action, erasing can be efficiently performed in a short time. It has been experimentally confirmed that the erasing efficiency is highest when the successive erasing magnetic fields have a phase difference of 90 ° as shown in FIG.

The operation of erasing a signal recorded on a desired track of the magnetic sheet 1 in the erasing apparatus shown in FIG. 3 will be described. For example, the magnetic head 3 is moved to the desired track position by a known feed mechanism, and the switch S1, The erasing signal is supplied to the magnetic head 3 by switching S2. Since the erasing signal includes the continuous vibration having a constant amplitude during the period T _E1 and the damping vibration during the period T _E2 , the above-mentioned erasing action is, in other words, the magnetic sheet 1 during the continuous vibration period T _E1. 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 damping 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 short time is shortened. Can be erased with. 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 leaking to the outside in the gap portion 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-described effects are basically exhibited in the same manner in both the recording / reproducing head and the dedicated erasing head.

(Second Embodiment Using Discoidal Record Carrier) (FIG. 5) In the first embodiment, the frequency _E of the erase signal is the same in the continuous oscillation period T _E1 and the decay oscillation period T _{E2 in} FIG. However, according to the second embodiment of the present invention, the frequency of the damped vibration is set higher than the frequency of the sustained vibration, or the relative rotation speed between the magnetic head and the record carrier is damped and vibrated. T
_By making the recording wavelength of the erase signal equivalently shorter by lowering it than the continuous oscillation period T _E1 in _E2 , the time for removing the residual distortion can be shortened as compared with the first embodiment, or the erase period can be the same. If so, the erasing efficiency can be further improved. Also in the second embodiment, if the erasing means of the present invention is applied, the node of the erasing magnetic field for all the relative rotations of the magnetic head and the record carrier at any point on the recording track of the record carrier. Can be prevented.

For the mode in which the frequency of the damped vibration is made higher than the frequency of the continuous vibration, the frequency of the continuous vibration is set as shown in FIG. 5 (A).
_E1 , the mode in which the frequency of the damped vibration is _E2 and _{E2 is set} to a specific frequency higher than _E1, and the frequency in the damped vibration period T ′ _E2 is set as ′ _E2 and ′ _E2 as shown in FIG.
It is considered that it is higher than _E1 and gradually higher with the passage of time. From the viewpoint of shortening the erasing time or improving the erasing efficiency, the damping vibration period T ′ shown in FIG.
_The mode in which the frequency'E2 is gradually increased at _E2 is superior. FIG. 6 shows an embodiment in which the damped vibration of FIG. 5 (B) is generated, and the portions shown by the same reference numerals as in FIG. 3 have essentially the same configuration and function. The cancellation signal source 10 'of FIG. 6 comprises two sets of ramp wave generators 12A and 12B, of which the ramp wave generator 12A is similar to the ramp wave generator 12 of FIG. Generates a ramp wave corresponding to the signal envelope, while ramp wave generator 12B
Generates a ramp wave whose level gradually rises following a constant low level as shown. The oscillator 11 is frequency-modulated by the output of the ramp wave generator 12B, and its output is multiplied by the output of the ramp wave generator 12A in a multiplier 13. 1
4 is a mode switching signal input terminal, and the switch S1 is switched to the a terminal by a recording mode signal applied to the terminal.
The switch S2 is switched to the d terminal, and similarly the switch S1 is switched to the b terminal by the reproduction mode signal. Further, the erase mode signal switches the switch S1 to the a terminal and the switch S2 to the c terminal, activates the oscillator 11, and activates the ramp wave generators 12A and 12B to generate the ramp wave, and ( These operations are stopped after the time T _E1 + T ′ _E2 ) has elapsed. With the above configuration, sustained vibrations _E1 to variable constant in duration vibration period T _E1 amplitude, _E2 is output damping oscillation period T 'damping vibrations _E2 at the frequency gradually increases'.

Figure 5 To generate a damped oscillation constant frequency _E2 at attenuating vibration period T _E2 (A), the example relatively low levels the ramp generator 12B of FIG. 6 in the period T _E1,
Control may be performed so as to generate a ramp wave having a relatively high level and a constant level in the period T _E2 .

As a mode of applying the invention to the erasing apparatus shown in FIG. 5 and FIG. 6, first, as shown in FIG. 5 (A), _E1 and _E2
Is constant, these frequencies may be set so as to satisfy the above (1) with respect to the rotation frequency _{V of the} seat 1. In this case, since _V in the equation (1) is constant, the values of m and n when expressed as the equation (1) in the setting of _E1 and _E2 described above are explained with reference to the equation (1). It is natural that the values will be different within the range satisfying the above condition. Next, when ′ _E2 changes gradually as shown in FIG. 5 (B), some of these changing frequencies do not satisfy the above formula (1), but the frequency changes immediately. Therefore, no node of the digestion magnetic field is generated for all rotations of the sheet 1 at any point on the recording track of the sheet 1.

In the second embodiment using a disk-shaped record carrier, instead of increasing the frequency of the damped vibration during the damped vibration period (T _E2 or T ′ _{E2 in} FIG. 5), the rotational frequency of the magnetic sheet 1 (generally, The same effect can be achieved by lowering the frequency of relative rotation between the magnetic head and the record carrier.
That is, generally, when the relative speed between the magnetic head 3 and the magnetic sheet 1 is ν _E , the frequency of the erase signal is _E , and the recording wavelength of the erase signal is λ _E Therefore, if the relative speed υ _E is decreased, the recording wavelength λ _E is shortened even if the frequency _{E of} the erase signal is constant, which is equivalent to increasing the frequency of the erase signal. Produce an effect. Therefore, for example, in FIG. 6, if the rotation frequency of the sheet 1 is lowered in the damping vibration period T _{E2 than} in the continuous vibration period T _E1 , the recording wavelength in the former is a constant wavelength shorter than the recording wavelength λ _E1 in the latter. The wavelength can be changed to λ _E2 , or to a wavelength λ ′ _E1 that is shorter than the recording wavelength λ _{E1 in the} latter and gradually shorter. As in the case of the above, the embodiment in which the recording wavelength λ ′ _E2 is gradually shortened in the damping oscillation period T _E2 is superior to the viewpoint of shortening the erasing time. In order to change the rotation frequency of the magnetic sheet 1, a speed control circuit, a reference clock generation source and a time limit circuit are attached to the sheet rotation motor (for example, 2 in FIG. 6) and the sheet rotation motor is supplied in response to the erase mode signal. , The reference clock generation source generates the reference clock signal of the first frequency while the time _delay circuit measures the time period T _E1, and the reference clock generation source operates while the time delay circuit measures the time period T _E2 . A reference clock signal of a second frequency lower than the frequency of 1 is generated, or a reference clock signal whose frequency is gradually decreased by voltage control is generated, and the speed control is performed based on these reference clock signals. The speed of the seat rotation motor 2 may be controlled by the circuit.

As an aspect in which the present invention is applied to the configuration in which the rotation frequency of the magnetic sheet 1 is changed, when λ _E1 and λ _E2 are constant, the formula (1) is equivalently satisfied with respect to the recording wavelength. The rotational speed _V of the magnetic sheet 1 may be set to (in the same manner as above, the values of m and n when expressed by the equation (1) in the setting of λ _E1 and λ _E2 are different from each other),
In the case where λ _'E2 changes gradually Of these wavelengths
Although there are some that do not satisfy the expression (1), the erasing magnetic field does not occur for all rotations of the sheet 1 at any point on the recording track of the sheet 1 because the recording wavelength changes immediately. . In the second embodiment described above, if the means for increasing the frequency of the erasing signal and the means for lowering the rotational speed of the magnetic sheet are used together during the above-described damped oscillation period, the erasing time is further shortened or the same. The erase efficiency can be further improved with respect to the erase time.

(Embodiment using 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 photographing a photograph made using a 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 present applicant has previously proposed that in a device configured to rotate a recording medium obliquely around a guide member for traveling and to scan the recording medium with a rotating recording head to record an image signal, the scanning of the recording 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 locus is effectively the same locus when the record carrier is running and when it is stationary, thereby providing a normal reproduction having no special function We have proposed a recording device that can reproduce still images with good image quality by the device (Japanese Patent Application No. 57-161645).

INDUSTRIAL APPLICABILITY The present invention can be applied to, for example, erasing a recording signal in an apparatus for recording or reproducing by stopping the magnetic tape and rotating the head as described above. In this case, if the relationship between the rotation frequency (taking into account the number of heads) and the erase signal frequency is set so as to satisfy the above equation (1), the magnetic tape of the head can be recorded at any point of the recording track on the magnetic tape. For all rotations relative to, the erasure field nodal can be avoided.

(Effect) As described above, according to the present invention, in the erasing device for erasing by rotating the magnetic head and the record carrier relatively to generate a magnetic field by the erasing signal in the magnetic head,
The relative rotation frequency is rotated so as to be f _V, and the frequency of the erased signal is changed to f _E (where f _E = m / n · f
_V , where m is a positive integer, n is an integer with n ≧ 3, m / n
Is an irreducible fraction), so that the erasing magnetic field node is not generated for all the relative rotations at any point on the recording track of the record carrier. Therefore, 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 device 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 device. FIG. 3 is a block diagram of an embodiment of the erasing device of the present invention using a disk-shaped record carrier, FIG. 4 (A) is an illustration of the erasing magnetic field in the embodiment of FIG. 3, and FIG. 3 (B) is the same. A diagram showing the relationship between the residual magnetic flux of the record carrier and the erasing magnetic field, FIGS. 5 (A) and 5 (B) are waveform diagrams showing other examples of the erasing signal in the erasing device of the present invention, and FIG. FIG. 6 is a block diagram of another embodiment of the erasing device of the present invention using a disc-shaped record carrier. DESCRIPTION OF SYMBOLS 1: Magnetic sheet as an example of record carrier, 2: Sheet rotation motor, 3: Magnetic head, 10, 10 ': Erase signal source, T _E1 : Continuous oscillation period, T _E2 , _T'E2 : Damped oscillation period.

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

Claims (3)

[Claims] 1. A means for rotating the magnetic head and the record carrier so that the rotation frequency is f _V when the magnetic head and the record carrier are relatively rotated, and the magnetic head has a frequency f _E (where f _E = m). / n · f _V , where m is a positive integer, n is an integer with n ≧ 3, and m / n is an irreducible fraction), and a magnetic field is generated by the erase signal. And an erasing device comprising: 2. An erasing device according to claim 1, further comprising means for rotating a disk-shaped record carrier with respect to the magnetic head. 3. An erasing device according to claim 1, further comprising means for rotating said magnetic head with respect to a tape-shaped record carrier.