KR900006768B1 - Rotray heads type magnetic recording or reproducing apparatus - Google Patents

Abstract

A magnetic recording and reproducing apparatus includes a signal adding/gate circuit (5) for receiving FM-Y signal, colour signal, FM audio signal, PCM audio signal, pilot signals (f1-f4) and head height control signal (f5); a gate pulse providing circuit (6) for providing gate signal to (5); recording amplifiers (7,8) for amplifying the output of the signal adding/gate circuit; and magnetic heads (11,12) for recroding signal on a magnetic tape. The appts. records tracking pilot signals using four frequencies which control head height.

Description

Rotating Head Type Magnetic Reproducing Device

1 is a plan view of a tape running system in an 8 milli-video format mat.

2 and 4 show a recording track format mat on an 8 milli video magnetic tape.

3 is a detailed explanatory diagram of a recording track for explaining the recording and reproducing period of the pilot signal f ₅ for controlling the relative height of the recording head.

5 is a frequency spectrum diagram for explaining the recording signal spectrum in 8 milli video.

6 is a recording track diagram for explaining a recording state of a pilot signal in the recording method of one embodiment of the present invention.

7 is a block diagram of a signal recording and reproducing circuit according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

5 addition and gate circuit 6 gate pulse generating circuit

7,8: recording amplifier 9,10: low-voltage transformer

11,12 magnetic head 13,14 playback amplifier

16: BPF 17: Sample holder circuit

18 Comparison Circuit

The present invention relates to a rotating head magnetic recording and reproducing apparatus, and more particularly, to recording means for tracking pilot signals.

In the 8 mm video standard, two heads A and B having different gap azimuth angles are attached to the 180 ° position of the rotary cylinder 3, and as shown in FIG. The magnetic tape 4 is rolled up and recorded by 221 degrees. The video signal and the FM modulated audio signal are recorded in approximately 180 ° portion L ₁ of the rotating cylinder. The trace T recorded on the magnetic tape becomes as shown in FIG.

The difference between the conventional VHS method and the like in the recording / reproducing method of 8 milli video, does not adopt the tracking 1 method by the fixed head, but superimposes the pilot signal for tracking with the video signal by the rotating head, In the following, the tracking pilot signal is used to properly track the rotating head. This tweaking pilot method uses a pilot signal of four frequencies (f ₁ , f ₂ , f ₃ , f ₄ ), and cyclically switches the pilot signal of four frequencies per track sequentially. At the time of playback, the crosstalk pilot component reproduced as a crosstalk component is taken out of two adjacent tracks adjacent to the main playback track, and tracking control is performed so that the level of the crosstalk pilot signal reproduced from the previous and subsequent tracks becomes equal. Will be. In the standard of 8 milli video, the relationship between the four frequencies is set as follows.

f₃-f₄

f_H f ₂ -f ₁

f ₃ -f ₄

f _H

f₄-f₁

3f_H f ₃ -f ₂

f ₄ -f ₁

3f _H

Where (f _H ) is the horizontal synchronization frequency of the television signal.

In this way, the relationship between the frequency of the pilot signal and the crosstalk pilot signal from the front track and the crosstalk pilot signal from the rear track can be easily separated.

By the way, in the 8 milli-video system, a pilot signal f ₅ for recording head height control which can be used to automatically match the relative heights of the magnetic heads mounted on the two movable plates at the time of recording is prepared.

When the recording head is attached on the movable plate, the recording and reproduction of the pilot signal f ₅ for controlling the relative height at the time of recording of the magnetic head will be described in detail with reference to FIG. 3 and FIG. .

3 shows one recording track taken out and displayed in detail. The pilot signal f ₅ for recording head height control can be written (f ₅ write) or reproduced (f ₅ read) in the region (C). The area of (C) is also shared as a margin for positional shift in the after-recording of PCM audio. The example may be shown for the distribution of the third degree (f ₅ write / read).

The (write / read) timing of (f ₅ ) on the tape will be described according to FIG. Since the track recorded by the rotating head is inclined to the tape and the tape is conveyed in the direction of the arrow at the speed of (V _t ), the star art position of the recording track is α _H between the adjacent tracks (α _H = 1H, H is shifted by the recording length of one horizontal scanning period). Therefore, the recording position C ₁ and the reproduction position C ₂ of the (f ₅ ) signal are also shifted between adjacent tracks (β _H ) as shown in FIG. 4 (a signal of f ₅ at the same distance from the tape end). We shall record.

First, (A) is a head (A ₁₎ a track is recorded, the then (B), but the head with (B ₁₎ sequentially recorded, as tracks, (A) the head in (A ₂₎ tracks, (B ₁₎ tracks When the (f ₅ ) signal is recorded in the instantaneous reproduction mode, the (f ₅ ) pilot signal recorded on the adjacent (A ₁ ) track is reproduced as a crosstalk signal. Next (A) When the head is recorded at (A ₂₎ a track (f ₅₎ If a momentary reproduction modal immediately after recording the pilot signal (B ₁₎ recorded on a track (f ₅₎ the pilot signal It reproduces as a crosstalk signal. In this way, the instantaneous reproduction mode reproduces the (f ₅ ) pilot signal recorded in the adjacent adjacent track as crosstalk. Therefore, the (f _5), pilot signal levels and (B) reproduced by the head (f ₅₎ pi hameuroseo Lot signal level is configured to control the height of one head so that at the same level, two head Play (A) the head To control the relative head height. (In this case, one head can be kept at a constant height without applying a control voltage, for example.)

As can be seen from FIG. 1, the other magnetic head is in the recording state during the instantaneous reproduction of the height control pilot signal f ₅ of the recording head by one magnetic head. In general, the pilot signal level reproduced from the magnetic head is extremely small and is about 100 μVpp or less, whereas the signal level at both ends of the recording head is about several volts. For example, it is quite difficult to remove the recording signal leaking out of the reproduction signal. The main place where the recording signal leaks out during the reproduction signal is generally a rotary transformer used in a video tape recorder. In general, the cross-channel crosstalk of the rotary transformers used in the public video tape recorder is about -30dB to -50dB, and the level difference of the recording signal with respect to the above-described reproduction signal is entirely insufficient compared to about + 90dB. In this way, when the signal level where the recording signal is leaked by the crosstalk of the rotary transformer is higher than the level of the reproduction pilot signal f ₅ , the means for reproducing the (f ₅ ) pilot signal satisfactorily. (f ₅₎ pi by Lot signal and using the difference between the frequency of the signal and the other filter ₍₅ f) I have no effective methods other than pulling out the pilot signal S / N well.

5 shows the frequency spectrum of the recording signal in 8 milli video. In FIG. 5, a (f ₅ ) pilot signal is recorded near 230 kHz, and (f ₅ ) a signal close in frequency to the pilot signal is a tracking pilot signal f ₁ , f ₂ , f ₃ , f ₄ ) and low-pass color signal. The center frequency is about 750 kHz for the low-conversion killer signal (C '), and the sideband level is considerably attenuated near 230 kHz (about -41 dB or less for the 750 kHz level for normal signals), and 750 kHz. It is enough to remove the nearby level with a filter, but since the tracking pilot signals f _l , f ₂ , f ₃ and f ₄ are close to the frequency with the (f ₅ ) pilot signal, it is extremely difficult to remove them sufficiently with the filter. Do. However, FM-A in FIG. 5 is a frequency modulated voice signal band.

In view of such a situation, the present invention provides a tracking pilot signal in (f ₅ ) a period of instantaneous reproduction (approximately one horizontal scanning period) and a recording signal recorded by the other recording head in order to reproduce the pilot signal. It is to exclude. In this way, even if a part of the pilot signal is not recorded, there is no problem in tracking during playback. (A dropout of 1 to 3 horizontal scanning periods occurs as if the tracking pilot signal is normally generated only at a specific track position. And there is no practical problem.)

In the present invention, in the instantaneous reproducing period of one head in contact with the tape for reproducing the pilot signal for recording head height control, the recording signal of another recording head which is in contact at the same time is made up of only the information signal. This is to improve the reproduction S / N of the pilot signal for height control.

6 is a diagram for explaining a specific example of a signal recording state on a recording track according to the present invention. In FIG. 6, in each recording track, immediately after the recording period C ₁ (f ₅ write period) of the recording head height control pilot signal, the reproduction time C ₂ of the pilot signal (f ₅ read). Period), and when one head is in the (f ₅ ) playback period (C ₂ ), the other head is in the recording state. In this period (Q period), the tracking pilot signal (f) _l , f ₂ , f ₃ , f ₄ ) are not recorded, only the video signal and the FM audio signal are recorded.

The (f ₅ write) (f ₅ read) period C ₁ (C ₂ ) in the recording track pattern of FIG. 6 indicates an example, and the recording and reproduction of (f ₅ ) in the standard of 8 milli video is performed. Since the processing period is allocated about 3H (H is the horizontal scanning period of the television signal), the period of recording and reproducing (f ₅ ) within this period may be set freely. Even if the period of recording and reproducing in (f ₅ ) is distributed, the tracking pilot signal in the recording signal of the other recording head in the period corresponding to the (f ₅ read) period may not be recorded.

7 is a circuit block diagram for explaining an example of the signal recording and reproducing circuit according to the present invention.

In Fig. 7, reference numeral 5 denotes a signal addition and gate circuit, and the inputs include the FM-Y signal, the color signal C ', and the FM audio signal from the terminals 1-1 to 1-6. The FM-A, the PCM audio signal PCM-A, the pilot signals f _{1 to} f ₄ , and the recording head height control signal f ₅ are input, and the respective signals are generated by the gate pulse generating circuit 6. The signal gated to the circuit 5 is delivered to the circuit 5, and various signals are recorded by the recording timing as _{shown in} FIG. In the period of instantaneous reproduction of the signal (f ₅ read period), the tracking pilot signal is removed from the signal recorded by the other recording head. (The Q period pilot signal in FIG. 6 is removed. In this way, the signals added and queried by the circuit 5 are amplified by the recording amplifiers 7 and 8, and are rotated through the rotary transformers 9 and 19. Are recorded on the magnetic tape by the pads 11 and 12. (13) and (14) are reproduction amplifiers, which in this case are the reproduction modes for instantaneous reproduction of the signal (f ₅ ).

Reproduction signal of the switch (SW ₁₎ is there out of the video signal and the FM audio signal output terminal 15 of the (SW ₁₎ through _{(SW 2), (SW 2} ) for inverting the each blood Ile period of the television signal From the output, the (f ₅ ) regeneration signal is taken out by the BPF 16 for taking out (f ₅ ), and the (f ₅ ) signal regenerated from the circuit 17 to each head is sample-held, respectively, (f ₅ ) The reproduction signal level is compared in the level comparison channel 18, and the error signal is taken out to the terminal 19. The error signal causes the height of the movable plate on which the head 11 is mounted, for example. (In this case, the head 12 is kept at a constant height), it is controlled so that the heights of both heads 11 and 12 are relatively coincident. From the terminal 20, a PCM audio signal is taken out at the time of reproduction. In addition, the transistors Q ₁ and Q ₂ are controlled to be in an off state when the corresponding head is in the recording mode, and to be in an on state in the reproduction mode. On the other hand, transistors Q ₃ and Q ₄ are controlled to be in an on state when the corresponding head is in the recording mode and in an off state when in the reproduction mode. The inverter circuits 21 and 22 are control signal inverter circuits for controlling the transistors Q _l (Q ₃ ) and (Q ₂ ) (Q ₄ ) to opposite modes, respectively. In addition, (C ₁ ) (C ₂ ) is an input capacitance for limiting a signal band during normal reproduction. Transistor Q ₅ (Q. ₆ ) is controlled to be turned on at the time of writing (including f ₅ read), and capacitor C ₃ and C ₄ are inserted in parallel only to the input of the reproduction amplifier, respectively, so that the input signal It acts to limit the band to low frequency band below (f ₅ ) pilot frequency.

In this way because it, by kamsoe the FM-Y signal, the FM audio signal, a color signal inputted to the reproduction amplifiers at the time of recording, to improve the (f ₅₎ the relative level of the reproduction signal and the other signal (e.g. The action of C ₃ and C ₄ attenuates components above 250 kHz so that the (f ₅ ) pilot signal and the (f _{1 to} f ₄ ) pilot signal pass as shown in the spectral diagram of FIG. As described above, in the reproducing timing (f ₅ ), since the pilot signal of (f _{1 to} f ₄ ) is controlled from the recording signal at the other head, even if there is cross torque in the rotary transformer (f _{1 to} f ₄ ) Since the pilot signal does not exist in the reproduction amplifier input, (f ₅ ) the S / N of the reproduction signal is improved, and the height control of the recording head is performed with high accuracy.

As described above, according to the present invention, the tracking pilot signals f ₁ , f ₂ , f ₃ , among the signals recorded by the other recording head during the period during which one head of the pilot signal f ₅ for height control of the recording head is reproduced. By eliminating f ₄ ), the S / N of the reproduction (f ₅ ) signal can be improved, and the relative height alignment at the time of recording of both heads can be precisely performed.

Claims (1)

With a plurality of magnetic heads (A) (B) mounted on the rotary cylinder (3) via a plurality of electrically controllable movable plates, the magnetic tape (4) is wound around the rotary cylinder (3), There is a period in which signals are sequentially recorded as discontinuous inclined recording trajectories, and at least two magnetic heads of the plurality of magnetic heads (A) and (B) simultaneously touch the magnetic tape 4 and simultaneously record the same. The magnetic head records the tracking pilot signal f _l (f ₂ ) (f ₃ ) (f ₄ ) for tracking control at the time of reproduction in addition to the information signal L _l (L ₂ ) such as a television signal, and performs the above operation. The instantaneous recording of the recording head height control pilot signal f ₅ for controlling the relative heights of the plurality of magnetic heads attached to the plate to coincide with the recording at the same time with one of the heads abutting the tape, Instantaneous playback on tracks recorded immediately before The recording head height control pilot signal is instantaneously reproduced, and the recording head height control pilot signal levels instantaneously reproduced by the respective magnetic heads are compared through a rectifying circuit having a long time constant, and at least one of the comparison error signals is used. In the member device, the tape for reproducing the recording head height control pilot signal f ₅ is controlled in the member apparatus such that the height of the movable plate is controlled so that the height of each magnetic head mounted on the movable plate is relatively equal. A rotating head configured to stop recording of the tracking pilot signal in the instantaneous reproducing period of one of the heads in contact with each other, using only the information signal as the recording signal from the other recording magnetic heads in contact with the tape; Type magnetic recording and reproducing apparatus.

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