JPS63231750A - Reproducing device - Google Patents

Abstract

PURPOSE:To detect a tracking deviation from a playback signal with simple constitution by obtaining tracking information from the difference between the outputs of two rotary heads which are fitted on a rotary drum while having a step. CONSTITUTION:The rotary heads HA and HB are fitted on the rotary head 1 while having the specific step PS. At this time, the track pitch PH and track pitch (recording track width) PT of the heads HA and HB on tracks are different and PH=PT+ or -PS. When guard bandless recording is performed, the track width WH of the heads is wider than the recording track width PT, so an on-track state is obtained by selecting the step PS properly. When the head HA is in the on-track state and the head HB is in an off-track state, playback signals SA and SB have a relation SA>SB and when they are in the reverse states, a relation SA<SB is obtained. The comparison error signal between the playback signals SA and SB is utilized as a tracking error signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a playback device suitable for use in, for example, a video tape recorder (VTR) or a digital audio tape recorder (DAT).

[Summary of the invention]

In a rotary head type reproducing device, at least two rotary heads for reproducing different tracks are mounted on a rotary drum with a step so that the pitch of the trajectory of the rotary heads on the tape is different from the track pitch. By obtaining track deviation information during playback from the output difference of the rotary head, tracking during playback can be performed with a simple circuit configuration without using a special tracking signal.

[Conventional technology]

In the playback mode of a normal rotating head type recording/playback device,
The tape speed is controlled so that the head correctly traces the recording pattern on the tape.

A method for performing tracking control by detecting deviations in the trajectory of the head relative to the recording pattern (track deviations) is to record CTL in the longitudinal direction of the tape using a control (CTL) head as a fixed head, and detect this during playback. There are two methods: the CTL method, which performs tracking control by recording a special signal for tracking on a diagonally recorded track, and the ATF method, which performs tracking control by recording a special signal for tracking on a diagonally recorded track. When recording by compressing the time axis and forming a diagonal trunk on a recording medium using multiple rotating heads without forming a guard band, each track is tracked independently as a recording area from the PCM signal in the longitudinal direction of each track. Multiple biloft signals are recorded, and during playback, the recording track is scanned by a rotating head whose scanning width is wider than the track width, and the rotating head is rotated by the reproduced output of pilot signals from tracks on both sides of the track being scanned. This controls the tracking of the head.

Further, as a simple method, it is also possible to perform tracking control by detecting the output level itself of the reproduction amplifier and detecting a track deviation from an increase or decrease in the output level.

[Problem that the invention seeks to solve]

By the way, in the case of the above-mentioned conventional methods, there are various drawbacks as follows. First, in the case of the CTL method, a dedicated fixed head is required, separate adjustment is required, and sometimes an erasing head is also required, and there are limits to miniaturization. Also,
In the case of the ATF method, it requires separation from signals such as video signals or audio signals, and has the disadvantage of being subject to limitations in circuit configuration or frequency band.

In addition, in the case of a method that detects the output level itself of the playback amplifier, since the absolute level changes when the type of tape is different, it is first necessary to find the output peak, and moreover, it is necessary to find the output peak first, and the direction of track deviation ( It is not easy to find out the positional relationship between the trunk and the head.
As a result, complex control is required.

In addition, in playback-only equipment, there are cases where it is not necessary to strictly control the level difference when mounting the head, so it is conceivable to actively utilize this fact.

The present invention has been made in view of the above, and it is an object of the present invention to provide a playback device capable of simple playback tracking that detects track deviation based on a playback signal without requiring a special tracking signal. .

[Means for solving problems]

The present invention provides a rotary head type reproducing device in which at least two rotary heads HA are used to reproduce different tracks.
, HB and a rotating head HΔ.

The HB is mounted on the rotating drum (1) with a step Ps so that the pitch PH of the locus on the tape of these rotating heads HA+ HB is different from the track pitch PT, and the output difference between the rotating heads HA+ HB is used to determine when playing back. The system is configured to obtain track deviation information.

[Effect]

The rotating heads HA and HB can be mounted on the rotating drum (1) with a predetermined step ps. Then, the rotating head H^
The pitch PR of the +Hfl locus on the tape becomes different from the two track pitches. In other words, PH=PT±P
It becomes s. By scanning the track with such rotary heads HA and HB, the difference in the direction of track deviation appears as a magnitude relationship between the outputs of both heads HA+HB.

As a result, track deviation information during reproduction can be obtained from the output difference between the rotary heads HA+HB, and tracking during reproduction can be performed with a simple circuit configuration without using a special tracking signal.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on FIGS. 1 to 8.

First, the basic principle of the present invention will be explained using a DAT as an example, with reference to FIGS. 3 to 8. Normal DAT
As shown in FIG.
is wrapped around the rotating drum (1) over an angular range narrower than its 180° angular range, for example 90°. Then, the rotating heads HA and H8 are rotated in the direction of arrow a at a rate of 30 revolutions per second, and the tape T is run at a predetermined speed in the direction indicated by the arrow. One diagonal magnetic trunk is formed on the magnetic tape T, for example in a so-called overwritten state, as shown in FIG.

In this case, the width directions of the gaps between the heads HA and HB are set to be different from each other with respect to the direction orthogonal to the scanning direction. In other words, the so-called azimuth angles are made different.

In FIG. 7, WH represents the track width of the head, and PT represents the recording track width. Normally, the track width WH of the head is larger than the recording track width P, about 1.5 times.

Figure 8 shows the ideal positional relationship between the trunk and the head during playback. In this case, the playback heads H^ and HB are mounted 180 degrees opposite each other at the same height on one plane of the rotating drum. It is being At this time, the pitch P)l of the trajectory of the heads H^ and HB is equal to the recording track width, that is, the track pitch PT.

Now, in this invention, we have focused on the fact that in playback-only equipment, there are cases where it is not necessary to strictly control the level difference when installing the head, and on the contrary, we actively utilize this to improve the head H^ and Hs is attached to the rotating drum (1) with a predetermined step Ps as shown in Fig. 3. Then, as shown in FIG. 4, for example, when the head HA is positioned evenly on the left and right sides of the track width, which is a so-called just track, the head HR is on track but slightly shifted to the left. The relationship between the pitch PH of the locus of the heads HA and Ha and the recording track width (track pitch) PT is not equal as in the case of FIG. 8; PH=PT±Ps
There is a relationship between In other words, with this invention, the head HAI! :
The HB is attached to the rotating drum (1) with a predetermined step Ps so that the pitch PM of the locus on the tape is different from the track pitch PT.

In the case of guard panless recording, as shown in FIG. 4, since the head track width W)l is wider than the recording track width PT, it can be seen that if an appropriate step Ps is selected, an on-track state can be obtained for both.

Therefore, the relationship between the head and the track and the output state when playing with the heads HA and HR attached to the rotating drum (1) with a predetermined step Ps in this way are explained below.
Examples are shown on the left and right sides of FIG. 5, respectively. Both of these two examples correspond to off-track states. That is, on the left side of FIG. 5, as shown in FIG. 5A, head HA'' is in an on-track state, but head H is in an off-track state, and the reproduced signals SA and SR at this time are as shown in FIG. As shown in B, the reproduced signal S^ of head H^ is larger than the reproduced signal SB of head HB, and this relationship holds true for heads HA and H.
are maintained as long as B are both shifted to the left.

On the other hand, the right side of Fig. 5 shows the head HB as shown in Fig. 5A.
is in the on-track state, but the head H^ is in the off-track state, and the reproduced signals sB and SA at this time are such that the reproduced signal Ss of head HB becomes the reproduced signal SA of head HA, as shown in FIG. 5B. , and this relationship is maintained as long as heads HB and HA are both shifted to the right.

It can be seen from FIG. 5 that the difference in the direction of track deviation is expressed as the magnitude relationship between the outputs of both heads HA and HB. In other words, if the track shifts to the right (corresponds to the left side in Figure 5 where the heads HA and Hg shift to the left)
, the playback signal S^ of the head H^ and the playback signal S of the head HB.
The magnitude relationship of R is SA > SB, and when the track shifts to the left (corresponding to the right side of Fig. 5 where heads HA and HR shift to the right), the playback signal SA of head HA and head H
The magnitude relationship of the reproduced signal SH of No. 8 is SA<SB.

Then, by comparing the reproduced signals SA and Ss, the comparison error signal can be used as a tracking error signal. In other words, the direction of track deviation can be determined from the magnitude relationship between the reproduced signals SA and SB, and the amount of track deviation can be determined from the difference between them, so that they can be used as a tracking error signal.

FIG. 1 shows the circuit configuration of this embodiment, in which I(Δ and HB are rotating heads exclusively for reproduction, and these heads H^ and HB are connected to the rotating drum (with a predetermined step Ps as described above). 1).

Signals SA and SR reproduced by heads H^ and HB, respectively
is amplified by the reproducing amplifiers (2) and (3) and becomes the signal SA1
After becoming SR1, they are mixed in a mixing circuit (4) and outputted to an output terminal (5) as one continuous reproduced output signal SPR. This signal system is a circuit system for obtaining a normal main reproduction output signal.

In this embodiment, envelope detection circuits (6) and (7) are provided on the output sides of the reproduction amplifiers (2) and (3), respectively, to detect the level of the reproduction signal. Detection outputs SA2 and S of these envelope detection circuits (6) and (7)
B2 is supplied to sample and hold circuits (8) and (9), respectively, where it is sampled and held. These sampled and held signals SA' and Sday' are supplied to a comparator circuit (10
) and the comparison error signal is supplied to the non-inverting input terminal and inverting input terminal of the tracking error signal SI! It is taken out to the output terminal (No. 1) as the output terminal.

Here, the tracking error signal SE obtained at the output terminal (11) is generated when the signal S^' is larger than Se2, that is, when the reproduced signal S^ of the head H^ is equal to the reproduced signal SB of the head Ha.
When it is larger, the polarity becomes positive, and conversely, the signal SB' goes to S'
When it is larger, that is, when the reproduced signal SB of the head HR is larger than the reproduced signal SA of the head HΔ, it becomes negative polarity,
This allows the direction of track deviation to be determined. Also, the signal S
The amount of track deviation can be determined from the difference between A' and Se2.

Figure 2 shows the relationship between the tracking error signal St and the track deviation obtained in this way, and shows that the reproduced signal is S.
When A > 3e, the tracking error signal is to the right, and the tracking error signal at that time is positive and increases approximately in proportion to the trunk shift. Conversely, when the playback signal is SA<SB, the trunk shift is to the left. It can be seen that the tracking error signal at that time has a negative polarity and decreases approximately in proportion to the track deviation.

In FIG. 2, TM is a dead zone of track deviation caused by the amount of step Ps in the head mounting, which occurs when the reproduction signal of the head HA and the reproduction signal of the head He are equal, as shown in FIG. This dead zone TM of track deviation has the relationship TM=WHPT Ps, and may be useful depending on the servo system. Here, in order to set TM=O, it is sufficient to set PS=WH-PT.

In this way, when this embodiment is used in a playback-only device, playback tracking becomes possible with a simple circuit configuration. Also,
Since the level difference is checked, no special adjustment is required on the playback machine side even if the tape has a different recording level. Furthermore, since the direction of track deviation can be determined based on the polarity (positive or negative) of the level difference, track correction control (not shown) can also be performed using CT.
It can be made equivalent to the L method and ATF method.

Although the above embodiment is for a playback-only machine, it can be similarly applied to a recording/playback machine if a playback-only head is used, and the track width Ws of the head and the head mounting are adjusted by the step Ps.
can be freely selected.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of rotary heads are mounted on a rotary drum with steps so that the pitch of the locus on the tape is different from the track pitch, and the difference in the output of the plurality of rotary heads is used to determine the difference during playback. Since track deviation information is obtained, tracking during playback is possible with a simple circuit configuration without using a special tracking signal, and the circuit configuration and cost can be reduced. It can be achieved without any restrictions.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of FIG. 1, and FIGS. 3 to 8 are diagrams for explaining the basic principle of this invention. It is a diagram. (1) is a rotating drum, (2), (31 is a reproduction amplifier,
(6), (71 is an envelope detection circuit, (8),
(9) is a sample hold circuit, and HA and HB are rotating heads.

Claims (1)

[Claims] A rotary head type reproducing device, comprising at least two rotary heads for reproducing different tracks, the rotary heads being arranged such that the pitch of the trajectory of the rotary heads on the tape is different from the track pitch. A playback device, characterized in that the playback device is mounted on a rotating drum with a step difference, and information on track deviation during playback is obtained from the difference in output between the rotating heads.