JPS6314407B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention provides the following features:
The present invention relates to a head tracking control device for a magnetic tape device suitable for recording and reproducing video signals, for example, using a fixed head that forms a large number of tracks at high density.

Various proposals have been made to use mechanically simple fixed heads as magnetic tape devices for recording broadband signals such as video signals. That is,
A running magnetic tape is brought into contact with a fixed head to form a continuous track along the running direction of the magnetic tape, but when recording video signals magnetically, the connection between the tape and the head is It is required to set the relative speed at a high speed, for example, 4 to 6 m/s, and the amount of tape used per unit time becomes long. For this reason, it has been considered to move the fixed head in pitch in the width direction of the running magnetic tape to form a large number of tracks on the magnetic tape to increase the recording density and the efficiency of use of the magnetic tape.

In such a magnetic tape device in which a large number of tracks are formed side by side in the width direction of the magnetic tape, tracking control is performed by moving the head in the width direction of the tape. The reference track for such head tracking control is usually the track closest to the side edge of the magnetic tape. For example, the reference track is electrically detected, and the head position is mechanically adjusted to the reference track. Initial adjustment is made to match the reference track, and tracking control is performed with respect to the reference track with sufficient reproducibility. When the head is to be moved to a desired track located at a specified distance from this reference track, the movement of the head is controlled according to the number of track pitches from the reference track to the desired track. It is something.

However, for example, in order to record a video signal, high-density recording can be considered in which 350 tracks each having a track width of 40 μm are set on a 1/2 inch wide tape. Therefore, in this case, in order to move the head from the reference track to the 350th track with a tracking accuracy of 5 μm, assuming that the errors simply accumulate, the movement of the head for one track must be 5/350 μm ( =
An accuracy of 0.0143μm must be maintained.

In fact, a head support mechanism that controls the movement of the head in the width direction of the magnetic tape is constructed by, for example, screwing a nut onto a rotating screw shaft, and fixing and supporting the head with this nut. It has been considered to control the linear position movement of the head by controlling the rotation angle of the head. By rotating the screw shaft by a specified amount of rotation angle, the head is moved by, for example, one track pitch.

The error in the amount of head movement relative to the track pitch is not something that is simply accumulated, as mentioned above, but the accuracy of the amount of head movement is completely dependent on the thread pitch accuracy of the screw shaft and the nut screwed into it. Become. In particular, the thread pitch distribution of the screw shaft is
This condition directly affects the tracking accuracy of the head for each track on the magnetic tape. In fact, even if the screw shaft and nut are manufactured with the utmost care for screw pitch accuracy, a periodic error distribution over 10 or so tracks will be observed. These error distributions do not occur uniformly, and it is extremely difficult to maintain the accuracy of the moving mechanism so that the tracking accuracy of 0.1 μm is satisfied for all tracks.

This invention has been made in view of the above points, and even if there is a movement amount error in the mechanical head movement mechanism, the head can be moved with respect to all tracks formed on the magnetic tape. It is an object of the present invention to provide a head tracking control device that can control the head so that it is reliably tracked.

First, in the present invention, a reference master tape on which electrical signals are recorded while maintaining accurate track intervals is used. Then, this master tape is loaded into a predetermined magnetic tape device, played back one track at a time, and head tracking is controlled so that the playback signal is maximized. Measure in relation to. For example, when using a head movement mechanism using a rotating screw shaft as described above and driving the screw shaft with a pulse motor, the amount of head movement between each track is counted as the number of pulses for driving the pulse motor. Store the corresponding number of pulses between all tracks. In this case, the amount of backlash caused by switching the direction of head movement is also measured and stored, if necessary. When this magnetic tape device is actually used, the amount of movement of one track in the head movement mechanism converted into the number of pulses is read out and used for tracking control of the head movement mechanism.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a magnetic tape device related to the present invention, in which a magnetic tape 11 has an endless configuration and is wound around the outer periphery of a fixed reel 12 in the shape of a circular ring. Then, a tape ejection hole 13 is formed in a part of the fixed reel 12 by a notch so that the wound tape 11 can be pulled out from the innermost circumferential part, and this pulled out tape 1
1, the head mechanism 15 is connected by the guide pole 14.
The tape is drawn out and run at a predetermined speed by a tape drive mechanism including a capstan 16 and a pinch roller 17. The tape 11 taken out from the tape drive mechanism is guided to the outer periphery of the wound tape 11 via appropriate guide plates 18 and 19, and is wound up. That is, the tape 11 wound around the outer periphery of the fixed reel 12 is rotated at the outer periphery of the reel 12 as shown by the arrow as the tape drive mechanism moves the tape, and the endless tape 11 is rotated by the head mechanism 15. It is continuously supplied to the parts.

FIG. 2 shows the head mechanism 15 taken out, and the magnetic tape 11 is run in a vertical plane along the surface of the head guide 20, riding on a step 21 on the lower side thereof. That is, the tape 11 is stably run with its lower edge regulated in height by the stepped portion 21, and is brought into contact with the head 22, which is moved up and down in the figure along the head guide 20. be.

The head 22 is attached to a head base 24 integrally formed with a head support 23 by adhesive or the like as appropriate, and is attached to the head base 24 via an appropriate piezoelectric element 25 or the like. Therefore, the height position of the head 23 may be finely adjusted using a voltage signal.

The head support body 23 is configured in the shape of a nut with a female thread formed in a vertical through hole, and is screwed onto a screw shaft 26 set perpendicularly to the substrate as appropriate, and this screw shaft 26 can be rotated. Therefore, the head 22 is moved in the vertical direction to control the movement of the head 22 in the width direction of the tape 11. The screw shaft 26 is coupled to a pulse motor 28 via a gear mechanism 27,
By driving and controlling the pulse motor 28 using counted pulse signals, the amount of movement of the head 22 is set and controlled.

That is, the head 22 is set toward the lower end of the tape 11 corresponding to the first track, and the endless tape 11 is run by a tape drive mechanism including a capstan 16 and a pinch roller 17. Each time, the pulse motor 28 is driven to raise the head 22 by one track pitch, thereby forming each number of magnetic tracks extending in the longitudinal direction of the tape 11, as shown in FIG.

In this case, the screw shaft 2 that controls the movement of the head 22
6 and the head support 23 are formed uniformly and accurately over the entire surface, the screw pitches are "1" to "1" as shown by the solid line in FIG.
The relationship between each track order of "350" and the amount of rotation of the screw shaft 26 is a linear relationship.

However, in reality, in the thread pitch of the screw shaft 26, etc., due to the limit of processing accuracy, an error distribution exists in the relationship between the track order and the screw rotation amount, for example, as shown by the one-dot chain line in the figure. For this reason, for example, 1
If you want to move the head 22 on the n-th track to the n-th track position, moving the head 22 by (n-1) times the standard one-track interval will not move the head 22 by N. In reality, the nth track can be accurately tracked by moving the head 22 by [1 track interval x (n-1)]-N.

Similarly, to move to the i-th track, the head 22 can be brought into alignment with the i-th track by moving the head 22 by [1 track interval x (i-1)] + I.

FIG. 5 shows the configuration of a tracking control device according to an embodiment of the present invention.
The reproduced video signal taken out from the head 22 of No. 5 is amplified by an amplifier 29 and supplied from a terminal 30 to a color signal demodulation circuit (not shown). Further, the video signal obtained from the amplifier 29 is passed through the filter circuit 3
1. Normally, the luminance signal component is FM modulated, so the color signal component is removed in the filter circuit 31.
Only the FM-modulated luminance signal component is extracted from 1. The luminance signal component extracted from the filter circuit 31 is demodulated by an FM demodulation circuit 32 and supplied from a terminal 33 to a video signal synthesis circuit (not shown) so that it can be expressed as an image.

The output signal from the filter circuit 31 is further supplied to an A/D converter 34, converted into a digital signal according to the signal level (amplitude), and supplied to a control circuit 35. FM, which usually forms the luminance signal
The amplitude of the modulation signal corresponds to the tracking state of the head 22, and an FM modulation signal of maximum amplitude is obtained in a state where accurate tracking is performed. That is, in the control circuit 35,
The dynamic Tracking control is now performed for each individual track.

Commands from the keyboard 37 are given to the control circuit 35 as appropriate. The keyboard 37 is used to specify and input the initial settings of the track and the track number to be selected.
is read-out controlled. This storage device 38 stores the amount of inter-track movement in the head mechanism 15 along with the correction value explained in FIG. 4, and also stores the backlash correction value, by means to be described later. That is, the control circuit 35 calculates the movement control amount from the track currently being scanned by the head 22 to the track specified on the keyboard 37 from the movement amount including the correction value stored in the storage device 38, and calculates the movement control amount from the track currently being scanned by the head 22 to the track specified on the keyboard 37, and calculates the movement control amount from the movement amount including the correction value stored in the storage device 38, and calculates the movement control amount from the track currently being scanned by the head 22 to the track specified on the keyboard 37. 36 and rotates the pulse motor 28 to move the head 22 to a target track position.

Here, the information on the inter-track head movement amount and backlash correction amount to be stored in the storage device 38 is as follows.
Store it as follows. That is, the head mechanism 15 of this magnetic tape device is used to reproduce a reference master tape on which an accurate track pattern is formed. Then, the tracks are played while switching sequentially from the first track that is initially set.
The above-mentioned dynamic tracking control is performed corresponding to each track. And a pulse motor 28 necessary for moving between each track.
The number of driving pulses is measured, and this measured value is taken out from the control circuit 35 as the amount of movement between each track.
Storage device 38 via PROM writing circuit 39
It is stored in a.

The information storage operation in the storage device 38a using this master tape is performed for each head mechanism 15 corresponding to the completed magnetic tape device, and is unique to each head mechanism 15 that is actually used. Information corresponding to the error distribution is
Obtained with each magnetic tape device. This storage device 38a is used as the storage device 38 of a corresponding magnetic tape device.

For example, head 22 in the nth track
When moving to the i-th track, (n
Between the +1)th and (n+2)th tracks,...
The number of pulses required to move the head between the (i+1)th and i-th tracks may be read out, and the pulse motor 28 may be driven using the integrated value. In this case, the currently existing track number of the head 22 is stored in the temporary storage section 40 made up of RAM in response to the movement of the head 22 between tracks. When the input of the track designation is received, n is read from the temporary storage section 40. Other information necessary in the process of program calculations, etc. is written into this temporary storage section 40. Based on the information read from the temporary storage section 40, each track from the n-th track to the i-th track is moved once according to the control program stored in the control storage section 41. The amount is read out by specifying an address from the storage device 38 as described above and integrated, thereby providing a drive signal for the pulse motor 28.

In this case, the current track number, input information from the keyboard 37, time, and other information stored in the temporary storage section 40 are displayed on the display 42 as appropriate on a display, a numeric display, or the like.

That is, in the magnetic tape device configured as described above, the inter-track movement amount is calibrated in accordance with the error distribution existing in the head movement mechanism of the head mechanism 15, and is measured using the reference master tape. Storage device 3 corresponding to each device
8 will be stored and set. Then, head 2 is moved according to the stored movement amount between each head.
Since the movement between the two tracks is controlled, tracking control is always performed based on the master tape.

For example, suppose that the pulse motor 28 is driven with 15 pulses in order to obtain a displacement of 40 μm, which is the amount of movement between one track.
Tracking control to the next track can be performed with an accuracy of 40/15=2.7 (μm).

In this case, the number of pulses IC required to move from the first reference track to the i-th track,
Similarly, calculate the difference I between the number of pulses (I-1)C required to move to the (i-1)th track,
If this is information indicating the amount of movement between the (i-1)th track and the i-th track, then
The error of 2.7 μm is not accumulated, and even in the i-th track, tracking control can be performed within an error range of 1 pulse = 2.7 μm. In this case, by changing the gear ratio of the gear mechanism 27 in the head moving mechanism, tracking control with even higher accuracy can be achieved.

Note that dynamic tracking by specifying a track and moving the head to this track may be performed by controlling the pulse motor 28 with a pulse signal, but it is more effective to perform this by controlling the voltage applied to the piezoelectric element 25. Therefore, tracking control by controlling the number of pulses can be simplified.

As described above, according to the present invention, even in a magnetic tape device that performs high-density recording in which a track pattern of 350 or more lines is formed on a 1/2-inch tape, errors in the head movement mechanism can be sufficiently compensated for. This is a device that allows tracks to track with high precision, and in particular enables high precision control of simple video magnetic tape devices used for home use, etc., and always uses the track pattern on the magnetic tape as a reference. It is something that can be matched with the master. In other words, tape compatibility between devices is ensured, and the effect is significant.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram illustrating a magnetic tape device related to the present invention, FIG. 2 is a diagram showing the head mechanism section of the device taken out, FIG. 3 is a diagram also showing the track pattern of the magnetic tape, and FIG. FIG. 5 is a diagram illustrating errors in the head moving mechanism, and FIG. 5 is a configuration diagram illustrating a tracking control device according to an embodiment of the present invention. 11... Magnetic tape, 15... Head mechanism, 16...
Capstan, 22... Head, 23... Head support, 26... Screw shaft, 28... Pulse motor, 31...
Filter, 34... A/D converter, 35... Control circuit, 38... Storage device.

Claims (1)

[Scope of Claims] 1. A magnetic tape in which a head fixed to a running magnetic tape is moved in the width direction of the tape to form a plurality of parallel tracks extending in the running direction on the magnetic tape. The apparatus includes a head moving mechanism that moves the head in the width direction of the magnetic tape, and a head moving mechanism that moves the head between adjacent tracks of the head moving mechanism based on a master tape with an accurate track pitch set in advance. The head moving mechanism is further provided with means for storing the control amount between all adjacent tracks, and means for reading out the stored control amount corresponding to a reference position of the magnetic tape to be loaded and controlling the head moving mechanism. Features a head tracking control device. 2 The head moving mechanism includes a screw shaft that screws and supports the head, and a pulse motor that rotates the screw shaft to move the head in a linear position.The pulse motor controls the control amount for moving the head between adjacent tracks. 2. The head tracking control device according to claim 1, wherein the number of pulses determines the amount of rotation angle of the head.