JPH02252116A - Automatic tracking device for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To make the center of a reproducing magnetic head coincident with the central line of a track without fail and to obtain the reproduced picture of most satisfactory picture quality by providing an auxiliary head, for which a scanning track is coincident with that of the reproducing magnetic head and an azimuth angles is different from that of the reproducing magnetic head, and comparing the output levels of the both heads. CONSTITUTION:In a magnetic tape 14, FM-modulated information signals are recorded in every two positive azimuth tracks 11 and in other every two negative azimuth tracks 12. Near a reproducing magnetic head 1 to reproduce these information signals, an auxiliary head 2 of the negative azimuth angle is provided so that the scanning track can be coincident with that of the reproducing magnetic head 1. When reproducing is started and the both heads 1 and 2 are unitedly oscillated to right and left, size relation between the reproduced output levels of these heads is inverted when the heads are oscillated to one side and to the other side. Two points, where the size relation between these levels is inverted, are detected by a level comparator circuit 4 and the central line position of the track to be scanned by the reproducing head 1 is detected from those two points. Then, tracking control is corrected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates directly to a magnetic recording/reproducing device in which information signals are azimuthally recorded, and particularly relates to a magnetic recording/reproducing device in which information signals are recorded azimuthally. [Prior technology] Helical scan type magnetic recording/reproducing device (hereinafter referred to as VT)
R), magnetic heads with different azimuth angles are used, so that every other track on the magnetic tape has a different azimuth angle than every other track.
An azimuth recording method is used in which information signals are recorded. When reproducing information signals from such a magnetic tape, tracking servo is applied so that each magnetic head reproduces a track having the same azimuth angle.

An example of a VTR tracking servo device was published in Japanese Patent Publication No. 6.
It is disclosed in the publication No. 0-191422.

To explain this simply, capstan motors and cylinder motors use control signals, frequency signals, and tack signals to control the rotational speed and rotational phase as usual, but in addition, each magnetic head The electro-mechanical transducer is connected to the top via an electro-mechanical transducer such as a bimorph plate, and the electro-mechanical transducer is distorted by distorting the first control voltage formed from the above-mentioned control signal, frequency signal, and tack signal. By controlling the magnetic head, the magnetic head reproduces and scans parallel to the tracks on the magnetic tape, and in addition, these electro-mechanical transducers are controlled by a second control voltage formed from the envelope of the reproduction signal of the magnetic head. By controlling the distortion by , the magnetic head is caused to perform reproduction scanning on the track so that the envelope of this re-increase signal is maximized.

According to the number of such tracking servo devices, the magnetic head always performs good reproduction scanning on the track, and a reproduction signal with a maximum envelope can be obtained. In the prior art, in order to accurately track the magnetic head, the magnetic head is configured to be movable in the direction of the rotational axis using a magnetic-mechanical conversion element, and is therefore expensive.

On the other hand, in a VTR for general home use, the tracking servo device has an offset so that when the device is operating stably, the magnetic head reproduces and scans the track with its center along the center line of the track. being done. As a result of this, the magnetic head will be able to read and scan the tracks correctly, but if it is playing back a magnetic tape that was recorded on another machine, it will not be able to track the magnetic tape that was recorded on the own machine. There may be a slight deviation in position, and in such a case, the magnetic head may be likely to deviate from its tracking relative to the set offset amount.

, 4 are provided so that the user can adjust the center of the magnetic head so that the center line of the track coincides with the center line of the track.

Incidentally, in a home VTR, the magnetic head is used for both recording and reproduction, and the width of the track formed on the magnetic tape is therefore narrower than the track width of the magnetic head. In addition, the track width of commercially available magnetic tapes (soft tapes) on which information ID numbers are recorded by the manufacturer is V
Wider than the track width of a TR magnetic head. In this way, when reproducing a magnetic tape whose track width does not match the track width of the magnetic head, even if the center of the reproducing magnetic head deviates from the track center line, the amount of deviation is within a predetermined range ζ. Ah, n, l=', the reproducing magnetic head scans the track for reproduction, and good reproduction is performed.

However, the only way to judge whether or not the reproduction magnetic head is performing good reproduction scanning is by visually observing the monitor image.In order to obtain the best reproduction condition, the image quality of the monitor image must be adjusted by operating the knobs mentioned above. Deterioration or good image 5 (
Based on this result, the height is set to a state in which the center of the magnetic head and the center line of the track are estimated to coincide. Moreover, the image quality of the monitor image does not change with the amount of rubbing within the above-mentioned predetermined range, and even if the image quality is degraded by operating the knob, this image quality deterioration does not suddenly appear, so the center of the reproducing magnetic head is It is very difficult to match the center line of the track.

Furthermore, users usually do not adjust this knob. For this reason, when playing back a magnetic tape recorded on another device, even if the reproduced image is degraded in image quality due to tracking, the player will still be able to view the image as it is. To provide an auto-tracking device for a magnetic recording and reproducing device which solves such problems and enables the center of a reproducing magnetic head to surely match the center line of a track to obtain a reproduced image of the best quality. It is in.

In order to achieve the above object, the present invention provides an auxiliary head near the reproducing magnetic head, whose scanning locus coincides with that of the reproducing magnetic head, and whose azimuth angle is different from that of the reproducing magnetic head. Level comparing means for comparing the magnitude of the reproduction output level of the reproduction magnetic head and the auxiliary head, and detecting two points at which the magnitude relationship of the reproduction output level is reversed to detect the position of the center line of the track. A calculation means is provided.

[Effect]

At the start of playback, when the playback magnetic head and the auxiliary head are swung from side to side, the magnitude relationship of the playback output level of the head is reversed when it swings toward the blade side and when it swings toward the other side. The position where the magnitude relationship of these playback output levels is reversed is the edge of the track, and the position of the center line of the track is calculated from these positions.The offset value of the tracking control circuit is corrected using this calculated information. is,
The center of the reproducing magnetic head now coincides with the center line of the track.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an auto-tracking mechanism of a magnetic recording and reproducing apparatus according to the present invention, in which 1 is a reproducing magnetic head, 2 is an auxiliary head, 3a3b is a playback level detection circuit, and 4 is a level comparison circuit.

5 is a microprocessor, 6 is a memory, 7 is a tracking control circuit, 8 is a capstan motor, 9 is a control head, 10 is a signal reproducing circuit, 11 is a positive azimuth track, 12 is a negative azimuth track, 16 is a control track, 14 is magnetic tape.

In the figure, a magnetic tape 14 (on which FM-modulated information signals are recorded such that every other track and every other track have different azimuth angles; The track 11 has a positive azimuth angle and is called a positive azimuth track, and the other every other track 12 has a negative azimuth angle and is called a negative azimuth track.
In this embodiment, a pair of recording/reproducing magnetic heads is provided, and one of these magnetic heads has a positive azimuth track number, etc. 7,8.

The azimuth angle is equal to the azimuth track. Here, a magnetic head with a positive azimuth angle (positive azimuth head) is shown as a reproducing magnetic head 1.

Furthermore, although it is assumed here that the width of the tracks 11 and 12 is wider than the track width of the magnetic head, the opposite may be true.

Near the reproducing magnetic head 1 (this is the auxiliary head (negative azimuth head 2) with the same track width and negative azimuth angle)
, so that the scanning trajectory matches that of the reproducing magnetic head 1 (here,
It is provided.

At the start of reproduction, the tracking control circuit 7 uses the control signal reproduced by the color control head 9 of the control track 13 of the magnetic tape 14.
The phase of the cab stan motor 8 is controlled so that the reproducing magnetic spatula 1°1 regenerates the positive azimuth track 11. An offset value for aligning the center of the reproducing magnetic head 1 with the center line of the positive azimuth track 11 is set in the dragging control circuit 7 . Therefore, in general,
The reproduction magnetic head 1 has a positive azimuth track 1 at its center.
These positive azimuth tracks 11 are scanned for reproduction so that their centers coincide with the center lines of the negative azimuth tracks 12, and the other reproduction magnetic head (not shown) also scans these negative azimuth tracks 12 so that their centers coincide with the center lines of the negative azimuth tracks Play and scan.

The reproduction signals from the reproduction magnetic head 1 and the auxiliary head 2 are supplied to reproduction level detection circuits 5a and 3b, respectively, and their levels are detected, and the magnitudes of these levels are compared by a level comparison circuit 4.

Now, looking at the reproduction signal levels of the reproduction magnetic head 1 and the auxiliary head 2, as shown in FIG. 2(B), the centers of these heads 1.2 coincide with the center line of the positive azimuth track 11. At times, the reproduction signal level of the reproduction magnetic head 1 is maximum and the reproduction signal level of the auxiliary head 2 is zero, and as shown in FIGS. 2(A) and 2(C), the centers of these heads 1 and 2 are When ζ coincides with the boundary line between the positive azimuth track 11 and the negative azimuth track 12,
The reproduction signal levels of these heads 1.degree. 2 become equal. Then, from the state shown in Fig. 2 03), the head 1.2
When deviates to the left with respect to the positive azimuth track 11ζ,
The reproduction signal level of the reproduction magnetic head 1 gradually decreases, and the reproduction signal level of the auxiliary magnetic head 2 gradually increases, as shown in FIG.
After these reproduction signal levels become equal in state 4),
The reproduction signal level of the auxiliary head 2 becomes higher than the reproduction signal level of the reproduction magnetic head 1. FIG. 2(B) (The same applies to the case where the state shown in FIG. is shown by a solid line and a dashed-dotted line.However, in the figure, A on the horizontal axis.

The reproduced signal levels at points B and C are shown in FIG. 2 (5), respectively.

(B) and (C) are the reproduced signal levels in the state shown.

When the tracking servo by the tracking control circuit 7 is almost stabilized by the start of playback, the microprocessor 5 controls the tracking control circuit 7 to control the capstan motor 8 to perform playback for one period during which the playback magnetic head 1 scans the magnetic tape 14. The magnetic head 1 and the auxiliary head 2 are integrated (swinged left and right about one track pitch) only once.The reproduction signal level of the reproduction magnetic head 1 and the auxiliary head 2 is then as shown in Fig. 3. However, when these heads 1.2 are displaced to the left from the state shown in FIG. Invert,
Further, when these heads 1.2 swing in the opposite direction and are displaced to the right from the state shown in FIG. are reversed in the same direction. The level is reversed from high to low when the output level of the level comparison circuit 4 is high when the reproduction signal level of the reproduction magnetic head 1 is higher than the reproduction signal level of the auxiliary head 2.

The microprocessor 5 operates during the scanning period of the magnetic tape in which the reproducing magnetic head 1 and the assistant head 2 are swung as described above.
The above-mentioned inversion of the output level of the level comparison circuit 4 is detected, and the positive azimuth track 1
1. Calculate the positions of both edges of
The position of the center line is calculated, and the offset value set in the tracking control circuit 7 is corrected using the obtained center line position information. As a result, the tracking control circuit 7
controls the capstan motor 8 so that the reproduction magnetic head 1 performs reproduction scanning so that its center coincides with the center line of the positive azimuth track 11.

Reproduction signals from the reproduction magnetic head 1 and the auxiliary head 2 are supplied to a signal reproduction circuit 10 and subjected to reproduction processing. The reproduction signal of the auxiliary head 2 is used for special reproduction and the like.

Note that the reproducing magnetic head 1 and the auxiliary head 2 can be a single double azimuth head.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to automatically obtain the best tracking state in which the center of the reproducing magnetic head coincides with the center line of the track from the start of reproduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an auto-tracking device for a magnetic recording/reproducing apparatus according to the present invention, and FIG. 2 is a diagram showing an example of positional deviation of the reproducing magnetic head and the auxiliary head in FIG. 1 with respect to the track. , FIG. 3 is a diagram showing changes in the reproduction signal level with respect to the positional deviation between the reproduction magnetic head and the auxiliary head. 1... Reproducing magnetic head 2... Sode assistant head 5a, 3
b...Reproduction level detection circuit 4...Level comparison circuit 5...Microprocessor 6...
...Memory 7...Tracking control circuit

Claims (1)

[Claims] 1. A magnetic tape on which information signals are recorded with different azimuth angles between every other track and every other track is read back and scanned with a playback head having a track width different from that of the track, and In a magnetic recording and reproducing device configured to reproduce an information signal, an auxiliary head is provided near the reproducing head and having an azimuth angle with respect to the track on which the signal is not reproduced by the reproducing head, in the longitudinal direction of the reproducing head and the track. a level comparison circuit that compares the level of the reproduction signal of the reproduction head and the auxiliary head; and a level comparison circuit that detects two different points at which the magnitude relationship of the levels is reversed and reproduces the reproduction signal from the two points. and an arithmetic unit for detecting the centerline position of the track scanned by the head, and by setting the centerline position data in a tracking control circuit, the playback head can be set to an optimal tracking state. Features: Auto-tracking device for magnetic recording and reproducing devices.