JPH03295016A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To control the position of a magnetic head with high accuracy, and also, extending over a wide range by detecting a variation of inductance of a coil depending on a distance of a conductive member moved simultaneously with a magnetic head and a detection coil opposed thereto, at the time of special reproduction. CONSTITUTION:In the case of executing special reproduction, when a control voltage corresponding to a moving amount of a magnetic head 1 determined in advance in every mode is supplied to a bimorph element 2 through a slip ring 5, and the head 1 and a conductive member 7 are moved, a distance of the member 7 and a detection coil 8 is varied. The variation quantity of inductance of the coil 8 is varied like an exponential function in accordance with the distance of the member 7 and the coil 8. Therefore, an exponential function- like output of a detector 11 for detecting a variation of the inductance is linearized by a linearity correcting device 12, and supplied to a control circuit 14 through an output changeover switch 13. In such a way, the moving amount determined in advance in every mode can be controlled with high accuracy, and also, stably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording/reproducing device capable of moving a magnetic head in a direction perpendicular to a recording track.
(hereinafter abbreviated as VTR), etc.

BACKGROUND OF THE INVENTION Traditionally, VTRs using helical scanning recording systems tilt the rotating direction of the drum and the running direction of the magnetic tape, and run the magnetic tape so that it is wrapped around a cylindrical drum. By rotating the magnetic tape, a predetermined inclination angle is formed with respect to the tape running direction, and a video signal is recorded on the magnetic tape.

With the above configuration, slow motion playback and quick motion
When performing special playback such as playback, the trajectory of the magnetic head changes with respect to the recording track on the magnetic tape, since the signal recorded at a tape running speed different from that during recording is played back.
It becomes difficult to trace the recording track completely. FIG. 4 shows a tape pattern diagram illustrating the locus of the magnetic head on the magnetic tape. 21 is a head trajectory during recording or normal reproduction. The head trajectory 21 is synthesized by a tape speed vector 22 and a magnetic head speed vector 23 caused by the rotating drum.

When the tape running speed changes, for example, when the tape speed quadruples, the head trajectory 25 becomes a composite of the tape speed vector 24 and the magnetic head speed vector 23 caused by the rotating drum, and several times at - degrees. passes over the recorded track, causing noise on the playback screen. To solve this problem, a head moving means using a bimorph element has been developed to move the magnetic head in the direction of arrow 26 and completely trace the recording track.

An example of a conventional magnetic recording/reproducing device incorporating the above-mentioned head moving means will be described below with reference to the drawings. FIG. 5 is a sectional view of a drum showing the structure of a head moving means using a conventional piezoelectric element. 1 is a magnetic head, 2 is a bimorph element which is a head moving means with a magnetic helad 1 fixed to its tip, 3 is a rotating drum to which the bimorph element 2 is fixed and is rotated at a constant number of rotations, and 4 is fixed to the VTR body. 5 is a slip ring for supplying a driving voltage to the bimorph element 2, and 6 is a magnetic tape wound around the drums 3 and 4 at a predetermined inclination.

The operation of the magnetic recording/reproducing apparatus configured as described above will be described below. When performing special playback such as slow motion scene playback or quick motion scene playback where the tape running speed is different from that during recording, the amount of movement of the magnetic head 1 is set so that the magnetic head 1 completely traces the recording track. A control voltage corresponding to the amount of movement is supplied to the bimorph element 2 via the slip ring 5. Due to the control voltage, the bimorph element 2 is deformed in the direction shown by the arrow,
The magnetic head 1 on the bimorph element 2 moves. That is, the amount of movement of the magnetic head 1 is set in advance according to each mode of special reproduction, and the recording track is traced by moving the magnetic head 1 by the amount of movement.

Problems to be Solved by the Invention However, in the above configuration, since the position of the magnetic heald 1 is not detected, hysteresis of the moving means 2,
Due to external vibrations, temperature changes, etc., the applied voltage and the amount of head movement do not match, causing an error between the target position and the actual position, making it difficult for the magnetic head 1 to completely trace the recording track. Met.

Furthermore, when a signal recorded using the above magnetic head is normally reproduced, the error during recording and the error during normal reproduction are added together, and the above error is doubled, causing a problem in that the reproduced image is significantly degraded. Therefore, it is necessary to separately provide fixed magnetic heads for recording and normal playback, and the cost is high because a total of 4 magnetic heads are used, 2 fixed magnetic heads for recording and normal playback, and 2 magnetic heads for special playback. This was a major factor in the increase.

Means for Solving the Problems In order to solve the above problems, a magnetic recording/reproducing apparatus of the present invention includes a rotating drum for rotating a magnetic head, and a head moving means for movable the magnetic head in a direction orthogonal to a recording track. a conductive member moved simultaneously with the magnetic head by the head moving means; a detection coil disposed at a position facing the conductive member; a detector that detects the amount of change due to a change in the inductance of the coil; a linearity correction device that corrects the linearity of the output of the detector;
An output switching means for switching between the output of the detector and the output of the linearity corrector according to each mode of recording and reproduction, and a position control means for controlling the position of the magnetic head by the output of the output switching means. It is something that

According to the above-described structure, the present invention has a conductive member that is moved at the same time as the magnetic head and a position opposite to the conductive member during special playback that requires accurate and wide-range position control. The position of the magnetic head can be determined with high precision by detecting the exponential change in inductance of the coil, which depends on the distance of the detection coil, and using the output linearized by the linearity corrector. , and
It becomes possible to control over a wide range.

In addition, recording that requires extremely high precision fixed position control,
During normal playback, by using only the portion of the exponential output output from the detector with high detection sensitivity, it is possible to control the position of the magnetic head to a completely fixed position.

Therefore, it is possible to use the same magnetic head for each mode of recording and reproduction, such as recording, normal reproduction, and special reproduction, and the cost of the apparatus can be reduced.

Example Below, regarding a magnetic recording and reproducing device according to an example of the present invention,
This will be explained with reference to the drawings.

FIG. 1 is a sectional view of a drum of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. 1 is a magnetic head, 2 is a bimorph element with magnetic head 1 fixed to the tip, and 3 is bimorph element 2.
4 is a fixed drum fixed to the VTR main body, 5 is a slip ring that supplies a driving voltage to the bimorph element 2, and 6 is a drum 3. 4 is a magnetic tape wound at a predetermined inclination, and 7 is fixed to the bimorph element 2 with a diameter of 8 mm.
1 Disc-shaped conductive member made of steel material with a thickness of 1 mm, 8
is a wire rod with a wire diameter of 0.16 mm fixed on a rotating drum 3 wound 10 turns, with an inner diameter of 3 mm and an outer diameter of 4 mm.
This is a detection coil with a thickness of 2 mm. Next, FIG. 2 shows a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. Components that are the same as those shown in FIG. 1 are designated by the same reference numerals and their description will be omitted. 11 is a detector consisting of a high frequency oscillator, a bridge circuit, a detection circuit, an amplifier, etc. in order to detect a change in the inductance of the M output coil 8 depending on the distance between the conductive member 7 and the detection coil 8; 12 is a detector of the detector 11; a linearity corrector consisting of a logarithmic amplifier circuit for correcting the linearity of the output; 13 is an output selector switch that outputs the output of the detector 11 during recording and normal playback, and takes out the output of the linearity corrector 12 during special playback; 14; is a position control circuit that controls the position of the magnetic head 1 based on the output of the output changeover switch 13.

The operation of the magnetic recording/reproducing apparatus configured as described above will be described below. When performing special playback such as slow motion/yong playback or quick motion playback, a control voltage is applied according to the amount of movement of the magnetic helad 1, which is predetermined for each mode, so that the recording track is completely traced. is supplied to the bimorph element 2 via the slip ring 5, the magnetic heald 1 and the conductive member 7 are moved, and the distance between the conductive member 7 and the detection coil 8 is changed.

Further, the high frequency current applied to the detection filter 8 generates an eddy current in the conductive member 7, and the inductance of the detection coil 8 changes due to this eddy current.

The amount of change in inductance is determined by the conductive member 7 and the detection coil 8.
There is a correlation with the distance of , resulting in an exponential characteristic as shown in FIG. Therefore, since the output of the detector 11 that detects this change in inductance becomes an exponential output, it is linearized by the linearity corrector 12 so that the position of the magnetic herad 1 can be controlled stably over a wide range. , is supplied to the control circuit 14 via the output selector switch 13, and the amount of movement predetermined for each mode is supplied to the control circuit 14 with high precision, and
Stable control.

Next, when performing recording and normal reproduction, in order to maintain a perfect recording and reproduction state, the magnetic head 1 is attached to the magnetic tape 6.
It is necessary to keep the position perfectly constant. For this reason, the target position is set to a region where the detection sensitivity of the exponential output of the detector 11 is low, for example, near the point X in FIG. 3, and the output changeover switch 13 controls the exponential output of the detector 11. It is supplied to the circuit 14 and controlled to keep the position of the magnetic helad 1 at a completely constant position. At this time, since the position control of the magnetic head 1 is a fixed position control, the non-linearity of the detector 11 is not a problem at all, and the position detection sensitivity of the detection coil 8 is several times the detection sensitivity during special reproduction. It becomes possible to detect the position of the magnetic head 1 with very high precision, and the position of the magnetic head 1 relative to the magnetic tape 6 can be kept completely constant.

In the above embodiment, a bimorph element is used as the moving means, but similar effects can be obtained with other moving means such as a moving magnet type or a moving coil type. In addition, although changes in inductance were detected as the output of the detector 11, the output changes exponentially even if a change in impedance due to a change in inductance or a change in resonant frequency is detected in a resonant circuit. If so, it will be possible to obtain the same effect.

Effects of the Invention As described above, according to the present invention, a rotating drum for rotating a magnetic head, a head moving means for movable the magnetic head in a direction orthogonal to a recording track, and a rotating drum for rotating the magnetic head by the head moving means. A conductive member that is moved at the same time, a detection coil that is disposed at a position facing the conductive member, and an amount of change due to a change in the inductance of the coil that depends on the distance between the conductive member and the detection coil. A detector for detecting, a linearity corrector for correcting the linearity of the output of the detector, and an output switching means for switching between the output of the detector and the output of the linearity corrector according to each mode of recording and reproduction. and a position control means for controlling the position of the magnetic head by the output of the output switching means, so that the magnetic detecting an exponential change in inductance of the coil depending on the distance between a conductive member that is moved simultaneously with the head and a detection coil disposed at a position facing the conductive member;
By using the output linearized by the linearity corrector, it becomes possible to control the position of the magnetic head with high precision over a wide range.

In addition, recording that requires extremely high precision fixed position control,
During normal playback, by using only the portion of the exponential output output from the detector with high detection sensitivity, it is possible to control the position of the magnetic head to a completely fixed position.

Therefore, it is possible to use the same magnetic head for each mode of recording and reproduction, such as recording, normal reproduction, and special reproduction, and the cost of the apparatus can be reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a drum of a magnetic recording/reproducing device according to an embodiment of the present invention, FIG. 2 is a block diagram of a magnetic recording/reproducing device according to an embodiment of the present invention, and FIG. 3 is a diagram showing inductance and conductivity of a detection coil. A characteristic diagram showing the relationship between the distance between the member and the detection coil, FIG. 4 is a tape pattern diagram showing the locus of the magnetic head on the magnetic tape, and FIG. 6 shows the configuration of a conventional head moving means using a piezoelectric element. FIG.

Claims (1)

[Scope of Claims] A rotating drum that rotates a magnetic head, a head moving means that allows the magnetic head to move in a direction perpendicular to a recording track, and a conductive drum that is moved simultaneously with the magnetic head by the head moving means. a member; a detection coil disposed at a position facing the conductive member; a detector for detecting an amount of change due to a change in inductance of the coil depending on a distance between the conductive member and the detection coil; a linearity corrector for correcting the linearity of the output of the detector; an output switching means for switching between the output of the detector and the output of the linearity corrector according to each mode of recording and reproduction; A magnetic recording/reproducing device comprising: position control means for controlling the position of the magnetic head by output.