JPH0832002B2 - Slow playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applied to improve reproduction image quality in, for example, a video tape recorder (hereinafter referred to as VTR), and is provided on a rotary drum. The present invention relates to a slow reproducing device in which the head can be displaced in the width direction of the magnetic tape, and the head locus during slow reproduction is traced faithfully to the locus during recording.

[Prior Art] FIG. 10 is a vertical cross-sectional view of a rotary drum in a conventional slow speed reproduction device. In FIG. 10, (1) is a rotary shaft,
(2) is a fixed lower drum, (3) is a rotating upper drum,
(4) is a head mounted on the upper drum (3) so as to be detachably attached, (5) is a head fixed to the tip of the head (4), and (6) is attached to the lower drum (2). On the other hand, a bearing that supports the rotating shaft (1) in a freely rotatable manner,
(7) is an upper transformer that rotates together with the upper drum (3), (8) is a fixed lower transformer, (9) is a pedestal supported by the rotating shaft (1) and carrying the upper drum (3), (13) is a magnetic tape.

The configuration of each of the above units will be described in more detail as follows.

The head (5) is fixed and held at a fixed position with respect to the upper drum (3), and the tip of the head (5) slightly protrudes from the outer periphery of the upper drum (3), and the connecting portion (10) and the wiring board (1).
1) It is electrically connected to the upper transformer (7) via the connection section (12). The upper drum (3) is rotated at a constant high speed, and the magnetic tape (13) is wound slightly obliquely around the outer peripheral surfaces of the upper drum (3) and the lower drum (2) and runs at a predetermined speed. . The head (5) contacts the magnetic tape (13) to magnetically record or reproduce a video signal or an audio signal.

The upper transformer (7) is attached to the pedestal (9) and rotates together with the pedestal (9). The lower transformer (8) faces the upper transformer (7) at a small interval, whereby the upper and lower transformers (7) and (8) are magnetically coupled and transmit signals to each other. The lower transformer (8) is connected to a control circuit (not shown) provided outside.

Moreover, in FIG. 10, (75) is a magnet attached to the upper drum (3), and (18) is a rotational position for detecting the magnetic line of the magnet (75) to detect the rotational position of the upper drum (3). It is a detector.

 Next, the operation of the above configuration will be described.

The head (5) diagonally crosses the magnetic tape (13) by the running of the magnetic tape (13) and the rotation of the head (5). These transverse lines are parallel to each other, as shown in FIG. In FIG. 11, (13a) is the trajectory of the magnetic tape (13), (V1) is the normal feeding speed of the magnetic tape (13),
(5A) is the trajectory of the head (5), (V0) is the rotation speed of the head (5), and the trajectory (13a) of the magnetic tape (13) and the trajectory (5A) of the head (5) are as shown in the figure. Intersects with.

Therefore, the relative locus drawn on the magnetic tape (13) by the head (5), that is, the above-mentioned transverse cutting line becomes (A) as shown in FIG. 11 (a), and the interval (P) is the track pitch. By the way, the feed speed (V1) at the time of still reproduction is 0, and the crossing line (Ao) is the head (5).
Matches the trajectory (5A) of. The relative locus of the head (5) with respect to the magnetic tape (13) at the time of slow reproduction in which the feeding speed of the magnetic tape (13) decreases from (V1) to (V1 / 4) is shown in FIG. 11 (b). Like (As). In this way, when the magnetic tape (13) is reproduced at a speed different from the normal speed (V1), for example, in the case of still reproduction, slow reproduction, high-speed search reproduction, the head (5) is the recording locus. If it is not accurately tracked, it will be displaced, and the signal level at which the head (5) picks up will be low, and it will be difficult to obtain a clear reproduced image and reproduced sound.
It causes noise and blurring.

As one of the solutions to such a problem, conventionally,
As disclosed in Japanese Examined Patent Publication No. 58-40874, there has been proposed one capable of performing slow reproduction in which the feeding speed of the magnetic tape is reduced to 1/2 of the normal speed in a state with less noise and blurring. This is a normal tape feed speed 1/2
Although it is possible to suppress the occurrence of noise and blur only during slow reproduction corresponding to the above, the above problems cannot be solved during slow reproduction at a speed lower than that.

Further, in order to solve the problem at the time of slow reproduction at 1/2 speed or less, as described in JP-A-57-17081, a capstan motor for driving a magnetic tape is intermittently driven. It has been known that a truck is configured to move one pitch in one field.

[Problems to be Solved by the Invention] In the conventional slow playback device configured as described above, the operation is repeated when the track is moved by one pitch during one field and then stopped. There is a problem in that the time axis of the vertical synchronizing signal and the horizontal synchronizing signal of the reproduced signal fluctuates due to the uneven rotation of the capstan motor, and the screen vibrates.

The present invention has been made in order to solve the above-mentioned problems, and can stably perform tape running even at an arbitrary speed of 1/2 or less of a normal tape feeding speed to obtain a high quality image with less blur and noise on the screen. An object of the present invention is to provide a slow playback device capable of obtaining a slow playback image.

[Means for Solving the Problems] A slow reproducing device is a pair of rotary heads for reproducing a video signal recorded on a magnetic tape, and a drive adapted to displace the rotary heads in the width direction of the magnetic tape. A rotary drum having a section, a capstan motor for driving the magnetic tape, a rotary pulse generator for outputting a pulse train proportional to the rotation speed of the capstan motor, and a time corresponding to a head switching signal. And a phase comparison circuit for outputting the voltage signal corresponding to the phase difference between the head switching signal and the phase signal while generating the voltage signal according to the phase signal recorded on the magnetic tape. , The voltage is not applied to the capstan motor for a predetermined time from the predetermined pulse edge in synchronization with the pulse edge of the pulse train, After that, a control circuit for applying the output of the phase comparison circuit to the capstan motor is provided until the next pulse edge, and the capstan motor is intermittently driven.

[Operation] According to the present invention, the head is magnetically displaced in the width direction of the tape in cooperation with the coil by supplying a control current from the outside to the drive section, whereby the head locus during reproduction is obtained. It is possible to match the recording track.

In addition, by driving the capstan motor with a pulse train that is inactive for a certain period of time in synchronization with the rotation speed of the capstan motor, low-speed rotation can be stably controlled, and the head switching signal By controlling the phase between the circumferential signal and the phase signal recorded on the tape, more stable slow reproduction can be performed.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing a main part of a rotary drum which is a constituent element of a slow speed reproducing device according to an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a vertical section showing the main part in more detail. FIG. 4 is a bottom view of FIG. 3, and in each of these drawings, (1) to (3) and (5) to (13) have the same structure as the conventional device shown in FIG. Therefore, the same reference numerals are given.

In FIGS. 1 and 2, (4a) is a drive unit for carrying the head (5) and displacing the head (5) in the width direction of the tape, and (14) is a drive current for the drive unit (4a). A non-rotating contactor for supplying, (15) a rotating electrode provided on a part of the pedestal (9) so as to make sliding contact with the contactor (14),
Reference numeral (16) is a connection portion for electrically connecting the electrode (15) to the drive portion (4a) via the wiring board (11).

In the main part shown in FIGS. 3 and 4, (41) is a non-magnetic leaf spring having a head (5) attached to the tip, (42)
Is a cylindrical coil mounted on a leaf spring (41), (43)
Is a cylindrical permanent magnet that causes a magnetic reaction to move the cylindrical coil (42) up and down, and (44) is a strong magnet mounted on the upper drum (3) that carries the cylindrical permanent magnet (43). The magnetic yoke (45) is a ferromagnetic plate attached to the yoke (44) to form a magnetic closed circuit together with the cylindrical permanent magnet (43). The ferromagnetic plate (45) extends in a direction away from the head (5) and has an attachment portion (45a) formed on the extension thereof. (46) is a screw for attaching the leaf spring (41) to the attachment portion (45a), (47) is a spacer, (48) is a washer, (49) is a screw for attaching the yoke (44) to the upper drum (3), (50) is a recess formed in the upper drum (3) for accommodating the drive section (4a).

The free end of the leaf spring (41) is movable up and down, and the cylindrical coil (42) carried by the leaf spring (41) includes a cylindrical permanent magnet (43) and a ferromagnetic plate (45). It is arranged in an annular gap formed between and can be displaced up and down,
An appropriate magnetic flux is generated in the coil (42) by passing a control current through the cylindrical coil (42), and the coil (42) is vertically displaced by the interaction with the permanent magnet (43). The leaf spring (41) is deformed along with the vertical displacement of the coil (42) so that the head (5) can be displaced in the width direction of the tape.

A round hole (52) for centering is formed substantially in the center of the leaf spring (41), and a cylindrical jig (53) is inserted into the round hole (52) to align with a cylindrical permanent magnet (43). As a result, the cylindrical coil (42) can be centered and positioned on the annular gear formed between the cylindrical permanent magnet (43) and the ferromagnetic plate (45). By tightening the screw (46) in this state, the drive unit (4a) is assembled as a unit.

The drive unit (4) thus assembled as a unit
a) is installed in the recess (50) of the upper drum (3) with screws (49). At this time, the amount and posture of the head (5) protruding from the outer peripheral surface of the upper drum (3) must be adjusted correctly. Therefore, two head position adjusting holes (51a), (51b), (51c) are provided in the upper drum (3). The four points including these three holes (51a), (51b), (51c) and the head (5) are arranged in a cross shape. A drive unit mounting hole (49a) is formed radially inward from the intersection of the cross-shaped arrangement by a distance (l), and the yoke (44) is screwed through the hole (49a) into the upper drum (3). ) Is attached to the specified condition. After that, position adjusting wedges are inserted into the head position adjusting holes (51a) to (51c) to generate a rotational force at the holes (51a) and (51b) to adjust the posture, and at the hole (51c), the head ( Adjust the protrusion amount of 5). Thereby, the position of the driving section (4a) with respect to the upper drum (3) becomes accurate. If necessary, further tighten the screw (49) in this state.

As described above, between the permanent magnet (43) and the ferromagnetic plate (45) in the high magnetic flux magnetic closed circuit composed of the permanent magnet (43), the yoke (44), and the ferromagnetic plate (45). The cylindrical coil (42) located in the annular gear of (4) can apply a magnetic force to the permanent magnet (43) by its control current to displace the leaf spring (41). )
In order to prevent the magnetic flux leaking toward, the mounting portion (45a), which is an extension of the ferromagnetic plate (45), is arranged farther from the head (5).

 Next, the operation of the above configuration will be described.

For example, if the tape feed speed (VS) is the normal feed speed (V
Magnetic head (5) for 1/4 of slow playback
When the head is moved from the fixed position in the direction of the arrow (T) in FIG. 11C, that is, in the width direction of the tape to change the trajectory of the head (5) from (5A) to (5B), the tape (13) The relative locus between the head and the head (5) coincides with the relative locus (A) at the time of recording. Even if the tape feed speed is other than the above-mentioned tape feed speed, by moving the head by about P (1-VS / V1) during one field in correspondence with the tape feed speed, the relative locus (as in the above) ( It can be matched to A).

FIG. 5 is a control circuit diagram of the rotary drum having the above-mentioned configuration. In the figure, the head is divided into two systems (5a) and (5b), and accordingly, all the constituent elements of each part (a),
The subordinate code of (b) is attached.

In FIG. 5, (61a) and (61b) are periodic signal generators controlled by a switching signal. The switching signal is detected by the magnet (75) attached to the movable part (74) and the position detection head (76) to detect the mechanical position of the movable part (74), and the switching signal generator (77) is detected accordingly. Created by.

The outputs of the periodic signal generators (61a) and (61b) are operational amplifiers (64a) and (64b), differential amplifiers (69a) and (69b),
Current limiters (65a), (65b), resistors (62a), (63a),
(68a), (70a), (62b), (63b), (68b), (70
b) and the capacitors (71a) and (71b) are supplied to the drive circuit. The output of this drive circuit, that is, the control current, is passed through the contactors (14-1), (14-3), electrodes (15-1), (15-3) on the individual control side to the coils (42a), ( 42
supplied to b). The non-control side terminals of the individual coils (42a) and (42b) are made common, and a reference potential is provided via a pair of common side electrodes (15-2) and common side contacts (14-2). It is connected to the. The control current is controlled by the individual coils (42
The magnetic field generated by being supplied to a) and (42b) causes a magnetic reaction with the cylindrical permanent magnet (43), causing mechanical displacement in the individual heads (5a) and (5b). Let
The displacement amount is controlled so that the head locus during reproduction matches the recording locus on the magnetic tape. Further, the control current is supplied to the coils (42a) and (42b) even when the heads (5a) and (5b) are not in contact with the magnetic tape. The signals reproduced by the individual heads (5a) and (5b) are transferred from the movable section (74) to the head amplifier by the electrode conversion action between the upper transformers (7a) and (7b) and the lower transformers (8a) and (8b). (72
a) and (72b), the output of which is output as a reproduction signal via a signal processor (78) via a switch (73) which is switched by a switching signal.

The current limiters (65a) and (65b) are window comparators (66a) and (66b) and current limiting means (67), respectively.
It consists of a) and (67b).

Also, the resistors (63a), (63b), (70a), (70
b), capacitors (71a), (71b), coils (42a),
(42b) is the resistance value of resistors (63a) and (63b)> resistance (70
The resistance values of a) and (70b), the impedances of the capacitors (71a) and (71b)> the resistance values of the coils (42a) and (42b) are set to have a relation.

Next, the operation of the rotary drum control circuit will be described.

The drive circuit has resistors (68a), (6
8b) voltage across the coil, that is, the current flowing through the coils (42a) and (42b) is detected by the differential amplifiers (69a) and (69b), and a loop that performs current feedback operation, and capacitors (71a) and (7b).
It has two feedback loops, a loop for performing voltage feedback operation via 1b).

When the frequency is high, the impedance of the capacitors (71a) and (71b) approaches zero. Therefore, the voltage feedback operation becomes dominant over the current feedback operation, and the voltage drive operation is performed. On the other hand, when the frequency is low, the capacitor (71a),
The impedance of (71b) approaches ∞. Therefore,
The current feedback operation becomes dominant over the voltage feedback operation, and the current feedback operation is performed. Here, the relationship between the drive fundamental frequency of the heads (5a) and (5b) cooperating with the coils (42a) and (42b) and the mechanical resonance frequency of the movable part (74) is: drive fundamental frequency <machine of drive part Resonance frequency. Therefore, output impedance is small at both ends of coil (42a), (42b) when voltage drive with small output impedance by current drive near drive fundamental frequency and voltage drive near resonance frequency. Short circuit braking is performed by absorbing the counter electromotive force.

The following circuit constants are selected in order to eliminate the difference in gain between the current driving operation and the voltage driving operation.

Gain of differential amplifier (69a) = resistance value of coil (42a) / resistance (68a) Gain of differential amplifier (69b) = resistance value of coil (42b) / resistance (68b) Also, window comparator (66a), (66b), current limiter (65a), (67b)
a) and (65b) are resistors (68a) and (68) inserted on the control side.
The voltage across both ends of b), that is, the current flowing through the coil, is detected and the displacement of the heads (5a) and (5b) is calculated as follows: | desired speed −1 | × track pitch <head displacement limit <
It is configured to limit the control current so that it is a structural displacement limitation of the head.

FIG. 6 shows an outline of the slow playback device, in which (700) is the control circuit of FIG. 5, and (800) is the upper drum (3) and the lower drum (2) shown in FIG. The rotating drum, (80) is a capstan, (82) is a pinch roller, and the capstan (80) and the pinch roller (82) press the magnetic tape (13) to drive it. (8
1) is a capstan motor, which has a drive control circuit, which will be described later, built therein, and performs torque control in proportion to the voltage applied to the terminal (83). (84) is a rotary pulse generator, which is attached to the capstan motor (81) and has a terminal (8
Output pulse to 5).

FIG. 7 shows a control circuit for low speed rotation of the capstan motor (81), which realizes variable speed slow reproduction of 1 / N, and the rotation pulse generator (84).
A drive wave is generated by the pulse output from the.

Hereinafter, a specific configuration of the control circuit shown in FIG. 7 will be described together with its operation.

A rotation pulse is output from an output terminal of a rotation pulse generator (84) connected to the capstan motor (81).
The number of rotation pulses is proportional to the number of rotations of the capstan motor (81).

For example, if the capstan motor (81) is rotated once per second and n rotation pulses are output per rotation, 1
Since one second corresponds to 60 fields, one field has n /
With 60 pulses, a rotation pulse having a waveform as shown in FIG. 8 (a) is output.

The rotation pulse (a) output from the terminal (85) is passed through one input terminal of the next stage EXCLUSIVEOR gate (104) and the delay circuit composed of the resistor (105) and the capacitor (106). It is led to the other input terminal of the EXCLUSIVE OR gate (104). From the output terminal of the EXCLUSIVE OR gate (104), a pulse is output in synchronization with the rising and falling edges of the rotation pulse (a). The monostable multivibrator (101) is a device for outputting a pulse having a predetermined width as shown in FIG. 8 (b) from the rising edge of a rotation pulse which is an input signal, and the width of the pulse (b) is the above-mentioned monostable multivibrator. It is determined by the time constants of the mono-multi adjustment volume (102) and the capacitor (103) connected to the vibrator (101).

Then, the output pulse (b) of the mono-multivibrator (101) passes through the resistor (108) and the transistor (110).
Entered in the base of. At this time, if the output of the mono-multivibrator (101) is at high level, the transistor (110) is turned on and the terminal (83) is grounded. Further, when the output of the mono multivibrator (101) is at low level, the transistor (110) is off. At this time, the potential of the terminal (83) is the transistor (119),
It is determined by the resistances (109) and (118).

On the other hand, when the head switching signal having the waveform as shown in FIG. 9 (d) is input to the terminal (91) and the set speed for slow reproduction is 1 / N, the head switching signal (d)
Is divided by N by a frequency divider (111). The frequency-divided signal, that is, the output signal of the frequency divider (111) having the waveform as shown in FIG.
12) is entered. Here, when the divided signal (e) is at a high level, the transistor (112-1) is turned on, the capacitor (112-2) is discharged, and the divided signal (e) becomes high. When the level changes to low level, the transistor (112-1) turns off and the capacitor (11
2-2) starts charging.

Further, a phase signal (g) recorded for each frame on the tape, for example, a control signal in a VTR is input to the terminal (90), and when this signal becomes high level, the switch (112-3) is turned on, Next stage condenser (112−
The potential is introduced to 4). The output voltage from the sample-hold circuit (112) changes according to the phase difference between the phase signal (g) shown in FIG. 9 (g) and the divided signal (e). For example, the operating voltage of the sample hold circuit (112) in the case of 1/4 slow is as shown in FIG. 9 (h).

The output signal (h) of the sample-hold circuit (112) is generated by the resistors (113), (114) and (115) and the bias power supply (116).
And an operational amplifier (117), and is input to the base of the transistor (119). When the base potential of the transistor (119) is high when the transistor (110) is OFF, the potential of the terminal (83) is low, and when the base potential of the transistor (119) is low, the terminal (83) is high. The potential of becomes high. That is, when the phase difference between the signal (e) obtained by dividing the head switching signal (d) by N and the phase signal (g) on the tape is small, the potential of the terminal (83) becomes low, and when the phase difference is large, the terminal (83) becomes large. The potential of (83) becomes high. When the potential of this terminal (83) becomes higher, the rotation speed of the capstan motor (81) becomes higher,
When the potential of the terminal (83) becomes lower, the rotation speed of the capstan motor (81) becomes lower, so the head switching signal (d) is divided by N (e) and the phase signal (g) on the tape. It is possible to control the phase between and.

As described above, the speed of the capstan motor (81) can be stably controlled by keeping the non-driving time constant, and the head switching signal (d) is divided by N (e) and the phase on the tape. By controlling the phase with the signal (g), more stable slow reproduction can be realized.

1 to 4, only one head (5) is shown on the upper drum (3) for the sake of simplification of description, but another head (5) is opposed to the upper drum (3). A magnetic head is fitted and these two magnetic heads (5
The control circuit for a) and (5b) is shown in FIG.
Each two of the four contactors supplies a control current to the cylindrical coils (42a), (42b) of the drive unit of the respective magnetic head.

Although the electrode (15) is shown as being integrated with the pedestal (9), it may not be integrated.

[Effects of the Invention] As described above, according to the present invention, the head is controlled so as to be changed in the width direction of the tape, so that the head is always accurately moved along the recording locus even at an arbitrary tape feeding speed. Tracing is possible, and a reproduction signal of a predetermined level can be obtained regardless of the tape feeding speed.
Moreover, the capstan motor that controls the tape running drive is made non-driving for a certain time from a predetermined pulse edge in synchronization with the pulse edge of the pulse train proportional to the rotation speed of the capstan motor, and after a certain time, the next Until the pulse edge, the capstan motor is driven at a voltage corresponding to the phase difference between the head switching signal and the phase signal recorded on the tape. It is possible to suppress fluctuations of the reproduction vertical synchronizing signal and the reproduction horizontal synchronizing signal on the time axis as much as possible.

From the above, the tape feed speed is 1 / the normal feed speed.
There is no noise or blur even when playing in slow speed of 2 or less,
It has an effect when stable and high-quality reproduction can be realized.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a main part of a rotary drum which is a constituent element of a slow speed reproducing device according to an embodiment of the present invention.
FIG. 4 is a plan view thereof, FIG. 3 is a vertical cross-sectional view showing the main part in more detail, FIG. 4 is a bottom view of FIG. 3, FIG. 5 is a control circuit diagram of a rotary drum, and FIG. FIG. 7 is a diagram showing the outline of FIG. 7, FIG. 7 is a control circuit diagram of a capstan motor, FIGS. 8 and 9 are waveform diagrams of respective parts, and FIG. 10 is a longitudinal section showing a main part of a rotary drum in a conventional slow speed reproducing device. FIG. 11 is a view for explaining the relative locus between the tape and the head in the VTR. (2), (3) ... upper and lower drums, (4a) ... drive unit,
(5), (5a), (5b) ... Head, (7), (8) ... Vertical transformer, (13) ... Tape, (14), (14-1),
(14-2), (14-3) ... Contact, (15), (15-
1), (15-2), (15-3) ... electrode, (41) ... leaf spring, (42), (42a), (42b) ... cylindrical coil, (43)
… Cylindrical permanent magnet, (80)… Capstan, (81)… Capstan motor, (84)… Rotation pulse generator, (90)
... Phase signal input terminal, (91) ... Head switching signal input terminal, (101) ... Mono multivibrator, (104) ... EXCL
USIVEOR gate, (117) ... differential amplifier, (111) ... divider, (112) ... sample and hold circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A pair of rotary heads for reproducing a video signal recorded on a magnetic tape, a rotary drum having a driving unit adapted to displace the rotary heads in the width direction of the magnetic tape, and the magnetic tape. A capstan motor that drives the vehicle, a rotation pulse generator that outputs a pulse train proportional to the number of revolutions of the capstan motor, and a voltage signal corresponding to the time in response to the head switching signal are generated. The voltage signal is extracted according to the recorded phase signal, and a phase comparison circuit that outputs a voltage corresponding to the phase difference between the head switching signal and the phase signal and a predetermined value in synchronization with the pulse edge of the pulse train No voltage is applied to the capstan motor for a predetermined time from the pulse edge of, and after the predetermined time, until the next pulse edge, Slow reproduction apparatus characterized by the output of the phase comparator circuit and a control circuit for applying to the capstan motor, and so as to intermittently drive the capstan motor.