JP2505037B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to, for example, a video tape recorder (hereinafter, referred to as
"VTR"), more specifically, to a circuit for generating a pseudo vertical sync signal of a VTR equipped with a movable video head.

[Conventional technology]

FIG. 5 is a sectional view showing a conventional rotary drum. In the figure, (1) is a rotary shaft, (2) is a fixed lower drum,
(3) is a rotating upper drum, (4) is a head stand screwed to the upper drum (3), (5) is a head fixed to the tip of the head stand (4), (6) is a bearing, ( (7) is an upper transformer that rotates together with the rotating drum (3), (8) is a stationary lower transformer, (9) is a pedestal supported by the rotating shaft (1) and carrying the rotating drum (3), (13) Is a magnetic tape, (75) is a magnet attached to the upper drum (3),
Reference numeral (18) is a rotational position detector for detecting the rotational position of the rotary drum (3) by sensing the magnetic force lines of the magnet (75).

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. FIG. 6 is a diagram for explaining this in detail. In the figure, (A1
3) is the track of the magnetic tape (13), V ₁ is the magnetic tape (13)
Is the normal feed rate of the head, A ₅ is the head, the locus of (5), and V is the rotational speed of the head (5). The locus A ₁₃ and the locus A ₅ intersect as shown. Thus, the relative locus (the transverse cutting line) drawn on the magnetic tape (13) by the head (5)
Is A as shown in FIG. 6 (a), and the interval P is a track pitch. By the way, V ₁ is 0 during still playback.
And the relative locus A _{0 at} this time corresponds to A ₅ . When the feeding speed of the magnetic tape (13) decreases from V ₁ to V _1/2 (for example, during slow reproduction), the relative locus of the head (5) with respect to the magnetic tape (13) is shown in FIG. 6 (b). As shown, it becomes A _S. In a magnetic recording / reproducing apparatus using such a drum, when reproducing the magnetic tape (13) at a speed other than the normal feed speed V ₁ , the pseudo vertical synchronizing signal combined with the reproduced video signal is different from the head switching signal. Are generated in a constant phase and are combined with the reproduced video signal.

[Problems to be Solved by the Invention]

When the magnetic tape (13) is reproduced at a speed different from the normal feeding speed V ₁ at the time of recording, the head (5) does not accurately follow the relative trajectory A at the normal feeding speed, that is, the recording trace, and deviates from it. Therefore, the signal level picked up by the head (5) becomes low, it becomes difficult to obtain a clear reproduced image, and noise is generated.

In order to solve such a problem, a rotary drum provided with a movable head so that the head (5) accurately traces a recording track even when the feeding speed of the magnetic tape is arbitrarily changed is used. There is.

FIG. 7 is a longitudinal sectional view of a rotary drum provided with a movable head, and (40) is a drive unit for displacing the head (5) in the width direction of the magnetic tape (13), including a contactor (14) and an electrode (15). )
A control signal is input from the outside via.

Displacement of the movable head in the case of slow reproduction of example V _1/2 is, as shown in FIG. 6 (c), during the reproducing one field, the A ₅ the locus of head (5) If you change to the position of A ₅₁ , it will match the track A of the tape. Even at other tape speeds, it is sufficient to move the head by a corresponding amount, and during one field reproduction, about P (1-V _{S / V} )
Just move it.

Thus driven speed of by connexion than normal feed speed V ₁ to the rotary drum for example provided with a movable head is, in case of reproducing at a speed of V _1/2, the duplicate tracing multiple of the same track Duplicate tracing is done. Fig. 6 (d)
Is head (5) is displaced in the width direction of the tape (13) causes the magnetic tape (13) to travel at V _1/2-speed trajectory A
It shows a case where the truck is driven so as to coincide with the above, and the track at the position of L ₀ is traced, and the head switching position at this time is S ₀ . At the next field, the track has moved P / 2 and moved to position L ₁ . Head (5) tape (13) to trace this track L _1.
The head switching position when displaced in the width direction of is S ₁ . At this time, when the track at the position L ₀ is traced and the track at the position L ₁ is traced, the phase of the reproduced video signal based on the head switching position is Only different. Here, “αh” is a constant determined by the recording mode, and as shown in FIG. 6 (d), the length (1H) from the horizontal synchronizing signal to the next horizontal synchronizing signal recorded on the tape is calculated. As a reference, the deviation of the starting end position between adjacent tracks is expressed in terms of time. In this way, when using a pseudo vertical sync signal generation circuit that generates a pseudo vertical sync signal at a constant phase based on a conventional head switching signal for a reproduced video signal whose phase is different for each trace,
The phase of the pseudo vertical sync signal and the playback video signal is However, there is a problem that the screen vibrates significantly in the vertical direction.

The present invention has been made for the purpose of solving such a problem, and it is possible to obtain a VTR equipped with a pseudo vertical sync signal generating circuit for generating a pseudo vertical sync signal with no phase shift regardless of the reproduction speed. With the goal.

[Means for solving the problem]

The magnetic recording / reproducing apparatus according to the present invention is a rotation device equipped with a movable head that is drive-controlled in the width direction of the magnetic tape so that the head trajectory during recording and the head trajectory during reproduction match at an arbitrary tape feeding speed. A drum, a video signal reproducing circuit for reproducing a signal reproduced by the movable head into a video signal, a rotation pulse generating means for generating a rotation pulse indicating the rotation of the capstan motor, and the magnetic tape recorded at a frame period. Tape phase reference detecting means for detecting the phase reference signal, a tape phase detector initialized by the tape phase reference signal and counting the rotation pulse, and the counted tape phase data by the edge of the head switching signal. A latch circuit for latching, [However, "αh" is a constant that represents the deviation of the start position between adjacent tracks, which is determined by the recording mode], and a delayed edge pulse delayed by a certain time T ₀ from the edge of the head switching signal. A pseudo vertical synchronizing signal time generation circuit for fetching the above-mentioned calculation data by the above, counting down the calculation data each time a time measurement pulse of a predetermined cycle is input, and outputting a borrow signal when the count value becomes 0; A pulse generating circuit for generating a pseudo vertical synchronizing signal when a borrow signal is input, and a signal synthesizing circuit for synthesizing the pseudo vertical synchronizing signal with the reproduced video signal and outputting the reproduced video signal are provided.

[Action]

Since the pseudo vertical synchronizing signal generating circuit according to the present invention generates the pseudo vertical synchronizing signal with respect to the tape phase reference signal in a constant phase relationship according to the tape feeding speed, the vertical synchronization of the reproduced image may be disturbed. Absent.

[Embodiment] An embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing the overall schematic configuration of this embodiment. (5a) and (5b) are movable heads, (700) is a rotary drum control circuit, (79) is a head movement width adjustment signal input terminal, (78) is a video signal reproduction circuit, which reproduces the video signal (12
0) is output to the terminal (90). (80) is a magnetic tape (1
A capstan that causes 3) to travel in pressure contact with a pinch roller (82), (81) a capstan motor, and (84) a rotary pulse generator installed in parallel with the capstan motor (81).
Output rotation pulse (100) to terminal (85). (86) is a tape phase reference signal detector installed so as to contact the magnetic tape (13), and outputs the tape phase reference signal (113) to the terminal (87). This tape phase reference signal (11
3) is recorded on the magnetic tape (13) at a frame cycle during recording. Reference numeral (900) is a pseudo vertical synchronization signal generation circuit which generates a pseudo vertical synchronization signal (112) at a phase related to the phase of the magnetic tape (13). A signal synthesizing circuit (1000) synthesizes the reproduced video signal (120) and the pseudo vertical synchronization signal (112) and outputs a combined reproduced video signal (121). FIG. 2 is a block circuit diagram of the rotary drum control circuit (700) of this embodiment. In the figure, (61a) and (61b) are periodic signal generators, which are controlled by a switching signal and have a phase of 180 °.
Generate different periodic signals. The switching signal (114) detects the mechanical position of the rotating drum (3) by the magnet (75) attached to the rotating drum (3) and the position detection head (76), and the switching signal generator accordingly. (77).

The outputs of the periodic signal generating circuits (61a) and (62b) are operational amplifier (64), differential amplifier (69), current limiter (65), resistor, (62) (63) (68) (70), respectively. , A capacitor (71), and drive circuits (600a) and (600b). The output of the drive circuits (600a) and (600b) (control current of the movable head) is the contact (14a) of each control side,
Drive unit (40) via (14b) and electrodes (15a) (15b)
Are supplied to the drive coils (42a) and (42b) of the. The non-control side terminals of the drive coils (42a) and (42b) are made common, and a pair of common side electrodes (15c) and common side contacts (14
It is connected to the reference potential via c). The magnetic field generated by the flow of the control current through the drive coils (42a) and (42b) causes a magnetic reaction with the cylindrical permanent magnet that constitutes the drive section (40), and the movable heads (5a) and ( 5b) is displaced. The amount of displacement is controlled so that the head locus A ₅ during reproduction coincides with the recording trace on the magnetic tape. The control current is supplied to the drive coils (42a) and (42b) even when the heads (5a) and (5b) are not in contact with the magnetic tape (13). The signals reproduced by the movable heads (5a) and (5b) are passed through the upper and lower transformers (7) and (8) to the head amplifier (72).
a) and (72b), the output of which is the switching signal (114)
Then, the signal is switched by the switch (73) and processed by the signal processing circuit (78) to output the reproduced video signal (120).

Next, the operation of the drive circuits (600a) and (600b) will be described. The drive circuits (600a) and (600b) have the same configuration,
Since the same operation is performed with a phase difference of 180 °, (600
Explain a).

In this embodiment, it is set to (resistance (63)) (resistance (70), impedance of capacitor (71)) (resistance value of coil (42)). It has a feedback loop, and the first one detects the voltage across the resistor (68) inserted in the control side (current flowing in the drive coil (42a)) with the differential amplifier 69) to perform the current feedback operation. The other is a loop for performing voltage feedback operation via the capacitor (71).

When the frequency is high, the impedance of the capacitor (71) approaches 0. 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 impedance of the capacitor (71) 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 head (5a) cooperating with the drive coil (42a) and the mechanical resonance frequency of the drive section (40) is (drive fundamental frequency) <resonance frequency of the rotating head). Therefore, current driving is performed at least near the driving fundamental frequency, and voltage driving is performed at least near the resonance frequency to perform short-circuit control.

Further, in order to eliminate the difference in gain between the current driving operation and the voltage driving operation, the circuit constants are selected as follows.

The window comparator (66) and the current limiting means (6
The current controller (65) composed of 7) detects the voltage of both terminals of the resistor (68) inserted in the control side (current flowing in the drive coil (42a)), and the displacement of the movable head (5a) is detected. , {|
The control current is limited so that the desired speed −1 | × the track pitch P <the displacement limit <the limit of the structural displacement amount of the movable head (5a)}. In other words, the current limiter (65) and the current feedback differential amplifier (69) work together with the voltage across the resistor (68).

Next, the pseudo vertical synchronizing signal generating circuit (900) of this embodiment will be described with reference to FIG. The number of rotation pulses (100) of the capstan motor (81) is
It is proportional to the rotation angle of the magnetic tape (13) and thus to the moving amount of the magnetic tape (13). The tape phase reference signal (11) detected on the tape by the rotation pulse (100) of the capstan motor and the tape phase reference signal detector (86).
3) is input to the tape phase detector (101), is periodically initialized by the tape phase reference signal (113), and the rotation pulse (100) is counted. Therefore, the output signal (tape phase data (102)) has a value proportional to the phase of the magnetic tape (13).

This tape phase data (102) is used by the edge detector (11
The tape phase data (104) latched by the latch circuit (103) by the edge pulse (116) of the head switching signal (114) detected in 5) and latched is input to the calculator (105). And the computing unit (105) Is calculated and the calculated data (106) is output.
However, “αh” is a constant determined by the recording mode.

The delay device (117) generates a delayed edge pulse (110) obtained by delaying the edge pulse (116) by a certain time T ₀ . Pseudo vertical sync signal time generator (107) is delayed edge pulse (110)
Each time the time measurement pulse (119) is input, the calculated data (106) is read by
06) is down-counted, and when the count value becomes 0, a borrow signal (108) is output. The generation time of the borrow signal (108) becomes the generation start time of the pseudo vertical synchronization signal (111) generated by the pulse generator (109). The borrow signal (108) is secured by the pulse generator (109) to have a pulse width as a vertical synchronizing signal, and the pseudo vertical synchronizing signal (11) is generated.
It is output as 1).

Figure 4 is a signal waveform diagram of each part of FIG. 3 when V _1/2-speed slow reproduction head switching signal (114), a tape phase reference signal (113), a tape phase data (102) latches tape phase Data (104) and pseudo vertical sync signal (112)
It is a figure which shows the relationship of. In the case of V _1/2 slow reproduction, one period and head switching signal of the tape phase reference signal (113) (1
Two cycles of 14) correspond.

The tape phase data (102) counts the rotation pulse (100) of the capstan motor, and the tape phase reference signal (11)
3), the waveform ((102) is changed to D /
(A) is the solid line in FIG. 4 (C). And
A signal obtained by latching the tape phase data (102) at both edges of the head switching signal (114) becomes a dotted line in FIG. 4 (C). The time T from the head switching position of the pseudo vertical synchronization signal (112) is Becomes (However, T _c is the delay time by the delay device (117), “αh” is determined by the recording mode, and is a constant that temporally represents the deviation of the starting end position between adjacent tracks.) [Effect of the invention] According to the invention, a rotary drum equipped with a movable head that is drive-controlled in the width direction of a magnetic tape so that the head locus during recording and the head locus during reproduction match at an arbitrary tape feeding speed, and the movable drum. A video signal reproducing circuit for reproducing the signal reproduced by the head into a video signal, a rotation pulse generating means for generating a rotation pulse indicating the rotation of the capstan motor, and a phase reference signal recorded at the frame period on the magnetic tape. Tape phase reference detection means for detecting, and initialized with the tape phase reference signal,
A tape phase detector that counts the rotation pulses, and a latch circuit that latches the counted tape phase data at the edge of the head switching signal, [However, "αh" is a constant that represents the deviation of the start position between adjacent tracks, which is determined by the recording mode], and a delayed edge pulse delayed by a certain time T ₀ from the edge of the head switching signal. A pseudo vertical synchronizing signal time generation circuit for fetching the above-mentioned calculation data by the above, counting down the calculation data each time a time measurement pulse of a predetermined cycle is input, and outputting a borrow signal when the count value becomes 0; The tape generation circuit includes a pulse generation circuit that generates a pseudo vertical sync signal when a borrow signal is input, and a signal synthesis circuit that synthesizes the pseudo vertical sync signal with the playback video signal and outputs the playback video signal. a pseudo vertical synchronizing signal even when played in normal playback speed V ₁ or faster, it is possible to maintain a constant phase of the reproduced video signal, the but connexion, Bed Without an effect of VTR can be obtained which can reproduce a stable image.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block circuit diagram showing an overall schematic configuration of an embodiment of the present invention, FIG. 2 is a block circuit diagram of a rotary drum control circuit of this embodiment, and FIG. A block circuit diagram of a pseudo vertical synchronizing signal generating circuit which is an essential part of the embodiment, FIG. 4 is a timing diagram of the circuit of FIG. 3, FIG. 5 is a longitudinal sectional view showing a structure of a conventional rotary drum, and FIG. FIG. 7 is a diagram showing the relationship between the track recorded on the magnetic tape and the scanning position of the head, and FIG. 7 is a longitudinal sectional view of a rotary drum provided with a movable head. (3) ... Rotary drum, (5a), (5b) ... Movable head,
(13) ... Magnetic tape, (78) ... Video signal reproduction circuit, (8
4) ... Rotation pulse generator, (86) ... Tape phase reference signal generator, (700) ... Rotation drum control circuit, (900) ... Pseudo vertical synchronization signal generation circuit, (1000) ... Signal synthesis circuit. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A rotary drum equipped with a movable head which is driven and controlled in the width direction of a magnetic tape so that a head locus during recording and a head locus during reproduction match at an arbitrary tape feeding speed, and a movable drum. A video signal reproducing circuit for reproducing the signal reproduced by the head into a video signal, a rotation pulse generating means for generating a rotation pulse indicating the rotation of the capstan motor, and a phase reference signal recorded on the magnetic tape at a frame period. A tape phase reference detecting means for detecting, a tape phase detector which is initialized by the tape phase reference signal and counts the rotation pulse, and a latch circuit which latches the counted tape phase data at the edge of the head switching signal. , [However, "αh" is a constant that represents the deviation of the start position between adjacent tracks in terms of time, which is determined by the recording mode], and a delay delayed by a certain time T ₀ from the edge of the head switching signal. A pseudo vertical synchronizing signal time generation circuit that takes in the above-mentioned operation data by an edge pulse, counts down the operation data each time a time measurement pulse of a predetermined cycle is input, and outputs a borrow signal when the count value reaches 0. A pulse generating circuit for generating a pseudo vertical synchronizing signal when the borrow signal is input, and a signal synthesizing circuit for synthesizing the pseudo vertical synchronizing signal with the reproduced video signal and outputting the reproduced video signal. And a magnetic recording and reproducing device.