JP2629977B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus having an automatic tracking function in slow motion reproduction, and more particularly to an apparatus which can be easily realized at low cost by using a microprocessor. is there.

2. Description of the Related Art In recent years, microprocessors have been remarkably popularized and used in many household electric appliances. The home video tape recorder (hereinafter abbreviated as VTR) is no exception, and it is the center of a system that controls a loading mechanism that draws a magnetic tape from a cassette and winds it around a rotating head, and a program reservation that combines a timer. Microprocessors have been actively used.

FIG. 9 is a block diagram showing a configuration of a servo mechanism at the time of reproducing a conventional VTR.
3 are close to each other, the rotating magnetic heads 91 and 92 are close to each other, and each of them is arranged at a position of about 180 °.
And 91 have the same azimuth angle, and the rotating magnetic heads 82 and 92
Rotating magnetic heads having different azimuth angles
A cylinder motor 2 that drives 81, 82, 91, 92, a first frequency generator 3 that detects the rotation speed of the cylinder motor 2, a phase detector 4 that detects the rotation phase of the cylinder motor 2, A first frequency discriminator 10 for detecting an error of the output signal of the first frequency generator 3 with respect to a reference cycle.
A reference signal generator 15; and a first phase comparator 11 for detecting a phase error between a rotational phase signal obtained from the phase detector 4 and a reproduction reference signal selected from the reference signal generator 15.
And the phase error output of the first phase comparator 11 and the first
A first adder 12 for mixing the speed error output of the frequency discriminator 10 with a first amplifier 13, a first drive circuit 14 for driving the cylinder motor 2, and a cap for moving the magnetic tape at a constant speed. A stun motor 6, a second frequency generator 7 for detecting the rotation speed of the capstan motor 6, a control head 5 for detecting a control signal recorded at the lower end of the magnetic tape 1, Generator 7
A second frequency discriminator 17 for detecting an error of the output signal with respect to a reference cycle, a tracking mono-multi circuit 16 which is triggered by an output signal of the reference signal generator 15 and has a variable delay time by a variable resistor 27, A second phase comparator 18 for detecting a phase error between a control signal obtained from the control head 5 and an output signal of the tracking mono-multi circuit 16, a phase error output of the second phase comparator 18, A second adder 19 for mixing the speed error output of the second frequency discriminator 17; a second amplifier 20; a second drive circuit 22 for driving the capstan motor 6; For intermittently driving the capstan motor based on the intermittent running command signal from the forcible acceleration command signal and the rotational phase signal and the control signal as a reference signal and An intermittent running control circuit 23 that outputs a motor ON / OFF signal, a current direction switching signal, and the like;
And a third adder 21 for mixing the output of the amplifier 20 with the forced acceleration command signal of the intermittent running control circuit 23.

The operation of the VTR configured as described above during normal playback will be briefly described with reference to the configuration diagram of FIG. 9 and the timing chart of the main part shown in FIG.

FIG. 10W is an output waveform of the reference signal generator 15 shown in FIG. 9, and this signal is used as a reference signal at the time of reproducing a VTR by using the first phase comparator 11 and the tracking mono-multi circuit.
Supplied to 16. The trapezoidal wave signal in FIG. 10X is the internal waveform of the first phase comparator 11, and is the phase reference signal of the cylinder motor triggered by the rising edge in FIG. The signal is sampled by the rotation phase signal obtained from the unit 4, that is, the falling edge of FIG. 10H, and its hold signal (not shown) and the speed error signal obtained from the first frequency discriminator 10 shown in FIG. The first
And is supplied to a first drive circuit 14 via a first amplifier 13. Therefore, the cylinder motors, that is, the four rotary heads 81, 82, 91, 92 rotate in phase synchronization with the reference signal of FIG. 10W. FIG. 10Y shows the charge / discharge waveform of the capacitor (not shown) in the tracking mono-multi circuit 16 of FIG. 9, which is triggered by the rising edge of FIG. 10 and the time constant of the variable resistor 27 of FIG. , The delay time can be varied. FIG. 10Z is the output waveform of the tracking mono-multi circuit 16, the trapezoidal wave signal of FIG. 10 is the internal waveform of the second phase comparator 18 of FIG. 9, and the falling edge of FIG. The phase reference signal of the capstan motor triggered by the above is sampled by the reproduction control signal obtained from the control head 5 in FIG. 9, that is, by the rising edge in FIG. The speed error signal obtained from the second frequency discriminator 17 shown in FIG. 9 is mixed with a second adder 19 and supplied to a second drive circuit 22 via a second amplifier 20. At this time, the forced acceleration command signal of the intermittent running control circuit 23 has a high impedance. Therefore, the capstan motor 6
Rotates in phase synchronization with the output signal of the tracking mono-multi circuit 16 of FIG. 10Z obtained by shifting the phase of the reference signal of FIG. 10W. As described above, at the time of normal reproduction of the VTR, the four rotary head groups optimize the tracks recorded on the magnetic tape 1 by synchronizing the phases of the four rotary head groups with the reproduction control signal (β in FIG. 10). Will be tracked.

Next, the operation at the time of slow motion reproduction will be described with reference to the timing chart shown in FIG. To improve the transient characteristics during slow motion playback, the second
The phase error output of the phase comparator 18 is grounded in an AC manner, and the capstan motor 6 is rotated by applying only the speed signal system. FIG. 11S is an intermittent running command signal, and based on this signal, the intermittent running control circuit 23 outputs the following control signals. 11 γ and δ are a forced acceleration command signal and a motor ON / OFF signal synchronized with the rotation phase signal of the cylinder motor of FIG. 11H, and FIG. 11 U is a current direction switching signal of the capstan motor 6. This is the output signal of the slow tracking mono-multi circuit (which is inside the intermittent running control circuit 23 and whose delay time can be set by the variable resistor 28) triggered by the control signal shown in FIG.
11) Set by ε) and reset after a predetermined time. Based on the above three signals (γ, δ, U in FIG. 11),
As shown in FIG. T, a motor current flows through the capstan motor 6, and the capstan motor 6 and the magnetic tape 1 shift from stop to acceleration to constant speed to deceleration to stop and intermittently drive.
The four rotating magnetic heads 81, 82, 91, and 92 are always rotating at a constant speed. When the magnetic tape 1 is stopped, the head is in a still playback state, and when the magnetic tape is transferred, the head is in a normal playback state.
By properly switching the output signals of the two rotating magnetic heads, a noiseless slow-motion playback image can be obtained, but the important thing here is to properly set the timing to move or stop the magnetic tape so that the playback image is not disturbed. is there.

Therefore, the timing for stopping the capstan motor 6 is important. To stop the capstan motor 6, the control signal is picked up as described above, and after a certain delay time, the signal is shifted to the deceleration state. The magnetic tape stops at a position where the rotating head stably traces a storage track (not shown) on the magnetic tape. If the format of the track recorded on the magnetic tape is completely compatible, the variable resistor 52 may be a fixed resistor,
Magnetic tape expands and contracts due to environmental changes such as temperature changes,
In addition, when performing slow motion playback on a tape recorded by another VTR in which an error in the mechanism has occurred, it is necessary to change the brake timing in order to make the tracking state optimal. Therefore, the variable resistor 28 shown in FIG. 9 is necessary. In addition, the variable resistor must be a click pointed volume in order to be operable by the user. Generally, the resistance value at the click point of a volume with a click point (not shown) varies, and another variable resistor (not shown) is required to correct the variation. Therefore, the conventional VTR requires not only an adjustment volume for tracking, but also an improvement in operability, that is, usability.

Means for solving the problem A magnetic recording / reproducing apparatus which performs a slow motion reproduction by repetition of stationary and moving of a magnetic tape transferred by a capstan motor, and means for intermittently driving the capstan motor, A drop-out detecting means for detecting a drop-out of a reproduced video signal from the rotary magnetic head when the magnetic tape is stationary; and a predetermined period before and after both edges of a head switching signal indicating rotation transfer of a cylinder motor for driving the rotary magnetic head. A total of 4
Tracking error detection means for detecting the pulse width of the dropout detection signal in one detection period, and outputting tracking error information comprising a tracking variable amount and a variable direction to be changed based on the detection result, and performing intermittent driving based on the tracking error information. The means is a magnetic recording / reproducing apparatus which controls the timing of applying a brake to the capstan motor. When the normal reproduction shifts to the still reproduction, the tracking error detecting means outputs the predetermined data as the tracking error information until the tracking error detection means outputs the predetermined data. The intermittent driving means self-excitedly continues the slow motion reproduction by the intermittent driving, and during the slow motion reproduction, the tracking error detecting means outputs the tracking error information based on the dropout detection signal for each intermittent driving by an external command signal. Also characterized It is.

Effect In the present invention, the above-described configuration allows the magnetic tape to expand and contract due to environmental changes such as temperature changes, and is also stable against so-called degraded tapes recorded on other VTRs having mechanical errors. It is possible to obtain a magnetic recording / reproducing apparatus that realizes a slow-motion reproduced image.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a VTR having an auto tracking function (hereinafter, referred to as auto slow tracking) at the time of slow motion reproduction according to an embodiment of the present invention. In addition, a head amplifier circuit 26, a drip-out detection circuit 25, and an auto-tracking processing circuit 24 are added. However, the head amplifier circuit 26 and the dropout detection circuit 25 are necessary as signal processing circuit blocks of the VTR, and are not newly added for the present invention.

FIG. 2 shows the internal configuration of the head amplifier circuit 26.
Two head-an circuits 261, 262, 263, 264, a first switch 265 to which the head amplifier circuits 261 and 262 are input,
A second switch 266 to which the head amplifier circuits 263 and 264 are input, and a third switch 267 to which the output of the first switch 265 and the output of the second switch 266 are input. The first switch 265 and the second switch 266 are connected to the third switch 267 by a head switching signal input from an input terminal 268, that is, a signal based on a rotational transfer signal obtained from the transfer detector 4 in FIG.
Is controlled by a head amplifier switching signal input from the intermittent running control circuit 23 in FIG.
Then, the output of the optimum head in contact with the magnetic tape among the four rotating magnetic heads is selected and output to the output terminal 260.

FIG. 3 is a configuration diagram showing mounting positions of four rotary magnetic heads 81, 82, 91, 92 mounted on the cylinder motor 2 of FIG. 1, and FIG. 4 is a diagram showing head widths of the four rotary magnetic heads. FIG.

As shown in FIG. 3, the rotating magnetic heads 81 and 82 are close to each other, the rotating magnetic heads 91 and 92 are close to each other, and each of them is arranged at a position of about 180 °. Rotating magnetic head with azimuth (L azimuth) angle
82 and 92 have different identical azimuth (R azimuth) angles. Further, as shown in FIG. 4, the rotating magnetic heads 81 and 92
The head width of the rotating magnetic heads 82 and 91 is larger than that of the rotating magnetic heads 82 and 91.
Thus, recording / reproduction in a low speed mode (long time mode) of the tape speed is performed. However, in the still state of the slow motion playback mode, in order to use a playback output of one recording track in order to realize a still image without screen blur, it is necessary to perform playback with a head having the same azimuth angle (referred to as field still playback). If the recording track is L azimuth, the head must be reproduced by the rotating magnetic heads 81 and 91. If the recording track is R azimuth, the head must be reproduced by the rotating magnetic heads 82 and 92. ing.

The operation of the VTR having the auto / slow tracking function configured as described above will be described with reference to the configuration diagrams shown in FIGS. 1 to 4 and the operation waveform diagrams shown in FIGS. 5 to 8. However, the basic operation at the time of slow motion reproduction is the same as that of the conventional example, and the description thereof is omitted.

FIGS. 5 and 6 show the track trajectory during still playback at different slow tracking points, the head amplifier circuit 26 in FIG. 2 and the dropout detection circuit 25 in FIG.
It is a waveform diagram of each part. Both are with the rotating magnetic head 81
FIG. 5 and FIG.
FIG. A is a track trajectory diagram showing trajectories of four magnetic heads tracing on recording tracks separated by oblique lines, and a portion where the azimuths of the track and the head match is reproduced as a head output. A waveform B is a signal obtained by switching the output signal of the first switch circuit 265, that is, the output signal of the head amplifier 261 of the rotary magnetic head 81 and the output signal of the head amplifier 262 of the rotary magnetic head 92, with a head switching signal shown by a waveform E. C represents the waveform of the output signal of the second switch circuit 266, that is, the output signal of the head amplifier 263 of the rotary magnetic head 82 and the output signal of the head amplifier 264 of the rotary magnetic head 91.
A waveform D is an output signal of the third switch 267, that is, the first signal.
The output signal of the switch circuit 265 and the second switch circuit 266 is an envelope signal which is switched by the head amplifier switching signal shown by the waveform F and is output to the output terminal 260, and the waveform E is the phase detector 4 of FIG. The waveform F is a head amplifier switching signal output by the intermittent running control circuit 23 shown in FIG. Is a field still of the L azimuth track, which is an in-phase signal of the head switching signal. The waveform G is the dropout detection circuit of FIG.
In the case of FIG. 5, a stable envelope signal is obtained and no dropout occurs because the tracking state is at the optimum point in FIG. 5, but in the case of FIG. 6, the tracking state deteriorates. reduced envelope signal level to have dropped out detection signals G _1, G _2, G ₃ represents as screen noise (not shown) is generated.

As can be seen by comparing FIGS. 5 and 6, the tracking state shown in FIG. 5 is optimal. In the case shown in FIG. Noise appears. If the tracking state shifts in the reverse direction of FIG. 6, the envelope output near the edge of the head switching signal decreases, and noise appears at the bottom of the screen. Therefore, the phase relationship of the dropout detection signal with respect to the head switching signal and the pulse width thereof are detected, and the amount of slow tracking is changed in accordance with the phase relationship to obtain the optimum tracking state (the fifth state).
(The state shown in the figure).

FIG. 7 is a timing chart for explaining the internal operation of the auto tracking processing circuit 24 in FIG. 1 in the still state when an auto tracking command signal is input from the outside during slow motion reproduction. H is a head switching signal, FIG. 7I is the same dropout detection signal as in FIG. 6G, and FIG. 7J is a waveform obtained by integrating the dropout detection signal with a low-pass filter. K is the progress of waveform shaping of the signal of FIG. 7J, and FIG. 7L is a quantized clock signal for detecting the pulse width of FIG. 7K or a timer interrupt signal in the case of a microcomputer. FIG. 7M shows an enable signal for detecting the pulse width of the dropout detection signal generated near the falling edge of the head switching signal. N is the enable signal for detecting the pulse width of the drop-out detection signal generated in the vicinity of the rising edge of the head switching signal, FIG. 7 O ₁ is generated immediately after the falling edge of the section, i.e. the head switching signal Figure 7 M The pulse width of the dropout detection signal obtained is quantized in FIG. 7L and the count value is expressed in an analog manner. FIG. 7 O ₂ shows the section in FIG. 7M, that is, immediately before the falling edge of the head switching signal. are those of the pulse width of the drop-out detection signal generated and the count value quantized in FIG. 7 L analog representation to, Figure 7 P ₁
FIG. 7P is an analog representation of the count value obtained by quantizing the pulse width of the dropout detection signal generated immediately before the rising edge of the head switching signal in the section of FIG. ₂ is a representation of a count value obtained by quantizing the pulse width of the drop-out detection signal generated immediately after the rising edge of the section, i.e. the head switching signal Figure 7 N in FIG. 7 L analog enemy. Therefore, the magnitude comparison between the addition results of the count values of FIGS. 7 O ₁ and O _{2 and} the count values of FIGS. 7 P ₁ and 7 P ₂ , that is, near the falling edge of the head switching signal The pulse width of the generated dropout detection signal and the pulse width of the dropout detection signal generated near the rising edge of the head switching signal are compared, and the larger value is used as the pulse width of the effective dropout detection signal. the pulse width of the effective dropout detection signal is regarded as the previous noise of the head switching signal edge (bottom of the screen noise), the head switching signal if the count value immediately before the interval and the clogging Figure 7 P ₁ and Fig. 7 O ₂ is the pulse width of the trailing segment and clogging Figure 7 P ₁ and their valid drop-out detection signal if there is a seventh count value in Fig O ₂ edges of the head switching signal edge Regarded as the rear noise (the top of the screen noise), and outputs a tracking variable command signal as shown in FIG. 7 Q based on the result to the intermittent driving control circuit 23 of FIG. 1. In the case of FIG. 7, a tracking-up command (data 2) is output as a noise of "5" at the top of the screen, and the slow tracking mono-multi circuit described in the conventional example is operated in a direction to shorten the delay amount. This can be realized by modulating the mono-multi reference voltage with the output of the D / A converter, or by digitally changing it as internal processing of the intermittent running control circuit 23.

Here, the tracking variable command signal, that is, the tracking error information (data 2 in FIG. 7Q) is not the pulse width itself of the effective dropout signal or data proportional thereto, but, for example, as shown in the table below, the tracking variable amount is changed for each variable direction. And the data corresponding to each as tracking error information Is set. That is, if the noise width is 6 or more at the bottom of the screen, the tracking error information is transmitted as data 6 to the intermittent running control circuit 23, and the intermittent running control circuit 23 increases the tracking amount by 4 and the noise width is 1 at the top of the screen. If so, the tracking error information is transmitted as data 1 to the intermittent running control circuit 23,
Reduces the tracking amount by one.

By performing the above operation, each time the capstan motor 6 is intermittently driven, the dropout detection signal is detected and the amount of the slow tracking shifter is modulated in accordance with the result, thereby obtaining the optimum slow tracking point (point where the tracking error information becomes data O). ).

By the way, when a VTR having a slow-motion playback function performs still playback from normal playback, still playback is generally performed after performing intermittent running of the slow-motion playback a predetermined number of times. Accordingly, residual noise is generated in still playback on a tape whose compatibility has deteriorated as in slow motion playback.

FIG. 8 is a timing chart when the VTR of the present invention shifts from the normal playback mode to the still playback mode,
FIG. 8S shows the same intermittent running command signal as FIG. 11S, FIG. 8T shows the same motor drive current of the capstan motor 6 as FIG. 11T, and FIG. FIG. 8V shows the drive current direction switching signal of the same caster motor 6, and FIG.
8H is a head switching signal, FIG. 8I is the same dropout detection signal as FIG. 7I, and FIG. 8Q is the output signal of FIG. This is the same tracking error information.

When shifting from the normal reproduction mode to the still reproduction mode, first, the drive current is reversed to apply a brake to stop the capstan motor. The stop state is the eighth
FIG. 8 shows a state in which only one frame has been transmitted by the intermittent running command signal in FIG. 8S, and still reproduction has been realized in this state in the conventional VTR. On a self-recording / reproducing tape or a tape whose compatibility is ensured, a still image without noise can be obtained. On a tape with poor compatibility, a dropout detection signal is generated as shown in FIG. Will be. Therefore, the noise is detected by the auto-tracking processing circuit 24 described with reference to FIG. 7, and the tracking error information shown in FIG. 8Q is transmitted to the intermittent running control circuit 23. Until the intermittent running command signal in FIG. 8S arrives, the intermittent running continues without interruption as shown in FIG. Therefore, in still reproduction, a clear still image without noise can be obtained for any tape.

However, if noise cannot be removed with an abnormal tape such as an extremely deviated tape or a demagnetized tape, the intermittent running will be continued forever. This prevents the adverse effects.

Also, a method is conceivable in which during slow-motion reproduction, the auto-slow tracking operation is performed for a fixed time or a predetermined number of intermittent runnings, and thereafter fixed.

In the present embodiment, the slow tracking system is a time management system based on constant speed traveling. However, the same means is used in the FG counting system for counting the number of pulses of the output signal (referred to as FG) of the frequency generator of the capstan motor. What can be realized can be easily analogized.

As is apparent from the above description, the magnetic recording / reproducing apparatus having the auto / slow tracking function of the present invention is capable of stopping the magnetic tape transferred by the capstan motor.
A magnetic storage reproducing apparatus for performing slow motion reproduction by repeating movement, and means for intermittently driving the capstan motor (in the embodiment, represented by an intermittent running control circuit 23 in FIG. 1). Drop-out detection means (in the embodiment, represented by the drop-out detection circuit 25 in FIG. 1) for detecting drop-out of a reproduced video signal from the rotating magnetic head when the magnetic tape is stationary, and rotation. The pulse width of the dropout detection signal in a total of four detection periods before and after a predetermined period of both edges of the head switching signal indicating the rotation phase of the cylinder motor that drives the magnetic head is detected, and the tracking variable amount to be varied based on the result is detected. Tracking error detecting means for outputting tracking error information consisting of variable directions (in the embodiment, the And the intermittent drive means controls the timing of applying a brake to the capstan motor based on the tracking error information. At the time of transition from the normal reproduction to the still reproduction, the intermittent driving means continues the self-excited slow-motion reproduction by the intermittent driving until the tracking error detection means outputs predetermined data as tracking error information. The tracking error detection means outputs the tracking error information based on the dropout detection signal at each intermittent drive by a signal. Recorded on other VTRs with errors It is possible to obtain a magnetic recording and reproducing apparatus also realizes stable auto slow tracking capabilities for the tape. Of course, an operability can be improved because an adjustment volume unlike the conventional VTR is not required.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic recording / reproducing apparatus having an auto tracking function according to an embodiment of the present invention, FIG. 2 is a block diagram showing a specific internal configuration of a head amplifier circuit 26 of FIG. 1, and FIG. FIG. 4 is a configuration diagram showing the mounting positions of four rotary magnetic heads mounted on the cylinder motor 2 in FIG. 1, FIG. 4 is a schematic diagram showing the head width of the four rotary magnetic heads, and FIGS. Track trajectories during still reproduction at different slow tracking points, the head amplifier circuit 26 in FIG. 2 and the dropout detection circuit in FIG.
FIG. 7 is a timing chart for explaining the internal operation of the auto-tracking processing circuit 24 in FIG. 1 in a still state during slow-motion playback, and FIG. 8 is a timing chart from normal playback to still playback. FIG. 9 is a timing chart for explaining a noise feed operation at the time of shifting, FIG. 9 is a block diagram showing a configuration of a servo mechanism during reproduction of a conventional VTR, and FIGS. 10 and 11 are main parts of FIG. 6 is a timing chart for explaining an operation. 1 ... magnetic tape, 2 ... cylinder motor, 6 ... capstan motor, 11 ... head amplifier, 23 ... intermittent running control circuit, 24 ... auto tracking processing circuit, 25 ...
Dropout detection circuit.

Claims (2)

(57) [Claims] 1. A magnetic recording / reproducing apparatus for performing slow-motion reproduction by repeatedly stopping and moving a magnetic tape conveyed by a capstan motor, comprising: means for intermittently driving the capstan motor; When the magnetic tape is stationary, that is, during still playback, both dropout detection means for detecting a dropout of a reproduced video signal from the rotating magnetic head and a head switching signal indicating the rotation phase of a cylinder motor for driving the rotating magnetic head. A tracking error detecting means for detecting a pulse width of the dropout detection signal in a total of four detection periods before and after a predetermined period of the edge, and outputting a tracking variable amount to be varied and tracking error information comprising a variable direction based on the result. The intermittent drive based on the tracking error information. Means for controlling the timing of applying a brake to the capstan motor, wherein the tracking error detection means outputs predetermined data as tracking error information when transitioning from normal reproduction to still reproduction. Until the intermittent driving means continues the slow motion reproduction by the intermittent driving self-excitedly, and during the slow motion reproduction, the tracking error detecting means outputs the tracking error information based on the dropout detection signal by the external command signal every intermittent driving. A magnetic recording / reproducing apparatus for outputting to a computer. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein a predetermined limit is set on the number of intermittent runnings accompanied by tracking modulation by the tracking error detecting means.