JPH0786987B2 - Intermittent feeding device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an intermittent feeding device for a magnetic tape used in a video tape recorder (VTR) or the like. And, the present invention sometimes uses frame-by-frame playback such as time-lapse.
It is an object of the present invention to provide an intermittent feeding device for a magnetic tape which is effective at the time of frame feeding reproduction.

(Prior Art) In recent years, as a security monitoring device, a device for recording an image of an illegal intruder by combining a video camera, a television receiver for monitor, and a time-lapse VTR (VTR capable of intermittent recording) has been sold. ing.

FIG. 6 shows a timing chart at the time lapse of the intermittent feeding device used in the conventional time lapse VTR, and FIG. 7 shows a block diagram of the intermittent feeding device.

DF that indicates the rotation phase of a rotating drum (not shown) that is provided with a magnetic head and is in sliding contact with the tape when the tape is stopped
In synchronization with the F signal, the FADV signal, which is a command signal for sending the tape by one frame (the amount by which one frame of the video signal is recorded or reproduced), is recorded by the servo circuit system (not shown). ) To the intermittent feeding device. Then, the intermittent feeding device starts the tape feeding operation. FADV
The signal is supplied as a reset signal to the counter 1 and the flip-flop circuit 4. The capstan FG signal supplied from the capstan motor 5 via the amplifier 6 and the Schmitt circuit 7 is counted by the counter 1 which is reset at the rising edge of the FADV signal. The count number in counter 1
When it becomes T1, the output of the counter 1 becomes high level, and the output turns on the switch 12 via the OR circuit 8 and the voltage E
Is supplied to the capstan drive amplifier 10 as a first tape drive signal via the switch 11. In addition, the capstan drive amplifier 10 is supplied with a first rotation direction control signal (generated by a mechanism control circuit (mechanical control) from output signals of the counters 1 and 2 and FADV signals) from the mechanical control, The amplifier 10 generates a capstan drive signal based on these two signals and supplies it to the capstan motor 5. It is assumed that the first rotation direction control signal causes the capstan motor 5 to rotate normally at a high level and reversely rotate at a low level.

When the count number of the counter 1 reaches C1, the output of the counter 1 becomes low level, the switch 11 is turned off, and the voltage supply to the capstan motor 5 is stopped. The output of the counter 1 resets the counter 2 and the counter 3 via the switch 13 when the count number C1 is reached. The capstan motor 5 continues to rotate due to inertia even after the voltage supply is stopped.

When the count value of the capstan FG signal becomes C2 in the reset counter 2, in order to completely stop the capstan motor 5, the first tape drive signal and the first rotation direction of the ray level instructing the reverse rotation The control signal is supplied to the capstan drive amplifier 10 for the period T2. This 2
The period T2 during which one signal is supplied is not a capstan FG signal count number, but a constant value determined by the structure of a capstan flywheel (not shown), the count numbers C1, C2, and the like. The first tape drive signal in the period T2 is supplied to the capstan drive amplifier 10 by the counter 2 triggering the mono-multivibrator 9 with the count number C2 to generate a pulse having a pulse width T2 and turning on the switch 12. Supplied. The capstan motor 5 stops during this period T2.

At the same time as the count number of the counter 3 which is reset at the same time as the counter 2 becomes a predetermined count number (the first rotation direction control signal rises), a mechanical brake signal is sent from the flip-flop circuit 4 connected to the counter 3. Is output. This mechanical brake signal mechanically presses a pad (not shown) against the outer peripheral surface of the capstan flywheel, so that the motor does not rotate due to disturbance or the like while the capstan motor is stopped.

Thus, during the time lapse, the video signal and the control signal for one frame are recorded while the tape is fed by one frame. Recording is suspended while the tape feed is stopped.

The above description is for recording (time lapse), but during frame-by-frame reproduction, the reset signal of the counters 2 and 3 becomes a reproduction control signal when the switch 13 is switched to the reproduction side.

During normal continuous feeding instead of intermittent feeding, the switch 11 switches from the intermittent feeding side to the normal feeding side, and the capstan motor 5 is controlled by the well-known capstan servo circuit 14.

(Problems to be Solved by the Invention) In the above-described conventional intermittent feeding device, the period from the start of the tape feeding to the end of the braking period T2 is set as the period for accurately feeding the tape for one frame. However, since the braking period T2 is not the count number of the capstan FG signal but a predetermined fixed period, the period T2
Does not correspond to the rotation state of the capstan motor 5 at that time, and if there is variation in inertial force of the capstan flywheel due to structure or material, temperature change, etc., the braking force becomes excessive or insufficient, and Was sometimes reversed too much. Therefore, the tape may not be accurately fed by one frame, and the tape feeding may vary for each intermittent feeding operation.

Further, since the mechanical brake and the pad are provided to maintain the stopped state of the capstan motor, there are the following problems.

a) The timing of applying the brake is delayed because the pad is moved by the solenoid.

b) The braking force changes due to changes in the pad shape due to an increase in the number of times of use and changes in the pad friction coefficient due to temperature characteristics.

c) When mounting the pad, it is difficult to reduce the cost and downsize because a mold or the like is required.

d) The braking force varies widely among the pads, and it is difficult to adjust the braking force.

(Means for Solving the Problems) Therefore, in order to solve the above problems, the present invention provides an amount by which a first capstan FG signal is supplied and a video signal corresponding to a natural multiple of one frame is recorded or reproduced. A tape drive signal generating circuit for generating a stop servo switching signal by counting the first capstan FG signal while generating a first tape drive signal for running the magnetic tape only. A stann FG signal and a second capstan FG signal having a predetermined phase difference between the first capstan FG signal and the first capstan FG signal are supplied to rectify the second capstan FG signal to drive a second tape. A stop servo circuit that generates a signal and a second rotation direction control signal based on the first and second capstan FG signals, and the first and second tape drive signals are supplied. The stop servo is supplied with a first switch that selectively outputs one of the signals in accordance with the stop servo switching signal, a first rotation direction control signal and the second rotation direction control signal. A switching circuit having a second switch that selectively outputs one of the signals in accordance with the switching signal, and a capstan drive circuit that is supplied with the output signal of the switching circuit to drive the capstan motor. The present invention provides an intermittent feeding device characterized by the above.

(Embodiment) FIG. 1 is a block diagram of an embodiment of the intermittent feeding device of the present invention, FIG. 2 is a timing chart at the time lapse thereof, and FIGS. 3 and 4 are signal waveform diagrams for explaining the operation thereof. , FIG. 5 is a timing chart at the time of frame advance reproduction.

This embodiment comprises a tape drive signal generation circuit 31, a stop servo circuit 32, a switching circuit 33, and a capstan drive amplifier 10 which is a capstan drive circuit.

The embodiment shown in FIG. 1 is different from the prior art in that the stop servo circuit 32 is provided so that an electric brake can be applied and a mechanical brake is no longer required. (There is a 90 ° phase difference between the two capstan signals).

In this embodiment, the same operation as the conventional example is performed until the tape feeding is started, the count number of the counter 2 becomes C2, and the deceleration by the reverse brake is started. Then, in this embodiment, the capstan FG signal is counted, the tape is fed with high accuracy to a position corresponding to one frame, and then the driving of the capstan motor 5 is stopped.
Switch to 32 and apply an electric brake to stop the capstan motor 5. This point is different from the conventional example.

In FIG. 1, the same parts as those in the conventional example are designated by the same reference numerals. As described above, since the operation from the tape feeding start to the counter 2 counting up to the count number C2 and the braking by the reverse rotation is the same as the conventional example,
The description is omitted here.

The switch 28 to which the first rotation direction control signal output from the mechanical controller and the second rotation direction control signal e output from the stop servo circuit 32 is supplied is located on the 28b side (cap stand lip side). It is switching. Further, the switch 27 to which the first tape drive signal is supplied from the tape drive signal generation circuit 31 and the second tape drive signal f is supplied from the stop servo circuit 32 is located on the 27b side (capstan drive side). It is switching.

When the count number of the counter 2 reaches C2, the capstan motor 5 that continues to rotate by inertial force has a first rotation direction control signal (a signal supplied from an external mechanism control circuit as described in the conventional example). ), The motor is driven in the reverse direction and the speed is rapidly reduced. Then, when the count number of the counter 3 which is reset at the same time as the counter 2 becomes C3, the switch 27 is switched to 27a by the stop servo switching signal g output from the flip-flop circuit 4.
To the side (stop servo side), the switch 28 is switched to the side 28b (stop servo side), and the stop servo mode is set. The pulse count (C1-T1) + C3 of the capstan FG signal corresponds to the exact tape feed amount for one frame. In the stop servo mode, the stop servo circuit 32 completely stops the capstan motor 5 and maintains the stopped state until the next tape feed instruction by the FADV signal comes.

Although the counters 1, 2, and 3, the mono-multivibrator 9, and the flip-flop circuit 4 have different circuit configurations, respectively, a single counter and a logic circuit or a microcomputer that outputs a signal according to the count value thereof. You may comprise by.

Next, the operation of the stop servo circuit 32 at the time lapse (at the time of recording) will be described in detail with reference to FIGS. 3 and 4.

After the capstan FG signal a (second capstan FG signal) is amplified by the amplifier 21, the Schmitt circuit 22 shapes the waveform and the signal b is used to full-wave rectify the capstan FG signal a by the operational amplifier 23. To do. Thereafter, the full-wave rectified signal has its DC level adjusted by an operational amplifier 24 and a variable resistor 25, which are DC level shift circuits, and is supplied to a switch 27 as a second tape drive signal f.

The phase difference with the capstan FG signal a is 90 °. The capstan FG signal b (first capstan FG signal) becomes the waveform-shaped signal d via the amplifier 6 and the Schmitt circuit 7. The signal b and the signal d are supplied to the exclusive OR circuit (Ex • OR circuit) 26 and become the second rotation direction control signal e, which is supplied to the switch 28.

While the tape is being sent for one frame (the amount by which a video signal for one frame is recorded or reproduced), the stop servo switching signal g is at a low level, and the second tape drive signal f and the second rotation are performed. The direction control signal e is applied to the switches 27 and 2
It is not supplied to the capstan motor 5 due to 8. When the stop servo switching signal g becomes high level (when the count number of the counter 3 becomes C3 and when the first rotation direction control signal is low level), the switch 27 is set to 27a.
Switch 28 to the stop servo mode. Then, the second tape drive signal f
Then, the second rotation direction control signal e is supplied to the capstan drive amplifier 10, a capstan drive signal is generated from these two signals, and the capstan drive signal is supplied to the capstan motor 5.

Even after the stop servo switching signal g becomes high level, the capstan motor 5 rotates in the forward direction by the inertial force, but the second tape drive signal f is at the minimum level (DC set by the variable resistor 25). 2), the second rotation direction control signal e, which is the output of the Ex.OR circuit 26, becomes low level and the capstan motor 5 is rotated in the reverse direction. When the reverse rotation is excessive, the signal e becomes high level and the capstan motor 5 is normally rotated. By this repetition, after the stop servo switching signal g becomes high level, the capstan motor 5 is completely stopped when the signal f becomes the minimum level after overrun of several pulses of the capstan FG signal. .

In this embodiment, an accurate tape feeding end position corresponding to one frame is determined by counting the capstan FG signal c by the counter 3 (where the count reaches C3,
It is set that accurate tape feeding for one frame has been completed. ). Therefore, even if the rotation state of the capstan motor changes due to variations in the inertial force of the capstan flywheel, temperature changes, etc., an accurate tape feed end position for one frame can follow the change in the rotation state. You can Further, the position where the capstan motor 5 actually stops and the tape feeding ends is deviated from the accurate end position by only a few pulses of the capstan FG signal c. The deviation of several pulses is very small as the deviation of the tape feeding amount, and therefore, the tape feeding for one frame can be performed substantially more accurately and more accurately than the conventional example.

Also, after the capstan motor 5 is stopped, due to disturbance or the like,
When the capstan motor 5 further tries to rotate in the forward direction, the second tape drive signal f rises from the minimum level, as shown in FIG. 4 (A). Then, the second rotation direction control signal e, which is the output of the Ex • OR circuit 26, immediately changes from the high level to the low level, controls the capstan motor 5 to drive in the reverse direction, and prevents the normal rotation. To do. When this forward rotation prevention state continues, the capstan motor 5 starts reverse rotation, but when it reverses beyond the minimum level of the signal f, the signal f rises again. Then, the signal e, which is the output of the Ex • OR circuit 26, immediately changes from the low level to the high level, and controls the capstan motor 5 to rotate normally. By repeating such operations, even after disturbance of the capstan motor 5, even if there is a disturbance or the like, at the position of the minimum level of the signal f (correct stop position of the capstan motor 5 before rotating due to the disturbance or the like), the capstan motor 5 is stopped. The stopped state of the motor 5 can be stably maintained.

As mentioned above, since the stable stop state of the capstan motor 5 can be maintained by the electric brake by the stop servo circuit 32, it is not necessary to provide a mechanical brake such as a pad. Therefore, the intermittent feeding device of the present embodiment can always obtain a stable braking force, and if this intermittent feeding device is used in a device such as a VTR, the device such as the VTR can be made smaller and lighter and the cost can be reduced.

Further, in this embodiment, since the minimum level (DC level) of the signal f which is the reference of the braking force can be adjusted by the variable resistance 25, the adjustment of the braking force is easy.

Next, the frame-advance reproduction will be described. FIG. 5 is a timing chart at the time of frame advance reproduction.

The frame feed control at the time of reproduction is different from the above-described time lapse time (at the time of recording) in that the counters 2 and 3 are reset by the reproduction control signal when the switch 13 is switched to the reproduction side. Further, the count numbers of the counters 1, 2, and 3, the value of the period T2, and the like may be different from those at the time lapse, if necessary.

During normal recording / playback (continuous recording / playback, not intermittent), switch 11 to 11b and switch 27 to 2
The 7b side and the switch 28 are fixed to the 28b side, and the capstan servo circuit 14 which is well known in the related art servos the capstan motor 5.

It should be noted that in the above-described embodiment, the tape feed amount for one time is set to one frame as an example, but it may be a predetermined period related to the repeating cycle of the video signal, and may be a natural multiple of the predetermined period. The same effect can be obtained as a minute.

(Effects of the Invention) As described above, in the intermittent feeding device of the present invention, the electric brake by the stop servo circuit can stably maintain the stopped state of the capstan motor, so that it is not necessary to provide a mechanical brake. Therefore, this intermittent feeding device
If used in a device such as
The cost can be reduced and a constant braking force can always be obtained. Further, according to the present invention, the number of pulses of the capstan FG signal is counted, and the capstan motor is stopped by switching to the electric brake by the stop servo circuit, so that the predetermined period (for example, 1 It is possible to carry out magnetic tape feeding by the amount of recording or reproducing a video signal that is a natural multiple of the number of frames) with much higher accuracy than before.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment, FIG. 2 is a timing chart at the time lapse, FIGS. 3 and 4 are waveform diagrams of signals for explaining the operation, and FIG. 6 is a timing chart of the conventional intermittent feeding device during time lapse, and FIG. 7 is a block diagram thereof. 10 …… Capstan drive amplifier, 31 …… Tape drive signal generation circuit, 32 …… Stop servo circuit, 33 …… Switching circuit.

Claims (1)

[Claims] 1. A first capstan FG signal is supplied, and a magnetic tape is run by an amount by which a video signal of a natural multiple of a predetermined period related to the repetition period of the video signal is recorded or reproduced. A tape drive signal generation circuit for generating a stop servo switching signal by counting the first capstan FG signal as well as generating the first tape drive signal, the first capstan FG signal, and the first capstan FG signal. A second capstan FG signal having a predetermined phase difference from the capstan FG signal is supplied, the second capstan FG signal is rectified to generate a second tape drive signal, and the first capstan FG signal is generated. And a stop servo circuit for generating a second rotation direction control signal based on the second capstan FG signal, and the stop servo switching signal supplied with the first and second tape drive signals. A first switch that selectively outputs one of the signals in accordance with the number of the signal, and a first rotation direction control signal from the external mechanism control circuit, and the second rotation direction control signal. A switching circuit having a second switch for selectively outputting one of the signals in accordance with the stop servo switching signal, and a capstan drive for driving a capstan motor by being supplied with the output signal of the switching circuit. An intermittent feeding device characterized by comprising a circuit.