JPH083953B2 - Tape counter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tape counter suitable for use in a video tape recorder or the like.

[Outline of Invention]

The present invention counts the positive polarity pulse signal and the negative polarity pulse signal generated when reproducing a pulse-shaped control signal recorded at a predetermined cycle in the longitudinal direction of the magnetic tape, and also determines the polarity of the one polarity. When the pulse of 1 is missing, the running amount of the magnetic tape is accurately measured by counting the pulse of the other polarity.

[Conventional technology]

Usually, in order to measure the running amount of the magnetic tape, a pulse-shaped control signal recorded at a predetermined position at a predetermined position in the longitudinal direction of the magnetic tape is reproduced, and one of the positive and negative pulse signals generated at that time is reproduced, for example. This is done by counting positive pulse signals with a counter.

FIG. 3 shows an example of a conventional tape counter,
In the figure, (1) is a magnetic tape, (2) is a control signal detecting head, (3) is an amplifier, (4) is a Schmitt circuit, and (5) is a counter. The control signal reproduced from the magnetic tape by the head (1) is amplified by the amplifier (3), waveform-shaped by the Schmitt circuit (4), supplied to the counter (5) and counted.

[Problems to be solved by the invention]

By the way, the magnetic tape (1) is usually formed by the head (2).
The control signal reproduced from the above is subjected to waveform shaping as described above and supplied to the counter (5), so that there is no particular problem during normal reproduction. However, during slow reproduction or the like, so-called spacing loss, in which the gap between the head and the tape becomes large, may increase, and dropout, which is a lack of pulses to be counted, may occur.

Also, during intermittent slow playback in which step feed is repeated and playback is performed at 1 / n speed, depending on the stop position of the tape, positive and negative pulses may not be obtained and only negative pulses may be obtained. is there. This will be described with reference to FIG.

That is, as shown in FIG. 4A, the control signal is the magnetic flux N, S on the predetermined position side in the longitudinal direction of the magnetic tape (1), for example, the lower end.
Is recorded in the form of FIG. 4B by scanning this from the magnetic flux N to the S side by the control signal detecting head (2).
A pulse signal of positive polarity as shown in Fig. 4 is obtained, and a pulse signal of negative polarity as shown in Fig. 4B is obtained by scanning from the magnetic flux S to N, and these are passed through the Schmitt circuit (4). As a result, a pulse signal as shown in FIG. 4C is formed, and the counter (5) counts the rising time of this pulse signal. When the traveling is started from the stop position of FIG. 4A, the magnetic flux change of N → S → N is normally generated in the head (2), so that the pulse signal is as shown on the left side of FIG. 4B. The generated control signal is reproduced correctly, but the change in magnetic flux at the point when the vehicle starts traveling from the stop position in FIG. 4A is not sufficiently added to the head (2), so that the right side of FIG. As shown, a positive pulse signal is not generated, but only a negative pulse signal due to the change of magnetic flux from S to N on the rear side, the Schmitt circuit (4) in the subsequent stage does not move, and the output side thereof is shown in FIG. No pulse signal is obtained as shown on the right side of C, and no control signal is supplied to the counter (5) in this case.

Therefore, although the magnetic tape (1) is running, the counter (5) remains uncounted,
The running amount of the magnetic tape (1) cannot be measured correctly.

This occurs in principle when compatible playback is performed and when the slow tracking control volume is shifted, and can be said to be a fatal problem in an editing machine or the like that requires editing accuracy.

The present invention has been made in view of deceptive points, and it is possible to count the pulse of the other polarity even if the pulse of one polarity is missing from the panel signals having positive and negative polarities generated by the magnetic head. It is intended to provide a counter.

Therefore, it is an object of the present invention to provide a tape counter capable of accurately measuring the running amount of a magnetic tape even when dropout occurs due to an increase in spacing loss during slow reproduction or the like. To do.

It is another object of the present invention to provide a tape counter capable of accurately measuring the running amount of a magnetic tape regardless of the stop position of the magnetic head in the case of intermittent slow reproduction or the like. It is what

[Means for solving problems]

The tape counter according to the present invention comprises a magnetic tape (1)
When the positive polarity pulse signal and the negative polarity pulse signal generated when reproducing the pulse-shaped control signal recorded at a predetermined cycle in the longitudinal direction of the pulse are counted and the pulse of the one polarity is missing. Is configured to measure the running amount of the magnetic tape by counting the pulses of the other polarity.

[Action]

When the control signal detection head (2) detects a pulse-shaped control signal recorded at a predetermined cycle in the longitudinal direction of the magnetic tape (1), positive and negative pulse signals are obtained. Then, normally, a pulse of one polarity, for example, a pulse of positive polarity is counted by the counter (5), and if a pulse to be counted is missing, a pulse of the other polarity, for example, a pulse of negative polarity is counted. That is, the pulses of the positive polarity and the negative polarity of the reproduced control signal are mutually interpolated and used. This substantially prevents the loss of control signals,
The accuracy of the counter is improved and the running amount of the magnetic tape can be measured correctly.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows the circuit configuration of the present embodiment. In FIG. 1, parts corresponding to those in FIG.

In this embodiment, a phase divider (1
0) is provided, and signals of opposite phases are obtained at the output side. That is, an output signal of the same phase as the input signal supplied to the phase divider (10) from the amplifier (3) is output to one output side of the phase divider (10), and the other of the phase divider (10) is output. An output signal having a phase opposite to that of the input signal supplied from the amplifier (3) to the phase divider (10), that is, a signal having a phase opposite to the output signal of one output side is output to the output side.

The output signals from the phase divider (10) are supplied to the waveform shaping circuits (11) and (12), respectively, and the waveform is shaped. The output signals from the waveform shaping circuits (11) and (12) that have undergone waveform shaping are supplied to the OR circuit (13) and added. The signals added by the OR circuit (13) are supplied to the monostable multivibrator (14), where they are substantially counted down and passed through the S side of the switch circuit (15) to the counter (5).
Is supplied to and counted.

The switch circuit (15) is switched by a mode switching signal, and is connected to the contact N side during normal reproduction and connected to the contact S side during intermittent slow reproduction.

In addition, a switch circuit (16) is provided on the output side of the waveform shaping circuits (11) and (12), and the switch circuit (16) is switched by a forward (FWD) and reverse (REV) switching signal, and contacts at the time of forward. It is connected to the F side and supplies the output signal of the waveform shaping circuit (11) to the microcomputer (17). At the time of reverse, it is connected to the contact R side and outputs the output signal of the waveform shaping circuit (12) to the microcomputer (17). Supply. The microcomputer (17) controls the tape feed timing, the tape stop position, and the like during intermittent slow playback.

Next, the circuit operation of FIG. 1 will be described with reference to FIG. 2 by taking the case of intermittent slow speed reproduction of 1/5 speed as an example.

Now, when the head (2) scans the magnetic tape (1), a pulsed control signal recorded at a predetermined position in the longitudinal direction of the magnetic tape (1) is detected by the head (2),
A pulse signal S ₁ having a positive polarity and a negative polarity as shown in FIG. 2A is obtained at the output side of the amplifier (3). In FIG. 2A, the positive pulse signal is normally generated at the positions of ,, and, and the positive pulse is missing at the positions of and for the reasons described above. In addition, in the case of 1/5 speed, T ₁ is about 166 ms (normal playback is about 33 m
s), T ₁ is approximately 16.6 to 25 ms (16.6 ms during normal playback).

This pulse signal S ₁ is supplied to the phase divider (10), phase-divided there, and one output side thereof has a pulse signal S _{2 in} phase with the pulse signal S ₁ as shown in FIG. 2B. As shown in FIG. 2C, a pulse signal S ₃ having a phase opposite to that of the pulse signal S ₁ (the pulse signal S ₂ and the pulse signal S ₂ have an opposite phase relationship) is obtained at the other output side.

These pulse signals S ₂ and S ₃ are respectively generated by the waveform shaping circuit (1
It is supplied to 1) and (12), and the waveform is shaped here. As a result, the output of the waveform shaping circuits (11) and (12) has waveform-shaped pulse signals S ₄ and S ₄ as shown in FIGS. 2D and 2E corresponding to the positive and negative pulses of the signal S ₁ , respectively. You get S ₅ . These pulse signals S ₄ and S ₅ are transmitted to the OR circuit (1
The pulse signal S ₆ shown in FIG. 2F is obtained at the output side of the OR circuit (13).

In the state of the pulse signal S ₆ , a control signal having twice the number of pulses in the normally reproduced portion and one pulse in the missing portion is obtained, which causes inconvenience. Therefore, a predetermined delay time (pulse A pulse signal S as shown in FIG. 2G, which is supplied with a pulse signal S ₆ to a monostable multivibrator (14) having a width S ₃ and is made to have an overall multiplication factor, that is, only a missing portion is replenished. _{Get 7} . The time T ₃ is, for example, about 50 ms.
Is.

This pulse signal S ₇ is supplied to the counter (5) via the contact S side of the switch circuit (15), and the edge of the pulse signal S ₇ , for example, a rising edge is counted as a control signal. In FIG. 2G, the rising edge of-corresponds to the portion of-in FIG. 2A, the missing portion is substantially supplemented, and the control signal is continuously counted.

Also, the switch circuit (16) contacts the contact F during forward.
Connected to the output side of the waveform shaping circuit (11) S ₄ (second
Pass pulse signal as shown in FIG. 2H corresponding to FIG. D)
S ₈ is supplied to the microcomputer (17), the switch circuit (16) is switched to the contact R side during reverse, and the panel signal (corresponding to the output signal S ₅ (FIG. 2E) of the waveform shaping circuit (12) ( A microcomputer (17) is not shown)
The tape is controlled to control the timing of tape feed and the tape stop position during intermittent slow playback. In addition,
Microcomputer (1
The pulse signal supplied to 7) is switched so that the control signal is generated substantially at the same reference position.

During normal reproduction, the switch circuit (15) is switched to the contact N side, and the output signal of the amplifier (3) is waveform-shaped by the Schmitt circuit (4) and supplied to the counter (5) for counting. At the time of normal reproduction, there is no loss of the control signal described with reference to FIG.
However, when the switch circuit (15) is switched to the contact N side during the intermittent slow reproduction, the pulse signal S ₁ obtained at the output side of the amplifier (3) is supplied to the Schmitt circuit (4) and the waveform is obtained. After being shaped, a pulse signal S ₉ as shown in FIG. 2I is generated at the output side of the Schmitt circuit (4), and this is counted by the counter (5), so the counter value in the counter (5) is deviated. The counter (5) will malfunction and this is just conventional operation. Therefore, in this embodiment, the switch circuit (15) is switched to the contact S side during the intermittent slow reproduction to operate as described above. As a result, the counter (5) always operates normally and the running amount of the magnetic tape (1) can be accurately measured.

〔The invention's effect〕

As described above, according to the present invention, even if a pulse having one polarity is missing from the pulse signals having positive and negative polarities generated by the magnetic head, the pulse having the other polarity can be counted.

Therefore, according to the present invention, there is an advantage that the running amount of the magnetic tape can be accurately measured even when dropout occurs due to an increase in spacing loss during slow reproduction or the like.

Further, according to the present invention, there is an advantage that the running amount of the magnetic tape can be accurately measured regardless of the stop position of the magnetic head in the case of intermittent slow reproduction or the like.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a circuit diagram showing an example of a conventional circuit. The figure is for explaining the operation of FIG. (1) is a magnetic tape, (2) is a control signal detecting head,
(5) is a counter, (10) is a phase divider, (11), (1
2) is a waveform shaping circuit, (13) is an OR circuit, (14) is a monostable multivibrator, (15) and (16) are stitch circuits, and (17) is a microcomputer.

Claims (2)

[Claims] 1. A magnetic head for reproducing a control signal recorded on a magnetic tape to generate a pulse signal whose positive and negative polarities are alternately changed, and a counter for counting the pulse signal obtained by the magnetic head. In a tape counter configured to measure the running amount of a magnetic tape by counting the counter, one of a positive pulse and a negative pulse of the pulse signal obtained by the magnetic head is used as a trigger signal. When one of the pulses is missing, the counter has a monostable multivibrator that uses the other pulse as a trigger signal, and the counter is configured to count the edges of the pulse signal output from the monostable multivibrator. The tape counter which is characterized by being. 2. A tape counter according to claim 1, wherein a phase divider for separating a positive pulse and a negative pulse from a pulse signal having positive and negative polarities obtained by the magnetic head, and the phase divider. An adder for adding two pulse signals obtained by the divider, wherein the monostable multivibrator receives the pulse signal output by the adder as a trigger signal, and the cycle of the pulse signal of positive and negative polarities. A tape counter, which is characterized in that it generates a pulse signal having a pulse width smaller and larger than the deviation between the positive polarity pulse and the negative polarity pulse.