JPS6286567A - Tape speed controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to tape speed control of a rotary head type VTR and a rotary head type digital audio tape recorder, and particularly relates to tape speed control for a rotary head type VTR and a rotary head type digital audio tape recorder, and in particular, to drive a reel to run the tape at a high speed and at a constant speed. The present invention relates to a control device suitable for controlling.

[Background of the invention]

In order to perform a high-speed search (to find the beginning of a song) at a speed several tens to hundreds of times faster than the normal playback speed in an audio tape recorder (audio tape recorder), it is necessary to search for the beginning of a song recorded in a track. In any case, control signals recorded at the same recording density as PCM signals, such as signals for displaying time, signals for indicating the number of songs from the beginning of the tape, etc., are It is necessary to read the speed tape while running. When a head attached to a rotary cylinder scans a tape running at a tape speed different from that during normal recording and playback, the scanning of the head records information on the tape, as illustrated in Japanese Patent Laid-Open No. 57-12448. It becomes a trajectory that crosses the track. At this time, if the rotation speed of the cylinder is constant, the time required to scan the tape is constant, but the trajectory of the head is different from the length of the track on the tape, so the relative speed of the tape head changes. This phenomenon occurs.

Rotating head digital audio tape recorders use a data punching circuit to reproduce digital signals from the reproduced signals, but the input transmission rate of this circuit usually has a margin for speed deviation and jitter in the tape running mechanism. It is about a few percent.

Therefore, if a high-speed search is performed at a tape speed that is significantly different from the normal playback speed, the relative speed of the head and tape may deviate.
If the transmission rate of the input signal changes, there is an inconvenience that a digital signal cannot be reproduced from the reproduced signal.

On the other hand, during normal playback, the tape running mechanism presses the capstan and pinch roller to drive the tape at a constant speed. However, this method is difficult, and a method is usually used in which the tape is wound by rotating the reel shaft.

In this method, the reel shaft rotational speed is generally constant, and the tape speed is determined by the amount of tape wound on the reel (winding diameter).
varies significantly. In order to keep the relative speed of the head and tape constant as described above, (1) cylinder rotation &
There are two methods that can be considered: (2) controlling the tape speed to be constant during high-speed tape running, and switching the cylinder speed to a rotational speed corresponding to the speed. Method (1) is also possible, but it is undesirable in that the search speed changes depending on the state in which the tape is wound.This point is also the same with general VTRs, and the search speed for picture search changes. There are drawbacks to this.

Therefore, the method (2) requires high-speed and constant-speed tape drive.
As shown in No. 12448, in addition to helical scanning of the head, tracks Φ are provided in the running direction of the tape and recorded at regular intervals on the tape.
A method has been proposed in which the tape speed is detected and controlled based on the frequency of the control signal read during high-speed running. However, this method does not work with VTRs that do not have control signals (e.g. 8-bit VTH).
Rotating head digital audio tape recorder)
&C cannot be handled.

In addition, as shown in JP-A-54-156506, means is provided to generate a signal corresponding to the rotational speed of both the reel shaft on the supply side and the take-up side. A method of keeping the tape speed constant has also been proposed.

However, this method has the disadvantage that errors due to the total length of the tape, the thickness of the tape, the diameter of the reel hub, the way the tape is wound, etc. [Object of the Invention] The purpose of the present invention is to An object of the present invention is to provide a tape speed control device for running a tape at high speed and accurately at a constant speed in a type of VTR without a tape.

[Summary of the invention]

In a picture search in a VTR or a high-speed search in a rotary head digital audio tape recorder, a search is not performed on an unrecorded tape, so it can be considered that signals have already been recorded on the tape.

The present invention focuses on the fact that the head scans across the tracks recorded on the tape during high-speed search, and since there is a one-to-one correspondence between the tape speed and the number of tracks crossed,
The purpose of this system is to count the number of tracks crossed, detect the tape speed, and control the motor that drives the reel shaft.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a block diagram of an embodiment of the present invention, showing the parts of a VTR, a rotary head type digital audio tape V coder, which are related to the present invention, and the structure of the present invention.

1 is a rotary cylinder, 2a and 2b are heads attached to the cylinder 1, and 3 is a magnetic tape, which will be described below by way of example with a winding angle of 90 degrees as shown in FIG. The signals reproduced from heads 24 and 2b are 1
．． Increase by 1 with 4 regenerative amplifiers! 3, the waveform equalizer 5 performs equalization, and the output is sent to another video signal processing circuit (not shown) in the case of a VTR, or to a PCM data punching circuit in the case of a rotary head digital audio tape recorder. (not shown). The output of the waveform equalizer 5 is
At the time of high-speed search, the waveform becomes as shown in FIG. 2 (α). Since the tape winding angle is 90 degrees, the signal output period is intermittent, and since the head crosses the recording track on the tape, the envelope has peaks and valleys corresponding to the recording track.

This situation will be explained with reference to FIG. In FIG. 3, numeral 5 indicates a magnetic tape, and arrow 19 indicates the running direction of the tape. arrow 2
0 indicates the scanning direction of the head, and 21 and 22 are tracks recorded on the tape by the two heads mounted on the cylinder.

The gaps between the two heads have different + and - azimuth angles with respect to the head running direction 20, and are recorded alternately on the tape. The track width of the normal head is
It is approximately 15 times the width of the track recorded on the tape,
For example, when the tape is run at high speed in the opposite direction to the tape running direction 19, the scanning locus of the head becomes m2S. Here, if the head with the azimuth angle on the + side scans as shown by the broken line 23, the playback output from the head will only include the part of the track recorded by the head with the azimuth angle of 10 (the hatched part). During reproduction, a track (for example, track 22) written by a head with a negative azimuth angle is not reproduced due to azimuth loss. Therefore, as the width of the hatched area '4I' in FIG. 5 changes over time as the head scans, peaks and valleys will occur in the envelope.

This signal is input to the envelope detection circuit 6 shown in FIG.
Extracting the envelope of the signal results in a waveform as shown in FIG. 2(b). Next, it is input to a band-pass P-wave filter (BPF') 7, which collects the remainder of the signal (high frequency component) corresponding to the carrier of the original signal and the overall undulations of the signal envelope caused by the quality of contact of the tape head. (low frequency components). The output signal further shaped by the waveform shaping circuit 8 is shown in FIG. 2 (10). At this time, the waveform shaping circuit 8 may be configured by, for example, a comparator.

Next, the gate signal generation circuit 12 generates a signal (2
P2 Figure 1 dl) '4 This is a generating circuit. Although this part is not a necessary part in the present invention, the contact between the head and the tape is often not good in the part where the head starts contacting the tape or the part before the head leaves the tape. This is a circuit whose purpose is to take out only the central part of No. 1g. In the end, the output of the AND gate 9 is as shown in Fig. 2 + 6), and if the counting circuit 10 counts each section of this pulse '49 Di, the count value will be proportional to the number of recording tracks that the head scans across. get. Also, this count value is
Since it is also proportional to the tape running speed, the tape running speed can be detected.

The circuit after the F-V converter 11 is a circuit that controls the reel drive motor 18 based on the tape running speed detected as described above.

The F-V converter 11 is a circuit that generates a voltage proportional to the count value of the counting circuit 10, and the subtracter 14 generates a voltage corresponding to the difference between this voltage and the reference voltage 13 (l!! difference voltage)! Output. 16 is a circuit for driving the motor 18, and the motor drive voltage passes through a delay circuit 17 and is added by the adder 15 by the above error voltage.

If the tape running speed is higher than the preset speed, the error voltage becomes negative and the motor drive voltage decreases by the error voltage. If the reverse sum tag running speed is smaller than the set value, the error voltage becomes positive and the motor drive voltage increases. In this way, the tape running speed can be kept constant. Furthermore, if it is desired to change the set value of the tape speed, this can be easily done by changing the 6 single voltages 13.

FIGS. 4 to 6 show an example of the specific circuit shown in FIG. 1. Figure 4 shows the Empero 4 detection circuit 6 in Figure 1.
In one embodiment of the waveform shaping circuit 80, the terminal 24 is a power supply terminal, the terminal 25 is an input terminal, and the terminal 26 is an output terminal.

27 to 32 are resistors, 33 to older brother are capacitors, 37.58
is a transistor, 39 is a crystalline mit-trigger inverter, and 40 is a coil. Capacitor 33 and resistor 27-2
9 and a transistor 37 are back-up amplifiers based on emitter 7 orers, and a transistor 38, a resistor 3o, and a capacitor 34 are an envelope detection circuit. Coil 40 and capacitor 36 constitute HPF, and capacitor 3
The parallel resistances of 5 and 31.52 constitute an LPF-g, and both form a BPF. At the same time, the resistances 51 and 52 are Shemite
A bias is applied to the trigger inverter 39, and a waveform in which the envelope waveform is added to this bias voltage is input to the inverter 39 and shaped into the waveform shown in FIG. 1cJ. The reason why the inverter 39 is of the Shemitt trigger type is that there is a small irregularity (level change 4EII) in the envelope of the reproduced signal, which is detected and appears as noise in the waveform shown in Figure 2+b). This is to prevent malfunctions during shaping. FIG. 5 shows a specific circuit example of the AND gate 9 to gate signal generation circuit 120 in FIG. The terminal to which the output is input, the terminal 42, is the terminal to which the output of the gate signal generation circuit 12 of FIG. 1 is input, and the AND gate 9 is the AND gate 9 of FIG. ag1. counter 45
, 44 are universal male terminals equivalent to TTL's 74L8193 connected in cascade, and constitute an up-down counter. The terminal 45 is an input terminal for a signal indicating the rotational position of the cylinder, and this signal causes the counter 45.
44 is cleared and counted up by pulses corresponding to the number of peaks in the envelope of the reproduced signal. Next, after counting the number of peaks, the gate signal at the terminal 42 becomes low level, and at the same time the input terminal 46 becomes high level, and the constant periodic signal input from the input terminal 47 is ANDed.
The data is inputted to the counter 4 through the gate 48 and counted down using the counted number of peaks as an initial value. On the other hand, the signal from the input terminal 46 is passed through the inverter 49 to the N
A clip 70 block consisting of AND gates 50 and 51 is set, and when the counters 45 and 44 count down and a borrow occurs, the 7-lip 70 block is reset. In other words, by counting down the number of peaks in the envelope of the reproduced signal using a constant Kook signal, it is possible to convert the number of peaks into a time corresponding to the number of peaks.

Next, constant current source 52. Analog switch pot diode 54
．． Resistor 5 wire FET57. An integrating circuit is composed of a capacitor 58 and an operational amplifier 59.
The ET 57 is turned on and reset, the switch 55 is closed for a period of time corresponding to the number of peaks mentioned above, and the battery is charged by the current from the constant current source 52. In other words, the output of the operational amplifier 59 becomes a voltage proportional to the number of peaks. Note that the terminal 56 is a negative voltage current source terminal for biasing the gate of the FET 57 negatively.

Resistance 60.61. Analog switch 62. capacitor 6
4. A sample-and-hold circuit is composed of the operational amplifier 64, and samples and holds the voltage when the output voltage of the integrating circuit reaches a voltage corresponding to the number of peaks mentioned above. In this way, a voltage corresponding to the number of peaks mentioned above is outputted to the output terminal 65.

Next, FIG. 6 shows a specific circuit example of the hexadecimal voltage delay circuit 17 shown in FIG. 77 is a resistor, 78 is a variable resistor, 79.80 is a capacitor, 81.
82 is an operational amplifier. Terminal 68 is an input terminal for a voltage corresponding to the above-mentioned peak, and variable resistor 78 and capacitor 79 correspond to reference voltage 13 in FIG. resistance 70
73 and the operational amplifier 81 are subtracters, and subtract voltages corresponding to the number of peaks from 6 single voltages. This output becomes the error voltage.

The resistors 74 to 76 and the arithmetic booster 82 are an adder, and the resistor 7
7 and capacitor 80 are delay circuits. The terminal 69 is a control voltage output of the motor that drives the reel shaft, and by delaying the current output and adding it to the error voltage, speed errors can be corrected.

〔Effect of the invention〕

As described above, according to the present invention, in a format without a control signal (such as a digital audio tape recorder (8m VTR, turn & head type digital audio tape recorder)), when the head is running at high speed, By detecting the number of tracks scanned across the reel and controlling the motor that drives the reel shaft, it is possible to run the tape at a high and constant speed.

As a result, in a VTR, the search speed of the picture search can be made constant, and in a rotary head type digital audio recorder, high-speed song selection is possible.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, and FIG. 3 is a diagram showing recording tracks on the tape and the scanning trajectory of the head during high-speed tape running. The fourth prisoner is @
1, a specific circuit from the envelope detector 6 to the waveform shaping circuit 8, FIG. 5 shows a specific circuit from the AND gate 9 to the gate signal generation circuit 12 in FIG. 1, and FIG. 6 shows the reference voltage 13 in FIG. This is a specific circuit of the delay circuit 17. DESCRIPTION OF SYMBOLS 1...Rotating cylinder, 2...Head, 3...Tape, 1B-...Reel shaft drive upper motor. First day! 2nd eye - 5 Kyouichi - /q Figure 4

Claims (1)

[Claims] In a rotary head type PCM recorder or VTR in which recording and reproduction is performed by scanning the magnetic tape with a head mounted on a rotating cylinder, a high-speed system in which the reel shaft is driven to run the magnetic tape at a faster speed than the normal recording and reproduction speed. a traveling means, a detection means for bringing the head into contact with the magnetic tape during high-speed travel and detecting an envelope of the reproduced output of the head, and causing the head to scan across a plurality of recording tracks on the magnetic tape during high-speed travel. a counting means for counting the number of peaks and/or troughs of the detection output occurring between the two; and a means for controlling the rotation speed of the reel shaft so that the count value of the counting means is a predetermined constant value. A tape speed control device comprising: