JPH0578097B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a helical scan type tape recorder, and when performing high-speed playback, the relative speed between the rotating head and the tape is kept constant, and the tape recorder is accurately recorded on the tape. The present invention relates to a tape recorder that can read recorded signals.

[Conventional technology]

Conventionally, when a helical scan type tape recorder is set to high-speed playback mode, a dedicated fixed head is used to control the tape running speed to a constant level based on the detection signal from this fixed head, and the tape running speed and tape at that time are The rotational speed of the drum equipped with a rotating head was changed in accordance with the running direction, so that the relative speed between the rotating head and the tape was kept constant.

[Problem that the invention seeks to solve]

Conventional helical scan tape recorders use a dedicated fixed head as mentioned above, which complicates the configuration of the tape running system and requires tape running speed control to maintain a constant relative speed. Two means were required: to determine the speed of rotation of the drum, and to determine the rotational speed of the drum.

This invention was made to solve the above-mentioned problems, and it is possible to control the relative speed between the rotating head and the tape during high-speed playback by using the playback signal from the rotating head, without using a dedicated fixed head. The purpose is to provide a tape recorder that can be kept constant.

[Means for solving problems]

The helical scan type tape recorder according to the present invention extracts an arbitrary constant frequency signal from a reproduction signal of a rotary head, and controls the rotational speed of the drum so that the frequency becomes constant.

[Effect]

In this invention, since a specific frequency component is extracted from the reproduction signal of the rotating head, the relative speed between the rotating head and the tape can be kept constant without using a dedicated fixed head, and the tape running system can be The configuration has been simplified.

〔Example〕

Before describing embodiments of the invention, the principle of the invention will first be described.

Helical scan tape recorders have
forming a signal for tracking a track on the tape, i.e. a tracking error signal, by a signal recorded on the tape without using a fixed head;
Automatic tracking by this
Some use the Track Finding (hereinafter referred to as ATF) method. One example is a rotary head digital audio tape recorder (hereinafter referred to as R-DAT) that records and plays back audio signals.
The track pattern is as shown in Figure 2. The signal for performing ATF is recorded in the shaded area in Figure 2 (the difference in the angle of the shaded line indicates the difference in recording azimuth), and the details of the recording pattern are as shown in Figure 3. .
As shown in Figure 3, the ATF signal recording area is
Signals with four different frequencies, numbered 1 to 4, are recorded. Note that this invention does not focus on the ATF method, and since it is well known how to perform tracking using these signals, a detailed explanation of the operation will be omitted.

Now, when this R-DAT is played back normally, the relative speed between the rotating head and the tape is a predetermined value, so
ATF signals 1 to 4 have a predetermined frequency, but as the tape running speed changes, the relative speed between the rotating head and the tape will deviate, resulting in
The frequencies of ATF signals 1 to 4 also change.

In view of the above, the present invention detects the frequency of the ATF signal and attempts to correct the relative speed deviation between the rotary head and the tape by controlling the rotational speed of the drum.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of a tape recorder according to the present invention. In the figure, 1 is a tape, 2 is a rotary head for reproducing the signal from the tape 1, and 3 is a head amplifier connected to the rotary head 2. 4 is a low-pass filter (or band-pass filter) that passes only one frequency signal included in the reproduced signal, and 5a and 5b are first filters that convert the output signal of the low-pass filter 4 and the output signal of the head amplifier 3 into TTL level signals, respectively. and a second waveform shaping circuit. Reference numeral 6 denotes one frequency counter connected to the first waveform shaping circuit 5a, which measures one signal period using the clock signal 24. 7 is a digital comparator that compares the measured value of one frequency with a reference value 26.

8 and 9 are the second waveform shaping circuits 5b, respectively.
The outputs of the two frequency detection circuit and the three frequency detection circuit are connected to the digital comparator 7 and the up-down pulse generator 11 via the OR gate 10.

Reference numeral 12 denotes an initial value memory circuit composed of an up-down counter, which stores reference data 28 and up-down pulses 29 from the up-down pulse generator 11.
Alternatively, the down pulse 30 is input. 13 is an error counter connected to the initial value memory circuit 12, 14 is an error latch circuit connected to the error counter 13, and 15 is an error latch circuit 1.
This is a speed error signal output circuit connected to 4. A motor drive amplifier 1 is connected to the output terminal of this speed error signal output circuit 15 via a low pass filter 16.
7, and this amplifier 17 drives the drum motor 1.
It is designed to drive 8. 19 is a rotating pulse generator attached to the drum motor 18;
A third waveform shaping circuit 5c for TTL level conversion is connected to its output terminal via a preamplifier 20. A pulse generator 21 is connected to the output terminal of the third waveform shaping circuit 5c, and is set to apply short width pulses 22 and 23 to the error latch circuit 14 and the error counter 13, respectively. . The above code 5c and 12 to 21
This constitutes a servo loop for controlling the rotational speed of the drum, and speed error detection is performed using a digital signal processing method. Note that 27 is a control signal output from the digital comparator 7 to the up-down pulse generator 11;
Reference numerals 2 and 33 are a head switching signal, a search command, and a search direction designation command which are input to the up-down pulse generator 11, respectively. 34 is
This is a latch pulse from OR gate 10.

Next, the operation of the above configuration will be explained.

Signals recorded on tape 1 are reproduced by rotary head 2 and amplified by head amplifier 3. The output signal of the head amplifier 3 is input to a low pass filter 4 that passes only one frequency signal, which is a constant low frequency signal included in the reproduced signal, and a second waveform shaping circuit 5b. The signal that has passed through the low-pass filter 4 is converted into a TTL level signal by the first waveform shaping circuit 5a and then sent to the next stage 1 frequency counter 6.
Here, one signal period is measured by a clock signal 24 having a frequency much higher than the one signal frequency.

On the other hand, the signal converted to the TTL level by the second waveform shaping circuit 5b is input to the two-frequency detection circuit 8 and the three-frequency detection circuit 9, where the two signals and
Detection of three signals is performed. As shown in the recording pattern in Figure 3, one signal is always recorded on adjacent tracks of two or three signals, so when one of the two or three signals is detected,
One signal period has already been measured, and the measured value 25 of the one frequency counter 6 is latched into the digital comparator 7 via the OR gate 10 by the output signal of the two frequency detection circuit 8 or the three frequency detection circuit 9. At this time, one signal will be reproduced by the reverse azimuth head, but its frequency is low enough that it is not affected by the azimuth effect much and does not pose a problem.

The digital comparator 7 compares the preset reference value (one signal period) 26 with the latched measurement value 25 and outputs a control signal 27 to the up-down pulse generator 11 in accordance with the difference.

The rotational speed of the drum is controlled by a rotational pulse generator 19 attached to the drum motor 18.
The rotational pulses generated by the rotation pulse are amplified by the preamplifier 20 and converted to TTL level by the third waveform shaping circuit 5c. The output signal of the third waveform shaping circuit 5c is
The signal is input to a pulse generator 21 which generates two successive short width pulses 22 and 23 synchronized, for example, with the rising edge of the input signal. The first pulse 2 generated by the pulse generator 21
2, the error latch circuit 14 outputs the error counter 1
The error counter 13 is latched with the second pulse 23 following the first pulse 22.
is the data of the counter initial value memory circuit 12.
LOAD. The speed error signal output circuit 15 outputs a speed error signal according to the count value latched in the error latch circuit 14, and outputs the speed error signal to the drum motor 18 via the next stage servo loop compensation low-pass filter 16 and motor drive amplifier 17. to drive.

This speed control servo loop has error counter 1
Control is performed so that the count value of 3 is always constant, that is, the rotation pulse period of the drum motor 18 is constant, and by changing the data in the initial value memory circuit 12, arbitrary values can be set. The rotation speed can be specified. In this embodiment, the initial value memory circuit 12 is constituted by an up-down counter, and during normal playback, reference data 28 is stored to maintain a predetermined drum rotation speed (2000 RPM). When the high-speed playback mode is entered, the stored data is updated based on the reference data 28 by the up pulse 29 or down pulse 30 generated by the up down pulse generator 11 in accordance with the controller signal 27 output by the digital comparator 7. It will be changed sequentially.

If the relative speed between the rotary head 2 and the tape 1 is slow, one signal period will be long, so in order to increase the rotation speed of the drum, the up-down pulse generator 1 is
1, an up pulse 29 is generated, and the data stored in the initial value memory circuit 12, which is constituted by an up/down counter, is counted up. Conversely, if the relative speed between the rotary head 2 and the deep drum 1 is high, one signal period becomes short, so in order to slow down the rotation speed of the drum, the down pulse 30 is generated from the up down pulse generator 11, and the initial value is The data stored in the memory circuit 12 is counted down.

The timing of generating the up pulse 29 or the down pulse 30 is synchronized with the rising and falling edges of the head switching signal 31.
This is done each time the rotary head 2 traces the track recorded on the tape 1. The control signal 27 output from the digital comparator 7 limits the number of up pulses 29 or down pulses 30 that are generated in synchronization with the head switching signal 31. For example, when the measured value Tx of one signal period is compared with the reference value To. Then, To−2%<
When it is within the range of Tx<To+2%, pulse generation is stopped, and when it is within the range of To±2% or more, the number of pulses is varied according to the difference,
I am trying to quickly pull it within To±2%.

The two-frequency detection circuit 8 and the three-frequency detection circuit 9 have frequency detection range characteristics that allow them to detect even if the relative speed deviates considerably, so that they will not be missed under normal conditions. If you shift to high-speed playback mode and suddenly change the tape run, the rotational speed of the drum will change slowly and the relative speed will deviate significantly, resulting in two signals or
In order to avoid missing the detection of the 3 signals, when the high-speed reproduction mode transition command (search command) 32 is input, the up-down pulse generator 11 generates a latch pulse output from the OR gate 10 in accordance with the search direction designation command 33. Up pulse 29 or down pulse 30 is generated until 34 is input. In other words, in the case of a forward direction search, the drum rotation speed must be increased.
In the case of a reverse direction search, continuous up pulses 29 are generated to slow down the drum rotation speed, but continuous down pulses 30 are generated to speed up the change in drum rotation speed. By updating the data in the initial value memory circuit 12 using the method described above, the rotational speed of the drum is controlled so that there is no relative speed deviation. As a result, one signal period always becomes a predetermined value, and the relative speeds of the rotary head 2 and tape 1 are kept constant.

〔Effect of the invention〕

As described above, according to the present invention, the specific signal frequency of the signal reproduced from the rotary head is detected and the rotation speed of the drum is controlled so that the frequency always becomes a predetermined value. The relative speed of the tape can be kept constant, making it possible to read signals accurately even when the tape is running at high speed. Furthermore, since a dedicated fixed head is not used, the tape running mechanism has the advantage of being simpler in configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a tape recorder according to the present invention, FIG. 2 is a diagram showing an R-DAT track pattern, and FIG. 3 is a detailed diagram of an ATF signal recording pattern. 2 is a rotating head, 4 is a low-pass filter (or band-pass filter), 6 is a frequency counter, 7 is a digital comparator, 8 and 9 are frequency detection circuits, 11 is an up-down pulse generator,
12 is an initial value memory circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A helical scan type tape recorder, comprising a filter that passes only a certain low frequency signal component included in a signal reproduced by a rotating head;
a first waveform shaping circuit that converts the output signal of the filter into a TTL level signal; a frequency counter that receives the output signal of the first waveform shaping circuit as an input and measures the period of the low frequency signal; A second waveform shaping circuit inputs the reproduced signal and converts it into a TTL level signal, and inputs the output signal of this second waveform shaping circuit and converts the other two types of frequency components included in the reproduced signal, respectively. First and second frequency detection circuits detect independently, and the value measured by the frequency counter is latched based on each output of the first and second frequency detection circuits, and the latched measurement value and A digital comparator that compares the value with a reference value and outputs a control signal according to the difference, and data stored in an initial value memory circuit that specifies the drum rotation speed based on the control signal output from the digital comparator. and a pulse generator that generates pulses for changing the data, the data in the initial value memory circuit is varied by the output pulse of the pulse generator, and the drum is rotated so that the period of the low frequency signal is constant. A tape recorder characterized by speed control. 2. The tape recorder according to claim 1, wherein the initial value memory circuit is an up-down counter. 3. The tape recorder according to claim 1, wherein the pulse generator is configured to vary the number of pulses generated in response to the output control signal of the digital comparator. 4. The tape recorder according to claim 1, wherein the timing of the pulses generated by the pulse generator is synchronized with the head switching signal. 5. Claim 1, wherein the rotational speed of the drum is varied by changing the data stored in the initial value memory circuit only in the high-speed playback mode.
Tape recorder as described in section. 6 From the time of transition to high-speed playback, the above first or second
2. The tape recorder according to claim 1, wherein said pulse generator is configured to generate continuous pulses until each frequency detection circuit detects a predetermined frequency signal.