JPH0568020B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] 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.

[Prior Art] 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 a detection signal from this fixed head. The rotational speed of a drum equipped with a rotating head is changed in accordance with the tape running speed and the tape running direction, so that the relative speed between the rotating head and the tape is kept constant.

[Problems to be solved by the invention] Conventional helical scan type tape recorders use a dedicated fixed head as described above, which complicates the configuration of the tape running system and makes it difficult to maintain a constant relative speed. Therefore, two means were required: controlling the running speed of the tape and determining 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 the Problems] The helical scan type tape recorder according to the present invention extracts an arbitrary constant frequency signal from the reproduction signal of the rotary head, and adjusts the rotational speed of the drum so that the frequency becomes constant. It is something to control.

[Operation] 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 The configuration of the driving system has been simplified.

[Example] Before describing the example of this invention, the principle of this invention will be described first.

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 of four different frequencies are recorded from f1 to f4. 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
The ATF signals f1 to f4 have a predetermined frequency, but as the tape running speed changes, the relative speed between the rotating head and the tape will deviate.
The frequencies of ATF signals f1 to f4 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 FIG. FIG. 1 shows the circuit configuration of an embodiment, in which a signal recorded on a tape 1 is reproduced by a rotary head 2 and amplified by a head amplifier 3. The output signal of the head amplifier 3 is input to a frequency discriminator (low-pass filter or band-pass filter) 4 that passes only the f1 frequency signal, and a second waveform shaping circuit 5b. The signal that has passed through the frequency discriminator 4 is input to the first waveform shaping circuit 5a, where it is converted to a TTL level signal and transmitted to the next stage f1 frequency counter 6, where the f1
Signal frequencies are counted.

On the other hand, the signal converted to the TTL level by the second waveform shaping circuit 5b is input to the f2 frequency detection circuit 8 and the f3 frequency detection circuit 9, where the f2 signal and
Detection of f3 signal is performed. As shown in the recording pattern in Figure 3, the f1 signal is always recorded next to the f2 or f3 signal, so by the time either the f2 or f3 signal is detected, the f1 signal frequency has already been counted. and f2 frequency detection circuit 8
Or OR by the output signal of f3 frequency detection circuit 9
Via gate 10, the count value of f1 frequency counter 6 is latched into digital comparator 7.
At this time, the f1 signal will be reproduced by the reverse azimuth head, but its frequency is sufficiently low and is not affected by the azimuth effect much, so it does not pose a problem.

The digital comparator 7 compares the preset reference value (1 signal frequency) with the latched count value, and transmits data to the digital adder 11 to correct the drum rotation speed according to the difference. It will be done. The digital adder 11 is a component of the speed control servo loop that controls the rotational speed of the drum, and rotational speed deviation data is also input here, and the data is added to the aforementioned rotational speed correction data and sent to the next stage low-pass filter 12. PWM output to. The low-pass filter 12 smoothes the PWM signal and converts it into an analog signal.
Drum motor 14 is driven.

Through the above operations, the rotational speed of the drum is controlled so that the f1 signal frequency reproduced by rotary head 2 always becomes a predetermined frequency, and the relative speed between the rotary head and the tape is kept constant. .

[Effects 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 rotational speed of the drum is controlled so that it always becomes a predetermined value. The relative speed between the rotating head and the tape can be made constant, making it possible to read signals accurately even when running a high-speed tape. 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 diagram showing a circuit configuration of an embodiment of a tape recorder according to the present invention, FIG. 2 is a diagram showing a track pattern of an R-DAT, and FIG. 3 is a detailed diagram of a recording pattern of an ATF signal. 2... Rotating head, 4... Frequency discriminator, 5a, 5
b... Waveform shaping circuit, 6... Frequency counter, 7... Digital comparator, 8, 9... Frequency detection circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A helical scan type tape recorder, which includes a frequency discriminator that passes only a certain low-frequency signal component included in the signal reproduced by the rotary head, and a frequency discriminator that converts the output signal of the frequency discriminator to a TTL level signal. a first waveform shaping circuit; a frequency counter that receives the output signal of the first waveform shaping circuit as an input and counts the frequency of the low frequency signal;
TTL by inputting the playback signal from the above rotating head.
a second waveform shaping circuit that converts the signal into a level signal;
first and second frequency detection circuits that input the output signal of the second waveform shaping circuit and independently detect the other two types of frequency components included in the reproduced signal; A digital comparator latches the value counted by the frequency counter based on each output of the frequency detection circuit, compares the latched count value with a reference value, and outputs correction data according to the difference. . A tape recorder, wherein the rotational speed of the drum is controlled based on the output of the digital comparator so that the frequency of the low frequency signal becomes a predetermined value.