JPS59215020A - Azimuth control system of tape recorder - Google Patents

Abstract

PURPOSE:To obtain an excellent reproducing characteristic by detecting an azimuth angle at reproduction and controlling the inclination of a magnetic head so as to correct the azimuth angle. CONSTITUTION:L and R channel signals reproduced from a reproducing magnetic head 22 are given respectively to preamplifiers 23, 23' and filters 24, 24', from which only a 10Hz component is extracted and inputted to a phase difference holding and output circuit 25. The said circuit 25 consists of a counter counting the phase difference of 10Hz component on the L and R channels, a register storing its count value and an output circuit converting the said count value into a time series pulse and outputting it. A stepping motor 26 is turned by an angle in response to the phase difference of the 10Hz component. The mounting base 32 of the magnetic head 22 changes its inclination around a support 33 by the turning of a screw 30.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to an azimuth control method for a tape recorder that improves azimuth angle loss during playback of a tape recorder.

(Background) During playback on a tape recorder, if the gap angle of the playback head deviates from that during recording, playback output loss increases. This is called azimuth angle loss.

In conventional tape decks, the azimuth angle is adjusted at the time of shipment, and the more expensive the machine is, the more rigid the mechanism is to reduce the fluctuations in the azimuth angle. Additionally, auto-reverse cassette tapes have recently become popular. In this device, the head is rotated or moved up and down as the tape rotates forward and backward. As a result, the azimuth angle differs between normal rotation and reverse rotation, causing a problem of increased azimuth angle loss.

FIGS. 1(a) and 1(b) are explanatory diagrams of azimuth angle loss. In the same figure (at, 1 is the tape, which is running in the direction of arrow 2. 3 is the gap of the playback head, which is in contact with the tape at an angle of θ compared to when recording. W is the tape) The reproduction signal is attenuated in proportion to the angle θ.

FIG. 5B is a characteristic diagram in which the attenuation of the reproduced output signal with respect to the angle θ is calculated according to theory. A in curve 4
The point is when θ is zero, that is, the playback head is correctly adjusted. Point B is a case where θ is tilted by 0.22 degrees, and the reproduction output is attenuated by approximately 3 dB compared to point A.

If θ fluctuates by ±0.1 degrees during playback due to meandering of the tape, etc., at point A, that is, if the playback head is correctly adjusted, the playback output waveform will be as shown by reference numeral 5. is accompanied by an amplitude variation of approximately 0.5 dB. On the other hand, it can be seen that in the case of point B, that is, when the reproducing head is tilted by 0.22 degrees, a large amplitude fluctuation of 5 dB occurs.

The above explanation is provided by the Television Society u Vo 134. Al
l.

I'(53) 1017.1980.

To prevent such azimuth angle loss effects, always set θ
must be kept at zero. However, keeping θ at zero means
In practice, this is difficult due to tape meandering, head installation errors and their fluctuations, and other causes.

Therefore, an adjustment method is required to automatically track θ to zero. Considering the principle of Cζ, there are four possible automatic adjustment methods. However, both methods have drawbacks and are difficult to apply when reproducing audio signals.

The first method is to detect the amplitude fluctuation of the reproduced output and adjust θ so that the amplitude fluctuation becomes the minimum Cζ.

However, this method is difficult to apply when the amplitude of the signal varies over time, such as in an audio signal.

The second method is to detect the reproduction amplitude and control the azimuth angle so as to maximize it.

This method has the disadvantage that, as seen in FIG. 1, the amplitude changes little with respect to the azimuth angle near the maximum amplitude.

The third method utilizes the fact that the reproduced waveform is distorted due to amplitude fluctuations. That is, in this method, components outside the signal band being reproduced and output are regarded as distortion components, and θ is adjusted to minimize them.

However, this method suffers from inaccuracies in separating components outside the signal band.

The fourth method is to directly measure and correct the azimuth angle. However, since the azimuth angle is determined based on the tape running direction 2, the effect will be low if the tape running direction 2 changes depending on the cassette.

As described above, each of the conventional methods that can be considered by those skilled in the art has its own drawbacks, and none of the methods has been able to significantly improve the azimuth angle loss during playback by a tape recorder.

(Objective) An object of the present invention is to provide a method for automatically adjusting the above-mentioned azimuth angle loss.

(Summary) The present invention is characterized by a means for reproducing, from a tape, a plurality of channels of azimuth angle calibration signals having different frequency bands from recording signals of the plurality of channels; The present invention includes means for comparing the phases of signals, means for outputting a signal according to the phase difference detected by the means, and means for changing the mounting angle of the magnetic head based on the signal from the output means. .

(Example) The present invention will be specifically described below. First, the present invention will be explained in detail using FIGS. 2 and 3.

FIG. 2 shows a two-channel recording tape. Two recording tracks 7 and 8 are recorded on the tape 1. These correspond to the left (left) and R (right) tracks of the stereo signal. In addition, in FIG. 2, in order to simplify the drawing,
The width of each track 7 and 8 is omitted, and only the center thereof is marked with a dotted line. 9 and 10 indicate the gap positions of the magnetic head during recording and reproduction, respectively. θ is the azimuth angle.

Assume now that the same sine wave is recorded on recording tracks 7 and 8, which are indicated by 7' and 8' in FIG. If the azimuth angle θ is zero during reproduction, that is, the magnetic head gap position 10 during recording coincides with the magnetic head gap position 9 during reproduction, the phases of the reproduced outputs coincide. but,
As shown in the figure, if the azimuth angle is shifted by θ, a corresponding phase difference of φ will occur. therefore,
Azimuth angle loss can be prevented by detecting this φ and adjusting the mounting angle of the reproducing head so that it becomes zero φ.

However, in the case of audio tape, track 7 and
Track 8 records L and R channel signals, respectively. For this reason, waveforms 7' and 8' do not become the same waveform as shown in FIG. 3, and therefore, no phase difference can be detected.

Therefore, in the present invention, waveforms corresponding to the waveforms 7' and 816ζ are recorded in the blank portions of both tracks. In a normal audio tape, there is usually a blank section, which is not recorded, at the beginning of the tape or between the recorded songs and the section between the songs. Waveforms 7' and 8'
The signal corresponding to is not necessarily a sine wave, but may be a rectangular wave or the like, and is recorded simultaneously at the time of recording. This will hereinafter be referred to as the blank signal or calibration signal.

Azimuth angle correction using a blank signal can only be performed during the blank period. Therefore, azimuth angle correction cannot be performed continuously during the entire reproduction period. However, this method also has sufficient effects from a practical standpoint.

Fluctuations in the azimuth angle during the regeneration period do not pose much of a problem in practice. That is, if the adjustment is made at the beginning of playback, there is no practical problem even if no adjustment is made thereafter, and it is even better if readjustment is made from time to time during playback. Such adjustment is particularly effective in the following cases.

The first case is when the data is played back using a tape recorder different from the tape recorder used for recording. Since the azimuth angle between different tape recorders generally differs, readjustment is necessary for good playback.

The second is auto reverse (
This is the case with a tape recorder (which automatically reverses the tape running direction). With the automatic reversal of the tape running direction, it is necessary to slide the magnetic head up and down from the A side to the 8th side, or in the opposite direction.

Or it is necessary to shift the position by rotation.

At this time, the azimuth angle tends to shift. Therefore, it is necessary to readjust the azimuth angle of the magnetic head Cζ.

As described above, the principle of the present invention is to use the blank signal inserted during the blank period to adjust the azimuth angle.

FIG. 4(a) shows a compact cassette tape 11,
Numbers in the figure indicate approximate dimensions (nursing device).

In the figure, one side of a tape 11 with a tape width of 3.8 VS is divided into two sides, A side and 8 sides, and L and R channel signals are recorded on the A side and B side, respectively, corresponding to stereo recording. Two tracks are provided. The width of the track is approximately 0.6 m.

17.18 indicates the center line of the A-side track and the R channel track, and the interval (track pitch) is approximately 0.9
It is vm.

FIG. fb1 shows the waveform of a blank signal for adjusting the azimuth angle similar to that in FIG. 3, and is recorded in the blank portion between songs of the recorded music signal. Waveforms 17' and 18' are set to 1 OHZ, for example, in order to distinguish them from music signals, etc.
A sine wave of is used.

Further, the waveforms 17' and 18' may be recorded in mutually opposite phases Cζ. If the running speed of the tape is 4.8 m/sec, the tape length l required to record one period of 10 Hz is 0.48 m.

Reference numeral 19 indicates the position where the magnetic rad gap hits during recording. It is natural that waveforms 17' and 18' are recorded in the same phase during recording. 2o indicates the case where the reproducing magnetic head is tilted by the azimuth angle θ, and the L and R channels iζ
The position of the hit head gap is shifted by Δl compared to the time of recording.

The size of Δl in the figure is given by the following formula (1): Δl=0.91an θ<m> ・・・・・・・・・
(1) The phase shift l between the reproduced signals corresponding to this Δl is given by the following equation (2).

For example, if θ-2°, φ becomes approximately 0.4 radian. Here, l indicates the length of tape required to record one cycle of waveforms 17' and 18'.

Next, one embodiment of the present invention will be described. FIG. 5 shows an embodiment of the present invention in which the azimuth angle θ is automatically adjusted to zero using the phase shift φ.

A reproducing magnetic head 22 is mounted on the stand 21.

The magnetic head for recording may be used for both the magnetic head for reproduction or may be provided separately, but illustration thereof is omitted here. Reference numeral 20 indicates a magnetic helad gap, which in FIG. 5 corresponds to the lower surface of the tape 1. L reproduced by the reproducing magnetic head 22
and the R channel signals are respectively transmitted through preamplifiers 23 and 23',
Only the aforementioned 10 Hz component is extracted through the filters 24 and 24' and input to the phase difference detection holding and output circuit 25. The circuit 25 has a 10Hz frequency on the L and R channels.
It is composed of a counter that counts the phase difference of the components, a register that holds the counted value, and an output circuit that converts the counted value into a time series pulse and outputs it. 26 is a stepping motor driven by the output pulse. In this way, the stepping motor 26 rotates by an angle corresponding to the phase difference of the 10 Hz component.

The rotation of the stepping motor 26 is controlled by a worm gear device 27 and spur gears 213 and 29 attached to its rotating shaft.
is transmitted to the screw 30 via. By rotating the screw 300 times, the mounting base 32 of the magnetic head 22 changes its inclination using the pillar 33 as a fulcrum. In this way, the magnetic rad gap 20
The azimuth angle with respect to the tape 1 is controlled according to the phase difference θ of the 10 Hz component, and corrected so that the phase difference θ becomes zero. 34 is a compression spring.

FIG. 6 is a block diagram for explaining the control circuit system of FIG. 5 in more detail.

The configuration and operation of the control circuit system will be explained using FIGS. 6 and 7. 61 (in FIG. 6, 20-1 and 20-2 are magnetic heads for L channel and R channel reproduction, which are made in the magnetic head 20. The reproduced signals thus obtained are input to waveform shaping circuits 35 and 35' through a preamplifier 23, a filter 24, an apparatus amplifier 23', and a filter 24', respectively.

In FIG. 7, a and b are respectively magnetic head 20-1.
, 20-2, that is, a waveform representing a blank signal or a calibration signal. A lead or a delay occurs between the output waveforms a and b depending on the azimuth angle. Therefore, correspondingly, two types of output waveforms of the magnetic head 20-2 are drawn: a waveform b1 with a delayed phase and a waveform b2 with an advanced phase. Output waveform C and d, e
are the output waveforms of waveform shaping circuits 35 and 35' of FIG. 6, respectively.

These output waveforms C and d or C and e are A,
The logical sum is taken by the ND circuit 38, and f in FIG.
Alternatively, a pulse waveform corresponding to the above-mentioned phase difference such as g can be obtained. Of the inputs to the AND circuit 38, the phase of the input from the waveform shaping circuit 35' is inverted. In addition, the output waveform f is a phase comparison pulse of the output waveform a,
Output waveform g is a phase comparison pulse between output waveforms a and b2.

On the other hand, the outputs of the waveform shaping circuits 35 and 35' pass through differentiating circuits 4], 41', diode circuits 42 and 42', and then go to a one-shit multivibrator circuit 43°43'.
is input.

The diode circuit 42 allows the rising and falling differential pulses of waveform C to pass through, and prohibits the falling differential pulse from passing through. on the other hand,
The diode circuit 42' allows the falling differential pulse of waveform d or e to pass through, and prohibits the passing of the rising differential pulse.

The output waveforms l and j in FIG. 7 are the output waveforms of the one-shot multi-node ibrator circuits 43 and 43', respectively.

In FIG. 6, 46 and 46' are OR circuits. At the input of the OR circuit 46, the waveform f or g shown in FIG.
Since the waveform f is input, only the output waveform f is output from the OR circuit 46.

Similarly, the output waveform f or g and the output waveform i or j are input to the OR circuit 46'.

Waveforms f and g are generated in correspondence with waveforms b1 and b2i, and do not occur at the same time. Therefore, when the OR circuit 46 outputs the pulse f, no output pulse appears in the OR circuit 46'. Similarly, when the OR circuit 46'l (pulse g) is output, the OR circuit 46 does not output a pulse. In this way, the output of the OR circuit 46 is the delayed phase code, The output is used as a leading phase code.

On the other hand, the pulse width of waveform f or g is counted by a clock signal 48 in a counting circuit 47. The counting result is stored in the register circuit 49. At the same time, the phase code is also stored. 50 outputs pulses to the stepping motor 26 in FIG. 5 in response to the contents of the register 49 to control its rotation angle.

The rotation direction of the stepping motor 26 is designated according to the above-mentioned phase code.

In this way, the azimuth angle is detected and corrected.

Once the correction is completed, the stepping motor 26 comes to rest. Thereafter, the azimuth angle detection signal recorded within the next blank period is detected. In this way, the azimuth angle change is corrected every time a blank period occurs.

In the above-described embodiment of the present invention, the case of a stereo magnetic tape was explained, but the present invention can also be applied directly to the case of multi-channel reproduction of two or more channels. In addition, many methods are generally known for detecting power of phase difference, and any configuration may be selected from among them and applied. The same applies to the mounting angle control mechanism of the magnetic head.

(Effects) According to the present invention, the azimuth angle at the time of reproduction is detected by reproducing the azimuth angle calibration signal of the magnetic head recorded on the blank portion of a tape recorded with multiple channels, and the azimuth angle of the magnetic head is detected. Tilt can be controlled. Therefore, it is possible to correct the azimuth angle and obtain good reproduction characteristics.

[Brief explanation of the drawing]

Fig. 1 ta)fb> is an explanatory diagram of azimuth angle loss, Fig. 2
The figure is an explanatory diagram of a 2-channel recording tape, Figure 3 is a waveform diagram of a blank signal, and Figure 4 (a) (bl is an explanatory diagram of a stereo signal and azimuth angle calibration signal recorded on a compact cassette tape. Fig. 5 is a block diagram of an embodiment of the present invention, Fig. 6 is a detailed block diagram of the phase difference detection/holding and output circuit, and Fig. 7 is a waveform diagram of the main parts of the signals in Fig. 6.1.・Tape, 20...Magnetic Rad Gap,
22... Magnetic head for reproduction, 23.23'... Preamplifier, 24.24'... Filter, 25...
・Phase difference detection holding and output circuit, 26... Stella pink motor, 27... Worm gear device, 2
8.29...Spur gear, 30...Screw, 32...
・Mounting stand, 33...Pillar Attorney Michihito Hiraki Figure 1 (G) (b)

Claims (2)

[Claims] (1) Means for reproducing, from the tape, azimuth angle calibration signals of multiple channels having different frequency bands from the recording signals of the multiple channels, and means for comparing the phases of the azimuth angle calibration signals reproduced from the multiple channels. An azimuth control system for a tape recorder, comprising means for outputting a signal according to the phase difference detected by the means, and means for changing the mounting angle of a magnetic head according to the signal from the output means. . (2) A patented azimuth control method characterized in that the azimuth angle calibration signal is recorded in a blank section between recorded signals.