JPH0644366B2 - Mode discriminating device for magnetic recording / reproducing apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mode discriminating apparatus for a magnetic recording / reproducing apparatus,
In particular, the present invention relates to a mode discriminating apparatus at the time of reproduction in a pilot signal type magnetic recording / reproducing apparatus capable of recording / reproducing at plural tape speeds.

[Prior Art] Conventionally, in a magnetic recording / reproducing apparatus, there are a tape speed running control method using a control signal and a method using a pilot signal. In the method using the control signal, the tape running control is performed by providing the magnetic tape with a control track different from the video signal track and recording / reproducing the control signal using the control track. Magnetic recording / reproducing devices that use this control signal include devices that can record / reproduce at multiple tape speeds, and that device has a mode determination device that automatically determines the tape running mode during reproduction. It was being done. Then, this mode discriminating device uses the control signal described above,
The tape running mode during playback was determined.

On the other hand, in the method using the pilot signal, a tape speed control pilot signal generated in synchronization with the rotation of the rotary magnetic head is recorded on the video signal track of the magnetic tape by superimposing the video signal on the track, and at the time of reproduction, The pilot signal is extracted from the reproduction signal and the tape running control is performed by the pilot signal. In the magnetic recording / reproducing apparatus that uses this pilot signal, recording / recording is currently performed at a single tape speed.
Only the playback device is commercially available. Therefore, it goes without saying that such a device is not provided with a mode discriminating device for discriminating the tape speed.

Next, tracking control in the pilot signal type magnetic recording / reproducing apparatus will be described. FIG. 1 shows a conventional magnetic recording / reproducing apparatus (VT) using a pilot signal.
It is a block diagram of the tracking control means of R). In the figure, a head switch signal input terminal 1 is connected to an adder 3 via a pilot signal generator 2. The head switch signal input terminal 1 is connected to the switch 18. The video signal input terminal 4 is connected to the changeover switch 6 via the adder 3 and the recording amplifier 5, and the changeover switch 6 is connected to the magnetic head 8 via the rotary transformer 7. The magnetic head 8 is provided on a rotating drum (not shown), and the magnetic head 8 rotates as the rotating drum rotates to obliquely scan a magnetic tape (not shown). A head switch signal input to the head switch signal input terminal 1 and representing the switching timing of the rotary magnetic head is applied to the pilot signal generator 2 and the switch 18. The pilot signal generator 2 sequentially generates pilot signals in response to the leading edge and trailing edge of the head switch signal.

At the time of recording, a video signal is input to the video signal input terminal 4, superposed on the pilot signal by the adder 3, and then input to the recording amplifier 5 for amplification. The changeover switch 6 is connected to the REC side, and the output of the recording amplifier 5 is supplied to the magnetic head 8 via the rotary transformer 7 and recorded on a magnetic tape (not shown).

The changeover switch 6 includes a regenerative amplifier 9 and a low-pass filter 10.
Is connected to the mixer 11 via. Further, the pilot signal generator 2 is connected to the mixer 11. During reproduction, the selector switch 6 is switched and connected to the PLAY side, and the video signal including the pilot signal reproduced by the magnetic head 8 is input to the reproduction amplifier 9 via the rotary transformer 7 and the selector switch 6. Is amplified. The output of the regenerative amplifier 9 is given to the low pass filter 10,
A pilot signal component is extracted from the reproduced signal. This pilot signal component and the above-mentioned pilot signal sequentially generated by the pilot signal generator 2 at the time of reproduction (hereinafter, referred to as carrier signal f _CR at the time of reproduction) are input to the mixer 11, and the frequency difference between the two signals is detected. A signal component having a corresponding frequency is output. The mixer 11 is connected to the bandpass filter 12 and the bandpass filter 13. The bandpass filter 12 is connected to the subtractor 16 via the detector 14, and the bandpass filter 13
Is connected to the subtractor 16 via the detector 15. The subtractor 16 is connected to the switch 18. Further, the subtractor 16 is connected to the switch 18 via the inverting amplifier 17. The switch 18 is connected to the tracking error signal output terminal 19. The output of the mixer 11 is simultaneously given to a bandpass filter 12 having a pass band of 16 kHz and a band pulse filter 13 having a pass band of 46 kHz. The signal passed through the bandpass filter 12 is envelope-detected by the detector 14, and its output is given to the subtractor 16. On the other hand, the signal passed through the bandpass filter 13 is envelope-detected by the detector 15, and the output thereof is also given to the subtractor 16. The output of the subtractor 16 is a signal of the same polarity as that of the switch 18 which is switched in response to the head switch signal or a signal of the opposite polarity through the inverting amplifier 17 to the tracking error signal output terminal 19. Is output.

FIG. 2 is a view showing a pattern of video signal tracks formed on the magnetic tape 20 in the longitudinal direction of the tape and pilot signals recorded on the respective video signal tracks by being superimposed with the video signals. The operation of the tracking control means shown in FIG. 1 will be described in more detail with reference to FIG. During recording, the pilot signal generator 2 generates pilot signals of four different frequencies f ₁ , f ₂ , f ₃ , f ₄ in synchronization with the leading edge and the trailing edge of the head switch signal for each field. To do. These four frequencies are, for example, f ₁ = 102 kHz, f ₂ = 118 kHz when recording an NTSC video signal.
, F ₃ = 164 kHz, f ₄ = 148 kHz, the frequency difference α between f ₁ and f ₂ is equal to the frequency difference between f ₄ and f _3, and between f ₄ and f ₂ . The frequency difference is set to a value that is almost twice the value of α. These pilot signals are superposed on the video signal and, as shown in FIG. 2, the magnetic head 8 forms and records video signal tracks inclined in the longitudinal direction on the magnetic tape 20 in the field order. In FIG. 2, video signal tracks F ₁ , F ₂ , F ₃ , and F ₄ are f ₁ , f ₂ , f ₃ , and
This shows that the pilot signal of the frequency of f ₄ is recorded.

At the time of reproduction, the magnetic head 8 reproduces the signal recorded from the video signal track on the magnetic tape 20, and this reproduction signal is input to the reproduction amplifier 9 via the rotary transformer 7 and the changeover switch 6 and amplified. Regenerative amplifier 9
Is output to the low-pass filter 10 and the pilot signal component contained in the reproduced signal is extracted. Here, for example, as shown in FIG. 2, considering the case where the magnetic head 8 is tracking the video signal track F ₁ on the magnetic tape 20, the pilot signal component reproduced by the magnetic head 8 includes: In addition to the pilot signal of frequency f ₁ superimposed on the video signal track F ₁ ,
Pilot signals superimposed on both adjacent video signal tracks (F ₂ and F _{4 in} the example of FIG. ₂ ) due to side league effect, crosstalk, etc. are also included at the same time. The magnitude of the pilot signal detected from these adjacent video signal tracks increases as the amount of positional deviation from the center of the video signal track tracked by the magnetic head 8 increases. The above-mentioned pilot signal component extracted by the low-pass filter 10 when tracking the video signal track F ₁ and the carrier signal f _CR = f ₁ generated by the pilot signal generator 2 are input to the mixer 11, and one of the adjacent 16 kHz of the difference between the pilot signal frequency f ₂ = 118 kHz of the video signal track F ₂ and the carrier signal frequency f _CR = f ₁ = 102 kHz
And a signal having a frequency of 46 kHz which is the difference between the pilot signal frequency f ₄ = 148 kHz and the carrier signal frequency f _CR = f ₁ = 102 kHz of the adjacent video signal track F _{4 on} the other side. And the ingredients are obtained.
The signal components of these 16 kHz and 46 kHz are further 1
Bandpass filter 12 having a pass band of 6 kHz and band pass filter 13 having a pass band of 46 kHz
Are extracted separately by. The output of the bandpass filter 12 is envelope-detected by the detector 14, and the output level thereof represents the amount of displacement of the magnetic head 8 to the adjacent video signal track F ₂ on the right side. on the other hand,
The output of the band-pass filter 13 is envelope-detected by the detector 15, and the output level thereof represents the amount of displacement of the magnetic head 8 to the adjacent video signal track F ₄ on the left side. By passing both of these outputs through the subtracter 16, the amount of positional deviation from the center of the video signal track of the magnetic head 8 can be obtained. However, the magnetic head 8
There and while tracking the video signal track F1 or F3, in the while tracking a video signal track F ₂ or F _4, since the frequency difference between the adjacent video signal tracks of the left and right are reversed relationship, The output of the subtractor 16 has the opposite polarity. Therefore, by providing the inverting amplifier 17 for inverting the polarity and switching the switch 18 by the head switch signal, when the magnetic head 8 tracks the video signal track F ₂ or F ₄ ,
It is necessary to invert the polarity of the output of the subtractor 16. In this way, the tracking error signal output terminal 19 outputs a tracking error signal having a voltage corresponding to the amount of displacement of the video signal track of the magnetic head 8 from the center, and this signal is fed back to the capstan motor. Thus, a servo system is formed and good tracking is performed.

SUMMARY OF THE INVENTION The present invention has been made under such a background. Therefore, a main object of the present invention is to record / reproduce at a plurality of tape speeds in a pilot signal type magnetic recording / reproducing apparatus. If you have configured a possible device, during playback,
An object of the present invention is to provide a mode discriminating apparatus capable of automatically discriminating a tape speed during recording.

To summarize the present invention, in a pilot signal type magnetic recording / reproducing apparatus, a pilot signal of a specific frequency is generated only within a predetermined time in synchronization with a signal indicating switching of a rotary magnetic head, and this is used as a carrier signal. , A plurality of pilot signals with different frequencies recorded by being superimposed on the information signal on the diagonal track on the magnetic tape are reproduced by the rotating magnetic head, and the frequency difference between the reproduced plurality of pilot signal frequencies and the carrier signal frequency is calculated. By extracting the signal component and applying the output obtained by detecting this frequency difference component to the comparison means having a preset threshold value,
It is a mode discriminating apparatus which discriminates the tape speed of a magnetic tape by producing a signal which replaces the control signal in the conventional magnetic recording and reproducing apparatus of the control signal system, and discriminating the tape speed of the magnetic tape from this signal and the output of the speed detecting means of the capstan motor.

The above objects and features of the present invention will become more apparent from the following description of embodiments with reference to the drawings.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. In the description of this embodiment, the description of the same parts as those in FIGS. 1 and 2 will be omitted as appropriate. FIG. 3 is a schematic block diagram of a mode discriminating apparatus in a pilot signal type magnetic recording / reproducing apparatus according to an embodiment of the present invention. The configuration of this embodiment differs from the configuration of the tracking control means of FIG. 1 in that the following circuit is added for mode discrimination. That is, the detector 14 includes the gate circuit 30 and the comparator 21.
Is connected to the selector circuit 23 via the
Reference numeral 5 is connected to the selector circuit 23 via the gate circuit 31 and the comparator 22. The selector circuit 23 and the speed signal input terminal 25 are connected to the comparison / determination circuit 24, and the comparison / determination circuit 24 is connected to the mode command signal output terminal 26. In addition, a gate circuit 32 is connected between the switch 18 and the tracking error signal output terminal 19. Both the gate circuits 30 and 31 have a detector 1 for a predetermined time T.
The gate circuits pass the outputs of Nos. 4 and 15 and do not pass the outputs at other times, and the comparators 21 and 22 are comparators having a predetermined threshold value S. The selector circuit 23 is a selector circuit which alternately selects and outputs the signals from the comparators 21 and 22, and can be constituted by, for example, a negative logic input SR flip-flop and an analog switch as shown in FIG. The comparison / discrimination circuit 24 is a comparison / discrimination circuit that discriminates the mode from a speed generator signal from the capstan motor input to the speed signal input terminal 25 and a signal that can replace the conventional control signal from the selector circuit 23. The output of the comparison / determination circuit 24 is output to the mode command signal output terminal 26. The gate circuit 32 is a gate circuit which does not pass an input for a predetermined time T, and passes this input at other times.

FIG. 4 is a time chart when the video signal track is accurately tracked by reproducing at the same tape speed (mode) as during recording. FIG. 5 is a time chart when the tape is reproduced at a tape speed which is ½ the recording speed. FIG. 6 is a time chart at the time of reproducing at a tape speed twice as high as that at the time of recording. In FIGS. 4, 5 and 6, (a) shows the head switch signal, (b) shows how the pilot signal at the time of recording is switched by the head switch signal (a), and (c) shows at the time of reproducing. The pilot signal is always set to F ₁ for a predetermined time T when the head switch signal (a) is switched, and other times are switched in the same manner as during recording. (D) is 16 kHz passed through the bandpass filter 12 having a pass band of 16 kHz
An output obtained through a gate circuit 30 that passes the output of the z component detected by the detector 14 for a predetermined time T, and
The relationship between the threshold value S of the comparator 21 and (e) is 4
The output obtained through the gate circuit 31 for passing the output of the 46 kHz component that has passed through the bandpass filter 13 having the 6 kHz pass band by the detector 15 for a predetermined time T and the threshold of the comparator 22. Regarding the relationship with the value S, (f) is the output of the selector circuit 23 that alternately selects the outputs of the comparators 21 and 22, and is a signal that can replace the conventional control signal.

As shown in FIG. 2, the magnetic head 8 moves the video signal track F ₁
Are being tracked. The playback signal has frequency f
_{If there is} a main component of ₁ and components of frequencies f ₄ and f ₂ adjacent to each other, and the carrier signal frequency f _CR is f ₁ , both adjacent components f ₄ −f ₁ = 46 kHz, f ₂ −f ₁ = 16 kH
The z components are almost equal, and this 16 kHz component and 4
The tracking error signal can be detected by the difference signal of 6 kHz component as shown in FIG.

Next, assuming that the magnetic head 8 is tracking the video signal track F ₂ , the reproduced signal has a main component of frequency f ₂ and components of both adjacent frequencies f ₁ and f ₃ .
At this time, if the carrier signal frequency f _CR is f ₁ ,
The main component f ₂ −f ₁ = 16 kHz and the adjacent component f ₃
A component of −f ₁ = 62 kHz is obtained, and at this time 16 k
Since the Hz component is the main component, it is much larger than the adjacent component.

Similarly, when the magnetic head 8 is tracking the video signal track F ₃ , the carrier signal frequency f _{CR is changed} to f ₁
Then, the main component f ₃ −f ₁ = 62 kHz component and both adjacent components f ₂ −f ₁ = 16 kHz component, f ₄ −
f ₁ = 46 kHz component is obtained, and when the carrier signal frequency f _CR is f ₁ while the magnetic head 8 is tracking the video signal track F ₄ , the main component f ₄ −f
₁ = 46 kHz component and adjacent component f ₃ −f ₁ = 62
A kHz component is obtained. Therefore, when the carrier signal frequency f _{CR is set} to f ₁ , the level is slightly different depending on the width of the magnetic head 8 and the width of the video signal track.
The maximum H z component is when the video signal track F ₂ is being traced, and the maximum 46 kHz component is when the video signal track F ₄ is being traced.

The above principle will be described with reference to FIGS. As shown in the time chart of FIG. 4, when reproducing at the same tape speed as at the time of recording, the carrier signal frequency f _CR which should be the same as that at the time of recording (b) should be Thus, the frequency f ₁ is always set as the carrier signal frequency f _CR for a predetermined time T in synchronization with the switching of the head switch signal (a). According to the above-mentioned principle, the signal passed through the bandpass filter 12 having a pass band of 16 kHz is 16
When the output of which the kHz component is detected by the detector 14 is passed through the gate circuit 30 for a predetermined time T, (d)
As described above, a large output is obtained while tracking the video signal track F _2, and the output obtained by detecting with the wave detector 15 the 46 kHz component that has passed through the bandpass filter 13 having a pass band of 46 kHz is predetermined. If the gate circuit 31 that allows passage only during the time T is passed, a large output can be obtained while tracking the video signal track F ₄ as shown in (e). Therefore, these gate circuits 3
A selector circuit capable of detecting the positions of the video signal tracks F ₂ and F ₄ by passing the outputs of 0 and 31 through comparators 21 and 22 having a predetermined threshold value S and alternately selecting the outputs of the comparators 21 and 22. By passing through 23, a signal like (f) is obtained. This signal has one pulse in a period corresponding to two fields and is equivalent to the control signal.

Similarly, as shown in the time chart of FIG. 5, considering the case where the tape is reproduced at a tape speed that is ½ times that at the time of recording, the phase control of the running control does not work properly. Is traveling at a speed substantially close to the above speed by speed control. At this time, when a carrier signal is generated as shown in (c), the same video signal track is traced twice, so the output of the gate circuit 30 becomes as shown in (d) and the output of the gate circuit 31 becomes (e). become that way. Therefore,
As shown in (f), the output of the selector circuit 23 becomes one pulse in the period corresponding to four fields and is equivalent to the control signal.

Similarly, as shown in the time chart of FIG. 6, when reproducing at a tape speed twice as high as that at the time of recording, since two video signal tracks are traced at one time, the gate circuit 3
The output of 0, the output of the gate circuit 31, and the output of the selector circuit 23 are as shown in (d), (e), and (f), respectively.
(F) has one pulse in the period corresponding to one field and is equivalent to the control signal.

Therefore, a signal equivalent to the conventional control signal can be obtained even if the tape speed at the time of recording and the tape speed at the time of reproducing are different. Therefore, the speed power generation from the output of the selector circuit 23 and the speed signal input terminal 25 from the capstan motor is performed. The mode (tape speed) can be discriminated from the machine signal by the comparison / discrimination circuit 24 in the same manner as the conventional method. That is, the tape speed is determined by counting the output pulses (speed generator signal) output from the speed generator at the time intervals of the output of the selector circuit 23 and comparing this count value with a predetermined reference value. You can The result of this determination is output as a mode command signal to the mode command signal output terminal 26 so that the mode during reproduction can be set to the same mode as during recording. In this case, the tracking error signal becomes abnormal only for the predetermined time T, but since the predetermined time T is a period of several horizontal scan periods at most, the conventional tracking control having a response band of several Hz is required. It has almost no effect on the system itself. Further, in this case, if the gate circuit 32 that holds the tracking error signal without passing the tracking error signal for a predetermined time T and passes the tracking error signal during the other time is provided, this effect is completely eliminated.

In the above embodiment, the pilot signal of frequency f ₁ is used as the carrier signal at the predetermined time T.
You may use the pilot signal of other frequencies.

As described above, according to the present invention, in the pilot signal type magnetic recording / reproducing apparatus, the pilot signal of the specific frequency is synchronized with the signal indicating the switching of the rotary magnetic head within a predetermined time. Generated and use this as a carrier signal,
A rotary magnetic head reproduces a plurality of pilot signals of different frequencies, which are recorded by being superimposed on an information signal on an oblique track on a magnetic tape, and a signal of a frequency difference between the reproduced pilot signal frequencies and a carrier signal frequency. A signal that replaces the control signal in the conventional control signal type magnetic recording / reproducing apparatus by extracting the component and applying the output obtained by detecting the frequency difference component to the comparing means having a preset threshold value. The time interval of this signal was measured from the output of the speed detection means of the capstan motor, and the tape speed of the magnetic tape was determined by comparing the measured time interval with a predetermined reference value. It is possible to obtain a mode discriminator capable of automatically discriminating the tape speed at the time of recording an information signal when reproducing the information signal. Kill.

Further, this mode discriminating device can be configured by adding a circuit such as a comparator to the conventional pilot signal type magnetic recording / reproducing device and using the conventional mode discriminating circuit based on the control signal. And can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a tracking control means in a conventional pilot signal type magnetic recording / reproducing apparatus (VTR). FIG. 2 is a diagram showing a relationship between a pattern of a video signal track formed on a magnetic tape and a pilot signal recorded by superimposing the video signal on the track and a magnetic head. FIG. 3 is a schematic block diagram of a mode discriminating apparatus in a pilot signal type magnetic recording / reproducing apparatus (VTR) according to an embodiment of the present invention. FIG. 4 is a time chart when the tape is reproduced at the same tape speed as at the time of recording. FIG. 5 is a time chart when the tape is reproduced at a tape speed which is ½ the recording speed. FIG. 6 is a time chart at the time of reproducing at a tape speed twice as high as that at the time of recording. FIG. 7 is a diagram showing a configuration example of the selector circuit. In the figure, 1 is a head switch signal input terminal, 2 is a pilot signal generator, 3 is an adder, 4 is a video signal input terminal, 5 is a recording amplifier, 6 is a changeover switch, 7 is a rotary transformer, 8 is a magnetic head, 9 is a regenerative amplifier, 10 is a low pass filter, 11 is a mixer, 12 and 13 are band pass filters, 14 and 15 are wave detectors, 16 is a subtractor, 17
Is an inverting amplifier, 18 is a switch, 19 is a tracking error signal output terminal, 20 is a magnetic tape, 21 and 22 are comparators, 23 is a selector circuit, 24 is a comparison / determination circuit, 25 is a speed signal input terminal, and 26 is a mode command signal. The output terminals 30, 31, 32 are gate circuits. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. When the rotary magnetic head records an information signal on an oblique track on a magnetic tape, a plurality of pilot signals having different frequencies are generated in synchronization with a signal indicating switching of the rotary magnetic head. Are repeatedly recorded on the diagonal track in a predetermined order by superimposing on the recording medium, and when the information signal is reproduced from the diagonal track by the rotary magnetic head, the plurality of pilot signals are reproduced from the reproduction signal reproduced from the diagonal track. Magnetic recording / reproduction of a pilot signal system for extracting in a predetermined order and detecting a tracking error signal for the oblique track of the rotary magnetic head based on the extracted plurality of pilot signals to control the running of the magnetic tape. In the device, the pilot signal generating means for generating the plurality of pilot signals, One of the plurality of pilot signals is generated only within a predetermined time in synchronization with the signal indicating the switching of the rotary magnetic head, and the plurality of pilot signals are output during the predetermined time. A signal component that is configured to be repeatedly generated in order, and is responsive to a frequency difference between any one of the plurality of pilot signals generated within the predetermined time and the extracted plurality of pilot signals. Of the first and second level detecting means for detecting the level of the above, and first and second for individually comparing the outputs of the first and second level detecting means with a preset threshold value.
Comparing means, selecting means for alternately selecting the outputs of the first and second comparing means, and a speed detecting means provided in a capstan motor for driving the magnetic tape and detecting a speed of the capstan motor. And a comparing / determining means for counting the time interval of the output of the selecting means from the output of the speed detecting means and comparing the measured time interval with a predetermined reference value to determine the tape speed of the magnetic tape. A mode discriminating apparatus for a magnetic recording / reproducing apparatus, comprising: