JPH06203434A - Tracking controller - Google Patents

Abstract

PURPOSE:To improve a tracking precision by performing the fine control of the tracking by changing over a time constant or the detection period of a detecting circuit for the detection of a reproduced FM envelope, after the tracking is roughly controlled. CONSTITUTION:By the envelope detecting circuit 8, a reproduced FM signal (a) is detected, and an amplitude information (b) is extracted and inputted to microcomputer 9. Based on this information (b), the delay amount is changed and delay data are supplied to a capstan servo circuit 10 to perform the tracking control. At this time, a time constant circuit 11 is selected by an SW1 at first, and the amplitude information (b) which is obtained by performing the envelope detection, is obtained by the time constant t1. When the tracking operation is stabilized to a constant value, a time constant circuit 12 is selected next, and the detection is made by a time constant t2 which is smaller than t1, to obtain the amplitude information (b). Thus, by performing the fine tracking after the malfunction due to an external disturbance is eliminated with the rough control, the accuracy of the automatic tracking is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for carrying out suitable tracking control for a helical scan type magnetic reproducing apparatus which requires tracking control during reproduction.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 2-46562 discloses a video tape recorder, etc., which samples a envelope of a reproduced video signal to a microcomputer (hereinafter, referred to as a microcomputer).
An automatic tracking device has been disclosed which controls the delay amount of a reproduction control signal (or reference signal) of a capstan servo system so that the envelope is maximized by taking it into a microcomputer.

The prior art shown in the above-mentioned prior application will be described below with reference to FIGS. 12, 13 and 14.

FIG. 12 is a block diagram showing an outline of a conventional tracking system. In FIG. 12, 1 is a reproducing head of a channel (hereinafter referred to as CH) 1, 2 is a reproducing head of CH 2, 3 is a magnetic tape. Reference numeral 4 is a head amplifier, 5 is a head switching circuit, 6 is a signal processing circuit, 7 is a reproduced video signal output terminal, 8 is an envelope detection circuit, 9 is a microcomputer, and 10 is a capstan servo circuit.

Outputs of the CH1 head 1 and the CH2 head 2, which are rotary heads, are amplified by a head amplifier 4 and input to a head switching circuit 5. Next, one of the reproduced FM signals that has become a single-system signal by the operation of the head switching circuit 5 is input to the signal processing circuit 6. The signal processing circuit 6 converts the amplified reproduced FM signal into a reproduced video signal and outputs it from the reproduced video signal output terminal 7. The reproduced FM signal output from the head switching circuit 5 is also input to the envelope detection circuit 8. The envelope detection circuit 8 performs envelope detection of the reproduced FM signal and outputs amplitude information to the microcomputer 9.

The microcomputer 9 has an A / D converter, converts the supplied analog value into a digital value by using the amplitude information output from the envelope detection circuit 8 as an input of the A / D converter, Capture at a predetermined timing. In the microcomputer 9, the amplitude information is thus A / D converted and input, and this is repeated at a predetermined sampling interval.
Then, the microcomputer 9 detects the maximum value of the values obtained by adding the sampling information for a predetermined time, and outputs the maximum value information to the capstan servo circuit 10. In the capstan servo circuit 10, based on the input maximum value information,
Control tracking. Next, the maximum value information of the amplitude will be described with reference to FIG.

FIG. 13 is a graph showing the tracking phase vs. amplitude characteristic. In FIG. 13, the horizontal axis represents the tracking phase and the vertical axis represents the amplitude. Z represents the characteristic of CH1.

The amplitude when the tracking phase changes is like a characteristic waveform (characteristic line) Z, and the maximum amplitude value V is from T1 to T2.
Spans the section. In this section, it is more preferable that the tracking is controlled to the tracking phase value of T1 or T2, which is the change point of the amplitude. The reason for this depends on the relationship between the recording track and the reproducing head. Next, this relationship will be described with reference to FIG.

FIG. 14 shows a trace locus of the reproducing head. In FIG. 14, L, M and N are reproducing heads, 3 is a magnetic tape, 22 is a CH1 recording track, and 23 is CH2.
It is a recording track of.

The track phase values L and M ((a) and (b) in FIG. 13) at which the edge of the CH1 recording track pattern 22 and the edge of the CH1 reproducing head are substantially aligned are T1, in FIG. T2, which is a track phase value N such that the CH1 reproducing head traces adjacent tracks 23, 23 on both sides of the CH1 recording track pattern 22.
((C) of FIG. 13) represents the period from T1 to T2 of FIG. It is empirically known that the tracking phase values L and M are disturbed only by adjacent tracks on one side, but the track phase value N is disturbed by adjacent tracks on both sides and the image quality is further deteriorated. Because it is
In many cases, the track phase values L and M are preferable as the tracking control position. For this reason,
It is desirable to control the tracking phase values to be near T1 and T2. The same applies to CH2.

[0011]

As described above, in the prior art, tracking control is performed so that the amplitude of the FM envelope reproduced by the rotary head becomes maximum.

However, in an actual VTR, the amplitude of the FM envelope reproduced from the rotary head has fluctuations due to disturbances other than the tracking information, and if automatic tracking is performed based on this FM envelope amplitude,
The tracking phase may be controlled at a position displaced from the desired phase. In this case, the user can view the image as it is even if the reproduced image quality is deteriorated due to the tracking phase shift.

Therefore, in order to solve the above-mentioned problems of the prior art, the present invention provides a magnetic recording / reproducing apparatus of a helical scan system for reproducing a video signal, which has a finer tracking than the conventional tracking control. The purpose of this control is to improve the accuracy of automatic tracking.

[0014]

In order to achieve the above object, in the present invention, as a first means, the time constant of a detection circuit for detecting the amplitude of a reproduced FM envelope in a series of automatic tracking operations, From time constant t1 to time constant t2 (t
A detection time constant switching means for switching to 1 <t2) is provided.

As a second means, a control means for controlling tracking is provided based on the amplitude information of the FM envelope in the sync pulse section of the reproduction signal.

As a third means, in a series of automatic tracking operations, immediately after the start of the operation, the detection circuit for detecting the amplitude of the reproduction envelope always detects, and then the synchronous pulse section of the reproduction signal is detected. The detection period switching means is provided.

As a fourth means, a control means for controlling tracking based on the S / N information of the sync pulse section of the reproduced video signal is provided.

As a fifth means, the control means for detecting the amplitude of the FM envelope reproduced from a plurality of rotary heads for each head and controlling the tracking based on the relationship of the amplitude information for each head. Was set up.

[0019]

By providing the first means to switch the time constant of the detection circuit for detecting the amplitude of the reproduced FM envelope within a series of automatic tracking operations, rough tracking control is performed and then finer tracking is performed. By controlling, it is possible to improve the automatic tracking accuracy.

Further, by providing the second means, the reproduction FM
By performing tracking control based on the amplitude information of the sync pulse section of the reproduction signal with relatively little variation in the envelope, it is possible to improve the automatic tracking accuracy.

Further, by providing the third means and switching the detection period of the detection circuit, rough tracking control is performed, and then finer tracking control is performed, thereby improving the automatic tracking accuracy. it can.

Further, if the fourth means is provided, the S / N information of the sync pulse section in the reproduced video signal can be detected almost accurately, so tracking control is performed based on the S / N information of the sync pulse section. By doing so, it is possible to improve the automatic tracking accuracy.

Further, according to the fifth means, the amplitude of the FM envelope reproduced from a plurality of rotary heads may differ from head to head, so the amplitudes at certain tracking phases are compared for each head. However, the automatic tracking accuracy can be improved by determining a specific tracking phase from the relationship and performing almost tracking control on the specific tracking phase.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a VTR tracking device according to a first embodiment of the present invention.

In FIG. 1, the FM signal reproduced from the magnetic tape 3 by the rotary heads 1 and 2 is the head amplifier 4
Is amplified by and input to the head switching circuit 5. The head switching circuit 5 functions to generate a single-system signal, and then one of the signals is input to the signal processing circuit 6. The signal processing circuit 6 converts the amplified FM signal into a reproduced video signal and outputs it from the reproduced video signal output terminal 7. Further, the reproduced FM signal a output from the head switching circuit 5 is
It is also input to the envelope detection circuit 8. The envelope detection circuit 8 performs envelope detection of the reproduced FM signal a and extracts the amplitude information b. The amplitude information b is input to the microcomputer 9, and if the tracking control is not appropriate, the delay amount is changed by a predetermined value according to an instruction from the microcomputer 9. Then, the delay data is input to the capstan servo circuit 10 and tracking control is performed.

Here, when performing the envelope detection, in a series of automatic tracking operations, at the start of the automatic tracking operation, the switch circuit 1 (hereinafter referred to as SW1) by the time constant switching control signal c output from the microcomputer 9. First, a time constant t1 having a detection time constant t1
The circuit 11 is selected. The detection speed of the envelope detection circuit 8 is determined by the time constant t1 of the selected circuit 11, envelope detection is performed, and tracking control is performed based on the amplitude information b. Next, the time constant t
When the amplitude information b in 1 settles to a substantially constant value, and the microcomputer 9 determines that the tracking control is roughly stable, the time constant switching control signal c output from the microcomputer 9 switches SW1 to detect Constant t
The time constant t2 circuit 12 having 2 is selected. And
Time constant t2 of the selected circuit 12 (however, t1 <t2)
According to the amplitude information b, the detection speed of the envelope detection circuit 8 is determined to perform envelope detection.
By performing tracking control, finer tracking control can be performed.

The time constant is changed from t1 to t2 (t1 <t
The reason for switching from 2) to a large value is as follows. That is, when the time constant is small, the response is fast, but the averaging is performed in a short time, so it is easily affected by external disturbances, and when the time constant is large, the response is slow but the average over a long time. Since it is converted into a different type, it is less affected by disturbances. Therefore, by performing the switching control of the time constant as described above, it is possible to realize high-performance tracking control in which the response is fast at the start of the tracking operation and is hardly affected by the disturbance after the tracking operation is stabilized.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing a VTR tracking device according to a second embodiment of the present invention.

In FIG. 2, the rotary heads 1 and 2, the magnetic tape 3, the head amplifier 4, the head switching circuit 5, the signal processing circuit 6, the reproduced video signal output terminal 7, the envelope detection circuit 8, the microcomputer 9, and the capstan. Servo circuit 1
0, time constant t1 circuit 11, time constant t2 circuit 12, SW1
Since the function of the portion configured by is the same as the content described with reference to FIG. 1, the description thereof will be omitted.

In FIG. 2, the reproduced video signal d output from the signal processing circuit 6 is a sync pulse detection circuit 13
Entered in. The sync pulse detection circuit 13 detects the sync pulse of the reproduced video signal d and outputs the section information to the gate pulse generation circuit 14. Gate pulse generation circuit 14
Then, a gate pulse for gating the synchronizing portion of the reproduced FM signal is generated from the input section information, and this is output to the gate circuit 15. The gate pulse output from the gate pulse generation circuit 14 and the reproduced FM signal a output from the head switching circuit 5 are input to the gate circuit 15, and the input reproduced FM signal a is synchronized by the gate pulse. The pulse period is gated, and only the reproduced FM signal in the synchronizing pulse period is output from the gate circuit 15 to the envelope detection circuit 8.

Normally, when a moving image is reproduced, the reproduced FM signal has a variation in amplitude due to image information.
In the reproduced FM signal during the sync pulse period, the amplitude does not fluctuate and is stable. Therefore, by inputting the reproduced FM signal in this synchronizing pulse period to the envelope detection circuit 8 and processing the amplitude information b by the microcomputer 9 for tracking control, it is possible to perform accurate tracking control. As shown in FIG. 2, as the amplitude information b, the microcomputer 9 is passed through a holding circuit 24 that intermittently takes in information in the sync pulse period and holds this value.
It is preferable to send to.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing a VTR tracking device according to a third embodiment of the present invention.

In FIG. 3, rotary heads 1 and 2, magnetic tape 3, head amplifier 4, head switching circuit 5, signal processing circuit 6, reproduced video signal output terminal 7, envelope detection circuit 8, microcomputer 9, capstan. Servo circuit 1
0, the time constant t1 circuit 11, the time constant t2 circuit 12, the synchronization pulse detection circuit 13, the gate pulse generation circuit 14, the gate circuit 15, and the function of the part configured by SW1 are the contents described with reference to FIG. Since it is equivalent to, the description thereof will be omitted.

In FIG. 3, the head switching circuit 5
One of the reproduced FM signals a output from is input to the switch circuit 2 (hereinafter, referred to as SW2) as it is, and the other is input to the gate circuit 15 to gate the synchronization pulse period. The reproduced FM signal is input to SW2. Here, when performing the envelope detection, within the series of automatic tracking operations, at the start of the automatic tracking operation, first, the detection period switching control signal f output from the microcomputer 9 is output from the head switching circuit 5 via the SW2. The output reproduced FM signal a as it is is selected. The selected reproduced FM signal a is input to the envelope detection circuit 8 and subjected to envelope detection,
Tracking control is performed based on the amplitude information b. Next, when the amplitude information b in the reproduced FM signal a has settled to a substantially constant value and the microcomputer 9 determines that the tracking control is roughly stable, the detection period switching control signal f switches SW2, The reproduced FM signal e gated in the sync pulse period is selected. The selected reproduced FM signal e is input to the envelope detection circuit 8 and subjected to envelope detection, and tracking control is performed based on the amplitude information b, so that finer tracking control can be performed.

Furthermore, the time constant switching control signal c
The switching of the SW1 by the above is synchronized with the switching timing of the SW2 by the detection period switching control signal f, and when the SW2 selects the reproduction FM signal a, the time constant t1 circuit 11 side and the reproduction FM signal e are changed. When selecting, the time constant t2 circuit 12 side is selected to enable even higher performance tracking control.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing a VTR tracking device according to a fourth embodiment of the present invention.

In FIG. 4, rotary heads 1 and 2, magnetic tape 3, head amplifier 4, head switching circuit 5, signal processing circuit 6, reproduced video signal output terminal 7, envelope detection circuit 8, microcomputer 9, capstan. Servo circuit 1
0, the time constant t1 circuit 11, the time constant t2 circuit 12, the synchronization pulse detection circuit 13, the gate pulse generation circuit 14, the gate circuit 15, the functions of the portion SW1, SW2 will be described with reference to FIG. Since it is the same as the contents described above, the description thereof is omitted.

In FIG. 4, as in the third embodiment, the reproduced FM signal a as output from the head switching circuit 5 and the reproduced FM signal e gated in the synchronizing pulse period are fed to the SW2. Is entered. Then, in a series of automatic tracking operations, the reproduced video signal d output from the signal processing circuit 6 is input to the sync pulse detection circuit 13, and the sync pulse detection circuit 13 detects the sync pulse from this input signal. Output section information. The outputted section information is inputted to the sync pulse judgment circuit 16, and when the sync pulse judgment circuit 16 judges that the sync pulse cannot be detected, a judgment signal g indicating that is outputted, and the judgment signal g is sent via SW2. The reproduction FM signal a side is selected. The selected reproduced FM signal a is supplied to the envelope detection circuit 8
To the envelope detection, and tracking control is performed based on the amplitude information b. Meanwhile also
When the sync pulse determination circuit 16 determines that the sync pulse can be detected based on the section information output from the sync pulse detection circuit 13, a determination signal g indicating that is output, and SW2 is switched by the determination signal g. Play through FM signal e
Side is selected. The selected reproduced FM signal e is envelope-detected by the envelope detection circuit 8, and tracking control is performed based on the amplitude information b, so that finer tracking control can be performed.

By doing so, the optimum tracking control can be selected according to the detection status of the synchronization pulse, and higher-performance tracking control with high operation reliability can be realized.

Here, another method of extracting the envelope amplitude information of the synchronizing pulse period in the second, third and fourth embodiments shown in FIGS. 2, 3 and 4 will be described with reference to FIG. To do. FIG. 5 is a block diagram showing a tracking device adopting a method of extracting envelope amplitude information of a synchronizing pulse period other than the above in the present invention.

In FIG. 5, the rotary heads 1 and 2, the magnetic tape 3, the head amplifier 4, the head switching circuit 5, the signal processing circuit 6, the reproduced video signal output terminal 7, the envelope detection circuit 8, the microcomputer 9, and the capstan. Servo circuit 1
0 and the function of the portion configured by the sync pulse detection circuit 13 are the same as those described with reference to FIGS.

To the microcomputer 9 in this example, the amplitude information b envelope-detected by the envelope detection circuit 8 and the section information detected by the sync pulse detection circuit 13 are input. The microcomputer 9 executes software processing based on a predetermined processing program created in advance, intermittently takes in the synchronization pulse period of the input amplitude information b according to the section information, and holds the data. There is. In this way, the software processing of the microcomputer 9 also makes it possible to detect the amplitude information in the sync pulse period.

Here, the automatic tracking display device 17 in FIG. 5 is used for the purpose of informing the user whether or not the tracking state that does not hinder the enjoyment of the reproduced image is realized. For example, immediately after the reproduction of the recorded tape is started, the rough automatic tracking control operation is started, and the automatic tracking display device 17 is turned on. Then, when the initial rough automatic tracking control operation is finished and the fine automatic tracking control operation is started, the automatic tracking display device 17 is turned off. Therefore, since the automatic tracking display device 17 is turned off, the user recognizes that the rough automatic tracking control operation has ended, and can judge that the tracking state that does not hinder the enjoyment of the reproduced image is realized. It has become. In addition, as the display device 17,
A fluorescent display tube attached to the front panel of the VTR or an on-screen display can be used.

In the tracking control device which performs rough tracking control first in the series of automatic tracking operations as described above and then shifts to fine tracking control, fine tracking control starts reproduction. It is preferable to continue to operate continuously not only after but throughout the reproduction period. For example,
When the control method according to the present invention as described later is adopted, even if the tape running system fluctuates during the reproduction period, the control can be continued to the optimum tracking phase to always provide a good reproduced image. it can. In such a case, when the rough tracking control is completed, if the display is switched so that the automatic tracking display device 17 is turned off, there is no problem in enjoying most of the images at this point. The user can recognize that the tracking control has been realized and that the tracking phase will continue to be controlled to the optimum tracking phase even after fluctuations in the tape running system, etc., and users can enjoy the playback image with a sense of security. You can

Next, a fifth embodiment of the present invention will be described with reference to FIG. 6, in which even if the tape running system fluctuates during the reproduction period, the tracking phase can be controlled to the optimum tracking phase. Figure 6
It is a block diagram which shows the tracking apparatus of the VTR which concerns on the 5th Example of this invention.

In FIG. 6, rotary heads 1 and 2, magnetic tape 3, head amplifier 4, head switching circuit 5, signal processing circuit 6, reproduced video signal output terminal 7, microcomputer 9,
Capstan servo circuit 10, sync pulse detection circuit 1
The configurations of 3, the gate pulse generation circuit 14, and the gate circuit 15 are the same as those described with reference to FIGS.

In FIG. 6, the reproduction video signal d output from the signal processing circuit 6 is directly input to the gate circuit 15, and the synchronization pulse detection circuit 13 and the gate pulse generation circuit 14 are also extracted from the reproduction video signal d. The gate pulse generated by is input. The gate circuit 15 detects only the sync pulse period of the reproduced video signal d by the gate pulse, and detects this as an S / N (Signal-to-noise ratio).
Output to the detection circuit 18. The S / N detection circuit 18 detects the S / N of the synchronizing pulse period of the reproduced video signal from the inputted reproduced video signal of the synchronizing pulse period, and outputs this to the microcomputer 9 as S / N information h.

S / N information h of the above-mentioned reproduced video signal
Has a correlation with the phase of tracking control. Specifically, as the tracking control phase deviates from the optimum phase, the S / N of the reproduced image becomes worse. Therefore, in the microcomputer 9, S / in the sync pulse period of the reproduced video signal
By performing the automatic tracking control based on the N information so as to match the tracking phase in which the S / N value is improved, highly accurate and high-performance automatic tracking control can be realized.

Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a block diagram showing a VTR tracking device according to a sixth embodiment of the present invention.

In FIG. 7, rotary heads 1 and 2, magnetic tape 3, head amplifier 4, head switching circuit 5, signal processing circuit 6, reproduced video signal output terminal 7, envelope detection circuit 8, microcomputer 9, capstan. Servo circuit 1
0, sync pulse detection circuit 13, gate pulse generation circuit 1
4, the structure of the gate circuit 15 is the same as the contents described with reference to FIGS. 2 to 4, and the S / N detection circuit 18 is the same as the contents described with reference to FIG. Therefore, the description thereof will be omitted.

In FIG. 7, the amplitude information b output from the envelope detection circuit 8 and the S / N information h output from the S / N detection circuit 18 are input to the microcomputer 9, and the microcomputer 9 outputs the respective information. Is used together to realize automatic tracking control. Further, the S / N information h output from the S / N detection circuit 18 is also input to the image quality adjustment circuit 19. The image quality adjusting circuit 19 adaptively controls the reproduced image based on the S / N information h. In this way, S
The circuit configuration can be simplified by using the / N detection circuit 18 for both tracking control and adaptive control of reproduction image quality.

Next, a method for detecting the optimum tracking phase according to the present invention will be described with reference to FIGS. FIG. 8 shows the trace locus of the reproducing head. In FIG. 8, 1 is a CH1 reproducing head (CH1 head), 2
Is a CH2 reproducing head (CH2 head), 3 is a magnetic tape, 20 is a CH1 recording track, and 21 is a CH2 recording track.

CH1 recorded on the magnetic tape is composed of two reproducing heads mounted on the rotary cylinder so as to face each other by 180 ° and used as reproducing heads for CH1 and CH2, respectively.
Tracking control that substantially aligns the edge of the track pattern with the edge of the CH1 head and tracking control that substantially aligns the edge of the CH2 track pattern recorded on the magnetic tape with the edge of the CH2 head are generally good. It is known to be tracking control.

As shown in FIG. 8, CH1 head 1 and CH
2 If the mounting position of the head 2 is ideal, CH1, CH
2 It is possible to control the edge of each head to coincide with the edge of each track pattern, but in reality, it is preferable for each head due to a step difference in the mounting position of the CH1 head 1 and the CH2 head 2 or the like. The tracking phase may be different. A tracking control method suitable for such a case will be described with reference to FIG.

FIG. 9 shows the tracking phase vs. amplitude characteristics when there is a step at the mounting position of the heads of CH1 and CH2. In FIG. 9, the horizontal axis represents the tracking phase and the vertical axis represents the amplitude. Also, X is CH
A characteristic waveform (characteristic line) showing the tracking phase vs. amplitude characteristic of one head, and Y is a characteristic waveform (characteristic line) showing the tracking phase vs. amplitude characteristic of the CH2 head. Ta shown on the abscissa is the edge of the track pattern 20 of CH1 recorded on the magnetic tape 3 and CH.
1 is a tracking phase value that substantially aligns the edges of the head 1, and Tb is C recorded on the magnetic tape 3.
Edge of H2 track pattern 21 and CH2 head 2
The tracking phase value is such that the edges of are almost aligned. Further, Vxa and Vya shown on the vertical axis are amplitude values of the waveform X and the waveform Y at the tracking phase value Ta, and Vxb and Vyb are amplitude values of the waveform X and the waveform Y at the tracking phase value Tb. It is a value.

Tracking control is performed based on the above-mentioned amplitude relationship. That is, C in Ta and Tb
The difference in the amplitude of the FM envelope reproduced by the H1 head 1 (Vxa-Vxb), and CH2 at Ta and Tb
Amplitude difference (V
ya-Vyb) is | Vxa-Vxb |> | Vya-Vyb |, tracking control is performed in the vicinity of the tracking phase point Ta, and if | Vxa-Vxb | <| Vya-Vyb | Tracking control is performed near the phase point Tb.

Here, the reproduced image quality for each tracking phase region will be described with reference to FIGS. 10 and 11. Figure 1
0 represents the trace locus of the reproducing head, and FIG. 11 represents the tracking phase-amplitude characteristic.

The tracking phase regions (or phase positions) of A, B and C in FIG. 11 correspond to the trace loci on the recording tracks 25 of the reproducing heads A, B and C shown in FIG. In the case of the trace position of the reproducing head A shown in FIG. 10A, the effective track width becomes small, and the S / N deterioration and the inversion phenomenon occur. In the case of the trace position of the reproducing head B of FIG. 10B, it is almost the optimum position, and in the case of the trace position of the reproducing head C of FIG. 10C, adjacent interference is picked up from the tracks on both sides. As a result, edge noise increases. That is, the tracking phase region A in FIG. 11 is a region where S / N deterioration and inversion phenomenon occur, and the tracking phase region C is a region where edge noise increases. Further, it is known that the reproduced image quality in each of the tracking phase regions A and C is generally more preferable in the tracking region C than in A.

Here, in FIG. 9, it is understood that the reproduced image quality of the tracking phase point Tb of the characteristic X is more preferable than the reproduced image quality of the tracking phase point Ta of the characteristic Y. Therefore, from the optimum phase point Ta of the characteristic X, the characteristic Y
The optimum control is to perform tracking control in the vicinity of the optimum phase point Tb of C.
Even if there is a difference between the channels of the H1 head and the CH2 head, optimum tracking control can be realized.

[0060]

As described above, according to the present invention,
In the tracking control device, within a series of automatic tracking operations, the time constant of the detection circuit for detecting the amplitude of the reproduced FM envelope is switched or the detection period of the detection circuit is switched to perform a rough tracking control, and then a finer control is performed. The automatic tracking accuracy can be improved by performing accurate tracking control.

Further, according to the present invention, it is possible to improve the automatic tracking accuracy by performing the tracking control based on the amplitude information of the sync pulse section of the reproduced signal with a relatively small variation in the reproduced FM envelope.

Further, by performing the tracking control based on the S / N information of the sync pulse section in the reproduced video signal, the automatic tracking accuracy can be improved.

Further, the tracking information for each head reproduced from a plurality of rotary heads is detected, and based on this information, the tracking phase considered to be comprehensively preferable is found and controlled to improve the automatic tracking accuracy. Can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts showing a VTR tracking device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of essential parts showing a tracking device of a VTR according to a second embodiment of the present invention.

FIG. 3 is a principal block diagram showing a VTR tracking device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of essential parts showing a VTR tracking device according to a fourth embodiment of the present invention.

FIG. 5 is a main part showing a VTR tracking device according to modified examples of the second to fourth embodiments, which adopts a method of extracting amplitude information of a synchronization pulse period different from the second to fourth embodiments of the present invention. It is a block diagram.

FIG. 6 is a block diagram of essential parts showing a VTR tracking device according to a fifth embodiment of the present invention.

FIG. 7 is a block diagram of essential parts showing a VTR tracking device according to a sixth embodiment of the present invention.

FIG. 8 is an explanatory diagram showing an example of a trace trajectory of a reproducing head.

FIG. 9 is an explanatory diagram showing an example of tracking phase versus amplitude characteristics.

FIG. 10 is an explanatory diagram showing an example of a trace locus of a reproducing head.

FIG. 11 is an explanatory diagram showing an example of tracking phase versus amplitude characteristics.

FIG. 12 is a principal block diagram showing a conventional VTR tracking device.

FIG. 13 is an explanatory diagram showing an example of tracking characteristics versus amplitude characteristics.

FIG. 14 is a diagram showing an example of a trace locus of a reproducing head.

[Explanation of symbols]

 1 CH (channel) 1 head 2 CH (channel) 2 head 3 magnetic tape 4 head amplifier 5 head switching circuit 6 signal processing circuit 7 playback video signal output terminal 8 envelope detection circuit 9 microcomputer (microcomputer) 10 capstan servo circuit 11 Time constant t1 circuit 12 Time constant t2 circuit 13 Sync pulse detection circuit 14 Gate pulse generation circuit 15 Gate circuit 16 Sync pulse determination circuit 17 Automatic tracking display device 18 S / N detection circuit 19 Image quality adjustment circuit 20 CH1 recording track 21 CH2 Recording track 24 Holding circuit 25 Recording track SW1 Switch circuit for switching time constant circuit SW2 Switch circuit for switching detection period a Playback FM signal b Amplitude information c Time constant switching control signal d Playback video signal e Synchronization It reproduced FM signal f detection period switching control signal g determination signal h S / N information of the pulse period

Claims (11)

[Claims] 1. A helical scan type magnetic reproducing apparatus comprising a detection circuit for detecting the amplitude of an FM envelope reproduced by a rotary head, and means for controlling tracking based on the amplitude information of the detection circuit. The detection circuit has at least two time constants that can be switched and selected, and within a series of automatic tracking operations, immediately after the start of tracking control, rough tracking control is performed at time constant t1, and then time constant t2 (t1 A tracking control device comprising means for performing finer tracking control by switching to <t2). 2. A helical scan type magnetic reproducing apparatus equipped with a detection circuit for detecting the amplitude of an FM envelope reproduced by a rotary head, and means for controlling tracking based on the amplitude information of the detection circuit. , The detection circuit is used for the F in the sync pulse section of the reproduction signal.
A tracking control device comprising means for detecting the amplitude of the M envelope and performing tracking control based on the amplitude information detected by the detection circuit. 3. A helical scan type magnetic reproducing apparatus comprising a detection circuit for detecting the amplitude of an FM envelope reproduced by a rotary head, and means for controlling tracking based on the amplitude information of the detection circuit. , In a series of automatic tracking operations, immediately after the start of tracking control, the detection circuit constantly detects and performs rough tracking control, and then the detection period of the detection circuit is switched to the sync pulse section of the reproduction signal, A tracking control device comprising means for performing finer tracking control. 4. The detection circuit according to claim 3, wherein the detection circuit has at least two switchable and selectable time constants, and when the detection circuit constantly detects the time in a series of automatic tracking operations, When the constant t1 is set and the detection period of the detection circuit is the sync pulse section of the reproduction signal,
A tracking control device comprising means for detecting by switching to a time constant t2 (t1 <t2). 5. The method according to claim 3 or 4, further comprising: means for detecting a sync pulse of the reproduction signal, wherein when the sync pulse is not normally detected, the detection circuit is operated by F
When the amplitude of the M envelope is constantly detected and tracking control is performed, and the synchronization pulse is normally detected, the detection period of the detection circuit is switched to the synchronization pulse section of the reproduction signal to perform tracking control. A tracking control device characterized by being provided. 6. The microcomputer according to claim 5, which controls a tracking operation,
Means for outputting the section information of the sync pulse of the reproduction signal to the microcomputer, and performing F processing of the sync pulse section by software processing in the microcomputer.
A tracking control device comprising means for performing tracking control by intermittently utilizing M envelope amplitude information. 7. The display according to claim 1, 3 or 4 or 5 or 6, wherein during a series of automatic tracking operations, a period during which rough tracking control is performed immediately after the start of tracking control is displayed. The tracking control device is provided with a display switching unit that does not perform the display during a period in which finer tracking control is performed. 8. A helical scan type magnetic reproducing apparatus comprising: means for detecting S / N information in a sync pulse section of a reproduced video signal; and means for performing tracking control based on the S / N information. A tracking control device characterized by being provided. 9. A helical scan type magnetic reproducing apparatus comprising a detection circuit for detecting the amplitude of an FM envelope reproduced by a rotary head, and means for controlling tracking based on the amplitude information of the detection circuit. Tracking control comprising means for detecting S / N information in the sync pulse period of the reproduction signal and means for performing tracking control by using the S / N information in combination with the FM envelope amplitude information. apparatus. 10. The tracking control device according to claim 8, further comprising means for adaptively controlling the image quality of a reproduced image using the S / N information. 11. A detection circuit for detecting the amplitude of an FM envelope reproduced by a plurality of rotary heads including at least first and second heads, and means for controlling tracking based on the amplitude information of the detection circuit. In the provided helical scan type magnetic reproducing apparatus, the tracking phase point Ta is set so that the edge of the track pattern recorded on the magnetic tape and the edge of the first head are substantially aligned, and the recording is performed on the magnetic tape. With respect to the tracking phase point Tb that substantially aligns the edge of the track pattern with the edge of the second head, T
The relationship between the amplitude difference ΔV1 of the FM envelope reproduced by the first head at a and Tb, and the difference ΔV2 of the amplitude of the FM envelope reproduced by the second head at Ta and Tb. Means for performing tracking control in the vicinity of the tracking phase point Ta if | ΔV1 |> | ΔV2 |, and means for performing tracking control in the vicinity of the tracking phase point Tb if | ΔV1 | <| ΔV2 | A tracking control device comprising: