JPH0234513B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is a magnetic recording and reproducing device (hereinafter referred to as VTR).
This invention relates to a method for detecting a tracking error signal, in particular, recording a pilot signal for tracking control by superimposing it on a video signal during recording.
To provide a novel tracking error signal detection method that eliminates the influence of flyback pulses of a television receiver in a method in which a pilot signal reproduced as a crosstalk signal from an adjacent track is used as a tracking error signal during reproduction. It is something.

A rotary head type VTR requires a tracking control system to cause the rotary head to on-track and scan the recording track during reproduction.

The conventional tracking control method for a two-head helical scan VTR uses a control signal, in which one frame is recorded on a control track provided on the magnetic tape according to the rotational phase of the rotating head during recording. In this method, a control signal is recorded for each time, and during playback, a signal corresponding to the difference between the rotational phase of the rotary head and the playback phase of the control signal is used as a tracking error signal, and the feeding speed of the magnetic tape is controlled using the error signal. be.

On the other hand, a pilot signal for tracking is recorded together with the information signal to be recorded, and during reproduction, the reproduction level of each pilot signal reproduced as a crosstalk signal from each adjacent track adjacent to the main scanning track is compared, A method has been proposed in which a signal corresponding to the level difference obtained at this time is used as a tracking error signal. Since this method does not require a control track or a control head, it has the advantage of making effective use of the magnetic tape. In addition, since the tracking error signal is obtained over the entire recording track, a rotary head is mounted on an electromechanical transducer composed of a piezoelectric element, and the tracking error signal obtained during playback is adjusted according to the tracking error signal obtained during playback. By displacing the head in the direction of the rotation axis, a tracking control system capable of following the curvature of the recording track can be constructed.

A tracking error signal detection method using a pilot signal includes, for example, the so-called burst pilot method (hereinafter referred to as the BP method), which is disclosed in Japanese Patent Application No. 129727/1982. An overview of the conventional BP system will be explained using a two-head helical scan VTR as an example.

FIG. 1 shows the recording magnetization locus on the magnetic tape.
In the figure, numeral 1 indicates a magnetic tape, which is transported in two directions of arrows. A ₁ , B ₁ , A ₂ , . . . are recording tracks recorded by the A head and the B head, and the rotary head scans in the three directions of the arrows. 1H indicates one horizontal scanning period, and FIG. 1 shows the magnetization locus when the H arrangement is 0.5H. A shaded signal P indicates a pilot signal, for example, a signal around 100 KHz.
Although the pilot signal may be recorded over the entire 1H period, damage to the color signal can be avoided by recording only one cycle during the horizontal aircraft signal period. In FIG. 1, 0 and π indicate the recording phase of the pilot signal.

As is clear from Figure 1, the pilot signal is
The tracks are recorded every 2H, and the recording positions are recorded so that they are lined up in the width direction of the tracks between each track within one frame, but are recorded so that they are not lined up every frame. Further, the recording phase of the pilot signal is the same on the A track, and is recorded inverted every 2H on the B track.

Next, a method for detecting a tracking error signal during reproduction will be described.

During playback, the head scans the main scanning track, e.g.
The pilot signal reproduced when reproducing and scanning track A ₂ shown in the figure is the same as the pilot signal recorded on track A ₂ and both adjacent tracks.
This is the pilot signal recorded on _B1 and _B2 . This is because even if the head does not perform reproduction scanning on tracks B ₁ and B ₂ , the relatively low frequency pilot signal in the vicinity of 100 KHz is reproduced as a crosstalk signal due to leakage magnetic flux. The pilot signal obtained at this time is supplied to the 2H delay circuit 5 from the terminal 4 shown in FIG. The signals before and after the 2H delay are added and subtracted, respectively, and output to terminals 6 and 7. When the head performs reproduction scanning on track _A2 , only the pilot signal recorded on track _A2 is taken out from terminal 6. This is because the pilot signals recorded on tracks _B1 and _B2 are inverted and recorded every 2H, so the signals before and after the 2H delay are canceled by adding them together. . For the same reason, the pilot signals output to terminal 7 are only those reproduced from tracks B ₁ and B ₂ . Truck B ₁ , B ₂
Each of the above pilot signals can be temporally separated based on the pilot signal reproduced from the main scanning track _A2 . Therefore, tracks B ₁ and B ₂
If a signal corresponding to the reproduction level difference between the respective pilot signals reproduced from the main scanning direction is used as a tracking error signal, the rotary head can be on-tracked on the main scanning track to perform reproduction scanning. In addition,
When the head reproduces and scans track B ₂ as the main scanning track, the signal output to terminal 6 shown in FIG. 2 is the pilot signal reproduced from tracks A ₂ and A ₃ , and the signal output to terminal 7. It is. Therefore, a tracking error signal can also be obtained at this time.

The above is an overview of the conventional BP method, but this conventional method has the drawback that the influence of periodic external noise that enters the rotating head appears as a noise component in the tracking error signal. For example, when a VTR is mounted on top of a television receiver, flyback pulses (hereinafter referred to as FB pulses) of the television receiver jump in from the rotating head of the VTR and adversely affect the tracking error signal. Since the FB pulse contains high-order harmonic components with relatively high energy,
It is not possible to separate the pilot signal near Hz and the FB pulse using a filter.

The influence of the FB pulse will be explained in more detail using FIG. In FIG. 3, time is plotted on the horizontal axis, and 1H indicates one horizontal scanning period. Figure a shows the FB pulse,
The f signal is reproduced every 1H. Signals a ₂ , b ₂ , a ₃ shown in b, c, d correspond to each track shown in FIG.
These are the pilot signals reproduced from A ₂ , B ₂ , and A ₃ . That is, FIG. 3 shows an example in which track _B2 is a main scanning track. Note that the sign of each signal indicates the O phase and the π phase. When the head reproduces and scans the track _B2 , the signals a to d shown in FIG. 3 are combined and input to the terminal 4 shown in FIG. Figure 3 e
The signal shown in is the signal obtained when the signal before the 2H delay and the signal after the delay are added, and the signal shown in f is the signal obtained when they are subtracted. Figure 3 e
As is clear from and f, if there is no influence of the FB pulse, the pilot signals 2a ₂ and 2a ₃ can be separated and extracted based on the pilot signal 2b ₂ , but if there is an FB pulse, the pilot signals 2a 2 and 2a ₃ can be extracted. The signal is a mixture of _2a3 and FB pulses, and a normal tracking error signal can be extracted.

Note that in Figure 3, the main scanning track is the same as that in Figure 1.
B ₂ , but when the main scanning track is set to A ₂ ,
An FB pulse is superimposed on the pilot signal reproduced from the main scanning track every 1H. For this reason,
This makes it difficult to determine the reference signal that separates the pilot signals reproduced from both adjacent tracks.

The present invention provides a novel tracking error signal detection method that can eliminate the influence of the FB pulse.

The details of the present invention will be explained below.

FIG. 4 shows the recorded magnetization locus according to the present invention,
A ₁ , B ₁ , A ₂ , . . . are recording tracks recorded on the A head and the B head. In the figure, O and π indicate the recording phase of the pilot signal. The pilot signal may be recorded over the entire 1H period, or may be recorded for only one cycle within the horizontal synchronization signal period. In the present invention, the recording phase of the pilot signal is reversed every 4H and recorded, and the pilot signal is recorded so that the switching points of the recording phase are not lined up in the width direction of the recording tracks in at least three adjacent recording tracks. do. During reproduction, by passing the reproduced pilot signal through a 1H delay circuit and subtracting the signals before and after the delay, the reproduced pilot signal can be separated from the main track and each adjacent track, and the FB pulse can be removed. .
This point will be explained in detail.

FIG. 5 shows a 1H delay circuit, in which a composite signal of pilot signal FB pulses reproduced from the main scanning track and both adjacent tracks is inputted to the terminal 8.
This signal is subtracted from the signal passed through the 1H delay circuit 9 and output to the terminal 10.

FIG. 6 is a diagram for explaining the output after subtraction, and shows the output state of each pilot signal obtained when the track _B2 shown in FIG. 4 is reproduced and scanned as a main scanning track. Also, Figure 6 shows the 3rd
Each symbol is set according to the same regulations as in the figure. In Figure 6, f is the FB pulse, a ₂ , b ₂ ,
_a3 is a pilot signal reproduced from each recording track _A2 , _B2 , _A3 . As is clear from the figure, the position where the phase of each pilot signal is reversed is 1H.
It is shifting gradually. If the composite signal of each signal shown in a to d is delayed by 1H and subtracted from the signal before delay, we get
Signals that are in phase before and after the delay are mutually canceled, and only signals that are in opposite phase are extracted. Therefore, as shown in Figure e, the signal after subtraction is output with each pilot signal recorded on each recording track separated in time, and with the FB pulse removed. be done. Therefore, if the position of the main scanning track can be determined, each pilot signal reproduced from each adjacent track can be separated and extracted, so that it can be used as a tracking error signal. The position of the pilot signal recorded on the main scanning track is
The signal with the highest level of the reproduction pilot signal may be used.Alternatively, as will be described later, a reference signal may be recorded in advance within the luminance signal, and the time position at which the reference signal is reproduced at the time of reproduction may be determined from the main scanning track. It may also be the reproduction time position of the pilot signal to be reproduced.

Next, specific embodiments of the present invention will be described.

FIG. 7 is a block diagram showing an embodiment of the present invention, FIG. 8 shows waveforms of various parts of the recording system shown in FIG. 7, and FIG. 9 shows waveforms of various parts of the reproducing system.

In FIG. 7, a video signal is input from a terminal 11. The luminance signal included in the video signal is separated from the color signal by a low-pass filter 12 and subjected to FM modulation by an FM modulation circuit 13.
On the other hand, the color signal is processed by a color signal processing circuit 1 such as a high-pass filter and a low-frequency conversion circuit (not shown).
4 and is superimposed on the FM-modulated luminance signal.

In addition, the video signal is transmitted to the recording side terminal R of the switch 18.
After that, a horizontal synchronizing signal is extracted by a horizontal synchronizing signal separation circuit 19. The circuit 20 is a phase comparison circuit,
Circuit 21 is a frequency dividing circuit, circuit 22 is a voltage controlled oscillation circuit, and circuits 20 to 22 constitute a PLL circuit. Therefore, the output of the frequency dividing circuit 21 outputs a signal phase-synchronized with the horizontal synchronizing signal, and when the frequency dividing circuit 21 divides the frequency by 1/48, the output of the voltage controlled oscillation circuit 22 is 48 _H ( _H is Outputs a signal with a frequency (horizontal sync signal frequency). The output of the frequency dividing circuit 21 is divided into 1/4 by the frequency dividing circuit 23 and input to the gate pulse generating circuit 24. The output of circuit 24 is
A gate pulse with a width of several μsec is generated every 4 hours. The circuit 25 is a gate circuit and gates the _48H signal. The output signal C of the circuit 25 is a signal used as a reference signal indicating the phase inversion position of the pilot signal of the main scanning track, as will be described later. The reference signal c is superimposed on the luminance signal a, and the phase relationship between the signals a and c is as shown in FIG. That is, the reference signal c, which is extracted with a width of several μses every 4H, is located within the horizontal synchronizing signal period including the retrace period.

Next, a circuit for creating a pilot signal will be explained. The output of the voltage controlled oscillation circuit 22 is converted into an _8H signal by a 1/6 frequency divider circuit 26, and the output signal Q and the output signal are inputted to an electronic switch 27. The electronic switch 27 is driven by the output of the 1/4 frequency divider circuit 23, and outputs _{an 8H} signal with phase inversion every 4H. Circuit 28 is a one-cycle gate circuit,
Extract only one cycle of the _8H signal. circuit 2
9 is a gate pulse generation circuit, which generates a gate pulse every 1H. The output of the circuit 28 is converted into a sine wave by a low pass filter 30 and becomes a pilot signal b. The signal b is a one-cycle signal located in the horizontal synchronizing signal period as shown in FIG. 8, and is a signal whose phase is inverted every 4H. Note that the reference signal c is located within the horizontal synchronizing signal period in which the first cycle of the signal is recorded when the phase of the pilot signal b is inverted.

The FM modulated luminance signal including the reference signal is combined with the low-frequency converted color signal and the pilot signal, and is supplied to the rotary head 17 via the recording amplifier circuit 15 and the recording side terminal R of the switch 16. These signals are then recorded as recorded magnetization trajectories on the magnetic tape. The above is the explanation of the recording circuit.

Next, the reproduction circuit will be explained.

A reproduction RF signal obtained when the rotary head 17 performs reproduction scanning on the recording track is amplified by the reproduction amplifier circuit 31 via the reproduction side terminal P of the switch 16. The amplified RF signal is passed through a low pass filter,
The original color video signal is restored in a color signal processing circuit 35 such as a high frequency conversion circuit (not shown). The luminance signal included in the reproduced RF signal is extracted by the high-pass filter 32 and demodulated by the FM demodulation circuit 32 to become a signal d. signal d
As shown in FIG. 9, is a luminance signal on which the reference signal REF is superimposed. The circuit 34 is a reference signal erasing circuit, and operates according to the output of the gate pulse generating circuit 37. The circuit 37 is created based on a signal synchronized with the horizontal synchronization signal of the reproduced video signal inputted from the reproduction side terminal P of the switch 18, and generates a gate pulse at a position corresponding to the reproduction position of the reference signal. The signal demodulated to the original luminance signal via the circuit 34 is combined with the output signal of the color signal processing circuit 35 and output to the terminal 36 as a reproduced video signal.

On the other hand, the reproduced RF signal is input to a low-pass filter 40, and only the pilot signal near 100 KHz is extracted. The circuit 41 is the 1H delay circuit described above, and the pre-delay and post-delay signals are subtracted to extract each pilot signal to be reproduced from each temporally separable recording track. The reproduced pilot signal passes through a low-pass filter 42 and a detection circuit 43 and is converted into a signal shown in FIG. 9h. The output _{of the} reproduction pilot signal shown _in FIG _. Truck A ₂ , B ₂ , A ₃
This corresponds to the playback output of each pilot signal recorded above. That is, when the head on-tracks and performs reproduction scanning on track _B2 , the reproduction level of pilot signal _b2 is the highest, and the reproduction levels of pilot signals _a2 and _a3 are equal. However, when the head shifts in the track A ₂ direction and performs reproduction scanning, the reproduction level of the pilot signal A ₂ changes.
It is larger than that of a ₃ , and the head is tracked on the contrary.
When the reproduction scanning is performed with a shift in the _A3 direction, the reproduction level of the pilot signal _a3 becomes higher than that of the pilot signal _a2 . Therefore, by comparing the relative levels of pilot signals _a2 and _a3 , it is possible to know the amount and direction of deviation when the reproduction scanning head deviates from the main scanning track and performs reproduction scanning.

In FIG. 7, a circuit 44 is a peak hold circuit, and holds voltage values corresponding to respective reproduction levels of reproduction pilot signals a ₂ , b ₂ , and a ₃ . In the peak hold circuit, the hold value is reset every 1H by the output j of the reset pulse generation circuit 45.
It is extracted as signal i. Signal i is input to sample and hold circuits 46 and 47. The sample pulses g and f are generated by a pulse gate circuit 38 extracting a reference signal superimposed on the luminance signal, and a sample pulse generation circuit 39 based on the reference signal. The phase relationship between the pulse e from which the reference signal is extracted and the sample pulses g and f is as shown in FIG. The signal extracted by sample pulse f has a voltage value corresponding to the reproduction output level of the pilot signal recorded on track A ₃ , and the signal extracted by sample pulse g has a voltage value corresponding to the reproduction output level of the pilot signal recorded on track A _2. This voltage value corresponds to the reproduction output level of the recorded pilot signal. Therefore, these two voltage values are compared to the voltage comparator circuit 48.
By comparing the levels at terminal 49, the signal output to terminal 49 can be used as a tracking error signal. By supplying the output signal obtained at the terminal 49 to the capstan motor as a phase error signal to control the tape feeding speed, the rotary head can perform reproduction scanning by on-tracking on the main scanning track. In addition, if the rotating head is a VTR mounted on an electromechanical transducer such as a piezoelectric element, it is possible to follow track bends by supplying the tracking error signal obtained at the terminal 49 to the electromechanical transducer. A control system can be configured.

As is clear from the above explanation, the present invention has the advantage of completely eliminating the influence of the TV FB pulse, which was a drawback of the conventional BP method, and also has the advantage that the delay circuit can be It has the advantage that the delay circuit can be a 1H delay circuit.

In the present invention, the method of recording a reference signal within the luminance signal in order to know the phase inversion position of the pilot signal recorded on the main scanning track has been explained as an example. The pilot signal with the highest reproduction level may be used as the pilot signal for the main scanning track.Also, for example, a reference signal may be recorded only during the vertical blanking period, and the output signal of the self-oscillator triggered by the reference signal may be used as the pilot signal for the main scanning track. Alternatively, a method may be used in which the reproduction position of the pilot signal reproduced from the main scanning track is determined.

Furthermore, in the present invention, the method of inverting and recording the phase of the pilot signal every 4H has been explained as an example, but the phase inversion is not limited to every 4H, and the phase inversion position of the pilot signal recorded on the main scanning track can be used as an example. It is clear that it is sufficient to record the data and the data recorded on both adjacent tracks so that they are not lined up in the width direction of the track.

Further, in the present invention, the magnetization trajectory when the H arrangement is 0.5H has been explained as an example, but the H arrangement is not limited to 0.5H. For example, if the H sequence is 1H, the first
The magnetization locus of the pilot signal shown in FIG. Even at this time, the phase inversion positions of the pilot signals are not aligned between the respective recording tracks. Therefore, the pilot signals reproduced from each recording track can be separated in time. In addition, the 10th
The symbols used in the figures have the same meanings as in Figure 4.

[Brief explanation of drawings]

Fig. 1 is a schematic recording pattern diagram for explaining the magnetization locus of the conventional burst pilot method, Fig. 2 is a main part block diagram for explaining the principle configuration of the conventional burst pilot method, and Fig. 3 is a diagram of a TV. FIG. 4 is a schematic recording pattern diagram for explaining the magnetization locus of the pilot signal according to the present invention, and FIG. 5 is a diagram for explaining the principle configuration of the present invention. 6 is a diagram for explaining the principle of flyback pulse removal according to the present invention, FIG. 7 is a block diagram showing a specific circuit example of the present invention, and FIG. 8 is a diagram for explaining the principle of flyback pulse removal according to the present invention. 9 is a waveform diagram of each part of the reproduction system of FIG. 7, and FIG. 10 is a diagram showing the recording pattern of the pilot signal when the present invention is applied when the H arrangement is 1H. . A ₁ , B ₁ ... Recording track, f ... Flyback, a ₂ , b ₂ , a ₃ ... Reproduction pilot signal, O, π
... Recording phase of pilot signal, 13 ... FM modulation circuit, 14, 35 ... Color signal processing circuit, 1
9...Horizontal synchronization signal separation circuit, 20, 21, 22
...PLL circuit, 21, 23, 26... frequency dividing circuit,
24, 29, 37...gate pulse generation circuit, 2
5...Gate circuit, 28...1 cycle gate circuit, 34...Reference signal erasing circuit, 38...Reference signal gate circuit, 39...Sample pulse generation circuit, 45...Reset pulse generation circuit, 44...
Peak hold circuit, 46, 47... Sample hold circuit, 48... Voltage comparison circuit.

Claims (1)

[Claims] 1. During recording, a pilot signal is recorded together with a video signal in each horizontal scanning period on the same recording track, and the phase of the pilot signal is inverted at a cycle that is an integral multiple of one horizontal scanning period, and the phase inversion positions are at least close to each other. The pilot signals are recorded between the three recording tracks so as not to line up in the width direction of the recording tracks, and are obtained by subtracting the reproduced pilot signal by one horizontal scanning period and the signal before the delay. From the reproduced pilot signal, each pilot signal recorded on the adjacent tracks before and after the main scanning track is temporally separated and extracted, and the reproduction level of each pilot signal extracted at this time is relatively compared. A tracking error signal detection method characterized by obtaining a tracking error signal.