JPH03290815A - Generating device for tracking error signal - Google Patents

Abstract

PURPOSE:To generate a tracking error signal for eliminating the influence of a fitting error of a pair head by subtracting the tracking error signal containing a DC component in a prescribed rotary phase from an output value of a reproducing time difference detecting means for outputting the tracking error signal containing a DC component. CONSTITUTION:The track shift quantity of an AC component outputted from a DC component eliminating circuit 91, the track shift quantity of a DC component outputted from a DC error signal detecting circuit 92, and an output of a wobbling waveform generating circuit 37 are added by an adder 34. Accordingly, by driving an electromechanical converting element 32 by their composite signal, a tracking control system which is not influenced by a fitting error of a pair head can be constituted. In such a way, a tracking error signal from which a DC component is eliminated is obtained, and a tracking error signal which is not influenced by a fitting error of the pair head is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a tracking error signal generating device in a magnetic recording/reproducing device.

In conventional magnetic recording and reproducing apparatuses, temporally continuous information signals are recorded on a magnetic tape as a group of discontinuous recording tracks.

The interval between each recording track (track pitch) becomes narrower as the tape format performs recording for a longer time on a constant tape amount. On the other hand, recording tracks should originally be recorded in a straight line on a magnetic tape, but in reality, they are usually recorded in a curved state due to mechanical errors specific to each deck. Since this track curvature differs from deck to deck, magnetic recording and reproducing devices with narrow track pitches have a problem in that the reproducing head does not scan on-track over the recording track during compatible reproduction.

In order to solve this problem, it is necessary to mount the reproducing head on an electromechanical transducer and automatically change the mechanical height position of the reproducing head in accordance with track bending. In order to perform this track bending follow-up control, it is necessary to obtain a tracking error signal over the entire recording track.

As a method of obtaining a tracking error signal over the entire recording track, there is a method using the reproduction time difference of the reproduction signal based on the azimuth angle, as shown in Japanese Patent Application Laid-Open No. 54-57287 (hereinafter, this method will be referred to as (referred to as the method using azimuth time difference). Since the present invention relates to this method, the basic concept of the conventional method using azimuth time difference will be briefly explained.

FIG. 11 is a diagram showing the relative positional relationship between the recording track and the reproducing head. In the figure, reference numeral 13 indicates a pair of heads (hereinafter simply referred to as a pair of heads) composed of heads 1 and 2 having different azimuth angles, and arrow 18
Scan in the direction. The method of recording and reproducing information signals using such paired heads is effective when the frequency band of the information signals to be handled is large. This is because when recording an information signal at a constant head scanning speed, the higher the recording frequency of the information signal, the shorter the recording wavelength recorded on the magnetic tape, and the shorter the recording wavelength, the more difficult it is to record and reproduce. If paired heads are used, the frequency band of the information signal can be divided and distributed to each head, so the recording wavelength can be set substantially longer.

18 and 17 are recording tracks recorded by paired heads. 19 and 20 indicate recording positions of specific signals;
A plurality of specific signals are recorded on the track. The specific signal is, for example, a horizontal synchronization signal in an analog VTR,
In a digital VTR, this is a sync signal added to each signal block.

The paired head 13 is shown on-track on the recording track. Heads 14 and 15 are also paired heads, and show mistracking to the right and left sides of the recording track, respectively. When a recording track is read back and scanned with a head having such a relative positional relationship, even signals recorded at the same time are played back at different times.

For example, at the scanning position of the paired head 13, the specific signals 19 and 20 are reproduced by the heads 1 and 2 for the same amount of time;
At the head scanning position of the paired head 14, the time during which the specific signal 20 is reproduced by the head 5 is slower than the time during which the specific signal 19 is reproduced by the head 6. In addition, pair rad 1
At head scanning position 5, the specific signal 20 is
The time at which the specific signal 19 is reproduced by the head 8 is faster than the time at which the specific signal 19 is reproduced by the head 8.

Therefore, by checking the time difference between the specific signals reproduced by each head making up the paired head, it is possible to know the track deviation.

FIG. 12 is a diagram showing the relationship between track slippage and the reproduction time difference of each specific signal reproduced by each head constituting the paired head. The horizontal axis shows the amount of track deviation, and the position indicated by zero is the on-track position. The relationship between the off-track and the time difference between the reproduced signals is the relationship shown by 21.

As mentioned above, the method of performing tracking control by detecting the time difference between the signals reproduced by the paired heads is effective when the center positions of the head gaps of the heads that make up the paired heads match exactly, but if they do not match, If not, track deviation will occur. This will be explained next.

Figure 9 shows the magnetization trajectory recorded by a pair of heads whose positions are exactly aligned when the heads are installed, and the recording track and playback head when playing back with a pair of heads whose positions are shifted. FIG. 22.
Reference numeral 23 indicates each head constituting the paired head, and 24 and 25 indicate recording positions of specific signals. The figure shows a state in which the paired heads scan on-track on the recording track. At this time, the difference in the reproduction time of each specific signal reproduced by the heads 22 and 23 depends on the attachment of the heads 22 and 23. is the time corresponding to the error. That is, even when on-track, a time difference occurs in the reproduced signal.

FIG. 10 shows the relationship between track slippage and the time difference between reproduced signals, and the vertical and horizontal axes have the same meanings as in FIG. 12. In the same figure, 21 is the same characteristic as the characteristic shown in FIG. That is, the on-track position is when the time difference is zero.

On the other hand, the characteristic indicated by 26 is the characteristic when the relationship between the head and the recording track is as shown in FIG. That is, the time difference does not become zero at the on-track position. If control is performed such that the time difference becomes zero at this time, the control system will be stabilized at the track position indicated by 27.

The mounting errors of each head that make up the pair head (hereinafter referred to as
The error (here, simply referred to as the error in the installation of paired heads) is determined by the mechanical accuracy during head assembly, and variations will always occur. Therefore, unless this problem is solved, the tracking error signal detection method using the azimuth time difference cannot be used practically.

As a conventional method for solving this problem, a method has been used in which a track bending follow-up control system using an azimuth time difference is combined with a control system for correcting direct current track deviation.

The conventional method will be explained below.

FIG. 7 is a diagram showing the configuration of a conventional tracking control system. In the figure, reference numerals 30 and 31 indicate magnetic heads constituting a pair of heads. 32 is an electromechanical transducer composed of a piezoelectric element or the like.

33 is a reproduction time difference detection circuit for detecting the reproduction time difference of the aforementioned specific signals, and the output of this detection circuit is sent to the adder 34;
The amount of displacement of the electromechanical transducer 32 is controlled via the drive circuit 35. Therefore, if the playback time difference of the specific signal indicates correct track bending information, the head 30.3
1, reproduction scanning follows track bending. 37 is a wobbling waveform generation circuit, and 36 is a DC error signal detection circuit for detecting a DC tracking error signal using a wobbling method, which will be described later.

Next, a method for detecting a tracking error signal using the wobbling method will be briefly described.

The wobbling method is a method in which the head is forcibly mistracked and the direction of the track deviation is detected by examining changes in the playback output at that time. FIG. 8 is a diagram showing the relative positional relationship between recording tracks and paired heads. In the figure, 38 and 39 are recording tracks recorded by a pair of heads. Reference numerals 40, 41, and 42 denote a pair of heads, which are respectively shown in a state shifted to the right side and a state shifted to the left side in the on-track state 9 drawing. Now, let us consider changes in the reproduction output of each head when the paired heads are forcibly displaced to the right and left in each state. When displaced to the right, the reproduction outputs of the pair heads 40 and 41 decrease, but the reproduction output of the pair head 42 increases.

Conversely, when it is displaced to the left, the paired heads 40 and 4
The reproduction output of the pair head 41 decreases, but the reproduction output of the pair head 41 increases. That is, in the on-track state, the reproduction output decreases regardless of whether the displacement is made to the left or right, but in the case of mistracking, the direction of displacement and the direction of increase/decrease in the reproduction output are reversed depending on the direction of mistracking.

Therefore, by using the wobbling method, it is possible to know the direction of mistracking, and it becomes possible to control the head to be on-track on the recording track.

In FIG. 7, the wobbling waveform generating circuit 37 is a circuit for generating a signal for forcibly displacing the head. For example, during the period when the head contacts the magnetic tape and scans, the wobbling waveform generating circuit 37 displaces the head to the right. A signal is generated to displace the head to the left during the next spatula contact period. The DC error signal detection circuit 36 detects the change in the reproduction output at this time, and detects the mistrack direction of the head. Then, a signal in the direction in which the head is on track is output.

If the conventional method shown in Fig. 7 is used, even if there is an error in the installation of the paired heads, which corresponds to a direct current track deviation,
By using the wobbling method in conjunction with the wobbling method, errors in pair head installation can be absorbed.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, there is a problem in that when a pair of heads is installed, mistracking occurs at the editing point when playing back a tape that has been edited on decks with different errors.

This problem will be explained below.

FIG. 5 is a diagram showing recording tracks edited by heads with different installation errors when paired heads are attached.

In the figure, 50, 51, and 52 indicate recording tracks recorded by paired heads, and 53 to 58 indicate recording positions of specific signals. 59 indicates an edit point, and the recording track in the area before the edit point indicated by the arrow 60 is recorded on a certain deck,
The recording track in the area after the edit point indicated by the arrow 61 is as follows:
This is a recording track recorded on another deck. When editing is performed using different decks as described above, the recording positions of specific signals before and after the editing point are usually different.

FIG. 6 is a diagram for explaining the follow-up characteristics of a conventional control system when the tape shown in FIG. 5 is reproduced. In FIG. 6, (a) shows head switching signals (H, SW signals). )1. The SW signal is a signal synchronized with the rotational phase of the rotary head, and the signal changes once during a half period of the H9SW signal.
Form the recording track of the book. (b) shows a tracking error signal.

The timing indicated by 62 indicates the timing of the editing point.

In other words, the low period of the H and SW signals indicated by 63 is the period during which the paired head reproduces and scans the recording track 50 (FIG. 5), and the high period of the H and SW signals indicated by 64 is the period during which the paired head reproduces the recording track 51. This is the period to scan. When the recording position of the specific signal changes before and after the editing point, even if the head is in an on-track state, the tracking error signal changes with a DC component superimposed thereon, as shown at 65.

The track bend follow-up control system is a control system that has a relatively fast response speed in order to follow the bend of the recording track. On the other hand, the wobbling control system described above has a relatively slow response speed because it detects a mistrack by generating a mistrack every head scan.

Therefore, when the above-mentioned tracking error signal changes at an editing point, the track bend follow-up control system responds immediately, but since the tracking error signal at this time is false information, there may be mistracking. become. Then, the wobbling control system detects this mistracking and gradually controls the reproducing head to an on-track state.

Therefore, in the conventional configuration described above, there is a problem in that the influence of errors cannot be removed when pair heads are attached at editing points.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a tracking error signal generating device in which the influence of errors in pair head attachment is removed.

Means for Solving the Problems In order to achieve the above object, the present invention provides a pair of magnetic heads composed of first and second magnetic heads having different azimuth angles, and a first magnetic head that is reproduced by the first magnetic head. reproduction time difference detection means for detecting a reproduction time difference between the specific signal and a second specific signal reproduced by the second magnetic head;
sample hold means for sample-holding the playback time difference at fixed time intervals in synchronization with the rotational phase of the rotary head; and calculating a value of the difference between the output value of the playback time difference detection means and the output value of the sample hold means. and calculation means.

Operation With the above-described configuration, the present invention subtracts the tracking error signal containing the DC component at a constant rotational phase from the output value of the reproduction time difference detection means that outputs the tracking error signal containing the DC component. A removed tracking error signal can be obtained.

EXAMPLE Before explaining the present invention in detail, the basic idea of the present invention will be explained.

FIG. 4 is a waveform diagram for explaining the basic idea of the present invention, (c) shows the H and SW signals, and (d) shows the waveforms.

(e) and (f) both show tracking error signals. The tracking error signal A shown in (d) is a value obtained by measuring the reproduction time difference of the specific signal, and is a tracking error signal containing a DC component. Tracking error signals 71 and 72 are error signals before and after the editing point, and mounting of the paired head indicates a state in which the DC level is changing due to the influence of the error. The tracking error signal B shown in (e) is an error signal obtained by subtracting the value of the tracking error signal at the scanning start point of the head from each tracking error signal. In other words, it is the value obtained by subtracting the value shown at 75 from each part of the tracking error signal shown at 70, 76 from 71, 77 from 72, etc.
...These are the values subtracted from each other.

The tracking error signal C shown in (f) is 75°76
．． 77, . . . are detected by the above-mentioned wobbling method, and are superimposed on the tracking error signal shown in (e).

In this way, if the method shown in (d) is to remove the DC component from the tracking error signal and then add the DC component obtained by the wobbling method, the pair head installation can generate a tracking error signal that is not affected by errors. Obtainable.

Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a tracking error signal generating device showing an embodiment of the present invention. In the same figure, 3
0.31 is each head that constitutes a pair head, and 32
is an electromechanical transducer composed of a piezoelectric element or the like. 3
Reference numeral 3 denotes a reproduction time difference detection circuit that detects the reproduction time difference of the specific signal, and 81 denotes a DC component removal circuit that removes a DC component from the output value of the reproduction time difference detection circuit 33. 34 is an adder, and 35 is a drive circuit for the electromechanical conversion element. 37 is a wobbling waveform generation circuit, and 92 is a DC error signal detection circuit that detects a DC track deviation obtained by the wobbling method and outputs a tracking error signal in a direction to bring the head on-track.

The DC error signal detection circuit 92 detects the DC component of track deviation at the head scanning start point.

With the above configuration, the amount of track deviation of the AC component output from the DC component removal circuit 91 and the amount of track deviation of the DC component output from the DC error signal detection circuit 92,
If the output of the wobbling waveform generation circuit 37 is added in the adder 34 and the electromechanical transducer 32 is driven by these combined signals, a tracking control system that is not affected by errors can be formed when mounting the paired head. Can be done.

Next, a specific embodiment of the circuit 90 for detecting the amount of track deviation of the AC component will be described.

FIG. 2 is a diagram showing a specific circuit configuration of the circuit block 90 shown in FIG. 1, and FIG. 3 is a diagram showing waveforms of each part in FIG. 2. In FIG. 2, terminals 100 and 101
The signals reproduced by the heads 30 and 31 forming the pair of heads are input from the head. Specific signal separation circuits 102 and 103 amplify each input signal and then separate and output specific signals (g) and (h). 104 is a gate signal generation circuit, which generates specific signals (g) and (h).
and the H and SW multiplied signal c) input from the terminal 105, an enable signal (k), a reset signal (m),
A latch pulse (n) and a subtraction pulse (0) are output respectively.

The phase relationship between these signals is shown in FIG. In FIG. 3, (C) includes H and SW multiplied signals, which are signals phase-synchronized with the rotational phase of the rotary head. (g) and (h) are specific signals reproduced by each head. (i) is a signal obtained by frequency-dividing the specific signal (g) by 172, and (j) is a signal obtained by frequency-dividing the specific signal (h) by 172. Each of these signals (i) and (j) is reset at the rising and falling edges of the H, SW signal. The enable signal (k) is a signal that outputs a high level when the specific signal (i) is in the high period and the specific signal (j) is in the low period. The reset signal (m) is a signal that outputs a high level when the specific signal (i) is in the low period and the specific signal (j) is in the high period. The latch pulse (n) is a pulse signal that is output after a certain period of time from the falling edge of the enable signal (k), and is
, SW is a signal that is output only one pulse in a period of 1/2 of the SW multiplied signal. The subtraction pulse (0) is the enable signal (k)
This is a pulse signal that is output a certain period of time after the falling edge of latch pulse (n), and is output at a timing that is later than the latch pulse (n).

The subtraction pulse (0) is output every time the enable signal (k) is output.

In FIG. 2, 105 is a counter circuit, and terminal 1
It counts and outputs the clock signal input from 06. The counter circuit 105 has an enable signal (k) of
t'X11J set signal (m
) The count value is reset at the rising edge of ).

(p) in FIG. 3 shows the count value expressed in levels. 107 is a latch circuit, and a latch pulse (n
) is input, the value of the count value (p) is held. A subtraction circuit 108 calculates and outputs the difference between the count value (p) and the latched value (q). 10
A D/A converter 9 converts the output value of the subtraction circuit 108 into an analog voltage and outputs a D/A conversion output value (r).

By performing each of the above processes, it is possible to obtain a tracking error signal from which the DC component has been removed.

Note that each of the above-mentioned processes is not limited to hardware, and can also be performed by software using a microcomputer.

Furthermore, in the embodiments of the present invention, a method for driving an electromechanical transducer by applying a tracking error signal from which a DC component has been removed is applied within a control system loop has been described. It may be used for the following purposes.

For example, it can be used when adjusting a tape running system when manufacturing a magnetic recording/reproducing device (VTR). When manufacturing VTRs, in order to maintain compatibility between each VTR, the linearity of the tracks recorded on the magnetic tape (track bending) is
must be kept within a certain specified value. If the present invention is used during this compatibility adjustment, it is possible to adjust the tape running system while directly observing track bending in real time, which has the advantage of shortening the time required to manufacture a VTR.

In another application of the present invention, track bending may be displayed on a display. Some recent VTR1s, especially broadcast VTRs, are equipped with large displays. This display shows various information such as time code, playback audio level, and the amount of tape on the reel. One of these pieces of information is
Track bending information may be displayed as a curve. By performing such a display, the user can grasp the reliability of the deck being used during compatible playback.

Additionally, since it is possible to obtain information regarding the track curvature of the deck due to changes over time, this is an important function for broadcasting stations that require high-quality reproduced images.

Effects of the Invention As is clear from the above explanation, the present invention subtracts a tracking error signal containing a DC component at a constant rotational phase from the output value of the reproduction time difference detection means that outputs a tracking error signal containing a DC component. As a result, it is possible to obtain a tracking error signal from which the direct current component has been removed, so that the attachment of the paired head has the effect of obtaining a tracking error signal that is not affected by errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a tracking error signal detection device in one embodiment of the present invention, FIG. 2 is a block diagram showing a specific example of the circuit block 90 in FIG. 1, and FIG. 2 is a waveform diagram showing the waveforms of each part, FIG. 4 is a waveform diagram for explaining the basic idea of the present invention, FIG. 5 is a schematic diagram showing the tape format at the editing point, and FIG.
The figure is a waveform diagram showing changes in the tracking error signal before and after the editing point, Figure 7 is a block diagram showing the configuration of a conventional tracking control system, and Figure 8 is the relative relationship between the recording track and the paired head to explain the wobbling method. Fig. 9 is a schematic diagram showing the relationship between a pair of heads with mounting errors and a recording track, and Fig. 10 is a characteristic showing changes in playback time difference due to pair heads with mounting errors. 11 is a schematic diagram showing the relative positional relationship between the recording track and the paired head, and FIG. 12 is a characteristic diagram showing changes in the reproduction time of each specific signal reproduced by the paired head. 1.2...Each head constituting the pair head, 13,
14. 15...pair head, 31.32...
magnetic head, 32... electromechanical conversion element, 34...
... Adder, 40-42 ... Pair head, 109
...D/A converter.

Claims (1)

[Scope of Claims] A pair of paired heads including first and second magnetic heads having different azimuth angles; a first specific signal reproduced by the first magnetic head;
reproduction time difference detection means for detecting a reproduction time difference with a second specific signal reproduced by the second magnetic head; and a sample hold for sampling and holding the reproduction time difference at fixed time intervals in synchronization with the rotational phase of the rotary head. A tracking error signal generating device, comprising: means for calculating a difference between an output value of the reproduction time difference detecting means and an output value of the sample hold means.