JP2007242201A - Servo signal detecting device and servo signal detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a servo signal detecting device for detecting a servo signal with high accuracy and in real time even in a clock timing of a feasible, relatively low frequency. <P>SOLUTION: The servo signal detecting device 1 is provided with an arithmetic circuit 2a for executing the procedures for: collecting a plurality of data points in a plurality of signal inverting parts constituting the waveform of a reproduced signal; finding a straight line that passes through or approximately passes through the plurality of data points in the respective signal inverting parts; finding, each time the straight line intersects, a reference line on which an output value of the reproduced signal is zero for each of the respective signal inverting parts; and calculating a difference between respective times. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a servo signal detection device and a servo signal detection method for detecting a servo signal written on a magnetic tape.

  In recent years, magnetic tapes have been developed with high density recording, and the interval between data tracks and the width of the data tracks themselves are gradually becoming narrower. A servo signal for servo-controlling the magnetic head is written on the magnetic tape so that the magnetic head can accurately follow the data track. 2. Description of the Related Art Conventionally, as a servo signal detection device, one that detects a servo signal by continuously obtaining approximate times at which the peak of a reproduction signal of the servo signal appears is known (see, for example, Patent Document 1). FIG. 6A referred to here is a waveform diagram of a servo signal detected by a conventional servo signal detection device, and FIG. 6B is an approximate time between when the peak of the reproduction signal of the servo signal appears. It is a time chart which shows a mode that the clock count which calculates | requires a difference is performed.

  As shown in FIGS. 6A and 6B, in the conventional servo signal detection apparatus, first, approximate positions of the peak P1 ′ and the peak P2 ′ corresponding to the peak P1 and the peak P2 of the reproduction signal of the servo signal. Is calculated. The positions of the approximate peaks P1 ′ and P2 ′ are obtained by n-th order approximation calculation based on three or more data points sampled in the vicinity of the peaks P1 and P2.

Next, the interval between the peak P1 ′ and the peak P2 ′ is determined in terms of time. The interval between the peak P1 'and the peak P2' is obtained by performing clock counting with a predetermined frequency as shown in FIG. That is, in the example shown in FIG. 6B, the clock unit of C seconds is applied between the peak P1 ′ and the peak P2 ′, so that the interval between the peak P1 ′ and the peak P2 ′ is 6C. Calculated to be seconds.
US Patent Application Publication No. 2006/0007570

  However, in the conventional servo signal detection device, the more the approximate peak P1 ′ and peak P2 ′ are approximated to the actual peak P1 and peak P2, the more data points are sampled. , The time required for the program processing of the nth-order approximation calculation becomes long. That is, there is a problem that it takes time until the positions of the peaks P1 ′ and P2 ′ are specified after the reproduction signal of the servo signal is acquired, and real-time processing cannot be performed.

  Further, in the conventional servo signal detection device, when the interval between the peak P1 ′ and the peak P2 ′ is determined by time by performing clock counting, as shown in FIG. 6B, the vicinity of the peak P1 ′ and / or An error time ET occurs near the peak P2 ′. When applied to the current servo pattern arrangement (interval), a clock count (clock timing) having a frequency that is difficult to achieve in order to eliminate the error time ET is required.

  On the other hand, as described above, in view of the current situation in which high-density recording of magnetic tapes is progressing, a servo signal detection device that can detect servo signals with higher accuracy and in real time is required.

  Accordingly, it is an object of the present invention to provide a servo signal detection device and a servo signal detection method capable of accurately detecting a servo signal in real time even at a relatively low frequency clock timing that can be realized. To do.

  The present invention for solving the above-mentioned problems is a servo signal detection device for detecting a servo signal recorded on a magnetic tape, and this reproduction is performed by A / D converting a reproduction signal of the servo signal at a predetermined sampling frequency. A procedure for sampling a plurality of data points according to the waveform of the signal, a procedure for collecting a plurality of the data points in each of a plurality of signal inverting sections constituting the waveform of the reproduction signal, and a plurality of data points in each of the signal inverting sections A procedure for obtaining a straight line that passes through or approximately passes through the data point, and for each signal inversion unit, obtains each time at which the straight line intersects a reference line at which the output value of the reproduction signal is zero. An arithmetic circuit that executes a procedure and a procedure for calculating a difference between the respective times is provided.

  When focusing on the waveform of the reproduced signal of the servo signal, the present inventors set a reference line where the output value becomes zero from the peak of the reproduced signal, that is, the maximum output value to the minimum output value. When the waveform from the maximum output value to the minimum output value is used as the approximate line, the position where the waveform from the maximum output value to the minimum output value intersects the reference line, and the approximate line described above is the reference line. The present invention has been reached by finding that the position intersecting the line coincides with each other, and that the time interval at the position intersecting with the reference line substantially coincides with the peak interval.

  In this servo signal detection device, the time interval at the position where the straight line obtained by the arithmetic circuit intersects with the reference line described above substantially coincides with the peak interval. That is, by obtaining the time interval, the peak interval is obtained and the servo signal is detected. At this time, the straight line described above is much simpler, unlike the case where the collected data points are processed by an n-th order approximation calculation program in order to obtain the peak approximately as in the conventional servo signal detection device. It is obtained by processing with a primary calculation program. Therefore, unlike the conventional servo signal detection device, the servo signal detection device of the present invention can detect the servo signal in real time without increasing the time required for the program processing.

  Further, in this servo signal detection apparatus, at least two data points need be collected at the signal inversion part of the waveform of the reproduction signal in order to obtain the straight line described above. Therefore, unlike the conventional servo signal detection device, this servo signal detection device can detect a servo signal with high accuracy even at a clock frequency having a relatively low frequency that can be realized.

  In such a servo signal detection device, the plurality of data points through which the straight line passes are the data points sampled by each signal inverting unit, the one having the maximum output value of the reproduction signal, and the reproduction signal It can be configured to have two points with the smallest output value.

  Further, in such a servo signal detection device, the plurality of data points through which the straight line approximately passes are composed of three or more data points sampled by each signal inversion unit, and the three or more straight lines are included. The least square method may be used based on the data points. According to this servo signal detection device, the servo signal can be detected with higher accuracy.

  According to the servo signal detection apparatus as described above, there is provided a servo signal detection method for detecting a servo signal recorded on a magnetic tape, wherein the reproduction signal of the servo signal is A / D converted at a predetermined sampling frequency. A first step of sampling a plurality of data points according to the waveform of the reproduction signal, a second step of collecting a plurality of the data points in each of a plurality of signal inversion units constituting the waveform of the reproduction signal, A third step of obtaining a straight line passing through or approximately passing through the plurality of data points in the signal inverting unit; and for each of the signal inverting units, the straight line has an output value of the reproduction signal of zero. Servo signal detection, comprising: a fourth step for obtaining each time intersecting with the reference line and a fifth step for calculating a difference between the respective times The law can be provided.

  According to the servo signal detection device and the servo signal detection method of the present invention, it is possible to detect a servo signal with high accuracy and in real time even with a relatively low frequency clock timing that can be realized.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a configuration diagram of a servo signal detection device according to an embodiment.

  As shown in FIG. 1, the servo signal detection device 1 includes a delivery reel 4 for feeding the magnetic tape MT, and a take-up reel 5 for taking up the magnetic tape MT from the feed reel 4. The take-up reel 5 is rotated by the reel drive device 6 to take up the magnetic tape MT. The reel drive device 6 takes up the take-up reel 5 based on the reel drive command signal 7a from the control device 2. The reel 5 is rotated. In such a servo signal detection device 1, the magnetic tape MT running between the delivery reel 4 and the take-up reel 5 is in sliding contact with the reproducing head 3. The reproducing head 3 can be constituted by an MR head, for example, and reproduces a servo signal recorded on the magnetic tape MT and outputs an analog reproducing signal to the control device 2.

The control device 2 is a device that controls the operation of each part of the servo signal detection device 1, and includes a CPU (Central Processing Unit), various memories, and the like. As described above, the control device 2 is configured to output the reel drive command signal 7 a to the reel drive device 6. And the control apparatus 2 in this embodiment is further provided with the arithmetic circuit 2a.
The arithmetic circuit 2a is configured to detect a servo signal according to a procedure described later and output a position error signal (PES) based on the detected servo signal.

  Next, the operation of the servo signal detection device 1 according to the present embodiment will be described with reference to the drawings as appropriate, and a servo signal detection method using the servo signal detection device 1 will be described. In the drawings to be referred to, FIG. 2A is a schematic diagram showing a servo signal recorded on a magnetic tape, FIG. 2B is a waveform diagram of a reproduction signal of the servo signal, and FIG. It is a schematic diagram showing a reproduction signal that has been A / D converted at a predetermined sampling frequency, and shows a case where there are two data points for calculating a straight line. FIG. 3 is a process diagram for explaining the procedure executed by the arithmetic circuit.

  First, when the servo signal detection device 1 is activated, the control device 2 outputs a reel drive command signal 7a to the reel drive device 6 as shown in FIG. The tape MT is taken up on the take-up reel 5. That is, the magnetic tape MT travels from the delivery reel 4 to the take-up reel 5 via the reproducing head 3. Then, the reproducing head 3 outputs an analog reproduced signal 7b to the arithmetic circuit 2a by reading a servo signal described below.

  The servo signal in this embodiment is a time base signal, and is recorded in a servo band SB extending in the longitudinal direction of the magnetic tape MT as shown in FIG. The servo signals SS1 and SS2 are provided with a magnetization 8 in one direction along the longitudinal direction in a region crossing the servo band SB at a predetermined angle θ with respect to the longitudinal direction of the magnetic tape MT. Is formed. In the present embodiment, a pair of non-parallel linear servo signals SS1 and SS2 form a square shape. Although not shown, a plurality of such servo signals SS1 and SS2 are formed so as to be aligned in the longitudinal direction of the servo band SB.

  The waveform of the reproduced signal 7b (see FIG. 1) of the servo signals SS1 and SS2 is such that the reproducing head 3 (see FIG. 1) reads the servo signal SS1 as shown in FIGS. 2 (a) and 2 (b). In this case, the waveform output value of the reproduction signal 7b (see FIG. 1) is zero after the positive peak P1 (maximum output value) of the reproduction signal 7b is reached until reaching the negative peak P3 (minimum output value). The reference line SL is exceeded. That is, the polarity of the waveform of the reproduction signal 7b is inverted from positive to negative. The waveform path from the peak P1 to the peak P3 is substantially a straight line.

  Further, when the reproducing head 3 (see FIG. 1) reads out the servo signal SS2, it reaches the negative peak P4 (minimum output value) after showing the positive peak P2 (maximum output value) of the reproduced signal 7b. By the time, the reference line SL where the output value becomes zero is exceeded. That is, the polarity of the waveform of the reproduction signal 7b is inverted from positive to negative. The waveform path from the peak P2 to the peak P4 is also a substantially straight line. In FIG. 2B, a waveform portion that is a substantially straight line is described as a signal inversion unit 10.

  As described above, the time interval tw at the position where each of the signal inversion units 10 that appear for each of the peaks P1 and P2 repeated in the waveform of the reproduction signal 7b intersects the reference line SL substantially matches the peak interval W1.

  Next, as shown in FIG. 3, the arithmetic circuit 2a first performs A / D conversion on the analog reproduction signal output from the reproduction head 3 (see FIG. 1) at a predetermined sampling frequency (step S1). The process of step S1 corresponds to a “first process” in the claims. The sampling frequency at this time can be set to about 50 to 200 MHz. As a result, the arithmetic circuit 2a samples a plurality of data points according to the waveform of the reproduction signal. Specifically, as shown in FIG. 2C, a data point that is the position of the tip of the A / D converted reproduction signal 7c (the position on the opposite side of the reference line SL) is sampled.

  Then, the arithmetic circuit 2a, as shown in FIG. 2C, among the data points sampled by the signal inverting units 10 and 10, the data point X at which the output value of the reproduction signal 7c is maximum, and the reproduction signal 7c. Is collected (step S2 in FIG. 3). The step S2 corresponds to the “second step” in the claims.

  Next, as shown in FIG. 2C, the arithmetic circuit 2a calculates a straight line 11 passing through the data point X and the data point Y (step S3 in FIG. 3). The step S3 corresponds to the “third step” in the claims.

  Then, the arithmetic circuit 2a obtains the times A and B at which the straight lines 11 and 11 intersect the reference line SL (step S4 in FIG. 3), and calculates the difference (B−A) between the times A and B. Calculate (step S5 in FIG. 3). The step S4 corresponds to the “fourth step” in the claims, and the step S5 corresponds to the “fifth step” in the claims.

  The arithmetic circuit 2a outputs a position error signal (PES: see FIG. 1) based on the detected servo signals SS1 and SS2 (see FIG. 2 (a)). The position error signal (PES) is output to a predetermined monitor (not shown) or the like when the servo signal detection device 1 is used as an inspection (verification) device for the servo signals SS1 and SS2. When this servo signal detection device 1 is used for a drive of the magnetic tape MT (see FIG. 2A), the position error signal (PES) follows the data head of the magnetic tape MT. Is output to the actuator to be operated.

  In the servo signal detection method executed by the servo signal detection apparatus 1 as described above, the difference between the time A and the time B (see FIG. 2C) is the time at the position where the signal reversing unit 10 and the reference line SL intersect. It coincides with or is very close to the interval tw. As described above, since the time interval tw substantially coincides with the peak interval W1, in this servo signal detection method, the difference between time A and time B (see FIG. 2C) is obtained. Thus, the servo signals SS1 and SS2 (see FIG. 2A) are detected. At this time, the above-described straight line 11 (see FIG. 2C) is the collected data point in order to approximately obtain the peaks P1 and P2 (see FIG. 6A) as in the conventional servo signal detection device. Is obtained by processing by a much simpler primary calculation program, unlike the case of processing by an n-order approximate calculation program. Therefore, unlike the conventional servo signal detection device, the servo signal detection device 1 (servo signal detection method) can detect the servo signal in real time without increasing the time required for processing by the program.

  Further, in this servo signal detection device 1 (servo signal detection method), data points X and Y (FIG. 2) in the signal inversion unit 10 (see FIG. 2B) of the waveform of the analog reproduction signal 7b (see FIG. 1). (C)) is collected and a straight line 11 (see FIG. 2 (c)) is obtained by the data points X and Y. Therefore, in order to obtain the straight line 11, there are two data points X and Y. It will be good. Therefore, unlike the conventional servo signal detection device, this servo signal detection device 1 (servo signal detection method) has high accuracy even if the clock timing has a relatively low frequency that can be realized (see FIG. 2). (See (a)) can be detected.

As mentioned above, although this embodiment was described, this invention is not limited to the said embodiment, It can implement with a various form.
In the embodiment, the straight line 11 is calculated based on two data points X and Y. However, the present invention may be a servo signal detection device that calculates a straight line based on three or more data points. . Here, a servo signal detection apparatus that collects five data points and detects servo signals SS1 and SS2 (see FIG. 2A) will be described as an example. FIG. 4 referred to here is a schematic diagram showing a reproduction signal subjected to A / D conversion at a predetermined sampling frequency, and shows a case where there are five data points for calculating a straight line.

  As shown in FIG. 4, the arithmetic circuit 2a (refer to FIG. 1) calculates the data point X (maximum output value) and the data point Y (minimum output value) as described above. In addition to the above, the data point X and the data point Y are composed of five points including three data points sampled from the signal inversion unit 10 (see FIG. 2B).

  The straight line 11a is obtained by the least square method based on the five data points, and the difference (B−A) between the times A and B at which the straight lines 11a and 11a intersect the reference line SL. ) Is detected, the servo signals SS1 and SS2 (see FIG. 2A) are detected. According to this servo signal detection device, even when the obtained straight line 11a does not coincide with the signal inversion unit 10 (see FIG. 2B) of the waveform of the reproduction signal, the straight line 11 ( Compared with FIG. 2 (c)), this straight line 11a is more approximate to the waveform signal inverting unit 10, so that the servo signals SS1 and SS2 (see FIG. 2 (a)) are detected more accurately. be able to.

  In the signal inversion unit 10 in the above embodiment, the waveform of the reproduction signal 7b is defined by the portion where the polarity is inverted from positive to negative. For example, the magnetization 8 of the servo signals SS1 and SS2 (FIG. 2). When the direction of (a) is reverse, the present invention is configured such that the signal inverting unit 10 is defined at a portion where the polarity of the waveform of the reproduction signal 7b is inverted from negative to positive. be able to.

Next, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention.
(Example 1, Example 2, and Comparative Example 1)
Here, the servo signal detection device 1 according to the above-described embodiment (hereinafter referred to as the servo signal detection device according to the first embodiment) and the servo signal detection device according to another embodiment described above (hereinafter referred to as the servo signal according to the second embodiment). And a conventional servo signal detection device (hereinafter referred to as the servo signal detection device of Comparative Example 1), and sampling the magnetic tape MT at a speed of 16 m / sec. The relationship between frequency and measurement error was obtained. The result is shown in FIG. FIG. 5 referred to here is a graph showing the relationship between the sampling frequency and the measurement error in each of the servo signal detection devices of Example 1, Example 2, and Comparative Example 1. FIG. Here, the “measurement error” indicates a distance difference between the position of the servo band specified by detecting the servo signals SS1 and SS2 and the actual position of the servo band SB.

  Incidentally, the servo signal detection apparatus according to the second embodiment sets the number of data points for calculating the straight line 11a (see FIG. 4) to five. Further, the servo signal detection apparatus of Comparative Example 1 calculates the approximate interval between the peak P1 ′ and the peak P2 ′ shown in FIG. 6B by assigning a predetermined sampling frequency.

  As shown in FIG. 5, when compared with the servo signal detection device of Comparative Example 1, the servo signal detection device of Example 1 has a measurement error of half or less even at a low sampling frequency. The servo signal detection apparatus according to the second embodiment is almost completely eliminated from the measurement error in almost the entire sampling frequency range, as compared with the servo signal detection apparatus according to the first comparative example.

It is a block diagram of the servo signal detection apparatus which concerns on embodiment. (A) is a schematic diagram showing a servo signal recorded on a magnetic tape, (b) is a waveform diagram of a reproduction signal of the servo signal, and (c) is a reproduction signal that is A / D converted at a predetermined sampling frequency. FIG. 4 is a diagram illustrating a case where there are two data points for calculating a straight line. It is process drawing for demonstrating the procedure which an arithmetic circuit performs. It is a schematic diagram showing a reproduction signal A / D converted at a predetermined sampling frequency, and shows a case where there are five data points for calculating a straight line. It is a graph which shows the relationship between the sampling frequency in each of the servo signal detection apparatus of an Example and a comparative example, and a measurement error. (A) is a waveform diagram of a servo signal detected by a conventional servo signal detection device, and (b) is a clock count for obtaining a difference between approximate times at which peaks of a reproduction signal of the servo signal appear. It is a time chart which shows a mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Servo signal detection apparatus 2a Arithmetic circuit 7b Reproduction signal SS1 Servo signal SS2 Servo signal 10 Signal inversion part 11 Straight line 11a Straight line A Time B Time MT Magnetic tape SL Reference line X Data point Y Data point

Claims (3)

A servo signal detection device for detecting a servo signal recorded on a magnetic tape,
A procedure for sampling a plurality of data points according to the waveform of the reproduction signal by A / D converting the reproduction signal of the servo signal at a predetermined sampling frequency;
A procedure for collecting a plurality of the data points in each of a plurality of signal inversion units constituting a waveform of a reproduction signal;
A procedure for obtaining a straight line that passes through or approximately passes through the plurality of data points in each of the signal inversion units;
For each of the signal inverting units, a procedure for obtaining each time when the straight line intersects a reference line where the output value of the reproduction signal is zero;
A procedure for calculating a difference between the times;
A servo signal detection device comprising an arithmetic circuit for executing   The plurality of data points through which the straight line approximately passes are composed of three or more data points sampled by each signal inversion unit, and the straight line is obtained by the least square method based on the three or more data points. The servo signal detection device according to claim 1, wherein A servo signal detection method for detecting a servo signal recorded on a magnetic tape,
A first step of sampling a plurality of data points according to the waveform of the reproduction signal by A / D converting the reproduction signal of the servo signal at a predetermined sampling frequency;
A second step of collecting a plurality of the data points in each of a plurality of signal inversion units constituting a waveform of a reproduction signal;
A third step of obtaining a straight line that passes through or approximately passes through the plurality of data points in each of the signal inversion units;
For each of the signal inverting units, a fourth step of obtaining each time when the straight line intersects a reference line where the output value of the reproduction signal becomes zero;
A fifth step of calculating a difference between the respective times;
A servo signal detection method comprising:

Images