JP4042989B2 - Servo track inspection device and servo writer - Google Patents

Description

  The present invention relates to an apparatus for inspecting a servo track written to control the running of a magnetic tape recording medium, and more particularly to a servo track inspection apparatus capable of detecting a servo track dropout (DO) with high resolution. .

On the magnetic tape recording medium, servo tracks are written in an area different from the area where data is recorded along the traveling direction of the magnetic tape recording medium.
Since the magnetic head for recording / reproducing data traces the magnetic tape recording medium based on the servo track, the servo track needs to be clearly written so that it can be accurately detected. If there is an unclear portion (dropout) in the writing of the servo track, the detection of the servo track becomes unstable and the reliability of data processing is lowered.
For this reason, the servo track is written at the time of manufacture of the magnetic tape recording medium, and quality control is performed to confirm that there is no dropout by a servo track inspection device (see, for example, Patent Document 1).
JP 2002-367101 A

In recent years, in order to further improve the reliability of data processing in magnetic tape recording media, there has been a demand to improve the inspection resolution so that inspection can be performed to every single level of the stripe of the smallest unit constituting the servo track. It is growing.
However, in the conventional dropout inspection, servo track areas where the writing is unclear (area where the output is less than 70% of the specified value) exist continuously in several tens of stripes (at a distance of several millimeters). It was extremely low resolution and sensitivity that would otherwise be impossible to detect. This is because the resolution of the induction head used as the magnetic head is low, and there is a limit to improving the resolution.

  Further, the servo track servo pattern format type differs depending on the standard of the magnetic tape recording medium, and the manufacturer of the magnetic tape recording medium needs to have a plurality of servo track inspection devices for each standard. was there. For this reason, the amount of money invested in the manufacturing equipment for magnetic tape recording media is increased, and when the production line is switched to a magnetic tape recording medium with a different standard, it takes a lot of labor to change the system and the productivity decreases. There was a problem to do.

  Accordingly, the present invention has been made for the purpose of solving the above-described problems, and it is possible to inspect the servo track dropout with high resolution up to the stripe level as a constituent unit, An object of the present invention is to provide a servo track inspection apparatus capable of inspecting various types of magnetic tape recording media of different format types with one unit.

  The present invention was devised to achieve the above-described object. First, the invention according to claim 1 is a servo track inspection apparatus for inspecting a servo track (ST) written on a magnetic tape recording medium. A tape running section for running the magnetic tape recording medium in a longitudinal direction; a detector for detecting a stripe as a constituent unit of the servo track from the passing magnetic tape recording medium and outputting an analog waveform signal thereof; An A / D converter that digitally samples a waveform signal at a time interval smaller than its waveform period and outputs a discrete signal; a maximum value extractor that extracts a maximum value signal indicating a maximum value from the discrete signal; and the maximum And a collator that compares the value signal with registered maximum value information.

According to such a configuration, it is possible to perform an inspection for confirming the presence or absence of dropout by improving the resolution to the level of the stripe which is the minimum unit constituting the servo track.
Here, the local maximum information is information uniquely corresponding to the format type of the servo track, and is registered in advance in the servo track inspection apparatus. Then, by confirming the maximum value information and the waveform signal detected by the detector, the presence or absence of the servo track dropout is confirmed.
As a result, it is possible to confirm whether or not this frame is composed of a prescribed number of stripes in a frame that is composed of a plurality of stripes and is a repetitive unit in the servo track.

  A second aspect of the present invention is the servo track inspection apparatus according to the first aspect, further comprising a filter that removes a noise frequency component of the waveform signal.

  According to such a configuration, the detection accuracy of the local maximum signal is improved.

  According to a third aspect of the present invention, in the servo track inspection apparatus according to the first or second aspect, an input unit for inputting the format type information of the servo track and an alternative based on the input format type information. And a storage device capable of storing a plurality of pieces of local maximum information that are selected on an automatic basis.

  According to this configuration, it is possible to inspect a plurality of types of magnetic tape recording media having different servo track format types with a single servo track inspection apparatus.

  According to a fourth aspect of the present invention, in the servo track inspection apparatus according to any one of the first to third aspects, the detector is an MR head.

  By using an MR head with high response, the waveform signal can be detected with high accuracy.

  In the servo writer according to claim 5, the servo track inspection device according to any one of claims 1 to 4 and the magnetic tape recording medium traveling upstream of the measuring unit. And a servo pattern writing unit for writing the servo track.

  According to this configuration, it is possible to inspect whether or not there is a dropout of the written servo track continuously while writing the servo track to the magnetic tape recording medium.

The servo track inspection apparatus according to the present invention has the following excellent effects.
In other words, the magnetic tape recording medium that has passed the inspection by the servo track inspection apparatus according to the present invention is guaranteed to have high data processing reliability, and the commercial value is improved.
Furthermore, even when multiple types of magnetic tape recording media with different format types are produced, there is no need to install multiple servo track inspection devices in accordance with this standard, reducing capital investment and improving productivity. Contribute to.

Embodiments of the present invention will be described below with reference to the drawings.
An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a basic configuration of a servo track inspection apparatus based on a timing-based method in this embodiment. FIG. 2A is a diagram showing a data band DB for recording / reproducing data and a servo track ST on which data is written in the magnetic tape recording medium MT. FIGS. 2B and 2C are diagrams illustrating the format type of the servo pattern of the servo track ST in the timing-based method. Figure 3 is a diagram showing details of the input information I _n inputted from the input unit 51. FIG. 4A is a diagram schematically showing a cross section of the stripe S, which is a structural unit, along the longitudinal direction of the servo track ST, and FIG. 4B shows the output of the detector 31 that detects the stripe S. FIG. 4 (c) is a diagram showing a waveform after the waveform signal H is converted into a discrete signal by digital sampling and then the noise component is removed by the filter 41. FIG. 4D is an enlarged view showing one period of the waveform subjected to the noise component removal processing, and FIG. 4E is a table showing the discrete signal J as the intensity signal A _{j with} respect to the time signal t _j . FIG. 4F is a table showing a maximum value signal K indicating the maximum value extracted from the discrete signal J.

(Description of servo track)
First, prior to the description of the servo track inspection apparatus according to the present embodiment, the servo track by the timing-based method will be described with reference to FIG.
As shown in FIG. 2A, in the magnetic tape recording medium MT, data bands DB (DB ₁ , DB ₂ , DB ₃ , DB ₄ ) are formed in large numbers (four in the figure). Further, each of these data bands DB (DB ₁ , DB ₂ , DB ₃ , DB ₄ ) is further subdivided into a plurality of data tracks (not shown).

Servo tracks ST (ST1, ST2, ST3, ST4, ST5) are written at the boundary portions of the regions of the data bands DB (DB1, DB2, DB3, DB4).
When one of these servo tracks ST is enlarged, as shown in FIG. 2B or FIG. 2C, the servo signal forms a servo pattern in which frames N _i and N _k having the same shape are repeated at a predetermined interval. is doing. The frames N _i and N _k are composed of a plurality of inclined stripes S. In the drawing, the frames N _i and N _k are composed of a large number of stripes S (10 in FIG. 2B and 15 in FIG. 2C), but this is just an example. As long as it includes at least a pair of two or more stripes S inclined with respect to each other.

By the way, when data is recorded on the magnetic tape recording medium MT, the magnetic head writes data so as not to overlap in the data band DB based on the detected position information of the servo track ST. When reproducing data on the magnetic tape recording medium MT, the magnetic head accurately traces a specific data track and reads the data based on the detected position information of the servo track ST.
As described above, the servo track ST serves as a reference for driving the magnetic head when data is recorded / reproduced on the magnetic tape recording medium MT, so that the stripe S as its constituent unit is clearly written on the servo track ST. And no dropout is required. At least the magnetic tape recording medium MT in which there is a dropout at the level of the frames _Ni and _Nk , which are the repeating units of the servo track ST, must be excluded by inspection.

(Description of servo track inspection equipment)
As shown in FIG. 1, the servo track inspection apparatus 10 according to the present embodiment includes a tape running unit 20, a measuring unit 30, a processing unit 40, an input unit 51, and a display unit 52. This is an inspection device that detects a stripe S, which is a constituent unit of the servo track ST, from the tape recording medium MT and measures the presence or absence of dropout with high resolution.

The tape running unit 20 includes a delivery reel 21 and a take-up reel 22, and runs the magnetic tape recording medium at a predetermined speed without causing a shake in the width direction.
The delivery reel 21 is wound with a magnetic tape recording medium MT on which a servo track ST (see FIG. 2A) is wound and a magnetic tape recording medium MT on which a servo track ST is not written. The case of being rotated can be considered. In the former case, the servo pattern writing unit 25 described later is unnecessary. On the other hand, in the latter case, the servo track ST is written on the magnetic tape recording medium MT by the servo pattern writing unit 25.

  The take-up reel 22 takes up the magnetic tape recording medium MT that is drawn out from the feed reel 21 and travels. It is assumed that the magnetic tape recording medium MT travels between the two reels 21 and 22 at a predetermined tape travel speed v, and without being shaken in the width direction.

The servo pattern writing unit 25 includes a pattern writer 23 and a write driver 24, and writes a stripe S, which is a constituent unit of the servo track ST, on the magnetic tape recording medium MT at a predetermined time interval. . As described above, the servo track inspection apparatus 10 can consider the case where the servo pattern writing unit 25 is added and the case where the servo pattern writing unit 25 is added. In some cases, the writing function is given priority and called the servo writer 10.
On the contact surface of the pattern writer 23 with the magnetic tape recording medium MT, a magnetic gap G corresponding to the servo pattern of the stripe S is formed like the write heads 23b and 23c shown in FIGS. Has been. A magnetic field leaks from the magnetic gap G, and the magnetization direction of the magnetic layer of the magnetic tape recording medium MT adjacent to the magnetic gap G is changed.

The write driver 24 dynamically changes the direction of the magnetic field generated from the magnetic gap G at the write operation frequency f. Incidentally, the servo pattern shown in FIGS. 2B and 2C is obtained by writing the write driver 24 continuously for five periods at the write operation frequency f ₁ , and then ₁ at the write operation frequency f ₂ (<f ₁ ). The operation of writing data for a period can be obtained continuously. The spacing between adjacent stripes S, S, S... Is determined by the relationship between the writing operation frequency f (f ₁ , f ₂ ) and the tape running speed v of the magnetic tape recording medium MT.

By the way, the tape running unit 20 may take a form in which a driving drive force is applied by bringing a capstan roller (not shown) into contact with the magnetic tape recording medium MT in order to realize running stability of the magnetic tape recording medium MT.
In addition, the tape running unit 20 allows the magnetic tape recording medium MT to run without being shaken in the width direction, but even if such a shake in the width direction occurs, There may be a function of appropriately correcting this blur in subsequent processing by detecting an edge position.

  The measuring unit 30 includes a detector 31, a detector driver 32, an amplifier 33, and an A / D converter 35, and travels on the stripes S, S, S... On the magnetic tape recording medium MT passing therethrough. The signal is sequentially detected in the direction, and the waveform signal H detected for each stripe S is digitally sampled and output to the processing unit 40.

  The detector 31 is arranged so as to contact the traveling magnetic tape recording medium MT, and the passing trajectory n (see FIG. 2b) of the detector 31 is in the stripes S, S, S. It intersects. Then, when the cross section of the passing trajectory n shown in FIG. 2B is shown in FIG. 4A, the detector 31 moves when the magnetic tape recording medium MT travels as shown in FIG. 4B. A change in magnetization at the boundary portion of the intersecting stripes S is detected, and a waveform signal H having a signal intensity proportional to the change amount is output as an analog signal.

Specific examples of the detector 31 include an MR (magneto resistive) head known for its high responsiveness (small time constant). The detector 31 further has high responsiveness and a signal intensity proportional to the amount of change in magnetization. The present invention is not limited to this as long as it exhibits a function of outputting an analog signal. The MR head utilizes the property that the electrical resistance varies when the external magnetic field varies.
Here, the fact that the peak top of the waveform signal H shown in FIG. 4B is detected later than the boundary of the actual stripe S is largely related to the time constant of the detector 31. That is, as the time constant increases, the peak top is detected later and the intensity is also detected smaller, and the waveform signal H becomes a waveform having a broad peak shape and a poor S / N ratio. On the other hand, if the detector 31 having a smaller time constant can be used, a sharper and stronger peak can be obtained than the waveform signal H shown in FIG. 4B, which contributes to improvement of peak detection accuracy. .
As described above, the time constant of the detector 31 is an important factor in determining whether the peak position / intensity is good or bad in performing the dropout inspection of the magnetic tape recording medium MT, and is shown in FIG. as such, the input fields as a device characteristic information U _n (included in the input information I _n which will be described later).

The detector driver 32 supplies power so that the detector 31 operates as described above.
The amplifier 33 amplifies the waveform signal H that is a weak analog signal output from the detector 31.

  The A / D converter 35 outputs a discrete signal J obtained by digitally sampling the waveform signal H (see FIG. 4B) analog-output from the detector 31 at a time interval Δt smaller than the waveform cycle ( In FIG. 4E, the noise component is further removed by the filter 41 after digital sampling.

  The processing unit 40 includes a filter 41, a maximum value extractor 42, a collator 43, a storage device 44, and a peripheral device connection terminal 45. Based on the discrete signal J input from the measurement unit 30, the processing unit 40 is servo-controlled. It is determined whether or not there is a dropout of the stripe S, which is a structural unit of the track ST.

Specifically, the input unit 51 is a keyboard, a mouse, an input tablet or the like operated by an operator (not shown). From the input unit 51, the input information I _n, as shown in FIG. 3 is input. This input information I _n is further classified into format type information Q _n , device control information R _n , device characteristic information U _n , and determination information T _n .

The format type information Q _n is the servo track pattern type, the prescribed dimensions of the frames N _i and N _k , the prescribed azimuth angle, etc. as distinguished from each other as shown in FIGS.
The device control information R _n is the tape running speed v, the writing operation frequency f, the control correction constant, and the like shown in FIG.
The device characteristic information U _n, the time constant of the magnetic head of the detector 31, is information about filtering characteristics of the gain characteristic and signal processing circuit.
These format type information Q _n, based on the input of the device control information R _n and device characteristic information U _n, from among a plurality of maximum value information F _n stored in the storage unit 44, the servo to be dropout inspection The local maximum information F _n corresponding to the pattern of the track ST is alternatively selected. However, for one of these devices the control information R _n and device characteristic information U _n, sometimes removed from consideration because variables are fine as compared to the format type information Q _n.

The local maximum information F _n is information uniquely corresponding to various format types as illustrated in FIG. 2B or 2C of the servo track ST illustrated in FIG. Specifically, information such as the peak top position and intensity of the waveform signal H (see FIG. 4B) when a specific servo track ST is detected by the detector 31 (see FIG. 1) is included. This is registered in advance in the storage device 44 of the servo track inspection apparatus 10. Then, by collating this maximum value information F _n with the waveform signal H detected by the detector 31, it is possible to confirm the presence or absence of the servo track ST dropout.
Furthermore, the maximum value information F _n is, different format type of the servo track ST, as illustrated in FIG. 2 (b) (c), separate maxima information F _n corresponding to the respective inspection dropout It will be applied to.
By this dropout inspection, it is possible to confirm whether or not the frames N _i and N _k are composed of a prescribed number of stripes S in the frames N _i and N _k which are the repeating units of the servo track ST. .

The determination information T _n is used by the collator 43 described later, and the printing of the stripe S on the magnetic tape recording medium MT is clear / unclear (specifically, whether or not the intensity signal A _j is within the detection allowable range). OK / NG threshold value used as a reference for judging, a judgment length indicating a unit length of the magnetic tape recording medium MT handled as a non-defective product or a defective product by this judgment, and magnetic tape recording continuously judged by a single inspection This is the processing tape length indicating the length of the medium MT.

The display unit 52 can select the input of the format type information Q _n , the device control information R _n , the device characteristic information _Un and the determination information T _n so that the operation by the input unit 51 can be visually performed. It is a thing. In addition, the judgment result of defective / non-defective product of the magnetic tape recording medium MT is displayed together with the position information.

  The filter 41 removes a low-frequency or high-frequency noise component included in the waveform signal H. Specifically, the discrete signal J input from the measurement unit 30 is Fourier-expanded to remove low frequency components and high frequency components. Here, as shown in FIG. 4B, the waveform signal H output from the detector 31 includes high-frequency noise (jagged portion) and low-frequency noise (swelled portion). When the waveform signal H including such noise passes through the filter 41, an accurate waveform is obtained as shown in FIG.

  The maximum value extractor 42 extracts a maximum value signal K indicating a maximum value from the discrete signal J digitally sampled as shown in FIG.

The collator 43 collates the local maximum signal K extracted by the local maximum value extractor 42 with the local maximum value information F _n selected from the storage unit 44, and first determines the time in the local maximum signal K. It is determined whether the signal t _j is missing or whether the intensity signal A _j has a predetermined intensity determined by the threshold value determined by the determination information T _n. If the condition is not satisfied, it is determined as dropout.

The storage device 44 stores and registers a plurality of maximum value information F _n corresponding to the servo pattern of the servo track ST. Then, the corresponding maximum value information F _n is selectively selected from among the plurality of maximum value information F _n registered in the storage device 44 based on the format type information Q _n input by the input unit 51. It will be.

The peripheral device connection terminal 45 is a terminal for connecting the servo track inspection device 10 to a peripheral device such as a CD drive, an FD drive, or a Web server on the Internet, and stores local maximum information F _n present in these terminals. It is to be loaded into the device 44.

Next, the operation of the servo track inspection apparatus 10 according to the present embodiment will be described with reference to FIGS. FIG. 5 is a flowchart for explaining the operation of the servo track inspection apparatus according to the present invention.
First, the input information I _n is input from the input unit 51 by the operator (S11). Format type information Q _n of the inputted input information I _n, by the device control information R _n and device characteristic information U _n, the maximum value information F _n is selected from among the storage unit 44 (S12).
Next, the tape running unit 20 starts running the magnetic tape recording medium MT (S13), and the detector 31 detects the stripe S of the servo track ST written on the magnetic tape recording medium MT, and the waveform signal H is obtained. Analog output is performed (S14).

  Next, the analog output waveform signal H is amplified by the amplifier 33 and then digitally sampled by the A / D converter 35 at a time interval Δt smaller than the waveform cycle (S15). Then, the discrete signal J digitally sampled at the time interval Δt is applied to the filter 41, and high frequency and low frequency noise components are removed (S16).

  Next, the maximum value extractor 42 extracts a maximum value signal K indicating the maximum value from the discrete signal J of the waveform signal H (S17).

Next, the collator 43 collates the local maximum value information F _n selected in the storage unit 44 with the local maximum signal K to check whether the time signal t _j is missing or the intensity signal A _j (see FIG. 4). Is detected based on whether or not is within a predetermined range of the threshold value determined by the determination information T _n (see FIG. 3) (S18). Such collation / error detection operation is repeated until the predetermined determination length of the magnetic tape recording medium MT is exceeded (S19). Then, whether the magnetic tape recording medium MT is good or bad is determined based on the predetermined determination length, and if an error is detected, an error is notified (S20, S21). Such a determination is repeated until the magnetic tape recording medium MT reaches a predetermined processing tape length (S22).

As described above, by configuring the servo track inspection device 10, the dropout inspection of the magnetic tape recording medium MT can be performed with a high resolution of the stripe S level, which is a constituent unit of the servo track ST.
An operator (not shown) simply inputs the input information I _n from the input unit 51, and downloads the desired maximum value information F _n from the outside as necessary, so that one servo track inspection apparatus 10 can be used. Inspection of the servo track ST corresponding to a plurality of format types can be performed. This eliminates the need to replace the servo track inspection apparatus 10 depending on the format type of the servo track ST in this inspection. Further, by providing the servo pattern writing unit 25 on the upstream side of the magnetic tape recording medium MT traveling in the servo track inspection apparatus 10 as described above, a servo writer that can perform dropout inspection immediately after writing the servo pattern. Is configured.

It is a block diagram which shows the basic composition of the servo track inspection apparatus in embodiment of this invention. (A) is a figure which shows the recording surface of the magnetic tape recording medium used for 1st Embodiment, (b) (c) is a figure which illustrates the format type of the servo pattern of the servo track in a timing-based system. is there. It is a figure which shows the detail of the input information input from the input part of the servo track inspection apparatus of this invention. (A) is a figure which shows typically the difference in the magnetization direction of the cross section of the stripe which is the structural unit along the longitudinal direction of servo track ST, (b) is the waveform which the detector which detected the stripe outputs It is a figure which shows a signal, (c) is a figure which shows the waveform after converting a waveform signal into a discrete signal by digital sampling, and performing the removal process of a noise component, (d) is a figure which performs the removal process of a noise component FIG. 5E is an enlarged view showing one period of the waveform, and FIG. 5E is a table showing the intensity signal A _{j with} respect to the time signal t _j in the discrete signal, and FIG. It is a table which extracts and shows the local maximum signal K which shows. It is a flowchart explaining operation | movement of the servo track inspection apparatus which concerns on this invention.

Explanation of symbols

10 Servo track inspection device (servo writer)
20 the tape running section 25 a servo pattern writing unit 30 measuring unit 31 detector 40 processing unit 42 the maximum value extractor 43 collator 44 storage unit 51 input unit F _n maximal value information I _n input information MT magnetic tape recording medium N _i frame Q _n format type information R _n device control information S stripe ST servo track T _n determination information _Un device characteristic information f writing operation frequency

Claims (5)

In a servo track inspection device for inspecting a servo track written on a magnetic tape recording medium,
A tape running section for running the magnetic tape recording medium in the longitudinal direction;
A detector that detects a stripe, which is a constituent unit of the servo track, from the magnetic tape recording medium that passes through and outputs an analog waveform signal thereof;
An A / D converter that digitally samples the waveform signal at a time interval finer than its waveform period and outputs a discrete signal;
A maximum value extractor for extracting a maximum value signal indicating a maximum value among the discrete signals;
A servo track inspection apparatus comprising: a collator that compares the local maximum signal with registered local maximum information.   The servo track inspection apparatus according to claim 1, further comprising a filter that removes a noise frequency component of the waveform signal. An input unit for inputting the format type information of the servo track;
The storage device capable of storing a plurality of pieces of local maximum information that are alternatively selected based on the input format type information. Servo track inspection device.   4. The servo track inspection apparatus according to claim 1, wherein the detector is an MR head. The servo track inspection device according to any one of claims 1 to 4,
A servo writer, comprising: a servo pattern writing unit for writing the servo track to the traveling magnetic tape recording medium upstream from the detector.

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