JP4448496B2 - Servo writer - Google Patents

Description

  The present invention relates to a servo writer that writes a servo signal for tracking control of a magnetic head onto a magnetic tape.

In recent years, high-density recording of magnetic tapes has progressed, and there are some which have a storage capacity of about 100 gigabytes for computer backup. Therefore, several hundred data tracks are formed on the magnetic tape in the width direction. Therefore, the width of the data track is very narrow. Therefore, it is difficult for a magnetic head for recording / reproducing data to trace a data track. Therefore, a servo track is provided between the data tracks, and a servo signal is written to the servo track in advance. When the data is recorded / reproduced, the servo head reads the servo signal, and the magnetic head stores the data on the desired data track. The position of the magnetic head in the width direction in the magnetic tape is servo-controlled so that recording and reproduction can be performed (see, for example, Patent Documents 1 to 6).
JP 08-30942 A (paragraphs 0021 to 0024) US Pat. No. 6,970,312 US Patent Application Publication No. 2005/0099718 US Patent Application Republished No. 2005/0105967 US Patent Application Publication No. 2005/0168869 US Patent Application Publication No. 2005/0219734

  The servo signal is servoed by a first servo pattern that is inclined not parallel to the width direction of the magnetic tape, and a second servo pattern that is inclined not parallel to the width direction of the magnetic tape and the first servo pattern. Stored in the track. Since the magnetic tape runs in a running direction perpendicular to the width direction, the interval between the first servo pattern and the second servo pattern in the running direction differs depending on the position on the servo track in the width direction. When a servo track is run on a magnetic head for reading servo signals that is narrower than the width of the servo track, the first servo pattern depends on which position in the width direction of the servo track the magnetic head for reading servo signals travels. And the time interval of reading between the second servo pattern and the second servo pattern changes. Based on this time interval variation, the relative position of the servo signal reading magnetic head in the width direction of the servo track can be grasped, and the servo signal reading magnetic head can be moved to a desired position. it can. If the magnetic head for servo signal reading is connected to the magnetic head that runs on the data track and records and reproduces the data, the data can be recorded and reproduced at a predetermined position in the width direction of the magnetic tape in the servo track. Can do.

  In the servo control of the position as described above, the fluctuation of the reading time interval between the first servo pattern and the second servo pattern is regarded as the fluctuation of the position in the width direction. The first servo pattern and the second servo pattern need to be repeatedly arranged at a constant distance. Further, even in a servo signal composed of a set of the first servo pattern and the second servo pattern, it is necessary to repeatedly arrange the servo signals at a constant distance.

  For this reason, conventionally, in a servo writer that writes a servo signal to a magnetic tape, the magnetic tape is run at a constant speed on the magnetic head for writing the servo signal, and the magnetic head for writing the servo signal at a constant time interval. The servo signal was recorded on the magnetic tape. However, the demand for these constant speeds and constant time intervals has increased the cost of the servo writer.

  Accordingly, it is an object of the present invention to provide a servo writer that can record servo signals on a magnetic tape at constant distance intervals without running the magnetic tape at a constant speed.

In order to solve the above-described problems, a servo writer according to the present invention has a traveling unit having a rotating body that rotates in response to the traveling of the magnetic tape, and a uniform rotation on the circumference around the rotation axis that rotates with the rotating body. A disk in which a plurality of pits are arranged at a pitch, a detection unit for detecting a waveform signal indicating a change accompanying the passage of each pit due to the rotation of the disk, and a servo signal recorded on the magnetic tape based on the write signal And a recording unit that outputs a write signal each time the number of changes in the waveform signal is counted a certain number of times . According to this feature, the travel distance of the magnetic tape can be converted into the travel distance of the pits on the disk via the rotating body, and the travel distance of the pits is a waveform indicating the change accompanying the passage of the pits due to the rotation of the disk. You can see from the signal. Even if the traveling speed of the magnetic tape is not constant, the traveling distance of the magnetic tape can be grasped from the waveform signal. If the traveling distance of the magnetic tape can be grasped, servo signals can be recorded on the magnetic tape at regular distance intervals.

  It is preferable that the disk has a reflective layer having irregularities that become pits. Light can be used to detect the waveform signal, and the detection unit can obtain the waveform signal from the disk without contact. The rotation axis of the disk is preferably the same as the rotation axis of the rotating body. According to this, the rotation of the rotating body can be reliably transmitted to the rotation of the disk. The detection unit preferably includes a laser irradiation unit that irradiates a disk with laser light and a light receiving unit that receives reflected light reflected by the disk. The detection unit can obtain a waveform signal from the disk without contact. Even if the rotation of the disk is decentered, the detection unit preferably has a first displacement unit that displaces the detection unit so that the waveform signal can be detected. Since the rotation of the disk may be decentered, the servo writer can be configured even if the mechanical accuracy of the disk is not high. It is preferable that the detection unit has a second displacement unit that displaces the detection unit so that the distance from the disk is kept constant even when the disk rotates. According to this, since the disk may not be flat but distorted, the servo writer can be configured even if the mechanical accuracy of the disk is not high.

  The size of the pit rotation direction is preferably 400 nm or less, and the wavelength of the laser light is preferably 650 nm or less. By reducing the size of the pit in the direction of rotation, the resolution of measuring the travel distance of the magnetic tape can be increased. On the other hand, in order to identify the presence or absence of a reduced pit, it is necessary to shorten the wavelength of the laser light in accordance with the size of the pit rotation direction. DVD (digital versatile disc) has a pit rotation size of 400 nm and a laser beam wavelength of 650 nm. DVD is a general-purpose device and is inexpensive and easily available. Therefore, the servo writer can easily capture the size of the 400 nm pit rotation direction of the DVD and the wavelength of the laser beam of 650 nm, and can provide an inexpensive servo writer. Of course, in order to increase the resolution of the measurement of the travel distance of the magnetic tape, it is possible to reduce the size of the 400 nm pit in the rotation direction and shorten the wavelength of the laser beam of 650 nm. .

  According to the present invention, it is possible to provide a servo writer capable of recording servo signals on a magnetic tape at regular distance intervals without running the magnetic tape at a constant speed.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the servo writer 1 has, as a running part, a winding reel 2 on which a magnetic tape 19 is wound and the magnetic tape 19 is fed, a feeding motor 3 that rotates the feeding reel 2, and a magnetic tape 19. Take-up reel 6, take-up motor 5 for rotating take-up reel 6, guide 7 for guiding magnetic tape 19 to servo signal writing head 8, and running of magnetic tape 19 so that magnetic tape 19 does not slip. Corresponding to the rotating body 13 rotating with the traveling of the magnetic tape 19, the rotating shaft 15 of the rotating body 13, the spindle motor 14 for rotating the rotating body 13, and the magnetic tape 19 in pressure contact with the rotating body 13. Prevents sliding on the rotating body 13, a rotating shaft 18 of the anti-slip roller 17, and a feed motor. , And a travel control unit 4 for driving to rotate the take-up reel 6 and the spindle motor 14 so as not loosened magnetic tape 19.

  The wound magnetic tape 19 called pancake is set on the delivery reel 2, and one end of the magnetic tape 19 passes through the guide 7 and the writing head 8 and passes between the rotating body 13 and the slip prevention roller 17. To the take-up reel 6. As the spindle motor 14 rotates and the rotating body 13 connected to the spindle motor 14 by the rotating shaft 15 rotates, the magnetic tape 19 pressed against the rotating body 13 does not slide on the rotating body 13, and the delivery reel Travel from the 2 side to the take-up reel 6 side.

  The delivery reel 2 rotates so that the magnetic tape 19 between the delivery reel 2 and the rotator 13 is not loosened or pulled to be cut or extended, and the magnetic tape 19 is delivered. If the magnetic tape 19 does not slack, it is not always necessary to use the delivery motor 3 to rotate the delivery reel 2.

  The take-up reel 6 is rotated by the take-up motor 5 so that the magnetic tape 19 between the take-up reel 6 and the rotating body 13 is not loosened, pulled, cut or extended. Wind up.

  The servo writer 1 also has a pulse generation circuit 9 that outputs a pulse d3 in response to a write signal d2 and a write head 8 that writes a servo signal to the magnetic tape 19 in response to a pulse d3 as a recording unit. . The recording unit records a servo signal on the magnetic tape 19 based on the write signal d2.

  Further, the servo writer 1 rotates with the rotating body 13 and the disk 12 in which a plurality of pits 16 are arranged at a uniform pitch P on a circumference 30 around the rotation shaft 15, and the pits 16 formed by the rotation of the disk 12. A detection unit 11 that detects a waveform signal d1 indicating continuous movement, and a write signal output unit 10 that outputs a write signal d2 so that the interval at which the servo signal is recorded on the magnetic tape 19 based on the waveform signal d1 is constant. Have. The rotating shaft of the disk 12 is common to the rotating shaft 15 of the rotating body 13, and the rotation of the rotating body 13 can be reliably transmitted to the rotation of the disk 12.

  According to the servo writer 1, the travel distance of the magnetic tape 19 can be converted into the travel distance of the pits 16 on the disk 12 via the rotating body 13, and the travel distance of the pits 16 is a series of pits 16 due to the rotation of the disk 12. It can be seen from the waveform signal d1 indicating the movement. Even if the traveling speed of the magnetic tape 19 is not constant, the traveling distance of the magnetic tape 19 can be determined from the waveform signal d1. If the traveling distance of the magnetic tape 19 can be grasped, servo signals can be recorded on the magnetic tape 19 at regular intervals.

  As shown in FIG. 2, the disk 12 is provided with a substrate 44, a reflection layer 45 provided on the substrate 44 that has projections and depressions that serve as pits 16 and reflects light, and is provided on the reflection layer 45 and transmits light. A transparent substrate 46 to be provided. According to this, light can be used for the detection of the waveform signal d1, and the detection unit 11 can obtain the waveform signal d1 from the disk 12 without contact.

  The detection unit 11 includes a laser irradiation unit 21 that irradiates the disk 12 with laser light L1 used for detection of the waveform signal d1, and a light reception unit 22 that receives the reflected light L2 reflected by the disk 12 and outputs the waveform signal d1. Have. As a result, the detection unit 11 can obtain the waveform signal d1 from the disk 12 without contact. The detection unit 11 is arranged so as to sandwich the disk 12 with respect to the write head 8, but is not limited to this arrangement, and the detection unit 11 and the write head 8 are arranged on the same side with respect to the disk 12. May be. In this arrangement on the same side, the pits 16 are arranged on the detection unit 11 side.

  The laser irradiation unit 21 includes a laser 26 that emits the laser light L1, a collimator lens 27 that converts the laser light L1 into a parallel light beam that travels straight without spreading, and a grating 28 that separates and selects the zero-order diffracted light from the laser light L1. And a half mirror 29 that reflects the laser beam L1 in the direction of the disk 12, and further has an objective lens 34 that condenses the laser beam L1 and irradiates the pit 16 in combination with the light receiving unit 22. Yes.

  The light receiving unit 22 includes an objective lens 34 that converts the reflected light L2 reflected by the reflection layer 45 from the laser light L1 irradiated to the pits 16 into parallel light that travels straight without spreading, and the reflected light L2 toward the light receiving element 31. A beam splitter 33 that divides the reflected light L2 that travels forward and the reflected light L3 that travels in the direction of the astigmatism generation element 36, a condenser lens 32 that condenses the reflected light L2 and irradiates the light receiving element 31, And a light receiving element 31 that outputs a waveform signal d1 based on an electric signal such as a current or a voltage having a correlation with the light intensity of the reflected light L2 based on the temporal change of the light intensity of the reflected light L2.

  Furthermore, the detection unit 11 includes a first displacement unit 23 that displaces the detection unit 11 so that the waveform signal d1 can be detected even if the rotation of the disk 12 is eccentric. Since the rotation of the disk 12 may be eccentric, the servo writer 1 can be configured even if the disk 12 does not have high mechanical accuracy. The first displacement part 23 is an astigmatism generating element 36 such as a cylindrical lens that gives astigmatism to the zeroth-order reflected light of the reflected light L3, and a light receiving element disposed in the non-focusing region of the astigmatism generating element 36. An element 37, a tracking error signal generator 38 that generates a tracking error signal d4 by a known push-pull method, and a detector for the disk 12 in the radial direction of the disk 12 so that no tracking error occurs based on the tracking error signal d4 11 and an actuator 39 for moving the relative position of the actuator 11. As shown in FIGS. 1 and 2, since the pits 16 of the disk 12 are formed in the track 20, and the track 20 is formed on the circumference 30, the laser beam is always emitted even if the disk 12 rotates eccentrically. The first displacement unit 23 moves the detection unit 11 in the radial direction of the disk 12 so that L1 is irradiated on the track 20 and further on the pit 16, so that the detection unit 11 is relative to the disk 12. Displace the position.

  The detection unit 11 includes a second displacement unit 24 that displaces the detection unit 11 so that the distance from the disk 12 is kept constant even when the disk 12 rotates. Since the disk 12 may not be flat but may be distorted, the servo writer 1 can be configured even if the machine accuracy of the disk 12 is not high. The second displacement unit 24 includes an astigmatism generation element 36 and a light receiving element 37 that are also used as the first displacement unit 23, a focus error signal generation unit 40 that generates a focus error signal d5 by a known astigmatism method, and a focus An actuator 41 that displaces the relative position of the detection unit 11 with respect to the disk 12 in the normal direction of the disk 12 so as not to cause a focus error based on the error signal d5.

  As shown in FIG. 3, the light receiving element 37 has light receiving surfaces C1, C2, C3, and C4 divided into four. The light receiving surfaces C1, C2, C3, and C4 are irradiated with 0th order reflected light given astigmatism of the reflected light L3, and a 0th order diffracted light spot 59 is projected. An image 60 of the track 20 is displayed in the 0th-order diffracted light spot 59. Based on the light intensity of the reflected light L3 applied to the respective light receiving surfaces C1, C2, C3, and C4 according to the brightness and darkness of the image 60 of the track 20, the light receiving element 37 is applied to the respective light receiving surfaces C1, C2, C3, and C4. Electric signals such as current and voltage having a correlation with the light intensity of the reflected light L3 irradiated are output. Hereinafter, electrical signals corresponding to the light receiving surfaces C1, C2, C3, and C4 are also expressed as C1, C2, C3, and C4.

  The focus error signal generation unit 40 includes an adder 51 that calculates the sum (C2 + C3) of the electric signals of the light receiving surfaces C2 and C3 based on a known astigmatism method using distortion of the shape of the 0th-order diffracted light spot 59; An adder 52 for calculating the sum (C1 + C4) of the electrical signals of the light receiving surfaces C1 and C4, and a difference {(C2 + C3) − (C1 + C4)} obtained by subtracting the sum (C1 + C4) from the sum (C2 + C3) to obtain a focus error signal It has a differential amplifier 56 that outputs as d5.

  The tracking error signal generator 38 calculates the sum (C1 + C3) of the electrical signals of the light receiving surfaces C1 and C3 based on the known push-pull method, and the sum of the electrical signals of the light receiving surfaces C2 and C4 (C2 + C4). ) And a differential amplifier 55 that calculates a difference {(C1 + C3) − (C2 + C4)} obtained by subtracting the sum (C2 + C4) from the sum (C1 + C3) and outputs the difference as a tracking error signal d4.

  As shown in FIGS. 1 and 2, when the rotating body 13 and the disk 12 rotate at the same rotational speed with the rotating shaft 15 of the rotating body 13 and the rotating shaft of the disk 12 in common, the traveling body travels by the rotation of the rotating body 13. The distance traveled by the magnetic tape 19 is r2 / r1 times the moving distance of the pit 16. Here, r1 is the rotation radius of the rotating body 13, and r2 is the radius of the circumference 30 where the pits 16 of the disk 12 are arranged. Here, for easy understanding, the rotation radius r1 of the rotating body 13 is set to 25 mm, and the radius r2 of the circumference where the pits 16 of the disk 12 are arranged is set to 50 mm. The ratio of r2 / r1 is doubled. The size of the pit 16 in the rotation direction is set to 400 nm, which is the same as that of the DVD, and the repetition pitch P of the pit 16 is set to 1000 nm, that is, 1 μm. If servo signals are recorded on the magnetic tape 19 at intervals of 5 μm, it is necessary to detect that the magnetic tape 19 has traveled by 5 μm. This detection can be performed as follows. When the magnetic tape 19 travels by 5 μm, the pit 16 moves 10 μm, which is twice (r2 / r1) 5 μm. Since the pitch P of the pits 16 is 1 μm while the pits 16 move 10 μm, ten pits 16 pass under the detection unit 11 in a row. That is, by counting 10 pits 16 through which the detection unit 11 passes, it can be detected that the magnetic tape has traveled by 5 μm.

  As shown in FIG. 4A, the detection unit 11 first writes the first servo signal at time t1. Thereafter, by detecting 10 pits 16 through which the detection unit 11 passes, it can be seen that the magnetic tape has traveled by 5 μm, and the second servo signal can be written at time t2. Similarly, by counting a total of 20 pits 16 through which the detection unit 11 passes, it can be seen that the magnetic tape has further traveled by 5 μm, and the third servo signal can be written at time t3. Furthermore, by counting a total of 30 pits 16 through which the detection unit 11 passes, it can be seen that the magnetic tape has further traveled by 5 μm, and the fourth servo signal can be written at time t4. Here, it should be noted that the time from the time t1 when the first servo signal is written to the time t2 when the second servo signal is written is three times from the time t2 when the second servo signal is written. This is that the time until the time t3 at which the servo signal is written is not equal to the time from the time t3 at which the third servo signal is written to the time t4 at which the fourth servo signal is written. 4A is considered to represent the traveling speed of the magnetic tape 19, the traveling speed of the magnetic tape 19 during the period from time t1 to time t2 is from time t2 to time t4. Despite being slower than the traveling speed of the magnetic tape 19 over time, the servo signals can be written at intervals of 5 μm at time t2, time t3, and time t4.

  As shown in FIG. 4B, the waveform signal d1 is scattered when the laser beam L1 is applied to the pits 16 to reduce the intensity, and is applied to the track 20 without the pits 16. Does not scatter and increases in intensity. Therefore, if there is a change in which the waveform signal d1 changes from a large value to a small value and becomes a large value again, it can be seen that one pit 16 has passed under the detector 11. If such a change is detected ten times, it can be seen that ten pits 16 have passed and the traveling distance of the magnetic tape 19 has reached 5 μm.

  When the traveling speed of the magnetic tape 19 is slow as in the time from the time t1 to the time t2, it takes time to change the waveform signal d1 from a large value to a small value and to a large value again. It will take time to change the batch. On the other hand, when the traveling speed of the magnetic tape 19 is fast as in the time from time t2 to time t4, it takes time to change the waveform signal d1 from a large value to a small value and to a large value again. In addition, 10 changes will not take much time.

  In order to determine that the change in which the waveform signal d1 changes from a large value to a small value and becomes a large value again has reached 10 times, the write signal output unit 10 in FIG. Have As shown in FIG. 4 (c), the counter counts the number of changes up to 10, then resets and counts up to 10 again. The tenth change is counted and the reset timing corresponds to times t2, t3, and t4. The count start time of the counter corresponds to t1.

  As shown in (d) of FIG. 4, the write signal d2 is output from the write signal output unit 10 of FIG. 1 at times t1, t2, t3, and t4.

  As shown in FIG. 4 (e), the pulse d3 corresponds to the pulse shown in FIG. 1 at each of the times t1, t2, t3, and t4 based on the write signal d2 input at each of the times t1, t2, t3, and t4. Output from the generation circuit 9. The pulse d3 is composed of a predetermined number of pulses. In FIG. 4E, the pulse d3 is composed of two pulses. In order to make the interval between the two pulses on the magnetic tape 19 constant, for example, the second pulse is generated when the count value of the counter in FIG.

  As shown in FIGS. 2 and 5, the write head 8 includes a first gap pattern 47 a that is not parallel to the width direction of the magnetic tape 19 but has an inclination, and a width direction of the magnetic tape 19 and a first gap pattern. A head gap 47 having a second gap pattern 47b that is not parallel to 47a but has an inclination is provided for each servo track 57. A data track 58 is formed between the servo tracks 57. The head gap 47 has a “C” shape. When the pulse d3 is input to the write head 8, a servo signal 48 is recorded on the magnetic tape 19 in contact with the head gap 47.

  The servo signal 48 has two first gap patterns 47a transferred, and the first servo pattern 48a and the second gap pattern 47b, which are not parallel to the width direction of the magnetic tape 19 to which the two first gap patterns 47a have been transferred, are inclined. The width direction of the magnetic tape 19 and the first servo pattern 48a are stored in the servo track 57 by the second servo pattern 48b which is not parallel but has an inclination. The servo signal 48 has a double-line “C” shape. The reason for the double line is that the pulse d3 is composed of two pulses. Since the reading time interval of the double line is constant no matter where the servo signal reading magnetic head travels in the width direction of the servo track, the double line reading time interval for data recording / reproduction is double. The line reading time interval can be the reference time of the reading time interval between the first servo pattern 48a and the second servo pattern 48b.

  As shown in FIGS. 5 and 4A, the servo signal 48 recorded at time t1 and the servo signal 48 recorded at time t2 can be formed at a pitch of 5 μm. Similarly, the servo signal 48 recorded at time t2 and the servo signal 48 recorded at time t3 can be formed at a pitch of 5 μm, and the servo signal 48 recorded at time t3 and at time t4. The recorded servo signal 48 can also be formed at a pitch of 5 μm.

  As described above, the servo writer 1 can record the servo signals 48 on the magnetic tape 19 at constant distance intervals without running the magnetic tape 19 at a constant speed. According to the servo writer 1, it is sufficient that the magnetic tape 19 is traveling and is not affected by the speed thereof. Therefore, the servo signal 48 can be generated even in a traveling portion where the traveling speed of the magnetic tape 19 varies such as acceleration or deceleration. It is possible to write at equal intervals at predetermined intervals. On the contrary, since a traveling part with a large speed deviation can be used, the apparatus cost of the servo writer 1 can be reduced. Further, since the servo signal 48 can be written during acceleration and deceleration, the range in which the servo signal 48 can be written can be widened at both ends of the magnetic tape 19, and the yield of the magnetic tape 19 can be improved.

It is a top view of the servo writer according to the embodiment. It is a side view of the servo writer concerning an embodiment. It is a block diagram of a tracking error signal generation unit and a focus error signal generation unit of the detection unit of the servo writer according to the embodiment. (A) is a graph showing the relationship between the number of pits and the number of servo signals with respect to time, (b) is a graph showing the time change of the waveform signal, (c) is a graph showing the time change of the count value, (D) is a graph showing the generation time of the write signal, and (e) is a graph showing the generation time of the servo signal. It is a figure which shows the positional relationship of the magnetic tape in which the servo signal was written, and a write head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Servo writer 2 Sending reel 6 Take-up reel 8 Write head 9 Pulse generation circuit 10 Write signal output part 11 Detection part 12 Disk 13 Rotating body 14 Spindle motor 15 Rotating shaft 16 Pit 17 Slip prevention roller 19 Magnetic tape 20 Track 21 Laser irradiation Unit 22 light receiving unit 23 first displacement unit 24 second displacement unit 47 head gap 48 servo signal 57 servo track 58 data track

Claims (7)

A traveling unit having a rotating body that rotates in response to the traveling of the magnetic tape;
A disk that rotates with the rotating body and has a plurality of pits arranged at a uniform pitch on the circumference around the rotation axis;
A detection unit for detecting a waveform signal indicating a change accompanying the passage of each pit by rotation of the disk;
A recording unit for recording a servo signal on the magnetic tape based on a write signal;
A servo writer comprising an output unit for outputting the write signal each time the number of changes of the waveform signal is counted a certain number of times .   The servo writer according to claim 1, wherein the disk has a reflective layer having irregularities to be the pits.   The servo writer according to claim 1, wherein a rotation axis of the disk is common to a rotation axis of the rotating body. The detector is
A laser irradiation unit for irradiating the disk with laser light;
4. The servo writer according to claim 1, further comprising: a light receiving unit that receives reflected light reflected by the disk. 5.   5. The detection unit according to claim 1, wherein the detection unit includes a first displacement unit that displaces the detection unit so that the waveform signal can be detected even if the rotation of the disk is eccentric. The servo writer according to item 1.   The said detection part has the 2nd displacement part which displaces the said detection part so that the distance with the said disk may be kept constant even if the said disk rotates, The Claim 1 thru | or 5 characterized by the above-mentioned. The servo writer according to item 1.   The servo writer according to any one of claims 1 to 6, wherein the size of the pit in the rotation direction is 400 nm or less, and the wavelength of the laser light is 650 nm or less.

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