JP2009154200A - Laser marking system and laser marking apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser marking system which forms a strain-free mark while installing a conveyance distance detecting means in a follower roller, and to provide a laser marking apparatus. <P>SOLUTION: The laser marking system forms a mark with a laser beam while a workpiece is transported, wherein the average value of a pulse period is calculated by sampling a pulse output from a conveyance distance detecting means installed in the follower roller. Coordinate data are corrected with a timing based on a correction pulse, whereby the strain-free mark is formed while the conveyance distance detecting means is installed in the follower roller. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser marking system and a laser marking apparatus that form a mark with a laser beam while conveying an object.

2. Description of the Related Art Conventionally, a laser marking device that forms a mark by scanning a moving object with a laser beam is known (see, for example, Patent Document 1).
In such a laser marking device, when a mark is formed on an object such as roll paper or a sheet-like label, the object on the roll is set on a conveyance line, and the object is being conveyed while the object is being conveyed. The mark is formed by the laser marking device installed in
JP 2000-202656 A

When forming a mark while transporting an object, it is necessary to correct the irradiation position of the laser light in accordance with the movement of the object.
For this reason, generally, a transport distance detecting means such as an encoder is installed on the driving roller of the transport line to detect the moving distance. Since the drive roller generally does not easily cause rotation unevenness, so-called flutter, if the encoder is installed on the drive roller, the moving distance of the object can be detected with high accuracy.

However, for convenience, there are situations in which an encoder cannot be attached to the drive roller. In this case, if the encoder is attached to the driven roller in the middle of the transport line, the driven roller may cause flutter due to slippage of the target object or elongation depending on the material of the target object. There is a problem that the mark may be distorted.
The present invention has been completed based on the above circumstances, and an object of the present invention is to provide a laser marking system and a laser marking device which can form a mark without distortion while installing a conveyance distance detecting means on a driven roller. To do.

In order to achieve the above object, a laser marking system for forming a mark with laser light while conveying an object, laser scanning means for scanning a scanning region with laser light based on coordinate data corresponding to the mark; A conveying means having a driving roller and a driven roller for conveying the object along a predetermined conveying path, and conveying the object within the scanning region set on the conveying path at a constant speed; , A transport distance detecting means for detecting a transport distance of the object by rotating the driven roller by a predetermined angle and outputting a pulse; and an average value of a pulse cycle by sampling a pulse inputted from the transport distance detecting means An average period calculation means for calculating the correction pulse, a correction pulse output means for outputting a correction pulse at the pulse period calculated by the average period calculation means, and the correction pulse At the timing based and a coordinate data correction means for correcting a predetermined distance minutes in the conveying direction of the coordinate data.
According to the present invention, the correction pulse is output with a pulse period obtained by averaging the pulse periods of the pulses output from the conveyance distance detection unit, and the coordinate data is corrected at the timing based on the correction pulse. Even if the pulse period of the output pulse is disturbed, the mark can be formed without distortion. Therefore, according to the present invention, the mark can be formed without distortion while the conveyance distance detecting means is installed on the driven roller.

  In the second invention, the average period calculation means calculates the average value of the pulse periods by counting the number of pulses input per predetermined time and dividing the predetermined time by the counted number of pulses.

  In a third invention, the predetermined time is a time required for the driven roller to make one rotation.

  According to a fourth aspect of the invention, the average period calculation means measures and measures a time from when sampling is started until a predetermined number of pulses including the first pulse are input after the first pulse is input. When the time is R and the predetermined number is X, the average value T of the pulse period is calculated by Equation 1.

  In a fifth invention, the predetermined number is the number of pulses output while the driven roller makes one rotation.

  According to a sixth aspect of the invention, the correction pulse output means outputs the correction pulse having the same pulse width and pulse interval, and the coordinate data correction means outputs the coordinates at both rising and falling timings of the correction pulse. Correct the data.

  According to a seventh aspect of the invention, the laser scanning means includes a laser light source that emits laser light, a galvanometer mirror that irradiates the laser light in the scanning region by changing the direction of the laser light from the laser light source, and the laser Data generating means for controlling on / off of the light source and generating the coordinate data for controlling the galvano mirror based on information representing the mark, and storage means for storing the coordinate data generated by the data generating means A trigger input means for taking in a trigger signal output by a trigger sensor arranged in the middle of the transport path as a result of detecting the passage of the scanning area and starting the scanning into the scanning area; and the trigger Based on the input means taking in the trigger signal, the coordinate data stored in the storage means is retrieved. And a control means for causing the formation of the mark to the object by scanning a laser beam on the object being transported by driving the galvanometer mirror.

An eighth invention is a laser marking device for forming a mark on an object conveyed in a scanning area at a constant speed with a laser beam, wherein the scanning area is formed with a laser beam based on coordinate data corresponding to the mark. Laser scanning means for scanning; external pulse input means for inputting an external pulse; average period calculating means for sampling the external pulse input to the external pulse input means to calculate an average value of pulse periods; Correction pulse output means for outputting a correction pulse at the pulse period calculated by the average period calculation means; and coordinate data correction means for correcting the coordinate data by a fixed distance in the transport direction based on the correction pulse.
According to the present invention, the correction pulse is output at a pulse period obtained by averaging the pulse period of the external pulse input to the external pulse input means, and the coordinate data is corrected at the timing based on the correction pulse. Even if the period is disturbed, the mark can be formed without distortion. Therefore, according to the present invention, the mark can be formed without distortion while the conveyance distance detecting means is installed on the driven roller.

  According to the present invention, the mark can be formed without distortion while the conveyance distance detecting means is installed on the driven roller.

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic diagram of a laser marking system 1 according to Embodiment 1 of the present invention. The laser marking system 1 forms marks at regular intervals on an object 11 such as roll paper or a sheet-like label.

The laser marking system 1 includes a transport mechanism 12, an encoder 13, a trigger sensor 14, a laser marking device 2, and the like.
The transport mechanism 12 (an example of a transport unit) includes a drive roller 15, a plurality of driven rollers 16 to 23, a drive unit 25, and the like. In FIG. 1, the driven roller 17 is hidden by the encoder 13 on the back side in the direction perpendicular to the paper surface and is not visible.

The driving roller 15 is driven by the driving unit 25 to rotate at a constant speed, and the object 11 is held between the driven roller 23 and conveyed in the A direction.
The plurality of driven rollers 16 to 23 are in contact with the object 11 and rotated. These driven rollers set the transport path of the object 11 by changing the traveling direction of the object 11.

  In this embodiment, the case where the cross section perpendicular to the rotation axis of the driven roller is circular will be described as an example. However, the cross section is not necessarily circular, and may be oval, rectangular, hexagonal, etc. It may be a polygon.

The drive unit 25 includes a drive source such as an electric motor and a control circuit that controls the drive source.
The drive roller 15 of the present embodiment does not wind up the object 11, but may be configured to wind up the object 11 with the drive roller 15. In that case, the control circuit may control so that the rotational speed of the driving roller 15 is gradually decreased so that the object 11 moves in the scanning region 24 at a constant speed from the winding start stage to the winding end stage.

  An example of the object 11 is shown in FIG. An object 11 shown in FIG. 2 has a tape-like mount 11a on which labels, stickers and the like are supported at equal intervals. A plurality of regions 11b indicated by rectangles are labels, stickers, and the like, and the laser marking system 1 forms marks in the rectangular region 11b while following the movement of the rectangular region 11b while moving in the scanning region 24. To do. Each rectangular area 11b has a reference mark 11c formed on the downstream side in the transport direction for determining the timing for forming the mark. The reference mark 11c is formed as a through hole. The reference mark 11c may be formed by printing.

  The encoder 13 shown in FIG. 1 (an example of a conveyance distance detection unit) includes a known rotary encoder and a control circuit. The rotary encoder rotating body 13a is provided so as to rotate integrally with the driven roller 17, and the rotary encoder outputs a pulse signal to the laser marking device 2 for each unit rotation angle as the rotating body 13a rotates. .

  The encoder 13 is used to detect that the object 11 has moved a certain distance. By the way, when the object 11 is moving at a constant speed, it is also possible to detect that the object 11 has moved a certain distance by measuring the moving time. However, in that case, if the moving speed changes, the movement for the same fixed distance cannot be detected unless the speed is input again by some method. On the other hand, the encoder has an advantage that the same constant distance can be detected without changing any setting even if the speed changes.

  In the present embodiment, the encoder 13 detects that the object 11 has moved a certain distance, but it may be detected by other methods. For example, an endless belt is spanned between the driven roller 17 and the driven roller 18, and through holes are formed in the endless belt at regular intervals in the circumferential direction. And the light which passed the through-hole is detected with a photoelectric sensor, and a pulse is output. As a result, a pulse is output every time the driven roller 17 rotates by a predetermined angle, and a movement of a certain distance can be detected.

  The trigger sensor 14 is composed of a photoelectric sensor or the like, and is provided in the middle of the transport path. When the reference mark 11c (see FIG. 2) comes to the position opposite to the trigger sensor 14, the trigger sensor 14 detects the light that has passed through the through hole by the photoelectric sensor, and outputs a trigger signal to the laser marking device 2. The trigger sensor 14 may be integrated into the laser marking device 2.

The laser marking device 2 performs two-dimensional scanning with a laser beam on the scanning area 24 set on the conveyance path based on coordinate data corresponding to the mark, thereby marking the object 11 conveyed in the scanning area 24. Form.
In the present embodiment, the laser marking device 2 is provided in the vicinity of the drive roller 15. This is because the moving speed of the object 11 becomes more stable as it is closer to the drive roller 15. Thereby, the object 11 is conveyed at a substantially constant speed at least in the scanning region 24. Hereinafter, the details of the laser marking device 2 will be described.

FIG. 3 is a schematic diagram of the laser marking device 2. The laser marking device 2 of the present embodiment adopts a so-called galvano scanning method, and includes a laser light source 31, galvanometer mirror devices 32 and 33, a data generation unit 34, a storage unit 35, a correction pulse generation unit 36, a control unit 37, and the like. It has.
The laser light source 31 is composed of, for example, a semiconductor laser light source that emits light in the infrared region, and emits laser light toward the galvanometer mirror devices 32 and 33.

  The galvano mirror device 32 includes a drive unit 32a and a galvano mirror 32b. Similarly, the galvano mirror device 33 includes a drive unit 33a and a galvano mirror 33b. One galvano mirror 32b is displaced in the vertical direction by the drive unit 32a, and the other galvano mirror 33b is displaced in the lateral direction by the drive unit 33a. As a result, the direction of the laser beam is changed in two directions, and the irradiation point of the laser beam moves two-dimensionally on the scanning region 24.

  The data generation unit 34 (an example of data generation means) decomposes a mark into line elements based on image information representing marks such as characters, symbols, and figures, and a plurality of coordinate data including the start and end points of those line elements (Two-dimensional data corresponding to the positional deviation from the irradiation position of the laser beam when the galvano mirrors 32b and 33b are at the rotation center position) is generated. This coordinate data indicates the position of each line element in the stationary coordinate system, and when the coordinate system moves, correction following the movement is necessary.

The storage unit 35 (an example of a storage unit) is configured by a volatile memory such as a RAM or a rewritable nonvolatile memory such as a flash memory, and stores the coordinate data generated by the data generation unit 34.
The correction pulse generation unit 36 (an example of an average period calculation unit, a correction pulse output unit, and an external pulse input unit) counts the number of pulses output per predetermined time from the encoder 13 and counts the predetermined time. Outputs a correction pulse whose pulse period is the time divided by the number. Details of the correction pulse generator 36 will be described below.

FIG. 4 is a block diagram schematically showing the correction pulse generator 36. The correction pulse generation unit 36 includes a time measurement circuit 36a, an averaging circuit 36b, a pulse generation circuit 36c, and the like.
An encoder pulse output from the encoder 13 is input to the time measurement circuit 36a, and a predetermined measurement time (predetermined time) set in advance from the control unit 37 is input. As the measurement time, it is desirable to set a time required for one rotation when the driven roller 17 rotates without flutter, or a time that is an integral multiple of the time. The time measurement circuit 36a counts the number of encoder pulses input per input measurement time, and outputs it to the averaging circuit 36b.

  The averaging circuit 36 b receives the number of pulses counted by the time measurement circuit 36 a and the above-described measurement time from the control unit 37. The averaging circuit 36b calculates the averaged pulse period by dividing the measurement time by the number of pulses, and outputs it to the pulse generation circuit 36c.

The pulse cycle averaged by the averaging circuit 36b is input to the pulse generation circuit 36c. When the pulse period is input, the pulse generation circuit 36 c generates a correction pulse with the input pulse period and outputs the correction pulse to the control unit 37.
FIG. 5 is a schematic diagram showing the relationship between the encoder pulse input to the time measurement circuit 36a and the correction pulse output from the pulse generation circuit 36c. When flutter occurs in the driven roller 17, the pulse period of the encoder pulse becomes unstable as shown in the figure. On the other hand, as shown in the figure, the correction pulse is a pulse in which the number of pulses per measurement time S is equal to that of the encoder pulse and the pulse cycle (T time in the figure) is equal. This pulse period corresponds to an average of the pulse periods of the encoder pulses, and is substantially equivalent to the pulse period of the encoder pulses obtained when the encoder 13 is installed on the drive roller 15.

  When the control unit 37 (an example of the trigger input unit and the control unit) illustrated in FIG. 3 receives the trigger signal from the trigger sensor 14, the control unit 37 controls the laser output of the laser light source 31 based on the coordinate data, and also includes the driving unit 32a, The galvanometer mirrors 32b and 33b are rotationally driven by controlling 33a. At this time, since the object 11 moves in the scanning region 24 at a constant speed, the control unit 37 forms a mark while correcting the coordinate data in order to follow the movement. The correction of the coordinate data will be described later.

Next, the relationship between the processing resolution of the laser marking device 2 and the detection resolution of the encoder 13 will be described.
The laser marking device 2 forms dots corresponding to the coordinate data on the object 11 in the scanning region 24 by scanning with laser light. The processing resolution refers to the number of dots that the laser marking device 2 can form per unit width in the transport direction. The detection resolution is the number of pulses that the encoder 13 can output per rotation angle corresponding to the unit width. In the present embodiment, it is assumed that the processing resolution of the laser marking device 2 is larger than the detection resolution of the encoder 13.

In other words, the processing resolution can be said to be the distance between dots, and the detection resolution is the distance that the object 11 moves between the time when the encoder pulse is output and the time when the next encoder pulse is output. It can be said. In this case, the fact that the processing resolution is larger than the detection resolution means that the distance between the dots is smaller than the distance that the object 11 moves while the encoder pulse is output.
Therefore, the laser marking device 2 can form a plurality of dots after the pulse is output from the encoder 13 until the next pulse is output.

Next, correction of coordinate data will be described.
FIG. 6 is a schematic diagram for explaining the correction of coordinate data. Here, for easy understanding, a straight line will be described as an example of the mark.
The trigger input indicates the timing at which a trigger signal is output from the trigger sensor 14 to the control unit 37.
The correction pulse input indicates a correction pulse generated by the correction pulse generator 36.

The clock (CK) indicates the time required for the laser marking device 2 to form one dot.
In the present embodiment, 4 dots are formed after a correction pulse is output until the next correction pulse is output. That is, in this embodiment, the dot is formed on the assumption that the object 11 has not moved during the period from the output of the correction pulse to the output of the next correction pulse. In this case, since the object 11 is actually moving, a dot is formed at a position shifted from the original position. However, since 1CK is a short time, the deviation is negligible.

x indicates a temporal transition of the dot formation position (x coordinate) in the transport direction when the mark (straight line) is formed.
When the correction pulse is output from the correction pulse generation unit 36, the control unit 37 regards that the object 11 has moved a certain distance downstream in the transport direction, and corrects the coordinate data by a certain distance. Here, the fixed distance corresponds to the moving distance of the object 11 when the driven roller 17 rotates without flutter from the angle at which the encoder pulse is output to the angle at which the next encoder pulse is output. In the figure, the coordinate data is corrected by a certain distance at the timings t2 to t7.

  Specifically, the correction for a certain distance is performed by shifting the center, for example. As described above, since the coordinate data is stored as a positional deviation from the center of the scanning region 24, the control unit 37 moves the center by a certain distance to the downstream side in the transport direction. As a result, the coordinate data is corrected so that the laser irradiation position as a whole moves downstream by a certain distance in the transport direction. As a result, a mark is formed following the movement of the object 11.

  Since the correction pulse is output with a pulse period substantially equal to the pulse period of the encoder pulse obtained when the encoder 13 is installed on the driving roller 15, when a correction for a certain distance is performed at the timing when the correction pulse is output, The distance that the object 11 has actually moved can be corrected almost accurately. As a result, the obtained straight line is less distorted to the same extent as the straight line obtained when the encoder 13 is installed on the drive roller 15.

Here, as a comparative example, FIG. 7 shows how correction is performed when the encoder pulse is used as it is.
If the coordinate data is corrected by a certain distance at the timing when the encoder pulse is output, for example, correction is performed at time points s2 and s3, but the time point s2 is a timing 1 CK later than the time point t2 shown in FIG. Also, the time point s3 is a timing 1CK earlier than the time point t3 shown in FIG. If the encoder pulse is used as it is, the distance that the object 11 has actually moved deviates from the above-mentioned fixed distance, resulting in a distorted line as shown.

  On the other hand, the laser marking system 1 does not use the encoder pulse as it is, but corrects it using the correction pulse, so that a straight line without distortion can be formed as shown in FIG.

Next, the operation of the laser marking system 1 will be described.
Here, an example will be described in which there is a margin part of a certain length on the front end side of the object 11 and the pulse period of the correction pulse is calculated while the margin part is being transported in the scanning region 24.
When the conveyance of the object 11 is started, an encoder pulse is output from the encoder 13 to the correction pulse generator 36. As described above, the correction pulse generator 36 counts the number of encoder pulses output per predetermined time, calculates the pulse period, and starts generating correction pulses. The processing up to this point is performed while the blank portion is being conveyed in the scanning region 24 as described above.

The controller 37 waits for the trigger signal to be output from the trigger sensor 14 when the conveyance is started. When conveyance of the blank portion is completed and the reference mark 11 c is detected by the trigger sensor 14, a trigger signal is output from the trigger sensor 14 to the control unit 37.
When the trigger signal is output, the control unit 37 corrects the coordinate data at the timing when the correction pulse is output and controls the laser light source 31 and the drive units 32a and 33a to scan the scanning region 24 with the laser light. A mark is formed on the object 11.
When the formation of one mark is completed, the control unit 37 waits for the next trigger signal to be output, and forms a mark in the same manner as the trigger signal is output. By repeating this, marks are formed on the object 11 at regular intervals.

  According to the laser marking system 1 according to the embodiment of the present invention described above, a correction pulse is output with a pulse period obtained by averaging the pulse periods of encoder pulses output from the encoder 13 installed on the driven roller 17, and this correction is performed. Since the coordinate data is corrected at the timing based on the pulse, the mark can be formed without distortion even if the pulse period of the encoder pulse is disturbed. Therefore, according to the laser marking system 1, the mark can be formed without distortion while installing the encoder 13 on the driven roller 17.

  Further, according to the laser marking system 1, the processing resolution of the laser marking device 2 is larger than the detection resolution of the encoder 13. If the processing resolution of the laser marking device 2 is larger than the detection resolution of the encoder 13, the influence of flutter tends to appear. According to the laser marking system 1, the coordinate data is corrected based on the correction pulse. Therefore, even when the processing resolution of the laser marking device 2 is larger than the detection resolution of the encoder 13, the influence of flutter is reduced and the mark is reduced. Can be formed without distortion.

<Embodiment 2>
FIG. 8 is a schematic diagram for explaining the calculation of the pulse period according to the second embodiment. In the second embodiment, when sampling is started, the time from when sampling is started to when the first encoder pulse is output until when a predetermined sampling number (predetermined number) of encoder pulses is output is measured. This sampling number may be the number of pulses output while the driven roller 17 rotates once.

  More specifically, the time from the start of sampling until the first encoder pulse rises to the rise of a predetermined number of sampling encoder pulses including the first encoder pulse is measured. For example, FIG. 8 shows an example in which the sampling number is 4, and the time from the rising edge of the first encoder pulse to the rising edge of the fourth encoder pulse is measured.

Then, when the measured time is R and the sampling number is X, the pulse period T is calculated by the following equation 1.
T = R / (X-1) Formula 1
In the example shown in FIG. 8, the pulse period T is calculated by dividing the measured time R by 3 (= 4-1).

FIG. 9 is a block diagram schematically illustrating the correction pulse generation unit 38 according to the second embodiment. The sampling number described above is input from the control unit 37 to the time measurement circuit 38a and the averaging circuit 38b. The time measuring circuit 38a measures the time R described above, and the averaging circuit 38b calculates the pulse period T described above. Since the pulse generation circuit 36c is the same as that of the first embodiment, the same reference numerals are given.
The second embodiment is substantially the same as the first embodiment in other points.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above embodiment, a case has been described by way of example in which there is a margin part of a certain length on the front end side of the object, and the pulse period of the correction pulse is calculated while winding the margin part. While the mark is being formed, the calculation of the pulse period may be repeatedly executed to always output the correction pulse having the latest pulse period.

  (2) In the above-described embodiment, an example has been described in which labels, seals, and the like are supported at equal intervals on a tape-shaped mount as the object. However, the object may be, for example, roll paper, resin, or metal. The belt may also be used. The object may be composed of an object on which a mark is formed and a belt that conveys the object. In this case, the belt may be an endless belt.

  (3) In the above embodiment, the correction pulse rising interval is described as the pulse period of the correction pulse, but the pulse falling interval may be the pulse period.

(4) In the above embodiment, only the rising edge of the correction pulse is used as the correction timing. However, both the rising edge and falling edge of the pulse are corrected by making the pulse width and the pulse interval of the correction pulse the same. You may make it utilize as a timing of.
Note that when only the rising timing of the correction pulse is used, the pulse width and the pulse interval need not be equal.

(5) In the above embodiment, the pulse generation circuit 36c generates a correction pulse with the pulse period output from the averaging circuit 36b or 38b, but the control unit 37 sets the pulse period to 1 as shown in FIG. The frequency may be divided by 2 to be used for correction timing. The pulse period may be 1/3 or 1/4.
Further, instead of dividing by the control unit 37, the pulse generation circuit 36c may output a correction pulse at a pulse period of 1/2 as shown in FIG. The pulse period may be 1/3 or 1/4.

The schematic diagram of the laser marking system which concerns on one Embodiment of this invention. The schematic diagram of the target object concerning one embodiment of the present invention. The schematic diagram of the laser marking apparatus which concerns on one Embodiment of this invention. The block diagram of the correction pulse production | generation means which concerns on one Embodiment of this invention. The schematic diagram which shows the relationship of the pulse which concerns on one Embodiment of this invention. The schematic diagram of the correction | amendment of the coordinate data which concerns on one Embodiment of this invention. The schematic diagram of the correction | amendment of the coordinate data which concerns on a comparative example. The schematic diagram which shows the relationship of the pulse which concerns on one Embodiment of this invention. The block diagram of the correction pulse production | generation means which concerns on one Embodiment of this invention. The schematic diagram of the pulse which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser marking system 2 ... Laser marking apparatus 11 ... Object 12 ... Conveyance mechanism 13 ... Encoder (conveyance distance detection means)
DESCRIPTION OF SYMBOLS 14 ... Trigger sensor 15 ... Drive rollers 16-23 ... Driven roller 24 ... Scanning region 25 ... Drive part (drive source)
31 ... Laser light sources 32b, 33b ... Galvano mirror 34 ... Data generation unit (data generation means)
35 ... Storage section (storage means)
36 ... Correction pulse generation unit (average period calculation means, correction pulse output means, external pulse input means)
37. Control unit (control means)
38 ... Correction pulse generation unit (average period calculation means, correction pulse output means, external pulse input means)

Claims (8)

A laser marking system for forming a mark with a laser beam while conveying an object,
Laser scanning means for scanning a scanning area with laser light based on coordinate data corresponding to the mark;
A transport unit that includes a driving roller and a driven roller, and transports the object along a predetermined transport path, the transport unit transporting the scanning region set on the transport path at a constant speed;
A transport distance detecting means for detecting a transport distance of the object and outputting a pulse by rotating the driven roller by a predetermined angle;
An average period calculating means for sampling pulses input from the transport distance detecting means and calculating an average value of pulse periods;
Correction pulse output means for outputting a correction pulse at the pulse period calculated by the average period calculation means;
Coordinate data correction means for correcting the coordinate data by a fixed distance in the transport direction at a timing based on the correction pulse;
A laser marking system comprising:   2. The laser according to claim 1, wherein the average period calculation unit calculates the average value of the pulse periods by counting the number of pulses input per predetermined time and dividing the predetermined time by the counted number of pulses. Marking system.   The laser marking system according to claim 2, wherein the predetermined time is a time required for the driven roller to make one rotation. The average period calculating means measures a time from when sampling is started until a predetermined number of pulses including the first pulse are input after the first pulse is input, and the measured time is R, the predetermined pulse The laser marking system according to claim 1, wherein when the number is X, the average value T of the pulse period is calculated by the following formula 1.
T = R / (X-1) Formula 1   The laser marking system according to claim 4, wherein the predetermined number is a pulse number output while the driven roller makes one rotation. The correction pulse output means outputs the correction pulse having the same pulse width and pulse interval,
6. The laser marking system according to claim 1, wherein the coordinate data correcting unit corrects the coordinate data at both rising and falling timings of the correction pulse. 7. The laser scanning means includes
A laser light source for emitting laser light;
A galvanometer mirror that irradiates laser light into the scanning region by changing the direction of the laser light from the laser light source;
Data generating means for controlling the laser light source on and off, and generating the coordinate data for controlling the galvanometer mirror based on information representing the mark;
Storage means for storing the coordinate data generated by the data generation means;
A trigger input means for taking in a trigger signal output by a trigger sensor arranged in the middle of the transport path as a result of detecting the passage of the scanning area;
Based on the trigger input means capturing the trigger signal, the galvano mirror is driven while taking out the coordinate data stored in the storage means, thereby scanning a laser beam on the object being conveyed and scanning the object. Control means for causing the mark to be formed on the object;
The laser marking system according to claim 1, comprising: A laser marking device for forming a mark with a laser beam on an object conveyed at a constant speed in a scanning region,
Laser scanning means for scanning the scanning area with laser light based on coordinate data corresponding to the mark;
An external pulse input means for inputting an external pulse;
An average period calculating means for sampling the external pulse input to the external pulse input means and calculating an average value of the pulse period;
Correction pulse output means for outputting a correction pulse at the pulse period calculated by the average period calculation means;
Coordinate data correction means for correcting the coordinate data by a fixed distance in the transport direction at a timing based on the correction pulse;
A laser marking device comprising:

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