WO2006093378A1

WO2006093378A1 - Marking method of fiber laser marker

Info

Publication number: WO2006093378A1
Application number: PCT/KR2006/000443
Authority: WO
Inventors: Sang-Kil Lee; Ko-Dong Park; Sung-Chul Kang; Byung-Hun Hyun; Goo-Cheol Gwon; Tae-Jung Kim; Byong-Gyu Lee; Jae-Hyuk Sho
Original assignee: Eo Technics Co., Ltd.
Priority date: 2005-03-03
Filing date: 2006-02-07
Publication date: 2006-09-08
Also published as: KR20060098519A; KR100628456B1

Abstract

Provided is a marking method of a fiber laser marker, the fiber laser marker including an optical pump outputting an optical signal to a resonator, and a Galvano scanner scanning at a predetermined location with a laser beam emitted from the resonator. The marking method includes: measuring a delay time for which the output of the laser beam is delayed, the delay time depending on a jump time between when the optical signal is output to the resonator and when the laser beam is emitted from the resonator; moving a mirror of the Galvano scanner to a starting point of a next marking; calculating the jump time for which the mirror of the Galvano scanner is moved to the starting point of the next marking; calculating the delay time depending on the jump time; driving the optical pump to apply the optical signal to the resonator, and making the mirror of the Galvano scanner stand by for the delay time; and driving the mirror of the Galvano scanner and performing the marking.

Description

MARKING METHOD OF FIBER LASER MARKER

Technical Field

[1] The present invention relates to a marking method of a fiber laser marker, and more particularly, to a marking method in which driving of a Galvano scanner of a fiber laser marker is synchronized with emission of a laser beam.

Background Art

[2] A fiber laser marker is an apparatus for printing characters and the like using a laser beam. Since the printed characters are permanent, the fiber laser marker is useful in printing a lot number on a small-sized product. The fiber laser marker is also used to print characters on compact products in the entire industrial field.

[3] FIG. 1 is a schematic configuration of a structure of a general fiber laser marker.

Referring to FIG. 1, a laser oscillator 1 includes a resonator 5, which amplifies a laser beam to have a predetermined wavelength, and an optical pump 10, which is connected to the resonator 5 and sends the laser beam with the predetermined wavelength into the resonator 5. A laser beam emitted from the laser oscillator 1 is transferred to a laser head 3 via an optical fiber 2, which is a light path. The laser head 3 includes a collimator 4 for collimating the laser beam received via the optical fiber 2, a mirror of a Galvano scanner 6 for scanning a predetermined location with the laser beam emitted from the resonator 5, and an f- θ lens 7 for focusing the laser beam reflected from the mirror of the Galvano scanner 6 on an object 8 by a uniform focal distance. The laser beam emitted from the laser head 3 is projected onto the object 8, which is on a table 9, and marks characters.

[4] Fiber Bragg gratings (not shown) are disposed on both sides of the resonator 5 and send a specific wavelength of the laser beam amplified by the resonator 5 to the laser head 3.

[5] The optical pump 10 sends an optical signal to the resonator 5 according to an electrical signal (not shown). The optical pump 10 may be a laser diode. The optical pump 10 serves to turn on or off the laser beam emitted from the resonator 5.

[6] The Galvano scanner 6 includes two mirrors, namely, an x mirror and a y mirror, and a driving unit for driving the two mirrors. Since the Galvano scanner 6 is well known, it will not be described in greater detail herein.

[7] FIG. 2 is a graph showing a delay time for which emission of an initial laser beam is delayed versus an input voltage applied to the optical pump 10 of the fiber laser marker of FIG. 1. Referring to FIG. 2, at a condition of 20 kHz frequency and 60% duty, the delay time vary at the same input voltage depending on a fiber laser used. Furthermore, in one fiber laser, a corresponding delay time varies with a change of the input voltage.

[8] FIG. 3 is a graph showing a delay time for which emission of an initial laser beam is delayed versus a jump time, namely, the time when the optical pump 10 is turned off during the use of the fiber laser marker of FIG. 1.

[9] The jump time denotes the duration time when the optical signal of the optical pump 10 is off for moving the laser beam to a next position after consecutively marking the predetermined points. Referring to FIG. 3, the delay time varies according to a fiber laser marker used and the jump time.

[10] FIG. 4 is a general timing diagram of the fiber laser marker of FIG. 1. Referring to

FIG. 4, when the optical pump 10 is driven by an electrical signal during laser marking (i.e., a duration from t0 to tl), the optical pump 10 outputs an optical signal in synchronization with the electrical signal. Referring to FIG. 4, the electrical signal has a pulse waveform. The optical signal is input to the resonator 5 of the fiber laser marker. At the same time, marking is executed while moving the mirror of the Galvano scanner 6.

[11] Then, at time tl, that is, when the fiber laser marker tries to move the mirror of the

Galvano scanner 6 to a next point, a jump time is occurred. Firstly, the mirror of the Galvano scanner 6 is stabilized before moving. The time required for this stabilization is a first jump delay JDl (JDl = t2 - tl). Thereafter, the mirror of the scanner 6 is moved to the next point, and then stabilized again. The time required for this second stabilization is a second jump delay JD2 (JD2 = t4 - 13). After the lapse of the second jump delay JD2, the Galvano scanner 6 is ready for another marking. In other words, the Galvano scanner 6 is ready for marking at time t4.

[12] At time t4, that is, when the Galvano scanner 6 is ready for another marking, when the optical pump 10 outputs an optical signal to the resonator 5, a time delay occurs according to a jump time (t4 - tl). That is, the time delay is t5 - 14. During the time delay t5 - 14, a laser beam is not emitted.

[13] However, because the time delay of the fiber laser marker is not consistent although the time (t4 - tl) required to move the mirror of the scanner 6 is consistent, an initial portion of the characters may not be marked.

[14] FIG. 5 illustrates a result of marking achieved by the fiber laser marker of FIG. 1.

Referring to FIG. 5, marking was not completely achieved because when a next line is to be printed after a line was marked, the mirror of the Galvano scanner 6 was moved at the next line, but a laser beam was not emitted due to the delay time. Disclosure of Invention

Technical Solution

[15] The present invention provides a marking method performed in consideration of a delay time for which a laser beam is delayed that depends on a jump time.

[16] According to an aspect of the present invention, there is provided a marking method of a fiber laser marker, the fiber laser marker including an optical pump outputting an optical signal to a resonator, and a Galvano scanner scanning at a predetermined location with a laser beam emitted from the resonator, the marking method comprising: measuring a delay time for which the output of the laser beam is delayed, the delay time depending on a jump time between when the optical signal is output to the resonator and when the laser beam is emitted from the resonator; moving a mirror of the Galvano scanner to a starting point of a next marking; calculating the jump time for which the mirror of the Galvano scanner is moved to the starting point of the next marking; calculating the delay time depending on the jump time; driving the optical pump to apply the optical signal to the resonator, and making the mirror of the Galvano scanner stand by for the delay time; and driving the mirror of the Galvano scanner and performing the marking, wherein the laser beam delayed for the delay time is emitted synchronously with the driving of the mirror of the Galvano scanner.

[17] The operation of measuring the delay time comprises: disposing a laser beam detection device at a position where the laser beam from the resonator is irradiated; determining n jump times; sending the optical signal to the resonator with the lapse of each of the n jump times; detecting the laser beam using the laser beam detection device; and calculating a delay time between when the laser beam is detected and when the optical signal is sent.

[18] The operation of measuring the delay time further comprises making a lookup table with the delay times depending on the jump times, and the operation of calculating the delay time is referring to the lookup table.

[19] The laser beam detection device may be a photodiode.

[20] The jump time may be a sum of a first jump delay for which the mirror of the scanner is stabilized, a time for which the mirror is rotated to a predetermined location, and a second jump delay for which the rotated mirror is stabilized again.

[21] According to another aspect of the present invention, there is provided a marking method of a fiber laser marker, the fiber laser marker including an optical pump outputting an optical signal to a resonator, and a Galvano scanner scanning at a predetermined location with a laser beam emitted from the resonator, the marking method comprising: measuring a delay time for which the output of the laser beam is delayed, the delay time depending on a jump time between when the optical signal is output to the resonator and when the laser beam is emitted from the resonator; moving a mirror of the Galvano scanner to a starting point of a next marking; calculating the jump time for which the mirror of the Galvano scanner is moved to the starting point of the next marking; calculating the delay time depending on the jump time; driving the optical pump for a pulse acceleration time that is a first time shorter than the delay time; and performing the marking, while driving the optical pump and driving the mirror of the Galvano scanner when the jump time is passed, wherein the laser beam is emitted synchronously with the driving of the mirror of the Galvano scanner.

Description of Drawings

[22] FIG. 1 is a schematic configuration of a general fiber laser marker.

[23] FIG. 2 is a graph showing a delay time when an initial laser beam is delayed and emitted versus an input voltage applied to an optical pump of the fiber laser marker of FIG. 1.

[24] FIG. 3 is a graph showing a delay time when an initial laser beam is delayed and emitted versus a jump time, namely, the time when the optical pump is turned off during the use of the fiber laser marker of FIG. 1.

[25] FIG. 4 is a general timing diagram of the fiber laser marker of FIG. 1.

[26] FIG. 5 illustrates a result of marking achieved by the fiber laser marker of FIG. 1.

[27] FIG. 6 is a block diagram of a marking control system of a fiber laser marker to which a marking method according to the present invention is applied.

[28] FIG. 7 is a flowchart illustrating a method of measuring a delay time for the fiber laser marker of FIG. 6, according to a first embodiment of the present invention.

[29] FIG. 8 is a graph showing a result of the delay time measurement shown in FIG. 7.

[30] FIG. 9 is a flowchart illustrating a marking method using the fiber laser marker, according to a second embodiment of the present invention.

[31] FIG. 10 is a timing diagram for illustrating the marking method of FIG. 9.

[32] FIG. 11 is a photograph of a result of marking achieved according to the marking method of FIG. 9.

[33] FIG. 12 is a flowchart illustrating a marking method using the fiber laser marker, according to a third embodiment of the present invention.

[34] FIG. 13 is a timing diagram for illustrating the marking method of FIG. 12.

Best Mode

[35] Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the invention with reference to the attached drawings.

[36] FIG. 6 is a block diagram of a marking control system of a fiber laser marker to which a marking method according to the present invention is applied. In FIG. 6, component elements substantially the same as those of FIG. 1 are not described in detail herein.

[37] Referring to FIG. 6, a controller 50 sends an electrical signal to an optical pump 52.

The optical pump 52 outputs an optical signal to a resonator 54 according to the electrical signal. The resonator 54 amplifies a laser beam using a laser medium and outputs the amplified laser beam. An optical sensor 56 is installed at the laser head 3 or on the table 9 on which the object 8 is mounted, and detects the laser beam emitted from the resonator 54. The optical sensor 56 outputs a laser beam detection signal to a comparator 58. When sending the electrical signal to the optical pump 52, the controller 50 also sends the electrical signal to the comparator 58. The comparator 58 calculates a delay time between when the electrical signal is received from the controller 50 and when the laser beam detection signal is received from the optical sensor 56 and outputs the delay time to the controller 50. The controller 50 controls a mirror driver 60 of the Galvano scanner 6 in consideration of the delay time.

[38] FIG. 7 is a flowchart illustrating a method of measuring a delay time for the fiber laser marker of FIG. 6, according to a first embodiment of the present invention. Referring to FIG. 7, in operation 101, the optical sensor 56, for example, a photodiode, is installed at a location irradiated by the laser beam from the resonator 54. The optical sensor 56 may be installed on the table 9. A voltage applied to the fiber laser and a condition of a frequency and a duty ratio are determined uniquely according to the type of an object.

[39] In operation 102, a plurality of jump times to be measured are determined. For example, a time at which delay times are converged is divided into n sections to thereby produce n jump times. The time at which delay times are converged may be 4700-5000 D as shown in FIG. 4.

[40] In operation 103, an iteration count (icount) is initialized as 1.

[41] In operation 104, when a laser beam is off after emitting the laser beamed from the fiber laser marker for a predetermined time and a predetermined jump time lapses, the controller 50 outputs an electrical signal to the optical pump 52. The optical pump 52 outputs an optical signal depending on the electrical signal to the laser medium of the resonator 54. The electrical signal output by the controller 50 may be a continuous wave signal or a pulse signal. A type of the optical signal by the optical pump 52 depends upon the type of the electrical signal. The controller 50 outputs the electrical signal to the comparator 58 at the same time when outputting the electrical signal to the optical pump 52.

[42] In operation 105, the optical sensor 56 detects the laser beam emitted from the resonator 54 and outputs a laser beam detection signal to the comparator 58.

[43] In operation 106, the comparator 58 calculates a delay time between when the controller 50 outputs the electrical signal to the optical pump 52 and when the laser beam detection signal is received from the optical sensor 56 and outputs the delay time to the controller 50.

[44] In operation 107, it is determined whether icount is n+1.

[45] If it is determined that icount is not n+1, that is, smaller than n+1, the method proceeds to operation 103. If it is determined that icount is n+1, the measurement of time delays depending on jump times is ended. The controller 50 stores the time delays depending on the jump times as a lookup table.

[46] FIG. 8 is a graph showing a result of the measurement of delay times depending on jump times of FIG. 7. Referring to FIG. 8, the horizontal axis indicates jump time, and the vertical axis indicates delay time. The longer the jump time is, the longer the delay time is. Jump times not actually measured may be calculated by interpolation method.

[47] FIG. 9 is a flowchart illustrating a marking method using the fiber laser marker, according to a second embodiment of the present invention. FIG. 10 is a timing diagram for illustrating the marking method of FIG. 9.

[48] Referring to FIGS. 9 and 10, when the optical pump 52 is driven by an electrical signal during laser marking (i.e., a duration between t0 and tl), an optical signal is output in synchronization with the electrical signal. The optical signal is input to the resonator 54, and almost simultaneously, a laser beam is emitted from the resonator 54. At the same time when the laser beam is emitted, the mirror of the Galvano scanner 6 is moved to perform marking. The duration between t0 and tl denotes a marking section. At time tl, the mirror of the Galvano scanner 6 is moved to a next marking location, in operation 201. When the fiber laser marker tries to move the mirror of the Galvano scanner 6 to a next marking point at time tl, a jump time is generated. Firstly, the mirror of the Galvano scanner 6 is stabilized before moving. The time required for this stabilization is a first jump delay JDl (JDl = t2 - tl). Then, the mirror of the Galvano scanner 6 is moved to a predetermined location during a duration between t2 and t3 and then stabilized again. The time required for this second stabilization is a second jump delay JD2 (JD2 = t4 - 13). After the lapse of the second jump delay JD2, the Galvano scanner 6 is ready for another marking. In other words, the Galvano scanner 6 is ready for marking at time t4.

[49] In operation 202, when the mirror of the Galvano scanner 6 is moved to a marking location, a time for which the fiber laser marker is in an off state before being re- operated, that is, a jump time (t4 - tl), is calculated.

[50] In operation 203, a delay time TD depending on the jump time (t4 - tl) is obtained from a lookup table that stores previously calculated delay times. In FIG. 10, the delay time TD is t5 - 14. Jump times not actually measured may be calculated by interpolation. In operation 204, the optical pump 52 is driven.

[51] In operation 205, the scanner 6 is driven after the lapse of the delay time TD, and simultaneously, a laser beam is emitted from the fiber laser marker. Hence, the operation of the scanner 6 occurs concurrently with the emission of the laser beam.

[52] FIG. 11 is a photograph of a result of marking achieved according to the marking method of FIG. 9. Referring to FIG. 11, when another marking is performed after a jump time, even an initial portion of a character (number or symbol) is precisely marked. In other words, even when a jump time is generated, driving of a scanner mirror synchronizes with emission of a laser beam.

[53] FIG. 12 is a flowchart illustrating a marking method using the fiber laser marker, according to a third embodiment of the present invention. FIG. 13 is a timing diagram for illustrating the marking method of FIG. 12.

[54] Referring to FIGS. 12 and 13, a period between tO and tl denotes a section where a marking is performed. In operation 301, at time tl, the mirror of the Galvano scanner 6 is moved to a location for a next marking. When the fiber laser marker tries to move the mirror of the Galvano scanner 6 to a next marking point at time tl, a jump time is generated. More specifically, the mirror of the Galvano scanner 6 is stabilized before moving. The time required for this stabilization is a first jump delay JDl (JDl = t2 - tl). Then, the mirror of the Galvano scanner 6 is moved to a predetermined location during a duration between t2 and t3 and then stabilized again. The time required for this second stabilization is a second jump delay JD2 (JD2 = t4 - 13). After the lapse of the second jump delay JD2, the Galvano scanner 6 is ready for another marking. In other words, the Galvano scanner 6 is ready for marking at time t4. Afterwards, the mirror of the Galvano scanner 6 is moved to a point where the next marking starts, in operation 301.

[55] In operation 302, a time (t4 - tl) for which the mirror of the Galvano scanner 6 is moved to the location for the next marking before starting the next marking is calculated. In operation 303, a delay time depending on the jump time (t4 - tl), which corresponds to the scanner moving time (t4 - tl), is obtained from a lookup table that stores previously calculated delay times.

[56] In operation 304, the optical pump 52 is driven for a pulse acceleration (PA) time

(t7 - 16), which is shorter than the scanner moving time (t4 - tl), and then stopped. At this time, a laser beam is not emitted from the fiber laser marker. The ending point of the PA time is at time t7, which is obtained by subtracting a predetermined time, for example, one cycle of a modulation frequency, from the time t4 when the delay time ends.

[57] In operation 305, the optical pump 52 is re-driven after the lapse of the jump time

(t4 - tl), and simultaneously, the next marking resumes. In other words, because the laser beam is emitted from the fiber laser marker without delay due to the PA time at time t4, and the scanner 6 is in an operation state at time t4, the operation of the scanner 6 occurs concurrently with the emission of the laser beam. Consequently, marking is smoothly executed. Compared with the second embodiment of FIG. 10, the next marking resumes without the delay time TD of the scanner shown in FIG. 10, so that the marking can be shortened. Industrial Applicability

[58] In a marking method of a fiber laser marker as described above, a delay time of a laser beam emitted from a resonator can be easily measured. Furthermore, the laser beam is irradiated onto an object driving the Galvano scanner in consideration of the measured delay time. Thus, an initial portion not to be marked by a conventional method can be marked by the present marking method.

[59] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims

[1] A marking method of a fiber laser marker, the fiber laser marker including an optical pump outputting an optical signal to a resonator, and a Galvano scanner scanning at a predetermined location with a laser beam emitted from the resonator, the marking method comprising: measuring a delay time for which the output of the laser beam is delayed, the delay time depending on a jump time between when the optical signal is output to the resonator and when the laser beam is emitted from the resonator; moving a mirror of the Galvano scanner to a starting point of a next marking; calculating the jump time for which the mirror of the Galvano scanner is moved to the starting point of the next marking; calculating the delay time depending on the jump time; driving the optical pump to apply the optical signal to the resonator, and making the mirror of the Galvano scanner stand by for the delay time; and driving the mirror of the Galvano scanner and performing the marking, wherein the laser beam delayed for the delay time is emitted synchronously with the driving of the mirror of the Galvano scanner.

[2] The marking method of claim 1, wherein the measuring of the delay time comprises: disposing a laser beam detection device at a position where the laser beam from the resonator is irradiated; determining n jump times; sending the optical signal to the resonator with the lapse of each of the n jump times; detecting the laser beam using the laser beam detection device; and calculating a delay time between when the laser beam is detected and when the optical signal is sent.

[3] The marking method of claim 2, wherein the measuring of the delay time further comprises making a lookup table with the delay times depending on the jump times, and the calculating of the delay time is referring to the lookup table.

[4] The marking method of claim 2, wherein the laser beam detection device is a photodiode.

[5] The marking method of claim 1, wherein the jump time is a sum of a first jump delay for which the mirror of the scanner is stabilized, a time for which the mirror is rotated to a predetermined location, and a second jump delay for which the rotated mirror is stabilized again.

[6] A marking method of a fiber laser marker, the fiber laser marker including an optical pump outputting an optical signal to a resonator, and a Galvano scanner scanning at a predetermined location with a laser beam emitted from the resonator, the marking method comprising: measuring a delay time for which the output of the laser beam is delayed, the delay time depending on a jump time between when the optical signal is output to the resonator and when the laser beam is emitted from the resonator; moving a mirror of the Galvano scanner to a starting point of a next marking; calculating the jump time for which the mirror of the Galvano scanner is moved to the starting point of the next marking; calculating the delay time depending on the jump time; driving the optical pump for a pulse acceleration time that is a first time shorter than the delay time; and performing the marking, while driving the optical pump and driving the mirror of the Galvano scanner when the jump time is passed, wherein the laser beam is emitted synchronously with the driving of the mirror of the Galvano scanner. [7] The marking method of claim 6, wherein the measuring of the delay time comprises: disposing a laser beam detection device at a position where the laser beam from the resonator is irradiated; determining n jump times; sending the optical signal to the resonator with the lapse of each of the n jump times; detecting the laser beam using the laser beam detection device; and calculating a delay time between when the laser beam is detected and when the optical signal is sent. [8] The marking method of claim 7, wherein the measuring of the delay time further comprises making a lookup table with the delay times depending on the jump times, and the calculating of the delay time is referring to the lookup table. [9] The marking method of claim 7, wherein the laser beam detection device is a photodiode. [10] The marking method of claim 7, wherein the jump time is a sum of a first jump delay for which the mirror of the scanner is stabilized, a time for which the mirror is rotated to a predetermined location, and a second jump delay for which the rotated mirror is stabilized again.