Laser marking device

Abstract

To provide a technique that maintains the color development (visibility) of laser marking and suppress an increase in the size, a reduction in reliability and an increase in costs of a laser marking device while increasing a printing speed.SOLUTION: A laser marking device includes: a laser oscillator; a beam shaping unit that shapes the laser beam; a scanning mirror that deflects the laser beam to an arbitrary position; and a focusing lens that focuses the laser beam onto a marking target. The laser marking device can emit the laser beam whose laser power density in a peripheral region of the cross-section of the laser beam focused on the marking target surface is equal to or greater than the laser power density required for marking on the target surface through color development or separation, and laser power density in a central region of the cross-section of the laser beam is lower than the laser power density required for marking.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a laser marking device. [Background technology]

[0002] A laser marking device scans a specified area using a laser beam, irradiating the surface of the object to be marked, such as a part or product, with the laser beam, and marks the surface of the object by foaming, condensing, carbonizing, coloring due to a chemical change, or by peeling off the surface of the object to be marked. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-288498 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to maintain the color development (visibility) of laser marking and increase the marking speed, it is conceivable to increase the laser output by increasing the laser pulse energy or repetition frequency. In that case, for example, the following problems are thought to arise.

[0005] When the laser output is increased, the amount of heat generated increases, so the size of the heat sink, fan, etc. also increases. A water cooling device may also be required. In order to increase the laser output, the output of the excitation semiconductor laser needs to be increased, and the size of the power supply unit for the excitation semiconductor laser needs to be increased. Furthermore, in order to increase the laser output, the resonator length needs to be increased. For these reasons, increasing the laser output leads to a larger laser, and since the laser size dominates the size of the laser marking device, this leads to an increase in the size of the laser marking device.

[0006] Increasing the output of the pumping semiconductor laser by increasing the laser output shortens the lifespan of the pumping semiconductor laser. In addition, an increase in laser output shortens the lifespan of optical components such as laser crystals, wavelength conversion crystals, mirrors, and lenses. This leads to a decrease in the reliability of the laser. Increasing the laser output requires a high-output pumping semiconductor laser and optical components compatible with high output, resulting in increased costs.

[0007] From this perspective, there is a need to maintain the color development (visibility) of laser marking, increase the printing speed, and prevent the laser marking device from becoming larger, becoming less reliable, and becoming more expensive. [Means for solving the problem]

[0008] According to the present invention, there is provided the following laser marking device. This laser marking device includes a laser oscillator, a beam shaping unit that shapes a laser beam, a scanning mirror that deflects the laser beam to an arbitrary position, and a focusing lens that focuses the laser beam on an object to be marked. The laser marking device is capable of irradiating a laser beam in which the laser power density of the peripheral portion of the cross section of the laser beam focused on the surface of the object to be marked is equal to or higher than the laser power density required for marking the object surface by color development or peeling, and the laser power density of the central portion of the cross section of the laser beam is lower than the laser power density required for marking. Effect of the Invention

[0009] According to the present invention, it is possible to provide a laser marking device that maintains the color development (visibility) of the laser marking, increases the printing speed, is small, highly reliable, and keeps costs down. Note that problems, configurations, and effects other than those described above will become clear from the description of the embodiment of the invention below. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 is a diagram showing the configuration of a laser marking device according to the prior art. [Diagram 2] FIG. 1 is a diagram showing the configuration of an example of a laser oscillator. [Diagram 3] FIG. 2 is a configuration diagram of an example of an elliptical ring beam shaping unit related to the technology of the present invention. [Figure 4A] 1A to 1C are diagrams showing an example of a cross-sectional shape and power density distribution of a laser beam. [Figure 4B] 1A to 1C are diagrams showing an example of a cross-sectional shape and power density distribution of a laser beam. [Figure 5A] 1A and 1B are diagrams showing an example of a cross-sectional shape and power density distribution of a typical laser beam. [Figure 5B] 1A and 1B are diagrams showing an example of a cross-sectional shape and power density distribution of a typical laser beam. [Figure 6] FIG. 11 is a configuration diagram of an example of a laser marking device according to a second embodiment. [Figure 7A] FIG. 13 is a diagram for explaining an example of a beam scanning method when an elliptical ring beam is used, showing an example of beam movement. [Figure 7B] FIG. 13 is a diagram for explaining an example of a beam scanning method when an elliptical ring beam is used, showing an example of a beam scan flow. [Figure 8A] 13A and 13B are diagrams for explaining the laser power reduction effect by an elliptical ring beam. [Figure 8B] 13A and 13B are diagrams for explaining the laser power reduction effect by an elliptical ring beam. [Figure 9] 1A and 1B are diagrams for explaining an example of a beam scanning method of an elliptical ring beam. [Figure 10] FIG. 2 is a diagram showing an example of the configuration of a controller. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment is an example for explaining the present invention, and appropriate omissions and simplifications are made for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural. In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings. When there are multiple components having the same or similar functions, they may be described by using the same reference numerals with different subscripts, or when there is no need to distinguish between these multiple components, the subscripts may be omitted.

[0012] First, an example of a conventional laser marking device will be described with reference to Figs. 1 and 2. As shown in Fig. 1, the laser marking device is composed of a laser oscillator 1, a beam expander 2 that expands the diameter of the laser beam emitted from the laser oscillator, a beam scanner 4, and a condenser lens 6 that condenses the laser beam 3 to a desired size on the surface of an object 5 to be marked. The beam scanner 4 includes a mirror (a scanning mirror for position control) and polarizes the laser beam 3 in a desired direction. The angle of the mirror can be adjusted by a rotation mechanism used to rotate the mirror. The rotation mechanism can be composed of an appropriate motor.

[0013] A laser oscillator generally used in a laser marking device is a pulsed laser that is oscillated using a short pulse generation method such as a Q-switch method. A configuration example of a UV (ultraviolet (UV)) Q-switched solid-state laser 7 is shown in FIG. 2. As shown in FIG. 2, this laser is composed of a laser resonator 11 consisting of a laser crystal 8 (YVO4 or Nd:YAG, etc.) for amplifying a fundamental wave (1064 nm), a Q-switch device 9 such as an acousto-optical element, and multiple mirrors 10, an excitation semiconductor laser 12 for optically exciting the laser crystal 8, a wavelength conversion crystal 13 that generates a second harmonic (532 nm) of the fundamental wave laser light, a wavelength conversion crystal 14 that generates a third harmonic (355 nm) of the fundamental wave laser light, and a cooling device 15 that cools the laser. A laser beam 16 is output from this laser.

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. First Embodiment The configuration of the laser marking device of this embodiment is almost the same as the configuration shown in FIG. 1, but an elliptical ring beam shaping unit is disposed after the beam expander 2 shown in FIG.

[0015] An example of the configuration of the elliptical ring beam shaping unit will be described with reference to Fig. 3. As shown in Fig. 3, the elliptical ring beam shaping unit 25 is composed of the following optical components. That is, the elliptical ring beam shaping unit 25 includes an axicon lens 20, a collimating lens 21, a cylindrical condensing lens 22, and a collimating lens 23. Note that the collimating lens 23 can be, for example, a cylindrical collimating lens.

[0016] In the elliptical ring beam shaping unit 25, first, a circular ring beam is formed from the incident beam 19 using the axicon lens 20, and then the beam is collimated by the collimator lens 21. Next, the collimated circular ring beam is converted into an elliptical ring beam by the cylindrical condenser lens 22, and then further converted into a collimated elliptical ring beam 24 by the collimator lens 23.

[0017] The power density distribution of the elliptical ring beam in this case is shown in Figure 4A. As shown in Figure 4A, the power density distribution of the cross-sectional shape of the laser beam (more specifically, the peripheral part of the cross-sectional shape) is a Gaussian distribution. Here, by placing a homogenizer in front of the axicon lens 20, the power density of the elliptical ring beam can be made uniform (uniformly distributed) as shown in Figure 4B.

[0018] As shown in Figures 5A and 5B, the cross section 17 of the laser beam irradiated onto the surface of the object to be marked in a typical laser marking device is circular, and the power density distribution within the cross section of the laser beam is a Gaussian distribution or a uniform distribution.

[0019] When the power density of the irradiated laser is equal to or greater than the power density (sometimes called threshold power density) required to color or peel off the surface of the object to be marked, the object to be marked 5 is marked by coloring or peeling off at the irradiated area.

[0020] 4A and 4B, the total power of the laser beam can be reduced by marking using a laser beam in which the laser power density in peripheral portion 18a of the cross section of the laser beam focused on the surface of the object to be marked is equal to or greater than the power density required for marking (i.e., the threshold power density) and the laser power density in central portion 18b of the cross section of the laser beam is lower than the laser power density required for marking. Here, the magnitude of the power density lower than the threshold power density and the area of ​​the region having that power density must be such that the visibility of the marking is not deteriorated.

[0021] <Second embodiment> Next, a second embodiment will be described. Descriptions similar to those of the above embodiment may be omitted. A configuration diagram of an example of a laser marking device of this embodiment is shown in FIG. 6. By using an elliptical ring beam, the marking line width becomes wider, enabling high-speed marking. However, when marking is performed by polarizing the elliptical ring beam using a beam scanner 4, the elliptical ring beam has a disadvantage that the marking line width differs depending on the beam scanning direction because the elliptical ring beam is rotationally asymmetric.

[0022] To solve this problem, as shown in Fig. 7A, it is necessary to rotate the elliptical ring beam shaping unit 25 so that the major axis direction of the elliptical ring beam 24 becomes perpendicular to the beam scan direction 27. Note that the rotating part may be the entire elliptical ring beam shaping unit 25 or only two lenses, the cylindrical condenser lens 22 and the collimator lens 23.

[0023] Rotation control of the elliptical ring beam 24 is performed using a rotation control unit 26, which is configured using, for example, a rotation mechanism including an appropriate motor. Next, an example of elliptical ring beam scanning will be described with reference to Fig. 7B.

[0024] The laser marking device includes a controller (not shown) for control purposes, and the controller first creates the coordinates of a marking pattern (S101).

[0025] Next, the controller creates beam scan direction 27 and scan sequence data based on the coordinates created in S101 (S102).

[0026] Next, the controller creates beam rotation angle data for the beam scan direction 27. Here, the controller acquires the beam scan direction 27 in S102, and based on that data, determines the rotation angle of the elliptical ring beam shaping unit 25 or a part thereof so that the major axis direction of the elliptical ring beam 24 is perpendicular to the beam scan direction 27 (S103).

[0027] Then, the controller performs marking by controlling the polarization direction of the beam with the beam scanner 4 so as to scan along the beam scan direction 27. Here, by rotating the elliptical ring beam shaping unit 25 or a part thereof using the rotation angle data obtained in S103, a beam rotation angle 28 is formed, enabling marking as shown in Fig. 7A, and even if scanning along the beam scan direction 27 using the elliptical ring beam 24, marking with a uniform marking line width becomes possible (S104).

[0028] <Third embodiment> Next, a third embodiment will be described. Descriptions similar to those of the above embodiments may be omitted. When reducing the laser power, if the laser power can be reduced to 1 / 2 or less, it is expected to have a significant effect on reducing the size of the laser, improving reliability, and reducing costs.

[0029] For simplicity's sake, if the power density distribution of the beam is uniform, an elliptical ring beam (Figure 8B) with the same outer circumference as the elliptical beam shown in Figure 8A (major axis radius (semi-major axis): r1, minor axis radius (minor axis): r2) and with a total beam power of less than half, can be obtained by simply satisfying the following conditions. (r1 r2 - r3 r4)≦r1 r2 / 2 Here, the power density inside the ring is assumed to be zero. In Fig. 8A, an elliptical beam is shown with a major axis length of 2·r1 and a minor axis length of 2·r2. In Fig. 8B, the radius of the major axis (major axis) on the inner side of the beam is r3 and the radius of the minor axis (minor axis) is r4, and an elliptical ring beam is shown with a major axis length of 2·r3 and a minor axis length of 2·r4 on the inner side of the beam.

[0030] <Fourth embodiment> Next, a fourth embodiment will be described. The same description as the above embodiment may be omitted. If the low power density region inside the ring is large, the visibility of the marking pattern may be deteriorated due to the increase in the area not marked. Therefore, in this embodiment, the scan described below is performed.

[0031] FIG. 9 shows an example of scanning using an elliptical ring beam. As shown in the enlarged portion of FIG. 9, the beam is scanned so that the high power density region of the irradiated beam overlaps the low power density region of the beam irradiated one before. In other words, when the laser marking device continuously irradiates the elliptical ring beam 24 along the beam scanning direction 27 on the surface of the marking object 5, the current elliptical ring beam 24 is irradiated so that the high power density region partially overlaps the portion corresponding to the low power density region of the previous elliptical ring beam 24 in the perpendicular direction to the beam scanning direction 27. In this way, if the coloring or peeling is insufficient in the low power density region inside the ring, the next irradiated beam can cause the inside of the ring to be colored or peeled. Therefore, the deterioration of visibility can be suppressed.

[0032] As a method of performing the scan described in the fourth embodiment, for example, there is a method of scanning along the beam scan direction 27 while vibrating in a direction perpendicular to the beam scan direction 27. In addition, there is a method of scanning along the beam scan direction 27 while changing the sizes of the high power density region and the low power density region by making the output of the elliptical ring beam different from the previous time.

[0033] In the embodiment, an example of irradiating an elliptical ring beam has been specifically described, but a circular laser beam may also be irradiated, and the laser marking device may be configured to irradiate a laser beam having a circular cross-sectional shape, a laser power density in the peripheral portion of the cross-section of the laser beam that is equal to or greater than the power density required for marking, and a laser power density in the central portion of the cross-section of the laser beam that is lower than the laser power density required for marking.

[0034] From the above explanation, the following laser marking device is provided. This laser marking device is equipped with a laser oscillator 1, a beam shaping unit 25 that shapes the laser beam, a position control scanning mirror that deflects the laser beam 3 to an arbitrary position, and a focusing lens 6 that focuses the laser beam 3 on a marking object 5. The laser power density of the peripheral portion of the cross section of the laser beam 3 focused on the surface of the marking object is equal to or higher than the laser power density required for marking the object surface by color development or peeling, and the laser power density of the central portion of the cross section of the laser beam 3 is lower than the laser power density required for marking.

[0035] The laser oscillator may be a pulsed laser oscillator.

[0036] Furthermore, the cross-sectional shape of the laser beam 3 focused on the surface of the marking object may be substantially elliptical. In this case, the marking line width can be made thicker than when the cross-sectional shape is circular.

[0037] The laser beam scanning method may further include a rotation mechanism that rotates an elliptical laser beam so that the cross-sectional shape of the laser beam focused on the surface of the object to be marked is substantially elliptical and the major axis direction of the laser beam is always perpendicular to the moving direction of the laser beam on the surface of the object to be marked controlled by the scanning mirror.

[0038] In addition, the laser marking device may be capable of irradiating a laser beam in which the cross-sectional shape and the area enclosed by the outer periphery of the cross-section of the laser beam are the same as those of a laser beam having a Gaussian distribution or a uniform distribution of laser power density when focused on the surface of the object to be marked, and the power of the laser beam is 1 / 2 or less.

[0039] Also, the laser marking device may irradiate with a high power density region of the laser beam a portion of the surface of the object to be marked that has been irradiated with a low power density region of the previous laser beam in scanning the laser beam on the surface of the object to be marked controlled by the scanning mirror. Also, this laser beam scanning method may be provided.

[0040] Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and includes various modifications and equivalent configurations within the spirit of the appended claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. In addition, for example, other configurations may be added, deleted, or replaced with respect to part of the configuration of the embodiment.

[0041] The controller is used to control the operation of the laser marking device and is appropriately configured, and as an example, can be configured to include a processing device 29 and a storage device 30 as shown in Fig. 10. The processing device 29 is an entity that executes predetermined processing, and can be configured, for example, using an appropriate processor (as an example, a CPU). The storage device 30 stores data such as programs used in the predetermined processing, and can be configured, for example, using a RAM (Random Access Memory), a ROM (Read Only Memory), etc.

[0042] The laser marking device may be configured to be connectable to an appropriate computer such as a personal computer (PC), etc. Then, a user may operate the computer, data relating to the operation may be output to a controller, and the controller may perform control based on the acquired data. [Explanation of symbols]

[0043] 1: Laser oscillator 2: Beam expander 3: Laser beam 4: Beam scanner 5: Marking object 6: Condenser lens 7:UV Q-switched solid-state laser 8: Laser crystal 9: Q-switch device 10: Mirror 11: Laser resonator 12: Excitation semiconductor laser 13: Wavelength conversion crystal for second harmonic generation 14:3 Wavelength conversion crystal for harmonic generation 15: Cooling device 16: Laser beam 17: Laser beam cross-sectional shape 18: Laser beam cross-sectional shape on the surface of the object to be marked 19: Laser beam 20: Axicon lens 21: Collimating lens 22: Cylindrical focusing lens 23: Collimating lens 24: Elliptical ring beam 25: Elliptical ring beam shaping section 26: Rotation control section 27: Beam scan direction 28: Beam rotation angle 29: Processing device 30: Storage device

Claims

1. A laser marking device, comprising: A laser oscillator; A beam shaping unit that shapes a laser beam; A scanning mirror that deflects the laser beam to any position; a focusing lens for focusing the laser beam on the object to be marked; Equipped with The laser marking device is It is possible to irradiate a laser beam having a laser power density at the peripheral portion of the cross section of the laser beam focused on the surface of the object to be marked that is equal to or higher than the laser power density required for marking the surface of the object by color development or peeling, and a laser power density at the central portion of the cross section of the laser beam that is lower than the laser power density required for marking. A laser marking device characterized by:

2. 2. The laser marking device according to claim 1, The laser oscillator includes: It is a pulsed laser oscillator. A laser marking device characterized by:

3. 2. The laser marking device according to claim 1, The laser marking device is It is possible to emit a laser beam having a cross-sectional shape of a substantially ellipse. A laser marking device characterized by

4. 2. The laser marking device according to claim 1, The laser marking device is a rotation control unit that rotates the laser beam so that the cross-sectional shape of the laser beam focused on the surface of the object to be marked is substantially elliptical and the major axis direction of the laser beam is always perpendicular to the moving direction of the laser beam on the surface of the object to be marked controlled by the scanning mirror; A laser marking device characterized by:

5. 2. The laser marking device according to claim 1, The laser marking device is It is possible to irradiate a laser beam having a cross-sectional shape and an area surrounded by the outer periphery of the cross section of the laser beam that is the same as that of a laser beam having a Gaussian distribution or a uniform distribution of laser power density when focused on the surface of the object to be marked, and the power of the laser beam is 1 / 2 or less. A laser marking device characterized by:

6. 2. The laser marking device according to claim 1, The laser marking device is In scanning the laser beam on the surface of the object to be marked by the laser beam controlled by the scanning mirror, a high power density region of the laser beam is irradiated on a portion of the surface of the object to be marked that was irradiated by a low power density region of the previous laser beam. A laser marking device characterized by:

Images