Source: http://www.google.com/patents/US7813404?dq=5319712
Timestamp: 2017-04-25 16:11:29
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Patent US7813404 - Laser processing apparatus and solid laser resonator - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsTo provide a laser processing apparatus compatible with increase in the output of the pumping light source without increasing the reflectance of the output mirror. A solid laser medium for generating laser oscillation when pumping light from an pumping light source enters through two end surfaces, a...http://www.google.com/patents/US7813404?utm_source=gb-gplus-sharePatent US7813404 - Laser processing apparatus and solid laser resonatorAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7813404 B2Publication typeGrantApplication numberUS 12/042,758Publication dateOct 12, 2010Filing dateMar 5, 2008Priority dateMar 15, 2007Fee statusPaidAlso published asUS20080225917Publication number042758, 12042758, US 7813404 B2, US 7813404B2, US-B2-7813404, US7813404 B2, US7813404B2InventorsMasao SatoOriginal AssigneeKeyence CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (16), Referenced by (4), Classifications (16), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetLaser processing apparatus and solid laser resonator
US 7813404 B2Abstract
a laser control portion including a laser pumping portion for generating a laser beam;
an pumping light transfer medium for transferring a laser beam generated by said laser control portion; and
a laser output portion including a laser beam scanning system for performing scanning with a laser beam transferred through said pumping light transfer medium, wherein
said laser output portion includes:
a crystal solid laser medium extending in one direction, has two end surfaces and generates laser oscillation when pumping light from said laser pumping portion through said pumping light transfer medium enters through said two end surfaces;
a splitting part for splitting pumping light outputted from said laser pumping portion into two paths so that different pumping components of pumping light enter through said respective end surfaces of said solid laser medium along said respective split paths;
dichroic mirrors placed along said split paths in such a manner as to face said respective end surface, allow pumping light to transmit and reflect laser oscillation light toward said end surfaces;
an output mirror placed in such a location as no-interference with said split paths and oriented in a direction approximately perpendicular to said laser oscillation light, and outputs said laser oscillation light from said dichroic mirrors; and
condenser lenses placed along said split paths in such a manner as to face said dichroic mirrors and condense pumping light that transmits through said dichroic mirrors so that the diameter of the spot where said end surfaces of said solid laser medium are pumped becomes smaller than in the TEM00 mode of said solid laser medium, and is formed so that pumping light enters through said respective end surfaces of said solid laser medium and said solid laser medium is pumped, wherein said laser beam scanning system in said laser output portion includes:
a Z axis scanner which has a lens through which light enters and a lens through which light is emitted, and can adjust the focal distance of said laser beam by changing the relative distance between said lens through which light enters and said lens through which light is emitted along said optical axes of said laser light emitted from said laser pumping portion and said lenses through which light enters and is emitted in such a state that these optical axes coincide;
an X axis scanner or Y axis scanner for performing scanning with a laser beam which transmits through Z axis scanner in the direction of the X or Y axis; and
a Y axis scanner or X axis scanner for performing scanning with said laser beam with which the X axis scanner or Y axis scanner performs scanning in the direction of the Y or X axis.
a crystal solid laser medium extending in one direction, has two end surfaces and generates laser oscillation when pumping light from said laser pumping portion through said pumping light transfer medium enters through said two end surfaces, where said end surfaces are
a first end surface which forms a surface through which pumping light enters, and
a second end surface which is on the opposite side to said first end surface and forms a surface through which pumping light enters and is emitted;
a splitting part for splitting pumping light outputted from said laser pumping portion into a first split path and a second split path, in such a manner said first and second pumping components of pumping light enter said first and second end surfaces of said solid laser medium through said first and second split paths, respectively;
a first dichroic mirror which is placed along said first split path in such a manner as to face said first end surface, allows pumping light to transmit, and reflects laser oscillation light toward said first end surface side;
a second dichroic mirror which is placed along said second split path in such a manner as to face said second end surface, allows pumping light to transmit, and reflects laser oscillation light;
an output mirror placed in such a location as no-interference with said split paths and oriented in a direction approximately perpendicular to said laser oscillation light, inputs and outputs light reflected from said second dichroic mirror;
a first condenser lens placed along said first split path in such a manner as to face said first dichroic mirror and condense a first pumping component of pumping light that transmits through said first dichroic mirror in such a manner that the diameter of the spot where said first end surface is pumped becomes smaller than in the TEM00 mode of said solid laser medium; and
a second condenser lens placed along said second split path in such a manner as to face said second dichroic mirror and condense a second pumping component of pumping light that transmits through said second dichroic mirror in such a manner that the diameter of the spot where said second end surface is pumped becomes smaller than in the TEM00 mode of said solid laser medium, and is formed so that said first and second pumping components of pumping light enter through said first and second end surfaces of said solid laser medium and said solid laser medium is pumped, wherein said splitting part splits entering light into said first pumping component and said second pumping component at a ratio set to approximately 2:1 to 4:1.
3. The laser processing apparatus according to claim 2, wherein the reflectance of said output mirror is 30% to 70%.
4. The laser processing apparatus according to claim 2, wherein said laser pumping portion comprises a semiconductor laser and pumping light emitted from said semiconductor laser is not polarized.
5. The laser processing apparatus according to claim 2, wherein a Q switch is provided between said output mirror and said second dichroic mirror.
6. The laser processing apparatus according to claim 2, wherein said laser output portion further includes:
a first reflecting mirror for reflecting said first or second pumping component resulting from said split by said splitting part approximately perpendicularly;
a second reflecting mirror for further reflecting said light reflected from said first reflecting mirror or said second or first pumping component resulting from said split by said splitting part in an approximately perpendicular direction; and
a third reflecting mirror for reflecting said light reflected from said second reflecting mirror approximately perpendicularly, wherein
said split paths, including said first and second split paths, said splitting part and said first, second and third reflecting mirrors, are formed in rectangular form, said solid laser medium and said first and second dichroic mirrors are placed on any side of said rectangular form, and the arrangement allows pumping light from said laser pumping portion to enter through any apex of said rectangular form and a line extending from either side of said rectangular form which includes said apex.
7. The laser processing apparatus according to claim 2, further comprising:
an pumping light coupling part for optically coupling said pumping light transfer medium to said splitting part; and
an aperture which is located between said second dichroic mirror and said output mirror and reshapes laser oscillation light.
8. The laser processing apparatus according to claim 2, wherein said laser beam scanning system in said laser output portion includes:
9. A solid laser resonator, comprising:
a pumping light source for generating pumping light;
a crystal solid laser medium which extends in one direction, has two end surfaces and generates laser oscillation when pumping light from said pumping light source enters through said two end surfaces;
a splitting part for splitting pumping light outputted from said pumping light source into two paths in such a manner that different pumping components of pumping light enter through the respective end surfaces of said solid laser medium along the respective split paths;
dichroic mirrors which are placed along said split paths in such a manner as to face the respective end surfaces, allow pumping light to transmit, and reflect laser oscillation light toward said end surfaces;
an output mirror which is placed in such a location as no-interference with said split paths and oriented in a direction approximately perpendicular to said laser oscillation light, and outputs laser oscillation light from said dichroic mirrors; and
condenser lenses which are placed along said split paths in such a manner as to face said dichroic mirrors and condense pumping light that transmits through said dichroic mirrors in such a manner that the diameter of the spot where said end surfaces of said solid laser medium are irradiated is smaller than in the TEM00 mode of said solid laser medium, and being formed so that pumping light enters the respective end surfaces of said solid laser medium and said solid laser medium is pumped, wherein said splitting part splits entering light into said first pumping component and said second pumping component at a ratio set to approximately 2:1 to 4:1.
10. A laser processing apparatus, comprising:
a pumping light transfer medium for transferring a laser beam generated in said laser control portion; and
a first end surface which forms a surface through which said pumping light enters, and
a second end surface which is on the opposite side to said first end surface and forms a surface through which said pumping light enters and is emitted;
a splitting part for splitting pumping light outputted from said laser pumping portion into a first split path and a second split path, in such a manner that first and second pumping components of pumping light enter through said first and second end surfaces of said solid laser medium through said first and second split paths, respectively, and said first pumping component being larger than said second pumping component;
a second dichroic mirror which is placed along said second split path in such a manner as to face said second end surface, allows pumping light to transmit, and reflects laser oscillation light; and
an output mirror placed in such a location as no-interference with said split paths and oriented in a direction approximately perpendicular to laser oscillation light, inputs and outputs light reflected from said second dichroic mirror, and is formed so that said first and second pumping components of pumping light enter said first and second end surfaces of said solid laser medium respectively, and said solid laser medium is pumped; and wherein said laser beam scanning system in said laser output portion further includes:
a Z axis scanner which has a lens through which light enters and a lens through which light is emitted, and adjust the focal distance of said laser beam by changing the relative distance between said lens through which light enters and said lens through which light is emitted along the optical axes of said laser light emitted from said laser pumping portion and said lenses through which light enters and is emitted in such a state that these optical axes coincide;
11. The laser processing apparatus according to claim 10, wherein the ratio with which said splitting part splits entering light into said first pumping component and said second pumping component is set to approximately 2:1.
12. The laser processing apparatus according to claim 10, wherein a Q switch is provided between said output mirror and said second dichroic mirror.
13. The laser processing apparatus according to claim 10, comprising:
a first condenser lens which is placed along said first split path in such a manner as to face said first dichroic mirror and condenses pumping light that transmits through said first dichroic mirror so that the diameter of the spot where said first end surface is irradiated with said first pumping component becomes smaller than in the TEM00 mode of said solid laser medium; and
a second condenser lens which is placed along said second split path in such a manner as to face said second dichroic mirror and condenses pumping light that transmits through said second dichroic mirror so that the diameter of the spot where said second end surface is irradiated with said second pumping component becomes smaller than in the TEM00 mode of said solid laser medium.
14. The laser processing apparatus according to claim 10, wherein
said laser output portion further includes:
15. The laser processing apparatus according to claim 10, further comprising:
a pumping light coupling part for optically coupling said pumping light transfer medium to said splitting part; and
an aperture, which is located between said second dichroic mirror and said output mirror, that reshapes laser oscillation light.
16. A laser processing apparatus, comprising:
a crystal solid laser medium which extends in one direction, has two end surfaces and generates laser oscillation when pumping light from said laser pumping portion enters through said two end surfaces, where said end surfaces are
a second end surface which is on the side opposite to said first end surface and forms a surface through which pumping light enters and is emitted;
a splitting part for splitting pumping light outputted from said laser pumping portion into a first split path and a second split path, so that first and second pumping components of pumping light enter through said first and second end surfaces of said solid laser medium through said first and second split paths, respectively;
a second reflecting mirror for further reflecting said light reflected from said first reflecting mirror or said second or first pumping component resulting from said split by said splitting part in an approximately perpendicular direction;
a third reflecting mirror for reflecting said light reflected from said second reflecting mirror approximately perpendicularly;
an output mirror which is placed in such a location as no-interference with said split paths and oriented in a direction approximately perpendicular to laser oscillation light, inputs and outputs light reflected from said second dichroic mirror, and is formed so that said solid laser medium and said first and second dichroic mirrors form a laser pumping portion, said first and second pumping components of pumping light enter said first and second end surfaces of said solid laser medium respectively, and said solid laser medium is pumped, and
said split paths, including said first and second split paths, said splitting part and said first, second and third reflecting mirrors, are formed in rectangular form, said solid laser medium and said first and second dichroic mirrors are placed on any side of said rectangular form, and the arrangement allows pumping light from said laser pumping portion to enter through any apex of said rectangular form and a line extending from either side of said rectangular form which includes said apex, and wherein said laser light scanning system in said laser output portion further includes:
a Z axis scanner which has a lens through which light enters and a lens through which light is emitted, and can adjust said focal distance of said laser beam by changing the relative distance between said lens through which light enters and said lens through which light is emitted along said optical axes of said laser light emitted from said laser pumping portion and said lenses through which light enters and is emitted in such a state that these optical axes coincide;
17. The laser processing apparatus according to claim 16, wherein
said splitting part splits pumping light from said laser pumping portion into a first pumping component which transmits in the direction in which said pumping light goes, and a second pumping component which is reflected at an approximately right angle relative to the straight direction in which said first pumping component goes,
said first reflecting mirror reflects said first pumping component which goes straight from said splitting part at an approximately right angle so that said first pumping component transmits through said first dichroic mirror and enters through said first end surface of said solid laser medium,
said second reflecting mirror reflects said second pumping component at an approximately right angle so that said second pumping component goes in a direction approximately parallel to the straight direction in which said first pumping component goes,
said third reflecting mirror reflects said light of said second pumping component which is reflected from said second reflecting mirror at an approximately right angle so that said reflected light transmits through said second dichroic mirror and enters through said second end surface of said solid laser medium, and
said light of said first pumping component which is reflected from said first reflecting mirror and said light of said second pumping component which is reflected from said third reflecting mirror are adjusted so as to face each other along the same axial line.
18. The laser processing apparatus according to claim 16, wherein
said splitting part splits pumping light from said laser pumping portion into a second pumping component which transmits in the direction in which said pumping light goes, and a first pumping component which is reflected at an approximately right angle relative to the straight direction in which said second pumping component goes,
said first reflecting mirror reflects said first pumping component which is reflected from said splitting part at an approximately right angle so that said first pumping component transmits through said first dichroic mirror and enters through said first end surface of said solid laser medium,
said second reflecting mirror reflects said second pumping component which goes straight from said splitting part at an approximately right angle,
19. The laser processing apparatus according to claim 16, wherein
said splitting part splits pumping light from said laser pumping portion into a first pumping component which transmits in the direction in which said pumping light goes, and a second pumping component which is reflected at an approximately right angle relative to the straight direction in which said first pumping component goes so that said first pumping component transmits through said first dichroic mirror and enters through said first end surface of said solid laser medium,
said first reflecting mirror reflects said second pumping component which is reflected from said splitting part at an approximately right angle at an approximately right angle,
said second reflecting mirror reflects light of said second pumping component which is reflected from said first reflecting mirror at an approximately right angle,
said transmitting light of said first pumping component which is split by said splitting part and said light of said second pumping component which is reflected from said third reflecting mirror are adjusted so as to face each other along the same axial line.
20. The laser processing apparatus according to claim 16, wherein
said splitting part splits pumping light from said laser pumping portion into a second pumping component which transmits in the direction in which said pumping light goes, and a first pumping component which is reflected at an approximately right angle relative to the straight direction in which said second pumping component goes so that said first pumping component transmits through
said first dichroic mirror and enters through said first end surface of said solid laser medium,
said first reflecting mirror reflects said second pumping component which transmits through said splitting part at an approximately right angle,
said first pumping component which is split by said splitting part and said light of said second pumping component which is reflected from said third reflecting mirror are adjusted so as to face each other along the same axial line.
21. The laser processing apparatus according to claim 16, wherein
said splitting part splits pumping light from said laser pumping portion into a first pumping component which transmits in the direction in which said pumping light goes, and a second pumping component which is reflected at an approximately right angle relative to the straight direction in which said first pumping component goes so that said second pumping component transmits through said second dichroic mirror and enters through said second end surface of said solid laser medium,
said first reflecting mirror reflects said first pumping component which transmits through said splitting part at an approximately right angle,
said second reflecting mirror reflects light of said first pumping component which is reflected from said first reflecting mirror at an approximately right angle,
said third reflecting mirror reflects said light of said first pumping component which is reflected from said second reflecting mirror at an approximately right angle so that said reflected light transmits through said first dichroic mirror and enters through said first end surface of said solid laser medium, and
said second pumping component which is split by said splitting part and said light of said first pumping component which is reflected from said third reflecting mirror are adjusted so as to face each other along the same axial line.
22. The laser processing apparatus according to claim 16, wherein
said splitting part splits pumping light from said laser pumping portion into a second pumping component which transmits in the direction in which said pumping light goes, and a first pumping component which is reflected at an approximately right angle relative to the straight direction in which said second pumping component goes so that said second pumping component transmits through said second dichroic mirror and enters through said second end surface of said solid laser medium,
said first reflecting mirror reflects said first pumping component which is reflected from said splitting part at an approximately right angle,
23. The laser processing apparatus according to claim 16, wherein
said second reflecting mirror reflects said light of said first pumping component which is reflected from said first reflecting mirror at an approximately right angle so that said reflected light transmits through said first dichroic mirror and enters through said first end surface of said solid laser medium,
said third reflecting mirror reflects said second pumping component which results from said split by said splitting part at an approximately right angle so that said second pumping component transmits through said second dichroic mirror and enters through said second end surface of said solid laser medium, and
said light of said first pumping component which is reflected from said second reflecting mirror and said light of said second pumping component which is reflected from said third reflecting mirror are adjusted so as to face each other along the same axial line.
24. The laser processing apparatus according to claim 16, wherein
25. The laser processing apparatus according to claim 16, wherein
said splitting part, said first reflecting mirror, said second reflecting mirror and said third reflecting mirror are placed in the same plane.
26. The laser processing apparatus according to claim 16, wherein
said split path, including said first and second split paths, is formed in rectangular form, and
said solid laser medium and said first and second dichroic mirrors are placed along either long side of said split path in rectangular form.
27. The laser processing apparatus according to claim 16, wherein
28. The laser processing apparatus according to claim 16, wherein
29. A laser processing apparatus, comprising:
a pumping light transfer medium for transferring a laser beam generated by said laser control portion; and
condenser lenses placed along said split paths in such a manner as to face said dichroic mirrors and condense pumping light that transmits through said dichroic mirrors and is formed so that pumping light enters through said respective end surfaces of said solid laser medium and said solid laser medium is pumped, and wherein said laser beam scanning system in said laser output portion includes:
30. The laser processing apparatus according to claim 29, wherein said splitting part splits said pumping light in such a manner that there is more of said first pumping component than said second pumping component.
31. The laser processing apparatus according to claim 30, wherein the ratio at which said splitting part splits entering light into said first pumping component and said second pumping component is set to approximately 2:1.
32. The laser processing apparatus according to claim 29, wherein the reflectance of said output mirror is 30% to 70%.
33. The laser processing apparatus according to claim 29, wherein said laser pumping portion comprises a semiconductor laser and pumping light emitted from said semiconductor laser is not polarized.
34. The laser processing apparatus according to claim 29, wherein a Q switch is provided between said output mirror and said second dichroic mirror. Description
In this technology, the diameter of the spot of pumping light (pump beam size) where the respective end surfaces of the solid laser medium are irradiated is slightly greater in size than the diameter in the TEM00 mode of the solid laser medium. In the case where the diameter of the spot of pumping light is small, there is a risk that pumping may become concentrated in a small area and pumping may not occur in deep portions of the solid laser medium, and thus a thermal lens or strong thermal lens effect may be generated. Therefore, the thermal lens effect can be reduced through pumping in a broad area.
FIG. 1 is a block diagram showing the configuration of the laser processing apparatus according to Embodiment 1 of the present invention;
The present invention will be described with reference to the drawings. Here, the embodiments described below illustrate a laser processing apparatus and a solid laser resonator for implementing the technological idea of the present invention, and the present invention does not limit the laser processing apparatus and solid laser resonator to those below. Further, the present specification by no means limits the members described in the claims to the members in the embodiments. Particularly, the dimensions, materials, form, relative arrangement and the like of the components described in the embodiments are not intended to limit those in the scope of the present invention unless otherwise stated, and are merely illustrative. Here, the dimensions and the positional relationship of the members shown in the figures may be exaggerated in order to make the illustration more clear. Furthermore, in the following description, the same names and symbols denote members which are the same or similar, and detailed description for these is omitted. Furthermore, in terms of the components of the present invention, a number of components may be formed of the same member so that one member has the function of the number of components in some embodiments, or the function of one member may be performed by a number of members.
FIG. 1 is a block diagram showing the configuration of a laser processing apparatus 100 according to Embodiment 1. The laser processing apparatus 100 shown in this diagram comprises a laser control portion 1 and a laser output portion 2. The laser control portion 1 forms a controller portion for controlling the laser output portion 2, and is optically connected to the laser output portion 2 through an pumping light transfer medium 3. Further, the laser output portion 2 outputs an output laser beam as a head portion for laser marking. This laser control portion 1 includes a laser pumping portion 10 which forms an pumping light source. Furthermore, an input portion 4 for inputting a process pattern when necessary and a display portion 5 for displaying screens of various settings are connected to the laser control portion 1. Meanwhile, the laser output portion 2 includes a laser resonant portion 20 for generating laser oscillation by entering the pumping light into the solid laser medium, and a laser beam scanning system 30 for scanning the surface of the object W to be processed (workpiece) with an outputted laser beam. A work region light condensing portion 40, for example an fθ lens, is placed on the output side of the laser beam scanning system 30 if necessary.
The input portion 4 is connected to the laser control portion 1, and allows the setting required to operate the laser processing apparatus 100 to be inputted and transmits it to the laser control portion 1. The contents of the setting are the conditions for operating the laser processing apparatus 100, the concrete contents of processing and the like. The input portion 4 is an input device, such as a keyboard, a mouse or a console. An additional display portion with which input information inputted through the input portion 4 is confirmed and which displays the state of the laser control portion 1 can be separately provided. A monitor, for example an LCD or cathode ray tube, can be used as the display portion 5. Further, in the case where a touch panel system is used, the display portion may be used as the input portion. Thus, the required settings for the laser processing apparatus 100 can be provided through the input portion without connecting to an external computer and the like.
The laser control portion 1 includes a control portion 50, a memory portion 52, a laser pumping portion 10 and a power supply circuit 54. The contents of the setting inputted through the input portion 4 are recorded in the memory portion 52. The control portion 50 reads the contents of the setting from the memory portion 52 if necessary, and operates the laser pumping portion 10 based on a processing signal corresponding to the contents of processing so that the solid laser medium 21 in the laser output portion 2 is excited. Semiconductor memories, such as RAMs and ROMs, can be used as the memory portion 52. Further, semiconductor memory cards, for example PC cards and SD cards (registered trademark) which can be built in or inserted into the laser control portion 1, as well as memory cards, for example card-type hard discs, can be used as the memory portion 52. The memory portion 52 formed of a memory card can be easily rewritten with an external device, such as a computer, so that the contents set by the computer are written into the memory card which is then set in the laser control portion 1, and thus, the setting can be initiated without connecting the input portion to the laser control portion. In particular, semiconductor memories provide high speed read-in and write-in of data, and no mechanically operating portions, and thus are tough against vibration, and therefore, can prevent accidental data erasure due to clashing, such as that which occurs in hard discs.
The laser pumping portion 10 includes an pumping light source 11 and an pumping light condensing portion 12 which are optically connected. An example of the laser pumping portion 10 is shown in the perspective view of FIG. 2. In the laser pumping portion 10 shown in this view, the pumping light source 11 and the pumping light condensing portion 12 are secured in an pumping casing 13. The pumping casing 13 is made of a metal having high thermal conductivity, such as copper, and efficiently releases heat from the pumping light source 11 to the outside. The pumping light source 11 is formed of a semiconductor laser (LD) or a lamp. In FIG. 2, an LD array or an LD bar where a plurality of LD elements are aligned in linear form is used, so that the laser oscillation from the respective elements is outputted in line shape. The emitting laser enters through the entrance surface of the pumping light condensing portion 12 and is outputted through the emission surface as a condensed laser pumping beam. The pumping light condensing portion 12 has a focusing lens and the like. The laser pumping beam from the pumping light condensing portion 12 enters the laser resonant portion 20 through an optical fiber 14 and the like. The pumping light source 11 and the pumping light condensing portion 12, as well as the optical fiber 14, are optically connected through space or an optical fiber. Further, an LD unit or an LD module in which such members are incorporated in advance can be used as the laser exciting portion 10. Here, an LD unit having an output of as high as 40 W to 50 W is used, and the pumping light is split by a splitting part. Furthermore, the pumping light emitted from the laser pumping portion 10 may be non-polarized light. Thus, it becomes unnecessary to take change in the state of polarization into consideration, and thus, the design is advantageous. In particular, it is preferable for the LD unit for bundling light gained from the respective LD elements in the LD array, where several tens of LD elements are aligned, by means of an optical fiber, and outputting light to be provided with a mechanism for converting the output light to non-polarized light. Alternatively, light may be in a non-polarized state (random polarization) during the process of transfer from the laser pumping portion 10 through an optical fiber cable, the process for optical coupling with a split path using an pumping light coupling part and the like in the configuration.
The laser pumping beam generated by the laser pumping portion 10 as described above is transferred to the laser output portion 2 through the pumping light transfer medium 3. An optical fiber cable or the like is used as the pumping light transfer medium 3. Further, the optical fiber 14 of the laser pumping portion 10 may be used as the pumping light transfer medium 3 as it is. The laser output portion 2 allows the laser pumping light to enter the laser resonant portion 20 so that the laser output beam is generated through laser oscillation, and at the same time, allows the laser beam scanning system 30 to scan a work region with the laser beam in a desired processing pattern.
The laser resonant portion 20 is a solid laser resonator or a laser oscillator unit for generating a laser beam by the laser oscillation. This laser resonant portion 20 includes an pumping light coupling part 22 for introducing pumping light from the pumping light source 11, a splitting part 23 for splitting pumping light introduced from the pumping light coupling part 22 into a first split path B1 and a second split path B2, a solid laser medium 21 into which pumping light enters through respective end surfaces from the first split path B1 and the second split path B2 and which is thus excited, a first dichroic mirror 24 and a second dichroic mirror 25 which are placed in such a manner as to face each other at a predetermined distance along the optical path of the induced emission light emitted by the solid laser medium 21, and an output mirror 26 which is placed in such a location as not to interfere with the split paths and outputs light reflected from the second dichroic mirror 25. Here, the first dichroic mirror 24 is referred to as a rear side mirror RM and the second dichroic mirror 25 is referred to as an emission side mirror FM. The rear side mirror RM is secured perpendicular to the direction in which the laser oscillation beam goes and the emission side mirror FM is secured diagonally at 45° relative to the direction of the entrance so that the laser oscillation beam is reflected toward the output mirror 26 side.
The splitting part 23 splits pumping light outputted from the pumping light source 11 into the first pumping component R1 and the second pumping component R2. The split first pumping component R1 and the second pumping component R2 are respectively allocated to the first split path B1 and the second split path B2 so that the first pumping component R1 and the second pumping component R2 of pumping light enter from the first split path B1 and the second split path B2 through the first end surface and the second end surface of the solid laser medium 21, respectively. A beam splitter BS, such as a half mirror or the like, can be used as the split part 23.
FIG. 3 shows a concrete example of the arrangement of optical members. In a laser resonant portion 201 shown in this figure, a solid laser medium 21, a rear side mirror RM and an emission side mirror FM are arranged on one long side of the split path in rectangular form (left in FIG. 3) and a beam splitter BS1 is arranged at the apex along the other long side (right in FIG. 3), on the side closer to the rear side mirror RM, so that the arrangement of the pumping light coupling part 22 in close proximity to the beam splitter BS1 allows pumping light to enter in a direction perpendicular to the long sides. That is, in FIG. 3, the beam splitter BS1 is arranged at the lower right apex of the rectangular form which is long in the longitudinal direction. A first reflection mirror M11 is arranged at the lower left apex, a second reflection mirror M21 is arranged at the upper right apex, and a third reflection mirror M31 is arranged at the upper left apex. Further, the first, second and third reflection mirrors M11 to M31 are secured in such a manner as to be inclined in a chamfering direction, that is, relative to the respective sides in such a direction that the interior angle is 135°, so that entering light is reflected at a right angle from each mirror. Meanwhile, the beam splitter BS1 is secured in such a manner as to be inclined in such a direction that the interior angle is 45° relative to each side, in order to split entering light into transmission light which goes straight and reflection light reflected at a right angle. An pumping light coupling part 22 is arranged on the right side of the beam splitter BS1 so that pumping light from the LD unit that enters through the optical fiber coupling portion 22 a which is linked to the optical fiber cable is reshaped to parallel light through the collimate lens 22 b and the pumping light enters toward the beam splitter BS1 (toward the left in FIG. 3). The beam splitter BS1 is secured in such a position as to be inclined at an angle of 45° relative to the entering light, so as to split pumping light into transmission light in the direction in which light goes straight, which is the first pumping component R1, and reflection light reflected upward, which is the second pumping component R2. The first reflection mirror M11 is secured on the left side of the beam splitter BS1 in such a manner as to be inclined by 45° relative to the entering light, so that the first pumping component R1 is reflected in the upward direction. This reflection light is condensed through the first condenser lens 61 and enters the rear side mirror RM. As described above, the first split path B1 is formed in L shape.
Meanwhile, the second pumping component R2 reflected by the beam splitter BS1 in the upward direction is reflected from the second reflection mirror M21, which is secured in such a position as to be inclined by 45° relative to the entering light in the horizontal direction (toward the left in FIG. 3). Reflection light goes parallel to transmission light which transmits through the beam splitter BS1, and is reflected from the third reflection mirror M31 which is secured in such a position as to be inclined by 45° relative to the entering light in the downward direction. This reflection light of the second pumping component R2 is condensed through the second condenser lens 62 so as to enter into the emission side mirror FM. As described above, the second split path B2 is formed in reverse L shape. As a result, the reflection light of the first pumping component R1 reflected from the first reflection mirror M11 and the reflection light of the second pumping component R2 reflected from the third reflection mirror M31 face each other along the same axis. Further, the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively, so that the laser is oscillated by the solid laser medium 21 placed between the dichroic mirrors, and induced emission light is emitted from the emission side mirror FM. That is, the laser oscillation light is reflected from the emission side mirror FM, which is secured in such a manner as to be inclined by 45° in the lateral direction (toward the left in FIG. 3) and reaches the output mirror 26 through the Q switch 28 and the aperture 27, and thus, laser output light is outputted.
The above described layout is one example, and the arrangement of the beam splitter BS, the pumping light coupling part 22 and the solid laser medium 21 can be changed. Next, FIG. 4 shows an example of the arrangement of the optical members of the solid laser oscillator according to Embodiment 2 as an example of a layout where the location of an pumping light coupling part 22 is changed. In a laser resonant portion 202 shown in this figure also, a solid laser medium 21, a rear side mirror RM and an emission side mirror FM are arranged along one long side of the split path formed in rectangular form (left side in FIG. 4), and a beam splitter BS2 is arranged at the apex along the other long side (left side in FIG. 4), on the side close to the rear side mirror RM. Here, the pumping light coupling part 22 is arranged in close proximity to the beam splitter BS2 so that pumping light enters in a direction which coincides with the long sides. Here, the arrangement of the optical members is similar to that in FIG. 3, and the beam splitter BS2 is arranged at the lower right apex of the rectangular form, which is long in the longitudinal direction, a first reflection mirror M12 is arranged at the lower left apex, a second reflection mirror M22 is arranged at the upper right apex, and a third reflection mirror M32 is arranged at the upper left apex. Further, the first, second and third reflection mirrors M12 to M32 are secured in such a direction as to chamfer the respective apexes, that is, in such a manner as to be inclined in such a direction that the interior angle is 135° relative to each side, in order to reflect the entering light at a right angle. Meanwhile, the beam splitter BS2 is secured at an angle of 45° so that the interior angles of the rectangular form is divided into two equal angles, in order to split the entering light into transmission light which goes straight and reflection light which is reflected at a right angle, in the same manner as in FIG. 3. Pumping light enters through the pumping light coupling part 22 arranged on the lower side of the beam splitter BS2 (in the upward direction in FIG. 4). The beam splitter BS2 is secured in an inclined position which is different from that in FIG. 3 by 90°, and splits pumping light into transmission light which goes straight, which is a second pumping component R2, and reflection light reflected in the horizontal direction (toward the left in FIG. 4), which is a first pumping component R1. The first reflection mirror M12 is secured on the left side of the beam splitter BS2 in such a manner as to be inclined by 45° relative to the entering light, in the same manner as in FIG. 3, and reflects the first pumping component R1 in the upward direction. The reflection light is condensed through a first condenser lens 61 and enters a rear side mirror RM. As described above, a first split path B1 is formed in L shape.
Meanwhile, the second pumping component R2, which transmits through the beam splitter BS2 in the upward direction, is reflected from the second reflection mirror M22, which is secured in such a position as to be inclined by 45° relative to the entering light in the horizontal direction (toward the left in FIG. 4). Reflection light goes parallel to light reflected from the beam splitter BS2 and is reflected from the third reflection mirror M32, which is secured in such a position as to be inclined by 45° relative to the entering light in the downward direction. The reflection light of the second pumping component R2 is condensed through a second condenser lens 62 and enters an emission side mirror FM. As described above, the second split path B2 is formed in reverse L shape. Subsequently, reflection light of the first pumping component R1 reflected from the first reflection mirror M12 and reflection light of the second pumping component R2 reflected from the third reflection mirror M32 face each other along the same axis, in the same manner as in FIG. 3, so that the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively, and the laser is oscillated.
FIG. 5 shows an example of the arrangement of the optical members of the solid laser oscillator according to Embodiment 3 as still another example of the layout. In a laser resonant portion 203 shown in this figure also, a solid laser medium 21, a rear side mirror RW and an emission side mirror FM are arranged along one long side of the split path formed in rectangular form (left side in FIG. 5). Here, a beam splitter BS3 is arranged at the apex along the same long side, and on the side close to the rear side mirror RM. Further, an pumping light coupling part 22 is arranged in close proximity to the beam splitter BS3 in such a manner that pumping light enters in a direction which coincides with the long side. Furthermore, in the arrangement of the optical members, the beam splitter BS3 is arranged at the lower left apex of the rectangular form, which is long in the longitudinal direction, a first reflection mirror M13 is arranged at the lower right apex, a second reflection mirror M23 is arranged at the upper right apex, and a third reflection mirror M33 is arranged at the upper right apex. Furthermore, the first, second and third reflection mirrors M13 to M33 are secured in such a position as to be inclined in such a direction as to chamfer each apex, that is, in such a direction that the interior angle is 135° relative to each side, in order to reflect the entering light at a right angle. Meanwhile, the beam splitter BS3 is secured at an angle of 45° so as to divide the interior angle of the rectangular form into two equal angles, in order to split the entering light into transmission light, which goes straight, and reflection light, which is reflected at a right angle, in the same manner as in FIG. 3, and the like. Pumping light enters through the pumping light coupling part 22, which is arranged on the lower side of the beam splitter BS3 (in the upward direction in FIG. 5), in the same manner as in FIG. 4, so that pumping light is split into transmission light which goes straight, which is a first pumping component R1, and reflection light reflected in the horizontal direction (toward the right in FIG. 5), which is a second pumping component R2. The first pumping component R1, which is transmission light, is condensed through a first condenser lens 61 and enters a rear side mirror RM. In this example, a first split path B1 is formed in linear form.
Meanwhile, the second pumping component R2 reflected from the beam splitter BS3 in the horizontal direction (toward the right in FIG. 5) is reflected from the first reflection mirror M13, which is secured in such a position as to be inclined by 45° relative to the entering light in a perpendicular direction (in the upward direction in FIG. 5). Reflection light goes parallel with light which transmits through the beam splitter BS3, and is reflected from the second reflection mirror M23, which is secured in such a position as to be inclined by 45° relative to the entering light in the horizontal direction (to the right in FIG. 5). Furthermore, the light is reflected from the third reflection mirror M33, which is secured in such a position as to be inclined by 45° relative to the entering light in the perpendicular direction (in the downward direction in FIG. 5). This reflection light of the second pumping component R2 is condensed through a second condenser lens 62 and enters the emission side mirror FM. As described above, a second split path B2 is formed in C shape. In this manner, the first pumping component R1, which transmits through the beam splitter BS3, and reflection light of the second pumping component R2, which is reflected from the third reflection mirror M33, face each other along the same axis, so that the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively, and the laser is oscillated.
FIG. 6 shows an example of the arrangement of the optical members of the solid laser oscillator according to Embodiment 4 as yet another example of the layout. In a laser resonant portion 204 shown in this figure also, a solid laser medium 21, a rear side mirror RM and an emission side mirror FM are arranged on one long side of the split path formed in rectangular form (left side in FIG. 6). Here, a beam splitter BS4 is arranged at the apex along the same long side and on the side close to the rear side mirror RM. Further, an pumping light coupling part 22 is arranged in close proximity to the beam splitter BS4 so that pumping light enters in a direction perpendicular to the long side (from left side of apex in FIG. 6). Furthermore, in the arrangement of the optical members, in the same manner as in FIG. 5, the beam splitter BS4 is arranged at the lower left apex of the rectangular form, which is long in the longitudinal direction, a first reflection mirror M14 is arranged at the lower right apex, a second reflection mirror M24 is arranged at the upper right apex, and a third reflection mirror M34 is arranged at the upper left apex. Furthermore, the first, second and third reflection mirrors M14 to M34 are secured in such a position as to be inclined in such a direction as to chamfer each apex, that is, in such a direction that the interior angle is 135° relative to each side, so that the entering light is reflected at a right angle. Meanwhile, the beam splitter BS4 is secured at an angle of 45° so as to divide the interior angle of the rectangular form into two equal angles, in order to split the entering light into transmission light, which goes straight, and reflection light, which is reflected at a right angle, in the same manner as in FIG. 3. In the same manner as in FIG. 5, pumping light enters through the pumping light coupling part 22, which is arranged on the left side of the beam splitter BS4, toward the right in FIG. 6, and pumping light is split into transmission light which goes straight, which is a second pumping component R2, and reflection light reflected in the perpendicular direction (in the upward direction in FIG. 6), which is the second pumping component R2. A first pumping component R1, which is reflection light, is condensed through a first condenser lens 61 and enters the rear side mirror RM. In this example also, the first split path B1 is formed in linear form.
Meanwhile, the second pumping component R2, which transmits through the beam splitter BS4 and goes straight toward the right in FIG. 6, is reflected from the first reflection mirror M14, which is secured in such a position as to be inclined by 45° relative to the entering light, in the same manner as in FIG. 5, in the perpendicular direction (in the upward direction in FIG. 6). The reflection light goes parallel with the light reflected from the beam splitter BS4, and is reflected from the second reflection mirror M24, which is secured in such a position as to be inclined by 45° relative to the entering light in the horizontal direction (toward the left in FIG. 6). Furthermore, the light is reflected from the third reflection mirror M34, which is secured in such a position as to be inclined by 45° relative to the entering light in a perpendicular direction (in the downward direction in FIG. 6). The reflection light of the second pumping component R2 is condensed through a second condenser lens 62 and enters into the emission side mirror FM. As described above, a second split path B2 is formed in C shape. In this manner, the first pumping component R1 reflected from the beam splitter BS4 and reflection light of the second pumping component R2 reflected from the third reflection mirror M34 face each other along the same axis, so that the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively, and the laser is oscillated.
Furthermore, FIG. 7 shows an example of the arrangement of the optical members of the solid laser oscillator according to Embodiment 5 as another example of the layout. In a laser resonant portion 205 shown in this figure also, a solid laser medium 21, a rear side mirror RM and an emission side mirror FM are arranged along one long side of the split path formed in rectangular form (left side in FIG. 7). Here, a beam splitter BS5 is placed at the apex along the same long side, on the side close to the emission side mirror FM. An pumping light coupling part 22 which is arranged in close proximity to the beam splitter BS5 is arranged in such a manner that pumping light enters in the direction perpendicular to the long side (left side of the apex in FIG. 7). In the arrangement of the optical members, the beam splitter BS5 is arranged at the upper left apex of the rectangular form, which is long in the longitudinal direction, a first reflection mirror M15 is arranged at the upper right apex, a second reflection mirror M25 is arranged at the lower right apex, and a third reflection mirror M35 is arranged at the lower left apex. Furthermore, the first, second and third reflection mirrors M15 to M35 are secured in such a position as to be inclined in such a direction as to chamfer each apex, that is, in such a direction that the interior angle is 135° relative to each side. Meanwhile, the beam splitter BS5 is secured at an angle of 45° so as to divide the interior angle of the rectangular form into two equal angles, in order to split the entering light into transmission light, which goes straight, and reflection light, which is reflected at a right angle, in the same manner as in FIG. 3. Here, pumping light enters through an pumping light coupling part 22, which is arranged on the left side of the beam splitter BS5 toward the right in FIG. 7, and pumping light is split into transmission light which goes straight, which is a first pumping light component R1, and reflection light reflected in a perpendicular direction (in the downward direction in FIG. 7), which is a second pumping component R2. The second pumping component R2, which is reflection light, is condensed through a second condenser lens 62 and enters the emission side mirror FM. In this example, a second split path B2 is formed in linear form.
Meanwhile, the first pumping component R1, which transmits through the beam splitter BS5 and goes straight toward the right in FIG. 7, is reflected from the first reflection mirror M15, which is secured in such a position as to be inclined by 45° relative to the entering light in the perpendicular direction (in the downward direction in FIG. 7). The reflection light goes parallel with the light reflected from the beam splitter BS5 and is reflected from the second reflection mirror M25, which is secured in such a position as to be inclined by 45° relative to the entering light in the lateral direction (toward the left in FIG. 7). Furthermore, the light is reflected from the third reflection mirror M35, which is secured in such a position as to be inclined by 45° relative to the entering light in the perpendicular direction (in the upward direction in FIG. 7). This light reflected from a first pumping component R1 is condensed through a first condenser lens 61 and enters the rear side mirror RM. As described above, the first split path B1 is formed in C shape. In this manner, the second pumping component R2 reflected from the beam splitter BS5 and reflection light of the first pumping component R1 reflected from the third reflection mirror M35 face each other along the same axis, so that the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively and the laser is oscillated.
Moreover, FIG. 8 shows an example of the arrangement of the optical members of the solid laser oscillator according to Embodiment 6 as another example of the layout. In a laser resonant portion 206 shown in this figure also, a solid laser medium 21, a rear side mirror RM and an emission side mirror FM are arranged along one long side of the split path formed in rectangular form (to the left in FIG. 8). Here, the beam splitter BS6 is arranged at the apex along the same long side and on the side close to the emission side mirror FM. Further, an pumping light coupling part 22 is arranged in close proximity to the beam splitter BS6 so that pumping light enters in a direction which coincides with the long side (upper side of the apex in FIG. 8). Furthermore, in the arrangement of the optical members, the beam splitter BS6 is arranged at the upper left apex of the rectangular form, which is long in the longitudinal direction, a first reflection mirror M16 is arranged at the upper right apex, a second reflection mirror M26 is arranged at the lower right apex, and a third reflection mirror M36 is arranged at the lower left apex, in the same manner as in FIG. 7. Furthermore, the first, second and third reflection mirrors M16 to M36 are secured in such a position as to be inclined in such a direction as to chamfer each apex, that is, in such a direction that the interior angle is 135° relative to each side, in order to reflect the entering light at a right angle. Meanwhile, the beam splitter BS6 is secured at an angle of 45° so that the interior angle of the rectangular form is divided into two equal angles, in order to split the entering light into transmission light, which goes straight, and reflection light, which is reflected at a right angle, in the same manner as in FIG. 3. Here, pumping light enters through an pumping light coupling part 22, which is arranged on the upper side of the beam splitter BS6 in the downward direction in FIG. 8, and pumping light is divided into transmission light which goes straight, which is a second pumping component R2, and reflection light reflected in the horizontal direction (to the right in FIG. 8), which is a first pumping component R1. The second pumping component R2, which is transmission light, is condensed through a second condenser lens 62 and enters an emission side mirror FM. In this example also, a second split path B2 is formed in linear form.
Meanwhile, the first pumping component R1, which is reflected from the beam splitter BS6 and goes straight toward the right in FIG. 8, is reflected from the first reflection mirror M16, which is secured in such a position as to be inclined by 45° relative to the entering light, in the same manner as in FIG. 7, in the perpendicular direction (in the downward direction in FIG. 8). The reflection light goes parallel with light which transmits through the beam splitter BS6 and is reflected from the second reflection mirror M26, which is secured in such a position as to be inclined by 45° relative to the entering light in the horizontal direction (toward the left in FIG. 8). Furthermore, the light is reflected from the third reflection mirror M36, which is secured in such a position as to be inclined by 45° relative to the entering light in a perpendicular direction (in the upward direction in FIG. 8). This reflection light of the first pumping component R1 is condensed through a first condenser lens 61 and enters through a rear side mirror RM. As described above, a first split path B1 is formed in reverse C shape. In this manner, the second pumping component R2, which transmits through the beam splitter BS6, and reflection light of the first pumping component R1, which is reflected from the third reflection mirror M36, face each other along the same axis, so that the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively, and the laser is oscillated.
Furthermore, FIG. 9 shows an example of the arrangement of optical members of the solid laser oscillator according to Embodiment 7 as another example of the layout. In a laser resonant portion 207 shown in this figure also, a solid laser medium 21, a rear side mirror RM and an emission side mirror FM are arranged along one long side of the split path formed in rectangular form (left side in FIG. 9). Here, a beam splitter BS7 is placed at the apex along the other long side (right side in FIG. 9) on the side close to the emission side mirror FM. Further, an pumping light coupling part 22 is arranged in close proximity to the beam splitter BS7 so that pumping light enters in a direction which coincides with this long side (upper side of the apex in FIG. 9). Furthermore, in the arrangement of optical members, the beam splitter BS7 is arranged at the upper right apex of the rectangular form, which is long in the longitudinal direction, a first reflection mirror M17 is arranged at the lower right apex, a second reflection mirror M27 is arranged at the lower left apex, and a third reflection mirror M37 is arranged at the upper left apex Furthermore, the first, second and third reflection mirrors M17 to M37 are secured in such a position as to be inclined in such a direction as to chamfer each apex, that is, in such a direction that the interior angle is 135° relative to each side, in order to reflect the entering light at a right angle. Meanwhile, the beam splitter BS7 is secured at an angle of 45° so that the interior angle of the rectangular form is divided into two equal angles, in order to split the entering light into transmission light, which goes straight, and reflection light, which is reflected at a right angle, in the same manner as in FIG. 3, and the like. Here, pumping light enters through an pumping light coupling part 22, which is arranged on the upper side of the beam splitter BS7 in the downward direction in FIG. 9, and the pumping light is split into transmission light which goes straight, which is a first pumping component R1, and reflection light reflected in the horizontal direction (toward the left in FIG. 9), which is a second pumping component R2. The third reflection mirror M37 is secured on the left side of the beam splitter BS7 in such a manner as to be inclined by 45° relative to the entering light, and reflects a second pumping component R2 in the downward direction. This reflection light is condensed through a second condenser lens 62 and enters the emission side mirror FM. As described above, a second split path B2 is formed in reverse L shape.
Meanwhile, the first pumping component R1, which transmits through the beam splitter BS7 and goes straight in the downward direction in FIG. 9 is reflected from the first reflection mirror M17, which is secured in such a position as to be inclined by 45° relative to the entering light in the horizontal direction (toward the left in FIG. 9). The reflection light goes parallel with light reflected from the beam splitter BS7 and is reflected from the second reflection mirror M27, which is secured in such a position as to be inclined by 45° relative to the entering light in the perpendicular direction (in the upward direction in FIG. 9). This reflection light of the first pumping component R1 is condensed through a first condenser lens 61 and enters the rear side mirror RM. As described above, the first split path B1 is formed in U shape. In this manner, the second pumping component R2 reflected from the third reflection mirror M37 and reflection light of the first pumping component R1 reflected from the second reflection mirror M27 face each other along the same axis, so that the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively, and the laser is oscillated.
Furthermore, FIG. 10 shows an example of the arrangement of optical members of the solid laser oscillator according to Embodiment 8 as an example of another layout. In a laser resonant portion 208 shown in this figure also, a solid laser medium 21, a rear side mirror RM and an emission side mirror FM are arranged along one long side of the split path, which is formed in rectangular form (on the left side in FIG. 10). Here, a beam splitter BS8 is arranged at the apex along the other long side (on the right side in FIG. 10), and on the side close to the emission side mirror FM. Further, an pumping light coupling part 22 is arranged in close proximity to the beam splitter BS8 so that pumping light enters in the direction perpendicular to the long side (on the right side of the apex in FIG. 10). Furthermore, in the arrangement of optical members, the beam splitter BS8 is arranged at the upper right apex of the rectangular form, which is long in the longitudinal direction, a first reflection mirror M18 is arranged at the lower right apex, a second reflection mirror M28 is arranged at the lower left apex, and a third reflection mirror M38 is arranged at the upper left apex, in the same manner as in FIG. 9. Furthermore, the first, second and third reflection mirrors M18 to M38 are secured in such a position as to be inclined in such a direction as to chamfer each apex, that is, in such a direction that the interior angle is 135° relative to each side, in order to reflect the entering light at a right angle. Meanwhile, the beam splitter BS8 is secured at an angle of 45° so that the interior angle of the rectangular form is divided into two equal angles, in order to split the entering light into transmission light, which goes straight, and reflection light, which is reflected at a right angle, in the same manner as in FIG. 3. Here, pumping light enters through the pumping light coupling part 22, which is arranged on the right side of the beam splitter BS8 toward the left in FIG. 10, and the pumping light is split into transmission light which goes straight, which is a second pumping component R2, and reflection light, which is reflected in the perpendicular direction (in the downward direction in FIG. 10), which is a first pumping component R1. The third reflection mirror M38 is secured on the left side of the beam splitter BS8 in such a manner as to be inclined by 45° relative to the entering light, and reflects the second pumping component R2 that transmits through the medium in the downward direction. This reflection light is condensed through a second condenser lens 62 and enters the emission side mirror FM. As described above, the second split path B2 is formed in reverse L shape.
Meanwhile, the first pumping component R1, which is reflected from the beam splitter BS8 and goes downward in FIG. 10, is reflected from the first reflection mirror M18, which is secured in such a position as to be inclined by 45° relative to the entering light in the horizontal direction (toward the left in FIG. 10). The reflection light goes parallel with light that transmits through the beam splitter BS8 and is reflected from the second reflection mirror M28, which is secured in such a position as to be inclined by 45° relative to the entering light in the perpendicular direction (in the upward direction in FIG. 10). This reflection light of a first pumping component R1 is condensed through a first condenser lens 61 and enters into a rear side mirror RM. As described above, the first split path B1 is formed in U shape. In this manner, the second pumping component R2, which is reflected from the third reflection mirror M38, and the reflection light of the first pumping component R1, which is reflected from the second reflection mirror M28, face each other along the same axis, so that the first pumping component R1 and the second pumping component R2 enter the rear side mirror RM and the emission side mirror FM, respectively, and the laser is oscillated.
The solid laser medium 21 is a crystal which extends in one direction and has two end surfaces in the longitudinal direction. Here, the end surfaces are a first end surface which forms a surface through which pumping light enters, and a second end surface which is on the side opposite to the first end surface and forms a surface through which pumping light enters and pumping light is emitted. In the example of FIG. 3, the second end surface is referred to as emission surface, and the first end surface is referred to as rear surface (entrance surface). Further, the emission surface and the rear surface face the emission side mirror FM and the rear side mirror RM, respectively. Furthermore, pumping light is split into a first pumping component R1 and a second pumping component R2 by the beam splitter BS, and the first pumping component R1 and the second pumping component R2 enter the rear surface side and the emission surface side, respectively.
The solid laser medium 21 crystal in rod form may be either in columnar form or prism form for use. Here, an Nd:YVO4 crystal in rectangular parallelepiped form having end surfaces of 3 mm (H)×3 mm (W) and a length (L) of 15 mm is used as the solid laser medium 21 crystal in prism form. Furthermore, it is preferable for the concentration of Nd to be 1% or less.
FIG. 14 is a graph showing the change in the efficiency of absorption for the wavelength of pumping light in Nd:YVO4 crystal. Here, the ratio of light absorption for the total pumping light was compared for a number of crystals where the length of crystal and the concentration of Nd vary in Nd:YVO4 crystal in parallelepiped form with end surfaces of 3 mm×3 mm. Concretely, measurement was carried out for the respective examples, where the concentration of Nd in the case where the length of the crystal is 15 mm was 0.10%, 0.20%, 0.27%, 0.30% and 0.40%, and the length of the crystal was changed to 10 mm in the case where the concentration of Nd was 0.27%. As shown in this figure, in general, the higher the concentration of Nd was, the higher the efficiency of absorption of the laser beam was. Further, the peak in the efficiency of absorption appeared in the vicinity of the wavelength of pumping light of 808 nm to 809 nm in all cases. Here, when the concentration of Nd was too high, the crystal became unstable and broke due to heat. Therefore, the concentration of Nd in the solid laser medium 21 is 1% or lower, preferably in a range from 0.1% to 0.4%. Here, there was inconsistency of approximately +/−0.03% to 0.05% in the concentration of Nd in the actual manufactured solid laser medium 21 crystal, and therefore, the concentration of Nd is set to approximately 0.22% to 0.32%, taking this into consideration. The efficiency of absorption can be maintained with good balance when the concentration of Nd is in the vicinity of 0.27%, which is most preferable. Furthermore, a tendency of the efficiency of absorption to lower when the length of the crystal (L) was short was observed, and therefore, the length of the crystal should be set to approximately 10 mm to 20 mm, preferably to 13 mm to 17 mm, and more preferably a crystal having a length in the vicinity of 15 mm is used.
Here, it suffices for the cross section of the solid laser medium 21 crystal to be greater than the diameter of the spot of pumping light, and the form of the crystal is not limited to a rectangular parallelepiped form, and columnar form and other appropriate forms can be used. In the case where the diameter of the spot of pumping light is φ1 mm, for example, a columnar form of the same size may be used. Here, in the case where the solid laser medium 21 crystal is narrow, a problem arises, such that the crystal easily breaks, and in addition, it is advantageous for the area of the end surfaces of the crystal and the form of the crystal to be constant, taking the ease of handling of the crystal at the time of assembly into consideration, and therefore, the end surfaces of the crystal is 3 mm×3 mm with the crystal in rectangular parallelepiped form.
In the laser processing apparatus where the solid laser medium 21 is excited, 30% to 40% of the pumping power becomes heat and is lost due to the limits of quantum efficiency. Therefore, it is necessary to solve various problems with heat, such as thermal birefringence, thermal lens and thermal complex lens, which surface due to intense pumping, and destruction due to heat, in order to gain limitative performance. In particular, in the LD pumping solid laser processing apparatus, heat emitted as a result of pumping light absorbed by the solid laser medium 21 induces a lens effect in the crystal itself so as to generate a thermal lens. The thermal lens greatly hinders the stability of the laser resonator and becomes a great hindrance to the design of the resonator. A two-directional pumping system is adopted in the present embodiment in order to solve these problems, and one pumping light source 11 is used as the laser pumping portion 10 so that light is divided in such a manner that light enters through the respective end surfaces in the configuration, and thus, thermal lens can successfully be prevented from being generated. In addition to this, effects are gained, such that the stability in terms of the wavelength of pumping light and the increase properties are improved.
FIG. 15 is a graph showing a comparison of the change in the laser output beam for the wavelength of the LD unit between one-directional pumping and two-directional pumping. Here again, the Nd:YVO4 crystal used was in rectangular parallelepiped form with end surfaces of 3 mm×3 mm, and the Nd concentration was 0.27% and the length of the crystal was 10 mm for one-directional pumping, while the Nd concentration was 0.27% and the length of the crystal was 15 mm for two-directional pumping. As shown in this figure, in one-directional pumping, when the wavelength of the pumping light shifts with 808 nm at the center, the laser output beam changes greatly. Therefore, the laser output changes, due to inconsistency in the peak wavelength of the LD unit, and it becomes difficult to gain a uniform laser processing apparatus. In particular, there is generally a difference in individual semiconductor light emitting elements, and inconsistency tends to be easily caused in the wavelength, and therefore, it is usually necessary to take error of approximately +/−2 nm to 3 nm into consideration. Furthermore, the wavelength of the pumping light is temperature-dependent, and therefore, temperature control becomes necessary in the LD element, where a Pelletier element or the like is used. For the above reasons, conventional laser processing apparatuses are designed for the lowest laser output, taking inconsistency in the wavelength into consideration, and thus, the inherent output is not used effectively.
Furthermore, FIG. 16 is a graph showing a comparison of the change in the laser output beam over time between one-directional pumping and two-directional pumping. In this figure also, the change in the laser output beam over time was measured when Nd:YVO4 crystal in rectangular parallelepiped form with end surfaces of 3 mm×3 mm where the Nd concentration is 0.27% was used, the wavelength of the LD unit was 806 nm, 808 nm and 810 nm, and the current in the LD unit was changed from 0 A to 35 A for one-directional pumping and two-directional pumping, respectively. Here, the length of the crystal was 10 mm (one-directional pumping) and 15 mm (two-directional pumping) for the sake of convenience in the test for comparison. As shown in this figure, a gentle increase is shown for one-directional pumping when the pumping wavelength is 808 nm and 810 nm, while overshoot was generated for 806 nm, where approximately 1.4 see was required before the output became stable. Meanwhile, in two-directional pumping, steep increase and quick stabilization are shown for all wavelengths, and thus, it was confirmed that the increase properties of the laser were excellent. Further, overshoot at 806 nm was kept at an extremely low level.
Furthermore, in order to confirm this, FIG. 17 shows a waveform of the change in the laser output beam over time as measured using a photodiode when the current in the LD unit is changed from 0 A to 45 A for two-directional pumping using Nd:YVO4 crystal in rectangular parallelepiped form of 3 mm×3 mm×15 mm with an Nd concentration of 0.27%, which is the same as in FIG. 16. As is clear from this figure, the laser output beam reached a desired level in an extremely short period of time of approximately 20 ms, and thus, it can be confirmed that stable output was gained without causing overshoot. Thus, in accordance with the conditions of the present embodiment, the time required for the output to be stabilized when the laser output beam increases can be reduced to 1/10 or less of the prior art, as a result of increase in the speed. Further, as a result, a high-speed process where response and tracking are higher and the standby time is shortened while precision in processing is maintained can be implemented. In conventional laser processes, the laser output cannot be changed for each block in the laser processing pattern due to problems with the response of the laser output, and standby time for the output to be stabilized (for example 300 ms) is required when the laser output is changed. In contrast, the above described configuration makes the stability at the time of increase excellent, and also makes high-speed tracking possible, and thus, it becomes possible to change the laser output for each block in the laser processing pattern, which is difficult in the prior art.
Laser pumping light split in two directions from the single pumping light source 11 pumps the solid laser medium 21 through the respective end surfaces in the longitudinal direction. At this time, the intensity of pumping light entering through the rear side mirror RM side is higher than the intensity of the pumping light entering through the emission side mirror FM side. As a result of diligent research conducted on thermal lenses by the present inventors, it was found out that the inside of the resonator is affected less by the thermal lens generated on the rear side of the solid laser medium than by that generated on the emission side. In the configuration of FIG. 3, the reflectance of the beam splitter BS is used to adjust the ratio of the split between the rear side mirror RM and the emission side mirror FM. That is, the higher the reflectance is, the higher the intensity of light with which the emission surface is irradiated becomes, and the lower the reflectance is, that is, the higher the transmittance is, the higher intensity of pumping light with which the rear surface is irradiated becomes. Here, it is preferable for the ratio of the split in the beam splitter BS of light entering through the crystal end surface on the rear surface side to be 50% or more of the total power in the configuration.
Meanwhile, the reflectance of the output mirror determines the amount of energy that can be taken out from the resonator. Therefore, it is necessary to set an optimum reflectance. In general, when the reflectance of the resonator is high, the energy that is contained inside the resonator becomes high, and therefore, the risk of damaging the optical members that form the inside of the resonator becomes high. Therefore, it is desirable for the design to be such that the reflectance in the output mirror at a low value, in order to reduce the load on the optical members. However, it is necessary to increase the density of pumping inside the crystal in order to achieve this, and there is a limit in terms of how much the density of pumping can be increased for conventional one-directional pumping, due to the thermal lens and damage in the crystal.
Here, FIG. 20 shows the formula for calculating the energy inside the resonator. As shown in this figure, the energy Ersn which is contained inside the resonator can be expressed as Ersn={(1+R)X}/(1−R), where X is the output emitted from the output mirror and R is the reflectance of the output mirror. Here, in the case where a laser processing apparatus for gaining a laser output beam of 10 W is designed, energy of 190 W accumulates inside the resonator when the reflectance of the output mirror is 90%. Such high energy causes heat to be generated in the optical members which form the resonator, and in some cases, causes the quality of the laser beam to deteriorate, due to optical thermal strain generated in the mirrors and the like. In particular, a peak power of several tens of kW is generated in the pulse laser where a Q switch is mounted, and as a result, the optical members which form the resonator are damaged.
Meanwhile, there is a risk that a problem may arise in the case where the reflectance of the output mirror is too low. FIGS. 21 and 22 show the change in the laser output relative to the reflectance of the output mirror in the two-directional pumping system and the change in the energy inside the resonator relative to the reflectance of the output mirror, respectively.
Here, the formula for calculating the laser output P is examined. The transmittance of the output mirror is denoted by T, the loss inside the resonator is Loss, the cross sectional area of the solid laser medium (effective pumping cross sectional area) is denoted by A, the length of the crystal of the solid laser medium (effective pumping length) is denoted by L, small signal gain generated inside the solid laser medium is denoted by g0, and the saturation constant is denoted by Is (=hv/δτf). At this time, the laser output P can be represented by the following Formula 1.
P=T·(T+Loss)·A·Is·g 0 ·L−T·A·Is/2 [Formula 1]
Topt=((sqrt(2·g 0 ·L/Loss)−1)Loss [Formula 2]
(1+R)·X/(1−R) [Formula 3]
g 0 =σ·N 0 ·Wp·τ f [Formula 4]
In the above formula, σ is the induction release cross sectional area, and τf is the life of fluorescence; both are property values determined by the type of solid laser medium (whether it is Nd:YVO4 or Nd:YLF). Meanwhile, N0 and Wp are respective pumping rates for the pumping source (number of atoms) which exist per volume unit, and the product of these N0·Wp is the number of atoms which are excited per time unit and volume unit. Accordingly in order to design a laser processing apparatus having a large g0, pumping light is condensed to a small volume, which is thus excited, so that the number of atoms excited per volume unit increases, and thus, increase in the pumping density leads to increase in g0. As a result, g0 becomes great in the case where the design allows the pumping volume to be small and the pumping density is high at the time of pumping, and as a result, a laser can be efficiently taken out from the output mirror, even when the reflectance of the output mirror is low. As a result, the risk of the coating used on the optical members that form the resonator being damaged can be reduced.
Furthermore, the diameter of the spot of pumping light in two-directional pumping is made smaller than in the TEM00 beam mode of the solid laser medium, and thus, further increase in the efficiency can be achieved. In conventional two-directional pumping, the diameter of the spot of pumping light for irradiating the respective end surfaces of the solid laser medium is made slightly greater in size than in the TEM00 mode of the solid laser medium, and thus, the pumping is concentrated in a small area, so that a problem of a thermal lens and the effects of a strong thermal lens being generated can be avoided. According to this method, however, it is difficult to achieve increase in the gain inside the solid laser medium crystal in the case where an LD unit having a high output is used, through cases where the output of the LD unit is low can be dealt with. Therefore, the crystal is excited with high density within a diameter of the spot for pumping which is smaller than in the TEM00 mode generated inside the resonator, and thus, the gain generated inside the solid laser crystal increases.
A work region on a workpiece W is scanned with the laser output beam generated by the laser resonant portion, as described above, in a desired processing pattern using a laser beam scanning system 30, so that the workpiece is processed. The laser resonant portion 20 and the laser beam scanning system 30 are optically connected, and bend the laser output beam emitted from the output mirror 26, for example as in FIG. 3, so that the laser output beam is transmitted to the laser beam scanning system 30 placed beneath.
A Z axis scanner 37 adjusts the diameter of the spot of the laser output beam, and thus, forms a beam expander 36 for adjusting the focal distance. That is, the beam expander 36 can change the relative distance between the lens through which light enters and the lens from which light is emitted, and thus, the diameter of the laser output beam can be made larger/smaller, and the location of the focal point can also be changed. The beam expander 36 effectively condenses light to a small spot, and therefore, is placed on the front stage of the galvano mirror, as shown in FIG. 24, so that the diameter of the laser output beam outputted from the laser resonant portion 20 is adjusted and the location of the focal point of the laser output beam is adjustable. A method according to which the Z axis scanner 37 adjusts the working distance is described in reference to FIGS. 29 to 31. FIGS. 29 and 30 are side views of a laser beam scanning system 30; FIGS. 29 and 30 show a case where the distance of the focal point of the laser output beam is made long and a case where the distance of the focal point of the laser output beam is made short, respectively. Further, FIG. 31A is a front view showing the Z axis scanner 37 and FIG. 31B is a cross-sectional view of the Z axis scanner 37. As shown in these figures, the Z axis scanner 37 includes a lens 38 through which light enters which faces the laser resonant portion 20 side, and a lens 39 through which light is emitted which faces the laser emission side so that the relative distance between these lenses can be changed. In the example of FIGS. 29 to 31, the lens 39 through which light is emitted is secured and the lens 38 through which light enters is slidable using a drive motor or the like in the direction of the optical axis. In FIGS. 31A and 31B, the lens 39 through which light is emitted is not shown, and the drive mechanism of the lens 38 through which light enters is shown. In this example, a movable member is slidable in the axial direction by means of a coil and a magnet, and the lens 38 through which light enters is secured to the movable member. Here, it is also possible to secure the lens through which light enters side so that the lens through which light is emitted side is movable, as well as to make both the lens through which light enters and the lens through which light is emitted movable.
A guide pattern which indicates the location for irradiation when the work region WS is scanned with the laser output beam can be displayed, in order to adjust the focal location to the center of the work region in a laser processing apparatus which makes three-dimensional processing possible. The laser beam scanning system 30 in the laser processing apparatus shown in FIGS. 24 and 25 is provided with a guiding light source 64 and a half mirror 65, which is one form of the guide light optical system for making the guide light GL from the guiding light source 64 coincide with the optical axis of the laser beam scanning system 30, which form the distance pointer, and at the same time, provided with a light source 66 for a pointer which emits pointer light PL, a scanner mirror 68 for a pointer formed on the rear surface of a Y axis scanner 32, and a fixed mirror 67 for further reflecting pointer light PL from the light source 66 for a pointer that is reflected from the scanner mirror 68 for a pointer so that the light is emitted toward the location of the focal point, which form the pointer light adjusting system. This distance pointer allows the pointer light PL indicating the location of the focal point of the laser output beam to be emitted from the light source 66 for a pointer, and adjusts the pointer light so that the approximate center of the guide pattern displayed with the guide light GL is irradiated with the point light PL, and thus, the location of the focal point of the laser output light is indicated.
Next, FIG. 32 shows the system configuration of a laser processing apparatus which can carry out three-dimensional processing. The laser processing system shown in this figure includes a marking head 2A, which forms a laser output portion, a controller 1A, which is a laser control portion 1 connected to the marking head 2A to control it, and a laser processing data setting apparatus 70, which is connected to the controller 1A in such a manner that data communication is possible and sets a processing pattern for the controller 1A as three-dimensional laser processing data. The marking head 2A and the controller 1A form a laser processing apparatus 100. Further, the laser processing data setting apparatus 70 installs a laser processing data setting program in the computer in the example of FIG. 32 so that a laser processing data setting function is implemented. A programmable logic controller (PLC) to which a touch panel is connected, as well as other dedicated hardware, in addition to a computer, can be used as the laser processing data setting apparatus. Furthermore, the laser processing data setting apparatus can function as a control apparatus for controlling the operation of the laser processing apparatus. For example, one computer may have a combined function, both as a laser processing data apparatus and as a controller for the laser output portion provided with a laser output portion. Furthermore, the laser processing data setting apparatus may be formed of other members than the laser processing apparatus or combined with the laser processing apparatus, and a laser processing data setting circuit or the like can be incorporated in the laser processing apparatus, for example.
The laser processing data, which is information to be set in order to three-dimensionally process processing data in plane form, is set by a laser processing data setting apparatus 70. FIG. 28 is a block diagram showing an example of the laser processing data setting apparatus 70. The laser processing data setting apparatus 70 shown in this figure includes an input portion 4 for inputting various types of settings, an operation portion 71 which forms a processing data generating section for generating laser processing data based on information inputted through the input portion 4, a display portion 5 for displaying the setting contents and laser processing data after operation, and a storage portion 72 for storing a variety of setting data. The display portion 5 includes a processing image display portion, which can display a three-dimensional image of the surface of the object to be surfaced, and a head image displaying section, which can display an image of the marking head 2A when a three-dimensional image of the surface of the object to be processed is displayed on the processing image display portion. The input portion 4 works as a processing condition setting portion for inputting processing conditions for processing in a desired processing pattern, and functions as a processed surface profile inputting section for inputting profile information showing the three-dimensional form on the processed surface of a workpiece, a processing pattern inputting section for inputting processing pattern information, a processing block setting section for setting a number of processing blocks inside the work region, which can set a processing pattern for each processing block, a group setting section for setting a processing group where a number of processing blocks which are set by the block setting section are collected, and a location adjusting section which can adjust the location of a processing pattern placed on the surface of the object to be processed. The processed surface profile inputting section further functions as a basic figure designating section for designating a basic figure representing the surface of the object to be processed and a three-dimensional form data inputting section for inputting three-dimensional form data representing the surface of the object to be processed from the outside. The storing portion 72 corresponds to the memory portion 52 in FIG. 1, and is a member for storing such information as profile information set in the input portion 4 and processing pattern information, and a storing medium, such as a fixed memory apparatus or a semiconductor memory, can be used for the storing portion. A dedicated display may be provided as the display portion 5, or the monitor of a computer connected to the system may be used. For the processing conditions set by this laser processing data setting apparatus 70, the processing power (laser output) and scanning speed, in addition to the working distance, the amount of defocus, the diameter of the spot and the type of workpiece (black coloring process on iron, black coloring process on stainless steel, material for workpiece, for example an ABS resin, a polycarbonate resin or a phenol resin, and purpose of processing, such as fusion of resin or roughening of surface), are set if necessary. Further, a number of processing blocks may be set, and processing pattern information may be set in processing block units. In particular, the power of the laser output beam and the diameter of the beam can be freely changed in the settings, such as the material for the workpiece, which is the object to be processed for each processing block, the processing pattern, the finished state or the time for processing, in laser processing apparatuses which can achieve a laser output beam having excellent increase properties. Furthermore, the processing parameters for the processing conditions that are once set are stored as setting data and can be called out when necessary.
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