Title: Laser beam machining device
Abstract: A laser material processing apparatus for processing a workpiece (22) in such a way as to separate one laser light (26) into two laser beams (26a, 26b) via first polarizer (25), one laser beam being passed via the mirrors (24), the other laser beam being scanned biaxially by a first galvano scanner (29), and conduct two laser beams (26a, 26b) to a second polarizer (27) for scanning via a second galvano scanner (30), wherein an optical path is constituted such that the laser beam (26b) transmitted through the first polarizer (25) is reflected by the second polarizer (27), and the laser beam (26a) reflected by the first polarizer (25) is transmitted through the second polarizer (27).
Patent Number: 6,984,802 Issued on 01/10/2006 to Kuroiwa, et al.
| Inventors:
|
Kuroiwa; Tadashi (Tokyo, JP);
Ijima; Kenichi (Tokyo, JP);
Kobayashi; Nobutaka (Tokyo, JP)
|
| Assignee:
|
Mitsubishi Denki Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
495781 |
| Filed:
|
November 13, 2002 |
| PCT Filed:
|
November 13, 2002
|
| PCT NO:
|
PCT/JP02/11838
|
| 371 Date:
|
May 17, 2004
|
| 102(e) Date:
|
May 17, 2004
|
| PCT PUB.NO.:
|
WO03/041904 |
| PCT PUB. Date:
|
May 22, 2003 |
Foreign Application Priority Data
| Nov 15, 2001[JP] | 2001-349664 |
| Current U.S. Class: |
219/121.73; 219/121.75; 219/121.77 |
| Current Intern'l Class: |
B23K 26/06 (20060101) |
| Field of Search: |
219/12173,121.74,121.75,121.7,121.71,121.77,121.83
|
References Cited [Referenced By]
U.S. Patent Documents
| 6424670 | Jul., 2002 | Sukhman et al.
| |
| 6521866 | Feb., 2003 | Arai et al.
| |
| 2002/0153361 | Oct., 2002 | Sakamoto et al.
| |
| 2004/0104208 | Jun., 2004 | Ijima et al.
| |
| Foreign Patent Documents |
| 9-29467 | Feb., 1997 | JP.
| |
| 11-314188 | Nov., 1999 | JP.
| |
| 2000/-190087 | Jul., 2000 | JP.
| |
| 2001/-269790 | Oct., 2001 | JP.
| |
| WO 00/5336/5 | Sep., 2000 | WO.
| |
Primary Examiner: Evans; Geoffrey S.
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
The invention claimed is:
1. A laser material processing apparatus for processing a workpiece in such a
way as to separate one laser light beam into two laser light beams, comprising:
a first polarizing means;
a second polarizing means;
a first galvano scanner;
a second galvano scanner; and
a plurality of mirrors,
wherein the first polarizing means, the second polarizing means, the first galvano
scanner, the second galvano scanner, and the plurality of mirrors are arranged
so that:
a first laser beam transmitted through said first polarizing means is reflected
by said second polarizing means, and is conducted to said second galvano scanner;
a second laser beam reflected by said first polarizing means is conducted to
both of said first galvano scanner and said second polarizing means, and
said second laser beam reflected by said first polarizing means is transmitted
through said second polarizing means, and is conducted to said second galvano scanner,
wherein the deflection angle by which said first galvano scanner scans is smaller
than the deflection angle by which said second galvano scanner scans.
2. A laser material processing apparatus for processing a workpiece in such a
way as to separate one laser light beam into two laser light beams, comprising:
a first polarizing means;
a second polarizing means;
a first galvano scanner;
a second galvano scanner; and
a plurality of mirrors,
wherein the first polarizing means, the second polarizing means, the first galvano
scanner, the second galvano scanner, and the plurality of mirrors are arranged
so that:
a first laser beam transmitted through said first polarizing means is reflected
by said second polarizing means, and is conducted to said second galvano scanner;
a second laser beam reflected by said first polarizing means is conducted to
both of said first galvano scanner and said second polarizing means, and
said second laser beam reflected by said first polarizing means is transmitted
through said second polarizing means, and is conducted to said second galvano scanner,
wherein each of the first and second laser beams is reflected by the same number
of mirrors on each optical path formed between said first polarizing means and
said second polarizing means.
3. A laser material processing apparatus for processing a workpiece in such a
way as to separate one laser light beam into two laser light beams, comprising:
a first polarizing means;
a second polarizing means;
a first galvano scanner;
a second galvano scanner; and
a plurality of mirrors,
wherein the first polarizing means, the second polarizing means, the first galvano
scanner the second galvano scanner and the plurality of mirrors are arranged so that:
a first laser beam transmitted through said first polarizing means is reflected
by said second polarizing means, and is conducted to said second galvano scanner;
a second laser beam reflected by said first polarizing means is conducted to
both of said first galvano scanner and said second polarizing means, and
said second laser beam reflected by said first polarizing means is transmitted
through said second polarizing means, and is conducted to said second galvano scanner,
wherein a stationary portion of at least one of the first and second polarizing
means is provided with a rotating mechanism around an axis perpendicular to a surface
containing the axes of two separated laser beams.
4. The laser material processing apparatus according to claim 3, characterized
in that an energy balance of said first and second laser beams is adjusted by changing
a transmission factor of the laser beam transmitted through one of the first and
second polarizing means by rotation of said rotating mechanism provided on said
at least one of the first and second polarizing means.
5. A laser material processing apparatus for processing a workpiece in such a
way as to separate one laser light beam into two laser light beams, comprising:
a first polarizing means;
a second polarizing means;
a first galvano scanner;
a second galvano scanner; and
a plurality of mirrors,
wherein the first polarizing means, the second polarizing means, the first galvano
scanner, the second galvano scanner, and the plurality of mirrors are arranged
so that:
a first laser beam transmitted through said first polarizing means is reflected
by said second polarizing means, and is conducted to said second galvano scanner;
a second laser beam reflected by said first polarizing means is conducted to
both of said first galvano scanner and said second polarizing means, and
said second laser beam reflected by said first polarizing means is transmitted
through said second polarizing means, and is conducted to said second galvano scanner, and
further comprising a laser beam selecting means for selecting any laser beam
from among the first and second laser beams.
6. The laser material processing apparatus according to claim 5, characterized
in that said laser beam selecting means controls a shutter provided on an optical
path of each of the first and second laser beams to be opened or closed to take
out the respective one of the first and second laser beams from that optical path.
7. The laser material processing apparatus according to 6, characterized by further
comprising detection means for detecting an energy balance of the first and second
laser beams on each optical path, so that the energy balance of each laser beam
detected by said detection means can be adjusted to be almost equivalent.
8. The laser material processing apparatus according to claim 7, characterized
in that said detection means consists of a power sensor provided near an XY table
on which the workpiece is laid.
Description
TECHNICAL FIELD
The present invention relates to a laser material processing apparatus mainly
intended for drilling the workpiece such as a printed board to improve the productivity.
BACKGROUND ART
FIG. 8 is a schematic constitutional view showing the conventional laser material
processing apparatus for drilling.
In FIG. 8, reference numeral 1 denotes a workpiece such as a printed board,
2 denotes a laser beam for drilling the workpiece 1 to make a via
hole or through hole, 3 denotes a laser oscillator for oscillating the laser
beam 2, 4 denotes a plurality of mirrors for reflecting the laser
beam 2 along the optical path, 5 and 6 denote a galvano scanner
for scanning the laser beam 2, 7 denotes an fθ lens for focusing
the laser beam 2 on the workpiece 1, and 8 denotes an XY stage
for moving the workpiece 1.
In the typical laser material processing apparatus for drilling, the laser beam
2 oscillated from the laser oscillator 3 is conducted via a necessary
mask and the mirrors 4 to the galvano scanners 5, 6 and focused
via the fθ lens 7 at a predetermined position of the workpiece 1
by controlling the deflection angle of the galvano scanners 5, 6.
The deflection angle of the galvano scanners 5, 6 via the fθ
lens 7 is limited to a range of 50 mm square, for example. Therefore, the
laser beam 2 is focused at the predetermined position of the workpiece 1
by controlling the XY stage 8 as well, thereby allowing the workpiece 1
to be machined in a broader range.
Herein, the productivity of the laser material processing apparatus is closely
related with the drive speed of the galvano scanners 5, 6 and the
processing area of the fθ lens 7.
To improve the drive speed of the galvano scanner, it is effective to change
the
design of an optical system by reducing the mass of a galvano mirror fixed to the
rotation shaft of the galvano scanner and driven by controlling the deflection
angle, or varying the distance between the galvano scanners 5, 6
and the fθ lens 7, and to reduce the deflection angle while the processing
range is maintained. However, if the mirror diameter of the galvano scanner is
made smaller to reduce the mass of the galvano mirror, the laser beam 2
has its peripheral portion intercepted by a mask in passing through the mask, and
the diameter once reduced, but the laser beam 2 is broadened in diameter
due to diffraction after passing through the mask, and has a larger diameter than
the galvano mirror when arriving at the galvano mirror of the galvano scanner 5,
6, causing a part of the laser beam 2 to get out of the galvano mirror,
so that an image of the mask is not correctly transferred onto the workpiece 1,
whereby the micro hole fabrication is not made.
Also, the deflection angle of the galvano scanners is reduced while the processing
range is maintained in such a way as to change the optical design, including changing
the positional relation between the fθ lens and the galvano scanners. However,
it takes a lot of time to design, and it is required to change the specification
of the very expensive fθ lens or the design of the overall optical system,
whereby it was difficult to improve the productivity easily and cheaply with a
single beam.
A laser material processing apparatus of the previously described type intended
to improve the productivity was disclosed in JP-A-11-314188, for example.
FIG. 9 is a schematic constitutional view of the laser material processing apparatus
as disclosed in JP-A-11-314188.
In FIG. 9, reference numeral 9 denotes a workpiece, 10 denotes a
mask, 11 denotes a half-mirror for separating a laser light, 12 denotes
a dichroic mirror, 13
a denotes a laser beam reflected from the half-mirror,
13
b denotes a laser beam transmitted through the half-mirror and
reflected from the dichroic mirror, 14 and 15 denote the mirrors,
16 denotes an fθ lens for focusing the laser beams 13
a and
13
b onto the workpiece 9, 17 and 18 denote galvano
scanners for conducting the laser beam 13
a to a processing area A1,
19 and 20 denote galvano scanners for conducting the laser beam 13
b
to a processing area A2, and 21 denotes an XY stage for moving
each part of the workpiece to the processing area A1 or A2.
The laser material processing apparatus as shown in FIG. 9 separates the laser
light passing through the mask 10 via the half-mirror 11 into plural
beams, conducts the separated laser beams 13
a and 13
b to
a plurality of galvano scanner systems arranged on the incident side of the fθ
lens 16, and scans the laser beams 13
a and 13
b with
the plurality of galvano scanner systems to be applied to the divided processing
areas A1 and A2.
The separated laser beam 13
a is introduced via the first galvano
scanner system 17, 18 into a half area of the fθ lens 16.
Also, the other separated laser beam 13
b is introduced via the second
galvano scanner system 19, 20 into a remaining half area of the fθ
lens 16. The first and second galvano scanner systems are arranged in symmetry
about the central axis of the fθ lens 16, whereby the half parts of
the fθ lens 16 are employed at the same time to improve the productivity.
However, in the apparatus as disclosed in JP-A-11-314188, the first galvano
scanner system 17, 18 and the second galvano scanner system 19,
20 scan the laser beams, into which laser light is separated via the half
mirror 11, to be applied on the processing areas A1 and A2
that are divided. Therefore, a dispersion in the quality of processed holes is
likely to occur due to a difference between reflection from and transmission through
the half mirror 11 between the laser beams 13
a and 13
b,
into which laser light is separated by the half mirror 11.
For example, when there is an energy difference between the separated laser beams
13
a and 13
b, a difference in the hole diameter or hole
depth of the processed holes is likely to occur on the workpiece 9. Therefore,
there is the possibility that the strict requirements for processing the hole are
not satisfied in terms of the dispersion in the hole diameter.
Herein, when the laser beam 13
a has a higher energy than the
laser beam 13
b, it is required to adjust the energy of laser beam
13
b to be decreased by further adding an expensive optical component
such as an optical attenuator on the optical path of laser beam 13
b.
The optical component such as the optical attenuator must be produced in the specification
of removing the energy at a certain percentage. For example, when the specification
of removing the energy of 5% and the specification of removing the energy of 3%
are required, two kinds of optical attenuator are produced. Thereby, the optical
attenuator is prepared in a few kinds of specification, and exchanged every time
the energy difference is adjusted.
Also, in the optical path constitution as shown in FIG. 9, there was a problem
that the optical path lengths of laser beams 13
a and 13
b,
into which laser light is separated after passing through the mask 10, up
to the workpiece 9 are different, so that the strict beam spot diameters
on the workpiece 9 are different.
Moreover, the fθ lens 16 is equally divided, and the divided
processing areas A1, A2 are machined at the same time. Therefore,
when the number of processed holes in the processing areas A1 and A2
is greatly varied, or when there is no processed hole of object in either the processing
area A1 or A2 such as an end portion of the workpiece, it is not
expected to improve the productivity.
DISCLOSURE OF THE INVENTION
This invention has been achieved to solve the above-mentioned problems, and
it is an object of the invention to provide a laser material processing apparatus
in which a difference in the energy or quality between separated laser beams is
minimized to provide an equal optical path length and an equal beam spot diameter
for the separated laser beams, and the separated laser beams are applied on the
same area to improve the productivity less expensively.
In order to achieve the above object, according to a first aspect of the invention,
there is provided a laser material processing apparatus for processing a workpiece
in such a way as to separate one laser light into two laser beams via first polarizing
means, one laser beam being passed via the mirrors, the other laser beam being
scanned biaxially by a first galvano scanner, and conduct two laser beams to second
polarizing means for scanning via a second galvano scanner, characterized in that
an optical path is constituted such that the laser beam transmitted through the
first polarizing means is reflected by the second polarizing means, and the laser
beam reflected by the first polarizing means is transmitted through the second
polarizing means.
Also, two polarizing means are arranged so that the reflection surfaces may
be opposed to each other to form an optical path in which the separated laser beams
have the equal optical path length.
Also, a stationary portion of polarizing means is provided with a rotating
mechanism around an axis perpendicular to a surface containing the axes of two
separated laser beams.
Also, an energy balance of the laser beam is adjusted by changing a transmission
factor of the laser beam transmitted through polarizing means by rotation of the
rotating mechanism.
The laser beam selecting means is provided for selecting any laser beam from
among the separated laser beams.
Also, the laser beam selecting means controls a shutter provided on the optical
path of each of the separated laser beams to be opened or closed to take out the
laser beam from any optical path.
Also, detection means is provided for detecting an energy balance of laser
beam on each optical path, in which the energy balance of each laser beam detected
by the detection means is adjusted to be almost equivalent.
Also, the detection means consists of a power sensor provided near an XY table
on which the workpiece is laid.
Also, the separated laser beams have the equal optical path length between
the first polarizing means and the second polarizing means.
Also, the deflection angle by which the first galvano scanner scans is smaller
than the deflection angle by which the second galvano scanner scans.
Also, each laser beam is reflected by the same number of mirrors on each optical
path formed between the first polarizing means and the second polarizing means.
Also, third polarizing means is provided between a laser oscillator and the
first polarizing means, in which two laser beams separated by the third polarizing
means are conducted to the first polarizing means and the second polarizing means
and further separated into 2n components.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view schematically showing an optical path constitution of a laser
material processing apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged view and a structural view of a portion for reflecting
and transmitting the laser beam in a polarized beam splitter within the optical
path constitution of the laser material processing apparatus according to the embodiment
of the invention.
FIG. 3 is a graph showing the dependency of reflection and transmission factors
on an incident angle of laser beam in the polarized beam splitter according to
the embodiment of the invention.
FIG. 4 is a flowchart of a program for automatically correcting the deflection
angle of a galvano scanner.
FIG. 5 is a flowchart of a program for automatically adjusting the angle of
the polarized beam splitter.
FIG. 6 is a view showing the schematic constitution of an example of the laser
material processing apparatus when four laser beams are employed to perform the
processing by adding polarizing means.
FIG. 7 is a flowchart of a program for automatically correcting the deflection
angle of the galvano scanner.
FIG. 8 is a view showing the schematic constitution of the conventional laser
material processing apparatus for drilling.
FIG. 9 is a view showing the schematic constitution of the conventional laser
material processing apparatus for drilling intended to improve the productivity.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
FIG. 1 is a schematic constitutional view showing a laser material processing
apparatus according to an embodiment of the present invention.
In FIG. 1, reference numeral
22 denotes a workpiece such as a printed
board,
23 denotes a mask for forming an image to transfer a desired processing
shape (e.g., circle) onto the workpiece
22,
24 denotes a plurality
of mirrors for reflecting a laser beam along the optical path,
25 denotes
a first polarized beam splitter as first polarizing means for separating a laser
light,
26a denotes a laser beam reflected from the first polarized
beam splitter,
26b denotes a laser beam transmitted through the first
polarized beam splitter,
27 denotes a second polarized beam splitter as
second polarizing means for transmitting the laser beam
26a and reflecting
the laser beam
26b,
28 denotes an fθ lens for focusing
the laser beams
26a and
26b onto the workpiece
22,
29 denotes a first galvano scanner for scanning the laser beam
26a
biaxially to be conducted to the second beam splitter,
30 denotes a
second galvano scanner for scanning the laser beams
26a and
26b
biaxially to be conducted to the workpiece
22,
31 denotes an
XY stage for moving the workpiece
22,
34 denotes a shutter as laser
beam selecting means provided on the optical path of laser beam and intercepting
the laser beam,
35 denotes a power sensor for measuring the energy of laser
beam emergent from the fθ lens
28,
36 denotes a CCD camera
that is an image pickup device for measuring the hole diameter or position of a
processed hole by the laser beam, and
37 denotes a workpiece for correcting
the deflection angle of galvano scanner.
FIG. 2 shows a portion for reflecting or transmitting the laser beam in the
polarized beam splitter
25 or
27. Reference numeral
32 denotes
a window for reflecting or transmitting the incident light,
33 denotes a
mirror for causing an incident light component reflected from the window
32
to be reflected at an angle of 90° relative to the incident light,
41
denotes a servo motor having a rotation axis disposed at a position where the emergent
angle and position of laser beam are unchanged even if the incident angle of laser
beam on the polarized beam splitter is changed,
42 denotes a bracket for
securing the servo motor
41, and
43 denotes a bracket for connecting
the polarized beam splitter and the servo motor.
For the window portion
32 of the polarized beam splitter
25,
27,
a material ZnSe is often employed in a case of CO
2 laser, but other
materials such as Ge may be employed.
In this invention, the oscillated laser light is circularly polarized and conducted
to the first polarized beam splitter
25 for separation into the laser beam
26b that is P wave transmitted through the first polarized beam splitter
in a polarization direction parallel to the incident plane and the laser beam
26a
that is S wave reflected in a polarization direction perpendicular to the incident plane.
The laser beam conducted to the first polarized beam splitter
25 may be
linearly polarized, but not circularly polarized, to make an angle of 45°
relative to the polarization directions of P wave and S wave.
Herein, when either the circularly polarized light or the linearly polarized
light is conducted to the first polarized beam splitter, it is required to oscillate
the laser light of linear polarization from the laser oscillator.
In order to conduct the laser light of circular polarization to the first polarized
beam splitter
25, it is required to employ a retarder for changing the linearly
polarized light to the circularly polarized light on the optical path, whereby
the laser light is incident at an angle of 90° between the incident light
and the reflected light in the retarder. Also, the polarization direction of laser
light incident on the retarder must make an angle of 45° relative to the line
of intersection between a plane made by the optical axis of incidence and the optical
axis of reflection as two sides and a reflection surface of the retarder. However,
the laser light of circular polarization includes evenly the polarization directions
of P wave and S wave, and there is no limitation on the polarization direction
when conducting the laser beam to the first polarized beam splitter
25,
whereby the optical path is designed with a high degree of freedom.
On the other hand, when the linearly polarized light is employed, it is required
to conduct the laser light to the first polarized light beam splitter
25
as the linearly polarized light making an angle of 45° relative to the polarization
directions of P wave and S wave separated by the first polarized beam splitter,
as previously described. Though there is a limitation on the design of the optical
path, it is unnecessary to provide the retarder and an adjusting mechanism for
adjusting the polarization direction of laser beam incident on the retarder, and
the angle of optical axis, and to make the adjustments, whereby it is possible
to simplify the optical path to contribute to reduction of the cost.
The laser beam
26b transmitted through the first polarized beam
splitter
25 is conducted via the bend mirrors
24 to the second polarized
beam splitter
27. On the other hand, the laser beam
26a reflected
from the first beam splitter
25 is caused to scan biaxially by the first
galvano scanner
29, and conducted to the second polarized beam splitter
27.
Thereafter, the laser beams
26a,
26b are
caused to scan biaxially by the second galvano scanner
30, and applied on
the workpiece through the fθ lens
28.
At this time, the laser beam
26a is applied at the same position
on the workpiece as the laser beam
26b by scanning of the first galvano
scanner
29.
Also, the laser beams can be applied at different two points on the workpiece
via the second galvano scanner
30 by causing the laser beam
26a
to scan within a preset range for the laser beam
26b, for example,
within a range of 4 mm square around the laser beam
26b by scanning
of the galvano scanner
29 in view of the characteristics of the window
32
for the beam splitter.
The laser beam
26a reflected from the first polarized beam splitter
25 is transmitted through the second polarized beam splitter
27,
and the laser beam
26b transmitted through the first polarized beam
splitter is reflected from the second polarized beam splitter
27.
Therefore, two separated laser beams are passed through both the reflection
and transmission processes, whereby it is possible to offset a variation in the
quality of laser beam or a breakdown in the energy balance.
For example, the reflection and transmission factors in the polarized beam splitter
are given near the Brewster angle in which the incident angle of laser beam on
the polarized beam splitter is ideal, as shown in FIG. 3.
The longitudinal axis of FIG. 3 is the reflection factor and the transmission
factor, which indicate 100% when the incident laser light is fully divided into
two beams. For example, when the reflection factor is 100%, the percentage of reflected
light to the incident light is 50%.
When the incident angle of laser beam has an error of -2° with respect
to the Brewster angle for two polarized beam splitters, the reflection factor of
laser beam is 99% and the transmission factor is 97% for each polarized beam splitter.
The energies of two laser beams obtained through the reflection or transmission
process twice are 98% and 94%, producing an energy difference of 4%, while the
energies of laser beams obtained through both the reflection and transmission processes
once are both 96%. By making the optical path as previously described, it is possible
to offset the characteristics.
Also, two polarized beam splitters may be identical, whereby the offset effect
is facilitated to contribute to reduction of the cost.
Two polarized beam splitters are arranged, as shown in FIG. 1, so that the optical
path lengths of the laser beams
26a and
26b between
the first polarized beam splitter
25 and the second polarized beam splitter
27 are equal. Thereby, the beam spot diameters of two separated laser beams
are equalized.
For example, in this embodiment of the invention, when the optical path is decomposed
into X, Y and Z directions, the same optical path length is obtained. Therefore,
when the design of optical path components is changed dimensionally, the optical
path can be extended or contracted in the X, Y and Z directions, whereby the optical
path lengths of laser beams
26a and
26b are kept invariant.
Also, the polarized beam splitter is integrated with the mirror
33,
so that the reflected light may be emergent at 90° with respect to the incident
angle, as shown in FIG. 2.
A stationary portion of the polarized beam splitter has a structure in which a
rotating mechanism is provided around the axis perpendicular to the plane containing
the axes of two separated laser beams
26a and
26b,
as shown in FIG. 2. When there is an energy difference between two separated laser
beams
26a and
26b, the energy difference is adjusted
using the dependency of reflection factor and transmission factor on the incident
angle of laser beam, as shown in FIG. 3. The precision of energy balance of two
laser beams
26a and
26b after passing through two polarized
beam splitters is enhanced in an inexpensive way without needing the other optical
components such as an optical attenuator.
Also, the rotation axis is located at the position where the emergent position
is unchanged even if the incident angle on the polarized beam splitter is changed.
Even if the polarized beam splitter is rotated to adjust the energy balance, it
is managed to minimize a change in the angle or position of succeeding optical path.
For example, in the case where the rotation axis is arranged at a point of intersection
between the window
32 and the mirror
33 in FIG. 2, when the polarized
beam splitter is rotated by ±5°, the incident angle of laser beam on
the window
32 is increased, but the incident angle on the mirror
33
is decreased. Or the incident angle of laser beam on the window
32 is decreased,
but the incident angle on the mirror
33 is increased. The emergent angle
of the laser beam being incident on the polarized beam splitter is 90° without
error by offsetting an angle error, and there is no variation in the emergent position.
Thereby, this effect is similarly provided, whether the window
32 or the
mirror
33 for the polarized beam splitter is on the incident side.
Owing to the relationship between the reflection and transmission factors and
the incident angle in the polarized beam splitter as shown in FIG. 3 and the above
effect, when the energy of laser beam
26a reflected from the first
polarized beam splitter
25 is high, the energy is decreased by rotating
the second polarized beam splitter
27, and adjusting the transmission factor
of laser beam
26a. Also, when the energy of laser beam
26b
transmitted through the first polarized beam splitter
25 is high, the
energy is decreased by rotating the first polarized beam splitter
25, and
adjusting the transmission factor of laser beam
26b. Thereby, the
later adjustment for the optical path is unnecessary, and the maintenance time
is shortened.
Referring to FIG. 4, a flow for automatically adjusting the angle of the
polarized beam splitter to control the energy balance of laser beams will be described below.
First of all, the power sensor
35 is moved to the position where a light
receiving portion of the power sensor
35 fixed on the XY stage
31
can receive laser beam emergent from the fθ lens
28 (step S
1).
Thereafter, the first shutter
34a is opened, and the second
shutter
34b is closed (step S
2). Then, a laser light is emitted
from the laser oscillator, not shown, and an energy of the laser beam
26a
is measured by the power sensor
35 (step S
3).
After measuring the energy, the oscillation of laser light is once stopped,
the first shutter
34a is closed, and the second shutter
34b
is opened (step S
4).
By emitting laser light again, an energy of laser beam
26b is measured
by the power sensor
35 (step S
5).
An energy difference between two laser beams
26a and
26b
measured by a control device is calculated (step S
6). If it is within
a tolerance value, the adjustment is ended. However, if it is out of the tolerance
value, the first polarized beam splitter
25 and the second polarized beam
splitter
27 are rotated to adjust the transmission factor of each polarized
beam splitter (step S
9), whereby the adjustment is repeated by measuring
the energies of two laser beams again until it is within the tolerance value.
Also, it is determined whether or not the tolerance value of energy difference
is within a preset range of rotation angle for the polarized beam splitter, for
example, within a range of ±5° (step S
8). If it is not within
the preset range, the circular polarization factor is reduced when the laser light
of circular polarization is conducted from the laser oscillator, or when the laser
light of linear polarization is conducted, it is judged that the apparatus is in
a condition requiring the maintenance for the angle deviation in the polarization
direction in which laser beam is conducted at an angle of 45° with respect
to the polarization direction of transmission or reflection in the first polarized
beam splitter
25, whereby the program is ended, and a message indicating
that the program is abnormally ended and prompting the maintenance is displayed
on the operation screen, not shown.
This automatic adjustment for the angle of the polarized beam splitter is made
periodically, for example, at the time of setup or starting the apparatus. Thereby,
the energy balance of laser beams is always maintained at high precision, and the
worker does not need the skills, thereby performing the stable machining.
Referring to FIG. 5, a flow for making the automatic correction for the
deflection angle of the galvano scanner to maintain or improve the precision of
processing position is shown.
First of all, the workpiece
37 (e.g., acrylic plate) for correction
that is placed beforehand on the XY stage
31 is moved to the processing
area of the fθ lens
28. The second shutter
34b is opened,
and the first shutter
34a is closed (step S
11). The laser
beam
26b is caused to scan by the second galvano scanner
30,
the machining before correcting the deflection angle of the second galvano scanner
30 is made within a preset range, for example, within a range of 50 mm square
of the workpiece (step S
12).
After making the machining, the positional precision of processed hole is measured
with the CCD camera
36 by driving the XY stage
31 (step S
13).
By comparing the measurement result with the reference position, the correction
value for the deflection angle of the second galvano scanner
30 is calculated
in the control device, not shown (step S
14).
Thereafter, the XY stage
31 is driven to move the workpiece
37
for correction within the processing area of the fθ lens
28, whereby
the workpiece
37 is machined after correcting the deflection angle of the
second galvano scanner
30 (step S
15).
After making the machining, the positional precision of processed hole is measured
with the CCD camera
36 by driving the XY stage
31 (step S
16),
and compared with the preset tolerance value (step S
17). When it is out
of the tolerance value, the program is ended to inform the operator that the apparatus
has the abnormality or there is an error in usage of the method, and a message
with the contents indicating that the program is abnormally ended is displayed
on the operation screen, not shown.
On the other hand, within the tolerance value, the correction for the deflection
angle of the second galvano scanner
30 is ended, and the correction for
the deflection angle of the first galvano scanner
29 is made.
In correcting the deflection angle of the first galvano scanner
29, the
first shutter
34a is opened, and the second shutter
34b
is closed (step S
18). Thereby, the laser beam
26a alone
is caused to scan by the first galvano scanner
29 and the second galvano
scanner
30, in which the machining before correcting the deflection angle
of the first galvano scanner
29 is made in the same range as at the time
of correcting the deflection angle of the second galvano scanner
30 (step S
19).
For example, the first galvano scanner
29 controls the laser beam
26a
to scan in a range of 4 mm square around the laser beam
26b,
and the second galvano scanner
30 controls the laser beam
26a
to scan in a range of 46 mm square around the laser beam
26a,
whereby the laser beam
26a passed via the first and second galvano
scanners
29 and
30 makes the machining in a range of 50 mm square.
After making the machining, the positional precision of processed hole is measured
with the CCD camera
36 by driving the XY stage
31 (step S
20)
By comparing the measurement result with the reference position, the correction
value for the deflection angle of the first galvano scanner
29 is calculated
in the control device (step S
21).
Thereafter, the XY stage
31 is driven to move the workpiece
37
for correction within the processing area of the fθ lens
28, whereby
the workpiece
37 is machined after correcting the deflection angle of the
first galvano scanner
29 (step S
22).
After making the machining, the positional precision of processed hole is measured
with the CCD camera
36 by driving the XY stage
31. When it is out
of the tolerance value, the program is ended to inform the operator that the apparatus
has an abnormality of the apparatus or there is an error in usage of the method
in the same manner as correcting the deflection angle of the second galvano scanner
30 and a message with the contents indicating that the program is abnormally
ended is displayed on the operation screen, not shown.
On the other hand, within the tolerance value, the correction for the deflection
angle of the first galvano scanner
29 is ended.
The automatic correction for the deflection angle of the galvano scanner is performed,
if any conditions are satisfied, for example, if the temperature of the galvano
scanner main body or the peripheral temperature is monitored to detect a temperature
change, or when a fixed time has passed. Thereby, the machining is always performed
at stable positional precision.
In this embodiment, means for conducting the laser light of circular polarization
to the polarized beam splitter and separating the laser light into beams is employed.
However, though not shown in the embodiment, the linearly polarized light may be
oscillated from the laser oscillator and conducted at an angle of 45° with
respect to the polarization directions of reflection and transmission that are
orthogonal to each other in the polarized beam splitter, whereby the same effects
are obtained.
Embodiment 2
After separation into laser beams by the polarized beam splitter, the laser
beams are circularly polarized again, or incident on the polarized beam splitter
at an angle of 45° with respect to the polarization directions of reflection
and transmission, whereby the separation into laser beams is repeated, and the
machining is made using not only two beams but also 2n laser beams.
FIG. 6 is a schematic constitutional view showing an example of the laser material
processing apparatus in which third polarizing means is added to make the machining
using four laser beams.
In the constitution as shown in FIG. 6, a laser light of circular polarization
or linear polarization is oscillated and conducted from the laser oscillator, not
shown, and separated into laser beams by a third polarized beam splitter
38.
The optical path is constituted so that the polarization direction of a laser beam
26 transmitted through the third polarized beam splitter
38 and the
polarization direction of a reflected laser beam
39 make an angle of 45°
with respect to the polarization directions of reflection and transmission in the
first polarized beam splitters
25 and
25A. Thereby, the laser beam
26 is separated into the laser beams
26a and
26b
and the laser beam
39 is separated into the laser beams
39a
and
39b.
The optical path following the first polarized beam splitters
25 and
25A
has the same constitution as in the embodiment of the invention as shown in FIG.
1, whereby the machining is made by applying four laser beams on the workpiece.
The optical path lengths from the third polarized beam splitter
38 for
separation to the workpiece subject to the laser beams are made equal, and the
beam spot diameters of four separated laser beams are made equal.
To adjust the beam splitter, by comparing the energy of laser beam
26
(sum
of laser beams
26a and
26b) when the first and second
shutters
34a and
34b are only opened, and the energy
of laser beam
39 (sum of laser beams
39a and
39b)
when the third and fourth shutters
34c and
34d are
only opened, the third polarized beam splitter
38 is rotated to change the
incident angle of laser light, so that the laser beam
26 transmitted through
the polarized beam splitter
38 and the energy of reflected laser beam
39
may be equal, as shown in FIG. 7.
Thereafter, by comparing the energy of laser beam
26a when
the first shutter
34a alone is opened and the energy of laser beam
26b when the second shutter
34b alone is opened, the
first polarized beam splitter
25 and the second polarized beam splitter
27 are rotated and adjusted so that the energy of laser beam
26 is
equally divided into the laser beams
26a and
26b (step S
32).
Finally, by comparing the energy of laser beam
39a when the
third shutter
34c alone is opened, and the energy of laser beam
39b
when the fourth shutter
34d along is opened, the first polarized
beam splitter
25A and the second polarized beam splitter
27A are
rotated, and adjusted so that the energy of laser beam
39 is equally divided
into the laser beams
39a and
39b (step S
33).
With the above adjustments, the energy balance of four laser beams conducted
to the workpiece
34 is enhanced.
For the automatic correction for the deflection angle of the galvano scanner,
the deflection angle of each galvano scanner is corrected by detecting a deviation
from the reference position with the laser beams
26a,
26b,
39a and
39b in a state where any one of the shutters
34 is opened.
As described above, if the laser material processing apparatus according to this
invention is employed, a difference in the quality or energy between separated
laser beams is equalized to improve the productivity. Also, by making the optical
path length of two separated laser beams equal, the beam spot diameters of two
laser beams are made equal. Also, a rotating mechanism is provided in the stationary
portion of polarizing means, whereby there is the effect that the variation in
the energy of two laser beams separated is minimized less expensively.
INDUSTRIAL APPLICABILITY
As described above, the laser material processing apparatus according to the
invention
is suitable for drilling the workpiece such as the printed board.
*
