TW202136857A - Beam splitting device and splitting ratio adjustment method - Google Patents

Abstract

According to the present invention, a first reflective mirror, a second reflective mirror, and a third reflective mirror are disposed in order in the propagation direction of a laser beam on the path of the laser beam to be incident on a polarization beam splitter. The first reflective mirror is supported in a tilt-adjustable manner by a first adjusting mechanism in a direction in which an angle between the polarization surface of the incident beam to the first reflective mirror and the optical axis of a reflective beam reflected by the first reflective mirror is changed. When the orientation of the first reflective mirror has been changed by the first adjusting mechanism, the second reflective mirror is supported by a second adjusting mechanism so as to be tilt-adjustable and movable in a direction in which the state in which a reflective beam from the first reflective mirror is incident on the second reflective mirror and the state in which a reflective beam from the second reflective mirror is incident on the third reflective mirror can be maintained. Thus, it is possible to slightly adjust the polarization direction of a laser beam incident onto the polarization beam splitter without increasing the number of optical components introduced in the path of the laser beam.

Description

Beam divergence device and method for adjusting divergence ratio

The invention relates to a beam divergence device and a method for adjusting the divergence ratio of laser beams. This application claims priority based on Japanese Patent Application No. 2020-045372 filed on March 16, 2020. The entire content of this Japanese application is incorporated in this specification by reference.

A dual-axis laser processing device is known. In order to improve the efficiency of laser processing, two pulses are cut out from one pulse of a pulsed laser beam output from a laser oscillator and processed with two laser beams (for example, , Please refer to the following patent document 1). In the laser processing device disclosed in Patent Document 1, one pulse of the pulsed laser beam is divided into two pulses on the time axis by an acousto-optic element, and the two pulses propagate in different optical paths. The acousto-optic element has the function of cutting out the pulse for processing from one pulse and the function of dividing an optical path into two optical paths. [Prior Technical Literature]

[Patent Document 1] JP 2013-71136 A

[The problem to be solved by the invention]

The angle formed by the two light paths diverged by the acousto-optic element is very small. Therefore, the optical components that should be arranged on the two divergent optical paths are prone to interference in space, which restricts the position where the optical components are arranged. Instead of the acousto-optic element, a polarizing beam splitter that splits the laser beam into two paths according to the polarization direction is used, so that one optical path can be split into two optical paths.

Due to the manufacturing deviation of the polarizing beam splitter, the divergence ratio of the laser beam varies among individuals. In order to set the intensity of the two divided laser beams to the target value, it is necessary to fine-tune the polarization direction of the laser beam incident on the polarizing beam splitter to fine-tune the intensity ratio of the P-polarized component and the S-polarized component. The Brewster window can be used to adjust the intensity ratio of the P-polarized component and the S-polarized component. If the Brewster window is inserted into the optical path of the laser beam only to adjust the intensity ratio of the P-polarized component and the S-polarized component, the number of optical components will increase. The additional optical components will cause various adverse effects such as thermal lens effect on the convergence and divergence of the laser beam.

The object of the present invention is to provide a beam splitting device and a split ratio adjustment method that can finely adjust the polarization direction of the laser beam incident on the polarizing beam splitter without increasing the number of optical components inserted into the optical path of the laser beam. [Technical means to solve the problem]

According to an aspect of the present invention, a beam splitting device is provided, which has: Polarized beam splitter, which splits the linearly polarized laser beam; and The polarization direction adjustment optical system guides the incident laser beam to the aforementioned polarized beam splitter, The aforementioned polarization direction adjustment optical system has: The first reflector, the second reflector, and the third reflector are sequentially arranged along the propagation direction of the laser beam on the path of the laser beam incident on the polarizing beam splitter; The first adjustment mechanism is to support the first mirror so as to change the angle between the polarization plane of the incident light incident on the first mirror and the optical axis of the reflected light reflected by the first mirror. Tilt adjustment in the direction; and The second adjustment mechanism supports the second mirror so that when the posture of the first mirror is changed by the first adjustment mechanism, the reflected light from the first mirror can be maintained to be incident on the second mirror. The state of the mirror and the reflected light of the second mirror are incident on the direction of the state of the third mirror, and the tilt can be adjusted.

According to another aspect of the present invention, a method for adjusting the divergence ratio is provided, The linearly polarized laser beam is incident on the path of the laser beam of the polarizing beam splitter that changes the branch ratio in accordance with the polarization direction to branch. The first mirror and the second mirror are arranged in order along the propagation direction of the laser beam Reflector, and third reflector, The tilt adjustment of the first mirror is performed in a direction that changes the angle between the polarization plane of the incident light incident on the first mirror and the optical axis of the reflected light after being reflected by the first mirror, The movement and tilt adjustment of the second mirror are performed to maintain the state where the reflected light of the first mirror is incident on the second mirror and the second reflection after the posture of the first mirror is changed. The state where the reflected light of the mirror is incident on the aforementioned third mirror. [Effects of Invention]

By performing the tilt adjustment of the first mirror and the movement and tilt adjustment of the second mirror, the polarization direction of the laser beam incident on the polarizing beam splitter can be adjusted without increasing the number of optical components.

Referring to FIGS. 1 to 3, a beam splitting device according to an embodiment will be described. Fig. 1 is a schematic perspective view of a beam splitting device according to an embodiment. A laser light source 20, a polarization direction adjusting optical system 30 and a polarization beam splitter 40 are supported on the optical platform 10. The polarization direction adjustment optical system 30 includes a first mirror 31, a second mirror 32, a third mirror 33, a first adjustment mechanism 36, and a second adjustment mechanism 37. The xyz rectangular coordinate system is defined as the upper surface of the optical table 10 as the xy plane, and the normal direction of the upper surface of the optical table 10 as the z-axis direction. For example, the xy plane is a horizontal plane, and the z axis faces vertically upward.

2A is a schematic plan view showing the arrangement of the optical components and the positional relationship of the optical axis of the laser beam, and FIG. 2B is a schematic plan view showing the arrangement of the optical components and the positional relationship of the optical axis of the laser beam when viewed along the x-axis Side view. In the following description, refer to Figure 1 and refer to Figures 2A and 2B as needed.

The laser light source 20 outputs a linearly polarized laser beam. The optical axis of the laser beam output from the laser light source 20 is parallel to the upper surface of the optical platform 10. For example, the optical axis of the laser beam output from the laser light source 20 is parallel to the xy plane, and the laser beam propagates in the negative direction of the x-axis. In this specification, the xy plane is referred to as a reference plane. The polarization direction PD of the laser beam is parallel to the y axis. That is, the polarization plane is parallel to the xy plane. The laser beam output from the laser light source 20 is sequentially reflected by the first mirror 31, the second mirror 32, and the third mirror 33 and enters the polarizing beam splitter 40.

The first reflecting mirror 31 faces the polarization plane of the incident laser beam (hereinafter referred to as incident light.) and any plane including the optical axis of the incident light and a plane orthogonal to the polarization plane. The optical axis of the reflected laser beam (hereinafter referred to as reflected light) is inclined to reflect the laser beam. For example, the optical axis of the reflected light reflected by the first mirror 31 is inclined with respect to either the reference plane (xy plane) and the zx plane (see FIG. 2B). In addition, the optical axis of the reflected light of the first mirror 31 is orthogonal to the optical axis of the incident light. That is, the optical axis of the reflected light of the first mirror 31 is parallel to the yz plane (see FIG. 2A).

The first adjustment mechanism 36 supports the first mirror 31 to change the angle between the polarization plane of the incident light incident on the first mirror 31 and the optical axis of the reflected light reflected by the first mirror 31 Adjust the tilt in the direction (see Figure 2B). When the tilt adjustment of the first mirror 31 is performed, the optical axis of the reflected light reflected by the first mirror 31 changes in a plane parallel to the yz plane, and the tilt angle ( Hereinafter, it is referred to as the elevation angle θ.) Changes.

The optical axis of the reflected light reflected by the second mirror 32 is perpendicular to the reference plane (xy plane) (see FIG. 2B). The second adjustment mechanism 37 supports the second mirror 32 so that even if the tilt adjustment of the first mirror 31 is performed, the reflected light of the first mirror 31 can be maintained to enter the second mirror 32 and the second mirror 32 The reflected light of the second mirror 32 moves in the direction of the state where the third mirror 33 is incident and can be tilted (refer to FIG. 2B). Even if the second mirror 32 moves, the position of the optical axis of the reflected light of the second mirror 32 in the xy plane does not change.

The third mirror 33 is fixed to the optical table 10. The optical axis of the reflected light of the third mirror 33 is parallel to the reference plane (xy plane), and the reflected light propagates in the positive direction of the x-axis (see FIG. 2A). That is, the propagation direction of the reflected light of the third mirror 33 is antiparallel to the propagation direction of the incident light of the first mirror 31. The reflected light of the third mirror 33 enters the polarized beam splitter 40. The polarization direction PD of the reflected light of the third mirror 33 is inclined with respect to the xy plane at an elevation angle θ (see FIG. 2B). For example, when the elevation angle θ is 45°, the polarization plane of the reflected light of the third mirror 33 is inclined by 45° with respect to the xy plane.

The polarized beam splitter 40 splits the incident laser beam into two optical paths, an optical path parallel to the x-axis and an optical path parallel to the z-axis. The divergence ratio depends on the polarization direction of the incident laser beam. When the polarization plane of the reflected light of the third mirror 33 is inclined by 45° with respect to the xy plane, the split ratio of the laser beam formed by the polarization beam splitter 40 becomes approximately 1:1.

FIG. 3 is a schematic front view of the second adjustment mechanism 37. As shown in FIG. A supporting member 51 is fixed to the optical table 10. The support member 51 has a guide surface parallel to the yz plane. On the guide surface of the support member 51, the elevating member 53 and the positioning block 52 are mounted so as to be movable in the z-axis direction. For example, the positioning block 52 penetrates the elongated hole 55 in the z-axis direction to be screw-fastened to the support member 51. The elevating member 53 penetrates a plurality of long holes 56 in the z-axis direction to be screw-fastened to the supporting member 51. When positioning the elevating member 53, first, the positioning block 52 is fixed to the supporting member 51 so that the surface facing the lower side of the elevating member 53 and the surface facing the upper side of the positioning block 52 are in contact.

A frame 54 is attached to the lifting member 53. On the frame 54, the second mirror 32 is supported so as to be tiltable.

Next, the excellent effects of the above-mentioned embodiment will be described. In the above embodiment, the first adjustment mechanism 36 performs the tilt adjustment of the first mirror 31 and adjusts the elevation angle θ (FIG. 2B), thereby adjusting the polarization direction of the laser beam incident on the polarizing beam splitter 40 . That is, the intensity ratio of the P polarization component and the S polarization component with respect to the polarization beam splitter 40 can be adjusted. Thereby, it is possible to absorb the individual difference in the divergence ratio caused by the manufacturing deviation of the polarized beam splitter 40, and to make the intensity of the two laser beams to be diverged the same.

Next, the tilt adjustment range of the first mirror 31 and the movement range of the second mirror 32 in the x-axis direction will be described. The range of the tilt adjustment of the first mirror 31 may be set according to the magnitude of the deviation between the branch ratios of the polarized beam splitter 40. If the range of the tilt adjustment of the first reflecting mirror 31 is enlarged, it is possible to cope with a larger deviation in the branch ratio of the polarized beam splitter 40. For example, in order to be able to cope with the standard deviation between the divergence ratios of the general polarized beam splitter 40, the adjustable range of the elevation angle θ (FIG. 2B) is set to include the range of 45˚±1˚. The range of tilt adjustment is sufficient.

The adjustable range of the elevation angle θ is sufficient as long as it can absorb the deviation between the divergence ratios of the polarized beam splitter 40, and it does not need to be enlarged too much. If the adjustable range of the elevation angle θ (FIG. 2B) is enlarged, the movable range of the second mirror 32 has to be enlarged in order to maintain the state where the reflected light of the first mirror 31 is incident on the second mirror 32. That is, the adjustable range formed by the supporting member 51 and the frame 54 (FIG. 3) that support the second mirror 32 to be movable has to be expanded. If the movable range of the second mirror 32 is too wide, the support member 51 and the frame 54 will be difficult to handle. Therefore, the range of the tilt adjustment of the first mirror 31 may be set so that the elevation angle θ can be adjusted within the range of 45°±5°.

If the distance between the optical axis of the incident light of the first mirror 31 and the optical axis of the reflected light of the third mirror 33 is denoted as L, the height from the third mirror 33 to the second mirror 32 is L× tanθ. When the elevation angle θ can be adjusted within a range of 45˚±5˚, the height of the second mirror 32 can be moved within the range of L×tan40˚ to L×tan50˚. As long as the second mirror 32 can be moved within this range, even if the tilt adjustment of the first mirror 31 is performed, the state where the reflected light of the first mirror 31 enters the second mirror 32 can be maintained. As an example, when the interval L is 143 mm, the height from the third mirror 33 to the second mirror 32 may be adjusted within a range of 120.0 mm or more and 170.4 mm or less.

In addition, the first mirror 31, the second mirror 32, and the third mirror 33 used in the above-mentioned embodiment are usually required to rotate the polarization direction of the laser beam output from the laser light source 20 by 45˚ Optical components. In the above-mentioned embodiment, the special optical components (such as Brewster window, etc.) for fine-tuning the polarization direction are not additionally arranged on the optical axis of the laser beam, and the polarization direction can also be fine-tuned. Therefore, it is possible to reduce the influence on the convergence and divergence of the laser beam caused by the increase in the number of optical components.

In addition, in the above embodiment, even if the tilt adjustment of the first mirror 31 is performed to change the elevation angle θ (FIG. 2B), the optical axis of the laser beam between the second mirror 32 and the third mirror 33 will not Move in the direction of the xy plane. Therefore, when adjusting the polarization direction, there is no need to perform position adjustment and tilt adjustment of the third mirror 33. Furthermore, even if the tilt adjustment of the first mirror 31 is performed, the distance between the optical axis of the laser beam output from the laser light source 20 and the optical axis of the laser beam incident on the polarization beam splitter 40 does not change. Therefore, even if the polarization direction is adjusted, there is no need to adjust the relative positional relationship between the laser light source 20 and the polarization beam splitter 40.

Next, a modification of the above-mentioned embodiment will be described. In the above embodiment, the polarization direction of the laser beam output from the laser light source 20 is parallel to the y-axis direction, but it can also be parallel to the z-axis direction. Furthermore, in the above embodiment, the propagation direction of the laser beam output from the laser light source 20 and the propagation direction of the laser beam incident on the polarizing beam splitter 40 are anti-parallel, but the two can also be parallel.

In the above-mentioned embodiment, although the optical axis of the laser beam reflected by the polarizing beam splitter 40 is parallel to the z-axis, it may also be parallel to the y-axis. In addition, in the above-mentioned embodiment, although the optical axis of the reflected light of the first mirror 31 is changed in the yz plane, it may be changed in a plane inclined with respect to the x-axis.

Next, referring to FIG. 4, a laser processing apparatus of another embodiment will be described. Fig. 4 is a schematic diagram of the laser processing apparatus of this embodiment. A laser light source 20, a polarization direction adjusting optical system 30, a polarization beam splitter 40 and a folding mirror 23 are supported on the upper surface of the optical platform 10. In addition, optical components (such as apertures, beam expanders, etc.) that adjust the beam diameter and divergence and convergence of the laser beam can be configured as needed. The laser beam output from the laser light source 20 is adjusted in the polarization direction by the polarization direction adjustment optical system 30 and enters the polarization beam splitter 40. As the polarization direction adjusting optical system 30, the polarization direction adjusting optical system 30 of the embodiment shown in FIGS. 1 to 3 is used.

The laser beam whose polarization direction is adjusted by the polarization direction adjustment optical system 30 is split into two by the polarization beam splitter 40. The laser beam reflected by the polarized beam splitter 40 passes through the opening provided in the optical platform 10 and is incident on the beam scanner 24A provided under the optical platform 10. The laser beam linearly passing through the polarizing beam splitter 40 is reflected downward by the folding mirror 23, passes through the opening provided in the optical platform 10, and enters the beam scanner 24B arranged under the optical platform 10.

The laser beams scanned by the beam scanners 24A and 24B pass through the condenser lenses 25A and 25B and enter the processing objects 60A and 60B, respectively. The objects 60A and 60B to be processed are, for example, printed circuit boards, which are drilled by the incidence of a laser beam.

The objects to be processed 60A and 60B are held by the moving mechanism 70 so as to be movable in the in-plane direction of the substrate. A power meter 26 is attached to the moving mechanism 70. The laser beam of one of the two laser beams is incident on the power meter 26, whereby the power of the laser beam can be measured. The control device 71 controls the laser light source 20, the beam scanners 24A and 24B, and the moving mechanism 70.

Next, the excellent effects of this embodiment will be described. While measuring the respective powers of the two laser beams with the power meter 26, the polarization direction adjustment optical system 30 adjusts the polarization direction of the laser beam incident on the polarization beam splitter 40, thereby enabling the two laser beams to be The power is equal. As the polarization direction adjustment optical system 30, since the polarization direction adjustment optical system 30 of the embodiment shown in FIGS. 1 to 3 is used, special optical components (such as Brewster window, etc.) for fine adjustment of the polarization direction are not arranged On the optical axis of the laser beam, the polarization direction can also be fine-tuned.

Next, a modification of the above-mentioned embodiment will be described. In the above-mentioned embodiment, one power meter 26 is used to measure the power of each of the two laser beams. However, as a modified example, two power meters may be installed in the moving mechanism 70. If two power meters are installed, the power of two laser beams can be measured at the same time. Therefore, it is possible to obtain the effect of facilitating the adjustment of the polarization direction adjustment optical system 30 for equalizing the power of the two laser beams.

Next, referring to FIG. 5, the polarization direction adjusting optical system of still another embodiment will be described. Hereinafter, a description of the configuration common to the polarization direction adjusting optical system 30 of the embodiment shown in FIGS. 1 to 3 will be omitted.

5 is a schematic diagram showing the positional relationship of the first mirror 31, the second mirror 32, and the third mirror 33 of the polarization direction adjusting optical system 30 of the present embodiment. In the embodiment shown in FIG. 2B, the moving direction of the second mirror 32 is parallel to the z-axis. Therefore, if the tilt adjustment of the first mirror 31 is performed, the optical path length between the first mirror 31 and the second mirror 32 and the optical path length between the second mirror 32 and the third mirror 33 are both Everything changes. On the other hand, in this embodiment, when the tilt adjustment of the first mirror 31 is performed, the second mirror 32 moves along the arc 38 centered on the incident point of the laser beam of the third mirror 33. Therefore, even if the polarization direction is adjusted, the optical path length between the second mirror 32 and the third mirror 33 does not change, and only the optical path length between the first mirror 31 and the second mirror 32 changes.

Next, the excellent effects of this embodiment will be described. In this embodiment, similar to the embodiment shown in FIGS. 1 to 3, no special optical components (such as Brewster window, etc.) for fine adjustment of the polarization direction are arranged on the optical axis of the laser beam. , It can also fine-tune the polarization direction.

Next, a modification of the above-mentioned embodiment will be described. In the above embodiment, when the tilt adjustment of the first mirror 31 is performed, the optical path length between the second mirror 32 and the third mirror 33 is not changed, but the first mirror 31 and the second mirror are changed. Optical path length between 32. Conversely, it is also possible to configure the optical path length between the second reflecting mirror 32 and the third reflecting mirror 33 without changing the optical path length between the first reflecting mirror 31 and the second reflecting mirror 32.

The foregoing embodiments are examples, and it is of course possible to make partial replacements or combinations of the configurations shown in different embodiments. Regarding the same action and effect produced by the same configuration of the plural embodiments, each embodiment will not be repeated one by one. Furthermore, the present invention is not limited to the above-mentioned embodiment. For example, it is obvious to those skilled in the art that various changes, improvements, combinations, etc. can be made.

10: Optical platform 20: Laser light source 23: folding mirror 24A, 24B: beam scanner 25A, 25B: Condenser lens 26: Power meter 30: Polarization direction adjustment optics 31: The first mirror 32: 2nd mirror 33: 3rd mirror 36: The first adjustment mechanism 37: The second adjustment mechanism 38: arc 40: Polarized beam splitter 51: Supporting member 52: positioning block 53: Lifting member 54: Frame 55, 56: Long hole 60A, 60B: Object to be processed 70: mobile mechanism 71: control device

[Fig. 1] is a schematic perspective view of a beam splitting device according to an embodiment. In [FIG. 2], FIG. 2A is a schematic plan view showing the arrangement of the optical components of the beam splitting device and the positional relationship of the optical axis of the laser beam, and FIG. 2B shows the arrangement of the optical components and the optical axis of the laser beam A schematic side view of the positional relationship. [Fig. 3] A schematic front view of the second adjustment mechanism. Fig. 4 is a schematic diagram of a laser processing apparatus according to a modification of the embodiment shown in Figs. 1 to 3. Fig. 5 is a schematic diagram showing the positional relationship of the first mirror, the second mirror, and the third mirror of the polarization direction adjusting optical system of another embodiment.

10: Optical platform

20: Laser light source

30: Polarization direction adjustment optics

31: The first mirror

32: 2nd mirror

33: 3rd mirror

36: The first adjustment mechanism

37: The second adjustment mechanism

40: Polarized beam splitter

PD: Polarization direction

Claims (8)

A beam divergence device, which has: Polarized beam splitter, which splits the linearly polarized laser beam; and The polarization direction adjustment optical system guides the incident laser beam to the aforementioned polarized beam splitter, The aforementioned polarization direction adjustment optical system has: The first reflector, the second reflector, and the third reflector are sequentially arranged along the propagation direction of the laser beam on the path of the laser beam incident on the polarizing beam splitter; The first adjustment mechanism supports the first mirror so that it can change the angle between the polarization plane of the incident light incident on the first mirror and the optical axis of the reflected light reflected by the first mirror. Tilt adjustment in the direction; and The second adjustment mechanism supports the second mirror so that when the posture of the first mirror is changed by the first adjustment mechanism, the reflected light of the first mirror is maintained to be incident on the second mirror. The state of the reflecting mirror and the reflected light of the second reflecting mirror are incident on the direction of the state of the third reflecting mirror, and the tilt can be adjusted. The beam splitting device according to claim 1, wherein The first adjustment mechanism supports the first reflector so as to be able to change the direction of the optical axis of the reflected light in a plane perpendicular to the optical axis of the incident light incident on the first reflector to perform tilt adjustment. The second adjustment mechanism supports the second mirror to be capable of changing the optical path length from the first mirror to the second mirror and from the second mirror to the third mirror. It moves in at least one direction of the optical path length and can be tilted. The beam splitting device described in claim 1 or claim 2, wherein The optical axis of the incident light incident on the first reflecting mirror and the optical axis of the reflected light of the third reflecting mirror are parallel to the reference plane. The beam splitting device according to claim 3, wherein The optical axis of the laser beam from the second mirror to the third mirror is perpendicular to the reference plane, The second adjustment mechanism supports the second mirror so as to be movable in a direction orthogonal to the reference plane. A method of adjusting the divergence ratio, in which The linearly polarized laser beam is incident on the laser beam path of the polarizing beam splitter that changes the branch ratio according to the polarization direction. The first mirror and the second mirror are arranged in order along the propagation direction of the laser beam. 2 mirrors, and 3 mirrors, The tilt adjustment of the first mirror is performed in a direction that changes the angle between the polarization plane of the incident light incident on the first mirror and the optical axis of the reflected light after being reflected by the first mirror, The movement and tilt adjustment of the second mirror are performed to maintain the state where the reflected light of the first mirror is incident on the second mirror and the second reflection after the posture of the first mirror is changed. The state where the reflected light of the mirror is incident on the aforementioned third mirror. The method of adjusting the divergence ratio as described in claim 5, where When performing the tilt adjustment of the first reflecting mirror, the optical axis of the reflected light is changed in a plane perpendicular to the optical axis of the incident light incident on the first reflecting mirror, When performing the movement and tilt adjustment of the second mirror, change the optical path length from the first mirror to the second mirror and the optical path length from the second mirror to the third mirror. At least one party. The method of adjusting the divergence ratio as described in claim 5 or 6, where The optical axis of the incident light incident on the first reflecting mirror and the optical axis of the reflected light of the third reflecting mirror are parallel to the reference plane. The method of adjusting the divergence ratio as described in claim 7, where The optical axis of the laser beam from the second mirror to the third mirror is perpendicular to the reference plane, When changing the position and posture of the second mirror, the second mirror is moved in a direction orthogonal to the reference plane.

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