JP7270514B2 - BEAM SHAPER, PROCESSING APPARATUS, AND PROCESSING METHOD - Google Patents

Description

The present invention relates to a beam shaper that converts a Gaussian beam into a Bessel beam. It also relates to a processing apparatus equipped with such a beam shaper. The present invention also relates to a processing method using such a beam shaper.

Axicon lenses are widely used to transform a collimated Gaussian beam into a Bessel beam. Patent Literature 1 discloses a beam shaper (“laser beam shaping device” in Patent Literature 1) having an axicon lens. The Bessel beam emitted from the axicon lens has high power in the interference region. Therefore, by forming the interference region of the Bessel beam emitted from the axicon laser on the workpiece, efficient processing becomes possible.

JP 2017-142402

Laser processing of metals has the following problems. First, when the power of the laser beam irradiated to the workpiece is high, the molten metal scattered from the periphery of the keyhole becomes spatter (the spatter must be removed after laser processing). Secondly, rapid cooling after laser irradiation causes thermal strain and cracks in the workpiece. Third, blowholes occur when the molten metal solidifies before the gas entrained in the molten metal is diffused.

In order to avoid such a problem, a technique called wobbling irradiation of laser light is used. In the wobbling irradiation, the trajectory of the irradiation point of the laser light is fluctuated, thereby suppressing the rapid temperature change of the workpiece and suppressing the above-described problems.

However, in conventional beam shapers, it has been difficult to achieve wobbling of the Bessel beam emitted from the axicon lens. This is because the interference region of the Bessel beam emitted from the axicon lens is formed in the vicinity of the axicon lens. For this reason, it is difficult to provide a mechanism for wobbling the Bessel beam (a movable mirror, a rotatable wedge substrate, etc.) between the axicon lens and the workpiece.

One aspect of the present invention has been made in view of the above problems. An object of one aspect of the present invention is to realize a beam shaper, a processing apparatus, or a processing method capable of suppressing sudden temperature changes of a work.

In the beam shaper according to aspect 1 of the present invention, an axicon lens, a half-wave plate arranged on an optical path of a Gaussian beam incident on the axicon lens, and the above-described a rotation mechanism for rotating a half-wave plate, and a beam cross section of the Gaussian beam that enters the axicon lens without passing through the half-wave plate in a plane perpendicular to the central axis of the Gaussian beam; , and the beam cross-section of the Gaussian beam that passes through the half-wave plate and enters the axicon lens is not symmetrical with respect to a straight line passing through the central axis of the Gaussian beam.

According to the above configuration, it is possible to realize a beam shaper capable of suppressing sudden temperature changes of the workpiece with a simple configuration.

In addition to the configuration of the beam shaper according to aspect 1 of the present invention, the beam shaper according to aspect 2 of the present invention further includes a collimating lens, and the axicon lens has a flat surface facing the convex surface of the collimating lens. The configuration is adopted.

According to the above configuration, even if the beam incident on the beam shaper is a diverging Gaussian beam, it is possible to realize a beam shaper capable of suppressing rapid temperature changes of the workpiece with a simple configuration.

In the beam shaper according to aspect 3 of the present invention, in addition to the configuration of the beam shaper according to aspect 1 or 2 of the present invention, in a plane orthogonal to the central axis of the Gaussian beam, the A configuration is adopted in which the beam cross-sectional area of the Gaussian beam incident on the axicon lens is larger than the beam cross-sectional area of the Gaussian beam incident on the axicon lens through the half-wave plate.

According to the above configuration, it is possible to realize a beam shaper capable of suppressing abrupt temperature changes of the workpiece and having a smaller loss with a simple configuration.

A processing apparatus according to aspect 4 of the present invention employs a configuration including a processing head including the beam shaper according to any one of aspects 1 to 3 of the present invention.

According to the above configuration, it is possible to realize a processing apparatus capable of suppressing sudden temperature changes of the workpiece with a simple configuration.

A processing method according to aspect 5 of the present invention is a processing method for irradiating a work with a Bessel beam emitted from an axicon lens, wherein the half-wavelength beam is arranged on the optical path of the Gaussian beam incident on the axicon lens. Rotating a plate around the central axis of the Gaussian beam as a rotation axis, the Gaussian beam entering the axicon lens without passing through the half-wave plate in a plane perpendicular to the central axis of the Gaussian beam. and the beam cross section of the Gaussian beam incident on the axicon lens through the half-wave plate are not symmetrical with respect to a straight line passing through the central axis of the Gaussian beam. ing.

According to the above configuration, it is possible to realize a machining method capable of suppressing sudden temperature changes of the workpiece with a simple configuration.

According to one aspect of the present invention, it is possible to realize a beam shaper, a processing apparatus, or a processing method capable of suppressing sudden temperature changes of a work.

(a) is a block diagram showing the configuration of a processing apparatus according to an embodiment of the present invention. (b) and (c) are cross-sectional views showing the configuration of a processing head provided in the processing apparatus. (a) is a graph showing the intensity distribution of the Bessel beam on the x-axis obtained by the processing apparatus shown in FIG. (b) is a graph showing the intensity distribution of the Bessel beam on the y-axis obtained by the processing apparatus shown in FIG. 1; (c) is a graph showing the intensity distribution of the Bessel beam on the xy plane obtained by the processing apparatus shown in FIG. In the processing apparatus shown in FIG. FIG. 10 illustrates a beam profile of a Bessel beam that 3 is a plan view showing a modification of the half-wave plate provided in the processing apparatus shown in FIG. 1; FIG.

(Configuration of processing equipment)
A configuration of a processing apparatus 1 according to one embodiment of the present invention will be described with reference to FIG. In FIG. 1, (a) is a block diagram showing the configuration of the processing device 1, and (b) and (c) are cross-sectional views of a processing head 13 provided in the processing device 1. As shown in FIG. Here, the cross section shown in FIG. 1(b) is the AA′ cross section obtained by cutting the processing head 13 along the AA′ line shown in FIG. 1(c), and the cross section shown in FIG. It is a BB' cross section of the head 13 taken along the BB' line shown in FIG. 1(b).

The processing device 1 is a device for processing a work W using laser light, and as shown in FIG. and has.

The laser light source 11 is a device that generates laser light. The delivery fiber 12 is an optical fiber that guides the laser light generated by the laser light source 11 . The processing head 13 is a device that irradiates the work W with laser light guided through the delivery fiber 12 . The movable stage 14 is a device that moves the workpiece W in a direction perpendicular to the traveling direction of the laser beam emitted from the processing head 13 . As the laser light source 11, for example, a fiber laser is used. A multimode fiber, for example, is used as the delivery fiber 12 . For example, a precision XY stage is used as the movable stage 14 .

The processing head 13, as shown in FIG. 136 and a rotating mechanism 137 . The collimator lens 131, the axicon lens 133, the half-wave plate 135, and the rotating mechanism 137 function as a beam shaper BS that shapes the beam with which the workpiece W is irradiated.

The housing 130 is a cylindrical structure with one end (upper end in FIG. 1) closed and the other end (lower end in FIG. 1) open. The delivery fiber 12 is drawn into the housing 130 through an insertion hole provided in the housing 130 . The light emitted from the delivery fiber 12 becomes a Gaussian beam G that diverges (the beam diameter gradually increases along the optical path).

A collimating lens 131 is arranged on the optical path of the Gaussian beam G. As shown in FIG. The collimating lens 131 is a plano-convex collimating lens having a flat surface and a spherical convex surface. It is fixed on the inside surface. A central axis of the collimator lens 131 coincides with the optical axis L of the delivery fiber 12 . The light emitted from the collimating lens 131 becomes a collimated Gaussian beam G' (having a constant beam diameter along the optical path).

An axicon lens 133 is arranged on the optical path of the Gaussian beam G'. Axicon lens 133 is a plano-convex axicon lens having a flat surface and a conical convex surface. It is fixed to the inner surface of the housing 130 . The optical axis of the axicon lens 133 coincides with the optical axis L of the delivery fiber 12 and collimator lens 131 . The light emitted from the axicon lens 133 becomes the Bessel beam B. As shown in FIG.

A half-wave plate 135 is arranged on the optical path of the Gaussian beam G' entering the axicon lens 133 . The half-wave plate 135 is a wave plate having a first flat surface and a second flat surface. The half-wave plate 135 has a first flat surface (of the half-wave plate 135) facing the spherical convex surface of the collimating lens 131, and a second flat surface (of the half-wave plate 135) facing the axis. It is held inside the housing 130 by a rotary holder 136 so as to face the flat surface of the cone lens 133 . The rotary holder 136 includes, for example, an inner holder 136a fixed to the end surface of the half-wave plate 135, an outer holder 136b fixed to the inner surface of the housing 130, and a space between the inner holder 136a and the outer holder 136b. and a bearing 136c interposed in the . As a result, the half-wave plate 135 can be freely rotated with the optical axis L as the rotation axis.

A half-wave plate 135 is positioned to act on a portion of the Gaussian beam G'. Of the Gaussian beam G', the phase of the Gaussian beam G'2 that passes through the half-wave plate 135 and is incident on the axicon lens 133 is the phase of the Gaussian beam G' that does not pass through the half-wave plate 135, It lags the phase of the Gaussian beam G′1 incident on the cone lens 133 by π. The shape or arrangement of the half-wave plate 135 is such that "on the plane orthogonal to the central axis of the Gaussian beam G', the beam cross section of the Gaussian beam G'1 and the beam cross section of the Gaussian beam G'2 are the same as the Gaussian beam G'. It is set so as to satisfy the condition A that it is not symmetrical with respect to a straight line passing through the central axis of. In this embodiment, the condition A is satisfied by making the plan view shape of the half-wave plate 135 a boat shape surrounded by an arc of a circle and a chord of the circle (a chord shorter than the diameter). I am letting

The rotating mechanism 137 is a mechanism for rotating the half-wave plate 135 with the central axis of the Gaussian beam G' as the rotation axis. The rotating mechanism 137 can be composed of, for example, a threaded shaft that engages with the gear-shaped outer surface of the inner holder 136a, and a motor (not shown) that rotates the shaft.

In this embodiment, the half-wave plate 135 is arranged on the optical path of the Gaussian beam G', that is, between the collimator lens 131 and the axicon lens 133. However, the present invention , but not limited to. For example, a configuration in which the half-wave plate 135 is arranged on the optical path of the Gaussian beam G, that is, between the delivery fiber 12 and the collimator lens 131 may be adopted. In short, the half-wave plate 135 should be placed on the optical path of the Gaussian beams G and G' entering the axicon lens 133 .

(Action of half-wave plate)
The action of the half-wave plate 135 provided in the processing apparatus 1 will be described with reference to FIGS. 2 and 3. FIG.

FIG. 2(a) is a graph showing the intensity distribution of the Bessel beam B on the x-axis obtained when the half-wave plate 135 is provided as shown in FIG. FIG. 2(b) is a graph showing the intensity distribution of the Bessel beam B on the y-axis obtained when the half-wave plate 135 is provided as shown in FIG. FIG. 2(c) is a graph showing the intensity distribution of the Bessel beam B on the xy plane obtained when the half-wave plate 135 is provided as shown in FIG. For definitions of the x-axis, y-axis, and z-axis, see (b) of FIG.

If the half-wave plate 135 is not provided, the Bessel beam B has a concentric beam profile in which bright areas, dark areas, bright areas, dark areas, . . . are alternately arranged in this order from the center. Therefore, in this case, the beam profile of the Bessel beam B remains unchanged with respect to rotation about the central axis of the Gaussian beam G'. Therefore, even if the half-wave plate 135 is rotated about the central axis of the Gaussian beam G', the beam profile of the Bessel beam B with which the workpiece W is irradiated does not change.

On the other hand, when the half-wave plate 135 is provided as shown in FIG. 1, the beam profile of the Bessel beam B is: (1) the first sector S1 including the x-axis positive portion and the x-axis negative portion In the third sector S3 including the y-axis positive portion, (2) the second sector S2 including the y-axis positive portion and In the fourth sector S4 including the y-axis negative portion, the beam profile becomes a concentric circular beam profile in which dark areas, bright areas, dark areas, bright areas, . . . are alternately arranged in this order from the center. Therefore, in this case, the beam profile of the Bessel beam B does not change with respect to rotation about the central axis of the Gaussian beam G'. Therefore, when the half-wave plate 135 is rotated around the central axis of the Gaussian beam G', the beam profile of the Bessel beam B with which the workpiece W is irradiated changes.

FIG. 3 shows the arrangement of the half-wave plate 135 and the irradiation of the workpiece W when the rotation angle θ of the half-wave plate 135 is 0°, 45°, 90°, 135°, and 180°. FIG. 3 illustrates the beam profile of the Bessel beam B that is processed; It can be seen from FIG. 3 that when the half-wave plate 135 is rotated around the central axis of the Gaussian beam G', the beam profile of the Bessel beam B with which the workpiece W is irradiated also rotates. When the beam profile of the Bessel beam B with which the work W is irradiated rotates, the intensity of the Bessel beam B with which each point of the work W is irradiated changes periodically. For this reason, the effect of suppressing a rapid temperature change of the work W can be obtained.

Note that when the above condition A is not satisfied (that is, in a plane perpendicular to the Gaussian beam G′, the beam cross section of the Gaussian beam G′1 and the beam cross section of the Gaussian beam G′2 are aligned with the center of the Gaussian beam G′. symmetrical with respect to a straight line passing through the axis), the Bessel beam B has a concentric circular beam profile in which dark regions, bright regions, dark regions, bright regions, . . . Therefore, in this case, the beam profile of the Bessel beam B remains unchanged with respect to rotation about the central axis of the Gaussian beam G'. Therefore, even if the half-wave plate 135 is rotated about the central axis of the Gaussian beam G', the beam profile of the Bessel beam B with which the workpiece W is irradiated does not change.

(Modified example of half-wave plate)
Several modifications of the half-wave plate 135 included in the processing apparatus 1 will be described with reference to FIG.

In this embodiment, as shown in FIG. 4A, the plan view shape of the half-wave plate 135 is surrounded by an arc of a circle and a chord of the circle (a chord shorter than the diameter). A boat-shaped configuration is adopted. However, the shape of the half-wave plate 135 is arbitrary as long as the condition A described above is satisfied.

For example, as shown in FIG. 4(b), the half-wave plate 135 has a planer shape surrounded by an arc of a circle and a chord of the circle (a chord longer than the diameter). may be adopted. Alternatively, as shown in FIG. 4C, the half-wave plate 135 may have a fan shape with a central angle of less than 180° in plan view. Alternatively, as shown in FIG. 4D, the half-wave plate 135 may have a sector shape in plan view with a central angle larger than 180°.

However, as shown in (a) or (c) of FIG. is preferably larger than the beam cross-sectional area G'2 of 2. This is because the loss that occurs when the Gaussian beam G' passes through the half-wave plate 135 can be kept small.

(Additional notes)
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the above embodiments are also included in the technical scope of the present invention.

Reference Signs List 1 processing device 11 laser light source 12 delivery fiber 13 processing head 130 housing 131 collimator lens 133 axicon lens 135 half-wave plate

Claims (5)

an axicon lens,
a half-wave plate disposed on the optical path of the Gaussian beam incident on the axicon lens;
a rotation mechanism that rotates the half-wave plate with the central axis of the Gaussian beam as a rotation axis;
In a plane orthogonal to the central axis of the Gaussian beam, a beam cross section of the Gaussian beam that enters the axicon lens without passing through the half-wave plate, and a beam cross section of the Gaussian beam that passes through the half-wave plate and enters the axicon lens The beam cross section of the incident Gaussian beam is not symmetrical with respect to a straight line passing through the central axis of the Gaussian beam,
A beam shaper characterized by: Equipped with a collimating lens,
The axicon lens is arranged such that its flat surface faces the convex surface of the collimator lens,
The beam shaper according to claim 1, characterized in that: In a plane orthogonal to the central axis of the Gaussian beam, the beam cross-sectional area of the Gaussian beam that enters the axicon lens without passing through the half-wave plate is larger than the beam cross section of a Gaussian beam incident on
3. The beam shaper according to claim 1 or 2, characterized in that: A processing head comprising the beam shaper according to any one of claims 1 to 3,
A processing device characterized by: A processing method for irradiating a workpiece with a Bessel beam emitted from an axicon lens,
rotating a half-wave plate placed on the optical path of the Gaussian beam incident on the axicon lens about the central axis of the Gaussian beam;
In a plane orthogonal to the central axis of the Gaussian beam, a beam cross section of the Gaussian beam that enters the axicon lens without passing through the half-wave plate, and a beam cross section of the Gaussian beam that passes through the half-wave plate and enters the axicon lens The beam cross section of the incident Gaussian beam is not symmetrical with respect to a straight line passing through the central axis of the Gaussian beam,
A processing method characterized by:

Images