JP2021085940A - Beam shaper, processing device, and beam shaping method - Google Patents

Abstract

To provide a beam shaper which allows for adjusting energy density without having to replace an axicon lens.SOLUTION: A processing head (13) provided herein functions as a beam shaper, the processing head comprising an axicon lens (132), and an adjustment mechanism (lens holder 133, and adjustment bolt 134) configured to adjust energy density of a Bessel beam by changing the beam diameter of a Gaussian beam incident on the axicon lens (132).SELECTED DRAWING: Figure 1

Description

The present invention relates to a beam shaper, a processing apparatus provided with the beam shaper, and a beam shaping method.

In recent years, the market for processing equipment for processing an object to be processed has been expanding by sweeping while irradiating the object to be processed with a high-power laser beam generated by a laser light source. Examples of processing applications include cutting and welding.

In these processing devices, the temperature of the processing site irradiated with the laser beam is from the temperature before the laser beam irradiation (for example, almost room temperature) to the temperature after the laser beam irradiation (for example, several hundred degrees to several thousand). Degree), it rises sharply. As a result, in the processing apparatus, spatter is likely to occur due to such a rapid temperature rise.

Preheating of the processed portion is considered to be effective in suppressing the occurrence of this spatter, and as a technique considered to be applicable for preheating the processed portion, for example, in FIG. 3 of Patent Document 1. Examples thereof include the described laser beam shaping apparatus (which can be read as the processing apparatus of the present invention). This laser beam shaping device is equipped with an axicon lens, and has a center lobe having a high peak intensity and a plurality of ring-shaped side lobes formed concentrically with the center lobe, and a side lobe having a low intensity. It is possible to generate a pseudo Bessel beam containing.

JP-A-2017-142401

By the way, the degree of preheating applied to the object to be processed often differs depending on the material constituting the object to be processed, the purpose of processing, and the like. Therefore, there is a demand for adjusting the energy density in a processing apparatus capable of generating a pseudo Bessel beam.

In order to adjust the energy density of the Bessel beam, it is conceivable to change the axicon lens included in the processing head to another axicon lens having a different apex angle. However, it takes time and effort to change the axicon lens included in the processing head to another axicon lens. Further, preparing a plurality of axicon lenses in order to adjust the energy density leads to an increase in the operating cost of the processing apparatus.

One aspect of the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a beam shaper whose energy density can be adjusted without exchanging an axicon lens.

In order to solve the above problems, the beam shaper according to the first aspect of the present invention is a vessel emitted from the axicon lens by changing the beam diameters of the axicon lens and the Gaussian beam incident on the axicon lens. It is equipped with an adjustment mechanism that adjusts the energy density of the beam.

According to the above configuration, since the energy density of the Bessel beam can be adjusted by using the adjusting mechanism, it is possible to provide a beam shaper whose energy density can be adjusted without exchanging the axicon lens.

In the beam shaper according to the second aspect of the present invention, the following configurations are adopted in addition to the configuration of the beam shaper according to the first aspect. That is, the Gaussian beam emitted from the emission point of the Gaussian beam is divergent light, and the adjustment mechanism changes the beam diameter by changing the distance from the emission point to the axicon lens. The configuration is adopted.

When the Gaussian beam emitted from the exit point of the Gaussian beam is divergent light, the collimating lens provided in the beam shaper according to aspects 3 and 4 of the present invention can be omitted. Therefore, according to the above configuration, the beam shaper can be configured with a small number of components.

In the beam shaper according to the fifth aspect of the present invention, the following configuration is adopted in addition to the configuration of the beam shaper according to any one of the second to fourth aspects. That is, the configuration is adopted in which the emission point is an emission end of an optical fiber that emits the Gaussian beam.

According to the above configuration, the Gaussian beam generated by the laser light source and guided by the optical fiber can be easily converted into a Bessel beam.

In the beam shaper according to the fourth aspect of the present invention, the following configurations are adopted in addition to the configuration of the beam shaper according to the first aspect. That is, a collimating lens arranged on the optical path of the Gaussian beam is further provided, and the adjusting mechanism measures the distance from the exit point of the Gaussian beam to the collimating lens by the Gaussian beam incident on the axicon lens. A configuration is adopted in which the beam diameter is changed by changing the distance from the collimating lens to the axicon lens while maintaining the divergent light distance.

In the beam shaper according to the fifth aspect of the present invention, the following configurations are adopted in addition to the configuration of the beam shaper according to the first aspect. That is, a collimating lens arranged on the optical path of the Gaussian beam is further provided, and the adjusting mechanism measures the distance from the exit point of the Gaussian beam to the collimating lens by the Gaussian beam incident on the axicon lens. A configuration is adopted in which the beam diameter is changed by changing the distance from the collimating lens to the axicon lens while maintaining the distance at which the light converges.

In one aspect of the present invention, the Gaussian beam incident on the axicon lens may be either divergent light or convergent light. According to the above configuration, the energy density can be easily adjusted.

In the beam shaper according to the sixth aspect of the present invention, the following configurations are adopted in addition to the configuration of the beam shaper according to the fourth or fifth aspect. That is, the adjustment mechanism includes a lens holder and a slide portion, the lens holder holds the collimating lens, and the slide portion slides the lens holder to obtain the axicon from the collimating lens. A configuration that changes the distance to the lens is adopted.

As a specific configuration of the adjustment mechanism as described above, a lens holder and a slide portion can be mentioned.

The processing apparatus according to the seventh aspect of the present invention is a processing apparatus provided with the beam shaper according to any one of the first to sixth aspects, and irradiates the object to be processed with a Bessel beam emitted from the beam shaper.

According to the above configuration, since the energy density of the Bessel beam can be adjusted by using the adjusting mechanism, it is possible to provide a processing apparatus capable of adjusting the energy density without exchanging the axicon lens.

In the processing apparatus according to the eighth aspect of the present invention, the following configurations are adopted in addition to the configuration of the processing apparatus according to the seventh aspect. That is, the photodetector that detects light at least in the vicinity of the irradiation point on which the Bessel beam is irradiated on the surface of the object to be processed, and the adjustment mechanism that controls feedback according to the light detected by the photodetector. A configuration is adopted that further includes a control unit for the operation.

According to the above configuration, according to the above configuration, the energy density can be adjusted according to the state of the processing target while processing the processing target. Therefore, the energy density of the Bessel beam emitted from the axicon lens can be suitably maintained during the entire processing period.

In the processing apparatus according to the ninth aspect of the present invention, the following configurations are adopted in addition to the configuration of the processing apparatus according to the eighth aspect. That is, the photodetector is a camera that images the vicinity of the irradiation point, and the control unit performs feedback control on the adjustment mechanism according to the image in the vicinity of the irradiation point captured by the camera. Has been adopted.

According to the above configuration, the ring interval can be adjusted according to the state near the irradiation point while processing the object to be processed. Therefore, the ring spacing of the Bessel beam emitted from the axicon lens can be suitably maintained during the entire processing period.

In order to solve the above problems, in the beam shaping method according to the tenth aspect of the present invention, the energy density of the Bessel beam emitted from the axicon lens is changed by changing the beam diameter of the Gaussian beam incident on the axicon lens. Includes an adjustment step to adjust.

In this beam shaping method including such an adjustment step, the energy density of the Bessel beam can be adjusted by changing the beam diameter of the Gaussian beam incident on the axicon lens, so that the axicon lens does not need to be replaced. The energy density can be adjusted.

In the beam shaping method according to the eleventh aspect of the present application, the following configuration is adopted in addition to the configuration of the beam shaping method according to the tenth aspect. That is, the adjustment step adopts a configuration in which the beam diameter is changed by changing the distance from the emission point of the Gaussian beam to the axicon lens.

According to the above configuration, the energy density can be easily adjusted.

According to one aspect of the present invention, it is possible to provide a beam shaper whose energy density can be adjusted without changing the axicon lens.

(A) is a block diagram showing a configuration of a processing apparatus according to an embodiment of the present invention, and (b) is a cross-sectional view of a processing head included in the processing apparatus shown in (a). (A) to (c) are sectional views of the processing head shown in FIG. 1 (a), and are sectional views showing the arrangement of a collimating lens and an axicon lens inside the processing head. (A) to (c) are sectional views of the processing head shown in FIG. 1 (a), and are sectional views showing the arrangement of a collimating lens and an axicon lens inside the processing head. It is a graph which shows the intensity distribution of the Bessel beam obtained when the spot diameter of the laser beam incident on an axicon lens is changed to 2mm, 4mm, and 6mm in the processing head which concerns on the reference example of this invention.

(Configuration of processing equipment)
The configuration of the processing apparatus 1 according to the embodiment of the present invention will be described with reference to FIG. In FIG. 1, FIG. 1A is a block diagram showing a configuration of a processing apparatus 1, and FIG. 1B is a cross-sectional view of a processing head 13 included in the processing apparatus 1.

The processing apparatus 1 is an apparatus for processing an object W, which is an object to be processed, by using a laser beam. As shown in FIG. 1A, a laser light source 11, a delivery fiber 12, and a processing head are used. A thirteenth, a camera 14, and a control unit 15 are provided.

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 object W with a laser beam guided through the delivery fiber 12. The camera 14 is an example of a photodetector that detects light in the vicinity of an irradiation point irradiated with a Bessel beam, which will be described later, on the surface of the object W, and is a device that images the vicinity of the irradiation point. In this case, the light in the vicinity of the irradiation point is mainly the reflected light in which the ambient light surrounding the object W is reflected in the vicinity of the irradiation point. Another example of the photodetector is a photodiode. In this case, the light in the vicinity of the irradiation point is the light caused by the plasma generated in the vicinity of the irradiation point when the Bessel beam is irradiated on the object to be processed. In this case, when a photodiode is used as the photodetector, a filter that transmits light included in a predetermined wavelength range may be provided between the irradiation point and the photodiode.

In one aspect of the present invention, the control unit 15 is a device that controls the processing head 13 so as to perform feedback control according to the light in the vicinity of the irradiation point detected by the photodetector to the adjustment mechanism described later. In the present embodiment, the control unit 15 performs feedback control according to the state near the irradiation point during processing based on the image (moving image or still image) in the vicinity of the irradiation point captured by the camera 14. It is a device that controls the processing head 13 as described above.

The control content of the feedback control is not limited, but the following examples can be given. During the processing performed by sweeping the laser beam, the camera 14 photographs the vicinity of the irradiation point irradiated with the laser beam and generates an image thereof. After acquiring the above image from the camera 14, the control unit 15 generates spatter amount information indicating the spatter amount per unit time based on the image. The control unit 15 further increases and decreases the distance D2 (see FIGS. 1 and 2), which is the distance from the collimating lens to the axicon lens, according to the spatter amount indicated by the spatter amount information. Change by a small amount to either. When the sputter amount increases by changing the distance D2 by a minute amount in this way, the control unit 15 changes the distance D2 by a minute amount in the direction opposite to the direction in which the distance D2 is changed by a minute amount first (decrease or increase). .. By repeating this, the control unit 15 can reduce the amount of spatter that may occur during processing.

The method by which the control unit 15 counts the spatter amount from the image is not limited, and examples thereof include a method of counting points where the brightness included in the image exceeds the threshold value. Further, the function of counting the spatter amount from the image in the control unit 15 can be substituted by a commercially available spatter counter.

Further, the control unit 15 may use any algorithm to determine the amount of change when increasing or decreasing the distance D2. Examples of the algorithm include numerical calculation algorithms such as the dichotomy method and the second method.

Further, in the case where a photodiode is adopted as the photodetector, the following examples can be given as the control contents of the feedback control. During the processing performed by sweeping the laser light, the photodiode detects light in the vicinity of the irradiation point and included in a predetermined wavelength range filtered by a filter. This predetermined range is set so as to be an index of the temperature of the plasma generated in the vicinity of the irradiation point when the Bessel beam is irradiated to the object to be processed, for example. Therefore, the control unit 15 generates temperature information representing the temperature of the plasma from the intensity of the light included in the predetermined wavelength range detected by the photodiode. The control unit 15 further changes the distance D2 by a minute amount in either the direction of increasing the distance D2 or the direction of decreasing the distance D2 according to the temperature indicated by the temperature information. When the temperature rises by changing the distance D2 by a minute amount in this way, the control unit 15 changes the distance D2 by a minute amount in the direction opposite to the direction in which the distance D2 is changed by a minute amount first (decrease or increase). By repeating this, the control unit 15 can keep the temperature of the plasma during processing within a predetermined temperature range (more preferably, keep it constant).

As shown in FIG. 1B, the processing head 13 includes a housing 130, a collimating lens 131, an axicon lens 132, lens holders 133a and 133b, adjustment bolts 134, protective glass 135, and gas. It is provided with a supply hole 136.

The housing 130 is a tubular structure in which one end (upper end in FIG. 1) is closed and the other end (lower end in FIG. 1) is open. The exit end, which is one end of the delivery fiber 12, is drawn into the housing 130 through an insertion hole provided in the housing 130. The emission end of the delivery fiber 12 is an example of the emission point of the Gaussian beam described in the claims.

On the optical path of the laser light emitted from the delivery fiber 12 (because it is a Gaussian beam, it will be described as described below), the Gaussian beam is refracted to bring it closer to the collimated light (that is, the divergence angle of the Gaussian beam is 0 degrees). A collimating lens 131 for (approaching) is arranged. In the processing head 13, the collimating lens 131 is arranged so that the divergence angle is a value other than 0 degrees. Therefore, the Gaussian beam transmitted through the collimating lens 131 becomes divergent light or convergent light. FIG. 1B shows a processing head 13 configured such that a Gaussian beam transmitted through a collimating lens 131 becomes divergent light. The collimating lens 131 has an incident surface that is a flat surface and an exit surface that is a spherical surface, and the incident surface (of the collimating lens 131) is arranged so as to face the exit surface of the delivery fiber 12. .. The optical axis of the collimating lens 131 coincides with the optical axis of the delivery fiber 12.

An axicon lens 132 for converting a Gaussian beam into a Bessel beam is arranged on the optical path of the Gaussian beam transmitted through the collimating lens 131. The axicon lens 132 has an incident surface that is a flat surface and an exit surface that is a conical surface, and the incident surface (of the axicon lens 132) is arranged so as to face the exit surface of the collimating lens 131. Has been done. The optical axis of the axicon lens 132 coincides with the optical axis of the delivery fiber 12 and the collimating lens 131. In the present embodiment, the optical axis common to the delivery fiber 12, the collimating lens 131, and the axicon lens 132 also coincides with the central axis (also simply referred to as an axis) of the housing 130 described later. Hereinafter, this common optical axis is also referred to as an optical axis of the processing head 13.

The lens holder 133a is a tubular structure with both ends open, and holds the collimating lens 131. A convex portion is formed on the outer surface of the lens holder 133a, and the convex portion fits into one of the two concave portions (the one closer to the delivery fiber 12) formed on the inner side surface of the housing 130. The width of the concave portion formed on the inner side surface of the housing 130 (the width in the axial direction of the housing 130) is set to be equal to the width of the convex portion formed on the outer surface of the lens holder 133a. Therefore, the lens holder 133a cannot be slid in the axial direction of the housing 130.

The lens holder 133b is a tubular structure with both ends open, and holds the axicon lens 132. A convex portion is formed on the outer surface of the lens holder 133b, and this convex portion fits into the other of the two concave portions (farther from the delivery fiber 12) formed on the inner surface of the housing 130. .. The width of the concave portion formed on the inner side surface of the housing 130 (the width in the axial direction of the housing 130) is set wider than the width of the convex portion formed on the outer surface of the lens holder 133b. Therefore, the lens holder 133b can be slid in the axial direction of the housing 130.

As described above, the other of the two concave portions formed on the inner surface of the housing 130 and the convex portion formed on the outer surface of the lens holder 133b form the axicon lens 132 while keeping the distance D1 constant. This is an example of a sliding portion that slides in parallel with the optical axis of the processing head 13 (that is, changes the distance D2). In the slide portion of the present embodiment, a concave portion is formed on the inner side surface of the housing 130, and a convex portion is formed on the outer surface of the lens holder 133b. However, in one aspect of the slide portion, a convex portion may be formed on the inner side surface of the housing 130, and a concave portion may be formed on the outer surface of the lens holder 133b.

The lens holder 133b moves away from the delivery fiber 12 by increasing the insertion amount of the adjustment bolt 134, and approaches the delivery fiber 12 by reducing the insertion amount of the adjustment bolt 134, for example. Therefore, by increasing or decreasing the insertion amount of the adjusting bolt 134, the distance D1 from the exit point of the Gaussian beam (the center point of the exit surface of the delivery fiber 12) to the collimating lens 131 is maintained, and the distance D1 from the collimating lens 131 to the axicon is maintained. The distance D2 to the lens 132 can be changed. The insertion amount of the adjusting bolt 134 (that is, the distance D2) can be electrically controlled by the control unit 15 by a mechanism (not shown), or can be manually controlled.

The lower limit of the distance D2 can be appropriately set within the range as long as it exceeds the thickness of the collimating lens 131. On the other hand, the upper limit of the distance D2 is not particularly limited, but it is preferably set appropriately within a range in which the beam diameter R is equal to or less than the radius of the axicon lens 132. When the beam diameter R exceeds the radius of the axicon lens 132, (1) the power of the Gaussian beam is lost, and (2) the gaussian beam that is not irradiated on the irradiation surface of the axicon lens 132 becomes stray light. This is because there are disadvantages such as.

A gas that functions as an assist gas in laser processing is supplied to the gas supply hole 136. The assist gas supplied to the gas supply hole 136 is concentrically sprayed from the lower end of the opened housing 130 onto the processed portion of the object W. The gas type used as the assist gas can be appropriately selected according to the application of laser processing (for example, cutting, welding, etc.). For example, in the case of cutting, a combustion action is required, so oxygen is preferable as the gas type of the assist gas, and in the case of welding, nitrogen is preferable as the gas type of the assist gas in order to suppress participation. The gas type of the assist gas is not limited to oxygen and nitrogen. In addition to the above-mentioned functions, the assist gas also has a function of suppressing the spatter generated during processing from adhering to the protective glass 135.

(Function of processing head)
The function of the processing head 13 will be described with reference to FIGS. 2 to 4. 2A to 2C are cross-sectional views of the processing head 13 including the optical axis, showing the arrangement of the collimating lens 131 and the axicon lens 132 inside the processing head 13. .. The processing head 13 shown in FIGS. 2A to 2C is configured such that the Gaussian beam transmitted through the collimating lens 131 becomes divergent light, as in the case of FIG. 1B. 3A to 3C are cross-sectional views of the processing head 13 including the optical axis, showing the arrangement of the collimating lens 131 and the axicon lens 132 inside the processing head 13. .. The processing head 13 shown in FIGS. 3A to 3C is configured such that the Gaussian beam transmitted through the collimating lens 131 becomes convergent light. In addition, in (a) to (c) of FIG. 2 and (a) to (c) of FIG. 3, only the collimating lens 131 and the axicon lens 132 are shown. Further, the z-axis shown in each of (a) to (c) of FIG. 2 and (a) to (c) of FIG. 3 is the optical axis of the processing head 13 ((a) to (c) of FIG. 2 and It is defined to be parallel to (not shown in each of (a) to (c) of FIG. 3). Further, the z-axis is defined so that the position corresponding to the exit surface of the delivery fiber 12 is the origin.

<When the Gaussian beam is divergent light>
In FIG. 2A, the distance D1 is determined so that the Gaussian beam emitted from the delivery fiber 12 passes through the collimating lens 131 to become divergent light. That is, the distance D1 is shorter than the focal length of the collimating lens 131. Further, the distance D1 is fixed. The distance D1 is the same in all of the processing heads 13 shown in FIGS. 2 (a) to 2 (c).

As described above, the processing head 13 can adjust the position of the lens holder 133b by using the adjusting bolt 134. Therefore, as shown in FIGS. 2A to 2C, the distance D2 is variable.

As shown in FIGS. 2A to 2C, the Gaussian beam transmitted through the collimating lens 131 is divergent light. Therefore, as shown in FIG. 2A, when the distance D2 is set to a predetermined value, the beam diameter R of the Gaussian beam transmitted through the collimating lens 131 on the incident surface of the axicon lens 132 corresponds to the distance D2. It is at a predetermined value. In this embodiment, the distance D2 shown in FIG. 2A is used as a reference. How to determine the reference distance D2 in the processing head 13 is not limited, but in the present embodiment, the distance D2 corresponding to the center of the range of motion of the lens holder 133b is used as the reference distance. It is defined in D2.

As shown in FIG. 2B, when the distance D2 is set to a value larger than the reference distance D2, the beam diameter R becomes larger than the beam diameter R shown in FIG. 2A.

As shown in FIG. 2C, when the distance D2 is set to a value smaller than the reference distance D2, the beam diameter R becomes smaller than the beam diameter R shown in FIG. 2A.

The exit surface of the axicon lens 132 is composed of two hypotenuses of an isosceles triangle when viewed in cross section as shown in FIGS. 2 (a) to 2 (c). In the following, in each of the two hypotenuses (a) to (c) of FIG. 2, the hypotenuse located on the upper side is referred to as the first hypotenuse, and the hypotenuse located on the lower side is referred to as the second hypotenuse. .. Therefore, as shown in FIG. 2A, when the collimated light is incident on the axicon lens 132, the first hypotenuse refracts the collimated light diagonally downward, and the second hypotenuse refracts the collimated light. Refracts light diagonally upward.

As shown in FIG. 2A, the light refracted diagonally downward by the first hypotenuse and the light refracted diagonally upward by the second hypotenuse are the light emitted from the emission surface of the axicon lens 132. It intersects in the interference region B, which is a neighboring region. Therefore, the radius of the interference region B increases as the distance from the exit surface of the axicon lens 132 increases, reaches a maximum value at the center of the interference region B, and further decreases as the distance from the exit surface of the axicon lens 132 increases. The maximum value of the radius of the interference region B substantially coincides with the beam diameter R.

Therefore, when the maximum value of the radius of the interference region B in the processing head 13 shown in FIG. 2 (a) is used as a reference, the maximum value of the radius of the interference region B in the processing head 13 shown in FIG. 2 (b) is used as a reference. Becomes larger, and the maximum value of the radius of the interference region B in the processing head 13 shown in FIG. 2 (c) becomes smaller.

Further, the light refracted diagonally downward by the first hypotenuse and the light refracted diagonally upward by the second hypotenuse interfere with each other in the interference region B. In the interference region B, a pseudo Bessel beam is formed as a result of interference between the light refracted diagonally downward by the first hypotenuse and the light refracted diagonally upward by the second hypotenuse. .. In the present embodiment, when the term Bessel beam is used without particular notice, it means a pseudo Bessel beam.

The beam shape of the Bessel beam is composed of a central lobe located on the optical axis and having the highest beam intensity, and a striped side lobe formed symmetrically on both sides of the central lobe.

The Bessel beam can propagate the beam over a long distance (corresponding to the length of the interference region, typically several mm) while suppressing the spot diameter of the beam as compared with the Gaussian beam. Therefore, since the processing apparatus 1 includes the processing head 13, the processing apparatus 1 can irradiate the object W with the Bessel beam. By using the Bessel beam for laser processing, for example, pores having a high aspect ratio can be formed on the object W as compared with the case where the Gaussian beam is used as the laser beam.

As described above, as shown in FIGS. 2A to 2C, the processing head 13 can change the maximum value of the radius of the interference region B by changing the distance D2. Further, as shown in FIGS. 2A to 2C, the power of the Gaussian beam incident on the Axicon lens 132 is constant even when the distance D2 is changed. Therefore, the energy density of the Bessel beam emitted from the axicon lens 132, and the energy density at a predetermined position, is to increase the distance D2 with reference to the energy density in the case shown in FIG. 2 (a). It becomes lower by reducing the distance D2 and becomes higher by reducing the distance D2. An example of a predetermined position is a position where the radius of the interference region B is the maximum value (that is, the center of the interference region B).

As described above, the processing head 13 functions as a beam shaper that forms a Bessel beam that irradiates the object W. Further, the slide portion, the lens holder 133b, and the adjustment bolt 134 function as an adjustment mechanism for adjusting the energy density of the Bessel beam emitted from the axicon lens 132 by changing the distance D2.

In this embodiment, it has been described that the emission point of the Gaussian beam is the emission end of the delivery fiber 12. However, the emission point of the Gaussian beam may be the emission point of the laser diode. A Gaussian beam, which is divergent light, is emitted from the emission end of the delivery fiber 12 or the light emitting point of the laser diode. Therefore, in the processing head 13 according to one aspect of the present invention, the collimating lens 131 shown in FIG. 1 can be omitted. That is, the lens holder 133b and the adjusting bolt 134 may be configured to change the beam diameter R by changing the distance from the exit end of the delivery fiber 12 to the axicon lens 132.

<When the Gaussian beam is convergent>
In FIG. 3A, the distance D1 is set so that the Gaussian beam emitted from the delivery fiber 12 passes through the collimating lens 131 to become convergent light. That is, the distance D1 is longer than the focal length of the collimating lens 131. Except for this point, the processing head 13 shown in FIG. 3A has the same configuration as the processing head 13 shown in FIG. 2A. Therefore, here, only the change in the energy density obtained when the distance D2 is changed in the processing head 13 shown in FIG. 3A will be described.

As described above, the processing heads 13 shown in FIGS. 3A to 3C are configured such that a Gaussian beam, which is convergent light, is incident on the axicon lens 132. Therefore, when the distance D2 shown in FIG. 3A is used as a reference, the beam diameter R becomes smaller by making the distance D2 larger than the reference distance D2 (see FIG. 3B). By making D2 smaller than the reference distance D2, the beam diameter R becomes large (see (b) in FIG. 3).

Therefore, the energy density of the Bessel beam emitted from the axicon lens 132, and the energy density at a predetermined position, is to increase the distance D2 with reference to the energy density in the case shown in FIG. 3A. It becomes higher by reducing the distance D2, and becomes lower by reducing the distance D2. An example of a predetermined position is a position where the radius of the interference region B is the maximum value (that is, the center of the interference region B).

As described above, the processing head 13 shown in FIG. 3 functions as a beam shaper that forms a Bessel beam irradiated to the object W. In particular, the lens holder 133b and the adjustment bolt 134 function as an adjustment mechanism for adjusting the energy density of the Bessel beam emitted from the axicon lens 132 by changing the distance D2.

[Reference example]
As a reference example of the present invention, the beam diameters R of the Gaussian beam incident on the incident surface of the same axicon lens 132 as the axicon lens 132 provided in the processing head 13 shown in FIG. 1 are set to R = 2 mm, 4 mm, and 6 mm. The beam profile in each of these cases is shown in FIG. In this reference example, the power of the Gaussian beam is the same in all cases of R = 2 mm, 4 mm, and 6 mm. Further, in this reference example, the Gaussian beam is parallel light.

According to FIG. 4, it was found that the smaller the beam diameter R, the higher the beam intensity, and the larger the beam diameter R, the lower the beam intensity. That is, it was found that the energy density of the Bessel beam emitted from the axicon lens can be changed by changing the beam diameter R of the Gaussian beam incident on the axicon lens.

In view of this result, it was found that the processing head 13 shown in FIG. 1 can change the beam diameter of the Gaussian beam incident on the axicon lens 132, so that the energy density of the Bessel beam can be adjusted. ..

[Additional notes]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

1 Processing equipment 11 Laser light source 12 Delivery fiber 13 Processing head 130 Housing 131 Collimating lens 132 Axicon lens 133a Lens holder 133b Lens holder (part of adjustment mechanism)
134 Adjustment bolt (part of adjustment mechanism)
135 Protective glass 136 Gas supply hole 14 Camera 15 Control unit W Object (processed object)

Claims (11)

Axicon lens and
It is provided with an adjusting mechanism for adjusting the energy density of the Bessel beam emitted from the axicon lens by changing the beam diameter of the Gaussian beam incident on the axicon lens.
A beam shaper that features that. The Gaussian beam emitted from the exit point of the Gaussian beam is divergent light, and is
The adjusting mechanism changes the beam diameter by changing the distance from the exit point to the axicon lens.
The beam shaper according to claim 1. The exit point is an exit end of an optical fiber that emits the Gaussian beam.
The beam shaper according to claim 2. Further, a collimating lens arranged on the optical path of the Gaussian beam is provided.
The adjustment mechanism moves the distance from the exit point of the Gaussian beam to the collimating lens from the collimating lens to the axicon lens while maintaining the distance at which the Gaussian beam incident on the axicon lens becomes divergent light. The beam diameter is changed by changing the distance.
The beam shaper according to claim 1. Further, a collimating lens arranged on the optical path of the Gaussian beam is provided.
The adjusting mechanism moves the distance from the exit point of the Gaussian beam to the collimating lens from the collimating lens to the collimating lens while maintaining the distance at which the Gaussian beam incident on the axicon lens becomes convergent light. The beam diameter is changed by changing the distance.
The beam shaper according to claim 1. The adjustment mechanism includes a lens holder and a slide portion.
The lens holder holds the collimating lens and holds the collimating lens.
The slide portion changes the distance from the collimating lens to the axicon lens by sliding the lens holder.
The beam shaper according to claim 4 or 5. A processing apparatus including the beam shaper according to any one of claims 1 to 6, wherein the beam shaper emits the Bessel beam.
A processing device characterized by this. A photodetector that detects light at least in the vicinity of the irradiation point on which the Bessel beam is irradiated on the surface of the object to be processed.
It further includes a control unit that performs feedback control according to the light detected by the photodetector to the adjustment mechanism.
The processing apparatus according to claim 7. The photodetector is a camera that captures an image in the vicinity of the irradiation point.
The control unit performs feedback control on the adjustment mechanism according to the image in the vicinity of the irradiation point captured by the camera.
The processing apparatus according to claim 8. It includes an adjustment step of adjusting the energy density of the Bessel beam emitted from the axicon lens by changing the beam diameter of the Gaussian beam incident on the axicon lens.
A beam shaping method characterized by that. The adjustment step changes the beam diameter by changing the distance from the emission point of the Gaussian beam to the axicon lens.
The beam shaping method according to claim 10.

Images