JP7411851B1 - Polarization adjustment device and laser processing machine - Google Patents

Abstract

The object of the present invention is to make it possible to align the polarization directions of two linearly polarized lights included in a randomly polarized laser beam in parallel, and to eliminate anisotropy with respect to the cutting progress direction of the two laser beams whose polarization directions are aligned in parallel.
A first optical element converts a randomly polarized laser beam into first linearly polarized light having a first polarization direction and a second straight line having a second polarization direction perpendicular to the first polarization direction. Separates into polarized light. The second optical element converts the polarization direction of the second linearly polarized light separated by the first optical element into the first polarization direction. The axicon lens spreads the second linearly polarized light emitted from the second optical element or the second linearly polarized light incident on the second optical element into a ring shape. The third optical element coaxially emits the first linearly polarized light separated by the first optical element and the second linearly polarized light expanded into a ring shape by the axicon lens.
[Selection diagram] Figure 2

Description

The present invention relates to a polarization adjustment device and a laser processing machine.

A laser processing machine cuts a metal workpiece using a laser beam emitted from a laser oscillator. The laser beam emitted by the laser oscillator is randomly polarized light including two linearly polarized light components (hereinafter referred to as p-polarized light and s-polarized light) that are orthogonal to each other. It is known that the absorption rate of a laser beam of a workpiece when cutting is performed using a randomly polarized laser beam changes depending on the incident angle at which the laser beam is incident on the workpiece. The absorption rate of a randomly polarized laser beam is the average value of the absorption rate of p-polarized light and the absorption rate of s-polarized light.

In a typical cutting process using a laser beam machine, a laser beam is incident on a workpiece at an incident angle of 82 degrees to 88 degrees, and the workpiece is cut. For example, when the metal of the workpiece is iron and the wavelength of the laser beam is in the 1 μm band, if the incident angle of the laser beam is 82 degrees to 88 degrees, the absorption rate of p-polarized light will be about 90% at maximum. On the other hand, the absorption rate of s-polarized light is less than 10%. The absorption rate of a randomly polarized laser beam is the average value of the absorption rate of p-polarized light and the absorption rate of s-polarized light, so the absorption rate of a randomly polarized laser beam is 40% or less, and the workpiece material This is one of the factors that reduces machining efficiency when cutting.

As a method to solve this problem, Patent Document 1 discloses that the polarization directions of two linearly polarized lights included in a randomly polarized laser beam are aligned in parallel, and the polarization directions of the two linearly polarized lights whose polarization directions are aligned in parallel are A laser processing machine has been disclosed that is controlled to match the cutting direction (hereinafter referred to as the cutting progress direction). By making the polarization direction of the linearly polarized light coincide with the cutting progress direction, the polarization direction of the laser beam with respect to the cutting front becomes p-polarized light, and the absorption rate of the laser beam of the workpiece becomes the absorption rate of p-polarized light. This improves the absorption rate of the laser beam of the workpiece and improves the processing efficiency. Note that the cutting front here refers to a cutting surface at the boundary between the non-melting region and the melting region in the direction of cutting progress when the workpiece is melted and cut.

Japanese Patent Application Publication No. 7-266071

The laser processing machine described in Patent Document 1 focuses two linearly polarized laser beams having the same polarization direction and wavelength using one focusing lens, and irradiates the workpiece with the laser beams. However, in principle, two laser beams with the same polarization direction and the same wavelength cannot be focused on the same position. Therefore, in reality, it is necessary to focus the two laser beams at different positions and arrange the two laser beams, for example, side by side and adjacent to each other. That is, since two laser beams whose polarization directions are parallel to each other travel along two different axes, the two laser beams have anisotropy with respect to the cutting direction. If the two laser beams have anisotropy with respect to the cutting direction, the cutting quality will not be constant during laser cutting in which the cutting direction of the workpiece changes arbitrarily, which may lead to a reduction in cutting quality.

Polarized light that can align the polarization directions of two linearly polarized lights included in a randomly polarized laser beam in parallel, and eliminate anisotropy with respect to the cutting progress direction of the two laser beams with parallel polarization directions. The emergence of an adjustment device and a laser processing machine equipped with such a polarization adjustment device is desired.

A first aspect of one or more embodiments includes: a first linearly polarized light having a first polarization direction; and a second linearly polarized light having a second polarization direction orthogonal to the first polarization direction. a first optical element that separates a randomly polarized laser beam containing the first linearly polarized light into the first linearly polarized light and the second linearly polarized light; and the second linearly polarized light separated by the first optical element. a second optical element that converts the polarization direction to the first polarization direction; and the second linearly polarized light emitted from the second optical element, or the second linearly polarized light that is incident on the second optical element. an axicon lens that spreads the linearly polarized light into a ring shape; the first linearly polarized light separated by the first optical element; and the second linearly polarized light spread by the axicon lens into a ring shape. The polarization adjusting device includes a third optical element that emits light coaxially and is also used as the first optical element or is separate from the first optical element.

A second aspect of one or more embodiments includes the polarization adjustment device of the first aspect, and the polarization directions of the first linearly polarized light and the second linearly polarized light coaxially emitted from the polarization adjustment device. and a polarization direction control mechanism that controls the laser beam to be parallel to a cutting progress direction when cutting the workpiece by irradiating the workpiece with a laser beam.

According to the polarization adjustment device according to one or more embodiments, it is possible to align the polarization directions of two linearly polarized lights included in a randomly polarized laser beam in parallel, and to align the polarization directions of two linearly polarized lights included in a randomly polarized laser beam in parallel. It is possible to eliminate anisotropy with respect to the cutting progress direction of the laser beam. According to the laser processing machine according to one or more embodiments, a workpiece can be processed using two non-anisotropic laser beams with parallel polarization directions.

FIG. 1 is a diagram showing an example of the overall configuration of a laser processing machine according to a first embodiment. FIG. 2 is a diagram showing an example of the configuration of the processing head according to the first embodiment. FIG. 3 is a diagram showing a configuration example of a special polarization beam splitter included in the processing head shown in FIG. 2. FIG. 4 is a diagram showing the polarization direction and shape of the laser beam in FIG. 2, and the positional relationship between the first and second linearly polarized lights when the first and second linearly polarized lights are coaxially emitted. FIG. 5 is a diagram showing an example of the configuration of a lens array included in the processing head shown in FIG. 2. FIG. FIG. 6A is a diagram showing the relationship between the cutting progress direction of the workpiece and the polarization direction of the laser beam irradiated onto the workpiece W. FIG. FIG. 6B is a diagram showing the relationship between the cutting progress direction of the workpiece and the polarization direction of the laser beam irradiated onto the workpiece W when the cutting progress direction of the workpiece draws a curve. FIG. 7A is a diagram showing the relationship between the cutting front, the polarization direction, and the cutting direction when the cutting front has a semicircular shape. FIG. 7B is a diagram showing the relationship between the cutting front, the polarization direction, and the cutting direction when the cutting front has a rectangular shape. FIG. 8 is a diagram showing a configuration example of a processing head according to the second embodiment. FIG. 9 is a diagram showing the polarization direction and shape of the laser beam in FIG. 8, and the positional relationship between the first and second linearly polarized lights when the first and second linearly polarized lights are coaxially emitted. FIG. 10 is a diagram showing a special mirror included in the processing head shown in FIG. 8.

A polarization adjustment device according to one or more embodiments includes a first optical element, a second optical element, an axicon lens, and a third optical element.

The first optical element generates a randomly polarized laser beam including first linearly polarized light having a first polarization direction and second linearly polarized light having a second polarization direction orthogonal to the first polarization direction. , the light is separated into first linearly polarized light and second linearly polarized light. The second optical element converts the polarization direction of the second linearly polarized light separated by the first optical element into the first polarization direction. The axicon lens spreads the second linearly polarized light emitted by the second optical element or the second linearly polarized light incident on the second optical element into a ring shape. The third optical element coaxially emits the first linearly polarized light separated by the first optical element and the second linearly polarized light expanded into a ring shape by the axicon lens. The third optical element is also used as the first optical element, or is separate from the first optical element.

[First embodiment]
Hereinafter, the polarization adjustment device and laser processing machine according to the first embodiment will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing an example of the overall configuration of a laser processing machine 100 including a polarization adjustment device according to the first embodiment. In FIG. 1, a laser processing machine 100 is a processing machine that cuts a workpiece W using a laser beam. The workpiece W to be processed is, for example, a mild steel plate. The workpiece W may be an iron-based sheet metal other than a mild steel plate such as stainless steel, or may be a non-iron-based sheet metal such as aluminum, aluminum alloy, copper, etc.

As shown in FIG. 1, the laser processing machine 100 includes a laser oscillator 10 that generates and emits a laser beam, a laser processing unit 20, and a laser processing unit 20 that transmits the laser beam emitted from the laser oscillator 10 to the laser processing unit 20. A process fiber 12 is provided. The laser processing machine 100 also includes an NC (Numerical Control) device 50 and an assist gas supply device 60. The NC device 50 is an example of a control device that controls each part of the laser processing machine 100.

As the laser oscillator 10, a laser oscillator that amplifies excitation light emitted from a laser diode and emits a laser beam of a predetermined wavelength, or a laser oscillator that directly uses the laser beam emitted from a laser diode is suitable. The laser oscillator 10 is, for example, a solid-state laser oscillator, a fiber laser oscillator, a disk laser oscillator, or a direct diode laser oscillator (DDL oscillator).

The laser oscillator 10 emits a laser beam in the 1 μm band with a wavelength of 900 nm to 1100 nm. Taking a fiber laser oscillator and a DDL oscillator as examples, the fiber laser oscillator emits a laser beam with a wavelength of 1060 nm to 1080 nm, and the DDL oscillator emits a laser beam with a wavelength of 910 nm to 950 nm.

Process fiber 12 transmits the laser beam emitted from laser oscillator 10 to laser processing unit 20 . In addition, in the first embodiment, the laser beam transmitted through the process fiber 12 has a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction orthogonal to the first polarization direction. It is a randomly polarized laser beam including linearly polarized light.

The laser processing unit 20 cuts the workpiece W using the laser beam transmitted by the process fiber 12. The laser processing unit 20 includes a processing table 21 on which a workpiece W is placed, a gate-shaped X-axis carriage 22, a Y-axis carriage 23, and a processing head 30A. The X-axis carriage 22 is configured to be movable along the X-axis direction on the processing table 21. The Y-axis carriage 23 is configured to be movable on the X-axis carriage 22 along the Y-axis direction perpendicular to the X-axis. The X-axis carriage 22 and the Y-axis carriage 23 move the processing head 30A along the surface of the workpiece W in the X-axis direction, the Y-axis direction, or any combination direction of the X-axis and the Y-axis. It functions as a mechanism.

The processing head 30A irradiates the workpiece W with the laser beam transmitted by the process fiber 12. The detailed structure of the processing head 30A will be described later with reference to FIGS. 2 to 4. A nozzle 24 for emitting a laser beam is detachably attached to the tip of the processing head 30A. A circular opening 25 is provided at the tip of the nozzle 24, and the workpiece W is irradiated with a laser beam from the opening 25.

The processing head 30A is fixed to a Y-axis carriage 23 that is movable in the Y-axis direction, and the Y-axis carriage 23 is provided on an X-axis carriage 22 that is movable in the X-axis direction. Therefore, the processing head 30A, that is, the position at which the laser beam is irradiated onto the workpiece W can be moved along the surface of the workpiece W (X-axis direction and Y-axis direction). Note that instead of the configuration in which the processing head 30A is moved along the surface of the workpiece W, a configuration may be adopted in which the workpiece W is moved while the position of the processing head 30A is fixed. The laser processing machine 100 may include a movement mechanism that moves the processing head 30A relative to the surface of the workpiece W.

The NC device 50 uses a machining program database (not shown) to create a machining program for cutting the workpiece W, and a first motor 41 and a second motor 42, which will be described later, in accordance with the machining program. Read out control information.

The processing program includes laser processing necessary for cutting the workpiece W, such as setting processing conditions, starting and stopping laser beam injection, and moving path of the processing head 30A (cutting processing path). Code that defines a series of operations of the machine 100 is written. The NC device 50 controls the first motor 41 and the second motor 42 based on the read information and moves the X-axis carriage 22 and Y-axis carriage to cut the workpiece W based on the processing program. 23.

The assist gas supply device 60 supplies assist gas to the processing head 30A when processing the workpiece W. The assist gas is nitrogen, oxygen, a mixture of nitrogen and oxygen, or air. For example, if the workpiece W is stainless steel, nitrogen is used as the assist gas, and if the workpiece W is a mild steel plate, oxygen is used as the assist gas. The assist gas is blown from the opening 25 of the nozzle 24 in a direction perpendicular to the workpiece W. The assist gas discharges the molten metal in the cutting groove in which the workpiece W is melted.

[Example of configuration of processing head 30A]
A detailed configuration example of the processing head 30A will be described with reference to FIGS. 2 to 5. FIG. 2 shows an example of the configuration of the processing head 30A. As shown in FIG. 2, the processing head 30A includes a collimating lens 31, a special polarizing beam splitter 32, a quarter-wave plate 33, a first reflecting mirror 34, an axicon lens 35, and a second reflecting mirror 36. The special polarization beam splitter 32, the quarter-wave plate 33, the first reflection mirror 34, the axicon lens 35, and the second reflection mirror 36 in FIG. , a first linearly polarized light L1 in a randomly polarized laser beam L including a second linearly polarized light L2 having a second polarization direction orthogonal to the first polarization direction is emitted as the first linearly polarized light L1, It functions as a polarization adjustment unit (polarization adjustment device) that converts the second linearly polarized light L2 into the second linearly polarized light L22 having the first polarization direction and emits the second linearly polarized light L22.

In the first embodiment, the special polarization beam splitter 32 functions as a dual-purpose optical element that serves both as a first optical element and a third optical element. Moreover, the quarter wavelength plate 33 and the first reflection mirror 34 function as a second optical element. The processing head 30A also includes a 1/2 wavelength plate 37, a first motor 41 that rotates the 1/2 wavelength plate 37, a lens array 38, a second motor 42 that rotates the lens array 38, and a focusing lens 39. . In addition, in FIG. 2, a double circle with a black center indicates the first linearly polarized light, and a double arrow indicates the second linearly polarized light.

A diverging laser beam emitted from the exit end of the process fiber 12 is incident on the collimator lens 31 . The diverging laser beam incident on the collimating lens 31 includes a first linearly polarized light L1 having a first polarization direction and a second linearly polarized light L2 having a second polarization direction orthogonal to the first polarization direction. This is a randomly polarized laser beam L including the following. The collimating lens 31 converts the incident randomly polarized laser beam L into parallel light (collimated light). The randomly polarized laser beam L converted into collimated light by the collimating lens 31 enters the special polarizing beam splitter 32 . The special polarization beam splitter 32 is arranged so that its surface forms an angle of 45 degrees with respect to the optical axis.

FIG. 3 shows an example of the configuration of the special polarization beam splitter 32. As shown in FIG. 3, the special polarization beam splitter 32 has an elliptical polarization separation region 321 at the center and a transmission region 322 around the polarization separation region 321. FIG. 4 shows the polarization direction and shape of the laser beam in FIG. 2, and the positional relationship between the first and second linearly polarized lights L1 and L2 when the first and second linearly polarized lights L1 and L2 are coaxially emitted. show. FIG. 4 schematically shows the external shapes of the randomly polarized laser beam L, the first linearly polarized light L1, and the second linearly polarized lights L2, L21, and L22. Further, the arrows in the randomly polarized laser beam L, the first linearly polarized light L1, and the second linearly polarized lights L2, L21, and L22 in FIG. 4 merely schematically indicate the polarization direction of each laser beam. Therefore, the difference in the length of the arrows has no particular meaning.

The polarization separation region 321 reflects the first linearly polarized light L1 in the incident randomly polarized laser beam L and transmits the second linearly polarized light L2, thereby forming a randomly polarized laser beam as shown in FIG. This is a polarizing beam splitter that separates first linearly polarized light L1 and second linearly polarized light L2 in L. The transmission region 322 is coated with an anti-reflection coating, and transmits the incident laser beam.

The randomly polarized laser beam L emitted from the collimating lens 31 enters the polarization separation region 321 of the special polarization beam splitter 32 . The polarization separation region 321 reflects the first linearly polarized light L1 included in the randomly polarized laser beam L downward in the Z-axis direction perpendicular to the X-axis and the Y-axis. Further, the polarization separation region 321 transmits the second linearly polarized light L2 included in the randomly polarized laser beam L, and causes the second linearly polarized light L2 to be incident on the quarter-wave plate 33.

The quarter-wave plate 33 is disposed between the special polarization beam splitter 32 and the first reflection mirror 34, and converts the second linearly polarized light L2 that has passed through the polarization separation region 321 of the special polarization beam splitter 32 into a second Convert to circularly polarized light of 1. The quarter-wave plate 33 is formed of, for example, crystal, and configured so that the phase delay of the laser beam that enters and passes through the quarter-wave plate 33 is 90° + n × 360° (n is an integer). is preferred. The quarter-wave plate 33 may be manufactured, for example, by bonding two crystal plates together so that their optical axes are in directions orthogonal to each other. The first circularly polarized light converted by the quarter-wave plate 33 enters the first reflection mirror 34 .

The first reflecting mirror 34 reflects the incident first circularly polarized light and emits it as second circularly polarized light whose phase is reversed to that of the first circularly polarized light. The second circularly polarized light emitted from the first reflecting mirror 34 enters the quarter-wave plate 33 . The quarter-wave plate 33 converts the second circularly polarized light reflected by the first reflecting mirror 34 into the first polarization direction.

With the above configuration, the quarter-wave plate 33 and the first reflection mirror 34 convert the second linearly polarized light L2 separated by the special polarization beam splitter 32 into the first polarized light, as shown in FIG. It is converted into second linearly polarized light L21 having a direction. The second linearly polarized light L21 emitted from the quarter-wave plate 33 enters the polarization separation region 321 of the special polarization beam splitter 32. The polarization separation region 321 reflects the second linearly polarized light L21 emitted from the quarter-wave plate 33 upward in the Z-axis direction.

The axicon lens 35 is arranged between the special polarization beam splitter 32 and the second reflection mirror 36. When viewed from the special polarization beam splitter 32, the laser beam entrance surface of the axicon lens 35 is a conical inclined surface, and the exit surface is a flat surface. The inclined surface of the axicon lens 35 spreads the second linearly polarized light L21 reflected upward by the polarization separation region 321 of the special polarization beam splitter 32 into a ring shape, as shown in FIG. Note that the second linearly polarized light L22 spread into a ring shape by the axicon lens 35 in FIG. 4 enters the second reflection mirror 36.

The second reflecting mirror 36 reflects the second linearly polarized light L22 emitted from the axicon lens 35. The second linearly polarized light L22 reflected by the second reflecting mirror 36 enters the flat surface of the axicon lens 35 and exits from the inclined surface. The axicon lens 35 converts the incident ring-shaped second linearly polarized light L22 into collimated light, and causes the collimated light to enter the transmission region 322 of the special polarization beam splitter 32.

The transmission region 322 transmits the ring-shaped second linearly polarized light L22 emitted from the axicon lens 35. The ring-shaped second linearly polarized light L22 that has passed through the transmission region 322 is placed outside the first linearly polarized light L1 that has been reflected by the polarization separation region 321, as shown in FIG.

With the above configuration, the polarization adjustment section generates ring-shaped second linearly polarized light having the first polarization direction on the outside of the first linearly polarized light L1 reflected downward by the polarization separation region 321 of the special polarization beam splitter 32. L22 is arranged to coaxially emit the first linearly polarized light L1 and the second linearly polarized light L22. As a result, the polarization directions of the two linearly polarized lights L1 and L2 included in the randomly polarized laser beam L can be aligned in parallel, and the anisotropy with respect to the cutting progress direction of the two laser beams with the polarization directions aligned in parallel can be achieved. You can eliminate gender.

The first linearly polarized light L1 and the second linearly polarized light L22 coaxially emitted from the special polarized beam splitter 32 enter the half-wave plate 37. The 1/2 wavelength plate 37 is disposed on the optical path of the first linearly polarized light L1 and the second linearly polarized light L22 coaxially emitted from the special polarized beam splitter 32, and is connected to the first motor 41 (first rotation mechanism). ), it is configured to be rotatable on the XY plane.

The first motor 41 is controlled by the NC device 50 (first control section) and rotates the 1/2 wavelength plate 37 on the XY plane. The NC device 50 sets the first linearly polarized light L1 and the second linearly polarized light L22 that have passed through the half-wave plate 37 so that their polarization directions are parallel to the cutting direction of the laser processing machine 100. The motor 41 is controlled.

As described above, the half-wave plate 37, the first motor 41, and the NC device 50 control the polarization directions of the first linearly polarized light L1 and the second linearly polarized light L22 emitted from the special polarization beam splitter 32. It functions as a polarization direction control mechanism that controls the laser beam to be parallel to the cutting progress direction when cutting the workpiece W by irradiating the workpiece W with a laser beam.

The laser processing machine 100 aligns the polarization directions of the first linearly polarized light L1 and the second linearly polarized light L2 included in the randomly polarized laser beam to the first polarization direction, and aligns the polarization directions to the first polarization direction. The polarization direction of the laser beam is controlled so that it is parallel to the cutting direction. By matching the polarization direction of the laser beam with the cutting direction, the cutting front, which is the cut surface at the boundary between the unmelted region and the molten region in the cutting direction when the workpiece W is melted and cut, is Since the polarization direction of the laser beam becomes p-polarized light, the absorption rate of the laser beam of the workpiece W can be improved.

A laser beam emitted from the 1/2 wavelength plate 37 and whose polarization direction is controlled to be parallel to the cutting direction enters the lens array 38 . The lens array 38 is placed on the optical path of the laser beam whose polarization direction is controlled by a half-wave plate 37 so that it is parallel to the direction of cutting progress, and is rotated by a second motor 42 (second rotation mechanism). configured as possible.

FIG. 5 shows an example of the configuration of the lens array 38. As shown in FIG. 5, the lens array 38 includes a plurality of rectangular lenses 38a arranged two-dimensionally. A laser beam whose polarization direction is controlled to be parallel to the cutting progress direction by the half-wave plate 37 is incident on each of the plurality of lenses 38a. In addition, each lens 38a in the plurality of lenses 38a may be a convex lens or a concave lens, and the lens array 38 is configured such that the entire plurality of lenses 38a is either a convex lens or a concave lens. .

The focusing lens 39 irradiates the processing point WP of the workpiece W with a rectangular laser beam with a uniform intensity distribution by focusing the laser beams that have passed through each lens 38a in the lens array 38 so as to overlap each other. .

The second motor 42 is controlled by an NC device 50 (second control section). The NC device 50 transmits the second laser beam so that one side of the rectangular laser beam that passes through the lens array 38 and the focusing lens 39 and irradiates the processing point WP of the workpiece W is parallel to the cutting progress direction. The motor 42 is controlled. Note that although the NC device 50 functions as the first and second control sections, a control section that controls the first motor 41 and a control section that controls the second motor 42 are provided separately. Good too.

As described above, the lens array 38, the second motor 42, the focusing lens 39, and the NC device 50 generate a laser beam whose polarization direction is controlled to be parallel to the cutting direction by the polarization direction control mechanism. It functions as a rectangular beam angle control mechanism that controls the rectangular shaped laser beam so that one side of the rectangular shaped laser beam is parallel to the cutting direction.

FIG. 6A shows the relationship between the cutting progress direction of the workpiece W and the polarization direction of the laser beam irradiated onto the workpiece W. FIG. 6A shows the laser beam when the first linearly polarized light L1 and the second linearly polarized light L22 coaxially emitted from the special polarizing beam splitter 32 are shaped into a rectangular shape by the lens array 38 and irradiated onto the workpiece. The outline of the beam is shown. As shown in FIG. 6A, the polarization direction control mechanism controls the polarization directions of the first linearly polarized light L1 and the second linearly polarized light L22 that are coaxially emitted from the special polarized beam splitter 32 and shaped into a rectangular shape by the lens array 38. P is controlled so as to be parallel to the cutting progress direction D when cutting the workpiece W by irradiating the workpiece W with a laser beam. The rectangular beam angle control mechanism shapes the laser beam, which is controlled so that the polarization direction P is parallel to the cutting direction D, into a rectangular shape, and one side of the rectangularly shaped laser beam is parallel to the cutting direction. control so that

FIG. 6B shows the relationship between the cutting progress direction of the workpiece W when the cutting progress direction of the workpiece W draws a curve and the polarization direction of the laser beam irradiated onto the workpiece W. FIG. 6B shows the laser beam when the first linearly polarized light L1 and the second linearly polarized light L22 coaxially emitted from the special polarizing beam splitter 32 are shaped into a rectangular shape by the lens array 38 and irradiated onto the workpiece. The outline of the beam is shown. FIG. 6B shows a case where a corner R of a product is cut, as an example of a case where the cutting progress direction of the workpiece W draws a curve. As shown in FIG. 6B, when the laser processing machine 100 cuts the corner R along the cutting path of the workpiece W, the NC device 50 controls the first and second motors 41 and 42. Then, the half-wave plate 37 and the lens array 38 are rotated so that the polarization direction P and one side of the rectangularly shaped laser beam are always parallel to the cutting direction D. As a result, during cutting, the polarization direction P of the laser beam at the cutting front and one side of the laser beam shaped into a rectangular shape at the cutting front are always parallel to the cutting progress direction.

FIG. 7A is a comparative example assuming that the processing head 30A does not include the lens array 38, and shows the relationship between the cutting front, the polarization direction, and the cutting direction when the cutting front has a semicircular shape. It shows. FIG. 7B shows the relationship between the cutting front, the polarization direction, and the cutting direction when the processing head 30A includes the lens array 38 and the cutting front has a rectangular shape. The shape of the cutting front here refers to the shape of the boundary between the non-melting area and the molten area in the cutting direction when the workpiece W is melted and cut, as seen from the surface of the workpiece W. be.

As shown in FIG. 7A, when the cutting front has a semicircular shape, even if the polarization direction P of the laser beam is parallel to the cutting progress direction D, as it approaches the outside in the width direction of the cutting groove, Therefore, the polarization direction P is no longer incident perpendicularly to the cutting front. Since p-polarized light acts when the polarization direction P is incident in the direction N perpendicular to the cutting front, the effect of p-polarized light becomes weaker as it approaches the outside in the width direction of the cutting groove, and the workpiece W The absorption rate of the laser beam decreases.

On the other hand, as shown in FIG. 7B, when the shape of the cutting front is rectangular, if the polarization direction P of the laser beam is parallel to the cutting progress direction D, at which position in the width direction of the cutting groove can Also, the polarization direction P is incident in the direction N perpendicular to the cutting front. Therefore, the p-polarized light acts efficiently on the cutting front, and the absorption rate of the laser beam of the workpiece W is improved.

The absorption rate of the laser beam of the workpiece W when cutting is performed using a conventional randomly polarized laser beam with a semicircular cutting front, that is, a circular cross-sectional shape, and the present embodiment The absorptivity of the laser beam of the workpiece W when cutting is performed using the laser processing machine 100 was compared using a computer simulation. In the simulation, the wavelength of the laser beam was 1.08 μm, the material of the workpiece W was iron, and the thickness was 8 mm. As a result, the absorption rate when cutting was performed using a conventional laser beam was about 55%. On the other hand, when cutting is performed using the laser processing machine 100 according to the present embodiment, the absorption rate of the laser beam of the workpiece W is approximately 74%, and it was confirmed that the absorption rate is improved by approximately 19%. .

[Operations and effects of the first embodiment]
As explained above, according to the first embodiment, the following effects can be obtained.

The polarization adjustment device according to the first embodiment adjusts first linearly polarized light L1 having a first polarization direction, which is included in a randomly polarized laser beam L, and a second polarization direction orthogonal to the first polarization direction. The polarization direction of the second linearly polarized light L2 is aligned with the first polarization direction and emitted coaxially. The polarization adjustment device according to the first embodiment has a ring shape having a first polarization direction on the outside of the first linearly polarized light L1 reflected by the polarization separation region 321 of the first optical element (special polarization beam splitter 32). , and the first linearly polarized light L1 and the second linearly polarized light L22 are coaxially emitted. As a result, the polarization directions of the two linearly polarized lights L1 and L2 included in the randomly polarized laser beam L can be aligned in parallel, and the anisotropy with respect to the cutting progress direction of the two laser beams with the polarization directions aligned in parallel can be achieved. You can eliminate gender.

Further, the laser processing machine 100 including the polarization adjustment device according to the first embodiment controls the polarization directions of two laser beams whose polarization directions are aligned in parallel to be parallel to the cutting progress direction. By making the polarization direction coincide with the cutting progress direction, the polarization direction of the laser beam with respect to the cutting front becomes p-polarized light, so that the absorption rate of the laser beam of the workpiece W can be improved.

Further, the laser processing machine 100 including the polarization adjustment device and the polarization direction control mechanism according to the first embodiment has the polarization direction of the first linearly polarized light L1 and the second linearly polarized light L22 coaxially emitted from the polarization adjustment device. P is controlled so as to be parallel to the cutting progress direction D when cutting the workpiece W by irradiating the workpiece W with a laser beam. The rectangular beam angle control mechanism of the laser processing machine 100 according to the first embodiment shapes the laser beam, which is controlled so that the polarization direction P is parallel to the cutting direction D, into a rectangular shape. Control is performed so that one side of the laser beam is parallel to the cutting direction.

Thereby, the workpiece W can be processed using two non-anisotropic laser beams with parallel polarization directions. Further, during the cutting process, the polarization direction P of the laser beam at the cutting front and one side of the laser beam shaped into a rectangular shape at the cutting front are always parallel to the cutting progress direction. At any position in the width direction of the cutting groove, the polarization direction P is incident in the direction N perpendicular to the cutting front. Therefore, the p-polarized light acts efficiently on the cutting front, and the absorption rate of the laser beam of the workpiece W is improved. Therefore, processing efficiency during cutting is improved.

[Second embodiment]
The polarization adjustment device and laser processing machine 100 according to the second embodiment will be described below with reference to FIGS. 8 to 10. FIG. 8 shows a configuration example of a processing head 30B according to the second embodiment. In FIG. 8, parts that are the same as those in FIG. 2 are given the same reference numerals, and detailed explanations may be omitted. The laser processing machine 100 according to the second embodiment has a difference in the internal configuration of the processing head compared to the laser processing machine 100 according to the first embodiment. The other configurations are the same as the laser processing machine 100 according to the first embodiment. Therefore, in the laser processing machine 100 according to the second embodiment, the parts that are different from the laser processing machine 100 according to the first embodiment will be mainly explained, and the same parts will not be explained again.

As shown in FIG. 8, the processing head 30B includes a collimating lens 31, a polarizing beam splitter 71, a third reflecting mirror 72, axicon lenses 73 and 74, a fourth reflecting mirror 75, a half-wave plate 76, a special It has a mirror 77. The polarizing beam splitter 71, the third reflecting mirror 72, the axicon lenses 73 and 74, the fourth reflecting mirror 75, the 1/2 wavelength plate 76, and the special mirror 77 in FIG. and a second linearly polarized light L2' having a second polarization direction perpendicular to the first polarization direction. It functions as a polarization adjustment unit (polarization adjustment device) that converts the second linearly polarized light L2' into a second linearly polarized light L22' having the first polarization direction and emits the linearly polarized light L1'.

In the second embodiment, the polarizing beam splitter 71 functions as a first optical element. Moreover, the 1/2 wavelength plate 76 functions as a second optical element. Furthermore, the special mirror 77 functions as a third optical element separate from the first optical element. Further, the processing head 30B of the laser processing machine 100 according to the second embodiment includes a 1/2 wavelength plate 37, a first motor 41, a lens array 38, a second motor 42, a fifth reflection mirror 78, a focusing lens It has 39. In addition, in FIG. 8, a double circle with a black center indicates the first linearly polarized light, and a double-headed arrow indicates the second linearly polarized light.

In FIG. 8, a diverging laser beam emitted from the exit end of the process fiber 12 is incident on the collimating lens 31. The diverging laser beam incident on the collimating lens 31 includes a first linearly polarized light L1' having a first polarization direction and a second linearly polarized light having a second polarization direction orthogonal to the first polarization direction. This is a randomly polarized laser beam L' including L2'. The collimating lens 31 converts the incident randomly polarized laser beam L' into collimated light. The randomly polarized laser beam L' converted into collimated light by the collimating lens 31 enters the polarizing beam splitter 71.

FIG. 9 shows the polarization direction and shape of the laser beam in FIG. 8, and the first and second linearly polarized lights L1' and L2' when the first and second linearly polarized lights L1' and L2' are emitted coaxially. Indicates the positional relationship between FIG. 9 schematically shows the outlines of the randomly polarized laser beam L', the first linearly polarized light L1', and the second linearly polarized lights L2', L21', and L22'. Further, the arrows in the randomly polarized laser beam L', the first linearly polarized light L1', and the second linearly polarized lights L2', L21', and L22' in FIG. 9 simply indicate the polarization direction of each laser beam. This is shown schematically, and the difference in length of the arrows has no particular meaning.

The polarizing beam splitter 71 transmits the first linearly polarized light L1' in the randomly polarized laser beam L' and reflects the second linearly polarized light L2', thereby converting the first linearly polarized light into the first linearly polarized light, as shown in FIG. It is a polarization beam splitter that separates L1' and second linearly polarized light L2'.

The polarizing beam splitter 71 transmits the first linearly polarized light L1' included in the randomly polarized laser beam L' and causes it to enter the special mirror 77. The first linearly polarized light L1' transmitted through the polarizing beam splitter 71 is incident on a transmission region 771 (see FIG. 10) of a special mirror 77, which will be described later. Further, the polarizing beam splitter 71 reflects the second linearly polarized light L2' included in the randomly polarized laser beam L' upward in the Z-axis direction perpendicular to the X-axis and the Y-axis. The second linearly polarized light L2' reflected upward by the polarizing beam splitter 71 is incident on the third reflecting mirror 72.

The third reflecting mirror 72 reflects the second linearly polarized light L2' reflected from the polarizing beam splitter 71 in the X-axis direction. The second linearly polarized light L2' reflected by the third reflecting mirror 72 enters the axicon lens 73. The axicon lens 73 is arranged with its conical inclined surface facing the third reflecting mirror 72 and its flat surface facing the axicon lens 74.

The inclined surface of the axicon lens 73 spreads the second linearly polarized light L2' reflected by the third reflection mirror 72 into a ring shape, as shown in FIG. The second linearly polarized light L21' spread into a ring shape by the axicon lens 73 is incident on the axicon lens 74. The axicon lens 74 is arranged with its flat surface facing the axicon lens 73 and its conical inclined surface facing the fourth reflecting mirror 75.

The axicon lens 74 converts the ring-shaped second linearly polarized light L21' emitted from the axicon lens 73 into collimated light, and causes the collimated light to enter the fourth reflection mirror 75. The fourth reflection mirror 75 reflects the ring-shaped second linearly polarized light L21' emitted from the axicon lens 73 and converted into collimated light by the axicon lens 74 downward in the Z-axis direction, and The light is made incident on the two-wavelength plate 76.

The half-wave plate 76 converts the polarization direction of the ring-shaped second linearly polarized light L21' reflected by the fourth reflection mirror 75 into the first polarization direction. With the above configuration, the half-wave plate 76 splits the second linearly polarized light L21' by the polarizing beam splitter 71 and spreads it into a ring shape by the axicon lens 73, as shown in FIG. It is converted into ring-shaped second linearly polarized light L22' having the first polarization direction. The ring-shaped second linearly polarized light L22' emitted from the half-wave plate 76 enters the special mirror 77.

FIG. 10 shows an example of the configuration of the special mirror 77. As shown in FIG. 10, the special mirror 77 has an elliptical transmission region 771 at the center and a reflection region 772 around the transmission region 771. The transmission region 771 is coated with an antireflection coating and transmits the incident laser beam. A highly reflective coating is applied to the reflective region 772, and the reflective region 772 reflects the incident laser beam.

The first linearly polarized light L1' transmitted through the polarizing beam splitter 71 enters the transmission region 771 of the special mirror 77. The transmission region 771 transmits the first linearly polarized light L1' that has passed through the polarization beam splitter 71. The ring-shaped second linearly polarized light L22' emitted from the half-wave plate 76 enters the reflection region 772 of the special mirror 77. The reflection region 772 reflects the incident ring-shaped second linearly polarized light L22' in the X-axis direction. As shown in FIG. 9, the ring-shaped second linearly polarized light L22' reflected by the reflection area 772 is placed outside the first linearly polarized light L1' that has passed through the transmission area 771.

With the above configuration, the polarization adjustment section creates a ring-shaped second straight line having the first polarization direction on the outside of the first linearly polarized light L1' that has passed through the polarization beam splitter 71 and the transmission area 771 of the special mirror 77. The polarized light L22' is arranged, and the first linearly polarized light L1' and the second linearly polarized light L22' are coaxially emitted. As a result, the polarization directions of the two linearly polarized lights L1' and L2' included in the randomly polarized laser beam L' can be aligned in parallel, and anisotropy with respect to the cutting direction of the laser beam can be eliminated. .

The first linearly polarized light L1' and the second linearly polarized light L22' coaxially emitted from the special mirror 77 enter the half-wave plate 37. The 1/2 wavelength plate 37 is arranged on the optical path of the first linearly polarized light L1' and the second linearly polarized light L22' coaxially emitted from the special mirror 77, and can be rotated on the XZ plane by the first motor 41. It is composed of

A laser beam emitted from the 1/2 wavelength plate 37 and whose polarization direction is controlled to be parallel to the cutting direction enters the lens array 38 . The lens array 38 is arranged on the optical path of a laser beam whose polarization direction is controlled to be parallel to the cutting direction by a half-wave plate 37, and is configured to be rotatable on the XZ plane by a second motor 42. be done.

The fifth reflection mirror 78 reflects the laser beam that has passed through the lens array 38 downward in the Z-axis direction and enters the focusing lens 39 .

The focusing lens 39 focuses the laser beam reflected by the fifth reflecting mirror 78 and irradiates the processing point WP of the workpiece W with a rectangular laser beam having a uniform intensity distribution.

The first motor 41 is controlled by the NC device 50 and rotates the 1/2 wavelength plate 37. The NC device 50 transmits the first linearly polarized light L1' and the second linearly polarized light L22' that have passed through the 1/2 wavelength plate 37 and the lens array 38, been reflected by the fifth reflection mirror 78, and passed through the focusing lens 39. The first motor 41 is controlled so that the direction of polarization of the light is parallel to the direction of cutting progress.

As described above, the 1/2 wavelength plate 37, the first motor 41, and the NC device 50 are capable of handling the first linearly polarized light L1' and the second linearly polarized light L22' coaxially emitted from the special mirror 77. It functions as a polarization direction control mechanism that controls the polarization direction of the workpiece W to be parallel to the cutting progress direction when the workpiece W is irradiated with a laser beam to cut the workpiece W.

The second motor 42 is controlled by the NC device 50 and rotates the lens array 38. The NC device 50 is configured such that one side of a rectangular laser beam that passes through the lens array 38, is reflected by the fifth reflecting mirror 78, passes through the focusing lens 39, and is irradiated onto the processing point WP of the workpiece W. The second motor 42 is controlled so as to be parallel to the cutting direction.

As described above, the lens array 38, the second motor 42, the focusing lens 39, and the NC device 50 generate a laser beam whose polarization direction is controlled to be parallel to the cutting direction by the polarization direction control mechanism. It functions as a rectangular beam angle control mechanism that controls the rectangular shaped laser beam so that one side of the rectangular shaped laser beam is parallel to the cutting direction.

[Operations and effects of the second embodiment]
As explained above, according to the second embodiment, the following effects can be obtained.

The polarization adjustment device according to the second embodiment has a polarization beam splitter 71, a third reflection mirror 72, axicon lenses 73 and 74, a fourth reflection mirror 75, a half-wave plate 76, and a special mirror 77. The polarization direction of the randomly polarized laser beam L' including the first linearly polarized light L1' and the second linearly polarized light L2' is aligned to the first polarization direction. Each optical element of the polarization adjustment device according to the second embodiment can be arranged so as not to reflect the laser beam toward the exit end of the process fiber 12. As a result, in the polarization adjustment device according to the first embodiment, a part of the second linearly polarized light L21 reflected by the first reflection mirror 34 and emitted from the quarter-wave plate 33 passes through the special polarization beam splitter 32. The risk of the light passing through and entering the exit end of the process fiber 12 can be reduced.

The present invention is not limited to the first or second embodiment described above, and various changes can be made without departing from the gist of the present invention.

32 Special polarizing beam splitter (first optical element, third optical element)
33 1/4 wavelength plate 33 (second optical element)
34 First reflecting mirror (second optical element)
35, 73, 74 Axicon lens 71 Polarizing beam splitter (first optical element)
76 1/2 wavelength plate (second optical element)
77 Special mirror (third optical element)
100 Laser processing machine L, L' Randomly polarized laser beam L1, L1' First linearly polarized light L2, L21, L22, L2', L21', L22' Second linearly polarized light

Claims (4)

A randomly polarized laser beam including a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction perpendicular to the first polarization direction is directed to the first straight line. a first optical element that separates the polarized light and the second linearly polarized light;
a second optical element that converts the polarization direction of the second linearly polarized light separated by the first optical element to the first polarization direction;
an axicon lens that spreads the second linearly polarized light emitted from the second optical element or the second linearly polarized light incident on the second optical element into a ring shape;
Also serves as the first optical element, coaxially emitting the first linearly polarized light separated by the first optical element and the second linearly polarized light spread in a ring shape by the axicon lens. or a third optical element separate from the first optical element;
A polarization adjustment device comprising: comprising a dual-purpose optical element that serves as both the first optical element and the third optical element,
The dual-purpose optical element reflects the first linearly polarized light in the incident randomly polarized laser beam and transmits the second linearly polarized light, thereby separating the first linearly polarized light and the second linearly polarized light. It has a polarization separation region in the center that separates the polarized light, and has a transmission region around the polarization separation region that transmits the linearly polarized light in the first polarization direction,
The second optical element includes a quarter-wave plate that converts the second linearly polarized light transmitted through the polarization separation region into a first circularly polarized light, and a quarter-wave plate that reflects the first circularly polarized light and converts the second linearly polarized light into a second circularly polarized light. a first reflecting mirror that emits circularly polarized light;
The quarter-wave plate converts the second circularly polarized light reflected from the first reflecting mirror into the second linearly polarized light in the first polarization direction,
The polarization separation region reflects the second linearly polarized light emitted from the quarter-wave plate,
The axicon lens spreads the second linearly polarized light reflected by the polarization separation region into a ring shape,
further comprising a second reflecting mirror that reflects the second linearly polarized light emitted from the axicon lens,
The axicon lens allows the second linearly polarized light reflected by the second reflecting mirror to enter the transmission region,
The polarization adjustment device according to claim 1, wherein the dual-purpose optical element coaxially emits the first linearly polarized light reflected by the polarization separation region and the second linearly polarized light transmitted through the transmission region. The third optical element is
is separate from the first optical element,
It has a transmissive region in the center that transmits the incident laser beam, and has a reflective region around the transmissive region that reflects the incident laser beam,
The first optical element transmits the first linearly polarized light in the randomly polarized laser beam and makes it enter the transmission region, and reflects the second linearly polarized light, thereby converting the first linearly polarized light into the first linearly polarized light. separating the second linearly polarized light,
further comprising a first reflecting mirror that reflects the second linearly polarized light reflected from the first optical element,
The axicon lens spreads the second linearly polarized light reflected from the first reflecting mirror into a ring shape,
further comprising a second reflective mirror that reflects the second linearly polarized light emitted from the axicon lens,
The second optical element is
It is a 1/2 wavelength plate,
converting the polarization direction of the second linearly polarized light reflected by the second reflecting mirror to the first polarization direction and making it incident on the reflection region;
2. The polarization adjustment device according to claim 1, wherein the third optical element coaxially emits the first linearly polarized light that has passed through the transmission region and the second linearly polarized light that has been reflected by the reflection region. The polarization adjustment device according to any one of claims 1 to 3,
The polarization directions of the first linearly polarized light and the second linearly polarized light coaxially emitted from the polarization adjustment device are set as the cutting progress direction when cutting the workpiece by irradiating the workpiece with a laser beam. a polarization direction control mechanism that controls the polarization direction so that it is parallel to the
A laser processing machine equipped with

Images