KR102104782B1 - Power balance device for laser light, laser processing device - Google Patents

Abstract

A laser processing device capable of easily performing stable laser processing on a workpiece, and a power balance device for laser light used in the laser processing device are obtained. A diffraction grating in which a plurality of convex portions made of the same material as the substrate material extend linearly in parallel in a set period P is formed on the main surface side of one of the opposing pair of main surfaces, and the structure of the diffraction grating is formed. A polarization phase difference plate in which laser light of far-infrared light is incident, formed using birefringence, wherein the period (P) of the diffraction grating is P <λ / n (λ is the wavelength of the incident light, n is the refractive index of the substrate material) A power balance device for laser light having a polarization retardation plate and a rotating mechanism for rotating the polarization retardation plate was satisfied.

Description

Power balance device for laser light, laser processing device

The present invention relates to a laser processing device that performs perforation processing on a workpiece, such as a printed board, and more particularly, to a power balance device for laser light and a laser processing device using the power balance device.

As a method of improving the productivity of a CO ₂ laser processing device for perforating a workpiece such as a printed board, there is a method of dividing a single laser light generated by a laser oscillator into a plurality and simultaneously punching a plurality of holes. have. In this method, when the energy of each of the divided laser lights is not uniform, a gap occurs in the processing quality such as the diameter of the processed life diameter.

For this reason, in the method described in Patent Document 1 below, a polarizer for polarization azimuth adjustment having a rotation adjustment mechanism around an optical axis is provided upstream of the optical path than a polarizer for spectroscopy. Then, by adjusting the polarization azimuth of the transmitted P-wave, the balance between the polarization direction P-wave component incident on the spectroscopic polarizer and the polarization direction S-wave component is adjusted, and the P-wave component passing through the spectroscopic polarizer and the spectroscopic The energy of the laser light divided into the S-wave component reflected by the polarizer is equally adjusted.

Patent Document 2 describes an example in which the power balance of the YAG laser light is adjusted as follows. A transmission type 1/4 wavelength (π / 2) phase difference plate having a rotation adjustment mechanism that performs rotation adjustment around the optical axis is provided upstream of the optical path than the spectroscopic polarizer, and the polarization direction P wave component incident on the spectroscopic polarizer And, by adjusting the S-wave component in the polarization direction, the energy of processing is uniformly adjusted.

As described below, in Patent Document 3, generation of a thermal lens is prevented by using a polarization azimuth adjustment mechanism that uses only S polarized light without using transmitted light.

In recent years, in a punching machine such as a printed circuit board, the output of laser light has been improved by high energy processing such as through-holes or by improving the processing speed.

International Publication No. 2003/082510 Brochure Japanese Patent Publication No. 9-108878 (Fig. 1) Japanese Patent Publication No. 2011-251306 Japanese Patent Publication No. 2014-29467

In the above-described conventional technique, for example, in the configuration described in Patent Document 1, the P-wave component that transmits the polarizer for polarization azimuth adjustment is propagated downstream of the optical path. For this reason, when the power of the laser light incident on the polarizer is high, the beam diameter of the laser light is changed by the thermal lens effect of the substrate material of the polarizer, and the energy intensity of the laser light passing through the mask compared to when the thermal lens effect is not occurring. Is distributed. Thereby, there exists a problem that the processing quality of a to-be-processed object deteriorates or becomes unstable.

In addition, when the polarizer was rotated and adjusted when the polarization azimuth was adjusted, there was a problem that the processing quality of the workpiece may deteriorate due to a slight difference in the center of the optical axis due to the refraction of light.

In addition, the structure described in Patent Document 2 is for YAG laser light having a wavelength of about 1 µm and cannot transmit far infrared light. The birefringent material that transmits far infrared light is cadmium sulfide (CdS), but it is difficult to handle it as a poison.

Further, in the configuration described in Patent Document 3, no transmitted light is used, only S polarized light is used, and efficiency is poor.

The present invention has been made in light of the above, and an object thereof is to obtain a laser processing apparatus capable of easily performing stable laser processing on a workpiece and a power balance device for laser light used in the laser processing apparatus.

In the present invention, a plurality of convex portions made of the same material as the substrate material are formed on the main surface side of one of the opposing pair of main surfaces, and a diffraction grating is formed in which each of the convex portions extends in parallel in a straight line at a set period P, and the diffraction grating A polarization phase difference plate in which laser light of far-infrared light is incident, formed using a structural birefringence of, wherein the period (P) of the diffraction grating is P <λ / n (λ is the wavelength of the incident light, n is the substrate material And a rotation mechanism for rotating the polarization retardation plate and the polarization retardation plate.

In the present invention, there is provided a laser processing device capable of easily performing stable laser processing on a workpiece, and a power balance device for laser light used in the laser processing device.

1 is a diagram showing an example of the configuration of a laser processing apparatus according to Embodiment 1 of the present invention;
FIG. 2 is a perspective view showing a configuration of an example of a polarization phase difference plate of the sub-wavelength grating structure of FIG. 1;
3 is a diagram showing an example of the configuration of a laser processing apparatus according to Embodiment 2 of the present invention;
4 is a perspective side view showing a secret configuration of an example of the power balance device for laser of FIG. 3,
Fig. 5 is a perspective side view showing a secret configuration of another example of the power balance device for laser of Fig. 3,
6 is a view for explaining the effect of the thermal lens phenomenon according to the present invention,
7 is a view for explaining the effect of suppression of the thermal lens phenomenon according to the present invention.

In the present invention, since a power balance device using a material having high transmittance for far-infrared light can be configured by a sub-wavelength grating structure, a laser processing device capable of preventing thermal lenses and obtaining high processing quality even in a high-power beam, and A power balance device for laser light used as the laser processing device is provided.

Hereinafter, a laser processing apparatus according to the present invention and a power balance apparatus for laser light used as the laser processing apparatus will be described with reference to drawings according to each embodiment. Incidentally, the same or equivalent parts are denoted by the same reference numerals for each embodiment, and overlapping descriptions are omitted.

Embodiment 1.

1 is a diagram showing an example of the configuration of a laser processing apparatus according to Embodiment 1 of the present invention.

<Configuration of laser processing device>

The laser processing apparatus 100 spectrolizes one laser light 2 into two scattered laser lights 8A and 8B by the polarization beam splitter 7 which is a spectroscopic section. Roughly, the two dispersive laser lights 8A, 8B are independently scanned, and finally through the fθ lenses 11A, 11B, two workpieces 13A, 13B on the XY tables 12A, 12B ) At the same time.

The irradiation position of the scattered laser light 8A with respect to the workpiece 13A is moved by the galvano scanner 10Ax in the X direction, and the galvano scanner 10Ay is moved in the Y direction. Similarly, the irradiation position of the scattered laser light 8B with respect to the workpiece 13B is moved by the galvano scanner 10Bx in the X direction, and the galvano scanner 10By is moved in the Y direction. In addition, the X-direction and the Y-direction are coordinates orthogonal to each other in the plane of the workpieces 13A and 13B, like the XY table, and are different from the xyz direction in the polarization phase difference plate 200 to be described later.

In the laser processing apparatus 100 of the first embodiment, a polarization phase difference plate 200 having a sub-wavelength grating structure is disposed upstream of the optical path than the polarization beam splitter 7. The polarization phase difference plate 200 is configured to be rotatable by rotation of the optical axis by the rotation mechanism 220.

<Sub-wavelength grid structure polarization phase difference plate>

The polarization phase difference plate 200 having a sub-wavelength grating structure capable of transmitting far infrared light has, for example, a structure shown in Patent Document 4 above. FIG. 2 is a perspective view showing a configuration of an example of the polarization phase difference plate 200 of the sub-wavelength grating structure of FIG. 1. The polarization phase difference plate 200 to which the laser light is incident is a diffraction grating 201 formed of the same material as the substrate 202 on the main surface of the substrate 202 and a pair of opposing main surfaces of the substrate 202. It is provided. The diffraction grating 201 has a plurality of convex portions 203 extending in a straight line parallel to the x direction among the x, y, and z directions representing directions perpendicular to each other with the x and y directions as the substrate surface, in the y direction. It is configured by arranging at set intervals according to the set period (P).

When light is incident on the diffraction grating 201 along the z direction,

an effective refractive index for a polarization component (TE polarization) in the x direction,

The effective refractive index for the polarization component in the y direction (TM polarization)

Different from each other, so-called structural birefringence occurs. As a result, an overall velocity difference occurs between TE polarization and TM polarization, and elliptical polarization occurs according to a phase difference (phase retardation) corresponding to this overall velocity difference.

P <λ / n (1)

P: Period of the diffraction grating (interval)

λ: wavelength of incident light

n: refractive index of the substrate material

It is known that if the above formula (1) is satisfied, even in vertical incident light, the loss of high-order diffracted light can be prevented. The cross-sectional shape of the convex portion 203 is formed in a tapered shape 206 at an angle α from the bottom to the top and bottom.

Specifically,

The substrate material of the substrate 202 is zinc sulfide (ZnS),

The height H of the convex portion 203, that is, the depth of the groove is 4.01 μm,

The inclination angle α of the tapered shape 206 is 22.2 degrees,

The peeling factor (f) is 0.468,

The phase delay is λ / 8 (= π / 4).

In addition, the peeling factor f is the ratio of the width W of the width W of the convex portion 203 to the period P at a position H / 2 of the height H of the convex portion 203, That is, f = W / P.

An antireflection film 207 is coated on the other main surface of the substrate 202 without the diffraction grating 201. The material of the antireflection film 207 is germanium.

<Linear polarization of the oscillator>

The laser oscillator 1 is a laser device that emits laser light 2 (λ = 9.29 µm) made of, for example, linearly polarized CO ₂ laser light as a pulse wave. The laser light 2 emitted from the laser oscillator 1 is guided to the polarization phase difference plate 200 which is a sub-wavelength grating phase difference plate via one or a plurality of reflection mirrors 6. The reflection mirror 6 is a mirror that reflects the laser light 2 or the scattered laser light 8A, 8B and guides them downstream of the optical path. The reflection mirror 6 is arranged at various positions on the optical path in the laser processing apparatus 100.

<Polarizing beam splitter>

The polarization beam splitter 7, which is a polarization beam splitter for spectroscopy, is a polarizer such as a beam splitter that spectralizes one laser beam 2 in the shape of a beam with two dispersion laser beams 8A and 8B. The polarization beam splitter 7 has a property of transmitting the P-wave component of the laser light 2 and reflecting the S-wave component.

<Operation of laser processing equipment>

Next, the operation processing procedure of the laser processing apparatus 100 will be described. The laser light 2 of the polarization azimuth angle θ guided from the laser oscillator 1 passes through the polarization phase difference plate 200 having a sub-wavelength grating structure, and then passes through the beam variable portion 5 to the mask 4. Are guided.

In the mask 4, the laser light 2 is shaped into a beam mode shape suitable for laser processing by transmitting only a desired portion of the laser light 2. The laser light 2 shaped by the mask 4 is reflected by one or a plurality of reflection mirrors 6 and guided to the polarizing beam splitter 7.

In the polarization beam splitter 7, the P-wave polarization component of the laser light 2 passes through the polarization beam splitter 7 and is emitted as the dispersed laser light 8A. In addition, the S-wave polarization component of the laser light 2 is reflected by the polarization beam splitter 7 and emitted as the dispersed laser light 8B. In order to prevent a gap in the quality of the machining holes of the two workpieces 13A and 13B, it is necessary that the energy of the dispersion laser light 8A and the energy of the dispersion laser light 8B are the same.

<Thermal lens>

The thermal lens effect is that when the high-power laser light passes through the substrate material of the polarization phase difference plate 200 of the sub-wavelength grating structure of FIG. 1, which is a polarizer, the temperature of the substrate material is increased by locally increasing the temperature of the polarizer. It is a phenomenon in which a refractive index distribution occurs, whereby a polarizer acts as a lens.

In addition, for example, in the case of Patent Document 1, a thermal lens effect is derived for a polarizer for polarization azimuth adjustment.

<Influence on processing of thermal lens>

6 is a view for explaining a thermal lens phenomenon when the P-wave component passing through the conventional polarizer 17 corresponding to the polarization phase difference plate 200 according to the present invention is guided downstream of the optical path of the polarizer 17. to be. In Fig. 6A, the laser beam intensity distribution in the case where the thermal lens phenomenon does not occur is shown. 6B shows the distribution of the laser beam intensity when a thermal lens phenomenon occurs.

When the thermal lens phenomenon of Fig. 6A does not occur, the laser light emitted from the laser oscillator 1 has a laser beam intensity distribution A1. Moreover, when the thermal lens phenomenon of FIG. 6B occurs, the laser light emitted from the laser oscillator 1 has a laser beam intensity distribution B1. The laser beam intensity distribution B1 has the same intensity distribution as the laser beam intensity distribution A1.

Then, the laser light 2 from the laser oscillator 1 passes through the polarizer 17. The polarizer 17 here is arranged at the same position as, for example, a conventional polarization azimuth adjustment device. At this time, if no thermal lens phenomenon occurs, the laser light of the laser beam intensity distribution (A1) becomes the laser light of the laser beam intensity distribution (A2) by passing through the polarizer (17). In addition, when the thermal lens phenomenon occurs, the laser light of the laser beam intensity distribution (B1) is transmitted through the polarizer 17, so that the laser beam intensity distribution (B2) is different from the laser beam intensity distribution (A2). Become a mania.

As shown in FIG. 6 (b), when a thermal lens phenomenon occurs in the polarizer 17, a thermal lens phenomenon does not occur in the polarizer 17, as shown in FIG. 6 (a). Compared to the case, the beam diameter of the laser light in the mask 4 changes. Since the degree of thermal lens development depends on the power of the laser light incident on the polarizer 17, the beam energy of the laser light passing through the mask 4 changes when thermal lens development occurs or not. For this reason, a gap arises in the energy of the laser light reaching the workpieces 13A and 13B in Fig. 1 in the case where the thermal lens phenomenon occurs or not. Specifically, when the thermal lens phenomenon has not occurred, the laser light of the laser beam intensity distribution A3 is guided downstream of the optical path. Further, when the thermal lens phenomenon occurs, the laser light of the laser beam intensity distribution B3 different from the laser beam intensity distribution A3 is guided downstream of the optical path. As a result, in the case where the thermal lens phenomenon occurs and not, a difference occurs in the quality of the machining hole of the workpiece.

<Excavation of a problem called absorption by TFP. It can also be implemented in transmissive type>

Also in this Embodiment 1, since the point which the laser beam transmits through the substrate with a thickness is the same with respect to the polarization phase difference plate 200 similarly to the said patent document 1, it is the thermal lens similarly by the temperature gradient in the radial direction of a substrate It can be considered that the phenomenon occurs.

In this regard, as a result of the investigation according to the present invention, the TFP (thin film polarizer) used in the polarizing beam splitter according to Patent Document 1 is actually used in a structure in which ThF ₄ (thorium fluoride) having a thickness of 1 µm or more is stacked in layers. It was. Specifically, a layer of ThF ₄ (thorium fluoride) is stacked in four or more layers. When the absorption coefficient in the membrane state of ThF ₄ was measured, it was 19 [cm ^-1 ], and it was 38000 times that of the base material ZnSe (zinc selenide) (5e- ⁴ [cm ^-1 ]). When the total thickness of ThF ₄ is about 5 μm and the substrate thickness of ZnSe is 5 mm, ThF ₄ absorbs the laser light 38 times. The heat absorbed by the TFP is poor in thermal conductivity in the radial direction because of the thin film, and causes a temperature difference in the radial direction. That is, it was found that the effect of heat absorption in the TFP is dominant.

<Operation and effect of sub-wavelength grating structure>

On the other hand, in the first embodiment, by setting the power balance device using a polarization phase difference plate 200 having a sub-wavelength grating structure, only a substrate material having high transmittance to far-infrared light can be used, and TFP can be eliminated. As a result, it becomes possible to form processing holes with stable processing quality in the workpieces 13A and 13B without being affected by the thermal lens phenomenon.

Moreover, in this Embodiment 1, ZnS (zinc sulfide) is used for the base material of the substrate 202 of the polarization phase difference plate 200 shown in FIG. 2, ie, material. Among the materials for infrared transmission, by using a small refractive index ZnS as a substrate, Fresnel reflection is prevented, and a film of a material having a high absorption rate such as YF ₃ (yttrium fluoride) is absorbed without being provided on the lattice. The wavelength plate, that is, the polarization retardation plate 200, can be formed of a single ZnS single material, so that generation of thermal lenses can be suppressed.

In addition, since the thermal conductivity of ZnSe is 18 [W / (mK)], the thermal conductivity of ZnS is 27.2 [W / (mK)], so temperature distribution is unlikely to occur and heat lens generation is suppressed.

As an example, as a power balance device of a laser processing device, when a polarization azimuth adjustment device using a conventional polarizer for polarization azimuth adjustment described in Patent Document 1 is provided, and power balance using a polarization phase difference plate 200 having a sub-wavelength grating structure Fig. 7 shows the results of evaluating the effect of the thermal lens phenomenon in the case where the device is provided. The power balance device of the laser processing device is arranged at the same position as in the first embodiment. The laser light from the laser oscillator 1 has a configuration in which only a desired portion is transmitted by the mask 4 through the beam variable portion 5 after passing through the power balance device.

7 (a) is a power balance device of a laser processing device, and when a conventional polarization azimuth adjustment device described in Patent Literature 1 is provided, the laser reaches the workpiece with respect to the frequency of pulse generation of the laser oscillator. It is a result of measuring the rate of change of the energy intensity of light. The horizontal axis represents the frequency (pulse frequency) of pulse generation of the laser oscillator, and the vertical axis represents the rate of change of the energy intensity of the laser light reaching the workpiece (processing point energy change rate).

The higher the pulse frequency, the higher the power of the laser light incident on the power balance device. The rate of change in the processing point energy is a value obtained by dividing the processing point energy when the pulse frequency is low at about 200 kHz as a denominator and the processing point energy at each pulse frequency as a numerator. When the pulse frequency is low, the processing point energy change rate is small, and as the pulse frequency increases, the processing point energy change rate is increasing. This indicates that the higher the power of the laser light passing through the polarization azimuth adjusting device, the greater the effect of the thermal lens, and the greater the rate of change of the energy intensity of the laser light passing through the mask.

Fig. 7 (b) is a power balance device of a laser processing device, and avoids the frequency of pulse generation of the laser oscillator when a power balance device using a polarization phase difference plate 200 having a sub-wavelength grating structure is provided. It is a result of measuring the rate of change of the energy intensity of the laser light reaching the workpiece. When the pulse frequency is changed from 200 kHz to 2400 kHz, the range of change in the energy change rate of the processing point is about 7.5% when a conventional polarization azimuth adjustment device is installed, and a polarization phase difference plate 200 having a sub-wavelength grating structure is used. When the power balance device is installed, it is about 6%, and the use of a power balance device using a polarization phase difference plate 200 having a sub-wavelength grating structure in a laser processing device shows that the generation of thermal lenses is suppressed.

From FIG. 7, a proportional relationship appears between the pulse frequency and the processing point energy change rate, and the higher the pulse frequency of the laser light from the laser oscillator 1 and the higher the power of the laser light, the polarization phase difference plate 200 having a sub-wavelength grating structure The effect of suppressing the thermal lens by the power balance device using is increased, so that high processing quality can be obtained even in a high-power beam.

<Other advantages of the transmissive phase difference plate method>

In Patent Document 1, the optical axis of the downstream changes depending on the rotation angle of the optical axis rotation of the polarization azimuth adjustment device, and in Patent Document 3, the optical axis downstream changes depending on the angle of the reflective surface with respect to the optical axis. Due to the eccentricity or inclination of the plate 200, the optical axis of transmitted light does not change. For this reason, a rotating mechanism with low precision may be used, and the cost can be reduced.

<Effects to make phase delay less than π / 2 (90 degrees), subject of sub-wavelength grating application>

Examples of π and π / 2 of the phase difference plate of Patent Document 2 are disclosed. In the sub-wavelength grating structure, in order to obtain a phase delay of π or π / 2, there is a problem in that processing is difficult because a thin and deep high aspect ratio fine structure is required.

The phase delay required for power balance adjustment is calculated below.

The separation directions indicated by 9A and 9B of the polarization beam splitter (PBS) 7 shown in FIG. 1 are directions a and b,

The polarization azimuth of the linearly polarized light incident on the polarization beam splitter 7 is θ,

The phase delay of the polarization phase difference plate 200 is φ,

2 is the TM polarization direction of the true axis angle ψ,

Let, be the incident light (e0)

<Wed 1>

Appears as The light e1 after the incident light e0 passes through the polarization phase difference plate 200,

<Wed 2>

Becomes The light e1 is separated from the polarizing beam splitter 7. Each separated polarization component (e1a, e1b)

<Wed 3>

It becomes.

The difference in power of each polarization with respect to the power of the incident light (ΔP) is

<Wed 4>

It becomes.

From the equation (5), the adjustment width of ΔP by changing ψ is because the second term is a fixed value, and the cos (4ψ-2θ) of the first term is from -1 to 1,

<Wed 5>

It becomes.

As for the adjustment of the power balance of the laser processing apparatus, an adjustment width of about ± 10% is sufficient, and from the equations (5) and (6) above, the phase delay φ required for the polarization phase difference plate 200 is

φ> 0.64rad = 37 degree

Becomes

As described above, the power balance device does not have a practical problem even with a phase delay much smaller than 90 degrees, thereby making the depth of the groove that is the height H of the convex portion 203 of the polarization phase difference plate 200 shallow. Can be made, and manufacturing becomes possible.

In addition, the smaller the phase delay φ, the narrower the adjustment width when rotating, that is, the balance fluctuation with respect to the rotation angle position shift becomes small, so there are some advantages that the rotating mechanism can be manufactured at low cost.

Moreover, in Embodiment 1, the polarization phase difference plate 200 of the sub-wavelength grating structure and the rotating mechanism 220 constitute a power balance device for lasers.

Embodiment 2.

3 is a diagram showing an example of the configuration of a laser processing apparatus according to Embodiment 2 of the present invention. 4 is a perspective side view showing an internal configuration of an example of the power balance device 300 for laser of FIG. 3. In the laser processing apparatus of the second embodiment of FIG. 3, the power balance device for a laser including the functions of the polarization phase difference plate 200 and the rotating mechanism 220 of the sub-wavelength grating structure of the first embodiment of FIG. 300) is provided. As shown in FIG. 4, the laser power balance device 300 overlaps the polarization phase difference plate 200 having a sub-wavelength grating structure on the copper mirror 210 which is a mirror, so that the grating structure faces the mirror, It is housed in a holder 214 and has a structure in which the O-ring 211 is inserted and inserted between the pressure plate 212 of the mirror holder 214 and the surface of the polarization phase difference plate 200.

The incident laser light 2 passes through the polarization phase difference plate 200 having a sub-wavelength grating structure, reflects from the surface of the copper mirror 210, and once more passes through the polarization phase difference plate 200 having a sub-wavelength grating structure. . Since the polarization phase difference plate 200 is transmitted twice as described above, the phase delay of the polarization phase difference plate 200 may be half.

In addition, the mirror holder 214 is provided with a rotating mechanism 213 capable of rotating the entire mirror holder 214 by normal rotation of the reflective surface of the copper mirror 210.

The other basic configuration is the same as that of the first embodiment in FIG. 1.

<Effect of superimposing mirror and wave plate>

4, since the back surface of the polarization phase difference plate 200 having a sub-wavelength grating structure is in contact with the reflection surface of the copper mirror 210, the heat absorbed by the polarization phase difference plate 200 is copper mirror 210 ) Direction and the polarization phase difference plate 200 is cooled. Since the direction in which the heat flows is in the optical axis direction as indicated by the arrow HE rather than in the radial direction, the occurrence of a temperature gradient in the radial direction can be suppressed. As a result, generation of a thermal lens can be prevented, and laser processing with higher power can be performed.

5 is a perspective side view showing another example of the power balance device 300 for laser of FIG. 3. In FIG. 5, the convex side of the polarization phase difference plate 200 of the sub-wavelength grating structure faces the surface side of the copper mirror 210, and the polarization phase difference plate 200 of the sub-wavelength grating structure on the copper mirror 210 is grating structure. It is stored in the mirror holder 214 by overlapping the main surface opposite to the outside. In this case, since the lattice does not come into contact with air, adhesion of foreign matter such as dust can be prevented.

As described above, according to the present invention, since a sub-wavelength grating structure can constitute a power balance device and a laser processing device using a material having high transmittance to far-infrared light, a thermal lens is prevented and high processing quality is achieved even at a high output beam. Can get

In addition, by setting the phase delay of the polarization phase difference plate to less than π / 2, the aspect ratio of the grating of the polarization phase difference plate becomes small, and manufacturing becomes easy.

In addition, since the material of the polarization phase difference plate is ZnS, generation of a thermal lens can be prevented.

Further, by superimposing the mirror on the polarization retardation plate, the back surface of the polarization retardation plate can be cooled by contacting with the mirror, so that the generation of thermal lenses can be prevented, and the phase delay of the polarization retardation plate 200 may be half. .

The power balance device and laser processing device for laser light according to the present invention are not limited to the above-described embodiments.

The power balance device and the laser processing device according to the present invention are applicable to laser processing in many fields.

1: laser oscillator 2: laser light
4: Mask 5: Beam variable part
6: Reflective mirror 7: Polarized beam splitter
8A, 8B: Dispersive laser light
10Ax, 10Ay, 10Bx, 10By: Galvano Scanner 11A, 11B: fθ lens
12A, 12B: XY table 13A, 13B: Workpiece
17: polarizer 100: laser processing device
200: polarization phase difference plate 201: diffraction grating
202: substrate 203: convex
206: taper shape 207: anti-reflection film
210: copper mirror 211: O-ring
212: pressure plate 213: rotating mechanism
214: mirror holder 220: rotating mechanism
300: power balance device

Claims (9)

A diffraction grating in which a plurality of convex portions made of the same material as the substrate material extend in a straight line in parallel with each other at a set period P is formed on the main surface side of one of the opposing pair of main surfaces, and the structure of the diffraction grating is formed. A polarization phase difference plate in which a laser light of far infrared rays is incident, formed using birefringence, wherein the period (P) of the diffraction grating is P <λ / n (λ is the wavelength of the incident light, n is the refractive index of the substrate material) The polarization retardation plate, and
And a rotating mechanism for rotating the polarization phase difference plate,
It is provided with an overlapping mirror in contact with the main surface of the polarization retardation plate
Power balance device for laser light. According to claim 1,
The phase retardation of the polarization retardation plate is less than π / 2
Power balance device for laser light. According to claim 1,
The material of the polarization phase difference plate is made of ZnS
Power balance device for laser light. According to claim 2,
The material of the polarization phase difference plate is made of ZnS
Power balance device for laser light. delete delete delete delete A power balance device for the laser light according to any one of claims 1 to 4,
A laser oscillator generating the laser light with respect to the polarization phase difference plate of the power balance device,
On the optical path from the polarization retardation plate to the workpiece, a spectroscopic unit for spectralizing the laser light with two laser lights is provided.
Laser processing equipment.

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