JP5135650B2 - Laser equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser device having a reflective aperture.
[0002]
[Prior art]
FIG. 2 is an explanatory view of a main part of a laser oscillator of a conventional general laser apparatus, which has a reflection type aperture.
In the figure, reference numeral 11 denotes a laser resonator unit, which comprises an emission side resonator unit 11a and a total reflection side resonator unit 11b. 12 is a laser beam extracted from the laser resonator unit 11 (hereinafter referred to as “external light” as appropriate), 13 is an excitation region where the laser medium is excited by discharge, 14 is a photon emitted when the laser medium transitions, and its photons The direction, 15 is a partial reflection mirror, and 16 is a total reflection mirror. The partial reflection mirror 15 and the total reflection mirror 16 are arranged at both ends of the excitation region 13 to constitute a resonance space portion.
Reference numerals 17 and 18 denote apertures for determining the mode order of the laser beam, 19 denotes a laser light energy absorber disposed on the excitation region 13 side of the aperture 17, and 20 denotes a laser disposed on the excitation region 13 side of the aperture 18. It is an absorber of light energy.
For a relatively low-power laser device, the aperture can be an absorptive aperture that absorbs laser light, for example, by plating alumite (Al ₂ O ₃ ) on an aluminum alloy. Depending on the cooling method and the like, such an absorption type aperture cannot be used when the laser beam has a high output because the aperture itself melts. Therefore, it is necessary to use a reflection type aperture instead of an absorption type in a high-power laser device.
[0003]
Next, the operation principle of the laser apparatus having the conventional reflective aperture shown in FIG. 2 will be described below.
In the laser oscillator, a high voltage is applied from a power source (not shown) to a discharge electrode (not shown) based on an output signal from a control device (not shown), and the laser medium is excited by the discharge. During the transition, the laser medium emits photons 14 having a specific wavelength in the medium in all directions. Of the photons 14, only those incident perpendicularly to the reflecting surfaces of the partial reflection mirror 15 and the total reflection mirror 16 are repeatedly reflected and amplified, and when the oscillation threshold exceeds a certain oscillation threshold, It is emitted as external light 12. The order of the laser beam is determined by the beam being cut by the openings of the apertures 17 and 18 in the process of reflection and amplification, and the components reflected by the reflecting surfaces 17a, 17b, 18a and 18b of the apertures 17 and 18 are as follows. The absorbent 19 or 20 is absorbed. On the other hand, the external light 12 taken out from the inside of the laser oscillator is collected by, for example, a lens at the tip of the optical path of a processing machine (not shown) and used for applications such as cutting and welding.
[0004]
[Problems to be solved by the invention]
The conventional laser apparatus has the above-described configuration. Here, problems of the conventional laser apparatus will be described.
FIG. 3 is a rewritten version of FIG. 2 for explaining the problem, and the same or corresponding parts as in FIG. In such a conventional laser device, apart from the light reflected and amplified between the partial reflection mirror 15 and the total reflection mirror 16, the main beam 21 has the apertures 17 and 18 facing each other in parallel. Light is reflected and amplified also between the respective excitation region side plane portions 17f and 18f, and so-called sub-beams 22 are generated. As a result, the laser medium is used not only for the amplification of the main beam 21 but also for the amplification of the sub beam 22, and as a result, there is a problem that the output of the main beam 21 falls below the value that should originally be obtained.
[0005]
In addition, because of the precision of manufacturing and mounting, the excitation region side plane portions 17f and 18f of the apertures 17 and 18 are not completely parallel, so that the sub beam 22 is emitted to the outside together with the main beam 21 by a slight angular deviation. There was a fear.
Here, examples of the intensity distribution of the external light 12 are shown in FIGS. An example of the intensity distribution when only the main beam 21 is emitted to the outside is shown in FIG. 4, and an example of the intensity distribution when the main beam 21 and the sub beam 22 are emitted together as the external light 12 is shown in FIG. Show. As can be seen from FIGS. 4 and 5, the intensity distribution of the external light in which the main beam 21 and the sub beam 22 are combined is irregular, and the traveling directions of the main beam 21 and the sub beam 22 are slightly different. There is a problem that the intensity distribution varies depending on the propagation distance of the beam and adversely affects cutting, which is a use application of laser light, and there has been a problem of eliminating this irregular intensity distribution.
[0006]
Japanese Utility Model Laid-Open No. 63-11060, Japanese Patent Laid-Open No. 6-152017, and the like show apertures in which the reflecting surface reaches the outer peripheral edge of the aperture and there is no excitation region side plane portion. These apertures 107 and 207 are shown in FIGS. 6 and 7, respectively. The reflecting surfaces 107a, 107b, and 207a shown in FIGS. 6 and 7 are surfaces having angles that are not perpendicular to the optical axis direction of the main beam 21.
However, in the structure shown in FIGS. 6 and 7 in which there is no excitation region side plane portion other than the original reflecting surface, a single aperture block may be provided in one aperture block. Problems arise when providing openings.
[0007]
When a plurality of openings are provided in one aperture block, one of the openings is inevitably eccentric. When the axis of the opening of the aperture is decentered with respect to the center of the block of the aperture whose outer peripheral shape is usually a circle, when trying to make the structure without the excitation region side plane, for example, as shown in FIG. The thickness of the aperture 27 in the optical axis direction becomes non-uniform as indicated by dimension b <dimension a in FIG. 8, and an absorber such as the absorber 29 having a complicated shape corresponding to the thickness is required. In addition, as shown by the shaded portion 25 in FIG. 8, since it extends to the absorber 29 side, that is, the excitation region side more than necessary, the material cost of the block of the aperture 27 increases and the excitation region also decreases. Such a structure is not preferable because it is desired to make the excitation region as wide as possible in order to obtain a high output as much as possible.
FIG. 9 shows an example of a block of the aperture 27 having a structure having two eccentric openings. In FIG. 9, as in FIG. 8, the shaded portion 25 corresponds to the portion extending to the excitation region side more than necessary as described above. If a structure in which the excitation region side plane portion does not exist under the condition that two openings, that is, two bowl-shaped reflecting surfaces are provided, a part of the outer peripheral edge of the block of the aperture 27 is shown in FIG. As shown by a point P in b), a part extending with a considerably large size inevitably occurs as an extension of the bowl-shaped reflecting surface. If the portion indicated by the shaded portion 25 in FIG. 9B is simply cut out along the dot-and-dash line, the portion indicated by the shaded portion 25 in FIG. 9A corresponds to the oscillation optical axis of the laser beam. It becomes a vertical excitation area side plane part.
On the other hand, even with a structure having an eccentric opening, the structure like the aperture 37 shown in FIG. 10 has a uniform thickness in the optical axis direction and can reduce the thickness as much as possible. However, the material cost of the aperture block can be reduced and the excitation area can be widened. However, in this case, since the excitation region side plane portion 37f exists, the generation of the sub beam cannot be avoided reliably.
[0008]
The present invention has been made to solve the above-described problems, and provides a laser apparatus capable of suppressing the generation of sub-beams due to an aperture with a simple configuration.
[0009]
[Means for Solving the Problems]
The laser device according to the present invention includes a resonator unit that reflects and amplifies laser light in a resonance space formed by a space portion where a pair of reflecting mirrors face each other, and the pair of resonators disposed in the resonance space. A reflection type aperture for determining a beam mode of the laser beam to be emitted to the outside from the resonator unit by passing a laser beam reciprocating between the units through a predetermined opening, and the reflection type aperture of the reflection type aperture The excitation region side plane is provided with a specific inclination angle different from the direction of the plane perpendicular to the oscillation optical axis of the laser beam that should pass through the opening.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
The form of the laser apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 corresponds to FIG. 3 showing a conventional example, and the same or corresponding parts as in FIG.
In the figure, d is the outer diameter of the aperture, L is the distance between the apertures 57 and 58, θ is perpendicular to the oscillation optical axis 23 of the laser beam connecting the centers of curvature of the partial reflection mirror 15 and the total reflection mirror 16. It is an inclination angle of the excitation region side plane portions 57f and 58f of the aperture with respect to the surface 24, and the inclination angle θ is tan θ = d / L.
And the direction of the inclination is matched with the apertures 57 and 58. That is, when viewed from the side, the inclined surfaces 57f and 58f are shaped like a letter C as shown in FIG. Actually, from the viewpoint of suppressing the generation of the sub beam 22, the range of the inclination angle θ is tan ⁻¹ (d / L) ≦ θ <π / 2.
Can also be written. However, increasing θ in the end means that the dimension b is increased with respect to the dimension a in the figure, and the structure of the absorber is complicated, the excitation region is decreased, the material cost of the blocks of the apertures 57 and 58 is increased, etc. Leads to problems. Therefore, θ is as small as possible, and tan θ = d / L is determined as an angle at which resonance does not occur between the excitation region side plane portions. Since the energy of a single photon before resonance occurs is very small, an absorber or the like for receiving the photon 14 reflected by the inclined excitation region side plane portions 57f and 58f is not particularly required.
[0011]
As an example, in the prototype, since L = 1600 mm and d = 100 mm, θ = 3.5 (degree) using the above equation. Since the tilt angle is as small as 3.5, the difference is as small as b = a + 6.5 mm, and the extension of the dimensions of the blocks of the apertures 57 and 58 to the excitation region side is very small, and the above-described problems occur. Therefore, only the sub beam can be effectively suppressed. In fact, in the prototype, it was confirmed that the power-up, beam mode and laser processing quality were improved by suppressing the sub-beam generation. FIG. 11 shows the difference in output between the conventional one and this embodiment. In FIG. 11, the horizontal axis represents input power, and the vertical axis represents the obtained power. The line indicated by a is that of this embodiment, and the line indicated by b is conventional. It can be seen that the power can be increased by suppressing the sub-beams according to this embodiment.
Further, only the excitation area side plane portions 57f and 58f of the apertures 57 and 58 are inclined, and the reflection surfaces 57a, 57b, 58a and 58b of the apertures 57 and 58 have the same reflection angle with respect to the optical axis. It will be the surface. This is a structural point different from that shown in Japanese Patent Laid-Open No. 1-253977. In the case of a configuration in which the aperture itself can be rotated as disclosed in Japanese Patent Laid-Open No. 1-253977, the aperture opening is disposed obliquely with respect to the optical axis of the laser depending on the rotation angle, and thereby, from the optical axis direction of the beam. The projected shape of the aperture opening seen is not a circle but an ellipse. Therefore, the beam emitted to the outside also has an elliptical shape, which adversely affects the processing by the laser. At this time, if the angle of the reflection surface of the aperture changes, the shape and arrangement of the absorber to be corresponding to the angle will be complicated.
[0012]
Further, the excitation region side plane portions 57f and 58f of the apertures 57 and 58 may be roughened to a degree that the carbon dioxide laser is sufficiently scattered, specifically, the surface particle diameter is equal to or greater than the laser wavelength by sandblasting or the like. As a result, the laser light hitting the excitation region side plane portion is scattered, so that resonance between the excitation region side plane portions does not occur, and sub-beams can be suppressed more effectively. The present invention is not limited to the laser device of FIG. 2 shown in the conventional example, but can be applied to all laser devices having a reflective aperture.
[0013]
【Effect of the invention】
According to the present invention, it is possible to suppress generation of sub-beams between the excitation region side plane portions of the aperture.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a main part of a laser oscillator of a laser device according to an embodiment of the present invention.
FIG. 2 is a configuration diagram showing a laser oscillator part of a conventional laser device.
FIG. 3 is a configuration diagram showing a laser oscillator portion of a conventional laser device.
FIG. 4 is an intensity distribution diagram of external light when only the main beam is emitted to the outside.
FIG. 5 is an intensity distribution diagram of external light when a main beam and a sub beam are emitted to the outside.
FIG. 6 is a diagram illustrating a conventional aperture structure in which an excitation region side plane portion does not exist.
FIG. 7 is a diagram showing a structure of another aperture that does not have a conventional excitation region side plane portion;
FIG. 8 is a diagram showing a conventional aperture structure in which an opening having no excitation region side plane portion is eccentric.
FIG. 9 is a diagram showing a conventional aperture structure in which a plurality of eccentric openings having no excitation region side plane portion are present.
FIG. 10 is a view showing a structure of a conventional aperture having an opening portion in which an excitation region side plane portion exists and is eccentric.
FIG. 11 is a diagram showing a difference in laser output.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Laser resonator part 12 External light 13 Excitation area | region 14 Photon 15 Partial reflection mirror 16 Total reflection mirror 19, 20 Absorber 21 Main beam 22 Sub beam 23 Oscillation optical axis 24 Surface 57, 58 perpendicular | vertical to an oscillation optical axis Reflection type aperture 57f 58f Excitation region side plane

Claims (1)

A resonator unit configured to reflect and amplify laser light in a resonance space formed by a space portion where the partial reflection mirror and the total reflection mirror face each other;
A predetermined opening that is disposed between the partial reflection mirror and the total reflection mirror in the resonance space and that passes a laser beam reciprocating between the partial reflection mirror and the total reflection mirror and determines a beam mode of the laser beam. In a laser device used for cutting and welding provided with a pair of reflective apertures having,
The shape of the openings of the pair of reflective apertures is a circle, the laser light reflecting surface around the openings is a bowl-shaped reflecting surface, and the oscillation light of the laser light that should pass through the openings Without inclining with respect to the axis, the plane with respect to the plane perpendicular to the oscillation optical axis of the laser light that should pass through the opening is formed so that the opposing excitation region side planes of the pair of reflective apertures have a C shape. A laser apparatus characterized in that an inclination angle θ of each excitation region side plane portion is set and the inclination angle θ is in the following range.
tan ⁻¹ (d / L) ≦ θ <π / 2
(D is the outer diameter of the pair of reflective apertures, and L is the distance between the pair of reflective apertures.)

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