JPH0818153B2 - Laser device - Google Patents

Description

The present invention relates to a laser device suitable for processing an object having a high reflectance.

(Prior Art) Generally, the processing performance when processing a high-reflectance material such as a metal with a laser beam largely changes depending on the polarization characteristics of the laser beam. That is, as shown in FIG. 2, even if the laser beam 1 is incident perpendicularly to the cutting portion 3 of the workpiece 2, if the laser beam 1 is advanced in the direction of arrow A in the drawing, the laser beam for the cutting surface is Since the incident angle φ of the light 1 is close to 90 degrees, the reflectance of P wave having an electric field vector in the direction parallel to the plane including the incident ray axis and the normal of the incident surface and S wave having an electric field vector perpendicular thereto is There will be a difference. For this reason, the state of the cut cross section greatly differs depending on the polarization direction of the laser light and the direction of the cut surface.

Therefore, it is desirable that the polarization direction always follows the cutting direction, but such follow-up control is generally difficult. For this reason, there has been conventionally adopted a method of obtaining a uniform cut surface for cutting any shape by eliminating the directionality of laser light by using circularly polarized light or elliptically polarized light whose polarization direction rotates with time. There is.

In order to generate such circularly polarized light or elliptically polarized light, as shown in FIG.
a transparent material and a folding mirror with a large incident angle installed in the laser oscillator 10, and the polarization direction is fixed by making a difference in the loss of the light inside the oscillator 10 with respect to the polarization direction. A linearly polarized laser beam 11 is generated. Next, the linearly polarized laser light 11 is incident on the 90 ° phase-delaying total reflection mirror 12 at an incident angle of 45 °, and further, the polarization direction is inclined at 45 ° with respect to the incident surface, thereby making the laser light incident.
11 may be decomposed into an X component and a Y component, and the phase thereof may be shifted by 90 °.

(Problems to be solved by the invention) However, in the wavelength range of far infrared laser such as carbon dioxide gas laser, the surface reflectance of metal is large, and particularly for copper, aluminum, etc., the reflectance is as large as 99%. The reflected light is strong at the start and at the time of vertical incidence at the time of high-speed cutting, and the laser oscillator passes through the diaphragm lens 13 and the reflecting mirror 14.
The reflected light returns to 10, causing damage to optical parts on the optical path, abnormal laser oscillation, etc., causing equipment failure, deterioration of life, etc., and reducing the output when processing highly reflective materials. There is a problem that the thickness of the material and the processing speed are limited because the processing is forced.

An object of the present invention is to provide a laser device capable of preventing a failure and a malfunction due to reflected light from a workpiece and improving the processing performance such as the processing speed and the processing thickness.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a laser oscillator that generates a linearly polarized laser beam, and the laser beam generated from the laser oscillator is elliptically or circularly polarized. In a laser device including a polarizing element, and processing an object by laser light elliptically polarized or circularly polarized by the polarizing element, between the laser oscillator and the polarizing element,
A transmission type polarized light reflection plate is provided, and the transmission type polarized light reflection plate is
The direction of the normal at the point where the laser light is incident and the direction of the electric field vector of the linearly polarized laser light are on the same plane, and the angle between the direction of the normal and the incident laser light is Arranged to form a Brewster's angle, guide the laser light generated from the laser oscillator to the polarizing element, and the laser light from the polarizing element reflected by the object is the laser oscillator. It is characterized by leading in another direction.

(Operation) The laser beam reflected from the work piece and returning to the laser oscillator side again undergoes a phase change of 180 ° when reflected by the work piece. For this reason, the circularly polarized wave P wave and S wave 90
° The phase relationship is opposite to that when entering the work piece. The circularly polarized wave with the opposite phase relationship is further
A phase difference of 90 ° is added and it becomes a linearly polarized wave again, but this linearly polarized wave has an azimuth angle orthogonal to the linearly polarized wave from the laser oscillator. That is, the P wave emitted from the laser oscillator becomes an S wave and is incident on the transmissive polarization reflector. Therefore, by arranging this transmissive polarizing reflector at Brewster's angle and setting the transmittance for P waves and the reflectance for S waves appropriately, the laser light reflected from the workpiece is laser oscillator side. Can be suppressed to return to.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention.
A transmission polarization reflector 15 is installed between the laser oscillator 10 and the 90 ° phase delay type total reflection mirror 12. This reflector
Reference numeral 15 is arranged so that the laser beam 11 (linearly polarized wave) from the laser oscillator 10 is incident at Brewster's angle θB, and the normal to the reflector and the plane of polarization are on the same plane L.
The transmittance is set so that the laser light 11 from 10 can be transmitted almost without reflection. The laser light 11 transmitted through this polarization reflection plate 15 is reflected by the 90 ° phase delay type total reflection mirror 12 to become a counterclockwise circularly polarized wave indicated by a solid arrow, and is directed by the lens 13 toward the surface of the workpiece 14. It is squeezed and irradiated.

At this time, when the reflectance of the workpiece 14 is high, the irradiated circularly polarized wave is reflected on the surface of the workpiece. Then, since the reflected circularly polarized wave undergoes a phase change of 180 ° when reflected, the 90 ° phase advance relationship between the P wave and the S wave is reversed, and as shown by the broken line A, it is opposite to that at the time of incidence. It becomes a circularly polarized wave in the clockwise direction of. This clockwise circularly polarized wave is incident on the reflecting mirror 12 again through the lens 13, but at this time, a phase difference of 90 ° is added, and as shown by the broken line, it becomes a linearly polarized wave again toward the laser oscillator 10. I will turn over. However, the linearly polarized wave returning from the reflecting mirror 12 has an orthogonal relationship in which the phase relationship with the linearly polarized wave from the laser oscillator 10 is completely inverted. That is, the P wave applied to the work piece 14 becomes an S wave due to the phase change received at the work piece 14 and the reflection mirror 12 and enters the polarization reflection plate 15. Therefore, if the reflectance of the polarized reflection plate 15 with respect to the S wave is set to be large, the S wave does not proceed to the laser oscillator 10 side,
It proceeds only in the direction of the absorber 16 that absorbs the energy of the S wave. In this case, the reflectance of the reflection plate 15 with respect to the S wave can be appropriately set by coating the laser light transmitting material with a multilayer dielectric film or the like while maintaining the transmittance with respect to the P wave.

A 90 ° (λ / 4) phase delay type total reflection mirror is used to perform circular polarization, but 45 ° (λ / 8), 22.5 ° (λ / 16)
Circularly polarized light may be performed by combining optical elements such as the phase delay type total reflection mirror and the quarter wave plate.

(Effects of the Invention) As described above, according to the present invention, the plane of polarization of laser light having linearly polarized light incident on the polarizer for circularly polarized light, and returning to the laser oscillator side through this polarizer. Focusing on the fact that the polarization plane of laser light is different, a transmission type polarization reflector is provided between the laser oscillator and the polarizer so as to form a Brewster's angle with respect to the incident laser light. The reflected laser light from the object does not return to the laser oscillator side, and it is possible to prevent failure or malfunction of the laser oscillator due to the reflected light from the work piece, and it is possible to emit the laser light of sufficient output necessary for processing. Therefore, there is an effect that the processing performance such as the processing speed and the processing thickness can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory view for explaining problems in processing a workpiece, and FIG. 3 is a workpiece with circularly polarized laser light. FIG. 10 is a block configuration diagram of a conventional laser device for processing a laser. 1,11 …… Laser light, 2,14 …… Workpiece, 3 …… Cutting part,
10 …… Laser oscillator, 12 …… 90 ° phase shift delay type total reflection mirror,
13 …… Lens, 15 …… Transmissive polarization reflector.

Claims (1)

[Claims] 1. A laser oscillator that generates a linearly polarized laser beam, and a polarizing element that elliptically or circularly polarizes the laser beam generated from the laser oscillator, and is elliptically or circularly polarized by the polarizing element. In a laser device for processing an object with a laser beam, a transmissive polarization reflector is provided between the laser oscillator and the polarizing element, and the transmissive polarization reflector has a point at which the laser light is incident. So that the direction of the normal line at and the direction of the electric field vector of the linearly polarized laser light are on the same plane, and the angle between the direction of the normal line and the incident laser light forms a Brewster's angle. Arranged, while guiding the laser light generated from the laser oscillator to the polarizing element, the laser light from the polarizing element reflected by the object is the laser oscillator The laser apparatus characterized by guiding the direction of.