JPH0366077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser processing apparatus for processing a workpiece having a high reflectance, typically a metal, using a laser beam.

[Conventional technology]

A conventional laser processing apparatus of this type is shown in FIG. FIG. 4 is a schematic configuration diagram showing a conventional laser processing apparatus. In the figure, 1 is a partially transmitting mirror for laser light, 2 is a reflecting mirror with a light transmittance of about 1%, 3 is a laser medium, 4 is a total reflecting mirror, 5 is a workpiece, 6 is a power meter, and 7a is the laser beam emitted from the partially transmitting mirror 1, 7b is the laser beam incident on the workpiece 5, 7c and 7d are the reflected laser beams from the workpiece 5, 70 and 71 are the leakage light transmitted through the reflecting mirror 2, and 8 is a laser oscillator.

Next, the operation of the conventional laser processing apparatus shown in FIG. 4 will be explained. In a laser oscillator 8 composed of a partially transmitting mirror 1 and a reflecting mirror 2, a laser beam generated by a laser medium 3 is amplified by repeatedly going back and forth within the laser oscillator 8, and a part of this laser beam ( Generally, about several 10%) is emitted as laser light for processing from the partially transmitting mirror 1 as an output laser light 7a. Further, a very small amount of laser light (for example, about 1%) leaks from the reflecting mirror 2 than the laser light for processing, and this leaked laser light is detected by the power meter 6. If the transmittances of the partially transmitting mirror 1 and the reflecting mirror 2 are known, the intensity of the emitted laser beam 7a can be determined from the output of the power meter 6. For example, if the transmittance of the partially transmitting mirror 1 and the reflecting mirror 2 are 20% and 1%, respectively, and the output detected by the power meter 6 is 100W, then
The intensity of the emitted laser beam 7a can be estimated to be 100×1/1%×20%=2kw.

Regarding the case of actual laser processing, when the workpiece 5 has a high reflectance at the wavelength of the incident laser beam 7b, the reflected laser beam 7b from the workpiece 5
c and 7d enter the laser oscillator 8, are amplified by the laser medium 3, and a very small amount of laser light is transmitted to the reflecting mirror 2.
The leakage light 71 is emitted from the light and enters the power meter 6.

[Problem that the invention seeks to solve]

Since the conventional laser processing device is configured as described above, during laser processing of the workpiece 5,
The reflected laser beams 7c and 7d from the workpiece 5 also enter the power meter 6. By the way, considering that the reflectance of the workpiece 5 changes randomly during the laser processing process, the reflected laser beams 7c and 7d become a large noise obstacle when monitoring the intensity of the emitted laser beam 7a. For,
It has been almost impossible to accurately monitor the output of laser light during laser processing. However,
In laser processing of a workpiece 5 having a complex shape, it is necessary to vary the output of the laser beam depending on the laser processing situation and speed. The output was controlled indirectly by controlling the input to the laser medium 3.
If the relationship between the input to the laser beam and the output of the laser beam changes temporarily, problems such as processing defects occur. Furthermore, if the reflectance of the workpiece 5 is extremely high, the influence of the reflected laser beams 7c and 7d within the laser oscillator 8 cannot be ignored, and therefore the quality of the laser beam generated by the laser oscillator may be affected. There was a problem that it would break and result in poor processing.

These problems can be similarly applied to laser processing apparatuses that process a workpiece by converting linearly polarized laser light emitted from a laser oscillator into circularly polarized light using a quarter-wave plate.

This invention was made to solve the above-mentioned problems, and provides a laser processing device that can perform processing using stable laser light without allowing the light reflected from the workpiece to return into the laser oscillator. It is.

[Means for solving problems]

The laser processing apparatus according to the present invention reflects the emitted laser light from the laser oscillator and transmits the reflected laser light from the workpiece between the laser oscillator and the quarter-wave plate, and reflects the emitted laser light and the 1/4 wavelength plate. A polarization splitter is provided to make the optical path of the laser beam different.

[Effect]

The polarization splitter in this invention reflects most of the linearly polarized output laser light emitted from the laser oscillator, but the reflected laser light reflected from the workpiece is linearly polarized light whose direction is 90° different from the above-mentioned output laser light. Therefore, most of it is transmitted so that the optical paths of the emitted laser light and the reflected laser light are different.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a laser processing apparatus which is an embodiment of the present invention, and the same parts as in FIG. 4 are indicated using the same reference numerals, and detailed explanation thereof will be omitted. In the figure, 10 is a damper, 20 is a total reflection mirror for S waves, 40 is a quarter-wave plate, 78 is a polarization splitter with coding 90, and 77a is an output beam from the polarization splitter 78 that is linearly changed in the S direction. A laser beam 77b is an incident laser beam 77 that is circularly polarized by the quarter-wave plate 40 and enters the workpiece 5.
c is the reflected laser beam from workpiece 5, 77d is 1/4
This is laser light that is polarized in the P direction by the wavelength plate 40 and enters the polarization splitter 78.

FIG. 2 is a diagram showing the degree of polarization of each laser beam in each part of the laser processing apparatus shown in FIG. 1. In the figure, S indicates the polarization of the S wave component laser beam,
P indicates the polarization of the P-wave component laser light.

Next, the operation of the laser processing apparatus shown in FIG. 1, which is an embodiment of the present invention, will be explained. A laser beam that is linearly polarized in the S direction is emitted from a laser oscillator composed of a partially transmitting mirror 1, a reflecting mirror 2, and a total reflecting mirror 20 for S waves. After being reflected by the splitter 78, the emitted laser beam 77a is circularly polarized by the 1/4 wavelength plate 40, and then becomes incident laser beam 77b to the workpiece 5 to be processed. conduct. At this time, the reflected laser beam 77c from the workpiece 5 is polarized in the P direction by the 1/4 wavelength plate 40 because the rotation direction of the circularly polarized light is reversed due to reflection.
It enters the polarization splitter 78 as a laser beam 77d. Due to the nature of the polarization splitter 78, most of the P-wave component is transmitted therethrough and is absorbed by the damper 10.

Therefore, the emitted laser beam 77 from the laser oscillator
a, 77b and reflected laser beam 77c from the workpiece,
The optical path of 77d becomes different. On the other hand, a part of the laser light generated within the laser oscillator is transmitted to the reflecting mirror 2.
The leakage light 70 leaks from the laser beam, and this leaked laser light enters the power meter 6. Therefore, with the above-described configuration, the power meter 6 can accurately detect only the power of the laser beam emitted from the laser oscillator.

In the above embodiment, an example was explained in which the intensity of the laser beam incident on the workpiece 5 is estimated using the leakage light 70 from the reflecting mirror 2. However, as shown in FIG. A configuration may also be adopted in which a window 50 is inserted between the light beam 78 and the reflected light 72, which is approximately 0.4% of the transmitted light, through the window 50.

Moreover, it is also possible to use a Brillusta window as the polarization splitter 78 used in the above invention.

〔Effect of the invention〕

As described above, according to the present invention, the polarization splitter reflects the emitted laser light from the laser oscillator and transmits the reflected laser light from the workpiece, so that the optical paths of the emitted laser light and the reflected laser light are different. is placed between the laser oscillator and the 1/4 wavelength plate, so stable laser light can be obtained and high-quality laser processing can be performed.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a laser processing apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the degree of polarization of laser light in each part of the laser processing apparatus according to an embodiment of the invention, and FIG. The figure is a schematic diagram showing a laser processing apparatus according to another embodiment of the present invention, and FIG. 4 is a schematic diagram showing a conventional laser processing apparatus. 5... Workpiece, 6... Power meter, 77a,
77b...Emission laser light, 77c, 77d...Reflected laser light, 40...1/4 wavelength plate, 78...Polarization splitter, 8...Laser oscillator. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A laser processing device comprising a laser oscillator that emits a linearly polarized laser beam, and a quarter-wave plate that circularly polarizes the laser beam and reflects it toward a workpiece. A polarization splitter that reflects the emitted laser light emitted from the oscillator and transmits the reflected laser light from the workpiece so that the optical paths of the emitted laser light and the reflected laser light are different is provided between the laser oscillator and the above 1. A laser processing device characterized by being disposed between a /4 wavelength plate. 2. The laser processing apparatus according to claim 1, wherein the laser oscillator is provided with means for monitoring its output during processing of the workpiece.