JPH03226393A - Laser beam machine - Google Patents

Abstract

PURPOSE:To perform stable working and to improve working efficiency by adjusting change of divergent property of laser beam followed by output change and holdering condensing property. CONSTITUTION:A laser beam oscillator 1, a laser beam guide 7 including a condensing device 10 which guides the laser beam 5 outputted from this laser beam oscillator 1 as far as a work piece 8 and irradiates the work piece 8, an output measuring device 4 to monitor the output of the laser beam 5, a movable laser beam divergent property converting device 11 arranged on the optical axis 6 of the laser beam 5 and a drive means 12 to move the laser beam divergent property converting device 11 along an optical axis 6 in accordance with an output level obtained from the output measuring device 4 are provided. In this way, the change of the laser beam divergent property followed by the output change can be compensated easily and machining can be executed without influencing the beam condensing property in irradiating the work piece 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laser beam that performs high-power thermal processing (welding, heat treatment, cutting, etc.) on a wide variety of materials such as metal materials, inorganic materials, and organic materials using laser light. This relates to processing equipment.

BACKGROUND OF THE INVENTION In recent years, laser processing equipment has been used for processing various materials.

An example of the configuration of a conventional laser processing device will be described with reference to FIG. In FIG. 5, 1 is a laser resonator, 2 is an output mirror, 3 is a terminal mirror, 4 is an output measuring device, 5 is a laser beam, 6 is an optical axis, 7 is a laser light guide, 8 is a workpiece, 9 is a beam bender, and 10 is a condenser.

The laser resonator 1 is a device that amplifies light between an output mirror 2 from which a laser beam 5 is extracted and a termination mirror 3. In a conventional laser processing device, the laser beam 5 travels along its front axis 6 and is guided by a laser beam guide 7 including a condenser 10 that irradiates the workpiece 8. A beam bender 9 is often provided on the optical axis 6. Further, an output measuring device 4 for monitoring the output of the laser beam 5 measures a minute amount (0.5~
(approximately 1%) are often taken out and measured.

Problems to be Solved by the Invention However, in such conventional laser processing (configuration), especially when using a high output CO2 laser, the output mirror 2
There is a problem in that the thermal lens effect that occurs can no longer be ignored, and the divergence characteristics of the laser beam change due to this thermal lens effect.

If the divergence characteristics of the laser beam 5 change, not only will there be a difference in beam diameter i, but also the same focusing characteristics (focal length, focused beam diameter, etc.) will differ even if the focusing device 10 is the same. This changes the processing conditions and causes a serious problem in practical use.

The present invention is intended to solve two of these conventional problems, and it is an object of the present invention to provide an excellent laser processing device that can maintain stable processing characteristics even over a wide range of output changes.

Means for Solving the Problems In order to achieve the above object, the present invention provides a laser resonator and a lighting device that guides a laser beam output from the laser resonator to a workpiece and irradiates the workpiece. a laser beam guide including a laser beam guide, an output measuring device for monitoring the output of the laser beam, a movable laser beam divergence characteristic converting device disposed on the optical axis of the laser beam, and a laser beam divergence characteristic converting device arranged on the optical axis of the laser beam, and a and a driving means for moving the laser beam divergence characteristic conversion device along the optical axis.

Effect of the Invention The present invention is capable of adjusting changes in laser light divergence characteristics due to the thermal lens effect of the output mirror with the above-mentioned configuration, maintaining stable light focusing characteristics even with wide output changes, and stabilizing processing characteristics. can be maintained.

Embodiment FIG. 1 is a schematic diagram showing an embodiment of the laser processing apparatus of the present invention, and the same elements as those of the conventional example shown in FIG. 5 are given the same reference numerals. In FIG. 1, l is a laser resonator, 2 is an output mirror, and 3 is a termination mirror. Reference numeral 4 denotes an output measuring device that evaluates the output of the laser beam 5 by monitoring the intensity of the laser beam 5' taken out from the end mirror 3. The laser beam 5 is extracted from the output mirror 2, goes back and forth between the output mirror 2 and the end mirror 3, is amplified, and is used for processing.

6 is the optical axis of the laser beam 5. 7 is a laser light guide that guides the laser light 5 to the workpiece 8.

A mirror 9 refracts the laser beam 5 toward the workpiece 8, and is generally called a beam bender. Reference numeral 10 denotes a laser beam focusing device (in this example, a lens), which is generally used for laser processing since it is necessary to increase energy density. Reference numeral 11 denotes a divergence characteristic conversion device that corrects changes in the divergence characteristic of the laser beam 5 due to the thermal lens effect of the output mirror 2, and is movable along the optical axis 6. Reference numeral 12 denotes a driving means for moving the divergence characteristic converting device 11, which provides a moving amount according to the signal level of the output measuring device 4 in order to compensate for the divergence characteristic depending on the output of the laser beam 5.

Next, the operation of the embodiment will be explained with reference to FIGS. 2 to 4.

FIG. 2 shows an example in which the divergence characteristics of laser light change due to changes in laser output. As the laser output increases, the heat absorption of the output mirror 2 increases, and the refractive index gradient due to thermally induced optical distortion also increases, indicating that the focal length shifts to a lens shape with a shorter focal length.

Figure 3 shows the focal length change of the output mirror 2 converted from the divergence characteristics of the laser beam, which is 1.5 at 4.5KW.
This is a difference of more than 1.51 compared to KW.

It is well known that when the divergence characteristics of laser light change, the condensing characteristics of the lens also change, and if the symbols shown in FIG.

The distance from the waist position of the light to the lens, Zll is the Rayley Range of the incident laser beam, S2 is the distance 1 from the lens to the waist position of the output laser beam, ZR2
is the Rayley Range of the emitted laser beam. R
ayleyRange represents the divergence characteristic of laser light, and is defined as the distance where the beam diameter is /F times the waist (narrowest beam part) diameter, that is, twice the beam area.

The above formula means that when an appropriate lens focal length raf is selected, the focusing position S2 is determined by two variables: the laser beam divergence characteristic ZRI and the lens position Sl, and the lens focal length f changes. This also shows that the emitted beam position can be corrected by appropriately selecting the lens position Sl as in the above embodiment.

Note that since the degree of the thermal lens effect varies depending on the material and shape of the output mirror 2, the heat absorption properties of the surface film, etc., the relationship between the laser output and focal length change naturally depends on the device. For this reason,
It is desirable that the correlation between the output of the laser beam 5 and the arrangement position of the laser beam divergence characteristic converting device 11 be set in advance and automatically variable according to the laser output.

However, usually during a particular process, the laser output is often kept almost constant (in this case, it is only necessary to drive the lens in advance and place it at an appropriate position as part of the process preparation).

Note that the laser beam divergence characteristic conversion device 11 need not be limited to a single lens, and of course may be a multiple lens system or a combined reflective optical system.

Effects of the Invention As is clear from the above embodiments, the present invention provides a laser resonator and a condensing device that guides the laser beam output from the laser resonator to a workpiece and irradiates the workpiece. a laser beam guide including a laser beam guide, an output measuring device for monitoring the output of the laser beam, a movable laser beam divergence characteristic converting device disposed on the optical axis of the laser beam, and a laser beam divergence characteristic converting device arranged on the optical axis of the laser beam, and a Since it is equipped with a driving means for moving the laser beam divergence characteristic conversion device along the optical axis, it is possible to easily compensate for changes in the laser beam divergence characteristic due to changes in output, and the beam concentration when irradiating the workpiece can be easily compensated for. It has the excellent effect that processing can be performed without affecting optical characteristics, and work efficiency can be greatly improved.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an embodiment of the laser processing device of the present invention, Fig. 2 is a graph showing an example of laser beam divergence characteristics when the output changes, and Fig. 3 is a graph showing the relationship between the laser output and the output mirror equivalent focal length. FIG. 4 is a graph showing an example of the relationship, FIG. 4 is an optical path diagram for explaining lens and laser beam focusing characteristics, and FIG. 5 is a schematic configuration diagram showing an example of a conventional laser processing apparatus. DESCRIPTION OF SYMBOLS 1...Laser resonator, 2...Output mirror, 3...Terminal mirror, 4...Output measuring device, 5.5゛...Laser light,
6... Optical axis, 7... Laser light guide, 8... Workpiece, 9... Beam bender 10... Concentrator,
11... Laser beam divergence characteristic conversion device, 12... Driving means.

Claims (1)

[Claims] a laser resonator, a laser light guide including a condenser that guides the laser light output from the laser resonator to a workpiece and irradiates the workpiece, and an output measurement device that monitors the output of the laser light. , a movable laser beam divergence characteristic converting device disposed on the optical axis of the laser beam, and moving the laser beam divergence characteristic converting device along the optical axis according to the output level obtained from the output measuring device. A laser processing device equipped with a driving means.