JPH03281080A - Laser beam machine - Google Patents

Abstract

PURPOSE:To improve the accuracy of laser beam machining irrespective of change of a condensed position of laser beam by controlling the position of an optical system so that the condensed position of the laser beam shows a prescribed position in accordance with a measured result of the condensed position. CONSTITUTION:The laser beam machine so constituted that the laser beam outputted from a laser beam oscillator 11 irradiates a material 17 to be machined through a condensing state by an optical system 16 are provided a condensed position measuring means 19 which measures a condensed position of laser beam and a control means 26 which controls a position by optical system 16 so that a condensed position of laser beam shows a prescribed position in accordance with the measured result by this condensed position measuring means. In this way, laser beam machining can be performed with high accuracy irrespective of change of a condensed position of laser beam.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a laser processing machine in which a workpiece is irradiated with laser light output from a laser oscillator in a condensed state by an optical system. Regarding.

(Conventional technology) An example of this type of laser processing machine is shown in FIG.

In FIG. 5, an output mirror 2 and a rear mirror 3 forming an optical resonator are arranged facing each other in the laser oscillator 1, and an output mirror 2 (not shown) is disposed facing each other. [With the discharge voltage being supplied to the poles, the laser gas in the laser oscillator 1 is discharged and laser light is output from the output mirror 2. This laser beam is reflected by the bending mirror 4, then condensed by the condensing lens 5 and irradiated onto the workpiece 6.
Laser processing such as cutting or welding is performed on the material.

In this case, the higher the degree of convergence of the laser beam on the workpiece 6, the more accurate the laser processing is.

(Problem to be Solved by the Invention) By the way, the intensity of the laser beam in the laser oscillator 1 is determined by the output of the laser beam being R, where the reflectance of the output mirror 2 is R.
This is the value divided by . For example, the output of laser light is 2KW.
, when the reflectance of the output mirror 2 is 50%, the output of the laser beam inside the laser oscillator 1 is 4 due to 210.5.
KW, so the laser oscillator 1 at the output mirror 2
The inner surface is constantly irradiated with a laser beam with high output intensity. For this reason, although the light absorption rate of the output mirror 2 is suppressed to a low level, the temperature of the output mirror 2 increases due to irradiation with extremely high-intensity laser light. This causes a so-called thermal lens effect that causes an abnormal or wheat-shaped refractive index distribution in the output mirror 2, changing the propagation characteristics of the laser beam. Since this thermal lens effect is associated with an increase in temperature, the thermal lens effect also changes as the output intensity of the laser beam changes, resulting in a change in the light propagation characteristics. Further, in the condensing lens, a thermal lens effect occurs as the temperature rises due to absorption of laser light, and the propagation characteristics of the laser light change in this case as well. If the propagation characteristics of the laser beam change due to such a thermal lens effect, the focal point of the laser beam will change by several degrees, making the processing conditions unstable and making it difficult to perform high-precision laser processing. The drawback is that it cannot be applied.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a laser processing machine that is capable of performing highly accurate laser processing even when the focusing position of the laser beam changes.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a laser processing machine in which a workpiece is irradiated with a laser beam output from a laser oscillator in a condensed state by an optical system. A focusing position measuring means for measuring a focusing position of the light is provided, and the position of the optical system is controlled so that the focusing position of the laser beam is a predetermined position based on the measurement result by the focusing position measuring means. A control means is provided.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, an output mirror 1 is included in the laser oscillator 11.
2 and a rear mirror 13 are arranged to face each other. Further, the laser oscillator 11 is provided with a discharge electrode (not shown), and when a discharge voltage is applied to this discharge electrode, the laser gas in the laser oscillator 11 is excited by discharge, and a laser beam is output from the output mirror 12. It is now possible to do so.

A bending mirror 14 is disposed on the optical axis of the laser beam, and the laser beam output from the laser oscillator 11 is reflected by the bending mirror 14 and bent approximately 90 degrees @#j,f.

"Laser optical axis reflected by bending mirror 14"
A condensing position adjusting device 15 is arranged at the second part. This focusing position adjustment device M15 has a built-in condensing lens 16 as an optical system, and the laser beam from the bending mirror 14 is condensed by the condensing lens 16.

A workpiece 17 is located below the condensing position adjusting device 15.
is located so that the surface of the workpiece 17 is irradiated with the laser light focused by the condenser lens 16.

In addition, a beam splitter 18 that reflects a part of the laser beam is disposed at a position below the condenser lens 16 in the condensing position: A adjustment device 15, and the beam splitter 18 that reflects a part of the laser beam is A condensing position measuring means 19 is provided to receive the laser beam. The condensing position measuring means 19 is configured to receive the laser beam reflected by the beam splitter 18 and measure the condensing position of the laser beam. Then, the condensing position: a adjustment device 15 is
It is provided so that it can be moved linearly along the laser optical axis by driving the motor 20, and the condensing position of the laser beam is moved along the laser optical axis by the movement.

Here, the specific configuration of the light condensing position measuring means 19 will be explained with reference to FIG. 2. This focusing position measuring means 19 is an application of a so-called pinhole scanning method. That is, the laser beam reflected by the beam splitter 18 is reflected by the rotating reflecting plate 22 rotated by the motor 21 at an angle with respect to the laser optical axis, and the reflected laser beam is attenuated by the beam damper 23. It has become. Here, the rotating reflector 22 is connected to the beam splitter 18
The setting is such that laser light from the rotary reflector plate 22 is focused on the rotating reflector plate 22. Note that a hole 23 that is sufficiently small compared to the diameter of the laser beam is formed in the rotating reflector 22, and the hole 24 is set to pass through the laser optical axis as the rotating reflector 22 rotates. .

An optical detector 25 is provided on the laser optical axis,
This measures the level of received laser light that passes through the hole 24 as the rotating reflector 22 rotates. Therefore, when the hole 24 moves to the laser beam irradiation position as the rotating reflector 22 rotates, a portion of the laser beam passes through the hole 24 and reaches the optical detector 25, so that the received light level is measured. It has become. At this time, when the condensing position of the laser beam is located on the rotating reflector 22, the irradiation area of the laser beam on the rotating reflector 22 is small and the light intensity is high.
The light reception level of the laser beam measured by the front detector 25 exhibits characteristics with a high peak and a narrow width, as shown by the solid line in FIG. In addition, the convergence position of the laser beam is
2, the irradiation area of the laser beam on the rotating reflector plate 22 is large and the light intensity is low.
The light reception level of the laser light measured by the optical detector 25 exhibits a characteristic that the peak is low and the width is wide, as shown by the dashed line in FIG. Therefore, it is possible to determine whether the laser beam is located on the rotating reflector plate 22, that is, on the workpiece 17, based on the measurement result by the optical detector 25.

Now, in FIG. 1, the measurement result outputted from the focused color Wl measuring means 19 is given to the control means 26, and the control means 26 controls, based on the measurement result, whether the laser beam is directed to the rotating reflector plate. It is determined whether or not the light is focused on 22, and based on the determination result, the motor 20 is driven and controlled as described below.

Next, the operation of the above configuration will be explained.

When a laser beam is output from the laser oscillator 11, the laser beam passes through a condensing lens 16 and a beam splitter 18, and then is irradiated onto the workpiece 17 in a condensed state. Laser processing is performed. Now, in the output mirror 12 and the condensing lens 16 that form the optical resonator, a thermal lens effect occurs as heat increases due to absorption of laser light. Then, as the propagation characteristics of the laser beam and the focal length of the condensing lens change due to the thermal lens effect,
The focusing position of the laser beam on the workpiece 17 changes.

When the focusing position of the laser beam changes, the measurement result by the focusing position measuring means 19 changes from the characteristic shown by the solid line in FIG. 3 to the characteristic shown by the dashed-dotted line. The control means 26 is
The motor 20 is driven when it is determined that the focus position of the laser beam has changed from the set position. Since the condensing position adjusting device 15 moves in accordance with the driving of the motor 20, the condensing lens 16 moves accordingly, and the condensing position of the laser beam on the workpiece 17 changes. At this time, the motor 20
When the peak of the measurement result by the focusing position measuring means 19 becomes lower than the characteristic shown by the dashed-dotted line in FIG. to drive the motor 20 in the opposite direction.

Then, when the measurement result by the focal position measuring means 19 becomes the characteristic shown by the solid line in FIG. 3, the driving of the motor 20 is stopped. As a result, the focus position of the laser beam is set at the workpiece 1.
7, laser pressurization can be efficiently applied to the workpiece 17.

In short, according to the above embodiment, when the focusing position of the laser beam on the workpiece 17 changes, the control means 26 controls the focusing position adjusting device based on the measurement result by the focusing position measuring means 19. 15 is adjusted so that the focusing position of the laser beam is on the workpiece 17, so unlike the conventional example where the position of the focusing lens is fixed, fluctuations in the focusing position of the laser beam due to the thermal lens effect can be avoided. Therefore, it is possible to avoid a decrease in the efficiency of laser processing.

In the above embodiment, a part of the laser beam that has passed through the condenser lens 16 is reflected by the beam splitter 18, so that fluctuations in the condensing position of the reflected light can be measured by the condensing position measuring means 1.
9 to determine the CI, but instead of this,
As shown in FIG. 4, a part of the laser beam before passing through the condensing lens 15 is reflected by the beam splitter 18,
The reflected laser beam may be condensed by the condensing lens 15, and the condensed position may be measured by the condensed position measuring means 19. According to such a configuration,
Since it becomes possible to measure fluctuations in the focusing position of the laser beam caused by the thermal lens effect of the output mirror 12, the focal color determined by the control means 26 can be adjusted. By adjusting the position of the adjusting device 15, it becomes possible to align the focusing position of the laser beam on the workpiece 17.

Further, the condensing position measuring means 19 may be configured to use a low-cheating wire system or a pyroelectric array instead of the configuration shown in FIG. Furthermore, a fluorescent plate may be provided at a position where the laser light is focused, and a CCD camera or the like may be used to measure the position where the laser light is strongly fluorescent.

[Effects of the Invention] As is clear from the above description, according to the laser processing machine of the present invention, the control means causes the laser beam to be focused at a predetermined position based on the measurement result by the focus position measuring means. Since the position of the optical system is configured to be controlled in this way, even if the focusing position of the laser beam changes, there is an excellent effect that highly accurate laser processing is possible.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a schematic diagram of the overall configuration, FIG. 2 is a perspective view showing the schematic configuration of the condensing position measuring means, and FIG. FIG. 4 is a diagram corresponding to FIG. 1 showing another embodiment of the present invention. FIG. 5 is a diagram corresponding to FIG. 1 showing a conventional example. In the figure, 11 is a laser oscillator, 16 is a condensing lens (optical system), 17 is a workpiece, 19 is a focusing position measuring means, and 26 is a control means.

Claims (1)

[Claims] 1. In a laser processing machine configured to irradiate a workpiece with a laser beam output from a laser oscillator while being focused by an optical system, a focusing position measuring means for measuring the focusing position of the laser beam; A laser processing machine comprising: a control means for controlling the position of the optical system so that the laser beam is focused at a predetermined position based on a measurement result by the focus position measuring means.