JPH07251277A - Device for monitoring laser beam in laser beam machine - Google Patents

Abstract

PURPOSE:To detect the optical axis and the intensity of the output of the laser beam with excellent precision. CONSTITUTION:A diffraction grating bender mirror 11 reflects most of the laser beam B to a converging lens 4, and diffracts a part of the laser beam to the different position from that for the reflected laser beam (the machining beam) Ba. The diffracted beam (monitoring beam) Bb is reflected by a reflecting mirror 18, and guided to a detector 23 through an aperture 21 and a band pass filter 22. The detector 23 detects the position of the coordinates of the monitoring beam Bb and outputs the detected value to a control device 25. The control device 25 controls monitors 15, 16 so that the position of the coordinate of the monitoring beam Bb may be the reference position, and adjusts the position of the diffraction grating bender mirror 11 to align the optical axis of the machining beam Ba to the center of the converging lens 4. The detector 23 also detects the intensity of the output of the machining beam. The stability to the mode change is excellent because the diffracted beam is used as the monitoring beam, and the optical axis and the intensity of the output of the machining beam can be detected with excellent precision.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam monitoring device in a laser processing machine for monitoring the laser beam of the laser processing machine and detecting the optical axis and output intensity of the processing beam incident on a condenser lens.

[0002]

2. Description of the Related Art A laser processing machine shown in FIG. 5 is known. This laser processing machine guides a laser beam B oscillated from a laser oscillator 1 to a condenser lens 4 via bender mirrors 2 and 3, and the condenser lens 4 makes 0.1.
The structure is such that the gas nozzle 5 irradiates the workpiece 6 with a spot of about 0.2 mm to irradiate the workpiece 6 and the workpiece 6 is processed (cut). The laser processing machine of FIG. 5 is a mounted laser processing machine in which the laser oscillator 1 is mounted on the X-axis moving table 8 that moves along the X-axis rail 7. Although the laser processing machine has different detailed structures depending on the application, the laser oscillator 1
The basic structure for guiding the laser beam B oscillated from the laser beam to the condenser lens 4 by one or more bender mirrors is the same regardless of the application.

In such a laser processing machine, if the laser beam B reflected by the bender mirror 3 and incident on the condenser lens 4 is not properly incident on the center of the condenser lens 4, the machining performance is deteriorated, Incident beam (processing beam)
If the optical axis of 2 is significantly deviated from the center of the condenser lens 4, the processing may not be performed correctly and the product may be defective.

Therefore, conventionally, the vendor mirror 3 is used.
A pinhole is provided at the center of the bender mirror 3 to allow a part of the laser beam B sent to the bender mirror 3 to pass backward, and the monitor light that has passed through the pinhole is received by an optical sensor. In other words, vendor mirror 3
The optical axis of the processing beam that is reflected by and is incident on the condenser lens 4 is detected. The optical sensor can detect the output intensity in addition to the optical axis of the processing beam.

[0005]

However, in the above-mentioned conventional laser beam monitoring apparatus, when the waveform of the monitor light passing through the pinhole is a multi-mode having a plurality of peaks, the optical axis of the processing beam and the output intensity are increased. There is a problem that can not be detected accurately.

An object of the present invention is to provide a laser beam monitoring device in a laser processing machine capable of accurately detecting the optical axis and output intensity of a processing beam.

[0007]

In order to achieve the above object, the present invention provides a laser beam oscillated from a laser oscillator which is reflected by a bender mirror and condensed by a condenser lens, and is then processed from a nozzle to a workpiece. In the laser processing machine that irradiates the laser beam onto the laser beam to process it, the bender mirror reflects most of the laser beam to the condenser lens side as the processing beam, and part of the laser beam is reflected on the portion other than the condenser lens by the diffraction phenomenon. A diffraction grating bender mirror that diffracts as the monitor light is used, and a detection device that receives the monitor light and detects the optical axis of the processing beam and the output intensity and the output intensity distribution is arranged in the path of the monitor light.

The detection device includes an aperture formed with a diaphragm hole for allowing the monitor light to pass, a bandpass filter for allowing only the monitor light having a wavelength within a predetermined range to pass, and a monitor light having passed through the aperture and the bandpass filter. It is preferable to have a configuration including a detector that receives and detects the optical axis of the processing beam and the output intensity. Further, at least the detector of the detection device is preferably attached to a lens holder that supports a condenser lens. Furthermore, at least one condenser mirror or condenser lens may be provided in the path of the monitor light.

[0009]

Most of the laser beam oscillated from the laser oscillator is reflected by the diffraction grating bender mirror toward the condenser lens, and part of it is diffracted by the diffraction grating bender mirror. The detection device receives the monitor light diffracted by the diffraction grating bender mirror and detects the optical axis and output intensity of the processing beam. If the detector is composed of the aperture, the bandpass filter, and the detector, unnecessary light can be removed, so that a small detector can be used and the detection accuracy can be improved. When the detector is attached to the lens holder,
Unless the condenser lens is moved up and down with respect to the diffraction grating bender mirror, the optical path length of the monitor light is kept constant, which facilitates the attitude control of the diffraction grating bender mirror. If at least one condenser mirror or condenser lens is provided in the path of the monitor light, the whole beam can be monitored and the mode monitoring and position detection of the laser beam can be accurately read.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the present invention, the diffraction grating bender mirror 11 is used as the bender mirror. The diffraction grating bender mirror 11 is a normal bender mirror formed with a diffraction grating that causes a diffraction phenomenon. Most of the laser beam B received from the bender mirror 2 (FIG. 5) is collected at an angle equal to the incident angle. The laser beam B is reflected by the optical lens 4 and a part of the laser beam B is diffracted to a position different from the above-mentioned reflected light (processing beam) Ba. When the tilt angle of the diffraction grating bender mirror 11 changes, the processing beam Ba and the position (optical axis) of the diffracted light change in a predetermined relationship.

The above diffracted light is stable with respect to the mode change, and is used as the monitor light Bb in the present invention. The light amount of the monitor light Bb is usually 1 of the processing beam Ba.
Although it is set to about / 100,000 to 1 / 1,000,000 or less, it depends on the groove width and depth of the diffraction grating. The diffraction grating is usually formed on the entire surface of the base mirror, but it may be formed only on a part such as the central portion of the mirror.

The diffraction grating bender mirror 11 is fixed to the mirror holder 12. The mirror holder 12 is attached to the frame 14 with a universal joint 13,
Female screws 12a and 12b are screwed onto output shafts 15a and 16a of attitude control motors 15 and 16 such as servomotors. Universal joint 13 and output shafts 15a, 16
Similarly to the diffraction grating bender mirror 11, a is annularly arranged at an outer periphery of a mirror holder 12 formed at a 120 degree interval.

The attitude controlling motors 15 and 16 move the diffraction grating bender mirror 11 together with the mirror holder 12 to adjust the tilt angle. That is, when the attitude controlling motor 15 is activated to rotate the output shaft 15a, the mirror holder 12 moves to the universal joint 13
And the output shaft 16a are rotated about a straight line, and when the output shaft 16a is rotated, the straight line connecting the universal joint 13 and the output shaft 15a is rotated as a support point.
When 5a and 16a simultaneously rotate in the same direction, the universal joint 13 is rotated to change the attitude of the diffraction grating bender mirror 11, that is, the tilt angle. This structure is simpler than the structure in which four output shafts or two universal joints and output shafts are arranged in a square shape to control the attitude of the diffraction grating bender mirror 11. The female screws 12a and 12b of the mirror holder 12 to which the output shafts 15a and 16a are screwed can move similarly to the universal joint 13.

A reflecting mirror 18 and a detecting device 19 are arranged in the path of the monitor light Bb. The reflector 18 is the monitor light B
b is reflected on the detection device 19, and the mounting bracket 20
It is fixed to the frame 14 with. In addition, the detection device 19
Receives the monitor light Bb and detects the optical axis and output intensity of the processing beam Ba that enters the condenser lens 4.
An aperture 21 formed with a diaphragm hole 21a that allows the monitor light Bb to pass therethrough, a bandpass filter 22 that allows only the monitor light Bb having a wavelength within a predetermined range to pass, and an aperture 21.
And a detector 23 that receives the monitor light Bb that has passed through the bandpass filter 22. The aperture 21 is attached to the frame 14, and the bandpass filter 22 and the detector 23 are attached to a lens holder 24 supporting the condenser lens 4.

The aperture 21 allows the use of a small detector 23 by passing the monitor light Bb through the diaphragm hole 21a to reduce the light diameter. Further, the bandpass filter 22 prevents only the monitor light Bb having a wavelength of 10.6 μm from passing and removes diffracted light (miscellaneous light) of other wavelengths, thereby preventing adverse effects due to miscellaneous light and thus the detector 23.
Improve the detection accuracy of.

As the detector 23, an infrared array element, an infrared CCD (charge coupled device) or the like is used. Detector 23
Is, for example, as shown in FIG.
The XY coordinate position (ΔPx, ΔPy) of the monitor light Bb which changes depending on the inclination angle of is detected and a signal is output. A control device 25 is connected to the detector 23. Control device 2
Reference numeral 5 controls the operation of the attitude control motors 15 and 16 based on the output signal of the detector 23 so that the position of the monitor light Bb becomes the reference position (O, O). Here, the above-mentioned reference position (O, O) is a position at which the optical axis of the processing beam Ba incident on the condenser lens 4 exactly coincides with the center of the condenser lens 4.

The detector 23, as shown in FIG.
The output intensity is detected from the height of b in the Z-axis direction. Since the output intensity of the processing beam Ba is proportional to the output intensity of the monitor light Bb, it can be easily determined from the output intensity of the monitor light. The output intensity detection signal is output from the detector 23 to another system, and is displayed or recorded as the output intensity of the laser beam B as required.

Further, the detector 23 can be used for both the detection of the optical axis and the detection of the output intensity as described above.
Only one of them may be used. The output intensity can also be detected at the bender mirror 2 in FIG. In this case, it goes without saying that the bender mirror 2 is a diffraction grating bender mirror. Further, the same effect can be obtained even if the detector 23 is directly attached to the diffraction grating bender mirror unit 14 of FIG. 1, specifically, the reflecting mirror 18.

The other structure of the laser processing machine is the same as that of the conventional laser processing machine. The same members as those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

Next, the operation of the laser beam monitoring device in the laser processing machine of the present invention having the above configuration will be described. The diffraction grating bender mirror 11 receives the laser beam B oscillated from the laser oscillator, reflects most of it on the condenser lens 4, and diffracts part of it on the reflecting mirror 18. The processing beam Ba reflected by the diffraction grating bender mirror 11 is focused by the condenser lens 4 to work on the workpiece 6. Further, the diffracted light diffracted by the diffraction grating bender mirror 11 becomes the monitor light Bb and is guided to the detection device 19 by the reflecting mirror 18.

The detector 23 of the detector 19 detects the monitor light Bb which has passed through the aperture 21 and the bandpass filter 22.
Then, the coordinate position and the output intensity are detected, and the coordinate position is output to the controller 25 and the output intensity is output to another system. Upon receiving the detection signal of the detector 23, the control device 25 receives the monitor light Bb.
The attitude control motors 15 and 16 are driven so that the coordinate position of is the reference position (O, O) at which the optical axis of the processing beam Ba coincides with the center of the condenser lens 4. Therefore, even if the optical axis of the processing beam Ba deviates from the center of the condenser lens 4 for some reason, it is immediately corrected, and laser processing is always performed in the best state without causing processing defects. be able to. Further, since the output intensity of the laser beam is also detected, it is possible to perform processing with a predetermined output intensity with high accuracy in this respect as well, and the reliability of the processing is improved as a whole. The aperture is not always necessary, and the reflecting mirror 18 can be configured as a condensing reflecting mirror. In this case, all the beams can be monitored, and the mode monitoring and position detection of the laser beam can be accurately read, further improving the reliability.

As shown in the figure, the detector 23 is attached to the lens holder 2
When the condenser lens 4 is attached to the diffraction grating bender mirror 11, the monitor light Bb
Does not change and the coordinate position change of the monitor light Bb with respect to the same tilt angle change of the diffraction grating bender mirror 11 is kept the same.
The control of 16 becomes easy. When the condenser lens 4 is moved up or down with respect to the diffraction grating bender mirror 11,
The coordinate position of the monitor light Bb is corrected according to the movement amount of the condenser lens 4, and the motors 15 and 16 are controlled. The detector 23 may be attached to a member such as the frame 14 other than the lens holder 24. The number of reflectors 18 used is the detector 2
It is increased or decreased depending on the mounting position of 3. In some cases, the attitude of the diffraction grating bender mirror 11 may be manually adjusted.

[0023]

As described above, according to the present invention, the laser beam oscillated from the laser oscillator is reflected by the bender mirror and condensed by the condenser lens, and the workpiece is irradiated with the nozzle and processed. In the laser processing machine, the bender mirror is a diffraction grating that reflects most of the laser beam to the condenser lens side as a processing beam and diffracts a part of the laser beam as a monitor light to a portion other than the condenser lens by a diffraction phenomenon. It is configured as a bender mirror, and a detection device that receives the monitor light and detects the optical axis of the processing beam and the output intensity and the output intensity distribution is arranged in the path of the monitor light. It is possible to accurately detect the optical axis of the beam, the output intensity, etc., and always process the workpiece in the best condition.

[Brief description of drawings]

FIG. 1 is a sectional view of essential parts showing an embodiment of a laser beam monitoring device in a laser processing machine according to the present invention.

FIG. 2 is a sectional view of a portion (II-II) in FIG.

FIG. 3 is a diagram showing an example of coordinate positions of monitor light in a detector.

FIG. 4 is a diagram showing an example of output intensity of monitor light in a detector.

FIG. 5 is an external view of a main part of a general laser processing machine.

[Explanation of symbols]

 4 Condensing Lens 5 Gas Nozzle 6 Workpiece 11 Diffraction Grating Bender Mirror 19 Detection Device 21 Aperture 21a Aperture Hole 22 Bandpass Filter 23 Detector B Laser Beam Ba Processing Beam (Reflected Light) Bb Monitor Light (Diffracted Light)

Claims (4)

[Claims] 1. A laser beam emitted from a laser oscillator is reflected by a bender mirror and condensed by a condenser lens,
In a laser processing machine that irradiates a workpiece with a nozzle and processes it, the bender mirror reflects most of the laser beam as a processing beam to the condenser lens side and also collects a part of the laser beam by a diffraction phenomenon. A portion other than the lens is a diffraction grating bender mirror that diffracts as monitor light, and a detection device that receives the monitor light and detects the optical axis of the processing beam and the output intensity and the output intensity distribution is provided in the path of the monitor light. A laser beam monitoring device in a laser processing machine, wherein the laser beam monitoring device is provided. 2. The detection device comprises an aperture formed with a diaphragm hole for passing monitor light, a bandpass filter for passing only monitor light having a wavelength within a predetermined range, and a monitor passing through the aperture and bandpass filter. The laser beam monitoring device in a laser beam machine according to claim 1, further comprising a detector that receives light and detects an optical axis and an output intensity of the processing beam. 3. A laser beam monitoring device in a laser beam machine according to claim 2, wherein at least a detector of the detection device is attached to a lens holder supporting a condenser lens. 4. A laser beam monitoring device in a laser beam machine according to claim 1, wherein at least one condenser reflecting mirror or condenser lens is provided in the path of the monitor light.