JPH1168218A - Laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser wherein displacement in oscillation light axis is automatically prevented. SOLUTION: Relating to a laser wherein a total reflection flat mirror 14 of an optical resonator 12 is so held that laser beam irradiation position may be adjusted, a beam splitter 41 for deflecting a part of laser beam LB from an oscillation light axis while the shape of laser beam LB is maintained on the out-going side of a laser oscillator, a laser light detector 51 for detecting such laser beam SB as deflected from the oscillation light axis, and a control device 61 wherein an oscillation light axis position is obtained based on the detected beam, such control signal as to position the oscillation light axis within a pre-set tolerable range is obtained, and the control signal is outputted to the total reflection mirroe holding device 21, are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device, and more particularly, to a laser device capable of adjusting an oscillation optical axis position. The laser device according to the present invention is used for welding, cutting, surface treatment, and other processing, and is suitable for a laser device having a relatively large output.

[0002]

2. Description of the Related Art At the actual site of laser processing technology, a laser processing system is recognized as a tool similar to a conventional machine such as a lathe or a milling machine, and a laser oscillator is equivalent to a mechanical motor. There is importance to do. However, the laser oscillator itself does not always have sufficient long-term stability as compared with a mechanical motor or the like. For this reason, the laser processing machine is one of the causes of being hardly accepted in the field. One of the problems in maintaining stable operation of a laser oscillator for a long period of time is to improve the spatial stability of the oscillation optical axis. In other words, the oscillation optical axis gradually deviates from the initially adjusted position due to pressure fluctuation of the device itself, external vibration in the installation environment of the device, temperature change, etc., deteriorating the laser output characteristics and the reproducibility of the processing point position. There is a problem. In particular, when a laser beam is transmitted to a welding head or a cutting head at a distance of 10 m or more from the laser oscillator, a deviation of the oscillation optical axis is likely to occur, and the deviation amount is large. In such a work site, the laser oscillator must be adjusted, for example, about several times a day. The adjustment takes about 1 to 5 hours even for a skilled person. Further, for adjustment, a He—Ne gas laser different from the processing laser, for example, is required. This is not only costly in terms of reduced operating rates and maintenance costs, but also requires specialized knowledge and skills, making it difficult to work at the field level and keeping field workers away from the laser beam machine. ing.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser device capable of automatically preventing the oscillation optical axis from being shifted.

[0004]

According to a laser apparatus of the present invention, a total reflection mirror of an optical resonator is held or moved or tilted so that a laser beam irradiation position can be adjusted. A total reflection mirror holding device for holding the laser beam, a beam splitter for deflecting a part of the laser beam from the oscillation optical axis while maintaining the shape of the laser beam on the emission side of the laser oscillator, and a laser beam diverted from the oscillation optical axis A laser light detector for detecting the position of the oscillating optical axis based on the detection beam, a control signal for positioning the oscillating optical axis within a predetermined allowable range, and outputting a control signal to the total reflection mirror holding device. And a control device that performs the control.

The laser device detects the optical axis position of the laser beam emitted from the laser oscillator, and performs feedback control of the position or orientation of the total reflection mirror of the optical resonator based on the detection result. Therefore, the deviation of the oscillation optical axis can be automatically prevented, and the laser beam can always be applied to the target position. Further, since a part of the laser beam is extracted by the beam splitter and the oscillation optical axis position is detected, the intensity of the laser beam incident on the laser light detector can be adjusted to be low. As a result, even a high-power laser device exceeding several kW can use a laser light detector with low power resistance. Further, a part of the laser beam emitted from the laser oscillator is directly extracted for detecting the position of the oscillation optical axis. Therefore, another laser oscillator (for example, a He-Ne gas laser) for adjusting the oscillation optical axis position is unnecessary, and the detection accuracy is high because the laser beam is directly extracted.

In the above laser device, a semi-transparent mirror or a chopper rod may be used as the beam splitter.
The chopper rod has a plane reflecting mirror formed on one surface, and is rotatably driven by a drive motor.

Further, in the above laser device, the laser oscillator may be a Q-switched CO ₂ laser oscillator. Further, a telescope may be configured by the total reflection concave mirror and the light condensing element of the optical resonator, and the chopper disk of the Q switch device may be arranged between the total reflection concave mirror and the light condensing element.

[0008]

FIG. 1 shows one embodiment of the present invention, and is a device configuration diagram schematically showing an outline of a laser device. In FIG. 1, devices and members necessary for a laser oscillator such as an electrode of a discharge excitation unit, a laser gas supply device, and a laser power supply are omitted. The discharge excitation unit 11 is formed in a casing (not shown), and is always supplied with a laser gas such as CO ₂ . The laser gas is excited by discharge to generate a laser beam.

The laser light generated by the discharge excitation section 11 is amplified by the optical resonator 12. The optical resonator 12 includes a semi-transparent mirror 13 and a total reflection mirror 14. The semi-transmissive mirror 13 is made of, for example, ZnSe and has a multi-layer surface coating, and has a reflectance of 50%. The total reflection mirror 14 is a flat mirror and is held by a total reflection mirror holding device 21.

The total reflection mirror holding device 21 includes a tilt stage 2
3 is connected to the base table 22 via a spring (not shown).
Attached to. The tilt stage 23 can tilt with respect to the base table surface. A pair of precision tilt screws 25 and 26 are attached to the tilt stage 23 in a diagonal direction. When the precision tilt screws 25 and 26 are driven by the servo motors 28 and 29 supported by the base table 22, respectively, the tilt stage 23 tilts with respect to the base table surface (vertical surface). The total reflection plane mirror 14 of the optical resonator 12 is fixed to a tilt stage 23. By driving the servo motors 28 and 29, the total reflection plane mirror 14 is tilted with respect to a plane perpendicular to the oscillation optical axis. As a result, the incidence or emission angle of the laser light with respect to the total reflection plane mirror 14 changes, and the position of the oscillation optical axis moves.

A beam splitter 41 is arranged on the emission side of the laser oscillator. The beam splitter 41 comprises a semi-transparent mirror 42 inclined at 45 ° to the oscillation optical axis. The semi-transparent mirror 42 of the beam splitter 41 is, for example, Z
It is made of nSe and has a reflectance of about 0.1 to 5%. At the start of the laser irradiation operation, the oscillation optical axis is set in advance to a reference position, and the semi-transparent mirror 42 is set at an inclination angle of 45 ° with respect to the reference oscillation optical axis.

The laser beam SB deviated from the oscillation optical axis by the beam splitter 41 and divided is detected by the laser beam detector 51. The laser light detector 51 is composed of a pyroelectric power meter. The laser light detector 51 is shown in FIG.
As shown in the figure, a circular B laser beam SB is detected. The laser light detector 51 may be four or more photodiodes arranged in a matrix or an area image sensor.

The laser light detector 51 is connected to a control computer 61. The control computer 61
The position of the center of gravity is obtained from the intensity distribution of the detected laser light based on the signal from the laser light detector 51. The position of the center of gravity is defined as the oscillation optical axis position of the laser beam LB emitted from the laser oscillator. For example, as shown in FIG. 3, the laser light detection plane is an XY coordinate plane whose origin is the reference position O of the preset oscillation optical axis, and the XY coordinate plane is divided into first to fourth quadrants. Then, the intensity integrated values of the detected laser light in each quadrant are calculated, and the barycentric position (center position of the laser beam LB) of the detected laser light intensity distribution is obtained from these integrated values in XY coordinate display. When the intensity distribution of the laser beam is not uniform, the intensity distribution is corrected by multiplying the intensity of each detection point by a weighting coefficient corresponding to the intensity distribution, and the center position of the laser beam LB is obtained. When the laser light detector 41 is a matrix photodiode or an area image sensor, the center C of the circle of the detected laser light B is obtained. Next, the deviation (magnitude and direction) δ of the optical axis position between the detected oscillation optical axis position C and the reference position O of the oscillation optical axis is determined, and it is determined whether or not the optical axis deviation δ is within the allowable range A. . The radius of the allowable range A is, for example, 0.05 to 0.1 mm. When the optical axis deviation δ is out of the allowable range A, the optical axis deviation δ
The control amount is calculated based on
8 and 29 are output. By driving the servo motors 28 and 29, the tilt stage 23, that is, the total reflection mirror 14 is tilted,
The oscillation optical axis is located in the allowable range A. The relationship between the optical axis deviation δ and the control amount is obtained in advance by experiments and stored in the control computer in the form of an arithmetic expression or a table. The direction of the oscillation optical axis changes due to the inclination of the inclination stage 23. In the present invention, the change in the direction is detected as the change in the position as described above, and the direction of the oscillation optical axis is controlled.

FIG. 4 shows another embodiment of the present invention. The same components as those shown in FIG. 1 are denoted by the same reference numerals, and a detailed description thereof will be omitted.

The optical resonator 16 comprises a semi-transparent mirror 13 and a telescope 17. The telescope 17 comprises a total reflection concave mirror 18 and a converging convex lens 19. The total reflection concave mirror 18 is made of copper or the like, and its surface is plated with gold. In the telescope 17, the total reflection surface may be either a spherical surface or a parabolic surface, and the optical axis is
3 coincides with the optical axis.

A Q switch device 71 is arranged on the telescope 17. The Q switch device 71 includes a disk-shaped chopper disk 72. Chopper disk 72
A number of slits (not shown) are provided along the circumference in the vicinity of the outer periphery. The chopper disk 72 is disposed such that the slit is located at the confocal point of the total reflection concave mirror 18 of the telescope 17 and the converging convex lens 19.
The chopper disk 72 is driven to rotate by a disk drive motor 73. The rotation speed is 1,000-100,
000 rpm.

In the total reflection mirror holding device 31, a Y-axis stage 33 is mounted on a base table 32 so as to be movable in the Y-axis (vertical) direction, as shown in FIG. A precision feed screw 35 is fitted on the Y-axis stage 33. A servomotor 37 is supported on the base table 32 by a metal fitting 39. When the precision feed screw 35 is driven by the servomotor 37, the Y-axis stage 33 moves forward and backward in the Y-axis direction with respect to the base table 32. An X-axis stage 34 is attached to the Y-axis stage 33 so as to be movable in the X-axis (horizontal) direction. Servo motor 3 supported on Y-axis stage 33
When the precision feed screw 36 is driven by 8, the X-axis stage 34 moves forward and backward with respect to the Y-axis stage 33 in the X-axis direction. The total reflection concave mirror 18 is attached to the X-axis stage 34. In this embodiment, the total reflection concave mirror 18 translates in a plane perpendicular to the oscillation optical axis. As a result, the position of the incident or emitted laser light with respect to the total reflection concave mirror changes, and the position of the oscillation optical axis moves. Total reflection concave mirror 18
Is equivalent to a change in the angle of the total reflection plane mirror 14 of the above embodiment.

The beam splitter 44 has a chopper rod 47 having a rectangular cross section attached to an output shaft 46 of a drive motor 45. One side of the chopper rod 47 is the reflecting mirror 4
8, the reflecting mirror 48 is inclined by 45 ° with respect to the oscillation optical axis. To reduce the moment of inertia of the chopper rod 47, a counterweight 49 is attached to one end of the chopper rod 47. The drive motor 45 rotates the chopper rod 47 to periodically sample the laser beam. If the sampling period is short,
That is, if the rotation of the chopper rod 47 is fast, the reflection mirror 4
Since there is no risk of image sticking of 8 and the frequency of position detection per second by the laser light detector 51 is increased, the detection accuracy of the oscillation optical axis position is improved.

The present invention is not limited to the above embodiment. For example, the telescope of FIG. 4 may be incorporated in the optical resonator of the apparatus of FIG. A semi-transmissive mirror may be used as the beam splitter in the apparatus shown in FIG.
Alternatively, the total reflection concave mirror of the telescope may be moved along the oscillation optical axis direction to adjust the spread angle of the laser beam or the focal position of the total reflection concave mirror.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The laser device is a Q incorporating a telescope.
A switched carbon dioxide laser device was used. Q switch CO
The output of the _two laser device was 10 kW. As the laser beam detector, a pyroelectric power meter having a light receiving surface divided into four was used. The control computer calculates the center of gravity of the laser beam intensity, obtains the amount of deviation of the oscillation optical axis from the reference position provided on the light-receiving surface of the laser light detector, and translates the total reflection concave mirror of the optical resonator in parallel. The drive motor was controlled so as to control the movement and return the oscillation optical axis to the reference position. In the initial setting, the oscillation optical axis was manually adjusted to the optimum position, and then the semi-transparent mirror of the beam splitter and the laser light detector were installed and fixed. At this time, the reference position of the laser light detector was determined.

As described above, as a result of controlling the oscillation optical axis position, it is possible to automatically control the oscillation optical axis within a radius of 3 mm around the oscillation optical axis reference point and to suppress the beam position stability to within ± 0.1 mm. Was completed.

[0022]

According to the present invention, the displacement of the oscillation optical axis can be automatically prevented. Therefore, it is not necessary to adjust the oscillation optical axis, and it is possible to improve the accuracy and work efficiency of laser processing.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a device configuration diagram schematically showing an outline of a laser device.

FIG. 2 is a perspective view of a total reflection mirror holding device provided in the device shown in FIG.

FIG. 3 is a drawing schematically showing a laser beam detected by a laser light detector.

FIG. 4 shows another embodiment of the present invention, and is a device configuration diagram schematically showing an outline of a laser device.

FIG. 5 is a perspective view of a total reflection mirror holding device provided in the device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Discharge excitation part 12, 16 Optical resonator 13 Semi-transmissive mirror 14 Total reflection plane mirror 17 Telescope 18 Total reflection concave mirror 19 Condensing convex lens 21, 31 Total reflection mirror holding device 22, 32 Base table 23 Tilt stage 25, 26 Precision tilt screw 28, 29 Servo motor 33 Y-axis stage 34 X-axis stage 35, 36 Precision feed screw 37, 38 Servo motor 41, 44 Beam splitter 42 Semi-transparent mirror 45 Drive motor 47 Chopper rod 48 Reflector mirror 51 Photodetector 61 Control computer 71 Q switch device 72 Chopper disk 73 Drive motor LB Laser beam SB Split beam

Claims (4)

[Claims] 1. A laser device in which a total reflection mirror of an optical resonator is held so that a laser beam irradiation position can be adjusted, a total reflection mirror holding device which holds the total reflection mirror so as to be movable or tiltable, A beam splitter that deflects a part of the laser beam from the oscillation optical axis while maintaining the shape of the laser beam on the emission side of the laser oscillator, a laser light detector that detects the laser beam deviated from the oscillation optical axis, and a detection beam And a control device for obtaining a control signal for positioning the oscillation optical axis within a predetermined allowable range based on the control signal, and outputting the control signal to the total reflection mirror holding device. Laser device. 2. The laser device according to claim 1, wherein the beam splitter comprises a semi-transparent mirror. 3. The laser device according to claim 1, wherein the beam splitter comprises a chopper rod having a plane reflecting mirror formed on one surface, and a drive motor for rotating and driving the chopper rod. 4. The laser oscillator is a Q-switched CO ₂ laser oscillator, the optical resonator comprises a semi-transparent mirror and a total reflection concave mirror, and a telescope is constituted by the total reflection concave mirror and a condensing element. Q between reflective concave mirror and condenser
The laser device according to claim 1, wherein a chopper disk of the switch device is disposed.