JP3437154B2 - Laser beam measuring device and control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser output measuring device, and more particularly to a measuring device for indirectly measuring a state of a processing laser beam vibrated by using a galvanometer mirror at a processing point, and a measuring device therefor. The present invention relates to a control device for a laser output device.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring a processing laser beam or the like, a beam profiler for measuring an intensity distribution in a direction perpendicular to an optical axis, a method for measuring a temporal change in laser output using a photoelectric conversion element, a slit There is a streak camera that converts the temporal change in the light intensity of the light incident through it into a spatial change in the light intensity on the fluorescent screen and displays the change. With these measurement methods, it is possible to measure the spread of the laser beam and the time change of the light intensity. Since the conventional laser processing technique is simple and there is no requirement to directly measure the beam characteristics during processing or use it for control, the conventional measurement method can perform satisfactory measurement.

Recently, however, the demand for laser processing has become higher, and for example, in order to prevent defects such as porosity from occurring in laser welding, a laser beam vibrated using a galvanomirror is processed. The method of irradiating the skin is also used. In addition, the laser beam is also pulsed, and a method in which both are used in combination is about to be used with the expectation of a greater effect. For research and development toward the practical application of such a new machining process, it is necessary to accurately grasp the state in which the beam is applied to the machining part.

In particular, when the pulse laser vibrates,
Since the interference relationship of variable parameters such as output pulse repetition frequency, output time change, and beam vibration state becomes extremely complicated, it is necessary to construct a database that defines welding conditions for practical use. Also, when performing optimal control of the laser processing apparatus, it is premised that an accurate processing database exists and that the laser irradiation state is measured in-process. Therefore, there is a demand for a convenient device that accurately measures the beam state during processing in real time. However, some conventional methods cannot measure the characteristics of a spatially moving laser beam in-process.

[0005]

Therefore, the problem to be solved by the present invention is to provide a convenient device for measuring the characteristics of a laser beam in-process, and particularly when irradiating an oscillating pulse laser. There is provided a laser beam measuring device for measuring the characteristics at the processing position and a laser beam control device using these measuring devices.

[0006]

In order to solve the above-mentioned problems, a laser beam measuring apparatus of the present invention comprises a partial reflection / transmission mirror to which a laser beam to be measured is incident and a part of which is taken out, and a period around a rotation axis. Equipped with a planar vibrating mirror that rotates dynamically, a linear or two-dimensional image sensor, and a data analysis device. A part of the laser beam extracted by the partial reflection / transmission mirror is reflected by the planar vibrating mirror and enters the image sensor. Then, the image sensor outputs a measurement signal of the amount of received light at the incident position, and the data analyzer measures the characteristics of the laser beam to be measured based on the received light amount measurement signal in the laser beam trajectory formed on the image sensor. It is characterized by being configured.

According to the laser beam measuring apparatus of the present invention,
The laser beam emitted from the laser device is incident on the partial reflection / transmission mirror, and a certain proportion of the light beam is reflected or transmitted with respect to the incident laser beam and is extracted for measurement. The divided laser beam light is incident on the plane vibration boundary, and becomes a weak laser beam that periodically oscillates due to the rotation of the plane vibration boundary, and is reflected and incident on the image pickup element. There are galvanometer mirrors in the plane vibration boundary. Even when the object to be measured is a high-power laser beam, only a part of the laser beam is incident on the detection element, so that a photodetection element which is normally used can be used as the imaging element. In addition, since the temporal change of the light intensity is expanded and detected by oscillating the laser beam, even when the light intensity of the laser beam changes at high speed, a detection element with a relatively slow response speed is used. Even then, the change in light intensity can be accurately detected.

Therefore, for example, a CCD element in which the detection cells are arranged in a straight line or in a plane may be used as the image pickup element. Since the CCD element detects the amount of incident light accumulated for each cell, it is possible to output the light intensity at each point on the irradiation point locus of the laser beam formed on the light receiving surface of the image pickup element. Since the laser beam moves on the light receiving surface of the image sensor and detects the amount of light in different detection cells at each instant, if the light intensity of the laser beam changes with time, the output of the detection cell should be traced along the beam irradiation trajectory. The intensity change can be captured with. The measuring device of the present invention,
Of the laser beams incident on the partial reflection / transmission mirror inserted in the laser optical path, only a very small portion is extracted for measurement, so the characteristics of the laser beam being used during processing are measured in real time. can do.

Further, in the second laser beam measuring apparatus of the present invention, the laser beam to be measured first enters the plane vibrating mirror and is reflected, and thereafter enters the partial reflection / transmission mirror. It is characterized in that a part thereof is taken out and made incident on the image pickup device. In the second laser beam measuring apparatus of the present invention, the entire amount of the laser beam emitted from the laser generator first enters a plane vibrating mirror such as a galvanometer mirror, and becomes a beam that oscillates in the partial reflection transmission mirror. Incident. In the partial reflection / transmission mirror, a large part of the incident laser beam becomes a main beam used for laser processing and the like, and a very small part is extracted and enters the image pickup element as a sub beam to detect the light intensity. Since the ratio between the main beam and the sub beam is predetermined, the energy of the original laser beam or the main beam can be measured in-process and in real time by measuring the energy of the weak sub beam.

The plane vibrating mirror of the laser beam measuring apparatus of the present invention may be provided with a two-axis rotating shaft, and an image pickup device having a two-dimensional detection surface may be used.
With such a configuration, the laser beam incident on the plane vibrating mirror is two-dimensionally driven to oscillate on the two-dimensional detection surface of the image sensor, so that a change in light intensity can be detected more clearly. . If a oscillating main beam formed of a plane vibrating mirror having two rotating shafts is used for laser processing, it is possible to suppress the generation of blow holes in welding processing, for example.

Further, when the laser beam is a pulse laser, if the oscillation period of the plane vibrating mirror is synchronized with the pulse period of the laser, the laser beam locus formed on the image pickup device can be stabilized. It is possible to measure the spatial and temporal changes in the light intensity within the pulse of a pulsed laser. Conventionally, the spatial and temporal distribution of the light intensity waveform in the pulse could not be known without using a precise and expensive streak camera or the like. Moreover, it has been difficult for a streak camera to perform continuous measurement over a long period of time. On the other hand, the laser beam measuring device of the present invention can easily measure the average light intensity change in the pulse continuously for a long time and repeatedly many times.

The pulse period of the laser beam can be determined by observing the laser beam locus formed on the image pickup device and sweeping the frequency of the plane vibrating mirror to check the frequency at which the laser beam locus stabilizes. Can be detected. The device of the present invention is the same as knowing the number of rotations from the frequency at which a rotating body seems to be stationary when stroboscopic light is applied to it, so that the periodic phenomenon of the laser pulse and the vibration of the planar vibrating mirror are synchronized. The points can be easily determined. With respect to the two-dimensionally oscillated laser beam, the pulse period can be easily known by adjusting the two rotary shafts.

By providing a condensing optical system including a lens and a reflecting mirror in front of the image pickup device and disposing the image pickup device at the focal position of the condensing optical system, the laser irradiation point on the image pickup surface is reduced. The oscillation state of the laser can be detected more clearly and the change in light intensity can be detected accurately.
Further, in laser processing, the laser beam is converged and processed near the focal point. Therefore, sharpening with a converging optical system better represents the characteristics of the laser beam in the processed portion, and more accurate measurement of the processing laser beam can be performed. . In addition, when a light reduction element such as a dark filter or a polarization filter is provided in front of the image pickup element to reduce the laser light entering the image pickup element,
This is preferable because it prevents the output saturation and deterioration of the image pickup device and makes it possible to use various photosensitive devices.

The laser beam measuring device of the present invention is
By separating the main beam for processing and the sub-beam for measurement by the partial reflection / transmission mirror, it can be used for in-process measurement of the processing laser. Furthermore, a partial reflection / transmission mirror is placed between the laser processing target position and the focusing optical system,
By arranging the image pickup surface position of the image pickup element so as to be optically equivalent to or similar to the position to be processed, the characteristics of the processing laser at the processing position can be known in real time.

Further, the laser beam control device of the present invention is characterized in that the laser oscillation device is adjusted based on the characteristics of the laser beam measured by the laser beam measuring device of the present invention. With the laser beam measuring device of the present invention, since the property of the laser beam can be measured in-process in real time, the measurement result is fed back to the laser generator, and the laser light intensity, the pulse oscillation frequency, and the intensity change pattern within the pulse are measured. Etc. can be controlled to match the target value. In particular, in the case where the image pickup element is arranged at the optical position corresponding to the irradiation position of the main beam, since the control is performed based on the result of accurately estimating the state of the laser beam at the processing position, the processing state is indirectly controlled. It will be. Similarly, based on the measured characteristics of the laser beam, the rotation of the plane vibrating mirror can be adjusted to adjust the vibration behavior of the main beam.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on embodiments with reference to the drawings. 1 is a block diagram showing a laser beam control apparatus according to a first embodiment of the present invention, FIG. 2 is a schematic diagram showing an irradiation trajectory on an imaging surface in the present embodiment, and FIG. 3 is a schematic diagram showing a measurement state of a pulse laser. , Fig. 4
5 is an output waveform diagram showing an example of an in-pulse light intensity change pattern of a pulse laser, FIG. 5 is a block diagram showing a laser beam control device of a second embodiment of the present invention, and FIG. 6 is a laser of a third embodiment of the present invention. FIG. 7 is a block diagram showing a beam control device, and FIG. 7 is a block diagram showing another aspect of the third embodiment of the present invention.

[0017]

First Embodiment A laser beam control apparatus according to the present embodiment is
It is a control system using the laser beam measurement apparatus of the embodiment. Referring to FIG. 1, a laser beam emitted from a laser oscillator 1 is incident on a partial reflection / transmission mirror 2 installed at an angle of 45 ° with respect to an optical path. Partial reflection mirror 2
Has a multi-layered thin film on its surface and transmits all but a slight reflection of the laser beam. The main beam transmitted through the partial reflection / transmission mirror 2 is used for laser processing.
The laser beam reflected by the partial reflection / transmission mirror may be used as the main beam, and the transmitted beam may be used for measurement. In this case, a partial reflection / transmission mirror having a characteristic of reflecting most of the beam and slightly transmitting it is used.

On the other hand, the measurement beam reflected in the vertical direction by the partial reflection / transmission mirror 2 enters the plane vibrating mirror 3. The illustrated plane vibration mirror 3 is a galvano mirror. Although the drawing conceptually shows one reflecting mirror, it is actually a combination of two reflecting mirrors, each of which has a rotation axis with a different direction, and the incident light is reflected by the first reflecting mirror. Then, the secondary surface can be scanned by being incident on and reflected by the second reflecting mirror. The tilt of the reflecting mirror surface can be reciprocated around the rotation axis at a constant speed or in a sinusoidal shape. The measurement beam is incident on the galvanometer mirror and is reflected, and is incident on the image sensor 4 while being two-dimensionally swung in accordance with the movement of the rotation axis. The image pickup device 4 is a CCD camera in which CCD devices are two-dimensionally arranged. Other cameras such as vidicons can also be used as long as they can photograph a plane.

When the two rotary shafts of the plane vibrating mirror 3 are reciprocally moved in a sinusoidal shape, the irradiation trajectory of the laser beam formed on the image pickup surface forms a Lissajous curve. For example, if the two rotary shafts reciprocate at the same frequency, the irradiation trajectory will draw a circle. A condensing optical system 5 and a dimming element 6 are provided between the plane vibrating mirror 3 and the image pickup element 4. Condensing optical system 5
Is a lens optical system that converges the measurement laser beam to form a sharp light spot on the image pickup surface of the image pickup device 4. Of course, it is also possible to use a reflective optical system configured by a reflecting mirror. Further, the dimming element 6 is a dimming filter that reduces the transmitted light intensity at a predetermined rate, and appropriately reduces the light intensity of the measurement laser to measure the amount of light that can be measured by the CCD element of the image pickup element 4. Has a function of limiting to.

For example, as shown in FIG. 2, the image pickup device 4 analyzes data by using a value corresponding to the accumulated light quantity as a measurement output for each detection cell along an irradiation trajectory formed by scanning the image pickup surface with a measuring laser. Supply to the device 7. The data analysis device 7 calculates the irradiation trajectory from the output of the image sensor 4 and also calculates the light intensity change at each point on the trajectory. Further, the change pattern of the light intensity is calculated by expanding the irradiation trajectory with time.

When measuring the pulse laser, the movement of the rotary shaft of the plane vibrating mirror 3 is appropriately adjusted to spatially separate the periodically repeated lighting period and extinguishing period. As shown in FIG. 3, the bright spot can be stopped at a fixed position of the Lissajous curve obtained on the imaging surface. In this way, when the bright spot position is stationary, the irradiation pulse is superposed on a fixed position on the locus, so that the light intensity pattern developed along the locus as shown in FIG. It will show the average value of the change. FIG. 4 shows the row of detection cells along the irradiation trajectory of the laser beam on the horizontal axis, and the illuminance that changes along the trajectory with the light intensity taken on the vertical axis. The graph shows the time change of the laser beam intensity. Will be represented. The data analysis device 7 can measure the intra-pulse intensity change of the pulse laser by analyzing the measurement output of the image sensor 4.

When the laser beam measuring apparatus according to the present embodiment is used, a part of the incident laser beam is extracted and measured. Therefore, even for a high-power laser beam, the light intensity and its change with time can be easily and easily measured. It can be measured in real time in the process. Further, when the laser oscillates in a pulsed manner, it is possible to average and measure the light intensity change pattern within the pulse by appropriately adjusting the movement of the plane vibrating mirror 3.

The laser beam controller of the present embodiment supplies the measurement result output from the data analyzer 7 to the controller 8. The control device 8 adjusts the movement around the rotation axis of the galvanometer mirror based on the shape of the irradiation trajectory drawn on the image pickup surface so that optimum light intensity measurement can be performed. Also,
The laser oscillator 1 is controlled based on the measured light intensity,
Adjust to the required laser intensity. Furthermore, the pulse oscillation state can be adjusted based on the measured value of the pulse period and the intensity change in the pulse.

[0024]

Second Embodiment A laser beam control apparatus according to the second embodiment is a laser beam measuring apparatus according to the second embodiment in which a processing laser after being converted into an oscillating beam by a galvanometer mirror is taken out by a partial reflection / transmission mirror for measurement. It is a control system using. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Referring to FIG. 5, the laser beam emitted from the laser oscillator 1 is reflected by the plane vibrating mirror 9 installed at an angle of 45 degrees with respect to the optical path and enters the partial reflection transmission mirror 10 inclined at an angle of 45 degrees. The plane vibrating mirror 9 is a galvanometer mirror, which oscillates about two axes and totally reflects the laser beam for processing to cause the laser beam to make an elliptic motion within a predetermined range. Since the galvano mirror used in this embodiment reflects the entire amount of the laser beam emitted from the laser oscillator 1, it is required to be much more robust than the plane vibrating mirror used in the first embodiment. It

The partial reflection / transmission mirror 10 is a reflection mirror having a multi-layered thin film on its surface, and slightly transmits the laser beam. The main beam reflected in the vertical direction by the partial reflection / transmission mirror 10 is converged by the condenser lens 11 and irradiated on the processing material 12 as an oscillating beam for laser processing. On the other hand, a condensing optical system 5 and a dimming element 6 are provided between the partial reflection / transmission mirror 10 and the image pickup element 4, and the measurement beam transmitted by the partial reflection / transmission mirror 2 oscillates two-dimensionally. However, it is appropriately dimmed to form an irradiation trajectory on the image pickup surface of the image pickup device 4, which is a two-dimensional CCD camera. The image pickup device 4 supplies the data analysis device 7 as a light intensity measurement output for each detection cell along the laser irradiation trajectory on the image pickup surface.

The data analysis device 7 calculates the irradiation trajectory and the light intensity change at each point on the trajectory, and develops the light intensity change pattern by expanding the irradiation trajectory over time. Since the imaging surface is at the focal point of the focusing optical system, the beam shape on the imaging surface is a far-field pattern, which is similar to the shape of the main beam at the processing point of the processing material. Is equivalent to measuring the beam intensity at. When measuring the pulsed laser, the Lissajous curve on the imaging surface is stopped by appropriately adjusting the rotational movement of the plane vibrating mirror 9 to know the laser intensity and the light intensity change in the pulse. You can As described above, with the laser beam measuring apparatus according to the present embodiment, the property of the processing laser beam at the processing point can be measured in-process in real time.

The measurement result output from the data analysis device 7 is supplied to the control device 8, which adjusts the movement around the rotation axis of the galvanometer mirror based on the shape of the irradiation trajectory on the imaging surface. , Adjust the processing conditions. Further, the laser oscillator 1 is controlled based on the measured value of the light intensity and the measured value of the pulse period and the change in the intensity of the pulse to adjust the laser intensity and the pulse oscillation state.

[0028]

[Third Embodiment] A laser beam control apparatus according to the third embodiment is configured to perform partial extraction and measurement immediately before irradiating a processing material with a processing laser used for beam oscillation.
It is a control system using the laser beam measurement apparatus of the embodiment. The same parts as those in the first or second embodiment are designated by the same reference numerals and the description thereof will be omitted. Figure 6
Referring to, the laser beam emitted from the laser oscillator 1 is reflected by the plane vibrating mirror 9 installed at an angle of 45 degrees with respect to the optical path, and reflected by the total reflection mirror 13 tilted by 45 degrees,
The condensing lens 11 converges and irradiates the processing material 12.

A partial reflection / transmission mirror 14 is inserted between the condenser lens 11 and the processing material 12, and a very small part of the laser beam is taken out as a measurement beam perpendicularly to the original optical path. The extracted measurement beam passes through the neutral density filter 6 and enters the image sensor 4. In the partial reflection / transmission mirror 14, the reflected laser may be a processing laser beam, and the transmitted laser may be measured. This is because an optical element that is not damaged even when a high-power laser passes is expensive.

In the configuration of this embodiment, a part of the processing laser beam that finally acts on the processing material is taken out and is converged on the image pickup surface at the focal position by using the condensing lens 11 for processing as it is. Because of the measurement, the measurement result corresponds very well to the shape of the main beam at the working point of the work material. That is, the irradiation trajectory formed by the measurement beam is similar to the trajectory drawn by the main beam on the processing material, and the light intensity measurement value of the measurement beam is similar to the intensity of the processing beam at the processing point. The output of the image sensor 4 is supplied to the data analysis device 7. The data analysis device 7 calculates the irradiation trajectory, the light intensity of the laser beam, and the light intensity change.

The control device 8 inputs the measurement output of the data analysis device 7, adjusts the galvanometer mirror based on the shape of the irradiation trajectory on the image pickup surface, performs suitable beam oscillation, and adjusts the processing conditions. . Further, the laser oscillator 1 is controlled based on the light intensity measurement value, the pulse period, and the measurement value of the intensity change in the pulse to adjust the laser oscillation.

The laser beam control system of the present embodiment has a galvanometer mirror 9 and a total reflection mirror 13 as shown in FIG.
It goes without saying that even if the positions of are switched, the same action and effect are exhibited. In the configuration of FIG. 7, since the optical path length from the galvano mirror 9 to the processing material 12 is short, it can be applied to the case where the amount of oscillation of the laser beam is reduced and fine processing is desired.

[0033]

As described above, according to the present invention, the characteristics of the laser beam can be measured in-process, and the laser device can be controlled online using the measured value. Furthermore, the measuring device of the present invention can measure the laser characteristics at the processing position, and can also measure the light intensity change within the pulse of the oscillating pulse laser.

[Brief description of drawings]

FIG. 1 is a block diagram showing a laser beam control device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing an irradiation trajectory on an image pickup surface in the present embodiment.

FIG. 3 is a schematic diagram showing a measurement state of a pulse laser in this example.

FIG. 4 is an output waveform diagram showing an example of an in-pulse light intensity change pattern of the pulse laser in the present embodiment.

FIG. 5 is a block diagram showing a laser beam control device according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a laser beam controller according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing another configuration example of the laser beam control device of the present embodiment.

[Explanation of symbols]

1 Laser oscillator 2 Partial reflection mirror 3 Plane vibrating mirror 4 image sensor 5 Focusing optical system 6 Dimming element 7 Data analysis device 8 control device 9 Galvo mirror 10 Partial reflection mirror 11 Condensing lens 12 Processing material 13 total reflection mirror 14 Partial reflection mirror

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01J 1/00-1/60 B23K 26/00-26/18 H01S 3/00

Claims (11)

(57) [Claims] 1. A partial reflection transmission mirror for extracting a part of an incident measured laser beam, a plane vibrating mirror having a rotation axis, a linear or two-dimensional image pickup device, and a data analysis device,
The plane vibrating mirror is periodically rotated around the rotation axis,
A part of the laser beam extracted by the partial reflection / transmission mirror is incident near the rotation axis of the planar vibrating mirror, is reflected by the planar vibrating mirror and is incident on the image sensor, and the image sensor is incident. A laser configured to output a measurement signal of the amount of received light at a position, and the data analyzer measures the characteristics of the laser beam to be measured based on the received light amount measurement signal in the laser beam trajectory formed on the image pickup device. Beam measuring device. 2. A plane vibrating mirror having a rotation axis, a partial reflection / transmission mirror for extracting a part of an incident light beam, a linear or two-dimensional image sensor, and a data analysis device, wherein the plane vibrating mirror is rotated. The laser beam to be measured is rotated about an axis periodically, and the measured laser beam is incident on the plane vibrating mirror in the vicinity of the rotating axis and is reflected, and is incident on the partial reflection / transmission mirror to be extracted from the laser beam. Part of the light enters the image sensor, the image sensor outputs a measurement signal of the amount of light received at the incident position, and the data analysis device locally changes the light intensity on the image sensor.
Imaging element along the laser beam path which is formed to expand in
A laser beam measuring device configured to measure a characteristic of a laser beam to be measured based on a received light amount measurement signal output from a child detection cell . 3. The plane vibrating mirror includes a two-axis rotating shaft,
The laser beam measuring device according to claim 1, wherein the image pickup device is an image pickup device having a two-dimensional detection surface. 4. The laser beam formed on the image sensor by synchronizing the oscillation period of the plane vibrating mirror with the pulse period of the laser beam, wherein the laser beam to be measured has a pulse oscillation characteristic with a constant period. The laser beam measuring device according to claim 1, wherein the trajectory is stabilized. 5. The laser beam to be measured has a pulse oscillation characteristic with a constant period, and the frequency of the plane vibrating mirror is swept so that the laser beam locus formed on the image sensor has a stable frequency. The laser beam measuring device according to any one of claims 1 to 4, wherein the pulse period of the measured laser beam is detected based on the pulse period. 6. A condensing optical system including a lens or a reflecting mirror is provided on a trajectory of the laser beam incident on the imaging device, and the imaging device is arranged at a focal position of the condensing optical system. The laser beam measuring device according to any one of claims 1 to 5. 7. The laser beam measuring device according to claim 6, further comprising a neutral density filter or a polarization filter on the trajectory of the laser beam incident on the image pickup device. 8. The laser beam measuring device according to claim 1, wherein the laser beam to be measured is a laser that performs laser processing. 9. A partial reflection / transmission mirror is provided between the focusing optical system and the image pickup device, the collecting optical system being provided on a trajectory of the laser beam incident on the image pickup device. A laser beam for laser processing and a laser beam incident on the image pickup device are separated, and the image pickup device is arranged at a focus position of the condensing optical system, and a processing position of the laser processing and the image pickup device. 9. The laser beam measuring device according to claim 8, wherein the positions of the image pickup surfaces are optically equivalent. 10. A laser oscillating device for generating the laser beam is adjusted based on the characteristics of the laser beam measured by the laser beam measuring device according to claim 1. Beam control device. 11. A laser beam control, wherein the rotation of the plane vibrating mirror is adjusted based on the characteristics of the laser beam measured by the laser beam measuring apparatus according to any one of claims 1 to 9. apparatus.