KR100491308B1 - Calibrating method of galvano scanner for lazer system - Google Patents

Abstract

The present invention relates to a drift and distortion correction method of a galvano scanner of a laser device. The drift and distortion correction method of the galvano scanner of the disclosed laser device, (a) measuring the drift of the galvano scanner; (b) if it is determined that the measured drift of the galvano scanner is out of a predetermined management range, correcting the drift of the galvano scanner; (c) measuring distortion of the second camera; (d) illuminating a standard image while adjusting an x-y mirror of the galvano scanner with an adjustment parameter value previously stored on the workpiece; (e) imaging the irradiated image with the second camera; (f) measuring a third deviation from the standard image after correcting the reflected image by reflecting the measured distortion of the second camera; And (g) changing and storing the adjustment parameter of the x-y mirror of the galvano scanner according to the third deviation.

Description

Calibrating method of galvano scanner for lazer system

The present invention relates to a drift and distortion correction method of a galvano scanner of a laser device, and more particularly, to measure and correct the drift of a galvano scanner, and to process the image and the standard image by using the galvano scanner with the drift corrected. A method of correcting the distortion of a galvano scanner to correct for deviations between.

If precise processing is required for fine processing using a laser device, it should be checked whether the fine processing is well done, and if it is not done well, the precision should be corrected by correcting the deviation. The deviation in laser processing is caused by the deviation due to the drift of the galvano scanner, the deviation from the camera which picks up the processed surface, and the distortion due to the distortion of the galvano scanner.

1 is a view schematically showing the configuration of a conventional laser processing system. Referring to FIG. 1, the laser beam oscillated from the laser oscillator 10 passes through the beam expander 12 to the x mirror 21 and the y mirror 22 and the f-theta lens 30 of the galvano scanner 20. The workpiece placed on the processing plate 40 is irradiated through the workpiece. And the processing state irradiated to the workpiece is reflected by the dichroic mirror 50 between the galvano scanner 20, the beam expander 12, and the galvano scanner 20 and is incident on the CCD camera 60. The image picked up by the camera 60 is compared with the standard image stored in the control unit 70 to adjust and output the galvano scanner 20 to correct the deviation.

2 is a view showing a phenomenon in which the irradiation position of the laser beam on the processing plate is drift by the drift of the galvano scanner. Referring to FIG. 2, it can be seen that the laser beam is irradiated to the point B out of a predetermined distance from the target point A. FIG. Correcting this drift simply corrects only the positional difference between the points A and B, which cannot solve the drift of the galvano scanner.

3A and 3B are diagrams illustrating a drift phenomenon of a galvano scanner.

In the galvano scanner, drift occurs due to the passage of time and the influence of the surrounding environment, which results in poor reproducibility, resulting in a decrease in laser processing quality.

Here, the drift means that the displacement of the galvano mirror measured by the position sensor measuring the position of the galvano mirror deviates from the predetermined position by the applied voltage.

3A and 3B are plots of the positions of the points irradiated onto the processing plate, that is, the actual distance (y-axis) according to the driving voltage (x-axis) of the galvano mirror, with solid lines indicating standard data and dotted lines The plotted data is plotted. Here, the drift is an offset drift (see Δy _{1 in} FIG. 3A) at which the angle of the galvano mirror deviates from the origin while the driving voltage of the galvano mirror is 0 V, and the distance at a given driving voltage. It can be distinguished by a gain drift in which displacement occurs (see Δy _{2 in} FIG. 3B).

4A to 4C are diagrams illustrating distortion of a camera capturing an image, in which the grid indicated by the dotted line is the actual grid, and the grid indicated by the solid line represents the grid photographed by the camera without scale.

As shown in FIG. 4A, a pincushion distortion phenomenon occurs in which a vertical line in the screen is bent or a corner screen is bent, and as shown in FIG. 4B, an image produced by the camera lens is reduced at the edge of the field of view. distortion phenomenon appears, and when they are synthesized, the camera distortion phenomenon as shown in FIG.

Accordingly, since the image photographed by the camera 60 is distorted by the distortion of the camera as illustrated in FIGS. 4A to 4C, the information distorted is input to the control unit 70, and thus the galvano scanner 20 is controlled from the control unit 70. There is a problem that the x mirror 21 and y mirror 22 adjustment values, which are output as N, are also distorted. That is, the control of the control unit 70 based on the distorted information causes the distortion of the galvano scanner 20.

In addition, when the dichroic mirror 50 is between the f-theta lens 30 and the laser oscillator 10, the difference in the refractive index of the visible light and the laser beam of the image in the processing plane in the f-theta lens 30 Due to this, there is a problem that the position of the image of the processing surface is incident to the camera to be distorted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a laser device for stepwise correcting the distortion from the galvano scanner and the distortion from the camera for imaging the object. To provide a method for correcting drift and distortion of galvano scanners.

In order to achieve the above object, the distortion correction method of the galvano scanner of the laser device of the present invention, the laser beam from the laser oscillator irradiates the workpiece placed on the processing plate through the galvano scanner and f-theta lens, a half mirror for passing a laser beam between the f-theta lens and the workpiece and partially reflecting visible light, and a first CCD camera for imaging the workpiece through the half mirror, disposed between the laser oscillator and the galvano scanner A method for correcting drift and distortion of a galvano scanner of a laser system comprising a second CCD camera for observing the workpiece through a decoded mirror,

(a) measuring the drift of the galvano scanner;

(b) if it is determined that the measured drift of the galvano scanner is out of a predetermined management range, correcting the drift of the galvano scanner;

(c) measuring distortion of the second camera;

(d) illuminating a standard image while adjusting an x-y mirror of the galvano scanner with an adjustment parameter value previously stored on the workpiece;

(e) imaging the irradiated image with the second camera;

(f) measuring a third deviation from the standard image after correcting the reflected image by reflecting the measured distortion of the second camera; And

and (g) changing and storing the adjustment parameter of the x-y mirror of the galvano scanner according to the third deviation.

In step (a),

(a1) driving an x-y mirror of the galvano scanner to target a standard point on the processing plate;

(a2) imaging the standard point with the first camera;

(a3) calculating a first deviation between the coordinates of the standard point and the coordinate of the photographed standard point;

(a4) repeating the steps at a plurality of standard points;

(a5) measuring an offset drift of the galvano scanner; And

(a6) measuring a gain drift of the galvano scanner.

Preferably, the plurality of standard points form a straight line, and the straight line passes a standard point on the processing plate corresponding to the origin of the galvano scanner.

In step (b),

(b1) correcting offset drift of the galvano scanner; And

(b2) correcting the gain drift of the galvano scanner.

Step (c) is,

(c1) placing a standard image on the processing plate and photographing the standard image with the camera;

(c2) calculating a second deviation between the standard image and the captured image; And

(c3) storing the second deviation in a control unit for controlling the galvano scanner.

In addition, the standard image is preferably a grid image covering the entire area of the workpiece.

Hereinafter, a distortion correction method of a galvano scanner of a laser device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this process, the thicknesses of layers or regions illustrated in the drawings are exaggerated for clarity.

5 is a view showing the configuration of a laser processing apparatus applied to a preferred embodiment of the present invention, the same reference numerals are used for the same components as those of the conventional invention, and detailed description thereof will be omitted.

Referring to FIG. 5, a laser processing apparatus includes a laser oscillator 10, a beam expander 12 that enlarges a laser beam oscillated from the laser oscillator 10, and the enlarged laser beam in a predetermined region. And a galvano scanner 20 for scanning in the XY direction, and an f-theta lens 30 for the incident laser beam to form a focal spot of the same size over the whole of the processing area. Reference numerals 21 and 22 reflect laser beams incident as x and y mirrors, respectively, and each mirror is connected to a drive driver (not shown) and changes its angle in accordance with an input command.

A dichroic mirror 150 is disposed between the beam expander 12 and the galvano scanner 20 to transmit an incident laser beam and reflect visible light. The visible light reflected from the dichroic mirror 150 is incident to the first CCD camera 160. The first CCD camera 160 receives the light from the workpiece on the processing plate 40 to generate an electrical image signal. The image signal captured by the camera 160 is transmitted to the control unit 170.

In addition, the f-theta A half mirror 180 is disposed between the lens 30 and the processing plate 40 to transmit an incident laser beam, and transmit only a part of visible light and reflect the rest. The visible light reflected from the half mirror 180 is incident to the second CCD camera 190 through the reflection mirror 182.

The CCD cameras 160 and 190 receive light from the workpiece on the processing plate 40 to generate an electrical image signal. The image signal captured by the cameras 160 and 190 is transmitted to the control unit 170. In addition, when the loss of image and the accuracy of the workpiece are lacking due to the limitation of the angle of view of the camera, a plurality of, for example, four cameras may divide the image of the entire workpiece into photographs and then resynthesize.

Charge coupled devices (CCDs) of the CCD cameras 160 and 190 are photoelectric conversion sensors that convert light into electric signals. The intensity of light entering the lens (not shown) in front of the cameras 160 and 190 is first recorded in the CCD. At this time, the light of the captured image is separated into different colors by the RGB color filter attached to the CCD. The separated colors are converted into electrical signals by the hundreds of thousands of light sensors (corresponding to the pixels) that make up the CCD. The analog signal from the CCD is converted into digital signals of 0 and 1, and an image signal is produced and output.

The control unit 170 controls the reflection angles of the x-y mirrors 21 and 22 of the galvano scanner 20 by data stored in predetermined software.

The distortion correction method of the galvano scanner according to the present invention using the laser device will be described in detail.

6 is a flowchart of a drift and distortion correction method of a galvano scanner of a laser device according to the present invention, and FIG. 7 is a flowchart of a drift measurement method of a galvano scanner.

First, a method of correcting drift of the galvano scanner 20 with the first CCD camera 160 will be described with reference to FIGS. 6 and 7. It is determined whether the drift of the galvano scanner 20 is to be measured (step 10).

When the drift of the galvano scanner 20 is measured (step 20), the xy mirrors 21 and 22 of the galvano scanner 20 are driven to target a predetermined standard point on the processing plate 40. (Step 21).

Subsequently, the standard point is captured by the first camera 150 (step 22). The standard point is reflected by the dechroic mirror 150 through the half mirror 180, the f-theta lens 30, and the galvano scanner 20 to be incident on the center of the first camera 160. The xy mirrors 21 and 22 of (20) must be adjusted. However, when a drift of the galvano scanner 20 occurs, the target standard point is out of a predetermined distance from the center point of the camera 160, and the captured standard point is located at the center of the camera 160.

Next, a first deviation between the coordinates of the target standard point and the coordinates of the picked standard point is calculated, and the result is stored in the control unit 17 (step 23).

Subsequently, the number of measured standard points is counted (step 24), and when the number of counts is less than the predetermined number N, step 21 is performed again (step 25). The predetermined plurality of standard points are located on a straight line passing through the origin of the x-y mirror 22 of the galvano scanner 20, and preferably pass obliquely through the processing target area.

When the count number reaches N, the drift of the galvano scanner 20 is calculated. First, the first deviation of the origins of the xy mirrors 21 and 22 of the galvano scanner 20, for example, the reference point at which the driving voltage corresponds to 0 volts is calculated, and is calculated by the offset drift of the galvano scanner 20. (Step 26).

Subsequently, coordinate shift is performed to solve the offset drift of the virtual straight line formed of the captured standard points, and then a gain drift corresponding to a deviation of the inclination with a straight line consisting of predetermined standard points is calculated (step 27). .

From the drift measurement result of the galvano scanner 20, it is determined whether the drift correction of the galvano scanner 20 is to be performed (step 30).

When correcting the drift of the galvano scanner, the drift of the galvano scanner 20 is corrected through a correction algorithm stored in the control unit 170 of the laser system (step 40). Specifically, the drift correction of the galvano scanner 20 includes correcting the offset drift of the galvano scanner 20 and correcting the gain drift.

Correction of the offset drift, as shown in Figure 3a, the coordinate transformation to correct the displacement of the standard point corresponding to the origin of the scanner.

Gain drift correction is a process of converting from the slope of the measured value converted to the standard slope to reflect the offset drift. To this end, the driving voltages of the x-y mirrors 21 and 22 are adjusted.

If it is determined that the drift measurement of the galvano scanner 20 is not performed in the tenth step or if it is determined that the drift correction of the galvano scanner 20 is not performed in the thirtieth step, a fifty-second step will be described.

Next, before correcting the distortion of the galvano scanner 20 for guiding the laser beam to the workpiece on the workpiece plate 40, first, the distortion of the second CCD camera 190 for imaging the workpiece on the workpiece plate 40. It describes how to measure.

First, it is determined whether the distortion of the second CCD camera 190 that picks up the image is measured (step 50).

When the distortion of the second camera 190 is measured, the standard grid is placed on the processing plate 40 and the image of the standard grid is captured by the CCD camera 190 (step 60). In this case, the standard grid is a grid covering the entire area of the machining area, and it is preferable that the intersection points are formed by x, y coordinates. In addition, it is preferable that the center point of the grid overlaps the standard point used in the drift correction process of the galvano scanner.

Next, the second deviations dx ₂ and dy ₂ at each intersection point between the grid of the camera 190 that has captured the standard grid and the standard grid are measured (step 12). The deviations dx ₂ and dy ₂ are large at the edge where the distortion phenomenon of the camera 160 is large and less at the center. The deviation at the point between the intersections is obtained by bilinear interpolation by two intersections. The second deviations dx ₂ and dy ₂ are stored in the control unit 170 (step 62).

Next, a method of correcting the processing distortion of the galvano scanner 20 with the camera 190 in which the distortion phenomenon is measured will be described.

First, a predetermined standard grid image is processed on the machining surface on the machining plate 40 while adjusting the xy mirrors 21 and 22 using the galvano scanner 20 of the laser processing apparatus as the stored adjustment parameter value (step 13). . This standard grid image may be the same as the standard grid in step 60.

Subsequently, the grid image irradiated onto the processing surface is imaged by the camera 190 in which the distortion degree is measured in the above step. The coordinates (x, y) of each of the grids measured in this way are converted into the corrected coordinates (x, y) by applying the second deviation (dx ₂ , dy ₂ ) reflecting the distortion of the camera in the above step. Then, the third deviation dx ₃ , dy ₃ between the transformed coordinate value and the position (x, y) of the corresponding grid of the standard grid is calculated (step 80).

Next, the control unit 170 stores an output value for changing the reflection angles of the x mirror 21 and the y mirror 22 of the galvano scanner 20 to reflect the third deviation dx ₃ and dy ₃ . (Step 90).

Subsequently, it is determined whether or not the galvano scanner 20 has been corrected, and if correction is to be performed again, step 70 is performed again. If it is determined that the calibration is completed, the calibration step of the galvano scanner is ended (step 92).

If it is determined in step 50 that camera distortion measurement is not performed, step 70 is performed.

As described above, according to the drift and distortion correction method of the galvano scanner of the laser device according to the present invention, the galvano scanner is calibrated after the primary correction of the galvano scanner and the camera photographing the laser processed image. By doing so, there is an advantage in that high precision of laser processing can be ensured.

Although the present invention has been described with reference to the embodiments with reference to the drawings, this is merely exemplary, it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined only by the appended claims.

1 is a view schematically showing the configuration of a conventional laser processing system.

2 is a view showing a phenomenon in which the irradiation position of the laser beam on the processing plate is drift by the drift of the galvano scanner.

3A and 3B are diagrams illustrating a drift phenomenon of a galvano scanner.

4A to 4C are diagrams illustrating distortion of a camera photographing an image.

5 is a view showing the configuration of a laser processing apparatus applied to a preferred embodiment of the present invention.

6 is a flowchart illustrating a drift and distortion correction method of a galvano scanner of a laser device according to the present invention.

7 is a flowchart illustrating a drift measurement method of a galvano scanner according to the present invention.

* Description of Signs of Major Parts of Drawings *

10: laser oscillator 12: beam expander

20: galvano scanner 21: x mirror

22: y mirror 30: f-theta lens

40: processing plate 50, 150: dichroic mirror

60, 160, 190: CCD camera 70, 170: control unit

Claims (9)

A half mirror for irradiating a laser beam from a laser oscillator to a workpiece placed on a processing plate through a galvano scanner and an f-theta lens, passing a laser beam between the f-theta lens and the workpiece and partially reflecting visible light; A first CCD camera for imaging the workpiece through the half mirror, and a second CCD camera for observing the workpiece through a dichroic mirror disposed between the laser oscillator and the galvano scanner. In the method for correcting the drift and distortion of the galvano scanner, (a) measuring the drift of the galvano scanner with the first CCD camera; And (b) if it is determined that the measured drift of the galvano scanner is out of a predetermined management range, correcting the drift of the galvano scanner; (c) measuring distortion of the second CCD camera; (d) illuminating a standard image while adjusting an x-y mirror of the galvano scanner with an adjustment parameter value previously stored on the workpiece; (e) imaging the irradiated image with the second CCD camera; (f) measuring a third deviation from the standard image after correcting by reflecting the measured distortion of the second CCD camera to the captured image; And (g) changing and storing the adjustment parameter of the x-y mirror of the galvano scanner according to the third deviation; and drift and distortion correction method of the galvano scanner of the laser device, characterized in that it further comprises. The method of claim 1, wherein step (a) comprises: (a1) driving an x-y mirror of the galvano scanner to target a standard point on the processing plate; (a2) imaging the standard point with the first camera; (a3) calculating a first deviation between the coordinates of the standard point and the coordinate of the photographed standard point; And (a4) repeating the steps at a plurality of standard points; a drift and distortion correction method of a galvano scanner of a laser apparatus, comprising: a. The method of claim 2, And the plurality of standard points form a straight line. The method of claim 3, wherein And the straight line passes a standard point on the processing plate corresponding to the origin of the galvano scanner. The method of claim 4, wherein (a5) measuring an offset drift of the galvano scanner; And (A6) measuring the gain drift of the galvano scanner; further comprising the drift and distortion correction method of the galvano scanner of the laser device. The method of claim 2, wherein step (b) comprises: (b1) correcting offset drift of the galvano scanner; And (b2) correcting the gain drift of the galvano scanner. delete The method of claim 1, wherein step (c) comprises: (c1) placing a standard image on the processing plate and imaging the standard image with the second CCD camera; (c2) calculating a second deviation between the standard image and the captured image; (c3) storing the second deviation in a control unit that controls the galvano scanner. The method of claim 8, The standard image is a grid image covering the entire area of the workpiece, the drift and distortion correction method of the galvano scanner of the laser device.