JPH0999386A - Automatic alignment device for laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically correct the installation angles of reflection mirrors in correspondence to the installation angle errors of these reflection mirrors and the distortions of the guide shafts of the reflection mirrors. SOLUTION: Plural stages of the reflection mirrors 2c, 2d, 2e are successively rectilinearly moved from the mirrors more proximate to a laser oscillator 1 toward the other end from the one end of the guide shafts. Simultaneously, the eccentric rates having the first projection position of a light spot as the origin are stored in association with the moving distances of the reflection mirrors at every specified moving increment of the reflection mirrors by the CCD photodetectors disposed on a laser output nozzle 4 side. The ratios of the eccentric rates of the light spot with respect to the moving distances of the reflection mirror are calculated as a linear proportional relation by an approximation means, such as method of least squares. The reflection mirror just before the moved reflection mirror is corrected to the correct installation angle by a motor in accordance with the calculated linear proportional relation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic laser beam alignment apparatus for a laser robot.

[0002]

2. Description of the Related Art In a multi-axis laser robot in which a laser output nozzle is movable in three dimensions, a laser beam emitted from a laser oscillator is guided to the output nozzle via a plurality of stages of reflecting mirrors. The reflecting mirrors are arranged so that they can be moved closer to each other or separated from each other, and the at least three reflecting mirrors movable in the X, Y, and Z directions perform the above-mentioned approaching / separating operation.

By the way, if the installation angle of each reflecting mirror is not adjusted accurately, the laser beam will not be incident on the focusing mirror immediately before the output nozzle at the correct position and angle, and a good laser spot diameter will be obtained on the surface of the work. I can't.

Therefore, in the conventional apparatus, an observable He-Ne (helium-neon) laser beam for adjustment is used to determine whether or not this beam is accurately incident on the center of each reflecting mirror. It has been performed that the attached target plates and the like are erected immediately before the reflecting mirror and visually checked one by one. When the light spot of the laser beam is off the center of the scale of the target plate, the reflecting mirror immediately before is manually adjusted to swing so as to coincide with the center of the scale.

However, such manual alignment is very inefficient. The reflecting mirror has to be removed for regular cleaning, but at present, it is necessary to perform a troublesome alignment work each time the mirror is attached and removed, and the cleaning must be postponed or omitted due to the operational need. Sometimes you don't get. However, regular cleaning of the reflecting mirror is very important, and it is not uncommon for the reflecting mirror to be fogged to reduce the laser output by 10% or more. When a laser is used with an output below the rating in this way, the work melting depth suddenly becomes shallow and welding defects are likely to occur. Even if a small amount of dust adheres to the reflecting mirror, the laser energy is absorbed by the dust and heats up, melting the gold thin film coated on the reflecting mirror to open a pinhole, and the gold thin film starts from this pinhole. They peel off one after another and the life of the reflecting mirror is shortened rapidly. Therefore, regular cleaning and alignment of the reflector is essential.

Therefore, recently, for example, Japanese Patent Laid-Open No. 3-180 has been proposed.
Automatic alignment with devices such as that disclosed in No. 292 is becoming popular. This device is equipped with a sensor that detects the amount of eccentricity of the laser beam from the normal projection position on the laser output nozzle side, and it is moved linearly sequentially from the reflecting mirror closer to the laser oscillator, and the eccentricity of the laser beam at that time is adjusted. In order to correct it, the installation angle of the reflector immediately before the moved reflector is automatically corrected.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The apparatus of No. 0292 is very convenient because it can perform automatic alignment, but there are still unsolved problems in terms of adjustment accuracy. That is, this automatic alignment device is premised on that the linear guide axis of the reflecting mirror is exactly a straight line, but there are inevitably small and irregular distortions in the actual guide axis, although there are differences in degree. To do. Therefore, when the reflecting mirror is placed at two positions before and after the movement on the linear guide axis and the installation angle error of the reflecting mirror immediately before the reflecting mirror is calculated from the eccentricity of the laser beam on the laser output nozzle side at that time, The distortion of the guide shaft in the middle part of the movement is completely ignored. That is, extremely speaking, if there is no distortion in the guide axis at the start and end points of movement of the reflecting mirror,
No matter how large the distortion is in the middle of the axis, it is completely ignored. As a result, the spot diameter of the laser beam projected from the laser output nozzle is set to a predetermined value due to the distortion of the intermediate portion of the guide shaft depending on the moving position of the laser output nozzle, although the installation angle of the reflecting mirror is corrected. Inconvenience that it does not converge to the size of

An object of the present invention is to make an optimum correction of the installation angle of the reflecting mirror by taking into consideration not only the installation error of the reflecting mirror but also the irregular distortion over the entire length of the guide axis of the reflecting mirror. Of the laser output nozzle, the spot diameter of the laser beam projected from the laser output nozzle does not deviate from the permissible tolerance range of the normal diameter in the entire movement stroke of the laser output nozzle.

[0009]

In order to solve the above problems, the present invention solves the above problems by eccentricizing a laser beam projected from a laser output nozzle at every constant movement increment while a reflecting mirror moves from one end to the other of a guide shaft. The amount of eccentricity is stored in association with the amount of movement from the movement start point of the reflecting mirror, and the ratio of the amount of eccentricity to the moving distance of the reflecting mirror is approximated by a linear proportional relationship from the stored values of a large number of eccentricities. Based on the proportional relationship, the immediately preceding reflecting mirror is adjusted to the correct angle by the swinging means, so that the optimum laser spot diameter can always be obtained at any moving position of the laser output nozzle.

In the laser alignment apparatus configured as described above, even if the installation angle of each reflecting mirror is correct and the guide axis of the reflecting mirror is a straight line without distortion, even if the reflecting mirror is moved linearly. The position and angle of the laser beam incident on the condenser mirror immediately before the laser output nozzle do not change, the laser beam is always projected on the regular projection position on the laser output nozzle side, and the laser spot diameter also converges within the allowable tolerance range.

On the other hand, if there is an error in the installation angle of a certain reflecting mirror or if there is a distortion in a certain guide axis, when the reflecting mirror immediately after the relevant reflecting mirror is moved along the guide axis, The position and angle of the laser beam incident on the optical mirror may change, the laser beam may deviate from the regular projection position on the laser output nozzle side, and the laser spot diameter may deviate from the allowable tolerance range in the excessive or excessive direction.

The present invention is based on the conventional Japanese Patent Laid-Open No. 3-180292.
No. 1 does not detect only the start and end of the movement locus of the laser beam projection spot, but the sensor detects the amount of eccentricity of the laser beam on the laser output nozzle side at each constant movement increment of the reflecting mirror. As a result, the distortion over the entire length of the guide shaft of the reflecting mirror is indirectly detected by the sensor as the amount of eccentricity of the laser beam. For this eccentricity,
Both those based on the installation error of the reflecting mirror and those based on the distortion of the guide axis are included.

The eccentricity amount of the laser beam is stored in the storage means in association with the movement amount of the reflecting mirror from the movement start point, and the ratio of the eccentricity amount to the moving amount of the reflecting mirror is linear by the approximation means such as the least square method. It is calculated in proportion. Based on this linear proportional relationship, the correction angle of the reflecting mirror immediately before the moved reflecting mirror is calculated, the reflecting mirror immediately before the moving mirror is corrected to the correct installation angle by the swinging means, and the laser beam serves as the guide axis of the reflecting mirror. It will proceed in a parallel direction. At this time, the partial distortion of the guide shaft is replaced with the uniform inclination of the entire guide shaft by the least square method and processed.

The least-squares method is schematically described. The horizontal axis represents the movement amount of the reflecting mirror and the vertical axis represents the eccentricity amount, and the relationship between the two is tentatively approximated by a straight line. This is one method of approximating means for calculating the total sum of squares of perpendicular distances drawn from each eccentricity plot point on a straight line and obtaining an approximate straight line that minimizes the total sum value. So this approximation means
This is a method of representatively replacing the entire inclination of one curve that continuously connects the eccentricity plot points for each increment of constant movement of the reflecting mirror with one straight line. Multiplication method, least n-th power method (n = 4,5,
…), The arithmetic mean method, etc. can be adopted.

Since the influence of the error in the installation angle of the reflecting mirror is accumulated as it approaches the output nozzle, the error is corrected sequentially from the reflecting mirror closer to the laser oscillator. The respective reflecting mirrors are sequentially oscillated and corrected by the oscillating means to correct the installation angle. When this correction is completed, eccentric movement of the laser beam and excess or deficiency of the laser spot diameter on the output nozzle side do not occur regardless of which reflector is linearly moved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the automatic alignment apparatus of the present invention is applied to a three-axis laser robot will be described below with reference to the drawings. FIG. 1 schematically shows a three-axis laser robot. This laser robot includes a processing laser oscillator 1, a plurality of stages of reflecting mirrors 2a, 2b ... 2e, a final stage condenser mirror 3, and a laser output. It has a nozzle 4. Reflecting mirror 2
c, 2d and 2e are movable in X, Y and Z directions by a linear guide shaft (not shown) in order to process the work 5 while moving the output nozzle 4 in three dimensions. . On the other hand, the other reflecting mirrors 2a and 2b are positioned at predetermined positions. Further, since the reflecting mirror 2e, the condenser mirror 3 and the output nozzle 4 are integrally assembled to the laser head portion, their relative positional relationship is unchanged. The laser oscillator 1 is replaced with a He-Ne laser oscillator for adjustment so as not to damage the CCD light receiving element 9 described later only during automatic alignment.

As shown in FIG. 2, the CCD light receiving element 9 is attached to the output nozzle 4 at a predetermined distance from the output nozzle 4 and at a right angle to the output nozzle 4 by means of a removable metal fitting 10. This CCD light receiving element 9 is for detecting the amount of eccentricity of the laser spot S. As long as it has the same function, a semiconductor position detecting element (PSD) applying a photodiode or a laser spot S is used. It may be various cameras capable of capturing images. The output nozzle 4 and the CCD light receiving element 9 need not be aligned with each other. This is because the position of the laser spot S at the movement start point of the reflecting mirror is set as the origin, and the eccentric amount of the laser spot S from the origin due to the movement of the reflecting mirror may be measured for each predetermined increment of movement of the reflecting mirror.

The reflecting mirrors 2b, 2c and 2d are provided with swinging means for automatically correcting the installation angle. This swinging means supports the reflecting mirror at three points, and the reflecting mirror 2b
As for the swinging means, as shown in FIGS. 3 and 4, the two motors 11a and 11b for individually driving the two screws screwed to the rear surface edge of the reflecting mirror 2b and the rear surface edge portion are provided. It is composed of a fulcrum pin 12 that abuts and supports it. The swinging means has the same structure for the other reflecting mirrors 2c and 2d.

The CCD light receiving element 9 is connected to a drive circuit 14 for the motors 11a and 11b via an arithmetic circuit 13, as shown in FIG. The arithmetic circuit 13 includes the reflecting mirror 2b.
For each constant movement increment (for example, every 1 cm), the eccentricity amount having the first projection position of the light spot S from the CCD light receiving element 9 as the origin is stored in association with the movement distance from the movement start point of the reflecting mirror 2b, and a minimum of two is stored. An error of the installation angle of the reflecting mirror 2b is calculated by multiplication, and a command signal for correcting this error is input to the motor drive circuit 14. The smaller the constant movement increment is, the more accurately the distortion of the guide axis of the reflecting mirror is detected as the number of detection points is increased.
The configuration of FIG. 4 is the same for the other two reflecting mirrors 2c and 2d.

In the present embodiment, the relationship between the moving distance of the reflecting mirror and the eccentricity of the laser spot is linearly approximated by the least square method. This approximation method will be described with reference to FIG. 5A and 5B, the horizontal axis represents the moving distance of the reflecting mirror, and the vertical axis represents the eccentricity of the laser spot. The left end of the horizontal axis corresponds to the movement start point on the guide axis of the reflecting mirror (the point closest to the previous reflection mirror), and the right end of the horizontal axis corresponds to the movement end point (the point farthest from the previous reflection mirror). In FIG. 5A, since the distortion of the guide axis of the reflecting mirror is small, the plot points of the eccentricity amount are not so far apart from the approximate straight line. On the other hand, FIG.
In (B), since the distortion of the guide axis of the reflecting mirror is large, the plot points of the eccentricity amount show undulations.

If the distortion of the guide axis is small as shown in FIG. 5 (A), even if the reflecting mirror is corrected by the conventional alignment by the linear relationship connecting the first and last two plot points of the eccentricity amount, the laser The diameter of the laser beam projected from the output nozzle does not largely deviate from the tolerance range.
However, when the distortion of the guide axis is large as shown in FIG. 5B, the reflecting mirror may be corrected by the linear relationship (two-dot chain line) connecting the plot points of the first and last two points of the eccentricity.
The plot points in the middle are greatly separated from the chain double-dashed line. This means that the diameter of the laser beam projected from the laser output nozzle becomes too large or too small outside the allowable tolerance range when the reflecting mirror is moving in the middle part of the guide shaft.

In this embodiment, instead of connecting the first and last two plot points, a straight line that minimizes the sum of squares of the perpendicular distances drawn from each plot point, that is, an approximate straight line by the least square method is used. The angle correction value of the reflecting mirror is calculated from the tilt angle. According to this method, the amount of eccentricity of each laser spot is reflected on the inclination angle of the approximate straight line, and by extension is reflected on the angle correction value of the reflecting mirror, the diameter of the laser beam projected from the laser output nozzle is equal to the normal diameter. It converges within the allowable tolerance range.

Next, the automatic alignment according to the above embodiment will be described. First, before starting the automatic alignment, the laser oscillator 1 is replaced with a He-Ne laser oscillator for adjustment, and the CCD light receiving element 9 is attached to the output nozzle 4 as shown in FIG. And He-Ne laser beam is CC
The installation angles of the reflecting mirrors 2b to 2d are roughly adjusted so as to reach the D light receiving element 9. This rough adjustment is performed by the motors 11a, 11
b is manually controlled. After that, the following alignment is automatically performed by turning on a predetermined start switch.

First, the reflecting mirror closer to the laser oscillator 1, that is, the reflecting mirror 2c to the reflecting mirror 2e in this embodiment.
Are sequentially moved linearly at a constant speed from the end of the guide shaft closer to the front reflector to the end on the opposite side. This moving direction may be opposite. FIG. 3 shows an example in which the reflecting mirror 2c is moved from the first position at one end of the guide shaft to the second position at the other end. If there is an error in the installation angle of the reflecting mirror 2b immediately before the reflecting mirror 2c, the reflection point of the laser beam B on the reflecting mirror 2c moves when the reflecting mirror 2c is moved, so that the CCD
The position of the light spot S also moves on the light receiving element 9.

The eccentricity amount with the first projection position of the light spot S as the origin is continuously detected by the CCD light receiving element 9, and from the movement starting point at every constant movement increment of the reflecting mirror 2c (for example, every 1 cm movement). Is input to the arithmetic circuit 13 in association with the moving distance of the. The arithmetic circuit 13 stores the data relating to the eccentricity amount, calculates the linear proportional relationship between the moving distance of the reflecting mirror and the eccentricity amount of the laser spot by the approximation method of FIGS. A control signal to the motor drive circuit 14 based on the
Is driven to automatically correct the swing of the reflecting mirror 2c to the correct installation angle.

The relationship between the inclination angle of the approximate straight line and the installation angle error of the reflecting mirror 2b is stored in the arithmetic circuit 13 in advance. Accordingly, when the inclination angle of the approximate straight line is input to the arithmetic circuit 13, the angle error of the reflecting mirror 2b is calculated. Then, a command signal for correcting this error is input to the drive circuit 14, the motors 11a and 11b are driven, and the reflecting mirror 2b is automatically corrected to a correct installation angle. This correction angle corresponds to the distortion of the guide shaft that could not be taken into consideration at the design stage, and does not simply correct the reflecting mirror 2b to the designed installation angle.

Next, the same angle correction is performed on the reflecting mirrors 2c and 2d.
After all angle corrections are completed, the He-Ne laser oscillator is replaced with the original laser oscillator 1 for processing, the CCD light receiving element 9 is removed, and the alignment work is completed.

[0028]

As described above, according to the present invention, the reflecting mirror is linearly moved from one end to the other end of the guide shaft sequentially from the side closer to the laser oscillator, and the laser beam is emitted by the sensor provided on the laser output nozzle side. The amount of eccentricity is detected, and this amount of eccentricity is stored in association with the moving distance for each constant movement increment of the reflecting mirror, and the ratio of the amount of eccentricity to the moving distance of the reflecting mirror is approximated as a linear proportional relationship by an approximating means. Since the reflection mirror is oscillated and corrected to the correct installation angle based on the proportional relationship, not only the laser spot diameter is excessive or insufficient due to the original installation angle error of the reflection mirror, but also the laser spot due to the distortion of the guide axis. The excess and deficiency of the diameter can be corrected at the same time. Therefore, the optimum laser spot diameter can always be obtained at any moving position of the laser output nozzle.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a three-axis laser robot.

FIG. 2 is a sectional view of an output nozzle section.

FIG. 3 is a plan view showing a reflection state of a laser beam.

FIG. 4 is a block diagram showing swing control of a reflecting mirror.

FIG. 5A is a diagram showing the relationship between the moving distance of the reflecting mirror and the eccentricity of the laser spot when the distortion of the guide axis is relatively small, and FIG. 5B shows the relationship when the distortion of the guide axis is relatively large. The figure which shows the relationship between the moving distance of a reflecting mirror, and the amount of eccentricity of a laser spot.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 laser oscillator 2a-2e reflecting mirror 3 condensing mirror 4 work 9 CCD light receiving element 10 fixing metal fittings 11a, 11b motor 12 fulcrum pin 13 arithmetic circuit 14 motor drive circuit B laser beam S light spot

Claims (3)

[Claims] 1. A laser beam emitted from a laser oscillator is guided to a laser output nozzle through a plurality of stages of reflecting mirrors, and the mutual spacing of the reflecting mirrors is made closer to or further from each other along a guide axis so that the laser output nozzle is made to move. In a moving laser robot, moving means for moving the reflecting mirror from one end of the guide shaft to the other end in a straight line from a position closer to the laser oscillator, and a laser output nozzle disposed in front of the laser output nozzle. A sensor for detecting the amount of eccentricity of the laser beam, a storage unit for storing the amount of eccentricity of the laser beam in association with the moving distance for each fixed increment of the moving distance of the reflecting mirror, and the storage unit An approximation means for approximating the ratio of the eccentricity to the moving distance of the reflecting mirror in a linear proportional relationship based on the values of the large number of eccentricity, and the moving distance and the deviation of the reflecting mirror. The amount and automatic alignment device of the laser beam, characterized by comprising a rocking means for rocking corrected to the correct mounting angle reflector of the immediately preceding based on linear proportional relationship. 2. The automatic laser beam alignment apparatus according to claim 1, wherein the approximating means approximates the ratio of the eccentricity amount to the moving distance of the reflecting mirror in a linear proportional relationship by the method of least squares. 3. The automatic laser beam alignment apparatus according to claim 1, wherein said approximating means approximates the ratio of the eccentricity amount to the moving distance of the reflecting mirror in a linear proportional relationship by the arithmetic mean method.