JPH063186A - Laser light detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a laser light detection device capable of accurately detecting the transverse mode and temporal variation of laser light in a short time with a simple mechanism. [Structure] A round bar 1A is provided which turns around a point M as an axis and crosses a light flux A of laser light at its tip. Plural pyro detectors 2x1 to 2x10 and 2y1 to 2 are provided on the left and right of the laser beam A.
Place y10. The intensity of the laser light beam at each reflection point of the light flux A of the laser light detected by each pyro detector and the detected value of the turning angle of the round bar are input to the microcomputer 6 for calculation to calculate the light flux A of the laser light. Detects the transverse mode of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam detecting device for detecting the position of the optical axis and the intensity distribution of laser beam emitted from a laser device.

[0002]

2. Description of the Related Art For example, in a laser device used for a carbon dioxide laser processing machine, the transmission path of laser light becomes long and complicated due to the increase in size and the increase in the number of operation axes. In such a laser device, for example, the optical axis of the laser beam or the spatial distribution of the beam of the laser beam, the so-called transverse mode, changes due to, for example, the temperature rise of the components of the transmission path of the laser beam and the deformation and deterioration of the optical components. Sometimes. If this transverse mode changes, the power required for laser processing and the processing accuracy will decrease, so the laser device must monitor the position of the optical axis of the laser beam and the spatial distribution of the beam of the laser beam. .

Therefore, conventionally, as shown in FIG. 6A, for example, a thin molybdenum rod 41 is swung so as to cross the light beam A at a right angle, and the tip is moved in one direction (for example, FIG. 6).
(A) X-axis direction), the intensity of the reflected light by the round bar 41 is detected at two places, and the laser light detection device for measuring the power distribution of the laser light is put into practical use. ing. FIG. 6A is a diagram showing the laser light detection device as viewed from the direction of the optical axis. The round bar 41 is a motor or the like on a surface that passes through the point M and is perpendicular to the light flux A of the laser light (that is, parallel to the paper surface). The pyro detectors 42 and 43 for detecting the intensity of the laser light reflected by the round bar 41 are arranged on both sides of the light flux A so as to face each other with the light flux A interposed therebetween. . If the positions of the pyro detectors 42 and 43 are projected onto the rotation surface of the round bar 41 as D1 and D2, respectively, the arc MD
1, MD2 have the same length and intersect at a point R at a right angle.
The round bar 41 and the pyro detectors 42 and 43 are motors, feed screws, linear guides, etc., which are not shown in the figure, and are X and Y in FIG.
It is attached to a stage (not shown) that moves in the direction.

In the laser light detecting device thus constructed, the laser light applied to the round bar 41 is reflected at a right angle to the axial direction of the round bar 41, so that the pyro detectors 42 and 43 are provided.
6A, the laser light detected at is only the light reflected at the points J and K on the perpendiculars of D1 and D2 of the round bar 41, respectively. The position at which the laser light is reflected by the pyro detectors 42 and 43 as the round bar 41 turns is the locus as shown in FIG. 6A, that is, the straight line MD.
There are two circles having a diameter of 1, MD2, and at the intersection R of the loci of these two circles, the respective tangent lines intersect at a right angle. The output of the pyro detector 42 when the round bar 41 moves from the intersection G to the intersection H is as shown in, for example, FIG. 6B, and it is possible to scan along the arc GRH.

That is, by observing the outputs of the pyro detectors 42 and 43 while rotating the round bar 41 at a constant speed, it is possible to detect the distribution of the intensity of the two-dimensional laser light at the position along the arc GRH. . Observing the outputs of the pyro detectors 42 and 43 while slightly moving in the X direction so that the intersection R passes through the center of the laser light and passes through the entire light beam, the distribution of the intensity of the laser light over the entire light beam is found. Can be detected.

[0006]

However, in the laser light detecting device having such a structure, the pyro detector is used.
The stage on which 42, 43, etc. are assembled moves slightly in the X-axis direction and traverses the entire light flux, so the laser light observed at the beginning and end of the movement may cause the detection time to deviate by the time required for the movement. Become. Therefore, with this laser light detection device, not only does it take a long time for measurement, but even if the intensity of the laser light fluctuates with time due to the state of the oscillator, etc., it cannot be detected.

That is, both the spatial intensity distribution and the temporal fluctuation are mixed in the observed data, and since they cannot be distinguished, the reliability of the observed data may be reduced. is there. Therefore, in the laser processing apparatus equipped with the conventional laser light detection device that cannot accurately observe the position of the optical axis of the laser light, the spatial distribution of the power, and the degree of temporal variation thereof, uniform processing accuracy can be maintained. You may not be able to. Further, since the moving stage requires a driving mechanism and a guide mechanism, the mechanism of the laser light detecting device is complicated and large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a laser light detecting device capable of detecting not only the transverse mode of laser light but also its temporal fluctuation with a simple mechanism in a short time and accurately. It is to be.

[0009]

A laser beam detecting device of the present invention comprises a reflecting rod driven by a turning device to traverse the laser beam,
A plurality of photoelectric elements arranged on both sides of the laser beam, a signal of the laser beam reflected by the reflecting rod and received by the photoelectric element, and a signal of the swiveling operation of the reflecting rod are input, and calculation of the distribution of the laser beam is performed. It is characterized by having means.

[0010]

The intensity of the laser light at a plurality of points on the cross section of the laser light is detected by a plurality of photoelectric elements that receive the laser light reflected by the rotating reflecting rod, and the positions of the plurality of reflecting points are It is detected by the turning angle. The intensity distribution of the laser light is calculated by the calculating means from the intensity of the laser light and the position of the reflection point.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a laser light detecting device of the present invention will be described below with reference to the drawings. In FIG. 1, A indicates a cross section of a light flux of laser light emitted from a laser oscillator (not shown) and transmitted to a laser processing machine (not shown). The round bars 1A, 1B, and 1C are motors equipped with rotation angle detectors such as pulse encoders, and are configured to rotate around a point M as an axis and at a right angle to the plane of the drawing, and to cross the light beam A of the laser light at a right angle. The axis of the round bar 1A passes through the point M, and the round bars 1B and 1C
Are assembled at 120 ° intervals so as to be symmetrical with respect to the round bar 1A at positions e apart from the point M, respectively. These round bars 1A, 1B, 1C are provided on both sides of the luminous flux A.
Pyro detector 2 for detecting the intensity of laser light reflected by
x1,2x2,2x3, ..., 2x10 and pyro detector 2y
1, 2y2, 2y3, ..., 2y10 are arranged at equal intervals on an arc centered on the point M and having a radius of 2R.

FIG. 2 is a block diagram showing the configuration of the control device of the laser light detecting device of the present invention, and 3 is the pyro detectors 2x1, 2x2, 2x3, ..., 2x10 shown in FIG. 1 and the pyro detector. An amplifier for amplifying the output signals of 2y1, 2y2, 2y3, ..., 2y10, 4 is an AD converter for converting the output of the amplifier 3 into a digital signal, 5 is a buffer memory for storing the output of the AD converter 4, 6 Is a microcomputer equipped with an input / output interface such as a display device and a keyboard, and peripheral devices such as a memory, and which processes the data stored in the buffer memory 5, and 7 is attached to the swivel drive unit of the round bar 1A. It is a rotation angle detector.

Next, the operation of the laser light detecting device constructed as described above will be described with reference to FIG. Since the laser light is reflected at a right angle to the axial direction of the round bar 1A,
The laser light of the portion shown by a plurality of equally spaced arcs in FIG. 3 is emitted by each of the pyro detectors 2x1 to 2x10 as the round bar 1A turns.
It is reflected by 2y1 to 2y10. That is, when viewed from the axial direction of the light beam, the point M and each of the pyro detectors 2x1, 2x2, 2x
3, ..., 2x10, 2y1, 2y2, 2y3, ..., 2y10
The laser light beam is scanned along a semicircle whose diameter is a line connecting with. The scanned data is stored in the buffer memory 5 from the amplifier 3 through the AD converter 4, and is taken into the microcomputer 6 together with the information on the turning angle of the round bar 1A sent from the pulse encoder. If the rotation speed of the round bar 1A is 3000 rpm, it takes 1 in 20 ms.
Since it rotates, the time required to cross the light flux A of the laser light is about several ms.

The relationship between the coordinates of the points scanned by the plurality of arcs and the turning angle of the round bar 1A will be described with reference to FIG. In FIG. 4, the X axis and the Y axis are taken as shown in FIG.
The point M, which is the axis of rotation of the round bar 1A, is the origin (0, 0),
The rotation angle of the round bar 1A from the X axis is θ, and the pyro detector 2i
If the distance between (i = x1, ..., X10, y1, ..., Y10) and the point M is 2R, and the angle between the line connecting the position of the pyrodetector 2i and the point M and the X axis is φi, then the scan The coordinates (Cφix, Cφii) of the center Cφi of the semicircle are Cφix = R cosφi (1) Cφii = R sinφi (2), and the point (x, y) on the circumference of the scan is (x−R cosφi). ) ² + (y−R sin φi) ² (3) In addition, the coordinates (x,
y), where r is the distance from the origin, x = r cos θ (4) y = r sin θ (5) Therefore, substituting equations (4) and (5) into equation (3) yields (r cos θ−R cos φi) ² + (r sin θ−R sin φi) ² = R ² (6), and solving this for r, r = 0 (7) r = 2R cos (φi−θ) (8) ). By substituting this into the equation (5), the position P (Pθφix, Pθφiy) of the laser light reflected by the detector at the position φi at the angle θ of the round bar 1A is Pθφix = 2R cos (φi −θ) cos θ (9) Pθφiy = 2R cos (φi−θ) sin θ (10) and can be calculated from the turning angle θ of the round bar 1A. The position P'of the laser light reflected by the pyro detector 2i 'which is on the Y-axis side and whose angle from the X-axis is φi'.
Similarly, (Pθφi′x, Pθφi′y) is expressed as Pθφi′x = 2R cos (φi′−θ) cosθ (11) Pθφi′y = 2R cos (φi′−θ) sinθ (12) You can

Therefore, the output of the pyro detector can be observed as a function of position, and the pyro detector 2i (i
= X1, ..., X10, y1, ..., Y10), the cross section of the laser beam can be scanned with the same number of semicircles.
Since multiple pyro detectors are arranged on both sides of the laser beam, the laser beam can be scanned in a grid pattern.
The spatial distribution of the intensity of laser light is known. From the obtained spatial distribution of intensity, the size of the laser beam can be determined by calculating the size of the area where the output above the specified threshold is detected.Furthermore, the center point and the position of the center of gravity can be determined. The position of the optical axis of the laser light can be known by performing the calculation.

Next, the position of the laser beam reflected by the round rods 1B and 1C which are eccentrically attached from the point M to e will be described with reference to FIG. Here, the round bar 1B,
And the center of rotation M of the round bar 1C as the origin (0,0),
The angle between B and 1C and the X axis is θ, and the pyro detector 2i (i =
x1, ..., x10, y1, ..., y10) and the distance between point M
The angle between the X axis and the line connecting the position of the R and pyro detectors 2i and the point M is φi. The position Q of the laser light reflected by the round bar 1C is (-) from the reflection position P when it is not eccentric.
Since the points are separated by e sin θ, e cos θ), the coordinates (Qθφix, Qθφiy) of the point Q are Qθφix = 2R cos (φi−θ) cosθ−e sinθ (13) as in the case of the round bar 1A. Qθφiy = 2R cos (φi−θ) sin θ + e cos θ (14)

Similarly, when the round bar 1B eccentrically mounted on the opposite side of the round bar 1C has a rotation angle θ, the coordinates (Sθφ) of the position S of the laser beam reflected by the pyro detector 2i are detected.
ix, Sθφii) can be expressed as Sθφix = 2R cos (φi−θ) cosθ + e sinθ (15) Sθφiy = 2R cos (φi−θ) sinθ-e cosθ (16). If the eccentricity e is set so that the two scan lines of the round bars 1B and 1C are placed at substantially equal intervals between the scan lines of the round bar 1A, the scanning can be performed without increasing the pyro detector. You can add more lines. That is, it is possible to obtain a scan line corresponding to (the number of pyro detectors × half the number of round bars).

Next, a method of calibrating the outputs of the plurality of pyro detectors will be described again with reference to FIG. A scan line near the center of the laser beam is defined as a reference line, and the output levels of the pyro detectors are equal at the intersections of the reference line and other scan lines. To this end, first, of the two rows of pyro detector groups, the scan line 1x5 of the pyro detector 2x5 at the center on the 2x side and the pyro detectors 2y1 and 2y on the 2y side.
The intersections with the scan lines 2, 2y3, ..., 2y10 are obtained. Among the respective scan lines of the pyro detector group on the 2y side, the data sampled when passing through the intersection and the data sampled at the intersection of the scan lines of the pyro detector 2x5 have the same value, Two
The correction coefficient applied to the data of each scan line of the y-side pyro detector group is calculated and corrected.

Next, data other than the pyro detector 2x5 of the scan line 1y5 of the pyro detector 2y5 at the center of the pyro detector group on the 2y side, which has been similarly corrected, except for the pyro detector 2x5 of the pyro detector group on the 2x side. The coefficient applied to the scan line data of the 2x side pyro detector group is calculated and corrected so that the scan line data and the scan line data have the same value at the intersection. The scan lines formed by the round bars 1B and 1C are similarly corrected. The outputs of the plurality of pyro detectors can be calibrated by these correction processing calculations.

By the way, this pyro detector outputs a current proportional to the temperature change, but has a response characteristic depending on the heat capacity and radiation coefficient of the element, the signal processing circuit and the like. Therefore, when pulsed light that fluctuates in a short time, such as reflected light from a rotating round bar, is applied to the pyrodetector, its output is not only a value proportional to the light intensity, but also distortion. May be included. In the laser light detection device of the present invention, when the response characteristics are known,
The distortion may be corrected by arithmetic processing. Thereby, the distortion of the detection result can be reduced.

Therefore, in the laser light detecting device having such a configuration, (1) a plurality of pyro detectors are arranged on both sides of the laser beam and the round bar is swung to scan the laser beam in a lattice pattern. Therefore, the spatial distribution of the intensity of the laser light and the temporal variation can be distinguished and detected in a short time. Further, a mechanism for sliding the pyro detector or the like is also unnecessary.

(2) The round bars 1B and 1C are eccentrically attached to the round bar 1A, and the rotation allows the scanning between the scan lines of the round bar 1A to be performed. It can be made smaller than the interval determined by.

(3) Since the output of the pyro detector input to the AD converter 4 is stored in the buffer memory 5, the output of the pyro detector is AD converted in a sufficiently small sampling time and stored in the buffer memory 5. It is not necessary to use a microcomputer having an excessive processing capacity because the processing can be performed after that.

(4) Since the output levels of the respective pyro detectors are corrected to be equal at the intersection of the scan line near the center of the laser beam and another scan line, the pyro detector and its processing circuit. It is possible to calibrate the variation of the characteristics of. Moreover, since the calculation is performed by software instead of the complicated manual adjustment, automation is easy.

[0025]

As described above, according to the present invention, a reflecting rod driven by a turning device to traverse a laser beam, a plurality of photoelectric elements arranged on both sides of the laser beam, and a photoelectric element reflected by the reflecting rod to receive light. By inputting the signal of the laser light and the signal of the turning operation of the reflecting rod, and providing the calculating means for calculating the distribution of the laser light, the intensity of the laser light at a plurality of points in the cross section of the laser light is reflected by the turning. The photoelectric element that receives the laser light reflected by the rod detects it, and the positions of multiple reflection points are detected by the turning angle of the reflection rod.The intensity of the laser light and the position of the reflection point indicate the intensity of the laser light. Since the distribution is calculated by the calculation means and detected, it is possible to obtain a laser light detection device capable of accurately detecting the transverse mode and temporal fluctuation of the laser light with a simple mechanism in a short time.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a laser light detection device of the present invention.

FIG. 2 is a block diagram showing a configuration of a control device of the laser light detection device of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a rotation angle of a round bar and a scan line of the laser light detection device of the present invention.

FIG. 4 is an explanatory diagram showing a method of calculating coordinates for scanning laser light of the laser light detection device of the present invention from the rotation angle of the reflecting rod and the position of the photoelectric element.

FIG. 5 is a view for explaining the action of a reflecting rod that is eccentrically attached to the laser light detection device of the present invention.

FIG. 6A is a diagram showing an example of a conventional laser light detection device. FIG. 6B is a diagram showing an example of a lateral mode detection result of laser light detected by a conventional laser light detection device.

[Explanation of symbols]

1A, 1B, 1C ... Round bar as a reflective bar, 2x1-2x
10, 2y1-10 ... Pyro detector as photoelectric element, 3 ...
Amplifier, 4 ... AD converter, 5 ... Buffer memory, 6 ... Microcomputer, 7 ... Rotation angle detector, A ... Luminous flux of laser light.

Claims (1)

[Claims] 1. A reflecting rod driven by a turning device to traverse the laser beam, a plurality of photoelectric elements arranged on both sides of the laser beam, and the laser beam reflected by the reflecting rod and received by the photoelectric element. And a signal of the turning operation of the reflecting rod are input, and a laser light detecting device comprising a calculating means for calculating the distribution of the laser light.