JPH01181987A - Method and device for controlling irradiation of laser beam - Google Patents

Abstract

PURPOSE:To control the shape of an irradiation light by spreading a laser beam by a convex mirror and adequately changing the distance between each mirror by stopping it in the vertical and horizontal directions by a pair of concave circular columnar mirrors. CONSTITUTION:The laser beam 20 inputted from an oscillator is transmitted to a convex mirror 3 via plane mirrors 11, 12 to relatively enlarge the longitudinal and horizontal diameters thereof. The beam is then input to the 1st recessed circular columnar mirror 4 to stop the component in the horizontal direction only and the component in the direction(the longitudinal direction component) displaced 90 deg. is stopped by inputting it to the 2nd recessed circular columnar mirror 5 having a curve in the longitudinal direction further. The beam is formed in the specified shape by adequately deforming one or both parts of the distance D1 between a convex mirror 3 and the 1st recessed circular columnar mirror 4 and the distance D2 between the 1st mirror 4 and 2nd mirror 5. The beam shape at the radiation part is thus controlled to the optimum one corresponding to the working and welding can well be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser beam irradiation method, and particularly to a method and apparatus for controlling the shape of irradiated light in laser beam irradiation.

2. Description of the Related Art In general, in laser processing, it is important to control the beam shape at the irradiation part to the optimum shape according to the processing. One example is rERW, which uses a laser to uniformly melt the thickness of the plate at the center of the plate thickness, where heat input tends to be insufficient when welding ERW pipes, thereby dramatically improving the quality of the weld. ：Laser composite welding method'' has the following limitations in order to perform optimal welding with respect to the shape of the input beam. In other words, the vertical diameter of the beam at the irradiation part must be changed according to the wall thickness of the tube.
On the other hand, I want to keep the horizontal frame of the beam below a certain value.

As a possible optical system for this purpose, the one shown in Figure 1 has been proposed so far (LaserFocus
, Nov, 1979, p. 88, A Conve.
x Beam Integrator). This system is a combination of a concave mirror and a convex mirror, and the beam shape at the irradiation section is controlled by changing the distance between both mirrors. Since the horizontal (vertical) diameter of the beam is also uniquely determined at the same time as the horizontal (vertical) diameter of the beam is set, it is not possible to set the vertical diameter and the horizontal frame to desired values at the same time. The reason will be explained below.

Figure 2 shows the vertical diameter of the beam depending on the distance from the concave mirror, ■
It shows how the horizontal frame H changes. As shown in the figure, the reason why there is a shift in both the V and H curves is due to the effect of astigmatism caused by the beam entering the convex mirror and the concave mirror at a certain angle, so that the horizontal focal length appears to be 1 vertical focal length. Therefore, the beam shape near the waist becomes A: horizontally long → B: circle → C: vertically long.

Experiments have confirmed that weldability is better when the horizontal frame H is smaller, so by determining the distance that minimizes dh in Figure 2, both graphs in Figure 2 are uniquely determined. . That is, since the vertical diameter V of the beam at this time is also uniquely determined, it is not possible to set the vertical diameter ■ to a desired negative value.

Problems to be Solved by the Invention As described above, the conventional technology has a problem in that the beam shape cannot be freely controlled. The present invention solves the above problems and provides an irradiation control method and apparatus that can control the shape of irradiated light.

Means for Solving the Problems A first invention for solving the above problems expands a laser beam emitted from a laser oscillator using a convex mirror, and then expands the laser beam in one direction using a first concave cylindrical mirror. Then, out of the laser beam, a directional component displaced by 90' with respect to the above direction is focused by a second concave cylindrical mirror, and the distance between the convex mirror and the first concave cylindrical mirror and the first This is a laser beam irradiation control method characterized by changing one or both of the distances between a concave cylindrical mirror and a second concave cylindrical mirror to obtain a laser beam having a desired shape.

Further, the diameters of the laser beams in the respective directions condensed by the first concave cylindrical mirror and the second concave cylindrical mirror are set to desired sizes in the laser irradiation section, and One of the mirrors is an integrating mirror, and the integrating mirror also controls the energy distribution of the laser beam in the laser irradiation section.

A second aspect of the present invention includes a convex mirror that magnifies a laser beam emitted from a laser oscillator, a first concave mirror that focuses the expanded laser beam in one direction, and a concave mirror that focuses the expanded laser beam in one direction. A second concave cylindrical mirror that condenses a directional component displaced by 80 degrees with respect to the convex mirror is installed inside the box, and the convex mirror and the first
A laser beam irradiation control device characterized in that a position adjustment device is provided for each of the concave cylindrical mirror and the second concave cylindrical mirror, and the first concave cylindrical mirror and the second concave cylindrical mirror It consists of an integrating mirror, one of which is divided in a direction perpendicular to the direction of curvature.

Operation Figure 1 shows the optical system of the present invention, which consists of three parts: a convex mirror 3, a concave cylindrical mirror 4 with a curve in the horizontal direction, and a concave cylindrical mirror 5 with a curve in the vertical direction. , , D2 can be changed. Here, if we pay attention to the horizontal frame of the beam, the concave cylindrical mirror 5, which has a curve in the vertical direction, only plays the role of a plane mirror in the horizontal direction, so the optical system that the horizontal frame of the beam feels is a two-piece optical system as shown in Figure 2. It is equivalent to a mirror optical system.

On the other hand, if we focus on the vertical beam diameter, the concave cylindrical mirror 4 with a curve in the horizontal direction only plays the role of a plane mirror in the vertical direction, so the optical system that senses the vertical beam diameter is a two-mirror optical system shown in Figure 3. They are originally equivalent.

If any two of mirrors 3 and 4.5 in Figure 3 are made movable, D□ and D2 can be changed independently. The distance Dl and the distance between both mirrors D1+D2 in FIG. 5 can be changed independently. And this means that the beam diameter in Figure 9 is
, Hl means that it is now possible to move each curve independently.

For example, while keeping Di constant in Fig. 1, D1+D2
As shown in FIG. 4, by decreasing , it is possible to change the beam diameter in the vertical direction, ie, the curve V, while keeping the beam diameter in the lateral direction, ie, the curve H, fixed as V A +vB+v. This means that the vertical diameter can be changed while keeping the horizontal frame constant at the welding point, and in this case the beam shape changes from A to B-C. As described above, by using the present invention, the beam shape at the laser irradiation section can be freely controlled.

EXAMPLE The apparatus of the present invention will now be described in more detail with reference to FIGS. 5 and 6.

FIG. 5 is a cross-sectional view showing a mirror system of a laser beam irradiation control device according to an embodiment of the present invention.

The convex cylindrical mirror 3 is fitted into a mirror holder 6, and the mirror holder 6 is rotatably attached to a support rod 7.

The first concave cylindrical mirror 4 is fitted into a mirror holder 6-1, and the mirror holder 6-1 is rotatably attached to a slider 8, and the slider 8 freely moves on a support rod 9. The cylindrical mirror 4 is placed facing the cylindrical mirror 3.

Next, the second concave cylindrical mirror 5 is arranged to face the first concave cylindrical mirror 4, and the slider 8-1 is moved freely onto the support rod 9-1 via the holder 6-2 as described above. It is rotatably mounted on the 11.12 is a flat mirror. The above mirror system is housed in the box 13.

FIG. 6 shows, for example, a mirror holder 6- of the first concave cylindrical mirror 4.
This is a more detailed view of the drive mechanism of No. 1, in which a shaft 10 is provided at the tip end of a shaft 10 protruding from a slider 8 which is movably inserted into a support rod 9 so as to be able to rotate about the center line of the shaft 10. A mirror holder 6-1 is attached.

In such a device, a beam emitted from an oscillator is transmitted by flat mirrors 11 and 12 and is emitted to a convex mirror. The beam projected by the convex mirror 3 has a shape in which both its vertical diameter and horizontal frame are expanded, that is, they are expanded in a similar manner.

When such a projection beam is input to the first concave cylindrical mirror 4, for example, a circular mirror having a curve in the horizontal direction, the cylindrical mirror 4 maintains the vertical spread of the input beam, and the horizontal component of the beam is The projection beam becomes focused. When this projection beam is further input into a second concave cylindrical mirror 5, for example, a cylindrical mirror having a curve in the vertical direction, in the cylindrical mirror 5, the lateral convergence of the input beam remains unchanged, but the direction is shifted by 90°. Only the longitudinal component of the beam becomes a focussed projection beam.

Now, in order to increase the vertical diameter of the irradiation part of the projection beam, the mirror opening distance is kept constant, that is, the distance between the convex mirror 3 and the concave mirror 4 having a curve in the horizontal direction is kept constant, and the mirror opening distance D1 + D2 is made small. do.

That is, the cylindrical mirror 5 is moved to reduce D2. By the above operation, the projection beam from the cylindrical mirror 5 is D1+D
The shape is controlled according to the value of 2 and projected to the welding point.

In this case, the cylindrical mirror 5 was moved, but in addition, the convex mirror 3
A similar effect can be obtained by moving the cylindrical mirror 4.

In addition, if you want to change the horizontal frame while keeping the vertical diameter constant, use D1.
It is sufficient to change D2 while keeping +D2 constant. In this case, any two of convex mirror 3, cylindrical mirror 4, and cylindrical mirror 5
This can be achieved by changing the position of the sheets. Also cylindrical mirror 4
A similar effect can be obtained by using a concave cylindrical mirror with a curve in the vertical direction and using a concave cylindrical mirror with a curve in the horizontal direction as the cylindrical mirror 5. In this case, if you want to keep the horizontal frame constant, you can keep D1+D2 constant, and if you want to keep the vertical diameter constant, you can keep D□ constant.

However, when applying the present invention to the rERW/laser combined welding method, it is necessary to optimize the energy distribution in the longitudinal direction. This can be achieved by adjusting the vertical light focusing direction of each segment that makes up this integral value.

Figure 7 shows an example of such an integral value, and the integral value 4-
Adjustment screws are provided on the back of each segment) 4-1-A and 4-1-B, and the direction of light collection is adjusted by operating each screw.

Generally, the shape and energy distribution of the input beam vary depending on the type of oscillator, but by using the integral value in this way, a desired energy distribution can be achieved regardless of the type of oscillator. For example, in the case of merging with ERW, the turning part is to make the longitudinal energy distribution uniform.

In the above explanation, the present invention was mainly applied to welding of electric resistance welded pipes, etc., but it is not limited to this, but is applicable to laser welding in general by optimizing the beam shape and energy distribution at the irradiation part according to the processing. Since control is extremely important, the present invention can be said to be extremely effective.

Next, the following results were obtained by focusing the laser beam using the optical system shown in FIG.

(Left below) Here, the focal length of the convex mirror 3 is f
, = -730 Focal length of the cylindrical mirror 4 having a curve in the horizontal direction f4 = 1300 Focal length of the cylindrical mirror 5 having a curve in the vertical direction fs = 1000 In the table, -dv is as defined below.

Dv = Distance between convex mirror 3 and cylindrical mirror 5 with a curve in the vertical direction DII: Convex mirror 3 and cylindrical mirror 4 with a curve in the horizontal direction
Distance Lv: Distance LH from the cylindrical mirror 5 to the waist in the vertical direction MLv from the cylindrical mirror 5 to the waist in the horizontal direction
-L,: distance d between the vertical waist and the horizontal waist
h+sin' Horizontal waist diameter dv: From the results of the vertical diameter at the horizontal waist position or more, by keeping DH constant and changing Dv, the vertical diameter was changed from 10i+n to 22mm while keeping the horizontal frame at 24mm.
It can be seen that it was possible to change the value continuously. In addition,
Since we were able to obtain a uniform energy distribution with no gaps in practical use, we conducted a combined ERW/laser welding experiment and found that the quality of the weld was dramatically improved.

Effects of the Invention As detailed above, the present invention (1) allows the vertical diameter and horizontal frame of the beam in the laser irradiation section to be controlled completely independently. ■It can be controlled very quickly by simply changing the position of the beam transmission mirror. In addition, if necessary, it is possible to control the energy distribution by adjusting each mirror that makes up the integral value, and this effect is extremely effective not only for welding electric resistance welded pipes but also for laser welding in general. It is.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the optical system of the present invention, Figs. 2 and 3 are diagrams showing the functions of the optical system of Fig. 1, and Fig. 4 is a diagram showing the laser beam controlled by the optical system of the present invention. 5 is a schematic sectional view of the device of the present invention, FIG. 6 is a schematic perspective view showing the mirror drive mechanism, and FIG. 7 is a schematic perspective view of the integrating mirror of the present invention. Figure 8 shows a conventional optical system that combines concave and convex mirrors, and Figure 9 shows changes in the beam shape controlled by the optical system in Figure 1 as a function of the distance from a concave cylindrical mirror with a vertical curve. It is a diagram expressed as a function. 1...Convex mirror, 2...Concave mirror, 3...Convex mirror, 4
-・φ1st concave cylindrical mirror, 5 and φ2nd concave cylindrical mirror, 4-
1φ conflict integral mirror, 13φ box body, 20φ conflict φ thrower beam, 21φ... projection beam.

Claims (5)

[Claims] 1. A laser beam emitted from a laser oscillator is spread by a convex mirror, then the laser beam is focused in one direction by a first concave cylindrical mirror, and a directional component of the laser beam displaced by 90° with respect to the above direction is focused into a second direction. In addition to narrowing down the concave cylindrical mirror, the distance between the convex mirror and the first concave cylindrical mirror, and the first
A laser beam irradiation control method comprising changing one or both of the distances between the concave cylindrical mirror and the second concave cylindrical mirror to obtain a laser beam having a desired shape. 2. 2. The laser beam irradiation control method according to claim 1, wherein the diameters of the respective laser beams focused by the first concave cylindrical mirror and the second concave cylindrical mirror in the laser irradiation section are adjusted to a desired size. 3. Claim 1 characterized in that either the first concave cylindrical mirror or the second concave cylindrical mirror is an integrating mirror, and the integrating mirror also controls the energy distribution of the laser beam in the laser irradiation section. The laser beam irradiation control method according to item 1 or 2. 4. A convex mirror that spreads the laser beam emitted from the laser oscillator, a first concave cylindrical mirror that focuses the spread laser beam in one direction, and a directional component of the focused laser beam that is displaced by 90 degrees with respect to the above direction. a second concave cylindrical mirror that narrows down the
A laser beam irradiation control device characterized in that a position adjustment device provided for each of the convex mirror, the first concave cylindrical mirror, and the second concave cylindrical mirror is installed in a box body. 5. The laser beam irradiation control device according to claim 4, wherein either the first concave cylindrical mirror or the second concave cylindrical mirror is constituted by an integrating mirror divided in a direction perpendicular to the curved direction. .