JPH0327316B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] 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. [Prior Art] In general, in laser processing, it is important to control the beam shape at the irradiation part to an optimal shape according to the processing. As an example, when welding electric resistance welded pipes, by injecting a laser into the center of the plate thickness, where heat input tends to be insufficient, we can uniformly melt the plate in the thickness direction, thereby dramatically improving the quality of the weld. We will explain the ``ERW (laser composite welding method)''. In order to perform optimal welding with respect to the shape of the input beam, the following restrictions are set. That is, the vertical diameter of the beam in the irradiation section must be changed according to the wall thickness of the tube, while the horizontal diameter of the beam must be kept below a certain value. As a possible optical system, the one shown in Figure 1 has been proposed so far (“Laser Focus”).
Nov.1979 Page 68 “A Convex Beam
This is a combination of a concave mirror and a convex mirror. [Problem to be solved by the invention] By the way, in this combination, the distance between both mirrors D
This is a system that controls the beam shape at the irradiation section by changing the beam shape.With this system, the vertical (horizontal) diameter of the beam is set to a desired value, and at the same time, the horizontal (vertical) diameter of the beam is also uniquely determined. It is not possible to set the vertical and horizontal diameters to desired values at the same time. The reason for this will be explained below. FIG. 2 is a diagram showing how the vertical diameter V and the horizontal diameter H of the beam change depending on the distance from the concave mirror. As shown in the figure, the deviation 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, and the horizontal focal length appears to be the vertical focal length. Therefore, the beam shape near the waist is A:
Horizontal → B: Circle → C: Vertical. Experiments have confirmed that the smaller the horizontal diameter H, the better the weldability, so the dh shown in Figure 2
If the distance D is determined such that the distance D is minimized, both graphs in FIG. 2 are uniquely determined. That is, since the vertical diameter V of the beam at this time is also uniquely determined, the vertical diameter V cannot be set to a desired value. 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] The first invention for solving the above problems is as follows:
A laser beam emitted from a laser oscillator is expanded in one direction by a first convex cylindrical mirror, and then a directional component of the laser beam displaced by 90° with respect to the above direction is expanded by a second convex cylindrical mirror, Further, the laser beam expanded in the two directions is focused by a concave mirror, and one or both of the distance between the first convex cylindrical mirror and the second convex cylindrical mirror and the distance between the second convex cylindrical mirror and the concave mirror A laser beam irradiation control method is characterized in that a laser beam having a desired shape is obtained by changing the diameter of each laser beam expanded by the first convex cylindrical mirror and the second convex cylindrical mirror. The desired size is set in the laser irradiation section, and one of the first convex cylindrical mirror and the second convex cylindrical mirror is used as an integrating mirror, and the energy distribution of the laser beam in the laser irradiation section is also controlled by the integrating mirror. It is characterized by this. A second aspect of the present invention includes a first convex cylindrical mirror that magnifies a laser beam emitted from a laser oscillator in one direction, and a directional component of the expanded laser beam that is displaced by 90 degrees with respect to the above direction. A second convex cylindrical mirror that focuses the laser beam expanded in the two directions and a concave mirror that focuses the laser beam expanded in the two directions are installed in the box, and each of the first convex cylindrical mirror, second convex cylindrical mirror, and concave mirror A laser beam irradiation control device characterized in that a position adjustment device is provided, and either one of the first convex cylindrical mirror and the second convex cylindrical mirror is divided in a direction perpendicular to the direction of curvature. It consists of an integrating mirror. [Operation] Fig. 3 is a drawing showing the optical system of the present invention, which consists of three parts: a convex cylindrical mirror 3 with a curve in the horizontal direction, a convex cylindrical mirror 4 with a curve in the vertical direction, and a concave mirror 5. The distances D ₁ and D ₂ can be adjusted as appropriate. If we pay attention to the horizontal diameter of the beam, the convex cylindrical mirror 4 with a curve in the vertical direction only serves as a plane mirror in the horizontal direction, so the optical system in which the horizontal diameter of the beam can be sensed is the two-mirror optical system shown in Figure 4. is equivalent to the system. On the other hand, if we pay attention to the vertical diameter of the beam, the convex cylindrical mirror 3 with a curve in the horizontal direction only plays the role of a plane mirror in the vertical direction.
The optical system for sensing the beam longitudinal diameter is equivalent to the two-mirror optical system shown in FIG. Here, 3 in Figure 3,
If you make any two of mirrors 4 and 5 movable,
D ₁ and D ₂ can be changed independently, and as a matter of course, the distance between both mirrors D ₁ in Fig. 4
+D ₂ and the distance D ₂ between both mirrors in FIG. 5 can be changed independently. This means that the curves of the beam systems V and H shown in FIG. 2 can now be moved independently. For example, if D ₂ is made smaller while keeping D ₁ + D ₂ constant in Figure 3, the change in beam diameter in the vertical direction (curve H) will change while the change in beam diameter in the horizontal direction (curve H) is fixed, as shown in Figure 6. V, V _A → V _B →
Can be run with V _C. This means that the vertical diameter at the welding point can be changed while keeping the horizontal diameter constant; in this case, the beam shape is A→B→
It becomes C. As described above, by using the present invention, the beam shape at the laser irradiation section can be freely controlled. (Example) Here, the apparatus of the present invention will be explained in more detail based on FIGS. 7 and 8. FIG. 7 shows an apparatus showing an embodiment of the present invention,
FIG. 2 is a cross-sectional view showing a mirror system of a laser beam irradiation device. The first convex cylindrical mirror 3 is fitted into a mirror holder 6, and the mirror holder 6 is connected to a support rod 7.
It is rotatably mounted on the The second convex cylindrical mirror 4 is fitted into a mirror holder 6-1, and the mirror holder 6-1 is rotatably attached to the slider 8.
moves freely on the support rod 9. The convex cylindrical mirror 4 is arranged facing the convex cylindrical mirror 3. Concave mirror 5
is disposed facing the second convex cylindrical mirror 4, and is similarly rotatably attached to a slider 8-1 which freely moves on a support rod 9-1 via a holder 6-2. 11 and 12 are flat mirrors. The above mirror system is housed in the box 13. FIG. 8 shows the mirror holder 6 of the second convex cylindrical mirror 4.
This is a more detailed view of the drive mechanism of -1, in which there is a shaft 10 at the tip of the shaft 10 protruding from the slider 8 which is movably fitted into the support rod 9 so as to be able to rotate around the center line of the shaft 10. A mirror holder 6-1 is attached. In such an apparatus, a beam emitted from an oscillator is transmitted by flat plate mirrors 11 and 12 and is emitted into a first convex cylindrical mirror 3, for example, a convex cylindrical mirror having a curve in the lateral direction. The beam projected by the convex cylindrical mirror 3 has a shape in which only the lateral diameter of the beam is expanded. When such a projection beam is input to the second convex cylindrical mirror 4, for example, a convex cylindrical mirror having a curve in the vertical direction, the lateral spread of the input beam remains unchanged in the convex cylindrical mirror 4, but the directional component is shifted by 90°. In other words, only the longitudinal component of the beam becomes a widened projection beam. Here, in order to increase the vertical diameter of the irradiation part of the projection beam, the inter-mirror distance D ₁ + D ₂ is kept constant, that is, the distance between the first convex cylindrical mirror 3 and the concave mirror 5 is kept constant, and the inter-mirror distance D _{2 is} only make it bigger. in this case,
Since it is necessary to reduce D ₁ by an amount corresponding to the increase in D ₂ , the convex cylindrical mirror 4 and the concave mirror 5 are moved at the same time. With the above operations, the projection beam from the concave mirror is
The shape is controlled according to the value of D ₂ and is projected to the welding point. In this case, the convex cylindrical mirror 4 and concave mirror 5 were moved, but the same effect can also be obtained by moving the convex cylindrical mirror 3 and convex cylindrical mirror 4, or by moving the convex cylindrical mirror 3 and concave mirror 5. is obtained. Note that if you want to change the horizontal diameter while keeping the vertical diameter constant, you can change D ₁ + D ₂ while keeping D 2 constant, but this naturally means _changing D ₁ while keeping D ₂ constant. It is equivalent to changing. This case can be realized by changing the positions of the convex cylindrical mirror 4 and the concave mirror 5, or by changing the position of only the convex cylindrical mirror 3. Further, the same effect can be obtained even if the convex cylindrical mirror 3 is a convex cylindrical mirror with a curve in the vertical direction, and the convex cylindrical mirror 4 is a convex cylindrical mirror with a curve in the horizontal direction. In this case, if you want to keep the horizontal diameter constant, D ₂ can be kept constant, and if you want to keep the vertical diameter constant, D ₁ +D ₂ can be kept constant. In addition, when applying the present invention to the above-mentioned "FRW: laser composite welding method", it is necessary to optimize the energy distribution in the longitudinal direction, but this requires that the convex cylindrical mirror 4 be bent in the direction of curvature. This can be achieved by using an integrating mirror that is divided at right angles and adjusting the vertical light focusing direction of each segment that makes up this integrating mirror. FIG. 9 shows an example of such an integrating mirror, in which each segment 4-1-A, 4-
Adjustment screws are provided on the back side of 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 an integrating mirror 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, it is possible to make the longitudinal energy distribution uniform. In the above explanation, the present invention has been mainly described with reference to welding of electric resistance welded pipes, etc., but it is not limited to this, but is applicable to controlling the beam shape and energy distribution at the irradiation part to the optimum one according to the processing in general laser processing. Because this is extremely important, the present invention is extremely effective. By actually focusing a laser beam using the optical system shown in FIG. 7, the following results were obtained.

〔Effect of the invention〕

As described in detail above, the present invention is capable of completely independently controlling the vertical and horizontal diameters of the beam at the laser irradiation section, and can be controlled very quickly by simply changing the position of the beam transmission mirror. It is possible by operation. Furthermore, it is possible to control the energy distribution by adjusting each mirror constituting the integrating mirror, and the effect is extremely large not only for welding electric resistance welded pipes but also for laser processing in general.

[Brief explanation of drawings]

Figure 1 shows a conventional optical system that combines concave and convex mirrors, and Figure 2 shows changes in the beam shape controlled by the optical system in Figure 1 as a function of distance from the concave mirror. , Fig. 3 is a diagram explaining the optical system of the present invention, Figs. 4 and 5 are diagrams showing the functions of the optical system of Fig. 3 in an exploded manner, and Fig. 6 is a diagram explaining the optical system of the present invention. A diagram showing a controlled change in the shape of a laser beam, FIG. 7 is a schematic cross-sectional view of an apparatus according to an embodiment of the present invention, FIG. 8 is a perspective view showing a mirror drive mechanism, and FIG. 9 is a perspective view of an integrating mirror. It is a diagram. 1... Convex mirror, 2, 5... Concave mirror, 3... Convex cylindrical mirror with a curve in the horizontal direction, 4... Convex cylindrical mirror with a curve in the vertical direction, 4-1... Integrating mirror, 6... Mirror Holder, 7, 9... Support rod, 8... Slider, 10... Shaft, 11, 12... Flat mirror, 13... Box body.

Claims (1)

[Claims] 1. A laser beam emitted from a laser oscillator is expanded in one direction by a first convex cylindrical mirror, and then a directional component of the laser beam displaced by 90° with respect to the above direction is expanded in a second direction. The laser beam is expanded by a convex cylindrical mirror, and the laser beam expanded in the two directions is focused by a concave mirror, and the distance between the first convex cylindrical mirror and the second convex cylindrical mirror, A laser beam irradiation control method comprising changing one or both of the distances of a concave mirror to obtain a laser beam with a desired shape. 2. The laser beam irradiation control method according to claim 1, wherein the diameter of each laser beam expanded by the first convex cylindrical mirror and the second convex cylindrical mirror is adjusted to a desired size in the laser irradiation section. 3. Claim 1, characterized in that either the first convex cylindrical mirror or the second convex 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 first convex cylindrical mirror that magnifies the laser beam emitted from the laser oscillator in one direction, and a second convex cylindrical mirror that magnifies the directional component of the expanded laser beam that is displaced by 90° with respect to the above direction. A mirror and a concave mirror that condenses the laser beam expanded in the two directions are installed in a box, and a position adjustment device is provided for each of the first convex cylindrical mirror, the second convex cylindrical mirror, and the concave mirror. A laser beam irradiation control device characterized by: 5. The laser beam according to claim 4, wherein either one of the first convex cylindrical mirror and the second convex cylindrical mirror is constituted by an integrating mirror divided in a direction perpendicular to the direction of curvature. Irradiation control device.