JPH04280218A - Cutting method of material by laser beam - Google Patents

Abstract

PURPOSE:To increase the space between an objective optical system and a material to be worked by diverging parallel beams from a laser oscillator by a beam diverging optical system and introducing the beams to the objective optical system. CONSTITUTION:Parallel beams outputted from a laser oscillator 1 are changed in advancing direction by a plane mirror 3 and a convex mirror 7, and introduced to a concave mirror 5 as a beam focusing objective optical system, and the beams are focused toward a material 6 to be worked by the concave mirror 5. As the beams diverged by the convex mirror 7 are entered, the diameter of the concave mirror 5 has a size possible to reflect all the incident beams. In this case, if the parallel beams are entered to the concave mirror 5, the beams are focused in its focusing position. As the beams diverged by the convex mirror 7 are entered to the concave mirror 5, however, the beams are focused far from the focusing point of the concave mirror 5. The material 6 to be worked is positioned in this beam focusing position.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention focuses a laser beam using a focusing optical system (objective optical system) and irradiates it onto an object.
Regarding the method of cutting this object.

0002

2. Description of the Related Art Beam objective focusing optical systems used in laser cutting include transmission optical systems using lenses and reflective optical systems using mirrors. FIG. 2 shows an example of laser cutting using a reflective beam focusing optical system. A parallel beam output from a laser oscillator 1 is redirected by plane mirrors 3 and 4 and introduced into a concave mirror 5 as an objective optical system for beam focusing, and the concave mirror 5 directs the laser beam to a predetermined position on a workpiece 6. Narrowed down.

[0003] A problem that arises during this type of laser cutting process is that various substances are scattered from the workpiece irradiated with the beam, and the scattered substances are scattered onto the objective optical system (concave mirror 5) for focusing the beam.
It is to adhere to things such as. When a substance with a high light absorption rate adheres to the surface of a lens or mirror, the energy of the laser beam is absorbed by the substance, causing instantaneous abnormal expansion of the surface of the lens or mirror, destroying the optical system. Even if the workpiece does not break, the energy irradiated to the workpiece decreases due to the absorption effect of the deposits, and the quality of the cut surface deteriorates.

0004

[Problems to be Solved by the Invention] As one of the measures to prevent objects scattered from the workpiece from adhering to the objective optical system for beam focusing, it is possible to use an objective optical system with a long focal length, so that the optical system and the workpiece There is a way to increase the distance between objects. By separating the objective optical system from the workpiece as much as possible, debris from the workpiece becomes less likely to adhere to the optical system. However, increasing the focal length of the focusing optics increases the diameter of the beam spot at the focal position (the spot diameter at the focal position is proportional to the focal length of the focusing optics), thus reducing the energy density of the focused beam. . As a result, cutting ability and characteristics deteriorate.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to reduce the energy density of the focused beam even if the distance between the objective optical system for beam focusing and the workpiece is increased. The purpose is to provide a method to prevent this from happening.

[0006]

[Means for Solving the Problems] Accordingly, in the present invention, a parallel beam from a laser oscillator is appropriately diverged by a beam diverging optical system and then introduced into an objective optical system for beam focusing. The beam is focused further away than the focal point.

[0007]

[Operation] When a parallel beam is introduced into the objective optical system, the beam is focused at its focal position. However, if the parallel beam is appropriately diverged by a beam diverging optical system and introduced into the objective optical system, the beam will be focused at a distance from the focal point. In other words, the combined focal length of both systems is longer than the focal length of the objective optical system alone.

[0008]

Embodiment FIG. 1 shows an embodiment in which a reflective optical system (concave mirror) is used as the objective optical system for beam focusing. The parallel beam output from the laser oscillator 1 has its traveling direction changed by a plane mirror 3 and a convex mirror 7, is introduced into a concave mirror 5 as an objective optical system for beam focusing, and is focused by the concave mirror 5 toward a workpiece 6. Ru.

The plane mirror 4 in the conventional optical system of FIG. 2 is replaced by a convex mirror 7 in the embodiment of FIG. This convex mirror 7 is the beam diverging optical system described above, and the parallel beam is appropriately diverged by the convex mirror 7 and is incident on the concave mirror 5. The focal length of the concave mirror 5 as the objective optical system for beam focusing may be the same as that of the conventional one shown in FIG. 2, but since the beam diverging by the convex mirror 7 is incident, the diameter of the concave mirror 5 must be set to reflect all of the incident beam. The size should be large enough to allow

As can be seen by comparing FIGS. 1 and 2, when a parallel beam is incident on the concave mirror 5, the beam is focused at its focal point. However, since the beam diverged by the convex mirror 7 is incident on the concave mirror 5, the beam is focused farther than the focal point of the concave mirror 5. Since the workpiece 6 is positioned at the beam focus position, the distance between the concave mirror 5 and the workpiece 6 can be made larger than before by the method of the present invention. Moreover, since the beam diameter at the concave mirror 5 increases, the spot diameter of the focused beam does not increase (the spot diameter d is inversely proportional to the beam diameter D incident on the concave mirror 5).
Energy density does not decrease. Of course, the present invention can also be implemented using a transmission type optical system using lenses.

[0011]

[Effects of the Invention] In this invention, since the parallel beam is appropriately diverged by the beam diverging optical system and introduced into the beam focusing objective optical system, the combined focal length of these optical systems becomes long, and the objective optical system The distance between the machine and the workpiece can be increased. On the other hand, since the beam diameter in the focusing optical system is increased by the diverging optical system, the spot diameter becomes smaller and the energy density of the focused beam does not decrease.
By separating the objective optical system from the workpiece as much as possible, it is possible to prevent debris from the workpiece from adhering to the optical system.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an optical system according to an embodiment of the present invention.

[Figure 2
] Configuration diagram of conventional optical system

[Explanation of symbols]

1 Laser oscillator 3 Plane mirror 4 Plane mirror 5 Concave mirror (objective optical system for beam focusing) 6 Workpiece 7 Convex mirror (optical system for beam divergence)

Claims (1)

[Claims] 1. A method in which a laser beam is focused by a beam focusing objective optical system and irradiated onto an object to be cut, wherein a parallel beam from a laser oscillator is appropriately diverged by a beam diverging optical system to focus the laser beam on the object. A method for cutting an object using a laser beam, the method comprising: introducing the laser beam into an optical system to focus the beam farther than the focal point of the objective optical system.