JPS6393494A - Parabolic mirror optical system for laser beam processing - Google Patents

Abstract

PURPOSE:To obtain a parabolic mirror optical system for laser beam processing which facilitates optical axis adjustment and is small in size by mounting a parabolic mirror to a curved receiving jig having a cooling layer and providing an adjusting means which can rotate the mirror biaxially and around the optical axis thereto. CONSTITUTION:A matching face 1 with a processing machine and the surface of a plane bearing receiving flange 2 are finished within 45 deg.+ or -0.05 angular accuracy to facilitate the optical path adjustment. The plane mirror 4 is housed in a unit integrated with the parabolic mirror 6 to reduce the size. The need for adjusting the angle of the plane mirror 4 is thereby eliminated. The processing result of good reproducibility is obtd. at the time of mounting and dismounting the entire parabolic mirror optical system for processing if the angle of the parabolic mirror 6 is adjusted by using an angle adjusting screw 5. A pipe 10 for inlet of a processing gas is mounted to a torch 12 so as to face the top end of the nozzle and the splashes returning to the parabolic mirror 6 through the torch 12 from a nozzle 13 are suppressed by the pressure of the processing gas. Another inlet for the processing gas is provided in order to entirely prevent the directivity of the processing. An annular nozzle for emitting the processing gas is mounted to a work.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a parabolic mirror laser processing optical system used, for example, when processing is performed by focusing high-power carbon dioxide laser light. .

(Prior Art) When cutting, welding, or heat-treating a workpiece with a laser beam, ZnSθ is conventionally used as an optical component that focuses the emitted light from a high-output carbon dioxide laser oscillator.

GaAs, KCQ, Ge, etc. are used. Such materials have a transmittance of over 99% for the wavelength of 1O96μs, but as the output increases to 5kW and 10kW, absorption of laser light accumulates, and substances such as dust and dirt in the atmosphere are absorbed by these materials. When it adheres to optical components, the absorption of those parts increases rapidly, damaging or burning those optical components and scattering harmful substances into the atmosphere. Even if there is no damage or combustion, the light collection characteristics may change over time due to an increase in absorption rate, a rise in temperature, and a change in the refractive index.

To solve this problem, there are a Cassegrain optical system, a spherical mirror optical system, etc. as a single reflection optical system. However, these optical systems have aggregation characteristics and are large in size, making them difficult to attach to a normal lens optical system. Furthermore, when a parabolic mirror is used as a processing optical system, it is difficult to adjust the optical axis, and the parabolic mirror is not widely used as a processing optical system.

In conventional lens optical systems, the inside of the torch is almost sealed, so the pressure is low, and the processing gas flows from the nozzle to the laser at the flow rate necessary to prevent splash adhesion to the lens and for processing. It was possible to eject light coaxially. However, in a reflective optical system, a method has been adopted in which a processing gas is normally caused to flow into the workpiece from the outside.

(Problems to be Solved by the Invention) In the above-mentioned conventional technology, in order to obtain the same or better light focusing characteristics and processing performance using the same handling method as the conventional lens optical system, it is necessary to Use condensing optical components to simplify the optical axis adjustment method, downsize the entire optical system, allow processing gas to flow uniformly regardless of the direction of processing, and provide measures to prevent splash adhesion to optical components. is a necessary development goal.

The object of the present invention is to have strong light resistance and heat resistance.

Optical axis adjustment is easy, and what's more, it is 5 times smaller than conventional lens systems.
An object of the present invention is to provide a small parabolic mirror laser processing optical system that can obtain processing performance equivalent to or better than that.

[Structure of the invention]

(Means for Solving the Problem) FIG. 2 shows a condensing optical path diagram of a parabolic mirror off-axis by 90 degrees. When the laser beam 15 is incident, the laser beam 15 is turned back 90' and focused, and theoretically, the light is focused to zero at the point of the effective focal length 16. However, in reality, since laser light is transmitted with a spread angle, it is focused over a certain area at the focal point. Also, the change in the angle of incidence with respect to the axis of the parabolic mirror that occurs during light adjustment is very sensitive to the light collection characteristics. FIG. 3 shows changes in spot diameter and focal position with respect to incident angle.

From this calculation result, it is found that when a laser beam with a divergence angle of 1 and 5 mrad is incident parallel to the axis of the parabolic mirror, the minimum sluggishness is calculated. The diameter is approximately 0.3I1m, which is approximately equal to or smaller than that of the lens system. However, when the incident angle changes as shown in the figure, the power density sharply decreases because the size of the spot diameter accompanying the change in the incident angle is added to this minimum spot diameter.

When this phenomenon was confirmed experimentally, it was found that it did not affect the processing results up to ±2 mrad. Therefore, the angle of the laser beam incident on this parabolic mirror is ±2 nrad
Accuracy within this range is required. For this purpose, an adjustment jig has conventionally been provided on the plane mirror in front of the parabolic mirror, but this adjustment jig has made it unclear which axis should be incident on the parabolic mirror. In order to solve this problem, in the present invention, the plane mirror used to make the light incident on the parabolic mirror is integrated with the parabolic mirror optical system, improving the accuracy of mechanical finishing, and eliminating the angle adjustment jig for the plane mirror. It is necessary. The laser beam reflected by the plane mirror in this manner enters the parabolic mirror and is condensed. Next, the optical path v4 of this parabolic mirror can be adjusted in the same manner as the lens system, assuming that it can be rotated by 2@ and the axis. Once adjusted in this way, the parabolic mirror optical system of the present invention can eliminate the need for adjustment at all by adopting a method of replacing the entire optical system up to the replacement of each mirror.

It is necessary to consider a method to prevent the splash generated during machining from adhering to the parabolic mirror. To solve this problem, a torch through which the laser beam passes, and a process gas is supplied almost coaxially with the laser beam. It is necessary to flow the gas toward the nozzle, and it is also necessary to consider a method that allows the gas to flow uniformly near the nozzle so that the flow direction of the processing gas does not depend on the direction of processing, and to ensure complete shielding.

(Function) In order to overcome the above problems, we invented a parabolic mirror processing optical system as shown in Figure 1.

In order to facilitate optical path adjustment, the mounting surface 1 with the processing machine is
The angular accuracy of the two surfaces of the plane mirror bone flange is 45゛±0.05.
Finished within
4 and make it smaller. This method eliminates the need to adjust the angle of the plane mirror 4, and once the angle of the parabolic mirror 6 is adjusted using several parabolic mirror angle adjustment screws 5, the entire parabolic mirror processing optical system can be removed and installed. , machining results with good reproducibility can be obtained.

To prevent spatter and shield processing heat (atmosphere creation) when using for processing, attach a vibrator 10 containing a processing gas to the torch 12 through which the laser beam passes so that it faces toward the nozzle tip. Accordingly, nozzle 1
3, passing through the torch 12 and returning to the paraboloid @6 can be suppressed by the processing gas pressure. Furthermore, in order to completely prevent the directionality of processing, the nozzle 13
A separate machining gas inlet was provided in the workpiece, and a ring-shaped nozzle for discharging the machining gas was attached to the workpiece.

(Example) Fig. 1 shows a configuration diagram of the parabolic mirror processing optical system of the present invention.
The contact surface 1 with the processing machine is angled with high precision.

Both planes are finished, and the angle with the two surfaces of the plane mirror bone flange is 45"±o, os" or less.

The plane mirror 4 has a structure in which it is cooled with water from the plane mirror water cooling pipe 3. The parabolic mirror 6 has a cavity inside the parabolic mirror so that it can be sufficiently cooled by water, and has a structure in which it is directly cooled by water. This parabolic mirror 6 is installed on a spherical pedestal 8 for adjusting the parabolic mirror, and has a structure in which it slides with the other spherical pedestal 7 for adjusting the paraboloid i11. The angle of the parabolic mirror 6 can be adjusted by using several parabolic mirror angle adjusting screws 5.

This parabolic mirror processing optical system is equipped with a torch 12 through which the laser beam passes, and the torch 12 has a blowout opening diagonally so that the processing gas flows toward a nozzle 13. A gas inlet vibe is installed. Also, the nozzle 13.

Another processing gas port 11 is provided, and a nozzle shown in the nozzle cross section 14 is provided so that the processing gas is ejected in a ring shape onto the workpiece.

The laser beam 15 transmitted from the oscillator is positioned perpendicularly to the fitting surface 1 with the processing machine because the angle between the 2 surfaces of the flat mirror flange and the 2 surfaces of the plane mirror flange is ensured with high precision. To some extent, the reflected light from the plane mirror 4 enters parallel to the axis of the parabolic mirror 6. To determine whether this reflected light is incident in parallel, it is determined whether the reflected light from the parabolic mirror 6 exits from the nozzle 13 perpendicularly by rotating it in two axial directions and using several parabolic mirror angle adjustment screws 5. This can be confirmed by adjusting the direction. Once this adjustment was made, it could be used with good reproducibility by attaching and detaching at the fitting surface 12 to the processing machine without having to adjust the angle.

In this way, the laser beam focused by the parabolic mirror 6 is irradiated from the center of the nozzle 13 onto the surface of the workpiece. The splash generated at this time passes through the center of the nozzle 13 and may reach the paraboloid Ji6, which was provided in the torch 12 through which the laser beam passes. Since the processing gas inlet vibrator 10 was mounted facing the nozzle 13, these splashes were prevented without being increased by the processing gas pressure.

Furthermore, when machining is performed in any direction.

When the machining gas inlet vibrator 10 alone is insufficient, the nozzle 13 has a structure that provides a ring-shaped
By employing the flow of processing gas in step 4, uniform processing was possible.

With the above embodiment, it is possible to avoid high-power laser beams such as high-power carbon dioxide lasers, which have been a problem with conventional lens systems.
It has been confirmed that a parabolic mirror with sufficiently strong light resistance and heat resistance can be processed with the same processing characteristics as a lens system, making it easy to adjust the optical path of a parabolic mirror, and once the optical path is adjusted,
It is no longer necessary to adjust the FJ until each mirror is replaced. Also,
By attaching and detaching the mirror at the interface with the processing machine, we were able to develop a compact parabolic mirror processing optical system with very good reproducibility in both light-gathering and processing characteristics.

The processing gas can also function as a splash prevention and processing gas to the same extent as conventional lens-based optical systems, making it possible to invent a parabolic mirror processing optical system that can perform non-directional processing. did it.

Another Embodiment FIG. 4 shows another embodiment of the present invention of a parabolic tlL adjustment section. In the case where a parabolic tlt adjustment bearing portion having a spherical surface portion was attached, performance equivalent to that of the case of the present invention shown in FIG. 1 was obtained.

FIG. 5 shows a structure in which a thermally cut-off part is made into four or more parts on the connecting surface of the parabolic mirror processing optical system of the present invention and the processing machine, and a thermocouple 19 is embedded in each part, and the laser beam 15 is By incorporating a method of detecting whether or not the light is incident perpendicularly to the surface that connects to the processing machine, the performance of the parabolic mirror processing optical system of the present invention can be guaranteed and processing can be performed safely. was completed.

〔Effect of the invention〕

As a condensing optical system required when performing welding, cutting, heat treatment, etc. using a high-output carbon dioxide laser, the 90° off-axis optical system is much stronger than optical components that are weak in light resistance and heat resistance, such as conventional lens systems. By using a parabolic mirror in combination with a plane mirror, and making the plane mirror smaller and integral with the exception of the optical axis gu, the system is almost as easy to handle as, or even easier than, conventional lens systems. We were able to provide the optical system. Further, according to the present invention, the parabolic mirror can be easily adjusted, and once adjusted, it can be attached and detached with good reproducibility using the same handling method as conventional lens systems. By inventing a method for flowing the processing gas, splash adhesion to the mirror was prevented, and the role of the processing gas in the conventional lens-based optical system could be fulfilled, making it possible to perform processing without directionality.

[Brief explanation of the drawing]

FIGS. 4 and 5 are explanatory diagrams showing the operation of the parabolic mirror laser processing optical system, and are partially detailed views showing other embodiments of the parabolic mirror laser processing optical system of the present invention. 4...Plane mirror 6...Parabolic mirror 7.8...
・Spherical cradle for parabolic mirror adjustment Agent Patent attorney Nori Chika Ken Yudo Hirofumi Mitsumata 7th floor, Kutsumei, first face Hanko piston 1 tension broken Figure 3 ± and 91 companies] [Fig. 4] 7th column, Fig. 5

Claims (3)

[Claims] (1) In a laser processing optical system in which the laser beam obtained from a laser oscillator is focused by a parabolic mirror that is 90 degrees off-axis, it is used as an integrated optical unit in combination with a plane mirror installed at 45 degrees to the optical axis. However, the plane mirror does not have an optical path adjustment jig, but the parabolic mirror is attached to a curved support jig with a cooling layer on the parabolic mirror side, and it can be rotated about two axes and the center of the optical axis. A parabolic mirror laser processing optical system characterized by being equipped with an adjustment jig. (2) Regarding claim 1, the invention is characterized in that the angle between the plane on which the plane mirror is attached and the receiving plane on which the entire parabolic mirror optical system is attached to the machine side is kept within 45°±0.05. Parabolic mirror laser processing optical system. (3) Regarding claim 1, when used as a processing optical system, it is equipped with a pipe-shaped torch through which the laser beam reflected by the 90° off-axis parabolic mirror passes through while being condensed. A parabolic mirror optical system is characterized in that the torch is equipped with a thin pipe so that an inert gas or an active gas flows obliquely toward a nozzle direction through which a laser beam passes. Furthermore, parabolic mirror laser processing is characterized in that near the laser beam exit, a nozzle is provided in a ring shape relative to the laser beam optical axis so that inert gas or active gas is ejected onto the workpiece. Optical system.