JP6184849B2 - Laser processing equipment - Google Patents

Description

  The present invention relates to a laser processing apparatus that can reduce the thermal lens effect of an acousto-optic element.

  In recent years, laser processing apparatuses that switch an optical path at high speed using an acousto-optic element have become widespread. (For example, refer to Patent Document 1.) FIG. 7 shows an example of the optical system. Laser light emitted from the laser generator 1 is collimated by the collimator 2, reduced by the beam diameter adjusting lens system 3, and then shaped by the aperture 4 (hereinafter referred to as the beam diameter adjusting lens system 3 and the aperture 4. After being deflected by the acoustooptic device 5, the optical path length is adjusted by the reflecting mirror system 7, deflected by the galvano scanners 11 a and 11 b, and placed on a stage (not shown) by the fθ lens 8. The work is processed by focusing on the workpiece (not shown). Here, the optical path length can be switched by the mirror moving device 9.

  An acoustooptic device is one in which ultrasonic waves are propagated in an element to form a dense and dense periodic structure in the element, and light is reflected (diffracted) using the diffraction grating as a diffraction grating. Therefore, if the beam diameter is large, the propagation time of the ultrasonic wave becomes long and the response speed becomes slow. Therefore, the beam diameter is made as narrow as possible to enter the acoustooptic device.

  However, with the recent increase in output of the laser generator 1, the portion of the acoustooptic device 5 through which the beam passes is heated and expanded to have a lens effect (hereinafter referred to as a thermal lens effect). It has come to affect the diameter (henceforth a spot diameter) condensed on a workpiece | work. For this reason, the diameter of the beam incident on the acoustooptic device 5 cannot be reduced, and in order to reduce the spot diameter in such a state, it is necessary to extend the optical path length by switching the reflecting mirror system 7. It was.

  In addition, it is necessary to change the spot diameter depending on the processing conditions. In this case, the beam diameter must be changed by the beam diameter adjusting optical system 3, and the input beam diameter to the acousto-optic element 5 is changed, resulting in a thermal lens effect. Therefore, adjustment for obtaining a desired spot diameter has been difficult.

  In order to reduce the thermal lens effect of the acoustooptic device as described above, for example, as described in Patent Document 2, the acoustooptic device is inserted between the collimator and the beam diameter adjusting optical system, and the beam diameter is enlarged. It is conceivable to enter the acoustooptic device. However, as described in Patent Document 2, if the beam diameter is expanded with a collimator, the response speed of the acousto-optic element is significantly reduced as described above, so that it cannot be expanded. It has been found that the thermal lens effect cannot be reduced because the output of the laser generator in recent years is further increased to the extent that it is not expanded.

JP 2000-263271 A JP 2003-230974 A

  An object of the present invention is to provide a laser processing apparatus having an optical system that reduces the thermal lens effect of the acoustooptic device as described above and does not require switching of the optical path length.

  Another object of the present invention is to prevent the reflected light from the aperture from being returned to the laser generator and causing laser noise in the conventional optical system.

  In order to solve the above problems, a laser generator (1) that emits a laser beam, a collimator (2) that converts the laser beam into a parallel beam, and an acoustic wave that deflects the laser beam and performs ON / OFF control. An optical element (5), a beam diameter adjusting optical system (3) for adjusting the beam diameter of the laser beam, and the laser beam whose beam diameter is adjusted by the beam diameter adjusting optical system (3, 4). A galvano scanner (11) for deflecting and scanning, an fθ lens (8) for condensing and processing the laser beam deflected by the galvano scanner on the work, and for placing the work The acoustooptic device (5) is arranged between the collimator (2) and the beam diameter adjusting system (3, 4), and the collimator Motor (2) the inter-lens distance of the variable may be used a laser machining apparatus being characterized in that so as to counteract the thermal lens effect of the acoustooptic element (5).

  In order to solve the above other problems, an optical element (10) having a function equivalent to a quarter-wave plate is provided between the acousto-optic element (5) and the beam diameter adjusting optical system (3,4). good. Thereby, since the polarization direction of not only the reflection from the aperture but also the reflection from the workpiece can be changed, the return light can be reduced in combination with the polarization reflection characteristic of the acoustooptic device.

  In addition, although the code | symbol in said parenthesis is for contrast with drawing, it does not have any influence on description of a claim by this.

  According to the present invention, the optimum beam diameter can be freely set by the beam diameter adjusting optical system, so that it is not necessary to switch the optical path length by the mirror moving device, and therefore there is no need to provide a conventional mirror moving device.

  Further, according to the present invention, the diameter of the beam incident on the acoustooptic device can be made constant at all times, so that adjustment when the beam diameter is changed is facilitated.

  Further, another invention according to the present invention can reduce the return light to the laser generator.

The example of the optical system of the laser processing apparatus which concerns on this invention is shown. The case where it injects into an acoustooptic device with parallel light with the collimator concerning this invention is shown. The case where the laser beam which gave the divergence angle with the collimator concerning this invention injects into an acousto-optic device is shown. The case where the laser beam which gave the narrow angle with the remedy based on this invention injects into an acousto-optic device is shown. The incident light to the aperture when a circularly polarizing mirror is used in the optical system according to the present invention is shown. 2 shows reflected light from an aperture when a circularly polarized mirror is used in the optical system according to the present invention. The example of the optical system of the conventional laser processing apparatus is shown.

  Hereinafter, embodiments of the present invention will be described.

FIG. 1 shows an example of an optical system of a laser processing apparatus according to the present invention, and the description of the same reference numerals as those in FIG. 7 is omitted. In the present invention, the acousto-optic element 5 is arranged between the collimator 2 and the beam diameter adjusting lens 3 as in Patent Document 2. However, the collimator 2 in front of the acoustooptic device 5 is not a beam diameter expanding optical system as in Patent Document 2, but is a collimator 2 composed of substantially equivalent lenses 2a and 2b as shown in FIG. The magnification is such that the output beam diameter of 1 is slightly expanded or reduced in order to match the optimum beam diameter (about φ10 mm) to the acoustooptic device 5. This is because when the beam diameter is expanded, the response speed of the acoustooptic device is significantly reduced as described above. However, it has been found that the high-power laser generator 1 in recent years has a thermal lens effect even with such a wide beam. Therefore, in the present application, the common-sense collimator 2 is set to fix the inter-lens distance to the sum (f _a + f _b ) of the focal length (f _a ) of the lens 2a and the focal length (f _b ) of the lens 2b. The distance between the lenses 2a and 2b is variable. As a result, as shown in FIG. 3, when the distance between the lenses is reduced, a beam having a divergence angle enters the acoustooptic device 5. This can be used to cancel out the thermal lens effect. When the distance between the lenses is increased, a beam having a narrow angle enters the acoustooptic device 5. By using this, it is possible to cancel the thermal lens effect (concave lens shape) of a beam having a concave beam profile.

  Further, by using the optical system as shown in FIG. 1, the lenses 3a, 3b, and 3c of the beam diameter adjusting lens 3 are adjusted so as to have an optimum beam diameter for a necessary processing spot diameter, and shaped by the aperture 4 and shaped by the galvanometer. Since it can be sent to the scanner 11 and the fθ lens 8, conventional optical path switching becomes unnecessary.

  Furthermore, in the present invention, since the circularly polarizing mirror 10 having the function of a quarter-wave plate is used between the acoustooptic device 5 and the beam diameter adjusting lens system 3, reflected light from the aperture is transmitted to the laser generator 1. Return light can be reduced. The principle will be described with reference to FIGS.

  FIG. 5 shows the polarization state of the light incident on the aperture. The light 12 emitted from the laser generator 1 is set to P-polarized light (the electric vector is in the incident plane of reflection by the acoustooptic element 5). This becomes circularly polarized light 13 by the circularly polarizing mirror 10 and enters the aperture. The (partial) circularly polarized light 13 reflected by the aperture is rotated in the reverse direction, and becomes S-polarized light (the electric vector is perpendicular to the incident surface of reflection by the acoustooptic device 5) by the circularly polarizing mirror 10 and the diffraction efficiency is lowered. The amount of light that is reflected again by the acoustooptic device 5 and returns to the laser generator 1 can be reduced. This is more effective in the case of an acoustooptic device using crystals. Needless to say, this effect can reduce not only the reflection from the aperture but also the return light due to the reflection from the workpiece.

Here, although the circularly polarized mirror is used in this embodiment, it is sufficient if it has a function equivalent to that of a quarter-wave plate, and a normal quarter-wave plate and a total reflection mirror are used in combination. Also good.

DESCRIPTION OF SYMBOLS 1 Laser generator 2 Collimator 3 Beam diameter adjustment lens system 4 Aperture 5 Acoustooptic element 6 Damper 7 Reflection mirror system 8 f (theta) lens 9 Mirror moving apparatus 10 Circularly polarized mirror 11 Galvano scanner 12 Polarization direction of laser beam (linearly polarized light) 13 Circle Polarized laser light 15 Polarization direction after being reflected by a circularly polarized mirror

Claims (2)

A laser generator for emitting a laser beam;
A collimator for collimating the laser beam;
An acousto-optic device for deflecting the laser beam to control ON-OFF;
A beam diameter adjusting optical system for adjusting the beam diameter of the laser beam;
A galvano scanner for deflecting and scanning the laser beam, the beam diameter of which has been adjusted by the beam diameter adjusting optical system;
An fθ lens for condensing and processing the laser beam deflected by the galvano scanner on a workpiece;
In a laser processing apparatus having a stage for placing the workpiece,
The laser processing apparatus characterized in that the acoustooptic element is disposed between the collimator and the beam diameter adjusting system, and the interlens distance of the collimator is made variable to cancel the thermal lens effect of the acoustooptic element. . The laser processing apparatus according to claim 1, wherein an optical element having a function equivalent to that of a quarter-wave plate is provided between the acousto-optic element and the beam diameter adjusting optical system.

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