JP2007275908A - Laser machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser machining apparatus which can perform high-speed shuttering of a laser beam. <P>SOLUTION: The laser machining apparatus 1 for machining a surface of a workpiece W by irradiating it with a laser beam emitted from a laser generator 11 comprises: a shutter optical system 12 provided with a polarization control element 23 for switching a polarization condition of a laser beam B to an s-polarized light component a p-polarized light component, and a polarization beam splitter 24 which permeates one of the laser beam of the s-polarized light component and the p-polarized light component and reflects anotgher one; and a controller 20 for controlling the switching of the polarized light components permeated through the polarization control element. The laser beam having the s-polarized light component or the p-polarized light component emitted from the laser generator 11 is controlled so as to be switched to the polarized light components permeating the polarization control element 23 by the controller 20, to thereby reflect the polarization beam splitter 24 to shut off the irradiation to the workpiece W, or to permeate the polarization beam splitter 24 to irradiate the workpiece W. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus that processes irregularities on the surface of a workpiece using a laser beam, and more particularly to a laser processing apparatus capable of complete shuttering of a laser beam.

  A laser processing apparatus using a YAG laser with good focusing performance is used as a laser processing apparatus for processing irregularities on the surface of a workpiece using a laser beam, and a laser processing apparatus provided with shutter means capable of high-speed response on the optical path. It is proposed in Japanese Patent Laid-Open No. 2002-160086. This is a solution to the problem that the acousto-optic device, which is the shutter means, leaks about 10% even when the laser beam is cut off during non-processing, and the work surface is damaged. is there.

In the laser processing apparatus, as shown in FIG. 6, a laser beam emitted from a laser oscillator 100 passes through a beam modulator 110 including two acoustooptic elements 101 and 102, an optical rotation means 103, and a mask 104. Then, the position is adjusted by the galvanometer mirror 120 and the work W is irradiated. In order to enhance the attenuation rate characteristic, the two acoustooptic elements 101 and 102 are arranged so that their inclinations are different from each other by 90 degrees, and in order to rotate the polarization plane of the laser beam, the optical rotation means 103 is λ / 2. It is a board. The beam modulator 110 performs a shuttering operation for passing or attenuating the laser beam according to an electrical signal from the controller 115.
JP 2002-160086 (page 3-4, FIG. 1)

The conventional laser processing apparatus has been devised so as not to affect the workpiece more by the shutter means using a plurality of acousto-optic elements. For this reason, even though the shutter means is used, the laser beam cannot be completely cut, and leakage light still exists.
Therefore, an object of the present invention is to provide a laser processing apparatus capable of complete shuttering of a laser beam in order to solve such a problem.

  A laser processing apparatus according to the present invention processes a surface of a workpiece by irradiating the workpiece with a laser beam emitted from a laser oscillator through an optical path provided with a beam expander or a condenser lens. A shutter optical system comprising: a polarization control element that switches a polarization state of a beam to an s-polarized component or a p-polarized component; and a polarizing beam splitter that transmits one of the laser beams of the s-polarized component or the p-polarized component and reflects the other And a controller for controlling switching of the polarization component transmitted through the polarization control element, and the polarization component transmitted through the polarization control element by the controller with respect to the laser beam of the s-polarized component or the p-polarized component emitted from the laser oscillator. By controlling the switching, the polarized beam splitter is reflected to irradiate the work Blocked or wherein the the polarizing beam splitter by transmitting is obtained so as to irradiate the workpiece.

  Further, the laser processing apparatus according to the present invention performs processing on the workpiece surface by irradiating the workpiece with the laser beam emitted from the laser oscillator through an optical path provided with a beam expander or a condenser lens. A birefringent element that divides the non-polarized laser beam emitted from the laser oscillator into two laser beams of s-polarized component and p-polarized component, and one of the two laser beams of s-polarized component and p-polarized component A half-wave plate that changes the polarization state of one laser beam to match the polarization state of the other laser beam, a polarization control element that switches the polarization state of the two laser beams to the s-polarization component or the p-polarization component, and s-polarization A polarizing beam splitter that transmits one of the component or p-polarized component laser beams and reflects the other, and two laser beams that have passed through the polarizing beam splitter. A half-wave plate that changes the polarization state of one of the beams, a birefringent element that converts two laser beams of s-polarized component and p-polarized component into one unpolarized laser beam, and a polarization control element And a controller for controlling the switching of the transmitted polarization component.

  Further, the laser processing apparatus according to the present invention performs processing on the workpiece surface by irradiating the workpiece with the laser beam emitted from the laser oscillator through an optical path provided with a beam expander or a condenser lens. The laser oscillator emits a linearly polarized laser beam, a polarization control element that switches a polarization state of the laser beam to an s-polarized component or a p-polarized component, and an s-polarized component or a p-polarized component laser beam. A polarization beam splitter that transmits one of them and reflects the other, and a controller that controls switching of polarization components that pass through the polarization control element.

In the laser processing apparatus according to the present invention, the laser oscillator is preferably a fiber laser oscillator.
In the laser processing apparatus according to the present invention, the polarization control element is preferably an electro-optic element (EOM), an acousto-optic element (AOM), or a Faraday rotator.

  Therefore, according to the laser processing apparatus of the present invention, the laser beam of the s-polarized component or the p-polarized component is arbitrarily switched by the polarization control element, and in one polarization state, the laser beam is irradiated to the workpiece through the polarizing beam splitter. In the other polarization state, the polarization beam splitter is totally reflected and branched from the normal optical path, so that the laser beam applied to the workpiece can be completely blocked.

  Next, an embodiment of a laser processing apparatus according to the present invention will be described below with reference to the drawings. The laser processing apparatus has a method of increasing / decreasing the laser output in addition to changing the processing speed as means for controlling the depth direction when processing the unevenness on the surface of the workpiece. Increase and decrease to control unevenness. FIG. 1 is a conceptual diagram showing a laser processing apparatus for performing such processing.

  The laser processing apparatus 1 of this embodiment includes a fiber laser oscillator 11. The main body has a plurality of semiconductor laser elements with fibers and a double clad fiber, and the laser beam output from the semiconductor laser element as a pumping light source is collected in a double clad fiber as a laser medium and resonated in the double clad fiber. A laser beam is emitted to the outside. The fiber laser oscillator 11 can obtain a laser beam with extremely high light condensing performance and straightness as compared with the conventional semiconductor laser oscillator.

  In this embodiment, a shutter optical system 12 that switches between irradiation and blocking of the workpiece W is disposed on the optical path of the laser beam B emitted from the fiber laser oscillator 11. Further, a plano-concave lens 13 and a plano-convex lens 14 that form a beam expander that expands the beam diameter of the laser beam B that has passed through the shutter optical system 12 are arranged in order. A reflection mirror 15 that changes the direction of the laser beam B is placed behind the condenser. A condensing lens 16 is disposed in front of the workpiece W at the destination of the reflected laser beam B. The workpiece W is fixed to a restraining jig on the XY table 17 and is configured to change the relative position of the irradiated laser beam B by moving the table according to the processing data.

  The laser processing apparatus 1 is used for applications such as three-dimensional engraving. Specifically, the irradiation position of the laser beam B moves from one end of the X axis to the other end at a constant speed. When the other end is reached, the Y axis moves several tens of μm, and at the same time, the X axis moves from the other end to one end. Next, while moving the laser beam B again, the movement from one end of the X axis to the other end at a constant speed is repeated. By adjusting on / off of the laser beam B and increase / decrease in its output, the surface of the resin is formed with irregularities, and a plurality of three-dimensional engravings can be manufactured at a time. The unevenness formed on the surface of the workpiece W is formed in a step shape as in the cross section shown in FIG. 3, and the width t for one step is about 40 μm. Therefore, the laser processing apparatus 1 performs processing by controlling the output for each step and changing the increase / decrease in the laser output for adjusting the processing depth at intervals of the width c.

By the way, although the fiber laser oscillator 11 is used as the laser oscillator in the present embodiment, for example, a lamp-excited YAG CW oscillator or an LD-excited YAG CW oscillator can be considered as an oscillator that increases or decreases the laser output.
The lamp-excited YAG CW oscillator increases and decreases analog laser output at high speed. The oscillator includes an AO-Q switch using an acousto-optic element, and an RF driver that drives the AO-Q switch is connected to the lamp-excited YAG CW oscillator. . In addition, the laser output is changed as shown in FIG. 4 by analog modulation of the RF power loaded on the AO-Q switch.

On the other hand, in the LD-pumped YAG CW oscillator, increase / decrease in laser output is adjusted by driving the output of the LD itself at high speed. Although it is possible to increase / decrease the laser output by increasing / decreasing the RF power applied to the AO-Q switch as in the case of lamp excitation, it is possible to collect light when compared with the same laser output (100 to 200 W class). Since it is inferior in performance, it is not suitable for fine processing. In this respect, the fiber laser has a good M ² value, which is a beam parameter, and has a very high light collecting property. However, the fiber laser has a slight time lag (on the order of several tens of msec) with respect to the on / off control when the laser beam is oscillated and stopped.

  Further, the YAG CW oscillator in addition to the above-described lamp-pumped laser oscillator can be driven at a very high speed (on the order of several hundreds nsec) by modulating the RF power loaded on the AO-Q switch with an analog signal. However, in this case, there is a problem that the laser output is increased or decreased by changing the Q value in the oscillator. Here, FIG. 5 is a diagram showing the waveform of the RF power and the laser transmission waveform as the Q value increases and decreases. In particular, FIG. 5A shows a case where the RF power is suddenly decreased, and FIG. 5B shows a case where the RF power is suddenly increased.

  When the Q value in the oscillator was changed as indicated by the solid line, the laser oscillation waveform at the time of the first pulse phenomenon in which the RF power was rapidly increased or decreased was not immediately stabilized but an unstable waveform change appeared. For example, when the Q value is sharply decreased and the RF power is rapidly reduced at t1 as shown in FIG. 5A, the laser output is increased to a predetermined value accordingly. However, until the laser output is stabilized at a predetermined value at that time, the value jumps up instantaneously as shown in the laser oscillation waveform from t1 to t2 and then stabilizes after fluctuating up and down. On the other hand, when the Q value is rapidly increased and the RF power is rapidly increased at t3 as shown in FIG. 5B, the laser output is lowered to a predetermined value accordingly. However, even in this case, until the laser output stabilizes to a predetermined value, the value rises and stabilizes after a certain period of time, as shown in the laser oscillation waveform from t3 to t4.

  As a result, when analog modulation is performed at high speed using the AO-Q switch, an unstable change occurs in the laser output in this way, so that stable energy cannot be supplied to the workpiece W, which affects fine processing. It will be. In the present embodiment, in consideration of such points, the fiber laser oscillator 11 using an LD laser as pumping light is used. However, since the fiber laser has a problem as described above, the present embodiment attempts to solve the problem as described below.

Next, the shutter optical system 12 constituting the laser processing apparatus 1 will be described with reference to FIG. FIG. 2 is a conceptual diagram showing the configuration of the shutter optical system 12.
The laser beam B emitted from the fiber laser oscillator 11 is generally randomly polarized light whose polarization is not controlled. Therefore, the shutter optical system 12 is first provided with a birefringent element 21 that divides the laser beam B into a p-polarized component component and an s-polarized component component.

  Of the laser beams of the p-polarized component and the s-polarized component, the half-wave plate 22 is arranged on the optical path of the p-polarized component, and the p-polarized component passes through the half-wave plate 22 and is changed to the s-polarized component. It is supposed to be. Therefore, the two laser beams in the polarized laser beam are once aligned with the s-polarized component. Further, an electro-optic element (EOM) 23 for switching and controlling the polarization state of the laser beam is disposed on the optical path so that two s-polarized light components are transmitted. The EOM 23 controls the polarization of two s-polarized components simultaneously. In this embodiment, when a load voltage is applied, the s-polarized light is changed to p-polarized light, and the s-polarized component and the p-polarized component are selectively used. Can be taken out.

  A polarization component splitter 24 is further arranged on the optical path of the laser beam. The polarization component splitter reflects or transmits the polarization component depending on the polarization state. In particular, the polarization component splitter 24 of the present embodiment reflects the p polarization component and transmits the s polarization component. Therefore, in the shutter optical system 12, the laser beam of the p-polarized component reflected by the polarization component splitter 24 is branched off from the normal optical path, and is irradiated to a damper (not shown).

  Further, a half-wave plate 25 is provided on the optical path on one side of the two s-polarized components transmitted through the polarization component splitter 24 on the regular optical path. In the present embodiment, a half-wave plate 25 is provided on the optical path on the p-polarized component side among the two divided by the birefringent element 21. Therefore, the laser beam is changed to the s-polarized component by the half-wave plate 22 and is again returned to the p-polarized component by the half-wave plate 25. A birefringent element 26 that transmits both the p-polarized component and the other s-polarized component transmitted through the polarization component splitter 24 is disposed on the optical path. The birefringent element 26 returns the laser beam of the p-polarized component and the s-polarized component to the same random polarization state as the laser beam B emitted from the fiber laser oscillator 11.

  Thus, the shutter optical system 12 is configured to perform shuttering in a state in which polarization control is possible, and irradiation on / off of the workpiece W is performed by control of the EOM 23. Therefore, the controller 20 is connected to the EOM 23 via the EO power source 18 as shown in FIG. In addition to the EOM 23, the controller 20 is connected to a laser power source 19 for driving the fiber laser oscillator 11 and an XY table 17 on which a work W is placed. For example, when the laser processing apparatus 1 performs the above-described processing of the three-dimensional engraving, a predetermined processing program is stored in the storage means of the controller 20, and based on this, the fiber laser oscillator 11, the EOM 23, and the XY table are stored. 17 is configured to drive and control.

  Then, next, the operation | movement is demonstrated about the laser processing apparatus 1 of this embodiment. In the laser processing apparatus 1, a control signal is sent from the controller 20 to the laser power source 19, and the excitation source of the fiber laser oscillator 11 is activated via the laser power source 19. Therefore, in the fiber laser oscillator 11, energy is supplied to the semiconductor laser element which is an excitation light source, and a laser beam is emitted. The laser beam emitted from the semiconductor laser element is collected in a double clad fiber that is a laser medium and resonates inside to become a laser beam B having extremely high light condensing properties and straightness.

  The laser beam B is randomly polarized, but is divided into an s-polarized component and a p-polarized component by the birefringent element of the shutter optical system 12. The divided p-polarized component is converted into an s-polarized component by the half-wave plate 22 on the optical path, and the two laser beams as the s-polarized component are transmitted through the EOM 23. The load voltage of the EOM 23 is controlled via the EO power source 18 by a control signal from the controller 20. Accordingly, either the s-polarized component or the p-polarized component laser beam can be selectively extracted by controlling the load voltage.

  Therefore, when blocking the irradiation of the laser beam B on the workpiece W, a load voltage is applied to the EOM 23. At this time, since the polarization state is changed in the EOM 23, the two laser beams pass through the EOM 23 and are changed from the s-polarized component to the p-polarized component. Then, the two laser beams of the p-polarized component are totally reflected by the polarization component splitter 24 and irradiated to a damper (not shown), so that the laser beam B emitted from the fiber laser oscillator 11 is all from the normal optical path. Come off. Thus, complete shuttering is performed without irradiating the workpiece W with the laser beam B by the control of the EOM 23.

  On the other hand, if no load voltage is applied to the EOM 23, the laser beam of the s-polarized component is transmitted through the EOM 23 as it is, and further transmitted through the polarization component splitter 24. One of the laser beams transmitted through the polarization component splitter 24 passes through the half-wave plate 25 and is converted into a p-polarized component. Then, this p-polarized component laser beam and another s-polarized component laser beam transmitted through the polarization component splitter 24 are transmitted through the birefringent element 26, where they are converted into one laser beam B in a randomly polarized state. Returned.

  The laser beam B exiting the shutter optical system 12 becomes parallel light expanded by the plano-concave lens 13 and the plano-convex lens 14 of the beam expander, and reflects the reflection mirror 15. Thereafter, the laser beam B is irradiated as a minimal spot on a predetermined processing point on the surface of the workpiece W by the condenser lens 16. A workpiece W is placed on the XY table 17 by a restraining jig, and the movement of the table is controlled based on the machining data. Accordingly, if the workpiece W on the XY table 17 is irradiated with the laser beam B, the irradiation position is relatively moved, and the on / off of the laser beam B and the increase / decrease in its output are adjusted. A predetermined laser processing is performed on the surface.

  Therefore, according to the laser processing apparatus 1 of the present embodiment, the laser beam B in the randomly polarized state is divided into the s-polarized component and the p-polarized component in the shutter optical system 12, and then the two laser beams are converted to the p-polarized light. It has become possible to completely block the laser beam B branched from the regular optical path and irradiated onto the workpiece W. Since the high-speed shuttering can be performed by the control of the EOM 23, the irradiation on / off of the work W can be performed by the control of the EOM 23, and the time lag which has been a problem in the control of the fiber laser oscillator 11 can be solved. It was.

In addition, the fiber laser has very little deterioration in beam parameters due to the high output characteristic of the laser oscillator of lamp excitation and LD excitation, and the spot diameter at the time of condensing can be expected to be a value as simulated, and more energy can be obtained at the time of condensing. The density can be increased. Therefore, according to the laser processing apparatus 1 of the present embodiment, since the shutter optical system 12 is provided, the finer and higher-speed processing of the workpiece W is processed by taking advantage of the fiber laser.
Further, in the shutter optical system 12, when the laser beam B is irradiated onto the workpiece W, the p-polarized component is once changed to s-polarized light and then returned to p-polarized light, so that the polarization state is the same as that emitted from the fiber laser oscillator 11. There is no energy loss because the work W is irradiated.

As mentioned above, although one Embodiment was described about the laser processing apparatus of this invention, this invention is not limited to this, A various change is possible in the range which does not deviate from the meaning.
For example, in the above embodiment, the fiber laser oscillator 11 emits a randomly polarized laser beam. However, a fiber that emits a linearly polarized laser beam that is provided with a Brewster window and can select only one polarized light. In the case of a laser oscillator, the birefringent elements 21 and 26 and the half-wave plates 22 and 25 that are divided into s-polarized light and p-polarized light can be omitted. Therefore, a fiber laser oscillator that emits a linearly polarized laser beam can be a simpler configuration and a compact laser processing apparatus.

In the above embodiment, the EOM 23 is used to switch the polarization state of the laser beam B in the shutter optical system 12, but other than this, a Faraday rotator or a polarization element that rotates a polarization direction called an optical isolator is used. AOM or the like may be used. Even when such a polarization control element such as a Faraday rotator or an AOM is used, high-speed shuttering is possible by performing on / off control in the same manner as the EOM 23.
In the above embodiment, the s-polarized component is incident on the EOM 23 and the p-polarized component is reflected by the polarization component splitter 24. However, this relationship may be reversed between the s-polarized light and the p-polarized light.

In the above embodiment, the fiber laser oscillator 11 is used to eliminate the time lag as described above. Instead of the fiber laser oscillator 11, a lamp YAG CW excitation oscillator that uses an AO-Q switch, An LD-excited YAG CW oscillator may be used. In this case, an unstable change occurs in the laser output as shown in FIG. 5. However, high-speed shuttering can be performed by on / off control by the EOM 23, and a stable laser beam can be irradiated to the workpiece W. become.
Furthermore, in the above-described embodiment, it has been described on the assumption that a sudden on / off control is performed on an optical element such as the EOM 23 that performs shuttering. However, a polarization component that is transmitted by analogly modulating the control signal is analog. You may make it modulate to.

It is the conceptual diagram which showed one Embodiment of the laser processing apparatus which concerns on this invention. It is the conceptual diagram which showed the shutter optical system which comprises the laser processing apparatus of embodiment. It is the figure which showed the process end surface of the workpiece | work. It is the figure which showed the relationship between RF power and a laser output on the graph. It is the figure which showed the waveform of RF power and the laser transmission waveform accompanying increase / decrease in Q value. It is the conceptual diagram which showed the conventional laser processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 11 Fiber laser oscillator 12 Shutter optical system 13 Plano-concave lens 14 Plano-convex lens 15 Reflection mirror 16 Condensing lens 17 XY table 18 EOM power supply 19 Laser power supply 20 Controller 21, 26 Birefringence elements 22, 25 1/2 wavelength plate 23 EOM
24 Polarization component splitter B Laser beam W Workpiece

Claims (5)

In a laser processing apparatus for processing a workpiece surface by irradiating the workpiece with a laser beam emitted from a laser oscillator through an optical path provided with a beam expander or a condenser lens,
Shutter optics comprising a polarization control element that switches the polarization state of a laser beam to an s-polarized component or a p-polarized component, and a polarizing beam splitter that transmits one of the s-polarized component or p-polarized component laser beams and reflects the other. A system and a controller for controlling the switching of the polarization component transmitted through the polarization control element,
For the laser beam of s-polarized component or p-polarized component emitted from the laser oscillator, the polarization beam splitter is reflected to control the irradiation of the workpiece by controlling the switching of the polarized component that passes through the polarization control element by the controller. Or a laser beam machining apparatus, wherein the workpiece is irradiated with light through a polarizing beam splitter. In a laser processing apparatus that processes a workpiece surface by irradiating the workpiece with a laser beam emitted from a laser oscillator through an optical path provided with a beam expander or a condenser lens,
A birefringent element that divides an unpolarized laser beam emitted from a laser oscillator into two laser beams of an s-polarized component and a p-polarized component;
a half-wave plate that changes the polarization state of one of the two laser beams of the s-polarization component and the p-polarization component to match the polarization state of the other laser beam;
A polarization control element that switches the polarization state of the two laser beams to an s-polarized component or a p-polarized component;
a polarizing beam splitter that transmits one of the laser beams of the s-polarized component or the p-polarized component and reflects the other;
A half-wave plate for changing the polarization state of one of the two laser beams transmitted through the polarizing beam splitter;
a birefringent element that converts two laser beams of an s-polarized component and a p-polarized component into one unpolarized laser beam;
A laser processing apparatus comprising: a controller that controls switching of a polarization component transmitted through the polarization control element. In a laser processing apparatus that processes a workpiece surface by irradiating the workpiece with a laser beam emitted from a laser oscillator through an optical path provided with a beam expander or a condenser lens,
The laser oscillator emits a linearly polarized laser beam,
A polarization control element that switches the polarization state of the laser beam to an s-polarized component or a p-polarized component;
a polarizing beam splitter that transmits one of the laser beams of the s-polarized component or the p-polarized component and reflects the other;
A laser processing apparatus comprising: a controller that controls switching of a polarization component transmitted through the polarization control element. In the laser processing apparatus according to any one of claims 1 to 3,
The laser processing apparatus, wherein the laser oscillator is a fiber laser oscillator. In the laser processing apparatus according to any one of claims 1 to 4,
The laser processing apparatus, wherein the polarization control element is an electro-optic element (EOM), an acousto-optic element (AOM), or a Faraday rotator.

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