JP4437878B2 - Q-switch carbon dioxide laser device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a high average output Q-switched carbon dioxide laser used for metal processing or the like, in order to improve the laser irradiation effect or to avoid deterioration of the surface properties of the processed material after processing. The present invention relates to a Q-switched carbon dioxide laser device that obtains a Q-switched laser pulse group that oscillates at time intervals.
[0002]
[Prior art]
When machining a small diameter or deep hole on the surface of a steel material with a pulse laser, if a large volume of metal is removed at once with a single laser pulse having a large energy, the spatter accompanying the machining and the adhesion of the melt around the hole Is generated and the surface properties of the workpiece are deteriorated. As a method of avoiding such spatter and adhesion of the melt around the hole, there is a method of performing one hole processing while gradually expanding the hole depth by using a plurality of laser pulses with relatively small energy. .
[0003]
As a method for obtaining the laser pulse group as described above, for example, in Japanese Patent Laid-Open No. 6-326395, a telescope is incorporated in a resonator of a carbon dioxide laser oscillator, and a high-speed slit having a slit near the confocal position of the telescope is provided. And a method of obtaining a Q-switched laser pulse group consisting of a plurality of Q-switched laser pulses by installing a chopper disk rotating at a time and driving a discharge for exciting a laser medium in synchronization with opening and closing of the slit of the chopper disk. Yes.
[0004]
[Problems to be solved by the invention]
However, in the invention disclosed in Japanese Patent Laid-Open No. 6-326395, the discharge for exciting the laser medium needs to be driven ON / OFF in synchronization with the timing when the slit on the chopper disk passes through the confocal position of the telescope optical system. For this reason, the conventional invention requires a high-speed switching power supply that turns on / off the discharge based on the signal of the slit opening detection device on the rotating chopper disk, and there is a problem that the device cost increases. Accordingly, an object of the present invention is to obtain a laser pulse group similar to the Q-switched carbon dioxide laser pulse group disclosed in JP-A-6-326395 without using expensive equipment such as a high-speed switching power supply. Is.
[0005]
[Means for Solving the Problems]
It is a gist of the present invention has a record over The resonator inside telescope, by installing a high-speed rotating chopper disk having a slit near the confocal position of the telescope, the laser oscillation Q switch oscillation In the Q-switch carbon dioxide laser device, two sets of telescopes, a chopper disk having a narrow aperture slit that rotates at high speed near each confocal position of the two sets of telescopes, and a chopper disc having a wide aperture are provided. A Q-switch carbon dioxide laser device characterized by comprising a chopper disk.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an exemplary view of a chopper disk having a plurality of minute slits S for Q-switch oscillation used in the present invention as a group St. FIG. 2 is an exemplary diagram of a Q-switched carbon dioxide laser oscillator configuration using the chopper disk, and the carbon dioxide laser resonator of the present invention includes the chopper disk 1, the chopper disk rotating motor 2, and the condensing optics shown in FIG. A telescope optical system 5 including a system 4, a resonator rear mirror 3, and a laser output window 6 are included. LB in FIG. 2 represents laser light.
[0007]
FIG. 3 shows the oscillation waveform (a) of the laser oscillator of FIG. 2, the timing when the slit opening S on the chopper disk passes in the vicinity of the confocal position of the telescope 5 (when the slit opening passes the confocal position, the open state is indicated) (B) shows the state (c) of the discharge input for exciting the laser medium. When the chopper disk of FIG. 1 is rotated, the loss of the carbon dioxide laser resonator is reduced when the slit opening S disposed on the chopper disk passes near the confocal position of the telescope, and a peak called a Q switch pulse is obtained. High value pulse laser oscillation occurs.
[0008]
In the chopper disk of FIG. 1, since the slit openings S are arranged in units of several (4 in the illustrated example) unit St, the chopper disk is rotated at a constant speed to give a constant excitation discharge input to the laser medium. Even in this case, the Q-switch pulse oscillation of the carbon dioxide laser is a laser oscillation in which a laser pulse group Pt composed of Q-switch laser pulses P1 to P4 with a period T1 is repeated with a period T2, as shown in FIG. Become. In FIG. 1, there are four micro slits S and four slit groups St, but it is not always necessary to be concerned with this numerical value, and there is one slit group St having two or more slits S as a unit. The Q switch pulse group consisting of a plurality of pulses corresponding to the number of slits S in the slit St can be generated by changing the slit arrangement pattern and the rotation speed of the chopper disk. I can get it.
[0009]
FIG. 4 shows a synthetic chopper disc (c) having a function equivalent to that of the chopper disc of FIG. 1 by bonding a chopper disc (a) having narrow aperture slits at equal intervals and a wide chopper disc (b). FIG. The Q-switched laser pulse group shown in FIG. 3A can also be obtained by using the synthetic chopper disk of FIG. 4C as the chopper disk 1 of the laser resonator of FIG.
[0010]
FIG. 5 is a block diagram of a Q-switched carbon dioxide laser device according to claim 3 of the present invention. Two sets of telescope optical systems 21 and 22 are provided between the two mirrors 11 and 12 constituting the laser resonator, and the chopper disk 23 illustrated in FIG. 4A near the confocal position of each telescope. And the chopper disk 24 illustrated in FIG. 4B is installed. On the chopper disk 23, narrow slits S1 with narrow openings are formed at equal intervals, and on the chopper disk 24, slit openings S2 with wide openings are formed at equal intervals. Each chopper disk is rotated at high speed by a motor 25.
[0011]
When a constant discharge excitation input is applied to the laser medium while the chopper disks 23 and 24 are rotated at high speed, the timing at which the slit openings of the chopper disks 23 and 24 simultaneously pass in the vicinity of the confocal positions of the telescopes 21 and 22. Thus, laser oscillation can be obtained by the Q switch pulse group as illustrated in FIG. 6A.
[0012]
Further, the slit position of the chopper disk 23 having the minute slit opening S1 is detected, and the opening of the chopper disk 24 having the wide opening S2 is also synchronized with the timing when the minute slit opening S1 passes the confocal position of the telescope 21. At the same time, when the rotation of the chopper disk 24 is controlled so as to pass the confocal position of the telescope 22, the opening / closing timing of the synthesis of the slits of the two chopper disks is synchronized as shown in FIG. 7, and the Q-switched laser pulse group Pt A Q-switched laser pulse group having a uniform pulse width of each Q-switched laser pulse Pn can be obtained.
[0013]
【Example】
[Example 1]
As a chopper disk having the slit group illustrated in FIG. 1, ten slit groups each having a slit width of 0.7 mm and four slits formed at intervals of 0.72 degrees are formed on a chopper disk having a diameter of 300 mm at intervals of 36 degrees. I made something. A Q-switched laser in which the chopper disk is rotated at a speed of 6000 revolutions per minute by a motor in the laser resonator of FIG. Got oscillation. The pulse width of each Q-switched laser pulse in the pulse laser group was 5 μs, and the average energy was 7 mJ.
[0014]
[Example 2]
As a chopper disk having equally-spaced micro slits illustrated in FIG. 4A, 500 slits having a slit width of 0.7 mm are formed on a chopper disk having a diameter of 300 mm at intervals of 0.72 degrees. As a chopper disk having equally spaced fine slits as illustrated in (b), a chopper disk having a diameter of 300 mm and 10 slits having a slit width of 3.0 mm formed on a chopper disk having a diameter of 300 mm is manufactured. A chopper disk having the structure shown in FIG.
A Q-switched laser in which the chopper disk is rotated at a speed of 6000 revolutions per minute by a motor in the laser resonator of FIG. Got oscillation. The pulse width of each Q-switched laser pulse in the pulse laser group was 5 μs, and the average energy was 7 mJ.
[0015]
[Example 3]
As a chopper disk having equally spaced micro slits illustrated in FIG. 4A, a chopper disk having a diameter of 300 mm and 500 slits having a slit width of 0.7 mm formed on a chopper disk having a diameter of 300 mm is manufactured. As a chopper disk having equally spaced fine slits as exemplified in 4 (b), a chopper disk having a diameter of 300 mm and 10 slits having a slit width of 3.0 mm formed at intervals of 36 degrees were produced.
The two chopper disks are used as 23 and 24 in the laser resonator of FIG. 5, and each chopper disk is rotated by a motor at a speed of 6000 revolutions per minute, and the frequency of 50 kHz illustrated in FIG. A Q-switched laser oscillation was obtained in which a laser pulse group formed by four Q-switched laser pulses oscillated at a frequency of 1 kHz. The pulse width of each Q-switched laser pulse in the pulse laser group was 5 μs, and the average energy was 7 mJ.
[0016]
[Example 4]
Using the laser oscillators of Examples 1, 2, and 3, dull hole processing was performed on the surface of the rolling roll. FIG. 8 is a schematic view of the used rolling roll dull processing apparatus. The processing apparatus includes the Q-switched laser oscillator 31 of the present invention described in the first and second embodiments, the bend mirror 32, the nozzle 33, the condenser lens 34, the single-axis stage 35, the work roll 36, and the roll rotation device 37. Composed.
[0017]
The Q oscillator pulse group Pt shown in FIGS. 3A and 6A is emitted from the laser oscillator 11. The rolling roll has a diameter of 450 mm and a width of 2000 mm (processing object width is 1300 mm). The rolling roll 36 is rotated at a constant speed of 17 rpm by a roll rotating device 37, and the condenser lens 34 and the processing nozzle 33 are parallel to the axis of the rolling roll 36 by a uniaxial stage 35 at a speed of 6.8 mm / min. Moving.
[0018]
The frequency of each Q-switched laser pulse Pn in the Q-switched laser pulse group Pt is 50 kHz, and the Q-switched pulses from P1 to P4 are irradiated at positions shifted by about 4 μm on the surface of the rolling roll. The amount of deviation 4 μm is sufficiently small compared to the spot diameter of the focused laser beam, so that it is as if four Q-switched laser pulses from P1 to P4 were irradiated at the same location on the surface of the rolling roll. Drilling with a single opening in which the hole depth is sequentially increased by four Q-switched laser pulses is performed on the surface of the rolling roll.
[0019]
On the other hand, since the repetition frequency of the Q-switched laser pulse group Pt is 1 kHz, the irradiation of the Q-switched laser pulse up to P4 is completed, and it takes about 900 μs until the first pulse P1 of the next laser pulse group Pt is irradiated. There is time, during which the outer circumference of the rolling roll is shifted by 400 μm. At this timing, four Q-switch laser pulses from P1 to P4 are irradiated again at a frequency of 50 kHz, and a dull hole having one opening is processed again on the roll surface.
In this way, a hole diameter of 80 μm and a depth of 30 μm were drilled on the surface of the rolling roll at a pitch of 400 μm.
[0020]
In the dull hole processing with the laser pulse group Pt, the dull hole formed by the front Q-switch laser pulse guides the subsequent Q-switch laser pulse to the inside by multiple reflection, and increases the absorption efficiency of the laser beam at the bottom of the hole. There is an effect. For this reason, processing advances selectively in the depth direction, and a dull hole processing with a smaller diameter and a deep hole can be performed than when processing with a single Q-switch laser pulse having a large energy.
[0021]
In the present embodiment, the above-mentioned dull hole processing with a diameter of 90 μm and a depth of 50 μm was possible with four Q-switched laser pulses having an energy of 7 mJ, but one Q-switched laser pulse having an energy of 28 mJ was rolled. When the roll surface was irradiated, a large and shallow dull hole process with a hole diameter of 120 μm and a depth of 25 μm was only obtained.
[0022]
Further, in this embodiment, by performing one dull hole processing by sequentially expanding the hole depth with P1 to P4 Q switch pulses having an energy of 10 mJ, the height of the melt adhering to the outer periphery of the hole called a rim is increased. When the dull hole processing was performed with one Q-switched laser pulse having an energy of 50 mJ, the rim formation with a height of 8 μm was observed. It was possible to achieve a cleaner drilling.
[0023]
【The invention's effect】
As described above, in a Q-switched carbon dioxide laser device using a rotating chopper disk, the chopper disk of the present invention or two sets of telescopes and two chopper disks oscillate at a time interval of the order of several tens of μs. The Q-switched laser pulse group can be obtained, and there is an advantage that the laser irradiation effect on the laser processing of the metal can be improved.
[Brief description of the drawings]
FIG. 1 is an exemplary view of a chopper disk used for Q-switched carbon dioxide laser oscillation of the present invention.
FIG. 2 is an exemplary diagram of a Q-switched carbon dioxide laser oscillator configuration according to the present invention.
FIG. 3 is a view showing an example of a laser oscillation waveform by the Q-switched carbon dioxide laser oscillator of the present invention.
FIG. 4 is a view showing an example of a chopper disk used in the Q-switched carbon dioxide laser oscillator of the present invention.
FIG. 5 is an exemplary diagram of a Q-switched carbon dioxide laser oscillator configuration according to the present invention.
FIG. 6 is a view showing an example of the laser oscillation waveform by the Q-switched carbon dioxide laser oscillator of the present invention and the opening / closing timing of two chopper disk slit openings.
FIG. 7 is a view showing an example of the laser oscillation waveform by the Q-switched carbon dioxide laser oscillator of the present invention and the opening / closing timing of two chopper disk slit openings.
FIG. 8 is a block diagram of a rolling roll dull processing apparatus using the Q-switched carbon dioxide laser of the present invention.
[Explanation of symbols]
P1, P2, P3, P4: Q-switched laser pulse waveform Pt: Q-switched laser pulse group T1: Q-switched laser pulse Pn period T2: Laser-pulsed group Pt period S, S1, S2: Slit opening St : Slit aperture group LB: Laser light 1, 23, 24: Chopper disk 2, 25: Motor 3: ZnSe concave mirror 4: ZnSe lenses 5, 21, 22: Telescope 6, 11: ZnSe half mirror for emitting laser light 12: ZnSe total reflection mirror 31: Q-switch laser oscillator 32 of the present invention 32: Bend mirror 33: Processing nozzle 34: Condensing lens 35: Single axis table 36: Rolling roll 37: Roll rotating device

Claims (1)

  Two sets of Q-switched carbon dioxide laser devices that have a telescope in the laser resonator and a high-speed rotating chopper disk having a slit near the confocal position of the telescope to make the laser oscillation Q-switched oscillation Q telescope, and two chopper discs including a chopper disc having a narrow aperture slit and a chopper disc having a wide aperture that rotate at high speed near the confocal positions of the two telescopes. Switch carbon dioxide laser device.

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