GB2499302A

GB2499302A - Laser oscillator and laser processing apparatus

Info

Publication number: GB2499302A
Application number: GB1300021.1A
Authority: GB
Inventors: Tuyoshi Nagano
Original assignee: Omron Corp; Omron Tateisi Electronics Co
Current assignee: Omron Corp
Priority date: 2012-02-09
Filing date: 2013-01-02
Publication date: 2013-08-14
Also published as: JP2013162114A; KR20130092440A; GB201300021D0

Abstract

A plurality of condensers 51-1 to 51-3 are arranged in a multistage manner to include a plurality of laser diodes 55-1 to 55-28 which generate excitation light and laser mediums56-1 to 56-3 which absorb the excitation light generated by the laser diodes to thereby emit laser beams. Cooling water that is cooled to a predetermined temperature by a cooler is circulated throughout the condensers through pipes. Valves 72-1 to 72-4 control the amount of cooling water supplied to each of the condensers based on the temperature of each of the condensers, the temperature being measured by an inlet temperature measuring unit 73 and outlet temperature measuring unit 74-1 to 74-3. The present invention can be applied to a laser processing apparatus.

Description

1

LASER OSCILLATOR AND LASER PROCESSING APPARATUS

[0001] The present invention relates to a laser oscillator and a laser processing apparatus, and particularly to an inexpensive and high output laser oscillator and an inexpensive and high output laser processing apparatus.

[0002] As a method for increasing the output power of a laser output from a laser oscillator, methods such as (1) increasing the output power of a laser diode; (2) increasing the number of laser diodes; and (3) making a laser medium thick are conceivable.

[0003] However, in the method (1), when current is being increased, laser output becomes saturated at a predetermined current value due to a thermal lens effect. Further, in the method (2), the length of a laser medium becomes long or a space between a laser diode and a laser medium becomes large,

which causes an extended pulse width or a high lasing threshold. Furthermore, in the method (3), a lasing threshold becomes high and beam quality is therefore deteriorated.

[0004] Accordingly, it is believed that arranging condensers in series is effective in order to achieve high output power without changing the pulse width, lasing threshold, and beam quality.

2

[0005] Therefore, in a conventional laser oscillator, in order to cool a plurality of condensers arranged in series, cooling water discharged from a single cooler is divided in parallel into the same number as the number of the condensers to thereby supply the same amount of cooling water to each of the condensers.

[0006] In Japanese Unexamined Patent Publication No. 1-26196, there is proposed, as a technique for cooling a plurality of condensers which are arranged in a multistage manner as above, a technique that achieves efficient cooling by distributing cooling water to a laser medium, a lamp for excitation, and a casing of the condenser at a rate of 30%, 60%, and 10%, respectively.

[0007] Further, in Japanese Patent No. 3290345, there is proposed a technique for controlling the oscillation wavelength of a laser diode so as to be a wavelength that is most effectively used in a laser medium by temperature regulation.

[0008] In the meantime, a condenser has a configuration in which laser diodes are arranged so as to surround a laser medium. Therefore, as the number of serially arranged condensers is larger, the preparing laser diodes having a similar operating current and a similar oscillation wavelength is more difficult in terms of cost. According to catalogs, it is obvious that, in a laser diode, the range of operating current is 25 to 30 A and the range of oscillation wavelength is 805 to 811 nm, for example. Therefore, there are variations in these ranges.

[0009] However, in an yttrium aluminum garnet crystal (YAG) which is a typical laser medium, for example, the range of wavelength in which the absorptivity thereof is equal to or more than half of the maximum absorptivity is an approximately 1 nm range. Therefore, even if the temperature of cooling water is regulated so that the laser output of a laser oscillator becomes maximum,

3

most of laser diodes emit excitation light at a wavelength at which the absorptivity is low. Such excitation light which is not converted into light is converted into heat to thereby raise the temperature of the condenser.

However, if excessive current is injected into a low gain condenser in expectation of a gain equal to the gain of a high gain condenser, although the gain is actually increased, the temperature of the low gain condenser is increased more and more. When the temperature of a specific condenser is increased, thermal lens effects lose balance. As a result, the laser output becomes saturated.

[0010] The present invention has been devised in view of the above circumstances. Particularly, even when a plurality of condensers are provided in a multistage manner, an inexpensive and high output laser oscillator is achieved by regulating a heat exchange amount for each of the condensers only with cooling water having the same temperature, the cooling water being supplied from a single cooler, by providing a valve for regulating the amount of cooling water with respect to each of the condensers so that the thermal lens effects can be uniformly maintained as a whole to thereby suppress saturation of the laser output.

[0011 ] In accordance with one aspect of the present invention, a laser oscillator includes a plurality of condensers each having a plurality of laser diodes generating excitation light and a laser medium absorbing the excitation light generated by the laser diodes to emit laser beams, a cooler for cooling cooling water for cooling the condensers to a predetermined temperature, a temperature

4

measuring unit for measuring a temperature of each of the condensers, and a valve for controlling an amount of cooling water supplied to each of the condensers based on the temperature of each of the condensers, the temperature being measured by the temperature measuring unit.

[0012] In the above aspect of the present invention, the plurality of laser diodes generate excitation light. The laser medium of each of the condensers absorbs the excitation light generated by the laser diodes to thereby emit laser beams. The cooler cools cooling water which cools the condensers to a predetermined temperature. The temperature measuring unit measures the temperature of each of the condensers. The valve controls an amount of cooling water supplied to each of the condensers based on the temperature of each of the condensers, the temperature being measured by the temperature measuring unit.

[0013] Accordingly, even when a plurality of condensers are arranged in a multistage manner, it is possible to uniformly maintain the thermal lens effects by uniformly controlling the temperatures of the condensers by the single cooler. Therefore, an inexpensive and high output laser oscillator can be achieved.

[0014] The temperature measuring unit may measure an inlet temperature and an outlet temperature of cooling water for cooling each of the condensers and obtain an average of the inlet temperature and the outlet temperature as the temperature of each of the condensers.

[0015] This makes it possible to measure the temperature of each of the condensers as the temperature of cooling water.

[0016] The valve may control an amount of cooling water supplied to each of the condensers so that temperatures of the condensers are controlled to be

5

equal to each other based on the temperature of each of the condensers measured by the temperature measuring unit.

[0017] According to this, since the condensers are controlled to have the same temperature, it becomes possible to uniformly maintain the thermal lens effects. As a result, a high output laser oscillator can be achieved,

[0018] The laser oscillator may further include a plurality of current output units each controlling an amount of current supplied to the laser diodes of each of the condensers. Further, each of the current output units may control the amount of current supplied to each of the condensers so as to equalize gains of the condensers after the amount of cooling water is controlled by the valve.

[0019] This makes it possible to equalize the gains of the condensers. As a result, a high output laser oscillator can be achieved.

[0020] The laser oscillator may further include a valve controller for controlling an opening degree of the valve for controlling the amount of cooling water supplied to each of the condensers, and a setting information storage unit for storing, as setting information, a temperature of each of the condensers, the temperature being measured by the temperature measuring unit after the opening degree of the valve is controlled by the valve controller.

[0021] This makes it possible to maintain the temperatures of the condensers at the same temperature. As a result, an inexpensive, stable, and high output laser oscillator can be achieved.

[0022] According to this, it becomes possible to achieve a high output laser oscillator and also achieve a laser processing apparatus using the high output laser oscillator.

[0023] According to the present invention, it is possible to achieve an

6

inexpensive and high output laser oscillator, and also achieve an inexpensive and high output laser processing apparatus.

In the drawings:

[0024] FIG. 1 is a block diagram illustrating a configuration example of a laser processing apparatus according to a first embodiment to which a laser oscillator of the present invention is applied;

FIG. 2 is a side view illustrating a laser beam generating mechanism of the laser oscillator of FIG. 1;

FIG. 3 is a diagram illustrating piping of cooling water of a cooling mechanism of the laser oscillator of FIG. 1;

FIG. 4 is a diagram illustrating an absorption spectrum of YAG and an emission spectrum of a laser diode;

FIG. 5 is a diagram illustrating waveforms each of which shows a differential temperature between an inlet temperature and an outlet temperature of cooling water with respect to a temperature of each of condensers when the condensers are cooled, the waveforms corresponding to different amounts of fWtlinn usatar-

'5? ■« WilVI ,

FIG. 6 is a diagram illustrating waveforms each of which shows a differential temperature between an inlet temperature and an outlet temperature of cooling water with respect to a temperature of each of condensers when the condensers are cooled to a temperature T1;

FIG. 7 is a flow chart illustrating a setting process performed by the laser oscillator of FIG. 1;

FIG. 8 is a block diagram illustrating a configuration example of a laser

7

processing apparatus according to a second embodiment to which the laser oscillator of the present invention is applied;

FIG. 9 is a side view illustrating a laser beam generating mechanism of the laser oscillator of FIG. 8;

FIG. 10 is a diagram illustrating piping of cooling water of a cooling mechanism of the laser oscillator of FIG. 8;

FIG. 11 is a flow chart illustrating a setting process performed by the laser oscillator of FIG. 8; and

FIG. 12 is a flow chart illustrating a monitoring process performed by the laser oscillator of FIG. 8.

[0025] Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as embodiments) will be described. Descriptions will be made in the following order.

1. First Embodiment (Example of Manual Setting)

2. Second Embodiment (Example of Setting by Laser Oscillator Controller)

rnn9Ri

<First Embodiment

[Configuration Example of Laser Processing Apparatus]

FIG. 1 is a diagram illustrating an embodiment of an optical system of a laser processing apparatus to which a laser oscillator of the present invention is applied.

[0027] A laser processing apparatus 1 of FIG. 1 performs laser processing on a processing object such as a substrate. Hereinafter, descriptions will be made

8

by giving a solar panel 2 as an example of the processing object.

[0028] An optical system of the laser processing apparatus 1 includes a laser oscillator 11, a beam expander 12, a slit 13, an imaging lens 14, a dichroic mirror 15, an objective lens 16, a lighting system 17, a condensing lens 18, a light obstruction body 19, a haif mirror 20, an imaging lens 21, and a charge coupled device (CCD) camera 22. Among these components, a processing optical system for directing a laser beam for processing onto the solar panel 2 includes the laser oscillator 11, the beam expander 12, the slit 13, the imaging lens 14, the dichroic mirror 15, and the objective lens 16. Further, an observing optical system for observing the solar panel 2 includes the objective lens 16, the lighting system 17, the condensing lens 18, the light obstruction body 19, the half mirror 20, the imaging lens 21, and the CCD camera 22.

[0029] First, the operation of the processing optical system will be described.

[0030] A laser beam which is emitted from the laser oscillator 11 is expanded in its beam diameter and also collimated by the beam expander 12. The beam diameter of the laser beam is limited to a predetermined size when the laser beam passes through the slit 13. After passing through the slit 13, the laser beam is collimated by the imaging lens 14, then reflected toward the objective lens 16 by the dichroic mirror 15, and then collected on a to-be-processed surface of the solar panel 2 by the objective lens 16. Further, a scanner (not shown) such as a galvanometer mirror scans the to-be-processed surface of the solar panel 2 with the laser beam. Accordingly, the to-be-processed surface of the solar panel 2 is processed by the laser beam.

[0031] Next, the operation of the observing optical system will be described.

[0032] The lighting system 17 is provided with a circular light source which

9

includes a monochromatic light emitting diode (LED) having a predetermined wavelength (0.6 jxm, for example). In this regard, the light source of the present invention can be regarded as a surface light source. Further, illumination light having a circular cross section which is emitted from the light source of the lighting system 17 is collected by the condensing lens 18, then reflected toward the objective lens 16 by the half mirror 20, and then imaged on a pupil of the objective lens 16. The illumination light which has been imaged on the pupil of the objective lens 16 is Fourier transformed by the objective lens 16, and then directed onto the solar panel 2.

[0033] The light which has been reflected on the solar panel 2 (hereinafter, referred to as a reflected light) is transmitted through the objective lens 16, the dichroic mirror 15, the half mirror 20, and the imaging lens 21, and then enters the CCD camera 22. At this time, after being transmitted through the objective lens 16, the reflected light is imaged on a light receiving surface of a CCD image sensor (not shown) of the CCD camera 22 by the imaging lens 21, so that an image by the reflected light is taken by the CCD camera 22.

[0034] Further, the light obstruction body 19 is provided between the

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condensing lens 18 at a side facing the half mirror 20. The light obstruction body 19 is formed, for example, by processing a metal plate such as stainless steel, and blocks illumination light that is transmitted through the vicinity of an optical axis of the condensing lens 18.

[0035]

[Configuration Example of Laser Oscillator of FIG. 1]

Next, a configuration example of the laser oscillator 11 will be described

10

with reference to FIG. 2 and FIG. 3. FIG. 2 is a side view illustrating a laser beam generating mechanism of the laser oscillator 11; and FIG. 3 is a diagram illustrating piping of cooling water of a cooling mechanism of the laser oscillator 11.

[0036] First, the laser beam generating mechanism will be described with reference to FIG. 2.

[0037] The laser beam generating mechanism of the laser oscillator 11 includes condensers 51-1 to 51-3, an extraction mirror 52, an end mirror 53, Q switches 54-1 to 54-6, laser diodes 55-1 to 55-28, laser mediums 56-1 to 56-3, and current output units 57-1 to 57-3. Further, the laser oscillator 11 includes a cooler 71, valves 72-1 to 72-4, an inlet temperature measuring unit 73, outlet temperature measuring units 74-1 to 74-3, an entrance pipe 75, and an exit pipe 76.

[0038] In this regard, when it is not particularly necessary to distinguish between the condensers 51-1 to 51-3, between the Q switches 54-1 to 54-6, between the laser diodes 55-1 to 55-28, between the laser mediums 56-1 to 56-3, between the current output units 57-1 to 57-3, between the valves 72-1 to 72-4, and between the outlet temperature measuring units 74-1 to 74-3, these components are just referred to as the condensers 51, the Q switches 54, the laser diodes 55, the laser mediums 56, the current output units 57, the valves 72, and the outlet temperature measuring units 74, respectively. Other components are also referred to in the same way.

[0039] More specifically, the laser oscillator 11 of FIG. 2 and FIG. 3 includes serially arranged three stages of condensers 51 which include the condensers 51-1 to 51-3. As shown in a cross sectional view of the condenser 51-1 shown

11

in the lower left part of FIG. 2, the cross sectional view being taken along line A-A shown in the upper part of FIG. 2, the laser diodes 55-1 to 55-8 are arranged at substantially regular intervals so as to form a generally concentric circle centering on the laser medium 56-1. That is, as shown in a schematic development cross sectional view of the condenser 51-1 shown in the lower right part of FIG. 2, the cross sectional view being taken along line B-B shown in the lower left part of of the condensers 51 of FIG. 2, when taking a side view of the condenser 51-1, the laser diodes 55-1 to 55-8 are arranged so as to surround the laser medium 56-1. Further, arrows shown in the schematic development cross sectional view taken along line B-B schematically show flows of cooling water in a cooling mechanism of the laser oscillator which will be described later.

[0040] Further, while not shown in the figure, each of the condensers 51-2 and 51-3 has the same configuration as the configuration of the condenser 51-1. Therefore, the laser diodes 55-11 to 55-18 are arranged so as to form a concentric circle centering on the laser medium 56-2 in the condenser 51-2. Further, the laser diodes 55-21 to 55-28 are arranged so as to form a concentric circle centering on the laser medium 56-3 in the condenser 51-3.

[0041] The Q switches 54-1 and 54-2 are respectively provided at front and back of the condenser 51-1; the Q switches 54-3 and 54-4 are respectively provided at front and back of the condenser 51-2; and the Q switches 54-5 and 54-6 are respectively provided at front and back of the condenser 51-3. The Q switches 54-1 to 54-6 are configured so that one of the Q switches 54 in which an ultrasonic wave propagates in a direction perpendicular to the sheet of FIG. 2 and one of the Q switches 54 in which an ultrasonic wave propagates in a direction parallel to the sheet of FIG. 2 are paired so as to face each other with

12

the condenser 51 interposed therebetween.

[0042] The current output units 57-1, 57-2, and 57-3 supply current to the laser diodes 55-1 to 55-8 of the condenser 51-1, the laser diodes 55-11 to 55-18 of the condenser 51-2, and the laser diodes 55-21 to 55-28 of the condenser 51-3, respectively. By this supplied current, each of the laser diodes 55-1 to 55-8, the laser diodes 55-11 to 55-18, and the laser diodes 55-21 to 55-28 generate excitation light L2. The generated excitation light L2 is directed to the laser mediums 56-1 to 56-3 each of which includes, for example, an yttrium aluminum garnet crystal (YAG) as indicated by arrows in FIG. 2. The laser mediums 56-1, 56-2, and 56-3 are excited by the excitation light L2 which is emitted by the laser diodes 55-1 to 55-8, the laser diodes 55-11 to 55-18, and the laser diodes 55-21 to 55-28, respectively, to thereby generate laser beams L1.

[0043] The extraction mirror 52 having a reflectivity of 60% is provided at the left end of the laser oscillator 11 of FIG. 2 and the end mirror 53 having a reflectivity of 100% is provided at the right end thereof.

[0044] Next, the operation of the laser beam generating mechanism will be described.

[0045] When current is supplied to ths laser diodes 55-1 to 55-8 of the condenser 51-1, the laser diodes 55-11 to 55-18 of the condenser 51-2, and the laser diodes 55-21 to 55-28 of the condenser 51-3 respectively from the current output units 57-1, 57-2, and 57-3, the laser diodes 55-1 to 55-8, the laser diodes

55-11 to 55-18, and the laser diodes 55-21 to 55-28 generate the excitation light L2 according to the supplied current and direct the generated excitation light L2 to the laser mediums 56-1 to 56-3, respectively. The laser mediums 56-1 to

56-3 are excited by the excitation light L2 to thereby generate seed lights. The

13

thus generated seed lights travel back and forth between the extraction mirror 52 and the end mirror 53 to thereby generate the laser beams L1. The thus generated laser beams L1 are transmitted through the extraction mirror 52 and emitted leftward in the figure. Further, the excitation light generated by the laser diodes 55 is converged onto the laser mediums 56 by a cylindrical lens, a light guide piate, or the like (not shown).

[0046] Next, the cooling mechanism will be described.

[0047] The cooling mechanism of the laser oscillator 11 includes the cooler 71, the valves 72-1 to 72-4, the inlet temperature measuring unit 73, the outlet temperature measuring units 74-1 to 74-4, the entrance pipe 75, and the exit pipe 76.

[0048] The cooler 71 cools cooling water which constitutes a part of the cooling mechanism of the laser oscillator 11 to a predetermined temperature after the cooling water cools each of the condensers 51-1 to 51-3 and the Q switches 54 (including all of the Q switches 54-1 to 54-6) and is then discharged through the exit pipe 76, and supplies the thus cooled cooling water to the condensers 51-1 to 51-3 and the Q switches 54 through the entrance pipe 75. That is, the cooler 71 cools cooling water that is required for cooling the condensers 51=1 to 51-3 and the Q switches 54 so as to be maintained at a predetermined temperature and circulates the cooling water throughout the laser oscillator 11 through the entrance pipe 75 and the exit pipe 76. Further, while not shown in the figure, a heat sink for cooling is provided in each of the laser diodes 55 of the condensers 51-1 to 51-3. The cooling water cools the heat sink through a pipe (not shown) which is provided inside the heat sink by heat exchange with the heat sink. By cooling the heat sink with the cooling water, each of the laser diodes 55 is cooled.

14

Further, in each of the condensers 51, since the laser diodes 55 and the laser medium 56 are arranged in parallel as shown in the cross sectional view at the lower right part of FIG. 2, the laser diodes 55 and the laser medium 56 are equally cooled. Accordingly, the condenser 51 is cooled as a whole.

[0049] The valves 72-1 to 72-4 are provided in the exit pipe 76 which is positioned downstream of the condensers 51-1 to 51-3 and the Q switches 54. The valves 72-1 to 72-4 regulate the amount of the cooling water which is circulated through the condensers 51-1 to 51-3 and the Q switches 54 by regulating the opening degrees of the valves. Although the valves 72-1 to 72-4 are provided in the exit pipe 76 which is positioned downstream of the condensers 51-1 to 51-3 and the Q switches 54 in FIG. 3, the valves 72-1 to 72-4 may also be provided in the entrance pipe 75 which is positioned upstream of the condensers 51-1 to 51-3 and the Q switches 54. Namely, each of the valves 72-1 to 72-4 may either be provided upstream or downstream of each of the condensers 51-1, 51-2, 51-3, and the Q switches 54 as long as each of the valves 72-1 to 72-4 can control the amount of cooling water supplied to each of the condensers 51-1, 51-2, 51-3, and the Q switches 54. Further, in the Q switches 54, although cooling pipes for the Q switches 54-1 to 54-6 are united to form a collecting pipe at the upstream side of the valve 72-4, the valve 72 may be provided in each of the individual cooling pipes without uniting the cooling pipes.

[0050] The inlet temperature measuring unit 73 measures a temperature of cooling water supplied from the cooler 71. Further, the outlet temperature measuring units 74-1 to 74-4 measure a temperature of cooling water at the side of the exit pipe 76 which is positioned downstream of the condensers 51-1 to

15

51-3 and the Q switches 54.

[0051] Next, the operation of the cooling mechanism of the laser osciilator 11 will be described.

[0052] A laser beam is generated by the operation of the laser beam generating mechanism. However, since the condensers 51 are configured in a multistage manner as shown in FIG. 2, there is variability in oscillation wavelength and operating current among the excitation light which is generated by the laser diodes 55. For example, in the laser diodes 55, when the laser medium 56 includes YAG, the emission spectrum of the excitation light at an operating temperature of 25°C and an operating current of 25 to 30 A is within the range shown by a waveform SP2 as compared to a waveform SP1 of the absorption spectrum of YAG, as shown in FIG. 4. That is, the range of wavelength in which the waveform SP2 which is the emission spectrum of the excitation light exhibits absorptivity equal to or more than half of the absorption spectrum of YAG exists only in an approximately 1 nm range around 808 nm.

[0053] Therefore, even if the temperature of cooling water is regulated so that the laser output of the laser oscillator becomes maximum, most of the laser diodes emit excitation light at a wavelength at which the absorptivity is low.

Such excitation light that is not absorbed are not converted into light, but converted into heat in the laser mediums 56 to thereby raise the temperature of the condenser 51. Further, if excessive current is injected into one of the condensers 51, the one having a low gain, in expectation of a gain equal to the gain of a high gain condenser, although the gain is actually increased, the temperature of the low gain condenser is increased more and more. As a result, when the temperature of a specific condenser is excessively increased, thermal

16

lens effects lose balance and the laser output therefore becomes saturated.

[0054] Therefore, in the laser oscillator 11 of FIG. 2, the valves 72-1 to 72-3 are provided for the respective condensers 51 at the outlet side of cooling water in the cooling mechanism. Namely, the amount of cooling water used in each of the condensers 51 is controlled by controlling the opening degree of each of the valves 72-1 to 72-3. Accordingly, the temperature of each of the condensers 51 is controlled by adjusting the heat exchange amount.

[0055] More specifically, when the temperature of the condenser 51 is raised, the oscillation wavelength of the laser diode is increased. It can be thought that when the wavelength reaches a wavelength at which the absorptivity of the laser medium 56 becomes maximum, the excitation light is most effectively converted into a laser beam, and the amount of heat generation of the condenser 51 therefore becomes minimum.

[0056] Therefore, in a case where the temperature of the condenser 51 is an average temperature of an inlet temperature and an outlet temperature of cooling water supplied to the condenser 51, and the temperature of the condenser 51 is in a steady state, namely, in a state where the amount of heat that is equal to the amount of heat generation of the condenser 51 is cooled by the cooling water, for example, the amount of heat generation of the condenser 51 becomes an equilibrium state under the following condition.

[0057]

Amount of Heat Generation of Condenser 51

= Cooled Amount of Heat of Condenser 51 = Difference between Inlet Temperature and Outlet Temperature of Cooling Water Supplied to Condenser 51 x Amount of Cooling Water

17

[0058] Even when ail of the laser diodes 55 are activated at the same temperature, each of the laser diodes 55 operates at a different oscillation wavelength due to a manufacturing error. Therefore, when the condenser 51 includes the laser diodes 55 each having a long oscillation wavelength, the absorptivity in the laser medium becomes maximum at a low temperature. On the other hand, when the condenser 51 includes the laser diodes 55 each having a short oscillation wavelength, the absorptivity in the laser medium becomes maximum at a high temperature.

[0059] For example, with respect to each of the condensers 51-1 to 51-3, the inlet temperature and the outlet temperature of cooling water supplied to the condenser 51 were measured with changing the amount of the cooling water. The result of the measurements are shown in FIG. 5, where the horizontal axis represents an average temperature of the inlet temperature and the outlet temperature, namely, a temperature T of the condenser 51, and the vertical axis represents a temperature difference AT between the inlet temperature and the outlet temperature.

[0060] In FIG. 5, waveforms L1 to L3 each of which is shown by a dashed-dotted line show a case of cooling water supplied to the condenser 51 -1, where the waveform L3 shows a case where the amount of the cooling water is smaller than that in the waveform L2, and the waveform L1 shows a case where the amount of the cooling water is larger than that in the waveform L2. Further, waveforms L11 to L13 each of which is shown by a solid line show a case of cooling water supplied to the condenser 51-2, where the waveform L13 shows a case where the amount of the cooling water is smaller than that in the waveform L12, and the waveform L11 shows a case where the amount of the cooling water

18

is larger than that in the waveform L12. Furthermore, waveforms L21 to L23 each of which is shown by a dashed-two dotted line show a case of cooling water supplied to the condenser 51-3, where the waveform L23 shows a case where the amount of the cooling water is smaller than that in the waveform L22, and the waveform L21 shows a case where the amount of the cooling water is larger than that in the waveform L22. In the relationships shown in FIG. 5, values of current supplied to the condensers 51-1 to 51-3 are equal to each other.

[0061] Therefore, it is understood from the relationships as shown in FIG. 5 that, in an average oscillation wavelength of laser beams generated by each of the laser diodes 55-1 to 55-8 of the condenser 51-1, the laser diodes 55-11 to 55-18 of the condenser 55-2, and the laser diodes 55-21 to 55-28 of the condenser 51-3, the average oscillation wavelength in the condenser 51-1 is longer than the average oscillation wavelength in the condenser 51-2, whereas the average oscillation wavelength in the condenser 51-3 is shorter than the average oscillation wavelength in the condenser 51-2. Further, as shown in the waveform L2 in FIG. 5, the rate of a difference "a" from a maximum value "b" of the temperature difference AT with respect to the maximum value "b" of the temperature difference AT is absorptivity a/b. That is, when the absorptivity becomes maximum, excitation light is most efficiently converted into a laser beam, and the amount of heat that is generated when excitation light cannot be converted into a laser beam therefore becomes minimum. As a result, the heat exchange amount by cooling water becomes minimum and the temperature difference AT thereby becomes minimum.

[0062] When a determination is made, for example, to control the temperatures

19

of all of the condensers 51-1 to 51-3 at 26°C in order to equalize the thermal lens effects of the condensers 51-1 to 51-3 which have the relationships as shown in FIG. 5, the temperature difference AT between the inlet temperature and the outlet temperature in each of the condensers 51 becomes approximately 1.0°C in the condenser 51-2, approximately 1.4°C in the condenser 51-1, and approximately 1,2°C in the condenser 51-3 by supplying a predetermined amount of cooling water equally to each of the condensers 51. In this case, temperatures of cooling water that should be supplied to the condensers 51-1, 51-2, and 51-3 are 25.5°C, 25.3°C, and 25.4°C, respectively. Therefore, if it is intended to cool each of the condensers 51-1 to 51-3 by an equal amount of cooling water as in the conventional laser oscillator, a single cooler which is capable of setting the temperature of cooling water only at a single predetermined temperature cannot cope with such a situation.

[0063] On the other hand, in the laser oscillator 11 of FIG, 2 to which the present invention is applied, it is possible to regulate the amount of cooling water by controlling the opening degree of each of the valves 72-1, 72-2, and 72-3 which are provided for the condensers 51-1, 51-2, and 51-3, respectively. Accordingly, it becomes possible to adjust the temperature difference AT between the inlet temperature and the outlet temperature in each of the condensers 51-1 and 51-3 at 1.0°C which is the same as the temperature difference AT in the condenser 51-2. That is, in the laser oscillator 11 of FIG. 2, cooling the three stages of condensers 51-1 to 51-3 generating different amounts of heat by different amounts of cooling water makes it possible to cool the condensers 51-1 to 51-3 so as to have the same temperature by the cooling water having the same temperature even when using a single cooler which is capable of setting the

20

temperature of cooling water only at a single predetermined temperature.

[0064] More specifically, as shown in FIG. 6, the opening degree of the valve 72-2 is controlled so that the amount of cooling water supplied to the condenser 51-2 becomes a medium amount as indicated by the waveform L11. Further, the opening degree of each of the valves 72-1 and 72-3 is controlled so that the amount of cooling water supplied to the condenser 51-1 becomes a small amount as indicated by the waveform L3 and the amount of cooling water supplied to the condenser 51-3 becomes a small amount as indicated by the waveform L23. As a result, the temperatures of the condensers 51-1 to 51-3 can be equalized at the temperature T1 = 26°C, thereby making it possible to equalize the thermal lens effects.

[0065] The example based on the temperature characteristics when currents of the same value are supplied to the condensers 51-1 to 51-3 has been described in the above. However, when the temperature of each of the condensers 51-1 to 51-3 is set to be a steady state as described above, the absorptivity of each of the condensers 51-1 and 51-3 is inferior to the absorptivity of the condenser 51-2. Namely, a gain to convert excitation light into laser beams in each of the condensers 51-1 and 51=3 is inferior to a gain to convert excitation light into laser beams in the condenser 51-2. Therefore, it is possible to equalize the gains by supplying current having a value larger than a value of current that is supplied to the condenser 51-2 to the condensers 51-1 and 51-3 (namely, to the laser diodes 55 of the condensers 51-1 and 51-3 ) after the temperatures become a steady state as described above.

[0066] In this case, however, the temperature difference AT between the inlet temperature and the outlet temperature in each of the condensers 51-1 and 51-3

21

becomes still larger than the temperature difference AT in the condenser 51-2. In such a case, the opening degree of each of the valves 72-1 and 72-3 is made larger to increase the amount of cooling water to thereby perform temperature control. As a result, the temperatures T of the condensers 51-1 to 51-3 can be controlled at the same temperature (T = 26°C, in this case), thereby making it possible to equalize the thermal lens effects and the gains of the condensers 51-1 to 51-3. Further, when it is not possible to increase the amount of cooling water supplied to each of the condensers 51-1 and 51-3, the value of the current supplied to the condenser 51-2 may be reduced to thereby reduce the gain of the condenser 51-2 so as to be the same as the gains of the condensers 51-1 and 51-3.

[0067] Further, although the laser oscillator 11 which includes three condensers 51, namely, the condensers 51-1 to 51-3, has been described as an example in the above, when four or more condensers 51 are used, the same description can also be applied thereto. Further, when the laser diodes provided in the condensers 51-1 and 51-3, each of the laser diodes having a long oscillation wavelength or a short oscillation wavelength, are collected and provided in a single condenser to thereby constitute a condenser 51-11 (not shown), and the laser oscillator 11 therefore includes two condensers 51, namely, the condensers 51-2 and 51-11, the same description can also be applied thereto. Further, in the laser oscillator 11 of FIG. 2, the description has been made with regard to the case where, in the average oscillation wavelength of the laser diodes 55 provided in each of the condensers 51-1 to 51-3, the average oscillation wavelength in the condenser 51-1 is longer than the average oscillation wavelength in the condenser 51-2, and the average oscillation wavelength in the

22

condenser 51-3 is shorter than the average oscillation wavelength in the condenser 51-2. However, the condensers 51-1 to 51-3 are not necessarily disposed according to the length of the wavelength and may be disposed in any order. Further, any combination of wavelengths may be applied to the condensers 51-1 to 51-3.

[0068]

[Setting Process by Laser Oscillator of FIG. 1]

Next, a setting method of the laser oscillator 11 of FIG. 1 will be described with reference to the flow chart of FIG. 7.

[0069] In step S1, the opening degree of each of the valves 72-1 to 72-3 is set to be fully open. That is, in this case, a maximum amount of cooling water that is cooled to a predetermined temperature by the cooler 71 is equally supplied to all of the condensers 51-1 to 51-3, so that the condensers 51-1 to 51-3 are cooled.

[0070] In step S2, the current output units 57-1, 57-2, and 57-3 supply current having a value at which the output of excitation light reaches approximately half of the rated output to the laser diodes 55-1 to 55-8 of the condenser 51-1, the laser diodes 55-11 to 55-18 of the condenser 51-2, and the laser diodes 55-21 to 55-28 of the condenser 51-3, respectively. According to this process, the laser diodes 55-1 to 55-8, 55-11 to 55-18, and 55-21 to 55-28 generate excitation light and direct the thus generated excitation light to the laser mediums 56-1, 56-2, and 56-3, respectively. Further, the laser mediums 56-1 to 56-3 become an excited state by the excitation light emitted by the laser diodes 55-1 to 55-8, 55-11 to 55-18, and 55-21 to 55-28, thereby generating the laser beams L1.

[0071] In a step 3, a laser output at each preset temperature of cooling water

23

that is cooled by the cooler 71 is measured by a laser output measuring device and the like (not shown) with changing the preset temperature. Further, the cooler 71 is set so as to cool the cooling water at a preset temperature at which the measured laser output becomes maximum.

[0072] In a step 4, the opening degree of the vaive 72 that cools the condenser 51 having a low temperature is decreased so that the temperature of the condenser 51 having a low temperature becomes the same as the temperature of the condenser 51 having a high temperature. As a result, the condensers 51-1 to 51-3 become a steady state in which the values of the supplied currents are equal to each other.

[0073] In a step 5, while reducing, at a predetermined rate, the value of current supplied to the condenser 51 in which the valve 71 is closed (the opening degree thereof is decreased) by the current output unit 57, the laser output is measured. Further, the current output unit 57 that supplies current to the condenser 51 in which the valve 72 is closed is set, on the basis of the measurement result, so as to supply current having a value that is close to a value at which the laser output is linearly changed in response to change of the current value. In other words, the linear change of the laser output in response to the current value change shows that the gain of the condenser 51 in which the valve 72 is closed substantially matches the gain of the condenser 51 in which the valve 72 is fully open. As a result, supplying current having the current value in this state makes it possible to set the gains for converting excitation light into laser beams of the condensers 51-1 to 51-3 so as to substantially match each other while cooling the temperature of the condensers 51-1 to 51-3 so as to have a constant temperature.

24

[0074] According to the above process, it becomes possible to cool the condensers having a multistage configuration so as to have the same temperature as each other by providing a valve for each of the condensers to thereby change the amount of cooling water, even when using a single cooler which is capable of setting the temperature of cooling water only at a single temperature. Accordingly, it is possible to provide a high output laser oscillator with an inexpensive configuration.

[0075] As a result, it is possible to achieve an inexpensive and high output laser processing apparatus.

[0076]

<Second Embodiment

[Another Configuration Example of Laser Processing Apparatus]

In the above, there has been described the example in which a user operates and sets the opening degree of each of the valves 72-1 to 72-4 and the value of current output by each of the current output units 57-1 to 57-3 while checking conditions in the above setting process. However, a laser oscillator controller for controlling the laser oscillator may be provided to perform the

Rp.ttinn nrnr.psR |— — —

[0077] FIG. 8 is a diagram illustrating a configuration example of a laser processing apparatus in which a laser oscillator controller for controlling the laser oscillator is provided and the setting process can be performed by the laser oscillator controller. In FIG. 8, the same names and the same reference numerals are applied to components having the same functions as those in FIG. 1 and description thereof will appropriately be omitted. Namely, differences of a laser processing apparatus 1 of FIG. 8 from the laser processing apparatus 1 of

25

FIG. 1 are that a laser oscillator 111 is provided instead of the laser oscillator 11, and a laser oscillator controller 112 for controlling the laser oscillator 111 is additionally provided.

[0078] Although the basic function of the laser oscillator 111 of FIG. 8 is the same as the function of the laser oscillator 11 of FIG. 1, there is a difference therebetween in that the operation of the laser oscillator 111 is controlled by the laser oscillator controller 112.

[0079] The laser oscillator controller 112 controls the operation of the laser oscillator 111, and includes a valve controller 121, a current controller 122, a temperature monitoring unit 123, a cooling water temperature controller 124, and a setting information storage unit 125.

[0080] The valve controller 121 controls the opening degree of each of valves 172-1 to 172-4 (see FIG. 10) of the laser oscillator 111 to thereby control the amount of cooling water supplied to each of condensers 51-1, 51-2, 51-3 and Q switches 54.

[0081] The current controller 122 controls each of current output units 157-1 to 157-3 (see FIG. 9) to thereby control a value of current supplied to each of the

^AnHaneare ^"1 = i fi^ Q

wi ivi^i igvi v) v r i lu \j i ij.

[0082] The temperature monitoring unit 123 obtains and monitors an inlet temperature of cooling water for cooling the condensers 51-1 to 51-3 and the Q switches 54 before cooling operation, the inlet temperature being measured by an inlet temperature measuring unit 173 (see FIG. 10), and an outlet temperature of cooling water from each of the condensers 51-1, 51-2, 51-3 and the Q switches 54 after the cooling operation, the outlet temperature being measured by each of outlet temperature measuring units 174-1 to 174-4 (see FIG. 10).

26

[0083] The cooling water temperature controller 124 controls a cooling temperature of a cooler 171 (see FIG. 10) based on information regarding the inlet temperature and the outlet temperatures of cooling water monitored by the temperature monitoring unit 123, or based on a relationship between the value of current output by each of the current output units 157-1 to 157-3 (see FIG. 9) and a laser output measured by a laser output measuring unit 191 (see FIG. 9).

[0084] The setting information storage unit 125 stores the opening degree of each of the valves 172 set by the valve controller 121, the value of the current output by each of the current output units 157, the value being set by the current controller 122, and the preset temperature of cooling water set by the cooling water temperature controller 124. In addition, the setting information storage unit 125 also stores a deviation of the preset temperature of cooling water caused by age-related deterioration. More specifically, in the laser diode 55, the oscillation wavelength tends to be longer along with age-related deterioration even if a constant temperature condition is maintained. Therefore, the setting information storage unit 125 stores a table including an installation period of the laser diode 55 that shows the tendency along with age-related deterioration and a correction temperature determined corresponding to an amount of the deviation (an amount of the deterioration) of the temperature of cooling water according to the installation period.

[0085]

[Configuration Example of Laser Oscillator of FIG. 8]

Next, a configuration example of the laser oscillator 111 will be described with reference to FIG. 9 and FIG. 10. FIG.9 is a side view illustrating a laser beam generating mechanism of the laser oscillator 111 of FIG. 8, FIG. 9

corresponding to FIG. 2 which is a side view illustrating the laser beam generating mechanism of the laser oscillator 11. Further, FIG. 10 is a diagram illustrating piping of cooling water of a cooling mechanism of the laser oscillator 111 of FIG. 8, FIG. 10 corresponding to FIG. 3 which is a diagram illustrating the piping of cooling water of the cooling mechanism of the laser oscillator 11, Further, in the laser oscillator 111 of FIG. 9 and FIG. 10, the same names and the same reference numerals are applied to components having the same functions as those in the laser oscillator 11 of FIG. 2 and FIG. 3 and description thereof will appropriately be omitted.

[0086] That is, differences of the laser oscillator 111 of FIG. 9 and FIG. 10 from the laser oscillator 11 of FIG. 2 and FIG. 3 are that current output units 157-1 to 157-3, a cooler 171, valves 172-1 to 172-4, an inlet temperature measuring unit 173, and outlet temperature measuring units 174-1 to 174-4 are provided instead of the current output units 57-1 to 57-3, the cooler 71, the valves 72-1 to 72-4, the inlet temperature measuring unit 73, and the outlet temperature measuring units 74-1 to 74-4, respectively, and a laser output measuring unit 191 is additionally provided.

rnnft71 Thca nirrfant niitnrit unite 1^7_1 tn 1 thg cooler 171 thP V^IVf^ 17?-1

^vwvi j i i iw vm i i wi iv vvi Mil wl ii hw i w r i fcv I v/ i ir 1^ uwivi If If LI i vu1v i f l i to 172-4, the inlet temperature measuring unit 173, and the outlet temperature measuring units 174-1 to 174-4 have the same function as the current output units 57-1 to 57-3, the cooler 71, the valves 72-1 to 72-4, the inlet temperature measuring unit 73, and the outlet temperature measuring units 74-1 to 74-4, respectively. Further, there is a difference in that the current output units 157-1 to 157-3 are controlled by the current controller 122, the cooler 171 is controlled by the cooling water temperature controller 124, the valves 172-1 to 172-4 are

28

controlled by the valve controller 121, and the inlet temperature measuring unit 173 and the outlet temperature measuring units 174-1 to 174-4 are controlled by the temperature monitoring unit 123.

[0088] That is, the current output units 157-1 to 157-3, the cooler 171, the valves 172-1 to 172-4, the inlet temperature measuring unit 173, and the outlet temperature measuring units 174-1 to 174-4 are controlled by the laser oscillator controller 112. Therefore, in the case of FIG. 10, each of the valves 172-1 to 172-4 includes, for example, a motor valve whose opening degree is controllable, a magnetic valve, or the like. Further, the inlet temperature measuring unit 173 and the outlet temperature measuring units 174-1 to 174-4 provide the laser oscillator controller 112 with measurement results including the inlet temperature and the outlet temperature. Namely, in the laser oscillator 111 of FIG. 8, a setting operation by a user is not required in the setting process described above with reference to the flow chart of FIG. 7. Therefore, the setting process can be substantially automatically achieved. Further, a setting process by the laser oscillator 111 of FIG. 8 will later be described in detail with reference to a flow chart of FIG. 11.

[0089] The laser output measuring unit 191 measures a laser output that is output from the laser oscillator 111, and provides the laser oscillator controller 112 with a measurement result.

[0090]

[Setting Process by Laser Oscillator of FIG. 8]

Next, a setting method of the laser oscillator 111 of FIG. 8 will be described with reference to the flow chart of FIG. 11.

[0091] In step S21, the valve controller 121 of the laser oscillator controller 112

29

controls the opening degree of each of the valves 172-1 to 172-3 so as to be fully open. That is, in this case, a maximum amount of cooling water that is cooled to a predetermined temperature by the cooler 171 is equally supplied to all of the condensers 51-1 to 51-3, so that the condensers 51-1 to 51-3 are cooled.

[0092] In step S22, the current controller 122 performs control so that the current output units 157-1, 157-2, and 157-3 supply current having a value at which the output of excitation light reaches approximately half of the rated output to the laser diodes 55-1 to 55-8 of the condenser 51-1, the laser diodes 55-11 to

55-18 of the condenser 51-2, and the laser diodes 55-21 to 55-28 of the condenser 51-3, respectively. According to this process, the laser mediums

56-1 to 56-3 generate the laser beams L1.

[0093] In step S23, the cooling water temperature controller 124 changes the preset temperature of cooling water that is cooled by the cooler 171 at a predetermined rate. Further, at this time, the laser output measuring unit 191 measures the output of the laser beam L1 which is output from the laser oscillator 111 and provides the laser oscillator controller 112 with the measured output. The cooling water temperature controller 124 calculates a temperature at which the laser output becomes maximum based on a relationship between the laser output measured by the laser output measuring unit 191 and a preset temperature of cooling water that is cooled by the cooler 171 at the timing of the output measurement, and then sets the temperature of cooling water to the thus calculated temperature.

[0094] In a step 24, the valve controller 121 calculates the temperature of each of the condensers 51 based on the measurement results measured by the temperature monitoring unit 123, namely, based on an average value of the inlet

30

temperature and the outlet temperature, and controls the opening degree of each of the valves 172-1 to 172-3. That is, the valve controller 121 performs control in such a manner that the opening degree of the valve 172 that cools the condenser 51 having a low temperature is decreased so that the temperature of the condenser 51 having a low temperature becomes the same as the temperature of the condenser 51 having a high temperature. As a result, the condensers 51-1 to 51-3 become a steady state in which the values of the supplied currents are equal to each other.

[0095] In a step 25, the current controller 122 reduces the value of the current supplied to the condenser 51 in which the valve 172 is closed (the opening degree thereof is decreased) by the current output unit 157 at a predetermined rate. At this time, the laser output measuring unit 191 measures a laser output and provides the laser oscillator controller 112 with a measurement result. The current controller 122 controls, on the basis of the changing current value and the measurement result measured by the laser output measuring unit 191, the current output unit 157 that supplies current to the condenser 51 in which the valve 172 is closed so as to supply current having a value that is close to a value at which the laser output is linearly changed in response to change of the current value.

[0096] In other words, the linear change of the laser output in response to the current value change shows that the gain of the condenser 51 in which the valve 172 is closed substantially matches the gain of the condenser 51 in which the valve 172 is fully open. As a result, supplying current having the current value in this state makes it possible to cool the condensers 51-1 to 51-3 so as to have a constant temperature and, at the same time, set the gains for converting

31

excitation light into laser beams of the condensers 51-1 to 51-3 so as to substantially match each other.

[0097] In step S26, the setting information storage unit 125 stores the opening degree of each of the valves 172 set by the valve controller 121, the value of the current output by each of the current output units 157, the value being set by the current controller 122, and the preset temperature of cooling water set by the cooling water temperature controller 124 at this moment, and also the temperature of each of the condensers 51-1 to 51-3 in this state, and then finishes the process.

[0098] According to the above process, it becomes possible to cool the condensers having a multistage configuration so as to have the same temperature as each other by individually setting the amount of cooling water supplied to each of the condensers, even when using a single cooler which is capable of setting the temperature of cooling water only at a single temperature. Accordingly, it is possible to provide a high output laser oscillator with an inexpensive configuration. Further, the laser oscillator controller 112 makes it possible to set the opening degree of each of the valves 172-1 to 172-3, the preset temperature of cooling water supplied to the condensers 51, and the value of current supplied from each of the current output units 157 without intervention of a user. Accordingly, it is possible to easily use an inexpensive and high output laser oscillator.

[0099] Further, the use of the laser oscillator of the present invention makes it possible to achieve an inexpensive and high output laser processing apparatus and make the use thereof easy.

[0100]

32

[Monitoring Process]

Next, a monitoring process performed by the laser oscillator 111 of FIG. 8 will be described with reference to a flow chart of FIG. 12.

[0101] In step S41, the temperature monitoring unit 123 measures the temperature of each of the condensers 51-1 to 51-3 as an average of an inlet temperature and an outlet temperature of cooling water based on the inlet temperature provided by the inlet temperature measuring unit 173 and the outlet temperature provided by each of the outlet temperature measuring units 174-1 to 174-4.

[0102] In step S42, the temperature monitoring unit 123 determines, on the basis of information regarding the temperature of each of the condensers 51-1 to 51-3, the information being stored in the setting information storage unit 125 as setting information, as to whether or not the thus measured present temperature of each of the condensers 51-1 to 51-3 matches the setting information by determining as to whether or not the present temperature is different from the temperature stored as the setting information.

[0103] When it is determined, in step S42, that the present temperature is not in a state that matches the setting information, namely, the present temperature is in a state that is different from a state set in the setting process, a setting process is carried out in step S43. That is, since the setting information has been changed from the state that is set in the previous setting process, the setting process is again carried out. The setting process in step S43 is the same as the process described above with reference to the flow chart of FIG. 11. Therefore, description thereof will be omitted.

[0104] On the other hand, when it is determined, in step S42, that the present

33

temperature of each of the condensers 51-1 to 51-3 matches the setting information, namely, the present temperature of each of the condensers 51-1 to 51-3 is the temperature that is set in the setting process, it is deemed that a steady state in which the setting is executed properly is maintained, and the process of step S43 is therefore skipped.

[0105] In step S44, the valve controller 121 determines as to whether or not it is necessary to take into account the change of wavelength caused by age-related deterioration based on duration of use of each of the laser diodes 55 used in the condensers 51-1 to 51-3 with reference to a age-related deterioration table which is stored in the setting information storage unit 125. In the age-related deterioration table stored in the setting information storage unit 125, a level of deterioration with respect to average duration of use of the laser diode 55 is shown. In particular, there is configured a table of a correction temperature for correcting a oscillation wavelength which is extended due to deterioration with respect to duration of use when used at the same temperature.

[0106] The valve controller 121 stores a replaced time (a time of starting the use) of each of the condensers 51 in advance and determines as to whether or not it is necessary to correct the oscillation wavelength based on duration of use from the replaced time of the laser diodes 55 used in each of the condensers 51-1 to 51-3. Although deterioration progresses from day to day, a level of deterioration due to which the correction is required may be set by a predetermined step function and the like, for example. Also, a determination may be made as to whether or not it is necessary to change the correction temperature based on whether the duration of use has reached duration in which a deterioration level moves one step further or not.

34

[0107] When it is determined, in step S44, that it is necessary to take into account the change of wavelength caused by age-related deterioration, the valve controller 121 reads out a correction temperature corresponding to the duration of use based on the age-related deterioration table, and then corrects a previously stored preset temperature of the condenser 51 in the setting information according to the read-out correction temperature to thereby set the corrected temperature in step S45.

[0108] In step S46, the valve controller 121 gradually increases the opening degree of each of the valves 172-1 to 172-4 so that the temperature of each of the condensers 51-1 to 51-3, the temperature being monitored by the temperature monitoring unit 123, becomes a temperature in which the correction temperature is taken into account, after which the process returns to step S41.

[0109] Further, when it is determined, in step S44, that it is not necessary to take into account the change of wavelength caused by age-related deterioration, the processes in the S45 and S46 are skipped.

[0110] According to the above process, when an abnormality occurs in the condensers, the cooler, and the like due to any cause after the setting process of the laser oscillator is finished, the setting process is again carried out.

Therefore, it becomes possible to constantly output a laser beam at high output power. Further, since it is taken into account that the oscillation wavelength of a laser diode is extended due to age-related deterioration, even when the duration of use becomes long, a laser beam can be continuously output with high efficiency.

[0111] In the present specification, each of the processes includes not only a process in which step S for carrying out the process are performed in the

35

described order and in a time series manner, but also a process in which step S are not necessarily performed in a time series manner but performed in a parallel manner or individually.

[0112] Further, in the present specification, the term "system" indicates a whole apparatus including a plurality of devices.

36

Claims

CLAIMS:

1. A laser oscillator comprising:

a plurality of condensers each having a plurality of laser diodes generating excitation light and a laser medium absorbing the excitation light generated by the laser diodes to emit laser beams;

a cooler for cooling cooling water for cooling the condensers to a predetermined temperature;

a temperature measuring unit for measuring a temperature of each of the condensers; and a valve for controlling an amount of cooling water supplied to each of the condensers based on the temperature of each of the condensers, the temperature being measured by the temperature measuring units.

2. The laser oscillator according to claim 1, wherein the temperature measuring unit measures an inlet temperature and an outlet temperature of cooling water for cooling each of the condensers and obtain an average of the inlet temperature and the outlet temperature as the temperature of each of the condensers.

3. The laser oscillator according to claim 1, wherein the valve controls an amount of cooling water supplied to each of the condensers so that temperatures of the condensers are controlled to be equal to each other based on the temperature of each of the condensers measured by the temperature measuring unit.

37

4. The laser oscillator according to claim 1, further comprising a plurality of current output units each controlling an amount of current supplied to the laser diodes of each of the condensers, wherein each of the current output units controls the amount of current supplied to each of the condensers so as to equalize gains of the condensers after the amount of cooling water is controlled by each of the valves.

5. The laser oscillator according to claim 1, further comprising:

a valve controller for controlling an opening degree of the valve for controlling the amount of cooling water supplied to each of the condensers; and a setting information storage unit for storing, as setting information, a temperature of each of the condensers, the temperature being measured by the temperature measuring unit after the opening degree of each of the valves is controlled by the valve controller.

6. A laser processing apparatus using the laser oscillator according to any one of claims 1 to 5.

7. A laser oscillator substantially as herein described with reference to, and as illustrated in, Figs. 1 to 7 or Figs. 8 to 12, of the accompanying drawings.

•.'????.• INTELLECTUAL

*.*. .V PROPERTY OFFICE

38

Application No: GB1300021.1 Examiner: Dr Claire Williams

Claims searched: all Date of search: 11 April 2013

Patents Act 1977: Search Report under Section 17

Documents considered to be relevant: