JP2008244077A - Gas laser device and method for starting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas laser device that enhances an operation rate of a laser device by surely reducing moisture included in medium gas in a short period of time, while improving the stability of discharge characteristics of the medium gas, and to provide a method for starting the same. <P>SOLUTION: A control unit 11 of the gas laser device is provided with a moisture detector 13 for measuring moisture amount in a medium gas, a first determination part 14 for comparing a moisture amount measured by the moisture detector 13, with a first threshold being an allowable moisture amount contained in the medium gas; a preliminary-discharge control part 15 for controlling preliminary discharge of the medium gas that is executed at a low voltage, until the moisture amount measured by the moisture detector 13 becomes lower than the first threshold; and a main-discharge control part 16 which controls main discharge of the medium-gas that is executed at a high voltage, in order to oscillate laser light to the outside, after when the moisture amount measured by the moisture detector 13 exceeds the first threshold. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas laser device that generates a laser beam by exciting a medium gas in a discharge tube by discharge, and a starting method of the gas laser device.

  In general, an example of a gas laser apparatus that generates laser light by exciting a medium gas by electric discharge is disclosed in FIG. The gas laser device 50 is a high-speed axial flow type carbon dioxide laser device, and applies a high voltage to a medium gas mixed with carbon dioxide, nitrogen, helium, etc. that circulates in the discharge tube 54 at a high speed. Is discharged to oscillate laser light. The gas laser device 50 includes a resonator unit 51, a blower unit 52, and a gas controller unit 53. The resonator unit 51 includes a cylindrical discharge tube 54, mirrors 55a and 55b disposed at both ends of the discharge tube 54, a discharge tube, and holders 56a and 56b that hold the mirror. The blower unit 52 includes a gas circulator 57 that circulates the medium gas in the discharge tube 54, heat exchangers 58 a and 58 b that cool the circulated medium gas, and a gas tube 59 that is connected to the discharge tube 54. . The heat exchanger 58 on the upstream side of the gas circulator 57 cools the medium gas heated by the discharge, and the heat exchanger 58 on the downstream side of the gas circulator 57 releases the compression heat from the gas circulator 57. . The resonator unit 51 and the blower unit 52 constitute a vacuum system, and normally, air does not enter the vacuum system except for the mirror cleaning described later and the oil exchange of the blower unit.

  The gas controller unit 53 includes a vacuum exhaust valve 61, a gas supply valve 62, a vacuum pump 63, and a controller 64. The controller 64 opens and closes the vacuum exhaust valve 61 and the gas supply valve 62, controls the exhaust amount of the vacuum pump 63 and the gas supply amount from the gas container 65, and controls the medium gas in the discharge tube 54 and the gas tube 59. The pressure is controlled to a predetermined pressure. The vacuum pump 63 discharges the medium gas in the resonator unit 51 and the blower unit 52 to the outside. The medium gas is supplied from the gas container 65 into the resonator unit 51 and the blower unit 52 by opening the gas supply valve 62.

  In such a gas laser device 50, when laser oscillation is continuously performed, dirt adheres to the surfaces of the mirrors 55a and 55b of the resonator unit 51, and the laser output is lowered or the laser output becomes unstable. Since the characteristics (quality) of the laser beam deteriorate, it is necessary to periodically clean the mirrors 55a and 55b by opening the vacuum system. In addition, when replacing the oil of the blower unit 52, it is necessary to open the vacuum system to the atmosphere. In such a case, moisture in the atmosphere enters the resonator unit 51 and the blower unit 52 and adheres to the inner wall surface of the discharge tube 54 and the surface of the components such as the mirrors 55a and 55b and the holders 56a and 56b. There is a problem that the medium gas discharge is unstable due to the voltage discharge and the discharge of the medium gas becomes unstable, and a stable output cannot be obtained.

  Such a problem also occurs when the gas laser apparatus is assembled in the atmosphere, and moisture in the atmosphere adheres to the discharge tube 54, the gas tube 59, the mirrors 55a and 55b, the holders 56a and 56b, etc. exposed in the atmosphere. As a result, the discharge of the medium gas immediately after the completion of the assembly work may become unstable, or a stable output may not be obtained.

  As an example of a starting method of a gas laser device that starts discharge (high-pressure discharge) after reducing the amount of moisture in the medium gas and stabilizing the medium gas, there is one disclosed in Patent Document 1. In this conventional example, before starting the discharge, the amount of water in the medium gas in the medium gas supply step is measured, and the medium gas is discharged without discharging the medium gas until it becomes a predetermined value or less. The replacement is repeated a predetermined number of times. However, reducing the amount of water in the medium gas only by gas replacement is less efficient than reducing the amount of water by discharge heating, and there is a problem that it takes time to start discharging the medium gas. It was.

  As another conventional example of the gas laser device startup method, there is a preliminary discharge method in which the medium gas is discharged at an output lower than the rated output in order to reduce the moisture in the medium gas. As shown in FIG. 12, this method is a method capable of efficiently reducing the moisture in the medium gas in a short time compared to the case where only the medium gas is exhausted. The discharge state is confirmed by confirming the discharge voltage, and is performed as follows. As shown in FIG. 13, when the preliminary discharge is performed, the moisture adhering to the surface of the components constituting the resonator unit 51 and the blower unit 52 is absorbed in the medium gas, and the moisture is contained together with the medium gas by the gas circulation. Is discharged to the outside, and the discharge voltage gradually drops. The time when the discharge voltage drop ended and the voltage became constant was regarded as the completion point of the preliminary discharge, which was confirmed by the voltage monitor 67 attached to the excitation power supply 66.

  However, depending on the composition ratio of the medium gas, the laser output (discharge characteristic of the medium gas) may not be stable even when the discharge voltage is stable. In such a case, it is necessary to perform the preliminary discharge for a long time. However, since it is not known how long the preliminary discharge should be performed, there is a problem that the preliminary discharge is performed longer than necessary. That is, in the method of monitoring the discharge voltage and determining when to end the preliminary discharge, there is a problem that the laser output becomes unstable or the preliminary discharge takes more time than necessary.

JP-A-7-176816

  The present invention can surely reduce the moisture contained in the medium gas in a short time, thereby improving the operating rate of the laser device and improving the stability of the discharge characteristics of the medium gas. It is an object of the present invention to provide a gas laser device and a gas laser device activation method.

  In order to achieve the above object, the gas laser device according to claim 1 has a control unit, and in the gas laser device that oscillates a laser beam by exciting a medium gas in a discharge tube by discharge, the control unit includes the medium. Prior to the main discharge that outputs the laser beam and the measurement unit that measures the moisture content in the gas, the moisture content in the medium gas measured by the measurement unit is the allowable moisture content included in the medium gas. And means for repeatedly executing preliminary discharge until a predetermined first threshold value is reached.

  According to a second aspect of the present invention, in the gas laser device according to the first aspect, the means for repeatedly executing the preliminary discharge is low until the amount of water measured by the measuring unit is equal to or lower than the first threshold value. It is a preliminary discharge control part which controls the preliminary discharge of the said medium gas implemented with a voltage.

  Further, the invention according to claim 3 is the gas laser apparatus according to claim 1 or 2, wherein the moisture amount measured by the measuring unit is equal to or larger than the first threshold value. And when the water content does not fall below the second threshold value within a predetermined time after the preliminary discharge is first started, the medium gas in the discharge tube is exhausted. The preliminary discharge is performed in a new medium gas.

According to a fourth aspect of the present invention, in the gas laser device according to any one of the first to third aspects, the medium gas includes helium, nitrogen, and carbon dioxide gas.
The invention of claim 5 is characterized in that, in the gas laser device according to any one of claims 1 to 4, the measurement section is numerically controlled.
The invention of claim 6 is the gas laser device according to any one of claims 1 to 3, wherein the measurement of the water content by the measurement unit is Fourier transform infrared absorption spectroscopy, quadrupole mass It is characterized by being performed by an analytical method.

  The gas laser device according to claim 7 is a gas laser device activation method for oscillating laser light by exciting a medium gas in a discharge tube by discharging, and measuring the amount of moisture in the medium gas, and the amount of moisture and the medium A first threshold value that is an allowable moisture content contained in the gas is compared, and the medium gas is pre-discharged at a low voltage until the moisture content becomes equal to or lower than the first threshold value, and the moisture content exceeds the first threshold value. In order to oscillate the laser beam to the outside after exceeding, the medium gas is mainly discharged at a high voltage.

  The invention according to claim 8 is the gas laser device start-up method according to claim 7, wherein the water content is greater than the first threshold value within a predetermined time after the preliminary discharge is first started, or The preliminary discharge is performed by exhausting the medium gas in the resonator and inserting a new medium gas when the set threshold value is not equal to or less than the second threshold value.

  As described above, according to the invention of the gas laser device and the start method of the gas laser device, the amount of water in the medium gas of the discharge tube or gas tube is measured, and the measured amount of water and the allowable amount of water contained in the medium gas are By comparing with the first threshold value, it is possible to determine whether the preliminary discharge should be terminated or whether the preliminary discharge should be further performed. For this reason, it is possible to prevent the laser output from becoming unstable or taking more time than necessary for the preliminary discharge as in the conventional case where the discharge voltage is monitored. Therefore, the moisture contained in the medium gas can be reliably reduced in a short time, and the operating rate of the laser device can be increased. In addition, the stability of the discharge characteristics of the medium gas is improved, and the quality reliability of laser processing is improved.

  Further, since the discharge tube is opened to the atmosphere for a long time, a large amount of moisture in the atmosphere enters the discharge tube, and the amount of moisture is equal to the first threshold value within a predetermined time after the preliminary discharge is first started, or When it is determined that it does not fall below the second threshold, which is a larger set value, the moisture in the discharge tube can be reduced in a short time by exhausting the medium gas in the discharge tube and introducing a new medium gas. That is, by sharing the preliminary discharge and the replacement of the medium gas by the exhaust, the moisture in the discharge tube can be reduced in a short time even when the amount of moisture in the discharge tube is large.

  Specific examples of embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of a gas laser apparatus according to the present invention. The gas laser device 10 of the present embodiment includes a resonator unit 51, a blower unit 52, and a gas controller unit 11, and is the same as the conventional gas laser device 50 except for the configuration of the gas controller unit 11. Therefore, the same components in the present embodiment and the conventional example are denoted by the same reference numerals, and redundant description will be omitted, and different components will be described.

  The gas controller unit 11 includes a vacuum exhaust valve 61, a gas supply valve 62, a vacuum pump 63, a controller 12, and a moisture detector (measurement unit) 13. The controller 12 opens and closes the vacuum exhaust valve 61 and the gas supply valve 62 to control the exhaust amount of the vacuum pump 63 and the gas supply amount from the gas container 65, and the pressure of the medium gas in the discharge tube 54 and the gas tube 59. Is controlled to a predetermined pressure, or the moisture detector 13 is functioned to measure the amount of moisture in the medium gas.

  As shown in FIG. 2, the controller 12 includes a first determination unit 14 that compares the moisture amount measured by the moisture detector 13 with a first threshold value that is an allowable moisture amount contained in the medium gas, and a moisture detector. Until the water content measured by 13 is equal to or lower than the first threshold value, the preliminary discharge control unit 15 that controls the preliminary discharge of the medium gas performed at a low voltage, and the water content measured by the water detector 13 are the first. And a main discharge control unit 16 for controlling the main discharge of the medium gas performed at a high voltage in order to oscillate the laser beam to the outside after exceeding the threshold value. That is, the gas laser device 10 is controlled to perform preliminary discharge before performing main discharge in order to reduce the amount of water contained in the medium gas.

  The preliminary discharge is performed after the gas supply valve 62 is opened and a medium gas having a predetermined pressure is supplied into the discharge tube 54 and the gas tube 59. After the supply of the medium gas is completed, a voltage lower than the voltage for performing the main discharge is applied between electrodes (not shown) provided in the discharge tube 54 to start the preliminary discharge of the medium gas. The medium gas pressure in the discharge tube 54 and the gas tube 59 during preliminary discharge is maintained at a predetermined pressure by controlling the opening and closing of the vacuum exhaust valve 61 and the gas supply valve 62 by the controller 12.

The preliminary discharge of the gas laser device 10 is executed according to the sequence shown in FIG. In step 1A, preliminary discharge is prepared, and in step 2A, preliminary discharge is started. In step 3A, the amount of water contained in the medium gas during the preliminary discharge is measured by the moisture detector 13 shown in FIG. 1 and the like, and the amount of water R in the medium gas becomes equal to or less than the amount of water R ₁ determined experimentally. The preliminary discharge is repeatedly executed until it is confirmed that the predetermined amount R ₁ or less is reached, and the preliminary discharge process is completed in step 4A.

Further, the preliminary discharge of the present embodiment can also be executed according to the sequence shown in FIG. That is, in step 2A-1, a mask time T ₁ may be set, and a step of starting the moisture amount monitoring after T _{1 has} elapsed from the start of the preliminary discharge may be added. The preliminary discharge is executed until the water content R in the medium gas becomes equal to or less than the predetermined water content R ₁ as in the sequence of FIG. As shown in FIG. 5, this sequence assumes a case where a certain delay time occurs from the start of preliminary discharge until the amount of water in the medium gas increases. In the figure, when the delay time does not occur, the moisture in the air is absorbed in the medium gas in the vacuum system because the vacuum system is opened to the atmosphere. When the delay time occurs, the moisture adhering to the components constituting the vacuum system is not absorbed by the medium gas and the medium gas is dry. In this case, the influence of the delay time can be eliminated by measuring the moisture amount at intervals of a preset mask time. That is, when the medium gas in the vacuum system is dry, the moisture adsorbed on the components constituting the vacuum system is not absorbed by the medium gas immediately after the preliminary discharge is started, so the moisture amount is accurately determined. Although it cannot be measured, the moisture content can be accurately measured after a predetermined time has elapsed.

  Next, a second embodiment of the gas laser device according to the present invention will be described. In the gas laser device of the present embodiment, as shown in FIG. 6, the controller 20 compares the amount of water measured by the moisture detector 13 with a second threshold value that is equal to or larger than the first threshold value. The second determination unit 21 is different from the controller 12 of the first embodiment in that the second determination unit 21 is provided. The other configuration of the gas laser device is the same as that of the first embodiment.

The preliminary discharge of this embodiment is performed according to the sequence shown in FIG. Before T ₂ elapses from the start of the preliminary discharge (step 4B), the preliminary discharge ends (step 6B) when the amount of water in the medium gas becomes equal to or less than the threshold R _{1 for} completing the preliminary discharge (step 3B). On the other hand, if the amount of water is still equal to or greater than the threshold value R ₂ even if the pre-discharge time exceeds T ₂ , the pre-discharge is stopped (step 5B), the vacuum exhaust valve 61 of the gas control unit 19 (see FIG. 6) is opened, The gas supply valve 62 is closed, and the medium gas in the discharge tube 54 and the gas tube 59 is exhausted (step 1B). After exhausting, the gas supply valve 62 is opened, the vacuum exhaust valve 61 is closed, the medium gas is supplied to the discharge tube 54 and the gas tube 59, and preliminary discharge is performed again (step 2B). This assumes the case where preliminary discharge is performed after the atmosphere is released for a long time.

  That is, as shown in FIG. 9, after the atmosphere has been released to the atmosphere for a long time, the amount of water in the medium gas may not decrease easily even after continuous preliminary discharge. In this case, the preliminary discharge, gas exhaust, gas By repeatedly performing the process of supplying, the amount of water in the medium gas can be reduced efficiently. A large amount of moisture is released into the medium gas due to the preliminary discharge, but this gas containing a large amount of moisture is immediately exhausted from the inside of the discharge tube, and the dried medium gas is refilled into the discharge tube effectively. The amount of moisture in the medium gas in the discharge tube can be reduced.

Note that in this embodiment as well, the preliminary discharge can be executed by a sequence in which the mask time T1 until the start of moisture content measurement is set, as in the _first embodiment. The sequence in this case is shown in FIG. In this case, after a lapse of T ₁ from the start of preliminary discharge (step 2B-1), the moisture amount monitor is started (step 2B-2). If the moisture content in the medium gas after the passage of T ₂ from the start of the moisture content monitoring is R ₁ , the preliminary discharge is terminated (step 6B). If the amount of water is still equal to or greater than the threshold value R ₂ even after the time T ₂ has elapsed since the start of the moisture amount monitoring, the preliminary discharge is stopped (step 5B), the gas in the vacuum system is exhausted, and the medium gas is again discharged. Is supplied (step 1B).

  In the first and second embodiments, a measuring instrument for measuring the moisture content in the laser gas during preliminary discharge may be a general hygrometer such as a dielectric hygrometer, but is well known. Highly reliable data can be obtained by measuring with a detector (hereinafter abbreviated as gas analyzer) capable of measuring water content in ppm order, such as a quadrupole mass spectrometer or Fourier transform infrared absorption spectrometer. Obtainable.

Further, the mask time T ₁ , the reference time T ₂ , the threshold values R ₁ and R ₂ may be different values for each preliminary discharge sequence. In addition, the medium gas is supplied from the gas container to the discharge tube and the gas tube prior to the preliminary discharge, but the gas pressure at this time is not necessarily the gas pressure at the rated output. Further, a gas different from the medium gas used at the rated output may be used.

  In the first and second embodiments, the amount of moisture in the medium gas is measured by the moisture detector, but the amount of molecules other than moisture, such as ethanol, may be measured by other detectors. . Ethanol is used as a cleaning agent when performing mirror cleaning in the discharge tube, and a large amount of ethanol exists on the surface of the component immediately after mirror cleaning. Similar to water, it is known that the molecules discharged from the wall surface into the medium gas are replaced with the medium gas constituent molecules by repeating the preliminary discharge sequence. The amount of molecules mixed in the vacuum system when the atmosphere is exposed to the atmosphere or when the parts are exposed to the atmosphere may be measured, and the preliminary discharge sequence may be repeated until the amount is equal to or less than a preset value.

It is a lineblock diagram showing a 1st embodiment of a gas laser device of the present invention. It is a figure which shows the structure of the controller of the gas laser apparatus of FIG. It is a flowchart which shows a preliminary discharge sequence. It is a flowchart which shows the preliminary discharge sequence at the time of providing mask time by the time of a moisture content measurement start. Regarding the change in the amount of water in the medium gas due to the preliminary discharge, a comparison is made between the case where the amount of water in the medium gas increases immediately after the start of the preliminary discharge and the case where a delay time occurs before the amount of water increases. FIG. It is a block diagram which shows 2nd Embodiment of the gas laser apparatus of this invention. It is a flowchart which shows the preliminary discharge sequence at the time of setting a fixed upper limit to the duration of preliminary discharge. It is explanatory drawing which compared the preliminary discharge time in the case where air release time is long and when it is short. It is explanatory drawing which shows the relationship between the moisture content at the time of performing preliminary discharge and gas exhaustion repeatedly, and preliminary discharge time. It is a flowchart of the preliminary discharge sequence which added the step by mask time to the preliminary discharge sequence of FIG. It is a block diagram which shows an example of the conventional gas laser apparatus. It is explanatory drawing which showed the comparison of the processing time required until a rated output becomes stable when a gas substitution is performed repeatedly and when a preliminary discharge is performed. It is explanatory drawing which shows the time change of the discharge voltage during preliminary discharge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Gas laser apparatus 11 Gas control unit 12,20 Controller 14 1st determination part 15 Preliminary discharge control part 16 Main discharge control part 21 2nd determination part 51 Resonator unit 52 Blower unit 53 Gas controller unit 54 Discharge tube

Claims (8)

In a gas laser device that has a control unit and oscillates a laser beam by exciting a medium gas in a discharge tube by discharge,
The control unit is
A measurement unit for measuring the amount of water in the medium gas;
Prior to the main discharge for outputting the laser light, the water content in the medium gas measured by the measurement unit is equal to or lower than a first threshold value set in advance, which is an allowable water content contained in the medium gas. Means for repeatedly performing preliminary discharge;
A laser apparatus comprising:   The means for repeatedly executing the preliminary discharge is a preliminary discharge control unit that controls the preliminary discharge of the medium gas that is performed at a low voltage until the moisture amount measured by the measurement unit becomes equal to or less than the first threshold value. The gas laser device according to claim 1, wherein the gas laser device is provided. A determination unit that compares the amount of water measured by the measurement unit with a second threshold value that is greater than or equal to the first threshold value;
When the amount of water does not fall below the second threshold value within a predetermined time after the preliminary discharge is first started, the medium gas in the discharge tube is exhausted and put into a new medium gas, and the preliminary discharge is performed. The gas laser device according to claim 1, wherein:   The gas laser device according to claim 1, wherein the medium gas includes helium, nitrogen, and carbon dioxide gas.   The gas laser device according to claim 1, wherein the measuring unit is numerically controlled.   The gas laser apparatus according to any one of claims 1 to 5, wherein the measurement of the water content by the measurement unit is performed by Fourier transform infrared absorption spectroscopy or quadrupole mass spectrometry. . In the starting method of the gas laser device that oscillates the laser light by exciting the medium gas in the discharge tube by discharge,
Measure the amount of water in the medium gas,
Comparing the amount of water with a first threshold value that is an allowable amount of water contained in the medium gas;
The medium gas is pre-discharged at a low voltage until the water content is equal to or lower than the first threshold value,
After the water content exceeds the first threshold value, the medium gas is mainly discharged at a high voltage in order to oscillate the laser beam to the outside.
A starting method for a gas laser device.   In a predetermined time after the preliminary discharge is first started, the moisture content is not greater than or equal to the first threshold value or less than a second threshold value that is equal to the set value. 8. The method of starting a gas laser device according to claim 7, wherein the preliminary discharge is performed by exhausting a medium gas and introducing a new medium gas.

Images