JPH04354391A - Method and device for output monitor of laser oscillator - Google Patents

Abstract

PURPOSE:To measure laser output at a nearest position of an output mirror without picking up laser light to the outside of the laser oscillator and to enable safety and accurate alignment operation of an output mirror and a total reflection mirror to be carried out. CONSTITUTION:A beam damper 5 for receiving laser light which is output from an oscillator main body 1A, a supply/discharge path switching means 11 for taking out refrigerant by going around a part of a refrigerant supply system 9 for cooling the beam damper 5 and an output measurement means 16 which detects a difference of holding heat energy of refrigerant between the outward path side and the inward path side which is introduced through the supply/discharge path switching means 11 and operates laser output are provided. The output measurement means 16 can be connected to the laser oscillator 1 removably through the supply/discharge path switching means 11. Accurate laser output is measured based on heat energy which is detected by the output measurement means 16 and optical axis of the laser oscillator 1 can be adjusted accurately.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a method and apparatus for monitoring the output of a laser oscillator, and more specifically, it measures the laser output without using a monitor light when adjusting the optical axis of an output mirror or a total reflection mirror. The present invention relates to a method for monitoring the output of a laser oscillator, which allows alignment adjustment of each mirror to be performed with high precision, and a device for realizing the method.

0002

2. Description of the Related Art A laser oscillator is used when cutting, welding, or other processing of a workpiece is performed using a laser beam. Figure 4
is an example of a laser oscillator 1, which generally includes an output mirror 3 that reflects about 40% to 60% of the laser beam on the front side of the discharge tube 2, and a total reflection mirror 4 that transmits about 1% of the laser beam on the rear side. It is equipped with Laser oscillation is caused to occur in a state where both mirrors are placed facing each other in a parallel state, and laser output can be extracted. In addition, output mirror 3
The optimum reflectance is selected depending on the output level and oscillation efficiency of the laser oscillator. The above-mentioned total reflection mirror 4 is coated with a coating that allows a small amount of laser light to pass therethrough, so that a laser light 41 for output monitoring can be extracted. For this purpose, a monitor output detector 42 that receives the monitor light 41 is provided outside the rear of the laser oscillator 1 . For example, when the laser output is 1KW and the reflectance of the output mirror 3 is 50%, the laser output of the oscillator body is 2KW and the monitor output is 20W. The monitor output detector 42 converts the small monitor output into an electrical signal, and the observer can know the laser output value from the detected value displayed on the output meter 43. According to such a method of indirectly detecting the laser output from the monitor light 41, there is an advantage that the laser output can be detected even during laser processing. In addition,
Since the monitor light 41 has a very weak output,
A detector with a small heat capacity can be used, and the response speed is therefore high, which is very advantageous for high-speed control of laser output.

0003

However, the above method has a drawback in that when the actual laser output varies, it does not match the detected monitor output variation. That is, when we installed a laser output detector 44 in the front and confirmed the actual laser output using an output meter 45 connected to it, we found that the fluctuation range of the monitor output displayed by the output meter 43 compared to the actual level output. is large, and the fluctuation period tends to be irregular. When looking at the temporal changes in each output using the respective output totals 43 and 45, for example, as shown in FIG. 5, the monitor output M fluctuates irregularly to a greater extent than the actual laser output N. Note that the monitor output M in the figure is electrically amplified to the same level as the laser output N for ease of understanding. By the way, in order to maximize the laser output from the laser oscillator and operate it efficiently, the optical axes of the output mirror 3 and the total reflection mirror 4, which face each other with the discharge tube 2 in between, must be accurately adjusted, that is, aligned. It is necessary to keep it. For example, when attaching the output mirror 3 and the total reflection mirror 4 to the laser oscillator 1 or replacing them for maintenance, the postures of the mirrors 3 and 4 are tilted, as shown in the exaggerated view (a) of FIG. There are many cases. In this case, the output mirror 3 and the total reflection mirror 4 are each rotated in the direction of the arrow to set them in a parallel state as shown in FIG.
It will be like this. From (a) to (b) in Figure 6,
), furthermore, the laser output when in the state (c) is
It changes as shown in FIG. Assuming that the difference in laser output between states (a) and (b) in FIG. It is difficult to distinguish whether the relationship of the total reflection mirror 4 is in the state shown in FIG. 6(a) or in the state shown in FIG. 6(b). Therefore, alignment accuracy will further deteriorate if a monitor output with large output fluctuations is monitored. Incidentally, when the laser oscillator is operated, it is inevitable that the temperature of each mirror 3, 4 will rise, causing local deformation or distortion. It is necessary to prevent this, and for this purpose, although not shown, each mirror 3, 4 is provided with a cooling mechanism.

However, as mentioned above, the reason why the monitor output is different from the laser output is that there is still a difference in thermal deformation due to temperature changes in the mirrors 3 and 4. That is, the refrigerant such as cooling water supplied to each mirror 3, 4 is adjusted to a predetermined temperature by a separately provided temperature regulator, etc.
A certain degree of temperature error is allowed for control purposes. For example, when the control target temperature is 15°C, if there is an error of ±1°C, the temperature of the cooling water supplied to the output mirror 3 and the temperature of the cooling water supplied to the total reflection mirror 4 may differ. be. This is because in such a case, not only the laser output itself fluctuates, but also the monitor output changes in a manner that is not proportional to the laser output. Therefore, when adjusting the optical axes of the output mirror and the total reflection mirror of the laser oscillator, the laser output can be directly monitored without using monitor light, and alignment can be performed so that the output is maximized. However, in the alignment work, it is not easy to grasp the posture of each mirror that maximizes the laser output, and when accurate mirror adjustment is required, as shown in Figure 8,
A receiver 46 and a laser power meter 47 are separately placed outside the laser oscillator 1, and a shutter 48 installed on the output side is moved away from the broken line as shown in the solid line to block the laser light and ensure safety. Adjustments will be made while monitoring the actual laser output. However, some laser processing systems have a laser oscillator built into the main body of a processing machine, some are installed at a high place, and some are movable over a workpiece, and the usage patterns vary depending on the user. Therefore, it is often difficult to secure space for installing a light receiver or a laser power meter as an output measuring device. Further, even if a light receiver can be installed, the installation position must be adjusted accurately, and preparation for detection requires time and effort. In addition, in order to extract laser light to the outside of the laser oscillator, it may be necessary to remove a beam guide or the like, and various improvements are desired.

The present invention was developed against the background that it is difficult to perform accurate alignment based on a minute amount of monitor light because the fluctuation value and fluctuation period are different between the minute amount of monitor output and the actual laser output. It is something that The purpose of this is that there is no need to take out the laser light outside the laser oscillator, and as a result, there is no need to secure space for arranging a laser power meter in front of the laser oscillator. To be able to measure the laser output and perform alignment adjustment work safely and accurately, and to detect the laser output by using the shutter that has been installed in the laser oscillator and the cooling system for that purpose. In order to maintain the miniaturization of the laser oscillator without causing a significant increase in the number of parts to be installed, so as not to impair its mountability in a laser processing system, etc., and to install a device for detecting laser output as necessary. As a configuration that can be attached or removed, it can be applied to any laser oscillator,
It is an object of the present invention to provide a method and device for monitoring the output of a laser oscillator, which realizes the compactness of the detection device itself and the ease of installation.

[0006]

The present invention is applied to a laser oscillator output monitoring method for adjusting the optical axis of the oscillator while monitoring the laser output during laser oscillation. Referring to FIG. 1, the feature is that the laser beam is directly or indirectly received by the beam damper 5 installed on the output side of the laser oscillator 1, and the amount of heat absorbed by the beam damper 5 is calculated based on the amount of heat absorbed by the beam damper 5. This is to measure the laser output. In the device invention, the oscillator body 1
A beam damper 5 for directly or indirectly receiving the laser beam output from A is installed on the output side of the laser oscillator 1 so as to be movable back and forth. A coolant supply system 9 is introduced into the laser oscillator 1 to supply and discharge a coolant for cooling the beam damper 5. Supply path 9A of the refrigerant supply system 9
A supply/discharge path switching means 11 is provided for taking out the refrigerant by bypassing a part of the refrigerant and a part of the discharge path 9B. Then, the laser output is measured by detecting the difference between the energy possessed by the refrigerant flowing through the bypass outward path 14A detoured from the supply path 9A and the energy possessed by the refrigerant flowing through the bypass return path 14B detoured from the discharge path 9B. The output measuring means 16 thus configured is connected to the supply/discharge path switching means 11. In addition,
It is preferable to provide a flow rate control body 17 on the bypass outward path 14A toward the beam damper 5 to adjust the flow rate of the refrigerant to a constant value. Furthermore, it is preferable that the output measuring means 16 described above can be detachably connected to the supply/discharge path switching means 11.

[0007]

[Effects of the Invention] According to the present invention, the laser output is measured from the heat absorbed by the beam damper in the laser oscillator, so the laser output can be accurately measured at the position closest to the output mirror. , the optical axis of the laser oscillator can be adjusted with high precision. Further, the laser output is not taken out to the outside, and a high level of operational safety is ensured during alignment. In the invention of the device, the shutter that has been installed in the laser oscillator can be used as a beam damper, suppressing the increase in the number of parts installed in the laser oscillator, maintaining the miniaturization of the laser oscillator, and improving the processing system. There is no reduction in the ease of mounting on other vehicles. Furthermore, the output measuring means can also be made more compact. At this time, there is no need for any equipment or equipment that must be installed in front of the laser oscillator, and the laser output can be monitored and alignment work can be easily performed even in places where space is limited. If the above output measuring means is provided with a flow rate controller, the flow rate of the coolant flowing through the beam damper can be made constant, and the measurement accuracy of the laser output can be maintained even higher. If the output measuring means is configured to be detachable from the supply/discharge path switching means, it is easy to attach and remove the output measuring means to the laser oscillator, and it is also easy to apply it to other laser oscillators.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings of embodiments thereof. FIG. 1 is a schematic diagram showing the overall configuration of a carbon dioxide laser oscillator 1 including a laser oscillator output monitoring device that is capable of adjusting alignment while monitoring the laser output during laser oscillation. The laser oscillator 1 is provided with an output mirror 3 that reflects, for example, about 50% of the laser beam on the output side of a discharge tube 2 filled with carbon dioxide gas, and on the monitor side of the rear end.
A total reflection mirror 4 that transmits about 1% of the laser beam is provided. The output mirror 3 and the total reflection mirror 4 are arranged opposite to each other so as to be parallel to each other, and the laser beam from the discharge tube 2 is transmitted to both the mirrors 3 and 4.
It is designed to oscillate a laser by reflecting it off.

The laser oscillator 1 is provided with a shutter 5 that blocks the oscillated laser beam to ensure safety when processing operations such as cutting and welding are interrupted. This shutter 5 also functions as a beam damper, and via a bracket 6 pivotally supported on the oscillator main body 1A,
It is installed so that it can move forward and backward from the front of the output side as shown by the two-dot chain line or the solid line. This shutter 5 has a cone 7 formed therein so as to be able to receive laser light and absorb and remove the energy it has when not being processed, and is water-cooled or oil-cooled. That is, the back of the cone 7 is covered with a jacket 8 so that the refrigerant for absorbing the energy is supplied and discharged, and is connected to a refrigerant supply system 9 consisting of a supply path 9A and a discharge path 9B. Note that this refrigerant supply system 9 is provided with a refrigerant pump 10A and a temperature control device 10B having a heat radiation function. In the laser oscillator 1 connected to such a refrigerant supply system 9, the refrigerant is taken out by bypassing a part of the supply path 9A and a part of the discharge path 9B, and a part of the supply path 9A and a part of the discharge path are taken out. A supply/discharge path switching means 11 is provided that can prevent the refrigerant from flowing through a part of 9B. It consists of an upstream switching device 11A and a downstream switching device 11B, each of which includes two three-way switching valves 12. A connector 13 is attached to each three-way switching valve 12 for connecting or disconnecting a bypass pipe 14 of an output measuring means 16, which will be described below. The bypass pipe 14 includes a bypass outward path 14A and a bypass return path 14B.
By connecting the bypass outward path 14A and the bypass return path 14B to the upstream switching device 11A and the downstream switching device 11B, the refrigerant can flow. A temperature measuring section 15 is installed in the bypass outgoing path 14A and the bypass incoming path 14B to detect the temperature of the refrigerant flowing therein.

The output measuring means 16, which includes a temperature measuring section 15, an output calculating section 19 to be described later, etc., uses the fact that the temperature difference of the refrigerant is proportional to the laser output if the flow rate of the refrigerant is constant. It is now possible to measure the laser output absorbed by 5. That is, the laser output is determined by detecting or calculating the difference between the energy possessed by the refrigerant flowing through the bypass outward path 14A detoured from the supply path 9A and the energy possessed by the refrigerant flowing through the bypass return path 14B detoured from the discharge path 9B. Can be measured indirectly. In this example, the temperature measurement unit 15 has two temperature sensors 15A and 15B, and the refrigerant temperature signal in the bypass outward path 14A and the refrigerant temperature signal in the bypass return path 14B detected thereby are output to the output calculation unit. 19 is input. Then, based on the temperature difference obtained there, the amount of heat absorbed by the beam damper 5 is calculated, and the result is displayed on the CRT 20 or the like.

[0011] Furthermore, in the bypass outgoing path 14A heading toward the temperature measuring section 15, there is a flow rate control body 1 that adjusts the refrigerant flow rate to a constant level.
In addition, a calibration heater 1 is provided on the bypass outgoing path 14A going from the temperature measuring section 15 to the beam damper 5.
8 is interposed. The flow rate control body 17 is a flow rate adjustment valve that adjusts the flow rate of refrigerant flowing through the bypass outgoing path 14A and defines a predetermined flow rate necessary for detecting the refrigerant temperature. The calibration heater 18 is a heating coil for applying thermal energy to the refrigerant flowing through the bypass outward path 14A when the laser oscillator 1 is not oscillating. This heating coil 1
8 is used to determine in advance how much error the laser output value obtained by the output measuring means 16 has with respect to the actual laser output. That is, when the refrigerant flowing through the bypass outward path 14A is heated by the heating coil 18 to, for example, 1 KW, it is possible to measure in advance how much the value measured by the output measuring means 16 deviates from 1 KW. can. This is because the refrigerant may dissipate heat while passing through the beam damper 5 and the temperature may drop, or unavoidable errors may occur in the measurement device, so correct them and improve calculation accuracy. This was done with consideration given to ensuring that The flow rate regulating valve 17 and the heating coil 18 described above may be operated in response to instructions from a microcomputer device including the output measuring means 16 described above or a separately provided control device. Note that although the flow rate regulating valve 17 and the heating coil 18 are not absolutely necessary, it goes without saying that the measurement accuracy will be improved if they are installed to perform the above-described functions.

According to the configuration described above, the optical axes of the mirrors 3 and 4 can be precisely adjusted after replacing the output mirror 3 and the total reflection mirror 4, as described below. After attaching new output mirrors 3 and total reflection mirrors 4 placed before and after the discharge tube 2 to mounting members (not shown), each mirror 3, 4
A predetermined temperature is maintained by a cooling mechanism (not shown) attached to the. Just as when operating the laser oscillator 1 for laser processing, when operating the laser oscillator 1 for output measurement for optical axis adjustment, each mirror 3 and 4 may be deformed or distorted. This is to prevent them from doing so. Next, to the four connectors 13 provided in the refrigerant supply system 9,
The bypass pipe 14 of the output measuring means 16 is connected, the three-way switching valve 12 is switched, and the refrigerant pump 10A is driven to circulate the refrigerant. In this state, rotate the beam damper 5 installed in front of the output mirror 3 to the solid line position, and
A predetermined voltage is applied to the discharge tube 2 with the front surface thereof in a shielded state. The accelerated electrons impart high energy to carbon dioxide molecules, which stimulate the emission of light with a wavelength unique to carbon dioxide gas. When this stimulated emission phenomenon overlaps, the light is intensified, and is amplified while repeating reflection between the output mirror 3 and the total reflection mirror 4, passes through the output mirror 3 as a laser beam, and is received by the beam damper 5. Ru. When the laser output becomes stable, the temperature sensors 15A and 15B of the temperature measurement unit 15 detect the temperature of the refrigerant flowing through the bypass outward path 14A and the temperature of the refrigerant flowing through the bypass return path 14B. The detected temperature signal is input to the output calculation section 19, and the temperature difference is calculated. This temperature difference is corrected as necessary,
It is output as the amount of heat absorbed by the refrigerant in the beam damper 5. By looking at the value displayed on the CRT 20 or a recorder (not shown), it is possible to know the laser output of the laser oscillator 1 at that time. In addition, in this temperature detection,
If the amount of refrigerant flowing through the bypass pipe 14 is not a predetermined constant amount, the flow rate is controlled by the flow rate regulating valve 17. If the amount of refrigerant flowing through the bypass outward path 14A is large, the opening degree is reduced, and if the amount of refrigerant is small, the opening degree of the flow rate regulating valve 17 is increased. If the amount of refrigerant is kept constant in this way, the temperature rise of the refrigerant will be proportional to the laser output, so
The laser output oscillated from the laser oscillator 1 can be quantitatively grasped. In the above measurement, if the amount of energy absorbed by the beam damper 5 has not reached a predetermined value or has not reached the maximum value, the postures of the output mirror 3 and the total reflection mirror 4 are adjusted. Each mirror 3, 4 has an attitude adjustment device (not shown), and is reset by turning a screw or the like. Then, the temperature difference is detected in the same manner as above, and whether or not the alignment is accurate is reexamined. Once the optical axis has been adjusted, the three-way switching valve 12 is switched, the output measuring means 16 is preferably removed from the laser oscillator 1 at the connector 13, and the beam damper 5 is moved around the pivot point of the bracket 6. If it is rotated and retracted to the position indicated by the two-dot chain line, laser processing can be performed. If it is desired to temporarily block the laser beam being oscillated during laser processing, the beam damper 5 may function as a shutter. Of course, when the optical axis adjustment is not performed, the output measuring means 16 can be removed from the laser oscillator 1 because the flow of the refrigerant in the output measuring means 16 is cut off by switching the supply/discharge path switching means 11. That is, although the output measuring means 16 may be incorporated into the laser oscillator 1 in advance, it is preferable from various points of view to make it detachable.

Furthermore, in order to achieve a purpose different from the optical axis adjustment work of the output mirror 3 and the total reflection mirror 4, as in the past,
A detector 42 for the transmitted laser beam 41 is located outside the rear of the total reflection mirror 4.
can be set. That is, by detecting the laser beam 41 transmitted from the total reflection mirror 4 with the detector 42, it is possible to check the laser output status during laser processing. Of course, if other appropriate confirmation means capable of confirming such output status is provided, the detector 42 may be omitted.

FIG. 2 shows beam dampers 25 of different shapes.
This is an example of a cylindrical body 26 arranged at an angle. Such a cylindrical body 26 is also surrounded by a jacket 27, and the laser output can be measured based on the amount of heat absorbed by the coolant flowing therethrough. The beam damper 35 shown in FIG. 3 has a cone 36 fixed to a side part inside the laser oscillator, and a reflecting mirror 37 rotatably installed in front of an output mirror (not shown). In either example, the laser is directly or indirectly received and absorbed by multiple reflections, and the laser output for alignment adjustment during non-processing can be measured. During laser processing, the cylindrical body 26 may be rotated as shown by the line arrow or translated in parallel as shown by the white arrow, and the reflecting mirror 37 may be rotated and retracted. On the other hand, when the processing operation is interrupted during laser oscillation, it can be made to function as a shutter at the illustrated position. At that time, the laser energy is absorbed by the coolant flowing inside each jacket 27, 38.

In the above description, the temperature measuring section 15
Although a temperature sensor is used in this embodiment, a thermistor or a platinum resistor may be used instead, and a bridge circuit may be constructed in the output calculation section 19. Alternatively, the temperature difference between the bypass outward path 14A and the bypass return path 14B can be directly converted into a voltage using a thermocouple, and the amount of heat absorbed in the beam damper 5 can be measured based on the voltage. Furthermore, a known calorimeter is installed on each of the bypass outbound route 14A and the bypass return route 14B,
The laser output may also be measured. in this way,
In the output measuring means 16, various detection, calculation, and measurement forms can be adopted by applying known techniques. Incidentally, although the above example deals with a carbon dioxide laser oscillator, if the laser output can be measured based on the thermal energy absorbed by the beam damper, it is possible to use not only a carbon dioxide laser oscillator but also other gas laser oscillators. The present invention can also be applied to oscillators such as lasers or solid-state lasers.

As can be seen from the above explanation, the laser output received by the beam damper is converted into endothermic energy of the refrigerant flowing through the beam damper, and the amount of energy increased due to the increased temperature of the refrigerant is calculated. , the laser output can be measured. The laser beam for the measurement is focused inside the laser oscillator and very close to the output mirror, so that the laser output is measured as accurately as possible. Therefore, based on this, the optical axis adjustment of the output mirror and the total reflection mirror can be performed quickly and accurately. In this case, the large output fluctuations that occur when the laser output is measured indirectly via the monitor light as described in the related art section can be avoided. In addition, there is no need to place measurement equipment that requires high precision in the installation position outside the laser oscillator, and the output measurement means can be easily attached to the laser oscillator, allowing it to be used even when there are space constraints. can do. In addition, the laser light does not exit outside, ensuring the safety of workers during alignment work. On the other hand, in laser oscillators, the shutter that is often installed in the past can function as a beam damper, and many changes to the internal structure are not required for measuring laser output. Miniaturization is achieved, and existing laser oscillators can be easily modified. The output measuring means can be configured as a unit that can be easily attached and detached, and can be easily connected to a laser oscillator or applied to other laser oscillators at any time, resulting in an extremely versatile device.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of an example of a laser oscillator to which the laser oscillator output monitoring method and apparatus according to the present invention are applied.

FIG. 2 is a schematic diagram of a beam damper with different configurations.

[Fig. 3] Another example of a beam damper using a reflecting mirror as a shutter.

FIG. 4 is an explanatory diagram of a laser output monitor in the prior art.

5 is an output diagram illustrating the difference in fluctuation between the laser output and monitor output in FIG. 4. FIG.

[Figure 6] Shows the installation status of the output mirror and total reflection mirror, (a
) is an installation diagram when the mirror is tilted, (b) is an installation diagram when the optical axis has been adjusted, and (c) is an installation diagram when the mirror is rotated excessively.

FIG. 7 is a graph illustrating the amount of difference in laser output between when the optical axis is adjusted and when the optical axis is not adjusted.

FIG. 8 is a diagram illustrating a conventional example, and is a state diagram of laser output measurement in which a light receiver and the like are installed outside a laser oscillator.

[Explanation of symbols]

1... Laser oscillator, 1A... Oscillator body, 5, 25, 35
...beam damper, 9...refrigerant supply system, 9A...supply path, 9
B...Discharge path, 11...Supply/discharge path switching means, 14...Bypass pipe, 14A...Bypass outward path, 14B...Bypass return path, 16
...Output measuring means, 17...Flow rate control body (flow rate adjustment valve).

Claims (4)

[Claims] Claim 1. A laser oscillator output monitoring method for adjusting the optical axis of the oscillator while monitoring the laser output during laser oscillation, wherein the laser beam is directly emitted by a beam damper installed on the output side of the laser oscillator. Or, a method for monitoring the output of a laser oscillator, characterized in that the laser output is measured based on the amount of heat absorbed by the beam damper after receiving the light indirectly. 2. An output monitoring device for a laser oscillator that is capable of adjusting the optical axis of the oscillator while monitoring the laser output during laser oscillation,
A beam damper is installed movably on the output side of the laser oscillator in order to directly or indirectly receive the laser light output from the oscillator main body, and the laser A refrigerant supply system introduced into the oscillator, a supply/discharge path switching means for taking out the refrigerant by bypassing a part of the supply path and a part of the discharge path of the refrigerant supply system, and a bypass bypassed from the supply path. and an output measuring means configured to measure laser output by detecting the difference between the energy possessed by the refrigerant flowing on the outward path and the energy possessed by the refrigerant flowing through the bypass return path detoured from the discharge path. Features: Laser oscillator output monitoring device. 3. The output monitoring device for a laser oscillator according to claim 2, wherein a flow rate control body for adjusting a coolant flow rate to a constant level is provided on the bypass outward path toward the beam damper. 4. The output measuring means is detachably connected to the supply/discharge path switching means.
Or the laser oscillator output monitoring device according to claim 3.