JP2005026381A - Laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To safely, easily, and stably take out high-output laser light over a long period of time, to make a plane of polarization of the laser light rotatable continuously, and to display an operating condition. <P>SOLUTION: A 1/2 wavelength board 30 installed immediately after a resonator R is rotated to rotate a plane of polarization of output laser light of the resonator R. The output laser light is divided into rectilinear propagation light and branched light by means of a polarizer 31 which passes only horizontal deflection. The power F<SB>out</SB>of the present output laser light is detected by an optical detector 36. Based on the detected value, an angle of rotation of the 1/2 wavelength board 30 is determined to make the power of the rectilinear propagation light constant. By rotating the polarizer 31 and the 1/2 wavelength board 30, the plane of polarization of the laser light can be continuously rotated. The output F<SB>in</SB>of the resonator is found from the present output and the angle of rotation of the 1/2 wavelength board 30, and is indicated on a display together with the present output and memorized maximum output. When the output of the resonator comes close to a set value of the present output, an alarm is displayed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser apparatus, and more particularly to a laser apparatus that stably outputs a high-power laser beam suitable for a processing machine, an exposure apparatus, and the like for a long period of time and displays an operation state.
[0002]
[Prior art]
Conventionally, a solid-state laser device that emits light of a short wavelength with a combination of a solid-state laser medium and a nonlinear optical crystal is used as a fine processing device or an illumination device for exposure. This type of solid-state laser device requires compact output control in addition to extremely small fluctuations in the laser output in order to perform processing on the workpiece in a stable state with a high output. Has been. A semiconductor laser light source used as an excitation light source for exciting a solid-state laser medium has been increased in output. At the same time, a solid-state laser device has been researched and developed for higher output and higher efficiency. In addition, there is a demand for higher output and higher efficiency as well as downsizing of the laser device, and it is desired to be able to adjust the output of the laser light safely and even when the laser device is in use. Several examples of conventional laser devices are given below.
[0003]
Patent Document 1 discloses a solid-state laser device in which a resonator is miniaturized by using a prism. As shown in FIG. 6, the solid-state laser device disclosed in Patent Document 1 includes a solid-state laser medium and a polarizer on a first optical axis between a reflecting mirror and a trapezoidal prism. A Pockels cell and a quarter-wave plate are provided on the second optical axis between the reflecting mirror and the trapezoidal prism. In this solid-state laser device, light that has passed through the solid-state laser medium from the polarizer side is equivalently transmitted through the half-wave plate in the reflecting mirror. That is, it passes through the quarter-wave plate, is reflected by the half mirror, and passes through the quarter-wave plate again. Then, in the resonator between the reflecting mirrors, the light stimulated and emitted in the solid-state laser medium excited by the excitation means reciprocates in the resonator on the optical axis folded back by the trapezoidal prism. Laser oscillation.
[0004]
Patent Document 2 discloses an exposure illumination device that can accurately control the amount of light during exposure without using a mechanical shutter. As shown in FIG. 7, the light source of the exposure illumination device generates ultraviolet light in a predetermined polarization state. A polarization state of light from the light source is changed by a half-wave plate which is a polarization control means. The light intensity control means is a polarizer that changes the intensity of light from the polarization control means in accordance with the polarization state. A part of the light from the light intensity control means is reflected by the beam splitter. The amount of reflected light from the beam splitter is detected by a photodetector. The polarization control means is controlled so that the amount of light detected by the photodetector is constant.
[0005]
Patent Document 3 discloses a solid-state laser device that can stably control the intensity even when high-power laser oscillation light is output. As shown in FIG. 8, on the first optical axis between the polarizer and the first reflecting mirror (left in the figure), the first optical having a solid-state laser medium and a first quarter-wave plate. There is a system. The reflecting surface of the first reflecting mirror is perpendicular to the first optical axis. There is a second optical system having a Pockels cell and a second quarter-wave plate on the second optical axis between the polarizer and the second reflecting mirror (lower right in the figure). The reflecting surface of the second reflecting mirror is perpendicular to the second optical axis. The polarizer transmits the first polarization component of the light incident along the first optical axis. The second polarization component orthogonal to the first polarization is reflected in the direction of the second optical axis. A solid-state laser medium is optically excited with an excitation light source to generate an inversion distribution. The rotation driving unit rotates the first quarter-wave plate with the first optical axis as the central axis. A part of the laser oscillation light transmitted through the polarizer is branched by a beam splitter. A light detector detects the intensity of the branched light. Based on the detected light intensity, the rotation drive unit is controlled by the control circuit. By adjusting the rotation angle of the first quarter-wave plate, the intensity of the laser oscillation light output from the solid-state laser device can be adjusted.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 56-76587 [Patent Document 2]
JP-A-9-199394 [Patent Document 3]
Japanese Patent Application Laid-Open No. 11-97782
[Problems to be solved by the invention]
However, in the solid-state laser device disclosed in Patent Document 1, the intensity of laser oscillation light can be adjusted to some extent by controlling the excitation means, but it is difficult to stably control the intensity of laser oscillation light. There is a problem that.
[0008]
In addition, the solid-state laser device disclosed in Patent Document 3 needs to include a second optical system having a first optical system and a quarter-wave plate, which causes a problem that the optical system becomes complicated. In addition, adjusting the laser output in the resonator also changes the laser output absorbed in the laser medium in the resonator, so the thermal gradient inside the laser medium changes and the optical path in the resonator changes. There is also a problem that the beam shape and properties of the laser light output outside the resonator change. On the other hand, if the user of the laser apparatus has an output adjusting means disposed outside the container, alignment with the laser optical axis output from the container is required, and dust countermeasures and safety measures are required. is there.
[0009]
In the device disclosed in Patent Document 2, consideration is given to adjusting or keeping the laser output constant, but due to long-term use, excitation light source deterioration, vibration, nonlinear optical crystal deterioration, etc. No consideration has been given to countermeasures for the case where the laser power itself required for processing the workpiece falls below the required specified value. That is, in the LD (laser diode) pumped solid-state laser device, the laser output decreases with time because the optical axis of the resonator is shifted due to the lifetime of the pumping light source LD and the vibration of the LD-pumped solid-state laser device. In order to stably control the laser output for a long time, a method of increasing the LD current as the laser output decreases is a known technique. However, even if this technique is used, the time for keeping the LD at a constant output is about Since it is as short as 5000 hours, the life of the LD-pumped solid-state laser device affected by this is as short as possible, and further long-term stability of the laser output is required.
[0010]
LD-pumped solid-state laser devices for industrial use are often used with the laser output maintained at a certain set value. However, when laser output stability control is performed by increasing the LD current, the laser output of the LD depends on the life of the LD. When the laser power drops significantly, the laser output cannot satisfy the set value output. In such a state, the LD-pumped solid-state laser device must be stopped to repair the LD-pumped solid-state laser device. In addition, since it takes time for a repair person to come, the work process is greatly delayed. Therefore, it is required to provide a function for generating an alarm one step before the set value of the laser output is not satisfied, and to contact the LD pump laser device manufacturer in advance for quick repair. However, in the above-described stable output control, it is very difficult to predict or measure the time during which the laser output of the LD can be controlled to be constant. Therefore, it is impossible to issue an alarm one step before the laser output set value is not satisfied. there were. The same can be said for the deterioration of the nonlinear optical crystal as well as the LD.
[0011]
When the optical axis of the laser beam of the LD-pumped solid-state laser device is bent by a total reflection mirror, for example, when the total reflection mirror is arranged at an angle of ... with respect to the optical axis and the laser beam is bent in the direction ... Therefore, in order to bend the optical axis with a high output, it is necessary to adjust the angle of the polarization plane. As shown in FIG. 9 (a), the total reflection mirror is arranged at an angle with respect to the optical axis, and the reflectance when the optical axis of the laser beam is bent with the total reflection mirror is determined by the laser. Depending on the polarization plane (P wave, S wave) of light, the reflectance changes as shown in FIG. In order to adjust the angle of the polarization plane, there is a known technique of inserting a half-wave plate into the optical axis of the laser beam. .
[0012]
On the other hand, in an LD-pumped solid-state laser device for research use, characteristics of a nonlinear crystal or a polarizer that greatly depends on the polarization plane may be measured by continuously changing the polarization plane while keeping the output constant. As a known technique, there is a method in which a half-wave plate is inserted into the exit of an LD-pumped solid-state laser and rotated around the optical axis. When changing the laser output, the LD current is adjusted, so that the shape and properties of the beam may change. If the output is changed, the laser output cannot be stably maintained for a long time due to the influence of the life of the LD. There is a problem that the polarization plane cannot be continuously changed while the laser output is freely changed and the output is kept constant for a long time.
[0013]
An object of the present invention is to solve the above-described conventional problems, and even when outputting high-power laser oscillation light, it is possible to safely and easily perform a long-term operation without changing the beam shape and properties of the laser light. To provide a laser apparatus that can take out laser output stably over a long period of time and can continuously change the polarization plane of the laser while maintaining the output of the laser for a long time, and that allows the operating state to be easily observed. is there.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, a laser device having a resonator that reflects and amplifies laser light excited in a laser medium arranged between a pair of mirrors between the pair of mirrors, A half-wave plate that receives the laser light from the resonator and rotates the plane of polarization; a polarizer that separates the laser light into a first polarized light that is a straight light and a second polarized light that is a branched light; A light detecting means for detecting the intensity of the output laser light that has passed through the half-wave plate and the polarizer, and a half-wave plate based on the output of the photodetector so that the intensity of the output laser light becomes a predetermined value. And a control circuit for driving and controlling, a maximum output display unit for displaying the maximum output of the laser beam from the resonator, and a current output display unit for displaying the output of the output laser beam that has passed through the polarizer. . With this configuration, the laser output can be stabilized and the operating state of the laser device can be easily monitored.
[0015]
Further, based on the first calculation circuit to which the rotation angle of the half-wave plate and the output from the photodetector are input, and from the photodetector in accordance with the rotation angle of the half-wave plate based on the calculation output of the calculation circuit And an angle vs. power graph display unit for displaying the output. With this configuration, the rotation angle of the half-wave plate can be easily confirmed, and the rotation position of the half-wave plate corresponding to the maximum output can be detected. Furthermore, when the half-wave plate or the polarizer is damaged, the angle vs. power graph does not become cos ² (2θ), so the state of the optical component can also be confirmed.
[0016]
Further, the laser output from the resonators and the resonator output F _in, when the power of the output laser light passing through the polarizer and the current output F _out, the output from the rotational angle of 1/2-wavelength plate and the light detector Is input, and a second arithmetic circuit that processes the calculation of F _in = F _out (1 / cos ² (2θ)), and a resonator output display unit that displays a value obtained by the arithmetic circuit as a resonator output. The configuration was as follows. With this configuration, the resonator output can be constantly monitored, and the laser device can be easily maintained.
[0017]
Further, a comparison circuit that compares the current output F _out and the resonator output F _in and displays that the resonator output F _in has a predetermined ratio with respect to the current output F _out based on the output of the comparison circuit. It was set as the structure provided with the alarm display part. With this configuration, the resonator output and the current output are compared in real time, the repair timing can be determined more reliably, and the operating efficiency can be improved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.
[0019]
(Embodiment)
The embodiment of the present invention rotates the half-wave plate provided immediately after the laser resonator according to the power detection value of the current output laser beam, rotates the polarization plane of the laser beam from the laser resonator, This is a solid-state laser device that separates straight light and branched light with a polarizer to make the power of the straight light constant, and displays the state of the device such as the resonator output.
[0020]
FIG. 1 is a configuration diagram of a solid-state laser device according to an embodiment of the present invention. In FIG. 1, mirrors 10 and 11 are a pair of reflecting mirrors. The laser rods 13 and 14 are laser media that generate a fundamental wave of 1064 nm. The fundamental wave may be another wavelength. The excitation modules 15 and 16 are units that excite light. The laser diodes 17 and 18 are devices that excite a laser medium with laser light. The beam splitter 19 is an optical element that transmits the harmonic laser beam and reflects the fundamental laser beam. The Q switch 20 is a switch that controls laser oscillation. The nonlinear optical crystals 21 and 22 are optical elements that generate harmonic laser light from fundamental laser light. The harmonic generation module 23 is a unit that generates harmonic laser light. The output variable means A is means for adjusting the intensity of the laser light. The optical axis L1 is the optical axis of the fundamental laser beam. The resonator R is a resonator that oscillates laser light. The container T is a container that houses a component that generates laser light. The 1st arm T1 is an arm part which accommodates an excitation part among containers. The 2nd arm T2 is an arm part which accommodates a harmonic generation part among containers. 3rd arm T3 is an arm part which accommodates an output adjustment means among containers. The output window W is a window for leading laser light from the container to the outside.
[0021]
This solid-state laser device includes an excitation module 15 including laser rods 13 and 14 which are laser media that generate a fundamental wave of 1064 nm on an optical axis L1 between a pair of mirrors 10 and 11 forming a resonator R. 16 are arranged in series. The laser rods 13 and 14 are, for example, Nd: YVO ₄ . These excitation modules 15 and 16 include laser diodes 17 and 18 on the side surfaces of the respective laser rods in order to excite the laser rods 13 and 14. In this example, two excitation modules are arranged in series, but may be three. A Q switch 20 is disposed between the mirror 10 and the excitation module 15.
[0022]
Between the excitation module 16 and the reflection mirror 11, a beam splitter 19 and a harmonic generation module 23 composed of nonlinear optical crystals 21 and 22 that generate the third harmonic are provided. In this example, LBO type II that generates the third harmonic is used. When generating the second harmonic, LBO type I is used. Other nonlinear optical crystals, KTP, KDP, LNO, BBO, CLBO may be used. Optical components such as the mirrors 10 and 11, the excitation modules 16 and 17, the beam splitter 19, and the harmonic generation module 23 are accommodated in a T-shaped container T. The container T further accommodates an output variable means A that adjusts the power of the harmonic laser beam separated from the beam splitter 19.
[0023]
Excitation modules 15 and 16 and a Q switch 20 are accommodated in a portion of the T-shaped first arm T1 with the beam splitter 19 as a boundary. The harmonic generation module 23 is accommodated in the portion of the T-shaped second arm T2. The output variable means A is accommodated in the T-shaped third arm T3. The container T is filled with an inert gas such as nitrogen so that the laser oscillates stably. As shown in FIG. 1, the output variable means A is disposed between the beam splitter 19 and an output window W provided on the T-shaped third arm T3.
[0024]
FIG. 2 is a schematic diagram of output variable means used in the solid-state laser device according to the embodiment of the present invention. In FIG. 2, a half-wave plate 30 is a means for rotating the polarization plane of the output laser light from the resonator R. The polarizer 31 is means for separating a horizontal polarization component and a vertical polarization component. The motor 32 is means for rotating the half-wave plate 30 and is driven according to the number of pulses from a motor driver circuit described later. The motor 33 is means for rotating the polarizer 31. The beam splitter 50 is an optical element that branches a part of the laser light. The photodetector 36 is means for detecting the intensity (power) of the laser beam branched by the beam splitter 50. The output variable means A includes a half-wave plate 30, a polarizer 31, a motor 32, a motor 33, a photodetector 36, and a drive control device. The child 31 is on the laser optical axis L2.
[0025]
The signal processing circuit 70 is a circuit that amplifies the output of the photodetector 36 after compensating for the light loss in the beam splitter 50 and converts an analog value into a digital value. The control circuit 72 is a control circuit incorporating a microcomputer, is connected to the motor drive circuit 74, and is coupled to the operation setting / display device 76 by RS232C communication means. The motor drive circuit 74 is a circuit that drives the motor 32 by pulse output. For example, the motor 32 is driven to rotate once by 9000 pulses. Although not shown, the rotation angle θ of the half-wave plate 30 corresponding to the number of pulses is supplied to the arithmetic circuit.
[0026]
The first arithmetic signal processing circuit 80 is a circuit that receives an output pulse from the motor drive circuit 74 and an output from the signal processing circuit 70 and performs arithmetic processing on the number of pulses, that is, the relationship between the rotation angle of the motor 32 and the laser power. is there. The second arithmetic signal processing circuit 82 is a circuit for obtaining the resonator output from the current output value and the rotation angle of the half-wave plate 30. Receiving the number of output pulses from the motor drive circuit 74 (rotation angle of the motor 32) and the output from the signal processing circuit 70, the power of the output laser is divided by the function value according to the rotation angle of the motor 32, and the resonator output Get. The first display drive circuit 84 is means for receiving the output of the first arithmetic signal processing circuit 80 and causing the display unit 86 to display an angle versus power graph. The second display drive circuit 88 is means for receiving the output of the second arithmetic signal processing circuit 82 and driving the resonator output display unit 90 that displays the resonator output.
[0027]
The storage circuit 92 is a memory that receives the output from the first arithmetic signal processing circuit 80 and stores the maximum value of the resonator output. The comparison circuit 94 is means for comparing the output of the storage circuit 92 and the output of the second arithmetic signal processing circuit 82. The third display drive circuit 96 is means for receiving an output from the comparison circuit 94, displaying on the alarm display unit 98 that the resonator output has decreased to a predetermined value, and warning the user of the laser device. The fourth display drive circuit 100 is means for receiving the output of the storage circuit 92 and causing the maximum output display unit 102 to display the maximum output value of the resonator of the laser device. The fifth display drive circuit 104 is means for receiving the output of the signal processing circuit 70 and causing the current output display unit 106 to display the current output output from the beam splitter 50.
[0028]
The display units 86, 90, 98, 102 and 106 are provided in the operation setting / display device 76. The operation setting / display device 76 includes command means for starting the motor drive circuit 74 and means for setting the laser output from the beam splitter 50.
[0029]
FIG. 3 is a graph (a) showing the laser output relative value (power) of the horizontal polarization of the laser when the half-wave plate is tilted by the angle θ in the solid-state laser device in the embodiment of the present invention, and 1 FIG. 6B is a graph (b) showing output characteristics (amplitude) of a laser when the / 2 wavelength plate is tilted by an angle θ. FIG. 4 is a graph showing the time relationship between the laser output relative value of the solid-state laser device, the rotation angle of the half-wave plate, and time.
[0030]
An operation of the solid-state laser device according to the embodiment of the present invention configured as described above will be described. First, an outline of functions of the solid-state laser device will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the laser light is repeatedly reflected between the first mirror 10 and the second mirror 11 to resonate at the fundamental frequency. The fundamental laser beam is converted into the third harmonic by the harmonic generation module 23. Only the converted third harmonic is taken out of the container T by the beam splitter 19 via the output variable means A.
[0031]
As shown in FIG. 2, the laser light (optical axis is L2) transmitted through the half-wave plate 30 built in the output variable means A is incident on the polarizer 31. The polarizer 31 corresponds to light having a wavelength of 355 nm, which is the third harmonic. The polarizer 31 is held on the optical axis L2 of the laser beam that has passed through the half-wave plate 30 at an angle that maximizes the transmission intensity of the horizontally polarized light. The polarizer 31 functions as a light intensity control unit in cooperation with the half-wave plate 30. The intensity of the laser beam that passes through the polarizer 31 changes according to the angle of the polarization plane of the laser beam that has passed through the half-wave plate 30. The laser beam whose intensity is changed by passing through the polarizer 31 is emitted from the output window of the container T and irradiated on the workpiece, and is used for performing various processes.
[0032]
Next, a method for adjusting the intensity of the output laser beam will be described with reference to FIGS. An example in which light from a light source is horizontally polarized will be described, but the same applies to vertically polarized light. The light from the light source may be linearly polarized light at a specific angle. In this example, it is assumed that the laser light output from the resonator R is horizontally polarized light. The rotation angle of the polarizer 31 is adjusted so that the horizontally polarized light that is the first polarized light is transmitted and the vertically polarized light that is the second polarized light is branched. The polarizer 31 holds the horizontally polarized light so that it is transmitted and the vertically polarized light is branched. In response to a command from the operation setting / display device 76, the motor 32 is rotated via the control circuit 72 and the motor drive circuit 74. Then, the half-wave plate 30 rotates, and the polarization plane of the laser light incident on the polarizer 31 rotates. When the polarization plane of the laser light from the resonator R is rotated by the half-wave plate 30 and the current output becomes maximum, the angle θ of the half-wave plate 30 at that time is set to 0 °. When polarized light from the half-wave plate 30 is passed through the polarizer 31, the horizontally polarized light component is transmitted. The vertically polarized component is branched by the polarizer 31 in the direction outside the optical axis of the horizontally polarized light and is absorbed by a damper (not shown).
[0033]
In the solid-state laser apparatus, the rotational angle of 1/2-wavelength plate 30 and閘, the intensity of the laser beam emitted from the resonator R and the resonator output F _in. The intensity of the laser beam that is transmitted through the polarizer 31 and output is the current output _Fout . The current output is
F _out = F _in cos ² (2 閘)
It becomes. That is, in this solid-state laser device, as shown in FIGS. 3A and 3B, the current output F _out which is the intensity of the output laser light depends on the rotation angle の of the half-wave plate 30. Change.
[0034]
A drive signal is given to the motor 32 via the control circuit 72 and the motor drive circuit 74 in accordance with a command from the operation setting / display device 76. When the half-wave plate 30 is rotated by an angle 閘, the laser light transmitted through the half-wave plate 30 becomes linearly polarized light having a polarization plane angle of 2 閘. The current output F _out, which is the intensity of the laser beam that is transmitted through the polarizer 31, continuously changes corresponding to the rotation angle の of the half-wave plate 30. In this way, the intensity (current output) of the laser light emitted from the polarizer 31 can be continuously changed. Examples of the polarizer include a Glan laser prism, a Glan tailor prism, a Glan Thompson prism, and a polarization beam splitter.
[0035]
Third, a method for maintaining the intensity of the output laser beam at a predetermined value will be described with reference to FIG. The maximum intensity of the output laser beam from the resonator R is defined as the maximum output _Fmax . The intensity of the output laser beam of the resonator R to the resonator output F _in. The intensity of the laser beam output to the outside is defined as a current output _Fout . A relative value based on the maximum output F _max is defined as a laser output relative value. Current output _{F out} is always to keep a certain percentage (e.g. 80%) of the max _{F max,} by a command from the operation setting and display unit 76, sets the logic of the control circuit 72. The predetermined ratio may be such that the laser output relative value of the current output is within the range of 0.3 to 0.95. A value close to 1.0 is not practical because it becomes immediately uncontrollable. As shown in FIG. 4, in the initial use of the laser apparatus, the resonator R has the highest output, and the laser output relative value of the resonator output is 1. When a certain time elapses, the laser output relative value of the resonator output decreases due to the temporal change of the laser medium and the excitation light source. For example, setting the laser output relative value of the current output _{F out} in 0.8, in the initial use of the laser device, the rotation angle of the 1/2-wavelength plate 30 is approximately 13.5 °. In the state where the laser output relative value of the resonator output is 0.9, the rotation angle of the half-wave plate 30 is about 10 °. In the initial stage of using the laser, the half-wave plate 30 is rotated via the control circuit 72 and the motor drive circuit 74 according to a command from the operation setting / display device 76, and a power graph is displayed on the angle vs. power graph display unit 86. Is displayed. The peak value of the graph at that time is the maximum output _Fmax . The angle at which the peak appears is 0 °, which is the reference value for the rotation angle of the half-wave plate 30.
[0036]
After setting the maximum output value, the light branched from the beam splitter 50 is detected by the photodetector 36. In response to the detection output from the photodetector 36, the motor 32 is pulse-driven by the signal output from the control circuit 72 to rotate the half-wave plate 30. Depending on the rotation angle, the plane of polarization of the laser light from the resonator R rotates. Even if the intensity of the laser beam from the resonator R decreases with time, the current output can be reduced by reducing the rotation angle 閘 of the half-wave plate 30 in accordance with the decrease in the intensity of the laser beam from the resonator R. Can be kept constant.
[0037]
For example, from the rotation angle の of the half-wave plate 30 and the current output F _out detected by the photodetector 36,
F _in = F _out (1 / cos ² (2θ))
In, obtaining the resonator output _{F in.} From the resonator output F _in , the rotation angle 鐔 quote of the half-wave plate 30 at which the current output F _out becomes the maximum output F _max × 0.8,
F _out = F _in cos ² (2 鐔 quote) = F _max × 0.8
Find and solve. If the rotation angle of the half-wave plate 30 is set to 鐔 quote, the current output can be kept constant. That is, the angle of the half-wave plate may be feedback controlled so that the input value to the control circuit matches the set value.
[0038]
Fourth, the display unit will be described with reference to FIGS. First arithmetic signal processing circuit 80 is an arithmetic means for graphical display of the current output F _out for 1/2 rotation angles閘wavelength plate 30. Via the signal processing circuit 70, the output of the photodetector 36 and the pulse output from the motor drive circuit 74 are supplied. As shown in FIG. 5, the current output with the rotation angle の of the half-wave plate 30 as the horizontal axis is displayed on the angle versus power graph display unit 86 via the first display drive circuit 84. The maximum output F _max when the rotation angle の of the half-wave plate 30 is 0 ° is stored in the storage circuit 92. The rotational position of the half-wave plate 30 at the maximum output F _max is stored in the storage circuit as 0 °. The value of the maximum output F _max is also stored in the storage circuit 92. As shown in FIG. 5, the value is displayed on the display unit 102 via the fourth display drive circuit 100.
[0039]
Second arithmetic signal processing circuit 82 is an arithmetic unit for displaying the resonator output F _in. The output of the light detector 36 via the signal processing circuit 70 (current output F _out ) and the pulse output from the motor drive circuit 74 (the angle の of the motor 32) are input. Arithmetic expression F _in = F _out (1 / cos ² (2θ))
Are operations according to the resonator output F _in is obtained. As shown in FIG. 5, the calculation result is displayed on the resonator output display unit 90 via the second display drive circuit 88. The value of the current output detected by the photodetector 36 is supplied via the signal processing circuit 70 and the fifth display drive circuit 104, and the current output _Fout is displayed on the current output display unit 106 as shown in FIG. Is done.
[0040]
Outputs of the storage circuit 92 and the second arithmetic signal processing circuit 82 are supplied to the comparison circuit 94. Laser output relative value of the resonator output F _in, for example in the case of a 0.85 displays a warning on the alarm display unit 98 via the third display drive circuit 96 from the comparator circuit 94, a laser device Inform the user that repair is necessary. In a state where the laser output of the solid-state laser device is stably controlled, the laser output relative value of the resonator output can be known from the rotation angle θ around the optical axis of the half-wave plate 30. It is assumed that the initial output (F _max ) of the laser light source is reduced to the current resonator output (F _in ) due to a change with time. In the second arithmetic signal processing circuit 82, the resonator output (F _in ) is
F _in = (F _out ) × (1 / cos ² (2θ))
Calculated by An alarm can be issued when the resonator output (F _in ) approaches the current output (F _out ), making it difficult to control the output stably. For example, an alarm is issued when the laser output relative value of the resonator output approaches 0.8 and it becomes difficult to stably control the output. It can be effectively used for early repair of the laser device.
[0041]
As described above, in the embodiment of the present invention, the solid-state laser device is rotated from the laser resonator by rotating the half-wave plate provided immediately after the laser resonator according to the power detection value of the current output laser beam. The polarization plane of the laser light is rotated and separated into straight light and branched light by a polarizer to make the power of the straight light constant, and the device status such as resonator output is displayed. It can be reduced, the laser output can be stabilized, and the state of the apparatus can always be grasped.
[0042]
【The invention's effect】
As is clear from the above description, in the present invention, a laser device having a resonator that reflects and amplifies laser light excited in a laser medium disposed between a pair of mirrors between the pair of mirrors. A half-wave plate that receives the laser light from the resonator and rotates the plane of polarization; a polarizer that separates the laser light into a first polarized light that is a straight light and a second polarized light that is a branched light; A light detecting means for detecting the intensity of the output laser light that has passed through the half-wave plate and the polarizer, and a half-wave plate based on the output of the photodetector so that the intensity of the output laser light becomes a predetermined value. And a control circuit for driving and controlling, a maximum output display unit for displaying the maximum output of the laser beam from the resonator, and a current output display unit for displaying the output of the output laser beam that has passed through the polarizer. So the laser output can be stabilized The operation state of the laser device can be easily monitored.
[0043]
Further, based on the first calculation circuit to which the rotation angle of the half-wave plate and the output from the photodetector are input, and from the photodetector in accordance with the rotation angle of the half-wave plate based on the calculation output of the calculation circuit The angle vs. power graph display unit that displays the output of the half-wave plate can be easily checked, and the rotation angle of the half-wave plate with the highest output can be detected. If the half-wave plate or the polarizer is damaged, the angle vs. power graph does not become cos ² (2θ), so the state of the optical component can also be confirmed.
[0044]
Furthermore, the laser output from the resonator as a resonator output F _in, when the power of the output laser light passing through the polarizer and the current output F _out, the output from the rotational angle of 1/2-wavelength plate and the light detector Is input, and a second arithmetic circuit that processes the calculation of F _in = F _out (1 / cos ² (2θ)), and a resonator output display unit that displays a value obtained by the arithmetic circuit as a resonator output. With this configuration, the resonator output can be constantly monitored, and maintenance of the laser device is facilitated.
[0045]
Also displays a comparison circuit for comparing the current output F _out and the resonator output F _in, that the resonator output F _in based on the output of the comparator circuit becomes a predetermined ratio to the current output F _out Since it was set as the structure provided with the warning display part, the timing of repair can be judged appropriately and operation efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a solid-state laser device in an embodiment of the present invention;
FIG. 2 is a schematic diagram of output varying means of the solid-state laser device in the embodiment of the present invention;
FIG. 3 is a graph showing a horizontal polarization laser output relative value and output characteristics when a half-wave plate is tilted at an angle θ in the solid-state laser device according to the embodiment of the present invention;
FIG. 4 is a graph showing a laser output relative value, a rotation angle of a half-wave plate, and a time relationship in the solid-state laser device according to the embodiment of the present invention;
FIG. 5 is a schematic diagram of a display unit in the setting operation / display device of the solid-state laser device in the embodiment of the present invention
FIG. 6 is a conceptual diagram showing a configuration of a first example of a conventional solid-state laser device;
FIG. 7 is a conceptual diagram showing a configuration of a second example of a conventional solid-state laser device;
FIG. 8 is a conceptual diagram showing the configuration of a third example of a conventional solid-state laser device;
FIG. 9 is a graph showing the reflectivity of the beam splitter, S wave, and P wave of the laser device.
[Explanation of symbols]
10, 11 Mirror 13, 14 Laser rod 15, 16 Excitation module 17, 18 LD (laser diode)
19 Beam splitter 20 Q switch 21, 22 Nonlinear optical crystal 23 Harmonic wave generation module 30 1/2 wave plate 31 Polarizer 32, 33 Motor 36 Photo detector 50 Beam splitter 70 Signal processing circuit 72 Control circuit 74 Motor drive circuit 76 Operation Setting / display device 80 First arithmetic signal processing circuit 82 Second arithmetic signal processing circuit 84 First display drive circuit 86 Angle vs. power graph display unit 88 Second display drive circuit 90 Resonator output display unit 92 Storage circuit 94 Comparison circuit 98 Alarm display section 96 Third display drive circuit 100 Fourth display drive circuit 102 Maximum output display section 104 Fifth display drive circuit 106 Current output display section

Claims (4)

In a laser device having a resonator that reflects and amplifies laser light excited in a laser medium disposed between a pair of mirrors between the pair of mirrors, a polarization plane that receives the laser light from the resonator A half-wave plate that rotates the laser beam, a polarizer that outputs the laser light by separating it into first polarized light that is straight light and second polarized light that is branched light, and the half-wave plate and polarizer Detecting means for detecting the intensity of the output laser beam that has passed through, and a control for driving and controlling the half-wave plate based on the output of the photodetector so that the intensity of the output laser beam becomes a predetermined value A laser comprising: a circuit; a maximum output display unit that displays a maximum output of the laser beam from the resonator; and a current output display unit that displays an output of the output laser beam that has passed through the polarizer. apparatus. Based on the first computing circuit to which the rotation angle of the half-wave plate and the output from the photodetector are input, and the computation output of the arithmetic circuit, the light according to the rotation angle of the half-wave plate The laser apparatus according to claim 1, further comprising an angle vs. power graph display unit that displays an output from the detector. Wherein the resonator output F _in the laser output from the resonator, when the power of the output laser light that has passed through the polarizer and the current output F _out, from the optical detector and the rotation angle of the half-wave plate Is output, and a second arithmetic circuit that processes the calculation of F _in = F _out (1 / cos ² (2θ)) and a resonator output display that displays the value obtained by the arithmetic circuit as the resonator output The laser apparatus according to claim 1, further comprising: a section. A comparator circuit for comparing the current output F _out and the resonator output F _in, that said resonator output F _in based on the output of the comparator circuit becomes a predetermined ratio to the current output F _out The laser apparatus according to claim 3, further comprising an alarm display unit that displays

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