JPH09153654A - Automatic optical shaft coordination method for laser resonator and laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an automatic optical shaft coordination capable of controlling coordination precision instead of a simple structure without remarkably reducing laser output when turned on again. SOLUTION: A laser mirror 3 constituting a laser resonator is held by a movable end plate 12 arranged outside a fixing end plate 11, a voltage pulse is applied to an electrostricitve element 21 arranged in the movable end plate 12, and a male screw 20 which is screwed with this electrostricitive element 21, and which is pressed against the fixing end plate 11 is drived to rotate so that an angle of the laser mirror 3 is intermittently and finely displaced. By comparing laser outputs before and after the fine displacement, when the laser output before the fine displacement is greater, a voltage pulse of finely displacing an angle of the laser mirror 3 in the same direction is applied to the electrostrictive element, and when the laser output before the fine displacement is smaller, a voltage pulse of finely displacing an angle of the laser mirror 3 in the opposite direction is applied to the electrostrictive element 21, to perform an automatic optical shaft coordination of the laser resonator. A pulse width of the above voltage pulse has been beforehand coordinated to coordinate a fine displacement amount of an angle of the laser mirror 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic optical axis adjusting method for a laser resonator and a laser device having the automatic optical axis adjusting function.

[0002]

2. Description of the Related Art The application field of lasers has been increasing more and more in recent years with the technical progress thereof. For example,
The He-Cd laser (main oscillation wavelength: 325 nm) is used for designing and manufacturing models and molds using a photoresist light source and photo-curable resin, and for using CT data to model human structures and bones. It is used in various fields as a light source for curing, a light source for fluorescence analysis, and the like for curing the photocurable resin in an optical modeling technique for manufacturing.

The laser mirror that constitutes the laser resonator is
Except for a small internal mirror type He-Ne laser, a semiconductor laser, etc., it is held by three or four ultra-low expansion metal rods, and is designed so that the optical axis of the laser mirror is kept stable. However, in a laser device with a relatively long cavity length of 1 m or more, a laser device with large heat generation, etc.,
Even if the laser resonator is supported by an ultra-low expansion metal rod, the temperature of the laser mirror will change due to the temperature gradient generated by heat generation during long-time operation of the laser device and the ambient temperature change at the laser device installation location. The axis changes. This change causes a problem that the laser output changes, a predetermined laser output cannot be obtained, and the laser operation needs to be temporarily stopped for readjustment of the optical axis.

Therefore, for example, in a large-sized argon ion laser device, an automatic optical axis controller in which an electromagnetic transducer for driving a laser mirror after the rod is water-cooled to a constant temperature and a phase sensitive detection circuit are combined is incorporated. The light output fluctuation is 1%
Within. However, since such an automatic optical axis controller is complicated and expensive, even if it can be practically used in an expensive laser device such as a large argon ion laser device or a carbon dioxide gas laser device, it cannot be used like a He-Cd laser. A relatively inexpensive laser device which is usually used often has a problem in terms of economy.

Therefore, the present inventors previously have an automatic optical axis adjusting method and an automatic optical axis adjusting function for a laser resonator, which has a simpler structure and is cheaper than such an automatic optical axis controller. A laser device was proposed. Details of these are described in JP-A-4-317383 and JP-A-4-364083.
As described in the publication, the outline is as follows.

FIG. 5 is a diagram showing an example of a laser resonator. The laser resonator includes a pair of mirror holding units 1, two sets of alignment mechanisms 2 for adjusting the laser mirror angles, a pair of laser mirrors 3 including a total reflection mirror and an output mirror,
It is composed of a fixed end plate support rod 4. Mirror holder 1
Is composed of a fixed end plate 11 fixed to the fixed end plate support rod 4 and a movable end plate 12 to which the laser mirror 3 is attached.
In FIG. 5, only the mirror holding unit 1 holding the total reflection mirror is shown.

The alignment mechanism 2 intermittently minutely displaces the angle of the laser mirror 3 which constitutes the laser resonator, and the alignment mechanism 2 moves the laser mirror 3 on the basis of an XY plane perpendicular to the preset optical axis Z. In order to be able to change the angle, the fixed end plate 11 is attached to each of a corner portion Q and a corner portion R located on both sides of the corner portion P of the fixed end plate 11 as a fulcrum.

FIG. 6 shows the details of the alignment mechanism 2. The alignment mechanism 2 has a built-in drive motor 201 such as a stepping motor.
01 is fixed to the fixed end plate 11 by the fixing metal fitting 205. The rotary shaft 202 of the drive motor 201 is connected to a displacement adjusting micrometer head 204 via a flexible coupling 203 made of, for example, a bellows. The micrometer head 204 is fixed to the fixed end plate 11 by a fixing member 207, and the shaft 206, which is a movable portion of the micrometer head 204, is fixed to the fixed end plate 1.
Each of the corners Q and R of FIG.

A manual adjustment screw 208 is screwed into the movable end plate 12, and the tip thereof is inserted into the through hole 13 of the fixed end plate 11. Between the fixed end plate 11 and the movable end plate 12, a spring 20 for exerting an elastic force in a direction in which the fixed end plate 11 and the movable end plate 12 approach each other.
9 is provided, and the spring 209 allows the manual adjustment screw 208 to constantly press the shaft 206 via the hard ball 210 serving as a cushioning member.

Therefore, after the rough adjustment by the manual adjustment screw 208, the control means 9 controls the rotary shaft 2 of the drive motor 201 based on the detection result of the laser output detection means 8 described later.
When 02 rotates, the shaft 206 of the micrometer head 204 moves forward or backward via the flexible coupling 203. For example, when the shaft 206 moves forward (the direction indicated by the arrow L in FIG. 6), the manual adjustment screw 208 is pressed via the hard ball 210. Manual adjustment screw 20
Since 8 is fixed after the rough adjustment, the corresponding corner portion of the movable end plate 12 is displaced in the direction away from the fixed plate end 11 against the spring 209. On the contrary, when the shaft 206 retracts, the corresponding corner portion of the movable end plate 12 is displaced by the spring 209 in the direction approaching the fixed end plate 11.

FIG. 7 shows an example in which the laser resonator, the laser output detecting means 8 and the controlling means 9 shown in FIG. 5 are applied to a He-Cd laser head. Here, 5 is a laser tube,
Inside the laser tube 5, a discharge thin tube 51, an anode 52,
The cathode 53 and the like are arranged. 6 is a case.

The automatic optical axis adjusting method previously proposed by the present inventors is, for example, as shown in FIG. 7, a laser output detecting means 8 on the optical axis on the side of a total reflection mirror where a low output laser beam is output. The alignment mechanism 2 is automatically controlled by the control means 9 based on the detection result from the laser output detection means 8. That is, during the laser operation, the drive motor 201 including the stepping motor of the alignment mechanism 2 shown in FIG. 6 is driven by one step, and the laser output before and after this one-step driving is detected by the laser output detection means 8 and compared. When the laser output after one-step driving is large, the driving direction of the drive motor 201 is maintained, and when it is small, the driving direction is reversed. This operation is repeated during the laser operation, and the mirror angle is controlled so that the laser output is always near the maximum value. The specific configurations and operations of the laser output detection means 8 and the control means 9 are described in JP-A-4-31738.
No. 3 and Japanese Patent Laid-Open No. 4-364083. By adopting such a laser resonator having an automatic optical axis adjusting function, maintenance can be easily performed and long-term stability can be secured even in a laser device incorporated in a place where optical axis adjustment is difficult by manual operation.

[0013]

The automatic optical axis adjusting method as described above is (a) simple in construction. (B) Since the control signal is not the absolute value of the laser output to be monitored but the magnitude comparison of the laser output before and after one-step driving of the drive motor of the alignment mechanism, the laser tube containing the laser medium or the laser The change in absolute output due to deterioration of the chamber and laser mirror should not affect the optical axis control. However, there are the following problems.

(1) When a stepping motor is used as the drive motor of the alignment mechanism, the phase relationship of each phase of the exciting coil of the stepping motor is reset to the initial value when the power is turned on. Therefore, when the power is turned on, the laser mirror is always positioned at the same angle position, and the angle of the laser mirror when the laser device that previously performed the automatic optical axis adjustment was stopped is not maintained.

If the relationship between the phases of the exciting coils of the stepping motor when the laser device was stopped last time is significantly different from the reset phase relationship when the power is turned on again, the angular position of the laser mirror is changed to the previous automatic position. This causes a significant deviation from the position at the time of adjusting the optical axis, resulting in a large decrease in the laser output at the start of the automatic optical axis adjusting operation. Therefore, for example, if the laser output greatly decreases to the vicinity of the oscillation stop when the laser mirror is displaced, the laser oscillation may stop during the one-step driving, and the automatic optical axis adjustment operation becomes impossible. .

(2) When the automatic optical axis adjusting operation using the alignment mechanism shown in FIG. 6 is applied to the laser device in which the transverse mode of the laser is a single mode, the displacement of the alignment mechanism for each step of the stepping motor is applied. The amount may be too large. For example, in FIG. 6, when a 5-phase stepping motor is used as the drive motor and the operation is performed in the half step drive mode and the rotation angle for each step is 0.36 degrees, the displacement amount of the alignment mechanism is 0.5 μm. Becomes

This value seems to be small at first glance, but a smaller displacement amount is required for a laser whose transverse mode is single mode. This is because the laser having a single transverse mode has a large diffraction loss of the resonator, and therefore the change in the laser output per one-step drive is larger than that of the multimode laser, and the laser mirror near the optimum position of the optical axis is This is because the position may not be controlled in some cases. For example, when considering the recovery rate to the maximum output, the recovery rate may not recover to about 90% or more.

(3) In the alignment mechanism shown in FIG. 6, a screw for manual adjustment is separately attached from the outside of the case of the laser device, that is, from the outside of the movable end plate. Therefore, a drive motor or the like having a large volume must be mounted from the inside of the laser resonator, which limits the structure of the laser resonator.

(4) In the alignment mechanism as shown in FIG. 6, the displacement means itself is a micrometer, and the shaft of this micrometer is not made of a material having an extremely low expansion. Therefore, if there is a change in the ambient temperature during laser operation, the shaft may expand or contract depending on the change in the ambient temperature, resulting in a laser output fluctuation.

The present invention has been made under the circumstances as described above, and the first object of the present invention is to maintain the laser mirror angle at the time of the previous automatic optical axis adjustment even when the power is turned on again. (EN) Provided is a laser device having an automatic optical axis adjusting method and an automatic optical axis adjusting function. A second object of the present invention is to provide an automatic optical axis adjusting method for a laser resonator and a laser device having an automatic optical axis adjusting function, in which the amount of displacement at each step during automatic optical axis adjustment is small. A third object of the present invention is to provide a laser device which itself does not cause a laser output fluctuation depending on a change in ambient temperature and can increase the degree of freedom in the structure of a laser resonator.

[0021]

According to the first and third aspects of the present invention, the laser mirror constituting the laser resonator is held by a movable plate installed outside the fixed plate,
By applying a voltage pulse to the electrostrictive element installed on the movable plate, the screw part that is screwed into the electrostrictive element and presses the fixed plate is rotationally driven and controlled so that the laser output becomes maximum. Since the laser mirror angle is automatically controlled,
The position of the screw part is maintained at the previous position even when the power is turned on again. Therefore, unlike the conventional case where a stepping motor is adopted, the laser mirror angle at the time of the previous automatic optical axis adjustment is maintained, and the laser output does not decrease greatly even when the automatic optical axis adjustment operation is restarted, and it is driven by one step. Occasionally, the problem that laser oscillation stops does not occur.

Further, since the screw for manual adjustment which can be operated from the outside of the laser resonator can also be used as the screw portion, the manual adjustment of the optical axis can be easily performed.
Further, since the screw portion and the electrostrictive element are attached from the outside of the movable plate, there is no conventional drive motor having a large volume attached to the inside of the laser resonator. The degree of freedom increases.

According to the second and fourth aspects of the present invention, the function of adjusting the pulse width of the voltage pulse applied to the electrostrictive element is added to the first and third aspects of the invention. Due to the function of the electrostrictive element, by adjusting the pulse width of the voltage pulse, the drive amount of the screw part can be made smaller, and the amount of displacement of the laser mirror can be made smaller than when using a conventional stepping motor. It is possible to make it smaller. Therefore, when intermittently slightly displacing the angle of the laser mirror, compared with a laser device in which the transverse mode is multimode,
Even in a laser device in which the transverse mode is a single mode in which the change in laser output per one-step drive is large, it is possible to accurately perform automatic optical axis adjustment of the laser resonator.

According to the invention of claim 5 of the present invention, since the screw portion in the invention of claims 3 and 4 is made of a low expansion metal material, even when the ambient temperature changes during laser operation. The expansion and contraction of the screw part itself is small, and it is possible to ignore the fear of causing fluctuations in the laser output.

[0025]

FIG. 1 shows details of an embodiment of the alignment mechanism according to the present invention. The alignment mechanism 2 includes a male screw 20 made of an ultra-low-expansion metal, and the male screw 20 is screwed to the male screw 20 by an electric input such as a voltage pulse.
It is composed of an electrostrictive element 21 for rotating the element in a desired direction and a spring 22.

The electrostrictive element 21 is, for example, N of the American country.
Those manufactured by ew Focus are known. This changes the rotation direction of the male screw by changing the waveform of the applied voltage pulse, for example, the waveform of the triangular wave generated by the triangular wave generator. Further, the rotation angle per pulse can be controlled by controlling the width of the voltage pulse, that is, the width of the base of the triangular wave. For details, Indeco Co., Ltd. (1-11-14 Kasuga, Bunkyo-ku, Tokyo) is 1 in Hong Kong.
See the booklet "the PICOMOTOR" published in 993.

The electrostrictive element 21 is fixed to the movable end plate 12, and the male screw 20 which is the movable portion is inserted into through holes (not shown) provided in the corners Q and R of the movable end plate 12, respectively. It is said to be free to go back and forth. For the positions of the corners Q and R, see FIG. A spring 22 is provided between the fixed end plate 11 and the movable end plate 12 so as to exert an elastic force in a direction in which they approach each other. The spring 22 keeps the male screw 20 constantly pressing the fixed end plate 11. Has become.

Therefore, when the alignment mechanism 2 shown in FIG. 1 is applied to a laser head as shown in FIG. 7, for example,
After the optical axis is roughly adjusted by the male screw 20, the electrostrictive element 21 is operated by the controller 9 based on the detection result of the laser output detector 8 to rotate the male screw 20 to move it forward or backward. For example, when the male screw 20 moves forward (in the direction indicated by the arrow L in FIG. 1), the fixed end plate 11 is fixed by the fixed end plate support rod 4, so that the corresponding corner portion of the movable end plate 12 becomes the spring 22. It is displaced in the direction away from the fixed plate end 11. On the contrary, when the male screw 20 moves backward, the corresponding corner portion of the movable end plate 12 is moved to the fixed end plate 1 by the spring 22.
It is displaced in the direction approaching 1.

That is, as shown in FIG. 1, the alignment mechanism 2 according to the present invention has a fixed end plate 11 of a laser resonator.
Install from outside. With such mounting,
Conventionally, as shown in FIG. 6, a stepping motor or the like that occupies a large space inside the laser resonator, that is, inside the fixed end plate 11, is omitted. Therefore, the degree of freedom in structural design of the laser resonator is increased.

Further, this male screw 20 can have the same function as the screw for manual optical axis adjustment in the conventional configuration shown in FIG. 6, and the overall structure becomes simpler and more compact. Further, since the material of the male screw 20 is an ultra-low expansion metal such as Super Invar (trade name), the male screw 20 hardly expands or contracts even when the ambient temperature changes during laser operation, and the laser output does not fluctuate. .

In the laser device having the automatic optical axis adjusting function according to the present invention, for example, in the structure shown in FIG. 7, the alignment mechanism 2 of the laser resonator shown in FIG. Laser output detecting means 8 is provided on the optical axis of the total reflection mirror side from which the laser light of
The alignment mechanism 2 is automatically controlled by the control means 9 based on the detection result from the laser output detection means 8.

That is, during laser operation, one voltage pulse is applied to the electrostrictive element 21, the male screw 20 is rotated by one pulse, and the laser output before and after one pulse rotation is detected by the laser output detection means 8. And compare. When the laser output after one pulse rotation is large, the rotation direction of the male screw 20 is maintained, and when it is small, the rotation direction is reversed. This operation is repeated during the laser operation, and the mirror angle is controlled so that the laser output is always near the maximum value.

When the voltage pulse is a triangular wave, the rotation angle per pulse can be precisely changed by adjusting the width of the base of the triangular wave. Therefore, for example, the displacement at each step during the automatic optical axis adjustment It is possible to perform automatic optical axis adjustment even for a laser device in which the transverse mode of the laser whose amount is required to be small is a single mode.

The automatic adjustment of the mirror angle will be described below with reference to FIGS. 2 and 3. FIG. 2 is a block diagram showing an example of the laser output detection means 8 and the control means 9.
FIG. 3 is a timing chart of the laser output detection means 8 and the control means 9. The laser output detection means 8 compares and detects the laser output before and after the intermittent minute displacement of the angle of the laser mirror 3, and the control means 9 considers the above detection result.
When the laser output after the micro displacement is larger than the laser output before the micro displacement, the angle of the laser mirror 3 is in the same direction, and when the laser output after the micro displacement is small, the angle of the laser mirror 3 is in the opposite direction. The alignment mechanism 2 is controlled so as to be slightly displaced.

As shown in FIG. 2, laser output detecting means 8
Is, for example, a photoamplifier 81 that detects a laser output,
The sample-and-hold circuit 82 holds the laser output immediately before the minute angular displacement of the laser mirror 3, and the comparator 83 which compares and detects the laser output before and after the minute angular displacement of the laser mirror 3. That is, the laser output immediately before the electrostrictive element 21 of the alignment mechanism 2 is driven is detected by the photoamplifier 81, held in advance by the sample hold circuit 82, and this signal is input to the non-inverting input terminal of the comparator 83. The laser output immediately after driving the electrostrictive element 21 is input to the inverting input terminal of the comparator 83.

The control means 9 includes a direction indicating circuit 91,
The pulse width variable circuit 92 and the electrostrictive element drive circuit 93 are included. The direction indicating circuit 91 is, for example, the timing circuit 3
1, mono-multi vibrator 32, 33 AND circuit 3
4 and a toggle flip-flop circuit 35.
Here, the J and K inputs of the toggle flip-flop circuit 35 are set to the H level, and the AND circuit 34 is input at the CLK input.
When the output signal X ₅ of rises, so that the output signal X ₆ of the Q output of toggle flip-flop circuit 35 is inverted from H level to L level, the output signal X ₇ of the R output is inverted from L level to H level It has become. When one of the output signals X ₆ and X ₇ is H level, the other is always L level.

In the direction indicating circuit 91, the output signal X ₂ of the mono-multivibrator 32 is the electrostrictive element drive circuit 9
3 is input to the triangular wave generator (1) and the triangular wave generator (2) and converted into a drive signal for driving the electrostrictive element 21 of the alignment mechanism 2. On the other hand, the output signals X ₆ and X ₇ of the toggle flip-flop circuit 35 are used as the direction indicating signals for the minute displacement of the angle of the laser mirror 3.

The electrostrictive element drive circuit 93 includes, for example, triangular wave generators (1), (2), resistors R ₁ , R ₂ , R ₃ ,
R ₄ , analog switches (1), (2), inverting amplifier O
P, a high voltage amplifier AMP. Triangular wave generator (1)
Generates a triangular wave (1) having a gentle rise and a sharp fall when the output signal X ₂ of the mono multivibrator 32 is input. The triangular wave generator (2) generates a triangular wave (2) having a steep rise and a gradual fall when the output signal X ₂ of the mono-multivibrator 32 is input. The triangular wave generator (1) is, for example, an integrator of the waveform of the input signal X ₂ , and the triangular wave generator (2) is, for example, the input signal X 2.
_It is composed of a combination of a differentiator with a waveform of ₂ and a rectifier. The triangular wave (1) and the triangular wave (2) are amplified by the inverting amplifier OP and the high voltage amplifier AMP and input to the electrostrictive element 21 of the alignment mechanism 2. Here, the triangular wave (1) is an instruction signal for setting the rotation direction of the male screw 20 to the clockwise direction, and the triangular wave (2) is an instruction signal for setting the rotation direction of the male screw 20 to the counterclockwise direction. The resistors R ₁ and R
₂ , R ₃ and R ₄ form an adder circuit together with the inverting amplifier OP. That is, the high voltage defining the magnitude of the input to the amplifier AMP, the magnitude of the input of the R ₃ / R ₂ to a high voltage amplifier AMP of the triangular wave (2) of the triangular wave (1) R ₃ / R ₁ Is prescribed. Also R ₃ / R
₄ defines the DC level of the high voltage amplifier AMP input when the triangular wave (1) and the triangular wave (2) are not generated.

The analog switch (1) is turned on when the H level output signal X ₆ of the toggle flip-flop circuit 35 is input. On the other hand, the analog switch (2)
When the H-level output signal X _{7 of the} toggle flip-flop circuit 35 is input, it turns on. That is, whether the analog switches (1) and (2) are in the H level state of the output signals X ₆ and X ₇ of the toggle flip-flop circuit 35 used as the direction indicating signal of the minute displacement of the angle of the laser mirror 3. The triangular wave (1) and the triangular wave (2) input to the electrostrictive element 21 are selected depending on the L level.

The specific operation is as follows. In the direction indicating circuit 91, the output signal X of the timing circuit 31
₁ is a rectangular wave having a period T ₀ as shown in FIG. When the output signal X ₁ falls to the L level hold signal, the sample and hold circuit 82 holds and outputs the laser output signal detected by the photoamplifier 81. On the other hand, the output signal X of the timing circuit 31
₁ is also output to the mono multivibrator 32, and when this output signal X ₁ falls, the output signal X ₂ of the mono multivibrator 32 becomes H level. This H level output signal X ₂ is converted into a drive signal for driving the electrostrictive element 21 of the alignment mechanism 2 as described above. The output signal X ₂ is input to the triangular wave generator (1) and the triangular wave generator (2) of the electrostrictive element drive circuit 93.

The comparison of the laser output before and after the minute angular displacement of the laser mirror 3 is performed as follows. As described above, when the output signal X ₁ of the timing circuit 31 is the L level hold signal, the output signal of the sample and hold circuit 32 is the laser output signal before the minute displacement detected by the photoamplifier 81. This signal is input to the non-inverting terminal of the comparator 83. on the other hand,
The laser output immediately after the minute displacement is detected by the photoamplifier 81, and this detection signal is directly input to the inverting terminal of the comparator 83. Therefore, comparing these two signals input to the comparator 83 is a comparison of the laser outputs before and after the minute angular displacement of the laser mirror 3.

Here, when the laser output after the slight displacement of the angle of the laser mirror 3 becomes small, the output signal X ₄ of the comparator 83 becomes H level. When the output signal X _{4 of} H level is input to the AND circuit 34, the output signal X ₅ of the AND circuit 34 becomes H level at the timing when the output signal X _{3 of the} monomultivibrator 33 becomes H level. C of the toggle flip-flop circuit 35
The output signal X of the AND circuit 34 input to the LK terminal
_{When 5} becomes H level, toggle flip-flop circuit 3
The levels of the output signals X ₆ and X ₇ of 5 are inverted. Therefore, the triangular wave input to the electrostrictive element 21 changes and the male screw 2
The rotation direction of 0 is reversed.

On the other hand, when the laser output after the slight displacement of the angle of the laser mirror 3 becomes large, the comparator 8
The output signal X _{4 of} 3 becomes the L level. When this L level output signal X ₄ is input to the AND circuit 34, the output signal X ₅ of the AND circuit 34 maintains the L level. When the output signal X ₅ of the AND circuit 34 input to the CLK terminal of the toggle flip-flop circuit 35 is L level, the output signal X ₆ of the toggle flip-flop circuit 35,
The level of X ₇ is maintained. Therefore, the triangular wave input to the electrostrictive element 21 does not change, and the rotation direction of the male screw 20 is maintained.

The pulse width variable circuit 92 added to the mono multivibrator 32 of the direction indicating circuit 91 is, for example,
It is composed of a capacitor C and a variable resistor VR ₁ . The pulse width of the output signal X ₂ of the mono multivibrator 32 is
It is determined by the product of the value of the capacitor C and the variable resistor VR ₁ . Since this signal X ₂ is converted into a triangular wave (1) and a triangular wave (2) by the triangular wave generator (1) and the triangular wave generator (2), by selecting the value of the variable resistor VR ₁ , 1), the width of the base of the triangular wave (2) is adjusted, and as described above, the rotation angle of the male screw 20 per pulse can be precisely controlled. That is, it is possible to perform automatic optical axis adjustment even for a laser device in which the lateral mode of the laser is a single mode, which requires a small amount of displacement at each step during automatic optical axis adjustment.

In the present embodiment, the rotation angle of the male screw per step is ⅕ of the rotation angle in the conventional case in which the 5-phase stepping motor and the micrometer head are combined, and as a result, the rotation angle per step is The amount of male screw displacement was 0.1 μm, and the resolution could be increased five times compared to the conventional product.

Next, FIG. 4 shows how the laser output P (θ) is adjusted based on the output signal X ₆ shown in FIG. In FIG. 4, the horizontal axis represents the angle of the laser mirror 3, and the vertical axis represents the laser output. Also, in FIG.
P (A), P (B), P (C), and P (D) are laser outputs when the angles of the laser mirror 3 are A, B, C, and D, and (a), (b), (C), (d), and (e) show the magnitude and direction of the one-step drive of the male screw 20 of the alignment mechanism 2 that drives the laser mirror 3 for automatic optical axis adjustment.

For example, if the angle of the laser mirror 3 deviates from the optimum angle C at which the laser output is maximized to the angle A at any time, the laser output P (A) at the angle A is the output of the timing circuit 31. When the signal X ₁ falls, the sample-and-hold circuit 82 holds the signal and the mono-multivibrator 32
Output signal X ₂ of H level is input to the triangular wave generators (1) and (2) and converted into triangular wave (1) and triangular wave (2). At this time, the male screw 20 of the alignment mechanism 2 causes the analog switch (1), the analog switch (1), depending on the states of the output signals X ₆ and X ₇ of the toggle flip-flop circuit 35.
Any one of (2) is turned on, and is driven to rotate in either the clockwise direction or the counterclockwise direction, and
The angle of the laser mirror 3 is slightly displaced by a step.

Assuming that the angular displacement direction of the laser mirror 3 is the arrow direction shown in FIG.
The angular displacement of the laser mirror 3 is generated by the amount of (a), the angle of the laser mirror 3 becomes B, and the laser output at this time becomes P (B).

Next, the laser output P (B) is detected by the photoamplifier 81 and input to the comparator 83, and the laser output P (A) before the minute displacement and the laser output P (B) after the minute displacement are compared. To be done. When the laser output P (B) after the minute displacement is larger than the laser output P (A) before the minute displacement, the output signal X ₄ of the comparator 83 becomes the L level and the output signal X ₅ of the AND circuit 34 maintains the L level. However, the output signals X ₆ and X ₇ of the toggle flip-flop circuit 35 are not inverted. Therefore, the rotation direction of the male screw 21 is maintained as it is, and the alignment mechanism 2 performs the next intermittent minute displacement. That is, (b) in FIG.
The angular displacement of the laser mirror 3 is caused by the amount of (b) in the direction of the arrow indicated by (3), the angle of the laser mirror 3 becomes C, and the laser output at this time becomes P (C).

On the contrary, when the angle of the laser mirror 3 is displaced from C to D, that is, when the angle of the laser mirror 3 is displaced by the amount of (c) in the direction of the arrow shown in (c) of FIG. Since the laser output P (D) after the minute displacement is smaller than the laser output P (C) before the minute displacement, the output signal X ₄ of the comparator 83 becomes H level. Therefore, the output signal X ₅ of the AND circuit 34 becomes the H level, the output signals X ₆ and X _{7 of} the toggle flip-flop circuit 35 are inverted, the rotation direction of the male screw 21 is inverted, and the alignment mechanism 2 moves the next signal. Intermittent small displacement is performed. That is, in the direction of the arrow shown in (d) of FIG. 4, the angular displacement of the laser mirror 3 occurs by the amount of (d), the angle of the laser mirror 3 becomes C, and the laser output at this time is P (C). Become.

Such an intermittent small displacement is, for example,
By repeating the fixed cycle T ₀ determined by the output signal X ₁ of the timing circuit 31, the angle of the laser mirror 3 is the peak value of the laser output within the range of the resolution of the laser output detecting means 8 (C). It is adjusted so that it is always maintained in the vicinity.

With the above procedure, in the laser resonator shown in FIG. 5, the alignment mechanism 2 for the corner Q causes the laser to rotate in one direction, that is, in the direction of rotation about the line connecting the fulcrum P and the other corner Q. The automatic adjustment work of the angle of the mirror 3 is completed. Next, the other alignment mechanism 2 repeats the above procedure to automatically adjust the angle of the laser mirror 3 in another direction, that is, in the rotation direction about the line connecting the fulcrum P and the other corner R. The work is finished and the laser power will always be kept near maximum.

According to this embodiment, since the alignment mechanism 2 is attached from the outside of the fixed end plate 11 of the laser resonator, the stepping motor and the like which conventionally occupy a large space inside the fixed end plate 11 are omitted. , The degree of freedom in the structural design of the laser cavity has increased. In addition, the alignment mechanism 2
Since the male screw 20, which is a movable part of the above, can also be used as a screw for manual optical axis adjustment, the structure of the alignment mechanism 2 as a whole is simple and compact. Furthermore, since the material of the male screw 20 is an ultra-low expansion metal, even if the ambient temperature changes during laser operation, the male screw 20 hardly expands or contracts, and laser output fluctuation does not occur.

Then, based on the detection result from the laser output detection means 8, the control means 9 automatically controls the alignment mechanism 2 so as to increase the laser output, so that the optical axis can be automatically adjusted. Here, since the driving unit of the alignment mechanism 2 is configured by the male screw 20 and the electrostrictive element 21, the angle of the laser mirror when the laser device that previously performed the automatic optical axis adjustment is stopped even when the power is turned on again. Is maintained, and the automatic optical axis adjusting action is stabilized in a short time. Further, by adjusting the pulse width with the pulse width variable circuit 92 of the control means 9, the male screw 20 per pulse is adjusted.
The automatic optical axis adjustment is performed even for a laser device in which the lateral mode of the laser is a single mode, in which the rotation angle of the laser is precisely controlled and the amount of displacement at each step during automatic optical axis adjustment is required to be small. It becomes possible.

Although the embodiments of the present invention have been described above, various other means can be used as the laser output detecting means and the control means. In addition, the alignment mechanism 2 may be installed in the facing mirror holder, and the facing 2
By alternately adjusting the angles of the two laser mirrors,
The optical axis can be adjusted more accurately.

[0056]

According to the present invention, the laser mirror constituting the laser resonator is held by the movable plate installed outside the fixed plate, and the voltage pulse is applied to the electrostrictive element installed on the movable plate. Since the screw part that is screwed into the electrostrictive element and presses the fixing plate is rotationally controlled, and the laser mirror angle is automatically controlled so that the laser output is maximized, the screw part is turned on even when the power is turned on again. The previous position is maintained. Therefore, unlike the case where the stepping motor is adopted as in the conventional case, the laser mirror angle at the time of the previous automatic optical axis adjustment is maintained, and the laser output does not greatly decrease even when the automatic optical axis adjustment operation is restarted. The problem that the laser oscillation stops during driving does not occur.

Further, since the screw for manual adjustment which can be operated from the outside of the laser resonator can also be used as the screw portion, the manual adjustment of the optical axis can be easily performed.
Further, since the screw portion and the electrostrictive element are attached from the outside of the movable plate, there is no conventional drive motor having a large volume attached to the inside of the laser resonator. The degree of freedom increases.

Further, by adjusting the pulse width of the voltage pulse applied to the electrostrictive element, the drive amount of the screw portion can be made smaller, and the laser mirror can be made finer than when a conventional stepping motor is used. It is possible to reduce the displacement amount. Therefore, when intermittently slightly displacing the angle of the laser mirror, even in a laser device in which the transverse mode has a large change in the laser output per step drive as compared with a laser device in which the transverse mode is multimode, It is possible to accurately perform automatic optical axis adjustment of the laser resonator.

Further, by constructing the screw portion with a low expansion metal material, the expansion and contraction of the screw portion itself is small even when there is a change in ambient temperature during laser operation, and it is possible to ignore fluctuations in the laser output. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an alignment mechanism according to the present invention.

FIG. 2 is a block diagram showing an example of laser output detection means and control means.

FIG. 3 is an explanatory diagram of a timing chart of signals in the laser output detection means and the control means shown in FIG.

FIG. 4 is a diagram illustrating a correspondence between a change in a rotation angle of a laser mirror and a change in a laser output.

FIG. 5 is a diagram showing an example of a laser resonator.

FIG. 6 is a diagram showing a conventional alignment mechanism.

FIG. 7 is a diagram showing an example in which a laser resonator, laser output detection means, and control means are applied to a He—Cd laser head.

[Explanation of Codes] 1 Mirror Holding Part 2 Alignment Mechanism 3 Laser Mirror 4 Fixed End Plate Support Rod 5 Laser Tube 6 Case 8 Laser Output Detection Means 9 Control Means 11 Fixed End Plate 12 Movable End Plate 13 Through Hole 20 Male Screw 21 Electric Distortion element 22 Spring 31 Timing circuit 32 Mono multivibrator 33 Mono multivibrator 34 AND circuit 35 Toggle flip-flop circuit 51 Discharge capillary tube 52 Anode 53 Cathode 81 Photoamplifier 82 Sample and hold circuit 83 Comparator 91 Direction indicator circuit 92 Pulse width variable circuit 93 Electrostrictive element drive circuit 201 Drive motor 202 Rotating shaft 203 Flexible coupling 204 Micrometer head 205 Fixing metal fitting 206 Shaft 207 Fixing metal fitting 208 Manual adjustment screw 209 Spring 210 Hard sphere P, Q, R Corner X ₁ , X ₂ , X ₃ , X ₄ , X ₅ , X ₆ , X ₇
Output signal T ₀ cycle C capacitor VR ₁ variable resistor R ₁ , R ₂ , R ₃ , R ₄ resistor OP inverting amplifier AMP high voltage amplifier

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hironari Haneda 1194 Sado, Bessho-cho, Himeji-shi, Hyogo Ushio Electric Co., Ltd.

Claims (5)

[Claims] 1. A laser mirror constituting a laser resonator is held by a movable plate installed outside a fixed plate, and a voltage pulse is applied to an electrostrictive element installed on the movable plate,
The screw portion that is screwed into the electrostrictive element and presses the fixing plate is rotationally driven to intermittently make a minute displacement of the laser mirror angle, and the laser outputs before and after the minute displacement are compared. When the output is large, a voltage pulse that slightly displaces the laser mirror angle is applied to the electrostrictive element in the same direction as the direction in which the laser mirror angle is slightly displaced, and in the opposite direction when the laser output after the minute displacement is small. A method for automatically adjusting the optical axis of a laser resonator, wherein a voltage pulse for slightly displacing the laser mirror angle is applied to the electrostrictive element. 2. The automatic optical axis adjusting method for a laser resonator according to claim 1, wherein the pulse width of the voltage pulse is adjusted in advance to adjust the minute displacement of the laser mirror angle. 3. A laser medium, a laser resonator, a laser output detecting means, and a control means, wherein the laser resonator is movable to hold a mirror outside a pair of fixing plates fixed to a rod. In a laser device including a mirror holder on which a plate is installed and an alignment mechanism attached to at least one of the mirror holders, the alignment mechanism includes a screw portion for pressing the fixing plate and a screw portion for screwing the screw portion. And an electrostrictive element that rotationally drives the screw portion in a predetermined direction when a predetermined voltage pulse is input, and the control means outputs a laser output based on a result detected by the laser output means. To increase, select either the first voltage pulse or the second voltage pulse for driving the screw portion to rotate clockwise or counterclockwise, respectively. Enter the electrostrictive element Te laser apparatus characterized by driving the screw portion. 4. The laser device according to claim 3, wherein pulse width control means for the first voltage pulse and the second voltage pulse is added to the control means. 5. The laser device according to claim 3, wherein the screw portion is made of a low expansion metal material.