JPH0513857A - Optical fiber light convergence correction equipment in solid laser equipment - Google Patents

Abstract

PURPOSE:To automatically adjust light convergence on an optical fiber to be the optimum state, by detecting the spread state of a laser beam, adjusting a condenser lens to be at a suitable position, and moving the second actuator by the same distance. CONSTITUTION:The intensity distribution of a laser beam is detected with a detection part 8. Said distribution shows the spread state of the laser beam, and data are inputted in an operation part 12. When the spread state exceeds a specified region, a signal for driving an actuator 9 is sent out to move a detection part 8, and a condenser lens 7 for correction use is moved. Since the refraction position of the laser beam is changed, the spread state of the laser beam in the detection part 8 is changed. When the spread is in the contraction direction, the loop is repeated. Thereby the first actuator 9 is controlled as far as a position where the spread of the laser beam becomes minimum. When the area of the focus in the detection part 8 becomes minimum, this is judged to be the optimum state by the operation part 12, which drives the second actuator by the travelling distance amount of the first actuator 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for correcting the spread of a laser beam due to a thermal lens effect or output fluctuation in a solid-state laser device.

[0002]

2. Description of the Related Art Generally, in a laser resonator of a type in which a laser medium is excited by a pump lamp to cause laser oscillation, it is known that a laser beam spreads due to a thermal lens effect. This phenomenon is caused by the fact that the laser medium forms a refractive index distribution in the radial direction of the laser medium by heating. Therefore, there is a property that the focal length of laser light fluctuates with time due to factors such as the thermal lens effect and fluctuations in output.

[0003]

When the spread of the laser light changes in this way, the focal length between the condenser lens and the optical fiber changes when the laser light enters the optical fiber.

Therefore, in the past, the output was suppressed or the cooling device for the laser medium was improved to prevent the laser medium from overheating and stabilize the spread of the laser beam. Cannot be obtained or the device becomes large.

Moreover, although the fluctuation range can be reduced by these methods, it cannot be completely stabilized, so that it is necessary to manually adjust the optical system in response to the fluctuation. However, this adjustment is extremely troublesome, and if the adjustment is insufficient, there are problems that the efficiency at the time of incidence on the optical fiber is reduced and the optical fiber is damaged.

The present invention has been made in view of the above-mentioned matters. Even if the laser output fluctuates, the focused laser beam can always be made incident on the optical fiber, and at the same time, a compact and sufficient output can be obtained. It is a technical object to provide an optical fiber condensing correction device in such a solid-state laser device.

[0007]

In order to solve the above technical problems, the present invention provides a laser beam output from a laser oscillator equipped with a laser medium and a pump lamp for introducing pumping light into the laser medium. The laser device that enters the optical fiber through the condenser lens has the following configuration.

That is, a branching device for splitting a part of the laser light output from the laser oscillator, a correcting condensing lens provided at the next stage of the branching device and having the same characteristics as the condensing lens, and this correcting lens. Section for receiving the laser beam that has passed through the optical condensing lens, a first actuator for moving the detecting section or the correcting condensing lens in the optical axis direction, and a light receiving port of the optical fiber or the condensing lens for the optical axis. A second actuator that moves in a direction, and a calculation unit that receives the signal from the detection unit and controls the first and second actuators, and the calculation unit irradiates the detection unit with the correction condensing lens. If the focal point of the generated laser light is deviated, it is detected and the detector or the correction condenser lens is moved in the direction of the optical axis so as to form a focus. Same as quantity The amount, the technical means by being configured to move the light receiving port of the condenser lens or an optical fiber.

A bandpass filter may be inserted between the correcting condenser lens and the branching device.

[0010]

The detecting unit detects the spread state of the laser beam, operates the first actuator based on the data, adjusts the position of the correcting condenser lens to an appropriate position, and based on this data, operates the second actuator. Since it is configured to move by the same distance, it is possible to automatically and automatically adjust the converging property of the laser beam to the optical fiber to the optimum state. Therefore, the coupling efficiency with the optical fiber does not deteriorate.

Further, since the laser output is not suppressed or the cooling of the laser medium is not strengthened, a small size and sufficient output can be obtained. Here, the correcting condenser lens has the same characteristics as the condenser lens. That is, the refractive index,
All conditions and characteristics such as focal length, presence or absence of coating, and type of coating material are the same.

The branching device may be a beam splitter, a prism, a semi-transmissive mirror or the like. The meaning of moving the condenser lens or the light receiving port of the optical fiber by the same amount as that of the detector or the correcting condenser lens is as follows.

First, when the amount of movement of the correcting condenser lens is detected and the condenser lens is moved, the condenser lens is moved in the same direction by the same distance. When the amount of movement of the detector is detected and the condenser lens is moved, they are moved in the opposite direction by the same distance.

When the amount of movement of the correcting condenser lens is detected and the light receiving port of the optical fiber is moved, it is moved in the opposite direction by the same distance. When the amount of movement of the detector is detected to move the light receiving port of the optical fiber, they are moved in the same direction and by the same distance.

[0015]

Embodiment An embodiment of the present invention will be described with reference to FIG.
An excitation lamp 2 for injecting excitation light is arranged in the vicinity of a rod-shaped laser medium 1, and a total reflection mirror 20a and a semi-transmission mirror 20b are arranged on both ends of the laser medium 1. .. Then, laser light is generated from the laser medium 1 excited by the excitation lamp 2, and laser light is amplified by repeating reflection between the total reflection mirror 20a and the semi-transmission mirror 20b. ing.

A beam splitter 6 as a branching device is installed on the laser transmitting side of the semi-transmissive mirror 20b, whereby the laser beam output from the laser oscillator 3 is branched into a straight traveling direction and a perpendicular direction. Then, the laser light branched in the right angle direction enters the optical fiber 5 through the condenser lens 4. The condenser lens 4 is supported by the second actuator 11 so that it can move in the optical axis direction.

On the other hand, a bandpass filter 21 for passing only a specific frequency is provided on the back surface of the beam splitter 6, and the passing frequency is set to 1.06 μm so as to remove visible light. A correcting condenser lens 7 having the same characteristics as the condenser lens 4 is provided at the next stage of the bandpass filter 21.

A one-dimensional photodetector array serving as a detector 8 for receiving the laser beam that has passed through the correcting condensing lens 7 is provided after the correcting condensing lens 7. The detector 8 is supported by the first actuator 9 and is movable in the optical axis direction.

The first actuator 9 may movably support either the photodetector array 8 or the correcting condenser lens 7, and the second actuator 11 may be the light receiving port 10 of the optical fiber 5. It suffices if one of the condenser lenses 4 is movably supported.

The output signal of the detection unit 8 is input to the calculation unit 12, and the spread state of the laser beam applied to the detection unit 8 is digitized. The first actuator 9 is actuated by calculating how much the correction condensing lens 7 should be moved in which direction to minimize the divergence of the laser beam. A servo motor, a stepping motor, or a linear stepping motor is used as the first actuator 9 and the second actuator 11, and the first actuator 9 and the second actuator 11 can be moved by a predetermined distance according to a command from the arithmetic unit 12.

Further, a potentiometer, a rotary encoder, a linear encoder, etc. are attached to each actuator as moving amount detecting means, and the focal position of the correcting condensing lens 7 or the condensing lens 4 is set as an absolute position. The movement amount of the actuator can be output to the calculation unit 12.

When the actuator is a stepping motor, the control amount when the correction lens is moved to focus the image can be used as it is as the movement amount, so that the actuator itself constitutes the movement amount detecting means.

An operation example will be described below. Laser oscillator 3
During operation of the laser beam, the laser beam is split at a right angle by the beam splitter 6 and the light receiving port 1 of the optical fiber 5 is split.
The laser beam that has entered 0 and transmitted through the beam splitter 6 illuminates the detection unit 8 via the bandpass filter 21 and the correction condenser lens 7. And the detection unit 8
The intensity distribution of the laser beam is detected by.

This intensity distribution shows the spread state of the laser beam, and this information is input to the arithmetic unit 12. Then, the calculation unit 12 determines whether or not the spread state is within the specified range.
Is sent to move the detector 8.

In this case, the intensity distribution of the laser beam in the detection unit 8 is recognized as a pattern, and in which direction the correction condensing lens 7 is moved to reduce the spread, it is also determined. If not, the correcting condensing lens 7 is moved in either direction.

When the correcting condenser lens 7 moves, the refraction position (focal length) of the laser beam changes, so that the spread state of the laser beam in the detector 8 changes. Then, it is determined whether or not the change direction is the direction in which the spread is reduced.

When the changing direction of the divergence is the reducing direction, the first actuator 9 is moved to a position where the divergence of the laser beam is minimized by repeating the loop described above.
To control. On the other hand, when the changing direction of the spread is the expanding direction, the first actuator 9 is driven in the opposite direction, and then the first actuator 9 is similarly controlled to a position where the spread of the laser beam is minimized.

When the focus in the detection unit 8 reaches the minimum area, the calculation unit 12 determines that it is in the best state and drives the second actuator by the same distance as the moving distance of the first actuator 9.

Since the condensing lens 4 and the correcting condensing lens 7 have the same characteristics, the condensing lens 4 stops at the position where the light receiving port 10 of the optical fiber 5 is focused. By the above operation, a good quality laser beam without spread can be obtained and energy can be concentrated. Therefore, it becomes easy to enter the optical fiber 5, and it is possible to enter a strong laser beam without loss.

In the above embodiment, the condenser lens 4 and the detector 8 are moved in the optical axis direction to detect the best point, but in addition to this, the condenser lens 4 and the detector 8 are also arranged. It is also possible to move 8 and 8 respectively in the direction perpendicular to the optical axis to detect the best point in two dimensions, and move the condenser lens 4 and the detection unit 8 in three dimensions. In this case, the detection unit 8 may be a two-dimensional photodetector array, and the first and second actuators 9 and 11 may be three-dimensional corresponding three-channel type. This method enables complete focus management.

Another specific example for realizing this three-dimensional movement control will be described as a second embodiment. This is the third actuator 30 that integrally moves the detection unit 8 and the correction condensing lens 7 in the direction orthogonal to the optical axis in the first embodiment,
A fourth actuator 31 that integrally moves the light receiving port 10 of the optical fiber and the condenser lens 4 in a direction orthogonal to the optical axis.
And is further provided.

Then, the calculation unit 12 detects the deviation of the irradiation position of the laser beam irradiated on the detection unit 8 by the correction condensing lens 7, and detects this, and the detection unit 8 and the correction condensing lens 7 are detected. Is moved in the direction orthogonal to the optical axis, and the condenser lens 4 and the light receiving port 10 of the optical fiber 5 are moved by the same amount as the movement amount of the detection unit 8 and the correction condenser lens 7 at this time.

More specifically, FIG. 2 to FIG.
As described above, the light receiving port 10 is supported integrally with the condenser lens 4 by the support arm 22. The condenser lens 4 is supported by the fourth actuator 31 and is configured to be movable on the XY plane orthogonal to the optical axis. The support arm 22 is provided with the second actuator 11 that acts in the same manner as the second actuator of the first embodiment to adjust the focus of the condenser lens 4.
This is to adjust the distance between the condenser lens 4 and the light receiving port 10 to be wide or narrow.

The fourth actuator 31 is a stepping motor 31 for moving the condenser lens 4 in the X direction.
a and a stepping motor 3 for moving in the Y direction
It consists of 1b. The stepping motor 31a is attached to the frame 31c.
The condenser lens 4 is slidably supported on the.
The condenser lens 4 and the stepping motor 31a are connected by a rack and pinion mechanism. The stepping motor 31b is attached to the fixed frame 31d,
The frame 31c is slidably provided on the fixed frame 31d. And this frame 31c
The stepping motor 31b and the stepping motor 31b are connected by a rack and pinion mechanism.

On the other hand, on the back side of the beam splitter 6, there is a bandpass filter 2 for passing only a specific wavelength.
1 is provided, and its passing wavelength is set to 1.06 μm so as to remove visible light. A correcting condenser lens 7 having the same characteristics as the condenser lens 4 is provided at the next stage of the bandpass filter 21.

A two-dimensional photodiode array serving as a detector 8 for receiving the laser beam that has passed through the correcting condenser lens 7 is provided at the subsequent stage of the correcting condenser lens 7. The correction condenser lens 7 is an arm 23.
It is fixed to the detection unit 8 via the, and can be moved integrally with the detection unit 8. The detector 8 is supported by the third actuator 30 and is movable in the direction orthogonal to the optical axis. That is, the third actuator 30 includes a stepping motor 30a for moving the detecting unit 8 in the X direction and a stepping motor 30b for moving the detecting unit 8 in the Y direction. And the arm 23
In addition, a first actuator 9 that adjusts the focus of the condenser lens 4 by operating similarly to the first actuator of the first embodiment is provided. This is to adjust the distance between the condenser lens 7 and the detector 8 to be wide or narrow.

The stepping motor 30a is a frame 30.
The detection unit 8 is slidably supported on the frame 30c. The detection unit 8 and the stepping motor 30a are connected by a rack and pinion mechanism. The stepping motor 30b is attached to a fixed frame 30d, and the frame 30c is slidably provided on the fixed frame 30d. The frame 30c and the stepping motor 30b are connected by a rack and pinion mechanism.

The output signal of the detection unit 8 is input to the calculation unit 12, and the position of the laser beam irradiated on the detection unit 8 on the XY coordinates is digitized. Then, the third actuator 30 is operated by calculating how much the detecting unit 8 should be moved in any direction so that the position of the laser beam becomes the central portion of the detecting unit 8 (including a predetermined specific position). Is configured to operate.

In addition to the stepping motor, the third actuator 30 and the fourth actuator 31 are also
A servo motor or a linear stepping motor can be used, and the drive amount thereof is controlled by a command from the arithmetic unit 12.

Further, a potentiometer, a rotary encoder, a linear encoder, etc. are attached to each actuator as moving amount detecting means, and the moving amount of the actuator is sent to the calculating unit 12 with the center of the detecting unit 8 as an absolute position. It can be output.

When the actuator is a stepping motor, the control amount when the correction lens is moved and the irradiation position is adjusted can be used as it is as the movement amount, so that it constitutes the movement amount detecting means itself.

An operation example will be described below. Laser oscillator 3
During the operation of 1, the laser beam is branched in a right angle direction by the beam splitter 6 and is incident on the light receiving port 10 of the optical fiber 5 via the condenser lens 4. On the other hand, the laser beam transmitted through the beam splitter 6 irradiates the detection unit 8 via the bandpass filter 21 and the correction condenser lens 7. Then, the detector 8 detects the irradiation position of the laser beam.

This information is input to the arithmetic unit 12. Then, the calculation unit 12 determines whether or not the spread state is within the specified range, and when the irradiation position is deviated from the reference position of the detection unit 8, a signal for driving the actuator 30 is sent to determine the irradiation position. The detection unit 8 is moved so as to reach the reference position. Here, the calculation unit 12 stores this movement amount as a distance on the XY coordinates.

Subsequently, the arithmetic unit 12 sets the fourth actuator 31 to the third actuator 30 based on this storage.
It is driven by the same distance in the same direction as the moving direction and moving distance. Since the condenser lens 4 and the correcting condenser lens 7 have the same characteristics, the irradiation position of the condenser lens 4 is the optical fiber 5
Coincides with the center position of the light receiving port 10.

In addition to the above operation, the same operation as the focus adjustment described in the first embodiment is performed by the first and second actuators 9 and 11 and the arithmetic unit 12. By the above operation, energy can be concentrated and highly efficient coupling is possible.

As described above, according to the second embodiment, the focal point of the condenser lens 4 can be adjusted to the light receiving port 10, and the irradiation position of the laser beam can be adjusted to the center of the light receiving port 10 so that The coupling with the fiber can be better.

[0047]

According to the present invention, the divergence state of the laser beam is detected by the detector, and the first state is detected based on the data.
Since the actuator is operated to obtain the distance information to be corrected, and then the second actuator is operated by the distance information to focus on the light receiving port of the optical fiber, the converging property of the laser beam is always maintained. It can be managed and adjusted automatically. Therefore, even if the focus of the condenser lens on the optical fiber deviates due to factors such as the thermal lens effect, this can be immediately corrected, and the coupling with the optical fiber can always be in the best state.

Further, the focus can be controlled without suppressing the laser output or strengthening the cooling of the laser medium, and a sufficient output can be obtained in a small size.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of the present invention.

FIG. 2 is a side view showing a second embodiment of the present invention.

FIG. 3 is a perspective view of an essential part showing a second embodiment of the present invention.

FIG. 4 is a perspective view of an essential part showing a second embodiment of the present invention.

[Explanation of symbols]

 1 Laser Medium 2 Excitation Lamp 3 Laser Oscillator 4 Condenser Lens 5 Optical Fiber 6 Beam Splitter 7 Corrective Condenser Lens 8 Detecting Section 9 First Actuator 10 Light Receiving Port 11 Second Actuator 12 Arithmetic Section 30 Third Actuator 31 Fourth Actuator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuyoshi Sato 3 Miyachi Technos Co., Ltd. 3 at 95 Futatsuka, Noda City, Chiba Prefecture

Claims (1)

Claim: What is claimed is: 1. A laser beam output from a laser oscillator having a laser medium and a pump lamp for introducing pump light into the laser medium is incident on an optical fiber through a condenser lens. In the laser device, a branching device for splitting a part of the laser beam output from the laser oscillator, a correcting condensing lens provided in the next stage of the branching device and having the same characteristics as the condensing lens, and the correcting lens Detecting section for receiving the laser beam that has passed through the light collecting condenser lens, and a first moving the detecting section or the correcting light collecting lens in the optical axis direction.
An actuator, a second actuator that moves a light receiving port or a condenser lens of the optical fiber in an optical axis direction, and a computing unit that receives a signal from the detection unit and controls the first and second actuators, The arithmetic unit detects this when the focus of the laser beam irradiated on the detection unit by the correction condenser lens is deviated,
The detecting unit or the correcting condenser lens is moved in the optical axis direction to form a focal point, and the same amount as the moving amount of the detecting unit or the correcting condenser lens at this time, the receiving lens or the optical fiber receiving port An optical fiber condensing correction device in a solid-state laser device, characterized in that it is configured to move.