JP2016042550A - Laser irradiation apparatus and laser irradiation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser irradiation apparatus and a laser irradiation method capable of properly irradiating a moving object.SOLUTION: The laser irradiation apparatus is an apparatus that irradiates a moving object with a laser beam. The laser irradiation apparatus includes: a first deformable mirror that corrects the focal position based on the change of distance between the moving object and the laser irradiation apparatus; a second deformable mirror that performs correction based on the fluctuation of the atmosphere; and a laser irradiation unit that irradiates a moving object with the laser beam via the first deformable mirror and the second deformable mirror.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a laser irradiation apparatus and a laser irradiation method.

There is a laser irradiation apparatus that irradiates an object at a long distance with laser light.
Here, the laser light propagating in the atmosphere causes wavefront distortion (disturbance of the light wavefront) due to fluctuations in the atmosphere. When wavefront distortion occurs, the irradiation beam diameter expands and the energy density at the irradiation surface decreases.
Therefore, a technique has been proposed in which wavefront distortion due to atmospheric fluctuations is detected, the shape of the deformable mirror is changed based on the detected wavefront distortions, and correction is performed based on atmospheric fluctuations.
However, when the object to be irradiated is a moving body, the distance between the moving body and the laser irradiation apparatus changes.
When the distance between the moving body and the laser irradiation apparatus changes, the focal position needs to be corrected according to the distance.
In this case, if the focus position is also corrected using a deformable mirror that performs correction based on atmospheric fluctuations, it may not be possible to correct the focal position properly, or the correction based on atmospheric fluctuations may be adversely affected. There is a risk.
Therefore, development of a laser irradiation apparatus and a laser irradiation method that can perform appropriate irradiation on a moving body has been desired.

JP 2011-185567 A

  The problem to be solved by the present invention is to provide a laser irradiation apparatus and a laser irradiation method capable of performing appropriate irradiation on a moving body.

The laser irradiation apparatus according to the embodiment is a laser irradiation apparatus that irradiates a moving body with laser light.
The laser irradiation apparatus includes a first deformable mirror that corrects a focal position based on a change in a distance between the moving body and the laser irradiation apparatus, and a second that performs correction based on atmospheric fluctuations. A laser irradiation unit configured to irradiate the movable body with the laser light via a deformable mirror, the first deformable mirror, and the second deformable mirror;

It is a block diagram for illustrating laser irradiation apparatus 1 concerning this embodiment. 4 is a flowchart for illustrating the operation of the laser irradiation apparatus 1.

Hereinafter, embodiments will be illustrated with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.
FIG. 1 is a block diagram for illustrating a laser irradiation apparatus 1 according to the present embodiment.
The laser irradiation apparatus 1 irradiates a laser beam L1 toward a moving body 100 that moves in the atmosphere.
The moving body 100 may be one that moves in the air, or one that moves on land or water.
As shown in FIG. 1, the laser irradiation apparatus 1 includes a laser irradiation unit 2, a focus control unit 3, a wavefront control unit 4, and a tracking control unit 5.

The laser irradiation unit 2 irradiates the moving body 100 with the laser light L <b> 1 through the first deformable mirror 32 and the second deformable mirror 43.
The laser irradiation unit 2 is provided with a laser light source 21 and optical elements 22a to 22f.
The laser light source 21 is not particularly limited as long as it can be irradiated with a high-power laser.
For example, the laser light source 21 can have an output of several tens of kW or more.
In this case, the laser light source 21 can be, for example, a solid laser, a chemical laser, a free electron laser, or the like.

The optical elements 22 a to 22 f guide the laser light L <b> 1 emitted from the laser light source 21 to the tracking control unit 5.
The optical elements 22a and 22b can be, for example, beam splitters. The optical elements 22c to 22f may be laser mirrors, for example.
In addition, there is no limitation in particular in the kind of optical element, Various optical elements can be provided as needed. In addition, the number and arrangement of optical elements can be changed as appropriate.

Here, when the diameter of the irradiation beam irradiated to the moving body 100 is increased, the energy density in the irradiated portion is decreased, and the purpose of irradiation may not be achieved.
In this case, if the output of the laser irradiation unit 2 is increased, a desired energy density can be obtained even if the diameter of the irradiation beam is increased.
However, if the output of the laser irradiation unit 2 is increased, the laser irradiation apparatus 1 is increased in size and cost.

Moreover, it is necessary to consider that the mobile body 100 is at a long distance and moves in the atmosphere.
That is, in order to make the diameter of the irradiation beam irradiated to the moving body 100 appropriate, it is necessary to consider the change in the focal position accompanying the movement of the moving body 100 and the fluctuation of the atmosphere.
In this case, if the correction of the focal position based on the change in distance and the correction based on the fluctuation of the atmosphere are performed, the diameter of the irradiation beam irradiated on the moving body 100 becomes appropriate. be able to.

The correction of the focal position based on the change in distance and the correction based on the fluctuation of the atmosphere can be performed using, for example, a deformable mirror.
However, the performance required for the deformable mirror differs between the correction of the focal position based on the change in distance and the correction based on the fluctuation of the atmosphere.

When the focus position is corrected based on the change in distance, it is necessary to cope with the movement of the moving body 100 at a long distance, and thus it is preferable that the deformation amount of the reflecting surface can be increased. . On the other hand, since it is sufficient that the focal position can be corrected, it is not necessary to perform high-order aberration correction at high speed.
When correcting the focal position based on the change in distance, for example, the number of elements in the deformable mirror is 100 or less, the deformation amount of the reflecting surface is 100 μm or less, and the response speed is 10 Hz or less. It is sufficient if aberration correction by second derivative can be performed.

When correction based on atmospheric fluctuations is performed, it is necessary to cope with atmospheric fluctuations, and thus higher-order aberration correction must be performed at high speed. On the other hand, the deformation amount of the reflecting surface may be small.
When performing correction based on atmospheric fluctuations, for example, the number of elements in the deformable mirror should be 400 or less, the amount of change in the reflecting surface should be 10 μm or less, the response speed should be 1000 Hz or less, and the fourth order differential It is only necessary to be able to correct aberrations by means of.

As described above, the performance required for the deformable mirror differs between the correction of the focal position based on the change in distance and the correction based on the fluctuation of the atmosphere.
Therefore, if the focus position correction based on the change in distance and the correction based on the fluctuation of the atmosphere are performed by one deformable mirror, the diameter of the irradiation beam irradiated on the moving body 100 is appropriate. There is a risk that it will not be.
Therefore, the laser irradiation apparatus 1 is provided with the focus control unit 3 and the wavefront control unit 4 so that the diameter of the irradiation beam irradiated to the moving body 100 becomes appropriate.

The focus control unit 3 is provided with a distance measurement unit 31, a first deformable mirror 32, and a first control unit 33.
Since the moving body 100 moves, the distance between the laser irradiation apparatus 1 and the moving body 100 changes.
For this reason, if the focal position is made constant, the diameter of the irradiation beam irradiated to the moving body 100 may not be appropriate.
The focus control unit 3 corrects the focus position based on the change in distance.

The distance measuring unit 31 measures the distance between the laser irradiation apparatus 1 and the moving body 100.
The distance measuring unit 31 is not particularly limited as long as it can measure the distance, but it is preferable that the distance measuring unit 31 can accurately measure the distance to the moving body 100 at a long distance.
The distance measuring unit 31 can be, for example, a laser distance meter (distance measuring device).
When the distance measuring unit 31 is a laser distance meter, the distance measuring unit 31 irradiates the moving body 100 with the laser light L2. Then, the distance measuring unit 31 calculates the distance to the moving body 100 based on the difference between the wavelength of the reflected light from the moving body 100 and the internal reference wavelength.

As described above, it is preferable that the first deformable mirror 32 can increase the amount of deformation of the reflecting surface. On the other hand, the first deformable mirror 32 need not be capable of performing high-order aberration correction at high speed.
Therefore, the first deformable mirror 32 can be, for example, a bimorph deformable mirror.
When the first deformable mirror 32 is a bimorph deformable mirror, the first deformable mirror 32 may have a plurality of elements obtained by bonding two thin piezoelectric elements.
In addition, a dielectric multilayer film formed using an electron beam vapor deposition method may be provided on the reflective surfaces of the plurality of elements.

The first control unit 33 calculates a control amount in the first deformable mirror 32 based on the distance measured by the distance measurement unit 31.
For example, the first control unit 33 calculates a wavefront shape (for example, a radius of curvature) of condensing based on the distance measured by the distance measuring unit 31. The wavefront shape of the condensed light corresponds to the order Z20 of the Zernike polynomial.

Further, the first control unit 33 adds the order Z20 separated by the second control unit 44 described later to the calculated wavefront shape of the condensed light.
The first control unit 33 calculates a control amount (for example, a drive voltage for each of the plurality of piezoelectric elements) in the first deformable mirror 32 based on the calculated value in consideration of the order Z20.

The first control unit 33 controls the first deformable mirror 32 based on the calculated control amount. When the first deformable mirror 32 is a bimorph deformable mirror, the first control unit 33 controls driving voltages of a plurality of piezoelectric elements provided in the first deformable mirror 32, respectively.
When the first control unit 33 controls the first deformable mirror 32, a shape based on the calculated value with the order Z20 added is formed on the reflection surface of the first control unit 33.

The wavefront control unit 4 includes a reference laser irradiation unit 41, a wavefront sensor 42, a second deformable mirror 43, a second control unit 44, and an optical element 45.
Since the moving body 100 moves in the atmosphere, the diameter of the irradiation beam irradiated to the moving body 100 changes due to fluctuations in the atmosphere.
The wavefront control unit 4 performs correction based on atmospheric fluctuations.

The reference laser irradiation unit 41 irradiates the moving body 100 with the reference laser light L3.
In this case, the optical axis of the reference laser beam L3 irradiated from the reference laser irradiation unit 41 does not necessarily have to be coaxial with the optical axis of the laser beam L1 irradiated from the laser light source 21. However, the optical axis of the reflected light of the reference laser light L3 incident on the wavefront sensor 42 described later is coaxial with the optical axis of the laser light L1.

The wavefront sensor 42 measures wavefront distortion (wavefront shape, intensity distribution, etc.) in the reference laser light L3 (reflected light) reflected by the moving body 100.
The wavefront sensor 42 can be, for example, a CCD sensor (Charge Coupled Device Image Sensor) having a predetermined resolution and a predetermined response speed.
The wavefront sensor 42 can be, for example, a Shack-Hartmann type wavefront sensor having a response speed of 1 kHz or more.

As described above, it is preferable that the second deformable mirror 43 can perform high-order aberration correction at high speed. On the other hand, the second deformable mirror 43 need not be capable of increasing the amount of deformation of the reflecting surface.
The second deformable mirror 43 can be, for example, a face sheet type deformable mirror. When the second deformable mirror 43 is a face sheet type deformable mirror, it can be provided with a deformable film and a plurality of piezoelectric elements provided on the back side of the film.
In addition, the surface of the deformable film (reflecting surface) may be provided with a dielectric multilayer film formed by using an electron beam evaporation method.

The second control unit 44 calculates a control amount in the second deformable mirror 43 based on the wavefront distortion measured by the wavefront sensor 42.
For example, the second control unit 44 approximates the wavefront distortion to a Zernike polynomial, and separates the wavefront distortion into the order Z20 and the order Z21 or later.
The second control unit 44 calculates a control amount (for example, a driving voltage for each of the plurality of piezoelectric elements) in the second deformable mirror 43 based on the wavefront distortion after the order Z21.

In the case where the second deformable mirror 43 is a face sheet type deformable mirror, the second control unit 44 controls drive voltages of a plurality of piezoelectric elements provided in the second deformable mirror 43, respectively. To do.
When the second control unit 44 controls the second deformable mirror 43, a shape obtained by inverting the measured wavefront is formed on the reflection surface of the second deformable mirror 43.

The optical element 45 guides the reference laser beam L3 emitted from the reference laser irradiation unit 41 to the tracking control unit 5.
The optical element 45 can be, for example, a laser mirror.
The optical element 45 is not necessarily required, and may be provided as necessary.
Further, the type, number, arrangement, and the like of the optical element 45 can be appropriately changed as necessary.

The tracking control unit 5 controls the irradiation directions of the laser beams L1 and L3 so that the moving body 100 is irradiated with the laser beams L1 and L3.
The tracking control unit 5 includes a first base 51, a second base 53, a fine movement mirror 53, optical elements 54a to 54d, a detection device (not shown), and a control device (not shown).

The first base 51 is rotated around the vertical axis by a driving device (not shown).
The second base 53 is provided on the first base 51 and is rotated around a horizontal axis by a driving device (not shown).
The fine movement mirror 53 is provided on the second base 53 and swings about the vertical axis and the horizontal axis by a driving device (not shown). The fine movement mirror 53 is provided to finely correct the irradiation direction of the laser beams L1 and L3.

The optical elements 54 a to 54 c are provided on the first base 51.
The optical element 54 d is provided on the second base 53.
The optical elements 54a to 54d can be laser mirrors, for example.
Note that the type, number, arrangement, and the like of the optical elements can be changed as needed.

A detection device (not shown) detects the position of the moving body 100. The detection device (not shown) can be, for example, an infrared sensor.
A control device (not shown) calculates the position of the moving body 100 based on an output from a detection device (not shown). A control device (not shown) controls a drive device (not shown) so that the laser beams L1 and L3 are irradiated to the moving body 100 based on the calculation result.

Next, the laser irradiation method according to the present embodiment will be exemplified together with the operation of the laser irradiation apparatus 1.
FIG. 2 is a flowchart for illustrating the operation of the laser irradiation apparatus 1.
As shown in FIG. 2, the moving body 100 is detected by a detection device (not shown).
In this case, the position (direction) and distance of the moving body 100 are detected by a detection device (not shown).

The focus control unit 3 corrects the focus position based on a change in the distance between the moving body 100 and the laser irradiation apparatus 1.
First, the distance measuring unit 31 measures the distance between the laser irradiation apparatus 1 and the moving body 100. For example, the distance measuring unit 31 irradiates the moving body 100 with the laser light L2. Then, the distance measuring unit 31 calculates the distance to the moving body 100 based on the difference between the wavelength of the reflected light from the moving body 100 and the internal reference wavelength.

Next, the first control unit 33 calculates a wavefront shape (for example, a radius of curvature) of light collection based on the distance measured by the distance measurement unit 31. The wavefront shape of the condensed light corresponds to the order Z20 of the Zernike polynomial.
Next, the first control unit 33 adds the order Z20 separated by the second control unit 44 described later to the calculated wavefront shape of the condensed light.

Next, the first control unit 33 calculates a control amount (for example, a driving voltage for each of the plurality of piezoelectric elements) in the first deformable mirror 32 based on the calculated value in consideration of the order Z20.
Subsequently, the first control unit 33 controls the first deformable mirror 32 based on the calculated control amount.

When the first deformable mirror 32 is a bimorph deformable mirror, the first control unit 33 controls driving voltages of a plurality of piezoelectric elements provided in the first deformable mirror 32, respectively.
When the first control unit 33 controls the first deformable mirror 32, a shape based on the calculated value with the order Z20 added is formed on the reflection surface of the first control unit 33.
As described above, the focus control unit 3 corrects the focus position.

On the other hand, the wavefront control unit 4 performs correction based on atmospheric fluctuations.
First, the reference laser irradiation unit 41 irradiates the moving body 100 with the reference laser light L3.
Next, the wavefront sensor 42 receives (receives) the reference laser light L <b> 3 (reflected light) reflected by the moving body 100.
Next, the wavefront sensor 42 measures the wavefront distortion (wavefront shape, intensity distribution, etc.) of the received reflected light.

Next, the second control unit 44 approximates the measured wavefront distortion to a Zernike polynomial, and separates it into the order Z20 and the order Z21.
The separated order Z20 is provided to the first control unit 33.

Next, the second control unit 44 calculates a control amount (for example, a driving voltage for each of the plurality of piezoelectric elements) in the second deformable mirror 43 based on the wavefront distortion after the order Z21.
Subsequently, the second control unit 44 controls the second deformable mirror 43 based on the calculated control amount.

In the case where the second deformable mirror 43 is a face sheet type deformable mirror, the second control unit 44 controls drive voltages of a plurality of piezoelectric elements provided in the second deformable mirror 43, respectively. To do.
When the second control unit 44 controls the second deformable mirror 43, a shape obtained by inverting the measured wavefront is formed on the reflection surface of the second deformable mirror 43.
As described above, the wavefront control unit 4 performs correction based on atmospheric fluctuations.

Next, the laser light source 21 emits the laser light L1.
The irradiated laser beam L1 passes through the first deformable mirror 32 in which the focus position is corrected, the second deformable mirror 43 in which correction based on atmospheric fluctuations is performed, and the tracking control unit 5. The moving body 100 is irradiated.

Laser light having an appropriate irradiation beam diameter through the first deformable mirror 32 in which the focus position is corrected and the second deformable mirror 43 in which correction based on atmospheric fluctuations is performed. L1 is irradiated to the moving body 100.
Further, the laser beam L <b> 1 can be irradiated to a predetermined position of the moving body 100 via the tracking control unit 5.

Next, the effect of irradiation with the laser beam L1 is confirmed.
For example, when the moving body 100 cannot be captured by a detection device (not shown), it can be determined that there is an effect of irradiation with the laser light L1.
When it is determined that there is an effect of irradiation with the laser beam L1, the operation of the laser irradiation apparatus 1 can be stopped.
Further, when the moving body 100 can be captured by a detection device (not shown), it can be determined that there is no effect of irradiation with the laser light L1.
When it is determined that there is no effect of irradiating the laser beam L1, the correction of the focal position and the correction based on the fluctuation of the atmosphere are performed again, and the moving body 100 can be irradiated with the laser beam L1 again.

As illustrated above, the laser irradiation method according to the present embodiment can include the following steps.
A step of correcting the focal position based on a change in the distance between the moving body 100 and the laser irradiation apparatus 1 using the first deformable mirror 32.
A step of performing correction based on atmospheric fluctuations using the second deformable mirror 43;
A step of irradiating the moving body 100 with the laser light L1 via the first deformable mirror 32 that has corrected the focal position and the second deformable mirror 43 that has performed correction based on atmospheric fluctuations. .

In this case, the following can be performed in the process of performing correction based on atmospheric fluctuations.
The moving body 100 is irradiated with the reference laser beam L3.
The wavefront distortion in the reflected light of the reference laser beam L3 is measured.
The measured wavefront distortion is approximated to a Zernike polynomial, and is separated into an order Z20 and an order after Z21.
Based on the wavefront distortion after the order Z21, the control amount in the second deformable mirror 43 is calculated.
The second deformable mirror 43 is controlled based on the calculated control amount.

In the step of correcting the focal position, the following can be performed.
The distance between the moving body 100 and the laser irradiation apparatus 1 is measured.
Based on the measured distance, the wavefront shape of the condensed light is calculated.
The separated order Z20 is added to the calculated wavefront shape of the condensed light.
Based on the result of taking the separated order Z20 into account, the control amount in the first deformable mirror 32 is calculated.
The first deformable mirror 32 is controlled based on the calculated control amount.
In addition, since the content of each process can be the same as that of what was mentioned above, detailed description is abbreviate | omitted.

  As mentioned above, although several embodiment of this invention was illustrated, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

  DESCRIPTION OF SYMBOLS 1 Laser irradiation apparatus, 2 Laser irradiation part, 3 Focus control part, 4 Wavefront control part, 5 Tracking control part, 21 Laser light source, 31 Distance measurement part, 32 1st deformable mirror, 33 1st control part, 41 Reference laser irradiation unit, 42 wavefront sensor, 43 second deformable mirror, 44 second control unit, 100 moving body, L1 laser beam, L2 laser beam, L3 reference laser beam

Claims (7)

A laser irradiation apparatus for irradiating a moving body with laser light,
A first deformable mirror that corrects a focal position based on a change in the distance between the moving body and the laser irradiation device;
A second deformable mirror that performs correction based on atmospheric fluctuations;
A laser irradiation unit configured to irradiate the movable body with the laser light via the first deformable mirror and the second deformable mirror;
A laser irradiation apparatus comprising: The first deformable mirror is a bimorph deformable mirror;
The laser irradiation apparatus according to claim 1, wherein the second deformable mirror is a face sheet type deformable mirror.   3. The laser irradiation apparatus according to claim 1, wherein a dielectric multilayer film is provided on a reflection surface of the first deformable mirror and a reflection surface of the second deformable mirror. A reference laser irradiation unit for irradiating the movable body with a reference laser beam;
A wavefront sensor for measuring wavefront distortion in reflected light of the reference laser beam;
A control unit for controlling the second deformable mirror based on the wavefront distortion;
Further comprising
The laser irradiation apparatus according to claim 1, wherein the wavefront sensor is a Shack-Hartmann wavefront sensor having a response speed of 1 kHz or more. A laser irradiation method for irradiating a moving body with laser light,
Using the first deformable mirror, correcting the focal position based on a change in the distance between the moving body and the laser irradiation device;
Using the second deformable mirror to perform correction based on atmospheric fluctuations;
Irradiating the laser beam to the moving body via the first deformable mirror that has corrected the focal position and the second deformable mirror that has been corrected based on fluctuations in the atmosphere. And a process of
A laser irradiation method comprising: In the step of performing correction based on the atmospheric fluctuation,
Irradiating the moving body with a reference laser beam,
Measure wavefront distortion in the reflected light of the reference laser light,
Approximating the measured wavefront distortion to a Zernike polynomial and separating it into an order Z20 and an order after Z21;
Based on the wavefront distortion after the order Z21, the control amount in the second deformable mirror is calculated,
The laser irradiation method according to claim 5, wherein the second deformable mirror is controlled based on the calculated control amount. In the step of correcting the focal position,
Measure the distance between the moving body and the laser irradiation device,
Based on the measured distance, calculate the wavefront shape of the light collection,
In consideration of the separated order Z20 to the calculated wavefront shape of the condensed light,
Based on the result of taking into account the separated order Z20, a control amount in the first deformable mirror is calculated,
The laser irradiation method according to claim 6, wherein the first deformable mirror is controlled based on the calculated control amount.

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