JP2011185567A - High output laser irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein in a laser irradiation device irradiating a target by outgoing of high output laser beams to a space, since the laser beams are transmitted in the atmosphere, an atmosphere compensation device correcting effects by fluctuation of the atmosphere is required. <P>SOLUTION: An irradiation target is irradiated with laser beams. Reflected light reflected on the irradiation target surface is received by a reflected light receiver, and a light wave front receiving distortion by the atmosphere is detected by an atmosphere compensation signal processing part. In the atmosphere compensation signal processing part, a control signal is output to each optical phase shifter to output a wave front shape obtained by inverting the detected wave front. Since each optical phase shifter receiving the signal changes a laser beam phase in each light path, the high output laser beam wave front shape after composition is changed and the irradiation target is irradiated. By repeating this control, the effects by the atmosphere are corrected. Expansion of a condensing spot of the laser beams can be suppressed on the irradiation target all the time, and sufficient irradiation effects can be provided even for a target in a long distance. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser irradiation apparatus that emits high-power laser light to a space and irradiates a target.

  A high-power laser system that breaks down a target by emitting high-power laser light to a space and irradiating the target is generally known (for example, see Patent Document 1).

  When emitting high-power laser light into space, the laser light propagating in the atmosphere causes disturbance of the light wave front due to fluctuations in the atmosphere, and when condensed in that state, the condensing spot expands and the energy density in the condensing spot Will decline. Since the influence increases as the propagation distance becomes longer, a sufficient irradiation effect cannot be given to a long-distance irradiation object.

  On the other hand, in order to solve the atmospheric fluctuation problem of light, the light wavefront of light that has propagated through the atmosphere and reached from a distance is detected by a lightwave sensor, and the deformable mirror that has been changed to a shape obtained by inverting the detected wavefront shape, An adaptive optics device that corrects a distorted light wavefront is known (see, for example, Patent Document 2).

JP 11-340555 A JP-A-6-250108

  However, when the conventional adaptive optical device shown in Patent Document 2 is applied to a laser irradiation device, the heat load on the mirror surface of the deformable mirror due to the high-power laser light is large, and the deformable mirror is thermally deformed. There is a problem that it becomes impossible to correct an optical wavefront whose mirror surface is distorted.

  Although this heat load can be reduced by spreading the laser beam, in this case, a large-diameter mirror surface is used, and the weight of the mirror itself increases. For this reason, the mechanical load of the actuator that changes the shape of the mirror of the laser light wavefront increases, and another problem arises that high-speed atmospheric compensation to cope with fluctuations in the light wavefront becomes difficult.

  The present invention has been made to solve such a problem, and a high-power laser irradiation apparatus capable of suppressing the spread of a focused spot by correcting distortion of a laser light wavefront caused by atmospheric fluctuations. The purpose is to get.

  A high-power laser irradiation apparatus according to the present invention includes a laser light source that generates a laser, an optical distributor that distributes the laser light generated by the laser light source, and a phase of each laser light distributed by the optical distributor. A plurality of optical phase shifters, a plurality of optical amplifiers that respectively amplify the laser light whose phases are changed by the respective optical phase shifters, and the respective laser lights amplified by the respective optical amplifiers are combined and output. An output optical system; a reflected light receiver that detects the reflected light that has been emitted from the output optical system, reflected by the irradiation target, propagated back through the atmosphere, and returned; and the detection signal of the reflected light receiver And an atmospheric compensation signal processing unit that detects the distortion of the optical wavefront due to fluctuation and controls the variable phase of the optical phase shifter so as to correct the distortion of the optical wavefront.

  According to the present invention, it is possible to suppress the spread of the focused spot on the irradiation target by correcting the distortion of the laser light wavefront caused by atmospheric fluctuations. In addition, it is possible to suppress a decrease in laser irradiation energy to the irradiation target due to atmospheric fluctuations with respect to a long-distance irradiation target.

It is a figure which shows the structure of the high output laser irradiation apparatus by Embodiment 1 which concerns on this invention. It is a figure which shows an example of the reflected light receiver by Embodiment 2 which concerns on this invention. It is a flowchart which shows an example of the operation processing of the high output laser irradiation apparatus by Embodiment 2 which concerns on this invention.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of a high-power laser irradiation apparatus according to Embodiment 1 of the present invention. In the figure, the high-power laser irradiation apparatus mainly includes a high-power laser 7, a laser radiator 11, and an atmospheric compensation signal processing unit 12.

  The high-power laser 7 includes a reference laser light source 1, an optical distributor 2, a plurality (N, N is an integer of 4 or more) optical phase shifters 3, a plurality (N) optical amplifiers 4, and a plurality It is composed of (N + 1) partial reflecting mirrors 5 and an optical phase synchronization processing circuit 6. The light distributor 2 distributes the laser light output from the reference laser light source 1 to the required (N + 1) optical paths. Of the optical paths distributed by the optical distributor 2, laser light of N optical paths is input to each optical phase shifter 3 and one partial reflector 5. The optical amplifier 4 amplifies the laser light of each optical path distributed by the optical distributor 2 and phase-shifted by the optical phase shifter 3 to a predetermined output. Most of each laser beam amplified by each optical amplifier 4 passes through each of the N partial reflecting mirrors 5 and is output to the laser radiator 11. A part of each laser beam amplified by each optical amplifier 4 is reflected by the partial reflection mirror 5 and input to the optical phase synchronization processing circuit 6.

  The optical phase synchronization processing circuit 6 detects the phase error of the amplified laser beam in each optical path with respect to the phase of the reference laser beam. At this time, the optical phase synchronization processing circuit 6 detects a phase error of the laser beam by subtracting this offset value from the phase error of the laser beam using a correction phase described later as an offset value. The optical phase synchronization processing circuit 6 outputs a phase control signal to the optical phase shifter 3 in each optical path so that the phase error of the laser light in each optical path becomes zero and the laser light in each optical path is synchronized. By performing the feedback control as described above, the high-power laser beam in which the phase of the light wavefront is adjusted with high accuracy from the high-power laser 7 is output to the laser radiator 11. The optical phase synchronization processing circuit 6 synchronizes the phase so that the wavefront of the laser light from each optical amplifier 4 incident on the partial reflection mirror 5 is substantially a true plane when the correction phase described later is 0. Let

  The laser radiator 11 includes an output optical system 8, a reflecting mirror 9, and a reflected light receiver 10. The high-power laser beams output from the respective partial reflecting mirrors 5 of the high-power laser 7 are synthesized by the output optical system 8 and are emitted to the space as output light 14. The output optical system 8 includes a plurality of condensing lenses and a plurality of reflecting mirrors, and has a two-dimensional plane wavefront in which the high-power lasers 7 transmitted through the partial reflecting mirrors 5 of the high-power lasers 7 have the same phase. An optical path is provided so as to synthesize and output a light beam having no phase shift. The high-energy output light 14 emitted from the output optical system 8 propagates in the atmosphere and is collected on the irradiation target (target) 13. At this time, a part of the output light 14 is reflected as reflected light 15 on the surface of the irradiation target 13. The reflected light 15 propagates again in the atmosphere and returns to the reflecting mirror 9 of the laser radiator 11. The reflected light 15 incident on the laser radiator 11 is received by the reflected light receiver 10 by the reflecting mirror 9. The reflected light receiver 10 detects the wavefront phase change from the reference wavefront phase at each part of the wavefront of the reflected light due to distortion of the light wavefront of the reflected light 15 by converting the received light into an electric signal, and this wavefront phase An electric signal corresponding to the change is output. A detailed configuration example of the reflected light receiver 10 will be described later in a second embodiment.

  The electrical signal output by the reflected light receiver 10 is input to the atmospheric compensation signal processing unit 12. The atmospheric compensation signal processing unit 12 generates a wavefront phase correction amount that cancels the wavefront phase change in each wavefront part based on the electrical signal corresponding to the wavefront phase change in each wavefront part from the reflected light receiver 10. Calculated as the amount of phase correction for each. The phase correction amount for each optical phase shifter 3 calculated by the atmospheric compensation signal processing unit 12 is output to the optical phase shifter 3 as a phase control signal. The atmospheric compensation signal processing unit 12 outputs the phase correction amount for each optical phase shifter 3 to the optical phase synchronization processing circuit 6 as a correction phase.

  The optical phase shifter 3 controls the phase of the laser light in each optical path according to a signal obtained by adding the phase control signal from the optical phase synchronization processing circuit 6 and the phase control signal from the atmospheric compensation signal processing unit 12. By controlling the phase of the laser beam by the optical phase shifter 3, the wavefront shape of the output light 14 is formed so as to form a light wavefront shape obtained by inverting the wavefront of the light wavefront shape of the laser light irradiated on the irradiation target 13. Changes. Thereby, the distortion effect of the optical wavefront due to the fluctuation of the atmosphere at the propagation destination is offset, and the focused spot on the irradiation target 13 is corrected to have an optimum diameter.

  The laser light from the reference laser light source 1 is amplified to high-power laser light at the subsequent stage of the optical amplifier 4, and the partial reflecting mirror 5 and the output optical system 8 provided at the subsequent stage have a movable portion and a deformable portion. Since there is no need to provide a structural member, it can be made up of structural members that have a strong structural strength against the thermal load, so the effects of thermal load due to high-power laser light (occurrence of distortion of the optical wavefront due to thermal deformation of the optical system) are suppressed. Is done. Further, since the reflected light 15 attenuated by the reciprocation of the atmosphere enters the reflecting mirror 9 and the reflected light receiver 10, the influence of the thermal load is suppressed.

  The high-power laser irradiation apparatus according to the first embodiment is configured as described above, and can compensate for the atmosphere without using the deformable mirror disclosed in Patent Document 2. For this reason, there is an effect that an optimum irradiation effect can be given to a target at a long distance without requiring a complicated optical system and without being greatly influenced by the thermal load on the optical system.

  As described above, in the laser irradiation apparatus according to the first embodiment, the wavefront shape of the high-power laser light propagating through the atmosphere is controlled by electrically controlling the phase of the laser light. It can be controlled so that the distortion is offset. For this reason, wavefront distortion due to atmospheric fluctuations can be compensated at high control speed against atmospheric fluctuations that increase due to long-distance propagation. In addition, since it is possible to suppress a decrease in the laser irradiation energy density to the irradiation target due to the expansion of the laser irradiation spot due to atmospheric fluctuations, the effective range of the laser irradiation device can be extended to a distance that cannot be handled by conventional atmospheric compensation devices. There is an effect that it can be stretched.

Embodiment 2
In the second embodiment, a detailed configuration of the reflected light receiver 10 and an operation example of the high output laser irradiation apparatus using the reflected light receiver 10 in the high-power laser irradiation apparatus described in the first embodiment will be described. . FIG. 2 is a diagram showing an example of a reflected light receiver according to Embodiment 2 of the present invention.

As shown in FIG. 2, the reflected light receiver 10 includes a microlens array 16 and a light receiving element array 17. The microlens array 16 divides and collects the input reflected light 15. The light receiving element array 17 is configured by two-dimensionally arranging a plurality of light receiving elements, and each light receiving element individually receives each condensed beam from the microlens array 16.
Each light receiving element of the light receiving element array 17 is associated with each of the N optical paths in the high-power laser 7 on a one-to-one basis, and the received light of each light receiving element is converted into an electric signal, and the atmospheric compensation signal processing unit 12 is output. In the reflected light receiver 10, the reference position of the beam spot position on the light receiving element array 17 when the reflected light 15 is input to the reflected light receiver 10 as a plane wave is specified in advance. Each light receiving element of the light receiving element array 17 outputs a different electric signal according to the beam spot position on the light receiving element, thereby detecting the change amount of the beam spot position from the reference position.
Note that an optical attenuator may be provided in front of the reflecting mirror 9 and the microlens array 16 so that the light intensity of the reflected light 15 incident on the microlens array 16 is attenuated. Keep the phase of the surface from changing.

The atmospheric compensation signal processing unit 12 is data indicating the correspondence between the amount of change in the phase of the laser light in each optical path in the high-power laser 7 and the amount of change from the reference position of each beam spot position on the light receiving element array 17. Are previously recorded in the internal database.
The atmospheric compensation signal processing unit 12 determines the amount of change of each beam spot position on the light receiving element array 17 recorded in advance in the internal database based on the amount of change of the detected beam spot position from the reference position and the high-power laser 7. By referring to the data indicating the correspondence of the change amount of the phase of the laser beam in each optical path, the change amount of the phase of the laser beam in each optical path in the corresponding high-power laser 7 is obtained. At this time, the amount of change in the phase of the laser beam in each optical path in the high-power laser 7 may be obtained by appropriately performing interpolation or extrapolation calculation on the recording data in the internal database.

  The atmospheric compensation signal processing unit 12 changes the wavefront of the irradiated laser light into a shape obtained by inverting the wavefront disturbed by the atmosphere based on the change amount of each beam spot position on the light receiving element array 17 from the reference position. Thus, the phase change amount of the laser beam in each optical path in the high-power laser 7 to be controlled is derived.

The reflected light receiver 10 is configured as described above and operates as follows. FIG. 3 is a flowchart showing an example of atmospheric compensation processing by the high-power laser irradiation apparatus according to the second embodiment.
Here, the high-power laser irradiation apparatus is installed on a two-axis gimbal that can rotate around the pitch axis and the yaw axis, and the high-power laser irradiation apparatus is controlled by driving and controlling the two-axis gimbal. Rotate around. By operating the biaxial gimbal, the operator can adjust the emission direction of the high-power laser beam of the high-power laser irradiation device so as to be directed in a desired direction. The high-power laser irradiation apparatus can be operated by an operator to start and stop laser irradiation.

First, a target to be irradiated 13 is captured and tracked by another optical device, and information on the position, speed, and direction of the tracked target is output. The operator selects a target to be the irradiation target 13 based on the target position, speed, and direction information output from other optical devices (step S110).
Thereafter, the biaxial gimbal is driven and controlled by the operation of the operator, and adjustment is performed so that the emission direction of the high-power laser light of the high-power laser irradiation apparatus is directed to the direction in which the target to be the irradiation target 13 is selected. After the adjustment, laser irradiation of the high-power laser irradiation apparatus is started by the operator's operation (step S111).

  When the reflected light can be detected by the light receiving element array 17 (step S112), the atmospheric compensation signal processing unit 12 performs the operation on each light receiving element of the light receiving element array 17 based on the electric signal output from the light receiving element array 17. The beam condensing position at is detected (step S113).

If the reflected light is not detected by the light receiving element array 17, the atmospheric compensation signal processing unit 12 detects that the intensity of the electric signal from the light receiving element array 17 is equal to or less than a predetermined threshold, and irradiates the light. It determines with the reflected light 15 by the laser irradiation to the object 13 not being detected. If the atmospheric compensation signal processing unit 12 determines that the reflected light 15 is not detected, it notifies the operator that the reflected light 15 is not detected.
When the operator knows that the reflected light 15 is not detected, the operator returns to the processing from step S110 to step S111 again, instructs the other optical device to perform target capturing and tracking processing again, and performs the target acquisition by the other optical device. The target to be irradiated 13 is reselected from the information on capture and tracking (target position, velocity, and direction information), and the re-selected irradiation target 13 is subjected to laser irradiation with respect to the high-power laser irradiation apparatus. Let it begin.

After detecting the beam condensing position in step S113, the atmospheric compensation signal processing unit 12 determines whether or not the condensing position is within an allowable value (step S114).
If the result of the determination is that it is not within the permissible value, the beam compensation position is optimized by performing optical phase control on the optical phase shifter 3 of the high-power laser 7 by the atmospheric compensation signal processing unit 12 (step) S115).

In parallel, the operator determines the presence / absence of the target and the destruction status of the target from information on target acquisition and tracking (information on the target position, velocity, and direction) by other optical devices and target image information. Is confirmed (step S116).
As soon as the destruction of the target is confirmed, the operator finishes the laser irradiation by the high-power laser irradiation device (step S117).

  As described above, the laser irradiation apparatus according to Embodiment 2 simply detects the wavefront phase distortion of the laser reflected light by the reflected light receiver 10 and electrically controls the phase of the laser light, so that the atmospheric fluctuation is simply performed. Can be compensated. For this reason, for example, the scale of the laser irradiation device can be reduced and the system can be simplified as compared with the case where an atmospheric fluctuation compensation device by mirror surface control of a deformable mirror as shown in Patent Document 2 is attached to the laser irradiation device. It has the effect of becoming. In addition, the simplification of the system has the effect of improving the maintainability of the laser irradiation apparatus.

  1 reference laser light source, 2 distributor, 3 optical phase shifter, 4 optical amplifier, 5 partial reflection mirror, 6 optical phase synchronization processing circuit, 7 high output laser, 8 output optical system, 9 reflection mirror, 10 reflection light receiver , 11 Laser radiator, 12 Atmospheric compensation signal processing unit, 13 irradiation target, 14 output light, 15 reflected light, 16 microlens array, 17 light receiving element array.

Claims (2)

A laser light source for generating a laser;
An optical distributor for distributing laser light generated by the laser light source;
A plurality of optical phase shifters each varying the phase of each laser beam distributed by the optical distributor;
A plurality of optical amplifiers for respectively amplifying the laser light whose phases have been varied by the optical phase shifters;
An output optical system for combining and outputting the laser beams amplified by the optical amplifiers;
A reflected light receiver that detects reflected light emitted from the output optical system, reflected by an irradiation target, and propagated back through the atmosphere;
An atmospheric compensation signal processing unit that detects a distortion of an optical wavefront due to atmospheric fluctuation from a detection signal of the reflected light receiver, and controls a variable phase of the optical phase shifter so as to correct the distortion of the optical wavefront;
High-power laser irradiation device with   The reflected light receiver includes a lens array that divides the reflected light into optical signals corresponding to the laser beams distributed by the optical distributor and collects the light, and an optical signal that is divided and condensed by the lens array. 2. The high-power laser irradiation apparatus according to claim 1, further comprising: a light-receiving element array that receives each of the first and second light-receiving elements and outputs a signal corresponding to a phase shift from a reference light wavefront to the atmospheric compensation signal processing unit.

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