JP7724128B2 - Laser Irradiation System - Google Patents

Description

The present disclosure relates to a laser irradiation system including a laser irradiation device that emits a laser beam.

Patent Document 1 discloses a laser irradiation device that includes a light source, a laser irradiation unit, and an optical system that guides the laser from the light source to the laser irradiation unit. The laser irradiation device is installed on a structure such as a building or a mobile object on the ground.

Patent No. 6654028

In a laser irradiation system equipped with a laser irradiation device, it is desirable to eliminate factors that hinder the straightness or focusing of the laser beam as much as possible in order to increase the accuracy of irradiation at the target. For example, the temperature distribution of the air along the laser beam's ray affects the straightness or focusing of the laser beam.

The purpose of this disclosure is to provide a laser irradiation system that has excellent laser beam straightness and focusing properties.

A laser irradiation system according to one aspect of the present disclosure includes a laser irradiation device having a laser irradiation unit that emits a laser beam, a structure to which the laser irradiation device is attached so that the laser irradiation unit protrudes, and a temperature difference suppression mechanism that reduces the temperature difference between the air temperature near the structure and the air temperature in a region on the structure along the ray of the laser beam.

This disclosure makes it possible to provide a laser irradiation system with excellent laser beam straightness and focusing properties.

FIG. 1 is a side view showing a simplified laser irradiation system including a laser irradiation device installed on a ground structure. FIG. 2 is a side view of the laser irradiation device. FIG. 3 is a perspective view of the laser irradiation device. FIG. 4 is a schematic diagram for explaining factors that affect the straightness and focusing of a laser beam. FIG. 5 is a side view showing the laser irradiation system according to the first embodiment of the present disclosure. FIG. 6 is a side view showing another example of the first embodiment. FIG. 7A is a side view of the laser irradiation system according to the second embodiment, and is a cross-sectional view taken along line VIIA-VIIA of FIG. 7B. FIG. 7B is a top view of the laser irradiation system according to the second embodiment. FIG. 8 is a cross-sectional side view of another example of the laser irradiation system according to the second embodiment. FIG. 9 is a side view showing a laser irradiation system according to the third embodiment. FIG. 10 is a side view showing an example in which the laser irradiation system of the present disclosure is mounted on a moving object.

Embodiments of a laser irradiation system according to the present disclosure will be described in detail below with reference to the drawings. The laser irradiation system according to the present disclosure is a laser system for irradiating a target with a high-power laser to neutralize the target or for transmitting energy to the target. The target of this system is, for example, a flying or hurricane-causing harmful object. The harmful object may be, for example, a flying or hurricane-causing harmful bird or animal. The target may also be an aircraft or projectile, such as an aircraft with a propulsion system and fixed wings, or an aircraft with single or multiple rotors. The target aircraft or projectile may also be an aircraft, including an unmanned aerial vehicle.

[System configuration]
1 is a side view schematically illustrating the configuration of a laser irradiation system S according to an embodiment of the present disclosure. The laser irradiation system S includes a laser irradiation device 1 installed on a structure 4 on the ground. The laser irradiation device 1 is mounted on the structure 4. The structure 4 is a building fixed to the ground G. The structure 4 has a surface 41 facing upward, and the laser irradiation device 1 is attached to the structure 4 so that a portion of the laser irradiation device 1 protrudes from the surface 41.

The laser irradiation device 1 comprises a laser oscillator 11, a laser irradiation unit 12, and a support mechanism 13. The laser oscillator 11 is a light source that generates a laser beam Lb. The laser irradiation unit 12 emits the laser beam Lb to the outside. The laser irradiation unit 12 guides the laser beam Lb oscillated by the laser oscillator 11 in a desired direction while irradiating it. The support mechanism 13 supports the laser irradiation unit 12 so that it can rotate and tilt.

The laser oscillator 11 is installed inside the structure 4. Meanwhile, the laser irradiation unit 12, which emits the laser beam Lb to the outside, is attached to the structure 4 via a support mechanism 13 so as to protrude from the surface 41 of the structure 4. Figure 1 shows the laser irradiation unit 12 pointing in the X-axis direction, which is the left direction on the page, and the laser beam Lb being emitted in the X-axis direction. As mentioned above, the laser irradiation unit 12 can rotate and tilt, so the X-axis direction changes depending on the orientation of the laser irradiation unit 12. The surface 41 of the structure 4 is a surface that extends along the line obtained by projecting the ray of the laser beam Lb onto a horizontal plane. Because the laser irradiation unit 12 can rotate using the support mechanism 13, the surface 41 of the structure 4 also changes depending on the direction of the ray of the laser beam Lb. For the sake of convenience in the following explanation, in the embodiment of the present disclosure, the direction in which the laser beam is emitted is defined as the X-axis direction, the extension direction of the tilt axis 33a of the support mechanism 13 (described later) is defined as the Y-axis direction, and the extension direction of the pivot axis 31a of the support mechanism 13 is defined as the Z-axis direction. Furthermore, the direction of the line obtained by projecting the ray of the laser beam Lb onto a horizontal plane is defined as the ray direction.

The laser beam Lb generated by the laser oscillator 11 can be of any type as long as it is a high-power laser beam, but an iodine laser or fiber laser is suitable. An iodine laser is a type of gas laser generated by a chemical reaction between excited oxygen and iodine. When using an iodine laser, the laser oscillator 11 is equipped, for example, with an excited oxygen generator that generates excited oxygen, an iodine supply device that supplies iodine that reacts with the excited oxygen generated by the generator, and a laser resonator that generates laser oscillation through a chemical reaction between the excited oxygen and iodine. Fiber lasers are a type of electrically driven laser that oscillates using an optical fiber doped with a laser-active element, and have advantages such as highly efficient oscillation and high beam quality. When using a fiber laser, the laser oscillator 11 is equipped, for example, with a semiconductor laser as the excitation light source, a coupler that couples the semiconductor laser light to an optical fiber doped with an active element that serves as a medium, and a laser resonator that extracts laser light from the optical fiber in a state excited by the semiconductor laser.

2 and 3 are a side view and a perspective view showing the details of the laser irradiation unit 12 and the support mechanism 13. In this description, the side refers to the side of the laser irradiation unit 12, and refers to a surface perpendicular to the Y axis. The laser irradiation unit 12 includes a housing 21, an optical module 22, an irradiation window 23, a tracking camera 24, and a shooting window 25.

The housing 21 is a roughly rectangular cylindrical housing that houses the optical module 22 and tracking camera 24. The optical module 22 is a group of optical components that focus the laser beam Lb output from the laser oscillator 11 and direct it in the desired direction. It is composed of optical elements including transmissive and reflective optical elements. Examples of transmissive optical elements include focusing lenses and refractive lenses, and examples of reflective optical elements include concave and convex mirrors. The irradiation window 23 is a transparent member made of a glass plate or the like that can transmit the laser beam Lb output from the optical module 22. The irradiation window 23 is attached to the front end surface 21a of the housing 21, which is the exit for the laser beam Lb. The tracking camera 24 is an imaging device that photographs the target in order to capture and track it. The imaging window 25 is a transparent member made of a glass plate or the like that is attached to the front end surface 21a of the housing 21 to capture images into the tracking camera 24.

The laser irradiation unit 12 emits a laser from the optical module 22 through the irradiation window 23 while its attitude is controlled so that it is directed at the target captured by the tracking camera 24.

The irradiation window 23 and the imaging window 25 are airtightly attached to the front end surface 21a of the housing 21. In other words, the interior of the housing 21 is sealed. Dry gas is sealed inside this sealed housing 21. The dry gas fills the interior of the housing 21 and removes air, thereby reducing the amount of water vapor and impurities remaining inside the housing 21. This prevents water vapor from absorbing the laser beam Lb passing through the housing 21, and ultimately prevents the refractive index of the laser beam Lb from changing due to the temperature rise associated with this absorption.

The support mechanism 13 is a so-called two-axis gimbal mechanism. The laser irradiation unit 12 supported by the support mechanism 13 is capable of rotation as indicated by arrow A1 and tilt as indicated by arrow A2 in Figures 2 and 3. In this embodiment, the rotation indicated by arrow A1 is rotation around the Z axis, which is parallel to the vertical axis, which is the up-and-down direction of the structure 4. In this embodiment, the tilt indicated by arrow A2 is rotation around the Y axis, which is perpendicular to the Z axis. The rotation indicated by arrow A1 is achieved by operation of a Z-axis motor provided in the support mechanism 13, and the tilt indicated by arrow A2 is achieved by operation of a Y-axis motor provided in the support mechanism 13.

Specifically, the support mechanism 13 includes a base 31, a rotating body 32, and a pair of support legs 33 that support the laser irradiation unit 12 from both sides in the Y-axis direction. The base 31 is a disk-shaped platform fixed to the surface 41 of the structure 4. The rotating body 32 is a disk-shaped rotating body placed on the base 31. The rotating body 32 is pivotally supported on the base 31 via a pivot 31a extending in the Z-axis direction. The pair of support legs 33 are members that protrude upward in the Z-axis direction from the rotating body 32 and are arranged to sandwich the laser irradiation unit 12 from both sides. Each support leg 33 pivotally supports the laser irradiation unit 12 via a tilting shaft 33a extending in the Y-axis direction.

As the rotating body 32 rotates, the laser irradiation unit 12 rotates around the Z axis together with the support leg 33. Furthermore, as the tilting operation is performed, the laser irradiation unit 12 rotates around the Y axis relative to the support leg 33. Because the laser irradiation unit 12 is supported by the support mechanism 13 in a state that allows for such rotation and tilting, the front end surface 21a, on which the irradiation window 23 and the imaging window 25 are located, can be directed in all directions.

The laser irradiation unit 12 and laser oscillator 11 are connected via a light guide path 18, shown simply in Figure 3. The light guide path 18 is a path for introducing the laser beam Lb emitted from the laser oscillator 11 into the optical module 22 inside the laser irradiation unit 12. When irradiating the target with the laser beam Lb, the laser beam Lb is introduced from the laser oscillator 11 into the optical module 22 via the light guide path 18. The laser beam Lb introduced into the optical module 22 is then guided to the outside through the irradiation window 23.

[Factors that hinder laser beam propagation]
FIG. 4 is a schematic diagram illustrating factors affecting the straightness and focusing of the laser beam Lb. The straightness and focusing of the laser beam Lb are impaired by atmospheric fluctuations along its propagation path after it leaves the laser irradiation device 1, such as wandering and wavefront distortion within the beam cross section. The atmospheric fluctuations are primarily caused by convection generated by the difference in air temperature between the propagation path of the laser beam Lb and its surrounding area. As shown in FIG. 4 , let T1 be the air temperature in a structure vicinity area AR1 on the surface 41 of the structure 4, which is a region adjacent to the propagation path of the laser beam Lb, and T2 be the air temperature in a laser ray area AR2 on the surface 41 along the ray of the laser beam Lb. If T1 = T2 or T1 ≈ T2, no significant convection occurs.

In contrast, when there is an air temperature distribution such that T1 > T2 or T1 < T2, air convection occurs. For example, when the surface 41 of the structure 4 is heated by solar heat and a state in which T1 > T2 occurs, an updraft occurs from the surface 41 toward the line of sight of the laser beam Lb. In the initial stage of the updraft-like convection, as shown schematically in Figure 4, large turbulences Tu1 and Tu2, which are turbulent masses of different air densities, occur, which then break down to form small turbulences Tu3 and Tu4. Eventually, the large turbulences Tu1 and Tu2 and the small turbulences Tu3 and Tu4 become intertwined. For ease of understanding, Figure 4 distinguishes between the large turbulences Tu1 and Tu2 and the small turbulences Tu3 and Tu4.

Large turbulences Tu1 and Tu2 are turbulence units larger in scale than the cross section of laser beam Lb, and each can be treated as a single temperature distribution unit. Small turbulences Tu3 and Tu4 are turbulence units smaller in scale than the cross section of laser beam Lb, and each can similarly be treated as a single temperature distribution unit. Large turbulence Tu1, which has a certain air density, and large turbulence Tu2, which has a different air density, exhibit different refractive indices. Therefore, when laser beam Lb passes through an area where large turbulences Tu1 and Tu2 are occurring, the laser beam Lb is refracted at the boundary between the large turbulences Tu1 and Tu2. This causes wandering, in which the entire laser beam Lb oscillates. When wandering occurs, the straightness of laser beam Lb deteriorates.

On the other hand, when laser beam Lb passes through an area where small turbulences Tu3 and Tu4 are occurring, collision with these small turbulences Tu3 and Tu4 causes wavefront distortion of the traveling laser wave in the beam cross section. This wavefront distortion creates beam components traveling in various directions, making it difficult to focus laser beam Lb to a single point even with an optical lens in place. Naturally, this also worsens the focusing ability of laser beam Lb. From the above perspective, in order to suppress atmospheric fluctuations that cause wandering and wavefront distortion in the beam cross section, it is preferable to equip laser irradiation system S with a structure that minimizes the air temperature difference |T1-T2|. Below, various embodiments of a temperature difference suppression mechanism that reduces the temperature difference between air temperatures T1 and T2 are illustrated.

[First embodiment]
In the first embodiment, an example is shown in which the temperature difference suppression mechanism is made of a heat input suppression layer that suppresses heat input due to sunlight to the surface 41 of the structure 4. Fig. 5 is a side view showing a laser irradiation system S1 equipped with an example of the heat input suppression layer. The laser irradiation system S1 is equipped with an infrared reflective paint 51 applied to the surface 41 of the structure 4 as the heat input suppression layer. The infrared reflective paint 51 reflects infrared rays, which are a heating component contained in sunlight, and serves to suppress a temperature rise in the surface 41.

Surface 41 is a surface exposed to the atmosphere around laser irradiation unit 12. When it acquires a temperature different from that of the atmosphere, surface 41 exists within a range that generates significant air convection in the region along the ray direction of laser beam Lb. In this embodiment, laser irradiation unit 12 is rotatable around the Z axis, and therefore the range of surface 41 changes with changes in the X-axis direction in which laser beam Lb is emitted. In other words, there are multiple possible ray directions for laser beam Lb. Surface 41 can be set based on one of the possible ray directions for laser beam Lb, or it can be set based on multiple or all ray directions. While Figure 5 shows an example in which surface 41 is a simple flat surface, surfaces consisting of inclined surfaces, curved surfaces, uneven surfaces, etc. also fall within the category of surface 41 as long as they satisfy the above conditions. This definition of surface 41 applies to the embodiments described below.

In this embodiment, the infrared reflective paint 51 is applied to at least the area of the surface 41 located below the ray of the laser beam Lb in the Z-axis direction. When the laser irradiation unit 12 rotates 360 degrees, the infrared reflective paint 51 is applied to the entire surface 41. However, even when the laser irradiation unit 12 can only rotate 360 degrees or less, it is desirable to provide a coating layer of infrared reflective paint 51 on the entire surface 41. This is because even if the area directly below the ray of the laser beam Lb is covered with infrared reflective paint 51, the uncoated portion of the surface 41 may heat up and become very hot, potentially generating an updraft that reaches directly below the ray. The infrared reflective paint 51 can be, for example, a general-purpose paint made by mixing infrared-reflective pigments or ceramic chips with a binder resin. The infrared reflective paint 51 may also have insulating properties in addition to its infrared reflecting properties. Providing insulating properties can further suppress temperature increases in the surface 41.

Figure 6 is a side view showing a laser irradiation system S2 equipped with another example of the heat input suppression layer. The laser irradiation system S2 includes, as the heat input suppression layer, multiple infrared reflective plates 52 laid on the surface 41 of the structure 4. In this embodiment, the infrared reflective plates 52 are rectangular flat plates capable of reflecting infrared rays, but the shape of the infrared reflective plates 52 can be modified as needed depending on the shape of the surface 41. The infrared reflective plates 52 can be plates made of an infrared reflective material or base plates coated with infrared reflective paint. The multiple infrared reflective plates 52 are densely packed on the surface 41 to prevent the temperature of the surface 41 from rising due to solar heat irradiation. As with the infrared reflective paint 51, it is desirable to lay the infrared reflective plates 52 over the entire surface 41.

Note that the scope of this disclosure also includes installing a solar cell panel as the infrared reflection plate 52. Commercially available solar cell panels not only have the inherent photoelectric conversion function, but also have a corresponding infrared reflection function. Therefore, installing a solar cell panel on the surface 41 of the structure 4 can prevent the temperature of the surface 41 from rising. Another advantage is that the electricity generated by the solar cell panel can be used to power various electrical devices equipped on the structure 4, such as lighting equipment, air conditioning equipment, or batteries that are ancillary devices for the laser irradiation device 1.

According to the first embodiment described above, the formation of a heat input suppression layer, such as infrared reflective paint 51 or infrared reflective plate 52, suppresses the input of solar heat to the surface 41 of the structure 4. This suppresses the occurrence of convection due to the air temperature distribution along the propagation path of the laser beam Lb immediately after it is emitted from the laser irradiation unit 12. This makes it possible to provide laser irradiation systems S1 and S2 that can maintain the linearity and focusing of the laser beam Lb even when the surface 41 of the structure 4 is exposed to sunlight.

Second Embodiment
In the second embodiment, an example is shown in which the temperature difference suppression mechanism is composed of a cooling mechanism or a heating mechanism for the structure 4. Fig. 7A is a cross-sectional view of a laser irradiation system S3 equipped with an example of the cooling mechanism as viewed from the Y-axis direction, and Fig. 7B is a top view of the laser irradiation system S3. Note that Fig. 7A is a cross-sectional view taken along line VIIA-VIIA of Fig. 7B. The laser irradiation system S3 is equipped with a cooling pipe 53 disposed inside near the surface 41 of the structure 4 as the cooling mechanism. By cooling the structure 4, the cooling pipe 53 prevents the temperature of the surface 41 of the structure 4 from increasing even if solar heat is input to the surface 41 of the structure 4, thereby suppressing thermal radiation into the atmosphere.

The cooling pipe 53 is a pipe for circulating a refrigerant. The refrigerant is any liquid or gas capable of heat exchange, such as water. The cooling pipe 53 is installed near the bottom of the surface 41 so as to be able to cool substantially the entire surface 41. The cooling pipe 53 has an inlet pipe 531 at one end, which serves as the inlet for the refrigerant, and an outlet pipe 532 at the other end, which serves as the outlet for the refrigerant. The refrigerant introduced through the inlet pipe 531 flows through the cooling pipe 53, exchanging heat with the structure 4 to cool the structure 4, and is then discharged through the outlet pipe 532. In this embodiment, the cooling pipe 53 is serpentine, i.e., the inlet pipe 531 is located at the top right and runs leftward to approximately the left end of the structure 4. When the refrigerant reaches approximately the left end of the structure 4, the pipe changes direction 180 degrees and runs rightward to approximately the right end. Thereafter, the cooling pipe 53 changes direction by 180 degrees each time it reaches the approximate right or left end of the structure 4 or the periphery of the laser irradiation device 1, and is arranged to cover approximately the entire surface 41 of the structure 4, before finally returning to the upper right outlet pipe 532 arranged around the inlet pipe 531. However, the positions of the inlet pipe 531 and outlet pipe 532 and the path arrangement of the cooling pipe 53 are arbitrary, as long as it is arranged so that approximately the entire surface 41 of the structure 4 can be cooled. Alternatively, the surface 41 may be divided into multiple areas, and the cooling pipes 53 may be arranged so that each of the multiple areas can be cooled individually. In this case, it is possible to selectively cool areas below the irradiation direction of the laser beam Lb.

The inlet pipe 531 and outlet pipe 532 are connected by a circulation pipe 533. A pump 534 and a chiller 535 are incorporated into the circulation pipe 533. The pump 534 pressurizes the refrigerant, circulating it through the cooling pipe 53 and circulation pipe 533, which form a circulation path. The chiller 535 cools the refrigerant, which has completed heat exchange with the structure 4 and is now heated and discharged from the outlet pipe 532, to the required temperature. The refrigerant, restored to an appropriate temperature by the chiller 535, is then introduced back into the inlet pipe 531. In this way, the structure 4, which may be heated by solar heat or the like, can be cooled by circulating the refrigerant through the cooling pipe 53. In this embodiment, the chiller 535 used to cool the laser irradiation device 1 is also used to cool the refrigerant in the cooling mechanism; however, a separate chiller may be provided to cool the refrigerant in the cooling mechanism.

The cooling mechanism is an example of a temperature difference suppression mechanism used when solar heat is input to the surface 41 of the structure 4, resulting in T1 > T2. However, there are cases where the surface 41 of the structure 4 becomes colder than the atmosphere due to, for example, radiative cooling, creating an air temperature difference such that T1 < T2, resulting in convection. In this case, the cooling pipe 53 can be treated as a heating pipe, and a heating medium such as hot water can be circulated through the heating pipe. Alternatively, the cooling pipe 53 may be configured to be switchable between a refrigerant flow system and a heating medium flow system. Furthermore, a temperature measuring device that measures the temperatures T1 and T2 may be installed on the surface 41 of the structure 4 and in the line of sight of the laser beam Lb. The temperatures T1 and T2 may be measured, and the surface 41 of the structure 4 may be cooled or heated based on the measured T1 and T2, such that cooling is performed when T1 > T2 and heating is performed when T1 < T2.

Figure 8 is a cross-sectional view of a laser irradiation system S4 according to another example of the second embodiment, as viewed from the Y-axis direction. The laser irradiation system S4 includes a cooling mechanism that directly exchanges heat between the surface 41 of the structure 4 and the coolant W. Specifically, the laser irradiation system S4 includes a spray nozzle 54 that discharges the coolant W as the heat exchange mechanism. The coolant W is any liquid capable of heat exchange with the surface 41 of the structure 4, such as water. The coolant W discharged from the spray nozzle 54 directly cools the surface 41 through heat exchange with the surface 41. This allows the surface 41 to be cooled even if solar heat is input to the surface 41, thereby suppressing heat radiation into the atmosphere. The spray nozzle 54 can be a type that sprays the coolant W in a fountain-like manner or a type that sprays the coolant W in a mist-like manner. Alternatively, a perforated pipe with multiple spray holes may be used instead of the spray nozzle 54. The spray nozzle 54 or perforated pipe is positioned at least in an area of the surface 41 that is below the direction of the laser beam Lb. When the laser irradiation unit 12 rotates 360 degrees, it is positioned over the entire surface 41.

Multiple spray nozzles 54 are attached to the structure 4 at a predetermined pitch so as to protrude slightly from the surface 41. The laser irradiation system S4 further includes a spray pipe 541 and a manifold section 542. The spray pipe 541 supplies coolant W from a supply source of coolant W to the spray nozzles 54. The manifold section 542 distributes the coolant W supplied from the spray pipe 541 to the multiple spray nozzles 54 at uniform pressure. The spray pipe 541 incorporates a pump 543 that pressurizes the coolant W and a liquid temperature regulator 544 that adjusts the temperature of the coolant W to the required temperature. The liquid temperature regulator 544 may be configured to be heatable, if necessary, so that the coolant W serves as a heat transfer medium. The coolant W may also be configured to be switchable between on and off, so that coolant W is only emitted from the spray nozzles 54 located below the irradiation direction of the laser beam Lb.

According to the second embodiment described above, even if the temperature of the structure 4 becomes higher or lower than the temperature of the propagation path of the laser beam Lb, the structure 4 can be cooled or heated by the cooling mechanism or heating mechanism, such as the cooling pipe 53 or spray nozzle 54 described above. Therefore, it is possible to suppress the occurrence of convection due to the air temperature distribution along the propagation path of the laser beam Lb immediately after emission, and it is possible to maintain the straightness or focusing of the laser beam Lb.

[Third embodiment]
In the third embodiment, an example is shown in which the temperature difference suppression mechanism is a convection suppression mechanism that suppresses the generation of an air current heading from the structure 4 toward the ray of the laser beam Lb. Fig. 9 is a side view showing a laser irradiation system S5 equipped with an example of the convection suppression mechanism. The laser irradiation system S5 includes, as the convection suppression mechanism, an air blower 55 that generates an air current FL between the surface 41 of the structure 4 and the ray of the laser beam Lb. The air blower 55 blows away the rising air current Ud heading from the surface 41 toward the ray of the laser beam with the air current FL, thereby suppressing the generation of an air temperature distribution.

The air blowing device 55 is equipped with a blowing fan and a drive motor to rotate the fan. The air blowing device 55 generates an air flow FL in the direction pointed by the front end surface 21a of the laser irradiation unit 12, i.e., in the same direction as the ray of the laser beam Lb. The air blowing device 55 rotates in sync with the laser irradiation unit 12 so that it can generate an air flow FL that follows the ray even when the laser irradiation unit 12 rotates. To enable synchronous rotation, the air blowing device 55 is mounted on the rotating body 32 of the support mechanism 13.

When the surface 41 of the structure 4 is heated by solar heat or the like, and the air temperature near the surface 41 becomes higher than the air temperature on the ray of the laser beam Lb, an updraft Ud is generated, as shown in Figure 9. This updraft Ud creates atmospheric fluctuations on the ray of the laser beam Lb. To suppress the occurrence of this atmospheric fluctuation, the air blower 55 generates an air flow FL to replace the air on the surface 41. This eliminates or reduces the temperature difference between the air temperature near the surface 41 and the air temperature on the ray of the laser beam Lb. Note that it is desirable that the air flow FL is not a gentle breeze, but a strong wind strong enough to dispel the updraft Ud, for example, a wind speed of approximately 5 m/s or more.

The air blowing device 55 may have a function to prevent the air flow FL generated by the device itself and the updraft Ud blown away by the air flow FL from affecting the ray of the laser beam Lb. For example, a louver that can adjust the direction of the air flow FL is attached to the outlet of the air blowing device 55. By operating the louver, the direction of the air flow FL and the blown updraft Ud can be adjusted so that they do not affect the ray of the laser beam Lb.

Instead of the embodiment shown in Figure 9, multiple air blowing devices 55 may be fixedly installed at appropriate locations on the surface 41. Furthermore, instead of the air blowing devices 55, air suction devices that suck air near the surface 41 may be used. Furthermore, in addition to the air blowing devices 55, the infrared reflective paint 51 or infrared reflective plate 52 of the first embodiment, or the cooling piping 53 of the second embodiment may be installed in combination on the surface 41 of the structure 4.

According to the fourth embodiment described above, the air on the surface 41 of the structure 4 can be replaced using the air blower 55 or air suction device described above, eliminating or reducing the temperature difference between the air temperature near the surface 41 and the air temperature on the ray of the laser beam Lb. This makes it possible to suppress the occurrence of convection due to the air temperature distribution on the propagation path of the laser beam Lb immediately after emission, and maintain the straightness or focusing of the laser beam Lb.

[Example of a moving structure]
In the above-described embodiment, an example has been shown in which the structure 4 is a building fixed to the ground G. The laser irradiation system of the present disclosure can also be mounted on a mobile body. Fig. 10 is a side view showing an example in which the laser irradiation system is mounted on a vehicle 40 as the mobile body. The vehicle 40 includes a container 42 loaded on the bed of the vehicle body and a cabin 43 in which a driver rides.

The laser irradiation device 1 is mounted on a container 42. The laser oscillator 11 of the laser irradiation device 1 is disposed inside the container 42, while the laser irradiation unit 12 is attached so as to protrude upward from the top surface 421 of the container 42. As described above, the laser irradiation unit 12 can be rotated by the support mechanism 13, and emits a laser beam Lb toward the front of the vehicle 40, as shown in Figure 10, for example.

In the embodiment of Figure 10, the temperature difference between the air temperature in the area AR3 near the top surface 421 of the container 42 and the area AR4 near the top surface 431 of the cabin 43, and the air temperature in the area along the ray of the laser beam Lb, becomes a problem. If this temperature difference becomes large, atmospheric fluctuations occur, adversely affecting the propagation of the laser beam Lb. Therefore, the measures of the first, second, and third embodiments described above are applied to the top surfaces 421 and 431 to suppress the occurrence of atmospheric fluctuations.

Specifically, a temperature difference suppression mechanism is installed, such as applying infrared reflective paint 51 (FIG. 5) or laying infrared reflective plates 52 (FIG. 6) on the upper surfaces 421, 431, arranging cooling pipes 53 directly below the upper surfaces 421, 431 (FIGS. 7A, 7B), locating spray nozzles 54 (FIG. 8), or installing an air blower 55 that generates airflow FL along the upper surfaces 421, 431 (FIG. 9). These temperature difference suppression mechanisms can maintain the linearity and focusing ability of the laser beam Lb emitted by the laser irradiation device 1 mounted on a moving object such as a vehicle 40. To solve the problems described herein, each of the temperature difference suppression mechanisms described above may be used alone, or any combination of temperature difference suppression mechanisms may be used.

Summary of the Disclosure
The specific embodiments described above include disclosures having the following configurations.

A laser irradiation system according to one aspect of the present disclosure includes a laser irradiation device having a laser irradiation unit that emits a laser beam, a structure to which the laser irradiation device is attached so that the laser irradiation unit protrudes, and a temperature difference suppression mechanism that reduces the temperature difference between the air temperature near the structure and the air temperature in a region on the structure along the ray of the laser beam.

Atmospheric conditions affect the propagation of the laser beam. For example, when solar heat is incident on a structure, the complex temperature distribution created in the surrounding atmosphere leads to refractive index disturbances, adversely affecting the straightness and focusing of the laser beam. In particular, if factors that deteriorate the straightness exist near the laser beam's emission point, the impact increases in proportion to the propagation distance. In the above-mentioned laser irradiation system, the temperature difference suppression mechanism suppresses the temperature difference between the air temperature near the structure and the air temperature on the laser beam's ray of incidence above the structure. In other words, the atmosphere in the area through which the laser beam will propagate immediately after being emitted from the laser irradiation unit can be maintained in a state where temperature distribution is unlikely to occur. Therefore, a laser irradiation system can be provided that can maintain high levels of straightness and focusing of the laser beam, regardless of weather conditions.

In the above laser irradiation system, the structure may have a surface extending in the direction of the laser beam, and the temperature difference suppression mechanism may be configured to include a heat input suppression layer that suppresses heat input to the surface.

With this laser irradiation system, the formation of a heat input suppression layer reduces the amount of solar heat input to the surface of the structure. This reduces the occurrence of air temperature variations along the propagation path of the laser beam immediately after emission, and maintains the straightness and focusing properties of the laser beam.

In the above laser irradiation system, the heat input suppression layer can be configured to consist of infrared reflective paint applied to the surface, or an infrared reflective plate laid on the surface.

These laser irradiation systems can reduce the heat input from sunlight to the surface of a structure through simple methods such as applying infrared-reflective paint or installing infrared-reflective plates.

Furthermore, it is desirable that the infrared reflective plate is a solar panel. This configuration not only reduces heat input to the surface of the structure, but also has the advantage that the power generated by the solar panel can be used to power the electrical equipment equipped in the structure or the battery attached to the laser irradiation system.

In the above laser irradiation system, the temperature difference suppression mechanism can be configured to consist of a cooling mechanism or a heating mechanism for the structure.

With this laser irradiation system, even if the structure becomes hotter or colder than the surrounding atmosphere, the cooling mechanism or heating mechanism can cool or heat the structure. This prevents air temperature variations along the propagation path of the laser beam immediately after emission, maintaining the straightness and focusing of the laser beam.

In the above-mentioned laser irradiation system, it is desirable that the cooling mechanism or the heating mechanism comprises piping arranged inside the structure and a refrigerant or heating medium circulating within the piping. In this configuration, a structure that can be heated can be cooled by circulating a refrigerant through the cooling piping.

Alternatively, the structure may have a surface extending in the direction of the laser beam, and the cooling mechanism may be configured to exchange heat between the surface and a coolant. In this configuration, the surface can be cooled, for example, by flowing cooling water directly over the surface.

In the above laser irradiation system, the temperature difference suppression mechanism may be a convection suppression mechanism that suppresses the generation of air currents from the structure toward the ray of the laser beam.

For example, rising air currents generated when the air temperature near the surface of a structure is higher than the air temperature in the path of the laser beam cause thermal fluctuations in the air, adversely affecting the straightness of the laser beam. With the above-described laser irradiation system, the convection suppression mechanism suppresses air currents from the structure toward the path of the laser beam, thereby maintaining the straightness and focusing of the laser beam.

It is desirable that the structure have a surface extending in the direction of the laser beam's radiation, and that the convection suppression mechanism be an air blowing device that generates an air flow along the space between the surface and the laser beam's radiation. In this configuration, the air flow from the air blowing device can blow away the air flow heading from the surface of the structure toward the laser beam's radiation, thereby preventing the occurrence of air temperature distribution.

In the above-mentioned laser irradiation system, the structure may be a building fixed on the ground, or a mobile object equipped with a laser irradiation device. According to the present disclosure, a laser irradiation system with excellent laser beam straightness and focusing properties can be provided, regardless of whether the structure is a building or a mobile object.

REFERENCE SIGNS LIST 1 Laser irradiation device 12 Laser irradiation unit 4 Structure 40 Vehicle (moving structure)
41 Surface 42 Container 421 Top surface (surface)
43 Cabin 431 Top (surface)
51 Infrared reflective paint (heat input suppression layer)
52 Infrared reflection plate (heat input suppression layer)
53 Cooling piping (cooling mechanism)
54 Spray nozzle (heat exchange mechanism)
55 Air blower (convection suppression mechanism)
S1 to S5 Laser irradiation system Lb Laser beam T1, T2 Air temperature W Coolant FL Air flow Ud Updraft (air flow heading toward the line of fire)

Claims (12)

a laser irradiation device including a laser irradiation unit that emits a laser beam;
a structure having a surface extending in the direction of the laser beam, and to which the laser irradiation device is attached so that the laser irradiation portion protrudes from the surface ;
a temperature difference suppression mechanism that reduces a temperature difference between the air temperature in the vicinity of the structure and the air temperature in a region along the ray of the laser beam on the structure;
A laser irradiation system comprising: 2. The laser irradiation system according to claim 1 ,
The temperature difference suppression mechanism comprises a heat input suppression layer that suppresses heat input to the surface. 3. The laser irradiation system according to claim 2,
The heat input suppression layer is formed of an infrared reflective paint applied to the surface. 3. The laser irradiation system according to claim 2,
A laser irradiation system, wherein the heat input suppression layer is an infrared reflective plate laid on the surface. 5. The laser irradiation system according to claim 4,
A laser irradiation system, wherein the infrared reflecting plate is a solar panel. 2. The laser irradiation system according to claim 1,
A laser irradiation system, wherein the temperature difference suppression mechanism comprises a cooling mechanism or a heating mechanism for the structure. 7. The laser irradiation system according to claim 6,
A laser irradiation system, wherein the cooling mechanism or the heating mechanism comprises a pipe disposed inside the structure, and a refrigerant or a heating medium circulating within the pipe. 7. The laser irradiation system according to claim 6 ,
A laser irradiation system, wherein the cooling mechanism or the heating mechanism is a mechanism for heat exchange between the surface and a cooling liquid. 2. The laser irradiation system according to claim 1,
The temperature difference suppression mechanism comprises a convection suppression mechanism that suppresses the generation of an air current that flows from the structure toward the line of incidence of the laser beam. 10. The laser irradiation system according to claim 9 ,
The laser irradiation system, wherein the convection suppression mechanism comprises an air blowing device that generates an air flow between the surface and the ray of the laser beam. The laser irradiation system according to any one of claims 1 to 10,
A laser irradiation system, wherein the structure is a building fixed on the ground. The laser irradiation system according to any one of claims 1 to 10,
A laser irradiation system, wherein the structure is a mobile body equipped with a laser irradiation device.