Laser irradiation device, laser irradiation method, and laser irradiation-treated surface

Abstract

A laser irradiation device and the like that suppresses local deterioration of the surface quality of an object to be irradiated. [Solution] A laser irradiation device that irradiates an irradiation object O with laser light L includes a scan pattern forming unit (20, 50) that periodically changes at least one of the emission direction and shift amount of the laser light so that the irradiation point (BS) of the laser light periodically moves on a predetermined plane along a predetermined scan pattern (C), a scan pattern movement speed detection unit (130) that detects the movement speed of the scan pattern relative to the plane, and an irradiation control unit (110) that intermittently stops the irradiation of the laser light or intermittently reduces the intensity of the laser light (S06) when the movement speed of the scan pattern is equal to or less than a predetermined value (S05 YES).

Description

[Technical Field]

[0001] The present invention relates to a laser irradiation device that irradiates a laser so that the irradiation spot scans the surface of an irradiation object, a laser irradiation method, and a laser irradiation treatment surface. [Background technology]

[0002] As a technology relating to surface treatment using laser light, for example, Patent Document 1 describes that a wedge prism that deflects the laser light by a predetermined deflection angle is provided in an irradiation head that irradiates the laser light onto an object to be irradiated, and by irradiating the laser light while rotating this wedge prism, the irradiation point scans the surface of the object to be irradiated while rotating, and old paint film, foreign matter, etc. adhering to the surface of the object to be irradiated are removed (cleaned). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. WO2013 / 133415 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Patent Document 1, the irradiation point (beam spot) of the laser beam rotates (circulates) on the surface of the object to be irradiated along a predetermined irradiation circle, and the irradiation head is translated or oscillated up, down, left, right, etc. to remove any deposits adhering to the surface of the object to be irradiated, or to perform surface treatment on the object to be irradiated. Therefore, in areas away from the trajectory of the center of the irradiation circle (for example, near the top and bottom ends when the irradiation circle moves horizontally), the laser irradiation, in which the irradiation point progresses almost parallel to the direction of movement of the center of the irradiation circle, overlaps more than in other areas, sometimes leaving deep irradiation marks (grooves) relative to other areas. Furthermore, when the irradiation head is handheld by a worker during construction, in areas where the irradiation head moves slower than in other areas (areas where it stagnates), the number of laser irradiations is locally higher than in other areas, which increases the overlap rate, which is an index showing the degree of overlap of the passing trajectories of the irradiated areas, and can result in the formation of deep irradiation marks. It is desired to prevent the number of laser irradiations from increasing locally and forming deep irradiation marks, thereby making the laser irradiation state uniform and improving surface quality. In view of the above-mentioned problems, an object of the present invention is to provide a laser irradiation device, a laser irradiation method, and a laser irradiation-treated surface that suppress local deterioration of the surface quality of an object to be irradiated. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, a laser irradiation device according to one aspect of the present invention is a laser irradiation device that irradiates an irradiation object with laser light, and is characterized by comprising: a scan pattern forming unit that periodically changes at least one of the emission direction and shift amount of the laser light so that the irradiation point of the laser light moves periodically along a predetermined scan pattern on a predetermined plane; and an irradiation control unit that stops the irradiation of the laser light directed toward an over-irradiation prevention area set in a partial area of ​​the scan pattern, or reduces the intensity of the laser light with respect to the laser light directed toward an area other than the over-irradiation prevention area. This allows an over-irradiation prevention area to be set in a location in the scanning pattern where a local increase in the number of irradiations is likely to occur, and by stopping the irradiation of laser light or reducing the intensity of the laser light in this over-irradiation prevention area, it is possible to suppress local deterioration of surface quality caused by a local increase in the number of irradiations. In this specification, claims, etc., the scanning pattern includes both an area where the laser light is irradiated and an area where the laser light irradiation is stopped but which would be irradiated if the laser light emission were continued. Furthermore, the predetermined plane can typically be a plane including the movement locus of the focal position of the laser beam when it moves along the scanning pattern, or another plane parallel to this plane. As an example, when a circular scanning pattern (irradiation circle) is formed by rotating a deflection optical system such as a wedge prism that imparts a deflection angle to the laser beam, the predetermined plane can be a plane that is perpendicular to the rotation center axis of the deflection optical system and coincides with or adjacent to the focal position of the laser beam.

[0006] In the present invention, the over-irradiation prevention area can be configured to be set so that when the laser light is irradiated, the angle that the irradiated area makes with respect to the plane relative to the direction of travel of the scanning pattern with respect to the plane is less than a predetermined value. This makes it possible to appropriately obtain the above-mentioned effects. For example, in the case of a scanning pattern in which the irradiation point (beam spot) rotates along a predetermined circumference, the direction of travel of the irradiation point is the direction of movement of the irradiation point along the circumference, and the direction of travel of the scanning pattern is the direction of movement of the center of the circumference.

[0007] In the present invention, the scan pattern forming unit has the scan pattern that moves the irradiation location along a circumference, and the irradiation control unit can be configured to set the over-irradiation prevention area to be an area that is spaced apart from the movement trajectory of the center of the circumference by a predetermined value or more in the radial direction of the circumference, on the plane, and perpendicular to the movement trajectory. According to this, when the irradiation location is moved along the circumference, the above-mentioned effect can be effectively obtained by a relatively simple control. When a scanning pattern is formed by changing the deflection angle given to the laser light, the size of the scanning pattern will change depending on the distance between the irradiation device and the object to be irradiated. However, the above-mentioned predetermined value can be set in a specific reference irradiation state, such as a state in which the irradiation point substantially coincides with the focal position of the laser light (focus state). In the present invention, the scan pattern forming unit has a deflection optical system that deflects the laser light and rotates around a predetermined rotation center axis, and the irradiation control unit can be configured to stop the irradiation or reduce the intensity of the laser light when the angular position of the deflection optical system is within a predetermined range with respect to the traveling direction of the scan pattern relative to the plane. This makes it possible to appropriately obtain the above-mentioned effects through simple control. In the present invention, the scan pattern forming unit may include a galvano scanner having at least one mirror that reflects the laser and oscillates around a predetermined rotation center axis. According to this, by using a galvanometer scanner, the degree of freedom in setting the scanning pattern can be increased, and the effect of improving the surface quality described above can also be obtained.

[0008] In the present invention, a scan pattern movement direction detection unit is provided that detects the movement direction of the scan pattern relative to the plane, and the irradiation control unit can be configured to change the setting location of the over-irradiation prevention area in the scan pattern in accordance with changes in the movement direction. This means that even if an operator or the like changes the feed direction of the irradiation head, the location where the over-irradiation prevention area is set in the scanning pattern can be automatically changed to be appropriate according to the changed feed direction, thereby improving convenience.

[0009] In the present invention, a scanning pattern movement speed detection unit is provided that detects the movement speed of the scanning pattern relative to the plane, and the irradiation control unit can be configured to intermittently stop the irradiation of the laser light or intermittently reduce the intensity of the laser light when the movement speed of the scanning pattern is equal to or less than a predetermined value. Furthermore, a laser irradiation device according to another aspect of the present invention is a laser irradiation device that irradiates an irradiation object with laser light, and is characterized by comprising: a scan pattern forming unit that periodically changes at least one of the emission direction and shift amount of the laser light so that the irradiation point of the laser light moves periodically along a predetermined scan pattern on a predetermined plane; a scan pattern movement speed detection unit that detects the movement speed of the scan pattern relative to the plane; and an irradiation control unit that intermittently stops the irradiation of the laser light or intermittently reduces the intensity of the laser light when the movement speed of the scan pattern is equal to or less than a predetermined value. According to each of these inventions, when the movement speed of the scanning pattern becomes slow and there is a concern that the number of irradiations will increase across the entire scanning pattern, the irradiation can be stopped intermittently or the intensity of the laser light can be stopped intermittently, thereby suppressing local deterioration in surface quality caused by a local increase in the number of irradiations.

[0010] In each of the above inventions, the irradiation control unit can be configured to set the ratio of the time during which the irradiation of the laser light is intermittently stopped or the intensity of the laser light is intermittently reduced to the irradiation time so that it increases according to the decrease in the moving speed of the scanning pattern. This allows the number of irradiations and the energy to be applied to be appropriately set in accordance with changes in the movement speed of the scanning pattern, thereby making it possible to suppress deterioration of surface quality due to a decrease in the movement speed of the scanning pattern. In the present invention, the configuration may include an output unit that notifies a user when the moving speed of the scanning pattern is equal to or greater than a predetermined upper limit value that is higher than the predetermined value. This prevents the movement speed of the scanning pattern from becoming too fast and forming an unirradiated area (irradiation gap) between the latest irradiation locus and the previous irradiation locus, thereby ensuring surface quality.

[0011] In the present invention, the laser beam irradiation device may have an overlap ratio detection unit that detects an overlap ratio, which is the overlap ratio of the passing range of the irradiation point in the first irradiation and the second irradiation that are performed sequentially on the plane for each cycle of the scanning pattern, and the irradiation control unit may be configured to intermittently stop the irradiation of the laser light or intermittently reduce the intensity of the laser light when the overlap ratio is equal to or greater than a predetermined value. Furthermore, a laser irradiation device according to another aspect of the present invention is a laser irradiation device that irradiates an irradiation object with laser light, and is characterized by comprising: a scan pattern forming unit that periodically changes at least one of the emission direction and shift amount of the laser light so that the irradiation point of the laser light moves periodically along a predetermined scan pattern on a predetermined plane; an overlap ratio detection unit that detects an overlap ratio, which is the overlap ratio of the passing range of the irradiation point in a first irradiation and a second irradiation that are performed sequentially on the plane for each cycle of the scan pattern; and an irradiation control unit that intermittently stops the intensity of the laser light or intermittently reduces the intensity of the laser light when the overlap ratio is equal to or greater than a predetermined value. According to each of these inventions, when the movement speed of the scanning pattern becomes slow and the overlap rate becomes large, and there is a concern that the number of irradiations will increase across the entire scanning pattern, the irradiation can be stopped intermittently or the intensity of the laser light can be stopped intermittently, thereby suppressing local deterioration in surface quality caused by a local increase in the number of irradiations. In each of these inventions, the irradiation control unit can be configured to set the ratio of the time during which the irradiation of the laser light is intermittently stopped or the intensity of the laser light is intermittently reduced to the irradiation time so that it increases as the overlap rate increases. This allows the number of irradiations and the energy to be irradiated to be appropriately set in accordance with changes in the overlap ratio in response to changes in the movement speed of the scanning pattern, thereby preventing deterioration of surface quality due to an excessive increase in the overlap ratio.

[0012] In each of the above inventions, the irradiation control unit can be configured to intermittently stop the irradiation of the laser light or intermittently reduce the intensity of the laser light in an irradiation limited area set in a part of the scanning pattern, and to sequentially change the range occupied by the irradiation limited area within the scanning pattern. According to this, by disposing discretely regions where irradiation is stopped intermittently or the intensity of the laser light is reduced, it is possible to suppress variations in the quality of the surface after processing.

[0013] In the present invention, the configuration may include a construction status acquisition unit that acquires information regarding the construction status when the irradiation control unit stops irradiating the laser light or reduces the intensity of the laser light for other areas. This makes it possible to obtain information about the construction status through in-process monitoring when there is no reflected laser light or when the reflected light is weak, and this information can be fed back to irradiation parameters, for example, or construction can be stopped in the event of an abnormality, thereby further improving surface quality. In this case, the construction state acquisition unit may be configured to include an imaging unit that captures an image of the surface of the irradiation object. By this means, by performing image processing on the captured image, it is possible to appropriately grasp the removal state of the object to be removed and the formation of a heat-affected zone such as an oxide film on the treatment surface. In this case, the laser beam irradiation device may be configured to include a focus detection unit that detects the position of the focus of the laser beam relative to the surface of the irradiation object. This makes it possible to appropriately detect and correct the defocus state, thereby ensuring processing efficiency and surface quality.

[0014] In order to solve the above-mentioned problems, a laser irradiation method according to one aspect of the present invention is a laser irradiation method for irradiating an object with laser light, characterized in that at least one of the emission direction and shift amount of the laser light is periodically changed so that the irradiation point of the laser light moves periodically along a predetermined scanning pattern on a predetermined plane, and irradiation of the laser light directed toward an over-irradiation prevention area set in a partial area of ​​the scanning pattern is stopped or the intensity of the laser light is reduced relative to the laser light directed toward an area other than the over-irradiation prevention area. Furthermore, a laser irradiation method according to another aspect of the present invention is a laser irradiation method for irradiating an irradiation object with laser light, characterized in that at least one of the emission direction and shift amount of the laser light is periodically changed so that the irradiation point of the laser light moves periodically along a predetermined scanning pattern on a predetermined plane, and when the moving speed of the scanning pattern relative to the plane is equal to or less than a predetermined value, the irradiation of the laser light is intermittently stopped or the intensity of the laser light is intermittently reduced. Furthermore, a laser irradiation method according to another aspect of the present invention is a laser irradiation method for irradiating an irradiation object with laser light, characterized in that at least one of the emission direction and shift amount of the laser light is periodically changed so that the irradiation point of the laser light moves periodically along a predetermined scanning pattern on a predetermined plane, and when an overlap rate, which is the overlap rate of the passing range of the irradiation point in a first irradiation and a second irradiation performed sequentially for each cycle of the scanning pattern on the plane, is equal to or greater than a predetermined value, the irradiation of the laser light is intermittently stopped or the intensity of the laser light is intermittently reduced. In each of these inventions, the same effects as those of the invention relating to the laser irradiation device described above can be obtained.

[0015] In order to solve the above-mentioned problems, a laser irradiation treatment surface according to one embodiment of the present invention is characterized in that laser irradiation marks, which are arc-shaped grooves having irradiation start marks and irradiation end marks at both ends, are periodically arranged along the width direction of the grooves in the center of the arcs. In the present invention, the same effects as those of the invention relating to the laser irradiation device described above can be obtained. In this specification and claims, the term "arc" is not limited to a part of the circumference of a perfect circle, but also includes a shape equivalent to a part of an ellipse. [Effects of the Invention]

[0016] As described above, the present invention can provide a laser irradiation device, a laser irradiation method, and a laser irradiation-treated surface that suppress local deterioration of the surface quality of an object to be irradiated. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of an irradiation head in a first embodiment of a laser irradiation device to which the present invention is applied. [Figure 2] 1 is a block diagram schematically showing a system configuration of a laser irradiation device according to a first embodiment. [Figure 3] FIG. 3 is a diagram showing an example of a trajectory of a beam spot in the first embodiment. [Figure 4] FIG. 10 is a diagram showing the relationship between the direction of movement of the irradiation circle and the number of irradiations in the first embodiment. [Figure 5] FIG. 4 is a diagram showing an example of the relationship between the distance from the center of the irradiation circle and the number of irradiations in the first embodiment. [Figure 6] 4 is a flowchart showing an outline of irradiation control in the laser irradiation device of the first embodiment. [Figure 7] 10A and 10B are diagrams showing an example of a movement mode of an irradiation circle on the surface of an irradiation object. [Figure 8] 10A and 10B are diagrams showing an example of a switching mode between irradiation and irradiation stop when the irradiation circle is divided and intermittent irradiation control is performed in the first embodiment. [Figure 9] 5A and 5B are diagrams schematically showing examples of irradiation trajectories in the laser irradiation devices of the comparative example and the first embodiment. [Figure 10] FIG. 2 is a diagram schematically showing a laser irradiation treatment surface according to the first embodiment. [Figure 11]FIG. 10 is a diagram showing an example of the distribution of irradiation ranges and irradiation stop ranges on an irradiation circle in a second embodiment of a laser irradiation device to which the present invention is applied. [Figure 12] FIG. 10 is a diagram schematically illustrating the configuration of a third embodiment of a laser irradiation device to which the present invention is applied. [Figure 13] FIG. 10 is a diagram schematically illustrating the configuration of a fourth embodiment of a laser irradiation device to which the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0018] First Embodiment A first embodiment of a laser irradiation device, a laser irradiation method, and a laser irradiation treatment surface to which the present invention is applied will be described below. The laser irradiation device and laser irradiation method of the first embodiment irradiate the surface of an object (irradiation target) with laser light to remove adhesions on the surface, remove parts of the surface, modify the surface by heat input, etc., and adjust the base material by forming irradiation marks. Examples of the irradiation target include, but are not limited to, various metal products such as steel and aluminum alloys, and non-metal products. For example, if the object to be irradiated is a steel structure, the laser irradiation device and laser irradiation method of the first embodiment can be used to remove old paint, rust, dirt, salt, etc. attached to the surface (so-called laser cleaning).

[0019] FIG. 1 is a cross-sectional view of an irradiation head in a laser irradiation device of the first embodiment. The irradiation head 1 forms a laser beam L using continuous wave (CW) laser light transmitted from a laser oscillator 2 via a fiber F (see FIG. 2), and irradiates an irradiation object O with the laser beam L. The irradiation head 1 is, for example, a handheld type that can be held by an operator while tracing a predetermined irradiation path, but it can also be attached to a robot that can move the irradiation head 1 along a predetermined path (see the third embodiment). Alternatively, the irradiation object O may be displaced relative to the irradiation head 1 while the irradiation head 1 is fixed.

[0020] The irradiation head 1 includes a focus lens 10, a wedge prism 20, a protective glass 30, a rotary cylinder 40, a motor 50, a motor holder 60, a protective glass holder 70, a housing 80, a duct 90, and the like.

[0021] The focus lens 10 is an optical element onto which the laser beam L transmitted from the laser oscillator 2 to the irradiation head 1 via the fiber F passes through a collimator lens (not shown) and then enters. A collimating lens is an optical element that converts (collimates) the laser light emitted from the end of the fiber into a substantially parallel beam. The focus lens 10 is an optical element that condenses (focuses) the laser beam L emitted from the collimator lens at a predetermined focal position. The focus lens 10 may be, for example, a convex lens having a positive power.

[0022] The beam spot BS, which is the point of irradiation on the surface of the object O with the laser beam L, is positioned so that it coincides with the focal position or is close to the focal position within the focal depth (focused state), or is spaced apart from the focal position within a predetermined range (defocused state). If the amount of defocus is excessively large, the beam spot BS becomes excessively large, and the energy density decreases, which requires correction from the viewpoint of surface quality and processing efficiency. The depth of focus means the range in the optical axis direction in which the beam diameter is equal to or smaller than the diameter of a predetermined allowable circle of confusion.

[0023] The wedge prism 20 is an optical element that deflects the laser beam L emitted by the focus lens 10 by a predetermined deflection angle θ (see FIG. 1) to make the optical axis angles on the incident side and the exit side different. The wedge prism 20 is formed in the shape of a plate whose thickness changes continuously so that the thickness on one side in a direction perpendicular to the optical axis direction on the incident side is greater than the thickness on the other side. The wedge prism 20 cooperates with the motor 50 to function as the scanning pattern forming section of the present invention. The protective glass 30 is an optical element made of a flat glass or the like and arranged adjacent to the wedge prism 20 on the focal position side (on the irradiation object O side, on the beam spot BS side) along the optical axis direction.

[0024] The protective glass 30 is a protective member that prevents foreign matter such as peeled matter and dust that scatters from the irradiation object O side from adhering to other optical elements such as the wedge prism 20. The protective glass 30 is an optical element that is positioned closest to the focal position along the optical axis direction among the optical systems possessed by the irradiation head 1, and is exposed to the irradiation object O side through the space A and the inside of the duct 90 described later. The focus lens 10, wedge prism 20, and protective glass 30 are configured by applying coatings for the purpose of preventing reflection, surface protection, etc. to the surfaces of members made of a transparent material such as optical glass.

[0025] The rotary cylinder 40 is a cylindrical member that holds the focus lens 10 and the wedge prism 20 on its inner diameter side. The rotary cylinder 40 is formed concentrically with the optical axis of the focus lens 10 and the optical axis of the laser beam L incident on the focus lens 10 (the optical axis of the collimator lens). The rotary cylinder 40 is supported by a bearing (not shown) relative to the housing 80 so as to be rotatable about a central axis of rotation that coincides with the optical axis of the focus lens 10 . The rotary cylinder 40 is made of metal such as an aluminum alloy, engineering plastic, or the like.

[0026] The motor 50 is an electric actuator that rotates the rotary cylinder 40 relative to the housing 80 around the central axis of rotation. The motor 50 is configured, for example, as a ring-shaped motor that is concentric with the rotary cylinder 40 and provided on the outer diameter side of the rotary cylinder 40 . A stator (not shown) of the motor 50 is fixed to the housing 80 via a motor holder 60 (described later). A rotor (not shown) of the motor 50 is fixed to the rotary barrel 40 . The motor 50 is controlled by the motor drive control section 120 of the control unit 100 so that the rotation speed of the rotating barrel 40 substantially coincides with a desired target rotation speed.

[0027] The orientation of the irradiation head 1 is maintained so that the rotational center axis of the rotating cylinder 40 is perpendicular to the surface of the irradiation object O near the beam spot BS, and the motor 50 rotates the wedge prism 20 together with the rotating cylinder 40, so that the beam spot BS rotates and scans in an arc around the rotational center axis of the rotating cylinder 40 along the surface of the irradiation object O. This arc is the scanning pattern in the laser irradiation device of the first embodiment, and will be referred to as irradiation circle C in the following description. In this state, when the irradiation head 1 is translated along the surface of the irradiation object O, the beam spot BS scans the surface of the irradiation object O while revolving in an arc along the irradiation circle C. As a result, when focusing on an arbitrary point on the irradiation object O, the laser beam L is intermittently incident (the beam spot BS passes) for only a short period of time, and rapid heating and rapid cooling are sequentially performed within a short period of time. At this time, any deposits or the like attached to the surface of the irradiation object O are crushed and scattered.

[0028] The motor holder 60 is a support member that holds the stator of the motor 50 in a predetermined position inside the housing 80. The main body of the motor holder 60 is formed in a cylindrical shape and is fixed to the housing 80 in a state where it is inserted into the inner diameter side of the housing 80 . The inner peripheral surface of the motor holder 60 is disposed opposite the outer peripheral surface of the motor 50 and is fixed to the stator of the motor 50 .

[0029] The purge gas flow path 61 is an opening formed by penetrating a part of the motor holder 60 in the axial direction of the motor 50 . The purge gas PG discharged from the purge gas flow path 61 passes through a flow path provided in the housing 80 and is introduced into the inner diameter side of the inner cylinder 91 of the duct 90 .

[0030] The protection glass holder 70 is a member that is fixed to the inner diameter side of the housing 80 while holding the protection glass 30 . The protective glass holder 70 is formed, for example, in the shape of a disk with a circular opening formed in the center. The laser beam L passes through the opening from the wedge prism 20 side to the irradiation object O side. A recess into which the protective glass 30 is fitted is formed on the surface of the protective glass holder 70 facing the irradiation object O. The protective glass 30 is held inside the housing 80 in a state where it is fitted into this recess.

[0031] The protective glass 30 is detachably attached to a protective glass holder 70 so that it can be replaced if it becomes contaminated or burned. The surface of the protective glass holder 70 opposite to the irradiation object O side is disposed opposite to the end face of the motor holder 60 on the irradiation object O side with a gap therebetween. This gap constitutes part of a flow path (part of a fluid supply portion) that introduces the purge gas PG introduced from the purge gas flow path 61 of the motor holder 60 into the space A on the irradiation object O side of the protective glass 30.

[0032] The housing 80 is a cylindrical member that constitutes the enclosure of the main body of the irradiation head 1. The housing 80 contains the above-mentioned focus lens 10, wedge prism 20, protective glass 30, rotating cylinder 40, motor 50, motor holder 60, protective glass holder 70, etc., as well as the end of the fiber on the irradiation head 1 side (not shown), a collimator lens, etc.

[0033] The duct 90 is a double-tube member provided so as to protrude from the end of the housing 80 on the irradiation object O side. The duct 90 includes an inner cylinder 91, an outer cylinder 92, a dust collector connection cylinder 93, and the like. The motor holder 60, the protective glass holder 70, and the housing 80 are made of metal such as an aluminum alloy, engineering plastic, or the like.

[0034] The inner cylinder 91 is formed in a cylindrical shape. The laser beam L passes through the inner diameter side of the inner cylinder 91 and is emitted toward the irradiation object O side. The inner cylinder 91 has a small diameter portion 91a at its end on the housing 80 side, the small diameter portion 91a being stepped smaller than the other portions. A purge gas PG is introduced from the inside of the housing 80 into the space A inside the small diameter portion 91a.

[0035] The inner cylinder 91 has a tapered portion 91b formed at its end on the irradiation object O side, the tapered portion 91b narrowing toward the irradiation object O side. The tapered portion 91b has the function of allowing the laser beam L to pass through, while throttling the flow of the purge gas PG to increase the flow rate.

[0036] The outer cylinder 92 is a cylindrical member that is arranged concentrically with the inner cylinder 91 and is provided on the outer diameter side of the inner cylinder 91 . A continuous gap is formed between the inner peripheral surface of the outer cylinder 92 and the outer peripheral surface of the outer cylinder 91 over the entire circumference. The outer cylinder 92 has a small diameter portion 92a at its end on the housing 80 side, the small diameter portion 92a being stepped smaller than the other portions. The small diameter portion 92a is fitted into and fixed to the end of the housing 80 on the irradiation target O side. The edge of the end 92b of the outer tube 92 on the side of the object to be irradiated O is formed at an angle with respect to the rotational axis of the rotating tube 40 so that during normal use when irradiating with the rotational axis of the rotating tube 40 horizontal, the upper side is closer to the housing 80 than the lower side.

[0037] The dust collector connection tube 93 is a cylindrical body that protrudes outward from the outer tube 92 and is connected in a state of communication with the inner diameter side of the outer tube 92 near the end of the outer tube 92 on the side of the irradiation object O. The dust collector connection tube 93 is provided below the outer tube 92 during normal use as described above. The dust collector connection tube 93 is disposed at an angle relative to the outer tube 92 so as to move from the irradiation object O side toward the housing 80 side and move away from the outer tube 92. The other end of the dust collector connection tube 93 is connected to a dust collector (not shown) and is adapted to be vacuum-suctioned so that the inside is at negative pressure.

[0038] FIG. 2 is a block diagram schematically showing the system configuration of the laser irradiation device of the first embodiment. In addition to the above-mentioned irradiation head 1, the laser irradiation device further includes a laser oscillator 2, a control unit 100, an input / output device 200, and the like.

[0039] The laser oscillator 2 is a device that generates a continuous wave (CW) laser. As the laser oscillator 2, for example, an oscillator such as a semiconductor laser, a fiber laser, a YAG laser, or a CO2 laser having an output of about several kW can be used. The laser oscillator 2 has the function of sequentially switching on and off the emission of laser light in response to commands from the irradiation control unit 110 of the control unit 100, and of continuously or stepwise changing the output (intensity) during emission.

[0040] The control unit 100 is a device that comprehensively controls various functions of the laser irradiation device. The control unit 100 can be configured as a microcomputer having, for example, an information processing unit such as a CPU, a storage unit such as a RAM or a ROM, an input / output interface, and a bus connecting these. A position sensor 101, an acceleration sensor 102, a camera 103, a laser scanner 104, and the like are connected to the control unit 100.

[0041] The position sensor 101 is provided on the motor 50 and has an angle encoder that detects the angular position (phase) of the rotor relative to the stator. The angular position of the rotor coincides with the angular position of the wedge prism 20 . An irradiation control section 110 of the control unit 100 (described later) can detect the angular position of the wedge prism 20 around the central axis of rotation based on the output of the position sensor 101.

[0042] The acceleration sensor 102 detects the acceleration of the translational movement of the irradiation head 1 in three orthogonal axis directions (typically, the direction of the rotation axis of the wedge prism 20 and two axes perpendicular to this rotation axis), as well as the angular acceleration around these three orthogonal axes. The acceleration sensor 102 may have a configuration including a small acceleration sensor and a vibration gyroscope formed using, for example, a three-dimensional MEMS process.

[0043] The camera 103 is an imaging device that captures an image of the surface of the irradiation object O when irradiation of the laser light, which will be described later, is interrupted. The camera 103 includes a solid-state image sensor such as a CMOS, an image pickup optical system such as a lens group, an image processing device that processes the output of the image sensor, and the like. The camera 103 is provided, for example, at the tip of the duct 90 of the irradiation head 1 so that the imaging range faces the irradiation object O side.

[0044] The laser scanner 104 is a 3D LIDAR that emits a weak pulsed laser light toward the irradiation object O while changing the emission direction, and detects the surface shape of the irradiation object O and its relative position with respect to the irradiation head 1 based on the reflected light. Based on the output of the laser scanner 104, the relative position between the focal position of the laser beam L and the irradiation object O (correlated with the amount of defocus) and the inclination of the irradiation head 1 with respect to the surface of the irradiation object O can be detected.

[0045] The control unit 100 includes an irradiation control unit 110, a motor drive control unit 120, an irradiation head behavior calculation unit 130, an image processing unit 140, a focus state detection unit 150, and the like. These may each be configured with independent hardware, or may be realized by software that uses common hardware for multiple functions.

[0046] The irradiation control unit 110 controls whether or not the laser oscillator 2 generates laser light (turns the output on and off), and the output (intensity) when the laser light is generated. The irradiation control unit 110 has a function of temporarily stopping the generation of laser light when the position of the beam spot BS on the surface of the irradiation object O is in an over-irradiation prevention area, which will be described later. The irradiation control unit 110 detects the deflection direction of the laser beam L emitted from the irradiation head 1 based on the output of the position sensor 101, and grasps the angular position (phase) of the beam spot BS on the irradiation circle C. In addition, the irradiation control unit 110 has the function of intermittently stopping the generation of laser light when the movement speed (feed speed of the irradiation head 1) on the surface of the irradiation object O at the center of the irradiation circle C based on the calculation results of the irradiation head behavior calculation unit 130 is in a predetermined low speed state. These points will be explained in more detail later.

[0047] The motor drive control unit 120 issues commands to a drive circuit (not shown) of the motor 50 to control whether the motor 50 rotates or stops, and the rotation speed when the motor 50 rotates. The motor drive control unit 120 has a function of controlling the actual rotation speed of the motor 50 so that it coincides with a predetermined target rotation speed that is set according to the properties of the irradiation object O and the irradiation conditions of the laser beam L.

[0048] The irradiation head behavior calculation unit 130 integrates the acceleration and angular acceleration output by the acceleration sensor 102 to calculate the translational movement speed of the irradiation head 1 in the directions of three orthogonal axes and the angular velocity around the three orthogonal axes. Based on these speeds, angular speeds, and the distance between the irradiation head 1 and the irradiation object O, the moving direction and moving speed of the center of the irradiation circle C on the surface of the irradiation object O can be calculated. In the following description, the movement direction and movement speed of the irradiation circle C refer to the movement direction and movement speed of the center of the irradiation circle C unless otherwise specified. The irradiation head behavior calculation unit 130 cooperates with the acceleration sensor 102 to function as a scan pattern movement direction detection unit, a scan pattern movement speed detection unit, and an overlap ratio detection unit of the present invention.

[0049] The image processing unit 140 performs known image processing on the image data output by the camera 103, thereby determining the state of the surface of the irradiation object O by in-process monitoring. For example, in an image of the surface of the irradiation object O after irradiation, it is possible to determine the removal state of the object to be removed, such as old paint, rust, and dirt, and the formation state of an oxide film, based on the brightness value and color of each pixel (correlation of the brightness of each RGB color).

[0050] The focus state detection unit 150 recognizes the relative position of the irradiation head 1 with respect to the irradiation object O based on the output of the laser scanner 104, and detects the positional relationship between the focal position of the laser beam L and the surface of the irradiation object O. The focus state detection unit 150 has a function of distinguishing between a focus state in which the focal position of the laser beam L is near the surface of the irradiation object O and a defocus state other than the focus state, and of calculating the amount of defocus in the defocus state. The focus state detection unit 150 also has a function of recognizing the inclination of the irradiation head 1 with respect to the surface of the irradiation object O. In the case where such an inclination exists, when the beam spot BS rotates along the irradiation circle, it may happen that some areas are in focus and other areas are out of focus. During irradiation processing, it may be preferable to irradiate in a predetermined defocus state, but if the actual defocus amount is larger than the target defocus amount, correction is required. The image processing unit 140 and the focus state detection unit 150 cooperate with the camera 103 and the laser scanner 104 to function as a construction state acquisition unit of the present invention.

[0051] Furthermore, an input / output device 200 is connected to the control unit 100 via wired or wireless communication means. The input / output device 200 has a function that allows a user (for example, an operator or worker) (not shown) to input and set various parameters for the laser irradiation device and to check input parameters. Furthermore, the input / output device 200 has a function of informing the user of the operating state of the laser irradiation device and of any abnormalities that may occur during operation (construction) of the device. The input / output device 200 can be configured as, for example, an image display device such as an LCD having a touch panel input function, or a tablet terminal having an audio output device.

[0052] Next, the irradiation process in the laser irradiation device of the first embodiment will be described. In the first embodiment, by rotating the rotating cylinder 40 and the wedge prism 20 while emitting the laser beam L, the beam spot BS rotates along an irradiation circle C of a predetermined radius on a predetermined plane (typically the surface of the irradiation object O along a plane perpendicular to the rotation center axis of the wedge prism 20; hereinafter, the surface of the irradiation object O will be used as an example for explanation). In this state, by moving the irradiation head 1 in a relative translational motion along the surface of the irradiation object O, or by swinging (shaking) it around a predetermined rotation axis, it is possible to perform a process in which the beam spot BS scans the surface of the irradiation object O while the irradiation circle C, which is the scanning pattern, moves on the surface at a predetermined feed speed. As the beam spot BS passes, the surface of the irradiated object O is given a spike-like thermal history in which it instantly heats up and then cools down, and the object to be removed on the surface is crushed or melted and scattered around, and is removed.

[0053] The definition of the overlap rate in the first embodiment will be explained below. The overlap ratio is a value that indicates the percentage of the path of the beam spot BS on the surface that overlaps with the path of the beam spot BS in the previous irradiation when the beam spot BS repeatedly passes through a predetermined location in the scanning pattern. In other words, the overlap rate is the overlap rate of the passing range of the beam spot BS in the first irradiation and the second irradiation, which are performed sequentially at the front end or rear end of the direction of travel of the irradiation pattern (from left to right along the horizontal direction in the case of Figure 3) for each period (one rotation) of the scanning pattern (irradiation circle C) on the surface of the irradiation object O. FIG. 3 is a diagram showing an example of the trajectory of the beam spot BS in the first embodiment. FIG. 3 shows the locus of the beam spot BS on a plane that is perpendicular to the central axis of rotation of the wedge prism 20 and that includes the focal position of the laser beam L. As shown in FIG. 3, the beam spot BS rotates along the irradiation circle C in response to the rotation of the wedge prism 20, and moves in the feed direction of the irradiation head 1 relative to the irradiation object O. As a result, when the wedge prism 20 rotates one revolution (360°), an offset occurs between the previously irradiated path P0 (the locus of the beam spot) and the newly irradiated path P1. Therefore, in this specification, claims, etc., the overlap ratio is defined as the ratio (w / d × 100 (%)) of the width w of the overlap between the most recently irradiated path P0 and the latest path P1 to the diameter d of the beam spot BS (which essentially coincides with the groove width of the irradiation mark).

[0054] Here, when the scanning pattern is a circular rotation as in the first embodiment, the width w can also be defined as the scanning amount (the amount of feed of the irradiation head) during the period (during one cycle) in which the wedge prism 20 rotates 360°. In other words, the overlap ratio can be defined as the ratio of the diameter of the beam spot to the feed speed of the scanning pattern in one period of the scanning pattern. For example, in the regions on the left and right of the circular rotation trajectory in Figure 3, the overlap ratio according to this definition is substantially the same as the overlap ratio defined above.

[0055] FIG. 4 is a diagram showing the relationship between the direction of movement of the irradiation circle and the number of irradiations in the first embodiment. In FIG. 4, a continuous arc-shaped curve indicates the movement locus of the beam spot BS. As described above, when the beam spot BS has a scanning pattern that rotates in an arc, the number of laser irradiations increases locally at the ends (top and bottom ends in the case of Figure 4) of the irradiation area in a direction perpendicular to the moving direction of the center of the scanning pattern (horizontal direction in the case of Figure 4) compared to other areas.

[0056] FIG. 5 is a diagram showing an example of the relationship between the distance from the center of the irradiation circle and the number of irradiations in the first embodiment. In FIG. 5, the horizontal axis indicates the distance from the irradiation circle center locus (the vertical distance from the horizontal line passing through the irradiation circle center in FIG. 4), and the vertical axis indicates the average number of irradiations. In FIG. 5, the diameter of the irradiation circle is 26 mm, the diameter of the beam spot BS is 0.43 mm, and the overlap ratio is 20%. As shown in FIG. 5, it can be seen that the number of irradiations increases locally near the upper and lower ends of the irradiation region. In such areas, deep grooves are formed on the surface of the irradiated object O due to overlapping laser irradiation marks parallel to or at a small angle to the feed direction (horizontal direction in Figure 4), which may cause deterioration of the surface quality (variation in surface roughness, formation of heat-affected layers such as oxide films, etc.).

[0057] Therefore, in the first embodiment, the following control is performed to prevent the occurrence of areas where the number of irradiations increases locally. FIG. 6 is a flowchart showing an outline of irradiation control in the laser irradiation device of the first embodiment. Each step will be explained in order below.

[0058] <Step S01: Detecting irradiation head acceleration, etc.> The irradiation head behavior calculation unit 130 of the control unit 100 detects the translational movement speed of the irradiation head 1 in the three orthogonal axis directions and the angular velocity around the three orthogonal axes based on the output of the acceleration sensor 102. Then, proceed to step S02.

[0059] <Step S02: Calculate the direction and speed of irradiation circle movement> The irradiation control section 110 of the control unit 100 calculates the moving direction and moving speed of the center of the irradiation circle C on the surface of the irradiation object O based on the behavior of the irradiation head 1 detected in step S01. For example, when the irradiation head 1 faces the irradiated surface so that the rotational axis of the wedge prism 20 coincides with the normal direction of the irradiated surface, the direction and speed of translational movement of the irradiation head 1 in two axial directions perpendicular to the rotational axis of the wedge prism 20 substantially coincide with the direction and speed of movement of the center of the irradiation circle C. Furthermore, when the irradiation head 1 is rotated (swinged) around the two axes, the center of the irradiation circle C moves along the irradiated surface by an amount corresponding to the swing angle and focal length. Then, proceed to step S03.

[0060] <Step S03: Determine the wedge prism angle position where irradiation stops> The irradiation control section 110 of the control unit 100 determines the angular position of the wedge prism 20 at which irradiation of the laser light is stopped, depending on the moving direction of the center of the irradiation circle C calculated in step S02. FIG. 7 is a diagram showing an example of the movement of the irradiation circle on the surface of the irradiation object. 7 is illustrated on the premise that the beam spot BS (irradiation point) is in a focused state where it substantially coincides with the focal position of the laser beam L, and the rotational axis of the wedge prism 20 coincides with the normal direction of the irradiated surface (the irradiation head 1 faces the irradiated surface). In other words, it shows a state where the irradiated surface of the irradiation object O is a predetermined plane that is perpendicular to the rotational axis of the wedge prism 20 and includes the focal position of the laser beam L. During actual construction, depending on the positional relationship between the irradiation head 1 and the object to be irradiated O, the irradiated surface and the rotation center axis of the wedge prism 20 may be tilted, in which case the irradiation circle C may be deformed into an ellipse. In this case, the focus state changes continuously (partially becomes defocused and the defocus amount changes) depending on the position on the circumference of the ellipse. Furthermore, depending on the positional relationship between the irradiation head 1 and the irradiation object O, the focal position of the laser beam L may become defocused with respect to the irradiated surface. Such a defocused state may be intentionally created in order to adjust the energy density in the beam spot BS. Even in such cases, the effects of the present invention can be obtained by performing the irradiation control described below in the laser irradiation device. In FIG. 7, the radius of the irradiation circle is d. where 0 <d′<dとし、d×sinα=d′とする。 Furthermore, the angle formed by the line Q′Q connecting the centers of the irradiation circle C before and after the movement and the line QA is defined as β. β indicates the direction of movement of the center of the irradiation circle C due to the behavior of the irradiation head 1. The angular position θ of the beam spot BS on the irradiation circle C corresponds to the angular position of the wedge prism 20 detected by the position sensor 101 .

[0061] The irradiation control unit 110 stops the irradiation of the laser light when, for example, α+β≦θ≦π-α+β and π+α+β≦θ≦2π-α+β are satisfied. The region where the irradiation of the laser light is stopped is the over-irradiation prevention region PA (see FIG. 9) of the present invention. In other words, the over-irradiation prevention area PA is set so that the angle formed by the traveling direction D1 (moving direction along the tangent to the irradiation circle C) of the beam spot BS, which is the irradiation point, relative to the surface (specified plane) of the object to be irradiated O and the traveling direction D2 of the center of the irradiation circle C, which is the scanning pattern, relative to the surface, is less than a specified value. This allows laser irradiation to be stopped at both ends of the locus of the irradiation circle C that is perpendicular to the movement direction on the plane of the center of the irradiation circle C and whose distance from the center of the irradiation circle along the radial direction of the irradiation circle C is d' or more, thereby suppressing a local increase in the average number of irradiations. For example, as shown in FIG. 5, when the overlap rate is 20%, in order to keep the average number of irradiations at 4 or less, it is found that d' should be set to approximately 12.2 mm. Such an over-irradiation prevention area is an area where the angle formed by the direction of travel of the beam spot BS along the irradiation circle C due to the rotation of the wedge prism 20 with respect to the direction of travel (feed direction) of the irradiation circle C is less than a predetermined value (an area where the direction of travel of the beam spot BS and the direction of travel of the irradiation circle C are close to each other).

[0062] The value of d' can be set appropriately depending on irradiation conditions such as the properties of the irradiation object O, the purpose of the laser processing, the laser output, the beam spot diameter, and the rotation speed of the wedge prism 20. For example, when the uniformity of the surface after irradiation processing is important, it is preferable to set d' relatively small with respect to the irradiation circle diameter d in order to suppress an increase in the average number of irradiations. On the other hand, a state in which the average number of irradiations is locally large may be preferable in terms of efficiency, for example, in removing deposits (for example, removing relatively thick rust), so d' may be set relatively large in a rough processing (rough cutting) state such as the initial stage of irradiation, or d' may be made to match d so that the laser light irradiation is not stopped. In this case, d' may be set small relative to d in the finishing process to finish the surface smoothly. Then, proceed to step S04.

[0063] <Step S04: Execute irradiation control and motor drive control> The irradiation control unit 110 and the motor drive control unit 120 of the control unit 100 cause the laser oscillator 2 to generate laser light while rotating the motor 50 at a preset target rotation speed, and cause the irradiation head 1 to irradiate the irradiation object O with the laser beam L. At this time, the irradiation control unit 110 controls the laser oscillator 2 so as to periodically stop irradiating the laser light at the angular position of the wedge prism 20 determined in step S03. This prevents the laser beam L from being emitted toward the over-irradiation prevention area PA.

[0064] In addition, when temporarily stopping irradiation in the over-irradiation prevention area PA, the laser irradiation device can perform in-process monitoring such as capturing an image of the surface of the irradiation object O using a camera 103 and measuring the position of the surface of the irradiation object O using a laser scanner 104. If the image processing unit 140 determines a predetermined surface condition (for example, insufficient removal of the object to be removed or formation of an oxide film) based on the image captured by the camera 103, it can be configured to provide feedback to the irradiation control unit 110 and change irradiation parameters such as the output of the laser light. Furthermore, if the focus state detection unit 150 determines a predetermined defocus state or a tilt of the irradiation head 1 from a state of facing the irradiation object O (which can cause periodic defocus states) based on the positioning results by the laser scanner 104, the control unit 100 gives instructions to a user (not shown) via the input / output device 200 to correct the relative position and attitude of the irradiation head 1 with respect to the irradiation object O and correct the defocus state. Then, proceed to step S05.

[0065] <Step S05: Irradiation circle movement speed determination (1)> The irradiation control section 110 of the control unit 100 compares the moving speed of the center of the irradiation circle C on the surface of the irradiation object O with a preset first threshold value. The first threshold value can be set in consideration of the moving speed at which the overlap rate at the front end of the irradiation circle C in the moving direction is, for example, 25%. If the moving speed is equal to or less than the first threshold, the process proceeds to step S06, otherwise the process proceeds to step S07.

[0066] <Step S06: Execute intermittent irradiation control> The irradiation control section 110 of the control unit 100 calculates the overlap rate at the front end of the irradiation circle in the movement direction, and executes intermittent irradiation control to intermittently stop irradiation of the laser light according to the overlap rate. Table 1 shows an example of the relationship between the overlap rate and the emission state of the laser light. [Table 1] As shown in Table 1, the frequency at which the laser light is stopped from emitting (which can be expressed as the ratio of the time the light is emitted to the total irradiation time (construction time), which is the sum of the time the light is emitted and the time the light is stopped from emitting) is set to increase as the overlap rate increases (as the moving speed of the center of the irradiation circle (scanning pattern) C relative to the surface of the object to be irradiated O decreases). For example, when the overlap ratio is equal to or greater than 25% and less than 50%, irradiation is stopped while the wedge prism 20 makes one rotation, and then irradiation is continued for three subsequent rotations. From this point, the moving speed of the center of the irradiation circle C decreases, and when the overlap ratio becomes 50% or more and less than 75%, irradiation is stopped for one rotation of the wedge prism 20, and irradiation is resumed during the next rotation, and the number of times (frequency) irradiation is stopped is made more than when the overlap ratio is 25% or more and less than 50%. When the moving speed of the center of the irradiation circle C further decreases and the overlap ratio becomes 75% or more, irradiation is stopped for three rotations of the wedge prism 20, and then irradiation is continued for one rotation, and the number of times (frequency) that irradiation is stopped is made more than when the overlap ratio is 50% or more and less than 75%.

[0067] Furthermore, the irradiation circle C may be divided into a plurality of regions according to the angular position around the center, and irradiation may be switched on and off for each region in sequence. FIG. 8 is a diagram showing an example of switching between irradiation and irradiation stop when the irradiation circle is divided and intermittent irradiation control is performed in the first embodiment. 8(a) to 8(d) show the irradiation area and the irradiation stop area (irradiation restricted area) when the beam spot BS rotates around the irradiation circle C once. In this specification, even in an area where irradiation is stopped, a location where a beam spot BS would be formed if laser light were emitted is referred to as a beam spot BS for convenience. Also, the irradiation circle C is assumed to include an area that is not actually irradiated.

[0068] In the example shown in Fig. 8, the irradiation circle showing one cycle of the irradiation pattern is divided into four regions, each with a central angle of 90°, and each time the beam spot BS rotates around one circle, it sequentially irradiates one region at a time. In addition, the regions other than those irradiated are irradiation stop regions where irradiation is stopped. The number of divisions and the division pattern of the irradiation circle C are not limited to this and can be changed as appropriate, and the order and frequency of irradiation of each area are also not particularly limited. Furthermore, when irradiation is stopped in such intermittent irradiation control, the above-described in-process monitoring can be performed. In the first embodiment, in addition to such intermittent irradiation control, irradiation is also stopped at both ends of the irradiation area (over-irradiation prevention area PA) as described in step S03. After that, the series of processes ends (returns).

[0069] <Step S07: Irradiation circle movement speed determination (2)> The irradiation control section 110 of the control unit 100 compares the moving speed of the center of the irradiation circle on the surface of the irradiation object O with a second threshold value (second threshold value>first threshold value) set in advance. The second threshold value can be set in consideration of the moving speed at which the overlap rate at the front end of the irradiation circle in the moving direction becomes, for example, 0%. If the moving speed is equal to or greater than the second threshold, the process proceeds to step S08, otherwise the series of processes is ended (returned).

[0070] <Step S08: Movement speed suppression warning output> The control unit 100 outputs a warning to a user (not shown) via the input / output device 200, indicating that the moving speed of the irradiation circle C on the surface of the irradiation object O is excessively high. In this state, in at least some areas of the irradiation circle C, the passing trajectory of the beam spot BS does not overlap (overlap) with the passing trajectory during the previous rotation of the irradiation circle C, and there are unirradiated gaps between the passing trajectories of each rotation (a so-called gap state). The warning can be issued, for example, by displaying an image, sounding an alarm, or vibrating a device carried by the worker. Alternatively, instead of outputting the alarm, or simultaneously with outputting the alarm, the emission of the laser beam L may be stopped or the output of the laser beam L may be reduced. After that, the series of processes ends (returns).

[0071] The effects of the first embodiment will be described below in comparison with a comparative example of the present invention, which will be described below. In the comparative example and embodiment described below, the same parts as those in the previous embodiment are denoted by the same reference numerals and their description will be omitted, and differences will be mainly described. The laser irradiation device and laser irradiation method of the comparative example emit the laser beam L at all times during processing, regardless of the angular position of the wedge prism 20. FIG. 9 is a diagram schematically showing an example of irradiation loci in the laser irradiation devices of the comparative example and the first embodiment. 9(a) and 9(b) show the irradiation loci of the comparative example and the first embodiment, respectively. In the comparative example shown in FIG. 9(a), it can be seen that regions where the number of irradiations locally increases are formed at both ends of the band-shaped irradiation region formed by the movement of the irradiation circle. This may result in excessively deep groove-like irradiation marks being formed on the surface of the irradiation object O, which may deteriorate the surface quality. In contrast, in the first embodiment shown in Figure 9(b), the above-mentioned over-irradiation prevention area PA is set near both ends of the irradiation area, and irradiation is stopped, thereby suppressing a local increase in the number of irradiations. Here, the location where the over-irradiation prevention area PA is set is an area where the distance d' in the radial direction of the irradiation circle C, which is perpendicular to the movement locus T of the center of the irradiation circle C, is equal to or greater than a predetermined value. This prevents excessively deep groove-like irradiation marks from being formed, and improves the surface quality.

[0072] Next, the laser irradiation treatment surface of the first embodiment will be described. FIG. 10 is a diagram schematically showing a laser irradiation treatment surface according to the first embodiment. On the laser irradiation treatment surface 300 of the first embodiment, a plurality of groove-shaped irradiation marks 310 are formed by melting the base material (for example, steel) of the irradiation object O when the beam spot BS passes through and then re-solidifying. The irradiation marks 310 are formed, for example, in an arc shape along the outer periphery of the irradiation circle C, and a plurality of irradiation marks 310 are arranged along the width direction of the central portion in the longitudinal direction. When the laser irradiation device of the first embodiment is used, an arc that is convex on the movement direction side of the irradiation circle and an arc that is convex on the opposite side are actually formed by superimposing them on each other, but in Figure 10, only the former arc is shown to make the illustration and understanding easier.

[0073] At one end of the irradiation mark 310 in the longitudinal direction, an irradiation start mark 311 formed by starting irradiation of the laser beam L is formed. At the other end of the irradiation mark 310 in the longitudinal direction, an irradiation stop mark 312 formed by stopping the irradiation of the laser beam L is formed. Both ends of the irradiation mark 310 are interrupted by an irradiation start mark 311 and an irradiation stop mark 312, and the irradiation mark 310 does not continue to other irradiation marks 310. At the center in the longitudinal direction of the irradiation mark 310, it overlaps with another adjacent irradiation mark 310 by an overlap width W1 in the groove width direction. Here, if the groove width of the irradiation mark 310 itself is W2, W1 / W2 is the overlap ratio described above. When the rotational axis of the wedge prism 20 is aligned along the normal direction of the irradiated surface, the irradiation mark 310 has an arc shape that is a part of a perfect circle, but when this rotational axis is tilted relative to the normal direction, the irradiation mark 310 has a shape that is a cut-out part of an ellipse. A laser irradiation treated surface having such irradiation marks 310 is also included within the technical scope of the present invention.

[0074] According to the first embodiment described above, the following effects can be obtained. (1) By setting over-irradiation prevention areas PA near both ends of the irradiation circle movement range (areas far from the movement trajectory of the center of the irradiation circle C) where a local increase in the number of irradiations is likely to occur in the irradiation circle C, which is the scanning pattern, and stopping the irradiation of laser light, it is possible to suppress local deterioration of surface quality caused by a local increase in the number of irradiations. (2) By setting the over-irradiation prevention area PA in an area where the angle between the direction of travel of the beam spot BS along the irradiation circle C and the direction of travel of the irradiation circle is less than a predetermined value, the above-mentioned effects can be appropriately obtained. (3) By setting the scanning pattern to an irradiation circle C and the over-irradiation prevention area PA to an area that is more than a predetermined distance away from the movement trajectory of the center of the irradiation circle C, when the beam spot BS is moved along the irradiation circle C, the above-mentioned effect can be effectively obtained with relatively simple control. (4) Equipped with an acceleration sensor 102 that detects the movement direction of the irradiation circle C relative to the irradiation object O, and an irradiation head behavior calculation unit 130, and by changing the setting location of the over-irradiation prevention area PA according to changes in the movement direction, even if, for example, an operator or the like changes the feed direction of the irradiation head 1, the setting location of the over-irradiation prevention area in the irradiation circle C can be automatically changed to be appropriate according to the changed feed direction, thereby improving convenience. (5) When the moving speed of the irradiation circle C relative to the irradiation object O is equal to or less than the first threshold, by intermittently stopping the irradiation of the laser light, it is possible to suppress deterioration of surface quality caused by a local increase in the number of irradiations even when the moving speed of the irradiation circle C becomes slow and the overlap ratio becomes excessively large. (6) By setting the ratio (frequency) of the time for which the laser light irradiation is intermittently stopped to the irradiation time so that it increases according to the decrease in the moving speed of the irradiation circle C, the number of irradiations and the irradiated energy can be appropriately set according to the change in the moving speed of the irradiation circle C, and deterioration of surface quality due to the decrease in the moving speed of the irradiation circle C can be suppressed. (7) By setting an irradiation-restricted region where irradiation is intermittently stopped as part of the irradiation circle C and sequentially changing the range of the irradiation-restricted region within the irradiation circle C, the regions where irradiation is intermittently stopped can be discretely distributed, thereby suppressing quality variations on the processed surface. (8) When the moving speed of the irradiation circle C, which is the scanning pattern, relative to the object to be irradiated is equal to or greater than the second threshold, an alarm is output by the input / output device 200. This prevents the moving speed of the irradiation circle C from becoming excessively fast, thereby preventing the formation of an unirradiated gap between the latest irradiation trajectory and the previous irradiation trajectory, thereby ensuring surface quality. (9) By capturing an image of the object O to be irradiated with the camera 103 when the irradiation of the laser light is temporarily stopped, the surface condition of the object O to be irradiated can be obtained through in-process monitoring, and the surface condition can be fed back to the setting of irradiation conditions, etc., to improve the quality of the work. (10) When the irradiation of the laser light is temporarily stopped, the laser scanner 104 detects the focus state of the laser beam L on the surface of the object to be irradiated O, and when a defocus state is detected, the user is prompted to correct it, thereby improving the focus state during irradiation and improving the construction quality.

[0075] Second Embodiment Next, a second embodiment of the laser irradiation apparatus and laser irradiation method to which the present invention is applied will be described. In the second embodiment, the behavior (speed, angular velocity, etc.) of the irradiation head 1 is not detected, and the laser light irradiation is stopped periodically at regular intervals when the beam spot BS is within a predetermined angular range on the irradiation circle C.

[0076] FIG. 11 is a diagram showing an example of the distribution of irradiation ranges and irradiation stop ranges on an irradiation circle in the laser irradiation device of the second embodiment. The irradiation circle C has two predetermined irradiation stop ranges (over-irradiation prevention ranges) on its circumference where the emission of the laser light is stopped. The irradiation stop ranges are set in two places, for example, so that the angular positions seen from the center of the irradiation circle C are shifted by 180°. When the angular position of the wedge prism 20 detected by the position sensor 101 corresponds to the irradiation stop range, the irradiation control unit 110 issues a command to the laser oscillator 2 to stop the generation of the laser light.

[0077] Here, the width of the irradiation stop range (for example, the angular range when viewed from the center of the irradiation circle C) and the position where the irradiation stop range is set may be configured so that the user or the like can set it as appropriate. For example, the position of the irradiation stop range can be set according to the feed direction of the irradiation circle C (the direction of movement of the irradiation head 1) that is easiest for each worker to perform the work, and the width of the irradiation stop range can be set according to the degree of surface roughness required for the work quality.

[0078] According to the second embodiment described above, for example, when the movement direction of the irradiation head 1 during construction (the feed direction of the irradiation circle C) is predetermined, an increase in the number of localized irradiations can be suppressed by a simple device configuration and control without detecting the behavior of the irradiation head 1. In such a configuration, a detection means may be provided to detect whether the feed direction of the irradiation circle C is different from a predetermined direction, and an alarm or the like may be output if the feed direction is different from the predetermined direction.

[0079] Third Embodiment Next, a third embodiment of the laser irradiation apparatus and laser irradiation method to which the present invention is applied will be described. FIG. 12 is a diagram schematically showing the configuration of a laser irradiation device according to the third embodiment. In the third embodiment, the irradiation head 1 is held and moved by a robot 400. The robot 400 is, for example, a six-axis robot that holds the irradiation head 100 and moves the irradiation head 100 relative to the irradiation object O so that the irradiation circle C moves on the surface of the irradiation object O according to a predetermined irradiation path.

[0080] The robot 400 includes a robot controller 410 . The robot control device 410 controls the actuators (motors) and the like provided on each axis of the robot 400 in an integrated manner. The robot control device 410 is configured to include an information processing means such as a CPU, a storage means such as a RAM or a ROM, an input / output interface, and a bus connecting these. The robot control device 410 holds information about the irradiation path that has been taught in advance, and issues commands to the actuators of the robot 400 so that the irradiation head 1 moves at a predetermined feed rate along the processing path.

[0081] In the third embodiment, the robot control device 410 provides the control unit 100 of the laser irradiation device with information regarding the moving direction and moving speed of the irradiation circle C relative to the irradiation object O. The irradiation control unit 110 of the control unit 100 sets the over-irradiation prevention area and irradiation restriction area in substantially the same manner as in the first embodiment, based on information regarding the movement direction and movement speed of the irradiation circle C obtained from the robot control device 410. According to the third embodiment described above, when the irradiation head 1 is moved by the robot 400, it is possible to prevent deterioration of the surface quality due to an increase in the number of localized irradiations with a simple configuration.

[0082] <Fourth embodiment> Next, a fourth embodiment of the laser irradiation apparatus and laser irradiation method to which the present invention is applied will be described. FIG. 14 is a diagram schematically showing the configuration of a laser irradiation device according to the fourth embodiment. In the fourth embodiment, a scanning pattern (illumination circle C as an example) is formed by a galvano scanner 520.

[0083] The galvano scanner 500 has a laser oscillator (not shown) and mirrors 510 and 520 that sequentially reflect the laser beam L emitted from the focusing optical system. The mirrors 510 and 520 are supported so as to be swingable around a predetermined rotation center axis, and are driven in the swing direction by actuators 511 and 521, respectively. The rotational axes of mirrors 510 and 520 are arranged in a twisted position, and by oscillating mirror 510, the beam spot BS can be displaced in a first direction on a predetermined plane (typically the irradiated surface of the irradiation object O), and by oscillating mirror 520, the beam spot BS can be displaced in a second direction on the plane that is different from the first direction (typically perpendicular to the first direction).

[0084] In the fourth embodiment, the actuators 511 and 521 are controlled by a control device (not shown) to oscillate the mirrors 510 and 520 in a predetermined pattern in synchronization, thereby moving the beam spot BS in any direction on the above plane. Furthermore, even when the galvano scanner 500 is stationary relative to the irradiation object O, it is possible to move the irradiation circle C on the surface to be irradiated. As an example, in the fourth embodiment, similar to the first embodiment described above, an irradiation restricted area PA is set in an area that is spaced apart from the direction of movement of the center of the irradiation circle C in the radial direction of the irradiation circle C by a predetermined value or more.

[0085] The shape of the scanning pattern and the setting of the irradiation restricted area PA are not limited to this and can be changed as appropriate. For example, when the angle formed by the movement direction of the beam spot with respect to the movement direction of the scanning pattern relative to the irradiation object O is equal to or smaller than a predetermined value, the emission of the laser beam L can be stopped or the intensity can be reduced. According to the fourth embodiment described above, even when the scanning pattern is formed by the galvano scanner 500, it is possible to obtain the same effects as those of the first embodiment described above.

[0086] (Variation) The present invention is not limited to the above-described embodiments, and various modifications and variations are possible, and these are also within the technical scope of the present invention. (1) The configurations of the laser irradiation device, the laser irradiation method, and the surface to be treated by laser irradiation are not limited to those of the above-described embodiments, and can be modified as appropriate. For example, the type of object to be irradiated, the purpose of the laser irradiation process, the irradiation conditions, etc. can be changed as appropriate. (2) In each embodiment, the laser light irradiation is temporarily stopped in the over-irradiation prevention area and the irradiation suppression area. However, instead of this, the laser light intensity may be reduced compared to normal. Furthermore, when stopping and restarting the irradiation of the laser light, or when reducing and restoring the intensity of the laser light, the intensity of the laser light may be gradually changed continuously or in stages. (3) In each embodiment, for example, a rotating wedge prism is used to form an irradiation circle, which is a circumferential scanning pattern. However, the shape of the scanning pattern and the method for forming the scanning pattern are not limited to this and can be changed as appropriate. For example, instead of giving a deflection angle to the laser beam, the laser beam may be irradiated while being rotated in a state where it is shifted (eccentric) in parallel (so-called weaving, in which the amount of shift is periodically changed). Furthermore, the shape of the scanning pattern is not limited to a circle, but may be, for example, a polygon or other shape. Furthermore, the configuration of the optical system that forms the scanning pattern is not particularly limited, and for example, a galvano scanner or a polygon mirror may be used alone or in combination with other methods. (4) The method for detecting the moving direction and moving speed of the scanning pattern on the surface of the irradiation object is not limited to the configurations of the respective embodiments and can be modified as appropriate. (5) The method of performing in-process monitoring when irradiation is stopped and the events to be monitored are not limited to those described in the respective embodiments and can be changed as appropriate. [Explanation of symbols]

[0087] 1 irradiation head 2 laser oscillator 10 focus lens 20 Wedge prism 30 Protective glass 40 Rotating cylinder 50 Motor 60 motor holder 61 purge gas flow path 70 Protective glass holder 80 Housing 90 Duct 91 Inner cylinder 91a Small diameter section 91b Tapered section 92 Outer cylinder 92a Small diameter section 92b End 93 Dust collector connection tube O Irradiation target L Laser beam BS Beam spot C Irradiation circle (scanning pattern) PA Over-irradiation prevention area A Space PG Purge gas 100 control unit 101 position sensor 102 Acceleration sensor 103 Camera 104 Laser Scanner 110 Irradiation control unit 120 Motor drive control unit 130 irradiation head behavior calculation unit 140 image processing unit 150 Focus state detection unit 200 I / O devices 300 Laser irradiation treatment surface 310 Irradiation marks 311 Irradiation start mark 312 Irradiation stop mark 400 Robot 410 Robot control device 500 Galvanometer Scanner 510,520 Mirror 511,521 Actuator

Claims

1. A laser irradiation device comprising a scanning pattern forming unit that periodically changes at least one of the emission direction and shift amount of the laser beam so that the irradiation point of the laser beam irradiated onto the object to be irradiated moves periodically along a predetermined scanning pattern on a predetermined plane, The scanning pattern is scanned on the plane such that the passage ranges of the irradiation points in the first irradiation and the second irradiation, which are performed sequentially in each cycle of the scanning pattern, overlap. A scanning pattern movement speed detection unit for detecting the movement speed of the scanning pattern relative to the plane, The system further includes an irradiation control unit that intermittently stops the irradiation of the laser light or intermittently reduces the intensity of the laser light when the movement speed of the scanning pattern is below a predetermined value. A laser irradiation device characterized by the following.

2. The irradiation control unit is configured to set the ratio of the time spent intermittently stopping the irradiation of the laser light or intermittently reducing the intensity of the laser light to the construction time to increase in proportion to the decrease in the movement speed of the scanning pattern. A laser irradiation device according to claim 1, characterized by the following:

3. The system includes an output unit that notifies the user when the movement speed of the scanning pattern is greater than or equal to a predetermined upper limit that is higher than the predetermined value. A laser irradiation device according to claim 1 or 2, characterized by the above.

4. A laser irradiation device that irradiates an object to be irradiated with laser light, A scanning pattern forming unit that periodically changes at least one of the emission direction and shift amount of the laser beam so that the area irradiated by the laser beam moves periodically along a predetermined scanning pattern on a predetermined plane, A overlap rate detection unit detects the overlap rate, which is the overlap rate of the passing range of the irradiated area in the first and second irradiations that are performed sequentially in each cycle of the scanning pattern on the plane, The system includes an irradiation control unit that intermittently stops the laser beam or intermittently reduces the intensity of the laser beam when the overlap rate exceeds a predetermined value. A laser irradiation device characterized by the following.

5. The irradiation control unit sets the ratio of the time spent intermittently stopping the irradiation of the laser light or intermittently reducing the intensity of the laser light to the irradiation time to increase in proportion to the overlap rate. The laser irradiation apparatus according to claim 4, characterized by the following:

6. The irradiation control unit intermittently stops the irradiation of the laser light or intermittently reduces the intensity of the laser light in an irradiation restriction area set in a part of the scanning pattern, and sequentially changes the range occupied by the irradiation restriction area within the scanning pattern. A laser irradiation device according to any one of claims 1 to 5, characterized by the above.

7. A laser irradiation device that irradiates an object to be irradiated with laser light, A scanning pattern forming unit that periodically changes at least one of the emission direction and shift amount of the laser beam so that the area irradiated by the laser beam moves periodically along a predetermined scanning pattern on a predetermined plane, An irradiation control unit that stops the irradiation of the laser beam directed to an over-irradiation prevention area set in a part of the scanning pattern, or reduces the intensity of the laser beam relative to the laser beam directed to an area other than the over-irradiation prevention area, thereby suppressing local deterioration of surface quality due to a localized increase in the number of laser beam irradiations. Equipped with, The over-irradiation prevention region is a region in the scanning pattern where the number of irradiations increases locally compared to the region other than the over-irradiation prevention region. A laser irradiation device characterized by the following.

8. The over-irradiation prevention region is set such that, when the laser light is irradiated, the direction of travel of the beam spot (the irradiation point) relative to the plane is such that the angle it makes with respect to the direction of travel of the scanning pattern relative to the plane is less than or equal to a predetermined value. The laser irradiation apparatus according to claim 7, characterized by the following:

9. The system includes a scanning pattern movement direction detection unit that detects the movement direction of the scanning pattern relative to the plane, The irradiation control unit changes the setting location of the over-irradiation prevention region in the scanning pattern in accordance with the change in the direction of movement. A laser irradiation device according to claim 7 or 8, characterized by the following:

10. The irradiation control unit has a construction status acquisition unit that acquires information regarding the construction status when the irradiation control unit stops the irradiation of the laser light or reduces the intensity of the laser light relative to other areas. A laser irradiation device according to any one of claims 1 to 9, characterized by the following:

11. A laser irradiation method comprising periodically changing at least one of the emission direction and shift amount of the laser beam so that the irradiation point of the laser beam irradiated onto the object to be irradiated moves periodically along a predetermined scanning pattern on a predetermined plane, The scanning pattern is scanned on the plane such that the passage ranges of the irradiation points in the first irradiation and the second irradiation, which are performed sequentially in each cycle of the scanning pattern, overlap. When the movement speed of the scanning pattern on the plane is below a predetermined value, the irradiation of the laser light is intermittently stopped or the intensity of the laser light is intermittently reduced. A laser irradiation method characterized by the following.

12. A laser irradiation method that irradiates an object to be irradiated with laser light, The laser beam emits at least one of the laser beam's emission direction and shift amount is periodically changed so that the area irradiated by the laser beam moves periodically along a predetermined scanning pattern on a predetermined plane. If the overlap rate, which is the overlap rate of the passing ranges of the irradiated areas in the first and second irradiations performed sequentially in each cycle of the scanning pattern on the plane, is greater than or equal to a predetermined value, the irradiation of the laser light is intermittently stopped or the intensity of the laser light is intermittently reduced. A laser irradiation method characterized by the following.

13. A laser irradiation method that irradiates an object to be irradiated with laser light, The laser beam emits at least one of the laser beam's emission direction and shift amount is periodically changed so that the area irradiated by the laser beam moves periodically along a predetermined scanning pattern on a predetermined plane. On the aforementioned plane, the passage ranges of the irradiation points in the first irradiation and the second irradiation, which are performed sequentially in each cycle of the scanning pattern, are made to overlap. The irradiation of the laser beam directed towards the over-irradiation prevention region set in a part of the scanning pattern is stopped, or the intensity of the laser beam is reduced relative to the laser beam directed towards the region other than the over-irradiation prevention region. A laser irradiation method characterized by suppressing localized deterioration of surface quality due to a localized increase in the number of laser beam irradiations.

14. A laser irradiation method that irradiates an object to be irradiated with laser light, The laser beam emits at least one of the laser beam's emission direction and shift amount is periodically changed so that the area irradiated by the laser beam moves periodically along a predetermined scanning pattern on a predetermined plane. The irradiation of the laser beam directed towards the over-irradiation prevention area set in a part of the scanning pattern is stopped, or the intensity of the laser beam is reduced relative to the laser beam directed towards areas other than the over-irradiation prevention area, thereby suppressing local deterioration of surface quality due to a localized increase in the number of laser beam irradiations. The over-irradiation prevention region is a region in the scanning pattern where the number of irradiations increases locally compared to the region other than the over-irradiation prevention region. A laser irradiation method characterized by the following.

15. The laser irradiation marks, which are arc-shaped grooves having irradiation start marks and irradiation end marks at both ends, are periodically arranged along the width direction of the grooves in the central part of the arc. In the central part of the arc, it overlaps with other adjacent laser irradiation marks in the width direction of the groove. A laser-irradiated surface characterized by the following.

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