JP4552848B2 - Variable shape mirror and laser processing apparatus using the variable shape mirror - Google Patents

Description

  The present invention relates to a deformable mirror for correcting wavefront distortion of a light wave such as a laser beam, particularly astigmatism, and a laser processing apparatus using the deformable mirror.

  The deformable mirror corrects wavefront distortion of light waves and is used in various optical products. For example, an astronomical telescope is used to correct wavefront distortion (aberration) due to atmospheric fluctuations and improve image quality (see, for example, Patent Document 1). In addition, optical pickups such as CDs and DVDs are used to correct aberrations that occur due to the tilt and waviness of the optical disk surface (see, for example, Patent Document 2). Further, the laser beam machine is used to correct the wavefront distortion of the laser beam due to distortion of a lens, a reflecting mirror, etc. so that a laser beam having a high roundness and a small spot diameter can be obtained (for example, patent document). 1).

There are two types of deformable mirrors, one is an integral mirror type (for example, see Patent Document 1) and the other is a split mirror type (for example, see Patent Document 3). The mirror shape is changed. In addition, a device using a drive element driven by electrostatic force has been reported (see, for example, Patent Document 2). Since these have a large number of drive elements, the degree of freedom of deformation is high. If the number of drive elements is sufficiently large, an arbitrarily shaped reflection surface can be created, and an arbitrarily shaped wavefront distortion can be corrected.
In order to adjust the focal length of the laser beam and the like, a deformable mirror has also been reported that applies force to the plate-like reflecting mirror holding the outer peripheral portion from the back surface by one drive element (see Patent Document 4). .

Japanese Patent Laid-Open No. 7-66463 Japanese Patent Laid-Open No. 2005-122878 JP-A-5-136509 Japanese Patent Laid-Open No. 9-293915

  Since the deformable mirror having a large number of drive elements has a high degree of freedom in how to apply a deformation force, it can create a reflecting surface having an arbitrary shape and has the advantage of a large degree of freedom in correcting wavefront distortion. However, the number of drive elements is large and the structure is complicated. In the case of the split mirror type, since a large number of mirrors are required, the number of parts is further increased and the structure becomes complicated. Since a large number of parts are required and it is necessary to manufacture them precisely, a deformable mirror having a large number of drive elements becomes expensive.

  Depending on the application, there is a case where it is not necessary to have a high degree of freedom in correcting wavefront distortion, and only astigmatism may be corrected. For example, in processing such as cutting, drilling, and welding with a laser beam, a laser oscillator or a reflector or lens that constitutes a transmission optical path to a processing point has a manufacturing error called ass in a manufacturing process such as cutting, grinding, or polishing. Is likely to occur. Asperity is an error in which the focal length differs between the X direction and the Y direction when the uniaxial direction perpendicular to the optical axis is the X direction and the direction perpendicular to both the optical axis and the X direction is the Y direction. Astigmatism is caused by this asphalt, and the quality of laser processing often decreases. If astigmatism can be corrected, the quality in laser processing can be improved.

The deformable mirror that applies a force by one drive element is only for changing the focal length and the like, and the deformable mirror using one drive element for the purpose of correcting the astigmatism of the light wave is Never before.
An object of the present invention is to obtain a deformable mirror capable of correcting astigmatism.

  The deformable mirror according to the present invention includes a reflecting mirror having a reflecting surface on one side, a first shaft member fixed at two positions on the back surface of the reflecting mirror, and two legs fixed on the back surface of the reflecting mirror. And a second shaft member straddling the first shaft member, and a distance changing mechanism for changing a distance between the second shaft member and the first shaft member, and a portion for fixing the first shaft member And a line segment connecting a portion of the second shaft member where the foot is fixed intersects.

  Also, a reflecting mirror having a reflecting surface on one side, a first shaft member fixed at two positions on the back surface of the reflecting mirror, one end fixed to the first shaft member, and the other end fixed to the back surface of the reflecting mirror The first and second distance changing mechanisms are connected, and a line segment connecting a portion fixing the first shaft member intersects with a line segment connecting the first and second distance changing mechanisms. It is characterized by doing.

  The deformable mirror according to the present invention includes a reflecting mirror having a reflecting surface on one side, a first shaft member fixed at two positions on the back surface of the reflecting mirror, and two legs fixed on the back surface of the reflecting mirror. And a second shaft member straddling the first shaft member, and a distance changing mechanism for changing a distance between the second shaft member and the first shaft member, and a portion for fixing the first shaft member Since the line connecting the second shaft member and the line connecting the portion where the foot is fixed intersects, the astigmatism of the light reflected by the reflecting mirror can be corrected. .

  Also, a reflecting mirror having a reflecting surface on one side, a first shaft member fixed at two positions on the back surface of the reflecting mirror, one end fixed to the first shaft member, and the other end fixed to the back surface of the reflecting mirror The first and second distance changing mechanisms are connected, and a line segment connecting a portion fixing the first shaft member intersects with a line segment connecting the first and second distance changing mechanisms. Therefore, the astigmatism of the light reflected by the reflecting mirror can be corrected.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining the concept of the deformable mirror according to Embodiment 1 of the present invention. The circular reflecting mirror 1 which is a reflecting mirror is a plane parallel to each other in which the mirror surface 1A and the back surface 1B which are reflecting surfaces for reflecting light are circular. On the back surface 1B, an X axis that is a first axis passing through the center of the outer circumference circle and a Y axis that is a second axis that intersects with the center of the outer circumference at right angles to the X axis are defined. A load A is applied in the direction of pushing perpendicularly to the back surface 1B in the vicinity of the two X-axis intersection points 1C, which are the intersection points of the outer periphery circle of the back surface 1B and the X axis. On the other hand, in the vicinity of the two Y-axis intersection points 1D that are the intersection points of the outer circumference circle of the back surface 1B and the Y-axis, the load B is applied in a direction that is perpendicular to the back surface 1B. In this way, the mirror surface 1A of the circular reflecting mirror 1 has a concave shape in which the center is recessed on a straight line parallel to the X axis, and a convex shape in which the center protrudes on a straight line parallel to the Y axis. The surface 1A is deformed. In addition, the magnitude | size of the load A and the load B is the same, and the concave curve shape on the X-axis and the convex curve shape on the Y-axis are opposite and have the same shape. .

  When the focal length of the light reflected by the circular reflecting mirror 1 is short, that is, the direction in which the power is strong is matched with the Y axis, the focal length of the reflected light becomes long because it is convex on the Y axis, and the focal point of the reflected light because it is concave on the X axis. The distance becomes shorter. This means that the difference in power between the X axis and the Y axis is reduced. In other words, astigmatism can be corrected with the X-axis and Y-axis powers made equal by appropriately adjusting the degree of deformation of the saddle shape. The degree of deformation of the circular reflecting mirror 1 is assumed to be about 0.1 to 10 μm with respect to the circular reflecting mirror 1 having a diameter of several tens of millimeters. Note that the present invention can be applied to cases where the degree of deformation is larger or smaller than this assumption. Alternatively, the X axis may be convex and the Y axis may be concave.

  FIG. 2 shows an assembly diagram for explaining the structure of the deformable mirror in the first embodiment. The deformable mirror according to the first embodiment has two piezo actuators 2 capable of accurately controlling the length by applying a voltage by the piezo inverse piezoelectric effect, and the vicinity of two X-axis intersections 1C shown in FIG. The load A in the direction of pushing the circular reflecting mirror 1 and the load B in the direction of pulling the circular reflecting mirror 1 near the two Y-axis intersections 1D can be generated. On the back side of the circular reflecting mirror 1, there is a deformation force generating mechanism 3 that generates a force that deforms the mirror surface 1A of the circular reflecting mirror 1 into a bowl shape. The deformation force generating mechanism 3 includes an X-axis member 4 that is a first shaft member fixed to the back surface 1B of the circular reflecting mirror 1 at two positions corresponding to the vicinity of the X-axis intersection 1C on the X-axis in FIG. A Y-axis member 5 which is a second shaft member which is fixed to the back surface 1B of the circular reflecting mirror 1 at two positions corresponding to the vicinity of the Y-axis intersection 1D on the Y-axis and is disposed across the X-axis member 4; The piezoelectric actuator 2 is a distance changing mechanism that is disposed between the shaft member 4 and the Y-axis member 5 and changes the distance therebetween. Thus, the circular reflecting mirror 1 can be deformed into a bowl shape by the deformation force generating mechanism 3 having a simple structure that applies force to four points.

The X-axis member 4 is a circular X-axis back plate 4A having the same diameter as the circular reflector 1 and having a predetermined thickness, and is perpendicular to the X-axis back plate 4A from the surface of the X-axis back plate 4A on the circular reflector 1 side. It is composed of two prismatic X-axis legs 4B standing upright. Since the lengths of the two X-axis legs 4B are the same, the X-axis back plate 4A is parallel to the circular reflecting mirror 1 when fixed to the circular reflecting mirror 1. The shape of the cross section perpendicular to the length direction of the X-axis foot 4B is substantially square, and has the same cross-sectional shape in the length direction. The bottom surface of the X-axis foot 4B is referred to as the X-axis foot bottom surface 4C. The two X-axis feet 4B are at the end of the X-axis back plate 4A, and a line segment connecting the centers of the two X-axis foot bottom surfaces 4C passes through the center of the X-axis back plate 4A. Here, a straight line connecting the centers of the two X-axis soles 4C becomes the X-axis. A notch 4D for passing the Y-axis member 5 is provided in the vicinity of the intersection of the Y-axis that passes through the center of the X-axis back plate 4A and is orthogonal to the X-axis and the outer circumference circle. The X-axis back plate 4A and the X-axis foot 4B may be integrally formed, or may be formed by joining those formed as separate parts. Further, the X-axis member 4 and the circular reflecting mirror 1 may be formed from the same material by cutting or the like. The same applies to the Y-axis member 5.
The X-axis foot bottom surface 4C is a plane perpendicular to the X-axis foot 4B and has a substantially square shape. The two X-axis foot bottom surfaces 4C are fixed to the back surface 1B of the circular reflecting mirror 1 by an appropriate method such as screwing, brazing, or bonding with an adhesive so that the fixing surface is not peeled off by a pulling force. . Pay attention to the same points in the fixing method in other places.

  The Y-axis member 5 has the same shape as the X-axis member 4 and is composed of a Y-axis back plate 5A and two Y-axis legs 5B. Two Y-axis foot bottom surfaces 5 </ b> C of the Y-axis member 5 are fixed to the back surface 1 </ b> B of the circular reflecting mirror 1. The shape of the Y-axis member 5 is different from the X-axis member 4 in the following two points. (1) The length of the Y-axis foot 5B is longer than that of the X-axis foot 4B. (2) The Y-axis back plate 5A has no notch. A straight line connecting the centers of the two Y-axis soles 5C is referred to as a Y-axis. Since the straight line connecting the centers of the two notches 4D of the X-axis back plate 4A is orthogonal to the X-axis, it is defined by the two Y-axis legs 5B that respectively enter the two notches 4D. The Y axis is perpendicular to the X axis.

Here, regarding the X-axis back plate 4A and the Y-axis back plate 5A, the first surface and the second surface are defined as follows. The first surface is a surface on the side opposite to the circular reflecting mirror 1 side. The second surface is a surface on the back side of the first surface. One end of the piezo actuator 2 is fixed to the X-axis back plate center 4E (not shown) of the first surface of the X-axis back plate 4A and the Y-axis back plate center 5E of the second surface of the Y-axis back plate 5A. To do. Since both the X-axis back plate center 4E and the Y-axis back plate center 5E are on a straight line passing through the center of the circular reflecting mirror 1 and perpendicular to the circular reflecting mirror 1, the piezo actuator 2 is also on this straight line. That is, the piezo actuator 2 changes the distance between both ends on a straight line perpendicular to the circular reflecting mirror 1.
The difference in length between the X-axis foot 4B and the Y-axis foot 5B is set to be the same as the length when the length of the piezo actuator 2 is approximately in the middle of the changeable range. A predetermined voltage is applied to the piezo actuator 2 and the length of the piezo actuator 2 is the same as the difference between the lengths of the X-axis foot 4B and the Y-axis foot 5B. The bottom surface 5 </ b> C is fixed to the back surface 1 </ b> B of the circular reflecting mirror 1. In this way, when the length of the piezo actuator 2 is increased, the mirror surface 1A is deformed in a bowl shape so as to be concave on the X axis and convex on the Y axis, and when the length of the piezo actuator 2 is shortened, it is convex on the X axis and concave on the Y axis. The mirror surface 1A is deformed in a bowl shape.

The cross-sectional shape and size of the X-axis foot 4B and the thickness of the X-axis back plate 4A are appropriately adjusted so as to obtain a strength that does not damage the applied force. Further, the shape and area of the X-axis bottom surface 4C can be fixed to the back surface 1B of the circular reflecting mirror 1, can be appropriately deformed in a bowl shape, and the fixing surface cannot be peeled off by the pulling force on the fixing surface. Adjust as follows. The Y-axis back plate 5A and the Y-axis foot 5B are adjusted with attention to the same points.
The rigidity of the circular reflecting mirror 1, the X-axis member 4, and the Y-axis member 5 is such that appropriate deformation can occur. If the rigidity of the X-axis member 4 and the Y-axis member 5 is made smaller than that of the circular reflecting mirror 1, the ratio of the deformation of the circular reflecting mirror 1 to the change in distance by the distance changing mechanism becomes small, and the fine deformation of the circular reflecting mirror 1 is reduced. It becomes easy to control.

  The deformable mirror has a cylindrical shape including the deformation force generating mechanism 3 and is accommodated in a cylindrical mirror holder 6 (not shown) so as to be rotatable with respect to the mirror holder 6. For this reason, the deformable mirror can be installed at an arbitrary rotation angle, and astigmatism can be corrected with higher accuracy. The Y-axis back plate 5A is provided with a hole (not shown) through which wiring for sending electricity for driving the piezoelectric actuator 2 is passed.

Next, the operation will be described by taking as an example a case where the astigmatism of the laser beam of the laser processing apparatus is corrected by the deformable mirror. Although the configuration of the laser processing apparatus is not shown, it is assumed that a deformable mirror is installed in the middle of the transmission optical path from the laser oscillator to the processing point. Note that astigmatism can be corrected by a similar operation even when the present invention is applied to a device other than a laser processing apparatus.
When there is astigmatism, the laser beam shape becomes an ellipse. A cylindrical deformable mirror is rotated in the mirror holder 6 so that the direction in which the diameter of the laser beam shape is long or the direction in which the diameter is short coincides with the X axis or Y axis of the shape deformable mirror. The length of the piezo actuator 2 is changed by a predetermined amount in the direction of increasing or decreasing the length. If the laser beam shape changes from an ellipse to a perfect circle when changed by a predetermined amount, the length of the piezo actuator 2 is changed in the same direction as it is, and the laser beam shape is set to a length that is closest to the true circle. . If the flatness of the laser beam shape increases when the length of the piezoelectric actuator 2 is changed by a predetermined amount, the length of the piezoelectric actuator 2 is changed in the opposite direction so that the laser beam shape is closest to a perfect circle. Set to a length of The laser beam shape is always monitored at the time of laser processing, and when it deviates from a perfect circle, the length of the piezo actuator 2 is changed and corrected so as to be closest to the perfect circle. Note that being closest to a perfect circle means being in a predetermined allowable range from the state closest to the perfect circle.

  In order to explain the effect of adjusting the length of the piezo actuator 2 in both the longer and shorter directions from the initial state, the operation in the case where the length of the piezo actuator 2 can be changed only in one direction longer or shorter from the initial state. Also explained. A cylindrical deformable mirror is rotated in the mirror holder 6 so that the direction in which the diameter of the laser beam shape is long or the direction in which the diameter is short coincides with the X axis or Y axis of the shape deformable mirror. When the length of the piezo actuator 2 is changed by a predetermined amount in the direction in which the length of the piezo actuator 2 can be changed, the length of the piezo actuator 2 is changed in the same direction as long as the laser beam shape changes from an ellipse to a perfect circle. When the length of the piezo actuator 2 is changed by a predetermined amount, if the degree of flatness of the laser beam shape increases, the length is changed after the variable shape mirror is rotated 90 degrees in the mirror holder 6. . The length of the piezo actuator 2 is changed while monitoring the laser beam shape, and the laser beam shape is set to a length that is closest to a perfect circle.

  Since the length of the piezo actuator 2 can be changed in both the longer and shorter directions from the initial state, the operation of the deformable mirror for correcting astigmatism is easier than in the case where the length can be changed only in one long or short direction. Become. In order to be able to change the length of the piezo actuator 2 in both the long and short directions from the initial state, the piezo actuator 2 and the deformation force generating mechanism 3 are bonded to the circular reflecting mirror 1, and the piezo actuator 2 is energized and adjusted. The mirror surface 1A of the circular reflecting mirror 1 may be processed into a flat surface in a state where the length is substantially in the middle of the possible range.

By using the piezo actuator 2, the piezo actuator 2 can be continuously controlled and the astigmatism can be corrected even when the magnitude of astigmatism changes with time. If the astigmatism hardly changes with time, any mechanism can be used as long as the distance can be adjusted and the distance can be maintained, such as a screw, instead of the piezoelectric actuator 2. Even when used, astigmatism can be corrected.
Although one distance changing mechanism is used, two or more distance changing mechanisms may be used.
Although the deformable mirror is circular here, it may not be circular. Note that the circular shape has an advantage that the deformable mirror can be easily rotated in order to match one of the two axes in which the shape of the deformable mirror is deformed to the direction in which the focal length is maximized or minimized.

Although the two axes on which the deformable mirror is deformed are orthogonal to each other, they are not necessarily orthogonal. Even when the two deforming axes are not orthogonal, the angle difference between the point where the deformation is maximum in the concave and the point where the maximum is convex is almost 90 degrees, and the straight line passing through the point where the deformation is maximum in the concave Considering the X axis, the straight line passing through the point where the deformation becomes maximum convexly is considered the Y axis, and aligning either the X axis or the Y axis with the longer or shorter direction of the light shape, Astigmatism can be corrected by deforming the deformable mirror.
The intersection of the line segment connecting the fixed locations of the two first shaft members and the line segment connecting the fixed locations of the two second shaft members is positioned at the midpoint of the line segment. There may be no intersection at the midpoint of the line segment. If there is no intersection point at the middle point in the line segment connecting the fixed parts of the first shaft member, the force acting on both ends of this line segment is the distance from the intersection point so that the rotational moments on both sides of the intersection point are the same. The size is proportional to the inverse. The same applies to the fixing position of the second shaft member. From the balance of forces, the sum of the forces acting on the fixing points of the two first shaft members and the sum of the forces acting on the fixing points of the two second shaft members are the same.

  Since the force acting on the fixed portion of the first shaft member and the fixed portion of the second shaft member acts perpendicularly to the reflecting mirror, the possibility of unnecessary deformation is small. In addition, if the rigidity of the reflecting mirror and the deformation force generating mechanism is sufficiently increased so that unnecessary deformation does not occur, the force acting on the fixing portion of the first shaft member and the fixing portion of the second shaft member is applied to the reflecting mirror. However, it does not have to be vertical. If a non-vertical force component is useful for causing a desired deformation in the deformable mirror, the force may be applied in a predetermined direction that is not vertical.

Since the piezo actuator 2 is arranged on a straight line perpendicular to the circular reflecting mirror 1 and passing through the intersection point of the X axis and the Y axis, it is possible to reduce unnecessary or obstructive force for deforming the deformable mirror into a desired shape. If the unnecessary or disturbing force for deforming the deformable mirror into a desired shape can be reduced or made harmless by some means, a straight line passing through two points at both ends of the piezo actuator 2 that changes the distance is formed on the reflecting mirror. It may not be vertical or may not pass through the intersection of the X axis and the Y axis.
As the first shaft member and the second shaft member, those having a shape having two legs on the back plate are used, but shapes having other shapes may be used. The first shaft member may be any member as long as the portion where one end of the piezoelectric actuator 2 is fixed is disposed at a predetermined position with respect to the fixed portion of the first shaft member. The same applies to the second shaft member.
The reflecting surface of the reflecting mirror may have a predetermined shape suitable for an application such as a convex surface or a concave surface.
The above also applies to other embodiments.

Embodiment 2. FIG.
The second embodiment is a case where the first embodiment is changed so that a screw component is used as a distance changing mechanism instead of the piezo actuator. FIG. 3 shows an assembly diagram for explaining the structure of the deformable mirror according to the second embodiment. Compared with FIG. 2 in the case of the first embodiment, only different points will be described.
Instead of a single piezo actuator, there is a single screw component 7 with male threads of different pitches cut at both ends.

  In the X-axis back plate center 4E (not shown) of the first surface of the X-axis back plate 4A, a screw hole 4F having a female screw that engages with a screw on one side of the screw component 7 is centered at the center of the X-axis back plate 4A. It is provided in accordance with the plate center 4E. In the Y-axis back plate center 5E (not shown) of the second surface of the Y-axis back plate 5A, a screw hole 5F having a female screw that engages with a screw on the other side of the screw component 7 is centered. It is provided in accordance with the Y-axis back plate center 5E.

  The screw component 7 is screwed into the screw hole 4F of the X-axis member 4, the opposite side of the screw component 7 is screwed into the screw hole 5F of the Y-axis member 5, the screw component 7 is turned in a predetermined direction, and the X-axis foot bottom surface 4C and the Y-axis bottom 5C are on the same plane, and the screw component 7 is adjusted to a position where it can rotate as much as necessary in both directions. In order to enable such adjustment, the difference in length between the X-axis foot 4B and the Y-axis foot 5B, the length of the screw portion on both sides of the screw component 7, the difference in the pitch of the screws on both sides, the screw component 7 Properly manufacture the overall length of the. In such a state, the X-axis bottom surface 4C and the Y-axis bottom surface 5C are fixed to the back surface 1B of the circular reflecting mirror 1.

  Next, the operation will be described. As in the first embodiment, the direction in which the diameter of the laser beam shape is long or the direction in which the diameter is short matches the X axis or Y axis of the deformable mirror. The screw component 7 is rotated by a predetermined amount. If the laser beam shape approaches from an ellipse to a perfect circle, the screw component 7 is rotated as it is in the same direction, and the laser beam shape is set to a length that is closest to the perfect circle. If the flatness of the laser beam shape is increased by rotating the screw component 7 by a predetermined amount, the screw component 7 is rotated in the opposite direction to the position where the laser beam shape is closest to a perfect circle. Rotate.

As described above, even when a screw component is used, astigmatism of light reflected by the deformable mirror can be corrected by deforming the deformable mirror into a saddle shape.
By using screw parts, the structure of the deformable force generating mechanism of the deformable mirror is simplified. In addition, since screw parts are used, it is necessary to apply to an object whose astigmatism hardly changes with time.

The screws on both sides of the screw component 7 need only have a predetermined pitch difference, and the pitch difference may be produced by a right screw and a left screw. If the pitch difference is reduced, it becomes easy to finely adjust the saddle shape deformation of the deformable mirror. Alternatively, screw parts having screw holes with different pitches on both sides may be used, and rod-like portions provided with male threads on the X-axis member and Y-axis member may be provided and inserted into the screw holes of the screw parts. .
The above also applies to other embodiments.

Embodiment 3 FIG.
The third embodiment is a case where the second embodiment is changed so that a normal screw is used as the distance changing mechanism. FIG. 4 is an assembly diagram for explaining the structure of the deformable mirror according to the third embodiment. Only differences from FIG. 3 in the second embodiment will be described.
A normal screw 8 with a screw on one side and a head on the other side is used. The Y-axis member 5 which is a member far from the reflecting mirror has a through-hole 5G having a diameter slightly larger than the diameter of the screw 8 and smaller than the diameter of the head of the screw 8 instead of the screw hole 5F. Provided at the center of 5A. With the X-axis bottom surface 4C and the Y-axis bottom surface 5C fixed to the back surface 1B of the circular reflecting mirror 1, the screw 8 passes through the through hole 5G and the male screw of the screw 8 provided at the center of the X-axis back plate 4A Screw the female screw to be screwed into the screw hole 4F. When the back side of the head of the screw 8 is brought into contact with the Y-axis back plate 5A and the screw component 7 is further screwed, the circular reflecting mirror 1 is deformed into a bowl shape.
If the back side of the head of the screw 8 and the Y-axis back plate 5A are not in contact with each other, a force for deforming the reflecting mirror in a saddle shape cannot be generated, so that the saddle shape can be deformed only in the direction in which the X axis becomes convex.

  Next, the operation will be described. As in the first embodiment, the direction in which the diameter of the laser beam shape is long or the direction in which the diameter is short matches the X axis or Y axis of the deformable mirror. The screw 8 is rotated by a predetermined amount. If the laser beam shape changes from an ellipse to a perfect circle, the screw 8 is rotated in the same direction as it is. When the flatness of the laser beam shape increases when the screw 8 is rotated by a predetermined amount, the deformable mirror is rotated 90 degrees in the mirror holder 6 and then the screw 8 is rotated in the same direction. The screw 8 is rotated while monitoring the shape of the laser beam, and the screw 8 is screwed to a position where the laser beam shape is closest to a perfect circle.

  Thus, even when a normal screw is used, the astigmatism of the light reflected by the deformable mirror can be corrected by deforming the deformable mirror into a saddle shape.

Embodiment 4 FIG.
In the fourth embodiment, two piezo actuators are used. FIG. 5 shows an assembly diagram for explaining the structure of the deformable mirror according to the fourth embodiment.
The circular reflecting mirror 1 is the same as in the first to third embodiments. The deformation force generating mechanism 3 includes a structural member 9 and two piezo actuators 2. The shape of the structural member 9 is substantially the same as the shape of the X-axis member 4 in the case of Embodiment 1, and has a back plate 9A and two legs 9B. However, there is no notch 4D in the X-axis member 4 in the case of the first embodiment, and the piezo actuator 2 is fixed at the position where the notch is present. The lengths of the two legs 9B are the same, and are equal to the length when the length of the piezoelectric actuator 2 is approximately in the middle of the changeable range.

  The bottom surface of the foot 9B is referred to as a foot bottom surface 9C. A straight line connecting the centers of the two bottom surfaces 9C is called an X axis, and a straight line orthogonal to the X axis and the center of the back plate 9A is called a Y axis. One end of one piezo actuator 2 is fixed to the end portions 9D on both sides of the back plate 9A on the Y axis. In the state where the piezo actuator 2 is energized and the length of the piezo actuator 2 is the same as that of the foot 9B, the other end of the piezo actuator 2 and the bottom surface 9C are fixed to the back surface 1B of the circular reflecting mirror 1. The lengths of the two legs 9B may be the same as the length when the piezo actuator 2 is shortest, so that the piezo actuator 2 is not energized when fixed to the back surface 1B of the circular reflecting mirror 1. Get better. However, the mirror surface 1A needs to be polished to a flat surface in a state where the piezo actuator 2 is energized, or only a saddle-shaped deformation in which the central portion is recessed along the Y axis is possible.

  Here, the structural member 9 is a first shaft member, and the piezo actuator 2 is a first and second distance changing mechanism. On the back surface 1B of the circular reflecting mirror 1, a line segment connecting the locations where the two legs 9B are fixed intersects with a line segment connecting the locations where the ends of the two piezoelectric actuators 2 are fixed.

Next, the operation will be described. If the lengths of the two piezo actuators 2 are adjusted to meet the same restriction, the deformable mirror can be deformed in a bowl shape. Astigmatism can be corrected if the direction of the deformable mirror and the direction in which astigmatism occurs are adjusted appropriately to adjust the degree of saddle deformation.
As described above, the astigmatism of the light reflected by the deformable mirror can be corrected by deforming the deformable mirror in a saddle shape using the two piezoelectric actuators 2.

Instead of the piezo actuator, a screw component or the like may be used as the distance changing mechanism. Any distance changing mechanism may be used as long as one end is fixed to the first shaft member and the other end is fixed to the back surface of the reflecting mirror and the length thereof can be changed.
The above also applies to other embodiments using the first and second distance changing mechanisms.

Embodiment 5 FIG.
In the fifth embodiment, the second embodiment is changed so that the deformable mirror is deformed into a bowl shape instead of a bowl shape. FIG. 6 shows an assembly diagram for explaining the structure of the deformable mirror according to the fifth embodiment. Only differences from FIG. 3 in the second embodiment will be described. FIG. 7 is a diagram for explaining the concept of the deformable mirror in the fifth embodiment.
The X-axis foot 4B has a long lateral width, and the X-axis foot 4B is provided in all portions of the X-axis that are not the screw holes 4F. Therefore, since the load A is evenly applied to almost the entire X axis, the displacement is the same on a straight line parallel to the X axis, and the deformable mirror is deformed into a bowl shape as shown in FIG. 7 instead of a bowl shape. It will be. In addition to the deformation that the center appears on a straight line parallel to the Y-axis as shown in FIG. 7 and the displacement is the same on the straight line parallel to the X-axis, the center on the straight line parallel to the Y-axis A deformation that causes the same displacement on a straight line parallel to the dent X axis (a deformation that looks at the surface of the ridge from the inside) is also referred to as a ridge shape.
Since the X-axis foot 4B is horizontally long, the X-axis foot 4B is fixed to the back surface 1B of the circular reflector 1 at a place other than the screw hole 4F on the X-axis, and a line segment connecting both ends of the X-axis foot 4B. The X-axis member 4 is fixed to the back surface 1B of the circular reflecting mirror 1 even near the intersection with the central Y-axis. When the X-axis member 4 is not fixed near the intersection with the Y-axis and deforms into a bowl shape, the vicinity of the intersection with the Y-axis is compared with both ends by the load B acting on the two fixed positions of the Y-axis foot 5B. Therefore, the displacement is greatest on the X axis. On the other hand, when the X-axis member 4 is fixed in the vicinity of the intersection with the Y-axis on the X-axis, it is almost impossible to displace at this fixed position, and the displacement on the X-axis and a straight line parallel to the X-axis is It is almost the same regardless of the position.

When the focal length of the light reflected by the circular reflector 1 deformed into a bowl shape is short, that is, when the direction in which the power is strong is matched with the Y axis, the focal length of the reflected light becomes long because the Y axis is convex, and the X axis is linear. Therefore, the focal length of the reflected light does not change. This means that the power of the Y axis is made closer to the power of the X axis, and the difference in power is reduced. In other words, astigmatism can be corrected with the X-axis and Y-axis powers made equal by appropriately adjusting the degree of deformation of the saddle shape.
The fifth embodiment also operates in the same manner as the second embodiment, except that the deformable mirror is deformed into a bowl shape instead of a bowl shape.

As described above, the astigmatism of the light reflected by the deformable mirror can be corrected by deforming the deformable mirror into a bowl shape.
A piezo actuator may be used instead of the screw component 7.
The X-axis member 4 has two horizontally long X-axis legs 4B, and the force in the same direction can be applied to almost the entire X-axis other than the screw holes 4F. The X-axis member 4 may be fixed to the back surface of the reflecting mirror at three or more locations on the X-axis by increasing the number of X-axis legs 4B. It should be noted that at least one place other than both ends is near the intersection with the center Y-axis of the line segment connecting the X-axis feet 4B at both ends, that is, in the case of saddle-shaped deformation so that a difference in displacement hardly occurs on the X-axis. On the X axis, it is arranged in the vicinity of the position where the displacement is the largest compared to both ends. When the screw hole 4F is not necessary, the X-axis member 4 may be fixed to the back surface of the reflecting mirror almost entirely on the X-axis by one linear X-axis foot 4B.
The above also applies to other embodiments.

Embodiment 6 FIG.
The sixth embodiment is a case where the fourth embodiment is changed so that the deformable mirror is deformed into a bowl shape using two piezoelectric actuators. FIG. 8 is an assembly diagram illustrating the structure of the deformable mirror according to the sixth embodiment. Only differences from FIG. 5 in the case of the fourth embodiment will be described.
There are three legs 9B of the structural member 9, and the legs 9B are fixed to the back surface 1B of the circular reflecting mirror 1 even in the vicinity of the intersection with the central Y axis in addition to both ends on the X axis. Note that the heights of the legs 9B are all the same. Since there is the middle leg 9B, even if the lengths of the two piezo actuators 2 are changed, the displacement is almost the same on a straight line parallel to the X axis, and the deformable mirror is deformed into a bowl shape.

  Also in the sixth embodiment, the deformable mirror can be deformed into a bowl shape by changing the lengths of the two piezoelectric actuators 2, and the astigmatism of the light reflected by the deformable mirror is deformed into the bowl shape. Can be corrected.

Embodiment 7 FIG.
The seventh embodiment is a case where any of the variable shape mirrors of the first to sixth embodiments is applied to a laser processing apparatus. FIG. 9 shows a configuration diagram of the laser processing apparatus. A laser beam 51 emitted from the laser oscillator 50 is transmitted by a reflecting mirror 52 or the like in the middle of the optical path, and is two-dimensionally scanned and condensed by two sets of galvanometers 53 and a galvanometer scanner mirror 54 that is rotationally driven by the rotation of the galvanometer 53. The lens 55 positions and irradiates the workpiece 56. A square range surrounded by a dotted line on the workpiece 56 is a scannable range 57. The workpiece 56 is placed on a table 58, and the table 58 can be moved two-dimensionally within a predetermined range by two table driving mechanisms 59.

FIG. 10 shows a photograph of the surface of a workpiece that has been drilled by a laser processing apparatus when astigmatism correction is not performed. Drilling was performed while changing the focal position in the optical axis direction at equal intervals in the vertical direction in the figure (moving the condenser lens 55 or the workpiece 56 at equal intervals along the optical axis direction). Is. If it is only once, it is difficult to judge whether the processing accuracy is good or not. Therefore, in FIG. 10, there are a plurality of rows of drilled holes. In FIG. 10, only one row, the fourth row from the top, is acceptable as a laser beam. Whether or not the laser beam is acceptable is determined based on a predetermined standard such that the roundness of the drilled hole is, for example, 90% or more.
As the focal position changes, the shape of the processed hole changes from a vertically long ellipse to a horizontally long ellipse. The processed hole shape represents the shape of a laser beam spot on the surface of the workpiece. That is, astigmatism that cannot be ignored occurs in this machining optical system.

For this processing optical system, the deformable mirror according to any one of the first to sixth embodiments is used as the reflecting mirror 52 to correct astigmatism. The deformable mirror is installed so that the X axis or Y axis of the deformable mirror is aligned with the major axis or minor axis direction of the ellipse of the machining hole shown in FIG. 10 so that the elliptical machining hole approaches a perfect circle. In addition, the deformation amount of the deformable mirror is controlled by the driving voltage of the piezo actuator or the rotation amount of the screw. FIG. 11 shows a photograph of the hole on the workpiece surface obtained by performing drilling under the same conditions as in FIG. 10 after correcting astigmatism in this way. In FIG. 11, the allowable laser beams are the fifth to third rows from the top to the seventh row. It can be seen that astigmatism decreases and the depth of focus increases.
By expanding the depth of focus, stable laser processing can be realized even if there is a undulation on the surface of the workpiece. A mirror in the middle of the optical path other than the reflecting mirror 52 may be a variable shape mirror.

  In the seventh embodiment, as shown in FIG. 9, the laser beam 51 and the table 58 for holding the workpiece 56 are used in a two-dimensionally scanned laser processing apparatus, but the effect of using the deformable mirror is the processing. It acts on astigmatism of the optical system and does not depend on the scanning method. That is, the same effect can be obtained even in a laser processing apparatus in which any one of the laser beam 51, the condensing lens 55, and the table 58 performs one-dimensional, two-dimensional, or three-dimensional scanning or scanning. The laser beam may be a single pulse, a plurality of pulses, or continuous oscillation. The processing content is not limited to drilling, and any processing content can be used as long as it can be processed by laser such as cutting, deformation, welding, heat treatment, or marking. Further, any change may be generated in the workpiece as long as it can be generated by a laser such as combustion, melting, sublimation, or discoloration.

Single-pulse, multi-pulse, or continuous-wave laser beams are positioned and irradiated on the workpiece surface, and the workpiece is burned, melted, sublimated, or discolored, and cut, drilled, deformed, welded, heat-treated, or marked. If the laser processing device has a astigmatism correction mechanism having a deformable mirror that can be deformed so that the reflecting surface has a saddle shape or a saddle shape, the astigmatism of the laser beam is corrected. This can improve the processing accuracy.
In addition, single-pulse, multiple-pulse or continuous-wave laser beams are positioned and irradiated on the workpiece surface, and the workpiece is burned, melted, sublimated or discolored, and cut, drilled, deformed, welded, heat-treated, Alternatively, in a laser processing method that performs processing such as marking, a laser beam processing method that corrects astigmatism of a laser beam by deforming a reflecting mirror in the middle of a transmission optical path so that the reflecting surface has a bowl shape or a bowl shape. For example, the astigmatism of the laser beam can be corrected and the processing accuracy can be improved.

It is a figure for demonstrating the concept of the deformable mirror in Embodiment 1 of this invention. It is an assembly drawing explaining the structure of the variable shape mirror in Embodiment 1 of this invention. It is an assembly drawing explaining the structure of the variable shape mirror in Embodiment 2 of this invention. It is an assembly drawing explaining the structure of the variable shape mirror in Embodiment 3 of this invention. It is an assembly drawing explaining the structure of the variable shape mirror in Embodiment 4 of this invention. It is an assembly drawing explaining the structure of the variable shape mirror in Embodiment 5 of this invention. It is a figure for demonstrating the concept of the deformable mirror in Embodiment 5 of this invention. It is an assembly drawing explaining the structure of the variable shape mirror in Embodiment 6 of this invention. It is a block diagram of the laser processing apparatus in Embodiment 7 of this invention. It is a photograph of the surface of the workpiece drilled by the laser processing apparatus when the astigmatism correction in the seventh embodiment of the present invention is not performed. It is a photograph of the surface of the workpiece drilled by the laser processing apparatus when correcting astigmatism due to deformation of the deformable mirror in Embodiment 7 of the present invention.

Explanation of symbols

1: Circular reflector (reflector)
1A: Mirror surface (reflection surface)
1B: Back surface 1C: Intersection of outer periphery circle of back surface 1B and X axis (X axis intersection)
1D: Intersection of the outer circumference of the back surface 1B and the Y axis (Y axis intersection)
2: Piezo actuator (distance changing mechanism)
3: Deformation force generating mechanism 4: X-axis member (first shaft member)
4A: X-axis back plate 4B: X-axis foot 4C: X-axis foot bottom surface 4D: Notch 4E: X-axis back plate center 4F: Screw hole 5: Y-axis member (second shaft member)
5A: Y-axis back plate 5B: Y-axis foot 5C: Y-axis foot bottom 5E: Y-axis back plate center 5F: Screw hole 5G: Through hole 6: Mirror holder 7: Screw component (distance changing mechanism)
8: Screw (distance changing mechanism)
9: Structural member (first shaft member)
9A: Back plate 9B: Foot 9C: Bottom of foot 9D: End 50 on Y axis: Laser oscillator 51: Laser beam 52: Reflective mirror (variable shape mirror)
53: Galvanometer 54: Galvano scanner mirror 55: Condensing lens 56: Work piece 57: Scanable range 58: Table 59: Table drive mechanism A: Load B: Load

Claims (10)

A reflecting mirror having a reflecting surface on one side, a first shaft member fixed at two positions on the back surface of the reflecting mirror, and two legs fixed on the back surface of the reflecting mirror; A second shaft member straddling, a distance changing mechanism for changing a distance between the second shaft member and the first shaft member, and a line segment connecting a portion for fixing the first shaft member and the second shaft A deformable mirror characterized in that a line segment connecting the portions of the member fixing the legs intersects. A reflecting mirror having a reflecting surface on one side, a first shaft member fixed at two positions on the back surface of the reflecting mirror, one end fixed to the first shaft member, and the other end fixed to the back surface of the reflecting mirror A line segment that includes a first and a second distance changing mechanism, and a line segment that connects a portion that fixes the first shaft member intersects a line segment that connects the location that fixes the first and second distance change mechanisms. A deformable mirror characterized by A reflecting mirror having a reflecting surface on one side; a first shaft member linearly fixed to the back surface of the reflecting mirror; and two legs fixed to the back surface of the reflecting mirror. A second shaft member straddling; a distance changing mechanism for changing a distance between the second shaft member and the first shaft member; and a line segment of a portion for fixing the first shaft member and the second shaft member A deformable mirror characterized in that a line segment connecting portions where the legs are fixed intersects. A reflecting mirror having a reflecting surface on one side, a first shaft member linearly fixed to the back surface of the reflecting mirror, one end fixed to the first shaft member, and the other end fixed to the back surface of the reflecting mirror A first and second distance changing mechanism, and a line segment that fixes the first shaft member intersects a line segment that connects the first and second distance changing mechanisms. A variable shape mirror. The first shaft member is fixed to the back surface of the reflecting mirror even in the vicinity of the intersection of the second shaft member and the line connecting the portion where the foot is fixed on the line connecting the portion where the first shaft member is fixed. The deformable mirror according to claim 1. The first shaft member is placed on the back surface of the reflecting mirror even in the vicinity of the intersection with the line segment that connects the first and second distance changing mechanisms on the line segment that connects the portion that fixes the first shaft member. The deformable mirror according to claim 2, wherein the deformable mirror is fixed. The variable shape mirror according to any one of claims 1 to 6, wherein a piezo actuator is used for the distance changing mechanism. The variable shape mirror according to claim 1, wherein a screw is used for the distance changing mechanism. The variable shape mirror according to any one of claims 1 to 6, wherein a screw component having screws with different pitches on both sides is used for the distance changing mechanism. A laser processing apparatus comprising: a laser oscillator that oscillates a laser beam; and a processing optical system that transmits the laser beam from the laser oscillator to a workpiece. The variable shape mirror according to any one of claims 1 to 9 A laser processing apparatus having the processing optical system.

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