Optical element and laser irradiation device

Abstract

The present invention appropriately suppresses non-uniformity in the optical intensity of laser light. At least one of an incidence surface (30) and an emission surface (32) of an optical element (22) is shaped such that, in the Y direction, the profile of the wavefront aberration of laser light (L2) is continuous, and the curvature of the curvature profile of the wavefront aberration of the laser light (L2) has a maximum value at a first position and a smaller value than the maximum value at the first position at a second position and a third position and such that, in the X direction, the profile of the wavefront aberration of the laser light (L2) is continuous, and the curvature of the curvature profile of the wavefront aberration of the laser light (L2) has a maximum value at a first position and a smaller value than the maximum value at the first position at a second position and a third position.

Description

Optical Element and Laser Irradiation Device

[0001] The present disclosure relates to an optical element and a laser irradiation device.

[0002] Laser light has a distribution in light intensity. For example, a single-mode laser has a Gaussian profile. In the case of a Gaussian profile, the light intensity is high near the optical axis and decreases as the distance from the optical axis increases. However, depending on the application, a laser having a uniform light intensity may be required. For example, Patent Document 1 describes a technique for making the light intensity of a linearly long laser beam uniform in one direction by performing top-hat conversion using a Powell lens. Patent Document 2 also describes using a DOE (Diffractive Optical Element, diffractive optical element). Even when using a DOE, it is possible to make the light intensity of the laser light uniform. Patent Document 3 describes a technique for realizing a line light with uniform light intensity in a first direction by making the wavefront aberration in a first direction orthogonal to the propagation direction larger than the diffraction limit and making the wavefront aberration in a second direction orthogonal to the first direction below the diffraction limit.

[0003] U.S. Patent No. 4,826,299, Japanese Patent Application Laid-Open No. 2002-520651, Patent No. 6,496,894

[0004] Here, there is room for improvement in appropriately suppressing the non-uniformity of the light intensity of the laser light.

[0005] An object of the present disclosure is to provide an optical element and a laser irradiation device capable of appropriately suppressing the non-uniformity of the light intensity of laser light.

[0006] The optical element according to this disclosure has an incident surface into which laser light is incident and an exit surface from which the laser light is emitted, and at least one of the incident surface and the exit surface has a continuous wavefront aberration profile of the laser light emitted from the exit surface in a first direction perpendicular to the direction of propagation of the laser light, the curvature of the wavefront aberration profile of the laser light emitted from the exit surface is at a maximum value at a first position, the curvature at the second and third positions is at a value smaller than the maximum value at the first position, and in the direction of propagation Furthermore, in a second direction perpendicular to the first direction, the wavefront aberration profile of the laser light emitted from the emission surface is continuous, and the curvature of the wavefront aberration curvature profile of the laser light emitted from the emission surface takes a maximum value at a first position, and the curvature at the second and third positions is smaller than the maximum value at the first position, wherein the first position is a position between the second and third positions and is closer to the optical axis of the laser light than the second and third positions.

[0007] The laser irradiation device according to this disclosure comprises the optical element and a light source that emits the laser light onto the optical element.

[0008] According to this disclosure, non-uniformity in the light intensity of laser light can be appropriately suppressed.

[0009] Figure 1 is a schematic diagram of a laser irradiation device according to the first embodiment. Figure 2 is a schematic diagram of a laser irradiation device according to the first embodiment. Figure 3 is a schematic diagram of an optical element according to the first embodiment. Figure 4 is an explanatory diagram illustrating the wavefront in the first embodiment. Figure 5 is an explanatory diagram illustrating the wavefront in the first embodiment. Figure 6 is a diagram showing an example of the light intensity distribution of a laser according to the embodiment. Figure 7 is a diagram showing an example of the light intensity distribution of a laser according to the embodiment. Figure 8 is a schematic diagram showing the intensity distribution of laser light viewed from the optical axis direction. Figure 9 is a schematic diagram showing an example of the surface shape of an optical element. Figure 10 is a schematic diagram of a laser irradiation device according to another example 1 of the first embodiment. Figure 11 is a schematic diagram of a laser irradiation device according to another example 1 of the first embodiment. Figure 12 is a schematic diagram of a laser irradiation device according to another example 2 of the first embodiment. Figure 13 is a schematic diagram of a laser irradiation device according to another example 2 of the first embodiment. Figure 14 is a schematic diagram of a laser irradiation device according to another example 3 of the first embodiment. Figure 15 is a schematic diagram of a laser irradiation device according to another example 3 of the first embodiment. Figure 16 is a schematic diagram of a laser irradiation device according to another example 4 of the first embodiment. Figure 17 is a schematic diagram of a laser irradiation device according to another example 5 of the first embodiment. Figure 18 is a schematic diagram showing an example of a conversion element. Figure 19 is a schematic diagram showing an example of a conversion element. Figure 20 is a schematic diagram showing an example of a conversion element. Figure 21 is a schematic diagram showing an example of a conversion element. Figure 22 is a schematic diagram showing an example of a conversion element. Figure 23 is a schematic diagram showing an example of a conversion element. Figure 24 is a schematic diagram showing an example of a conversion element. Figure 25 is a schematic diagram of a laser irradiation device according to the second embodiment. Figure 26 is a schematic diagram of a laser irradiation device according to the second embodiment. Figure 27 is a schematic diagram showing an example of the surface shape of an optical element in the second embodiment. Figure 28 is a schematic diagram showing the intensity distribution of laser light as viewed from the optical axis direction. Figure 29 is a schematic diagram of a laser irradiation device according to another example of the second embodiment. Figure 30 is a schematic diagram of a laser irradiation device according to another example of the second embodiment. Figure 31 is a schematic diagram of a laser irradiation device according to a modified example of the second embodiment. Figure 32 is a schematic diagram of a laser irradiation device according to a modified example of the second embodiment. Figure 33 is a schematic diagram of a laser irradiation device according to another example 1 of a modified example of the second embodiment.Figure 34 is a schematic diagram of a laser irradiation device according to another example 1 of the modifications of the second embodiment. Figure 35 is a schematic diagram of a laser irradiation device according to another example 1 of the modifications of the second embodiment. Figure 36 is a schematic diagram of a laser irradiation device according to another example 2 of the modifications of the second embodiment. Figure 37 is a schematic diagram of a laser irradiation device according to another example 2 of the modifications of the second embodiment. Figure 38 is a schematic diagram of a laser irradiation device according to another example 2 of the modifications of the second embodiment. Figure 39 is a schematic diagram of a laser irradiation device according to another example 3 of the modifications of the second embodiment. Figure 40 is a schematic diagram of a laser irradiation device according to another example 3 of the modifications of the second embodiment. Figure 41 is a schematic diagram of a laser irradiation device according to another example 3 of the modifications of the second embodiment. Figure 42 is a schematic diagram of a laser irradiation device according to another example 4 of the modifications of the second embodiment. Figure 43 is a schematic diagram of a laser irradiation device according to the third embodiment. Figure 44 is a schematic diagram of a laser irradiation device according to the third embodiment. Figure 45 is a schematic diagram showing an example of the surface shape of an optical element in the third embodiment. Figure 46 is a schematic diagram showing the intensity distribution of laser light as viewed from the optical axis direction. Figure 47 is a schematic diagram of a laser irradiation device according to another example of the third embodiment. Figure 48 is a schematic diagram of a laser irradiation device according to another example of the third embodiment. Figure 49 is a schematic diagram of a laser irradiation device according to a modified example of the third embodiment. Figure 50 is a schematic diagram of a laser irradiation device according to a modified example of the third embodiment. Figure 51 is a schematic diagram of a laser irradiation device according to another example of a modified example of the third embodiment. Figure 52 is a schematic diagram of a laser irradiation device according to another example of a modified example of the third embodiment. Figure 53 is a schematic diagram of a laser irradiation device according to another example of a modified example of the third embodiment. Figure 54 is a schematic diagram of a laser irradiation device according to another example of a modified example of the third embodiment. Figure 55 is a schematic diagram of a laser irradiation device according to another example of a modified example of the third embodiment. Figure 56 is a schematic diagram of a laser irradiation device according to another example of a modified example of the third embodiment. Figure 57 is a schematic diagram of a laser irradiation device according to another example of a modified example of the third embodiment. Figure 58 is a schematic diagram of a laser irradiation device according to another example of a modification of the third embodiment. Figure 59 is a schematic diagram of a laser irradiation device according to another example of a modification of the third embodiment. Figure 60 is a schematic diagram of a laser irradiation device according to another example of a modification of the third embodiment.Figure 61 is a schematic diagram of a laser irradiation device in an example where multiple light sources are installed. Figure 62 is a schematic diagram of a laser irradiation device in an example where multiple light sources are installed. Figure 63 is a schematic diagram of a laser irradiation device in an example where multiple light sources are installed. Figure 64 is a schematic diagram of a laser irradiation device in an example where multiple light sources are installed. Figure 65 is a schematic diagram of a laser irradiation device in configuration example 1. Figure 66 is a schematic diagram of a laser irradiation device in configuration example 1. Figure 67 is a schematic diagram of a laser irradiation device in configuration example 2. Figure 68 is a schematic diagram of a laser irradiation device in configuration example 2. Figure 69 is a schematic diagram of a laser irradiation device in configuration example 3. Figure 70 is a schematic diagram of a laser irradiation device in configuration example 3. Figure 71 is a schematic diagram of a laser irradiation device in configuration example 4. Figure 72 is a schematic diagram of a laser irradiation device in configuration example 4. Figure 73 is a schematic diagram of a laser irradiation device in configuration example 5. Figure 74 is a schematic diagram of a laser irradiation device in configuration example 5.

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the attached drawings. However, this disclosure is not limited to these embodiments, and if there are multiple embodiments, they may be combinations of these embodiments.

[0011] (First Embodiment) (Configuration of Laser Irradiation Device) Figures 1 and 2 are schematic diagrams of a laser irradiation device according to the first embodiment. As shown in Figure 1, the laser irradiation device 1 according to this embodiment has a light source 10 and an optical element unit 12. The laser irradiation device 1 is a device that irradiates an object 100 with laser light L. Hereafter, the direction of propagation of the laser light L will be referred to as the Z direction, one direction along a plane perpendicular to the Z direction will be referred to as the X direction, and another direction along a plane perpendicular to the Z direction will be referred to as the Y direction. That is, the Y direction is the first direction perpendicular to the direction of propagation of the laser light L, and the X direction is the second direction perpendicular to the Z direction and the Y direction. Also, hereafter, the central axis of the laser light L along the Z direction, i.e., the optical axis, will be referred to as the optical axis AX. Figure 1 is a diagram in which the X direction is oriented in the direction of the paper, and Figure 2 is a diagram in which the Y direction is oriented in the direction of the paper.

[0012] (Light source) The light source 10 emits laser light L1 and directs the emitted laser light L1 towards the optical element unit 12.

[0013] (Laser Light) The laser light L1 emitted by the light source 10 has a predetermined light intensity distribution. In this embodiment, the laser light L1 is a single-mode laser light, and its light intensity distribution is a Gaussian distribution. The wavelength of the laser light L1 is, for example, 400 nm or more and 1600 nm or less. The laser light L1 is divergent light, and its beam width increases as it moves in the Z direction. The numerical aperture (NA), which indicates the beam width divergence angle of the laser light L1, is preferably greater than 0 and 0.5 or less, and more preferably greater than 0 and 0.4 or less. The NA is 1 / e of the maximum intensity of the laser light L1. ２ The beam width may be measured using the distance between two points that doubles the beam width. However, the characteristics of the laser light L1 are not limited to those described above. The laser light L1 may have any wavelength, and the NA value may also be arbitrary. Furthermore, the laser light L1 is not limited to being divergent light.

[0014] Furthermore, in this embodiment, the beam width of the laser beam L1 in the X direction and the beam width in the Y direction are approximately the same. More specifically, the beam width of the laser beam L1 in each direction perpendicular to the optical axis AX is approximately the same. In other words, the laser beam L1 in this embodiment is a circular Gaussian beam that appears as a circle when viewed from the optical axis AX. Here, "approximately the same" may mean that the difference between the beam widths is less than 5% of the beam width of one beam. That is, for example, if the difference between the beam width in the X direction and the beam width in the Y direction is less than 5% of the beam width in the X direction, then the beam widths in the X direction and the beam widths in the Y direction can be said to be approximately the same.

[0015] However, the laser beam L1 is not limited to having beam widths in the X direction and Y direction that are approximately the same. For example, the laser beam L1 may have beam widths in the X direction and Y direction that are not the same. That is, for example, the laser beam L1 may be an elliptical Gaussian beam that is visible as an ellipse when viewed from the optical axis AX.

[0016] (Optical Element Unit) The optical element unit 12 is a unit having multiple optical elements and is provided on the Z-direction side of the light source 10. In this embodiment, the optical element unit 12 has a collimating lens 20, an optical element 22, and a converging lens 24 as multiple optical elements. The collimating lens 20, the optical element 22, and the converging lens 24 are arranged in this order along the Z-direction from the light source 10 side.

[0017] The collimating lens 20 is an optical element that focuses light. The collimating lens 20 receives laser light L1 emitted from the light source 10, adjusts the incident laser light L1 into parallel light, and emits it. The laser light L1 emitted from the collimating lens 20 as parallel light travels in the Z direction and is incident on the optical element 22. In the examples in Figures 1 and 2, the collimating lens 20 has a planar incident surface (the surface opposite to the Z direction) and a convex exit surface (the surface on the Z direction side), but this shape is just an example, and it can be any shape that focuses light.

[0018] The optical element 22 receives laser light L1 from the collimating lens 20 (light source 10), imparts a predetermined wavefront aberration to the incident laser light L1, and then emits it. The laser light L2 emitted from the optical element 22 (the laser light L1 with the predetermined wavefront aberration imparted by the optical element 22) travels in the Z direction and enters the converging lens 24. Details of the optical element 22 will be described later.

[0019] The focusing lens 24 is an optical element that focuses light. Laser light L2 emitted from the optical element 22 is incident on the focusing lens 24. The focusing lens 24 focuses the incident laser light L2 as laser light L3 so that its focal point is aligned with the object to be illuminated 100 and emits it. In other words, the laser light L3 from the focusing lens 24 is directed toward the object to be illuminated 100 at the focal point Pf. The focal point Pf can also be said to be the position of the beam waist of the laser light L3 (the position where the beam radius is smallest). In the examples in Figures 1 and 2, the focusing lens 24 has a convex shape on the incident surface (the surface opposite to the Z direction) and a planar shape on the exit surface (the surface on the Z direction side), but this shape is just an example, and it can be any shape that focuses light.

[0020] If laser beams L1, L2, and L3 are not distinguished, they will be referred to as "laser beam L."

[0021] (Optical Element) Figure 3 is a schematic diagram of an optical element according to the first embodiment. As shown in Figure 3, the optical element 22 is an optical element that transmits laser light, and its material can be any material, but it may be made of transparent glass or resin. The optical element 22 has an incident surface 30 and an exit surface 32. The incident surface 30 is the surface of the optical element 22 opposite to the Z direction (the light source 10 side), and the exit surface 32 is the surface of the optical element 22 on the Z direction side. That is, the exit surface 32 is the surface facing the incident surface 30 in the Z direction (the surface opposite to the incident surface 30).

[0022] The optical element 22 receives laser light L1 from the collimating lens 20 (light source 10) from the incident surface 30. The laser light L1 incident from the incident surface 30 travels through the interior 31 of the optical element 22 and is emitted as laser light L2 from the exit surface 32. The optical element 22 imparts a predetermined wavefront aberration to the laser light L1 in both the X and Y directions. That is, the laser light L2 emitted from the optical element 22 has a predetermined wavefront aberration in both the X and Y directions. The predetermined wavefront aberration here refers to a wavefront aberration greater than the diffraction limit. Note that in Figure 3, the phase of the laser light L1 changes when it is incident from the incident surface 30 into the interior 31 so that it becomes the laser light L2 described above, but the refraction is negligibly small. However, the laser light L1 may be refracted to a level greater than negligible when it is incident from the incident surface 30 into the interior 31.

[0023] At least one of the incident surface 30 and the exit surface 32 of the optical element 22 is shaped such that the wavefront aberration profile of the laser light L2 in both the X and Y directions satisfies predetermined conditions. In other words, at least one of the incident surface 30 and the exit surface 32 of the optical element 22 imparts wavefront aberration to the laser light L1 such that the wavefront aberration profile in both the X and Y directions satisfies predetermined conditions. To put it another way, by passing through the optical element 22, the laser light L1 becomes laser light L2 whose wavefront aberration profile in both the X and Y directions satisfies predetermined conditions. As a result, the optical element 22 imparts predetermined wavefront aberration to the laser light L2 in both the X and Y directions, thereby appropriately suppressing non-uniformity of the light intensity of the laser light L in both the X and Y directions. Details of the predetermined conditions for the wavefront aberration profile and the shape of at least one of the incident surface 30 and the exit surface 32 will be described later.

[0024] (Wavefront Aberration) Wavefront aberration is the amount of deviation (aberration) of the wavefront of light (in this case, laser light L2) from the reference ideal wavefront. A wavefront is the plane connecting the points of equiphase light rays (a plane perpendicular to the light rays), and in the example in Figure 3, it is the wavefront W. Here, the ideal wavefront is the wavefront of parallel light, so the ideal wavefront is planar. In other words, the wavefront aberration in this embodiment represents the deviation from a planar wavefront. Note that wavefront aberration is derived from the phase of light and can be said to be an aberration that also takes into account the diffraction of light.

[0025] Furthermore, curvature is a quantity that refers to the degree of curvature of a curve or surface, and is the reciprocal of the radius of curvature, which is the radius of a circle that approximates the local curvature of the curve or surface. In other words, the radius of curvature of a wavefront (wavefront aberration) is the radius of a circle that approximates the local curvature of the wavefront (wavefront aberration) profile, and the curvature of a wavefront (wavefront aberration) is the reciprocal of its surface radius.

[0026] (Wavefront Aberration Profile in the Y Direction) Figure 4 is an explanatory diagram illustrating the wavefront in the first embodiment. Curve A1 in Figure 4 shows an example of the wavefront (wavefront aberration) profile along the Y direction of laser light (i.e., laser light L2 emitted from the optical element 22) whose wavefront (wavefront aberration) profile in the Y direction satisfies predetermined conditions. Curve A2 shows the curvature profile of the wavefront (wavefront aberration) along the Y direction of laser light (i.e., laser light L2 emitted from the optical element 22) whose wavefront aberration profile in the Y direction satisfies predetermined conditions. In other words, the predetermined conditions are satisfied if the profile is as shown in Figure 4, which will be explained later.

[0027] Curve A0 shows the light intensity distribution on the exit pupil (here, on the exit surface of the focusing lens 24) of laser light (i.e., laser light L2 emitted from the optical element 22) whose wavefront (wavefront aberration) profile in the Y direction satisfies predetermined conditions. Although the laser light L2 has already been subjected to wavefront aberration on the exit pupil, the light intensity distribution has not yet changed to be uniform and remains a Gaussian distribution. Therefore, the light intensity distribution of the laser light L2 on the exit pupil has a maximum light intensity at position Y0 on the optical axis AX, and the light intensity decreases as it moves away from position Y0.

[0028] Here, the wavefront aberration profile of the laser beam L2 is obtained by subtracting the profile of the planar ideal wavefront, i.e., a constant value, from the profile of the laser beam L2. Therefore, the wavefront profile of the laser beam L2 shown in curve A1 can also be called the wavefront aberration profile of the laser beam L2. As shown in curve A1, the wavefront (wavefront aberration) of the laser beam L2 takes a minimum value at position Y0 on the optical axis AX, is smaller than at other positions along the Y direction, and increases as it moves away from position Y0. Furthermore, the wavefront profile of the laser beam L2 has a shape that is symmetrical with respect to the optical axis AX. In addition, the wavefront (wavefront aberration) profile of the laser beam L2 is continuous and differentiable along the Y direction. Furthermore, the value WA0, which is the difference between the minimum and maximum values ​​of the wavefront (wavefront aberration) of the laser beam L2, is a length of more than one wavelength of the laser beam L2.

[0029] As shown in curve A2, in the wavefront curvature profile of laser light L2 that satisfies predetermined conditions, the curvature of the wavefront (wavefront aberration) is greater near the optical axis AX, or more specifically, on the optical axis AX, than at positions further away from the optical axis AX. Furthermore, the curvature of the wavefront (wavefront aberration) is smoothly continuous along the Y direction and is differentiable. In addition, the wavefront curvature profile of laser light L2 has a shape that is symmetrical with respect to the optical axis AX, but is not limited to that.

[0030] Here, as shown in Figure 4, the first position Y1 is defined as a position between the second position Y2 and the third position Y3 in the Y direction. This first position Y1 is closer to the optical axis AX (i.e., position Y0) than the second position Y2 and the third position Y3. In this embodiment, the first position Y1 is on position Y0, i.e., the optical axis AX, and the second position Y2 and the third position Y3 are at the same distance from the first position Y1. In this case, as shown in curve A2, the curvature of the wavefront (wavefront aberration) of the laser light L2 is an upward-convex peak value (maximum value) at the first position Y1 (here, position Y0), and decreases as it moves away from the first position Y1. Also, the value of the wavefront curvature at the second position Y2 and the third position Y3 is smaller than the value at the first position Y1, and is a downward-convex peak value (minimum value). In other words, the wavefront curvature profile of the laser beam L2 has a peak value (maximum value) at the first position Y1, and the value decreases as you move away from the first position Y1 to the second position Y2 and the third position Y3. Then, from the second position Y2 and the third position Y3, the value of the wavefront curvature profile increases as you move further away from the first position Y1. Thus, the wavefront curvature of the laser beam L2 is greater near the optical axis AX than in the surrounding areas. In this embodiment, the first position Y1 was on the optical axis AX, but it does not have to be on the optical axis AX as long as it is closer to the optical axis AX than the second position Y2 and the third position Y3.

[0031] Here, in the light intensity distribution (curve A0) on the exit pupil of the laser beam L2, the light intensity is 1 / e of the light intensity at position Y0. ２Let position Yg be the position where the curvature doubles. Let length Dg be the length along the Y direction from position Y0 to position Yg. Let length Dm be the length along the Y direction from position Y0 to the third position Y3. Position Yh is a position between position Y0 (first position Y1) and the third position Y3, where the curvature at position Yh is the average of the curvature at position Y0 (first position Y1) and the curvature at the third position Y3. Let length Dh be the length from position Y0 (first position Y1) to position Yh. Here, the third position Y3 is a position other than position Y0 where the peak value (extremum) of curvature is taken, and is the position closest to position Y0 (optical axis AX). In this case, it is desirable that the curvature of the wavefront of the laser beam L2, length Dh, is smaller than length Dg.

[0032] Furthermore, in the light intensity distribution (curve A0) of the laser beam L2 on the exit pupil, position Yf is defined as the position where the light intensity is half that of position Y0. The length from position Y0 to position Yf is defined as length Df. Also, position Yr is defined as the position of the exit pupil, that is, the position of the end of the optical element 22 or focusing lens 24 in the Y direction. The length from position Y0 to position Yr is defined as length Dr. In this case, length Df refers to the length of the laser beam L2 in the Y direction at the exit pupil position. Length Dr refers to the length from the center to the end of the optical element 22 or focusing lens 24, i.e., the radius. In this case, it is preferable that length Df is smaller than length Dr. That is, the relationship between length Df and length Dr means that the laser beam L2 is focused in the Y direction such that the length Df along the Y direction in the region where the intensity of the laser beam L2 is half or more is smaller than the length Dr of the exit pupil.

[0033] (Wavefront Aberration Profile in the X Direction) Figure 5 is an explanatory diagram illustrating the wavefront in the first embodiment. Curve A1 in Figure 5 shows an example of the wavefront (wavefront aberration) profile along the X direction of laser light (i.e., laser light L2 emitted from the optical element 22) whose wavefront (wavefront aberration) profile in the X direction satisfies predetermined conditions. Curve A2 shows the curvature profile of the wavefront (wavefront aberration) along the X direction of laser light (i.e., laser light L2 emitted from the optical element 22) whose wavefront aberration profile in the X direction satisfies predetermined conditions. In other words, the predetermined conditions are satisfied if the profile is as shown in Figure 5, which will be explained later.

[0034] Curve A0 shows the light intensity distribution on the exit pupil (here, on the exit surface of the focusing lens 24) of laser light (i.e., laser light L2 emitted from the optical element 22) whose wavefront (wavefront aberration) profile in the X direction satisfies predetermined conditions. Note that although the laser light L2 has already been subjected to wavefront aberration on the exit pupil, the light intensity distribution has not yet changed to become uniform and remains a Gaussian distribution. Therefore, the light intensity distribution of the laser light L2 on the exit pupil has a maximum light intensity at position X0 on the optical axis AX, and the light intensity decreases as it moves away from position X0.

[0035] As shown in curve A1, the wavefront (wavefront aberration) of the laser beam L2 takes a minimum value at position X0 on the optical axis AX, is smaller than at other positions along the X direction, and increases as it moves away from position X0. Furthermore, the wavefront profile of the laser beam L2 is symmetrical with respect to the optical axis AX. In addition, the wavefront (wavefront aberration) profile of the laser beam L2 is continuous and differentiable along the X direction. Moreover, the value WA0, which is the difference between the minimum and maximum values ​​of the wavefront (wavefront aberration) of the laser beam L2, is longer than one wavelength of the laser beam L2.

[0036] As shown in curve A2, in the wavefront curvature profile of laser light L2 that satisfies predetermined conditions, the curvature of the wavefront (wavefront aberration) is greater near the optical axis AX, or more specifically, on the optical axis AX, than at positions further away from the optical axis AX. Furthermore, the curvature of the wavefront (wavefront aberration) is smoothly continuous along the X direction and is differentiable. In addition, the wavefront curvature profile of laser light L2 is symmetrical with respect to the optical axis AX, but is not limited to that.

[0037] Here, as shown in Figure 5, the first position X1 is defined as a position between the second position X2 and the third position X3 in the X direction. This first position X1 is closer to the optical axis AX (i.e., position X0) than the second position X2 and the third position X3. In this embodiment, the first position X1 is on position X0, i.e., the optical axis AX, and the second position X2 and the third position X3 are at the same distance from the first position X1. In this case, as shown in curve A2, the curvature of the wavefront (wavefront aberration) of the laser light L2 is an upward-convex peak value (maximum value) at the first position X1 (here, position X0), and decreases as it moves away from the first position X1. Also, the value of the wavefront curvature at the second position X2 and the third position X3 is smaller than the value at the first position X1, and is a downward-convex peak value (minimum value). In other words, the wavefront curvature profile of the laser beam L2 has a peak value (maximum value) at the first position X1, and the value decreases as you move away from the first position X1 to the second position X2 and the third position X3. Then, from the second position X2 and the third position X3, the value of the wavefront curvature profile increases as you move further away from the first position X1. Thus, the wavefront curvature of the laser beam L2 is greater near the optical axis AX than in the surrounding areas. In this embodiment, the first position X1 was on the optical axis AX, but it does not have to be on the optical axis AX as long as it is closer to the optical axis AX than the second position X2 and the third position X3.

[0038] Here, in the light intensity distribution (curve A0) on the exit pupil of the laser beam L2, the light intensity is 1 / e of the light intensity at position X0. ２Let position Xg be the position where the curvature doubles. Let length Dg be the length along the X direction from position X0 to position Xg. Let length Dm be the length along the X direction from position X0 to the third position X3. Position Xh is a position between position X0 (first position X1) and the third position X3, where the curvature at position Xh is the average of the curvature at position X0 (first position X1) and the curvature at the third position X3. Let length Dh be the length from position X0 (first position X1) to position Xh. Here, the third position X3 is a position other than position X0 where the peak value (extremum) of curvature is taken, and is the position closest to position X0 (optical axis AX). In this case, it is desirable that the curvature of the wavefront of the laser beam L2, length Dh, is smaller than length Dg.

[0039] Furthermore, in the light intensity distribution (curve A0) of the laser beam L2 on the exit pupil, position Xf is defined as the position where the light intensity is half that of position X0. The length from position X0 to position Xf is defined as length Df. Also, position Xr is defined as the position of the exit pupil, that is, the position of the end of the optical element 22 or focusing lens 24 in the X direction. The length from position X0 to position Xr is defined as length Dr. In this case, length Df refers to the length of the laser beam L2 in the X direction at the exit pupil position. Length Dr refers to the length from the center to the end of the optical element 22 or focusing lens 24, i.e., the radius. In this case, it is preferable that length Df is smaller than length Dr. That is, this relationship between length Df and length Dr means that the laser beam L2 is focused in the X direction such that the length Df along the X direction in the region where the intensity of the laser beam L2 is half or more is smaller than the length Dr of the exit pupil.

[0040] (Wavefront aberration profile in other directions) In this embodiment, the wavefront (wavefront aberration) profile of the laser light L2 satisfies the predetermined conditions described above not only in the X and Y directions, but also in each direction perpendicular to the Z direction. That is, in this embodiment, at least one of the incident surface 30 and the exit surface 32 of the optical element 22 is shaped such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction satisfies the predetermined conditions.

[0041] (Relationship between profiles of wavefront aberrations in each direction) In the present embodiment, the profile of the wavefront of the laser beam L2 in the X direction is the same as the profile of the wavefront of the laser beam L2 in the Y direction. Also, the curvature profile of the wavefront of the laser beam L2 in the X direction is the same as the curvature profile of the wavefront of the laser beam L2 in the Y direction. Furthermore, in the present embodiment, the profiles of the wavefronts of the laser beam L2 in the directions orthogonal to the Z direction are equal to each other, and the curvature profiles of the wavefronts of the laser beam L2 in the directions orthogonal to the Z direction are equal to each other. Thus, by having the same profiles of the wavefronts and curvatures in each direction, it is possible to obtain a laser beam with a circular beam shape in which non-uniformity of the light intensity distribution is suppressed in both the X and Y directions. Also, when the laser beam L1 incident on the optical element 22 is elliptical, it is possible to obtain a laser beam with an elliptical beam shape. Note that having the same profile means that the respective profiles are congruent in shape, and it can also be said that the slopes, minimum values, and maximum values of the profiles are the same.

[0042] However, the profile of the wavefront of the laser beam L2 in the X direction and the profile of the wavefront of the laser beam L2 in the Y direction may be different, and the curvature profile of the wavefront of the laser beam L2 in the X direction and the curvature profile of the wavefront of the laser beam L2 in the Y direction may be different. Thus, by having different profiles of the wavefronts and curvatures in the X and Y directions, it is possible to obtain a laser beam with an elliptical beam shape in which non-uniformity of the light intensity distribution is suppressed in both the X and Y directions. Also, when the laser beam L1 incident on the optical element 22 is elliptical, it is also possible to obtain a laser beam with a circular beam shape by adjusting the installation angle between the laser beam L 1 (light source 10) and the optical element 22 as viewed from the optical axis direction.

[0043] (Intensity Distribution of Laser Light) According to this embodiment, the curvature profile of the laser light L2 satisfies the above predetermined conditions in both the Y and X directions, thereby suppressing non-uniformity of the light intensity in both the Y and X directions. Figures 6 and 7 show examples of the light intensity distribution of a laser according to this embodiment. Curve A3 in Figure 6 shows an example of the light intensity distribution along the Y direction of a laser light whose wavefront (wavefront aberration) profile in the Y direction satisfies the predetermined conditions. Curve A3 in Figure 7 shows an example of the light intensity distribution along the X direction of a laser light whose wavefront (wavefront aberration) profile in the X direction satisfies the predetermined conditions. Curve A3 shows the light intensity distribution of the laser light L at the focal position Pf. As shown in curve A3, it can be seen that the non-uniformity of the light intensity distribution of the laser light L is suppressed in both the Y and X directions at the focal position Pf. In other words, the laser light L can have a top-hat shaped profile in both the Y and X directions.

[0044] Figure 8 is a schematic diagram showing the intensity distribution of laser light as viewed from the optical axis direction. Figure 8 is a schematic diagram showing the intensity distribution of laser light L emitted from the optical element 22 as viewed from direction Z. Figure 8 shows the intensity distribution of laser light L at the focal position Pf. As shown in Figure 8, the laser light L at the focal position Pf has a circular beam shape with beam diameters in the X and Y directions being approximately equal. However, as mentioned above, the beam shape of the laser light L may be elliptical.

[0045] (Shape of the optical element) FIG. 9 is a schematic diagram showing an example of the surface shape of the optical element. At least one of the incident surface 30 and the exit surface 32 of the optical element 22 may have an arbitrary shape that allows the profile of the wavefront of the laser beam L2 to satisfy a predetermined condition. However, for example, as shown in FIG. 9, at least one of the incident surface 30 and the exit surface 32 is preferably aspherical so that the profile of the wavefront of the laser beam L2 can satisfy a predetermined condition. For example, a line passing through the center of the optical element 22 along at least one of the incident surface 30 and the exit surface 32 and extending in the X direction may be a spline curve with a non-constant radius of curvature. Also, for example, a line passing through the center of the optical element 22 along at least one of the incident surface 30 and the exit surface 32 and extending in the Y direction may be a spline curve with a non-constant radius of curvature. Furthermore, as shown in FIG. 9, in the present embodiment, lines passing through the center of the optical element 22 and extending in each direction orthogonal to the Z direction along at least one of the incident surface 30 and the exit surface 32 (the incident surface 30 in the example of FIG. 9) are spline curves with non-constant radii of curvature. In the examples of FIGS. 1 to 3 and 9, at least one of the incident surface 30 and the exit surface 32 is an aspherical concave shape, but it is not limited thereto and may be an aspherical convex shape. When at least one of the incident surface 30 and the exit surface 32 is concave, the depth of the concave (the distance in the Z direction between the deepest part of the concave and the periphery of the concave) is preferably not less than 1 μm and not more than 100 μm. Thereby, aberration can be appropriately imparted. When at least one of the incident surface 30 and the exit surface 32 is convex, the height of the convex (the distance in the Z direction between the highest part of the convex and the periphery of the convex) is preferably not less than 1 μm and not more than 100 μm. Thereby, aberration can be appropriately imparted.

[0046] More specifically, at least one of the incident surface 30 and the exit surface 32 may have a shape that satisfies the following equation (1).

[0047] z = τ(a) / (1 - n) ··· (1)

[0048] Here, z represents the surface coordinates in the Z direction of at least one of the incident surface 30 and the exit surface 32. τ(a) represents the wavefront (wavefront aberration) of the laser light L2 at a predetermined position a in direction a. n represents the refractive index of the optical element 22 at the wavelength of the laser light L1 (laser light L2). In other words, equation (1) represents a profile showing the surface coordinates in the Z direction of at least one of the incident surface 30 and the exit surface 32 at each position along direction a. Direction a is the direction perpendicular to the Z direction. That is, for example, if the curvature profile in the X direction satisfies predetermined conditions, direction a points to the X direction, and if the curvature profile in the Y direction satisfies predetermined conditions, direction a points to the Y direction. Also, if the curvature profiles in each direction perpendicular to the Z direction satisfy predetermined conditions, direction a points to each direction perpendicular to the Z direction.

[0049] In the examples shown in Figures 1 to 3, the incident surface 30 has a shape that allows the curvature profile of the laser beam L2 to satisfy predetermined conditions, while the exit surface 32 does not have a shape that allows the curvature profile of the laser beam L2 to satisfy predetermined conditions, and is, for example, planar. However, it is not limited to this, and the incident surface 30 does not have to have a shape that allows the curvature profile of the laser beam L2 to satisfy predetermined conditions, nor does the exit surface 32 have to have a shape that allows the curvature profile of the laser beam L2 to satisfy predetermined conditions. Furthermore, both the incident surface 30 and the exit surface 32 may have shapes that allow the curvature profile of the laser beam L2 to satisfy predetermined conditions.

[0050] (Effective Diameter) As shown in Figure 3, the effective diameter of the optical element 22 is defined as the effective diameter D1, and the beam diameter of the laser light L1 at the position where it enters the optical element 22 (incident surface 30) is defined as the beam diameter D2. The effective diameter D1 refers, for example, to the diameter of the aspherical region of at least one of the incident surface 30 and the exit surface 32. The beam diameter D2 is 1 / e of the maximum intensity of the laser light L1. ２This refers to the distance between two points that is doubled. In this case, the ratio of the effective diameter D1 to the beam diameter D2 is preferably 1.5 or more, and more preferably 2.0 or more. Furthermore, the ratio of the effective diameter D1 to the beam diameter D2 is preferably 1.5 or more and 3.0 or less, and more preferably 2.0 or more and 2.5 or less. By making the effective diameter D1 larger than the beam diameter D2 in this way, the shape accuracy of the top-hat-shaped profile of the laser beam L3 can be increased, and a more stable profile can be obtained. In addition, by setting the upper limit of the ratio of the effective diameter D1 to the beam diameter D2 as described above, it is possible to suppress the size of the optical element 22 from becoming too large, and thus increase its versatility.

[0051] In this embodiment, it is preferable that the ratio of the effective diameter D1 to the beam diameter D2 satisfies the above range in both the X and Y directions. By having an effective diameter D1 larger than the beam diameter D2 in both the X and Y directions, the shape accuracy of the top-hat-shaped profile of the laser beam L3 can be increased, and a more stable profile can be obtained.

[0052] However, for example, if the optical element 22 has a shape that satisfies a predetermined condition for the curvature profile of the laser beam L2 in the Y direction, but does not satisfy the predetermined condition for the curvature profile of the laser beam L2 in the X direction, thus resulting in aberration-free operation in the X direction, then the laser beam L3 will be a long line in the Y direction and will have a top-hat shaped profile in the Y direction. In such a case, since the X direction is less affected by the shape of the laser beam L1, the ratio of the effective diameter D1 to the beam diameter D2 may be set to satisfy the above range only in the Y direction. In this case, the ratio of the effective diameter D1 to the beam diameter D2 in the X direction may be lower than the ratio of the effective diameter D1 to the beam diameter D2 in the Y direction.

[0053] (Effects) As described above, at least one of the incident surface 30 and the exit surface 32 of the optical element 22 according to this embodiment has a shape such that the curvature profile of the laser light L2 satisfies predetermined conditions in both the Y and X directions. This makes it possible to suppress non-uniformity of light intensity in both the Y and X directions. Therefore, according to this embodiment, the optical element 22 that can suppress non-uniformity of light intensity can be used in various specifications, making it highly versatile and contributing to cost reduction. Furthermore, it is possible to extend the function of the optical element 22 or stabilize its performance.

[0054] Furthermore, the optical element 22 of this embodiment has a shape such that the curvature profile of the laser beam L2 satisfies predetermined conditions in each direction orthogonal to the Z direction. Therefore, according to this embodiment, it is possible to provide a circular or elliptical laser beam L3 with uniform light intensity in both the Y and X directions.

[0055] (Another Example 1 of the First Embodiment) Next, another example 1 of the first embodiment will be described. In this other example 1, the parts that have the same configuration as the first embodiment will not be described. Figures 10 and 11 are schematic diagrams of a laser irradiation device according to this other example 1 of the first embodiment.

[0056] In the first embodiment, the optical element 22 is provided between the collimating lens 20 and the converging lens 24 in the Z direction, but the position of the optical element 22 relative to other optical elements in the Z direction is not limited to this and may be arbitrary. For example, as shown in Figure 10, the optical element 22 may be provided on the opposite side of the Z direction from the collimating lens 20 (between the light source 10 and the collimating lens 20). Alternatively, as shown in Figure 11, the optical element 22 may be provided on the Z side from the converging lens 24 (between the converging lens 24 and the object to be illuminated 100).

[0057] Furthermore, when the optical element 22 is placed in a section where the laser beam L is divergent, as shown in Figure 10, or when the optical element 22 is placed in a section where the laser beam L is convergent, as shown in Figure 11, the numerical aperture (NA) of the laser beam L1 when the optical element 22 is placed in a divergent section as in Figure 10 and the numerical aperture (NA) of the laser beam L3 when the optical element 22 is placed in a convergent section as in Figure 11 are preferably greater than 0 and 0.2 or less, and more preferably greater than 0 and 0.1 or less.

[0058] (Another Example 2 of the First Embodiment) Next, another example 2 of the first embodiment will be described. In this other example 2, the parts that have the same configuration as the first embodiment will not be described. Figures 12 and 13 are schematic diagrams of a laser irradiation device according to this other example 2 of the first embodiment.

[0059] In the first embodiment, the laser irradiation device 1 had a collimating lens 20 that made the laser light L into parallel light and a converging lens 24 that made the laser light L into focused light. However, the type and number of optical elements other than the optical element 22 are not limited to these and can be arbitrary. For example, as shown in Figures 12 and 13, the laser irradiation device 1 may have a condensing lens 20A instead of the two elements, the collimating lens 20 and the converging lens 24. The condensing lens 20A is an optical element that focuses light. In this example, the condensing lens 20A is an element that makes diffuse light into focused light. In the example of Figures 12 and 13, the incident surface and the exit surface of the condensing lens 20A are convex, but their shape can be arbitrary. In this example, the optical element 22 may be provided on the opposite side of the Z direction from the condensing lens 20A (between the light source 10 and the condensing lens 20A), as shown in Figure 12, or it may be provided on the Z direction side from the condensing lens 20A (between the condensing lens 20A and the object to be illuminated 100), as shown in Figure 13.

[0060] Alternatively, for example, the laser irradiation device 1 may not have a focusing lens 24, but instead have a collimating lens 20 and an optical element 22. In this case, the optical element 22 is given a focusing function to focus light. That is, the optical element 22 receives the laser light L1, which has been made into parallel light by the collimating lens 20, and focuses it while adding the above-mentioned wavefront aberration to the laser light L1, thereby emitting laser light L2 (laser light L3), which is focused light with wavefront aberration.

[0061] Alternatively, for example, the laser irradiation device 1 may not have a collimating lens 20, but instead have an optical element 22 and a focusing lens 24. In this case, the optical element 22 is given a focusing function (a function to collimate divergent light into parallel light). That is, the optical element 22 receives the laser light L1, which is divergent light, and focuses it while imparting the above-mentioned wavefront aberration to the laser light L1, thereby emitting the laser light L2, which is parallel light with wavefront aberration.

[0062] (Another Example 3 of the First Embodiment) Next, another example 3 of the first embodiment will be described. In this other example 3, the parts that have the same configuration as the first embodiment will not be described. Figures 14 and 15 are schematic diagrams of a laser irradiation device according to this other example 3 of the first embodiment.

[0063] As shown in Figure 14, the laser irradiation device 1 of the other example 3 is a Keplerian type irradiation device. The laser irradiation device 1 of the other example 3 has a light source 10, a collimating lens 20, an optical element 22, and a focusing lens 24, as well as lenses 26A and 26B. Lenses 26A and 26B constitute a Keplerian beam expander optical system.

[0064] Lens 26A is an optical element that focuses light. In the examples of Figures 14 and 15, lens 26A is an element that focuses parallel light into focused light. In the examples of Figures 14 and 15, the incident surface of lens 26A is convex and the exit surface is planar, but its shape can be arbitrary. Lens 26A is provided on the Z-direction side of collimating lens 20, and more specifically, it is provided between collimating lens 20 and focusing lens 24 in the Z-direction.

[0065] Lens 26B is an optical element that converts diffused light into parallel light. In the examples shown in Figures 14 and 15, the incident surface of lens 26B is planar and the exit surface is convex, but its shape can be arbitrary. Lens 26B is provided on the Z-direction side of lens 26A, and more specifically, it is provided between lens 26A and the converging lens 24 in the Z-direction.

[0066] The optical element 22 is provided between lens 26A and lens 26B in the Z direction. The optical element 22 may be provided between lens 26A and lens 26B on the opposite side of the Z direction from the focal point of the laser beam L, as shown in Figure 14, or it may be provided between lens 26A and lens 26B on the Z side of the focal point of the laser beam L, as shown in Figure 15.

[0067] In this example, the laser light L emitted from the light source 10 passes through the collimating lens 20 to become parallel light, passes through lens 26A to converge and focus, then diffuses, passes through lens 26B to become parallel light, passes through the converging lens 24 to become focused light, and irradiates the object 100. In the example in Figure 14, the laser light L passes through the optical element 22 between lens 26A and lens 26B at a position opposite to the focal point in the Z direction, thereby introducing wavefront aberration. In the example in Figure 15, the laser light L passes through the optical element 22 between lens 26A and lens 26B at a position on the Z side of the focal point, thereby introducing wavefront aberration.

[0068] In this way, by applying the optical element 22 to the Keplerian beam expander optical system, non-uniformity of light intensity can be appropriately suppressed, even when the input or output beam diameter is large. Furthermore, by appropriately positioning the optical element 22 at a location where the beam diameter of the incident laser light L corresponds to the effective diameter of the optical element 22, fine adjustment of the installation position in the optical axis direction is possible, so that non-uniformity of light intensity can be appropriately suppressed even if there is variation in the beam spread of the light source 10. In other words, the optical element 22 can be easily repurposed for systems with different beam diameters by appropriately adjusting its installation position. Also, by placing the optical element 22 in the Keplerian beam expander optical system, smaller optical elements 22 can be reused. In addition, depending on the application, if it is possible to combine the optical element 22 with a collimator or focusing lens, the number of lenses can be reduced. That is, for example, the number of lenses can be reduced by integrating the optical element 22 with at least one of the collimating lens 20, focusing lens 24, lens 26A, and lens 26B. Alternatively, the collimating lens 20 and lens 26A may be treated as an integrated optical element, with the collimating lens 20 being endowed with the function of lens 26A. Furthermore, the lens 26B and focusing lens 24 may be treated as an integrated optical element, with the focusing lens 24 being endowed with the function of lens 26B.

[0069] (Another Example 4 of the First Embodiment) Next, another example 4 of the first embodiment will be described. In this other example 4, the parts that have the same configuration as the first embodiment will not be described. Figure 16 is a schematic diagram of a laser irradiation device according to this other example 4 of the first embodiment.

[0070] As shown in Figure 16, the laser irradiation device 1 of another example 4 is a Galilean irradiation device. The laser irradiation device 1 of another example 4 has a light source 10, a collimating lens 20, an optical element 22, and a focusing lens 24, as well as lenses 26C and 26D. Lenses 26C and 26D constitute a Galilean beam expander optical system.

[0071] Lens 26C is an optical element that diffuses light. In the example shown in Figure 16, lens 26C is an element that converts parallel light into divergent light. In the example shown in Figure 16, the incident surface of lens 26C is concave and the exit surface is planar, but its shape can be arbitrary. Lens 26C is provided on the Z-direction side of collimating lens 20, and more specifically, it is provided between collimating lens 20 and focusing lens 24 in the Z-direction.

[0072] Lens 26D is an optical element that focuses light. In the example in Figure 16, lens 26D is an element that converts diffused light into parallel light. In the example in Figure 16, the incident surface of lens 26D is planar and the exit surface is convex, but its shape can be arbitrary. Lens 26D is provided on the Z-direction side of lens 26C, and more specifically, it is provided between lens 26C and the focusing lens 24 in the Z-direction.

[0073] The optical element 22 is provided between lens 26C and lens 26D in the Z direction.

[0074] In this example, the laser light L emitted from the light source 10 passes through the collimating lens 20 to become parallel light, passes through lens 26C to become divergent light, passes through lens 26D to become parallel light again, passes through the converging lens 24 to become focused light, and is then irradiated onto the object to be irradiated 100. The laser light L passes through the optical element 22 between lens 26C and lens 26D, and wavefront aberration is introduced.

[0075] In this way, by applying the optical element 22 to the Galilean beam expander optical system, non-uniformity of light intensity can be appropriately suppressed, even when the input or output beam diameter is large. Furthermore, by appropriately positioning the optical element 22 at a location where the beam diameter of the incident laser light L corresponds to the effective diameter of the optical element 22, fine adjustment of the installation position in the optical axis direction is possible, so that non-uniformity of light intensity can be appropriately suppressed even if there is variation in the beam spreading of the light source 10. In other words, the optical element 22 can be easily adapted to systems with different beam diameters by appropriately adjusting its installation position. Also, depending on the application, if it is possible to combine the optical element 22 with a collimator or focusing lens, the number of lenses can be reduced. That is, for example, the number of lenses can be reduced by integrating the optical element 22 with the collimating lens 20, the focusing lens 24, lens 26C, and at least one of lens 26C.

[0076] (Another Example 5 of the First Embodiment) Next, another example 5 of the first embodiment will be described. In other example 5, the parts that have the same configuration as the first embodiment will not be described. Figure 17 is a schematic diagram of a laser irradiation device according to other example 5 of the first embodiment. In other example 5, the light source 10 emits an elliptical laser beam L1, and the conversion element 27 converts the elliptical laser beam L1 into a circular laser beam L1, which is different from the first embodiment. Note that other example 5 is also applicable to the first to other examples 4. That is, in the first to other examples 4, the conversion element 27 may be provided to convert the elliptical laser beam L1 from the light source 10 into a circular laser beam L1 using the conversion element 27.

[0077] The laser irradiation device 1 includes a light source 10, a collimating lens 20, an optical element 22, a focusing lens 24, and a conversion element 27. In this example, the light source 10 emits an elliptical laser beam L1. The conversion element 27 is an optical element that has the function of changing the shape of the laser beam L when viewed from the optical axis direction. In this example, the conversion element 27 converts the elliptical laser beam L1 into a circular laser beam L1. The conversion element 27 may be provided between the collimating lens 20 and the optical element 22 in the Z direction. That is, in this example, the elliptical laser beam L emitted from the light source 10 passes through the collimating lens 20 to become parallel light, passes through the conversion element 27 to become circular parallel light, passes through the optical element 22 to have wavefront aberration added, passes through the focusing lens 24 to become focused light, and is irradiated onto the object to be irradiated 100. Hereafter, the elliptical laser beam L1 incident on the conversion element 27 will be referred to as laser beam L1A as appropriate, and the circular laser beam L1 that passes through the conversion element 27 and is emitted will be referred to as laser beam L1B as appropriate.

[0078] The conversion element 27 may have any configuration capable of converting an elliptical laser beam L1 into a circular laser beam L1, but an example configuration will be described below. Figures 18 to 24 are schematic diagrams showing examples of the conversion element.

[0079] As shown in Figure 18, the conversion element 27 may be composed of multiple (for example, two) prisms. The conversion element 27 in this example can also be described as an anamorphic prism pair.

[0080] In the example shown in Figure 19, the conversion element 27 may combine the functions of a collimating lens 20 and the function of converting laser light L1A to laser light L1B; in other words, the conversion element 27 and the collimating lens 20 may be integrated. In this case, for example, the conversion element 27 may be composed of multiple (for example, two) cylindrical lenses. The conversion element 27 is arranged such that the curved surface of one cylindrical lens is curved in the X direction, and the curved surface of the other cylindrical lens is curved in the Y direction. In this example, the laser light L1A, which is an elliptical diffuse light emitted from the light source 10, is converted into a circular parallel light, the laser light L1B, in the conversion element 27.

[0081] As shown in Figures 20 and 21, the conversion element 27 may be composed of cylindrical lenses 27A and 27B. In this example, the cylindrical lens 27A has a convex curved surface as its incident surface and a flat surface as its exit surface. The cylindrical lens 27B is located on the Z-direction side of the cylindrical lens 27A, has a flat surface as its incident surface and a convex curved surface as its exit surface. The cylindrical lenses 27A and 27B are arranged so that their curved surfaces are curved in the direction along the major axis of the ellipse of the laser beam L1A (the Y-direction in Figures 20 and 21). As a result, the elliptical parallel laser beam L1A is converted into a circular parallel laser beam L1B by narrowing the major axis of the ellipse in the cylindrical lenses 27A and 27B. In this example, as shown in Figure 20, the beam diameters of laser beam L1A and laser beam L1B are equal in the X direction, and as shown in Figure 21, the beam diameter of laser beam L1A in the Y direction may be larger than the beam diameter of laser beam L1B in the Y direction. Also, the beam diameter of laser beam L1B in the Y direction may be equal to the beam diameter in the X direction of laser beam L1B.

[0082] As shown in Figures 22 and 23, the conversion element 27 may be composed of cylindrical lenses 27C and 27D. In this example, the cylindrical lens 27C has a convex curved surface as its incident surface and a flat surface as its exit surface. The cylindrical lens 27D is located on the Z-direction side of the cylindrical lens 27C, has a flat surface as its incident surface and a concave curved surface as its exit surface. The cylindrical lenses 27C and 27D are arranged so that their curved surfaces are curved in the direction along the major axis of the ellipse of the laser beam L1A (the Y-direction in Figures 22 and 23). As a result, the elliptical parallel laser beam L1A is converted into a circular parallel laser beam L1B by widening the minor axis of the ellipse in the cylindrical lenses 27C and 27D. In this example, as shown in Figure 22, the beam diameters of laser beam L1A and laser beam L1B are equal in the X direction, and as shown in Figure 23, the beam diameter of laser beam L1A in the Y direction may be larger than the beam diameter of laser beam L1B in the Y direction. Also, the beam diameter of laser beam L1B in the Y direction may be equal to the beam diameter in the X direction of laser beam L1B.

[0083] As shown in Figure 24, the conversion element 27 may consist of a focusing lens 27E, an optical fiber 27F, and a lens 27G. The focusing lens 27E is an element that focuses light, and its shape may be arbitrary. The optical fiber 27F is positioned on the Z-direction side of the focusing lens 27E and is a single-mode optical fiber extending in the Z-direction. The incident surface of the optical fiber 27F (the end opposite to the Z-direction) is preferably located at the focal position of the laser light L emitted from the focusing lens 27E. The lens 27G is an element that focuses light (more specifically, an element that collimates divergent light into parallel light), and its shape may be arbitrary. In this example, the laser light L1A, which is an elliptical parallel light, is converted into focused light by the focusing lens 27E, incident on the optical fiber 27F, emitted from the optical fiber 27F as circular diffuse light, passes through the lens 27G, and is emitted as circular parallel light, laser light L1B.

[0084] Thus, in this example, by providing the conversion element 27, the elliptical laser beam L1 can be converted into a circular laser beam L1, and then wavefront aberration can be introduced by the optical element 22. Therefore, according to this example, it can be applied to a light source 10 that emits an elliptical laser beam L1, thus increasing its versatility.

[0085] (Second Embodiment) Next, a second embodiment will be described. The second embodiment differs from the first embodiment in that the slope of the wavefront profile of the laser beam L2 is smaller in the direction between the X direction and the Y direction (third direction). In the second embodiment, the parts that have the same configuration as the first embodiment will not be described.

[0086] Figures 25 and 26 are schematic diagrams of a laser irradiation device according to the second embodiment. In the second embodiment, at least one of the incident surface 30 and the exit surface 32 of the optical element 22 has a shape such that the wavefront aberration profile of the laser light L2 in both the X and Y directions satisfies predetermined conditions, similar to the first embodiment. Therefore, in the second embodiment as well, non-uniformity of light intensity can be suppressed in both the Y and X directions.

[0087] Furthermore, in the second embodiment, the wavefront profile of the laser light L2 in the X direction and the wavefront profile of the laser light L2 in the Y direction are the same.

[0088] On the other hand, the incident surface 30 and the exit surface 32 of the optical element 22 according to the second embodiment have a shape such that the wavefront aberration profile of the laser light L2 in the third direction between the X and Y directions satisfies predetermined conditions, but the slope of the wavefront aberration profile is greater than the slope of the wavefront aberration profile in the X and Y directions. That is, in the second embodiment, the wavefront aberration profile of the laser light L2 in the third direction satisfies predetermined conditions in the same way as in the X and Y directions, but the slope of the wavefront aberration profile is greater than that of the profiles in the X and Y directions. Also, in the second embodiment, the curvature profile of the wavefront aberration of the laser light L2 in the third direction satisfies predetermined conditions in the same way as in the X and Y directions, but the slope and maximum value are greater than those of the profiles in the X and Y directions. The third direction is the direction between the X and Y directions, and refers to the direction in which the angle with respect to the X direction is 45° when the angle with respect to the X direction is 90°.

[0089] Furthermore, in the second embodiment, the wavefront aberration profile of the laser light L2 in each direction orthogonal to the Z direction increases in slope as you move from the X direction to the third direction, and decreases as you move from the third direction to the Y direction. That is, for example, if the X direction is the 0° direction, the third direction is the 45° direction, and the Y direction is the 90° direction, and the wavefront aberration profiles of the laser light L2 in each direction from the 0° direction to the 45° direction are arranged in this order, the slope of each profile will gradually increase in the order they are arranged. On the other hand, if the wavefront aberration profiles of the laser light L2 in each direction from the 45° direction to the 90° direction are arranged in this order, the slope of each profile will gradually decrease in the order they are arranged.

[0090] Figure 27 is a schematic diagram showing an example of the surface shape of an optical element in the second embodiment. In the second embodiment, at least one of the incident surface 30 and the exit surface 32 may be any shape such that the wavefront profile of the laser light L2 satisfies predetermined conditions in the X, Y, and third directions, and the inclination in the third direction is large, but it is preferable that it be aspherical, as shown in Figure 27, for example. In the examples of Figures 25 to 27, at least one of the incident surface 30 and the exit surface 32 is an aspherical concave shape, but it is not limited to this and may be an aspherical convex shape. When at least one of the incident surface 30 and the exit surface 32 is concave, it is preferable that the depth of this concave shape (the distance in the Z direction between the deepest part of the concave and the periphery of the concave) is 1 μm or more and 100 μm or less. This allows for appropriate aberration to be introduced. Furthermore, if at least one of the incident surface 30 and the exit surface 32 is convex, the height of this convexity (the distance in the Z direction between the highest point of the convexity and the periphery of the convexity) is preferably 1 μm or more and 100 μm or less. This allows for appropriate aberration to be introduced.

[0091] More specifically, it is preferable that at least one of the incident surface 30 and the exit surface 32 has a shape that satisfies the above-mentioned equation (1) in the X and Y directions. On the other hand, it is preferable that at least one of the incident surface 30 and the exit surface 32 has a shape that does not satisfy the above-mentioned equation (1) in the third direction.

[0092] Figure 28 is a schematic diagram showing the intensity distribution of laser light as viewed from the optical axis direction. Figure 28 is a schematic diagram showing the intensity distribution of laser light L emitted from the optical element 22 of the second embodiment as viewed from direction Z. Figure 28 shows the intensity distribution of laser light L at the focal position Pf. According to the second embodiment, as shown in Figure 28, a laser beam with a square shape can be obtained, suppressing non-uniformity of the light intensity distribution in both the X and Y directions. If the laser light L1 incident on the optical element 22 is elliptical, a laser beam with a rectangular shape can be obtained by introducing appropriate aspherical shapes in the X and Y directions to match the elliptical beam size.

[0093] In the examples shown in Figures 25 to 27, the incident surface 30 has a shape that allows the curvature profile of the laser beam L2 to satisfy the predetermined conditions, while the exit surface 32 does not have a shape that allows the curvature profile of the laser beam L2 to satisfy the predetermined conditions, and is, for example, planar. However, it is not limited to this, and the conditions of the incident surface 30 and the exit surface 32 may be reversed, with the incident surface 30 having a shape that does not allow the curvature profile of the laser beam L2 to satisfy the predetermined conditions (for example, planar), and the exit surface 32 having a shape that allows the curvature profile of the laser beam L2 to satisfy the predetermined conditions. Furthermore, the sum of both the incident surface 30 and the exit surface 32 may result in a shape that allows the curvature profile of the laser beam L2 to satisfy the predetermined conditions (i.e., the sum of the wavefront aberration profiles of the incident surface 30 and the exit surface 32 is a shape that satisfies the predetermined conditions).

[0094] Figures 29 and 30 are schematic diagrams of a laser irradiation device according to another example of the second embodiment. Figures 29 and 30 show an example in which the sum of both the incident surface 30 and the exit surface 32 is such that the curvature profile of the laser beam L2 satisfies predetermined conditions.

[0095] In this example, the incident surface 30 has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the X direction satisfies predetermined conditions. On the other hand, the incident surface 30 has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy predetermined conditions. More specifically, the incident surface 30 has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction is constant along the Y direction and is small (below Mareshal's tolerance) at all positions along the Y direction. Therefore, it can be said that the incident surface 30 has a shape that imparts wavefront aberration in the X direction but does not impart wavefront aberration in the Y direction (aberration-free). Here, aberration-free means that the wavefront aberration is below Mareshal's tolerance (diffraction limit).

[0096] In this example, the exit surface 32 has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the Y direction satisfies predetermined conditions. On the other hand, the exit surface 32 has a shape such that the wavefront aberration profile of the laser light L2 in the X direction does not satisfy predetermined conditions. More specifically, the exit surface 32 has a shape such that the wavefront aberration profile of the laser light L2 in the X direction is constant along the X direction and is small (below Mareshal's tolerance) at all positions along the X direction. Therefore, it can be said that the incident surface 30 has a shape that imparts wavefront aberration in the Y direction but does not impart wavefront aberration in the X direction (i.e., is aberration-free).

[0097] In this example as well, the sum of the wavefront aberration profiles of the incident surface 30 and the exit surface 32 results in a wavefront aberration profile of the laser beam L2 in the third direction that satisfies the predetermined conditions, but has a shape in which the slope of the wavefront aberration profile in the X and Y directions is greater than that of the wavefront aberration profiles in the X and Y directions.

[0098] In this example, by passing the laser beam L1 through the incident surface 30 and the exit surface 32, a laser beam L2 can be obtained whose curvature profile satisfies predetermined conditions in the X and Y directions.

[0099] Furthermore, the second embodiment and the above examples described above can be modified using other examples 1 to 5 of the first embodiment. That is, for example, in the second embodiment and the above examples, the optical element 22 may be placed in the position shown in other example 1 of the first embodiment. Also, for example, in the second embodiment and the above examples, a condensing lens 20A may be placed instead of the two elements, the collimating lens 20 and the converging lens 24, and the optical element 22 may be placed in the position shown in other example 2 of the first embodiment. Also, for example, in the second embodiment and the above examples, the laser irradiation device 1 may be modified using the Keplerian irradiation device shown in other example 3 of the first embodiment. Also, for example, in the second embodiment and the above examples, the laser irradiation device 1 may be modified using the Galilean irradiation device shown in other example 4 of the first embodiment. Also, for example, in the second embodiment and the above examples, the conversion element 27 shown in other example 5 of the first embodiment may be placed in the laser irradiation device 1.

[0100] (Modification of the Second Embodiment) Next, a modification of the second embodiment will be described. This modification differs from the second embodiment in that the optical element 22 is realized by a plurality of optical elements. In this modification, parts that have the same configuration as the second embodiment will not be described.

[0101] Figures 31 and 32 are schematic diagrams of a laser irradiation device according to a modified example of the second embodiment. The optical element 22 according to the modified example of the second embodiment has a first optical element 22A and a second optical element 22B. In this example, the optical element 22 is composed of two optical elements (first optical element 22A and second optical element 22B), but it may be composed of three or more optical elements.

[0102] (First Optical Element) The first optical element 22A has a shape (for example, aspherical) on one of its incident surface 30A and exit surface 32A such that the wavefront aberration profile of the laser light L2 in the Y direction satisfies predetermined conditions. On the other hand, one of the incident surface 30A and exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in the X direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30A and exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in the X direction is constant along the X direction and is small (below Mareshal's tolerance) at all positions along the X direction. Therefore, it can be said that one of the incident surface 30A and exit surface 32A has a shape that imparts wavefront aberration in the Y direction but does not impart wavefront aberration in the X direction (resulting in aberration-free).

[0103] The first optical element 22A has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy predetermined conditions. More specifically, the other of the incident surface 30A and the other of the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30A and the exit surface 32A is planar. However, it is not limited to this, and the other of the incident surface 30A and the exit surface 32A may be spherical with constant curvature (convex or concave).

[0104] In the examples shown in Figures 31 and 32, the exit surface 32A is aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the incident surface 30A is planar. However, it is not limited to this, and the incident surface 30A may be aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the exit surface 32A may be planar.

[0105] (Second Optical Element) The second optical element 22B is provided on the Z-direction side of the first optical element 22A. The second optical element 22B has a shape (for example, aspherical) on either the incident surface 30B or the exit surface 32B such that the wavefront aberration profile of the laser light L2 in the X direction satisfies predetermined conditions. On the other hand, one of the incident surface 30B or the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30B or the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction is constant along the Y direction and is small (below Mareshal's tolerance) at all positions along the Y direction. Therefore, it can be said that one of the incident surface 30B or the exit surface 32B has a shape that imparts wavefront aberration in the X direction but does not impart wavefront aberration in the Y direction (resulting in aberration-free).

[0106] The second optical element 22B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30B and the exit surface 32B is planar. However, it is not limited to this, and the other of the incident surface 30B and the exit surface 32B may be spherical with constant curvature (convex or concave).

[0107] In the examples shown in Figures 31 and 32, the incident surface 30B is aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the exit surface 32B is planar. However, it is not limited to this, and the exit surface 32B may be aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the incident surface 30B may be planar.

[0108] Furthermore, the wavefront aberration profile obtained by adding the wavefront aberration profile of the laser light L that has passed through the first optical element 22A and the wavefront aberration profile of the laser light L that has passed through the second optical element has a shape in which the wavefront aberration profile in the third direction satisfies predetermined conditions, but is greater than the slope of the wavefront aberration profiles in the X and Y directions.

[0109] According to this modification, the laser light L1 is subjected to wavefront aberration in the Y direction by passing through the first optical element 22A, and wavefront aberration in the X direction by passing through the second optical element 22B. Therefore, even with this modification, a laser light L2 can be obtained in which the curvature profile satisfies predetermined conditions in both the X and Y directions.

[0110] (Another Modification Example 1) Next, another modification example 1 of the second embodiment will be described. In this other example 1, the parts that have the same configuration as the modification example of the second embodiment will not be described. Figures 33 to 35 are schematic diagrams of a laser irradiation device according to this other modification example 1 of the second embodiment.

[0111] In the above-described modification, the first optical element 22A and the second optical element 22B are provided between the collimating lens 20 and the converging lens 24 in the Z direction. However, the positions of the first optical element 22A and the second optical element 22B relative to other optical elements in the Z direction are not limited to this and may be arbitrary. For example, as shown in Figure 33, the first optical element 22A and the second optical element 22B may be provided on the opposite side of the Z direction from the collimating lens 20 (between the light source 10 and the collimating lens 20). Alternatively, as shown in Figure 34, the first optical element 22A and the second optical element 22B may be provided on the Z side from the converging lens 24 (between the converging lens 24 and the object to be illuminated 100). Alternatively, as shown in Figure 35, for example, the first optical element 22A may be provided on the opposite side of the Z direction from the collimating lens 20 (between the light source 10 and the collimating lens 20), and the second optical element 22B may be provided on the Z direction side from the converging lens 24 (between the converging lens 24 and the object to be illuminated 100).

[0112] (Another Modification Example 2) Next, another modification example 2 of the second embodiment will be described. In this other example 2, the parts that have the same configuration as the modification example of the second embodiment will not be described. Figures 36 to 38 are schematic diagrams of a laser irradiation device according to this other modification example 2 of the second embodiment.

[0113] In the above-described modification, the laser irradiation device 1 had a collimating lens 20 that made the laser light L into parallel light and a converging lens 24 that made the laser light L into focused light. However, the type and number of optical elements other than the optical element 22 are not limited to these and can be arbitrary. For example, as shown in Figures 36 to 38, the laser irradiation device 1 may have a condensing lens 20A instead of the two elements, the collimating lens 20 and the converging lens 24, similar to the other example 2 of the first embodiment. The condensing lens 20A is an optical element that focuses light. As shown in Figure 36, the first optical element 22A and the second optical element 22B may be provided on the Z-direction and the opposite side of the Z-direction from the condensing lens 20A (between the light source 10 and the condensing lens 20A). Also, for example, as shown in Figure 37, the first optical element 22A and the second optical element 22B may be provided on the Z-direction side from the condensing lens 20A (between the condensing lens 20A and the object to be irradiated 100). Alternatively, as shown in Figure 38, for example, the first optical element 22A may be provided on the opposite side of the Z direction from the condensing lens 20A (between the light source 10 and the condensing lens 20A), and the second optical element 22B may be provided on the Z direction side from the condensing lens 20A (between the condensing lens 20A and the object to be illuminated 100).

[0114] Alternatively, for example, the laser irradiation device 1 may not have a focusing lens 24, but instead have a collimating lens 20 and an optical element 22. In this case, the optical element 22 is provided with a focusing function to focus light. Alternatively, for example, the laser irradiation device 1 may not have a collimating lens 20, but instead have an optical element 22 and a focusing lens 24. In this case, the optical element 22 is provided with a focusing function to focus light (a function to collimate divergent light into parallel light).

[0115] (Another Modification Example 3) Next, another modification example 3 of the second embodiment will be described. In this other example 3, the parts that have the same configuration as the modification example of the second embodiment will not be explained. Figures 39 to 41 are schematic diagrams of a laser irradiation device according to this other modification example 3 of the second embodiment.

[0116] As shown in Figure 39, the laser irradiation device 1 of the other example 3 is a Keplerian type irradiation device. The laser irradiation device 1 of the other example 3 has a light source 10, a collimating lens 20, a first optical element 22A, a second optical element 22B, and a focusing lens 24, as well as lenses 26A and 26B. Lenses 26A and 26B constitute a Keplerian beam expander optical system. The configuration of lenses 26A and 26B is the same as in the other example 3 of the first embodiment, so a description is omitted.

[0117] The first optical element 22A and the second optical element 22B are provided between lens 26A and lens 26B in the Z direction. The first optical element 22A and the second optical element 22B may be provided between lens 26A and lens 26B on the opposite side of the Z direction from the focal point of the laser beam L, as shown in Figure 39, or they may be provided between lens 26A and lens 26B on the Z side from the focal point of the laser beam L, as shown in Figure 40. Alternatively, as shown in Figure 41, the first optical element 22A may be provided between lens 26A and lens 26B on the opposite side of the Z direction from the focal point of the laser beam L, and the second optical element 22B may be provided between lens 26A and lens 26B on the Z side from the focal point of the laser beam L.

[0118] (Another Modification Example 4) Next, another modification example 4 of the second embodiment will be described. In this other example 4, the parts that have the same configuration as the modification example of the second embodiment will not be described. Figure 42 is a schematic diagram of a laser irradiation device according to this other modification example 4 of the second embodiment.

[0119] As shown in Figure 42, the laser irradiation device 1 of the other example 4 is a Galilean type irradiation device. The laser irradiation device 1 of the other example 4 has a light source 10, a collimating lens 20, a first optical element 22A, a second optical element 22B, and a focusing lens 24, as well as lenses 26C and 26D. Lenses 26C and 26D constitute a Galilean beam expander optical system. The configuration of lenses 26C and 26D is the same as in the other example 3 of the first embodiment, so a description is omitted.

[0120] In this example, the first optical element 22A and the second optical element 22B are provided between lens 26C and lens 26D in the Z direction.

[0121] (Another example of a modified form 5) Next, another example of a modified form of the second embodiment will be described. In this other example 5, the parts that have the same configuration as the modified form of the second embodiment will not be explained.

[0122] The laser irradiation device 1 according to another example 5 of the modification of the second embodiment has a conversion element 27, similar to the modification 5 of the first embodiment. The configuration of the conversion element 27 is the same as that of the modification 5 of the first embodiment, so a description is omitted.

[0123] (Third Embodiment) Next, a third embodiment will be described. The third embodiment differs from the second embodiment in that the wavefront profile of the laser light L2 in the X direction and the wavefront profile of the laser light L2 in the Y direction are different from each other. In the third embodiment, parts that have the same configuration as the second embodiment will not be described.

[0124] Figures 43 and 44 are schematic diagrams of a laser irradiation device according to the third embodiment. In the third embodiment, at least one of the incident surface 30 and the exit surface 32 of the optical element 22 has a shape such that the wavefront aberration profile of the laser light L2 in both the X and Y directions satisfies predetermined conditions, similar to the first and second embodiments. Therefore, in the third embodiment as well, non-uniformity of light intensity can be suppressed in both the Y and X directions.

[0125] On the other hand, in the third embodiment, the wavefront profile of the laser light L2 in the X direction and the wavefront profile of the laser light L2 in the Y direction are different from each other.

[0126] Furthermore, in the third embodiment, the incident surface 30 and the exit surface 32 of the optical element 22 are shaped such that, similar to the second embodiment, the wavefront aberration profile of the laser light L2 in the third direction satisfies predetermined conditions, but the slope of the wavefront aberration profile is greater than the slope of the wavefront aberration profile in the X and Y directions. In other words, in the third embodiment, the wavefront aberration profile of the laser light L2 in the third direction satisfies predetermined conditions similar to those in the X and Y directions, but the slope of the wavefront aberration profile is greater than that of the profiles in the X and Y directions. Also, in the third embodiment, the curvature profile of the wavefront aberration of the laser light L2 in the third direction satisfies predetermined conditions similar to those in the X and Y directions, but the slope and maximum value are greater than those of the profiles in the X and Y directions.

[0127] Figure 45 is a schematic diagram showing an example of the surface shape of an optical element in the third embodiment. In the third embodiment, at least one of the incident surface 30 and the exit surface 32 may be any shape such that the wavefront profile of the laser light L2 satisfies predetermined conditions in the X, Y, and third directions, and the inclination in the third direction is large, but it is preferable that it be aspherical, as shown in Figure 45, for example. In the examples of Figures 43 to 45, at least one of the incident surface 30 and the exit surface 32 is an aspherical concave shape, but it is not limited to this and may be an aspherical convex shape. When at least one of the incident surface 30 and the exit surface 32 is concave, the depth of this concave (the distance in the Z direction between the deepest part of the concave and the periphery of the concave) is preferably 1 μm or more and 100 μm or less. This allows for appropriate aberration to be introduced. Furthermore, if at least one of the incident surface 30 and the exit surface 32 is convex, the height of this convexity (the distance in the Z direction between the highest point of the convexity and the periphery of the convexity) is preferably 1 μm or more and 100 μm or less. This allows for appropriate aberration to be introduced.

[0128] More specifically, it is preferable that at least one of the incident surface 30 and the exit surface 32 has a shape that satisfies the above-mentioned equation (1) in the X and Y directions. On the other hand, it is preferable that at least one of the incident surface 30 and the exit surface 32 has a shape that does not satisfy the above-mentioned equation (1) in the third direction.

[0129] Figure 46 is a schematic diagram showing the intensity distribution of laser light as viewed from the optical axis direction. Figure 46 is a schematic diagram showing the intensity distribution of laser light L emitted from the optical element 22 of the third embodiment as viewed from direction Z. Figure 46 shows the intensity distribution of laser light L at the focal position Pf. According to the third embodiment, as shown in Figure 46, a laser beam with a rectangular shape can be obtained with non-uniformity of the light intensity distribution suppressed in both the X and Y directions. If the laser light L1 incident on the optical element 22 is elliptical, a laser beam with a square shape can be obtained. Furthermore, if the laser light L1 incident on the optical element 22 is elliptical, a laser beam with a square shape can also be obtained by adjusting the installation angle between the laser light L1 (light source 10) and the optical element 22 as viewed from the optical axis direction.

[0130] In the examples shown in Figures 44 to 46, the incident surface 30 has a shape that allows the curvature profile of the laser beam L2 to satisfy the predetermined conditions, while the exit surface 32 does not have a shape that allows the curvature profile of the laser beam L2 to satisfy the predetermined conditions, and is, for example, planar. However, it is not limited to this, and the conditions for the incident surface 30 and the exit surface 32 may be reversed, with the incident surface 30 having a shape that does not allow the curvature profile of the laser beam L2 to satisfy the predetermined conditions (for example, planar), and the exit surface 32 having a shape that allows the curvature profile of the laser beam L2 to satisfy the predetermined conditions. Alternatively, both the incident surface 30 and the exit surface 32 may have shapes that allow the curvature profile of the laser beam L2 to satisfy the predetermined conditions.

[0131] Figures 47 and 48 are schematic diagrams of a laser irradiation device according to another example of the third embodiment. Figures 47 and 48 show an example in which both the incident surface 30 and the exit surface 32 have a shape that allows the curvature profile of the laser beam L2 to satisfy predetermined conditions.

[0132] In this example, the incident surface 30 has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the X direction satisfies predetermined conditions. On the other hand, the incident surface 30 has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy predetermined conditions. More specifically, the incident surface 30 has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction is constant along the Y direction and is small (below Mareshal's tolerance) at all positions along the Y direction. Therefore, it can be said that the incident surface 30 has a shape that imparts wavefront aberration in the X direction but does not impart wavefront aberration in the Y direction (i.e., is aberration-free).

[0133] In this example, the exit surface 32 has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the Y direction satisfies predetermined conditions. On the other hand, the exit surface 32 has a shape such that the wavefront aberration profile of the laser light L2 in the X direction does not satisfy predetermined conditions. More specifically, the exit surface 32 has a shape such that the wavefront aberration profile of the laser light L2 in the X direction is constant along the X direction and is small (below Mareshal's tolerance) at all positions along the X direction. Therefore, it can be said that the incident surface 30 has a shape that imparts wavefront aberration in the Y direction but does not impart wavefront aberration in the X direction (i.e., is aberration-free).

[0134] In this example as well, the incident surface 30 and the exit surface 32 are shaped such that the wavefront aberration profile of the laser beam L2 in the third direction satisfies the predetermined conditions, but the slope of the wavefront aberration profile in the X and Y directions is smaller than that of the wavefront aberration profiles in the X and Y directions.

[0135] In this example, by passing the laser beam L1 through the incident surface 30 and the exit surface 32, a laser beam L2 can be obtained whose curvature profile satisfies predetermined conditions in the X and Y directions.

[0136] Furthermore, the third embodiment and the above examples described above can be modified to apply the other examples 1 to 5 of the first embodiment. That is, for example, in the third embodiment and the above examples, the optical element 22 may be placed in the position shown in the other example 1 of the first embodiment. Also, for example, in the third embodiment and the above examples, a condensing lens 20A may be placed instead of the two elements, the collimating lens 20 and the converging lens 24, and the optical element 22 may be placed in the position shown in the other example 2 of the third embodiment. Also, for example, in the third embodiment and the above examples, the laser irradiation device 1 may be modified to apply to the Keplerian irradiation device shown in the other example 3 of the first embodiment. Also, for example, in the third embodiment and the above examples, the laser irradiation device 1 may be modified to apply to the Galilean irradiation device shown in the other example 4 of the first embodiment. Also, for example, in the third embodiment and the above examples, the conversion element 27 shown in the other example 5 of the first embodiment may be placed in the laser irradiation device 1.

[0137] (Modification of the Third Embodiment) Next, a modification of the third embodiment will be described. This modification differs from the second embodiment in that the optical element 22 is realized by a plurality of optical elements. In this modification, the parts that have the same configuration as the second embodiment will not be described.

[0138] Figures 49 and 50 are schematic diagrams of a laser irradiation device according to a modified example of the third embodiment. The optical element 22 according to the modified example of the third embodiment has a first optical element 22A and a second optical element 22B. In this example, the optical element 22 is composed of two optical elements (first optical element 22A and second optical element 22B), but it may be composed of three or more optical elements.

[0139] (First Optical Element) The first optical element 22A has a shape (for example, aspherical) on one of its incident surface 30A and exit surface 32A such that the wavefront aberration profile of the laser light L2 in the Y direction satisfies predetermined conditions. On the other hand, one of the incident surface 30A and exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in the X direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30A and exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in the X direction is constant along the X direction and is small (below Mareshal's tolerance) at all positions along the X direction. Therefore, it can be said that one of the incident surface 30A and exit surface 32A has a shape that imparts wavefront aberration in the Y direction but does not impart wavefront aberration in the X direction (resulting in aberration-free).

[0140] The first optical element 22A has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy predetermined conditions. More specifically, the other of the incident surface 30A and the other of the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30A and the exit surface 32A is planar. However, it is not limited to this, and the other of the incident surface 30A and the exit surface 32A may be spherical with constant curvature (convex or concave).

[0141] In the examples of Figures 49 and 50, the exit surface 32A is aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the incident surface 30A is planar. However, it is not limited to this, and the incident surface 30A may be aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the exit surface 32A may be planar.

[0142] (Second Optical Element) The second optical element 22B is provided on the Z-direction side of the first optical element 22A. The second optical element 22B has a shape (for example, aspherical) on either the incident surface 30B or the exit surface 32B such that the wavefront aberration profile of the laser light L2 in the Y direction satisfies predetermined conditions. On the other hand, one of the incident surface 30B or the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in the X direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30B or the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in the X direction is constant along the X direction and is small (below Mareshal's tolerance) at all positions along the X direction. Therefore, it can be said that one of the incident surface 30B or the exit surface 32B has a shape that imparts wavefront aberration in the Y direction but does not impart wavefront aberration in the X direction (resulting in aberration-free).

[0143] The second optical element 22B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30B and the exit surface 32B is planar. However, it is not limited to this, and the other of the incident surface 30B and the exit surface 32B may be spherical with constant curvature (convex or concave).

[0144] In the examples of Figures 49 and 50, the incident surface 30B is aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the exit surface 32B is planar. However, it is not limited to this, and the exit surface 32B may be aspherical in shape so that the wavefront aberration profile of the laser light L2 satisfies predetermined conditions, and the incident surface 30B may be planar.

[0145] Furthermore, the wavefront aberration profile obtained by adding the wavefront aberration profile of the laser light L that has passed through the first optical element 22A and the wavefront aberration profile of the laser light L that has passed through the second optical element has a shape in which the wavefront aberration profile in the third direction satisfies predetermined conditions, but is greater than the slope of the wavefront aberration profiles in the X and Y directions.

[0146] According to this modification, the laser light L1 is subjected to wavefront aberration in the Y direction by passing through the first optical element 22A, and wavefront aberration in the X direction by passing through the second optical element 22B. Therefore, even with this modification, a laser light L2 can be obtained in which the curvature profile satisfies predetermined conditions in both the X and Y directions.

[0147] Furthermore, the configurations of other examples 1 to 5 of the modified version of the second embodiment can also be applied to the modified version of the third embodiment. Since these configurations correspond to other examples 1 to 5 of the modified version of the second embodiment, their explanation will be omitted. However, in the modified version of the third embodiment, a different configuration may be adopted compared to the modified version of the second embodiment. This will be explained in detail below.

[0148] Figures 51 to 53 are schematic diagrams of a laser irradiation device relating to another example of a modification of the third embodiment. The laser irradiation device 1 in Figures 51 to 53 corresponds to another example 1 of the modification of the second embodiment shown in Figures 33 to 35.

[0149] In the configurations shown in Figures 33 and 51, the first optical element 22A and the second optical element 22B are arranged between the light source 10 and the collimating lens 20, that is, in the section where the laser light L becomes divergent light. In another example 1 of the second embodiment shown in Figure 33, in order to generate a square-shaped laser beam L3, the second optical element 22B on the Z-direction side is larger than the first optical element 22A (i.e., the effective diameter of the second optical element 22B is larger than the effective diameter of the first optical element 22A) to match the beam size of the laser light L. On the other hand, as shown in Figure 51, in the third embodiment, the first optical element 22A and the second optical element 22B may have the same shape. In other words, as shown in Figure 51, the effective diameter of the first optical element 22A and the effective diameter of the second optical element 22B may be the same. In this case, the second optical element 22B is positioned 90° offset from the first optical element 22A in the circumferential direction when the Z-direction of the first optical element 22A and the second optical element 22B is oriented as the axial direction. Then, in the Z-direction, one of the first optical element 22A and the second optical element 22B is positioned at a location corresponding to the major axis of the elliptical laser beam L1, and the other of the first optical element 22A and the second optical element 22B is positioned at a location corresponding to the major axis of the elliptical laser beam L1. As a result, a rectangular laser beam L3 can be appropriately generated from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B of the same shape. Cost reduction can be achieved by using the first optical element 22A and the second optical element 22B of the same shape in this way.

[0150] In the configurations shown in Figures 34 and 52, the first optical element 22A and the second optical element 22B are positioned on the Z-direction side of the converging lens 24, that is, in the section where the laser beam L becomes a focused beam. In another example 1 of the second embodiment shown in Figure 34, in order to generate a square-shaped laser beam L3, the second optical element 22B on the Z-direction side is smaller than the first optical element 22A (i.e., the effective diameter of the second optical element 22B is smaller than the effective diameter of the first optical element 22A) to match the beam size of the laser beam L. On the other hand, as shown in Figure 52, in the third embodiment, the first optical element 22A and the second optical element 22B may have the same shape (same effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned at locations corresponding to the major and minor axes of the laser beam L1). This allows for the appropriate generation of a rectangular laser beam L3 from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B, which have the same shape. By using the first optical element 22A and the second optical element 22B, which have the same shape, cost reduction can be achieved.

[0151] In the configurations shown in Figures 35 and 53, the first optical element 22A is positioned between the light source 10 and the collimating lens 20 (in the divergent light section), and the second optical element 22B is positioned on the Z-direction side of the converging lens 24 (in the converging light section). In another example 1 of the second embodiment shown in Figure 35, in order to generate a square-shaped laser beam L3, the first optical element 22A and the second optical element 22B are made to have the same shape (same effective diameter), and are positioned in the Z-direction at locations where the beam diameter of the laser beam L is the same. As shown in Figure 53, in the third embodiment as well, the first optical element 22A and the second optical element 22B may also have the same shape (same effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned at locations corresponding to the major and minor axes of the laser beam L1). This allows for the appropriate generation of a rectangular laser beam L3 from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B, which have the same shape. By using the first optical element 22A and the second optical element 22B, which have the same shape, cost reduction can be achieved.

[0152] Figures 54 to 56 are schematic diagrams of a laser irradiation device relating to another example of a modification of the third embodiment. The laser irradiation device 1 in Figures 54 to 56 corresponds to another example 2 of the modification of the second embodiment shown in Figures 36 to 38.

[0153] In the configurations shown in Figures 36 and 54, the first optical element 22A and the second optical element 22B are arranged between the light source 10 and the focusing lens 20A, that is, in the section where the laser beam L becomes divergent light. In Figure 36, in order to generate a square-shaped laser beam L3, the second optical element 22B on the Z-direction side is larger than the first optical element 22A (i.e., the effective diameter of the second optical element 22B is larger than the effective diameter of the first optical element 22A) to match the beam size of the laser beam L. On the other hand, as shown in Figure 54, in the third embodiment, the first optical element 22A and the second optical element 22B may have the same shape (effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and arranged at positions corresponding to the major and minor axes of the laser beam L1). This allows for the appropriate generation of a rectangular laser beam L3 from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B, which have the same shape. By using the first optical element 22A and the second optical element 22B, which have the same shape, cost reduction can be achieved.

[0154] In the configurations shown in Figures 37 and 55, the first optical element 22A and the second optical element 22B are positioned on the Z-direction side of the focusing lens 20A, that is, in the section where the laser beam L becomes a focused beam. In Figure 37, in order to generate a square-shaped laser beam L3, the second optical element 22B on the Z-direction side is smaller than the first optical element 22A (i.e., the effective diameter of the second optical element 22B is smaller than the effective diameter of the first optical element 22A) to match the beam size of the laser beam L. On the other hand, as shown in Figure 55, in the third embodiment, the first optical element 22A and the second optical element 22B may have the same shape (same effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned at locations corresponding to the major and minor axes of the laser beam L1). This allows for the appropriate generation of a rectangular laser beam L3 from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B, which have the same shape. By using the first optical element 22A and the second optical element 22B, which have the same shape, cost reduction can be achieved.

[0155] In the configurations shown in Figures 38 and 56, the first optical element 22A is positioned between the light source 10 and the collimating lens 20 (in the divergent light section), and the second optical element 22B is positioned on the Z-direction side of the converging lens 24 (in the converging light section). In Figure 38, in order to generate a square-shaped laser beam L3, the first optical element 22A and the second optical element 22B are made to have the same shape (same effective diameter), and are positioned in the Z-direction at locations where the beam diameter of the laser beam L is the same. As shown in Figure 56, in the third embodiment as well, the first optical element 22A and the second optical element 22B may also have the same shape (same effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned at locations corresponding to the major and minor axes of the laser beam L1). This allows for the appropriate generation of a rectangular laser beam L3 from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B, which have the same shape. By using the first optical element 22A and the second optical element 22B, which have the same shape, cost reduction can be achieved.

[0156] Figures 57 to 59 are schematic diagrams of a laser irradiation device relating to another example of a modification of the third embodiment. The laser irradiation device 1 in Figures 57 to 59 corresponds to another example 3 of the modification of the second embodiment shown in Figures 39 to 41.

[0157] In the Keplerian configurations shown in Figures 39 and 57, the first optical element 22A and the second optical element 22B are positioned between the lens 26A and the focal point of the laser beam L, that is, in the section where the laser beam L becomes a focused beam. In Figure 39, in order to generate a square-shaped laser beam L3, the second optical element 22B on the Z-direction side is smaller than the first optical element 22A (i.e., the effective diameter of the second optical element 22B is smaller than the effective diameter of the first optical element 22A) to match the beam size of the laser beam L. On the other hand, as shown in Figure 57, in the third embodiment, the first optical element 22A and the second optical element 22B may have the same shape (effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned at locations corresponding to the major and minor axes of the laser beam L1). As a result, in a Keplerian configuration, a rectangular laser beam L3 can be appropriately generated from an elliptical laser beam L1 using a first optical element 22A and a second optical element 22B of the same shape. By using a first optical element 22A and a second optical element 22B of the same shape in this way, cost reduction can be achieved.

[0158] In the Keplerian configurations shown in Figures 40 and 58, the first optical element 22A and the second optical element 22B are positioned between the focal point of the laser beam L and the lens 26B, that is, in the section where the laser beam L becomes divergent. In Figure 40, in order to generate a square-shaped laser beam L3, the second optical element 22B on the Z-direction side is larger than the first optical element 22A (i.e., the effective diameter of the second optical element 22B is larger than the effective diameter of the first optical element 22A) to match the beam size of the laser beam L. On the other hand, as shown in Figure 58, in the third embodiment, the first optical element 22A and the second optical element 22B may have the same shape (effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned at locations corresponding to the major and minor axes of the laser beam L1). As a result, in a Keplerian configuration, a rectangular laser beam L3 can be appropriately generated from an elliptical laser beam L1 using a first optical element 22A and a second optical element 22B of the same shape. By using a first optical element 22A and a second optical element 22B of the same shape in this way, cost reduction can be achieved.

[0159] In the Keplerian configuration shown in Figures 41 and 59, the first optical element 22A is positioned between the lens 26A and the focal point of the laser beam L (in the section where the laser beam L becomes a focused beam), and the second optical element 22B is positioned between the focal point of the laser beam L and the lens 26B (in the section where the laser beam L becomes a divergent beam). In Figure 41, in order to generate a square-shaped laser beam L3, the first optical element 22A and the second optical element 22B are made to have the same shape (same effective diameter), and are positioned in the Z direction at locations where the beam diameter of the laser beam L is the same. As shown in Figure 59, in the third embodiment as well, the first optical element 22A and the second optical element 22B may also have the same shape (same effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned to correspond to the major and minor axes of the laser beam L1). This allows for the appropriate generation of a rectangular laser beam L3 from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B of the same shape in a Keplerian configuration. By using the first optical element 22A and the second optical element 22B of the same shape in this way, cost reduction can be achieved.

[0160] Figure 60 is a schematic diagram of a laser irradiation device relating to another example of a modification of the third embodiment. The laser irradiation device 1 in Figure 60 corresponds to another example 4 of the modification of the second embodiment shown in Figure 42.

[0161] In the Galilean configurations shown in Figures 42 and 60, the first optical element 22A and the second optical element 22B are positioned between lens 26C and lens 26D, that is, in the section where the laser beam L becomes divergent. In Figure 42, in order to generate a square-shaped laser beam L3, the second optical element 22B on the Z-direction side is larger than the first optical element 22A (i.e., the effective diameter of the second optical element 22B is larger than the effective diameter of the first optical element 22A) to match the beam size of the laser beam L. On the other hand, as shown in Figure 60, in the third embodiment, the first optical element 22A and the second optical element 22B may have the same shape (effective diameter). In this case, the arrangement of the first optical element 22A and the second optical element 22B in the circumferential and Z-directions may be the same as in Figure 51 (i.e., they may be shifted by 90° in the circumferential direction and positioned at locations corresponding to the major and minor axes of the laser beam L1). As a result, in a Galilean configuration, a rectangular laser beam L3 can be appropriately generated from an elliptical laser beam L1 using the first optical element 22A and the second optical element 22B of the same shape. By using the first optical element 22A and the second optical element 22B of the same shape in this way, cost reduction can be achieved.

[0162] (Example of arranging multiple light sources) Next, the configuration of the laser irradiation device 1 when multiple light sources 10 are arranged will be described for the first to third embodiments (and their modified forms and other examples).

[0163] (Example 1) Figure 61 is a schematic diagram of a laser irradiation device in which multiple light sources are installed. As shown in Figure 61, the laser irradiation device 1 in this example has a light source 10, a collimating lens 20, an optical element 22, a focusing lens 24, and a combining element 25.

[0164] In the example shown in Figure 61, multiple light sources 10 are provided, namely light sources 10A, 10B, and 10C. Light sources 10A, 10B, and 10C emit laser light L in different wavelength bands. The wavelength bands of the laser light L emitted by light sources 10A, 10B, and 10C can be arbitrary, but for example, light source 10A may emit laser light L in the green wavelength band, light source 10B may emit laser light L in the red wavelength band, and light source 10C may emit laser light L in the blue wavelength band. Note that the number of light sources 10 is not limited to three, but can be any number.

[0165] In the example shown in Figure 61, the collimating lens 20 includes collimating lenses 20A, 20B, and 20C. Collimating lens 20A collimates the laser light L from the light source 10A and is provided on the side of the light source 10A that is in the direction of propagation of the laser light L from the light source 10A. Collimating lens 20B collimates the laser light L from the light source 10B and is provided on the side of the light source 10B that is in the direction of propagation of the laser light L from the light source 10B. Collimating lens 20C collimates the laser light L from the light source 10C and is provided on the side of the light source 10C that is in the direction of propagation of the laser light L from the light source 10C.

[0166] The combining element 25 is an optical element that combines laser beams L emitted from different light sources 10. For example, the combining element 25 may be a dichroic mirror. In the example shown in Figure 61, the combining element 25 has combining element 25A and combining element 25B. Combining element 25A combines the laser beam L from light source 10B with the laser beam L from light source 10A. Combining element 25B combines the laser beam L from light source 10C with the laser beam L from light source 10A. The combining element 25 is located on the opposite side of the Z direction (the direction of propagation of the laser beam L from light source 10A) from the optical element 22, and more specifically, it is located between the collimating lens 20A and the optical element 22.

[0167] In the example shown in Figure 61, the light source 10A is located on the side opposite to the Z direction of the collimating lens 20A. The light source 10B is located on the side of the combining element 25A that intersects the Z direction (the direction of propagation of the laser light L from the light source 10A). The light source 10C is located on the side of the combining element 25B that intersects the Z direction (the direction of propagation of the laser light L from the light source 10A).

[0168] In this example, the laser light L emitted from light source 10A passes through the collimating lens 20A and the combining element 25A. On the other hand, the laser light L emitted from light source 10B passes through the collimating lens 20B, is reflected by the combining element 25A, and is combined with the laser light L emitted from light source 10A, and propagates in the Z direction. This combined laser light (combined light of the laser light L from light sources 10A and 10B) propagates in the Z direction and passes through the combining element 25B. On the other hand, the laser light L emitted from light source 10C passes through the collimating lens 20C, is reflected by the combining element 25B, and is combined with the combined laser light, and propagates in the Z direction. This combined laser light (combined light of the laser light L from light sources 10A, 10B, and 10C) propagates in the Z direction, passes through the optical element 22, and, with wavefront aberration added, passes through the focusing lens 24, which is an achromatic lens, and irradiates the object to be irradiated 100.

[0169] The optical element 22 has low wavelength dependence and can easily function with light of any wavelength. Therefore, by using the optical element 22 with laser light L that is a combination of different wavelength bands, as in this example, the non-uniformity of the light intensity can be appropriately suppressed for each wavelength band.

[0170] (Example 2) Figure 62 is a schematic diagram of a laser irradiation device in an example where multiple light sources are installed. As shown in Figure 62, the configuration of the collimating lens 20 of the laser irradiation device 1 in this example is different from that of the laser irradiation device 1 in Example 1. In the laser irradiation device 1 in this example, the parts that are common in configuration with the laser irradiation device 1 in Example 1 will not be explained.

[0171] The collimating lens 20 in this example has the function of changing the shape of the laser beam L when viewed from the optical axis direction. More specifically, the collimating lens 20 in this example has the function of changing an elliptical laser beam L into a circular laser beam L. The configuration that gives the collimating lens 20 the function of changing the shape of the laser beam L can be arbitrary, but in this example it is realized by two cylindrical lenses aligned in the optical axis direction. This will be explained in detail below.

[0172] In this example, the collimating lens 20A has lenses 20A1 and 20A2. Lens 20A1 is a cylindrical lens in which at least one of its incident surface and exit surface is curved in one direction perpendicular to the optical axis direction of the laser beam L from the light source 10A. Lens 20A2 is positioned relative to lens 20A1 on the side in the direction of propagation of the laser beam L from the light source 10A. Lens 20A2 is a cylindrical lens in which at least one of its incident surface and exit surface is curved in one direction perpendicular to the optical axis direction of the laser beam L from the light source 10A. The direction in which the surface of lens 20A2 is curved is perpendicular to the direction in which the surface of lens 20A1 is curved.

[0173] Similarly, the collimating lens 20B has lenses 20B1 and 20B2. Lens 20B1 is a cylindrical lens in which at least one of its incident surface and exit surface is curved in one direction perpendicular to the optical axis direction of the laser beam L from the light source 10B. Lens 20B2 is positioned relative to lens 20B1 on the side in the direction of propagation of the laser beam L from the light source 10B. Lens 20B2 is a cylindrical lens in which at least one of its incident surface and exit surface is curved in one direction perpendicular to the optical axis direction of the laser beam L from the light source 10B. The direction in which the surface of lens 20B2 is curved is perpendicular to the direction in which the surface of lens 20B1 is curved.

[0174] Similarly, the collimating lens 20C has lenses 20C1 and 20C2. Lens 20C1 is a cylindrical lens in which at least one of its incident surface and exit surface is curved in one direction perpendicular to the optical axis direction of the laser beam L from the light source 10C. Lens 20C2 is positioned on the side of lens 20C1 that is in the direction of propagation of the laser beam L from the light source 10C. Lens 20C2 is a cylindrical lens in which at least one of its incident surface and exit surface is curved in one direction perpendicular to the optical axis direction of the laser beam L from the light source 10C. The direction in which the surface of lens 20C2 is curved is perpendicular to the direction in which the surface of lens 20C1 is curved.

[0175] In this example, the elliptical laser beams L emitted from light sources 10A, 10B, and 10C pass through collimating lenses 20A, 20B, and 20C, are converted into circular laser beams L, are combined by combining elements 25A and 25B, and then incident on the optical element 22. Therefore, in this example, elliptical laser beams L of different wavelength bands can be converted into a circular combined laser beam before being incident on the optical element 22, and non-uniformity of light intensity can be appropriately suppressed for each wavelength band.

[0176] In the example shown in Figure 62, the optical element 22 has a configuration that includes a first optical element 22A and a second optical element 22B, as in the modified example of the second embodiment. Therefore, in the example shown in Figure 62, a square laser beam L with suppressed non-uniformity of light intensity can be generated from an elliptical laser beam L of different wavelength bands. However, the optical element 22 in this example may be any configuration described in the above embodiments or modifications. For example, if the optical element 22 in this example is from the first embodiment, a circular laser beam L with suppressed non-uniformity of light intensity can be generated. Also, for example, if the optical element 22 in this example is from the third embodiment, a rectangular laser beam L with suppressed non-uniformity of light intensity can be generated.

[0177] Furthermore, the light source 10 in this example is not limited to emitting an elliptical laser beam L, but may also emit a circular laser beam L, for example. In this case, the collimating lens 20 can irradiate the optical element 22 with an elliptical laser beam L, so if the optical element 22 is the one shown in the first embodiment, an elliptical laser beam L with suppressed non-uniformity of light intensity can be generated. If the optical element 22 is the one shown in the second embodiment, a rectangular laser beam L with suppressed non-uniformity of light intensity can be generated. If the optical element 22 is the one shown in the third embodiment, a square laser beam L with suppressed non-uniformity of light intensity can be generated by adjusting the installation angle of the optical element 22.

[0178] (Example 3) In Example 2, the elliptical laser beam L is converted to a circular beam and then combined, but as in this example, the elliptical laser beam L may be combined first and then the combined laser beam may be converted to a circular beam. Figure 63 is a schematic diagram of a laser irradiation device in an example where multiple light sources are installed. As shown in Figure 63, the laser irradiation device 1 in this example differs from the laser irradiation device 1 in Example 1 in that it has cylindrical lenses 25C and 25D. In the laser irradiation device 1 in this example, the parts that are in common with the laser irradiation device 1 in Example 1 will not be explained.

[0179] The laser irradiation device 1 in this example has a conversion element. The conversion element is an optical element that has the function of changing the shape of the laser beam L when viewed from the axial direction. More specifically, the conversion element in this example has the function of changing an elliptical laser beam L into a circular laser beam L. The configuration that gives the conversion element the function of changing the shape of the laser beam L may be arbitrary, but in this example it is realized by two cylindrical lenses 25C and 25D that are aligned in the optical axis direction. This will be explained in detail below. The cylindrical lenses 25C and 25D are achromatic lenses.

[0180] The cylindrical lens 25C is provided between the point where the laser beams L from the light sources 10A, 10B, and 10C are combined (combination element 25B in this example) and the optical element 22 in the Z direction. The cylindrical lens 25C is a cylindrical lens in which at least one of the incident surface and the exit surface is curved in one direction perpendicular to the Z direction (here, the Y direction). For example, the cylindrical lens 25C may be a cylindrical lens in which the incident surface is curved convexly along the Y direction. The cylindrical lens 25D is positioned on the Z direction side relative to the cylindrical lens 25C. The cylindrical lens 25D is a cylindrical lens in which at least one of the incident surface and the exit surface is curved in one direction perpendicular to the Z direction (here, the Y direction). For example, the cylindrical lens 25D may be a cylindrical lens in which the exit surface is curved concavely along the Y direction. The direction in which the surface of cylindrical lens 25D curves is the same as the direction in which the surface of cylindrical lens 25C curves.

[0181] In this example, the elliptical laser beams L emitted from light sources 10A, 10B, and 10C are combined and then incident on cylindrical lenses 25C and 25D to form an elliptical combined laser beam which is then incident on the optical element 22. Therefore, in this example as well, elliptical laser beams L of different wavelength bands can be converted into a circular combined laser beam before being incident on the optical element 22, and non-uniformity of light intensity can be appropriately suppressed for each wavelength band.

[0182] In the example shown in Figure 63, the optical element 22 has a configuration that includes a first optical element 22A and a second optical element 22B, as in the modified example of the second embodiment. Therefore, in the example shown in Figure 63, a square laser beam L with suppressed non-uniformity of light intensity can be generated from an elliptical laser beam L of different wavelength bands. However, the optical element 22 in this example may be any configuration described in the embodiments or modifications described above. For example, if the optical element 22 in this example is from the first embodiment, a circular laser beam L with suppressed non-uniformity of light intensity can be generated. Also, for example, if the optical element 22 in this example is from the third embodiment, a rectangular laser beam L with suppressed non-uniformity of light intensity can be generated.

[0183] Furthermore, the light source 10 in this example is not limited to emitting an elliptical laser beam L, but may also emit a circular laser beam L, for example. In this case, the cylindrical lenses 25C and 25D can irradiate the optical element 22 with an elliptical laser beam L, so that if the optical element 22 is the one shown in the first embodiment, an elliptical laser beam L with suppressed non-uniformity of light intensity can be generated. If the optical element 22 is the one shown in the second embodiment, a rectangular laser beam L with suppressed non-uniformity of light intensity can be generated. If the optical element 22 is the one shown in the third embodiment, a square laser beam L with suppressed non-uniformity of light intensity can be generated by adjusting the installation angle of the optical element 22.

[0184] (Example 4) In Examples 1 to 3 described above, there were multiple light sources 10 with different wavelength bands of emitted laser light L. However, as in this example, multiple light sources 10 that emit laser light L of the same wavelength band may be provided. Figure 64 is a schematic diagram of a laser irradiation device according to an example in which multiple light sources are installed. As shown in Figure 64, the laser irradiation device 1 in this example differs from the laser irradiation device 1 in Example 1 in that it has a light source 10D. In the laser irradiation device 1 of this example, the parts that have the same configuration as the laser irradiation device 1 in Example 1 will not be explained.

[0185] As shown in Figure 64, the laser irradiation device 1 in this example includes a light source 10D, a collimating lens 20D, a half-wave plate 25E, and a combining element 25F.

[0186] Light source 10D emits laser light L in the same wavelength band as light source 10A. The collimating lens 20D collimates the laser light L from light source 10D and is installed on the side of the light source 10D that is in the direction of propagation of the laser light L from light source 10D.

[0187] The combining element 25F is an optical element that combines laser beams L emitted from different light sources 10. The combining element 25F combines the laser beam L from light source 10D and the laser beam L from light source 10A. The combining element 25F may also be a polarizing beam splitter. The combining element 25F is located on the opposite side of the Z direction from the optical element 22, and more specifically, it is located between the collimating lens 20A and the optical element 22.

[0188] In the example shown in Figure 64, the light source 10D is positioned on the side of the composite element 25F that intersects the Z direction (the direction of propagation of the laser light L from the light source 10A).

[0189] The half-wave plate 25E is an element that converts the polarization direction of light. The half-wave plate 25E converts the polarization direction of the laser light L from the light source 10D. The half-wave plate 25E is placed between the light source 10D (collimating lens 20D) and the composite element 25F in the optical axis direction of the laser light L from the light source 10D.

[0190] In this example, the laser light L emitted from the light source 10A passes through the collimating lens 20A and the combining element 25F. On the other hand, the laser light L emitted from the light source 10D passes through the collimating lens 20D and the half-wave plate 25E, and after its polarization direction is converted, it is incident on the combining element 25F and reflected by the combining element 25F. The laser light L from the light source 10D reflected by the combining element 25F is combined with the laser light L emitted from the light source 10A and propagates in the Z direction. This combined laser light (the combined light of the laser light L from light sources 10A and 10D) is combined with the laser light L from light sources 10B and 10C and incident on the optical element 22.

[0191] In this example, by synthesizing laser light L of the same wavelength band and then injecting it into the optical element 22, the light intensity can be increased while suppressing non-uniformity of the light intensity.

[0192] In Figure 64, the synthesis of laser light L of the same wavelength band and the synthesis of laser light L of different wavelength bands are performed, but the configuration may only perform the synthesis of laser light L of the same wavelength band. In other words, in this case, the light sources 10B and 10C, collimating lenses 20B and 20C, and synthesis elements 25A and 25B may not be provided. Furthermore, the configuration of this example can also be applied to Examples 2 and 3.

[0193] (Other Configuration Examples of the Optical Element) Next, other configuration examples of the optical element 22 will be described. Unless otherwise specified, the configurations of the embodiments, modifications, and examples described above can be applied to the following configuration examples.

[0194] (Configuration Example 1) Figures 65 and 66 are schematic diagrams of a laser irradiation device according to Configuration Example 1. In Configuration Example 1, the optical element 22 is shaped to widen the irradiation shape at the irradiated object 100 at the focal point Pf in a second direction (in this example, the X direction), and one of the incident surface 30A and the exit surface 32A is convex (corresponding to the case of a convex surface shown in the first embodiment described above. The same effect can be obtained with both a concave and a convex surface). According to Configuration Example 1, in the irradiation shape at the focal point Pf, the second direction (in this example, the X direction) can be made larger than the first direction (in this example, the Y direction), for example, a top hat line shape with uniform intensity in the second direction can be achieved. A detailed explanation follows below.

[0195] The optical element 22 in Configuration Example 1 expands the irradiation shape of the irradiated object 100 at the focal point Pf in a second direction (in this example, the X direction). As shown in Figures 65 and 66, the optical element 22 in Configuration Example 1 has the same shape as the second optical element 22B described in the second embodiment (see Figures 31 and 32). However, the optical element 22 in Configuration Example 1 differs from the concave second optical element 22B illustrated in Figures 31 and 32 in that one of the incident surface 30A and the exit surface 32A is convex. Specifically, in Configuration Example 1, one of the incident surface 30A and the exit surface 32A of the optical element 22 has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the X direction satisfies predetermined conditions. Furthermore, in the optical element 22 of Configuration Example 1, one of the incident surface 30A and the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy a predetermined condition. More specifically, in the optical element 22 of Configuration Example 1, one of the incident surface 30A and the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction is constant along the Y direction and is small (below Mareshal's tolerance) at all positions along the Y direction. Therefore, it can be said that one of the incident surface 30A and the exit surface 32A has a shape that imparts wavefront aberration in the X direction but does not impart wavefront aberration in the Y direction (resulting in aberration-free).

[0196] In Configuration Example 1, the optical element 22 has a shape such that the other of the incident surface 30A and the exit surface 32A does not satisfy a predetermined condition for the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction. More specifically, in the optical element 22 in Configuration Example 1, the other of the incident surface 30A and the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30A and the exit surface 32A is planar. However, it is not limited to this, and the other of the incident surface 30B and the exit surface 32B may be spherical with constant curvature (convex or concave).

[0197] In the configuration example 1, the optical element 22 has an incident surface 30A that is aspherical in shape to satisfy predetermined conditions for the wavefront aberration profile of the laser light L2, and an exit surface 32A that is planar (or spherical). However, it is not limited to this, and the exit surface 32A may be aspherical in shape to satisfy predetermined conditions for the wavefront aberration profile of the laser light L2, and the incident surface 30A may be planar (or spherical).

[0198] Curve A3 in Figures 65 and 66 shows the illumination light intensity distribution on the illuminated object 100 at the focal point Pf. As shown in curve A3, the optical element 22 in Configuration Example 1 makes it possible to make the shape of the illumination light intensity distribution at the focal point Pf longer in the X direction than in the Y direction. Furthermore, the optical element 22 in Configuration Example 1 suppresses the non-uniformity of the illumination light intensity distribution in the X direction at the focal point Pf in the X direction by introducing wavefront aberration in the X direction, making it possible to create a top-hat shaped line profile in the X direction.

[0199] Note that the position of the optical element 22 and the configuration of elements other than the optical element 22 shown in Figures 65 and 66 are examples, and the positions and element configurations described in each embodiment, modified example, and configuration of each example described above can be applied.

[0200] (Configuration Example 2) Figures 67 and 68 are schematic diagrams of a laser irradiation device according to Configuration Example 2. In Configuration Example 2, each of the multiple optical elements 22 is shaped to widen the irradiation shape of the object 100 at the focal point Pf in a second direction (in this example, the X direction). According to Configuration Example 2, the irradiation shape of the object 100 at the focal point Pf can be made into a linear irradiation shape in which the second direction (in this example, the X direction) is longer than the first direction (in this example, the Y direction). Furthermore, by providing multiple optical elements 22, the size of the irradiation shape in the second direction (in this example, the X direction) of the object 100 at the focal point Pf can be made longer than when a single optical element 22 is provided, for example, as in Configuration Example 1.

[0201] As shown in Figures 67 and 68, in Configuration Example 2, a plurality of optical elements 22 are provided, aligned in the optical axis direction (Z direction) of the laser beam L. Specifically, the optical elements 22 in Configuration Example 2 include a first optical element 22A and a second optical element 22B. In this example, it is composed of two optical elements (first optical element 22A and second optical element 22B), but it may be composed of three or more optical elements 22 aligned in the optical axis direction. Each optical element 22 in Configuration Example 2 differs from each optical element 22 in the second embodiment in that the direction in which aberrations are applied is the same. This will be explained in detail below.

[0202] The first optical element 22A of Configuration Example 2 expands the irradiation shape of the irradiated object 100 at the focal point Pf in a second direction (the X direction in this example). In Configuration Example 2, one of the incident surface 30A and the exit surface 32A of the first optical element 22A has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the X direction satisfies predetermined conditions. The other side of the incident surface 30A and the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy predetermined conditions. More specifically, the wavefront aberration profile of the laser light L2 in the Y direction is constant along the Y direction and is small (below Mareshar's tolerance) at all positions along the Y direction. Therefore, it can be said that one of the incident surface 30A and the exit surface 32A has a shape that introduces wavefront aberration in the X direction but does not introduce wavefront aberration in the Y direction (i.e., it is aberration-free).

[0203] In the first optical element 22A of configuration example 2, the other of the incident surface 30A and the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30A and the exit surface 32A has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30A and the exit surface 32A is planar. However, it is not limited to this, and the other of the incident surface 30A and the exit surface 32A may be spherical with constant curvature (convex or concave).

[0204] In the examples shown in Figures 67 and 68, the first optical element 22A has an aspherical exit surface 32A that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and a planar incident surface 30A. However, it is not limited to this, and the incident surface 30A may be aspherical that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and the exit surface 32A may be planar (or spherical).

[0205] The second optical element 22B of Configuration Example 2 expands the irradiation shape of the irradiated object 100 at the focal point Pf in a second direction (the X direction in this example). The second optical element 22B of Configuration Example 2 is provided on the Z side of the first optical element 22A. In Configuration Example 2, one of the incident surface 30B and the exit surface 32B of the second optical element 22B has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the X direction satisfies predetermined conditions. In Configuration Example 2, one of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser beam L2 in the Y direction is constant along the Y direction, and is small (below Mareshal's tolerance) at all positions along the Y direction. Therefore, it can be said that one of the incident surface 30B and the exit surface 32B has a shape that imparts wavefront aberration in the X direction but does not impart wavefront aberration in the Y direction (i.e., is aberration-free).

[0206] In the second optical element 22B of configuration example 2, the other of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small at all positions (a value below Mareshal's tolerance). Specifically, the other of the incident surface 30B and the exit surface 32B is planar. However, it is not limited to this, and the other of the incident surface 30B and the exit surface 32B may be spherical with constant curvature (convex or concave).

[0207] In the examples shown in Figures 67 and 68, the second optical element 22B has an aspherical incident surface 30B that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and a planar exit surface 32B. However, it is not limited to this, and the exit surface 32B may be aspherical that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and the incident surface 30B may be planar (or spherical).

[0208] Curve A3 in Figures 67 and 68 shows the distribution of illumination light intensity on the illuminated object 100 at the focal point Pf. As shown in curve A3, the optical element 22 in Configuration Example 2 is provided with multiple optical elements 22 (first optical element 22A and second optical element 22B in this example) that widen the illumination shape at the focal point Pf in the same second direction (X direction in this example). Therefore, according to Configuration Example 2, the illumination shape at the focal point Pf can be made into a line-shaped illumination shape that is longer in the X direction than in the Y direction, and by providing multiple optical elements 22, a line-shaped illumination shape that is longer in the X direction can be realized. Furthermore, according to Configuration Example 2, by applying wavefront aberration in the X direction with multiple optical elements 22, a top-hat-shaped line profile that is longer in the X direction can be achieved.

[0209] In the second configuration example, the unevenness of one of the incident surface 30A and the exit surface 32A of the first optical element 22A coincides with the unevenness of one of the incident surface 30B and the exit surface 32B of the second optical element 22B. That is, if one of the incident surface 30A and the exit surface 32A of the first optical element 22A is concave, then one of the incident surface 30B and the exit surface 32B of the second optical element 22B will also be concave. On the other hand, if one of the incident surface 30A and the exit surface 32A of the first optical element 22A is convex, then one of the incident surface 30B and the exit surface 32B of the second optical element 22B will also be convex. This makes it possible to appropriately increase the length in the X direction of the irradiation shape at the irradiated object 100 at the focal point Pf.

[0210] Note that the positions of each optical element 22 and the configuration of elements other than the optical element 22 shown in Figures 67 and 68 are examples, and the positions and element configurations described in the embodiments, modified examples, and configurations described above can be applied.

[0211] (Configuration Example 3) Figures 69 and 70 are schematic diagrams of a laser irradiation device according to Configuration Example 3. In Configuration Example 3, multiple optical elements 22 are arranged in the same way as in Configuration Example 2, both in a direction that widens the irradiation shape at the irradiated object 100 at the focal position Pf in the second direction (in this example, the X direction). However, here it differs from Configuration Example 2 in that the aberration-inducing surface of the optical element is a concave surface on one side and a convex surface on the other. In this case, the curvatures of the two are in opposite signs, so when they are superimposed, they cancel each other out in the direction of wavefront aberration. Therefore, a wavefront aberration equivalent to the difference between the two is applied in the second direction (in this example, the X direction), resulting in a smaller wavefront aberration than when using one optical element 22 each, and the irradiation size in the second direction (in this example, the X direction) at the focal position Pf can be made smaller than in Configuration Example 1 and Configuration Example 2, resulting in a short, line-shaped irradiation shape.

[0212] As shown in Figures 69 and 70, in Configuration Example 3, a plurality of optical elements 22 are provided aligned in the optical axis direction (Z direction) of the laser beam L. Specifically, the optical elements 22 in Configuration Example 3 include a first optical element 22A and a second optical element 22B. In this example, it is composed of two optical elements (first optical element 22A and second optical element 22B), but it may be composed of three or more optical elements 22 aligned in the optical axis direction. Configuration Example 3 differs from Configuration Example 2 in that the shapes of the surfaces that give wavefront aberration to the plurality of optical elements include both concave and convex surfaces. In this case, the curvature of the concave and convex surfaces are in opposite signs, so when they are superimposed, they cancel each other out in the direction of wavefront aberration. Therefore, the aberrations of the concave surfaces and the aberrations of the convex surfaces are added together, and the wavefront aberration corresponding to the difference between the sum of the aberrations of the concave surfaces and the sum of the aberrations of the convex surfaces is given in the second direction (X direction in this example). A more detailed explanation follows below.

[0213] The first optical element 22A in Configuration Example 3 expands the illumination shape on the illuminated object 100 at the focal point Pf in a second direction (the X direction in this example). The shape of the first optical element 22A in Configuration Example 3 is the same as that of the first optical element 22A in Configuration Example 2 (see Figures 67 and 68), so its description is omitted.

[0214] The second optical element 22B in Configuration Example 3 expands the irradiation shape on the irradiated object 100 at the focal point Pf in a second direction (the X direction in this example). The second optical element 22B in Configuration Example 3 is provided on the Z side of the first optical element 22A. In Configuration Example 3, one of the incident surface 30B and the exit surface 32B of the second optical element 22B has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the X direction satisfies predetermined conditions. In Configuration Example 3, one of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser beam L2 in the Y direction is constant along the Y direction, and is small (below Mareshal's tolerance) at all positions along the Y direction. Therefore, it can be said that one of the incident surface 30B and the exit surface 32B has a shape that imparts wavefront aberration in the X direction but does not impart wavefront aberration in the Y direction (i.e., is aberration-free).

[0215] In the second optical element 22B of configuration example 3, the other of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30B and the exit surface 32B has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small at all positions (a value below Mareshal's tolerance). Specifically, the other of the incident surface 30B and the exit surface 32B is planar. However, it is not limited to this, and the other of the incident surface 30B and the exit surface 32B may be spherical with constant curvature (convex or concave).

[0216] In the examples shown in Figures 69 and 70, the second optical element 22B has an aspherical incident surface 30B that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and a planar exit surface 32B. However, it is not limited to this, and the exit surface 32B may be aspherical that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and the incident surface 30B may be planar (or spherical).

[0217] Curve A3 in Figures 69 and 70 shows the illumination light intensity distribution on the illuminated object 100 at the focal point Pf. As shown in curve A3, in the optical element 22 of Configuration Example 3, the surface that imparts aberration to the optical element in the second direction (X direction in this example) is a concave surface for the first optical element 22A and a convex surface for the second optical element 22B. Therefore, according to Configuration Example 2, the illumination shape at the focal point Pf can be made into a line shape that is longer in the X direction than in the Y direction, and a line-shaped illumination shape with a relatively shorter length in the X direction can be realized compared to Configuration Examples 1 and 2. Furthermore, according to Configuration Example 3, by imparting wavefront aberration in the X direction with the optical element 22, the non-uniformity of the light intensity distribution of the laser light L2 in the X direction can be appropriately suppressed, and a line-top hat shaped profile with a relatively short length in the X direction can be achieved.

[0218] In configuration example 3, the unevenness of one of the incident surface 30A and the exit surface 32A of the first optical element 22A does not coincide with the unevenness of one of the incident surface 30B and the exit surface 32B of the second optical element 22B. That is, if one of the incident surface 30A and the exit surface 32A of the first optical element 22A is concave, one of the incident surface 30B and the exit surface 32B of the second optical element 22B will be convex. On the other hand, if one of the incident surface 30A and the exit surface 32A of the first optical element 22A is convex, one of the incident surface 30B and the exit surface 32B of the second optical element 22B will be concave. As a result, the length in the X direction of the illumination shape on the illuminated object 100 at the focal point Pf can be made relatively short.

[0219] Note that the positions of each optical element 22 and the configuration of elements other than the optical element 22 shown in Figures 69 and 70 are examples, and the positions and element configurations described in the embodiments, modified examples, and configurations described above can be applied.

[0220] (Configuration Example 4) Figures 71 and 72 are schematic diagrams of a laser irradiation device according to Configuration Example 4. Configuration Example 4 is provided with three or more optical elements 22, and at least two of the optical elements 22 have different directions in which they widen the irradiation shape on the object 100 at the focal point Pf. According to Configuration Example 3, the irradiation shape at the focal point Pf can be made into a rectangle (a rectangle in this example) widened in the second direction and the first direction.

[0221] As shown in Figures 71 and 72, in Configuration Example 4, three or more optical elements 22 are provided, aligned in the optical axis direction (Z direction) of the laser beam L. Specifically, the optical elements 22 in Configuration Example 4 include a first optical element 22A, a second optical element 22B, and a third optical element 22C. In this example, it is composed of three optical elements (first optical element 22A, second optical element 22B, and third optical element 22C), but it may be composed of four or more optical elements 22 aligned in the optical axis direction.

[0222] The first optical element 22A in Configuration Example 4 expands the illumination shape on the illuminated object 100 at the focal point Pf in a second direction (the X direction in this example). The shape of the first optical element 22A in Configuration Example 4 is the same as that of the first optical element 22A in Configuration Example 2 (see Figures 67 and 68), so a description is omitted.

[0223] The second optical element 22B in Configuration Example 4 expands the illumination shape on the illuminated object 100 at the focal point Pf in a second direction (the X direction in this example). The second optical element 22B in Configuration Example 4 is located on the Z-direction side of the first optical element 22A. The shape of the second optical element 22B in Configuration Example 4 is the same as that of the second optical element 22B in Configuration Example 2 (see Figures 67 and 68), so a description is omitted.

[0224] The third optical element 22C in Configuration Example 4 expands the irradiation shape on the object 100 at the focal point Pf in a first direction (Y direction in this example). The third optical element 22C in Configuration Example 4 is provided on the opposite side from the Z direction (towards the light source 10) from the first optical element 22A. In Configuration Example 4, one of the incident surface 30C and the exit surface 32C of the third optical element 22C has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the Y direction satisfies predetermined conditions. In Configuration Example 4, one of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser light L2 in the Y direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser beam L2 in the X direction is constant along the X direction, and is small (below Mareshal's tolerance) at all positions along the X direction. Therefore, it can be said that one of the incident surface 30C and the exit surface 32C has a shape that imparts wavefront aberration in the Y direction but does not impart wavefront aberration in the X direction (i.e., is aberration-free).

[0225] In the third optical element 22C of configuration example 4, the other of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small at all positions (a value below Mareshal's tolerance). Specifically, the other of the incident surface 30C and the exit surface 32C is planar. However, it is not limited to this, and the other of the incident surface 30C and the exit surface 32C may be spherical with constant curvature (convex or concave).

[0226] In the examples shown in Figures 71 and 72, the third optical element 22C has an aspherical incident surface 30C that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and a planar exit surface 32C. However, it is not limited to this, and the exit surface 32C may be aspherical that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and the incident surface 30C may be planar (or spherical).

[0227] Curve A3 in Figures 71 and 72 shows the irradiation light intensity distribution on the irradiated object 100 at the focal point Pf. As shown in curve A3, the optical element 22 in Configuration Example 4 is provided with multiple optical elements 22 (first optical element 22A and second optical element 22B in this example) that broaden the irradiation shape at the focal point Pf in a second direction (X direction in this example), and an optical element 22 (third optical element 22C in this example) that broadens it in a first direction (Y direction in this example). Therefore, according to Configuration Example 4, the irradiation shape at the focal point Pf can be broadened in both the X and Y directions, and can be made into a rectangular shape where the X direction is longer than the Y direction. Furthermore, according to Configuration Example 4, by applying wavefront aberration in both the X and Y directions with multiple optical elements 22, the non-uniformity of the light intensity distribution of the laser light L2 in the X and Y directions can be more appropriately suppressed, and a top-hat shaped profile can be made in the X and Y directions.

[0228] Thus, in this configuration example, the illumination shape at the focal point Pf can be made into a rectangular shape that is elongated in the second direction by making the number of optical elements 22 that spread in the second direction greater than the number of optical elements 22 that spread in the first direction. However, in this configuration example, the number of optical elements 22 that spread in the second direction may be the same as the number of optical elements 22 that spread in the first direction. This makes it possible to make a square illumination shape.

[0229] Note that the positions of each optical element 22 and the configuration of elements other than the optical elements 22 shown in Figures 71 and 72 are examples, and the positions and element configurations described in the embodiments, modified examples, and configurations described above can be applied.

[0230] (Configuration Example 5) Figures 73 and 74 are schematic diagrams of a laser irradiation device according to Configuration Example 5. Configuration Example 5 is provided with three or more optical elements 22 that spread the irradiation shape at the focal position Pf in directions that are different from each other. According to Configuration Example 3, the irradiation shape at the focal position Pf can be made into a polygon with many sides (an octagon in this example).

[0231] As shown in Figures 73 and 74, in Configuration Example 5, three or more optical elements 22 are provided, aligned in the optical axis direction (Z direction) of the laser beam L. Specifically, the optical elements 22 in Configuration Example 5 include a first optical element 22A, a second optical element 22B, a third optical element 22C, and a fourth optical element 22D. In this example, it is composed of four optical elements (first optical element 22A, second optical element 22B, third optical element 22C, and fourth optical element 22D), but it may be composed of three or more optical elements 22 aligned in the optical axis direction.

[0232] The first optical element 22A in Configuration Example 5 expands the illumination shape at the focal point Pf in a second direction (the X direction in this example). The shape of the first optical element 22A in Configuration Example 4 is the same as that of the first optical element 22A in Configuration Example 2 (see Figures 67 and 68), so its description is omitted.

[0233] The second optical element 22B in Configuration Example 5 broadens the illumination shape at the focal point Pf in the first direction (Y direction in this example). The second optical element 22B in Configuration Example 5 is located on the opposite side from the Z direction of the first optical element 22A. The shape of the second optical element 22B in Configuration Example 5 is the same as that of the third optical element 22C in Configuration Example 4 (see Figures 71 and 72), so a description is omitted.

[0234] The third optical element 22C in Configuration Example 5 expands the illumination shape at the focal point Pf in a third direction different from the first and second directions (in this example, an oblique direction between the X and Y directions). The third optical element 22C in Configuration Example 5 is located on the Z-direction side of the first optical element 22A.

[0235] In the third optical element 22C of Configuration Example 5, one of the incident surface 30C and the exit surface 32C has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the third direction (oblique direction) satisfies predetermined conditions. Furthermore, in the third optical element 22C of Configuration Example 5, one of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser light L2 in the direction perpendicular to the third direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser light L2 in the direction perpendicular to the third direction is constant along the direction perpendicular to the third direction, and is a small value (a value below Mareshal's tolerance) at all positions along the direction perpendicular to the third direction. Therefore, it can be said that one of the incident surface 30C and the exit surface 32C has a shape that imparts wavefront aberration in the third direction, but does not impart wavefront aberration (is aberration-free) in the direction perpendicular to the third direction.

[0236] In the third optical element 22C of configuration example 5, the other of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30C and the exit surface 32C has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30C and the exit surface 32C is planar. However, it is not limited to this, and the other of the incident surface 30C and the exit surface 32C may be spherical with constant curvature (convex or concave).

[0237] In the examples shown in Figures 73 and 74, the third optical element 22C has an aspherical incident surface 30C that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and a planar exit surface 32C. However, it is not limited to this, and the exit surface 32C may be aspherical that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and the incident surface 30C may be planar (or spherical).

[0238] The fourth optical element 22D in Configuration Example 5 expands the illumination shape at the focal point Pf in a fourth direction (in this example, a direction perpendicular to the third direction) that is different from the first, second, and third directions. The fourth optical element 22D in Configuration Example 5 is located on the Z-direction side of the third optical element 22C.

[0239] In the fourth optical element 22D of Configuration Example 5, one of the incident surface 30D and the exit surface 32D has a shape (for example, aspherical) such that the wavefront aberration profile of the laser light L2 in the fourth direction satisfies predetermined conditions. Furthermore, in the fourth optical element 22D of Configuration Example 5, one of the incident surface 30D and the exit surface 32D has a shape such that the wavefront aberration profile of the laser light L2 in a direction perpendicular to the fourth direction does not satisfy predetermined conditions. More specifically, one of the incident surface 30D and the exit surface 32D has a shape such that the wavefront aberration profile of the laser light L2 in a direction perpendicular to the fourth direction is constant along the direction perpendicular to the fourth direction, and is a small value (a value below Mareshal's tolerance) at all positions along the direction perpendicular to the fourth direction. Therefore, it can be said that one of the incident surface 30D and the exit surface 32D has a shape that imparts wavefront aberration in the fourth direction, but does not impart wavefront aberration (is aberration-free) in the direction perpendicular to the fourth direction.

[0240] In the fourth optical element 22D of configuration example 5, the other of the incident surface 30D and the exit surface 32D has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction does not satisfy a predetermined condition. More specifically, the other of the incident surface 30D and the exit surface 32D has a shape such that the wavefront aberration profile of the laser light L2 in each direction perpendicular to the Z direction is constant and small (below Mareshal's tolerance) at all positions. Specifically, the other of the incident surface 30D and the exit surface 32D is planar. However, it is not limited to this, and the other of the incident surface 30D and the exit surface 32D may be spherical with constant curvature (convex or concave).

[0241] In the examples shown in Figures 73 and 74, the fourth optical element 22D has an aspherical incident surface 30D that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and a planar exit surface 32D. However, it is not limited to this, and the exit surface 32D may be aspherical that satisfies predetermined conditions for the wavefront aberration profile of the laser light L2, and the incident surface 30D may be planar (or spherical).

[0242] Curve A3 in Figures 73 and 74 shows the illumination light intensity distribution at the focal point Pf. As shown in curve A3, the optical element 22 in Configuration Example 5 is provided with three or more optical elements 22 (in this example, the first optical element 22A, the second optical element 22B, the third optical element 22C, and the fourth optical element 22D) that spread the illumination shape at the focal point Pf in different directions (in this example, the first to fourth directions). Therefore, according to Configuration Example 5, the illumination shape at the focal point Pf can be spread in three or more directions to become a polygon with many sides (hexagon or more). In the example of Figures 73 and 74, by spreading the illumination shape at the focal point Pf in the first to fourth directions, an octagonal illumination shape can be achieved. Furthermore, according to Configuration Example 5, by applying wavefront aberration in each direction using multiple optical elements 22, the non-uniformity of the illumination light intensity distribution at the focal point Pf in each direction can be more appropriately suppressed, resulting in a top-hat shaped profile.

[0243] In the above explanation, the illumination shape at the focal point Pf was made octagonal by arranging four optical elements 22 in the optical axis direction, each having a different direction of spreading the illumination shape at the focal point Pf (which may be described as the direction along the generatrix) (for example, shifted by 45 degrees each). In contrast, for example, the illumination shape at the focal point Pf can be made hexagonal by arranging three optical elements 22 in the optical axis direction, each having a different direction of spreading the illumination shape at the focal point Pf (the direction along the generatrix) (for example, shifted by 60 degrees each). Also, for example, the illumination shape at the focal point Pf can be made decagonal by arranging five optical elements 22 in the optical axis direction, each having a different direction of spreading the illumination shape at the focal point Pf (the direction along the generatrix) (for example, shifted by 36 degrees each). For example, by arranging two optical elements 22 that have the same direction of expanding the illumination shape at the focal point Pf (the direction along the generatrix), and two optical elements 22 whose direction of expanding the illumination shape at the focal point Pf (the direction along the generatrix) is shifted by 90 degrees relative to those optical elements, the illumination shape at the focal point Pf can be made square. On the other hand, by arranging two optical elements 22 that have the same direction of expanding the illumination shape at the focal point Pf (the direction along the generatrix), and two optical elements 22 whose direction of expanding the illumination shape at the focal point Pf (the direction along the generatrix) is shifted by 45 degrees relative to those optical elements, the illumination shape at the focal point Pf can be made parallelogram. Also, for example, by arranging two optical elements 22 that expand the illumination shape at the focal point Pf in one direction and in a direction perpendicular to it (i.e., optical elements 22 that can make the illumination shape square) such that their directions of expanding the illumination shape (the direction along the generatrix) are shifted by 45 degrees, the illumination shape at the focal point Pf can be made octagonal.

[0244] Note that the positions of each optical element 22 and the configuration of elements other than the optical element 22 shown in Figures 73 and 74 are examples, and the positions and element configurations described in the embodiments, modified examples, and configurations described above can be applied.

[0245] (Effects) As described above, the optical element 22 according to this disclosure has an incident surface 30 into which laser light L1 is incident and an exit surface 32 from which laser light L2 is emitted. At least one of the incident surface 30 and the exit surface 32 has a shape such that, in a first direction (Y direction) perpendicular to the propagation direction (Z direction) of the laser light L2, the wavefront aberration profile of the laser light L2 is continuous, the curvature in the wavefront aberration curvature profile of the laser light L2 is at a maximum value at a first position Y1, and the curvature at the second position Y2 and third position Y3 is smaller than the maximum value at the first position Y1 (i.e., the wavefront profile satisfies predetermined conditions). Furthermore, at least one of the incident surface 30 and the exit surface 32 has a shape such that, in a second direction (X direction) perpendicular to the propagation direction of the laser beam L2 and the first direction, the wavefront aberration profile of the laser beam L2 is continuous, the curvature in the wavefront aberration curvature profile of the laser beam L2 is at a maximum value at the first position X1, and the curvature at the second position X2 and the third position X3 is smaller than the maximum value at the first position X1 (i.e., the wavefront profile has a shape that satisfies predetermined conditions). The first position is a position between the second position and the third position, and is closer to the optical axis AX of the laser beam L than the second and third positions.

[0246] According to this disclosure, non-uniformity of the light intensity of the laser beam L can be appropriately suppressed in both the Y and X directions. Therefore, according to this disclosure, the optical element 22 that can suppress non-uniformity of light intensity can be used in various specifications, making it highly versatile and contributing to cost reduction. Furthermore, the functions of the optical element 22 can be expanded and its performance stabilized.

[0247] At least one of the incident surface 30 and the exit surface 32 may have a shape such that, in each direction perpendicular to the propagation direction (Z direction) of the laser beam L, the wavefront aberration profile of the laser beam L2 is continuous, the curvature in the wavefront aberration curvature profile of the laser beam L2 is at a maximum value at a first position, and the curvature at the second and third positions is smaller than the maximum value at the first position (i.e., the wavefront profile satisfies predetermined conditions). According to this disclosure, non-uniformity of the light intensity of the laser beam L can be appropriately suppressed, and for example, a circular laser beam L with uniform light intensity can be generated.

[0248] At least one of the incident surface 30 and the exit surface 32 may have a greater slope in the wavefront aberration profile of the laser beam L2 in a third direction between the first and second directions than the wavefront aberration profiles of the laser beam in the first and second directions. According to this disclosure, non-uniformity of the light intensity of the laser beam L can be appropriately suppressed, and for example, a square or rectangular laser beam L with uniform light intensity can be generated.

[0249] The wavefront aberration profile of the laser beam L2 in the first direction and the wavefront aberration profile of the laser beam L2 in the second direction may be the same. According to this disclosure, the non-uniformity of the light intensity of the laser beam L can be appropriately suppressed, and for example, a square laser beam L with uniform light intensity can be generated.

[0250] The wavefront aberration profile of the laser beam L2 in the first direction and the wavefront aberration profile of the laser beam L2 in the second direction may be different. According to this disclosure, the non-uniformity of the light intensity of the laser beam L can be appropriately suppressed, and for example, a rectangular laser beam L with uniform light intensity can be generated.

[0251] The optical element 22 may include a first optical element 22A and a second optical element 22B. The first optical element 22A has a shape such that at least one of its incident surface 30 and exit surface 32 is such that in a first direction (Y direction) perpendicular to the propagation direction (Z direction) of the laser light L2, the wavefront aberration profile of the laser light L2 is continuous, the curvature in the wavefront aberration curvature profile of the laser light L2 is at a maximum value at a first position Y1, and the curvature at the second position Y2 and third position Y3 is smaller than the maximum value at the first position Y1 (i.e., the wavefront profile satisfies predetermined conditions). The second optical element 22B has a shape such that at least one of the incident surface 30 and the exit surface 32 has a wavefront aberration profile of the laser light L2 that is continuous in a second direction (X direction) perpendicular to the propagation direction of the laser light L2 and the first direction, the curvature of the wavefront aberration profile of the laser light L2 is at a maximum value at the first position X1, and the curvature at the second position X2 and the third position X3 is smaller than the maximum value at the first position X1 (i.e., the wavefront profile has a shape that satisfies predetermined conditions). According to this disclosure, non-uniformity of the light intensity of the laser light L can be appropriately suppressed.

[0252] The first optical element 22A and the second optical element 22B are optical elements of the same shape, and the second optical element 22B is positioned at a 90° offset from the first optical element 22A in the circumferential direction when the optical axis direction (Z direction) is taken as the axial direction. According to this disclosure, costs can be reduced by using optical elements of the same shape.

[0253] The ratio of the effective diameter D1 to the beam diameter D2 of the laser beam L is preferably 1.5 or greater. According to this disclosure, the shape accuracy of the top-hat shaped profile of the laser beam L3 can be increased, and a more stable profile can be obtained.

[0254] The optical element 22 may have at least one of its incident surface 30 and exit surface 32 be aspherical. According to this disclosure, non-uniformity of the light intensity of the laser beam L can be appropriately suppressed.

[0255] The laser irradiation device 1 of this disclosure includes an optical element 22 and a light source 10 that emits laser light L into the optical element 22. According to this disclosure, the non-uniformity of the light intensity of the laser light L can be appropriately suppressed.

[0256] Although embodiments of the present disclosure have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above.

[0257] 1 Laser irradiation device 10 Light source 12 Optical element unit 20 Collimating lens 22 Optical element 24 Focusing lens 30 Incident surface 32 Exit surface L, L1, L2, L3 Laser light

Claims

1. The device has an incident surface into which laser light is incident and an exit surface from which the laser light is emitted, and at least one of the incident surface and the exit surface has a shape such that, in a first direction perpendicular to the direction of propagation of the laser light, the wavefront aberration profile of the laser light emitted from the exit surface is continuous, the curvature in the wavefront aberration curvature profile of the laser light emitted from the exit surface has a maximum value at a first position, and the curvature at the second and third positions is smaller than the maximum value at the first position; and in a second direction perpendicular to the direction of propagation and the first direction, the wavefront aberration profile of the laser light emitted from the exit surface is continuous, the curvature in the wavefront aberration curvature profile of the laser light emitted from the exit surface has a maximum value at a first position, and the curvature at the second and third positions is smaller than the maximum value at the first position. An optical element wherein the first position is a position between the second position and the third position, and is closer to the optical axis of the laser beam than the second position and the third position.

2. The optical element according to claim 1, wherein at least one of the incident surface and the exit surface has a shape such that, in each direction perpendicular to the direction of propagation of the laser light, the profile of the wavefront aberration of the laser light emitted from the exit surface is continuous, the curvature of the curvature profile of the wavefront aberration of the laser light emitted from the exit surface is at a maximum value at the first position, and the curvature at the second and third positions is smaller than the maximum value at the first position.

3. The optical element according to claim 1, wherein, in a third direction between the first and second directions, the slope of the wavefront aberration profile of the laser light emitted from the output surface is greater than the wavefront aberration profiles of the laser light in the first and second directions.

4. The optical element according to claim 3, wherein the wavefront aberration profile of the laser light in the first direction and the wavefront aberration profile of the laser light in the second direction are the same.

5. The optical element according to claim 3, wherein the wavefront aberration profile of the laser light in the first direction and the wavefront aberration profile of the laser light in the second direction are different.

6. The optical element according to claim 3, comprising: a first optical element having an incident surface or an exit surface such that, in the first direction, the wavefront aberration profile of the laser light emitted from the exit surface is continuous, the curvature in the wavefront aberration curvature profile of the laser light emitted from the exit surface is at a maximum value at a first position, and the curvature at the second and third positions is smaller than the maximum value at the first position; and a second optical element having an incident surface or an exit surface such that, in the second direction, the wavefront aberration profile of the laser light emitted from the exit surface is continuous, the curvature in the wavefront aberration curvature profile of the laser light emitted from the exit surface is at a maximum value at a first position, and the curvature at the second and third positions is smaller than the maximum value at the first position.

7. The optical element according to claim 6, wherein the first optical element and the second optical element are optical elements of the same shape, and the second optical element is positioned at a 90° offset from the first optical element in the circumferential direction when the optical axis direction is considered as the axial direction.

8. The optical element according to claim 1, wherein the ratio of the effective diameter to the beam width of the laser light is 1.5 or more.

9. The optical element according to claim 1, wherein at least one of the incident surface and the exit surface is an aspherical surface.

10. A laser irradiation device comprising an optical element according to any one of claims 1 to 8, and a light source that emits the laser light onto the optical element.

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