Beam homogenizer

Abstract

A beam homogenizer (30) for converting a laser radiation beam into a flat-top intensity distribution having brighter or darker edges includes a first lens array (32), a second lens array (14), and a positive lens (16). The first lens array (32) includes a plurality of lens elements (20) separated by a gap (34) without optical magnification. A brighter or darker edge is created by selecting a distance between the first lens array and the second lens array that is smaller or larger than the focal length of the lens elements of the second lens array.

Description

Technology Field

[0001] (preference)

[0002] This application claims priority to U.S. provisional application No. 62 / 817,331 filed on March 12, 2019, the disclosure of which is incorporated herein in its entirety.

[0003] (Technology field)

[0004] The present invention generally relates to shaping light from a laser. It is particularly related to shaping light from one or more lasers into a radiation beam having a uniform cross-section having a brighter or darker edge. Background Technology

[0005] Lasers have become an essential source for uniform illumination in a wide range of applications, including surface inspection of semiconductor materials, heat treatment of display screen glass, metal hardening, and rapid analysis (assay) of biomedical fluids. A common requirement is a long, narrow laser radiation beam that uniformly illuminates lines on flat surfaces or planes of transparent material volumes. Such long, narrow laser beams are generally referred to as "line beams."

[0006] Diode lasers are efficient devices that convert electrical power into coherent optical power. For high-power applications, diode laser bars with multiple diode laser emitters provide a convenient method for scaling the optical power available from a single diode laser emitter. These diode laser emitters are spaced apart and arranged in a linear array. Although diode laser bars inherently have a long, slender emission cross-section, it is necessary to overcome the non-uniform intensity distribution caused by emissions from multiple spatially distributed diode laser emitters.

[0007] An optical device that converts a laser beam so that its intensity is uniform across the cross-section of the converted beam is generally called a "beam homogenizer." A beam homogenizer often comprises one or two "microlens arrays," each containing multiple small lenses that are much smaller than the incident beam. Each microlens serves as an illumination source contributing to the converted beam. The "pitch" of a beam homogenizer is the distance between the centers of adjacent microlenses. Additional optical devices are required to collect and shape the multiple rays emanating from all the microlenses that intercept the incident ray. A linear array of microlenses can be used as a beam homogenizer for a long, thin beam of laser radiation emitted by a diode laser bar. An example of such a beam homogenizer is described in U.S. Patent No. 7,265,908.

[0008] Diode-pumped solid-state lasers, including fiber lasers, generally produce a Gaussian intensity distribution. The Gaussian laser beam is converted into an approximately uniform intensity distribution by a Powell lens or an equivalent optical device and can then be homogenized using a lens array. Collimated laser beams from a plurality of such diode-pumped solid-state lasers can be combined and homogenized using a lens array.

[0009] Slab lasers include diode-pumped solid-state lasers, gas discharge CO2 lasers, and excimer lasers. Slab lasers inherently generate a line beam. However, the line beam may not have a uniform cross-section, and the cross-sectional intensity distribution may be unstable. Lens arrays are used to homogenize the line beam from a slab laser and to combine the line beams of multiple slab lasers.

[0010] In processes involving heating a portion of a workpiece with laser illumination, a perfectly uniform cross-sectional intensity distribution may not produce uniform laser processing due to heat transfer away from the illuminated portion. To ensure uniform heating, illumination with a laser beam having higher intensity at the edges of the intensity distribution would be desirable. In other processes where it is necessary to pass a line beam multiple times to illuminate a large area of ​​the workpiece, complete exposure is ensured if adjacent paths slightly overlap, but differences in processing between the portions illuminated once and twice may occur. To prevent overexposure, illumination with a laser beam having lower intensity at the edges of the intensity distribution would be desirable. The problem to be solved

[0011] A beam shaping device is required to form a laser beam having different uniform cross-sectional intensity distributions with brighter or darker edges. Preferably, the optical device will have the elegance, simplicity, and miniaturization of a lens array homogenizer. means of solving the problem

[0012] In one embodiment, a beam homogenizer according to the present invention comprises a first lens array having a plurality of identical lens elements. Each lens element of the first lens array has a focal length (F1). Adjacent lens elements of the first lens array are separated by a gap, and each gap has a common width. A second lens array is provided. Each lens element of the second lens array has a focal length (F2). The first lens array and the second lens array are separated by a distance not equal to F2. A positive lens is provided and positioned. The positive lens has a focal length (F3). The first lens array, the second lens array, and the positive lens are arranged in order along the optical axis.

[0013] In another embodiment, a beam homogenizer according to the present invention comprises a first lens array having a plurality of identical lens elements. Each lens element of the first lens array has a flat central portion and a curved outer portion. The central portion has no optical power, and the outer portion has a focal length (F1). A second lens array is provided. Each lens element of the second lens array has a focal length (F2). The first lens array and the second lens array are separated by a distance not equal to F2. A positive lens is provided that is positioned on an optical axis and has a focal length (F3). The first lens array, the second lens array, and the positive lens are arranged in order along the optical axis.

[0014] In another embodiment, laser radiation passes through the lens element and the gap of the first lens array, passes through the second lens array, and passes through the positive lens, and propagates onto an illumination plane in that order. The illumination plane is located at a distance (F3) from the positive lens. The laser radiation propagating through the lens element of the first lens array has a different magnification on the illumination plane than the laser radiation propagating through the gap of the first lens array.

[0015] In another embodiment, laser radiation passes through the first lens array, passes through the second lens array, and passes through the positive lens, and propagates onto an illumination plane in that order. The illumination plane is located at a distance (F3) from the positive lens. The laser radiation on the illumination plane is converted from a different uniform intensity distribution into a homogenized intensity distribution having brighter or darker edges. Brief explanation of the drawing

[0016] The attached drawings included in this specification and constituting a part thereof schematically illustrate preferred embodiments of the present invention and serve to explain the principles of the present invention together with the general description above and the detailed description of preferred embodiments below. FIG. 1a is a schematic plan view illustrating a conventional beam homogenizer comprising a first lens array, a second lens array, and a positive lens. Collimated laser radiation propagating parallel to the optical axis is incident on the first lens array and propagates through the beam homogenizer. FIGS. 1B and FIGS. 1C are plan views schematically illustrating imaging through the beam homogenizer of FIG. 1A. An inverted magnified image of each lens element of the first lens array is formed and superimposed on the illumination plane. FIGS. 2a to 2c are schematic plan views illustrating a preferred embodiment of a beam homogenizer according to the present invention. The beam homogenizer of the present invention comprises a first lens array, a second lens array, and a positive lens. Each lens element of the first lens array is separated by a gap with no optical power. The distance between the first lens array and the second lens array is slightly greater than the focal length of each lens element of the second lens array. FIGS. 3a and 3b are schematic plan views illustrating another preferred embodiment of a beam homogenizer according to the present invention, which is similar to the embodiments of FIGS. 2a to 2c, but has a distance between the first lens array and the second lens array that is slightly smaller than the focal length of each lens element of the second lens array. FIG. 4a schematically illustrates the intensity distribution in the illumination plane for a laser radiation beam propagating through the beam homogenizer of FIG. 2a to 2c. Figure 4b schematically illustrates the intensity distribution in the illumination plane for a laser radiation beam propagating through the beam homogenizer of Figures 3a and 3b. FIGS. 5a and 5b are schematic plan views illustrating the diffraction effect of a laser radiation beam propagating through the beam homogenizer of FIGS. 2a to 2c. FIG. 6a schematically illustrates a camera image of the intensity distribution in the illumination plane for a laser radiation beam propagating through an example of the beam homogenizer of FIG. 3a and FIG. 3b. Figure 6b is a graph schematically showing the intensity distribution along the AA line of Figure 6a. Specific details for implementing the invention

[0017] Now, referring to drawings in which similar components are designated by similar numbers, FIG. 1a schematically illustrates a conventional beam homogenizer (10) having a first linear lens array (12), a second linear lens array (14), a positive lens (16), and an optical axis (18). Each identical lens element (20) of the lens array (12) has a focal length (F1), each identical lens element (22) of the lens array (14) has a focal length (F2), and the lens (16) has a focal length (F3). Each lens element (20, 22) has a common width (d). The lens arrays (12, 14) are separated by a distance (F2). The drawing illustrates a beam (24) of laser radiation propagating through the beam homogenizer (10). In this example, the laser radiation incident on the lens array (12) is collimated and propagated parallel to the optical axis (18).

[0018] FIGS. 1B and FIGS. 1C schematically illustrate imaging through a beam homogenizer (10). An inverted magnified image (26) of laser radiation incident on each lens element (20) is formed on an illumination plane (28) located at a distance (F3) from the lens (16). The inverted magnified image (26) of all illuminated lens elements (20) overlaps on the illumination plane (28) and has a width (D). FIG. 1B illustrates imaging of a ray originating from the center of each lens element (20). FIG. 1C illustrates imaging of a ray originating from a position displaced by a distance X1 from the center of each lens element (20). These rays are projected onto a position on the illumination plane (28) displaced by a distance X2 from the optical axis (18). The imaging magnification It is the ratio of.

[0019] The lens array (12) does not directly affect homogenization, and the focal length (F1) does not determine the magnification. The purpose of the lens array (12) is to increase the angle of acceptance for the light rays (24) incident on the beam homogenizer (10). Although the incident light rays (24) are depicted parallel to the optical axis (18), the incident light rays can be incident up to the maximum angle relative to the optical axis (18) while projecting as a superimposed image on the illumination plane (28). At the maximum angle of acceptance, the peripheral light rays focused by each lens element (20) will be incident on the edge of the corresponding lens element (22). There is a trade-off between the maximum angle of acceptance and the area of ​​each illuminated lens element (22). Reducing F1 relative to F2 increases this area, thereby reducing the vulnerability of the lens element (22) to optical damage, while simultaneously reducing the maximum angle of acceptance.

[0020] FIGS. 2a to 2c schematically illustrate a preferred embodiment of a beam homogenizer (30) according to the present invention. The beam homogenizer (30) is such that adjacent lens elements (20) of a first lens array (32) are separated by the same gap (34), and the distance between the first lens array (32) and the second lens array (14) is a distance F2+ It is similar to the beam homogenizer (10) except for the fact that each lens element (20) has a common width (d1), each gap (34) has a common width (d2), and each lens element (22) has a common width (d = d1 + d2). Distance is smaller than the focal length (F2). For example, It is desirable that it be less than 20% of F2. It is more preferably less than 10% of F2 and most preferably less than 5% of F2.

[0021] The gap (34) is described as an empty gap or "air gap." The gap (34) may also be made of transparent glass or polymer. The gap (34) is most preferably made of the same material as the lens element (20), has a planar parallel surface, and thus has no optical power. Generally, it would be practical to grind or mold the lens array (32) from a single piece of material in which each gap is fixedly connected to the adjacent lens element. FIG. 2a illustrates a beam (24) of laser radiation propagating through the lens element (20). FIG. 2b illustrates a beam (36) of laser radiation propagating through the gap (34). FIG. 2c shows an enlarged view of both the beam (24) (solid line) and the beam (36) (dotted line) around the illumination plane (28) and around the lens array (32).

[0022] To explain imaging through the beam homogenizer (30) of the present invention, it is useful to consider a ray-transfer matrix analysis or an ABCD matrix analysis as is known in the field of optics. First, referring to FIG. 1c, the ray-transfer matrix for focusing by the lens (16) and propagation between the lens (16) and the illumination plane (28) is as follows:

[0023]

[0024] Therefore, the displacement X2 of the light ray from the optical axis (18) in the illumination plane (28) is the angle of incidence of the lens (16). Depends only on:

[0025]

[0026] Returning to FIGS. 2a and 2b, the ray transmission matrix for focusing by each lens element (20), propagation between the lens array (32) and the lens array (14), and focusing by the corresponding lens element (22) is as follows:

[0027]

[0028] In the illustrated example of collimated laser radiation incident on the lens array (32), the angle of incidence of the ray with respect to the lens (16) is therefore the displacement X1 of the ray from the center of the lens element (20) and the distance It depends on:

[0029]

[0030] Therefore, the displacement X2 of the ray from the optical axis (18) in the illumination plane (28) is as follows:

[0031]

[0032] Corresponding to the "ideal imaging" of the beam homogenizer (10) When = 0, mathematical expression 5 is simply as follows:

[0033]

[0034] It should be noted that under these ideal imaging conditions, the total magnification of the beam homogenizer does not depend on the focal length (F1). However, In the case where ≠0, of mathematical formula 5 The scaling factor changes due to the term. In the case of the beam homogenizer of the present invention having >0, the magnification factor is different for a ray (24) incident on a lens element having a focal length (F1) and a ray (36) incident on a gap (34) having an essentially infinite focal length. In the case of a ray incident on the gap, The term is 0 and the absolute magnification is the same as the absolute magnification of ideal imaging. This becomes the case. In the case of light rays incident on the lens element, the absolute magnification is smaller It should be noted that having an air gap or an optically inert gap alone is not sufficient. Condition ≠0 is necessary so that the ray incident on the gap and the ray incident on the lens element have different magnifications.

[0035] Referring to FIG. 2a, the inverted image (26) of all illuminated lens elements (20) is superimposed on the illumination plane (28). The image (26) It is expanded by that amount, and therefore the width It has. Now, referring to FIG. 2b, the inverted images (40a, 40b) of all illuminated gaps (34) are also superimposed on the illumination plane (28). The two gap images are divided according to the lens elements (22) of the lens array (14) to which each ray is incident. The gap images (40a, 40b) are all It is magnified by that amount. Therefore, each gap image is width It has. Now, referring to FIG. 2c, the smaller absolute magnification of image (26) creates a dark gap between image (26) and gap images (40a, 40b).

[0036] It is insightful to consider the beam homogenizer (30) in terms of the ideal imaging described above. Within the beam homogenizer (30), an image plane (38) located at a distance (F2) from the lens array (14) is accurately imaged onto the illumination plane (28) by the lens array (14) and the lens (16). The image plane (38) is illuminated by a converging ray (24) focused by the lens element (20) and a parallel ray (36) propagating through the gap (34). The illumination of the image plane (38) is a repeated pattern of wider and narrower bands as shown in FIG. 2c. The illumination of the image plane (38) It is projected onto and superimposed on the illumination plane (28) by the lens array (14) and lens (16) at a magnification ratio.

[0037] The two descriptions of the beam homogenizer (30), one using a ray transmission matrix and the other being an ideal imaging aspect, are identical. The homogenizer creates a uniform or "flat top" intensity distribution in an illumination plane where the intensity is reduced toward the edges of other uniform intensity distributions. The relative position and width of the dark gap within the intensity distribution are determined by the focal length (F1), gap width (d2), and distance. Select and control.

[0038] FIGS. 3a and 3b schematically illustrate another preferred embodiment of a beam homogenizer (50) according to the present invention. The beam homogenizer (50) has a smaller distance F2 between the lens arrays (32 and 14). It is similar to the beam homogenizer (30) except for the fact that... The ray transmission matrix analysis for the beam homogenizer (50) is the same as that for the beam homogenizer (30). Image (26) is Expanding and width While having, width It has. Therefore, for the ray (24) incident on the lens element (20), the absolute magnification is greater than for the ray (36) incident on the gap (34). This greater magnification creates an overlap between the image (26) and the gap images (40a, 40b). The overlap creates two bright peaks toward the edges of different uniform intensity distributions. Imaging onto the illumination plane (28) is illustrated in FIG. 3b, and for convenience of explanation, illumination by a ray propagating through the lens element (20) and the gap (34), distinguished by their respective left and right offsets, is used.

[0039] In terms of ideal imaging, the image plane (38) is located in the path of the ray (24) incident on the lens element (20) and the ray (36) incident on the gap (34) prior to the lens array (32). Again, for convenience of illustration, the illumination of the image plane (38) by the rays (24 and 36) is distinguished by their respective left and right offsets. Although the image plane (38) is uniformly illuminated, the portion of the plane illuminated by the ray (36) (right offset) is imaged through both the lens element (20) and the gap (34). For example, the dotted line (52) depicted on the lens element (20) originates from the portion of the image plane illuminated by the ray (36). The portion imaged through both the lens element and the gap will appear brighter when projected onto the illumination plane (28). Thus, the beam homogenizer (50) creates a uniform intensity distribution in the illumination plane with increased intensity toward the edges.

[0040] FIG. 4a schematically illustrates a nominally uniform intensity distribution in an illumination plane (28) having a dark gap toward the edge of the intensity distribution generated by the beam homogenizer (30). The overall intensity distribution is illustrated by a thick line and a base intensity distribution generated by a ray propagating through the lens element (20), and the gap (34) is illustrated by a lighter line. Similarly, FIG. 4b schematically illustrates a nominally uniform intensity distribution in an illumination plane (28) having a bright peak toward the edge of the intensity distribution generated by the beam homogenizer (50). The overall width D of the intensity distribution is the gap width (d2) and the distance It should be noted that it is independent of. A dark gap appears in the intensity distribution of Fig. 4a because D > D1 + 2 D2. A bright peak appears in the intensity distribution of Fig. 4b because D < D1 + 2 D2.

[0041] A beam homogenizer having a lens array (32) configured and arranged to be translated longitudinally parallel to the optical axis (18) can be adjusted to produce a continuum of intensity distribution having a darker edge (as in FIG. 4a) or a brighter edge (as in FIG. 4b), or completely uniform intensity. This intensity distribution has a constant overall width (D) and also constant intensity over most distances (D2) from the edge. Mechanical devices for accurate linear translation of the optical device are commercially available, and a detailed description of such devices is not necessary to understand the principles of the invention. An intensity distribution with a darker edge has slightly higher intensity over the distance (D1) between the dark gaps. An intensity distribution with a brighter edge has slightly lower intensity over the distance (D1) between the bright peaks. When the lens array (32) has a gap (34) with a width (d2) that is small compared to the width (d1) of the lens element (20), this difference in intensity will be relatively small. For example, a ratio smaller than 0.12 or a ratio smaller than 0.06 am.

[0042] FIGS. 5a and 5b schematically illustrate some of the effects of diffraction for the beam homogenizer (30) of FIGS. 2a through 2c. Diffraction will occur at the edges of each lens element (20) of the illustrated example lens array (32). Light rays propagating through the gap (34) and approaching neighboring lens elements (20) are distributed angularly. Light rays passing very close to the lens elements (20) are distributed over the entire angle φ. It should be noted that the intensity distribution due to diffraction at the edges is not uniform, and rather, the diffraction intensity decreases as the angle increases. The entire angle φ is distinguished here to explain the effects of this diffraction. Additionally, it should be noted that the diffracted light rays may be directed toward one of the two lens elements (22), namely the lens element (22) corresponding to the diffracting lens element (20) or another lens element (22) that is a neighbor of the corresponding lens element. All of these lens elements (22) are located within the entire angle φ.

[0043] FIG. 5a illustrates only the diffracted rays propagating through the corresponding lens elements (22) of the lens array (14). These rays are projected onto the same range of locations on the illumination plane (28) as in the case without diffraction. FIG. 5b illustrates only the diffracted rays propagating through the adjacent lens elements (22). These rays are projected onto the range of locations on the illumination plane (28) outside the nominally uniform intensity distribution in the case without diffraction. Overall, diffraction slightly reduces illumination over distance D2 inside each edge of the nominally uniform intensity distribution and weakly illuminates distance D2 outside each edge of the intensity distribution. Thus, edge contrast is reduced by diffraction.

[0044] FIG. 6a schematically illustrates a camera image of an intensity distribution obtained using an experimental beam homogenizer (50). The image was scaled up in the vertical dimension relative to the horizontal dimension. The beam homogenizer was partially illuminated by a collimating beam of an excimer laser. The lens array (32) has 25 lens elements (20), and most of these lens elements were illuminated. The lens array (32) With a ratio of = 0.026, the width d = d1 + d2 was several millimeters. FIG. 6b is a graph schematically showing the intensity distribution measured along the AA line superimposed on FIG. 6a. FIG. 6a and FIG. 6b are shown on the same horizontal scale. The measured intensity distribution has bright peaks at each edge and relatively uniform intensity between the bright peaks. Translating the lens array (32) in the longitudinal direction and the distance By changing, the inventors From a perfectly uniform intensity distribution when θ is approximately 0 mm It showed continuous development with an intensity distribution that was depicted as having a bright edge when the value was about 9 mm.

[0045] Although a gap in the first lens array without optical magnification is illustrated and described herein, the requirement for creating an intensity distribution with a dark gap or a bright peak is a "gap" (34) in the first lens array having an optical magnification substantially smaller than the optical magnification of the lens element (20) in the first lens array (32). For example, the gap (34) may be occupied by a weaker lens element, and the weaker lens element has a focal length at least five times longer than the focal length (F1) of the lens element (20). An increase in the focal length of the weaker lens element increases the contrast between the dark gap or the bright peak and the uniform portion of the intensity distribution.

[0046] The gap (34) of the first lens array without optical magnification may have the form of a slab having a plane parallel to the surface. Such a slab will not modify the angle of the light rays propagating through it. Alternatively, the gap (34) may have the form of a wedge having a plane but not a plane parallel to the surface. The wedge angle is another variable that can be selected to position a dark gap or a bright peak within a different uniform intensity distribution, either toward the optical axis or away from the optical axis.

[0047] Another preferred embodiment of a beam homogenizer for generating the intensity distribution shown in FIGS. 4a and 4b is similar to the beam homogenizer of FIGS. 3a and 2a, but the first lens array (32) is replaced with a different lens array of the present invention. This different lens array of the present invention can be manufactured from a prior art lens array (12) by machining the central portion of each lens element to be flat. The resulting lens array will have a plurality of identical lens elements, each lens element having a flat central portion and a curved outer portion. The central portion has no optical magnification, and the outer portion has a focal length (F1). Light rays passing through the flat portion are imaged onto the illumination plane at a different magnification than light rays passing through the curved portion. An advantage of this embodiment of the beam homogenizer is that the first lens array can be manufactured by simply grinding and polishing a commercially available prior art lens array. For example, it is available at Thorlabs of Newton, New Jersey. The disadvantage of this embodiment is that it has a smaller acceptance angle for the light beam incident on the beam homogenizer.

[0048] The ray transmission matrix analysis presented above assumes a thin lens and uses a paraxial approximation. An analysis using these assumptions is sufficient to explain the principles and operation of the present invention. Those skilled in the art will recognize that accurate calculations are required to adequately describe the shape of the optical element and will recognize when including such additional parameters.

[0049] In summary, a laser radiation beam can be converted from a different uniform intensity distribution into a homogenized intensity distribution having brighter or darker edges using the beam homogenizer of the present invention. The beam homogenizer comprises a first lens array having a plurality of identical lens elements separated by a gap having a common width. A second lens array has a plurality of identical lens elements having a focal length (F2). The first and second lens arrays are separated by a distance that is close to but not equal to F2. If the separation distance is less than F2, a bright peak is produced, and if the separation distance is greater than F2, a dark gap is produced that is located toward the edge of the intensity distribution.

[0050] The present invention has been described above in connection with preferred embodiments and other embodiments. However, the present invention is not limited to the embodiments described and illustrated herein. Rather, the present invention is limited only by the claims appended herein.

Claims

Claim 1 A first lens array having a plurality of identical lens elements, wherein each lens element of the first lens array has a focal length (F1), adjacent lens elements of the first lens array are separated by a gap, said gap has no optical power, and each gap has a common width; a second lens array having a plurality of identical lens elements, wherein each lens element of the second lens array has a focal length (F2), and the first lens array and the second lens array are F 2 ± The second lens array separated by a distance of , and a positive lens located on an optical axis having a focal length (F3), wherein the first lens array, the second lens array, the positive lens, and an illumination plane are arranged in that order along the optical axis, and the illumination plane is located at a distance of F3 from the positive lens; comprising, wherein F1, F2, F3 and A light ray incident on a lens element at a position spaced apart by a distance X1 from the center of the lens element of the first lens array, A beam homogenizer characterized by being selected to project onto an illumination plane at a position spaced apart from the optical axis by a distance X2, wherein each lens element and positive lens of the second lens array project an image onto the illumination plane, the enlarged image is positioned around the optical axis, the images projected by all lens elements of the second lens array overlap each other, the gap of the first lens array is aligned with the edge of the lens element of the second lens array so that a light ray propagating through the gap of the first lens array is incident on one of two identical lens elements within the second lens array, and accordingly, the light ray propagating through the gap of the first lens array is emitted from the two lens elements of the second lens array. Claim 2 In claim 1, the first lens array and the second lens array are F2+, which is greater than F2. A beam homogenizer characterized by separation by a distance. Claim 3 In claim 1, the first lens array and the second lens array are F2- smaller than F2 A beam homogenizer characterized by separation by a distance. Claim 4 In Article 1, A beam homogenizer characterized by having less than 10% of F2. Claim 5 In Paragraph 4, A beam homogenizer characterized by having less than 5% of F2. Claim 6 A beam homogenizer according to any one of claims 1 to 5, characterized in that the gap between adjacent lens elements of the first lens array is an empty gap or an air gap. Claim 7 A beam homogenizer according to any one of claims 1 to 5, characterized in that the gap between adjacent lens elements of the first lens array is made of the same material as the lens elements of the first lens array. Claim 8 A beam homogenizer according to claim 7, characterized in that the material on which the gap of the first lens array and the lens element are made is transparent glass or a polymer. Claim 9 A beam homogenizer according to any one of claims 1 to 5, wherein the gap between adjacent lens elements of the first lens array is fixedly connected to the adjacent lens elements. Claim 10 delete Claim 11 A beam homogenizer according to claim 1, characterized in that the gap between adjacent lens elements of the first lens array is in the form of a slab having a planar parallel plane. Claim 12 A beam homogenizer according to claim 1, characterized in that the gap between adjacent lens elements of the first lens array is in the shape of a wedge, which is planar but not parallel. Claim 13 delete Claim 14 A beam homogenizer according to any one of claims 1 to 5, characterized in that an image having a repeating pattern of a wider and narrower band located in an image plane at a distance F2 from the second lens array is imaged onto the illumination plane. Claim 15 A beam homogenizer according to any one of claims 1 to 5, characterized in that the first lens array is configured and arranged to be translated in the longitudinal direction parallel to the optical axis. Claim 16 A beam homogenizer characterized by comprising: a first lens array having a plurality of identical lens elements, wherein each lens element of the first lens array has a flat central portion and a curved outer portion, wherein the central portion has no optical power and the outer portion has a focal length (F1); a second lens array having a plurality of identical lens elements, wherein each lens element of the second lens array has a focal length (F2), and the first lens array and the second lens array are separated by a distance not equal to F2; and a positive lens positioned on an optical axis having a focal length (F3), wherein the first lens array, the second lens array, and the positive lens are arranged in that order along the optical axis. Claim 17 A beam homogenizer according to claim 16, characterized in that the first lens array is configured and arranged to be translated in the longitudinal direction parallel to the optical axis. Claim 18 A beam homogenizer for laser radiation, comprising: a first lens array having a plurality of identical lens elements, wherein each lens element of the first lens array has a focal length (F1), adjacent lens elements of the first lens array are separated by a gap, said gap has no optical magnification, and each gap has a common width; and a second lens array having a plurality of identical lens elements, wherein each lens element of the second lens array has a focal length (F2), and the first lens array and the second lens array are F 2 ± The second lens array separated by a distance of , and a positive lens having a focal length (F3), wherein the laser radiation passes through the lens element and the gap of the first lens array, passes through the second lens array, passes through the positive lens, and propagates in that order onto an illumination plane located at a distance (F3) from the positive lens; wherein the laser radiation propagating through the lens element of the first lens array has a different magnification on the illumination plane than the laser radiation propagating through the gap of the first lens array, and the F1, F2, F3 and A light ray incident on a lens element at a position spaced apart by a distance X1 from the center of the lens element of the first lens array, A beam homogenizer for laser radiation, characterized in that it is selected to be projected onto an illumination plane at a position spaced apart from the optical axis by a distance X2, each lens element and positive lens of the second lens array project an image onto the illumination plane, the enlarged image is positioned around the optical axis, the images projected by all lens elements of the second lens array overlap each other, the gap of the first lens array is aligned with the edge of the lens element of the second lens array so that a light ray propagating through the gap of the first lens array is incident on one of two identical lens elements within the second lens array, and accordingly, the light ray propagating through the gap of the first lens array is emitted from the two lens elements of the second lens array. Claim 19 In claim 18, the first lens array and the second lens array are F2+, which is greater than F2. A beam homogenizer for laser radiation characterized by being separated by a distance, wherein the laser radiation propagates through the lens elements of the first lens array and has a smaller magnification than the laser radiation propagating through the gap of the first lens array. Claim 20 In claim 18, the first lens array and the second lens array are F2- smaller than F2 A beam homogenizer for laser radiation characterized by being separated by a distance, wherein the laser radiation propagates through the lens elements of the first lens array and has a greater magnification than the laser radiation propagating through the gap of the first lens array. Claim 21 A beam homogenizer for laser radiation, comprising: a first lens array having a plurality of identical lens elements, wherein adjacent lens elements of the first lens array are separated by a gap, said gap having no optical magnification, and each gap having a common width; and a second lens array having a plurality of identical lens elements, wherein each lens element of the second lens array has a focal length (F2), and the first lens array and the second lens array are separated by a distance not equal to F2. A positive lens having a focal length (F3), wherein the laser radiation passes through the lens element and the gap of the first lens array, passes through the second lens array, passes through the positive lens, and propagates in that order onto an illumination plane located at a distance (F3) from the positive lens, and the laser radiation on the illumination plane is converted into a homogenized intensity distribution having brighter or darker edges, and is converted into a single uniform intensity distribution between the brighter or darker edges; wherein each lens element of the second lens array and the positive lens project an image onto the illumination plane, the enlarged image is positioned around the optical axis, and the images projected by all lens elements of the second lens array overlap each other, and the gap of the first lens array is aligned with the edge of the lens element of the second lens array, so that a light ray propagating through the gap of the first lens array is incident on one of two identical lens elements within the second lens array. A beam homogenizer for laser radiation, characterized in that the light rays propagating through the gap of the first lens array are emitted from the two lens elements of the second lens array.

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