System and method for profile examination of a laser beam across a galvanometer scanning field

Abstract

A system for profiling a focused laser beam of a galvanometer scanner, the system comprising: an attenuation optic (500) positioned to receive a focused laser beam (520) from a laser beam source of a galvanometer scanner, the attenuation optic (500) comprising: a first meniscus lens (505) having a first surface (507) with a radius of curvature and a highly reflective coating arranged to face the focused laser beam source (520) and a second surface (509) opposite the first surface (507) with a radius of curvature and an anti-reflection coating, the first meniscus lens (505) being inclined at a fixed angle of incidence relative to an optical axis of the focused laser beam (520); a second meniscus lens (510) having a first surface (512) with a radius of curvature and a highly reflective coating arranged to face the second surface (509) of the first meniscus lens (505), and having a second surface (514) opposite the first surface (512) with a radius of curvature and an anti-reflection coating, wherein the second meniscus lens (510) is tilted at substantially the same fixed angle of incidence relative to the optical axis of the focused laser beam (520) as the first meniscus lens (505) and is rotated by approximately 90° relative to the first meniscus lens (505); wherein the radius of curvature of the first surface (507) of the first meniscus lens (505), the radius of curvature of the second surface (509) of the first meniscus lens (505), the radius of curvature of the first surface (512) of the second meniscus lens (510), and the radius of curvature of the second surface (514) of the second meniscus lens (510) are substantially equal; and a pixelated detector (515) arranged parallel to a scanning field of the galvanometer scanner, the pixelated detector (515) being intended to receive the focused laser beam (520) from the second meniscus lens (510).

Description

BACKGROUND OF THE INVENTION

[0001] Optical galvanometer scanners, also called galvos or galvo scanners, are motorized systems used for controlling or scanning laser beams. Galvo scanners are ideal for moving small laser beams quickly, accurately, and precisely. Galvanometer scanners are used wherever laser beams are steered, for example, in materials processing, laser light shows, manufacturing, packaging, cutting, marking, welding, and numerous other applications.

[0002] In galvo scanners, a laser beam continuously moves across a scan field. Profiling the laser beam for galvo scanners is a challenging task given the dynamic nature of the motion and the high power of the focused laser beam. A common device for profiling a focused laser beam is a pixelated detector, such as a CMOS (complementary metal-oxide semiconductor) sensor, a CCD (charged-coupled device), or another suitable two-dimensional array. The problem with these sensors is that they can only handle power in the microwatt range, whereas the lasers used industrially for galvo scanners operate in the watt- to kilowatt-range. Consequently, the laser must be attenuated in some way, which further complicates the measurement, as attenuation techniques are known to lead to undesirable beam deviations.

[0003] Additionally, most industrial laser scanning systems are non-telecentric, meaning the laser beam impinges on the processing field at an angular range greater than + / - 20 degrees. At this extreme angle, the normally round laser beam becomes elliptical due to the tilt of the beam at the surface, even though the beam is focused. This is due to the angular conical cut within the scan field. While this problem can be solved with telecentric optics, these systems are optically much more complex and, due to this complexity, generally have much smaller scan fields and are therefore not as widely used as non-telecentric systems.

[0004] DE 10 2015 001 421 A1 describes a device for determining geometric parameters of a laser beam. For this purpose, a device is proposed which includes an optical system, a device for coupling out radiation, a beam diagnostic device, and a reflector element. The optical system is designed to focus a laser beam into a processing area. The device for coupling out radiation is designed to couple out radiation that travels through the optical system in a direction opposite to the laser beam. The reflector element has a first surface that is partially reflective and curved. The reflector element can be positioned in a positioning area between the optical system and the processing area.The curvature of the first surface of the reflector element is equal to an average curvature of a wavefront of the laser beam focused by the optical system in the positioning region of the reflector element. The invention also relates to a method for determining geometric parameters of a laser beam, which comprises the following method steps: A laser beam is focused into a processing region by means of an optical system. A reflector element with a first surface is positioned in a positioning region between the optical system and the processing region. The first surface of the reflector element is curved, and the reflector element is positioned in a positioning region in which an average curvature of the wavefront of the laser beam focused by the optical system is equal to the curvature of the first surface of the reflector element.A portion of the focused laser beam is reflected back toward the optical system by the first surface of the reflector element. A portion of the reflected beam is coupled out. At least one geometric parameter is determined from the coupled-out beam using a beam diagnostic device.

[0005] Accordingly, there is a need for a system and method for evaluating the focused laser beam at any location in the scan field without altering the beam by profiling the beam as the material being processed by the laser would see the light.

[0006] However, in view of the overall state of the art at the time of the invention, it was not obvious to the person skilled in the art how the limitations of the prior art could be overcome. SUMMARY OF THE INVENTION

[0007] In various embodiments, the present invention provides a method and apparatus for profiling a focused laser beam across a galvanometer scan field.

[0008] In one embodiment, a system for profiling a focused laser beam of a galvanometer scanner comprises attenuation optics arranged to receive a focused laser beam from a laser beam source of a galvanometer scanner. The attenuation optics comprise a first meniscus lens and a second meniscus lens separate from the first meniscus lens. The first meniscus lens has a first surface with a radius of curvature and a highly reflective coating arranged to face the focused laser beam source, and a second surface opposite the first surface with a radius of curvature and an anti-reflection coating, wherein the first meniscus lens is tilted at a fixed angle of incidence with respect to an optical axis of the focused laser beam.The second meniscus lens has a first surface having a radius of curvature and a highly reflective coating arranged to face the second surface of the first meniscus lens, and a second surface opposite the first surface having a radius of curvature and an anti-reflection coating, wherein the second meniscus lens is tilted at substantially the same fixed angle of incidence relative to the optical axis of the focused laser beam as the first meniscus lens and is rotated 90° relative to the first meniscus lens. In particular, the radius of curvature of the first surface of the first meniscus lens, the radius of curvature of the second surface of the first meniscus lens, the radius of curvature of the first surface of the second meniscus lens, and the radius of curvature of the second surface of the second meniscus lens are substantially the same.The system further includes a pixelated detector arranged parallel to a scanning field of the galvanometer scanner to receive the focused laser beam from the second meniscus lens.

[0009] The attenuation optics may further include one or more filters disposed between the second surface of the second meniscus lens and the pixelated detector, wherein the one or more filters have a normal angle of incidence relative to the optical axis of the focused laser beam.

[0010] The system may further include an optical axis adjustment device coupled to the attenuation optics. The optical axis adjustment device is configured to adjust the angle of incidence of the attenuation optics to maintain the fixed angle of incidence of the first meniscus lens and the second meniscus lens and to maintain the normal angle of incidence of the one or more filters relative to the optical axis of the focused laser beam across a scanning area of the galvanometer scanner.

[0011] The system may further include a pixelated detector alignment device coupled to the pixelated detector. The pixelated detector alignment device is configured to position the pixelated detector to receive the focused laser beam as the galvanometer scanner moves across the scan field.

[0012] In another embodiment, a method for profiling a focused laser beam of a galvanometer scanner is provided. The method includes positioning an attenuator optic for receiving a focused laser beam from a laser beam source of a galvanometer scanner. The attenuator optic includes a first meniscus lens and a second meniscus lens separate from the first meniscus lens. The first meniscus lens has a first surface with a radius of curvature and a highly reflective coating arranged to face the focused laser beam source, and a second surface opposite the first surface with a radius of curvature and an anti-reflection coating, wherein the first meniscus lens is tilted at a fixed angle of incidence relative to an optical axis of the focused laser beam.The second meniscus lens has a first surface having a radius of curvature and a highly reflective coating arranged to face the second surface of the first meniscus lens, and a second surface opposite the first surface having a radius of curvature and an anti-reflection coating. The second meniscus lens is tilted at substantially the same fixed angle of incidence with respect to the optical axis of the focused laser beam as the first meniscus lens and is rotated by approximately 90° relative to the first meniscus lens. In particular, the radius of curvature of the first surface of the first meniscus lens, the radius of curvature of the second surface of the first meniscus lens, the radius of curvature of the first surface of the second meniscus lens, and the radius of curvature of the second surface of the second meniscus lens are substantially the same.

[0013] The method further includes positioning a pixelated detector parallel to a scan field of the galvanometer scanner to receive the focused laser beam from the second meniscus lens. The method further includes attenuating the focused laser beam received at the attenuation optics, transmitting the attenuated focused laser beam to the pixelated detector, and measuring the attenuated focused laser beam at the pixelated detector to examine a profile of the focused laser beam from the laser beam source of the galvanometer scanner.

[0014] The method may further comprise positioning one or more filters in the attenuation optics between the second surface of the second meniscus lens and the pixelated detector, wherein the one or more filters have a normal angle of incidence relative to the optical axis of the focused laser beam.

[0015] The method may further comprise coupling an optical axis adjustment device to the attenuation optics, wherein the optical axis adjustment device adjusts the angle of incidence of the attenuation optics such that the fixed angle of incidence of the first meniscus lens and the second meniscus lens is maintained relative to the optical axis of the focused laser beam and the normal angle of incidence of the one or more filters is maintained relative to the optical axis of the focused laser beam across a scanning area of the galvanometer scanner.

[0016] The method may further comprise coupling a pixelated detector alignment device to the pixelated detector. The pixelated detector alignment device is configured to position the pixelated detector to receive the focused laser beam as the galvanometer scanner moves across the scan field.

[0017] In various embodiments, the present invention provides a system and method for evaluating a focused laser beam of a galvanometer scanner at any location within the scan field without altering the laser beam.

[0018] These and other important objects, advantages and features of the invention will become apparent as the description proceeds.

[0019] The invention accordingly comprises the features of construction, combination of elements and arrangement of parts exemplified in the following description, and the scope of the invention is indicated in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] For a better understanding of the nature and objects of the invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 is a diagram showing a system with an attenuation optics having two optical elements for attenuating a laser beam without introducing aberration into the laser beam, according to an embodiment of the present invention. Fig. Figure 2A is a scatter plot showing a laser profile without the attenuation optics of the present invention. Fig. Figure 2B is a scatter plot showing a laser profile with the attenuation optics of the present invention. Fig. Figure 3 is a scatter plot showing a laser profile where one of the mirrors in the attenuation optics has been removed. Fig. 4A is a diagram showing a cross-sectional view of an attenuation optics system having a plano-convex optical element and a plano-concave optical element for attenuating a laser beam without introducing aberration into the laser beam, according to an embodiment of the present invention. Fig. 4B is an enlarged view of the Fig. 4A shown damping optics. Fig. 5 is a diagram showing a system having an attenuation optics with two meniscus lenses for attenuating a laser beam without introducing aberration into the laser beam according to an embodiment of the present invention. Fig. Figure 6A is a cross-sectional view of the system of Fig. 5 with an attenuation optic having two meniscus lenses for attenuating a laser beam without introducing aberration into the laser beam, in accordance with an embodiment of the present invention. Fig. Figure 6B is an enlarged view of the damping optics of Fig. 6A. Fig. 7 is a diagram showing the system of Fig. 5, further comprising an optical axis adjustment device for adjusting the angle of the attenuation optics based on the angle of the laser beam relative to the scan field and a pixel detector adjustment device for adjusting the position of the pixel detector within the scan field according to an embodiment of the present invention. Fig. 8 is a diagram showing the system of Fig. 7 including a beam trap. DETAILED DESCRIPTION OF THE INVENTION

[0021] In various embodiments, the present invention enables laser beam profiling of a scan field for a high-power laser galvanometer system used in any two-dimensional scan field of a galvanometer scanner that directs a focused laser beam across a large field for marking, cutting, drilling, 3D powder bedding, or various other high-power laser applications with a galvanometer scanner device. The system and method of the present invention are effective at attenuating a high-power laser beam so that it can be viewed by a pixelated detector without introducing aberration into the laser beam, thereby providing the ability to directly measure the profile of the focused laser beam at any location within the scan field of a laser-based galvanometer scanner system.

[0022] Mapping the laser beam profile of a galvanometer scan field, such as a 3D additive powder bed or a 2-DF theta lens galvanometer scan field, has not been possible until now without requiring complex methods or covering only a limited area of the scan field. Currently available systems do not provide users of 3D additive machines with the confidence to determine what the laser beam looks like in the outermost regions of the scan field. Assuming a perfect Gaussian beam at the 0,0 position of the scan field, the round beam at an outer corner of the scan field for any non-telecentric scanner system becomes elliptical due to the angle of the beam at the extreme field position. This also assumes that the scanner is diffraction-limited and has no aberrations at these extreme field points.The difficulty lies in both the high power of continuous-wave lasers, ranging from several hundred watts to more than a kilowatt, and the angular movement of the beam across the scan field, which makes attenuation of the beam difficult without creating aberration in the source beam. In the various embodiments of the present invention, a system and method for imaging a large scan field of a laser-based scanner for an additive 3D system with a laser power of more than 1 kilowatt can now be realized. Furthermore, the system is compact, aberration-free, fast, and very easy to operate.

[0023] In various embodiments, the present invention provides a system and method for beam attenuation that does not contribute to the aberration of the focused laser beam of a galvanometer scanner.

[0024] The beam attenuation system of the present invention, in its broadest sense, comprises two highly reflective mirrors arranged at an angle of incidence to the optical axis of the laser beam, with each mirror tilted 90° to each other on opposite axes. Generally, the first attenuation mirror is positioned to receive the light from the galvanometer scanner's laser beam, has a substrate suitable for the light to be measured, and has a highly reflective coating of >99% on a first surface and an anti-reflection coating with a reflectivity of <1.0% on a second surface. The second attenuation mirror has a coating and substrate comparable to that of the first attenuation mirror. A suitable substrate for the reflective mirrors may be fused silica for a high-power fiber laser or ZnSe (zinc selenide) for a CO2 laser.If the power level of the transmitted light is low enough to avoid thermal lensing, a substrate of absorbing material can be used so that any ghost images caused by the second surface reflections of the two mirrors are attenuated and not detected by the pixelated detector. This absorbing substrate with a highly reflective coating can be placed anywhere in front of the pixelated detector if the power from the first two attenuating mirrors is very high. By combining the two attenuating mirrors according to the invention, the laser light can be focused directly onto the pixelated detector without altering the beam.

[0025] Referring to Fig. 1, an attenuation optic 100, in one embodiment, includes a first attenuation mirror 105 and a second attenuation mirror 110. The attenuation optic 100 is arranged to receive a focused laser beam 120 from a laser beam source of a galvanometer scanner. In this embodiment, the first attenuation mirror 105 and the second attenuation mirror 110 are arranged at an angle of incidence of 45° to the optical axis of the laser beam 120. As described later, an angle of incidence of 22.5° may be a better alignment, but to demonstrate the influence of the tilted optic on the focused laser beam 120, the 45° angle of incidence is used to discuss the problem of optical aberration. As shown, the first attenuation mirror 105 and the second attenuation mirror 110 are tilted 90° to each other on opposite axes.The part of the laser beam exiting the second attenuation mirror 110 is measured by the pixelated detector 115, which is arranged parallel to a scanning field of the galvanometer scanner.

[0026] Fig. Figure 2A shows a diagram of the beam from Fig. 1 through the focal point, and the same beam without attenuation optics is in Fig. 2B. As can be seen, there is no change in optical performance, so the attenuation optics 100 of the present invention provides attenuation without introducing harmful aberrations. If one of the two attenuation mirrors 105, 110 is removed, the absence of the second attenuation mirror, which is rotated 90° with respect to the first attenuation mirror, results in the Fig. 3, which changes drastically. This shows that with only one tilted attenuator, the optical path length in one axis is longer than in the other axis by the square root of twice the thickness of the window, which naturally leads to astigmatism due to this difference in path length between the two axes.

[0027] While Fig. 1 shows the basic principle of the present invention, there are other embodiments that offer advantages for the deposition of the reflected high power laser radiation and are therefore more desirable.

[0028] Fig. 4A and Fig. 4B shows an attenuation optic 400 with a first optic 405 and a second optic 410. The first optic 405 comprises a plano-concave element and a plano-convex element, wherein the plano-concave element and the plano-convex element have substantially equal but opposite signs of the radii of curvature. The second optic 410 also comprises a plano-concave element and a plano-convex element, wherein the plano-concave element and the plano-convex element have substantially equal but opposite signs of the radii of curvature. The radii of curvature of these two optics 405, 410 are substantially equal, so that these two optics, which are in close proximity to each other but never touch, have no "optical power." The distance between the optics 405, 410 can be <1 mm to mitigate the power influence.In this embodiment, the concave surface of the plano-concave element 405 has a highly reflective coating such that <1.0% of the light 420 is transmitted. The flat surface of the plano-concave element 405 has an anti-reflection coating with a reflectance of <1.0%. The convex surface of the plano-convex element 410 has a highly reflective coating such that <1.0% of the light 420 is transmitted. The flat surface of the plano-convex element 410 has an anti-reflection coating with a reflectance of <1.0%. The combination of first optics 405 and second optics 410 is tilted at an angle of 22.5° to allow the light reflected from the concave surface of the first optics 405 to pass through, which would cause the substantially reflected light to begin to expand toward a ray channel (not shown) after reflection from the concave surface.The attenuation optics 400 further includes a filter pair 450 having the same optical thickness as the plano-concave 405 / plano-convex 410 element pair. The filter pair 450 includes a laser light transmission filter 425 and a neutral density filter 430. The laser light transmission filter 425 can be a short-pass filter, a long-pass filter, a narrow bandpass filter, or any other filter known in the art that effectively blocks unwanted residual light and transmits the laser light incident on the pixelated detector. The filter pair 450 is incident substantially perpendicularly to the focused laser beam 420.

[0029] Another embodiment for providing divergent reflections without adding optical power to the optical attenuator pair is described in Fig. 5. As shown in Fig. 5, a system for profiling a focused laser beam of a galvanometer scanner includes attenuation optics 500 positioned to receive a focused laser beam 520 from a laser beam source of a galvanometer scanner. The attenuation optics 500 includes a first meniscus lens 505 and a second meniscus lens 510 separate from the first meniscus lens 505. The first meniscus lens 505 has a first surface with a radius of curvature and a highly reflective coating positioned to face the focused laser beam source 520, and a second surface opposite the first surface with a radius of curvature and an anti-reflection coating. The first meniscus lens 505 is tilted at a fixed angle of incidence relative to an optical axis of the focused laser beam 520.The second meniscus lens 510 has a first surface with a radius of curvature and a highly reflective coating arranged to face the second surface of the first meniscus lens 505, and a second surface opposite the first surface with a radius of curvature and an anti-reflection coating. The second meniscus lens 510 is tilted at substantially the same fixed angle of incidence relative to the optical axis of the focused laser beam 520 as the first meniscus lens 505 and is rotated by approximately 90° relative to the first meniscus lens 505. In particular, the radius of curvature of the first surface of the first meniscus lens 505, the radius of curvature of the second surface of the first meniscus lens 505, the radius of curvature of the first surface of the second meniscus lens 510, and the radius of curvature of the second surface of the second meniscus lens 510 are substantially the same.The attenuation optics may further include a filter element 550, which may include a laser light transmission filter 525 and a neutral density filter 530, as previously described. The filter element 550 is arranged at a normal angle of incidence relative to the optical axis of the focused laser beam 520. The system further includes a pixelated detector 515 arranged parallel to a scanning field of the galvanometer scanner, wherein the pixelated detector is to receive the focused laser beam from the second meniscus lens 510.

[0030] A cross-sectional view of the embodiment of Fig. 5 is in Fig. 6A and Fig. 6B. Fig. 6B is an enlarged version of the damping optic 500 from Fig. 6A. As in Fig. 5, the lenses of the attenuation optics 500 are essentially meniscus lenses 505, 510, since the radii of curvature for the first surface 507 and the second surface 509 of the first meniscus lens 505 and for the first surface 512 and the second surface 514 of the second meniscus lens 510 are essentially the same. As a result, the focused beam 520 passing through these lenses 505, 510 is not adversely affected by the optical performance. The first surface 507 of the first meniscus lens 505 has a highly reflective coating of >99% and transmits <1% of the light 520. The second surface 509 of the first meniscus lens 505 has an anti-reflection coating with a reflectance of <1%. The second meniscus lens 510 has the same coatings as the first meniscus lens 505, but is rotated 90° relative to the first meniscus lens 505 to achieve the nominal tilt of 22.5°.As a result, the optical path length in the X and Y axes of the laser beam 520 is essentially the same, so no optical aberration is added, and the beam 520 has a form factor that does not add any additional optical power.

[0031] The preferred angle of incidence of the first meniscus lens 505 and the second meniscus lens 510 is 22.5°, as previously described. This is because at such an extreme angle, less vignetting of the beam 520 occurs than at the commonly used 45°, and the 22.5° angle of incidence allows for greater compression of the optics to keep the system as compact as possible. An even shallower angle of incidence is possible, but the problem is handling the reflected high-power laser radiation. The 22.5° angle of incidence is not intended to be limiting, and an angle of incidence between approximately 10° and 45° is contemplated within the scope of the invention.

[0032] Since the galvanometer scanner can move the focused laser beam 520 by more than + / - 20 degrees, a mechanism is provided that aligns the attenuation optics 500 to maintain the fixed angle of incidence of the first meniscus lens 505 and the fixed angle of the second meniscus lens 510, as shown in Fig. 7. This mechanism ensures that the optical path length is always the same at every point in the scan field. The angle of the attenuation optics 500 can be adjusted by gimbal adjustment of the attenuation optics 500 and rotation adjustment of the attenuation optics 500, so that an aberration-free beam can impinge on the pixelated detector 515 in the same way at every point in the scan field, thereby keeping the optical beam path constant. Various gimbal adjustment and rotation adjustment devices are well known in the art.

[0033] The area of the pixelated detector 515 is smaller than the area of the scan field of the galvanometer scanner. Therefore, it is necessary to move the pixelated detector 515 in the XY direction as the focused laser beam 520 is moved through the galvanometer scanner. To position the pixelated detector 515 to receive the focused laser beam 520 across the scan field, the system may further include a pixelated detector alignment device coupled to the pixelated detector 515. The pixelated detector alignment device is configured to track the position of the galvanometer scanner and position the pixelated detector 515 to receive the focused laser beam 520 as the galvanometer scanner moves across the scan field. The pixelated detector alignment device may be manual or motorized to enable XY positioning of the pixelated detector 515 within the scan field.Various manual and motorized adjustment mechanisms are known in the art to enable adjustment of the pixelated detector 515.

[0034] In a specific embodiment of the system of the present invention, the optical axis adjustment device coupled to the attenuation optics 500 and the pixel detector adjustment device coupled to the pixel detector 515 may consist of four motors. A first motor is configured to tilt the attenuation optics 500 to match the angle of the galvanometer scanner so that the angle of incidence of the focused laser beam 520 is always at the preferred 22.5°. A second motor is configured to rotate the attenuation optics 500 to adapt to each XY coordinate slice across the scan field and maintain the nominal 22.5° angle of incidence to the meniscus lenses 505, 510. The third and fourth motors are configured to position the entire system in the XY plane of the scan field so that the pixelated detector 515 can direct the focused laser beam 520 into its field of view, ieinto the sensor.

[0035] Furthermore, it is desirable to have a light-blocking filter so that the pixelated detector 515 sees only the laser wavelength and no ambient light, and it is desirable to have additional neutral density filtering to ensure that the pixelated detector 515 is not overexposed to the laser radiation. As in Fig. For this purpose, as shown in Figure 7, the attenuation optics may comprise a filter pair 550 comprising a laser light transmission filter 525 and a neutral density filter 530, or an absorbing filter with a highly reflective coating on one surface, arranged at a small angle below the second meniscus lens 510. The laser light transmission filter 525 and the neutral density filter 530 are at a normal angle of incidence with respect to the optical axis of the focused laser beam 520 and move with the attenuation optics 500 to maintain the normal angle of incidence across the entire range of the scan field. It is important to note that the pixelated detector 515 itself does not tilt, but is always parallel to the plane of the scan field. For a particular position of the pixelated detector 515, the user could scan the clear aperture of the pixelated detector 515.The position of the attenuation optics 500 and the pixelated detector 515 would ideally be synchronized with the movement of the galvanometer system, allowing a user to create a detailed profile map of the entire scan field with a resolution limited only by the pixel size of the pixelated detector 515. The device would therefore have four axes of motion: gimbal tilt and rotation of the attenuation optics 500; X and Y positioning of the attenuation optics 500 and the pixelated detector 515 around the scan field.

[0036] In a further embodiment, the profile examination system can be Fig. 7 also have a beam trap to process the reflected high-power laser radiation. Beam traps are well known in the art. In a Fig.In the embodiment shown in Figure 8, a conical beam channel 560 can be positioned to surround the attenuating optics 500 so that the reflected high-intensity light 562, 564 from the attenuating optics 500 is blocked by the beam channel 560. Although this example of a beam trap is large and conical, any beam trap that would block the reflection from the first meniscus lens 505 would be sufficient to prevent damage to the surrounding area. A single blocking plate placed in the direction of the reflected beam 562, 564, for example, would suffice, or even a square trap placed around the scan field would also provide protection.

Claims

[1] A system for profiling a focused laser beam of a galvanometer scanner, the system comprising: an attenuation optic (500) positioned to receive a focused laser beam (520) from a laser beam source of a galvanometer scanner, the attenuation optic (500) comprising: a first meniscus lens (505) having a first surface (507) with a radius of curvature and a highly reflective coating arranged to face the focused laser beam source (520) and a second surface (509) opposite the first surface (507) with a radius of curvature and an anti-reflection coating, the first meniscus lens (505) being inclined at a fixed angle of incidence relative to an optical axis of the focused laser beam (520); a second meniscus lens (510) having a first surface (512) with a radius of curvature and a highly reflective coating arranged to face the second surface (509) of the first meniscus lens (505), and having a second surface (514) opposite the first surface (512) with a radius of curvature and an anti-reflection coating, wherein the second meniscus lens (510) is tilted at substantially the same fixed angle of incidence relative to the optical axis of the focused laser beam (520) as the first meniscus lens (505) and is rotated by approximately 90° relative to the first meniscus lens (505); wherein the radius of curvature of the first surface (507) of the first meniscus lens (505), the radius of curvature of the second surface (509) of the first meniscus lens (505), the radius of curvature of the first surface (512) of the second meniscus lens (510), and the radius of curvature of the second surface (514) of the second meniscus lens (510) are substantially equal; and a pixelated detector (515) arranged parallel to a scanning field of the galvanometer scanner, the pixelated detector (515) being intended to receive the focused laser beam (520) from the second meniscus lens (510). [2] The system of claim 1, wherein the fixed angle of incidence of the first meniscus lens (505) and the second meniscus lens (510) with respect to the optical axis of the focused laser beam (520) is between about 10° and about 45°. [3] The system of claim 1, wherein the fixed angle of incidence of the first meniscus lens (505) and the second meniscus lens (510) with respect to the optical axis of the focused laser beam is about 22.5°. [4] The system of claim 1, wherein the highly reflective coating of the first surface (507) of the first meniscus lens (505) and the highly reflective coating of the first surface (512) of the second meniscus lens (510) have a reflectivity of greater than about 99%. [5] The system of claim 1, wherein the anti-reflection coating of the second surface (509) of the first meniscus lens (505) and the anti-reflection coating of the second surface (514) of the second meniscus lens (510) have a reflectivity of less than about 1%. [6] The system of claim 1, wherein the first meniscus lens (505) comprises a substrate made of a high-quality laser glass based on the laser beam source. [7] The system of claim 1, wherein the second meniscus lens (510) comprises a substrate selected from a high-quality laser glass based on the laser beam source and an absorbing glass having an optical density (OD) of at least -1. [8] The system of claim 1, wherein the attenuation optics (500) further comprises one or more filters selected from a laser light transmission filter (525) and a neutral density filter (530) disposed between the second surface (514) of the second meniscus lens (510) and the pixelated detector (515), the one or more filters having a normal angle of incidence relative to the optical axis of the focused laser beam (520). [9] The system of claim 1, further comprising a beam trap positioned to receive a portion of the focused laser beam reflected by the attenuation optics (500). [10] The system of claim 1 further comprising an optical axis adjustment device coupled to the attenuation optics (500), the optical axis adjustment device adjusting the angle of incidence of the attenuation optics (500) to maintain the fixed angle of incidence of the first meniscus lens (505) and the second meniscus lens (510) and to maintain the normal angle of incidence of the one or more filters relative to the optical axis of the focused laser beam (520) over a scan range of the galvanometer scanner. [11] The system of claim 1 further comprising a pixelated detector alignment device (515) coupled to the pixelated detector (515), the pixelated detector alignment device (515) configured to position the pixelated detector (515) to receive the focused laser beam (520) as the galvanometer scanner moves across the scan field. [12] A method for profile examination of a focused laser beam (520) of a galvanometer scanner, the method comprising: positioning an attenuation optic (500) to receive a focused laser beam (520) from a laser beam source of a galvanometer scanner, the attenuation optic (500) comprising: a first meniscus lens (505) having a first surface (507) with a radius of curvature and a highly reflective coating arranged to face the focused laser beam source, and a second surface (509) opposite the first surface (507) with a radius of curvature and an anti-reflection coating, the first meniscus lens (505) being inclined at a fixed angle of incidence relative to an optical axis of the focused laser beam (520); a second meniscus lens (510) having a first surface (512) with a radius of curvature and a highly reflective coating arranged to face the second surface (509) of the first meniscus lens (505), and having a second surface (514) opposite the first surface (512) with a radius of curvature and an anti-reflection coating, wherein the second meniscus lens (510) is tilted at substantially the same fixed angle of incidence relative to the optical axis of the focused laser beam (520) as the first meniscus lens (505) and is rotated by approximately 90° relative to the first meniscus lens (505); wherein the radius of curvature of the first surface (507) of the first meniscus lens (505), the radius of curvature of the second surface (509) of the first meniscus lens (505), the radius of curvature of the first surface (512) of the second meniscus lens (510) and the radius of curvature of the second surface (514) of the second meniscus lens (510) are substantially the same; positioning a pixelated detector (515) parallel to a scan field of the galvanometer scanner, the pixelated detector (515) receiving the focused laser beam (520) from the second meniscus lens (510); attenuating the focused laser beam (520) received at the attenuating optics (500) and transmitting the attenuated focused laser beam to the pixelated detector (515); and measuring the attenuated focused laser beam (520) at the pixelated detector (515) to analyze a profile of the focused laser beam (520) from the laser beam source of the galvanometer scanner. [13] The method of claim 12, wherein the fixed angle of incidence of the first meniscus lens (505) and the second meniscus lens (510) relative to the optical axis of the focused laser beam (520) is between about 10° and about 45°. [14] The method of claim 12, wherein the fixed angle of incidence of the first meniscus lens (505) and the second meniscus lens (510) with respect to the optical axis of the focused laser beam (520) is approximately 22.5°. [15] The method of claim 12, wherein the highly reflective coating of the first surface (507) of the first meniscus lens (505) and the highly reflective coating of the second surface (514) of the second meniscus lens (510) have a reflectivity of greater than about 99%. [16] The method of claim 12, wherein the anti-reflection coating of the second surface (509) of the first meniscus lens (505) and the anti-reflection coating of the second surface (514) of the second meniscus lens (510) have a reflectivity of less than about 1%. [17] The method of claim 12, wherein one or more filters selected from a laser light transmission filter (525) and a neutral density filter (530) are disposed in the attenuation optics (500) between the second surface (514) of the second meniscus lens (510) and the pixelated detector (515), the one or more filters having a normal angle of incidence with respect to the optical axis of the focused laser beam (520). [18] The method of claim 12 further comprising positioning a beam trap to receive a portion of the focused laser beam (520) reflected by the attenuation optics (500). [19] The method of claim 12, further comprising coupling an optical axis adjustment device to the attenuation optics (500), wherein the optical axis adjustment device adjusts the angle of incidence of the attenuation optics (500) to maintain the fixed angle of incidence of the first meniscus lens (505) and the second meniscus lens (510) with respect to the optical axis of the focused laser beam (520) and to maintain the normal angle of incidence of the one or more filters with respect to the optical axis of the focused laser beam (520) over a scan range of the galvanometer scanner. [20] The method of claim 12, further comprising coupling a pixelated detector alignment device (515) to the pixelated detector (515), the pixelated detector alignment device (515) configured to position the pixelated detector (515) to receive the focused laser beam (520) as the galvanometer scanner moves across the scan field.

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