A laser beam profile measurement technique for high-energy lasers used in metal manufacturing processes

Abstract

A system for measuring a laser beam profile of industrial high-power lasers. The setup incorporates UV fused silica windows for beam attenuation and a combination of reflective and absorptive neutral density filters to further reduce beam intensity. Achromatic doublet lenses refocus the attenuated beam, to create a magnified low-power replica suitable for high-resolution measurements. This configuration allows for continuous real-time monitoring of the laser caustic parameters and the laser beam profile along its optical axis.

Description

A LASER BEAM PROFILE MEASUREMENT TECHNIQUE FOR HIGH-ENERGY LASERS USED IN METAL MANUFACTURING PROCESSES

[0001] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under grant / contract number 2245141 awarded by the National Science Foundation. The government has certain rights in the invention.

[0003] CROSS REFERENCE TO RELATED APPLICATION

[0004] This application claims priority to U.S. Provisional Patent Application No. 63 / 656,727, filed June 6, 2024, entitled "A Low-Cost Laser Beam Profile Measurement Technique for High-Energy Lasers Used in Metal Manufacturing Processes," the disclosure of which is expressly incorporated herein by reference in its entirety.

[0005] BACKGROUND

[0006] The power of industrial high-energy lasers can get up to 2000 Watts and they are widely used in welding, metal additive manufacturing, and metal cutting processes. There are many challenges to measure beam intensity of such lasers. For example, the high power of the lasers themselves is challenging. Regular cameras cannot be used since their image sensors would be damaged by the laser. Most of the current commercial devices that are used for measuring laser beam profiles are only compatible with low-power lasers and their sensors damage threshold is up to 50 W / cm2which makes them incompatible for industrial high-energy lasers. Another challenge is the short focal length the laser head and the laser focal plane. Since the laser power needed to be attenuated first through some optical setup, the space under the laser head was not enough to position the camera sensor at the laser focal plane.

[0007] Measuring the beam profile of lasers with output power exceeding 0.5 W may pose several significant challenges. These lasers may be usually operated at powers above 10 W in welding and additive manufacturing, and may have a high intensity that can melt most materials, including the sensors of standard CCD / CMOS cameras, due to their low damage threshold of less than 50 W / cm2. Additionally, the short focal distance of some laser heads may leave insufficient space to measure the laser beam intensity distribution,necessitating either refocusing the laser beam or developing a compact measurement setup.

[0008] As such, there is a need for an improved optical setup to measure beam profile intensity distribution of high-energy lasers.

[0009] SUMMARY

[0010] Described herein is an example optical setup to measure the laser beam profile of industrial high-power lasers. The setup incorporates UV fused silica windows for beam attenuation and a combination of reflective and absorptive neutral density filters to further reduce beam intensity. Achromatic doublet lenses were employed to refocus the attenuated beam, to create a magnified low-power replica suitable for high-resolution measurements. This configuration allows for continuous real-time monitoring of the laser beam profile along its optical axis. Using a commercial ytterbium laser with maximum nominal power of 400 W, the results revealed that the laser beam profile deviated from the ideal symmetric Gaussian beam and instead resembled an Airy disk distribution. The study also found that the laser focal spot location depends on the input laser power due to the Kerr effect, which alters the refractive index of optical lenses. Additionally, the laser beams focal spot shifted along the optical axis within the first 20 seconds after the laser was turned ON, likely due to the transient behavior of the laser source. This beam profile measurement technique has the potential to improve process control and material properties in laserbased metal processing applications.

[0011] In some aspects, the techniques described herein relate to a system for real-time monitoring and measurement of laser beam profiles in high-power lasers, the system including: a primary attenuation system including two wedged UV fused silica windows positioned to intercept a high-power laser beam; a secondary attenuation system including a reflective neutral density filter and a series of absorptive neutral density filters; a beam refocusing system including a first achromatic doublet lens and a second achromatic doublet lens; and a detection system including a high-resolution camera and a graduated manual stage.

[0012] In some aspects, the techniques described herein relate to a method for real-time monitoring and measurement of laser beam profiles in high-power lasers, the method including: reflecting a high-power laser beam with a first wedged UV fused silica window toreflect a first portion of the laser beam; reflecting the reflected first portion with a second wedged UV fused silica window to reflect a second portion of the laser beam; attenuating the reflected second portion using a reflective neutral density filter and a series of absorptive neutral density filters; collimating the attenuated laser beam using a first achromatic doublet lens; focusing the collimated beam using a second achromatic doublet lens; and capturing beam profile images using a high-resolution camera mounted on a graduated manual stage.

[0013] In some aspects, the techniques described herein relate to a system including: a first Uncoated UV Fused Silica (UVFS) window that attenuates laser beam energy from a source laser beam to reflect a first predetermined portion of a source laser power; a first beam trap that receives a second predetermined portion of the source laser power from the first UVFS, the first predetermined portion being less than the second predetermined portion; a second UVFS that receives and attenuates the first predetermined portion of the source laser power; a second beam trap that receives a third predetermined portion of the source laser power from the second UVFS; and a filter and doublet lenses that receives a fourth predetermined portion of the source laser power from the second UVFS, the fourth predetermined portion being less than the third predetermined portion of the source laser power, wherein the doublet lenses have a predetermined focal length and collimate the fourth predetermined portion of the source laser beam to be provided to a camera.

[0014] Other systems, methods, features and / or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and / or advantages be included within this description and be protected by the accompanying claims.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The foregoing summary, as well as the following detailed description of illustrative implementations, is better understood when read in conjunction with the appended drawings. To illustrate the implementations, there are shown in the drawings example constructions; however, the implementations are not limited to the specific methods and instrumentalities disclosed. In the drawings:

[0017] FIG. 1A illustrates a schematic of a laser beam profiler optical setup design in accordance with an example implementation of the present disclosure.

[0018] FIG. IB illustrates a ZEMAX model of the example doublet lenses system of the present disclosure.

[0019] FIG. 2A illustrates laser beam profile measurements along the laser optical axis for 415 W power.

[0020] FIGS. 2B-2C illustrate 2D and ID laser beam profile distribution at the focal plane.

[0021] FIG. 2D illustrates a sample of laser exposed ZAP-lt paper that exhibits an airy disk pattern.

[0022] FIG. 3 illustrates ID laser beam profile plots for laser beams with 415 W, 324 W, and 227 W power levels along the optical axis at different points.

[0023] FIG. 4 illustrates a schematic of a Kerr effect caused by the nonlinearity in the refractive index of optical lenses for high-intensity lasers.

[0024] FIGS. 5A-5D illustrate online transient focus shift during the first 20 seconds of the laser activation.

[0025] FIG. 6 is a schematic of real-time monitoring optical system for an LDED metal additive manufacturing system in accordance with aspects of the present disclosure.

[0026] DETAILED DESCRIPTION

[0027] Disclosed herein is a laser beam profile monitoring system for high-intensity lasers in metal manufacturing. In various embodiments, the system may enable real-time measurement and monitoring of laser beam characteristics to improve process control and material properties in applications such as laser welding and metal additive manufacturing. Various types of lasers, such as ytterbium and CO2 lasers may be used in metal processing applications due to their specific advantages. Ytterbium lasers, for example, are favored for their high efficiency and ability to produce fine features, making them ideal for precision cutting, welding, surface treatment, and additive manufacturing. The optical components may work together to attenuate, refocus, and detect the laser beam profile without interrupting the manufacturing process.

[0028] Example Laser Beam Profile Measurement System

[0029] FIG. 1A illustrates an example schematic of a laser beam profiler optical setup 100 in accordance with the present disclosure. The setup includes a laser head 102, laser beamattenuation using reflective UV fused silica (UVFS) windows 104, 106, a series of reflective and absorptive ND filters 108, and a pair of doublet lenses 110 for refocusing the attenuated laser beam onto a sensor plane of a camera 118.

[0030] The UV fused silica windows 104, 106 reflect a small fraction of a laser beam 112 as part of the attenuation process. Given the relatively short focal length of high-power lasers, the attenuated beam 120 diverges after being attenuated. To address this, a pair of achromatic lenses 110 re-focus the diverging, attenuated laser beam 120 and create a low- power replica of the high-power laser beam. These lenses 110 can be configured to magnify the laser beam profile, thereby achieving higher resolution measurements, as described below.

[0031] As shown in FIG. 1A, the laser beam 112 coming out of the laser head 102 along the laser axis passes through the UVFS windows 104, 106 to obtain attenuated laser beam through reflection. These UVFS windows 104, 106 may be wedged to prevent formation of ghost images on the camera sensor plane. In the example setup 100, each UVFS window 104, 106 reflects only 6.51% of the incident laser power, with the transmitted beams being dumped into beam traps 114, 116. The reflected laser beam (attenuate laser beam 120) from the second UVFS 106 window may be only 0.424% of the original laser power.

[0032] To prevent any laser damage to the camera sensor, the reflective ND filter 108 may have an optical density (OD) of 0.3 to further reduce the laser intensity. The OD values on the ND filters 108 are nominal and may not be the actual OD for the specific wavelength of 1070 nm. Different sets of absorptive ND filters may be used for each power level. The absorptive ND filters 108 then bring the laser intensity below the damage threshold for the camera 118, e.g., 50 W / cm2.

[0033] The pair of achromatic doublet lenses 110 may be used for re-focusing the laser beam. The first doublet lens, with an example focal length of 100 mm, collimates the diverging laser beam. The second doublet lens, with an example focal length of 200 mm, refocuses the laser beam on a sensor plane of the camera 118. Due to the selected example focal lengths for the doublet lenses 110, the laser beam profile was magnified by a factor of 2 (M=2), enabling higher resolution measurements.

[0034] Thus, as described above, the optical setup 110 creates a low-power replica of the high-power laser which allows measurement with the camera 118 without damaging the sensor. Further, using the example setup 100 of FIG. 1A, the laser beam intensitydistribution along the optical axis can be measured and the laser beam can be continuously monitored in real time. The benefits of this approach are significant, and the results can be applied in modeling and numerical studies for metal additive manufacturing and welding processes. Additionally, the ability to real-time monitor the laser beam profile during operation is unique to this technique, as the current commercial devices lack this capability. This method is cost-effective, adjustable in terms of magnification, and adaptable for use with most high-power lasers by modifying the attenuation optics.

[0035] Example Components

[0036] In the setup 100, the laser head 102 may be an ytterbium single-mode continuous wave (CW) laser from IPG Photonics (Wixom, Ml, USA), model YLR-400-AC. This laser 102 operates at a wavelength of 1070 nm with a maximum power output of 400 W, and it is non-polarized. A PRECITEC (Wixom, Ml, USA) laser head, model YW30, may be used to focus the laser beam. It includes optical lenses to collimate the laser coming from the laser source through an optical fiber and then focus it for welding or additive manufacturing purposes. This laser head 102 is designed for Laser Direct Energy Deposition (LDED) process and contains four nozzles for delivering metal powders. The uncoated UVFS windows 104, 106, may be obtained from Thorlabs, and are 1 inch (model WW41050) and 2 inches (model WW42012) in diameter. The camera 118 for beam profile measurements may be SP932U, obtained from Ophir-Spiricon Inc. (North Logan, UT, USA), with a pixel size of 3.45 pm x 3.45 pm, a sensor size of 2048 pixel x 1536 pixel, and an active area of 7.06 mm x 5.3 mm. The camera's spectral range is 190-1100 nm, which is sensitive to the laser used in this study. The absorptive ND filters 108 were obtained from STANDA Ltd. (10WA168 - Variable Wheel Attenuator). The achromatic doublet lenses 110 may be obtained from Edmund optics (Barrington, NJ, USA) and the models were 50 mm Dia. x 100 mm FL, NIR II Coated, Achromatic Lens and 50 mm Dia. x 200 mm FL, NIR II Coated, Achromatic Lens. The above components and specifications are provided for example purposes only and do not serve to limit the scope of the disclosure and / or claims as other components having similar properties may be used.

[0037] Example Alignment Process

[0038] The optics in FIG. 1A may be initially installed using the guide beam from the IPG laser source for rough alignment. Each optic may be mounted on kinematic mounts toadjust their orientations during the alignment process. The IPG laser may be operated at its lowest possible power and gradually increased to avoid any laser hazards. A Thorlabs laser detector (VRC5 - IR Detector Card, 700 - 1400 nm) may be used to trace the laser through the optical setup. The first achromatic doublet lens may be positioned 100 mm from the laser's real focal plane along the optical axis and was adjusted to collimate the transmitted beam. The second achromatic doublet lens (200 mm focal length) may be then placed to focus the collimated and attenuated laser beam. The positions and orientations of all optics including the doublet lenses 110, reflective, and absorptive ND filters 108 may be fixed after the alignment. The camera 118 may be installed on a graduated manual stage (MT1 from Thorlabs) to record the laser beam profile at different locations along the laser axis. Additionally, alignment papers from ZAP-IT Laser Alignments (Concord, NH, USA) may be used for aligning the high-power laser and determining the focal plane range of the laser. The laser exposure time on the Zap-lt papers may be 1 millisecond. FIG. IB illustrates a ZEMAX model 150 of the doublet lenses system of FIG. 1A. The above components and specifications are provided for example purposes only and do not serve to limit the scope of the disclosure and / or claims as other components having similar properties may be used.

[0039] Beam Profile Measurements / Experimental Results

[0040] To confirm the benefits and advantages of the setup 100, beam profiles were measured at distances of around ±7 mm from the laser focal plane in 1 mm increments. Since the beams are magnified by factor of M=2, each 1mm distance is equal to 0.5 mm distance in the high-power area of the laser. Measurements were conducted at three laser power levels: 60%, 80%, and 100% of the total power, corresponding to actual powers of 227, 324, and 415 Watts, respectively. The total power was measured by a built-in sensor inside the IPG laser source unit. Camera measurements were performed using BeamGage software by Ophir Optics. To eliminate errors and background noise, the built-in Ultracal function was used for calibration. Measurements were converted from pixel sensor readings to laser intensity units based on input power and intensity distribution. Beam profile images were exported as TIFF files from HDF5 data using a MATLAB code provided by Spiricon- Ophir Optics. Finally, the TIFF images were analyzed and compared using FIJI ImageJ.

[0041] Laser Beam Profile along the Laser Axis

[0042] With reference to FIGS. 2A-2D results of the setup of FIG. 1A are now described. FIG. 2A illustrates laser beam profile measurements along the laser optical axis for 415 Wpower. FIGS 2B-2C illustrate 2D and ID laser beam profile distribution at the focal plane. FIG. 2D illustrates a sample of laser exposed ZAP-lt paper that exhibits an airy disk pattern.

[0043] The laser beam profile was measured along the optical axis using the system described in the Methods section. FIG 2A illustrates the measured beam profile 2 for a laser power of 415 W (100% of the nominal power) around the focal plane in ±7 mm distance with 1 mm increments. As illustrated, the beam profile deviates from the ideal symmetric Gaussian beam and instead resembles more of an Airy disk distribution. These results indicate the propagation of a non-Gaussian beam, potentially deviating from Gaussian characteristics. This observation contradicts the common assumption held by the metal additive manufacturing and welding communities that the laser beam is considered as a gaussian beam for similar laser sources and laser heads.

[0044] To investigate whether the laser beam was diffracted by the designed optical system, ZAP-lt papers were placed under the laser-head. Multiple experiments were conducted, with the papers exposed to the laser beam for 1 millisecond at various distances along the optical axis. The burn patterns on the paper exhibited an Airy disk distribution, indicating that the optical system is not the source of this diffraction. A sample of the burn pattern is shown in FIG. 2D. This phenomenon is due to the optics within the PRECITEC laser head, either the collimation or the focusing lenses or both. It is important to note that using ZAP-lt papers is not an ideal method for determining the beam spot size, as papers burn at low laser intensities, resulting in a burn spot larger than the actual laser beam size, which may be misleading. However, these papers were used to demonstrate that the laser beam exhibits a non-Gaussian distribution before being attenuated and refocused by our developed optical system.

[0045] Influence of Laser Power on Focal Spot Position

[0046] The laser beam distribution at points before and after the focal plane (FP) for laser powers of 415 W, 324 W, and 227 W, along the laser travel direction with 0.5 mm increments, is shown in FIG. 3. As shown in FIG. 3, the laser beam profiles along the optical axis exhibit different patterns at different power levels. This variation is due to the dependence of the refractive index of the lenses on intensity, which introduces nonlinearity in the laser beam profile. Therefore, it is necessary to measure the beam profile at each power level separately rather than relying on simplified paraxial assumptions. For instance, in FIG. 3, the distribution at 324 W differs from that at 415 W. The maximum intensity at thefocal plane for 324 W appears lower than at its adjacent planes, which can be attributed to the non-Gaussian behavior of the laser beam resulting from the nonlinearity in the refractive index (Eq. 1, below).

[0047] It was observed that the laser focal plane location depends on the input laser power as it varies for different laser powers. This phenomenon is known as Kerr effect and arises from the dependence of the refractive index of optical lenses on laser intensity, as described by the Eq. 1: n = nQ+ n2I (1) where n, nQ, n2, and I are the refractive index, linear refractive index component, nonlinear refractive index component, and light intensity, respectively. While n2is typically a small number for most materials, at high laser intensities, the second term (n2I) becomes significant, altering the overall refractive index of the material.

[0048] Consequently, the location and size of the laser beam's focal spot depend on the input laser power and must be determined for each power level. This implies that the laser spot size at a specific position (or distance) varies with different input power. This phenomenon is shown in FIG. 4, which is a schematic of Kerr effect which happens due to the nonlinearity in the refractive index of optical lenses for high-intensity lasers.

[0049] Additionally, due to the intensity distribution of the laser beam, the high and low intensity portions of the laser beam bend differently as they pass through the optical lenses inside the laser head. This contributes to the asymmetry of the laser beam profile on both sides of the focal plane, resulting in a non-Gaussian beam as was shown in FIG. 2A.

[0050] In LDED metal additive manufacturing, the laser beam is usually operated out of focus to achieve a larger beam size to improve the powder catchment efficiency. In this scenario, the change in the laser beam spot size is smaller compared to when the laser beam is operated at its focal plane, as in laser welding applications. However, any variation in the beam spot size introduces potential for error in any size.

[0051] Due to the focal spot movement exceeding the range of the translation stage on which the camera was mounted, precise measurements could not be obtained for comparison. However, the movement of the laser focal spot was observable and exceeded 6 mm when comparing the 415 W and 227 power levels. Given that the laser beam was magnified by a factor of 2 (M=2) due to the doublet lenses, a distance of 12 mm in theattenuated laser beam area corresponds to a movement of 6 mm for the high-power laser beam.

[0052] Online Transient Focus Shift

[0053] Observations during the laser measurements revealed that the laser beam focal spot shifts along the optical axis within the first 20 seconds after the laser is turned ON. FIGS. 5A-5D. illustrate the beam profile measurements at a fixed location at different times. Similar behavior has been reported in the literature. Although this focal shift could be attributed to thermal effects of the laser; however, consecutive experiments yielded consistent results, indicating that this phenomenon is not just due to just thermal effects. Instead, it may be attributed to the transient behavior of the laser source itself. This observation also implies that employing ZAP-lt papers to determine the focal spot location will not provide accurate results, as the papers are exposed to the laser for a very short amount of time during the initial focal shifting period.

[0054] One of the benefits of the optical setup 100 is its capability for real-time monitoring. By placing the first UVFS windows on the path of the laser beam inside the laser head, a sample of the laser beam profile will be reflected and can be used for beam profile monitoring using the same optical system. FIG. 6 shows a schematic of the real-time monitoring system. However, since it reduces the laser power by reflecting 6.51% of the laser power into the beam profiler system, the optical setup can be used as a movable insert on the laser head to monitor the laser beam as needed. This approach eliminates the need to halt the process for measurements, unlike current commercial methods.

[0055] FIG. 6 illustrates an example schematic of real-time monitoring optical system 600 for an LDED metal additive manufacturing system. The system 600 shares a similar configurate as setup 100. The laser 102 heats deposited material 602 on a substrate 604 to generate a melt pool 606.

[0056] Although only a few implementations have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). It is to be understood that the methods and systems are not limited to specific synthetic methods, specific components, or to particular compositions. It is also to be understood that the terminology used herein isfor the purpose of describing particular implementations only and is not intended to be limiting.

[0057] As used in the specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another implementation includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another implementation. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0058] "Optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and "comprises," means "including but not limited to," and is not intended to exclude, for example, other additives, components, integers or steps. "Exemplary" means "an example of" and is not intended to convey an indication of a preferred or ideal implementation. "Such as" is not used in a restrictive sense, but for explanatory purposes. Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed that while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific implementation or combination of implementations of the disclosed methods.

Claims

WHAT IS CLAIMED:

1. A system for real-time monitoring and measurement of laser beam profiles in high-power lasers, the system comprising: a primary attenuation system comprising at least two wedged UV fused silica windows positioned to intercept a high-power laser beam; a secondary attenuation system comprising a reflective neutral density filter and a series of absorptive neutral density filters; a beam refocusing system comprising a first achromatic doublet lens and a second achromatic doublet lens; and a detection system comprising a high-resolution camera and a graduated manual stage.

2. The system of claim 1, wherein the first wedged UV fused silica window reflects less than 7% of an incident laser power toward the detection system as a remaining transmitted beam.

3. The system of claim 2, wherein the second wedged UV fused silica window reflects the remaining transmitted beam such that less than 1% of the incidence laser power is directed to the detection system.

4. The system of claim 1, wherein the reflective neutral density filter may have an optical density of at least 0.3.

5. The system of claim 1, wherein the series of absorptive neutral density filters are configured to reduce laser intensity below a camera damage threshold of 50 W / cm2.

6. The system of claim 1, wherein the first achromatic doublet lens has a focal length of determined in accordance with a laser power and is positioned to collimate a diverging attenuated laser beam.

7. The system of claim 1, wherein the second achromatic doublet lens has a focal length of determined in accordance with a laser spot size and is positioned to re-focus a collimated beam.

8. The system of claim 1, wherein the first achromatic doublet lens and second achromatic doublet lens are configured to magnify the laser beam.

9. The system of claim 1, wherein the high-resolution camera has a pixel size of 3.45 pm x 3.45 pm.

10. The system of claim 1, wherein the graduated manual stage is configured to allow movement of the camera in 1 mm increments along an optical axis.

11. The system of claim 1, wherein the first wedged UV fused silica window is positioned inside a laser head from which the high-power laser beam is incident.

12. A method for real-time monitoring and measurement of laser beam profiles in high-power lasers, the method comprising: reflecting a high-power laser beam with a first wedged UV fused silica window to reflect a first portion of the laser beam; reflecting the reflected first portion with a second wedged UV fused silica window to reflect a second portion of the laser beam; attenuating the reflected second portion using a reflective neutral density filter and a series of absorptive neutral density filters; collimating the attenuated laser beam using a first achromatic doublet lens; focusing the collimated beam using a second achromatic doublet lens; and capturing beam profile images using a high-resolution camera mounted on a graduated manual stage.

13. The method of claim 12, further comprising: moving the camera in increments along an optical axis to capture beam profiles at different positions relative to a focal plane.

14. The method of claim 12, further comprising: converting pixel sensor readings to laser intensity units based on input power and intensity distribution.

15. The method of claim 12, further comprising: positioning the first wedged UV fused silica window inside a laser head to enable real-time monitoring without interrupting a manufacturing process.

16. The method of claim 12, further comprising: detecting a shift in focal plane location with changing laser power.

17. The method of claim 12, further comprising: detecting a transient focus shift within a first 20 seconds after laser activation.

18. A system comprising: a first Uncoated UV Fused Silica (UVFS) window that attenuates laser beam energy from a source laser beam to reflect a first predetermined portion of a source laser power; a first beam trap that receives a second predetermined portion of the source laser power from the first UVFS, the first predetermined portion being less than the second predetermined portion; a second UVFS that receives and attenuates the first predetermined portion of the source laser power; a second beam trap that receives a third predetermined portion of the source laser power from the second UVFS; and a filter and doublet lenses that receives a fourth predetermined portion of the source laser power from the second UVFS, the fourth predetermined portion being less than the third predetermined portion of the source laser power, wherein the doublet lenses have a predetermined focal length and collimate the fourth predetermined portion of the source laser beam to be provided to a camera.

19. The system of claim 18, wherein the first predetermined portion of the source laser power is less than 7%, and wherein the fourth predetermined portion of the source laser power is less than 0.5%.

20. The system of claim 18, wherein the focal length of the doublet lenses is between 100 mm and 200 mm.

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