Apparatus and method for aligning a laser system

Abstract

An apparatus and method are disclosed for enabling automatic alignment of optical components in the beam path of a laser by acquiring images of the beam at one or more positions in the beam path, deriving alignment information from the images, and possibly other information, and then controlling actuators to change the alignment of optical components in the beam path based on the derived information.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to U.S. Patent Application No. 63 / 390,757, filed July 20, 2022, and U.S. Patent Application No. 63 / 471,996, filed June 9, 2023, each of which is incorporated herein by reference in its entirety.

[0002] BACKGROUND OF THE INVENTION

[0002] The disclosed subject matter relates to systems in which components of a laser system require alignment, such as some components of a laser-generated light source used to perform a photolithographic integrated circuit manufacturing process. [Background technology]

[0003] Photolithography is the process of patterning semiconductor circuits on a substrate such as a silicon wafer. A photolithography light source provides deep ultraviolet (DUV) light, which is used to expose photoresist on the wafer. Often, the light source is an excimer laser source, and the light is a pulsed laser beam. The light beam passes through a beam delivery unit, a reticle, or a mask, and is then projected onto a prepared silicon wafer. In this way, the chip design is patterned on the photoresist, which is then developed, etched, and cleaned before the process is repeated.

[0004]

[0004] In many systems that generate laser beams (e.g., laser generators) or utilize laser beams (e.g., photolithography systems), there is an optical train that includes one or more optical components (e.g., mirrors, gratings, prisms, optical switches, filters, etc.) that are often contained in modules. The laser beam enters the optical train and produces one or more exits after passing through the optical train. The optical components of the optical train may, in whole or in part, reflect, process, filter, modify, focus, expand, etc. the laser beam to produce one or more desired laser beam outputs.

[0005]

[0005] For optimal laser operation, the laser beam must be properly aligned with respect to each optical component in the optical train and / or as it exits the optical train. Alignment is when the laser beam intersects or impinges on a desired point or points (real or virtual in space) after passing through one or more optical components (e.g., after passing through one optical component or after passing through part or all of the optical train).

[0006]

[0006] Aligning a laser is essential to generate sufficient energy and beam quality for use in a lithography process. Conventionally, there are several systems and procedures for aligning the entire system. However, no system or method is capable of automatically identifying alignment targets or automating physical alignment adjustments.

[0007] Improved laser beam alignment and / or laser beam diagnostic apparatus and methods are the subject of embodiments of the invention herein. Summary of the Invention

[0008] The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of the invention. This summary is not an extensive overview of all contemplated embodiments, nor is it intended to identify key or critical elements of all embodiments, nor is it intended to delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

[0009] According to one aspect of the embodiment, an apparatus and method are disclosed for enabling automatic alignment of optical components in a beam path of a laser by acquiring images of the beam at one or more positions in the beam path, deriving alignment information based on the images, and then controlling actuators to change the alignment of optical components in the beam path.

[0010] According to another aspect of an embodiment, an apparatus for aligning an optical module disposed along a beam path of a beam in a laser light source is disclosed, the apparatus comprising: a beam imager arranged to capture an image of the beam after the beam interacts with the optical module; an image analysis module arranged to receive the image and adapted to make an alignment determination of an alignment state of the optical module based at least in part on the image and to generate a control signal based on the alignment determination; and an actuator mechanically coupled to the optical module and arranged to change the alignment state of the optical module based on the control signal.

[0011]

[0011] The beam path may include a power ring amplifier (PRA) alignment path including an optical module. The optical module may include at least one of a master oscillator (MO) wavefront engineering box (WEB), a PRA WEB, a PRA chamber, a beam reverser (BR), and an autoshutter module. The optical module may include a BR, and an image is acquired from the beam in the autoshutter module. The autoshutter module may include a combined autoshutter and metrology module.

[0012]

[0012] The image analysis module may be adapted to make an alignment determination based at least in part on detecting at least one edge of an aperture in the optical module. The image analysis module may be adapted to control an actuator to sweep a beam across the aperture to detect at least one edge of the aperture. The image analysis module may be adapted to detect at least one edge of the aperture using a Hough transform. The image analysis module may be adapted to detect a window and determine a center of the window using an object detection model. The image analysis module may be adapted to detect a window and determine a center of the window using a Haar cascade classifier.

[0013] The image analysis module may be adapted to make an alignment determination of the optical module based at least in part on labeling one or more contours in the image as one of the main beam and the secondary beam. The image analysis module may be adapted to control the actuator to merge the secondary beam and the main beam to form a merged beam. The image analysis module may be adapted to control the actuator to increase symmetry of the merged beam.

[0014] According to another aspect of an embodiment, a method for aligning an optical module disposed along a beam path of a beam in a laser light source is disclosed, the method including acquiring an image of the beam after the beam interacts with the optical module, making an alignment determination of an alignment state of the optical module based at least in part on the image, generating a control signal based on the alignment determination, and using the control signal to control an actuator mechanically coupled to the optical module to change the alignment state of the optical module.

[0015]

[0015] The beam path may include a PRA alignment path. The optical module may include at least one of an MO WEB, a PRA WEB, a PRA chamber, a BR, and an autoshutter module in the PRA alignment path. The optical module may include a BR, and an image is acquired from the beam in the autoshutter module. The autoshutter module may include a combined autoshutter and metrology module.

[0016]

[0016] Making an alignment determination of an alignment state of the optical module may include detecting at least one edge of an aperture in the optical module.

[0017]

[0017] The method may further include controlling the actuator to sweep the beam across the aperture to detect at least one edge of the aperture. Detecting the at least one edge of the aperture in the optics module may include using a Hough transform.

[0018]

[0018] Making an alignment determination of the alignment state of the optical module based at least in part on an image can be performed using an image analysis module adapted to detect apertures or illuminated surfaces using an object detection model and to determine the center and size of the object.

[0019]

[0019] Using an image analysis module adapted to detect apertures or illuminated surfaces using an object detection model and to determine the center and size of the object may include using a Haar cascade classifier. Making an alignment determination of an alignment state of the optical module may include labeling one or more contours in the image as one of a main beam and a secondary beam.

[0020]

[0020] The method may further include controlling the actuator to merge the primary beam and the secondary beam to form a merged beam. The method may further include controlling the actuator to increase symmetry of the merged beam.

[0021] According to another aspect of the embodiment, an apparatus for aligning an optical module with a beam path of a beam in a laser light source is disclosed. The apparatus includes a memory; a beam imager arranged to acquire an image of the beam after the beam interacts with the optical module; an image analysis module arranged to receive the image, measure one or more beam characteristics from the image, and store information indicative of the one or more beam characteristics in the memory; a controller adapted to generate a control signal based on the one or more beam characteristics; and an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal. The image analysis module is further arranged to perform subsequent measurements of the one or more beam characteristics from the image, and the controller is arranged to generate a control signal to control the actuator to reduce a difference between the one or more beam characteristics measured by the subsequent measurements and the stored information.

[0022] The beam characteristics may include beam distortion. The information indicative of one or more beam characteristics may include a target beam distortion. The image analysis module may be further configured to perform a subsequent measurement of the beam distortion, and the controller may be configured to generate a control signal to control the actuator to reduce a difference between the subsequent measurement of the beam distortion and the target beam distortion.

[0023] The beam characteristics may include a measured position of a centroid of an image of one of the main and secondary beam components of the beam. The information indicative of the one or more beam characteristics may include the measured position of the centroid. The image analysis module may further be arranged to perform a subsequent measurement of the position of the centroid of the other of the main and secondary beam components. The controller may be arranged to generate a control signal to control an actuator to move the position of the centroid of the other of the main and secondary beam components to the measured position stored in the memory.

[0024]

[0024] The apparatus may further include a beam component blocking element positioned to block one of the first beam component and the second beam component when the image analysis module is measuring the position of the center of gravity of the other of the first beam component and the second beam component.

[0025] According to another aspect of an embodiment, a method is disclosed for aligning an optical module with a beam path of a beam in a laser light source, the method including obtaining an image of the beam after the beam interacts with the optical module, measuring one or more beam characteristics from the image, storing information indicative of the one or more beam characteristics in a memory, generating a control signal based on the one or more beam characteristics, actuating an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal, performing subsequent measurements of the one or more beam characteristics, and generating a control signal to control the actuator to reduce a difference between the one or more beam characteristics measured by the subsequent measurements and the stored information.

[0026] The beam characteristics may include a beam distortion. The information indicative of the one or more beam characteristics may include a target beam distortion. Taking subsequent measurements of the one or more beam characteristics may include taking subsequent measurements of the beam distortion. Generating the control signal may include generating a control signal to control an actuator to reduce a difference between the subsequent measurements of the beam distortion and the target beam distortion.

[0027] The beam characteristics may include a measured position of a centroid of an image of one of the main and secondary beam components of the beam. The information indicative of the one or more beam characteristics may include a measured position of the centroid. Taking a subsequent measurement of the one or more beam characteristics may include taking a subsequent measurement of a position of the centroid of the other of the main and secondary beam components. Generating the control signal may include generating a signal to control an actuator to move the position of the centroid of the other of the main and secondary beam components to the measured position stored in memory.

[0028]

[0028] The method may further include blocking one of the first beam component and the second beam component while measuring the position of the center of gravity of the other of the first beam component and the second beam component.

[0029] According to another aspect of an embodiment, an apparatus for aligning an optical module with a beam path of a beam in a laser light source is disclosed, the apparatus comprising: a beam imager arranged to acquire an image of the beam after the beam interacts with the optical module, an image analysis module arranged to receive the image and perform a probabilistic Hough Line transform to identify locations of one or more features in the image, a controller adapted to generate a control signal based on the one or more features identified in the image, and an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal.

[0030]

[0030] The one or more features identified in the image may include illuminated frames within the image.

[0031] The one or more features identified in the image may include the location of the center of the illuminated frame.

[0032] According to another aspect of an embodiment, a method for aligning an optical module with a beam path of a beam in a laser light source is disclosed, the method including acquiring an image of the beam after the beam interacts with the optical module, performing a probabilistic Hough Line transform to identify locations of one or more features in the image, generating a control signal based on the one or more features identified in the image, and altering an alignment state of the optical module based on the control signal.

[0033]

[0033] The one or more features identified in the image may include illuminated frames within the image.

[0034] The one or more features identified in the image may include the location of the center of the illuminated frame.

[0035]

[0035] Further embodiments, features, and advantages of the subject matter of the present disclosure, as well as the structure and operation of the various embodiments, are described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0036]

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate the present invention and, together with the description, serve to explain the principles of the invention and to enable those skilled in the art to make and use the invention.

[0037] [Figure 1]

[0037] A schematic diagram, not to scale, showing the overall broad concept of a photolithography system. [Figure 2]

[0038] 2 is a schematic diagram, not to scale, illustrating the overall broad concept of an illumination system that may be used in the photolithography system of FIG. 1. [Figure 3]

[0039] 1 is a schematic, not-to-scale, illustration of a system for alignment of components of a lighting system according to an aspect of an embodiment; [Figure 4A]

[0040] 1 is a schematic, not-to-scale, illustration of another system for alignment of components of a lighting system in accordance with an aspect of an embodiment; [Figure 4B]

[0041] 1 is a schematic, not-to-scale, illustration of another system for alignment of components of a lighting system in accordance with an aspect of an embodiment; [Figure 5A]

[0042] 1 is a schematic, not-to-scale, illustration of a module for a lighting system according to an aspect of an embodiment; [Figure 5B]

[0043] FIG. 5B is a cutaway plan view of the module of FIG. 5A. [Figure 6A]

[0044] 1 is a diagram of an example of an image that may appear within an alignment path in accordance with an aspect of an embodiment; [Figure 6B]

[0044] A diagram of an example of an image that may appear within an alignment path according to one aspect of an embodiment. [Figure 7]

[0045] 1 is a diagram of an example of an image that may appear within an alignment path in accordance with an aspect of an embodiment; [Figure 8A]

[0046] 1 is an example of an image that may appear within an alignment path in accordance with an aspect of an embodiment. [Figure 8B]

[0047] 10 is an example of the results of an edge detection process according to an aspect of an embodiment. [Figure 9]

[0048] 1 is a flowchart illustrating steps in a process for boundary detection according to an aspect of an embodiment. [Figure 10]

[0049] 1 is a flowchart of a process for contour labeling and distortion adjustment according to an aspect of an embodiment. [Figure 11]

[0050] 1 is a flowchart of a process for aperture detection according to an aspect of an embodiment. [Figure 12]

[0051] 1 is a functional block diagram, not to scale, of a system for aligning an optical module in accordance with an aspect of an embodiment; [Figure 13]

[0052] 10 is a flowchart of a portion of a process for aligning an optical module in accordance with an aspect of an embodiment. [Figure 14]

[0053] 10 is a flowchart of a portion of a process for aligning an optical module in accordance with an aspect of an embodiment. [Figure 15A]

[0054] 1 is a diagram of an image that may be obtained in accordance with an aspect of an embodiment. [Figure 15B]

[0055] FIG. 15B is an illustration of an analysis result of the image of FIG. 15A according to one aspect of an embodiment.

[0038]

[0056] Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings provided herein. DETAILED DESCRIPTION OF THE INVENTION

[0039]

[0057] Various embodiments will now be described with reference to the drawings. Like reference numerals are used to refer to like elements throughout the drawings. In the following description, numerous specific details are set forth to facilitate a thorough understanding of one or more embodiments. However, it may be apparent that in some or all cases, any of the embodiments described below can be practiced without employing the specific design details described in conjunction with that embodiment. In other instances, well-known structures and devices are shown in block diagram form to facilitate describing one or more embodiments. This summary is not an extensive overview of all contemplated embodiments, nor is it intended to identify key or critical elements of all embodiments, nor is it intended to delineate the scope of any or all embodiments.

[0040]

[0058] Systems such as those described herein can provide benefits in a wide range of applications and implementations. For ease of explanation with a specific, non-limiting example, one such application is semiconductor photolithography. FIG. 1 shows a photolithography system 100 that includes an illumination system 105. As described more fully below, the illumination system 105 includes a light source that generates and directs a pulsed light beam 110 to a photolithography exposure apparatus or scanner 115. The photolithography exposure apparatus or scanner 115 patterns microelectronic and other features on a wafer 120. The wafer 120 is positioned on a wafer table 125. The wafer table 125 is constructed to hold the wafer 120 and is connected to a positioner 127 configured to precisely position the wafer 120 according to certain parameters.

[0041]

[0059] The pulsed light beam 110 may have a wavelength in the deep UV range, such as a wavelength of 248 nanometers (nm) or 193 nm. The scanner 115 includes an optical system 117 having, for example, one or more condenser lenses, a mask, and an objective. The mask is movable along one or more directions, for example, along the optical axis of the pulsed light beam 110 or in a plane perpendicular to the optical axis. The objective includes a projection lens and enables image transfer from the mask to a photoresist on the wafer 120. The illumination system 105 adjusts the angular range of the pulsed light beam 110 incident on the mask. The illumination system 105 also homogenizes (uniforms) the intensity distribution of the pulsed light beam 110 on the mask.

[0042]

[0060] The scanner 115 may include, among other features, a lithography controller 130 that controls how layers are printed on the wafer 120. The lithography controller 130 may include memory that stores information such as a process recipe. The process recipe determines parameters including the length of exposure of the wafer 120 based on, for example, the mask used and other factors that affect the exposure. During lithography, successive pulses of the pulsed light beam 110 illuminate the same area of the wafer 120 to constitute an illumination dose.

[0043]

[0061] Photolithography system 100 also preferably includes a control system 135. Control system 135 typically includes one or more of digital electronic circuitry, computer hardware, firmware, and software. Control system 135 can be centralized or partially or wholly distributed throughout photolithography system 100.

[0044]

[0062] FIG. 2 illustrates a pulsed laser source generating a pulsed laser beam as light beam 110 as an example of illumination system 105. While FIG. 2 illustrates a two-chamber laser system as a non-limiting example, it will be understood that the principles described herein are equally applicable to single-chamber laser systems or laser systems having three or more chambers. A gas discharge laser system may include, for example, a solid-state or gas discharge master oscillator (“MO”) seed laser system 140, an amplification stage such as, for example, a power ring amplifier (“PRA”) stage 145, relay optics 150, and a laser system output subsystem 160. Seed system 140 may include, for example, an MO chamber 165 including a pair of electrodes 167 and 168.

[0045]

[0063] The MO seed laser system 140 may also include a master oscillator output coupler (“MO OC”) 175. The MO OC 175 may include a partially reflective mirror, which, together with a reflective grating (not shown) in a line narrowing module (“LNM”) 170, forms an oscillator cavity within which the MO seed laser 140 oscillates to form seed laser output pulses, i.e., MO 165. The MO seed laser system 140 may also include a line center analysis module (“LAM”) 180. The MO wavefront engineering box (“WEB”) 185 serves to redirect the output of the MO seed laser system 140 to the amplification stage 145 and may include, for example, a multi-prism beam expander (not shown) and an optical delay path (not shown).

[0046]

[0064] The amplification stage 145 may include, for example, a PRA laser oscillation chamber 200. This may be an oscillator formed by seed beam injection and output coupling optics (not shown), which may be incorporated, for example, into a PRA WEB 210. The beam may be redirected back through the gain medium within the chamber 200 by a beam reverser (“BR”) 220. The PRA WEB 210 may incorporate a partially reflective input / output coupler (not shown), a maximum reflecting mirror for the nominal operating wavelength (e.g., about 193 nm for an ArF system), and one or more prisms. The PRA laser oscillation chamber 200 may also include a pair of electrodes 207 and 208.

[0047]

[0065] The bandwidth analysis module ("BAM") 230 receives the output laser light beam pulse from the PRA laser oscillation chamber 200 and can select a portion of the light beam for metrology purposes, such as measuring the output bandwidth and pulse energy. The laser output light beam pulse then passes through the PRA WEB 210 to an optical pulse stretcher ("OPuS") 240 and an autoshutter, in this case a combined autoshutter metrology module ("CASMM") 250, which may be located in the pulse energy measurement instrument. One purpose of the OPuS 240 is to convert, for example, a single output laser pulse into a pulse train. Secondary pulses generated from an initial single output pulse may be delayed relative to each other. By dispersing the initial laser pulse energy within the secondary pulse train, the effective pulse length of the laser can be increased while simultaneously reducing the peak pulse intensity. In this way, the OPuS 240 can receive the laser beam from the PRA WEB 210 and direct its output to the CASMM 250.

[0048]

[0066] The PRA laser operation chamber 200 and MO 165 are configured as a chamber in which an electrical discharge between electrodes can create a lasing gas discharge in a lasing gas, creating a population inversion of energetic molecules including, for example, Ar, Kr, F2, and / or Xe, to produce a relatively broadband radiation that can be line narrowed by LNM 170 to a relatively very narrow bandwidth and center wavelength selected.

[0049]

[0067] As previously mentioned, alignment is the process of adjusting the position, orientation, etc. of these optical components so that the laser beam propagates along a desired beam path. Aligning a module with respect to the laser beam and other components may entail adjusting the components that make up the module. For example, the alignment of an amplifier stage may be determined with respect to the PRA alignment path 260, shown in dashed lines in FIG. 2 . The illustrated PRA alignment path 260 includes the BR 220, the PRA chamber 200, the BAM 230, the PRA WEB 210, the OPuS 240, and the CASMM 250. The illustrated example PRA alignment path 260 also includes the path of the seed laser beam from the MO WEB 185.

[0050]

[0068] Alignment and other beam characteristics are determined by obtaining information about the beam at alignment ports ("APs") at various locations within the PRA alignment path 260 (referred to herein as imaging the beam). For example, the beam may be imaged at a first location 270 on the BR 220. The beam may also be imaged at a location 272 on the PRA WEB 210 and at a location 274 on the CASMM 250. These images may be near-field or far-field images. Beam imaging may include obtaining information about beam / aperture edge detection, beam profile, beam cross-sectional structure, relay optics position, etc.

[0051]

[0069] For ease of explanation by way of specific, non-limiting examples, the following discussion is conducted in terms of an image acquired at position 270, a far-field image acquired at position 274, and a near-field image acquired at position 274. However, one skilled in the art will readily recognize that these are merely examples and that the teachings provided herein are applicable to other images acquired at other positions.

[0052]

[0070] Furthermore, those skilled in the art will recognize that the alignment process does not necessarily involve alignment of the optical component physically closest to the location in the relay optics where the image is acquired. For example, a far-field image acquired at location 274 may indicate the alignment of an optical component, such as BR 220, that is several components away from that location.

[0053]

[0071] It would therefore be advantageous to perform alignment by an alignment system that can automate some or all aspects of the alignment process, including beam imaging, analysis, and alignment. Figure 3 is a diagram of such an alignment system 300. In Figure 3, beam 305 propagates along beam path 310 (dashed line) that best matches alignment path 315 (dotted line). Beam path 310 includes relay optics in the form of first optical module 320, second optical module 325, and third optical module 330. These optical modules may correspond to units BR 220, PRA chamber 200, BAM 230, PRA WEB 210, OPuS 240, and CASMM 250, respectively, as shown in Figure 2.

[0054]

[0072] Alignment system 300 also includes element 335 for deflecting a portion of radiation from beam 305 from position A into image capture module 340. Element 335 may be a beam splitter that splits off a small portion of radiation from beam 305. Element 335 may additionally or alternatively be an element that can be moved into or out of beam path 310 depending on whether measurements are desired. Image capture module 340 captures an image of the beam at element 335 (position A) and provides a signal indicative of the capture result to control unit 350. Image capture module 340 may also perform a combination of image analysis, such as edge detection, contour detection / labeling, aperture detection, and computer vision / pattern recognition, based on identification techniques as described in more detail below, or these functions may be performed by control module 350. It will be appreciated that the functions of image capture module 340 and control module 350 may be combined into one unit or distributed between these two units or across more than two units. The control unit 350 generates a control signal C1 that the control unit 350 provides to the actuator 360. The actuator 360 is coupled to the first optical module 320 and is arranged to change the alignment state of the first optical unit 320 by changing the position, orientation, etc. of the optical components within the first optical module 340 under the control of the control signal C1.

[0055]

[0073] Alignment system 300 also includes element 365 for deflecting a portion of radiation from beam 305 from position B into image capture module 370. Element 365 may also be a beam splitter that splits off a small portion of radiation from beam 305. Element 365 may additionally or alternatively be an element that can be moved into or out of beam path 310 depending on whether measurements are desired. Image capture module 370 captures and analyzes an image of the beam at element 365 (position B) and provides a signal indicative of the analysis to control unit 350. It will be appreciated that the functions of image capture module 370 and control unit 350 may be combined into one unit or distributed among three or more units. Control unit 350 generates a control signal C2 that control unit 350 provides to actuator 375. Actuator 375 is coupled to second optical module 325 and is arranged to change the alignment state of second control module 325 under control of control signal C2.

[0056]

[0074] Alignment system 300 also includes element 380 for deflecting a portion of radiation from beam 305 from position C into image capture module 385. In the example of FIG. 3, element 380 is an example of a deflector that is part of an optical module, such as third optical element 330, rather than being positioned between optical modules. Element 380 may also be a beam splitter that splits off a small portion of radiation from beam 305. Image capture module 385 captures and analyzes an image of the beam at element 380 (position C) and provides a signal indicative of the analysis to control unit 350. It will be appreciated that the functions of image capture module 385 and control unit 350 may be combined into one unit or distributed across both units or more than two units. Control unit 350 generates a control signal C3 that control unit 350 provides to actuator 390. Actuator 390 is coupled to third optical module 330 and is arranged to change the alignment state of third control module 330 under the control of control signal C3.

[0057]

[0075] Control signals C1, C2, and C3 may also be generated based on image information acquired at locations in the system that are separate from the locations where the images are acquired. For example, control signal C1 may be based on an image acquired at location C. In other words, the image at location C may be adjusted by changing the alignment of optical module 320, i.e., by moving (e.g., translating or rotating) optical components within optical module 320.

[0058]

[0076] Alignment system 300 also includes a user interface 395 arranged to exchange data with control unit 350. User interface 395 and control unit 350 may be connected by a hardwired connection or wirelessly. User interface 395 and control unit 350 may be directly connected or indirectly connected via intermediate components, ports, buses, etc. User interface 395 allows a user, such as a field service technician, to monitor the automatic alignment process and view the various beam images that are acquired. User interface 395 also allows a user to override the automatic alignment adjustments if desired.

[0059]

[0077] Generally, the user interface 395 can be used to invoke a manual alignment mode, which allows the user to view images and control actuators. The user interface 395 can also provide the user with the ability to move to different steps in the alignment process. The user interface 395 provides the user with visual indicators of the current step in the alignment process, the next step in the alignment process, and any errors in the alignment process, and allows the user to view the current image. The user interface 395 also allows the user to review the results of the automatic alignment process, save alignment images, and save configurations and settings for the image capture module, actuators, etc.

[0060]

[0078] Actuators 360, 375, and 390 may be through-wall adjusters ("TWAs") that pass through the housing walls of each optical module 320, 325, and 330. Each TWA may include an electrically controlled motor that causes the end of the TWA to translate along an axis according to the direction of shaft rotation, changing the alignment of the optical component to which the TWA is coupled. Using such electrically actuated TWAs allows for automation of the alignment process, with control unit 350 controlling the TWA to perform the alignment.

[0061]

[0079] The TWA motor may be, for example, a stepper motor or a servo motor. Potential advantages of using a stepper motor include the ability to generate extremely large torque at zero speed, being generally compact and inexpensive, and the ability to provide holding torque when needed. Servomotors, on the other hand, can provide large and consistent levels of torque at high speeds. Servomotors also typically operate at approximately 80-90% efficiency and can function with AC or DC drives, but are larger, more costly, and more complex. Those skilled in the art will recognize that the choice of whether to use a stepper motor or a servo motor generally depends on the requirements of a particular application.

[0062]

[0080] FIG. 4A is a diagram of an alignment system 400 having a different architecture than alignment system 300. Alignment system 400 of FIG. 4 includes a laser 405 and a computing unit 410. Computing unit 410 may be, for example, a portable computer used by a field service technician. Laser 405 includes an optical module, which in the example of FIG. 4 is a CASMM250, in addition to several modules necessary to generate a laser beam. Laser 405 also includes a set of relay optics 415. Relay optics 415 includes image capture module 385, which may be, for example, a camera. Image capture module 385 communicates image data to image processing module 387 in computing unit 410. Relay optics 415 also includes a communications module 420 that handles communications between laser 405 and computing unit 410. Communications module 420 is also arranged to communicate with actuator controller software 397, which in turn communicates with actuator 390. Actuator 390 may be coupled to, for example, BR 220. While Figure 4A shows only one image capture module and only one actuator, one skilled in the art will readily recognize that alignment system 400 can be generalized to any number of image capture modules and actuators.

[0063]

[0081] The computing unit 410 also includes a control module 350 and a communications module 425 that interfaces with the communications module 420 in the laser 405. The computing unit 410 also includes a user interface 395, which may be, for example, a GUI.

[0064]

[0082] In use, image capture module 385 relays image data to image processing module 387. Image processing module processes the image data and then provides a signal indicative of an alignment error to control module 350. Control module 350 then communicates via communications modules 425 and 420 with actuator controller software 397, which then controls actuator 390, which may be a stepper motor, to change the alignment of CASMM 250. Simultaneously, information from image processing module 387, control module 350, and communications module 425 is provided to user interface 395.

[0065]

[0083] Figure 4B shows another possible setup for the alignment system 450. In the example of Figure 4B, the alignment system captures images of the BR AP 455, the CASMM near-field AP 460, and the CASMM far-field AP 465. Images of these alignment ports are captured by the image processing module 387. Information from the image processing module 387 is passed to the control unit 350. The control unit 350 generates control signals that control the actuator 390. The entire process is controlled by the GUI / controller 470.

[0066]

[0084] FIG. 5A shows an example of an optical module that may be used in the alignment system of FIG. 3, 4A, or 4B. The example optical module in FIG. 5A is BR 220. As can be seen, BR 220 has a housing 560 and an aperture 510 through which beams 305 and 307 pass. BR 220 also includes a TWA 520 for aligning the horizontal position of the optical components within BR 220, which in this example is prism 560 as shown in FIG. 5B, and a TWA 530 for aligning the vertical position of prism 560 within BR 220. Also shown is a TWA 550 for adjusting an alignment tool prism so that an image of beam 305 is available at BR port 540. Each of the TWAs includes an actuator (e.g., a stepper motor or servo motor) that moves a through-wall adjuster in response to a control signal, as described above.

[0067]

[0085] As shown in FIG. 5B, prism 565 can incorporate two total internal reflection surfaces 570, 575 and input surface 580. These and other details regarding possible implementations of beam reversers can be found in U.S. Patent No. 7,885,309, entitled "Laser System," filed February 8, 2011. All patent applications, patents, and publications cited herein are incorporated by reference in their entirety, except for definitions, disclaimers, or disclaimers of subject matter, and except to the extent that the included material is inconsistent with the express disclosure of this specification. In such cases, the language of this disclosure will control.

[0068]

[0086] Again using the example of the alignment procedure involving the BR220 image and the CASMM250 near-field and far-field images, these images can be acquired by looking at the AP image. Thus, in this example, position 270 (FIG. 2) can be referred to as AP270. AP270 is at the BR220, and images there are acquired by placing a camera at the BR alignment port, i.e., AP270. The CASMM250 near-field and far-field images are at the CASMM250, or at the autoshutter module in systems that have an autoshutter module but not a CASMM. The CASMM250 typically already includes a camera for acquiring images there. If an autoshutter is used, it typically has an alignment port onto which a camera can be mounted.

[0069]

[0087] As shown in FIG. 6A, a misaligned beam typically produces an image, such as image 600, that includes an image of the beam 605 and an illuminated device, such as the edge of a window 610. In this illustration, it is necessary to characterize the inner "box" or aperture 615 to find its center, which serves as the central target location. It is also necessary to identify the center of the beam to determine the position of the beam within the aperture. For alignment purposes, it is desirable to move the center of the beam to the center of the aperture to obtain image 650, as shown in FIG. 6B. Generally speaking, crosshairs 620 are not illuminated and cannot be used for beam centering.

[0070]

[0088] One method for finding the appropriate aperture size and location to establish the centering target position involves using a pre-trained object detection model to recognize features of interest. Any of a number of object detection models can be used. In the following example, a Haar cascade classifier is used as an example of using an object detection model to identify bounding boxes, such as aperture edges, and then establish the target. The Haar cascade classifier is described in "Rapid object detection using a boosted cascade of simple features," by Viola, P. and Jones, M., in Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR2001 (Vol. 1, pp. I-9), December 2001. Once the model is properly trained, it can be used for alignment.

[0071]

[0089] Generally, the model can be trained by capturing alignment port images, performing image augmentation on the captured images to increase the number of sample images, labeling the images, and then using the training procedure of the object detection model being utilized on the labeled images.

[0072]

[0090] This process can automatically locate and identify several important features in the image, such as alignment targets, illuminated window edges, or recognizable reference locations, for later use. Furthermore, known window dimensions can be used to adjust for potential false positive results, ensuring that the detected window size is appropriate; in other words, results can be discarded if they do not fall within a range of possible dimensions. Using information gained from image processing, the procedure can provide recommendations and directions that are used to control actuators to move the beam toward the target, thereby aligning the image.

[0073]

[0091] FIG. 7 shows another example of a beam image. Beam image 700 in FIG. 7 is an example of a far-field image that may be acquired at the alignment port (location 274 in FIG. 2) of CASMM 250. Image 700 includes a MOPA seed beam 710 and two auxiliary or secondary "daughter" beams 720A and 720B. The alignment goal for an image such as image 700 may be to converge the daughter beams 720A, 720B onto the MOPA beam 710 while minimizing divergence and maximizing PRA energy. This process may involve detecting which of the beams is the MO seed beam and which is the MOPA beam propagating along the PRA beam path, for example, using pixel distortion. In this case, left and right side distortions may be used as metric indicators to align and overlap the beams by minimizing the distortion coefficients.

[0074]

[0092] In other words, image 700 is ideally a centered, symmetrical, single-beam image. If the image is not aligned, several visual beams (MOPA and daughter beams) will be visible. Up to five beams can be present in the image at one time. As part of the alignment process, it is necessary to identify or label the MOPA and daughter beams and select the appropriate daughter beam to track during alignment. The alignment procedure generally focuses on the MOPA beam and the third beam if five beams are detected, or on the darker beam if two beams are observed.

[0075]

[0093] In the image shown in Figure 7, the beam of interest is the darkest visual beam image, or daughter beam 720B. This beam is used by the alignment system to adjust the module to merge these beams into one beam. Once there is a single combined beam, additional processing can be done to make the beam symmetrical along the x and y axes.

[0076]

[0094] According to one aspect of the embodiment, computer vision techniques are used to determine and label the beams as shown in image 700, including MOPA seed beam 710 and daughter beams 720A, 720B. As described in more detail below, these techniques include pre-processing the image, determining all contours or shapes in the image, using features of the daughter (secondary) beams to determine their validity, and may include logic for the proper ordering and labeling of each valid contour or secondary beam.

[0077]

[0095] Automatic contour labeling determines how and where to move the target secondary beam. Once the alignment system determines that a single contour has been achieved, it calculates the pixel-sum distortion, or symmetry measure, in both the vertical and horizontal directions of the contour. This measurement determines the direction to move the secondary beam to reduce the distortion and obtain a more symmetric target beam.

[0078]

[0096] Thus, according to another aspect of the embodiment, the alignment system can sequentially classify valid contours and provide a label for every shape found on the image. One advantage of this classification function is that the system can zero in on the secondary beam of interest and adjust it by moving the actuator so that the secondary beam at the location of interest coincides with the target beam and only one contour is present. If the system makes such a determination, it can apply additional adjustment metrics (distortions) to make the beam more symmetrical.

[0079]

[0097] FIG. 8A shows an example of a near-field image 800 of a combined MO seed beam and PRA beam. The MO seed beam does not "fill" the entire aperture profile, as indicated by the manually added "box" lines in FIGS. 8A and 8B. This can cause problems when aligning to the central aperture boundary, because the aperture profile is not visible in the image of FIG. 8A available to the system. Without determining the proper aperture boundary, the alignment system cannot determine the center of the aperture, which can be used for alignment. For proper alignment, it is desirable to move the center of the beam to the center of the aperture.

[0080]

[0098] According to one aspect of the embodiment, line detection, logic, and sequential search are used to move the beam to detect and preserve the near-field aperture boundary. Figure 8B shows the results of the boundary detection. Once the system detects the aperture edge, these values can be preserved to establish the location of the aperture center, which can be used to align the system. The beam can be automatically moved around the aperture edge. Additionally, the center of the contour (visually imaged beam outline) can be preserved and used to calculate alignment errors.

[0081]

[0099] More specifically, beam image 800 in FIG. 8A is an example of a near-field image that may be acquired at CASMM 250 (position 274 in FIG. 2 ). Image 800 includes an image of MO seed beam 810 and a box trace 820 showing the aligned position of the non-illuminated aperture at position 274. The alignment goal for an image such as image 800 may be to find the edge of the non-illuminated aperture and center MO seed beam 810 over the aperture. This may involve using edge detection to identify edge 830 of MO seed beam 810 in image 820, as shown in FIG. 8B .

[0082]

[0100] One method of edge detection can be to use feature extraction techniques known in the field of image analysis, such as a Hough transform, e.g., a standard Hough transform or a probabilistic Hough transform, to detect edges. Other edge detection methods can also be used, such as integral transforms, e.g., a Radon transform, or pixel intensity transitions. Other techniques known in the field of image analysis can also be used. It is also possible to use an open-loop solution to determine the aperture position by controlling an associated actuator to sweep the beam across the aperture and using the sum of bright spots to determine the location of the aperture edge. The edge detection can be used in a feedback loop to cause the actuator to stop sweeping in the current direction and start sweeping along a new path to find the other edge of the aperture. Once the aperture is identified, the alignment system can determine the pixel error determined between the beam centroid and the aperture center.

[0083]

[0101] As mentioned above, part of the image analysis may include locating unilluminated (dark) crosshair targets or frames. One measure to improve the overall determination of beam alignment may be to position the beam so that it is close to the center of the target, and then use additional image processing to detect the location of the dark target and realign it to the exact target center. Another possibility is to illuminate the target from the module access port using an external instrument light source without firing a beam.

[0084]

[0102] Those skilled in the art will recognize that the alignment process can be iterative in the sense that a first element (such as a folding mirror of the PRA WEB) is aligned, then a second element (such as a folding mirror of the MO WEB) is aligned, and then misalignment of the second element may cause misalignment of the first element, and vice versa, thus requiring additional alignment of the first element, with the process converging to an optimal alignment achieved through repeated iterations.

[0085]

[0103] 9 is a flowchart illustrating a process for boundary detection according to one aspect of an embodiment. The process begins in step S10, where an image is acquired. Then, in step S20, it is determined whether the location of the target (e.g., crosshairs, aperture edge) has been established. Once the target location has been established, then in step S30, beam alignment is performed using the established beam center and target. The process then ends in step S40, where an alignment indicator is returned indicating the alignment status and parameters.

[0086]

[0104] However, if, in step S20, it is determined that a target has not been established, the process proceeds to the automatic boundary detection subroutine 1000. In step S50 of the automatic boundary detection subroutine, the image is pre-processed to enhance features. Such pre-processing may include, for example, increasing contrast. Then, in step S60, horizontal and vertical line detection techniques are used, and in step S70, it is determined whether the detection techniques have actually detected horizontal and vertical lines.

[0087]

[0105] If step S70 is negative, the process proceeds to step S100, where the beam path is adjusted to a new position, and then returns to execution of step S60. On the other hand, if horizontal and vertical lines are detected, the lines are retained and their positions are restored. In step S90, it is determined whether a stopping criterion has been met. If the stopping criterion has been met, the subroutine 1000 ends, and in step S110, the alignment target is determined as the aperture center using the retained lines. On the other hand, if step S90 determines that the stopping criterion has not been met, the process again proceeds to step S100, where the beam path is adjusted to a new position, and then the process returns to step S60.

[0088]

[0106] 10 is a flowchart of a process for contour labeling (and distortion adjustment) according to one aspect of an embodiment. In this process, contour labeling can be used to align one or more secondary beams with the main beam. The process begins in step S200, where an image is acquired. Then, in step S210, it is determined from the acquired beam image whether the beams are aligned and symmetric. If the beams are aligned and symmetric, the process ends in step S220, where an alignment indicator is returned indicating the alignment status and parameters.

[0089]

[0107] However, if in step S210 it is determined that the beams are not aligned and symmetric, the process of Figure 10 proceeds to the automatic contour labeling subroutine 1100. In step S230 of the automatic boundary contour labeling subroutine 1100, the image is pre-processed to highlight features. Such pre-processing may include, for example, increasing contrast. Then, in step S240, all contours in the image are determined. Then, in step S250, filtering and logic are used to identify which of the determined contours are valid, i.e., can be associated with a beam.

[0090]

[0108] In step S260, it is determined whether multiple contours have been identified. If yes, in step S270, the contours are labeled with the appropriate label representing the beam, e.g., MOPA or daughter beam, using labeling based on contour area and sorting logic. Then, in step 280, the appropriate beam for tracking (of either daughter beam) is determined based on the sort order, and the daughter beam is moved toward the MOPA beam to create a single merged beam. The process then returns to step 240.

[0091]

[0109] However, if multiple contours are not determined in step S260, contour labeling is considered complete, and additional processing is then performed to determine the distortion of the merged beam about the vertical and horizontal axes using pixel summation. Then, in step S300, the beam is adjusted to reduce the vertical and horizontal distortion. The automatic contour labeling subroutine then ends, and in step S210, it is determined whether the beam is aligned and symmetric. If, in step S210, it is determined that the beam is not yet aligned and symmetric, the process returns to step S230. On the other hand, if, in step S210, it is determined that the beam is aligned and symmetric, the process ends in step S220 and returns the alignment indicator.

[0092]

[0110] 11 is a flow chart illustrating an example of a procedure that includes detecting aperture edges and centers according to an aspect of an embodiment. The process begins in step S400 with acquiring an image, which may be, for example, an alignment port image.

[0093]

[0111] In step S410, it is determined whether to use an object detection model or a predefined coarse region of interest (ROI) location.

[0094]

[0112] If step S410 determines to use an object detection model, then step S420 passes the image through the object detection model to determine a coarse ROI subset within the image. Alternatively, if step S410 determines to use a predefined ROI location, then step S430 uses a predefined coarse ROI to isolate an approximate area around the aperture.

[0095]

[0113] Regardless of whether step S420 or S430 is used, step S440 then uses deterministic image processing on either the coarse ROI image subset (step S420) or the approximate area around the aperture (step S430) to determine the aperture edges and center. Step S450 then determines whether the determined aperture internal dimensions are "valid," i.e., whether the determined internal dimensions correspond to known aperture dimensions. If step S450 determines that the determined aperture size is not valid, step S460 returns the alignment status and performance metrics. The process then ends in step S470 and repeats by returning to the start step S400.

[0096]

[0114] However, if step S450 determines that the determined aperture size is reasonable, then the location of the aperture center is determined and maintained in step S480.The center of gravity ("COG") of the beam is then identified in step S490.

[0097]

[0115] Next, in step S500, the distance and direction (delta) between the beam COG and the determined aperture center is determined. Then, in step S510, it is determined whether the distance in the x-dimension (Δx) and the distance in the y-dimension (Δy) between the aperture center and the beam COG are within specified limits (e.g., 5 pixels). If either Δx or Δy, or both, exceed their respective specified limits, then in step S520, the alignment status, performance indicators, and movement commands (actuator control signals) are returned, and the process then returns to step S500. On the other hand, if it is determined that neither Δx nor Δy exceed their respective specified limits, the process proceeds to step S460 and then ends in step S470 to repeat, starting again from step S400.

[0098]

[0116] The process steps may be performed in various orders. Not all alignment processes use all of the steps and methods outlined above. Some steps are iterative, i.e., can be repeated several times in succession to converge on the desired alignment. Later alignment steps may require repeating earlier alignment steps. A specific example of the overall alignment procedure could begin by using an MO seed beam in the CASMM to find the aperture boundary, scan to find the boundary using the MO WEB TWA, identify the boundary using Hough-line edge detection, and then center the MO seed beam on the identified boundary. Next, several iterations of operating the MO WEB TWA to position the MO seed beam at the previously identified CASMM aperture center and the PRA WEB TWA to center the beam on the BR alignment port crosshairs may be performed.

[0099]

[0117] At some point, the PRA OC can be aligned and then intentionally dealigned. The BR TWA is then manipulated to place the MO seed beam at the previously identified CASMM aperture center. The PRA chamber can then be aligned. The PRA OC can then be realigned by contour detection, making the beam more symmetrical by reducing distortion.

[0100]

[0118] It is also possible to perform several iterations and combinations of iterations of the steps described above and / or to perform additional sub-steps.

[0101]

[0119] As described above, according to one embodiment, an image analysis module can be used to determine the alignment status of the optical module by acquiring an image of the beam at or optically downstream of the optical module and labeling one or more contours in the image as a main beam component or a secondary beam component. The image analysis module can then control an actuator to merge the secondary beam component with the main beam component to form a merged beam. The image analysis module can be adapted to control the actuator to increase the symmetry of the merged beam. For example, the image analysis module can control the actuator to increase horizontal (left-right) symmetry, vertical (up-down) symmetry, or both.

[0102]

[0120] There may be instances where the main beam components exhibit a high degree of symmetry. In such instances, according to one embodiment, the system may store in memory the current distortion value (a measure of symmetry) of a beam image, such as the far-field image of the beam, as a target distortion value. Then, during the process of merging the main beam component with the secondary beam component, the system may target the distortion value stored in memory to bring the symmetry of the merged beam as close as possible to the symmetry of the previous merged beam for which the distortion value was stored.

[0103]

[0121] A system for performing this procedure is illustrated in FIG. 12. As shown, the optical module 900 presents the beam image to the image analysis module 910 (indicated by the arrow). The image analysis module 910 measures the value of a property of the image, which in this example is distortion. The image analysis module 910 provides the measured distortion value to the controller 920. The controller 920 controls the actuator 905 to properly align the optical module 900. The image analysis module 910 also stores the measured distortion value in the memory 930 as a target distortion value. Then, in the next measurement where the primary and secondary beam components are merged, the image analysis module 910 measures the current distortion value, i.e., the distortion value acquired during the next measurement, and transmits the current distortion value to the controller 920. The controller 920 accesses the target distortion value stored in the memory 930 and controls the actuator to reduce the difference between the current distortion value and the target distortion value. In some embodiments, the controller 920 controls the actuator to make the current distortion value substantially equal to the target distortion value.

[0104]

[0122] 13 is a flow chart describing this procedure. In step S600, distortion values are measured from beam images from the optical module to be aligned. In step S610, the measured distortion values are converted into target distortion values S T Then, in step S620, the current distortion value S is stored as C Measure S C and S T In other words, S is set to target the previously memorized distortion value. C Adjust.

[0105]

[0123] According to another aspect of the embodiment, the image analysis module can be adapted to store in memory the location of the center of gravity of one of the plurality (e.g., two) far-field beam images, then optically block the far-field beam image whose center of gravity location is stored, and then move the center of gravity of the remaining (unblocked) far-field beam image to the center of gravity location stored in memory. To this end, as shown in FIG. 12 , the image analysis module 910 can include a partial image blocker 915. The partial image blocker 915 is arranged to have a first state in which the partial image blocker 915 allows passage of the plurality (e.g., two) beam images to the image analysis module 910, and a second state in which the partial image blocker 915 blocks at least one (e.g., one of two) of the plurality of beam images presented to the image analysis module 910.

[0106]

[0124] During operation, the image analysis module 910 measures the position of the centroid of one of the images in the image information from the optical module 900 and stores a value indicative of this position. The image analysis module 910 stores this centroid position value in memory 930. The partial image blocker 915 then blocks the image of the beam whose centroid position was measured and stored, and then measures the centroid position of the other beam image. The controller 920 controls the actuator 905 to move the measured centroid position of the other beam image toward the centroid position stored in memory 930.

[0107]

[0125] 14 is a flowchart describing this procedure. In step S700, a beam image centroid position is measured in a first beam image from the optical module to be aligned, and the measured centroid position is stored as a target centroid position value. Then, in step S710, the first beam image is blocked. Then, in step S720, a centroid position of a second beam image is measured while adjusting the alignment of the optical module, and the centroid position of the second beam image is moved to the previously stored target centroid position value stored in memory.

[0108]

[0126] These same procedures can be used to align other optical modules in the optical train. For example, some setups may have two OPuS modules, specifically a vertical OpuS and a horizontal Opus. The procedures described above can be used to perform vertical OPuS alignment and horizontal OPuS alignment. Vertical OPuS alignment can be performed using symmetry overlapping as described above in connection with FIG. 7 or FIGS. 12 and 13. Horizontal OPuS alignment can be performed using a Hough transform or Haar cascade classifier to identify beam and component positions during horizontal OPuS alignment.

[0109]

[0127] According to another aspect of the embodiment, features such as lines and contours are detected in an image acquired by one or more alignment ports using a probabilistic Hough Line Transform (PHT). The PHT is an extension of the standard Hough Line Transform. Rather than considering all possible lines in the image, the PHT considers only a random subset of the detected edge points, thereby improving the efficiency of the PHT. The PHT works by first extracting edge points in the image using an edge detection procedure such as a Canny edge detector. A random subset of these edge points is then selected and used to generate line segments in parameter space using the same representation as the standard Hough Transform. A voting scheme is then used to determine which of these line segments correspond to actual lines in the image. This is done by incrementing a count for each point along the line segment in the image. The line segment with the highest count is then considered to be a valid line in the image. Finally, this process is repeated multiple times using different subsets of edge points to improve the accuracy of line detection.

[0110]

[0128] For example, at the PRA WEB and BR alignment ports, the PHT is used to detect the illuminated outer window or frame of the image. From there, the center of the window for the target can be determined. Figure 15A is a diagram of a beam image acquired at the BR alignment port. The grayscale in the diagram may be reversed in the actual image. As can be seen, the image includes reflections 950 and 960 from the aperture edges and an illuminated frame 970. Also present is a beam image 980 and crosshairs 990.

[0111]

[0129] The image shown in Figure 15A is subjected to PHT to identify features within the image. Figure 15B is an illustration of the results of performing PHT on the image of Figure 15A. Again, the grayscale in the illustration may be inverted in the actual PHT results. As can be seen, the PHT identifies the locations 955 and 965 of the edges of apertures 950 and 960, respectively. The PHT also identifies the location 975 of the illuminated frame 970, the location 985 of the beam image 980, and the center 995 of the illuminated frame 970.

[0112]

[0130] The PHT can be performed by the image analysis module 910 (FIG. 12). The controller 920 (FIG. 12) can use the locations of features in the image identified by the PHT to align the optical module 900 (FIG. 12).

[0113]

[0131] The above description includes examples of multiple embodiments. Of course, it is not possible to describe every conceivable combination of components or methodologies for purposes of describing these embodiments, and one of ordinary skill in the art will recognize that many other combinations and arrangements of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent the term "include" is used in either the detailed description or the claims, such term is intended to be inclusive, similar to the way the term "comprising" is interpreted when used as a transitional term in a claim. Also, although elements of the above-described aspects and / or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Furthermore, unless otherwise stated, all or a portion of any aspect and / or embodiment can be utilized with all or a portion of any other aspect and / or embodiment.

[0114]

[0132] The embodiments can be further described using the following clauses. 1. An apparatus for aligning an optical module with a beam path of a beam in a laser light source, comprising: a beam imager positioned to capture an image of the beam after it interacts with the optical module; an image analysis module disposed to receive the image and adapted to make an alignment determination of an alignment state of the optical module relative to the beam based at least in part on the image, and to generate a control signal based on the alignment determination; an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on a control signal; An apparatus comprising: 2. The apparatus of clause 1, wherein the beam path includes a power ring amplifier (PRA) alignment path that includes an optical module. 3. The apparatus of clause 2, wherein the optical module includes at least one of a master oscillator (MO), wavefront engineering box (WEB), PRA WEB, PRA chamber, beam reverser (BR), and autoshutter module. 4. The apparatus according to clause 3, wherein the optical module includes a BR and the image is acquired from the beam in an autoshutter module. 5. The apparatus of clause 4, wherein the autoshutter module comprises a combined autoshutter and metrology module. 6. The apparatus of clause 1, wherein the image analysis module is adapted to make an alignment determination based at least in part on detection of at least one edge of the aperture in the optical module. 7. The apparatus of clause 6, wherein the image analysis module is adapted to control the actuator to sweep the beam across the aperture to detect at least one edge of the aperture. 8. The apparatus of clause 6, wherein the image analysis module is adapted to detect at least one edge of the aperture using a Hough transform. 9. The apparatus of clause 1, wherein the image analysis module is adapted to detect the window and determine the center of the window using an object detection model. 10. The apparatus of clause 9, wherein the image analysis module is adapted to detect windows and determine window centers using a Haar cascade classifier. 11. The apparatus described in clause 1, wherein the image analysis module is adapted to make an alignment determination of the optical module based at least in part on labeling one or more contours in the image as one of a main beam and a secondary beam. 12. The apparatus of clause 11, wherein the image analysis module is adapted to perform alignment determination of the optical module based on the at least one main beam and the at least one secondary beam, and to control the actuator to merge the secondary beam and the main beam to form a merged beam. 13. The apparatus of clause 12, wherein the image analysis module is adapted to control the actuator to increase the symmetry of the merged beam. 14. A method for aligning an optical module with a beam path of a beam in a laser light source, comprising: acquiring an image of the beam after the beam interacts with the optical module; making an alignment determination of an alignment state of the optical module based at least in part on the image; generating a control signal based on the alignment determination; using the control signal to control an actuator mechanically coupled to the optical module to change an alignment state of the optical module; A method comprising: 15. The method of clause 14, wherein the beam path includes a power ring amplifier (PRA) alignment path. 16. The method of clause 14, wherein the optical module includes at least one of a master oscillator (MO) wavefront engineering box (WEB), a PRA WEB, a PRA chamber, a beam reverser (BR), and an autoshutter module in the PRA alignment path. 17. The method according to clause 16, wherein the optical module includes a BR and the image is acquired from the beam in an autoshutter module. 18. The method of clause 16, wherein the autoshutter module comprises a combined autoshutter and metrology module. 19. The method of clause 14, wherein making an alignment determination of an alignment state of the optical module includes detecting at least one edge of an aperture in the optical module. 20. The method of clause 19, further comprising controlling an actuator to sweep the beam across the aperture to detect at least one edge of the aperture. 21. The method of clause 19, wherein detecting at least one edge of the aperture in the optical module includes using a Hough transform. 22. The method of clause 14, wherein making an alignment determination of the alignment state of the optical module based at least in part on the image is performed using an image analysis module adapted to detect apertures or illuminated surfaces using an object detection model and to determine the center and size of the object. 23. The method of clause 22, wherein using an image analysis module adapted to detect apertures or illuminated surfaces using an object detection model and to determine the center and size of the object includes using a Haar cascade classifier. 24. The method of clause 14, wherein making an alignment determination of the alignment state of the optical module includes labeling one or more contours in the image as one of a main beam and a secondary beam. 25. The method of clause 24, wherein labeling one or more contours in the image as one of a main beam and a secondary beam includes labeling at least one contour in the image as a main beam and at least one contour in the image as a secondary beam, and further includes converging the main beam and the secondary beam to form a converging beam. 26. The method of clause 25, further comprising increasing the symmetry of the merged beam. 27. An apparatus for aligning an optical module with the beam path of a beam in a laser light source, comprising: Memory and a beam imager positioned to capture an image of the beam after it interacts with the optical module; an image analysis module configured to receive the image, measure one or more beam characteristics from the image, and store information indicative of the one or more beam characteristics in a memory; a controller adapted to generate a control signal based on the one or more beam characteristics; an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on a control signal; wherein the image analysis module is further configured to perform subsequent measurements of one or more beam characteristics from the images, and the controller is configured to generate control signals to control the actuators to reduce differences between the one or more beam characteristics measured by the subsequent measurements and the stored information. 28. The apparatus of clause 27, wherein the beam characteristic is a beam distortion, and the information indicative of one or more beam characteristics is a target beam distortion, and the image analysis module is further configured to perform a subsequent measurement of the beam distortion, and the controller is configured to generate a control signal to control the actuator to reduce a difference between the subsequent measurement of the beam distortion and the target beam distortion. 29. Apparatus as described in clause 27, wherein the beam characteristic is a measured position of the centroid of an image of one of the main and secondary beam components of the beam, and the information indicative of the one or more beam characteristics is the measured position of the centroid, the image analysis module is further arranged to perform a subsequent measurement of the position of the centroid of the other of the main and secondary beam components, and the controller is arranged to generate a control signal to control an actuator to move the position of the centroid of the other of the main and secondary beam components to the measured position stored in the memory. 30. The apparatus described in clause 29, further comprising a beam component blocking element arranged to block one of the first beam component and the second beam component when the image analysis module is measuring the position of the center of gravity of the other of the first beam component and the second beam component. 31. A method for aligning an optical module with a beam path of a beam in a laser light source, comprising: acquiring an image of the beam after the beam interacts with the optical module; measuring one or more beam characteristics from the image; storing information indicative of one or more beam characteristics in a memory; generating a control signal based on the one or more beam characteristics; activating an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal; performing a subsequent measurement of one or more beam characteristics; generating control signals to control the actuators to reduce the difference between the one or more beam characteristics measured by subsequent measurements and the stored information; A method comprising: 32. The method of clause 31, wherein the beam characteristic is a beam distortion, the information indicative of the one or more beam characteristics is a target beam distortion, making subsequent measurements of the one or more beam characteristics includes making subsequent measurements of the beam distortion, and generating control signals includes generating control signals to control actuators to reduce a difference between the subsequent measurements of the beam distortion and the target beam distortion. 33. The method of clause 31, wherein the beam characteristic is a measured position of the centroid of an image of one of the main and secondary beam components of the beam, and the information indicative of the one or more beam characteristics is the measured position of the centroid, and wherein making a subsequent measurement of the one or more beam characteristics includes making a subsequent measurement of the position of the centroid of the other of the main and secondary beam components, and generating a control signal includes generating a signal to control an actuator to move the position of the centroid of the other of the main and secondary beam components to the measured position stored in memory. 34. The method of clause 33, further comprising blocking one of the first beam component and the second beam component while measuring the position of the center of gravity of the other of the first beam component and the second beam component. 35. An apparatus for aligning an optical module with a beam path of a beam in a laser light source, comprising: a beam imager positioned to capture an image of the beam after it interacts with the optical module; an image analysis module configured to receive an image and perform a probabilistic Hough Line transform to locate one or more features within the image; a controller adapted to generate a control signal based on one or more features identified in the image; an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on a control signal; An apparatus comprising: 36. The apparatus of clause 35, wherein the one or more features identified in the image include an illuminated frame in the image. 37. The apparatus of clause 35, wherein the one or more features identified in the image include the location of a center of the illuminated frame. 38. A method for aligning an optical module with a beam path of a beam in a laser light source, comprising: acquiring an image of the beam after the beam interacts with the optical module; performing a probabilistic Hough Line transform to locate one or more features within the image; generating a control signal based on one or more features identified in the image; changing an alignment state of the optical module based on the control signal; A method comprising: 39. The method of clause 38, wherein the one or more features identified in the image include an illuminated frame in the image. 40. The method of clause 38, wherein the one or more features identified in the image include the location of the center of the illuminated frame.

[0115]

[0133] The above and other embodiments are within the scope of the following claims.

Claims

1. 1. An apparatus for aligning an optical module with a beam path of a beam in a laser light source, comprising: a beam imager positioned to capture an image of the beam after it interacts with the optical module; an image analysis module disposed to receive the image and adapted to perform an alignment determination of an alignment state of the optical module relative to the beam based at least in part on the image, and to generate a control signal based on the alignment determination; an actuator mechanically coupled to the optical module and arranged to change the alignment state of the optical module based on the control signal; An apparatus comprising:

2. The apparatus of claim 1 , wherein the beam path includes a power ring amplifier (PRA) alignment path that includes the optical module.

3. The apparatus of claim 2 , wherein the optical module includes at least one of a master oscillator (MO) wavefront engineering box (WEB), a PRA WEB, a PRA chamber, a beam reverser (BR), and an autoshutter module.

4. The apparatus of claim 3 , wherein the optical module includes the BR, and the image is acquired from the beam in the autoshutter module.

5. The apparatus of claim 4 , wherein the auto-shutter module comprises a combined auto-shutter and metrology module.

6. The apparatus of claim 1 , wherein the image analysis module is adapted to make the alignment determination based at least in part on detection of at least one edge of an aperture in the optical module.

7. The apparatus of claim 6 , wherein the image analysis module is adapted to control the actuator to sweep the beam across the aperture to detect at least one edge of the aperture.

8. The apparatus of claim 6 , wherein the image analysis module is adapted to detect the at least one edge of the aperture using a Hough transform.

9. The apparatus of claim 1 , wherein the image analysis module is adapted to detect a window using an object detection model and determine a center of the window.

10. The apparatus of claim 9 , wherein the image analysis module is adapted to detect the window and determine a center of the window using a Haar cascade classifier.

11. 2. The apparatus of claim 1, wherein the image analysis module is adapted to determine the alignment of the optical module based at least in part on labeling one or more contours in the image as one of a main beam and a secondary beam.

12. 12. The apparatus of claim 11, wherein the image analysis module is adapted to determine the alignment of the optical module based on at least one main beam and at least one secondary beam, and to control the actuator to merge the secondary beam and the main beam to form a merged beam.

13. The apparatus of claim 12 , wherein the image analysis module is adapted to control the actuator to increase symmetry of the merged beam.

14. 1. A method for aligning an optical module with a beam path of a beam in a laser light source, comprising: acquiring an image of the beam after it interacts with the optical module; making an alignment determination of an alignment state of the optical module based at least in part on the image; generating a control signal based on the alignment determination; using the control signal to control an actuator mechanically coupled to the optical module to change an alignment state of the optical module; A method comprising:

15. The method of claim 14 , wherein the beam path includes a power ring amplifier (PRA) alignment path.

16. 15. The method of claim 14, wherein the optical module includes at least one of a master oscillator (MO) wavefront engineering box (WEB), a PRA WEB, a PRA chamber, a beam reverser (BR), and an autoshutter module in the PRA alignment path.

17. The method of claim 16 , wherein the optical module includes the BR, and the image is acquired from the beam at the autoshutter module.

18. The method of claim 16 , wherein the auto-shutter module comprises a combined auto-shutter and metrology module.

19. The method of claim 14 , wherein performing an alignment determination of an alignment state of the optical module includes detecting at least one edge of an aperture in the optical module.

20. 20. The method of claim 19, further comprising controlling the actuator to sweep the beam across the aperture to detect the at least one edge of the aperture.

21. 20. The method of claim 19, wherein detecting at least one edge of an aperture in the optical module includes using a Hough transform.

22. 15. The method of claim 14, wherein performing an alignment determination of an alignment state of the optical module based at least in part on the image is performed using an image analysis module adapted to detect apertures or illuminated surfaces using an object detection model and to determine centers and sizes of objects.

23. 23. The method of claim 22, wherein using an image analysis module adapted to detect apertures or illuminated surfaces using an object detection model and determine object centers and sizes comprises using a Haar cascade classifier.

24. The method of claim 14 , wherein performing an alignment determination of an alignment state of the optical module comprises labeling one or more contours in the image as one of a main beam and a secondary beam.

25. 25. The method of claim 24, wherein labeling one or more contours in the image as one of a main beam and a secondary beam comprises labeling at least one contour in the image as a main beam and at least one contour in the image as a secondary beam, and further comprising converging the main beam and the secondary beam to form a converging beam.

26. 26. The method of claim 25, further comprising increasing the symmetry of the merged beam.

27. 1. An apparatus for aligning an optical module with a beam path of a beam in a laser light source, comprising: Memory and a beam imager positioned to capture an image of the beam after it interacts with the optical module; an image analysis module configured to receive the image, measure one or more beam characteristics from the image, and store information indicative of the one or more beam characteristics in the memory; a controller adapted to generate a control signal based on the one or more beam characteristics; an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal; wherein the image analysis module is further configured to perform subsequent measurements of the one or more beam characteristics from the images, and the controller is configured to generate the control signal to control the actuator to reduce a difference between the one or more beam characteristics measured by the subsequent measurements and the stored information.

28. 28. The apparatus of claim 27, wherein the beam characteristic is a beam distortion, and the information indicative of the one or more beam characteristics is a target beam distortion, and the image analysis module is further configured to perform a subsequent measurement of the beam distortion, and the controller is configured to generate the control signal to control the actuator to reduce a difference between the subsequent measurement of the beam distortion and the target beam distortion.

29. 28. The apparatus of claim 27, wherein the beam characteristic is a measured position of a centroid of an image of one of the main and secondary beam components of the beam, the information indicative of the one or more beam characteristics is the measured position of the centroid, the image analysis module is further configured to perform a subsequent measurement of a position of the centroid of the other of the main and secondary beam components, and the controller is configured to generate the control signal to control the actuator to move the position of the centroid of the other of the main and secondary beam components to the measured position stored in the memory.

30. 30. The apparatus of claim 29, further comprising a beam component blocking element positioned to block the one of the first beam component and the second beam component when the image analysis module is measuring the position of the center of gravity of the other of the first beam component and the second beam component.

31. 1. A method for aligning an optical module with a beam path of a beam in a laser light source, comprising: acquiring an image of the beam after it interacts with the optical module; measuring one or more beam characteristics from the image; storing information indicative of the one or more beam characteristics in a memory; generating a control signal based on the one or more beam characteristics; activating an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal; performing a subsequent measurement of the one or more beam characteristics; generating the control signal to control the actuator to reduce a difference between the one or more beam characteristics measured by the subsequent measurement and the stored information; A method comprising:

32. 32. The method of claim 31 , wherein the beam characteristic is a beam distortion, the information indicative of the one or more beam characteristics is a target beam distortion, performing a subsequent measurement of the one or more beam characteristics includes performing a subsequent measurement of the beam distortion, and generating the control signal includes generating the control signal to control the actuator to reduce a difference between the subsequent measurement of the beam distortion and the target beam distortion.

33. 32. The method of claim 31 , wherein the beam characteristic is a measured position of a centroid of an image of one of the main and secondary beam components of the beam, the information indicative of the one or more beam characteristics is the measured position of the centroid, performing a subsequent measurement of the one or more beam characteristics includes performing a subsequent measurement of a position of the centroid of the other of the main and secondary beam components, and generating the control signal includes generating the signal to control the actuator to move the position of the centroid of the other of the main and secondary beam components to the measured position stored in the memory.

34. 34. The method of claim 33, further comprising blocking the one of the first beam component and the second beam component while measuring the position of the center of gravity of the other of the first beam component and the second beam component.

35. 1. An apparatus for aligning an optical module with a beam path of a beam in a laser light source, comprising: a beam imager positioned to capture an image of the beam after it interacts with the optical module; an image analysis module configured to receive the image and perform a probabilistic Hough Line transform to locate one or more features within the image; a controller adapted to generate a control signal based on the one or more features identified in the image; an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal; An apparatus comprising:

36. 36. The apparatus of claim 35, wherein the one or more features identified in the image include an illuminated frame in the image.

37. 36. The apparatus of claim 35, wherein the one or more features identified in the image include a location of a center of the illuminated frame.

38. 1. A method for aligning an optical module with a beam path of a beam in a laser light source, comprising: acquiring an image of the beam after it interacts with the optical module; performing a probabilistic Hough Line transform to locate one or more features within the image; generating a control signal based on the one or more features identified in the image; changing an alignment state of the optical module based on the control signal; A method comprising:

39. 39. The method of claim 38, wherein the one or more features identified in the image include an illuminated frame in the image.

40. 39. The method of claim 38, wherein the one or more features identified in the image include a location of a center of the illuminated frame.

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