Apparatus and method for aligning a laser system

Abstract

An apparatus and method are disclosed that allow for automatic alignment of optical components in the beam path of a laser. An image of the beam is obtained at one or more locations in the beam path. Alignment and possibly other information is derived from the image, and then an actuator is controlled based on the derived information to change the alignment of the optical component in the beam path.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 63 / 390,757, filed on July 20, 2022, and U.S. Application No. 63 / 471,996, filed on June 9, 2023, each of which is incorporated herein by reference in its entirety. Technical Field

[0003] The disclosed subject matter relates to systems in which components of a laser system need to be aligned with some components of a light source that generates laser light for performing a photolithographic integrated circuit manufacturing process. Background Art

[0004] Photolithography is the process of patterning semiconductor circuits on a substrate such as a silicon wafer. The photolithography light source provides deep ultraviolet ("DUV") light for exposing the photoresist on the wafer. Typically, the light source is an excimer laser source, and the light is a pulsed laser beam. The beam is passed through a beam delivery unit, a reticle or mask, and then projected onto the prepared silicon wafer. In this way, the chip design is patterned onto the photoresist, which is then developed, etched, and cleaned, and then the process is repeated.

[0005] In many systems that generate laser beams (such as laser generators) or use laser beams (such as lithography systems), there is an optical sequence that includes one or more optical components (such as mirrors, gratings, prisms, optical switches, filters, etc.) that are usually included in a module. The laser beam enters the optical sequence and produces one or more outputs after passing through the optical sequence. The optical components of the optical sequence can reflect, process, filter, modify, focus, expand, etc. the laser beam in whole or in part to obtain one or more desired laser beam outputs.

[0006] Optimal laser operation requires that the laser beam be properly aligned relative to each optical component of the optical sequence and / or upon exiting the optical sequence. Alignment refers to the laser beam intersecting or colliding with a desired point or points (whether real or virtual in space) after passing through one or more optical components (such as after passing through an optical component or passing through a portion or the entire optical sequence).

[0007] Aligning the laser is critical to generating sufficient energy and beam quality for use in the lithography process. Traditionally, there are several systems and processes to align the entire system. However, there is no system or method that can automatically identify the alignment target or automate physical alignment adjustments.

[0008] Improved laser beam alignment and / or laser beam diagnostics apparatus and methods are the subject of embodiments of the invention herein. Summary of the invention

[0009] A concise summary of one or more embodiments is given below to provide a basic understanding of the present invention. This summary is not an extensive overview of all foreseen embodiments, and is not intended to identify the key or important elements of all embodiments, nor is it intended to describe the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a condensed form as a prelude to a more detailed description presented later.

[0010] According to one aspect of the embodiments, an apparatus and method are disclosed that allow automatic alignment of optical components in a beam path of a laser. An image of the beam is obtained at one or more locations in the beam path. Alignment information is derived based on the image, and an actuator is then controlled to change the alignment of the optical component in the beam path.

[0011] According to another aspect of the embodiment, a device for aligning an optical module arranged along a beam path of a light beam in a laser light source is disclosed, the device comprising: a beam imager arranged to acquire an image of the light beam after the light beam has interacted with the optical module; an image analysis module arranged to receive the image and suitable for making an alignment determination of an alignment state of the optical module based at least in part on the image, and suitable for generating 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.

[0012] The beam path may include a power ring amplifier (PRA) alignment path, which includes 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 automatic shutter module. The optical module may include a BR, and wherein an image of the beam is acquired at the automatic shutter module. The automatic shutter module may include a combined automatic shutter and metering module.

[0013] The image analysis module may be adapted to make an alignment determination based at least in part on detection of 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 light 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.

[0014] The image analysis module may be adapted to make an alignment determination of the optical module based at least in part on marking one or more contours in the image as one of the primary beam and the secondary beam. The image analysis module may be adapted to control the actuator to cause the secondary beam and the primary beam to merge to form a merged beam. The image analysis module may be adapted to control the actuator to increase the symmetry of the merged beam.

[0015] According to another aspect of an embodiment, a method of aligning an optical module in a beam path of a light beam arranged in a laser light source is disclosed, the method comprising: acquiring an image of the light beam after the light beam has interacted 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.

[0016] The beam path may include a PRA alignment path. The optical module may include one of a MO WEB, a PRAWEB, a PRA chamber, a BR, and an automatic shutter module in the PRA alignment path. The optical module may include a BR, and wherein an image of the beam is acquired at the automatic shutter module. The automatic shutter module may include a combined automatic shutter and metering module.

[0017] 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.

[0018] The method may further include controlling the actuator to sweep the light beam across the aperture to detect at least one edge of the aperture.Detecting at least one edge of the aperture in the optical module may include using a Hough transform.

[0019] Alignment determination of an alignment state of the optical module based at least in part on the image may be performed using an image analysis module adapted to detect the aperture or illuminated surface and determine a center and size of the object using an object detection model.

[0020] Using an image analysis module adapted to detect an aperture or illuminated surface and using an object detection model to determine the center and size of the object may include using a Haar cascade classifier.Making an alignment determination of the alignment state of the optical module may include marking one or more contours in the image as one of the primary beam and the secondary beam.

[0021] The method may further include controlling the actuator to combine the primary beam and the secondary beam to form a combined beam. The method may further include controlling the actuator to increase the symmetry of the combined beam.

[0022] According to another aspect of the embodiment, a device for aligning an optical module to a beam path of a light beam in a laser light source is disclosed, the device comprising: a memory; a beam imager arranged to acquire an image of the light beam after the light beam has interacted 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 suitable for generating a control signal based on the one or more beam characteristics; 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, wherein the image analysis module is also arranged to make 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 the difference between the one or more beam characteristics measured by the subsequent measurement and the stored information.

[0023] The beam characteristics may include beam skewness, the information indicative of one or more beam characteristics may include a target beam skewness, and the image analysis module may also be arranged to perform subsequent measurements of the beam skewness, and the controller may be arranged to generate a control signal to control the actuator to reduce the difference between the subsequent measurements of the beam skewness and the target beam skewness.

[0024] The beam characteristics may include a measured position of the centroid of an image of one of the primary beam component and the secondary beam component of the beam, information indicative of one or more beam characteristics may include the measured position of the centroid, and the image analysis module may also be arranged to perform subsequent measurements of the position of the centroid of the other of the primary beam component and the secondary beam component, and the controller may be arranged to generate a control signal to control the actuator to move the position of the centroid of the other of the primary beam component and the secondary beam component to a measured position stored in a memory.

[0025] The apparatus may further comprise 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 centroid of the other of the first beam component and the second beam component.

[0026] According to another aspect of an embodiment, a method for aligning an optical module to a beam path of a light beam in a laser light source is disclosed, the method comprising: acquiring an image of the light beam after the light beam has interacted with the optical module; measuring one or more beam characteristics from the image; storing information indicating the one or more beam characteristics in a memory; generating a control signal based on the one or more beam characteristics; actuating an actuator based on the control signal, the actuator being mechanically coupled to the optical module and arranged to change the alignment state of the optical module; 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.

[0027] The beam characteristics may include beam skewness, the information indicative of one or more beam characteristics may include a target beam skewness, making subsequent measurements of one or more beam characteristics may include making subsequent measurements of the beam skewness, and generating a control signal may include generating a control signal to control an actuator to reduce a difference between a subsequent measurement of the beam skewness and the target beam skewness.

[0028] The beam characteristic may include a measured position of the centroid of an image of one of the primary beam component and the secondary beam component of the beam, information indicative of one or more beam characteristics may include the measured position of the centroid, and making subsequent measurements of the one or more beam characteristics may include making subsequent measurements of the position of the centroid of the other of the primary beam component and the secondary beam component, and generating a control signal includes generating a control signal to control an actuator to move the position of the centroid of the other of the primary beam component and the secondary beam component to a measured position stored in a memory.

[0029] The method may further include blocking the one of the first beam component and the second beam component during measuring the position of the centroid of the other of the first beam component and the second beam component.

[0030] According to another aspect of the embodiment, a device for aligning an optical module to a beam path of a light beam in a laser light source is disclosed, the device comprising: a beam imager arranged to acquire an image of the light beam after the light beam has interacted with the optical module; an image analysis module arranged to receive the image and perform a probabilistic Hough line transform to locate the position of one or more features in the image; a controller suitable for generating a control signal based on the one or more features located in the image; 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.

[0031] The one or more features located in the image may include an illuminated frame in the image.

[0032] The one or more features located in the image may include the location of the center of the illuminated frame.

[0033] According to another aspect of an embodiment, a method of aligning an optical module to a beam path of a light beam in a laser light source is disclosed, the method comprising: acquiring an image of the light beam after the light beam has interacted with the optical module; performing a probabilistic Hough line transform to locate the position of one or more features in the image; generating a control signal based on the one or more features located in the image; and changing the alignment state of the optical module based on the control signal.

[0034] The one or more features located in the image may include an illuminated frame in the image.

[0035] The one or more features located in the image may include the location of the center of the illuminated frame.

[0036] 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 DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and enable one skilled in the relevant art(s) to make and use the invention.

[0038] Figure 1 is a not-to-scale schematic diagram of the overall broad concept of a lithography system.

[0039] Figure 2 Such as can be Figure 1 A not-to-scale schematic diagram of the overall broad concept of an illumination system used in a lithography system.

[0040] Figure 3 is a not-to-scale schematic diagram of a system for aligning components of an illumination system according to an aspect of an embodiment.

[0041] Figure 4A is a not-to-scale schematic diagram of another system for aligning components of an illumination system according to an aspect of the embodiments.

[0042] Figure 4B is a not-to-scale schematic diagram of another system for aligning components of an illumination system according to an aspect of the embodiments.

[0043] Figure 5A is a not-to-scale perspective view of a module for an illumination system according to one aspect of the embodiment.

[0044] Figure 5B yes Figure 5AA cross-sectional plan view of a module.

[0045] Fig. 6A and Figure 6B is an illustration of an example of an image that may appear in an alignment path according to an aspect of an embodiment.

[0046] Figure 7 is an illustration of an example of an image that may appear in an alignment path according to an aspect of an embodiment.

[0047] Fig. 8A is an example of an image that may appear in an alignment path according to one aspect of an embodiment.

[0048] Figure 8B is an example of the result of an edge detection process according to one aspect of the embodiment.

[0049] Fig. 9 is a flow chart indicating steps in a process for boundary detection according to one aspect of the embodiment.

[0050] Fig.10 is a flow chart of a process for contour marking and skew adjustment according to one aspect of an embodiment.

[0051] Fig.11 is a flow chart of a process for aperture detection according to one aspect of the embodiment.

[0052] Fig.12 is a not-to-scale functional block diagram of a system for aligning an optical module according to one aspect of an embodiment.

[0053] Fig.13 is a flow chart of a portion of a process for aligning an optical module according to an aspect of an embodiment.

[0054] Fig.14 is a flow chart of a portion of a process for aligning an optical module according to an aspect of an embodiment.

[0055] Fig.15A is a representation of an image such as may be acquired according to one aspect of the embodiments.

[0056] Fig. 15B According to one aspect of the embodiment Fig.15A Representation of the results of the analysis of the image.

[0057] The other 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 only for illustrative purposes. Based on the teachings presented herein, additional embodiments will be apparent to those skilled in the relevant art. DETAILED DESCRIPTION

[0058] Various embodiments are now described with reference to the accompanying drawings, wherein similar reference numerals are used to refer to similar elements throughout. In the following description, many specific details are set forth to facilitate a thorough understanding of one or more embodiments. However, in some or all instances, it may be apparent that any embodiment described below may be practiced without adopting the specific design details set forth in conjunction with the embodiment. In other instances, well-known structures and devices are shown in block diagram form to facilitate the description of one or more embodiments. The present disclosure is not an extensive overview of all foreseen embodiments, and is not intended to identify the key or important elements of all embodiments, nor to describe the scope of any or all embodiments.

[0059] Systems such as those described herein may present benefits in a wide range of applications and implementations. To have a specific non-limiting example for ease of description, one such application is in semiconductor lithography. Figure 1 A lithography system 100 is shown that includes an illumination system 105. As described more fully below, the illumination system 105 includes a light source that generates a pulsed light beam 110 and directs it to a lithography exposure device or scanner 115 that patterns microelectronics and other features on a wafer 120. The wafer 120 is placed on a wafer stage 125 that is configured to hold the wafer 120 and is connected to a positioner 127 that is configured to accurately position the wafer 120 according to certain parameters.

[0060] The pulsed light beam 110 may have a wavelength in the DUV range, for example, having a wavelength of 248 nanometers (nm) or 193 nm. The scanner 115 includes an optical device 117 having, for example, one or more focusing lenses, a mask, and an objective lens arrangement. The mask may be moved along one or more directions, such as along the optical axis of the pulsed light beam 110 or in a plane perpendicular to the optical axis. The objective lens arrangement includes a projection lens and enables image transfer from the mask to the photoresist on the wafer 120. The illumination system 105 adjusts the angular range at which the pulsed light beam 110 impinges on the mask. The illumination system 105 also homogenizes the intensity distribution of the pulsed light beam 110 across the mask (making it uniform).

[0061] 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 a memory that stores information such as a process recipe that determines parameters including the length of the exposure on the wafer 120 based on, for example, the mask used and other factors that affect the exposure. During lithography, a train of pulses of the pulsed light beam 110 illuminates the same area of ​​the wafer 120 to constitute an exposure dose.

[0062] The lithography system 100 also preferably includes a control system 135. Typically, the control system 135 includes one or more of digital electronic circuits, computer hardware, firmware, and software. The control system 135 can be centralized, or partially or completely distributed throughout the lithography system 100.

[0063] As an example of the illumination system 105, Figure 2 A pulsed laser source is shown that produces a pulsed laser beam as beam 110 . Figure 2 A dual chamber laser system is shown as a non-limiting example, but it will be understood that the principles explained herein are equally applicable to single chamber laser systems or laser systems having more than two chambers. The gas discharge laser system may include, for example, a solid state or gas discharge master oscillator ("MO") seed laser system 140, an amplification stage (e.g., a power ring amplifier ("PRA") stage 145), relay optics 150, and a laser system output subsystem 160. The seed system 140 may include, for example, a MO chamber 165, which includes a pair of electrodes 167 and 168.

[0064] The MO seed laser system 140 may further include a master oscillator output coupler (“MO OC”) 175, which may include a partially reflecting mirror to form an oscillator cavity together with a reflective grating (not shown) in a line narrowing module (“LNM”) 170, in which the MO seed laser 140 oscillates to form seed laser output pulses, i.e., to form MO 165. The MO seed laser system 140 may further include a line center analysis module (“LAM”) 180. A MO wavefront engineering box (“WEB”) 185 may be used to redirect the output of the MO seed laser system 140 toward the amplification stage 145, and may include, for example, a multi-prism beam expander (not shown) and an optical delay path (not shown).

[0065] The amplification stage 145 may include, for example, a PRA laser generation chamber 200, which may also be an oscillator, such as formed by seed beam injection and output coupling optics (not shown) that may be incorporated into the PRA WEB 210. The beam may be redirected back by a beam reverser ("BR") 220 to pass through the gain medium in the chamber 200. The PRA WEB 210 may incorporate a partially reflecting input / output coupler (not shown) and a maximum reflective mirror for a nominal operating wavelength (e.g., at about 193 nm for an ArF system) and one or more prisms. The PRA laser generation chamber 200 may also include a pair of electrodes 207 and 208.

[0066] The bandwidth analysis module ("BAM") 230 can receive the pulsed output laser beam from the PRA laser generation chamber 200 and pick a portion of the beam for metrology purposes, such as to measure the output bandwidth and pulse energy. The pulsed laser output beam then passes through the PRA WEB 210 to the optical pulse stretcher ("OPuS") 240 and the automatic shutter, which in this case is a combined automatic shutter metering module ("CASMM") 250, which can also be the location of the pulse energy meter. One purpose of the OPuS 240 can be, for example, to convert a single output laser pulse into a pulse sequence. The secondary pulses generated from the original single output pulse can be delayed relative to each other. By distributing the original laser pulse energy into a sequence of secondary pulses, the effective pulse length of the laser can be extended while reducing the peak pulse intensity. Therefore, the OPuS 240 can be arranged to receive the laser beam from the PRA WEB 210 and direct its output to the CASMM 250.

[0067] The PRA laser generation chamber 200 and MO 165 are configured as a chamber in which an electrical discharge between electrodes induces a laser generation gas discharge in the laser generation gas to produce an inversion population of high energy molecules (including, for example, Ar, Kr, F2 and / or Xe) to produce relatively broadband radiation, which can be line-narrowed to a relatively very narrow bandwidth and center wavelength selected in LNM 170.

[0068] As stated, alignment is the process of adjusting the position, orientation, etc. of these optical components so that the laser beam propagates along the desired beam path. Alignment of a module relative to the laser beam and other components may require adjustment of the components that make up the module. For example, the alignment may be relative to the laser beam. Figure 2The PRA alignment path 260 shown by the dashed line in FIG. determines the alignment of the amplification stage. The PRA alignment path 260 as shown includes the BR 220, the PRA chamber 200, the BAM 230, the PRA WEB 210, the OPuS 240 and the CASMM 250. The PRA alignment path 260 in the example shown also includes the path of the seed laser beam from the MO WEB 185.

[0069] Alignment and other beam characteristics are determined by obtaining information about the beam at the alignment port ("AP") at various locations in the PRA alignment path 260, referred to herein as imaging the beam. For example, the beam can be imaged at a first location 270 at the BR 220. The beam can also be imaged at a location 272 at the PRA WEB 210 and at a location 274 at the CASMM 250. These images can be near-field images or far-field images. Beam imaging can include obtaining information about beam / aperture edge detection, beam profile, beam cross-sectional structure, location of relay optics, etc.

[0070] To have a specific example for ease of explanation, the following discussion is in terms of an image acquired at location 270, a far-field image acquired at location 274, and a near-field image also acquired at location 274. However, one of ordinary skill in the art will readily recognize that these are merely examples and that the teachings provided herein may also be applied to other images acquired at other locations.

[0071] Furthermore, one of ordinary skill will recognize that the alignment process does not necessarily require alignment of optical components physically proximal to the location where the image is acquired in the relay optics. For example, a far field image acquired at location 274 may indicate alignment of optical components (such as BR 220) in several components remote from that location.

[0072] Therefore, it would be advantageous if alignment could be performed by an alignment system in which some or all aspects of the imaging, analysis, and alignment of the alignment beams process could be automated. Figure 3 is a diagram of such an alignment system 300. Figure 3 , the light beam 305 propagates along a beam path 310 (dashed line) that best coincides with the alignment path 315 (dotted line). The beam path 310 includes relay optics in the form of a first optical module 320, a second optical module 325, and a third optical module 330. These optical modules may correspond to Figure 2 One of the units BR 220, PRA chamber 200, BAM 230, PRAWEB 210, OPuS 240 and CASMM 250 shown in FIG.

[0073] The alignment system 300 also includes an element 335 for deflecting some of the radiation from the beam 305 from position A to the image capture module 340. The element 335 may be a beam splitter that separates a small portion of the radiation from the beam 305. The element 335 may also or alternatively be an element that can be moved into or out of the beam path 310 depending on whether a measurement is desired. The image capture module 340 captures an image of the beam at the element 335 (position A) and provides a signal indicating the result of the capture to the control unit 350. The image capture module 340 may also perform a combination of image analysis such as edge detection, contour detection / marking, aperture detection, and identification techniques based on computer vision / pattern recognition, as described in more detail below, or these functions may be performed in the control module 350. It will be understood that the functions of the image capture module 340 and the control unit 350 may be combined into one unit, or may be distributed between the two units or across more than two units. The control unit 350 generates a control signal C1, which the control unit 350 supplies to the actuator 360. The actuator 360 is coupled to the first optical module 320 and is arranged to modify the alignment state of the first optical unit 320 by changing the position, orientation, etc. of optical components in the first optical unit 340 under the control of the control signal C1.

[0074] The alignment system 300 also includes an element 365 for deflecting some of the radiation from the beam 305 from position B into the image capture module 370. Again, the element 365 may be a beam splitter that separates a small portion of the radiation from the beam 305. The element 365 may also or alternatively be an element that can be moved into or out of the beam path 310 depending on whether a measurement is desired. The image capture module 370 captures and analyzes an image of the beam at the element 365 (position B) and provides a signal to the control unit 350 indicating the result of the analysis. It will be understood that the functions of the image capture module 370 and the control unit 350 may be combined into one unit, or may be distributed across more than two units. The control unit 350 generates a control signal C2, which the control unit 350 supplies to the actuator 375. The actuator 375 is coupled to the second optical module 325 and is arranged to change the alignment state of the second optical module 325 under the control of the control signal C2.

[0075] Alignment system 300 also includes element 380 for deflecting some of the radiation from beam 305 from position C into image capture module 385. Figure 3In the example of , element 380 is an example of a deflector that is part of an optical module such as the third optical element 330, rather than being located between optical modules. Again, element 380 can be a beam splitter that separates a small portion of radiation from the beam 305. The image capture module 385 captures and analyzes the image of the beam at element 380 (position C) and provides a signal indicating the result of the analysis to the control unit 350. It will be understood that the functions of the image capture module 385 and the control unit 350 can be combined into one unit, or can be distributed across two units or more than two units. The control unit 350 generates a control signal C3, which the control unit 350 supplies to the actuator 390. The actuator 390 is coupled to the third optical module 330 and is arranged to change the alignment state of the third optical module 330 under the control of the control signal C3.

[0076] Again, control signals C1, C2, and C3 may be generated based on image information acquired at a location in the system that is away from the location where the image is 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 in optical module 320.

[0077] The alignment system 300 also includes a user interface 395 arranged to exchange data with the control unit 350. The user interface 395 and the control unit 350 may be connected by a hardwired connection or wirelessly. The user interface 395 and the control unit 350 may be connected directly, or indirectly through an intermediate component, port, bus, etc. The user interface 395 allows a user such as a field service engineer to monitor the automatic alignment process and see various acquired images of the beam. The user interface 395 also allows the user to override any automatic alignment adjustments as desired.

[0078] Typically, the user interface 395 can be used to call a manual alignment mode that 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 can provide the user with a visual indicator of the current step in the alignment process, the next step in the alignment process, and the error in the alignment process, and view the current image. The user interface 395 can allow the user to confirm the result of the automatic alignment process and save the alignment image and the configuration and settings for the image capture module, actuators, etc.

[0079] Actuators 360, 375, and 390 may be through-wall adjusters ("TWAs") that feed through the wall of the housing of their respective optical modules 320, 325, and 330. The TWAs may each include an electrically controlled motor that causes the end of the TWA to translate along its axis depending on the direction of rotation of the shaft to change the alignment of the optical component coupled to the TWA. The use of such electrically actuated TWAs enables automation of the alignment process, wherein a control unit 350 controls the TWA to perform the alignment.

[0080] The TWA motor may be, for example, a stepper motor or a servo motor. Potential advantages of using a stepper motor include that they can generate very high torque at zero speed, they are generally compact and economical, and they can provide holding torque if needed. On the other hand, servo motors are able to provide high and consistent torque levels at high speeds. They also typically operate at about 80%-90% efficiency and can work with either AC or DC drives, although they are larger, more expensive, and more complex. In general, one of ordinary skill in the art will recognize that the choice of using a stepper motor or a servo motor will depend on the requirements of a particular application.

[0081] Figure 4A 4 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 engineer. Laser 405 includes an optical module, which in the example of FIG. 4 is a CASMM 250, and all other modules required to generate a laser beam. Laser 405 also includes a set of relay optics 415. Relay optics 415 includes an image capture module 385, which may be, for example, a camera. Image capture module 385 transmits image data to image processing module 387 in computing unit 410. Relay optics 415 also includes a communication module 420 that handles communications between laser 405 and computing unit 410. Communication 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 BR 220, for example. although Figure 4A Only one image capture module and only one actuator are shown, but one of ordinary skill in the art will readily recognize that alignment system 400 may be generalized to any number of image capture modules and actuators.

[0082] The computing unit 410 also includes a control module 350 and a communication module 425 to interface with the communication module 420 in the laser 405. The computing unit 410 also includes a user interface 395, which may be, for example, a GUI.

[0083] In use, the image capture module 385 relays the image data to the image processing module 387. The image processing module processes the image data and then provides a signal indicating the alignment error to the control module 350. The control module 350 then communicates with the actuator controller software 397 through the communication modules 425 and 420, which then controls the actuator 390, which may be a stepper motor, to change the alignment of the CASMM 250. At the same time, information from the image processing module 387, the control module 350, and the communication module 425 is provided to the user interface 395.

[0084] Figure 4B Another possible arrangement 450 of an alignment system is shown. Figure 4B In the example of FIG. 4 , the alignment system captures images at the BR AP 455, the CASMM near field AP 460, and the CASMM far field AP 465. The images of these alignment ports are captured by the image processing module 387. The 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.

[0085] Figure 5A It shows that Figure 3 , Figure 4A or Figure 4B Examples of optical modules used in the alignment system. Figure 5A An example of an optical module in BR 220 is BR 220. As can be seen, BR 220 has a housing 560 and an aperture 510 through which light beams 305 and 307 pass. BR 220 also includes TWA 520 and TWA 530, with TWA 520 being used to align optical components (in this case, such as Figure 5B 5 (a) and (b) of the prism 560 shown in FIG. 5 , and TWA 530 is used to align the vertical position of prism 560 in BR 220. TWA 550 is also shown for adjusting the 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 the through-wall adjuster in response to a control signal as mentioned above.

[0086] like Figure 5BAs shown in , prism 565 may include two total internal reflection surfaces 570, 575 and an input face 580. These and other details regarding possible implementations of beam reversers may be obtained from U.S. Patent No. 7,885,309, issued February 8, 2011, and entitled “Laser System.” All patent applications, patents, and printed publications cited herein are incorporated herein by reference in their entirety, except to the extent any limitation, subject matter disclaimer, or disclaimer is in place, and unless the incorporated material is inconsistent with the express disclosure herein, in which case the language of the disclosure controls.

[0087] Using again the example of an alignment process involving the BR 220 image and the CASMM 250 near field image and the CASMM 250 far field image, these images can be acquired by viewing the AP image. Thus, in this example, the position 270 ( Figure 2 ) may be referred to as AP 270. AP 270 is located at BR 220 and acquires images there by placing a camera at the BR alignment port (i.e., AP 270). CASMM 250 near-field images and far-field images are located at CASMM 250, or at an automatic shutter module in a system with an automatic shutter module instead of a CASMM. CASMM 250 will typically already include a camera for acquiring images there. If an automatic shutter is used, it will typically have an alignment port on which a camera can be mounted.

[0088] like Fig. 6A , typically, a misaligned beam will produce an image such as image 600, which will include an image of the beam 605 and any illuminated equipment such as the edge 610 of a window. In this figure, the inner "box" or aperture 615 needs to be characterized in order to find its center, which will be used as the center target position. In order to determine the position of the beam within the aperture, it is also necessary to identify the center of the beam. It is desirable to move the center of the beam to the center of the aperture to obtain a Figure 6B , to obtain alignment. Generally, crosshairs 620 are not illuminated and cannot be used to center the beam.

[0089] One method of finding the appropriate aperture size and position for establishing a centered target position involves using a pre-trained object detection model to identify 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 a bounding box (such as an aperture edge) that will be used to establish a target. The Haar cascade classifier is described in "Rapid object detection using a boosted cascade of simple features" by Viola, P. and Jones, M., December 2001 (Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001 (Vol. 1, pp. I-9). Once the model is properly trained, it can be used for alignment.

[0090] Typically, the model can be trained by capturing alignment port images and then performing image augmentation on the captured images to increase the number of sample images. The images are then labeled, and the training process of the applied object detection model is then used on the labeled images.

[0091] This process can automatically determine and identify the locations of several key features within the image, such as an alignment target, an illuminated window edge, or a discernible reference location to be used later. In addition, a known window size can be used to adjust potential false positive results to ensure that the detected window size is appropriate. In other words, if the result does not fall within the range of possible sizes, the result can be discarded. Using the information obtained from the image processing, the process can provide recommendations and guidance that will be used to control the actuator to move the beam toward the target, thereby aligning the image.

[0092] Figure 7 Another example of a beam image is shown. Figure 7 The beam image 700 in FIG. 7 is a beam image that can be viewed at the alignment port ( Figure 2274 in FIG. 27A . An example of a far-field image acquired at position 274 in FIG. 27A . Image 700 includes a MOPA seed beam 710 and two auxiliary or secondary "daughter" beams 720A and 720B. The purpose of alignment of an image such as image 700 may be to converge the daughter beams 720A, 720B into the MOPA beam 710 while minimizing divergence and maximizing PRA energy. This process may involve using, for example, pixel deflection to detect which of the beams is the MO seed beam and which is the MOPA beam propagating along the PRA beam path, where left and right deflections may be used as metric indicators to align and overlap the beams by minimizing the skew factor.

[0093] In other words, image 700 is ideally an image of a single, centered, symmetrical beam. When the image is not aligned, several visual beams (MOPA and daughter beams) are visible. There may be up to five potential beams in the image at one time. As part of the alignment process, it is necessary to identify (i.e., mark) the MOPA and daughter beams, and select the appropriate daughter beam to track when adjusting. When five beams are detected, the alignment process typically focuses on the MOPA beam and the third beam, or if two beams are observed, the alignment process focuses on the darker beam.

[0094] exist Figure 7 In the image shown in , the beam of interest is the darkest visual beam image, i.e., daughter beam 720B. This beam will be used by the alignment system to adjust the modules to merge the beams into one beam. Once there is a single merged beam, additional processes can be performed to make the beam symmetrical along the x and y axes.

[0095] According to one aspect of the embodiment, computer vision techniques are used to determine and label beams such as those shown in image 700, including the MOPA seed beam 710 and the daughter beams 720A, 720B. As described in more detail below, these techniques may include image pre-processing, determining all contours or shapes within the image, utilizing characteristics of the daughter (secondary) beams to determine their validity, and providing logic for proper sequencing and labeling of each valid contour or secondary beam.

[0096] Automatic profile marking determines how and where to move the secondary beam of interest. Once the alignment system determines that a single profile has been achieved, it calculates the skew, a measure of symmetry, over the sum of pixels in both the vertical and horizontal directions of the profile. This measurement determines the direction to move the secondary beam in order to reduce the skew and obtain a more symmetrical target beam.

[0097] Thus, according to another aspect of an embodiment, the alignment system can sequentially sort the valid profiles and provide a marker to all shapes found on the image. One benefit of this sorting capability is that the system can focus on the secondary beam of interest and move the actuator to adjust the position of the secondary beam of interest to be more consistent with the target beam so that only a single profile exists. When the system makes such a determination, it can then perform additional adjustment measurements (skew) to make the beam more symmetrical.

[0098] Fig. 8A is an example of a near-field image 800 of a combined MO seed beam and PRA beam. The MO seed beam does not “fill in” the Fig. 8A and Figure 8B The entire aperture outline is indicated by the manually added "box" lines in the image. This can cause problems when aligning to the central aperture boundary, as the aperture outline is not visible on the image available to the system. Fig. 8A Without determining the proper aperture boundaries, the alignment system will not be able to determine the center of the aperture that can be used for alignment. It is desirable to move the center of the beam to the center of the aperture to obtain proper alignment.

[0099] According to one aspect of the embodiment, the beam is moved using line detection, logic, and sequential searching to detect and maintain near-field aperture boundaries. Figure 8B The results of the boundary detection are shown. Once the system detects the aperture edge, it can maintain these values ​​and establish the location of the center of the aperture for alignment of the system. The beam can be automatically moved near the aperture edge. In addition, the center of the profile (visual image processing beam outline) can be maintained and used to calculate the alignment error.

[0100] In more detail, Fig. 8A The beam image 800 is a beam image that can be viewed in the CASMM 250 ( Figure 2 800 includes an image of an MO seed beam 810 and a box trace 820 indicating the aligned position of the unilluminated aperture at position 274. The purpose of alignment of an image such as image 800 may be to find the edge of the unilluminated aperture and center the MO seed beam 810 on the aperture. This may involve using edge detection to identify the edges of the unilluminated aperture. Figure 8B Edge 830 of the MO seed beam 810 in image 820 shown in FIG.

[0101] One method of edge detection can be to use feature extraction techniques known in the field of image analysis, such as a Hough transform, for example a standard Hough transform or a probabilistic Hough transform, to detect edges. Other edge detection methods can be used, such as integral transforms (e.g., Radon transforms) or pixel intensity transitions. Other techniques known in the field of image analysis can also be used. An open loop technical solution can also be used to determine the aperture position by controlling the associated actuators to sweep the beam across the aperture and using the sum of bright spots to determine the position of the aperture edge. Edge detection is 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. After the aperture is located, the alignment system can determine the determined pixel error between the position of the beam centroid and the center of the aperture.

[0102] As mentioned, part of the image analysis may involve: locating the position of an unilluminated (dark) crosshair target or frame. One measure to improve the overall determination of beam alignment may be to position the beam near the center of the target, and then use additional image processing to detect the position of the dark target and recalibrate to the exact target center. Another possibility is to illuminate the target from the module access port using an external fixture light source where the beam is not excited.

[0103] One of ordinary skill in the art will recognize that the alignment process can be iterative in the sense that a first element can be aligned (such as a folding mirror in a PRA WEB), then a second element can be aligned (e.g. a folding mirror in a MO WEB), and then the first element may again require additional alignment because a shift in the alignment of the second element may also result in a shift in the alignment of the first element, and vice versa. The process converges to an optimal alignment achieved with repeated iterations.

[0104] Fig. 9 is a flow chart illustrating a process for boundary detection according to one aspect of an embodiment. The process begins at step S10, where an image is obtained. Then, in step S20, it is determined whether the position of a target (e.g., crosshairs, aperture edge) has been established. If the position of the target has been established, then in step S30, beam alignment is performed using the established beam center and target, and then the process ends at step S40, where the process can return alignment metrics indicating alignment status and parameters.

[0105] However, if it is determined in step S20 that the target has not been established, the process returns to the automatic boundary detection subroutine 1000. In step S50 of the automatic boundary detection subroutine, the image is preprocessed to enhance features. Such preprocessing may include, for example, enhancing contrast. Then, in step S60, horizontal and vertical line detection techniques are applied, and in step S70, it is determined whether the detection techniques have actually detected horizontal and vertical lines.

[0106] If the determination in step S70 is negative, the process goes to step S100 where the beam path is adjusted to the new position, and then returns to execution of step S60. However, if horizontal and vertical lines are detected, the lines are maintained and their positions are returned. In step S90, it is determined whether the stop criteria have been met. If the stop criteria have been met, subroutine 1000 terminates, and in step S110, the alignment target is determined as the center of the aperture using the maintained lines. However, if it is determined in step S90 that the stop criteria have not been met, the process again goes to step S100 where the beam path is adjusted to the new position, and then the process returns to step S60.

[0107] Fig.10 1 is a flow chart of a process for contour marking (and skew adjustment) according to one aspect of an embodiment, wherein contour marking can be used to align one or more secondary beams with a primary beam. The process begins at step S200, where an image is acquired. Then, in step S210, it is determined whether the beams are aligned and symmetrical based on the acquired beam images. If the beams are aligned and symmetrical, the process ends at step S220, where the process can return alignment metrics indicating alignment status and parameters.

[0108] However, if it is determined in step S210 that the beam is not aligned and symmetrical, then Fig.10 The process calls the automatic contour marking subroutine 1100. In step S230 of the automatic boundary contour marking subroutine 1100, the image is preprocessed to enhance features. Such preprocessing may include, for example, enhancing 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.

[0109] In step S260, it is determined whether multiple profiles have been identified. If so, then in step 270, marking is applied and sorting logic is used based on the profile area to mark the profiles with the appropriate markings for the beams they represent (e.g., MOPA or daughter beams). Then, in step 280, the appropriate beam (of any daughter beams) for tracking is determined based on the sorting order, and the daughter beams are moved toward the MOPA beam to produce a single merged beam. The process then returns to step 240.

[0110] However, if multiple contours are not determined in step S260, the contour marking is considered complete and an additional process is then performed to determine the skew of the merged beam with respect to the vertical and horizontal axes using pixel summation. The beam is then adjusted in step S300 to reduce the skew in the vertical and horizontal directions. The automatic counter marking subroutine then terminates and a determination is made in step S210 as to whether the beam is aligned and symmetrical. If it is determined in step S210 that the beam is still not aligned and symmetrical, the process returns to step S230. On the other hand, if it is determined in step S210 that the beam is aligned and symmetrical, the process ends in step 220 and returns to the alignment metric.

[0111] Fig.11 is a flow chart illustrating an example of a process including detecting aperture edges and centers according to an aspect of an embodiment. The process begins in step S400 by obtaining an image. The image may be, for example, an alignment port image.

[0112] In step S410, it is determined whether to use an object detection model or to pre-define a coarse region of interest (ROI) location.

[0113] If it is determined in step S410 that an object detection model is to be used, then in step S420, the image is passed through the object detection model to determine a coarse ROI subset in the image. Conversely, if it is determined in step S410 that a predefined ROI position is to be used, then in step S430, the predefined coarse ROI is used to isolate an approximate area around the aperture.

[0114] Then, regardless of which of steps S420 or S430 is used, deterministic image processing is used in step S440 on the coarse ROI image subset (step S420) or the approximate area around the aperture (step S430) to determine the aperture edge and the center of the aperture. Then, in step S450, it is determined whether the determined internal dimensions of the aperture are "reasonable", that is, whether the determined internal dimensions correspond to the known aperture size. If it is determined in step S450 that the determined aperture size is not reasonable, then the alignment status and performance metrics are returned in step S460. The process then ends at step S470 and is then repeated by looping back to the start step S400.

[0115] However, if, on the contrary, it is determined in step S450 that the determined aperture size is reasonable, then the location of the center of the aperture is determined and maintained in step S480. Then in step S490, the center of gravity ("COG") of the beam is identified.

[0116] Next, in step S500, the distance and direction (δ) between the COG of the beam and the center of the determined aperture 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 center of the aperture and the COG of the beam are within specified limits (e.g., 5 pixels). If Δx or Δy or both exceed their respective specified limits, then the alignment status, performance metrics, and movement commands (actuator control signals) are returned in step S520, and then the process returns to step S500. However, if it is determined that neither Δx nor Δy exceeds their respective specified limits, then the process proceeds to step S460, and then ends at step S470 to repeat again starting with step S400.

[0117] The steps of the process can be performed in various orders. Not every alignment process will use all of the steps and methods outlined above. Some of these steps can be iterative, i.e., repeated multiple times in succession to converge on the desired alignment. Later alignment steps may require repeating earlier alignment steps. A specific example of an overall alignment process can begin with using the MO seed beam at the CASMM to find the aperture boundary, by using the MO WEB TWA to scan the boundary and using Hough line edge detection to identify the boundary, and then centering the MO seed beam to the center of the identified boundary. This can be followed by several iterations of manipulating the MO WEB TWA to place the MO seed beam at the previously identified CASMM aperture center and manipulating the PRA WEB TWA to center the beam on the BR alignment port crosshairs.

[0118] At a certain point, the PRA OC can be aligned and then intentionally de-aligned. The BR TWA will then be manipulated to center 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 using profile detection and the beam made more symmetrical by reducing its skewness.

[0119] Several iterations and combinations of iterations of the above steps may be performed, and / or additional sub-steps may be performed.

[0120] As mentioned, according to an embodiment, the image analysis module can be used to determine the alignment state of the optical module by acquiring an image of the light beam at the optical module or optically downstream of the optical module, and marking one or more contours in the image as a primary beam component or a secondary beam component. The image analysis module can then control the actuator so that the secondary beam component and the primary beam component merge to form a merged light beam. The image analysis module can be adapted to control the actuator to increase the symmetry of the merged light beam. For example, the image analysis module can control the actuator to increase horizontal (left-right) symmetry, vertical (up-down) symmetry, or both.

[0121] There may be instances where a primary beam component may exhibit a high degree of asymmetry. In such instances, according to an embodiment, the system may store a current skew value (a measure of symmetry) of a beam image (e.g., a far-field image of the beam) as a target skew value in memory. Then, subsequently during the process of merging the primary beam component with the secondary beam component, the system may target the skew value stored in memory to bring the symmetry of the merged beam as close as possible to the symmetry of the previously merged beam for which the skew value was stored.

[0122] exist Fig.12 9 shows a system for performing this process. As shown, the optical module 900 presents the beam image (indicated by the arrow) to the image analysis module 910. The image analysis module 910 measures the value of the characteristic of the image (in this example, its skewness). The image analysis module 910 supplies the measured skewness value to the controller 920, and the controller 920 controls the actuator 905 to properly align the optical module 900. The image analysis module 910 also stores the measured skewness value in the memory 930 as the target skewness value. Then, in the case of merging the primary beam component and the secondary beam component, in the subsequent measurement, the image analysis module 910 measures the current skewness value, that is, the skewness value obtained during the subsequent measurement, and sends the current skewness value to the controller 920. The controller 920 also accesses the target skewness value stored in the memory 930, and controls the actuator to reduce the difference between the current skewness value and the target skewness value. In some embodiments, the controller 920 controls the actuator to make the current skewness value substantially equal to the target skewness value.

[0123] Fig.13 is a flow chart describing the process. In step S600, a skewness value is measured from the beam image from the optical module to be aligned. In step S610, the measured skewness value is stored as a target skewness value S T Then, in step S620, during the adjustment of the alignment of the optical module, the current skewness value S is measured while combining the primary beam component and the secondary beam component. C, to adjust S C To reduce S C With S T The difference between (i.e., targeting the previously stored skewness value).

[0124] According to another aspect of the embodiment, the image analysis module may be adapted to store the position of the centroid of one of a plurality of (e.g., two) far-field beam images in a memory, then optically block the far-field beam image whose centroid position has been stored, and then move the centroid of the remaining (unblocked) far-field beam image to the centroid position stored in the memory. To this end, Fig.12 As shown in , a partial image blocker 915 can be supplied to the image analysis module 910, and the partial image blocker 915 is arranged to have a first state and a second state, in which the partial image blocker 915 allows multiple (e.g., two) light beam images to be passed to the image analysis module 910, and in the second state, the partial image blocker 915 blocks at least one (e.g., one of the two) of the multiple light beam images presented to the image analysis module 910.

[0125] In operation, the image analysis module 910 measures and stores a value indicating the position of the centroid of one of the images in the image information from the optical module 900. The image analysis module 910 stores the centroid position value in the memory 930. Then, the partial image blocker 915 blocks the image of the light beam whose position of the centroid is measured and stored, and then measures the position of the centroid of the other light beam image. The controller 920 controls the actuator 905 so that the position of the centroid of the other light beam image moves toward the centroid position stored in the memory 930.

[0126] Fig.14 is a flow chart describing the process. In step S700, the beam image centroid position is measured in a first beam image from an 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, the centroid position of the second beam image is measured, while adjusting the alignment of the optical module to move the centroid position of the second beam image to a previously stored target centroid position value stored in a memory.

[0127] These same processes can be used to align other optical modules in the optical train. For example, some devices may have two OpuS modules, specifically a vertical Opus and a horizontal Opus. The above process can be used to align the vertical OpuS and to align the horizontal OpuS. The alignment of the vertical OpuS can be done using the above combined Figure 7 or Fig.12 and Fig.13The alignment of the horizontal OPus may be performed using a Hough transform or a Haar cascade classifier to identify the beam position as well as the component position during alignment of the horizontal OPus.

[0128] According to another aspect of the embodiment, a probabilistic Hough line transform (PHT) is used to detect features such as lines and contours in an image obtained at one or more alignment ports. PHT is an extension of the standard Hough line transform. In PHT, instead of considering all possible lines in the image, only a random subset of detected edge points is considered, which makes PHT more efficient. PHT works by first detecting edge points in the image using an edge detection process such as the Canny edge detector. Then, a random subset of these edge points is selected and used to generate line segments in parameter space using the same representation as in the standard Hough transform. Next, a voting scheme is used to determine which of these line segments correspond to actual lines in the image. This is done by increasing the count for each point along the line segment in the image. Then, the line segment with the highest count is considered to be a valid line in the image. Finally, the process is repeated multiple times using different subsets of edge points to improve the accuracy of line detection.

[0129] For example, for the alignment ports of PRA WEB and BR, PHT is used to detect the illuminated outer window or frame of the image. From this the center of the window for the target can be determined. Fig.15A is a representation of the beam image obtained at the alignment port of the BR. The grayscale in this representation can be inverted in the actual image. As can be seen, the image includes reflections 950 and 960 from the edges of the aperture and the illuminated frame 970. There is also a beam image 980 and crosshairs 990.

[0130] exist Fig.15A PHT is performed on the image represented in to identify features in the image. Fig. 15B Yes Fig.15A 950 and 960. The PHT also locates the position 975 of the illuminated frame 970 and the position 985 of the beam image 980 and the center 995 of the illuminated frame 970.

[0131] PHT can be provided by the image analysis module 910 ( Fig.12 ) is executed. Controller 920( Fig.12 ) can use the position of features in the image located by the PHT to align the optical module 900 ( Fig.12 ).

[0132] The above description includes examples of multiple embodiments. Of course, it is not possible to describe every conceivable combination of parts or methods for the purpose of describing these embodiments, but those of ordinary skill in the art will recognize that many other combinations and arrangements of various embodiments are possible. Therefore, the described embodiments are intended to include all such changes, modifications and variations that fall within the spirit and scope of the appended claims. In addition, with respect to the use of the term "comprising" in the detailed description or claims, such terms are intended to be inclusive in a manner similar to the manner in which the term "comprising" is interpreted when "comprising" is used as a transitional word in the claims. In addition, although the elements of the described aspects and / or embodiments may be described or claimed in the singular, plural forms are foreseen unless explicitly stated to be limited to the singular. In addition, all or part of any aspect and / or embodiment may be used together with all or part of any other aspect and / or embodiment, unless otherwise stated.

[0133] The embodiments may be further described using the following terms.

[0134] 1. A device for aligning an optical module to a beam path of a light beam in a laser light source, the device comprising:

[0135] a beam imager arranged to acquire an image of the beam after the beam has interacted with the optical module;

[0136] an image analysis module arranged to receive the image and adapted to make an alignment determination of an alignment state of the optical module relative to the light beam based at least in part on the image and to generate a control signal based on the alignment determination; and

[0137] An actuator is mechanically coupled to the optical module and is arranged to change the alignment state of the optical module based on the control signal.

[0138] 2. An apparatus according to clause 1, wherein the optical beam path includes a power ring amplifier (PRA) alignment path, and the power ring amplifier (PRA) alignment path includes the optical module.

[0139] 3. The device of clause 2, wherein the optical module comprises at least one of a master oscillator (MO), a wavefront engineering box (WEB), a PRA WEB, a PRA chamber, a beam reverser (BR), and an automatic shutter module.

[0140] 4. The apparatus of clause 3, wherein the optical module comprises the BR, and wherein the image of the light beam is acquired at the automatic shutter module.

[0141] 5. The apparatus of clause 4, wherein the automatic shutter module comprises a combined automatic shutter and metering module.

[0142] 6. The apparatus of clause 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.

[0143] 7. An apparatus according to clause 6, wherein the image analysis module is adapted to control the actuator to sweep the light beam across the aperture to detect at least one edge of the aperture.

[0144] 8. Apparatus according to clause 6, wherein the image analysis module is adapted to detect the at least one edge of the aperture using a Hough transform.

[0145] 9. An apparatus according to clause 1, wherein the image analysis module is adapted to detect a window and determine the center of the window using an object detection model.

[0146] 10. An apparatus according to clause 9, wherein the image analysis module is adapted to detect the window and determine the center of the window using a Haar cascade classifier.

[0147] 11. The apparatus of clause 1, wherein the image analysis module is adapted to make the alignment determination of the optical module based at least in part on marking one or more contours in the image as one of a primary beam and a secondary beam.

[0148] 12. An apparatus according to clause 11, wherein the image analysis module is suitable for performing the alignment determination of the optical module based on at least one primary beam and at least one secondary beam, and is suitable for controlling the actuator so that the secondary beam and the primary beam are merged to form a merged beam.

[0149] 13. Apparatus according to clause 12, wherein the image analysis module is adapted to control the actuator to increase the symmetry of the combined light beam.

[0150] 14. A method of aligning an optical module to a beam path of a light beam in a laser light source, the method comprising:

[0151] acquiring an image of the light beam after the light beam has interacted with the optical module;

[0152] performing an alignment determination of an alignment state of the optical module based at least in part on the image;

[0153] generating a control signal based on the alignment determination; and

[0154] The control signal is used to control an actuator mechanically coupled to the optical module to change an alignment state of the optical module.

[0155] 15. The method of clause 14, wherein the beam path comprises a power ring amplifier (PRA) alignment path.

[0156] 16. A method according to clause 14, wherein the optical module includes one of a master oscillator (MO) wavefront engineering box (WEB), a PRA WEB, a PRA chamber, a beam reverser (BR) and an automatic shutter module in the PRA alignment path.

[0157] 17. The method of clause 16, wherein the optical module comprises the BR, and wherein the image of the light beam is acquired at the automatic shutter module.

[0158] 18. The method of clause 16, wherein the automatic shutter module comprises a combined automatic shutter and metering module.

[0159] 19. The method of clause 14, wherein making an alignment determination of an alignment state of the optical module comprises detecting at least one edge of an aperture in the optical module.

[0160] 20. The method of clause 19, further comprising controlling the actuator to sweep the light beam across the aperture to detect the at least one edge of the aperture.

[0161] 21. The method of clause 19, wherein detecting at least one edge of an aperture in the optical module comprises using a Hough transform.

[0162] 22. A method according to clause 14, wherein the 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, which is suitable for detecting an aperture or an illuminated surface and determining the center and size of the object using an object detection model.

[0163] 23. The method of clause 22, wherein using an image analysis module adapted to detect apertures or illuminated surfaces and using an object detection model to determine the center and size of the object comprises using a Haar cascade classifier.

[0164] 24. The method of clause 14, wherein making an alignment determination of an alignment state of the optical module comprises marking one or more contours in the image as one of a primary beam and a secondary beam.

[0165] 25. A method according to claim 24, wherein marking one or more contours in the image as one of a primary beam and a secondary beam includes marking at least one contour in the image as a primary beam and marking at least one contour in the image as a secondary beam, and the method also includes merging the primary beam and the secondary beam to form a merged beam.

[0166] 26. The method of clause 25, further comprising increasing the symmetry of the combined light beam.

[0167] 27. An apparatus for aligning an optical module to a beam path of a light beam in a laser light source, the apparatus comprising:

[0168] Memory;

[0169] a beam imager arranged to acquire an image of the beam after the beam has interacted with the optical module;

[0170] 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;

[0171] a controller adapted to generate a control signal based on the one or more beam characteristics; and

[0172] an actuator mechanically coupled to the optical module and arranged to change an alignment state of the optical module based on the control signal,

[0173] Wherein the image analysis module is further arranged to make subsequent measurements of the one or more beam characteristics from the image, and the controller is arranged to generate the control signal to control the actuator to reduce the difference between the one or more beam characteristics measured by the subsequent measurements and the stored information.

[0174] 28. An apparatus according to claim 27, wherein the beam characteristic is a beam deflection, the information indicative of the one or more beam characteristics is a target beam deflection, and wherein the image analysis module is also arranged to perform subsequent measurements of the beam deflection, and the controller is arranged to generate the control signal to control the actuator to reduce the difference between the subsequent measurements of the beam deflection and the target beam deflection.

[0175] 29. An apparatus according to claim 27, wherein the beam characteristic is a measured position of the centroid of an image of one of a primary beam component and a secondary beam component of the beam, the information indicative of the one or more beam characteristics is the measured position of the centroid, and wherein the image analysis module is also arranged to perform subsequent measurements of the position of the centroid of the other of the primary beam component and the secondary beam component, and the controller is arranged to generate the control signal to control the actuator to move the position of the centroid of the other of the primary beam component and the secondary beam component to the measured position stored in the memory.

[0176] 30. The device according to clause 29 further includes a beam component blocking element, which is 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 centroid of the other of the first beam component and the second beam component.

[0177] 31. A method of aligning an optical module to a beam path of a light beam in a laser light source, the method comprising:

[0178] acquiring an image of the light beam after the light beam has interacted with the optical module;

[0179] measuring one or more beam characteristics from the image;

[0180] storing information indicative of the one or more beam characteristics in a memory;

[0181] generating a control signal based on the one or more beam characteristics;

[0182] actuating an actuator based on the control signal, the actuator being mechanically coupled to the optical module and arranged to change an alignment state of the optical module;

[0183] performing subsequent measurements of the one or more beam characteristics; and

[0184] The control signal is generated to control the actuator to reduce a difference between the one or more beam characteristics measured by the subsequent measurement and the stored information.

[0185] 32. A method according to clause 31, wherein the beam characteristic is beam skewness, the information indicative of the one or more beam characteristics is a target beam skewness, making subsequent measurements of the one or more beam characteristics includes making subsequent measurements of the beam skewness, and generating the control signal includes generating the control signal to control the actuator to reduce the difference between the subsequent measurements of the beam skewness and the target beam skewness.

[0186] 33. A method according to clause 31, wherein the beam characteristic is a measured position of the centroid of an image of one of a primary beam component and a secondary beam component of the beam, the information indicative of the one or more beam characteristics is the measured position of the centroid, and wherein making subsequent measurements of the one or more beam characteristics includes making subsequent measurements of the position of the centroid of the other of the primary beam component and the secondary beam component, 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 primary beam component and the secondary beam component to the measured position stored in the memory.

[0187] 34. The method of clause 33, further comprising blocking the one of the first beam component and the second beam component during measuring the position of the centroid of the other of the first beam component and the second beam component.

[0188] 35. An apparatus for aligning an optical module to a beam path of a light beam in a laser light source, the apparatus comprising:

[0189] a beam imager arranged to acquire an image of the beam after the beam has interacted with the optical module;

[0190] an image analysis module arranged to receive the image and perform a probabilistic Hough line transform to locate the position of one or more features in the image;

[0191] a controller adapted to generate a control signal based on the one or more features located in the image; and

[0192] An actuator is mechanically coupled to the optical module and is arranged to change an alignment state of the optical module based on the control signal.

[0193] 36. An apparatus as described in clause 35, wherein the one or more features located in the image include an illuminated frame in the image.

[0194] 37. An apparatus as recited in clause 35, wherein the one or more features located in the image include the position of a center of the illuminated frame.

[0195] 38. A method of aligning an optical module to a beam path of a light beam in a laser light source, the method comprising:

[0196] acquiring an image of the light beam after the light beam has interacted with the optical module;

[0197] performing a probabilistic Hough line transform to locate the position of one or more features in the image;

[0198] generating a control signal based on the one or more features located in the image; and

[0199] An alignment state of the optical module is changed based on the control signal.

[0200] 39. The method of clause 38, wherein the one or more features located in the image comprise an illuminated frame in the image.

[0201] 40. The method of clause 38, wherein the one or more features located in the image include the position of a center of the illuminated frame.

[0202] The implementations described above and other implementations are within the scope of the following claims.

Claims

1. A device for aligning an optical module to a beam path of a light beam in a laser light source, the device comprising: a beam imager arranged to acquire an image of the beam after the beam has interacted 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 relative to the light beam based at least in part on the image and to generate a control signal based on the alignment determination; as well as An actuator is mechanically coupled to the optical module and is arranged to change the alignment state of the optical module based on the control signal.

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

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

4. The apparatus of claim 3, wherein the optical module comprises the BR, and wherein the image of the light beam is acquired at the automatic shutter module.

5. The apparatus of claim 4, wherein the automatic shutter module comprises a combined automatic shutter and metering 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 light 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 and determine a center of the window using an object detection model.

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

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

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

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

14. A method of aligning an optical module to a beam path of a light beam in a laser light source, the method comprising: acquiring an image of the light beam after the light beam has interacted with the optical module; performing 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; as well as The control signal is used to control an actuator mechanically coupled to the optical module to change an alignment state of the optical module.

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

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

17. The method of claim 16, wherein the optical module comprises the BR, and wherein the image of the light beam is acquired at the automatic shutter module.

18. The method of claim 16, wherein the automatic shutter module comprises a combined automatic shutter and metering module.

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

20. The method according to claim 19, further comprising: The actuator is controlled to sweep the light beam across the aperture to detect the at least one edge of the aperture.

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

22. The method of claim 14, wherein the 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 an aperture or an illuminated surface and to determine a center and size of an object using an object detection model.

23. The method of claim 22, wherein using an image analysis module adapted to detect apertures or illuminated surfaces and using an object detection model to determine the center and size of the object comprises: Use Haar cascade classifier.

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

25. A method according to claim 24, wherein marking one or more contours in the image as one of a primary beam and a secondary beam includes marking at least one contour in the image as a primary beam and marking at least one contour in the image as a secondary beam, and the method also includes merging the primary beam and the secondary beam to form a merged beam.

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

27. An apparatus for aligning an optical module to a beam path of a light beam in a laser light source, the apparatus comprising: Memory; a beam imager arranged to acquire an image of the beam after the beam has interacted 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; as well as 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 arranged to make subsequent measurements of the one or more beam characteristics from the image, and the controller is arranged to generate the control signal to control the actuator to reduce the difference between the one or more beam characteristics measured by the subsequent measurements and the stored information.

28. An apparatus according to claim 27, wherein the beam characteristic is a beam skewness, the information indicative of the one or more beam characteristics is a target beam skewness, and wherein the image analysis module is also arranged to perform subsequent measurements of the beam skewness, and the controller is arranged to generate the control signal to control the actuator to reduce the difference between the subsequent measurements of the beam skewness and the target beam skewness.

29. An apparatus according to claim 27, wherein the beam characteristic is a measured position of the centroid of an image of one of a primary beam component and a secondary beam component of the beam, the information indicative of the one or more beam characteristics is the measured position of the centroid, and wherein the image analysis module is also arranged to perform subsequent measurements of the position of the centroid of the other of the primary beam component and the secondary beam component, and the controller is arranged to generate the control signal to control the actuator to move the position of the centroid of the other of the primary beam component and the secondary beam component to the measured position stored in the memory.

30. The device according to claim 29 further includes a beam component blocking element, which is 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 centroid of the other of the first beam component and the second beam component.

31. A method of aligning an optical module to a beam path of a light beam in a laser light source, the method comprising: acquiring an image of the light beam after the light beam has interacted 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 based on the control signal, the actuator being mechanically coupled to the optical module and arranged to change an alignment state of the optical module; performing subsequent measurements of the one or more beam characteristics; and The control signal is generated to control the actuator to reduce a difference between the one or more beam characteristics measured by the subsequent measurement and the stored information.

32. A method according to claim 31, wherein the beam characteristic is a beam skewness, the information indicative of the one or more beam characteristics is a target beam skewness, making subsequent measurements of the one or more beam characteristics includes making subsequent measurements of the beam skewness, and generating the control signal includes generating the control signal to control the actuator to reduce the difference between the subsequent measurements of the beam skewness and the target beam skewness.

33. A method according to claim 31, wherein the beam characteristic is a measured position of the centroid of an image of one of a primary beam component and a secondary beam component of the beam, the information indicative of the one or more beam characteristics is the measured position of the centroid, and wherein making subsequent measurements of the one or more beam characteristics includes making subsequent measurements of the position of the centroid of the other of the primary beam component and the secondary beam component, 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 primary beam component and the secondary beam component to the measured position stored in the memory.

34. The method of claim 33, further comprising: During measuring the position of the centroid of the other of the first and second beam components, the one of the first and second beam components is blocked.

35. An apparatus for aligning an optical module to a beam path of a light beam in a laser light source, the apparatus comprising: a beam imager arranged to acquire an image of the beam after the beam has interacted with the optical module; an image analysis module arranged to receive the image and perform a probabilistic Hough line transform to locate the position of one or more features in the image; a controller adapted to generate a control signal based on the one or more features located in the image; as well as An actuator is mechanically coupled to the optical module and is arranged to change an alignment state of the optical module based on the control signal.

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

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

38. A method of aligning an optical module to a beam path of a light beam in a laser light source, the method comprising: acquiring an image of the light beam after the light beam has interacted with the optical module; performing a probabilistic Hough line transform to locate the position of one or more features in the image; generating a control signal based on the one or more features located in the image; and An alignment state of the optical module is changed based on the control signal.

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

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

Images