Method and apparatus for compensating for thermotropic beam pointing error in laser processing system

Abstract

A laser machining system for machining a workpiece is adapted to estimate a thermal response of at least one of a number of beam path members to a laser energy beam during a predetermined machining cycle while the workpiece is to be machined, generate one or more commands based at least in part on the estimated thermal response, and outputting the one or more commands to one or more components of the system, and outputting commands to one or more components of the system to machine the workpiece during the machining cycle.

Description

Technical Field

[0001]

[0014] Embodiments of the present invention generally relate to systems and methods for positioning a beam of laser energy, and more particularly, positioning a beam of laser energy in a manner that compensates for thermally induced beam pointing errors. Background Art

[0002] Laser processing systems typically use lasers to process (e.g., cut, weld, drill, etc.) workpieces such as printed circuit boards, sheet metal, and the like. Such systems typically include optical components such as a beam positioning system (e.g., a pair of orthogonally oriented galvanometer mirrors) for scanning or otherwise positioning the laser energy beam relative to the workpiece, and a scanning lens for focusing the scanned laser energy beam at or near the workpiece. Other optical components (e.g., mirrors, lenses, beam expanders, wave plates, polarizers, acousto-optic devices, etc.) are typically disposed in the beam path between the laser source (which generates the laser energy beam) and the beam positioning system. Optical components such as a scanning lens are typically disposed in the beam path optically downstream of the beam positioning system, for example, to focus the laser energy beam onto the workpiece so that the beam waist of the focused laser energy beam is positioned at or near the workpiece.

[0003] The optical components in the aforementioned laser processing systems typically absorb a small portion of the optical power within the laser energy beam, whereby the absorbed optical power is converted into heat within the optical components. When the laser energy beam has sufficiently high power (e.g., exceeding 100 W), the absorbed optical power can induce thermal lensing effects or aberrations within some of the optical components themselves. If the thermal gradient within the optical components is relatively stable during workpiece processing, thermal lensing and other distortions or aberrations can generally be accounted for to ensure satisfactory workpiece processing. However, the stability of the thermal gradient can be compromised depending on one or more factors related to system operation, such as changing the optical power used to process the workpiece, temporarily suspending the delivery of laser energy through the scan lens (e.g., when replacing a new workpiece to be processed), and the like. If the thermal gradient within the optical components is not sufficiently stable (i.e., "unstable"), the spatial deviation between the position where the laser energy beam waist is intended to be delivered relative to the workpiece and the position where the waist is actually delivered to the workpiece (i.e., "thermally induced beam pointing error") may be undesirably large. The absorbed optical power may also induce thermal deformation in mounting devices used to precisely position or orient optical elements within the laser machining system, which may also lead to thermally induced beam pointing errors.

[0004] One technique for avoiding thermally induced beam pointing errors is to design and operate the laser processing system so that the optical elements in the system are thermally stable while the workpiece is being processed. Generally, this solution requires that all optical elements in the system be exposed to a constant optical power from the laser energy beam, which is not always practical. Other techniques for avoiding thermally induced beam pointing errors typically involve measuring the temperature of optical elements in the beam path (e.g., galvanometer mirrors, scan lenses) (e.g., using temperature sensors) and then adjusting the operation of the beam positioning system based on the measured temperature. However, such techniques do not respond satisfactorily to gradual or rapid changes in the measured temperature. Summary of the Invention

[0005] One embodiment of the present invention can be broadly characterized as a laser processing system for processing a workpiece. The system can include: a laser source operable to output a laser energy beam that can propagate along a beam path; and a plurality of beam path components disposed within the beam path. The plurality of beam path components can include: a beam positioning system operable to deflect the beam path within a scan field in response to a position command; and a scan lens configured to focus the laser energy beam deflected by the beam positioning system, thereby producing a focused laser energy beam having a beam waist. The system can further include a controller communicatively coupled to the beam positioning system. The controller can be configured to generate the position command based at least in part on an estimated thermal response of at least one of the plurality of beam path components to the laser energy beam during a predetermined processing cycle, and to output the generated position command to the beam positioning system to operate the beam positioning system during the processing cycle.

[0006] Another embodiment of the present invention can be broadly characterized as a laser processing system for processing a workpiece. The system can include: a laser source operable to output a laser energy beam that can propagate along a beam path; and a plurality of beam path components disposed within the beam path, wherein the plurality of beam path components include a scan lens configured to focus the laser energy beam deflected by a beam positioning system, thereby producing a focused laser energy beam having an optical waist. The system can further include: at least one stage operable to impart relative movement between the optical waist and the workpiece in response to a stage position command; and a controller communicatively coupled to the beam positioning system of the at least one stage. The controller can be configured to generate the stage position command based at least in part on an estimated thermal response of at least one of the plurality of beam path components to the laser energy beam during a predetermined processing cycle, and to output the generated stage position command to the at least one stage to operate the at least one stage during the processing cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 Laser processing systems according to various embodiments of the present invention are schematically depicted.

[0008] Figure 2 Drawings can be incorporated into Figure 1 An embodiment of a beam modulator in a laser processing system is shown in FIG.

[0009] Figure 3 FIG. 1 is a block diagram of an embodiment of the present invention that can be incorporated into Figure 1 Laser beam monitoring system as part of the laser processing system shown.

[0010] Figure 4 Schematically depicting an embodiment of the present invention Figure 1 The controller implementation shown in the application analysis module.

[0011] Figure 5 Schematically depicts an embodiment of the present invention Figure 4 The thermal compensation module shown in . DETAILED DESCRIPTION

[0012] The exemplary embodiments are described herein with reference to the accompanying drawings. Unless otherwise expressly stated, in the drawings, the sizes, positions, etc. of components, features, elements, etc. and any distances therebetween are not necessarily drawn to scale but are exaggerated for clarity.

[0013] The terminology used herein is for the purpose of describing specific example embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be recognized that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise specified, when reciting a range of values, the range of values ​​includes both the upper and lower limits of the range and any subranges therebetween. Unless otherwise specified, terms such as "first," "second," and the like are used solely to distinguish one element from another. For example, one node may be referred to as a "first node," and similarly, another node may be referred to as a "second node," or vice versa. The section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described.

[0014] Unless otherwise indicated, the terms "about," "around," and the like mean that amounts, sizes, recipes, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as necessary, reflecting tolerances, conversion factors, rounding, measurement errors, and the like, as well as other factors known to those of ordinary skill in the art.

[0015] Spatially relative terms, such as "below," "beneath," "lower," "above," and "upper," and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element or feature, as illustrated in the figures. It should be recognized that the spatially relative terms are intended to encompass different orientations in addition to the orientation depicted in the figures. For example, if the object in the figures is turned over, an element described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both orientations of above and below. Objects may be otherwise oriented (e.g., rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein should be interpreted accordingly.

[0016] The same symbols refer to the same elements throughout the text. Therefore, the same or similar symbols may be described with reference to other figures, even if such symbols are not mentioned or described in the corresponding figures. In addition, even elements not indicated by reference symbols may be described with reference to other figures.

[0017] It should be understood that many different forms and embodiments are possible without departing from the spirit and teachings of the present disclosure, and therefore the present disclosure should not be construed as limited to the exemplary embodiments set forth herein. Rather, these examples and embodiments are provided so that the present disclosure will be thorough and complete, and will convey the scope of the present disclosure to those skilled in the art. I. Embodiments Generally Relating to Laser Processing Systems and Associated Components

[0018] refer to Figure 1 A laser processing system, such as system 100, for processing a workpiece 101 includes a laser source 102, a beam modulator 104, one or more optical elements 106, a beam positioning system 108, a scan lens 110, and a controller 112. System 100 may also include a workpiece stage 114 for positioning or otherwise holding the workpiece 101.

[0019] like Figure 1, the laser energy output by the laser source 102 propagates along a beam path (indicated by a dotted line) 103. Disposed in the beam path 103 are a beam modulator 104, one or more optical components 106, a beam positioning system 108, and a scan lens 110. As used herein, the term "beam path" refers to the path that the laser energy beam actually travels as it propagates from the laser source 102 to (and through) the scan lens 110 (e.g., to the workpiece 101), and also refers to the path that the laser energy beam will travel once it is output by the laser source 102. The optical components 106, the beam positioning system 108, and the scan lens 110 are generally referred to herein as "beam path components."

[0020] Generally speaking, the laser source 102 is configured to generate a high-power laser energy beam and may be provided as a CO2 laser source, a CO laser source, a high-power fiber laser, a high-power disk laser, or the like, the output of which manifests as a series of laser pulses or as a continuous wave (CW) or quasi-CW (QCW) laser energy beam. As used herein, characterizing the laser energy beam as "high power" indicates that the optical power in the laser energy beam is sufficient to induce beam pointing errors in one or more of the aforementioned beam path components. In some embodiments, the high-power laser energy beam manifesting as a series of laser pulses may be characterized as having a peak power greater than or equal to 1 kW (e.g., greater than or equal to 1.5 kW, 2 kW, 3 kW, etc., or any values ​​between such values). In other embodiments, the high-power laser energy beam manifesting as a CW or QCW laser energy beam may have an average power greater than or equal to 100 W (e.g., greater than or equal to 150 W, 200 W, 300 W, 400 W, 500 W, etc., or any values ​​between such values). It should be understood that the power value may vary, for example, depending on the wavelength of the laser energy beam or other factors such as pulse duration, pulse repetition rate, beam diameter, light absorption characteristics of beam path components, or the like, or any combination thereof.

[0021] The beam modulator 104 is operable to selectively and variably attenuate the laser energy beam output by the laser source 102 (e.g., in response to one or more control signals output by the controller 112). After being output from the beam modulator 104, the laser energy beam further propagates from the beam modulator 104 along the beam path 103 to other components of the system 100 and ultimately to the workpiece 101. Examples of the beam modulator 104 may include one or more systems such as a variable neutral density filter, an acousto-optic (AO) modulator (AOM), an AO deflector (AOD), an electro-optic (EO) modulator (EOM), an EO deflector (EOD), a liquid crystal variable attenuator (LCVA), a microelectromechanical system (MEMS)-based VOA, an optical attenuator wheel, a polarizer / waveplate filter, or the like, or any combination thereof. The degree of attenuation imparted to the laser energy beam by the beam modulator 104 may range from 0% to 100%, depending on the configuration of the beam modulator 104. Thus, the beam modulator 104 can selectively and variably operate to transmit some or all of the laser energy beam incident thereon to the remaining beam path components, or to prevent transmission thereof entirely to the beam path components. In some embodiments, the beam modulator 104 can function as a "pulse picker" (e.g., to selectively transmit only certain pulses within a laser pulse train in the laser energy beam) or as a "pulse clipper" (e.g., to selectively transmit only one or more certain portions of one or more laser pulses in the laser energy beam, or to divide a CW or QCW laser energy beam into a plurality of pulses).

[0022] In one embodiment, and with reference to Figure 2 The beam modulator 104 may be provided as an AO device 200 (such as an AOM or AOD) and a driving circuitry 202 electrically coupled to the AO device 200 .

[0023] The AO device 200 includes an AO unit and at least one ultrasonic transducer attached to the AO unit, as is known in the art. Generally, the material from which the AO unit is formed will depend on the wavelength of the laser energy beam to be attenuated. For example, if the laser energy beam has a wavelength in the range of 2 micrometers (μm) (or so) to 20 μm (or so), the AO unit may be formed from a material comprising crystalline germanium, as is known in the art.

[0024] The drive circuitry 202 may include one or more RF synthesizers and one or more amplifiers coupled to the outputs of the one or more RF synthesizers. Each RF synthesizer is configured to generate an RF signal having any desired or otherwise suitable waveform, and each amplifier is configured to amplify the RF signal output by the RF synthesizer and output an amplified RF signal. The amplified RF signal may be output as a drive signal to at least one transducer of the AO device 200.

[0025] As one skilled in the art will appreciate, AO devices, such as AO device 200, utilize diffraction events caused by one or more acoustic waves to modulate a laser energy beam incident on and propagating through the AO unit. In this case, the acoustic waves can be transmitted into the AO unit by applying a drive signal to at least one transducer of AO device 200, as is known in the art. Upon diffracting the incident laser energy beam, a diffraction pattern is generated that typically includes zeroth-order and first-order diffraction peaks. The diffraction pattern may also include other higher-order diffraction peaks (e.g., second-order, third-order, etc.). The amount of optical power diffracted into the first-order diffraction peak (e.g., compared to the zeroth-order diffraction peak) can be affected by one or more factors, namely, the amplitude of the drive signal applied to the at least one transducer of AO device 200, the frequency of the drive signal applied to the at least one transducer of AO device 200, and, when multiple transducers are provided, the phase relationship between the drive signals applied simultaneously to the transducers of AO device 200. As is known in the art, the portion of the diffracted laser energy beam in the zeroth order diffraction peak is referred to as the "zeroth order" beam, the portion of the diffracted laser energy beam in the first order diffraction peak is referred to as the "first order" beam, and so on.

[0026] Generally speaking, the zero-order beam and other diffracted order beams (e.g., the first-order beam) propagate along different beam paths after leaving the AO unit (e.g., passing through the optical output side of the AO unit). For example, the zero-order beam propagates along the zero-order beam path, the first-order beam propagates along the first-order beam path, and so on. Figure 2 , a zero-order beam path is identified at zero-order beam path 204, and a first-order beam path is identified at first-order beam path 206. As is known in the art, the angle Θ (also referred to herein as the "deflection angle") between the zero-order beam path 204 and the first-order beam path 103 may depend on one or more factors, such as the frequency of a drive signal applied to at least one transducer of the AO device 200. Although not shown, one or more beam traps may be provided to absorb or otherwise intercept laser energy propagating along the zero-order beam path 204 (and any other higher-order beam paths) while allowing laser energy propagating along the first-order beam path 206 to travel to various other components of the system 100 and ultimately to the workpiece 101. Thus, at all locations optically downstream of the beam modulator 104, the first-order beam path 206 corresponds to Figure 1 The beam path 103 is shown in FIG.

[0027] In one embodiment, the beam modulator 104 can be provided as a series of optically coupled optical (AO) devices, such as AO device 200, optically arranged in series to deflect a beam of laser energy propagating along the beam path 103 (e.g., relative to the beam positioning system 108) within a two-dimensional scanning field. For example, the beam modulator 104 can be provided as a first AO device and a second AO device arranged optically "downstream" from the first AO device. As with AO device 200, each of the first and second AO devices can be electrically coupled to a driver circuitry, such as driver circuitry 202. The first AO device can be configured and operable to deflect the beam path 103 (e.g., relative to the beam positioning system 108) within a first one-dimensional scanning field (e.g., within a one-dimensional scanning field extending along a first axis, such as the X-axis) of the two-dimensional scanning field, and the second AO device can be configured and operable to deflect the beam path 103 (e.g., relative to the beam positioning system 108) within a second one-dimensional scanning field (e.g., within a one-dimensional scanning field extending along a second axis, such as the Y-axis) of the two-dimensional scanning field. In this case, the first AO device diffracts the incident laser energy beam propagating from the laser source 102, and the second AO device diffracts the first-order beam generated by the first AO device. Although not shown, one or more beam traps are provided to absorb or otherwise intercept laser energy from each of the first and second AO devices propagating along all beam paths except the first-order beam path.

[0028] Return Reference Figure 1 The optical element 106 may include one or more components, such as a beam expander, beam shaper, beam splitter, aperture, filter, collimator, lens, mirror, prism, polarizer, phase retarder, diffractive optical element, refractive optical element, or the like, or any combination thereof, to focus, expand, collimate, shape, polarize, filter, split, combine, crop, or otherwise modify, condition, absorb, reflect, diffract, refract, etc., the laser energy beam as it propagates along the beam path 103 from the beam modulator 104 to the beam positioning system 108. Although not shown, one or more optical elements 106 may also be disposed in the beam path 103 between the laser source 102 and the beam modulator 104. The optical element 106 may be positioned in the beam path 103 using one or more associated devices, such as a housing, bracket, mount, frame, platform, etc. (each generally referred to as a "mounting device"), as known in the art. Such mounting devices may then be attached to a frame (not shown) of the system 100 in any manner suitable or otherwise known in the art.For purposes of discussion, a mounting device will be considered part of its associated optical element 106.

[0029] The beam positioning system 108 is operable to reflect, diffract, and / or refract an incident laser energy beam propagating along the beam path 103 (e.g., in response to one or more control signals output by the controller 112), thereby aligning the beam path 103 (e.g., relative to the scan lens 110) along one or more axes (e.g., along Figure 1 The X-axis shown in Figure 1 The beam positioning system 108 is configured to deflect the beam path 103 within a scanning field extending along the X-axis (e.g., the Y-axis of the X-axis and Z-axis shown in FIG, or the like, or any combination thereof). In one embodiment, the beam positioning system 108 is provided as galvanometer mirrors optically arranged in series. In some embodiments, the beam positioning system 108 may include one or more components, such as galvanometer mirrors, fast steering mirrors, AODs, EODs, MEMS-based scanning systems, or the like, or any combination thereof. For example, the beam positioning system 108 may include: a first galvanometer mirror configured and operable to deflect the beam path 103 within a first scanning field extending along the X-axis; and a second galvanometer mirror configured and operable to deflect the beam path 103, previously deflected by the first galvanometer mirror within the first scanning field, within a second scanning field extending along the Y-axis. Thus, the beam positioning system 108, including the first and second galvanometer mirrors, is configured to deflect the beam path 103 within a two-dimensional scanning field. It will be appreciated that as the beam path 103 is deflected within the scan field of the beam positioning system 108, the beam waist of the focused laser energy beam (when ultimately delivered to the workpiece 101) will necessarily be located or positioned within the scan field of the beam positioning system 108. It will be further appreciated that in embodiments where the beam modulator 104 is configured and operable to deflect the beam path 103 (e.g., as described above), the scan field associated with the beam modulator 104 will be superimposed on the scan field of the beam positioning system 108 (e.g., such that the beam positioning system 108 deflects the scan field of the beam modulator 104).

[0030] Generally speaking, the scan lens 110 is configured to focus the laser energy beam propagating along the beam path 103 (e.g., such that the beam waist of the focused laser energy beam is located at or near the workpiece 101). Thus, the scan lens 110 can be considered to be configured to project the scan field of the beam positioning system 108 onto the workpiece 101. The scan lens 110 can be provided as an f-theta scan lens, a telecentric f-theta scan lens, or the like. In an alternative embodiment, the scan lens 110 can be replaced by a concave mirror configured to reflect the laser energy beam onto the workpiece 101 while also focusing the reflected laser energy beam.

[0031] Although not shown, the system 100 may optionally include at least one optical platform configured and operable to move the scan lens 110 (e.g., in response to one or more control signals output by the controller 112). For example, the at least one optical platform may be operable to translate the scan lens 110 along one or more of the X-axis, the Y-axis, or the Z-axis, rotate the scan lens 110 about one or more of the X-axis, the Y-axis, or the Z-axis, and so forth, or any combination thereof. In this case, the scan lens 110 may be incorporated into a housing that houses the beam positioning system 108, such as the scan head 116, and the at least one optical platform may be mechanically coupled to the scan head 116.

[0032] The workpiece platform 114 may include a chuck (e.g., a vacuum chuck, an electrostatic chuck, a mechanical chuck, etc.) operable to prevent or minimize movement of the workpiece 101 while the workpiece 101 is supported on the workpiece platform 114. Furthermore, the workpiece platform 114 may be provided as one or more motion platforms configured and operable to move the workpiece 101 (e.g., in response to one or more control signals output by the controller 112). For example, the workpiece platform 114 may be operable to translate the workpiece 101 along one or more of the X-axis, the Y-axis, or the Z-axis, rotate the workpiece about one or more of the X-axis, the Y-axis, or the Z-axis, etc., or any combination thereof.

[0033] The controller 112 is operable to generate and output one or more control signals to one or more components of the system 100, such as the laser source 102, the beam modulator 104, the beam positioning system 108, the workpiece stage 114, the optical stage, or the like, or any combination thereof, to control the operation of such components in any manner suitable or otherwise known in the art.

[0034] According to an embodiment of the present invention, the control signals output by controller 112 convey commands generated by the application analysis module of controller 112. The application analysis module (not shown) is operable to access a computer file containing an application dataset representing (e.g., in terms of size, shape, location, orientation, etc.) one or more features (e.g., slots, grooves, through-holes, holes, openings, cut streets, etc.) to be formed in workpiece 101 during machining of workpiece 101. In one embodiment, the computer file may also contain workpiece data representing certain characteristics of the workpiece 101 to be machined (e.g., in terms of type, material construction, dimensions, etc.). In another embodiment, the workpiece data may be appended to or otherwise associated with the application dataset through user interaction with a user interface (not shown) of system 100. The application analysis module is operable to process in any suitable manner known in the art, or to analyze the application data and the workpiece data to obtain, derive, or otherwise generate (by any technique suitable or otherwise known in the art) a series of commands intended to coordinate and control the operation of one or more components of the system 100 (e.g., the laser source 102, the beam modulator 104, the beam positioning system 108, the optical stage, the workpiece stage 114, or the like, or any combination thereof) so that the workpiece 101 will be processed to form features therein (e.g., as described in a computer file).

[0035] For example, the application analysis module may generate one or more commands that, when output to the laser source 102, cause the laser source 102 to output a laser energy beam having a specific average power, peak power, temporal power distribution, pulse duration, duty cycle, etc. The commands output to the laser source 102 are generally referred to as "laser commands." Laser commands intended to control the average, instantaneous, or peak power of the output laser energy beam are generally referred to herein as "laser power commands."

[0036] In another example, the application analysis module may output one or more commands that, when output to the beam modulator 104, cause the beam modulator 104 to attenuate the optical power of the laser energy beam incident thereon. Optionally, the degree to which the laser energy beam is to be attenuated may take into account one or more factors, such as the average power, peak power, temporal power distribution, pulse duration, etc. of the laser energy beam output by the laser source 102, predetermined known optical absorption characteristics of beam path components, or the like, or any combination thereof. The commands to be output to the beam modulator 104 are referred to as "transmit commands."

[0037] The beam modulator 104 is provided as the aforementioned AO device 200 and relative to Figure 2In the embodiment of the drive circuitry 202 discussed above, and to the extent that the deflection angle θ can be varied by varying the frequency of the drive signal applied to at least one transducer of the AO device 200, the application analysis module can be operable to generate and output one or more commands to the drive circuitry 202 to vary the frequency of the one or more drive signals applied to the at least one transducer of the AO device 200 at least once (e.g., to deflect the beam path 103 to a desired position). These commands are output to the drive circuitry 202 simultaneously with one or more corresponding transmission commands (e.g., as discussed above) and are referred to as "frequency-modulated position commands." In the embodiment where the beam modulator 104 is provided as one or more of the aforementioned AO devices (and associated drive circuitry), and to the extent that the deflection angle θ can be varied by varying the frequency of the drive signal applied to at least one transducer of the AO device, the application analysis module can output a first frequency-modulated position command to the drive circuitry associated with the first AO device and a second frequency-modulated position command to the drive circuitry associated with the second AO device.

[0038] In another example, the application analysis module may output one or more commands that, when output to the beam positioning system 108, cause the beam positioning system 108 to deflect the beam path 103 within its scan field (e.g., to a desired position at a desired speed, etc.). The commands to be output to the beam positioning system are generally referred to as "beam position commands." In the embodiment where the beam positioning system 108 is provided as a pair of galvanometer mirrors, the application analysis module may output a first beam position command to the first galvanometer mirror and a second beam position command to the second galvanometer mirror. Because the beam position commands and the frequency modulation position commands can affect the relative position between the workpiece 101 and the beam waist of the focused laser energy beam propagating from the scan lens 110, the beam position commands and the frequency modulation position commands may be different embodiments of "position commands."

[0039] In another example, the application analysis module may output one or more commands to the optical table to cause the optical table to move the scan lens 110 or the scan head 116 (e.g., to a desired position at a desired speed, etc.), and the commands to be output to the optical table system are referred to as "optical table position commands." In yet another example, the application analysis module may output one or more commands to the workpiece stage 114 to cause the workpiece stage 114 to move the workpiece 101 (e.g., to a desired position at a desired speed, etc.), and the commands are referred to as "workpiece stage position commands." Optical table position commands and workpiece stage position commands may be generally referred to herein as "stage position commands." Because stage position commands can affect the relative position between the workpiece 101 and the beam waist of the focused laser energy beam propagating from the scan lens 110, stage position commands may be considered a different embodiment of a "position command."

[0040] The control signals conveying the aforementioned commands can be output sequentially in a coordinated manner (e.g., by any suitable or otherwise known technique in the art) so that the workpiece 101 is machined to form features therein as desired. As the workpiece 101 is machined, a beam of laser energy is delivered to numerous locations on the workpiece 101 (e.g., as a series of laser pulses and / or as a CW or QCW beam of laser energy). The total amount of time during which the workpiece 101 is machined can be divided, at least conceptually, into a series of machining cycles of arbitrary or predetermined duration, optionally taking into account the update rate of one or more of the aforementioned components of the system 100. In some embodiments, the machining cycle can range from 0.5 μs (or so) to 150 μs (or so), such as 0.5 μs, 1 μs, 5 μs, 10 μs, 25 μs, 50 μs, 75 μs, 100 μs, 150 μs, etc., or any value between these values.

[0041] Generally, the controller 112 includes one or more processors operable to generate the aforementioned command and control signals (e.g., after executing one or more instructions). The processor may be provided as a programmable processor operable to execute instructions (e.g., including one or more general-purpose computer processors, microprocessors, digital signal processors, or any other suitable form of circuitry, including a programmable logic device (PLD), a central processing unit (CPU), a graphics processing unit (GPU), an accelerated processing unit (APU), a real-time processing unit (RPU), a field-programmable gate array (FPGA), a field-programmable object array (FPOA), an application-specific integrated circuit (ASIC)—including digital, analog, and mixed analog / digital circuitry—or the like, or any combination thereof). Execution of instructions may be performed on a single processor, distributed among multiple processors, performed in parallel across processors within a device or across a network of devices, or the like, or any combination thereof.

[0042] Generally speaking, these instructions may be embodied as software (e.g., executable code, files, library files, or the like, or any combination thereof), hardware configuration (e.g., in the case of FPGA, ASIC, etc.), or the like, or any combination thereof, which instructions may be readily specified by one of ordinary skill in the art from the description provided herein (e.g., written in C, C++, Visual Basic, Java, Python, Tel, Perl, Scheme, Ruby, assembly language, hardware description language (e.g., LUCID, VHDL, or VERILOG, etc.)). Software is typically stored in one or more data structures conveyed by a tangible medium such as computer memory, which can be accessed by a processor (e.g., via one or more wired or wireless communication links). Examples of tangible media include magnetic media (e.g., tapes, hard drives, etc.), optical discs, volatile or non-volatile semiconductor memory (e.g., RAM, ROM, NAND flash memory, NOR flash memory, SONOS memory, etc.), or the like, or any combination thereof, and can be accessed locally, remotely (e.g., over a network), or any combination thereof.

[0043] It should be noted that various functions performed by controller 112 are described as being implemented by certain modules. This division of modules is for illustrative purposes only. In alternative aspects, the functions implemented by a particular module may be divided among multiple modules. Furthermore, in alternative aspects, two or more modules described herein may be integrated into a single module. Each module described herein may be implemented using hardware (e.g., an FPGA device, an ASIC, etc.), software (e.g., instructions executable by a processor), or any combination thereof.

[0044] Although the system 100 has been described above as including a single beam positioning system 108 and scan lens 110 (e.g., incorporated into a single common scan head 116), it should be understood that in other embodiments, the system 100 may include multiple scan heads 116, each of which includes a beam positioning system 108 and a scan lens 110 (and optionally independently movable by a separate optical stage). In such other embodiments, an optical switch may be provided and operable to selectively deflect the beam path 103 (e.g., from the beam positioning system 108 of one scan head 116 to the beam positioning system 108 of another scan head 116, and vice versa). In such cases, the optical switch would be provided in the beam path 103 optically upstream or downstream of the beam modulator 104 and communicatively coupled to the controller 112 (e.g., so as to be operable to deflect the beam path 103 in response to one or more commands output by the application analysis module). Alternatively, in embodiments where the beam modulator 104 is provided as a device capable of deflecting the beam path 103 (e.g., an AOM, AOD, EOM, EOD, etc. as described above), the beam modulator 104 is operable (e.g., in response to one or more frequency-modulated position commands output by an application analysis module) to selectively deflect the beam path 103 from the beam positioning system 108 of one scan head 116 to the beam positioning system 108 of another scan head 116, and vice versa.

[0045] although Figure 1 Not shown, the system 100 may optionally include a laser beam monitoring system operable to measure the optical power or energy in the laser energy beam propagating along the beam path 103. In one embodiment, the laser beam monitoring system may be provided as Figure 3 The laser beam monitoring system 300 shown in FIG.

[0046] refer to Figure 3, the laser beam monitoring system 300 includes a mirror 302 and a laser sensor 304. The mirror 302 is disposed within the beam path 103 and is provided as a partially transmissive mirror configured to reflect most of the light in the incident laser energy beam propagating along the beam path 103 (i.e., into the beam path 103r) and transmit a small amount of light (e.g., 2% or so) into the beam path 103t. Figure 3 In the embodiment, the mirror 302 can be arranged in the beam path 103 at any position optically "upstream" or "downstream" of the beam modulator 104. In this case, the beam path 103r corresponds to the above-mentioned Figure 1 Beam path 103 is shown and described. Laser sensor 304 is positioned to receive laser energy transmitted through mirror 302 (eg, propagating along beam path 103t).

[0047] In one embodiment, the laser sensor 304 is configured to measure the instantaneous optical power of the laser energy beam incident thereon and generate sensor data based on the sensing or measurement. The sensor data may be output to the controller 112 by any suitable means (e.g., via wired or wireless communication, as is known in the art). The controller 112 causes the sensor data to be stored (e.g., locally within the controller 112, on some computer memory within the system 100 accessible by the controller 112, or on some computer memory located remote from the system 100 but communicatively connected to the system 100 via one or more networks). In another embodiment, the sensor data output to the controller 112 may be further processed (e.g., time-integrated) at the controller 112 to derive the energy content of the laser energy beam incident on the laser sensor 304 (e.g., over a predetermined duration, etc.), and the processed sensor data may be stored (e.g., as described above).

[0048] In another embodiment, the laser sensor 304 is provided as an integrated detector (e.g., configured to measure the instantaneous optical power in a laser energy beam incident thereon and integrate the measured optical power to derive the energy content of the beam) and generates sensor data. The sensor data may be output to the controller 112 by any suitable means (e.g., via wired or wireless communication, as known in the art) and stored (e.g., as described above).

[0049] In some embodiments, sensor data obtained or otherwise processed or derived and stored or accessible at the controller 112 (e.g., periodically, during preventative maintenance cycles, or the like, or any combination thereof) may be monitored to determine whether the laser source 102 is operating properly. If it is determined that the laser source 102 is not operating properly, the controller 112 may control the operation of the beam modulator 104 to compensate for the operation of the laser source 102. For example, if the sensor data indicates that the measured or derived power or energy is below a target threshold, the controller 112 may adjust the operation of the beam modulator 104 to reduce the degree to which the beam modulator attenuates the incident laser energy beam. Similarly, if the sensor data indicates that the measured or derived power or energy is above a target threshold, the controller 112 may adjust the operation of the beam modulator 104 to increase the degree to which the beam modulator attenuates the incident laser energy beam.

[0050] When the mirror 302 is located optically downstream of the beam modulator 104 and the beam modulator 104 is as described above with respect to Figure 2 In the embodiment described above, the mirror 302 is disposed within the first-order beam path 206. However, in another embodiment, the mirror 302 may be disposed within the zero-order beam path 204. II. Embodiments for Compensating for Thermally Induced Beam Pointing Errors

[0051] According to embodiments described herein, one or more of the aforementioned beam path components will absorb at least some small portion of the energy within the high-power laser energy beam propagating along the beam path 103 from the beam modulator 104. Consequently, the stability of thermal gradients within the beam path components may be compromised (e.g., depending on one or more factors related to the operation of the system, as described above), resulting in thermally induced beam pointing errors that can adversely affect the accuracy and / or quality of processing the workpiece 101.

[0052] The present inventors have discovered that the aforementioned thermally induced beam pointing errors can generally be categorized as errors associated with "drift," "shift," or "scaling." As described in greater detail below, embodiments of the present invention implement thermal compensation techniques that can more quickly compensate for (i.e., prevent or otherwise reduce the effects of) one or more of these thermally induced beam pointing errors compared to the conventional techniques described above.

[0053] As used herein, "drift" refers to the movement of the waist of the focused laser energy beam along one or more axes (e.g., the aforementioned X-axis and / or Y-axis) of the scan field projected by the scan lens 110 onto the workpiece 101. Drift in one axis may be different from drift in another axis. Similarly, drift in any one axis may vary from system to system 100 and between different scan heads 116 in the same system 100 (e.g., depending on how the components in the beam path 103 of any system 100 are mounted and aligned). In some cases, heat buildup within an optical component 106 (e.g., a mirror) or within a mounting device associated with the optical component 106 may cause undesirable drift.

[0054] As used herein, "shift" refers to the movement of the optical waist of the focused laser energy beam along the beam path 103 as it propagates from the scan lens 110. Generally speaking, heat accumulation within the transmissive optical component 106 (e.g., a lens, prism, etc.) or the scan lens 110 can cause the optical waist to move away from the workpiece 101 (e.g., in a direction toward the scan lens 110), thereby changing (typically increasing) the size of the spot of the laser energy beam at the workpiece 101. Similarly, heat loss within the transmissive optical component 106 or the scan lens 110 can cause the optical waist to move away from the scan lens 110 (e.g., in a direction toward the workpiece 101), thereby changing (typically decreasing) the size of the spot of the laser energy beam at the workpiece 101.

[0055] As used herein, "zoom" refers to the degree to which the intended size of the scan field projected by the scan lens 110 is reduced or increased (e.g., due to the corresponding shortening or lengthening of the focal length of the scan lens 110 described above). Generally speaking, heat accumulation within the scan lens 110 can shrink the scan field (e.g., of the beam positioning system 108, etc.) projected therethrough onto the workpiece 101. Similarly, heat loss within the scan lens 110 can expand the scan field (e.g., of the beam positioning system 108, etc.) projected therethrough onto the workpiece 101.

[0056] To the extent that the aforementioned thermally induced beam pointing errors may be undesirably large, embodiments of the present invention compensate for their effects, for example, by counteracting or otherwise minimizing or reducing thermally induced drift, shift, and / or scaling. A. Generally speaking, embodiments of thermal compensation modules

[0057] According to an embodiment of the present invention, and with reference to Figure 4The application analysis module includes a thermal compensation module 400 operable to implement one or more thermal compensation techniques. As will be described in greater detail below, the thermal compensation module 400 processes laser power data 402 (and optionally beam position data 404) to estimate thermal response (e.g., of one or more beam path components or generally of the system 100, or any combination thereof) during a given processing cycle. As used herein, "thermal response" is a measure of how quickly thermal gradients can grow, dissipate, or otherwise change (e.g., in one or more beam path components or generally of the system 100, or any combination thereof) during a given processing cycle (e.g., in the presence or absence of optical power in a laser energy beam) to produce one or more of the aforementioned thermally induced beam pointing errors.

[0058] The thermal compensation module 400 may then apply one or more correction functions (also discussed in more detail below) to the estimated thermal response and, if applicable, any input preliminary position command 406 to generate one or more position command corrections 408. For example, and in Figure 5 In one embodiment shown in FIG, the thermal compensation module 400 may include one or more thermal response modules 500 operable to estimate the thermal response of the system 100, and a correction function module 502 operable to apply a correction function to the estimated thermal response.

[0059] Because the thermal compensation technique does not involve temperature measurement of any of the beam path components, the system 100 does not include any temperature sensors (e.g., thermocouples, thermistors, resistance thermometers, pyrometers, infrared thermometers, etc.) for measuring (directly or indirectly) the temperature of any of the aforementioned beam path components of the system 100, and thermally induced beam pointing errors can be quickly and accurately compensated during processing of the workpiece 101.

[0060] Laser power data 402 represents, is otherwise associated with, or relates to the amount of optical power or energy at one or more of the beam path components during a particular processing cycle. Laser power data 402 may be derived (e.g., by an application analysis module) or otherwise correspond to laser power commands, transmission commands, sensor data, or the like, or any combination thereof.

[0061] The beam position data 404 represents, is otherwise associated with, or relates to the position of the beam path 103 at one or more of the beam path components during a particular processing cycle. The beam position data 404 may be derived (e.g., by an application analysis module) or otherwise correspond to a position command, such as a beam position command, a frequency modulated position command, or the like, or any combination thereof.

[0062] Optionally, any of the aforementioned position commands (e.g., a beam position command, a frequency-modulated position command, an optical table position command, a workpiece table position command, or any combination thereof) may also be input to the thermal compensation module 400 to facilitate estimating the thermal response of the system 100 during a given processing cycle. The position commands, which serve as inputs to the thermal compensation module 400, are also referred to herein as "preliminary position commands" 406.

[0063] In general, the position command corrections 408 output by the thermal compensation module 400 will correspond to preliminary position commands associated with one or more of the aforementioned beam path components, the beam modulator 104, or any combination thereof. Accordingly, the application analysis module can be operable to apply (e.g., add, as indicated at 410) each position command correction 408 generated by the thermal compensation module 400 to the corresponding preliminary position command 406 to thereby generate a corrected position command 412. After the position command corrections 408 are applied to the corresponding preliminary position command 406, the preliminary position command 406 is adjusted based on the estimated thermal response of one or more of the beam path components during a given processing cycle, and the adjustment compensates for one or more of the aforementioned thermally induced beam pointing errors.

[0064] For example, one or more preliminary position commands 406 (e.g., the first beam position command and / or the first frequency modulated position command) may be adjusted at 410 to compensate for an estimated position shift in the positive direction along the X-axis (i.e., in the positive direction) during a given processing cycle. Figure 1 The drift that occurs along the X-axis (in the right direction as shown in FIG), and the adjustment is made to compensate for the estimated drift by generating one or more correction position commands 412 that, when operated by the beam positioning system 108 or the beam modulator 104, cause the estimated drift to decrease in the negative direction along the X-axis (i.e., in the right direction) during a given processing cycle. Figure 1 (leftward as depicted in the figure). While the examples provided above discuss compensation for estimated drift in the positive X-axis direction, it should be appreciated that drift estimated to occur in the negative X-axis direction can be compensated in a similar manner. Furthermore, while the examples provided above discuss compensation for estimated drift along the positive X-axis, it should be appreciated that compensation for estimated drift along the Y-axis can be implemented in a similar manner.

[0065] In another example, one or more preliminary position commands 406 (e.g., a first beam position command and / or a first frequency-modulated position command) may be adjusted at 410 to compensate for scaling estimated to cause a reduction in the field size along the X-axis during a given positioning cycle, and the adjustment may compensate for the estimated scaling by generating one or more correction position commands 412, which, when operated by the beam positioning system 108 or the beam modulator 104, offset the estimated scaling by increasing the deflection of the beam path 103 along the X-axis during the given cycle. While the examples provided above discuss compensation for estimated scaling (i.e., reduction) in the field size along the X-axis, it should be understood that an expansion of the field size estimated to occur along the X-axis may be compensated in a similar manner. Furthermore, while the examples provided above discuss compensation for estimated scaling along the X-axis, it should be understood that compensation for estimated scaling (i.e., reduction or expansion of the field size along the Y-axis) may be implemented in a similar manner.

[0066] In another example, one or more preliminary position commands 406 (e.g., optical table position commands and / or workpiece stage position commands) may be adjusted at 410 to compensate for a displacement estimated to cause the optical waist to move toward the scan lens 110 during a given positioning cycle, and the adjustment compensates for the estimated displacement by generating one or more correction position commands 412 that, when operated by the optical table and / or workpiece stage 114, offset the estimated displacement by moving the scan lens 110 toward the workpiece 101 and / or moving the workpiece 101 toward the scan lens 110 during the given cycle. Although the examples provided above discuss the displacement of the optical waist toward the scan lens 110 (i.e., in the positive Z-axis direction or upwards, as in FIG. 1 ), the optical table position commands 412 may be adjusted to compensate for the estimated displacement by generating one or more correction position commands 412 that, when operated by the optical table and / or workpiece stage 114, offset the estimated displacement by moving the scan lens 110 toward the workpiece 101 and / or moving the workpiece 101 toward the scan lens 110 during the given cycle. Figure 1 ), but it will be appreciated that the estimated shift occurring in the negative Z-axis direction may be compensated for in a similar manner.

[0067] While the examples described above have described exemplary procedures by which the corrective position commands 412 may be generated and output to individually compensate for thermally induced drift, shift, and scaling, it should be understood that the embodiments may be combined or otherwise adapted as needed to generate corrective beam position commands adapted to compensate for one or more of thermally induced drift, shift, and scaling along one or more axes. The application analysis module may be operable to output the corrective position commands 412 (e.g., as position commands conveyed by one or more control signals) to one or more of the beam modulator 104, the beam positioning system 108, the optical stage, the workpiece stage 114, or any combination thereof (e.g., in a coordinated manner, as described above), thereby ensuring that the workpiece 101 is processed during a given processing cycle in a manner that compensates for one or more of the aforementioned thermally induced beam pointing errors. B. Example of Estimation of Thermal Response

[0068] As mentioned above, thermal compensation module 400 processes laser power data 402 (and optionally beam position data 404) to estimate one or more thermal responses of system 100 during a given processing cycle, insofar as the thermal response is associated with one or more of the aforementioned thermally induced beam pointing errors.

[0069] In one embodiment, the thermal response of system 100 may be estimated by estimating the thermal response of one or more of the beam path components of system 100. Thus, the thermal response of system 100 during, for example, the nth processing cycle may be described as the sum of all estimated thermal responses of the beam path components in system 100, for example, as given by the following function (1): , (1) where i represents a beam path component of the system 100 having m beam path components. Therefore, TR(n) i represents the estimated thermal response of the i-th beam path component during the n-th processing cycle, P(n) i represents the laser power data for the i-th beam path component during the n-th processing cycle, P(n-1) i represents the laser power data of the i-th beam path component during the previous processing cycle (ie, during the n-1-th processing cycle), and a i is the time constant associated with the i-th beam path component. In general, the time constant a i is a parameter that characterizes the general response of the i-th beam path component to a thermal input. According to various embodiments described herein, a may be empirically set, modeled, or otherwise determined (e.g., via system calibration) using any suitable or known technique in the art. i The value of .

[0070] In one embodiment, and to the extent that thermally induced beam pointing errors produced by beam path components are a response of the beam path components to heat, the time constant a i can be considered as a parameter that characterizes how quickly thermally induced beam pointing errors are generated in response to a thermal input. However, depending on the beam path components and / or the thermally induced beam pointing errors, the inventors have discovered that thermally induced beam pointing errors may be generated attributable to multiple responses of the beam path components to the thermal input, where the multiple responses are associated with different time scales. Therefore, the time constant a i It can be a single value, or if thermally induced beam pointing errors occur due to multiple responses, the time constant a i Can be represented as a combination (e.g., linearly or otherwise) of multiple values ​​(e.g., each value associated with a separate value in a different time scale).

[0071] In another embodiment, and to the extent that different thermally induced beam pointing errors produced by beam path components may occur on different time scales, the time constant a i can be represented as a combination (e.g., linear or otherwise) of multiple values ​​(e.g., each value associated with a respective value in a different time scale). However, in another embodiment, different time constants a i (whether expressed as a single value or as a combination of values, as described above) can be used in different instances of function (1) to estimate different thermal responses of system 100 during a given processing cycle. For example, a first instance of function (1) can be used to estimate the thermal response of system 100 responsible for drift (i.e., the sum of the thermal responses of all beam path components), a second instance of function (1) can be used to estimate the thermal response of system 100 responsible for displacement (i.e., the sum of the thermal responses of all beam path components), and a third instance of function (1) can be used to estimate the thermal response of system 100 responsible for scaling (i.e., the sum of the thermal responses of all beam path components). If a beam path component does not contribute to a particular thermally induced beam pointing error, then the time constant a for that beam path component i will be zero. The first instance of function (1) is also referred to herein as the "drift estimation function," the second instance of function (1) is also referred to herein as the "shift estimation function," and the third instance of function (1) is also referred to herein as the "scale estimation function."

[0072] In another embodiment, and to the extent that different thermally induced beam pointing errors produced by beam path components can be produced on the same time scale, the common time constant a i (whether expressed as a single value or as a combination of values, as described above) can be used in a common instance of function (1) to estimate the thermal response of system 100 that causes different thermally induced beam pointing errors during a given processing cycle. For example, a common instance of function (1) can be used to estimate the common thermal response of system 100 responsible for generating the shift and scale (i.e., the sum of the thermal responses of all beam path components). The common instance of function (1) in this embodiment may also be referred to herein as a "shift / scale estimation function." Similarly, if a beam path component does not contribute to any of the different thermally induced beam pointing errors, then the time constant a for that beam path component is i will be zero.

[0073] As mentioned above, if the beam path component does not contribute to a specific thermally induced beam pointing error, then the time constant a for the beam path component iwill be zero. In an alternative embodiment, if the contribution of a beam path component to a particular thermally induced beam pointing error is less than a predetermined threshold amount, then the contribution to the estimated thermal response for the beam path component is not included in each of the functions (1). For example, the beam positioning system 108 may not contribute to shift and scale (or contribute less than a predetermined threshold amount); therefore, the estimated thermal response of the beam positioning system 108 need not be included in the shift and / or scale estimation functions. In another example, the scan lens 110 may not contribute to drift (or contribute less than a predetermined threshold amount); therefore, the estimated thermal response of the scan lens need not be included in the drift estimation function.

[0074] In general, each beam path optical component absorbs some small portion of the optical power in the laser energy beam propagating along beam path 103. Thus, the laser power data P(n) for one beam path component during a given processing cycle may differ from the power data for a different beam path component during the same processing cycle. Further depending on the configuration of the system, the difference in laser power data for at least two of the m beam path components may be relatively small or insignificant, and thus, in another embodiment, the same laser power data associated with a given processing cycle may be used for at least two of the m beam path components.

[0075] In another embodiment, the thermal response of the system 100 as a whole can be estimated without explicitly considering the individual thermal responses of the beam path components of the system 100. In this sense, the thermal response of the system 100 will simply be related to one or more thermally induced beam pointing errors detected (e.g., through direct or indirect observation, measurement, etc.) at the output location (e.g., at the workpiece 101) relative to the scan lens 110. Thus, the thermal response of the system 100 during the nth processing cycle can be given by the following function (2): , (2) Where TR(n) represents the estimated thermal response of the system 100 during the nth processing cycle, P(n) represents the laser power data of the scan lens 110 during the nth processing cycle, P(n-1) represents the laser power data of the scan lens 110 during the previous (n-1th) processing cycle, and the time constant α indicates how quickly the temperature of the system 100 changes in response to the presence or absence of laser energy propagating along the beam path 103. The value of α can be set empirically or otherwise set using any suitable or known technique in the art. As with function (1), different instances of function (2) can be used to estimate the thermal response associated with different thermally induced beam pointing errors. For example, the first instance of function (2) can be provided as the aforementioned "drift estimation function", the second instance of function (2) can be provided as the aforementioned "shift estimation function", and the third instance of function (2) can be provided as the aforementioned "scale estimation function". In another example, the common instance of function (2) can be provided as the aforementioned "shift / scale estimation function".

[0076] As will be appreciated, functions (1) and (2) above are examples of first-order infinite impulse (IIR) filters. Such filters may be provided as digital filters, analog filters, or the like, or any combination thereof. Nevertheless, embodiments of the present invention are not limited to the use of IIR filters to estimate the thermal response associated with system 100. For example, other filters that may be used (whether implemented digitally or analogously) include biquad filters, Butterworth filters, or the like, or any combination thereof. The coefficients and their respective orders of any filter implementation in each thermal response module 500 may be selected or set empirically or by any other technique suitable or known in the art. C. Examples of Correction Functions

[0077] As mentioned above, the thermal compensation module 400 is operable to apply one or more correction functions to the estimated thermal response, and optionally any input preliminary position command 406, to generate one or more position command corrections 408. In general, the correction function can be provided as a combination of any suitable function or basis functions suitable for modeling thermally induced beam pointing errors caused by drift, shift, or scaling. Examples of suitable functions include a first-order linear regression function, an n-th order polynomial function (where n is two or greater), or the like.

[0078] The correction function used to generate the position command correction 408 may vary depending on the estimated thermal response to which it is applied, on the type of thermally induced beam pointing error to be compensated, on the preliminary position command to which it is intended to be adjusted, or the like, or any combination thereof. An example of a correction function n that may be applied to compensate for drift in the X and Y axes during a given processing cycle may be described by the following correction functions (3) and (4): , (3) , (4) The values ​​of the coefficients Adx, Bdx, Ady, and Bdy may be set empirically or otherwise using any suitable or known technique in the art, Adx and Ady may be the same or different, and Bdx and Bdy may be the same or different. In this example, TR(n) represents the estimated thermal response output by a drift estimation function, such as that associated with function (1) or (2).

[0079] An example of a correction function n that may be applied to compensate for displacement (eg, in the Z axis) during a given machining cycle may be described by the following correction function (5): , (5) The values ​​of the coefficients Asz and Bsz may be set empirically or otherwise using any suitable or known technique in the art, and Asz, Adx, and Ady may be the same or different, and Bsz, Bdx, and Bdy may be the same or different. In this example, TR(n) represents the estimated thermal response output by the aforementioned shift estimation function or shift / scaling estimation function associated with function (1) or (2).

[0080] Examples of correction functions that may be applied to compensate for scaling in the X and Y axes during a given machining cycle may be described by the following correction functions (6) and (7): , (6) , (7) The values ​​of the coefficients Asz and Bsz may be set empirically or otherwise using any suitable or known technique in the art, and Asz, Adx, and Ady may be the same or different, and Bsz, Bdx, and Bdy may be the same or different. Xprelim_pos_command(n) represents a first beam position command and / or a first frequency-modulated position command to be preliminarily adjusted by a corresponding position command correction 408 and thereafter applied to the first galvanometer mirror and / or the first AO device, respectively, to deflect the beam path 103 in a desired manner along the X-axis (e.g., as described above) during the nth processing cycle. Yprelim_pos_command(n) represents a second beam position command and / or a second frequency-modulated position command to be preliminarily adjusted by the corresponding position command correction 408 and thereafter applied to the second galvanometer mirror and / or the second AO device, respectively, to deflect the beam path 103 in a desired manner along the Y axis (e.g., as described above) during the nth processing cycle. In this example, TR(n) represents the estimated thermal response output by the aforementioned scaling estimation function associated with function (1) or (2).

[0081] The coefficients of the correction functions (3) to (7) may be empirically set, modeled, or otherwise determined (e.g., via system calibration) using any technique suitable or known in the art. Furthermore, the coefficients of the correction functions (3) to (7) may vary depending on the size, number, and density of features to be formed in the workpiece 101, on the placement of the workpiece 101 on the workpiece platform 114, on the utilization of the scan field projected by the scan lens 110, on the position of the scan field (or the position of the centroid of the scan field) within the scan lens during a processing cycle, or the like, or any combination thereof. III. Conclusion

[0082] The foregoing description describes embodiments and examples of the present invention and should not be construed as limiting thereof. Although several specific embodiments and examples have been described with reference to the drawings, it should be readily apparent to those skilled in the art that many modifications to the disclosed embodiments and examples and other embodiments are possible without materially departing from the novel teachings and advantages of the present invention.

[0083] For example, the embodiments described above provide systems and techniques for real-time compensation of thermally induced beam pointing errors. It should be appreciated that the embodiments described can be adapted for non-real-time compensation of thermally induced beam pointing errors. For example, the application analysis module can generate a set of preliminary position commands necessary to form features in the workpiece 101 as needed (e.g., as described above) and input those preliminary position commands to the thermal compensation module 400. The thermal compensation module 400 can process the preliminary position commands in the set (e.g., as described above) to generate a set of position command corrections 408. The application analysis module can then apply each position command correction 408 to the corresponding preliminary position command (e.g., at 410, as discussed above) to generate a set of corrected position commands 412. After the set of corrective position commands 412 are generated, the corrective position commands 412 may be sequentially output (e.g., to the beam modulator 104, the beam positioning system 108, the optical table, and / or the workpiece table 114) as described above and in a coordinated manner with commands output to any other components of the system 100 (e.g., the laser source 102) so that the workpiece 101 will be processed to form features therein as desired.

[0084] In another example, although compensation for the estimated displacement has been discussed above as being achieved by adjusting the position of the optical stage and / or the workpiece stage 114, it should be understood that the displacement can be compensated for in other ways. For example, and in embodiments where the beam modulator 104 includes the aforementioned first and second AO devices (and associated drive circuitry), the beam modulator 104 can be operated to rapidly move the beam waist toward or away from the scan lens 110 by “chirping” the frequency of the drive signals applied to the first and second AO devices in any manner suitable or otherwise known in the art.

[0085] Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the claims. For example, one of ordinary skill in the art will understand that the subject matter of any sentence, paragraph, example, or embodiment may be combined with some or all of the subject matter of any other sentence, paragraph, example, or embodiment, unless such combinations are mutually exclusive. The scope of the present invention is therefore to be determined by the following claims, and equivalents of the claims are intended to be included within the scope of the present invention.

Claims

1. A laser processing system for processing a workpiece, characterized in that: The system includes: a laser source operable to output a beam of laser energy, wherein the beam of laser energy propagates along a beam path; a plurality of beam path components disposed within the beam path, the plurality of beam path components comprising: a beam positioning system operative to deflect the beam path within a scan field in response to position commands; and a scan lens configured to focus the laser energy beam deflected by the beam positioning system, thereby producing a focused laser energy beam having a beam waist; and A controller communicatively coupled to the beam positioning system, the controller configured to generate the position command based at least in part on an estimated thermal response of at least one of the plurality of beam path components to the laser energy beam during a predetermined processing cycle, and to output the generated position command to the beam positioning system to operate the beam positioning system during the processing cycle.

2. The system according to claim 1, wherein The at least one of the plurality of beam path components includes the scan lens.

3. The system according to claim 1, wherein: The at least one of the plurality of beam path components includes the beam positioning system.

4. The system according to claim 1, wherein: The controller is further configured to estimate the thermal response of the at least one of the plurality of beam path components.

5. The system according to claim 4, wherein: The controller is configured to estimate the thermal response of the at least one of the plurality of beam path components based at least in part on laser power data corresponding to an amount of optical power or energy present at the at least one of the plurality of beam path components during the processing cycle.

6. The system according to claim 5, wherein: The controller is configured to estimate the thermal response of the at least one of the plurality of beam path components based at least in part on beam position data corresponding to a position of the beam path at the at least one of the plurality of beam path components during the processing cycle.

7. The system according to claim 5, wherein: The controller is configured to estimate the thermal response of the at least one of the plurality of beam path components based at least in part on preliminary position command beam position data corresponding to a position of the beam path at the at least one of the plurality of beam path components during the processing cycle.

8. The system according to claim 1, wherein: It further includes a beam modulator operative to attenuate the laser energy.

9. The system according to claim 1, wherein: It further includes a laser beam monitoring system operable to measure an optical quality of the laser energy beam and generate sensor data representative of the measured optical quality.

10. The system according to claim 9, wherein: The controller is configured to estimate the thermal response of the at least one of the plurality of beam path components based at least in part on the sensor data.

11. The system according to claim 1, wherein: The system does not include a temperature sensor configured to sense the temperature of the beam positioning system or the scan lens.

12. The system according to claim 1, wherein It further includes at least one stage operative to impart relative movement between the optical waist and the workpiece in response to stage position commands.

13. The system according to claim 12, wherein: The at least one platform is operative to move the workpiece.

14. The system according to claim 12, wherein: The at least one stage is operative to move the scan lens.

15. The system of claim 12, wherein: The controller is communicatively coupled to the beam positioning system of the at least one stage, the controller being configured to generate the stage position command based at least in part on the estimated thermal response of at least one of the plurality of beam path components to the laser energy beam during the predetermined processing cycle, and to output the generated stage position command to the at least one stage to operate the at least one stage during the processing cycle.

16. A laser processing system for processing a workpiece, characterized in that: The system includes: a laser source operable to output a beam of laser energy, wherein the beam of laser energy propagates along a beam path; a plurality of beam path components disposed within the beam path, the plurality of beam path components comprising: a scan lens configured to focus the laser energy beam deflected by the beam positioning system, thereby producing a focused laser energy beam having a beam waist; and at least one stage operative to impart relative movement between the optical waist and the workpiece in response to stage position commands; and a controller communicatively coupled to the beam positioning system of the at least one stage, the controller configured to generate the stage position command based at least in part on an estimated thermal response of at least one of the plurality of beam path components to the laser energy beam during a predetermined processing cycle, and to output the generated stage position command to the at least one stage to operate the at least one stage during the processing cycle.

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