Patent Application
20250164831
Embodiments of the present invention relate generally to acousto-optic deflectors, laser-processing apparatus incorporating the same, and techniques of operating the same.
Referring to
In order to effect extremely rapid deflection of the beam path 112 in two dimensions relative to the workpiece 102 (e.g., along the X-axis and Y-axis, which is orthogonal to the illustrated X-and Z-axes), the positioner 106 can include a galvanometer mirror scanning system and an acousto-optic deflector (AOD) scanning system arranged optically “upstream” of the galvanometer mirror scanning system. The galvanometer mirror scanning system typically includes a pair of galvanometer mirrors arranged optically in series with each other (e.g., such that one galvanometer mirror is operative to deflect the beam path 112 along the X-axis and the other galvanometer mirror is operative to deflect the beam path 112 along the Y-axis). The AOD scanning system typically includes a pair of acousto-optic deflectors (AODs) arranged optically in series with each other. For example, and with reference to
As will be recognized by those of ordinary skill in the art, AODs utilize diffraction effects caused by one or more acoustic waves propagating through an AO cell to diffract an incident optical wave (i.e., a beam of laser energy, in the context of the present application) contemporaneously propagating through the AO cell. Upon driving an AOD to diffract an incident beam of laser energy, a diffraction pattern is produced that typically includes zeroth- and first-order diffraction peaks, and may also include other higher-order diffraction peaks (e.g., second-order, third-order, etc.). Generally, the amount of optical power diffracted into the first-order diffraction peak (e.g., as compared to the zeroth-order diffraction peak) is determined by the manner in which the AOD is driven to diffract the incident beam of laser energy. As is known in the art, the portion of the diffracted beam of laser energy in the zeroth-order diffraction peak is referred to as a “zeroth-order” beam, the portion of the diffracted beam of laser energy in the first-order diffraction peak is referred to as a “first-order” beam, and so on. Generally, the zeroth-order beam and other diffracted-order beams (e.g., the first-order beam) propagate along different beam paths upon exiting the AO cell (e.g., through an optical output side of the AO cell). For example, the zeroth-order beam propagates along a zeroth-order beam path, the first-order beam propagates along a first-order beam path, and so on.
In
The AO cell of an AOD will absorb some amount of the beam of laser energy that propagates through it. If the beam of laser energy is sufficiently high in power, the absorbed energy can locally heat the material from which the AO cell is formed and induce a thermal lensing phenomenon within the AO cell. Thermal lensing can focus, defocus, or otherwise distort the wavefront of the beam of laser energy propagating along the beam path 112. Thermal lensing within an AO cell is not, by itself, necessarily undesirable. If the thermal gradient within the AO cell is relatively constant and stationary (e.g., while processing the workpiece 102), then wavefront distortion effects (e.g., focusing effects, defocusing effects or other wavefront distortions, as noted above) can usually be taken into account to ensure that the workpiece 102 is satisfactorily processed. However, if the thermal gradient within the AO cell is not relatively constant or stationary, then it becomes very difficult to adequately compensate for changes in wavefront distortion effects.
In the context of the positioner 106 shown in
One embodiment of the present invention can be characterized as a system that includes a first acousto-optic deflector (AOD) for diffracting an incident beam of laser energy to thereby produce and output therefrom a first beam of laser energy and a second beam of laser light, a second AOD arranged to receive the first beam of laser energy and for diffracting the received first beam of laser energy to thereby produce and output therefrom a third beam of laser energy and a fourth beam of laser energy, at least one first beam trap arranged and configured to absorb the second beam of laser energy output from the first AOD, at least one second beam trap arranged and configured to absorb the fourth beam of laser energy output from the second AOD and a controller communicatively coupled to the first AOD and to the second AOD, wherein the controller is configured to operate of the first AOD while not operating the second AOD.
Another embodiment of the present invention can be characterized as a system that includes a first AOD operative to diffract an incident beam of laser light to thereby produce and output therefrom a first beam of laser light and a second beam of laser light, a second AOD arranged to receive the first beam of laser light and operative to diffract the received first beam of laser light to thereby produce and output therefrom a third beam of laser light, at least one first beam trap arranged and configured to absorb the second beam of laser light output from the first AOD, at least one exercise beam trap arranged and configured to absorb the third beam of laser light output from the second AOD and a controller communicatively coupled to the first AOD and to the second AOD. The controller is configured to command a first RF driver to apply a first drive signal to a transducer of the first AOD and command a second RF driver to apply a second drive signal to a transducer of the second AOD. The controller is operative to operate the first AOD to diffract the incident beam of laser light along an exercise beam path to the second AOD. The second AOD is configured to diffract the beam of laser light from the first AOD along an exercise beam path to an exercise beam trap. The drive signal is modulated through a range of RF frequencies, thereby controlling a temperature gradient within the first AOD and the second AOD.
Example embodiments are described herein with reference to the accompanying FIGS. Unless otherwise expressly stated, in the drawings the sizes, positions, etc., of components, features, elements, etc., as well as any distances therebetween, are not necessarily to scale, but are exaggerated for clarity.
The terminology used herein is for the purpose of describing particular 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, a range of values, when recited, includes both the upper and lower limits of the range, as well as any sub-ranges therebetween. Unless indicated otherwise, terms such as “first,” “second,” etc., are only used to distinguish one element from another. For example, one node could be termed a “first node” and similarly, another node could be termed a “second node”, or vice versa. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.
Unless indicated otherwise, the term “about,” “thereabout,” “substantially,” etc., means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art.
Spatially relative terms, such as “below,” “beneath,” “lower,” “above,” and “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature, as illustrated in the FIGS. It should be recognized that the spatially relative terms are intended to encompass different orientations in addition to the orientation depicted in the FIGS. For example, if an object in the FIGS. is turned over, elements 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 an orientation of above and below. An object may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.
Like numbers refer to like elements throughout. Thus, the same or similar numbers may be described with reference to other drawings even if they are neither mentioned nor described in the corresponding drawing. Also, even elements that are not denoted by reference numbers may be described with reference to other drawings.
It will be appreciated that many different forms and embodiments are possible without deviating from the spirit and teachings of this disclosure and so this disclosure should not be construed as limited to the example embodiments set forth herein. Rather, these examples and embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the disclosure to those skilled in the art.
According to embodiments of the present invention, the AOD scanning system in the positioner 106 described above with respect to in
Furthermore, the AOD scanning system 300 shown in
Generally, the AO cell of each of the first AOD 302 and second AOD 304 is formed of a material that is susceptible to thermal lensing (e.g., as described above) in the presence of a beam of laser energy having a sufficiently high optical power propagating along the beam path 112. For example, the AO cell of each of the first AOD 302 and second AOD 304 can be formed of crystalline germanium. In this example, the beam of laser energy propagating along the beam path 112 would have a wavelength in a range from 2 μm (or thereabout) to 20 μm (or thereabout) and be of a sufficiently high average power (e.g., greater than or equal to 150 W, or thereabout) to induce thermal lensing within the AO cell of the first AOD 302 and the second AOD 304. In this case, the beam of laser energy can be generated by a laser source (e.g., the laser source 104) provided as a suitably high-power carbon dioxide or carbon monoxide gas laser, for example. Typically, high-power carbon dioxide or carbon monoxide gas lasers are configured to generate continuous wave (CW) or quasi-CW (QCW) beams of laser energy, or to generate beams laser energy comprised of discrete pulses (typically many tens of microseconds, or longer, in duration).
Although not illustrated, each of the first AOD 302 and the second AOD 304 includes at least one transducer attached to the AO cell thereof. Generally, the transducer is a piezoelectric transducer operative to vibrate in response to an externally-applied RF signal (i.e., drive signal). The transducer is attached to the AO cell of an AOD such that the vibrating transducer creates a corresponding acoustic wave that propagates within the AO cell. As will be understood by those of ordinary skill, the amplitude, frequency and duration of the acoustic wave correspond to the amplitude, frequency and duration of the RF power in the applied drive signal.
Drive signals can be applied to an input of the transducer by an associated RF driver. Thus the AOD scanning system 300 can, for example, include a first RF driver 314 electrically connected each transducer of the first AOD 302 and a second RF driver 316 electrically connected each transducer of the second AOD 304. Generally, each of the RF driver 314 and the second RF driver 316 can include an RF synthesizer, an amplifier coupled to an output of the RF synthesizer and an impedance matching circuit coupled to an output of the amplifier. The RF synthesizer (e.g., a DDS synthesizer) generates and outputs a preliminary signal of a desired frequency; the amplifier amplifies the preliminary signal to a desired amplitude, thereby transforming the preliminary signal into the drive signal; and the drive signal is applied to the input of the transducer via the impedance matching circuit.
Operations of the first RF driver 314 and the second RF driver 316 can be controlled in response to command signals output by a controller (e.g., controller 318) to generate drive signals of different frequencies and amplitudes, which can be rapidly applied (e.g., at rates up to or greater than 1 MHz) to each transducer of their respective AODs. The controller 318 will thus replace the controller 110 shown in
Generally, when an AOD is driven in response to an applied drive signal, the ratio of optical power diffracted into the first-order beam path 112 vs. a zeroth-order beam path is determined by the amplitude of RF power in the applied drive signal and, in some cases, the frequency of the RF power in the applied drive signal. Furthermore, the amount of optical power diffracted into the first-order beam path 112 will increase with increasing RF power, until it reaches a maximum at some saturation level of RF power. The act of setting or otherwise modulating the amplitude of the RF power in a drive signal to be applied to the AOD is referred to herein as “amplitude modulation control.” The act of setting or otherwise adjusting the amount of optical power diffracted into the first order beam path 112 can be considered as setting or adjusting the “transmission” of the AOD.
When an AOD includes multiple transducers, the transmission of the AOD may also be adjusted by applying a drive signal to each of the transducers, wherein the RF frequency of each applied drive signal is the same, but slightly out of phase with one another. As a result, acoustic waves generated within the AO cell of the AOD interfere in at least a somewhat destructive manner. Such destructively-interfering acoustic waves have the effect of decreasing the transmission of the AOD, whereby the degree to which the AOD transmission is decreased corresponds to the degree to which the acoustic waves interfere destructively with each other within the AO cell. The act of selecting or otherwise modulating the phase relationship of drive signals to be applied to different transducers of a common AOD is referred to herein as “phase modulation control.” It should be noted, however, that phase modulation control cannot be used to completely prevent optical power from diffracted into the first order beam path 112.
By successively driving the first AOD 302 and second AOD 304 using drive signals of different frequencies, the AOD scanning system 300 can be operated to rapidly deflect the first-order beam path 112″ at different angles, to different positions within a two-dimensional scan field. Moreover, the amplitude of RF power in each drive signal successively applied to first AOD 302 and/or the second AOD 304 can be varied (if necessary) as a function of the frequency of the drive signal to ensure that amount of optical power propagating along the first-order beam path 112″ is at least substantially constant, regardless of the frequencies in the drive signals applied to the first AOD 302 and the second AOD 304.
According to embodiments discussed herein, the beam of laser energy propagating along the beam path 112 to the AOD scanning system 300 is generated by a suitably high-power laser (e.g., a carbon dioxide or carbon monoxide gas laser as described above) and the controller 318 is configured to operate the first RF driver 314 and the second RF driver 316 to drive the first AOD 302 and the second AOD 304, respectively, to create temporally-sliced pulses of laser energy from the incident beam. These temporally-sliced pulses of laser energy are thus output from the AOD scanning system 300 along beam path 112″ to propagate to the scan lens 108.
For example, and with reference to
Although
Referring now to
In
For purposes of facilitating discussion herein, it is assumed that the drive signals applied to the first AOD 302 giving rise to the temporal transmission profile delineated by 408 have the same frequencies, and it is also assumed that the drive signals applied to the second AOD 304 giving rise to the temporal transmission profile delineated by 410 have the same frequencies. Alternatively, however, the frequency in the drive signal applied to the first AOD 302 giving rise to the temporal transmission profile delineated by 408 during the first slice period 406 can be different from the frequency in the drive signal applied to the first AOD 302 giving rise to the temporal transmission profile delineated by 408 during the second slice period 406. Likewise, the frequency in the drive signal applied to the second AOD 304 giving rise to the temporal transmission profile delineated by 410 during the first slice period 406 can be different from the frequency in the drive signal applied to the second AOD 304 giving rise to the acoustic waveform delineated by 410 during the second slice period 406. In these alternative cases, the amplitude and/or phase (in embodiments in which the first AOD 302 and/or the second AOD 304 include multiple transducers) of the drive signals applied to the first AOD 302 and/or the second AOD 304 and giving rise to the temporal transmission profiles delineated by 408 and 410 during the first and second slice periods 406 can be set (e.g., as discussed above) to ensure that the average optical power in the laser pulse 404 created during the first slice period 406 is at least substantially the same as the average optical power in the laser pulse created during the second slice period 406.
As shown in
Provided as described above, the first beam trap 310 of the AOD scanning system 300 prevents the zeroth-order beam path 306 from reaching the AO cell of the second AOD 304, thereby avoiding problems discussed above with respect to
Because the AO cell of the second AOD 304 is formed of a material that is susceptible to thermal lensing in the presence of laser energy propagating from the first AOD 302 along the first-order beam path 112′, the AO cell of the second AOD 304 may introduce wavefront distortion effects such as described above, or none at all, to the beam of laser energy propagating therefrom along the first-order beam path 112″ (and, ultimately, to scan lens 108) depending on manner in which the first AOD 302 has been previously driven. For example if, prior to time t1 in
To prevent or beneficially reduce the undesirable evolution of thermal gradients within the AO cell of the second AOD 304, the first AOD 302 is driven (in response to one or more drive signals applied by the first RF driver 314 as commanded by the controller 318) during one or more time periods (each referred to herein as a “optical exercise period”) occurring outside a slice period. However, the second AOD 304 is not driven during any optical exercise period. Thus, during an optical exercise period, laser energy incident upon the AO cell of the first AOD 302 is diffracted to propagate along its respective first-order beam path 112′ (e.g., as discussed above). The AO cell of the second AOD 304 then absorbs a portion of the laser energy propagating along the first-order beam path 112′ of the first AOD 302, which results in local heating of—and thermal lensing within—the AO cell of the second AOD 304. Heating of the second AOD 304 in this manner can herein be described as optically “exercising” the second AOD 304.
Generally, the timing and duration of the optical exercise periods are selected in order to ensure that the thermal gradient within the AO cell of the second AOD 304 is relatively constant over time so that changes in wavefront distortion effects are negligible or otherwise sufficiently reduced so as to ensure that a workpiece, such as workpiece 102, can be satisfactorily processed. For example, prior to time t1 in
To prevent or beneficially reduce the undesirable evolution of thermal gradients within the AO cell of the second AOD 304 during a slice period or across successive slice periods, the controller 318 may cause an optical exercising operation to be performed, e.g., as shown in
Although
As mentioned above, although
To prevent or beneficially reduce the undesirable dissipation or diminishment of thermal gradients within the AO cell of the second AOD 304 between slice periods associated with successively-generated laser pulses 402 (e.g., between slice periods 406′and 406″, respectively associated with laser pulses 402′ and 402″), the controller 318 may cause one or more optical exercising operations to be performed, e.g., as shown in
As shown in
Further, as shown in
Although
From the embodiments discussed above, it will be appreciated that the controller 318 is configured to perform one or more optical exercising operations (e.g., as described above) during the entirety of any non-slice period, during the entirety of any head portion of a laser pulse, during the entire of any tail portion of a laser pulse, or any combination thereof. In other embodiments, the controller 318 causes optical exercising operations to be performed during only a portion of any non-slice period, during only a portion of any head portion of a laser pulse, during only a portion of any tail portion of a laser pulse, or any combination thereof. In embodiments in which the controller 318 causes optical exercising operations to be performed during only a portion of any non-slice period (as opposed to an entire non-slice period), during only a portion of a head portion of a laser pulse (as opposed to an entire head portion of the laser pulse) and/or during only a portion of any tail portion of a laser pulse (as opposed to an entire tail portion of the laser pulse), the optical exercise period 500 may be referred to as a “tailored optical exercise period” 500.
According to embodiments of the present invention, the duration of any tailored optical exercise period 500, during which an optical exercising operation is performed, can correspond to the optical power in the laser pulse (e.g., laser pulse 402) during the tailored optical exercise period 500. For example, less laser energy will be diffracted to the AO cell of the second AOD 304 during a tailored optical exercise period 500 that occurs near the beginning of the head portion (or near the end of the tail portion) of a laser pulse 402 as compared to a tailored optical exercise period 500 that occurs near the end of the head portion (or near the beginning of the tail portion) of the laser pulse 402. Accordingly, the controller 318 may be configured to perform an optical exercising operation during a relatively long tailored optical exercise period 500 occurring near the beginning of the head portion of a laser pulse 402 or during a relatively short tailored optical exercise period 500 occurring near the end of the head portion of the laser pulse 402. Likewise, the controller 318 may be configured to perform an optical exercising operation during a relatively short tailored optical exercise period 500 occurring near the beginning of the tail portion of a laser pulse 402 or during a relatively long tailored optical exercise period 500 occurring near the end of the tail portion of the laser pulse 402.
According to other embodiments of the present invention, the duration of any tailored optical exercise period 500, during which an optical exercising operation is performed, can also correspond to the actual or estimated thermal gradient within the AO cell of the second AOD 304 just prior to the tailored optical exercise period 500. To facilitate performance of an optical exercising operation during a tailored optical exercise period, the controller 318 may be provided with (or otherwise have access to, e.g., via one or more wired or wireless networks, not shown) pulse shape information describing the temporal optical power profile of the laser pulse 402 (i.e., from the beginning of the head portion to the end of the tail portion) or amount of energy within the laser pulse 402 in various temporal “slices” of the laser pulse 402.
As mentioned above, the controller 318 may be provided with (or otherwise have access to, e.g., via one or more wired or wireless networks, not shown) pulse shape information to facilitate performance of an optical exercising operation during a tailored optical exercise period. The controller 318 may receive information indicating the pulse shape information associated with laser pulses to be generated by the laser source 104, or may otherwise derive such pulse shape information based on the received information. Such received information may be input (e.g., via a user interface of the apparatus 100, not shown) by a user or otherwise set by an operator or technician of the apparatus 100, read out from a computer file transmitted or otherwise conveyed to the controller 318, or the like or any combination thereof.
The pulse shape information may be stored (e.g., in a look-up table or other data structure in a computer memory of the controller 318 or otherwise accessible to the controller 318) in association with other information (also referred to herein as “supplemental information”) describing laser parameters under which the laser pulse 402 in the beam of laser energy is generated (e.g., the pulse duration of the laser pulse 402 generated by the laser source 104, the pulse repetition frequency at which the laser pulse 402 was generated, the average power at which the laser pulse 402 was generated, or the like or any combination thereof). The controller 318 may then use the pulse shape information and, optionally, any associated supplemental information, to determine when, during the creation of sliced pulses 404 from a laser pulse 402, any optical exercising operation should be performed, and for how long the optical exercising operation should be performed (i.e., the duration of the tailored optical exercise period 500) in order to maintain a substantially constant thermal gradient within the AO cell of the second AOD 304 during operation of the apparatus 100.
In one embodiment, pulse shape information may be generated using any known or suitable laser energy monitoring system incorporated within the AOD scanning system 300, or otherwise within the apparatus 100 that includes the AOD scanning system 300. For example, and with reference to
The mirror 802 is arranged within beam path 806 and is provided as a partially-transmissive mirror configured to reflect a majority of light in the incident beam of laser energy propagating along beam path 806 (into beam path 806r) and transmit a small amount of the light (e.g., 2% or thereabout) into beam path 806t. In
The laser sensor 804 is arranged to receive laser energy transmitted through the mirror 802 (e.g., propagating along beam path 806t). In one embodiment, the laser sensor 804 is configured to measure the instantaneous optical power in the beam of laser energy incident thereon and generate sensor data based on the sensing or measurement. The sensor data can be output to the controller 318 by any suitable means (e.g., via wired or wireless communication, as is known in the art). The controller 318 causes the sensor data to be stored (e.g., locally within the controller 318, on some computer memory within the apparatus 100 accessible to the controller 318, on some computer memory located remote from the apparatus 100 but communicatively connected to the apparatus 100 via one or more networks) as pulse shape information describing the temporal optical power profile of the laser energy incident upon the laser sensor 804 over a set time duration (e.g., during a temporal “slice” of the laser pulse 402, as will be described in greater detail below).
In another embodiment, the sensor data output to the controller 318 can be further processed (e.g., time-integrated) to derive the energy content of the beam of laser energy incident upon the laser sensor 804 over the set time duration. In this embodiment, the processed sensor data can be stored (e.g., as described above) as pulse shape information describing the amount of energy within the laser pulse energy over the set time duration (e.g., during a temporal “slice” of the laser pulse 402, as will be described in greater detail below).
In another embodiment, the laser sensor 804 is provided as an integrating detector (e.g., configured to measure the instantaneous optical power in the beam of laser energy incident thereon and integrate the measured optical power to derive the energy content of the beam) and generate sensor data. The sensor data can be output to the controller 318 by any suitable means (e.g., via wired or wireless communication, as is known in the art) and is stored (e.g., as described above) as pulse shape information describing the amount of energy within the laser pulse energy over the set time duration (e.g., during a temporal “slice” of the laser pulse 402, as will be described in greater detail below).
In one embodiment, the laser source 104, AOD scanning system 300 and laser energy monitoring system 800 can be operated to perform a pulse shape analyzing process to generate the pulse shape information. During the pulse shape analyzing process, the laser source 104 is operated (e.g., as described above) to generate a beam of laser energy that includes a sequence of laser pulses 402 generated under a particular set of laser parameters. For example, all laser pulses in the sequence of laser pulses may have the same (or substantially the same) pulse duration, and all laser pulses may be generated at the same (or substantially the same) pulse repetition frequency.
The AOD scanning system 300 is operated (e.g., as described above) during the pulse shape analyzing process to cause laser energy in each laser pulse 402 of the sequence of laser pulses to propagate along the beam path 806 during at least one period of time (each period of time also referred herein to as the aforementioned temporal “slice” of the laser pulse 402 or, more simply, as a “slice window”). When the laser energy propagates along the beam path 806, the slice window can be considered to be “open”. When laser energy is not propagating along the beam path 806, the slice window can be considered “closed.” The duration of each slice window may be equal to or about 2 μs, 1 μs, 0.5 μs, 0.25 μs, 0.1 μs, 0.05 μs etc., or between of these values, and all slice windows created during a sequence of laser pulses have the same duration.
When a slice window is open, the laser sensor 804 generates the sensor data and outputs the same to the controller 318. The sensor data is stored (e.g., as discussed above) in association with other information, such as the aforementioned supplemental information as well as slice information describing temporal aspects of the slice window during which the sensor data was generated. Examples of slice information can include the time when the slice window opened (e.g., relative to the time when the laser trigger command signal transitioned from a low state to a high state, or the like), the time when the slice window closed (e.g., relative to the time when the laser trigger command signal transitioned from a low state to a high state, or the like), the duration of the slice window, or any combination thereof.
Generally, the duration of each slice window associated with a laser pulse 402 is less than the pulse duration of the laser pulse 402, but slice windows associated with different laser pulses 402 in the sequence of laser pulses 402 are opened and closed at different times so that sensor data generated by the laser sensor 804 effectively represents all portions of a representative laser pulse 402 in the sequence of laser pulses 402. For example, and with reference to
As mentioned above, the AO cells of each of the first AOD 302 and the second AOD 304 are formed of a material that is susceptible to thermal lensing in the presence of laser energy propagating along the beam path 112 or along the first-order beam path 112′. However, driving the first AOD 302 and the second AOD 304 will also result in heating of the AO cells therein in a manner sufficient to create thermal gradients capable of inducing thermal lensing effects such as those described above. Characteristics of the thermal gradient within an AO cell of an AOD will change depending on the manner in which the AOD is driven (e.g., taking into account the amount of RF energy and RF frequency(ies) applied to the AOD during a slice period). However, thermal gradients within the AO cells which induce the thermal lensing may dissipate in the absence of any laser energy propagating therethrough (e.g., during the period between time t17 of pulse 402′ and time t22 of pulse 402″, as shown in
To prevent or otherwise minimize undesirable changes in thermal gradients within the AO cells of the first AOD 302 and the second AOD 304 across periods when laser energy from successive laser pulses 402 propagate therethrough, the first AOD 302 and the second AOD 304 may be driven during inter-pulse intervals. As used herein, an “inter-pulse interval” refers to the time period when laser energy from successive laser pulses 402 does not propagate through the first AOD 302 and the second AOD 304 (e.g., interval 600, which occurs during the period between time t7 of pulse 402′ and time t2 of pulse 402″ as shown in
Referring to
The controller 318 controls the operation of the first RF driver 314 and second RF driver 316 such that there is a time delay between the RF exercise period 1200 and a subsequent successive slice period (occurring after time t22, as discussed above). Generally, the duration of the time delay should be sufficiently long (e.g., greater than or equal to or about 2 μs, 1 μs, 0.5 μs, 0.25 μs, 0.1 μs, etc., or between of these values, depending on one or more factors such as the amplitude and velocity of the acoustic wave propagating in the AO cell and the size of the optical aperture of the AOD) to allow transient acoustic waves in the AO cells of the first AOD 302 and the second AOD 304 at the end of the RF exercise period 1200 to dissipate before the first AOD 302 and the second AOD 304 are driven to diffract when a slice period 406 begins. Although not illustrated, it should be appreciated that the drive signals applied to the first AOD 302 and the second AOD 304 may contain other RF pulses of any suitable frequency, amplitude and duration (as symbolically represented by the dashed lines therein) in order to create the laser pulses 404 discussed above, in order to perform any of the optical exercising operations discussed above, or the like or any combination thereof.
The amplitude and duration of the first RF exercising pulse 1202 and second RF exercising pulse 1204 may also be chosen in any manner desired or beneficial, in order to ensure that the thermal gradient within the AO cells of the first AOD 302 and second AOD 304 are relatively constant over time so that changes in wavefront distortion effects are negligible or otherwise sufficiently reduced so as to ensure that a workpiece, such as workpiece 102, can be satisfactorily processed. In the embodiment shown in
The RF frequency content of the RF exercising pulses 1202 and 1204 may also be chosen in any manner desired or beneficial. In some cases (e.g., depending on the configuration of the transducer(s) attached to the AO cell, the efficiency with which the transducer can launch an acoustic wave into the AO cell, etc.), absorption of RF energy by the AO cell may be dependent on the frequency of the drive signal. In one embodiment, the RF exercising pulses 1202 and 1204 may contain a subset of one or more discrete frequencies within a frequency band, or may contain all of such discrete frequencies. Furthermore, the frequencies of RF exercising pulses 1202 and 1204 applied during different RF exercise periods may be the same or different. That is, the frequency (or frequencies) in an RF exercise pulse applied during a first RF exercise period may be the same as or different from the frequency (or frequencies) in an RF exercise pulse applied during a second RF exercise period. For example, during a first RF exercise period 1200, a first subset of frequencies may be output to the transducer of first AOD 302 and/or second AOD 304 for the entirety of a RF exercise period 1200 and, during a subsequent RF exercise period 1200, a second subset of the frequencies (which may or may not contain some of the same frequencies included in the first subset) are output to the transducer of first AOD 302 and/or second AOD 304.
In another embodiment, the RF exercising pulses 1202 and 1204 may contain some or all of the frequencies within a specific frequency band by chirping or “smearing” the frequency of the RF exercising pulse during an RF exercise period. Generating and applying such chirped or “smeared” RF exercise pulses can be beneficial over RF exercise pulses containing one or more discrete frequencies (each also referred to herein as a “discrete frequency RF exercise pulse”) if a discrete frequency RF exercise pulse radiates an undesirable level of electromagnetic radiation (e.g., which could interfere with electronic devices in the vicinity of the laser-processing apparatus 100).
Although RF exercising has been discussed above in connection with AOD scanning system 300, it will also be appreciated that RF exercising may be performed with any system having any number of suitably-equipped AODs (e.g., a system having only one AOD, or a system having more than two AODs).
As described above, optical exercising may be beneficially used to maintain the thermal state of the AO cells in the first AOD 302 and the second AOD 304 when laser energy propagating through the first AOD 302 and the second AOD 304 is not to be propagated to the workpiece 102. As also described above, RF exercising may be employed to maintain the thermal state of the AO cells in the first AOD 302 and the second AOD 304 when no laser energy is propagating through the first AOD 302 or the second AOD 304 (and, thus, is not propagating to the workpiece 102); for example, during the aforementioned inter-pulse intervals.
However, there can be situations when it is desirable to prevent the workpiece 102 from being irradiated with laser energy, while the laser source 104 is still generating a beam of laser energy (e.g., to maintain stable operation of the laser source 104), but for relatively long periods of time where optical exercising is not effective or feasible (e.g., because second AOD 304 is not being driven for a relatively long period of time while the first AOD 302 is being driven). Such situations can, for example, arise during workpiece processing where there is a long distance between features to be successively-formed in a workpiece, when a processed workpiece is being removed from (or loaded into) the system, etc. In order to maintain the thermal state of the AO cells in the first AOD 302 and the second AOD 304 during such situations, and with reference to
Referring to
The amplitude of the drive signals applied to the first AOD 302 and the second AOD 304 may be constant or may vary in any manner desired or beneficial to ensure that the thermal gradient within the AO cells of the first AOD 302 and second AOD 304 are relatively constant over time so that changes in wavefront distortion effects are negligible or otherwise sufficiently reduced so as to ensure that a workpiece, such as workpiece 102, can be satisfactorily processed.
In one embodiment, phase modulation control is additionally employed while driving the first AOD 302 and/or second AOD 304 reduce the optical power propagating along the beam path 112″ to the exercise beam trap 1302. Doing so can be desirable if the average or peak power in the laser energy that would otherwise propagate to the exercise beam trap 1302 along beam path 112″ would undesirably damage or degrade the beam trap 1302.
As shown in
As should be apparent, the frequency of each drive signal applied from the first RF driver 314 and the second RF driver 316 is selected to direct laser energy propagating along the first-order beam path 112″ to the exercise beam trap 1302. Generally, the frequency of the drive signal applied from the first RF driver 314 (also referred to herein as a “first frequency”) can be any frequency within a first frequency range. Likewise, the frequency of the drive signal applied from the second RF driver 316 (also referred to herein as a “second frequency”) can be any frequency within a second frequency range. The bandwidth of the first frequency range can be larger than, equal to, or smaller than the bandwidth of the second frequency range. In one embodiment, the first frequency range overlaps the second frequency range (i.e., frequencies contained in the first frequency range are contained in the second frequency range). In another embodiment, the first frequency range does not overlap the second frequency range (i.e., frequencies contained in the first frequency range are not contained in the second frequency range, and vice versa).
The RF frequency content of the drive signals applied to the first AOD 302 and the second AOD 304 during a beam trap exercising operation may be chosen in any manner desired or beneficial. For example, the drive signal applied to the first AOD 302 may contain one or more discrete frequencies within the first frequency range, or may contain a plurality of frequencies within the first frequency range that are chirped or “smeared” as described above in embodiments relating to RF exercising. Likewise, the drive signal applied to the second AOD 304 may contain one or more discrete frequencies within the second frequency range, or may contain a plurality of frequencies within the second frequency range that are chirped or “smeared” as described above in embodiments relating to RF exercising.
Although beam trap exercising has been described above as involving use of the exercise beam trap in connection with an AOD scanning system 1300 that includes the exercise beam trap 1302, it will be appreciated that, in another embodiment, the exercise beam trap 1302 may be replaced with one or more optical components (e.g., one or more mirrors, lenses, or the like or any combination thereof) arranged and configured to intercept laser energy, propagating along the first-order beam path 112″ during a beam trap exercising operation, and redirect the laser energy into the first beam trap 310 or the second beam trap 312. In yet another embodiment, the second beam trap 312 may be configured to intercept laser energy, propagating from the second AOD 304 along the first-order beam path 112″ during a beam trap exercising operation.
Although beam trap exercising has been discussed above in connection with AOD scanning system 1300, it will also be appreciated that RF exercising may be performed with any system having any number of suitably-equipped AODs (e.g., a system having only one AOD, or a system having more than two AODs) and a beam trap. Furthermore, although
As discussed above, the temporal transmission profiles of the first AOD 302 and second AOD 304 during a slice period, which are delineated by 408 and 410, respectively, is constant (or at least substantially constant) for the entire duration of slice period 406. As a result, the temporal optical power profile of a laser pulse 404 created during a slice period (i.e., the optical power in a laser pulse 404 output from the AOD scanning system 300, during a slice period, as a function of time) will be approximately congruent to the temporal optical power profile of the portion of the laser pulse 402 incident to the AOD scanning system 300 during the slice period. For example, during any slice period shown in
However, it can often be the case that the optical power in the main portion of the laser pulse 402 will vary undesirably. As a result, the temporal optical power profiles of portions of the laser pulse 402 during different slice periods will be sufficiently different from one another, making it difficult to efficiently develop laser-based processes and form multiple features using different laser pulses 404 sliced from a common laser pulse 402. In some embodiments, the temporal optical power profile of the laser pulse 402 can be adjusted by changing the manner in which the laser source 104 is operated (e.g., by varying the optical power of the laser pulses generated, by varying the pulse repetition rate, by varying the pulse duration of laser pulses generated, by modulating the duty cycle of the laser trigger command signal (e.g., via pulse-width modulation) applied to the laser source 104, or the like or any combination thereof).
As an alternative to (or in conjunction with) modifying the operation of the laser source 104, the amplitude and/or phase (in embodiments in which the first AOD 302 and/or the second AOD 304 includes multiple transducers) of the drive signals applied to the first AOD 302 and/or second AOD 304, which give rise to the temporal transmission profiles delineated by 408 and/or 410 respectively, during a slice period 406 can be made variable during the slice period 406 (e.g., as described above). According to embodiments of the present invention, the amplitude and/or phase of a drive signal applied to the first AOD 302 and/or second AOD 304 during a slice period 406 can be made variable such that the temporal optical power profile of a laser pulse 404 created during the slice period 406 is not approximately congruent to the temporal optical power profile of the portion of the laser pulse 402 incident to the AOD scanning system 300 during the slice period 406.
For example, and with reference to
Therefore, according to embodiments of the present invention, and as exemplarily shown in
Although
Furthermore, although
Lastly, although it has been discussed above that the temporal transmission profile of the first AOD 302 and/or second AOD 304 can be varied in the presence of a portion of a laser pulse 402 having a temporal optical power profile that is not substantially horizontally flat be varied during a slice period to create a laser pulse 404 with temporal optical power profile that is at least substantially horizontally flat, it will be appreciated that the amplitude of the applied drive signal(s) can be varied in any other manner to create a laser pulse 404 having any other temporal optical power profile that is or is not approximately congruent to the temporal optical power profile of the portion of the laser pulse 402 present during the slice period.
To the extent that pulse shape information that describes or otherwise approximates temporal optical power profiles of laser pulses generatable by the laser source 104, such pulse shape information can be accessed by the controller 318. Thereafter, the controller 318 can generate data characterizing a temporal amplitude profile of at least one drive signal to be generated by at least one RF driver (e.g., the first RF driver 314, the second RF driver 316 or a combination thereof) that will result in the creation of a laser pulse 404 having a desired temporal optical power profile that is not congruent to the temporal optical power profile of the portion of the laser pulse 402 from which it was created. The controller 318 can thereafter output the data to the appropriate RF driver in the form of a command signal for the RF driver.
Generally, the controller 118 includes one or more processors operative to generate the aforementioned commands and control signals (e.g., upon executing one or more instructions). A processor can be provided as a programmable processor (e.g., including one or more general purpose computer processors, microprocessors, digital signal processors, or any other suitable form of circuitry including programmable logic devices (PLDs), central processing units (CPUs), graphics processing units (GPUs), accelerated processing units (APUs), real-time processing units (RPUs), field-programmable gate arrays (FPGAs), field-programmable object arrays (FPOAs), application-specific integrated circuits (ASICs)—including digital, analog and mixed analog/digital circuitry—or the like, or any combination thereof) operative to execute the instructions. Execution of instructions can be performed on one processor, distributed among multiple processors, made parallel across processors within a device or across a network of devices, or the like or any combination thereof.
Generally, the instructions may be embodied as software (e.g., an executable code, file, library file, or the like or any combination thereof), hardware configuration (e.g., in the case of FPGAs, ASICs, etc.), or the like or any combination thereof, which can be readily specified by artisans, from the descriptions provided herein (e.g., written in C, C++, Visual Basic, Java, Python, Tel, Perl, Scheme, Ruby, assembly language, hardware description language such as LUCID, VHDL or VERILOG, etc.). Software is commonly stored in one or more data structures conveyed by tangible media such as computer memory, which is accessible (e.g., via one or more wired or wireless communications links) by a processor. Examples of tangible media include magnetic media (e.g., magnetic tape, hard disk drive, etc.), optical discs, volatile or non-volatile semiconductor memory (e.g., RAM, ROM, NAND-type flash memory, NOR-type flash memory, SONOS memory, etc.), or the like or any combination thereof, and may be accessed locally, remotely (e.g., across a network), or any combination thereof.
Although various embodiments of the present invention have been described above with respect to
The foregoing is illustrative of embodiments and examples of the invention and is not to be construed as limiting thereof. Although a few specific embodiments and examples have been described with reference to the drawings, those skilled in the art will readily appreciate that many modifications to the disclosed embodiments and examples, as well as other embodiments, are possible without materially departing from the novel teachings and advantages of the invention. For example, although embodiments concerning exercising operations have been described above as being used with the beam positioner shown in
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2023/062640 | 2/15/2023 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63314437 | Feb 2022 | US | |
| 63314438 | Feb 2022 | US | |
| 63338876 | May 2022 | US | |
| 63417889 | Oct 2022 | US |
