Dynamic compensation for acousto-optic deflectors

Abstract

An optical scanner may include a sampler that receives a light beam and provides a sampling beam comprising a portion of the light beam, a dispersive element that spectrally disperses the sampling beam along a dispersion direction, one or more detectors that receive at least a portion of the sampling beam dispersed along the dispersion direction, one or more acousto-optic deflectors (AODs) configured to deflect the light beam from the sampler, and a controller that can determine a center of mass of the sampling beam dispersed along the dispersion direction based on signals from at least one of the one or more detectors, and generate a drive signal based on the center of mass to deflect the light beam from the sampler at at least one of the one or more AODs along a specified deflection angle.

Description

[Technical Field]

[0001] The present disclosure is directed generally to optical beam scanners, and more particularly to dynamic correction for optical beam scanners in the presence of scanning beam spectral variations. [Background technology]

[0002] Acousto-optic deflectors (AODs) can be used as optical beam scanning devices in a wide range of applications. AODs advantageously provide relatively high scanning speeds, but are sensitive to spectral variations in the optical beam during scanning. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 7,483,196 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, it would be desirable to develop a system and method that addresses the above-listed shortcomings. [Means for solving the problem]

[0005] An optical scanner is disclosed in accordance with one or more exemplary embodiments of the present disclosure. In some exemplary embodiments, the optical scanner includes a sampler that receives a light beam and provides a sampling beam comprising a portion of the light beam. In some exemplary embodiments, the optical scanner includes a dispersive element that spectrally disperses the sampling beam along a dispersion direction. In some exemplary embodiments, the optical scanner includes one or more detectors that receive at least a portion of the dispersed sampling beam along the dispersion direction. In some exemplary embodiments, the optical scanner includes one or more acousto-optic deflectors (AODs) that deflect the light beam from the sampler. In some exemplary embodiments, the optical scanner includes a controller. In some exemplary embodiments, the controller determines a center of mass (center of gravity) of the dispersed sampling beam along the dispersion direction based on signals from at least one of the one or more detectors. In one exemplary embodiment, the controller also generates a drive signal based on the center of mass to deflect the light beam from the sampler along a specified deflection angle in at least one of the one or more AODs listed above.

[0006] A system is disclosed in accordance with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, the system includes a light source configured to generate a light beam. In an exemplary embodiment, the system includes a scanner. In an exemplary embodiment, the scanner includes a sampler that receives the light beam and provides a sampling beam including a portion of the light beam, a dispersive element that spectrally disperses the sampling beam along a dispersion direction, one or more detectors that receive at least a portion of the dispersed sampling beam along the dispersion direction, and one or more acousto-optic deflectors (AODs) that deflect the light beam from the sampler. In an exemplary embodiment, the system includes a controller. In an exemplary embodiment, the controller determines a center of mass of the dispersed sampling beam along the dispersion direction based on a signal from at least one of the one or more detectors. In an exemplary embodiment, the controller generates a drive signal based on the center of mass to deflect the light beam from the sampler at at least one of the one or more AODs along a specified deflection angle. In one illustrative embodiment, the system also includes one or more focusing optics configured to focus the light beam deflected by the one or more AODs onto the sample.

[0007] A method is disclosed in accordance with one or more exemplary embodiments of the present disclosure. In some exemplary embodiments, the method generates a sampling beam from a received optical beam, where the sampling beam includes a portion of the optical beam. In some exemplary embodiments, the method spectrally disperses the sampling beam along a dispersion direction. In some exemplary embodiments, the method detects at least the portion of the sampled beam dispersed along the dispersion direction with one or more detectors. In some exemplary embodiments, the method determines a center of mass of the sampled beam dispersed along the dispersion direction based on a signal from at least one of the one or more detectors. In some exemplary embodiments, the method generates a drive signal based on the center of mass for deflecting the optical beam with an acousto-optic deflector (AOD) along a specified deflection angle. In some exemplary embodiments, the method deflects the optical beam with the AOD driven by the drive signal.

[0008] Both the foregoing general description and the following detailed description are exemplary and explanatory only and do not necessarily limit the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the general description, serve to explain the principles of the invention.

[0009] Those skilled in the art can better appreciate the many advantages of the present disclosure by referring to the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1 is a block diagram of an optical scanner according to one or more embodiments of the present disclosure. [Figure 1B] FIG. 1 is a block diagram of a system having an optical scanner according to one or more embodiments of the present disclosure. [Figure 2] FIG. 1 is a simplified schematic diagram of an acousto-optic deflector (AOD) according to one or more embodiments of the present disclosure. [Figure 3]FIG. 1 is a plot of a spatially dispersed sampled beam according to one or more embodiments of the present disclosure. [Figure 4A] FIG. 2 is a simplified conceptual diagram of a first spectrally dispersed sampling beam including a single lobe associated with a first wavelength, in accordance with one or more embodiments of the present disclosure. [Figure 4B] FIG. 10 is a simplified conceptual diagram of a second spectrally dispersed sampling beam including a single lobe associated with a second wavelength, in accordance with one or more embodiments of the present disclosure. [Figure 4C] FIG. 10 is a simplified conceptual diagram of a third spectrally dispersed sampling beam including a first lobe associated with a third wavelength and a second lobe associated with a fourth wavelength, according to one or more embodiments of the present disclosure. [Figure 5] FIG. 1 is a simplified schematic diagram of a portion of an optical scanner according to one or more embodiments of the present disclosure that includes an additional detector for monitoring AOD performance. [Figure 6] FIG. 1 is a flow diagram depicting steps performed in a method for dynamic control of an optical scanner in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Reference will now be made in detail to the disclosed subject matter, which is illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with reference to certain embodiments and specific features thereof. The embodiments described herein are to be understood as illustrative and not limiting. Various changes and modifications in form and detail may be made without departing from the spirit and scope of the present disclosure.

[0012] Embodiments of the present disclosure are directed to systems and methods for compensating for spectral variations in a light beam (e.g., a laser beam) through dynamic control of an optical scanner.

[0013] In certain embodiments, an optical scanner includes at least one acousto-optic deflector (AOD) for receiving and redirecting (e.g., scanning) a light beam, one or more detectors for monitoring spectral variations in the light beam, and a controller for providing drive signals to the AOD, wherein the AOD is dynamically adjusted to compensate for spectral variations in the light beam that are measurable by at least one of the one or more detectors.

[0014] An AOD may include one or more transducers that generate acoustic waves within a host material, and may be driven with a periodic drive signal to form a diffraction grating within the host material. In this way, an incident light beam can be redirected by diffraction, the deflection angle of the light beam from the AOD (e.g., the angle of diffraction at the diffraction grating) can be controlled depending on the frequency of the drive signal, and the intensity of the light beam from the AOD can be controlled depending on the amplitude of the drive signal.

[0015] As contemplated herein, such AODs advantageously provide higher scanning speeds than mechanical scanners (e.g., galvanometer mirrors, rotating polygons, etc.), but can be highly sensitive to spectral variations in the scanning light beam. Specifically, spectral variations in the light beam can lead to variations in the angle of diffraction of the light beam by the AOD, and thus variations in the angle of deflection of the light beam. In contrast, the disclosed systems and methods dynamically compensate for spectral variations, enabling fast and accurate optical scanning with an AOD, regardless of spectral variations.

[0016] Additional embodiments of the present disclosure are directed to systems and methods for dynamically compensating for power fluctuations in a light beam when using wavelength-sensitive polarization optics. Some polarization optics may exhibit non-uniform performance (e.g., transmittance and / or reflectance) across wavelengths. When such wavelength-sensitive polarization optics are used in an optical scanner, spectral variations in the light beam can lead to power fluctuations. In certain embodiments, the controller can also dynamically adjust the amplitude of a drive signal to an AOD to adjust the power of the light beam exiting the AOD and thereby compensate for power fluctuations associated with interactions with the wavelength-sensitive polarization optics. Such wavelength-sensitive polarization optics may be located either before or after the AOD.

[0017] Additional embodiments of the present disclosure are directed to systems and methods for dynamically compensating for beam size variations of an optical beam. For example, when the power distribution of an optical beam dynamically changes between different spectral bands, the beam size and placement accuracy of the optical beam can be directly affected. Furthermore, in practice, spectral variations of an optical beam are related to operation of an associated light source (e.g., a laser light source) in various optical modes, and each optical mode can result in different beam characteristics (e.g., beam size, beam divergence, etc.). In turn, switching between these different modes (e.g., mode hopping) and / or simultaneous laser emission in different modes can lead to some combination of spectral and / or beam characteristic variations. In certain embodiments, an optical scanner includes one or more detectors for monitoring the beam size of the optical beam and one or more adaptive optics (e.g., deformable mirrors, microelectromechanical systems (MEMS) devices, phase modulators, etc.), and a controller dynamically generates drive signals for the adaptive optics to compensate for the beam size variations.

[0018] 1A-6, systems and methods for optical scanning in the presence of spectral and / or beam size variations will now be described in more detail, in accordance with one or more embodiments of the present disclosure.

[0019] Figure 1A is a block diagram of an optical scanner 100 according to one or more embodiments of the present disclosure. Figure 1B is a block diagram of a system 102 including the optical scanner 100 according to one or more embodiments of the present disclosure.

[0020] In certain embodiments, an optical scanner 100 includes a light source 104 that generates a light beam 106 and at least one AOD 108 that controls a deflection angle of the light beam 106. The optical scanner 100 may further include a controller 110 associated with one or more processors 112 configured to execute a set of program instructions stored in a memory 114 (e.g., a storage device), which may cause the controller 110 to generate at least one drive signal 116 for the AOD 108. The controller 110 may then direct or otherwise control the AOD 108 to direct the light beam 106 along a particular deflection angle, scan pattern, etc., based on the drive signal 116. As described in more detail below, the controller 110 may further adjust one or more characteristics of the drive signal 116 to compensate for spectral variations in the beam 106 and to provide the light beam 106 with a consistent deflection angle via the AOD 108. For example, optical scanner 100 can monitor spectral variations in light beam 106 by sampling a portion of light beam 106 with sampler 118 to form sampled beam 120, spectrally dispersing sampled beam 120 with dispersive element 122, and collecting at least a portion of the spectrally dispersed sampled beam 120 with one or more detectors 124 coupled to controller 110.

[0021] Additionally, although not explicitly shown in FIG. 1A , optical scanner 100 may generally include any number of AODs 108. For example, optical scanner 100 may include multiple AODs 108 arranged to scan light beam 106 along multiple directions (e.g., orthogonal directions). When multiple AODs 108 are present, controller 110 may adjust one or more characteristics of drive signal 116 associated with each AOD 108 to compensate for spectral variations in light beam 106 and to provide a consistent deflection angle for light beam 106 from each AOD 108. Thus, any discussion herein of the operation or correction of an AOD 108 may be extended to apply to multiple AODs 108.

[0022] The one or more processors 112 included in the controller 110 may include any processor or processing element known in the art. In this sense, the one or more processors 112 may include any microprocessor-based device configured to execute algorithms and / or instructions. For purposes of this disclosure, the term "processor" or "processing element" may be broadly defined to encompass any device having one or more processing or logic elements (e.g., one or more microprocessor devices, one or more application-specific integrated circuit (ASIC) devices, one or more field-programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)). In this sense, the one or more processors 112 may include any device configured to execute algorithms and / or instructions (e.g., program instructions stored in memory). In certain embodiments, the one or more processors 112 may be embodied as a desktop computer, mainframe computer system, workstation, image computer, parallel processor, networked computer, or any other computer system configured to execute an appropriately configured program to operate or cooperate with optical scanner 100 as described elsewhere in this disclosure. Furthermore, various subsystems of optical scanner 100 may include processors or logic elements suitable for performing at least a portion of the steps described elsewhere in this disclosure. Therefore, the above description should be construed as merely illustrative and not limiting on the embodiments of this disclosure. Furthermore, the steps described elsewhere in this disclosure may be performed by a single controller or, alternatively, by multiple controllers. Additionally, controller 110 may include one or more controllers housed within a common housing or within multiple housings.In this manner, any controller or controller combination can be individually packaged as a module suitable for incorporation into optical scanner 100.

[0023] Memory 114 may include any storage medium known in the art suitable for storing program instructions executable by one or more associated processors 112. For example, memory 114 may include a non-transitory storage medium. For example, memory 114 may include, but is not limited to, read-only memory (ROM), random access memory (RAM), magnetic or optical storage devices (e.g., disks), magnetic tape, solid-state drives, etc. It is further noted that memory 114 may be housed with one or more processors 112 within a common controller housing. In certain embodiments, memory 114 may be located remotely relative to the physical location of the one or more processors 112 and controller 110. For example, one or more processors 112 in controller 110 may access a remote memory (e.g., a server) accessible via a network (e.g., the Internet, an intranet, etc.).

[0024] Alternatively, the controller 110 may include or be coupled to one or more encoders (e.g., optical encoders) that may be used for any suitable purpose, including, but not limited to, monitoring the position of the light beam along one or more scan axes and providing related feedback for control.

[0025] The optical scanner 100 can be integrated into any suitable dynamic beam control system. As an example, FIG. 1B depicts the use of the optical scanner 100 in a system 102 suitable for materials processing. In certain embodiments, the system 102 includes a stage 126 that supports a specimen 128. In certain embodiments, the system 102 includes one or more focusing optics 130 that focus the light beam 106 from the optical scanner 100 onto the specimen 128. Thus, the system 102 can direct the light beam 106 across the specimen 128 according to any pattern, scan the light beam 106 over the specimen 128, and adjust the AOD 108 in the optical scanner 100 to compensate for spectral variations in the light beam 106, thereby ensuring a consistent position of the light beam 106 on the specimen 128 regardless of spectral variations.

[0026] The focusing optics 130 can include any number or type of focusing optics suitable for focusing the light beam 106 onto the specimen 128. In certain embodiments, the focusing optics 130 includes an F-theta lens, which allows for consistent focusing of the light beam 106 across a flat surface and linear displacement across the specimen 128 as a function of the angle of incidence (e.g., related to the deflection angle of the light beam 106 from the optical scanner 100).

[0027] In certain embodiments, system 102 includes one or more additional components that provide additional control over the position of light beam 106 on specimen 128. For example, stage 126 can include a translation stage with one or more linear or angular actuators, thereby adjusting the position of specimen 128 along any number of degrees of freedom. Alternatively, system 102 can include an additional deflector 132, such as, but not limited to, a galvanometer mirror, a pivoting polygon, or an additional AOD, as depicted in FIG. 1B. This can extend the scanning range beyond that of optical scanner 100. For example, a mechanical beam scanner, such as the galvanometer mirror and stage 126 depicted in FIG. 1B, can provide a wider scanning range than that of optical scanner 100, but at a relatively slower scanning speed.

[0028] System 102 may further include several additional optics to control various characteristics of light beam 106, such as, but not limited to, optical relays, beam expanders, polarizers, spectral filters, spatial filters, or apodizers. Although not explicitly depicted, such additional optics may be interspersed throughout system 102 and / or at any suitable location within optical scanner 100.

[0029] In certain embodiments, system 102 and / or optical scanner 100 further include adaptive optics 134 that provide spatially resolved control over portions of light beam 106. In this way, characteristics of light beam 106 deflected by AOD 108, such as, but not limited to, beam size, beam divergence, or focusing characteristics, can be adjusted to provide consistent performance regardless of variations in light beam 106. For example, adaptive optics 134 can be used in system 102 to provide a consistent focused spot size on specimen 128 regardless of variations in light beam 106.

[0030] Referring generally to FIG. 1A, various aspects of optical scanner 100 will now be described in more detail, in accordance with one or more embodiments of the present disclosure.

[0031] The light beam 106 may include light of one or more specified wavelengths, including, but not limited to, ultraviolet (UV), visible, or infrared (IR) radiation. Furthermore, the light beam 106 from the light source 104 may have any temporal profile, including, but not limited to, a continuous wave (CW) profile, a pulsed profile, or a modulated profile.

[0032] Light source 104 may generally include any type of illumination source suitable for providing at least one light beam 106, including, but not limited to, a laser light source or a light emitting diode (LED). It is noted that light source 104 may be integrated within optical scanner 100, system 102, or may be an external component. In certain embodiments, light source 104 comprises a narrowband laser light source that provides light concentrated around a center frequency. It is contemplated herein that the narrower the bandwidth of light beam 106, the less spatial dispersion induced by a dispersive element, such as, but not limited to, AOD 108.

[0033] In certain embodiments, the light source 104 is a carbon dioxide (CO2) laser light source. For example, a CO2 laser can provide a light beam 106 having a wavelength in the range of 9-12 nanometers, but this is intended to be illustrative and not limiting.

[0034] AOD 108 may include any type of deflector known in the art that is suitable for controlling the deflection angle of light beam 106 through diffraction by acoustic waves in a material. Figure 2 is a simplified schematic diagram of AOD 108 according to one or more embodiments of the present disclosure.

[0035] In certain embodiments, the AOD 108 includes at least one transducer 202 coupled to a host material 204. The host material 204 can include any type of material suitable for interacting with the light beam 106, such as, but not limited to, glass or quartz. For example, the host material 204 can be transparent to the light beam 106. As an example, the host material 204 can have an absorption below a specified threshold at the wavelength associated with the light beam 106 and / or a transmittance above a specified threshold at the wavelength associated with the light beam 106.

[0036] The transducer 202 may be any suitable material for generating acoustic waves within the host material 204. In certain embodiments, the transducer 202 is a piezoelectric material that can expand and contract in response to an applied voltage (e.g., drive signal 116), thereby generating acoustic waves within the host material 204.

[0037] In certain embodiments, the AOD 108 (e.g., one or more transducers within the AOD 108) can be driven with a periodic drive signal 116 to generate a periodic acoustic wave distribution within the host material 204, which can act as a diffraction grating 206 suitable for diffracting the light beam 106. In particular, the periodic acoustic wave distribution can result in a periodic refractive index distribution within the host material 204, which can act as a diffraction grating 206.

[0038] Diffraction of the light beam 106 by the diffraction grating 206 may generally result in several diffraction orders (e.g., a zeroth diffraction order 208, a first diffraction order 210, a second diffraction order 212, etc.). In this configuration, any diffraction order may be used as the deflected light beam 106. In certain embodiments, the AOD 108 is configured so that the light beam 106 interacts with the diffraction grating 206 at or near the Bragg angle, such that a significant portion of the energy in the light beam 106 is diffracted as a first diffraction order 210 (e.g., a +1st diffraction order or a −1st diffraction order). The first diffraction order 210 may then be representative of the deflected light beam 106, and the deflection angle 214 of the light beam 106 from the AOD 108 may be mapped to the first diffraction order angle 216.

[0039] The diffraction of the light beam 106 by the diffraction grating 206 in the AOD 108 is generally governed by the grating equation: d(sinθ i -sinθ m )=mλ (1) where d is the period of the diffraction grating 206, m is the diffraction order, λ is the wavelength of the light beam 106, and θ i is the angle of incidence of the light beam 106, θ m is the diffraction angle of the associated diffraction order of the light beam 106. Therefore, the first diffraction order angle 216 is θ1=asin(sinθ i -λ / d) (2) which varies depending on the wavelength (λ) of the light beam 106 and the period (d) of the diffraction grating 206. More generally, equation (1) indicates that non-zero diffraction orders, including but not limited to the first diffraction order 210, are spectrally dispersed, and thus the diffraction angle θ m varies depending on the wavelength (λ) of the light beam 106.

[0040] The power of the first diffraction order 210, and therefore the efficiency of the AOD 108 in deflecting the light beam 106, may depend on various factors, including, but not limited to, the amplitude of the refractive index perturbation of the host material 204 associated with the diffraction grating 206 (Δn, where n is the refractive index of the host material 204), which may be referred to as the modulation depth of the diffraction grating 206. In the AOD 108, the modulation depth (Δn) may depend on the amplitude of the acoustic wave generated by the transducer 202.

[0041] For a given wavelength (λ) of the light beam 106, the first-order diffraction angle 216, and therefore the deflection angle 214 of the light beam 106 from the AOD 108, can be varied within a scan range (e.g., a walking window) by adjusting the frequency of the drive signal 116. The period (d) of the diffraction grating 206 can be inversely related to the frequency of the drive signal 116. For example, the controller 110 can generate the drive signal 116 and adjust the frequency of the drive signal 116 according to any specified pattern, thereby adjusting the deflection angle 214 according to any specified pattern.

[0042] It is contemplated herein that light source 104 may exhibit various instabilities, such as, but not limited to, instabilities in the beam size or spectrum of light beam 106. In the case of a laser light source, such instabilities may, but need not, involve mode hopping between different supported modes, each of which may have different wavelengths (e.g., center wavelengths).

[0043] Spectral variations in the light beam 106 (e.g., those related to instabilities in the light source 104, or more generally, those related to any mechanism) can cause errors in the deflection angle of the light beam 106. Considering the non-limiting example illustration in Figure 2, spectral variations in the light beam 106 can affect the first-order diffraction angle 216 according to equations (1) and (2), and thus the deflection angle 214 of the light beam 106 from the AOD 108. As a result, a shift in the wavelength (λ) of the light beam 106 from an expected value (e.g., due to spectral variations) can result in an error in the deflection angle 214 from the AOD 108.

[0044] Although it may be possible to avoid such deflection angle errors by using wavelength-insensitive scanning techniques (e.g., mechanical techniques such as, but not limited to, galvanometer mirrors or rotating polygons) or by selecting a light source 104 with low spectral variation, such approaches are not always desirable. For example, mechanical beam scanning techniques can generally have low positioning speeds (e.g., scanning speeds), which can limit system throughput. Also, for example, techniques that provide a light beam 106 with high spectral stability can limit the achievable power of the light beam 106. In other words, mode hopping (and associated spectral instability) can be a consequence of high-power operation of certain laser light sources, such as, but not limited to, CO laser sources.

[0045] Therefore, it may be desirable in certain applications to utilize an optical scanner 100 having an AOD 108 in combination with a light source 104 that exhibits spectral variations. In this manner, the light source 104 can be selected to provide a light beam 106 with a specified power regardless of spectral instability and without sacrificing scanning speed or accuracy.

[0046] Referring again to FIGS. 1A and 1B, in certain embodiments, optical scanner 100 includes various components that compensate for spectral variations in light beam 106.

[0047] In certain embodiments, optical scanner 100 includes a sampler 118 that generates sampling beam 120 from light beam 106, a dispersive element 122 that spectrally disperses sampling beam 120, and one or more detectors 124 that capture at least a portion of the spectrally dispersed sampling beam 120. The one or more detectors 124 can then generate signals indicative of spectral variations in sampling beam 120 and, therefore, the spectral variations in light beam 106. Controller 110 can then adjust drive signal 116 to AOD 108 to compensate for the spectral variations in light beam 106 over time, thereby ensuring that deflection angle 214 of light beam 106 is accurate regardless of the spectral variations.

[0048] Sampler 118 may include any optical element known in the art suitable for extracting a portion of light beam 106 as sample beam 120. For example, sampler 118 may include, but is not limited to, an optical wedge or a beam splitter. For example, sampler 118 may include a mirror with less than 100% reflectivity, through which a portion of light beam 106 propagates and is used as sample beam 120.

[0049] Dispersive element 122 can include any optical element known in the art that is suitable for spatially dispersing sample beam 120, such as, but not limited to, a diffraction grating or a prism. This allows dispersive element 122 (and detector 124) to function as a type of in-line or real-time spectrometer. For example, in the case of a diffraction grating, dispersive element 122 can generate multiple diffraction orders according to equation (1), and spectrally disperse the non-zero diffraction orders. In certain embodiments, as described above in connection with diffraction grating 206 of AOD 108, dispersive element 122 can be arranged to satisfy the Bragg condition, thereby ensuring that a significant portion of the power in sample beam 120 is diffracted into the first diffraction order.

[0050] Dispersive element 122 can generally have any dispersion value. In certain embodiments, the dispersion in dispersive element 122 is sufficient to allow detection of spectral variations in sample beam 120 by at least one of one or more detectors 124. By way of example, dispersive element 122 may have a diffraction grating with 150 lines per millimeter ruling, although this is not required, thereby providing sufficient dispersion to allow detection of spectral variations in sample beam 120 by at least one of one or more detectors 124.

[0051] 3 is a plot of a spatially dispersed sampled beam 120 according to one or more embodiments of the present disclosure. In particular, FIG. 3 corresponds to a plot of a spatially dispersed sampled beam 120 for a CO laser, depicting light dispersed along a dispersion direction 302.

[0052] Spectral variations in light beam 106 may manifest in multiple ways and may depend on the details of light source 104. In certain embodiments, the power of light beam 106 may be concentrated around a single wavelength (e.g., a single center wavelength), and that wavelength may shift over time. For example, but not limited to, such behavior may be related to thermal variations in light source 104. In certain embodiments, as depicted in FIG. 3 , the power of light beam 106 generated by light source 104 may be concentrated around one or more wavelengths associated with one or more optical modes. Thus, several optical modes (and associated wavelengths) may be present at any discrete time, and the wavelength distribution may change over time (e.g., due to mode hopping).

[0053] The one or more detectors 124 can include any type of detector known in the art that is suitable for detecting spectral variations in sample beam 120 when combined with dispersive element 122. In certain embodiments, detector 124 is formed as a multi-pixel detector with at least two of its pixels interspersed along the direction 302 of dispersion provided by dispersive element 122. In this manner, different pixels of detector 124 along dispersion direction 302 can capture different wavelengths or wavelength ranges of sample beam 120.

[0054] The lateral shift of light along the dispersion direction 302 may be measured by detector 124 and calibrated for a wavelength shift in sampled beam 120 based on the amount of dispersion introduced by dispersive element 122 and the separation distance between dispersive element 122 and detector 124. For example, the amount of dispersion introduced by dispersive element 122 may be characterized as Δθ / Δλ, i.e., an angular shift of Δθ in deflection angle 214 may be related to a wavelength shift of Δλ, which may then be mapped to a linear shift Δl on detector 124.

[0055] Controller 110 may then provide drive signal 116 to AOD 108 using any suitable technique to compensate for spectral variations in light beam 106 (e.g., those measured on sampled beam 120). In certain embodiments, controller 110 determines the center of mass (COM) of spectrally resolved sampled beam 120 and dynamically adjusts the frequency of drive signal 116 to AOD 108 based on the COM of spectrally resolved sampled beam 120.

[0056] As an example, a first frequency (f0) of drive signal 116 can be calculated in controller 110. The first frequency can be selected based on the expected wavelength (λ0) of sampling beam 120, and thus the expected COM (COM0) of spectrally dispersed sampling beam 120 as measured by detector 124, to provide a desired deflection angle 214 for light beam 106.

[0057] The expected COM (COM) of spectrally dispersed sampling beam 120 can be associated with any value and can be associated with a central position on detector 124. For example, if the spectrum of light beam 106 (and thus sampling beam 120) varies within a known spectral range, the associated COM of spectrally dispersed sampling beam 120 will vary within a known range of positions on the plane of detector 124. In this case, detector 124 can be placed anywhere suitable to capture that known range of positions. In certain embodiments, the center of detector 124 is placed at the center of that known range of positions.

[0058] A signal indicative of the COM of the spectrally dispersed sampling beam 120 can be received by the controller 110 from the detector 124. The controller 110 can then determine the adjustment frequency (Δf) required to compensate for the shift (ΔCOM) of the COM of the spectrally dispersed sampling beam 120 from its expected value.

[0059] The controller 110 can then provide a drive signal 116 to the AOD 108 at a second frequency (f2) corresponding to the first frequency (f1) plus or minus an adjustment frequency (Δf) based on any measured deviation (ΔCOM) of the COM of the spectrally dispersed sampled beam 120 from the expected value.

[0060] It is contemplated herein that adjusting the frequency of drive signal 116 based on deviations in the COM of spectrally dispersed sampling beam 120 provides a robust and efficient technique suitable for compensating for a wide range of spectral variations. Yet, it is not necessary for detector 124 following dispersive element 122 to resolve the spectral power in each optical mode or at each individual wavelength of sampling beam 120. Rather, the COM of spectrally dispersed sampling beam 120 can provide an indication of the spectral variation relevant to compensating for the effect of the spectral variation on deflection angle 214.

[0061] For example, if the spectral power of sampling beam 120 (and thus light beam 106) is concentrated around a single center frequency and that center frequency shifts over time, the COM of sampling beam 120 can be mapped to that center frequency, and the frequency (f2) of drive signal 116 can be adjusted to track that center frequency.

[0062] For example, if the spectrum of sampling beam 120 is more complex, with its power appearing at multiple wavelengths and these wavelengths shift over time, the COM of sampling beam 120 can be assigned to the effective center wavelength of the spectral power distribution. In some cases, sampling beam 120 may have no power at its effective center wavelength. However, by adjusting deflection angle 214 of optical beam 106 based on the effective center wavelength, accurate optical scanning based on the effective center frequency of the spectral power distribution can be achieved.

[0063] 4A-4C, by way of example, illustrate COM variations of a sampling beam 120 in response to various spectral variations, according to one or more embodiments of the present disclosure. FIG. 4A is a simplified conceptual diagram of a first spectrally dispersed sampling beam 120 including a single lobe 402 associated with a first wavelength (λ), according to one or more embodiments of the present disclosure. FIG. 4B is a simplified conceptual diagram of a second spectrally dispersed sampling beam 120 including a single lobe 404 associated with a second wavelength (λ), according to one or more embodiments of the present disclosure. FIG. 4C is a simplified conceptual diagram of a third spectrally dispersed sampling beam 120 including a first lobe 406 associated with a third wavelength (λ) and a second lobe 408 associated with a fourth wavelength (λ), according to one or more embodiments of the present disclosure.

[0064] In Figures 4A-4C, lobes 402-408 each have a symmetric power distribution (not shown) and the same physical size. In Figures 4A and 4B, the entire power of sample beam 120 resides in each of lobes 402 and 404. In Figure 4C, the power of sample beam 120 is evenly distributed between lobes 406-408.

[0065] In Figure 4A, the COM of sampling beam 120 can be associated with the center of lobe 402. Furthermore, the center of lobe 402 can be associated with the physical center of detector 124, which can be associated with the expected COM position (COM0). According to this situation, Figure 4A can be associated with the case where no compensation for the frequency of drive signal 116 is required.

[0066] 4B, the COM of the spectrally distributed sampling beam 120 can be associated with the center of lobe 404. This situation can be associated with a simple shift in the center frequency of sampling beam 120 from λ to λ and a corresponding COM shift (Δ) of the spectrally distributed sampling beam 120. Therefore, a frequency adjustment (Δf) can be provided by controller 110 to compensate for the COM shift (Δ).

[0067] In Figure 4C, the COM of the spectral power distribution sampling beam 120 can be associated with an additional wavelength λ4, regardless of whether the sampling beam 120 provides light at that wavelength. For example, two lobes are depicted in Figure 4C at wavelengths λ2 and λ3, and the COM is associated with an additional wavelength λ4 located between the two lobes. In either case, this wavelength λ4 can be associated with a COM of the spectral power distribution of the sampling beam 120 and thus provide a convenient wavelength to use as the basis for adjusting the frequency of the drive signal 116 for deflecting the light beam 106. The COM of the power of the light beam 106 can be associated with this additional wavelength λ4 even if various portions of the light beam 106 have different deflection angles 214.

[0068] 4A-4C, it should be understood that Figures 4A-4C and the associated description are presented for illustrative purposes only and should not be construed as limiting. Rather, the spectral distribution sampling beam 120 may have any distribution across the detector 124.

[0069] Referring again to FIG. 1A, the optical scanner 100 can include any type of detector 124 suitable for determining the COM of the spectrally distributed sampling beam 120 .

[0070] In certain embodiments, detector 124 comprises a multi-pixel sensor array, such as, but not limited to, a line sensor for 1D measurements or an area sensor for 2D measurements. For example, detector 124 may take the form of, but not limited to, a complementary metal-oxide semiconductor (CMOS) sensor, a charge-coupled device (CCD), or an array of single-pixel photodiodes. The COM of spectrally distributed sampling beam 120 may be determined using any suitable technique. For example, each pixel may be associated with a wavelength range of sampling beam 120, allowing the COM to be determined based on the signal amplitudes of various pixels.

[0071] In certain embodiments, the detector 124 includes a position-sensitive sensor, such as, but not limited to, a segmented sensor or a transverse effect photodiode. For example, a segmented sensor can have one or more pixels in each of two or more segments. The COM of the incident light can then be determined by the relative ratio of the signals in each segment. For example, a segmented sensor with two segments interspersed along the dispersion direction 302 can perform unidirectional measurement of the COM along the dispersion direction 302. For another example, a segmented sensor with four segments arranged as a quadrant can perform bidirectional measurement, which may be suitable for, but is not limited to, accounting for misalignment between the detector 124 and the dispersive element 122. For example, the transverse effect photodiode can have a single elongated photodiode element with multiple contacts attached, and the COM of the incident light can be determined based on the relative signals from the multiple contacts.

[0072] As contemplated herein, position sensitive sensors typically have shorter readout times than multi-pixel sensor arrays due to their relatively smaller pixel count and / or readout efficiency. As a result, position sensitive sensors can sample sampled beam 120 at a relatively higher rate than multi-pixel sensor arrays, thereby enabling faster correction for the frequency of drive signal 116. However, multi-pixel sensor arrays can provide more precise measurements of the spectral distribution of sampled beam 120 than position sensitive sensors. Therefore, optical scanner 100 may include some combination of position sensitive sensors and multi-pixel sensor arrays.

[0073] It is further contemplated herein that 1D measurements may be sufficient to provide compensation along multiple scan axes for multiple AODs 108. 2D measurements may be preferred for configurations where the light beam 106 is sampled after the AODs 108 and frequency correction is performed in a closed loop that returns the COM relative to the 2D center on the image plane of the AOD 108 plane (e.g., after the beam sampler and optical relay).

[0074] In certain embodiments, the optical scanner 100 and / or system 102 includes an adaptive optics element 134 that provides spatially adjustable control of various portions of the light beam 106. For example, the adaptive optics element 134 may include, but is not limited to, a deformable mirror, a MEMS device, a spatial light modulator (SLM), or a piezoelectric mirror (or mirror pair). The adaptive optics element 134 may be suitable for controlling any beam parameter, such as, but not limited to, beam size, beam divergence, or beam propagation direction.

[0075] The adaptive optics 134 may be located in any suitable location in the optical scanner 100. For example, as depicted in Figures 1A and 1B, the adaptive optics 134 may be located in the post-AOD 108 path of the light beam 106, thereby modifying one or more characteristics of the light beam 106 after deflection by the AOD 108. Furthermore, the adaptive optics 134 may be communicatively coupled to the controller 110, which may in turn provide a drive signal 136 for the adaptive optics 134 to control one or more characteristics of the adaptive optics 134. As an example, the controller 110 may adjust the drive signal 136 for the adaptive optics 134 based on signals from any of the one or more detectors 124.

[0076] In certain embodiments, the adaptive optics 134 provides adjustable optical power. For example, the adaptive optics 134 can operate as a lens with an adjustable focal length. Thus, the adaptive optics 134 can provide adjustable optical power based on the spectrum of the light beam 106 (e.g., as measured by the sample beam 120). Furthermore, the adaptive optics 134 can provide separate optical power along two directions (e.g., along two scan directions). In this way, the adaptive optics 134 can operate as a cylindrical focusing element.

[0077] As contemplated herein, various instabilities in the light beam 106 can result from variations in the spot size and / or divergence of the light beam 106 after deflection by the AOD 108. For example, if the light beam 106 contains light of multiple wavelengths, different wavelengths will result in different deflection angles 214 from the AOD 108 (e.g., based on equation (1)). This can be true even when the frequency of the drive signal 116 to the AOD 108 has been adjusted as described herein. As a result, spectral variations in the light beam 106 can result in variations in the beam divergence at the AOD 108. Also, for example, different optical modes of the light source 104 can cause the light beam 106 to emerge with different spot sizes, beam profiles, and / or divergences due to different mode profiles at the light source 104. Thus, various characteristics of the light beam 106 can vary before reaching the AOD 108.

[0078] Therefore, the optical power of the adaptive optics 134 may be adjusted (e.g., by a drive signal 136 provided by the controller 110) to provide consistent beam characteristics (e.g., divergence, spot size, beam profile, etc.) regardless of variations in the light beam 106.

[0079] As one example, the optical power of adaptive optics 134 can be adjusted based on signals from one or more detectors 124 to provide a collimated light beam 106 regardless of variations in light beam 106. As another example, in the system 102 depicted in FIG. 1B, the optical power of adaptive optics 134 can be adjusted based on signals from one or more detectors 124 to provide a consistent focused spot size on specimen 128 (e.g., in conjunction with additional components such as focusing optics 130 or additional optics).

[0080] As contemplated herein, the controller 110 can utilize any type of detector 124 to modify the drive signal 136 for the adaptive optics 134. In certain embodiments, the controller 110 can utilize a multi-pixel sensor array (e.g., a line sensor, an array sensor, etc.) and thus take advantage of the additional information provided by such a sensor. For example, it may be desirable to adjust the optical power of the adaptive optics 134 based on the spectral width of the sampled beam 120, which may affect the total divergence of the light beam 106 from the AOD 108 along the scan direction. In turn, the increased spectral resolution provided by a multi-pixel sensor array can facilitate more sensitive spectral width measurements than position-sensitive detectors. However, it should be understood that this is merely an example and should not be considered limiting. In some cases, the controller 110 can utilize a signal from a position-sensitive detector to adjust the drive signal 136 for the adaptive optics 134.

[0081] Referring again generally to FIGS. 1A and 1B, various additional aspects of optical scanner 100 will now be described in more detail, in accordance with one or more embodiments of the present disclosure.

[0082] In certain embodiments, the optical scanner 100 includes one or more components suitable for monitoring the performance of the AOD 108. For example, thermal drift in the AOD 108 can affect the refractive index of the host material 204 and / or the modulation depth (e.g., the amplitude of the refractive index fluctuations Δn forming the diffraction grating 206) of the diffraction grating 206. Thermal drift in the AOD 108 can in turn affect the diffraction efficiency of the diffraction grating 206 and the power of the light beam 106 deflected by the AOD 108.

[0083] Figure 5 is a simplified schematic diagram of a portion of optical scanner 100 according to one or more embodiments of the present disclosure that includes an additional detector 502 for monitoring the performance of AOD 108. Specifically, Figure 5 is a modified version of Figure 2, and the description of Figure 2 can be extended to Figure 5.

[0084] In certain embodiments, the optical scanner 100 includes at least one additional detector 502 that monitors the power of at least one diffraction order of the light beam 106 generated by the AOD 108. For example, although the diffraction efficiency of the first diffraction order 210 by the AOD 108 is typically high (particularly when operating in the Bragg condition), at least some power typically exists in additional, non-zero diffraction orders. For example, at least a few percent of the power of the light beam 106 may exist as a second diffraction order 212 and / or as an additional first diffraction order 504 having an opposite sign to the first diffraction order 210 associated with the main polarization of the light beam 106. For example, when operating in the Bragg condition, a significant portion of the power of the light beam 106 will be the first diffraction order 210, as discussed in connection with FIG. 2; this first diffraction order 210 may be referred to as either a +1 or a −1 diffraction order, depending on the sign convention. On the other hand, it may also be true that at least some smaller portion of the power of light beam 106 may be in the form of additional first order diffracted beam 504 of opposite sign.

[0085] As contemplated herein, these additional non-zero diffraction orders can be advantageously physically separated from the main-scan range (e.g., the main working window) for easy access and without subtracting from the power output of the AOD 108. In contrast, monitoring the thermal drift of an AOD using certain alternative techniques may require injecting an additional weak drive signal into the AOD to generate weak diffractions at other angles and tracking the stability of the weak diffractions. In certain embodiments, such an additional drive signal can eliminate the need for a separate dispersive element 122, especially if the additional drive signal has a higher frequency than the drive signal 136. In this configuration, the detector 124 can be positioned to capture dispersed light associated with diffraction from the grating produced by the additional drive signal (e.g., by the periodic acoustic wave generated by the additional drive signal).

[0086] The controller 110 can then be coupled to the additional detector 502 to monitor the power of the relevant non-zero diffraction orders. For example, the power increase in such non-zero diffraction orders can be a measure of the thermal drift of the AOD 108.

[0087] If the light beam 106 exhibits spectral fluctuations, those spectral fluctuations may further affect the power of one or more additional non-zero diffraction orders. In such cases, the controller 110 can separate the relative effect of thermal drift in the AOD 108 from the spectral fluctuations based on the signals from one or more detectors 124. For example, the spectral fluctuations in the light beam 106 will typically occur on a shorter timescale than the thermal drift in the AOD 108. Therefore, by measuring the power fluctuations of the additional non-zero diffraction orders with the additional first-order diffracted beam 504 and then filtering out or ignoring those that correspond to observable spectral fluctuations in the controller 110, the thermal drift in the AOD 108, which occurs on a relatively longer timescale, can be monitored.

[0088] In certain embodiments, the controller 110 is further configured to adjust the amplitude of the drive signal 116 to the AOD 108 based on signals from any of the one or more detectors 124. As described earlier in this application in connection with Figure 2, the amplitude of the drive signal 116 can control the modulation depth of the induced diffraction grating 206, and thus the diffraction efficiency of the light beam 106. In this way, the controller 110 can adjust the intensity or power of the light beam 106 deflected by the AOD 108.

[0089] In certain embodiments, the controller 110 adjusts the amplitude of the drive signal 116 to provide the light beam 106 with a constant power. As contemplated herein, the power of the light beam 106 may fluctuate for a variety of reasons. In any case, the controller 110 adjusts the amplitude of the drive signal 116 to provide the light beam 106 with a constant power over time.

[0090] For example, the power of light beam 106 from light source 104 may fluctuate. Such power fluctuations may be detected using any suitable technique and provided to controller 110. For example, the power fluctuations of sampling beam 120 may comprise a fixed percentage of the power of light beam 106, which may be monitored using one or more detectors 124.

[0091] Also, for example, since the power of the light beam 106 deflected by the AOD 108 may fluctuate due to thermal drift of the AOD 108, an additional first order diffracted beam 504 may be used to detect it, as described in connection with FIG. 5.

[0092] Also for example, the power of light beam 106 propagating through a wavelength-sensitive polarizing element (e.g., polarization rotator, polarizer, polarizing beam splitter, etc.) may fluctuate in response to spectral variations in light beam 106. Such power fluctuations may be monitored by an additional detector (not shown) and / or predicted based on the known wavelength response of the element and the spectral variations in light beam 106 as measured by one or more detectors 124.

[0093] Referring again to Figures 1A and 1B, it is contemplated herein that the controller 110 may use any technique known in the art to generate any of the adjustments described herein (e.g., frequency and / or amplitude of the drive signal 116 for the AOD 108, the drive signal 136 for the adaptive optics 134, etc.).

[0094] In certain embodiments, controller 110 generates the adjustment using a model and / or a lookup table based on the model. According to one non-limiting example, when generating a frequency adjustment (Δf) of drive signal 116 in response to spectral variations in sampled beam 120, the relationship between the COM of spectrally dispersed sampled beam 120 at the plane of detector 124 and the associated spectral variations can be determined based on the dispersion of dispersive element 122 and the separation between dispersive element 122 and detector 124. Thus, controller 110 can directly calculate the required frequency adjustment (Δf) based on the signal from detector 124 or can use a lookup table containing pre-calculated values.

[0095] In certain embodiments, the controller 110 generates adjustments using control loops (e.g., PID control loops, etc.) or machine learning based techniques.

[0096] In this configuration, the optical scanner 100 (and / or system 102) may include one or more detectors (not explicitly shown) that monitor specific characteristics of the optical beam 106 as feedback. Furthermore, a strict relationship between the parameter being adjusted and the feedback is not required. Rather, the feedback may be used to actively control and / or predict the amount of adjustment required. By way of one non-limiting example, when generating a frequency adjustment (Δf) of the drive signal 116, feedback from a detector monitoring the position of the optical beam 106 after deflection by the AOD 108 may provide suitable feedback for controlling the value of the frequency adjustment (Δf). By way of another non-limiting example, when adjusting the power of the optical beam 106, feedback from a detector monitoring the power of the optical beam 106 at a desired position may provide suitable feedback for controlling the amplitude of the drive signal 116. By way of another non-limiting example, when adjusting the spot size of the light beam 106 (e.g., on the specimen 128 depicted in FIG. 1B), a detector that monitors the spot size can provide feedback suitable for adjusting the drive signal 136 to the adaptive optics 134.

[0097] Reference is now made to Figure 6, which is a flow diagram illustrating steps performed in a method 600 for dynamic control of an optical scanner in accordance with one or more embodiments of the present disclosure. Applicant notes that the embodiments and enabling technologies described herein in the context of optical scanner 100 should be understood to apply to method 600. However, it is further noted that method 600 is not limited to optical scanner 100 in its architecture.

[0098] In certain embodiments, method 600 includes step 602, which generates a sampled beam 120 from received light beam 106, the sampled beam 120 comprising a portion of light beam 106. For example, step 602 may be performed by a sampler 118, such as, but not limited to, an optical wedge or a beam splitter.

[0099] In certain embodiments, method 600 includes step 604, in which sample beam 120 is spectrally dispersed along dispersion direction 302. For example, step 604 can be performed with a dispersive element 122, such as, but not limited to, a prism, a diffraction grating, or the like.

[0100] In certain embodiments, method 600 includes step 606 in which at least a portion of sampled beam 120 dispersed along dispersion direction 302 is detected with one or more detectors 124 .

[0101] In certain embodiments, in step 608 of method 600, the center of mass of sampled beam 120 dispersed along dispersion direction 302 is determined based on signals from at least one of its one or more detectors 124.

[0102] In certain embodiments, in step 610 of method 600, a drive signal 116 is generated for the AOD 108 based on its center of mass to deflect the light beam 106 along the specified deflection angle 214. Furthermore, if there are multiple AODs 108 (e.g., those for different scan directions), a drive signal 116 may be generated for each AOD 108. The drive signals 116 for the AODs 108 may be the same if they are operated at the same frequency, or may be different if they are operated at different frequencies. For example, operating at different frequencies may advantageously address specific portions of the overall 2D field of view.

[0103] In certain embodiments, in step 612 during method 600 , the light beam 106 is deflected with the AOD 108 driven by the drive signal 116 .

[0104] The subject matter described herein is often depicted with various components embedded within or connected or coupled to other components. It should be understood that such illustrated architectures are merely exemplary, and that in fact, many other architectures may be implemented that achieve the same functionality. Conceptually, any arrangement of components that achieve the same function is effectively "integrated" to achieve the desired function. Thus, any two components herein that are combined to achieve a particular function can be viewed as being "integrated" with each other to achieve the desired function, regardless of the architecture or intervening components. Similarly, any two components so integrated can also be viewed as being "connected" or "coupled" to each other to achieve the desired function, and any two components that can be integrated in this manner can also be viewed as being "combinable" with each other to achieve the desired function. Examples of what can be coupled include, but are not limited to, physically matable and / or physically interacting components, and / or wirelessly interactable and / or wirelessly interacting components, and / or logically interactable and / or logically interacting components.

[0105] The present disclosure and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes can be made in the form, construction and arrangement of the parts without departing from the disclosed subject matter or diminishing all of its essential advantages. The described form is illustrative only, and it is the intent of the following claims to encompass and embrace all such modifications. It is the appended claims which further define the invention.

Claims

1. 1. An optical scanner comprising: a sampler for receiving the light beam and providing a sampled beam comprising a portion of the light beam; a dispersive element for spectrally dispersing the sampled beam along a dispersion direction; one or more detectors configured to receive at least a portion of the sampled beam dispersed along the dispersion direction; one or more acousto-optic deflectors (AODs) configured to deflect the light beam from the sampler; a controller communicatively coupled to at least the one or more AODs and the one or more detectors, the controller having one or more processors configured to execute program instructions; and wherein execution of the program instructions causes the one or more processors to: determining a center of mass of the dispersed sample beam along the dispersion direction based on a signal from at least one of the one or more detectors; and generating a drive signal based on the center of mass for deflecting the light beam from the sampler along a specified deflection angle in at least one of the one or more AODs; Optical scanner.

2. 2. The optical scanner according to claim 1, wherein when generating the drive signal, calculating a first frequency of the drive signal that results in the specified deflection angle based on an expected value of the center of mass that is related to an expected wavelength of the sample beam; calculating an adjustment frequency based on a deviation of the center of mass of the sampled beam dispersed along the dispersion direction from the expected value of the center of mass; and generating the drive signal at a second frequency based on the first frequency and the adjusted frequency; Optical scanner.

3. 10. The optical scanner of claim 1, wherein the one or more detectors include a position sensitive sensor.

4. 4. An optical scanner according to claim 3, wherein the position sensing sensor comprises: An optical scanner comprising a segmented sensor having two or more segments, the center of mass being determinable based on the relative intensities of the sampling beam in the two or more segments.

5. 5. An optical scanner according to claim 4, wherein the segmented sensor has two segments interspersed along the dispersion direction, and the center of mass can be determined based on the relative intensities of the sampled beam in the two segments.

6. 5. An optical scanner as recited in claim 4, wherein the segmented sensor has four segments arranged in quadrants, and the center of mass can be determined based on the relative intensities of the sampling beam in the four segments.

7. 10. The optical scanner of claim 1, wherein the one or more detectors include a multi-pixel sensor array.

8. 8. The optical scanner of claim 7, wherein the multi-pixel sensor array comprises: An optical scanner comprising a line array sensor having a single row of pixels, the pixels of the row being interspersed along the dispersion direction.

9. 8. The optical scanner of claim 7, wherein the multi-pixel sensor array comprises: An optical scanner comprising an area array sensor having two or more rows of pixels, the pixels within each row being interspersed along the dispersion direction.

10. 10. The optical scanner of claim 1, further comprising: an adaptive optics element having adjustable optical power, the adaptive optics element configured to receive the light beams from the one or more AODs, and the program instructions further include causing the one or more processors to: An optical scanner configured to generate an additional drive signal for controlling the optical power at the adaptive optic.

11. 11. The optical scanner according to claim 10, wherein when generating the additional drive signal for controlling the refractive power of the adaptive optical element, an optical scanner that generates the additional drive signal for controlling the refractive power of the adaptive optics so that the light beam is collimated;

12. 11. The optical scanner according to claim 10, wherein when generating the additional drive signal for controlling the refractive power of the adaptive optical element, An optical scanner that generates the additional drive signal for controlling the refractive power of the adaptive optical element so that the light beam has a focused spot size when focused by at least one of the adaptive optical element and an additional focusing element.

13. 11. The optical scanner according to claim 10, wherein when generating the additional drive signal for controlling the refractive power of the adaptive optical element, An optical scanner that generates the additional drive signal for controlling the optical power of the adaptive optic based on the center of mass.

14. 11. The optical scanner according to claim 10, wherein when generating the additional drive signal for controlling the refractive power of the adaptive optical element, an optical scanner that generates the additional drive signal for controlling the refractive power of the adaptive optics, the additional drive signal taking into account the width of the sampled beam dispersed along the dispersion direction, based on a signal from at least one of the one or more detectors.

15. 10. The optical scanner of claim 1, further comprising: a wavelength-sensitive polarizing optics on a path of the light beam, the program instructions further causing the one or more processors to: An optical scanner configured to adjust the amplitude of the drive signal based on the center of mass so as to produce the light beam of a specified power from the wavelength-sensitive polarization optics and the one or more AODs.

16. 10. The optical scanner of claim 1, further comprising: an additional detector configured to receive at least a portion of the additional diffraction orders of the light beam from the one or more AODs; The program instructions may further cause the one or more processors to: an optical scanner configured to monitor thermal drift of the one or more AODs based on the power of the additional diffraction orders;

17. 2. The optical scanner of claim 1, wherein the program instructions further cause the one or more processors to: comparing the power of the additional diffraction orders to the center of mass; and separating the thermal drift of the one or more AODs from spectral fluctuations of the sampled beam based on the center of mass; Optical scanner.

18. 10. The optical scanner of claim 1, wherein the sampler, the dispersive element, and the one or more AODs are configured to operate at wavelengths in the range of 9 to 12 micrometers.

19. 1. A system comprising: a light source configured to generate a light beam; It is a scanner, a sampler for receiving the light beam and providing a sampled beam comprising a portion of the light beam; a dispersive element for spectrally dispersing the sampled beam along a dispersion direction; one or more detectors configured to receive at least a portion of the sampled beam dispersed along the dispersion direction; one or more acousto-optic deflectors (AODs) configured to deflect the light beam from the sampler; a scanner comprising: a controller communicatively coupled to at least the one or more AODs and the one or more detectors, the controller having one or more processors configured to execute program instructions that cause the one or more processors to: determining a center of mass of the dispersed sample beam along the dispersion direction based on a signal from at least one of the one or more detectors; and generating a drive signal based on the center of mass for deflecting the light beam from the sampler along a specified deflection angle in at least one of the one or more AODs; A controller; one or more focusing optics configured to focus the light beam deflected by the one or more AODs onto a specimen; A system comprising:

20. 20. The system of claim 19, wherein the light source comprises: Carbon dioxide (CO ２ ) A system comprising a laser light source.

21. 21. The system of claim 20, wherein the light beam has a wavelength in the range of 9 to 12 micrometers, and the sampler, the dispersive element, and the one or more AODs are configured to operate at wavelengths in the range of 9 to 12 micrometers.

22. 20. The system of claim 19, wherein generating the drive signal comprises: calculating a first frequency of the drive signal that results in the specified deflection angle based on an expected value of the center of mass that is related to an expected wavelength of the sample beam; calculating an adjustment frequency based on a deviation of the center of mass of the sampled beam dispersed along the dispersion direction from the expected value of the center of mass; and generating the drive signal at a second frequency based on the first frequency and the adjusted frequency; system.

23. 20. The system of claim 19, wherein the one or more detectors include a position sensitive sensor.

24. 24. The system of claim 23, wherein the position sensing sensor comprises: A system comprising a segmented sensor having two or more segments, the system being capable of determining the center of mass based on the relative intensities of the sampled beam in the two or more segments.

25. 25. The system of claim 24, wherein the segmented sensor has two segments interspersed along the dispersion direction, and the center of mass can be determined based on the relative intensities of the sampled beam in the two segments.

26. 25. The system of claim 24, wherein the segmented sensor has four segments arranged in quadrants, and the center of mass can be determined based on the relative intensities of the sampled beam in the four segments.

27. 20. The system of claim 19, wherein the one or more detectors include a multi-pixel sensor array.

28. 28. The system of claim 27, wherein the multi-pixel sensor array comprises: A system comprising a line array sensor having a single row of pixels, the pixels of the row being interspersed along the dispersion direction.

29. 28. The system of claim 27, wherein the multi-pixel sensor array comprises: A system comprising an area array sensor having two or more rows of pixels, the pixels within each row being interspersed along the dispersion direction.

30. 20. The system of claim 19, further comprising: an adaptive optics element having adjustable optical power, the adaptive optics element configured to receive the light beams from the one or more AODs, and the program instructions further include causing the one or more processors to: A system configured to generate an additional drive signal for controlling the optical power at the adaptive optic.

31. 31. The system of claim 30, wherein generating the additional drive signal for controlling the optical power of the adaptive optic comprises: A system for generating the additional drive signal for controlling the optical power at the adaptive optics such that the light beam is collimated.

32. 31. The system of claim 30, wherein generating the additional drive signal for controlling the optical power of the adaptive optic comprises: a system for generating the additional drive signal for controlling the optical power of the adaptive optics such that, upon focusing by at least one of the adaptive optics and an additional focusing element, a focused spot size of the light beam is provided.

33. 31. The system of claim 30, wherein generating the additional drive signal for controlling the optical power of the adaptive optic comprises: A system for generating the additional drive signal for controlling the optical power at the adaptive optic based on the center of mass.

34. 31. The system of claim 30, wherein generating the additional drive signal for controlling the optical power of the adaptive optic comprises: a system for generating the additional drive signal for controlling the optical power of the adaptive optics, the additional drive signal taking into account the width of the sampled beam dispersed along the dispersion direction, based on a signal from at least one of the one or more detectors.

35. 20. The system of claim 19, further comprising: a wavelength-sensitive polarizing optics on a path of the light beam, the program instructions further causing the one or more processors to: A system configured to adjust the amplitude of the drive signal for the AOD based on the center of mass so as to produce a specified power of the light beam from the wavelength-sensitive polarization optics and the AOD.

36. 20. The system of claim 19, further comprising: an additional detector configured to receive at least a portion of the additional diffraction orders of the light beam from the AOD; The program instructions may further cause the one or more processors to: A system configured to monitor thermal drift of the AOD based on the power of the additional diffraction orders.

37. 20. The system of claim 19, wherein the program instructions further cause the one or more processors to: comparing the power of the additional diffraction orders to the center of mass; and separating the thermal drift of the AOD from spectral fluctuations of the sampled beam based on the center of mass; system.

38. 1. A method comprising: generating a sampling beam from the received light beam, the sampling beam including a portion of the light beam; spectrally dispersing the sampled beam along a dispersion direction; detecting at least a portion of the sampled beam dispersed along the dispersion direction with one or more detectors; determining a center of mass of the dispersed sample beam along the dispersion direction based on a signal from at least one of the one or more detectors; generating a drive signal based on the center of mass for deflecting the light beam along a specified deflection angle with an acousto-optic deflector (AOD); deflecting the light beam with the AOD driven by the drive signal; method.

39. 39. The method of claim 38, further comprising: A method for generating an additional drive signal for causing an adaptive optics element to at least one of collimate and focus the light beam based on at least one of the width and center of mass of the sampled beam dispersed along the dispersion direction.

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