WO2022146991A1 - High-speed linear light valve array - Google Patents

Abstract

High-speed laser modulation is disclosed, A linear array of dynamic elements is illuminated with a line beam. Cantilever array elements are displaced to modulate pixels along the linear array for projection. Projected images are characterized by high resolution, high speed, high efficiency and high contrast. A high power modulated and projected laser line fuses material for additive manufacturing.

Description

HIGH-SPEED LINEAR LIGHT VALVE ARRAY

BACKGROUND OF THE INVENTION

Field of the Invention

[001] The field of the invention is laser-based material processing with a spatially modulated laser spot. More particularly, the invention relates to material processing with a selectively modulated linear spot.

Background of the Invention

[002] Additive manufacturing (also known as three-dimensional printing) techniques have been used to manufacture three-dimensional structures of almost any shape. Using an additive process, successive layers of material are deposited to form the structure based on data defining a 3D model of the structure. In some methods, the successive layers forming the structure are produced by depositing successive layers of powder material and using a light beam (e.g., laser light) to bind or fuse the powder material in selected regions of each layer. Examples of these methods include selective laser sintering (SLS) wherein the laser sinters the powder particles in the selected regions to form each build layer of the structure and selective laser melting wherein the laser melts the powder in the selected regions such that the melted material hardens to form each build layer of the structure.

[003] Although such laser additive manufacturing (LAM) techniques have been successful, the movement of the laser to the selected regions often slows the build rate and the speed of manufacturing. Multiple beams have been used in an effort to increase speeds, but scanning multiple beams across the powder layers may result in stresses being created in the fused material of each build layer. The thermal energy, for example, may cause thermal part stress, which may deform the three-dimensional structure as the build layers are formed. As such, LAM techniques have not been as successful when used with certain materials such as superalloys because thermal stresses may result in cracking. Also, LAM techniques have not been as successful when used with powder material having larger particle sizes because the power of the laser may not be sufficient to melt and fuse larger particles sizes without causing excessive thermal stress.

[004] Moreover, faster build rates generally require energy to be introduced into the powder bed faster (i.e., at higher power). Increasing the power of a LAM system is challenging because optical elements must be larger and cooling must be increased to withstand the higher power. The scanning mirror in such systems becomes less responsive with the increased size, which decreases the scanning speed and reduces build speed. Dallarosa et al. in United States Patent 10,399,183 disclose a light source array to provide an improved scanned multiple beam selective laser melting system.

[005] In laser projection equipment for material processing applications such as 3D printing, projectors are generally based on 2 dimensional micro-mirror arrays such as the Texas Instruments Digital Light Processing (DLP) technology using Digital Micro-mirror Device (DMD) chips. Current high-speed DMD pattern rates are 15 kHz to 33 kHz in TI DLP devices. For laser processing with DLP, pattern rates may be 12.5 kHz for a binary 1280 x 800 pattern. These devices use micron scale mirrors, and energy diffracted by the mirror array contributes to reduction of efficiency and contrast ratio that can be achieved, and so generally there is a trade-off between actuation speed (smaller mirror size) and high contrast (low diffraction losses).

[006] Another laser projection scheme for material processing uses a linear array of modulator elements, for example the Silicon Light Machines suspended ribbon Grating Light Valve (GLV) MEMS (micro-electrojnechanical system) device. The GLV modulates a line of laser light by varying a diffraction grating profile. The grating is a linear array of ribbons and phase heights of multiple fixed angle ribbons (e.g. 4 ribbons per pixel) are set to control diffraction on a pixel by pixel basis.

[007] More recently, Silicon Light Machines has introduced the planar light valve (PLV). The planar light valve uses an array of variable phase height discs for light modulation. The actuated discs introduce a phase shift of 180 degrees so that light is either reflected or diffracted for modulation.

[008] Many aspects of electrostatically driven L-shaped MEMS ribbons are described in U.S. Pat. No. 8848278 (‘278) the disclosure of which is hereby incorporated by reference in its entirety. As shown in FIG. 1 and FIG. 2, the ‘278 modulator bends ribbons to contour the linear array surface.

[009]

[010] Accordingly, there is a need for an additive manufacturing system and method that allows faster build rates while reducing thermal stresses in the fused material. BRIEF SUMMARY OF THE INVENTION

[Oi l] In at least one embodiment of the present invention in a laser scanning based projection system, a method of a light modulation is provided. The method incudes characterizing the optical response of dynamic blazed grating elements in a 1 -dimensional linear array of electrostatically actuated reflective dynamic blazed grating elements over a range of control voltages and temporal control voltage waveforms, correlating at least one projected pixel intensity with the characterized optical response, generating a set of operational control voltage waveforms such that actuation of grating elements provides a predetermined light distribution in the pixel array, illuminating the 1- dimensional linear array of reflective dynamic blazed grating elements with a line beam, reflecting and directing a portion of the line beam to a projection optical system with actuated blazed grating elements, modulating the line beam with the array by applying a sequence of sets of control voltage waveforms to one or more sets of grating elements to displace one or more respective grating element to selectively modulate the reflected light according to a predetermined light distribution pattern in a sequence of 1 dimension pixel array images, so that the projection optical system images a modulated portion of the reflected illumination to form a projected image.

[012] Light modulation may include scanning the 1 dimensional array image across an image field and sequentially modulating pixels of the array to form a 2 dimensional scanned image frame, modulating pixels at or above 100 kHz and forming a projected frame of a video or cinema image at a frame rate of at least 24 frames per second with a modulation bit depth of at least 10 bits. A color image may be projected using at least 3 different laser source wavelengths and respective modulators.

[013] Temporal control voltage waveforms can include pulse width and pulse amplitude modulation voltages within a pixel exposure period.

[014] The steps of characterizing and correlating may include determining control voltage values for a pixel based on the predetermined pixel intensity value and the intensity value of at least one other pixel in the array, and the steps of characterizing and correlating may include comprise determining control values of a pixel based on the predetermined pixel value and the value of at least one preceding or subsequent pixel the scanned image. [015] In other embodiments of the present invention, a high-speed system for modulating a line beam of light with a micro-electro-mechanical-system (MEMS) is provided. The system includes a one-dimensional MEMS array of at least partially reflective dynamic grating elements on a substrate configured to receive and modulate line beam illumination. Each dynamic element has an L-shaped cross section in a plane parallel to the axis of the array and perpendicular to the plane of the substrate. The L-shaped cross section extends along each grating element in a direction parallel to the substrate and non-parallel to the axis of the array. A pedestal is rigidly coupled to the substrate extending from the substrate in a direction normal to the plane of the substrate, and an elongated cantilever is rigidly coupled to the pedestal such that the cross section of the pedestal and the cantilever forms the L-shape with a void between the substrate and the cantilever. The cantilever includes an addressable top electrode and the substrate includes a common bottom electrode. Dynamic grating elements are controllably displaceable about an axis parallel to both the substrate and the grating element length. The element displacement varies an angle between a portion of the grating element reflective surface and the substrate such that the height of the cantilever end corresponds to a control voltage potential between the top electrode and the bottom electrode. The voltage is correlated to a desired line beam modulation profile, and the modulation profile of a projected image of the modulated line beam profile corresponds to a desired pixel array modulation profile.

[016] In a first pixel actuation state, multiple adjacent grating elements are displaced and in a second pixel actuation state a single grating element displaced. The efficiency of the first pixel state is greater than the second pixel state.

[017] The bottom electrode may be reflective.

[018] The MEMS array may have a planarized top reflector.

[019] The system may include an addressable voltage controller to apply control voltages to multiple elements of the dynamic array.

[020] Non-displaced grating elements may reflect light in an OFF-state with diffracted light energy less than .1 % in an adjacent diffraction order,

[021] Non-displaced grating elements may reflect light in an OFF-state with diffracted light energy less than ,025% in an adjacent diffraction order. [022] In at least one embodiment, the displacement of a plurality of elements is limited by cantilever contact with the substrate. The reflective surface contour forms a phase optimized blazed grating. Displacement of the end of the cantilever may be X/2 and the reflective surface shape of the cantilever contacting the substrate may be modified with the control voltage.

[023] In at least one embodiment, the displacement of an element corresponds to a control voltage, the cantilever surface comprises a variable blazed surface corresponding to the control voltage, and the end of the cantilever is suspended. The unactuated cantilever is suspended in a range of 2-3 X over the substrate and an actuated cantilever tip is displaced by X/2.

[024] The displacement of multiple grating elements corresponds to the intensity of a single pixel and the intensity of a pixel may be modulated by a pulse width modulation control voltage waveform over a pixel exposure period with 10 or 12 bit light levels.

[025] The control voltage includes a rising edge from 10% to 90%, a peak voltage period with variable duration and a falling edge from 90% to 10%. The rise time from a light modulator off state to a light modulator on state may be below 300 ns and the dynamic element resonant frequency may be at least 2.5 MHz. The off-state cantilever and substrate reflections from the dynamic array are phase optimized to provide a high contrast ratio > 5000:1. The on-state cantilever and substrate reflections from the dynamic array are phase optimized to provide efficient pixel modulation.

[026] In at least one embodiment, a high-speed micro-electro-mecbanical-system line beam light modulator includes a plurality of reflective L-shaped dynamic grating elements in an optically phase matched linear array on a substrate. Each element is responsive to a control voltage waveform for electrostatic actuation from a non-energized off state to an energized on state.

[027] In at least one embodiment, a high power laser modulator includes an array of L-shaped dynamic blazed grating elements disposed on a substrate, each element has a reflective cantilever in thermal contact with a substrate through a thermally conductive pedestal along a fixed edge of the dynamic grating element to the substrate, and the length of thermal contact is greater that the width of the blazed grating element. Thermal conductivity of the thermal contact is greater than thermal conductivity along the length of the cantilever. The pedestal comprises a low thermal resistance thermal contact. [028] In at least one embodiment a high-speed, high-power, laser-based additive manufacturing system is provided. A laser source is characterized by wavelength, average power, and M^A2 , source providing an input beam. An illumination subsystem is configured to receive the input beam and image the beam to a uniform intensity line beam at an image plane. The uniform line beam has a first line beam aspect ratio of length divided by width. A high-speed SLY (Silicon Light Valve) modulator is configured to receive the uniform line beam, to modulate one or more portions of the line beam, and to reflect the modulated line beam along a projection optical axis. The SLY has a characteristic laser damage threshold. A projection lens subsystem is configured to receive the modulated line beam and project a processing line beam on fusible material and to selectively fuse portions of the fusible material by modulated laser irradiation. The processing fine beam has a second line beam aspect ratio. A relative motion system provides controllable displacement between the modulated line beam and the fusible material such that predetermined areas of fusible material are sequentially processed to add material to a workpiece. The first aspect ratio is less than the second aspect ratio, and the difference in aspect ratios provides one or more of reduced laser fluence impinging the SLY and an improved processing speed. The first aspect ratio is greater than one and has a top hat illumination profile along the length of the line. There may be less than 10 percent variation in the top hat between 90 percent threshold line ends and the second aspect ratio may be a variable ratio.

[029] In at least one embodiment a high-speed modulator provides selective pulse width modulation to one or more portions of the processing line beam, and predetermined areas of fusible material are processed. Multiple actuations of a blazed grating element may modulate a portion of the line beam and control integrated power delivered to a corresponding voxel.

[030] In at least embodiment, a high-speed SLY modulator is responsive to volumetric control signals and is configured to receive the uniform line beam, to modulate one or more portions of the line beam that correspond io workpiece voxels, and to reflect the modulated line beam along a projection optical axis.

[031] In at least one embodiment, a relative motion system provides controllable displacement along a predetermined trajectory between the modulated line beam and the fusible material such that predetermined areas of fusible material are sequentially processed to add material to a workpiece. The relative motion comprises a trajectory of the processing line beam at a layer of a workpiece according to a workpiece build plan, and volumetric control signals comprise a pixelated modulation profile of the line beam that is temporally coordinated with the trajectory.

[032] In at least one embodiment, a non-zero diffraction order corresponds to one of a snap-down state and a suspended cantilever state of selected portions of the SLV modulator, the non-zero difiraction order resulting from diffraction at one or more portions of a blazed grating profile along the SLV.

[033] In at least one embodiment, a high-speed, high-power, laser-based additive manufacturing method for adding material to a workpiece is provided. The method include the step of generating a laser processing input beam with a laser source that is characterized by wavelength, average power, and M^A2, propagating the input beam through an illumination subsystem, forming a uniform intensity line beam at an image plane with the illumination subsystem, modulating one or more portions of the line beam with a high-speed SLV modulator, reflecting the modulated line beam along a projection optical axis with the high-speed SLV modulator, propagating the modulated line beam through a projection lens subsystem, transforming the modulated line beam to a processing line beam with the projection lens subsystem, projecting the processing line beam onto fusible material, selectively fusing portions of the fusible material with modulated laser irradiation, and displacing the modulated line beam relative to the fusible material with a relative motion system along a predetermined build trajectory, wherein the line beam modulation and the displacement deposit a predetermined laser energy dose profile to fusible material voxels according to a build plan such that a stable melt process sequentially adds material to a workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

[034] The above and other aspects, features and advantages of the disclosure will become more readily apparent with the aid of the following drawings, in which:

[035] Fig. 1 provides a view of a prior art L-shaped dynamic elements.

[036] Fig. 2 provides a view of a prior art linear array modulator.

[037] Fig. 3 provides a view of a projection system.

[038] Fig. 4 provides a cross sectional view of L-shaped dynamic elements

[039] Fig. 5a provides diagram of a line image projection system

[040] Fig. 5b provides diagram of a line image projection system [041] Fig. 6a provides a cross sectional view of unactuated L-shaped dynamic elements

[042] Fig. 6b provides a cross sectional view of actuated L-shaped dynamic elements

[043] Fig. 6c provides a graph of a control voltage and actuated optical response

[044] Fig. 7 is a graph of contrast ratio vs wavelength

[045] Fig. 8 provides a graph of diffraction response vs angle

[046] Fig. 9a provides a graph of deflection versus time

[047] Fig. 9b provides a graph of diffraction efficiency versus deflection

[048] Fig. 10a provides a cross sectional view of unactuated suspended L-shaped dynamic elements

[049] Fig. 10b provides a cross sectional view of actuated suspended L-shaped dynamic elements

[050] Fig. 1 1 a provides a graph of temperature vs cantilever distance

[051] Fig. 1 lb provides a view of a cantilever position reference

[052] Fig. 12 provides a graph of a cantilever resonant optical response

[053] Fig. 13provides a cross sectional view of L-shaped dynamic dements with a surface defect

[054] Fig. 14 provides a graph of reflectivity vs wavelength for several materials

[055] Fig. 15 provides a cross sectional view of L-shaped dynamic elements with a bottom reflector

[056] Fig. 16 provides a block diagram of a modulator control system

DETAILED DESCRIPTION OF THE INVENTION

[057] In laser material processing applications, high-speed high-resolution and efficient modulation is needed in dynamic beam patterning systems. Further, it will be appreciated that laser material processing may utilize a monochromatic projector with a single illumination source. The present invention utilizes a modulation system for laser projection sources to provide improvements in these critical areas. Various modulator features may be adapted to a specific laser material processing including wavelength, modulation speed, and pixel dimensions.

[058] Laser sources contemplated are sources with sufficient power to fuse material at high processing rates. The present invention distributes and modulates applied laser energy to facilitate effective high-speed additive manufacturing. While the invention is not limited to any particular laser source, fiber lasers with visible green wavelengths from 515 nm to 540 nm and infrared from 980 nm to 1100 nm are of particular interest. Laser wavelength and other laser properties may be optimized for the material to be fused. For example green wavelengths may be preferred for copper processing. Laser power can range from several watts up to the kilowatt range depending on particular process material properties.

[059] The invention is particularly well-suited to delivering laser beams with high beam quality, for example lasers that generate beams with an M² value between 1 and 20. Lasers may be CW, quasi-CW or pulsed with laser beam delivery automatically controlled.

[060] Generally the laser source is transformed into a line beam for modulation. The line beam comprises a line width and length where the length divided by the wide comprises the aspect ratio of the line beam. Efficient transformation into a line beam is highly desirable, with minimal power losses and minimal degradation to laser beam quality. Ideally, high uniformity illumination along the length in a top hat shape provides maximized efficiency by minimizing modulation needed to achieve uniform beam delivery, the beam transformation system is configured to handle the high power laser source with appropriate element materials, surface coatings, surface apertures, and back-reflection management. Many examples of line beam generation are well-known.

[061] Systems and methods for additive manufacturing, consistent with the present disclosure, use a modulated line beam of light (e.g., laser light) simultaneously to expose powder material in selected regions until the powder material fuses to form voxels. Sequential exposure of layers forms build layers of a three-dimensional structure. The light may be generated from single or multiple sources, transformed to one or more line beam, modulated and projected with an optical head to different locations on each of the powder layers. The modulated line beam may provide distributed exposures forming a distributed exposure pattern including beam spots that are spaced sufficiently to separate the fused regions formed by each exposure. The modulated line beam may be moved using various techniques (e.g., by moving the optical head) and according to various scan patterns such that a plurality of distributed exposures form each build layer.

[062] By using a modulated line beam distributed exposures and by using certain scan strategies, the additive manufacturing system and method may increase build speeds while reducing stresses caused in the build layers, the additive manufacturing system may be used to form three- dimensional structures for a wide range of three-dimensional printing or rapid prototyping applications and from a variety of materials depending upon the application. The powder material may include, without limitation, metals, alloys and superalloys. More specifically, the powder materials may include, without limitation, powdered Ti-6A1-4V, nickel titanium or nitinol, nickel based superalloys (e.g., austenite nickebchromium-based superalloys known as Inconel) aluminum, stainless steel and cobalt chrome. Stainless steel 316L and cobalt chrome, for example, both provide good corrosion resistance and high strength. Stainless steel may be used, for example, for food processing or medical applications due to its sterilisability and resistance to fatigue and shock. Cobalt chrome may be used, for example, for medical implants due to its high wear resistance and ability to form small features with high strength, 'file powder material may also include any other powder material known for use in powder bed fusion additive manufacturing.

[063] Because of the higher powers available, particularly fiber lasers, the particle size of the powders may not be an issue when using the modulated line beam additive manufacturing systems and methods described herein. The additive manufacturing systems and methods may be used with powders having asymmetric particle sizes, including particle sizes smaller than 5 microns and particle sizes greater than 30 microns. The modulated line beam additive manufacturing systems and methods may also be used with powders having larger particle sizes, for example, greater than 50 microns.

[064] As used herein, "exposure” refers to an exposure of light for a defined period of time and "modulated line beam distributed exposure" refers to an exposure using a modulated line beam such that the beam provides exposures in different locations along a projected image of the line at the same time. As used herein, "powder material" refers to a material in the form of particles suitable for use in powder bed fusion additive manufacturing. As used herein, "fuse" refers to combining particles of powder material together as a single structure as a result of melting and/or sintering. As used herein, the terms "melt pool" and "melt ball" are used interchangeably to refer to a three-dimensional region of melted powder material formed by an exposure to a light beam. A "melt pool” or "melt ball" may have a generally spherical or spheroid shape but is not necessarily limited to any particular shape. As used herein, a "fused region" is a region of powder material that has been fused as a result of an exposure of a light beam forming a "melt pool" or "melt ball" and "distributed fused regions" refers to "fused regions” that are separated and formed generally simultaneously by a modulated line beam distributed exposure. As used herein, a "voxel" is a unit of three-dimensional space in a three-dimensional structure. A "voxel" may correspond to a "melt pool" or "melt ball" or "fused region" but is not necessarily the same size and shape as the melt pool or melt ball or fused region.

[065] Although the example embodiments described herein are used primarily for powder additive manufacturing using metal powders, the concepts described herein may be used with other materials and other types of additive manufacturing using lasers or light. Other materials may include, for example, resins, plastics, polymers and ceramics.

[066] Aspects and features of additive manufacturing systems are disclosed by Dallarosa et al. in United States Patent 10,399,183. Figure 1 and the accompanying description at column 6 line 27 through column 10 line 30 of the Dallarosa patent are incorporated herein by reference. The Dallarosa disclosure relates to additive manufacturing system including multiple beams from an array of light sources 130. The modulated line beam of the present invention in place of or in addition to the Dallarosa light source array can be applied as a modulated line beam distributed expose to fusible material in an additive manufacturing system, for example system 100.

[067] Contrast ratio can be measured for linear array embodiments of the present invention as the ratio of light transmitted in an on state to light transmitted in an off state. In contrast ratio measurements, parameters may be varied, for example illumination conditions, illumination wavelength, number of elements actuated, number of pixels actuated, temporal control, and pixel modulation levels.

[068] Efficiency can be evaluated for a projection system and for different parts of a projection system as a ratio of light output to light input at the brightest scene level. Various losses contribute to reductions in efficiency, for example diffraction losses and absorption in a reflective modulator. The combination of losses includes surface reflection, coating and bulk scatter, coating and bulk absorption, vignetting, and beam clipping, from illumination, modulation, and projection.

[069] Scanned line projection systems have the potential to provide significant improvements over prior art projection systems. In particular, the present invention can provide a high contrast ratio and high resolution using high-speed high resolution linear array modulators. Referring to FIG. 3, projector 300 projects modulated pixels 301 line image 302 onto target material 303. The target material is illuminated by scanning the modulated line image 302 across the screen while modulating the line image. . Horizontal scanning is depicted, but vertical scanning or other line sweep scanning is within the scope of the invention. Frames or voxel layers may be formed by a single sweep per frame or composite sweeps. For clarity, a vertical scan field is depicted, however for material processing applications the projection field may be a horizontal surface, or a surface in any orientation.

[070] By scanning a row, a column or along a scan trajectory segment, the pixel modulation rate can be determined by the sweep velocity and the number of pixels along the scan. Within each pixel period a combination of modulation techniques including pulse width modulation (PWM) and greyscale (i.e. analog) modulation can contribute to modulation bit depth.

[071] In at least one embodiment of the present invention referring to FIG. 4, a variable blazed grating MEMS device 400 is formed by lithography techniques on wafer substrate 401. The variable blazed grating is a linear array of L-shaped dynamic grating elements 402’ with a grating pitch 403. The grating elements are narrow deformable ribbons separated by gap 404. The dynamic elements are controlled by applied voltage 406 across void 407 to electrostatically change the grating profile shape.

[072] As shown in FIG. 5a and FIG. 5b, the grating array functions as light valve 500 to modulate the intensity of a line of pixels 501 that is projected with scanning optical system 502, the projected line 503 is scanned along scan axis 504 across a target scan field Each modulator pixel 505 corresponds to a scanned projected pixel 506. Referring now to FIG. 6a, each L-shape dynamic grating element is a cantilever 601 attached to supporting pedestal 602. Respective top electrodes 603’ are formed on the cantilever and bottom electrode 604 is formed on the substrate. Electrode 604 may be a common electrode for the device to minimize electrical device contacts while grating elements are electronically addressed by discrete electrodes 603’. By applying voltage 605 across the electrodes 603, 604 as illustrated in FIG. 6b, the cantilever is electrostatically charged and attracted to the substrate.

[073] The voltage required for actuation depends on many cantilever design parameters for example, mechanical material properties, thickness, length, and range of deflection. Actuation voltages can be calculated to model device performance. In general, low voltage actuation is preferred for high speed operation. This suggests long thin cantilevers with minimum deflection. For example, a 400 nm thick by 10 micron long Si3N4 cantilever deflected 260 nm may require 55 volts for actuation. Doubling the length to 20 microns or halving the thickness to 200 nm decreases this voltage to 14 volts. Maximum voltages possible may be limited by breakdown in the SLV elements, SLV package or supporting electronics.

[074] Many of the same parameters that are considered for drive voltage affect mechanical resonances of the cantilever. High resonance is desirable for stable high speed actuation. Higher resonance suggests shorter and thicker cantilevers; this in turn means higher drive voltage. So there is a fundamental trade-off between low voltage and high speed, and voltage limitations might result in speed limitations. For example, 20V DC may correspond to 3 MHz switching.

[075] An SLV driver 614 generates control voltages 605 across top and bottom electrodes for electrostatic actuation of one or more cantilever structure. Driver 614 provides controlled voltages to each element of the variable blazed grating. Referring to FIG. 6c, control voltage 615 is a bipolar signal with alternating polarity. Either polarity actuates the grating element and generates an optical response, so each voltage step effects an optical response in the grating element as shown in normalized optical response 616. The bipolar control voltage may help mitigate the effects of device charging and stiction to promote a uniform, stable optical response over extended operation. [076] Multiple grating elements may be grouped and driven together, for example as a pixel. This grouping limits the extent of interconnectivity required and simplifies the integration of a chip package. However, driving individual elements is within the scope of the present invention. It will be appreciated that different combinations and permutations of driven elements may be employed for example to effect pixel shifting or modified pixel modulation depth.

[077] The driver may have multiple drive modules, each module supplied with a voltage addressed for controlling a set of associated grating elements. For example, a grating of 2000 elements may be driven by 10 driver modules, each module driving 200 grating elements.

[078] Modulator chips may be connected with conventional chip interconnection technologies. For example, devices may be wire bonded. With high grating element counts, interconnection may be limiting and dense interconnect techniques like flip chip mount may be used. Packaged devices maybe mounted in sockets such as ZIF sockets to facilitate rapid removable and replacement.

[079] With voltage applied, and as the cantilever is displaced, the height, angle, and shape of the reflective top electrode are modified and the dynamic element in the array is switched from nominally flat to blaze angle 606. When the grating elements are flat, most incident light 607 is reflected at the angle of incidence in reflected light 608 and blocked at spatial filter 609. When grating elements are displaced and blazed, incident light 607 is diffracted as light 610 and 61 1 at different angles according to well-known diffraction theory. The blazed grating is optimized for efficient diffraction into light 611 passing through spatial filter 609.

[080] Finite gaps between mirror elements resulting from wafer processing and other systematic imperfections of the un-actuated device render a diffraction grating and energy diffracted away from desired diffraction orders to adjacent diffraction orders will limit modulation and result in a lower contrast ratio. 1 have recognized that light passing by the cantilever through the gaps to the substrate can be reflected and return from the underlying substrate. Based on the round trip optical path length from the top reflector to the bottom reflector and phase shifts of the reflectors, the relative phase of the bottom reflection can be controlled. This phase control can be used to minimize undesirable diffracted energy and increase the contrast ratio. For example, with a round trip path length 612 of N x X in the OFF state, the top and bottom reflections is are in phase and the device surface functions like a constant phase surface. With a continuous in phase reflection, the OFF slate has very little energy diverted by diffraction.

[081] It will be appreciated that results for phase matching distances may vary from simple optical path length calculations, for example the full grating structure geometry may be analyzed and optimized with rigorous coupled wave analysis and other methods using commercially available optical simulation software such as GSolver©. More advance analysis for complex structures may be needed in commercial software packages such as Photon Design, Lumerical, and Virtual lab fusion. Complete modeling may require custom or customized software.

[082] In the actuated ON state, referring again to FIG. 6b, the surface is a blazed diffraction grating. Deflection of the cantilever tip is N x X/2, so relative phase of the round trip 613 between top and bottom reflections is preserved. The blaze profile can be highly efficient, with a small portion of energy diffracted into other orders. But even a hypothetically perfect blazed surface will still diffract into higher orders. The ‘278 system is limited by this diffraction and attendant leakage from the blocked actuated state into the projected beam. In the present invention, this diffracted light is effectively blocked. So, there may be a slight reduced efficiency transmitting the actuated state versus the unactuated state, but this maintains a high contrast ratio relative to the ultra-low diffraction unactuated state.

[083] Both very high contrast ratio and high diffraction efficiency >90% can be achieved with this design. By controlling voltage to elements of the dynamic grating, light is switched from OFF state (e.g. flat mirrors) to a blazed grating ON state (e.g. tilted mirrors). As discussed, in the OFF state the flat cantilever array has very low diffraction into 1st, 2d or higher diffraction orders. GSolver© modeling indicates that the L-shape design can achieve a contrast ratio >100K:l in the OFF state. FIG. 7 shows a calculated contrast ratio as a function of wavelength for a L-shaped modulator device confirming the potential for a contrast ratio > 100,000:1. Test device data plotted in FIG. 8 as angular intensity for on and off (actuated and unactuated) dynamic grating element positions. Each state shows multiple diffraction order peaks with the maximum actuated diffraction order 801 corresponding to a very low unactuated diffraction order 802 and high contrast ratio modulation.

[084] While this level of contrast may be desirable for 10 or 12 bit depth laser projection and for precise grey scale rendering, is expected that many laser processing application will not require this level of modulation depth. For threshold limited processes, binary modulation (1 bit) may be sufficient, for example to control a distributed melt process when a uniform line beam is modulated. It will be appreciated that higher speed modulation and or slower actuation response are possible with shallow bit depth modulation. For example, 3 bit modulation might be 4 times faster than 12 bit modulation, and a cantilever might be optimized for shallow bit depth with lower voltage requirements and or limited dynamic response.

[085] With approximately 90% diffraction efficiency in the ON state, diffracted light is directed to a projection system. It will be appreciated that efficiency will be lower when small numbers of grating elements are used for a discrete pixel, but 2 elements per pixel is expected to yield acceptable image contrast. Tliis contrasts with GLV devices without the blaze angle advantage where typically 4 ribbons are used for high efficiency.

[086] Device operation is contemplated for 1st or 2d diffraction order operation, with X/2 and X peak blazed grating height change respectively. In this way, light reflecting from adjacent grating elements sees IX or 2X relative phase delay at respective first or second diffraction order angles. The actual displacement needed for high efficiency may be influenced by local topology of the device and materials. Rigorous grating analysis, taking into account the detailed grating structure, gaps, divots and the like, in passive and active states is used to better estimate contrast and efficiency.

[087] Modulator chips can be designed to operate in a “contact mode”, as in FIG. 6a and FIG. 6b where the etched void between the cantilever and the substrate is provide a X/2 cantilever tip deflection (in first order operation). When actuated in contact mode, the end of the cantilever is displaced through the void thickness λ/2 and “snaps down” to contact the substrate. After contact, the cantilever may experience stiction and design and control measures may be used to manage irregular operation artifacts resulting from stiction.

[088] The contact mode is essentially a binary displacement that can be used for pulse width modulation (PWM) over a pixel exposure period of about 10 ps. PWM can account for 5 bits. However with finite modulation pulse rise and fall (e. g. 10% to 90% rise/fall times) there is a nonlinear modulation effect. Preferably, driver rise and fall times are three times faster than cantilever rise and fall times. FIG. 9a shows modulator deflection pulses 901 and 902 with respective rising edges 903 and 904, respective pulse peaks 905 and 906 and respective falling edges 907 and 908. FIG. 9b is plot of diffraction efficiency vs deflection for different diffraction orders showing nonlinear reduced efficiency at the rising and falling edges, litis effect can be used to increase PWM depth by one or more bit.

[089] In contact mode, the shape of the cantilever surface may be affected by contact forces. For example the catenary shape of a deflected beam may be modified to an s-bend shape profile. Furthermore, the degree of deformation may be affected by the applied voltage. Optimization of the modulator may account for this s-bend shape, and applied deflection voltages may be modified to adjust the degree of s-shape bending. For example, a high voltage pulse may be used to initiate snap-down and contact followed by a reduced holding voltage to optimize the mirror surface contour.

[090] In a different embodiment, As shown in FIG. 10a and FIG. 10b, a “suspended mode” has a void 1001 of approximately 2-3 X. The larger suspended mode void avoids the snap down effect with potential stiction and it provides a variable cantilever displacement depending on drive voltage. As with contact mode the suspended mode can be used with pulse width modulation and using variable displacement, suspended mode can also use Pulse Width Pulse Amplitude Modulation (PWPAM). Nominally with PWM cantilever displacement 1002 is V2. Controlled deviations from nominal deflection 1003 reduce diffraction efficiency and this provides additional modulation control that can be combined with PWM for PWPAM. The additional modulation effectively adds modulation bit depth.

[091] In each of the above embodiments, multiple elements form a single pixel to get high efficiency. However, elements within a pixel can be independently actuated for subpixel modulation. For example, a single actuated ribbon may have reduced efficiency, so using one element of a 2 element pixel would yield additional bit depth options for amplitude modulation in both PWM and PWPAM.

[092] In greyscale imaging 10 bit depth and 12 bit depth may be desirable. However, in high power laser processing such as material fusing, a more limited modulation depth may be perfectly acceptable. Indeed, in some cases single bit modulation may facilitate high resolution additive manufacturing operations. Bulk material preheating or preheating exposure can essentially fill lower modulation “bits” and leave the single high-speed bit to tip the process over the melting threshold to achieve uniform fused material.

[093] In one aspect of the invention, thermal management is improved in comparison to other MEMS based optical modulators. In the DMD, a 2-d array of tilting mirrors, absorbed energy is conducted down below the device through the flexure mechanism to the substrate. In ribbon based light valves, absorbed energy is conducted along the length of the ribbon. In both of these devices, the cross sectional area for thermal conduction is necessarily small. In contrast, the present invention with the L-shaped dynamic grating element conducts heat away from the working reflector along the foil edge of the cantilever in addition to conduction along the anchored cantilever ribbon. With superior conduction, it is expected that the L-shape dynamic grating modulator will operate at lower surface temperatures with higher laser power handling capability. [094] Linear modulator devices can accommodate increased pixel area. With an anamorphic relay optical system, high aspect ratio pixels at the modulator are transformed to requisite projected pixel size. The width of the illuminating line beam can be many times the pixel pitch of the modulator. Indeed, width is limited by anamorphism and structural limits of the modulator chip. Thus, pixel width can be a multiple of pixel pitch, for example 2x, 4x, or 10x. Pixel widths may be from 10 microns to 200 microns. It will be appreciated that as the pixel width increases, the area increases, the heat conduction path increases and incident power can be increased in proportion to the multiplication factor.

[095] In a thermal analysis of an L-shaped structure, light incident on the reflective surface is partially absorbed based on the reflectivity of the top surface material. The absorbed energy can be modelled as a steady state heat source on the l-shaped structure. In the worst case, the 1-shape is considered at a uniformly illuminated over a large area. From the surface of the structure, heat escapes by convection, radiation and conduction. Again, considering a worst case, convection and radiation are assumed to be negligible and all heat is conducted from the cantilever via the post structure. Temperature at the top of the post can be estimated based on thermal conductivity of the post material, the height of the post and the width of the post.

[096] For example a post made from silicon nitride might be 1.5 microns wide support the edge of a ribbon 100 microns in length. The post may be approximately ¹2 wave high (H) at 520 nm, or H = 260 nm. With top and bottom temperatures, power conducted from the ribbon to the substrate can be estimated using the equation Pconducted kA(T_top-T_bottom)/H where k is the thermal conductivity of the post material, A is the cross sectional area of the post, T_top and T_bottom are top (ribbon) and bottom (substrate) temperatures respectively, for example 70°C and 30°C. Absorbed power is distributed across N ribbons, so total power conducted is the sum of N individual ribbons. Considering the absorption of the reflective ribbon, about 7% for aluminum, incident power required to raise ribbon temperature can be estimated.

[097] For the above values, incident power that could be conducted through 200 posts is approximately 2.8 kW. It will be appreciated that over the relatively small area of the modulator this is on the order of 1.4 GW/cm^{^}2. So it is expected that the damage threshold of the cantilever reflective coating will limit power handling of the device and that superior cooling by high capacity conduction to the substrate will maintain low surface temperature to help avoid surface deterioration, breakdown, laser damage and device failure.

[098} In the cantilever, heat primarily is conducted across the width of the ribbon to the post. With extended illumination along the length of the ribbon. Heat flow is approximated as a one dimensional flow across the ribbon. Since the thickness of the ribbon is thin, typically thinner than the post, it will be appreciated that temperature is not uniform across the ribbon. At the tip of the ribbon only absorbed incident energy flows to the post. However, nearer to the post the heat flow is tiie sum of all absorbed energy from further out on the cantilever. This means that the temperature gradient increases closer to the post to facilitate the increased heat flow. Thus, the illuminated cantilever will experience a non-linear temperate profile, and the highest temperature will be at the tip of the cantilever, for example as shown in FIG 11 a and FIG 11 b.

[099] It may be advantageous to limit the surface temperature of the cantilever to a point below a threshold temperature. For example, the tip of the cantilever may be held below at temperature where there are chemical material changes in the cantilever, the cantilever structure or the cantilever surface material. These changes may include changes to mechanical properties of the cantilever, increased absorption of the surface reflective material, decreased adhesion of coating layers to the cantilever structure, and variation in electrostatic properties. Undesirable changes could increase device temperature, degrade device performance characteristics, and limit device service life.

[0100] Speed of operation is limited by the resonant frequency of the MEMS structure. High mechanical resonance of the cantilever structure means that high speed actuation approaching the resonance frequency is possible. In tested devices with 10 micrometer wide cantilevers the resonant frequency is approximately 2-3.5 MHz. Referring to FIG 12, cantilever optical response 1201 to an applied control voltage signal 1202 is shown to be close to the calculated mechanical resonance value. In the example, the period of mechanical resonance is measured as 0.36 microseconds corresponding to a frequency of 2.8 MHz. This result demonstrates that cantilever based modulators are capable of MHz modulation rates. The same factors that promote high speed actuation, namely thick short cantilevers also help to limit cantilever tip temperature and increase device power handling capability. At the same time, increased pixel width does not impact speed of actuation. This means that the cantilever based modulator is well-suited to both high speed and high power modulation. This power handling capability opens the door to high power laser material processing applications such as 3D printing, lithography, additive manufacturing, surface treatment, and high-speed web processing.

[0101] Linear modulators can be configured with different grating lengths and different number of elements within the linear array. As higher pixel counts are employed, laser power can be distributed over a longer target image. For scanned, velocity limited processes, for example in powder bed melt additive manufacturing, increased line length supports increased processing power al predetermined scan velocities and melt pool dwell times. 'That is to say doubling the length of a projected line could double the applied processing laser power with attendant decrease in total processing time. Further benefits include reducing the number of scan-to-scan transitions, and simultaneous processing of larger features without loss of detail.

(0102] Consideration for providing high power devices include utilizing highly reflective materials, high thermal conductivity materials, and increased cantilever thickness. With controlled surface temperatures, sealed devices without access to convective cooling of the reflective surface may none the less have high power capability. Forced gas fluid cooling may be provided to increase power handling capability. For best power handling, the back side of the wafer can be actively cooled for example the back side may be liquid cooled. The mirror side may be gas cooled however fast gas flow might perturb mirror surfaces.

[0103] The chip manufacturing process can lead to systematic surface defects such as a divot 1301 (a shallow groove) as shown in FIG. 13 being present on the top of the cantilever parallel to the ribbon. The divot defect or similar systematic defects can significantly increase diffraction in the OFF state with resulting contrast ratio degradation; the divot is preferably smaller than 3 nm, Planarization process steps on the top surface may be used to eliminate or minimize defects 1302 to negligible size. Planarization may be further improved with an operational bias voltage. The bias voltage would correct small amounts of unactuated cantilever bend such as upward curling. Bias voltages can be applied uniformly or individually to every ribbon to improve contrast on a pixel by pixel basis.

[0104] Differential properties of deposition layers can result in undesirable curling of the cantilever structure. Well-known techniques for managing layer to layer stress can be employed to improve cantilever flatness. I ayer material selection, layer thickness, deposition techniques and annealing processes may be utilized. However, it is recognized that in threshold limited laser material processes where high contrast is not strictly required, cantilever mirror curl may not significantly affect processing results.

[0105] Top electrode materials contemplated are aluminum (Al) and silver (Ag). Referring to FIG. 14, Al has lower reflectivity than Ag for red, blue, and green, but Al is more common material in MEMS fabrication. More complex multilayer coating designs, for example a dielectric stack or a dielectric enhanced metal could be also considered for higher reflectivity as may be desirable in higher power applications. Phase errors introduced by reflective coatings are to be considered with respect to phase matching previously discussed.

(0106] High thermal conductivity materials such as aluminum nitride (AIN) may be employed to increase cantilever thermal conduction and increase the modulator thermal loading capability.

[0107] Highest device contrast ratio may be achieved with a conductive bottom electrode as shown in FIG. 15, and a high reflectivity metal 1501 on the bottom electrode is desirable. It will be appreciated the reflective coatings may impart an optical phase error that should be considered in the overall device design optimization. For example, thickness of Si3N4 on top of a typical titanium tungsten alloy (TiW) adhesion layer on the bottom electrode could be optimized for maximum reflectivity ("-60%) and phase matched to top electrode material.

[0108] Referring to FIG. 16, the MEMS based SLV cantilever array structure 1601 is fabricated on a die or “chip” 1602 and the chip is packaged as a modulator device package 1603. The device may include an optical window that seals the SLV chip environment to prevent contamination, and to control the gas envelope that immerses the chip. Properties of the gas may be controlled to affect device performance. For example, gas density may be selected to provide fluid damping forces during cantilever actuation. A sealed SLV environment may act to prevent deterioration of the device including degradation of reflective minor coatings, for example oxidation of silver or aluminum mirrors.

[0109] Programmable logic module 1604, for example one or more FPGA, receives and decodes serial data command stream 1605 from a system controller 1606, buffers the desired pixel or voxel values, and logic block 1607 converts the stream to a command stream 1608 of N parallel SLV pulse amplitude and pulse width modulation timing patterns. The timing patterns are received by analog drive electronics 1609 to provide N analog drive voltage waveforms 1610 to the modulator package. The programmable logic module at logic block 1611 communicates with the positioning system at interface 1612 to control material scanning and pixel/voxel synchronization. The programmable module also communicates with laser system at logic block 1613 to provide laser control and laser synchronization at interface 1614.

[0110] Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments of the invention described herein. It is therefore to be understood that the foregoing embodiments are presented by way of example only and that within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described. The present disclosure is directed to each individual feature, system, material and/or method described herein. In addition, any combination of two or more such features, systems, materials and/or methods, if such features, systems, materials and/or methods are not mutually inconsistent, is included within the scope of the present invention.

Claims

1. A high-speed system for modulating a line beam of light with a microelectro-mechanical-system (MEMS) comprising. a one-dimensional MEMS array of at least partially reflective dynamic grating elements on a substrate configured to receive and modulate line beam illumination, each dynamic element characterized by an L-shaped cross section in a plane parallel to the axis of the array and perpendicular to the plane of the substrate, the L-shaped cross section extending along each grating element in a direction parallel to the substrate and non-parallel to the axis of the array, said L-shaped cross section comprising a pedestal rigidly coupled to the substrate extending from the substrate in a direction normal to the plane of the substrate, and an elongated cantilever rigidly coupled to the pedestal such that the cross section of the pedestal and the cantilever forms the L-shape with a void between the substrate and the cantilever, the cantilever comprising an addressable top electrode, the substrate comprising a common bottom electrode; wherein one or more dynamic grating element is controllably displaceable about an axis parallel to both the substrate and the grating element length, the element displacement comprising a variable angle between a portion of the grating element reflective surface and the substrate such that the height of the cantilever end corresponds to a control voltage potential between the top electrode and the bottom electrode, the voltage correlated to a desired line beam modulation profile, and wherein the modulation profile of a projected image of the modulated line beam profile corresponds to a desired pixel array modulation profile.

2. The system as in claim 1 wherein a first pixel actuation state comprises multiple adjacent displaced grating elements and a second pixel actuation state comprises a single displaced grating element, where in the efficiency of the first pixel state is greater than the second pixel state.

3. The system as in claim 1 wherein a portion of the bottom electrode is reflective.

4. The system as in claim 1 wherein said MEMS array comprises a planarized top reflector.

5. The system as in claim 1 further comprising an addressable voltage controller configured to provide control voltages to multiple elements of the dynamic array.

6. The system as in claim 1 wherein non-displaced grating elements reflect light in an OFF-state with diffracted, light energy less than .1% in an adjacent diffraction order.

7. The system as in claim 1 wherein non-displaced grating elements reflect light in an OFF-state with diffracted light energy less than .025% in an adjacent diffraction order.

8. The system as in claim I wherein the displacement of a plurality of elements is limited by cantilever contact with the substrate forming a reflective surface contour such that at least a portion of the reflective surface contour is a phase optimized blazed grating.

9. The system as in claim 8 wherein the cantilever is in contact with the substrate and the reflective cantilever surface shape is a controllable modified shape corresponding to the respective control voltage.

10. The system as in claim 8 wherein the light is characterized by a wavelength of the light X and displacement of the element at the end of the cantilever is λ/2.

11. The system as in claim 1 wherein the displacement of an element corresponds to a control voltage, the cantilever surface comprises a variable blazed surface corresponding to the control voltage, and the end of the cantilever is suspended.

12. The system as in claim 11 further comprising light characterized by a wavelength λ, wherein the unactuated cantilever is suspended in a range of 2-3 X over the substrate and the wherein an actuated cantilever tip is displaced by λ/2.

13. The system as in claim 1 wherein displacement of multiple grating elements corresponds to the intensity of a single pixel.

14. The system as in claim 1 wherein the intensity of a pixel is modulated by a pulse width modulation control voltage waveform over a pixel exposure period.

15. The system as in claim I wherein the modulated light level is characterized by 10 bits.

16. The system as in claim 1 wherein the modulated light level is characterized by 12 bits.

17. The system as in claim 1 wherein the control voltage comprises a rising edge from 10% to 90%, a peak voltage period with variable duration and a falling edge from 90% to 10%.

18. The system as in claim 1 wherein off-state cantilever and substrate reflections from the dynamic array are phase optimized to provide a high contrast ratio > 5000: 1.

19. The system as in claim 1 wherein on-state cantilever and substrate reflections from the dynamic array are phase optimized to provide efficient pixel modulation.

20. The system as in claim 1 wherein dynamic element resonant frequency is at least 2.5 MHz.

21. The system as in claim 1 wherein the pedestal comprises a low thermal resistance thermal contact

22. The system as in claim 1 wherein a 10% to 90% rise time of electrostatic actuation from a light modulator off stale to a light modulator on state with is below 300 ns.

23. A high-speed micro-electro-mechanical-system line beam light modulator comprising, a plurality of reflective L-shaped dynamic grating elements in an optically phase matched linear array on a substrate, each element responsive to a control voltage waveform for electrostatic actuation from a non-energized off state to an energized on state.

24. A high power laser modulator comprising: an array of L-shaped dynamic blazed grating elements disposed on a substrate, each element comprising a reflective cantilever in thermal contact with a substrate through a thermally conductive pedestal along a fixed edge of the dynamic grating element to the substrate, wherein the length of thermal contact is greater that the width of the blazed grating element whereby the thermal conductivity of the thermal contact is greater than thermal conductivity along the length of the cantilever.

25. In a laser scanning based projection system, a light modulation method comprising: characterizing the optical response of dynamic blazed grating elements in a 1- dimensional linear array of electrostatically actuated reflective dynamic blazed grating elements over a range of control voltages and temporal control voltage waveforms, correlating at least one projected pixel intensity with the characterized optical response, generating a set of operational control voltage waveforms such that actuation of grating elements provides a predetermined light distribution in the pixel array, illuminating the 1 -dimensional linear array of reflective dynamic blazed grating elements with a line beam, reflecting and directing a portion of the line beam to a projection optical system with actuated blazed grating elements, and modulating the line beam with the array by applying a sequence of sets of control voltage waveforms to one or more sets of grating elements to displace one or more respective grating element to selectively modulate the reflected light according to a predetermined light distribution pattern in a sequence of 1 dimension pixel array images, whereby the projection optical system images a modulated portion of the reflected illumination to form a projected image.

26. The method as in claim 25 wherein light modulation comprises scanning the 1 dimensional array image across an image field and sequentially modulating pixels of the array to form a 2 dimensional scanned image frame, wherein at least one pixel is modulated at or above 100 kHz.

27. The method as in claim 25 wherein the scanned pixel array forms a projected frame of a video or cinema image at a frame rate of at least 24 frames per second with a modulation bit depth of at least 10 bits.

28. The method as in claim 25 further comprising projecting a color image using at least 3 different laser source wavelengths and respective modulators.

29. The method as in claim 25 wherein temporal control voltage waveforms comprise pulse width modulation voltages within a pixel exposure period.

30. The method as in claim 25 wherein temporal control voltage waveforms comprise pulse amplitude modulation voltages within a pixel exposure period.

31. The method as in claim 25 wherein the steps of characterizing and correlating further comprise determining control voltage values for a pixel based on the predetermined pixel intensity value and the intensity value of at least one other pixel in the array.

32. The method as in claim 25 wherein the steps of characterizing and correlating further comprise determining control values of a pixel based on the predetermined pixel value and the value of at least one preceding or subsequent pixel the scanned image.

33. A high-speed, high-power, laser-based additive manufacturing system comprising, a laser source characterized by wavelength, average power, and M^A2 , the laser source providing an input beam, an illumination subsystem configured to receive the input beam and image the beam to a uniform intensity line beam at an image plane, the uniform line beam having a first line beam aspect ratio of length divided by width, a high-speed SLV modulator configured to receive the uniform line beam, to modulate one or more portions of the line beam, and to reflect the modulated line beam along a projection optical axis, the SLV having a characteristic laser damage threshold, a projection lens subsystem configured to receive the modulated line beam and project a processing line beam on fusible material, and to selectively fuse portions of the fusible material by modulated laser irradiation, the processing line beam having a second line beam aspect ratio, and a relative motion system providing controllable displacement between the modulated line beam and the fusible material such that predetermined areas of fusible material are sequentially processed to add material to a workpiece, wherein the first aspect ratio is less than the second aspect ratio, whereby the difference in aspect ratios provides one or more of reduced laser fluence impinging the SLV and improved processing speed.

34. The system as in claim 33 wherein the first aspect ratio is greater than one.

35. The system as in claim 33 wherein the uniform line has a top hat illumination profile along the length of the line with less than 10 percent variation in the top hat between 90 percent threshold line ends.

36. The system as in claim 33 wherein the second aspect ratio is a variable ratio.

37. A high-speed, high-power, laser-based additive manufacturing system comprising, a laser source characterized by wavelength, average power, and M^A2 , the laser source providing an input beam, an illumination subsystem configured to receive the input beam and image the beam to a uniform intensity line beam at an image plane, a high-speed SLV modulator configured to receive the uniform line beam, to modulate one or more portions of the line beam with pulse width modulation, and to reflect the modulated line beam along a projection optical axis, a projection lens subsystem configured to receive the modulated line beam and project a processing line beam on fusible material, and to selectively fuse portions of the fusible material by modulated laser irradiation, and a relative motion system providing controllable displacement between the modulated line beam and the fusible material such that predetermined areas of fusible material are sequentially processed to add material to a workpiece, wherein the high-speed modulator provides selective pulse width modulation to one or more portions of the processing line beam, whereby the predetermined areas of fusible material are processed

38. The system as in claim 37 wherein pulse width modulation comprises multiple actuations of a blazed grating element, the multiple actuations modulating a portion of the line beam and controlling integrated power delivered to a corresponding voxel.

39. A high-speed, high-power, laser-based additive manufacturing system comprising, a laser source characterized by wavelength, average power, and M^A2 , the laser source providing an input beam, an illumination subsystem configured to receive the input beam and image the beam to a uniform intensity line beam at an image plane, a high-speed SLV modulator responsive to volumetric control signals configured to receive the uniform line beam, to modulate one or more portions of the line beam, the modulated portions or the line beam corresponding to workpiece voxels, and to reflect the modulated line beam along a projection optical axis, a projection lens subsystem configured to receive the modulated line beam and project a processing line beam on fusible material, and to selectively fuse portions of the fusible material by modulated laser irradiation, and a relative motion system providing controllable displacement along a predetermined trajectory between the modulated line beam and the fusible material such that predetermined areas of fusible material are sequentially processed to add material to a workpiece, wherein relative motion comprises a trajectory of the processing line beam at a layer of a workpiece according to a workpiece build plan, and wherein the volumetric control signals comprise a pixelated modulation profile of the line beam that is temporally coordinated with the trajectory.

40. A high-speed, high-power, laser-based additive manufacturing system comprising, a laser source characterized by wavelength, average power, and M^A2 , the laser source providing an input beam, and an anamorphic illumination subsystem configured to receive the input beam and image the beam to a uniform intensity line beam at an image plane, and a high-speed SLV modulator configured to receive the uniform line beam, to modulate one or more portions of the line beam, and to reflect the modulated line beam along a projection optical axis, and an anamorphic projection lens subsystem configured to receive the modulated line beam and project a processing line beam on fusible material, and to selectively fuse portions of the Risible material by modulated laser irradiation, and a relative motion system providing controllable displacement between the modulated line beam and the fusible material such that predetermined areas of fusible material are sequentially processed to add material to a workpiece, and wherein the relative motion system comprises a beam rotator configured to orient the processing line beam relative to the workpiece according to a build plan trajectory

41. A high-speed, high-power, laser-based additive manufacturing system comprising, a laser source characterized by wavelength, average power, and M^2 , the laser source providing an input beam, an illumination subsystem configured to receive the input beam and image the beam to a uniform intensity line beam at an image plane, a high-speed SLV modulator configured to receive the uniform line beam, to modulate one or more portions of the line beam, and to reflect the modulated line beam in a nonzero diffraction order along a projection optical axis, an projection lens subsystem configured to receive the modulated line beam and project a processing line beam on fusible material, and to selectively fuse portions of the fusible material by modulated laser irradiation, and a relative motion system providing controllable displacement between the modulated line beam and the fusible material such that predetermined areas of fusible material are sequentially processed to add material to a workpiece, wherein the non-zero diffraction order corresponds to one of a snap-down state and a suspended cantilever state of selected portions of the SLV modulator, the non-zero diffraction order resulting from diffraction at one or more portions of a blazed grating profile along the SLV.

42. A high-speed, high-power, laser-based additive manufacturing method for adding material to a workpiece, the method comprising, generating a laser processing input beam with a laser source characterized by wavelength, average power, and M^A2, propagating the input beam through an illumination subsystem, forming a uniform intensity line beam at an image plane with the illumination subsystem, modulating one or more portions of the line beam with a high-speed SLV modulator, reflecting the modulated line beam along a projection optical axis with the high-speed SLV modulator, propagating the modulated line beam through a projection lens subsystem, transforming the modulated line beam to a processing line beam with the projection lens subsystem, projecting the processing line beam onto fusible material, selectively fusing portions of the fusible material with modulated laser irradiation, and displacing the modulated line beam relative to the fusible material with a relative motion system along a predetermined build trajectory, wherein the line beam modulation and the displacement deposit a predetermined laser energy dose profile to fusible material voxels according to a build plan such that a stable melt process sequentially adds material to a workpiece.