Laser marking system and method

Abstract

A laser marking system and method of operating the same are disclosed, the laser marking system including a spatial light modulator (SLM) having a linear array of multiple pixels based on micro-electromechanical system (MEMS) based diffractors. Generally, the laser marking system includes, in addition to the SLM, a laser operable to illuminate the SLM, imaging optics operable to focus a substantially linear modulated light stripe onto a surface of a workpiece, the linear light stripe including light from the multiple pixels of the SLM, and a controller operable to control the SLM, the laser, and the imaging optics to mark the surface of the workpiece to record a two-dimensional image on the surface of the workpiece. In one embodiment, the diffractors include a plurality of electrostatically deflectable strips suspended over a substrate. In another case, each diffractor is two-dimensional, including an electrostatically deflectable first mirror operable to optically interfere with light reflected from a second mirror surface on the panel or from an adjacent diffractor.

Description

[0001] Cross-reference to related applications

[0002] This application is an international application of U.S. non-provisional application No. 17 / 591,884, filed February 3, 2022, and claims the benefit of U.S. provisional patent application serial number 63 / 146,488, filed February 5, 2021, and U.S. provisional patent application serial number 63 / 183,789, filed May 4, 2021, all of which are incorporated herein by reference in their entirety. Technical Field

[0003] This invention relates generally to a laser marking system, and more specifically, to a laser marking system including a spatial light modulator and a method of operating the same, wherein the spatial light modulator has a multi-pixel linear array of diffractors based on a microelectromechanical system. Background Technology

[0004] Laser marking systems are widely used across industries to create images or markings (such as text, logos, barcodes, or 2D QR codes) on the surface of parts or articles. Common marking methods include oxidation, annealing, etching, ablation, or surface discoloration. Advantages of laser marking include its ability to be performed on a wide variety of materials, its permanence, and the fact that it does not require physical contact to mark the workpiece surface.

[0005] Laser marking systems typically use a single laser beam that scans the surface of a workpiece using a galvanometer mirror, marking one dot at a time. Therefore, depending on the size and complexity or density of pixels in the mark or image, current laser marking systems can have marking times of two minutes or longer to mark the surface of a single workpiece. Furthermore, attempts have been made to use laser marking systems incorporating spatial light modulators (SLMs) and liquid crystal on silicon (LCOS) modulators, such as digital micromirror devices (DMDs) available from Texas Instruments, to print or mark larger areas. However, these existing SLMs cannot handle the high-power laser required to mark larger areas compared to marking a single dot at a time.

[0006] Accordingly, there is a need for a laser marking system capable of marking a larger area than a single point in a single pass, thereby reducing marking time and increasing system throughput. Furthermore, there is a further need for a laser marking system capable of using higher-powered lasers to reduce marking time and increase the area that can be marked in a single pass. Summary of the Invention

[0007] A laser marking system with a spatial light modulator (SLM) and its operation method are disclosed. The spatial light modulator includes a multi-pixel linear array of diffractors based on microelectromechanical systems (MEMS). Typically, in addition to the SLM, the laser marking system also includes: a laser operable to illuminate the SLM; an imaging optics operable to focus a substantially linearly modulated light stripe onto the surface of a workpiece, the linear light stripe including light from multiple pixels of the SLM; and a controller operable to control the SLM, laser, and imaging optics to mark the surface of the workpiece, thereby recording a two-dimensional image on the surface of the workpiece.

[0008] In one embodiment, each of the MEMS-based diffractors includes a plurality of electrostatically deflectable bands suspended on a substrate, each band having a light-reflecting surface. Electrostatic deflection of one or more bands causes light reflected from the light-reflecting surface of a first electrostatically deflectable band to interfere with light reflected from the light-reflecting surfaces of bands in the same or adjacent diffractors, thereby modulating the light incident thereon.

[0009] In another embodiment, the MEMS-based diffractors are two-dimensional diffractors, each comprising: a piston layer suspended on the surface of the substrate by pillars located at corners of the substrate, the piston layer including an electrostatically deflectable piston and a plurality of flexures through which the piston is coupled to the pillars; a first reflective surface on the top surface of the piston; and a panel suspended on the piston layer, the panel including a second reflective surface on the top surface of the panel and an aperture for exposing the piston. The electrostatic deflection of the piston causes light reflected from the first reflective surface to interfere with light reflected from the second reflective surface, thereby modulating the incident light.

[0010] Further features and advantages of embodiments of the present invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0011] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which corresponding reference numerals denote corresponding parts. Furthermore, the accompanying drawings, which are incorporated herein and form a part of this specification, illustrate embodiments of the invention and, together with the description, further serve to explain the principles of the invention and enable those skilled in the art to make and use the invention.

[0012] Figure 1 This is a block diagram of a laser marking system including a spatial light modulator (SLM);

[0013] Figures 2A to 2C This is a schematic block diagram illustrating an embodiment of an SLM including a strip microelectromechanical system (MEMS) based diffractor;

[0014] Figures 3A to 3C This is a schematic block diagram illustrating an embodiment of an SLM including a MEMS-based two-dimensional (2D) diffractor;

[0015] Figure 4 This is a top-down schematic block diagram of an SLM, which includes MEMS-based 2D diffractors (e.g., Figures 3A to 3C A multi-pixel linear array of diffractors (as shown);

[0016] Figure 5A and Figure 5B This is a schematic block diagram of an embodiment of a laser marking system, which includes: an SLM having a multi-pixel linear array of MEMS-based diffractors; and a galvanometer reflector for scanning;

[0017] Figures 6A to 6C This is a schematic block diagram illustrating single-strip and multi-strip scanning using a laser marking system, which includes an SLM with a multi-pixel linear array of MEMS-based diffractors for surface modification.

[0018] Figure 7 This is an optical diagram illustrating the illumination and imaging optical path along the vertical or longitudinal axis of a linear array for a laser marking system, which includes a multi-pixel linear array of MEMS-based diffractors for surface modification.

[0019] Figure 8 This is a schematic block diagram of an embodiment of a laser marking system, which includes: an SLM having a multi-pixel linear array of diffractors based on MEMS; and a movable fixing device or platform for fixing a workpiece thereto.

[0020] Figure 9 This is a schematic block diagram of another embodiment of a laser marking system, which includes an SLM with a multi-pixel linear array of MEMS-based diffractors, and the focal point of the laser marking system is in front of a galvanometer reflector for scanning.

[0021] Figure 10 It is a flowchart of a method for modifying or marking a surface using a surface modification system, including a MEMS-based SLM.

[0022] Figures 11A to 11C This is a schematic block diagram illustrating a method for modifying or marking a surface using alternating scans of two or more surfaces; and

[0023] Figure 12A and Figure 12B This is a schematic block diagram of two adjacent eight-pixel groups in a linear array of MEMS-based 2D diffractors, illustrating a pixel shaping method for recording images with high-density patterns. Detailed Implementation

[0024] This article describes a laser marking system and its operation method with reference to the accompanying drawings. The laser marking system includes a spatial light modulator (SLM) having a multi-pixel linear array of diffractors based on microelectromechanical systems (MEMS).

[0025] In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. In other instances, well-known structures and techniques have not been shown in detail or illustrated in block diagram form to avoid unnecessarily obscuring the understanding of the description.

[0026] References to "one embodiment" or "embodiment" in the description mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing in different places in the specification does not necessarily refer to the same embodiment. As used herein, the term "coupling" can include direct electrical connection of two or more components or elements, as well as indirect connection via one or more intermediate components.

[0027] Figure 1 This is a block diagram of a laser marking system 100 including a spatial light modulator (SLM 102) having a multi-pixel linear array of a microelectromechanical system (MEMS)-based diffractor (not shown in the figure). In short, in addition to the SLM 102, the laser marking system 100 includes: a laser 104 operable to illuminate the SLM; an imaging optics 106 operable to focus a substantially linearly modulated light stripe onto the surface of a workpiece on a fixture 108 or platform; and a controller 110 operable to control the SLM, laser, and imaging optics to scan the linearly modulated light stripe across the surface of the workpiece to record a two-dimensional (2D) image on the surface of the workpiece. Typically, as in the illustrated embodiment, the laser marking system 100 further includes an illumination optics 112 having a beam-forming optics system to guide a rectangular beam onto the linear array of the SLM 102.

[0028] Typically, laser 104 is capable of operating in continuous wave (CW) mode or pulsed mode at infrared (IR) wavelengths ranging from 355 nanometers (nm) to up to about 2000 nm in ultraviolet (UV) wavelengths, with pulse width or duration ranging from about 1 femtosecond (fs) to about 500 nanoseconds (ns), repetition rate ranging from about 10 kHz to about 300 kHz, and energy range from about 10 microjoules (μJ) to more than 10 millijoules (mJ). In one embodiment particularly useful for laser marking systems, laser 104 is capable of operating at a visible wavelength (λ) of about 514 nm, a pulse energy of about 200 μJ, a pulse width or duration of about 260 fs, and a repetition rate of 100 kHz.

[0029] As described above, SLM 102 includes a multi-pixel linear array of MEMS-based diffractors, which are grouped or coupled to provide approximately 10 to approximately 1088 individually addressable pixels. Suitable SLM 102 includes SLMs having the following components: a linear array of strip-type electrostatically tunable diffraction gratings, such as a grating light valve (GLV). TM ); and MEMS-based two-dimensional (2D) diffractors, such as linear planar light valves (LPLVs). TM Both of these are available from Silicon Light Machines Inc. in San Jose, California, and are described in detail below.

[0030] Imaging optics 106 may include dynamic optical elements that scan a linearly modulated light stripe across the surface of a workpiece, and a plurality of static optical elements that guide the modulated light to a galvanometer mirror and / or focus the modulated light from the galvanometer mirror onto the surface of the workpiece.

[0031] The fixture 108 for placing or securing the workpiece to be marked may include a static fixture or a movable platform operable to move or reposition the workpiece relative to a substantially stationary linearly modulated light stripe, such that the linearly modulated light stripe scans the surface of the workpiece. In either embodiment, whether static or movable, the fixture 108 preferably includes multiple sensors and signaling devices to signal other components of the laser marking system when the workpiece is in the appropriate position for marking. In some embodiments described in more detail below, the fixture 108 includes a movable platform capable of moving along two orthogonal axes, thereby enabling multiple parallel light stripes to scan to record or mark a larger 2D image on the workpiece. In other embodiments, the laser marking system 100 includes an imaging optics 106 with a galvanometer mirror and a movable platform (fixture 108) capable of moving along a single axis orthogonal to the direction of the galvanometer mirror scanning the linearly modulated light stripe to record or mark a larger 2D image on the workpiece.

[0032] Laser 104, illumination optics 112, SLM 102, imaging optics 106, and the workpiece held on fixture 108 are optically coupled in the direction indicated by arrow 114. Furthermore, laser 104, illumination optics 112, SLM 102, imaging optics 106, and fixture 108 are electrically coupled to controller 110 via control bus 116 in a signal communication manner, and are also electrically coupled to each other. Specifically, controller 110 provides digital image data to SLM 102, controls the power level of laser 104, controls the operation of the galvanometer mirror in imaging optics 106, and controls the movable platform of fixture 108 (if included) via control bus 116. Furthermore, when the workpiece is in the appropriate position for marking, the fixing device 108 can send signals to the controller 110, SLM 102 and / or laser 104, and when the image data loaded onto the SLM is ready to be recorded on the workpiece, the SLM can send signals to the laser so that the laser can emit pulses.

[0033] Optionally, as in the illustrated embodiment, the laser marking system 100 may further include a second (or more) axis controller 118, which is electrically coupled via a second control bus 116 to the SLM 102, the imaging optics 106, and the movable platform of the fixing device 108 (if included) in a signal communication manner, thereby controlling the movement of the linear light stripe along one of the two orthogonal axes.

[0034] Now refer to Figures 2A to 2C The description includes MEMS-based strip electrostatic tunable diffractors (such as GLV). TMAn embodiment of a multi-pixel linear array SLM is described below. For clarity, many details of general SLMs and, in particular, MEMS-based strip diffractors unrelated to the invention are omitted in the following description. The accompanying drawings are schematic only and not limiting. In the drawings, the sizes of some elements may be exaggerated and are not drawn to scale for illustrative purposes. Dimensions and relative dimensions may not correspond to an actual reduction in the implementation of the invention.

[0035] Referring to the embodiments shown Figure 2A and Figure 2B The SLM 200 includes a linear array 202 consisting of thousands of independent, addressable electrostatically actuated strips 204, each strip having a light-reflecting surface 206 supported above a surface of a substrate 208. Multiple strips are grouped together to form a MEMS-based diffractor. Each of the strips 204 includes an electrode 210 and can be deflected toward the substrate 208 via electrostatic forces through gaps or cavities 212 generated when a voltage is applied between the electrode 210 in the strip 204 and a base electrode 214 formed in or on the substrate. Each of the electrodes 210 is driven by one of a plurality of drive channels 216 in a driver 218, which may be integrally formed on the same substrate 208 as shown in the embodiments, or formed on a second substrate or chip and electrically coupled to the linear array (not shown).

[0036] Figure 2B It shows Figure 2A A schematic side view of the SLM 200 with section 204. (Reference) Figure 2B The strip 204 includes an elastic mechanical layer 220, a conductive layer or electrode 210, and a reflective layer 224 that support the strip above a surface 222 of a substrate 208. The reflective layer includes a reflective surface 206 covering the mechanical layer and the conductive layer.

[0037] Typically, the mechanical layer 220 comprises a taut silicon nitride film and is flexibly supported at both ends of the strip 204 above the surface 222 of the substrate 208 by a plurality of pillars or structures, typically also made of silicon nitride. As shown, a conductive layer or electrode 210 may be formed on and in direct physical contact with the mechanical layer 220, or formed beneath the mechanical layer. The conductive layer or electrode 210 may comprise any suitable conductive or semiconductor material compatible with standard MEMS fabrication techniques. For example, the conductive layer for the electrode 210 may comprise a doped polycrystalline silicon (polyethylene) layer or a metal layer. Alternatively, if the reflective layer 224 is metallic, the reflective layer may also serve as the electrode 210.

[0038] Individual, discrete reflective layers 224 (if included) may comprise any suitable metal, dielectric, or semiconductor material compatible with standard MEMS fabrication techniques and can be patterned using standard photolithography techniques to form reflective surface 206.

[0039] In the illustrated embodiment, multiple bands are grouped together to form a large number of MEMS channels or pixels 226, each driven by a much smaller number of drive channels 216. Deflection of band 204 causes constructive or destructive interference between light reflected from reflective surfaces 206 and light reflected from reflective surfaces of adjacent bands, thereby enabling pixels 226 to switch between on / off, off / dark, or intermediate gray levels. In particular, it is noteworthy that the grayscale control of the MEMS-based diffractometer can provide precise dosing of light from each pixel to the surface of the workpiece to compensate for non-uniformity of light illuminating the SLM 200 or non-uniformity of modulated light transmitted from the SLM to the surface of the workpiece via imaging optics.

[0040] refer to Figure 2C In one embodiment suitable for a laser marking system, the linear array 202 includes 1088 individually addressable strips 204, which can be combined together to form channels or pixels 226, having any number of strips depending on pixel size requirements. Furthermore, the SLM may include drive channels 216 with up to 10-bit amplitude modulation (e.g., Figure 2A (As shown), to support grayscale levels and to modulate or switch at speeds up to 350kHz. See again... Figure 2C The shaded rectangle illustrates the illuminated area 228 on the linear array 202 illuminated by a rectangular beam pointing onto the SLM 200. In some embodiments of the laser marking system, it is desirable to provide a pixel configuration with a square aspect ratio. For example, in the illustrated embodiment where the linear array 202 includes approximately 204 bands each having a width of approximately 25 μm and the illuminated area 228 has a width of approximately 75 μm, the bands can be grouped to form 360 square pixels 226a, each comprising a portion of three adjacent bands. Alternatively, the width of the illuminated area can be reduced to approximately 50 μm, and the bands 204 can be grouped to form 512 50 μm × 50 μm square pixels 226b, each comprising a portion of two adjacent bands, or the width of the illuminated area can be further reduced to approximately 25 μm, such that each band forms 1088 25 μm × 25 μm square pixels 226c.

[0041] The advantages of the SLM 200 based on strip MEMS include:

[0042] a. The linear array 202 pixels has a count ranging from approximately 1,000 to approximately 8,000 pixels 226;

[0043] b. Capable of modulating a wide range of laser wavelengths from 355nm to 1064nm (including approximately 514nm);

[0044] c. The low mass and high tension of the 204 band enable high-speed switching of less than about 300 ns, which is up to ten times faster than digital micromirror devices (DMDs) and a thousand times faster than liquid crystal on silicon (LCOS) devices.

[0045] d. Natural analog grayscale control of modulated light intensity, wherein the amplitude resolution is limited only by the bit depth of the drive channel 216;

[0046] e. High power handling, due to the 204 band being made of silicon nitride, a robust amorphous high-temperature ceramic with a power density reaching and exceeding 10 kW / cm². 2 ;

[0047] f. It exhibits a non-contact, high-reliability lifespan of >10,000 hours even under high-throughput UV irradiation;

[0048] g. Boundless pixels with an image are formed by spatial filtering of angle-modulated light, thereby eliminating the “masking gate” effect of the projected pixel image.

[0049] Now refer to Figures 3A to 3C and Figure 4 This describes another type of SLM particularly advantageous for use in laser marking, which comprises a multi-pixel linear array of MEMS-based two-dimensional (2D) diffractors, such as a linear planar light valve (LPLV) available from Silicon Photonics Machines, Inc. in San Jose, California, USA. TM ).

[0050] For clarity, many details of fabricating and operating MEMS-based two-dimensional (2D) diffractors, which are well known and irrelevant to the present invention, are omitted in the following description. MEMS-based 2D diffractors are described in more detail, for example, in commonly assigned U.S. Patent Serial No. 7,064,883, entitled “Two-Dimensional Spatial Light Modulator,” published June 20, 2006, by Alexander Payne et al., which is incorporated herein by reference in its entirety.

[0051] Figure 3A The illustration shows a schematic block diagram of a cross-sectional side view of a 2D modulator or diffractor 300 in a stationary or undriven state. (Reference) Figure 3AThe 2D diffractor 300 typically includes a piston layer 302, which is suspended above the surface of the substrate 304 by struts 306 located at the corners of the piston layer and / or the 2D diffractor. The piston layer 302 includes an electrostatically deflectable piston 302a and a plurality of flexures 302b, through which the piston is flexibly or movably coupled to the struts 306. A panel 308 overlying the piston layer 302 includes a first light-reflecting surface 310 and a hole or cutout portion 312 that separates the panel from a second light-reflecting surface 314 on or attached to the piston 302a. The second light-reflecting surface 314 may be formed directly on the top surface of the piston 302a, or, as shown in the embodiment, formed on a mirror 316 supported above the piston 302a and separated from the piston by a central strut 318 extending from the piston to the mirror. The first light-reflecting surface 310 and the second light-reflecting surface 314 have equal areas and reflectivities, such that during operation, the electrostatic deflection of the piston 302a caused by the electrode 320 formed in or on the piston layer 302 and the electrode 322 in the substrate 304 causes the light reflected from the first light-reflecting surface 310 to undergo constructive or destructive interference with the light reflected from the second light-reflecting surface 314.

[0052] Typically, the electrode 322 in substrate 304 is coupled to one of a plurality of drive channels in a drive circuit or driver 324, which may be integrally formed in a substrate adjacent to or beneath the 2D diffractor 300, as in the illustrated embodiment. The electrode 322 in substrate 304 may be coupled to driver 324 via a via extending from the driver to the electrode through the substrate, and the electrode 320 formed in or on piston layer 302 may be coupled to driver or electrically ground via a conductor extending through pillar 306 and one of the piston layers. As explained in more detail below, typically, a plurality of individual 2D diffractors 300 are grouped or clustered together under the control of a single drive channel to serve as a single pixel in a multi-pixel linear array of an SLM.

[0053] Figure 3B It is in an active or driven state. Figure 3A A schematic block diagram of the 2D diffractor 300, showing a piston 302a deflected toward the substrate 304, and Figure 3C yes Figure 3A and Figure 3B A top view of a 2D diffractor, illustrating a static first light-reflecting surface 310 and a movable second light-reflecting surface 314.

[0054] Now refer to Figure 4 The block diagram describes an exemplary multi-pixel linear array of densely packed 2D diffractors based on MEMS. Figure 4This is a plan view of the SLM 400, which includes a 2D diffractor 402 (e.g., Figures 3A to 3C A linear array 401 of diffractors (shown in the diagram), which together are grouped into or coupled to multiple drive channels or pixels.

[0055] refer to Figure 4 In one embodiment, 2D diffractors 402 are grouped into a linear array 401 of staggered channels or pixels 404 along a first horizontal or vertical axis 406. Each of the 2D diffractors 402 in a single pixel 404 shares a common drive channel or driver 408. Although in the illustrated embodiment, each pixel 404 is depicted as having a single column of 12 2D diffractors 402 grouped along a transverse or vertical axis 410 perpendicular to the horizontal or vertical axis 406 of the array, this is merely for the purpose of illustrating the array. It should be understood that each channel or pixel may include any number of 2D diffractors arranged in one or more columns of any length across the width or vertical or transverse axis of the array without departing from the spirit and scope of the invention. For example, in one embodiment of the SLM 400, which is particularly suitable for the spectral shaping system and method disclosed herein, each pixel 404 includes a single column of 40 diffractors grouped along the transverse axis 410 of the array. Similarly, the SLM 400 can comprise an array 401 of any number of pixels 404 or multiple separate arrays 401 placed end-to-end. Because the optically effective area of ​​the array 401 increases by increasing the number of diffractor columns per pixel, the latter configuration can help increase the power handling of the SLM 400. If the damage threshold for each diffractor is constant, the power handling can increase proportionally to the area increase.

[0056] To maximize the contrast of the SLM 400 or provide it with sufficient contrast, the incident light from the illumination source is expected to have a numerical aperture (NA) or cone angle (Θ) smaller than the first-order diffraction angle (θ) of the diffracting SLM 400. The diffraction angle (θ) of the SLM is defined as the angle between the light reflected from pixel 404 in the 0th-order mode or state and the light reflected from the same pixel in the positive and / or negative 1st-order modes. However, according to the grating equations, the diffraction angle of a periodic surface (e.g., the array 401 of the SLM 400) is set by the ratio of the wavelength of the light incident on the array to the spatial period or spacing of the features of the periodic surface (i.e., pixel 404). Specifically, the grating equations state:

[0057] sinθ=mλ / Λ

[0058] Where θ is the diffraction angle of light reflected from the surface, m is the order (integer) of the diffracted ray, λ is the wavelength of the incident light, and Λ is the space or spacing of the diffractors 402. When a single pixel with multiple 2D diffractors 402 is concentrated and the incident light is an ideal plane wave or has a numerical aperture (NA) = 0, the light diffuses due to the Huygens-Fresnel principle. The diffusion angle Θ is defined as:

[0059] Θ=λ / D

[0060] Where D is the pixel size.

[0061] Achieving sufficient contrast with a conventional grating-based SLM requires either aperture-limited illumination (NA) (and suffers associated throughput loss) or a large diffraction angle by reducing the size and spatial period or spacing of individual diffractors. However, the latter approach has problems for several reasons, including the need for larger, higher-voltage drive circuitry to drive the smaller movable grating element, and the resulting reduction in the SLM's optical power handling capability due to the smaller grating element.

[0062] Compared to traditional grating-based SLMs, including MEMS-based 2D diffractors 402 SLMs 400 (such as LPLV) TM The array is configured to have multiple pixels 404, each pixel including a plurality of 2D diffractors 402 (twelve in the illustrated embodiment) arranged along the transverse or vertical axis 410 of the array, but the number of diffractors arranged along the horizontal or vertical axis 406 is much smaller, typically only one or two diffractors. Therefore, the diffusion angle Θ of the diffracted light from pixel 404 along the vertical axis (where the pixel size is much smaller than along the vertical or transverse axis) is... H Much larger than the diffusion angle Θ of the pixel along the horizontal axis V Conversely, the numerical aperture of illumination in the vertical direction (short axis of the array) can be much larger than that in the horizontal direction (long axis of the array) because the latter is limited by the diffraction angle of the SLM in order to obtain sufficient contrast. Therefore, by combining a linear array of 2D diffractors with asymmetric illumination NAs in both the longitudinal and transverse directions, the overall throughput of the spectrum shaper can be improved.

[0063] Figure 5A This is a schematic block diagram of an embodiment of a laser marking system 500, which includes: an SLM 502 having a multi-pixel linear array of MEMS-based diffractors; and a galvanometer reflector for scanning. For clarity and simplicity of the figures, the optical path is shown unfolded, making the SLM 502 appear translucent. However, it should be understood that because the SLM 502 is reflective, the actual optical path is folded at the SLM at an angle of 90° or less.

[0064] refer to Figure 5A In addition to the SLM 502, the laser marking system 500 further includes: a laser 504 operable to generate a laser for irradiating the SLM; an illumination optics 506 that directs the laser onto the SLM; an imaging optics 508 operable to focus a substantially linear modulated light stripe 510 onto the surface 512 of a workpiece 514, which is mounted on or fixed to a fixture 516 or platform; and a controller 518 operable to control the SLM, the laser, and the imaging optics to scan the linear modulated light stripe across the surface of the workpiece, thereby recording a 2D image thereon.

[0065] As described above, the laser 504 is capable of operating in CW mode or pulsed mode at UV wavelengths from 355 nm to IR wavelengths up to about 2000 nm, with a width or duration of about 1 fs to about 500 ns, a repetition rate of about 10 kHz to about 300 kHz, and an energy range of about 10 microjoules (μJ) to more than 10 millijoules (mJ).

[0066] SLM 502 can include MEMS-based ribbon diffractors (e.g. Figures 2A to 2C (as shown) a multi-pixel linear array or a 2D diffractometer (e.g.) Figures 3A to 3C and Figure 4 (as shown) a multi-pixel linear array.

[0067] The illumination optics 506 may include a beam-forming optics system to guide the laser beam onto the SLM 502. (Reference) Figure 5A The components of the beam-forming optical system may include a Powell lens 520, a long-axis collimating lens 521, and a cylindrical short-axis focusing lens 522 to shape or focus the illumination into a rectangular beam or illumination line that extends substantially uniformly through a linear array of SLM 502.

[0068] The imaging optics 508 may include: a galvanometer mirror 524 for scanning the linear modulation light strip 510 on the surface 512 of the workpiece 514; a plurality of cylindrical lenses 526 for guiding the modulation light toward the galvanometer mirror; a Fourier aperture 528 for separating the 0th order beam from the 1st order beam in the modulation light; and a Fourier transform (FT) lens 530 for focusing the modulation light onto the surface of the workpiece.

[0069] Preferably, the cylindrical lens 526 and FT lens 530 of the imaging optics include fused silica lenses to reduce thermal focus shift of the modulated light focused on the surface 512 of the workpiece 514. In some embodiments, one or more of the lenses 520, 521, and 522 of the illumination optics 506 may also include fused silica lenses to reduce thermal focus shift of the laser focused on the SLM 502.

[0070] The fixing device 516 for placing or securing the workpiece 514 to be marked may include a static fixing device or a movable platform operable to move or reposition the workpiece relative to a substantially stationary linearly modulated light stripe so that the linearly modulated light stripe scans the surface of the workpiece. As described above, in any embodiment, whether static or movable, the fixing device 516 preferably includes a plurality of sensors and signaling devices to signal other components of the laser marking system when the workpiece is in the appropriate position for marking.

[0071] exist Figure 5B In the alternative embodiment shown, the fixture 516 includes a movable belt 516a operable to rapidly and efficiently move multiple individual parts or workpieces 514a past the focal point of 500, thereby marking or recording one or more images on the multiple parts or workpieces. It should be understood that because the speed at which data can be loaded to the controller 518 for the SLM 502 is independent of and significantly greater than the speed at which the fixture 516 or belt 516a moves and records images, the laser system 500 can customize the images recorded on each individual part or workpiece 514 / 514a. Such images may include, for example, serial numbers, part numbers, and part data or data sheets.

[0072] Depending on the size of the linear modulation stripe 510 and / or the image to be recorded, the image can be recorded on the surface 512 of the workpiece 514 in a single scan or single stripe of the linear modulation stripe 510 spanning the surface along a single axis, or by multiple scans or stripes (multiple stripes) of the linear modulation stripe on the surface along a first axis perpendicular to the long axis of the linear modulation stripe, and then the linear modulation stripe is repositioned along a second axis parallel to the long axis.

[0073] Figures 6A to 6C The illustration shows the use of a laser marking system (e.g.) Figure 5A and Figure 5B The diagram shows a schematic block diagram of single-strip and multi-strip scanning of the laser marking system shown.

[0074] Figure 6AAn embodiment of single-strip scanning is illustrated, wherein a linearly modulated light stripe 602 moves once across the surface 604 of a workpiece 606 in a single direction to record an image in a single pass or scan. It should be understood that this embodiment provides the shortest write time (less than 1 second in some embodiments) and can reduce the complexity of the laser marking system by requiring only a single-axis scanner in the X direction. However, it should be noted that laser marking systems using single-strip scanning may require higher-energy lasers of 1 millijoules or higher, depending on the physical size of the pixels in the linear array of the SLM relative to the linearly modulated light stripe 602. The resolution and contrast of a laser marking system using single-strip scanning may be lower compared to a multi-strip system that uses smaller or shorter linearly modulated light stripes 602 and stitches multiple scans or passes together to form an image.

[0075] Figure 6B An embodiment of multi-strip scanning is illustrated, wherein a linearly modulated light stripe 602 moves multiple times along the X direction on the surface 604 of a workpiece 606, followed by rotation or repositioning of the linearly modulated light stripe along the Y direction and repeated scanning along the same X direction, to record an image using multiple scans or passes stitched together. By stitching together, it can mean that the second and subsequent scans overlap with the previous scans, or that the scans are adjacent or adjacent to each other on the surface 604 of the workpiece 606 with substantially no overlap. It should be understood that although the writing time of this multi-strip method is longer than that of the single-strip method, it is still much faster than the point-by-point method of existing laser marking systems using DMD or LCOS modulators. It will be further understood that the shorter long axis of the linearly modulated light stripe 602 enables the use of a lower-power laser while providing higher resolution and contrast in the recorded image.

[0076] Figure 6C Another embodiment of multi-striped scanning is illustrated, wherein the linear modulation stripe 602 is not reset to its initial starting point on the X-axis before the start of a second or subsequent scan, but rather the linear modulation stripe is rotated or repositioned in the Y-direction so that the scanning direction along the X-direction is reversed. It should be understood that, with... Figure 6B Compared to the previous embodiment, this embodiment offers a shorter write time due to the elimination of the need to reposition the X-axis galvanometer mirror, movable platform, or fixed device after each scan in the X direction, while demonstrating the same improvement in resolution and contrast and enabling the use of lower power lasers. (See also the section on...) Figure 6B In the described embodiments, multiple scans or passes can be stitched together in overlapping or non-overlapping passes.

[0077] Figure 7This diagram illustrates the unfolded optical path of the illumination and imaging beam along a vertical or longitudinal axis of a linear array used in a laser marking system, showing the separation of the 0th-order beam from the 1st-order beam in the modulated light. For clarity and simplification, the optical path is shown unfolded, making the SLM 702 appear translucent. However, as stated above, it should be understood that because the SLM 702 is reflective, the actual optical path is folded into an acute angle at the SLM.

[0078] refer to Figure 7 The optical path begins at laser 704 and passes through morphing illumination optics 706 to illuminate a substantially linear portion of the linear array of SLM 702, and through imaging optics 708 to focus the modulated light onto surface 710 of workpiece 712. In some embodiments (such as the one shown), illumination optics 706 is morphing illumination optics and may include a Powell lens 714, a long-axis collimating lens 716, and a cylindrical short-axis focusing lens 718 to shape or focus the illumination into a substantially rectangular beam or illumination line that extends substantially uniformly through the linear array of SLM 702. Imaging optics 708 may include: a plurality of cylindrical lenses 720 that guide the modulated light to one or more galvanometer mirrors 722; a first Fourier transform (FT) lens 724; a Fourier aperture 726 that separates the 0th order beam 728 of the modulated light from the positive 1st order beam 730 and the negative 1st order beam 732; and a second inverse Fourier transform (FT) lens 734.

[0079] Figure 8 This is a schematic block diagram of another embodiment of a laser marking system 800, which includes: an SLM 802 having a multi-pixel linear array of MEMS-based diffractors; and a movable fixing device or platform 804 for fixing a workpiece 806 thereto. (Reference) Figure 8 The laser marking system 800 further includes: a laser 808 operable to generate a laser for irradiating the SLM 802; an illumination optics 810 for guiding the laser onto the SLM; an imaging optics 812 operable to focus a substantially linearly modulated light stripe 814 onto the surface 816 of a workpiece 806 located on or fixed to the movable fixture or platform 804; and a controller 820 operable to control the SLM, the laser, and the movable platform to scan the surface of the workpiece with the linearly modulated light stripe, thereby recording a 2D image on the surface of the workpiece.

[0080] As described above, the laser 808 is capable of operating in CW mode or pulsed mode at UV wavelengths from 355 nm to IR wavelengths up to about 2000 nm, with a width or duration of about 1 fs to about 500 ns, a repetition rate of about 10 kHz to about 300 kHz, and an energy range of about 10 microjoules (μJ) to greater than 10 millijoules (mJ).

[0081] SLM 802 can include MEMS-based ribbon diffractors (e.g. Figures 2A to 2C (as shown) a multi-pixel linear array or a 2D diffractometer (e.g.) Figures 3A to 3C and Figure 4 (as shown) a multi-pixel linear array.

[0082] The illumination optics 810 may include a beam-forming optics system 822 to guide a substantially rectangular beam onto the SLM 802. Although not shown in the figure, elements of the beam-forming optics system 822 may include a Powell lens and a long-axis collimating lens, as shown in Figure 5 and Figure 7 As shown. The illumination optics 810 may further include a cylindrical short-axis focusing lens 824 to guide or focus a rectangular beam substantially uniformly onto the linear array of SLM 802.

[0083] Imaging optics 812 may include: a first Fourier transform (FT) lens 826; a Fourier aperture 828 for separating the 0th-order beam from the positive and negative 1st-order beams in the modulated light; and a second inverse Fourier transform (FT) lens 830 for focusing the modulated light onto the surface 816 of the workpiece 806. As described in the embodiments above, the FT lenses 826 and 830 of imaging optics 812 may include fused silica lenses to reduce thermal focus shift of the modulated light focused onto the surface 816 of the workpiece 806. In some embodiments, one or more elements of the beam forming optics system 822 and the focusing lens 824 of illumination optics 810 may also include fused silica lenses to reduce thermal focus shift of the laser focused onto the SLM 802.

[0084] The fixture or platform 804 for placing or securing the workpiece 806 to be marked can move relative to a stationary, substantially linearly modulated light strip 814 or at least along a first axis or X-axis to perform the action described above. Figure 6A The single-strip scanning described. More preferably, the platform 804 is further operable to reposition the workpiece 806 held on the platform relative to the linear modulation light stripe 814 along a second axis parallel to the long axis of the linear light stripe or the Y-axis, to perform as described above. Figure 6B and Figure 6C One of the described multi-stripe scans.

[0085] Figure 9 This is a schematic block diagram of another embodiment of a laser marking system 900, which includes: an SLM 902 having a multi-pixel linear array of MEMS-based diffractors and an imaging optics 904 including optical elements operable to focus a modulated beam in front of galvanometer mirrors 906 for scanning the modulated beam across a surface 908 of a workpiece 910. (Refer to the above reference...) Figure 5A and Figure 5B As with the embodiments shown and described, the optical path is shown unfolded for clarity and simplicity of the drawings, making the SLM 902 appear to be translucent. However, it should be understood that because the SLM 902 is reflective, the actual optical path is folded at the SLM at an angle of 90° or less.

[0086] refer to Figure 9 The laser marking system 900 further includes: a laser 912 operable to generate laser light for illuminating the SLM 902; an illumination optics 914 that directs the laser light onto the SLM; a static fixture 916 on which the workpiece 910 to be marked is placed or fixed; and a controller 918 operable to control the SLM, the laser, and the galvanometer reflector 906 to scan a linearly modulated light stripe 920 across the surface 908 of the workpiece to record a 2D image on the surface of the workpiece. It should be noted that although the light modulated from the SLM 902 by the imaging optics 904 is shown as a separate modulated beam or small beam 921 to represent light and dark modulated light from individual pixels or groups of pixels (as in the embodiments of the laser marking systems 500, 800 described above), the imaging optics 904 of the laser marking system 900 is operable to illuminate the surface 908 of the workpiece 910 with a substantially linear or rectangular modulated light stripe 920. Optionally, as in the illustrated embodiment, the laser marking system 900 may further include a window 922 located in a housing (not shown) that encloses the laser marking system to protect the galvanometer reflector 906.

[0087] As described above, the laser 912 is capable of operating in CW mode or pulsed mode at UV wavelengths from 355 nm to IR wavelengths up to about 2000 nm, with a width or duration of about 1 fs to about 500 ns, a repetition rate of about 10 kHz to about 300 kHz, and an energy range of about 10 microjoules (μJ) to greater than 10 millijoules (mJ).

[0088] As also mentioned above, the SLM 902 may include MEMS-based strip diffractors (e.g., Figures 2A to 2C(as shown) a multi-pixel linear array or a 2D diffractometer (e.g.) Figures 3A to 3C and Figure 4 (as shown) a multi-pixel linear array.

[0089] The illumination optics 914 may include a beam-forming optics system 924 to form a rectangular beam and guide it substantially uniformly onto the linear array of the SLM 902. Although not shown in the figure, elements of the beam-forming optics system 924 may include a Powell lens and a long-axis collimating lens, as shown in Figure 5 and Figure 7 As shown.

[0090] According to this embodiment, the imaging optical device 904 includes: a first focusing cylindrical lens 926, which is located in front of the galvanometer reflector 906 and is used to focus light along the X-axis onto the surface 908 of the workpiece 910, wherein the X-focus determines the width of the modulation light stripe 920; and a second focusing cylindrical lens 928, which is used to focus light along the Y-axis, wherein the Y-focus determines the height of the modulation light stripe.

[0091] Finally, as in the embodiments described above, the lenses 926, 928 of the imaging optics 904 may include fused silica lenses to reduce thermal focus shift of the modulated light focused onto the surface 908 of the workpiece 910. In some embodiments, one or more elements of the beam forming optics 924 of the illumination optics 914 may also include fused silica lenses to reduce thermal focus shift of the laser focused onto the SLM 902.

[0092] Figure 10 This is a flowchart illustrating a method for modifying or marking surfaces using a laser marking system, including a MEMS-based SLM. (Reference) Figure 10The method begins by positioning the workpiece on a fixture of the laser marking system and sending digital image data to the SLM of the laser marking system (1002). When it is detected that the workpiece is positioned on the fixture, the digital image data is received by the SLM, and the diffractometer is positioned, light is generated from the laser (1004). Typically, this is achieved by sending pulses of appropriate duration to the laser via a control bus. Next, the light from the laser is optically coupled to the SLM to substantially uniformly illuminate the linear array of the SLM, and the light incident on the SLM is modulated (1006). The modulated light from the SLM is then projected and focused into a basic linear stripe on the surface of the workpiece using imaging optics; this linear stripe comprises light from multiple pixels of the SLM (1008). Next, the laser, the SLM, and a scanner or galvanometer mirror in the imaging optics are operated to scan the linearly modulated stripe across the surface of the workpiece to record an image on the surface of the workpiece (1010). It is then determined whether multiple stripes are necessary or desired (1012). If multiple stripes are not required, i.e., if a single stripe scan is sufficient to record the desired image, the process ends. If multiple stripes are required due to the size of the image, the length of the linear modulation stripe, or the desired resolution or contrast in the recorded image, the linear modulation stripe is repositioned or rotated (1014) on the surface of the workpiece along an axis parallel to the long axis of the linear stripe, and the process is repeated.

[0093] Optionally, as in Figure 10 As in the illustrated embodiment, the method may further include an initial calibration step (step 1016) in which the laser marking system is calibrated using test marks or patterns on a workpiece or test piece positioned on a fixture, and grayscale control of modulated light intensity is used to adjust the precise dose of light projected onto the workpiece for each pixel to calibrate non-uniformity in the light. Evaluation of the test marks can be performed manually by the user of the laser marking system or automatically using a scanner or camera integrated into the system.

[0094] Figures 11A to 11C This is a schematic block diagram illustrating a method for modifying or marking a surface using alternating scans of two or more surfaces. 20. Reference Figure 11A The method begins by controlling the laser, SLM, and imaging optics of the laser marking system to scan a linearly modulated light stripe across the surface of the workpiece in a first pass, marking a first number of points 1102 at a first location, and referencing... Figure 11B The second pass involves scanning the linearly modulated light stripe across the workpiece surface to mark a second number of points 1104 at second positions that intersect with the first position, thereby recording the desired image 1106, as shown. Figure 11CAs shown in these figures, the SLM is modulated along the vertical or Y direction, while scanning the workpiece along the horizontal or X direction. It should be understood that this method reduces the thermal load on the SLM and imaging optics.

[0095] In another embodiment, the method may further include pixel shaping to improve the resolution of an image with a high-density pattern. Figure 12A and Figure 12B It is a MEMS-based 2D diffractometer (such as LPLV) TM A schematic block diagram of two adjacent eight-pixel groups 1202 and 1204 in a linear array 1208 illustrates a pixel shaping method for recording images with high-density patterns. (Reference) Figure 12A As can be seen, when all eight pixels 1206 in adjacent groups 1202 and 1204 attempt to record adjacent points on the surface of the workpiece, crosstalk between pixel groups produces printed lines 1210 instead of the expected adjacent points. Figure 12B As shown, by closing the adjacent pixels 1206 between adjacent groups 1202 and 1204, the resolution is improved, thereby producing the desired adjacent point 1212.

[0096] Therefore, embodiments of a laser marking system including a spatial light modulator (SLM) with a multi-pixel linear array of MEMS-based diffractors, and systems using the laser marking system have been described. Embodiments of the invention have been described above with the aid of functional and schematic block diagrams illustrating the specified functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are properly performed.

[0097] The foregoing description of specific embodiments so fully reveals the general nature of the invention that others, by applying knowledge of the art, can readily modify and / or adapt various applications of these specific embodiments without departing from the general conception of the invention, without excessive experimentation. Therefore, based on the teachings and guidance presented herein, these modifications and adjustments are intended to be within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the wording or terminology used herein is for descriptive and not limiting purposes, and that the terminology or terminology of this specification will be interpreted by those skilled in the art based on the teachings and guidance.

[0098] It should be understood that the Detailed Description section, rather than the Summary and Abstract sections, is intended to interpret the claims. The Summary and Abstract sections may set forth one or more, but not all, exemplary embodiments of the invention as conceived by the inventors, and are therefore not intended to limit the invention and the appended claims in any way.

[0099] The breadth and scope of this invention should not be limited by any of the exemplary embodiments described above, but should be defined only by the appended claims and their equivalents.

Claims

1. A laser marking system comprising: a fixture on which a workpiece is positioned, the workpiece having a surface to be marked; a spatial light modulator comprising a plurality of micromechanical system-based diffractors in a linear array of pixels; a laser operable to illuminate the spatial light modulator; imaging optics operable to focus a substantially linear modulated light stripe onto the surface of the workpiece, the linear light stripe comprising light from a plurality of pixels of the spatial light modulator; and a controller operable to control the fixture, the spatial light modulator, the laser and the imaging optics to mark the surface of the workpiece to record an image on the surface of the workpiece, wherein the spatial light modulator is operable to signal the laser when image data loaded from the controller to the spatial light modulator is ready to be recorded on the workpiece, enabling the laser to fire a pulse. Each of the micromechanical system-based diffractors comprises a plurality of electrostatically deflectable ribbons suspended over a substrate, each ribbon having a light reflecting surface, wherein electrostatic deflection of the plurality of electrostatically deflectable ribbons causes light reflected from the light reflecting surface of a first electrostatically deflectable ribbon to interfere with light reflected from the light reflecting surface of a second electrostatically deflectable ribbon.

2. The laser marking system of claim 1, wherein, Each of the micromechanical system-based diffractors comprises:

3. The laser marking system of claim 1, wherein, a piston layer suspended over a surface of a substrate by struts located at corners of the substrate, the piston layer comprising an electrostatically deflectable piston and a plurality of flexures, the piston being coupled to the struts by the flexures; a first reflecting surface located on a top surface of the piston; and a faceplate suspended over the piston layer, the faceplate comprising a second reflecting surface located on a top surface of the faceplate and an aperture for exposing the piston, wherein electrostatic deflection of the piston causes light reflected from the first reflecting surface to interfere with light reflected from the second reflecting surface. The controller is operable to provide grey scale control of the micromechanical system-based diffractors to provide a precise dose of light from each pixel onto the surface of the workpiece to compensate for non-uniformity of light illuminating the spatial light modulator or non-uniformity of modulation transmitted from the spatial light modulator through the imaging optics.

4. The laser marking system of claim 3, wherein, The imaging optics comprise a plurality of galvanometer mirrors and wherein the controller is operable to control the plurality of galvanometer mirrors to cause the linear modulated light stripe to scan over the surface of the workpiece to record a two-dimensional image on the surface of the workpiece.

5. The laser marking system of claim 1, wherein, The imaging optics comprise a plurality of cylindrical lenses to focus modulated light from the spatial light modulator onto the plurality of galvanometer mirrors and a focusing lens to focus a linear modulated light stripe from the plurality of galvanometer mirrors onto the surface of the workpiece.

6. The laser marking system of claim 5, wherein, ​ 7. The laser marking system of claim 1, wherein, The fixture includes a plurality of sensors to send signals to the controller, the spatial light modulator, and the laser when the workpiece is in position for image recording at the position, and wherein the controller is operable to control the fixture to provide relative motion of the fixture and the linearly modulated light stripe to cause the linearly modulated light stripe to scan across the surface of the workpiece to record a two-dimensional image on the surface of the workpiece.

8. The laser marking system of claim 7, wherein, The fixture includes a moveable platform on which the plurality of workpieces are positioned, and the controller is operable to move the plurality of workpieces on the moveable platform through a focal point of the imaging optics to record images sequentially on the plurality of workpieces, and wherein the images recorded on each of the plurality of workpieces can be different.

9. The laser marking system of claim 6, wherein, The controller is operable to reposition the linearly modulated light stripe in a second direction perpendicular to the first direction after causing the linearly modulated light stripe to scan a predetermined distance across the surface of the workpiece in the first direction, and to cause the linearly modulated light stripe to repeat the scan in a third direction parallel to and opposite the first direction across the surface of the workpiece for the predetermined distance.

10. A laser marking system, comprising: a fixture on which a workpiece is positioned, the workpiece having a surface to be marked; a laser; a spatial light modulator including a multipixel linear array of microelectromechanical system-based diffractors; illumination optics operable to illuminate the spatial light modulator with light from the laser, the illumination optics including a beam forming optical system to direct a rectangular beam onto the spatial light modulator; imaging optics operable to focus a substantially linearly modulated light stripe onto a surface of a workpiece, the imaging optics including: a first cylindrical lens to focus modulated light from the spatial light modulator in an X focal plane of the surface of the workpiece; a second cylindrical lens to focus modulated light from the spatial light modulator in a Y focal plane, wherein the Y-focal point determines a light height of the linearly modulated light stripe on the surface of the workpiece; and a plurality of galvanometer mirrors disposed in an optical path between the first and second cylindrical lenses and the surface of the workpiece; and a controller operable to control the laser, the spatial light modulator, and the plurality of galvanometer mirrors to cause the linearly modulated light stripe to scan across the surface of the workpiece to record a two-dimensional image on the surface of the workpiece, wherein the spatial light modulator is operable to send a signal to the laser when image data loaded into the spatial light modulator from the controller is ready to be recorded on the workpiece, so that the laser can fire a pulse, and wherein the fixture includes a plurality of sensors to send signals to the controller, the spatial light modulator, and the laser when the workpiece is in position for image recording at the position.

11. The laser marking system of claim 10, wherein, Each of these microelectromechanical system-based diffractors includes a plurality of electrostatically deflectable strips suspended over a substrate, each strip having a light-reflecting surface, wherein electrostatic deflection of the plurality of electrostatically deflectable strips causes light reflected from the light-reflecting surface of a first electrostatically deflectable strip to interfere with light reflected from the light-reflecting surface of a second electrostatically deflectable strip.

12. The laser marking system of claim 10, wherein, Each of these microelectromechanical system-based diffractors includes: a piston layer suspended over a surface of a substrate by struts located at corners of the substrate, the piston layer including an electrostatically deflectable piston and a plurality of flexures by which the piston is coupled to the struts; a first reflective surface located on a top surface of the piston; and a faceplate suspended over the piston layer, the faceplate including a second reflective surface located on a top surface of the faceplate and an aperture for exposing the piston, wherein electrostatic deflection of the piston causes light reflected from the first reflective surface to interfere with light reflected from the second reflective surface.

13. The laser marking system of claim 10, wherein, The imaging optics further include a window disposed in an optical path between the plurality of galvanometer mirrors and the surface of the workpiece.

14. The laser marking system of claim 10, further comprising a moveable stage on which the plurality of workpieces are positioned, and the controller is operable to move the plurality of workpieces on the moveable stage through a focal point of the imaging optics to sequentially record two-dimensional images on the plurality of workpieces, and wherein, The image recorded on each of the plurality of workpieces can be different.

15. The laser marking system of claim 10, wherein, The controller is operable to, after causing the linearly modulated light strip to scan a predetermined distance across the surface of the workpiece in a first direction, reposition the linearly modulated light strip in a second direction perpendicular to the first direction, and cause the linearly modulated light strip to repeat the scan of the predetermined distance across the surface of the workpiece in a third direction parallel to the first direction and opposite the first direction.

Images