Methods and systems for multi-element linkages for fiber scanning displays

Abstract

To provide favorable methods and systems for multi-element linkage for a fiber scanning display.SOLUTION: A multi-element fiber scanner for scanning electromagnetic imaging radiation includes a base having a base plane and a longitudinal axis orthogonal to the base plane, and a first fiber link passing through the base in a direction parallel to the longitudinal axis. The first fiber link is operatively coupled to at least one electromagnetic radiation source. The multi-element fiber scanner also includes a plurality of additional links joined to and extending from the base, and a retention collar disposed at a predetermined distance along the longitudinal axis from the base. The first fiber link and the plurality of additional links are joined to the retention collar.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] (Citation of Related Application) This application claims priority to U.S. Provisional Patent Application No. 62 / 438,415, filed December 22, 2016, entitled "Methods and Systems for Fabrication of Shaped Fiber Elements using Laser Ablation," the disclosure of which is incorporated herein by reference in its entirety for all purposes.

[0002] The following U.S. applications (including this application) are filed concurrently, the entire disclosures of which are incorporated herein by reference in their entirety for all purposes: U.S. Patent Application No. 15 / _ (filed December 21, 2017, entitled "METHODS AND SYSTEMS FOR FABRICATION OF SHAPE FIBER ELEMENTS FOR SCANNING FIBER DISPLAYS," Attorney Docket No. 101782-1060973-002210US); U.S. Patent Application No. 15 / _ (filed December 21, 2017, entitled "METHODS AND SYSTEMS FOR FABRICATION OF SHAPE FIBER ELEMENTS USING LASER ABLATION," Attorney Docket No. 101782-1060976-002310US), and U.S. Patent Application No. 15 / _ (filed December 21, 2017, entitled "METHODS AND SYSTEMS FOR MULTI-ELEMENT LINKAGE FOR FIBER SCANNING DISPLAY," Attorney Docket No. 101782-1060978-002410US).

[0003] BACKGROUND OF THE INVENTION Modern computing and display technology has facilitated the development of systems for so-called "virtual reality" or "augmented reality" experiences in which digitally reproduced images, or portions thereof, are presented to a viewer in a manner that appears and can be perceived as real. Virtual reality, or "VR," scenarios typically involve the presentation of digital or virtual image information without transparency to other actual, real-world visual input, while augmented reality, or "AR," scenarios typically involve the presentation of digital or virtual image information as an extension of the viewer's visualization of the real world around them.

[0004] Despite the advances made in these display technologies, there remains a need in the art for improved methods and systems relating to augmented reality systems, and particularly display systems. Summary of the Invention [Problem to be solved by the invention]

[0005] (Summary of the Invention) The present invention relates generally to methods and systems related to fiber scanning projection display systems. More specifically, embodiments of the present invention provide methods and systems for multi-element linkages that allow a scanning fiber to oscillate in a plane, in a set of planes, or along an arc. The present invention is applicable to a variety of applications in computer vision and image display systems. [Means for solving the problem]

[0006] According to one embodiment of the present invention, a multi-element fiber scanner for scanning electromagnetic imaging radiation is provided. The multi-element fiber scanner includes a base having a base plane and a longitudinal axis orthogonal to the base plane, and a first fiber link passing through the base in a direction parallel to the longitudinal axis. The first fiber link is operably coupled to at least one electromagnetic radiation source. The multi-element fiber scanner also includes a plurality of additional links joined to the base and extending from the base, and a retaining collar positioned a predetermined distance from the base along the longitudinal axis, the first fiber link and the plurality of fiber links also joined to the retaining collar. The plurality of additional links can extend from the base in a direction substantially parallel to the longitudinal axis. During operation, the multi-element fiber scanner can scan electromagnetic imaging radiation along an axis parallel to the base plane.

[0007] According to another embodiment of the present invention, a method of fabricating a multi-element fiber scanner is provided. The method includes providing a fiber optic cable having a cladding region and a fiber core, and focusing a laser beam at a series of predetermined locations inside the cladding region of the fiber optic cable. The method also includes creating a plurality of damage sites at the predetermined locations, exposing the fiber optic cable to an etching solution, and preferentially etching the plurality of damage sites to form a base having a base plane and a longitudinal axis perpendicular to the base plane, a retaining collar positioned a predetermined distance from the base along the longitudinal axis, a first fiber link including a fiber core passing through the base plane and bonded to the retaining collar, and a plurality of additional links extending from the base bonded to the base to the retaining collar and bonded to the retaining collar.

[0008] For example, the method can further include rotating the fiber optic cable about a longitudinal axis while creating the plurality of damage sites at the predetermined locations. Additionally, creating the plurality of damage sites at the predetermined locations can include forming a latticework damage site, which can include a plurality of radial vias passing through the cladding region toward the fiber core. In one implementation, creating the plurality of damage sites at the predetermined locations includes first creating a first portion of the plurality of damage sites adjacent to the fiber core, and subsequently creating a second portion of the plurality of damage sites adjacent to the periphery of the cladding region. In addition to the fiber cladding and fiber core, the fiber optic cable can include a plurality of sacrificial regions disposed within the cladding region. The plurality of sacrificial regions can be air cavities or include a material having a higher etching rate than the cladding region.

[0009] According to a specific embodiment of the present invention, a method of fabricating a multi-element fiber scanner is provided. The method includes fabricating a preform including structural precursors for at least one fiber waveguide, a fiber support, and a sacrificial material, and drawing the preform to form a fiber structure. The method also includes exposing the fiber structure to an etching solution to preferentially etch the sacrificial material to form a base having a base plane and a longitudinal axis perpendicular to the base plane, a retaining collar positioned a predetermined distance from the base along the longitudinal axis, a first fiber link including at least one fiber waveguide passing through the base plane and bonded to the retaining collar, and a plurality of fiber supports bonded to the base, extending from the base to the retaining collar, and bonded to the retaining collar.

[0010] According to another specific embodiment of the present invention, a method of operating a multi-element fiber scanner is provided. The method includes providing an electromagnetic radiation source and passing the electromagnetic radiation from the source through a first fiber link. The first fiber link passes through a base having a base plane and a longitudinal axis perpendicular to the base plane. The method also includes supporting a retaining collar positioned a predetermined distance from the base along the longitudinal axis. A plurality of additional links join the base and the retaining collar. The method further includes translating the base within the base plane, translating the retaining collar within a set of planes parallel to the base plane, and scanning the electromagnetic radiation in one or more axes.

[0011] According to certain embodiments of the present invention, a multi-element fiber scanner for scanning electromagnetic imaging radiation is provided. The multi-element fiber scanner includes a base having a base plane and a longitudinal axis orthogonal to the base plane, and a first fiber link passing through the base in a direction parallel to the longitudinal axis. The first fiber link is operably coupled to at least one electromagnetic radiation source. The multi-element fiber scanner also includes a plurality of actuating elements joined to the base and extending from the base along the longitudinal axis, and a retaining collar positioned a predetermined distance from the base along the longitudinal axis. The plurality of actuating elements can be arranged to surround the first fiber link. The first fiber link and the plurality of actuating elements are joined to the retaining collar. During operation, the first fiber link is operable to scan electromagnetic imaging radiation along an axis parallel to the base plane.

[0012] According to another specific embodiment of the present invention, a method of operating a multi-axis fiber scanner is provided. The method includes providing an electromagnetic radiation source and passing electromagnetic radiation from the source through a first fiber link. The first fiber link passes through a base having a base plane and a longitudinal axis perpendicular to the base plane. The method also includes supporting a retaining collar disposed a predetermined distance from the base along the longitudinal axis. A plurality of piezoelectric actuators connect the base and the retaining collar. A first piezoelectric actuator of the plurality of piezoelectric actuators connects one side of the base to one side of the retaining collar. A second piezoelectric actuator of the plurality of piezoelectric actuators connects an opposite side of the base to an opposite side of the retaining collar. The first piezoelectric actuator and the second piezoelectric actuator are located in a scanning plane. The method further includes actuating a first piezoelectric actuator of the plurality of piezoelectric actuators to decrease a distance from one side of the base to one side of the retaining collar, actuating a second piezoelectric actuator of the plurality of piezoelectric actuators to increase a distance from the opposite side of the base to the opposite side of the retaining collar, and scanning the first fiber link in the scanning plane. As described herein, the method can include alternately actuating a first one of the piezoelectric actuators to decrease or increase the distance between the base and the retaining collar on one side while synchronously actuating a second one of the piezoelectric actuators to decrease or increase the distance between the base and the retaining collar on a second side.

[0013] According to another embodiment of the present invention, a multi-element fiber scanner for scanning electromagnetic imaging radiation is provided. The multi-element fiber scanner includes a base having a base plane and a longitudinal axis orthogonal to the base plane, and a first fiber link passing through the base in a direction parallel to the longitudinal axis. The first fiber link is operably coupled to at least one electromagnetic radiation source. The multi-element fiber scanner also includes a plurality of motion actuation links joined to the base and extending from the base. Each of the plurality of motion actuation links includes a first piezoelectric element proximate the base and a second piezoelectric element coupled to the first piezoelectric element at a location distal to the base. The multi-element fiber scanner further includes a retaining collar positioned a predetermined distance from the base along the longitudinal axis. The first fiber link and the second piezoelectric element of each of the plurality of motion actuation links are joined to the retaining collar. During operation, the first piezoelectric element contracts / expands when the second piezoelectric element expands / contracts.

[0014] According to yet another embodiment of the present invention, a multi-element fiber scanner for scanning electromagnetic imaging radiation is provided. The multi-element fiber scanner includes a base having a support surface defining a base plane, a mounting surface opposite the support surface, and a longitudinal axis perpendicular to the base plane, and a plurality of motion actuators coupled to the support surface of the base. The multi-element fiber scanner also includes a multi-link fiber structure coupled to the mounting surface. The multi-link fiber structure includes a fiber base and fiber links passing through the fiber base in a direction parallel to the longitudinal axis. The fiber links are operably coupled to at least one electromagnetic radiation source. The multi-link fiber structure also includes a plurality of motion actuation elements (e.g., piezoelectric actuators) joined to the fiber base and extending from the fiber base along the longitudinal axis, and a retaining collar positioned a predetermined distance from the fiber base along the longitudinal axis. The fiber links and the plurality of motion actuation elements are joined to the retaining collar. The present specification also provides, for example, the following items: (Item 1) 1. A multi-element fiber scanner for scanning electromagnetic imaging radiation, said multi-element fiber scanner comprising: a base having a base plane and a longitudinal axis perpendicular to the base plane; a first fiber link passing through the base in a direction parallel to the longitudinal axis, the first fiber link being operably coupled to at least one electromagnetic radiation source; a plurality of additional links joined to and extending from the base; a retaining collar positioned a predetermined distance from the base along the longitudinal axis; Equipped with The first fiber link and the plurality of additional links are joined to the retaining collar. (Item 2) Item 2. The multi-element fiber scanner of item 1, wherein the first fiber link passes through the retaining collar in a direction parallel to the longitudinal axis. (Item 3) Item 10. The multi-element fiber scanner of item 1, further comprising a piezoelectric actuator mechanically coupled to the base and operable to translate the base in the base plane. (Item 4) Item 4. The multi-element fiber scanner of item 3, wherein the retaining collar is operable to translate in a set of planes parallel to the base plane. (Item 5) Item 10. The multi-element fiber scanner of item 1, wherein one or more of the plurality of additional links pass through the base parallel to the longitudinal axis and are operably coupled to the at least one electromagnetic radiation source. (Item 6) Item 2. The multi-element fiber scanner of item 1, wherein the plurality of additional links are arranged to surround the first fiber link. (Item 7) Item 2. The multi-element fiber scanner of item 1, wherein the plurality of additional links extend from the base in a direction parallel to the longitudinal axis. (Item 8) Item 10. The multi-element fiber scanner of item 1, wherein the plurality of additional links extend from the base at an angle tilted toward the first fiber link. (Item 9) Item 9. The multi-element fiber scanner of item 8, wherein the retaining collar is operable to translate along a curved arc. (Item 10) Item 9. The multi-element fiber scanner of item 8, wherein the first fiber link is operable to emit the electromagnetic imaging radiation toward a focal point. (Item 11) 1. A method of operating a multi-element fiber scanner, the method comprising: providing a source of electromagnetic radiation; passing electromagnetic radiation from the electromagnetic radiation source through a first fiber link, the first fiber link passing through a base having a base plane and a longitudinal axis perpendicular to the base plane; supporting a retaining collar disposed a predetermined distance from the base along the longitudinal axis, with a plurality of additional links joining the base and the retaining collar; translating the base in the base plane; translating the retaining collar in a set of planes parallel to the base plane; scanning said electromagnetic radiation in one or more axes; A method comprising: (Item 12) Item 12. The method of item 11, wherein translating the base within the base plane includes actuating the base in a first direction and actuating the base in a second direction orthogonal to the first direction. (Item 13) Item 12. The method according to item 11, wherein translating the retaining collar in the set of planes parallel to the base plane includes tilting the plurality of additional links. (Item 14) Item 12. The method of item 11, wherein one or more of the plurality of additional links pass through the base, the method further comprising passing the electromagnetic radiation from the electromagnetic radiation source through one or more of the plurality of additional links. (Item 15) Item 12. The method of item 11, wherein the electromagnetic radiation is intensity modulated. (Item 16) 1. A multi-element fiber scanner for scanning electromagnetic imaging radiation, said multi-element fiber scanner comprising: a base having a base plane and a longitudinal axis perpendicular to the base plane; a first fiber link passing through the base in a direction parallel to the longitudinal axis, the first fiber link being operably coupled to at least one electromagnetic radiation source; a plurality of actuation elements joined to the base and extending from the base along the longitudinal axis; a retaining collar positioned a predetermined distance from the base along the longitudinal axis; Equipped with The multi-element fiber scanner, wherein the first fiber link and the plurality of actuating elements are joined to the retaining collar. (Item 17) Item 17. The multi-element fiber scanner of item 16, wherein the first fiber link passes through the retaining collar in a direction parallel to the longitudinal axis. (Item 18) Item 17. The multi-element fiber scanner of item 16, wherein the plurality of actuating elements comprises a plurality of piezoelectric tube stacks. (Item 19) Item 17. The multi-element fiber scanner of item 16, wherein the plurality of actuating elements comprises a first piezoelectric element positioned on a first side of the first fiber link and operable to contract / expand, and a second piezoelectric element positioned on a second side of the first fiber link opposite the first side and operable to expand / contract opposite to the first piezoelectric element. (Item 20) Item 17. The multi-element fiber scanner of item 16, wherein the plurality of actuating elements further comprise: a third piezoelectric element positioned on a third side of the first fiber link and operable to contract / expand; and a fourth piezoelectric element positioned on a fourth side of the first fiber link opposite the third side and operable to expand / contract opposite to the third piezoelectric element.

[0015] Numerous advantages are achieved by the methods of the present invention over conventional techniques. For example, embodiments of the present invention provide methods and systems for scanning a fiber optic support in a substantially planar manner, thereby providing an image field having a known profile. These and other embodiments of the present invention, along with many of their advantages and features, are described in more detail in the following text and in conjunction with the accompanying figures. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a simplified perspective view illustrating a multi-element fiber scanner according to one embodiment of the present invention. [Figure 2] FIG. 2 is a simplified diagram illustrating two scanning positions for a multi-element fiber scanner, according to one embodiment of the present invention. [Figure 3] FIG. 3 is a simplified diagram illustrating a multi-element fiber scanner with tilted links, according to one embodiment of the present invention. [Figure 4] FIG. 4 is a simplified diagram illustrating elements of a fiber scanning system according to one embodiment of the present invention. [Figure 5] FIG. 5 is a simplified flowchart illustrating a method for fabricating a multi-element fiber scanner, according to one embodiment of the present invention. [Figure 6] FIG. 6 is a simplified flowchart illustrating a method of fabricating a multi-element fiber scanner according to another embodiment of the present invention. [Figure 7] FIG. 7 is a simplified flowchart illustrating a method of operating a multi-element fiber scanner, according to one embodiment of the present invention. [Figure 8A] FIG. 8A is a simplified perspective view illustrating a multi-axis fiber scanner, according to one embodiment of the present invention. [Figure 8B] FIG. 8B is a simplified flowchart illustrating a method of operating a multi-axis fiber scanner, according to one embodiment of the present invention. [Figure 9A]FIG. 9A is a simplified side view illustrating a multi-segment motion actuation element, according to one embodiment of the present invention. [Figure 9B] FIG. 9B is a simplified side view illustrating the oscillatory motion of the multi-segment motion actuation element shown in FIG. 9A, according to an embodiment of the present invention. [Figure 9C] FIG. 9C is a simplified side view illustrating a multi-element fiber scanner with the multi-element motion actuation element illustrated in FIG. 9A, according to an embodiment of the present invention. [Figure 9D] FIG. 9D is a simplified perspective view of a piezoelectric motion actuator according to one embodiment of the present invention. [Figure 9E] FIG. 9E is a simplified end view illustrating a multi-element motion actuator, according to one embodiment of the present invention. [Figure 9F] FIG. 9F is a simplified side view illustrating a multi-segment motion actuation structure, according to one embodiment of the present invention. [Figure 10] FIG. 10 is a multi-element fiber scanner for scanning electromagnetic imaging radiation according to one embodiment of the present invention. [Figure 11] FIG. 11 is a simplified side view of a fiber optic cable and a laser ablation beam according to one embodiment of the present invention. [Figure 12] FIG. 12 is a simplified flowchart illustrating a method for fabricating a multi-element fiber scanner, according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Detailed Description of Specific Embodiments

[0001] Embodiments of the present invention relate to methods and systems related to fiber scanning projection display systems. More specifically, embodiments of the present invention provide methods and systems for a multi-element linkage that allows a scanning fiber to oscillate in a plane or along an arc. The present invention is applicable to a variety of applications in computer vision and image display systems.

[0018] FIG. 1 is a simplified perspective view illustrating a multi-element fiber scanner according to one embodiment of the present invention. The multi-element fiber scanner 100 can be used to scan electromagnetic imaging radiation, thereby forming an element of a display system. The multi-element fiber scanner includes a base 110, which may also be referred to as an actuator base. The base can be characterized by a longitudinal axis 112 disposed in a base plane and perpendicular to the base plane.

[0019] The multi-element fiber scanner also includes a retaining collar 130 positioned a predetermined distance D from the base 110 along the longitudinal axis 112. In some embodiments, the retaining collar 130 is parallel to the base and perpendicular to the longitudinal axis. The region between the base 110 and the retaining collar 130 may be referred to as a post segment.

[0020] The first fiber link 114, which may also be referred to as a waveguide, passes through the base in a direction parallel to the longitudinal axis. The first fiber link 114 is operably coupled to at least one electromagnetic radiation source (not shown) so that modulated light can be passed through the first fiber link while the distal end of the fiber tip is mechanically scanned to generate an image, which can then be coupled through a display system. The first fiber link can be fixed to the base where it passes through the base or can move freely in the plane of the base. The first fiber link passes through a retaining collar and can be fixed to the retaining collar where it passes through the collar or can move freely in the plane of the retaining collar and / or can move freely in a direction parallel to the longitudinal axis (i.e., axially). In some embodiments, the first fiber link passes through the retaining collar in a direction parallel to the longitudinal axis.

[0021] In alternative embodiments, the first fiber link can be replaced with another optical waveguide structure that can be fabricated using processes other than a fiber drawing process, for example, using microelectromechanical systems (MEMS) or micro-optical-electromechanical systems (MOEMS) microfabrication processes. Thus, molded components and optical waveguides fabricated using additive manufacturing are also included within the scope of the present invention (e.g., cantilevered structures, channel waveguides, etc.). These optical waveguide structures can be fabricated from a variety of materials, including silicon, silicon carbide, silicon oxide, silicon nitride, combinations thereof, etc.

[0022] In addition to the first fiber link, multiple additional links 116 extend from the base. These additional links can be fabricated from a glass material and are bonded to the base at one end and to the retaining collar at the other end. As a result, the retaining collar is mechanically bonded to the additional links. The plane in which the retaining collar is disposed can be considered one of a set of motion planes because the retaining collar will vibrate as it moves through this set of planes. In the embodiment illustrated in FIG. 1, the multiple additional links are arranged to surround the first fiber link, but this is not required by the present invention. In other embodiments, the number and location of each of the additional links can be modified as needed for a particular application. Furthermore, while the multiple additional links illustrated in FIG. 1 extend from the base in a direction parallel to the longitudinal axis, this is not required by the present invention, as will be explained more fully in connection with FIG. 3.

[0023] The additional links can provide solely mechanical functionality, or they can also provide optical functionality. By way of example, the additional links can be replaced with piezoelectric elements that can expand and contract to provide motion actuation. In these embodiments, one or more of the multiple additional links can be operably coupled to at least one electromagnetic or other source of electromagnetic radiation, passing through the base parallel to the longitudinal axis and through the retaining collar. In these embodiments, modulated light can be delivered through all of the fiber links that provide the optical functionality. It should be understood that the additional links can be fabricated in a variety of ways and using a variety of materials. While some embodiments are described in terms of glass links fabricated from optical fiber, the present invention is not limited to this material or manufacturing method, and other materials and manufacturing processes can also be used in connection with the additional links.

[0024] A multiple-core fiber scanner provides an array of sources associated with multiple pixels, which can be scanned to generate a displayed image with multiplicative resolution as a function of the number of sources. In some embodiments, one set of additional links is used for mechanical support, and another set is used as additional light sources, complementing the first fiber link. Accordingly, embodiments of the present invention include implementations with a single fiber core and mechanical support (e.g., multiple peripheral supports), multiple fiber cores and mechanical supports, and multiple fiber cores that provide both optical and mechanical functionality. The mechanical support can be made from glass, similar to the first fiber core, or other suitable materials with sufficient flexibility and rigidity, including piezoelectric materials, metals, ceramics, polymers, etc. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0025] In an alternative embodiment, multiple fiber cores terminating at different longitudinal positions can be implemented in conjunction with the fiber scanners described herein, in which the depth plane associated with each of the fiber cores can be varied to provide different signals at different depths.

[0026] Referring to FIG. 1 , the multi-element fiber scanner can also include a piezoelectric actuator 105 mechanically coupled to a base 110. The piezoelectric actuator is operable to translate the base within the base plane, for example, along a lateral direction 107 or in a transverse direction pointing into or out of the plane of the figure. By way of example, the piezoelectric actuator 105, which may also be referred to as a base, can include multiple piezoelectric elements that can contract and expand as needed to generate desired vibrations within the base. In embodiments in which the base is translated laterally, the first fiber link is scanned laterally in the plane of the figure, and the electromagnetic imaging radiation is scanned along an axis parallel to the base plane. Light rays 115 emitted from the first fiber link are illustrated as light exiting an optical fiber 114.

[0027] The additional links are mechanically coupled to each other in both the base plane and the plane of the retaining collar, so that movement of the base in the base plane, for example using piezoelectric actuator 105, will result in movement of the top of the additional link and the retaining collar in a set of planes parallel to the plane of the retaining collar.

[0028] FIG. 2 is a simplified diagram illustrating two scanning positions for a multi-element fiber scanner according to one embodiment of the present invention. As illustrated in FIG. 2, movement of the base 110 in the base plane will result in movement of the retaining collar 130 horizontally (and, in some implementations, vertically). Two positions of the retaining collar are shown to illustrate the ends of an exemplary range of motion. In the center position, with the retaining collar directly above the base, the retaining collar will be separated from the base by a vertical distance greater than the position shown. However, for small angles (e.g., angles less than a few degrees), variation in the distance between the base and the retaining collar is slight, resulting in movement of the retaining collar in a substantially single plane (which may be referred to as the plane of motion) parallel to the base plane. When the additional fiber link tilts and / or bends in response to base movement due to the mechanical coupling between the top of the additional link and the retaining collar, the retaining collar remains parallel to the base plane. The shear motion illustrated in FIG. 2 is desirable from an optical perspective. This is because the image field associated with the first fiber link can be substantially flat or curved in a predetermined manner, which is useful in various optical configurations. While additional fiber links are illustrated in FIG. 2, embodiments of the present invention may utilize other materials and structures for the additional links. By way of example, MEMS structures may be utilized to provide unique advantages in embodiments of the present invention. Accordingly, references to additional links, linkages, and the like should be understood to include, but are not limited to, MEMS structures, including silicon flexures.

[0029] FIG. 3 is a simplified diagram illustrating a multi-element fiber scanner with tilted links, according to one embodiment of the present invention. Referring to FIG. 3 , a base 110 is provided, to which fiber links 310 and 312 are mechanically attached. An electromagnetic radiation source 330 (e.g., a diode laser or a light-emitting diode) is optically coupled to the first fiber link 114. In the embodiment illustrated in FIG. 3 , fiber link 312 is optically coupled to electromagnetic radiation source 331. Thus, depending on the implementation, one or more of a plurality of additional links can pass through the base in a direction substantially parallel to the longitudinal axis and can be operatively coupled to one or more electromagnetic radiation sources. Fiber link 310 extends from the base at an angle θ, and fiber link 312 extends from the base at an opposing angle −θ, such that both fiber links are tilted toward the first fiber link 114. Fiber links 310 and 312 are mechanically coupled to a retaining collar 130. The first fiber link 114 can be fixed to the retaining collar or can have a slide fit within the retaining collar.

[0030] Due to the tilt present in fiber links 310 and 312, for small angles, e.g., angles less than about a few degrees, the movement of retaining collar 130 (and therefore fiber tip) will follow an arc 320 having a center coincident with intersection point R of the lines extending from the fiber links. In other words, the radius of curvature of arc 320 is equal to r. Thus, in this configuration, the retaining collar translates along a curved arc (which may also be referred to as a curved vibration section). As the retaining collar vibrates, light from first fiber link 114 is emitted toward intersection point R (which may be referred to as a focal point) at the center of the arc. Thus, compared to some systems in which the emitting fiber moves through a convex image field, embodiments of the present invention move the emitting fiber through a concave image field, such as arc 320. At larger angles, the fiber tip may deviate from arc 320, and such deviation can be compensated for by modifications to the optical design. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0031] In one embodiment, each of fiber links 310 and 312, in addition to first fiber link 114, carries an optical signal; in this example, each of the three fiber cores allows a beam to be emitted, all of which are directed toward a focal point. Fabrication of this structure can begin with a preform containing the structural precursor of the fiber link in the form of a pillar of a first material, embedded in a larger pillar of a second material that is more easily etched. To fabricate this structure, a two-step process can be used: a first thermal drawing process can be used to draw the preform in a tapered fashion so that the outer or peripheral fiber cores are angled toward the central fiber core. A subsequent laser ablation / selective etching process can then be used to remove the second material from the pillar regions. Alternatively, the embodiment shown in FIG. 3 can be assembled from separate components.

[0032] The fiber links 114, 310, and 312 can include optical fibers. They can be fabricated using methods known to those skilled in the art, such as hot drawing. In some embodiments, the collar 130 and / or base 110 include silicon, silica, or metal disks with through-holes for the fiber links. The fiber links can be bonded to the collar or base using adhesive, water glass, frit glass, or metal bonding. Frit glass can be applied to the splice as a preform (e.g., toroidal and surrounding the surrounding fiber) to facilitate consistent fabrication. Metals such as gold can be deposited on the fiber, collar, and / or base using, for example, an evaporation process. A deformable microbump structure can be applied to one of the surfaces to facilitate metal-to-metal bonding under mechanical pressure. Alternatively, metal-to-metal bonds can be formed using heat. In some embodiments, the fiber is inserted through the collar, bonded to it, and then ground and polished as a unit to ensure a flush termination of the optical waveguide.

[0033] From an optical perspective, the embodiment illustrated in FIG. 3 offers advantages not available using conventional techniques. FIG. 4 is a simplified diagram illustrating elements of a fiber scanning system according to one embodiment of the present invention. As illustrated in FIG. 4, the projection system includes an electromagnetic radiation source 421 (e.g., a diode laser) optically coupled to a first fiber link 415 and a ball lens 410 toward which light from the first fiber link is directed. The ball lens 410 can be positioned approximately at the intersection or focal point R illustrated in FIG. 3 to cover a large field of view while using a compact optical system. The ball lens can image the light from the fiber into the eyepiece of the display system. In addition to the ball lens, other entrance pupils of the optical system can also be utilized as focal points. As the first fiber link and retaining collar sweep through arc 405, light emitted by the first fiber link is directed toward the ball lens or entrance pupil from all oscillation positions 420, 422, and 424. The tilt of the fiber tip toward ball lens 410 allows for the use of less costly optical elements than would otherwise be required if the fiber tip were tilted away from the center as it was moved toward the end of its range of motion.

[0034] The construction of multi-element fiber scanners is suitable for use with laser ablation and laser engraving techniques described in U.S. Provisional Patent Application No. 62 / 438,408, entitled "Methods and Systems for Fabrication of Shaped Fiber Elements Using Laser Ablation," filed December 22, 2016, the disclosure of which is incorporated herein by reference. By way of example, starting with a multi-core fiber preform, the preform can be drawn to form the fiber, and laser ablation and etching can be used to remove material from the post sections, leaving the desired fiber links. The base and / or retaining plate can be formed from glass from the original drawn fiber.

[0035] 11 is a simplified side view of a fiber optic cable and a laser ablation beam, according to an embodiment of the present invention. A laser beam is provided and propagates toward a lens 1110, which focuses the laser beam to a focal spot 1120 inside the cladding 1115 of an optical fiber 1125. Focusing the laser beam to the focal spot results in the creation of a damage site at the focal spot. By rotating the fiber along its longitudinal axis, which is aligned with the fiber core, a series of damage sites can be created at a given radial distance.

[0036] The movement of the laser beam and associated optical elements is illustrated in Figure 11, where a second focal spot 1130 is formed at a greater distance from the surface of the fiber as the laser beam is moved longitudinally to a second location. In response to rotation of the fiber about its longitudinal axis, a series of damage sites are created at a smaller radial distance from the fiber core than the series of damage sites associated with focal spot 1120. A third longitudinal position is also illustrated in Figure 11, forming a third focal spot 1140. Using this process, a substantially continuous series of damage sites 1150, illustrated in this embodiment by a tapered dashed profile, is created.

[0037] In some embodiments, the lens is moved to adjust the position of the focused spot, while in other embodiments, the focal power of the lens can be adjusted so that the lens remains in substantially the same position while the focused spot moves. The use of the term "substantially" is used because focal power changes often result from moving elements inside the lens (e.g., a camera zoom lens).

[0038] As described below, an etching process can be used to preferentially etch along the series of damage sites, forming a tapered fiber profile in the embodiment illustrated in FIG. 11, and separating portions of the fiber cladding at radial distances greater than the series of damage sites.

[0039] In some embodiments, as light propagates into the fiber toward the fiber core, the fiber acts as a cylindrical lens in the direction extending into the figure. In the plane of the figure, the fiber does not introduce any focusing effect. The cylindrical lens effect introduced by the fiber can adversely affect the size of the focal spot where the series of damage sites 1150 are created. Therefore, an astigmatic lens can be incorporated into the optical path along which the laser beam propagates. By way of example, a cylindrical lens can be used as an astigmatic lens to introduce correction in the plane extending into the figure and compensate for focusing by the fiber. In some implementations, the astigmatic lens and / or lens 1110 have variable optical parameters so that the amount of astigmatism introduced and / or focal length can be adjusted during operation of the system.

[0040] In some embodiments, the separate lenses can be combined into a single lens, which can be a multi-element compound lens that both focuses the laser light into the fiber and provides astigmatism pre-correction to compensate for cylindrical focusing that occurs within the fiber.

[0041]

[0013] Figure 12 is a simplified flowchart illustrating a method of fabricating a multi-element fiber scanner according to an embodiment of the present invention. The method described in connection with Figure 12 is applicable to fabricating various structures described herein, including a multi-element fiber scanner having a base, a retaining collar, a first fiber link including a fiber core and fiber cladding, and a plurality of additional links connecting the base to the retaining collar. Method 1200 includes providing a fiber optic cable (1210), focusing a laser beam at a predetermined location inside the fiber optic cable (1212), and creating a lesion at the predetermined location (1214).

[0042] The method includes focusing 1216 the laser beam at a series of additional predetermined locations inside the fiber optic cable and creating 1218 a plurality of additional damage sites at the additional predetermined locations. In another embodiment, the damage site and the additional damage sites define a multi-element structure including a waveguide element and a mechanical support element, as illustrated in FIGS. 1, 3, 8A, and 10. The mechanical support element can include a base, a retaining collar, and a mechanical support coupled between the base and the retaining collar. In an embodiment, the damage site and the additional damage sites define a tapered profile having a decreasing diameter toward the fiber emitting tip as a function of longitudinal distance, thereby producing a tapered fiber.

[0043] The method further includes exposing the fiber optic cable to an etching solution 1220, preferentially etching the damaged site and a plurality of additional damaged sites 1222, and separating a portion of the fiber optic cable and releasing elements of the multi-element fiber scanner 1224. After the preferential etching process, the portion of the structure can include a waveguide element, such as one or more fiber elements having a fiber core and fiber cladding, and a mechanical structure.

[0044] According to certain embodiments of the present invention, focusing of light by the fiber as the laser beam propagates to the focal point / damage site and multiple additional damage sites is compensated for by using an astigmatic lens that introduces an amount of focusing equal and opposite to the focusing that occurs as the laser beam propagates through the fiber. Because the damage sites will be located at varying depths within the fiber cladding, i.e., varying distances from the core of the fiber, the corrective lens, in some implementations, can be adjusted as the laser traverses through different radial distances within the fiber cladding.

[0045] In some embodiments, creating multiple additional damage sites at additional predetermined locations can include forming latticework damage sites in the cladding of the fiber optic cable. For example, in some embodiments, multiple radial vias can pass through the cladding region toward the fiber core. The focus of the laser beam can be controlled so that a first portion of the multiple additional damage sites is first created adjacent to the fiber core (i.e., at a short radial distance from the fiber core), followed by a second portion of the multiple additional damage sites at a greater distance from the fiber core (i.e., a longer radial distance to the diameter of the cladding region). This technique provides a damage-free material through which the laser beam propagates, reducing or preventing degradation in beam quality.

[0046] The fiber core is characterized by a longitudinal axis, and the method can include creating multiple additional damage sites at additional predetermined locations while rotating the fiber about the longitudinal axis. While Figure 11 illustrates the fiber optic cable as being made of a substantially homogenous material, the fiber optic cable can include a cladding region and multiple sacrificial regions disposed within the cladding region. The multiple sacrificial regions can include a material having a higher etch rate than the cladding region, or can be air cavities through which an etchant can flow.

[0047] It should be understood that the specific steps illustrated in FIG. 12 provide a particular method of fabricating a multi-element fiber scanner in accordance with certain embodiments of the present invention. Other sequences of steps may be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Furthermore, individual steps illustrated in FIG. 12 may include multiple sub-steps that may be performed in various sequences depending on the needs of the individual step. Furthermore, additional steps may be added or removed depending on the particular application. Those skilled in the art will recognize many variations, modifications, and alternatives.

[0048] FIG. 5 is a simplified flowchart illustrating a method of fabricating a multi-element fiber scanner according to one embodiment of the present invention. The method 500 of fabricating a multi-element fiber scanner includes providing a fiber optic cable having a cladding region and a fiber core (510), focusing a laser beam at a series of predetermined locations inside the cladding region of the fiber optic cable (512), and creating a plurality of damage sites at the predetermined locations (514). Creating the plurality of damage sites at the predetermined locations may include forming latticework damage sites, a plurality of radial vias passing through the cladding region toward the fiber core, or the like. In one implementation, the process of creating the plurality of damage sites at the predetermined locations may be performed by first creating a first portion of the plurality of damage sites adjacent to the fiber core, followed by creating a second portion of the plurality of damage sites adjacent to the periphery of the cladding region.

[0049] The method also includes exposing (516) the optical fiber cable to an etching solution and preferentially etching (518) the plurality of damaged areas to form a base having a base plane and a longitudinal axis perpendicular to the base plane, a retaining collar positioned a predetermined distance from the base along the longitudinal axis, a first fiber link including a fiber core passing through the base plane and bonded to the retaining collar, and a plurality of additional fiber links bonded to the base, extending from the base to the retaining collar, and bonded to the retaining collar.

[0050] According to certain embodiments of the present invention, the method can also include rotating the fiber optic cable about a longitudinal axis during the process of creating the multiple damage sites at the predetermined locations. In some implementations, the fiber optic cable can be fabricated to include multiple sacrificial regions located within the cladding region that are made using a material having a higher etch rate than the cladding region, allowing the sacrificial material to be preferentially removed. The sacrificial regions can alternatively include air cavities or a combination of sacrificial material and air cavities.

[0051] 6 is a simplified flowchart illustrating a method 600 of fabricating a multi-element fiber scanner according to another embodiment of the present invention. The method 600 of fabricating a multi-element fiber scanner includes fabricating 610 a preform including at least one fiber waveguide, a fiber support, and a sacrificial material, and drawing 612 the preform to form a fiber structure.

[0052] In the fiber drawing process, the fiber preform can include a sacrificial region, which can include a material with a lower etch resistance than the material utilized to define the first fiber link and the multiple additional links or other mechanical support. By way of example, the first fiber link and the multiple additional links can be resistant to etching, e.g., by sulfuric acid or other suitable etchants, while the sacrificial region, which can be doped or otherwise provided to reduce their etch resistance (with an etch rate that depends on the dopant and the concentration and type of etchant), can be etched by sulfuric acid. In various embodiments, the dopant can include one or more of fluorine, fluoride, germanium, boron, phosphorus, gallium, indium, arsenic, and antimony. In some embodiments, the etch rate of the fiber link and / or the multiple additional links can depend on the purity of the glass (e.g., sodium / boron / phosphorus content) and whether the glass is annealed.

[0053] The method includes exposing the fiber structure to an etching solution (614) and preferentially etching (616) the sacrificial material to form a base having a base plane and a longitudinal axis perpendicular to the base plane, a retaining collar positioned a predetermined distance from the base along the longitudinal axis, a first fiber link including at least one fiber waveguide passing through the base plane and bonded to the retaining collar, and a plurality of fiber supports bonded to the base, extending from the base to the retaining collar, and bonded to the retaining collar.

[0054] The base and retaining collar can be masked to protect them during the etching process during the preferential sacrificial etching process. Materials can be selected for their mechanical properties in addition to their optical properties. Thus, in some embodiments, the base and retaining collar can be excluded from the laser damage treatment to reduce their susceptibility to etching.

[0055] FIG. 7 is a simplified flowchart illustrating a method of operating a multi-element fiber scanner according to an embodiment of the present invention. As described below, when the actuator base is translated laterally in a base plane, the retaining collar translates laterally in a set of planes as it oscillates. For small angles, the fiber tip oscillates in a substantially single plane, which provides a flat image field. In some embodiments, the fiber tip maintains a vertical orientation while oscillating in a set of planes. A method 700 of operating a multi-element fiber scanner includes providing an electromagnetic radiation source (710) and passing electromagnetic radiation from the source through a first fiber link (712). The first fiber link passes through a base having a base plane and a longitudinal axis perpendicular to the base plane.

[0056] The method also includes supporting a retaining collar (714) positioned a predetermined distance from the base along the longitudinal axis. A plurality of additional links, in some embodiments, join the base and the retaining collar. One or more of the plurality of additional links can pass through the base. In this case, the method can include passing electromagnetic radiation from the source (or another source) through one or more of the plurality of additional links. The electromagnetic radiation can be intensity modulated to present an image.

[0057] The method further includes translating the base in the base plane (716), translating the collar in a set of planes parallel to the base plane (718), and scanning the electromagnetic radiation in one or more axes (720). Considering the movement of the collar, the present invention includes substantially in-plane movement of the collar over a small angle. Thus, for these examples, when the collar oscillates laterally, it may move vertically out of its original plane by a small amount at the end of its range of motion. By way of example, the collar's vertical deviation from its original position may be in the micron-millimeter range, e.g., 500 μm or greater, in some embodiments. As the angle of oscillation and range of motion increase, the collar moves both laterally and vertically, so that its motion is defined by a set of planes parallel to the base plane and includes vertical variation. As described herein, because the collar moves in a plane parallel to the base plane, the fiber tip is directed vertically during movement, providing related advantages in optical imaging system design.

[0058] In some embodiments, translating the base in the base plane is accomplished by actuating the base in a first direction and actuating the base in a second direction orthogonal to the first direction to provide two-dimensional motion. Translating the retaining collar in a set of planes parallel to the base plane can include tilting a plurality of additional links.

[0059] 8A is a simplified perspective view illustrating a multi-axis fiber scanner according to one embodiment of the present invention. The multi-element fiber scanner can be used to scan electromagnetic imaging radiation. The multi-element fiber scanner 800 includes a base 110 having a base plane and a longitudinal axis orthogonal to the base plane. The multi-element fiber scanner also includes a first fiber link 114 passing through the base in a direction parallel to the longitudinal axis. The first fiber link is operably coupled to at least one electromagnetic radiation source (not shown) at a location below the base 110.

[0060] Additionally, the multi-element fiber scanner includes multiple actuating elements 810 joined to the base 110 and extending from the base along, e.g., parallel to, a longitudinal axis. The multiple actuating elements can independently expand 812 and contract 814. The use of opposing actuating elements 810 as illustrated in FIG. 8A enables independent scanning of a first fiber link in two directions (e.g., along the x-axis and y-axis, both orthogonal to the longitudinal axis) such that light from the first fiber link can be directed to pixels defining an array parallel to the x-axis and y-axis and perpendicular to the longitudinal axis (i.e., the z-axis).

[0061] The multiple actuating elements can be fabricated using multiple piezoelectric tube stacks and can be arranged to surround the first fiber link. Additional description related to the piezoelectric tube stacks is provided in connection with Figures 9A-9F. In addition to mechanically constraining the base to the retaining collar, the actuating element 810 can be used to control the distance between the base and the retaining collar 130, which is positioned a predetermined distance from the base along the longitudinal axis. The first fiber link and the multiple actuating elements are bonded to the retaining collar. The first fiber link passes through the retaining collar in a direction parallel to the longitudinal axis.

[0062] Referring to FIG. 8A, the actuation element can include a first piezoelectric element positioned on a first side of the first fiber link and operable to contract / expand, and a second piezoelectric element positioned on a second side of the first fiber link opposite the first side and operable to expand / contract in a manner opposite to the first piezoelectric element. These movements will result in tilting of the retaining collar about a first axis perpendicular to a line connecting the first and second piezoelectric elements. Additionally, a third piezoelectric element can be positioned on a third side of the first fiber link and operable to contract / expand. This third piezoelectric element is paired with a fourth piezoelectric element positioned on a fourth side of the first fiber link opposite the third side and operable to expand / contract in a manner opposite to the third piezoelectric element. Movement of the third and fourth piezoelectric elements will result in tilting of the retaining collar about a second axis perpendicular to a line connecting the third and fourth piezoelectric elements.

[0063] When the multi-element fiber scanner is operated using the actuation elements described above, the first fiber link can be scanned to move the electromagnetic radiation point along an axis parallel to the base plane. In this embodiment, the scanning functionality is built into the mechanical support, for example, with a piezoelectric actuator acting as a servo element (e.g., a piston).

[0064] 8A, this particular shape is not required by the present invention, and other cross-sections are within the scope of the present invention, including rectangular, square, hexagonal, etc. The cross-section of the actuating element may be uniform or non-uniform along the length of the actuating element.

[0065] FIG. 8B is a simplified flowchart illustrating a method of operating a multi-axis fiber scanner according to an embodiment of the present invention. A method 850 of operating a multi-element fiber scanner includes providing an electromagnetic radiation source (860) and passing electromagnetic radiation from the source through a first fiber link (862). The first fiber link passes through a base having a base plane along a longitudinal axis perpendicular to the base plane. The method also includes supporting a retaining collar (864) positioned a predetermined distance from the base along the longitudinal axis. A plurality of piezoelectric actuators connect the base and the retaining collar. As illustrated in FIG. 8A, a first piezoelectric actuator of the plurality of piezoelectric actuators connects one side of the base to one side of the retaining collar, and a second piezoelectric actuator of the plurality of piezoelectric actuators connects the opposite side of the base to the opposite side of the retaining collar. The first piezoelectric actuator and the second piezoelectric actuator are in the scanning plane. In some embodiments, the scan plane may include the central waveguide / fiber, but with two other actuators, the tip of the fiber may not be limited to the plane containing the two opposing piezoelectric actuators and the rest of the central waveguide / fiber. Thus, one mode of operation is to drive a first pair of opposing actuators at the resonant frequency of the fiber and drive the remaining (e.g., two) opposing actuators at a lower frequency that may be related to the vertical scan frequency. In yet another mode of operation, a spiral scan pattern is utilized.

[0066] The method further includes actuating a first piezoelectric actuator of the plurality of piezoelectric actuators to decrease a distance from one side of the base to one side of the retaining collar (866) and actuating a second piezoelectric actuator of the plurality of piezoelectric actuators to increase a distance from an opposite side of the base to an opposite side of the retaining collar (868). In response to these actuations, the method enables the first fiber link to be scanned in the scan plane (870).

[0067] FIG. 9A is a simplified side view illustrating a multi-segment motion actuation element, according to an embodiment of the present invention. As illustrated in FIG. 9A, multi-segment element 905 includes a first piezoelectric element 910 coupled to a second piezoelectric element 912. Multi-segment element 905 may be referred to as a piezoelectric tube stack because several piezoelectric elements are stacked to form the element. In some embodiments, first piezoelectric element 910 is proximal to the base, and second piezoelectric element 912 is positioned at a location distal to the base. Each of the piezoelectric elements is contractible or expandable, and as illustrated in FIG. 9A, the piezoelectric elements can be operated such that the lower section contracts / expands while the upper section expands / contracts. In some embodiments, each piezoelectric element includes multiple sectors (e.g., four sectors) such that one side of each tube can be contracted while the other side expands. This mode of operation will generate vibratory motion, as illustrated in FIG. 9B.

[0068] Figure 9B is a simplified side view illustrating the oscillatory motion of the multi-segment motion actuation element shown in Figure 9A, according to one embodiment of the invention. When the first piezoelectric element 910 contracts (920), the second piezoelectric element 912 expands (922), causing the multi-segment motion actuation element to assume a sigmoid shape. In the next stage of vibration, when the first piezoelectric element 910 expands (924), the second piezoelectric element 912 contracts (926), causing the multi-segment motion actuation element to assume a second sigmoid shape that mirrors the first sigmoid shape. By alternately expanding and contracting the piezoelectric elements that make up the segments, the multi-segment element vibrates as illustrated by Figure 9B, forming the illustrated shape and its horizontal mirror image in an alternating manner.

[0069] FIG. 9C is a simplified side view illustrating a multi-element fiber scanner with the multi-element motion actuation element illustrated in FIG. 9A , according to an embodiment of the present invention. As illustrated in FIG. 9C , the use of a multi-segment motion element 905 coupling the base 110 to the retaining collar 130 reduces the amount of bending where the bottom and top of the actuation element join the base and retaining collar, respectively. With reduced bending at these points, stresses are reduced, and life and reliability can be improved. As illustrated in FIG. 9C , the vertical distance (measured along the vertical direction) between the retaining collar 130 and the base 110 decreases as the retaining collar moves horizontally laterally from a center position. For small vibrations of the retaining collar 130, the motion of the retaining collar will be substantially planar. As the retaining collar moves laterally away from the center, the vertical height may decrease, but the motion is in a plane parallel to the base plane, and the orientation of the retaining collar remains substantially parallel to the base. Because the retaining collar remains parallel to the base plane as it moves, the tip of fiber 940 remains oriented along the vertical direction. The field curvature associated with the lateral (and vertical) movement of the retaining collar can be considered in designing the optical system to generate an image of the fiber as it is being scanned. A fiber scanner in which the fiber tip tilts away from the center as it moves laterally toward the end of its range of motion necessitates a larger numerical aperture optical system to efficiently collect image light from the fiber. A larger numerical aperture requirement generally leads to a larger, more complex, and more costly optical system. The size of the optical system is an important consideration for optical systems to be integrated into augmented reality glasses. In contrast, embodiments of the present invention maintain the fiber tip in a vertical orientation because the retaining collar remains parallel to the base plane throughout the entire range of motion. As the tip tilts at the end of its range of motion, light may be emitted at a steeper angle, which can result in a more complex and expensive lens design due to the high level of field curvature and the need to correct for the steep angle. Using embodiments of the present invention maintains the fiber tip orientation as the scanning fiber greatly simplifies the complexity and cost of lenses.One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0070] FIG. 9D is a simplified perspective view of a piezoelectric motion actuator, according to one embodiment of the present invention. The piezoelectric motion actuator 955 illustrated in FIG. 9D includes four actuation inputs (+X, −X, +Y, and −Y) disposed within a cylindrical casing. A fiber optic cable passes through an orifice 957, and actuation of the four actuation inputs allows the fiber optic cable to be scanned in two dimensions. In FIG. 9D, contraction of the +X actuation input and expansion of the −X actuation input tilts the piezoelectric motion actuator toward the +X axis. While the motion illustrated in FIG. 9D is two-dimensional (i.e., along a plane defined by the x- and y-axes), embodiments can also expand or contract all four actuation inputs together to contract / expand along the z-axis. Thus, embodiments of the present invention provide for the use of a cylindrical actuator that not only provides motion in both the x- and y-directions, but also compresses / expands in the z-direction.

[0071] In addition to the cylindrical motion actuator illustrated in FIG. 9D , the scope of the present invention includes implementations in which other geometric shapes are utilized for the motion actuator. By way of example, in one embodiment, the motion actuator includes multiple opposing motion actuation elements (e.g., piezoelectric elements) that cooperate with one another as a multi-element motion actuator. FIG. 9E is a simplified end view illustrating a multi-element motion actuator, according to one embodiment of the present invention. The view illustrated in FIG. 9E is aligned with the vertical axis. As illustrated in FIG. 9E , a first motion actuation element 962 positioned on one side of a fiber optic cable 960 and a second motion actuation element 964 positioned on the opposite side of the fiber optic cable can contract / expand in conjunction to move the fiber optic cable in a horizontal plane. A third motion actuation element 966 positioned on a third side of the fiber optic cable 960 and a fourth motion actuation element 968 positioned on the opposite side of the fiber optic cable can contract / expand in conjunction to move the fiber optic cable in a vertical plane. By actuating all four motion actuation elements, the fiber can be scanned in two dimensions as needed for use in a projection display. The embodiment illustrated in Figure 9E can provide a lighter weight system by reducing the piezoelectric mass. In addition to the rectangular geometry illustrated in Figure 9E, other geometries, including hexagons, triangles, etc., are within the scope of the invention.

[0072] Typically, the actuation inputs are driven with a predetermined phase relationship between the inputs, e.g., 90° out of phase, 180° out of phase, etc. By way of example, to achieve the motion illustrated in FIG. 9D , a contraction of the +X actuation input and an expansion of the −X actuation input can be accomplished by driving these actuation inputs with signals that are 180° out of phase with respect to each other. Referring to FIGS. 9A and 9C , a first piezoelectric element 910 can be driven as illustrated in FIG. 9D to bend the first element toward the +X direction. In parallel, a second piezoelectric element 912 can be driven in an opposite manner, i.e., an expansion of the +X actuation input and a contraction of the −X actuation input, to bend the second element toward the −X direction. As a result, the motion illustrated in FIG. 9B can be achieved by the coordinated actuation of these piezoelectric elements. Thus, the phase relationship between the actuation inputs of each element and the phase relationships between the various elements can be controlled to achieve the desired motion.

[0073] FIG. 9F is a simplified side view illustrating a multi-segment motion actuation structure according to one embodiment of the present invention. As illustrated in FIG. 9F, a piezoelectric structure 979 includes two piezoelectric elements similar to the multi-segment element illustrated in FIG. 9A. The piezoelectric structure 979 may be referred to as a piezoelectric tube stack because, in this embodiment, two piezoelectric elements (also referred to as piezoelectric motion actuators) are stacked to form the structure. The lower portion of the piezoelectric structure 979 is attached to a fixed base, allowing the upper portion of the structure to move in response to an electrode driving voltage. Comparing FIGS. 9A, 9D, and 9F, the single piezoelectric element illustrated in FIG. 9D would be stacked with a second piezoelectric element to form the tube stack illustrated in FIGS. 9A and 9F. For purposes of clarity, the actuation inputs on the outer surfaces of the piezoelectric elements (see FIG. 9D) are omitted, and the electrodes connected to the actuation inputs are illustrated. The interior of the piezoelectric elements is metallized and connected to ground. As described herein, four phases are applied to the actuation inputs arranged at 90° angles relative to each other around the outer surface of the piezoelectric element.

[0074] Although tube stacks are discussed in connection with FIG. 9F, embodiments of the present invention are not limited to multi-piezoelectric element implementations. In some embodiments, monolithic multi-section piezoelectric elements having lower and upper sections can be utilized as fabricated from monolithic piezoelectric tubes. According to alternative embodiments, optical fibers with modulated light can be passed through the piezoelectric structures 979. Thus, these piezoelectric structures are useful not only for mechanical functionality but also for light delivery as well.

[0075] Signal generator 970 is connected to electrodes 973 and 975, which in turn provide outputs that are connected to corresponding actuation inputs (e.g., +Y and −Y in FIG. 9D ). Signal generator 970 is connected to first 90° phase adjuster 971 and second 90° phase adjuster 972, which are connected to electrodes 974 and 976, which in turn are connected to corresponding actuation inputs (e.g., +X and −X in FIG. 9D ). Thus, the signal generator, in conjunction with the phase adjusters, provides four phases that are 90° out of phase with each other.

[0076] At intersection 980 of the first and second piezoelectric elements, the electrodes form a spiral configuration that shifts the electrode positions by 180°. This spiral configuration allows for a 180° alternation of the piezoelectric drive electrodes at intersection 980, which corresponds to an inflection point in the S-curve. Thus, for example, electrode 974 contacting the actuation input in region 977 (i.e., the left side of the first piezoelectric element) shifts to contact the actuation input in region 978 (i.e., the right side of the second piezoelectric element). A similar 180° shift in electrode position also occurs for other electrodes, resulting in an electrode contacting the right / left or front / back side of the first piezoelectric element contacting the left / right or back / front side of the second piezoelectric element. As an example, the phase shift between the electrodes for the first piezoelectric element can be defined as 0° for electrode 973 (i.e., front actuation input), 90° for electrode 974 (left actuation input), 180° for electrode 975 (i.e., back actuation input), and 270° for electrode 976 (i.e., right actuation input).

[0077] In operation, an electric field is applied radially from the actuation inputs on the outer surfaces of the piezoelectric elements to a common ground electrode on the inner surfaces of the piezoelectric elements. Because the left / right and front / back actuation inputs are driven by electrodes 180° out of phase, the left / front side of the piezoelectric element contracts and the right / back side of the piezoelectric element expands. In the embodiment illustrated in FIG. 9F, the presence of a spiral structure at intersection 980 results in opposing actuation inputs on the two piezoelectric elements responding in the same manner. For example, because the +X actuation input on the first piezoelectric element and the -X actuation input on the second piezoelectric element are connected to the same electrode (e.g., electrode 974), they will both contract and expand in unison. Thus, as illustrated in FIG. 9B, an S-curve behavior results from the electrode drive configuration illustrated in FIG. 9F when region 977 contracts and region 978 contracts in response to a voltage present on electrode 974. Since the electrodes on opposite sides of the piezoelectric element are 180° out of phase, the expansion of the opposing regions 977 and 978 will contribute to the S-curve behavior.

[0078] As the voltage applied to each of the four actuation inputs is varied as a function of time, the free end 981 of the second piezoelectric element can sweep a circle in a plane perpendicular to the longitudinal direction (i.e., the z-direction).

[0079] 8A and 9A-9F, in some embodiments, one or more of the fiber links may be replaced with motion-actuated links, for example, incorporating the multi-segment motion-actuated element illustrated in FIG. 9A. Thus, embodiments of the present invention provide a multi-element fiber scanner for scanning electromagnetic imaging radiation. The multi-element fiber scanner includes a base having a base plane and a longitudinal axis orthogonal to the base plane, and a first fiber link passing through the base in a direction parallel to the longitudinal axis. The first fiber link is operably coupled to at least one electromagnetic radiation source.

[0080] The multi-element fiber scanner also includes a plurality of motion actuation links joined to and extending from the base. Each of the plurality of motion actuation links includes a first piezoelectric element proximate the base and a second piezoelectric element coupled to the first piezoelectric element at a location distal to the base. The multi-element fiber scanner further includes a retaining collar positioned a predetermined distance from the base along the longitudinal axis. The first fiber link and the second piezoelectric element of each of the plurality of motion actuation links are joined to the retaining collar.

[0081] 10 illustrates a multi-element fiber scanner for scanning electromagnetic imaging radiation, according to one embodiment of the present invention. The multi-element fiber scanner 1000 can be used in a display for scanning electromagnetic imaging radiation and includes a base 1005 having a support surface 1011 (a lower surface of the base 1005) defining a base plane, a mounting surface 1007 opposite the support surface 1011, and a longitudinal axis perpendicular to the base plane. The multi-element fiber scanner also includes a plurality of motion actuators 1009 coupled to the support surface 1011 of the base 1005.

[0082] A multi-link fiber structure is coupled to the mounting surface 1007. The multi-link fiber structure includes a fiber base 1010, which may be similar to base 110, and fiber links 1014 passing through the fiber base 1010 in a direction parallel to the longitudinal axis. The fiber links 1014 are operatively coupled from at least one electromagnetic radiation source (not shown) to a distal (top, in the perspective of FIG. 10 ) end of the fiber links 1014.

[0083] The multi-link fiber structure also includes a plurality of motion actuating elements 1040 (e.g., piezoelectric actuating elements) joined to the fiber base 1010 and extending from the fiber base 1010 along a longitudinal axis, and a retaining collar 1030 positioned a predetermined distance from the fiber base along the longitudinal axis. The fiber links 1014 and the plurality of motion actuating elements 1040 are joined to the retaining collar 1030.

[0084] In some embodiments, one or more of the plurality of motion actuation elements 1040 are replaced with additional links coupled to an electromagnetic radiation source. Additionally, any number of additional links coupled to the same or different electromagnetic radiation sources can be utilized to simultaneously output multiple pixels for a multi-pixel display.

[0085] Actuation of the base 1005 using multiple motion actuators 1009 acts as a piston to cause tilting of the base about an axis of the base 1005. Tilting can occur about a single axis or about multiple axes. In some embodiments, actuation of the motion actuation elements to tilt the base and tilt the retaining collar provides control of the movement, e.g., vibration, of the fiber link to direct light emitted from the fiber link toward a display screen.

[0086] In some configurations, translation and / or tilting of the holding collar can provide scanning of the fiber link in a first direction, and tilting of the base can provide scanning of the fiber link in a second direction that can be orthogonal to the first direction. In certain embodiments, the first direction is a fast direction (similar to the horizontal scan of a raster scan display) and the second direction is a slow direction (similar to the vertical scan rate of a raster scan display). By way of example, the holding collar can be vibrated laterally and the base can be tilted laterally. In addition to tilting the base, the base can be translated vertically in unison with the expansion / contraction of all of the motion actuators.

[0087] It is also to be understood that the examples and embodiments described herein are for illustrative purposes only, and in light thereof, various modifications or changes will be suggested to those skilled in the art and are to be included within the spirit and scope of the present application and the appended claims.

Claims

1. 1. A method of operating a multi-axis fiber scanner having a base including a base plane, the method comprising: providing a source of electromagnetic radiation; passing electromagnetic radiation through a fiber link, the fiber link passing through the base plane of the base along a longitudinal axis perpendicular to the base plane; supporting a retaining collar including a retaining collar plane positioned at a distance from said base plane, said base plane and said retaining collar plane facing each other at said distance; decreasing a first distance between a first side of the base and the collar by actuating a first piezoelectric actuator of a plurality of piezoelectric actuators; increasing a second distance between a second side of the base and the collar by actuating a second piezoelectric actuator of the plurality of piezoelectric actuators; scanning the fiber link in a scan plane, the scan plane being defined as a plane passing through longitudinal axes of the first piezoelectric actuator and the second piezoelectric actuator; A method comprising: the first side and the second side of the base are disposed on the base plane; the fiber link and each of the plurality of piezoelectric actuators are spatially separated by an air gap; method.

2. The method of claim 1 , wherein the distance is a distance along the longitudinal axis.

3. The method of claim 1 , wherein the plurality of piezoelectric actuators interface the base plane of the base and the collar plane of the collar.

4. the first piezoelectric actuator of the plurality of piezoelectric actuators joins the first side of the base to a first side of the collar, and the second piezoelectric actuator of the plurality of piezoelectric actuators joins the second side of the base to a second side of the collar; The method of claim 1 , wherein the first side and the second side of the retaining collar are disposed on the retaining collar plane.

5. The method of claim 4 , wherein the first side of the base and the second side of the base are on opposite sides of the base plane.

6. The method of claim 4 , wherein the first side of the collar and the second side of the collar are opposite sides on the collar plane.

7. 5. The method of claim 4, further comprising: initiating movement of the fiber link in a lateral direction perpendicular to the longitudinal axis by actuating the first piezoelectric actuator and the second piezoelectric actuator in parallel.

8. the plurality of piezoelectric actuators further include a third piezoelectric actuator and a fourth piezoelectric actuator, the third piezoelectric actuator joining a third side of the base to a third side of the collar, and the fourth piezoelectric actuator joining a fourth side of the base to a fourth side of the collar; the third side of the base and the fourth side of the base are disposed on the base plane; The method of claim 4 , wherein the third side of the collar and the fourth side of the collar are disposed on the collar plane.

9. 9. The method of claim 8, wherein the third side of the base and the fourth side of the base are on opposite sides of the base plane, and the third side of the retaining collar and the fourth side of the retaining collar are on opposite sides of the retaining collar plane.

10. operating the first piezoelectric actuator and the second piezoelectric actuator at a horizontal scanning frequency; operating the third piezoelectric actuator and the fourth piezoelectric actuator at a vertical scan frequency; The method of claim 8 further comprising:

11. initiating movement of the fiber link in a lateral direction perpendicular to the longitudinal axis by actuating the first piezoelectric actuator and the second piezoelectric actuator in parallel; actuating the third piezoelectric actuator and the fourth piezoelectric actuator in parallel to initiate movement of the fiber link in a transverse direction perpendicular to the lateral direction; The method of claim 8 further comprising:

12. The method of claim 1 , wherein the fiber link, the first piezoelectric actuator, and the second piezoelectric actuator are in the scan plane.

13. The method of claim 1 , wherein the plurality of piezoelectric actuators comprises a plurality of piezoelectric tube stacks.

14. The method of claim 1 , further comprising translating the retaining collar in a set of planes parallel to the base plane.

15. The method of claim 1 , wherein the retaining collar is operable to translate along a curved arc.

16. The method of claim 1 , wherein the plurality of piezoelectric actuators are arranged to surround the fiber link.

17. The method of claim 1 , wherein scanning the fiber link comprises scanning the fiber link in a spiral scan pattern.

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