Abstract:
An actuator for tilting a moveable object such as a mirror includes a base and a coil-object assembly that includes first and second pairs of coils each of which is attached to the object, the first pair of coils being arranged along a longitudinal axis, and the second pair of coils being arranged along a transverse axis substantially orthogonal to the longitudinal axis. A gimbal has an attachment section attached to the object, and mounting sections connected via a plurality of beams to the attachment section, the mounting sections being attached to the base. A permanent magnet is positioned adjacent a corresponding one of each of the coils such that when current flows through the coils a rotational force is generated that causes the coil-object assembly to rotate about an axis. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Description:
RELATED APPLICATIONS  
       [0001]    This application is related to co-pending applications: Ser. No. ______, filed ______, entitled, “GIMBAL FOR SUPPORTING A MOVEABLE MIRROR”; and Ser. No. ______, filed ______, entitled, “PHOTONIC SWITCH FOR AN OPTICAL COMMUNICATION NETWORK”; both of which are assigned to the assignee of the present application. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to apparatus and methods for movement of objects; specifically, objects such as mirrors that direct light beams in optical systems and networks.  
         BACKGROUND OF THE INVENTION  
         [0003]    Fiberoptic technologies and systems have been widely deployed in recent decades. However, certain key components remain expensive and inefficient, which hinders the expansion of optical systems and optical communication networks. One of these components is the wavelength switch, which routes and redirects a light beam from one fiber to another fiber so that the signal can be provisioned and managed according to the demand. A typical wavelength switch used today converts the input light signal into an electronic signal to detect the routing information, switches the electronic signal, and then eventually reconverts it back into a light signal for further transmission. This device, commonly referred to as an Optical-Electrical-Optical (OEO) switch, not only depends on current semiconductor technologies and processes, but also requires a transmitter and a receiver for each transmission port. These factors cause OEO switches to be large in size (e.g., occupying two or more 7-foot tall racks), to have high power consumption (e.g., kilowatts), to be network protocol and transmission rate dependent, to lack scalability, and to be costly.  
           [0004]    Thus, there is a need for an alternative apparatus for directing a light beam in an optical system that can be manufactured efficiently and provide improved performance in optical systems and fiber optic-based networks.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    The present invention will be understood more fully from the detailed description that follows and from the accompanying drawings, which however, should not be taken to limit the invention to the specific embodiments shown, but are for explanation and understanding only.  
         [0006]    [0006]FIGS. 1A &amp; 1B are top views of a gimbal used in accordance with one embodiment of the present invention.  
         [0007]    [0007]FIG. 2 illustrates a platform that mounts to the gimbal of FIGS. 4A &amp; 4B in an actuator-mirror assembly according to one embodiment of the present invention.  
         [0008]    [0008]FIG. 3 is a bottom perspective view of an integrated mirror/pedestal  210  utilized in accordance with one embodiment of the present invention.  
         [0009]    [0009]FIG. 4 illustrates an actuator-mirror assembly at an intermediate point of construction according to one embodiment of the present invention.  
         [0010]    [0010]FIG. 5 illustrates an actuator-mirror assembly at a further point of construction according to one embodiment of the present invention.  
         [0011]    [0011]FIG. 6 is a perspective view of an actuator-mirror assembly according to another embodiment of the present invention.  
         [0012]    [0012]FIGS. 7A &amp; 7B are top and side views of a magnet-housing arrangement for an actuator-mirror assembly in accordance with one embodiment of the present invention.  
         [0013]    [0013]FIG. 8 is a top view of a magnet-housing arrangement for an actuator-mirror assembly in accordance with another embodiment of the present invention.  
         [0014]    [0014]FIG. 9 is a cross-sectional side view of an actuator-mirror assembly according to one embodiment of the present invention.  
         [0015]    [0015]FIGS. 10A &amp; 10B are cross-sectional side views of an actuator-mirror assembly tilted in two different directions in accordance with one embodiment of the present invention.  
         [0016]    [0016]FIGS. 11A &amp; 11B show top and side views of a bobbin coil assembly utilized in accordance with an alternative embodiment of the present invention.  
         [0017]    [0017]FIG. 12 illustrates the relative position of a coil and magnet assembly in accordance with an alternative embodiment of the present invention.  
         [0018]    [0018]FIG. 13 is a top view of a gimbal utilized in accordance with an alternative embodiment of the present invention.  
         [0019]    [0019]FIG. 14 is a cross-sectional side view of an actuator-mirror assembly in accordance with an alternative embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0020]    An actuator and a mirror assembly to guide a light beam for a variety of applications is described. In the following description numerous specific details are set forth, such as angles, material types, configurations, etc., in order to provide a thorough understanding of the present invention. However, persons having ordinary skill in the opto-mechnical arts will appreciate that these specific details may not be needed to practice the present invention.  
         [0021]    According to one embodiment of the present invention, a tilting actuatormirror assembly is provided to control the path of a light beam. The present invention has numerous consumer, medical, and/or industrial applications. For example, laser marking, laser display, optical scanning devices, windshield auto projection, helmet display, personal digital assistant (“PDA”), fiber optic communication network (e.g., an all-optical switch), and mobile phone projection display, to name a few, can all benefit from the present invention.  
         [0022]    In a particular embodiment, a dual-axis tilting actuator is provided as a rotary moving coil actuator suspended by a flexing, electrically conductive gimbal component. The gimbal is comprised of a pair of beams that move about the axis of rotation under the influence of an electromagnetic actuator. The conductive connections in the rotary moving coil actuator are integrated with the flexing part of the gimbal. In various embodiments, the actuator may rotate about either a single axis or a dual axis.  
         [0023]    Referring now to FIGS. 1A &amp; 1B, there is shown a top plan view of a gimbal  200  utilized in accordance with one embodiment of the present invention. Gimbal  200  is made from a single, integral sheet of thin metal. FIG. 1A shows gimbal  200  after removal of the “cutout” areas from the sheet metal. FIG. 1B shows the gimbal after removal of the end section and perimeter material, which step is performed during the construction of the actuator-mirror assembly according to one embodiment of the present invention.  
         [0024]    The sheet metal used for gimbal  200  is preferably a fully hardened material, such as stainless steel, having high fatigue strength. Other materials providing similar properties may also be used. The material selected should allow the gimbal to rotate the attached mirror (or mirror-coil assembly) with a high rotational angle (e.g., +/−15 degrees) over millions of movement cycles. The material may also be heat-treated. The sheet metal material is also preferably non-magnetic to prevent reluctance forces induced by the magnets in the actuator. In some cases, the sheet metal may also be coated with a corrosion-resistant material, such as titanium-nickel or gold.  
         [0025]    Gimbal  200  comprises four attachment pads  201 - 204  that are centrally located symmetrical about the x-axis (i.e., longitudinal axis) and y-axis (i.e., transverse axis). A mirror, or mirror-pedestal assembly, is adhesively attached to pads  201 - 204 . Thus, in the completed assembly, pads  201 - 204  are all affixed in a rigid plane, remaining stationary or moving in unison, depending on the particular embodiment of the final actuator-mirror assembly. Thin, elongated beams  191 - 194  support each of pads  201 - 204 , respectively. In operation, pairs of adjacent beams  191  &amp;  192  and  193  &amp;  194  each twist longitudinally about the x-axis to permit the mirror (attached to pads  201 - 204 ) to rotate about the x-axis.  
         [0026]    In FIG. 1A, beams  191  &amp;  192  are shown being integrally connected to end section  251  through respective intermediate sections  221  &amp;  222 . Similarly, beams  193  &amp;  194  are integrally connected to end section  253  through intermediate sections  223  &amp;  224 , respectively. Intermediate sections  221 - 224  are also integrally connected with thin, elongated beams  195 - 198 , respectively, which permit rotation of the mirror about the y-axis. During rotation of the mirror about the x-axis, pairs of adjacent beams  195  &amp;  196  and  197  &amp;  198  remain substantially rigid. Similarly, during rotation of the mirror about the y-axis, pairs of adjacent beams  195  &amp;  196  and  197  &amp;  198  twist longitudinally about the y-axis, while pairs of adjacent beams  191  &amp;  192  and  193  &amp;  194  remain substantially rigid.  
         [0027]    Beams  195  &amp;  196  are shown in FIG. 1A being connected to end section  252  via respective L-shaped mounting sections  240  &amp;  241 . Likewise, beams  197  &amp;  198  are both integrally connected to end section  254  through respective L-shaped mounting sections  242  &amp;  243 . All of the end sections  251 - 254  are attached together through a set of perimeter connecting sections  246 - 249 . For example, end section  251  attaches to end sections  252  &amp;  254  via connecting sections  246  &amp;  249 , respectively. End section  253  attaches to end sections  252  &amp;  254  via connecting sections  247  &amp;  248 , respectively. In this embodiment, end sections  251 - 254  (beyond dashed lines  250  in FIG. 1A) are removed along with the perimeter connecting sections during the assembly process. FIG. 1B shows gimbal  200  after these metal sections have been removed. This assembly process of this embodiment is described in more detail below.  
         [0028]    Each of the mounting sections  240 - 243  of gimbal  200  is fixedly mounted (e.g., with adhesive) to a stationary point or platform mount of the actuator-mirror assembly. FIG. 2 shows one possible implementation of a platform  270  that may be used for this purpose. Platform  270  comprises a base  271  that supports four rigid posts  272 - 275  of equal height. Each of the posts  272 - 275  has a flat end surface  282 - 285 , respectively. The dimensions of end surfaces  282 - 285  and the position of posts  272 - 275  is such that end surfaces  282 - 285  align with the rectangular surface areas of mounting sections  240 - 243  (see FIG. 1B) in a corresponding manner. This permits the mounting sections  240 - 243  to be adhesively attached to corresponding end surfaces  282 - 285 .  
         [0029]    [0029]FIG. 2 also shows a set of four thin wires  292 - 295 , each of which is adhesively bonded to respective posts of platform  282 - 285 . These wires connect with the coils that comprise the actuator of the final assembly. Two of the wires are used to energize the coils disposed about the x-axis, and the other two are used to energize the coils disposed about the y-axis.  
         [0030]    After gimbal  200  has been mounted to platform  270  each of the wires  292295  are soldered to corresponding tabs of the mounting sections  240 - 243 . For example, if surface  282  is attached to mounting section  240 , wire  292  may be soldered to tab  255 . Continuing with this example, with surfaces  283 - 285  respectively attached to mounting sections  241 - 243 , wires  293 - 295  may be soldered to tabs  256 - 258 , respectively. Note that in gimbal  200  of FIG. 1B each of tabs  255 - 258  provides separate electrical connection with respective pads  202 ,  203 ,  204 , and  201 . This feature is utilized to establish electrical connection to the coils of the actuator-mirror assembly, as discussed in more detail shortly.  
         [0031]    Metal may be removed from a single piece of thin sheet metal to achieve the gimbal cutout patterns shown in FIGS. 1A &amp; 1B using a variety of conventional methods, such as chemical etching, press cutting, milling, etc. Although a specific rectilinear cutout pattern is shown in these figures, it is understood that other embodiments may have different patterns or a different arrangement of beams, pads, etc., yet still provide rotational movement along the x and y axes in accordance with the present invention.  
         [0032]    In the embodiment illustrated by FIGS. 1A &amp; 1B, beams  191 - 198  are each about 0.05 mm wide, mirror-attachment pads  201 - 204  are each about 0.4 mm×0.6 mm in dimension, and the thickness of the single piece of sheet metal is about 0.0254 mm. Wires  292 - 295  are also about 0.0254 mm thick. In certain embodiments, beams  191 - 198  may be partially etched to make them thinner than the rest of the sheet metal material. For example, beams  191 - 198  may be chemically etched to a thickness less than 0.0254 mm to increase flexibility and thus achieve a higher degree of rotation.  
         [0033]    [0033]FIG. 3 is a bottom perspective view of an integrated mirror/pedestal  210  utilized in accordance with one embodiment of the present invention. In the drawing, the polished, reflective surface of mirror  214  faces down and into the page. Integrated mirror/pedestal  210  may be manufactured from a single piece of material such as silicon, Pyrex®, quartz, sapphire, aluminum, or other types of suitable materials. Integrated mirror/pedestal  210  includes a pedestal portion  212  having a flat surface  211 . The length and width of surface  211  is such that it matches or fit within the combined area of pads  201 - 204  (see FIG. 1B). During the assembly process, surface  211  is adhesively bonded to one side of pads  201 - 204 .  
         [0034]    Integrated mirror/pedestal  210  also includes a base plate  213  between pedestal portion  212  and the back of mirror  214 . Base plate is sized smaller than mirror  214  such that a step  216 , comprising a peripheral area of the back of mirror  213 , is realized. It is appreciated that other embodiments may be constructed from discrete parts (e.g., separate mirror, base plate, and pedestal) rather than being manufactured in integral form. In either approach, the mirror may be about 0.25 mm thick and 2×2 mm in area. The mirror surface may be lapped to a highly polished optical-flat surface. A reflective surface can also be applied by numerous methods, including plating or sputtering gold, silver, or aluminum on a layer of nickel.  
         [0035]    [0035]FIG. 4 shows a bottom perspective view of an actuator-mirror assembly after pads  201 - 204  have been bonded to surface  211  of integrated mirror/pedestal  210 . FIG. 4 also shows four coils  206 - 209  adhesively bonded to step  216  around the side back surface of mirror  214 . Thus, coils  206 - 209 , mirror  214 , and pads  201 - 204  of gimbal  200  are all rigidly coupled together, and move as a single unit, in the actuator-mirror assembly according to one embodiment of the present invention. Note that although FIG. 4 shows the end sections of gimbal  200  before removal at this stage of the assembly process, this is not required. That is, the end and peripheral connecting sections of gimbal  200  may be removed either before or after attachment to the mirror/pedestal assembly.  
         [0036]    [0036]FIG. 5 is another view of the assembly of FIG. 4 after soldering of pairs of coil wires to the back of pads  201 - 204 . (Note that not all of the cutout portions of the gimbal are shown in this view for clarity reasons.) For example, wires  226  &amp;  227  of coil  208 , and wires  224  &amp;  225  of coil  206 , are shown soldered to pads  202  &amp;  203 , respectively. Similarly, wires  228  &amp;  229  of coil  207 , and wires  230  &amp;  231  of coil  209 , are soldered to pads  204  &amp;  201 , respectively.  
         [0037]    Upon removal of the end sections of gimbal  200 , each of the pads  201 - 204  is electrically connected to a separate one of the mounting sections  240 - 243 . In other words, removal of the end sections of the gimbal creates four distinct conductive paths in the remaining sheet metal material from each of the four mounting sections to a corresponding one of the pads  201 - 204 . According to one embodiment of the present invention, current flows through these four paths to control movement of the attached mirror via coils  206 - 209 . This embodiment therefore utilizes the metal of gimbal  200  to conduct electrical current delivered to the moving coil. That is, the electrical connections to the coil wires are integrated with the flexing part of the gimbal. This arrangement thereby eliminates movement of wires during operation of the mirror-gimbal assembly.  
         [0038]    Following attachment of the gimbal to platform  270  (see FIG. 2) wires  292 - 295  may be soldered to tabs  255 - 258  to establish an electrical connection to coils  206 - 209 . Thus, the conductive paths provided through the flexing beams of gimbal  200  may be used to energize the coils in order to control tilting of the mirror along the x-axis and the y-axis. By way of example, one pair of wires  292 - 295  may be used to energize one pair of opposing coils (i.e., coils  207  &amp;  209 ) to control rotation of the mirror about the x-axis, with the remaining pair of wires  292 - 295  being used to energize the other pair of opposing coils (i.e., coils  206  &amp;  208 ) to control rotation of the mirror about the y-axis. In the final assembly, permanent magnets are attached within the central opening of each of the coils  206 - 209 .  
         [0039]    Torque is developed on the mirror-coil assembly upon application of an appropriate current through the coils, in the presence of the permanent magnetic field. The direction of the force is made to be opposite on each side of the mirror-coil assembly such that the resulting torque rotates or tilts the mirror attached to the top of gimbal  200 . Since the mirror-coil assembly is fixedly attached to gimbal  200 , gimbal pads  201 - 204  and mirror  214  rotate together as the mirror-coil assembly rotates. When the applied current is interrupted or halted, the restoring spring force of gimbal  200  returns the assembly to a rest position.  
         [0040]    [0040]FIG. 6 is a perspective view of another embodiment of an actuator-mirror assembly according to the present invention. The actuator-mirror assembly shown in FIG. 6 rotates about a single axis. In this embodiment, two coils  50  and  55  are adhesively attached to step  216  on opposite sides of mirror  214  and base plate  213 . The gimbal for this embodiment comprises two rectilinear, or I-bar, shaped members  10   a  &amp;  10   b  of thin sheet metal. Ends  12   a  &amp;  12   b  of respective I-bar members  10   a  &amp;  10   b  are bonded to surface  211  of pedestal  212 . Wires  60   a  &amp;  60   b  of coil  50  are soldered to ends  12   a  &amp;  12   b , respectively. Likewise, wires  65   a  &amp;  65   b  of coil  55  are also soldered to ends  12   a  &amp;  12   b , respectively. A stationary platform similar to that shown in FIG. 2, but having two posts, supports the assembly of FIG. 6, with the end surfaces of the posts being bonded to ends  14   a  &amp;  14   b  of I-bar members  10   a  &amp;  10   b.  A wire attached to each of the mounting posts may be soldered to ends  14   a  &amp;  14   b  to provide electrical connection through the gimbal members  10   a  &amp;  10   b  to energize coils  50  &amp;  55 .  
         [0041]    [0041]FIGS. 7A &amp; 7B show top and side views of a magnet-housing arrangement for a single actuator-mirror assembly in accordance with one embodiment of the present invention. This magnet-housing arrangement, for example, may be utilized in the actuator-mirror assembly shown in FIG. 4. Magnets  81 - 84  are bonded on the side surfaces of steel returns  85 , attached to a base  86 . Magnets  81 - 84  are positioned adjacent the moving coils (e.g., coils  206 - 209 ). The polarities of the magnets are shown by conventional nomenclature for north (N) and south (S). In one embodiment, the magnet material is Neodymium-Iron-Boron. Of course, other types of magnetic materials may be used as well.  
         [0042]    [0042]FIG. 8 shows a top view of a larger magnet-housing arrangement for use with multiple actuator-mirror assemblies.  
         [0043]    [0043]FIG. 9 is a cross-sectional side view of an actuator-mirror assembly utilizing gimbal  200  according to one embodiment of the present invention. A pair of magnets  87  is shown attached to a steel return on opposite sides of the mirror-coil-gimbal assembly. One pair of magnets  87  are positioned adjacent coil  206 , and the other pair of magnets  87  are positioned adjacent coil  209 . Each of the coils is bonded to a notched edge surface of mirror plate  214 . A pedestal  212  is shown attached to the back of mirror plate  214  and also to pads  201  &amp;  202  of gimbal  200 . The end surfaces of posts  74  &amp;  75  are shown respectively bonded to mounting sections  240  &amp;  243 , with wires  94  &amp;  95  soldered to sections  240  and  243  in accordance with the wiring scheme described above.  
         [0044]    Also included in the cross-section of FIG. 9 is an optional balancing plate  80  attached to the bottom of the coils  206 - 209 . Balancing plate  80  acts to counterbalance the weight of the mirror so that the center of rotation is at the center of gravity. This feature improves external shock and dynamic settling of the actuator. As shown in FIG. 9, balancing plate  80  comprises a solid, flat metal plate with several openings that allow the stationary posts to attach to the gimbal and also permit the gimbal-mirror-coil assembly to move. Instead of having several openings to accommodate mounting of the mirror-coil-gimbal onto stationary posts, balancing plate  80  may also be implemented with a single, centrally located opening. For instance, balancing plate  80  may comprise a rectangular frame having its sides adhesively attached to the coils, as shown in FIGS. 10A &amp; 10B.  
         [0045]    The embodiment of FIG. 9 further illustrates the use of an optional damper coating  333 , which covers beams  191 - 198  and gimbal pads  201 - 204 . Damper coating  333  comprises a low viscosity polymer (e.g., an ultraviolet curing resin) that becomes a flexible gel upon curing. Damper coating  333  acts to damp gimbal resonances and improve the settling time of the actuator; yet, because coating  333  is flexible, it does not appreciably affect the stiffness of the gimbal. Damper coating  333  also improves reliability by minimizing the effect of external shock and vibration.  
         [0046]    [0046]FIGS. 10A &amp; 10B are cross-sectional side views of an actuator-mirror assembly with appropriate current applied to coils  206  &amp;  209  to tilt mirror  214  in two different directions along a single longitudinal axis of movement. Note that in FIGS. 10A &amp; 10B only the rigid sections of gimbal  200  are shown for clarity reasons. Precise movement of mirror  214  along both the x-axis and y-axis is achieved by controlling the current applied to the four coils  206 - 209  for the embodiments described above.  
         [0047]    [0047]FIGS. 11A &amp; 11B show top and side views of a bobbin-coil assembly utilized in accordance with an alternative embodiment of the present invention. In this embodiment, the coils  301 ,  302 ,  303 , and  304  are made from fine copper wire with single-built insulation, and are each wrapped around a post member on a side of bobbin  310 . Coils  301 ,  302 ,  303 , and  304  are physically located between one or more permanent magnets (not shown in this view) in the final assembly. FIG. 12 shows the relative position of a coil and magnet assembly in accordance with this alternative embodiment. The coil windings are supported by and encircle the protruding side members of bobbin  310 , shaped in accordance with the dimensions of the permanent magnets. Bobbin pedestal  330  provides a surface for bonding (e.g., adhesive attachment) to a gimbal that suspends bobbin  310  between the permanent magnets.  
         [0048]    By way of example, in the embodiment of FIGS. 11A &amp; 11B, each coil may include approximately 48 turns made from 6 layers, with each layer having 8 turns. The number of turns and layers may vary based on the type of coil used, the application, etc. Bobbin  310  may be made from a variety of machined materials (e.g., polymers) as is known in the art. In operation, application of current through the coils generates a magnetic field that interacts with the field of the permanently mounted magnets to torque to tilt the actuator.  
         [0049]    The bobbin coil assembly of FIGS. 11A &amp; 11B may be bonded to a variety of conventional gimbals. FIG. 13 shows a top view of a conventional gimbal  320  of a type well known in the industry, which may be used to suspend the bobbin-coil assembly shown in FIGS. 11A &amp; 11B. Gimbal  320  is formed of a single sheet of material (e.g., sheet metal) that provides for dual-axis rotation of the bobbin-coil assembly. Bobbin pedestal  330  may, for instance, be bonded to central area  323  of gimbal  320 .  
         [0050]    [0050]FIG. 14 shows a cross-sectional side view of an actuator-mirror assembly in accordance with an alternative embodiment of the present invention. In this view, permanent magnets  396  &amp;  397  are positioned on steel returns  395  &amp;  394  adjacent coils  381  &amp;  382 , respectively. Coils  381  &amp;  382  are located on opposite sides of a bobbin  310 , which is bonded to the center of a gimbal  320 , such as that shown in FIG. 13. In this example, gimbal  320  is secured to stationary steel returns  394  &amp;  395 . A mirror  391  is secured on the center-top area of gimbal  320 .  
         [0051]    Torque is developed on the bobbin-coil assembly upon application of an appropriate current through coils  381  &amp;  382 , in the presence of the permanent magnetic field. The direction of the force is made to be opposite on each side of bobbin  310  such that the resulting torque rotates or tilts mirror  391  attached to the top of gimbal  320 . The bobbin-coil assembly is attached to a gimbal  320  and therefore the gimbal  320  and the mirror  391  will rotate as the bobbin-coil assembly rotates. When the applied current is interrupted or halted, the restoring spring force of gimbal  320  returns the assembly to the rest position shown in FIG. 14.