Abstract:
A rolling micromirror is disclosed which comprises a micromirror guided in movement by a reference surface. The micromirror is suspended adjacent to the reference surface by a suspension element. An actuator moves the micromirror in relationship with a control signal. The suspension element provides a restoring force that returns the micromirror to an initial position when the actuator applies less than a minimal force to the micromirror. The micromirror optionally includes a stationary or movable pivot point about which the micromirror rotates and tilts. The preferred embodiment is integrated on a single substrate and is a micro-electro-mechanical device.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to the use and design of optical components for communications systems. The present invention more particularly relates to electromechanical optical devices that reflect and redirect an optical signal.  
         BACKGROUND OF THE INVENTION  
         [0002]    Certain prior art micro-electro-mechanical systems, or MEMS, employ mirrors that are positioned by means of an electrostatic actuator. Typically an actuator tilts the mirror about a single axis. The degree of rotational freedom of the mirror is usually small and tightly limits the maximum available range of a trajectory of a reflection of a light beam. Prior art trajectories of reflected light beams are therefore typically linear, straight and short in length. The modest ranges of prior art trajectories limit the number of receiving waveguides that can be positioned to fall within the prior art trajectory. This prior art limitation in the quantity of waveguides to which the mirror can redirect an incident light beam correspondingly limits the number of light beam or optical signal channels available for optical signal transmission from the mirror.  
           [0003]    There is, therefore, a long felt need to increase the trajectory length of the receiving plane in order to increase the number of receiving waveguides available for receiving the light beam as reflected by the movable mirror, and to increase the accuracy of positioning of the light beam on a receiving plane or an output device or waveguide.  
         OBJECTS OF THE INVENTION  
         [0004]    It is an object of the present invention to provide a method and apparatus that increases the length of a trajectory located within a receiving plane for the reflection of a light beam from a movable mirror.  
           [0005]    It is an object of certain alternate preferred embodiments of the present invention to provide a method and apparatus that increases the accuracy of redirecting a light beam from the movable mirror and onto a receiving plane of the reflected light beam.  
           [0006]    It is an object of certain still alternate preferred embodiments of the present invention to provide a method and apparatus that increases the number of light beam receiving positions available to receive the reflected light beam, whereby the number of channels transmitting the reflected light beam from the apparatus is increased.  
           [0007]    It is an additional object of certain other preferred embodiments of the present invention to provide a method and apparatus that decreases the driving voltage required to move a movable mirror.  
           [0008]    It is an object of certain alternate preferred embodiments of the present invention to provide a method and apparatus that includes and comprises an electro-mechanical semiconductor device to reflect and redirect an optical signal.  
           [0009]    It is an object of certain further alternate preferred embodiments of the present invention to provide a method and apparatus that comprises a micro-electro-mechanical system, or MEMS, to reflect and redirect an optical signal.  
           [0010]    It is an object of certain further alternate preferred embodiments of the present invention to provide a method and an apparatus that provides a micromirror that reflects an optical signal along a circular reflection pathway.  
           [0011]    It is an object of certain still further alternate preferred embodiments of the present invention to provide a method and an apparatus that provides a micromirror that reflects an optical signal within a circular area, or another suitable surface area shape known in the art.  
           [0012]    It is an object of certain yet alternate preferred embodiments of the present invention to provide a method and an apparatus that provides a micromirror having a pivot point and that enables the movement of the micromirror in least one rotational degree of freedom.  
           [0013]    It is an object of certain yet alternate preferred embodiments of the present invention to provide a method and an apparatus comprising a micromirror and that enables a micromirror to move within at least two degrees of freedom.  
           [0014]    It is an object of certain yet other alternate preferred embodiments of the present invention to provide a method and an apparatus comprising a micromirror, wherein the apparatus enables a micromirror to move from one discrete position to at least one other discrete position.  
         SUMMARY OF THE INVENTION  
         [0015]    According to the method of the present invention, a rolling mirror, having a movable micromirror is provided. The invented rolling mirror redirects a light beam in a trajectory, where the trajectory lies within a receiving plane. Various alternate preferred embodiments of the invented rolling mirror generate trajectories having a suitable two dimensional shape known in the art, for example as selected from the group of shapes consisting of a circle, a substantially circular shape, a partially circular shape, and an ellipse.  
           [0016]    A preferred embodiment of the invented rolling mirror includes a movable micromirror having a body, a reference surface, an actuator, a suspension element and an optional pivot point. The actuator is operatively coupled with the micromirror and applies force to move the micromirror. The micromirror moves along a path of motion that includes at least one section within which the motion of the micromirror is guided by the reference surface. As the micromirror moves about the reference surface a reflection of a light beam incident to the micromirror is reflected at a movable point within a certain trajectory of a receiving plane. This trajectory is partially determined by the shape of the body of the micromirror and the shape of the reference surface. The reference surface may have one, two, or a plurality of sections. A section may comprise one, two or a plurality of suitable surface shapes known in the art, to include a plane surface, a conical surface, a curved surface, an arced surface, a ramped surface, a spiraled ramp surface and a helical surface.  
           [0017]    The micromirror has a reflecting surface and a body with a contact edge, and an optional micromirror pivot feature. The contact edge may be located on or proximate to a periphery of the micromirror or the reflecting surface, or alternatively, in certain alternate preferred embodiments of the present invention the contact edge may be located on the micromirror body in a path that is of uniform or of varying distance from the periphery of the micromirror or the reflecting surface. The reflecting surface may be concave, convex or flat reflecting surface in various preferred embodiments of the present invention. The micromirror may be shaped as a relatively thin body having a larger two-dimensional reflecting surface. Alternatively, the micromirror may have a cone shaped body or a frustum shaped body, or a body shaped according to another suitable shape known in the art.  
           [0018]    Certain alternate preferred embodiments of the present invention comprise a micromirror body having two or more body layers, where at least two body layers have different cross-sectional sizes or shapes. Certain alternate preferred embodiments of the present invention comprise a cone-like micromirror body, where the cone-like micromirror body is similar to, or topographically equivalent to, or contained within a conical bounding cone. The cone-like micromirror body may have two or more micromirror body layers. The micromirror body layers have different cross-sectional sizes, and the smaller of two layers, or the smallest body layer of a plurality of body layers micromirror series of body layers is positioned closer to a center of the actuator or a plurality of actuators.  
           [0019]    The actuator of the preferred embodiment may be a suitable actuator known in the art, to include one, two or a plurality of actuators selected from the group consisting of an electro-static actuator, a piezo-electric actuator, a thermo-mechanical actuator, an electromagnetic actuator, and a polymer actuator, or other suitable actuators known in the art. One or more polymer actuators may be selected from the group consisting of an electro-active polymer actuator, an optical-active polymer, a chemically active polymer actuator, a magneto-active polymer actuator, an acousto-active polymer actuator and a thermally active polymer actuator, or other suitable polymer actuators known in the art.  
           [0020]    Certain preferred embodiments of the present invention comprise an actuator assembly, where the actuator assembly has two or more actuator layers, where at least two actuator layers have different cross-sectional sizes or shapes. Certain alternate preferred embodiments of the present invention comprise an actuator comprising a plurality of low profile layers, where the height of most of the layers is small in comparison to the remaining two dimensions of the layer&#39;s cross section, and the layers are assembled together to be contained within a conical bounding surface, and/or the actuator has a shape that is substantially topologically similar to, or equivalent to, a cone.  
           [0021]    The suspension element is operatively coupled with the micromirror and provides a restoring force that returns the micromirror to a zero actuation position when the actuator provides no force, or force below a minimum level to the micromirror. The suspension element may be or comprise one or more suitable suspension components known in the art, or as selected from the group consisting of a spring, a beam, a tether, and a diaphragm. The suspension element may be at least partly flat, corrugated and/or perforated.  
           [0022]    In certain alternate preferred embodiments of the present invention the movable micromirror and the reference surface are pivotably coupled wherein the micromirror moves about a pivot point as the actuator moves the micromirror.  
           [0023]    Certain alternate preferred embodiments of the present invention are integrated on a single substrate. Certain still alternate preferred embodiments of the present invention are incorporated as a micro-electro-mechanical systems, or MEMS, or a MEMS device.  
           [0024]    In operation, the micromirror of certain preferred embodiments is moved about the pivot point while maintaining a point of contact between the contact edge and the reference surface. The position of the micromirror is determined by forces provided by the actuator and the suspension element. The point of contact between the micromirror and the reference surface shifts along the contact edge and along the reference surface as the micromirror moves.  
           [0025]    Other objects, features, and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description which follows below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which:  
         [0027]    [0027]FIGS. 1A and 1B are isometric views of a preferred embodiment of the present invention in a zero actuation position and in an actuated position respectively.  
         [0028]    [0028]FIGS. 2A and 2B are side views of the preferred embodiment of the present invention of FIGS. 1A and 1B in a zero actuation position and in an actuated position.  
         [0029]    [0029]FIGS. 3A, 3B and  3 C are perspective views of a first alternate preferred embodiment of the present invention having a set of actuator plates arranged in a cone-like shape, wherein a micromirror rotates about a pivot point from a zero actuation position and to an actuated position  
         [0030]    [0030]FIGS. 4A and 4B are side views of the first alternate preferred embodiment of the present invention of FIGS. 3A, 3B and  3 C in a zero actuation position and in an actuated position.  
         [0031]    [0031]FIGS. 5A and 5B are side views of a second alternate preferred embodiment of the present invention having a pair of layers with actuators arranged in a shape that is substantially similar to, or topologically equivalent to, a cone, and wherein a micromirror is shown in a zero actuation position and in an actuated position respectively.  
         [0032]    [0032]FIGS. 6A and 6B are isometric views of the second alternate preferred embodiment of the present invention of FIGS. 5A and 5B in a zero actuation position and in an actuated position.  
         [0033]    [0033]FIGS. 7A and 7B are side views of a third alternate preferred embodiment of the present invention, wherein a micromirror has a conical body, and where the micromirror is shown in a zero actuation position and in an actuated position respectively.  
         [0034]    [0034]FIGS. 8A and 8B are side views of a fourth alternate preferred embodiment of the present invention, wherein a micromirror has a body comprised of layers, and the micromirror body is substantially similar to, or topologically equivalent to, a cone, and wherein the micromirror is shown in a zero actuation position and in an actuated position respectively.  
         [0035]    [0035]FIGS. 9A and 9B are isometric views of a micromirror, in two different actuation positions, and having a plurality of teeth extending from the micromirror.  
         [0036]    [0036]FIG. 10 has top views of three micromirrors of different shape and each having pluralities of teeth extending from the micromirror.  
         [0037]    [0037]FIG. 11 is an example of an alternate pivot point enabling structure that has a movable pivot point.  
         [0038]    [0038]FIGS. 12A and 12B show and contrast the ranges of micromirror tilt motion of a prior art MEMS, as per FIG. 12A, versus the tilt range of the rolling mirror of FIG. 1, as presented in FIG. 12B.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0039]    While the description above provides a full and complete disclosure of the preferred embodiments of the present invention, various modifications, alternate constructions, and equivalents will be obvious to those with skill in the art. Thus the scope of the present invention is limited solely by the appended claims.  
         [0040]    Referring now generally to the Figures and particularly to FIG. 1A, a preferred embodiment of the present invention  2 , or rolling mirror  2 , has a micromirror  4  having a reflecting surface  5 . The micromirror  4  is suspended by a suspension element  6  and is movable by force applied by an actuator  8 . Actuator  8  comprises of a plurality of electrostatic actuators  8 A. The micromirror  4  is in an initial position Z 1 , or zero actuation position Z 1 , wherein the actuator  8  provides no force, or less than a minimal amount of force, required to move the micromirror  4 . The suspension element  6  comprises at least one suspension component  10 . The suspension components  10  may be or be comprised within a diaphragm, or the components  10  may be separate and where each element  10  is separately attached to the micromirror  4  and to the rolling mirror  2 . Alternatively or additionally, each suspension component  10  my be or comprise a tether, a beam, a diaphragm and/or a spring. In the exemplary preferred embodiment  2  of the present invention, the component  10  is mechanically connected with an individual mount  12  of a frame  14 , and the frame  14  is mechanically coupled with the plurality of electrostatic actuators  8 A. A flat or planar reference surface  16  encompassing the plurality of electrostatic actuators  8 A is pre-positioned to make contact with a contact edge  18 , or edge  18 , of the micromirror  4  as the edge  18  rotates about the flat reference surface  16  of the rolling mirror  2 .  
         [0041]    Referring now generally to the Figures and particularly to FIG. 1B, the micromirror  4  has moved to an actuation position A 1  wherein the edge  18  is in contact with the reference surface  16 . The micromirror  4  moves while maintaining a moving point of contact  19  between the edge  18  and the reference surface  16 . The movement and position of the micromirror  4  are determined by the actuation forces provided by the plurality of electrostatic actuators  8 A and a restoring force provided by the suspension element  6 .  
         [0042]    Referring now generally to the Figures and particularly to FIG. 2A, a side view of the rolling mirror  2  in the zero actuation position of Z 1 , as shown in FIG. 1A, is presented.  
         [0043]    Referring now generally to the Figures and particularly to FIG. 2B, a side view of the rolling mirror  2  in the actuation position of A 1 , as shown in FIG. 1B, is presented. The micromirror  4  may be rolled around the reference surface  16  while providing the micromirror  4  with at least one rotational degree of freedom. The rolling mirror  2  may thereby be moved as a reflecting mirror system having a single circular dimension of reflection pathway. For example, the micromirror  4  may be rotated about the reference surface  16  to form a circular reflection pattern of light reflected from the micromirror  4 . The edge  18  of the micromirror  4  moves about the reference surface  16  while maintaining a movable point of contact  19  between the edge  18  and the reference surface  16 .  
         [0044]    Referring now generally to the Figures and particularly to FIGS. 3A, 3B and  3 C, the FIGS. 3A and 3B are isometric views of a first alternate preferred embodiment of the present invention  20 , having a set of electrostatic actuators plates  22  arranged in a cone-like shape. The electrostatic actuators plates  22  are individually shaped for forming a cone when combined and positioned to form an actuator cone  24 . The micromirror  4  is shown in a zero actuation position Z 2  in FIG. 3A and in an actuated position A 2  in FIG. 3B, respectively.  
         [0045]    Referring now generally to the Figures and particularly to FIG. 3C, the micromirror  4  of the first alternate preferred embodiment  20  rotates in two degrees of freedom about a pivot point  26 . The pivot point  26  may be enabled by a mirror pivot feature  28  and an actuator pivot feature  30 . The micromirror pivot feature  28  mechanically interacts with the actuator pivot feature  30  to establish the geometric pivot point  26 , whereby the micromirror  4  rotates about the pivot point  26  as the micromirror  4  is tilted by the actuator plates  22 , as shown in FIG. 3A. The micromirror  4  moves about the pivot point  26  in reaction to the forces imposed on the micromirror  4  by the actuator plates  22  and the suspension components  10 .  
         [0046]    Referring now generally to the Figures and particularly to FIG. 4A, a side view of the first alternate rolling mirror  20  in the zero actuation position of Z 2 , as shown in FIG. 3A, is presented. The actuator plates  22  are separated by gaps  32 . An underside  34  of the micromirror  4  is shown as the micromirror  4  suspended in the zero actuation position Z 2 .  
         [0047]    Referring now generally to the Figures and particularly to FIG. 4B, a side view of the first alternate rolling mirror  20  is shown in the actuation position of A 2 , as shown in FIG. 3A, is presented in side view. The micromirror  4  moves about a reference surface  36  while maintaining a movable point of contact  37  with the reference surface  36 . The actuator plates  22  may be individually shaped to substantially form a pyramid or alternatively a cone  24 , or a substantially pyramidal or conical shape, or a shape contained within a pyramid-bounding or a cone-bounding surface. In operation, the actuator plates  22  apply electrostatic forces to move the micromirror  4  about the pivot point  26  and to bring the micromirror into contact with a reference surface  36 .  
         [0048]    Referring now generally to Figures and particularly to FIGS. 5A and 5B, the micromirror  4  of a second alternate preferred embodiment  38 , or second alternate  38 , is shown in a zero actuation position Z 3  in FIG. 5A, and in an actuated position A 3  in FIG. 5B respectively. A plurality of shaped actuator plates  40  are sized to be combined as a quasi-cone  41  that decreases in cross-sectional area from the frame and towards the micromirror  4 . The quasi-cone  41  is similar to, or topologically equivalent to, a cone or a pyramid, or is contained within a conical or a pyramidal bounding surface. In operation, the shaped actuator plates  40  apply electrostatic force to move the micromirror  4  towards and about the pivot point  26  and to bring the micromirror  4  into contact with reference surface  16  and thereby place the second alternate rolling mirror  38  into the actuated position A 3 . The edge  18  of the micromirror  4  moves about the reference surface  16  while maintaining a shifting point of contact  19  between the edge  18  and the reference surface  16 .  
         [0049]    Referring now generally to the drawings and particularly to FIGS. 6A and 6B, FIG. 6A and 6B are isometric views of a third alternate preferred embodiment of the present invention  44 , having a micromirror  46  with a cone body  47 .  
         [0050]    The micromirror  46  is shown in a zero actuation position Z 4  in FIG. 6A and in an actuated position A 4  in FIG. 6B respectively. The third alternate preferred embodiment  44 , or third alternate  44 , has a pivot point  26  located distal from the reflecting surface  5  of the micromirror  46 . The micromirror  46  moves about the pivot point  26  in reaction to the forces imposed on the micromirror  46  by the actuators  8 A and the suspension element  6 . In operation, the actuators  8 A apply electrostatic force to move the micromirror  46  towards and about the pivot point  26  and to bring the micromirror  46  into contact with the reference surface  16 .  
         [0051]    Referring now generally to the Figures and particularly to FIG. 7A, a side view of the third alternate rolling mirror  44  in the zero actuation position of Z 4 , as shown in FIG. 6A, is presented in side view. A sloped underside  48  of the cone body  47  of the micromirror  46  is shown as the micromirror  46  is suspended in the zero actuation position Z 4 .  
         [0052]    Referring now generally to the Figures and particularly to FIG. 7B, a side view of the third alternate rolling mirror  44  is shown in the actuation position of A 4 , as shown in FIG. 6B, is presented in side view. A reference surface  49  may comprise the actuators  8 A and optionally the frame  14 . When the third alternate rolling mirror  44  is actuated to be in actuation position A 4 , the micromirror sloped underside  48  touches the reference surface  49 . The edge  18  of the micromirror  46  moves about the reference surface  49  while maintaining a movable line of contact  50  between the cone  47  and the reference surface  49 .  
         [0053]    Referring now generally to the Figures and particularly to FIGS. 8A and 8B, a fourth alternate preferred embodiment of the present invention  52 , or fourth alternate  52 , is shown in a zero actuation position Z 5  in FIG. 8A and in an actuated position A 5  in FIG. 8B respectively. A micromirror body  54  of a micromirror  56  is similar to, or topologically equivalent to, a cone, or is contained within a bounding cone shape. The micromirror  56  moves about the pivot point  26  in reaction to the forces imposed on the micromirror  56  by the actuators  8 A and the suspension element  6 . In operation, the actuators  8 A apply electrostatic forces to move the micromirror  56  about the pivot point  26  and to bring the micromirror  56  into contact with reference surface  16  and thereby place the fourth alternate rolling mirror  52  into the actuated position A 5 . The edge  18  of the micromirror  52  moves about the reference surface  16  while maintaining a shifting point of contact  19  between the edge  18  and the reference surface  16 .  
         [0054]    Referring now generally to the Figures and particularly to FIGS. 9A and 9B, a micromirror  58  has a plurality of teeth  60  along the edge  18  of the micromirror  58 . FIGS. 9A and 9B show the micromirror  58  in a zero actuation position Z 6  in FIG. 5A and in an actuated position A 6  in FIG. 5B respectively. The teeth  60  extend from the reflecting surface  5  and to make contact with the reference surface  16  as the micromirror  58  is moved by the actuator  8 . FIG. 9B shows two teeth  60  touching the reference surface  16  simultaneously.  
         [0055]    Referring now generally to the Figures and particularly to FIG. 10, top views of three micromirrors  58 ,  62 , &amp;  64  are shown to have pluralities of teeth  60 .  
         [0056]    Referring now generally to the Figures and particularly to FIGS.  11 , an alternate example of a pivot point and enabling structures is presented. The alternate pivot structure  66 , as shown in FIG. 11, has a flexible beam  68  that couples the micromirror  4  to the reference surface  16 . The micromirror  4  tilts, as affected by the actuators  8 A, about an individual pivot point  30  located within a pivot point range  70 . A pivot point actuator  72  is operatively coupled with the beam  68  and affects the beam  68  to determines the location of the pivot point  30 , within the range of 70, about which the micromirror  4  tilts.  
         [0057]    Referring now generally to the Figures and particularly to FIGS. 12A and 12B, the range of micromirror tilt motion of a prior art MEMS  74 , as per FIG. 12A, is about one third of the tilt range of the rolling mirror  2  of FIG. 1, as presented in FIG. 12B. The voltage required by the actuators  8 A to move a prior art micromirror  76  of FIG. 12A is inversely proportional to the square of the distance between the prior art micromirror  76  and the actuators  8 A.  
         [0058]    Referring now generally to the Figures and particularly to FIG. 12B, the voltage required by the actuators  8 A to move the micromirror  4  of rolling mirror  2  is inversely proportional to the square of the distance between the micromirror  4  and the actuators  8 A. As the micromirror  4  is brought into contact with the reference surface  18  during operation of the rolling mirror  2 , the minimum distance between the plane B and the micromirror  4  may be at zero or close to zero while the actuators  8 A are moving the micromirror  4 . The voltage required to move the micromirror  4  of the rolling mirror  2  to reflect a light beam is therefore less than the voltage required by the prior art MEMS mirror  74  to move the prior art micromirror  76  within the tilt range between plane M 1  and plane M 2 . This optional reduction in operation voltage requirements for moving the micromirror  4  is an object of certain preferred embodiments of the method of the present invention.  
         [0059]    The invention has been described in conjunction with the preferred embodiment. Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.