Abstract:
A hand-held laser pointer is disclosed wherein the laser beam is isolated from unwanted hand tremor motions of the laser pointer housing. A laser beam is directed toward a pair of passively inertially stabilized mirrors disposed within the housing that are biased to a neutral position by a spring and damper. Both the laser beam that exits the housing and the laser dot appearing at a target are minimally affected by laser jitter associated with hand tremor.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to laser pointers. More particularly, the present invention relates to hand-held laser pointers. Even more particularly, the present invention relates to a hand-held laser pointer stabilized against hand tremor. 
         [0003]    2. Prior Art 
         [0004]    Various hand-held laser pointers have been taught for visually pointing out a target on, for example, a whiteboard, chart, map, or projected display. Laser pointers typically include a laser diode module that produces a collimated laser beam. The laser diode module is packaged within a housing and is battery powered. In operation, a user holds the pointer in one hand and directs the laser beam towards a target, generally during a presentation or the like. 
         [0005]    The effectiveness of such hand-held laser pointers for particularly pointing out a target is reduced by the unintentional tremor of the user&#39;s hand. Human tremor is an involuntary trembling or shaking of the muscles of the body associated with physical weakness, emotional stress, or excitement. The small angular movements of the hand from tremor impart undesirable motion to the laser pointer and its corresponding laser beam and image, which is generally a small dot indicating where the beam is striking the target. This unwanted motion is amplified as the distance between the laser diode and the target increases and generally results in visibly shaky movements of the laser dot. The jitter of the laser dot limits the user&#39;s pointing resolution which may distract an audience, expose nervousness and may serve to discredit the user. 
         [0006]    To address this problem, Wilson and Sanchez, in U.S. Patent Application Publication number 20050128749, disclose a laser module isolated from unwanted hand tremor motions of the laser pointer housing while still operable for pointing the laser beam in an arbitrary direction. In the embodiment disclosed in the aforesaid application, the laser itself is used as part of the inertial mass that is stabilized from unwanted hand tremor motion. 
         [0007]    Applications other than laser pointers such as, for example, optical recording and laser ranging also require a jitter-free dot. While recent improvements in jitter-stabilized lasers have attempted to address the dot-jitter problem, there remains a need for a compact, hand-held laser pointer wherein the stability of the laser dot position on a target is unaffected by hand tremor. 
       SUMMARY 
       [0008]    In a preferred embodiment of a hand-held laser pointer operable for providing a laser beam having a direction defining a longitudinal axis, the laser pointer comprises: (a) a housing; (b) a laser module enclosed within the housing; (c) a power supply enclosed within the housing and in electrical communication with the laser module; (d) a counterweight rigidly attached to a mirror by a bridge, the mirror, counterweight and bridge collectively forming an inertial mass having a center of gravity disposed on the bridge; (e) a gimbal affixed to said housing and said bridge at the center of gravity of said inertial mass, said gimbal pivoting on two intersecting and mutually perpendicular axes; and (f) means for biasing said gimbal-mounted inertial mass to a neutral position with respect to said housing, said biasing means being operable for damping angular vibration between said inertial mass and said housing while enabling said laser pointer to be panned. 
         [0009]    The counterweight is preferably adjustable towards and away from said mutually perpendicular pivot axes of said gimbal. The means for biasing the inertial mass to a neutral position preferably employs a magnetic field interaction between a magnetic or ferromagnetic first material disposed on the inertial mass, and a ferromagnetic or magnetic second material affixed to said housing. An electrically conductive non-magnetic material may be disposed on the inertial mass in proximity to a second magnetic material affixed to the housing. The magnetic interaction therebetween provides a damping effect by the generation of eddy currents therein. Preferably, the magnetic material is movably mounted to the housing and adjustable towards and away from the conductive, non-magnetic material disposed on the inertial mass. 
         [0010]    The mirrors are respectively mounted about pitch and yaw inertially stabilized frames disposed within the housing that provides for pivoting of the mirrors with respect to the housing about two axes that are orthogonal to the longitudinal axis (i.e., the beam axis) and to each other. The inertial stabilization is accomplished passively. The final mirror frame serves as an inertial mass that is balanced to be substantially free from gravitational influence while gimballed to the housing. The inertial mass is spring biased to a neutral position with respect to the housing. Damping elements may be positioned interior the housing and is provided to improve stabilization. 
         [0011]    The aforesaid laser pointer provides a beam with low dot jitter. Low frequency angular movements of the housing such as occur during panning are transmitted to the laser beam while angular movements of the housing substantially at or above a predetermined frequency and, preferably, in a range similar to the frequencies associated with hand tremor, are isolated from the laser beam. The features of the invention believed to be novel are set forth with particularity in the appended claims. However the invention itself, both as to organization and method of operation, together with further objects and advantages thereof may be best understood by reference to the following description taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a tremor-stabilized, hand-held laser pointer in accordance with the present invention. 
           [0013]      FIG. 2  is a longitudinal bottom plan view of the laser pointer of  FIG. 1 . 
           [0014]      FIG. 3  is a longitudinal side plan view of the laser pointer of  FIGS. 1 and 2 . 
           [0015]      FIG. 4  is a schematic view of a gimbal included in a laser pointer according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    Referring alternately to both  FIGS. 1 and 2 , the preferred embodiment of a hand-held laser pointer in accordance with the present invention is shown at  10 . The laser pointer  10  generally includes a housing  12 , a laser assembly  40  ( FIG. 2 ), and a power source  16  ( FIG. 2 ). The housing  12  has a inner surface  26 . The housing  12  defines an open interior chamber  28 . A transparent material  30  ( FIG. 3 ) such as clear plastic, glass, or other optically transparent material separates the interior chamber  28  of the housing  12  from the external environment. The housing  12  includes a power supply access  32  for facilitating the mounting and dismounting of the power source  16 . The power source  16  is preferably a single battery or a plurality of batteries. 
         [0017]    The laser assembly  40  is well known in the art and includes a collimating lens, a laser element and a driving circuit. The laser element is preferably a laser diode that emits coherent light of a desired color such as red, green, blue, or infrared laser light. Suitable laser elements are produced by Nichia Corporation having a principle place of business at 491 Oka, Kaminaka-Cho, Anan-Shi, Tokushima 774-8601, Japan and by Cree, Inc., having a place of business at 4600 Silicon Drive, Durham, N.C. 27703. 
         [0018]    The laser assembly  40  is rigidly attached to a structural element  14  affixed to the housing  12  and its output beam is aimed towards a mirror  45  affixed to gimbal element  13 . Mirror  45  reflects the beam X towards a mirror  46 . Mirror  46  reflects the beam towards mirror  47  to reflect a beam X 1 . The reflected beam X 1  points in a direction substantially parallel with the first beam X exiting the front of the housing  12 . The bridging element  50  is suspended in the housing  12  by a low friction gimbal  60  that pivots about substantially perpendicular first and second axes  62  and  64 , each of which axes being perpendicular to longitudinal axis x 1  (i.e., the beam axis). The gimbal  60  is pivotally mounted to the housing  12 . Such pivotal mounting may be accomplished via pairs of pin and cup mechanisms  74  or other low friction bearing elements. The laser module assembly  40  and the bridging element  50  act as a pivoting inertial mass suspended by the gimbal  60 . The housing for the laser module  40  and the bridging element  50  may be formed from either synthetic resinous materials or metallic materials. 
         [0019]    In a preferred embodiment of the stabilized laser pointer  10 , a threaded shaft  81  mounted to the housing  12  contains a magnet  80  and a ferromagnetic pin  82 . The magnetic field from magnet  80  is focused though the ferromagnetic pin  82 . A ferromagnetic pin  84  is mounted within a conductive non-magnetic material  83  mounted to the bridging element  50 . The magnetic field of magnet  80  is focused through pin  82  to interact with the ferromagnetic material  84  to provide a small magnetic spring coupling between the pivoting inertial mass and the housing  12 . The assembly comprising threaded element  81 , pin  82 , and magnet  80  can be adjusted towards or away from pin  84  to increase or decrease the magnetic restoring force. 
         [0020]    A conductive non-magnetic material  92  is mounted on a non-magnetic shaft  93  connected to the bridging element  50 . A ferromagnetic tube  94  and ferromagnetic washers  95  contain the magnetic field lines produced by ring magnet elements  90  and concentrate the magnetic field strength through the metallic non-magnetic discs  91  and  92  attached to shaft  93 . Non-magnetic elements  93  axial restrain the magnets  90 . A non-magnetic retainer flange  95  longitudinally restrains the magnets  90  within tube  94 . The magnetic field produced by the magnets  90  is used to dampen the magnetic spring coupling between the pivoting inertial mass and the housing  12 . For zero or small angular displacements of the inertial mass, only disc  91  is contained within the magnetic field. For large displacements, both discs  92  and  91  are within the magnetic field providing additional damping. 
         [0021]    Essential tremor and postural tremor frequencies are generally between 4 Hz and 12 Hz. As such, the spring (magnetic coupling) and damping characteristics are sized for effective isolation of angular motion imparted to the gimbal assembly  60  ( FIG. 3 ) about axes  62 ,  64  within this frequency range, while providing adequate angular motion coupling about axes  62 ,  64  for effective panning and tilting of the laser beam XI during use. Various arrangements of these or other spring and damping materials may be employed to provide alternate or adjustable spring and damping characteristics. 
         [0022]    Power is supplied to the laser assembly  40  by actuating the switch  58 . Electrical connections between the power source  16 , the switch  58 , and the laser assembly  40  may be comprised of flexible wiring. A switch cover  59  protrudes through housing  12  and is direct contact with switche  58 . Switch cover  59  can be pressed to activate switch  58 . 
         [0023]    When the user grasps the laser pointer  10  with his/her hand and switches on the switch  58 , the laser beam is emitted from the laser assembly  40  through the transparent aperture  30  of the housing  12  towards a target. Low frequency angular movements of the housing are transmitted to the emitted laser beam X 1  while angular movements of the housing  12  substantially at or above a predetermined frequency and, preferably, in a range similar to the frequencies associated with hand tremor, will be isolated from the laser beam XI. The preferred embodiment of the present invention passively accomplishes stabilization of the dot formed on a target from hand tremor that may be imparted to the laser pointer  10 . A power source is not required for stabilization. It is relatively inexpensive to stabilize the laser assembly  14  in a passive fashion in accordance with the present invention than employing active stabilization. 
         [0024]    While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. For example, this invention can be used to improve handheld laser range finding, laser targeting, surgical laser devices, handheld imaging devices, and handheld projectors. In addition, the laser pointer may be mounted on a transportable device, as, for example, on a vehicle, and still enjoy the advantages of the stabilization system. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.