Patent Publication Number: US-2022214008-A1

Title: Rotation mechanism with sliding joint

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation from U.S. patent application Ser. No. 16/975,723 filed Aug. 26, 2020 (now allowed), which was a 371 application from international patent application PCT/IB2019/061360 filed on Dec. 25, 2019, which claims priority from U.S. Provisional Patent Applications No. 62/789,150 filed on Jan. 7, 2019 and No. 62/809,897 filed on Feb. 25, 2019, both of which are expressly incorporated herein by reference in their entirety. 
    
    
     FIELD 
     Embodiments disclosed herein relate in general to rotation mechanism and in particular to rotation mechanisms for various elements in small digital cameras included in electronic devices. 
     BACKGROUND 
     Cameras for surveillance, automotive, etc. include mechanisms that enable advanced optical function such as optical image stabilization (OIS) and/or scanning the camera field of view (FOV). Such mechanisms may actuate (e.g. displace, shift or rotate) an optical element (e.g. lens, image sensor, prism, mirror or even an entire camera) to create the desired optical function. 
     Rotation mechanisms for rotating a payload (e.g. an optical element as above) in two degrees of freedom (DOF) are known. In known mechanisms in which one DOF is an internally rotating DOF and the other DOF is an external DOF, there is normally a problem in that the internally rotating DOF has its rotation axis rotated by the external DOF (Gimbal design). Known rotation mechanisms that solve the Gimbal problem use two fixed (not rotating) motors with more than three bearings or two rotating motors with two bearings. 
     SUMMARY 
     Aspects of embodiments disclosed herein relate to rotation mechanisms for rotating a payload in two DOFs. We propose a method of having two rotation axes around two rotation points. 
     In various exemplary embodiments there are provided rotation mechanisms for rotating a payload in two, first and second DOFs, comprising a static base, a first rotation arm coupled mechanically to the static base through a first rotation joint and used for rotating the payload relative to the static base around a first rotation axis that passes through the first rotation joint, a second rotation arm coupled mechanically to the static base through a second rotation joint and used for rotating the payload relative to the static base around a second rotation axis that passes through the second rotation joint, and a follower member rigidly coupled to the payload and arranged to keep a constant distance from the second rotation arm, wherein the rotation of the first arm rotates the payload around the first DOF and the rotation of the second arm rotate the payload around the second DOF. 
     In some embodiments, the follower member is a magnetic member separated from the second rotation arm by a constant air-gap. 
     In some embodiments, the payload is coupled mechanically to the first rotation arm through an inner rotation joint. 
     In some embodiments, a rotation mechanism further comprises a first motor for rotating the payload relative to the static base around the first rotation axis and a second motor for rotating the payload relative to the static base around the second rotation axis, wherein the first and second motors are rigidly attached to the static base 
     In some embodiments, the second rotation arm is a ring section centered around the first rotation axis. 
     In some embodiments, the rotation mechanism further comprises at least one sensing mechanism for determining a position of the payload. 
     In some embodiments, a sensing mechanism comprises at least one pair of a magnet and a Hall sensor. 
     In some embodiments, a sensing mechanism is operable to determine a position of the payload relative to the static base in the first and second DOFs. 
     In some embodiments, a pair of a magnet and a Hall sensor comprises a first pair of a magnet and a Hall sensor that allows determination of a rotation of the payload around the first DOF, and a second pair of a magnet and a Hall sensor that allows determination of a rotation of the payload around the second DOF. 
     In some embodiments, determinations of the position of the payload relative to the static base in the two DOFs are decoupled from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects, embodiments and features disclosed herein will become apparent from the following detailed description when considered in conjunction with the accompanying drawings, in which: 
         FIG. 1A  shows schematically in a perspective view an embodiment of a rotation mechanism for rotating a payload in two DOFs disclosed herein, at zero position; 
         FIG. 1B  shows the mechanism of  FIG. 1A  coupled with exemplary first and second motors; 
         FIG. 1C  shows in side view the mechanism of  FIG. 1A  at zero (non-rotated) position; 
         FIG. 1D  shows in side view the mechanism of  FIG. 1A  at a rotated position around the first rotation axis; 
         FIG. 1E  shows the rotation of a second rotation arm in the mechanism of  FIG. 1A  around a second rotation axis; 
         FIG. 2A  shows schematically in a perspective view another embodiment of a rotation mechanism for rotating a payload in two DOFs disclosed herein, at zero position. 
         FIG. 2B  shows in side view the mechanism of  FIG. 2A  at a rotated position, around both rotation axes; 
         FIG. 3A  shows schematically in a perspective view yet another embodiment of a rotation mechanism for rotating a payload in two DOFs disclosed herein, at zero position. 
         FIG. 3B  shows the mechanism of  FIG. 2A  in a top view; 
         FIG. 3C  shows one perspective view of an examplary case in which the first rotation arm is rotated around the first DOF; 
         FIG. 3D  shows another perspective view of the examplary case of  FIG. 3C . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  shows schematically in a perspective view an embodiment of a rotation mechanism (or simply “mechanism”) disclosed herein and numbered  100 . Mechanism  100  is used for rotating a payload  102  in two DOFs disclosed herein, at zero position (initial position, without any actuation, not rotated). An exemplary XYZ coordinate system shown applies also to all following perspective views. Payload  102  is shown as a prism, but may be any element, and in particular any optical element, such as (and not limited to) a lens, an image sensor, a prism, a mirror or an entire camera. Mechanism  100  includes a static base  104  (i.e. a fixed base that does not move), a first rotation arm  106 , a second rotation arm  108  and a magnetic follower  116 . First rotation arm  106  can rotate relative to static base  104  around a first rotation axis  109  (shown exemplarily in the Y direction). First rotation axis  109  passes through a first rotation joint  110  that couples first rotation arm  106  mechanically with static base  104  (e.g. using a ball bearing). Second rotation arm  108  has a shape of a circle section with a center on a first rotation axis  109 . A second rotation axis  118  passes through a second rotation point  112  that mechanically connects second rotation arm  108  with static base  104  (e.g. using a ring ball bearing). Second rotation arm  108  can rotate relative to static base  104  around second rotation axis  118  (shown exemplarily in the X direction). The first and second rotation axes may be perpendicular to each other. Magnetic follower  116  may made of a permanent (fixed) magnet (or at least the tip facing second rotation arm is made of a permanent magnet). Second rotation arm  108  may be made of a ferromagnetic material. Alternatively, the second rotation arm may be made of a rigid material such as a plastic material or a non-ferromagnetic metal covered with a ferromagnetic material on a side facing magnetic follower  116 . Magnetic follower  116  is distanced from second rotation arm  108  by an air-gap  111  ( FIG. 1C ), and allows payload  102  to follow second rotation arm  108  without having magnetic follower  116  touch second rotation arm  108  directly. 
     First rotation arm  106  and second rotation arm  108  can be rotated relative to rotation joints  110  and  112  respectively (each arm around one rotation point). The rotation can be performed by any motor (e.g. stepper, DC, brushless, VCM, etc.). An inner rotation point  114  connects payload  102  to first rotation arm  106  (e.g. using ring ball bearing) and allows payload  102  to rotate in a second DOF (see  FIG. 1E ). First rotation arm  106 , first rotation joint  110  and inner rotation point  114  are similar to elements of a gimbal. Note that inner rotation point  114  is on second rotation axis  118  at zero point (as seen in  FIG. 1A ) but when first rotation arm  106  is rotated inner rotation point  114  rotates with it and is shifted from second rotation axis  118 , as seen for example in  FIG. 2B . 
       FIG. 1B  shows mechanism  100  coupled with exemplary first and second motors  120  and  122 , which drive a rotation movement around the first and second rotation axes respectively. Advantageously, motors  120  and  122  are stationary relative to static base  104 . In other embodiments, motors  120  and  124  may have different shapes and sizes, may be equal to one another or different in size, technology of actuation, etc. 
       FIG. 1C  shows mechanism  100  in a zero, non-rotated position (same as in  FIG. 1A ), while  FIG. 1D  shows mechanism  100  in a second, rotated position. Both  FIGS. 1C and 1D  are given in a side view in an examplary X-Z plane (looking from positive to negative Y direction). In  FIG. 1D , first rotation arm  106  is rotated around first rotation axis  109  (e.g. using first motor  120 ) relative to the base  104  and payload  102  rotates with it. Magnetic follower  116  stays distanced from second rotation arm  108  by a constant distance (air-gap  111 ). The rotation around first rotation point may be in any angle α. The angle limitation shown in  FIGS. 1A-E  is due only to the length of second rotation arm  108 , which as shown is about a quarter of a circle in length. In other embodiments, the second rotation arm may be a complete circle, such that rotation of the first rotation arm around the first rotation axis may be up to 360 degrees. 
       FIG. 1E  shows the rotation of second rotation arm  108  (e.g. using second motor  122 ) around the second rotation axis. Magnetic follower  116  is pulled to second rotation arm  108  by the magnetic force and thus rotates with it and rotates payload  102  relative to first rotation arm  106  around inner rotation point  114  in the second DOF. The rotation of the magnetic follower is independent of the rotation of first rotation arm  106  around first rotation axis  109  in the first DOF, because magnetic follower  116  is pulled to the second rotation arm  108  equally in all positions along first DOF. Magnetic follower  116  following second rotation arm  108  forms a “sliding joint”, e.g. a joint that allows magnetic follower  116  to follow second rotation arm  108  in one (first) DOF while sliding without interference in a second DOF. 
       FIGS. 2A and 2B  show in perspective views another embodiment of a rotation mechanism disclosed herein and numbered  200 . Mechanism  200  is similar to mechanism  100 , with identical parts in both mechanisms numbered with identical numerals. In mechanism  200 , the payload is a exemplarily a camera  202 , and a second rotation arm  208  is a full circle, which enables rotation around the first rotation axis by 360 degrees. In  FIG. 1A , mechanism  200  is shown in a rest (non-rotated) position, while in  FIG. 1B , mechanism  200  is shown in position rotated by 30 degrees from the rest position. 
       FIGS. 3A-D  show yet another embodiment of a rotation mechanism disclosed herein and numbered  300 . Rotation mechanism  300  is similar to mechanism  100 , with identical parts in both mechanisms numbered with identical numerals. Relative to mechanism  100 , mechanism  300  is equipped with two position sensing mechanisms, enabling determining a relative position (orientation/rotation) of payload  102  relative to frame  104  in two DOF. The position sensing mechanisms comprise at least one pair of a magnet and a Hall sensor. In some embodiments, a position sensing mechanism may comprise more than one magnet and/or more than one Hall sensor.  FIG. 3A  shows a perspective view of mechanism  300 , and  FIG. 3B  shows a top view. Mechanism  300  comprises a first magnet  302  rigidly coupled to first rotation arm  106  and a first Hall sensor  304  rigidly coupled to base  104 . Mechanism  300  further comprises a second magnet  306  rigidly coupled to payload  102 , and a second Hall sensor  308  rigidly coupled to base  104 . In an example, the position of the second Hall sensor is on first rotation axis  109 . In an example, Hall sensors  304  and  308  can measure the intensity of the magnetic field in the Y direction. In particular, first Hall sensor  304  is positioned close to first magnet  302  and can measure the intensity of the magnetic field of first magnet  302 , which can be correlated with the rotation of the payload around the first DOF. Second Hall sensor  308  is positioned close to second magnet  306  and can measure the intensity of the magnetic field of second magnet  306 , which can be correlated with the rotation of the payload around the second DOF.  FIGS. 3C and 3D  show, from two different perspective views, an exemplary case where the first rotation arm  106  is rotated around the first DOF (e.g. in 30 degrees). The relative position of first magnet  302  and first Hall bar  304  is changed, while the relative position of second magnet  306  and second Hall bar  308  is unchanged. Similarly, when rotating payload  102  around the second DOF using second rotation arm  108 , the relative position of first magnet  302  and first Hall bar  304  is unchanged, while the relative position of second magnet  306  and second Hall bar  308  is changed. Thus the measurements of the two DOFs are decoupled from each other. 
     In summary, disclosed above are rotation mechanisms having a design with at least the following advantages: 
     Ability to rotate around two degrees of freedom. 
     The motors are stationary. 
     Only three mechanical connection points (bearings) are used to create the rotation, compared with at least four bearings in other designs in which the motors are stationary, for example in “Dynamic modeling and base inertial parameters determination of a 2-DOF spherical parallel mechanism” Danaei. B. et al., Multibody Syst. Dyn. (2017) 41: 367. doi:10.1007/s11044-017-9578-3, and “Optimal Design of Spherical 5R Parallel Manipulators Considering the Motion/Force Transmissibility”, Chao Wu et al., J. Mech. Des. (2010) 132(3), doi:10.1115/1.4001129. 
     While this disclosure describes a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of such embodiments may be made. For example, the magnetic follower can be replaced with a mechanical follower. 
     In general, the disclosure is to be understood as not limited by the specific embodiments described herein, but only by the scope of the appended claims. 
     All references mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual reference was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present application.