Abstract:
A zoom lens apparatus with focus adjusting and an optical imaging device therewith are provided, wherein a combination of screw-driven ultra sonic motor and voice coil motor is adopted to drive different optical lens sets ( 25,61 ). For the ultra sonic motor, the screw motion of the rotor ( 23 ) is transformed into a simple rectilinear motion by providing a third tube ( 24 ) placed in the rotor ( 23 ) and radially fixed relative to the stator ( 22 ). Thus the zoom lens apparatus with focus adjusting produced with the combination can well maintain the stability of the optical axis, moreover, the combination of different driving methods integrates and makes better use of lens sets of different functions and hence simplifies the overall structure.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to optics, more particularly, to a zoom lens apparatus with focus adjusting and a corresponding optical imaging device therewith. 
       PRIOR ART 
       [0002]    With the popularization and spreading of digital imaging technology, optical imaging devices have been widely applied in various types of equipments. Among them, a large variety of portable and small optical imaging devices meets extensive demands. 
         [0003]    As for miniaturized imaging devices, to obtain the ability to accurately adjust focal length, a screw-driven ultrasonic motor (USM) is proposed to adjust focal length (referring to the PCT application WO2007/118418). One basic structure of the USM consists of an outer tube as a rotor with a plurality of piezoelectric elements attached thereon and an inner tube as a stator for holding an optical lens set, wherein the plurality of piezoelectric elements are excited by electric signals to drive the outer tube to generate a traveling wave, so as to drive the inner tube to rotate through the threads of the outer tube matching with the threads of the inner tube, thus producing a linear displacement of the inner tube relative to the outer tube. However, some issues are caused by the structure when the optical lens set is rotated with the inner tube, such as the deviation of optical axis occurred during the installation is difficult to be corrected. 
         [0004]    To solve the aforementioned issues, a method has been proposed (referring to a Chinese patent application No. 200810142713.6, publish No. CN101425762). In this method, a new tube is added and placed in the rotor, wherein with the sliding grooves arranged at both ends of the new tube, the new tube may be radially fixed to the stator; and with the engagement between the threads on the outer surface of the new tube and the threads on the inner surface of the rotor, the screw motion of the rotor then may be transformed into a simple rectilinear motion; and by mounting the optical lens set in the new tube (hence the new tube is called as lens tube) placed in the rotor, the rotation of the optical axis may be avoided. However, an optical imaging device is usually provided with multiple optical lens sets which can be adjusted independently, such as an optical lens set for zooming and an optical lens set for focusing; therefore the optical imaging device which utilizes multiple USMs having the aforesaid structure becomes more complex. 
       SUMMARY 
       [0005]    In accordance with an aspect of the present disclosure, a zoom lens apparatus with focus adjusting comprises: a first tube with threads formed on the inner surface thereof; a second tube with threads formed on both outer and inner surfaces thereof, wherein the second tube is placed in the first tube, the pitch and/or the spiral direction of the threads on the outer surface is different from that of the threads on the inner surface, and the threads on the outer surface are arranged to match with the threads on the inner surface of first tube; a first set of piezoelectric elements attached on the outer surface of the first tube and excited by electric signals to propel the first tube to generate a traveling wave, so as to force the second tube to rotate relative to the first tube; a third tube placed in the second tube, wherein threads are formed on the outer surface of the third tube for matching with the threads on the inner surface of the second tube, the hollow portion of the third tube is arranged to hold a first optical lens set, and the third tube is radially fixed relative to the first tube such that the third tube is moved in a straight line along the rotary axis of the second tube during the rotation of the second tube; and a voice coil motor comprising a stationary portion and a movable portion, wherein one of the stationary portion and the movable portion comprises a magnet and the other one comprises a conductor, the conductor is excited by electric signals for driving the movable portion to move in a straight line relative to the stationary portion, the stationary portion is fixed relative to the first tube such that the motion path of the movable portion is parallel to the rotary axis of the second tube, and the movable portion is arranged to fix a second optical lens set thereon. 
         [0006]    In accordance with another aspect of the present disclosure, an optical imaging device comprises an aforesaid zoom lens apparatus with focus adjusting as well as optical lens sets and a photo sensor. 
         [0007]    In the specific examples disclosed herein, a combination of screw-driven USM and VCM is adopted to drive different optical lens sets, and for the USM, the screw motion of the rotor is transformed into a simple rectilinear motion by providing a third tube placed in the rotor and radially fixed relative to the stator, thus the zoom lens apparatus with focus adjusting produced with the combination can well maintain the stability of the optical axis, moreover, combining different driving methods integrates and make better use of lens sets of different functions, thus simplifying the overall structure. 
         [0008]    Hereinafter is given embodiments of the zoom lens apparatus with focus adjusting and optical imaging device according to the present disclosure with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic view showing a longitudinal section of the optical imaging device according to an embodiment of the present disclosure; 
           [0010]      FIG. 2  is an exploded view of part of the structure shown in  FIG. 1 ; 
           [0011]      FIG. 3  is a schematic view showing a longitudinal section of the optical imaging device according to another embodiment of the present disclosure; 
           [0012]      FIG. 4  is a schematic view showing a longitudinal section of the optical imaging device according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
       [0013]    A first embodiment of the zoom lens apparatus with focus adjusting according to the present disclosure comprises two independently controlled zooming and focusing structures, i.e., structure  20  and structure  60  as shown in  FIG. 1  and  FIG. 2 . The structure  20  driven by USM comprises a first tube  22 , a second tube  23 , a first set of piezoelectric elements  21  and a third tube  24 . The structure  60  is driven by voice coil motor (VCM). 
         [0014]    The threads  221  are formed on the inner surface of the first tube  22 . The second tube  23  with threads  231  on the outer surface thereof and threads  232  on the inner surface thereof is placed in the first tube  22 , wherein the thread pitch and/or the spiral direction of the threads on the outer surface is different from that of the threads on the inner surface. The threads  231  on the outer surface are arranged to match with the threads  221  on the inner surface of the first tube  22 . The first set of piezoelectric elements  21  attached on the outer surface of the first tube  22  is excited by electric signals to propel the first tube  22  to generate a traveling wave, so as to force the second tube  23  to rotate relative to the first tube  22 . 
         [0015]    The first tube  22  and the second tube  23  as well as the first set of piezoelectric elements  21  form a screw-driven USM, the exploded view of which is shown in  FIG. 2 . The first tube  22  may be called as a stator and the second tube  23  as a rotor. The first set of piezoelectric elements  21  may be the set of piezoelectric pieces shown in  FIG. 2  (e.g. a set of sheets made of piezoelectric ceramics) and is shaped as a regular polygon and attached on the outer surface of the stator by pasting or welding. Of course, the piezoelectric elements may also be other shapes and forms in other embodiments, as long as the stator can be vibrated to generate circumferential traveling wave. In other embodiments, the surfaces of the threads where the stator matching with the rotor may be treated to be abrasion resistant or coated with an abrasion resistant material; of course, other places referring to screw engagement may be treated in a similar process, which will not be described herein. A detailed description of the screw-driven USM may be referred to the PCT application No. WO2007118418. 
         [0016]    The third tube  24  with threads  241  formed on the outer surface thereof is placed in the second tube  23 , wherein the threads  241  are arranged to match with the threads  232  on the inner surface of the second tube  23 . The third tube  24  is radially fixed relative to the first tube, such that the third tube  24  is moved in a straight line alone the rotary axis of the second tube  23  during the rotation of the second tube  23 . The hollow portion of the third tube  24  is arranged to place a first optical lens set  25 , hence the third tube is also called as a lens tube. 
         [0017]    The VCM comprises a stationary portion and a movable portion, one of which includes a magnet and the other portion includes a conductor. The conductor is excited by electric signals to drive the movable portion to move in a straight line relative to the stationary portion, such that the motion path of the movable portion is parallel with the rotary axis of the second tube  23 . The movable portion of the VCM is arranged to fix a second optical lens set  61  thereon. 
         [0018]    A variant of the first embodiment of the optical imaging device according to the present disclosure comprises the aforesaid embodiment of the zoom lens apparatus with focus adjusting, accompanied with a first optical lens set  25 , a second optical lens set  61  and a photo sensor  15 , referring to  FIG. 1  and  FIG. 2 . The first optical lens set  25  having an optical axis parallel to the rotary axis of the rotor of the USM is placed inside the third tube  24 . The second optical lens set  61  having an optical axis identical to the optical axis of the first optical lens set  25  is fixed on the movable portion of the VCM. The photo sensor  15  having a photosensitive side perpendicular to the optical axis of the first optical lens set  25  is disposed on the optical path behind the second optical lens set  61 . Due to the characteristic of the USM such as small size, long stroke and etc., the first optical lens set  25  may be used for zooming. Owing to the mature processing of the VCM and the feature of small stroke thereof meeting the requirements for application of focus, the second optical lens set  61  may be used for focus. 
         [0019]    Referring to  FIG. 1  and  FIG. 2 , in other embodiments of the zoom lens apparatus with focus adjusting, a structure may be further applied to implement the lens tube radially fixed relative to the stator of the USM. Specifically, the structure comprises at least one rod  10  which is radially fixed relative to the first tube  22 . At least one through hole parallel to the rotary axis of the second tube  23  is formed within the wall of the third tube  24 . The rod  10  passes through the through hole of the third tube  24  such that the third tube  24  may be moved in a straight line along the rod  10  during the rotation of the second tube  23 . Of course, the lens tube may also be fixed radially by other ways, such as by the limit structure arranged at both ends of the lens tube. As for the structure, since the lens tube is fixed radially by the rod passing through the wall of the lens tube, the structure can not only be fixed simply, but also be independent with the lens tube; which not only ensures the stability of the optical axis of the optical lens sets installed inside the lens tube, but also make the manufacture and assembly of related components easier, thus achieving precision requirements. 
         [0020]    Since the rod  10  is used for fixing the lens tube, to make the lens tube immovable, at least one rod is needed. Considering a better force balance and the stability and accuracy of the structure, two rods are symmetrically disposed (as shown in  FIG. 1  and  FIG. 2 ) or multiple rods are uniformly distributed with respect to the rotary axis of the rotor. Of course, a same number of through holes are needed to be formed at corresponding positions on the wall of the lens tube. 
         [0021]    Referring to  FIG. 1  and  FIG. 2 , in other embodiments of the zoom lens apparatus with focus adjusting, a structure may be applied to implement the lens tube radially fixed relative to the stator of the USM. Specifically, the structure comprises a first base  11  having a hole  111  and a second base  12  having a hole  121 , wherein the first base  11  and the second base  12  are respectively provided with limit holes  112  and  122 , the first tube  22  is fixed on the first base  11 , and both ends of the rod  10  are respectively inserted or passed through the limit holes on the first base  11  and the second base  12 . Correspondingly, the structure of the stationary portion of VCM fixed relative to the first tube  22  is as follow: the stationary portion of VCM is fixed on a third base  14  which is fixedly connected to the second base  12  and used for holding the photo sensor  15 . As the rod  10  fixed relative to the first tube  22  is based on the first base  11 , the accuracy of design may be more easily to be ensured during the manufacture of components and the assembly may be more simple and reliable. Of course, in other embodiments, the rod  10  may also be implemented in other ways and forms to be radially fixed relatively to the first tube  22 ; for example, bending an end of the rod  10  and inserting or welding the bended end on the wall of the first tube  22 . 
         [0022]    Referring to  FIG. 1  and  FIG. 2 , in other embodiments of the zoom lens apparatus with focus adjusting, to ensure a better accuracy of assembly, a seventh tube  13  is provided. The first tube  22  is placed in the seventh tube  13 . One end of the seventh tube  13  is fixedly connected to the first base  11 , and the other end is fixedly connected to the second base  12 . A preferred structure of the seventh tube  13  fixedly connected to the two bases may be implemented by providing positioning holes and corresponding positioning protrusions formed on an end of the seventh tube  13  and corresponding base, snapping the positioning protrusions into the corresponding positioning holes, thus further increasing the precision of assembly. 
       Second Embodiment 
       [0023]      FIG. 3  shows a second embodiment of the zoom lens apparatus with focus adjusting according to the present disclosure. Compared with the first embodiment, in the second embodiment, an independently controlled focus structure, i.e., structure  40 , is added between the structure  20  and the structure  60  so as to meet a wider application requirement. 
         [0024]    The added structure  40  is similar to the structure  20  in that it is also a USM-driven structure. Specifically, the structure  40  comprises a fourth tube  42 , a fifth tube  43 , a second set of piezoelectric elements  41 , and a sixth tube  44 . 
         [0025]    Similar to the structure  20 , the fourth tube  42  and the fifth tube  43  as well as the second set of piezoelectric elements  41  form a screw-driven USM, wherein the fourth tube  42  is the stator of the USM, the fifth tube  43  is the rotor of the USM, and the sixth tube  44  is a lens tube whose hollow portion is used for accommodating an optical lens set  45 . The fourth tube  42  is fixed relative to the first tube  22 , and the rotary axis of the fifth tube  43  is same as that of the second tube  23 . The structural relationship among the fourth tube  42 , the fifth tube  43 , the second set of piezoelectric elements  41  and the sixth tube  44  is similar to that among the first tube  22 , the second tube  23 , the first set of piezoelectric elements  21  and the third tube  24 . It shall be noted that, though the structural relationship of the components in the structure  40  is same to that in the structure  20 , the dimensions of the components and the thread curve used between the components may be different so as to meet the requirements of different controlling precision, adjusted speed and running length. 
         [0026]    Yet one variant of the second embodiment of the optical imaging device according to the present disclosure comprises the aforesaid embodiment of the zoom lens apparatus with focus adjusting, accompanied with a first optical lens set  25  (which is USM-driven by the structure  20 ) for zooming, a second optical lens set  61  (which is VCM-driven by the structure  60 ) for focus, a third optical lens set  45  (which is USM-driven by the structure  40 ) for zooming compensation, and a photo sensor  15 , as shown in  FIG. 3 . The optical axes of the three optical lens sets are identical and parallel to the rotary axis of the rotor of the USM. 
         [0027]    Referring to  FIG. 3 , in other variants of the second embodiment of the zoom lens apparatus with focus adjusting, the two USM-driven structures is similar to the USM-driven structure mentioned in the First Embodiment, wherein the rod  10  is utilized to implement the lens tube radially fixed relative to the stator of the USM. The rod  10  may be shared by the structure  20  and the structure  40 . In an embodiment, there are two rods  10  symmetrically disposed with respect to the rotary axis of the rotor of the USM. 
         [0028]    Referring to  FIG. 3 , in other variants of the second embodiment of the zoom lens apparatus with focus adjusting, a structure may be applied to implement the lens tube radially fixed relative to the rotor of the USM. Specifically, the structure comprises a first base  11  having a hole and a second base  12  having a hole, wherein the first base  11  and the second base  12  are respectively provided with limit holes, the first tube  22  is fixed on the first base  11 , the fourth tube  42  is fixed on the second base  12 , and both ends of the rod  10  are respectively inserted or passed through the limit holes on the first base  11  and the second base  12 . 
         [0029]    Referring to  FIG. 3 , in other variants of the second embodiment of the zoom lens apparatus with focus adjusting, to ensure a better precision of assembly, a seventh tube  13  is provided. The structure  20  and the structure  40  are placed in the seventh tube  13 . One end of the seventh tube  13  is fixedly connected to the first base  11 , and the other end is fixedly connected to the second base  12 . Such structure may be more suitable for ensuring the parallel between the rod  10  and the rotary axis of the rotor of the USM and the consistency of the optical axes of the two optical lens sets. 
       Third Embodiment 
       [0030]      FIG. 4  shows a third embodiment of the zoom lens apparatus with focus adjusting and the corresponding optical imaging device according to the present disclosure. Compared with the First Embodiment, an optical path adjusting element is added in this embodiment. The optical path adjusting element is arranged on the optical path at front of the first optical lens set  25  for bending the optical path of the incident ray. For example, the incident ray is bended 90 degree by an added periscope structure  44  before entering the subsequent focus structure, thus the imaging device applied in mobile phone may be laid horizontally so as to reduce the height of the imaging device, thus meeting the thickness requirement of the devices such as mobile phones, etc. 
         [0031]    It should be noted that, the above described embodiments serve only to help to understand the present disclosure, but not to limit the protection scope of the present disclosure. It will be apparent to those of ordinary skill in the art that various modifications and variations can be made without departing from the scope or spirits of the present disclosure.