Abstract:
A zoom camera having a lens barrel assembly with adjustable focus and resolution power of photographing lens, the zoom camera including a zoom lens barrel assembly including a plurality of barrels for performing a zooming and focusing operation while reciprocating in a direction of an optical axis, the zoom lens barrel assembly being fixed on a camera body, a rotational barrel coupled to one of the lens barrels of the zoom lens barrel assembly and rotatable and movable in the direction of the optical axis for adjusting the focus of the lens, and a lens frame containing a lens and rotatably coupled to the rotational barrel for adjusting the resolution power of the lens.

Description:
This application claims priority of pending Korean Application No. 2003-23779, filed on Apr. 15, 2003. 
     FIELD OF THE INVENTION 
     The present invention relates to a camera, and more particularly, to a zoom camera having a lens barrel assembly that is designed to be capable of adjusting the focus position and resolution power of a lens to compensate the focus and resolution power errors often caused by a production tolerance during a manufacturing process of the lens barrel assembly. 
     BACKGROUND OF THE INVENTION 
     A zoom camera, whether it is a film type camera or a digital camera, generally includes a zoom lens barrel assembly having a zooming function for varying magnification (i.e., a focal length) of a photographing lens and a focusing function for varying a focal point in response to the distance to a subject. 
     The zoom lens barrel includes front and rear lens barrel assemblies. The rear lens barrel assembly includes a lens whose focal length may be slightly deviated from the optimal by a production tolerance. In order to adjust the deviated focal length, a plate having a predetermined thickness is inserted between the lens barrel and a film or between the lens barrel and a charging surface of a charge coupled device (CCD) in the course of assembling the lens to the lens barrel. Alternatively, a screw or a cam may be used to adjust the focal length. 
     The above-described adjusting methods have an advantage of accurately adjusting the focus at a central portion of the lens. However, there is still a problem that the focus at a periphery of the lens (i.e., a resolution power) may be varied due to the production and assembling tolerances, thus deteriorating a resolution power of the lens or the zoom camera. In this disclosure, adjusting of the focus means an adjustment or correction activity to make a lens barrel or a whole camera incorporating such a lens barrel to be in focus with respect to an infinity subject. 
     In order to adjust the focus and the resolution power at the periphery of the lens, the barrel should be disassembled, or the barrel should be rotated and reassembled, or the lens should be replaced with a new one, after which a test should be performed again. This may cause the increase of the working time, deteriorating the productivity. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a zoom camera having a zoom lens barrel assembly that substantially obviates one or more problems described above due to limitations and disadvantages of the conventional art. 
     It is an objective of the present invention to provide a zoom camera having a lens barrel assembly that can adjust the focus of the lens barrel assembly by adjusting the axial location of a lens, and also the resolution power at a periphery of a lens by rotating the lens for reorientation of the lens along the optical axis of the camera. 
     To achieve the object, the present invention provides a zoom lens barrel assembly for a camera, comprising: a plurality of lens barrels for performing a zooming and focusing operation while reciprocating in a direction of an optical axis; a rotational barrel coupled with one of the plurality of lens barrels and configured to rotate and move in the direction of the optical axis for adjusting the focus of the zoom lens barrel assembly; and a lens frame comprising a lens and rotatably coupled with the rotational barrel for adjusting a resolution power of the lens barrel assembly. 
     According to another aspect of the present invention, there is provided a zoom camera having a lens barrel assembly, the lens barrel assembly of the camera comprising: a plurality of lens barrels reciprocating in a direction of an optical axis for a zooming operation of the camera via a driving source of the camera; a lens guide ring coupled to one of the lens barrels and movable in the direction of the optical axis, the lens guide ring including a circumferential screw at an inner circumference of the lens guide ring; a rotational barrel including at an outer circumference a corresponding screw engaged with the screw of the lens guide ring for moving the rotational barrel in the direction of the optical axis by rotating the rotational barrel to adjust the focus of the camera, the rotational barrel including a rotation guide formed at an inner circumference thereof; and a lens frame comprising a lens, the lens frame coupled with the rotation guide of the rotational barrel and rotatable relative to the rotational barrel to adjust a resolution power of the camera. 
     According to still another aspect of the present invention, there is provided a zoom camera having a lens barrel assembly, the lens barrel assembly of the camera comprising: a plurality of lens barrels reciprocating in a direction of an optical axis for a zooming operation of the camera via a driving source of the camera; a lens guide ring coupled to one of the lens barrels and movable in the direction of the optical axis, the lens guide ring including a circumferential screw at an inner circumference thereof; a rotational barrel including at an outer circumference a corresponding screw engaged with the screw of the lens guide ring for moving the rotational barrel in the direction of the optical axis by rotating the rotational barrel to adjust the focus of the camera, the rotational barrel including first and second guide projections at an inner circumference thereof; and a lens frame comprising a lens, the lens frame including a third projection at an outer circumference thereof coupled with the first and second guide projections of the rotational barrel for rotating the lens frame relative to the rotational barrel to adjust a resolution power of the camera. 
     According to still another aspect of the present invention, the lens barrel assembly is first fixed on a jig. Then, when the rotational barrel is rotated in one direction by a tool (such as the pincette) inserted in a focus adjusting groove of the rotational barrel, the rotational barrel rotates and moves in the direction of the optical axis. As a result, the lens frame also moves together. The rotation of the rotational barrel is stopped by a worker at a location where the focus is accurately adjusted, and the rotational barrel and the fixing barrel are fixed to each other by, for example, a bonding process. In addition, when the lens frame is rotated by the tool inserted in a resolution power adjusting groove of the (rear) lens frame, the lens frame rotates, after which a worker fixes the (rear) lens frame on the rotational barrel at a location where the resolution power at the peripheral upper, lower, left and right portions of the lens becomes maximum while referring to the resolution power chart. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a front schematic view of a zoom camera according to one preferred embodiment of the present invention; 
         FIG. 2  is a plane view of  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of a lens barrel assembly of a zoom camera according to one preferred embodiment of the present invention; 
         FIG. 4  is a front view of the zoom ring depicted in  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of a rear lens barrel assembly according to one preferred embodiment of the present invention; 
         FIG. 6  is an assembled perspective view of the rear lens barrel depicted in  FIG. 5 ; 
         FIG. 7  is an assembled front view of  FIG. 5 ; and 
         FIG. 8  is a sectional view of a rear lens barrel assembly. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIGS. 1 and 2  show a camera according to one preferred embodiment of the present invention. 
     As shown in the drawing, a zoom camera comprises a camera body,  1 , a zoom motor  3  that is a zoom driving source and a power transmission gear group  5  for reducing the rotational force and transmitting the same to a barrel. 
     Provided on a top of the camera body  1  are tele and wide switches  7  and  9  and a release switch  11 . The tele and wide switches  7  and  9  are associated with a control circuit  13  received in the camera body  1  to drive the zoom motor  3 . 
     The zoom motor  3  is installed in the camera body  1  and is associated with the control circuit  13  such that it can rotate clockwise or counterclockwise in response to the operation of the tele and wide switches  7  and  9 , thereby realizing the zooming operations. 
     The power transmission gear group  5  comprises a first reduction gear  15  for transmitting driving force of the zoom motor  3 , a second reduction gear  17  engaged with the first reduction gear  15 , a third reduction gear  19  engaged with a second reduction gear  17 , and a fourth reduction gear  21  engaged with the third reduction gear  19 . The power transmission gear group  5  functions to reduce the driving force of the zoom motor  3  but the number of gears thereof is not limited to this embodiment. That is, the number of gears may be varied in accordance with the design of the cameras. 
     In addition, the fourth reduction gear  21  is engaged with a barrel idle gear  23  (see  FIGS. 1 and 3 ) to transmit the driving force of the zoom motor  3  to the zoom lens barrel assembly  25  so that portions of the barrel assembly can move in a direction of an optical axis for the zooming operation. 
       FIG. 3  shows an exploded perspective view of a zoom lens barrel assembly according to one preferred embodiment of the present invention. 
     As shown in the drawing, a lens base  27  is fixed on the camera body  1 . A plurality of helicoids grooves  27   a  are formed on an inner circumference of the lens base  27 . A reciprocal guide groove  27   b  is also formed on the inner circumference of the lens base  27  in a direction of the optical axis. The barrel idle gear  23  engaged with the fourth reduction gear  21  is coupled on an end of the lens base  27 . 
     A cam ring  29  is provided with a helicoids projection  29   a  that is engaged with the helicoids groove  27   a  to be movable in the direction of the optical axis while rotating. A gear  29   b  is formed next to the helicoids projection  29   a  and engaged with the barrel idle gear  23  such that it can rotate and move the cam ring  29  in the direction of the optical axis by receiving the driving force from the zoom motor  3 . 
     The cam ring  29  is provided at an inner circumference with a zoom ring guide helicoids groove  29   c  and a rear lens frame guide helicoids groove  29   d.    
     A guide ring  31  is coupled on a film side of the cam ring  29 . By a relative motion of the guide ring  31  to the cam ring  29  as will be described below, a zoom ring  35  can linearly move in the direction of the optical axis. 
     The guide ring  31  is provided at an outer circumference with projections  31   d,    31   e  and  31   f  that are engaged with linear guide grooves  27   b  (only one is shown in the drawing) formed on the inner circumference of the lens base  27  such that it can relatively slide in the direction of the optical axis while allowing relative rotation of the cam ring  29  with respect to the guide ring  31 . 
     The guide ring  31  is provided with linear guide members  31   a,    31   b  and  31   c  spaced apart from each other at a predetermined interval and extended in the direction of the optical axis. 
     A rear lens guide ring  33  is provided at an outer circumference with a plurality of cam pins  33   a  and  33   b  (only two is shown in the drawing with hidden one(s) omitted for simplicity purposes). The cam pins  33   a  and  33   b  are engaged with the rear lens guide helicoids groove  29   d  provided on the inner circumference of the cam ring  29  to allow the rear lens guide ring  33  to move in the direction of the optical axis. 
     The rear lens guide ring  33  is provided with three linear guide members  33   c,    33   d  and  33   e.  The rear lens guide ring  33  is provided at an inner circumference with a circumferential female screw  33   k  (see  FIG. 5 ). The circumferential screw groove  33   k  is screw-coupled with a rear lens barrel assembly  51  ( FIG. 5 ) that will be described later to allow the rear lens barrel assembly  51  to rotate and move in the direction of the optical axis, thereby adjusting the focus of a rear lens that will be also described later. 
     The zoom ring  35  is provided at an end of the outer circumference with a male helicoides  35   a  engaged with the zoom ring guide helicoids groove  29   c  of the cam ring  29  such that it can linearly move in the direction of the optical axis by the linear guide ring  31 . 
     As shown in  FIG. 4 , the zoom ring  35  is provided at an inner circumference with guide grooves  35   b,    35   c  and  35   d  in which the linear guide members  31   a,    31   b  and  31   c  of the guide ring  31  are inserted. Therefore, the zoom ring  35  is designed to linearly move in the direction of the optical axis by the linear guide members  31   a,    31   b  and  31   c.    
     The zoom ring  35  is further provided with guide grooves  35   e,    35   f  and  35   g  in which the linear guide members  33   c,    33   d  and  33   e  of the rear lens guide ring  33 . Therefore, the rear lens guide ring  33  is designed to relatively move in the direction of the optical axis with respect to the zoom ring  35 . 
     A shutter block  37  is coupled in the zoom ring  35 . The shutter block  37  is provided at an inner circumference with a helicoids portion  37   a  engaged with a front lens  40 . That is, the front lens  40  is provided at an outer circumference with a helicoids portion  40   a  inserted in the helicoids portion  37   a  of the shutter block  37 . A focus adjusting lever  41  is rotatably coupled on an outer circumference of a front lens barrel  43  fixed on an outer circumference of the front lens  40  and is provided with a projection  41   a  having a distal groove coupled with a focus adjusting pin  37   b  provided on the shutter block  37 . 
     Accordingly, the focusing operation of the front lens  40  is realized as the front lens  40  linearly moves while rotating. 
     Meanwhile, as shown in  FIG. 5 , the rear lens barrel assembly  51  is coupled on the rear lens guide ring  33 . The rear lens barrel assembly  51  comprises a rear lens frame  55  on which the rear lens  53  is coupled, a rotational barrel  57 , on an inner circumference of which the rear lens frame  55  is coupled, and a fixing plate  59  for preventing the rear lens frame  55  from separating from the rotational barrel  57 . 
     The rotational barrel  57  is provided at an outer circumference with a male screw engaged with the female screw  33   k  of the rear lens guide ring  33 . The rotational barrel  57  is provided at an inner circumference with first projections  57   b  that are disposed at an interval of 120° and second projections  57   c  that are disposed at an interval of 120°. Provided between the first and second projections  57   b  and  57   c  is a guide portion  57   d  allowing the rear lens frame to rotate in a circumferential direction. 
     The rear lens frame  55  is provided at an outer circumference with a plurality of third projections  55   a  that can be blocked by the first projections  57   b  of the rotational barrel  57  to suppress the movement of the rear lens frame  55  in the direction of the optical axis. Formed between the third projections  55   a  are grooves  55   b  in which the second projections  57   c  of the rotational barrel  57  can be inserted. 
     Likewise, the rotational barrel  57  and the rear lens frame  55  are engaged with each other such that the rear lens  53  cannot move in the direction of the optical axis but can rotate to change the orientation of the rear lens  53 . However, the structure of the rotational barrel  57  and the rear lens frame  55  are not limited to this particular embodiment. That is, any structures that do not allow its relative movement in the direction of the optical axis but permitting rotation there-between can be employed to the present invention. 
     The fixing plate  59 , as shown in  FIG. 8 , functions to prevent the rear lens frame  55  fitted within the rotational barrel  57  from being detached from the rotational barrel  57 . In particular, the fixing plate  59  is provided with a plurality of grooves  59   a  in which the second projections  57   c  of the rotational barrel  57  can be inserted. The fixing plate  59  is further provided with fourth projections  59   b  between the grooves  59   a  to stop the third projections  55   a,  thereby preventing the third projections  55   a  from being detached toward the subject. 
     That is, the rear lens barrel assembly  51  is coupled to the rear lens guide ring  33  such that it can move in the direction of the optical axis while rotating to adjust the focus of the rear lens  53 . The rear lens frame  55  is rotatably coupled on the rotational barrel  57  so that it is possible to adjust the resolution power by rotating the rear lens  53  clockwise or counterclockwise. 
     The rotational barrel  57  is provided with a focus adjusting groove  57   e  in order for a worker to be able to rotate the rotational barrel using a tool such as a pincette (see  FIGS. 5–7 ). The rear lens frame  55  is also provided with a resolution power adjusting groove  55   c  in order for the worker to be able to rotate the rear lens frame  55  using the pincette (see  FIGS. 5–7 ). 
     An operation process for moving the zoom lens barrel assembly in the direction of the optical axis will be described hereinafter. 
     When the tele or wide switch  7  or  9  is manipulated with the camera power turned on, the zoom motor  3  is driven to rotate the barrel idle gear  23  through the power transmission gear group  5 . As the barrel idle gear  23  is engaged with the gear  29   b  of the cam ring  29 , the cam ring  29  also rotates as the helicoids projection  29   a  of the cam ring  29  slides along the helicoids groove  27   a  of the lens base  27  to move in the direction of the optical axis. As the cam ring  29  and the guide ring  31  move in the direction of the optical axis, the rear lens guide ring  33  and the zoom ring  35  also move in the direction of the optical axis. 
     The front lens barrel  43  moves in the direction of the optical axis in response to the movement of the zoom ring  35 , thereby realizing a zooming operation. 
     A process for assembling the rear lens guide ring  33  with the rear lens barrel assembly  51  and a process for adjusting the focus and resolution power will be described hereinafter. 
     Describing first the process for assembling the rear lens guide ring  33  with the rear lens barrel assembly  51 , the second projections  57   c  of the rotational barrel  57  are first inserted through the grooves  55   b  of the rear lens frame  55  such that the third projection  55   a  of the rear lens frame  55  contacts the first projection  57   b  of the rotational barrel  57  so as to be stopped at a predetermined location. Then, the rear lens frame  55  is rotated in a direction, and the third projection  55   a  of the rear lens frame  55  is blocked to move backwards by the second projection  57   c  of the rotational barrel  57  so as not to be removed towards the subject but to be positioned at a predetermined location. As such, the outer circumference of the rear lens frame  55  can rotate along the guide portion  57   d  of the rotational barrel  57 . Furthermore, by rotating the fixing plate  59  in a direction with the second projections  57   c  of the rotational barrel  57  inserted through the grooves  59   a  of the fixing plate  59 , the third projections  55   a  of the rear lens frame  55  contact the fourth projections  59   b  of the fixing plate  59  in order to stop the rear lens frame  55  from being removed toward the subject. Since the fixing plate  59  has the first and second projections  59   a  and  59   b  spaced away from each other by an interval of 120°, it prevents the rear lens frame  55  from being removed even when the rear lens frame  55  rotates above a certain angle. 
     After that, the male screw formed on the outer circumference of the rotational barrel  57  is engaged with the thread groove  33   k  formed on the inner circumference of the rear lens guide ring  33 . 
     A process for adjusting the focus and resolution power will be described hereinafter. 
     The rear lens guide ring  33  and the rear lens barrel assembly  51  that are assembled to each other or a partly assembled zoom lens barrel assembly is first fixed on a jig. Then, when the rotational barrel  57  is rotated in a direction by a tool such as a pincette inserted in the focus adjusting groove  57   e,  the rotational barrel  57  rotates along the thread groove  33   k  of the rear lens guide ring  33  and moves in the direction of the optical axis. As a result, the rear lens  53  also moves together. As this point, the rotation of the rotational barrel  57  is stopped at a location where the focus is optionally realized, after which the rotational barrel  57  and the rear lens guide ring  33  are fixed to each other by, for example, a bonding process. 
     Thereafter, when the rear lens frame  55  is rotated by the tool inserted in the resolution power adjusting groove  55   c,  the rear lens frame  55  rotates. At this point, the rear lens frame  55  does not move in the direction of the optical axis, but only rotates. The worker then fixes the rear lens frame  55  on the rotational barrel  57  at a location where the resolution power at the upper, lower, left and right periphery becomes maximum while referring to the resolution power chart. 
     As described above, the zoom lens camera of the present invention is designed to adjust the focus as well as the resolution power by simply adjusting the front and/or rear lens groups, thereby improving the camera imaging quality. 
     Meanwhile, a film camera is generally designed to adjust its focus and resolution power by adjusting a rear lens group proximal to the film as described above while a digital still camera is often designed to adjust the focus and resolution power by adjusting a front lens group proximal to the subject. Even though the present invention has been described with embodiments adjusting the rear lens group, it is not limited thereto. Therefore, the present invention is applicable to adjust either the front or rear lens groups, accordingly, the present invention can be applied to both the film and digital still cameras. Likewise, utilizing a similar or equivalent construction as described in this disclosure or known in the art, adjustment of the focus and the resolution power of a zoom camera by adjusting the front lens group is particularly contemplated by this invention. 
     In addition, when there is a focus error and/or a resolution power error by the production tolerances of the optical components, since the barrel of the present invention is designed to be adjusted in a state where it is assembled and fixed on a jig, such errors can be effectively adjusted, thereby improving reliability of the products and reducing the manufacturing costs. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.