Abstract:
A zoom lens system is provided including a flat cam for driving the zoom lens mechanism. In one particular embodiment, the same flat cam used by the zoom lens system is used to correlate the effective focal length of the zoom lens to the viewfinder. Additional particular embodiments of a viewfinder adjustment mechanism are provided wherein the viewfinder adjustment mechanism includes a diopter adjustment mechanism to adjust the ocular lens of the viewfinder to compensate for imperfections in the user&#39;s sight.

Description:
PRIORITY  
       [0001]    The present application claims priority from co-pending provisional patent application serial number 60/413,079, Filed on Sep. 23, 2002, entitled IMAGE CAPTURE DEVICE and co-pending provisional patent application serial No. 60/488,927, Filed on Jul. 21, 2003, both entitled IMAGE CAPTURE DEVICE, and additionally co-pending provisional patent application serial No. 60/450,556, Filed on Feb. 27, 2003, entitled VIEWFINDER DIOPTER LENS ADJUSTMENT MECHANISM. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to image capture devices and more particularly, to a zoom optical system for an image capture device.  
         BACKGROUND OF THE INVENTION  
         [0003]    In the interest of making cameras smaller with thinner profiles, optical zoom mechanisms are being necessarily scaled down. Often, the lens barrels of a camera that are responsible for zooming are driven by a cam. There is a need for a zoom mechanism wherein the zoom lens barrels and the driving cam mechanism can be made appropriately compact.  
           [0004]    Also, in a camera having an optical zoom lens, there is a problem of correlating the zoom effect undergone by the zoom lens with the scene shown to the user through an optical viewfinder.  
           [0005]    When viewing a scene through a viewfinder, it is sometimes necessary to fine tune the viewfinder assembly to accommodate for less than perfect vision of the photographer.  
           [0006]    What is needed is a zoom optical system that can be made compactly and still be accurately experienced by the user.  
         SUMMARY OF THE INVENTION  
         [0007]    A zoom lens system is provided including a flat cam for driving the zoom lens mechanism.  
           [0008]    In one particular embodiment, the same flat cam used by the zoom lens system is used to correlate the effective focal length of the zoom lens to the viewfinder.  
           [0009]    Additional particular embodiments of a viewfinder adjustment mechanism are provided wherein the viewfinder adjustment mechanism includes a diopter adjustment mechanism to adjust the ocular lens of the viewfinder to compensate for imperfections in the user&#39;s sight.  
           [0010]    Other particular features and embodiments will become apparent from the following detailed disclosure of the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings an exemplary embodiment that is presently preferred, it being understood however, that the invention is not limited to the specific methods and instrumentality&#39;s disclosed. Additionally, like reference numerals represent like items throughout the drawings. In the drawings:  
         [0012]    [0012]FIG. 1 is a front plan view of the image capture device in accordance with one embodiment of the present invention, wherein a lens cover has been opened to expose the taking lens and viewfinder front apertures.  
         [0013]    [0013]FIG. 2 is a rear plan view of an image capture device in accordance with one particular embodiment of the present inventions.  
         [0014]    FIGS.  3 - 7  are views of a zoom lens device in accordance with one particular embodiment of the present invention.  
         [0015]    FIGS.  8 - 11  are views taken from differing angles of a flat cam in accordance with one particular embodiment of the present invention.  
         [0016]    [0016]FIG. 12 is a top perspective view of zoom lens housing in accordance with one particular embodiment of the present invention.  
         [0017]    FIGS.  13 - 20  and  22 - 23  are various views of a viewfinder assembly in accordance with one particular embodiment of the present invention.  
         [0018]    [0018]FIG. 21 is a perspective view of a portion of the zoom lens housing including a cam flat and viewfinder assembly in accordance with one particular embodiment of the present invention.  
         [0019]    FIGS.  24 - 26  are partial perspective views of a cam flat with noise reducing spring in accordance with one particular embodiment of the present invention.  
         [0020]    [0020]FIG. 27 is a perspective view of a spring useful with one embodiment of the present invention.  
         [0021]    [0021]FIG. 28 is bottom elevational view of a cam flat in accordance with another embodiment of the present inventions.  
         [0022]    [0022]FIG. 29 is a bottom elevational view of viewfinder guide levers and an adjustment plate in accordance with another embodiment of the present inventions.  
         [0023]    [0023]FIGS. 30 and 31 are top and bottom elevational views, respectively, of the guide levers of FIG. 29 in combination with the cam flat of FIG. 28.  
         [0024]    [0024]FIG. 32 is a partial cut-away view of a viewfinder assembly showing one embodiment of a diopter adjustment mechanism in accordance with one embodiment of the present invention.  
         [0025]    [0025]FIG. 33 is a partial perspective view of a portion of a diopter adjustment mechanism in accordance with one particular embodiment of the present invention.  
         [0026]    [0026]FIG. 34 is an isometric view of a diopter adjustment mechanism including a detent spring in accordance with one particular embodiment of the present invention.  
         [0027]    [0027]FIG. 35 is a partial perspective view of a portion of an image capture device including one embodiment of a diopter adjustment mechanism of the present invention.  
         [0028]    [0028]FIG. 36 is a partial perspective view including a translucent portion showing an internal portion of one embodiment of a diopter adjustment mechanism of the present invention.  
         [0029]    [0029]FIG. 37 is a partial perspective view of an image capture device including one embodiment of a diopter adjustment mechanism of the present invention.  
         [0030]    [0030]FIG. 38 is a partial front plan view of an image capture device including one embodiment of a diopter adjustment mechanism of the present invention.  
         [0031]    [0031]FIG. 39 is a partial perspective view of a portion of an image capture device showing details of a part of one embodiment of a diopter adjustment mechanism.  
         [0032]    [0032]FIG. 40 is a partial perspective view of an image capture device without the back shell showing the front view of one embodiment of a diopter adjustment mechanism.  
         [0033]    [0033]FIG. 41 is a perspective view showing the rear portion of some of the diopter adjustment mechanism components.  
         [0034]    [0034]FIG. 42 is a perspective view showing the rear portion of some of the diopter adjustment mechanism components.  
         [0035]    [0035]FIG. 43 is a rear cutaway perspective view showing the rear portion of some of the diopter adjustment mechanism components.  
         [0036]    [0036]FIG. 44 is a rear partial perspective view of a diopter adjustment mechanism installed through the back shell of an image capture device in accordance with one embodiment of the present invention.  
         [0037]    [0037]FIG. 45 is a top plan cut-away view of a diopter mechanism having the mechanism housing removed shown in accordance with one embodiment of the present invention.  
         [0038]    [0038]FIG. 46 is a top plan cut-away view of a diopter mechanism in accordance with one embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]    Before explaining the disclosed embodiments of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.  
         [0040]    The Image Capture Device Housing Referring now to FIGS. 1 and 2, there is shown an image capture device  10  made in accordance with one particular embodiment of the present invention. Image capture device  10  includes a front housing  12  and a rear housing  14  that matingly engage to surround the internal workings of the image capture device  10 . A compartment door  15  may engage either or both of the front and rear housings  12  and  14  to provide access to a battery compartment and/or to output connectors. Such output connectors may be used to connect the image capture device  10  to an external device such as a television, a computer a printer, a cell phone, etc.  
         [0041]    Front housing  12  of image capture device  10  includes a plurality of apertures formed therethrough, such as a taking lens/viewfinder window  12   a , an aperture  13  for a red eye reduction mechanism and a flash window  18 . When the lens door is open, as shown in FIG. 1, the taking lens aperture  17   a  and viewfinder aperture  17   b  of the lens mask  17  are exposed.  
         [0042]    Rear housing  14  additionally includes a plurality of apertures therethrough. For example, the rear housing  14  of the present particular embodiment includes openings a rotary switch  24 , nested tactile switch  26 , a rotary diopter adjustment knob  28 , an LCD display  30  a view finder rear aperture  32  and signal indicators  34 . Other user interface devices, buttons and switches may be included.  
         [0043]    A battery door  15  extends across an aperture through a side face of the image capture device  15 .  
         [0044]    The Zoom Mechanism  
         [0045]    The image capture device  10  may include a zoom mechanism. One particular embodiment of a zoom mechanism that may be used with the image capture device  10  will now be described in connection with FIGS.  3 - 12 . Housed in a zoom housing  450  are the two zoom barrels, front barrel  460  and rear barrel  470 . Aligned on the optical axis through the front and rear barrels  460 ,  470  is an image sensor  475 . Other elements may be included in the overall lens design, such as, a shutter lens  370 , a focusing lens  455  and glass plate  476 .  
         [0046]    The distance between the front barrel  460  and the rear barrel  470  determines the magnification factor of the image between the wide angle (FIGS. 38 and 39) and the telephoto positions (FIGS. 40 and 41). In the present particular embodiment, a linear cam flat  480  controls the zooming of the image capture device  10  by locating the front and rear lens barrels  460 ,  470  at discrete positions, each with the barrels  460 ,  470  a predetermined distance apart.  
         [0047]    The cam flat  480  is directly coupled with one barrel (in the present embodiment, the front barrel  460 ) of the zoom lens via the zoom coupling linkage  498  and is coupled to the other barrel  460  by a zoom lever  490 . The cam flat  480  is located on and guided by the zoom housing  450 . Guides are realized on the zoom housing  450  by two straight ribs  452 ,  454  and counter surfaces  456 ,  457 ,  458  on the zoom housing  450 . These ribs  452 ,  454  and counter surfaces  456 ,  457 ,  458  define the position of the cam in two directions and permit only linear motion. For example, the ribs  452 ,  454  interact with linear grooves  481   a  and  481   b  defined on the bottom surface of the cam flat  480 . If desired, tracks, such as tracks  482   a  and  482   b , may additionally be defined on the cam flat  480  to interact with the counter surfaces  456 ,  457 ,  458 . Due to the counter surfaces  456 ,  457 ,  458  contact with the surface, the zoom housing provides a 3 point guide for the cam flat  450 . Three small areas near these points but in opposite directions serve the same function. This permits the cam flat  480  to operate even if there is a slight deflection or if there is variation to the tolerances during manufacture, but without a loss of performance.  
         [0048]    Additionally, misalignment of the straight ribs  452  and  454  would create high friction or prevent free movement of the cam flat  480 . This is avoided by reducing the guide lengths  481   a ,  481   b  inside the cam flat  480  to a minimum. Therefore an additional deflection of the cam flat  480  and/or misalignment of the straight ribs  452 ,  454  will not deteriorate the guide quality.  
         [0049]    The non-proportional movement of the zoom lever  490  is realized by the cam profile  482  inside the cam flat  480 , which generates the relative positions of both barrels as defined by an optical calculation. As such, when the cam flat  480  advances linearly, the rear barrel  470  is advanced linearly by an amount not directly proportional to the amount of advancement of the cam flat  480 , as defined by the cam profile  482 . In contrast to this, it can be seen that the front barrel  460 , which is directly coupled to the cam flat  480 , will be moved by an amount proportional to (if not the same as) the amount moved by the cam flat  480 . The integral cam profile  482  followed by the lever  490 , is optimized in order to have the lever  490 , and correspondingly the lenses, follow a particular optical prescription which incorporates a non-proportional motion.  
         [0050]    A spring  495  (chosen to be a torsion spring in the present embodiment) is supported on the zoom housing  450  by a pin  450   a  and presses a finger  471  on the rear barrel  470  against the zoom lever  490 , which in turn leans on the inner side of the cam profile  482  to make it follow the prescribed path when the cam flat  480  is moving. A second supporting spring  496  (FIG. 41), which in this particular embodiment, has also been chosen to be a torsion spring, is used to generate an additional force on the cam flat  480 . The reason for this spring  496  in this embodiment is to ensure that the cam flat  480  is biased so as to create a force in the direction of arrow Z (FIG. 37) against the nut  500  (FIG. 37) of the driving device, regardless of the position or direction of travel of the cam flat  480 . The driving mechanism chosen for the present embodiment includes a stepping motor  510  with a threaded lead screw  512  that passes through the nut  500 . Nut  500  includes a finger that passes through an aperture in the cam flat  480  in order to stabilize the nut  500  so that when the threaded lead screw  512  is rotated, the nut  500  does not rotate. The engagement between the cam flat  480 , the nut  500  and the threaded lead screw  512  permits the motor to advance and retract the cam flat  480 .  
         [0051]    Note that in the present embodiment, the cam profile  482  is chosen to be very shallow towards the tele position (and deeper in the wide position) and the force vector of the pin  491  of the zoom lever  490  is nearly zero in the linear direction (not considering friction).  
         [0052]    The coupling zoom linkage  498  creates the direct link between the cam flat  480  and the front barrel  460 . It is stiff and acts in a push/pull linear manner for precise movement of the front barrel  460 , but is flexible for torsion and deflection to compensate for misalignment of the cam flat. The coupling zoom linkage  498  is attached to connector portions  485   a  and  485   b  on the side of the cam flat  480 , and is similarly attached to the frame of the front lens barrel  460  at connector portions  460   a  and  460   b.    
         [0053]    As can be seen from the zoom curve profile, in operation, when the cam flat is advancing away from the motor  510 , the directly linked front lens group  460  is additionally advancing away from the motor  510 , while the rear group is moving towards the motor  510  and away from the front lens group  460 . Similarly, when the cam flat  480  and front lens group  460  are moving towards the motor  510 , the rear lens group  470  is moving away from the motor  510  and towards the front lens group  460 . As such, it can be seen that during operation of the present particular embodiment, the front and rear lens barrels  460 ,  470  are always moving in the opposite direction from each other. A finger  465  on the front lens barrel  460  may be used in connection with a photointerrupter (not shown) to inform a processor of the precise location of the lens barrel  460 .  
         [0054]    One particular method of assembling the mechanism in a simple fashion will be described. In this method, the zoom lever  490  is mounted first, then the barrels  460 ,  470 , and the cam flat  480  is placed last. During assembly, the zoom lever  490  is moved beyond its operational position. At that time the cam flat  480  is slid into place on the housing  450  and the zoom lever  490  is rotated into its position through the open side  483   a  of the cam profile  483 . The coupling zoom linkage  498 , is then mounted to the front lens barrel  460  and fixed onto the cam flat  480 . Also at this time, the cam drive stepping motor  510  will be engaged with the cam flat  480  at the cam flat yoke  484  and with the nut  500 .  
         [0055]    It should be understood that other methods of assembling the zoom lens mechanism may be used. Additionally, although in the described embodiment the front barrel  460  is linked to the cam using the cam zoom linkage  498  and the rear barrel  470  using the lever  490 , with a slight modification to the cam profile  483 , the cam zoom linkage  498  may be used to drive the rear group  470  and the lever  490  used to drive the front group  460 .  
         [0056]    Referring now to FIGS.  24 - 26 , there is shown another embodiment of a cam flat  610 , that may be used in the above described system in place of cam flat  480 . The cam flat  610  engages the zoom housing  450 , as described above in connection with cam flat  480 . Additionally, the bottom surface of the cam flat  610  includes the cam profiles, as described in connection with cam profile  483 .  
         [0057]    Similarly, the cam flat  610  will be driven by the cam drive stepping motor  510 . As with the earlier described embodiment, cam drive stepping motor  510  includes a threaded lead screw  512  that passes through the nut  500 . The threaded lead screw  512  rests on a cam flat yoke  625 , made in the shoulder portion  620 . The nut  500  mates with the threaded lead screw  512  on the opposite side of the shoulder  620  from the stepping motor  510 .  
         [0058]    The cam flat  610  includes on the upper surface thereof, a channel defined by the walls  630   a ,  630   b  and the rear wall of the shoulder  620 . A finger  500   a  on the nut  500  is captured in the channel, by the spring  650 . The spring  650  is captured at one end by a spur  640  that extends from the upper surface of the cam flat  610  and is fixed at the other end using a hole  622 , through the shoulder  620 . One leg of the spring clip  650  is used to provide a low force to bias the finger  500   a  axially (perpendicular to the axis of rotation of the lead screw  512 ) against the inner surface  630   c  of the wall  630   a , to stabilize the nut  500 .  
         [0059]    Without the spring  650 , the metal nut of the zoom drive would create a noise when the stepping motor was activated. Friction between the nut  500  and the lead screw  512 , created by a relatively large axial force on the thread, creates oscillation of the nut  500  as far as mechanically permitted by the channel. The axial friction between the nut  500  the cam flat walls is not enough to prevent this oscillation. It is undesirable for the nut  500  to be too tight against the shoulder  620  because misalignment of the cam flat  610  needs to be compensated for, and additionally, there needs to be as little external forces on the cam flat  610  as possible to achieve the highest possible efficiency.  
         [0060]    The spring  650  provides a low force to keep the nut  500  pressed against the cam flat  610  at the reference surface  630   c . Additionally, the spring  650  provides a tolerance for the axial displacement of the nut  500  from the cam flat  610  if the motor should overrun a mechanical stop of the cam flat  610 . When the motor  510  reverses, proper alignment is re-established, as the nut  500  is maintained in place relative to the threaded lead screw  512  by the spring  650 . Additionally, as described above, the spring  650  discourages the oscillation of the nut, and reduces the amount of noise made by the drive mechanism.  
         [0061]    If desired, the cam flat  610  may be similar to the cam flat  480  in all other respects.  
         [0062]    Referring now to FIG. 27, there is shown a spring  650 ′, which may be used in one embodiment of the present invention. The spring  650 ′ includes an engagement portion  650   a ′ for engaging a structure on the cam flat, such as the spur  640  of FIG. 16. Additionally, an open end  650   b ′ of the spring  650 , may be used to further engage a structure on the cam flat, such the hole  622  of FIGS. 17 and 18. To cause such engagement, the legs  650   g ′ and  650   d ′ may be pinched towards each other until the ends  650   e ′ and  650   f ′ can be inserted into the hole  622 , as with the operation of a safety pin. The spring  650  additionally includes a spring bias bent portion  650   c ′ to create a spring bias on the leg  650   d′.    
         [0063]    Please note that the use of the spring  650 ′ as the spring  650  in FIGS.  24 - 26  is not meant to be limiting. It can be seen how other forms of torsion springs and/or compression springs can be used in connection with the embodiment of FIGS.  24 - 26  to bias the finger  500   a  against a portion of the cam flat  610 , to stabilize the nut and reduce noise.  
         [0064]    A Viewfinder Mechanism  
         [0065]    Referring now to FIGS.  13 - 23 , there will be shown a viewfinder mechanism through which the user can view the scene at the same effective magnification chosen by zoom mechanism. A viewfinder housing  550  is located adjacent to the zoom housing  450  (see FIG. 55). All viewfinder lenses are captured in the viewfinder housing  550 . The viewfinder housing  550  additionally contains two prisms  557 ,  559 , for directing the view of the user around a turn in the housing  550 . The middle lens  565  and the rear lens  560  are guided in the lower portion on pins  575  and  570 , which are cylindrical in the present particular embodiment.  
         [0066]    In the upper portion, pins  560   a  and  565   a  (part of the lenses  560  and  565 , respectively) are being guided within a slot (not shown) in the viewfinder cover. An extension spring  580  pushes the rear and the middle lenses  560 ,  565  apart from one another (See FIGS.  49 - 51 ) to allow a constant force on the lens levers  590  and  595 . The two lens levers  590  and  595  are captured by an adjustment plate  600 . Additionally, pins on the free ends of the levers  590 ,  595  are captured in grooves  486  and  487  on the cam flat  480 , respectively. The levers  590 ,  595  are driven by the same cam flat  480  as the zoom mechanism, which correspondingly moves the rear and middle lenses  565  and  560  of the viewfinder due to the contact between the lens levers  590 ,  595  and the lens frame tabs  575   a  and  565   a . As such, as the lens levers  590 ,  595  move together and apart based on the profiles of the cam grooves  486  and  487  on the cam flat  480 , the viewfinder experiences an apparent zooming view that corresponds to the effective zooming action experienced at the image sensor due to the cam flat  480  moving the front and rear zoom barrels  460 ,  470  of the zoom lens mechanism.  
         [0067]    The middle lens lever  595  couples to the middle lens  565  by a connector bearing  565   a . The arrangement of the connector bearing  565   a  is such that it always pulls the lenses into one sideways, direction, thus preventing an erratic sideways motion of the middle lens  565  during zooming. No additional spring is necessary for the prevention of erratic sideways movement.  
         [0068]    The rear lens lever  590  interacts with a slanted surface on the pin of the rear lens, which also prevents sideways motion. As such, the two levers  590 ,  595  are driving, by means of the cam flat  480 , the two movable zoom lenses  560 ,  565  according to the designated motion with the use of only one spring. The spring  580  is captured in a unique way by forcing the lenses always against the lever bearing connection. Backlash is relatively eliminated and a smooth motion of the viewfinder zoom action is secured. The additional connector bearing piece prevents an erratic sideways motion of the lenses during zoom activation.  
         [0069]    Referring now to FIGS.  28 - 31 , there is shown an alternate embodiment of the design of a cam flat  700  including first and second viewfinder guide grooves  710  and  720 , respectively, and an alternate embodiment of a zoom lens guide groove  730 . Due to the altered design of the cam grooves in the cam flat  700 , the first and second guide levers  740  and  750 , respectively, have been redesigned to work with the cam groove profiles of the cam flat  700 . As with the other embodiments, the first and second viewfinder guide levers are pivotally fixed to an adjustment plate  760 . The guide levers  740  and  750  engage the cam flat at pins  745  and  755 , respectively, and follow the viewfinder guide grooves  710  and  720  when the cam flat  700  is moved. The remaining free ends of the guide levers  740  and  750  are used to bias the viewfinder lenses, as described in connection with the above embodiments. Note that in the present embodiment, unlike the previously described embodiment secures the guide lever  750  to the adjustment plate  760  using a pivot pin  770  located at the distal end of the adjustment plate  760  instead of in the middle of the guide lever, as with the pivot pin  780  of the present embodiment, or as with the embodiment of FIGS.  13 - 21 .  
         [0070]    Tuning the Viewfinder During Assembly  
         [0071]    Referring now To FIGS.  21 - 23 , the rear lens lever  590  and the middle lens lever  595  are captured on an adjustment plate  600 . The adjustment plate is located on the zoom structure by a bearing rivet  605 , although other means of attachment are possible. An accentor pin  610  is riveted to the adjustment plate as well and guided between a slot of the zoom structure. By turning the accentor pin  610  clockwise or counter clockwise, the adjustment plate  600  can be rotated around the bearing rivet  605 . The rear lens lever  590  can now be moved in a rotary motion and in return, through the connection between the rear lenses, moves the rear lens forward and backwards. The rear lens can now be adjusted in the viewfinder lens system to correct any deviation between the lenses. The accentor pin  610  at the same time is being held by friction (in the present embodiment, by the use of a washer) against unwanted rotation. By mounting the two lens levers  590 ,  595  on one rotational adjustment plate  600  and by the use of one accentor pin  610 , an easy adjustment (using merely a screwdriver, in the present embodiment) of the viewfinder lens system is possible.  
         [0072]    Viewfinder Diopter Adjustment  
         [0073]    Referring now to FIGS. 2 and 32- 34 , there is shown one particular embodiment of a viewfinder diopter adjustment mechanism that may be used with an image capture device, such as image capture device  10 . The viewfinder eye lens (diopter lens)  32  is adjusted using a knob  28  mounted to the rear housing  14 . The eye lens  32  is mounted to the viewfinder housing  550  by means of slot  550   a , in which tab  32   a  is seated. The slot includes enough clearance for the tab  32   a  to move forward and back, in response to rotation of knob  28 . However, rotation of the knob  28  would be limited by the confines of the slot, such that when the tab  32   a  would hit the front or back end bearing surfaces of the slot, the knob  28  could not be turned further. As will be described below, a detent spring or mechanism may be included to prevent the rotation of the knob to these extremes. The slot bearing area is closed and secured by the viewfinder housing cover (see FIG. 47). Opposite the tab  32   a , an arm  325  connects the lens  32  to a bearing pin  310 . A protrusion  325   a  is located on the planar face of the arm  325 , opposite the planar face supporting the bearing pin  310 .  
         [0074]    One end  310   a  of the bearing pin  310  is located in a cylindrical hole in the viewfinder housing  150 . A compression spring  300  mounted coaxially around the bearing pin  310  biasing the protrusion  325   a  against a rotational cam  28   a  resembling, a helical ramp, which is incorporated within the diopter knob  28 . The rotational cam  28   a  is located in a bearing hole of the back cover  14  of the image capture device  10 . By rotating the diopter knob  28  clockwise or counterclockwise, the cam  28   a  inside the diopter knob  28  rotates, moving the diopter lens forward or backward, as the protrusion  325   a  is biased against portions of the ramp having greater or lesser heights. This movement of the diopter lens enables the user to adjust the sharpness of the viewfinder zoom lens system. As can be seen more particularly in FIG. 23, the coil spring  300   is  compressed between a bearing shoulder on the bearing pin  310  and the viewfinder housing  150 . As the knob  28  is rotated, the compression spring  300  maintains the protrusion  325   a  in contact with the cam  28   a  based on the force on the bearing shoulder of the bearing pin  310  compressing or decompressing the spring  300  against the viewfinder housing  150  as the cam ramp  28   a  height increases or decreases, respectively. As can be seen, the change in height of the ramp  28   a  results in a corresponding linear movement of the viewfinder diopter lens  32 .  
         [0075]    Additionally, a detent spring  320  having a frictional spring arm  320   a  is connected to the diopter knob  28  against the inner surface  14   b  of the rear housing  14 . Inner surface  14   b  should include a number of detent notches, not shown, with which to engage the frictional spring arm  320   a  when the diopter knob  28  is turned. This serves to capture the frictional spring arm  320   a  to prevent unintentional movement of the diopter knob  28 . The detent spring  320  can be used as a friction position device or as a detent mechanism. The diopter knob  28  may be fastened to the rear cover by means of a heat stake or ultrasonic welding.  
         [0076]    Referring now to FIGS.  35 - 46 , there is shown another embodiment of a diopter adjustment mechanism in accordance with the present invention. The image capture device includes a back shell  810  upon which is located a mechanism cover  812  for the viewfinder diopter adjustment mechanism. Additionally located on the rear cover  810 , is the viewfinder ocular lens or diopter lens  814 , the position of which is adjusted by the diopter adjustment mechanism of the present invention. Extending through the mechanism cover  812  is the diopter wheel  816 . Diopter wheel  816  is a toothed gear rotatable by the thumb or finger of the user.  
         [0077]    Referring now to FIGS.  36 - 40 , beneath the diopter mechanism cover  812 , the diopter wheel  16  is mounted on a bearing pin or post  818  extending from the back shell  810 . The teeth of the diopter wheel engage the teeth of the diopter knob gear  820 , as shown. Additionally, an end position stop block  822  is molded on the back shell  810 , near the post  818 . The end positions of the diopter wheel  816  are determined by a slot  816   a  configured in the rear surface of the diopter wheel  816  and by the stop block  822  on the back shell  810 . As such, the diopter wheel  816  may be adjusted clockwise/counterclockwise to the limits of the slot  816   a , until the stop block  822  contacts an end of the slot  816   a  and stops the diopter wheel  816  from turning any further in that direction. As will be discussed more fully below, the diopter knob gear  820  additionally includes an alignment point  
         [0078]    Referring now to FIGS.  41 - 46 , there is shown the interaction between the diopter wheel  816 , the diopter knob gear  820  and the movement of the diopter lens  814 . The reverse of the diopter knob gear  820  has a raised ramp  820   c  of steadily increasing height and being disposed in a predetermined relationship to the alignment point  820   a . Additionally, the reverse portion of the diopter knob gear  820  is heat staked to a detent spring  830  at heat stake portions  820   b . The detent spring  830  includes a spring arm  830   a  which seats in position indentations  810   a  in the back shell  810 . Rotation of the diopter wheel  16  causes the diopter knob gear  820  to correspondingly rotate and to turn the detent spring  830  such that spring arm  830   a  rests and locks in the discrete locations defined by the indentations  810   a , to keep the gear  820  from drifting.  
         [0079]    Additionally, the viewfinder ocular lens  814  includes a cam following arm  835  extending outward therefrom. The cam following arm  835  rests against the top surface of the ramp  820   c . A bearing pin  837  including a spring  840  thereround, which continuously biases the cam following arm  835  against the ramp  820   c . When the detent knob gear  820  rotates clockwise/counter-clockwise, the cam following arm  835  follows the ramp  820   c , which converts the rotational motion of the knob gear  820  into linear motion of the ocular lens  814 . The bearing pin  837  fits into a recess  842  in the image capture device body  845 , thus ensuring that the spring  840  constantly applies pressure between the image device body and the cam following arm  835 , maintaining the arm  835  in continuous contact with the ramp  820   c . As the cam follower arm  835  follows the ramp  820   c , the ocular lens  814  of the viewfinder moves linearly along the viewfinder axis X (FIG. 45). As can be understood, the present diopter adjustment mechanism is for fine-tuning of the viewfinder ocular/diopter lens only. The viewfinder ocular lens&#39; maximum amount of linear movement along the viewfinder axis X is defined by the total change in height ramp  820   c  portion that the arm  835  is permitted to travel, based upon the final positions of the stop block  822  in the groove  816   a  (FIG. 38).  
         [0080]    While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.