Abstract:
Three elongate, circular rods are secured to the inner peripheral surface of a lens barrel to extend axially thereof and in angularly spaced relation to each other. Each of two cylindrically shaped lens housings is mounted coaxially in the barrel for axial adjustment therein by means of three sets of rollers, each of which sets is mounted on the housing to have rolling, point engagement with a different one of the rails. At least one set of rollers on each housing is urged resiliently into rolling engagement with the associated rail, and each housing is connected to one of two camming rings which is rotatably mounted on the barrel to effect axial adjustment of the housings.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to optical zoom lens systems, and more particularly to an improved guiding mechanism for controlling the moving parts or elements in such a lens system. It has long been customary in zoom lens systems of the type described, to employ ball bearing rollers for guiding moving parts of a zoom lens within the lens barrel. It has also been customary heretofore to employ in such lens barrel various parts which are mounted for sliding movement relative to each other to effect variation in magnification of an observed object. Lenses of the type described are frequently employed in motion picture photography and television broadcasting, which usually demand the highest of image quality. Typically such a zoom lens system includes in the lens barrel two movable sets of lenses, the first or forward group of lenses being disposed to vary the angle of view, the second set being operative to restore the focus upon adjustment of the first group. 
     Among the disadvantages of prior such zoom lenses has been the difficulty encountered in accurately, and in some instances quietly, moving the respective sets of lenses. Such prior art devices also require a nearly polished finish on the inner bore wall of the lens barrel, thus contributing significantly to the manufacturing costs of the lens systems. 
     Accordingly, it is an object of this invention to provide an improved optical zoom lens system of the type described in which the lenses can be moved accurately and with precision not heretofore available. 
     Still another object of this invention is to provide an improved guiding mechanism for moving parts of an optical zoom lens system of the type described, which mechanism is easier to manufacture and is longer lasting than prior such guiding mechanisms. 
     Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     The tubular barrel of a zoom lens mechanism has secured in the bore thereof a plurality (three in the embodiment illustrated) of elongate, circular rods which are secured to the inner peripheral surface of the barrel to extend axially thereof and in angularly spaced relation to each other. Each of a plurality of cylindrically shaped lens housings are mounted coaxially in the bore of the barrel for axial adjustment therein by means of a plurality of sets of rollers on each housing, each of which sets on each housing has rolling, point engagement with a different one of the rails. One set of rollers on each housing is urged resiliently into rolling engagement with the associated rail, while the other two sets of rollers in such housing are rotatable about axes which are fixed with respect to the associated housing. Each housing has thereon a pin which projects through a slot in the barrel and into a cam groove formed in one of two different zoom or camming rings which are rotatably mounted on the barrel. The rolling point contact between the rails and the rollers on the housing, significantly improve the accuracy and life of the mechanism. 
    
    
     THE DRAWINGS 
     FIG. 1 is an elevational view of an elongate cylindrical lens barrel containing two zoom lens housings or cells and the improved mechanism for adjusting the housings longitudinally of the lens barrel, the zoom ring containing the cam slots for manipulating the lens housings being shown only fragmentarily; 
     FIG. 2 is an end view of the lens barrel and associated parts as seen when looking in the lower end of the lens barrel as shown in FIG. 1; 
     FIG. 3 is a fragmentary sectional view taken generally along the line  3 — 3  in FIG. 2 looking in the direction of the arrows, the two lens housings, however, being shown in full; 
     FIG. 4 is a slightly enlarged sectional view taken generally along the line  4 — 4  in FIG. 3 looking in the direction of the arrows, and illustrating an end view of one of the two lens housings mounted for adjustment in the lens barrel; 
     FIG. 5 is a bottom plan view of the lens housing shown in FIG. 4, when viewed along the line  5 — 5  in FIG. 4 looking in the direction of the arrows; and 
     FIG. 6 is a perspective view of the lens housing shown in FIG. 5 when such housing is viewed from the side thereof diametrally opposite to the surface shown in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings by numerals of reference,  10  denotes generally a tubular lens barrel having intermediate its ends an elongate tubular section  12  of uniform outer diameter, and extending between circumferential flange sections  13  and  14  of slightly larger diameter that are formed on opposite ends respectively of barrel  10 . Barrel  10  has therethrough an axial bore defining in the barrel an inner, annular bore wall  15  having therein an annular recess  16  for use in mounting in one end of the barrel a front lens (not illustrated) of conventional design. The bore wall  15  has releasably secured thereagainst, and at equi-angularly spaced points about the axis thereof, three elongate, cylindrical guide rods  17 ,  18  and  19 , which extend parallel to each other and longitudinally of barrel  10 . 
     To secure the rods  17 - 19  to wall  15 , barrel  10  has fixed therein, and adjacent each end thereof, three, similarly shaped, locating pins  21 , which are secured at one end in the barrel  10  and project at their opposite ends radially inwardly from the bore wall  15  at equi-angularly spaced points thereabout. Adjacent opposite ends thereof each of the rods  17 ,  18  and  19  has one diametral side thereof seated against a pair of the pins  21 , as shown for example in FIG. 3, and is engaged at its diametrally opposite side by the cone-shaped heads of two screws  22 , the shanks of which are releasably threaded into the bore wall  15 . Thus, each of the guide rods  17 ,  18  and  19  is secured in a stationary position against a pair of pins  21  by the cone-shaped heads of a pair of screws  22 . 
     Mounted for axial adjustment within the bore of barrel  10  are two cylindrically shaped lens housings or cells, which are denoted generally by the numerals  25  and  26 . The lenses and mountings therefor in housings  24  and  25  may be of conventional design and therefore are not described in detail herein. In a manner to be described in greater detail hereinafter, each of the lens housings  25  and  26  is supported on the three guide rods  17 ,  18  and  19  for axial adjustment selectively in opposite directions in the lens barrel  10 . The means for supporting the respective housings  25  and  26  on the guide rods  17 - 19  is the same for each housing, so the mounting means will be described in detail in connection with the housing  25 , but it will be understood that the housing  26  will be supported in the same manner for movement on the guide rods  17 - 19 . 
     Referring now to FIGS. 4 to  6 , and first to FIG. 5, the housing  25  has formed in the outer peripheral surface which confronts upon the guide rod  17 , a rectangularly shaped recess  31  having a flat or planar bottom surface. The midsection of a generally S-shaped spring rod  32  is secured against the bottom of recess  31  by the cone-shaped head of a screw  33 , the shank of which is threaded into the bottom of recess  31  to urge the midsection of the spring  32  against a pair of pins  34  which are fixed to and project upwardly from the bottom of recess  31 . Spring element  32  has spaced, parallel end sections  35  each of which is supported resiliently outwardly from the bottom of recess  31 , and has rotatably mounted thereon a roller  36 , which rotates in a registering recess  37  formed in the adjacent end of the housing  25 . As shown in FIGS. 3 and 4, the rollers  36  are thus urged by the spring element  32  resiliently into rolling engagement with the peripheral surface of the guide rod  17 , whereby the rollers  36  in effect, have point contact with the periphery of the guide rod  17 . As noted above, the mounting and guide means for the lens housing  26  are the same as for the housing  25 , so that as indicated in FIG. 3, housing  26  has a similar set of rollers  36  that have rolling engagement with guide rod  17 . 
     In addition to the recess  31 , housing  25  has therein in its outer peripheral surface two additional, rectangular recesses  41  and  51 , respectively. The center of recess  41  is angularly spaced from the center of the recess  31  by 120°, while the center of recess  51  is likewise spaced 120° from the center of recess  31  and the center of recess  41 . Instead of having in recess  41  an S-shaped spring member of the type denoted by numeral  32 , recess  41  has secured against opposite sides thereof (adjacent opposite ends of housing  25 ) a pair of wheel mounting pins or axles  45  opposite ends of which are secured against the adjacent end wall of recess  41  by the cone-shaped heads of a pair of screws  43 . Rotatably mounted on each pin  45  intermediate the ends thereof is a ball bearing wheel  46 , which is rotatable in a registering recess  47  formed in the adjacent end of the housing  25 . The wheels  46 , as shown in FIGS. 3 and 4, have rolling, point engagement with the outer peripheral surface of the guide rod  18 . In the manners similar to that of the pins or axles  45 , the recess  51  has secured therein adjacent opposite ends of housing  25  a pair of axles or pins  55 , each of which is secured adjacent opposite ends thereof beneath the cone-shaped heads of a pair of screws  53  which secure the associated pin  55  in a stationary position at one end of the recess  51 . Intermediate its ends each pin  55  has rotatably mounted thereon a ball bearing wheel which rotates in a registering recess  57  formed in the adjacent end of the housing  25 . Each of the wheels  56  of the lens housing  25 , as shown in FIG. 4, has rolling, point contact with the outer peripheral surface of the guide rod  19 , as the housing  25  is shifted axially in barrel  10 . Although not illustrated, it will be understood that housing  26  is guided by a similar pair of rollers that having rolling point contact with the guide rod  19 . 
     From the foregoing it will be apparent that each of the housings  25  and  26  has rotatably mounted thereon three pairs of ball bearing wheels  36 ,  46  and  56 , respectively, the wheels of each pair being rotatably mounted adjacent opposite ends, respectively of each such housing. Moreover, only one pair of wheels, wheels  36 , are spring-loaded into rolling engagement with the guide rod  17 . The remaining two pairs of wheels,  46  and  56 , however, are mounted to rotate on axles  45  and  55 , respectively, which are secured against movement in the associated recesses  41  and  51 . 
     Referring again to FIGS. 1 to  4 , it will be noted that each housing  25  and  26  has projecting from the upper end thereof, as illustrated in the drawing, a cylindrically shaped guide pin  25 ′ and  26 ′, respectively, each of which pins projects slidably through an elongate guide slot  12 ′ (FIG. 1) formed in section  12  of the lens barrel to extend longitudinally between opposite ends thereof. Pins  25 ′ and  26 ′ also extend at their outer ends slidably into a pair of near helically shaped cam grooves  61  and  62  (FIG. 1) formed in the inner peripheral surfaces of a pair of conventional zoom rings  63  and  64  that are mounted on section  12  of the lens barrel  10  for rotation relative thereto in a manner that will be known to one skilled in the art, to effect corresponding axial movements of the lens housings  25  and  26  in barrel  10 . 
     From the foregoing it will be apparent that the present invention provides a very accurate and more inexpensive guide mechanism or means for repeatedly and accurately adjusting the zoom lenses of the type carried by housing  25  and  26  accurately to achieve the desired magnification and focus of the mechanism. The point contact between the guide rods  17 - 19  and the associated ball bearing wheels  36 ,  46  and  56  of the respective lens housings  25  and  26 , provide simple, point contact between the wheels and the associated guide rods thereby reducing not only wear of the equipment during axial adjustment of the housings  25  and  26 , but also reduces the effort required to make such adjustments. The guide rods  17 - 19  preferably are precision ground steel rods, thus providing extremely hard, smooth contact surfaces necessary for precision motion of housings  25  and  26  and they eliminate the need for providing a highly polished finish on the interior bore of barrel  10  as was previously required by known zoom lens mechanisms. 
     While this invention has been illustrated and described in detail in connection with only certain embodiments thereof, it will be apparent that it is capable of still further modification, and that this application is intended to cover any such modification as may fall within the scope of one skilled in the art, or the appended claims.