Optical apparatus having a mount

Abstract: An optical apparatus having a mount molded of plastic comprises a mount sliding surface formed on the mount and providing a fiducial surface in the direction of the optic axis, and a depression formed in the area of a parting line during molding on the mount sliding surface.

Description: This invention relates to an optical apparatus according to the preamble of claim 1. Heretofore, mounts for optical apparatuses such as camera bodies, interchangeable lenses, intermediate tubes and various converters have been made by cutting and machining a metallic material. Such mounts are known from the document EP-A-0 037 623 describing an optical apparatus according to the preamble of claim 1. As a practical matter, it has been difficult for the following reasons to use a mount for an optical apparatus molded of plastic as a product: (1) If a material excellent in slidability is used with importance attached to the operability of mounting or dismounting a mount, the mechanical strength of the mount will become weak and the mount will be readily damaged when a force is applied to a lens barrel or the like. Also, if a reinforcing material such as glass fiber is much mixed to increase the strength of plastic, the operability of mounting or dismounting the mount will become worse. (2) During molding, burrs are produced on the parting lines of a metal mold and if these burrs lie at a locations which are important in surface accuracy, the optical performance will become worse. It is the object of the invention to provide an optical apparatus having a mount, which is lower in cost and compact, and by means of which an accurate and smooth movement of a lens group can be accomplished. This object is achieved by means of the features defined in claim 1. Preferable embodiments are defined in the subclaims. In the following the present invention is further illustrated by embodiments with reference to the enclosed figures. Figure 1 is a cross-sectional view of an interchangeable lens barrel of an optical apparatus according to a first embodiment. Figure 2 is a perspective view of only the cam plate of Figure 1. Figure 3 is a forward perspective view of only the essential portions of Figure 1. Figure 4 is a rearward perspective view of only the essential portions of Figure 1. Figure 5 is a perspective view showing the essential portions of a second embodiment. Figures 1 to 4 show a first embodiment of the present invention. Figure 1 is a cross-sectional view containing the optic axis of an interchangeable lens barrel including a bayonet mount, Figure 3 is a perspective view of the essential portions of the interchangeable lens barrel of Figure 1, as they are seen from the front, Figure 4 is a perspective view of the said essential portions as they are seen from the rear, and Figure 2 is a perspective view of the cam plate shown in Figure 1. In Figures 1 to 4 the reference numeral 101 designates a bayonet mount made by injection molding of plastic, the reference character 101a denotes a support member of a support portion molded integrally with the mount during the molding of the mount and extending in the direction of the optic axis, and the reference character 101b designates bosses forming a part of said support portion which are also molded integrally with the mount during the molding of the mount and into which rods may be forced. This bosses 101b are formed with apertures into which the rods may be forced. The reference character 101c denotes a positioning projection formed at the tip end of the support member 101a. The reference numeral 102 designates a guide rod holding plate formed with apertures 102a for supporting the other ends of guide rods 103. One end of the guide rods 103 is forced into and supported by the boss 101b and the other ends are inserted in the apertures 102a in the plate 102 and supported thereby. The reference numeral 104 denotes a cam plate, the reference character 104a designates an aperture at the center of rotation of the cam plate, the reference characters 104b and 104c denote cam slots, the reference numeral 105 designates a screw for the rotary shaft of the cam plate 104, the reference numeral 106 denotes a forward group lens moving frame, the reference character 106a designates the sleeve portion of the moving frame 106, the reference character 106b denotes a cam pin integral with the moving frame 106, the reference numeral 107 designates a rearward group lens frame, the reference character 107a denotes a sleeve integral with the lens frame 107, the reference character 107b designates a cam pin integral with the lens frame 107, the reference numeral 110 denotes protective glass, and the reference numeral 111 designates a screw. L1 denotes a forward group lens, and L2 designates a rearward group lens. In the above-described construction, one end of the guide rods 103 is firmly forced into the aperture in the boss 101b of the bayonet mount 101 so as not to come out readily. The plate 102 positioned at a proper location by the relation thereof with the aperture 102b into which the positioning projection 101c is inserted is fixed to the end portion of the support member 101a of the bayonet mount 101 by the screw 111. Also, the other ends of the guide rods 103 are fitted in and supported by the apertures 102a in the plate 102. Inserted into and supported by the central aperture 104a in the cam plate 104 is the screw 105 fixed to the support member 101a, and the cam plate 104 is rotatable about the screw 105. The forward group moving frame 106 holding the forward group lens holding frame 108 therein by a helicoid thread is supported on the guide rod 103 for movement in the direction of the optic axis by the sleeve 106a. The rearward group lens frame 107 also has its sleeve 107a held on the guide rod 103 for movement in the direction of the optic axis. The cam pins 106b and 107b protruding from the forward group lens holding frame 108 and the rearward group lens frame 107 fit in the cam slots 104b and 104c, respectively, in the cam plate 104 without back-lash, and the lens frames 108 and 107 can be moved in the direction of the optic axis by the action of the cam as the cam plate 104 is rotatively moved. Figure 5 shows a second embodiment. In Figure 5, the reference numeral 131 designates a bayonet mount, the reference character 131a denotes a support member, the reference character 131b designates bosses into which rods are forced, and the reference numeral 132 denotes guide rods. In the present embodiment, as in the first embodiment, the guide rods 132 are forced into and supported by the bayonet mount 131 molded of plastic, but where the guide rods 132 are short, the plate 102 shown in the first embodiment is eliminated to thereby attempt to achieve further compactness and reduced cost. As described above, in the embodiments of Figures 1 to 5, the bayonet mount of the inter-changeable lens is molded of plastic, and one end of the guide rods which are guide members for the moving lens is forced into the bayonet mount to thereby ensure the distance between the guide rods. In the first embodiment, the otehr ends of the guide rods are supported by a plate, whereby the distance between the portions of the rods which are adjacent to the plate (the other ends) is also determined accurately. Thus, the plurality of guide rods can maintain their parallel state. Also, the plate is guided and fixed at a proper position by the positioning projection provided on the end portion of the support member for the bayonet mount, whereby the plurality of guide rods are prevented from torsion and are corrected so as to become parallel to the optic axis. As a result, it has become possible to eliminate the cylindrical fixed cylinder which has heretofore been necessary and it has also become possible to force the guide rods directly into the bayonet mount which provides the reference for mounting the mount on the camera body, without the intermediary of any other member, thereby making the support accuracy of the moving lens group higher than before. Further, the fact that the cylindrical fixed cylinder has become unnecessary leads to the possibility of using an inexpensive cam plate in place of the conventional cylindrical cam cylinder, and this also leads to the great effect of compactness and reduced cost. In the embodiments of Figures 1 to 5, when the mount to be mounted and dismounted with respect to the camera body is molded of plastic, the support portion for supporting the guide rods as guide members for the lens group is also molded integrally with the mount and thus, the guide rods are substantially directly supported by the mount. Accordingly, the positional accuracy of the guide rods can be made high correspondingly to the mount which provides the reference of the optical position, and accurate and smooth movement of the lens group can be accomplished. Also, by the guide rods being supported by the mount, it also becomes possible to eliminate the cylindrical fixed cylinder which has heretofore been necessary for supporting the guide rods and thus, there can be provided acompact interchangeable lens barrel, and the elimination of the fixed cylinder further leads to the possibility of providing an interchangeable lens barrel which will not become bulky even if an inexpensive cam plate is used as a cam member. Also, by a support member for movably supporting said cam plate being molded integrally with said mount during the molding of said mount, there can be provided an interchangeable lens barrel which is still lower in cost and compact.

Claims: An optical apparatus having a mount (101), said optical apparatus comprising: a lens group (L1; L2); and a movement mechanism for moving said lens group in the direction of an optical axis; characterized by a support portion (101b, 101a), for supporting a member for regulating a movement of said lens group in said movement mechanism, said support portion being molded of plastic integrally with said mount. An optical apparatus according to claim 1, wherein said member is a guide rod (103) for moving said lens group only in the direction of the optical axis. An optical apparatus according to claim 1, wherein said member is a cam (104) having a cam portion for moving said lens group. An optical apparatus according to claim 2, wherein said supporting portion is a cylinder (101b) into which said guide rod (103) is inserted. An optical apparatus according to claim 3, wherein said supporting portion (101a) is possible to move said cam (104) only in a predetermined direction and is formed extending out in the direction of the optical axis. An optical apparatus according to claims 3 or 5, wherein said cam (104) is plate-like. An optical apparatus according to claims 5 or 6, wherein said support portion (101a) is plate-like. An optical apparatus according to any one of claims 1 to 7, further comprising: a cylinder portion extending from said mount in the direction of the optical axis and molded integrally with said mount to reinforce said mount. An optical apparatus according to claim 8, wherein the fixing of mount to the body of said optical apparatus is accomplished by screw-setting said cylinder portion. An optical apparatus according to claim 9, wherein the screw-set position of said cylinder portion is set within the phase of a bayonet pawl of said mount. An optical apparatus according to claim 8, wherein an optical lens is held by said cylinder portion. An optical apparatus according to claims 9 or 10, wherein said cylinder portion is disposed near the outer diameter of said mount. An optical apparatus according to claim 11, wherein said cylinder portion is disposed near the inner diameter of said mount. An optical apparatus according to any one of claims 1 to 13, wherein said optical apparatus is an interchangeable lens.

Inventors: IIZUKA TOSHIMI, IIZUKA, TOSHIMI
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1990
Main classification: G02B7
IPC codes: B29C33, G02B7