Abstract:
An arrangement for adjusting the position of a lens held in a barrel in a lens mounting for performing optical function such as focusing or zooming by moving an optical member or members along an optical axis as in the interchangeable objective. The barrel is divided into two parts each containing a lens, and the relative positions of the first and second barrels are infinitely adjusted by a cam.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an adjusting device for a lens mounting which enables the separation between optical elements and the fall of an optical member in a direction perpendicular to the optical axis to be adjusted. 
     2. Description of the Prior Art 
     As a conventional example, there is Japanese Laid-Open Patent Application No. SHO 56-77807 (entitled &#34;Lens Separation Adjusting Device&#34;, in which an end surface of the axial length of one lens barrel is provided with a plurality of stair-like stepped portions, and an end surface of the axial length of another lens barrel is provided with a projected portion corresponding to the aforesaid stepped portion, so that when these two barrels are connected to each other, the aforesaid projected portion abuts on the one of the step surfaces of the aforesaid stepped portions which provides the required lens separation. Because the axial distance between the successive two of the stepped portions is relatively long, there is a drawback that infinitely fine spacing adjustment is impossible to carry out. 
     Also, after the spacing has been adjusted to the prescribed value, both barrels are fixedly secured to each other by set screws on the outer periphery thereof. Therefore, there is another drawback that the tightening on the outer periphery causes deformation of the barrel, giving a bad influence on the optical performance. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to improve the drawbacks of the above-described conventional device, and to provide a lens mounting which enables the spacing between two optical elements to be adjusted in the axial direction while observing the optical performance by the measuring instrument. 
     To achieve this object, in a lens mounting according to the invention, one end of a first barrel is provided with first and second camming surfaces of similar form to each other positioned in axially displaced concentric relation, and one end portion of the outer surface of a second barrel is provided with an engagement portion having a third camming surface in contact with the aforesaid second camming surface, and a fourth camming surface almost similar to the third camming surface, whereby when the second barrel is turned about the optical axis relative to the first barrel, the second barrel moves axially forward or backward. Thus, the spacing between optical elements in the first and second barrels can be infinitely adjusted to establish a best optical performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a relay lens barrel. 
     FIG. 2 is a sectional view of the barrel of FIG. 1. 
     FIG. 3 is a sectional view in enlarged scale of the main part of FIG. 2. 
     FIG. 4 is an expanded view of the cam portion of the relay barrel. 
     FIG. 5 is a longitudinal section view of a zoom lens mounting to which the invention is applied. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 to 5 illustrate an embodiment of the invention applied to the relay barrel of a zoom lens mounting. 
     As shown in FIG. 5, the zoom lens comprises a focusing lens unit I, a variator lens II, a compensator lens III and a relay lens unit IV. A first barrel 1 holding a front part IVa and IVb of the relay lens unit IV, has a plurality of first camming surfaces 1a, 1a, 1a, . . . , formed on one end surface, and a plurality of second camming surfaces 1b, 1b, 1b, . . . , substantially similar to the aforesaid first camming surfaces, positioned axially inward from the aforesaid one end and displaced radially inward. The first camming surfaces 1a, 1a, . . . are provided with a plurality of threaded screw-holes 1c, 1c, . . . , or tap holes, for securing a second barrel 4. The inner periphery of the first barrel 1 has a fit surface 1d for the second barrel 4. The first barrel 1 is fixed to a secured barrel 2 by a screw 3. The second barrel 4 holds lenses IVc and IVd of the relay lens unit IV. The outer periphery of the barrel 4 is provided with projected portions 4a having third camming surfaces 4b, 4b, . . . for engagement with the second camming surfaces 1b, 1b, . . . of the aforesaid first barrel 1. The surfaces of the projected portion 4a opposite to the camming surfaces 4b, have fourth camming surfaces 4c, 4c, . . . substantially similar to the third camming surface 4b. The width 4a&#34; of the projected portion 4a is formed wider than the step difference between the first and second camming surfaces 1a and 1b. A retainer member 5, for fixedly securing the second barrel 4 to the first barrel 1 under pressure, is formed with an L-shaped cross-section and has an over-bored hole for a screw fastener 6. 
     6 is the screw fasteners by which the retainer member 5 is secured to the first barrel 1; 7 is a mount member for position determination on a camera; 8 is a fixed barrel having a bayonet ring for coupling to the camera; 9 is an index ring; 10 is an operating ring which, upon axial movement, effects zooming and, upon rotation about the optical axis, effects focusing; 11 is a linearly movable barrel arranged to move axially when zooming; 12 is a key member for restraining the barrel 11 from rotation; 13 is a longitudinally elongated guide groove provided in the fixed barrel 2 and engaging with the key 12; 14 is a cam ring for controlling the movements of a variator cell 15 and a compensator cell 16; 17 is a focusing lens cell arranged, upon rotation of the operating ring 10, to move axially to effect focusing. 
     In the construction of the aforesaid embodiment, only main parts are described below. 
     When the second barrel 4 is inserted into the first barrel 1 at the inner peripheral fit surface 1d, the third camming surfaces 4b of the second barrel 4 abut on the second camming surfaces 1b of the first barrel 1. When the second barrel 4 is turned about the optical axis in a direction of arrow A with respect to the first barrel 1, the second barrel 4 axially moves according to the lead of the camming surfaces 4b,  thereby adjusting the separation between the lenses IVb and IVc of the relay lens unit IV. 
     When the separation has been adjusted to a prescribed value, the retainer members 5 are put on the fourth camming surfaces 4c of the second barrel 4, and then fixedly secured to the first barrel 1 by the screw fasteners 6. Thus, the second barrel 4 is fixedly secured to the first barrel 1. At that time, the projected amount (l in FIG. 3) of the camming surface 4c of the second barrel 4 out of the first camming surface 1a of the first barrel 1 is ensured to be substantially constant at any angular position of the second barrel 4. Also when securing the second barrel 4 to the first barrel 1, as a slight clearance is provided between the inner peripheral fit surface 1d of the first barrel 1 and the outer diameter of the projected portions 4a of the second barrel 4, it is also possible to perform adjustment even in a direction radial to the optical axis. 
     As has been described above, by such a simple construction that the camming surface of the first barrel abuttingly contacts with the camming surface of the second barrel, an advantage is produced that the axial air separation between two optical elements in the respective barrels can be infinitely finely adjusted. Also because the second barrel can be fixedly secured in a direction parallel to the optical axis, there is another advantage that without causing deformation of the barrels and without badly influencing the optical performance, the adjusting and securing operation can be carried out easily and quickly. 
     Further, because of the presence of a radial clearance between the first and second barrels, another adjustment in a direction radial to the optical axis can be carried out at the same time. 
     In the above-described embodiment, since the axial adjustment of the position of the second barrel member 4 relative to the first barrel member is carried out by rotating the former about the optical axis, the leads of the first and second camming surfaces 1a and 1b are equalized so that the distance, l, (in FIG. 3) does not change despite the rotation of the second barrel member 4, and always has a constant value. Therefore, the tightening force of the retainer member 5 can be maintained constant. 
     Recently developed plastic molding techniques are able to finish molded products to a very high precision in size. On this account, the first camming surface 1a of the first barrel member 1 may be formed not to a cam, but to a plane-like end surface, and the above-identified distance, l, may be set to a minimum, while the front and rear camming surfaces 4b and 4c of the projected portions of the second barrel member 4 may be equalized to each other in the lead.