| 摘要 |
1,061,741. Photographic objectives. K. VOCKENHUBER. March 2, 1964 [March 1, 1963], No.8776/64. Heading G2J. In a zoom photographic objective it may be difficult to place the diaphragm in the desired position as the aperture may have to be varied in accordance with the focal length to keep the relative aperture constant and accordingly the objective 1, 2, 3, Fig. 1 which forms an image at B1 is provided with an inverting system 7 which transforms the intermediate image at B1 into a real image at B2 in the plane of the film the diaphragm being placed at B1II between B1 and B2 so that in effect an image of the diaphragm is formed at B1II by means of a field lens 6 adjacent B1. As shown applied to a zoom lens wherein negative lens 3 is movable to effect variation of focal length and positive lens 1 is moved to compensate for image shift, the effective position B1II of the diaphragm varies according to the focal length. A viewfinder semi-transparent mirror 9 may be inserted before the diaphragm so that the image at B3 viewed by eyepiece 10 does not vary with aperture setting. The inverting system may have a magnification differing from unity so that an objective producing an intermediate image suitable for 8 mm film can have a magnifying inverting system associated therewith to produce an image for 16 mm film. Alternatively an objective for 16 mm film can be used with 8 mm film. To produce a zoom ratio of 10 to 1 or more an objective (33)-(35), Fig. 10 (not shown) having a movable negative member (34) is associated with an inverting system (37) which is also movable so that part of the variation in focal length is caused by member (34) and part by system (37). Moreover if due to variation of member (34) the intermediate image position varies, this can be corrected by suitable movement of system (37) so that the final image (B2) is in a constant plane. Numerical data are provided for the focal lengths of the various members and their spacings for six examples. |
