GB1054994A - - Google Patents

Abstract

1,054,994. Zoom lenses. K. VOCKENHUBER and R. HAUSER. March 9, 1964 [March 8, 1963; May 10, 1963], No.9779/64. Heading G2J. A variable focal length objective is provided with a fixed focus setting by arranging that the full depth of field available is usable at every focal length setting. This is accomplished by automatically moving one of the members during changes of focal length so that one of the two planes defining the depth of field is maintained at a constant distance from the image plane at all focal lengths. As shown, Fig. 3, members 101, 102, are movable during zooming but a small additional movement is superimposed on member 101, such as by shaping the controlling cam somewhat differently from what it would otherwise be, so that at one particular aperture setting, e.g. the maximum aperture, the curves 110, 111, Fig. 5 (not shown), showing the variation with focal lengthf of the limiting planes defining the depth of field are such that one plane, in this case the further plane, curve 110, is at a constant distance from the image plane. By a constant displacement of the front member 101 independently of focal length, the entire depth of field can be displaced towards the objective and curves 113, 114 are obtained. Similarly by another constant displacement curves 116, 117 are obtained. Thus by having detents for the front member a suitable set of curves can be readily provided as the curves overlap so much and thereafter during zooming no separate close-up adjustment is necessary.