GB562438A - Improvements in or relating to lens systems - Google Patents

Abstract

562,438. Lens systems. KODAK, Ltd. Dec. 28, 1942, No. 18425. Convention date, Feb. 9. [Classes 97 (i) and 98 (i)] In a lens system, flare-producing reflections. from refracting surfaces forming an air space are reduced by a zero power light filter movable into and out of said air space. The filter may be inserted only when the system is being used at low apertures ; and its mount may be coupled with the diaphragm-setting means so that the filter is inserted automatically at a certain stage in the reduction of the aperture. In one form, for a photographic camera, a slide having a large unobstructed aperture and also a small aperture covered by a neutral density filter is displaceable across the lens axis independently of the diaphragm - setting apparatus. In another, a similar slide 37, Fig. 4, serving also as a diaphragm regulator, has a series of diaphragm apertures 31, 32 &c., of which those smaller than a certain value, are all covered by a neutral density filter 36 ; and in this form the adjacent unobstructed aperture 33 and obstructed aperture 34 are of the same size, so that in changing from one to the other the light diminution is effected solely by the filter 36. In a form of the automatic kind, the diaphragm is set by turning a ring 41, Fig. 6, bearing an aperture index 40 and a cam 42 which, as the aperture is changed from F/5.6 to F/8 rocks a pivoted mount 44 so as to move a filter 46 carried therein into operative position 44<1>. Preferably, in this form also, the size of the aperture is not changed as the index 40 passes from F/5.6 to F/8, and this may be provided for by employing a modified adjusting means in which the diaphragm is set by a surrounding toothed ring operated by a mutilated gear on a shaft carrying also a second mutilated gear which is adapted, when the gap in the firstmentioned gear encounters the diaphragmoperating ring, to operate through a toothed wheel the pivoted mount of the filter so as to bring the filter into the optical axis, whereafter the second-mentioned gear disengages, and the first-mentioned gear resumes its drive on the diaphragm-operating ring.