GB612531A - Improvements in or relating to combined view finders and range finders for photographic cameras - Google Patents

Abstract

612,531. View and range-finders for photographic cameras. ROTHSCHILD, W. J. April 6, 1946, No. 101691. [Class 98 (i)] A combined view and range-finder comprises (1) an inverted Galilean telescope with a semireflecting mirror c between the objective a and eyepiece b serving to reflect the rangefinder beam into the eyepiece after this beam has passed through a second negative lens d of the same power as, but smaller than, the objective a and at the same optical distance from the eyepiece b as the objective; (2) a frame k in the range-finder beam at the principal focus of the view-finder eyepiece, and outside the field of the lens d, i.e. in a position such that after reflection in the mirror c the rays of light from all points on the frame emerge as a parallel beam and a virtual image of the frame appears superimposed on the object under observation, the size of the frame being chosen to indicate the correct field of view, and the frame being illuminated by light from the object through an aperture in the camera wall; and (3) means to deflect the range-finder beam according to the focusing movement of the camera lens, or according to a dial marked in distance, which means may be a prism e rotatable about a pivot e<1>, or rotary wedges or a variable angle prism. The frame k may be viewed through a positive annular lens surrounding, and maybe integral with, the lens d, and may be formed by lines engraved on a glass plate into which light is admitted through a polished edge. With interchangeable camera lenses, several interchangeable frames or a multiple frame may be used.