Patent ID: 6064835
Filing Date: 2000-05-16
Classification: G03B

Abstract:
A field frame comprising:a reference field frame with its center arranged in line with an optical axis;two L-shaped field switch means which are movably arranged opposite to each other with respect to the optical axis;a driving means for displacing said L-shaped field switch means relatively to each other so that the combination of said L-shaped field switch means can produce a rectangular space by the inner-angles of said L-shaped field switch means, whereupon a part of the visual field of said reference field frame is laterally or longitudinally concealed by the presence of said rectangular space, whereby an aspect ratio of said field frame can be changed;each of said L-shaped field switch means having a dowel pin and two elongated holes; the main body of said reference field frame having two dowel pins; and said L-shaped field switch means being superposed on each other on said reference field frame in such a manner that said elongated holes are superposed and said dowel pins of said reference field frame are disposed in the superposed elongated holes;said elongated holes being disposed in the ends of legs of said L-shaped field switch means, said legs having inner edges that meet at the juncture of said legs, said inner edges bounding said visual field.