Photographic objective with four lenses - has aperture ratio of 1 to 2.8 and picture angle of at least 43 degrees

摘要

Four lenses in three groups form a photographic objective with a relative aperture of 1:2.8 and a picture view angle of at least 43 deg. The four lenses, in sequence from the aperture stop (BL) are respectively a thick biconvex converging lens, a thin bi-concave diverging lens and a cemented pair consisting of a thin bi-concave lens in contact with a thick bi-convex lens. The radii of curvature of the seven spherical surfaces are (for f=100)+38.8, -508.2, -71.7, + 31.4, -341.1, +39.5, -54.3. The lens thickness (and spacings) are 11.2, (5.4), 1.8, (7.6), 2.6, 18.4. The refractive indices are approx. 1.70, 1.60, 1.54 and 1.70 and the Abbe numbers 53.3, 35.1, 44.8 53.3.