Pancratic lens typically with nine elements - has four groups with second and third groups axially adjustable by amount dependent on focal length of first two groups (OE 15.7.78)

摘要

The pancratic lens comprises a first fixed negative lens (L1), a second axially adjustable positive lens pair (L2, L3), a third axially adjustable negative lens pair (L4, L5), an aperture stop (B) and a lens group of fixed focal length comprising four lenses (L6, L7, L8, L9). The geometrical arrangement is such that the focal lengths (f1, f2) of the first two lens groups (G1 = L1, G2 = L2+L3) are linked by the inequalities 1.5W mod (f1) 1.5f2 and f2 7y, where W is the adjustment length along the axis of the second positive group and y is the radius of the image field. The radii of curvature of the faces of the first lens follow the relationship r2 mod (r1) 2.5 r2. Some other inequalities relate functions of the other lenses. Detailed conditions are specified for three examples wwith aperture f1. 4.