PURPOSE: To reduce a spherical aberration even when a numerical aperture is increased by combining plural cylindrical lenses.
CONSTITUTION: A 1st group lens 1, a 2nd group lens 2, and a 3rd group lens consist of cylindrical lenses which have concave surface on the sides of a light source 4 and also have convex surfaces with radii r2, r4, and r6 of curvature larger than the radii r1, r3, and r5 of the convex surfaces on the sides of the light source 4. The radius r5 of the convex surface of the 3rd lens 3 on the sides of the light source 4 is smaller than the radius r3 of curvature of the convex surface of the 2nd group lens 2 on the side of the 2nd lens 2. Namely, the plural cylindrical lenses are combined to obtain a lens which has a less aberration and a larger numerical aperture than when a single cylindrical lens is used.
JPS52153734A | 1977-12-21 |