| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lens which is less degraded in the light quantity in its peripheral part and has the low possibility of the occurrence of a coma aberration by eccentricity at the time of assembly and adjustment by constituting the converging lens of a front group G1 of a single lens which satisfy specific conditions and has weak power and a rear group which has a convergence effect and making the front group exchangeable for the purpose of spherical aberration adjustment. SOLUTION: This converging lens comprises, successively from an incident side of parallel luminous fluxes, the front group G1 of the single lens having the weak power and the rear group G2 having the convergence effect. The front group G1 is exchangeable for the purpose of the spherical aberration adjustment. The power of the front group G1 is determined in a range satisfying the conditions|f/f1|<0.100 when the focal length over the entire part of the converging lens is defined as (f) and the focal length of the front group G1 as fl. A parallel plane plate of which the exit side of the parallel luminous fluxes is a plane and the incident side surface is a plane, a planoconvex lens of a convex face and a planoconcave lens of a concave face are usable for the front group G1. The correction of the spherical aberrations by exchanging only the front group G1 is made possible without moving the rear group G2 having the convergence effect according to this constitution.
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