| 摘要 |
PURPOSE:To obtain a lens of good resolving power of low frequency components by satisfying prescribed conditions in a lens system of positive, negative, positive and positive 4-group constitution disposed successively from the object side. CONSTITUTION:In a lens system of 4-group constitution consisting of a positive meniscus lens, a biconcave lens, a positive lens and a positive meniscus lens successively from the object side, the conditions of the equations (1)-(9) are satisfied. Here, (f) is the combined focal length of a entire system, fi, ni, ri are the focal length, refractive index and the radius of curvature of the 1st refractive surface of the i-th group lens respectively, and rL, D4 are the radius of curvature and thickness of the image side face of the 4th group lens respectively. Curvature of field and spherical aberrations are corrected by the conditions (1)- (4), the compensation effect for the deficiency of the correction thereof is obtained by the conditions (5), (6), comas are suppressed by the conditions (7), inward and outward comas are suppressed by the conditions (8), (9), and the lens of good resolving power of low frequency components is obtained. |
