| 摘要 |
PURPOSE:To obtain an aperture-prepositive photographic lens of 2.8F and about 64 deg. angle of view which is compact and is well corrected of aberrations, by satisfying prescribed conditions in a lens system constituted of positive meniscus, concave, biconvex and negative meniscus 4-group lenses successively from an object side and disposed with an aperture in front of the 1st lens. CONSTITUTION:In a lens system constituted of positive meniscus, concave, biconvex, and negative meniscus 4-group lenses successively from an object side and disposed with an aperture in front of the 1st lens, conditions of the equations (1)-(5) are satisfied. Here, f12 is the composite focal length of the 1st and 2nd lenses, f3 is the focal length of the 3rd lens, (f) is the focal length of the entire system r5 and r6 are the radii of curvature of the refracting faces on the object side and image side of the 3rd lens, SIGMAd is the overall length of the lens system, SIGMAdf is the axial interface-distance from the object face of the 1st lens up to the image side face of the 3rd lens, f123 is the composite focal length of the 1st, 2nd, 3rd lenses, and d6 is the air space between the 3rd and 4th lens. Thus the compact aperture-prepositive photographic lens of a wide angle of view is obtained. |
