JP2909958B

• Main Author: FUJISAKI JUNICHI
• Format: Patent
• Language: English
• Published: 23.06.1999
• Edition: 6
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

PROBLEM TO BE SOLVED: To provide a super wide-angle lens system which has its distortion aberration suppressed relatively small and also has the image formation aberration characteristics of the whole effective picture plane corrected excellently in spite of being a bright lens system having a field angle of about 115 deg. and an F number of about 1.4. SOLUTION: This lens system consists of a 1st lens L1 composed of a negative meniscus lens which has its convex surface on its object side, a 2nd lens L2 composed of a negative meniscus lens which has its convex surface on its object side, a 3rd lens L3 composed of a biconcave lens, a 4th lens L4 composed of a biconvex lens, a stop S, a 5th lens group L5 which is composed of a joined lens of a negative meniscus lens having its convex surface on its object side and a biconvex lens and is biconvex on the whole, and a 6th lens group L6 which consists of a joined lens of a negative meniscus lens having its convex surface on its object side and a biconvex lens and is biconvex on the whole in order from the object side; and conditional expressions N1 <1.75 and 2.18<R12 /f<2.22 are satisfied, where N1 is the refractive index of the 1st lens to a (d) line, (f) is the focal length of the whole lens system, and R12 is the radius of curvature of the image-side surface of the 1st lens.