| 摘要 |
PROBLEM TO BE SOLVED: To provide a wide-angle lens whose angle of view exceeds 100 deg. without making it larger by satisfying a specified condition concerning the focal distance of an entire lens system, the synthetic focal distance and the radii of curvature of respective lenses. SOLUTION: This lens is composed of 1st to 3rd lenses 11 to 13, a 1st composite lens 21 constituted by bonding 4th and 5th lenses 14 and 15, a 2nd composite lens 22 constituted by bonding 6th and 7th lenses 16 and 17, and a 8th lens 18. It satisfies respective conditional expressions; fB/f>0.8, 0.5>|f12 |/f<1.2, 0.7<R2 /R4 <1.2, ν6 -ν7 >12, N4>1.7 and N6>1.7. In the expressions, f0 means the focal distance of the entire lens system, fB means the back focus thereof, f12 means the synthetic focal distance of the 1st and the 2nd lenses 11 and 12, R2 and R4 mean the radii of curvature of the image-side surfaces of the 1st and the 2nd lenses 11 and 12, ν6 and ν7 mean the Abbe numbers of the 6th and 7th lenses 16 and 17, and N4 and N6 mean the refractive indexes of the 4th and the 6th lenses 14 and 16 to a d-line.
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