Wide-angle optical system, and imaging device
AssigneeKonica Minolta Opto, Inc.
InventorsMakoto Jin, Keiji Matsusaka, Toru Nakatani
Life of this patent
Estimating the term…
Abstract
The present invention provides a wide-angle optical system constituted of, in order from the object side to the image side, front group 11, stop 12, and rear group 13. The front group 11 is constituted, in order from the object side to the image side, of first lens 111 having negative optical power, second lens 112 having negative optical power, and third lens 113 having positive optical power. The rear group 13 is constituted, in order from the object side to the image side, of fourth lens 131 having positive optical power, and fifth lens 132 having negative optical power. The opposite surface from the stop of each of the paired lenses 113 and 131 arranged at the both sides of the stop 12 is a convex surface.
Claims13
A wide-angle optical system comprising, in order from an object side to an image side:
- a front group;
- a stop;
- and
- a rear group,
- wherein the front group comprises, in order from the object side to the image side,
- a first lens having a negative optical power,
- a second lens having a negative optical power, and
- a third lens having a positive optical power,
- the rear group comprises, in order from the object side to the image side,
- a fourth lens having a positive optical power, and
- a fifth lens having a negative optical power,
- an opposite surface from the stop of each of a pair of lenses which are arranged at the both sides of the stop is a convex surface, and
- the wide-angle optical system satisfies the following conditional expressions:
- 1.7<νd4/νd3<2.7 (3),
- 2.43≧νd4/νd5>1.5 (4),
- Ff/Fr>0 (5),
- −2<F5/F4<−1 (7),
- where νd3 is an Abbe number of the third lens,
- νd4 is an Abbe number of the fourth lens,
- νd5 is an Abbe number of the fifth lens,
- Ff is a focal length of the front group,
- Fr is a focal length of the rear group,
- F4 is a focal length of the fourth lens, and
- F5 is a focal length of the fifth lens.
Dependencies are inferred from the claim text.