| 摘要 |
PROBLEM TO BE SOLVED: To provide a 3-lens imaging optical system which is compact and yet is well corrected for various aberrations.SOLUTION: An imaging optical system LN comprises, in order from the object side, a diaphragm ST, a positive first lens L1 having a convex object-side surface, a second lens L2, and a positive third lens L3 having a convex object-side surface, where the lenses L1-L3 are made of plastic. The imaging optical system satisfies conditional expressions; 0.9≤f1/f<6, 0.03<d12/TL<0.09, and 0.03<d23/TL<0.12. (f1: focal length of the first lens, f: focal length of the entire imaging optical system, d12: distance between an image-side surface of the first lens and an object-side surface of the second lens along the optical axis, d23: distance between an image-side surface and the object-side surface of the third lens along the optical axis, TL: optical length between the object-side surface of the first lens and an image plane) |
