Single focus lens
View Patent ↗A single focus lens comprises: a first lens of positive power having a convex-shaped surface on an object side; a second lens of a negative meniscus lens having, on the object side, a concave-shaped surface on its paraxial axis; and a third lens of an aspheric lens having, on the object side, a convex-shaped surface on its paraxial axis, in this order from the object side, wherein the single focus lens satisfies the predetermined conditions.
1. A single focus lens comprising:
a first lens of positive power having a convex-shaped surface on an object side;
a second lens of a negative meniscus lens having, on the object side, a concave-shaped surface on its paraxial axis; and
a third lens of an aspheric lens having, on the object side, a convex-shaped surface on its paraxial axis, in this order from the object side, wherein the single focus lens satisfies the following conditions:
1.5>f1/f>0.6 (1)
69<ν (2)
55<νdB<59 (3)
1.55>NdA (4)
1.55>NdB>1.48 (5)
1.8>L/D (6)
0.30<RA/f<0.40 (7)
where
f: Entire focal distance,
f1: Focal distance of the first lens,
νdA: Abbe number of the first lens,
νdB: Abbe number of the second lens and the third lens,
NdA: Refractive index at d-line of the first lens,
NdB: Refractive index at d-line of the second lens and the third lens,
RA: Paraxial curvature radius of a surface at the object side of the first lens,
L: Distance on an optical axis from the surface at the object side of the first lens to an imaging position, and
D: Maximum image height.
2. The single focus lens according to claim 1 , further comprising an aperture stop disposed at the object side from a surface at an image side of the first lens on the optical axis.