Single-lens optical system
View Patent ↗A single-lens optical system including a stop and a lens sequentially arranged from an object side, and reducing distortion by controlling a distance between the stop and the lens.
1. A single-lens optical system comprising a stop and a lens sequentially arranged from an object side, the lens and the stop satisfying
0.1 EFL≦L≦ 0.3 EFL and
| K|≧ 100,
where L represents a distance between the stop and the lens, EFL represents a focal length of the single-lens optical system, and K represents a conic constant of an image side surface of the lens; and
wherein the lens is configured to defocus an image with respect to a paraxial image plane in forming the image.
2. The system of claim 1 , wherein the lens is configured to defocus the image with respect to the paraxial image plane by 1/20 EFL or more.
3. The system of claim 1 , wherein the lens has two aspherical surfaces.
4. The system of claim 3 , wherein at least one of the two aspherical surfaces satisfies:
x
=
cy
2
1
+
1
-
(
K
+
1
)
c
2
h
2
+
Ah
4
+
Bh
6
+
Ch
8
+
Dh
10
+
Eh
12
+
Fh
14
+
Gh
16
+
Hh
18
|
,
where x represents a distance from a vertex of the lens in an optical axis direction, y represents a distance in a direction perpendicular to the optical axis direction, K represents a conic constant, A, B, C, D, E, F, G, and H represent aspherical coefficients, and c represents an inverse number of a radius of curvature at the vertex of the lens.
5. The system of claim 1 , wherein an Abbe number of the lens is equal to or greater than 55.
6. The system of claim 1 , wherein the lens is a biconvex lens.
7. The system of claim 1 , wherein a vignette effect is provided from an upper side of an object side surface of the lens.
8. The system of claim 1 , wherein the lens is formed of glass.
9. The system of claim 1 , wherein the lens has a positive refractive power.
10. The system of claim 1 , further comprising an infrared filter disposed between the lens and an image plane.