JP2012208148A5

JP2012208148A5 -

Info

Publication number: JP2012208148A5
Application number: JP2011071476A
Authority: JP
Filing date: 2011-03-29
Publication date: 2014-05-08

Description

上述した課題を解決し、目的を達成するために、本発明の撮像光学系は、複数のレンズを有し、複数のレンズは、物体側より順に、正の屈折力の第１レンズと、負の屈折力の第２レンズと、正の屈折力の第３レンズと、正の屈折力の第４レンズと、負の屈折力の第５レンズからなり、最も物体側に絞りが配置され、以下の条件式（１）、（３’’’）を満足することを特徴とする。
−４．０＜（ｒ６＋ｒ７）／（ｒ６−ｒ７）＜−０．５１（１）
−７．０＜Ｒ９／ｄ９＜−１．６（３’’’）
但し、
ｒ６は第３レンズの物体側面の近軸曲率半径、
ｒ７は第３レンズの像側面の近軸曲率半径、
Ｒ９は第４レンズの像側面の近軸曲率半径、
ｄ９は第４レンズと第５レンズの光軸上の空気間隔、
である。 In order to solve the above-described problems and achieve the object, the imaging optical system of the present invention has a plurality of lenses, and the plurality of lenses, in order from the object side, a first lens having a positive refractive power and a negative lens. A second lens having a positive refractive power, a third lens having a positive refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power. The following conditional expressions (1) and (3 ′ ″) are satisfied.
−4.0 <(r6 + r7) / (r6-r7) <− 0.51 (1)
−7.0 <R9 / d9 <−1.6 (3 ′ ″)
However,
r6 is the paraxial radius of curvature of the object side surface of the third lens,
r7 is the paraxial radius of curvature of the image side surface of the third lens,
R9 is the paraxial radius of curvature of the image side surface of the fourth lens,
d9 is the air space on the optical axis of the fourth lens and the fifth lens,
It is.

ここで、条件式（３）に代えて、以下の条件式（３’）を満足するのが好ましい。
−７．０＜Ｒ９／ｄ９＜−２．４ (３’)
また、条件式（３）に代えて、以下の条件式（３”）を満足するのがより好ましい。
−５．９＜Ｒ９／ｄ９＜−２．８ (３”)
あるいは、条件式（３）に代えて、以下の条件式（３’’’）を満足しても良い。
−７．０＜Ｒ９／ｄ９＜−１．６（３’’’） Here, it is preferable that the following conditional expression (3 ′) is satisfied instead of conditional expression (3).
−7.0 <R9 / d9 <−2.4 (3 ′)
Further, it is more preferable that the following conditional expression (3 ″) is satisfied instead of conditional expression (3).
−5.9 <R9 / d9 <−2.8 (3 ″)
Alternatively, the following conditional expression (3 ′ ″) may be satisfied instead of conditional expression (3).
−7.0 <R9 / d9 <−1.6 (3 ′ ″)

Claims

Having a plurality of lenses,
The plurality of lenses are, in order from the object side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a fourth lens having a positive refractive power. , Consisting of a fifth lens with negative refractive power,
The iris is placed on the most object side,
An imaging optical system characterized by satisfying the following conditional expressions (1) and (3 ′ ″):
−4.0 <(r6 + r7) / (r6-r7) <− 0.51 (1)
−7.0 <R9 / d9 <−1.6 (3 ′ ″)
However,
r6 is the paraxial radius of curvature of the object side surface of the third lens;
r7 is the paraxial radius of curvature of the image side surface of the third lens;
R9 is the paraxial radius of curvature of the image side surface of the fourth lens,
d9 is the air spacing on the optical axis of the fourth lens and the fifth lens,
It is.

The imaging optical system according to claim 1, wherein the following conditional expression (2) is satisfied.
1.21 <φL5edmax / φst <6.52 (2)
However,
φL5edmax is the effective diameter of the fifth lens,
φst is the diameter of the diaphragm,
It is.

The imaging optical system according to claim 1, wherein the third lens is a meniscus lens having a convex surface directed toward the object side.

The imaging optical system according to claim 1, wherein the following conditional expression (4) is satisfied.
-12.7 <r3 / f1 <-1.6 (4)
However,
r3 is the paraxial radius of curvature of the first lens image side surface;
f1 is the focal length of the first lens,
It is.

The imaging optical system according to any one of claims 1 to 4, wherein the following conditional expression (5) is satisfied.
1.3 <r7 / f (5)
However,
r7 is the paraxial radius of curvature of the third lens image side surface;
f is the focal length of the entire imaging optical system,
It is.

The imaging optical system according to claim 1, wherein the following conditional expression (6) is satisfied.
0.4 <r6 / f <2.1 (6)
However,
r6 is the paraxial radius of curvature of the side surface of the third lens object;
f is the focal length of the entire imaging optical system,
It is.

The imaging optical system according to any one of claims 1 to 6, wherein the following conditional expression (7) is satisfied.
1.1 <f3 / f4 <7.6 (7)
However,
f3 is the focal length of the third lens,
f4 is the focal length of the fourth lens,
It is.

The imaging optical system according to claim 1, wherein the following conditional expression (8) is satisfied.
1.0 <(r10 + r11) / (r10−r11) <3.4 (8)
However,
r10 is the paraxial radius of curvature of the object side surface of the fifth lens;
r11 is the paraxial radius of curvature of the image side surface of the fifth lens;
It is.

The imaging optical system according to any one of claims 1 to 8, wherein the following conditional expression (9) is satisfied.
0.4 <f1 / f <1.8 (9)
However,
f1 is the focal length of the first lens,
f is the focal length of the entire imaging optical system,
It is.

The imaging optical system according to any one of claims 1 to 9, wherein the following conditional expression (10) is satisfied.
−1.5 <f5 / f <−0.3 (10)
However,
f5 is the focal length of the fifth lens,
f is the focal length of the entire imaging optical system,
It is.

The imaging optical system according to any one of claims 1 to 10, wherein the first lens is a biconvex lens.

The imaging optical system according to any one of claims 1 to 11, wherein the second lens is a meniscus lens having a convex surface directed toward the object side.

The fourth lens is a meniscus lens having a concave surface facing the object side,
The imaging optical system according to any one of claims 1 to 12, wherein the shape of the object side surface is a concave shape from the center to the periphery.

An imaging apparatus comprising: the imaging optical system according to any one of claims 1 to 13; and an imaging element.

The imaging apparatus according to claim 14, wherein the imaging optical system and the imaging element are integrated.

16. The imaging apparatus according to claim 14, wherein the imaging optical system is integrated with an autofocus mechanism.