Eyepiece optical system, optical apparatus and method for manufacturing the eyepiece optical system
Provided is an eyepiece optical system including, in order from an observation object (Ob): a first lens (L 11 ) having positive refractive power; a second lens (L 12 ) which has negative refractive power and of which an observation object (Ob) side lens surface is concave; and a third lens (L 13 ) which has positive refractive power and of which an eye point (EP) side lens surface is convex. The third lens (L 13 ) is fixed on the optical axis with respect to the observation object (Ob) when adjusting the diopter, and the following conditional expressions are satisfied: 0.65< R 31/ fe< 1.30 (1) −0.80<( R 32+ R 31)/( R 32− R 31)<−0.10 (2) where fe denotes a focal length of the eyepiece optical system, R 31 denotes a radius of curvature of the observation object (Ob) side lens surface of the third lens (L 13 ), and R 32 denotes a radius of curvature of the eye point (EP) side lens surface of the third lens (L 13 ).
1. An eyepiece optical system comprising, in order from an observation object:
a first lens having positive refractive power;
a second lens which has negative refractive power and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex,
the third lens being fixed on an optical axis with respect to the observation object when adjusting a diopter, and
the following conditional expressions being satisfied:
0.65 <R 31 /fe <1.30 (1)
−0.80<( R 32 +R 31)/( R 32 −R 31)<−0.10 (2)
1.00 <fe/f 3<1.60 (3A)
where fe denotes a focal length of the eyepiece optical system, R31 denotes a radius of curvature of an observation object side lens surface of the third lens, R32 denotes a radius of curvature of the eye point side lens surface of the third lens, and f3 denotes a focal length of the third lens.
2. The eyepiece optical system according to claim 1 , wherein the observation object is an image display element.
3. The eyepiece optical system according to claim 2 , wherein the image display element is a liquid crystal display element.
4. The eyepiece optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.60 <fe/f 1<2.00
where fe denotes a focal length of the eyepiece optical system, and f1 denotes a focal length of the first lens.
5. The eyepiece optical system according to claim 1 , wherein the following conditional expression is satisfied:
0.40 <f 3/ f 1<2.50
where f1 denotes a focal length of the first lens, and f3 denotes a focal length of the third lens.
6. The eyepiece optical system according to claim 1 , wherein the following conditional expression is satisfied:
−2.00<( R 12 +R 11)/( R 12 −R 11)<−0.75
where R11 denotes a radius of curvature of an observation object side lens surface of the first lens, and R12 denotes a radius of curvature of an eye point side lens surface of the first lens.
7. The eyepiece optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.35<( R 22 +R 21)/( R 22− R 21)<2.40
where R21 denotes a radius of curvature of the observation object side lens surface of the second lens, and R22 denotes a radius of curvature of an eye point side lens surface of the second lens.
8. The eyepiece optical system according to claim 1 , wherein the following conditional expression is satisfied:
1.60 <fe /(− f 2)<2.20
where fe denotes a focal length of the eye piece optical system, and f2 denotes a focal length of the second lens.
9. The eyepiece optical system according to claim 1 , wherein the first lens, the second lens and the third lens are all made of plastic.
10. The eyepiece optical system according to claim 1 , wherein
the observation object side lens surface of the second lens is aspherical.
11. The eyepiece optical system according to claim 1 , wherein the eye point side lens surface of the third lens is aspherical.
12. The eyepiece optical system according to claim 1 , wherein the diopter is adjusted by moving the first lens and the second lens along the optical axis.
13. An optical apparatus comprising:
an objective lens;
a picture element that captures an image formed by the objective lens;
an image display element that displays the image captured by the picture element; and
an eyepiece optical system for observing the image displayed on the image display element,
the eyepiece optical system being the eyepiece optical system according to claim 1 .
14. An eyepiece optical system comprising, in order from an observation object along an optical axis:
a first lens having positive refractive power;
a second lens which has negative refractive power, and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex,
at least one lens surface, out of lens surfaces constituting the first lens, the second lens and the third lens, being aspherical, and
the following conditional expressions being satisfied:
0.40 <f 3 /f 1<2.50 (5)
1.40<( R 12 +R 11)/( R 12− R 11)<−0.75 (6A)
1.35<( R 22 +R 21)/( R 22 −R 21)<2.40 (7)
where f1 denotes a focal length of the first lens, f3 denotes a focal length of the third lens, R11 denotes a radius of curvature of an observation object side lens surface of the first lens, R12 denotes a radius of curvature of an eye point side lens surface of the first lens, R21 denotes a radius of curvature of the observation object side lens surface of the second lens, and R22 denotes a radius of curvature of an eye point side lens surface of the second lens.
15. The eyepiece optical system according to claim 14 , wherein the following conditional expression is satisfied:
1.60 <fe /(− f 2)<2.20
where fe denotes a focal length of the eyepiece optical system, and f2 denotes a focal length of the second lens.
16. The eyepiece optical system according to claim 14 , wherein the following conditional expression is satisfied:
0.60 <fe/f 1<2.00
where fe denotes a focal length of the eyepiece optical system.
17. An optical apparatus comprising:
an objective lens;
a picture element that captures an image formed by the objective lens;
an image display element that displays the image captured by the picture element; and
an eyepiece optical system for observing the image displayed on the image display element,
the eyepiece optical system being the eyepiece optical system according to claim 14 .
18. A method for manufacturing an eyepiece optical system including, in order from an observation object side:
a first lens having positive refractive power;
a second lens which has negative refractive power and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex, the third lens being fixed on an optical axis with respect to the observation object when adjusting a diopter,
the method comprising:
disposing each lens in a lens barrel so as to satisfy the following conditional expressions:
0.65 <R 31 /fe< 1.30 (1)
−0.80<( R 32 +R 31)/( R 32− R 31)<−0.10 (2)
1.00 <fe/f 3<1.60 (3A)
where fe denotes a focal length of the eyepiece optical system, R31 denotes a radius of curvature of an observation object side lens surface of the third lens, R32 denotes a radius of curvature of the eye point side lens surface of the third lens, and
f3 denotes a focal length of the third lens.
19. A method for manufacturing an eyepiece optical system including in order from an observation object side along an optical axis:
a first lens having positive refractive power;
a second lens which has negative refractive power and of which an observation object side lens surface is concave; and
a third lens which has positive refractive power and of which an eye point side lens surface is convex,
at least one lens surface, out of lens surfaces constituting the first lens, the second lens and the third lens, being aspherical,
the method comprising:
disposing each lens in a lens barrel so as to satisfy the following conditional expression:
0.40 <f 3 /f 1<2.50 (5)
1.40<( R 12 +R 11)/( R 12 −R 11)<−0.75 (6A)
1.35<( R 22 +R 21)/( R 22− R 21)<2.40 (7)
where f1 denotes a focal length of the first lens, f3 denotes a focal length of the third lens, R11 denotes a radius of curvature of an observation object side lens surface of the first lens, R12 denotes a radius of curvature of an eye point side lens surface of the first lens, R21 denotes a radius of curvature of the observation object side lens surface of the second lens, and R22 denotes a radius of curvature of an eye point side lens surface of the second lens.