Optical system for laser riflescope
View Patent ↗An optical system for a laser riflescope includes, an objective lens group ( 1 ), an eyepiece lens element ( 3 ) defining an optical axis with the objective lens group, and an erector lens group ( 2 ) positioned between the objective lens group and the eyepiece lens element. The eyepiece lens element includes an aspheric element having a diffractive configuration ( 33 ). The aspheric element combines with a spherical lens so as to form a hybrid lens. Thus, the spherical aberration of the optical system is eliminated by the aspheric element and the chromatic aberration is eliminated by the diffractive configuration.
1. An optical system for a riflescope comprising an objective lens group, an eyepiece lens element defining an optical axis with the objective lens group, and an erector lens group positioned between the objective lens group and the eyepiece lens element, the eyepiece lens element comprising an aspheric element having a diffractive configuration and combining with a spherical lens;
wherein, the diffractive configuration of the aspheric element faces the erector lens group, and the aspheric element satisfies the following equation:
Z
=
cH
2
1
+
[
1
-
(
K
+
1
)
c
2
H
2
]
1
/
2
+
AH
4
+
BH
6
+
CH
8
+
DH
10
where: Z is Sag value along the optical axis, c is the curvature (1/radius) of the surface, H is the semi-diameter height, K is the conic coefficient, and A, B, C and D are the 4 th -order, 6 th -order, 8 th -order and 10 th -order aspheric coefficients, respectively; wherein the eyepiece lens element satisfies the following condition: 3<S/F<4, where F is the focal length of the eyepiece lens element and S is the incremental sag of the aspheric element at a clear aperture of the eyepiece lens element.
2. The optical system for a riflescope as claimed in claim 1 , wherein the coefficients for the aspheric element are: c=1/70, K=−43.4177, A=−2.44156E−6, B=0, C=0 and D=0.
3. The optical system for a riflescope as claimed in claim 1 , wherein the diffractive configuration of the aspheric element satisfies the following phase equation:
Φ
(
H
)
=
2
π
λ
0
[
K
1
H
2
+
K
2
H
4
+
K
3
H
6
+
K
4
H
8
+
K
5
H
10
]
where: H is the height in the vertical direction from the optical axis, λ 0 is the design wavelength, and K 1 , K 2 , K 3 , K 4 , and K 5 are phase coefficients.
4. The optical system for a riflescope as claimed in claim 3 , wherein the phase coefficients for the diffractive configuration of the aspheric element are: K 1 =0.84838, K 2 =−0.043438, K 3 =−7.463554E−5, K 4 =0 and K 5 =0.
5. The optical system for a riflescope as claimed in claim 1 , wherein the aspheric element is made of a resin material.
6. The optical system for a riflescope as claimed in claim 5 , wherein the aspheric element has a thickness between 0.07 mm and 0.15 mm along the optical axis.
7. The optical system for a riflescope as claimed in claim 1 , wherein the spherical lens is made of glass.
8. An optical system for a riflescope comprising an objective lens group, an eyepiece lens element defining an optical axis with the objective lens group, and an erector lens group positioned between the objective lens group and the eyepiece lens element, the eyepiece lens element comprising an aspheric element having a diffractive configuration and combining with a spherical lens, and satisfying the following condition: 3<S/F<4, where F is the focal length of the eyepiece lens element and S is the incremental sag of the aspheric element at a clear aperture of the eyepiece lens element.
9. The optical system for a riflescope as claimed in claim 8 , wherein the diffractive configuration of the aspheric element faces the erector lens group.
10. The optical system for a riflescope as claimed in claim 9 , wherein the aspheric element eliminates the spherical aberration of the optical system and the diffractive configuration eliminates the chromatic aberration of the optical system.
11. The optical system for a riflescope as claimed in claim 9 , wherein the aspheric element satisfies the following equation:
Z
=
cH
2
1
+
[
1
-
(
K
+
1
)
c
2
H
2
]
1
/
2
+
AH
4
+
BH
6
+
CH
8
+
DH
10
where: Z is Sag value along the optical axis, c is the curvature (1/radius) of the surface, H is the semi-diameter height, K is the conic coefficient, and A, B, C and D are the 4 th -order, 6 th -order, 8 th -order and 10 th -order aspheric coefficients, respectively.
12. The optical system for a riflescope as claimed in claim 9 , wherein the diffractive configuration satisfies the following phase equation:
Φ
(
H
)
=
2
π
λ
0
[
K
1
H
2
+
K
2
H
4
+
K
3
H
6
+
K
4
H
8
+
K
5
H
10
]
where: H is the height in the vertical direction from the optical axis, λ 0 is the design wavelength, and K 1 , K 2 , K 3 , K 4 and K 5 are phase coefficients.
13. The optical system for a riflescope as claimed in claim 9 , wherein the aspheric element is made of a resin material, and has a thickness between 0.07 mm and 0.15 mm along the optical axis.
14. An optical system for a riflescope comprising
an objective lens group;
an eyepiece lens element, defining an optical axis with the objective lens group, and comprising an aspheric element which has a diffractive configuration and combines with a spherical lens, wherein the aspheric element eliminates the spherical aberration of the optical system and the diffractive configuration thereon eliminates the chromatic aberration of the optical system; and
an erector lens group positioned between the objective lens group and the eyepiece lens element;
wherein, the eyepiece lens element satisfies the following condition: 3<S/F<4, where F is the focal length of the eyepiece lens element and S is the incremental sag of the aspheric element at a clear aperture of the eyepiece lens element.
15. The optical system for a riflescope as claimed in claim 14 , wherein the spherical lens is made of glass, and the aspheric element is made of resin.
16. The optical system for a riflescope as claimed in claim 15 , wherein the aspheric element has a thickness between 0.07 mm and 0.15 mm along the optical axis.