Lens system, optical device with lens system, and method of manufacturing lens system
A lens system has the following components in order from an object side: one negative lens component; a positive lens component; a negative lens component having a concave surface of a large curvature on an image side; an aperture stop; a negative lens component having a concave surface of a large curvature on the object side; and a positive lens component; the lens system satisfies a condition of the following expression: 0.75<SF1<1.60, where SF1=(R1+R2)/(R1−R2), and where R1 is a radius of curvature of an object-side lens surface of the negative lens component located nearest to the object side, R2 is a radius of curvature of an image-side lens surface thereof, and SF1 is a shape factor thereof.
1. A lens system comprising the following components in order from an object side:
a first negative lens component being a most object-side lens component of the lens system;
at least one positive lens component;
a second negative lens component having a concave surface on an image side thereof, the concave surface having a smaller radius of curvature than an object-side surface of the second negative lens component;
an aperture stop;
a third negative lens component having a concave surface on the object side thereof, the concave surface having a smaller absolute value of the, radius of curvature than an image-side surface of the third negative lens component; and
at least one positive lens component, including a positive lens component being a most image-side lens component of the lens system,
the aperture stop being disposed with no intervening lens component between the aperture stop and the concave surface of the second negative lens component and no intervening lens component between the aperture stop and the concave surface of the third negative lens component;
the lens system satisfying the following conditional expressions:
0.75<SF1<1.60,
0.5 <|Rs− 1 /Rs+ 1|<1.3,
where SF1=(R1+R2)/(R1−R2),
where R1 is a radius of curvature of an object-side lens surface of the first negative lens component, R2 is a radius of curvature of an image-side lens surface of the first negative lens component, and SF1 is a shape factor of the first negative lens component, and
where Rs−1 is a radius of curvature of the concave surface of the second negative lens component and Rs+1 is a radius of curvature of the concave surface of the third negative lens component.
2. A lens system according to claim 1 ,
wherein the most image-side positive lens component satisfies the following conditional expression:
−0.9 <SFi< −0.8,
where SFi=(Ri1+Ri2)/(Ri1−Ri2), and
where Ri1 is a radius of curvature of an object-side lens surface of the most image-side positive lens component, Ri2 is a radius of curvature of an image-side lens surface thereof, and SFi is a shape factor thereof.
3. A lens system according to claim 1 , comprising a positive lens component between the most image-side positive lens component and the third negative lens component.
4. A lens system according to claim 1 , wherein each of the second negative lens component and the third negative lens component is comprised of a cemented lens.
5. A lens system according to claim 1 , comprising a plurality of positive lens components between the first negative lens component and the second negative lens component .
6. A lens system according to claim 1 , satisfying the following conditional expression:
1.0<(− fn )/ f <2.3,
where fn is a focal length of the first negative lens component and f is a focal length of an overall system of the lens system.
7. A lens system according to claim 1 , wherein every optical element with a refracting power located on the image side with respect to the third negative lens component has a positive refracting power.
8. An optical device comprising the lens system as set forth in claim 1 .
9. A method of manufacturing a lens system, comprising a step of arranging, in order from an object side, a first negative lens component being a most object-side lens component of the lens system, at least one positive lens component, a second negative lens component having a concave surface on an image side thereof with a smaller radius of curvature than an object-side surface of the second negative lens component, an aperture stop, a third negative lens component having a concave surface on an object side thereof with a smaller absolute value of the radius of curvature than an image-side surface thereof, and at least one positive lens component including a positive lens component being a most image-side lens component of the lens system, the aperture stop being disposed with no intervening lens component between the aperture stop and the concave surface of the second negative lens component and no intervening lens component between the aperture stop and the concave surface of the third negative lens component;
the lens system satisfying the following conditional expressions:
0.75<SF1<1.60,
0.5 <|Rs −1 /Rs+ 1|<1.3,
where SF1=(R1+R2)/(R1−R2), and
where R1 is a radius of curvature of an object-side lens surface of the first negative lens component, R2 is a radius of curvature of an image-side lens surface thereof, and SF1 is a shape factor thereof, and
where Rs−1 is a radius of curvature of the concave surface of the second negative lens component and Rs+1 is a radius of curvature of the concave surface of the third negative lens component.
10. A method according to claim 9 , wherein the most image-side positive lens component satisfies the following conditional expression:
−0.9<SFi<−0.8,
where SFi=(Ri1+Ri2)/(Ri1−Ri2), and
where Ri1 is a radius of curvature of an object-side lens surface of said most image-side positive lens component, Ri2 is a radius of curvature of an image-side lens surface thereof, and SFi is a shape factor thereof.
11. A method according to claim 9 , comprising arranging a positive lens component between the positive lens component located nearest to the image side and the third negative lens component.
12. A method according to claim 9 , wherein each of the second negative lens component and the third negative lens component is comprised of a cemented lens.
13. A method according to claim 9 , comprising arranging a plurality of positive lens components between the first negative lens component the second negative lens component.
14. A method according to claim 9 , satisfying the following conditional expression:
1.0<(− fn )/ f <2.3,
where fn is a focal length of the first negative lens component and f is a focal length of an overall system of the lens system.
15. A method according to claim 9 , wherein every optical element with a refracting power located on the image side with respect to the third negative lens component has a positive refracting power.
16. An optical device comprising the lens system manufactured by the method as set forth in claim 9 .
17. A lens system comprising the following components in order from an object side:
a first negative lens component being a most object-side lens component of the lens system;
at least one positive lens component;
a second negative lens component having a concave surface on an image side thereof, the concave surface having a smaller radius of curvature than an object-side surface of the second negative lens component;
an aperture stop;
a third negative lens component having a concave surface on the object side thereof, the concave surface having a smaller absolute value of the radius of curvature than an image-side surface of the third negative lens component; and
at least one positive lens component, including a positive lens component being a most image-side lens component of the lens system,
the aperture stop being disposed with no intervening Lens component between the aperture stop and the concave Surface of the second negative lens component and no Intervening lens component between the aperture stop and the Concave surface of the third negative lens component;
the lens system satisfying the following conditional expression:
0.75<SF1<1.60,
where SF1=(R1+R2)/(R1−R2), and
where R1 is a radius of curvature of an object-side lens surface of the first negative lens component, R2 is a radius of curvature of an image-side lens surface of the first negative lens component, and SF1 is a shape factor of the first negative lens component, and
wherein said most image-side positive lens component satisfies the following conditional expression:
−0.9<SFi<−0.8,
where SFi=(Ri1+Ri2)/(Ri1−Ri2), and
where Ri1 is a radius of curvature of an object-side surface of said most image-side positive lens component, Ri2 is a radius of curvature of an image-side surface thereof, and SFi is a shape factor thereof.
18. The lens system according to claim 17 , satisfying the following conditional expression:
0.5 <|Rs− 1 /Rs +1|<1.5,
wherein Rs−1 is a radius of curvature of the concave surface of the second negative lens component and Rs+1 is a radius of curvature of the concave surface of the third negative lens component.
19. The lens system according to claim 17 wherein each of the second negative lens component and the third negative lens component is comprised of a cemented lens.
20. The lens system according to claim 17 satisfying the following conditional expression:
1.0<(− fn )/ f <2.3,
where fn is a focal length of the first negative lens component and f is a focal length of an overall system of the lens system.