US 6,665,131 B2 · Imaging optical system

Abstract

An imaging optical system having superior optical performance with the improved correction of chromatic aberration over a wide wavelength range extending from the visible wavelength range to the infrared wavelength range is provided. According to one aspect, an imaging optical system includes, in order from an object, a front lens group GF with a positive refractive power having at least one lens element, an aperture stop SP and a rear lens group GR with a positive refractive power having at least one lens element. The front lens group GF includes a double convex positive lens GT arranged to the most object side. At least one of the front lens group GF and the rear lens group GR includes a triple cemented lens GS being adjacent to the aperture stop SP having a negative refractive power as a whole composed of a first positive lens, a negative lens, and a second positive lens. Predetermined conditional expression is satisfied.

Claims16

Dependent claims

An imaging optical system comprising, in order from an object:

a front lens group with a positive refractive power;
an aperture stop;
and
a rear lens group with a positive refractive power;
and
wherein the front lens group includes, at the most object side thereof, a double convex positive lens;
wherein at least one of the front lens group and the rear lens group includes a triple cemented lens being adjacent to the aperture stop having a negative refractive power as a whole composed of a first positive lens, a negative lens, and a second positive lens;
and
wherein the following conditional expression is satisfied;
0.3<|fs|/f<5.0 (1)
where fs denotes the focal length of the cemented lens at e-line (λ=546.07 nm) and f denotes the focal length of the imaging optical system at e-line.

8 more elements

An imaging optical system comprising, in order from an object:

a front lens group having a positive refractive power;
an aperture stop;
and
a rear lens group having a positive refractive power;
and
wherein the front lens group includes, in order from the object;
a first lens component having a positive refractive power;
and
a second lens component having a negative refractive power and including at least two lens elements having, respectively, a positive and negative power, all lens elements of the second lens component being cemented together, wherein the second lens component has a meniscus shape having a concave surface facing to the image side, and a lens element of the second lens component arranged closest to the aperture stop has a largest curvature surface in the second lens component away from the space where the aperture stop exists;
wherein the rear lens group includes, in order from the object;
a third lens component having a negative refractive power and including at least two lens elements having, respectively, a negative and positive power, all lens elements of the third lens component being cemented together, wherein the third lens component has a meniscus shape having a concave surface facing to the object side;
and
a fourth lens component having a positive refractive power with a meniscus shape having a concave surface facing to the object side;
and
wherein the following conditional expressions are satisfied;
−0.01<RSA/f<0.01 (9)
−0.0085<LAM/f<0.0085 (10)
where RSA denotes the maximum value of spherical aberration at e-line (λ=546.07 nm), LAM denotes the maximum value of longitudinal chromatic aberration of the imaging optical system between 435.8 nm and 1014 nm as measured with respect to an e-line reference wavelength, and f denotes the focal length of the imaging optical system at e-line.

15 more elements

Dependencies are inferred from the claim text.

Imaging optical system

Life of this patent

Imaging optical system

Life of this patent

Abstract

Claims16