Compact large-aperture photographic lens system with long back focal length
AssigneeOlympus Optical Co., Ltd.
InventorToshihiro Imai
Life of this patent
Estimating the term…
Abstract
A compact large-aperture photographic lens system having six-component seven-element lens configuration and comprising a first, second, third, fourth, fifth and sixth lens components, in which the first and second lens components are positive meniscus lenses, the third lens component is a negative meniscus lens, the fourth lens component is a cemented meniscus doublet, the fifth lens component is a positive meniscus lens and the sixth lens component is a positive lens, the compact large-aperture photographic lens having a short overall length and long back focal length.
Claims7
A compact large-aperture photographic lens system with long back focal length comprising a first, second, third, fourth fifth and sixth lens components, said first lens components being a positive meniscus lens, said second lens component being a positive meniscus lens, said third lens component being a negative meniscus lens, said fourth lens component being a cemented meniscus doublet, said fifth lens component being positive meniscus lens, said sixth lens component being a positive lens, said compact large-aperture photographic lens system with long back focal length satisfying the following conditions:
- (L/f) <
- 1 (L = .SIGMA.d) (1)
- 0.6f <
- -r.sub.8 <
- 1.1.f (2)
- 0.1 <
- n.sub.4 - n.sub.5 <
- 0.2, 24 <
- .nu..sub.5 - .nu..sub.4 <
- 35 (3) ##EQU3##
- 1.5 <
- r5/r4 <
- 1.87, d.sub.4 <
- 0.05f (5)
- 0. 16f <
- d.sub.3 + d.sub.4 + d.sub.5 <
- 0.19f, 0.14f <
- d.sub.7 + d.sub.8 <
- 0.17f (6)
- 1.7 <
- n.sub.1, n.sub.2, n.sub.3, n.sub.4 <
- 1.86 (7)
- 1.6 <
- n.sub.5, n.sub.6, n.sub.7 <
- 1.82 (8)
- 40 <
- .nu..sub.5, .nu..sub.5, .nu..sub.7 <
- 60 (9)
- Wherein reference symbol L represents the overall length of the lens system, reference symbol r.sub.4 represents the radius of curvature of the surface on the image side of the second lens component, reference symbol r5 represents the radius of curvature of the surface on the object side of the third lens component, reference symbol r8 represents the radius of curvature of the cemented surface of the fourth lens component, reference symbols d3 and d5 respectively represent thicknesses of the second and third lens components, reference symbols d7 and d8 respectively represent thicknesses of respective lenses constituting the fourth lens component, reference symbol d4 represents the airspace between the second and third lens components, reference symbols n1 through n7 respectively represent refractive indices of respective lenses, reference symbols .nu.4 and .nu.5 respectively represent Abbe's numbers of respective lenses constituting the fourth lens component, reference symbols .nu.6 and .nu.7 respectively represent Abbe's numbers of the fifth and sixth lens components, reference symbol f represents the focal length of the lens system as a whose, reference symbol f23 represents the total focal length of the second and third lens components and reference symbol f45 represents the focal length of the fourth lens component.
Dependencies are inferred from the claim text.