f.multidot..theta. Lens
AssigneeNippon Kogaku K.K.
InventorMasato Shibuya
Life of this patent
Estimating the term…
Abstract
An f.multidot..theta. lens includes, in succession from the incident light side, a first group having a negative refractive power, a second group having a meniscus lens component having its convex surface facing the incident light side, a third group having a meniscus lens component having its convex surface facing the emergent light side, and a fourth group having a positive refractive power.
Claims8
An f.multidot..theta. lens having a total focal length f for condensing an incident light ray angled at .theta. with respect to the optical axis to a position of distance f.multidot..theta. from the optical axis while substantially maintaining telecentricity and in which a pupil of the entire lens lies on the incident light side of the lens, said f.multidot..theta. lens comprising, in succession from the incident light side:
- a negative lens group having a composite negative refractive power and being disposed most adjacent to the pupil;
- a first meniscus lens component having its convex surface facing the incident light side and having two lens surfaces of substantially equal radius of curvature;
- a second meniscus lens component having its convex surface facing the emergent light side and having a substantially concentric circular shape;
- and
- a positive lens group having a composite positive refractive power.
A telecentric f.multidot..theta. lens having a pupil of the entire lens on the incident light side thereof and having a total focal length f for condensing an incident light ray angled at .theta. with respect to the optical axis to a position of distance f.multidot..theta. from the optical axis, said f.multidot..theta. lens comprising a first meniscus lens component convex toward the pupil and having surfaces of substantially equal radius of curvature for compensating for higher order distortion, a second meniscus lens component concave toward the pupil and having two surfaces of concentric circular shape and being disposed at the emergent light side of the first meniscus lens component for compensating Petzval sum and coma, said two meniscus lens components being disposed adjacent to each other with the concave surfaces thereof facing each other, a compositely negative lens group disposed on that side of said first meniscus lens component which is adjacent to the incident light side, and a compositely positive lens group disposed on that side of said second meniscus lens component which is adjacent to the emergent light side for producing negative distortion inherent in the f.multidot..theta. lens.
Dependencies are inferred from the claim text.