Imaging lens and image reading apparatus using it
AssigneeCanon Kabushiki Kaisha
InventorsTADAO HAYASHIDE, KAZUYUKI KONDO
Life of this patent
Estimating the term…
Abstract
An imaging lens is used in image reading and adapted to image information of an original on a reading device. In the imaging lens at least one surface out of a plurality of surfaces forming the imaging lens has refracting power rotationally asymmetric with respect to the optical axis.
Claims35
An imaging lens for use in image reading, for imaging image information of an original on reading means, wherein at least one surface out of a plurality of surfaces forming the imaging lens has refracting power rotationally asymmetric with respect to the optical axis.
An imaging lens for use in image reading, for imaging image information of an original on reading means, said imaging lens having a stop in the imaging lens, wherein at least one surface not facing said stop, out of a plurality of surfaces forming the imaging lens, has refracting power rotationally asymmetric with respect to the optical axis.
An imaging lens for use in image reading, for imaging image information of an original on reading means, wherein at least one surface at which an overlapping area of a range of up to 70% of a distance from a center to the outermost periphery of each of on-axis rays and outermost off-axis rays is not more than 50% of an area of a range of up to 70% of the distance from the center to the outermost periphery of the on-axis rays, out of a plurality of surfaces forming the imaging lens, has refracting power rotationally asymmetric with respect to the optical axis.
An imaging lens for use in image reading, for imaging image information of an original on reading means, said imaging lens comprising five lenses, which are a positive, first lens of the meniscus shape with a convex surface thereof facing the side of the original, a second lens whose lens surfaces both are concave surfaces, a third lens whose lens surfaces both are convex surfaces, a positive or negative, fourth lens of a meniscus shape with a convex surface thereof facing the side of the reading means, and a negative, fifth lens of the meniscus shape with a convex surface thereof facing the side of the reading means, arranged in the named order from the original side,
- wherein at least one surface out of a plurality of surfaces forming the imaging lens has refracting power rotationally asymmetric with respect to the optical axis.
An imaging lens for use in image reading, for imaging image information of an original on reading means, said imaging lens comprising four lenses, which are a positive, first lens of the meniscus shape with a convex surface thereof facing the side of the original, a second lens whose lens surfaces both are concave surfaces, a third lens whose lens surfaces both are convex surfaces, and a negative, fourth lens of the meniscus shape with a convex surface thereof facing the side of the reading means, arranged in the named order from the original side,
- wherein at least one surface out of a plurality of surfaces forming the imaging lens has refracting power rotationally asymmetric with respect to the optical axis.
An imaging lens for use in image reading, for imaging image information of an original on reading means, wherein at least one surface out of a plurality of surfaces forming the imaging lens has refracting power rotationally asymmetric with respect to the optical axis,
- wherein in such a coordinate system that an origin lies at an intersecting point of said one surface with the optical axis, x along a direction of the optical axis, y along a reading direction of the reading means, and z along a direction perpendicular to the optical-axis direction x and to the reading direction y,
- letting R(y) be a radius of local curvature at a certain point in said reading direction y on an xy section of said one surface, and r(y) be a radius of local curvature in a direction perpendicular to the xy plane and normal to the shape of the xy section in the reading direction y,
- the following condition is satisfied in a range of the reading direction y from 0 to a passing position y′ of an outermost off-axis principal ray;
- 0≦|[R(y)−r(y)]/[fd(Nd−1)]|≦0.15
- where fd:
- focal length of the overall system of the imaging lens at the d-line;
- and
- Nd:
- index of refraction of a lens with said one surface formed therein, at the d-line.
Dependencies are inferred from the claim text.