Wide-angle, single focus lens
AssigneeFuji Photo Optical Co., Ltd.
InventorKenichi Sato
Life of this patent
Estimating the term…
Abstract
A wide-angle, single focus lens is disclosed that is formed of four lens elements of negative, positive, negative, and positive refractive power, in sequential order from the object side. The first lens element is concave on its object side, the second lens element has at least one surface that is aspheric, and the fourth lens element is convex on its image side and has at least one surface that is aspheric. Specified conditions are preferably satisfied in order to reduce aberrations and provide a bright image while maintaining a short overall lens length.
Claims3
A wide-angle, single focus lens comprising four lenses of negative, positive, negative, and positive refractive power, in sequential order from the object side, wherein:
- the first lens is concave on the object side;
- the second lens has at least one surface that is aspheric;
- the fourth lens is convex on the image side and has at least one of its surfaces aspheric;
- and
- the following conditions are satisfied
- −2.0<f/f1<−0.5
- 0.5<f/f2<2.0
- 0.5<f/f4<2.0
- where
- f is the focal length of the wide-angle, single focus lens,
- f1 is the focal length of the first lens,
- f2 is the focal length of the second lens, and
- f4 is the focal length of the fourth lens.
A wide-angle, single focus lens comprising four lenses of negative, positive, negative, and positive refractive power, in sequential order from the object side, wherein:
- the first lens in order from the object side is concave on the object side;
- the second lens in order from the object side has at least one surface that is aspheric;
- and
- the fourth lens in order from the object side is convex on the image side and has at least one surface that is aspheric;
- and
- the following condition is satisfied:
- −2.0<f/f1<−0.5
- where
- f is the local length of the wide-angle, single focus lens, and
- f1 is the focal length of the first lens.
Dependencies are inferred from the claim text.