Single focus lens having short overall length
AssigneeFuji Photo Optical Co., Ltd.
InventorKenichi Sato
Life of this patent
Estimating the term…
Abstract
A single focus lens is disclosed that is formed of only four lens components, which are arranged in positive, negative, positive and relatively weak positive or negative refractive power order from the object side, with a stop arranged between the first and second lens components. The third lens component has a convex surface on its image side, and the fourth lens component has a meniscus shape, is made of plastic, includes at least one aspheric surface, and is concave on its image side. The second lens component is formed of a single lens element, and various conditions are preferably satisfied so as to provide a compact lens having a short overall length while favorably correcting various aberrations.
Claims4
A single focus lens comprising, in order from the object side:
- a first lens component having positive refractive power;
- a stop;
- a second lens component having negative refractive power;
- a third lens component having positive refractive power with a convex surface on the image side;
- and
- a fourth lens component that is formed of plastic so as to have a meniscus shape, said fourth lens component serving as a correction plate for correction of aberrations, with at least one surface of the fourth lens component being aspheric and with the image-side surface of the fourth lens component being concave, wherein an expression which defines the shape of the aspheric surface of the fourth lens component includes at least one, non-zero, odd-numbered coefficient.
A single focus lens comprising, in order from the object side:
- a first lens component having positive refractive power;
- a stop;
- a second lens component having negative refractive power;
- a third lens component having positive refractive power with a convex surface on the image side;
- and
- a fourth lens component that is formed of plastic so as to have a meniscus shape, said fourth lens component serving as a correction plate for correction of aberrations, with at least one surface of the fourth lens component being aspheric and with the image-side surface of the fourth lens component being concave,
- wherein
- the second lens component is formed of a single lens element and the following Conditions (1) to (3) are satisfied:
- Nd2 > 1.8 Condition (1) νd2 < 25 Condition (2) |f/f4| < 0.8 Condition (3) where Nd2 is the refractive index at the d-line of the lens element of the second lens component, in order from the object side, νd2 is the Abbe number at the d-line of the lens element of the second lens component, in order from the object side, f is the focal length of the single focus lens, and f4 is the focal length of the fourth lens component, in order from the object side, wherein an expresion which defines the shape of the aspheric surface of the fourth lens component includes at least one, non-zero, odd-numbered coefficient.
A single focus lens comprising, in order from the object side:
- a first lens component having positive refractive power, said first lens component consisting of a single lens element having a surface positioned at the object side of said single focus lens;
- a stop;
- a second lens component having negative refractive power;
- a third lens component having positive refractive power with a convex surface on the image side;
- and
- a fourth lens component that is formed of plastic so as to have a meniscus shape, said fourth lens component serving as a correction plate for correction of aberrations, with at least one surface of the fourth lens component being aspheric and with the image-side surface of the fourth lens component being concave.
Dependencies are inferred from the claim text.