| 摘要 |
Arranging a negative first lens, a positive second lens, a negative third lens, a positive fourth lens, and a negative fifth lens from the object side, in which the image side surface of the fifth lens has an aspherical shape with one or more inflection points and a concave shape toward the image side in a paraxial region, and, when the focal length of the entire lens system, radius of curvature of the image side surface of the first lens, radius of curvature of the image side surface of the second lens, overall optical length, focal length of jth lens, and Abbe number of jth lens are taken as f, R2, R4, TL, fj, and νj respectively, the image capturing lens is configured to simultaneously satisfy conditional expressions (1a): −1.5<f/R2<1.6, (2a): −1.6<f/R4<0.05, (3a): 0.95≦f4/f≦4.3, (5a): 1.0≦TL/f≦2.2, and (12b): −2.0<Σ(fj/νj)/f<0.5. |
| 主权项 |
1. An image capturing lens substantially consisting of a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a negative refractive power, a fourth lens having a positive refractive power, and a fifth lens having a negative refractive power, arranged in this order from the object side, wherein:
the image side surface of the fifth lens has an aspherical shape with one or more inflection points and a concave shape toward the image side in a paraxial region; and the image capturing lens satisfies the following conditional expressions (1a), (2a), (3a), (5a), and (12b) simultaneously:
−1.5<f/R2<1.6 (1a);−1.6<f/R4<0.05 (2a);0.95≦f4/f≦4.3 (3a),1.0≦TL/f≦2.2 (5a); and−2.0<Σ(fj/νj)/f<0.5 (12b),where:
f is a focal length of the entire lens system; R2 is a radius of curvature of the image side surface of the first lens; R4 is a radius of curvature of the image side surface of the second lens; f4 is a focal length of the fourth lens; TL is an overall optical length when a distance from the image side surface of the fifth lens to the image plane is represented by an air equivalent length; Σ(fj/νj)/f is [(f1/ν1)+(f2/ν2)+(f3/ν3)+(f4/ν4)+(f5/ν5)]/f; f1 is a focal length of the first lens; f2 is a focal length of the second lens; f3 is a focal length of the third lens; f5 is a focal length of the fifth lens; ν1 is an Abbe number of the first lens; ν2 is an Abbe number of the second lens; ν3 is an Abbe number of the third lens; ν4 is an Abbe number of the fourth lens; and ν5 is an Abbe number of the fifth lens. |
