Imaging lens

Abstract

An imaging lens is provided and has, in order from the object side, a first lens (G1) of a positive lens having a convex surface on the object side thereof; a second lens (G2) in a meniscus shape having a concave surface on an image side thereof; a third lens (G3) in a meniscus shape having a convex surface on the image side thereof; and a fourth lens (G4) of a positive or negative lens, both surfaces of the fourth lens being aspheric and the fourth lens having a concave surface on the image side and in a vicinity of an optical axis of the fourth lens. The first lens (G1) is a positive lens having a convex surface on the object side, for example, a double convex lens. The second lens (G2) is a negative meniscus lens having a concave surface on the image side. The third lens (G3) is a positive meniscus lens having a convex surface on the image side. The fourth lens (G4) is a positive or negative aspheric lens having a concave surface on the image side and in the vicinity of the optical axis. The Abbe numbers of the first and second lenses as well as the focal distances of the first to fourth lenses satisfies specific conditions.

Description

technical field [0001] The present invention relates to an imaging lens mounted on a video camera using an imaging element such as a CCD (Charge Couple Device) or a CMOS (Complementary Metal Oxide Semiconductor). Background technique [0002] Imaging elements such as CCDs and CMOSs ​​are progressing towards very small size and high speed in recent years. For this reason, small and high-performance devices are also required for the main body of the camera and the lens mounted thereon. In addition, in order to correspond to a high-pixel imaging element, telecentricity is sought, that is, the incident angle to the imaging element is close to parallel to the optical axis (the incident angle to the imaging element is close to perpendicular). Conventionally, most imaging lenses mounted on, for example, a mobile phone with a video camera consist of three lenses, but the number of lenses tends to increase further in order to cope with higher pixel count. Patent Document 1 describe...

AI Technical Summary

Problems solved by technology

[0004] However, the imaging lens described in Patent Document 1 has room for improvement in terms of chromatic aberration.

In addition, in an imaging lens with a four-element structure, in order to ensure telecentricity, it is conceivable to place an aperture stop on the object side as much as possible. However, in this case, as in the imaging lens described in Patent Document 1, if If the surface on the object side is concave, the manufacturing sensitivity will increase, and if there is a misalignment of the lens during manufacturing, for example, image plane fluctuations will easily occur

Images