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...

Examples

Embodiment 1

[0055] In the imaging lens according to Example 1, both surfaces of the first lens G1 , the second lens G2 , the third lens G3 , and the fourth lens G4 are all aspherical. exist Figure 5 In the basic lens data of (A), as the curvature radii of these aspheric surfaces, the numerical values ​​of the curvature radii near the optical axis are indicated. exist Figure 5 Among the numerical values ​​shown as aspheric data in (B), the symbol "E" indicates that the data immediately following it is a "power exponent" with base 10, indicating that it will be represented by an exponential function with base 10 multiplied by the value before "E". For example, if it is "1.0E-02", it means "1.0×10 -2 ".

[0056] As the aspheric surface data, each coefficient B in the formula representing the aspheric surface shape represented by the following formula (A) i , The value of KA. More specifically, Z represents the length (mm) of a perpendicular line drawn from a point on the aspheric sur...

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...

Examples

Embodiment 1

[0055] In the imaging lens according to Example 1, both surfaces of the first lens G1 , the second lens G2 , the third lens G3 , and the fourth lens G4 are all aspherical. exist Figure 5 In the basic lens data of (A), as the curvature radii of these aspheric surfaces, the numerical values ​​of the curvature radii near the optical axis are indicated. exist Figure 5 Among the numerical values ​​shown as aspheric data in (B), the symbol "E" indicates that the data immediately following it is a "power exponent" with base 10, indicating that it will be represented by an exponential function with base 10 multiplied by the value before "E". For example, if it is "1.0E-02", it means "1.0×10 -2 ".

[0056] As the aspheric surface data, each coefficient B in the formula representing the aspheric surface shape represented by the following formula (A) i , The value of KA. More specifically, Z represents the length (mm) of a perpendicular line drawn from a point on the aspheric sur...

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