A projection lens structure mainly includes a first group of lenses with a negative dioptric value, a second group of lenses with a positive dioptric value, a third group of lenses with a positive dioptric value and a fourth group of lenses with a negative dioptric value. The first group of lenses further includes at least a first lens and a second lens, of which the first lens ha a plastic aspheric lens in a meniscus shape with a focal length between −25˜−80 mm. The second group of lenses further includes at least a third lens. The third group of lenses further includes at least a first doublet with a focal length between 25˜80 mm. The fourth group of length further includes at least a group of doublets, a fourth lens and a fifth lens.

Provided is an objective optical system including: a first spherical lens and a second spherical lens that are arrayed in this order from an object; and at least one of a first optical medium and a second optical medium, wherein the first optical medium is a solid or liquid disposed at an object side of the first spherical lens and is in close contact with a surface on the object side of the first spherical lens, over an entire optical path; and the second optical medium is a solid or liquid disposed at an opposite side of the second spherical lens from the object and is in close contact with a surface on the opposite side of the second spherical lens from the object, over the entire optical path.

An embodiment provides an imaging lens comprising first to fourth lenses that are sequentially arranged from an object side towards an image side and satisfying mathematical formula 1, wherein the first lens has negative refractive power, the second lens and the third lens have positive refractive power, and the fourth lens has negative refractive power. −40.0<R1+R2<−20.0 where R1 is the curvature radius of the object side surface of the first lens, and R2 is the curvature radius of the image side surface of the first lens.

An embodiment provides an imaging lens comprising first to fourth lenses that are sequentially arranged from an object side towards an image side and satisfying mathematical formula 1, wherein the first lens has negative refractive power, the second lens and the third lens have positive refractive power, and the fourth lens has negative refractive power. −40.0<R1+R2<−20.0 where R1 is the curvature radius of the object side surface of the first lens, and R2 is the curvature radius of the image side surface of the first lens.

An optical imaging lens includes a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element has positive refracting power, an optical-axis region of the object-side surface of the second lens element is convex, a periphery region of the object-side surface of the second lens element is convex, and an optical-axis region of the image-side surface of the second lens element is convex. The Abbe number of the first lens element is ν1, the Abbe number of the second lens element is ν2 and the Abbe number of the third lens element is ν3 to satisfy 61.119≤ν1+ν2+ν3≤96.733.

An optical imaging lens includes a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element has positive refracting power, an optical-axis region of the object-side surface of the second lens element is convex, a periphery region of the object-side surface of the second lens element is convex, and an optical-axis region of the image-side surface of the second lens element is convex. The Abbe number of the first lens element is ν1, the Abbe number of the second lens element is ν2 and the Abbe number of the third lens element is ν3 to satisfy 61.119≤ν1+ν2+ν3≤96.733.

The maximum principal ray incident angle to an image surface is reduced in an image pickup device provided with an image pickup element. The image pickup device includes an image pickup lens, the image pickup element, and a cover glass. In the image pickup device, the cover glass is stuck on the image pickup element without containing air between them. In addition, in the image pickup device, the maximum incident angle of principal rays from the image pickup lens, to the cover glass is larger than 35 degrees. Furthermore, in the image pickup device, the refractive angle of the cover glass is at least 5 degrees smaller than the maximum incident angle.

The present disclosure discloses an optical imaging system, the optical imaging system including sequentially, along an optical axis from an object side to an image side, a first lens, a second lens, a third lens and a fourth lens. The first lens has a positive refractive power or a negative refractive power, an object-side surface of the first lens is a concave surface, and an image-side surface of the first lens is a convex surface; both the second lens and the third lens have positive refractive powers; and the fourth lens has a positive refractive power or a negative refractive power, wherein an abbe number V1 of the first lens and an abbe number V4 of the fourth lens satisfy: |V1-V4|30; and the abbe number V1 of the first lens and an abbe number V2 of the second lens satisfy: 20|V1-V2|50.

The present disclosure discloses an optical imaging system, the optical imaging system including sequentially, along an optical axis from an object side to an image side, a first lens, a second lens, a third lens and a fourth lens. The first lens has a positive refractive power or a negative refractive power, an object-side surface of the first lens is a concave surface, and an image-side surface of the first lens is a convex surface; both the second lens and the third lens have positive refractive powers; and the fourth lens has a positive refractive power or a negative refractive power, wherein an abbe number V1 of the first lens and an abbe number V4 of the fourth lens satisfy: |V1-V4|30; and the abbe number V1 of the first lens and an abbe number V2 of the second lens satisfy: 20|V1-V2|50.

A projection lens structure mainly includes a first group of lenses with a negative dioptric value, a second group of lenses with a positive dioptric value, a third group of lenses with a positive dioptric value and a fourth group of lenses with a negative dioptric value. The first group of lenses further includes at least a first lens and a second lens, of which the first lens ha a plastic aspheric lens in a meniscus shape with a focal length between 2580 mm. The second group of lenses further includes at least a third lens. The third group of lenses further includes at least a first doublet with a focal length between 2580 mm. The fourth group of length further includes at least a group of doublets, a fourth lens and a fifth lens.