Patent ID: 8988789
Filing Date: 2015-03-24
Classification: G02B

Abstract:
1. An optical image system comprising, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with negative refractive power; a third lens element with refractive power, wherein an object-side surface and an image-side surface of the third lens element are aspheric; a fourth lens element with refractive power having a convex image-side surface, wherein an object-side surface and the image-side surface of the fourth lens element are aspheric; end a fifth lens element with refractive power having a concave image-side surface, wherein an object-side surface and the image-side surface of the fifth lens element are aspheric, and the fifth lens element has at least one inflection point on the image-side surface thereof; wherein the optical image system has a total of five lens elements with refractive power, the optical image system further comprises at least one flat element located between the fifth lens element and an image plane, a focal length of the optical image system is f, a curvature radius of the image-side surface of the fifth lens element is R10, a distance between the optical axis and the non-axial critical point on the image-side surface of the fifth lens element is Yc52, an axial distance between the object-side-surface of the first lens element and the image-side surface of the fifth lens element is Td, a linear expansion coefficient of the flat element at 20° C. is αPE, and the following relationships are satisfied: