Optical Imaging System

An optical imaging system, sequentially comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens from an object side to an image side along an optical axis, wherein an image-side surface of the seventh lens is a concave surface;

• the optical imaging system meets the following conditional expressions:
• TTL/ImgH<1.3,
• f/EPD<1.8,
• ImgH>6 mm and
• 0<R15/f8<0.8,
• wherein TTL is a distance from an object-side surface of the first lens to an imaging surface of the optical imaging system on the optical axis;
• ImgH is a half of diagonal length of an effective pixel region on the imaging surface;
• f is a total effective focal length of the optical imaging system;
• EPD is an entrance pupil diameter of the optical imaging system;
• R15 is a curvature radius of an object-side surface of the eighth lens;
• and f8 is an effective focal length of the eighth lens.