Optical imaging system

An optical imaging system, comprising:

• a lens group, sequentially comprising, from an object side to an image side along a first direction, a first lens, a second lens, a third lens, a fourth lens and a fifth lens with refractive power;
• wherein
• a first prism, arranged on the object side of the lens group and configured to reflect light incident into the first prism along a second direction to be emergent from the first prism along the first direction;
• and
• a second prism, arranged on the image side of the lens group and configured to reflect light incident into the second prism along the first direction to be emergent from the second prism along a third direction,
• wherein the first direction, the second direction and the third direction are perpendicular to one another,
• at least one lens in the lens group is a plastic lens, and at least one surface of the plastic lens is an aspherical surface, the first lens has positive refractive power, the second lens has positive refractive power, the third lens has negative refractive power, the fourth lens has positive refractive power, and the fifth lens has negative refractive power;
• and
• ImgH is a half of a diagonal length of an effective pixel region on an imaging surface of the optical imaging system, a total effective focal length f of the optical imaging system and ImgH meet 8<f/ImgH<10.