Optical imaging system

An optical imaging system comprising:

• a first lens having a positive refractive power and a convex object-side surface in a paraxial region thereof;
• a second lens having a refractive power, a convex object-side surface in a paraxial region thereof, and a concave image-side surface in a paraxial region thereof;
• a third lens having a negative refractive power;
• and
• a fourth lens having a positive refractive power, a convex object-side surface in a paraxial region thereof, and a concave image-side surface in a paraxial region thereof,
• wherein the first to fourth lenses are sequentially disposed in ascending numerical order along an optical axis of the optical imaging system from an object side of the optical imaging system toward an imaging plane of the optical imaging system,
• the optical imaging system has a total of four lenses,
• 0.8<TTL/f<1.5 is satisfied, where TTL is a distance along the optical axis from the object-side surface of the first lens to the imaging plane, and f is an overall focal length of the optical imaging system,
• FOV≤40° is satisfied, where FOV is a field of view of the optical imaging system, and
• 1.3<TTL/BFL<3.5 is satisfied, where BFL is a distance along the optical axis from the image-side surface of the fourth lens to the imaging plane.