Optical imaging system

An optical imaging system comprising:

• a first lens having a positive refractive power;
• a second lens having a negative refractive power;
• a third lens having a refractive power;
• a fourth lens having a positive refractive power;
• a fifth lens having a negative refractive power;
• a sixth lens having a refractive power;
• a seventh lens having a refractive power;
• an eighth lens having a refractive power;
• and
• a ninth lens having a refractive power,
• wherein the first to ninth 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, and
• the optical imaging system satisfies 0.9<(TTL/(2×IMG HT))×Fno≤0.95, where TTL is a distance along the optical axis from an object-side surface of the first lens to the imaging plane, IMG HT is one half of a diagonal length of the imaging plane, and Fno is an F-number of the optical imaging system.