US Patent 11269161 Optical imaging system having six lenses of +−+−+− refractive powers

An optical imaging system includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens sequentially arranged from an object side. The optical imaging system satisfies 0.35<R1/f<0.40; N2+N3+N4>4.8; and TTL/(2*IMG HT)<0.70, where R1 is a radius of curvature of an object-side surface of the first lens, f is an overall focal length of the optical imaging system including the first to sixth lenses, N2 is a refractive index of the second lens, N3 is a refractive index of the third lens, N4 is a refractive index of the fourth lens, TTL is a distance from the object-side surface of the first lens to an image capturing surface of an image sensor, and IMG HT is half of a diagonal length of the image capturing surface of the image sensor.