Optical imaging system

An optical imaging system, comprising:

• a first lens having a convex object-side surface in a paraxial region thereof;
• a second lens having a negative refractive power, a convex object-side surface in a paraxial region thereof, and a refractive index of 1.65 or more;
• a third lens having a concave image-side surface in a paraxial region thereof;
• a fourth lens having a convex object-side surface in a paraxial region thereof;
• a fifth lens having a refractive power;
• a sixth lens having a positive refractive power, and having a convex object-side surface in a paraxial region thereof;
• and
• a seventh lens having a convex object-side surface, and having a concave image-side surface in a paraxial region thereof,
• wherein the optical imaging system comprises a total of seven lenses with refractive power,
• wherein the first lens through the seventh lens are sequentially disposed in ascending numerical order from an object side of the optical imaging system toward an imaging plane of the optical imaging system,
• wherein a thickness of the fourth lens is greater than a distance from an image-side surface of the third lens to an object-side surface of the fourth lens,
• wherein a distance from an image-side surface of the fourth lens to an object-side surface of the fifth lens is greater than a thickness of the second lens, and
• wherein the optical imaging system satisfies the following conditional expression:
• −31<V3−V4,
• where V3 is an Abbe number of the third lens, and V4 is an Abbe number of the fourth lens.