Imaging lens system

An imaging lens system comprising:

• a first lens having a positive refractive power;
• a second lens having a refractive power;
• a third lens having a refractive power and a convex object-side surface in a paraxial region thereof;
• a fourth lens having a refractive power and a convex object-side surface in a paraxial region thereof;
• and
• an optical path folding member disposed on an image side of the fourth lens and comprising four or more reflective surfaces,
• wherein the first to fourth lenses are sequentially disposed in ascending numerical order along an optical axis of the imaging lens system from an object side of the imaging lens system toward an imaging plane of the imaging lens system,
• the imaging lens system has a total number of four or five lenses having a refractive power,
• the imaging lens system satisfies 0.7<BFL/TTL<0.9, where BFL is a distance along the optical axis from an image-side surface of a rearmost lens of the imaging lens system disposed closest to the imaging plane to the imaging plane, and TTL is a distance along the optical axis from an object-side surface of the first lens to the imaging plane,
• the imaging lens system satisfies −1.2<fR/PL<−0.40 or 1.52< (TTL+ImgHT)/PL<2.32, where fR is a focal length of the rearmost lens, ImgHT is a height of the imaging plane, and PL is a distance along the optical axis from an incident surface of the optical path folding member to an exit surface of the optical path folding member, and
• a thickness of the second lens along the optical axis is greater than a thickness of the third lens along the optical axis.