Photographing lens optical system

A lens optical system comprising first, second, third, fourth, and fifth lenses that are sequentially arranged between an object and an image sensor on which an image of the object is formed, wherein

• the first lens has a positive (+) refractive power and is biconvex,
• the second lens has a negative (−) refractive power and has a meniscus shape that is convex toward the object,
• the third lens has a positive (+) refractive power,
• the fourth lens has a positive (+) refractive power and has a meniscus shape that is convex toward the image sensor, and
• the fifth lens has a negative (−) refractive power, and at least one of an incident surface and an exit surface of the fifth lens is an aspherical surface,
• wherein the incident surface of the fifth lens has no inflection point, and the exit surface of the fifth lens has a plurality of inflection points,
• wherein the incident surface of the fifth lens is concave toward the object at a center portion thereof and around the center portion, and
• wherein the entire region of an incident surface of the second lens is convex toward the object,
• wherein a focal length f of the lens optical system is greater than or equal to 4.8 mm and smaller than or equal to 4.89 mm,
• wherein a focal length f1 of the first lens is greater than or equal to 3.346 mm and smaller than or equal to 3.414 mm, and
• wherein the focal length f of the lens optical system and the focal length f1 of the first lens satisfy the following inequality:
• 1.42<|f/f1 |<1.5.