An optical system comprising, arranged in order from an object side to an image side: an aperture; a first lens having a positive refractive power and disposed along an optical axis and to face an object, the first lens further having a first convex face (S1) facing the object, wherein the aperture is arranged on the face of the first lens which faces the object side; a second lens having a positive refractive power and disposed along the optical axis adjacent to the first lens , the second lens further having a second convex face (S3) facing the object; a third lens having a negative refractive power and disposed along the optical axis adjacent to the second lens , the third lens further having a third concave face (S6) facing the image side; a fourth lens disposed along the optical axis adjacent to the third lens , the fourth lens being an aspherical lens; a fifth lens disposed along the optical axis adjacent to the fourth lens , the fifth lens being an aspherical lens and having a fourth face (S9) facing the object, the fourth face being convex where the fifth lens intersects the optical axis; and a sixth lens disposed along the optical axis adjacent to the fifth lens , the sixth lens being an aspherical lens, wherein each of the fourth face (S9) of the fifth lens and a fifth face (S1 1) of the sixth lens facing the object has at least one inflection point, and characteristics of the optical system satisfy equation 0.4 < f f 2 < 1.6 wherein "f" represents a focal distance of the optical system, and "f2" represents a focal distance of the second lens , wherein characteristics of the third lens satisfy equation − 0.6 < R 6 R 5 < 0.6 wherein "R5" represents a curvature radius of a face (S5) of the third lens facing the object, and "R6" represents a curvature radius of the third concave face (S6) of the third lens facing the image side, characterized in that characteristics of the fourth lens satisfy equation − 0.15 < f/f4 < 0.15 wherein "f4" represents a focal distance of the fourth lens. an aperture; a first lens having a positive refractive power and disposed along an optical axis and to face an object, the first lens further having a first convex face (S1) facing the object, wherein the aperture is arranged on the face of the first lens which faces the object side; a second lens having a positive refractive power and disposed along the optical axis adjacent to the first lens , the second lens further having a second convex face (S3) facing the object; a third lens having a negative refractive power and disposed along the optical axis adjacent to the second lens , the third lens further having a third concave face (S6) facing the image side; a fourth lens disposed along the optical axis adjacent to the third lens , the fourth lens being an aspherical lens; a fifth lens disposed along the optical axis adjacent to the fourth lens , the fifth lens being an aspherical lens and having a fourth face (S9) facing the object, the fourth face being convex where the fifth lens intersects the optical axis; and a sixth lens disposed along the optical axis adjacent to the fifth lens , the sixth lens being an aspherical lens, wherein each of the fourth face (S9) of the fifth lens and a fifth face (S1 1) of the sixth lens facing the object has at least one inflection point, and characteristics of the optical system satisfy equation 0.4 < f f 2 < 1.6 wherein "f" represents a focal distance of the optical system, and "f2" represents a focal distance of the second lens , wherein characteristics of the third lens satisfy equation − 0.6 < R 6 R 5 < 0.6 wherein "R5" represents a curvature radius of a face (S5) of the third lens facing the object, and "R6" represents a curvature radius of the third concave face (S6) of the third lens facing the image side, characterized in that characteristics of the fourth lens satisfy equation − 0.15 < f/f4 < 0.15 wherein "f4" represents a focal distance of the fourth lens. <EOS>