An optical system (100, 200, 300, 400, 500) comprising, arranged in order from an object side to an image side: an aperture; a first lens (101, 201, 301, 401, 501, 601) 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 facing the object, wherein the aperture is arranged on the face of the first lens which faces the object side; a second lens (102, 202, 302, 402, 502, 602) having a positive refractive power and disposed along the optical axis adjacent to the first lens (101, 201, 301, 401, 501, 601), the second lens further having a second convex face facing the object; a third lens (103, 203, 303, 403, 503, 603) having a negative refractive power and disposed along the optical axis adjacent to the second lens (102, 202, 302, 402, 502, 602), the third lens further having a third concave face facing the image side; a fourth lens (104, 204, 304, 404, 504, 604) disposed along the optical axis adjacent to the third lens (103, 203, 303, 403, 503, 603), the fourth lens being an aspherical lens; a fifth lens (105, 205, 305, 405, 505, 605) disposed along the optical axis adjacent to the fourth lens (104, 204, 304, 404, 504, 604), the fifth lens being an aspherical lens and having a fourth face facing the object, the fourth face being convex where the fifth lens intersects the optical axis; and a sixth lens (106, 206, 306, 406, 506, 606) disposed along the optical axis adjacent to the fifth lens (105, 205, 305, 405, 505, 605), the sixth lens being an aspherical lens, wherein each of the fourth face 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 (102, 202, 302, 402, 502, 602), wherein characteristics of the third lens (103, 203, 303, 403, 503, 603) satisfy equation − 0.6 < R 6 R 5 < 0.6 wherein "R5" represents a curvature radius of a face of the third lens facing the object, and "R6" represents a curvature radius of the third concave face of the third lens facing the image side, characterized in that characteristics of the fourth lens (104, 204, 304, 404, 504, 604) satisfy equation − 0.15 < f/f4 < 0.15 wherein "f4" represents a focal distance of the fourth lens. an aperture; a first lens (101, 201, 301, 401, 501, 601) 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 facing the object, wherein the aperture is arranged on the face of the first lens which faces the object side; a second lens (102, 202, 302, 402, 502, 602) having a positive refractive power and disposed along the optical axis adjacent to the first lens (101, 201, 301, 401, 501, 601), the second lens further having a second convex face facing the object; a third lens (103, 203, 303, 403, 503, 603) having a negative refractive power and disposed along the optical axis adjacent to the second lens (102, 202, 302, 402, 502, 602), the third lens further having a third concave face facing the image side; a fourth lens (104, 204, 304, 404, 504, 604) disposed along the optical axis adjacent to the third lens (103, 203, 303, 403, 503, 603), the fourth lens being an aspherical lens; a fifth lens (105, 205, 305, 405, 505, 605) disposed along the optical axis adjacent to the fourth lens (104, 204, 304, 404, 504, 604), the fifth lens being an aspherical lens and having a fourth face facing the object, the fourth face being convex where the fifth lens intersects the optical axis; and a sixth lens (106, 206, 306, 406, 506, 606) disposed along the optical axis adjacent to the fifth lens (105, 205, 305, 405, 505, 605), the sixth lens being an aspherical lens, wherein each of the fourth face 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 (102, 202, 302, 402, 502, 602), wherein characteristics of the third lens (103, 203, 303, 403, 503, 603) satisfy equation − 0.6 < R 6 R 5 < 0.6 wherein "R5" represents a curvature radius of a face of the third lens facing the object, and "R6" represents a curvature radius of the third concave face of the third lens facing the image side, characterized in that characteristics of the fourth lens (104, 204, 304, 404, 504, 604) satisfy equation − 0.15 < f/f4 < 0.15 wherein "f4" represents a focal distance of the fourth lens.