US 7,321,474 B1
Photographic lens
Sung-ho Jo, Seongnam-si (Korea, Republic of)
Assigned to Samsung Techwin Co., Ltd., Changwon (Korea, Republic of)
Filed on Jan. 25, 2007, as Appl. No. 11/698,331.
Claims priority of application No. 10-2006-0087517 (KR), filed on Sep. 11, 2006.
Int. Cl. G02B 9/34 (2006.01); G02B 13/18 (2006.01); G02B 3/02 (2006.01)
U.S. Cl. 359—773  [359/715] 24 Claims
OG exemplary drawing
 
1. A photographic lens comprising:
a first lens having positive refractive power;
a second lens having negative refractive power and a convex surface facing the object side;
a third lens having positive refractive power; and
a fourth lens having negative refractive power at a center portion, in which the negative refractive power becomes weaker from the center portion toward the peripheral portion of the fourth lens, and having a positive refractive power at the peripheral portion thereof,
wherein the lenses are numbered in order of location from the object side, and,
wherein the condition 0.9≤(r4+r5)/(r4−r5)≤1.8 is satisfied,
where r4 denotes the radius of curvature of the surface of the second lens facing the object side, and r5 denotes the radius of curvature of the surface of the second lens facing the image side.