Imaging lens

Abstract

An imaging lens substantially consists of five lenses of a first lens having a meniscus shape with its convex surface facing an object side and negative refractive power, a second lens having negative refractive power, and the image-side surface of which has a convex shape facing an image side in the vicinity of an optical axis, a third lens having positive refractive power, a stop, a fourth lens having positive refractive power, and a fifth lens having negative refractive power. At least one of the surfaces of the first lens through the fifth lens is aspherical. A predetermined conditional formula about a distance on the optical axis from an object-side surface of the first lens to an image plane and a distance on the optical axis from the object-side surface of the first lens to the image-side surface of the second lens is satisfied.

What is claimed is: 
     
         1 . An imaging lens consisting of five lenses of:
 a first lens having a meniscus shape with its convex surface facing an object side and negative refractive power;   a second lens having negative refractive power;   a third lens having positive refractive power;   a fourth lens having positive refractive power; and   a fifth lens having negative refractive power, which are in this order from the object side,   wherein at least one of the surfaces of the first lens through the fifth lens is aspherical, and   wherein the following conditional formulas are satisfied:
   0.11< d 1-4/ L   (2-1);
 
   0.08< d 4-5/ f   (7);
 
   0.08< d 10/ f< 0.54  (8-2);
 
   0.48< f 3/ f   (9);
 
   1.5<Bf/ f< 3.0  (10-1);
 
   −5.0< r 10/ f<− 0.50  (11-1);
 
   5.0< L/f< 20.0  (12-1);
 
   and 
   ( r 8+ r 9)/( r 8− r 9)<2.0  (13-1),
 
   
       where
 L: a distance on the optical axis from an object-side surface of the first lens to an image plane (a distance between the fifth lens and the image plane is a distance in air), 
 d1-4: a distance on the optical axis from the object-side surface of the first lens to the image-side surface of the second lens, 
 d4-5: a distance on the optical axis from the image-side surface of the second lens to the object-side surface of the third lens, 
 f: a focal length of an entire system, 
 d10: the thickness of a fifth lens on an optical axis, 
 f3: a focal length of a third lens, 
 Bf: a back focus of an entire system, 
 r10: a curvature radius of an object-side surface of a fifth lens in the vicinity of an optical axis, 
 r8: a curvature radius of an object-side surface of a fourth lens in the vicinity of an optical axis, and 
 r9: a curvature radius of an image-side surface of a fourth lens in the vicinity of an optical axis. 
 
     
     
         2 . The imaging lens, as defined in  claim 1 , wherein the following conditional formula is satisfied:
   2.0< f 3/ f< 20.0  (9-1),
   
       where
 f3: a focal length of the third lens, and 
 f: a focal length of an entire system.