A single focus imaging lens comprises: a front lens group including one or two lenses and having a positive refractive power as a whole; a rear lens group including two or three lenses and having a negative refractive power as a whole; and a focusing lens, disposed between the front lens group and the rear lens group, that has a positive refractive power and moves on an optical axis for adjusting focus, wherein the following conditional expression is satisfied: 1.0< FL/f <5.0 (X) where f: focal length of the single focus imaging lens; FL: focal length of the focusing lens.
1. A single focus imaging lens comprising:
a front lens group including one or two lenses and having a positive refractive power as a whole;
a rear lens group including two or three lenses and having a negative refractive power as a whole; and
a focusing lens disposed between the front lens group and the rear lens group, the focusing lens consists of a single integral lens that has a positive refractive power and is made to move on an optical axis for adjusting focus,
wherein the following conditional expression is satisfied:
1.0 <FL/f< 5.0(X)
where
f: focal length of the single focus imaging lens;
FL: focal length of the focusing lens that consists of a single integral lens.
2. A single focus imaging lens comprising, in order from an object side thereof:
a first lens having a positive refractive power;
a second lens having a positive refractive power;
a third lens having a negative refractive power with an object side surface including a concave surface in the vicinity of the optical axis; and
a fourth lens having a positive meniscus shape with an object side surface including a convex surface in the vicinity of the optical axis,
wherein the first lens is made to function as a front lens group including one lens and having a positive refractive power as a whole,
the third lens and the fourth lens are made to function as a rear lens group including two lenses and having a negative refractive power as a whole,
the second lens is made to function as a focusing lens disposed between the front lens group and the rear lens group, that has a positive refractive power, and the second lens is made to move on an optical axis for adjusting focus, and
wherein the following conditional expression is satisfied:
1.0 <FL/f< 5.0(X)
where
f: focal length of the single focus imaging lens;
FL: focal length of the second lens.
3. The imaging lens as set forth in claim 2 , wherein the following conditional expressions are satisfied:
1.0 <f 1/ f< 3.0 (1)
1.0 <f 2/ f< 5.0 (2)
0.5 <|f 3/ f|< 1.0 (3)
0.5 <f 4/ f< 1.0 (4)
Where
f: focal length of the single focus imaging lens;
f1: focal length of the first lens;
f2: focal length of the second lens;
f3: focal length of the third lens;
f4: focal length of the fourth lens.
4. The imaging lens as set forth in claim 2 ,
wherein the first lens has an object side surface including a convex shape in the vicinity of the optical axis,
the second lens has an image side surface including a convex shape in the vicinity of the optical axis,
the third lens has a concave shape in the vicinity of the optical axis on both sides thereof, and
the fourth lens satisfies the following conditional expression:
0.15 <R 4 A/f< 0.35 (5),
where
f: focal length of the single focus imaging lens;
R4A: paraxial radius of curvature of the object side surface of the fourth lens.
5. The imaging lens as set forth in claim 3 ,
wherein the first lens has an object side surface including a convex shape in the vicinity of the optical axis,
the second lens has an image side surface including a convex shape in the vicinity of the optical axis,
the third lens has a concave shape in the vicinity of the optical axis on both sides thereof, and
the fourth lens satisfies the following conditional expression:
0.15 <R 4 A/f< 0.35 (5),
where
f: focal length of the single focus imaging lens;
R4A: paraxial radius of curvature of the object side surface of the fourth lens.