Imaging lens, camera module, and portable terminal apparatus
View Patent ↗An imaging lens comprises, in order from an object side: a first lens having a positive refractive power and a meniscus shape and having a convex surface directed to the object side; a second lens having a negative refractive power in the vicinity of an optical axis of the imaging lens; and a third lens having a positive refractive power in the vicinity of the optical axis, wherein at least one surface of each of the second lens and the third lens is an aspheric surface; and the imaging lens satisfies the following conditional expression expressions: 0.7 <If 1 /fl <0.8 . . . (1) 0.3<1f 2 /fl <0.8 . . . (2) 7.5 <vd 1 <96 . . .(3) TL/ 2 Y <0.9 . . . (4) where f: focal length of the imaging lens; f 1 : focal length of the first lens; f 2 : focal length of the second lens; vd 1 : Abbe number of the first lens for the d-line; TL: length between the object-side surface of the first lens to an image forming position of the imaging lens; and Y: maximum image height.
1. An imaging lens comprising, in order from an object side:
a first lens having a positive refractive power and a meniscus shape and having a convex surface directed to the object side;
a second lens having a negative refractive power in the vicinity of an optical axis of the imaging lens; and
a third lens having a positive refractive power in the vicinity of the optical axis,
wherein at least one surface of each of the second lens and the third lens is an aspheric surface; and
the imaging lens satisfies the following conditional expressions:
0.7<| f 1/ f|< 0.8 (1)
0.3<| f 2 /f|< 0.8 (2)
75< ν d 1 <96 (3)
TL/ 2 Y< 0.9 (4)
where
f: focal length of the imaging lens;
f 1 : focal length of the first lens;
f 2 : focal length of the second lens;
ν d 1 : Abbe number of the first lens for the d-line;
TL: length between the object-side surface of the first lens to an image forming position of the imaging lens; and
Y: maximum image height.
2. The imaging lens according to claim 1 , further satisfying the following conditional expression:
0.5< f 3/ f< 1.0 (5)
where f 3 is a focal length of the third lens.
3. The imaging lens according to claim 2 ,
wherein an object-side surface of the second lens has an aspheric shape and a negative refractive power increasing from the vicinity of the optical axis toward a periphery, and
an image-side surface of the second lens has an aspheric shape and a positive refractive power decreasing from the vicinity of the optical axis toward a periphery.
4. The imaging lens according to claim 2 , further satisfying the following conditional expression:
1.68<Nd 2 (6)
where Nd 2 is a refractive index of the second lens for the d-line.
5. The imaging lens according to claim 1 ,
wherein an object-side surface of the second lens has an aspheric shape and a negative refractive power increasing from the vicinity of the optical axis toward a periphery, and
an image-side surface of the second lens has an aspheric shape and a positive refractive power decreasing from the vicinity of the optical axis toward a periphery.
6. The imaging lens according to claim 5 , further satisfying the following conditional expression:
1.68<Nd 2 (6)
where Nd 2 is a refractive index of the second lens for the d-line.
7. The imaging lens according to claim 1 , further satisfying the following conditional expression:
1.68<Nd 2 (6)
where Nd 2 is a refractive index of the second lens for the d-line.
8. A camera module comprising:
the imaging lens according to claim 1 ; and
an imaging device that outputs an imaging signal corresponding to an optical image formed by the imaging lens.
9. A portable terminal apparatus comprising the camera module according to claim 8 .