Image reading lens and image reading apparatus
An image reading lens is provided and includes: in order from an object side of the image reading lens, a first lens of a negative lens having a meniscus shape directing a concave surface toward the object side thereof; a second lens having a biconvex shape; a stop; a third lens of a positive lens having a meniscus shape directing a convex surface toward an image side thereof; and a fourth lens of a negative lens having a meniscus shape directing a concave surface toward the object side thereof. The image reading lens satisfies the following conditional expressions: 2.4< f 3/ f <3.5 0.007< D 2/ f <0.028 where f represents a focal length of the image reading lens, f 3 represent a focal length of the third lens, and D 2 represents a spacing between an image-side surface of the first lens and an object-side surface of the second lens.
1. An image reading lens comprising: in order from an object side of the image reading lens,
a first lens of a negative lens having a meniscus shape directing a concave surface toward the object side thereof;
a second lens having a biconvex shape;
a stop;
a third lens of a positive lens having a meniscus shape directing a convex surface toward an image side thereof; and
a fourth lens of a negative lens having a meniscus shape directing a concave surface toward the object side thereof,
the image reading lens satisfying conditional expressions:
2.4< f 3/ f< 3.5
0.007< D 2/ f< 0.028
wherein f represents a focal length of the image reading lens, f 3 represent a focal length of the third lens, and D 2 represents a spacing between an image-side surface of the first lens and an object-side surface of the second lens.
2. The image reading lens according to claim 1 , further satisfying conditional expressions:
Nd 3+0.01×ν d 3<2.05
−1.56< f 1/ f<− 1.26
0.38< f 2/ f< 0.44
0.05< D 5/ f< 0.08
0.09< D 7/ f< 0.17
wherein Nd 3 represents a refractive index of the third lens at the d-line, νd 3 represents an Abbe number of the third lens at the d-line, f 1 represents a focal length of the first lens, f 2 represents a focal length of the second lens, D 5 represents a spacing between the stop and an object-side surface of the third lens, and D 7 represents a spacing between an image-side surface of the third lens and an object-side surface of the fourth lens.
3. The image reading lens according to claim 1 , further satisfying conditional expression:
Nd 3+0.01×ν d 3<2.05
wherein Nd 3 represents a refractive index of the third lens at the d-line, and νd 3 represents an Abbe number of the third lens at the d-line.
4. The image reading lens according to claim 1 further satisfying conditional expression:
−1.56< f 1/ f<− 1.26
wherein f 1 represents a focal length of the first lens.
5. The image reading lens according to claim 1 , further satisfying conditional expression:
0.38< f 2/ f< 0.44
wherein f 2 represents a focal length of the second lens.
6. The image reading lens according to claim 1 , satisfying conditional expression:
0.05< D 5/ f< 0.08
wherein D 5 represents a spacing between the stop and an object-side surface of the third lens.
7. The image reading lens according to claim 1 , further satisfying conditional expression:
0.09< D 7/ f< 0.17
wherein D 7 represents a spacing between an image-side surface of the third lens and an object-side surface of the fourth lens.
8. An image reading apparatus comprising an image reading lens according to claim 1 .
9. An image reading apparatus comprising an image reading lens according to claim 2 .