Imaging lens system and imaging device comprising seven lenses of −−++−+− refractive powers
A vehicle-mounted wide-angle lens that simultaneously achieves a high resolution necessary for sensing, a size small enough to be mounted on a vehicle, and a low price. An imaging lens includes, sequentially from the object side, a first lens having a negative power and being concave on the image side, a second lens having a negative power and being concave on the image side, a third lens having a positive power and being convex on the object side, an aperture stop, a fourth lens having a positive power and being convex on the image side, a fifth lens, a sixth lens whose object side is bonded to the image side of the fifth lens and a seventh lens having a negative power and being convex on the image side, and the fourth lens is an aspheric glass lens.
1. An imaging lens comprising, sequentially from an object side:
a first lens having a negative power and being concave on an image side;
a second lens having a negative power and being concave on the image side;
a third lens having a positive power and being convex on an object side;
an aperture stop;
a fourth lens having a positive power and being convex on the image side;
a fifth lens;
a sixth lens whose object side is bonded to the image side of the fifth lens; and
a seventh lens having a negative power and being convex on the image side,
wherein the fourth lens is an aspheric glass lens.
2. The imaging lens according to claim 1 , wherein the fourth lens has the highest power out of lenses having a positive power among the first lens to the seventh lens.
3. The imaging lens according to claim 1 , wherein a following expression (2) is satisfied:
2.8< f 4/ f< 3.5 (2)
where a focal length of the fourth lens is f4 and a focal length of an entire lens optical system is f.
4. The imaging lens according to claim 1 , wherein a following expression (1) is satisfied:
−3.0< f 5/ f← 2.2 (1)
where a focal length of the fifth lens is f5 and a focal length of an entire lens optical system is f.
5. The imaging lens according to claim 1 , wherein the image side of the fifth lens and the object side of the sixth lens each have an aspheric shape.
6. The imaging lens according to claim 1 , wherein the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens are plastic lenses.
7. An imaging device comprising:
an imaging lens system according to claim 1 ,
a flat-plate cover glass placed on an object side of the imaging lens system; and
an image sensor placed at an image location of the imaging lens system.