Patent ID: 11874433
Assignee: TOKYO VISIONARY OPTICS CO., LTD.
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. An imaging lens comprising in order from an object side to an image side,
a first lens having positive refractive power,
a second lens,
a third lens,
a fourth lens having negative refractive power,
a fifth lens having positive refractive power,
a sixth lens, and
a seventh lens, wherein said fourth lens has a convex surface facing the image side near the optical axis, and the following conditional expressions (2a), (3), (13) and (16) are satisfied:

−7.1<f2/f<−2.5  (2a)

0.3<t2/t3<3.3  (3)

50<νd7<60  (13)

2.5<|f34|/f<12.0  (16)

where
f: a focal length of the overall optical system,
f2: a focal length of the second lens,
f34: a composite focal length of the third lens and the fourth lens,
t2: a distance along the optical axis from an image-side surface of the second lens to an object- side surface of the third lens,
t3: a distance along the optical axis from an image-side surface of the third lens to an object-side surface of the fourth lens, and
vd7: an abbe number at d-ray of the seventh lens.