Lens for image pickup
View Patent ↗A lens for image pickup is provided in which various aberrations are corrected satisfactorily, the optical length is at maximum approximately 6 mm, and moreover a sufficient back focus is secured. This lens for image pickup comprises a first lens, an aperture diaphragm, and a second lens, positioned in this order from the object side toward the image side. The first lens is a resin lens with a meniscus shape, with the convex surface facing the object side, and having positive refractive power. The second lens is a resin lens with a meniscus shape, with the convex surface facing the image side, and having positive refractive power.
1. A lens for image pickup, having a first lens L 1 , aperture diaphragm S 1 and second lens L 2 , configured with the first lens L 1 , aperture diaphragm S 1 and second lens L 2 positioned in order from the object side toward the image side; and wherein
the first lens L 1 is a resin lens having a meniscus shape with the convex surface facing the object side, and having positive refractive power;
the second lens L 2 is a resin lens having a meniscus shape with the convex surface facing the image side, and having positive refractive power; and,
the distance in air from the object-side incident surface of said first lens to the image plane is, at maximum, 6 millimeters.
2. The lens for image pickup according to claim 1 , wherein both surfaces of said first lens L 1 are aspherical, and both surfaces of said second lens L 2 are aspherical.
3. The lens for image pickup according to claim 1 , wherein the following conditions are satisfied:
0.2<| r 5 / f|< 3.1 (1)
3.0<( r 5 + r 6 )/( r 5 − r 6 )<19.0 (2)
1.0< d/f< 1.5 (3)
0.5< r 1 / r 2 <2.0 (4)
0.08< D 2 / f< 0.1 (5)
where f is the focal length of the entire lens system; r 5 is the curvature radius near the optical axis of the object-side surface of the second lens L 2 (axial curvature radius); r 6 is the curvature radius near the optical axis of the image-side surface of the second lens L 2 (axial curvature radius); d is the distance (in air) from the object-side surface of the first lens L 1 to the image plane; r 1 is the curvature radius near the optical axis of the object-side surface of the first lens L 1 (axial curvature radius); r 2 is the curvature radius near the optical axis of the image-side surface of the first lens L 1 (axial curvature radius); and D 2 is the interval between the first lens L 1 and the second lens L 2 .
4. The lens for image pickup according to claim 1 , wherein said first lens L 1 and said second lens L 2 constituting the lens for image pickup are formed from material having an Abbe number between 30 and 60.
5. The lens for image pickup according to claim 1 , wherein said first lens L 1 and said second lens L 2 constituting the lens for image pickup are formed from a cycloolefin plastic or from polycarbonate.
6. The lens for image pickup according to claim 1 , wherein aberration is corrected such that the magnitude of distortion aberration for an image height of 2.25 mm or less is within 3.00%.