Single focus lens
View Patent ↗A single focus lens includes, in order from the object side: a glass first lens component of positive refractive power and with a convex surface on the object side; a diaphragm stop; a second lens component of plastic, a meniscus shape with its concave surface on the object side, and which includes at least one aspheric surface; and a third lens component of plastic, a meniscus shape with it convex surface on the object side, and which includes two aspheric surfaces. Each lens component may consist of a single lens element. Specified conditions are satisfied in order to reduce aberrations, to insure that the light rays at the image plane are substantially orthogonal to the image plane, and to insure that a sufficient back focus is provided so as to enable the insertion of other optical elements.
1. A single focus lens comprising, arranged along an optical axis in order from the object side:
a first lens component having positive refractive power, having a convex object-side surface, and being made of glass;
a stop;
a second lens component having a meniscus shape with a concave object-side surface, being made of plastic, and having at least one aspheric surface;
a third lens component having a meniscus shape with a convex object-side surface, being made of plastic, and each of the object-side surface and the image-side surface being aspheric;
wherein
the following conditions are satisfied:
1.0 <f 1 / f <2.5
R 1 / f <3.0
1.0 <ΔZF/ΔZR <2.0
0.3 <ΔZRA/ΔZR <0.6
0.7<( Bf−ΔZR )/ M
0.6<(| R 2 |− R 1 )/( R 1 +| R 2 |)
where
f 1 is the focal length of the first lens component,
f is the focal length of the single focus lens,
R 1 is the radius of curvature of the object-side surface of the first lens component,
ΔZF is the object-side shape displacement at the maximum height at which an image forming light ray passes through the image-side surface of the third lens component,
ΔZR is the image-side shape displacement at the maximum height at which an image forming light ray passes through the image-side surface of the third lens component,
ΔZRA is the image-side shape displacement at one-half the maximum height at which an image forming light ray passes through the image-side surface of the third lens component,
Bf is the back focal length of the single focus lens based on air being between the image-side surface of the single focus lens and the image plane,
M is the maximum image height at the image plane, and
R 2 is the radius of curvature of the image-side surface of the first lens component.
2. The single focus lens of claim 1 , wherein the first lens component is a lens element.
3. The single focus lens of claim 2 , wherein the second lens component is a lens element.
4. The single focus lens of claim 3 , wherein the third lens component is a lens element.
5. The single focus lens of claim 1 , wherein the first lens component, the second lens component, and the third lens component are arranged in that order along the optical axis from the object side without any intervening lens element.
6. The single focus lens of claim 5 , wherein each of the first, second, and third lens components consists of a lens element.
7. The single focus lens of claim 1 , wherein the single focus lens is formed of only three lens components.
8. The single focus lens of claim 7 , wherein the first lens component is a lens element.
9. The single focus lens of claim 8 , wherein the second lens component is a lens element.
10. The single focus lens of claim 9 , wherein the third lens component is a lens element.
11. The single focus lens of claim 1 , wherein the first lens component is plano-convex in shape with the planar surface on the image side and each of the object-side surface and the image-side surface of the second lens component is aspheric.
12. The single focus lens of claim 11 , wherein the first lens component is a lens element.
13. The single focus lens of claim 12 , wherein the second lens component is a lens element.
14. The single focus lens of claim 13 , wherein the third lens component is a lens element.
15. The single focus lens of claim 11 , wherein the first lens component, the second lens component, and the third lens component are arranged in that order along the optical axis from the object side without any intervening lens element.
16. The single focus lens of claim 15 , wherein each of the first, second, and third lens components consists of a lens element.
17. The single focus lens of claim 11 , wherein the single focus lens is formed of only three lens components.
18. The single focus lens of claim 17 , wherein the first lens component is a lens element.
19. The single focus lens of claim 18 , wherein the second lens component is a lens element.
20. The single focus lens of claim 19 , wherein the third lens component is a lens element.