Compact wide-angle imaging lens system
View Patent ↗A compact wide-angle imaging lens system includes, in order from the object side to the image side, a first lens ( 1 ) of negative refractive power, a free-form surface prism ( 2 ) of positive refractive power, a second lens ( 3 ) of positive refractive power and a third lens ( 7 ) of negative refractive power. The free-form surface prism has an incidence surface (S 3 ), a reflection surface (S 4 ) and an exit surface (S 5 ). The first lens and the free-form surface prism are arranged in a juxtaposed manner, and the second and third lenses are disposed below the free-form surface prism and adjacent to the image side. The free-form surface prism functions equivalent to a right-angle prism with aspheric surfaces.
1. A compact wide-angle imaging lens system consisting of, in order from the object side to the image side, a first lens of negative refractive power, a free-form surface prism of positive refractive power, a second lens of positive refractive power and a third lens of negative refractive power, wherein the first lens and the free-form surface prism are arranged in a juxtaposed manner, and the second and third lenses are disposed below the free-form surface prism and adjacent to the image side.
2. The compact wide-angle imaging lens system as claimed in claim 1 , wherein the second lens and the third lens are cemented as an integral part, and satisfy the condition of 0.8<(R 34 )/f<1.8, wherein f represents the effective focal length of the compact wide-angle imaging lens system, and R34 represents the curvature radius of a cementing surface between the second and third lenses.
3. The compact wide-angle imaging lens system as claimed in claim 2 , satisfying the condition of 1.0<|f 1 /|f|<1.9, wherein f 1 represents the effective focal length of the first lens.
4. The compact wide-angle imaging lens system as claimed in claim 3 , satisfying the condition of 1.6<f 2 /f<3.2, wherein f 2 represents the effective focal length of the free-form surface prism.
5. The compact wide-angle imaging lens system as claimed in claim 2 , satisfying the condition of 2.5 <(f 34 )/f<4.5, wherein f 34 represents the combined effective focal length of the second lens and the third lens.
6. The compact wide-angle imaging lens system as claimed in claim 1 , further comprising an aperture stop disposed between the free-form surface prism and the second lens.
7. The compact wide-angle imaging lens system as claimed in claim 1 , further comprising a glass cover disposed between the third lens and the image side.
8. The compact wide-angle imaging lens system as claimed in claim 1 , wherein the first lens has at least one aspheric surface.
9. The compact wide-angle imaging lens system as claimed in claim 1 , wherein the free-form surface prism has an incidence surface facing the first lens, a reflection surface inclinedly positioned on an optical axis of the compact wide-angle imaging lens system, and an exit surface positioned toward the image side.
10. The compact wide-angle imaging lens system as claimed in claim 9 , wherein both the incidence surface and the exit surface of the free-form surface prism are aspheric surfaces.
11. The compact wide-angle imaging lens system as claimed in claim 9 , wherein both the incidence surface and the exit surface of the free-form surface prism are convex surfaces, and the reflection surface of the free-form surface prism is a planar surface.
12. The compact wide-angle imaging lens system as claimed in claim 1 , wherein the first lens and the free-form surface prism are made of plastic.
13. The compact wide-angle imaging lens system as claimed in claim 12 , wherein the second lens and the third lens are made of glass.
14. A compact wide-angle imaging lens system comprising, in order from the object side to the image side, a first lens of negative refractive power, a free-form surface prism of positive refractive power, a second lens of positive refractive power and a third lens of negative refractive power; wherein the second
and third lenses are cemented as an integral part, and the compact wide-angle imaging lens system satisfy the following conditions:
1.0 <|f 1 /f |<1.9;
1.6 <f 2 /f <3.2;
2.5 <f 34 /f <4.5; and
0.8 <R 34 /f <1.8,
where, f represents the effective focal length of the compact wide-angle imaging lens system, f 1 and f 2 respectively represent the effective focal lengths of the first lens and the free-form surface prism, f 34 represents the combined effective focal length of the second and third lenses, and R 34 represents the curvature radius of a cementing surface between the second and third lenses.
15. The compact wide-angle imaging lens system as claimed in claim 14 , wherein the first lens and the free-form surface prism are arranged in a juxtaposed manner, and the second and third lenses are disposed below the free-form surface prism and adjacent to the image side.
16. The compact wide-angle imaging lens system as claimed in claim 15 , wherein the free-form surface prism functions equivalent to a right-angle prism with aspheric surfaces.
17. The compact wide-angle imaging lens system as claimed in claim 16 , wherein the free-form surface prism has an incidence surface facing the first lens, a reflection surface inclinedly positioned on an optical axis of the compact wide-angle imaging lens system, and an exit surface positioned toward the image side.
18. The compact wide-angle imaging lens system as claimed in claim 14 , wherein both the first lens and the free-form surface prism are made aspheric.
19. The compact wide-angle imaging lens system as claimed in claim 14 , further comprising an aperture stop disposed between the free-form surface prism and the second lens, and a glass cover disposed between the third lens and the image side.