Fresnel lens and an illuminating device provided with the Fresnel lens
A refractive Fresnel lens part is provided on an upper surface of a plate-like lens at a central portion. A reflective Fresnel lens part is provided on a lower surface of the plate-like lens at a peripheral portion.
1. A Fresnel lens comprising:
a transparent plate member;
a refractive Fresnel lens part comprising a plurality of refractive faces formed on an upper surface of the plate member; and
a reflective Fresnel lens part comprising a plurality of reflective faces formed on a lower surface of the plate member;
wherein the refractive Fresnel lens part is formed on a central part of the plate member, and the reflective Fresnel lens part is formed on a peripheral part of the plate member,
a peripheral portion of the refractive Fresnel lens part and an inner edge portion of the reflective Fresnel lens part overlapping in top plan view.
2. The Fresnel lens according to claim 1 , wherein at least one surface formed of the refractive Fresnel lens part or the reflective Fresnel lens part has a predetermined curved surface.
3. The Fresnel lens according to claim 1 , furthermore comprising at least one LED chip disposed on or adjacent to a common central axis of the refractive Fresnel lens part and the reflective Fresnel lens part.
4. The Fresnel lens according to claim 1 , wherein each of the refractive Fresnel lenses and the reflective Fresnel lenses has a vertex of an angle larger than 52°.
5. A Fresnel lens comprising:
a transparent plate member; and
a refractive Fresnel lens part formed on an upper surface of the plate member and a reflective Fresnel lens part formed on a lower surface of the plate member;
wherein a central axis of the refractive Fresnel lens part is not congruent with a central axis of the reflective Fresnel lens part.
6. The Fresnel lens according to claim 5 , wherein at least one surface formed of the refractive Fresnel lens part or the reflective Fresnel lens part has a shape of an ellipse.
7. The Fresnel lens according to claim 5 , further comprising at least one LED chip disposed adjacent to at least one central axis of the refractive Fresnel lens part or the reflective Fresnel lens part.
8. The Fresnel lens according to claim 5 , wherein at least one surface formed of the refractive Fresnel lens part or the reflective Fresnel lens part has a predetermined curved surface.
9. The Fresnel lens according to claim 5 , further comprising two LED chips, one of said LED chips being disposed on the central axis of the refractive Fresnel lens part and one of said LED chips being disposed on the central axis of the reflective Fresnel lens part.
10. A Fresnel lens comprising:
a transparent plate member; and
a refractive Fresnel lens part formed on a surface of the plate member, and a reflective Fresnel lens part formed on the same surface of the plate member;
wherein a central axis of the refractive Fresnel lens part is not congruent with a central axis of the reflective Fresnel lens part.
11. The Fresnel lens according to claim 10 , furthermore comprising at least one LED chip disposed adjacent to at least one of the central axis of the refractive Fresnel lens part or the reflective Fresnel lens part.
12. The Fresnel lens according to claim 10 , further comprising two LED chips, one of said LED chips being disposed on the central axis of the refractive Fresnel lens part and one of said LED chips being disposed on the central axis of the reflective Fresnel lens part.