Light source device
A light source device includes a Fresnel lens having a light incidence surface and a light emission surface, and equipped with a light transmissive part and a light reflective part provided on an outside of the light transmissive part; and a light emitting element that is disposed opposite the light incidence surface of the Fresnel lens, and is disposed below the light transmissive part and part of the light reflective part on the light transmissive part side.
1. A light source device comprising:
a Fresnel lens having a light incidence surface and a light emission surface, and equipped with a light transmissive part and a light reflective part provided on an outside of the light transmissive part; and
a light emitting element including a semiconductor stack and a pair of electrodes, the light emitting element being disposed to face the light incidence surface of the Fresnel lens at a position below the light transmissive part and part of the light reflective part adjacent to the light transmissive part of the Fresnel lens, wherein
the Fresnel lens has a plurality of unit lenses arranged along a circumferential direction on the light incidence surface at the light reflective part, and
the unit lenses have lens surfaces and rise surfaces located between the lens surfaces, are set to a pitch of 60 μm or less, and satisfy the following Formulas (1) and (2):
1.0 x≤y≤ 2.5 x (1)
0.1 z≤x≤ 2.0 z (2)
where x is the maximum width of a light emission face of the light emitting element, y is an effective diameter of the Fresnel lens, and z is the shortest distance between the light emitting element and the light transmitting part of the Fresnel lens,
the shortest distance between the light emitting element and the light transmissive part of the Fresnel lens is from 0.2 to 1.0 mm.
2. The light source device according to claim 1 , wherein
the light emission surface of the Fresnel lens has a texture shape surface.
3. The light source device according to claim 1 , wherein
the maximum width of the light emission face of the light emitting element is from 0.9 to 2.9 mm.
4. The light source device according to claim 1 , wherein
the effective diameter of the Fresnel lens is from 1.5 to 5.0 mm.
5. The light source device according to claim 1 , wherein
the unit lenses have the convex vertices and concave vertices at which the lens surfaces and rise surfaces are linked, and each of the convex vertices and concave vertices is a rounded-off shape.
6. The light source device according to claim 1 , wherein
a height of the each unit lens decreases toward a center of the Fresnel lens.
7. The light source device according to claim 1 , further comprising
a light transmissive member disposed on the light emission surface of the light emitting element.
8. The light source device according to claim 7 , wherein
the light transmissive member contains a fluorescence substance that can convert a wavelength of light from the light emitting element.
9. The light source device according to claim 1 , further comprising
an additional Fresnel lens linked to the Fresnel lens, and
an additional light emitting element disposed below the additional Fresnel lens.
10. The light source device according to claim 1 , wherein
the semiconductor stack of the light emitting element is a nitride semiconductor stack including a first semiconductor layer, a light emitting layer, and a second semiconductor layer.
11. The light source device according to claim 1 , wherein
the light emitting element is flip-chip mounted on a mounting board.
12. The light source device according to claim 1 , wherein
the light emission face of the light emitting element is arranged on an opposite side of a surface on which the electrodes are arranged.