Lens member and light-emitting device using same

1. A light-emitting device comprising a lens member,

the lens member comprising:

a light-incident side;

a light-exit side that is opposite to the light-incident side;

a Fresnel lens arranged on the light-incident side to be centered around a center axis of the light-incident side; and

a diffraction grating structure arranged around a periphery of the Fresnel lens and arranged to be centered around the center axis;

a light source arranged to face the light-incident side of the lens member and including a light-emission surface whose center is aligned with the center axis of the lens member,

wherein R is defined as a radius of the light-emission surface of the light source, r is defined as a radial distance of the light-incident side of the lens member from the center axis of the light-incident side, h is defined as a distance from the light-emission surface of the light source to the light-incident side of the lens member, and Δθ is defined as a range of incident angle of light from the light-emission surface of the light source incident on the light-incident side of the lens member, and

the diffraction grating structure satisfies

Δθ=arctan{( r+R )/ h }−arctan{( r−R )/ h}≤ 15°.

2. The light-emitting device according to claim 1 ,

wherein the Fresnel lens includes a first Fresnel lens and a second Fresnel lens, the first Fresnel lens arranged with the center axis of the light-incident side at a center and comprises annular prisms that are divided from a convex lens, and the second Fresnel lens arranged around the periphery of the first Fresnel lens with the center axis of the light-incident side at the center and comprises annular prisms that are divided from a total internal reflection (TIR) lens.

3. The light-emitting device according to claim 1 ,

wherein the diffraction grating structure comprises annular minute grooves, each of the annular minute groves arranged with a constant groove pitch.

4. The light-emitting device according to claim 1 ,

wherein an outer peripheral edge of the light-emission surface of the light source is positioned inside an inner diameter of the diffraction grating structure arranged centering around the center axis of the light-incident side.

5. The light-emitting device according to claim 2 ,

wherein a range of incident angle of light to be received at the annular prisms included in the Fresnel lens is different from a range of incident angle of light to be received at the diffraction grating structure.

6. The light-emitting device according to claim 2 ,

wherein each top end of the annular prisms in the first Fresnel lens, each top end of the annular prisms in the second Fresnel lens, and a top end of the diffraction grating structure arranged around the periphery of the Fresnel lens are of uniform height.

7. The light-emitting device according to claim 2 ,

wherein the first Fresnel lens further comprises a convex lens positioned on the center axis, the diffraction grating structure comprises annular minute groves, and

a top portion of the convex lens, each top end of the annular prisms in the first Fresnel lens, each top end of the annular prisms in the second Fresnel lens, and a top end positioned between the annular minute grooves that are included in the diffraction grating structure are of uniform height.

8. The light-emitting device according to claim 2 ,

wherein R is defined as a radius of the light-emission surface of the light source, and r is defined as a radial distance of the light-incident side of the lens member from the center axis of the light-incident side, and

the first Fresnel lens satisfies r<R.

9. The light-emitting device according to claim 2 ,

wherein R is defined as a radius of the light emission surface of the light source, r is defined as a radial distance of the light-incident side of the lens member from the center axis of the light-incident side, and Δθ is defined as a range of an incident angle of light which is from the light emission surface of the light source incident on the light-incident side of the lens member, and

the second Fresnel lens satisfies

r≥R and Δθ>15°.

10. The light-emitting device according to claim 3 ,

wherein each of the annular minute grooves comprises an outer slope and an inner slope that is positioned closer to the center axis of the light-incident side than the outer slope, and an inclination angle of the outer slope and an inclination angle of the inner slope in each of the annular minute grooves change on the basis of distance from the center axis.

11. A light-emitting device comprising a lens member,

the lens member comprising:

a light-incident side;

a light-exit side that is opposite to the light-incident side;

a Fresnel lens arranged on the light-incident side to be centered around a center axis of the light-incident side; and

a diffraction grating structure arranged around a periphery of the Fresnel lens and arranged to be centered around the center axis, and comprising annular minute grooves;

a light source arranged to face the light-incident side of the lens member and including a light-emission surface whose center is aligned with the center axis of the lens member,

wherein R is defined as a radius of the light-emission surface of the light source, r is defined as a radial distance of the light-incident side of the lens member from the center axis of the light-incident side, h is defined as a distance from the light-emission surface of the light source to the incident side of the lens member, θ′ is defined as an angle formed between a line of light, which is from the light-emission surface of the light source and incident on the light-incident side of the lens member and the center axis, p is defined as a groove pitch of the annular minute grooves of the diffraction grating structure, H is defined as a groove depth of each of the annular minute grooves, and n is defined as a refractivity of the lens member, and

each of the annular minute grooves in the diffraction grating structure has an inclination angle α of an outer slope and an inclination angle β of an inner slope, the inclination angles α and β satisfy following formulas:

Tan α= P/H −tan β

β=45−{(arcsin{sin(90−θ′−α)/ n }+α)}/2

arctan{( r−R )/ h }≤θ′≤arctan{( r+R )/ h }.

12. The light-emitting device according to claim 11 ,

wherein the Fresnel lens includes a first Fresnel lens and a second Fresnel lens, the first Fresnel lens arranged with the center axis of the light-incident side at a center and comprises annular prisms that are divided from a convex lens, and the second Fresnel lens arranged with the center axis of the light-incident side at the center, and comprises annular prisms that are divided from a total internal reflection (TIR) lens.

13. The light-emitting device according to claim 11 ,

wherein the annular minute grooves of the diffraction grating structure are each arranged with a constant groove pitch.

14. The light-emitting device according to claim 11 ,

wherein each of the annular minute grooves comprises an outer slope and an inner slope that is positioned closer to the center axis of the light-incident side than the outer slope, and an inclination angle of the outer slope and an inclination angle of the inner slope in each of the annular minute grooves change on the basis of distance from the center axis.

15. The light-emitting device according to claim 11 ,

wherein an outer peripheral edge of the light-emission surface of the light source is positioned inside an inner diameter of the diffraction grating structure arranged centering around the center axis of the light-incident side.

16. The light-emitting device according to claim 12 ,

wherein a range of incident angle of light to be received at the annular prisms included in the Fresnel lens is different from a range of incident angle of light to be received at the diffraction grating structure.

17. The light-emitting device according to claim 12 ,

wherein each top end of the annular prisms in the first Fresnel lens, each top end of the annular prisms in the second Fresnel lens, and a top end of the diffraction grating structure arranged around the periphery of the Fresnel lens are of uniform height.

18. The light-emitting device according to claim 12 ,

wherein the first Fresnel lens further comprises a convex lens positioned on the center axis, the diffraction grating structure comprises annular minute groves, and

a top portion of the convex lens, each top end of the annular prisms in the first Fresnel lens, each top end of the annular prisms in the second Fresnel lens, and a top end positioned between the annular minute grooves that are included in the diffraction grating structure are of uniform height.

19. The light-emitting device according to claim 12 ,

wherein R is defined as a radius of the light-emission surface of the light source, r is defined as a radial distance of the light-incident side of the lens member from the center axis of the light-incident side, and

the first Fresnel lens satisfies r<R.

20. The light-emitting device according to claim 12 ,

wherein R is defined as a radius of the light emission surface of the light source, r is defined as a radial distance of the light-incident side of the lens member from the center axis of the light-incident side, and Δθ is defined as a range of an incident angle of light which is from the light emission surface of the light source incident on the light-incident side of the lens member, and

the second Fresnel lens satisfies

r≥R and Δθ>15°.