Thin direct-view LED backlights
A light-emitting apparatus including a light-emitting element and a lens covering the light-emitting element. The lens includes an upper surface having a convex shape and a lower surface including a cavity to which light emitted from the light-emitting elements is incident, in which the cavity includes an apex facing an upper surface of the light-emitting element and configured to reduce Fresnel reflections emitted vertically.
1. A surface light source apparatus, comprising:
light emitting elements disposed on a printed circuit board (PCB); and
illumination lenses disposed over the light emitting elements, respectively, each of the illumination lenses including:
an internal surface having an arch shaped 2-fold and non-4-fold rotational symmetric, elongated horizontal cross-section, and configured to intercept light emitted by the light emitting element; and
a 2-fold and non-4-fold rotational symmetric external surface having a central cusp,
wherein the PCB has a shape elongated in a first direction, and
wherein the horizontal cross-section of the internal surface of the illumination lens is elongated in the first direction.
2. The surface light source apparatus of claim 1 , wherein the internal surface cross-section of the illumination lens has a length to width ratio at its base of about 2.5:1.
3. The surface light source apparatus of claim 1 , wherein:
the external surface is horizontally elongated in the same direction as the elongated horizontal cross-section of the internal surface; and
the external surface has a length to width ratio of 16:15.
4. The surface light source apparatus of claim 1 , wherein the illumination lens comprises a transparent material having a refractive index in a range of 1.45 to 1.65.
5. The surface light source apparatus of claim 1 , wherein the illumination lens further includes a bottom surface that interconnects the internal surface and the external surface.
6. The surface light source apparatus of claim 5 , wherein the bottom surface is configured to absorb Fresnel reflections from the internal surface.
7. The surface light source apparatus of claim 1 , further comprising:
a light diffusion member disposed on a side surface of the external surface of the illumination lens; and
a reflecting diffusive sheet disposed on the PCB,
wherein the reflecting diffusive sheet comprises a hole configured to allow light emitted from the illumination lens to escape, and the reflecting diffusive sheet is configured to block Fresnel reflections that occur outside of the illumination lens.
8. The surface light source apparatus of claim 1 , comprising a plurality of PCBs arranged parallel to each other at a first interval,
wherein the light emitting elements are arranged on each PCB at a second interval less than the first interval.
9. The surface light source apparatus of claim 8 , wherein:
the internal surfaces of the illumination lenses comprise elongated horizontal cross-sections, respectively; and
the horizontal cross-sections of the internal surfaces are elongated in the first direction.
10. A display apparatus, comprising:
a surface light source apparatus; and
an illumination target member configured to receive light from the surface light source apparatus,
wherein the surface light source apparatus comprises:
light emitting elements disposed on a printed circuit board (PCB); and
illumination lenses disposed over the light emitting elements, respectively,
wherein the illumination lens comprises:
an internal surface configured to intercept light emitted by the light emitting element, the internal surface comprising an arch shaped 2-fold and non-4-fold rotational symmetric, elongated horizontal cross-section; and
a 2-fold and non-4-fold rotational symmetric external surface comprising a central cusp,
wherein the PCB has a shape elongated in a first direction, and
wherein the horizontal cross-section of the internal surface is elongated in the first direction.
11. The display apparatus of claim 10 , wherein the internal surface cross-section of the illumination lens has a length to width ratio at its base of 2.5:1.
12. The display apparatus of claim 10 , wherein:
the external surface is horizontally elongated in the same direction as the elongated horizontal cross-section of the internal surface; and
the external surface has a length to width ratio of 16:15.
13. The display apparatus of claim 10 , wherein the illumination lens further includes a bottom surface that interconnects the internal surface and the external surface.
14. The display apparatus of claim 13 , wherein the bottom surface is configured to absorb Fresnel reflections from the internal surface.
15. The display apparatus of claim 10 , further comprising:
a light diffusion member disposed on a side surface of the external surface of the illumination lens; and
a reflecting diffusive sheet disposed on the PCB,
wherein the reflecting diffusive sheet comprises a hole configured to allow light emitted from the illumination lens to escape, and the reflecting diffusive sheet is configured to block Fresnel reflections that occur outside of the illumination lens.
16. The display apparatus of claim 10 , further comprising a plurality of PCBs arranged parallel to each other at a first interval,
wherein:
the light emitting elements are arranged on each PCB at a second interval less than the first interval;
the internal surfaces of the illumination lenses include elongated horizontal cross-sections, respectively; and
the horizontal cross-sections of the internal surfaces are elongated in the first direction.