Patent ID: 9477028
Filing Date: 2016-10-25
CPC Classification: F21V,G02B

Claim Text:
1. A back light module comprising: a lens comprising a light extraction surface defining a plurality of first recesses and a light incident surface defining a plurality of second recesses; each of the plurality of first recesses having a pair of first inclined surfaces, and an angle between the first inclined surface and a plane where the light incident surface is located being larger than or equal to a critical angle of total reflection of the lens; each of the plurality of second recesses having a pair of second inclined surfaces, and an angle between the second inclined surface and the plane where the light incident surface is located being less than or equal to the angle between the first inclined surface and the plane where the light incident surface is located; and a plurality of light emitting diode (LED) elements configured to emit light that penetrates the lens from the light incident surface and travels out of the lens from the light extraction surface, each LED element corresponding to one first recess, which is symmetric about the optic axis of the corresponding LED element, and each second recess being located between two adjacent LED elements; wherein a plurality of third recesses are further defined in the light incident surface and located at lateral sides of the second recesses, each third recess comprises a first flank and a second flank, an angle between the second flank and the plane where the light incident surface is located is less than the angle between the second inclined surface and the plane where the light incident surface located, and the first flank is closer to the second recess than the second flank of the each third recess.