Light emitting device and backlight source

A backlight source, comprising a light emitting device, which comprises a light emitting diode and an optical lens,

• wherein the light emitting diode comprises a light emission surface, and the optical lens being a rotation symmetry disposed above the light emitting diode, and the optical lens comprises a light incidence surface and a light exit surface, wherein the light incidence surface comprises a concave surface, and the light exit surface comprises a convex surface;
• and in the condition that a symmetry axis of the optical lens passes a center of the light emission surface of the light emitting diode,
• the concave surface comprises a first light incidence surface and a second light incidence surface adjoining the first light incidence surface, wherein the first light incidence surface passes the symmetry axis of the optical lens, and a ratio of the minimum one to the maximum one of distances between respective points on the first light incidence surface and the center of the light emission surface belongs to an closed interval ranging from 0.5 to 0.7;
• and a ratio of the minimum one to the maximum one of distances between respective points on the second light incidence surface and the center of the light emission surface belongs to an closed interval ranging from 0.683 to 0.695;
• and
• the convex surface comprises a first light exit surface and a second light exit surface adjoining with the first light exit surface, where the first light exit surface passes the symmetry axis of the optical lens, and a ratio of the minimum one to the maximum one of distances between respective points on the first light exit surface and the center of the light emission surface belongs to an closed interval ranging from 0.771 to 0.913;
• and a ratio of the minimum one to the maximum one of distances between respective points on the second light exit surface and the center of the light emission surface belongs to an closed interval ranging from 0.883 to 0.921.