a first plurality of ball lenses and a first plurality of first light sources, the first plurality of ball lenses comprising ball lenses of a first type, the first light sources are the same; and

a second plurality of ball lenses and a second plurality of second light sources, the second plurality of ball lenses comprising ball lenses of a second type in which the first type is different than the second type, the second light sources are the same,

wherein the ball lenses of the first plurality and the second plurality of ball lenses are configured to:

receive light from the respective light sources and condense the received light; and

output the condensed light;

each light source of the respective light sources having a light emitting surface, wherein

each light source of the respective light sources is configured to emit the light toward each ball lens of the respective ball lenses via the respective light emitting surface, and

the respective light emitting surface is located closer to the respective ball lens than a focal position of the respective ball lens; and

an optical sheet configured to:

pass a first portion of the output light that is output from the first plurality and second plurality of ball lenses; and

reflect a second portion of the output light to return to the first plurality and second plurality of ball lenses,

wherein the first plurality and second plurality of ball lenses include a material having a uniform refractive index.