Thin hollow backlights with beneficial design characteristics

An edge-lit backlight, comprising:

• a front and back reflector forming a hollow light recycling cavity having a cavity depth H and an output region of area Aout;
• and
• a number N of one or more light sources disposed proximate a periphery of the light recycling cavity and emitting light into the light recycling cavity;
• wherein the output region is generally rectangular in shape and has a diagonal measure of at least 30 inches;
• wherein the output region exhibits a VESA 9 uniformity value of at least 50%;
• wherein the one or more light sources have an average plan view source separation of SEP and collectively have an active light emitting area Aemit;
• wherein a first parameter equals Aemit/Aout;
• wherein a second parameter equals SEP/H;
• and
• wherein the backlight is characterized by the first parameter being in a range form 0.0001 to 0.1, and by the second parameter being in a range from 3 to 10.

A backlight, comprising:

• a front and back reflector forming a hollow light recycling cavity having an output region;
• and
• a number N of light sources disposed to emit light into the light recycling cavity, the N light sources including a subset of M light sources that are adjacent to each other, where M is at least 10% of N, or is at least 2, or both;
• wherein the backlight exhibits a VESA brightness uniformity value over its output region of at least 50% both when all N light sources are energized and when all of the M light sources are selectively turned off;
• and
• wherein the front reflector has a hemispherical reflectivity for unpolarized visible light of Rfhemi, and the back reflector has a hemispherical reflectivity for unpolarized visible light of Rbhemi, and Rfhemi * Rbhemi is at least 0.70.