Display backlight having lightguide with variable density light extraction elements

A lighting device comprising:

• a light source;
• a rectangular light guide plate having a top surface, a bottom surface, and a plurality of peripheral edge surfaces, the light source arranged to project light into a first of the peripheral edge surfaces;
• a reflecting member arranged proximate the bottom surface of the light guide plate, and configured to reflect back to the bottom surface light exiting from such bottom surface;
• a plurality of reflecting elements disposed on the top surface of the light guide plate, each of the reflecting elements extending in a first direction parallel to the first peripheral edge surfaces of the light guide plate, the plurality of reflecting elements arranged at intervals in a second direction orthogonal to the first peripheral edge surface, the reflecting elements configured to help cause light travelling within the light guide plate to exit through the top surface of the light guide plate;
• a plurality of cylindrical lenses formed on the bottom surface of the light guide plate and arranged in the first direction and extending in the second direction, a first density of the plurality of cylindrical lenses on the bottom surface being lower near the first peripheral edge surface than distal from the first peripheral edge surface;
• and
• a plurality of flat portions formed on the bottom surface of the light guide plate, each flat portion proximate to at least one of the plurality of cylindrical lenses, a second density of the plurality of flat portions on the bottom surface being higher near the first peripheral edge surface than distal from the first peripheral edge surface.