A backlight system comprises at least two light-emitting panels (1; 11) having a front wall (2; 12), an opposing rear wall (3; 13) and opposite edge surfaces (4, 14; 5, 15). At least one of the edge surfaces (4; 14) is light-transmitting and associated with a plurality of light sources (6, 16). Light originating from the light sources (6; 16) is diffused in the panel (1; 11). Sub-surfaces (8, 18) of the rear walls (3, 13) are provided with means for extracting light from the panel (1, 11). In operation, said sub-surfaces (8, 18) project light on areas (9, 19) of an (imaginary) plane (40) which is positioned parallel to the light-emitting panels (1, 11). Said projected areas (9, 19) in the plane (40) are substantially contiguous. Preferably, said sub-surfaces (8, 18) are remote from the light-transmitting edge surfaces (4; 14). Preferably, each of said sub-surfaces (8, 18) forms a single surface covering half the front wall (2, 12) of the light-emitting panel (1, 11). Alternatively, the sub-surfaces encompass a substantial area of the rear walls, the distribution of the means for extracting light from the panel being such that the amount of extracted light changes as a function of the distance to the light-transmitting edge surfaces. Preferably, the light source comprises a plurality of red, green, blue (and amber) LEDs, each preferably having a luminous flux of at least 5 lumen.
A compact backlighting system for illuminating a display device (12) comprises a light-emitting panel (1) having a front wall (2), an opposing rear wall (3) and edge areas (4). At least one of the edge areas (4) is capable of transmitting light. The backlighting system includes a light source (6) comprising at least one LED, and a light-mixing panel 5 for mixing the light originating from the light source (6). Light originating from the light source (6) is coupled into the light-mixing panel (5) via a light input surface (7), which light is mixed in the light-mixing panel (5) and coupled out via a light output surface (8). The light-mixing panel (5) and the light-emitting panel (1) are arranged so as to extend substantially parallel to each other. Between the light-mixing panel 5 and the light-emitting panel 1, the backlighting system comprises a light transport chamber (9) for transporting the light from the light-mixing panel (5) to the light-emitting panel (1). Preferably, the light transport chamber (9) has elliptical, reflective inner wall (10).
A liquid crystal display apparatus has R, G, and B LEDs and a light guide plate for guiding and diffusing the light entering through an incident surface evenly over the plate. The bottom surface of the light guide plate has a diffusion portion where microdot pattern is printed to diffuse incident light. The liquid crystal display apparatus also has an optical sensor for receiving the light exiting from the light guide plate through a side surface, and a light-shielding member mounted in front of the optical sensor. The light-shielding member has pinholes to block the light incident on the optical sensor in the direction from the incident surface to the opposite surface at an incidence angle greater than a given angle. The luminance of the LEDs is controlled based on the light detected by the optical sensor.
In a display device equipped with a light source device, a second light-guide member is provided to the back surface of a first light-guide member that has an emitted light control sheet provided to the front surface thereof. The emitted light control sheet is composed of a flat plate portion and protrusions. A first light source mounted to a side surface of the first light-guide member, and a second light source mounted to a side surface of a second light-guide member are switched and turned on. The emitted light control sheet has light-condensing effects when the first light source is on, and has diffusing effects when the second light source is turned on. The angle range of illuminating light can thereby be switched.
A data display device including a light-guide element made of an optically transparent material having at least two polished surfaces faced to one another, whereby at least one surface contains at least one gravure forming a diffuse-reflective character, and a light source arranged close to the light-guide element to illuminate said character.
