Holographic backlight for flat panel displays

Claim 2

The backlight (10) of Claim 1 wherein the white light source (11) is characterized by a cold cathode fluorescent tube (11).

Claim 3

The backlight (10) of Claim 1 wherein the means (12) for injecting is characterized by a non-imaging concentrator (12).

Claim 4

The backlight (10) of Claim 1 wherein the light pipe (13) is tapered.

Claim 5

The backlight (10) of Claim 1 wherein the double-layer reflection/transmission hologram (16) is characterized by an array of reflection/transmission hologram doublets (16) that is varied across the surface of the backlight (10) so as to select different angular portion of the light injected into the light pipe (13).

Claim 6

The backlight (10) of Claim 1 wherein the phase retarding layer (14) has zero retardance.

Claim 7

The backlight (10) of Claim 1 wherein the double-layer reflection/transmission hologram (16) produces quasi-collimated s-polarized light having well-defined spectral colors that is transmitted in an array of red, green, and blue patches of light.

Claim 8

The backlight (10) of Claim 1 wherein the double-layer reflection/transmission hologram (16) is laminated to the first surface (15) of the tapered light pipe (13).

Claim 9

The backlight (10) of Claim 1 wherein the light pipe (13) is characterized by a plane-parallel light pipe (13a) and wherein the backlight (10) is further characterized by: a second white light source (11b) for emitting white light; second light injecting means (12b) for injecting the white light from the second white light source (11b) into the light pipe (13); and a second double-layer reflection/transmission hologram (16b) disposed on an output surface (17) of the light pipe (13) that is oriented orthogonal to the other hologram (16).

Claim 10

A holographic backlight (10) for use with a liquid crystal display (21), said backlight (10) characterized by: a cold cathode fluorescent tube (11) for emitting white light; a non-imaging concentrator (12) for concentrating the white light emitted by the fluorescent tube (11); a substantially flat tapered light pipe (13) for receiving concentrated light provided by the concentrator (12) and for providing an emitting surface that emits white light of substantially uniform brightness; a phase retarding film layer (14) disposed on a first surface (15) of the tapered light pipe (13); and a double-layer reflection/transmission hologram (16) disposed on a second, output surface (17) of the tapered light pipe (13); and wherein light emitted by the cold cathode fluorescent tube (11) is injected into the tapered light pipe (13) and is diffracted off of the double-layer hologram (16) so that quasi-collimated s-polarized light having well-defined spectral colors is transmitted thereby as an array of red, green, and blue patches of light corresponding to the clear apertures of the red, green, and blue elements (22) of the liquid crystal display (21).

Claim 11

The system (10) of Claim 10 wherein the liquid crystal display (21) is characterized by an active matrix liquid crystal display (21).

Claim 12

The system (10) of Claim 10 wherein the double-layer reflection/transmission hologram (16) is laminated to the first side of the tapered light pipe (13).

Claim 13

A liquid crystal display system (20) characterized by: a cold cathode fluorescent tube (11) for emitting white light; a non-imaging concentrator (12) for concentrating the white light emitted by the fluorescent tube (11); a light pipe (13) for receiving the white light transmitted by the non-imaging concentrator (12); a phase retarding film layer (14) disposed on a first surface (15) of the light pipe (13); a double-layer reflection/transmission hologram (16) disposed on a second, output surface (17) of the light pipe (13) for diffracting the light emitted from the light pipe (13) to produce quasi-collimated s-polarized light having well-defined spectral colors; a liquid crystal display (21) disposed adjacent the hologram (16) for receiving the quasi-collimated s-polarized light transmitted by the hologram (16); and a diffusing screen to spread the light into a desired angular viewing zone; wherein light emitted by the cold cathode fluorescent tube (11) is injected into the light pipe (13) and is diffracted off of the double-layer hologram (16) to produce the quasi-collimated s-polarized light having well-defined spectral colors which is transmitted as an array of red, green, and blue patches of light corresponding to the clear apertures of the red, green, and blue elements (22) of the liquid crystal display (21).

Claim 14

The system (20) of Claim 13 wherein the liquid crystal display (21) is characterized by an active matrix liquid crystal display (21).

Claim 15

The system (20) of Claim 13 wherein the light pipe (13) is tapered.

Claim 16

The system (20) of Claim 13 wherein the light pipe (13) is characterized by a plane-parallel light pipe (13) and wherein the system (20) is further characterized by: a second white light source (11b) for emitting white light; second light injecting means (12b) for injecting the white light from the second white light source (11b) into the light pipe (13); and a second double-layer reflection/transmission hologram (16b) disposed on an output surface (17) of the light pipe (13) that is oriented orthogonal to the other hologram (16).