Backlit LCD device with reduced power consumption
AssigneeNokia Corporation
InventorsMika Grohn, Heikki Alakontiola
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Abstract
A backlit liquid crystal display (LCD) device has a fluorescent layer inserted between the light source and the light guide. The fluorescent layer is stimulated by each light pulse from the light source, causing the fluorescent layer to emit light. After the end of each light pulse, the fluorescent layer continues to emit light at a particular intensity and frequency for a certain period. In addition, the light emitted by the fluorescent layer serves to balance out the spectrum of light emitted by the light source.
Claims20
A backlit liquid crystal display (LCD) device for use in a portable electronic device, comprising:
- an edge light source for emitting pulses of light that provide backlighting for the LCD device, wherein a frequency of the emitted pulses of light is less than about 25 Hz;
- a fluorescent layer positioned adjacent to said edge light source to receive pulses of light from the edge light source, being selected to emit a fluorescence emission after each light pulse, and being selected to allow pulses of light to pass therethrough;
- a planar light guide positioned to receive, by means of an edge facing the edge light source, the pulses of light which pass through the fluorescent layer, being selected to redirect the received light out of a top surface, and being selected to balance an intensity distribution of the redirected light leaving the top surface, wherein the fluorescent layer is interposed between the edge light source and the edge facing the edge light source;
- and
- a liquid crystal cell comprised of:
- a rear polarizer positioned to receive the redirected light from the top surface of the planar light guide and being selected to allow only light of a first polarization to pass therethrough;
- a liquid crystal element positioned to receive the light of the first polarization from the rear polarizer, being selected to change the first polarization of the received light to a polarization orthogonal to the first polarization when no voltage is applied to said liquid crystal element, and for passing the light of the first polarization therethrough when a voltage is applied to said liquid crystal element;
- and
- a front polarizer positioned to receive light from the liquid crystal element and being selected to allow only light of a second polarization to pass therethrough.
A backlit liquid crystal display (LCD) device comprising:
- an edge light source for emitting pulses of light that provide backlighting for the LCD device;
- a fluorescent layer positioned to receive pulses of light from the edge light source, being selected to emit a fluorescence emission after each light pulse, and being selected to allow pulses of light to pass therethrough;
- and
- a planar light guide positioned to receive, by means of an edge facing the edge light source, the pulses of light which pass through the fluorescent layer, being selected to redirect the received light out of a top surface, and being selected to balance an intensity distribution of the redirected light;
- wherein the fluorescent layer is interposed between the edge light source and the planar light guide.
Dependencies are inferred from the claim text.