Field emission display having multiple brightness display modes

A field emission display, comprising:

• a display screen having a conductive surface;
• a cathodoluminescent coating disposed on said inner surface;
• an extraction grid disposed a predetermined distance away from said inner surface, said grid having a plurality of openings;
• a plurality of emitters each aligned with a corresponding one of said openings, said emitters arranged in sets that each include at least one emitter;
• and
• a plurality of emitter drivers each coupled to the emitters in a corresponding one of said sets, each of said drivers connected to receive a control signal having first and second ranges of values, said driver driving said emitters in said corresponding set with a first current within a first range of currents in response to said control signal having a value within said first range of values, said driver driving said emitters in said corresponding set with a second current within a second range of currents in response to said control signal having a value within said second range of values, the gain of said driver when said control signal has a value within said second range of values being significantly greater than the gain of said driver when said control signal has a value within said first range of values.

A field emission display, comprising:

• a display screen having a conductive inner surface;
• a cathodoluminescent coating disposed on said inner surface;
• an extraction grid disposed a predetermined distance away from said inner surface, said grid having a plurality of openings;
• a plurality of emitters each aligned with a corresponding one of said openings, said emitters arranged in sets that each include at least one emitter;
• and
• a plurality of emitter drivers each coupled to the emitters in a corresponding one of said groups, each of said drivers connected to receive a luminance signal that varies within a first range of voltage values and within a second range of voltage values, each driver having an impedance element that has a nonlinear voltage-current characteristic, each driver coupling said luminance signal across said impedance element to generate an emitter current and driving said corresponding group of said emitters with said emitter current such that when said luminance signal varies within said first range of voltage values, said display screen displays an image in a first brightness mode, and when said luminance signal varies within said second range of voltage values, said display screen displays said image in a second brightness mode.

A field emission display, comprising:

• a display screen having a conductive inner surface;
• a cathodoluminescent coating disposed on said inner surface;
• an extraction grid disposed a predetermined distance away from said inner surface, said grid having a plurality of openings;
• a plurality of emitters each aligned with a corresponding one of said openings, said emitters arranged in sets that each include one or more emitters that are coupled together at an emitter node;
• and
• a plurality of emitter-current generators each coupled to the emitters of an associated one of said sets, each of said emitter-current generators including,
• a voltage generator having a luminance-signal input terminal,
• an impedance element coupled to said emitter node and to said voltage generator, said impedance element having a nonlinear current-voltage characteristic, and
• each of said emitter-current generators operating over a first approximately linear portion of said nonlinear current-voltage characteristic to cause said display screen to display an image in a first brightness mode, each of said emitter-current generators operating over a second approximately linear portion of said nonlinear current-voltage characteristic to cause said display screen to display an image in a second brightness mode, the average slope of said first approximately linear portion significantly different than the average slope of said second approximately linear portion.

A device for generating and displaying a video image, comprising:

• a video processing circuit coupled to receive and process a video signal, and to generate a display signal from said video signal;
• and
• a field emission display coupled to receive said display signal and to display said video image, said field emission display including,
• a display screen having a conductive inner surface,
• a cathodoluminescent coating disposed on said inner surface,
• an extraction grid disposed a predetermined distance away from said inner surface, said grid having a plurality of openings,
• a plurality of emitters each aligned with a corresponding one of said openings, said emitters arranged in sets that each include at least one emitter, and
• a plurality of emitter drivers each coupled to the emitters in a corresponding one of said sets, each of said drivers connected to receive a control signal having first and second ranges of values, said drivers driving said emitters such that said display screen displays a first image in a first brightness mode when said control signal is within said first range of values, said drivers driving said emitters such that said display screen displays a second image in a second brightness mode when said control signal is within said second range of values, the ratio of the maximum brightness of said first image in said first brightness mode to the maximum brightness of said second image in said second brightness mode being significantly greater than the ratio of the maximum value of said second range of values to the maximum value of said first range of values.