Method and apparatuses for providing uniform electron beams from field emission displays

• US 20020190663A1
• Filed: 08/14/2002
• Published: 12/19/2002
• Est. Priority Date: 07/17/2000
• Status: Active Grant

• Current Assignee: Robert T. Rasmussen
• Original Assignee: Robert T. Rasmussen
• Inventors: Rasmussen, Robert T.
• Granted Patent: US 7,049,753 B2
• Time in Patent Office: Days
• US Class Current: 315/169.1
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: H01J 2201/319 Circuit elements associated with the emitters by direct integration
• CPC Class Codes: H01J 2329/4695 Potentials applied to the electrodes
• CPC Class Codes: H01J 29/467 Control electrodes for flat display tubes, e.g. of the type covered by group H01J31/123
• CPC Class Codes: H01J 29/481 Electron guns using field-emission, photo-emission, or secondary-emission electron source
• CPC Class Codes: H01J 31/127 using large area or array sources, i.e. essentially a source for each pixel group

Abstract

The invention includes field emitters, field emission displays (FEDs), monitors, computer systems and methods employing the same for providing uniform electron beams from cathodes of FED devices. The apparatuses each include electron beam uniformity circuitry. The electron beam uniformity circuit provides a grid voltage, V_Grid, with a DC offset voltage sufficient to induce field emission from a cathode and a periodic signal superimposed on the DC offset voltage for varying the grid voltage at a frequency fast enough to be undetectable by the human eye. The cathodes may be of the micro-tipped or flat variety. The periodic signal may be sinusoidal with peak-to-peak voltage of between about 5 volts and about 50 volts.

Claims

1. A field emission display comprising:

a faceplate comprising;

a transparent screen;

a cathodoluminescent layer; and

a transparent conductive anode layer disposed between said transparent screen and said cathodoluminescent layer and biased at an anode voltage;

a baseplate vacuum sealed to said faceplate comprising;

an insulating substrate;

a row electrode disposed upon said insulating substrate and biased to ground voltage;

a cathode structure disposed upon said row electrode;

an insulating layer disposed around said cathode structure and upon said row electrode; and

a column electrode disposed upon said insulating layer; and

an electron beam uniformity circuit coupled to said column electrode for periodically varying grid voltage about a DC offset sufficient to extract electrons from said cathode structure, said circuit for providing a wave signal with excursions above and below said DC offset.

2. The field emission display of claim 1, wherein said circuit for periodically varying said grid voltage about a DC offset operates at frequencies of about 50 Hertz or greater.

3. The field emission display of claim 1, wherein said circuit for periodically varying said grid voltage about a DC offset provides a rectangular wave signal with excursions above and below said DC offset of about between 5 and 50 volts.

4. The field emission display of claim 3, wherein said rectangular wave signal has a duty cycle of between about 10 percent and 90 percent.

5. The field emission display of claim 1, wherein said circuit for periodically varying said grid voltage about a DC offset provides a sinusoidal signal with excursions above and below said DC offset having peak-to-peak voltage of about between 5 volts and 50 volts.

6. A field emission display monitor comprising:

a video monitor chassis;

a video driver circuitry housed within said video monitor chassis;

a field emission display coupled to said video monitor chassis and in communication with said video driver circuitry comprising;

a faceplate comprising;

a transparent screen;

a cathodoluminescent layer; and

a transparent conductive anode layer disposed between said transparent screen and said cathodoluminescent layer and biased at an anode voltage;

a baseplate vacuum sealed to said faceplate comprising;

an insulating substrate;

a row electrode disposed upon said insulating substrate and biased to ground voltage;

a cathode structure disposed upon said row electrode;

an insulating layer disposed around said cathode structure and upon said row electrode; and

a column electrode disposed upon said insulating layer; and

an electron beam uniformity circuit coupled to said column electrode for periodically varying grid voltage about a DC offset sufficient to extract electrons from said cathode structure, said circuit for providing a wave signal with excursions above and below said DC offset; and

user controls coupled to said video monitor chassis and in communication with said video driver circuitry adapted for adjusting video images displayed on said field emission display.

7. The field emission display monitor of claim 6, wherein said circuit for periodically varying said grid voltage about a DC offset operates at frequencies of about 50 Hertz or greater.

8. The field emission display monitor of claim 6, wherein said circuit for periodically varying said grid voltage about a DC offset provides a rectangular wave signal with excursions above and below said DC offset of about between 5 and 50 volts.

9. The field emission display monitor of claim 8, wherein said rectangular wave signal has a duty cycle of between about 10 percent and 90 percent.

10. The field emission display monitor of claim 6, wherein said circuit for periodically varying said grid voltage about a DC offset provides a sinusoidal signal with excursions above and below said DC offset having peak-to-peak voltage of about between 5 volts and 50 volts.

11. A computer system comprising:

an input device;

an output device;

a processor device operably coupled to said input device and said output device; and

a field emission display coupled to said processor device comprising;

a faceplate comprising;

a transparent screen;

a cathodoluminescent layer; and

a transparent conductive anode layer disposed between said transparent screen and said cathodoluminescent layer and biased at an anode voltage;

a baseplate vacuum sealed to said faceplate comprising;

an insulating substrate;

a row electrode disposed upon said insulating substrate and biased to ground voltage;

a cathode structure disposed upon said row electrode;

an insulating layer disposed around said cathode structure and upon said row electrode; and

a column electrode disposed upon said insulating layer; and

an electron beam uniformity circuit coupled to said column electrode for periodically varying grid voltage about a DC offset sufficient to extract electrons from said cathode structure, said circuit for providing a wave signal with excursions above and below said DC offset.

12. The computer system of claim 11, wherein said circuit for periodically varying said grid voltage about a DC offset operates at frequencies of about 50 Hertz or greater.

13. The computer system of claim 11, wherein said circuit for periodically varying said grid voltage about a DC offset provides a rectangular wave signal with excursions above and below said DC offset of about between 5 and 50 volts.

14. The computer system of claim 13, wherein said rectangular wave signal has a duty cycle of between about 10 percent and 90 percent.

15. The computer system of claim 11, wherein said circuit for periodically varying said grid voltage about a DC offset provides a sinusoidal signal with excursions above and below said DC offset having peak-to-peak voltage of about between 5 volts and 50 volts.

18. The field emission display of claim 17, wherein said circuitry for periodically varying said grid voltage provides a rectangular wave signal with excursions above and below said grid voltage of about between 5 and 50 volts.

19. The field emission display of claim 18, wherein said rectangular wave signal has a duty cycle of between about 10 percent and 90 percent.

20. The field emission display of claim 17, wherein said circuitry for periodically varying said grid voltage provides a sinusoidal signal with excursions with peak-to-peak voltage of about between 5 volts and 50 volts.

16. A method of controlling electron beam uniformity in a field emission display comprising:

providing a field emission display comprising;

a faceplate comprising;

a transparent screen;

a cathodoluminescent layer; and

a transparent conductive anode layer disposed between said transparent screen and said cathodoluminescent layer and biased at an anode voltage;

a baseplate vacuum sealed to said faceplate comprising;

an insulating substrate;

a row electrode disposed upon said insulating substrate and biased to ground voltage;

a cathode structure disposed upon said row electrode;

an insulating layer disposed around said cathode structure and upon said row electrode; and

a column electrode disposed upon said insulating layer; and

a circuit for controlling electron beam uniformity coupled to said column electrode for providing a wave signal periodically varying grid voltage at a frequency of about 50 Hertz or greater.

17. A field emission display comprising:

a faceplate comprising;

a transparent screen;

a cathodoluminescent layer; and

a transparent conductive anode layer disposed between said transparent screen and said cathodoluminescent layer and biased at an anode voltage;

a baseplate vacuum sealed to said faceplate comprising;

an insulating substrate;

a row electrode disposed upon said insulating substrate and biased to ground voltage;

a cathode structure disposed upon said row electrode;

an insulating layer disposed around said cathode structure and upon said row electrode; and

a column electrode disposed upon said insulating layer; and

a circuit for controlling electron beam uniformity coupled to said column electrode, wherein said circuit for controlling said electron beam uniformity includes circuitry for providing a wave signal periodically varying grid voltage at frequencies of about 50 Hertz or greater.

21. A method for providing uniform electron beams in a field emission display having a faceplate with a cathodoluminescent layer and conductive anode layer, a baseplate with a row electrode, cathode structure and column electrode, and an electron beam uniformity circuit;

said method comprising;

biasing said conductive anode layer to an anode voltage;

biasing said row electrode to a ground voltage;

generating an electrical potential between said row electrode and said column electrode amounting to an initial DC voltage of sufficient strength to cause field emission of electrons from said cathode structure; and

increasing and decreasing said electrical potential at a specific rate with said electron beam uniformity circuit in order for providing an oscillating signal having an offset substantially equal to said initial DC voltage.