Method and apparatus for adjustment of fed image

Information

  • Patent Grant
  • 6346931
  • Patent Number
    6,346,931
  • Date Filed
    Monday, March 27, 2000
    24 years ago
  • Date Issued
    Tuesday, February 12, 2002
    22 years ago
Abstract
The image rendered by a field emission display is altered. The display includes emitter tips, an extraction grid, and conductive elements in a display screen. A first voltage is applied to at least one emitter tip, a second voltage is applied to the extraction grid at a location proximate the emitter tip to which the first voltage is applied, and a third voltage is applied to a portion of the display screen. The second and third voltages are separately variable so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages. The first, second, and third voltages cooperate with the structure to generate an electron emission stream impinging upon a first area of the display screen. The area of the display screen impinged by the electron emission stream is changed.
Description




FIELD OF THE INVENTION




The present invention relates to field emission devices (“FEDs”). More specifically, the present invention relates to a method and an apparatus with the capability to adjust on-line image definition on FED screen displays.




BACKGROUND OF THE INVENTION




Currently, in the world of computers and elsewhere, the dominate technology for constructing flat panel displays is liquid crystal display (“LCD” technology and the current benchmark is active matrix LCDs (“AMLCDs”). The drawbacks of flat panel displays constructed using AMLCD technology are the cost, power consumption, angle of view, smearing of fast moving video images, temperature range of operation, and the environmental concerns of using mercury vapor in the AMLCD's backlight.




A competing technology is cathode ray tube (“CRT”) technology. In this technology area, there have been many attempts in the last 40 years to develop a practical flat CRT. In the development of flat CRTs, there has been the desire to use the advantages provided by the cathodoluminescent process for the generation of light.




The point of failure in the development of flat CRTs has centered around the complexities in the developing of a practical electron source and mechanical structure.




In recent years, FED technology has come into favor as a technology for developing low power, flat panel displays. FED technology has the advantage of using an array of cold cathode emitters and cathodoluminescent phosphors for the efficient conversion of energy from an electron beam into visible light. Part of the desire to use FED technology for the development of flat panel displays is that is very conductive for producing flat screen displays that will have high performance, low power, and light weight. Some of the specific recent advances associated with FED technology that have made it a viable alternative for flat panel displays are large area 1 μm lithography, large area thin-film processing capability, high tip density for the electron emitting micropoints, a lateral resistive layer, anode switching, new types of emitter structures and materials, and low voltage phosphors.




Referring to

FIG. 1

, a representative cross-section of a prior art FED is shown generally at


100


. As is well known, FED technology operates on the principal of cathodoluminescent phosphors being exited by cold cathode field emission electrons. The general structure of a FED includes silicon substrate or baseplate


102


onto which thin conductive structure is disposed. Silicon baseplate


102


may be a single crystal silicon layer.




The thin conductive structure may be formed from doped polycrystalline silicon that is deposited on baseplate


102


in a conventional manner. This thin conductive structure serves as the emitter electrode. The thin conductive structure is usually deposited on baseplate


102


in strips that are electrically connected. In

FIG. 1

, a cross-section of strips


104


,


106


, and


108


is shown. The number of strips for a particular device will depend on the size and desired operation of the FED.




At predetermined sites on the respective emitter electrode strips, spaced apart patterns of micropoints are formed. In

FIG. 1

, micropoint


110


is shown on strip


104


,micropoints


112


,


114


,


116


, and


118


are shown on strip


106


, and micropoint


120


is shown on strip


108


. With regard to the patterns of micropoints, on strip


106


,a square pattern of 16 micropoints, which includes micropoints


112


,


114


,


116


, and


118


, may be positioned at that location. However, it is understood that one or a pattern of more than one micropoint may be located at any one site.




Preferably, each micropoint resembles an inverted cone. The forming and sharpening of each micropoint is carried out in a conventional manner. The micropoints may be constructed of a number of materials. Moreover, to ensure the optimal performance of the micropoints, the tips of the micropoints can be coated or treated with a low work function material.




Alternatively, the structure substrate, emitter electrode, and micropoints may be formed in the following manner. The single crystal silicon substrate may be made from a P-type or an N-type material. The substrate may then treated by conventional methods to form a series of elongated, parallel extending strips in the substrate. The strips are actually wells of a conductivity type opposite that of the substrate. As such, if the substrate is P-type, the wells will be N-type and vice-versa. The wells are electrically connected and form the emitter electrode for the FED. Each conductivity well will have a predetermined width and depth (which it is driven into the substrate). The number and spacing of the strips are determined to meet the desired size of field mission cathode sites to be formed on the substrate. The wells will be the sites over which the micropoints will be formed. No matter which of the two methods of forming the strips is used, the resulting parallel conductive strips serve as the emitter electrode and form the columns of the matrix structure.




After either of two methods of forming the emitter electrode are used, dielectric insulating layer


122


is deposited over emitter electrode strips


104


,


106


, and


108


, and the pattern micropoints located at predetermined sites on the strips. The insulating layer may be made from silicon dioxide (SiO


2


).




A conductive layer is disposed over insulation layer


122


. This conductive layer forms extraction structure


132


. The extraction structure


132


is a low potential anode that is used to extract electrons from the micropoints. Extraction structure


132


may be made from chromium, molybdenum, or doped polysilicon or silicided polysilicon. Extraction structure


132


may be formed as a continuous layer or as a parallel strips. If parallel strips form extraction structure


132


, it is referred to as an extraction grid, and the strips are disposed perpendicular to emitter electrode strips


104


,


106


, and


108


. The strips when used to form extraction structure


132


, they are the rows of the matrix structure. Whether a continuous layer or strips are used, once either is positioned on the insulating layer, they are appropriately etched by conventional methods to surround but be spaced away from the micropoints.




At each intersection of the extraction and emitter electrode strips or at desired locations along emitter electrode steps when a continuous extraction structure is used, a micropoint or pattern of micropoints are disposed on the emitter strip. Each micropoint or pattern of micropoints are meant to illuminate one pixel of the screen display.




Once the lower portion of the FED is formed according to either of the methods described above, faceplate


140


is fixed a predetermined distance above the top surface of the extraction structure


132


. Typically, this distance is several hundred μm. This distance is maintained by spacers that are formed by conventional methods and have the following characteristics: (1) non-conductive to prevent an electrical breakdown between the anode (at faceplate


140


) and cathode (at emitter electrodes


104


,


106


, and


108


), (2) mechanically strong and slow to deform, (3) stable under electron bombardment, (4) order of 400° C., and (5) small enough not to interfere with the operation of the FED. Representation spacers


136


and


138


are shown in FIG.


1


.




Faceplate


140


is a cathodoluminescent screen that is constructed from clear glass or other suitable material. A conductive material, such as indium tin oxide (“ITO” is disposed on the surface of the glass facing the extraction structure. ITO layer


142


serves as the anode of the FED. A high vacuum is maintained in area


134


between faceplate


140


and baseplate


102


.




Black matrix


149


is disposed on the surface of the ITO layer


142


facing extraction structure


132


. Black matrix


149


defines the discreet pixel areas for the screen display of the FED. Phosphor material is disposed on ITO layer


142


in the appropriate areas defined by black matrix


149


. Representative phosphor material areas that define pixels are shown at


144


,


146


, and


148


. Pixels


144


,


146


, and


148


are aligned with the openings in extraction structure


132


so that a micropoint or group of micropoints that are meant to excite phosphor material are aligned with that pixel. Zinc oxide is a suitable material for the phosphor material since it can be excited by low energy electrons.




A FED has one or more voltage sources that maintain emitter electrode strips


104


,


106


, and


108


, extraction structure


132


, and ITO layer


142


at three different potentials for proper operation of the FED. Emitter electrode strips


104


,


106


, and


108


are at “−” potential, extraction structure


132


is at a “+” potential, and the ITO layer


142


at a “++”. When such an electrical relationship is used, extraction structure


132


will pull an electron emission stream from micropoints


110


,


112


,


114


,


116


,


118


, and


120


, and, thereafter, ITO layer


142


will attract the freed electrons.




The electron emission streams that emanate from the tips of the micropoints fan out conically from their respective tips. Some of the electrons strike the phosphors at 90° to the faceplate while others strike it at various acute angles. The contrast and brightness of the screen display of the FED are optimized when the emitted electrons strike or impinge upon the phosphors at 90°.




Typically, color FEDs use a switched anode scheme in providing color images. In such a scheme, the pixel colors red, green, and blue are arranged in columns. All of the red columns are tied together, all of the blue are tied together, and all of the green columns are tied together. For each frame, the red, green, and blue images are sequentially displayed. There are, however, other methods of providing color in FEDs, which are known.




In computer graphical images, an issue that must be addressed is the aliasing problem. This problem is manifest at the edges of a computer image which make them look stairstepped rather than straight, polygons crawl across a screen in steps rather than advance smoothly, and thin lines break up into dotted lines.




The aliasing problem is created because of the need to approximate what each whole pixel will be as a color. As such, it can result in reducing an image that has great detail, such as a photographic picture, to one of lesser detail. Specifically, the result is usually a digitized version of the photographic picture.




In many cases, the aliasing problem can be corrected but usually at great cost. This cost is for the extra processing that is needed for the purpose of preventing aliasing. This processing is referred to as antialiasing.




Antialiasing is not a process that is used to correct a picture with aliasing, but a process that is used in the original processing of the image data before the pixels of the image are determined. When antialiasing is properly performed, there is a greater degree of sharpness in the computer graphical image that is created.




Referring to

FIGS. 2 and 3

, the aliasing problem will be described in greater detail. A pixel may theoretically be capable of having many different colors simultaneously, however, in reality, when a image on a screen display is presented, a single color is computerized for any one pixel at a given point in time rather than a single pixel having a complex combination of colors. A typical way to do this, which demonstration of the aliasing problem, is that the color for a particular pixel is determined by the color that is at the center point of the pixel.




Referring to

FIG. 2

, a 5×4 block of pixels is shown generally at


200


. The centers of each of the pixels is indicated. Polygon


202


crosses this block of pixels as shown. There can be a substantial error in the representation polygon if the center of pixel method is used to determine the color of the respective pixels when attempting to replicate the actual polygon shape on the screen display.




Referring to

FIG. 3

, generally at


250


, the shape of the polygon


202


results in polygon


252


when the center method is used. As is shown, the sharp line of polygon


202


becomes stairstepped in polygon


252


. If two colors are being considered, for example, black and white, when polygon


202


crosses a pixel such that it does not cover the center, the complete pixel, will be white; on the other hand, if the polygon does cover the center of the pixel, the entire pixel will be the second color, which in this case will mean the pixel will black. Therefore, a straight line of a polygon, upon inspection, will appear stairstepped. If this polygon is moving across the screen, as the edge of the polygon crosses the center points of the various pixels, there will be line break ups and crawling in steps.




A first solution to the aliasing problem is to make smaller pixels which will increase resolution. However, this is expensive and does not eliminated the problem only makes it less perceptible. Another possible solution is using an oversampling technique in which the polygon is sampled at several points in the pixel rather than just at the center. This will effect a result similar to that of using higher resolution without actually making the pixels smaller.




Referring to

FIGS. 4 and 5

, the oversampling method will be described. In

FIG. 4

, a 3×2 block of pixels is shown generally at


300


. This block includes pixels


302


,


304


,


306


,


308


,


310


, and


312


. Each of these pixels has been divided into four subpixels and the centers of the subpixels are indicated. This has the effect of increasing the resolution for purpose of defining images, but at a fraction of the cost as it would be to actually create such a higher resolution FED.




In

FIG. 4

, polygon


314


crosses pixels


302


,


304


,


306


,


308


,


310


, and


312


as shown. In

FIG. 5

, generally at


350


, the screen display representation of polygon


314


is shown as polygon


352


. Although there is stairstepping, its effect is less because of the apparent higher resolution so the line of polygon


352


will appear closer to the line of polygon


314


, thus providing a sharper image.




In FED images, like other computer graphical images, pixels can typically have a random access variability of intensity from a minimum value near zero (0) footlamberts to a maximum of 10-1000 footlamberts. A footlambert is equal to 3.42626 cadela/meter


2


(cd/m


2


). In spatial color displays, the pixels have different CIE (Comite International de Eclairage) primary color coordinates for light emission. The most common is that ⅓ are red pixels, {fraction (


1


/


3


)} are green pixels, and ⅓ are blue pixels. Normally, the different colored pixels are separated by a black region such that a black grid or grill is formed around the pixels.




Aliasing along with the existence of the black grid will result in very sharp definitions at the edges of images. Moreover, when the border regions between pixels are aggressively separated by using a black grid or grill, a crisp digitized appearance is visually apparent to someone viewing a screen image. This, also can lead to the image appearing grainy because of the existence of the block grid and, in the worst case, the image can have a chicken-wire effect. This latter problem is not corrected solely by employing antialiasing techniques.




When the border regions are not aggressively separated, such as by use of a black grid, the effect is that there can be undesirable blending of the colors of two adjoining pixels. This appears to the viewer as an overlap of the edges of two polygons. As such, the blending may appear as a blurring of the lines between two polygons. This also is not solved solely by employing antialiasing techniques.




In order to attempt to correct the pixel separation problems in FEDs that are not solved by employing antialiasing techniques, there are several procedures that have been used to set the pixel element definition of the screen display. An approach is to adjust the distance between the light emitting pixel elements of the screen display during the time the screen display is fabricated. Examples of the use of this technique are: (1) the distance is adjusted between the phosphor elements of respective pixels on the faceplate of the FED by means of the black matrix or grid, (2) the distance is adjusted between the color filters again by means of the black matrix or grid, (3) the distance is adjusted between the faceplate and baseplate of the FED, and (4) the use of microlens optics between the viewer and the screen display to optically diffuse the pixel edges toward each other.




Although, the four (4) methods have been proposed, they all suffer from the problem that in each of these cases, there is a lack of an ability to make further adjustments in order to achieve the desire affect in the images on the screen display once an initial adjustment is made early in the fabrication stage or made permanently in the fabrication of the apparatus. This problem could be solved by adding an additional electron beam focusing element to the FED structure so that there can be deflection of the electron beams. This method is not particularly desirable because it requires considerable baseplate processing challenges and is expensive.




Therefore, it is very desirable to have a solution that is simple and inexpensive that can be applied to FED system to solve the problems associated with image definition that are not solved with antialiasing techniques.




SUMMARY OF THE INVENTION




The present invention is a low cost system and method for making adjustments to the pixel boundaries of images in a screen display of an FED to overcome the problems created by pixel separation which are not solved by antialiasing techniques. Moreover, the present invention provides a system and method that can actively adjust the pixel edge definition of images on a screen display to obtain the viewer's desired screen display effect.




According to the present invention, in order to provide the desired adjustment to the pixel boundaries of the images on the screen display, it is necessary to accurately control the voltages on the extraction structure and anode. The voltage to the extraction structure, which is positive with respect to the electron emitter and micropoints, induces an high electrical field with regard to a associated micropoint. This induces Fowler-Nordheim tunneling and electron emission according to the expression:






J
=


C
1

·

E
2

·

e


C
2

/
E










where
,






J
=

The





emitted





current





density







(

amps
/

m
2


)

.









C
1

,


C
2

=

The constants which depend of material's work function,
surface potential, and Fermi level.









E
=

The





electric













field










(

volts
/
m

)

.















The voltage that is applied to the extraction structure frees the electron emission streams that are attracted by the anode to the phosphor elements of a pixel. An electron emission stream has a horizontal (or lateral) component and a vertical component (toward the faceplate). The lateral component is nearly completely controlled by the voltage on the extraction structure because the space charge effect in FEDs is relatively small compared to the high field strengths caused by the extraction structure voltage that cause the electron emission stream to be emitted from a micropoint. As such, the larger the extraction structure voltage, the larger the lateral trajectory of the electron emission stream. To the contrary, the smaller the extraction structure voltage, the smaller the lateral trajectory of the electron emission stream.




The vertical component to the emission is affected substantively by the voltage that is applied to the ITO layer (anode) at the faceplate of the FED. Typically, at a minimum, this anode voltage is four (4) times larger that the extraction structure voltage. Preferably, the anode voltage is much higher than this with respect to the extraction structure voltage.




The anode voltage imparts a vertical acceleration on the electron emission. This attracts the electron emission stream to the phosphor material of a pixel at the bottom surface of the faceplate to produce the cathodoluminescent photons, which the viewer sees. The higher the anode voltage, the greater the acceleration of the electrons of the electron emission stream toward the anode. This also will mean that the time that the electron emission stream is influenced by lateral forces imparted by the extraction structure voltage will be short and be of less affect. The contrary is true when the anode voltage is lower. As such, the anode voltage has an influence on the spot size for a particular electron emission stream at a phosphor material of a pixel on the faceplate.




The final spot size of an electron emission stream on a phosphor element on the faceplate is a function of the time of travel of the electrons of the electron emission, which is controlled by the anode voltage, and the lateral component, which is controlled by the extraction structure voltage. In a system in which the distance between the emitter electrode and anode (at the faceplate) is fixed, a fixed gap system, the final spot size depends on the ratio of the anode voltage to the extraction structure voltage. If the ratio is increased, the final spot will be smaller, and if the ratio is decreased, the final spot will become larger. The on-line active adjustment of the spot size at the phosphor material at the faceplate will increase and decrease the distance between pixels to effect adjustment of the pixel boundaries. Therefore, the images on the screen display can have their definition actively adjusted as desired by the viewer.




An object of the present invention is to provide a FED system that permits the viewer to actively adjust the image definition on-line.




Another object of the present invention is to provide a FED system in which the desired effect at the borders of images on the screen display is attainable.




A yet further object of the present invention is to provide a FED system in which the ratio of the anode voltage and the extraction structure voltage may be actively adjusted to obtain a desired screen display effect.




These and other objects of the present invention will be discussed in detail in the remainder of the specification referring to the drawings. dr




BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

shows a partial cross-section of a prior art FED.





FIG. 2

shows a polygon that crosses a series of pixels of a screen display.





FIG. 3

shows the digitized representation of the polygon in

FIG. 3

when the center method is used to control the color of the pixels.





FIG. 4

show a series of pixels of a screen display that have been further divided into sub-pixels and a polygon that crosses this series pixels.





FIG. 5

shows the digitized representation of the polygon in

FIG. 4

when the oversampling method is used to control the color of the pixels.





FIG. 6A

shows a screen display of an FED in which the chicken-wire effect is present.





FIG. 6B

shows a screen display of an FED in which the chicken-wire effect is eliminated and there is a blending (or softening) of the image boundaries.





FIG. 7

shows the preferred embodiment of the FED of the present invention.





FIG. 8

shows the controller of the FED shown in

FIG. 7

in greater detail.





FIG. 9

shows the preferred embodiment of the FED of the present invention in which the ratio of the anode voltage to extraction structure voltage is large, which adjusts the spot of the electron emission to be smaller for very sharp pixel edge definition.





FIG. 10

shows the preferred embodiment of the present invention in which the ratio of the anode voltage to extraction structure voltage is small which adjusts the spot of the electron emission stream to be larger for a blended pixel edge definition.











DETAILED DESCRIPTION OF THE DRAWINGS




The present invention is a low cost system and method for making adjustments on-line to the pixel boundaries of images in a screen display of a FED. The system and method of the preferred invention actively adjust the edge definition of images on a screen display to achieve the desired screen display effect.




Referring to

FIG. 7

, a partial cross-section of the preferred embodiment of the FED of the present invention is shown generally at


500


. According to this embodiment, emitter electrode


504


is formed in wells in substrate


502


by any of a number of conventional semiconductor processing methods, such as diffusion or ion field implantation techniques. Generally, the emitter electrode will consist of a number of spaced apart, parallel wells that are electrically connected. Emitter electrode


504


is one of the parallel disposed wells. The number and spacing of the parallel spaced apart wells is determined by the needs of the FED.




Preferably, substrate


502


is formed from a P-type single crystal silicon structure and the emitter electrode


504


is N-type single crystal silicon structure, which is the opposite conductivity type. It is understood, however, the conductivity types for substrate


502


and emitter electrode


504


can be reversed and still be within the scope of the present invention. Emitter electrode


504


is the cathode conductor of the FED of the present invention.




At predetermined locations on emitter electrode


504


above which pixels will be situated, one of more micropoints are formed on emitter electrode


504


. These micropoints are formed on emitter electrode


504


and sharpened by conventional semiconductor processing methods. In

FIG. 7

, two spaced apart micropoints are shown, micropoint


506


and micropoint


508


. Preferably, the micropoints are integrally formed from the same material as emitter electrode


504


and have their tips coated with a low work function material. Suitable low work function materials are cermet (Cr


3


Si+SiO


2


), cesium, rubidium, tantalum nitride, barium, chromium silicide, titanium carbide, molybdenum, and niobium. These are deposited on the micropoints using conventional semiconductor processing methods, such as vapor deposition. It is understood that other suitable materials also may be used.




Each micropoint is surrounded with insulating layer


510


. As is shown in

FIG. 7

, insulating layer


510


is spaced away from micropoints


506


and


508


. Insulating layer


510


electrically insulates the positive electrical elements of the FED of the present invention from the negative emitter electrode. Preferably, insulating layer


504


is formed from silicon dioxide (SiO


2


).




Conductive layer


516


is disposed on insulating layer


510


. Conductive layer is positioned on insulating layer


510


by conventional semiconductor processing methods. Preferably, conductive layer


516


is formed from doped polysilicon or silicided polysilicon.




Conductive layer


516


surrounds micropoints


506


and


508


for the purpose of causing an electron emission stream to be emitted from these micropoints and others of the FED. Conductive layer


516


also may be a series of electrically connected parallel strips disposed on insulating layer


510


. In either configuration, conductive layer


516


serves as an extraction structure and, hereafter, will be referred to as such.




Spaced above extraction structure


516


is faceplate


522


. Faceplate


522


is a cathodoluminescent screen that preferably is made from a clear, transparent glass. However, it is understood that other transparent materials may be used, and still be within the scope of the present invention. Faceplate


522


must be capable of transmitting the light of cathodoluminescent photons, which the viewer sees.




ITO layer


524


is disposed on the bottom surface of faceplate


522


which faces extraction structure


516


. ITO layer


524


is a layer of electrically conductive material that may be disposed as a separate layer on faceplate


522


or made as part of the faceplate. ITO layer


524


, in any case, is transparent to the light from cathodoluminescent photons and serves as the anode for the FED.




In

FIG. 7

, pixels


526


(in-part),


528


,


530


, and


532


(in-part) are shown disposed on the surface of ITO layer


524


facing extraction structure


516


. As is shown, pixel


528


is disposed over micropoint


506


and pixel


530


over micropoint


508


. The micropoints for pixels


526


and


532


are not shown. In

FIG. 7

, there is only one micropoint associated with one pixel; however, it is understood that more than one micropoint may be associated with a pixel, such a 4×4 or 5×5 square pattern of micropoints or a generally random array of micropoints.




The pixel areas have a phosphor material deposited on the bottom of ITO layer


524


in a desired pattern. Generally, the pixels are square in shape. The phosphor materials that is used is preferably one that can be excited by low energy electrons. Zinc oxide is a preferred phosphor materials but other suitable phosphor materials may be used and still be within the scope of the present invention.




The pixels are divided by black matrix


525


. Black matrix


525


may be of any suitable material. Preferably, it is made from a plastic material. It is understood that other materials that are opaque to the transmission of light and not affected by electron bombardment also may be used.




As is shown in

FIG. 7

, faceplate


522


is spaced away from substrate


502


. This is a predetermined distance usually in the 100-200 μm range. This spacing is maintained by spacers which are not shown. The area between faceplate


522


and substrate


502


, preferably, is under high pressure.




Referring to

FIGS. 7 and 8

, controller


534


connects to image observer


538


via line


536


, ITO layer


524


via line


540


, extraction structure


516


via line


542


, emitter electrode


504


via line


544


, and user interface


535


via line


537


. Controller


534


is shown in detail in

FIG. 8

at


550


. Controller provides the voltage potentials to the emitter electrode


504


, extraction structure


516


, and ITO layer


524


to obtain the desired screen display effect. Controller


534


also receives signals from image observer


538


, and send and receives signals to user interface


535


.




Image observer


538


provides feedback signals to controller


534


with respect to current visual representation of images on the screen display. For example, image observer will detect whether the edges of the images on the screen display are sharply defined and screen display suffers from the chicken-wire effect or, on the opposite extreme, the color of the images are very highly blended along the edges between images and there is no chicken-wire effect seen.




Now to discuss controller


534


in detail, referring to

FIGS. 7 and 8

, line


544


of controller


534


connects to ground


560


. Line


544


also connects to emitter electrode


504


. As such, emitter electrode


504


is maintained at ground voltage.




Line


542


of controller


534


connects to extraction structure


516


. Line


542


also connects to voltage source


562


via variable resistor


564


that is shown as Z


g


in FIG.


8


. Voltage source


562


applies a positive voltage to extraction structure


516


that is sufficient to cause an electron emission stream to be emitted from the micropoints, such as micropoints


506


and


508


. Representative emissions from micropoints


506


and


508


are shown at


507


and


509


, respectively. Although adjustment of variable resistor


564


will change the voltage that is applied to extraction structure


516


, the voltage that is applied to the extraction structure is always sufficient to cause the emission of an electron stream from the micropoints. The voltage that is applied to extraction structure controls the lateral trajectory of the electron emission streams.




Line


540


of controller


534


connects to ITO layer


524


. Line


542


also connects to voltage source


556


via variable resistor


558


, which is shown as Z


a


in FIG. Voltage source


556


applies a positive voltage to ITO layer


524


and this voltage is larger than the voltage that is applied to extraction structure


516


. Variable resistor


558


, Z


a


, adjusts the voltage that is applied to ITO layer


524


, the anode, but the voltage always is sufficient to cause an electron emission stream to be attracted to the anode. The voltage that is applied to the anode controls the vertical component of the trajectory of the electron emission streams.




Operation of controller


534


is controlled by CPU


552


and controller electronics


554


. CPU


552


and controller electronics


554


receiver inputs from image observer


538


regarding the current condition of the screen display. CPU


552


and controller electronics


554


control the voltages that are applied to extraction structure


516


and ITO layer


524


by adjusting variable resistors


558


and


564


to control the lateral and vertical components of the electron emission streams. The control of lateral and vertical components control the diameter of the spot that impinges on the phosphor material. The method of control, according to the present invention, will be discussed in greater detail referring to

FIGS. 9 and 10

.




User interface


535


is used by the viewer to send command signals to controller


534


to produce the screen display effect that the viewer desires. This interface may be equipped with an appropriate display that will display visual or textual information regarding the display screen conditions. This will permit the viewer to assess the display screen condition in light of the command signals that he or she provides to the controller.




It is understood that the FED system of the present invention may have a controller which has the necessary controls that the user can access for controlling the ratio of the anode voltage to the extraction voltage, thus obviating the need for user interface


535


.




The FED has been described as including image observer


538


; however, it is within the scope of the present invention that the device does not have to include an image observer but the viewer will visually inspect the screen display and determine when the desired visual effect has been achieved. This can be done using the naked eye or by using some type magnification device. In either case, the viewer will view the screen display as the adjustment commands take affect and when the desired effect is achieved the viewer will cease adjusting the screen display.




Referring to

FIGS. 9 and 10

, on-line, active adjustment of the diameter of the electron emission stream will be described which will result in the viewer controlling the screen display effect ranging from very sharp with the chicken-wire effect present to a soft, blended effect with no chicken-wire effect present. In describing the operation of the present invention, reference will be made to

FIGS. 6A and 6B

which show a sharply defined and blended image, respectively.




When the viewer desires a very sharply defined image, like


372


in

FIG. 6A

, which also may even result in the chicken-wire effect as is shown in

FIG. 6A

generally at


370


, he or she will send commands to controller


534


, via user interface


535


, to increase the ratio of the anode voltage to the extraction structure voltage. This will cause either variable resistor


558


to increase the anode voltage with regard to the extraction structure voltage, or cause variable resistor


564


to decrease the extraction structure voltage with respect to the anode voltage, or cause variable resistor


558


to increase the anode voltage and variable resistor


564


to decrease the extraction structure voltage to provide the greatest operable ratio of the anode voltage to the extraction structure voltage.




As the ratio of the anode voltage to the extraction structure voltage increases, the lateral component of the electron emission stream trajectory, which is controlled by the extraction structure voltage, will have less of an affect and the vertical component of the electron emission stream trajectory, which is controlled by the anode voltage, will have a greater affect. The result is as shown in

FIG. 9

, the diameter of the electron emission stream is smaller as it impinges on the pixel. When this is the case, even though the image is sharper, the black matrix, which separates the pixels, can create the chicken-wire effect in the screen display image that is presented. However, because the present invention provides for on-line, active adjustment of the anode and extraction structure voltages, the ratio of these voltages can be adjusted to keep the sharp image but eliminate the chicken-wire effect.




It is understood that in carrying out the operation of the FED according to the present invention as just described, the viewer may choose to use image observer


538


, the naked eye, or the naked eye assisted by a magnification device to evaluate the condition of the images on the screen display and determine when the desired screen display effect is achieved.




Referring now to

FIGS. 6B and 10

, when the viewer desires a softer image, like image


382


in

FIG. 6B

, which eliminates the chicken-wire effect and blends the edges of images (as is shown in

FIG. 6B

generally at


380


), he or she will sent commands to controller


534


, via user interface


535


, to decrease the ratio of the anode voltage to the extraction structure voltage. This will cause either variable resistor


558


to decrease the anode voltage with regard to the extraction structure voltage, or cause variable resistor


564


to increase the extraction structure voltage with respect to the anode voltage, or cause variable resistor


558


to decrease the anode voltage and variable resistor


564


to increase the extraction structure voltage to provide the smallest operable ratio of the anode voltage to the extraction structure voltage.




As the ratio of the anode voltage to the extraction structure voltage decreases, the lateral component of the electron emission stream trajectory, which is controlled by the extraction structure voltage, will have more of an effect and the vertical component of the electron emission stream trajectory, which is controlled by the anode voltage, will have less of an affect. The result is as shown in

FIG. 10

, the diameter of the electron emission stream as it impinges on the pixel is larger. When this happens, there is a blending of the light eliminating from adjacent pixels and an elimination from view of the black matrix, which separates the pixels. Here again, because the present invention provides for active adjustment of the anode and extraction structure voltages, the ratio of these voltages can be adjusted to achieve the desired blending or softening of the images.




As discussed previously, it is understood that in carrying out the operation of the FED according to the present invention as just described, the viewer may choose to use image observer


538


, the naked eye, or the naked eye assisted by a magnification device to evaluate the condition of the images on the screen display and determine when the desired screen display effect is achieved.




The terms and expressions which are used herein are used as terms of expression and not of limitation. There is no intention in the use of such terms and expressions of excluding the equivalents of the features shown and described, or portions thereof, it being recognized that various modifications are possible in the scope of the present invention.



Claims
  • 1. A field emission device system, comprising:a substrate; a first electrically conductive structure disposed over the substrate; electron emitting structures disposed above, and extending upward relative to, the first electrically conductive structure; an insulating layer disposed above the first electrically conductive structure, with the insulating layer having an opening therein for receiving and surrounding each electron emitting structure; a second electrically conductive structure disposed above the insulating layer, with the second electrically conductive layer having an opening aligned with each opening in the insulating layer and an opening in the second electrically conductive structure surrounding an electron emitting structure; a light transmissive faceplate disposed above the second electrically conductive structure; a third electrically conductive structure disposed below the faceplate toward the second electrically conductive structure; phosphor material disposed below the third electrically conductive structure toward the second electrically conductive structure with the phosphor material being capable of emitting light when excited by electrons; a controller that is electrically connected to the first, second, and third conductive structures for controllably providing a first voltage to the first electrically conductive structure, an adjustable second voltage to the second electrically conductive structure, and an adjustable third voltage to the third electrically conductive structure, with the first voltage being at a predetermined level, the second and third voltages being more positive than the first voltage, and the second and third voltages being separately adjustable so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages, the second and third voltages being adjustable in respective ranges to effect an electron emission stream from each electron emitting structure that is controllable with regard to an area of phosphor material upon which a particular electron emission stream impinges.
  • 2. The system as recited in claim 1, wherein the first electrically conductive structure comprises an emitter electrode.
  • 3. The system as recited in claim 2, wherein the emitter electrode further comprises a plurality of electrically connected parallel disposed strips.
  • 4. The system as recited in claim 2, wherein the second electrically conductive structure comprises an extraction structure.
  • 5. The system as recited in claim 4, wherein the extraction structure further comprises a plurality of electrically connected parallel disposed strips.
  • 6. The system as recited in claim 4, wherein the extraction structure further comprises a continuous layer of electrically conductive material.
  • 7. The system as recited in claim 4, wherein the third electrically conductive structure comprises an anode.
  • 8. The system as recited in claim 7, wherein the first voltage includes a ground voltage.
  • 9. The system as recited in claim 8, wherein the adjustable second voltage is a positive voltage that is adjustable in a range that will cause an electron emission stream to be emitted from each electron emitting structure.
  • 10. The system as recited in claim 9, wherein the adjustable third voltage is a positive voltage that is greater than the adjustable second voltage, with the adjustable third voltage being adjustable in a range that will cause the electron emission stream emitted from each electron emitting structure to be attracted to the anode.
  • 11. The system as recited in claim 10, wherein the system further includes a user interface that is connected to the controller for providing signals to the controller for adjusting the adjustable second and third voltages.
  • 12. The system as recited in claim 11, wherein the system further includes a faceplate monitor that is connected to the controller for providing feedback to the controller regarding a current visual representation of images on the faceplate.
  • 13. A field emission device system, comprising:a substrate; a first electrically conductive structure disposed over the substrate; electron emitting structures disposed above, and extending upward relative to, the first electrically conductive structure; an insulating layer disposed above the first electrically conductive structure, with the insulating layer having an opening therein for receiving and surrounding each electron emitting structure; a second electrically conductive structure disposed above the insulating layer, with the second electrically conductive layer having an opening aligned with each opening in the insulating layer and an opening in the second electrically conductive structure surrounding an electron emitting structure; a light transmissive faceplate disposed above the second conductive structure; a third electrically conductive structure disposed below the faceplate toward the second electrically conductive structure; phosphor material disposed below the third electrically conductive structure toward the second electrically conductive structure with the phosphor material being capable of emitting light when excited by electrons; a matrix structure disposed below the third conductive structure toward the second conductive structure; a controller that is electrically connected to the first, second, and third conductive structures for controllably providing a first voltage to the first conductive structure, an adjustable second voltage to the second conductive structure, and an adjustable third voltage to the third conductive structure, with the first voltage being at a predetermined level, the second and third voltages being more positive than the first voltage, and the second and third voltages being separately adjustable so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages, the second and third voltages being adjustable in respective ranges to effect an electron emission stream from each electron emitting structure that is controllable with regard to an area of phosphor material upon which a particular electron emission stream impinges; and a user interface that is connected to the controller for provide signals to the controller for separately adjusting the adjustable second and third voltages so that an adjustment causing a voltage change in one of the second and third voltages can be made without causing a corresponding voltage change in the other of the second and third voltages.
  • 14. The system as recited in claim 13, wherein the system further includesa faceplate monitor that is connected to the controller for providing feedback to the controller regarding a current visual representation of images on the faceplate in response to adjustments made to the electron emission streams emitted by the electron emitter structures with respect to the area of phosphor material upon which particular electron emission stream impinges.
  • 15. The system as recited in claim 14, wherein the first electrically conductive structure comprises an emitter electrode.
  • 16. The system as recited in claim 15, wherein the emitter electrode further comprises a plurality of electrically connected parallel disposed strips.
  • 17. The system as recited in claim 15, wherein the second electrically conductive structure comprises an extraction structure.
  • 18. The system as recited in claim 17, wherein the extraction structure further comprises a plurality of electrically connected parallel disposed strips.
  • 19. The system as recited in claim 17, wherein the extraction structure further comprises a continuous layer of electrically conductive material.
  • 20. The system as recited in claim 17, wherein the third electrically conductive structure comprises an anode.
  • 21. The system as recited in claim 20, wherein the first voltage includes a ground voltage.
  • 22. The system as recited in claim 21, wherein the adjustable second voltage is a positive voltage that is adjustable in a range that will cause an electron emission stream to be emitted from each electron emitting structure.
  • 23. The system as recited in claim 22, wherein the adjustable third voltage is a positive voltage that is greater than the adjustable second voltage, with the adjustable third voltage being adjustable is a range that will cause the electron emission stream emitted from each electron emitting structure to be attracted to the anode.
  • 24. A method for on-line adjustment of image definition at a faceplate of a field emission device system, with the field emission display system including a first electrically conductive structure, electron emitting structures disposed above, and extending upward relative to, the first electrically conductive structure, a second electrically conductive structure disposed above the first electrically conductive structure, a third conductive structure disposed above the second electrically conductive structure, phosphor material disposed below the third electrically conductive structure toward the second electrically conductive structure, and a controller that is electrically connected to the first, second, and third electrically conductive structures for controllably providing a first voltage to the first conductive structure, an adjustable second voltage to the second electrically conductive structure, and an adjustable third voltage to the third electrically conductive structure, with the first voltage being at a predetermined level, and the second and third voltages being separately adjustable so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages, the second and third voltages being adjustable in respective ranges to effect an electron emission stream from each electron emitting structure that is controllable with regard to an area of phosphor material upon which a particular electron emission stream impinges, comprising:(a) viewing a current visual representation of an image on a faceplate disposed above the second electrically conductive structure; and (b) by at least one adjustment to at least one of said second and third voltages, each said adjustment to one of said second and third voltages being separate from each said adjustment to the other of said second and third voltages so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages, adjusting a ratio of the adjustable third voltage to the adjustable second voltage to cause the electron emission streams emitted by the electron emitter structures to respectively impinge upon a lesser area of a phosphor than before the adjustment to the ratio was made.
  • 25. A method for on-line adjustment of image definition at a faceplate of a field emission device system, with the field emission display system including, a first electrically conductive structure, electron emitting structures disposed above, and extending upward relative to, the first electrically conductive structure, a second electrically conductive structure disposed above the second electrically conductive structure, a third conductive structure disposed above the second electrically conductive structure, phosphor material disposed below the third electrically conductive structure toward the second electrically conductive structure, and a controller that is electrically connected to the first, second, and third electrically conductive structures for controllably providing a first voltage to the first conductive structure, an adjustable second voltage to the second electrically conductive structure, and an adjustable third voltage to the third electrically conductive structure, with the first voltage being at a predetermined level, and the second and third voltages being separately adjustable so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages, the second and third voltages being adjustable in respective ranges to effect an electron emission stream from each electron emitting structure that is controllable with regard to an area of phosphor material upon which a particular electron emission stream impinges, comprising:(a) viewing a current visual representation of an image on a faceplate disposed above the second electrically conductive structure; and (b) by at least one adjustment to at least one of said second and third voltages, each said adjustment to one of said second and third voltages being separate from each said adjustment to the other of said second and third voltages so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages, adjusting a ratio of the adjustable third voltage to the adjustable second voltage to cause the electron emission streams emitted by the electron emitter structures to respectively impinge upon a greater area of a phosphor than before the adjustment to the ratio was made.
  • 26. A field emission display, comprising:a substrate assembly having a plurality of emitter tips thereabove; a conductive grid assembly disposed in spaced relation to said substrate, said grid including a plurality of conductive elements; a display screen disposed in spaced relation to said grid assembly and on the opposite side of said grid assembly from said substrate assembly, said screen including a plurality of conductive elements; and a control assembly configured to couple a first voltage to said conductive elements of said grid assembly and to couple a second voltage to said conductive elements of said screen assembly, said control assembly operable to vary the magnitude of said first and second voltages, said control assembly operable to vary the magnitude of one of said first and second voltages separately from varying the other of said first and second voltages so that an adjustment causing a voltage increase in one of the first and second voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the first and second voltages.
  • 27. A field emission display, comprising:a substrate assembly having a plurality of emitter tips thereabove, said emitter tips operable to emit electrons at least partially in response to a first voltage applied thereto; a conductive grid assembly disposed in spaced relation to said substrate, said conductive grid assembly comprising a plurality of conductive elements; a display screen disposed in spaced relation to said grid assembly, said display screen comprising a plurality of conductive elements; a first variable voltage supply coupled to said conductive elements of said grid assembly; and a second variable voltage supply coupled to said conductive elements of said display screen, said first and second variable voltage supplies being separately variable so that an adjustment causing a voltage increase in one of the first and second variable voltage supplies can take effect concurrently with another adjustment causing a voltage decrease in the other of the first and second variable voltage supplies.
  • 28. A method of adjusting the image output of a field emission display having a plurality of emitter tips, an extraction grid, and a display screen, comprising:applying a first voltage to a first plurality of said emitter tips; applying a second voltage to at least a portion of said extraction grid; applying a third voltage to at least a portion of said display screen, said second and third voltages being separately variable so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages; and varying at least one of said second and third voltages sufficiently to alter the image rendered by said display.
  • 29. A method of altering the image rendered by a field emission display including a plurality of emitter tips, an extraction grid and conductive elements in a display screen, comprising:applying a first voltage to at least one emitter tip of said plurality of emitter tips; applying a second voltage to said extraction grid at a location proximate said emitter tip to which said first voltage is applied; applying a third voltage to a portion of said display screen, said second and third voltages being separately variable so that an adjustment causing a voltage increase in one of the second and third voltages can take effect concurrently with another adjustment causing a voltage decrease in the other of the second and third voltages, said first, second and third voltages cooperating with said structure to generate an electron emission stream impinging upon a first area of said display screen; and changing the area of said display screen impinged by said electron emission stream.
  • 30. The method of claim 29, wherein changing the area impinged by said electron beam emission includes varying at least one of said second voltage and said third voltage.
CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 08/746,314, filed Nov. 12, 1996 now U.S. Pat. No. 6,801,246.

GOVERNMENT RIGHTS

This invention was made with Government support under Contract No. DABT63-93-C-0025 awarded by the Advanced Research Projects Agency (ARPA). The Government may have certain rights in this invention.

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Continuations (1)
Number Date Country
Parent 08/746314 Nov 1996 US
Child 09/535964 US