Abstract:
A system for enhancing brightness and resolution while correcting certain types of convergence, geometry, color and luminance errors caused by the display device, the viewing position or both. This system involves merging images from two or more sources, overlapping and offsetting pixels, or overlapping scanning lines “merged raster” in a CRT or several (3) “merged rasters” in color CRT&#39;s, and adjusting video content and timing, to compensate for the current viewing position and/or device distortion. Display and/or viewing perspective distortion characteristics are measured from the observers viewing position for the raster or each non-converged raster and stored as correction factor data in non-volatile memory. This data is used to modify the digital addressing of video image memory, to read and to correct pixel data for each image, adjust color, modify magnitude, and to drive the displays video amplifier at the correct time with the corrected amplitude and image data. Making these changes within the video path provides substantial improvements in image quality and in cost savings.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims priority of U.S. provisional application Serial No. 60/194,620 filed Apr. 5, 2000.  
         [0002]    This application is being filed as a PCT application by GENESIS MICROCHIP, INC. a Canadian national and United States resident, as applicant for Europe, Japan, Republic of Korea; AND James R. Webb, United States national and resident, Steve Selby, Canadian national and resident and Gheorghe Berbecel, Canadian national and resident as applicants/inventors for United States only. This PCT application designates Europe, Japan, Republic of Korea and United States. 
     
    
     
       FIELD OF THE INVENTION  
         [0003]    The present invention pertans to video displays and more particularly to enhancing brightness and resolution and correcting certain types of errors caused by display devices.  
         DEFINITIONS  
         [0004]    ALIGN means to cause a video image to be adjusted so that distortion characteristics are minimized and the video image that is displayed on the cathode ray tube forms an image that is pleasing to the eye.  
           [0005]    ALIGNMENT CAMERA means the video used to generate a signal that is representative of the image displayed on the cathode ray tube in a manner described in U.S. Pat. No. 5,216,504.  
           [0006]    ALIGNMENT SPECIFICATIONS means a limit set for the distortion data of each correction factor parameter to provide an aligned video image.  
           [0007]    BAR CODE means any sort of optically encoded data.  
           [0008]    CATHODE RAY TUBE (CRT) means the tube structure, the phosphor screen, the neck of the tube, the deflection and control windings, including the yoke and other coils, and the electron guns.  
           [0009]    CHARACTERIZATION MODULE means a device that is coupled in some manner to a display device and may include a storage device for storing correction factor data or an identification number for the display device, and/or a processing device such as a microprocessor or other logic device, and/or driver and correction circuits, and/or control circuitry. The characterization module can also store parametric data for use in aligning monitors that employ standardized transformation equations.  
           [0010]    COORDINATE LOCATIONS means the discrete physical locations on the face of the cathode ray tube, or a physical area on the display screen.  
           [0011]    CORRECTION AND DRIVER CIRCUITRY means one or more of the following: digital to analog converters, interpolation engine, pulse width modulators and pulse density modulators, as well as various summing amplifiers, if required. These devices are capable of producing correction control signals that are applied to control circuitry to generate an aligned video image.  
           [0012]    CORRECTION CONTROL SIGNALS means correction factor signals that have been combined in a manner to be applied to either horizontal control circuitry, vertical control circuitry, or electron gun circuitry.  
           [0013]    CORRECTION FACTOR DATA comprises the encoded digital bytes or any other form of data that are representative of the amount of correction required to align a video signal at a particular physical location on a cathode ray tube to counteract distortion characteristics at that location. Correction factor data may include data from the gain matrix table, data relating to electron gun characteristics and/or data relating to geometry characteristics of the cathode ray tube.  
           [0014]    CORRECTION FACTOR PARAMETERS include various geometry characteristics of the cathode ray tube including horizontal size, vertical size, horizontal center, vertical center, pin cushion, vertical linearity, keystone, convergence, etc., and various electron gun characteristics of the cathode ray tube including contrast, brightness, luminosity, focus, color balance, color temperature, electron gun cutoff, etc.  
           [0015]    CORRECTION FACTOR SIGNALS means digital correction signals that have been integrated or filtered.  
           [0016]    CORRECTION SIGNALS means digital correction signals and correction factor signals.  
           [0017]    DECODER means a device for generating an electronic signal in response to one or more data bytes that may include PWMs, PDMs, DACs, interpolation engines, onscreen display chips, etc.  
           [0018]    DIGITAL CORRECTION SIGNALS means signals that are generated by decoders, such as pulse width modulators, pulse density modulators, digital to analog converters, etc. in response to correction factor data.  
           [0019]    DIGITAL IMAGE SIGNAL means digital data that has been processed to correct for display device artifacts.  
           [0020]    DIGITIZED SIGNAL is any electrical signal that has a digital nature.  
           [0021]    DIGITIZED VIDEO SIGNAL is an input video signal that has been sent in a digital form or converted to a digital form, that can be stored in RAM or other digital storage device and processed with digital processing devices.  
           [0022]    DIRECTION means up, down, left, right, brighter, dimmer, higher, lower, etc.  
           [0023]    DISCRETE LOCATIONS may mean individual pixels on a cathode ray tube screen or may comprise a plurality of pixels on a cathode ray tube screen.  
           [0024]    DISPLAY PRODUCT means the packaged display product made for viewing video signals containing one or more display devices.  
           [0025]    DISPLAY DEVICE means a CRT, tube and yoke assembly, LCD, DMD, Microdisplay, etc. and the associated viewing screen.  
           [0026]    DISPLAY IMAGE SIGNAL means the corrected output video signal that drives the display device.  
           [0027]    DISPLAY SCREEN means the surface that the video image is viewed.  
           [0028]    DISTORTION CHARACTERISTICS means the amount of distortion as indicated by the distortion data at a number of different points on the cathode ray tube.  
           [0029]    DISTORTION DATA is a measure of the amount of distortion that exists on a display with regard to the geometry characteristics of the display device, and/or transfer characteristics of the display device. For example, distortion data can be measured as a result of misalignment of a video image or improper amplitude or gain of a video image signal. Distortion data can be a quantitative measure of the deviation of correction factor parameters from a desired quantitative value. Distortion data can be measured at coordinate locations on the display device.  
           [0030]    DRIVER SIGNALS are the electrical signals that are used to drive the deflection and control windings, and electron guns of the cathode ray tube, display image signal, and the addressing data for a pixilated display.  
           [0031]    EXIT CRITERIA means a limit set for the distortion data of each correction factor parameter that allows generation of correction factor data that is capable of producing an aligned video image.  
           [0032]    FRAME GRABBER means an electronic device for capturing a video frame.  
           [0033]    GAIN MATRIX TABLE means a table of values that are used to indicate how a change in correction factor data for one correction factor parameter influences the change in the correction factor data for other correction factor parameters, as disclosed in U.S. patent application Ser. No. 08/611,098, filed Mar. 5, 1996, entitled “Method and Apparatus for Making Corrections in a Video Monitor.” 
           [0034]    GOLDEN TUBE/DISPLAY means a sample display device having limit distortion characteristics for a particular model of display device.  
           [0035]    INTEGRATORS means a device for generating an integrated signal that is the time integral of an input signal.  
           [0036]    INTERPOLATION ENGINE means a device for generating continuously variable signals, such as disclosed in U.S. patent application Ser. No. 08/613,902 filed Mar. 11, 1996, U.S. Pat. No. 5,739,870, by Ron C. Simpson entitled “Interpolation Engine for Generating Gradients.” 
           [0037]    LOGIC DEVICE means any desired device for reading the correction factor data from a memory and transmitting it to correction and driver circuitry, including a microprocessor, a state machine, or other logic devices.  
           [0038]    MAGNETIC STRIP means any sort of magnetic storage medium that can be attached to a display device.  
           [0039]    MAXIMUM CORRECTABLE DISTORTION DATA means the limits of the distortion data for which an aligned video signal can be generated for any particular display device using predetermined correction and driver circuitry, and control circuitry.  
           [0040]    MEMORY comprises any desired storage medium including, but not limited to, EEPROMs, RAM, EPROMs, PROMs, ROMs, magnetic storage, magnetic floppies, bar codes, serial EEPROMs, flash memory, etc.  
           [0041]    MULTI-MODE DISPLAY means a multi-sync monitor using multi-sync technology.  
           [0042]    NON-VOLATILE ELECTRONIC STORAGE DEVICE means an electrical memory device that is capable of storing data that does not require a constant supply of power.  
           [0043]    PATTERN GENERATOR means any type of video generator that is capable of generating a video signal that allows measurement of distortion data.  
           [0044]    PIXILATED DISPLAY means any display having discrete picture elements; examples are liquid crystal display panels, Digital Micro-mirror Display (DMD), and Micro Displays.  
           [0045]    PROCESSOR means a logic device including, but not limited to, serial EEPROMs, state machines, microprocessors, digital signal processors (DSPs), etc.  
           [0046]    PRODUCTION DISPLAY DEVICE means a display device that is manufactured in volume on a production line.  
           [0047]    PULSE DENSITY MODULATION means a device for generating pulse density modulation signals in response to one or more data bytes, such as disclosed in U.S. patent application Ser. No. 08/611,098, filed Mar. 5, 1996 by James R. Webb et al entitled “Method and Apparatus for Making corrections in a Video Monitor.” 
           [0048]    PULSE WIDTH MODULATOR means a device that generates pulse width modulated signals in response to one or more data bytes, such as disclosed in U.S. patent application Ser. No. 08/611,098, filed Mar. 5, 1996 that is cited above and U.S. Pat. No. 5,216,504.  
           [0049]    STORAGE DISK comprises any type of storage device for storing data including magnetic storage devices such as floppy disks, optical storage devices, magnetic tape storage devices, magneto-optical storage devices, compact disks, etc.  
           [0050]    SUMMING AMPLIFIERS means devices that are capable of combining a plurality of input signals such as disclosed in U.S. patent application Ser. No. 08/611,098 filed Mar. 5, 1996, that is cited above.  
           [0051]    TRANSFORMATION EQUATION means a standard form equation for producing a correction voltage waveform to correct distortion characteristics of a display device.  
           [0052]    UNIVERSAL MONITOR BOARD means a device that includes one or more of the following: vertical control circuitry, horizontal control circuitry, electron gun control circuitry, correction and driver circuitry, a logic device and a memory. A universal monitor board may comprise an actual chassis monitor board used with a particular monitor, an ideal chassis board, a chassis board that can be adjusted to match the characteristics or specifications of a monitor board, etc.  
           [0053]    VIDEO IMAGE means the displayed image that appears on the display device screen that is produced in response to a video signal.  
           [0054]    VIDEO PATTERN is the video image of a pattern that appears on the viewing screen of the display device as a result of the video signal generated by the pattern generator.  
           [0055]    VIDEO SIGNAL means the electronic signal that is input into the display product.  
         DESCRIPTION OF THE BACKGROUND  
         [0056]    In the field of video technology, conventional methods and systems for displaying video signals on video display devices have inherent characteristics that result in visual artifacts in the displayed video images. These artifacts are considered errors in the image, inasmuch as the picture intended for displaying and viewing differs from the image actually displayed and viewed. Errors arise in many types of multi-mode and pixilated video displays, including computer cathode ray tube (CRT) monitors, computer liquid crystal display (LCD) monitors, DMD projectors, Micro Displays, and high definition television (HDTV) receivers. Thus, traditional display systems and methods do not provide the best picture possible within existing standards.  
           [0057]    One artifact common in current multi-mode and pixilated displays is less than optimal brightness and resolution. Sub-optimal brightness and resolution occurs from gaps that exist between picture elements (pixels) on the display screen. Because of the gaps, the electronic beam in the display cannot illuminate or address the entire display surface. Gaps between pixels result in what is known as low fill factor, wherein no light is emitted between pixels. The center-to-center spacing of these pixels is separate, fixed, and discrete. Low fill factor lowers potential brightness and reduces resolution resulting in jagged edges on alphanumeric characters and diagonal lines. The viewer is often aware of the spaces between lines and pixels, almost like looking at a scene through a screen door. This becomes annoying and even uncomfortable to the viewer, leading to eyestrain, fatigue, and loss of productivity. In non-pixilated displays one way of improving brightness and resolution is to merge or over-merge scan lines in the raster, so that the scan lines overlap. However, current multi-mode and pixilated displays cannot take advantage of the over-lapping characteristics of merging and over-merging scan lines because in modes that operate at pixel densities below the merged raster density there are gaps between the pixels in the image.  
           [0058]    Displays with magnetic or electrostatic deflection of the addressing beam or beams often exhibit other forms of distortion like pincushion, keystone, and other non-linearities. These distortions are a result of the electron beam being improperly deflected across the viewing screen of the CRT. The electron beam is quite sensitive to fluctuations in the electromagnetic field through which it passes. As a result, improper deflection can occur for many reasons, including coil misadjustment and the earth&#39;s magnetic field. Traditional methods and systems have been employed to attempt to fix these distortions by using additional deflection coils and electronic circuitry in the monitor to finely adjust the position of the electron beams; however, these methods cannot compensate completely for erroneous beam deflection, and require significant additional capital expenditures for the necessary components.  
           [0059]    [0059]FIG. 3 illustrates a display screen  300  of a cathode ray tube (CRT) display device, in which the electron beam is sweeping at a nonlinear speed. The electron beam starts out at a faster speed and slows down as it sweeps from the left side of the screen  300  to the right side of the screen. Below the display screen  300  in FIG. 3 is an illustration of a video signal  302  with video data The video data is used by the electron gun of the display device to draw straight vertical lines  304 ,  306 ,  308 , and  310  on the screen  300 . The video signal  102  is sending data represented by vertical pulses  312 ,  314 ,  316 ,  318 , and  320  separated equally in time at time points  322 ,  324 ,  326 ,  328 , and  330  respectively. The intent of the video signal  302  is to instruct the display device to draw the lines  304 ,  306 ,  308 , and  310  with equal distance between them. The video signal  302  is typically output in a clocked fashion so that video data pulses  312 ,  114 ,  316 ,  318 , and  320  are equally spaced in time. Without the affects of the nonlinearity in the speed of the electron beam, the equally timed pulses of video signal  302  would map to equally spaced lines on the screen  300 . However, because of the nonlinearity of the speed of the electron gun, the video data is not displayed equally in space on the screen  300 . Prior art solutions to nonlinearity involve employing complicated circuitry and coils in the display device, requiring installation and rigorous testing and retesting to fine tune the speed of the beam across the screen. However, even with the cost, time, and effort in prior art techniques, nonlinearity is still not completely fixed.  
           [0060]    [0060]FIG. 5 illustrates left/right pin cushioning error and inner pin cushioning error in a display screen  500 . Pin cushioning is the result of the physical construction of the deflection yoke, gun to screen distance, screen curvature, and the rate at which the electron beam is deflected across the display screen. Below the screen  500  is a representation of a video signal  502  having video data in the form of vertical pulses  504 ,  506 ,  508 ,  510 , and  511  equally spaced in time at times  512 ,  514 ,  516 ,  518 , and  520 , respectively. The pulses  504 ,  506 ,  508 ,  510 , and  511  are intended to generate straight vertical lines on the screen; however, because of the pin cushioning effect of the display device, the left border line  522  and the right border line  524  are bowed inward. There is also slight inner pin cushioning of inner line  532  and inner line  534 . Prior art techniques used to fix the affects of pin cushioning involve employing complicated circuitry.  
           [0061]    [0061]FIG. 7 illustrates top/bottom pin cushioning error in a cathode ray tube (CRT). As a result of well-known inherent physical and electromechanical characteristics of typical CRTs, a top/bottom pin cushioning effect is created on the screen. Top line  700  on the screen  702  is intended to be a straight line. Similarly bottom line  704  is intended to be a straight line. Below the screen  702  is a depiction of a top scan line  706  having a downward bowed trajectory. When the electron beam of the CRT follows the bowed scan line  706  the resultant pattern on the screen  702  is not a straight, horizontal line, but rather, a bowed line  708 .  
           [0062]    [0062]FIG. 9 illustrates a misconvergence error on a CRT screen. A red raster line  900  is shown scanning from left to right across the screen. A green raster line  902  is shown scanning across the screen from left to right. The red raster line  900  is shown at a diagonal relative to the green raster line  902 . This illustrates misregistration of the red raster of the CRT and the green raster of the CRT. A similarly misregistration is depicted with a red line  906  and a green line  904  at the bottom of the screen. Below the figure of the screen is an enlarged view of redline  900  sweeping adjacent to and intersecting with the green line  902 . The redline  900  converges with the green line  902  only in the middle of the green line in a yellow section,  908 . The pattern that was intended to be drawn upon the screen is a straight horizontal line, but because of the misregistration of the red raster of the CRT, only a small section of a horizontal yellow line is created. Furthermore, on either side of the yellow section,  908 , are an unintended green line and unintended red line. Misregistration also occurs in the case of the blue raster.  
           [0063]    In color CRT displays, including those displaying an HDTV format, three electron beams are deflected to form rasters registered upon a single viewing screen of the display. Similarly, in the case of other types of projectors, such as liquid crystal display (LCD) projectors and digital micro mirror display (DMD) projectors, three light beams are registered upon a viewing screen. When forming an image, if a CRT or projector is working correctly, the three beams converge at the same point for each point in the image. When the three beams do not converge perfectly, colored edges, or halos, appear around text and pictures in the image. Misconvergence may occur when the beams are not aimed properly at the viewing screen. Misconvergence reduces image clarity, contrast, and resolution.  
           [0064]    Also, when interlacing is used as in a raster scanning CRT, the line structure of the display may become visible. Furthermore, in color displays, at lower resolution modes the individual raster lines are often visible as separate red, green, and blue lines with black gaps between where no light is produced.  
           [0065]    Accordingly there is a need for a method for improving display resolution and brightness and correcting errors in displays.  
         SUMMARY OF THE INVENTION  
         [0066]    The present invention overcomes the disadvantages and limitations mentioned above by providing, in general, a system of correcting for video image errors in advance of the display device. The effective resolution and brightness of the image can be increased using merged images that overlap each area of the viewing surface with more than one position addressable illumination source. The entire viewing surface can emit light without gaps or spaces. A video signal can be over sampled to create a denser address space, corrected for display or viewing perspective distortion and enhanced to produce artifact-free video images.  
           [0067]    The present invention preferably comprises a video signal display system for creating video images that include a display device to generate an image on a screen, which has addressable screen locations. The system also includes a digitized video signal memory storing pixel information representing a digitized video signal, and a video processor module configured to receive screen information from the display device. The screen information defines a screen parameter. The video processor module is preferably configured to map the screen parameter to an address in the image memory containing pixel information corresponding to the screen parameter.  
           [0068]    The present invention may also comprise a characterization module having a translation data table indexable by the screen information to obtain a screen location or a time associated with a screen location. The characterization module communicates the addressable screen location to the video processor module.  
           [0069]    The present invention may also include a method of displaying a video image by receiving information defining an addressable screen location from a display device. The method further comprises retrieving image pixel information corresponding to the addressable screen location, and driving an illumination source in the display device to illuminate the addressable screen location using the image pixel information. The method may further include loading a counter module with a time value representing when a corrected video image should be generated. The present invention may also include computer readable media having computer readable instructions for performing the method.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0070]    [0070]FIG. 1( a ) is a schematic diagram of the system of the present invention for pre-correcting a digitized image signal in an embodiment of the present invention.  
         [0071]    [0071]FIG. 1( b ) is a schematic diagram of the system of the present invention for pre-correcting a digitized image signal in an embodiment of the present invention.  
         [0072]    [0072]FIG. 2 is a schematic illustration of a monitor having a characterization module coupled to a video processor module that uses correction factor data to generate a pre-corrected video signal.  
         [0073]    [0073]FIG. 3 illustrates a display screen exhibiting nonlinearity error of the scan beam as it sweeps across the screen.  
         [0074]    [0074]FIG. 4 illustrates a display screen having a precorrected image correcting nonlinearity error shown in FIG. 3 in accordance with the present invention.  
         [0075]    [0075]FIG. 5 illustrates a display screen exhibiting left/right pin cushioning error.  
         [0076]    [0076]FIG. 6 illustrates a display screen having a precorrected image correcting left/right and inner pin cushioning error shown in FIG. 5 in accordance with the present invention.  
         [0077]    [0077]FIG. 7 illustrates top/bottom pin cushioning on a display screen.  
         [0078]    [0078]FIG. 8 illustrates a screen displaying a precorrected image correcting top/bottom pin cushioning shown in FIG. 7 in accordance with the present invention.  
         [0079]    [0079]FIG. 9 illustrates a display screen having misconvergence error.  
         [0080]    [0080]FIG. 10 illustrates a display screen displaying a precorrected image correcting misconvergence shown in FIG. 9 in accordance the present invention.  
         [0081]    [0081]FIG. 11 is a schematic diagram of a display screen with scanning beam lines drawing an image in an exemplary embodiment of the present invention.  
         [0082]    [0082]FIG. 12 is a schematic diagram of physical screen locations mapped to corresponding image memory addresses in the present invention.  
         [0083]    [0083]FIG. 13 is a flow control diagram illustrating a method of precorrecting an image in accordance with an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0084]    The invention is described in detail below with reference to the drawing figures. When referring to the figures, like structures and elements shown throughout are indicated with like reference numerals.  
         [0085]    [0085]FIG. 1( a ) illustrates a system for generating a corrected display image signal  116  to display an image on a screen  120  of a cathode ray tube (CRT)  118  display device. The corrected video signal adjusts the timing and content of image data to correct for errors that would otherwise be caused by the CRT  118 . A video processor module  100  maps digitized video signal data to physical screen locations and generates a corrected digital image signal  130  and then an analog display image signal  602  of FIG. 6 to correct for geometric errors introduced by the CRT  118 . The mapping may be viewed as occurring in time and physical space across the CRT  118 . The video processor module  100  receives a video signal from a video signal source  102 , in either digital or analog form. Control logic  104  may contain an analog to digital converter and a multiplexer to send a digitized video signal to RAM buffer  108 . A video signal source  102  may be for example, a computer having a microprocessor and a graphics controller card having memory storing digitized video signal data and be able to send a video signal in either a digitized video signal, using a digital visual interface (DVD connection or a more conventional analog video signal using a standard video graphic adapter (VGA) connection. Digitized video signal data includes any binary encoded form of a video signal. Digitized video signal data can be in any format, including, but not limited to, tagged image file format (TIFF) and Joint Photographic Experts Group (JPEG) format. The video signal source  102  might also be a digital video disk (DVD) player. To further illustrate, the video signal source  102  could comprise a video cassette recorder (VCR), or a set top box receiving an analog or a digital video signal from a television network. The video signal source  102  may be a frame buffer storing an entire frame of digitized video signal data Alternatively, the video signal source  102  may store only a single line of digitized video signal data. One skilled in the art will recognize that the video signal source  102  may be able to store any number of lines of data of a digitized video signal.  
         [0086]    As shown in FIG. 1( a ), in one embodiment of the present invention, the video image processor module  100  is in operable communication with the video signal source  102  via a communication channel  103 . Control logic  104  in the video processor module  100  receives a video signal from the video signal source  102  via channel  103 . Control logic  104  then processes the video signal. Control logic  104  may contain an analog to digital converter and a multiplexer to first select the video input type and then send the digitized video signal data to a RAM buffer  108 . Processing may involve storing parts of the image data in the RAM buffer  108  via connector  106 . The RAM buffer  108  stores digitized video signal data and/or any other type of program data necessary for the operation of the processor  100 . Connectors  106  provide address data to RAM buffer  108  so the control logic  104  may read or write the image and programming data from RAM buffer  108 . Digitized video signal data may also be transmitted from RAM buffer  108  to control logic  104  via connectors  106 . A clock and processing module  112  is in operable communication with RAM buffer  108  via connector  110 . The clock and processing module  112  is also in operable communication with control logic  104  via connector  124 .  
         [0087]    Electron gun control module  114  modulates the amplitude and gain of the corrected display image signal  116  that is amplified and applied to the electron guns of the CRT  118 . The electron gun control module  114  includes a digital to analog converter (DAC) for converting digital image signal  130  data into an analog display image signal. The electron gun control module  114  operates to convert the digital image signal  130  data to a corrected analog video display image signal  116  by modulating a voltage signal with the digital image signal  130  data.  
         [0088]    The CRT  118  has a screen  120  upon which an electron beam is deflected to illuminate addressable illuminating elements on the screen  120 . The addressable illuminating elements can be phosphor dots that are excited by the electron beam, and illuminate in response. The arrangement of the illuminating elements on the screen  120  defines picture elements (pixels) that make up a video image that is produced on the screen  120 . The CRT  118  has one or more illuminating sources for firing a beam toward the screen  120  to produce an image on the screen  120 . For example, in one embodiment, the illuminating source may be a single electron gun that fires an electron beam at the screen  120 . In another embodiment, three electron guns fire three electron beams, each beam illuminating either red, green, or blue phosphor dots on the screen  120 . Typically, the electron beam or beams are deflected by coils  119  in the CRT  118  which create a magnetic field causing the electron beam to move from left to right and up and down over the screen  120 . The electron gun control module  114  generates a video signal output  116  that is amplified and applied to the electron guns to adjust the bias and drive for the electron guns. Adjusting the bias and drive of the electron guns causes the intensity of the electron beam to vary as the beam moves in time across physical locations on the screen  120 .  
         [0089]    In one embodiment of the invention shown in FIG. 1( a ), the control logic  104  receives a signal from a sensor  121  on the CRT  118 . The sensor  121  can be an optical sensor sensing the physical screen location of the electron beam. The sensor can also be a yoke current sensor sensing current in the CRT and producing a signal that is a function of beam location. Any other detection device detecting beam screen location can be used for sensor  121 . The signal from the sensor  121  has a voltage level that is a function of the physical screen location of the electron beam. The signal from the sensor is used by the control logic  104  to determine an address in image memory of RAM buffer  108  corresponding to the physical screen location. The control logic  104  sends the signal to the characterization module  126 , which indexes a correction factor data table to retrieve a value representing the physical screen location. The characterization module  126  sends the value representative of the physical screen location back to the control logic  104 , which sends the value to the clock and processing module  112  via connector  124 . The clock and processing module  112  uses the value representing the physical screen location to address the RAM buffer  108  and generate a corrected display image data that is sent to the electron gun control circuitry  114 . The corrected physical address is sent to the control logic  104 , which looks up image data corresponding to the corrected physical address. The control logic  104  retrieves corresponding image information and it is sent to the electron gun control circuitry  114 . The electron gun control circuitry  114  uses the image information to modulate a signal to create the corrected display image signal  116 . The system in this embodiment can be viewed as a closed loop control system, wherein the beam position is sent to the video processing module  100 , which generates the corrected display image signal  116 , which is fed back to the CRT  118  causing an adjustment in the intensity of the electron beam.  
         [0090]    An alternative embodiment is shown in FIG. 11( b ) an open loop system in which the characterization module  126  stores values representing pixel time lengths. A pixel time length is the time it takes a beam to move from one pixel to a subsequent pixel on the viewing screen  120 . With an elapsed time, the characterization module  126  can look up a time value representing when the next pixel should be displayed to correct for the nonlinearity of the speed of the scanning beam. The characterization module  126  can be constructed and loaded with elapsed time and pixel time information when the display device is manufactured as described in U.S. Pat. No. 6,014,168. The video processing module  100  can receive pixel time information from the characterization module  126  and set a counter module  127  with the pixel time value. The counter module  127  will then count down from the pixel time. In this embodiment, when the counter module  127  gets to zero, the video signal is modulated with the next pixel information.  
         [0091]    While the counter module  127  is counting down, the clock and processing module  112  of video processing module  100  retrieves pixel data corresponding to the next pixel at the next physical screen position. The effect of this method is to adjust in time when video signal information changes in accordance with the nonlinearity of the CRT. The nonlinearity of scan time is built into the characterization module  126 . The pixel time data provided by the characterization module  126  dictates when the video processing module  100  changes pixel data and transmits a corrected display image signal  116 . This embodiment may be viewed as an open loop system, wherein the characterization module  126  stores data that allows for the time position of the scanning beam of the CRT and adjustment of the corrected display image signal  116  to be synchronized.  
         [0092]    [0092]FIG. 2 is a schematic block diagram illustrating a monitor  200  constructed in accordance with an embodiment of the present invention. The monitor  200  includes a cathode ray tube  202 , a series of deflection and control windings  204 , a characterization module  206  coupled to the coils  204 , vertical control circuitry  208 , electron gun control circuitry  210 , and horizontal control circuitry  212 . A horizontal sync signal  214  and a vertical sync signal  216  are applied to characterization module  206 . Characterization module  206  has a correction factor data table having CRT characteristic data representative of desired characteristics of the CRT. Characterization module  206  generates an output  228  that is applied to video processor module  230 . Using data from the output  228 , the video processor module  230  generates a precorrected video image signal  218 , which is transmitted to the electron gun control circuitry  210 . The vertical control circuitry  208  generates driver signals that are applied by connectors  222  to the coils  204 . The electron gun control circuitry  210  generates a video signal  224  that is applied to the electron guns of the cathode ray  210  to project electron beams onto the screen of the CRT for producing an image. The horizontal control circuitry  212  generates a driver signal that is coupled to coils  204  via connectors  226 . Characterization module  206  can comprise a nonvolatile memory, a processor, and correction and driver circuitry (not shown).  
         [0093]    In operation, the monitor  200  of FIG. 2 has correction factor data stored in a device such as an EEPROM in the characterization module  206 . The characterization module produces correction factor signals  228  that are communicated to the video processor module via output  228 . The correction factor data stored in the characterization module  206  indicates the distortion characteristics of the particular cathode ray tube  202  that have been derived in a cathode ray tube production facility using a system such as that described in U.S. Pat. No. 6,014,168. The characterization module  206  can also include CRT parametric data, which may be generated using the system described in U.S. Pat. No. 5,216,504, issued to James R. Webb, et al, entitled “Automatic Precision Video Monitor Alignment System,” incorporated herein by reference for all that it teaches and discloses. Various components of the characterization module  206  read the correction factor data and generate screen parameters related to desired specifications for displayed video images. The generated specifications are related to the physical characteristics such as nonlinearity in the speed of the electron beam as it sweeps across the screen. For example, the characterization module  206  may store values representing time required for the electron beam to sweep past each adjacent pixel on the screen.  
         [0094]    As also shown in FIG. 2, a correction parameter signal  228  is generated and sent to a video processing module  230 . The video processing module uses parameters from the characterization module to generate a corrected video image signal  218 , which is transmitted to the electron gun control circuitry  210 . The corrected video image signal  218  corrects for distortions in the cathode ray tube by modulating a signal with digital video signal data corresponding to the position of the electron beam to satisfy desired specifications in the cathode ray tube  202 .  
         [0095]    [0095]FIG. 4 illustrates a display screen having a precorrected image correcting nonlinearity error in accordance with an embodiment of the present invention. Nonlinearity error is caused by the acceleration or deceleration of the electron beam as is sweeps across the screen, such as the viewing screen  120  of FIG. 1. FIG. 4 depicts a screen  400  having an image displayed on it by a display device, such as cathode ray tube  118  in FIG. 1( a ). The image consists of vertical lines  402 ,  404 ,  406 ,  408 , and  410  equally spaced from left to right across the screen  400 . An illumination source, such as an electron gun in a CRT  118 , projects an illuminating beam, such as an electron beam, on the screen  400  to create the image. The electron gun fires an electron beam at the back of the screen  400  which is coated with phosphor dots that are excited and light up in response to being struck by electrons carried by the electron beam. The electron gun is driven by a video signal as represented by a precorrected video signal  411 .  
         [0096]    The precorrected video signal includes pulses  412 ,  414 ,  416 ,  418 , and  420  being transmitted at times  422 ,  423 ,  425 ,  427 , and  429 . The video pulses  412 ,  414 ,  416 ,  418 , and  420  in the embodiment of FIG. 4 contain pixel information for the image on the screen  400 . If the video signal  411  were not precorrected in time, the pulses  412 ,  414 ,  416 ,  418 , and  420 , would have been located at times  422 ,  424 ,  426 ,  428 , and  430 . However, as shown in FIG. 3, the electron beam travels at a nonlinear speed across the screen, so at transition times  424 ,  426 , and  428 , the video pulses  414 ,  416 , and  418  would have been received too late by the electron gun. The times  412 ,  414 ,  416 ,  418 , and  420  at which the pulses  412 ,  414 ,  416 ,  418 , and  420  are sent using the system of FIG. 1, adjust for the nonlinearity in the beam scanning speed. The adjustment made to the timing of pulses  412 ,  414 ,  416 ,  418 , and  420  is performed using timing data in a correction factor data table in the characterization module  106  of FIG. 1( b ). When the CRT is manufactured, characteristic CRT data is stored in the characterization module  106  to adjust the displayed image according to desired CRT specifications. For example, higher or lower values of characteristic beam scanning speed data can be stored in the characterization module to make the image displayed more or less uniform across the screen  400 . A video processor module, such as video processor module  100  of FIG. 1, creates and transmits the video signal  411  to the electron gun in the cathode ray tube (CRT). While the embodiment of FIG. 4 depicts a black and white image, it should be understood that the image could be any color in an embodiment using a color CRT. In the color CRT embodiment, there is a video signal for each of three primary colors, red, green, and blue. Each of the video signals in the color CRT embodiment drives one of three electron guns.  
         [0097]    [0097]FIG. 6 illustrates a display screen having a precorrected image correcting left/right and inner pin cushioning error in accordance with an embodiment of the present invention. FIG. 6 illustrates a representation of a display screen  600  displaying an image. The image on display screen  600  is created by an electron beam generated by an electron gun in a CRT, such as the CRT  118  in FIG. 1( b ). The electron gun receives a video signal represented by a corrected video signal  602  having a series of image data pulses  604 ,  606 ,  608 ,  610 , and  611 . Image data pulses  604 ,  606 ,  608 ,  610 , and  611  are spaced in time relative to equally spaced time units  612 ,  614 ,  616 ,  618 , and  620 . The corrected video signal  602  is corrected in time by the video processor module  100  in the embodiment of FIG. 1( b ). In the embodiment of FIG. 1( b ), the video processor module  100  receives time data from the characterization module  126  and uses the time data to adjust when the electron gun control circuitry  114  transmits pixel data. For example, in the middle of the vertical interval, image data pulse  604  is positioned in time prior to time unit  612 . The pulse  604  arrives at the electron gun before it would have without precorrection. In response to the earlier receipt of the pulse  604 , the electron gun fires a beam that creates a vertical line  622 . To correct for inner pin-cushioning error that is shown in FIG. 5, image pulse  606  is positioned in time prior to time unit  614  so that a vertical line  632  is created in the image. The time difference between when pulse  606  is sent and time unit  614  is dictated by correction factor data in the characterization module  126 . As was discussed earlier, the correction factor data in characterization module  126  is created by calculating time values associated with physical screen positions on the CRT. Image pulse  608  is transmitted at time  616  to create a vertical line in the middle of the image. By sending image pulse  610  after time  618 , which is when pulse  610  would have been sent without precorrection, a vertical line  634  is created to correct for inner pin cushioning that would otherwise result as shown in FIG. 5. Similarly, the image pulse  611  is delayed relative to a time  620  to adjust for the pin cushioning effect of the CRT. By delaying the image pulse  611  a vertical line  624  is created on the right side of screen  600 .  
         [0098]    [0098]FIG. 8 illustrates a pre-warping solution to top/bottom pin cushioning in accordance with the preferred embodiment of the present invention. FIG. 8 illustrates a CRT screen having a straight line  800  on the top of a screen  801 , and a straight line  802  on the bottom of the screen. Below the screen depicted in FIG. 8 is a representation of three scan lines,  804 ,  806 , and  808 , used to draw the straight line  800 . As the electron beam moves along the scan line  804 , information about the electron beam&#39;s screen location is transmitted from the CRT to the video processing module. There are several techniques of determining the electron beam location. One way is to attach an optical sensor to the CRT that senses position of the electron beam. Another way is to attach a yoke current sensor to the yoke of the CRT to sense current in the coils of the CRT. The optical sensor or the yoke current sensor can produce a signal that is some function of the beam location. In one embodiment, the signal is proportional to the beam location. In an alternative embodiment, sensors are not used to track the electron beam location, but rather the beam location can be characterized and determined as a function of time and other display control settings. When a sensor is used as in the first embodiment, this may be viewed as a closed loop feedback control system. When sensors are not used but rather the electron beam position is calculated as a function of time and display control settings, this may be viewed as an open loop system. Any other mechanism may be used to determine addressable screen location as the electron beam sweeps across the screen  801 . The video processor module  100  receives the electron beam location information from the sensor and uses the information to determine the physical screen location of the beam. The video processor module  100  then uses the physical screen location to retrieve pixel information from an image memory address corresponding to the screen location.  
         [0099]    As the electron beam in FIG. 8 scans along scan line  804 , the video processor module  100  determines its position as described above, and retrieves image pixel information corresponding to the position. On the leftmost side of scan line  804 , pixel information associated with that position is full intensity, typically  255 , to indicate a solid line. The full intensity pixel information is used to modulate a video signal which is transmitted to the electron gun. The video signal drives the electron gun to transmit a full intensity beam in the section  810 . Similarly, as the electron beam moves along scan line  806 , information regarding the beam&#39;s screen position is transmitted to the video processor module so that the video processor module can determine the addressable screen location. The electron beam moves through section  812 , the corresponding pixel information in image memory is  255 , indicating a solid line. The pixel information is used to modulate the video signal that is transmitted to the electron gun such that the electron gun fires at full intensity to draw a solid line in section  812 . When scan line  806  moves through section  816 , video processor module locates corresponding pixel information in image memory. Along section  816 , the corresponding pixel information indicates a value of 255 corresponding to a full intensity beam. The pixel information is used to modulate the video signal communicated to the electron gun so that the electron gun fires a beam at full intensity at section  816  to create a solid visible line. Similarly, as the electron beam travels along scan line  808  position information is communicated to the video processor module  100  so that the video processor module  100  can determine the addressable screen location of the electron beam. When the electron beam enters section  814 , the video processor module  100  retrieves corresponding pixel information used to drive the electron beam in that section  814 . In the section  814 , the pixel information is 255 indicating a solid line. Thus, in the embodiment of FIG. 8, three scan lines are used to draw a single straight line. In order to draw  802 , a similar method of beam position determination and pixel information indexing is utilized to turn the electron beam on and off at appropriate times as it travels along a plurality of scan lines.  
         [0100]    [0100]FIG. 10 illustrates a display screen displaying a precorrected image correcting misconvergence in accordance with an embodiment of the present invention. FIG. 10 illustrates a representation of a rectangular screen  1001  on a CRT (such as CRT  118  in FIG. 1( a )) having a top yellow horizontal line  1000  on the top of the screen  1001  and a bottom yellow horizontal line  1002  going across the bottom of the screen  1001 . Below the figure of the screen are a series of raster lines  1004 . In this illustration, it is assumed that the red raster is misregistered relative to the green raster. Thus a red scan line  1006  sweeps in a diagonal fashion from left to right, whereas a green scan line  1007  sweeps from left to right horizontally. Similarly, red scan line  1008  and red scan line  1010  sweep from left to right diagonally relative to green scan lines. In the embodiment, a green scan line  1011 , and sections of red scan line  1006 , red scan line  1008 , and red scan line  1010 , are used to create a yellow image pattern  1012 . The green scan line  1011  is parallel to the green scan line  1007  and is hidden from view by yellow image line  1012 . The green scan  1011  spans a plurality of pixels at a plurality of screen locations. The yellow image pattern  1012  is a horizontal line created from the green scan line  1011  and sections of red scan lines  1006 ,  1008 , and  1010 .  
         [0101]    In one embodiment, as red scan lines sweep from left to right, a sensor on the CRT transmits a signal to the video processor module  100 . The sensor signal has information defing screen location. The information in the sensor signal can be a function of the beam location as it sweeps across the CRT screen. In the embodiment, the signal is proportional to the beam location. The video processor module  100  can use the signal information to determine an addressable screen location for the red beam  1006 . In one embodiment, the video processor module  100  communicates the sensor information to the characterization module to get the addressable screen location. The characterization module can use the sensor information to index a correction factor data table to retrieve the addressable screen location. The characterization module then communicates the addressable screen location to the video processor module  100 . The video processor module  100  uses the addressable screen location to retrieve corresponding pixel data from a digitized video signal memory. In an embodiment having color video images on a color screen, there may be three video signal sources ( 102  of FIG. 1( a )), each storing image data for either the red, green, or blue colors in the image. Alternatively, there may be a single video signal source  102  having three sections of memory, with each section of memory containing red, green, or blue image data.  
         [0102]    The yellow horizontal line  1012  is intended to be drawn along the green horizontal raster line  1011 . As the red scan line  1006  proceeds from left to right, the video processor module  100  receives screen location information from the CRT sensor and determines a corresponding address in a red image memory (such as video signal source  102  in FIG. 1( a )). The addressable screen location corresponding to the left side of the red scan line  1006  corresponds to an image memory address having red image data of zero, indicating the red electron beam should not fire. When the red scan line  1006  enters pixels spanned by green scan line  1011 , image memory address corresponding to that screen location is accessed to retrieve corresponding pixel information. The video processor module  100  uses the corresponding pixel information to create a red video signal which is communicated to the red electron beam. The red video signal instructs the red electron beam to fire at full red intensity level so that yellow is created when the red electron beam converges with the green electron beam. In a similar fashion, as red scan line  1008  sweeps from across the screen  1001  in a diagonal fashion, the video processor module  100  receives the red electron beam&#39;s position and determines an addressable screen location. When the addressable screen location of the red scan line  1008  includes pixels spanned by the green scan line  3 , the video processor module  100  retrieves non-zero data from image memory corresponding to the addressable screen location. The video processor module  100  uses the non-zero pixel information to create a red video signal that drives the red electron gun at full intensity to create a yellow section of yellow line  1012  along green scan line  1011 . As the red scan line  1008  proceeds from green line  3  to raster line  4 , the video processor module  100  continues to drive the red electron beam with full intensity. When red scan line  1008  intersects exits the screen locations spanned by green scan line  1011 , information in the red image memory is zero. Thus the video processor module  100  creates a red video signal constructing the red electron beam to operate at its lowest intensity. In other words, red scan line  1008  turns off outside the boundaries of the yellow image line  1012 . Next red scan line  1010  is used to create the left side of horizontal yellow line  1012 . As red scan line  1010  proceeds from left to right, video processor module  100  retrieves pixel information from the red image memory corresponding to the addressable screen location.  
         [0103]    Red scan line  1010  begins at the left edge of green scan line  1011  and sweeps in a diagonal fashion across the screen  1001 . In the screen locations spanned by green scan line  1001 , the corresponding pixel information in red image memory is the full value, which is typically  255  to indicate the full intensity of the red scan beam in that section. The full intensity pixel value is used to modulate the red video signal to the red electron gun, so that the electron beam fires at full intensity as it scans in the region spanned by green scan line. Thus, in the screen locations spanned by green scan line  1011 , the red electron gun fires at full intensity. As a result, the red beam converges with the green scan beam to create the yellow-horizontal line  1012 . As can be seen, sections of the three red scan lines,  1006 ,  1008 , and  1010 , are used to create the yellow horizontal line  1012 . By screen locations spanned by the different sections of the red beam gun to corresponding addresses in red image memory, the red beam is turned on at the proper time. The misregistration of the red and green electron guns does not result in misconvergence because the correct image information retrieved from image memory based on where the beam is on the screen  1001 . Those skilled in the art will recognize that a minimum buffer size of video image memory data will be required in the video signal source  102  to use more than one section of a raster line to create one image line. This minimum buffer of image data is related to the maximum distortion of the CRT yoke deflection because the maximum distortion determines the number of raster lines required. Testing has shown that an image buffer storing enough image data for two percent of the vertical interval of the screen is generally sufficient.  
         [0104]    [0104]FIG. 11 is a schematic diagram of a portion of a display screen with scanning beam lines drawing an image in an exemplary embodiment of the present invention. A display screen  1100  displays an image  1102  having image lines line  1  ( 1104 ), line  2  ( 1106 ), line  3  ( 1108 ), and line  4  ( 1110 ). Line  1 ( 1104 ) is shown as an invisible line. In other words, there is no visible image pattern along line  1  ( 1104 ). Similarly line  2  ( 1106 ) is an invisible line having no image pattern. The line  3  ( 1108 ) has a visible image pattern in the form of a horizontal line spanning from the left side of the image  1102  to the right side of the image  1102 . Line  4  ( 1110 ) is another image line having no visible image pattern. Also shown in FIG. 11 are scanning beam lines  1112 ,  1114 ,  1116 , and  1118 . Scanningbeam line  1112  depicts the trajectory of an electron beam being fired from an electron gun (not shown) while moving across the screen. Scanning beam line  1114  illustrates another trajectory of the electron beam sweeping in a diagonal fashion across the screen. Similarly, scanning beam lines  1116  and  1118  depict diagonal trajectories of the electron beam as it sweeps back and forth across the screen. As will be shown in FIG. 12 as scanning beam lines  1112 ,  1114 ,  1116 , and  1118  sweep back and forth across the screen  1100 , they turn on and off depending on where the image  1102  is supposed to be drawn on the screen  1100 .  
         [0105]    [0105]FIG. 12 is a schematic diagram of physical screen locations mapped to corresponding image memory addresses in an exemplary embodiment of the present invention. In FIG. 12 image line  2  ( 1106 ), and image line  3  ( 1108 ) from FIG. 11 are enlarged. Also shown are the four scan lines  1112 ,  1114 ,  1116 , and  1118  showing an enlarged view of the trajectory of the electron beam as it passes through image line  2  ( 1106 ) and image line  3  ( 1108 ). As discussed earlier, the electron beam is modulated to varying intensities depending on where the image is located on the screen. The location of the image on the screen is defined by data representing the image  1102  in an image memory  1210 . An addressable screen location  1200  is a physical screen location where the electron beam impacts the screen  1100 . Also shown are exemplary addressable screen locations  1202  and  1204 . The image memory  1210  stores image pixel data  1212  in addressable locations in memory. Pixel data  1212 ,  1214 , and  1216 , are used to modulate a video signal, which drives the electron gun as it fires the electron beam as it scans across the screen  1100 .  
         [0106]    In FIG. 12, as the electron beam follows scan line  1116  the electron beam passes a physical screen location  1200 . Physical screen location  1200  may be thought of as a pixel on the image  1102  being drawn. Inage pixel data  1212  corresponds to the physical screen location  1200  in image memory  1210 . Information regarding physical screen location  1200  is transmitted to the video processor module  100  which determines a corresponding address in image memory  1210  having corresponding image data  1212  The video processor module  100  determines the physical screen location  1200  using the information sent to it by accessing the characterization module  126 . The video processor module  100  sends information regarding the physical screen location  1200  to the characterization module  126 , which uses the information to index into a correction factor data table having physical screen location data. The characterization module  126  sends the physical screen location data to the video processor module  100  which can calculate the physical screen location. The characterization module may send the physical screen location  1200  such that the video processor module  100  does not need to perform any additional calculations. After the video processor module  100  receives the physical screen location  1200 , the video processor module  100  can locate a corresponding image memory address.  
         [0107]    In FIG. 12, image data  1214  corresponds to the physical screen location  1200 . The video processor module  100  determines the address having image data  1214  based on the base address of image memory  1210 , the resolution of the image, and the resolution of the screen. The video processor module  100  retrieves image data  1214  and uses it to modulate the video signal that is sent to the electron gun in the CRT. Image data  1214  is 0, meaning that the electron beam should not illuminate physical screen location  1200 . Thus, on line  1106  at the physical screen location  1200  the electron beam does not illuminate physical screen location  1200 . The electron beam continues along the path defined by the scan line  1116  and when the beam reaches the physical screen location  1201 , data related to the physical screen location  1201  is sent to the video processor module  100 . The video processor module  100  determines the physical screen location  1200  so that it can look up corresponding image data  1212  in image memory  1210 . One unit of image data  1212  may correspond to more than one physical screen location, depending on the resolution of the image and the resolution of the monitor. Image pixel data  1214  is retrieved for physical screen location  1201 . The electron beam does not illuminate the screen at the physical location  1202  because the corresponding image data  1214  is zero indicating the lowest intensity beam level. To illustrate further as the electron beam follows scan line  1118  the electron beam passes physical screen location  1204 . The video processor module  100  receives information related to the physical screen location  1204  and determines a corresponding address in image memory  1210 .  
         [0108]    In FIG. 12, the address determined has image data  1216  stored in it. The video processor module  100  uses the image data  1216  to modulate a video signal that is transmitted to the electron gun of the CRT. As shown in the FIG. 12 image data  1216  has a value of 255 indicating the maximum intensity beam level at that physical screen location. Thus the electron beam illuminates the screen at the physical screen location  1204  in response to the video signal received from the video processor module  100 . To further illustrate, as the electron beam continues to travel along scan line  1118  it passes the physical screen location  1202 . The video processor module  100  determines an address image memory  1210  corresponding to the physical screen location  1202 . The physical screen location of  1202  corresponds to the address and memory  1210  holding image data  1218 . Image data  1218  has a value of 255 indicating the corresponding physical screen location  1202  should be illuminated. As the electron beam travels along scan line  1112 ,  1114 ,  1116 , and  1118  image data  1212  is retrieved from image memory  1210  at a manner similar to that described above, whereby the image  1102  or FIG. 11 is produced on the screen  1102 .  
         [0109]    In the embodiment of FIG. 12, depending on the resolution of the display screen and the resolution of the digital image, there may not be a corresponding image memory address associated with the screen location. The video processor module  100  makes a determination whether a corresponding image memory address having corresponding pixel data exists. If no corresponding image memory location is found, the video processor module  100  has a resolution enhancement module configured to determine pixel data by creating a merged pixel. The merged pixel data is a function of pixel values for pixels adjacent to the screen location. The function of adjacent pixels may include linear interpolation, quadratic interpolation, or any other function that optimizes a specification of the video processor module or the display screen. For example, if processing time is not limited, quadratic interpolation may be practical to yield an image with an optimized resolution or brightness. Processing time may not be a practical concern if the video processor module  100  is implemented as an integrated circuit. On the other hand, if processor time is a concern, the function of adjacent pixels may include setting the merged pixel value equal to the value of an adjacent pixel. Thus, the function used to generate a merged pixel can be varied to improve image quality or optimize the system. Interpolation techniques are discussed in U.S. Pat. No. 5,379,241, issued to Lance Greggain, entitled “Method and Apparatus for Quadratic Interpolation,” which is incorporated herein by reference for all that it teaches and discloses.  
         [0110]    [0110]FIG. 13 illustrates a flow control diagram illustrating a method of generating a corrected video image signal. Control initially transfers to start operation  1300  wherein initialization processing begins and the system powers up. Control then transfers to the receiving operation  1302  wherein the video processor module receives parametric screen information from the CRT. The parametric screen information can be a time value indicating a time duration for the electron beam to sweep across a pixel on the screen. The parametric information can also be screen location information that the video processor module can use to determine the location of the electron beam. The parametric information could include any other information regarding desired specifications of the cathode ray tube stored in the characterization module, as described in U.S. Pat. No. 6,014,168. Control then transfers to the setting operation  1306  wherein the video processor module sets a counter module  127  (FIG. 1( b )) with a value representative of the time duration for the electron beam to travel from one screen location to another screen location. The counter then begins counting down and when it reaches zero the counter indicates to send a corrected video image signal. After the counter module is set in operation  1306 , control transfers to a determining operation  1304  wherein the video processor module determines an image memory address corresponding to a screen location. The image memory address contains binary encoded pixel data corresponding to the screen location. After the corresponding image memory address is determined in operation  1304 , control transfers to the retrieving operation  1308 . In the retrieving operation  1308  the pixel data is retrieved from the previously determined image memory address.  
         [0111]    Depending on the resolution of the screen and the resolution of the image, there may not be a corresponding image memory address for a screen location. If no corresponding image memory address is found, pixel data for a plurality of pixels adjacent to the screen location are retrieved from image memory in the retrieving operation  1308 . Control then transfers to a creating operation  1309  wherein merged pixel data is created for the screen location using the retrieved pixel data for the plurality of adjacent pixels. A resolution enhancement module can be included with the video processor module  100  of FIG. 1( b ) and configured to create merged pixel data. Creating a merged pixel preferably involves performing high order interpolation function on the retrieved plurality of pixel data. Any other function of pixel data can be used to create a merged pixel. For example, to save processing time, the function may simply involve setting the merged pixel value equal to the value of a single adjacent pixel. A merged pixel may be viewed as a combination of adjacent pixels. The combination of adjacent pixels may be configured so that resolution and brightness of the image is improved.  
         [0112]    Control transfers to a modulating operation  1310  wherein the signal is modulated with the previously retrieved pixel data to generate a corrected video image signal. Modulation may be in response to the counter module reaching zero. After modulating the video image signal in step  1310  control transfers to a transmitting operation  1312  wherein the corrected video image signal is transmitted to the electron gun of the cathode ray tube (CRT). Control then transfers to a returning operation  1314  wherein control is returned to the calling operation.  
         [0113]    Two or more DMDs, LCDs or other pixilated displays can be superpositioned optically to form a merged image display using these same methods to correct the resulting viewed image. Applications include ‘heads up’ cockpit and automotive displays, AR goggle displays and projection systems in general. Using multiple overlapping pixel arrays enhances resolution, brightness and image quality in the presence of viewing-perspective induced distortions.  
         [0114]    Nearly all displays have the pixel element sized, about 0.5° of arc, for the application, such that the human viewer will be unaware of “seeing” individual elements nor can he distinguish or resolve between the color elements that make up individual pixels. However on nearly every display, viewers can perceive texture and coloration of edges of lines that do not follow the pixel structure. The viewer is far more sensitive to this structure and eliminating or minimizing it requires more than double the resolution.  
         [0115]    With offset arrays, the pixel spot size remains the same but the spatial address space quadruples. The display will be capable of producing images with the appearance of a much higher resolution without the display actually physically having it. This is one reason National Television System Committee (NTSC) TV had such acceptance over the years, the image may have only 525 lines vertically per frame with less than 480 visible after blanking and with not much more than that resolution horizontally but the phase space horizontally is far greater. This allows a pixel on adjacent lines to be positioned almost infinitely horizontally (phase space) giving the appearance of continuity to diagonal lines and edges without increasing the video bandwidth, with the exception of computer generated graphics used in weather reports.  
         [0116]    Another way of saying this is given a fixed display surface size and viewing distance there will be a limit to the viewers&#39; ability to distinguish between distinct spots (pixels) or pairs of black and white lines. Once this is reached there is little reason to make the spots (pixels) smaller as the observer will “see” only gray. However there is great benefit from being able to position this smallest spot at will with out being limited to a fixed grid spaced the size of the spot. This will allow spots or groups of spots to overlap, minimizing jagged edges to images that do not coincide with the pitch of the grid. Furthermore, should two or more, in the case of color, arrays be superimposed but not exactly registered, Digital Dynamic registration can be made by finding the corrected address for the spots that do coincide so that they may be used to produce an image that is distortion and convergence free.  
         [0117]    This method of increasing addressing space may be built into the image receiving display device or the image-generating device such as a graphics card in a PC. This will allow the construction of even higher “resolution” display formats than those used today without increasing the video bandwidth or memory requirements. We may see 4 by 3 images with 4096 by 3072 or 8172 by 6144 “resolution” but really only using and displaying 2048 by 1536 or 1536 by 1152 memory and pixels.  
         [0118]    The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.  
         [0119]    The logical operations of the various embodiments of the present invention are implemented (1) as a sequence of computer implemented acts or program modules running on a computing system and/or (2) as interconnected machine logic circuits or circuit modules within the computing system. The implementation is a matter of choice dependent on the performance requirements of the computing system implementing the invention. Accordingly, the logical operations making up the embodiments of the present invention described herein are referred to variously as operations, structural devices, acts or modules. It will be recognized by one skilled in the art that these operations, structural devices, acts and modules may be implemented in software, in firmware, in special purpose digital logic, and any combination thereof without deviating from the spirit and scope of the present invention as recited within the claims attached hereto.  
         [0120]    It will be clear that the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. While a presently preferred embodiment has been described for purposes of this disclosure, various changes and modifications may be made which are well within the scope of the present invention. For example, the characterization module may have rules for processing the video image data. As a further example, in the open loop embodiment, a voltage controlled oscillator may be employed to vary the timing of the transmission of the corrected video signal according to specification data stored in the correction factor data table of the characterization module. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the invention disclosed and as defined in the appended claims.