Abstract:
An apparatus to automatically adjust image distortions is disclosed. The apparatus comprises a driver operable to generate images on a screen. The apparatus further comprises a plurality of sensors coupled to the screen. Each sensor detects whether the area under the sensor is illuminated. The apparatus further comprises a circuit coupled to the plurality of sensors and the driver. The circuit is configured to adjust the driver based on illumination of a sub-set of the plurality of sensors.

Description:
FIELD OF THE INVENTION 
     The present invention relates to adjusting a display on a monitor. More particularly, the present invention relates to automatically adjusting size, center, and geometrical distortions on a monitor. 
     BACKGROUND 
     Monitors are an important element in computer systems. Typically, monitors are coupled to a personal computer and provide the user with a visual interface of the personal computer&#39;s data contents. Although, current monitors offer unique packaging and different display qualities, the cathode ray tube (“CRT”) remains an integral element in the design of most monitors. The CRT converts an electrical signal into visual information using an electron beam that is modulated and deflected onto a cathodoluminescent screen surface. 
     Improvements in monitor designs has led to computer systems that provide the user with compact and sharp displays. The design improvements, however, have not led to improvements in the display orientation of the monitors. Conventional monitors typically have built in controls to adjust the positioning and sizing of images. The controls allow the user to alter the deflection angle of the electron beam by increasing/decreasing the magnetic flux created by the deflection coils in a CRT device. 
     FIG. 1 illustrates one embodiment of a prior art CRT. CRT  100  includes a vacuum tube  106  coupled to screen  110 . Deflection coil  105  is used to position magnetic flux  115  around electron beam  120 . A control signal (not shown) allows a user to adjust the magnitude of the electric signals on deflection coil  105 , thus adjusting the magnitude of magnetic flux  115 . The change in magnetic flux  115  increases/decreases deflection angle  130  form the Z-axis, thus varying the position of electron beam  120  on screen  110 . Varying the position of beam  120  allows the user to vary the position and orientation of an image displayed on screen  110 . Although using control inputs to adjust images on screen  110  creates provides the user with greater flexibility, manual control inputs create a number of disadvantages. 
     One disadvantage of the conventional control inputs is that the CRT requires multiple adjustments. Typically, CRT&#39;s require adjustments because magnetic flux  115 &#39;s alignment is easily skewed by extraneous magnetic fields. For example, the earth&#39;s magnetic field causes distortion in a monitor display. Similarly, an extraneous electrical device can cause a magnetic field that causes distortion in a monitor display. Accordingly, in conventional monitors, the user is required to locate different control inputs on the monitor and manually adjust the distorted image. 
     FIG. 2 illustrates typical distortions in a conventional monitor display. Image  210  shows an image that is shifted upwards and increase in width as electron beam  120  scans up the vertical axis of screen  110 . Conversely image  230  show an image that is shifted downwards and increase in width as electron beam  120  scans down the vertical axis of screen  110 . Additionally, images  220  and  240  illustrate image distortion caused by a negative degree rotation and a positive degree rotation, respectively. Accordingly, in the prior art the user is required to adjust the distortions illustrated in FIG. 2 via manual controls. 
     Another disadvantage of manual control inputs occurs during the manufacturing of computer systems. In particular, during the manufacturing process of computer systems installation of a new monitor requires adjustment of the monitor display to align an image or remove image distortions. The adjustment is necessary because the manufacture is unable to anticipate the different magnetic variance that affect each computer system. Manual adjustment of monitors during the manufacturing process, however, is costly and tedious. 
     To automate image alignment and distortion correction of newly manufactured monitors, some manufactures introduce a camera and a microprocessor to the manufacturing process. The camera records an image displayed on the monitor and the processor adjusts the displayed image on each monitor. Although the camera and microprocessor automate monitor adjustment, the camera and microprocessor are not available to users outside the manufacturing process. Thus, in non-manufacturing environments the user adjusts distortions via manual controls. Additionally, the camera and microprocessor reduce efficiency in the manufacturing process because the camera and microprocessor introduces extraneous steps to the manufacturing process. 
     SUMMARY OF THE INVENTION 
     An apparatus to automatically adjust image distortions is disclosed. The apparatus comprises a driver operable to generate images on a screen. The apparatus further comprises a plurality of sensors coupled to the screen. Each sensor detects whether the area under the sensor is illuminated. The apparatus further comprises a circuit coupled to the plurality of sensors and the driver. The circuit is configured to adjust the driver based on illumination of a sub-set of the plurality of sensors. A method for automatically adjusting image distortions of a video monitor is also disclosed. 
     Other features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements and in which: 
     FIG. 1 illustrates a prior art cathode ray tube; 
     FIG. 2 illustrates image distortions in a prior art monitor; 
     FIG. 3 shows one embodiment of a feed-back device for adjusting image distortions at the CRT surface; 
     FIG. 4 shows one embodiment of a converter and a sensor included in a feed-back device for adjusting image distortions at the CRT surface; 
     FIG. 5 illustrates size and center image distortions; 
     FIG. 6 illustrates a state machine diagram for correcting image distortions in a monitor; 
     FIG. 7 illustrates geometrical distortions in a video monitor; and 
     FIG. 8 illustrates geometrical distortions in a video monitor. 
    
    
     DETAILED DESCRIPTION 
     A method and apparatus used to automatically adjust image distortions on a monitor is disclosed. The apparatus, hereinafter a self adjusting monitor, includes a feedback loop comprising sensors, a converter, a processor, a cathode ray tube (“CRT”), and the CRT&#39;s driver mechanism. The self adjusting monitor uses the sensors to determine image location on the CRT&#39;s surface and adjusts the image displayed on the screen via the processor and driver circuitry. The feedback loop allows the processor to incrementally change the size, orientation, and location of the displayed image until all distortions are removed. For one embodiment, the monitor comprises a video monitor used in a computer system. For an alternative embodiment, the monitor comprises a flat panel display. The method includes the incremental steps performed by the processor to incrementally change the size, orientation, and location of the displayed image until all distortions are removed. 
     An intended advantage of an embodiment of the invention is to provide a self adjusting monitor that automatically corrects image distortions. For one embodiment, the self adjustment is used in a manufacturing process to adjust the image display of manufactured monitors. For an alternative embodiment, the self adjustment is used in daily operation of a computer system. 
     Another intended advantage of an embodiment of the invention is to provide embedded sensors in a CRT screen. The embedded sensor allow automatic adjustment of an image without obstructing the user&#39;s primary interface. Yet another intended advantage of an embodiment of the invention is to incorporate self adjusting circuitry in a standard monitor design. 
     FIG. 3 illustrates one embodiment of a self adjusting monitor. In particular, system  300  removes distortions from images displayed on the screen area of CRT  330 . System  300  comprises a cathode ray tube (CRT  330 ), driver  320 , microprocessor  315 , converter  310 , and sensors  335 . As illustrated in FIG. 3, the components of system  300  are coupled in a feed-back loop from CRT  330  to driver  320 . CRT  330  displays images via an electron beam (not shown) positioned on the screen of CRT  330 . Driver  320  comprises drive circuitry that adjusts the electron beam to vary the size, position, and orientation of an image displayed by CRT  330 . 
     System  300  adjusts the output of driver  320  to remove orientation and geometrical distortions from images displayed by CRT  330 . The level of adjustment is determined by sensors  335 . Control over the actual adjustments, however, is determined by converter  310  and microprocessor  315 . For one embodiment, sensors  335  comprise photo-electric diodes placed on the edge of CRT  330 &#39;s screen. The photo-electric diodes produce an analog signal indicating whether the surface area beneath a given photo-electric diode is illuminated. For an alternative embodiment, sensors  335  comprise transparent photo-electric diodes incorporated into the anti-reflective screen of CRT  330 . The transparent photo electric diodes are not constrained to the edge of the screen and may be placed at any location on CRT  330 &#39;s screen. 
     For one embodiment, system  300  includes six photo-electric diodes. The six photo-electric diode produces an analog output indicating the screen illumination created by a predetermined image. The analog outputs are coupled to converter  310  via line  305 . Converter  310  transforms the analog signals into a digital signal used in microprocessor  315 . In particular, converter  310  produces a binary output indicating whether a set of photoelectric diodes is covering a section of the predetermined image. The binary output is used by microprocessor  315  to adjust CRT  330 &#39;s electron beam via driver  320 . The adjusted image is displayed by CRT  330  and creates an new set of analog outputs from sensor  335 . Following the feed-back loop, the new analog outputs are used by microprocessor  315  to readjust the image until the distortions of the image are corrected. For one embodiment, the predetermined image is stored in microprocessor  315 . For an alternative embodiment, the predetermined image comprises a white rectangular shape matching the dimensions of CRT  330 &#39;s screen. Accordingly, all distortions are removed from the predetermined image when all six photo-electric diodes indicate no illumination. To remove the distortions, microprocessor  315  incrementally adjusts the output of driver  320  until the binary output of converter  310  indicates that sensors  335  cover a non-illuminated area. 
     For one embodiment, system  300  comprises a video monitor in a computer system. The computer system uses system  300  as an interface to display graphic and text information included in the computer system. Accordingly, the computer system uses drive logic and drive circuitry (not shown) in conjunction with driver  320  to control/adjust CRT  330 &#39;s electron beam, thus providing different images on CRT  330 &#39;s screen. For one embodiment, driver  320  provides seven control signals to adjust CRT  330 &#39;s electron beam. The control signals include horizontal size adjust, horizontal center adjust, vertical size adjust, vertical center adjust, rotation adjust, barrel adjust, and trapezoid adjust. Accordingly, based on the data from sensor  335  and converter  310 , microprocessor  315  incrementally adjusts a set of the seven control signals to remove distortions from CRT  330 &#39;s screen. 
     FIG. 4 illustrates one embodiment of a converter ( 400 ) coupled to a sensor ( 410 ) in a self adjusting monitor. Converter  400  includes an amplifier, a comparator, resistive elements, and a capacitor. The elements in converter  400  are coupled to transform the analog signal of sensor  410  into a digital signal. For one embodiment, sensor  410  comprises a photo-electric diode with light illumination recognition characteristics that parallel the sensitivity of the human eye. 
     As shown in FIG. 4, sensor  410  is coupled to both inputs of comparator  440 . For one embodiment, sensor  410  outputs a low voltage analog signal indicating the detection of a light source. Accordingly, comparator  440  is used to determine whether the low voltage analog signals is greater than a pre-determined threshold voltage. The threshold voltage is determined by the properties of the photo-electric selected. 
     Sensor  410  is also coupled to capacitor  415  and resistor  420 . Capacitor  415  and resistor  420 , in turn, are coupled to the output of amplifier  440  and one input of amplifier  450 . The other input of amplifier  450  is coupled to resistor  425  and resistor  430 . Both the output of amplifier  450  and resistor  430  are coupled to output  460 . Amplifier  450  transforms the output of comparator  440  to digital voltage levels VSS and ground. For one embodiment, VSS equals 35 volts and ground equals 0 volts. Accordingly, a voltage level of 35 volts is used to define a binary value of ‘1’ and a voltage level of 0 volts is used to define a binary value of ‘0’. Based on the values of resistors  425 - 430 , the value of capacitor  415 , and the specific type of photoelectric diode used in sensor  410  a predetermined illumination range is detected by converter  400 . Accordingly, converter  400  generates a binary ‘1’ on output  460  when an illumination source that passes the predetermined illumination range is placed in close proximity to sensor  410 . 
     FIG. 5 illustrates size and center distortions. In particular, based on the number and location of sensors illuminated, the type of size/center image distortion is ascertained by microprocessor  315 . For one embodiment, microprocessor  315  uses this preliminary evaluation to adjusts driver  320  via the afore-mentioned control signals. Images  510  through  540  show an example of possible size and center distortions. In image  510  only the left side sensors are illuminated, thus indicating a horizontal alignment distortion. Similarly, in image  515  only the right side sensor are illuminated, thus indicating a horizontal alignment distortion. In image  520  none of the sensor are illuminated, thus indicating a possible size distortion. Alternatively, in image  535  all the sensor are illuminated, thus indicating a correct image or an enlargement distortion. 
     In image  530 , the bottom sensors are not illuminated, thus indicating a positive vertical alignment distortion. Similarly, in image  535  the top sensors are not illuminated, thus indicating a negative vertical alignment distortion. Finally, in image  540  only the center sensors are illuminated, thus indicating a vertical size distortion. Using these initial image distortions, microprocessor corrects size and center distortions by adjusting the CRT  330 &#39;s electron beam via driver  320 . 
     FIG. 6 illustrates one embodiment of a state machine diagram for implementing image correction in a self adjusting monitor. In particular, state diagram  600  shows the state transitions followed by microprocessor  315  during size and center adjustments of a monitor. For one embodiment, the monitor includes two sensors. The first sensor is located at the midpoint of the monitor&#39;s left screen edge, hereinafter left sensor. The second sensor is located at the midpoint of the monitor&#39;s right screen edge, hereinafter right sensor. For alternative embodiments, the monitor includes multiple sensors. Accordingly, for multiple sensors the number of state transitions in state diagram  600  increases because microprocessor  315  receives additional inputs. 
     State  610  is the initial state in state diagram  600 . In state  610 , a computer system coupled to the self adjusting monitor displays an image on the monitor&#39;s screen. For one embodiment, state  610  occurs during a reset of the computer system coupled to the self adjusting monitor. For an alternative embodiment, state  610  occurs when a button is depresses on the self adjusting monitor. For yet another embodiment, state  610  occurs when a unique key combination is depressed on a keyboard coupled to the computer system. Provided state  610  is reached, state diagram  600  transitions to state  615 . 
     In state  615 , microprocessor  315  obtains sensor data from converter  310 . In particular, for one embodiment, a predetermined image is displayed on CRT  330 . The predetermined image results in the illumination or non-illumination of the left sensor. Similarly, the predetermined image results in the illumination or non-illumination of the right sensor. Accordingly, in state  615 , the sensor data from each sensor is converted to digital data, via converter  310 , and transferred to microprocessor  315 . Provided microprocessor  315  receives the sensor data, state diagram  600  transitions to state  620 . In state  620 , microprocessor  315  examines the sensor data to determine which sensor is illuminated. For one embodiment, a logic ‘1’ value from converter  310  indicates that the sensor is illuminated. Accordingly, a ‘0’ value for both the left sensor and the right sensor indicates that neither of the sensors is illuminated, hereinafter a non-illuminated sensor is denoted as an off sensor. Provided neither of the sensors is off, state diagram  600  transitions to state  625 . 
     In state  625 , microprocessor  315  increases the size of the predetermined image. In particular, in state  625  microprocessor  315  increases the horizontal dimension of the predetermined image. For one embodiment, microprocessor  315  uses driver  320 &#39;s horizontal size adjust signal to increases the horizontal dimension of the predetermined image. After an initial size increase, state diagram  600  returns to state  620 . As previously described, in state  620  microprocessor  315  determines whether both the left and right sensors are illuminated. Provided neither of the sensors is off, state diagram  600  returns to state  625 . State diagram  600  continues to transition between state  620  and state  625  until both sensors are illuminated. Accordingly, states  620  and  625  allow microprocessor  315  to incrementally increase the size of predetermined image. Provided both the left and right sensor are illuminated, state diagram  600  transitions to state  630 . 
     In state  630 , microprocessor  315  begins the horizontal adjustment of the predetermined image using the left sensor. In particular, in state  630  microprocessor  315  shifts the predetermined image to the right edge of the monitor&#39;s screen. For one embodiment, microprocessor  315  uses driver  320 &#39;s horizontal center adjust signal to shift the predetermined image. After an initial right shift, state diagram  600  transitions to state  635 . In state  635 , microprocessor  315  determines whether the left sensor is off. Provided the left sensor is illuminated, state diagram  600  returns to state  630 . State diagram  600  continues to transition between state  630  and state  635  until the left sensor is off. Accordingly, states  630  and  635  allow microprocessor  315  to incrementally shift the predetermined image to the monitor screen&#39;s right edge. Provided the left sensor is off, state diagram  600  transitions to state  640 . 
     In state  640 , microprocessor  315  stores the right center value of the predetermined image. The right center value is used to determine the predetermined image&#39;s furthest right boundary relative to the left sensor. Subsequent to determining the right center value, state diagram  600  transitions to state  645 . 
     In state  645 , microprocessor  315  begins the left horizontal adjustment of the predetermined image using the right sensor. In particular, in state  630  microprocessor  315  shifts the predetermined image to the left edge of the monitor&#39;s screen. For one embodiment, microprocessor  315  uses driver  320 &#39;s horizontal center adjust signal to shift the predetermined image. After an initial left shift, state diagram  600  transitions to state  650 . In state  650 , microprocessor  315  determines whether the right sensor is off. Provided the right sensor is illuminated, state diagram  600  returns to state  645 . State diagram  600  continues to transition between state  645  and state  650  until the right sensor is off. Accordingly, states  645  and  650  allow microprocessor  315  to incrementally shift the predetermined image to the monitor screen&#39;s left edge. Provided the left sensor is off, state diagram  600  transitions to state  655 . 
     In state  655 , microprocessor  315  stores the left center value of the predetermined image. The left center value is used to determine the predetermined image&#39;s furthest left boundary relative to the right sensor. Subsequent to determining the left center value, state diagram  600  transitions to state  660 . In state  660 , microprocessor  315  calculates the center location of the predetermined image by averaging the right center value and the left center value. 
     For one embodiment, microprocessor  315  adjusts the center location of the monitor using the center location calculated in state  660 . In particular, microprocessor  315  calibrates system  300 &#39;s electron beam, via driver  320 , in accordance with the center position calculated in state  660 . Accordingly, location distortions are reduced from images displayed by the monitor. Subsequent to the center calculation, state diagram  600  transitions to state  665 . In the present embodiment, because of the left and right sensor&#39;s location on the monitors screen, microprocessor  315  increments driver  320 &#39;s horizontal center adjust to orient the predetermined image. For alternative embodiments, however, multiple sensors located in different areas of the monitor screen are contemplated. Accordingly, microprocessor  315  uses a combination of driver  320 &#39;s horizontal center adjust and vertical center adjust to determine the center position of the predetermined image. 
     In state  665 , microprocessor  315  further adjusts the size of the predetermined image. In particular, the size expansion of state  620  is reduced until the dimensions of the predetermined image coincide with the dimensions of the monitor. Accordingly, in state  665  microprocessor  315  decreases the size of the predetermined image. For one embodiment, microprocessor  315  uses driver  320 &#39;s horizontal size adjust signal to decreases the size of the predetermined image. After an initial size decrease, state diagram  600  transitions to state  670 . In state  670 , microprocessor  315  determines whether both sensors are off. Provided either sensor is illuminated, state diagram  600  returns to state  655 . State diagram  600  continues to transition between state  655  and state  670  until both sensors are off. Accordingly, states  655  and  670  allow microprocessor  315  to incrementally decreases the size of the predetermined image to coincide with the monitor&#39;s dimensions. Provided both sensors are off, state diagram  600  transitions to state  680 . 
     In state  680 , microprocessor  315  stores the size and center adjustments of the predetermined image. For one embodiment, microprocessor  315  adjusts the size and center display of the monitor using the size adjustments derived in state  680 . In particular, microprocessor  315  calibrates system  300 &#39;s electron beam, via driver  320 , in accordance with the size and center adjustments calculated in state  660 . Accordingly, size and center distortions are reduced from images displayed by the monitor. For alternative embodiments, multiple sensors located in different areas of the monitor screen are contemplated. Accordingly, microprocessor  315  uses a combination of both the horizontal size adjust and the vertical size adjust to adjust the size of the predetermined image. 
     State diagram  600  illustrates the state transitions used by system  300  to implement size and center image correction in a self adjusting monitor with two sensors. Varying the location and number of sensors allows for the detection of different distortions. In particular, a specific type of image distortion is ascertained by microprocessor  315  based on the number and location of illuminated sensors. For one embodiment, microprocessor  315  applies this preliminary evaluation to a predetermined image displayed by system  300 . Subsequently, driver  320  is adjusted to remove the distortion from the predetermined image via the horizontal size adjust, horizontal center adjust, vertical size adjust, vertical center adjust, rotation adjust, barrel adjust, and trapezoid adjust control signals. For one embodiment, microprocessor  315  calibrates system  300 &#39;s electron beam, via driver  320 , in accordance with the afore-mentioned control signals. Accordingly, distortions are reduced from images displayed by system  300 &#39;s monitor. 
     FIGS. 7 and 8 show examples of possible distortions isolated by system  300 &#39;s six sensors. In particular, FIG. 7 illustrates the correlation between sensors and the detection of barrel and tilt shape distortions. Image  700  shown an image without any distortions. As illustrated in FIG. 7, the non-distorted image&#39;s borders align with the six sensors. Accordingly, all six sensor are illuminated. In the distorted images, however, a subset of the sensors are off. 
     Images  710 - 725  shows four possible image distortions found on system  300 &#39;s display. In particular, images  710  and  715  show examples of a barrel shape distortion. In image  710  the left-center sensor and the right-center sensor are off. In image  715  the top-left, top-right, bottom-left, and bottom-right sensor are off. For one embodiment, using the detection of illuminated/non-illuminated sensor microprocessor  315  identified the barrel distortion shown in image  710  and image  715 . Accordingly microprocessor  315  uses the control signals horizontal size adjust, horizontal center adjust, vertical size adjust, vertical center adjust, and barrel adjust to remove the barrel distortion from the displayed image. 
     Images  729  and  725  show examples of tilt shape distortions. In both images the top-left, top-right, bottom-left, and bottom-right sensor are off. For one embodiment, using the detection of illuminated/non-illuminated sensor microprocessor  3315  identified the tilt distortion shown in image  720  and image  725 . Accordingly microprocessor  315  uses the control signals horizontal size adjust, horizontal center adjust, vertical size adjust, vertical center adjust, and rotation adjust to remove the tilt distortion from the displayed image. 
     FIG. 8 illustrates the correlation between system  300 &#39;s six sensors and the detection of one-sided barrel shape, trapezoid shape, and parallelogram shape distortions. Images  810  and  815  show examples of a one-sided barrel shape distortion. In image  810  the left-top sensor and the left-bottom sensor are off. Similarly, in image  815  the right-top sensor and the right-bottom sensor are off. For one embodiment, using the detection of illuminated/non-illuminated sensor microprocessor  3315  identified the one-sided barrel distortions shown in images  810  and  815 . Accordingly microprocessor  315  uses the control signals horizontal size adjust, horizontal center adjust, vertical size adjust, vertical center adjust, rotation adjust and barrel adjust to remove the barrel distortion from the displayed image. 
     Images  820  and  825  show examples of a trapezoid shape distortion. In image  820  the left-top sensor and the right-top sensor are off. Similarly, in image  825  the right-bottom sensor and the left-bottom sensor are off. For one embodiment, using the detection of illuminated/non-illuminated sensor microprocessor  3315  identified the trapezoid distortions shown in images  820  and  825 . Accordingly microprocessor  315  uses the control signals horizontal size adjust, horizontal center adjust, vertical size adjust, vertical center adjust, and trapezoid adjust to remove the barrel distortion from the displayed image Images  830  and  835  show examples of a parallelogram shape distortion. In image  830  the left-top sensor and the right-bottom sensor are off. Similarly, in image  835  the right-bottom sensor and the left-top sensor are off. For one embodiment, using the detection of illuminated/non-illuminated sensor microprocessor  3315  identified the parallelogram distortions shown in images  830  and  835 . Accordingly microprocessor  315  uses the control signals horizontal size adjust, horizontal center adjust, vertical size adjust, vertical center adjust, rotation adjust, barrel adjust, and trapezoid adjust to remove the parallelogram distortion from the displayed image. 
     The placement of multiple sensors allows system  300  to identify many different image distortions in a video monitor. Accordingly, the placement of multiple sensors in conjunction with driver  320 &#39;s multiple control signals allow the correction of different image distortions. FIG.  7  and FIG. 8 illustrate different image distortions in a monitor with six sensor located on the edge of the monitor. For alternative embodiments, however, additional sensor located throughout the surface of the monitor are contemplated. Accordingly, the increased number of sensors allow for the identification and subsequent correction of additional distortions. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereof without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.