A method and apparatus for reducing visibility of damping wire artifacts in aperture grill display tubes comprises a sensor device for locating the artifacts and responsively generating amplitude values, a processor for receiving the generated amplitude values and responsively calculating correction values, and a compensator device coupled to the processor for utilizing the correction values to correct said artifacts.
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1. Apparatus for reducing the visibility of the shadow cast by a damping wire on the screen of a display device, comprising:
a sensor device for locating said shadow on said screen of said display device and responsively generate amplitude values of the area of said screen immediately adjacent said shadow; a processor for receiving said generated amplitude values and responsively calculating correction values; and a compensator device coupled to said processor for utilizing said correction values for reducing the visibility of said shadow on said screen.
9. A method for reducing the visibility of the shadow cast by a damping wire on the screen of a display device comprising the steps of:
using a sensor device to locate said shadow on the screen of said display device and responsively generate amplitude values of the area of said screen immediately adjacent said shadow; calculating correction values from said generated amplitude values using a processor; and utilizing said correction values to reduce the effects of the visibility of said shadow on the screen of said display device by using a compensator device coupled to said processor.
20. Apparatus for reducing the visibility of the shadow caused by a damping wire on the screen of a display device, comprising:
means for using a sensor device to locate said shadow on the screen of said display device and responsively generate amplitude values of the area of said screen immediately adjacent said shadow; means for calculating correction values from said generated amplitude values using a processor; and means for utilizing said correction values to reduce the visibility of said shadow on the screen of said display device by using a compensator device coupled to said processor.
0. 21. An apparatus for reducing the visibility of a shadow cast by a damping wire on a screen of a display device, comprising:
a control module for providing a first address corresponding to a current location of an electronic beam in the display device; a memory for storing a display list including a correction value and address corresponding to a predetermined location on the screen associated with the shadow; and a comparing module for comparing the first and second addresses, and responsive to a match, utilizing the correction value for reducing the visibility of the shadow on the screen.
17. A computer-readable medium comprising program instructions for reducing the visibility of the shadow cast by a damping wire on the screen of a display device by performing the steps of:
using a sensor device to locate said shadow on said screen of said display device and responsively generate amplitude values of the area of said screen immediately adjacent said shadow; calculating correction values from said generated amplitude values using a processor; and utilizing said correction values to reduce the visibility of said shadow on said screen of said display device by using a compensator device coupled to said processor.
18. A computer-readable medium comprising program instructions for correcting artifacts on the screen of a display device by performing the steps of:
using a sensor device to locate said artifacts on said screen of said display device and responsively generate amplitude values of the area of said screen immediately adjacent said artifacts, wherein said artifacts may include at least one damping wire shadow that is visible on the screen of said display device; calculating correction values from said generated amplitude values using a processor; and utilizing said correction values to reduce the visibility of said artifacts on said screen of said display device by using a compensator device coupled to said processor, said display device comprising a cathode ray tube.
4. Apparatus for correcting artifacts on the screen of a display device, comprising:
a sensor device for locating said artifacts on said screen and responsively generating amplitude values of the area of said screen immediately adjacent said artifacts, wherein said artifacts may include at least one damping wire shadow that is visible on said screen, a processor for receiving said generated amplitude values and responsively calculating correction values, said correction values being converted into video values which are alternately and sequentially stored in a plurality of display lists along with corresponding location addresses; and a compensator device coupled to said processor for utilizing said correction values for reducing the visibility of said artifacts on said screen of said display device, said display device comprising a cathode ray tube.
12. A method for correcting artifacts on the screen of a display device comprising the steps of:
using a sensor device to locate said artifacts on the screen of said display device and responsively generate amplitude values of the area of said screen immediately adjacent said artifacts, wherein said artifacts may include at least one damping wire shadow that is visible on the screen of said display device; calculating correction values from said generated amplitude values using a processor, said correction values being converted into video values which are alternately and sequentially stored in a plurality of display lists along with corresponding location addresses; and utilizing said correction values to reduce the effects of the visibility of said artifacts on the screen of said display device by using a compensator device coupled to said processor, said display device comprising a cathode ray tube.
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1. Field of the Invention
This invention relates generally to video display monitors and more particularly to a method and apparatus for reducing visibility of damping wires in aperture grill display tubes.
2. Description of the Background Art
Accurate representation of visual information is a significant consideration of manufacturers, designers and user of video display monitors. Aperture grill cathode ray tubes (CRTs) are devices which are often used in conventional video display monitors.
Referring now to
Referring now to
A countermeasure employed to minimize the extent of the ringing is the addition of one or more damping wires 210 stretched across the grill 120 assembly, perpendicular to the vertical slits. As a result of friction with the moving aperture grill 120 and internal elastic losses, this wire dissipates mechanical energy to thereby reduce the extent of the ringing. The damping wires 210 cast a shadow on the phosphor-coating 114, but since the damping wire 120 diameter is smaller than that of the visible beams 118 cross section, the shadow is of relatively low contrast. There are typically two damping wires 210 present if CRT 110 is 17 inches or larger and there is typically one damping wire if CRT 110 is smaller than 17 inches. The damping wire shadow is caused by the modulation of the amplitude of the electron beams 118 incident on the phosphor coating 114.
Since there are only one or two damping wire 210 shadows on the screen of CRT 110, and they are perpendicular to the regular fine-pitch structure of the vertical stripes, they are sometimes easily observed, though often not distracting. None the less, when first observed, these shadows are often perceived by as defects in CRT 110. This perception is sometimes a factor in customer satisfaction and overall perception of image and product quality. Therefore, an improved method and apparatus for reducing visibility of damping wires in aperture grill display tubes is needed.
In accordance with the present invention, a method and apparatus are disclosed for reducing visibility of damping wires in aperture grill display tubes. This invention reduces the visibility of damping wire shadows by modulating the amplitude of the CRT electron beam to compensate for the modulation imposed by the damping wires, thus canceling the damping wire shadow. The invention is composed of an apparatus and technique to locate the damping wire shadow with respect to the displayed video image, and an apparatus that generates the compensation signal and applies to the video signal to compensate for the damping wire shadow.
In the preferred embodiment of the present invention, a detector device measures amplitude values of selected areas on a CRT screen as individual CRT scan rows are sequentially illuminated. The measured amplitude values are then processed with a differentiation routine to determine the specific location of the damping wire shadow on the CRT screen.
Correction values to compensate for the damping wire shadow are calculated by subtracting the scan row amplitude value at the damping wire shadow from an average of the scan row amplitude values for the two scan rows adjacent the damping wire shadow. The correction values are then converted into corresponding video values which are stored sequentially and alternately into two display lists along with corresponding location information such as column and row addresses.
A compensator device then sequentially provides the video values and their corresponding location information to video amplifiers to drive the display CRT. The present invention thus advantageously compensates the CRT electron beam current at the appropriate time to effectively remove the damping wire shadows from the aperture grill display tube.
The present invention discloses a method and apparatus for reducing visibility of damping wires in aperture grill display tubes and comprises a sensor device for locating the artifacts and responsively generating amplitude values, a processor for receiving the generated amplitude values and responsively calculating correction values, and a compensator device coupled to the processor for utilizing the correction values to correct said artifacts.
Referring now to
Referring now to
Then, in step 412, the present invention calculates correction values which correspond to the location and intensity of the damping wires 210. Further details for calculating correction values are discussed below in conjunction with FIG. 9. Next, the present invention, in step 414, builds display lists 320 by converting the calculated correction values into corresponding video values and then storing the converted video values along with their corresponding locations on the CRT 110 screen. Construction of display lists 320 is further discussed below in conjunction with FIG. 10. Finally, in step 416, the present invention applies the converted video values to a video amplifier in CRT 110 using damping wire compensator 322 which is further discussed below in conjunction with FIG. 11.
Referring now to
The location of each of the measurement areas 510 relative to their screen 112 location is known, and they are analyzed to determine the position of the damping wire 210 shadow (all the way across the screen 112) and the transmission reduction due to the shadow at each measurement area 510 affected by the shadow. The amount of attenuation of the shadow at each measurement area 510 can be measured to determine the amount of compensation required, or a nominal correction for the particular display CRT 110 under consideration can be used. These data are then used to generate a display list 320 (
Referring now to
Referring now to
Referring now to
The differentiation routine removes the low-frequency variation in amplitude that results from non-uniform sensitivity of the photo detector probe and facilitates location of damping wire 210. The amplitude of the particular scan row 610 of damping wire 210 may then be compared with the two adjacent scan rows 610 to determine the amount of correction needed to compensate for the damping wire 210 shadow.
The error caused by the damping wire 210 shadow may be found by subtracting the
Referring now to
In the preferred embodiment, the intensity of the electron beam 118 at scan row 3 must be increased by a factor equal to A/B to compensate for the shadow cast by damping wire 210. In other words, the amplitude B must be increased by a value equal to A minus B, to effectively raise the amplitude of value B until it equals the amplitude of value A. Alternatively, once the location of the damping wire 210 shadow is found, successive correction values may be applied to that location until the amplitude at that location equals the average of the two adjacent locations.
Referring now to
In the preferred embodiment, CPU 312 converts the calculated correction values into corresponding video values and then stores the video values into display lists 320. The conversion process is typically performed through the use of a conversion table which reflects the luminance correction transfer function of CRT 110. The conversion table may be constructed by measuring display screen 112 for those luminance changes which correspond to the range of possible correction values. CPU 312 may then readily convert calculated correction values into video values by referencing the compiled conversion table.
In practice, display lists 320 include display list A 1010 and display list B 1040 which each comprise a series of video values and corresponding row and column addresses. Each video value represents the calculated amount of adjustment needed to compensate for the damping wire 210 shadow at a given location on screen 112. The row and column addresses correspond to the specific location on screen 112 to which a particular video value pertains.
The display lists 320 are sets of addresses and video values that are applied whenever the corresponding addresses are encountered by beam 118 on screen 112. As such, a nominal value relating to no gain increase is applied at the start of the first row and column, and then when another row and column (whose address corresponds to an entry in the display lists 320) are encountered, the corresponding video value for that address is applied to the beam current 118. The display lists 320 are kept in the same sequence as the addresses are generated, and alternate entries are kept in two sets of display list A and B (1010 and 1040) so that the data from one display list can be read out while the contents of the other display list is being fetched. This approach allows the use of lower speed processes.
The scanning of screen 112 (scan row 610 by scan row 610) to detect the location of the damping wire 210 shadow (if a spatial imaging device is not used) is ideally performed by loading the appropriate address and video values into the display lists 320 and then using them to drive the CRT 110 video amplifier inputs rather than the gain modulation inputs. Alternatively, the host system 310 (the system providing the video source) can provide a signal corresponding to a full white raster, and an extra bit or reserved value in the video value register can be used to blank screen 112 in all but the selected row segments.
Referring now to
In the preferred embodiment, control logic 1110 provides an address corresponding to the current location of electron beam 118 (on screen 112) to address comparator 1170. Display list A 1010 and display list B 1040 contain alternate sequential entries of video values and their corresponding column and row addresses, as described above in conjunction with FIG. 10. Initially, control logic 1110 gates row/column address information from display list A 1010 into multiplexer (MUX) 1140, and simultaneously provides data (video values) from display list A 1010 into multiplexer (MUX) 1160.
Control logic 1110 preferably selects the "Display list A" input of MUX 1140 to provide the row/column address to address comparator 1170 and the corresponding correction value to data latch 1180. When the row/column address of the correction data matches the current address (location) of the electron beam 118, address comparator 1170 gates the correction value from data latch 1180 through D-to-A converter and on to the gain modulation circuit of the video amplifiers controlling electron beam gun 116.
Address comparator 1170 then sends an acknowledge signal to control logic 1110 to report that the correction value has been sent to the gain modulation circuit. Control logic 1110 then responsively repeats the above process using display list B 1040 as the source of the correction information. By repeating the above sequences, compensator 322 thus alternately and sequentially fetches correction information from the two display lists (1010 and 1040) and thus effectively compensates for the shadow caused on display screen 112 by damping wire 210.
A number of additional considerations and alternate techniques should be mentioned in connection with the present invention. For example, the correction signal may be applied to the gain modulation inputs of the Red, Green and Blue video amplifiers. It should only be necessary to generate one signal to apply to all three channels, but in the case of a system with severely degraded vertical convergence, separate corrections for Red, Green and Blue may be worthwhile.
For the case in which two or more scan rows 610 are affected by a single damping wire 210 shadow, the amplitudes of the correction signals on the two damping wires 210 can be adjusted so they both contribute to the compensation in proportion to their respective affects from the damping wire 210 shadow. In other words, each line would be compensated just enough to bring its amplitude over that segment up to the level it would be at if there were no shadow.
The
Multiple raster formats may advantageously be accommodated automatically by using multiple memory devices. Furthermore, the compensation could be made to track changes in raster size and position by monitoring the deflection current and high voltage.
Raster shifts resulting from changes in the ambient magnetic fields can be corrected. Shifts in the vertical and horizontal directions resulting from changes in the magnetic fields along the respective horizontal axis and vertical axis of CRT 110 would result in the most noticeable changes in the compensation. The scan row and column addresses in display lists 320 can be adjusted by adding or subtracting counts proportional to the intensity of the ambient magnetic fields in the respective horizontal axis and vertical axis of CRT 110.
The invention has been explained above with reference to a preferred embodiment. Other embodiments will be apparent to those skilled in the art in light of this disclosure. For example, the present invention may be used to effectively compensate for variations in amplitude from causes other than the damping wires 210 described in the preferred embodiment above. Therefore, these and other variations upon the preferred embodiments are intended to be covered by the present invention, which is limited only by the appended claims.
Patent | Priority | Assignee | Title |
Patent | Priority | Assignee | Title |
4106866, | Jul 25 1974 | Sony Corporation | Image projection system |
4240073, | May 15 1978 | Thomas Electronics, Inc. | Cathode ray tube display system with display location memory |
4387394, | Dec 31 1980 | RCA Corporation | Sensing focus of a color kinescope |
4441120, | May 03 1979 | U S PHILIPS CORPORATION | Device for measuring and methods for adjusting the convergence of the electron beams in color display tubes |
4602272, | Nov 13 1984 | RCA LICENSING CORPORATION, TWO INDEPENDENCE WAY, PRINCETON, NJ 08540, A CORP OF DE | Electron beam intensity profile measuring system and method |
4602273, | Aug 30 1983 | RCA LICENSING CORPORATION, TWO INDEPENDENCE WAY, PRINCETON, NJ 08540, A CORP OF DE | Interpolated progressive-scan television display with line-crawl artifact filtration |
5265200, | Nov 01 1990 | International Business Machines Corporation | System and method for automatic image saturation, gamma, and exposure correction in a digitizing video capture system |
5363011, | Nov 12 1992 | Zenith Electronics Corporation | Strip-type shadow mask effective to alleviate degrouping |
5369330, | Jun 13 1991 | NEC Corporation | Damp rod construction for CRT grid structures |
5382871, | Oct 24 1991 | Sony Corporation | Color selecting structure for a cathode-ray tube |
5391957, | Dec 28 1992 | Zenith Electronics Corporation | Vibration damping means for a strip shadow mask |
5394051, | Dec 28 1992 | Zenith Electronics Corporation | Vibration-damping configuration in a strip shadow mask |
5424780, | May 22 1989 | Technology Licensing Corporation | Apparatus and method for spacial scan modulation of a video display |
5432349, | Mar 15 1993 | The United State of America as represented by the Secretary of the Navy; UNITED STATES OF AMERICA, THE, AS REPRESENTED BY THE SECRETARY OF THE NAVY | Fourier transform microscope for x-ray and/or gamma-ray imaging |
5512961, | Mar 24 1993 | Apple Computer, Inc. | Method and system of achieving accurate white point setting of a CRT display |
5594248, | Feb 25 1993 | NEC Corporation | Infrared imaging device and infrared imaging system using same |
5739870, | Mar 11 1996 | Display Laboratories, Inc. | Math engine for generating font gradients |
5793344, | Mar 24 1994 | SEMICONDUCTOR ENERGY LABORATORY CO , LTD | System for correcting display device and method for correcting the same |
6489713, | Aug 16 1999 | MT PICTURE DISPLAY GERMANY GMBH | Color picture tube with a tension mask |
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