Method and apparatus to minimize burn lines on a display

• US 6,369,851 B1
• Filed: 09/24/1999
• Issued: 04/09/2002
• Est. Priority Date: 09/24/1999
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Marflak, Thomas Adreon, Arnold, David Scott, Kiga, Hirohide
• Primary Examiner(s): Harvey, David E.
• Application Number:
  US09/405,657
• Time in Patent Office: 928 Days
• Field of Search: H04/N.544, H04/N.568, H04/N.546, 348/173, 348/445, 348/556, 348/687, 348/725, 348/805
• US Class Current: 348/173
• CPC Class Codes: H04N 3/20 Prevention of damage to cathode-ray tubes in the event of failure of scanning
• CPC Class Codes: H04N 7/0122 the input and the output signals having different aspect ratios

Abstract

A method and apparatus for displaying a video signal is described. A video signal is received representing an image having a first aspect ratio, with the image having a top and bottom edge. An edge modification signal is generated. The image is displayed on a display having a second aspect ratio with the top and bottom edge modified in accordance with the edge modification signal. Accordingly, burn lines are minimized through use of the edge modification signal to reduce brightness levels at the top and bottom edge of the image.

Claims

1. A method for displaying a video signal, comprising:

receiving a video signal representing an image having a first aspect ratio, with said image having a top and bottom edge;

generating an edge modification signal; and

displaying said image on a display having a second aspect ratio with said top and bottom edge modified in accordance with said edge modification signal, wherein said generating comprises;

receiving a dynamic focus waveform signal comprising a horizontal parabola signal and a vertical parabola signal;

filtering said waveform signal to isolate said vertical parabola signal; and

modifying said vertical parabola signal by multiplying said vertical parabola signal with itself at least twice to form said edge modification signal.

2. The method of claim 1, further comprising:

scaling said edge modification signal by brightness level of said image; and

amplifying said edge modification signal.

3. A method for displaying a video signal, comprising:

receiving a video signal representing an image having a first aspect ratio, with said image having a top and bottom edge;

generating an edge modification signal; and

displaying said image on a display having a second aspect ratio with said top and bottom edge modified in accordance with said edge modification signal, wherein said displaying comprises;

retrieving said image from said video signal;

sending said image to an electron gun for a cathode ray tube display system;

sending said edge modification signal to a shading grid for said cathode ray tube display system;

displaying said retrieved image on a fluorescent screen of said cathode ray tube display system by sending a stream of electrons representing portions of said image from said electron gun to said fluorescent screen through said shading grid, and with said shading grid modifying said stream of electrons using said edge modification signal to reduce brightness levels at said top and bottom edge of said retrieved image.

4. A method to generate an edge modification signal, comprising:

receiving a waveform signal comprising a horizontal parabola signal and a vertical parabola signal;

filtering said waveform signal to isolate said vertical parabola signal; and

modifying said vertical parabola signal by multiplying said vertical parabola signal with itself at least twice to form said edge modification signal.

5. The method of claim 4, further comprising:

scaling said edge modification signal by a brightness level; and

amplifying said edge modification signal.

6. An apparatus to display a video signal, comprising:

a video receiver to receive a video signal representing an image having a first aspect ratio, with said image having a top and bottom edge;

an edge modification signal generator to generate an edge modification signal; and

a cathode ray tube display system having a second aspect ratio, said cathode ray tube display system comprising at least one electron gun, a shading grid and a fluorescent screen, with said electron gun sending a quantity of electrons representing said top and bottom edge portions of said image to said fluorescent screen through said shading grid, and with said shading grid decreasing said quantity of electrons using said edge modification signal.

7. The apparatus of claim 6, wherein said first aspect ratio is a 16:

9 aspect ratio.

8. The apparatus of claim 6, wherein said second aspect ratio is a 4:

3 aspect ratio.

9. The apparatus of claim 6, further comprising a mirror and a display screen.

10. The apparatus of claim 6, wherein said edge modification signal generator comprises:

a dynamic waveform generator to generate a dynamic focus waveform signal comprising a horizontal parabola signal and a vertical parabola signal;

a filter to filter said waveform signal and isolate said vertical parabola signal;

a first multiplier to multiply said vertical parabola signal with itself; and

a second multiplier to multiply said multiplied vertical parabola signal with itself to form said edge modification signal.

11. The apparatus of claim 10, further comprising:

a scaler to scale said edge modification signal by a brightness level of said image; and

an amplifier to amplify said edge modification signal.

12. The apparatus of claim 10, wherein said filter is a low-pass filter.

13. The apparatus of claim 11, wherein said scaler receives automatic brightness limiting control signals proportional to said image to scale said edge modification signal.

14. The apparatus of claim 10, wherein said dynamic focus waveform is a small signal dynamic focus waveform.

15. The apparatus of claim 6, further comprising:

a shading circuit coupled to said edge modification signal generator to receive said edge modification signal and output said edge modification signal to said shading grid.

16. An edge modification signal generator, comprising:

a dynamic waveform generator to generate a dynamic focus waveform signal comprising a horizontal parabola signal and a vertical parabola signal;

a filter to filter said waveform signal and isolate said vertical parabola signal;

a first multiplier to multiply said vertical parabola signal with itself; and

a second multiplier to multiply said multiplied vertical parabola signal with itself to form said edge modification signal.

17. The edge modification generator of claim 16, further comprising:

a scaler to scale said edge modification signal by a brightness level; and

an amplifier to amplify said edge modification signal.

18. An apparatus to display a video signal, comprising:

a video receiver to receive and decode a video signal representing an image having a first aspect ratio, with said image having a top and bottom edge;

a cathode ray tube display system having a second aspect ratio to display said image using a vertical sweep cycle, said vertical sweep cycle having a beginning point and an end point representing said top and bottom edge of said image, respectively; and

a video processing circuit to receive said decoded video signal and produce a flat gain response in the center of said vertical sweep cycle, with said gain decreasing towards said beginning point and said end point of said vertical sweep cycle.