Method and apparatus for preventing display screen burn-in

• US 6,262,772 B1
• Filed: 11/23/1998
• Issued: 07/17/2001
• Est. Priority Date: 11/23/1998
• Status: Expired due to Fees

• Current Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Original Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Inventors: Shen, Richard C., Cavallerano, Alan
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Tran, Trang U.
• Application Number:
  US09/198,057
• Time in Patent Office: 967 Days
• Field of Search: 348/445, 348/458, 348/449, 348/913, 348/556, 348/558, 348/173, 348/469
• US Class Current: 348/445
• CPC Class Codes: H04N 7/0122 the input and the output signals having different aspect ratios
• CPC Class Codes: Y10S 348/913 Letterbox, e.g. display 16:9 aspect ratio image on 4:3 screen

Abstract

When viewing a 4:3 aspect ratio image on a widescreen display, disturbing black bands appear to the left and right of the displayed image. Similarly, when viewing a letterbox image on a 4:3 aspect ratio display, disturbing black bands appear above and below the displayed image. These black bands result in uneven ageing of the phosphors in the display screen. An apparatus is provided which detects these black bands and automatically expands the image in the appropriate direction such that these black bands are automatically eliminated.

Claims

1. An apparatus for automatically eliminating horizontal and vertical black bands from the border of a displayed video image, said apparatus comprising:

first means for performing a first detection of the occurrence of a black level in an input video signal for at least n lines at the beginning and end of a frame in the video signal;

second means for performing a second detection of the occurrence of a black level in an input video signal for at least m pixels at the beginning and end of each line in the video signal;

means for vertically up-converting the lines in the video signal in dependence on said first detection; and

means for horizontally expanding the lines in the video signal in dependence on said detection, wherein said apparatus further comprises;

an input for receiving a video signal;

a demultiplexer having an input coupled to said input, a first output coupled to said vertically up-converting means, a second output coupled to said horizontal expanding means, a third output, and a control input;

a multiplexer having a first input coupled to an output of said vertically up-converting means, a second input coupled to an output of said horizontal expanding means, a third input coupled to the third output of said de-multiplexer, an output and a control input;

an output coupled to an output of said multiplexer for supplying an output video signal in which any black bands are suppressed; and

a black level detector comprising said first and second detection means, said black level detector having an input coupled to said input of said apparatus and an output coupled to the control inputs of said demultiplexer and said multiplexer, wherein said black level detector switches said demultiplexer and said multiplexer to said first output and said first input, respectively, on said first detection, to said second output and said first input, respectively, on said second detection, and otherwise to said third output and said third input, respectively.

2. The apparatus as claimed in claim 7, wherein said first means and said second means perform said first and second detections simultaneously.

3. The apparatus as claimed in claim 7, wherein said first means and said second means perform said first and second detections for a predetermined number of consecutive frames.

4. The apparatus as claimed in claim 7, wherein n=20.

5. The apparatus as claimed in claim 7, wherein n=20.