Television – Image signal processing circuitry specific to television – Sweep expansion or reduction
Reexamination Certificate
1999-09-24
2001-11-27
Kostak, Victor R. (Department: 2711)
Television
Image signal processing circuitry specific to television
Sweep expansion or reduction
C348S377000, C348S173000, C348S445000
Reexamination Certificate
active
06323915
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to image devices in general. More particularly, the invention relates to a method and apparatus for enhancing a border area of a cathode ray tube (CRT) display used in an image display device such as a television.
BACKGROUND OF THE INVENTION
The presentation of moving images on a display has been a popular medium of communication for many years. As a result, many innovations have evolved to make movies and films capable of reproducing the visual and audible depth, robustness and acuity of the human senses. For example, digital image processing and communication techniques are capable of producing images and movies of exceptional high quality.
As with many industries, the evolution of technologies presents problems, particularly with respect to transitioning from an older technology to a newer technology. For example, in the wireless communications industry, much of the existing infrastructure and cellular telephones were designed to carry analog signals. Due to quality and capacity issues, digital systems and digital cellular telephones were designed. Since development of an entirely new digital system would take a number of years, however, an interim cellular telephone was developed that was capable of communicating using both analog and digital signals (sometimes referred to as “dual-mode” telephones).
The television industry is currently facing a similar problem. In particular, the television industry is presently transitioning from an existing video standard referred to as the National Television Systems Committee (NTSC) standard or the Electronic Industries Association (EIA) standard RS-170A developed in the late 1940s to the High Definition Television (HDTV) standard finalized in the early 1990s. A video signal “standard” specifically prescribes a video signal's synchronization timing, electrical voltage levels, and quality measures.
As a result, many television manufacturers are now developing televisions that are cable of displaying the present NTSC standard signals as well as the new HDTV standard signals. One key difference between these two standards, however, is the aspect ratio. The term “aspect ratio” refers to the dimensions of an image or picture which is calculated by dividing the image's horizontal width by its vertical height. In the present NTSC standard, the aspect ratio is a “4:3” aspect ratio, where 4 is the horizontal dimension and 3 is the vertical dimension. In other words, the horizontal dimension of the image is 1.33 times wider than the vertical dimension. By way of contrast, the HDTV standard calls for a “16:9” aspect ratio. When a 16:9 aspect picture is displayed on a 4:3 aspect ratio television, the horizontal width of the 16:9 aspect picture matches the horizontal width of the 4:3 aspect ratio television, but not the vertical height. Consequently, black bands appear at the top and bottom of the television screen. This is sometimes referred to as a “letterbox” effect, and is shown in FIG.
1
.
FIG. 1
is a picture of a 16:9 aspect ratio picture displayed on a 4:3 aspect ratio television display. Displaying a 16:9 aspect picture on a 4:3 aspect ratio television creates a problem referred to as CRT burning. This burning is caused by the phosphors of the CRT being active in the 16:9 portion (shown in white in FIG.
1
and denoted with number
106
), but not active in the border area (shown in black in FIG.
1
and denoted with numbers
102
). As the phosphors are activated they begin to age and produce less brightness. Thus, the phosphors in the active 16:9 portion begin to age at a rate that is faster than the inactive border area, causing a difference in brightness output that is most noticeable at the transition points (lines between white
106
and black
102
denoted by numbers
104
). If the 4:3 aspect ratio television is used to display only 16:9 aspect ratio signals, the burning at the transition points cannot be visually detected. If the television is used to display a 4:3 aspect ratio picture, after sufficient amount of time displaying a 16:9 aspect ratio picture, however, it is possible to visually detect a burn line (lines
104
) along the top and bottom edges of the 16:9 aspect ratio picture. This effect is shown in FIG.
2
.
FIG. 2
is a picture of CRT burn lines caused by displaying a 16:9 aspect ratio picture on a 4:3 aspect ratio television. As demonstrated in
FIG. 2
, when a 4:3 aspect ratio picture is once again displayed on the 4:3 aspect ratio television, a pair of noticeable burn lines
202
appear at the top and bottom edges of the previously displayed 16:9 aspect ratio picture. These noticeable horizontal burn lines
202
adversely effect picture quality and distract a viewer.
Another problem associated with displaying a 16:9 aspect ratio picture on a 4:3 aspect ratio display occurs when a 4:3 aspect ratio picture is once again displayed on the 4:3 aspect ratio television. More particularly, the border area created by the 16:9 aspect ratio picture is not active during the display of the 16:9 aspect ratio picture. Because the border area is inactive, the phosphors are not aging at the same rate as the area used for the 16:9 aspect ratio picture. Consequently, when a 4:3 aspect ratio picture is once again displayed on the 4:3 aspect ratio screen, the border area looks brighter than the area used for the 16:9 aspect ratio picture.
At least one previous attempt has been made to solve the CRT burning problem. This attempt, however, is less than satisfactory for a number of reasons. For example, the counter measure attempts to avoid the CRT burning problem by using deflection waveforms to make the 16:9 aspect ratio picture cover the full 4:3 aspect ratio screen. In other words, the 16:9 aspect ratio picture is vertically stretched to cover the black bands at the top and bottom of the 4:3 aspect ratio television display. If the deflection is linear, however, objects in the 16:9 aspect ratio picture appear disproportionately taller than normal. If the deflection is non-linear, shape distortion occurs in the 16:9 aspect ratio picture. Thus, in both instances, the displayed image is noticeably distorted or different from the original image.
In view of the foregoing, it can be appreciated that a substantial need exists for a method and apparatus capable of displaying a 16:9 aspect ratio signal on a 4:3 aspect ratio television that minimizes CRT burning without distorting the 16:9 aspect ratio picture.
SUMMARY OF THE INVENTION
One embodiment of the invention comprises a method and apparatus for displaying a video signal. A first video signal is received representing a first image having a first aspect ratio. The first image is displayed on a display having a second aspect ratio and a display area, with the first image having a smaller area than the display area forming a border area. A second video signal is received representing a second image having the second aspect ratio. A border modification signal is generated. The second image is displayed on the display with the border area modified in accordance with the border modification signal.
With these and other advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims and to the several drawings attached herein.
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Arnold David Scott
Kiga Hirohide
Marflak Thomas Adreon
Kostak Victor R.
Mayer Fortkort & Williams PC
Sony Corporation
Williams Esq. Karin L.
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