Computer graphics processing and selective visual display system – Display driving control circuitry – Adjusting display pixel size or pixels per given area
Reexamination Certificate
2002-07-18
2004-10-05
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Display driving control circuitry
Adjusting display pixel size or pixels per given area
C345S213000, C345S214000
Reexamination Certificate
active
06801221
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scanning line interpolation equipment for interpolating scanning lines displayed by a video signal.
2. Description of the Background Art
A scanning line interpolation equipment interpolating scanning lines is employed for converting a video signal of an interlaced scanning system to a video signal of a progressive scanning system or increasing the number of scanning lines in the progressive scanning system.
Such a scanning line interpolation equipment calculates the value of a pixel (hereinafter referred to as an interpolated pixel) forming a scanning line (hereinafter referred to as an interpolated scanning line) to be created by interpolation on the basis of the values of pixels of upper and lower scanning lines.
In this case, it is proposed to calculate the value of the interpolated pixel with pixels vertically located with respect to the interpolated pixel in general and to calculate the value of the interpolated pixel with pixels obliquely located with respect to the interpolated pixel in an image having an oblique edge or an image having thin oblique lines. To this end, a correlation determination circuit determining a direction having high correlation in an image displayed by a video signal is employed.
The conventional correlation determination circuit detects the difference value between two vertical pixels and that between two oblique pixels about the interpolated pixel, for determining the angle of the direction having high correlation on the basis of the differences value. In such a method employing the difference value between two pixels, however, the angle may be falsely detected.
Therefore, it is proposed to calculate the value of the interpolated pixel with the vertically located pixels if the difference value between two pixels located in the determined direction is greater than a threshold while calculating the value of the interpolated pixel with the oblique pixels if the difference value between the two pixels located in the determined direction is less than the threshold.
In the aforementioned scanning line interpolation equipment, however, the value of the interpolated pixel is so dispersed that no smooth image can be obtained if the difference value between the two pixels located in the determined direction is approximate to the threshold.
Consider an image having an oblique edge as shown in FIG.
13
, for example. It is assumed that the values of two pixels
81
and
82
located above and under an interpolated pixel IN are “0” and “100” respectively, the values of a first pair of oblique pixels
83
and
84
are “0” and “100” respectively, and the values of a second pair of oblique pixels
85
and
86
are “80” and “120” respectively. It is also assumed that a threshold is “40”.
In this case, the difference value between the two pixels
81
and
82
located above and under the interpolated pixel IN is “100”, that between the first pair of oblique pixels
83
and
84
is “100” and that between the second pair of oblique pixels
85
and
86
is “40”, and hence the direction having high correlation is along a straight line connecting the pair of pixels
85
and
86
with each other. In this case, the difference value between the pair of pixels
85
and
86
is not more than the threshold, and hence the value of the interpolated pixel IN is calculated with the oblique pair of pixels
85
and
86
. For example, the average “100” of the pair of pixels
85
and
86
defines the value of the interpolated pixel IN.
If the value of the pixel
85
is “75”, however, the difference value between the pair of pixels
85
and
86
is greater than the threshold, and hence the value of the interpolated pixel IN is calculated with the two pixels
81
and
82
in the vertical direction. For example, the average “50” between the values of the two pixels
81
and
82
defines the value of the interpolated pixel IN.
Thus, it follows that the value of the interpolated pixel IN varies by “50” when the value of the pixel
85
varies merely by “5”. Consequently, no smooth image can be obtained.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a scanning line interpolation equipment capable of smoothly interpolating an image having an oblique edge.
A scanning line interpolation equipment according to an aspect of the present invention, interpolating a scanning line by calculating the value of a pixel to be interpolated on the basis of an input video signal, comprises first interpolation means calculating a first interpolated value by interpolation employing pixels of upper and lower scanning lines vertically located with respect to the pixel to be interpolated, input means inputting a signal indicating the direction of an image with respect to the pixel to be interpolated, difference calculation means calculating the difference value between the values of pixels of upper and lower scanning lines located in the direction indicated by the signal input by the input means with respect to the pixel to be interpolated, second interpolation means calculating a second interpolated value by interpolation employing the pixels of the upper and lower scanning lines located in the direction indicated by the signal input by the input means with respect to the pixel to be interpolated and interpolated value output means outputting the second interpolated value calculated by the second interpolation means as the value of the pixel to be interpolated when the difference value calculated by the difference calculation means is not more than a first value, outputting the first interpolated value calculated by the first interpolation means as the value of the pixel to be interpolated when the difference value calculated by the difference calculation means is not less than a second value greater than the first value, and calculating a third interpolated value by an operation employing the first interpolated value calculated by the first interpolation means and the second interpolated value calculated by the second interpolation means and outputting the third interpolated value as the value of the pixel to be interpolated when the difference value calculated by the difference calculation means is within the range between the first value and the second value.
In the scanning line interpolation equipment according to this aspect of the present invention, the first interpolation means calculates the first interpolated value by the interpolation employing the pixels of the upper and lower scanning lines vertically located with respect to the pixel to be interpolated. Further, the input means inputs the signal indicating the direction of the image with respect to the pixel to be interpolated, and the difference calculation means calculates the difference value between the values of the pixels of the upper and lower scanning lines located in the direction indicated by the input signal with respect to the pixel to be interpolated. The second interpolation means calculates the second interpolated value by the interpolation employing the pixels of the upper and lower scanning lines located in the direction indicated by the input signal with respect to the pixel to be interpolated. The interpolated value output means outputs the second interpolated value as the value of the pixel to be interpolated when the difference value is not more than the first value, outputs the first interpolated value as the value of the pixel to be interpolated when the difference value is in excess of the second value greater than the first value, and calculates the third interpolated value by the operation employing the first and second interpolated values and outputs the third interpolated value as the value of the pixel to be interpolated when the difference value is within the range between the first and second values.
Thus, the value of the pixel to be interpolated is calculated by the operation employing the first interpolated value calculated with the vertical pixels and the second interpolated value calculated with
Daigi Tomoaki
Kasahara Mitsuhiro
Kawamura Hideaki
Greenblum & Bernstein P.L.C.
Shankar Vijay
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