Television – Format conversion – Line doublers type
Reexamination Certificate
1998-10-13
2001-09-11
Eisenzopf, Reinhard J. (Department: 2614)
Television
Format conversion
Line doublers type
C348S441000, C348S452000, C348S458000, C348S459000
Reexamination Certificate
active
06288745
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scanning line interpolation device. More particularly, the invention relates to a scanning line interpolation device for converting an interlace signal into a non-interlace signal in image signal processing in a non-interlaced scanning CRT, a video printer, a matrix-type display device such as a plasma display, a liquid crystal display, an LED display, a field emission display, and a digital micromirror device, and the like.
2. Description of the Background Art
FIG. 15
shows a conventional scanning line interpolation device disclosed in Japanese Patent Application Laid-Open No. P05-68240A (1993). In
FIG. 15
, the reference numeral
101
designates a delay circuit for delaying input image data by a predetermined time interval;
102
designates a correlation judgement portion for judging the correlation between images;
103
designates a threshold value calculation circuit;
104
designates a binarization circuit;
105
designates an interpolation direction judgement circuit;
106
designates an interpolation calculation portion;
107
designates a selection circuit;
108
designates an adder;
109
designates a multiplier; the reference character Pi designates input image data; a, c, e, f, h and j designate reference pixel data extracted by the delay circuit
101
and required for interpolation; SH designates a threshold value; l, m, n, x, y and z designate results of binarization of the extracted pixels; IS designates interpolation direction selection data; PU and PD designate data selected for the interpolation; and Po designates an interpolation result.
The operation of the device shown in
FIG. 15
will be described below. The two-dimensional image data Pi quantized using a predetermined sampling frequency is inputted to the delay circuit
101
which in turn extracts the reference pixels a, c, e, f, h and j. The reference pixels extracted by the delay circuit
101
are inputted to the threshold value calculation circuit
103
, the binarization circuit
104
, and the selection circuit
107
. The threshold value calculation circuit
103
calculates the threshold value data SH to output the threshold value data SH to the binarization circuit
104
. The binarization circuit
104
compares each of the reference pixels with the threshold value SH. If each of the reference pixels is not less than the threshold value, the binarization circuit
104
outputs “1.” If each of the reference pixels is less than the threshold value, the binarization circuit
104
outputs “0.” The binary data l, m, n, x, y and z corresponding respectively to the reference pixels a, c, e, f, h and j are inputted to the interpolation direction judgement circuit
105
for use as the addresses of an interpolation table in the interpolation direction judgement circuit
105
. Then, the interpolation direction selection data IS is outputted from the interpolation direction judgement circuit
105
. The selection circuit
107
selects one of vertical interpolation, right slant interpolation, and left slant interpolation, depending on the interpolation direction selection data IS. For the vertical interpolation, the selection circuit
107
selects the reference pixels c and h, and the adder
108
adds the reference pixels c and h together. Then, the multiplier
109
multiplies the sum of the reference pixels c and h by ½ to output the interpolation result Po. The selection circuit
107
selects the reference pixels e and f for the right slant interpolation, and selects the reference pixels a and j for the left slant interpolation.
For the interpolation of an uppermost or lowermost scanning line, the reference pixels in a single reference line are directly used for the interpolation or the reference pixels in the reference line which should be present on opposite side from the single reference line are set to “0”.
FIG. 16
shows the relationship between an intended pixel Po located in an interpolation pixel position and the reference pixels. The circles of
FIG. 16
denote the reference pixels, and the crosses denote interpolation pixels.
The interpolation table illustrated in
FIG. 17
shows the relationship between the interpolation directions and the binary data l, m, n, x, y and z. The open circles “◯” of
FIG. 17
represent binary data “0”; the solid circles “•” represent binary data “1”; the vertical lines “|” represent the vertical interpolation; the slashes “/” represent the right slant interpolation; and the backslashes “\” represent the left slant interpolation.
The conventional scanning line interpolation device constructed as above described always performs a function as a vertical low pass filter upon the input image, thus deteriorating high-frequency components and providing only an interpolation image with fuzzy horizontal edges. Additionally, as a result of the interpolation of a comer part at which horizontal and vertical edges intersect, the comer part is rounded off since the slant interpolation is selected in accordance with the interpolation table. In particular, the interpolation performed on image data with sharp edges such as the image data of characters and graphics results in conspicuous edge fuzziness and significantly reduced interpolation image qualities.
FIG. 18
shows a result of the interpolation performed by the conventional scanning line interpolation device. For the interpolation of horizontal edges, the conventional scanning line interpolation device always selects the vertical interpolation to provide median values as the interpolation values. For the interpolation of comer parts, the conventional scanning line interpolation device always selects the slant interpolation to provide white data as the interpolation values. The values in the interpolation line after the interpolation completely differ from those before the interpolation. In visual terms, the resultant image has fuzzy horizontal edges and rounded corners.
For example, image data “T” (ID
1
) as shown in
FIG. 19A
is contemplated which is comprised of first- and second-field image data ID
2
and ID
3
shown in
FIGS. 19B and 19C
, respectively. With such a configuration, when in-field interpolation is performed upon the first-field image data, interpolated image data ID
4
has a joint part of “T” which is rounded off by means of an interpolation table t
1
and a stem end to which white data is provided by means of an interpolation table t
2
, as shown in FIG.
19
B. Likewise, the in-field interpolation performed upon the second-field image data designated by ID
3
of
FIG. 19C
provides interpolated image data ID
5
.
SUMMARY OF THE INVENTION
A first aspect of the present invention is intended for a scanning line interpolation device for converting an interlace signal into a non-interlace signal. According to the present invention, the scanning line interpolation device comprises: storage means for storing preceding-field image data; reference pixel data extraction means for extracting a plurality of reference pixel data from current-field image data and the preceding-field image data provided from the storage means, the plurality of reference pixel data including pixel data located in an interpolation pixel position which is not present in the current-field image data and in positions surrounding the interpolation pixel position; inter-field motion detection means for detecting whether or not there is a motion of an image between a preceding field and a current field, based on the plurality of reference pixel data; in-field interpolation data calculation means for calculating in-field interpolation data associated with the interpolation pixel position based on pixel data in the current field among the plurality of reference pixel data; and interpolation pixel selection means operative to select the in-field interpolation data when the inter-field motion detection means detects that there is a motion, and to select pixel data in the preceding-field image data which is located in the interpolation pixe
Arimoto Hironobu
Okuno Yoshiaki
Someya Jun
Desir Jean W.
Eisenzopf Reinhard J.
Mitsubishi Denki & Kabushiki Kaisha
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