Television – Basic receiver with additional function – Multimode
Reexamination Certificate
1997-12-29
2001-07-31
Eisenzopf, Reinhard J. (Department: 2614)
Television
Basic receiver with additional function
Multimode
C348S443000, C348S448000, C348S449000, C348S458000, C348S556000
Reexamination Certificate
active
06268887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a preferred signal display system applicable to image display apparatuses, display devices or television sets for displaying a plurality of video signals having different scanning frequencies such as video signals of the NTSC system, output video signals from personal computers (hereinafter, alternatively referred to as PC signals) and the like. More particularly, the present invention further relates to a multimedia type personal computer capable of outputting both PC display signals (such as VGA signals) and interlace scanning signals (such as an NTSC signal) converted to double-speed (hereinafter, alternatively called “double-speed signal”), and also relates to an image display apparatus possibly connected thereto for displaying both the image of a PC display signal and a double-speed signal, i.e., capable of displaying such differing signals simultaneously as well as at differing times. Especially, the present invention relates to an image display apparatus that has a high picture quality and which is capable of displaying both the image of a PC display signal and a double-speed signal, and to a personal computer connected to it.
2. Description of Related Art
A personal computer of a so-called multimedia type having a capability of outputting both television signals (such as NTSC signals) and PC display signals has been sold in recent years. However, an incompatibility problem arises in that display signals for NTSC system television sets use a 15.75 kHz horizontal deflection frequency, for example, while display signals for personal computers generally use a 31.5 kHz or more horizontal deflection frequency, for example. In order to solve such incompatibility problem, a multimedia computer may have a tuner that can receive broadcast television signals such as NTSC signals, and further may have a double-speed converter for converting a signal demodulated by the tuner to a double-speed signal.
Despite the ability to display the NTSC signal, when-an interlace scanning signals such as an NTSC signal is converted to a double-speed signal, it was found that a vertical resolution of this image declines. Still further, in a case where a still image is displayed, vertical resolution degradation becomes visible. The following background is helpful in understanding the resolution degradation problem associated with changing (e.g., doubling) a scanning speed of a display signal (e.g., when changing such scanning speed substantially to match the scanning speed of a second type of display signal and/or display image apparatus being used for display).
More particularly, attention is directed to FIG.
3
and to
FIGS. 4
a
-
4
b
representing an odd-field display frame
70
and even-field display frame
80
, respectively, of an interlaced scanning arrangement. Such
FIGS. 4
a
-
4
b
will first be used to describe a normal interlacing operation and an exemplary resolution pattern (which has not experienced resolution degradation). More specifically, in
FIG. 4
a
's display frame
70
, assume for a moment that only solid scan lines
71
,
73
,
75
are present and represent original odd-field scan lines, and that such scan lines
71
,
73
,
75
are black lines. Similarly, in
FIG. 4
b
's display frame
80
, assume that only long/short dashed scan lines
81
,
83
,
85
are present and represent original even-field scan lines, and that such scan lines
81
,
83
,
85
are white lines. In normal interlacing (i.e., overlapping
FIG. 4
a
's odd-field display frame
70
onto
FIG. 4
b
's even-field display frame
80
), the odd-field and even-field scan lines would be combined in an interlaced fashion to result in a display frame having the following arrangement of scan lines from top to bottom: line
71
(black), line
81
(white), line
73
(black), line
83
(white), line
75
(black), line
85
(white), i.e., to result in an exemplary (alternating) black-white-black-white . . . pattern (not illustrated).
Next, FIG.
3
and
FIGS. 4
a
-
4
b
will be used for purposes of discussion to describe a speed-changed, but resolution degraded, interlacing operation. More specifically, assume again that solid scan lines
71
,
73
,
75
are present within
FIG. 4
a
and represent original black odd-field scan lines, and that long/short dashed scan lines
81
,
83
,
85
are present within
FIG. 4
b
and represent original white even-field scan lines. For scanning speed doubling (e.g., when changing such scanning speed substantially to match the scanning speed of a different display signal and/or display apparatus), an original display scanning line waveform
60
(
FIG. 3
) and its corresponding original horizontal period waveform
61
are each duplicated (via double-speed conversion arrangements described ahead) to become double-speed signals
62
and
63
, respectively, having horizontal scanning periods compressed to ½. More particularly, each single scanning line is duplicated into two scanning lines as illustrated in
FIGS. 4
a
-
4
b
.More specifically: original scanning line
71
now becomes dual scanning lines
71
,
72
; original scanning line
73
now becomes dual scanning lines
73
,
74
; . . . original scanning line
81
now becomes dual scanning lines
81
,
82
; original scanning line
83
now becomes dual scanning lines
83
,
84
; etc.
A problem, however, exists in that as a result of duplication, various odd-field scan lines and various even-field scan lines are now vertically positioned at positions within the odd-field display frame
70
and even-field display frame
80
, respectively, such that odd-field scan lines and even-field scan lines will substantially overlap each other during an interlacing operation. For example, white odd-field scan line
72
in a preceding interlace frame will be overlapped by black even-field scan line
81
in a succeeding interlace frame, and vice versa. Such alternating overlapping of white scan lines and black scan lines between frames will appear to the human eye as a grey scanning line. Thus resolution degradation is experienced in that, instead of seeing the expected exemplary (alternating) black-white-black-white . . . pattern, a series of grey scan lines appear as a pattern.
Discussion finally turns to a speed-change operation which avoids the resolution degradation problem, i.e., via vertical shifting of selected scan lines. More particularly, like the immediately preceding example, each single scanning line is duplicated to form two scanning lines as again illustrated in
FIGS. 4
a
-
4
b
.However, this time to avoid the overlapping and resultant resolution degradation problem, a further vertical shifting operation is applied to each duplicate scan line, such that each original scan line and its duplicate scan line are caused to overlap one another. For example, in
FIG. 4
a
, duplicate scan line
72
is vertically shifted (vector or arrow
77
) substantially to overlap original scan line
71
, using a one-half horizontal period waveform
64
(FIG.
3
). Similar discussion can be made with respect to the other shift arrows
78
-
79
and
86
-
87
. As a result thereof, when the
FIG. 4
a
odd-field display frame
70
is overlapped with the
FIG. 4
b
even-field display frame
80
, the result is the
FIG. 4
c
interlaced display frame
89
not having overlapped odd-field/even-field scan lines, and thus not experiencing a resolution degradation problem. More particularly, the interlaced display frame
89
has the following arrangement of scan lines from top to bottom: overlapped odd-field lines
71
,
72
(both black), overlapped even-field lines
81
,
82
(both white), overlapped odd-field lines
73
,
74
(both black), overlapped even-field lines
83
,
84
(both white), overlapped odd-field lines
75
,
76
(both black), even-field line
85
(white), i.e., the original and expected exemplary (alternating) black-white-black-white . . . pattern is maintained.
One technique for overcoming the resolution degradation problem is disclosed
Kabuto Nobuaki
Tsukahara Masahisa
Watanabe Toshimitsu
Antonelli Terry Stout & Kraus LLP
Eisenzopf Reinhard J.
Hitachi , Ltd.
Yenke Brian P.
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