Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1997-06-05
2001-09-25
Jankus, Almis R. (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S100000, C345S208000
Reexamination Certificate
active
06295042
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a display apparatus using a liquid crystal, an electrochromic material, an electroluminescent material, plasma, micromirrors, etc., particularly a display apparatus including a matrix electrode structure comprising a group of scanning electrodes and a group of data electrodes.
FIG. 11
is a schematic illustration of a display apparatus
16
having a matrix electrode structure. The display apparatus
16
includes a display panel
21
which in turn includes a matrix electrode structure composed of scanning electrodes
18
and data electrodes
19
intersecting the scanning electrodes
18
. The scanning electrodes
18
are connected to a scanning signal application circuit
15
, and the data electrodes
19
are connected to a data signal application circuit
17
.
Ordinarily, the scanning signal application circuit
15
sequentially selects one scanning electrode and supplies a scanning selection signal thereto at a time while simultaneously supplying a scanning non-selection signal to the remaining scanning electrodes. On the other hand, the data signal application circuit
17
supplies to the data electrodes with data signals for determining display states of respective pixels each formed at each intersection of the scanning electrodes and the data electrodes in synchronism with the scanning selection signal.
Hereinbelow, an example description will be presented regarding a liquid crystal display apparatus.
In a liquid crystal apparatus including a liquid crystal display unit (liquid crystal display panel)
21
including a matrix electrode structure as shown in
FIG. 11
, the liquid crystal at each pixel is directly driven by a drive signal waveform applied to associated electrodes
18
and
19
in a display panel
21
from a scanning signal application circuit
15
and a data signal application circuit
17
inclusively represented as a drive circuit
20
(which more appropriately represents a scanning signal application circuit
15
) as shown in FIG.
12
. Now, a drive signal waveform applied to a drive circuit-side end as represented by a point A in
FIG. 12
of an electrode (
18
) in the display panel
21
is a rising rectangular wave as shown at WFA in FIG.
13
. Such a rectangular wave may be regarded as a waveform having a high-frequency component at the rising portion.
Incidentally, one electrode (
18
) in a liquid crystal display panel
21
may be represented by an equivalent circuit comprising a number of resistances R each representing a resistance per unit length and a number of load resistances C each representing a load resistance per unit length. A circuit as represented by such an equivalent circuit may be regarded as having an impedance Z
0
calculated by the following equation:
Z
0
=
R
2
+
R
2
4
+
R
2
π
f
C
The transfer ratio A is calculated by the following equation:
A
=
1
-
R
R
2
+
R
2
4
+
R
2
π
f
C
Accordingly, an electrode of the liquid crystal display panel may be regarded as having a frequency characteristic of transfer ratio (a frequency-dependent transfer ratio) as shown in FIG.
15
and may be regarded as equivalent to a low-pass filter having a cut-off frequency (=¼&pgr;RC) determined by C and R.
When each electrode of the liquid crystal display panel
21
having such a frequency characteristic is supplied with a drive signal for direct driving having a frequency component exceeding the cut-off frequency, the frequency component exceeding the cut-off frequency is gradually attenuated the further away the drive signal is from the input terminal, so that only a frequency component below the cut-off frequency (=¼&pgr;RC shown in
FIG. 15
) required for display a picture or a character is transmitted to an opposite (or remote) end of the electrode in the liquid crystal display panel.
As a result, a drive signal waveform applied to a remote terminal of the electrode as represented by a point B in
FIG. 12
becomes a “dull” drive signal waveform from which a frequency component exceeding the cut-off frequency has been removed as shown at WFB in FIG.
13
. Such a waveform may also be called a “slowly rising waveform”.
However, in a liquid crystal apparatus including a liquid crystal display panel to be driven for display operation by application of a drive signal waveform, in case where a rectangular drive signal waveform regarded as including a frequency component exceeding the cut-off frequency at its rising portion and falling portion is applied to an electrode of a liquid crystal display panel for driving, a transient large current TCA (
FIG. 13
) is flowed at the time of falling and rising of the rectangular wave due to a frequency component exceeding the cut-off frequency contained in the rising or falling portion of the rectangular wave.
Such a transient large current is liable to cause difficulties, such as a fluctuation in power supply potential or ground potential of the liquid crystal apparatus, occurrence of radiation noise, heat-generation at the liquid crystal display panel, and an increase of current consumption.
According to the inventor's knowledge, such a phenomenon can be practically free of problems in cases where the display panel is small in size, but can cause difficulties, leading to a lower reliability, such as a malfunction of the apparatus and a lower picture display quality, in a case of a high-definition and large-size display panel of 38 cm or larger in diagonal size having 1280×1024 or more pixels.
SUMMARY OF THE INVENTION
Accordingly, a principal object of the present invention is to provide a display apparatus wherein a drive signal waveform having a frequency component below a prescribed frequency can be selectively applied to electrodes in the display unit.
According to the present invention, there is provided a display apparatus, comprising:
a display unit including electrodes arranged in a matrix form,
a circuit for generating a signal waveform applied to the electrodes of the display unit, and
a low-pass filter for removing a frequency component exceeding a prescribed frequency from the signal waveform to inlet ends of the electrodes in the display unit.
As a frequency component exceeding a prescribed frequency is removed from a drive signal waveform supplied to matrix electrodes of the display unit from a drive circuit, a drive signal selectively containing a frequency component below the prescribed frequency can be applied to the electrodes of the display unit, whereby the occurrence of a transient large current liable to occur at pixels close to the inlet ends of the electrodes can be effectively suppressed.
According to another aspect of the present invention, there is provided a display apparatus, comprising:
a display unit including electrodes arranged in a matrix form, and
drive means for generating a rectangular signal waveform having a rising portion and a falling portion, superposing split pulses with the rising portion and the falling portion of the rectangular signal waveform and integrating the rectangular signal waveform superposed with the split pulses so as to provide a drive signal having moderately sloped rising and falling portions and supply the drive signal to inlet ends of the electrodes in the display unit.
According to a further aspect of the present invention, there is provided a liquid crystal display apparatus, comprising:
a liquid crystal display unit including waveforms arranged in a matrix form, and a liquid crystal disposed so as to form pixels in combination with the electrodes,
rectangular signal waveform-generating means for generating a rectangular signal waveform having a rising portion and a falling portion,
split pulse-generating means for generating split pulses,
superposing means for superposing the split pulses with the rising and falling portions of the rectangular signal waveform, and
integration means for integrating the rectangular signal waveform having rising an falling portions sup
Awad Amr
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Jankus Almis R.
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