 |
Claims  |
|
|
We claim:
1. A method for displaying an image having more than two different
brightness levels in a line sequential scanning type of a binary image
display device in which an image is displayed by sequentially activating
scan lines one by one, and in which one complete display image is formed
by at least a plurality of continuous frames or fields, said display
device having an orthogonal array of column and row electrodes, pixels
being formed at intersections in said orthogonal array, each of said
electrodes having an individually associated driver, said method
comprising the steps of:
(a) changing a brightness of the whole display screen in units of one frame
or field during each one period corresponding to one frame or field, and
(b) logically multiplying all column drive video signals which are to be
applied to a series of column drivers with a selected one of a plurality
of brightness level signals, said logical multiplication being with the
same selected one of the plurality of brightness level signals;
(c) applying said signals which are logically multiplied in step (b)
through a series of column drivers to corresponding column electrodes of
the display device, respectively; and
(d) applying said signals which are logically multiplied in step (b)
through a series of row drivers to each of all row so that the respective
logically multiplied row drive video signals are applied through the
series of row drivers to corresponding row electrodes of the display
device, respectively, whereby each display pixel can have a brightness
level which is respectively defined by combinations of brightness levels
given by an input display data and the selected one of said plurality of
brightness levels of the whole of the display screen.
2. A method claimed in claim 1, wherein said plurality of brightness level
signals are composed of at least two blanking signals having different
inactive periods.
3. A method in claim 1 wherein said plurality of brightness level signals
are composed of at least two toggle pulses having frequencies which are
different from each other.
4. A circuit for displaying an image having more than two different
brightness levels in a line sequential scanning type of binary image
display device in which an image is displayed by sequentially activating
scan lines one by one, one complete display image being formed by at least
first and second continuous alternating frames or fields of display data,
the image display device having a plurality of row electrodes and a
plurality of column electrodes intersecting with one another in a
two-dimensional plane so that each intersecting point between the row
electrodes and the column electrodes forms one pixel, said circuit
comprising a data selector connected to receive first and second
continuous alternating frames or fields of display data, respectively, a
counter connected to receive a vertical synchronism signal for counting
received vertical synchronizing signals and for generating a switching
signal at each vertical synchronizing signal, the switching signal being
supplied to the data selector so that the data selector responds to the
switching signal to alternately select either the first or the second
continuous frames or field of display data, the selection being made
responsive to an occurrence of each frame or field, a shift register
connected to serially receive the display data outputted from the data
selector in synchronism with a clock pulse so as to accumulate one frame
or field of display data, a latch circuit having a plurality of parallel
outputs and being coupled to receive in parallel the one frame or field of
display data held in the shift register and to hold the received frame or
field of display data during each horizontal scan period, a plurality of
column drivers each having an input connected through an AND gate circuit
to a corresponding one of said parallel outputs of the latch circuit and
also having an output connected to a corresponding column electrode of the
display device, a row signal generator connected to receive a horizontal
synchronizing signal and having a plurality of parallel outputs, a
plurality of row drivers each having an input connected through an AND
gate to a corresponding one of said parallel outputs of said row signal
generator and having an output connected to a corresponding row of
electrode of the display device, the row generator responding to the
horizontal synchronizing signal so as to selectively activate only one of
the parallel outputs for each one horizontal scan, and a controller
connected to receive a count value of the counter for controlling the
opening and closing of the AND gate circuits connected to said column
driver and said row driver during each horizontal scan period in a manner
such that in at least each two continuous frames or fields an open period
of the AND gate circuits connected to said column driver and said row
driver for one of the two continuous frames or fields is different from an
open period of the gate circuits connected to said column driver and said
row driver for the other of the two continuous frames or fields, the
controller being composed of a blanking signal generator for alternately
generating a first blanking signal for the first frame or field of display
data and a second blanking signal for the second frame or field of display
data, the first and second blanking signals having active periods which
are different from each other, and each first and second blanking signals
being generated in synchronism with the horizontal scan signal and for
every horizontal scan period.
5. A circuit for displaying an image having more than two different
brightness levels in a line sequential scanning type of binary image
display device in which an image is displayed by sequentially activating
scan lines one by one, one complete display image being formed by at least
first and second continuous alternating frames or fields of display data,
the image display device having a plurality of row electrodes and a
plurality of column electrodes intersecting with one another in a
two-dimensional plane so that each intersecting point between the row
electrodes and the column electrodes forms one pixel, said circuit
comprising a data selector connected to receive first and second
continuous alternating frames or fields of display data, respectively, a
counter connected to receive a vertical synchronism signal for counting
received vertical synchronizing signals and for generating a switching
signal at each vertical synchronizing signal, the switching signal being
supplied to the data selector so that the data selector responds to the
switching signal to alternately select either the first or the second
continuous frames or field of display data, the selection being made
responsive to an occurrence of each frame or field, a shift register
connected to serially receive the display data outputted from the data
selector in synchronism with a clock pulse so as to accumulate one frame
or field of display data, a latch circuit having a plurality of parallel
outputs and being coupled to receive in parallel the one frame or field of
display data held in the shift register and to hold the received frame or
field of display data during each horizontal scan period, a plurality of
column drivers each having an input connected through an AND gate circuit
to a corresponding one of said parallel outputs of the latch circuit and
also having an output connected to a corresponding column electrode of the
display device, a row signal generator connected to receive a horizontal
synchronizing signal and having a plurality of parallel outputs, a
plurality of row drivers each having an input connected through an AND
gate to a corresponding one of said parallel outputs of said row signal
generator and having an output connected to a corresponding row electrode
of the display device, the row generator responding to the horizontal
synchronizing signal so as to selectively activate only one of the
parallel outputs for each one horizontal scan, and a controller connected
to receive a count value of the counter for controlling the opening and
closing of the AND gate circuits connected to said column driver and said
row driver during each horizontal scan period in a manner such that in at
least each two continuous frames or fields an open period of the AND gate
circuits for one of the two continuous frames or fields is different from
an open period of the AND gate circuits connected to said column driver
and said row driver for the other of the two continuous frames or fields,
the controller being composed of a toggle pulse generator for alternately
generating a first toggle pulse for the first frame or field of display
data and a second toggle pulse for the second frame or field of display
data, the first and second toggle pulses having frequencies which are
different from each other, and each first and second toggle pulses being
generated in synchronism with the horizontal scan signal and for every
horizontal scan period. |
|
 |
|
 |
Claims |
|
|
|
Description |
|
|
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a multilevel image display method, and
more specifically to a method and system for displaying a multilevel image
by using a binary display apparatus.
2. Description of related art
Drive circuits for two-dimensional display panels such as plasma display
panels, liquid crystal display panels, and LED (light emitting diode)
display panels are constructed to selectively drive, on the basis of a
given display data, a plurality of row electrodes and a plurality of
column electrodes which are arranged orthogonal to each other.
FIG. 1 shows a block diagram of one conventional typical drive circuit for
the two-dimensional display panel. The shown circuit includes a shift
register 10 having a serial input connected to a data input port 12 so
that a display data D is serially inputted through the input port 12 to
the shift register 10 in synchronism with a clock pulse CK, so that the
display data corresponding to one horizontal line or row is accumulated in
the shift register 10. The shift register 12 having parallel outputs
connected to a latch circuit 14, so that the display data of one
horizontal line or row accumulated in the shift register 10 is transferred
in parallel to and latched by the latch circuit 14 in synchronism with a
horizontal scan or synchronism signal Hs and held in the latch circuit 14
during each one horizontal scan period. Each bit of the latch circuit 14
is connected to an input of a corresponding column driver 16, which
applies or does not apply a voltage to a corresponding column electrodes
18 of a display panel 20 in accordance with a binary value held in the
corresponding bit of the latch circuit 14.
The shown drive circuit also includes a row signal generator 22 connected
to receive the horizontal scan or synchronism signal Hs and having a
plurality of parallel outputs, which are connected through row drivers 24
to corresponding row electrodes 26 of the display panel 20. Thus, the row
signal generator 22 responds to the horizontal scan or synchronism signal
Hs so as to selectively activate only one of the parallel outputs for each
one horizontal scan period so that only the row driver connected to the
activated output of the row signal generator 22 applies a voltage to the
corresponding one row electrode.
With the arrangement as mentioned above, display data D is inputted through
the input port 12 to the shift register 10 in synchronism with the clock
pulse CK so that the display data D corresponding to one horizontal scan
period or line is accumulated in the shift register 10. The accumulated
display data of one horizontal scan line is latched to the latch circuit
14 in synchronism with the horizontal scan signal Hs. For a next
horizontal scan period, each of the column drivers 16 connected to the
latch circuit 14 applies a voltage corresponding to the binary value held
in the corresponding bit of the latch circuit 14, to the corresponding
column electrode 18 of the display panel. On the other hand, the row
signal generator 22 sequentially activates the row electrodes through the
row drivers 24, one electrode by one electrode, in synchronism with the
horizontal scan signal Hs. As a result, of intersecting points 28 between
the activated row electrode 26 and all the column electrodes 18,
intersecting points on column electrodes corresponding to binary display
data of "1" is fired by a potential difference between the voltage applied
to the column electrodes and the voltage applied to the activated row
electrode. However, intersecting points on column electrodes corresponding
to binary display data of "0" is not fired since these intersecting points
are applied with only the voltage applied to the activated row electrode.
Thus, an image is indicated on the display panel in accordance with the
input display data D.
In the above mentioned display system, however, the display panel is of the
binary display type so that each intersecting point (display pixel or dot)
between the row electrodes and the column electrodes is simply fired in an
ON/OFF manner by the associated drivers in accordance with the input
display data. In other words, it is not possible to modify the brightness
of the display pixel or dot, and therefore, a displayed image or picture
having a multilevel brightness cannot be obtained.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a display
method and system which has overcome the above mentioned defect of the
conventional one.
Another object of the present invention is to provide a display method and
system which can realize a multilevel brightness image display while using
a binary display device.
The above and other objects of the present invention are achieved in
accordance with the present invention by a method for displaying an image
in a multilevel manner by using an image display device in which an image
is displayed by sequentially activating scan lines one by one, and one
complete display image is formed by at least a plurality of continuous
frames or fields, comprising the step of changing a brightness of the
whole of the display screen in units of one frame or field, so that each
display pixel can have brightness levels which are respectively defined by
combinations of brightness levels given by an input display data and
brightness levels of the whole of the display screen.
Even in a binary image display device, the brightness of the whole of the
display screen can be easily modified or changed. Therefore, as mentioned
above, if the brightness of the whole of the display screen is changed in
units of one frame or field, the display pixels or dots can have
brightness levels which are defined by not only the brightness levels
given by an input display data but also by the brightness levels of the
whole of the display screen. Thus, one complete displayed image formed by
at least a plurality of continuous frames or fields can be indicated with
a brightness.
According to another aspect of the present invention, there is provided a
circuit for driving, in a multilevel manner, a binary image display device
in which an image is displayed by sequentially activating scan lines one
by one, and one complete display image is formed by at least first and
second continuous alternating frames or fields of display data, the image
display device having a plurality of row electrodes and a plurality of
column electrodes intersecting to one another in a two-dimensional plane
so that each of intersecting points between the row electrodes and the
column electrodes froms one pixel, comprising a data selector connected to
receive the first and second continuous alternating frames or fields of
display data, respectively, a counter connected to receive a vertical
synchronism signal for counting the received vertical synchronism signal
and for generating a switching signal at each vertical synchronism signal,
the switching signal being supplied to the data selector so that the data
selector responds to the switching signal to alternately select the first
and second continuous frames or field of display data at each frame or
field, a shift register connected to serially receive the display data
outputted from the data selector in synchronism with a clock pulse so as
to accumulate one frame or field of display data, a latch circuit coupled
to receive in parallel the one frame or field of display data held in the
shift register and to hold the received one frame or field of display data
during each horizontal scan period, a plurality of column drivers each
having an input connected through a gate circuit to one of parallel
outputs of the latch circuit and also having an output connected to a
corresponding one of the column electrodes of the display device, a row
signal generator connected to receive a horizontal synchronism signal and
having a plurality of parallel outputs, which are connected through row
drivers to corresponding row electrodes of the display device, the row
signal generator responding to the horizontal synchronism signal so as to
selectively activate only one of the parallel outputs for each one
horizontal scan, and a controller connected to receive a count value of
the counter for controlling the open and close of the gate circuits during
each horizontal scan period in such a manner that in at least each two
continuous frames or fields, a open period of the gate circuits for one of
the two continuous frames or fields is different from that of the gate
circuits for the other of the two continuous frames or fields.
The above and other objects, features and advantages of the present
invention will be apparent from the following description of preferred
embodiments of the invention with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of one conventional typical drive circuit for the
two-dimensional display panel;
FIG. 2 is a diagram similar to FIG. 1, but showing one embodiment of the
drive circuit for the two-dimensional display panel in accordance with the
present invention;
FIG. 3 is a waveform diagram illustrating an operation of the circuit shown
in FIG. 2; and
FIG. 4 is a diagram similar to FIG. 1, but showing another embodiment of
the drive circuit for the two-dimensional display panel in accordance with
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 2, there is shown a diagram of one embodiment of the
drive circuit for the two-dimensional display panel in accordance with the
present invention. The shown circuit comprises a data selector 30 having
two inputs connected to a pair of data input ports 32 and 34,
respectively. The input port 32 and 34 are supplied with two continuous
frame (or fields) of display data DA and DB, respectively. Namely, each
set of two continuous frames of display data DA and DB will form one
complete display image. Furthermore, there is provided a counter 36
connected to receive a vertical synchronism signal Vs. The counter 36
counts the received vertical synchronism signal Vs for generating a
switching signal 38 at each vertical synchronism signal Vs, namely at each
time the frame is changed. Thus, the data selector 30 responds to the
switching signal 38 to alternately select the two continuous frames of
display data DA and DB at each frame (or field). The display data
outputted from the data selector 30 is inputted to a serial input of a
shift register 40 and sequentially accumulated in the shift register 40 in
synchronism with a clock pulse CK. Thus, the display data DA or DB
corresponding to one horizontal line or row is accumulated in the shift
register 40. The shift register 40 having parallel outputs connected to a
latch circuit 44, so that the display data of one horizontal line or row
held in the shift register 40 is transferred in parallel to and latched by
the latch circuit 44 in synchronism with the horizontal scan or
synchronism signal Hs and held in the latch circuit 44 during a one
horizontal scan period. Each bit of the latch circuit 44 is connected
through an AND gate 46 to an input of a corresponding column driver 48,
which applies or does not apply a voltage to a corresponding column
electrodes 50 of a display panel 52 in accordance with a binary value held
in the corresponding bit of the latch circuit 44.
The shown drive circuit also includes a row signal generator 54 connected
to receive the horizontal synchronism or scan signal Hs and having a
plurality of parallel outputs, which are connected through AND gates 56
and row drivers 58 to corresponding row electrodes 60 of the display panel
52. Thus, the row signal generator 54 responds to the horizontal
synchronism or scan signal Hs so as to selectively activate only one of
the parallel outputs for each one horizontal scan so that only the row
driver connected to the activated output of the row signal generator 54
applies a voltage to the corresponding one row electrode.
Furthermore, a count output of the counter 36 is supplied to a blanking
signal generator 62 in synchronism with the horizontal scan signal Hs.
This blanking signal generator 62 operates to generate a brightness
modification signal on the basis of a count value of the counter 36
supplied in synchronism with each horizontal scan signal Hs. This signal
will be called a "blanking signal" hereinafter, since the shown embodiment
is intended to change the brightness of the whole of the display screen by
controlling a period during which a display pixel is not fired, namely, a
pixel non-firing period. This period will be called a "blanking period".
This blanking signal 64 is applied to the remaining input of each of the
AND gates 46 and 56, so that the passage of the display data signal and
the row selection signal is controlled by these AND gates 46 and 56.
With the above mentioned embodiment, at each time the vertical synchronism
signal Vs is applied to the counter 36, the counter 36 counts vertical
synchronism signal Vs. In this embodiment, it is sufficient if the counter
can take two states of "0" and "1", and therefore, the counter 36 can be
formed by using a flipflop circuit. When the output of the counter 36 is
"1" indicative of an odd frame, the data selector 30 selects the display
data DA, and on the other hand, when the output of the counter 36 is "0"
indicative of an even frame, the data selector 30 selects the display data
DB. The selected display data of one horizontal row or line is
sequentially written and accumulated into the shift register 40 in
synchronism with the clock CK for one horizontal scan period. The display
data accumulated in the shift register is transferred and latched into the
latch circuit 44 in synchronism with a next horizontal scan signal Hs.
The count value of the counter 36 is outputted to the blanking signal
generator 62 in synchronism with each horizontal scan signal Hs, and the
blanking signal generator 62 generates the blanking signal 64 as shown in
FIG. 3. For example, when the count value of the counter 36 is "1"
indicative of the odd frame, the blanking signal generator 62 generates a
blanking signal which gives a blanking period of 50% in each one
horizontal scan period. On the other hand, when the count value of the
counter 36 is "0" indicative of the even frame, the blanking signal
generator 62 generates a blanking signal which gives a blanking period of
0% in each one horizontal scan period. In the shown embodiment, namely,
the display data DA corresponds to the 50% blanking period, and the
display data DB corresponds to the 0% blanking period. As mentioned
hereinbefore, one complete image or picture is formed by two frames of
image, which are formed by one pair of the display data DA and the display
data DB.
Here, assuming that the blanking period is 50% in one vertical synchronism
or scan period for the display data DA, and the blanking period is 0% in a
next vertical synchronism or scan period for the display data DB, the
blanking period of 50% and the blanking period of 0% will alternately
appear in a sequence of vertical scan periods. In this case, if both of
the display data DA and the display data DB are a firing data, the
displayed image will have a maximum brightness. If the display data DA is
a non-firing data and the display data DB is a firing data, the displayed
image will have a second brightness which is lower than maximum brightness
but higher than two levels of brightness explained hereinafter. If the
display data DA is a firing data and the display data DB is a non-firing
data, the displayed image will have a third brightness which is lower than
the second brightness. If both of the display data DA and the display data
DB are a non-firing data, the displayed image will have a minimum or
darkest brightness. Thus, four levels of brightness can be obtained.
Therefore, assuming that the blanking period for the data DA is .alpha. %
and the blanking period for the data DB is .beta. % and .alpha.>.beta.,
four levels of brightness modulation can be obtained as shown in the
following table:
______________________________________
Data DA Data DB Modulation Rate
______________________________________
(1) non-firing
non-firing
0%
(2) firing non-firing
##STR1##
(3) non-firing
firing
##STR2##
(4) firing firing 100%
______________________________________
In the above mentioned embodiment, it is set that .alpha.=50% and 62 =0%,
and therefore, the brightness modulatio rate will be 0% in the first case
(1) of the above table, 33.3% in the second case (2), 66.6% in the third
case (3) and 100% in the fourth case (4).
Incidentally, in the above mentioned embodiment, the brightness has been
modulated with four different levels. However, if two or more different
blanking signals are generated, it is possible to obtain more different
levels of brightness.
The embodiment shown in FIG. 2 can be applied for driving a liquid crystal
display panel, an LED display panel and an EL (electroluminescence)
display panel.
Referring to FIG. 4, there is shown an embodiment of the display drive
circuit suitable to a plasma display panel. The shown embodiment is
adapted to realize the multilevel display method of the present invention
by controlling a frequency of a so-called toggle pulse. In FIG. 4, circuit
elements similar to those shown in FIG. 2 are given the same Reference
Numerals, and therefore, explanation thereof will be omitted.
As seen from comparison between FIGS. 2 and 4, the embodiment shown in FIG.
4 has a toggle pulse generator 70 in place of the blanking signal
generator 62. The toggle pulse generator 70 operates on the basis of the
count value of the counter 38 so as to generate a toggle pulse of a
frequency f.sub.A for the display period of the data DA (namely the odd
frame) and a toggle pulse of a frequency f.sub.B for the display period of
the data DB (namely the even frame). Here, it is set that f.sub.A is less
than f.sub.B.
In the plasma display panel, the higher the frequency of the toggle pulse
is, the higher the brightness becomes. With the above mentioned
arrangement, therefore, if both of the data DA and the data DB are a
firing data, the display panel will give a highest brightness. If the data
DA is a non-firing data and the data DB is a firing data, the resultant
image is displayed at a second bright brightness. Further, if the data DA
is a firing data and the data DB is a non-firing data, the display panel
is fired at a third bright brightness. If both of the data DA and the data
DB are a non-firing data, the display panel will give a lowest brightness.
The invention has thus been shown and described with reference to the
specific embodiments. However, it should be noted that the present
invention is in no way limited to the details of the illustrated
structures but changes and modifications may be made within the scope of
the appended claims.
* * * * *
|
|
|
|
|
|
|
Description |
|
