Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-06-06
2003-04-01
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S691000, C345S694000
Reexamination Certificate
active
06542141
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid-crystal display system in which a halftone display is presented by applying two voltages to a pixel of a liquid-crystal display panel alternately in successive frames. More particularly, it relates to a liquid-crystal display system which is most suited to present a flickerless halftone display.
2. Related Art
Heretofore, a method of displaying halftone in a liquid-crystal display system has prevented flicker in such a way that the timing for alternately applying two voltages is different for adjacent lines, as stated in the official gazette of Japanese Patent Application Laid-open No. 62-195628. With this method, however, when displaying a specified display pattern in which the halftone display is presented every second line by way of example, the effect of preventing the flicker using different timings as mentioned above will be canceled and so flicker is again incurred.
The prior-art technique will be described in detail with reference to FIGS.
63
~
65
. In these figures, a black box represents “display-OFF”, a hatched box a “halftone display”, and a blank box “display-ON”.
FIG. 63
is a diagram showing the display patterns of respective frames in the case where four illustrated lines are all displayed at a halftone level by the use of the prior art (hereinbelow, the patterns shall be called “halftone patterns”). Timings for bestowing the display-ON and the display-OFF states are made different for the adjacent lines in such a manner that the odd lines are in the display-OFF state in the odd frames and in the display-ON state in the even frames, whereas the even lines are in the display-ON state in the odd frames and the display-OFF state in the even frames. Thus, the halftone display is presented within a certain area (the four lines in FIG.
63
).
FIG. 64
illustrates a display example being the condition which is perceived by the eye when respective frames are successively displayed on an actual display screen. Although the halftone display is presented for all the four lines in the example of
FIG. 63
, the halftone is displayed only every second line in this example of FIG.
64
.
FIG. 65
is a diagram showing the display patterns of the respective frames in the case of the display depicted in FIG.
64
.
A liquid crystal displays the halftone between white (display-ON) and black (display-OFF) when repeatedly endowed with the display-ON and the display-OFF states alternately in successive frames. However, when adjacent lines are simultaneously in halftone display states, the repetition of display-ON and display-OFF of these lines at the same timings gives rise to flicker. As illustrated in
FIG. 63
, therefore, the timings are made different between the adjacent lines so as to prevent the liquid crystal display from flickering.
However, in such a case where the odd lines are set at the halftone display and the even lines at display-ON as shown in
FIG. 64
, the liquid crystal display flickers as seen from
FIG. 65
illustrative of the display patterns of the respective frames. More specifically, in the odd frames, the odd lines are in the display-OFF state, and the even lines are in the display-ON state, while in the even frames, all the lines are in the display-ON state, so that only the odd lines repeatedly alternate between display-ON and display-OFF. The prior-art technique mentioned above does not take into consideration the flickering which is ascribable to the interference between the display pattern as shown in FIG.
64
and the timings for alternately applying the two voltages.
Incidentally, each of the official gazettes of Japanese Patent Applications Laid-open No. 3-2722 and No. 3-20780 discloses a method of driving a liquid-crystal display system wherein tone or grayscale display of different brightnesses in several steps is accomplished by setting a plurality of frames as one cycle and then ON-driving pixels over the number of frames, which corresponds to a grayscale level of display data, within the cycle. In this method, a plurality of adjacent pixels (for example, four pixels or eight pixels) are combined into one group, and the display data for stipulating a tone is designated in group units. Such a method, is intended to reduce the flickering of the displays. This technique, however, adopts a so-called areal modulation system designating a tone in plural-pixel unit and is not directly applicable to a system designating a tone (halftone) in single-pixel unit.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid-crystal display system which is not restricted to the areal modulation system, and which can present halftone displays with reduced flicker irrespective of display patterns.
A liquid-crystal halftone display system according to the present invention comprises a data driver which accepts liquid-crystal display data corresponding to input display data representing any of display-ON, display-OFF and halftone for every pixel, for one line, and which delivers the liquid-crystal display data for one line as horizontal display data; a scan driver which appoints a line for displaying the horizontal display data; a liquid-crystal panel which displays the horizontal display data as visible information; a line memory in which the input display data are stored for, at least, one line; and halftone display means for generating the liquid-crystal display data to be afforded to the data driver, by the use of the stored contents of the line memory and the input display data; the halftone display means generating ON data in response to the input display data which represents display-ON for a pixel; generating OFF data in response to the input display data which represents display-OFF for a pixel; and generating the ON data and the OFF data alternately in successive frames as halftone data in response to the input display data which represents halftone display for a pixel, and also comparing the input display data of a pertinent line and those of a preceding line for every line so as to invert a phase of changing-over the ON data and the OFF data in accordance with a result of the comparison.
Another liquid-crystal halftone display system according to the present invention comprises a data driver which accepts liquid-crystal display data corresponding to input display data, for one line, and which delivers the liquid-crystal display data for the one line as horizontal display data; a scan driver which appoints a line for displaying the horizontal display data; a liquid-crystal panel which displays the horizontal display data as visible information; and halftone data generation means provided in correspondence with each at least two of a plurality of tones expressed by the input display data, for delivering first data and second data as the liquid-crystal display data for one pixel alternately in successive frames, wherein a phase of changing-over the first data and the second data is made different for every pixel or for every plurality of pixels and for every line or every plurality of lines.
In operation, with the first liquid-crystal halftone display system of the present invention, the halftone display is presented using the liquid-crystal panel which is capable of ON/OFF (binary) control in pixel units. To this end, the input display data (requiring at least 2 bits per pixel) which represents any of display-ON, display-OFF and halftone states, is received for every pixel, thereby attaining a ternary display brightness per pixel. More specifically, in presenting the halftone display, the halftone display means generates the ON data for the input display data which represents the display-ON of the pixel, generates the OFF data for the input display data which represents display-OFF of the pixel, and generates the ON data and the OFF data alternately in successive frames as the halftone data, for the input display data which represents halftone display of the pixel. Moreover, regarding the halftone display pixel, the halftone display me
Furuhashi Tsutomu
Futami Toshio
Kasai Naruhiko
Kitajima Masaaki
Mano Hiroyuki
Antonelli Terry Stout & Kraus LLP
Bell Paul
Hitachi , Ltd.
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