Display-driving device and display-driving method performing...

Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix

Reexamination Certificate

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C345S690000, C345S691000

Reexamination Certificate

active

06483492

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display-driving device and a display-driving method for driving a panel type display such as a liquid crystal display, a plasma display, and a display for displaying a picture image corresponding to an image signal on an optical waveguide plate by controlling leakage light at a predetermined position of the optical waveguide plate by controlling the displacement action of an actuator element in a direction to make contact or separation with respect to the optical waveguide plate in accordance with an attribute of the image signal to be inputted (conveniently referred to as “electrostrictive type display”).
2. Description of the Related Art
Those hitherto known as displays include display devices such as cathode ray tubes (CRT), liquid crystal displays, and plasma displays.
Those known as the cathode ray tube include, for example, ordinary television receivers and monitor units for computers. Although the cathode ray tube has a bright screen, it consumes a large amount of electric power. Further, the cathode ray tube involves a problem that the depth of the entire display device is large as compared with the size of the screen. Further, for example, the cathode ray tube involves drawbacks in that the resolution is decreased in the circumferential areas of the display images, the image or the graphic is distorted, there is no memory function, and it is impossible to present display in a large scale.
The reason for the foregoing phenomenon is as follows. That is, in the case of the cathode ray tube, the electron beam emitted from the electron gun is greatly deflected. Therefore, the light emission point (beam spot) is expanded at portions at which the electron beam reaches the fluorescent screen of the Braun tube in an inclined manner, and thus the image is displayed in an inclined manner. For this reason, strain occurs on the display image. Moreover, there is a limit for the maintenance to keep a large space at the inside of a Braun tube to be in a vacuum.
On the other hand, the panel type display, for example, the liquid crystal display is advantageous in that the entire device can be miniaturized, and the display consumes a small amount of electric power. The plasma display and the electrostrictive type display can be miniaturized, because the display section itself does not have a large volume, in the same manner as the liquid crystal display as described above. They are advantageous in that there is no trouble in viewing the screen, because the display surface is flat. Especially, the AC type plasma display and the electrostrictive type display are also advantageous in that the refresh memory is unnecessary owing to the memory function of the cell.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a display-driving device and a display-driving method which make it possible to effectively reduce electric power consumption and achieve high brightness in a panel type display as described above.
Another object of the present invention is to provide a display-driving device and a display-driving method which make it possible to effectively reduce electric power consumption and achieve high brightness in gradation control based on subfield driving.
Still another object of the present invention is to provide a display-driving device and a display-driving method which make it possible to reduce the total number of subfields and effectively reduce electric power consumption in gradation control based on subfield driving.
According to the present invention, there is provided a display-driving device for a display comprising a driving section including a large number of picture elements arranged in a matrix form for displaying a picture image corresponding to a supplied image signal; the display-driving device comprising a first driving circuit for selecting the picture elements at least in one row unit, a second driving circuit for outputting display information composed of an ON signal and an OFF signal to a selected row, and a signal control circuit for controlling the first and second driving circuits; wherein assuming that a display period for one image is one field in order to perform gradation control based on at least a temporal modulation system, the signal control circuit determines, in the one field, a light emission start timing and a light emission maintenance period having a variable length irrelevant to a selection/unselection state of the concerning picture element depending on a gradation level of the selected picture element.
Assuming that the display period for one image is one field, the light emission start time of the concerning picture element and the light emission maintenance period having the variable length irrelevant to the selection/unselection state of the concerning picture element are determined in the one field depending on the gradation level of the selected picture element, in accordance with the control performed by the signal control circuit. Accordingly, the light emission is started for the concerning picture element substantially in synchronization with the light emission start timing, and the light emission state is maintained over the light emission maintenance period.
This arrangement makes it possible to effectively reduce the electric power consumption as compared with other driving systems in which one field is divided into a plurality of subfields, and forcible reset is performed for each of the subfields (as adopted, for example, for the plasma display). Further, the light emission state is maintained over the light emission maintenance period. Therefore, it is also possible to realize the improvement in brightness.
In the display-driving device constructed as described above, it is also preferable that one selection period and display cycles of a number corresponding to a maximum gradation level are allotted in the one field; each of the display cycles is composed of an unselection period and a reset period; and the signal control circuit is operated such that the concerning picture element is in a light emission state when the ON signal indicating light emission is inputted during the selection period, or the concerning picture element is in a light off state when the OFF signal indicating light off is inputted during the reset period in the display cycle.
Accordingly, assuming that the selection period is allotted to the head of the one field, one display cycle is selected, or a plurality of display cycles are continuously selected from the head of the one field depending on the gradation level of the concerning picture element. The ON signal is outputted at the head of the selected display cycle, and the OFF signal is outputted in the reset period of the display cycle next to the selected display cycle. In other words, the head of the selected display cycle is the light emission start timing, and the period corresponding to the selected display cycle is the light emission maintenance period.
In this arrangement, only one cycle is used for the light emission and the light off for the concerning picture element in the one field. Accordingly, it is possible to effectively reduce the electric power consumption. Further, the good linearity is obtained for the gradation and the brightness, and thus it is possible to make highly accurate gradational expression. Furthermore, the efficiency of the light emission time is also enhanced.
In the display-driving device constructed as described above, it is also preferable that signal levels are determined for the unselection period and the reset period so that the light emission state of the concerning picture element is maintained during the light emission maintenance period; and signal levels are determined for the selection period and the unselection period so that the light off state of the concerning picture element is maintained during any period other than the light emission maintenance period. In this arrangement, it is easy to achieve the maintenance of light emission during th

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