Display device

• US 5,606,343 A
• Filed: 09/14/1994
• Issued: 02/25/1997
• Est. Priority Date: 07/24/1991
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tsuboyama, Akira, Mizutome, Atsushi, Iwayama, Mitsuo
• Primary Examiner(s): SARAS, STEVEN J
• Application Number:
  US08/302,989
• Time in Patent Office: 895 Days
• Field of Search: 371/66, 364/707, 345/1, 345/3, 345/11, 345/87, 345/97, 345/94, 345/98, 345/200, 345/99, 345/10
• US Class Current: 345/97
• CPC Class Codes: G06F 1/3218 of display devices
• CPC Class Codes: G09G 2310/0205 Simultaneous scanning of several lines in flat panels
• CPC Class Codes: G09G 2310/0245 Clearing or presetting the whole screen independently of waveforms, e.g. on power-on G09G2310/063 takes precedence
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A display device for displaying an image in accordance with image signal by applying a drive signal to a ferroelectric liquid crystal which holds an optical state even in a zero electric field state from drive means through scan electrodes and information electrodes in accordance with image information stored in image information memory means, comprises change detection means for detecting change in the image information stored in the image information memory means, and drive control means for controlling drive means in accordance with detection result by the change detection means to apply a signal to erase the display, stop the application of the drive signal or resume the application of the drive signal.

Claims

1. A display apparatus comprising:

a liquid crystal display panel having pixels arranged in a matrix of scan electrodes, each defining a scanning line, and information electrodes and having a ferroelectric liquid crystal driven by an electrical field applied through the scan electrodes and the information electrodes;

image information memory means for storing image information to be displayed on said liquid crystal display panel;

change detection means for detecting a change in the image information stored in said image information memory means;

drive means for applying a scan signal to said scan electrodes and an information signal to said information electrodes in accordance with the information stored in said image information memory means to effect a screen display; and

drive control means for controlling said drive means so that said drive means, in response to the stored image information, executes display drive scanning in one of a partial rewriting scan and a full screen refreshing scan, wherein, when a change is detected in the information stored in said image information memory means, the partial rewriting scan is performed by non-interlace scanning for only the scanning lines corresponding to the changed information, and, when no change is detected in the information stored in said image information memory means, the full screen refreshing scan is performed by interlace scanning for the scanning lines of the full screen, said drive means applying a display erasing voltage between a group of the scan electrodes and a group of the information electrodes to erase the screen display when said change detection means detects that the stored image information has not changed over a predetermined time interval, and after applying the display erasing voltage, said drive means either applies a same voltage to the group of scan electrodes and the group of information electrodes or said drive means places the group of scan electrodes and the group of information electrodes into a high impedance state, with said drive means resuming the display drive scanning when said detection means detects that a change in the stored image information has taken place.

2. A display apparatus according to claim 1, wherein the screen display is erased into a white display state.

3. A display apparatus according to claim 1, wherein the screen display is erased into a black display state.

4. A display apparatus comprising:

a liquid crystal display panel having pixels arranged in rows and columns and defined by pairs of opposing electrodes with a liquid crystal disposed between the pairs of electrodes, with the pixels on the rows being connected in common by scanning lines and the pixels on the columns being connected in common by information lines;

image information memory means for storing image information to be displayed on said liquid crystal display panel;

change detection means for detecting a change in the image information stored in said image information memory means;

drive means for applying a scan signal to said scan lines and an information signal to said information lines in accordance with the information stored in said image information memory means to effect a screen display; and

drive control means for controlling said drive means so that said drive means, in response to the stored image information, executes display drive scanning in one of a partial rewriting scan and a full screen refreshing scan, wherein, when a change is detected in the information stored in said image information memory means, the partial rewriting scan is performed by non-interlace scanning for only the scanning lines corresponding to the changed information, and, when no change is detected in the information stored in said image information memory means, the full screen refreshing scan is performed by interlace scanning for the scanning lines of the full screen, said drive means applying a display erasing voltage between a group of the scan electrodes and a group of the information electrodes to erase the screen display when said change detection means detects that the stored image information has not changed over a predetermined time interval, and after applying the display erasing voltage, said drive means either applies a same voltage to the group of scan electrodes and the group of information electrodes or said drive means places the group of scan electrodes and the group of information electrodes into a high impedance state, with said drive means resuming the display drive scan when said detection means detects that a change in the stored image information has taken place.

5. A display apparatus according to claim 4, wherein the screen display is erased into a white display state.

6. A display apparatus according to claim 4, wherein the screen display is erased into a black display state.

7. A display apparatus comprising:

a liquid crystal display panel having pixels arranged in a matrix of scan electrodes, each defining a scanning line, and information electrodes and having a liquid crystal having a memory function driven by an electrical field applied through the scan electrodes and the information electrodes;

image information memory means for storing image information to be displayed on said liquid crystal display panel;

change detection means for detecting a change in said image information memory means;

drive means for applying a scan signal to the scan electrodes and an information signal to the information electrodes in accordance with the information stored in said image information memory means to effect a screen display; and

drive control means for controlling said drive means so that said drive means executes, in response to the stored image information, display drive scanning in one of a partial rewriting scan and a full screen refreshing scan, wherein, when a change is detected in the image information stored in said image information memory means, the partial rewriting scan is performed by a first scanning operation for the scanning lines corresponding to the changed information, and when no change is detected in the information stored in said image information memory means, the full screen refreshing scan is performed by a second scanning operation, and said drive means applies a display erasing voltage between a group of the scan electrodes and a group of the information electrodes to erase the screen display when said change detection means detects that the stored image information has not changed over a predetermined time interval, wherein the second scanning operation is performed for successive scanning in a manner of skip selection of the scan electrodes, and the first and second scanning operations are performed for selecting the scan electrode so that a display area scanned by the second scanning operation is greater than a display area scanned by the first scanning operation.

8. A display apparatus according to claim 7, wherein the first scanning operation is a non-interlace scanning, and the second scanning operation is an interlace scanning.

9. A display apparatus according to claim 7, wherein said liquid crystal is a ferroelectric liquid crystal.