Driving method for display apparatus

• US 5,856,814 A
• Filed: 08/01/1996
• Issued: 01/05/1999
• Est. Priority Date: 08/02/1995
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Yagyu, Mineto
• Primary Examiner(s): Chow, Dennis-Doon
• Application Number:
  US08/690,997
• Time in Patent Office: 887 Days
• Field of Search: 345/147, 345/87, 345/89, 345/102, 349/25, 349/29, 349/173, 349/85, 349/30
• US Class Current: 345/89
• CPC Class Codes: G02F 1/135 Liquid crystal cells structurally associated with a photoconducting or a ferro-electric layer, the properties of which can be optically or electrically varied G02F1/133348 takes precedence
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2360/141 the light conveying information used for selecting or modulating the light emitting or modulating element
• CPC Class Codes: G09G 3/002 to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT
• CPC Class Codes: G09G 3/02 by tracing or scanning a light beam on a screen
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A display apparatus includes an optical modulation device comprising a pair of electrodes, and a photoconductor layer and an optical modulation substance layer between the electrodes, a signal light source for supplying light data carrying gradation data to the photoconductor layer, and a readout light source for supplying readout light for reading out image data to the optical modulation substance layer. The display apparatus is driven by a method including: scanningly supplying the light data to the photoconductor layer, and scanningly supplying the readout light to the optical modulation substance layer. Preferably, the lighting time of the readout light source is controlled to modulate an overlapping time between a period of the optical modulation substance assuming a prescribed optical state and the lighting time depending on given gradation data.

Claims

1. A driving method for a display apparatus including an optical modulation device comprising a pair of electrodes, and a photoconductor layer and an optical modulation substance layer disposed between the electrodes, a signal light source for supplying light data carrying gradation data to the photoconductor layer, and a readout light source for supplying readout light for reading out image data to the optical modulation substance layer, said driving method comprising:

scanningly supplying the light data to the photoconductor layer, and scanningly supplying the readout light to the optical modulation substance layer, wherein a lighting time of the readout light source is controlled to modulate an overlapping time between a period of the optical modulation substance assuming a prescribed optical state and the lighting time depending on given gradation data.

2. A driving method according to claim 1, wherein a portion of the photoconductor layer is supplied with the light data as one horizontal scanning and thereafter a corresponding portion of the optical modulation substance layer is scanned with the readout light.

3. A driving method according to claim 1, wherein the signal light source supplies at least two types of light data having mutually different wavelength regions.

4. A driving method according to claim 1, wherein the signal light source supplies light data of red, green and blue.

5. A driving method according to claim 1, wherein the display apparatus includes a plurality of signal light sources and an equal number of optical modulation devices corresponding thereto.

6. A driving method according to claim 1, wherein the readout light is scanningly moved by a movable mirror.

7. A driving method according to claim 1, wherein the readout light is divided into spectra by means of a mirror selectively transmitting or reflecting a prescribed wavelength of light.

8. A driving method according to claim 1, wherein the display apparatus includes a CRT, a movable mirror and a polarization beam splitter.

9. A driving method according to claim 1, wherein the optical modulation device is supplied with reset light prior to the supply of the light data.

10. A driving method according to claim 1, wherein a reset voltage of one polarity is applied and then a writing voltage is applied between the pair of electrodes.

11. A driving method according to claim 1, wherein the optical modulation device includes a plurality of scanning lines and a plurality of data lines disposed to intersect the scanning lines so as to form a matrix of pixels each at an intersection of the scanning lines and the data lines, each pixel comprising the pair of electrodes, and the photoconductor layer and the optical modulation substance layer are disposed between the electrodes.

12. A driving method according to claim 11, wherein the pixels on all the scanning lines are simultaneously supplied with a reset voltage.

13. A driving method according to claim 11, wherein the photoconductor layer corresponding to the pixels or all the scanning lines is simultaneously supplied with reset light.

14. A driving method according to claim 11, wherein one horizontal scanning with the readout light is performed in synchronism with one horizontal scanning with the light data.

15. A driving method according to claim 1, wherein the readout light is supplied to a pixel for a period wherein the optical modulation substance in the pixel can change its optical state.

16. A driving method according to claim 1, wherein the optical modulation substance changes its optical state at a point in time which varies depending on the supplied light data within a period for supplying the readout light.

17. A driving method according to claim 1, wherein the optical modulation substance comprises a liquid crystal having a memory characteristic.

18. A driving method according to claim 1, wherein the optical modulation substance comprises a chiral smectic liquid crystal.

19. A driving method according to any one of claims 1-18, wherein the readout light is continuously supplied for a period of at most 1/30 sec.

20. A driving method according to any one of claims 1-18, wherein the readout light is continuously supplied for a period of at most 1/60 sec.

29. A driving method according to claim 20, wherein the readout light is supplied to a pixel for a period such that the optical modulation substance in the pixel can change its optical state.

21. A driving method for a display apparatus including (a) an optical modulation device comprising a plurality of two-dimensionally arranged pixels, each comprising an optical modulation element formed by disposing an optical modulation substance layer between a pair of electrodes and a drive element for supplying an electric signal carrying gradation data to the optical modulation element, and (b) a readout light source for supplying readout light for reading out image data to the optical modulation substance layer, said driving method comprising:

supplying the electric signal to a scanningly selected pixel,

scanning the pixels with readout light to supply the readout light to the optical modulation substance layer at the selected pixel, and

controlling a lighting time of the readout light source to modulate an overlapping time between a period of the optical modulation substance assuming a prescribed optical state and the lighting time depending on given gradation data.

22. A driving method according to claim 21, wherein one horizontal row of pixels including the selected pixel are supplied with electric signals and thereafter the row of pixels is scanned with the readout light.

23. A driving method according to claim 21, wherein the drive element comprises a transistor.

24. A driving method according to claim 21, wherein the drive element comprises a transistor and a resistive element.

25. A driving method according to claim 21, wherein the drive element comprises a transistor, a resistive element, and a capacitive element.

26. A driving method according to claim 21, wherein the readout light is illuminated for a period longer than a scanning selection period of a pixel.

27. A driving method according to claim 21, wherein a point in time when a voltage applied to the optical modulation substance subsides below a prescribed value is modulated.

28. A driving method according to claim 21, wherein the drive element comprises a transistor connected to a pixel and having a source, a gate and a drain, and the electric signal is supplied to the source.

30. A driving method according to claim 21, wherein the optical modulation substance changes its optical state at a point in time which varies depending on the supplied light data within a period for supplying the readout light.

31. A driving method according to claim 21, wherein the optical modulation substance comprises a liquid crystal having a memory characteristic.

32. A driving method according to claim 21, wherein the optical modulation