Liquid crystal display apparatus

• US 5,717,421 A
• Filed: 02/20/1996
• Issued: 02/10/1998
• Est. Priority Date: 12/25/1992
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Okada, Shinjiro, Inaba, Yutaka, Katakura, Kazunori
• Primary Examiner(s): WU, XIAO MIN
• Application Number:
  US08/603,189
• Time in Patent Office: 721 Days
• Field of Search: 345/101, 345/102, 345/98, 345/99, 345/100, 345/207, 359/43, 359/44, 359/45, 359/85, 359/86, 359/87, 348/790, 348/792, 348/793, 349/54, 349/72
• US Class Current: 345/101
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/065 Waveforms comprising zero voltage phase or pause
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• 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 3/207 by domain size control G09G3/3637 takes precedence
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3637 with intermediate tones displayed by domain size control domain size control in flat matrix panels other than liquid crystal displays having memory effects G09G3/207
• CPC Class Codes: G09G 3/3674 Details of drivers for scan electrodes

Abstract

A display panel includes a matrix of pixels each constituted by a pair of oppositely disposed electrodes and a liquid crystal disposed between the electrodes. A current signal, particularly one associated with inversion of spontaneous polarization of the liquid crystal is detected at plural pixels. The display panel is driven by applying drive signals thereto while correcting the drive signals based on the detected current signal. As a result, a threshold distribution typically attributable to a temperature distribution on the display panel is accurately compensated for. The display system thus constituted is particularly useful for gradational display.

Claims

1. A liquid crystal display apparatus, comprising:

(a) a display panel comprising a plurality of scanning electrodes, a plurality of data electrodes intersecting said scanning electrodes, and a liquid crystal disposed between said scanning electrodes and said data electrodes so as to form a pixel at each intersection of said scanning electrodes and said data electrodes

(b) a temperature sensor disposed in proximity to said display panel;

(c) a current detection control circuit for determining a currant detection condition in response to temperature data detected by said temperature sensor;

(d) a voltage application circuit for applying a voltage pulse based on the determined current detection condition to at least one of said scanning electrodes;

(e) a current detection circuit connected to at least one of said data electrodes for detecting a current flowing to said at least one data electrode in response to said voltage pulse applied to said at least one scanning electrode;

(f) a display signal control circuit for correcting a drive signal to be applied to a pixel for picture display based on the detected current data; and

(g) a drive signal application circuit for applying the corrected drive signal to the pixel.

2. An apparatus according to claim 1, wherein said current detection circuit detects current signals flowing across a plurality of prescribed pixels and wherein a plurality of the detected current signal originates from plural prescribed pixels which are disposed at least two distant positions on the display panel, a correction factor for correcting the drive signals for a pixel not among said plural prescribed pixels being derived from said plurality of the detected current signal.

3. An apparatus according to claim 2, wherein the correction factor changes over time.

4. An apparatus according to claim 1, wherein said current detection circuit detects current signals flowing across a plurality of prescribed pixels and said plural prescribed pixels are mutually adjacent pixels and a common current signal is detected therefrom.

5. An apparatus according to claim 4, wherein said plural prescribed pixels are disposed on a common scanning electrode.

6. An apparatus according to claim 4, wherein said plural prescribed pixels are disposed on a common data electrode.

7. An apparatus according to claim 1, wherein the display signal control circuit corrects the drive signal based on a peak value of the detected current signal.

8. An apparatus according to claim 1, wherein the display signal control circuit corrects the drive signal based on an integrated value of the detected current signal.

9. An apparatus according to claim 1, wherein the display signal control circuit corrects the drive signal based on a peak half-width value of the detected current signal.

10. An apparatus according to claim 1, wherein the display signal control circuit corrects the drive signal based on a time required for the detected current signal to reach a prescribed value.

11. An apparatus according to claim 1, further including a backlight disposed behind the display panel.

12. An apparatus according to claim 11, further including image data communication means.

13. An apparatus according to claim 11, further including image data recording means.

14. An apparatus according to claim 1, wherein said liquid crystal is a smectic liquid crystal.

15. An apparatus according to claim 1, further including heating means for heating the liquid crystal.

16. An apparatus according to claim 1, wherein after the current detection by said current detection circuit, said drive signal application circuit applies a scanning selection signal preferentially to only said at least one scanning electrode having received said voltage pulse and data signals to associated data electrodes.

17. A liquid crystal display apparatus comprising:

a display panel comprising a first substrate having a plurality of scanning lines thereon, a second substrate having a plurality of data lines thereon, and a liquid crystal disposed between the first and second substrates so as to form a pixel at each intersection of said scanning and data lines;

an application circuit for applying a signal for current detection to the liquid crystal through at least one scanning line;

a detection circuit for detecting, at least one data line, a current signal flowing through the liquid crystal at a pixel associated with said at least one scanning line;

drive means for applying a drive signal to a pixel on said display panel;

a circuit for correcting the drive signal depending on the detected current signal; and

a changeover switch for switching between a detecting state of connecting the application circuit, said at least one scanning line, said at least one data line and the detection circuit, and a driving state of connecting the drive circuits, said at least one scanning line and said at least one data line, so as to preferentially supply a scanning signal to said at least one scanning line having received the signal for current detection in the detecting state and supply data signals for pixels on said at least one scanning line to the data lines, thereby partially rewriting the display states of the pixels on said at least one scanning line.

18. An apparatus according to claim 17, wherein data lines connected to pixels other than the pixel associated with said at least one scanning line are grounded.

19. An apparatus according to claim 17, wherein data lines connected to pixels other than the pixel associated with said at least one scanning line are placed in a high impedance state.

20. An apparatus according to claim 17, further including a backlight disposed behind the display panel.

21. An apparatus according to claim 20, further including image data communication means.

22. An apparatus according to claim 20, further including image data recording means.

23. An apparatus according to claim 17, wherein said liquid crystal is a smectic liquid crystal.

24. An apparatus according to claim 17, further including heating means for heating the liquid crystal.

25. An apparatus according to claim 17, wherein said signal for current detection is applied to plural scanning lines.

26. An apparatus according to claim 17, wherein the signal for current detection rewrites pixels on said at least one scanning line to which the signal is applied.