Liquid crystal display apparatus

• US 5,754,154 A
• Filed: 05/05/1995
• Issued: 05/19/1998
• 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
• Application Number:
  US08/435,956
• Time in Patent Office: 1,110 Days
• Field of Search: 345/101, 345/102, 345/98, 345/99, 345/100, 345/207, 345/94, 345/95, 345/96, 345/208, 345/209, 359/43, 359/44, 359/45, 359/85, 359/86, 359/87, 348/790, 348/792, 348/793, 349/72, 349/33, 349/34, 349/37
• US Class Current: 345/97
• 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, including:

a display panel comprising a matrix of pixels each comprising a pair of oppositely disposed electrodes and a ferroelectric liquid crystal disposed between the electrodes;

detection means for detecting a polarization inversion current signal flowing across the liquid crystal at one of the pixels on the display panel;

drive means for applying drive signals to the display panel; and

correction means for correcting the drive signals based on the polarization inversion current signal detected by the detection means,

wherein said polarization inversion current signal is a difference between a first signal detected from the one pixel when polarization inversion is caused at the one pixel and a second signal detected from the signal when polarization inversion is not caused at the one pixel.

2. An apparatus according to claim 1, wherein one of said pair of oppositely disposed electrodes comprises a scanning electrode and said polarization inversion current signal is detected by applying a detection input signal to said scanning electrode and detecting an output signal from the other of said pair of oppositely disposed electrodes.

3. An apparatus according to claim 2, wherein said detection input signal includes a plurality of waveform signals applied in succession, wherein all of the waveform signals have an identical waveshape including at least one pulse, and where at least a specific one of the at least one pulse of each of the waveform signals has a respective pulsewidth different from the pulsewidths of the others of the specific pulses.

4. A liquid crystal display apparatus including:

a display panel comprising a matrix of pixels each comprising a pair of oppositely disposed electrodes, one of said pair of electrodes comprising a scanning electrode and another of said pair of electrodes comprising a data electrode, and a ferroelectric liquid crystal disposed between the electrodes;

detection means comprising a differential circuit for detecting a polarization inversion current signal flowing across the liquid crystal at first and second pixels on the display panel;

drive means for applying drive signals to the display panel; and

correction means for correcting the drive signals based on the polarization inversion current signal detected by the detection means,

wherein said differential circuit outputs a difference between a first signal detected from the first pixel when polarization inversion is caused at the first pixel and a second signal detected from the second pixel when polarization inversion is not caused at the second pixel, and

said current signal is detected by applying a detection input signal to said scanning electrode and detecting an output signal from said data electrode.

5. An apparatus according to claim 4, wherein said detection input signal includes a plurality of different waveform signals applied in succession.