Operating method for active matrix addressed bistable reflective cholesteric displays

• US 6,850,217 B2
• Filed: 04/18/2001
• Issued: 02/01/2005
• Est. Priority Date: 04/27/2000
• Status: Active Grant

• Current Assignee: Manning Ventures, Inc.
• Original Assignee: Manning Ventures, Inc.
• Inventors: Huang, Xiao-Yang, Miller, Nick Martin IV
• Primary Examiner(s): AWAD, AMR A
• Application Number:
  US09/836,329
• Publication Number:
  US 20010050666A1
• Time in Patent Office: 1,385 Days
• Field of Search: 345 87-100, 345211-212, 349/37, 349/41, 349/42, 349/49
• US Class Current: 345/97
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2300/0486 Cholesteric liquid crystals, including chiral-nematic liquid crystals, with transitions between focal conic, planar, and homeotropic states
• CPC Class Codes: G09G 2310/04 Partial updating of the display screen
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2330/022 in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 5/363 Graphics controllers

Abstract

An operating method for a color display system including an active matrix bistable liquid crystal display (LCD) having a plurality of pixels arranged in a matrix based on color data and status bits corresponding to each of the pixels stored in a memory includes steps for generating voltage data corresponding to the pixels based on the color data and the status bits stored for each of the pixels, converting the voltage data to drive signals suitable for driving the active matrix bistable LCD, and applying the drive signals to the active matrix bistable LCD. In an exemplary embodiment, the active matrix bistable LCD is a Cholesteric LCD. Advantageously, the generating, converting, and applying steps are repeated for a corresponding pixel N times, where N is an integer established by the status bits.

Claims

1. An operating method for a color display system including an active matrix bistable cholesteric liquid crystal display (LCD) having a plurality of pixels arranged in a matrix based on color data and status bits corresponding to each of the pixels stored in a memory, comprising:

generating voltage data corresponding to the pixels of the active matrix bistable cholesteric LCD based on the color data and the status bits stored for each of the pixels;

converting the voltage data to drive signals suitable for driving the pixels of the active matrix bistable cholesteric LCD to states of reflectance;

applying the drive signals to the pixels of the active matrix bistable cholesteric LCD effective to place the pixels in one of said reflectance states; and

maintaining said liquid crystal material of the pixels in said reflectance states such that all of said reflectance states are stable after removing the drive signals without application of any electric field.

2. The method as recited in claim 1, wherein the generating step is performed when the status bits for the respective one of the pixels correspond to a non-zero binary number.

3. The method as recited in claim 1, wherein the generating, converting, and applying steps are repeated for a corresponding pixel N times, where N is an integer established by the status bits.

4. An operating method for a color display system including an active matrix bistable cholesteric liquid crystal display (LCD) having a plurality of pixels arranged in a matrix, comprising:

storing color data and status bits corresponding to each of the pixels of the active matrix bistable cholesteric LCD;

generating voltage data corresponding to the pixels of the active matrix bistable cholesteric LCD based on the color data and the status bits stored for each of the pixels;

converting the voltage data to drive signals suitable for driving the pixels of the active matrix bistable cholesteric LCD to states of reflectance;

applying the drive signals to the pixels of the active matrix bistable cholesteric LCD effective to place the pixels in one of said reflectance states; and

maintaining said liquid crystal material of the pixels in said reflectance states such that all of said reflectance states are stable after removing the drive signals without application of any electric field.

5. The method as recited in claim 4, wherein the generating step is performed when the status bits for the respective one of the pixels correspond to a non-zero binary number.

6. The method as recited in claim 4, wherein the generating, converting, and applying steps are repeated for a corresponding pixel N times, where N is an integer established by the status bits.

7. A method for operating a graphics controller including a memory, which stores color data and status bits corresponding to a plurality of pixels, coupled to a low power color display, which includes an active matrix bistable liquid crystal display (LCD) having a plurality of cells arranged in a matrix, each cell corresponding to respective one of the pixels, via driver circuitry, the LCD receiving drive signals suitable for driving the active matrix bistable LCD from the driver circuitry responsive to voltage data, comprising:

generating the voltage data for each respective one of the pixels based on the color data and the status bits for that pixel;

decrementing the status bits by 1 to thereby produce decremented status bits for that pixel;

overwriting the status bits for that pixel with the decremented status bits; and

repeating the generating, the decrementing, and the overwriting steps until the status bits stored in the memory for that pixel represent a zero value.

8. The method as recited in claim 7, wherein the LCD comprises a Cholesteric LCD.

9. The method as recited in claim 7, further comprising the step of setting the status bits to a predetermine value when the corresponding color data for a respective one of the pixels stored in the memory is replaced by new color data.

10. A method for operating a graphics controller including a memory, which stores color data and status bits corresponding to a plurality of pixels, coupled to a low power color display, which includes an active matrix bistable liquid crystal display (LCD) having a plurality of cells arranged in a matrix, each cell corresponding to respective one of the pixels, via driver circuitry, the LCD receiving drive signals suitable for driving the active matrix bistable LCD from the driver circuitry responsive to voltage data, comprising:

generating the voltage data for each respective one of the pixels based on the color data and the status bits for each pixel having non-zero status bits;

decrementing the status bits by 1 to thereby produce decremented status bits for each pixel having the non-zero status bits;

overwriting the status bits with the decremented status bit for each pixel having the non-zero status bits; and

repeating the generating, the decrementing, and the overwriting steps until the status bits stored in the memory for all of the pixels represent a zero value.

11. The method as recited in claim 10, further comprising:

generating a sleep signal when all of the status bits for all of the pixels represent zero values, wherein;

the driver circuitry has on and off states, and

the driver circuitry switches from the on state to the off state responsive to the sleep signal.

12. The method as recited in claim 10, wherein the LCD comprises a Cholesteric LCD.

13. The method as recited in claim 10, further comprising the step of setting the status bits to a predetermined value when corresponding color data for a respective one of the pixels is stored in the memory.

14. The method as recited in claim 10, wherein a first value represented by the status bits corresponding to a first one of the pixels is not equal to second value represented by the status bits corresponding to a second one of the pixels.

15. The method as recited in claim 10, wherein a first value represented by the status bits corresponding to a first one of the pixels is equal to a second value represented by the status bits corresponding to a second one of the pixels.

16. The method as recited in claim 10, wherein:

the method further comprises the step of;

examining the status bits stored in the memory, the examining step being performed prior to the generating step; and

the generating step comprises generating the voltage data for each respective one of the pixels having non-zero status bits based on the color data and the status bits for that pixel.

17. The method as recited in claim 10, wherein:

the method further comprises the step of;

examining the status bits stored in the memory, the examining step being performed concurrent with the generating step; and

the generating step comprises generating the voltage data for each respective one of the pixels having non-zero status bits based on the color data and the status bits for that pixel.

18. An A method of operating a color active matrix bistable cholesteric liquid crystal display (LCD) comprising the step of:

storing pixel information including color data and status bits;

generating non-zero voltage data corresponding to the pixels of the active matrix bistable cholesteric liquid crystal display based on the color data when the status bits stored for each of the pixels is non-zero;

converting the voltage data to drive signals suitable for driving the pixels of the active matrix bistable cholesteric LCD to states of reflectance;

applying the drive signals to the pixels of the active matrix bistable cholesteric LCD effective to place the pixels in one of said reflectance states; and

maintaining said liquid crystal material of the pixels in said reflectance states such that all of said reflectance states are stable after removing the drive signals without application of any electric field.

19. An operating method for a color active matrix bistable cholesteric liquid crystal (LCD) comprising a plurality of pixels, the method comprising the steps of:

storing color data in memory corresponding to each of the pixels of the active matrix bistable cholesteric LCD;

storing status data different from the color data in the memory, the status data also corresponding to each of the pixels of the active matrix bistable cholesteric LCD;

generating voltage data corresponding to the pixels of the active matrix bistable cholesteric LCD based on the color data and also based on the status data;

converting the voltage data to drive signals suitable for drying the pixels of the active matrix bistable cholesteric LCD to states of reflectance;

applying the drive signals to the pixels of the active matrix bistable cholesteric LCD effective to place the pixels in one of said reflectance states; and

maintaining said liquid crystal material of the pixels in said reflectance states such that all of said reflectance states are stable after removing the drive signals without application of any electric field.

20. The method as recited in claim 19, wherein the generating step is performed when the status data for the respective one of the pixels correspond to a non-zero binary number.

21. The method as recited in claim 20, wherein the generating, converting, and applying steps are repeated for a corresponding pixel N times, where N is an integer established by the status data.

22. An operating method for a color display system including an active matrix bistable cholesteric liquid crystal display (LCD) having a plurality of pixels arranged in a matrix, the method comprising the steps of:

storing color data containing image information corresponding to each of the pixels of the active matrix bistable cholesteric LCD;

storing status data different from the color data, the status data also corresponding to each of the pixels of the active matrix bistable cholesteric LCD;

generating voltage data corresponding to the pixels of the active matrix bistable cholesteric LCD based on the color data and the status data stored for each of the pixels;

converting the voltage data to drive signals suitable for drying the pixels of the active matrix bistable cholesteric LCD to states of reflectance;

applying the drive signals to the active matrix bistable LCD effective to place the pixels in one of said reflectance states; and

maintaining said liquid crystal material of the pixels in said reflectance states such that all of said reflectance states are stable after removing the drive signals without application of any electric field.

23. The method as recited in claim 22, wherein the generating step is performed when the status data for the respective one of the pixels correspond to a non-zero binary number.

24. The method as recited in claim 22, wherein the generating, converting, and applying steps are repeated for a corresponding pixel N times, where N is an integer established by the status data.

25. A method of driving an active matrix bistable cholesteric LCD having a driver, the method comprising the steps of:

storing color data containing image information corresponding to each of the pixels of the active matrix bistable cholesteric LCD;

storing status data corresponding to each of the pixels of the active matrix bistable cholesteric LCD, with the status data having a value representing a positive integer;

generating voltage data for each respective one of the pixels of the active matrix bistable cholesteric LCD based on the color data and the status data for each pixel;

repeating the generating step for a corresponding pixel N times, wherein N is an integer established by the status data;

converting the voltage data to drive signals suitable for driving the pixels of the active matrix bistable cholesteric LCD to states of reflectance;

applying the drive signals to the pixels of the active matrix bistable cholesteric LCD effective to olace the pixels in one of said reflectance states; and

maintaining said liquid crystal material of the pixels in said reflectance states such that all of said reflectance states are stable after removing the drive signals without application of any electric field.

26. The method as recited in claim 25, wherein the driver has an on and an off state, the method further comprising the steps of:

generating a sleep signal after said repeating step is completed; and

switching the driver from the on state to the off state responsive to the sleep signal.

27. The method as recited in claim 25, further comprising the step of setting the status data to a predetermined value when corresponding color data for a respective one of the pixels is stored in the memory.

28. The method as recited in claim 25, wherein a first integer N corresponding to a first one of the pixels is not equal to a second integer N corresponding to a second one of the pixels.

29. The method as recited in claim 25, wherein a first integer N corresponding to a first one of the pixels is equal to a second integer N corresponding to a second one of the pixels.

30. The method as recited in claim 25, wherein:

the method further comprises the steps of;

examining the status data stored in the memory, the examining step being performed prior to the generating step; and

the generating step comprises generating the voltage data for each respective one of the pixels having non-zero status data based on the color data and the status data for that pixel.

31. The method as recited in claim 25, wherein the method further comprises the steps of:

examining the status data stored in the memory, the examining step being performed concurrent with the generating step; and

the generating step comprises generating the voltage data for each respective one of the pixels having non-zero status data based on the color data and the status data for that pixel.

32. A method of driving a bistable LCD display having a driver, the method comprising the steps of:

storing color data containing image information corresponding to each of the pixels;

storing status data corresponding to each of the pixels, with the status data for a corresponding pixel having a value representing a non-zero positive integer;

generating voltage data for each respective one of the pixels based on the color data and the status data for each pixel;

decrementing the status data by 1 to thereby produce decremented status data for each pixel having the non-zero status data;

overwriting the status data with the decremented status data for each pixel having the non-zero status data;

repeating the generating, the decrementing, and the overwriting steps until the status data stored in the memory for all of the pixels represent a zero value, wherein a zero voltage is applied to the pixel after the status data becomes zero.

33. A method of operating a display driver for driving an active matrix bistable color cholesteric liquid crystal display having a plurality of pixels, said method for driving a pixel of said plurality of pixels, comprising the steps of:

examining previous pixel information;

examining updated pixel information;

when the updated pixel information has changed from the previous pixel information, applying drive signals to the pixel to reflect the updated pixel information effective to place the pixel into a new state of reflectance; and

when the updated pixel information has not changed from the previous pixel information, applying a zero or near zero maintenance voltage to the pixel according to maintain the current pixel information to maintain a current state of reflectance of the pixel,

wherein all states of reflectance of the pixel are stable after removing said drive signals and said maintenance voltage without application of any electric field.

34. An operating method for a display system including an active matrix cholesteric liquid crystal display (LCD) having a plurality of pixels arranged in a matrix, comprising:

storing image data and status data corresponding to the pixels of the active matrix cholesteric LCD;

generating driving data corresponding to the pixels based on the image data and the status data stored for the pixels of the active matrix cholesteric LCD;

converting the driving data to drive signals suitable for driving the pixels of the active matrix cholesteric LCD to levels of brightness;

applying the drive signals to the pixels of the active matrix cholesteric LCD effective to place the pixels in one of said levels of brightness; and

maintaining said liquid crystal material of the pixels of the active matrix cholesteric LCD in said levels of brightness such that all of said levels of brightness are stable after removing the drive signals without application of an electric field.

35. A method of driving an active matrix cholesteric liquid crystal display having a plurality of pixels, said method for driving a pixel of said plurality of pixels comprising the steps of:

examining previous pixel information;

examining updated pixel information;

when the updated pixel information has changed from the previous pixel information, applying drive signals to the pixel according to the updated pixel information effective to place the pixel in a new level of brightness; and

when the updated pixel information has not changed from the previous pixel information, applying a zero or near zero maintenance voltage according to the current pixel information to maintain a current level of brightness of the pixel,

wherein all levels of brightness of the pixel are stable after removing said drive signals and said maintenance voltage without application of any electric field.