Process for producing shaded colored images using dithering techniques

• US 5,757,347 A
• Filed: 05/17/1993
• Issued: 05/26/1998
• Est. Priority Date: 12/24/1991
• Status: Expired due to Term

• Current Assignee: S3 Graphics Co., Ltd. (HTC Corporation)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Han, Robin S.
• Primary Examiner(s): SARAS, STEVEN J
• Application Number:
  US08/061,802
• Time in Patent Office: 1,835 Days
• Field of Search: 358/455, 358/429, 382/54, 382/169, 345/89, 345/88, 345/113, 345/136, 345/139, 345/147, 345/148, 345/149, 345/150, 345/152, 345/153
• US Class Current: 345/88
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/2051 with use of a spatial dither pattern
• CPC Class Codes: G09G 3/2077 by a combination of two or more gradation control methods
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

In a flat-panel display device, the ON/OFF duty cycle of each picture element of the array of picture elements is modulated during a multi-frame display sequence according to attribute information of respective picture element data to be displayed. The timing of ON/OFF and OFF/ON state transitions (i.e., the modulations) of the picture elements are coordinated within predetermined neighborhoods throughout the array of picture elements such that the state transitions occur substantially uniformly in space and time within a display neighborhood during the multi-frame display sequence. Advantage is taken of the visual averaging property by causing state transitions to occur substantially uniformly in space and time within each neighborhood throughout the array of picture elements during a multi-frame display sequence. Individual state transitions, which by themselves constitute display noise, are not perceived; instead, a coherent pattern of state transitions blending is provided that effectively simulates non-monochrome image displays. Dithering techniques are applied to realize a greater number of display colors than would otherwise be possible using conventional color LCD displays.

Claims

1. In a color display apparatus having an array of picture elements each including plural picture sub-elements each of a different color and each having more than two display states selected between using at least two input terminals, each of which has two possible inputs, an ON input and an OFF input, a method of simulating display colors in addition to a number of display colors otherwise available using said color display apparatus, comprising the steps of:

modulating an ON/OFF duty cycle of a least significant one of said at least two input terminals of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating the timing of ON/OFF and OFF/ON input transitions on said least significant input terminal of each picture sub-element within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that said input transitions cause state transitions of said picture sub-elements to occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

wherein said color display apparatus is a thin-film transistor LCD display,

wherein each picture element has at least eight display states selected between using at least three input terminals,

wherein said multi-frame sequence is 64 frames long and is logically divided into four sub-sequences each 16 frames long,

wherein 260 shades of each picture sub-element are realized by causing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element to have a value within the set {0, 1/64, 2/64, . . . , 64/64}, and

wherein the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during each of said four 16-frame sub-sequences of said 64 frame sequence is caused to have a value within the set {0, 1/16, 2/16, . . . , 16/16}.

2. The method of claim 1 comprising the further step of allowing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during each of said four 16-frame sub-sequences of said 64 frame sequence to assume one of two adjacent values only within the set {0, 1/16, 2/16, . . . , 16/16}.

3. The method of claim 1 comprising the further step of allowing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during at least one, but not all, of said four 16-frame sub-sequences of said 64 frame sequence to assume only a first of two adjacent values within the set {0, 1/16, 2/16, . . . , 16/1} and allowing the duty cycle of said least significant input terminal of each picture sub-element during the others of said four 16-frame sequences to assume only a second of said two adjacent values.

4. In a color display apparatus having an array of picture elements each including plural picture sub-elements each of a different color and each having more than two display states selected between using at least two input terminals, each of which has two possible inputs, an ON input and an OFF input, a method of simulating display colors in addition to a number of display colors otherwise available using said color display apparatus, comprising the steps of:

modulating an ON/OFF duty cycle of a least significant one of said at least two input terminals of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating the timing of ON/OFF and OFF/ON input transitions on said feast significant input terminal of each picture sub-element within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that said input transitions cause state transitions of said picture sub-elements to occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

wherein said color display apparatus is a thin-film transistor LCD display,

wherein each picture element has at least eight display states selected between using at least three input terminals,

wherein said multi-frame sequence is M×

N frames long, M and N being integers, and is logically divided into M sub-sequences each N frames long,

wherein M×

N+1 shades of each picture sub-element are realized by causing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element to have a value within the set {0, 1/M×

N, 2/M×

N, M×

N/M×

N}, and

wherein the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during each of said M N-frame sub-sequences of said M×

N frame sequence is caused to have a value within the set {0, 1/N, 2/N, . . . , N/N}.

5. The method of claim 4 comprising the further step of allowing the duty cycle of said least significant input terminal of each picture sub-element during each of said M N-frame subsequences of said M×

N frame sequence to assume one of two adjacent values only within the set {0, 1/N, 2/N, N/N}.

6. The method of claim 4 comprising the further step of allowing the duty cycle of said least significant input terminal of each picture sub-element during at least one, but not all, of said M N-frame sub-sequences of said M×

N frame sequence to assume only a first of two adjacent values within the set {0, 1/N, 2/N, . . . , N/N} and allowing the duty cycle of said least significant input terminal of each picture sub-element during the others of said M N-frame sub-sequences to assume only a second of said two adjacent values.

7. A method of simulating display colors in addition to a number of display colors otherwise available using a color display device that has an array of picture elements each including plural picture sub-elements each of a different color and each having only two display states, an ON state and an OFF state, comprising the steps of:

modulating an ON/OFF duty cycle of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating the timing of ON/OFF and OFF/ON state transitions of picture sub-elements within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that the state transitions occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

wherein said multi-frame sequence is sixty-four frames long,

wherein said multi-frame sequence sixty-four frames long is logically divided into four sub-sequences each sixteen frames long,

wherein sixty-five display shades of each picture sub-element are realized by causing the ON/OFF duty cycle of each picture element to have a value within the set {0, 1/64, 2/64, . . . , 64/64}, and

wherein the ON/OFF duty cycle of each picture sub-element during each of said four sixteen-frame sub-sequences of said sixty-four-frame sequence is caused to have a value within the set {0, 1/16, 2/16, . . . , 16/16}.

8. The method of claim 7 comprising the further step of allowing the duty cycle of each picture sub-element during each of said four sixteen-frame sub-sequences of said sixty-four-frame sequence to assume one of two adjacent values only, within the set {0, 1/16, 2/16, . . . , 16/16}.

9. The method of claim 7 comprising the further step of allowing the duty cycle of each picture sub-element during at least one, but not all, of said four sixteen-frame sub-sequences of said sixty-four-frame sequence to assume only a first of two adjacent values within the set {0, 1/16, 2/16, . . . , 16/16} and allowing the duty cycle of each picture element during the others of said four sixteen-frame sub-sequences of said sixty-four-frame sequence to assume only a second of said two adjacent values.

10. A method of simulating display colors in addition to a number of display colors otherwise available using a color display device that has an array of picture elements each including plural picture sub-elements each of a different color and each having only two display states, an ON state and an OFF state, comprising the steps of:

modulating an ON/OFF duty cycle of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating the timing of ON/OFF and OFF/ON state transitions of picture sub-elements within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that the state transitions occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

wherein said multi-frame sequence is M×

N frames long, M and N being integers, and is logically divided into M sub-sequences each N frames long,

wherein M×

N+1 display shades of each picture sub-element are realized by causing the ON/OFF duty cycle of each picture sub-element to have a value within the set {0, 1/M×

N, 2/M×

N, . . . , M×

N/M×

N}, and

wherein the ON/OFF duty cycle of each picture sub-element during each of said M N-frame sub-sequences of said M×

N frame sequence is caused to-have a value within the set {0, 1/N, 2/N, . . . , N/N}.

11. The method of claim 10, comprising the further step of allowing the duty cycle of each picture sub-element during each of said M N-frame sub-sequences of said M×

N frame sequence to assume one of two adjacent values only, within the set {0, 1/M, 2/M . . . M/M}.

12. The method of claim 10, comprising the further step of allowing the duty cycle of each picture sub-element during at least one, but not all, of said M-frame sub-sequences of said M×

N frame sequence to assume only a first of two adjacent values within the set {0, 1/M, 2/M . . . M/M} and allowing the duty cycle of each picture sub-element during the other of said M N-frame sub-sequences of said M×

N frame sequence to assume only a second of said two adjacent values.

13. A color display apparatus having an array of picture elements each including plural picture sub-elements each of a different color and each having more than two display states selected between using at least two input terminals, each of which has two possible inputs, an ON input and an OFF input, said apparatus comprising:

modulating means for modulating an ON/OFF duty cycle of a least significant one of said at least two input terminals of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating means for coordinating the timing of ON/OFF and OFF/ON input transitions on said least significant input terminal of each picture sub-element within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that said input transitions cause state transitions of said picture sub-elements to occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

whereby said color display apparatus simulates display colors in addition to a number of display colors that would otherwise be available using said color display apparatus

wherein said color display apparatus has a thin-film transistor LCD display,

wherein each picture element has at least eight display states selected between using at least three input terminals,

wherein said multi-frame sequence is 64 frames long and is logically divided into four sub-sequences each 16 frames long,

wherein 260 shades of each picture sub-element are realized by causing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element to have a value within the set {0, 1/64, 2/64, . . . , 64/64},

wherein the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during each of said four 16-frame sub-sequences of said 64 frame sequence is caused to have a value within the set {0, 1/16, 2/16, . . . , 16/16}.

14. The apparatus of claim 13, further comprising:

means for allowing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during each of said four 16-frame sub-sequences of said 64 frame sequence to assume one of two adjacent values only within the set {0, 1/16, 2/16, . . . , 16/16}.

15. The apparatus of claim 13, further comprising:

means for allowing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during at least one, but not all, of said four 16-frame sub-sequences of said 64 frame sequence to assume only a first of two adjacent values within the set {0, 1/16, 2/16, . . . , 16/1} and allowing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during the others of said four 16-frame sub-sequences of said 64 frame sequence to assume only a second of said two adjacent values.

16. A color display apparatus having an array of picture elements each including plural picture sub-elements each of a different color and each having more than two display states selected between using at least two input terminals, each of which has two possible inputs, an ON input and an OFF input, said apparatus comprising:

modulating means for modulating an ON/OFF duty cycle of a least significant one of said at least two input terminals of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating means for coordinating the timing of ON/OFF and OFF/ON input transitions on said least significant input terminal of each picture sub-element within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that said input transitions cause state transitions of said picture sub-elements to occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

whereby said color display apparatus simulates display colors in addition to a number of display colors that would otherwise be available using said color display apparatus

wherein said color display apparatus has a thin-film transistor LCD display,

wherein each picture element has at least eight display states selected between using at least three input terminals,

wherein said multi-frame sequence is M×

N frames long, M and N being integers, and is logically divided into M sub-sequences each N frames long,

wherein M×

N+1 shades of each picture sub-element are realized by causing the ON/OFF duty cycle of said least significant input terminal of each picture sub-element to have a value within the set {0, 1/M×

N, 2/M×

N, M×

N/M×

N},

wherein the ON/OFF duty cycle of said least significant input terminal of each picture sub-element during each of said M N-frame sub-sequences of said M×

N frame sequence is caused to have a value within the set {0, 1/N, 2/N, . . . , N/N}.

17. The apparatus of claim 16 further comprising:

means for allowing the duty cycle of said least significant input terminal of each picture sub-element during each of said M N-frame sub-sequences of said M×

N frame sequence to assume one of two adjacent values only within the set {0, 1/N, 2/N, . . . , N/N}.

18. The apparatus of claim 16 further comprising:

means for allowing the duty cycle of said least significant input terminal of each picture sub-element during at least one, but not all, of said M N-frame sub-sequences of said M×

N frame sequence to assume only a first of two adjacent values within the set {0, 1/N, 2/N, . . . , N/N} and means for allowing the duty cycle of said least significant input terminal of each picture sub-element during the other of said M N-frame sub-sequences of said M×

N frame sequence to assume only a second of said two adjacent values.

19. A color display apparatus having an array of picture elements each including plural picture sub-elements each of a different color and each having only two display states, an ON state and an OFF state, comprising:

modulating means for modulating an ON/OFF duty cycle of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating means for coordinating the timing of ON/OFF and OFF/ON state transitions of picture sub-elements within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that the state transitions occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

whereby said color display apparatus simulates display colors in addition to a number of display colors otherwise available using said color display apparatus

wherein said multi-frame sequence is sixty-four frames long and is logically divided into four sub-sequences each sixteen frames long,

wherein sixty-five display shades of each picture sub-element are realized by causing the ON/OFF duty cycle of each picture element to have a value within the set {0, 1/64, 2/64, . . . , 64/64}, and

wherein the ON/OFF duty cycle of each picture sub-element during each of said four sixteen-frame sub-sequences of said sixty-four-frame sequence is caused to have a value within the set {0, 1/16, 2/16, . . . , 16/16}.

20. The apparatus of claim 19 further comprising:

means for allowing the duty cycle of each picture sub-element during each of said four sixteen-frame sub-sequences of said sixty-four-frame sequence to assume one of two adjacent values only, within the set {0, 1/16, 2/16, . . . , 16/16}.

21. The apparatus of claim 19 further comprising:

means for allowing the duty cycle of each picture sub-element during at least one, but not all, of said four sixteen-frame sub-sequences of said sixty-four-frame sequence to assume only a first of two adjacent values within the set {0, 1/16, 2/16, . . . , 16/16} and means for allowing the duty cycle of each picture sub-element during the other of said four sixteen-frame sub-sequences of said sixty-four-frame sequence to assume a second of said two adjacent values.

22. A color display apparatus having an array of picture elements each including plural picture sub-elements each of a different color and each having only two display states, an ON state and an OFF state, comprising:

modulating means for modulating an ON/OFF duty cycle of each picture sub-element of the array of picture elements during a multi-frame display sequence according to attribute information of respective picture element data to be displayed; and

coordinating means for coordinating the timing of ON/OFF and OFF/ON state transitions of picture sub-elements within each of a plurality of predetermined display neighborhoods throughout the array of picture elements such that the state transitions occur substantially uniformly in space and time, within each display neighborhood, during the multi-frame display sequence

whereby said color display apparatus simulates display colors in addition to a number of display colors otherwise available using said color display apparatus

wherein said multi-frame sequence is M×

N frames long, M and N being integers, and is logically divided into M sub-sequences each N frames long,

wherein M×

N+1 display shades of each picture sub-element are realized by causing the ON/OFF duty cycle of each picture sub-element to have a value within the set {0, 1/M×

N, 2/M×

N, . . . , M×

N/M×

n}, and

wherein the ON/OFF duty cycle of each picture sub-element during each of said M N-frame sub-sequences of said M×

N frame sequence is caused to-have a value within the set {0, 1/N, 2/N, . . . , N/N}.

23. The apparatus of claim 22, further comprising:

means for allowing the duty cycle of each picture sub-element during each of said M N-frame subsequences of said M×

N frame sequence to assume one of two adjacent values only, within the set {0, 1/M, 2/M . . . M/M}.

24. The apparatus of claim 22, further comprising:

means for allowing the duty cycle of each picture sub-element during each of said M N-frame sub-sequences of said M×

N frame sequence to assume only a first of two adjacent values within the set {0, 1/M, 2/M . . . M/M} and means for allowing the duty cycle of each picture sub-element during a second of said M N-frame sub-sequences of said M×

N frame sequence to assume only a second of said two adjacent values.