Ferroelectric liquid crystal display apparatus and method

• US 5,416,496 A
• Filed: 03/19/1993
• Issued: 05/16/1995
• Est. Priority Date: 08/22/1989
• Status: Expired due to Term

• Current Assignee: Acacia Patent Acquisition Corporation (Acacia Research Corporation)
• Original Assignee: Lawson A. Wood
• Inventors: Wood, Lawson A.
• Primary Examiner(s): Weldon, Ulysses
• Assistant Examiner(s): WU, XIAO MIN
• Application Number:
  US08/034,694
• Time in Patent Office: 788 Days
• Field of Search: 340/784, 340/793, 340/703, 340/765, 340/767, 359/54, 359/55, 359/56, 359/48, 359/50, 345/89, 345/88, 345/87, 345/99, 345/102, 345/147, 345/148, 345/153, 345/155
• US Class Current: 345/102
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/2081 with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A liquid crystal display apparatus includes a ferroelectric LCD panel and a backlighting unit which emits flashes of red light, flashes of green light, and flashes of blue light. The pixels of the LCD panel are turned on in accordance with the most significant bits of the red component of an image, and a red flash is emitted at a first level. Then all of the pixels are turned off. Pixels are turned on again in accordance with the second-most significant bit of the red component of the image, and then the red light is flashed at a level which is half that of the preceding flash. This procedure continues bit-by-bit until the pixels are turned on in accordance with the least significant bit of the red component of the image and the red light is flashed at a level commensurate with the least significant bit. Then the blue and green component of the frame are displayed in the same way. In another embodiment, the intensity of red, green, and blue fluorescent tubes behind a ferroelectric LCD panel is controlled as pixels are being turned on and off. The rate at which they are turned on and off may also be controlled to provide different intensity levels.

Claims

1. A method of displaying a sequence of frames of video information on a ferroelectric LCD panel having a matrix of pixels, the video information for a frame including a plurality of multi-bit video words, each video word corresponding to a respective pixel and including at least a first bit and a second bit, said method comprising the steps of:

(a) turning on the pixels which correspond to video words whose first bit has a predetermined value, by subjecting the pixels which correspond to video words whose first bit has the predetermined value to a voltage v-on while keeping pixels which correspond to video words whose first bit does not have the predetermined value isolated from the voltage v-on;

(b) turning off the pixels that were turned on during step (a), by subjecting the pixels which correspond to video words whose first bit has the predetermined value to a voltage v-off while keeping pixels which correspond to video words whose first bit does not have the predetermined value isolated from the voltage v-off;

(c) turning on the pixels which correspond to video words whose second bit has the predetermined value, by subjecting the pixels which correspond to video words whose second bit has the predetermined value to the voltage v-on while keeping pixels which correspond to video words whose second bit does not have the predetermined value isolated from the voltage v-on; and

(d) turning off the pixels that were turned on during step (c), by subjecting the pixels which correspond to video words whose second bit has the predetermined value to the voltage v-off while keeping pixels which correspond to video words whose second bit does not have the predetermined value isolated from the voltage v-off.

2. The method of claim 1, wherein the LCD panel has a plurality of row electrodes and a plurality of column electrodes, and wherein step (a) comprises:

(a-1) transferring the first bits of the video words corresponding to the pixels in a first row to a column shift register having a plurality of stages;

(a-2) selectively connecting the column electrodes to an ON voltage source depending on the content of the stages of the column shift register;

(a-3) bringing the first of the row electrodes to a predetermined potential;

(a-4) transferring the first bits of the video words corresponding to the pixels in the next row to the column shift register;

(a-5) selectively connecting the column electrodes to the ON voltage source depending on the content of the stages of the column shift register;

(a-6) bring the next row electrode to the predetermined potential; and

(a-7) repeating steps (a-4) to (a-6) until the last row electrode has been brought to the predetermined potential.

3. The method of claim 2, wherein the predetermined potential is ground potential, wherein step (a-3) is conducted by bringing the first of the row electrodes to ground potential while the rest of the row electrodes are in an electrically floating state, and wherein step (a-6) is conducted by bringing the next row electrode to ground potential while the rest of the row electrodes are in an electrically floating state.

4. The method of claim 2, wherein step (b) comprises:

(b-1) transferring the first bits of the video words corresponding to the pixels in the first row to the column shift register;

(b-2) selectively connecting the column electrodes to an OFF voltage source depending on the content of the stages of the column shift register;

(b-3) bringing the first of the row electrodes to the predetermined potential;

(b-4) transferring the first bits of the video words corresponding to pixels in the next row to the column shift register;

(b-5) selectively connecting the column electrodes to the OFF voltage source depending on the contents of the stages of the column shift register;

(b-6) bringing the next row electrode to the predetermined potential; and

(b-7) repeating steps (b-4) to (b-6) until the last row electrode has been brought to the predetermined potential.

5. The method of claim 4, wherein step (c) comprises:

(c-1) transferring the second bits of the video words corresponding to the pixels in the first row to the column shift register;

(c-2) selectively connecting the column electrodes to the ON voltage source depending on the content of the stages of the column shift register;

(c-3) bringing the first of the row electrodes to the predetermined potential;

(c-4) transferring the second bits of the video words corresponding to the pixels in the next row to the column shift register;

(c-5) selectively connecting the column electrodes to the ON voltage source depending on the content of the stages of the column shift register;

(c-6) bringing the next row electrode to the predetermined potential; and

(c-7) repeating steps (c-4) to (c-6) until the last row electrode has been brought to the predetermined level.

6. The method of claim 1, further comprising the steps of exposing the panel to a flash of light at a first level after step (a) is conducted, and exposing the panel to a flash of light at a second level after step (c) is conducted.

7. The method of claim 6, wherein the step of exposing the panel to a flash of light at a first level comprises charging a capacitor to a predetermined potential, and discharging the capacitor through an illuminating source for a first predetermined duration, and wherein the step of exposing the panel to a flash of light at a second level comprises charging the capacitor to the predetermined potential, and discharging the capacitor through the illuminating source for a second predetermined duration.

8. The method of claim 6, wherein the step of exposing the panel to a flash of light at a first level comprises storing a first amount of energy, and discharging the stored energy through an illuminating source, and wherein the step of exposing the panel to a flash of light at a second level comprises storing a second amount of energy, and discharging the stored energy through the illuminating source.

9. The method of claim 1, further comprising the steps of steadily exposing the panel to light at a first level while steps (a) and (b) are conducted, and steadily exposing the panel to light at a second level while steps (c) and (d) are conducted.

10. The method of claim 1, further comprising the steps of exposing the panel to light during at least one period while steps (a) and (b) are conducted, and exposing the panel to light during at least one period while steps (c) and (d) are conducted, the exposing steps being conducted so that the light while steps (a) and (b) are conducted has a different level than when steps (c) and (d) are conducted.

11. The method of claim 1, wherein steps (a) and (b) are conducted at a different rate than steps (c) and (d).

12. The method of claim 11, further comprising the step of steadily exposing the panel to light while steps (a) through (d) are conducted.

13. The method of claim 11, further comprising the step of exposing the panel to light at a constant level during at least one period while steps (a) through (d) are conducted.

14. A method of displaying a sequence of frames of video information on a ferroelectric LCD panel having a matrix of pixels, the video information for a frame including a plurality of first multi-bit video words for a first primary color component of an image, a plurality of second multi-bit video words for a second primary color component of the image, and a plurality of third multi-bit video words for a third primary color component of the image, each pixel corresponding to one of the first multi-bit video words, one of the second multi-bit video words, and one of the third multi-bit video words, each of the multi-bit video words including at least a most significant bit and a least significant bit, comprising:

(a) turning on the pixels which correspond to the first video words whose most significant bit has a predetermined value, by subjecting the pixels which correspond to first video words whose most significant bit has the predetermined value to a voltage v-on while keeping pixels which correspond to first video words whose most significant bit does not have the predetermined value isolated from the voltage v-on;

(b) turning off the pixels that were turned on during step (a), by subjecting the pixels which correspond to first video words whose most significant bit has the predetermined value to a voltage v-off while keeping pixels which correspond to first video words whose most significant bit does not have the predetermined value isolated from the voltage v-off;

(c) turning on the pixels which correspond to first video words whose least significant bit has the predetermined value, by subjecting the pixels which correspond to first video words whose least significant bit has the predetermined value to the voltage v-on while keeping pixels which correspond to first video words whose least significant bit does not have the predetermined value isolated from the voltage v-on; and

(d) turning off the pixels that were turned on during step (c), by subjecting the pixels which correspond to first video words whose least significant bit has the predetermined value to the voltage v-off while keeping pixels which correspond to first video words whose least significant bit does not have the predetermined value isolated from the voltage v-off.

15. The method of claim 14, further comprising the steps of:

(e) turning on the pixels which correspond to second video words whose most significant bit has the predetermined value, by subjecting the pixels which correspond to second video words whose most significant bit has the predetermined value to the voltage v-on while keeping pixels which correspond to second video words whose most significant bit does not have the predetermined value isolated from the voltage v-on;

(f) turning off the pixels that were turned on during step (e), by subjecting the pixels which correspond to second video words whose most significant bit has the predetermined value to the voltage v-off while keeping pixels which correspond to second video words whose most significant bit does not have the predetermined value isolated from the voltage v-off;

(g) turning on the pixels which correspond to second video words whose least significant bit has the predetermined value, by subjecting the pixels which correspond to second video words whose least significant bit has the predetermined value to the voltage v-on while keeping pixels which correspond to second video words whose least significant bit does not have the predetermined value isolated from the voltage v-on; and

(h) turning off the pixels that were turned on during step (g), by subjecting the pixels which correspond to second video words whose least significant bit has the predetermined value to the voltage v-off while keeping pixels which correspond to second video words whose least significant bit does not have the predetermined value isolated from the voltage v-off.

16. The method of claim 15, further comprising the steps of:

(i) turning on the pixels which correspond to third video words whose most significant bit has the predetermined value, by subjecting the pixels which correspond to third video words whose most significant bit has the predetermined value to the voltage v-on while keeping pixels which correspond to third video words whose most significant bit does not have the predetermined value isolated from the voltage v-on;

(j) turning off the pixels that were turned on during step (i), by subjecting the pixels which correspond to third video words whose most significant bit has the predetermined value to the voltage v-off while keeping pixels which correspond to third video words whose most significant bit does not have the predetermined value isolated from the voltage v-off;

(k) turning on the pixels which correspond to third video words whose least significant bit has the predetermined value, by subjecting the pixels which correspond to third video words whose least significant bit has the predetermined value to the voltage v-on while keeping pixels which correspond to third video words whose least significant bit does not have the predetermined value isolated from the voltage v-on; and

(l) turning off the pixels that were turned on during step (k), by subjecting the pixels which correspond to third video words whose least significant bit has the predetermined value to the voltage v-off while keeping pixels which correspond to third video words whose least significant bit does not have the predetermined value isolated from the voltage v-off.

17. The method of claim 14, further comprising the steps of exposing the panel to a first flash of light at a first level after step (a) is conducted, the first flash having the first primary color, and exposing the panel to a second flash of light at a second level after step (c) is conducted, the second flash having the first primary color.

18. The method of claim 14, further comprising the steps of steadily exposing the panel to light at a first level while steps (a) and (b) are conducted, and steadily exposing the panel to light at a second level while steps (c) and (d) are conducted, the light at the first level and the light at the second level having the first primary color.

19. The method of claim 14, further comprising the steps of exposing the panel to light during at least one period while steps (a) and (b) are conducted, and exposing the panel to light during at least one period while steps (c) and (d) are conducted, the exposing steps being conducted so that the light while steps (a) and (b) are conducted has a different level than when steps (c) and (d) are conducted, the exposing steps being conducted with light of the first primary color.

20. The method of claim 14, wherein steps (a) and (b) are conducted at a slower rate than steps (c) and (d).

21. A method of displaying a sequence of frames of video information on a ferroelectric LCD panel having a matrix of pixels, the video information for a frame including a plurality of multi-bit video words, each video word corresponding to a respective pixel and including at least a first bit and a second bit, said method comprising the steps of:

(a) turning on the pixels which correspond to video words whose first bit has a predetermined value;

(b) turning off the pixels that were turned on during step (a);

(c) turning on the pixels which correspond to video words whose second bit has the predetermined value;

(d) turning off the pixels that were turned on during step (c);

(e) steadily exposing the panel to light at a first level while step (a) is conducted and while step (b) is conducted; and

(f) steadily exposing the panel to light at a second level while step (c) is conducted and while step (d) is conducted.

22. A method of displaying a sequence of frames of video information on a ferroelectric LCD panel having a matrix of pixels, the video information for a frame including a plurality of multi-bit video words, each video word corresponding to a respective pixel and including at least a first bit and a second bit, said method comprising the steps of:

(a) turning on the pixels which correspond to video words whose first bit has a predetermined value;

(b) turning off the pixels that were turned on during step (a);

(c) turning on the pixels which correspond to video words whose second bit has the predetermined value; and

(d) turning off the pixels that were turned on during step (c),

wherein steps (a) and (b) are conducted at a different rate than steps (c) and (d) .

23. The method of claim 22, further comprising the step of steadily exposing the panel to light while steps (a) through (d) are conducted.

24. The method of claim 22, further comprising the step of exposing the panel to light for at least one period while step (a) is conducted, for at least one period while step (b) is conducted, for at least one period while step (c) is conducted, and for at least one period while step (d) is conducted.

25. A method of displaying a sequence of frames of video information on a ferroelectric LCD panel having a matrix of pixels, the video information for a frame including a plurality of first multi-bit video words for a first primary color component of an image, a plurality of second multi-bit video words for a second primary color component of the image, and a plurality of third multi-bit video words for a third primary color component of the image, each pixel corresponding to one of the first multi-bit video words, one of the second multi-bit video words, and one of the third multi-bit video words, each of the multi-bit video words including at least a most significant bit and a first intermediate bit with half the binary significance of the most significant bit, comprising:

(a) turning on the pixels which correspond to the first video words whose most significant bit has a predetermined value;

(b) turning off the pixels that were turned on during step (a);

(c) turning on the pixels which correspond to first video words whose first intermediate bit has the predetermined value;

(d) turning off the pixels that were turned on during step (c);

(e) exposing the panel to light of the first primary color while steps (a)-(d) are conducted;

(f) turning on the pixels which correspond to second video words whose most significant bit has the predetermined value;

(g) turning off the pixels that were turned on during step (f);

(h) turning on the pixels which correspond to second video words whose first intermediate bit has the predetermined value;

(i) turning off the pixels that were turned on during step (h);

(j) exposing the panel to light of the second primary color while steps (f)-(i) are conducted;

(k) turning on the pixels which correspond to third video words whose most significant bit has the predetermined value;

(l) turning off the pixels that were turned on during step (k);

(m) turning on the pixels which correspond to third video words whose first intermediate bit has the predetermined value; and

(n) turning off the pixels that were turned on during step (m),

wherein step (e) is conducted by steadily exposing the panel to light at a high level during step (a) and during step (b), and by steadily exposing the panel to light at half the high level during step (c) and during step (d).

26. A method of displaying a sequence of frames of video information on a ferroelectric LCD panel having a matrix of pixels, the video information for a frame including a plurality of first multi-bit video words for a first primary color component of an image, a plurality of second multi-bit video words for a second primary color component of the image, and a plurality of third multi-bit video words for a third primary color component of the image, each pixel corresponding to one of the first multi-bit video words, one of the second multi-bit video words, and one of the third multi-bit video words, each of the multi-bit video words including at least a most significant bit and a first intermediate bit with half the binary significance of the most significant bit, comprising:

(a) turning on the pixels which correspond to the first video words whose most significant bit has a predetermined value;

(b) turning off the pixels that were turned on during step (a);

(c) turning on the pixels which correspond to first video words whose first intermediate bit has the predetermined value;

(d) turning off the pixels that were turned on during step (c);

(e) exposing the panel to light of the first primary color while steps (a)-(d) are conducted;

(f) turning on the pixels which correspond to second video words whose most significant bit has the predetermined value;

(g) turning off the pixels that were turned on during step (f);

(h) turning on the pixels which correspond to second video words whose first intermediate bit has the predetermined value;

(i) turning off the pixels that were turned on during step (h);

(j) exposing the panel to light of the second primary color while steps (f)-(i) are conducted;

(k) turning on the pixels which correspond to third video words whose most significant bit has the predetermined value;

(l) turning off the pixels that were turned on during step (k);

(m) turning on the pixels which correspond to third video words whose first intermediate bit has the predetermined value; and

(n) turning off the pixels that were turned on during step (m),

wherein step (e) is conducted by exposing the panel to light for at least one period during step (a), at least one period during step (b), at least one period during step (c), and at least one period during step (d), the total amount of light received by the panel during steps (a) and (b) being double the total amount of light received by the panel during steps (c) and (d) .

27. A method of displaying a sequence of frames of video information on a ferroelectric LCD panel having a matrix of pixels, the video information for a frame including a plurality of first multi-bit video words for a first primary color component of an image, a plurality of second multi-bit video words for a second primary color component of the image, and a plurality of third multi-bit video words for a third primary color component of the image, each pixel corresponding to one of the first multi-bit video words, one of the second multi-bit video words, and one of the third multi-bit video words, each of the multi-bit video words including a most significant bit and a first intermediate bit with half the binary significance of the most significant bit, comprising:

(a) turning on the pixels which correspond to the first video words whose most significant bit has a predetermined value;

(b) turning off the pixels that were turned on during step (a);

(c) turning on the pixels which correspond to first video words whose first intermediate bit has the predetermined value;

(d) turning off the pixels that were turned on during step (c);

(e) turning on the pixels which correspond to second video words whose most significant bit has the predetermined value;

(f) turning off the pixels that were turned on during step (e);

(g) turning on the pixels which correspond to second video words whose first intermediate bit has the predetermined value;

(h) turning off the pixels that were turned on during step (g);

(i) turning on the pixels which correspond to third video words whose most significant bit has the predetermined value;

(j) turning off the pixels that were turned on during step (i);

(k) turning on the pixels which correspond to third video words whose first intermediate bit has the predetermined value; and

30. The method of claim 27, wherein the panel is steadily exposed to light of the first primary color during steps (a)-(c), to light of the second primary color during steps (e)-(h), and light of the third primary color during steps (i)-(l) .

31. The method of claim 27, wherein the panel is exposed to light of the first primary color for at least one period during each of steps (a)-(c), to light of the second primary color for at least one period during each of steps (e)-(h), and to light of the third primary color for at least one period during each of steps (i)-(l).

28. (l) turning off the pixels that were turned on during step (k),

29. wherein steps (a) and (b) are conducted half as fast as steps (c) and (d), steps (e) and (f) are conducted half as fast as steps (g) and (h) , and steps (i) and (j) are conducted half as fast as steps (k) and (l).