Electro-optical material-based display device having analog pixel drivers

• US 6,329,974 B1
• Filed: 04/30/1998
• Issued: 12/11/2001
• Est. Priority Date: 04/30/1998
• Status: Expired due to Term

• Current Assignee: Wistron Corporation
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Walker, Richard C., Blalock, Travis N., Gaddis, Neela B.
• Primary Examiner(s): Shankar, Vijay
• Application Number:
  US09/070,487
• Time in Patent Office: 1,321 Days
• Field of Search: 345/102, 345/154, 345/8, 345/82, 345/87, 345/98, 345/100, 345/90, 345/92, 345/96
• US Class Current: 345/98
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• 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 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

The display device operates in response to an information signal and comprises analog drive circuits in a two-dimensional array of rows and columns, an analog sampling circuit that derives the analog samples from the information signal, and a sample distribution circuit. The sample distribution circuit receives the analog samples from the analog sampling circuit and distributes them to the analog drive circuits. The sample distribution circuit includes input gates corresponding to the analog drive circuits, column busses corresponding to the columns of the array, and a row selector having outputs corresponding to the rows of the array. The column busses distribute the analog samples column-wise to the analog drive circuits. The input gates connect the analog drive circuits to the column busses. Each output of the row selector is connected to control the input gates in one of the rows. The row selector sequentially opens the input gates in the rows to select the analog samples on the column busses row-wise. A grey scale is generated by modulating light using an electro-optical material. An analog sample is derived from the information signal, a drive signal is generated in response to the analog sample, and the drive signal is applied to the electro-optical material. The drive signal generated in response to the analog sample includes a sequence of a first temporal portion having a time duration that has a pre-determined relationship to the analog sample, and a second temporal portion that is the temporal complement of the first.

Claims

1. A display device based on an electro-optical material, the display device operating in response to an information signal, and comprising:

analog drive circuits arranged in a two-dimensional array of rows and columns;

an analog sampling circuit that derives the analog samples from the information signal; and

a sample distribution circuit that receives the analog samples from the analog sampling circuit and distributes the analog samples to the analog drive circuits, the sample distribution circuit including;

input gates corresponding to the drive circuits;

column busses corresponding to the columns of the array through which the analog samples are distributed column-wise to the analog drive circuits, the analog drive circuits being connected to the column busses by the input gates, and

a row selector having outputs corresponding to the rows of the array, each of the outputs being connected to control the input gates in one of the rows, the row selector opening the input gates in the rows sequentially to perform a row-wise selection of the analog samples on the column busses.

2. The display device of claim 1, in which the analog sampling circuit includes:

a sampling circuit comprising a row of sample-and-hold circuits, each of the sample-and-hold circuits corresponding to one of the column busses, each of the sample-and-hold circuits comprising;

an output connected to the one of the column busses,

an input connected to receive the information signal, and

a column control signal input; and

a column selector connected to the column control signal inputs of the sample-and-hold circuits, the column selector generating column control signals for the sample-and-hold circuits at a signal rate related to the information signal, the column control signal for a one of the sample-and-hold circuits being in an opposite state to the column control signals for the remaining ones of the sample-and-hold circuits, the column control signal in the opposite state moving progressively along the row of sample-and-hold circuits at the signal rate.

3. The display device of claim 2, in which:

the information signal is a video signal having a pixel rate and a line rate;

the signal rate of the column control signal generated by the column selector is equal to the pixel rate of the video signal; and

the row selector sequentially opens the input gates in the rows at a rate equal to the line rate of the video signal.

4. The display device of claim 1, in which:

the information signal includes odd-numbered sequences interleaved with even-numbered sequences;

the analog drive circuits include respective odd sections that process ones of the analog samples derived from the odd-numbered sequences and even sections that process ones of the analog samples derived from the even-numbered sequences;

the input gates are odd input gates and connect the odd sections of the analog drive circuits to the column busses;

the sample distribution circuit additionally includes;

even input gates that connect the even sections of the analog drive circuits to the column busses,

an odd-even selector interposed between the row selector and the analog drive circuits and having odd outputs and even outputs, each of the odd outputs and even outputs being connected to control the odd input gates and even input gates, respectively, in one of the rows, the odd input gates being opened when the analog samples on the column busses are derived from the odd-numbered sequences, the even input gates being opened when the analog samples on the column busses are derived from the even-numbered sequences.

5. The display device of claim 4, in which the display device additionally comprises a sequencer that receives a color video signal comprising color components and generates a color-sequential video signal from the color video signal and that provides the color-sequential video signal as the information signal, the color-sequential video signal including the odd-numbered sequences interleaved with the even-numbered sequences, each of the sequences corresponding to a frame of one of the color components of the color video signal.

6. The display device of claim 5, in which the sequencer generates each of the sequences of the color-sequential video signal with a time duration equal to a time duration of the frame of the color video signal.

7. The display device of claim 5, in which the sequencer generates each of the sequences of the color-sequential video signal with a time duration equal to 1/n of a time duration of the frame of the color video signal, where n is the number of color components in the color video signal.

8. The display device of claim 1, in which:

the information signal is a color video signal comprising n color components;

the analog sampling circuit includes a sampling circuit corresponding to each of the color components, each sampling circuit receiving one of the color components and deriving ones of the analog samples therefrom;

the sample distribution circuit includes;

in each of the analog drive circuits, an input gate corresponding to each one of the color components;

for each of the columns of the array, a column bus corresponding to each one of the color components through which the analog samples derived from the one of the color components are distributed column-wise to the analog drive circuits, the analog drive circuits being connected to the column busses corresponding to the one of the color components by the input gates corresponding to the one of the color components, and each of the outputs of the row selector is connected to control the input gates in the respective one of the rows.

9. The display device of claim 8, in which:

the color video signal includes odd-numbered frames interleaved with even-numbered frames;

the analog drive circuits include respective odd sections that process ones of the analog samples derived from the odd-numbered frames and even sections that process ones of the analog samples derived from the even-numbered frames;

the input gates are odd input gates and connect the odd sections of the drive circuits to the column busses;

the sample distribution circuit additionally includes;

even input gates that connect the even sections of the analog drive circuits to the column busses,

an odd-even selector circuit interposed between the row selector circuit and the drive circuits and having odd outputs and even outputs, each of the odd outputs and even outputs being connected to control the odd input gates and even input gates, respectively, in one of the rows, the odd input gates being opened when the analog samples on the column busses are derived from the odd-numbered frames, the even input gates being opened when the analog samples on the column busses are derived from the even-numbered frames.

10. The display device of claim 1, in which:

the row selector is a first row selector, each of the outputs of the first row selector being connected to control a first sequence of the input gates in one of the rows of the array; and

the sample distribution circuit additionally comprises a second row selector having outputs corresponding to ones of the rows of the array, each of the outputs being connected to control the input gates of a second sequence of the input gates in the one of the rows of the array, the second row selector and the first row selector collectively performing the row-wise selection of the analog samples on the column busses.

11. The display device of claim 10, in which:

the first row selector opens the first sequence of the input gates for an opening time that extends beyond a settling time of the analog samples on the column busses connected to the first sequence of the input gates; and

the second row selector opens the second sequence of the input gates for an opening time that extends beyond a settling time of the analog samples on the column busses connected to the second sequence of the input gates.

12. The display device of claim 10, in which the first row selector and the second row selector operate at a predetermined timing difference.

13. The display device of claim 1, in which:

the information signal is a video signal composed of lines and frames; and

the location in each of the lines of the video signal from which the analog sampling circuit derives the analog samples that the sample distribution circuit distributes to each one of the column busses depends on the location of the one of the column busses in the array.

14. A display device based on an electro-optical material, the display device operating in response to an information signal, the display device comprising:

an array of pixels, each of the pixels including;

an electrode electrically coupled to the electro-optical material, and

an analog drive circuit including an output electrically connected to the electrode; and

a sample distribution circuit that distributes an analog sample derived from the information signal to the analog drive circuit of each of the pixels, in which;

the analog drive circuit generates a drive signal composed of a sequence of a first temporal portion and a second temporal portion, the first temporal portion having a time duration that has a predetermined relationship to the analog sample, the second temporal portion being a temporal complement of the first temporal portion; and

is the display device additionally comprises a light source that illuminates the electro-optical material simultaneously with the analog drive circuit generating the drive signal.

15. The display device of claim 14, in which:

the information signal is composed of odd-numbered sequences interleaved with even-numbered sequences; and

the analog drive circuit includes;

an odd sample selection section that temporarily stores the analog sample taken from each of the odd-numbered sequences,

an even sample selection section that temporarily stores the analog sample taken from each of the even-numbered sequences, and

a drive signal generator that, during the even-numbered sequences, generates the drive signal in response to the analog sample stored in the odd sample selection section, and, during the odd-numbered sequences, generates the drive signal in response to the analog sample stored in the even sample selection section.

16. The display device of claim 14, in which the analog drive circuit includes:

a sample selection section that stores the analog sample received from the sample distribution circuit; and

a drive signal generator that generates the drive signal in response to the analog sample stored in the sample selection section.

17. The display device of claim 14, in which:

the sequence of the first temporal portion and the second temporal portion is a first sequence of the first temporal portion and the second temporal portion;

the analog drive circuit generates the drive signal in a first electrical state during the first temporal portion and in a second electrical state during the second temporal portion, and generates the drive signal additionally composed of a second sequence of the first temporal portion, in which the drive signal is in the second electrical state, and the second temporal portion, in which the drive signal is in the first electrical state, the first temporal portion and the second temporal portion being in any order in the second sequence; and

the light source illuminates the electro-optical material during the first sequence.

18. The display device of claim 14, in which:

the information signal is a color video signal comprising n color components;

the sample distribution circuit includes;

a sampling circuit corresponding to each one of the color components, the sampling circuit receiving the one of the color components and deriving ones of the analog samples therefrom,

for each of the columns of the array, a column bus corresponding to each one of the color components, the column bus being connected to the sampling circuit corresponding to the one of the color components

in the analog drive circuit of each of the pixels, an input gate and sample storage section corresponding to each one of the color components, the input gate corresponding to the one of the colors being connected to the column bus corresponding to the one of the colors; and

a row selector having outputs corresponding to the rows of the array, each of the outputs being connected to control the input gates of the analog drive circuits in one of the rows, the row selector opening the input gates in the rows sequentially to perform a row-wise selection of the analog samples on the column busses; and

the analog drive circuit of each of the pixels includes;

a sample storage section corresponding to each one of the color components, the sample storage section corresponding to the one of the color components storing one of the analog samples received from the sample distribution circuit, the one of the analog samples being derived from the one of the color components, and

a drive signal generator that generates the drive signal in response to the analog sample of each one of the color components stored in the sample selection section corresponding to the one of the color components, the drive signal including n first temporal portions each having a duration that has a predetermined relationship to the analog sample of a different one of the color components, and additionally including n second temporal portions, each of the second temporal portions being temporally complementary to a different one of the first temporal portions.

19. The display device of claim 18, in which the light source illuminates the electro-optical material with light of a color corresponding to the color component in response to which the drive signal generates the drive signal.

20. The display device of claim 18, in which:

the color video signal comprises frames;

the drive signal generator includes an error factor that changes the predetermined relationship between the duration of the first temporal portion and the analog sample, the error factor having a sense; and

the drive signal generator additionally includes means for alternating the sense of the error factor between consecutive frames of the color video signal.

21. The display device of claim 20, in which the drive signal generator includes:

an comparator including a first input and a second input and having an invertable comparison sense;

a reference signal;

means for connecting the analog sample alternately to the first input and the second input and for connecting the reference signal alternately to the second input and the first input during alternate frames of the color video signal; and

means for inverting the comparison sense of the comparator during alternate frames of the color video signal.