Liquid crystal display and a driving method thereof

• US 7,095,393 B2
• Filed: 08/19/2002
• Issued: 08/22/2006
• Est. Priority Date: 11/26/2001
• Status: Expired due to Term

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Baek-Woon
• Primary Examiner(s): Tran, Henry N.
• Application Number:
  US10/223,641
• Publication Number:
  US 20030098839A1
• Time in Patent Office: 1,464 Days
• Field of Search: 345 87- 92, 345/690, 345/204, 345/596, 345/601, 345/602
• US Class Current: 345/89
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/06 Adjustment of display parameters
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

Disclosed is an LCD and driving method thereof. The LCD according to the present invention generates modification image signals by considering image signals of present and previous frames, and then supplies data voltages corresponding to the generated modification image signals to the data lines. At this time, the value for modifying the present frame image signal varies according to a modification parameter that is at least one among a temperature, an image quality selected by a user, and an environment of the LCD.

Claims

1. A liquid crystal display (LCD) comprising:

an LCD panel comprising a plurality of gate lines for transmitting scanning signals, a plurality of data lines that cross the gate lines for transmitting image signals, and a plurality of pixels that are arranged in a matrix and have switching elements connected to the gate lines and the data lines;

a data gray signal modifier that receives gray signals from an external device, and modifies gray signals of a present frame based on gray signals of present and previous frames and at least a modification parameter including a temperature, an image quality selected by a user, and an environment of the LCD;

a gate driver sequentially applying the scanning signals to the gate lines; and

a data driver that converts the modified gray signals into data voltages and applies the data voltages to the data lines,

wherein the data gray signal modifier includes a look-up table (LUT) for a reference value of the at least a modification parameter, the LUT has modification values for modifying gray signals, and each modification value of the LUT is represented by G_ij, the present frame gray signal G_n matching with G_ij is expressed as G_n=(i−

1)×

2<sup>8−

y</sup>, and the previous frame gray signal G<sub>n−

1</sub> matching with G_ij is expressed as G<sub>n−

1</sub>=(j−

1)×

2<sup>8−

y</sup>.

2. The LCD of claim 1, wherein the data gray signal modifies the modification value G_ij of the LUT so as to produce a modified modification value G_ij′

corresponding to a first value of the at least a modification parameter different from the reference value that satisfies;

G_ij′

=G_ij+α

(G_ij−

G_ii)+β

(G_ij−

G_ii)²+γ

(G_ij−

G_ii)⁴+. . . ,

where G_ii=(i−

1)×

2<sup>8−

y</sup>, and α

, β

, and γ

are modification coefficients compensating the difference between the first value and the reference.

3. The LCD of claim 2, wherein the data gray signal modifier sets the value of the modification coefficient to be greater than one when the first value is lower than the reference value, and sets the value of the modification coefficient to be less than one when the first value is higher than the reference value.

4. The LCD of claim 3, wherein the modification parameter is transmitted from the external device as a gray signal during a data blank period.

5. A method for driving a liquid crystal display (LCD), the LCD having a plurality of gate lines, a plurality of data lines insulated from and crossing the gate lines, and a plurality of pixels formed in an area surrounded by the gate lines and data lines and arranged as a matrix pattern arid having switching elements connected to the gate lines and data lines, the method comprising:

(a) sequentially supplying scanning signals to the gate lines;

(b) receiving image signals from an image signal source, and generating modification image signals from image signals of present and previous frames in accordance with one or more modification parameters; and

(c) supplying data voltages corresponding to the generated modification image signals to the data lines,

wherein the one or more modification parameters are at least one of a temperature, an image quality selected by a user, and an environment of the LCD, and

wherein the generation of the modification image signals comprises;

selecting one of a plurality of conversion tables containing modification values matching with the previous frame image signal and the present image signal for different values of the one or more modification parameters,

wherein the generation of modification image signals further comprises;

generating a new conversion table by converting the modification values of the selected conversion table according to a particular value of the one or more modification parameters, and generating the modification image signals based on the new conversion table.

6. The method of claim 5, wherein the image signals are identified as digital gray signals.

7. The method of claim 5, wherein the generation of the new conversion table is performed during a data blank period.

8. A liquid crystal display (LCD), comprising:

an LCD panel comprising a plurality of gate lines for transmitting scanning signals, a plurality of data lines that cross the gate lines for transmitting image signals, and a plurality of pixels that are arranged in a matrix and have switching elements connected to the gate lines and the data lines;

a data gray signal modifier that receives gray signals from an external device, and modifies gray signals of a present frame (“

present gray signals) based on gray signals of present and previous frames and at least a modification parameter including a temperature, an image quality selected by a user, and an environment of the LCD;

a gate driver sequentially applying the scanning signals to the gate lines; and

a data driver that converts the modified array signals into data voltages and applies the data voltages to the data lines,

wherein the data gray signal modifier includes a storage device including a plurality of look-up tables (LUT) for different values of the at least a modification parameter, each LUT storing modification values for modifying gray signals,

wherein the data array signal modifier further comprises;

an LUT selector selecting one of the plurality of LUT based on a value of the at least a modification parameter; and

a modified signal generator that reads modification values corresponding to gray signals of present and previous frames from the selected LUT and generates the modified gray signals based on the modification values,

wherein the LUT selector generates a coefficient value for converting modification values of the selected LUT based on a value of the at least a modification parameter, the data gray signal modifier further comprises an LUT converter converting modification values of the selected LUT based on the coefficient value to generate a modified LUT, and the modified signal generator reads modification values corresponding to gray signals of present and previous frames from the selected LUT or the modified LUT and generates the modified gray signals based upon the modification values.

9. The LCD of claim 8, wherein the data gray signal modifier modifies the gray signals so as to output a modification data voltage V_n′

that satisfies the following equation;

|V_n′

|=|V_n|+ƒ

(|V_n|−

|V<sub>n−

1</sub>|)

where the data voltage of the present frame is set to be V_n, and that of the previous frame is set to be V<sub>n−

i</sub>.

10. The LCD of claim 8, wherein the data gray signal modifier further comprises a frame memory for storing gray signals for one frame and outputs the stores gray signals as the gray signals of a previous frame (“

previous gray signals”

).

11. The LCD of claim 10, further comprising a controller controlling writing and reading the gray signals of the frame memory.

12. The LCD of claim 11, wherein the controller operates in synchronization with a clock frequency of the gray signals inputted from the external device.

13. The LCD of claim 11, wherein the controller operates asynchronous from a clock frequency of the gray signals inputted from the external device.

14. The LCD of claim 13, wherein the LCD further comprises:

a combiner combining the gray signals to be synchronized with a clock signal frequency with which the controller is synchronized, and outputting the combined gray signals to the frame memory and the data gray signal converter; and

a divider for dividing the gray signals output by the data gay signal modifier so as to be synchronized with a frequency with which the gray signals transmitted by the external device are synchronized.

15. A liquid crystal display (LCD), comprising:

an LCD panel comprising a plurality of gate lines for transmitting scanning signals, a plurality of data lines that cross the gate lines for transmitting image signals, and a plurality of pixels that are arranged in a matrix and have switching elements connected to the gate lines and the data lines;

a data gray signal modifier that receives a plurality of pairs of gray signals, each pair of gray signals including a gray signal of a present frame (“

present gray signal”

) and a gray signal of a previous frame (“

previous gray signal”

), and modifies the present gray signals based on the pairs of gray signals and at least a modification parameter including a temperature, an image quality selected by a user, and an environment of the LCD;

a gate driver applying the scanning signals to the gate lines; and

a data driver that converts the modified gray signals into data voltages and applies the data voltages to the data lines,

wherein each of the present and the previous gray signals includes most significant bit (MSB) and least significant bit (LSB) and the data gray signal modifier includes at least a look-up table storing modification variables as function of pairs of MSBs of present and previous gray signals and a calculator generating the modified gray signals based on the modification variables and the LSB of the present gray signals,

wherein the modification variables include first variable (f) related to each pair of MSBs and second and third variables (a and b) representing the difference between values of the first variable related to adjacent pairs of MSBs.

16. The LCD of claim 15, wherein the modified gray signal G_n′

for a present gray signal G_n and a previous gray signal G<sub>n−

1</sub> is given by,

$G_n^{\mathrm{\prime <br><br>}}=f<br><br>\left({\left[G_n\right]}_z,{\left[G_{n-1}\right]}_z\right)+a<br><br>\left({\left[G_n\right]}_z,{\left[G_{n-1}\right]}_z\right)·<br><br>\frac{{}_y<br><br>\left[G_n\right]}{2^z}-b<br><br>\left({\left[G_n\right]}_z,{\left[G_{n-1}\right]}_z\right)·<br><br>\frac{{}_y<br><br>\left[G_n\right]}{2^z}$

where z is the bit number of the LSBs, [G_n]_z represents the MSB of G_n, [G_n]_z represents the MSB of G<sub>n−

1</sub>, and _y[G_n] represents the LSB of G_n.

17. The LCD of claim 16, wherein a and b are positive integers.

18. A liquid crystal display (LCD), comprising:

an LCD panel comprising a plurality of gate lines for transmitting scanning signals, a plurality of data lines that cross the gate lines for transmitting image signals, and a plurality of pixels that are arranged in a matrix and have switching elements connected to the gate lines and the data lines;

a data gray signal modifier that receives a plurality of pairs of gray signals, each pair of gray signals including a gray signal of a present frame (“

present gray signal”

) and a gray signal of a previous frame (“

previous gray signal”

), and modifies the present gray signals based on the pairs of gray signals and at least a modification parameter including a temperature, an image quality selected by a user, and an environment of the LCD;

a gate driver applying the scanning signals to the gate lines; and

a data driver that converts the modified gray signals into data voltages and applies the data voltages to the data lines,

wherein each of the present and the previous gray signals includes most significant bit (MSB) and least significant bit (LSB) and the data gray signal modifier includes at least a look-up table storing modification variables as function of pairs of MSBs of present and previous gray signals and a calculator generating the modified gray signals based on the modification variables and the LSB of the present gray signals,

wherein the at least a look-up table includes a plurality of look-up tables (LUT) for different values of the at least a modification parameter,

wherein the data gray signal modifier further comprises;

an LUT selector that selects one of the plurality of LUT and generates a coefficient value for converting modification variables of the selected LUT based on a value of the at least a modification parameter; and

an LUT converter converting modification variables of the selected LUT based on the coefficient value to generate a modified LUT, and

wherein the calculator calculates values of the modified gray signals from the modification variables corresponding to MSBs of present and previous gray signals from the selected LUT or the modified LUT and LSBs of the present gray signals,

wherein the modification variables include a first variable (f) related to each pair of MSBs and second and third variables (a and b) representing the difference between values of the first variable related to adjacent pairs of MSBs.

19. The LCD of claim 18, wherein the modified gray signal G_n′

for a present gray signal G_n and a previous gray signal G<sub>n−

1</sub> is given by,

$G_n^{\mathrm{\prime <br><br>}}=f<br><br>\left({\left[G_n\right]}_z,{\left[G_{n-1}\right]}_z\right)+a<br><br>\left({\left[G_n\right]}_z,{\left[G_{n-1}\right]}_z\right)·<br><br>\frac{{\hspace{0.17em}<br><br>}_y<br><br>\left[G_n\right]}{2^z}-b<br><br>\left({\left[G_n\right]}_z,{\left[G_{n-1}\right]}_z\right)·<br><br>\frac{{\hspace{0.17em}<br><br>}_y<br><br>\left[G_n\right]}{2^z},$

where z is the bit number of the LSBs, [G_n]_z represents the MSB of G_n, [G_n]<sub>z represents the MSB of Gn−

1</sub>, and y[G_n] represents the LSB of G_n.

20. The LCD of claim 19, wherein the converted second variable (a_ij′

) of the second variable (a_ij) and the converted third variable (b_ij′

) of the third variable (b_ij) satisfy the following equations;

$a_{\mathrm{ij}}=G_{i+1,j}-G_{\mathrm{ij}},<br><br>a_{\mathrm{ij}}^{\mathrm{\prime <br><br>}}=G_{i+1,j}^{\mathrm{\prime <br><br>}}-G_{\mathrm{ij}}^{\mathrm{\prime <br><br>}},<br><br>\begin{array}{c}=<br><br>[G_{i+1,i+1}+\mathrm{\alpha <br><br>}<br><br>\left(G_{i+1,j}-G_{i+1,j+1}\right)+\\ <br><br>\mathrm{\beta <br><br>}<br><br>{\left(G_{i+1,j}-G_{i+1,j+1}\right)}^2+\mathrm{\dots <br><br>}<br><br>]\end{array}<br><br>=-[G_{\mathrm{ii}}+\mathrm{\alpha <br><br>}\left[G_{\mathrm{ij}}-G_{\mathrm{ii}}\right)+{\mathrm{\beta <br><br>}<br><br>\left(G_{\mathrm{ij}}-G_{\mathrm{ii}}\right)}^2+\mathrm{\dots <br><br>}<br><br>]<br><br>=\begin{array}{c}<br><br>2^{8-y}+\mathrm{\alpha <br><br>}<br><br>\left(a_{\mathrm{ij}}-2^{8-y}\right)+\\ <br><br>\mathrm{\beta <br><br>}<br><br>\left(a_{\mathrm{ij}}-2^{8-y}\right)\times <br><br>{\left\{a_{\mathrm{ij}}-2^{8-y}+2<br><br>\left(G_{\mathrm{ij}}-G_{\mathrm{ii}}\right)\right\}}^2+\mathrm{\dots <br><br>}<br><br>,\end{array}$ $b_{\mathrm{ij}}=G_{i,j+1}-G_{\mathrm{ij}},\mathrm{and}$ $b_{\mathrm{ij}}^{\mathrm{\prime <br><br>}}=G_{i,j+1}^{\mathrm{\prime <br><br>}}-G_{\mathrm{ij}}^{\mathrm{\prime <br><br>}},<br><br>\begin{array}{c}=<br><br>[G_{\mathrm{ij}}+\mathrm{\alpha <br><br>}<br><br>\left(G_{i,j+1}-G_{\mathrm{ii}}\right)+{\mathrm{\beta <br><br>}<br><br>\left(G_{i,j+1}-G_{\mathrm{ii}}\right)}^2+\mathrm{\dots <br><br>}<br><br>]\\ <br><br>-[G_{\mathrm{ii}}+\mathrm{\alpha <br><br>}<br><br>\left(G_{\mathrm{ij}}-G_{\mathrm{ii}}\right)+{\mathrm{\beta <br><br>}<br><br>\left(G_{\mathrm{ij}}-G_{\mathrm{ii}}\right)}^2+\mathrm{\dots <br><br>}<br><br>]\end{array}<br><br>=\mathrm{\alpha <br><br>}<br><br><br><br>b_{\mathrm{ij}}+\mathrm{\beta <br><br>}<br><br><br><br>b_{\mathrm{ij}}<br><br>{\left\{b_{\mathrm{ij}}+2<br><br>\left(G_{\mathrm{ij}}-G_{\mathrm{ii}}\right)\right\}}^2+\mathrm{\dots <br><br>}$