JP4982760B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device in which the response speed of the liquid crystal display device in a wide temperature range is improved.

  In the liquid crystal display device, a signal voltage is applied to each liquid crystal cell to change the state of the liquid crystal, thereby changing the transmittance and changing the gradation. When the gradation is changed in 256 steps of 8 bits, for example, as shown in the graph of FIG. 1, a curve predetermined corresponding to the gradation values in 256 steps from the display data value 0 to the data 255 on the horizontal axis. The voltage value on the upper vertical axis is applied to the liquid crystal display element.

  In a liquid crystal display device, the data changes from frame to frame, so if you look at a single liquid crystal display element, the applied grayscale data changes, the applied voltage changes, and the transmittance does not change accordingly. However, the response speed of the liquid crystal is not always fast. The response speed is usually defined as the time required to reach 10% to 90% of the desired luminance.

  This response speed tends to be particularly slow at low temperatures. For example, devices used in cold regions such as Scandinavia, such as in-car car navigation systems, may start from a minus tens of degrees Celsius. At start-up, the liquid crystal has a high viscosity at low temperatures, so the response is slow, the moving subject cannot be tracked, and the display may be inadequate in quality, such as a blurred image or lack of display itself. .

  As one method for improving the response speed of the liquid crystal, overdrive is generally known.

  In the liquid crystal, the voltage applied to the liquid crystal cell is determined with respect to the gradation (for example, 256 levels from 0 level to 255 level), but the voltage (higher than the voltage applied to a certain gradation) is higher. This is a technique in which the change in the state of the liquid crystal is accelerated by applying a voltage to the gradation.

  In order to finely control the overdrive voltage for each pixel, it has been proposed to predict gradation data for each pixel in the previous frame image and output overdriven gradation data based on this prediction. (See Patent Document 1).

  However, even in the method of Patent Document 1, since the overdrive is updated every frame, when the response speed of the liquid crystal is very slow such as in a low temperature environment, the amount of change in the gradation data after one frame is very large. There is a problem that the predicted value is small and the effect of overdrive does not appear.

  For this reason, in the previous application (Japanese Patent Application No. 2008-1111730), the inventor of the present invention prepares a look-up table of predicted gradation values after a predetermined frame for each temperature, for example, liquid crystal at a low temperature. Even when the activity of the molecule is low and the response speed is slow, the overdrive value set in advance is used, and overdrive with the same number of frames is performed using the predicted gradation value after the predetermined frame at that temperature. Proposed to improve the response speed of the liquid crystal display device.

JP 2005-107531 A

  However, in the configuration in the previous application, it is necessary to always calculate and control the drive voltage for all the pixels with reference to the predicted value. In addition, since the look-up table for storing overdrive values must have data for all combinations of gradations at the start and end of overdrive, there is also a problem that the storage capacity increases.

For example, 14-step temperatures from −30 ° C. to 35 ° C. (−30, −25, −20, −15, −10, −5, 0, 5, 10, 15, 20, 25 in 8-bit gray scale display) , 30, 35 ° C.), 256 × 256 × 8 × 14 =
7.3Mbit memory is required. If the display gray scale and temperature conditions are set more finely, more memory is required, which increases costs.

  On the other hand, if the look-up table every 5 ° C. is taken into account that the response time of the liquid crystal is extremely sensitive to temperature, the interval may be too wide. For this reason, when the temperature changes rapidly, there is a problem that the difference in image quality can be clearly understood when the look-up table changes.

  Therefore, it is desired to finely control the temperature by finely setting the temperature, but there is a problem that it is difficult to realize it due to memory restrictions.

  Further, particularly in a liquid crystal television or the like, double speed or quadruple speed driving is performed in order to improve the response speed to a fast motion of a moving image. When there is a temperature drop, there is a problem that it cannot be followed by high-speed driving. Therefore, it is considered to apply the feedback type control using the above-described lookup table.

  Regarding the above-mentioned memory capacity, it is disclosed in Patent Document 1 described above that the memory for storing the overdrive value is used as a pair of one-dimensional tables to reduce the capacity. The display characteristics could not be maximized.

  Accordingly, an object of the present invention is to provide a liquid crystal display device capable of improving display quality by performing finer overdrive control without increasing the memory capacity.

In order to solve the above problems, according to the present invention,
A liquid crystal display module;
A temperature sensor provided in the liquid crystal display module;
An arithmetic device that calculates and outputs an overdrive voltage for the liquid crystal display module and a predicted value for the next frame from a start gradation value and an end gradation value in image data;
A frame memory that stores the prediction value and outputs the start gradation value to the arithmetic unit;
The arithmetic unit is:
A first comparator for detecting whether the start gradation value and the end gradation value match;
A first one-dimensional lookup table representing a relationship between a gradation value and an offset amount normalized so that a curve formed by a square value of a voltage corresponding to the gradation value matches;
A one-dimensional second look-up table representing a relationship between a gradation value and a square value of a voltage corresponding to the gradation value;
An arithmetic unit for obtaining an intermediate output value for overdrive related to the square value of the voltage with reference to the start gradation value, the end gradation value, and the values of the first and second lookup tables When,
A second comparator for determining whether the output of the computing unit is greater than a predetermined maximum value, less than a predetermined minimum value, or an intermediate value;
A one-dimensional third look-up table for calculating an overdrive value referred to according to the outputs of the first and second comparators;
A one-dimensional fourth look-up table for calculating a predicted value referred to according to the outputs of the first and second comparators,
The first to fourth look-up tables are updated as needed according to the value of the temperature sensor,
In the first case where the start gradation value and the end gradation value coincide with each other using the outputs of the first comparator, the second comparator, and the arithmetic unit, the gradation difference is the predetermined maximum. 4 in the fourth case where the gradation difference is between the predetermined maximum value and the minimum value in the second case where the gradation difference is smaller than the predetermined minimum value. There is provided a liquid crystal display device comprising a selector / data generator for generating an overdrive output and a predicted output according to one case.

  According to this liquid crystal display device, a lookup table to be used can use a plurality of one-dimensional ones instead of the conventional two-dimensional ones by adopting a voltage square value as one of the relation quantities. Therefore, the required memory capacity can be reduced and the cost can be reduced, or a look-up table with a narrower temperature interval can be used, so that more appropriate overdrive is possible and image quality is improved. Can do.

4 is a graph showing a relationship between data and a voltage applied to a liquid crystal display element in a liquid crystal display device. It is a block diagram which shows schematic structure of the principal part of the liquid crystal display device concerning this invention. FIG. 3 is a block diagram showing a first embodiment of the overdrive / predictive computing device shown in FIG. 2. It is a graph which shows the content of the prediction value look-up table which shows the prediction gradation value when the minimum value and the maximum value are given as an overdrive value with respect to the start gradation value. It is the graph which plotted the numerical value of FIG. It is a graph in which the horizontal axis is the square of the voltage finally applied to the liquid crystal element, the vertical axis is the final gradation value, and the start gradation value is a parameter. In the graph of FIG. 6, it is a graph which shows that one curve is obtained by giving an offset to each line. It is the graph which plotted the memory content of the lookup table LUT_G2Vs in the structure of FIG. It is the graph which plotted the memory content of the look-up table LUT_G2VV in the structure of FIG. It is the graph which plotted the memory content of the lookup table LUT_G2VV2G in the structure of FIG. It is a flowchart showing the operation | movement in the structure of FIG. FIG. 4 is a block diagram showing a second embodiment of the overdrive / prediction arithmetic device shown in FIG. 2. 13 is a graph in which the stored contents of a lookup table LUT_G2VsVe in the configuration of FIG. 12 are plotted. 13 is a graph in which stored contents of a lookup table LUT_VsVe2G in the configuration of FIG. 12 are plotted. 13 is a flowchart illustrating an operation in the configuration of FIG. 13 is a graph showing an operation example when the start gradation value and the end gradation value do not change in the configuration of FIG. 12. 13 is a graph showing an operation example when the change from the start gradation value to the end gradation value is moderate with respect to the overdrive voltage in the configuration of FIG. 13 is a graph showing an operation example when the change from the start gradation value to the end gradation value exceeds the output range of the overdrive voltage in the configuration of FIG. 12.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, examples of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  FIG. 2 is a block diagram showing a schematic configuration of a main part of the liquid crystal display device according to the present invention.

  As is well known, the liquid crystal display element LQ forms a liquid crystal panel 10 arranged in a matrix so as to form a pixel configuration of 640 × 480 in the case of a VGA display screen, for example, and the gate is selected by the row decoder 11. Each liquid crystal display element LQ is connected via a transistor TR connected to a row line RL and having a source connected to a column line (data line) controlled by the column decoder 12.

  The row line RL is activated by the row decoder RD for each line display period, and is applied to the column line CL sequentially activated by the column decoder CD. When a voltage corresponding to a desired gradation is applied to the column line CL corresponding to the liquid crystal display element selected by the conversion unit 13, the transmissivity of the liquid crystal changes and display is performed. The liquid crystal panel 10 is provided with temperature information acquisition means 14 for acquiring information related to temperature in order to measure the environmental temperature, that is, the actual temperature of the liquid crystal. Any temperature information acquisition means may be used as long as it generates a physical quantity related to temperature. In this embodiment, for example, a temperature sensor that directly measures temperature is used.

  The voltage converter 13 is supplied with an overdrive value from the overdrive / prediction computing device 20, and the voltage finally supplied to each liquid crystal display element is a voltage corresponding to the gradation value to which the overdrive is applied. .

  The output of the temperature sensor 14 is given to the overdrive / prediction arithmetic unit 20, and the overdrive value OD and the predicted value PD after one frame are based on the output of the temperature sensor 14 using the input image data as the end gradation value Gn. Is output. The prediction value PD is fed back to the overdrive / prediction calculation device 20 as a start gradation value Gn−1 with reference to the frame memory 15 and calculation is performed. The frame memory is composed of display data of all pixels for one frame, and in the case of a VGA image, the data is for 640 × 480 pixels.

  There are two types of liquid crystal: normally black, which is black when no voltage is applied, and normally white, which is white in the same case, but in the following description, normally black (tone 0) Black)

  FIG. 3 is a block diagram showing the configuration of the first embodiment of the overdrive / predictive arithmetic unit shown in FIG.

  In the following, it is assumed that display is performed at 60 frames / second, and image data is input every frame (about 16.7 ms). In the following processing, parallel processing and time-sharing processing are performed for all pixels in one row. However, in order to simplify the description, the following description will be given focusing on one pixel.

  The start gradation value Gn-1 and the end gradation value Gn are first input to the comparator 21 to compare whether or not they are the same value, and the 1-bit output as the comparison result is the first output of the selector / data generator 22. 1 is input to the selection input Sel0.

  The start gradation value Gn-1 and the end gradation value Gn are also input to the calculator 23, and these input values are used as addresses to retrieve data with reference to the two lookup tables LUT_G2Vs and LUT_G2VV to perform a predetermined calculation. The overdrive operation value VVod is output to the selector / data generator 22 and the comparator 26. These lookup tables will be described later.

  The comparator 26 compares the overdrive value with the maximum value, the minimum value, or another value, and the result is input to the second selection input Sel1 of the selector / data generator 22 as a 2-bit output. .

  The start gradation value Gn-1 and the end gradation value Gn are also input to the selector / data generator 22 via timing adjusting delays (DL) 29 and 30, respectively. 22, based on these five input data, the two look-up tables LUT_VV2G and LUT_Predict are referred to, and finally the overdrive value OD and the predicted value PD are output. The overdrive value OD is predicted to the liquid crystal panel 10. The value PD is given to the frame memory 15 respectively.

  Next, the configuration of the lookup table will be described. In the following description, it is assumed that the stored contents for a certain temperature, for example, −10 ° C. are described. When the temperature changes particularly in a low temperature range, a large change occurs in the characteristics of the liquid crystal. Therefore, it is necessary to change the look-up table to be referred to, and a look-up table is usually created every 5 ° C.

  As a basic example of the lookup table in the present invention, numerical values at a temperature of −10 ° C. are shown in FIG. 4 and a graph in which the numerical values are plotted. These are described as 64 gradations from 0 to 63.

  In FIG. 4, the left column is the start gradation value, the middle column is the predicted gradation value after one frame when the overdrive value is the minimum 0, and the right column is the maximum overdrive value 63. The predicted gradation value after one frame is shown.

  For example, when the start gradation is 0, that is, black, even if the maximum overdrive value 63 is applied at this temperature, the gradation after one frame only increases to 4, so the predicted gradation value is set to 4 or more. In this case, the overdrive value may be set to 63. Conversely, when the start gradation is 63, that is, white, even if the overdrive value is set to 0, only the gradation 51 is lowered. When the value is 51 or less, the overdrive value may be set to 0.

  Accordingly, in the graph of FIG. 5, the overdrive value 63 is applied to the predicted gradation value above the upper solid line, and the overdrive value 0 is applied to the predicted gradation value below the lower solid line. The overdrive value is determined by the method described below in the region between them.

  In other words, if the two one-dimensional lookup tables in FIG. 4 corresponding to the two solid lines shown in FIG. 5 are provided, the overdrive value and the predicted value can be determined using these values.

  The solid line data shown in FIG. 5 is stored in the lookup table LUT_Predict 28 in FIG. The data content of this look-up table is only data of two curves, there is no need for conventional matrix data corresponding to 64 gradations, the data capacity is 2/64 = 1/32, and the memory capacity is increased. It can be significantly reduced. In the case of a 256 gradation display liquid crystal display device, the data capacity can be further reduced to 1/128.

  By the way, when the inventor plots the square value of the voltage applied to the liquid crystal on the horizontal axis and the gradation value reached by the liquid crystal after one frame period with the overdrive value as a parameter, the horizontal axis is as shown in FIG. It was found that even when the overdrive values are different, the shape of each reached gradation value curve is approximate, especially the central part can be approximated by a straight line, and the slopes thereof are almost the same.

  Therefore, when an appropriate offset is given and moved in the horizontal axis direction, as shown in FIG. 7, all the characteristic curves can be made to coincide with one reached gradation value curve. In other words, this graph predicts the reached gradation after one frame if the square value Ve ^ 2 of the voltage applied to the liquid crystal and the state of the liquid crystal immediately before application, that is, the offset voltage Vsoffset corresponding to the start gradation are known. It shows that this is possible and is the basis for the idea of the present invention.

  It has been confirmed that the relationship of FIG. 7 is established over a wide liquid crystal operating temperature range.

  Next, the lookup table used in FIG. 3 will be described.

  FIG. 8 is a graph showing data stored in the LUT_G2Vs 24. The horizontal axis indicates a 6-bit gradation value, and the vertical axis indicates the offset applied voltage Vsoffset. It becomes a table. The unit of the vertical axis is dimensionless and is simply a relative value for comparison. That is, this graph shows relatively how much offset is required for the overdrive gradation value.

  FIG. 9 is a graph showing the relationship stored in the look-up table LUT_G2VV25, plotted with the horizontal axis representing 6-bit gradation values and the vertical axis representing the squared value Ve ^ 2 (8-bit value) of the normalized applied voltage Ve. In FIG. 10, the lookup table LUT_VV2G27 is plotted by exchanging the vertical axis and the horizontal axis of the lookup table LUT_G2VV25. Both are one-dimensional lookup tables.

  Next, the operation in the configuration of FIG. 3 using these lookup tables will be described with reference to FIG.

  When the start gradation value Gn-1 and the end gradation value Gn are input, the comparator 21 compares these values to determine whether or not they are the same value (step S101). Outputs the overdrive value OD as Gn and the predicted gradation value PD as Gn (step S111).

  When the start gradation value Gn-1 and the end gradation value Gn are different, the calculator 23 refers to the look-up tables LUT_G2Vs24 and LUT_G2VV25 to obtain VVod = LUT_G2Vs (Gn) -LUT_G2Vs (Gn-1) + LUT_G2VV (Gn) The VVod is supplied to the comparator 26 and sent to the selector / data generator 22 (step S102).

  Here, VVod is a value representing a required overdrive value as a square value of a normalized liquid crystal applied voltage.

  In the comparator 26, the value of VVod is compared with the maximum value (MaxVV) and the minimum value MinVV of VV (step S103). When the value is larger than MaxVV, the overdrive value OD is set to 63 when A represents saturation maximum overdrive. As the predicted gradation value PD, values for Gn-1 and the overdrive value 63 are extracted from the lookup table LUT_Predict and output (step S112). On the other hand, when the value is smaller than MinVV, B represents the saturation minimum overdrive, and the overdrive value OD is 0, the predicted gradation value PD is Gn-1 and values for the overdrive value 0 are extracted from the lookup table LUT_Predict and output. (Step S113).

  When the value of VVod is between the maximum value (MaxVV) and the minimum value MinVV of VV, the overdrive value OD is referred to the look-up table LUT_VV2G27 as C when representing an appropriate overdrive, and the gradation corresponding to VVod It takes out as a value and outputs the predicted value PD as Gn (step S114).

  In this embodiment, all the LUTs to be referred to are one-dimensional, and the capacity of the LUT can be reduced and high-precision control is possible.

  A second embodiment of the present invention will be described with reference to FIGS.

  FIG. 12 is a block diagram showing the configuration of the second embodiment of the overdrive / predictive arithmetic unit shown in FIG.

  Since the configuration is similar to that of the first embodiment shown in FIG. 3, the description of the same components is omitted.

  The difference from FIG. 3 is that LUT_G2VsVe31 and LUT_G2VV25 are used instead of LUT_G2Vs24 as a lookup table to be referred to by the arithmetic unit 23 to generate the output VVod, and the selector / data generator 22 uses the overdrive value OD and the predicted value. The LUT_VV2G27 and the LUT_Predict28 are replaced with the LUT_G2VsVe2G32 as a lookup table to be referred to in order to generate the PD.

  FIG. 13 shows the stored contents of LUT_G2VsVe31, and FIG. 14 shows the stored contents of LUT_VsVe2G32.

  The horizontal axis of LUT_G2VsVe31 is the gradation value from 0 to 63, but the vertical axis is the offset applied voltage Vsoffset plus the value of Ve ^ 2, and its size is 64 × 1 × It is 13 bits.

That is, LUT_G2VsVe = LUT_G2VV + LUT_G2Vs
The relationship is established.

  The look-up table LUT_VsVe2G32 shown in FIG. 14 is obtained by exchanging the vertical axis and the horizontal axis of the LUT_G2VsVe31 shown in FIG. 13 and has a size of 8192 (corresponding to 13 bits) × 1 × 6 bits. Note that 13 bits is a case where an operating temperature range up to −30 degrees is considered, and when only a narrower (higher temperature side) operating temperature range is considered, the number of bits may be smaller.

  FIG. 15 is a flowchart showing the operation of the configuration of FIG. 12 corresponding to FIG. 11 in the first embodiment.

  When the start gradation value Gn-1 and the end gradation value Gn are input, the comparator 21 compares these values to determine whether or not they are the same value (step S201). Outputs the overdrive value OD as Gn and the predicted gradation value PD as Gn (step S211).

When the start gradation value Gn-1 and the end gradation value Gn are different, the computing unit 23 first refers to the lookup tables LUT_G2VsVe31 and LUT_G2VV25.
Vs (Gn-1) = LUT_G2VsVe (Gn-1)-LUT_G2VV (Gn-1)
Asking. next,
VVod = LUT_G2VsVe (Gn)-Vs (Gn-1)
Both are supplied to the selector / data generator 22, but only VVod is sent to the comparator 26 (step S202).

  In the comparator 26, the value of VVod is compared with the maximum value (MaxVV) and the minimum value MinVV of VV (step S203). When the value is greater than MaxVV, the value A indicates saturation maximum overdrive. The predicted gradation value PD is output as LUT_VsVe2G (LUT_G2VV (63) + Vs (Gn-1)) (step S212).

  On the other hand, when the value of VVod is smaller than MinVV, the overdrive value is 0 as the saturation minimum overdrive, and the predicted gradation value PD is output as LUT_VsVe2G (LUT_G2VV (0) + Vs (Gn-1)). Step S213).

  When the value of VVod is between the maximum value (MaxVV) and the minimum value MinVV of VV, the overdrive value OD is converted into a gradation value by the lookup table LUT_VV2G (VVod) as C when representing an appropriate overdrive. The predicted value PD is output as Gn (step S214).

  Also in this embodiment, the LUTs to be referred to are one-dimensional, and the capacity of the LUT can be reduced, and high-precision control is possible.

  16 to 18 start with three curves representing Vsoffset, the squared value Ve ^ 2 (= VV) of the normalized end voltage Ve, and the total value Ve ^ 2 + Vsoffset (= VsVe). It is explanatory drawing which shows the procedure which calculates | requires value Gn-1, end value Gn, overdrive value God, and predicted value Gpredict. Here, the symbol V means a value based on voltage, and G means a gradation value.

  As described above, Vsoffset is the storage content of the lookup table LUT_G2Vs24, Ve ^ 2 is the storage content of the lookup table LUT_G2VV25, and Ve ^ 2 + Vsoffset is the storage content of the lookup table LUT_G2VsVe31.

FIG. 16 shows a case where the start gradation value Gn−1 and the end gradation value Gn are the same. (Gn = Gn-1 = 32)
In this case, since the overdrive value OD is Gn and the predicted gradation value PD is Gn from FIGS.
Gn-1 = Gn = God = Gpredict
Therefore, God = Gpredict = 32 is determined without referring to the value on the vertical axis of each curve.

  In this case, the stored contents of the lookup table LUT_G2VsVe31 are defined. That is, the value of Vsoffset for each gradation and the sum of the values of Ve ^ 2 are values on Ve ^ 2 + Vsoffset for the same gradation value.

In FIG. 16, the total value 171 of the value 54 extracted from the lookup table LUT_G2Vs24 and the value 117 extracted from the lookup table LUT_G2VV25 is the value for the gradation value 32 of the lookup table LUT_G2VsVe31. Hereinafter, the lookup table LUT_G2VsVe31 can be created by referring to the two lookup tables for each gradation value.
LUT_G2VsVe (x) = LUT_G2Vs (x) + LUT_G2VV (x); where x is an arbitrary gradation value 0 to 63
After the lookup table is created, the value of Vsoffset can be obtained from the two lookup tables LUT_G2VsVe31 and LUT_G2VV25, so that the lookup table LUT_G2Vs24 becomes unnecessary as shown in FIG.

  FIG. 17 shows a case where the start gradation value Gn−1 and the end gradation value Gn are appropriately separated, and shows a case where the start gradation value Gn−1 is 8 and the end gradation value Gn is 32. . This is an example of an appropriate OD in FIG. 11 and FIG.

  First, refer to the points (32, 171) on the curve Ve ^ 2 + Vsoffset. In order to obtain the end gradation Gn = 32 at this point, Ve ^ 2 + Vsoffset = 171 is necessary. Next, looking at the points (8, 26) on the curve Vsoffset, it can be seen that the Vsoffset for the start gradation Gn−1 = 8 is 26. Therefore, the value of Ve ^ 2 necessary for overdrive is the remaining 171-26 = 145 (= VVod). If this is referred to on the curve Ve ^ 2, it becomes a point (44, 145). That is, the overdrive tone value God is 44. Since the predicted gradation value is equal to the end gradation, Gpredict = Gn = 32.

  Further, these will be described in comparison with FIG. First, since the start gradation Gn-1 is changed from 32 to 8, Vsoffset is changed by -28 from 54 to 26. To compensate this amount with Ve ^ 2, Ve ^ 2 needs to be +28. That is, Ve ^ 2 = 117 + 28 = 145. At this time, the gradation value 44 becomes God. In this way, the same end gradation value Gn can be achieved by balancing so that Ve ^ 2 + Vsoffset maintains a constant value.

  Thus, in an example of a moderate OD, the predicted gradation value does not need to be obtained by calculation, and Gpredict = Gn is always established.

  FIG. 18 shows the case of maximum overdrive, in which the start gradation value Gn-1 is 0 and the end gradation value Gn is 60. This is an example of case A in FIGS.

  First, see the point (60, 301) on the curve Ve ^ 2 + Vsoffset. In order to obtain the end gradation Gn = 60 at this point, Ve ^ 2 + Vsoffset = 301 is necessary. On the other hand, when the point (0, 0) on the curve Vsoffset is seen, it can be seen that Vsoffset for the start gradation Gn−1 = 0 is zero. Therefore, the value of Ve ^ 2 necessary for overdrive is the remaining 301-0 = 301 (= VVod). However, referring to the point (63, 255) on the curve Ve ^ 2, the maximum value of Ve ^ 2 (maxVV) is 255 when God = 63. That is, the remaining 301-255 = 46 cannot be compensated even by the maximum overdrive (VVod> maxVV). In this case, 63 is output as the maximum overdrive God, and the predicted gradation value Gpredict is 54 when it is seen on the curve Ve ^ 2 + Vsoffset that Ve ^ 2 + Vsoffset = 0 + 255 = 255. (Gpredict ≠ Gn)

  These will be described in comparison with the case where Gn = Gn-1 = 60. First, since the start gradation Gn-1 has changed from 60 to 0, Vsoffset has changed by 77 from 77 to 0. It is necessary to compensate for this by Ve ^ 2, that is, overdrive. Therefore, Ve ^ 2 should be +77 from 224 to 301. However, since the maximum value (maxVV) of Ve ^ 2 is 255, the actual compensation is not sufficient as 255−224 = + 31, and the end gradation value Gn cannot be achieved.

The calculations performed so far in the description of FIGS. 16 to 18 are shown again by calculation formulas using a lookup table.
VVod = LUT_G2VsVe (Gn) −LUT_G2Vs (Gn−1) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Example 2
= LUT_G2Vs (Gn) + LUT_G2VV (Gn) −LUT_G2Vs (Gn−1)... Example 1
Here, the transformation from the second embodiment to the first embodiment is performed by substituting the above-described relational expression.
OD = LUT_VV2G (VVod) (when 0 <VVod <255)
= 63 (when VVod> 255)
= 0 (when VVod <0)
PD = LUT_VsVe2G (LUT_G2Vs (Gn-1) + LUT_G2VV (VVod))
= LUT_VsVe2G (LUT_G2VsVe (Gn-1) -LUT_G2VV (Gn-1) + LUT_G2VV (VVod))) ... Example 2

The above-described relational expression was also used for the above-described expression modification. Furthermore, although it can be said that PD is determined by two variables of Gn-1 and VVod, when VVod is in the range of 0 to 255, the predicted gradation value matches the end gradation (PD = Gn), so there is no need to obtain it by calculation. . Therefore, if only the predicted gradation values when VVod = 0 and VVod = 255 are obtained in advance, the calculation can be simplified as two one-dimensional lookup tables. That is,
PD = LUT_predict (Gn-1, OD0 / OD255) ... Example 1

  In this way, by employing a lookup table in which the square of the voltage value is a coordinate value, the configuration of the apparatus is simplified and the calculation is facilitated.

  Since the temperature characteristics of the liquid crystal change dramatically depending on the temperature, it was assumed that the liquid crystal was provided at 5 ° C. in the example. However, the amount of memory capacity is reduced, and the temperature increment of the lookup table is reduced. You can also sort them into

  The above description is merely an example, and modifications, replacements, and the like normally performed by those skilled in the art are within the scope of the present invention.

  The liquid crystal display device according to the present invention described above is used for various electronic devices such as a mobile phone, a digital camera, a PDA (personal digital assistant), an automobile display, an aircraft display, a digital photo frame, or a portable DVD player. It is particularly suitable for use in a low temperature environment.

DESCRIPTION OF SYMBOLS 10 Liquid crystal panel 11 Row decoder 12 Column decoder 13 Voltage conversion part 14 Temperature sensor 15 Frame memory 20 Overdrive / prediction arithmetic unit 21 Comparator 22 Selector 23 Calculator 24 Look-up table LUT_G2Vs
25 Lookup table LUT_G2VV
26 Selector / Data Generator 22
27 Lookup table LUT_VV2G
28 Lookup table LUT_Predict
29 Delay device 30 Delay device 31 Look-up table LUT_G2VsVe
32 Lookup table LUT_VsVe2G

Claims (4)

A liquid crystal display module;
A temperature sensor provided in the liquid crystal display module;
An arithmetic device that calculates and outputs an overdrive voltage for the liquid crystal display module and a predicted value for the next frame from a start gradation value and an end gradation value in image data;
A frame memory that stores the prediction value and outputs the start gradation value to the arithmetic unit;
The arithmetic unit is:
A first comparator for detecting whether the start gradation value and the end gradation value match;
A first one-dimensional lookup table representing a relationship between a gradation value and an offset amount normalized so that a curve formed by a square value of a voltage corresponding to the gradation value matches;
A one-dimensional second look-up table representing a relationship between a gradation value and a square value of a voltage corresponding to the gradation value;
An arithmetic unit for obtaining an intermediate output value for overdrive related to the square value of the voltage with reference to the start gradation value, the end gradation value, and the values of the first and second lookup tables When,
A second comparator for determining whether the output of the computing unit is greater than a predetermined maximum value, less than a predetermined minimum value, or an intermediate value;
A one-dimensional third look-up table for calculating an overdrive value referred to according to the outputs of the first and second comparators;
A one-dimensional fourth look-up table for calculating a predicted value referred to according to the outputs of the first and second comparators,
The first to fourth look-up tables are updated as needed according to the value of the temperature sensor,
In the first case where the start gradation value and the end gradation value coincide with each other using the outputs of the first comparator, the second comparator, and the arithmetic unit, the gradation difference is the predetermined maximum. 4 in the fourth case where the gradation difference is between the predetermined maximum value and the minimum value in the second case where the gradation difference is smaller than the predetermined minimum value. A liquid crystal display device comprising a selector / data generator for generating an overdrive output and a predicted output according to one case. The second lookup table stores the normalized squared value of the liquid crystal applied voltage with respect to the gradation value;
2. The liquid crystal display device according to claim 1, wherein the third look-up table stores a gradation value with respect to a square value of the normalized liquid crystal applied voltage.   3. The liquid crystal display device according to claim 1, wherein the fourth look-up table stores a relationship between the start gradation value and the predicted gradation value. The first look-up table is obtained by adding the square value of the voltage defined by the second look-up table to the normalized offset amount with respect to the gradation value,
The liquid crystal display device according to claim 1 or 2, wherein the fourth look-up table is obtained by exchanging the abscissa and ordinate of the first look-up table.

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