JP3856460B2 - Gradation calibration method for liquid crystal display device - Google Patents

Description

  The present invention relates to a gradation calibration method for a liquid crystal display device used for various applications.

  As a method for increasing the luminance resolution in a liquid crystal display device which is an example of a two-dimensional monochrome bit plane display device, the light amount of a pixel has been changed as disclosed in the following Patent Documents 1 and 2 and Patent Document 3 below. Those using sub-pixels have been studied. In these display devices, as a method of changing the amount of transmitted light of the sub-pixel, a method of mounting an ND filter (neutral density filter) having a different transmittance is described. However, there is a problem as described below. .

  For example, if the target luminance resolution is 1500, the accuracy required for such an ND filter is 1/1500 or less, but it is realistic to obtain an accuracy of 0.1% or less with the current ND filter. It is extremely difficult. For this reason, as a practical method, a configuration has been devised in which a light-shielding mask having different opening areas is attached to sub-pixels as disclosed in Patent Document 4 below. However, in a configuration in which a minute subpixel that is 1 / n with respect to a subpixel having a large aperture area is provided, and a light amount divided in n stages is added to a light amount change of 1 bit increase of the large subpixel. Since the sub-pixels constituting the liquid crystal pixels interact with each other, it is extremely difficult to obtain a target gradation. The reason will be described below.

  Although the polarization angle of the liquid crystal changes depending on the applied electric field, there is a phenomenon that the liquid crystal is affected by a leakage electric field component between subpixels constituting one pixel. In FIG. 14, subpixel 1, subpixel 2 and subpixel 3 constituting one pixel are subpixels having different amounts of transmitted light by providing openings having different areas in the light shielding mask. FIG. 15 shows the measurement of the change in the amount of light for 8 bits (256 gradations) for each of the subpixels 1, 2 and 3, and the input to the three subpixels simultaneously with 8 bits ( This is an actual measurement example in which the change in the amount of light is measured by changing (256 gradations). The TI obtained by numerically adding the light amounts of the three sub-pixels measured independently has a considerable difference compared to the GI obtained by simultaneously outputting the three sub-pixels with 256 gradations.

  This is because the polarization angle of the liquid crystal of other subpixels is slightly affected by the electric field applied to one subpixel. Even if the sum of the light amounts is simply calculated by providing minute subpixels, if such a difference is about 1%, the reproducibility of the gradation accuracy can be displayed only with the luminance resolution ability of 100 gradations or less. I can't understand. This cannot be used for medical X-ray image display or the like that requires 1500 gradations or more. In such a configuration that finely divides the change in luminance of one bit of a large sub-pixel, it is difficult to produce a gradation with uniform stepping when the gradation is monotonously increased.

  In particular, as disclosed in Patent Document 4 below, even when a minute sub-pixel having an aperture area of exactly 1 / n is provided, the transmittance between sub-pixels affects each other. It is practically impossible to fill a 1-bit gradation change of a pixel so as to be divided accurately by n. For this reason, a new means of calibration is required. In the worst case, even if the smallest sub-pixel has the maximum light amount, if it is less than the change amount of 1 bit of other large sub-pixels, a large jump can be made in the gradation, so that correct calibration is impossible.

  Further, if the transmitted light amount of the sub-pixels constituting one pixel is biased, the center of the light amount may move. For example, in a configuration using three subpixels whose light transmittance is a power of 2, if one pixel outputs 8 bits (256 gradations), the combination of the three subpixels becomes 24 bits. . Here, there are a plurality of combinations of gradations of the sub-pixels that realize a certain combined luminance. For example, when the aperture area ratio of each sub-pixel is 100%, 50%, and 25%, the amount of light of one pixel is basically the same for those having the same composite luminance values shown below.

However, even if the combined luminance is the same, if the bit combination is biased toward the sub-pixel of one pixel, the center of gravity of the pixel is shifted, that is, the center of light is shifted. This is a size within one pixel, but becomes a big problem in the case of a high-quality display device.
JP-A-11-31971 Japanese Patent Application Laid-Open No. 11-352594 JP 2000-20038 A JP 2001-242828 A

  The present invention has been made to solve the above-described problems, and its object is to make the center of gravity of light in one pixel substantially constant in a liquid crystal display device in which one pixel is composed of a plurality of subpixels. Thus, it is to provide a calibration method for determining a combination of input bits for sub-pixels.

A feature of the present invention is that a pair of electrodes are arranged on both sides of a liquid crystal and has a display function by applying an electric field to the liquid crystal, and one pixel is composed of at least two subpixels, and the maximum light amount of each subpixel. Is applied to a liquid crystal display device configured to be different from each other, and a look-up table representing a relationship between a target luminance of the pixel and an input bit corresponding to an electric field applied to each of the subpixels in order to realize the target luminance in the method of calibration, said all of the sub-pixel input bits Yuki by simultaneously predetermined bits each increase or decrease, the input bit when the luminance of the pixel becomes closest to the target luminance among the sub-pixels, most light amount of the larger subpixel fixed as a first input bit, then for all of the remaining sub-pixels While at the same time a predetermined bit at a time increases or decreases from the first input bit, the input bit when the luminance of the pixel becomes closest to the target luminance among the sub-pixels, the larger subpixels amount in the second The second input bit is fixed, and the input bits are sequentially determined for all the subpixels. In this case, for each of a plurality of temperatures, a lookup table is created that represents the relationship between all target luminances and input bits corresponding to the target luminances for all the sub-pixels, and the lookup table at the plurality of temperatures. Based on the above, it is preferable that the converted temperature input bits are obtained by interpolation or extrapolation on a nonlinear function to determine the input bits of all the sub-pixels at the actual operating temperature.

According to these, to calibrate the look-up table so that the input bits go determined input bits in order from a large sub-pixel of the light transmission, all the subpixels are close while ensuring the target luminance of the pixels since it is, may be a liquid crystal display device that does not centroid of light is little variation in the pixel. Further, even when the operating temperature of the liquid crystal display device is not temperature controlled, a desired lookup table at the operating temperature can be obtained.

  The gradation calibration method for a liquid crystal display device according to the present invention includes a light-shielding mask in which the opening area is changed between the sub-pixels, and an ND filter in which the light transmission amount is changed between the sub-pixels. And changing the light transmission area of each of the sub-pixels to each other can be applied to a liquid crystal display device configured to have different maximum light amounts.

  In order to facilitate understanding of the present invention, the configuration and basic operation principle of a general liquid crystal display device will be briefly described before the detailed description of embodiments according to the present invention. FIG. 1 is a basic configuration diagram of a liquid crystal display device 11 using a normal nematic liquid crystal. In the figure, dielectric anisotropy consisting of 4-methoxybenzylidene-4′-butylaniline (MBBA) and 4-ethoxybenzylidene-4′-butylaniline (EBBA) between two transparent electrodes 13a and 13b. The negative liquid crystal mixture 15 is enclosed, and constitutes the cell 17 together with the transparent electrodes 13a and 13b.

  The long axes of the liquid crystal molecules are aligned in advance so as to be aligned in a direction perpendicular to the surfaces of the electrodes 13a and 13b. In order to make the molecular axis of the liquid crystal 15 vertical, a method of coating the electrode surface with a surfactant or adding a vertical alignment agent is employed. A voltage can be applied between the transparent electrodes 13 a and 13 b by the power source E, and an electric field can be applied to the liquid crystal 15. 14a and 14b are transparent glass plates, which are arranged adjacent to the transparent electrodes 13a and 13b. Further, the polarizing plates 16a and 16b are arranged so as to sandwich the transparent glass plates 14a and 14b.

  In the liquid crystal display device 11 shown in FIG. 1, the polarization direction of light that has passed through the liquid crystal 15 is normal because the light traveling direction and the optical axis of the liquid crystal 15 coincide with normal incident light from the light source. Since the surface does not change, light is blocked by the light-detecting polarizing plate 16b and does not pass through. On the other hand, when a voltage is applied to the cell 17 and an electric field is applied to the liquid crystal 15, the liquid crystal molecules rotate, and the molecular axes are not perpendicular to the surfaces of the electrodes 13a and 13b. Therefore, the transmitted light becomes elliptically polarized light due to the birefringence effect, and part of the light passes through the polarizing plate 16 b and can display characters, numbers, and the like on the liquid crystal display device 11.

  FIG. 2 is a schematic diagram showing a system for driving the liquid crystal display device 21 in which one pixel is composed of three sub-pixels SP1, SP2 and SP3. With reference to FIG. 2, the function will be described mainly. Based on the input image signal, the controller 23 calculates how much electric field should be applied to the liquid crystal of each of the subpixels SP1, SP2 and SP3. The controller 23 transmits each signal to the intensity setting device 25 and the time setting device 27 based on the strength and time of the electric field applied to the calculated subpixels SP1, SP2 and SP3.

  The intensity setting device 25 and the time setting device 27 respectively set the voltage (input bit) to be applied to the electrodes of the subpixels SP1, SP2 and SP3 or the time based on the signal from the controller 23, and correspond. Send a signal. Signals from the intensity setting device 25 and the time setting device 27 are applied as drive signals to the electrodes of the subpixels SP1, SP2 and SP3 through the driver 29, and drive the subpixels to display a desired image.

  FIG. 3 is a diagram conceptually showing a main part of the first embodiment of the present invention. In FIG. 3, a liquid crystal display device 31 is obtained by dividing one pixel into three cells of subpixels 32a, 32b, and 32c as compared with the normal liquid crystal display device described in FIG. The common electrode 33a that is one side of the transparent electrodes described in FIG. 1 covers the entire pixel in this embodiment, and the counter electrode 33b that is the other side of the transparent electrode is a divided subpixel. One of the same type is arranged for each of 32a, 32b, and 32c. The electrodes 33a and 33b are both transparent electrodes, and a liquid crystal 35 is sealed between the electrodes 33a and 33b.

  In the configuration of the liquid crystal display device shown in FIG. 3, one pixel is divided into three subpixels 32a, 32b, and 32c, and a counter electrode 33b is provided for each subpixel. Therefore, each counter electrode 33b, common electrode 33a, Since the light luminance generated by one pixel can be formed by the combination of the respective light luminances (light amounts) generated by the three sub-pixels 32a, 32b, and 32c, by applying the voltage between the two pixels separately. There is an advantage that the number of gradation levels can be realized.

  In a liquid crystal transmission part (cell) 37 in which the common electrode 33a and the counter electrode 33b corresponding to the subpixels 32a, 32b, and 32c are provided with the liquid crystal 35 interposed therebetween, a third electrode 38 is provided between the counter electrodes in the planar direction. In FIG. 3, the third electrode 38 includes a horizontal electrode 38a extending in a direction in which the subpixels 32a, 32b, and 32c in the pixel are arranged, and a vertical electrode 38b that is orthogonal to the horizontal electrode 38a. Yes. The third electrode 38 is connected to a certain voltage. In FIG. 3, the transparent glass plate and the polarizing plate are omitted.

  In the liquid crystal display device shown in FIG. 3, the shield effect is obtained by the presence of the third electrode 38 as a shield electrode between the adjacent subpixels 32a, 32b, and 32c. As a result, the influence of the electric field leaking from one subpixel is reduced, the dependence of each subpixel 32a, 32b, and 32c can be ignored, and the amount of transmitted light can be set independently for each subpixel.

  In the present embodiment, the third electrode 38 has a lattice shape, but the third electrode 38 of the present invention is not limited to this shape, and each of the opposing electrodes provided in the subpixels 32a, 32b, and 32c. Any shape can be applied as long as it is arranged between the electrodes 33b and can reduce the influence of the electric field between the sub-pixels 32a, 32b, and 32c. Further, the number of sub-pixels constituting one pixel does not necessarily have to be three as shown in FIG. 3, and an arbitrary number is allowed as long as there are a plurality of sub-pixels.

  A second embodiment of the present invention will be described with reference to FIG. As described with reference to FIGS. 14 and 15, in the case where the input bits for applying an electric field to the liquid crystal are simultaneously increased for all the subpixels, the input bits are set so as to increase the light intensity independently for each subpixel. In many cases, the overall light luminance tends to decrease compared to the case where the light intensity is increased.

  FIG. 4 shows that one pixel is divided into three subpixels SP1 by mounting a light shielding mask 41 having three openings 43a, 43b, 43c having different opening areas S1, S2, S3 (S1> S2> S3). , Subpixel SP2 and subpixel SP3. The light shielding mask 41 is disposed, for example, between the transparent electrode 13b and the transparent glass plate 14b in FIG.

  FIG. 5 shows a case where the input bits (B) for giving light luminance to the three subpixels SP1, subpixels SP2 and subpixels SP3 shown in FIG. 4 are increased by one bit each. This shows the change in light luminance (I). The amount of light transmitted through each of the sub-pixels SP1, SP2, SP3 is generated according to the respective opening areas provided in the light shielding mask. The diagram of FIG. 5 shows the light luminance characteristics of the subpixel SP1, the subpixel SP2, and the subpixel SP3 from the top, and all increase stepwise as the setting bit increases.

Here, since the opening area S3 is the smallest, the maximum light luminance Max (P3) of the sub-pixel SP3 having the smallest transmitted light amount is equal to or larger than the light luminance change d2n corresponding to the minimum bit of the sub-pixel SP2 having the second largest opening area S2. The opening areas S1, S2 and S3 are set so that the same relationship is established between the subpixel SP2 and the subpixel SP1 (the embodiment shown in FIG. 5). Then, Max (P3)> d2n and Max (P2)> d1n). If this relationship is expressed in mathematical formulas,
Max (P3) ≧ d2n
Max (P2) ≧ d1n
It becomes.

  In the case of a liquid crystal display device composed of subpixels that maintain such a relationship, a subpixel with a smaller aperture area covers the entire range of light intensity change for the minimum bit of a subpixel with a larger aperture area by one step. Therefore, even if the total light quantity sum is reduced by the above-described interaction between the sub-pixels, the smaller sub-pixel can compensate for the decrease in light luminance.

  A third embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows that one pixel is divided into three subpixels SP4, subpixels SP5, and subpixels SP6 by mounting a light shielding mask 61 having an opening 63 having the same shape and the same area. Yes. For the liquid crystal of each sub-pixel in FIG. 6, the light intensity of each sub-pixel is set by changing the voltage application time by using the time setting device 27 in FIG. In this case, the time integral value per frame, which is the time for scanning the entire matrix (not shown), is the light intensity of each subpixel.

  The time (drive time) for applying the voltage for generating the electric field to each of the subpixels SP4, SP5, SP6 is different from each other, and as shown in FIG. 6, t1, t2, t3 (t1> t2> t3), respectively. Is set. FIG. 7 shows the light obtained by time-integrating the input bits of each subpixel when the input bits of each subpixel SP4, SP5, SP6 shown in FIG. This shows a change in luminance characteristics. The diagram shows the light luminance characteristics of the subpixel SP4, the subpixel SP5, and the subpixel SP6 from the top, all of which increase in a stepped manner as the input bit increases.

Also in this case, as in the second embodiment, the maximum light amount Max (P6) of the sub-pixel SP6 with the smallest transmitted light amount is set to be not less than the light amount change d5n for the minimum bit of the second largest sub-pixel SP5. It is designed so that the relationship is also established between the subpixel SP5 and the subpixel SP4 (Max (P6)> d5n and Max (P5)> d4n in the embodiment shown in FIG. 7). If this relationship is expressed in mathematical formulas,
Max (P6) ≧ d5n
Max (P5) ≧ d4n
It becomes.

  If the liquid crystal display device is composed of sub-pixels that maintain such a relationship, even if the total light amount is reduced by the interaction between the sub-pixels, the smaller sub-pixel can compensate for the light amount reduction.

  A fourth embodiment of the present invention will be described with reference to FIG. FIG. 8 shows three subpixels SP7, SP8, SP9 constituting one pixel in the liquid crystal display device. The pixel is covered with a light shielding mask 81, and a plurality of opening elements 83 having the same area and the same shape are provided at positions corresponding to the sub-pixels of the light shielding mask 81. Here, the shape of the aperture element 83 is a crescent shape with little influence of light diffraction, as shown in the figure, with 28 sub-pixels SP7 having the largest transmitted light amount and 14 sub-pixels SP8 having the second largest transmitted light amount. The sub-pixel SP9 having the smallest transmitted light amount is provided with five aperture elements 83. Since the shape of the aperture element 83 is the same, diffraction of the transmitted light has the same condition for all the subpixels SP7, SP8, SP9 regardless of the aperture area of each subpixel.

  A fifth embodiment of the present invention will be described with reference to FIG. FIG. 9 shows three subpixels SP10, SP11, SP12 constituting one pixel in the liquid crystal display device. Similarly to FIG. 8, the pixel is covered with a light shielding mask 91, and opening elements 93 having the same area and the same shape are provided at positions corresponding to the three subpixels SP10, SP11, SP12.

  Here, the shape of the opening element 93 is a rounded quadrangle. The number of the sub-pixel SP10 having the largest transmitted light amount is eight, the number of the sub-pixel SP11 having the second largest transmitted light amount is four, and the most transmitted light amount. The small subpixel SP12 has two openings. That is, the number of opening elements 93 included in each of the subpixels SP10, SP11, SP12, in other words, the opening area of each of the subpixels SP10, SP11, SP12 is a ratio of powers of 2 to each other (SP10 is 2). 3rd power, SP11 is the second power of 2, and SP12 is the second power of 2.

  That is, 1/2 bit of the input bit of the sub-pixel SP10 having the largest transmitted light amount corresponds to 1 bit of the sub-pixel SP11 having the second largest transmitted light amount, and the input bit of the sub-pixel SP11 having the second largest transmitted light amount. ½ bits correspond to 1 bit of the sub-pixel SP12 having the smallest transmitted light amount, and all binary relationships are maintained. This means that the input bits of the sub-pixels with low light transmittance shifted by one bit become the input bits of the sub-pixel with the next highest light transmittance. This facilitates the calibration method described in the seventh embodiment. In addition, this can reduce the potential difference between the sub-pixels and reduce crosstalk. Furthermore, since the potential difference between the sub-pixels can be set freely, the characteristics of the liquid crystal display device can be easily corrected.

  Of course, as described in the fourth embodiment, since the shape of the aperture element 93 included in each of the subpixels SP10, SP11, SP12 is the same, the diffraction of the transmitted light has the same conditions in all the subpixels SP10, SP11, SP12. Needless to say.

  A sixth embodiment of the present invention will be described with reference to FIG. FIG. 10B shows three subpixels SP13, SP14, and SP15 constituting one pixel in the monochrome liquid crystal display device. In the color liquid crystal display device, the position of the three subpixels corresponding to RGB of the color filter 105 is instead applied to a place where the color filter 105 shown in FIG. In addition, a plurality of opening elements 103 having the same shape are provided.

  Here, FIG. 16 shows a normal active matrix type color liquid crystal display device 181. In the figure, a color liquid crystal display device 181 includes a liquid crystal 185 sandwiched between a common electrode 183a and a drive electrode 183b, and transparent glass plates 189a and 189b, and a color filter between the common electrode 183a and the transparent glass plate 189a. 187 is interposed. As shown in the figure, the RGB filters are regularly arranged in the color filter 187, respectively. In the sixth embodiment, in the manufacturing process of the color liquid crystal display device 181 shown in FIG. 16, only the light shielding mask 101 is disposed in place of the color filter 187, and there is no need to make other changes in the manufacturing process. In addition, a monochrome liquid crystal display device can be manufactured.

  The position of the step of disposing the light shielding mask 101 may be the position of disposing the color filter 187 in the manufacturing process of the color liquid crystal display device 181, or otherwise, before applying the liquid crystal in the step of manufacturing the liquid crystal panel. It may be formed as a light-shielding mask made of aluminum or the like in a process step such as TFT. Thus, it is economically advantageous that a monochrome liquid crystal panel with high luminance resolution can be produced using an existing color liquid crystal panel. Further, a liquid crystal display device equipped with an ND filter instead of the light shielding mask 101 can be manufactured in the same process, and the effects of the present invention can be achieved.

  A seventh embodiment of the present invention will be described with reference to FIGS. 11 to 13 show a liquid crystal display device in which each sub-pixel SP1 constituting one pixel is mounted by mounting a light shielding mask 41 having three openings 43a, 43b, and 43c having different opening areas (S1> S2> S3). , SP2 and SP3 (described above in FIG. 4) with different light amounts are shown in the procedure for gradation calibration.

  11 (a), 12 (a), and 13 (a) represent each sub-pixel, and characters in the opening indicate fixed input bits at the time of each gradation calibration. 11 (b), 12 (b), and 13 (b) are graphs showing the relationship between input bits and light luminance at the time of gradation calibration. FIGS. 11 (c), 12 (c), and 13 (c) ) Is a table showing the relationship between the input bit of each sub-pixel and the light intensity at the time of gradation calibration.

  11 (b), 12 (b), and 13 (b), the horizontal axis of the graph is an input bit at the time of gradation calibration, and the vertical axis is a high-accuracy light amount monitor placed closely on the screen of the liquid crystal display device. The measured light intensity is shown. Further, the solid line indicates the desired output characteristics, and the rectangles stacked in the vertical direction indicate the light intensity of the subpixels SP1, SP2 and SP3 in FIG. 11B and the subpixels SP2 and SP3 in FIG. FIG. 13B shows a state in which the light luminance of the sub-pixel SP3 is changed during gradation calibration.

As an example, in the DICOM standard, the desired output characteristic must be the light power characteristic of the power of 2.2 with respect to the input bit. As for this characteristic, if the maximum light luminance (Lmax) and the transmission luminance (Lmin) at the time of complete shutoff are obtained in advance with all the sub-pixels opened, the curve of the desired output characteristic is automatically determined. Here, the amount of light of the backlight has temperature characteristics, so it is necessary to monitor the amount of light in a place where it does not transmit the liquid crystal and separately stabilize the amount of light so that a constant amount of backlight can be obtained in advance. It is. If the maximum number of gradations to be set is, for example, 2048 gradations, the target luminance (Ln) that must be set as the nth gradation is as follows.
Ln = n * (Lmax−Lmin) / 2047 + Lmin

  A procedure for determining the input bit of each subpixel corresponding to the target luminance (Ln) will be described below. First, the input bits of all the subpixels SP1, SP2 and SP3 are made the same and gradually increased. When the input bit is closest to Ln (Ln + α), the input bit is fixed as the input bit of the subpixel SP1 (FIG. 11 ( a), (b), (c) represented by k). Next, the input bits of the subpixels SP2 and SP3 are made the same, gradually increase or decrease from k, and when the input bit is closest to Ln (Ln + β (α> β)), the input bit is set to the subpixel SP2. It is fixed as a bit (represented by k-2 in FIGS. 12A, 12B, and 12C).

  Next, similarly, the input bits of the subpixels SP1 and SP2 are fixed to k and k-2, respectively, and the input bit of the subpixel SP3 is gradually increased or decreased from k, and the point closest to Ln (Ln + γ (Β> γ)), the input bit is fixed as the input bit of the sub-pixel SP3 (represented by k-3 in FIGS. 13A, 13B, and 13C). In this way, the input bit of the subpixel closest to the target luminance Ln can be determined. If the desired number of gradations is 2048, it is possible to obtain a lookup table (Look Up Table: LUT) corresponding to all gradations (L0 to L2047) by repeating n from 0 to 2047 or more. . In FIGS. 11 (c), 12 (c), and 13 (c), only the light intensity column is entered when it is closest to Ln, and the other cases are omitted.

  At the beginning of the above procedure, the input bits of all the subpixels SP1, SP2 and SP3 are made the same and gradually increased. However, in this case, they may be decreased from the high luminance side. Further, the input bits to be increased or decreased do not necessarily have to be one bit at a time, and it goes without saying that any input bit value may be used.

  Embodiment 8 of the present invention will be described below. The LUT obtained in the seventh embodiment differs depending on the temperature of the environment to be measured. For this reason, it is required to create a plurality of LUTs at several temperatures and to appropriately use the LUTs at the environmental temperature at the time of use according to the use temperature. In order to easily create an LUT at an ambient temperature, LUTs at two or more ambient temperatures are used, and an LUT calibrated at an actual use temperature is created therefrom. For example, assume that the following is obtained as the LUT when the environmental temperature is 15 ° C. and 55 ° C.

When the actual use temperature is T ° C., the input bit of the subpixel SP1 is set to m (T) k1 at the stage of the composite luminance Lk.
If the input bit of the subpixel SP2 is m (T) k2, and the input bit of the subpixel SP3 is m (T) k3,
m (T) k1 = (T-15) * {m (55) k1-m (15) k1} / 40 + m (15) k1
m (T) k2 = (T-15) * {m (55) k2-m (15) k2} / 40 + m (15) k2
m (T) k3 = (T-15) * {m (55) k3-m (15) k3} / 40 + m (15) k3

  By calculating only the number of gradations for k, an LUT at temperature T can be created as follows. Note that the LUTs at a plurality of temperatures described above may be created each time the gradation is calibrated, or may be created in advance.

In a narrow temperature range, as described above, a new LUT can be created by linear interpolation or extrapolation using several LUTs. However, it is difficult to calibrate by simply linear extrapolation or interpolation using a limited LUT at any wide service temperature. Such nonlinear characteristics of the liquid crystal itself can be obtained as a function g (T) of the temperature T that can be measured in advance. Such a function has the same curve shape and can be represented by an enlargement ratio a and an offset component b (here, coefficients in the combined luminance k are represented as ak and bk). That is,
fk (T) = ak · g (T) + bk
m (T) kj = fk (T) (j = 1, 2, 3)
fk (15) = m (15) kj (j = 1, 2, 3)
fk (55) = m (55) kj (j = 1, 2, 3)

  M (T) kj can be obtained by simultaneously determining the above equations and determining ak and bk. If this is obtained for all k, the desired LUT at temperature T is obtained.

  In the first, second, seventh, and eighth embodiments of the present invention described above, the light quantity between the sub-pixels is made different from each other by using the light shielding mask having the openings having different opening areas between the sub-pixels. The present invention can be applied not only to a liquid crystal display device, but also to a liquid crystal display device equipped with an ND filter in which the amount of light transmission differs between subpixels, or a liquid crystal display device in which the light transmission areas of the subpixels themselves are different from each other. .

It is a basic block diagram of a liquid crystal display device. It is the schematic showing the system which drives a liquid crystal display device. It is the schematic of the liquid crystal display device by Embodiment 1 of this invention. It is a figure showing the sub pixel of the liquid crystal display device by Embodiment 2 of this invention. It is a figure showing the relationship between the input bit and light luminance of the liquid crystal display device by Embodiment 2 of this invention. It is a figure showing each sub pixel of the liquid crystal display device by Embodiment 3 of this invention, and its drive time. It is a figure showing the relationship between the input bit and light luminance of the liquid crystal display device by Embodiment 3 of this invention. It is a figure showing each sub pixel of the liquid crystal display device by Embodiment 4 of this invention. It is a figure showing each sub pixel of the liquid crystal display device by Embodiment 5 of this invention. FIG. 7A is a diagram illustrating a color filter of a liquid crystal display device, and FIG. 7B is a diagram illustrating each subpixel of the liquid crystal display device according to Embodiment 6 of the present invention. The figure (a) showing each sub pixel in the 1st procedure of the liquid crystal display device by Embodiment 7 of this invention, the graph (b) showing the relationship between the input bit at the time of gradation calibration, and light intensity, and gradation calibration It is a figure (c) showing the table | surface which shows the relationship between the input bit of each sub pixel at the time, and light luminance. The figure (a) showing each sub pixel in the 2nd procedure of the liquid crystal display device by Embodiment 7 of this invention, the graph (b) showing the relationship between the input bit at the time of gradation calibration, and light intensity, and gradation calibration It is a figure (c) showing the table | surface which shows the relationship between the input bit of each sub pixel at the time, and light luminance. The figure (a) showing each sub pixel in the 3rd procedure of the liquid crystal display device by Embodiment 7 of this invention, the graph (b) showing the relationship between the input bit at the time of gradation calibration, and light intensity, and gradation calibration It is a figure (c) showing the table | surface which shows the relationship between the input bit of each sub pixel at the time, and light luminance. It is a figure showing each sub pixel of the liquid crystal display device which conventionally comprised 1 pixel from the several sub pixel from which opening area differs. It is a figure showing the relationship between the input bit and light luminance of the liquid crystal display device which conventionally comprised 1 pixel from the several sub pixel from which opening area differs. It is a figure showing the conventional color liquid crystal display device.

Explanation of symbols

11, 21, 31, 181 ... liquid crystal display devices, 32a to 32c, SP1 to 15 ... subpixels, 13a, 33a, 183a, 13b, 33b, 183b ... electrodes, 15, 35, 185 ... liquid crystal, 17, 37 ... cells , 38 ... third electrode, 41, 61, 81, 91, 101 ... light shielding mask, 83, 93, 103 ... aperture element, 105, 187 ... color filter

Claims (2)

A pair of electrodes is arranged on both sides of the liquid crystal, and has a display function by applying an electric field to the liquid crystal, and one pixel is composed of at least two subpixels, and the maximum light quantity of each subpixel is different from each other. In a calibration method of a look-up table, which is applied to a liquid crystal display device , and represents a relationship between a target luminance of the pixel and an input bit corresponding to an electric field applied to each of the subpixels to realize the target luminance ,
The Yuki and the input bits for all the sub-pixels were simultaneously given bit at increased or decreased, the input bit when the luminance of the pixel becomes closest to the target luminance among the sub-pixels, the most amount of light larger sub When a pixel is fixed as a first input bit , and then, for all remaining sub-pixels, the first input bit is simultaneously increased or decreased by a predetermined number of bits , and the luminance of the pixel is closest to the target luminance . input bits, among the sub-pixels, the larger subpixels amount to the second fixed as a second input bit, all of the sub-pixels sequentially, the calibration method of the look-up table to determine the input bits. The method of calibrating a lookup table according to claim 1,
For each of the plurality of temperatures, for each of the sub-pixels, create a lookup table that represents the relationship between all target luminances and input bits corresponding to the target luminance, and based on the lookup table at the plurality of temperatures A lookup table calibration method in which reduced temperature input bits are obtained by interpolation or extrapolation on a non-linear function to determine the input bits of all the sub-pixels at the actual operating temperature.

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