JP4812795B2 - Gamma value acquisition method and gamma value acquisition system for liquid crystal display device, liquid crystal display device and gamma value acquisition computer used in the system, and program thereof - Google Patents

Description

  The present invention relates to a technique for obtaining a gamma value of a liquid crystal display device.

  The gamma value of a liquid crystal display device changes due to variations in liquid crystal, backlight, color filter, etc. and aging. Is preferably adjusted. As a method for adjusting the gamma value, first, a gamma value corresponding to each gradation value is obtained by measuring the luminance of the screen for each gradation value given to the liquid crystal display device. In general, the input / output conversion characteristics of a look-up table built in the liquid crystal display device are rewritten so as to be displayed.

Conventionally, the following is known as a method for obtaining a gamma value of a liquid crystal display device (for example, see Patent Document 1).
(1) First, the luminance of an arbitrary gradation is measured for a liquid crystal display device from which a gamma value is to be acquired. The luminance is measured at a constant gradation interval (for example, every 16 gradations), or the number of measurement gradations is increased near the minimum gradation or the maximum gradation where the gamma value varies greatly. The number of measurement gradations is set to be small in the intermediate gradation region where the value fluctuation is small.
(2) Subsequently, each measured gradation value and each measured luminance are normalized, and a gamma value corresponding to each measured gradation value is calculated.
(3) Further, the gamma value corresponding to the gradation value that is not measured is estimated by linearly interpolating the gamma value of the measured gradation value.
After the gamma values of all the gradations of the liquid crystal display device are obtained by the above procedures (1) to (3), a lookup table built in the liquid crystal display device is set so as to obtain a desired gamma value.
According to this method, since it is not necessary to measure the luminance for all the gradations, the gamma values for all the gradations of the liquid crystal display device can be efficiently acquired in a short time.
JP 2005-338451 A

However, the conventional example having such a configuration has the following problems.
Hereinafter, a description will be given with reference to FIG. 12A shows a change characteristic diagram of the gamma value showing the relationship between the gradation value and the gamma value of the liquid crystal display device, and FIG. 12B shows the relationship between the gradation of the liquid crystal display device and the measured luminance. FIG. In FIG. 12B, the solid line is the characteristic obtained by the conventional method described above, and the chain line is the characteristic obtained by measuring the luminance corresponding to all gradations.

  As is clear from the gradation-luminance characteristic shown in FIG. 12B, the characteristic A obtained by the conventional method and the characteristic B obtained by measuring the luminance of all gradations are completely coincident. There are some errors ε. Since such an error is conspicuous when gradation display is performed on the liquid crystal display device, it needs to be improved.

  The present invention has been made in view of such circumstances, and can obtain a gamma value of a liquid crystal display device capable of obtaining gamma values of all gradations of the liquid crystal display device efficiently and accurately in a short time. It is an object to provide a method, a gamma value acquisition system, a liquid crystal display device used in the system, a gamma value acquisition computer, and a program thereof.

As a result of earnest research to solve the above problems, the present inventor has obtained the following knowledge.
That is, as can be seen from the gradation-gamma value specification shown in FIG. 12A, the characteristics of the gamma value obtained by measuring the luminance of all gradations do not necessarily change smoothly according to the gradation. Instead, it has an inflection point F that is a point at which the gamma value changes abruptly. This inflection point F is recognized not only in the vicinity of the minimum gradation or the maximum gradation but also in the intermediate gradation area. In specifying the gradation-gamma value having such a bending point, the gradation value at the point where the gamma value changes abruptly when the gamma value is obtained by measuring the luminance at regular gradation intervals as in the conventional method. May not be selected as the luminance measurement gradation value (measurement gradation value). For example, the points drawn with circles in FIG. 12A are measurement points set at a constant gradation interval, and in this case, the bending point indicated by the symbol F in the figure is out of the measurement points. Even if the number of measurement gradations is increased near the minimum gradation or the maximum gradation where the gamma value varies greatly, the bending point F is not necessarily selected as the measurement gradation value. Therefore, as is clear from FIG. 13 showing the gradation-gamma value specification partially enlarged, the gamma value estimated by linear interpolation is used for the part where the bending point F is not selected as the measurement gradation value. There is a large error between (a point indicated by a triangle in FIG. 13) and a gamma value (a point indicated by a black circle in FIG. 13) obtained by measuring the luminance of the gradation value corresponding to the bending point. It has been found that ε occurs.

  Furthermore, the inventor found that the point where the gamma value changes abruptly appears in almost the same gradation value for a group of liquid crystal display devices having a common component specification (called “lot” in the manufacturing process of the liquid crystal display device). I figured out what to do. This is presumed to be caused by a controller, a driver IC or the like built in the liquid crystal display device. Moreover, it was also found that the point at which the gamma value changes abruptly (flexion point) does not change over time. Therefore, even if the bending point is not specified for all of the group of liquid crystal display devices, if the bending point is specified in advance for any selected liquid crystal display device, the bending point is determined for the other liquid crystal display devices. It is possible to obtain a gamma value by measuring the luminance at a location (tone value) corresponding to.

The present invention based on the above knowledge has the following configuration.
That is, the invention described in claim 1 is a method for obtaining gamma values of all gradation values that can be displayed by the liquid crystal display device, and is selected arbitrarily from a group of liquid crystal display devices. The gamma value acquisition process of all gradation values, which acquires the gamma value corresponding to all gradation values by measuring the luminance of all gradation values, and the acquired all gradations A tone value extraction process for extracting the tone value corresponding to the inflection point, which is a point at which the gamma value changes rapidly, from the gamma value corresponding to the value, and then performing the group of liquid crystal displays. For other liquid crystal display devices in the apparatus, corresponding to each gradation value of a measurement gradation value group having at least gradation values corresponding to the bending point and having a gradation number smaller than the total gradation number The luminance measurement process of the measurement gradation value group for measuring the luminance, and the measurement A measurement gradation that obtains a gamma value corresponding to each gradation value of the measurement gradation value group from each gradation value of the gradation value group and each measurement value of luminance corresponding to each gradation value of the measurement gradation value group A non-measurement gradation value group that estimates a gamma value corresponding to each gradation value of the non-measurement gradation value group by interpolating the gamma value acquisition process of the value group and each gamma value of the measurement gradation value group The gamma value estimation process is performed.

  In the present invention, a target for obtaining a gamma value corresponding to all gradations by measuring the luminance of all gradation values is a liquid crystal display apparatus arbitrarily selected from a group of liquid crystal display apparatuses. For the remaining liquid crystal display devices, by measuring the luminance corresponding to each gradation value of the measurement gradation value group having the number of gradations smaller than the total number of gradations, it corresponds to each gradation value of the measurement gradation value group. A gamma value is acquired, and each gamma value of the non-measurement gradation value group is estimated by interpolating each gamma value of the measurement gradation value group. Therefore, the time for measuring the luminance is reduced compared to the case where the gamma value is obtained by measuring the luminance of all gradation values for all of the group of liquid crystal display devices. The key gamma value can be acquired efficiently in a short time.

  Further, according to the present invention, by measuring the luminance of all gradation values for a liquid crystal display device arbitrarily selected from a group of liquid crystal display devices, a gamma value corresponding to all gradation values is obtained. Acquired, and from the gamma values corresponding to all the acquired gradation values, the gradation value corresponding to the inflection point, which is the point at which the gamma value changes rapidly, is extracted in advance. The gradation values corresponding to these bending points are included in the above-described measured gradation value group. Since the gamma value obtained by measuring the luminance corresponding to each gradation value of the measurement gradation value group is interpolated to estimate each gamma value of the non-measurement gradation value group, the estimated non-measurement Each gamma value of the gradation value group has an extremely small error from the gamma value corresponding to all the gradations obtained by actual measurement, and the gamma values of all gradations can be obtained with high accuracy.

  The invention described in claim 2 is a liquid crystal display device, a gamma value acquisition computer connected to the liquid crystal display device, and a luminance of an image displayed on the liquid crystal display device connected to the gamma value acquisition computer. In a gamma value acquisition system that has a luminance measuring device and acquires the gamma values of all the gradation values that can be displayed by the liquid crystal display device, the gradation value corresponding to the inflection point, which is the point at which the gamma value changes rapidly And the gamma value acquisition computer includes at least gradation values corresponding to the inflection points stored in the storage means, and a measured gradation value group having a gradation number smaller than the total number of gradations. Display control means for sequentially providing an input signal corresponding to each gradation value to the liquid crystal display device, and a luminance reading means for reading a measurement value of the luminance measured by the luminance measuring instrument each time the input signal is given Then, a gamma value corresponding to each gradation value of the measurement gradation value group is calculated from each gradation value of the measurement gradation value group and each measurement value of luminance corresponding to each gradation value of the measurement gradation value group. A gamma value calculating means; and a gamma value estimating means for estimating a gamma value corresponding to each gradation value of the non-measurement gradation value group by interpolating each gamma value of the measurement gradation value group. Features.

  According to the present invention, the gradation value corresponding to the inflection point at which the gamma value changes rapidly is stored in the storage means. For example, when a group of liquid crystal display devices are shipped from a factory, the gradation values corresponding to such inflection points are measured by measuring the luminance of all gradation values for a liquid crystal display device arbitrarily selected. To obtain the gamma value corresponding to all the gradation values, and extract the gradation value corresponding to the inflection point, which is the point where the gamma value changes abruptly, from the gamma values corresponding to all the obtained gradation values Can be obtained. When the user of the liquid crystal display device adjusts (calibrates) the gamma value of the liquid crystal display device, the gamma value acquisition computer is connected to the liquid crystal display device, and the gamma value is acquired by the following procedure.

  First, the display control means of the gamma value acquisition computer includes each gradation of the measured gradation value group having at least gradation values corresponding to the inflection points stored in the storage means and having fewer gradations than the total number of gradations. An input signal corresponding to the value is sequentially given to the liquid crystal display device. Each time an input signal is given, the luminance of the liquid crystal display device is measured by a luminance measuring instrument. The luminance reading means of the gamma value acquisition computer reads the luminance corresponding to each gradation value of the measurement gradation group. The gamma value calculating means of the gamma value acquisition computer converts each gradation value of the measurement gradation value group and each measurement value of the luminance corresponding to each gradation value of the measurement gradation value group to each gradation value of the measurement gradation value group. Calculate the corresponding gamma value. The gamma value estimating means of the gamma value acquisition computer estimates each gamma value of the non-measurement gradation value group by interpolating each gamma value of the measurement gradation value group.

  As described above, according to the gamma value acquisition system according to the present invention, since the gradation value corresponding to the inflection point is stored in the storage means, for example, after the liquid crystal display device is shipped from the factory, the user can When adjusting the display characteristics of the display device, the gamma value of the measurement gradation value group is obtained by measuring the luminance of the measurement point including the gradation value corresponding to the bending point stored in the storage means. By interpolating the gamma values of these measured tone value groups, it is possible to accurately estimate the gamma values of the non-measured tone value groups.

  It is preferable that the liquid crystal display device used in the above-described gamma value acquisition system includes a storage unit that stores a gradation value corresponding to an inflection point at which the gamma value changes abruptly. With this configuration, when the user tries to adjust the gamma value of the liquid crystal display device, the gamma value can be obtained by taking out the gradation value corresponding to the bending point in a timely manner from the storage means provided in the liquid crystal display device. it can.

  It is also preferable that the gamma value acquisition computer used in the above-described gamma value acquisition system includes a storage unit that stores gradation values corresponding to inflection points at which the gamma value changes abruptly (the invention according to claim 4). With this configuration, the gradation value corresponding to the inflection point at which the gamma value changes abruptly is stored centrally at a liquid crystal display manufacturing plant or the like, and when the user requests it, It can be sent to a gamma value acquisition computer via a communication line and taken into the storage means.

  The invention according to claim 5 is a program of a gamma value acquisition computer used in the gamma value acquisition system according to claim 2, wherein the gamma value acquisition computer corresponds to the bending point stored in the storage means. Display control means for sequentially providing to the liquid crystal display device an input signal corresponding to each gradation value of the measurement gradation value group including at least the gradation value and having a smaller number of gradations than the total number of gradations; and the input signal is provided. A luminance reading means for reading a luminance measurement value measured by the luminance measuring instrument, and each luminance value corresponding to each gradation value of the measurement gradation value group and each gradation value of the measurement gradation value group; From the gamma value calculating means for calculating the gamma value corresponding to each gradation value of the measurement gradation value group, and interpolating each gamma value of the measurement gradation value group, each level of the non-measurement gradation value group Gauge corresponding to key value Is a program for functioning as a gamma value estimation means for estimating the Ma value. According to the program described in claim 5, the computer can be suitably applied to the gamma value acquisition system described in claim 2.

  According to the method for obtaining a gamma value of a liquid crystal display device according to the present invention, a gradation value corresponding to an inflection point, which is a point at which the gamma value changes rapidly, is included in the measurement gradation value group. By interpolating each gamma value corresponding to each gradation value, the gamma value of the non-measured gradation value is estimated, so that the gamma value of all gradations of the liquid crystal display device can be acquired efficiently in a short time. The gamma values of all gradations can be obtained with high accuracy.

  Further, according to the gamma value acquisition system of the present invention, the gradation value corresponding to the inflection point at which the gamma value changes abruptly is stored in the storage means, so that the gradation corresponding to the inflection point is stored from this storage means. The value can be read out in a timely manner, and the gamma characteristic of the liquid crystal display device can be adjusted efficiently and accurately.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 is a flowchart illustrating the procedure of the gamma value acquisition method according to the first embodiment.

  The gamma value acquisition method according to the present embodiment is a gamma value acquisition method of a liquid crystal display device that acquires gamma values of all gradation values that can be displayed by the liquid crystal display device. In steps S1 to S2, a group of liquid crystal values is acquired. Gamma values corresponding to all gradation values are obtained by measuring the luminance of all gradation values for a liquid crystal display device arbitrarily selected from the display devices (step S1). From the gamma values corresponding to all gradation values, the gradation values corresponding to the inflection point, which is the point at which the gamma value changes rapidly, are extracted (step S2). Step S1 corresponds to the gamma value acquisition process of all gradation values in the present invention, and step S2 corresponds to the gradation value extraction process of the bending point in the present invention.

  Steps S3 to S5 include at least a gradation value corresponding to the bending point for a liquid crystal display device other than the liquid crystal display device selected in Steps S1 and S2 from the group of liquid crystal display devices, The luminance corresponding to each gradation value of the measurement gradation value group having the number of gradations smaller than the total number of gradations is measured (step S3), and then each gradation value of the measurement gradation value group and the measurement gradation value group A gamma value corresponding to each gradation value of the measurement gradation value group is acquired from each luminance measurement value corresponding to each gradation value (step S4), and finally each gamma value of the measurement gradation value group is interpolated. Thus, each gamma value of the non-measurement gradation value group is estimated (step S5). Step S3 corresponds to the luminance measurement process of the measurement gradation value group in the present invention, Step S4 corresponds to the gamma value acquisition process of the measurement gradation value group in the present invention, and Step S5 corresponds to the non-measurement in the present invention. This corresponds to the gamma value estimation process of the gradation value group. Hereinafter, each step will be described in detail.

Step S1 (gamma value acquisition process of all gradation values)
S1-1: Arbitrary Selection of Liquid Crystal Display Device A liquid crystal display device that acquires gamma values of all gradation values is arbitrarily selected from a group of liquid crystal display devices. As a group of liquid crystal display devices, for example, a group of liquid crystal display devices commonly referred to as lots in the manufacturing process of the liquid crystal display device, which have common component specifications, for example, corresponds. The number of liquid crystal display devices to be selected may be one or more. In the case of a plurality, the average value or representative value of the obtained gamma values of each liquid crystal display device is used.

S1-2: Measurement of luminance of all gradation values The luminance of all gradations is measured for an arbitrarily selected liquid crystal display device. Specifically, in the case of a color liquid crystal display device, gamma values corresponding to all gradations are acquired for the three primary colors red (R), green (G), and blue (B). One appropriate color (for example, red) is selected. Then, an input signal corresponding to a gradation value of a level from 0 to 255 is sequentially given to the liquid crystal display device, and the luminance of each gradation value image (for example, a so-called “solid image” of one red color) is measured.

S1-3: Normalization of measured luminance By setting the luminance corresponding to the minimum gradation value (level 0) to “0” and the luminance corresponding to the maximum gradation value (level 255) to “1”, respectively. Then, the “luminance ratio” that is a value obtained by normalizing the luminances of the other intermediate gradation value groups (levels 1 to 254) is calculated.

S1-4: Calculation of gradation ratio By setting the minimum gradation value (level 0) to “0” and the maximum gradation value (level 255) to “1”, another intermediate gradation value group The “gradation ratio”, which is a normalized value of (level 1 to 254), is calculated.

S1-5: Calculation of gamma value The gamma value corresponding to all gradation values is calculated by the following equation.
γ = LogY ′ / LogX ′
Here, Y ′ is a luminance ratio and X ′ is a gradation ratio. For the minimum gradation value (level 0) and the maximum gradation value (level 255), the gamma value cannot be calculated from the above equation, and therefore a predetermined gamma value is set in advance.

  As described above, after obtaining the gamma values corresponding to all gradation values for one of the three primary colors (for example, red), the other primary colors (for example, green and blue) are sequentially selected and selected. Similarly, for each primary color, gamma values corresponding to all gradation values are acquired.

  When the process of step S1 ends, the process proceeds to step S2. In this process, for each of the three primary colors, the tone value corresponding to the inflection point, which is the point at which the gamma value changes abruptly, is extracted from the gamma value corresponding to the acquired all tone values. Hereinafter, details of the process in step S2 will be described with reference to FIG.

Step S2 (bending point tone value extraction process)
S2-1: Calculation of Gamma Value Change A gamma value change amount Δγ _i for each gradation value is calculated based on the gamma values corresponding to all gradation values (see FIG. 4).
Δγ _i = γ _i −γ _i−1
However, i = an integer from 1 to 255

S2-2: Extraction of candidate point of measurement gradation value (1)
Based on the change amount Δγ _i of the gamma value for each gradation value calculated in step S2-2, the gradient (Δγ _i ) of the change in the gamma value at a certain gradation value changes from positive to negative or from negative to positive. It is determined whether or not to do. If there is a changing point (for example, γ _{i + 1} in FIG. 4), the gradation value at that point is stored as a candidate point for the measured gradation value (S2-5).

S2-3: Extraction of candidate points of measurement gradation value (2)
In step S2-3, it is determined whether or not the change amount Δγ _i of the gamma value at a certain gradation value is larger than a predetermined threshold value Δγ _SH . This threshold value Δγ _SH is appropriately determined in advance from the apparent smoothness of the change characteristic of the gamma value (see FIG. 4). If the change amount Δγ _i of the gamma value is larger than a predetermined threshold value Δγ _SH , the gradation value is stored as a candidate for the measurement gradation value (S2-5).

S2-4: Extraction of candidate points of measurement gradation value (3)
In step S2-4, an angle θ _i (maximum is 180 degrees) formed by a straight line connecting gamma value plots in a certain gradation value and one gradation value before and after the gradation value is a predetermined threshold value θ. _It is determined whether it is smaller than _SH (see FIG. 5). This threshold value θ _SH is appropriately determined in advance from the apparent smoothness of the change characteristic of the gamma value. When the angle θ _i is smaller than the predetermined threshold value θ _SH , the gradation value is stored as a candidate for the measurement gradation value (S2-5).

  After extracting the candidate points of the measurement gradation value by the above processes of Steps S2-1 to S2-5, the processes of S2-6 to S2-12 are performed, and the candidate points of the measurement gradation value are extracted. From this, a measurement point that is a target of luminance measurement, that is, a bending point that is a point at which the gamma value changes rapidly is determined. The details of steps S2-6 to S2-12 will be described below.

Step S2-6
In step S2-6, the lowest gradation value (level 0) and the highest gradation value (level 255) are registered as measurement points.

Step S2-7
When an approximate line is drawn based on the least square method for a set of adjacent candidate points of measurement gradation values, an error ε _i of each measurement gradation value candidate point with respect to the approximate line is determined in advance. It is determined whether there is a candidate point that is larger than the threshold value ε _SH and has the maximum error ε _i . Here, candidate points that have already been registered as measurement points are not included in the set of candidate points for which an approximate straight line is obtained. The threshold value ε _SH is appropriately determined in advance from the apparent smoothness of the change characteristic of the gamma value. In the process of step S2-7, first, as shown in FIG. 6, the lowest gradation value (level 0) and the highest gradation value (level 255) are measured points (indicated by black circles in FIG. 6). since registered, we obtain an approximate straight line L ₁ set of candidate points of all measured tone values extracted by the range up to level 1 to 254 (indicated by white circles in FIG. 6) as a target. The approximation line L error epsilon _i candidate points of each measurement tone value for _a is determined whether greater than the threshold epsilon _SH is, candidate points of large measured tone value than the threshold epsilon _SH A candidate point (point of gradation value i in FIG. 6) where the maximum error ε _MAX occurs is extracted from the group. The gradation value of the candidate point of the maximum error ε _MAX is registered as a measurement point (step S2-8).

Subsequently, the same step S2-7 is repeated to search for further measurement points. In this process, since the gradation value i is registered as a measurement point in the previous process, the gradation value i is removed to determine a set of candidate points to be processed. Here, as shown in FIG. 7, a set of two candidate points C2 and C3 become a target of processing, obtaining an approximate straight line L _2, L ₃ in each of the sets C2 and C3. The error epsilon candidate points of each measurement gradation value to determine whether greater than the threshold epsilon _SH for each approximate line L _2, L _3, larger measured tone value than the threshold epsilon _SH extracting candidate points having the greatest error epsilon _MAX from the candidate point group, (in the example of FIG. 7, the gradation value h and j) gray scale values of the candidate point of the maximum error epsilon _MAX as measurement points Register (step S2-8).

Further, in step S2-7, which is repeatedly performed, as shown in FIG. 8, each of four sets C4 to C7 from which candidate points (gradation values h, i, j) already registered as measurement points are excluded is measured. Perform point extraction processing. Step S2-7 is repeated, and if the error ε _i of each candidate point of the measured gradation value with respect to the approximate line is all smaller than a predetermined threshold value ε _SH , the process proceeds to the next step S2-9. .

S2-9
In step S2-9, when an approximate line is drawn based on the least square method for a set of adjacent candidate points of measurement gradation values, an error ε of each measurement gradation value candidate point with respect to the approximate line. Whether or not there is a candidate point that is smaller than a predetermined threshold value ε _SH and has a gamma value change specific appearance that is not sufficiently smooth for a gradation range where a set of candidate points exists. judge. If there is a point where the change characteristic of the gamma value is not sufficiently smooth, the candidate point is registered as a measurement point (step S2-10).

Step S2-11
In step S2-11, whether or not all the measurement gradation value candidate points are registered as measurement points, or the error ε of each measurement gradation value candidate point with respect to the approximate straight line obtained by the least square method is calculated. It is determined whether or not a change characteristic of the gamma value that is smaller than the threshold value ε _SH and has a sufficiently smooth appearance is obtained by a plurality of approximate lines. When a gamma value change characteristic with a sufficiently smooth appearance is obtained by a plurality of approximate straight lines, a series of determination processes is terminated (step S2-12). If not obtained, the process goes to step S2-6. Return and repeat a series of discrimination processing. FIG. 9 is a schematic diagram showing the distribution of measurement points (bending points) registered by the processes of steps S1 and S2, in which black dots indicate measurement points obtained in the present embodiment, and white circles indicate conventional ones. That is, the measurement points determined at a constant gradation interval are shown. As can be understood from FIG. 9, according to the present embodiment, in the change characteristic of the gamma value, a bending point that is a point at which the gamma value changes rapidly is extracted as a measurement point.

  When the gradation value corresponding to the measurement point (that is, the inflection point where the gamma value changes rapidly) is extracted by the processing in steps S1 and S2 in FIG. 1, the process proceeds to step S3 in FIG.

Step S3 (measurement of luminance in the measurement gradation value group)
In step S3, other liquid crystal display devices other than the liquid crystal display device selected in steps S1 and S2 are included, and at least gradation values corresponding to registered measurement points (bending points) are included. The luminance corresponding to each gradation value of the measurement gradation value group having a small number of gradations is measured. In this embodiment, the luminance of all measurement points extracted in steps S1 and S2 is measured. Since measurement points are obtained for each of the three primary colors, in this step S3, the luminance of the measurement points for each of the three primary colors is measured. Note that the number of measurement points is extracted only from the point where the gamma value is changing rapidly, and naturally, it is smaller than the total number of gradations (256), and is usually around 25.

Step S4 (Acquire gamma value of measured gradation value group)
Based on the gradation values of the measurement gradation value group obtained in step S3 and the luminance corresponding to these gradation values, the same method as described in step S1 is used to correspond to the gradation values of the measurement gradation value group. The calculated gamma value is calculated. A gamma value is obtained for each of the three primary colors.

Step S5 (gamma value estimation process of non-measured gradation value)
By interpolating each gamma value of the measured gradation value group, the gamma value of the non-measured gradation group is estimated. In this embodiment, the gamma value is estimated by linear interpolation. Figure 10 is a diagram showing how the estimated by linear interpolation the gamma value in the non-measurement tone value is between the measured tone value X _A and X _B. The gamma value γ _{A + k} of the measured gradation value can be obtained by the following equation.
γ _{A + k} = γ _A + k × (γ _B −γ _A ) / (h + 1)
Here, h is the number of unmeasured tone value is between the measured tone value X _A and X _B.

  Through steps S3 to S5 described above, gamma values of all gradations can be acquired for liquid crystal display devices other than the liquid crystal display device selected in steps S1 and S2. In the processes of steps S3 to S5, since only the luminance corresponding to the extracted bending point is measured, the gamma value is efficiently compared with the case of measuring the luminance corresponding to all gradation values. It can be acquired in a short time. Moreover, since the luminance of the gradation value corresponding to the inflection point, which is the point at which the gamma value changes rapidly, is measured, the gamma value of the non-measurement gradation value group is changed from the gamma value corresponding to the measurement gradation value group. When estimating by linear interpolation, the gamma value can be estimated with high accuracy.

Next, an embodiment of a gamma value acquisition system according to the present invention will be described with reference to the drawings.
FIG. 11 is a block diagram illustrating a schematic configuration of the gamma value acquisition system according to the second embodiment.

<Schematic configuration of gamma value acquisition system>
The gamma value acquisition system according to the present embodiment is roughly divided into a liquid crystal display device 10 from which a gamma value is acquired, a gamma value acquisition computer 20 connected to the liquid crystal display device 10, and the gamma value acquisition. A luminance measuring device 30 that is connected to the computer 20 and measures the luminance of an image displayed on the liquid crystal display device 10 is provided. This gamma value acquisition system is based on a function for acquiring gamma values of all gradation values (in this embodiment, gradation values of levels 0 to 255) that can be displayed by the liquid crystal display device 10 and the acquired gamma values. And a calibration function for calibrating the display characteristics of the liquid crystal display device 10.

<Configuration of Liquid Crystal Display Device 10>
The liquid crystal display device 10 receives an input signal for display from the gamma value acquisition computer 20, particularly an input unit 11 that receives an input signal of a measured gradation value during the gamma value acquisition process, and takes in via this input unit 11. Between the signal processing unit 12 that performs appropriate signal processing such as color conversion on the input signal, the display unit 13 that displays the image given the signal-processed input signal, and the gamma value acquisition computer 20 Are provided with a communication unit 14 for communicating various data, a CPU 15 for controlling the entire liquid crystal display device 10, and a storage unit 16.

<About the storage unit 16>
The storage unit 16 stores a plurality of gradation values (measurement gradation value group) for measuring the luminance when the gamma value of the liquid crystal display device 10 is acquired. In particular, the measurement tone value group is characteristic in that the tone value corresponding to the bending point, which is the point at which the gamma value changes rapidly, is included. The measurement gradation value group is a number smaller than the number of all gradations (in this embodiment, the number of levels is 256), and is, for example, about 25 measurement gradation values. A measurement gradation value group including measurement gradation values corresponding to the bending point is stored in the storage unit 16 in advance when the liquid crystal display device 10 is shipped from the factory. Since the method for acquiring the measurement gradation value group corresponding to the inflection point has been described in the first embodiment, description thereof is omitted here. The storage unit 16 corresponds to storage means in the present invention.

<Configuration of Gamma Value Acquisition Computer 20>
The gamma value acquisition computer 20 includes a display control unit 21 that outputs an input signal for display to the liquid crystal display device 10 and exchanges various data. In addition, the gamma value acquisition computer 20 includes a luminance reading unit 22 that reads measurement values of each luminance of the measurement gradation value group of the liquid crystal display device 10 (specifically, the display unit 13) measured by the luminance measuring device 30. ing. The read luminance measurement value is given to the gamma value calculation unit 23. The gamma value calculation unit 23 calculates the gradation value of the measurement gradation value group captured from the liquid crystal display device 10 via the display control unit 21 and the luminance measurement value corresponding to the gradation value of the measurement gradation value group. A gamma value corresponding to each gradation value of the measurement gradation value group is calculated. The gamma value corresponding to each gradation value of the calculated measurement gradation value group is given to the gamma value estimation unit 24. The gamma value estimation unit 24 estimates the gamma value of the non-measurement gradation by interpolating (in the present embodiment, linear interpolation) each gamma value of the measurement gradation value group. The gamma value of the measurement gradation group and the estimated gamma value of the non-measurement gradation value group are given to the calibration unit 25. The calibration unit 25 determines the contents of the lookup table (LUT) 12A provided in the signal processing unit 12 of the liquid crystal display device 10 based on the gamma values of the measurement gradation value group and the non-measurement gradation value group. Data for rewriting is given to the liquid crystal display device 10. The display control unit 21, the luminance reading unit 22, the gamma value calculation unit 23, the gamma value estimation unit 24, and the calibration unit 25 described above are stored in a storage medium (not shown) provided in the gamma value acquisition computer 20. It is realized by a program.

<About the luminance measuring instrument 30>
In this embodiment, the luminance measuring device 30 is a luminance measuring camera installed at a position several tens of centimeters away from the display unit (display screen) 13 of the liquid crystal display device 10 or a position in contact with the display screen. The brightness of a set of multiple pixels is measured. The three primary colors (R, G, B) are displayed in order, and the luminance corresponding to each gradation of the measurement gradation value group of each primary color is measured.

<Operation of gamma value acquisition system>
Next, the operation of the gamma value acquisition system according to this embodiment will be described.
For example, when the user of the liquid crystal display device 10 tries to calibrate the display characteristics of the liquid crystal display device 10, the gamma value acquisition computer 20 is connected to the liquid crystal display device 10 and the luminance measuring device 30 is connected to the gamma value acquisition computer 20. To do. Note that the gamma value acquisition computer 20 is realized by porting a program for executing the gamma value acquisition method described in the first embodiment to a general-purpose computer that is normally connected to the liquid crystal display device 10. be able to.

  In acquiring the gamma value of the liquid crystal display device 10, first, each gradation value of the measured gradation value group is read from the storage unit 16 provided in the liquid crystal display device 10 and is taken into the display control unit 21 of the gamma value acquisition computer 20. . The display control unit 21 provides the liquid crystal display device 10 with an input signal corresponding to each gradation value of the captured measurement gradation value group. This input signal is given to the display unit 13 via the input unit 11 and the signal processing unit 12 of the liquid crystal display device 10. The display unit 13 sequentially displays images corresponding to the gradation values of the measurement gradation value group (so-called “solid display” of any one of the three primary colors). The luminance measuring device 30 measures the luminance of the display unit 13 for each gradation value. The luminance reading unit 22 of the gamma value acquisition computer 20 reads the luminance corresponding to each gradation value of the measurement gradation value group. Then, the gamma value calculation unit 23 determines the measurement gradation value group based on the gradation values of the measurement gradation value group given from the display control unit 21 and the luminance measurement values corresponding to the read gradation values. A gamma value corresponding to each gradation value is calculated. The gamma value estimation unit 24 estimates a gamma value corresponding to each gradation value of the non-measurement gradation group by linearly interpolating the gamma value corresponding to each gradation value of the measurement gradation value group. Since the gamma value calculation method and the gamma value interpolation method have been described in the first embodiment, description thereof will be omitted here.

  Each gamma value of the measurement gradation value group and the non-measurement gradation value group obtained as described above is given to the calibration unit 25. Based on the given gamma value group, the calibration unit 25 rewrites data for rewriting the look-up table 12A provided in the signal processing unit 12 of the liquid crystal display device 10 via the display control unit 21. 10 is given. The CPU 15 of the liquid crystal display device 10 calibrates the display characteristics of the liquid crystal display device 10 by rewriting the lookup table 12A based on the given data.

  As described above, according to the gamma value acquisition system according to the present embodiment, the gradation value corresponding to the inflection point at which the gamma value changes abruptly is stored from the storage unit 16 provided in the liquid crystal display device 10 by the user. Since the measurement gradation value group included in the data is read out in a timely manner and the luminance corresponding to each gradation value of the measurement gradation group is measured, the gamma value of the liquid crystal display device 10 can be acquired. Even after the product is shipped from the factory, the gamma value can be obtained with high accuracy, so that the display characteristics of the liquid crystal display device 10 can be calibrated correctly.

The present invention is not limited to the above embodiments, and can be modified as follows.
(1) In the second embodiment described above, the liquid crystal display device 10 is configured to include the storage unit 16 that stores the gradation value group (measurement gradation value group) corresponding to the bending point at which the gamma value changes rapidly. . However, the present invention is not limited to this, and a similar storage unit may be provided in the gamma value acquisition computer 20. With this configuration, the gradation value corresponding to the inflection point at which the gamma value changes abruptly is stored centrally at a liquid crystal display manufacturing plant or the like, and when the user requests it, It can be sent to the gamma value acquisition computer 20 using a communication line and taken into the storage unit. Alternatively, the measured gradation value group is stored in a storage medium such as a CD-ROM and shipped together with the liquid crystal display device 10, and this CD-ROM is set in the gamma value acquisition computer 20, and the measured gradation value group is stored in the CD-ROM. You may make it take in into the memory | storage part of the gamma value acquisition computer 20 from ROM.

  (2) In the above-described embodiment, the measurement gradation value group is composed of only the gradation value group corresponding to the bending point where the gamma value changes rapidly. However, the measurement gradation value group may be configured to include, for example, points set within a range of all gradations at a constant gradation value interval as measurement gradation values. Alternatively, for the vicinity of the minimum gradation value and the maximum gradation value, measurement points set at narrow intervals may be included in the measurement gradation value group.

3 is a flowchart illustrating a procedure of a gamma value acquisition method according to the first embodiment. It is the flowchart which showed the procedure of the extraction process of a measurement candidate point. It is the flowchart which showed the procedure of the process which determines a measurement point from a measurement candidate point group. It is a figure for demonstrating an example of the method of extracting a measurement candidate point. It is a figure for demonstrating the other example of the method of extracting a measurement candidate point. It is a figure for demonstrating one process of the process which determines a measurement point from a measurement candidate point group. It is a figure for demonstrating one process of the process which determines a measurement point from a measurement candidate point group. It is a figure for demonstrating one process of the process which determines a measurement point from a measurement candidate point group. It is a schematic diagram of the change characteristic of the gamma value which showed the distribution state of the measurement point. It is a figure for demonstrating the linear interpolation process in Example 1. FIG. It is the block diagram which showed schematic structure of the gamma value acquisition system which concerns on Example 2. FIG. (A) is a schematic diagram of the change characteristic of the gamma value used for description of the conventional method. (B) is a characteristic diagram showing the relationship between the luminance value and the gradation value for explaining the problems of the conventional method. It is a partial enlarged view of the change characteristic of a gamma value for explanation of the problem of the conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display part 13 ... Display part 16 ... Memory | storage part 20 ... Gamma value acquisition computer 21 ... Display control part 22 ... Luminance reading part 23 ... Gamma value calculation part 24 ... Gamma value estimation part 30 ... Luminance measuring device

Claims (5)

In a gamma value acquisition method of a liquid crystal display device that acquires gamma values of all gradation values that can be displayed by the liquid crystal display device,
For liquid crystal display devices arbitrarily selected from a group of liquid crystal display devices,
A gamma value acquisition process for all gradation values, which obtains a gamma value corresponding to all gradation values by measuring the luminance of all gradation values;
Performing a gradation value extraction process of a bending point, extracting a gradation value corresponding to a bending point, which is a point at which the gamma value changes abruptly, from gamma values corresponding to all the acquired gradation values;
Next, for other liquid crystal display devices in the group of liquid crystal display devices,
Measuring the luminance of the measurement gradation value group, which measures the luminance corresponding to each gradation value of the measurement gradation value group including at least the gradation value corresponding to the inflection point and less than the total number of gradations Process,
Obtaining a gamma value corresponding to each gradation value of the measurement gradation value group from each gradation value of the measurement gradation value group and each measurement value of luminance corresponding to each gradation value of the measurement gradation value group; Gamma value acquisition process of measurement tone value group,
Performing a gamma value estimation process of the non-measurement gradation value group, in which a gamma value corresponding to each gradation value of the non-measurement gradation value group is estimated by interpolating each gamma value of the measurement gradation value group. A method for obtaining a gamma value of a liquid crystal display device. A liquid crystal display device, a gamma value acquisition computer connected to the liquid crystal display device, and a luminance measuring instrument connected to the gamma value acquisition computer for measuring the luminance of an image displayed on the liquid crystal display device, In a gamma value acquisition system that acquires gamma values of all gradation values that can be displayed by a liquid crystal display device,
Storage means for storing a gradation value corresponding to an inflection point, which is a point at which the gamma value changes rapidly,
The gamma value acquisition computer is:
An input signal corresponding to each gradation value of the measurement gradation value group having at least gradation values corresponding to the inflection points stored in the storage means and having a gradation number smaller than the total number of gradations is sequentially applied to the liquid crystal display device. Display control means for providing,
A luminance reading means for reading a measurement value of luminance measured by the luminance measuring instrument each time the input signal is given;
A gamma that calculates a gamma value corresponding to each gradation value of the measurement gradation value group from each gradation value of the measurement gradation value group and each luminance value corresponding to each gradation value of the measurement gradation value group. A value calculating means;
Gamma value acquisition means comprising gamma value estimating means for estimating a gamma value corresponding to each gradation value of the non-measurement gradation value group by interpolating each gamma value of the measurement gradation value group system. A liquid crystal display device used in the gamma value acquisition system according to claim 2,
The liquid crystal display device includes the storage unit that stores a gradation value corresponding to a bending point that is a point at which a gamma value changes rapidly. A gamma value acquisition computer used in the gamma value acquisition system according to claim 2,
The said gamma value acquisition computer is a gamma value acquisition computer provided with the said memory | storage means which memorize | stored the gradation value corresponding to the bending point which is a point where a gamma value changes rapidly. A program for a gamma value acquisition computer used in the gamma value acquisition system according to claim 2,
The gamma value acquisition computer;
An input signal corresponding to each gradation value of the measurement gradation value group having at least gradation values corresponding to the inflection points stored in the storage means and having a gradation number smaller than the total number of gradations is sequentially applied to the liquid crystal display device. Display control means for providing,
A luminance reading means for reading a measurement value of luminance measured by the luminance measuring instrument each time the input signal is given;
A gamma that calculates a gamma value corresponding to each gradation value of the measurement gradation value group from each gradation value of the measurement gradation value group and each luminance value corresponding to each gradation value of the measurement gradation value group. A value calculating means;
A program for functioning as gamma value estimating means for estimating a gamma value corresponding to each gradation value of a non-measurement gradation value group by interpolating each gamma value of the measurement gradation value group.

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