JP2004134853A - Method, program and apparatus for generating gradation characteristic table, and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a gradation characteristic table reflecting a subjective sense on parameters. <P>SOLUTION: A CPU calculates a brightness parameter γ for adjusting the brightness of an image (step S5), inputs a variation parameter I for adjusting the variation of the image (step S6), then calculates the output brightness values y1, y2, y3 at correction points (step S7), and finally obtains other points by interpolation, based on the correction points, to generate a gradation characteristic table having stored gradation characteristics. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of generating a gradation characteristic table used for setting gradation characteristics of an image, a generation program thereof, a generation device thereof, and an image display device using the same.
[0002]
[Prior art]
Conventional image display devices perform various corrections in order to match the display characteristics of the display to the human visual characteristics. For this reason, a technique for converting an image using a sigmoid function is known (for example, Non-Patent Document 1).
[0003]
[Non-patent document 1]
“Tone conversion using a sigmoid function in a digital camera system,” Journal of the Imaging Society of Japan, Vol. 3-10, 2002.
[0004]
[Problems to be solved by the invention]
By the way, since a display image is evaluated based on human perception, it is desirable to use a subjective one as a correction parameter. However, in the conventional technique, since the subjective sensation does not sufficiently reflect the parameter, there is a problem that control is complicated to obtain a desired image.
[0005]
The present invention has been made in view of the above circumstances, and provides a method of generating a gradation characteristic table in which a subjective feeling is reflected in a parameter, a generation program thereof, a generation device thereof, and an image display device using the same. The task is to
[0006]
[Means for solving the problem]
In order to solve the above-described problem, a method of generating a gradation characteristic table according to the present invention is used for setting gradation of an image, and stores an input data value and an output data value in association with each other. A first step of setting a plurality of input data values and setting a first parameter for adjusting the brightness of the image and a second parameter for adjusting the sharpness of the image. An operation including the first parameter and the second parameter is performed on each input data value to generate each output data value, and each set of the set input data value and the generated output data value is converted to each correction point. And a third step of performing an interpolation process on each of the correction points to generate a set of another input data value and an output data value.
[0007]
According to the present invention, since human sensations such as image brightness and image sharpness are employed as parameters, it is possible to accurately reflect the intention at the time of control in the gradation characteristic table. In other words, since the subjective sensation is used as a parameter, it is possible to convert the input image into an attractive image by simple control.
In the first step, after setting a plurality of input data values, the first parameter and the second parameter may be set, or after setting the plurality of input data values, the first parameter and the second parameter may be set. After the setting, a plurality of input data values may be set.
[0008]
Here, in the first step, three input data values satisfying X1 <X2 <X3 are set, and in the second step, output data values corresponding to X1, X2, and X3 are set to Y1, Y2 , And Y3, the operation is to generate Y1, Y2, and Y3 from X1, X2, and X3 by an exponential operation, and the exponent part of the exponent operation for generating Y1 is the first parameter or The value of the exponent part is set to increase as the second parameter increases. The exponent part of the exponential operation for generating Y2 is the first parameter, and the exponent part of the exponential operation for generating Y3 is It is preferable that the value of the exponent is increased when the first parameter is increased, and the value of the exponent is decreased when the second parameter is increased. . Note that the exponent calculation may be performed after performing the normalization processing on X1, X2, and X3.
[0009]
More specifically, the first parameter is γ, the second parameter is I, as, bs, cs, and ds are constants, and the exponent part of the exponent calculation for generating the Y1 is K1, and the Y2 is generated. K1 = (1 + as · I) γ + bs, K2 = γ, K3 = (1 + cs · I) γ + ds, where K2 is the exponent part of the exponent operation to be performed and K3 is the exponent part of the exponent operation for generating the Y3. , As> 0, bs> 0, cs <0, ds <0.
[0010]
Further, the absolute value of as is preferably smaller than the absolute value of cs.
[0011]
Preferably, in the first step, the first parameter is set in consideration of an average value of target input image data. More specifically, in the first step, an average value of target input image data is calculated, the average value is converted into an average value after conversion according to a predetermined rule, and the average value is set as a base. Preferably, the first parameter is set as logarithmic processing of the converted average value.
[0012]
In addition, it is preferable that, in the second step, instead of calculating the Y2 by an exponential operation, the Y2 be the average value after the conversion. In this case, the process of calculating Y2 can be omitted.
[0013]
In the first step, it is preferable that the second parameter is set in consideration of a frequency distribution of target input image data. This is because the sharpness of an image is related to how gradations are distributed.
[0014]
Next, a tone characteristic table generation device according to the present invention is a tone characteristic table generation device that stores input data values and output data values in association with each other and is used for setting the tone characteristics of an image. Means for selecting a plurality of input data values in the gradation characteristic table; means for setting a first parameter for adjusting brightness of an image and a second parameter for adjusting sharpness of the image; Means for calculating an output data value corresponding to the selected plurality of input data values using the second parameter and the second parameter; and correcting each set of the selected plurality of input data values and the corresponding output data value to a correction point. Means for performing an interpolation process on the correction point to generate a set of another input data value and an output data value. According to the present invention, since human sensations such as image brightness and image sharpness are employed as parameters, it is possible to accurately reflect the intention at the time of control in the gradation characteristic table. In other words, since the subjective sensation is used as a parameter, it is possible to convert the input image into an attractive image by simple control.
[0015]
Further, an image display device according to the present invention includes a device for generating the above-described gradation characteristic table, a display unit for displaying an image by a drive signal, and the output data stored in the drive signal and the gradation characteristic table. A storage unit that stores the relationship in advance, a drive table generation unit that generates a drive table that specifies the relationship between the input data and the drive signal with reference to the gradation characteristics table and the storage content of the storage unit, A driving unit that generates the driving signal from input image data with reference to the driving table. According to the present invention, since the above-described gradation characteristic table is used, it is possible to display a good-looking image on the display unit.
[0016]
In this case, for example, the driving table stores the relationship between the pulse specifying the pulse width and the input image data, and the driving unit reads the pulse corresponding to the input image data, and It may output a drive signal that has been pulse-width modulated based on it.
[0017]
Further, the image display device includes a device for generating a gradation characteristic table, a display unit for displaying an image by a drive signal, a conversion table generation unit for generating a conversion table based on the gradation characteristic table, and the conversion table. A conversion unit that converts input image data into output image data, and converts the drive signal based on the output image data.
And a driving unit that generates the data.
[0018]
Next, the generation program according to the present invention is used for setting a gradation characteristic of an image, and generates, by a computer, a gradation characteristic table in which input data values and output data values are stored in association with each other. Means for selecting a plurality of input data values in the tone characteristic table, means for setting a first parameter for adjusting brightness of an image and a second parameter for adjusting sharpness of the image, Means for calculating an output data value corresponding to the selected plurality of input data values using the second parameter, each set of the selected plurality of input data values and the corresponding output data value as a correction point, An interpolating process is performed on the correction point to generate a set of another input data value and output data value. According to the present invention, since human sensations such as image brightness and image sharpness are employed as parameters, it is possible to accurately reflect the intention at the time of control in the gradation characteristic table. In other words, since the subjective sensation is used as a parameter, it is possible to convert the input image into an attractive image by simple control.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First embodiment>
FIG. 1 shows a block diagram of an image display device 100 according to the first embodiment of the present invention. The image display device 100 includes an image data analysis unit 10, a gradation characteristic setting unit 20, a pulse selection unit 30, a PWM circuit 40, and a display panel 50. Among these components, the image data analysis unit 10, the gradation characteristic setting unit 20, the pulse selection unit 30, and the PWM circuit 40 are configured by a CPU, a RAM, and a ROM.
[0020]
The display panel 50 is, for example, a transflective panel. When the amount of external light is large, the display panel 50 uses reflected light for image display. When the amount of external light is small, the display panel 50 uses a backlight for image display. Is used. The display panel 50 uses liquid crystal as an electro-optical material and is formed with a plurality of data lines (segment electrodes) extending in a column direction, while a plurality of scanning lines (common electrodes) extend in a row direction. And a pixel is formed corresponding to each intersection of the data line and the scanning line. Each pixel includes a liquid crystal layer and a thin film diode (TFD) that is an example of a switching element.
[0021]
Further, each data line of the display panel 50 is driven by a drive signal V output from the PWM circuit 40. The drive signal V is a pulse-width modulated signal, and the pulse width is specified by a pulse called GCP. Since the luminance of each pixel is determined by the effective value of the voltage applied to the liquid crystal, the increment of the pulse width of the drive signal V corresponds to the increment of the output luminance of the display panel 50. The display panel 50 of this example displays 64 gradations. Therefore, the pulse width of the drive signal V is specified by the selection pulse selected based on the input image data Din from the 64 pulses.
[0022]
The image data analysis unit 10 generates analysis information 10a indicating image characteristics obtained by extracting features of the input image data Din. The analysis information 10a includes an average value Pin of one frame image. More specifically, the image data analysis unit 10 is configured by a CPU and a RAM, the CPU stores one frame of input image data Din in the RAM, accumulates the data value of each dot, and outputs the accumulation result as a dot. The average value Pin is calculated by dividing by a number.
[0023]
The gradation characteristic setting unit 20 sets gradation characteristics that determine the relationship between the input image data Din, the output luminance of the display panel 50, and the input image data Din based on the analysis information 10a. More specifically, the gradation characteristic setting unit 20 is configured by a CPU, a RAM, and a ROM. The ROM stores a luminance conversion table TBL1 and reference gradation characteristic data Dref. The brightness conversion table TBL1 is used to convert the average brightness. The reference gradation characteristic data Dref indicates a relationship between the input image data Din indicating a standard image and the output luminance of the display panel 50.
[0024]
FIG. 2 is a flowchart showing the operation of the CPU constituting the gradation characteristic setting unit 20. First, the CPU calculates an output luminance corresponding to the average value Pin with reference to the reference gradation characteristic data Dref (step S1). In the following description, the calculated output luminance of the display panel 50 is referred to as input average luminance Pave. For example, if the reference gradation characteristic Qref indicated by the reference gradation characteristic data Dref is a dotted line shown in FIG. 3, the average value Pin and the input average luminance Pave have a relationship shown in FIG.
[0025]
Next, the CPU converts the input average luminance Pave with reference to the luminance conversion table TBL1 (Step S2). In the following description, the converted luminance is referred to as output average luminance Pave '. FIG. 4 shows an example of a conversion characteristic of the luminance conversion table TBL1 by a solid line. For reference, the characteristics in the case where the luminance is not converted are indicated by dotted lines. In this example, the input average luminance Pave and the output average luminance Pave 'have the relationship shown in FIG. The conversion characteristics of the brightness conversion table TBL1 may be set so that, for example, a point passes through a point (0.5, 0.5) and its inclination is smaller than 1. In this case, if the input average luminance Pave is lower than 0.5, the output average luminance Pave 'is higher than the input average luminance Pave, and if the average luminance is higher than 0.5, the output average luminance Pave' is It is lower than the input average luminance Pave.
[0026]
Thereafter, the CPU sets a correction point (step S3). In this example, three correction points are set. For example, if the gradation characteristics are as shown in FIG. 5, the correction points are P1 to P3. However, in step S3, only the input data A, B, and C are set, and the corresponding output luminances y1, y2, and y3 are calculated in the next step S4.
[0027]
In step S4, the CPU sets a gradation characteristic that passes through the correction point according to a predetermined rule. FIG. 6 is a flowchart showing the operation of the CPU in the gradation characteristic setting process. First, the CPU calculates a brightness parameter γ for adjusting the brightness of an image (step S5). This calculation is given by Equations 1 and 2 below.
Pave '= (Pin / 255) ＾ γ Expression 1
γ = log _{(Pin / 255)} Pave '... Equation 2
[0028]
Next, the CPU inputs a sharpness parameter I for adjusting sharpness of the image (step S6). In this example, it is assumed that the sharpness parameter I is predetermined. Thereafter, the CPU calculates the output luminances y1, y2, y3 at the respective correction points P1 to P3 according to the following equations 3 to 5 (step S7). Since y2 has already been determined as Pave ', the calculation can be omitted.
y1 = (A / 255) {(1 + asI) .gamma. + bs} Equation 3
y2 = (B / 255) ＾ γ ... Equation 4
y3 = (C / 255) {(1 + csI) .γ + ds} Equation 5
Here, as, bs, cs, and ds are variables, and as> 0, bs ≧ 0, 0> cs, and 0 ≧ ds. Here, preferably, as = 0.6, bs = 0, cs = −0.8, ds = −0.2, A = 64, B = Pin, and C = 192.
[0029]
Thereafter, the CPU obtains other points by interpolation based on the correction points P1 to P3, and generates a gradation characteristic table TBL2 storing gradation characteristics (step S8). Note that linear interpolation, spline interpolation, or the like can be used for the interpolation processing.
[0030]
The reason for using the above formula will be described. First, γ is similar to the numerical value of the γ characteristic usually used in a television system or the like. Since γ affects the exponents of y1, y2, and y3, the control of brightness can be performed by controlling γ. Specifically, since (A / 255), (B / 255), and (C / 255) are obtained by normalizing input data to 0 to 1, when γ is large, y1, y2, and y3 become small. It becomes dark gradation characteristics. On the other hand, when γ is small, y1, y2, and y3 become large, resulting in a bright gradation characteristic.
[0031]
FIG. 7 shows an example of gradation characteristics in which I is fixed and γ is changed. These gradation characteristics are B = 128, and the other variables are the same as those in the above-described example, and γ is changed to 0.8, 1.0, 1.2, 1.4, and 1.7. From this figure, it can be seen that the smaller the γ, the more the gradation characteristic shifts in a direction to increase the output luminance.
[0032]
The sharpness parameter I acts to increase or decrease the value of the exponent part of y1 and y3. Note that y2 is irrelevant to the sharpness parameter I. Here, since as is positive in y1, by increasing I, the exponent part of y1 increases. As the exponent increases, the value of y1 decreases, emphasizing dark areas. On the other hand, since cs is negative in y3, increasing I increases the exponent part of y3. As the exponent decreases, the value of y3 increases, emphasizing the bright part.
[0033]
FIG. 8 shows an example of a gradation characteristic in which I is fixed and γ is changed. These gradation characteristics are B = 128, and the other variables are the same as in the above-described example, and I is changed to 0.1, 0.3, 0.5, 0.7, and 0.9. From this figure, as I increases, the gradient of the gradation characteristics increases, and a sharp image can be obtained.
[0034]
Although the values of as, bs, cs, and ds are shown here as an example, it is preferable that the absolute values of cs and ds are larger than the absolute values of as and bs. This is because cs and ds determine the degree of change of y3, but for the same I, y3 is changed more than y1. The reason why y3 is largely changed is that it is necessary to change the bright part more than the dark part in order to perceive the same amount of change in human sense.
[0035]
By controlling γ, light and dark can be controlled, and by controlling I, sharpness can be controlled. In such a conventional control, control based on a subjective sensation such as "brightness" or "brightness" could not be performed, so the method of the present embodiment is practically effective as a control method based on a subjective sensation. .
[0036]
As is clear from FIG. 3, when the average value of the input image data Din is low, the correction point P2 is set to a high position, and the gradation characteristic Q1 is higher than the reference gradation characteristic Qref. As a result, a correction is made so as to make the image brighter. FIG. 9 shows a correction example. The dotted line shown in FIG. 9 shows the frequency distribution when the reference gradation characteristic Qref shown in FIG. 3 is applied to certain input image data, and the solid line shown in FIG. 9 applies the gradation characteristic Q1. It shows the frequency distribution in the case of performing. From the figure, it can be confirmed that the frequency of the low-luminance portion decreases and the image shifts to a brighter direction when viewed as a whole.
[0037]
The description returns to FIG. The pulse selection unit 30 has a function of generating a selection table TBL4 used in the PWM circuit 40, and includes a CPU, a RAM, and R0M. The ROM stores a pulse width-gradation table TBL3. In the pulse width-gradation table TBL3, driving characteristics that determine the relationship between the output luminance of the display panel 50 and the pulse width are stored in advance.
[0038]
FIG. 10 is a flowchart illustrating the operation of the CPU configuring the pulse selection unit 30. First, the CPU acquires a gradation characteristic table TBL2 indicating gradation characteristics and a pulse width-gradation table TBL3 indicating driving characteristics (steps S10 and S11). Thereafter, the CPU selects the input image data Din for which the pulse width is to be set in the gradation characteristics, and obtains the corresponding output luminance (step S12). For example, if the gradation characteristics are as shown in FIG. 11 and the value of the input image data Din is “64”, the corresponding output luminance is L1.
[0039]
Next, the CPU refers to the pulse width-gradation table TBL3, specifies the pulse width corresponding to the output luminance closest to the output luminance acquired in step S12, and associates the pulse width with the value of the input image data Din. Then, the information is stored in the RAM (step S13). For example, if the drive characteristics indicated by the pulse width-gradation table TBL3 are as shown in FIG. 12 and the output luminance closest to the output luminance L1 is L1 ', the value of the pulse width is "280". In this case, the value “64” of the input image data Din is associated with the value “280” of the pulse width.
[0040]
Thereafter, the CPU determines whether or not the processes of steps S12 and S13 have been completed by a number (for example, 64) that can be set by the driver of the display panel 50 (step S14), and all the associations are completed. The selection process of the pulse width is repeated until the operation is completed. When all the associations are completed, the CPU stores the associated input image data Din and the pulse width in the RAM as the selection table TBL4 (step S15).
[0041]
As described above, the pulse selection unit 30 uses the output luminance as a key to associate the gradation characteristic that determines the relationship between the output luminance and the input image data Din with the drive characteristic that determines the relation between the output luminance and the pulse width. Then, the PWM circuit 40 generates a drive signal V having a pulse width corresponding to the value of the input image data Din with reference to the selection table TBL4. As a result, an attractive image is displayed on the display panel 50.
[0042]
<2. Second Embodiment>
Next, FIG. 13 shows a block diagram of an image display device 200 according to the second embodiment. The image display device 200 is different from the image display device 200 in that the conversion table generation unit 60 is used instead of the pulse selection unit 30, the data conversion unit 70 is used, and the selection table TBL4 included in the PWM circuit 40 is fixed. 1 has the same configuration as the image display device 100 of the first embodiment shown in FIG.
[0043]
The conversion table generation unit 60 has a function of generating a gradation conversion table TBL6 used for converting the input image data Din into the output image data Dout, and includes a CPU, a RAM, and a ROM. The ROM stores a display characteristic table TBL5. Although the storage contents of the selection table TBL4 are changed in the first embodiment, the storage contents of the selection table TBL4 of the second embodiment are fixed. The display characteristics table TBL5 stores display characteristics when an image is displayed using such a selection table TBL4.
[0044]
FIG. 14 is a flowchart showing the operation of the CPU constituting the conversion table generation unit 60. First, the CPU acquires a gradation characteristic table TBL2 indicating gradation characteristics and a display characteristic table TBL5 indicating display characteristics (steps S20, S21). Next, the CPU selects the input image data Din for which a table value is to be set in the gradation characteristics, and obtains a corresponding output luminance (step S22). For example, if the gradation characteristics shown in the gradation characteristic table TBL2 are as shown in FIG. 11 and the value of the input image data Din is "64", the corresponding output luminance is L1.
[0045]
Next, the CPU specifies the value of the input image data Din corresponding to the output luminance closest to the output luminance obtained in step S22 with reference to the display characteristic table TBL5, and uses this as the value of the output image data Dout. The value of the input image data Din and the value of the output image data Dout in step S22 are stored in the RAM in association with each other (step S23). For example, if the display characteristic shown in the display characteristic table TBL5 is as shown in FIG. 15 and the output luminance closest to the output luminance L1 is L1 ′, the value of the output image data Dout is “92”. In this case, the value “64” of the input image data Din is associated with the value “92” of the output image data Dout.
[0046]
Thereafter, the CPU determines whether or not the processing of steps S22 and S23 has been completed for all the values of the input image data Din indicated by the gradation characteristics (step S24), and until all the associations are completed. Repeat the conversion process. When all the associations are completed, the CPU stores the associated input image data Din and output image data Dout in the RAM as the gradation conversion table TBL6 (step S25). In this case, the input image data Din selected in step S22 becomes an address of the gradation conversion table TBL6, and the output image data Dout selected in step S23 becomes data of the gradation conversion table TBL6. That is, conversion from input image data Din to output luminance is performed based on the set gradation characteristics, and conversion from output luminance to output image data Dout is performed based on the set display characteristics.
[0047]
FIG. 16 shows an example of the stored contents of the gradation conversion table TBL6. Since the data of the gradation characteristics (horizontal axis) is once converted by the table in FIG. 16, the data conversion unit 70 performs the gradation conversion using the gradation conversion table TBL6, and the data is initially set. It is possible to display as the same gradation characteristics.
[0048]
As described above, in the present embodiment, the relationship between the input image data Din and the drive signal V can be adjusted by a plurality of parameters such as brightness and sharpness so that the display image can be easily viewed. In the second embodiment, the display characteristic table TBL5 is used, but there is an advantage that the data amount is smaller than that of the pulse width-gradation table TBL3. Specifically, in the first embodiment, it is necessary to store the data (for example, 400) of all the pulses that can be output by the driver as the pulse width-gradation table TBL3. Only the number of gradations (for example, 256, 64) may be stored.
[0049]
From the above viewpoint, even in a system in which the storage capacity is to be reduced as much as possible, the image display device 200 according to the second embodiment can simplify the procedure for setting the gradation and the circuit for performing the setting. As a result, an effect of reducing the software scale and circuit scale (circuit area) and an effect of reducing power consumption can be obtained.
[0050]
Furthermore, some LCD drivers employ a system that selects and sets the pulse width only at power-on (or only at reset). In this case, it is not practical to use the configuration of the first embodiment, but by using the configuration of the second embodiment, even in such a system, the functions and effects described above are achieved.
[0051]
<3. Modification>
The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible.
(1) In each of the embodiments described above, the sharpness parameter I is input as a predetermined value. However, the present invention is not limited to this, and may be changed by reflecting the characteristics of the image. For example, when extracting features of an image in the image data analysis unit 10, a frequency distribution of luminance is calculated, and its variance or standard deviation is calculated. The variance or standard deviation indicates how widely the luminance is distributed. In general, a larger value is widely distributed from a bright portion to a dark portion, indicating that it is visually preferable. Therefore, when the variance or the standard deviation is small, I is increased to set a gradation characteristic with a large sharpness, and when large, I is decreased to set a gradation characteristic with a small sharpness. By this method, an appropriate gradation setting that further reflects the characteristics of the image can be performed.
[0052]
(2) In each of the embodiments described above, the display panel 50 has been described as an example of a liquid crystal panel. However, the present invention is not limited to this. Electroluminescence (EL), digital micromirror device (DMD), Alternatively, an electro-optical device or the like using various electro-optical elements using plasma emission, fluorescence by electron emission, electrophoresis, or the like may be used.
[0053]
(3) In each of the embodiments described above, the control program of the CPU is stored in the ROM. However, when the image display device has a communication function, the control program may be downloaded via a communication network such as the Internet. Good.
[0054]
(4) In each of the above-described embodiments, the image display device 100 or 200 is, for example, a liquid crystal television, a viewfinder type, a video tape recorder of a monitor direct view type, a car navigation device, a pager, an electronic notebook, a calculator, a word processor. , A workstation, a mobile phone, a POS terminal, a device equipped with a touch panel, and the like.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image display device 100 according to a first embodiment of the present invention.
FIG. 2 is a flowchart illustrating an operation of a CPU configuring a gradation characteristic setting unit 20.
FIG. 3 is a graph showing an example of a gradation characteristic when an average value is low.
FIG. 4 is a graph showing an example of a conversion characteristic of a luminance conversion table TBL1.
FIG. 5 is a graph showing an example of a gradation characteristic for explaining setting of a correction point.
FIG. 6 is a flowchart illustrating an operation of a CPU in a gradation characteristic setting process.
FIG. 7 is a graph showing an example of gradation characteristics in which I is fixed and γ is changed.
FIG. 8 is a graph illustrating an example of a gradation characteristic in which γ is fixed and I is shifted.
FIG. 9 is a graph showing a frequency distribution of a correction example when the average value is low.
FIG. 10 is a flowchart showing an operation of a CPU constituting the pulse selection unit 30.
FIG. 11 is a graph showing an example of a gradation characteristic of a gradation characteristic table TBL2.
FIG. 12 is a graph showing an example of a pulse width-gradation table TBL3.
FIG. 13 is a block diagram of an image display device 200 according to a second embodiment of the present invention.
FIG. 14 is a flowchart showing an operation of a CPU constituting the conversion table generation unit 60.
FIG. 15 is a graph showing display characteristics of a display characteristic table TBL5.
FIG. 16 is a graph showing an example of conversion characteristics of a gradation conversion table TBL6.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Image data analysis part, 20 ... Gradation characteristic setting part, 30 ... Pulse selection part, 40 ... PWM circuit, 50 ... Display panel, 60 ... Conversion table generation part, 70 ... Data conversion part, 100, 200 ... Image display Apparatus, Din: input image data, Dout: output image data, TBL4: selection table (drive table), TBL6: gradation conversion table, V: drive signal.

Claims (11)

A method for generating a gradation characteristic table which is used for setting gradation of an image and stores an input data value and an output data value in association with each other,
A first step of setting a plurality of input data values and a first parameter for adjusting brightness of an image and a second parameter for adjusting sharpness of an image; A second step of performing an operation including one parameter and the second parameter to generate each output data value, and generating each set of the set input data value and the generated output data value as each correction point; A third step of performing an interpolation process on each of the correction points to generate a set of another input data value and another output data value. In the first step, three input data values satisfying X1 <X2 <X3 are set;
In the second step, assuming that output data values corresponding to X1, X2, and X3 are Y1, Y2, and Y3, the calculation is performed by exponential calculation from X1, X2, and X3 to Y1, Y2, and Y3. Which generates
The exponent part of the exponent operation for generating Y1 is set so that the value of the exponent part increases as the first parameter or the second parameter increases,
The exponent part of the exponent operation for generating Y2 is the first parameter,
The exponent part of the exponent calculation for generating Y3 is set so that the value of the exponent part increases as the first parameter increases, and the value of the exponent part decreases as the second parameter increases. The method for generating a gradation characteristic table according to claim 1, wherein: The first parameter is γ, the second parameter is I, as, bs, cs, and ds are constants, the exponent part of the exponential operation for generating the Y1 is K1, and the exponent part of the exponential operation for generating the Y2. Is K2, and the exponent part of the exponent calculation for generating the Y3 is K3.
K1 = (1 + as · I) γ + bs
K2 = γ
K3 = (1 + cs · I) γ + ds
And as> 0, bs> 0, cs <0, ds <0
3. The method according to claim 2, wherein: 4. The method according to claim 3, wherein the absolute value of as is smaller than the absolute value of cs. 5. The gradation characteristic table according to claim 1, wherein, in the first step, the first parameter is set in consideration of an average value of target input image data. 6. Generation method. In the first step,
Calculate the average value of the target input image data,
The average value is converted to an average value after conversion according to a predetermined rule,
6. The method according to claim 5, wherein the first parameter is set as a logarithmic process of the converted average value with the average value as a base. 7. The method according to claim 1, wherein in the first step, the second parameter is set in consideration of a frequency distribution of target input image data. An apparatus for generating a gradation characteristic table that stores an input data value and an output data value in association with each other and is used for setting a gradation characteristic of an image,
Means for selecting a plurality of input data values in the gradation characteristic table;
Means for setting a first parameter for adjusting the brightness of the image and a second parameter for adjusting the sharpness of the image;
Means for calculating an output data value corresponding to the selected plurality of input data values using the first parameter and the second parameter;
Means for generating each set of the selected plurality of input data values and the corresponding output data values as a correction point, performing interpolation processing on the correction points to generate another set of input data values and output data values. An apparatus for generating a gradation characteristic table, comprising: An apparatus for generating a gradation characteristic table according to claim 8,
A display unit for displaying an image by a drive signal;
A storage unit that stores in advance the relationship between the drive signal and the output data stored in the gradation characteristic table,
A drive table generation unit that generates a drive table that specifies the relationship between the input data and the drive signal with reference to the gradation characteristic table and the storage content of the storage unit; An image display device comprising: a driving unit configured to generate the driving signal from data. An apparatus for generating a gradation characteristic table according to claim 8,
A display unit for displaying an image by a drive signal;
A conversion table generation unit that generates a conversion table based on the gradation characteristic table;
A conversion unit that converts the input image data into output image data with reference to the conversion table,
A driving unit that generates the driving signal based on the output image data. A generation program used by a computer to generate a gradation characteristic table that is used for setting gradation characteristics of an image and stores an input data value and an output data value in association with each other,
Computer
Means for selecting a plurality of input data values in the gradation characteristic table,
Means for setting a first parameter for adjusting the brightness of the image and a second parameter for adjusting the sharpness of the image;
Means for calculating an output data value corresponding to the selected plurality of input data values using the first parameter and the second parameter;
Each pair of the selected plurality of input data values and the corresponding output data values is used as a correction point, and the correction point is subjected to interpolation processing to generate a set of other input data values and output data values. A program for generating a gradation characteristic table to be performed.

Images