JP4103528B2 - Gradation characteristic table generation method, generation program, generation apparatus, and image display apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a generation method of a gradation characteristic table used for setting gradation characteristics of an image, a generation program thereof, a generation apparatus thereof, and an image display apparatus using the same.
[0002]
[Prior art]
The conventional image display apparatus performs various corrections in order to match the display characteristics of the display with 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]
"Gradation conversion using sigmoid function in digital camera system," Journal of the Imaging Society of Japan, Vol. 41, No. 1, pp. 3-10, 2002.
[0004]
[Problems to be solved by the invention]
By the way, since the display image is evaluated by human senses, it is desirable to use a subjective one as a correction parameter. However, the conventional technique does not sufficiently reflect the subjective feeling in the parameters, so that there is a problem that the control becomes complicated in order to obtain a desired image.
[0005]
The present invention has been made in view of the above-described 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 do.
[0006]
[Means for solving the problems]
In order to solve the above-described problem, a gradation characteristic table generation method according to the present invention is used for gradation specific setting of an image, and a gradation characteristic table in which input data values and output data values are stored in association with each other. A first step of setting a plurality of input data values, setting a first parameter for adjusting the brightness of the image, and a second parameter for adjusting the sharpness of the image; Each input data value is subjected to a calculation including the first parameter and the second parameter to generate each output data value, and each set of the set input data value and the generated output data value is set to each correction point. And a third step of generating a set of other input data values and output data values by performing interpolation processing on each correction point.
[0007]
According to the present invention, human senses such as image brightness and image sharpness are adopted as parameters, so that the intention at the time of control can be accurately reflected in the gradation characteristic table. In other words, since the subjective feeling is used as a parameter, the input image can be converted into an image that looks good 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. After setting a plurality of input data values, the first parameter and the second parameter are set. After 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 calculation generates Y1, Y2, and Y3 from X1, X2, and X3 by exponential calculation, and the exponent part of the exponential calculation that generates 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 exponent operation for generating Y2 is the first parameter, and the exponent part of the exponent operation for generating Y3 is It is preferable 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. . In addition, you may perform an exponential calculation, after performing normalization processing to X1, X2, and X3.
[0009]
More specifically, the first parameter is γ, the second parameter is I, as, bs, cs, and ds are constants. The exponent part of the exponent operation for generating Y1 is K1, and 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 to generate Y3, and , As> 0, bs> 0, cs <0, ds <0.
[0010]
Furthermore, the absolute value of as is preferably smaller than the absolute value of cs.
[0011]
In the first step, it is preferable that 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 the target input image data is calculated, the average value is converted into a converted average value according to a predetermined rule, and the average value is used as a base. It is preferable that the first parameter is set as a logarithmic process of the average value after conversion.
[0012]
In addition, in the second step, instead of calculating Y2 by exponential calculation, Y2 is preferably used as the average value after conversion. In this case, the process of calculating Y2 can be omitted.
[0013]
In the first step, the second parameter is preferably set in consideration of the frequency distribution of the target input image data. This is because the sharpness of the image is related to how the gradation is distributed.
[0014]
Next, a gradation characteristic table generating apparatus according to the present invention is a gradation characteristic table generating apparatus that is used for setting gradation characteristics of an image and stores input data values and output data values in association with each other. 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, and the first parameter Means for calculating an output data value corresponding to the selected plurality of input data values using the second parameter, and a correction point for each set of the selected plurality of input data values and the corresponding output data value And means for interpolating the correction point to generate another set of input data values and output data values. According to the present invention, human senses such as image brightness and image sharpness are adopted as parameters, so that the intention at the time of control can be accurately reflected in the gradation characteristic table. In other words, since the subjective feeling is used as a parameter, the input image can be converted into an image that looks good by simple control.
[0015]
The image display device according to the present invention includes the above-described gradation characteristic table generation device, a display unit that displays an image using a drive signal, and the output data stored in the drive signal and the gradation characteristic table. A storage unit that pre-stores the relationship, and 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 storage characteristics of the gradation characteristic table and the storage unit, And a drive unit that generates the drive signal from input image data with reference to the drive table. According to the present invention, since the above-described gradation characteristic table is used, it is possible to display an attractive image on the display unit.
[0016]
In this case, for example, the drive table stores the relationship between the pulse designating the pulse width and the input image data, and the drive unit reads out the pulse corresponding to the input image data, A drive signal that is pulse-width modulated based on the output may be output.
[0017]
In addition, the image display device includes a gradation characteristic table generation device, a display unit that displays an image using a drive signal, a conversion table generation unit that generates a conversion table based on the gradation characteristic table, and the conversion table. With reference to the above, a conversion unit that converts input image data into output image data and a drive unit that generates the drive signal based on the output image data may be provided.
[0018]
Next, a generation program according to the present invention is used for setting the gradation characteristics of an image, and generates a gradation characteristic table in which an input data value and an output data value are stored in association with each other by a computer. Means for selecting a plurality of input data values in the gradation characteristic table; means for setting a first parameter for adjusting image brightness; and a second parameter for adjusting image sharpness; the first parameter; 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, The correction point is interpolated to function as means for generating a set of other input data values and output data values. According to the present invention, human senses such as image brightness and image sharpness are adopted as parameters, so that the intention at the time of control can be accurately reflected in the gradation characteristic table. In other words, since the subjective feeling is used as a parameter, the input image can be converted into an image that looks good by simple control.
[0019]
DETAILED DESCRIPTION OF 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 apparatus 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 configurations, 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, and uses reflected light for image display when the amount of external light is large, while using backlight for image display when the amount of external light is small. The transmitted light is used. The display panel 50 uses liquid crystal as an electro-optical material, and a plurality of data lines (segment electrodes) are formed extending in the column direction, while a plurality of scanning lines (common electrodes) are extended in the row direction. The pixel is formed corresponding to each intersection of the data line and the scanning line. Each pixel includes a liquid crystal layer and a TFD (Thin Film Diode) which 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 designated 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 step of the pulse width of the drive signal V corresponds to the step of the output luminance of the display panel 50. The display panel 50 in this example displays 64 gradations. Therefore, the pulse width of the drive signal V is specified by a selection pulse selected from the 64 pulses based on the input image data Din.
[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 includes 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 displays the accumulated 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 define the relationship among 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 includes a CPU, a RAM, and a ROM. In the ROM, a luminance conversion table TBL1 and reference gradation characteristic data Dref are stored. The luminance conversion table TBL1 is used for converting the average luminance. The reference gradation characteristic data Dref indicates the 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 the 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 the dotted line shown in FIG. 3, the average value Pin and the input average luminance Pave have the 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 conversion characteristics of the luminance conversion table TBL1 with a solid line. For reference, the characteristics when 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 luminance conversion table TBL1 may be set so that, for example, the point (0.5, 0.5) passes and the 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 becomes 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 the image (step S5). This calculation is given by Equation 1 and Equation 2 below.
Pave ′ = (Pin / 255) ^ γ ... Formula 1
γ = log _{(Pin / 255)} Pave '... Formula 2
[0028]
Next, the CPU inputs a sharpness parameter I for adjusting the sharpness of the image (step S6). In this example, it is assumed that the sharpness parameter I is predetermined. Thereafter, the CPU calculates output luminances y1, y2, and y3 at the respective correction points P1 to P3 according to the following formulas 3 to 5 (step S7). Since y2 has already been determined as Pave ', the calculation can be omitted.
y1 = (A / 255) ^ {(1 + asI) · γ + bs} Equation 3
y2 = (B / 255) ^ γ ... Formula 4
y3 = (C / 255) ^ {(1 + csI) · γ + ds} Equation 5
However, 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 the 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 γ characteristics that are normally used in television systems and the like. Since γ depends on the exponents of y1, y2, and y3, the brightness can be controlled by controlling γ. Specifically, since (A / 255), (B / 255), and (C / 255) are obtained by normalizing input data to 0 to 1, y1, y2, and y3 are small when γ is large. Dark gradation characteristics. On the other hand, when γ is small, y1, y2, and y3 become large and bright gradation characteristics are obtained.
[0031]
FIG. 7 shows an example of gradation characteristics in which I is fixed and γ is shaken. These gradation characteristics are B = 128, and other variables are the same as in the above-described example, and γ is set to 0.8, 1.0, 1.2, 1.4, and 1.7. From this figure, it can be seen that the gradation characteristic shifts in the direction of increasing the output luminance as γ is reduced.
[0032]
The sharpness parameter I acts to increase or decrease the values of the exponent parts of y1 and y3. Note that y2 is irrelevant to the sharpness parameter I. Here, since as is positive at y1, increasing I increases the exponent of y1. As the exponent part increases, the value of y1 becomes smaller and the dark part is emphasized. On the other hand, since cs is negative at y3, increasing I increases the exponent of y3. As the exponent part decreases, the value of y3 increases and emphasizes the bright part.
[0033]
FIG. 8 shows an example of gradation characteristics in which γ is fixed and I is shaken. These gradation characteristics are B = 128, other variables are the same as the above-described example, and I is set to 0.1, 0.3, 0.5, 0.7, and 0.9. From this figure, as I increases, the gradient of the gradation characteristic increases, and a sharp image can be obtained.
[0034]
The values of as, bs, cs, and ds are shown here as examples. However, the absolute values of cs and ds are preferably larger than the absolute values of as and bs. This is because cs and ds determine the degree of change of y3, but y3 is changed more greatly than y1 even with the same I. The reason why y3 is greatly changed is that, in order to make the same amount of change perceived by humans, it is necessary to change the bright part more than the dark part.
[0035]
By controlling γ, contrast can be controlled, and by controlling I, sharpness can be controlled. In such conventional control, control based on subjective feelings such as “brightness” and “brightness” cannot be performed, so the method of the present embodiment is practically effective as a control method based on subjective feelings. .
[0036]
As is apparent 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, correction is performed to brighten the image. 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. This shows the frequency distribution in the case of the above. From this figure, it can be confirmed that the frequency of the low-luminance portion is reduced, and the image is shifted in the brighter direction as viewed as the whole image.
[0037]
Returning 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, drive characteristics that define 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 showing the operation of the CPU constituting the pulse selector 30. First, the CPU acquires a gradation characteristic table TBL2 indicating gradation characteristics and a pulse width-gradation table TBL3 indicating drive characteristics (steps S10 and S11). Thereafter, the CPU selects the input image data Din for which the pulse width is desired 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, it 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 brightness closest to the output brightness 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 processing of steps S12 and S13 has been completed by the number (for example, 64) that can be set by the driver of the display panel 50 (step S14), and all the associations are completed. Repeat the pulse width selection process until 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]
In this way, the pulse selection unit 30 associates the gradation characteristic that defines the relationship between the output luminance and the input image data Din with the drive characteristic that defines the relationship between the output luminance and the pulse width, using the output luminance as a key. 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, a nice-looking image is displayed on the display panel 50.
[0042]
<2. Second Embodiment>
Next, FIG. 13 shows a block diagram of an image display apparatus 200 according to the second embodiment. The image display apparatus 200 is different from that shown in FIG. 1 except 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 is configured similarly to 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 to the output image data Dout, and is configured by a CPU, a RAM, and a ROM. A display characteristic table TBL5 is stored in the ROM. In the first embodiment, the storage content of the selection table TBL4 is changed, but the storage content of the selection table TBL4 in the second embodiment is fixed. The display characteristic 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 and S21). Next, the CPU selects 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 characteristic shown in the gradation characteristic table TBL2 is 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 refers to the display characteristic table TBL5, specifies the value of the input image data Din corresponding to the output luminance closest to the output luminance acquired in step S22, 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 associated with each other and stored in the RAM (step S23). For example, if the display characteristics shown in the display characteristic table TBL5 are as shown in FIG. 15 and the output luminance closest to the output luminance L1 is L1 ′, the value “92” of the output image data Dout is obtained. In this case, the value “64” of the input image data Din and the value “92” of the output image data Dout are associated with each other.
[0046]
Thereafter, the CPU determines whether or not the processing of steps S22 and S23 is 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 a gradation conversion table TBL6 (step S25). In this case, the input image data Din selected in step S22 is the address of the gradation conversion table TBL6, and the output image data Dout selected in step S23 is the data of the gradation conversion table TBL6. That is, the input image data Din → output luminance is converted based on the set gradation characteristics, and the output luminance → output image data Dout is converted based on the set display characteristics.
[0047]
FIG. 16 shows an example of the contents stored in the gradation conversion table TBL6. Since the gradation characteristic data (horizontal axis) has been converted once according to the table of FIG. 16, the data conversion unit 70 initially set the gradation conversion using the gradation conversion table TBL6. It is possible to display as the 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 seen. 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 data (for example, 400 pieces) of all pulses that can be output by the driver as the pulse width-gradation table TBL3. Only the number of gradations (for example, 256 or 64) need be stored.
[0049]
From the above viewpoint, even in a system in which the storage capacity is desired to be reduced as much as possible, the image display apparatus 200 according to the second embodiment can simplify the gradation setting procedure and the circuit for performing the same. As a result, there are the effects of reducing the software scale and circuit scale (circuit area) and reducing the power consumption.
[0050]
Furthermore, some LCD drivers may employ a system that selects and sets the pulse width only when the power is turned on (or only when 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, the above-described operation and effects can be achieved even with such a system.
[0051]
<3. Modification>
The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.
(1) In each of the above-described embodiments, the sharpness parameter I is input as determined in advance. However, the present invention is not limited to this, and the image characteristics may be changed to reflect. For example, when the image data analysis unit 10 extracts image features, the luminance frequency distribution is calculated, and the variance or standard deviation thereof is calculated. The variance or standard deviation indicates how widely the luminance is distributed. In general, a larger value means that the luminance is widely distributed from a bright part to a dark part, which is preferable for appearance. For this reason, when the variance or standard deviation is small, I is set to a large gradation characteristic, and when it is large, I is set to a small gradation characteristic with a small sharpness. By this method, it is possible to set an appropriate gradation reflecting the characteristics of the image.
[0052]
(2) In each embodiment described above, the display panel 50 has been described by taking a liquid crystal panel as an example, but the present invention is not limited to this, and electroluminescence (EL), digital micromirror device (DMD), Alternatively, it may be an electro-optical device using various electro-optical elements using plasma emission, fluorescence by electron emission, electrophoresis, or the like.
[0053]
(3) In each of the embodiments described above, the CPU control program is stored in the ROM. However, if the image display device has a communication function, it may be downloaded via a communication network such as the Internet. Good.
[0054]
(4) In the above-described embodiments, the image display device 100 or 200 includes, for example, a liquid crystal television, a viewfinder type, a monitor direct-view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, and a word processor. It may be an electronic device such as a workstation, a mobile phone, a POS terminal, or a device having a touch panel.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image display apparatus 100 according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of a CPU constituting the gradation characteristic setting unit 20;
FIG. 3 is a graph showing an example of gradation characteristics when the average value is low.
FIG. 4 is a graph showing an example of conversion characteristics of a luminance conversion table TBL1.
FIG. 5 is a graph showing an example of gradation characteristics for explaining the setting of correction points.
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 shaken.
FIG. 8 is a graph showing an example of gradation characteristics in which γ is fixed and I is shaken.
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 the operation of a CPU constituting the pulse selection unit 30.
FIG. 11 is a graph showing an example of gradation characteristics 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 apparatus 200 according to a second embodiment of the present invention.
FIG. 14 is a flowchart showing the 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 production | generation part, 70 ... Data conversion part, 100, 200 ... Image display Device, Din: input image data, Dout: output image data, TBL4: selection table (drive table), TBL6: gradation conversion table, V: drive signal.

Claims (6)

A method of generating a gradation characteristic table that is used to set gradation characteristics of an image and stores an input data value and an output data value in association with each other,
First, the three input data values satisfying X1 <X2 <X3 are set, the first parameter for adjusting the brightness of the image is set to γ, and the second parameter for adjusting the sharpness of the image is set to I Steps,
When the output data values corresponding to the set input data values of X1, X2, and X3 are Y1, Y2, and Y3, the X1, X2, and X3 are obtained by exponential operation on the normalized input data values. Generating Y1, Y2, and Y3 from each to generate each output data value, and generating each set of the input data value and the generated output data value as each correction point;
A third step of generating a set of other input data values and output data values by subjecting each correction point to interpolation processing;
With
With as, bs, cs, and ds as constants, the exponent part of the exponent operation for generating Y1 is K1, the exponent part of the exponent operation for generating Y2 is K2, and the exponent part of the exponent operation for generating Y3 is K3 When
K1 = (1 + as · I) γ + bs
K2 = γ
K3 = (1 + cs · I) γ + ds
And as> 0, bs> 0, cs <0, ds <0.
And
The first parameter is an average value of target input image data is converted into a converted average value according to a predetermined rule, and is set as a logarithmic process of the converted average value based on the average value,
The method for generating a gradation characteristic table, wherein the second parameter is set so that a frequency distribution of target input image data falls within a predetermined range .   2. The gradation characteristic table generation method according to claim 1, wherein an absolute value of as is smaller than an absolute value of cs. An apparatus for generating a gradation characteristic table used for setting gradation characteristics of an image and storing an input data value and an output data value in association with each other,
Means for selecting three input data values satisfying X1 <X2 <X3 in the gradation characteristic table;
Means for setting a first parameter for adjusting the brightness of the image to γ and setting a second parameter for adjusting the sharpness of the image to I;
When the output data values corresponding to the set input data values of X1, X2, and X3 are Y1, Y2, and Y3, the X1, X2, and X3 are obtained by exponential operation on the normalized input data values. Means for generating said Y1, Y2 and Y3 from
With as, bs, cs, and ds as constants, the exponent part of the exponent operation for generating Y1 is K1, the exponent part of the exponent operation for generating Y2 is K2, and the exponent part of the exponent operation for generating Y3 is K3 When
K1 = (1 + as · I) γ + bs
K2 = γ
K3 = (1 + cs · I) γ + ds
And as> 0, bs> 0, cs <0, ds <0.
Means for generating each output data value corresponding to each said input data value;
Means for setting each set of the input data value and the generated output data value as a correction point, and interpolating the correction point to generate a set of other input data value and output data value;
With
The first parameter is set as a logarithmic process of the converted average value based on the average value by converting the average value of the target input image data into a converted average value according to a predetermined rule,
The second parameter is set so that the frequency distribution of the target input image data falls within a predetermined range.
An apparatus for generating a gradation characteristic table. The gradation characteristic table generating device according to claim 3;
A display unit for displaying an image by a drive signal;
A storage unit for storing 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 drive unit that refers to the drive table and generates the drive signal from input image data. The gradation characteristic table generating device according to claim 3;
A display unit for displaying an image by a drive signal;
A conversion table generating unit that generates a conversion table based on the gradation characteristic table;
A conversion unit that converts input image data into output image data with reference to the conversion table;
An image display device comprising: a drive unit that generates the drive signal based on the output image data. A generation program that is used to set the gradation characteristics of an image and that generates a gradation characteristic table in which input data values and output data values are stored in association with each other.
Computer
Means for selecting three input data values satisfying X1 <X2 <X3 in the gradation characteristic table;
Means for setting a first parameter for adjusting the brightness of the image to γ and setting a second parameter for adjusting the sharpness of the image to I;
When the output data values corresponding to the set input data values of X1, X2, and X3 are Y1, Y2, and Y3, the X1, X2, and X3 are obtained by exponential operation on the normalized input data values. Means for generating said Y1, Y2 and Y3 from
With as, bs, cs, and ds as constants, the exponent part of the exponent operation for generating Y1 is K1, the exponent part of the exponent operation for generating Y2 is K2, and the exponent part of the exponent operation for generating Y3 is K3 When
K1 = (1 + as · I) γ + bs
K2 = γ
K3 = (1 + cs · I) γ + ds
And as> 0, bs> 0, cs <0, ds <0.
Means for generating each output data value corresponding to each input data value,
Means for setting each set of the input data value and the generated output data value as a correction point, and interpolating the correction point to generate another set of input data value and output data value
Function as
The first parameter is set as a logarithmic process of the converted average value based on the average value by converting the average value of the target input image data into a converted average value according to a predetermined rule,
The second parameter is set so that the frequency distribution of the target input image data falls within a predetermined range.
A gradation characteristic table generation program characterized by the above.

Images