JP3839024B2 - Color correction method - Google Patents

Description

  The present invention relates to a color correction method, and more particularly to a color correction method that distributes the distribution state of the original display value of video data, which method obtains a fitting display value by a fitting curve function of one section, A color correction method suitable for color image processing of a liquid crystal display, in which a lookup table is created, a corrected grayscale signal is quickly acquired by the lookup table, and the grayscale distribution state of the panel is adjusted. Involved.

  A liquid crystal display (hereinafter referred to as LCD) belongs to a kind of flat display in photoelectric products, and has many advantages such as small volume, low mass, thinness, low power consumption, no flickering, no electromagnetic wave generation, etc. In the image processing technology, the inherent properties of liquid crystal molecules are affected, for example, the viscosity coefficient, dielectric constant, elastic modulus, etc. are affected, and the response time becomes too long or afterimage phenomenon occurs. There is a need to improve the video quality by an improved driving method, among which the active matrix driving method has the most industrial application value, and this kind of driving method is active at the intersection of the electrodes of the originally arranged pixels The most popular TFT (Thin Film Transistor) technology is one of these, with the addition of elements. Furthermore one of the counter electrode in addition to the intersection of the originally arranged to have the pixel electrodes on Le is further that provided an active element on the thin film at the intersection of the three electrodes.

  Each pixel (Pixel) of the LCD panel can generate the three primary colors of red light (Red), green light (Green), and blue light (Blue), abbreviated as RGB, and in fact, the liquid crystal originally has no color The color is generated by the light passing through the color filter provided on the LCD panel, and the brightness of the color is controlled by the amount of light passing through the pixel, the degree of brightness is independent of the color filter, This is called the gray level.

Inside the liquid crystal display, the gray level is driven by the voltage generated by the driving component, and one 8-bit driving component can transmit 256 grayscale voltages, and is determined in the middle chromaticity, ie, the driving component. Since the optical transmission of the liquid crystal is non-linear, the intermediate voltage value must be corrected to obtain uniform chromaticity distribution characteristics. The relationship between the voltage and pixel luminance input and output is a curve. Similar to the function, light output = input voltage ^r , its parameter is γ (gamma) display, and a curve displaying the correspondence between gray level and luminance (or called display value) on coordinates is a gamma curve ( gamma curve), which is shown in FIG. When the input pixel value data is divided into RGB three-color light, the gamma curve becomes as shown in FIG. 2, and generally the original data of this gamma curve is normalized to obtain the three-color light curve. In FIG. 3, a gamma curve having the same starting point and ending point is acquired, and as shown in FIG. 3, generally the correction of the color of the image is performed based on the normalized gamma curve.

  For the driving chip including the driving method, in order to display the best color on the display panel, that is, to obtain the best gamma curve state, first, the display value of the panel is measured by the color measuring system or device, and then originally In order to obtain a gamma curve by a display panel that displays 8 bits for one color of light, the color measurement system must always have 768 gradations. Therefore, the inventors of the present invention greatly shortened the color measurement time and further increased the color generation speed by a novel and effective correction method. And succeeded in enriching.

  In addition, for a liquid crystal display, one 8-bit controller can generate 256 gradations, and each primary color on a pixel displays 256 color changes, 256 × 256 × 256, In other words, 16,777,216 colors can be displayed, but this does not satisfy the color change required by the human eye, and when the display screen displays dynamics, the color is displayed. I don't know the difference in change, but when displaying stillness, the human eye clearly feels that the grayscale change is not smooth, and Frame Rate Control (FRC) technology is used to solve this problem. Developed, this method subdivides video data into several frame data within the time that one image spends for display. When switching between a relatively dark place and a relatively bright place in the changing process, the pixel can generate intermediate chromaticity in the switching process, and can display gray levels more smoothly, while simultaneously changing the color The expression can be further enriched. If the two adjacent pixels become brighter or darker at the same time during the switching of video colors, a flicker phenomenon occurs, giving the viewer an unpleasant feeling. In order to solve this phenomenon, it is necessary to generate different gray levels for the two pixels, and the generation method associates the original gray level in the original gamma curve with the target curve and obtains it. The target curve is formed based on the characteristics of the liquid crystal display panel, or one of the RGB gamma curves is set as the target curve, and the correction signal obtained after the correspondence is processed by the FRC technique, and the gray scale is displayed on the display. Display status. The color processing method in the known technique is a method according to the process shown in FIG. 4 and corresponds to the display value on the target curve by the process 1 through the original gray level of the gamma curve in one color light, that is, the process 2 Is the luminance that indicates the direction, and this luminance can be expressed as 128.5 by the gray level of the original gamma curve, ie the method of step 3, but this gray level is between 128 and 129. Therefore, it is necessary to raise the operation bit from 8 bits to 9 bits, and the corresponding display value can be obtained by a linear spline, and if the intermediate gray level generated is between 128.5 and 129, or In the case of between 128 and 128.5, the operation bit needs to be raised to 10 bits or more, which is a burden in terms of hardware, It can not be made to correspond exactly to the target curve at a high speed by the calculation by the linear spline al.

  The inventor of the present invention has improved the above-mentioned drawbacks, and has further improved the speed of video data processing and enriched color expression by a novel color correction method.

  A main object of the present invention is to provide a color correction method that shortens the time of color measurement by quickly acquiring display values of video data.

  Another object of the present invention is to obtain the display value after correcting the video data quickly, so that the liquid crystal display can distribute the gray scale state based on this corrected gray scale signal, and the color representation of the display can be changed. Further, the present invention is to provide a color correction method that is further abundant and does not lower the analysis degree of the image.

  In order to solve the above-mentioned object, the color correction method of the present invention performs numerical calculation on each selected data of each color, obtains a function of a fitting curve obtained by curve fitting gray level data of each section, Use this fitting curve function to obtain the gray level fitting display value in the section, create a lookup table, and then normalize the grayscale data of the input video, and then obtain the gamma curve The gamma curve is made to correspond to a predetermined target curve, and at the time of the correspondence, first, the two gamma curves are logarithmized, a corrected grayscale signal is obtained through a lookup table, and the corrected grayscale signal is processed by the FRC technique. Displays the gray scale distribution on the display, especially for each type of liquid crystal It is a suitable color correction method to display.

、別々にこのガンマパラメータに基づいて、区間内における全ての選出されたデータを関数によってカーブフィッティングし、それによって各区間のフィッティング曲線関数を取得し、
（５）各色の光における毎区間のフィッティング曲線関数を利用し、区間内の各グレイレベルのフィッティング表示値を取得し、さらにグレイレベルとフィッティング表示値の対応数値を序列し、ルックアップテーブル（lookup table）を作成し、
（６）映像の元々のグレイスケールデータを正規化（normalized）し、別々に各色の光が含むグレイレベル（Ｘ）と表示値（Ｙ）のグレイスケール信号のガンマ曲線（gamma curve）を取得し、ガンマ曲線の関数はy=X^rであり、γはガンマパラメータであり、
（７）ガンマ曲線の関数がy=X^rである映像グレイスケール信号を予め設けられた目標曲線関数

に対応させ、即ちX_tをXと等しくさせ、反復法によって修正グレイスケール信号を取得し、その工程は、
（a）別々にガンマ曲線関数と目標関数を対数化し、そのため

となり、これにより目標表示値y_tを取得し、
（b）移行グレイレベルX_nが前記ルックアップテーブルを参照し、対応する移行表示値y_nを取得し、
（c）移行表示値y_nと目標表示値y_tを比較し、二者の差が許容誤差より小さい場合、y_nがy_tに取って代わり、さらに前記移行グレイレベルX_nがX_tに取って代わり、許容誤差より小さくない場合は上述の工程を繰り返し、
（d）目標グレイレベルX_tを含む修正グレイスケール信号を出力し、
（８）修正グレイスケール信号の出力により、ディスプレイに補正グレイスケール号に基づいてグレイスケール分布状態を表示させる
方法を含むことを特徴とする色の補正方法である。 The invention of claim 1 is a color correction method, and as the method,
(1) Measure the gray scale and display value of the light source displayed on the display by the color measurement system,
(2) Gray level and display value are normalized, and N sets of gray levels (P) and display values (Q) are selected, N is a positive integer, and the minimum value is 2. The maximum value is the maximum value that the display can display,
(3) Each n sets of values selected in the above-mentioned process is defined as one section, n is a positive integer, and is 2 or more and N or less,
(4) The gray level (P) and display value (Q) of each section are logarithmically divided and then divided to obtain a gamma parameter (gamma).

Separately, based on this gamma parameter, curve-fit all selected data in the interval with a function, thereby obtaining a fitting curve function for each interval,
(5) Using the fitting curve function of each interval in each color light, obtain the fitting display value of each gray level in the interval, and further rank the corresponding numerical values of the gray level and the fitting display value, and look up the lookup table (lookup table)
(6) Normalize the original grayscale data of the video and separately obtain the gamma curve of the grayscale signal of the gray level (X) and display value (Y) included in each color light. , The function of the gamma curve is y = X ^r , γ is the gamma parameter,
(7) Target curve function in which a video gray scale signal whose gamma curve function is y = X ^r is provided in advance

I.e., X _t is equal to X and a modified grayscale signal is obtained by an iterative method,
(A) Logarithmically separate the gamma curve function and the target function, and therefore

Thus, the target display value y _t is obtained,
(B) The transition gray level X _n refers to the lookup table to obtain the corresponding transition display value y _n ,
(C) comparing the migration display value y _n and the target display value y _t, when the difference between the two parties is smaller than the allowable error, instead y _n is taken y _t, the more the transition gray level X _n is X _t If not, if not less than the tolerance, repeat the above process,
(D) outputting the modified gray scale signal containing the target gray level X _t,
(8) A color correction method including a method of displaying a grayscale distribution state on the display based on the corrected grayscale number by outputting a corrected grayscale signal.

  The invention according to claim 2 is the color correction method according to claim 1, wherein the display light source is RGB three-color light.

であることを特徴とする請求項１に記載の色の補正方法である。 In the invention of claim 3, in each section, the adjacent gray level and the maximum display value are taken, and the gamma parameter is obtained.

The color correction method according to claim 1, wherein:

であり、ｎは２以上でありＮ以下の正整数であり、a_m、a₁およびa₀はこの関数の係数であり、且つそれぞれの多項式のa _n-1にし、r^mの値は各区間内のグレイレベルによって決定されることを特徴とする請求項１に記載の色の補正方法である。 In the invention of claim 4, the function is a polynomial based on a gamma parameter.

, N is a positive integer greater than or equal to 2 and less than or equal to N, a _m , a ₁ and a ₀ are the coefficients of this function, and a _n−1 of the respective polynomial, and the value of r ^m is 2. The color correction method according to claim 1, wherein the color correction method is determined by a gray level in the section.

、別々にこのガンマパラメータに基づいて、区間内における全ての選出されたデータを関数によってカーブフィッティングをし、それによって各区間のフィッティング曲線関数を取得し、
（５）各色の光における毎区間のフィッティング曲線関数を利用し、区間内の各グレイレベルのフィッティング表示値を取得し、それによりディスプレイに補正後のグレイレベルと表示値に基づいて予測グレイスケール分布状態を表示させる
方法を含むことを特徴とする色の補正方法である。 The invention of claim 5 is a color correction method, and as the method,
(1) Measure the gray scale and display value of the light source displayed on the display by the color measurement system,
(2) Gray level and display value are normalized, and N sets of gray levels (P) and display values (Q) are selected, N is a positive integer, and the minimum value is 2. The maximum value is the maximum value that the display can display,
(3) Each n sets of values selected in the above-mentioned process is defined as one section, n is a positive integer, and is 2 or more and N or less,
(4) The gray level (P) and display value (Q) of each section are logarithmically divided and then divided to obtain a gamma parameter (gamma).

Separately, based on this gamma parameter, curve-fit all selected data in the interval with a function, thereby obtaining a fitting curve function for each interval,
(5) Using the fitting curve function of each section in each color light, the fitting display value of each gray level in the section is acquired, and thereby the predicted gray scale distribution based on the corrected gray level and display value on the display A color correction method comprising a method of displaying a state.

であることを特徴とする請求項１に記載の色の補正方法である。 In the invention of claim 6, in each section, the adjacent gray level and the maximum display value are taken, and the gamma parameter is obtained.

The color correction method according to claim 1, wherein:

であり、ｎは２以上であり、Ｎ以下の正整数であり、a_m、a₁およびa₀はこの関数の係数であり、且つそれぞれの多項式のa_n-1を０にし、r_mの値は各区間内のグレイレベルによって決定されることを特徴とする請求項５に記載の色の補正方法である。 In the invention of claim 7, the function is a polynomial based on a gamma parameter.

N is a positive integer less than or equal to N, a _m , a ₁ and a ₀ are coefficients of this function, and a _n-1 of each polynomial is set to 0, and r _m 6. The color correction method according to claim 5, wherein the value is determined by a gray level in each section.

  According to an eighth aspect of the present invention, the light source is three-color light of red, green, and blue, and the measured gray level of red light is 0, 31, 63, 95, 127, 159, 191, 207, 223, 239, 255. The measured gray levels of green light are 31, 63, 95, 127, 159, 191, 207, 223, 239, 255, and the measured gray levels of blue light are 30, 63, 96, 129, 162, 6. The color correction method according to claim 5, wherein the color correction method is 195, 215, 235, 255.

  The invention according to claim 9 is the color correction method according to claim 5, wherein the display is a liquid crystal display.

  The invention of claim 10 is the color correction method according to claim 5, wherein the display is a projector.

  The invention of claim 11 is the color correction method according to claim 5, wherein the display is a plasma display panel.

に対応させ、即ちX_tをXと等しくさせ、反復法によって修正グレイスケール信号を取得し、その工程は、
(a)別々にガンマ曲線関数と目標関数を対数化し、そのため

となり、これにより目標表示値y_tを取得し、
(b)移行グレイレベルX_nが前記ルックアップテーブルを参照し、対応する移行表示値y_nを取得し、
(c)移行表示値y_nと目標表示値y_tを比較し、二者の差が許容誤差より小さい場合、y_nがy_tに取って代わり、さらに前記移行グレイレベルX_nがX_tに取って代わり、許容誤差より小さくない場合は上述の工程を繰り返し、
(d)目標グレイレベルX_tを含む修正グレイスケール信号を出力し、
（２）修正グレイスケール信号の出力により、ディスプレイに修正グレイスケール信号に基づいてグレイスケール分布状態を表示させる
方法を含むことを特徴とする色の補正方法である。 The invention of claim 12 is a color correction method,
(1) A target curve function in which a video gray scale signal whose gamma curve function is y = X ^r is provided in advance.

I.e., X _t is equal to X and a modified grayscale signal is obtained by an iterative method,
(a) Log the gamma curve function and target function separately,

Thus, the target display value y _t is obtained,
(b) The transition gray level X _n refers to the lookup table to obtain the corresponding transition display value y _n ,
(c) comparing the migration display value y _n and the target display value y _t, when the difference between the two parties is smaller than the allowable error, instead y _n is taken y _t, the more the transition gray level X _n is X _t If not, if not less than the tolerance, repeat the above process,
(d) outputting the modified gray scale signal containing the target gray level X _t,
(2) A color correction method including a method of displaying a grayscale distribution state on the display based on the corrected grayscale signal by outputting the corrected grayscale signal.

  The invention according to claim 13 is the color correction method according to claim 12, wherein the lookup table is obtained by user adjustment, and each gray level includes a corresponding display value. .

The color correction method of the present invention can reduce the color measurement time of the display, can make the error smaller than the allowable range of the measurement device, can further enrich the color expression gradation, and It was possible to give a three-dimensional appearance to the display color without compromising the resolution of the screen.

Taking a liquid crystal display as an example, in order to correct the brightness display state of the liquid crystal display panel, the gray level of light of different colors is input, and the display value of the liquid crystal display panel is measured by a color measuring device or system. After obtaining the gamma curve of each light as shown in FIG. 2 and normalizing as shown in FIG. 3, the present invention does not process 256 gray levels and display values in each color light, and N sets And the gamma curve is simply calculated, N is a positive integer, the minimum value is 2, the maximum value is the maximum value in the range of gray levels that the display can display, For this reason, the smaller the N value, the faster the measurement speed, but the lower the accuracy, and the larger the N value, the longer the measurement time. In the case of a display in which the light source is displayed by RGB three-color light as an example, the best selection total is 30 sets, and the measured gray level of red light is 0, 31, 63, 95, 127, 159, 191, 207, 223, 239, 255, and the measured gray level of green light is 31, 63, 95, 127, 159, 191, 207, 223, 239, 255, and the measured gray level of blue light Are 30, 63, 96, 129, 162, 195, 215, 235, and 255, and after measuring the display value (Q) of the gray level (P) described above, every n sets are defined as one section, where n is a positive value. If it is an integer, 2 or more and N or less, and every two gray scale data are taken as one section, the maximum gray level and display value in the section are taken, and after taking the logarithm, Divided in to obtain the gamma parameter function (a).

によって区間内の選出された全てのデータをカーブフィッティングし、係数aとbを取得し、それによって各区間にフィッティング曲線関数を取得させ、さらにそれを保存し、各色の光における毎区間のフィッティング曲線関数を利用して区間内の各グレイレベルのフィッティング表示値を取得し、さらにルックアップテーブルを作成し、後続の色彩処理または補正に使用することができる。 Based on this gamma parameter, the power function

Curve fitting all the selected data in the section by obtaining the coefficients a and b, thereby obtaining the fitting curve function in each section, further saving it, and fitting curve for each section in each color light A function can be used to obtain a fitting display value for each gray level in the interval, and a lookup table can be created and used for subsequent color processing or correction.

によって区間内の選出された全てのデータをカーブフィッティングし、係数a、b、cを取得し、それによって各区間にフィッティング曲線関数を取得させ、さらにそれを保存する。 If every 3 sets of grayscale data are taken as one section, similarly take the gray level of the two adjacent sections and the maximum value of the display value, and substitute it into the formula (a) to obtain the gamma parameter. Based on polynomial

Curve fitting all selected data in the section to obtain coefficients a, b and c, thereby obtaining a fitting curve function in each section, and further storing it.

によって区間内の選出された全てのデータをカーブフィッティングし、関数係数a_m、a₁、およびa₀を取得し、且つそれぞれの多項式のa_n-1を０にし、r_mを各区間内のグレイスケールデータによって決定させ、ｎ＝４を例にすると、

であり、赤色光の一区間はグレイレベル２０７，２２３，２３９，２５５を含み、即ちr₄イレベル２５５およびその表示値をガンマパラメータ関数（a）に代入することによって決定され、r₂レイレベル２３９およびその表示値によって決定され、r₁レイレベル２２３およびその表示値によって決定され、四つのグレイレベルと表示値をQの関数に代入し、各係数の解を出すと前記区間のフィッティング曲線関数を取得することができ、各色の光における毎区間のフィッティング曲線関数を利用することにより、区間内における各グレイレベルのフィッティング表示値を取得し、ルックアップテーブルを作成し、後続の色彩処理に使用することができる。 When n sets of gray scale data are taken as one section, when n is a positive integer of 2 or more and N or less, first, similarly, the gray level of the two adjacent sections and the maximum value of the display value are taken. a) Substituting into the equation to get the gamma parameter, and based on this parameter, the polynomial (b)

Curve-fit all selected data in the interval to obtain function coefficients a _m , a ₁ , and a ₀ , set a _n-1 of each polynomial to 0, and set r _m to each interval For example, if n = 4 is determined by grayscale data,

A section of red light includes gray levels 207, 223, 239, 255, that is, determined by substituting r ₄ level 255 and its display value into the gamma parameter function (a), r ₂ ray level 239 And the display value thereof, determined by the r ₁ ray level 223 and its display value, substituting the four gray levels and the display value into a function of Q, and solving each coefficient, the fitting curve function of the interval is By using the fitting curve function of each interval in the light of each color, the fitting display value of each gray level in the interval is acquired, a lookup table is created, and used for subsequent color processing be able to.

  The process described above can be the process shown in the flowchart of FIG. 7, and by performing the process, a complete lookup table can be created, in other words, the lookup table is at different gamma parameters. It is composed of different gray levels and corresponding display values, and by comparing experimental data, the error between the gamma curve obtained by this kind of method and the gamma curve obtained by measurement is within the tolerance range of the measuring device. It turns out that this kind of curve fitting color correction method not only shortens the time to measure the display effectively, but can also obtain highly accurate measurements, and this kind of color correction The method is suitable for each type of display, such as a liquid crystal display, a projector, a plasma display, and the like.

に対応させようとし、Y_tは目標表示値であり、r’標曲線のガンマパラメータであり、ディスプレイに補正後のグレイスケール信号に基づいて色彩表現を処理させることができ、その方法は、関数（ｃ）（ｄ）の対数をとり、X_t＝Xにし、関数を取得し、（c’）

（ｄ’）

であり、上述の式の演算から得られる関数（e）は、

であり、関数（e）によって目標表示値Y_tを取得でき、座標によって表す場合、図３のようになり、対数座標軸はそれぞれグレイレベルおよび表示値であり、関数（c’）と（ｄ’）の数値はそれぞれ傾斜度がγおよびγ’である直線を形成しており、映像データのグレイレベルX_inを入力後、工程1および２によって目標表示値Y_tを取得でき、更に工程３によって、即ち傾斜度を−γ’とする直線によって横軸上のX_outを取得し、X_outを移行グレイレベルX_nとして上述のルックアップテーブルを参照し、対応する移行表示値Y_tを取得し、Y_nとY_tを比較し、二者の差が許容誤差内である場合はY_nがY_tに取って代わり、移行グレイレベルX_nが目標グレイレベルX_tに取って代わり、許容誤差内でない場合はY_nとY_tの差が許容誤差内になるまで上述の工程を繰り返し、続いて目標グレイレベルX_tの修正グレイスケール信号を出力し、FRC技術によって修正グレイスケール信号をあらわし、上述の工程の流れ図は図６に示すものであり、前記工程によって取得されたグレイレベルの正確度は、上述のルックアップテーブルによって提供される異なるガンマパラメータの下、異なるグレイレベル、対応する表示値によって決定することができ、ハードの制限を受けることがなく、そのために表現できる色彩の階調をさらに豊富にでき、元々のグレイスケールデータと補正グレイスケールデータを対応させ、ルックアップテーブルを作成し、ディスプレイに依拠を提供し、グレイスケール分布状態を表示することができる。 After the original grayscale data signal of the video is input to the display, the function of the gamma curve of this video data is a function of γ (C) Y = X ^r , X and Y are the gray level of the grayscale signal and the display value The target curve function (d) provided with this gamma curve function in advance

Y _t is the target display value, the gamma parameter of the r ′ curve, and allows the display to process the color representation based on the corrected grayscale signal, which is a function (C) Take the logarithm of (d), set X _t = X, get the function, (c ′)

(D ')

And the function (e) obtained from the calculation of the above equation is

When the target display value Y _t can be obtained by the function (e) and expressed by coordinates, it is as shown in FIG. 3, and the logarithmic coordinate axes are the gray level and the display value, respectively, and the functions (c ′) and (d ′ ) Form straight lines with slopes γ and γ ′, respectively, and after inputting the gray level X _in of the video data, the target display value Y _t can be obtained by steps 1 and 2, and further by step 3. That is, X _out on the horizontal axis is obtained by a straight line having a slope of −γ ′, and the corresponding transition display value Y _t is obtained by referring to the above lookup table with X _out as the transition gray level X _n. , Y _n and Y _t and if the difference between the two is within tolerance, Y _n replaces Y _t and transition gray level X _n replaces target gray level X _t , tolerance If not within the repeat above steps until the difference Y _n and Y _t is the tolerance , Followed by outputting the modified gray-scale signal of the target gray level X _t, represents the modified gray-scale signal by FRC technology, flow diagram of the steps described above are those shown in FIG. 6, it has been a gray level obtained by the step The accuracy can be determined by different gray levels, corresponding display values under the different gamma parameters provided by the look-up table described above, and is not subject to hard limitations and can therefore be represented by the scale of colors that can be represented. Tones can be enriched, the original grayscale data and corrected grayscale data can be matched, a lookup table can be created, a display can be provided, and the grayscale distribution status can be displayed.

  With a 9-bit device, 128.5 gray levels can be processed and displayed by the linear spline method, but when the gray level is 128.7, the approximate value is 128.5. In the method of the present invention, the subsequent processing by the FRC technique is directly performed as gray level 128.7 data, and an accurate gray level is output.

Therefore, the present invention has the following advantages.
1. According to the color correction method of the present invention, it is possible to shorten the time for measuring the color of the display, and the error can be made smaller than the allowable range of the measuring apparatus, which has extremely excellent industrial competitive value.

2. According to the color correction method of the present invention, the color expression gradation can be further abundant, and the three-dimensional effect can be given to the color of the display without lowering the resolution of the screen.

The present invention can reliably achieve the object, and is a color correction method that makes the display correction process quick, rich in color, and has a three-dimensional effect, and has an extremely high industrial utility value. Is.

It is a figure which shows the gamma curve in a well-known structure. It is a figure which shows the original gamma curve in the light of a different color. It is a figure which shows the gamma curve after the normalization in the light of a different color. It is a figure which shows the method of matching the gamma curve in a well-known structure with a target curve. It is a figure which shows the process in which the input pixel value acquires the target display value of the target function curve in the color correction method of this invention. It is a figure which shows the comparison with the color correction method of this invention, and the method by a well-known technique. It is a flowchart which shows the preparation process of the look-up table of the fitting display value of the gray level in the light of each color in the color correction method of this invention. 4 is a flowchart showing a process of acquiring a corrected grayscale signal in the color correction method of the present invention.

Claims (13)

This is a color correction method.
(1) Measure the gray scale and display value of the light source displayed on the display by the color measurement system,
(2) Gray level and display value are normalized, and N sets of gray levels (P) and display values (Q) are selected, N is a positive integer, and the minimum value is 2. The maximum value is the maximum value that the display can display,
(3) Each n sets of values selected in the above-mentioned process is defined as one section, n is a positive integer, and is 2 or more and N or less,
(4) The gray level (P) and display value (Q) of each section are logarithmically divided and then divided to obtain a gamma parameter (gamma).

Separately, based on this gamma parameter, curve-fit all selected data in the interval with a function, thereby obtaining a fitting curve function for each interval,
(5) Using the fitting curve function of each interval in each color light, obtain the fitting display value of each gray level in the interval, and further rank the corresponding numerical values of the gray level and the fitting display value, and look up the lookup table (lookup table)
(6) Normalize the original grayscale data of the video and separately obtain the gamma curve of the grayscale signal of the gray level (X) and display value (Y) included in each color light. , The function of the gamma curve is y = X ^r , γ is the gamma parameter,
(7) Target curve function in which a video gray scale signal whose gamma curve function is y = X ^r is provided in advance

I.e., X _t is equal to X and a modified grayscale signal is obtained by an iterative method,
(A) Logarithmically separate the gamma curve function and the target function, and therefore

Thus, the target display value Y _t is obtained,
(B) The transition gray level X _n refers to the lookup table to obtain the corresponding transition display value Y _n ,
(C) comparing the migration display value Y _n and the target display value Y _t, when the difference between the two parties is smaller than the allowable error, instead Y _n is taken Y _t, the more the transition gray level X _n is X _t If not, if not less than the tolerance, repeat the above process,
(D) outputting the modified gray scale signal containing the target gray level X _t,
(8) A color correction method comprising: a method of causing a display to display a grayscale distribution state based on a corrected grayscale number by outputting a corrected grayscale signal.   The color correction method according to claim 1, wherein the display light source is RGB three-color light. In each section, the adjacent gray level and the maximum display value are taken and the gamma parameter is obtained, i.e.

The color correction method according to claim 1, wherein: The function is a polynomial based on the gamma parameter

, N is a positive integer greater than or equal to 2 and less than or equal to N, a _m , a ₁ and a ₀ are coefficients of this function, and a _n-1 of each polynomial is set to 0, and the value of r _m 2. The color correction method according to claim 1, wherein is determined by a gray level in each section. This is a color correction method.
(1) Measure the gray scale and display value of the light source displayed on the display by the color measurement system,
(2) Gray level and display value are normalized, and N sets of gray levels (P) and display values (Q) are selected, N is a positive integer, and the minimum value is 2. The maximum value is the maximum value that the display can display,
(3) Each n sets of values selected in the above-mentioned process is defined as one section, n is a positive integer, and is 2 or more and N or less,
(4) The gray level (P) and display value (Q) of each section are logarithmically divided and then divided to obtain a gamma parameter (gamma).

Separately, based on this gamma parameter, curve-fit all selected data in the interval with a function, thereby obtaining a fitting curve function for each interval,
(5) Using the fitting curve function of each section in each color light, the fitting display value of each gray level in the section is acquired, and thereby the predicted gray scale distribution based on the corrected gray level and display value on the display A color correction method comprising a method of displaying a state. In each section, the adjacent gray level and the maximum display value are taken and the gamma parameter is obtained, i.e.

The color correction method according to claim 1, wherein: The function is a polynomial based on the gamma parameter

N is a positive integer less than or equal to N, a _m , a ₁ and a ₀ are coefficients of this function, and a _n-1 of each polynomial is set to 0, and r _m 6. The method according to claim 5, wherein the value is determined by a gray level in each section.   The light source is three-color light of red, green, and blue, and the measurement gray level of red light is 0, 31, 63, 95, 127, 159, 191, 207, 223, 239, and 255, and the measurement of green light is performed. The gray levels are 31, 63, 95, 127, 159, 191, 207, 223, 239, and 255. The measured gray levels of blue light are 30, 63, 96, 129, 162, 195, 215, 235, and 255. The color correction method according to claim 5, wherein:   The color correction method according to claim 5, wherein the display is a liquid crystal display.   The color correction method according to claim 5, wherein the display is a projector.   6. The color correction method according to claim 5, wherein the display is a plasma display panel. This is a color correction method.
(1) A target curve function in which a video gray scale signal whose gamma curve function is y = X ^r is provided in advance.

I.e., X _t is equal to X and a modified grayscale signal is obtained by an iterative method,
(a) Log the gamma curve function and target function separately,

Thus, the target display value y _t is obtained,
(b) The transition gray level X _n refers to the lookup table to obtain the corresponding transition display value y _n ,
(c) comparing the migration display value y _n and the target display value Y _t, when the difference between the two parties is smaller than the allowable error, instead y _n is taken Y _t, the more the transition gray level X _n is X _t If not, if not less than the tolerance, repeat the above process,
(d) outputting the modified gray scale signal containing the target gray level X _t,
(2) A color correction method comprising a method of displaying a grayscale distribution state on the display based on the corrected grayscale signal by outputting the corrected grayscale signal. 13. The color correction method according to claim 12, wherein the look-up table is obtained by user adjustment, and each gray level includes a corresponding display value.

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