TWI849990B - Color gamut calibration method and color gamut calibration system - Google Patents

Abstract

The present invention discloses a color gamut calibration method, which first converts a group of m original data nodes and their corresponding m target data nodes in an input RGB grayscale data into an XYZ color space, and measures the corresponding m measured data nodes from the display device. When the color difference value between the measured data node and the target data node is not within the error range, the m original data nodes are first iteratively updated, and then the color difference value is recalculated until the color difference value is less than the error range, and the iterative update is stopped. Afterwards, the next group of m original data nodes and their corresponding m target data nodes are selected from the input RGB grayscale data, and the same RGB grayscale data calibration steps are repeated. Furthermore, when selecting the next group of m original data nodes, a value transfer operation can be performed, thereby determining the next group of m original color domain data nodes based on the previous group of m original color domain data nodes that have completed calibration, thereby accelerating the calculation speed.

Description

Color gamut calibration method and color gamut calibration system

The present invention relates to the field of flat panel display devices, and more particularly to a color gamut calibration method that utilizes a 3D-LUT to perform color gamut calibration of a display device/display driver chip before shipment.

As is known, flat panel displays include non-self-luminous flat panel displays and self-luminous flat panel displays, wherein liquid crystal displays are a type of non-self-luminous flat panel displays that have been used for a long time, while organic light-emitting diode (OLED) displays and light-emitting diode (LED) displays are self-luminous flat panel displays that are currently in mainstream applications. FIG1 is a block diagram of a known OLED display device. As shown in FIG. 1 , a known OLED display device 1a includes an OLED panel 11a and at least one display driver IC (DDIC) 12a, wherein the display driver IC 12a receives an input display data (i.e., RGB grayscale data) from a host computer 2a (e.g., an application processor of a smart phone), pre-processes the input display data into a display driver data (i.e., VDATA), and finally drives the OLED panel 11a for display according to the output display data.

It should be known that the color gamut is used to indicate the color range that the display panel 11a can display. In the same color space, the higher the color gamut percentage, the wider the color range that the display panel 11a can display. In order to define the color gamut more clearly, the International Commission on Illumination (CIE) has developed a method for describing the color gamut: the CIE-xyY chromaticity diagram. Figure 2 shows the known CIE-xy chromaticity diagram. According to the current industry definition, the so-called wide color gamut of smartphones and displays refers to a color gamut higher than 100% sRGB. Simply put, the sRGB and P3 color gamuts are color systems used by wide color gamut flat panel display devices.

Compared to the best color gamut of traditional LCD panels, which is only 72% NTSC at most, OLED display panels have the characteristics of wide color gamut, and their best color gamut can reach or even exceed 100% NTSC. Unfortunately, as shown in FIG. 2, the color gamut performance of the actual OLED display panel still does not meet the standard sRGB color gamut. Therefore, before the display driver chip 12a used to drive the OLED panel 11a is shipped, the manufacturer will first perform a color gamut calibration process, thereby generating a look-up table (LUT) 121a set in the display driver chip 12a for implementing color gamut mapping (or color gamut calibration). Thus, after receiving an input display data (i.e., RGB grayscale data) from the host computer 2a, the display driver chip 12a maps the input display data into an output display data by searching the lookup table 121a, and then pre-processes the input display data into a display drive data (i.e., VDATA). Finally, the display driver chip 12a drives the OLED panel 11a for display according to the output display data, so that the color gamut performance of the OLED panel 11a when displaying images can meet the standard sRGB color gamut.

In order to generate the lookup table 121a, the prior art is to divide the color space of the OLED panel 11a into small color spaces according to the measurement points. Then, in the color space with a smaller range, the RGBW color coordinates are measured while driving the OLED panel 11a to display multiple test images, and then the conversion matrix between the color gamut of the OLED panel 11a and the target color gamut (i.e., sRGB or P3) is calculated, and a lookup table is generated. After that, the lookup table is written into the display driver chip 12a, and then the aforementioned RGBW color coordinate measurement step is repeated to confirm whether the lookup representation meets the error range. In this way, after multiple iterations, a lookup table that meets the error range can be obtained.

However, practical experience shows that in order to generate a more accurate lookup table, the color space of the OLED panel 11a must be divided into smaller color spaces to obtain a large number of measurement points. However, iterating a large number of measurement points at the same time will increase the iteration time and even lead to a situation where convergence cannot occur. Therefore, it can be seen that the color gamut calibration process of the prior art still needs to be improved.

From the above description, it can be seen that a new color gamut calibration method is urgently needed in this field.

The main purpose of the present invention is to provide a color gamut calibration method, which is performed by a color gamut calibration system. In the color gamut calibration method, a group of m original data nodes and their corresponding m target data nodes in an input RGB grayscale data are first converted to an XYZ color space, and the corresponding m measured data nodes are measured from the display device. When the color difference value between the measured data node and the target data node is not within the error range, the m original data nodes are first iteratively updated, and then the color difference value is recalculated until the color difference value is less than the error range and the iterative update is stopped. Afterwards, the next group of m original data nodes and their corresponding m target data nodes are selected from the input RGB grayscale data, and the same RGB grayscale data calibration steps are repeated. Furthermore, when selecting the next group of m original data nodes, a value transfer operation can be performed, thereby determining the next group of m original color domain data nodes based on the previous group of m original color domain data nodes that have completed calibration, thereby accelerating the calculation speed.

To achieve the above-mentioned purpose, the present invention proposes an embodiment of the color gamut calibration method, which is executed by a color gamut calibration system and includes the following steps: Establish a three-dimensional lookup table based on an input RGB grayscale data transmitted to a display driver chip; wherein the first data axis, the second data axis and the third data axis of the three-dimensional lookup table are respectively the R axis, the G axis and the B axis of the RGB color space; Perform a data node selection operation to select a group of m primary color gamut data nodes from the three-dimensional lookup table, wherein m is a positive integer; Perform a conversion operation to convert the m primary color gamut data nodes into m groups of XYZ target values corresponding to m target color gamut data nodes; wherein X, Y, and Z are tristimulus values (tristimulus values); When a display panel is driven by the display driver chip, a measurement operation is performed on the display panel to measure m sets of XYZ measurement values corresponding to the m original color gamut data nodes; A color difference value calculation operation is performed to calculate m color difference values using the m sets of XYZ measurement values and the m sets of XYZ target values; When the color difference value is greater than a predetermined value, an iterative update operation is performed on the m original color gamut data nodes, and then the aforementioned conversion operation, measurement operation and color difference value calculation operation are repeatedly performed; After repeating the aforementioned iterative update operation, conversion operation, measurement operation and color difference value calculation operation until each original color gamut data node is corrected to the corresponding color difference value being less than the predetermined value, the next data node selection operation is performed, and then the conversion operation, the measurement operation, the color difference value calculation operation and the iterative update operation are performed on the next group of m original color gamut data nodes; and the processed multiple original color gamut data nodes are stored as an output RGB grayscale data corresponding to the input RGB grayscale data.

In one embodiment, the color gamut calibration system uses the following mathematical formulas (1), (2) and (3) to complete the conversion operation: ····························· (1); ····························· (2); ·························· (3); Among them, , and is an input R grayscale value, an input G grayscale value and an input B grayscale value contained in an original color domain data node. , and is an R grayscale value, a G grayscale value and a B grayscale value included in a target color gamut data node, T1 is a first conversion matrix used to convert the input R grayscale value, the input G grayscale value and the input B grayscale value into three primary color gamut stimulus values (tristimulus values), and T2 is a second conversion matrix used to convert the R grayscale value, the G grayscale value and the B grayscale value into three target color gamut stimulus values.

In one embodiment, the color gamut calibration system uses the following mathematical formula (4) to complete the color difference value calculation operation: (4); Among them, is the color difference value, is the luminance difference (Delta luminance), is the chromaticity difference (Delta chromaticity), is the hue difference (Delta hue), is the brightness weight factor, is the chroma weight factor, is the hue weight factor, To correct brightness, To correct the color, To correct hue, and is a blue space correction parameter.

In one embodiment, the color gamut calibration system uses the following mathematical formulas (5), (6), (7), (8), (9), and (10) to complete the calculation of the brightness, chroma, and hue of each original color gamut data node and the calculation of the brightness, chroma, and hue of each target color gamut data node, and then uses the aforementioned mathematical formula (4) to complete the color difference value calculation operation: ·····················(5); ····························(6); ····························(7); ···································· (8); ································· (9); ··································· (10); where c1 is the first constant, , and are three standard tristimulus values, L is brightness, Indicates the color components from green to red, Indicates the components from blue to yellow, H is hue, S is saturation, and C is chroma.

In one embodiment, the color gamut calibration system uses the following mathematical formulas (11), (12), (13), (14), (15), and (16) to complete the iterative update operation: ························(11); ························(12); ························(13); ·····································(14); ·····································(15); ································· (16); wherein R', G', and B' are an iteratively updated R grayscale value, an iteratively updated G grayscale value, and an iteratively updated B grayscale value of the original color domain data node, and , , are an R grayscale iteration constant, a G grayscale iteration constant and a B grayscale iteration constant; wherein, , , are the three primary color gamut stimulus values contained in a primary color gamut data node, and , , It is the three target color gamut stimulus values contained in a target color gamut data node.

In one embodiment, when the color difference value is less than the predetermined value, the color gamut calibration system uses the following mathematical formulas (17), (18) and (19) to perform a value transfer operation to determine the next set of m original color gamut data nodes: ··········································(17); ··········································(18); ····································· (19); wherein Rn, Gn, and Bn are an input R grayscale value, an input G grayscale value, and an input B grayscale value in the next group of m original color gamut data nodes, , , is an R grayscale value ratio, a G grayscale value ratio, and a B grayscale value ratio.

Furthermore, the present invention also proposes an embodiment of a color gamut calibration system, which includes: A detection device facing a display panel; and An electronic device coupled to the detection device and at least one display driver chip for driving the display panel to display images; Wherein, the electronic device is configured to control the display driver chip and the detection device to operate to execute a color gamut calibration method, and the color gamut calibration method includes the following steps: A three-dimensional lookup table is established based on an input RGB grayscale data transmitted to a display driver chip; wherein the first data axis, the second data axis and the third data axis of the three-dimensional lookup table are respectively the R axis, the G axis and the B axis of the RGB color space; Perform a data node selection operation to select a group of m primary color gamut data nodes from the three-dimensional lookup table, where m is a positive integer; Perform a conversion operation to convert the m primary color gamut data nodes into m groups of XYZ target values corresponding to m target color gamut data nodes; where X, Y, and Z are tristimulus values in the CIE1931 color space; When a display panel is driven by the display driver chip, perform a measurement operation on the display panel to measure m groups of XYZ measurement values corresponding to the m primary color gamut data nodes; Perform a color difference value calculation operation to calculate m color difference values using the m groups of XYZ measurement values and the m groups of XYZ target values; When the color difference value is greater than a predetermined value, an iterative update operation is performed on the m original color gamut data nodes, and then the aforementioned conversion operation, measurement operation and color difference value calculation operation are repeatedly performed; After repeating the aforementioned iterative update operation, conversion operation, measurement operation and color difference value calculation operation until each original color gamut data node is corrected to its corresponding color difference value less than the predetermined value, the next data node selection operation is performed, and then the conversion operation, measurement operation, color difference value calculation operation and iterative update operation are performed on the next group of m original color gamut data nodes; and The processed plurality of original color gamut data nodes are stored as an output RGB grayscale data corresponding to the input RGB grayscale data.

In one embodiment, the electronic device uses the following mathematical formulas (1), (2) and (3) to complete the conversion operation: ····························· (1); ····························· (2); ·························· (3); Among them, , and is an input R grayscale value, an input G grayscale value and an input B grayscale value contained in an original color domain data node. , and is an R grayscale value, a G grayscale value and a B grayscale value included in a target color gamut data node, T1 is a first conversion matrix used to convert the input R grayscale value, the input G grayscale value and the input B grayscale value into three primary color gamut stimulus values (tristimulus values), and T2 is a second conversion matrix used to convert the R grayscale value, the G grayscale value and the B grayscale value into three target color gamut stimulus values.

In one embodiment, the electronic device uses the following mathematical formula (4) to complete the color difference value calculation operation: (4); Among them, is the color difference value, is the luminance difference (Delta luminance), is the chromaticity difference (Delta chromaticity), is the hue difference (Delta hue), is the brightness weight factor, is the chroma weight factor, is the hue weight factor, To correct brightness, To correct the color, To correct hue, and is a blue space correction parameter.

In one embodiment, the electronic device uses the following mathematical formulas (5), (6), (7), (8), (9), and (10) to complete the calculation of the brightness, chroma, and hue of each original color gamut data node and the calculation of the brightness, chroma, and hue of each target color gamut data node, and then uses the aforementioned mathematical formula (4) to complete the color difference value calculation operation: ·····················(5); ····························(6); ····························(7); ···································· (8); ································· (9); ··································· (10); where c1 is the first constant, , and are three standard tristimulus values, L is brightness, Indicates the color components from green to red, Indicates the components from blue to yellow, H is hue, S is saturation, and C is chroma.

In one embodiment, the electronic device uses the following mathematical formulas (11), (12), (13), (14), (15), and (16) to complete the iterative update operation: ························(11); ························(12); ························(13); ·····································(14); ·····································(15); ································· (16); wherein R', G', and B' are an iteratively updated R grayscale value, an iteratively updated G grayscale value, and an iteratively updated B grayscale value of the original color domain data node, and , , are an R grayscale iteration constant, a G grayscale iteration constant and a B grayscale iteration constant; wherein, , , are the three primary color gamut stimulus values contained in a primary color gamut data node, and , , It is the three target color gamut stimulus values contained in a target color gamut data node.

In one embodiment, when the color difference value is less than the predetermined value, the electronic device uses the following mathematical formulas (17), (18) and (19) to perform a value transfer operation to determine the next set of m original color gamut data nodes: ··········································(17); ··········································(18); ····································· (19); wherein Rn, Gn, and Bn are an input R grayscale value, an input G grayscale value, and an input B grayscale value contained in a primary color gamut data node of the next group of m primary color gamut data nodes, , , is an R grayscale value ratio, a G grayscale value ratio, and a B grayscale value ratio.

In order to enable the Review Committee to further understand the structure, features, purpose, and advantages of the present invention, the following are attached with drawings and detailed descriptions of preferred specific embodiments.

FIG. 3 is a block diagram of a color gamut calibration system applying a color gamut calibration method of the present invention. As shown in FIG. 3 , the color gamut calibration system 2 includes: a detection device 21 and an electronic device 22 , wherein the detection device 21 is configured to face a display panel 11 , and the electronic device 22 is coupled to the detection device 21 . The device 21 and at least one display driving chip 12 are used to drive the display panel 11 to display images. In one embodiment, the detection device 21 may be, but is not limited to, a spectroradiometer that can directly measure XYZ tristimulus values, and the display panel 11 may be an LCD panel, an OLED panel, LED panel, Micro-LED panel, or QLED panel. On the other hand, the electronic device 22 may be, but is not limited to, an industrial computer, a desktop computer, a notebook computer, an all-in-one computer, or a tablet computer.

In particular, the present invention proposes a color gamut calibration method, which is executed by the electronic device 22 of the color gamut calibration system 2, thereby controlling the display driver chip 12 and the detection device 21 to operate to execute a color gamut calibration procedure on the display panel 11, and generating a look-up table (LUT) 121 for realizing color gamut mapping (or color gamut calibration) based on the calibration data of the color gamut calibration procedure (i.e., the calibrated RGB grayscale data). Thus, after receiving an input display data (i.e., input RGB grayscale data) from the host computer 2, the display driver chip 12 maps the input display data into an output display data (i.e., output RGB grayscale data) by searching the lookup table 121, and then pre-processes the input display data into a display driver data (i.e., VDATA). Finally, the display driver chip 12 drives the display panel 11 according to the output display data, so that the color gamut performance of the display panel 11 when displaying images can meet a standard target color gamut (e.g., sRGB color gamut or P3 color gamut).

FIG. 4A and FIG. 4B show a flow chart of a color gamut calibration method of the present invention. As shown in FIG. 4A and FIG. 4B , the method flow first executes step S1: a three-dimensional lookup table (3D LUT) is established based on an input RGB grayscale data transmitted to a display driver chip 12. FIG. 5 is a first schematic diagram of the three-dimensional lookup table. As shown in FIG. 5 , the first data axis, the second data axis, and the third data axis of the three-dimensional lookup table are the R axis, the G axis, and the B axis of the RGB color space, respectively. Next, the method flow executes step S2: a data node selection operation is performed to select a set of m primary color gamut data nodes from the three-dimensional lookup table, such as the multiple nodes marked in FIG. 5 . Next, the method flow executes step S3: executing a conversion operation to convert the m original color gamut data nodes into m sets of XYZ target values corresponding to the m target color gamut data nodes; wherein X, Y, and Z are tristimulus values in the CIE1931 color space. As shown in FIG5 , a data node in the RGB color space includes an R grayscale data, a G grayscale data, and a B grayscale data, and the data node can be converted from the RGB color space to the CIE1931 color space to include X, Y, and Z tristimulus values. Specifically, the electronic device 22 of the color gamut calibration system 2 uses the following mathematical formulas (1), (2), and (3) to complete the conversion operation: ······························· (1) ································ (2) ································(3)

As shown in FIG5 , a three-dimensional lookup table can be built in an RGB color space using an input RGB grayscale data. Therefore, any primary color domain data node selected from the three-dimensional lookup table has an input R grayscale value, an input G grayscale value, and an input B grayscale value. Therefore, in the above equations (1), (2), and (3), , and is an input R grayscale value, an input G grayscale value and an input B grayscale value included in a primary color gamut data node, and T1 is a first conversion matrix for converting the input R grayscale value, the input G grayscale value and the input B grayscale value into three primary color gamut stimulus values (tristimulus values). , and is an R grayscale value, a G grayscale value and a B grayscale value included in a target color gamut data node, and T2 is a second conversion matrix used to convert the R grayscale value, the G grayscale value and the B grayscale value into three target color gamut stimulus values. Thus, using the above formulas (1), (2) and (3), each original color gamut data node can be converted into a corresponding target color gamut data node, and the target color gamut data node includes three target color gamut stimulus values (i.e., the XYZ target values described in step S3) in the CIE1931 color space.

As shown in FIG. 4A and FIG. 4B , the method flow then executes step S4: when a display panel 11 is driven by the display driver chip 12, the detection device 21 of the color gamut calibration 2 is used to perform a measurement operation on the display panel 11, thereby measuring m sets of XYZ measurement values corresponding to the m primary color gamut data nodes. Inspection engineers familiar with OLED panel defect detection and/or color gamut calibration of OLED displays should know that commercially available luminance and colorimeter (Spectroradiometer) can directly measure the XYZ measurement value of each pixel (including R sub-pixel, G sub-pixel and B sub-pixel). Alternatively, a CCD camera can be used to photograph the OLED panel, and then the back-end electronic device 22 uses a conversion mathematical formula to convert each detection pixel into a corresponding XYZ measurement value. Next, the method flow executes step S5: performing a color difference value calculation operation, thereby calculating m color difference values using the m sets of XYZ measurement values and the m sets of XYZ target values. Specifically, the electronic device 22 of the color gamut calibration system 2 performs the color difference value calculation operation using the following mathematical formula (4): ···· (4)

In the above formula (4), is the color difference value, is the luminance difference (Delta luminance), is the chromaticity difference (Delta chromaticity), is the hue difference (Delta hue), is the brightness weight factor, is the chroma weight factor, is the hue weight factor, To correct brightness, To correct the color, To correct hue, and is a blue color space correction parameter. To explain in more detail, the aforementioned lightness L, chroma C and hue H are used to complete the calculation of the lightness, chroma and hue of each original color domain data node and the calculation of the lightness, chroma and hue of each target color domain data node using the following mathematical formulas (5), (6), (7), (8), (9), and (10), and then the aforementioned mathematical formula (4) is used to complete the color difference value calculation operation: ···························(5) ··································(6) ··································(7) ·········································· (8) ······································· (9) ··············································(10)

In the above formulas (5), (6), (7), (8), (9) and (10), c1 is the first constant, , and are three standard tristimulus values, L is brightness, Indicates the color components from green to red, represents the component from blue to yellow, H is hue, S is saturation, and C is chroma. Inspection engineers familiar with OLED panel defect inspection and/or OLED display color gamut calibration should know that the above equations (5), (6), and (7) are used to convert a data node from the CIE1931 XYZ color space to L Color space. Then, the hue, saturation and chroma of a data node can be calculated using the above formulas (8), (9) and (10). In this way, after measuring the XYZ measurement value of a primary color gamut data node (i.e., a node in Figure 5), the lightness L, hue H and chroma C of the primary color gamut data node can be calculated. Similarly, after using the conversion matrix to convert the three primary color gamut stimulus values of a primary color gamut data node into the three target color gamut stimulus values contained in a target color gamut data node, the lightness L, hue H and chroma C of the target color gamut data node can be calculated. Afterwards, the lightness difference can be calculated. , color difference Difference in color , then calculate the color difference .

As shown in FIG. 4B , the method flow then executes step S6: when the color difference value is greater than a predetermined value, an iterative update operation is performed on the m original color domain data nodes, and then the conversion operation of step S3, the measurement operation of step S4, and the color difference value calculation operation of step S5 are repeatedly performed. In one embodiment, the predetermined value can be set to 2. In this way, if >2, the following mathematical formulas (11), (12), (13), (14), (15), and (16) are used to complete the iterative update operation of each primary color domain data node: ·······························(11) ································(12) ································(13) ···········································(14) ··········································(15) ··········································(16)

In the above equations (11), (12), (13), (14), (15) and (16), R', G', B' are an iteratively updated R grayscale value, an iteratively updated G grayscale value and an iteratively updated B grayscale value of the original color domain data node, and , , are an R grayscale iteration constant, a G grayscale iteration constant, and a B grayscale iteration constant. On the other hand, , , are the three primary color gamut stimulus values contained in a primary color gamut data node, and , , are the three target color gamut stimulus values contained in a target color gamut data node. In other words, when iterative updating is performed, if ΔX>0, R increases proportionally to become R', otherwise it decreases proportionally to become R'. Similarly, when ΔY>0, G increases proportionally to become G', otherwise it decreases proportionally to become G'. Similarly, when ΔZ>0, B increases proportionally to become B', otherwise it decreases proportionally to become B'.

It should be noted that during the iteration process, if the difference between a certain component is too large and the differences between the other components are small, only the component with the large difference can be updated. For example, if ΔX is large but ΔY and ΔZ are small, then only the R value can be iteratively updated and adjusted. This iterative update method increases the flexibility of the color gamut calibration method, allowing the original color gamut data nodes to be iteratively updated faster to within the error range (i.e. ＜2), so as to be close to the corresponding target color gamut data node.

To further explain, assume that there is a jth difference between the R'/G'/B' value updated at the jth iteration and the target R'/G'/B' value, and there is a j+1th difference between the R'/G'/B' value updated at the j+1th iteration and the target R'/G'/B' value. If the jth difference and the j+1th difference have the same sign, it means that the iterative update constant (i.e., , , ) is too small. In this case, an iterative update constant greater than 1 should be used. Otherwise, an iterative update constant less than 1 should be used.

As shown in FIG. 4B , the method flow then executes step S7: after repeating the iterative update operation of step S6, the conversion operation of step S3, the measurement operation of step S4, and the color difference value calculation operation of step S5 until each original color gamut data node is corrected to its corresponding color difference value less than the predetermined value, the next data node selection operation (i.e., step S2) is performed, and then the conversion operation (i.e., step S3), the measurement operation (i.e., step S4), the color difference value calculation operation (i.e., step S5), and the iterative update operation (i.e., step S6) are performed on the next group of m original color gamut data nodes. Finally, after all data nodes of the input RGB grayscale data are updated iteratively and the color gamut calibration is completed, in step S8, the processed multiple original color gamut data nodes are stored as an output RGB grayscale data corresponding to the input RGB grayscale data. Finally, a three-dimensional lookup table 121 can be made using one or more sets of input RGB grayscale data, i.e., the corresponding output RGB grayscale data, and stored in the display driver chip 12, so that the display driver chip 12 can use the lookup table 121 to map an input display data received from a host computer into an output display data.

According to the design of the present invention, when the color difference value is less than the predetermined value (i.e., <2), the method flow will then proceed to step S7. At this time, in order to speed up the calculation speed, the electronic device 22 of the color gamut calibration system 2 can use the following mathematical formulas (17), (18) and (19) to perform a transfer operation to determine the next set of m original color gamut data nodes: ···············································(17) ···············································(18) ···············································(19)

In the above equations (17), (18) and (19), Rn, Gn, and Bn are an input R grayscale value, an input G grayscale value, and an input B grayscale value contained in a primary color gamut data node among the next group of m primary color gamut data nodes. , , is an R grayscale value transfer ratio, a G grayscale value transfer ratio and a B grayscale value transfer ratio. FIG6 is a second schematic diagram of the three-dimensional lookup table. As shown in FIG6, after the value transfer operation is performed on the data node N1 using the above formula (17), the data node N2 is determined. On the other hand, after the value transfer operation is performed on the data node N1 using the above formula (18), the data node N3 is determined. And, after the value transfer operation is performed on the data node N1 using the above formula (19), the data node N4 is determined.

Thus, the color gamut calibration method of the present invention has been fully and clearly described above; and, from the above, it can be known that the present invention has the following advantages:

(1) The present invention discloses a color gamut calibration method, which is performed by a color gamut calibration system. In the color gamut calibration method, a group of m original data nodes and their corresponding m target data nodes in an input RGB grayscale data are first converted to an XYZ color space, and the corresponding m measured data nodes are measured from the display device. When the color difference value between the measured data node and the target data node is not within the error range, the m original data nodes are first iteratively updated, and then the color difference value is recalculated until the color difference value is less than the error range and the iterative update is stopped. Thereafter, the next group of m original data nodes and their corresponding m target data nodes are selected from the input RGB grayscale data, and the same RGB grayscale data calibration steps are repeated. Furthermore, when selecting the next group of m original data nodes, a value transfer operation can be performed, thereby determining the next group of m original color domain data nodes based on the previous group of m original color domain data nodes that have completed calibration, thereby accelerating the calculation speed.

It must be emphasized that what is disclosed in the above-mentioned case is a preferred embodiment. Any partial changes or modifications that are derived from the technical ideas of this case and are easily inferred by people familiar with the art do not deviate from the scope of the patent rights of this case.

In summary, this case shows that its purpose, means and effects are all different from the known technology, and it is the first invention that is practical and indeed meets the patent requirements for invention. We sincerely request the review committee to examine this carefully and grant a patent as soon as possible to benefit the society. This is our utmost prayer.

1a: OLED display device

11a: OLED panel

12a: Display driver chip

121a: Lookup Table

11: Display Panel

12: Display driver chip

121: Lookup Table

2: Color gamut calibration system

21: Detection device

22: Electronic devices

S1: Create a 3D lookup table based on an input RGB grayscale data sent to a display driver chip

S2: Perform a data node selection operation to select a set of m primary color gamut data nodes from the three-dimensional lookup table.

S3: Perform a conversion operation to convert the m original color gamut data nodes into m sets of XYZ target values corresponding to the m target color gamut data nodes.

S4: When a display panel is driven by the display driver chip, a measurement operation is performed on the display panel to measure m sets of XYZ measurement values corresponding to the m primary color gamut data nodes.

S5: Perform a color difference value calculation operation to calculate m color difference values using the m sets of XYZ measurement values and the m sets of XYZ target values.

S6: When the color difference value is greater than a predetermined value, an iterative update operation is performed on the m original color domain data nodes, and then the aforementioned conversion operation, measurement operation and color difference value calculation operation are repeatedly performed.

S7: After repeating the aforementioned iterative updating operation, conversion operation, measurement operation, and color difference value calculation operation until each original color gamut data node is corrected to a color difference value corresponding to it that is less than the predetermined value, the next data node selection operation is performed, and then the conversion operation, the measurement operation, the color difference value calculation operation, and the iterative updating operation are performed on the next group of m original color gamut data nodes.

S8: storing the processed multiple original color domain data nodes as an output RGB grayscale data corresponding to the input RGB grayscale data

FIG. 1 is a block diagram of a known OLED display device; FIG. 2 is a known CIE-xy chromaticity diagram; FIG. 3 is a block diagram of a color gamut calibration system using a color gamut calibration method of the present invention; FIG. 4A and FIG. 4B are flow charts of a color gamut calibration method of the present invention; FIG. 5 is a first schematic diagram of a three-dimensional lookup table; and FIG. 6 is a second schematic diagram of a three-dimensional lookup table.

11: Display panel

12: Display driver chip

121: Lookup table

2: Color gamut calibration system

21: Detection device

22: Electronic devices

Claims (10)

A color gamut calibration method is performed by a color gamut calibration system and includes the following steps: establishing a three-dimensional lookup table according to an input RGB grayscale data transmitted to a display driver chip; wherein the first data axis, the second data axis and the third data axis of the three-dimensional lookup table are respectively the R axis, the G axis and the B axis of the RGB color space; performing a data node selection operation to select a group of m primary color gamut data nodes from the three-dimensional lookup table, wherein m is a positive integer; performing a conversion operation to convert the m primary color gamut data nodes into m groups of XYZ target values corresponding to the m target color gamut data nodes; wherein X, Y, and Z are tristimulus values (tristimulus 1, 2, and 3) of the CIE1931 color space; values); when a display panel is driven by the display driver chip, a measurement operation is performed on the display panel to measure m groups of XYZ measurement values corresponding to the m original color gamut data nodes; a color difference value calculation operation is performed to calculate m color difference values using the m groups of XYZ measurement values and the m groups of XYZ target values; when the color difference value is greater than a predetermined value, an iterative update operation is performed on the m original color gamut data nodes, and then the conversion operation, measurement operation and color difference value calculation operation are repeatedly performed; after the iterative update operation, conversion operation, measurement operation and color difference value calculation operation are repeated until each original color gamut data node is corrected to the corresponding color difference value less than the predetermined value, the next data node selection operation is performed, and then the next group of m The method comprises the steps of: performing the conversion operation, the measurement operation, the color difference value calculation operation and the iterative update operation on the plurality of original color gamut data nodes; and storing the processed plurality of original color gamut data nodes as an output RGB grayscale data corresponding to the input RGB grayscale data; wherein the color gamut calibration system uses the following mathematical formula (4) to complete the color difference value calculation operation:

Wherein, △ E ₀₀ is the color difference value, △ L' is the luminance difference (Delta luminance), △ C' _is the chromaticity difference (Delta chromaticity), △ H' is the hue difference (Delta hue), K _L is the luminance weight factor, K _C is the chromaticity weight factor _, K _H is the hue weight factor, SL is the corrected luminance, SC is the corrected chroma, SH is _the corrected hue, and RT _is a blue space correction parameter. The color gamut calibration method as described in claim 1, wherein the color gamut calibration system uses the following mathematical formulas (1), (2) and (3) to complete the conversion operation:

Among them, R _o , G _o and B _o are an input R grayscale value, an input G grayscale value and an input B grayscale value included in a primary color gamut data node, R _t , G _t and B _t are an R grayscale value, a G grayscale value and a B grayscale value included in a target color gamut data node, T1 is a first conversion matrix used to convert the input R grayscale value, the input G grayscale value and the input B grayscale value into three primary color gamut stimulus values (tristimulus values), and T2 is a second conversion matrix used to convert the R grayscale value, the G grayscale value and the B grayscale value into three target color gamut stimulus values. The color gamut calibration method as described in claim 1, wherein the color gamut calibration system uses the following mathematical formulas (5), (6), (7), (8), (9), and (10) to complete the calculation of the brightness, chroma and hue of each original color gamut data node and the calculation of the brightness, chroma and hue of each target color gamut data node, and then uses the aforementioned mathematical formula (4) to complete the color difference value calculation operation:

C=H+S． ． ． ． ． ． ． _． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． _． ． ． ． ． ． ． ． ． ． (10); wherein c1 is the first constant, X0 , _Y0 and Z0 are three standard tristimulus values, L is lightness, a* represents the component from green to red, b* represents the component from blue to yellow, H is hue, S is saturation, and C is chroma. The color gamut calibration method as described in claim 3, wherein the color gamut calibration system uses the following mathematical formulas (11), (12), (13), (14), (15), and (16) to complete the iterative update operation:

△X= Xt _- Xo _． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． (14); △Y= Y _t - Y _o ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． (15); △Z= Z _t - Z _o ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． (16); wherein R', G', B' are an iteratively updated R grayscale value, an iteratively updated G grayscale value and an iteratively updated B grayscale value of the original color gamut data node, and △ R , △ G , △ B are an R grayscale iteration constant, a G grayscale iteration constant and a B grayscale iteration constant; wherein Xo _, Yo _, Zo are three original color gamut stimulus values contained in an original color gamut data _node , and Xt _, Yt _, Zt are three target color gamut stimulus values contained in _a target color gamut data node. The color gamut calibration method as described in claim 4, wherein, when the color difference value is less than the predetermined value, the color gamut calibration system uses the following mathematical formulas (17), (18) and (19) to perform a value transfer operation to determine the next set of m original color gamut data nodes:

Among them, Rn, Gn, Bn are an input R grayscale value, an input G grayscale value and an input B grayscale value contained in a primary color gamut data node among the next group of m primary color gamut data nodes, VR _, VG , _{VB are} an R grayscale value ratio, a G grayscale value ratio and a B grayscale value ratio. A color gamut calibration system includes: a detection device facing a display panel; and an electronic device coupled to the detection device and at least one display driver chip for driving the display panel to display images; wherein the electronic device is configured to control the display driver chip and the detection device to operate to execute a color gamut calibration method, and the color gamut calibration method includes the following steps: establishing a three-dimensional lookup table according to an input RGB grayscale data transmitted to a display driver chip; wherein the three-dimensional The first data axis, the second data axis and the third data axis of the lookup table are respectively the R axis, the G axis and the B axis of the RGB color space; a data node selection operation is performed to select a group of m primary color gamut data nodes from the three-dimensional lookup table, wherein m is a positive integer; a conversion operation is performed to convert the m primary color gamut data nodes into m groups of XYZ target values corresponding to the m target color gamut data nodes; wherein X, Y, and Z are tristimulus values of the CIE1931 color space; when a display panel is driven by the display driver chip, a measurement operation is performed on the display panel to measure the m groups of XYZ measurement values corresponding to the m primary color gamut data nodes; A color difference value calculation operation is performed to calculate m color difference values using the m sets of XYZ measurement values and the m sets of XYZ target values; when the color difference value is greater than a predetermined value, an iterative update operation is performed on the m original color domain data nodes, and then the aforementioned conversion operation, measurement operation, and color difference value calculation operation are repeatedly performed; the aforementioned iterative update operation, conversion operation, measurement operation, and color difference value calculation operation are repeated until each original color domain data node is corrected to its corresponding After the color difference value of the input RGB grayscale data is less than the predetermined value, the next data node selection operation is performed, and then the conversion operation, the measurement operation, the color difference value calculation operation and the iterative update operation are performed on the next group of m original color domain data nodes; and the processed plurality of original color domain data nodes are stored as an output RGB grayscale data corresponding to the input RGB grayscale data; wherein the electronic device uses the following mathematical formula (4) to complete the color difference value calculation operation:

Wherein, △ E ₀₀ is the color difference value, △ L' is the luminance difference (Delta luminance), △ C' _is the chromaticity difference (Delta chromaticity), △ H' is the hue difference (Delta hue), K _L is the luminance weight factor, K _C is the chromaticity weight factor _, K _H is the hue weight factor, SL is the corrected luminance, SC is the corrected chroma, SH is _the corrected hue, and RT _is a blue space correction parameter. The color gamut calibration system as described in claim 6, wherein the electronic device uses the following mathematical formulas (1), (2) and (3) to complete the conversion operation:

Among them, o _R , o _G and o _B are an input R grayscale value, an input G grayscale value and an input B grayscale value included in a primary color gamut data node, t _R , t _G and t _B are an R grayscale value, a G grayscale value and a B grayscale value included in a target color gamut data node, T1 is a first conversion matrix used to convert the input R grayscale value, the input G grayscale value and the input B grayscale value into three primary color gamut stimulus values (tristimulus values), and T2 is a second conversion matrix used to convert the R grayscale value, the G grayscale value and the B grayscale value into three target color gamut stimulus values. The color gamut calibration system as described in claim 7, wherein the electronic device uses the following mathematical formulas (5), (6), (7), (8), (9), and (10) to complete the calculation of the brightness, chroma, and hue of each original color gamut data node and the calculation of the brightness, chroma, and hue of each target color gamut data node, and then uses the aforementioned mathematical formula (4) to complete the color difference value calculation operation:

C=H+S． ． ． ． ． ． ． _． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． _． ． ． ． ． ． ． ． ． ． (10); wherein c1 is the first constant, X0 , _Y0 and Z0 are three standard tristimulus values, L is lightness, a* represents the component from green to red, b* represents the component from blue to yellow, H is hue, S is saturation, and C is chroma. The color gamut calibration system of claim 8, wherein the electronic device uses the following mathematical formulas (11), (12), (13), (14), (15), and (16) to complete the iterative update operation:

△X= Xt _- Xo _. ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． (14); △Y= Y _t - Y _o . ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． (15); △Z= Z _t - Z _o ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． ． (16); wherein R', G', B' are an iteratively updated R grayscale value, an iteratively updated G grayscale value and an iteratively updated B grayscale value of the original color gamut data node, and △ R , △ G , △ B are an R grayscale iteration constant, a G grayscale iteration constant and a B grayscale iteration constant; wherein Xo _, Yo _, Zo are three original color gamut stimulus values contained in an original color gamut data _node , and Xt _, Yt _, Zt are three target color gamut stimulus values contained in _a target color gamut data node. The color gamut calibration system as claimed in claim 9, wherein, when the color difference value is less than the predetermined value, the electronic device uses the following mathematical formulas (17), (18) and (19) to perform a value transfer operation to determine the next set of m original color gamut data nodes:

Among them, Rn, Gn, Bn are an input R grayscale value, an input G grayscale value and an input B grayscale value contained in a primary color gamut data node among the next group of m primary color gamut data nodes, VR _, VG , _{VB are} an R grayscale value ratio, a G grayscale value ratio and a B grayscale value ratio.

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