JP5354699B2 - Chromaticity correction circuit, display device, and chromaticity correction method - Google Patents

Description

  The present invention relates to a chromaticity correction circuit for suppressing a change in chromaticity in a display device, a display device using the same, and a chromaticity correction method.

  The chromaticity of a backlight used in a display device such as a liquid crystal display is not constant, and varies depending on, for example, the ambient temperature and usage time (see FIGS. 6 and 7). FIG. 6 is a conceptual diagram showing a change in chromaticity (or color temperature) with use time, and FIG. 7 is a conceptual diagram showing a change in chromaticity (or color temperature) with ambient temperature. The chromaticity also changes depending on the command value for driving the backlight. Further, the amount of change in chromaticity according to the amount of change in command value also varies depending on the backlight.

  For example, in medical / graphic design applications, a display device is required to have high stability. Therefore, there is a need for a chromaticity correction circuit that maintains constant display characteristics by correcting the chromaticity of the backlight. There are the following techniques for constructing such a chromaticity correction circuit.

  Patent Document 1 describes a chromaticity correction circuit that corrects chromaticity based on usage time, and is detected by an integration counter (timer) using the fact that chromaticity of a display device changes based on usage time. A technique for correcting the chromaticity according to the usage time is shown.

  Patent Document 2 describes a chromaticity correction circuit that corrects chromaticity based on the output of a temperature sensor, and utilizes the fact that the chromaticity of a display device changes based on the ambient temperature, according to the detected ambient temperature. A technique for correcting chromaticity is shown.

  Patent Document 3 describes a chromaticity correction circuit that detects and corrects backlight chromaticity using a color sensor. The RGB (red, green, blue) output light level of the backlight is determined using three sensors for each color of RGB. A method for detecting and controlling the backlight current so as to obtain a predetermined luminance and controlling the display signal of the liquid crystal panel so as to obtain a predetermined chromaticity based on the detected value is shown.

  In Patent Document 4, a white sensor that detects the luminance of backlight light (white light) and a color sensor that detects the luminance of at least one of a plurality of colors (RGB) included in the backlight light are used. A chromaticity correction circuit that compensates for aging of the white balance of light is described. Patent Document 4 discloses a method for correcting a display signal of a liquid crystal panel by obtaining a change rate of a ratio of color luminance to white luminance (color luminance component) from luminance measurement values at different times.

JP 2007-156157 A JP 2007-028333 A JP 2008-116850 A Republished Patent No. WO2005 / 050613

  However, the method of correcting chromaticity based on the usage time as described in Patent Document 1 cannot correct the chromaticity change due to the backlight drive value or the ambient temperature. Even if the usage time is the same, there is an individual difference in the amount of change in chromaticity, so the chromaticity cannot be kept constant with this method.

  Further, in the method of correcting chromaticity based on a temperature sensor as described in Patent Document 2, chromaticity cannot be kept constant because individual differences and usage time cannot be reflected.

  Further, in the method of detecting and correcting the backlight chromaticity using the color sensor described in Patent Document 3 or Patent Document 4, in principle, the chromaticity of the backlight can be directly detected. It is difficult to keep the chromaticity of the display device constant due to these error factors. That is, the color sensor needs periodic calibration based on the RGB light source. However, when a backlight sensor is used, calibration is difficult because the light source is usually white only.

  Further, the internal temperature of the display device changes to about 0 to 60 ° C. Here, an output difference due to temperature characteristic variation between sensors (for example, R, G, B) is erroneously detected as a chromaticity change. In addition, the color filter portion is deteriorated (fading or yellowing due to an organic dye or resin), and sensor characteristics are likely to change. In addition, a color sensor having good characteristics is larger in size and expensive than a counter (timer), a temperature sensor, a luminance sensor, or the like.

  The present invention has been made in consideration of the above-described circumstances, solves the above-described problem, and provides a chromaticity correction circuit and a display that simply and accurately suppress a chromaticity change of a display device typified by a liquid crystal display. An object is to provide an apparatus and a chromaticity correction method.

  In order to solve the above problems, the present invention provides a luminance sensor that detects the luminance of a backlight in a display device, and a reference luminance value that serves as a reference for the luminance of the backlight in association with a driving value of the backlight. The luminance reduction from the reference luminance value is a ratio between the characteristic of 1 and the value corresponding to the luminance detected by the luminance sensor when the display color of the display device is digitized in a predetermined color system. A reference characteristic storage unit that stores a second characteristic that is expressed in association with a quantity; and reads out the reference luminance value from the first characteristic of the reference characteristic storage unit based on the input driving value of the backlight The amount of decrease in luminance is obtained from the reference luminance value and the luminance of the backlight detected by the luminance sensor, and the second characteristic of the reference characteristic storage unit is determined based on the amount of decrease in luminance. A backlight state calculation unit that reads the value of the ratio, and a chromaticity correction unit that corrects the chromaticity of the display signal input to the display device based on the value of the ratio read by the backlight state calculation unit It is characterized by providing.

  According to the present invention, without using a color sensor, the display characteristics of the display device stored in advance in association with the driving value of the backlight and the amount of decrease in luminance, and the luminance of the backlight detected by the luminance sensor Therefore, the change in chromaticity of the display device represented by the liquid crystal display can be simply and accurately suppressed.

It is a block diagram which shows the structure of embodiment of this invention. It is explanatory drawing which shows the general brightness | luminance lifetime characteristic of a display apparatus. It is explanatory drawing which shows the R / G / B luminance lifetime characteristic obtained from the luminance lifetime characteristic of FIG. It is explanatory drawing which shows RGB ratio with respect to normalization brightness | luminance. It is explanatory drawing which shows the outline | summary which calculates a brightness | luminance fall amount from a backlight brightness | luminance detection value and a backlight drive value. It is explanatory drawing which shows the chromaticity change of the display apparatus by use time. It is explanatory drawing which shows the chromaticity change of the display apparatus by ambient temperature.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a chromaticity correction circuit 10 and a display device 100 using the chromaticity correction circuit 10 according to an embodiment of the present invention. 1, the display device 100 includes a chromaticity correction circuit 10, a display unit 20, a backlight (hereinafter also referred to as BL) 30, a luminance sensor 40, and a white point chromaticity setting unit 50. . In FIG. 1, only the configuration relating to input / output of the chromaticity correction circuit 10, which is a configuration characterized by the present invention, is shown in the display device 100. That is, in addition to the above, the display device 100 displays information to the driving circuit of the backlight 30, a power supply circuit for supplying power to each unit, an operator for performing various settings by the user, and the user, for example. For example, a signal generation circuit for generating a signal for performing the control and a control circuit for controlling each unit.

  The chromaticity correction circuit 10 includes a BL chromaticity correction unit 1, a chromaticity correction unit 2, a BL state calculation unit 3, and a reference characteristic storage unit 4. The chromaticity correction circuit 10 performs chromaticity correction on a video signal input from a video output device 200 such as a personal computer or a video device connected to the display device 100, and a corrected video signal subjected to chromaticity correction. Is output to the display unit 20. The display unit 20 is a liquid crystal display unit that performs display using liquid crystal using the backlight 30 as a light source. In the present embodiment, the display unit 20 is configured using a transmissive liquid crystal display (also referred to as a transmissive liquid crystal panel) such as an LCD (liquid crystal display) or a PJ (projector), and is output from the chromaticity correction circuit 10. The video is displayed based on the corrected video signal.

  The backlight 30 is a light source of the display unit 20 and is provided on the back surface of the display unit 20. Further, the backlight 30 outputs a backlight driving value signal indicating the driving state of the backlight 30 to the BL state calculation unit 3. When the backlight 30 is driven by PWM (Pulse Width Modulation), the backlight drive value signal is a duty ratio (duty; on / off time ratio of the pulse width modulation signal (ON / OFF time of the pulse width). A signal representing a time ratio)). Alternatively, the backlight drive value signal may be a value representing input power to the backlight 30 or the like.

  The luminance sensor 40 detects the luminance value (white luminance value) of the output white light from the backlight 30 and outputs a signal indicating the backlight luminance value to the BL state calculation unit 3. The white point chromaticity setting unit 50 sends a white point chromaticity setting value signal representing a setting value of the white point chromaticity set in accordance with an operation on a predetermined operator by the user to the BL chromaticity correction unit 1. Output.

  The chromaticity correction circuit 10 shown in FIG. 1 can be composed of a computer such as a microcomputer and a peripheral circuit of the computer such as a memory and an input / output interface circuit. In this case, a predetermined value stored in the memory by the computer. It works by running the program. Alternatively, the chromaticity correction circuit 10 can be configured as an integrated circuit composed of a combination of circuits such as various logics.

  The BL chromaticity correction unit 1 sets the white point chromaticity setting value in the display by the display unit 20 (and the backlight 30) set by the user using the white point chromaticity setting unit 50, and the BL state calculation unit 3 The chromaticity correction value is calculated by receiving the RGB ratio read from the reference characteristic storage unit 4 and output to the chromaticity correction unit 2.

  The chromaticity correction unit 2 performs chromaticity correction using the chromaticity correction value input from the BL chromaticity correction unit 1 on the video signal input from the video output device 200 to obtain a corrected video signal. Output.

  The BL state calculation unit 3 reads a reference luminance value corresponding to the backlight drive value from the reference characteristic storage unit 4 based on the backlight drive value input from the backlight 30. Here, the reference luminance value is a reference value (or initial value) for the luminance of the backlight 30 of the display device 100 set before product shipment. This reference luminance value is a value set so as to correspond to the detected value of the backlight luminance value output from the luminance sensor 40 corresponding to each backlight driving value (or for each range of the predetermined backlight driving value). is there. Alternatively, the reference luminance value may be stored in the reference characteristic storage unit 4 in the form of a mathematical expression representing the relationship between the backlight driving value and the reference luminance value. Based on the backlight luminance value input from the luminance sensor 40, the BL state calculation unit 3 obtains the luminance reduction amount from the reference luminance value read from the reference characteristic storage unit 4 in a corresponding manner. Then, the BL state calculation unit 3 calculates the value of the luminance decrease amount (= 1−luminance decrease amount) from the reference luminance value when the reference luminance value is normalized to “1”. Here, (1-luminance reduction amount) is defined as normalized luminance. However, the luminance reduction amount is not limited to the difference from the reference luminance value, and may be obtained as a value of a ratio between the backlight luminance value input from the luminance sensor 40 and the reference luminance value.

  Further, the BL state calculation unit 3 reads the RGB ratio corresponding to the calculated normalized luminance from the reference characteristic storage unit 4 and outputs it to the BL chromaticity correction unit 1. Here, the RGB ratio means the ratio of the backlight luminance value W and the luminance value of each RGB color = R / W, G / W, B / W, and RGB when the normalized luminance is “1”. In each color, R / W, G / W, and B / W are set to have the same value (see FIG. 4). This RGB ratio is a reference value (or initial value) related to the display characteristics of the display device 100 set at the time of product development or the like, and is set so as to correspond to the normalized luminance. Note that the RGB ratio is the ratio of each of the numerical values R, G, and B when the display color by the display device 100 is digitized in the RGB color system and the backlight luminance value W, and the amount of decrease in luminance from the reference luminance value. This characteristic is expressed in association with each of the numerical values when the display color by the display device 100 is digitized in another predetermined color system and a value corresponding to the luminance detected by the luminance sensor 40. It is also possible to replace this ratio with other characteristics that are expressed in association with the amount of decrease in luminance from the reference luminance value. For example, tristimulus values XYZ in the XYZ color system can be used instead of RGB values.

  The reference characteristic storage unit 4 stores information representing a reference luminance value associated with the backlight driving value and an RGB ratio value associated with the normalized luminance. In other words, the reference characteristic storage unit 4 displays a reference luminance value that is a reference for the luminance of the backlight 30 in association with the backlight driving value and a display color by the display device 100 in a predetermined color system (in this case, (R, G, and B color system) stores characteristics representing the ratio between each numerical value (RGB) and the value corresponding to the luminance detected by the luminance sensor 40 in association with the amount of decrease in luminance from the reference luminance value. doing. Note that the above-described characteristic relating to the reference luminance value can be measured in a relatively short time, and is set corresponding to each display device 100, and the characteristic relating to the above ratio is due to a long-term characteristic change. Therefore, it is desirable to set a common setting corresponding to the plurality of display devices 100.

  Next, a procedure for obtaining a chromaticity correction value from a backlight luminance value, which is a feature of the present invention, during operation of the display unit 20 in the embodiment of the chromaticity correction circuit 10 and the display device 100 of FIG. 1 will be described.

  The RGB ratio (or XYZ value) described below is set in advance during product development and stored in the reference characteristic storage unit 4. The reference luminance value is set in advance for each display device 100 at the time of shipment from the factory and stored in the reference characteristic storage unit 4.

  First, the BL state calculation unit 3 receives the current backlight driving value from the backlight 30, and reads the reference luminance value corresponding to the backlight driving value from the reference characteristic storage unit 4. That is, the reference luminance value is a reference set as a relationship between the backlight driving value (horizontal axis) and the backlight luminance (vertical axis) as shown by a solid line in FIG. 5 stored in the reference characteristic storage unit 4. It is obtained from the set value (characteristic) of the luminance value corresponding to the backlight drive value. Note that the relationship between the backlight driving value and the backlight luminance can be usually obtained as a linear characteristic as shown in FIG.

  Next, the BL state calculation unit 3 receives the current backlight luminance value from the luminance sensor 40 and calculates the amount of decrease in luminance from the reference luminance value. For example, assume that the BL state calculation unit 3 obtains the current backlight drive value “A” and a backlight luminance value as a detection value indicated by a black circle in FIG. In this case, the BL state calculation unit 3 calculates a value obtained by normalizing the difference between the reference luminance value corresponding to the current backlight driving value “A” and the current backlight luminance value as the luminance reduction amount. In the example of FIG. 5, since the backlight luminance value is “70” with respect to the reference luminance value “100”, the luminance reduction amount is (100−70) ÷ 100 = 30%.

  Next, the BL state calculation unit 3 obtains normalized luminance by calculating (1-luminance reduction amount). Here, the luminance reduction amount is a value indicating a reduction ratio from the reference luminance value as described above. In the above example, normalized luminance = (1-30%) = (1-0.3) = 0.7.

Next, the BL state calculation unit 3 reads the RGB ratio corresponding to the obtained normalized luminance from the reference characteristic storage unit 4 and outputs it to the BL chromaticity correction unit 1. That is, the BL state calculation unit 3 calculates the normalized luminance based on the amount of decrease in luminance, and the RGB ratio value corresponding to the calculated normalized luminance is the characteristic information stored in the reference characteristic storage unit 4. And output to the BL chromaticity correction unit 1. FIG. 4 is a diagram illustrating an example of a correspondence relationship between the normalized luminance and the RGB ratio. In FIG. 4, the ratio R / W of the R value indicated by the alternate long and short dash line and the backlight luminance value W increases as the normalized luminance decreases with the luminance ratio of normalized luminance = “1” as a reference. The ratio G / W between the indicated G value and the backlight luminance value W is reduced, and the ratio B / W between the B value and the backlight luminance value W indicated by a two-dot chain line is greatly reduced.
Each characteristic of the RGB ratio can be set as a linear characteristic as shown in FIG. In the above example, RGB ratio values R / W, G / W, and B / W indicated by circles in the figure corresponding to normalized luminance = “0.7” are read from the reference characteristic storage unit 4 respectively. It is output to the BL chromaticity correction unit 1.

  Next, the BL chromaticity correction unit 1 calculates a chromaticity correction value based on the received RGB ratio and the white point chromaticity set by the user, and sets it in the chromaticity correction unit 2. That is, the BL chromaticity correction unit 1 calculates the current chromaticity from the RGB ratio, calculates a chromaticity correction value corresponding to the white point chromaticity set by the user using this, and outputs the video signal. Is output to the chromaticity correction unit 2 as a chromaticity correction value to be applied to. In addition, since this calculation can be generally performed by a well-known method, the detailed description is abbreviate | omitted.

  Next, the chromaticity correction unit 2 corrects the video signal by a technique such as multiplication according to the chromaticity correction value calculated by the BL chromaticity correction unit 1 and outputs the corrected video signal to the display unit 20. For example, the chromaticity correction unit 2 includes a conversion table that outputs a signal whose input value is a value indicated by a video signal (display signal) and whose output value is corrected by the chromaticity correction value. The correction values of the input video signal are sequentially read and output to the display unit 20.

  The RGB ratio stored in advance in the reference characteristic storage unit 4 can be obtained by the following procedure.

  For example, when the following color conversion Matrix (matrix) is applied to the luminance life characteristics (FIG. 2) of the display device 100 measured at the time of product development, the luminance life characteristics of each R / G / B are obtained. Is obtained (FIG. 3).

  In FIG. 2, the horizontal axis is the usage time, and the vertical axis is the initial value at the usage time “0” in the CIE (International Lighting Commission) 1931 standard color system (XYZ color system). It is a characteristic view which shows the change of tristimulus value XYZ. An alternate long and short dash line indicates a change in X, a solid line indicates a change in Y, and a broken line indicates a change in Z. Further, FIG. 3 shows characteristics indicating changes in the RGB values R, G, B and the backlight luminance value W when the horizontal axis is the usage time and the vertical axis is the usage time “0” and the initial value is “1”. FIG. A one-dot chain line indicates a change in R, a solid line indicates a change in W, a broken line indicates a change in G, and a two-dot chain line indicates a change in B. The W characteristic in FIG. 3 corresponds to the Y value in FIG. Since the liquid crystal display has a substantially constant color gamut even after long-term use, the color conversion Matrix may be a fixed value with respect to time.

  Next, in order to eliminate the time axis in FIG. 3, the R, G, and B values are each divided by the backlight luminance value W to make it dimensionless, and the backlight luminance value W (here, normalized luminance) is taken as the horizontal axis. What is shown is FIG. The reason for deleting the time axis is that the chromaticity cannot be estimated by the usage time.

  The graph of FIG. 4 shows the ratio of the luminances of R, G, and B to the specified normalized luminance (White Luminance), that is, the RGB ratio. The characteristics of the RGB ratio are stored in the reference characteristic storage unit 4 in FIG. Here, the graphs of FIGS. 2 and 3 are logarithmic curves typified by the Arrhenius rule, but the graph of FIG. 4 is characterized by being converted into a substantially straight line. That is, the nonlinear color change characteristic of the display device 100 can be replaced by a simpler linear conversion process in the present embodiment.

  Further, since the chromaticity change characteristics with respect to the ambient temperature and the backlight drive value also show the same change tendency with respect to the luminance, the correction according to the change of the ambient temperature and the backlight drive value can be performed by the above method.

  As described above, the chromaticity correction circuit 10 and the display device 100 of the present invention connect the chromaticity correction circuit 10 between the video output device 200 and the display unit 20 as shown in FIG. By correcting the video signal according to the following procedure, a change in chromaticity of the display unit 20 (or the display device 100) caused by factors such as ambient temperature, usage time, individual characteristics, and backlight drive value is suppressed.

  That is, the chromaticity correction circuit 10 detects the backlight luminance of the backlight 30 of the display unit 20 and calculates the difference (or ratio) from the reference luminance value (calculates the “decrease amount” in FIG. 5). This reference luminance value is a luminance value set in advance for each backlight driving value (PWM duty, input power, etc.). Then, using the correlation between the backlight luminance and the chromaticity, the normalized luminance is obtained from the difference from the reference luminance value, and the RGB ratio (R / W, G / W, B / W in FIG. 4) corresponding to the normalized luminance is obtained. ) In this case, the reference luminance value and the RGB ratio are represented by a straight line. Then, the current chromaticity is calculated from the RGB ratio, and the chromaticity correction value corresponding to the calculated chromaticity is applied to the video signal (FIG. 1).

  Due to these features, the chromaticity correction circuit 10 of the present invention detects the display characteristics of the display device stored in advance in association with the backlight driving value and the luminance decrease amount without using the color sensor, and the luminance sensor. Since the chromaticity change can be estimated based on the brightness of the backlight to be displayed, the chromaticity change of the display unit 20 (and the backlight 30) represented by the liquid crystal display can be suppressed simply and with high accuracy. it can. Since this method is based on the estimation of chromaticity from the backlight luminance, there is no need for the conventional temperature and usage time detection and color sensor for estimating the chromaticity change. Thus, according to the chromaticity correction circuit 10 of the present invention, the following effects can be obtained.

  (1) It is possible to suppress changes in chromaticity due to many causes such as usage time, ambient temperature, backlight drive value, and individual variation.

  (2) Since a luminance sensor that detects the luminance of the backlight is used as the sensor, it is only necessary that the sensor can be installed at a position where the luminance of the backlight can be measured. That is, it can be installed on the back of the screen without covering the screen display area. The chromaticity can be corrected without hindering the use of the display device.

  (3) Since there is no restriction on the position where the luminance sensor is installed, chromaticity can be corrected without being affected by screen unevenness by installing the sensor in the center of the screen.

  (4) Since the luminance sensor is a single sensor, it can be easily calibrated, color measurement errors due to temperature drift and optical spectrum characteristics, which are problems with color sensors, can be suppressed, and chromaticity correction performance can be improved.

  (5) Since the luminance sensor does not have a color filter that tends to fade due to aging, it is not necessary to consider changes in the backlight luminance value detected by the luminance line difference, and chromaticity correction can be performed stably. . That is, it is possible to avoid a decrease in correction performance due to aging, and high long-term reliability.

  (6) Since the correction is performed based on the actually measured luminance characteristic, it is easier to improve the accuracy than the timer / temperature sensor method.

  (7) Table correction is not required even with nonlinear characteristic changes (FIG. 2), and chromaticity can be detected by linear processing (FIG. 4).

  (8) Since the present invention is based on the luminance sensor and linear processing, the present invention can be realized at a lower cost than the color sensor method.

  (9) As a result, in the chromaticity correction circuit and the display device of the present invention, it is possible to suppress the change in chromaticity and improve the display image quality under a wide range of usage conditions. This is suitable mainly for medical and graphic design applications.

  In addition, embodiment of this invention is not limited to said thing, The following changes can be performed suitably. That is, a temperature sensor may be added for temperature correction of the luminance sensor. Further, what is detected by the sensor may be the backlight illuminance instead of the backlight luminance.

DESCRIPTION OF SYMBOLS 1 BL (backlight) chromaticity correction part 2 Chromaticity correction part 3 BL state calculation part 4 Reference | standard characteristic memory | storage part 10 Chromaticity correction circuit 20 Display part 30 Backlight 40 Luminance sensor 50 White point chromaticity setting part 100 Display apparatus 200 Video output device

Claims (7)

A luminance sensor for detecting the luminance of the backlight in the display device;
A first characteristic representing a reference luminance value serving as a reference of the luminance of the backlight in association with a driving value of the backlight, and each numerical value when the display color by the display device is digitized in a predetermined color system A reference characteristic storage unit that stores a second characteristic that represents a ratio of a value corresponding to the luminance detected by the luminance sensor and a luminance decrease amount from the reference luminance value;
The reference luminance value is read from the first characteristic of the reference characteristic storage unit based on the input driving value of the backlight, and from the reference luminance value and the luminance of the backlight detected by the luminance sensor. A backlight state calculation unit that obtains the luminance reduction amount and reads the value of the ratio from the second characteristic of the reference characteristic storage unit based on the luminance reduction amount;
A chromaticity correction circuit comprising: a chromaticity correction unit that corrects chromaticity of a display signal input to the display device based on the ratio value read by the backlight state calculation unit. The chromaticity correction circuit according to claim 1, wherein the first characteristic and the second characteristic are linear characteristics. The chromaticity correction circuit according to claim 1 or 2, wherein the drive value of the backlight is a signal corresponding to an on / off time ratio of a pulse width modulation signal or a signal corresponding to input power. The chromaticity correction circuit according to claim 1, wherein the display color is an RGB color system or an XYZ color system. The first characteristic is set for each of the display devices;
5. The chromaticity correction circuit according to claim 1, wherein the second characteristic is set corresponding to a plurality of the display devices. 6. With backlight,
A chromaticity correction circuit according to any one of claims 1 to 5,
And a liquid crystal display means using the backlight as a light source. A process in which the brightness sensor detects the brightness of the backlight in the display device;
Based on the inputted backlight driving value, the backlight state calculation unit expresses a reference luminance value serving as a reference for the backlight luminance in association with the backlight driving value, and stores it in the reference characteristic storage unit The reference luminance value is read out from the first characteristic, the luminance reduction amount is obtained from the reference luminance value and the luminance of the backlight detected by the luminance sensor, and based on the luminance reduction amount, A ratio between each numerical value when the display color by the display device is digitized in a predetermined color system and a value corresponding to the luminance detected by the luminance sensor is expressed in association with the luminance decrease amount from the reference luminance value. Reading the value of the ratio from the second characteristic stored in the reference characteristic storage unit;
A chromaticity correction unit comprising: correcting a chromaticity of a display signal input to the display device based on the value of the ratio read by the backlight state calculation unit. Correction method.

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