JP2003037852A - Picture display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a picture having fully naturalness and presence, by converting the picture by adapting it to its illuminating environment changing temporally, in a picture display for displaying miscellaneous pictures. SOLUTION: A picture correcting portion 1 so performs the picture correction for giving to inputted picture signals continuous correcting results based on the light reception outputs a,..., z fed from a plurality of light receiving portions 2a,..., 2z having different color sensitivities from each other each of which receives continuously its ambient illumination light as to output the corrected-off picture signals to a displaying portion 3. In the picture correction, there are used an operating means for converting the picture signals by operating the equations which have the light reception outputs as parameters and give continuous results; a continuous-table converting means for converting the picture signals by the table for registering continuously varying values; a discrete-table interpolation means for converting the picture signals by interpolating the values obtained from a discrete table for registering discrete values; and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention corrects an image in accordance with the lighting environment of a place where a display device for displaying an image such as a television screen is placed to display a natural and realistic image. The present invention relates to an enabled image display device.

[0002]

2. Description of the Related Art In recent years, with the advancement of high-definition television broadcasts such as the practical use of high-definition broadcasts, and the increase in the area of television screens, general consumers are also full of natural and realistic television images. I have come to expect good images. The realism and naturalness of the image depend on the definition and the screen size, but are not necessarily determined by these alone. For example, whether the environment (lighting) in which the viewer is watching TV and the colors displayed on the TV screen are balanced so that humans do not feel uncomfortable will also greatly affect the naturalness of the image. To do. This is because human color vision is affected not only by the TV screen but also by the surrounding environment.

Up to now, a technique for improving an image displayed on a television screen including such an illumination environment has not been sufficiently developed. As a result, viewers have not always been able to appreciate images that are natural and have a realistic feel.

There are the following two techniques as conventional techniques relating to an image display device that corrects an image in accordance with the illumination environment.

First, as a conventional technique (1), "a device for automatically correcting an image in a display device and a method thereof" (Japanese Patent Laid-Open No. 8-6).
5701). This technique has a unit for detecting an external lighting environment and a unit for storing image correction data according to the external lighting environment. According to the detection result of the lighting environment, the corresponding correction data is retrieved from the correction data and the image is corrected.

Further, as a conventional technique (2), there is a technique disclosed in "a device for determining ambient illumination light and an image correction control device using the determination" (Japanese Patent Laid-Open No. 10-304395). This technique has means for detecting a signal related to ambient illumination light, means for determining the type of light based on the detection signal, and image correction data stored in advance according to the determination result of the light type. Data is output and the image is corrected according to the correction data. When the illumination light changes, the image is gradually changed according to the adaptation time of human color vision.

According to the above conventional technique, the image is corrected on the basis of the detection result regarding the surrounding illumination light. Therefore, it is possible, to some extent, to balance the environment (lighting) in which the viewer is viewing an image such as a television image and the colors displayed on the screen so as not to feel uncomfortable.

Both technologies define in advance a method for correcting image such as image correction data (white point correction) corresponding to a specific type (for example, daytime outdoor light, fluorescent lamp, incandescent lamp, etc.). ) Is remembered,
Also, it is common that one of these image correction data is selected based on the detection data related to lighting to correct the image. Such a method has an advantage that it is easy to design an actual device because the number of illuminations to be assumed in advance can be limited to a limited number.

However, both have the following common problems. Only the image correction data for a predetermined limited number of illuminations are stored, and in order to make corrections based on this limited number of corrections, corrections for illuminations other than the stored data, such as intermediate states, are performed. Could not be done properly. In particular, there was a problem when the illumination light changed gradually.

For example, consider a case where a television image is viewed from a bright time before sunset (two hours before sunset) to after sunset in a room illuminated by an incandescent lamp with a window. The lighting of the room is dominated by the light from the window (which is much paler than the incandescent lamp) when you start watching TV, and by the reddish incandescent lamp when you finish watching. Over time, the color of the illumination light in the room changes from blue to red.

FIG. 7 shows changes in the white point of the image when the white point (white balance) of the image in the prior art is corrected. In the conventional technique (1), FIG.
As shown in Fig. 5, a sudden change in the white point occurs, and it looks unnatural. Further, in the conventional technique (2), the conventional technique (1)
To a lesser extent, as shown in FIG. 7 (B), the adaptation of human color vision (although not strictly specified in the conventional technique (2), the reference: co-authored by Mark D. Fairchild and Lisa Reniff. Time course of chromatic adaptation for color
-appearance judgments "(J. Opt. Soc. Am. A / Vol.
According to No.5 / May1995, pages 824 to 833), the white point changes along with 60% acclimation in about 10 seconds and then 90% in 50 seconds. Therefore, the changing period (for example, 10 seconds in which the color of the screen largely changes) looks unnatural.

[0012]

As described above, according to the conventional technique, only the correction data for the illumination light stored in advance can be used as a reference, so that the intermediate data and the like other than the stored data can be corrected. In some cases, the lighting correction could not be properly performed. In particular, it was difficult to correct an image so that it looks natural to humans, such as when the illumination light changes gradually.

The present invention solves the above problems and corrects an image in accordance with a gradually changing illumination environment in a place where a display device for displaying an image such as a television screen is placed (a place where an observer exists). The goal is to enable the display of natural and realistic images.

[0014]

In order to solve the above-mentioned problems, the present invention corrects an image based on the outputs of two or more light-receiving means having different color sensitivities for detecting the illumination characteristics around the device. To do. In the process of this detection and correction, the type of illumination light, which is indispensable in the above conventional techniques (1) and (2), is classified into one of the types stored in advance, and The correction process based on the result is not performed, but the process of correcting the image while maintaining the continuity of the output value is performed based on the output value of the light receiving unit.

The correction processing for maintaining continuity includes, for example, arithmetic operations by four arithmetic operations and operations by exponential functions (excluding special cases such as division by zero), processing by lookup table and interpolation operation, and sufficiently prepared steps. It is a conversion process using a lookup table or a combination thereof, and a correction process that does not result in a discontinuous result even if an operation or process is performed on a continuous numerical value.

By the above processing, it is possible to balance the environment (lighting) in which the viewer is viewing an image such as a television image and the color displayed on the screen so that the viewer does not feel uncomfortable. It is possible to correct not only the illumination light but also all the illumination light.
In particular, even when the illumination light changes gradually, which is a problem in the conventional technique, it is possible to correct the image so that it looks natural to humans.

FIG. 1 is a diagram for explaining the principle of image correction of the present invention. As shown in FIG. 1, the image correction unit 1 includes a plurality of light receiving units 2a, 2b, ..., 2 that receive ambient illumination light.
, z is corrected based on the received light outputs a, b, ..., Z of the z, and the light receiving units 2a, 2b ,.
, z is subjected to image correction that gives a continuous correction result, and a corrected image signal is output to the display unit 3. As a result, not only the correction for specific illumination light, but for all illumination light, the environment (lighting) for viewing the image and the color displayed on the screen should be balanced. Is possible.

Suitable corrections that give a continuous result are, for example, matrix conversion expressed by matrix operation, so-called gain control expressed by multiplication, and so-called γ correction expressed by exponential function. References: Mark D. Fairchild, "Color Ap
6 of "pearance Models" (ADDISON-WESLEY ISBN0
-201-63464-3), the adaptation of human color vision to the outside can be modeled by matrix conversion and gain control, and the effect on the color vision of the external environment such as illumination light can be used for image correction. This is because it can be reflected.
The use of an exponential function is also preferable because the influence of the surrounding environment on human color vision can be modeled by an exponential function.

Furthermore, a continuous table converting means for converting continuously changing values along the registered values of a continuous table, a discrete table interpolating means for interpolating and converting a discrete table in which discrete values are registered, etc. It is also effective to use. In both cases, continuous values can be converted into continuous target values at high speed, and the calculation results of complicated mathematical expressions and experimental data that are difficult to express by mathematical expressions can be registered as they are.

Further, in performing the correction, in order to prevent an extreme correction (correction to a white balance far from a light color of black body radiation, which is rare in an ordinary light source, large correction in a short time, etc.), correction is performed. There may be restrictions on the amount. In particular, it is also desirable to provide a process for referring to the current correction amount so that the fluctuation of the correction amount per unit time is not made extremely large.

In recent years, in general digital image processing, strictly speaking, discrete numerical values such as 8 bits and 10 bits are handled. However, such discretization, especially when considering the limits of human perceptual function,
In fact, it is a well-known fact that it can be regarded as a continuous value. Therefore, the present invention is also effective in a device that performs digital image processing.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a configuration example of the image display device according to the embodiment of the present invention. The image display device 10 is
Light receiving portion R11 and light receiving portion G which are sensors for receiving illumination light
12, a light receiving portion B13 and its respective light receiving outputs Sr, Sg, S
A correction processing unit 14 that corrects the image according to b and a display screen 15 that displays the correction result are provided.

In this example, as the light receiving section, three sensors, a light receiving section R11 mainly receiving red light, a light receiving section G12 mainly receiving green light and a light receiving section B13 mainly receiving blue light, are provided. It is prepared. As will be described later in detail, the intensity of the illumination (illuminance: Y [Lu
x]) and color (chromaticity values: x, y) are estimated, and correction is performed according to the estimation result.

Although the image to be corrected is not specified in the present embodiment, the image to be corrected may be, for example, a video output from a TV tuner, or an image output from a personal computer. It may be.

FIG. 3 shows an example of a usage environment of the image display device according to the present embodiment. The image display device 10 is always illuminated by the illumination light in the environment as shown in FIG. 3 regardless of the change of the light from the window depending on the time of day and the lighting or extinction of various electric lights (fluorescent light, incandescent light, etc.). It is possible to correct and display it together.

The correction processing unit 14 includes a matrix calculation unit 16
And a gain determination unit 17 and a gain control unit 18. FIG. 4 is a processing flowchart of the correction processing unit. Basically, as shown in FIG. 4, first, three light receiving outputs S from the light receiving portions R11, G12, and B13 are received.
r, Sg, Sb are read (step S10), and the received light output is illuminated by the matrix calculation unit 16 (illumination, chromaticity).
To an estimated value of (step S11). Next, the gain determination unit 17 calculates a gain (Gr, Gg, Gb) for correcting the input image data (Rin, Gin, Bin) to be corrected based on this estimated value (step S12). ). Finally, the gain control unit 18 applies a gain by gain control by multiplying each RGB value by a constant, and corrects the image data (step S13). The corrected image data is output (step S14). The above processing is repeated until the display of the image data is completed.

The specific processing procedure of the correction processing unit 14 will be described below. First, the matrix calculation unit 16 receives the light receiving outputs Sr, S from the light receiving units R11, G12, B13.
g and Sb are converted into illuminance (Y _est ) and chromaticity values (x _est , y _est ) by the following (Equation 1).

[0028]

[Equation 1]

The values of the 3 × 3 matrix in (Equation 1) may be determined based on the measured values, for example. Specifically, under the lighting of various fluorescent lamps (from various types such as standard type and three-wavelength type, those with different color temperature), incandescent lighting, and lighting from windows at different times. , Lighting i (i =
The relationship between the measured values (Xi, Yi, Zi) with respect to 1, ..., N) and the outputs (Sri, Sgi, Sbi) from the sensor is investigated in advance, and the matrix that minimizes the square error of (Equation 2) shown below. Should be set. Note that Ki is the importance for each illumination. For example, a special type of fluorescent lamp that is rarely used may be determined according to the frequency of use so as to reduce its importance.

[0030]

[Equation 2]

Through the above processing, the illuminance (Y _est ) and the chromaticity value (x _est , y _est ) are estimated.

The gain determining section 17 determines the gain according to the gain determining method described later. Next, the gain control unit 18 determines the gain (G
r, Gg, Gb), according to (Equation 3) below,
The image data (Rin, Gin, Bin) is corrected.

[0033]

[Equation 3]

By the gain in (Equation 3), for example,
By setting Gb to a small value, it is possible to correct an image in which bluishness is suppressed, and by setting both Gr and Gg to a small value, it is possible to correct an image in which yellowing is suppressed. That is,
It is possible to control the image data according to the color of the illumination light.

The specific method of determining the gain is as follows. Basically, the chromaticity (x ₀ , y
₀ ) is defined in advance, and the correction amount is increased as the deviation is larger with reference to the deviation of the chromaticity (x _est , y _est ) of the actual illumination light from (x ₀ , y ₀ ). For example,
(X ₀ , y ₀ ) may be the chromaticity value of the D50 light source.

Hereinafter, the display screen 15 when the correction is not performed
The correction is performed with reference to the white point (x _W0 , y _W0 ) of. For example, (x _W0 , y _W0 ) may be a chromaticity value of 9300K. If the chromaticity of the illumination light is just (x ₀ , y ₀ ), the white point of the display screen 15 remains (x _W0 , y _W0 ), and if the chromaticity of the illumination light shifts, the display screen 15 The white point of is also changed.

First, the corrected white point (x _Wnew , y _Wnew ) is determined by the following (Equation 4).

[0038]

[Equation 4]

Here, Kw is the ratio of the deviation reflected on the corrected white point, and for example, Kw = 0.3. Next, the white point on the display screen 15 is exactly (x _Wnew , y
(Gr, Gg, Gb) so that _Wnew ).
Specifically, it is calculated by the following (formula 5).

[0040]

[Equation 5]

Here, max () is a function that returns the maximum value in parentheses, and (X _R , Y _R , Z _R ), (X _G , Y _G ,
Z _G ), (X _B , Y _B , Z _B ) are tristimulus values of light emission of the respective RGB light emitters when white is displayed on the display screen 15. By using the value obtained by the above processing and performing the correction according to (Equation 3), it is possible to correct the image data according to the illumination light.

Since (Equation 1) includes division, (Equation 1) gives discontinuous calculation results when the denominator is 0, but since the illuminance cannot be negative, it is virtually continuous. It can be said that it is a mathematical expression that gives various values. It is clear that effective correction can be performed by using a mathematical expression that gives a continuous value within a certain fixed range within at least a practical range of illumination light, and it is obvious that this is included in the technical scope of the present invention. . Of course, it is desirable to use a mathematical expression that gives a continuous value within the range of practical illumination light.

Furthermore, it is also effective to make the following modifications to the above embodiment.

[Modification 1 of the above embodiment] In the above embodiment, the output of the light receiving unit is read, and the gain is immediately changed based on the value to correct the image. Such a configuration causes no problem when there is no sudden change in illumination light. However, when there is a rapid change in the illumination light, such as when a light is turned on, it seems more natural to change the gain value slowly rather than following the rapid change.
Therefore, it is also effective to add a clocking means for periodically sending an interrupt signal and a means for referring to the current gain to the above-mentioned embodiment to prevent a sudden change.

FIG. 5 shows a configuration example of an image display device according to the first modification of the present embodiment. The image display device 20 includes a light receiving part R21 and a light receiving part G2 which are sensors for receiving illumination light.
2. A light receiving unit B23, a correction processing unit 24 that corrects an image according to the light receiving outputs Sr, Sg, and Sb, a display screen 25 that displays the correction result, and a gain change in units such as 1 second. And a gain storage unit 30 that stores the current gain. The image is corrected by using the current gains (Gr, Gg, Gb) stored in the gain storage unit 30 continuously at the timing when the image needs to be displayed. Only when there is a specific interrupt signal.

The correction processing section 24 is the same as the correction processing section 14 described in FIG. 2, and the light receiving sections R21, G22,
A matrix calculation unit 26 for converting the received light outputs Sr, Sg, Sb from B23 into estimated values of illumination light (illuminance, chromaticity).
And a gain determination unit 27 that calculates a gain (Gr, Gg, Gb) for correcting the input image data (Rin, Gin, Bin), and image data by a gain control that multiplies each RGB value by the gain. It is composed of a gain control unit 28 for correction.

FIG. 6 is a flow chart of the gain determination process of the first modification of the present embodiment. First, (1, 1, 1) is stored in the gain storage unit 30 as the initial value of the current gain (step S20). Here, the correction processing unit 24
Sets a timer value for periodically generating an interrupt signal in the timer unit 29 and waits for an interrupt signal from the timer unit 29 (step S21).

For example, here, an interrupt signal is generated every one second.
Shall be entered. If there is an interrupt signal, gay
The gain determination unit 27 uses a new gain (Gr_tmp, Gg_tmp，
Gb _tmp) Is calculated (step S22). Next new
The maximum value of the difference between the calculated gain and the current gain, and 1
The maximum gain TH that can be changed per second is compared (step
S23), if TH is larger, it will be newly calculated.
Store the gain as the current gain
The data is stored in the unit 30 (step S24), and the process ends.
If TH is smaller in step S23,
Do not exceed TH even if the number of gain changes greatly
The calculation to change the gain is performed, and the calculated gain is
Is stored in the gain storage unit 30 as the gain of (step S
25), the process ends. TH is preset
It is the set value of the correction limit amount. For example, TH is 0.01
If so, the gain will not change more than 0.01 per second.
It is possible to prevent sudden changes.

[Modification 2 of the above-described embodiment] In the above-described embodiment, the configuration has three light-receiving portions, but the number of light-receiving portions is not limited to three. For example, it is possible to reduce the number to two. In reality, both the light from windows and artificial light sources such as incandescent lamps and fluorescent lamps are almost black body radiation (250
It is close to any of the emission colors of 0K to 10000K). Therefore, the illuminance and chromaticity of the illumination light can be estimated from the outputs of the two light receiving units (for example, Sr and Sb), although the accuracy is slightly lower than in the case of three.

For example, in a device having three light receiving parts in advance, a coefficient P that minimizes the error of the following equation under various kinds of illumination
When r, Prr, Pb, Pbb, Prb are obtained in advance and actually implemented as the image display device 10 of FIG. 2, the light receiving part G12 is omitted and the calculated value of Sg by the following equation (equation 6) is used. do it.

[0051]

[Equation 6]

[Modification 3 of the above embodiment] In the above embodiment, the constant 0.3 was used as Kw, but it is also effective to change this value according to, for example, the illuminance. The higher the illuminance, the more the color vision is strongly influenced by the lighting.
If the illuminance is low, the effect is small. For example, Kw may be determined by the following (Equation 7).

[0053]

[Equation 7]

The value of Kw is not calculated each time (Equation 7), but the value of Kw is calculated in advance at a fine interval (for example, 1 Lux interval) within a range of general indoor illuminance (for example, 2000 Lux or less). The value of may be calculated to create a table, and the value of this table may be referenced to obtain the value.

Furthermore, in advance through experiments (10
Some illuminance (for example, 20Lux, 50Lux, 100Lu, etc.)
x, 200Lux, 500Lux, 1000Lux, 2
000 Lux, etc.) and the actual Kw
In the calculation of, the two data closest to the value of Y _est may be interpolated.

The image display device 1 shown in FIGS. 2 and 5.
The correction processing units 14 and 24 in 0 and 20 can be configured by hardware circuits, but can also be realized by a computer and a software program executed by the computer. Also,
The program can be stored in an appropriate recording medium such as a computer-readable portable medium memory, a semiconductor memory, or a hard disk.

The features of the above-described embodiments are listed below.

(Supplementary Note 1) An image display device for displaying an image, wherein a plurality of light receiving means having different color sensitivities for detecting illumination characteristics around the device and an image according to output values of the plurality of light receiving means are displayed. Image correction means for correcting and outputting the corrected image, wherein the image correction means is configured to give continuous correction results to continuous output values of the light receiving means. Characteristic image display device.

(Supplementary Note 2) In the image display device according to Supplementary Note 1, the image correcting means performs arithmetic operation according to a continuous mathematical expression using the output value of the light receiving means as a parameter, or continuous arithmetic means. The continuous table conversion means for converting the value that changes to the value according to the registered value in the continuous table, or the discrete table interpolation means for interpolating and converting the value obtained from the discrete table in which the discrete value is registered An image display device comprising any combination of means.

(Supplementary Note 3) The image display apparatus according to Supplementary Note 1 or Supplementary Note 2, further comprising correction amount limiting means for limiting a change amount of an image correction amount.

(Supplementary Note 4) The image display device according to Supplementary Note 3, wherein the correction amount limiting means has a correction amount reference means for referring to an effective correction amount for the current display image. apparatus.

(Supplementary Note 5) The image display apparatus according to Supplementary Note 3 or Supplementary Note 4, wherein the correction amount limiting means controls the limit amount according to the illuminance.

(Supplementary Note 6) A method of correcting an image in an image display device for displaying an image, comprising a step of reading out light receiving outputs from a plurality of light receiving means having different color sensitivities for detecting illumination characteristics around the device; The process of estimating the illumination light from the output value of the light receiving means, the gain for correcting the image according to the illumination light is calculated from the estimated value of the illumination light, and the calculated gain is applied to the input image. And a step of correcting an image which is a continuous correction result for continuous output values of the light receiving means.

(Supplementary Note 7) A program for correcting an image in an image display device for displaying an image, which is a process for reading out light receiving outputs from a plurality of light receiving means having different color sensitivities for detecting illumination characteristics around the device. A process of estimating illumination light from the output values of the plurality of light receiving means, a gain for correcting an image in accordance with the illumination light is calculated from the estimated value of the illumination light, and the calculated gain is used as an input image. A program for image correction for causing a computer to execute a process of applying an image to obtain a continuous correction result for a continuous output value of the light receiving unit.

(Supplementary Note 8) A recording medium in which a program for correcting an image in an image display device for displaying an image is recorded, and a plurality of light receiving means having different color sensitivities for detecting illumination characteristics around the device are provided. A process of reading the received light output, a process of estimating illumination light from the output values of the plurality of light receiving means, and a gain for correcting an image according to the illumination light from the estimated value of the illumination light, and the calculation A program for causing a computer to execute a process of applying a gain to an input image and correcting an image which is a continuous correction result with respect to a continuous output value of the light receiving means is recorded. A program recording medium for image correction.

[0066]

As described above, according to the present invention,
Environment (lighting) where viewers are viewing images such as TV images
It is possible to realize an image display device that can balance the colors displayed on the screen so that there is no discomfort, and it is not a correction that targets only specific illumination light.
It is possible to realize an image display device capable of performing correction for any illumination light. In particular, even when the illumination light changes gradually, which is a problem in the conventional technique, it is possible to correct the image so that it looks natural to humans.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of image correction of the present invention.

FIG. 2 is a diagram showing a configuration example of an image display device according to the present embodiment.

FIG. 3 is a diagram showing an example of a usage environment of the image display device according to the present embodiment.

FIG. 4 is a processing flowchart of a correction processing unit.

FIG. 5 is a diagram showing a configuration example of an image display device according to a first modification of the present embodiment.

FIG. 6 is a flowchart of a gain determination process in the first modification of the present embodiment.

FIG. 7 is a diagram showing changes in the white point of an image when the white point (white balance) of the image is corrected in the conventional technique.

[Explanation of symbols]

1 Image correction unit 2 Light receiving part 3 Display 10 Image display device 11 Light receiving part R 12 Light receiving part G 13 Light receiving part B 14 Correction processing unit 15 Display screen 16 Matrix operation unit 17 Gain determiner 18 Gain control section 20 Image display device 21 Light receiving part R 22 Light receiving part G 23 Light receiving part B 24 Correction processing unit 25 Display processing unit 26 Matrix operation unit 27 Gain determination unit 28 Gain control section 29 Timekeeping section 30 gain storage

Continued front page    F-term (reference) 5C066 AA03 CA17 EA15 EB02 EC01                       FA02 GA01 GA32 GA33 KA12                       KD06 KE03 KE04 KE09                 5C082 AA21 BA34 BA35 CA81 CB03                       DA51 MM10

Claims (5)

[Claims] 1. An image display device for displaying an image, comprising:
A plurality of light receiving means having different color sensitivities for detecting illumination characteristics around the device; and an image correction means for correcting an image according to output values of the plurality of light receiving means and outputting the corrected image, The image display device, wherein the image correction means is configured to give a continuous correction result to a continuous output value of the light receiving means. 2. The image display device according to claim 1,
The image correction means is an operation means for performing conversion according to a continuous mathematical expression using the output value of the light receiving means as a parameter, or a conversion means for converting continuously changing values according to registered values in a continuous table. An image characterized by comprising any one of a combination of three means of a continuous table converting means for converting or a discrete table interpolating means for interpolating and converting a value obtained from a discrete table in which discrete values are registered. Display device. 3. The image display device according to claim 1 or 2, further comprising a correction amount limiting means for limiting a variation amount of an image correction amount. 4. The image display device according to claim 3,
The image display device, wherein the correction amount limiting means includes a correction amount reference means for referring to an effective correction amount for a current display image. 5. The image display device according to claim 3, wherein the correction amount limiting means controls the limit amount according to illuminance.