JP5605038B2 - Image processing apparatus, image display apparatus, and image processing method - Google Patents

Description

  The present invention relates to an image processing device, an image display device, and an image processing method.

  Image display devices such as liquid crystal display devices, plasma display devices, projectors, and the like may cause deterioration in gradation of bright portions and dark portions, decrease in contrast, etc., depending on the surrounding lighting environment, resulting in reduced visibility of the displayed image. is there. In particular, unlike a liquid crystal display device, a plasma display device, or the like, a projector displays an image by projecting image light onto a screen. Therefore, the visibility of a display image is reduced depending on the surrounding lighting environment. Become prominent.

  In Patent Document 1 below, the illuminance around the projector and the APL (average luminance level) of the image signal are detected, and at least one of white extension and black extension is performed in accordance with the detection results to increase the contrast. Discloses a technique for improving the visibility of a display image. For example, when it is detected that the periphery is bright and the detected APL is equal to or smaller than a predetermined set value, the visibility of the display image is improved by performing both white expansion and black expansion.

  Patent Document 2 below discloses a wavelength selection screen that is used in a projector and can display an image with high contrast even in a bright room. Here, the wavelength selection screen is a screen that reflects only light of the emission wavelength emitted from the projector toward the observer and absorbs light of other wavelengths. When this wavelength selection screen is used, an external light component is absorbed, so that an image with high contrast can be displayed even in a bright room.

JP 2009-276424 A JP 2006-350185 A

  By the way, although the technique disclosed in Patent Document 1 described above can correct the collapse of the gradation of the display image caused by the illumination environment, it cannot correct the color change of the display image according to the illumination environment. There's a problem. For example, the color of the display image illuminated with the fluorescent lamp is slightly different from the color of the display image illuminated with the incandescent lamp, but correcting the color difference according to the illumination environment There is a problem that you can not.

  When the wavelength selection screen disclosed in Patent Document 2 described above is used, light having a specific wavelength out of light incident on the wavelength selection screen is reflected without being absorbed. For this reason, even if white illumination light is incident on the wavelength selection screen, the reflected light has a color according to the reflection / absorption characteristics of the wavelength selection screen. Then, there exists a problem that the dark part of the display image displayed on a wavelength selection screen will color according to the color of the reflected light.

  Here, if the projector tries to correct the dark color (black color) of the display image, the black color and the contrast are in a trade-off relationship. Therefore, if priority is given to eliminating the black color, the brightness of the dark part of the display image will increase and the contrast will decrease. Conversely, if priority is given to the contrast of the display image, the black color will be sufficiently eliminated. There is a problem that can not be. Conventionally, in order to correct such a dark portion of the display image, the user has to perform manually according to the lighting environment.

  The present invention has been made in view of the above circumstances, and an image processing apparatus and an image display apparatus capable of automatically and appropriately correcting a dark coloration of a display image generated according to an illumination environment in consideration of contrast. And an image processing method.

The image processing apparatus of the present invention is an image processing apparatus that performs processing on the image signal input to a display device that displays an image corresponding to the image signal on a display surface, and displays an image in which the image signal is black. The color of the image displayed on the display surface under the usage environment of the display device when it is a corrected black color that minimizes the color difference from the color of the display surface in a completely non-lighted state or the same color as the corrected black color A color correction unit that corrects the image signal is provided so that colors can be obtained.
According to the present invention, when the image signal is to display a black image, the color of the image displayed on the display surface under the usage environment of the display device is different from the color of the display surface in a completely non-lighted state. The image signal input to the display device is corrected by the color correction unit so that the corrected black color that can be minimized or a color that can be viewed with the corrected black color is obtained. For this reason, it is possible to automatically and appropriately correct the coloring of the dark portion of the display image that occurs in accordance with the illumination environment in consideration of the contrast.
Here, the complete lightless state is a state in which no image is displayed on the display surface by the display device, and no external light is irradiated on the display surface.
The color that can be equated with the corrected black is a color having a color difference of 1 or less from the corrected black in a uniform color space.
In the image processing apparatus of the present invention, when the image signal displays a black image, the color of the image displayed on the display surface in a use environment of the display device is set to be in a completely non-lighted state. A color correction table storage unit for storing a correction black that minimizes a color difference from the color of the display surface or a color correction table that can be equated with the correction black; and the color correction unit includes the color correction The image signal is corrected using the color correction table stored in the table storage unit.
According to the present invention, a color correction table capable of realizing the above correction is generated under the usage environment of the display device, and the image signal is corrected using the color correction table. For this reason, it is possible to automatically and appropriately correct the coloring of the dark portion of the display image in consideration of the contrast under any lighting environment.
In addition, the image processing apparatus of the present invention stores a first color characteristic storage unit that stores color characteristics of an image displayed on the display surface by the display device, and a color characteristic of external light irradiated on the display surface. The display color gamut that can be displayed on the display surface under the usage environment of the display device is calculated using the second color characteristic storage unit and the color characteristics stored in the first and second color characteristic storage units. A display color gamut calculation unit and a color correction table generation unit that generates the color correction table using a calculation result of the display color gamut calculation unit are provided.
According to this invention, the display color gamut that can be displayed on the display surface under the usage environment of the display device using the color characteristics of the image displayed on the display surface by the display device and the color characteristics of the external light irradiated on the display surface. And a color correction table is generated using the calculated display color gamut. Therefore, correction can be performed in consideration of not only the illumination environment but also the characteristics of the display device, and the present invention can be applied to display devices having various display characteristics.
Further, the image processing apparatus according to the present invention is based on the display color gamut calculated by the display color gamut calculation unit, and displays a white image as the image signal under a use environment of the display device. The corrected white color to be displayed on the display surface and the corrected black color or the corrected black color to be displayed on the display surface under the usage environment of the display device when the image signal displays a black image. A correction color calculation unit that obtains a color that can be seen together, and the color correction table generation unit converts the white and black displayed on the display surface under the usage environment of the display device to the correction white and the correction black, respectively. The color correction table is generated.
According to the present invention, when the image signal is to display a white image, the corrected white color to be displayed on the display surface under the usage environment of the display device and the image signal is to display a black image. Correction black (or a color that can be equated with correction black) to be displayed on the display surface under the usage environment of the display device is required, and white and black displayed on the display surface under the usage environment of the display device are corrected white. Then, a color correction table for generating corrected black (or a color that can be equated with corrected black) is generated. For this reason, in addition to black, white and gray colors having no saturation are also appropriately eliminated.
An image display device according to the present invention includes the above image processing device that performs processing on an image signal input to the display device in an image display device including a display device that displays an image according to an image signal on a display surface. It is characterized by.
In addition, the image display device of the present invention includes a color sensor that detects a color characteristic of an image displayed on the display surface by the display device and a color characteristic of external light irradiated on the display surface. Yes.
According to the present invention, the color characteristics of the image displayed on the display surface by the display device and the color characteristics of the external light irradiated on the display surface are detected by the color sensor. However, it is possible to immediately correct an appropriate image signal in accordance with a change in the use environment.
The image processing method of the present invention is an image processing method for performing processing on the image signal input to a display device that displays an image corresponding to the image signal on a display surface, and the image signal displays a black image. The color of the image displayed on the display surface under the usage environment of the display device when it is a corrected black color that minimizes the color difference from the color of the display surface in a completely non-lighted state or the same color as the corrected black color It is characterized by having a color correction step for correcting the image signal so that the color can be obtained.
According to the present invention, when the image signal is to display a black image, the color of the image displayed on the display surface under the usage environment of the display device is different from the color of the display surface in a completely non-lighted state. The image signal input to the display device is corrected so that the corrected black color that is the smallest or a color that can be viewed with the corrected black color is obtained. For this reason, it is possible to automatically and appropriately correct the coloring of the dark portion of the display image that occurs in accordance with the illumination environment in consideration of the contrast.
In the image processing method of the present invention, when the color correction step is to display a black image, the color of the image displayed on the display surface under the use environment of the display device is determined. The image signal is corrected using a corrected black that minimizes the color difference from the color of the display surface in a completely non-lighted state or a color correction table that corrects the color to be equated with the corrected black.
According to the present invention, a color correction table capable of realizing the above correction is generated under the usage environment of the display device, and the image signal is corrected using the color correction table. For this reason, it is possible to automatically and appropriately correct the coloring of the dark portion of the display image in consideration of the contrast under any lighting environment.
The image processing method according to the present invention further includes a first color characteristic storing step for storing color characteristics of an image displayed on the display surface by the display device, and a color characteristic of external light irradiated on the display surface. The display color gamut that can be displayed on the display surface under the usage environment of the display device is calculated using the second color characteristic storage step and the color characteristics stored in the first and second color characteristic storage steps. A display color gamut calculating step; and a color correction table generating step for generating the color correction table using a calculation result of the display color gamut calculating step.
According to this invention, the display color gamut that can be displayed on the display surface under the usage environment of the display device using the color characteristics of the image displayed on the display surface by the display device and the color characteristics of the external light irradiated on the display surface. And a color correction table is generated using the calculated display color gamut. Therefore, correction can be performed in consideration of not only the illumination environment but also the characteristics of the display device, and the present invention can be applied to display devices having various display characteristics.
Further, the image processing method of the present invention is based on the display color gamut calculated in the display color gamut calculation step, and displays a white image as the image signal under a use environment of the display device. The corrected white color to be displayed on the display surface and the corrected black color or the corrected black color to be displayed on the display surface under the usage environment of the display device when the image signal displays a black image. A correction color calculation step for obtaining a color that can be seen with the display device, wherein the color correction table generation step converts the white color and the black color displayed on the display surface under the use environment of the display device to the correction white color and the correction color, respectively. It is a step of generating the color correction table to be black.
According to the present invention, when the image signal is to display a white image, the corrected white color to be displayed on the display surface under the usage environment of the display device and the image signal is to display a black image. Correction black (or a color that can be equated with correction black) to be displayed on the display surface under the usage environment of the display device is required, and white and black displayed on the display surface under the usage environment of the display device are corrected white. Then, a color correction table for generating corrected black (or a color that can be equated with corrected black) is generated. For this reason, in addition to black, white and gray colors having no saturation are also appropriately eliminated.

It is a block diagram which shows the principal part structure of the image processing apparatus by one Embodiment of this invention, and an image display apparatus. It is a figure for demonstrating the process performed with the image processing apparatus by one Embodiment of this invention. It is a figure for demonstrating the process performed with the image processing apparatus by one Embodiment of this invention. It is a figure which shows the sensory evaluation test result of the image correct | amended with the image processing apparatus by one Embodiment of this invention. 5 is a flowchart illustrating an image processing method according to an embodiment of the present invention. It is a figure which shows the principal part structure of the display apparatus with which the image display apparatus by one Embodiment of this invention is provided.

  Hereinafter, an image processing apparatus, an image display apparatus, and an image processing method according to an embodiment of the present invention will be described in detail with reference to the drawings. The embodiments described below show some aspects of the present invention and do not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention.

  FIG. 1 is a block diagram showing a main configuration of an image processing apparatus and an image display apparatus according to an embodiment of the present invention. Hereinafter, description will be given by taking a projector as an example of the image display device. As shown in FIG. 1, the projector 1 includes an image processing device 10, a display device 20, and a color sensor 30, and projects image light according to an image signal onto a screen 40 (display surface) to thereby screen. An image is displayed on 40. As shown in FIG. 1, it is assumed that the screen 40 is irradiated with external light (for example, illumination light from a fluorescent lamp) in the usage environment of the projector 1 in addition to the image light projected from the projector 1.

  The image processing apparatus 10 outputs an input image signal so that the dark coloration of the image generated according to the illumination environment (external light) is eliminated without deteriorating the contrast of the image displayed on the screen 40. Perform correction processing. The display device 20 projects light (image light) modulated on the basis of the image signal corrected by the image processing device 10 toward the screen 40 to thereby display an image corresponding to the image signal (corrected image signal). It is displayed on the screen 40. Details of the image processing device 10 and the display device 20 will be described later.

  The color sensor 30 is a sensor that detects the color of reflected light from the screen 40, and detects the color characteristics of an image displayed on the screen 40 by the display device 20 and the color characteristics of external light irradiated on the screen 40. Is provided. Even if the usage environment of the projector 1 changes, the color sensor 30 is provided to immediately correct an appropriate image signal according to the change in the usage environment.

  As the color sensor 30, for example, an RGB color sensor in which three types of photodiodes each having sensitivity to red, green, and blue are housed in a package can be used. The screen 40 on which the image light from the display device 20 is projected reflects only light having emission wavelengths (red, green, and blue light) emitted from the display device 20 and reflects light having other wavelengths. Absorbing wavelength selective screens can be used.

Next, the image processing apparatus 10 will be described in detail. First, before describing the details of each unit included in the image processing apparatus 10, the processing performed in the image processing apparatus 10 will be qualitatively described. 2 and 3 are diagrams for explaining processing performed by the image processing apparatus according to the embodiment of the present invention. 2 and 3, a two-dimensional color space is illustrated in which the horizontal axis represents saturation and the vertical axis represents lightness. The color space generally used is a uniform color space such as an L ^* a ^* b ^* color space or an L ^* u ^* v ^* color space. Here, the uniform color space refers to a space designed so that the distance / interval in the color space is similar to the perceptual color distance / interval. The L ^* a ^* b ^* color space, the L ^* u ^* v ^* color space, and the like are three-dimensional color spaces. Color space shown in FIG. 2 and 3, for ease of description, or projected these three-dimensional color space into a two-dimensional, or along a plane including the L ^* axis, saturation and brightness and the shaft It is intended to become.

  In FIG. 2, a region surrounded by straight lines L <b> 1 to L <b> 4 (a rectangular region with diagonal lines) indicates a display color gamut R <b> 1 that can be displayed on the screen 40 by the display device 20 under the usage environment of the projector 1. ing. That is, the projector 1 can display on the screen 40 if the color is within the display color gamut R1 under the usage environment, but cannot display a color outside the display color gamut R1.

  In FIG. 2, a point denoted by reference character W <b> 1 is a point indicating the maximum brightness white (hereinafter, referred to as white color W <b> 1) that can be displayed on the screen 40 by the display device 20. This is a point indicating the blackness of the minimum brightness that can be displayed on the screen 40 (hereinafter referred to as black B1). If the image signal is a 24-bit RGB signal (a signal composed of an 8-bit R signal, an 8-bit G signal, and an 8-bit B signal), white W1 is an RGB signal input to the display device 20. Is a color displayed when (255, 255, 255) is displayed, and black B1 is a color displayed when the RGB signal input to the display device 20 is (0, 0, 0).

  As described above, the color space shown in FIG. 2 has saturation on the horizontal axis and lightness on the vertical axis, and thus has no color (black, white, and colors between black and white). Gray) is normally located on the vertical axis (lightness axis). However, since both the white W1 and the black B1 have a color due to the influence of external light under the usage environment of the projector 1 or the characteristics of the screen 40, the white W1 and the black B1 are as shown in FIG. It will appear at a position off the vertical axis. Further, since the gray color, which is a color between black and white, also has a color, gray appears on a straight line L11 connecting the white W1 and the black B1 in FIG.

  The image processing apparatus 10 performs processing for correcting the white color W1 to the corrected white color W2 and correcting the black color B1 to a color that can be equated with the corrected black color B2 or the corrected black color B2 in order to eliminate the above coloration. Note that the straight line L11 in FIG. 2 is corrected to the straight line L12 by correcting the white color W1 and the black color B1 to the corrected white color W2 and the corrected black color B2, respectively. By performing such correction, in addition to black, white and gray colors having no saturation are also appropriately eliminated.

  Here, the corrected white color W2 is a white color having no saturation located on the vertical axis and the highest brightness that the display device 20 can display on the screen 40. Further, the correction black B2 is a black having the smallest color difference from the color of the screen 40 in the complete lightless state. The completely non-lighted state refers to a state where the display device 20 does not display an image on the screen 40 and the screen 40 is not irradiated with external light. For this reason, the color of the screen 40 in the completely non-lighted state becomes the color of the origin in the color space shown in FIG. 2 (hereinafter, referred to as complete black B0). As described above, the correction black B2 is the black that has the smallest color difference from the complete black B0, and is therefore black at the position of the perpendicular foot that descends from the origin with respect to the straight line L2.

  Here, according to the display color gamut R1 that can be displayed on the screen 40 by the display device 20, as shown in FIG. 3, a perpendicular line dropped from the origin to the straight line L2 intersects with an extension of the straight line L2 (FIG. 3 ( A case where the color is small as shown in a) and a case where the color directly intersects the straight line L2 (a case where the color is high as shown in FIG. 3B) are considered. As described above, since a color outside the display color gamut R1 cannot be displayed on the screen 40, the image processing apparatus 10 does not perform correction in the case shown in FIG. Correct only if indicated.

  As described above, the reason why the black B1 is corrected to the corrected black B2 that minimizes the color difference from the complete black B0 is to avoid a significant deterioration in contrast. That is, if only the coloration of the black B1 is eliminated, the black B1 is located on the vertical axis and has no saturation (the black at the point indicated by the symbol B3 in FIG. 2) as with the white W1. ). However, when such correction is performed, the brightness of black is increased and the contrast is greatly reduced. In the present embodiment, the black color B1 is corrected to the corrected black color B2 that minimizes the color difference from the complete black color B0 in order to appropriately eliminate the coloring while taking the contrast into consideration.

Here, when the color is eliminated by taking the contrast into consideration, it is desirable to correct the black B1 to the corrected black B2 as described above. However, it is possible to visually recognize a decrease in contrast and a change in color. You may make it correct | amend black B1 to the color (color which can be equated with correction | amendment black B2) which cannot be performed. The color that can be equated with the corrected black B2 is a color that can be displayed on the screen 40 by the display device 20, and the color difference from the corrected black B2 in the uniform color space (specifically, the L ^* a ^* b ^* color space, L ^* u ^* v ^{* is a} color having a color difference ΔE in the color space of 1 or less.

  As described above, the uniform color space is a space designed so that the distance / interval in the color space is similar to the perceptual color distance / interval. If it is 1 or less, it is said that the difference in color cannot be recognized. For this reason, you may correct | amend black B1 to the color which can be equated with correction | amendment black B2 whose color difference with correction | amendment black B2 is 1 or less. In addition, the color which can be equated with correction | amendment black B2 is a color in area | region R2 in FIG.3 (b), for example.

  FIG. 4 is a diagram showing sensory evaluation test results of an image corrected by the image processing apparatus according to the embodiment of the present invention. 4A is a diagram showing a sensory evaluation test result when the display device 20 has the display color gamut R1 shown in FIG. 3A, and FIG. 4B is a diagram showing the display device 20 in FIG. It is a figure which shows the sensory evaluation test result in the case of having display color gamut R1 shown to b). In the sensory evaluation test results shown in FIGS. 4A and 4B, the horizontal axis represents the variable δ indicating the correction amount of black B1, and the vertical axis represents the sensory evaluation value.

  The variable δ is a variable that takes a value between “0.0” and “1.0”. The black B1 shown in FIGS. 3A and 3B is corrected to a black color on a straight line connecting the black B1 and the black color at the point labeled B3 according to the value of the variable δ. When the value of the variable δ is “0.0”, the black color B1 is not corrected, and when the value of the variable δ is “1.0”, the black color B1 is blackened at the point denoted by the symbol B3. The The sensory evaluation value is a value obtained by quantitatively evaluating the black coloration and contrast of the image displayed on the screen 4, and the larger the value, the closer the image is to the original image. ing.

  Referring to the sensory evaluation test result shown in FIG. 4A, the sensory evaluation value is the largest when the value of the variable δ is “0.0”, and the sensory evaluation value decreases as the value of the variable δ increases. I can see that On the other hand, referring to the sensory evaluation test result shown in FIG. 4B, when the value of the variable δ is δ1 for correcting the black B1 to the corrected black B2, the sensory evaluation value is the largest, and the variable δ It can be seen that the sensory evaluation value decreases as the value becomes smaller than δ1 and as the value of the variable δ becomes larger than δ1. This is considered that when the value of the variable δ is smaller than δ1, the coloration of black is anxious, and when the value of the variable δ is larger than δ1, the contrast decreases and the sensory evaluation value decreases. It is done. From the above, the image processing apparatus 10 does not perform correction in the case shown in FIG. 3A, and only in the case shown in FIG. 3B, black B1 is corrected black B2 (a color that can be equated with corrected black B2). I am trying to correct it.

  Next, each unit of the image processing apparatus 10 that performs the processing described above will be described in detail. As shown in FIG. 1, the image processing apparatus 10 includes a display device color characteristic storage unit 11 (first color characteristic storage unit), an external light color characteristic storage unit 12 (second color characteristic storage unit), and a display color gamut calculation unit 13. A correction color calculation unit 14, a color correction table generation unit 15, a color correction table storage unit 16, and a color correction unit 17. The image processing apparatus 10 generates a color correction table capable of realizing the color correction described above using the detection result of the color sensor 30, and corrects an input image signal using the color correction table.

  The display device color characteristic storage unit 11 stores the color characteristics of an image displayed on the screen 40 by the display device 20 under the usage environment of the projector 1. Specifically, from the detection results (RGB) detected by the color sensor 30 when the image light having the maximum brightness of red, green, and blue is projected from the display device 20 onto the screen 40 irradiated with external light. XYZ tristimulus values converted by a conversion unit (not shown) are stored. The color characteristic (XYZ tristimulus value) stored in the display device color characteristic storage unit 11 is expressed by the following equation (1).

  The external light color characteristic storage unit 12 stores the color characteristics of the external light irradiated on the screen 40. Specifically, when the image signal displays a black image (for example, when the RGB signal input to the display device 20 is (0, 0, 0)), based on the image signal. The detection result detected by the color sensor 30 when the black image light is projected on the screen irradiated with external light by the display device 20 is stored. The color characteristics (XYZ tristimulus values) stored in the external light color characteristics storage unit 12 are expressed by the following equation (2).

The display color gamut calculation unit 13 can display the display device 20 on the screen 40 under the usage environment of the projector 1 using the color characteristics stored in the display device color characteristic storage unit 11 and the external light color characteristic storage unit 12. The display color gamut of the image is calculated. Specifically, the display color gamut indicated by the XYZ tristimulus values is calculated using an arithmetic expression indicated by the following expression (3). Note that the variables r, g, and b in the following expression (3) are based on values obtained by standardizing image signals (R signal, G signal, and B signal) input to the display device 20, and It is a variable that can take a value between 0 and 1 with the gamma value (γ) indicating the gradation characteristic as an index. Also, the following (3) vector X _L in the formula is a diagram showing the XYZ tristimulus values stored in the ambient light color characteristics storage unit 12 outside light. The XYZ tristimulus value of the external light corresponds to the black B1 in FIG. 2 indicated by the XYZ tristimulus value.

The correction color calculation unit 14 is based on the display color gamut calculated by the display color gamut calculation unit 13, and the correction white W2 and the correction black B2 (or a color that can be equated with the correction black B2) described with reference to FIG. Ask for. Specifically, a brighter color having a chromaticity (x _W , y _W ) specified in advance within the display color gamut of the image that can be displayed on the screen 40 by the display device 20 is set as the corrected white W2, and is shown in FIG. The color having the smallest color difference from the complete black B0 is defined as a corrected black B2.

More specifically, the correction color calculation unit 14 calculates the corrected white W2 by calculating variables α, r _W , g _W , and b _W that satisfy the following expression (4). However, the variables r _W , g _W , and b _W in the following equation (4) have a constraint that the value of at least one variable is “1”.

In addition, the correction color calculation unit 14 satisfies the following expression (5) and is a variable that minimizes the value of ΔE _K that indicates the distance from the complete black B0 in the uniform color space represented by the following expression (6). The corrected black B2 is obtained by calculating β and δ. However, the variable δ in the following equation (5) is a variable that takes a value between 0 and 1 shown in FIG. 4, and the variables r _K0 , g _K0 , and b _K0 are values of at least one variable. Is with a constraint that “0” is “0”. In addition, the vector _XK0 in the following (5) Formula shows the black in the point to which the code | symbol B3 in FIG. 2 was attached | subjected by the XYZ tristimulus value.

The color correction table generation unit 15 corrects white W2 and black B2 displayed on the screen 40 under the usage environment of the projector 1 by the correction color calculation unit 14 using the calculation result of the display color gamut calculation unit 13. A color correction table for correcting to white W2 and correction black B2 is generated. Here, the color correction table is corrected for RGB signals (R _in , G _in , B _in ) that are image signals input to the image processing apparatus 10 and is output from the image processing apparatus 10 to the display apparatus 20. It is a table to which RGB signals (R _out , G _out , B _out ) that are image signals are assigned. Specifically, the color correction table generation unit 15 generates a color correction table using the following equation (7). Note that the variable D in the following equation (7) is a fixed value indicating the maximum value of the image signal.

  The color correction table storage unit 16 stores the color correction table generated by the color correction table generation unit 15. The color correction unit 17 reads the color correction table stored in the color correction table storage unit 16 and displays the read color correction when displaying an image according to the image signal input to the image processing device 10 on the display device 20. The image signal is corrected using the table.

  Next, the operation of the projector 1 having the above configuration will be described. FIG. 5 is a flowchart illustrating an image processing method according to an embodiment of the present invention. The process of the flowchart illustrated in FIG. 5 is started, for example, when the user turns on the power of the projector 1 or when the user gives an instruction for color correction to the projector 1 in a state where the power is turned on.

  When the processing of the flowchart shown in FIG. 5 is started, first, processing for acquiring the color characteristics of the display device 20 is performed (step S11: first color characteristics storage step). In this process, the screen 40 irradiated with external light from the display device 20 is sequentially irradiated with red, green, and blue maximum luminance image light, and the reflected light when each image light is irradiated. Are sequentially detected by the color sensor 30. And the detection result of the color sensor 30 is preserve | saved in the display apparatus color characteristic preservation | save part 11 as a color characteristic shown by (1) Formula mentioned above.

  Next, a process of acquiring color characteristics of external light is performed (step S12: second color characteristic storage step). In this processing, black image light is irradiated from the display device 20 to the screen 40 irradiated with external light, and reflected light when the image light is irradiated is detected by the color sensor 30. And the detection result of the color sensor 30 is preserve | saved in the external light color characteristic preservation | save part 12 as a color characteristic shown by (2) Formula mentioned above.

  When the process of acquiring the above color characteristics is completed, the display color gamut of the image that can be displayed on the screen 40 by the display device 20 under the usage environment of the projector 1 is calculated (step S13: display color gamut calculation step). Specifically, the color characteristics stored in the display device color characteristic storage unit 11 and the external light color characteristic storage unit 12 are read out, and the display color gamut calculation unit 13 calculates the arithmetic expression represented by the above-described equation (3). The display color gamut indicated by the XYZ tristimulus values is calculated.

Next, based on the display color gamut calculated by the display color gamut calculation unit 13, the process of calculating the corrected white color W2 (step S14: correction color calculation step) and the color that can be viewed with the corrected black color B2 (or the corrected black color B2) ) (Step S15 correction color calculation step) is sequentially performed. Specifically, in the process of calculating the corrected white W2, the correction color calculation unit 14 changes the variables α, r _W , g _W , and b _W that satisfy the above-described expression (4) into the variables r _W , g _W , and b _W. The corrected white color W2 is obtained by calculating under the constraint that at least one of the values is “1”.

Further, in the process of calculating the corrected black B2, the positive color calculation unit 14 satisfies the above-described equation (5) and ΔE indicating the distance from the complete black B0 in the uniform color space represented by the above-described equation (6). _The corrected black B2 is obtained by calculating the variables β and δ that minimize the value of _K. However, the variables r _K0 , g _K0 , and b _K0 in the equation (5) have a constraint that at least one value is “0”.

When the corrected white W2 and the corrected black B2 are obtained, a process of generating a color correction table for correcting the white W2 and the black B2 displayed on the screen 40 in the usage environment of the projector 1 to the corrected white W2 and the corrected black B2. Is performed (step S16: color correction table generation step). In this process, the color correction table generation unit 15 uses the corrected white color W2 and the corrected black color B2 obtained in steps S15 and S16 and the above-described equation (7) to input an image signal ( R _in , G _in , B _in ) and an image signal (R _out , G _out , B _out ) output from the image processing device 10 to the display device 20 are generated. The generated color correction table is stored in the color correction table storage unit 16.

  Next, the color correction table stored in the color correction table storage unit 16 is read and applied to the color correction unit 17 (step S17). By applying the color correction table to the color correction unit 17 by this processing, correction processing based on the color correction table in the color correction unit 17 becomes possible. In a state where the color correction table is not applied to the color correction unit 17, the image signal input to the image processing device 10 is output to the display device 20 as it is without any correction.

When the above processing is completed, the color correction unit 17 performs processing for inputting an image signal (step S18), and then corrects the image signal subjected to the input processing using the color conversion table applied in step S17. Processing is performed (step S19: color correction step). That is, the above-described step S18 (7) image signals in Formula _{(R in, G in, B} in) process of inputting is performed, the image signal in step _{S19 (R in, G in,} B in) Is corrected to an image signal (R _out , G _out , B _out ) using a color correction table.

The image signals (R _out , G _out , B _out ) corrected by the color correction unit 17 are output to the display device 20, and image light corresponding to the corrected image signals is projected onto the screen 40. An image is displayed on the screen 40 (step S20). Since the image displayed on the screen 40 is based on the image signal corrected using the color correction table, the colors originally displayed as white W2 and black B2 under the usage environment of the projector 1 are used. Are corrected to the corrected white color W2 and the corrected black color B2, respectively, and displayed on the screen 40. Thereby, in addition to black, white and gray coloring without saturation are also appropriately eliminated.

  When there is an image signal input to the image processing apparatus 10 (when step S21 is “YES”), the processes of steps S18 to S20 are repeated. On the other hand, when there is no image signal input to the image processing apparatus 10 (when step S21 is “NO”), the series of processes shown in FIG. 5 ends. As described above, in this embodiment, a color correction table that can eliminate the coloring of the dark portion without reducing the contrast of the image displayed on the screen 40 is created, and the image corrected using the color correction table is created. The display device 20 displays an image according to the signal.

  Here, since the color correction table is created according to the illumination environment (external light applied to the screen 40), the color correction table is automatically added with the contrast of the coloring of the dark portion of the display image under any illumination environment. Can be corrected appropriately and appropriately. Further, since the color correction table is generated using the display color gamut obtained from the color characteristics of the image displayed on the screen 40 by the display device 20 and the color characteristics of the external light irradiated on the screen 40, only the lighting environment is used. In addition, correction can be performed in consideration of the characteristics of the display device 20, and the present invention can be applied to display devices having various display characteristics. Here, since the color characteristic is detected using the color sensor 30, even if the usage environment of the projector 1 changes, an appropriate correction of the image signal corresponding to the change in the usage environment is immediately performed. be able to.

  Next, the display device 20 will be described in detail. FIG. 6 is a diagram showing a main configuration of a display device included in the image display device according to the embodiment of the present invention. 6 illustrates an example in which the display device 20 is configured by a so-called three-plate type liquid crystal projector. However, the display device included in the image display device according to the present invention is configured by a so-called three-plate type liquid crystal projector. It is not limited to things.

  As shown in FIG. 6, the display device 20 includes a light source 51, integrator lenses 52 and 53, a polarization conversion element 54, a superimposing lens 55, an R dichroic mirror 56R, a G dichroic mirror 56G, a reflection mirror 57, and an R field lens 58R. , A G field lens 58G, an R liquid crystal panel 59R, a G liquid crystal panel 59G, a B liquid crystal panel 59B, a relay optical system 60, a cross dichroic prism 61, and a projection lens 62. The liquid crystal panels used as the R liquid crystal panel 59R, the G liquid crystal panel 59G, and the B liquid crystal panel 59B are transmissive liquid crystal display devices. The relay optical system 60 includes relay lenses 71 to 73 and reflection mirrors 74 and 75.

  The light source 51 is composed of, for example, an ultra-high pressure mercury lamp, and emits at least R component light, G component light, and B component light. The integrator lens 52 has a plurality of small lenses for dividing the light from the light source 51 into a plurality of partial lights. The integrator lens 53 has a plurality of small lenses corresponding to the plurality of small lenses of the integrator lens 52. These integrator lenses 53 are provided to make the illuminance of light emitted from the light source 51 uniform.

  The polarization conversion element 54 has a polarization beam splitter array and a λ / 2 plate, and converts light from the light source 51 into substantially one type of polarized light. The polarization beam splitter array has a structure in which a polarization separation film that separates partial light divided by the integrator lens 52 into p-polarization and s-polarization, and a reflection film that changes the direction of light from the polarization separation film are alternately arranged. Have. The polarization direction of the two types of polarized light separated by the polarization separation film is aligned by the λ / 2 plate. Light that has been converted into substantially one type of polarized light by the polarization conversion element 54 is applied to the superimposing lens 55. The superimposing lens 55 superimposes the partial light emitted from the plurality of small lenses of the integrator lens 52 on the liquid crystal panel.

  The light from the superimposing lens 55 enters the R dichroic mirror 56R. The R dichroic mirror 56R reflects R component light and transmits G component and B component light. The light transmitted through the R dichroic mirror 56R enters the G dichroic mirror 56G, and the light reflected by the R dichroic mirror 56R is reflected by the reflection mirror 57 and enters the R field lens 58R. The G dichroic mirror 56G reflects the G component light and transmits the B component light. The light transmitted through the G dichroic mirror 56G enters the relay optical system 60, and the light reflected by the G dichroic mirror 56G enters the G field lens 58G.

  The relay optical system 60 includes relay lenses 71 to 73 in order to minimize the difference between the optical path length of the B component light transmitted through the G dichroic mirror 56G and the optical path lengths of the other R component and G component light. Use to correct the difference in optical path length. The light transmitted through the relay lens 71 is reflected by the reflection mirror 74 and enters the relay lens 144. The light transmitted through the relay lens 72 is reflected by the reflection mirror 75 and enters the relay lens 72. The light transmitted through the relay lens 73 is applied to the B liquid crystal panel 59B.

On the other hand, the light incident on the R field lens 58R is converted into parallel light and irradiated onto the R liquid crystal panel 59R. The light applied to the G field lens 58G is converted into parallel light and is incident on the G liquid crystal panel 59G. The R liquid crystal panel 59R, the G liquid crystal panel 59G, and the B liquid crystal panel 59B each function as a light modulation element, and output image signals (R _out , G _out , B) output from the image processing apparatus 10 shown in FIG. _out )), the transmittance (passage rate, modulation rate) changes.

Therefore, light irradiated on the R liquid crystal panel 59R is modulated based on image signals R _out, the light emitted to the liquid crystal panel 59G for G is modulated on the basis of an image signal G _out, the liquid crystal panel 59B for B Is modulated based on the image signal _Bout . The light modulated by the R liquid crystal panel 59R, the G liquid crystal panel 59G, and the B liquid crystal panel 59B is incident on the cross dichroic prism 61, respectively.

  Here, the R liquid crystal panel 59R, the G liquid crystal panel 59G, and the B liquid crystal panel 59B have the same configuration. Each liquid crystal panel is a liquid crystal, which is an electro-optical material, sealed in a pair of transparent glass substrates. For example, a polysilicon thin film transistor is used as a switching element, and the transmittance of each color light corresponding to the image signal of each sub-pixel. Modulate. In this embodiment, a liquid crystal panel as a light modulation element is provided for each color component constituting one pixel, and the transmittance of each liquid crystal panel is controlled by an image signal corresponding to a sub pixel.

The cross dichroic prism 61 combines and emits light from the R liquid crystal panel 59R, the G liquid crystal panel 59G, and the B liquid crystal panel 59B. The projection lens 62 is a lens that projects the light (image light) synthesized by the cross dichroic prism 61 toward the screen 40. An image corresponding to the image light projected by the projection lens 62 is displayed on the screen 40. Here, the image signals (R _out , G _out , B _out ) that modulate the transmittance of the R liquid crystal panel 59R, the G liquid crystal panel 59G, and the B liquid crystal panel 59B are imaged using the color correction table described above. This is an image signal corrected by the processing device 10. For this reason, on the screen 40, an image in which the coloring of the dark portion is eliminated in consideration of the contrast is displayed.

  The image processing apparatus, the image display apparatus, and the image processing method according to the embodiment of the present invention have been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. . For example, the following modifications are possible

(1) Although the projector has been described as an example of the image display device in the above embodiment, the present invention is not limited to this. The image display device according to the present invention is applicable to all image display devices that perform image display, such as liquid crystal display devices, plasma display devices, and organic EL display devices.

(2) In the above embodiment, the light valve using a transmissive liquid crystal panel is used as the light modulation element. However, the present invention is not limited to this. For example, DLP (Digital Light Processing) (registered trademark), LCOS (Liquid Crystal On Silicon), or the like may be employed as the light modulation element.

(3) In the above embodiment, a light valve using a so-called three-plate transmissive liquid crystal panel as the light modulation element has been described as an example. However, the present invention is not limited to this. For example, a light valve using a single-plate liquid crystal panel or a transmissive liquid crystal panel of two or four plates or more may be employed.

(4) In the above embodiment, the image processing apparatus 10 illustrated in FIG. 1 has been described by taking an example in which the image signal input to the display apparatus 20 is corrected. However, the present invention is not limited to this. . For example, a program describing a procedure for realizing the image processing method of the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read by a computer so that hardware and software cooperate with each other. Thus, the image signal may be corrected by realizing the image processing method of the present invention.

(5) In the above embodiment, the projector 1 is described as including the image processing device 10, the display device 20, and the color sensor 30, but the present invention is not limited to this. For example, the projector (display device) and the image processing device may be separate.

DESCRIPTION OF SYMBOLS 1 ... Image display apparatus, 10 ... Image processing apparatus, 11 ... Display apparatus color characteristic storage part, 12 ... External light color characteristic storage part, 13 ... Display color gamut calculation part, 14 ... Correction color calculation part, 15 ... Color correction table Generation unit, 16 ... color correction table storage unit, 17 ... color correction unit, 20 ... display device, 30 ... color sensor, 40 ... screen, B0 ... completely black, B1 ... black, B2 ... corrected black, W1 ... white, W2 ... corrected white

Claims (11)

An image processing device that performs processing on the image signal input to a display device that displays an image according to the image signal on a display surface,
When the image signal is to display a black image, the color of the image displayed on the display surface under the usage environment of the display device is not displayed on the display surface by the display device, In addition, the image is so adjusted that the color difference with the color of the display surface in the completely non-lighted state, in which the display surface is not irradiated with external light, is the smallest or the same color as the corrected black. An image processing apparatus comprising a color correction unit for correcting a signal. The image processing apparatus according to claim 1 , wherein the color that can be equated with the corrected black color is a color having a color difference of 1 or less from the corrected black color in a uniform color space. When the image signal is to display a black image, the color of the image displayed on the display surface under the use environment of the display device is the color difference between the color of the display surface in a completely non-lighted state. A color correction table storage unit that stores a correction black to be reduced or a color correction table to be corrected to a color that can be equated with the correction black;
The image processing apparatus according to claim 1 , wherein the color correction unit corrects the image signal using the color correction table stored in the color correction table storage unit. A first color characteristic storage unit that stores color characteristics of an image displayed on the display surface by the display device;
A second color characteristic storage unit for storing color characteristics of external light applied to the display surface;
A display color gamut calculation unit that calculates a display color gamut that can be displayed on the display surface under the use environment of the display device, using the color characteristics stored in the first and second color characteristic storage units;
The image processing apparatus according to claim 3 , further comprising: a color correction table generation unit that generates the color correction table using a calculation result of the display color gamut calculation unit. Based on the display color gamut calculated by the display color gamut calculation unit, when the image signal is to display a white image, a corrected white color to be displayed on the display surface under the use environment of the display device And, when the image signal is to display a black image, a correction color calculation unit that obtains the correction black to be displayed on the display surface under the use environment of the display device or a color that can be equated with the correction black With
The color correction table generation unit, claims and generates the color correction table, respectively white and black is displayed on the display surface in the environment of use to said correcting white and the correction black of the display device Item 5. The image processing apparatus according to Item 4 . In an image display device including a display device that displays an image according to an image signal on a display surface,
An image display device comprising the image processing device according to claim 1, which performs processing on an image signal input to the display device. The image display device according to claim 6, further comprising a color sensor that detects a color characteristic of an image displayed on the display surface by the display device and a color characteristic of external light irradiated on the display surface. An image processing method for performing processing on the image signal input to a display device that displays an image according to the image signal on a display surface,
When the image signal is to display a black image, the color of the image displayed on the display surface under the usage environment of the display device is not displayed on the display surface by the display device, In addition, the image is so adjusted that the color difference with the color of the display surface in the completely non-lighted state, in which the display surface is not irradiated with external light, is the smallest or the same color as the corrected black. An image processing method comprising a color correction step for correcting a signal. In the color correction step, when the image signal is to display a black image, the color of the image displayed on the display surface under the use environment of the display device is changed to the color of the display surface in a completely non-lighted state. 9. The image processing method according to claim 8, wherein the image signal is corrected using a corrected black that minimizes a color difference from the color or a color correction table that corrects the color to be equated with the corrected black. A first color characteristic storing step of storing color characteristics of an image displayed on the display surface by the display device;
A second color characteristic storing step for storing color characteristics of external light applied to the display surface;
A display color gamut calculation step of calculating a display color gamut that can be displayed on the display surface under the use environment of the display device, using the color characteristics stored in the first and second color characteristic storage steps;
The image processing method according to claim 9 , further comprising: a color correction table generation step of generating the color correction table using a calculation result of the display color gamut calculation step. Based on the display color gamut calculated in the display color gamut calculation step, when the image signal is to display a white image, a corrected white color to be displayed on the display surface under the use environment of the display device And a correction color calculating step for obtaining the corrected black to be displayed on the display surface under the use environment of the display device or a color that can be equated with the corrected black when the image signal displays a black image Have
The color correction table generation step is a step of generating the color correction table that changes the white color and the black color displayed on the display surface under the use environment of the display device to the corrected white color and the corrected black color, respectively. The image processing method according to claim 10 .

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