JP6362468B2 - Gradation conversion characteristic / shading correction value calculation method, program, apparatus, and image display apparatus - Google Patents

Description

  The present invention relates to an apparatus and method used for correcting luminance unevenness and color unevenness, that is, shading, of an image displayed by an image projection apparatus or a direct-view display apparatus.

  As a method for automatically correcting shading including luminance unevenness and color unevenness of an image displayed by an image projection apparatus (hereinafter referred to as a projector) or a direct-view display device (hereinafter referred to as a direct-view display), the following is possible. is there.

  For example, Patent Document 1 discloses a method for suppressing shading of a display image using a captured image obtained by an imaging device that captures a display image by a projector or a direct-view display. Patent Document 2 discloses a method for correcting particularly shading in a display image using a captured image obtained from an imaging device that captured a display image by a projector.

JP 2011-150349 A JP 2005-017715 A

  However, in the methods disclosed in Patent Documents 1 and 2, an object is installed between a display surface on which a display image is displayed and an imaging device that captures the display image. It is not a method that considers even the case where an object is reflected. For example, a measuring device that can measure chromaticity such as a color illuminometer is arranged in front of the display surface (on the imaging device side), and a method of setting gamma characteristics using the chromaticity of the display image measured by this measuring device. In this case, a measuring instrument as an object appears in the captured image. In addition, when a measuring instrument is arranged behind a hole formed in a projection surface that is a display surface of a projector, the measuring instrument as an object is reflected in the captured image.

  In the method disclosed in Patent Document 1, a bandpass filter is applied to the entire captured image obtained by the imaging device. Therefore, if a filter with such an intensity that an object disappears from the captured image is used, shading from the captured image is performed. Even information about is lost. As a result, it becomes impossible to generate a correction value for favorably correcting the shading of the display image from the captured image. In addition, if the filter strength is weak, a correction value is generated corresponding to the object remaining in the captured image. Therefore, if this correction value is applied to the corresponding image portion in the display image, unnecessary correction is strongly applied. Become.

  A correction circuit that performs shading correction is generally configured to have a resolution that is considerably lower than the resolution of a light modulation element (such as a liquid crystal panel or a digital micromirror device <DMD>) that modulates light in a projector. For this reason, the resolution of the correction circuit is adjusted to the resolution of the light modulation element by interpolation processing. When a display image including a high frequency part is corrected by such a correction circuit, the correction of the high frequency part becomes insufficient, and the low frequency part is pulled by the object, and the color is reversed. An unintended color may be generated.

  Further, in the method disclosed in Patent Document 2, the same problem occurs when an object is reflected in a captured image.

  The present invention can obtain a correction value for satisfactorily correcting shading for a display image even when a measuring device for measuring chromaticity is reflected in the captured image obtained by capturing the display image. An apparatus and method are provided.

  A gradation conversion characteristic / shading correction value calculation method as one aspect of the present invention calculates a gradation conversion characteristic for converting a gradation of an input image signal into a gradation of a display image in an image display device, and A correction value for performing shading correction in the image display device is calculated using a captured image acquired by photographing the display image displayed on the display device with the imaging device. The method calculates the gradation conversion characteristics for obtaining the target chromaticity of the display image using chromaticity information obtained by measuring the chromaticity of the display image by the chromaticity measuring means, and the image display device A first captured image is acquired from the imaging device that captured the displayed first display image, and mapping from the imaging coordinate system of the imaging device to the shading correction coordinate system of the image display device is performed using the first captured image. A first mapping relationship is obtained, and a second captured image is obtained from an imaging device that has captured a second display image displayed by the image display device with gradations set based on the gradation conversion characteristics. The second part is obtained by detecting and removing the part corresponding to the chromaticity measuring means that is acquired and reflected in the second photographed image from the first mapping relation, or by removing the part specified by the user. For the second captured image The first gradation value, which is a part of the shading correction coordinate system, is obtained by performing mapping conversion using the mapping relationship of the two, and the gradation value is obtained by the mapping conversion in the shading correction coordinate system. A second gradation value which is a gradation value of an unexisting portion is obtained by an interpolation process using the first gradation value, and a correction value is calculated using the first and second gradation values. To do.

  A gradation conversion characteristic / shading correction value calculation method according to another aspect of the present invention calculates a gradation conversion characteristic for converting a gradation of an input image signal into a gradation of a display image in an image display apparatus. Then, a correction value for performing shading correction in the image display device is calculated using a captured image obtained by photographing the display image displayed by the image display device with the imaging device. The method calculates a gradation conversion characteristic for obtaining a target chromaticity of a display image using chromaticity information obtained by measuring the chromaticity of a display image by a chromaticity measuring unit, and displays it by an image display device. A first captured image is acquired from the imaging device that captured the first display image, and a mapping of the imaging coordinate system of the imaging device to the shading correction coordinate system of the image display device is performed using the first captured image. A first mapping relationship indicating the relationship is obtained, and a second captured image is obtained from an imaging device that has captured the second display image displayed by the image display device with gradations set based on the gradation conversion characteristics. Then, by detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship, or by removing the portion designated by the user, the second The mapping relationship is obtained, and the second is obtained for the second photographed image. Mapping conversion using mapping relation is performed to obtain a partial gradation value of the shading correction coordinate system, a first correction value which is a partial correction value of the shading correction coordinate system is obtained from the gradation value, and shading is performed. A second correction value, which is a correction value for a portion of the correction coordinate system in which a gradation value cannot be obtained by the mapping conversion, is obtained by interpolation processing using the first correction value.

  Note that a gradation conversion characteristic / shading correction value calculation program as a computer program for causing a computer to execute the gradation conversion characteristic / shading correction value calculation method also constitutes another aspect of the present invention.

  A gradation conversion characteristic / shading correction value calculation apparatus according to another aspect of the present invention calculates a gradation conversion characteristic for converting a gradation of an input image signal into a gradation of a display image in an image display apparatus. In addition, a correction value for performing shading correction in the image display device is calculated using a captured image obtained by photographing the display image displayed on the image display device with the imaging device. The calculation device includes means for calculating a gradation conversion characteristic for obtaining a target chromaticity of the display image using chromaticity information obtained by measuring the chromaticity of the display image by the chromaticity measuring means, and an image display Means for acquiring a first captured image from an imaging device that captured the first display image displayed by the device, and shading correction coordinates of the image display device from the imaging coordinate system of the imaging device using the first captured image Means for obtaining a first mapping relationship indicating the relationship of mapping to the system, and an imaging device that captures a second display image displayed on the image display device with gradations set based on the gradation conversion characteristics. Means for acquiring the second photographed image, and detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship or the user specified by the user By removing the part, the second mapping function Means for obtaining a first gradation value which is a part of the shading correction coordinate system by performing mapping conversion using the second mapping relationship on the second photographed image; Means for obtaining a second gradation value, which is a gradation value of a portion where a gradation value cannot be obtained by the mapping conversion in the shading correction coordinate system, by an interpolation process using the first gradation value; And means for calculating a correction value using the second gradation value.

  A gradation conversion characteristic / shading correction value calculation apparatus according to another aspect of the present invention calculates a gradation conversion characteristic for converting a gradation of an input image signal into a gradation of a display image in an image display apparatus. In addition, a correction value for performing shading correction in the image display device is calculated using a captured image obtained by photographing the display image displayed on the image display device with the imaging device. The calculation device includes means for calculating a gradation conversion characteristic for obtaining a target chromaticity of the display image using chromaticity information obtained by measuring the chromaticity of the display image by the chromaticity measuring means, and an image display Means for acquiring a first captured image from an imaging device that captured the first display image displayed by the device, and shading correction coordinates of the image display device from the imaging coordinate system of the imaging device using the first captured image Means for obtaining a first mapping relationship indicating the relationship of mapping to the system, and an imaging device that captures a second display image displayed on the image display device with gradations set based on the gradation conversion characteristics. Means for acquiring the second photographed image, and detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship or the user specified by the user By removing the part, the second mapping function Means for calculating a partial gradation value of the shading correction coordinate system by performing mapping conversion using the second mapping relation on the second photographed image, and shading correction coordinates from the gradation value. Means for obtaining a first correction value, which is a partial correction value of the system, and a second correction value, which is a correction value for a portion of the shading correction coordinate system for which no gradation value is obtained by the mapping conversion, And a means for obtaining by interpolation processing using the correction value.

  An image display apparatus that projects and displays a display image on a projection surface, and includes an imaging apparatus that captures the display image and the gradation conversion characteristic / shading correction value calculation apparatus. It constitutes another aspect of the invention.

  According to the present invention, it is possible to obtain a correction value for satisfactorily correcting shading for a display image even when the chromaticity measuring means is reflected in the captured image obtained by capturing the display image.

FIG. 3 is a diagram illustrating an arrangement of a gradation conversion characteristic / shading correction value calculation device, a projector, a camera, a screen, and a color illuminance meter according to the first embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration of the projector according to the first embodiment. FIG. 6 is a diagram illustrating a plurality of shading correction planes and representative points on each shading correction plane in the first embodiment. The figure which shows the image which set the shading correction value to the interpolation process which calculates the shading correction value of the correction point in Example 1, and a correction point (3, 3). FIG. 6 is a diagram illustrating a projection pattern in which different shading correction values are set for each of 1, 2, 4, or 8 pixel rows in the first embodiment. FIG. 3 is a diagram illustrating a projection pattern in which different shading correction values are set for each 1, 2, 4, or 8 pixel row in the first embodiment. 5 is a flowchart illustrating processing of the calculation apparatus according to the first embodiment. The figure which shows the measurement result (chromaticity information) of a color illuminometer in Example 1. FIG. FIG. 6 is a diagram illustrating an interpolation result of chromaticity information in the first embodiment. FIG. 6 is a diagram illustrating an example of a correction value calculation photographed image according to the first embodiment. FIG. 6 is a diagram illustrating a gradation distribution (before and after interpolation) of a correction value calculation photographed image according to the first embodiment. The figure which shows the guide which displays the estimation object area | region which interpolates a gradation in Example 2 of this invention. FIG. 10 is a diagram illustrating an arrangement of a gradation conversion characteristic / shading correction value calculation device, a projector, a camera, a screen, and a color illuminometer in a modification of the second embodiment. FIG. 10 is a diagram illustrating gradation distributions before and after gradation interpolation of an estimation target area in the second embodiment. FIG. 10 is a diagram illustrating tone distributions before and after tone interpolation of an estimation target region in a modification of Example 2; 10 is a flowchart showing processing of a gradation conversion characteristic / shading correction value calculation apparatus according to a third embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  1A and 1B show an image projection apparatus (hereinafter referred to as a projector) 101 as an image display apparatus and a gradation conversion characteristic / shading correction value calculation apparatus (hereinafter simply referred to as a first embodiment) of the present invention. A calculation device) 105 and an imaging device (hereinafter referred to as a camera) 104 are shown. The figure also shows a screen S as a projection surface (display surface) and a color illuminance meter 103 as chromaticity measuring means arranged on the back side of a hole 106 formed in the center of the screen S. These projector 101 to color illuminance meter 103 constitute an image projection system.

The projector 101 drives a light modulation element, which will be described later, according to the input video signal (input image signal), and projects the light modulated by the light modulation element onto the screen S, thereby generating a projection image 107 as a display image. indicate. The color illuminance meter 103 measures the chromaticity and illuminance at the center of the projected image 107 projected on the screen S. The camera 104 captures and captures a shooting range (view angle) including the projected image 107 on the screen S. Generate an image.

  The calculation device 105 is configured by a personal computer, and acquires chromaticity information and illuminance information obtained by measurement from the color illuminance meter 103. The calculation device 105 uses the chromaticity information to determine a gradation conversion characteristic for converting the input gradation, which is the gradation (luminance) of the input video signal, into a projection image gradation, in other words, the input gradation. A gamma correction characteristic for converting to a gradation corresponding to a gradation characteristic of a light modulation panel described later is calculated. In addition, the calculation device 105 calculates a correction value (hereinafter referred to as a shading correction value) for correcting shading including luminance unevenness and color unevenness included in the projection image 107 using the captured image acquired from the camera 104.

  As shown in the figure, in order to calculate the shading correction value, it is necessary to capture the projection image projected on the screen S by the imaging device 104. On the other hand, in order to calculate the gamma characteristic, the color illuminance meter 103 must be used, and the projection image 107 projected from the projector must be received by the color illuminance meter 103. For this reason, as shown in the figure, a hole 106 is formed in the screen S, and the light receiving part (sensor part) 103a of the color illuminance meter 103 arranged on the back side of the screen S is exposed from the hole 106. The color illuminance meter 103 may be disposed in front of the screen S (between the screen S and the camera 104). However, in these cases, since the color illuminance meter 103 is reflected in the captured image obtained by the camera 104, even if the captured image is used, the shading of the projected image is improved in the portion where the color illuminance meter 103 is reflected. A correctable shading correction value cannot be calculated.

  For this reason, in this embodiment, when the shading correction value is calculated, the shading correction value of the portion corresponding to the color illuminance meter 103 reflected in the photographed image is estimated (interpolated). Accordingly, it is possible to calculate a shading correction value that can satisfactorily correct the shading of the projection image without removing the color illuminance meter 103 (saving the trouble of removing), that is, efficiently and in a short time.

  In this embodiment, the calculation device 105, the camera 102, and the projector 101 are configured as independent devices. However, these may be configured as an integrated apparatus (projector).

  FIG. 2 shows the configuration of the projector 101. The projector 101 projects a specific image, which will be described later, in accordance with control from the correction value calculation device 105 as a function related to shading correction. Further, as the same function, the projector 101 writes the shading correction value in the shading correction circuit 201 for red (R), the shading correction circuit 202 for green (G), and the shading correction circuit 203 for blue (B). Further, initial shading correction values of these shading correction circuits 201 to 203 are stored.

  Each of the shading correction circuits 201 to 203 has a gradation value (hereinafter referred to as an input gradation value) of a pixel of each of RGB images (video signals) input thereto and a pixel position (hereinafter referred to as an input gradation value) having the input gradation value. The shading correction value for each RGB is calculated from the above. At this time, an interpolation process using a shading correction value at a representative point held in advance (hereinafter referred to as a representative point) is performed to calculate a shading correction value at a point other than the representative point. The representative point where the shading correction value is provided and the other points are collectively referred to as a correction point. The representative shading correction value at the representative point is calculated for the input tone value of the representative point among the correction points, and the interpolation processing is performed for the input tone value of the point other than the representative point among the correction points. Each shading correction value is added.

  In this way, each shading correction circuit does not hold shading correction values for all points in advance, but holds shading correction values at a predetermined number of representative points, and uses them to perform shading correction at other correction points. Calculate the value. The representative point and the shading correction value there are stored in a volatile area called a register, and the shading correction value can be written to and read from the register via the bus.

  Each of the R gamma correction circuit 204, the G gamma correction circuit 205, and the B gamma correction circuit 206 stores the gradation values input thereto in the form of a one-dimensional lookup table (1DLUT). The tone value is converted according to the gamma correction characteristic. Each gamma correction circuit has a 1DLUT in a register, and can read or rewrite the 1DLUT information via a bus.

  Each of the R light modulation panel 207, the G light modulation panel 208, and the B light modulation panel 209 as a light modulation element has a plurality of pixels, and modulates light from a light source (not shown) for each pixel. . As the light modulation panel, a transmissive liquid crystal panel, a reflective liquid crystal panel, DMD, or the like is used. The light is modulated by changing the transmittance in the transmissive liquid crystal panel, changing the reflectance in the reflective liquid crystal panel, and changing the ON duty ratio in the DMD. The light modulated by these light modulation panels 207 to 209 is projected onto the projection surface S via a projection optical system (not shown). In the following description, a case where a reflective liquid crystal panel is used as the light modulation panels 207 to 209 will be described.

  The video processing circuit 210 converts a video signal input from a video input terminal (not shown) into RGB gradation values. The video processing circuit 210 includes a raster generation circuit 211. The raster generation circuit 211 can generate a raster image as a specific image having an arbitrary gradation in each of RGB and output it from the video processing circuit 210.

  The information recording circuit 212 sets the gradation of the light modulation panels 207 to 209, that is, the reflectance (hereinafter referred to as panel reflectance) to a predetermined value such as linear with respect to the gradation values input to the gamma correction circuits 204 to 206. The 1DLUT of the gamma correction characteristic for changing the relationship is stored. The information recording circuit 212 also stores R, G, and B shading correction values calculated by the calculation device 105. These shading correction values are set in each of the R, G, and B shading correction circuits 201 to 203 when the projector 101 is activated.

  The communication circuit 213 communicates commands when controlling the projector 101 from the correction value calculation device 105. Commands from the correction value calculation device 105 to the projector 101 include a raster gradation setting command, a gamma setting command, a shading correction value write command, an initial shading correction value rewrite command, and the like. The raster gradation setting command is a command for setting RGB gradations to the raster generation circuit 211 and causing the video processing circuit 210 to output a raster image having the gradations. The gamma setting command is a command for setting the 1DLUT recorded in the information recording circuit 212 to the gamma correction circuits 204, 205, and 206. The shading correction value write command is a command that causes the shading correction circuits 201, 202, and 203 to write shading correction values. The initial shading correction value rewrite command is a command for rewriting the initial shading correction value stored in the information recording circuit 212 as the initial value of the shading correction value set in the shading correction circuits 201, 202, and 203.

  The control circuit 214 receives the command from the correction value calculation device 105 and performs control for executing processing corresponding to the command. Further, the control circuit 214 reads the initial value of each circuit from the information recording circuit 212 and sets it in each circuit when the projector 101 starts image projection.

  FIG. 3A schematically shows processing in the shading correction circuits 201 to 203. x represents the coordinates of the point in the horizontal direction of the image (video signal), and y represents the coordinates of the point in the vertical direction of the image. Further, the height in FIG. 3A indicates a gradation. The parallelograms shown in the figure indicate shading correction planes arranged in a plurality of specific gradations held in the registers of each shading correction circuit. In each shading correction plane, a shading correction value (hereinafter referred to as a representative shading correction value) is held for each of a predetermined number of representative points that is smaller than the total number of pixels of the image.

  The shading correction value at the correction point other than the representative point in the specific gradation is obtained by interpolation processing using the representative shading correction value at two or more (for example, four) representative points close to the correction point in the specific gradation. Calculated.

  Further, the shading correction value at the correction point in the correction target gradation other than the specific gradation is calculated as follows. First, the shading correction planes of two specific gradations sandwiching the correction target gradation are selected. Next, in each of the two selected shading correction planes, a shading correction value at a point corresponding to the correction point (a representative shading correction value or a shading correction value calculated by interpolation processing on the same plane) is selected. . Then, the shading at the correction point in the correction target gradation is performed by linear interpolation using the two selected shading correction values and the ratio between the two specific gradations that are the gradations of these shading correction values and the correction target gradation. A correction value is calculated.

  Note that for the correction target gradation lower than the shading correction plane of the lowest specific gradation, the shading correction value is obtained by linear interpolation with the shading correction value of the lowest gradation being 0. The same applies to the correction target gradation higher than the shading correction plane of the highest specific gradation.

  FIG. 3B shows one shading correction plane provided in each shading correction circuit. In the figure, the area surrounded by the mesh includes a white part and a gray part. The gray part indicates the effective pixel area of the light modulation panel, and the gray part and the white part are combined. Indicates a region where the shading correction value can be calculated by the shading correction circuit. The white part can be thought of as an extra area that is not necessary for calculating the shading correction value, but in many cases, the representative points are arranged at regular intervals in a mesh shape, so it is not necessarily an integer between the representative points. Double is not an effective pixel area. For this reason, generally, an area wider than the effective pixel area is often prepared as a shading correction area. The mesh-like lines shown here are shown for clearly indicating the representative points, and are not actually displayed on the light modulation panel. Each intersection of meshes is a representative point position.

  In this figure, a total of 192 representative points of 16 horizontal and 12 vertical are provided on one shading correction plane, and the representative shading correction value is held for each representative point. As described above, the shading correction values for correction points other than the representative points on the shading correction plane are calculated by linear interpolation from the representative shading correction values at the four representative points surrounding this correction point.

  FIG. 4A shows shading correction values calculated by linear interpolation from representative shading correction values at four representative points on the shading correction plane.

c _{i, j} , c _{i + 1, j} , c _{i, j + 1} , c _{i + 1, j + 1} are four representative points (i, j), (i + 1, j), (i, j + 1). , (I + 1, j + 1) are representative shading correction values. H indicates the arrangement interval of the representative points in the horizontal direction, and V indicates the arrangement interval of the representative points in the vertical direction. x ′ and y ′ indicate relative points of the correction point with respect to the representative point. The shading correction value at this correction point is

Can be calculated.

FIG. 4B shows a shading correction value for a gradation at an arbitrary correction point. The shading correction value at the correction point on the shading correction plane is obtained by the above-described calculation. In the figure, specific gradations in which a plurality of (here, five) shading correction planes are arranged are p ₁ , p ₂ , p ₃ , p ₄ , and p ₅ , respectively. The shading correction values are c ₁ , c ₂ , c ₃ , c ₄ , and c ₅ . Further, the gradation of the correction point is p, and the gradations of the two shading correction planes sandwiching the gradation p are _pn and _{pn + 1} ( _pn <p < _{pn + 1} ). Further, _{let the} shading correction values obtained from these two shading correction planes be c _n and c _{n + 1} .
At this time, the shading correction value for the correction point is

Is calculated by

  FIG. 4C shows an image after shading correction when a positive shading correction value is set at the correction point (3, 3). This image is a simulation of adding a shading correction value to the correction point (3, 3) of a raster image having a gradation at which the panel reflectivity output from the raster generation circuit 211 is 50%.

  5A to 5E and FIGS. 6A to 6E show shading corrections when the projector 101 projects an image in order to determine the correspondence between the coordinates of the captured image and the correction points. An example of a shading correction value pattern set in the circuit, that is, a projection pattern is shown. The correction value calculation device 105 projects a projection image having these projection patterns on the projector 101, causes the camera 104 to capture the image, and analyzes the captured image. This makes it possible to determine the correspondence between the shooting coordinate system of the camera 104 indicating the coordinates of the captured image and the coordinate system (shading correction coordinate system) of the shading correction circuit indicating the coordinates of the correction point.

  As a method close to this method, a method of calculating a coordinate correspondence from a binary image called a gray code pattern is known. However, in this embodiment, a plurality of projection patterns can be easily displayed by displaying the projection patterns using the already mounted shading correction circuit. It is also possible to project an image that is surely associated with a correction point for which a shading correction value is finally obtained. Furthermore, since the output from the shading correction circuit has a projection pattern that changes gently, the gradation distribution obtained by the background difference directly corresponds to the probability. For this reason, errors can be reduced when analyzing which correction point corresponds to the region. The area that is unclear as the probability can be determined with higher accuracy by calculating the distance from the part that is clearly determined to belong. By using this method, the surface to be projected does not necessarily have to be a flat surface when performing shading correction, and good shading correction can be performed even when projected onto a curved surface or a discontinuous surface. In addition, since the gradation distribution corresponding to the correction point is obtained, even when the color illuminance meter 103 is reflected in the photographed image, the original gradation in the area where the color illuminance meter 103 is reflected is estimated by interpolation processing. It becomes possible to do.

  The flowchart of FIG. 7 shows the flow of processing (gradation conversion characteristics / shading correction value calculation method) performed by the calculation device 105 in this embodiment. The calculation device 105 performs this processing by operating in accordance with a gradation conversion characteristic / shading correction value calculation program as a computer program.

  The overall flow of this process is as follows. First, the calculation device 105 generates information to be given to the gamma correction circuits 204 to 206 and information to be given to the shading correction circuits 201 to 203 from the chromaticity information acquired from the color illuminometer 103 and the captured image acquired from the camera 104. To do. Information given to the gamma correction circuits 204 to 206 is information indicating gamma correction characteristics such as a gamma correction table and a 2.2 characteristic table given according to the setting of the image mode such as the sRGB mode, and is stored in the information recording circuit 212. Is done. As described above, in this embodiment, the gamma correction characteristics are stored by 1DLUT, but may be stored by 3DLUT. Information given to the shading correction circuits 201 to 203 is information on shading correction values for reducing partial coloring on the screen S generated by the light modulation panels 207 to 209 and the optical members in the projector 101, and is an information recording circuit. 212 is stored. Further, the shading correction value includes a value that reduces an error of an actual shading outline with respect to a reference shading outline.

  The outline of the procedure for generating the shading correction value is as follows. First, the correspondence relationship (first mapping relationship) between the projection image 107 and its captured image, that is, the correction point where the shading correction value is set, and the pixels constituting the captured image is analyzed. Next, from the analysis result, the correspondence relationship in the estimation target region that is the region where the color illuminance meter 103 (and the hole 106) is reflected in the photographed image is removed, and the correspondence relationship after the removal (second mapping) Relationship) is used to estimate the gradation value of the correction point in the estimation target area by interpolation processing. Then, a shading correction value to be given to each correction point is calculated from the gradation values of all correction points. Details of this process will be described below.

  In step S702, the calculation apparatus 105 that has started the processing in step S701 causes the projector 101 to generate a raster image with the designated gradation and project the raster image. Then, the calculation device 105 causes the chromatic illuminance meter 103 to measure the chromaticity of the projected raster image, and acquires chromaticity information as a measurement result from the chromatic illuminance meter 103. At this time, conversion by the gamma correction circuits 204 to 206 and the shading correction circuits 201 to 203 is set to be invalid. As a result, a digital value as it is or appropriately bit-shifted is supplied to a panel driver (not shown) for driving each of the light modulation panels 207 to 209. In the present embodiment, the calculation device 105 projects a plurality of raster images while changing gradation values (hereinafter referred to as drive gradations) given to the RGB panel drivers, and acquires chromaticity information of each raster image. To do. At this time, when acquiring the chromaticity information for the drive gradation of one light modulation panel, the drive gradation of the other light modulation panel is set to a predetermined drive gradation (for example, 0). For example, when acquiring chromaticity information from the color illuminance meter 103 for the drive gradation given to the R panel driver, the drive gradation is set to 0 for the G and B panel drivers.

  FIG. 8 shows an example of the chromaticity information acquired in this step. Each panel driver has a 12-bit DAC, and controls the panel reflectivity by converting digital data of gradations 0 to 4095 shown on the horizontal axis into corresponding analog voltages. When a DMD is used as the light modulation panel, it is driven with a duty ratio corresponding to the digital data.

  In FIG. 8, chromaticity information (tristimulus values X, Y, and Z in the XYZ color system) indicated by the vertical axis from the color illuminometer 103 is changed every 128 gradations from gradation 0 to 4095. The example which acquired is shown. However, the gradation 4096 is substituted with the gradation 4095. As described above, when obtaining chromaticity information for the drive gradation of one light modulation panel, the drive gradations of the other light modulation panels are set to zero.

  In step S703, the calculation device 105 uses the chromaticity information (measured chromaticity) obtained from the chromatic illuminance meter 103 for each drive gradation for each light modulation panel in step S702 to obtain the measured chromaticity as desired. A data table indicating gamma correction characteristics for conversion to the target chromaticity is created. In the following description, a data table indicating gamma correction characteristics is referred to as a gamma correction table. These gamma correction tables are stored in the information recording circuit 212.

  Here, the calculation device 105 generates chromaticity information for all drive gradations capable of driving the light modulation panel by performing an interpolation process in the previous step S702. At this time, since the chromaticity information acquired from the color illuminance meter 103 always has an error, it is not a piecewise interpolation using spline interpolation or the like using the acquired chromaticity information, but a smooth operation using an estimation model. It is desirable to perform interpolation. In this embodiment, smooth interpolation is realized by assigning an appropriate weight to the error between the distortion amount and the sampled value. That is, in this embodiment, the evaluation value is

The estimated value that minimizes the evaluation value is used as the interpolated value of the chromaticity information. Note that the interpolation method of chromaticity information is not limited to this.

  FIG. 9 is a graph showing chromaticity information with respect to the drive gradation generated by the interpolation processing in XYZ chromaticity coordinates. The horizontal axis represents the drive gradation of the R light modulation panel, and the vertical axis represents the stimulus value X obtained from the illuminometer.

  In step S703, the calculation device 105 combines the gradation values for realizing the gamma correction characteristic for obtaining the target chromaticity from the response characteristic of the chromaticity information with respect to the driving gradation of the light modulation panel thus obtained. Search for. In this search, if an inverse function of illuminance (Y) with respect to the driving gradation of each light modulation panel is obtained, a rough combination of gradation values can be obtained by a simple matrix operation. By repeating this process, a more accurate combination of gradation values can be obtained. In most cases, sufficiently accurate gamma correction characteristics can be obtained by the solution obtained by this repeated process. When obtaining gamma correction characteristics with higher accuracy, it is possible to search for combinations of gradation values that can be realized in the vicinity of the above-described solution as finely as possible, and use the combination with the least error as the solution.

  After performing the above search discretely for the gamma correction characteristics to be obtained, a final gamma correction table can be created by performing interpolation processing such as spline interpolation. The calculation device 105 writes the created gamma correction table in the information recording circuit 212, and ends step S703.

  In step S704, the calculation apparatus 105 obtains a first mapping relationship that is a correspondence relationship between the shooting coordinate system of the camera 104, that is, the coordinate system of the shot image generated by the camera 104, and the shading correction coordinate system by the shading correction circuit. Perform the process to confirm. Specifically, the calculation device 105 first causes the projector 101 to project a plurality of projection images having the projection patterns shown in FIGS. 5 (A) to (E) and FIGS. 6 (A) to (E). The camera 104 is caused to capture a plurality of projection images. Then, the calculation device 105 acquires a plurality of photographed images (first photographed images) generated by photographing the plurality of projection images from the camera 104. The calculation device 105 also causes the projector 101 to project a projection image having a projection pattern obtained by setting the shading correction values of all correction points to 0, and causes the camera 104 to capture the projected image, thereby correcting the 0 correction value. Get an image. Furthermore, the calculation device 105 causes the projector 101 to project a projection image having a projection pattern obtained by setting the shading correction values of all correction points to a specific value other than 0, and causes the camera 104 to capture the projection image. To obtain a specific correction value image. These 0 correction value image and specific correction value image are also included in the first captured image. The projection pattern and the number thereof vary depending on the resolution of the shading correction circuits 201 to 203.

  The calculation device 105 was obtained by photographing the projection images having the projection patterns shown in FIGS. 5A to 5E and FIGS. 6A to 6E in order to obtain the first mapping relationship. Each pixel value of the captured image is normalized to a value from 0.0 to 1.0 using the 0 correction value image and the specific correction value image. Since the normalized pixel value takes a value close to 0 and a value close to 1, the correspondence between the coordinate system of the captured image (captured pixel position) and the shading correction coordinate system (correction point) is determined from the bit pattern that combines them. A first mapping relationship indicating the relationship can be determined.

  In step S705, the calculation device 105 generates at least one correction value calculation image in which gradation is set based on the gamma correction table created in step S703. Then, the calculation device 105 causes the projector 101 to project the correction value calculation image, and causes the camera 104 to capture the projected correction value calculation image.

  At this time, in step S703, the illuminance (Y) with respect to the drive gradation given to each light modulation panel is clarified. Therefore, the calculation device 105 generates at least one correction value calculation image that is set so that the panel reflectances of the respective light modulation panels are substantially the same, based on the information indicating the relationship between the drive gradation and the illuminance. To be projected on the projector 101. Then, the camera 104 is caused to capture the projected correction value calculation image. When a plurality of correction value calculation images are generated and photographed, the drive gradations in these correction value calculation images are made different. The calculation device 105 acquires a captured image (second captured image: hereinafter referred to as a correction value calculating captured image) from the camera 104.

  Here, the color illuminance meter 103 that has been used since the start of this process is reflected in the correction value calculation captured image acquired from the camera 104. For this reason, as described above, in a portion where the color illuminance meter 103 is reflected in the photographed image, it is not possible to obtain a shading correction value that enables good shading correction.

  FIG. 10 shows an achromatic image as a correction value calculation projection image in a state where the sensor unit of the color illuminance meter is exposed from the hole formed in the screen as shown in FIGS. 1 (A) and 1 (B). A correction value calculation photographed image obtained by projecting and photographing is shown.

  In step S706, the calculation device 105 matches the resolution of the shading correction circuits 201 to 203 based on the first mapping relationship determined in step S704, with respect to the at least one captured image for calculating the correction value acquired in step S705 ( Corresponding). The calculation device 105 performs this conversion independently for each RGB color of the correction value calculation photographic image, and acquires a gradation distribution (luminance distribution) for each color.

  At this time, the number of pixels of the photographed image mapped to each correction point in each shading correction circuit is different. For this reason, the calculation device 105 sets (calculates) a threshold value for the number of pixels mapped to each correction point. If the number of mapping pixels for the correction point is less than or equal to this threshold value, the gradation value at the correction point is calculated by interpolation processing described later.

  On the other hand, when the number of mapping pixels for the correction point is larger than the threshold value, the calculation device 105 calculates the variance (degree of variation) of the gradation values of the mapping pixels. When the variance value is equal to or greater than the predetermined value or greater than the variance value of other portions, the mapping relationship portion for the correction point is removed from the first mapping relationship. As a result, the second mapping relationship in which the mapping relationship of the portion corresponding to the color illuminometer 103 is removed from the first mapping relationship as the estimation target region described above is obtained. Note that a standard deviation may be used as an index indicating the degree of variation in gradation values.

  The calculation device 105 performs mapping conversion on the correction value calculation photographic image (second photographic image) using the second mapping relationship. Thereby, the first gradation value which is the gradation value of the correction point outside the estimation target region (that is, a part of the shading correction coordinate system) is obtained. Further, the calculation device 105 estimates a gradation value (second gradation value) with respect to a correction point in the estimation target region by an interpolation process described later using the first gradation value. In this way, the first and second gradation values, which are gradation values for all correction points, are obtained by mapping conversion or interpolation processing.

  An example of the tone distribution corresponding to the resolution of the shading correction circuit obtained in this way is shown in FIG. This figure shows a gradation distribution in which the gradation value of a portion to be subjected to gradation interpolation is 0, and an estimation target region is included in a portion surrounded by a black circle. After creating this gradation distribution, the gradation value of an area within a predetermined distance from the estimation target area may be obtained by interpolation processing as necessary.

  In FIG. 11A, a portion surrounded by a black line on the peripheral side is a portion where the gradation value corresponding to the correction point of the shading correction circuit cannot be determined. As described above, the gradation value is determined by photographing the reflected light of the projector projection light from the screen with the camera and calculating the gradation value corresponding to the luminance corresponding to the correction point on the shading correction circuit. The However, in general, since the shading correction circuit is intended for correction in an area wider than the area projected from the projector, the gradation values corresponding to all correction points cannot always be determined. For this reason, it is necessary to estimate the portion surrounded by the black line shown on the peripheral side using means such as interpolation, and calculate the gradation value.

  FIG. 11B shows a gradation distribution obtained by performing the interpolation process on the gradation distribution shown in FIG. In the interpolation processing in this embodiment, the evaluation value is

Find an estimate that minimizes. In the above expression, g _{x, y} is a gradation value converted so as to correspond to the resolution of the shading correction circuit, and indicates the gradation value at the coordinates (x, y). _{x and y} indicate estimated values of gradation values at coordinates (x, y). ω is a weighting factor. D1, D2, and D3 indicate a set of pixel regions that are the targets of the respective calculations.

  In this embodiment, the estimated value by interpolation is calculated by the above evaluation formula, but any other interpolation method may be used.

  In step S707, the calculation device 105 calculates a shading correction value for each color from the information of the gradation distribution for each RGB color converted so as to correspond to the resolution of the shading correction circuits 201 to 203 in step S706. A detailed description of the method for calculating the shading correction value is omitted.

  In step S708, the calculation device 105 writes the shading correction value calculated in step S707 into the information recording circuit 212. Then, the calculation device 105 ends this process in step S709.

  According to the present embodiment, an area in which the color illuminance meter 103 is reflected is automatically detected (determined) in a captured image (corrected value calculation captured image) used for calculation of the shading correction value, and the level of the area is determined. The key is estimated by interpolation. Thereby, the gamma correction table and the shading correction value can be calculated continuously without removing the color illuminance meter 103.

  In the first embodiment, a case has been described in which a region for interpolation of gradation (estimation target region) is detected by calculating a dispersion value of the gradation. On the other hand, in Embodiment 2 of the present invention, in order to omit the calculation, the gradation of the area designated by the user is interpolated. The constituent elements of the image projection system are denoted by the same reference numerals as those in the first embodiment.

  FIG. 12A shows an example of a guide displayed in the projection image so as to clearly indicate the estimation target region. On the screen S, 107 is a projection image (raster image) projected by the projector 101, and G is a region for calculating gradation by interpolation (the hole 106 of the screen S in Example 1 and the color exposed inside thereof). The guide which displays the area | region containing the illumination meter 103 is shown. This guide G displays the estimation target area designated by the user before starting the calculation of the gamma correction characteristic and the shading correction value.

  The calculation device 105 outputs information on the estimation target area designated by the user to the projector 101 together with the raster gradation setting command. In the projector 101, the raster generation circuit 211 generates a raster image, and the shading correction circuits 201 to 203 set different shading correction values for the estimation target area and other areas. As a result, the guide G indicating the estimation target area is displayed in the projected raster image.

  FIGS. 13A and 13B show a case where the color illuminance meter 103 is installed in front of the screen S by a support member such as a tripod in the image projection system having the same configuration as that of the first embodiment. In this case, as shown in FIG. 12B, an estimation target area including the color illuminance meter 103 and the support member is designated by the user, and a guide G corresponding to the estimation target area is included in the projection image (raster image) 107. Is displayed.

  In this embodiment, the processing for creating a gamma correction table and the processing for calculating the first and second gradation values using the first and second mapping relationships to calculate the shading correction value are described in the embodiment. Same as 1. 14A shows a gradation distribution before interpolation of the gradation of the estimation target area displayed by the guide G in FIG. 12A, and FIG. 14B shows the level of the estimation target area. The gradation distribution after interpolating the key is shown. FIG. 15A shows the gradation distribution before interpolation of the gradation of the estimation target area displayed by the guide G in FIG. 12B, and FIG. 15B shows the level of the estimation target area. The gradation distribution after interpolating the key is shown.

  As described above, in this embodiment, since the user designates the area where the gradation is interpolated, that is, the area where the color illuminance meter 103 is reflected, the possibility of erroneous detection of the area can be eliminated. .

  In the first and second embodiments, since the chromaticity is measured by the color illuminance meter 103 arranged in the center portion of the projection image and the gamma correction characteristic is adjusted, the shading correction value is not corrected in the center portion of the projection image. The case of calculating a shading correction value such that On the other hand, in the third embodiment of the present invention, a case where the color illuminometer is arranged at a position other than the central portion of the projection image will be described. The constituent elements of the image projection system are denoted by the same reference numerals as those in the first embodiment.

  The flowchart of FIG. 16 shows the flow of processing (gradation conversion characteristics / shading correction value calculation method) performed by the calculation device 105 in this embodiment. In Step S1902, the calculation apparatus 105 that has started the processing in Step S1901 projects a plurality of raster images on the projector 101 and acquires chromaticity information from the color illuminance meter 103 in the same manner as Step S702 in the first embodiment. .

  In step S1903, the calculation apparatus 105 creates a gamma correction table indicating gamma correction characteristics from the chromaticity information acquired in step S1902, and writes the gamma correction table in the information recording circuit 212, as in step S703 of the first embodiment.

  In step S1904, as in step S704 of the first embodiment, the calculation apparatus 105 displays a projection image having the projection patterns illustrated in FIGS. 5A to 5E and FIGS. 6A to 6E on the projector 101. This is projected, and this is photographed by the camera 104 to obtain a photographed image. At the same time, the calculation device 105 acquires chromaticity information from the color illuminance meter 103 and monitors the gradation change due to the projection pattern. Thereby, the relationship between the correction point by the shading correction circuit and the position where the chromaticity is measured by the color illuminance meter 103 (hereinafter referred to as the arrangement position of the color illuminance meter 103) is specified. As will be described later, the calculation device 105 calculates a shading correction value based on the arrangement position of the color illuminance meter 103. As a result, the color illuminance meter 103 can be arranged not only in the central portion of the screen S but also in a free position.

  In step S1905, as in step S705 of the first embodiment, the calculation apparatus 105 causes the projector 101 to project at least one correction value calculation image in which gradation is set based on the gamma correction table created in step S1904. Then, a captured image for correction value calculation is acquired from the camera 104 that captured the image.

  In step S1906, the calculation apparatus 105 converts the correction value calculation photographed image so as to correspond to the resolution of the shading correction circuits 201 to 203, as in step S706 of the first embodiment. In addition, the gradation value of the estimation target area is estimated by interpolation processing.

  In step S1907, the calculation apparatus 105 calculates a shading correction value as in step S707 of the first embodiment. In the present embodiment, the calculation device 105 sets the shading correction value at 0 on the basis of the arrangement position of the color illuminance meter 103 described above. Then, the shading correction value is calculated so that each of the gradations of the plurality of shading correction values is a fixed multiple of the reference shading outline described in the first embodiment.

  More specifically, the calculation device 105 sets the shading correction value at the chromaticity measurement position by the reference illuminance meter 103 to 0 for the gradation distribution of each light modulation panel. Then, the calculation device 105 determines a shading outline at a gradation to be realized from the reference position and a condition that the outline is a fixed multiple of the reference shading outline described above. By the processing so far, the reflectance-based shading correction value of each light modulation panel to be realized in one specific gradation is uniquely determined.

  The calculation device 105 performs the processing of this step also on the gradations of the shading correction planes of other specific gradations. Thereby, the total shading correction value to be given to each shading correction circuit is calculated.

  In step S1908, the calculation apparatus 105 writes the shading correction value calculated in step S1907 in the information recording circuit 212, as in step S708 of the first embodiment. Then, the calculation device 105 ends this process in step S1909.

  According to the present embodiment, the gamma correction table and the shading correction value can be efficiently calculated in a short time even when the color illuminance meter 103 is arranged at an arbitrary position.

  In each of the above embodiments, the first gradation of a part of the shading correction coordinate system (area outside the estimation target area) is performed by performing mapping conversion using the second mapping relation on the correction value calculation photographed image. A value was obtained, and a second gradation value of the estimation target region was obtained by interpolation processing using the first gradation value. However, a shading correction value (first correction value) of a part of the shading correction coordinate system (a region outside the estimation target region) is obtained from the first gradation value, and interpolation processing using this first correction value is performed. A shading correction value (second correction value) for the estimation target region may be obtained.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

101 Projector (image display device)
103 Color Illuminometer 104 Camera (Imaging Device)
105 Gradation conversion characteristic / shading correction value calculation device

Claims (8)

In the image display device, the gradation conversion characteristic for converting the gradation of the input image signal into the gradation of the display image is calculated, and the display image displayed by the image display device is captured by the imaging device and acquired. A gradation conversion characteristic / shading correction value calculation method for calculating a correction value for performing shading correction in the image display device using a captured image,
Calculating the gradation conversion characteristics for obtaining the target chromaticity of the display image using chromaticity information obtained by measuring the chromaticity of the display image by a chromaticity measuring means;
Obtaining a first captured image from the imaging device that captured the first display image displayed by the image display device;
Using the first photographed image, a first mapping relationship indicating a mapping relationship from the photographing coordinate system of the imaging device to the shading correction coordinate system of the image display device is obtained,
Acquiring a second captured image from the imaging device that has captured a second display image displayed by the image display device with gradation set based on the gradation conversion characteristics;
By detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship, or by removing the portion designated by the user. Seeking the mapping relationship of
Mapping conversion using the second mapping relationship is performed on the second captured image to obtain a first gradation value which is a partial gradation value of the shading correction coordinate system;
Obtaining a second gradation value which is a gradation value of a portion of the shading correction coordinate system where the gradation value cannot be obtained by the mapping conversion by an interpolation process using the first gradation value;
A gradation conversion characteristic / shading correction value calculation method, wherein the correction value is calculated using the first and second gradation values. In the image display device, the gradation conversion characteristic for converting the gradation of the input image signal into the gradation of the display image is calculated, and the display image displayed by the image display device is captured by the imaging device and acquired. A gradation conversion characteristic / shading correction value calculation method for calculating a correction value for performing shading correction in the image display device using a captured image,
Calculating the gradation conversion characteristics for obtaining the target chromaticity of the display image using chromaticity information obtained by measuring the chromaticity of the display image by a chromaticity measuring means;
Obtaining a first captured image from the imaging device that captured the first display image displayed by the image display device;
Using the first photographed image, a first mapping relationship indicating a mapping relationship from the photographing coordinate system of the imaging device to the shading correction coordinate system of the image display device is obtained,
Acquiring a second captured image from the imaging device that has captured a second display image displayed by the image display device with gradation set based on the gradation conversion characteristics;
By detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship, or by removing the portion designated by the user. Seeking the mapping relationship of
The second captured image is subjected to mapping conversion using the second mapping relationship to obtain a partial gradation value of the shading correction coordinate system,
Obtaining a first correction value that is a part of the correction value of the shading correction coordinate system from the gradation value;
A second correction value that is the correction value for a portion of the shading correction coordinate system where the gradation value cannot be obtained by the mapping conversion is obtained by an interpolation process using the first correction value. Gradation conversion characteristic / shading correction value calculation method.   The portion corresponding to the chromaticity measuring means is obtained as a portion where the degree of variation in gradation value obtained by mapping conversion using the first mapping relationship is a predetermined value or more or a portion larger than other portions. The gradation conversion characteristic / shading correction value calculation method according to claim 1 or 2. A computer calculates a gradation conversion characteristic for converting a gradation of an input image signal into a gradation of a display image in the image display device, and the imaging image is captured by the imaging device. A gradation conversion characteristic / shading correction value calculation program as a computer program for calculating a correction value for performing shading correction in the image display device using the captured image acquired
In the computer,
Using the chromaticity information obtained by measuring the chromaticity of the display image by chromaticity measuring means, to calculate the gradation conversion characteristics for obtaining the target chromaticity of the display image,
Obtaining a first captured image from the imaging device that captured the first display image displayed by the image display device;
Using the first photographed image, a first mapping relationship indicating a mapping relationship from the photographing coordinate system of the imaging device to the shading correction coordinate system of the image display device is obtained,
A second captured image is acquired from the imaging device that has captured a second display image displayed by the image display device with a gradation set based on the gradation conversion characteristic;
By detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship, or by removing the portion designated by the user. To find the mapping relationship of
Mapping conversion using the second mapping relationship is performed on the second photographed image to obtain a first gradation value which is a partial gradation value of the shading correction coordinate system;
A second gradation value which is a gradation value of a portion of the shading correction coordinate system where the gradation value cannot be obtained by the mapping conversion is obtained by an interpolation process using the first gradation value;
A gradation conversion characteristic / shading correction value calculation program, wherein the correction value is calculated using the first and second gradation values. A computer calculates a gradation conversion characteristic for converting a gradation of an input image signal into a gradation of a display image in the image display device, and the imaging image is captured by the imaging device. A gradation conversion characteristic / shading correction value calculation program as a computer program for calculating a correction value for performing shading correction in the image display device using the captured image acquired
In the computer,
Using the chromaticity information obtained by measuring the chromaticity of the display image by chromaticity measuring means, to calculate the gradation conversion characteristics for obtaining the target chromaticity of the display image,
Obtaining a first captured image from the imaging device that captured the first display image displayed by the image display device;
Using the first photographed image, a first mapping relationship indicating a mapping relationship from the photographing coordinate system of the imaging device to the shading correction coordinate system of the image display device is obtained,
A second captured image is acquired from the imaging device that has captured a second display image displayed by the image display device with a gradation set based on the gradation conversion characteristic;
By detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship, or by removing the portion designated by the user. To find the mapping relationship of
Performing a mapping transformation using the second mapping relationship on the second photographed image to obtain a partial gradation value of the shading correction coordinate system;
A first correction value that is a part of the correction value of the shading correction coordinate system is obtained from the gradation value;
A second correction value that is the correction value for a portion of the shading correction coordinate system in which the gradation value cannot be obtained by the mapping conversion is obtained by an interpolation process using the first correction value. Tone conversion characteristic / shading correction value calculation program. In the image display device, the gradation conversion characteristic for converting the gradation of the input image signal into the gradation of the display image is calculated, and the display image displayed by the image display device is captured by the imaging device and acquired. A gradation conversion characteristic / shading correction value calculation device for calculating a correction value for performing shading correction in the image display device using a captured image,
Means for calculating the gradation conversion characteristics for obtaining target chromaticity of the display image using chromaticity information obtained by measuring chromaticity of the display image by chromaticity measuring means;
Means for acquiring a first photographed image from the imaging device that photographed the first display image displayed by the image display device;
Means for obtaining a first mapping relationship indicating a mapping relationship from a shooting coordinate system of the imaging device to a shading correction coordinate system of the image display device using the first captured image;
Means for acquiring a second photographed image from the imaging device that photographed the second display image displayed by the image display device with gradations set based on the gradation conversion characteristics;
By detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship, or by removing the portion designated by the user. A means for obtaining the mapping relationship of
Means for obtaining a first gradation value which is a partial gradation value of the shading correction coordinate system by performing mapping conversion on the second photographed image using the second mapping relationship;
Means for obtaining a second gradation value, which is a gradation value of a portion where the gradation value cannot be obtained by the mapping conversion, in the shading correction coordinate system by an interpolation process using the first gradation value;
Means for calculating the correction value using the first and second gradation values; and a gradation conversion characteristic / shading correction value calculation device. In the image display device, the gradation conversion characteristic for converting the gradation of the input image signal into the gradation of the display image is calculated, and the display image displayed by the image display device is captured by the imaging device and acquired. A gradation conversion characteristic / shading correction value calculation device for calculating a correction value for performing shading correction in the image display device using a captured image,
Means for calculating the gradation conversion characteristics for obtaining target chromaticity of the display image using chromaticity information obtained by measuring chromaticity of the display image by chromaticity measuring means;
Means for acquiring a first photographed image from the imaging device that photographed the first display image displayed by the image display device;
Means for obtaining a first mapping relationship indicating a mapping relationship from a shooting coordinate system of the imaging device to a shading correction coordinate system of the image display device using the first captured image;
Means for acquiring a second photographed image from the imaging device that photographed the second display image displayed by the image display device with gradations set based on the gradation conversion characteristics;
By detecting and removing a portion corresponding to the chromaticity measuring means reflected in the second photographed image in the first mapping relationship, or by removing the portion designated by the user. A means for obtaining the mapping relationship of
Means for obtaining a partial gradation value of the shading correction coordinate system by performing mapping conversion on the second photographed image using the second mapping relationship;
Means for obtaining a first correction value that is a part of the correction value of the shading correction coordinate system from the gradation value;
Means for obtaining a second correction value, which is the correction value for a portion of the shading correction coordinate system for which the gradation value cannot be obtained by the mapping conversion, by an interpolation process using the first correction value. A gradation conversion characteristic / shading correction value calculation device characterized by An image display device that projects and displays a display image on a projection surface,
An imaging device for capturing the display image;
An image display device comprising the gradation conversion characteristic / shading correction value calculation device according to claim 6.