JP2012010250A - Optical luminance correction apparatus, optical luminance correction method, and optical luminance correction program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical luminance correction apparatus capable of detecting an illumination environment change during content projection by a projector and correcting an output luminance from the projector according to the change so that an RGB value observed by a camera becomes a predetermined luminance value.SOLUTION: The optical luminance correction apparatus for correcting a luminance of an image projected by the projector based on an image acquired by the camera that takes an image projected by the projector comprising: illumination change detection means for detecting a change of illumination onto which the image was projected from the image acquired by the camera and outputting illumination change correction information based on illumination change conditions when the illumination change is detected and projection luminance correction means for correcting the luminance of the image projected by the projector.

Description

  The present invention corrects or adjusts the output value of each pixel projected from the projector in a projector / camera system so that the luminance value of each pixel observed by the camera becomes a predetermined value according to a change in illumination state. The present invention relates to an optical brightness correction device, an optical brightness correction method, and an optical brightness correction program.

  Conventionally, in front projection or rear projection using a projector, there is a problem that the optical luminance on the screen changes when there is a change in the illumination environment surrounding the screen. For example, the brightness of each projected image on the screen is different in a dark room state with no light and in an environment illuminated with a fluorescent lamp or the like. Also, in the actual environment of presentations using slides, when the lighting state changes from the initial state when the slide is projected, the appearance on the screen changes, so the output luminance value from the projector is set according to the brightness of the environment. It is necessary to adjust.

In order to solve such a problem, in the projector / camera system, attention is paid to the correlation between the RGB luminance value from the projector and the RGB luminance value observed by the camera, and this is called a color mixing matrix (Color Mixing Matrix). The RGB output value P = (P _R , P _G , P _B from the projector is used so that the camera observes a predetermined RGB luminance value C = (C _R , C _G , C _B ) using the × 3 matrix V. ) Is known (see, for example, Non-Patent Document 1).

  However, since Non-Patent Document 1 does not consider the influence of ambient light, it is difficult to correct the luminance value from the projector so that a predetermined luminance value can be observed when there is a change in illumination. For such a problem, a method is known in which luminance correction is performed even in a dynamic scene in which the environment of the outside world changes in consideration of ambient light (see, for example, Non-Patent Document 2).

S. K. Nayar, H. Peri, M. D. Grossberg, and P. N. Belhumeur: "A Projection System with Radiometric Compensation for Screen Imperfections", Proc. Of ICCV Workshop on Projector-Camera Systems (PROCAMS), 2003. K. Fujii, MD Grossberg, and SK Nayar: "A Projector-Camera System with Real-Time Photometric Adaptation for Dynamic Environments", Proc. Of IEEE Computer Vision and Pattern Recognition (CVPR), vol.1, pp.814-821 , 2005.

  Since the method of Non-Patent Document 1 is a simple luminance correction model in which the RGB values of the projector and the RGB values observed using the camera are linked by a linear combination, the luminance correction can be performed in real time. . However, since the ambient light is not taken into consideration, there is a problem that when there is a change in illumination in the indoor environment, the luminance cannot be corrected following the change.

  On the other hand, the method of Non-Patent Document 2 assumes that the change in the illumination environment is very small, and can perform luminance correction on the change in the reflection characteristics on the projected target surface, that is, the dynamic scene. . However, as in the method of Non-Patent Document 1, there is no change in the premise that the illumination environment does not change, and when there is an illumination change in the projector projection environment, the output luminance from the projector is corrected following the change. There is a problem that it is difficult to do.

  The present invention has been made in view of such circumstances, and when there is a change in the illumination environment while projecting content from the projector, the change in the illumination environment is detected and the RGB values observed by the camera are detected. An object of the present invention is to provide an optical luminance correction apparatus, an optical luminance correction method, and an optical luminance correction program capable of correcting the output luminance from the projector according to the change so that becomes a predetermined luminance value.

  The present invention is an optical brightness correction device that corrects the brightness of a projection image projected by the projector based on an image obtained by a camera that captures a projection image projected by the projector, and is obtained by the camera. Illumination change detection means for detecting an illumination change in a state in which the projection image is projected from the image and outputting illumination change correction information based on the illumination change situation when the illumination change is detected; and the illumination change Projection luminance correction means for correcting the luminance of the projection image projected by the projector based on correction information.

  The present invention relates to a luminance value of a projected image projected by the projector and a luminance value of an image captured by the camera, and outputs a preliminary correction information for correcting the luminance of the projected image in an initial state. And a projection luminance correction unit correcting the luminance of the projection image based on the prior correction information when the projector is in an initial state.

  The present invention is an optical brightness correction device that corrects the brightness of a projection image projected by the projector based on an image obtained by a camera that captures a projection image projected by the projector, and is obtained by the camera. Illumination change detection means for detecting an illumination change in a state in which the projection image is projected from the image and outputting illumination change correction information based on the illumination change situation when the illumination change is detected; and the illumination change Based on the correction information, the projection brightness correction means for correcting the brightness of the projection image projected by the projector, the brightness value of the projection image projected by the projector and the brightness value of the image captured by the camera are associated with each other. Storage means storing pre-correction information for correcting the brightness of the projected image in the initial state, and the projection brightness Positive means, based on the pre correction information when the projector is in an initial state, and correcting the brightness of the projected image.

  The present invention provides an illumination change detection unit, a projection luminance correction unit, and a correction unit for correcting the luminance of a projection image projected by the projector based on an image obtained by a camera that captures a projection image projected by the projector. An optical brightness correction method in an optical brightness correction apparatus comprising: the illumination change detecting means detects an illumination change in a state where the projection image is projected from the image obtained by the camera, and the illumination change is detected. An illumination change detection step for outputting illumination change correction information based on the illumination change status when detected, and the projection luminance correction means for the projection image projected by the projector based on the illumination change correction information. A projection luminance correction step for correcting the luminance.

  The present invention includes an illumination change detecting unit and a projection luminance correcting unit for correcting the luminance of an image projected by the projector based on an image obtained by a camera that captures a projected image projected by the projector. An optical brightness correction program for causing a computer on an optical brightness correction apparatus to perform an optical brightness correction process, detecting an illumination change in a state in which the projection image is projected from the image obtained by the camera, and An illumination change detection step for outputting illumination change correction information based on the illumination change status when a change is detected, and a projection for correcting the brightness of the projection image projected by the projector based on the illumination change correction information A luminance correction step is performed by the computer.

  According to the present invention, while projecting content onto a screen using a projector, a change in illumination is detected, and an output luminance from the projector is corrected in accordance with the change. Correction becomes possible. Furthermore, even in a multi-projector system that uses multiple projectors to project to the same position, brightness correction that follows illumination changes can be used for each projector, so that high-quality and high-contrast projection images can be maintained. The effect of being able to be obtained.

It is a block diagram which shows the structure of one Embodiment of this invention. It is a flowchart which shows the processing operation of the apparatus shown in FIG. It is a flowchart which shows the detailed processing operation | movement of the prior correction part 8 shown in FIG. It is a flowchart which shows the detailed process operation | movement of the illumination change detection part 7 shown in FIG. It is a flowchart which shows the detailed processing operation of the projection brightness correction | amendment part 4 shown in FIG. It is a block diagram which shows the modification of the apparatus shown in FIG.

  Hereinafter, an optical brightness correction apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, reference numeral 1 denotes a projector that projects and projects an image on a screen or the like. Reference numeral 2 denotes a content database (hereinafter referred to as a content DB) in which content data of images projected by the projector 1 is stored in advance. Reference numeral 3 denotes a reproduction unit that reads out content data to be projected from the content DB 2, converts it into a video signal, and outputs the video signal. Reference numeral 4 denotes a projection luminance correction unit that corrects and outputs the luminance of an image projected by the projector 1 in accordance with a change in illumination with respect to the video signal output from the reproduction unit 3.

  Reference numeral 5 denotes a camera that outputs image data obtained by capturing a projected image projected on a screen or the like. Reference numeral 6 denotes an image input unit for inputting image data output from the camera 1. Reference numeral 7 denotes an illumination change detection that detects whether or not there is an illumination change in the image data input by the image input unit 6, and outputs illumination change correction information based on the detected illumination change state to the projection luminance correction unit 4. Part. Reference numeral 8 indicates that the RGB brightness value of the image projected by the projector 1 and the RGB brightness value observed by the camera are associated with each other, and pre-correction information for correcting the brightness in the initial state is output to the projection brightness correction unit 4. This is a pre-correction unit.

  The projection brightness correction unit 4 corrects the video signal output to the projector 1 based on the illumination change correction information output from the illumination change detection unit 7 and the advance correction information output from the advance correction unit 8. Image data (sample image) input from the camera 5 by the image input unit 6 is used in the precorrection unit 8 or the illumination change detection unit 7. As an example of an image input by the image input unit 6, it is desirable to use an image that is captured without hiding the entire screen. For example, an image taken so that only a screen is captured from a camera installed near the ceiling is used.

  Next, the processing operation of the entire apparatus shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a flowchart showing an operation in which the apparatus shown in FIG. 1 performs optical brightness correction. First, the prior correction unit 8 determines whether or not it is in an initial state (step S1), and if it is in the initial state, performs prior luminance correction processing and outputs the prior correction information to the projection luminance correction unit 4 ( Step S2). When it is not in the initial state, the prior correction unit 8 does not perform the prior luminance correction process. Here, the initial state is a state in which brightness correction should be performed in advance, such as immediately after the projector 1 is turned on or immediately after the setting of the projector 1 is changed.

  Next, the image input unit 6 acquires screen image data obtained by imaging with the camera 5 from the camera 5 (step S <b> 3), and outputs the acquired screen image data to the illumination change detection unit 7. In response to this, the illumination change detection unit 7 detects an illumination change from the screen image data (step S4), and outputs illumination change correction information to the projection luminance correction unit 4.

  Next, the projection luminance correction unit 4 performs illumination correction processing based on the illumination change correction information output from the illumination change detection unit 7 (step S5), and the content video signal output from the reproduction unit 3 is processed. Perform brightness correction. Then, as long as there is content data to be projected, the projection luminance correction unit 4 repeatedly performs the projection luminance correction process (step S7), and ends the processing when there is no content data to be projected.

  Next, with reference to FIG. 3, the detailed processing operation of the pre-correction unit 8 shown in FIG. 1 will be described. The prior correction unit 8 corrects the output luminance from the projector in the initial state. This correction process is a correction required when the lighting environment changes dramatically, for example, when the installation environment of the apparatus is changed indoors. The initial state here refers to the state when the projector 1 is turned on, or the time when the internal setting of the projector is changed, and sets the illumination state as a reference when detecting a change in illumination as an initial value. In addition, parameters necessary for luminance correction in the initial state (hereinafter referred to as correction parameters) are stored.

In order to estimate the correction parameter in the initial state, the conventional technique of Non-Patent Document 1 or Non-Patent Document 2 is used. Here, it is assumed that the screen surface is invariant with time. That is, the scene is static and the dynamic scene is excluded. Furthermore, it is assumed that the luminance value of the image projected from the projector 1 and the luminance value captured by the camera 5 respond linearly. According to Non-Patent Document 1 or Non-Patent Document 2, RGB values P = (P _R , P _G , P _B ) output from the projector 1 and RGB values C = (C _R , C _G , C) observed by the camera. _B ) can be linked by the relationship of the formula (1) and (2).

Here, F = (F _R , F _G , F _B ) is a component of ambient light other than the projector. As correction parameters, the pre-correction unit 8 calculates the 3 × 3 matrix elements of the matrix V and the vector amount of the ambient light F in the equation (2).

According to Non-Patent Document 1 or Non-Patent Document 2, these parameters can be obtained if at least four images are acquired. For example, the luminance values in the observation image by the camera 5 when the luminance values of all the pixels are output from the projector 1 with P ₀ = (P _r , P _g , P _b ) are represented by C ₀ = (C _r , C _g , C _b ). Next, the luminance value of the R channel is changed by ΔR, the luminance values of all the pixels are output from the projector 1 as P ₁ = (P _r + ΔR, P _g , P _b ), and the RGB luminance values observed by the camera 5 are obtained. _Let C ₁ = (C _r1 , C _g1 , C _b1 ).

Similarly, the luminance value of the G channel is changed by ΔG, the luminance values of all pixels are output from the projector 1 as P ₂ = (P _r , P _g + ΔG, P _b ), and the RGB luminance values observed by the camera 5 are _Let C ₂ = (C _r2 , C _g2 , C _b2 ). Similarly, the luminance value of the B channel is changed by ΔB, the luminance values of all the pixels are output from the projector 1 as P ₃ = (P _r , P _g , P _b + ΔB), and the RGB luminance values observed by the camera 5 are _Let C ₃ = (C _r3 , C _g3 , C _b3 ). In this way, by observing four types of images and calculating the expressions (3), (4), and (5) for each pixel, a 3 × 3 matrix element of the matrix V of the expression (2) is obtained. be able to.

On the other hand, when the color mixing matrix V is obtained, the ambient light component can be calculated by the equation (6).
F = C ₀ −VP ₀ (6)

分変化させ、全画素の輝度値を

とし、合計Ｎ枚の画像をプロジェクタ１から出力する。一方、各画像をカメラ５で観測したＲＧＢ輝度値をそれぞれ

とすると、各画素ごとに（７）、（８）、（９）式の連立方程式が得られる。 Alternatively, two or more images may be used for each channel in order to increase the accuracy of the elements of the color mixing matrix. For example, the luminance value of the R channel

Change the brightness value of all pixels.

And a total of N images are output from the projector 1. On the other hand, RGB luminance values obtained by observing each image with the camera 5 are

Then, simultaneous equations of (7), (8), and (9) are obtained for each pixel.

By solving these simultaneous equations, matrix elements V _RR , V _GR , and V _BR can be obtained. Similarly, matrix elements V _RG , V _GG , V _BG , and V _RB , V _GB , V _BB can be obtained by using sample images in which the luminance of the G channel and the B channel is changed in a plurality of stages.

  Based on the principle described above, the processing operation of the pre-correction unit 8 will be described with reference to FIG. First, the pre-correction unit 8 changes only the R channel with respect to the reference sample image and the reference image while determining whether or not the required number of sample images for the correction parameter has been obtained (step S11). A sample image is set by outputting from the projector 1 an image in which only the G channel is changed with respect to the image and the reference image, and an image in which only the B channel is changed with respect to the reference image (step S12). Thus, sample images corresponding to the respective are acquired (step S13).

  Next, when a sufficient number of images are obtained, the pre-correction unit 8 determines whether or not to obtain a correction parameter for the target pixel (step S14). This determination may be made for all pixels, but as long as the screen and the projector 1 and the camera 5 are calibrated, which pixel of the image output from the projector 1 is which pixel on the image obtained by the camera 5 Therefore, the pixels reflected and observed outside the screen can be handled as non-processing objects. That is, since it is more efficient to obtain correction parameters for pixels projected on the screen rather than obtaining correction parameters for all pixels, the target pixel is a pixel projected on the screen or a predetermined plane area. is there.

  When it is determined that a certain pixel is the target pixel, the pre-correction unit 8 extracts the target pixel (step S15), and from the pixel value output from the projector 1 and the pixel value on the sample image, Expression (3) to Using the equation (5), 3 × 3 matrix elements of the matrix V are calculated (step S16). If these elements are obtained, the pre-correction unit 8 obtains the vector F of the ambient light component using the equation (6) (step S17). When the above correction parameters are obtained, the pre-correction unit 8 temporarily stores them in the internal memory (step S18), and returns to step S14 to process the next pixel. When this process is performed for all the target pixels, the pre-correction unit 8 calculates and stores the matrix V and the vector amount F.

  Next, a detailed processing operation of the illumination change detection unit 7 shown in FIG. 1 will be described with reference to FIG. FIG. 4 is a flowchart showing a detailed processing operation of the illumination change detection unit 7 shown in FIG. The processing operation shown in FIG. 4 corresponds to the screen image acquisition (step S3), illumination change detection (step S4), and illumination correction processing (step S5) shown in FIG. The illumination change detection unit 7 always detects a change in illumination based on the image data output from the image input unit 6 while projecting content data by the projector 1.

First, the illumination change detection unit 7 acquires sample image data output from the image input unit 6 (step S21). Subsequently, the illumination change detection unit 7 calculates the luminance difference ΔC ^(t) by the equation (10) using C ^(t) as the sample image acquired at time t and C ⁽⁰⁾ as the sample image acquired in the initial state. (Step S22). And the illumination change detection part 7 calculates the absolute average value of the difference value in a certain target pixel.
ΔC ^(t) = C ^(t) −C ⁽⁰⁾ (10)

Subsequently, the illumination change detection unit 7 determines whether or not an illumination change is detected based on whether or not the absolute average value of the calculated difference values is greater than a predetermined value (step S23). If the absolute average value of the luminance difference ΔC ^(t) is equal to or smaller than the predetermined value, it is determined that there is no illumination change, and the process returns to step S21 to subsequently acquire a sample image for detecting the illumination change.

On the other hand, if the absolute average value of the luminance difference ΔC ^(t) is not less than the predetermined value and it is determined that there is an illumination change, the illumination change detection unit 7 determines whether or not the pixel is a target pixel (step S24). ) To select each pixel, and calculate the luminance correction amount F ^(t) associated with the illumination change by the equation (11) (step S25).
F ^(t) = F ⁽⁰⁾ -ΔC ^(t) (11)
However, F ⁽⁰⁾ is the vector quantity memorize | stored as an RGB luminance value of the environmental light in an initial state. The illumination change detection unit 7 outputs the brightness correction amount F ^(t) obtained here to the projection brightness correction unit 4 as illumination change correction information.

  Next, the detailed processing operation of the projection luminance correction unit 4 shown in FIG. 1 will be described with reference to FIG. FIG. 5 is a flowchart showing a detailed processing operation of the projection luminance correction unit 4 shown in FIG. This corresponds to the content luminance correction (step S6) shown in FIG. The projection luminance correction unit 4 corrects the luminance value of the image projected from the projector 1 onto the screen so that the RGB luminance value acquired by the camera 5 at time t becomes a predetermined luminance value.

First, the projection luminance correction unit 4 determines which correction amount to use depending on whether or not an illumination change is detected (step S31). If the RGB luminance value acquired by the camera 5 is substantially the same as the observed image C ⁽⁰⁾ obtained by correcting in the initial state, that is, if the illumination change detection unit 7 determines that there is no illumination change, the illumination change is detected. Since the accompanying projection luminance correction amount is not given, the RGB luminance value P ^(t) of the image projected by the projector 1 is calculated by the equation (12) using the correction amount obtained in the precorrection unit 8 (step S33). .
P ^(t) = V < ^-1 > (C ⁽⁰⁾ -F ⁽⁰⁾ ) (12)

On the other hand, when there is a change in illumination, the RGB brightness value P ^(t) of the image projected by the projector 1 is (13 ⁾ using the illumination correction data brightness correction amount F ^(t) output from the illumination change detection unit 7. ) (Step S32).
P ^(t) = V < ^-1 > (C ⁽⁰⁾ -F ^(t) ) (13)

When projecting the content data, the projection luminance correcting unit 4 calculates the corrected pixel value P ^(t) of all the pixels by the equation (12) or the equation (13), and the video output from the reproducing unit 3 The luminance correction of the signal is performed (step S34). Then, by outputting the corrected video signal to the projector 1, the content image is projected on the screen. This process is continuously performed when there is content to be projected (steps S35 and S36). Thereby, it is possible to stably project the content image in accordance with the illumination change.

  Next, a modification of the optical brightness correction apparatus shown in FIG. 1 will be described with reference to FIG. FIG. 6 is a block diagram showing a configuration of a modification of the optical brightness correction apparatus shown in FIG. In FIG. 6, the same parts as those of the apparatus shown in FIG. The apparatus shown in FIG. 6 is different from the apparatus shown in FIG. 1 in that a parameter storage unit 9 is provided instead of the preliminary correction unit 8. In the parameter storage unit 9, parameters similar to the parameters (matrix V and vector quantity F) obtained by the above-described precorrection unit 8 are obtained by other means and stored in advance. The projection brightness correction unit 4 reads out the parameters stored in the parameter storage unit 9 instead of the parameters output from the pre-correction unit 8, and performs the same processing operation as the projection brightness correction unit 4 shown in FIG. Thus, it is not necessary to perform a prior brightness correction process each time the projector 1 is turned on, and preparation work before using the projector 1 can be reduced. This is effective when the place where the projector 1 is used and the screen do not change and the environment is the same.

  In the above description, the example of correcting the optical luminance in one projector 1 and one camera 5, that is, a pair of projector / camera systems has been described. However, to a system using a plurality of projectors or cameras. Can also be easily applied.

  1 and 6 may be provided between the projector 1 and the projection luminance correction unit 4. In this case, the projection brightness correction unit 4 reads the content data from the content DB 2, performs the above-described brightness correction processing on the read content data, and reproduces between the projector 1 and the projection brightness correction unit 4. The brightness of the image projected by the projector 1 may be corrected by outputting to the unit 3.

  As described above, in order to correct the luminance of the image projected by the projector 1 based on the image obtained by the camera 5 that captures the projection image projected by the projector 1, the illumination change detection unit 7 includes the camera 5 detects an illumination change in a state in which the projection image is projected from the image obtained by 5 and outputs illumination change correction information based on the illumination change state when the illumination change is detected. Since the brightness of the projection image projected by the projector 1 is corrected based on the illumination change correction information, a change in illumination is detected while the content is projected on the screen using the projector. The brightness of the output from the projector can be corrected in an adaptable manner, and the brightness can be corrected following a change in illumination.

  A program for realizing the functions of the projection luminance correction unit 4, the illumination change detection unit 7 and the pre-correction unit 8 shown in FIGS. 1 and 6 is recorded on a computer-readable recording medium and recorded on the recording medium. The optical brightness correction processing may be performed by causing the computer system to read and execute the program. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  In a projector / camera system, it is indispensable to correct or adjust the output value of each pixel projected from the projector so that the luminance value of each pixel observed by the camera becomes a predetermined value according to a change in illumination state. Applicable to usage.

  DESCRIPTION OF SYMBOLS 1 ... Projector, 2 ... Content DB (database), 3 ... Playback part, 4 ... Projection brightness correction part, 5 ... Camera, 6 ... Image input part, 7 ... Illumination change detection unit, 8 ... preliminary correction unit, 9 ... parameter storage unit

Claims (5)

An optical brightness correction device for correcting the brightness of a projection image projected by the projector based on an image obtained by a camera that captures a projection image projected by the projector,
Illumination change detection that detects an illumination change in a state where the projection image is projected from the image obtained by the camera and outputs illumination change correction information based on the illumination change state when the illumination change is detected. Means,
An optical luminance correction apparatus comprising: a projection luminance correction unit that corrects luminance of the projection image projected by the projector based on the illumination change correction information. Pre-correction means for outputting pre-correction information for correcting the luminance of the projected image in the initial state by associating the luminance value of the projected image projected by the projector with the luminance value of the image captured by the camera ,
The optical brightness correction apparatus according to claim 1, wherein the projection brightness correction unit corrects the brightness of the projection image based on the prior correction information when the projector is in an initial state. An optical brightness correction device for correcting the brightness of a projection image projected by the projector based on an image obtained by a camera that captures a projection image projected by the projector,
Illumination change detection that detects an illumination change in a state where the projection image is projected from the image obtained by the camera and outputs illumination change correction information based on the illumination change state when the illumination change is detected. Means,
A projection luminance correction means for correcting the luminance of the projection image projected by the projector based on the illumination change correction information;
Storage means storing pre-correction information for correcting the luminance value of the projected image in the initial state by associating the luminance value of the projected image projected by the projector with the luminance value of the image captured by the camera;
The projection brightness correction unit corrects the brightness of the projection image based on the prior correction information when the projector is in an initial state. An optical brightness provided with illumination change detection means and projection brightness correction means for correcting the brightness of the projection image projected by the projector based on an image obtained by a camera that captures the projection image projected by the projector An optical brightness correction method in a correction device,
The illumination change detection means detects an illumination change in a state in which the projection image is projected from the image obtained by the camera, and an illumination change correction based on the illumination change situation when the illumination change is detected. An illumination change detection step for outputting information;
A projection luminance correction method, wherein the projection luminance correction means includes a projection luminance correction step of correcting the luminance of the projection image projected by the projector based on the illumination change correction information. Optical brightness correction comprising illumination change detection means and projection brightness correction means for correcting the brightness of an image projected by the projector based on an image obtained by a camera that captures a projection image projected by the projector An optical brightness correction program for causing a computer on the apparatus to perform optical brightness correction processing,
Illumination change detection that detects an illumination change in a state where the projection image is projected from the image obtained by the camera and outputs illumination change correction information based on the illumination change state when the illumination change is detected. Steps,
An optical luminance correction program that causes the computer to perform a projection luminance correction step of correcting the luminance of the projection image projected by the projector based on the illumination change correction information.

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