Image processing system, projector, program, information storage medium and image processing method

To provide an image processing system and the like which can correct image distortions and provide properly overlapped images when a plurality of projectors are used to project overlapped images, a projector includes: an image projection section projecting an image based on image signals to display the image in a manner to overlap another image projected from another projector at a projection target area; sensing section sensing an image and generating sensing information; overlap-area detecting section detecting projection areas for the projection target area, and detecting an overlap area at which the projection areas overlap, based on the sensing information; correction information generating section generating correction information indicating information for positions of the projection areas and a position of the overlap area; and projection area correction section correcting image signals, based on the correction information, to project an image onto a region corresponding to the overlap area.

Japanese Patent Application No. 2003-126876, filed on May 2, 2003, is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to an image processing system, projector, program, information storage medium and image processing method which can correct image signals so that images projected by a plurality of image projection means are overlapped at a projection target area.

To secure the brightness of an image and to improve the dynamic range and color in the image, there has been realized an image display system comprising a plurality of projectors for projecting images so that they could be overlapped one another at a projection target area such as a screen. Such a projection of images is also called “stack projection”.

In such an image display, however, the projection angles of the projectors are different from one another and consequently a distortion will occur in an image consisting of the projected and overlapped images. If a single projector is used to project an image and even when a distortion occurs therein, it is only required to regulate the distortion. If a plurality of projectors are used, however, it is required to regulate the projected mages to their proper display positions in addition to the regulation of the image distortions.

For such a reason, technical knowledge and great labor are required to perform the stack projection.

To facilitate the alignment in such overlapped images, for example, Japanese Patent Application Laid-Open No. 8-168039 has proposed a projection type display system which is operative to synthesize inspection for inspection patterns and video signals or to intermittently generate inspection signals, to project an image onto a screen, to detect the position of an inspection pattern image in the image projected onto the screen, to control the projecting position so that there is no misalignment.

In Japanese Patent Application Laid-Open No. 8-168039, however, it is presumed that a projected image is of rectangular shape. The projection type display system merely changes an optical projection axis in a hardware manner by detecting the position of the inspection pattern image and determining the amount of misalignment.

For such a reason, it is difficult that the technique of Japanese Patent Application Laid-Open No. 8-168039 causes the projection type display system to properly align the image positions under such a condition that a distortion of an image occurs as when a plurality of projectors are used or when a projector is not opposed directly to a screen.

In addition, Japanese Patent Application Laid-Open No. 8-168039 does not describe at all the fact that the projection type display system will change the color of a composite image by superimposing images.

BRIEF SUMMARY OF THE INVENTION

The present invention is made in view of the above-mentioned problem and its object is to provide an image processing system, projector, program, information storage medium and image processing method which can use a plurality of image projection means so that a plurality of images will properly be overlapped on one another by correcting distortions of the projected images.

An image processing system according to one aspect of the present invention includes:

a plurality of image projection means for projecting images based on image signals so that the images projected by the plurality of image projection means are displayed in a manner to overlap one another on a projection target area, the image projection means being disposed at different positions;

sensing means for sensing a predetermined image projected by each of the plurality of image projection means and generating sensing information;

overlap-area detecting means for detecting projection areas, each of the projection areas indicating a region in which the predetermined image is displayed in an sensing region of the sensing means and for detecting an overlap area at which the projection areas overlap one another, based on the sensing information;

correction information generating means for generating correction information which indicates information for positions of the projection areas and a position of the overlap area; and

projection area correction means for correcting image signals inputted into the plurality of image projection means, based on the correction information, so that an image is projected onto a region in the projection target area corresponding to the overlap area.

A projector according to another aspect of the present invention includes:

image projection means for projecting an image based on image signals to display the image in a manner to overlap another image projected from another projector at a projection target area, the image projection means being disposed at a different position from a position in which the other projector is disposed;

sensing means for sensing a predetermined image projected onto the projection target area and generating sensing information;

overlap-area detecting means for detecting projection areas, each of the projection areas indicating a region in which the predetermined image is displayed in an sensing region of the sensing means and for detecting an overlap area at which the projection areas for the projector and the other projector overlap, based on the sensing information;

correction information generating means for generating correction information which indicates information for positions of the projection areas and a position of the overlap area; and

projection area correction means for correcting image signals, based on the correction information, to project an image onto a region in the projection target area corresponding to the overlap area.

A projector according to a further aspect of the present invention includes:

image projection means for projecting an image based on image signals to display the image in a manner to overlap another image projected from another projector at a projection target area, the image projection means being disposed at a different position from a position in which the other projector is disposed;

sensing means for sensing a predetermined image projected onto the projection target area and generating sensing information;

overlap-area detecting means for detecting projection areas, each of the projection areas indicating a region in which the predetermined image is displayed in an sensing region of the sensing means and for detecting an overlap area at which the projection areas for the projector and the other projector overlap, based on the sensing information;

correction information generating means for generating correction information which indicates information for positions of the projection areas for the projector and the other projector and a position of the overlap area;

projection area correction means for correcting image signals, based on the correction information, to project an image onto a region in the projection target area corresponding to the overlap area; and

communication means for transmitting the correction information for the other projector to the other projector.

A program according to a still further aspect of the present invention is a computer-readable program for causing a computer to function as:

image projection means for projecting an image based on image signals to display the image in a manner to overlap another image projected from another projector at a projection target area, the image projection means being disposed at a different position from a position in which the other projector is disposed;

sensing means for sensing a predetermined image and generating sensing information;

overlap-area detecting means for detecting projection areas, each of the projection areas indicating a region in which the predetermined image is displayed in an sensing region of the sensing means and for detecting an overlap area at which the projection areas for the projector and the other projector overlap, based on the sensing information;

correction information generating means for generating correction information which indicates information for positions of the projection areas and a position of the overlap area; and

projection area correction means for correcting image signals, based on the correction information, to project an image onto a region in the projection target area corresponding to the overlap area.

A program according to an even further aspect of the present invention is a computer-readable program for causing a computer to function as:

image projection means for projecting an image based on image signals to display the image in a manner to overlap another image projected from another projector at a projection target area, the image projection means being disposed at a different position from a position in which the other projector is disposed;

sensing means for sensing a predetermined image and generating sensing information;

overlap-area detecting means for detecting projection areas, each of the projection areas indicating a region in which the predetermined image is displayed in an sensing region of the sensing means and for detecting an overlap area at which the projection areas for the projector and the other projector overlap, based on the sensing information;

correction information generating means for generating correction information which indicates information for positions of the projection areas and a position of the overlap area;

projection area correction means for correcting image signals, based on the correction information, to project an image onto a region in the projection target area corresponding to the overlap area; and

communication means for transmitting the correction information for the other projector to the other projector.

An information storage medium according to a yet further aspect of the present invention stores a computer-readable program for causing a computer to function as:

image projection means for projecting an image based on image signals to display the image in a manner to overlap another image projected from another projector at a projection target area, the image projection means being disposed at a different position from a position in which the other projector is disposed;

sensing means for sensing a predetermined image and generating sensing information;

overlap-area detecting means for detecting projection areas, each of the projection areas indicating a region in which the predetermined image is displayed in an sensing region of the sensing means and for detecting an overlap area at which the projection areas for the projector and the other projector overlap, based on the sensing information;

correction information generating means for generating correction information which indicates information for positions of the projection areas and a position of the overlap area; and

projection area correction means for correcting image signals, based on the correction information, to project an image onto a region in the projection target area corresponding to the overlap area.

An information storage medium according to an even more further aspect of the present invention stores a computer-readable program for causing a computer to function as:

image projection means for projecting an image based on image signals to display the image in a manner to overlap another image projected from another projector at a projection target area, the image projection means being disposed at a different position from a position in which the other projector is disposed;

sensing means for sensing a predetermined image and generating sensing information;

overlap-area detecting means for detecting projection areas, each of the projection areas indicating a region in which the predetermined image is displayed in an sensing region of the sensing means and for detecting an overlap area at which the projection areas for the projector and the other projector overlap, based on the sensing information;

correction information generating means for generating correction information which indicates information for positions of the projection areas and a position of the overlap area;

projection area correction means for correcting image signals, based on the correction information, to project an image onto a region in the projection target area corresponding to the overlap area; and

communication means for transmitting the correction information for the other projector to the other projector.

An image processing method according to a yet more further aspect of the present invention includes:

projecting projection area calibration images from the projectors onto a projection target area at different points of time using the projectors, at a time of calibration;

sensing the projection area calibration images projected by the projectors and generating sensing information;

converting sensing information in sensing coordinates into sensing information in projection target area coordinates, based on the sensing information that has been generated;

detecting projection areas based on the sensing information that has been converted and detecting an overlap area in which the projection areas overlap one another, each of the projection areas indicating a region in the sensing area in which each of the projection area calibration images is projected;

generating correction information which indicates information for positions of the projection areas and a position of the overlap area;

correcting image signals inputted into the projectors based on the correction information, so that an image is projected onto a region in the projection target area corresponding to the overlap area; and

projecting images by the projectors based on the image signals that have been corrected.

In accordance with the present invention, the image processing system and the like can use a plurality of image projection means such as projectors to project images so that the distortions of the images are corrected and the images are properly overlapped one another, by detecting an image overlap area to generate correction information and correcting image signals based on the correction information.

With the above image processing system,

the plurality of image projection means may project projection area calibration images at different points of time, and

the overlap-area detecting means may determine a peak position that is a brightest position in each of the projection area calibration images that have been sensed, based on the sensing information for the projection area calibration images, and detects the projection areas based on the peak position.

In any of the above projectors, the image projection means may project projection area calibration images at a point of time different form a point of time for another projector, and

the overlap-area detecting means may determine a peak position that is a brightest position in each of the projection area calibration images projected by the projector and the other projector, based on the sensing information for the projection area calibration images, and detects the projection areas based on the peak position.

The above image processing method may include:

determining a peak position that is a brightest position in each of the projection area calibration images that have been sensed, based on the sensing information for the projection area calibration images, and converting sensing information in sensing coordinates into sensing information in projection target area coordinates, based on the peak position.

Thus, the image processing system and the like can more accurately detect the image distortion by reducing the influence of color in the projection target area since they can determine the image distortion based on the distribution of brightness in an image rather than the hue thereof.

With the above image processing system, projectors, programs and information storage mediums, the overlap-area detecting means may detect the overlap area by adding a brightness index value of a pixel or a pixel block in each of the projection areas that have been detected.

The above image processing method may include: detecting the overlap area by adding a brightness index value of a pixel or a pixel block in each of the projection areas that have been detected.

Thus, the image processing system and the like can adequately detect the overlap area by determining a differential brightness index value between projection area calibration images even if the projection area calibration images are projected and sensed at different points of time.

The brightness index value used herein may include a luminance value (including a computationally deformed luminance value), an illuminance value, a lightness value and so on.

With the above image processing system, projectors, programs and information storage mediums, the overlap-area detecting means may detect a rectangular overlap area which is the overlap area, aspect ratio of which has been adjusted, and

the correction information generating means may generate, as the correction information, one of information that indicates positions of four corners in the rectangular overlap area and positions of four corners in each of the projection areas, information that indicates the positions of the four corners in the rectangular overlap area, and information that indicates differential values between the positions of the four corners in the rectangular overlap area and the positions of the four corners in each of the projection areas.

The above image processing method may include:

detecting a rectangular overlap area which is the overlap area, aspect ratio of which has been adjusted, and

generating, as the correction information, one of information that indicates positions of four corners in the rectangular overlap area and positions of four corners in each of the projection areas, information that indicates the positions of the four corners in the rectangular overlap area, and information that indicates differential values between the positions of the four corners in the rectangular overlap area and the positions of the four corners in each of the projection areas.

Thus, the image processing system and the like can correct image signals so that the projection area becomes the overlap area, by determining a differential value between each of the four corners in the rectangular projection area and each of the four corners of the rectangular overlap area.

The above image processing system may further include a color reproduction means for correcting color and brightness in an image based on color reproduction information, in order to reproduce color and brightness of an target image,

the plurality of image projection means may project color reproducing calibration images for correcting the color and brightness of an image in a manner to overlap one another onto the region in the projection target area corresponding to the overlap area, on condition that the image signals are corrected by the projection area correction means and an image is projectable onto the region in the projection target area corresponding to the overlap area,

the sensing means may sense the color reproducing calibration images that have been projected onto the region in the projection target area corresponding to the overlap area,

the correction information generating means may generate the color reproduction information based on the sensing information for the color reproducing calibration images, and

the color reproduction means may correct the image signals based on the color reproduction information.

Any of the above projectors may further include a color reproduction means for correcting color and brightness in an image based on color reproduction information, in order to reproduce color and brightness of an target image,

the image projection means may project color reproducing calibration images for correcting the color and brightness of an image in a manner to overlap one another onto the region in the projection target area corresponding to the overlap area, on condition that the image signals are corrected by the projection area correction means and an image is projectable onto the region in the projection target area corresponding to the overlap area,

the sensing means may sense the color reproducing calibration images that have been projected onto the region in the projection target area corresponding to the overlap area,

the correction information generating means may generate the color reproduction information based on the sensing information for the color reproducing calibration images, and

the color reproduction means may correct the image signals based on the color reproduction information.

Any of the above the programs and information storage mediums may cause a computer to function as a color reproduction means for correcting color and brightness in an image based on color reproduction information, in order to reproduce color and brightness of an target image,

the plurality of image projection means may project color reproducing calibration images for correcting the color and brightness of an image in a manner to overlap one another onto the region in the projection target area corresponding to the overlap area, on condition that the image signals are corrected by the projection area correction means and an image is projectable onto the region in the projection target area corresponding to the overlap area,

the sensing means may sense the color reproducing calibration images that have been projected onto the region in the projection target area corresponding to the overlap area,

the correction information generating means may generate the color reproduction information based on the sensing information for the color reproducing calibration images, and

the color reproduction means may correct the image signals based on the color reproduction information.

The above image processing method may include:

projecting color reproducing calibration images for correcting the color and brightness of an image in a manner to overlap one another onto the region in the projection target area corresponding to the overlap area, on condition that the image signals are corrected and an image is projectable onto the region in the projection target area corresponding to the overlap area;

sensing the color reproducing calibration images that have been projected onto the region in the projection target area corresponding to the overlap area;

generating the color reproduction information based on the sensing information for the color reproducing calibration images; and

correcting the image signals based on the color reproduction information.

Thus, the image processing system and the like can properly correct the color and brightness of the image by sensing the overlapped images on the region corresponding to the overlap area and correcting the color and brightness of those images.

DETAILED DESCRIPTION OF THE EMBODIMENT

The present invention will now be described in connection with a plurality of projectors for projecting images overlapped on one another onto a projection target area and with reference to the drawing. By the way, an embodiment shown in the following is not intended to limit the subject matter of the invention as described in the accompanying claims. Moreover, all the components shown in such an embodiment is not necessarily essential for practicing the invention defined by the accompanying claims.

Overall System

FIG. 1schematically shows a state when an image is projected.FIG. 2Aschematically shows images52and54in an sensing region coordinate system whileFIG. 2Bschematically shows images52and54in a projection target area coordinate system.FIG. 3Ais a schematic view of the image52projected by a left-side projector20-1whileFIG. 3Bis a schematic view of the image54projected by a right-side projector20-2.

The projector20-1of this embodiment cooperates with the other projector20-2to project overlapped images onto a screen10which is a kind of projection target area. For such a reason, the projector20-1is disposed on the left side as viewed toward the screen10while the projector20-2is disposed on the right side.

The projector20-1projects an image to the screen10to display the image52on the screen10. The projector20-2projects an image onto the screen10to display the image54on the screen10overlapping a part of the image52. The size of the images52and54may be different from each other.

In such a manner, the brightness of an image can sufficiently be ensured by displaying the overlapped images52and54projected from the projectors20-1and20-2.

Since the projections of the projectors20-1and20-2are oblique relative to the screen10as shown inFIG. 1, the images52and54will be distorted into keystone forms as viewed from the front of the screen10, as shown inFIG. 2B.

To correct such a keystone distortion, the projector20-1is equipped with a sensor30as shown inFIG. 1. The sensor30senses regions on the screen10that include the respective images52and54. The sensor30senses regions on the screen10that include the respective images52and54.

The sensor30generates sensing information by sensing the regions on the screen10that include the images52and54, respectively. The projector20-1can determine the images52and54within a sensing region ABCD in an sensing region coordinate system shown inFIG. 2A, based on the sensing information.

The projector20-1also converts the sensing information generated by the sensor30into sensing information in a projection target area coordinate system shown inFIG. 2B. Thus, the projector20-1can determine the images52and54within a projection target area A′B′C′D′ in the projection target area coordinate system.

As can be seen from the comparison betweenFIGS. 2B and 2A, the image52does not look to be distorted when it is viewed from the sensor30mounted on the projector20-1. It is thus difficult that the sensor30determines the distortion of the image52through the conventional techniques when it is viewed from the front of the screen10.

The projector20-1can adequately determine the distortion of the image52by converting the coordinates of the image52in the sensing region coordinates system into the coordinates of the image52in the image projecting region coordinate system which is viewed from the front of the screen10.

The projector20-1can also determine the luminance distributions in the images52and54, based on the sensing information for the images52and54in the projection target area coordinate system. For example, the image52in the projection target area coordinate system has its luminance distribution that is brighter on the left side and darker on the right side, as shown inFIG. 3Awhile the image54in the projection target area coordinate system has its luminance distribution that is brighter on the right side and darker on the left side, as shown inFIG. 3B. This is because in the arrangement shown inFIG. 1, the left-side portion of the52is nearer the light source of the projector20-1while the right-side portion of the image54is nearer the light source of the projector20-2.

In this embodiment, the projector20determines and corrects the distortions of the images52and54by determining such luminance distributions.

In this embodiment, the projector20also adjusts the positions and sizes of the displayed images such that they will be displayed on an overlap area60having a predetermined aspect ratio among temporary overlap areas on which the regions (projection areas) of the images52and54in the sensing region overlap.

By performing such an adjustment, the projector20can eliminate the image distortions and sufficiently ensure the brightness in the images.

Description of Block Diagrams

Functional blocks of the projector20having such a function will be described below.

FIG. 4is a functional block diagram of a projector20according to one example of an embodiment of the present invention.

The projector20comprises a signal input section110for inputting image signals, a color reproducing section120for correcting the image signals so that the color of an image accommodating to a target color can be reproduced, a projection area correcting section130for correcting image signals from the color reproducing section120so that images will be displayed on an overlap area60, a signal output section160for outputting the corrected image signals, and an image projecting section190for projecting images based on the image signals.

The projector20also comprises a calibration signal generating section112for generating calibration signals used to display a projection area calibration image and a color reproducing calibration image, an sensing section140for sensing a region on the screen10that includes projected images, an information generating section150for generating correction information used in the color reproducing section120and projection area correcting section130, based on the sensing information, and a communication section180for transmitting and receiving correction information and the like to and from the other projectors20.

The color reproducing section120comprises a color correcting section122for correcting the image signals to provide an image color accommodating to a target color, and a brightness correcting section124for correcting the image signals to provide an image brightness accommodating to the target color.

The information generating section150comprises a profile storage section154for storing a target color profile, a hardware profile for the projectors20and so on, a color reproduction information generating section152for generating color reproduction information based on the target color profile and the hardware profile for the projectors20, an overlap area detecting section156for detecting the projection area and overlap area60in the sensing region, and a correction information generating section158for generating correction information indicative of information for the respective positions of the overlap area60and projection area.

The information generating section150also comprises an sensing information storage section151, and a control information section159for generating control information used to control the other projector20.

The image projecting section190comprises a spatial light modulator192, a drive section194for driving the spatial light modulator192, a light source196, and a lens198.

The drive section194drives the spatial light modulator192based on the image signals from the signal output section160. The image projecting section190projects the light from the light source196through the spatial light modulator192and lens198.

In accordance with this embodiment, only the projector20-1is operative to sense the images, generate the correction information and adjust the color and brightness in the images. It is thus unnecessary for the projector20-2to include the sensing section140, sensing information storage section151, color reproduction information generating section152and correction information generating section158.

Hardware for causing a computer to function as the sections of the projector20may be implemented by the following equipment.

FIG. 5is a hardware block diagram illustrating a projector20according to one example of an embodiment of the present invention.

The signal input unit110may be implemented, for example, by an A/D converter930or the like; the color reproducing section120and the projection area correcting section130may be implemented, for example, by an image processing circuit970, RAM950, CPU910or the like; the signal output section160may be implemented, for example, by a D/A converter940or the like; the calibration signal generating section112and the information generating section150may be implemented, for example, by the image processing circuit970, RAM950or the like; the sensing section140may be implemented, for example, by a CCD camera or the like; and the spatial light modulator192may be implemented, for example, by a liquid crystal panel920, a ROM960for storing the liquid crystal light valve driver for driving the liquid crystal panel920or the like.

These units and sections are configured to mutually deliver the information therebetween through a system bus980. The sensor30forms part of the sensing section140.

The part or whole of each of these sections may be implemented in a hardware manner such as circuits or in a software manner such as drivers.

Furthermore, the functions of the projection area correcting section130and the like may be implemented into a computer by reading a program used to activate the computer out of an information storage medium900.

Such an information storage medium900may be accomplished, for example, by CD-ROM, DVD-ROM, ROM, RAM, HDD or the like through either of the contact or non-contact type reading mode.

In addition, the aforementioned functions may be implemented into the computer by downloading a program for implementing the above functions into the computer or the like from a host device or the like through a transmission channel, in place of the information storage medium900.

Image Processing

The flow of image processing using these sections will be described below.

FIG. 6is a flow chart illustrating a flow of image processing according to one example of an embodiment of the present invention.

First of all, a user starts the projectors20-1and20-2. The projector20-1projects a monochrome (e.g., white-colored) projection area calibration image (step S1). More particularly, the calibration signal generating section112generates image signals used to project the projection area calibration image, based on the control information from the control information generating section159. The image projecting section190then projects the image based on the image signals corrected by the color reproducing section120and the projection area correcting section130.

This projection area calibration image may be one of color reproducing calibration images described below.

The sensing section140of the projector20-1senses a region on the screen10that includes the projection area calibration image and then generates sensing information, and the sensing information storage section151stores the sensing information from the sensing section140(step S2).

The overlap area detecting element156then performs a luminance distribution analysis (step S3).

More particularly, the overlap area detecting element156detects the position of a pixel having the highest luminance value among luminance values of the all pixels included in the sensing information as a peak position. This technique of detecting the pixel position may be accomplished by detecting a portion near a pixel adjacent to another pixel in which the rate of change in the luminance value thereof becomes equal to one (1) as a peak position. Alternatively, it may detect a pixel having the highest luminance value in all pixels which have been stored in a memory, as a peak position.

For example, if the luminance value at the center of a sensed image is the highest, it will be judged that the projector20is positioned directly in the front of the screen10. If the left-side portion of a sensed image has the highest luminance value, it will be judged that the projector20inclines leftward relative to the screen10.

The overlap area detecting element156then converts the sensing information in the sensing region coordinate system into the converted sensing information in the projection target area coordinate system, based on the peak position and converting data, the converted sensing information being then stored in the sensing information storage section151(step S4).

FIG. 8schematically shows the structure of converting data according to one example of an embodiment of the present invention.

InFIG. 8, for example, H may be a numeric value indicative of the horizontal position and have a central position of 0.5. Furthermore, V may be a numeric value indicative of the vertical position and have the center of 0.5.

In such a manner, if the peak position is varied, the respective coordinates of the projection target area A′B′C′D′ in the projection target area coordinate system will be changed. Thus, the overlap area detecting element156can generate the converted sensing information depending on the degree of the change.

The control information generating section159then judges whether or not the projection of projection area calibration image in all the projectors20has been finished (step S5). If not so, control information is transmitted to the next projector20-2(step S6).

The projector20-2projects a projection area calibration image in a procedure similar to that of the projector20-1.

The sensing section140senses the projection area calibration images; the sensing information storage section151stores the sensing information of the projection area calibration images; and the overlap area detecting element156causes the sensing information storage section151to store the converted sensing information provided by converting the sensing information into the projection target area coordinate system.

In such a manner, the sensing section140judges whether or not the projection, pickup and conversion of the projection area calibration images from all the projectors20have been finished (step S5). If so, the sensing process is finished.

The overlap area detecting section156then detects the coordinates of the images52and54in the projection target area coordinate system and the coordinates of the overlap area60at which the images52and54in the projection target area coordinate system are overlapped each other, based on the converted sensing information for each projector20stored in the sensing information storage section151(step S7).

More particularly, the overlap area detecting section156detects a temporary overlap area for the images52and54, based on converted sensing information which has been converted to be able to handle in a coordinate system on the screen10(projection target area). The overlap area detecting section156detects the overlap area60within the temporary overlap area, whose position and size have been adjusted to ensure a desired aspect ratio (e.g., equal to 4:3, 16:9 or the like).

The technique of selecting the overlap area60from the temporary overlap area may be adapted to enlarge the region from the vertexes of that temporary overlap area or to enlarge the region from the center of that temporary overlap area.

The correction information generating section158then judges whether or not the region transmission process in all the projectors20has been finished (step S8). If not so, the correction information generating section158generates correction information indicative of the coordinates of the image54and overlap area60. The communication section180transmits the correction information toward the projector20-2(step S9).

The projection area correcting section130of the projector20-2corrects image signals so that an image is projected onto a region on the screen10corresponding to the overlap area60, based on the correction information. Moreover, the projection area correcting section130of the projector20-1corrects image signals so that an image is projected onto a region of the screen10corresponding to the overlap area60, based on the correction information indicative of the coordinates of the image52and overlap area60which have been generated by the correction information generating section158.

By the above-mentioned procedure, the projectors20-1and20-2can correct image signals so that the images will be projected onto the region on the screen10corresponding to the overlap area60.

In such a manner, the projector20-1correct the color and brightness in the images to provide a color and brightness of a target image under such a condition that the projectors20-1and20-2can project images onto the overlap area60(step S11).

FIG. 7is a flow chart illustrating a flow of process for correcting the color and brightness of an image according to one example of an embodiment of the present invention.

The control information generating section159transmits control information to the calibration signal generating section112, to generate calibration signals for the first calibration image. The calibration signal generating sections112of the projectors20-1and20-2generate calibration signals for the first color reproducing calibration image, based on the control information. Herein, the color reproducing calibration image may be a monochrome red-, green-, blue- or white-colored image, for example.

The image projecting sections190of the projectors20-1and20-2then project the first color reproducing calibration images, based on the calibration signals (step S31).

Thus, the first color reproducing calibration images will be projected from the projectors20-1and20-2onto the overlap area60of the screen10.

The sensor30then senses the screen10and the sensing information storage section151then stores the sensing information for the first color reproducing calibration images (step S32).

The control information generating section159judges whether or not the sensing information for all the color reproducing calibration images have been stored (step S33). If not so, the control information generating section159outputs a control information toward the calibration signal generating section112so that the next color reproducing calibration image will be projected (step S34).

In such a manner, if the sensing information for the four, first to fourth color reproducing calibration images (but, not limited to four colors) have been stored, the color reproduction information generating section152determines the amounts of correction for the color and brightness, based on the X-, Y- and Z-values of the sensing information and the target color profile and the hardware profile for the projectors20which are stored in the profile storage section154. The X-, Y- and Z-values used herein are tristimulus values which are machinery independence colors based on the International Standard defined by the International Commission on Illumination (CIE).

The color correcting section122updates a 3D-LUT (or three-dimensional lookup table) which is a kind of data for color correction, based on correction information for a color generated by the color reproduction information generating section152. The brightness correcting section124updates a ID-LUT (or one-dimensional lookup table) which is a kind of data for brightness correction, based on correction information for a brightness generated by the color reproduction information generating section152(step S35).

The color correcting section122then corrects the image signals based on the updated 3D-LUT and the brightness correcting section124corrects the image signals based on the updated 1D-LUT (step S36). Thus, the color and brightness of the image accommodates to the target color.

The projection area correcting section130corrects the image signals from the color reproducing section120so that an image will be projected on the region of the screen10corresponding to the overlap area60. The signal output section160converts the image signals from the projection area correcting section130into analog signals which is in turn outputted toward the image projecting section190.

The image projecting section190projects an image in which the position, distortion, color and brightness of the projected image have been corrected based on the image signals from the signal output section160(step S37).

By the above-mentioned procedure, the projectors20-1and20-2can display the images in which the positions, distortions, colors and brightnesses thereof have been corrected.

As described above, according to this embodiment, when images are projected and overlapped each other by a plurality of plural image projecting section190, the projectors20-1and20-2can automatically correct the image distortions to provide the adequately overlapped images by detecting the image overlap area60to generate the correction information and correcting the image signals based on the correction information.

Even if a user does not have any technical knowledge, that user can easily and simply project the adequately overlapped images through such an automatic correction.

Even if the number of projectors20is increased to two or four depending on the size of the projection target area to which the projectors20are to be applied, these projectors20can effectively project overlapped images.

According to this embodiment, the projector20can determine the image distortion based on the distribution of brightness in an image rather than a hue of that image. Therefore, the projector20can reduce the influence of color on the screen10and more precisely detect the image distortion.

According to this embodiment, the projectors20-1and20-2can adequately detect the overlap area60by determining a difference between the luminance values, even if the projection area calibration images projected at different points of time are to be sensed.

According to this embodiment, the projectors20-1and20-2can correct the image signals so that the images52and54will be overlapped each other at the overlap area60by determining the coordinates of the four corners in the rectangular images52and54, the coordinates of the four corners in the rectangular overlap area60and the differential values between these coordinates.

According to this embodiment, the projector20can further adequately correct the color and brightness of the integrated image by sensing an integrated image consisting of the overlapped images at the overlap area60and then correcting the color and brightness of the integrated image.

The projector20-1can properly correct the color and brightness of the integrated image under influence of the ambient lights such as illuminating and external lights, based on the sensing information from the sensor30.

The optical axis of the lens198in the image projecting section190may be coincident with the optical axis of the sensor30since the projector20will not directly determine the shape of an image. Therefore, the sensor30may be integrated into the projector20(or the sensor30may be included in the projector20).

Modifications

Although the preferred embodiment of the present invention has been described, the present invention is not limited to the aforementioned examples.

Although the embodiment has been described as to the correction information generating section158which generates information including the coordinate information for the four corners in the respective projection area and overlap area60as correction information, the information indicative of the differential values between the four-corner coordinates of the projection area and the four-corner coordinates of the overlap area60or only the four-corner coordinate information of the overlap area60may be generated if the projector20-2has determined the four-corner coordinates of the projection area without performing any zooming and any projection angle change. Even in such a manner, the projector20-2can adjust the position and size of the image54.

It is not necessary that the projector20includes the communication section180. For example, each of the projectors20may include the sensing section140and information generating section150, and may independently correct the position and size of the corresponding image as well as the color and brightness of the same.

As a further modification, the present invention may be applied to an image processing system including a plurality of image projecting sections190located at different positions and having an image processing unit which includes the sensing section140, the information generating section150and the like.

In the aforementioned embodiment, the overlap area60is detected by summing the luminance values of the projection area calibration images projected by the projectors20-1and20-2at different points of time. However, the projectors20-1and20-2may project projection area calibration images at the same time, for example, by adopting a technique of directly detecting the coordinates of the projection and overlap areas when the overlap area60is detected without being based on the difference between the luminance values.

If, in such a case, the projection area calibration images are different from each other in color, pattern or the like, the projection area calibration images can easily be identified.

In the aforementioned embodiment, the projector20performs the calibration of the color and brightness in the image after the calibration of the projection area has been carried out. As a further modification, however, such a processing may be carried out in the reverse order.

In the aforementioned embodiment, the projector20uses the luminance value as a brightness index value. As a further modification, however, any brightness index value other than the luminance value, such as illuminance value or lightness value may be applied to the present invention.

In the aforementioned embodiment, the projection target area is the screen10. As a further modification, however, it may be a wall or the like. In the aforementioned embodiment, the present invention can be applied to any one of various other kinds of projection target areas by adopting the technique of detecting the four-corner coordinates of the screen10based on the luminance distribution, rather than the technique of detecting directly the four-corner coordinates of the screen10.

In the aforementioned embodiment, the projector20is used as an image processing system. However, the present invention is effective for various other kinds of image processing systems such as Cathode Ray Tube (CRT), Light Emitting Diode (LED) rather than the projector20.

The projector20may be either of a liquid crystal projector, a projector using a Digital Micromirror Device (DMD) or the like. By the way, DMD is a trademark possessed by the U.S. Texas Instruments.

The functions of the aforementioned projector20may be implemented into a single projector or may be implemented dispersedly into a plurality of processing units (e.g., a projector and a PC).