Abstract:
A projection image display apparatus is disclosed which enable users to observe an image in an overlap area well. The apparatus comprises a first projector which projects a first image onto a projection surface, a projection area detector which acquires a projection area onto which a second projector projects a second image in a certain area of the projection surface. Further, the apparatus comprises a projection area controller which controls a projection area onto which the firs projector projects the first image, based on an input signal from the projection area detector.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to projection image display apparatuses suitable for projection of images onto a projection surface using a single or plural projectors and multi-projection systems. 
   Multi-projection systems (image display system) are conventionally used, which project plural images onto a projection surface by combination of plural projectors. 
   Of the systems, one is known which displays a magnified image by arranging plural image display areas onto which the plural projectors project images in a tiled manner (see Japanese Patent Laid-Open Application No. 2005-39849). 
   As another image display system, a so-called stack projection system is known in which plural projectors are combined and plural image areas of the respective projectors are overlapped with each other (see Japanese Patent Laid-Open Application No. 2004-228824). 
   The multi-projection system disclosed in  FIG. 1  of Japanese Patent Laid-Open Application No. 2005-39849 divides input image information into plural pieces and displays the pieces of information by the plural projectors that constitute the system. This system displays a smooth image that is a mostly seamless image on a screen. 
   The stack projection system disclosed in  FIG. 1  of Japanese Patent Laid-Open Application No. 2004-228824 overlaps the projection display areas of the respective projectors with high accuracy. This system can obtain a bright projection image by causing the respective projectors to display the same image information. 
   However, in a case where the respective projectors display images different from each other in the multi-projection system, the stack projection system disclosed in Japanese Patent Laid-Open Application No. 2004-228824 overlaps the different images. This results in making it hard to recognize the projection image. 
   The multi-projection system disclosed in Japanese Patent Laid-Open Application No. 2005-39849 can display the respective images independently since the respective projection areas are different from each other. However, since the projection areas are fixed, their positions cannot be moved freely. 
   Further, when a single projector projects an image onto the projection surface, the image and another image projected by another projector may overlap with each other. 
   Furthermore, when the plural projectors project plural images onto the screen, the projection areas of the images may overlap with each other thereon. 
   BRIEF SUMMARY OF THE INVENTION 
   One object of the present invention is to provide a projection image display apparatus and a multi-projection system which enable users to observe an image in an overlap area well in the above-described cases. 
   According to one aspect, the present invention provides a projection image display apparatus comprising a first projector which projects an image onto a projection surface, a projection area detector which acquires a projection area onto which a second projector projects an image in a certain area of the projection surface, and a projection area controller which controls a projection area onto which the firs projector projects the image, based on an input signal from the projection area detector. 
   According to another aspect, the present invention provides a multi-projection system comprising first and second projectors which project images on a projection surface, a projection area detector which acquires at least one of first and second projection areas onto which the images are respectively projected by the first and second projectors, and a projection area controller which controls at least one of the first and second projection areas, based on the detection result by the projection area detector. 
   Other objects and further features of the present invention will become readily apparent from the following description of the preferred embodiments with reference to accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an outline view showing the configuration of the multi-projection system that is Embodiment 1 of the present invention. 
       FIGS. 2A ,  2 B,  3 A and  3 B are schematic views of projection images in  FIG. 1 . 
       FIG. 4  is a flowchart showing the sequence in Embodiment 1. 
       FIG. 5  is an outline view showing the configuration of the multi-projection system that is Embodiment 2 of the present invention. 
       FIGS. 6A and 6B  are schematic views of projection images in  FIG. 5 . 
       FIG. 7  is a flowchart showing the sequence in Embodiment 2. 
       FIGS. 8A and 8B  are schematic views of projection images in Embodiment 2. 
       FIG. 9  is an explanatory figure showing another detection area of the projection area. 
       FIG. 10  is an outline view showing the configuration of the multi-projection system that is Embodiment 3 of the present invention. 
       FIGS. 11A and 11B  are schematic views of projection images in Embodiment 3. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A description will now be given of the preferred embodiments of the present invention by referring to the accompanying drawings. 
   Embodiment 1 
     FIG. 1  is an outline view showing the configuration of the main part of the multi-projection system that is Embodiment 1 of the present invention. 
   A first projector  1  and a second projector  2  respectively project images (video images) onto projection areas  6  and  7  of a screen (projection surface)  5 . Video input signals  9  and  10  are signals based on images to be displayed by the projectors  1  and  2 . 
   The projection areas  6  and  7  corresponding to the projectors  1  and  2  form an overlap area  8 . Therefore, when the projectors  1  and  2  project the images based on the video input signals  9  and  10  onto the screen  5 , the images overlap with each other in the overlap area  8 , resulting in making it hard to recognize the images. 
   The video input signals  9  and  10  are input to a projection area controller  4  and converted into video input signals  11  and  12  whose projection areas are controlled by the controller  4 . The video input signals  11  and  12  are input to the projectors  1  and  2 . 
   The projection area controller  4  is connected to a projection area detector  3  through a signal line  13 . The projection area detector  3  detects the dimensions, shape and the like of the projection areas  6  and  7  projected by the projectors  1  and  2  in a detection area  14  on the screen  5 . 
   The projection area controller  4  restricts the projection areas  6  and  7  formed by the projectors  1  and  2  based on the detection result of the projection areas  6  and  7  detected by the projection area detector  3 . Specifically, the projection area controller  4  generates from the video input signals  9  and  10  the area-controlled video input signals  11  and  12 , and controls the projection areas  6  and  7  of the projectors  1  and  2  based on these video input signals  11  and  12 . 
   For instance, the projection area controller  4  deletes the projection area of one of the projectors  1  and  2  in the overlap area  8 . 
   The embodiment has at least the first and second projectors  1  and  2  which project video images onto the screen (projection surface)  5 . 
   An image display area in the projection area of one of the first and second projection areas  6  and  7  respectively formed by the first and second projectors  1  and  2  in the projection surface  5  is detected by the projection area detector  3 . In addition, at least one of the image display areas formed in the first and second projection areas  6  and  7  is controlled by the projection area controller  4  based on the detection result by the projection area detector  3 . 
   For instance, the projected image by the first projector  1  in the overlap area  8  is deleted. 
   In this embodiment, the projection area detector  3  especially detects the projected image in the area  8  in which the first projection area  6  formed by the first projector  1  overlaps with the second projection area  7  formed by the second projector  2  to input the detection result to the projection area controller  4 . The projection area controller  4  controls the first projection area  6  of the first projector  1  based on the signal (detection result) input from the projection area detector  3 . For instance, the projection area controller  4  deletes the projection image. 
   The specific method for detecting the projection areas  6  and  7  and controlling thereof will hereinafter be described.  FIGS. 2A and 2B  schematically show the relationship between the detection area  14  and the projection areas  6  and  7  on the screen  5 . 
   The projection areas  6  and  7  form the overlap area  8 . First, as shown in  FIG. 2A , the first and second projectors  1  and  2  respectively display a fully white image  6   a  and a fully black image  7   b  on the screen  5  based on the signals from the projection area controller  4  (not shown in  FIG. 2A ). 
   In this state, the projection area detector  3  detects the projection areas. The projection area detector  3  has a function to pick up a two-dimensional image, picking up an image that shows a display state on the detection area  14 . 
   It is possible to recognize the projection area  6   a  of the first projector  1  based on the resulting picked-up image. 
   Next, as shown in  FIG. 2B , the second and first projectors  2  and  1  respectively display a fully white image  7   a  and a fully black image  6   b  on the screen  5  based on the signals from the projection area controller  4 . 
   In this state, the projection area detector  3  detects the projection areas. It is possible to recognize the projection area  7   a  of the second projector  2  in the detection area  14  based on the resulting picked-up image. 
   Thereby, information on dimensions, position, shape and the like of each of the projection areas  6   a  and  7   a  are acquired. 
     FIGS. 3A  and B are explanatory figures showing the control of the projection areas  6  and  7 , schematically showing each area on the screen  5  as  FIGS. 2A and 2B . 
   When a system user, not shown, indicates the projection area  7  of the second projector  2  or the projecting area  6  of the first projector  1  by using an area indicating means  40  as shown in  FIGS. 3A and 3B , an image projected by the projector whose projection area is indicated in the overlap area  8 . The position indicated by the area indicating means  40  is detected by the projection area detector  3 . Thereby, the image displayed in the overlap area  8  is controlled. 
   In addition, the projection area controller  4  inputs the video input signals  11  and  12  to the projectors  1  and  2 , respectively, the signals  11  and  12  being area-controlled such that black display is performed in an area corresponding to the overlap area  8  in the video input signals  9  and  10 . Black is not necessarily required in the present invention. Other colors, for instance, dark blue or full white may be employed. 
   Performing the black display in this embodiment substantially means that image projection (display) is not performed. 
   Further, although the description was made of the case where the black display was performed or the image projection was not performed in the overlap area  8 , the present invention is not limited thereto. For instance, the black display may be performed or the image projection may be not performed in a part of the overlap area  8 . 
   As described above, according to this embodiment, it is possible to prevent the image from being hard to recognize even though projected images are overlapped with each other and to control display of the projected image in accordance with a user&#39;s intention. 
   Although the description was made of a multi-projection system including two projectors in the above-described embodiment, the number of the projectors in the present invention is not limited thereto. 
     FIG. 4  shows an example of the sequence to control the image projection area in a case where i (i≧2) projectors are used. 
   STEP  1  (display detection mode) is a process to confirm the projection area. This step is carried out at the start of the system or every predetermined time period. 
   STEP  2  (confirmation of the projectors) is a process to detect how many projectors are connected to the system. The i projectors are detected in this step. 
   STEP  3  (acquisition of the i-th areas), STEP  4  (display and image pickup of the i-th area), STEP  5  (analysis and storage of the i-th area) and STEP  6  (determination of end) are processes to store the i areas sequentially detected by the projection area detector  3 . 
   STEP  7  (end of the display detection mode) is a process to start the control by the projection area controller  4 , based on the detection result of each area. 
   STEP  8  (detection of a user-indicated position) is a process to detect a position indicated by the area indicating means  40  shown in  FIGS. 3A and 3B . 
   Although fully white display or fully black display was performed in the detection of the projection areas  6  and  7  in the above-described embodiment, the present invention is not limited thereto. 
   For instance, a grid chart and a frame maybe employed. In addition, for instance, a blue frame and a red frame may be respectively and concurrently displayed by the first and second projectors  1  and  2 . In this case, picking up the color frame image by the projection area detector  3  makes it possible to acquire information on dimensions, position, shape and the like of each of the projection areas  6  and  7  simultaneously. 
   Furthermore, performing the area detection and control of the projection areas  6  and  7  during projection makes it possible to achieve a multi-projection system capable of responding increment/decrement of the overlap area  8  caused by movement of the projectors  1  and  2 . 
   Although this embodiment showed the case where the projection area detector  3  and the projection area controller  4  were separated from each other, they may be configured integrally. Further, the projectors  1  and  2  may have functions of the detector  3  and controller  4 . 
   Embodiment 2 
     FIG. 5  is an outline view showing the configuration of the multi-projection system that is Embodiment 2 of the present invention. In  FIG. 5 , first and second projectors  15  and  16  respectively project images onto projection areas  20  and  21  on a screen  19 . 
   Video signals  23  and  24  are input to the projectors  15  and  16 , respectively. A projection area detector  17  detects information on an image  20  projected in a predetermined detection area  25  on the screen  19  by the first projector  15 . 
   A projection area controller  18  is built in the main body of the first projector  15  and inputs a video signal generated by adding area-control to the video input signal  23  based on the detection result by the projection area detector  17 . The projector  15  displays the image on the screen  19 , based on the video signal. 
   A video input signal is input to the second projector  16  as it is, in other words, without control of the projection area. 
   The projection areas  20  and  21  corresponding to the projectors  15  and  16  form an overlap area  22 , as shown in  FIG. 5 . Therefore, when the projectors  15  and  16  project the images based on the video input signals  23  and  24  as they are onto the screen  19 , the images in the overlap area  22  become hard to recognize. 
   The specific method for detecting the projection areas  20  and  21  and controlling thereof will hereinafter be described.  FIGS. 6A and 6B  schematically show the relationship between the detection area  25  and the projection areas  20  and  21  on the screen  19 . 
   The projection areas  20  and  21  form the overlap area  22 . First, as shown in  FIG. 6A , the first projector  15  displays a fully black image on the screen  19  based on the signals from the projection area controller  18  (not shown in  FIG. 6A ). 
   In this state, the projection area detector  17  detects the projection area  21  other than that of the first projector  15 . The projection area detector  17  has a function to pick up a two-dimensional image. This makes it possible to recognize the projection area  21  of a projector other than the first projector  15 , that is, the second projector  16 . 
   Next, the first projector  15  displays a fully white image in the projection areas  20  and  21  on the screen  19 . In this state, the projection area detector  17  picks up an image of the detection area  25  and then detects the projection area  20  of the first projector  15  from the difference between the picked-up fully black image and the picked-up fully white image. 
   Since the image in the projection area is controlled by only the first projector  15 , the projection area controller  18  inputs the video input signal to the first projector  15 , the video input signal being area-controlled based on the detection result by the projection area detector  17  such that black display is performed in the overlap area  22 . 
   As a result, only the image projected by the second projector  16  is displayed in the overlap area  22  as shown in  FIG. 6B . 
   Although this embodiment describes a case where one projector capable of controlling the projection area and another projector are included, the same effect can be obtained in a case where two or more other projectors are included. 
     FIG. 7  shows the sequence to control the image projection apparatus in this embodiment. 
   STEP  11  (acquisition of a first projection area) is a process to acquire the projection area  20  of the first projector  15 . 
   STEP  12  (display of a fully black image) is a process to display the fully black image in the projection area  20 . 
   STEP  13  (acquisition of the image A in the detection area) is a process to pick up the fully black image A projected by the first projector  15  in the detection area  25 . 
   STEP  14  (acquisition of the image B in the detection area) is a process to pick up the fully white image B projected by the first projector  15  in the detection area  25 . 
   STEP  15  (calculation of the difference between the images A and B) is a process to calculate the difference between the images A and B picked up at STEPs  13  and  14 . 
   STEP  16  (detection) is a process to detect the projection area  20  of the first projector  15  based on the above-described difference and the overlap area  22 . 
   STEP  18  (image analysis and determination) is a process to determine whether or not the image is projected by the other projector (that is, the second projector) in the detection area  25 . If yes, the process proceeds to STEP  19 . If no, the process ends. 
   STEP  19  (set of the overlap area) is a process to set the overlap area  22 . 
   STEP  20  (black display in the overlap area) is a process to perform black display in the overlap area  22 . 
   Although the projection area controller  18  in this embodiment displays the fully white and fully black images, the present invention is not limited thereto. 
     FIGS. 8A and 8B  schematically show the projection areas  20  and  21  like  FIGS. 6A and 6B . The projector  15  displays a predetermined frame  39  on the screen  19 , instead of the fully black display. 
   The projection area detector  17  searches the position of the predetermined frame  39  and detects the projection area  20  of the first projector  15 . Analyzing an image which is picked up together with the image in the projection area  20  of the first projector  15  makes it possible to acquire the projection area  21  of the second projector  16 . 
   Although the description was made of the case where the detection area  25  included the projection areas  20  and  21  as shown in  FIG. 5 , the present invention is not limited thereto. If the detection area  25  includes at least the projection area  20  of the first projector  15 , it is possible to obtain a similar effect. 
   According to this embodiment, even when the position of the second projector  16  is moved, performing detection and control of the projection area makes it possible to display an image that has no image overlapping and is easy to recognize. 
   Although this embodiment showed the case where the projection area detector  17  was separated from the projector  15 , it may be built in the projector  15 . 
   Further, both the projection area detector  17  and the projection area controller  18  may be separated from the projector  15 . 
   Moreover, in this embodiment, the number of the projector may be one. In other words, the system may be constituted by, for example, only the projector  15 . 
   Furthermore, the second projector  16  may be treated as an apparatus not included in the system, and the projection area controller  18  may control images projected by both the first and second projectors  15  and  16  when the second projector  16  projects the image. 
   In this case, this is not a multi-projection system but a projection image display apparatus. 
   Specifically, the projector  15  projects an image onto a projection surface  19 . The projection area detector  17  detects a predetermined area in the projection surface  19 . The projection area controller  18  controls the projection area  20  of the projector  15 . 
   The projection area detector  17  detects the projection area  21  of the projector  16  in the predetermined area  25 , the projector  16  being a projector other than the projector  15 . The projection area controller  18  controls the projection area  20  projected by the projector  15 , based on a signal from the projection area detector  17 . 
   Embodiment 3 
     FIG. 10  is an outline view showing the configuration of the multi-projection system that is Embodiment 3 of the present invention. 
   In  FIG. 10 , first and second projectors  26  and  32  respectively project images onto projection areas  35  and  34  on a screen  36 . 
   The projector  26  is electrically connected to the projection area detector  27  and the projection area controller  30 . 
   The projector  26  is a projector for a large screen, which projects a video image based on a video input signal  31  onto the screen  36 . 
   On the other hand, the projector  32  is a small-sized portable projector which displays a video image based on a video input signal  33 . The projection area  34  of the portable projector  32  is included in, in other words, completely overlapped with a projection area  35  of the projector  26 . 
   A projection area detector  27  detects an image (projection area  35 ) in a detection area  37  on the screen  36 . The projector  26  receives a video input signal  28  which is area-controlled based on the detection result by the projection area detector  27  and displays an image based on the video input signal  28 . 
   Accordingly, the projection area controller  30  controls the projector  26  so that the image projected in the projection area  35  by the projector  26  does not overlap with the image of the projection area  34  of the portable projector  32 . 
   The method for this control will hereinafter be  5  described.  FIGS. 11A and 11B  schematically show the projection areas  35 ,  34  and the detection area  37 . 
   First, the projector  26  performs fully black display based on the video input signal  28  from the projection area controller  30  as shown in  FIG. 11A . 
   The projection area detector  27  has a function to pick up a two-dimensional image, picking up the detection area  37  in the state in which the projector  26  outputs the fully black image  35 . 
   At this point, the image in the projection area  34  of the portable projector  32  is picked up, thereby being confirmed what image exists in the detection area  37 . 
   Next, the projection area controller  30  displays markers  38 , which indicate four corners of the projection area  35  projected by the projector  26 . The projection area detector  27  picks up the image in the detection area  37  in this state. Detecting the markers  38  from the picked-up image specifies the projection area  35  of the projector  26 , as shown in  FIG. 11B . 
   The projection area controller  30  causes the projector  26  to display a black image only in a part of the projection area  35  of the projector  26 , the part corresponding to the projection area  34  of the portable projector  32 . This prevents the image from being hard to recognize by image overlapping. 
   Although the projector connected to the projection area controller  30  displays the fully black image and the markers  38  sequentially when detecting the projection area of the other projector in the projection area  35  in this embodiment, the present invention is not limited thereto. The positions of the markers  38  and the position of the image projected by the other projector may be simultaneously acquired by image processing on the image including the markers  38  in the detection area  37 . The shape of the markers  38  is not limited to that shown in the figure. 
   The detection by the projection area detector  27  and the control by the projection area controller  30  based on the detection result may be performed not only at the start of the system but also every predetermined time period. This makes it possible to prevent overlap of the projected images even when the position of the portable projector  34  is arbitrary changed. 
   Although the video input signals  31  and  28  are input through the signal lines in this embodiment, the signals may be input through various means such as wireless communication, and the format of the signals is arbitrary. 
   When the projection areas are overlapped with each other, a user of the system can select whether or not to prevent the image overlapping by the projection area controller  30  through an interface, not shown. 
   As described above, according to each of the embodiments, detecting the projection area of the projector makes it possible to facilitate detection of overlap of projected images. In addition, controlling the video input signal for the overlap area and inputting it to the projector make it possible to prevent overlap of images. 
   Moreover, the projection area detector detects the image projected by the projector other than one of first and second projectors in a predetermined area on the screen, and recognizes the image projected by the other projector in the projection area. Controlling the projection area of the one projector by the projection area controller based on the detection result makes it possible to prevent image overlapping. 
   In particular, it is possible to respond well to changes of the overlap area due to movements of the projector. 
   Further, when one of plural projectors which respectively project images based on plural video input signals is moved, image overlapping is generated, thereby making recognition of the images hard. 
   In contrast, the multi-projection system including plural projectors which were described in each of the embodiments can prevent the image overlapping that makes recognition of the images hard. 
   Furthermore, it is possible to achieve an arbitrary image space which is adaptable to changes of the projection area due to movements of the projector such as a portable projector. 
   Moreover, according to the above-described embodiments, it is possible to obtain a multi-projection system that can display easily-recognizable images even when the images are projected by plural projectors whose projection areas overlap with each other. 
   In addition, according to the above-described embodiments, it is possible to obtain a projection image display apparatus that display a predetermined image well even when an image projected by a single projector and an image projected by another projector overlap with each other. 
   Furthermore, the present invention is not limited to these preferred embodiments and various variations and modifications may be made without departing from the scope of the present invention. 
   This application claims foreign priority benefits based on Japanese Patent Application No. 2005-265867, filed on Sep. 13, 2005, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.