Patent Publication Number: US-2012026070-A1

Title: Projection display apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2010-171212, filed on Jul. 29, 2010; the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a projection display apparatus that displays an image on a projection surface in cooperation with a second projection display apparatus. 
     2. Description of the Related Art 
     Conventionally, projection display apparatuses have been known which include an imager configured to modulate light emitted from a light source and a projection optical system configured to project the light exiting from the imager onto a projection surface. 
     Here, a technology has been proposed which enables a display system including multiple projection display apparatuses to superpose images respectively projected by the multiple projection display apparatuses on a projection surface (for example, Japanese Patent Application Publication No. Heisei 8-23502). 
     However, it is conceivable that if the multiple projection display apparatuses are in a certain positional relationship, the images respectively projected by the multiple projection display apparatuses cannot be superposed on each other on a projection surface. In other words, the above-described technology necessitates pre-adjustment of the positional relationship between the multiple projection display apparatuses. 
     SUMMARY OF THE INVENTION 
     A projection display apparatus according to a first feature displays an image on a projection surface in cooperation with a second projection display apparatus. The projection image display apparatus includes: a detection unit (detection unit  320 ) that detects the position of the second projection display apparatus; and a switching unit (controller  330 ) that performs switching between a stack display mode and a tile display mode on the basis of the position of the second projection display apparatus. In the stack display mode, an image projected by the projection display apparatus and an image projected by the second projection display apparatus are displayed on the projection surface in a stacked manner. In the tile display mode, an image projected by the projection display apparatus and an image projected by the second projection display apparatus are displayed on the projection surface in a side-by-side manner. 
     In the first feature, the detection unit detects the position of the second projection display apparatus on the basis of an image obtained by capturing an image projected by the second projection display apparatus. 
     In the first feature, the projection display apparatus and the second projection display apparatus are capable of being connected to each other with a connection member. The detection unit detects the position of the second projection display apparatus on the basis of whether or not the projection display apparatus and the second projection display apparatus are connected to each other with the connection member. 
     In the first aspect, the projection display apparatus further includes an output unit (controller  330 ) that outputs assist information used to change a positional relationship between the projection display apparatus and the second projection display apparatus. 
     In the first aspect the projection display apparatus further includes a display unit (controller  330 ) that displays appended information in a region other than an overlap region of the image projected by the projection display apparatus and the image projected by the second projection display apparatus in the stack display mode, the appended information being appended to the image displayed in the overlap region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a projection display apparatus  100  according to a first embodiment. 
         FIG. 2  is a diagram for describing an optical configuration of the projection display apparatus  100  according to the first embodiment. 
         FIG. 3  is a block diagram showing a control unit  300  according to the first embodiment.  FIG. 4  is a diagram showing an example of detection of a second projection display apparatus  100  according to the first embodiment. 
         FIG. 5  is a diagram showing another example of detection of the second projection display apparatus  100  according to the first embodiment. 
         FIG. 6  is a diagram showing still another example of detection of the second projection display apparatus  100  according to the first embodiment. 
         FIG. 7  is a diagram showing an example of a stack display mode according to the first embodiment. 
         FIG. 8  is a diagram showing another example of the stack display mode according to the first embodiment. 
         FIG. 9  is a diagram showing still another example of the stack display mode according to the first embodiment. 
         FIG. 10  is a diagram showing an example of a tile display mode according to the first embodiment. 
         FIG. 11  is a flowchart showing operations of the control unit  300  according to the first embodiment. 
         FIG. 12  is a diagram showing a projection display apparatus  100  according to Modification  1 . 
         FIG. 13  is a diagram showing an example of marks  430  according to Modification 1. 
         FIG. 14  is a diagram showing another example of marks  430  according to Modification 1. 
         FIG. 15  is a diagram showing an example of detection of a second projection display apparatus  100  according to Modification 2. 
         FIG. 16  is a diagram showing another example of detection of the second projection display apparatus  100  according to Modification 2. 
         FIG. 17  is a diagram showing an example of a stack display mode according to Modification 3. 
         FIG. 18  is a diagram showing an example of displaying appended information according to Modification 4. 
         FIG. 19  is a diagram showing another example of displaying appended information according to Modification 4. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     A projection display apparatus according to embodiments of the present invention will be described below with reference to the accompanying drawings. In the following drawings, identical or similar constituents are denoted by identical or similar reference numerals. 
     It should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, the drawings also include portions having different dimensional relationships and ratios from each other. 
     [Outline of Embodiments] 
     A projection display apparatus according to an embodiment displays an image on a projection surface in cooperation with a second projection display apparatus. The projection display apparatus includes: a detection unit that detects the position of the second projection display apparatus; and a switching unit that performs switching between a stack display mode and a tile display mode on the basis of the position of the second projection display apparatus. In the stack display mode, an image projected by the projection display apparatus and an image projected by the second projection display apparatus are displayed on a projection surface in a stacked manner. In the tile display mode, an image projected by the projection display apparatus and an image projected by the second projection display apparatus are displayed on a projection surface in a side-by-side manner. 
     In an embodiment, the detection unit detects the position of the second projection display apparatus, and the switching unit performs switching between the stack display mode and the tile display mode on the basis of the position of the second projection display apparatus. Accordingly, it is possible to appropriately display an image on a projection surface in cooperation with the second projection display apparatus without adjustment of the positional relationship with respect to the second projection display apparatus. 
     First Embodiment 
     (General Configuration of Projection Display Apparatus) 
     Hereinafter, a general configuration of a projection display apparatus according to a first embodiment will be described with reference to the drawings.  FIG. 1  is a diagram showing a projection display apparatus  100  according to the first embodiment. 
     As shown in  FIG. 1 , the projection display apparatus  100  includes a case  200 , and projects an image on a projection surface (unillustrated). The case  200  is provided with a transmission region  210  configured to transmit light exiting from a projection optical system  110  to be described later. 
     In addition, the projection display apparatus  100  include an image sensor  410  and a communication unit  420 . 
     The image sensor  410  captures, for example, an image of the projection surface. The image sensor  410  is provided on, for example, one of the sidewalls of the case  200  on which the transmission region  210  is provided. 
     The communication unit  420  conducts wireless communication based on wireless LAN (for example, Bluetooth or IEEE 802.1 1a/b/g/n), IrDA, or the like with a second projection display apparatus  100 . Note that the communication unit  420  may conduct wired communication with the second projection display apparatus  100 . 
     Note that the size of the projection display apparatus  100  is approximately as large as a pet bottle having a capacity of 200 mL to 2 L. For example, the capacity of the projection display apparatus  100  is approximately 900 mL, and the weight of the projection display apparatus  100  is approximately 800 g. The size of an image displayed by the projection display apparatus  100  is, for example, approximately 20 inches. It should be noted that the distance between the projection display apparatus  100  and the projection surface is extremely short. 
     (Optical Configuration of Projection Display Apparatus) 
     Hereinafter, an optical configuration of the projection display apparatus according to the first embodiment will be described with reference to the drawings.  FIG. 2  is a diagram mainly showing an optical configuration of the projection display apparatus  100  according to the first embodiment. 
     As shown in  FIG. 2 , the projection display apparatus  100  includes the projection optical system  110 , a lighting optical system  120 , a cooling fan  130 , a battery  140 , a power supply board  150 , a main control board  160 , and an operation board  170 . In addition, the projection display apparatus  100  includes a DMD  70  and a reflection prism  80 . 
     The projection optical system  110  projects color component light (image light) exiting from the DMD  70  onto a projection surface. Specifically, the projection optical system  110  includes a projection lens group  111  and a reflection mirror  112 . 
     The projection lens group  111  causes the color component light (image light) exiting from the DMD  70  to exit toward the reflection mirror  112 . The projection lens group  111  includes lenses each having a substantially circular shape centered at an optical axis L of the projection optical system  110 , lenses each having a shape constituted of a part of a substantially circular shape centered at the optical axis L of the projection optical system  110  (for example, a shape of a lower half of a circular shape), or the like. 
     It should be noted that the lenses included in the projection lens group  111  become larger in diameter, as the lenses approach the reflection mirror  112 . 
     The reflection mirror  112  reflects color component light (image light) exiting from the projection lens group  111 . The reflection mirror  112  concentrates the image light and converts the image light into wide-angle light. For example, the reflection mirror  112  is an aspherical mirror having a concave surface on the side of the projection lens group  111 . Here, the reflection mirror  112  has a shape constituted of a part of a substantially circular shape centered at the optical axis L of the projection optical system  110  (for example, a shape of a lower half of a circular shape). 
     The image light condensed by the reflection mirror  112  is transmitted through the transmission region  210  provided on the case  200 . The transmission region  210  provided on the case  200  is preferably located in the vicinity of a position where the image light is condensed by the reflection mirror  112 . 
     The lighting optical system  120  includes a light source  10 , a dichroic prism  30 , a rod integrator  40 , a mirror  51 , a mirror  52 , a lens  61 , a lens  62 , and a lens  63 . 
     The light source  10  emits individual light components of multiple colors. Moreover, the light source  10  may be additionally provided with a heat sink configured to dissipate heat generated by the light source  10 . Note that the light source  10  includes, for example, a light source  10 R, a light source  10 G, and a light source  10 B. 
     The light source  10 R is a light source configured to emit red component light R, and is a red LED (Light Emitting Diode) or a red LD (Laser Diode), for example. The light source  10 R may be additionally provided with a heat sink constituted of a member having a high heat dissipation property, such as a metal member. 
     The light source  10 G is a light source configured to emit green component light G, and is a green LED or a green LD, for example. The light source  10 G may be additionally provided with a heat sink constituted of a member having a high heat dissipation property, such as a metal member. 
     The light source  10 B is a light source configured to emit blue component light B, and is a blue LED or a blue LD, for example. The light source  10 B may be additionally provided with a heat sink constituted of a member having a high heat dissipation property, such as a metal member. 
     The dichroic prism  30  synthesizes the red component light R emitted from the light source  10 R, the green component light G emitted from the light source  10 G, and the blue component light B emitted from the light source  10 B. 
     The rod integrator  40  has a light incident surface, a light exit surface, and a light reflection side surface provided to extend from the circumference of the light incident surface to the circumference of the light exit surface. The rod integrator  40  converts the color component light exiting from the dichroic prism  30  into uniform light. Specifically, the rod integrator  40  converts the color component light into uniform light by reflecting the color component light on the light reflection side surface. Note that the rod integrator  40  may be a solid rod constituted of glass or the like, or a hollow rod whose inner surface is a mirror surface. 
     For example, in the first embodiment, the rod integrator  40  has such a tapered shape that the cross section thereof perpendicular to the traveling direction of the light emitted from the light source  10  becomes larger in the traveling direction of the light. Note, however, that embodiments are not limited thereto. The rod integrator  40  may have such an inverted tapered shape that the cross section thereof perpendicular to the traveling direction of the light emitted from the light source  10  becomes smaller in the traveling direction of the light. 
     The mirror  51  and the mirror  52  are reflection mirrors configured to deflect an optical path of the light exiting from the rod integrator  40  in order to guide the light to the DMD  70 . 
     The lens  61 , the lens  62 , and the lens  63  are relay lenses configured to substantially form an image of the color component light emitted from the light source  10  on the DMD  70 , while suppressing the spreading of the color component light. 
     The cooling fan  130  communicates with the outside of the case  200 , and is configured to dissipate heat inside the case  200 . Alternatively, the cooling fan  130  may be configured to introduce the air into the case  200  from the outside of the case  200 . For example, the cooling fan  130  is provided in the vicinity of the light source  10 , and configured to cool the light source  10 . 
     The battery  140  stores power to be supplied to the projection display apparatus  100 . 
     The power supply board  150  is connected to the battery  140 , and has a power conversion circuit configured to convert AC power into DC power. 
     The main control board  160  includes a main control circuit (a control unit  300  to be described later) configured to control operations of the projection display apparatus  100 . 
     The operation board  170  is connected to an operation unit (buttons and the like) provided to the projection display apparatus  100 , and transmits operation signal inputted from the operation unit to the main control board  160  (the main control circuit). 
     The DMD  70  includes multiple micro mirrors, which are movable. Each of the micro mirrors basically corresponds to one pixel. The DMD  70  changes the angle of each of the micro mirrors to perform switching as to whether or not the color component light is reflected in order to guide the color component light toward the projection optical system  110  as effective light. 
     The reflection prism  80  transmits the light exiting from the lighting optical system  120  toward the DMD  70 . Meanwhile, the reflection prism  80  reflects the light exiting from the DMD  70  toward the projection optical system  110 . 
     (Configuration of Control Unit) 
     Hereinafter, a control unit according to the first embodiment will be described with reference to the drawings.  FIG. 3  is a block diagram showing the control unit  300  according to the first embodiment. The control unit  300  is provided in the projection display apparatus  100 , and controls the projection display apparatus  100 . 
     Note that the control unit  300  converts image input signal into image output signal. The image input signal includes a red input signal R in , a green input signal G in , and a blue input signal B in . The image output signal includes a red output signal R out , a green output signal G out , and a blue output signal B out . The image input signal and the output signal are signal inputted for each of the multiple pixels constituting one frame. 
     As shown in  FIG. 3 , the control unit  300  includes an image signal receiving unit  310 , a detection unit  320 , and a controller  330 . 
     The image signal receiving unit  310  receives image input signal from an external apparatus (unillustrated) such as a DVD player or a TV tuner. 
     The detection unit  320  detects the position of the second projection display apparatus  100 . Specifically, the detection unit  320  is connected to the image sensor  410 , and acquires an image captured by the image sensor  410 . 
     Here, a case where a projection display apparatus  100 B detects the position of a projection display apparatus  100 A is taken as an example. 
     As shown in  FIG. 4 , the projection display apparatus  100 A projects a pattern A in a first color onto a projection surface, whereas the projection display apparatus  100 B projects a pattern B in a second color different from the first color onto the projection surface. In such a case, the detection unit  320  of the projection display apparatus  100 B acquires an image obtained by capturing the pattern A and the pattern B from the image sensor  410 , and detects the position of the projection display apparatus  100 A on the basis of the color of a region where the pattern A and the pattern B overlap each other. It should be noted that the color of the overlap region is a mixture of the first color and the second color. 
     Alternatively, as shown in  FIG. 5 , the projection display apparatus  100 A projects a grid pattern A onto a projection surface, whereas the projection display apparatus  100 B projects another grid pattern B onto the projection surface. In such a case, the detection unit  320  of the projection display apparatus  100 B acquires an image obtained by capturing the pattern A and the pattern B from the image sensor  410 , and detects the position of the projection display apparatus  100 A on the basis of the moiré pattern in the overlap region of the pattern A and the pattern B. 
     Alternatively, as shown in  FIG. 6 , the projection display apparatus  100 A projects a pattern A including multiple wavefronts onto a projection surface. It should be noted that the normal lines of the multiple wavefronts in the pattern A pass through the projection display apparatus  100 A. In such a case, the detection unit  320  of the projection display apparatus  100 B acquires an image obtained by capturing the pattern A from the image sensor  410 , and detects the position of the projection display apparatus  100 A on the basis of the wavefronts included in the pattern A. Specifically, the detection unit  320  detects the position of the projection display apparatus  100 A on the basis of the normal lines of the wavefronts and the spreading of the wavefronts. 
     With reference to  FIG. 3  again, the controller  330  converts the image input signal into the image output signal, and controls the DMD  70  on the basis of the output signal. Moreover, the controller  330  controls the communication unit  420  such that the communication unit  420  communicates with the second projection display apparatus  100 . 
     Here, the controller  330  performs switching between the stack display mode and the tile display mode on the basis of the position of the second projection display apparatus  100 . In the stack display mode, an image projected by the projection display apparatus  100  (a first apparatus) and an image projected by the second projection display apparatus  100  are displayed on a projection surface in a stacked manner. On the other hand, in the tile display mode, an image projected by the projection display apparatus  100  (the first apparatus) and an image projected by the second projection display apparatus  100  are displayed on a projection surface in a side-by-side manner. 
     For example, the controller  330  selects the stack display mode, when the overlap region between a projectable range of the projection display apparatus  100  (the first apparatus) and a projectable range of the second projection display apparatus  100  is larger than a predetermined threshold (for example, 50% of a projectable range). On the other hand, the controller  330  selects the tile display mode, when the overlap region is not larger than the predetermined threshold. 
     Note that the controller  330  controls the DMD  70  such that the DMD  70  displays assist information used to change the positional relationship between the projection display apparatus  100  (the first apparatus) and the second projection display apparatus  100 . For example, when the captured image does not contain the pattern projected by the second projection display apparatus  100 , the controller  330  controls the DMD  70  such that the DMD  70  displays information notifying that the positional relationship between the projection display apparatuses  100  needs to be adjusted, as the assist information. Alternatively, the controller  330  controls the DMD  70  such that the DMD  70  displays information about the direction in which the projection display apparatus  100  (the first apparatus) or the second projection display apparatus  100  needs to be moved in order to employ the stack display mode, as the assist information. Alternatively, the controller  330  controls the DMD  70  such that the DMD  70  displays information about the direction in which the projection display apparatus  100  (the first apparatus) or the second projection display apparatus  100  needs to be moved in order to employ the tile display mode, as the assist information. 
     Hereinafter, a case is shown where the projection display apparatus  100 A and the projection display apparatus  100 B project an image on a projection surface in a cooperative manner. 
     As shown in  FIG. 7 , when a direction in which the projection display apparatus  100 A faces and a direction in which the projection display apparatus  100 B faces are opposite to each other, and the overlap region is larger than the predetermined threshold, the image projected by the projection display apparatus  100 A and the image projected by the projection display apparatus  100 B are superposed on each other (the stack display mode). 
     As shown in  FIG. 8 , when a direction in which the projection display apparatus  100 A faces and a direction in which the projection display apparatus  100 B faces are perpendicular to each other, and the overlap region is larger than the predetermined threshold, the image projected by the projection display apparatus  100 A and the image projected by the projection display apparatus  100 B are superposed on each other (the stack display mode). 
     As shown in  FIG. 9 , when a direction in which the projection display apparatus  100 A faces and a direction in which the projection display apparatus  100 B faces cross each other obliquely, and the overlap region is larger than the predetermined threshold, the image projected by the projection display apparatus  100 A and the image projected by the projection display apparatus  100 B are superposed on each other (the stack display mode). Note that, in the case shown in  FIG. 9 , the images are superposed on each other in a quadrangular region having a predetermined aspect ratio within the overlap region. Note that the quadrangular region having the predetermined aspect ratio is preferably set as large as possible within the overlap region. 
     As shown in  FIG. 10 , when a direction in which the projection display apparatus  100 A faces and a direction in which the projection display apparatus  100 B faces are opposite to each other, and the overlap region is not larger than the predetermined threshold, the image projected by the projection display apparatus  100 A and the image projected by the projection display apparatus  100 B are arranged in a side-by-side manner (the tile display mode). 
     (Operations of Control Unit) 
     Hereinafter, operations of the control unit according to the first embodiment will be described with reference to the drawings.  FIG. 11  is a flowchart showing operations of the control unit  300  according to the first embodiment. 
     As shown in  FIG. 11 , the control unit  300  detects the second projection display apparatus  100  in Step  10 . For example, the control unit  300  detects the second projection display apparatus  100  by transmitting searching packets on the basis of wireless communication technology, for example. 
     In Step  20 , the control unit  300  instructs the second projection display apparatus  100  to project the patterns exemplified in  FIGS. 4 to 6 . In Step  30 , the control unit  300  determines whether or not an image (pattern) projected by the second projection display apparatus  100  is detected on the basis of an image captured by the image sensor  410 . When the image (pattern) is detected, the control unit  300  proceeds to a process in Step  40 . When the image (pattern) is not detected, the control unit  300  proceeds to a process in Step  70 . 
     In Step  40 , the control unit  300  determines (selects) a display mode to be employed from the stack display mode and the tile display mode. 
     In Step  50 , the control unit  300  instructs the second projection display apparatus  100  to employ the display mode determined (selected) in Step  40 . 
     In Step  60 , the control unit  300  projects an image on a projection surface in accordance with the display mode determined (selected) in Step  40 . 
     In Step  70 , the control unit  300  projects assist information used to change the positional relationship between the projection display apparatus  100  and the second projection display apparatus  100  onto the projection surface. 
     (Operations and Effects) 
     In the first embodiment, the detection unit  320  detects the position of the second projection display apparatus  100 , and the controller  330  performs switching between the stack display mode and the tile display mode on the basis of the position of the second projection display apparatus  100 . Accordingly, it is possible to appropriately display an image on a projection surface in cooperation with the second projection display apparatus  100 , without adjustment of the positional relationship with respect to the second projection display apparatus  100 . 
     Modification 1 
     Hereinafter, Modification 1 of the first embodiment will be described. In the following description, differences from the first embodiment will mainly be described. Specifically, in the first embodiment, the detection unit  320  detects the position of the second projection display apparatus  100  on the basis of the image obtained by capturing an image projected by the second projection display apparatus  100 . In contrast, in Modification 1, the detection unit  320  detects the position of the second projection display apparatus  100  on the basis of a mark provided to the second projection display apparatus  100 . 
     For example, as shown in  FIG. 12 , the second projection display apparatus  100  has a mark  430  provided on a sidewall of the case  200 . Note that it is preferable to provide marks  430  in two positions (for example, on left and right sidewalls) of the case  200  so that the direction in which the second projection display apparatus  100  faces can be detected. For example, it is preferable to provide different kinds of marks  430  in two positions of the case  200  as shown in  FIGS. 13 and 14 . 
     Modification 2 
     Hereinafter, Modification 2 of the first embodiment will be described. In the following description, differences from the first embodiment will mainly be described. 
     Specifically, in the first embodiment, the detection unit  320  detects the position of the second projection display apparatus  100  on the basis of an image obtained by capturing the image projected by the second projection display apparatus  100 . In contrast, in Modification 2, the detection unit  320  detects the position of the second projection display apparatus  100  on the basis of whether or not the projection display apparatus  100  and the second projection display apparatus  100  are connected to each other with a connection member (cradles). 
     For example, description is given of a case where the projection display apparatus  100 A is mounted on a cradle  500 A, and the projection display apparatus  100 B is mounted on a cradle  500 B. 
     In such a case, the tile display mode is employed, when the cradle  500 A and the cradle  500 B are directly connected to each other as shown in  FIG. 15 . On the other hand, the stack display mode is employed, when the cradle  500 A and the cradle  500 B are connected to each other with a connection arm  510  as shown in  FIG. 16 . 
     Note that the cases shown in  FIGS. 15  and  FIG. 16  are mere examples. Depending on the shapes of the cradle  500 A and the cradle  500 B, the stack display mode may be employed when the cradle  500 A and the cradle  500 B are directly connected to each other. Likewise, depending on the shape of the connection arm  510 , the tile display mode may be employed when the cradle  500 A and the cradle  500 B are connected to each other with the connection arm  510 . 
     Modification 3 
     Hereinafter, Modification 3 of the first embodiment will be described. In the following description, differences from the first embodiment will mainly be described. 
     Specifically, in the first embodiment, the images are displayed in the stack display mode in such a manner as to be superposed on each other in a quadrangular region having a predetermined aspect ratio within an overlap region of projectable ranges of the multiple projection display apparatuses  100 . In contrast, in Modification  3 , the images are superposed on each other in a circular region within an overlap region of projectable ranges of multiple projection display apparatuses  100  (projection display apparatuses  100 A to  100 C) as shown in  FIG. 17 . 
     In this way, the images may be superposed on each other in a region having any shape. Moreover, any number of projection display apparatuses  100  may be used in cooperation. 
     Modification 4 
     Hereinafter, Modification 4 of the first embodiment will be described. In the following description, differences from the first embodiment will mainly be described. 
     In Modification 4, appended information is displayed in a region which is within the projectable range, and which is other than the region where the image is displayed. Note that the appended information may be information used for interactive operations (for example, drawing toolbar), information for guide to a region where characters can be inputted, information used for a video conference (for example, an image on your end or the other end), information about various menus, a sub screen, subtitles, the previous image slide of a material, information about operational instruction of the projection display apparatus  100 , results of speech recognition, alarm information of the projection display apparatus  100 , data broadcasting, news, date and time information, a calendar, time of image viewing, or the like. 
     Specifically, as shown in  FIG. 18 , the projection display apparatus  100 A displays an image A and also appended information A within the projectable range of the projection display apparatus  100 A in the tile display mode. Likewise, the projection display apparatus  100 B displays an image B and also appended information B within the projectable range of the projection display apparatus  100 B. It should be noted that the image A and the image B are arranged in a side-by-side manner to constitute a single image. 
     Alternatively, as shown in  FIG. 19 , the projection display apparatus  100 A displays an image A and also appended information A within a projectable range of the projection display apparatus  100 A in the stack display mode. Likewise, the projection display apparatus  100 B displays an image B and also appended information B within the projectable range of the projection display apparatus  100 B. It should be noted that the image A and the image B are superposed on each other to constitute a single image. 
     OTHER EMBODIMENTS 
     As described above, the details of the present invention have been disclosed by using the embodiments of the present invention. However, it should not be understood that the description and drawings which constitute part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be easily found by those skilled in the art. 
     In the embodiments, the DMD (Digital Micromirror Device) is shown as a mere example of the imager. The imager may be a liquid crystal panel of a reflection type, or a liquid crystal panel of a transmission type. 
     In the embodiments, the assist information is projected (displayed) on the projection surface. However, embodiments are not limited thereto. The assist information may be outputted as a voice or the like.