Patent Publication Number: US-2018039407-A1

Title: Display device and display control method

Description:
TECHNICAL FIELD 
     The present invention relates to a technology of splitting a screen into a plurality of areas to display an image in each of the areas. 
     BACKGROUND ART 
     In PTL 1, there is disclosed a technology of changing a projection ratio between a main image and a sub-image in a projection device for projecting the main image and the sub-image. This projection device projects a pointer, moves the position of the pointer in accordance with an operation of a cursor key, makes the size of a rectangular frame corresponding to the main image variable, and makes the size of a rectangle corresponding to the sub-image variable in an opposite direction to the variable direction of the main image to thereby change the projection ratio between the main image and the sub-image. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP-A-2009-133985 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the case of using the projector in, for example, a presentation, the user performs the presentation around the projected image. In the case of performing the presentation with, for example, a plurality of image sources projected in this state, it is necessary for the user to move to the place where the projector is installed to operate the projector, or to operate a remote controller, to thereby project the main image and the sub-image, and then change the projection ratio between the images thus projected. However, in the case of moving to the installation place of the projector to operate the projector main body, if the distance between the projector and the projection surface of the images is long, it takes time to move to the installation place of the projector. Further, although it is possible to change the projection ratio with the operation of a key of the remote controller, it is necessary to take along the remote controller or to keep the remote controller around, which requires great care. 
     The invention provides a technology of splitting an image displayed into a plurality of areas with a simple operation. 
     Solution to Problem 
     The invention provides a display device including an image acquisition section adapted to obtain a plurality of image signals, a display section adapted to display images represented by the image signals obtained by the image acquisition section, a position detection section adapted to detect a position pointed by a pointer on a screen displayed by the display section, a drawing section adapted to perform drawing in the screen in accordance with the position detected by the position detection section, an operation detection section adapted to detect an operation performed by the pointer on the screen, and a screen split section adapted to split the screen displayed by the display section into a plurality of areas in accordance with the position detected by the position detection section in a case in which a first operation is detected by the operation detection section, and allocate the images represented by the image signals obtained by the image acquisition section to the respective areas so that the images different from each other are displayed in the plurality of areas. 
     According to this display device, the screen can easily be split into a plurality of areas by an operation with the pointer. 
     The invention may adopt a configuration in which in a case in which the operation detection section detects a second operation in a state in which the screen is split, and then the position detected by the position detection section changes, the screen split section changes sizes of the plurality of areas in accordance with the position having been changed. 
     According to this configuration, the sizes of the split areas can be changed by a specific operation. 
     Further, the invention may adopt a configuration in which at least one of the first operation and the second operation is an operation of making the pointer have contact with the screen a plurality of times. 
     According to this configuration, the screen can be split into a plurality of areas by a simple operation. 
     Further, the invention may adopt a configuration in which the screen split section determines the number of the plurality of areas in accordance with the position detected by the position detection section. 
     According to this configuration, the number of the plurality of areas can be changed in accordance with the position of the pointer. 
     Further, the invention may adopt a configuration in which the screen split section determines the number of the plurality of areas in accordance with the number of the image signals obtained by the image acquisition section. 
     According to this configuration, the number of the plurality of areas can be changed in accordance with the presence or absence of the image signals. 
     Further, the invention may adopt a configuration in which in a case in which the operation detection section detects a third operation in a state in which the screen is split, the screen split section exchanges the image displayed in a first position pointed by the pointer and the image displayed in a second position pointed by the pointer for each other. 
     According to this configuration, the positions of the images displayed in the plurality of areas can be exchanged for each other. 
     Further, the invention may adopt a configuration in which the drawing section skips drawing in accordance with the position of the pointer with respect to an operation detected by the operation detection section. 
     According to this configuration, it is possible to prevent drawing from being performed in accordance with the operation of splitting the screen into a plurality of areas. 
     In addition, the invention provides a display control method including a position detection step of detecting a position pointed by a pointer on a screen displayed by a display section, a drawing step of performing drawing in the screen in accordance with the position detected in the position detection step, an operation detection step of detecting an operation performed by the pointer on the screen, and a screen split step of splitting the screen displayed by the display section into a plurality of areas in accordance with the position detected in the position detection step in a case in which a first operation is detected in the operation detection step, and allocating images represented by image signals obtained by an image acquisition section to the respective areas so that the images different from each other are displayed in the plurality of areas. 
     According to this method, the screen can easily be split into a plurality of areas by an operation with the pointer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing a device constituting a display system  1 . 
         FIG. 2  is a diagram showing a hardware configuration of a projector  10  and a pointer  20 . 
         FIG. 3  is a diagram showing information stored in a first table. 
         FIG. 4  is a functional block diagram of a control section  110  and a control section  210 . 
         FIG. 5  is a diagram showing an example of a time chart of detecting the pointer. 
         FIG. 6  is a flowchart showing a flow of a process executed by the control section  110 . 
         FIG. 7  is a diagram showing coordinates of a projection area. 
         FIG. 8  is a diagram showing a relationship between a split position Pos and the projection area thus split. 
         FIG. 9  is a flowchart showing a flow of a process executed by the control section  110 . 
         FIG. 10  is a diagram showing a relationship between the split position Pos and the projection area thus split. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 
       FIG. 1  is a diagram showing a device constituting a display system  1  according to an embodiment of the invention. The display system  1  is provided with a projector  10  for projecting an image on a screen SC (a projection surface), a pointer  20 , and a light emitting device  30 . 
     The projector  10  as an example of the display device is connected to an external device for supplying an image signal, and projects an image represented by the image signal, which is supplied from the external device, on the screen SC. Further, the projector  10  is provided with an interactive function of performing writing to the image projected with a finger or the pointer  20 . The projector  10  according to the present embodiment is disposed obliquely above the screen SC, and projects the image toward the screen SC. Although in the present embodiment, the projector  10  projects the image toward the screen SC, it is also possible to project the image on a wall surface (the projection surface) instead of the screen SC. Further, in the present embodiment, the projector  10  has a configuration of being mounted on the wall surface with a bracket, but can also be mounted on the ceiling. Further, the projector  10  is not limited to the configuration of being mounted on the wall surface or the ceiling, but can also be a standing type to be disposed on a table. 
     The pointer  20  having a pen-like shape functions as a pointing device for operating the projector  10 , and is used when the user operates the GUI (Graphical User Interface) projected by the projector  10 , when the user performs writing to the image thus projected, and so on. 
     The light emitting device  30  has a light emitting section for emitting light (infrared light in the present modified example). The light emitting device  30  is disposed above an upper end of the screen SC, and emits the light dispersed in a range of the angle θ downward. The light emitted from the light emitting device  30  forms a layer of light extending along the screen SC. In the present embodiment, the angle θ reaches about 180 degrees, and thus, the layer of light is formed on the roughly entire area of the screen SC. It is preferable for the surface of the screen SC and the layer of light formed by the light emitting device  30  to be adjacent to each other. The projector  10  controls emission of the light from the light emitting device  30 . 
       FIG. 2  is a diagram showing a hardware configuration of the projector  10  and the pointer  20 . The pointer  20  has a control section  210 , a communication section  220 , a light emitting section  230 , an operation section  240 , and a power supply  250 . The power supply  250  is, for example, a dry battery or a secondary cell, and supplies the control section  210 , the communication section  220 , the light emitting section  230 , and the operation section  240  with electric power. The operation section  240  is provided with a switch (not shown) for controlling the supply of the electric power from the power supply  250  to each of the sections. When the switch of the operation section  240  is set to the ON state, the electric power is supplied from the power supply  250  to each of the sections, and when the switch of the operation section  240  is set to the OFF state, the supply of the electric power from the power supply  250  to each of the sections is stopped. The light emitting section  230  has a light emitting diode for emitting infrared light, and is disposed on the tip of the pointer  20 . The control section  210  controls lighting and extinction of the light emitting section  230 . The light emitting section  230  is a point light source, and the light emitted by the light emitting section  230  spreads from the tip of the pointer  20  in a spherical manner. The communication section  220  is provided with a light receiving element for receiving the infrared light. The communication section  220  receives a variety of signals transmitted from the projector  10  with the infrared light. The communication section  220  converts the variety of signals thus received into electric signals, and then supplies the control section  210  with the electric signals. The control section  210  is connected to the light emitting section  230  and the communication section  220 . The control section  210  starts the control of the light emitting section  230  in accordance with the signal supplied from the communication section  220  to control lighting and extinction of the light emitting diode of the light emitting section  230 . The control section  210  and the light emitting section  230  function as a light emitting device for making the pointer  20  emit light. 
     The projector  10  is provided with a control section  110 , a storage section  120 , an operation section  130 , and a projection section  140 . Further, the projector  10  is provided with an image processing section  150 , an image interface  160 , an imaging section  170 , and a communication section  180 . The control section  110  is a microcomputer provided with a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). When the CPU executes a program stored in the ROM, the control section  110  controls each of the sections to realize a function of projecting an image on the screen SC, an interactive function, a function of using a finger and the pointer  20  as a pointing device, and so on in the projector  10 . 
     Further, in the projector  10 , there are realized a variety of functions such as a function of controlling emission of the infrared light from the light emitting device  30  connected to the control section  110 , a screen split function of splitting a rectangular projection area for displaying the image into a plurality of areas and projecting the image of the imagesignal supplied from an external device on the areas obtained by the split, a function of changing the number or the areas of the areas obtained by the split, and a function of exchanging the images to be projected on the areas obtained by the split. 
     The image interface  160  has a plurality of connectors supplied with an image signal such as RCA, D-sub, HDMI (registered trademark), or USB, and supplies the image processing section  150  with the image signal supplied from the external device to the connectors. The image interface  160  is an example of an image acquisition section for obtaining a plurality of image signals. It is also possible for the image interface  160  to have an interface for wireless communication such as wireless LAN or Bluetooth (registered trademark) to obtain the image signals with the wireless communication. 
     The storage section  120  stores a setting value related to the image quality of the image to be projected and information related to the setting of a variety of functions. Further, the storage section  120  stores a first table storing a correspondence relationship between the areas of the projection area split by the screen split function and the image signals of the images to be projected on the respective areas. 
     In the present embodiment, in the case in which the screen split function has been performed, the projection area is split into up to four areas, namely first through fourth areas. Therefore, in the first table in the initial state, regarding the first through fourth areas, a first image source S 1  is associated with the first area, a second image source S 2  is associated with the second area, a third image source S 3  is associated with the third area, and a fourth image source S 4  is associated with the fourth area, as shown in  FIG. 3 . 
     The operation section  130  is provided with a plurality of buttons for operating the projector  10 . By the control section  110  controlling each of the sections in accordance with the button having been operated, an adjustment of the image to be projected on the screen SC, setting of a variety of functions provided to the projector  10 , and so on are performed. Further, the operation section  130  is provided with a light receiving section (not shown) for receiving an infrared signal from a remote controller (not shown). The operation section  130  converts the signal transmitted from the remote controller into an electric signal to supply the control section  110 , and then the control section  110  controls each of the sections in accordance with the signal supplied. 
     The projection section  140  and the image processing section  150  function as a display section for displaying an image in cooperation with each other. 
     The image processing section  150  obtains the image signal supplied from the image interface  160 . Further, the image processing section  150  obtains the signal of an on-screen image such as a GUI for operating the projector  10 , a cursor showing a position pointed by the pointer  20 , and an image drawn with the interactive function from the control section  110 . The image processing section  150  is provided with a variety of image processing functions, and performs image processing on the image signal supplied from the image interface  160  to adjust the image quality of the image to be projected. In the case in which the image processing section  150  is supplied with the signal of the on-screen image from the control section  110 , the image processing section  150  supplies the projection section  140  with the image signal on which the signal of the on-screen image is superimposed. 
     Further, in the case in which the control section  110  performs the screen split function, the image processing section  150  splits the projection area into a plurality of areas, then generates an image signal in which the image of the image signal supplied from the external device is allocated to the areas obtained by the split, and then supplies the projection section  140  with the image signal thus generated. 
     The projection section  140  for projecting the image includes a light source  141 , a light valve  142 , a drive circuit  144 , and a projection optical system  143 . The light source  141  is a lamp for emitting light, and the light emitted by the light source  141  is dispersed by a plurality of dichroic mirrors and mirrors not shown into light beams of red, green, and blue, and the light beams of red, green, and blue obtained by the dispersion are guided to the light valve  142 . It should be noted that the light source  141  can also be a light emitting diode or a semiconductor laser device for emitting a laser beam instead of the lamp. 
     The drive circuit  144  obtains the image signal supplied from the image processing section  150 . The image signal supplied to the drive circuit  144  includes grayscale data representing a grayscale of a red component in the image to be projected, grayscale data representing a grayscale of a green component in the image to be projected, and grayscale data representing a grayscale of a blue component in the image to be projected. The drive circuit  144  extracts the grayscale data of each of the colors of red, green, and blue to drive the light valve  142  based on the grayscale data of each color thus extracted. 
     The light valve  142  includes a liquid crystal light valve to which the red light beam described above is input, a liquid crystal light valve to which the green light beam described above is input, and a liquid crystal light valve to which the blue light beam described above is input. The liquid crystal light valves are each a transmissive liquid crystal panel, and are each provided with pixels arranged in a matrix with a plurality of rows and a plurality of columns. The liquid crystal light valve to which the red light beam is input is driven based on the red grayscale data, the liquid crystal light valve to which the green light beam is input is driven based on the green grayscale data, and the liquid crystal light valve to which the blue light beam is input is driven based on the blue grayscale data. In each of the liquid crystal light valves, the drive circuit  144  controls each of the pixels to vary the transmittance of the pixel. By controlling the transmittance of the pixels, the light beams of the respective colors having been transmitted through the respective liquid crystal light valves form the images corresponding to the respective grayscale data. The images of the light beams of red, green, and blue having been transmitted through the respective liquid crystal light valves are combined with each other by a dichroic prism not shown, and then enter the projection optical system  143 . The projection optical system  143  is an optical system for enlarging the image having entered the projection optical system  143 , and projects the image having entered the projection optical system  143  on the screen SC in an enlarged manner using a lens or a mirror. 
     The imaging section  170  is provided with an imaging element (e.g., CMOS or CCD) for receiving the infrared light emitted by the light emitting section  230  and the infrared light, which has been emitted from the light emitting device  30  and then reflected by a finger, an optical system for forming an image on the imaging element, an aperture for limiting the light entering the imaging element, and so on. The imaging section  170  has an imaging range including the screen SC, generates an image of the range thus imaged, and then outputs an image signal representing the image thus generated. It should be noted that in the present embodiment, since the projector  10  is installed obliquely above the screen SC, it results that the imaging section  170  images the range including the screen SC from obliquely above. The communication section  180  is provided with a light emitting diode for emitting infrared light. The communication section  180  is controlled by the control section  110  in lighting and extinction of the light emitting diode, and transmits an infrared signal for controlling lighting and extinction of the light emitting section  230 . 
       FIG. 4  is a functional block diagram showing a configuration of functions realized by the control section  110  executing programs, and functions realized by the control section  210 . Firstly, there will be described the functions realized by the control section  110  of the projector  10 . 
     A distance acquisition section  111  obtains a distance from the imaging section  170  to the projection surface. Specifically, the distance acquisition section  111  controls the image processing section  150  to project a pattern image for measuring the distance from the imaging section  170  to the projection surface on the screen SC. When the pattern image is projected on the screen SC, the distance acquisition section  111  makes the imaging section  170  take the pattern image thus projected to obtain the distance to the projection surface based on the size of the pattern image thus taken. It should be noted that it is also possible for the distance acquisition section  111  to obtain the information related to the distance input by the user operating the remote controller or the operation section  130 . Here, the information necessary for the distance acquisition section  111  to obtain is not limited to the distance itself, but can also be information (information corresponding to the distance) related to the distance. In the case in which, for example, the projector  10  does not have a zoom function, since the screen size is determined in accordance with the distance from the imaging section  170  to the projection surface, it is also possible to arrange that the user is required to input the screen size as the information related to the distance. Further, regarding the distance from the imaging section  170  to the projection surface, it is possible to provide a distance sensor to the projector  10 , and then obtain the distance from the imaging section  170  to the projection surface from the measurement result of the distance sensor. 
     A position detection section  112  identifies a position pointed by the pointer  20  or a finger as an example of the pointer on the screen projected using, for example, the time chart shown in  FIG. 5 . The period for identifying the position pointed by the finger or the position pointed by the pointer  20  includes four phases, namely from a phase P 11  to a phase P 14  as shown in  FIG. 5 . When detecting the position pointed by the finger and the position pointed by the pointer  20 , the phases P 11  through P 14  are repeated. The phase P 11  is a phase for synchronizing the timing at which the projector  10  performs imaging with the imaging section  170  and the timing at which the pointer  20  emits light with each other. In the phase P 11 , the position detection section  112  controls the communication section  180  so that a sync signal of the infrared light is output in a predetermined period te 1 . 
     In the pointer  20 , the communication section  220  receives the light of the sync signal, and when a predetermined time has elapsed after receiving the sync signal, the control section  210  controls the light emitting section  230  so that the light emitting section  230  lights in the period te 2  set in advance. In the present embodiment, the light emitting section  230  is controlled so as to light from a starting point of each of the phases P 12 , P 13 , and P 14 . 
     Further, the position detection section  112  controls the light emitting device  30  so that the light emitting device  30  emits the infrared light in the period te 2  from the starting point of each of the phases P 12  and the phases P 14 . 
     In the phases P 12  through P 14 , the position detection section  112  controls the imaging section  170  to image the predetermined range including the screen SC at a shutter speed set to the imaging section  170 . In the imaging section  170 , an exposure period in which the exposure is performed using the electronic shutter function begins at the starting point of each of the phases P 12  and P 14 , and the point at which the exposure ends is determined in accordance with the shutter speed set to the imaging section  170 . The image signal of the image taken by the imaging section  170  in the exposure period of each of the phases P 12  through P 14  is supplied to the position detection section  112 . 
     The position detection section  112  identifies the position pointed by the finger or the pointer  20  on the image thus projected using the image represented by the image signal supplied to the position detection section  112  and the distance obtained by the distance acquisition section  111 . Specifically, in the second phase P 12  and the fourth phase P 14 , in the case in which the finger has contact with the screen SC, the infrared light, which has been emitted from the light emitting device  30  and then reflected by the finger, is reflected in the image obtained by the imaging section  170 . Further, in the second phase P 12  and the fourth phase P 14 , if the pointer  20  has contact with the screen SC, the infrared light having been emitted from the pointer  20  is also reflected in the image obtained by the imaging section  170 . In the third phase P 13 , since the light emitting device  30  does not emit the light, the infrared light emitted by the pointer  20  is reflected in the image obtained by the imaging section  170 . 
     The position detection section  112  identifies the infrared light located at a position closer to the position of the infrared light reflected in the image obtained by the imaging section  170  in the third phase P 13  out of the infrared light reflected in the image obtained by the imaging section  170  in the second phase P 12  and the infrared light reflected in the image obtained by the imaging section  170  in the fourth phase P 14 , and then determines the position of the infrared light thus identified as the position of the pointer  20 . Further, the position detection section  112  identifies the infrared light located at a position further from the position of the infrared light reflected in the image obtained by the imaging section  170  in the third phase P 13  out of the infrared light reflected in the image obtained by the imaging section  170  in the second phase P 12  and the infrared light reflected in the image obtained by the imaging section  170  in the fourth phase P 14 , and then determines the position of the infrared light thus identified as the position of the finger. The position thus identified is used when using the pointer  20  as a pointing device, or when performing the variety of functions. 
     An operation detection section  113  analyzes the image signal supplied from the imaging section  170 , and then detects a specific operation performed by the user on the projection surface based on the infrared light reflected in the image represented by the image signal. 
     In the case in which the operation detection section  113  detects the specific operation, a screen split section  114  splits the projection area into a plurality of areas in accordance with the position detected by the position detection section  112 , and then controls the image processing section  150  so that images different from each other are respectively displayed in the plurality of areas. 
     A drawing section  115  performs drawing in accordance with the position detected by the position detection section  112  in the image to be projected. It should be noted that regarding the position where the specific operation detected by the operation detection section  113  has been performed, the drawing section  115  does not perform drawing in accordance with the position detected by the position detection section  112 . 
     Then, there will be described the functions realized by the control section  210  of the pointer  20 . The signal acquisition section  211  obtains the sync signal received by the communication section  220 . A light emission control section  212  obtains the sync signal from the signal acquisition section  211 , and then controls the light emitting section  230  so that the light emitting section  230  lights in the period te 2  in each of the phase P 12  and the phase P 14  when a predetermined time elapses after the sync signal is obtained. 
     (Operation Example of Embodiment) 
     Then, an operation example of the present embodiment will be described with reference to  FIGS. 6 through 9 . It should be noted that in the following description, the explanation is presented assuming that the image signal supplied to a D-Sub connector of the image interface  160  is a first image source S 1 , the image signal supplied to an HDMI connector is a second image source S 2 , an image signal supplied to a USB connector is a third image source S 3 , and an image signal supplied to an RCA connector is a fourth source connector S 4 . 
     (Operation Example when Splitting Projection Screen into Two or More Areas to Project Image of Image Signal Supplied from External Device on Split Areas) 
       FIG. 6  is a flowchart showing a flow of a process of splitting the projection area into a plurality of areas and projecting the image of the image source supplied from the external device on the split areas. When a predetermined specific operation is performed, the control section  110  performs the process of splitting the projection area. In the present embodiment, the predetermined specific operation (a first operation) is an operation of “touching the projection surface with two fingers→separating the two fingers from the projection surface→making the two fingers have contact with the projection surface again→keeping the two fingers having contact with the projection surface for a period longer than a predetermined time”. The control section  110  analyzes the image signal supplied from the imaging section  170  to determine whether or not the predetermined specific operation has been performed by the user. 
     Specifically, when the user of the projector  10  firstly touches the projection surface with two fingers (e.g., a thumb and an index finger), the infrared light emitted from the light emitting device  30  is reflected by the two fingers touching the projection surface, and then the light thus reflected enters the imaging section  170 . The control section  110  analyzes the image signal supplied from the imaging section  170 , and in the case in which two infrared light beams having been reflected by the fingers are reflected in the image taken by the imaging section  170 , the control section  110  determines that the two fingers have contact with the screen SC to start the process shown in  FIG. 6 . 
     Firstly, the control section  110  determines whether or not the image signal, in which the infrared light beams having been reflected by the fingers are not reflected, is supplied from the imaging section  170  within a predetermined time after it has been determined that the two fingers have contact with the screen SC, namely whether or not the two fingers are separated from the projection surface within a predetermined time after the two fingers have had contact with the projection surface (step SA 1 ). Here, in the case in which the image signal, in which the infrared light beams having been reflected by the fingers are not reflected, is supplied from the imaging section  170  within a predetermined time after it has been determined that the two fingers have contact with the screen SC (YES in the step SA 1 ), the control section  110  determines that the two fingers are separated from the projection surface within the predetermined time. 
     Then, the control section  110  determines whether or not the image signal, in which the two infrared light beams reflected by the fingers are reflected, has been supplied from the imaging section  170  within a predetermined time after it has been determined YES in the step SA 1 , namely whether or not the two fingers have had contact with the projection surface again within the predetermined time (step SA 2 ). Here, in the case in which the two infrared beams reflected by the fingers are reflected in the image taken within the predetermined time after it has been determined YES in the step SA 1  (YES in the step SA 2 ), the control section  110  determines that the two fingers have had contact within the predetermined time. 
     In the case in which it has been determined YES in the step SA 2 , the control section  110  identifies the positions of the two fingers on the projection surface, and then determines the split position when splitting the projection area into two or more areas based on the position thus identified (step SA 3 ). Here, the control section  110  identifies the position of the midpoint of a line segment connecting the positions of the two fingers, and then uses the position thus identified as a split position Pos. 
     In the present embodiment, as shown in  FIG. 7 , assuming that the width of the projection area having a rectangular shape in the non-split state is w, and the height thereof is h, and the coordinate of the upper left vertex of the projection area is (0, 0), the coordinate of the upper right vertex becomes (w, 0), the coordinate of the lower left vertex becomes (0, h), and the coordinate of the lower right vertex becomes (w, h). The control section  110  splits the projection area as, for example, shown in  FIG. 8  in accordance with the coordinate of the split position Pos thus identified (step SA 4 ). 
     In the present embodiment, in the case in which the coordinate of the split position Pos is assumed as (a, b), if, for example, the coordinate in the horizontal direction of the split position Pos fulfills 0&lt;a&lt;w, and the coordinate in the vertical direction of the split position Pos fulfills 0&lt;b&lt;h, the control section  110  splits the projection area into four areas as shown in the second row and the second column of  FIG. 8 . Further, if the coordinate in the horizontal direction of the split position Pos fulfills 0&lt;a&lt;w, and the coordinate in the vertical direction of the split position Pos fulfills b=0 or b=h, the control section  110  splits the projection area into two areas as shown in the first row and the second column, or the third row and the second column of  FIG. 8 . Further, if the coordinate in the vertical direction of the split position Pos fulfills 0&lt;b&lt;h, and the coordinate in the horizontal direction of the split position Pos fulfills a=0 or a=w, the control section  110  splits the projection area into two areas as shown in the second row and the first column, or the second row and the third column of  FIG. 8 . 
     Then, the control section  110  controls the image processing section  150  so that the images of the image sources corresponding to the respective areas are projected in the respective areas obtained by the split in accordance with the information stored in the first table (step SA 5 ). For example, the control section  110  splits the projection area into four areas, and uses the upper left area as a first area A 1 , the upper right area as a second area A 2 , the lower left area as a third area A 3 , and the lower light area as a fourth area A 4  as shown in the second row and the second column of  FIG. 8 . Then, in the case in which the first table is in the state shown in  FIG. 3 , the control section  110  controls the image processing section  150  in accordance with the first table so that the image of the first image source S 1  is projected in the first area A 1 , the image of the second image source S 2  is projected in the second area A 2 , the image of the third image source S 3  is projected in the third area A 3 , and the image of the fourth image source S 4  is projected in the fourth area A 4 . 
     The control section  110  splits the projection area, and then determines whether or not the two infrared light beams reflected by the fingers are reflected in the image taken by the imaging section  170 , namely whether or not the two fingers have contact with the screen SC (step SA 6 ). In the case in which the infrared light beams reflected by the fingers are not reflected in the image thus taken, namely the fingers of the user are separated from the projection surface after splitting the projection area, the control section  110  terminates the process shown in  FIG. 6 . 
     Further, in the case in which the infrared light beams reflected by the two fingers are reflected in the image thus taken (YES in the step SA 6 ), the control section  110  determines that the two fingers have contact with the screen SC. In the case in which it has been determined YES in the step SA 6 , the control section  110  identifies the positions of the two fingers on the projection surface, and then determines the latest split position Pos when splitting the projection area into two or more areas based on the position thus identified (step SA 7 ). Here, in the case in which the two fingers have moved and the newly identified split position Pos is different from the position having been identified last time, the control section  110  splits the projection area in accordance with the split position Pos newly identified (step SA 8 ). Then, the control section  110  controls the image processing section  150  so that the images are projected in the respective areas obtained by the split in accordance with the information stored in the first table (step SA 9 ), and then returns the flow of the process to the step SA 6 . 
     For example, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills 0&lt;a&lt;w, and the coordinate in the vertical direction of the split position fulfills b=0, the control section  110  splits the projection area into two areas in the horizontal direction, uses the left area as the third area A 3 , and the right area as the fourth area A 4 , and controls the image processing section  150  so that the image of the third image source S 3  is projected in the third area A 3 , and the image of the fourth image source S 4  is projected in the fourth area A 4  as shown in the first row and the second column of  FIG. 8 . 
     Further, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills 0&lt;a&lt;w, and the coordinate in the vertical direction of the split position Pos fulfills b=h, the control section  110  splits the projection area into two areas in the horizontal direction, uses the left area as the first area A 1 , and the right area as the second area A 2 , and controls the image processing section  150  so that the image of the first image source S 1  is projected in the first area A 1 , and the image of the second image source S 2  is projected in the second area A 2  as shown in the third row and the second column of  FIG. 8 . 
     Further, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills a=0, and the coordinate in the vertical direction of the split position Pos fulfills 0&lt;b&lt;h, the control section  110  splits the projection area into two areas in the vertical direction, uses the upper area as the second area A 2 , and the lower area as the fourth area A 4 , and controls the image processing section  150  so that the image of the second image source S 2  is projected in the second area A 2 , and the image of the fourth image source S 4  is projected in the fourth area A 4  as shown in the second row and the first column of  FIG. 8 . 
     Further, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills a=w, and the coordinate in the vertical direction of the split position Pos fulfills 0&lt;b&lt;h, the control section  110  splits the projection area into two areas in the vertical direction, uses the upper area as the first area A 1 , and the lower area as the third area A 3 , and controls the image processing section  150  so that the image of the first image source S 1  is projected in the first area A 1 , and the image of the third image source S 3  is projected in the third area A 3  as shown in the second row and the third column of  FIG. 8 . 
     Further, in the case in which the coordinate of the split position Pos coincides with the coordinate of one of the vertexes of the projection area, the control section  110  selects the image to be projected in accordance with the first table and the coordinate of the split position Pos, and then projects the image thus selected. For example, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills a=0, and the coordinate in the vertical direction fulfills b=0, the control section  110  uses the projection area as the fourth area A 4 , and controls the image processing section  150  so that the image of the fourth image source S 4  is projected in the projection area as shown in the first row and the first column of  FIG. 8 . Further, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills a=w, and the coordinate in the vertical direction fulfills b=0, the control section  110  uses the projection area as the third area A 3 , and controls the image processing section  150  so that the image of the third image source S 3  is projected in the projection area as shown in the first row and the third column of  FIG. 8 . Further, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills a=0, and the coordinate in the vertical direction fulfills b=h, the control section  110  uses the projection area as the second area A 2 , and controls the image processing section  150  so that the image of the second image source S 2  is projected in the projection area as shown in the third row and the first column of  FIG. 8 . Further, in the case in which the coordinate in the horizontal direction of the split position Pos fulfills a=w, and the coordinate in the vertical direction fulfills b=h, the control section  110  uses the projection area as the first area A 1 , and controls the image processing section  150  so that the image of the first image source S 1  is projected in the projection area as shown in the third row and the third column of  FIG. 8 . 
     As described hereinabove, according to the present embodiment, it is possible to split the projection area into a plurality of areas, and then project the plurality of images without operating the operation section  130  or the remote controller. 
     (Operation Example when in the Case of Exchanging Images Projected in Split Areas) 
       FIG. 9  is a flowchart showing a flow of the process of exchanging the images projected in the split areas. When a predetermined specific operation is performed in the state in which the projection area is split, the control section  110  performs the process of exchanging the images projected in the two areas for each other. In the present embodiment, the predetermined specific operation (a third operation) triggering the process of exchanging the images projected in the split areas is an operation of “touching the projection surface with three fingers→separating the three fingers from the projection surface→making the three fingers have contact with the projection surface again→keeping the three fingers having contact with the projection surface for a period longer than a predetermined time”. The control section  110  analyzes the image signal supplied from the imaging section  170  to determine whether or not the predetermined specific operation has been performed with the fingers of the user. 
     Specifically, when the user of the projector  10  firstly touches the projection surface with three fingers (e.g., a thumb, an index finger, and a middle finger), the infrared light emitted from the light emitting device  30  is reflected by the three fingers touching the projection surface, and then the light thus reflected enters the imaging section  170 . The control section  110  analyzes the image signal supplied from the imaging section  170 , and in the case in which three infrared light beams having been reflected by the fingers are reflected in the image taken by the imaging section  170 , the control section  110  determines that the three fingers have contact with the screen SC to start the process shown in  FIG. 9 . 
     Firstly, the control section  110  determines whether or not the image signal, in which the infrared light beams having been reflected by the fingers are not reflected, is supplied from the imaging section  170  within a predetermined time after it has been determined that the three fingers have contact with the screen SC in the image taken, namely whether or not the three fingers are separated from the projection surface within a predetermined time after the three fingers have had contact with the projection surface (step SB 1 ). Here, in the case in which the image signal, in which the infrared light beams having been reflected by the fingers are not reflected, is supplied from the imaging section  170  within a predetermined time after it has been determined that the three fingers have contact with the screen SC (YES in the step SB 1 ), the control section  110  determines that the three fingers are separated from the projection surface within the predetermined time. 
     Then, the control section  110  determines whether or not the image signal, in which the three infrared light beams reflected by the fingers are reflected, has been supplied from the imaging section  170  within a predetermined time after it has been determined YES in the step SB 1 , namely whether or not the three fingers have had contact with the projection surface again within the predetermined time (step SB 2 ). Here, in the case in which the three infrared beams reflected by the fingers are reflected in the image taken within the predetermined time after it has been determined YES in the step SB 1  (YES in the step SB 2 ), the control section  110  determines that the three fingers have had contact within the predetermined time. 
     In the case in which it has been determined YES in the step SB 2 , the control section  110  identifies the positions of the three fingers on the projection surface, and then stores one of the coordinates of the three positions thus identified in the RAM as a first coordinate (step SB 3 ). It should be noted that although in the present embodiment, the coordinate of the position of the finger located at the uppermost position out of the positions of the three fingers is used as the first coordinate, it is also possible to use the coordinate of the position of the finger located at the lowermost position as the first coordinate. Further, the position of the finger closest to the origin in the horizontal direction out of the positions of the three fingers can also be used as the first coordinate, or the position of the finger furthest to the origin in the horizontal direction out of the positions of the three fingers can also be used as the first coordinate. 
     The control section  110  stores the first coordinate, and then analyzes the image signal supplied from the imaging section  170  to determine whether or not the three fingers have contact with the projection surface (step SB 4 ). In the case in which the infrared light beams are reflected in three places in the image represented by the image signal supplied from the imaging section  170 , namely in the case in which the fingers of the user are not separated from the projection surface, the control section  110  identifies the positions of the three fingers, and then stores one of the coordinates of the three positions thus identified in the RAM as a second coordinate (step SB 5 ). Then, the control section  110  returns the flow of the process to the step SB 4 , and then identifies the position of the finger located at the uppermost position out of the three fingers to update the second coordinate with the coordinate of the position thus identified during the period in which the three fingers of the user have contact. 
     In the case in which the infrared light beams are not reflected in the image represented by the image signal supplied from the imaging section  170 , namely in the case in which the three fingers of the user are separated from the projection surface (NO in the step SB 4 ), the control section  110  exchanges the images projected on the split areas based on the first coordinate and the second coordinate stored in the RAM (step SB 6 ). 
     Specifically, the control section  110  identifies a first exchange area including the first coordinate stored and a second exchange area including the second coordinate stored. 
     For example, assuming that the coordinate of the split position in the case in which the projection area is split into four areas is (a, b), and the first coordinate is (c, d), the control section  110  identifies the first area A 1  as the first exchange area in the case in which c&lt;a and d&lt;b are fulfilled, identifies the second area A 2  as the first exchange area in the case in which ca and d&lt;b are fulfilled, identifies the third area A 3  as the first exchange area in the case in which c&lt;a and c≧a are fulfilled, and identifies the fourth area A 4  as the first exchange area in the case in which c≧a and d≧b are fulfilled. 
     Further, assuming that the coordinate of the split position in the case in which the projection area is split into four areas is (a, b), and the second coordinate is (e, f), the control section  110  identifies the first area A 1  as the second exchange area in the case in which e&lt;a and f&lt;b are fulfilled, identifies the second area A 2  as the second exchange area in the case in which ea and f&lt;b are fulfilled, identifies the third area A 3  as the second exchange area in the case in which e&lt;a and f≧b are fulfilled, and identifies the fourth area A 4  as the second exchange area in the case in which e≧a and f≧b are fulfilled. 
     Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the first coordinate is (c, d), if 0&lt;a&lt;w and b=0 are fulfilled, the control section  110  identifies the third area A 3  as the first exchange area in the case of c&lt;a, and identifies the fourth area A 4  as the first exchange area in the case of c≧a. Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the second coordinate is (e, f), if 0&lt;e&lt;w and b=0 are fulfilled, the control section  110  identifies the third area A 3  as the second exchange area in the case of e&lt;a, and identifies the fourth area A 4  as the second exchange area in the case of e≧a. 
     Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the first coordinate is (c, d), if 0&lt;a&lt;w and b=h are fulfilled, the control section  110  identifies the first area A 1  as the first exchange area in the case of c&lt;a, and identifies the second area A 2  as the first exchange area in the case of c≧a. Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the second coordinate is (e, f), if 0&lt;e&lt;w and b=h are fulfilled, the control section  110  identifies the first area A 1  as the second exchange area in the case of e&lt;a, and identifies the second area A 2  as the second exchange area in the case of e≧a. 
     Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the first coordinate is (c, d), if 0&lt;b&lt;h and a=0 are fulfilled, the control section  110  identifies the second area A 2  as the first exchange area in the case of d&lt;b, and identifies the fourth area A 4  as the first exchange area in the case of d≧b. Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the second coordinate is (e, f), if 0&lt;f&lt;h and a=0 are fulfilled, the control section  110  identifies the second area A 2  as the second exchange area in the case of f&lt;b, and identifies the fourth area A 4  as the second exchange area in the case of f≧b. 
     Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the first coordinate is (c, d), if 0&lt;b&lt;h and a=w are fulfilled, the control section  110  identifies the first area A 1  as the first exchange area in the case of d&lt;b, and identifies the third area A 3  as the first exchange area in the case of d≧b. Further, assuming that the coordinate of the split position in the case in which the projection area is split into two areas is (a, b), and the second coordinate is (e, f), if 0&lt;f&lt;h and a=w are fulfilled, the control section  110  identifies the first area A 1  as the second exchange area in the case of f&lt;b, and identifies the third area A 3  as the second exchange area in the case of f≧b. 
     In the case in which the first exchange area and the second exchange area are the same, the control section  110  does not exchange the images projected in the split areas for each other but terminates the process shown in  FIG. 9 . In the case in which the first exchange area and the second exchange area are different from each other, the control section  110  exchanges the image source of the image projected in the first exchange area and the image source of the image projected in the second exchange area for each other. 
     For example, in the case in which the projection area is split into four areas, the first exchange area is the first area A 1 , and the second exchange area is the fourth area A 4 , the control section  110  exchanges the image source associated with the first area in the first table and the image source associated with the fourth area in the first table for each other. Thus, in the first table, the fourth image source S 4  is associated with the first area, and the first image source S 1  is associated with the fourth area. The control section  110  controls the image processing section  150  in accordance with the information stored in the first table thus updated so that the fourth image source S 4  is projected in the first area A 1  located in the upper left part, the second image source S 2  is projected in the second area located in the upper right part, the third image source S 3  is projected in the third area located in the lower left part, and the first image source S 1  is projected in the fourth area A 4  located in the lower right part. 
     As described hereinabove, according to the present embodiment, it is possible to exchange the images projected in the plurality of projection areas for each other without operating the operation section  130  or the remote controller. 
     Modified Examples 
     Although the embodiment of the invention is described hereinabove, the invention is not limited to the embodiment described above, but can be implemented in other various forms. For example, the invention can be implemented by modifying the embodiment described above as follows. It should be noted that the embodiment described above and the following modified examples can be implemented alone or in arbitrary combination. 
     In the embodiment described above, it is also possible to detect the presence or absence of the image sources supplied to the connectors of the image interface  160  to determine the number of the split areas in accordance with the presence or absence of the image sources supplied to the connectors of the image interface  160 . 
     For example, in the case in which the image sources are supplied to two of the four connectors, and the rest two of the four connectors are not supplied with the image source, even if the coordinate in the horizontal direction of the split position Pos fulfills 0&lt;a&lt;w, and the coordinate in the vertical direction of the split position Pos fulfills 0&lt;b&lt;h, it is also possible to arrange that the projection area is split vertically or horizontally into two areas, and to project the images of the image sources, which are supplied to the connectors, in the split areas. 
     Further, in the case in which the image sources are supplied to three of the four connectors, and the rest one of the four connectors are not supplied with the image source, if the coordinate in the horizontal direction of the split position Pos fulfills 0&lt;a&lt;w, and the coordinate in the vertical direction of the split position Pos fulfills 0&lt;b&lt;h, it is also possible to arrange that the projection area is split into three areas, and to project the images of the image sources, which are supplied to the connectors, in the split areas. In the case of splitting the projection area into three areas, it is also possible to arrange that, for example, the split is performed in either of the states shown in  FIGS. 10( a ) through 10( d ) . 
     In the embodiment described above, it is also possible to arrange that in the state in which the projection area is split, and the fingers are separated from the projection surface, when an operation (a second operation) of “touching the projection surface with two fingers→separating the two fingers from the projection surface→making the two fingers have contact with the projection surface again” is performed, the control section  110  makes the transition of the flow of the process to the step SA 6  of the flowchart shown in  FIG. 6 . According to this configuration, in the case in which the operation of “touching the projection surface with two fingers→separating the two fingers from the projection surface→making the two fingers have contact with the projection surface again” is performed in the state in which the projection surface is split, and then the two fingers are moved while having contact with the projection surface, the split position Pos is changed. 
     In the embodiment described above, the first operation, the second operation, and the third operation can also be operations other than the operations illustrated in the embodiment. 
     Although in the embodiment described above, the operation triggering the split of the projection area is assumed to be the operation with the fingers, the operation triggering the split of the projection area is not limited to the operation with fingers, but can also be an operation with, for example, the pointer  20 . 
     For example, it is also possible to arrange that when the operation of “touching the projection surface with the pointer  20 →separating the pointer  20  from the projection surface→making the pointer  20  have contact with the projection surface again→keeping the pointer  20  having contact with the projection surface for a period longer than a predetermined time” is performed in the state in which the function of performing drawing on the screen in accordance with the position of the pointer  20  is not performed, the control section  110  splits the projection area based on the position where the pointer  20  has contact. 
     Further, it is also possible to arrange that if the pointer  20  is moved in a spiral manner while keeping the pointer  20  having contact with the projection surface in the state in which the function of performing drawing on the screen in accordance with the position of the pointer  20  is not performed, the projection area is split based on the position where the pointer  20  has contact, or it is also possible to arrange that when the pointer  20  is moved on the projection surface so as to draw a specific character or symbol besides the spiral shape, the projection area is split based on the position where the pointer  20  has contact. 
     Further, it is also possible to provide a button to the pointer  20 , transmit a signal representing the fact that the button is held down from the pointer  20  to the projector  10  with wireless communication when the button is held down, and it is possible for the projector  10  to detect the position of the pointer  20  on the projection image when the projector  10  receives the signal, and then split the projection area based on the position thus detected. 
     Further, the operation triggering the execution of the process of exchanging the images projected in the split areas is not limited to the operation with the fingers, but can also be an operation with the pointer  20 . 
     Although in the embodiment described above, the device for displaying the image is assumed to be the projector  10  for projecting an image, a direct-view display device such as a liquid crystal television or a liquid crystal monitor can also be adopted. 
     REFERENCE SIGNS LIST 
     
         
           1  . . . display system 
           10  . . . projector 
           20  . . . pointer 
           30  . . . light emitting device 
           110  . . . control section 
           111  . . . distance acquisition section 
           112  . . . position detection section 
           113  . . . operation detection section 
           114  . . . screen split section 
           115  . . . drawing section 
           120  . . . storage section 
           130  . . . operation section 
           140  . . . projection section 
           150  . . . image processing section 
           160  . . . image interface 
           170  . . . imaging section 
           180  . . . communication section 
           210  . . . control section 
           211  . . . signal acquisition section 
           212  . . . light emission control section 
           220  . . . communication section 
           230  . . . light emitting section 
           240  . . . operation section 
           250  . . . power supply 
         SC . . . screen 
         Pos . . . split position 
         S 1  . . . first image source 
         S 2  . . . second image source 
         S 3  . . . third image source 
         S 4  . . . fourth image source