Patent Publication Number: US-2023142794-A1

Title: Image display method of display device

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-181876, filed Nov. 8, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an image display method of a display device. 
     2. Related Art 
     There has been known, for example, a conference system in which conference equipment such as a printer and a projector, a mediating machine set in a conference room, and information processing terminals used by participants in a conference are connected. For example, a conference system described in JP-A-2017-33396 (Patent Literature 1) includes an application server that stores a conference system application. The conference system application is an application used to use conference equipment and download materials distributed in a conference. In the conference system, when an information processing terminal and a mediating machine are connected, the mediating machine notifies access information for accessing the application server. The information processing terminal downloads a conference system application from the application server. 
     In the technique described in Patent Literature 1, when image projection is performed using a projector, after installing the conference system application in the information processing terminal, a user needs to designate the projector, which is a connection destination, in the conference system application. It takes time for the user to designate the projector. The user cannot immediately project an image using the projector. For example, after retrieving a connectable projector using the conference system application, checking identification information of the projector, and inputting the identification information of the projector in the conference system application, the user is capable of projecting an image using the projector. The user needs to perform such a series of work. The work is annoying for the user. 
     SUMMARY 
     An image display method of a display device according to an aspect of the present disclosure includes: establishing first communication between the display device and a terminal device; transmitting, to the terminal device, via the first communication, an application for transmitting image information from the terminal device to the display device and connection information used for second communication for transmitting the image information; establishing the second communication when receiving a connection request for requesting to establish the second communication, the connection request being transmitted by the application operating in the terminal device; receiving the image information from the terminal device via the second communication; and displaying an image based on the image information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram showing an image display system to which an image display method according to an embodiment is applied. 
         FIG.  2    is a block diagram showing the configuration of a projector. 
         FIG.  3    is a block diagram showing information stored in a storage device of the projector. 
         FIG.  4    is a block diagram showing functions of a CPU of the projector. 
         FIG.  5    is a block diagram showing the configuration of a terminal. 
         FIG.  6    is a block diagram showing information stored in a storage device of the terminal. 
         FIG.  7    is a block diagram showing functions of a CPU of the terminal. 
         FIG.  8    is a flowchart showing a procedure of an image display method according to a first embodiment. 
         FIG.  9    is a flowchart showing a procedure of an image display method according to a modification 3. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Modes for carrying out the present disclosure are explained below with reference to the drawings. However, in the drawings, dimensions and scales of units are differentiated from actual ones as appropriate. Embodiments explained below are preferred specific examples of the present disclosure. Therefore, technically preferred various limitations are added to the embodiments. However, the scope of the present disclosure is not limited to these embodiments unless specifically noted in the following explanation that the present disclosure is limited. 
     Image Display System  10   
     First, an image display system  10  to which an image display method of a display device according to an embodiment is applied is explained. After the image display system  10  is explained, the image display method of the display device is explained.  FIG.  1    is a schematic diagram showing the image display system  10  to which the image display method according to the embodiment is applied. The image display system  10  shown in  FIG.  1    can display a predetermined image using a network-type projector PJ. The projector PJ is connected to a terminal PC via a network. The projector PJ is an example of the display device. The terminal PC is an example of the terminal device. The projector PJ establishes connection to the terminal PC, receives image information from the terminal PC, and projects and displays an image on a screen SC. 
     Communication between the projector PJ and the terminal PC via the network includes “first communication” and “second communication”. The first communication is used to, for example, transmit a signal for requesting to establish the second communication and transmit a network projection application  34  and connection information  40  explained below. The second communication is used to transmit image information from the terminal PC to the projector PJ. The first communication and the second communication may be the same communication method or may be different communication methods. 
     Communication Method 
     The projector PJ and the terminal PC are connected by a wireless LAN. The projector PJ and the terminal PC may communicate in an ad hoc mode not via an access point. A communication method between the projector PJ and the terminal PC is not limited to the forms explained above. Various methods can be applied as the communication method between the projector PJ and the terminal PC according to an environment of use, requested communication speed, and the like. For example, the projector PJ and the terminal PC may communicate in an infrastructure mode via the access point. The communication method between the projector PJ and the terminal PC is not limited to a wireless scheme. The projector PJ and the terminal PC may be configured to perform communication with, for example, a wired scheme using an Ethernet, a Firewire, a fiber channel, an SCSI, a Bluetooth, or a PLC. Ethernet, Firewire, and Bluetooth are registered trademarks. SCSI is an abbreviation of “Small Computer System Interface”. PLC is an abbreviation of “Power Line Communication”. 
     Projector PJ 
       FIG.  2    is a block diagram showing the configuration of the projector PJ. The projector PJ shown in  FIG.  2    includes a CPU  11 , a storage device  12 , an input device  15 , a VRAM  16 , a graphic controller  17 , a communication device  18 , and a projection device  19 . The CPU  11 , the storage device  12 , the input device  15 , the VRAM  16 , the graphic controller  17 , and the communication device  18  are connected by a bus  21 . The projection device  19  is connected to the graphic controller  17 . CPU is an abbreviation of “Central Processing Unit”. VRAM is an abbreviation of “Video Random Access Memory”. 
     The input device  15  includes buttons operable by a user. The input device  15  may include, for example, a display that can be touched and operated. The storage device  12  may include, for example, a ROM, a RAM, an EEPROM, and a HDD. The EEPROM is a rewritable nonvolatile memory. ROM is an abbreviation of “Read Only Memory”. RAM is an abbreviation of “Random Access Memory”. HDD is an abbreviation of “Hard Disk Drive”. EEPROM is an abbreviation of “Electrically Erasable Programmable ROM”. The CPU  11  may include one processor or may include a plurality of processors. The CPU  11  may be configured by an SoC (System on Chip) integrated with a part or the entire storage device  12  or another circuit. The CPU  11  may be configured by a combination with a DSP (Digital Signal Processor) that executes predetermined arithmetic processing. 
       FIG.  3    is a block diagram showing information stored in the storage device  12  of the projector PJ. The storage device  12  stores various programs  31  for causing the projector PJ to operate. The storage device  12  stores a Web server program  32 , a network projection application  34 , an SSID  35 , a projector name  36 , a MAC address  37 , and authentication information  38 . The “network projection application” is hereinafter abbreviated as “projection application”. Web is an abbreviation of “World Wide Web”. SSID is an abbreviation of “Service Set Identifier”. MAC address is an abbreviation of “Media Access Control address”. The network projection application  34  is equivalent to the application. 
     The CPU  11  executes the Web server program  32 , whereby a Web page displayed using a Web browser of the terminal PC is generated. The CPU  11  executes the Web server program  32 , whereby a Web page for downloading the projection application  34  stored in the projector PJ is generated. 
     The Web server program  32  of the projector PJ includes a WebAPI  33 . The WebAPI  33  sets network connection between the projector PJ and the terminal PC. The WebAPI  33  has a Web control function. The WebAPI  33  causes a display  69  of the terminal PC to display a Web page. The WebAPI  33  controls the operation of the terminal PC via the Web browser. “API” is an abbreviation of “Application Programming Interface”. 
     The WebAPI  33  is an interface that causes an application and a system of the terminal PC to operate via a network using an HTTP protocol. The WebAPI  33  can cause the projection application  34  to operate in the terminal PC. The WebAPI can open the Web browser in the terminal PC. “HTTP protocol” is an abbreviation of “Hypertext Transfer Protocol”. 
     The projection application  34  is an application installed in the terminal PC from the projector PJ and operates in the terminal PC. The projection application  34  can execute an operation for connecting the terminal PC and the projector PJ and an operation for transmitting image information from the terminal PC to the projector PJ. 
     The projection application  34  performs network setting in the ad hoc mode of the terminal PC and the projector PJ and establishes connection. The projection application  34  selects the projector PJ set as a connection destination and establishes connection to the projector PJ. The projection application  34  selects, as the connection destination, the projector PJ in which the projection application  34  is stored before being transmitted to the PC. The projection application  34  transmits the image from the terminal PC to the projector PJ and projects the image using the projector PJ. 
     For example, the SSID  35 , the projector name  36 , the MAC address  37 , and the authentication information  38  are stored in the nonvolatile memory. The SSID  35 , the projector name  36 , the MAC address  37 , and the authentication information  38  are examples of the connection information. The authentication information  38  stored in the storage device  12  of the projector PJ is transmitted to the terminal PC. The connection information  40  is used to establish communication used to transmit image information from the terminal PC to the projector PJ. The communication used to transmit the image information is an example of the second communication. 
     The SSID  35  is an SSID in a wireless network to which the projector PJ and the terminal PC are connected. The MAC address  37  is a MAC address of the projector PJ. The authentication information  38  is used for authentication for establishing communication used when image information is transmitted. The authentication information  38  includes, for example, a password or a passphrase. 
     The graphic controller  17  causes the projection device  19  to project an image using the VRAM  16  as a buffer. The projection device  19  includes a liquid crystal-type projection mechanism and projects lights transmitted through liquid crystal panels for colors of RGB to display an image on the screen SC. The projection device  19  is not limited to a projection device to which the liquid crystal type is applied. Various schemes such as DLP scheme, an LCOS scheme, and a GLV scheme can be used. 
     The communication device  18  includes, for example, a wireless interface. The wireless interface is an interface for performing wireless communication in the ad hoc mode and can perform peer-to-peer connection to the terminal PC. The communication device  18  may include a network interface. The network interface is an interface used when the projector PJ is connected to a local area network of a wired scheme. 
       FIG.  4    is a block diagram showing functions of the CPU  11  of the projector PJ. The CPU  11  can control all the functions of the projector PJ by executing the programs  31  stored in the storage device  12 . The CPU  11  executes the programs  31  to function as a projection controller  41  and a communication controller  42 . The CPU  11  executes the Web server program  32  to function as a Web server executor  43  and a WebAPI executor  44 . The Web server executor  43  includes a Web page generator  45 , a download executor  46 , and an authenticator  47 . The WebAPI executor  44  includes a Web browser controller  48  and a projection application controller  49 . 
     The projection controller  41  controls, for example, the graphic controller  17  and causes the screen SC to display an image using the projection device  19 . The communication controller  42  controls communication between the projector PJ and the terminal PC using the communication device  18 . 
     The Web page generator  45  generates a Web page displayed via the Web browser of the terminal PC. The download executor  46  causes the terminal PC to download the projection application  34  and the connection information  40  stored in the projector PJ. The authenticator  47  performs authentication for establishing communication for image information transmission. Communication between the projector PJ and the terminal PC is established by the authenticator  47  performing the authentication. The projector PJ can receive image information transmitted from the terminal PC by the operation of the projection application  34 . The connection information  40  is equivalent to the connection information used for the second communication. The communication between the projector PJ and the terminal PC being established by the authenticator  47  performing the authentication is equivalent to the second communication. 
     After the communication between the terminal PC and the projector PJ is established, the Web browser controller  48  can open the Web page using the Web browser of the terminal PC. The projection application controller  49  can execute control for starting the projection application  34  in the terminal PC. 
     Terminal PC 
       FIG.  5    is a block diagram showing the configuration of the terminal PC. The terminal PC includes a CPU  61 , a storage device  62 , an input device  65 , a VRAM  66 , a graphic controller  67 , a communication device  68 , and a display  69 . The CPU  61 , the storage device  62 , the input device  65 , the VRAM  66 , the graphic controller  67 , and the communication device  68  are connected by a bus  75 . The display  69  is connected to the graphic controller  67 . 
     The input device  65  includes a keyboard and a pointing device operable by the user. The pointing device is, for example, a mouse. The storage device  62  may include, for example, a ROM, a RAM, an EEPROM, and a HDD. The CPU  61  may include one processor or may include a plurality of processors. The CPU  61  may be configured by an SoC (System on Chip) integrated with a part or the entire storage device  62  or another circuit. The CPU  61  may be configured by a combination with a DSP that executes predetermined arithmetic processing. 
       FIG.  6    is a block diagram showing information stored in the storage device  62  of the terminal PC. The storage device  62  stores various programs  71  for causing the projector PJ to operate. The storage device  62  stores a Web browser  72 , the projection application  34 , the SSID  35 , the projector name  36 , the MAC address  37 , the authentication information  38 , and connection history information  39 . The projection application  34 , the SSID  35 , the projector name  36 , the MAC address  37 , and the authentication information  38  are downloaded from the projector PJ and stored in the storage device  62 . 
     The connection history information  39  includes information concerning a connection history to the projector PJ connected using the projection application  34 . For example, the connection history information  39  includes identification information for identifying an individual projector PJ. The connection history information  39  may include information for correlating the projector PJ connected in the past and the connection information  40  for connection to the projector PJ. 
     The projection application  34 , the SSID  35 , the projector name  36 , the MAC address  37 , and the authentication information  38  stored in the storage device  62  are the connection information  40  downloaded from the projector PJ as explained above. 
     The graphic controller  67  causes the display  69  to display an image using the VRAM  66  as a buffer. 
     The communication device  68  includes, for example, a wireless interface. The wireless interface is an interface for performing wireless communication in the ad hoc mode and can perform peer-to-peer connection to the terminal PC. The communication device  68  may include a network interface. The network interface is an interface used when the projector PJ is connected to a local area network of a wired scheme. 
       FIG.  7    is a block diagram showing functions of the CPU  61  of the terminal PC. The CPU  61  can control all the functions of the terminal PC by executing the programs  71  stored in the storage device  62 . The CPU  61  executes the programs  71  to function as a communication controller  81  and a display controller  82 . The CPU  61  executes the Web browser  72  to function as a Web browser controller  85 . The Web browser executor  83  includes the Web browser controller  85 . The Web browser controller  85  executes control using the Web browser. The CPU  61  executes the projection application  34  to function as a network projection application executor  84 . The network projection application executor is hereinafter described as projection application executor. 
     The communication controller  81  controls communication between the terminal PC and the projector PJ using the communication device  68  of the terminal PC. The display controller  82  executes display control in the display  69  of the terminal PC. 
     The projection application executor  84  functions as a connection destination retriever  86 , an authentication information inputter  87 , an image capturer  88 , and an image transmitter  89 . The connection destination retriever  86  retrieves the projector PJ set as the connection destination from the connection information  40  downloaded from the projector PJ. Specifically, the connection destination retriever  86  specifies the projector PJ set as the connection destination referring to the SSID  35 , the projector name  36 , and the MAC address  37  included in the connection information  40 . 
     The authentication information inputter  87  transmits, to the projector PJ, the authentication information  38  downloaded from the projector PJ set as the connection destination. The image capturer  88  controls an operation for capturing image information displayed on the display  69  of the terminal PC. The image transmitter  89  controls an operation for transmitting the captured image information to the projector PJ. A procedure of these operations by the projection application executor  84  is explained below with reference to a flowchart of  FIG.  8   . 
     Image Display Method of the Display Device 
     An image display method of the display device is explained below. The image display method of the display device according to this embodiment can be executed using the projector PJ explained above. However, the image display method of the display device is not limited to the image display method executed using the projector PJ. 
     First Embodiment 
     An image display method according to a first embodiment is explained with reference to the flowchart of  FIG.  8   .  FIG.  8    is a flowchart showing a procedure of the image display method according to the first embodiment. 
     When causing the screen SC to display, using the projector PJ, an image displayed on the display  69  of the terminal PC, the user operates the terminal PC and connects the terminal PC and the projector PJ through a network. First, the CPU  61  of the terminal PC determines whether a request operation for connection to the network is received (step S 1 ). When the request operation for connection is received (YES in step S 1 ), the CPU  61  functions as the communication controller  81  and transmits a communication connection request to the projector PJ (step S 2 ). When the request operation for communication is not received (NO in step S 1 ), the CPU  61  repeats the processing in step S 1 . 
     The projector PJ receives the communication connection request transmitted from the terminal PC. The CPU  11  of the projector PJ functions as the communication controller  42 , receives the communication connection request, and, thereafter, executes communication establishment processing (step S 3 ). 
     Subsequently, the CPU  11  functions as the Web browser controller  48  and transmits a browser start request to the terminal PC (step S 4 ). The browser start request is equivalent to the start request for instructing to start the Web browser. The CPU  11  can function as the Web browser controller  48  and transmit a URL to the terminal PC. The CPU  11  transmits, to the terminal PC, an application presence or absence determination request for instructing the terminal PC to determine whether the projection application  34  is stored in the terminal PC (step S 5 ). In step S 5 , the CPU  11  functions as the WebAPI executor  44 . 
     The CPU  61  of the terminal PC starts the Web browser  72  while being triggered by the CPU  61  receiving the browser start request (step S 6 ). In step S 6 , the CPU  11  functions as the Web browser controller  85 . Subsequently, the CPU  61  determines whether the projection application  34  is stored in the storage device  62  (step S 7 ). When the projection application  34  is stored in the storage device  62  (YES in step S 7 ), the CPU  61  proceeds to step S 10 . 
     When the projection application  34  is not stored in the storage device  62  (NO in step S 7 ), the CPU  61  transmits, to the projector PJ, a download request for requesting the projector PJ to download the projection application  34  (step S 8 ). 
     The projector PJ receives the download request transmitted from the terminal PC. Subsequently, the CPU  11  transmits, to the terminal PC, the projection application  34  and the authentication information  38  stored in the storage device  12  (step S 9 ). The CPU  11  transmits the SSID  35 , the projector name  36 , and the MAC address  37  stored in the storage device  12  to the terminal PC. In step S 9 , the CPU  11  functions as the download executor  46 . 
     Instead of transmitting the projector name  36  to the terminal PC, the CPU  11  may change a file name of the authentication information  38  to a file name including the projector name  36  and transmit the authentication information  38  to the terminal PC using the changed file name. For example, when the file name of the authentication information  38  before the change is “crf.info” and the projector name is “EP123”, the CPU  11  may function as the download executor  46 , change the file name of the authentication information  38  to “EP123_crf.info”, and transmit the authentication information  38 . 
     The terminal PC receives the projection application  34 , the authentication information  38 , the SSID  35 , the projector name  36 , and the MAC address  37  transmitted from the projector PJ. The storage device  62  of the terminal PC stores the projection application  34 , the SSID  35 , the projector name  36 , the MAC address  37 , and the authentication information  38  received by the terminal PC. 
     Subsequently, the CPU  61  of the terminal PC starts the projection application  34  (step S 10 ). For example, the CPU  61  may start the projection application  34  in response to manual operation by the user. For example, the projection application controller  49  may start the projection application  34 . The CPU  61  may start the projection application  34  after step S 7  or step S 8  and before step S 9  is executed. Subsequently, the terminal PC functions as the connection destination retriever  86  and retrieves and specifies, based on the SSID  35 , the projector name  36 , and the MAC address  37  stored in the storage device  62 , the projector PJ set as the connection destination (step S 11 ). 
     Subsequently, the CPU  61  inputs, to the projector PJ, an authentication request and authentication information for establishing communication for image transmission (step S 12 ). The CPU  61  transmits the authentication request and the authentication information to the projector PJ. In step S 12 , the CPU  61  functions as the authentication information inputter  87 . 
     The projector PJ receives the authentication request and the authentication information transmitted from the terminal PC. The CPU  11  functions as the authenticator  47  and, while being triggered by the CPU  11  receiving the authentication request, executes authentication processing for collating the authentication information (step S 13 ). When the authentication information is correct, the CPU  11  establishes communication for image transmission from the terminal PC to the projector PJ. Consequently, the second communication is established. The projector PJ transmits, to the terminal PC, an approval response indicating that the second communication is approved to be established (step S 14 ). 
     The CPU  61  of the terminal PC receives the approval response transmitted from the projector PJ. Subsequently, the CPU  61  functions as the image capturer  88  and, while being triggered by an operation input of the user, captures image information displayed on the display  69  of the terminal PC (step S 15 ). The CPU  61  functions as the image transmitter  89  and transmits the captured image information to the projector PJ using the second communication (step S 16 ). 
     The CPU  11  of the projector PJ receives the image information transmitted from the terminal PC (step S 17 ). The CPU  11  functions as the projection controller  41  and projects an image indicated by the received image information onto the screen SC (step S 18 ). 
     With such an image display method, the projection application  34  and the connection information  40  stored in the storage device  12  of the projector PJ are transmitted to the terminal PC. Therefore, the terminal PC can easily retrieve, from the received connection information  40 , the projector PJ set as the connection destination. Consequently, the user does not need to manually retrieve the projector PJ set as the connection destination. As a result, time of the user for connecting the terminal PC to the projector PJ can be saved. 
     With the image display method, the authentication information  38  can be transmitted to the projector PJ using the projection application  34  transmitted from the projector PJ to the terminal PC. The projector PJ can perform the authentication processing using the authentication information  38  transmitted by the operation of the projection application  34  and establish the second communication. Consequently, time of the user for inputting the authentication information can be saved. Since the authentication information is automatically input by the projection application  34 , a mistake in inputting the authentication information  38  by the user can be prevented. 
     With the image display method, since the Web browser can be started in the terminal PC after the first communication is established, the projection application  34  to the terminal PC can be easily downloaded. With the image display method, the terminal PC and the projector PJ can be easily connected using the Web function of the projector PJ. 
     In the image display method, since the projector PJ and the terminal PC can be communicably connected using the wireless network, for example, the projector PJ suspended from the ceiling and the terminal PC can be easily connected. 
     The image display method of the display device includes establishing the first communication between the projector PJ and the terminal PC, transmitting, to the terminal PC, via the first communication, the projection application  34  for transmitting image information from the terminal PC to the projector PJ and connection information used for the second communication for transmitting the image information, establishing the second communication when receiving a connection request for requesting to establish the second communication, the connection request being transmitted by the projection application  34  operating in the terminal PC, receiving the image information from the terminal PC via the second communication, and displaying an image based on the image information. 
     In the image display method, the first communication can be established between the projector PJ and the terminal PC. In the image display method, the projection application  34  and the connection information can be transmitted from the projector PJ to the terminal PC via the first communication. With the image display method, the projection application  34  operates in the terminal PC, whereby the connection request for requesting to establish the second communication can be transmitted to the projector PJ. With the image display method, the projector PJ can establish the second communication when receiving the connection request for requesting to establish the second communication. With the image display method, the projector PJ can receive the image information from the terminal PC via the second communication. With the image display method, the projector PJ can display the image based on the image information. As a result, in the image display method, the user&#39;s time can be saved. 
     The image display method further includes, after the establishing the first communication, transmitting, to the terminal PC, via the first communication, a start request for instructing the terminal PC to start a Web browser. With the image display method, the Web browser can be started in the terminal PC after the first communication is established. Consequently, in the image display method, the user&#39;s time can be saved. The user does not need to start the Web browser. 
     The image display method further includes transmitting, to the terminal PC, via the first communication, a request for instructing the terminal PC to determine whether the projection application  34  is stored in the terminal PC. Consequently, in the image display method, the terminal PC can determine whether the projection application  34  is stored in the terminal PC. Accordingly, the user does not need to check whether the projection application  34  is stored. As a result, the user&#39;s time can be saved. When the projection application  34  is stored, the projection application  34  can be prevented from being downloaded. Accordingly, the user does not need to determine whether to download the projection application  34 . 
     In the image display method, the connection information includes authentication information for authenticating the connection request. In the image display method, the connection information including the authentication information can be transmitted to the terminal PC. Therefore, the user does not need to input the authentication information to the terminal PC. As a result, the user&#39;s time can be saved. 
     In the image display method, the projector PJ stores the projection application  34  and the connection information. In the image display method, the projection application  34  and the connection information stored in advance in the projector PJ can be transmitted to the terminal PC. In the image display method, the user can request the projector PJ, in which the projection application  34  and the connection information are stored, to establish the second communication. In the image display method, when requesting to establish the second communication, the user does not need to select the projector PJ. As a result, the user&#39;s time can be saved. 
     MODIFICATION 1 
     The image display method may be changed and executed as appropriate. In the embodiment explained above, the terminal PC determines whether the projection application  34  is stored in the storage device  62  of the terminal PC. However, without carrying out this determination processing, the terminal PC may request the projector PJ to download the projection application  34 . 
     MODIFICATION 2 
     In the embodiment explained above, the projection application  34  and the authentication information  38  are transmitted from the projector PJ to the terminal PC. However, the projection application  34  and the authentication information  38  may not be transmitted after the first communication is established. For example, when the projector PJ and the terminal PC were connected in the past and the projection application  34  and the authentication information  38  are stored in the storage device  62  of the terminal PC, the authentication information  38  stored in the storage device  62  can be used. When the projector PJ has already transmitted the authentication information  38  to the terminal PC, the projector PJ does not need to transmit the authentication information  38  to the terminal PC again. Similarly, when the projector PJ has already transmitted the connection information  40  such as the SSID  35 , the projector name  36 , and the MAC address  37  to the terminal PC, the projector PJ does not need to transmit the connection information  40  to the terminal PC again. The terminal PC can use the connection information  40  stored in the storage device  62 . The terminal PC can grasp a connection history of the terminal PC and the projector PJ set as the connection destination referring to the connection history information  39 . 
     The terminal PC can save the connection history information  39  after the second communication is established. The connection history information  39  includes information for identifying the projector PJ, which is the connection destination, and the connection information  40  of the projector PJ at the connection destination. 
     MODIFICATION 3 
     The projector PJ can transmit the projection application  34  including the connection information  40  to the terminal PC. The CPU  11  can function as the download executor  46 , read the projection application  34  and the connection information  40  stored in the storage device  12 , and set the connection information  40  as a file name of the projection application  34 . The CPU  11  can function as the download executor  46  and include, for example, the projector name  36 , which is the connection information  40 , in the file name of the projection application  34 . The CPU  11  can function as the download executor  46  and transmit the projection application  34 , in the file name of which the connection information  40  is included, to the terminal PC. The including the projector name  36 , which is the connection information  40 , in the file name of the projection application  34  is equivalent to the adding the connection information to the name of the application. 
       FIG.  9    is a flowchart showing a procedure of an image display method according to the modification 3. In  FIG.  9   , a procedure executed in the projector PJ is shown. The projector PJ waits for a connection request from the terminal PC and establishes communication between the projector PJ and the terminal PC (step S 31 ). The CPU  11  transmits a Web page having a Web control function to the terminal PC (step S 32 ). 
     A Web page including a link to the projection application  34  stored in the storage device  12  of the projector PJ is displayed on the display  69  of the terminal PC. By clicking the link to the projection application  34 , the user can request the projector PJ to download the projection application  34 . The projector PJ can receive the download request transmitted from the terminal PC. 
     The CPU  11  of the projector PJ determines whether the download request for the projection application  34  is received from the terminal PC (step S 33 ). When the download request is received (YES in step S 33 ), the CPU  11  proceeds to step S 34 . When the download request is not received (NO in step S 33 ), the CPU  11  waits for the download request and proceeds to step S 34 . 
     In step S 34 , the CPU  11  functions as the download executor  46  and reads binary data of the projection application  34  stored in the storage device  12 . Subsequently, the CPU  11  functions as the download executor  46  and embeds an IP address of the projector PJ in a name of a file of the projection application  34  (step S 35 ). Subsequently, the CPU  11  transmits, to the terminal PC, the binary data of the projection application  34  to which the IP address is added (step S 36 ). In step S 36 , the CPU  11  functions as the download executor  46 . 
     The terminal PC can read the file name of the received projection application  34  and acquire the IP address of the projector PJ set as the connection destination. Consequently, the terminal PC can specify the projector PJ set as the connection destination. The connection information  40  included in the projection application  34  is not limited to the IP address and the projector name. For example, the projection application  34  may include other connection information  40  such as a network name. 
     The CPU  61  of the terminal PC can store the received projection application  34  in the storage device  62  based on operation by the user. The CPU  61  of the terminal PC can start the projection application  34  based on operation by the user. The CPU  61  functions as the connection destination retriever  86 , reads the file name of the projection application  34 , and specifies the IP address of the projector PJ set as the connection destination and the network name of the projector PJ. The CPU  61  functions as the projection application executor  84  and transmits a network connection request for image transfer to the projector PJ set as the connection destination. The network connection for image transfer is an example of the second communication. 
     The CPU  11  of the projector PJ determines whether the network connection request for image transfer is received (step S 37 ). When the network connection request is received (YES in step S 37 ), the CPU  11  proceeds to step S 38 . When the network connection request is not received (NO in step S 37 ), the CPU  11  waits for reception of the network connection request and proceeds to step S 38 . 
     In step S 38 , the CPU  11  functions as the communication controller  42  and establishes network connection for image transfer. As explained above, the CPU  61  of the terminal PC functions as the image capturer  88  and captures an image displayed on the display  69  of the terminal PC. The CPU  11  functions as the image transmitter  89  and transmits image information based on the captured image to the projector PJ. The projection device  19  of the projector PJ projects the received image (step S 39 ). 
     In such an image display method according to the modification 3, the IP address of the projector PJ can be embedded in the application name of the projection application  34  and transmitted to the terminal PC. Therefore, the projection application  34  operating on the terminal PC can easily specify the projector PJ set as the connection destination from the application name. 
     In the image display method, for example, when the terminal PC of the user is connected to the projector PJ set in a conference room where the user is visiting, the user starts the Web browser in the terminal PC and selects the projector PJ displayed on the Web browser, whereby the first communication is established and the projection application  34  is downloaded to the terminal PC. The projection application  34  operating on the terminal PC can select the projector PJ set as the connection destination from the application name of the downloaded projection application  34  and request the projector PJ to establish the second communication for image transfer. As a result, a work load of the user in transferring an image is reduced. 
     In the image display method, since the projector PJ and the terminal PC can be wirelessly connected, when terminals PC of a plurality of users in a conference room are switched and the projector PJ is used, it is unnecessary to connect a connection cable again unlike the related art. 
     The image display method further includes adding the connection information to a name of the projection application  34  before transmitting the projection application  34  to the terminal PC. In the image display method, the connection information can be added to the name of the projection application  34 . The projection application  34 , to the name of which the connection information is added, can be transmitted to the terminal PC. The terminal PC can read the name of the projection application  34  and acquire the connection information. Consequently, the user&#39;s time can be saved. 
     MODIFICATION 4 
     In the embodiment explained above, the projector PJ transmits the projection application  34  and the authentication information to the terminal PC. However, the projector PJ may transmit the authentication information to the terminal PC without transmitting the projection application  34 . When the projection application  34  is stored in the storage device  62  of the terminal PC, the projector PJ can transmit the connection information  40  including the authentication information of the projector PJ set as the connection destination to the terminal PC without transmitting the projection application  34 . In the image display method, when the terminal PC is connected to another projector in the past, the projection application  34  is sometimes stored in the storage device  62 . In such a case, the projector PJ can transmit the connection information  40  to the terminal PC without transmitting the projection application  34 . Consequently, an increase in a communication amount can be suppressed. 
     The image display method further includes transmitting the connection information to the terminal PC without transmitting the projection application  34  when the projection application  34  is stored in the terminal PC. With such an image display method, an increase in a communication amount can be suppressed. 
     The embodiment explained above only indicates a representative mode of the present disclosure. The present disclosure is not limited to the embodiment explained above. Various changes and additions are possible without departing from the gist of the present disclosure. 
     In the embodiment explained above, the projector PJ is illustrated as the display device. However, the display device is not limited to the projector PJ. The display device may be another display device such as a liquid crystal display device. In the embodiment explained above, the terminal PC is illustrated as the terminal device. However, the terminal device may be another terminal device such as a smartphone or a tablet computer.