Patent Publication Number: US-10788977-B2

Title: System and method for displaying information on transparent display device

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application is a continuation application of U.S. application Ser. No. 14/031,483, filed Sep. 19, 2013, in the U.S. Patent and Trademark Office, which claims priority from Korean Patent Application No. 10-2012-00104156, filed on Sep. 19, 2012, and Korean Patent Application No. 10-2013-00106227, filed on Sep. 4, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     Methods and apparatuses consistent with exemplary embodiments relate to displaying information, and more particularly, to a system and method for displaying information related to an external object or an external device on a transparent display device. 
     2. Description of the Related Art 
     Transparent display devices are considered next generation display devices. A transparent display device has a degree of transparency that enables a user to see an external object or an external device through the transparent display device. 
     However, a transparent display device does not display information related to the external object or the external device. 
     SUMMARY 
     Exemplary embodiments provide a system, a method, and an apparatus for displaying information related to an external device seen through a screen of a transparent display device on the screen of the transparent display device, and a recording medium thereof. 
     Exemplary embodiments also provide a system, a method, and an apparatus for displaying information related to an object displayed on a screen of an external device seen through a screen of a transparent display device on the screen of the transparent display device, and a recording medium thereof. 
     Exemplary embodiments also provide a system, a method, and an apparatus for displaying information related to an external object seen through a screen of a transparent display device on the screen of the transparent display device, and a recoding medium thereof. 
     According to an aspect of an exemplary embodiment, there is provided a method of displaying information on a transparent display device, the method including: receiving a touch input on the transparent display device that selects an object displayed on an external device that is viewable through a screen of the transparent display device; requesting the external device for information related to the object; receiving the information related to the object from the external device; and displaying the received information on the screen of the transparent display device. 
     The touch input may indicate a contour line of the object that is viewable through the screen, a tap-based touch indicating a location on the screen at which the object is viewable through the screen, or indicate a closed region on the screen at which the object is viewable through the screen. 
     The information related to the object indicates at least one other object having a type that is the same as a type of the object, and a display location on a screen of the external device of the at least one other object differs from that of the object. 
     The information related to the object indicates information that is not displayed on a screen of the external device. 
     The displaying comprises displaying the received information at a display location on the screen of the transparent display device that corresponds to a display location of the object on a screen of the external device. 
     The method may further include editing the information that is displayed on the screen of the transparent display device based on an interaction between the transparent display device and the external device. 
     The method may further include displaying information related to the external device based on an augmented reality service on the screen of the transparent display device. 
     The requesting and the receiving the information are performed based on one of a direct communication between devices, a communication via a server, and a communication via a repeater. 
     According to another aspect of an exemplary embodiment, there is provided a transparent display device including: a transparent display configured to receive a touch input that selects an object displayed on an external device that is viewable through the transparent display; a communication unit configured to communicate with an external device that is viewable through the transparent display; and a processor configured to request the external device for information related to the object based on the touch input, via the communication unit, receive information related to the object from the external device in response to the request, via the communication unit, and control the transparent display to display the received information. 
     According to another aspect of an exemplary embodiment, there is provided a method of displaying information on a transparent display device, the method including: receiving a first touch input on a screen of the transparent display device indicating first position information of an external device that is viewable through the screen of the transparent display device and receiving a second touch input on the screen of the transparent display device indicating second position information of an object displayed on a screen of the external device viewable through the screen of the transparent display device; requesting the external device for information related to the object based on the first position information and the second position information; receiving information related to the object from the external device in response to the requesting; and displaying the received information on the screen of the transparent display device. 
     The first position information indicates a contour line of the external device viewable through the screen of the transparent display device. 
     The first touch input may be independent touch operations on a first point and a second point on the screen of the transparent display device that indicate a contour line of the external device that is viewable through the screen of the transparent display device. 
     The first touch input may be a touch-and-drag operation for connecting a first point and a second point on the screen of the transparent display device that indicates a contour line of the external device that is viewable through the screen of the transparent display device. 
     The first touch input may indicate a touch-based region adjusting operation for guide information displayed on the screen of the transparent display device, and a range related to the touch-based region adjusting operation for the guide information may be based on a contour line of the external device that is viewable through the screen of the transparent display device. 
     The first touch input may be a touch operation for selecting screen information of the external device, wherein the screen information may be included in a selectable screen information menu item about the external device, which is displayed on the screen of the transparent display device, and the screen information may include at least one of screen size information and screen type information. 
     The second position information may indicate a contour line of the object that is viewable through the screen on the transparent display device. 
     The second touch input may be a tap-based touch indicating a location on the screen of the transparent display device at which the object is viewable through the screen of the transparent display device. 
     The second touch input may indicate a closed region on the screen of the transparent display device through which the object is viewable on the screen of the transparent display device. 
     The information related to the object may indicate at least one other object having a type that is the same as a type of the object, and a display location on the screen of the external device of the at least one other object may differ from that of the object. 
     The method may further include editing the information that is displayed on the screen of the transparent display device based on an interaction between the transparent display device and the external device. 
     According to another aspect of an exemplary embodiment, there is provided a transparent display device including: a transparent display configured to receive a touch input indicating first position information of an external device that is viewable through the transparent display, and to receive a second touch input indicating second position information of an object displayed on a screen of the external device viewable through the transparent display; a communication unit configured to communicate with the external device; and a processor configured to request the external device for information related to the object based on the first position information and the second position information, via the communication unit, receive information related to the object from the external device in response to the request, via the communication unit, and display the received information on the transparent display. 
     According to another aspect of an exemplary embodiment, there is provided a method of displaying information on a screen of a transparent display device, the method including: receiving from the transparent display device a request for information related to at least one object displayed on the screen of an external device that is viewable through a screen of the transparent display device; selecting the at least one object in response to the request; and transmitting the information related to the selected object to the transparent display device, wherein the request for information related to the object comprises first position information of the external device indicated by a first touch input on the transparent display device and second position information of the object displayed on the screen of the external device indicated by a second touch input on the transparent display device. 
     According to another aspect of an exemplary embodiment, there is provided a non-transitory computer-readable recording medium having embodied thereon a program for implementing the methods discussed of displaying information on the transparent display device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1A  through  FIG. 1C  are block diagrams of an information display system according to an exemplary embodiment; 
         FIG. 2  is a flowchart illustrating a method of displaying information in a transparent display device, according to an exemplary embodiment; 
         FIGS. 3A through 3H  are diagrams showing examples of a first touch input according to exemplary embodiments; 
         FIGS. 4A through 4E  are diagrams showing other examples of a first touch input according to exemplary embodiments; 
         FIGS. 5A through 5E  are diagrams showing other examples of a first touch input according to exemplary embodiments; 
         FIGS. 6A through 6C  are diagrams showing a first touch input, a second touch input, and a screen displayed on a transparent display device according to the first and second touch inputs, according to exemplary embodiments; 
         FIGS. 7A through 7D  are diagrams showing screens for illustrating the first touch input, the second touch input, and editing processes according to the exemplary embodiments; 
         FIGS. 8A through 8G  are diagrams showing screens for illustrating the first touch input and the second touch input according to the exemplary embodiments; 
         FIGS. 9A through 9C  are diagrams showing screens for illustrating the first touch input and the second touch input according to the exemplary embodiments in a case where a transparent display device and an external device have equal size; 
         FIGS. 10A through 10D  are diagrams showing examples of the first touch input and the second touch input according to the exemplary embodiments; 
         FIG. 11  is a flowchart illustrating a method of displaying information to be performed by a transparent display device, according to another exemplary embodiment; 
         FIG. 12  is a flowchart illustrating a method of displaying information to be performed by a transparent display device, according to another exemplary embodiment; 
         FIGS. 13A and 13B  are side views of the transparent display device and the external device shown in  FIG. 12 ; 
         FIG. 14  is a flowchart illustrating a method of displaying information to be performed by a transparent display device, according to another exemplary embodiment; 
         FIG. 15  is a flowchart illustrating a method of displaying information to be performed by a transparent display device, according to another exemplary embodiment; 
         FIG. 16  is a functional block diagram of a transparent display device according to an exemplary embodiment; 
         FIG. 17  is a diagram showing an example of a transparent display unit shown in  FIG. 16 ; 
         FIG. 18  is a diagram illustrating a software layer stored in a storage unit of a transparent display device, according to an exemplary embodiment; 
         FIG. 19  is a functional block diagram of a transparent display device according to another exemplary embodiment; 
         FIG. 20  is a flowchart illustrating a method of displaying information to be performed by an external device, according to an exemplary embodiment; and 
         FIG. 21  is a flowchart illustrating a method of displaying information to be performed by a transparent display device according to another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     As the exemplary embodiments allow for various changes and numerous embodiments, particular exemplary embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the exemplary embodiments to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the disclosure are encompassed. In the description, certain explanations of well known related art are omitted. 
     While such terms as “first,” “second,” etc., may be used to describe various components, such components must not be limited to the above terms. The above terms are used only to distinguish one component from another. 
     The terms used in the present specification are merely used to describe particular exemplary embodiments, and are not intended as limiting. All terms including descriptive or technical terms used herein should be construed as having meanings that would be understood to one of ordinary skill in the art. However, the terms may have different meanings according to an intention of one of ordinary skill in the art, precedent cases, or the appearance of new technologies. Also, some terms may be arbitrarily selected by the applicant, and in this case, the meaning of the selected terms will be described in detail in the detailed description. Thus, the terms used herein have to be defined based on the meaning of the terms together with the description throughout the specification. Screens suggested in the present application are used only for descriptive purposes, and are not intended as limiting. 
     An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present specification, it is to be understood that the terms such as “including” or “having,” etc., are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, steps, actions, components, parts, or combinations thereof may exist or may be added. 
     As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     An object denotes a component or information displayed on an external device or a screen of the external device of a transparent display device. For example, an object may include an image, an image included in another image, an icon, a folder icon, an icon included in a folder icon, text, a pop-up window, an application execution window, a content included in an application execution window, a list, an item, a content, and a file included in a list; however, the present invention is not limited thereto. Examples of an object will be described in detail in various examples of screens that will be described later. The object may be referred to as an external object of the transparent display device. 
     Throughout the entire specification, a touch input denotes input information of a user input through a touch-based gesture using a finger of the user or a touch tool. The touch tool may be referred to as an external input device, a stylus, or a stylus pen. 
     The touch-based gesture may be variously defined. In other words, examples of the touch-based gesture may include touch-based motions on a touch screen, such as tap, touch-and-hold, double tap, drag, touch-and-drag, panning, flick, drag-and-drop, sweep, and swipe, but the touch-based gesture is not limited thereto. 
     The touch input may be replaced by a gesture based on an image captured by a camera, according to an input desired to represent based on the touch. For example, if the touch input is an input for selecting an object displayed on an external device, the touch input may be replaced by a gesture or operation according to a moving direction or sign of the hand captured by the camera. The camera may be configured based on an image sensor or an optical sensor. 
     The touch input may be replaced by a user voice signal based on natural language, according to an input desired to represent based on the touch. For example, if a touch input is an input for selecting an object including a certain letter or a name displayed on an external device, the touch input may be replaced by a user voice signal based on natural language representing the certain letter or the name of the object. 
     Hereinafter, exemplary embodiments will be described in detail with reference to accompanying drawings, wherein like reference numerals denote like elements to not provide repeated descriptions. 
       FIG. 1A  is a block diagram of an information display system according to an exemplary embodiment. 
     Referring to  FIG. 1A , the information display system includes a transparent display device  100  and an external device  110 . However, the information display system is not limited to the example shown in  FIG. 1A . That is, the information display system may further include other components, in addition to the components shown in  FIG. 1A . 
     For example, as shown in  FIG. 1B , the information display system may further include a server  120 . In this case, the transparent display device  100  and the external device  110  may transmit and/or receive information via the server  120 , and the transparent display device  100  may receive information based on an augmented reality service about the external device  110  from the server  120 . The communication through the server  120  may be wired or wireless internet, but is not limited thereto. The server  120  may include at least one of a cloud server, an information supply server, and a service server. The server  120  may manage and provide information based on the augmented reality service. 
     The information display system may further include an access point  130 , as shown in  FIG. 1C . In this case, the transparent display device  100  and the external device  110  may transmit and/or receive information via the access point  130 . The communication method via the access point  130  may be, for example, a wireless LAN communication method of infrastructure mode (or WiFi), but is not limited thereto. 
     When the information display system is configured as shown in  FIG. 1A , the transparent display device  100  and the external device  110  may transmit and/or receive information through a device-to-device direct communication. The device-to-device direct communication method may use, for example, a local area wireless communication method such as wireless LAN communication of Ad-hoc mode such as WiFi-direct, Bluetooth communication, ultra wideband (UWB) communication, and Zigbee communication, but is not limited thereto. 
     That is, the transparent display device  100  and the external device  110  may be connected to each other via a wire. For example, the transparent display device  100  and the external device  110  may be connected to each other via a universal serial bus (USB) or a universal asynchronous receiver/transmitter (UART) to transmit/receive data. The device-to-device direct communication method may be referred to as a machine-to-machine (M2M) communication method, a device-to-device (D2D) communication method, or a peer-to-peer (P2P) communication method. 
     Therefore, the communication between the transparent display device  100  and the external device  110  may be performed based on one of the direct communication between devices, the communication method via the access point  130 , and the communication method via the server  120 , according to elements of the information display system, but is not limited thereto. 
     The transparent display device  100  and the external device  110  may transmit and/or receive at least one of size information thereof, owner information thereof, and information sharable with other devices, through a short distance communication method such as a near field communication (NFC). 
     The size information of the device may be represented as, for example, (width×length×thickness) mm, but is not limited thereto. Screen information may include screen size information and screen type information, and is not limited thereto. The screen size information may be represented as, for example, A4, B5, 7 inches, or 5.5 inches, and is not limited thereto. The screen type information may represent whether the screen is a touch screen or a non-touch screen, and is not limited thereto. For example, the screen type information may represent whether the screen is a liquid crystal display (LCD) panel or an active matrix organic light emitting diodes (AMO LED) panel. 
     The transparent display device  100  may display the information about the external device  110 , which is transmitted from the external device  110  via a short distance communication method, such as the NFC, as information about the external device  110  based on the augmented reality service. For example, the transparent display device  100  may display the information about the external device  110  on a display area adjacent to the external device  110  that is seen through the transparent display device  100 . The display area is a part of a screen of the transparent display device  100 . The external device  100  that is seen through the transparent display device  100  may be referred to as the external device  100  that is seen via the screen of the transparent display device  100 . 
     The transparent display device  100  is a device having a transparent display. For example, the transparent display device  100  may be a mobile phone having a transparent display, a smartphone having a transparent display, a notebook computer having a transparent display, a tablet PC having a transparent display, a handheld PC having a transparent display, an electronic book terminal having a transparent display, a digital broadcasting terminal having a transparent display, a personal digital assistant (PDA) having a transparent display, a portable multimedia player (PMP) having a transparent display, a navigation device having a transparent display, a smart TV having a transparent display, a consumer electronic (CE) device having a transparent display (for example, a refrigerator having a transparent display, an air conditioner having a transparent display, a dish washing machine having a transparent display, etc.), and an iOS-convertible device having a transparent display, but is not limited thereto. The transparent display may be applied to various fields such as high added-value glass, glass as a functional car element, car dashboard, navigators, security electronic devices, solar batteries, electronic devices for military, game consoles, toys, and show windows, as well as smart windows. The screen of the transparent display device  100  may be referred to as a screen on the transparent display. 
     The transparent display device  100  may provide application execution function, communication function, media player function, web-browsing function, word-processing function, e-mail transmission function, messenger function, and/or data storage function, but is not limited thereto. 
     The transparent display device  100  requests information related to at least one object that is displayed on the external device  110  and seen through the transparent display device  100 , based on a touch input. When receiving the information related to the object from the external device  110 , the transparent display device  100  displays the received information. 
     The external device  110  is a device that is seen through the transparent display device  100 , through the screen of the transparent display device  100 , or through the transparent display of the transparent display device  100 . The external device  110  may be referred to as another device. The external device  110  may not include a transparent display. For example, the external device  110  may be a mobile phone, a smartphone, a notebook computer, a tablet PC, a handheld PC, an electronic book terminal, a digital broadcasting terminal, a PDA, a PMP, a navigation, a smart TV, a CE device (for example, a refrigerator, an air conditioner, a dishwashing machine having a display panel, etc.), and an iOS convertible device, but is not limited thereto. That is, the external device  110  may include a transparent display. 
     The external device  110  may provide application execution function, communication function, media player function, web-browsing function, word-processing function, e-mail transmission function, messenger function, and/or data storage function, but is not limited thereto. 
     When the transparent display device  100  requests the information related to at least one object that is displayed, the external device  110  selects the requested object and transmits information related to the requested object to the transparent display device  100 . 
       FIG. 2  is a flowchart illustrating a method of displaying information to be performed by the transparent display device  100 , according to an exemplary embodiment. 
     In operation S 201 , the transparent display device  100  receives a first touch input and a second touch input. The first touch input represents reference information of the external device  110  that is seen through the transparent display device  100 . The reference information is used to detect a display location of the object on the external device  110 , wherein the object is selected by the second touch input in the transparent display device  100 . The reference information may be referred to as first position information of the external device  110 . 
       FIGS. 3A through 3H  are diagrams showing examples of the first touch input. In  FIGS. 3A through 3H , the transparent display device  100  has a size that is greater than that of the external device  110 , and the external device  110  is seen through the transparent display device  100  as shown in  FIG. 3A . In the examples shown in  FIGS. 3A through 3H , a result of sensing the first touch input may or may not be displayed on the transparent display device  100 . 
       FIG. 3B  shows an example in which the first touch input is drawn along a contour line of the external device  110  that is seen through the transparent display device  100 . The contour line of the external device  110  may be referred to as a boundary of the screen of the external device  110 . The first touch input may be referred to as a first input that identifies the boundary of the screen of the external device  110 . The first touch input shown in  FIG. 3B  is based on drawing operation from a point S on the external device  110  that is seen through the transparent display device  100  along the contour line of the external device  110  to a point E. The point S denotes a start point of the touch operation, that is, a drawing operation along the contour line of the external device  110 . The point E denotes an end point of the touch operation along the contour line of the external device  110 . The point S and the point E may have the same display location (or xy coordinates). However, the point S and the point E may be adjacent to each other so that a closed area may be set according to the touch operation for drawing along the contour line of the external device  110 . 
     In  FIG. 3B , the point S is a left uppermost corner in the contour line of the external device  110 , but is not limited thereto. That is, the point S may be an arbitrary point on the contour line of the external device  110 . The point E is determined depending on the point S. 
     In  FIGS. 3C and 3D , the first touch input is based on independent touch operations at a first point and a second point on the transparent display device  100 . In  FIGS. 3C and 3D , the first point and the second point are in a diagonal relationship on the contour line of the external device  110  that is seen through the transparent display device  100 . 
     Referring to  FIG. 3C , the first point is a left uppermost point P 1  on the contour line of the external device  110 , and the second point is a right lowermost point P 2  on the contour line of the external device  110 . Because the point P 1  and the point P 2  are independently touched, the transparent display device  100  may trace the contour line of the external device  110  that is seen through the transparent display device  100  based on information about xy coordinates of the point P 1  and the point P 2  on the transparent display device  100 . That is, (x, y) coordinate information of a right uppermost point and a left lowermost point of the contour line, which are not touched, is detected based on the (x, y) coordinate information of the point P 1  and the point P 2 , and the detected points are connected to each other to trace the contour line of the external device  110 . 
     Referring to  FIG. 3D , the first point is a left lowermost point P 3  on the contour line of the external device  110  and the second point is a right uppermost point P 4  on the contour line of the external device  110 . When the point P 3  and the point P 4  are touched, the transparent display device  100  may trace the contour line of the external device  110  that is seen through the transparent display device  100  based on the xy coordinate information of the point P 3  and the point P 4  on the transparent display device  100 . The tracing of the contour line may be performed in the same way as described with reference to  FIG. 3C . 
       FIGS. 3E through 3H  show examples where the first touch input is based on a touch-and-drag operation connecting the first point and the second point to each other on the transparent display device  100 . In  FIGS. 3E through 3H , the first point and the second point are in the diagonal relationship with each other based on the contour line of the external device  110  that is seen through the transparent display device  100 . In the examples shown in  FIGS. 3E through 3H , the first point may denote a start point S and the second point may denote an end point E. 
     Referring to  FIG. 3E , the point S is a left uppermost point on the contour line of the external device  110  and the point E is a right lowermost point on the contour line of the external device  110 . Since the touch-and-drag operation is performed toward the point E after touching the point S, the transparent display device  100  may trace the contour line of the external device  110 . That is, as shown in  FIG. 3E , when a touch point according to the touch-and-drag operation is t 1 , (x, y) coordinate information of a point t 2  and a point t 3  on the contour line, wherein the points t 2  and t 3  are not touched, is detected based on the (x, y) coordinate information of the point S and the (x, y) coordinate information of the point t 1 , and then, the contour line of the external device  110  may be traced by connecting the point S, the points t 1 , t 2 , and t 3  based on the (x, y) information thereof. 
     The transparent display device  100  may display an arrow or a block setting shown in  FIG. 3E  based on a current touching location to show variation of the touched location according to the dragging. When the touch-and-drag operation finishes at the point E, the transparent display device  100  may end the arrow or the block setting display, and may display the contour line of the external device  110 . Otherwise, the arrow or the block display status may be maintained. 
       FIG. 3F  shows a case where the start point S of the touch-and-drag operation is the right uppermost point on the contour line of the external device  110  and the end point E is the left lowermost point on the contour line of the external device  110 .  FIG. 3G  shows a case where the start point S of the touch-and-drag operation is the left lowermost point on the contour line of the external device  110  and the end point E is the right uppermost point on the contour line of the external device  110 .  FIG. 3H  shows a case where the start point S of the touch-and-drag operation is the right lowermost point on the contour line of the external device  110  and the end point E is the left uppermost point on the contour line of the external device  110 . 
       FIGS. 4A through 4E  are diagrams showing other examples of the first touch input. In  FIGS. 4A through 4E , the transparent display device  100  is larger than the external device  110 , and as shown in  FIG. 4A , the external device  110  is seen through the transparent display device  100 . In the examples shown in  FIGS. 4A through 4E , a result of sensing the first touch input may or may not be displayed on the transparent display device  100 . 
     In  FIGS. 4A through 4E , the first touch input is based on a touch-based operation for adjusting a region with respect to guide information displayed on the transparent display device  100 , and the adjustable range of the guide information based on the touch operation is based on the contour line of the external device  110  that is seen through the transparent display device  100 . 
     The guide information may be, for example, camera focusing range information. The guide information may be displayed according to a request of a user of the transparent display device  100 . For example, the request of the user may include a request for displaying guide information for executing the information display method according to the exemplary embodiment, or request for executing the information display method. 
     As shown in  FIG. 4A , when the external device  110  is seen through the transparent display device  100 , the transparent display device  100  displays guide information G 1  as shown in  FIG. 4B . The guide information G 1  may be displayed on the transparent display device  100  according to a command of a user of the transparent display device  100 . When performing the region adjusting operation of the guide information G 1  toward four corners of the contour line of the external device in a state of contacting four points P 5 , P 6 , P 7 , and P 8 , as shown in  FIG. 4C , the guide information, the region of which is adjusted, is displayed on the transparent display device  100 . 
     Accordingly, the transparent display device  100  may trace the contour line of the external device  110  according to adjusted (x, y) coordinate values of the four points P 5 , P 6 , P 7 , and P 8  of the guide information G 1 . The tracing of the contour line may be performed by connecting the changed (x, y) coordinate values of the points P 5 , P 6 , P 7 , and P 8 , but is not limited thereto. The changed (x, y) coordinate value of each point may be obtained by adding a variation amount according to the dragging operation to the original (x, y) coordinate value, but is not limited thereto. That is, according to two-touch operations, that is, touching the four points P 5 , P 6 , P 7 , and P 8  of the guide information G 1  and touching the points representing the desired region, the original (x, y) coordinate values of the points may be updated to the (x, y) coordinate values of the second touched points. 
       FIGS. 4D and 4E  are diagrams showing examples of the region adjusting operation of the guide information G 1 . Referring to  FIG. 4D , the user moves touched point from the left uppermost point P 5  of the guide information G 1  to the left uppermost point of the contour line of the external device  110  after touching the point P 5 . The left uppermost point in the contour line of the external device  110  is a corner of the external device  110 , which corresponds to the point P 5  of the guide information G 1 . 
     Next, after touching the right lowermost point P 8  of the guide information G 1 , the touched point is dragged to the right lowermost point in the contour line of the external device  110 , the region of the guide information G 1  is moved from the points P 6 , P 7 , and P 8  except for the left uppermost point P 5 , and accordingly, the display state of the guide information G 1  is changed as shown in  FIG. 4C . 
     According to the examples shown in  FIGS. 4D, 4E, and 4C , after touching one point of the guide information G 1 , the touched point is moved to a corresponding corner of the external device  110 , and then, the diagonal point of the guide information G 1  is touched and dragged to the corresponding corner of the external device  110  so as to change a display location of the guide information G 1  or adjust displayed size of the guide information G 1 . 
     The one point and the diagonal point in the guide information G 1  are not limited to the examples shown in  FIGS. 4D and 4E . For example, the point P 6  of the guide information G 1  is touched and dragged to the corresponding corner in the contour line of the external device  110 , and then, the point P 7  that is in a diagonal relation with the point P 6  is touched and dragged so that the other points P 5 , P 7 , and P 8  of the guide information G 1  may be moved to the corresponding corners in the contour line of the external device  110 . 
       FIGS. 5A through 5E  are diagrams showing examples of the first touch input in a case where the transparent display device  100  is smaller than the external device  110 . That is, as shown in  FIG. 5A , when the transparent display device  100  is smaller than the external device  110 , the first touch input may be based on a touch operation of drawing along the contour line of the external device  110  that overlaps the transparent display device  100 . Here, a direction of the touch operation, that is, drawing direction along the contour line, may not be limited to one direction. 
     As shown in  FIG. 5A , the transparent display device  100  may be smaller than the external device  110 . Accordingly, when an object to be selected is displayed at a location adjacent to a center on a screen of the external device  110  so that the first touch input shown in  FIGS. 5B through 5E  is not applied, the transparent display device  100  may reduce a size of the external device  110  by using a zoom-out function of a camera to receive a first touch input and a second touch input. Here, the transparent display device  100  may detect a screen size of the external device  110  according to a zoom-out magnification. 
     Meanwhile, when the external device  110  is seen through the transparent display device  100  as shown in  FIG. 6A , the first touch input may be received when a touch operation of touching a start point S and dragging to the end point E along the contour line of the external device  110  that is seen through the transparent display device  100 . 
     Also, the first touch input may be based on a touch operation for selecting screen information of the external device  110 , which is included in a menu  910  shown in  FIG. 9B  and will be described later. The screen information may include at least one of screen size information of the external device  110  and screen type information of the external device  110  as described above. 
     The screen size information may represent, for example, whether the screen size of the transparent display device  100  is equal to a screen size of the external device, or certain size information such as A4, B5, 7 inches, 4 inches, etc. as shown in  FIG. 9B , but is not limited thereto. The first touch input may be based on a touch operation for selecting corresponding screen size from among the pieces of the screen size information. 
     If the screen size of the transparent display device  100  is different from the screen size of the external device  110 , the transparent display device  100  may change the (x, y) coordinate information on the transparent display device  100  according to the first touch input and the (x, y) coordinate information on the transparent display device  100  according to the second touch input into information according to the screen size of the external device  110 . 
     For example, when the transparent display device  100  has a screen size (length, width, area, etc.) of 4 inches and the external device  110  has a screen of 7 inches, the transparent display device  100  may change the coordinate information of the first touch input on the transparent display device  100  and the coordinate information of the second touch input on the transparent display device into coordinate information on the screen size of 7 inches, by using a function of converting the coordinate information of the screen size of 4 inches into coordinate information of the screen size of 7 inches. Here, the transparent display device  100  may use relational information between the (x, y) coordinate information on the transparent display device  100  according to the first touch input and the (x, y) coordinate information on the transparent display device  100  according to the second touch input (for example, difference information between the coordinate information). 
     Also, if the transparent display device  100  has a screen size of 10 inches and the external device  110  has a screen size of 4 inches, the transparent display device  100  may change the coordinate information of the first touch input on the transparent display device  100  and the coordinate information of the second touch input on the transparent display device  100  into coordinate information on the screen size of 4 inches, by using a function of converting the coordinate information of the 10-inch screen size into the coordinate information of 4-inch screen size. 
     The above described function of converting the coordinate information according to the screen size may be included in the external device  110 . When the external device  110  has the function of converting the coordinate information, the transparent display device  100  may transmit the (x, y) coordinate information on the transparent display device  100  according to the first touch input, the (x, y) coordinate information on the transparent display device  100  according to the second touch input, and the screen size information of the transparent display device  100  to the external device  110 . 
     The screen type information may include information representing whether the screen type of the external device  110  is a touch type or a non-touch type. If the screen of the external device  110  is the touch type screen, the external device  110  may recognize a region overlapping the transparent display device  100  and the external device  110 . Accordingly, the first touch input may not include information relating to the contour line of the external device  110 , but may only include the information representing that the screen of the external device  110  is the touch type screen. 
     In addition, in operation S 201  of  FIG. 2 , the second touch input is an input for selecting at least one object displayed on the external device  110 . The object that is displayed on the external device  110  is seen through the transparent display device  100 . The input for selecting the at least one object displayed on the external device  110  may be referred to as an input for selecting at least one position of the screen of the external device  110 . 
     The second touch input may be based on at least one of a touch operation, that is, touching an arbitrary point on a contour line of an object that is seen through the transparent display device  100  and dragging the touched location along the contour line of the object, and a touch operation of writing along the object (for example, text) that is seen through the transparent display device  100 . The second touch input may be referred to as a touch input on the screen of the transparent display device  100  indicating position information (or second position information) of the object displayed on the screen of the external device  110 . The second touch input may be referred to as an input that selects a position of the screen of the external device  110  viewable through the transparent display device  100 . The object is displayed on the screen of the external device  110  at the position. The position comprises one of a coordinate position of the screen of the external device  110  viewable through the transparent display device  100  and an area of the screen of the external device  110  viewable through the transparent display device  100 . 
       FIGS. 6A through 6C  are diagrams showing examples of the second touch input according to the exemplary embodiment. 
       FIG. 6A  shows the second touch input based on a touch operation of drawing along a contour line of an object and the first touch input based on a touch operation of drawing along the contour line of the external device  110 . 
     That is, referring to  FIG. 6A , the first touch input is received according to the touch operation of touching the point S and drawing a line to the point E along the contour line of the external device  110 , and the second touch input is received according to the touch operation of drawing a line along with a contour line of an icon. The touch operation of drawing a line along the contour line of the icon is performed by touching a point S 1  and drawing a line to a point E 1  along the contour line of the icon that is an object, and accordingly, the second touch input is received. The start point and the end point of the touch operation for drawing along the contour line of the icon are not limited to the examples shown in  FIG. 6A . That is, the start point is an arbitrary point in the contour line of the icon, and the end point is determined according to the start point as described above. In  FIG. 6A , the object displayed on the external device  110  is an icon, but the object displayed on the external device  110  may be another type of object, as discussed below. 
     Also, the touch operation between the start point and the end point of the touch operation for drawing along the contour line of the object may be performed continuously or discontinuously. If the touch operation is performed discontinuously, the end point of the touch operation for drawing along the contour line of the object may be changed. 
     For example, the touch operation for drawing along the contour line of the object in  FIG. 6A  starts from the start point S 1  and stops at a left lowermost point of the object, and then, the touch operation starts again from the start point S 1  or the end point E 1  to the left lowermost point of the object. In this case, the end point is the left lowermost point of the object, and the end point E 1  may be a connection point for connecting the contour line according to the touch operation. The point where the touch operation stops is not limited to the above example. That is, the touch operation may be stopped at an arbitrary point on the contour line of the object, or at a plurality of points on the contour line of the object. 
       FIG. 6B  shows an example where the second touch input is received based on a writing touch operation along the object (text). That is,  FIG. 6B  shows a second touch input based on the touch operation for writing an alphabet character P. As such, whereas the icon displayed on the external device  110  in  FIG. 6A  constituted the object, the alphabet character P is the object displayed on the external device  110  in  FIG. 6B . The second touch input based on the object writing touch operation may be performed by touching an arbitrary point in the text, and then, writing along the text. For example, after touching a point  601 , a writing touch operation along the object (text) may be performed in a direction denoted by an arrow of  FIG. 6B . However, the start point of the object writing touch operation is not limited to the example shown in  FIG. 6B , that is, an arbitrary point of the object may be the start point. In addition, the object writing touch operation may be performed continuously or discontinuously. When the object writing touch operation is performed discontinuously, at least one connection point as described above may be included between the start point and the end point. 
       FIGS. 7A and 7B  are diagrams showing examples of a screen for describing the first touch input and the second touch input, in a case where the transparent display device  100  has a screen that is larger than that of the external device  110 . That is, as shown in  FIG. 7A , when the external device  110  is seen through the transparent display device  100 , the first touch input is based on the touch operation for drawing along the contour line of the external device  110  and the second touch input is based on the touch operation for drawing along the contour line of the object displayed on the external device  110 . 
       FIGS. 8A through 8G  are diagrams showing other examples for illustrating the first touch input and the second touch input in a case where the transparent display device  100  is smaller than the external device  110 .  FIGS. 8A through 8G  shows examples in which pieces of an object that is displayed on the external device  110  are arranged by adjusting the overlapping locations of the transparent display device  100  and the external device  110 . Therefore, in the examples shown in  FIGS. 8A through 8G , the transparent display device  100  displays information of sensing the second touch input on the transparent display device  100 . 
     That is, when the screen displayed on the external device  110  is shown as  FIG. 8A , the transparent display device  100  overlaps the external device  110  as shown in  FIG. 8B . Here, the first touch input is based on a touch operation for drawing along the contour line of the external device  110  ( 801 ), and the second touch input is based on a touch operation for drawing along a contour line of the object ( 802 ). Here, information of sensing the second touch input ( 802 ) is displayed on the transparent display device  100 . 
     The transparent display device  100  detects relational information between (x, y) coordinate information on the transparent display device  100  according to the first touch input and (x, y) coordinate information on the transparent display device  100  according to the second touch input in  FIG. 8B , and stores the detected information. The relational information detected by the transparent display device  100  may include a difference between the (x, y) coordinate information on the transparent display device  100  according to the first touch input and the (x, y) coordinate information on the transparent display device  100  according to the second touch input. The external device  110  may recognize the object selected by the transparent display device  100  in  FIG. 8B  according to the (x, y) coordinate information according to the first touch input, the (x, y) coordinate information according to the second touch input, and the above relational information. 
     For example, when the coordinate information according to the first touch input ( 801 ) includes coordinates from (x(1), y(1)) to (x(1+m), y(1+m)), the coordinate information according to the second touch input ( 802 ) includes coordinates from (x(i), y(i)) to x((i+j), y(i+j)), and the number of pieces of the coordinate information obtained by the first touch input and the number of pieces of the coordinate information obtained by the second touch input are equal to each other, the transparent display device  100  may obtain relational information from coordinates (x(1)−x(i), y(1)−y(i)) to (x(1+m)−x(i+j), y(1+m)−y(i+j)). Here, m, i, and j are natural numbers that are equal to or greater than 2. 
     However, the number of pieces of coordinate information on the transparent display device  100  according to the first touch input and the number of pieces of coordinate information on the transparent display device  100  according to the second touch input may be different from each other. In this case, the transparent display device  100  may detect the above relational information by sampling the coordinate information obtained by the first touch input and the coordinate information obtained by the second touch input. A target to be sampled may be determined according to the display location thereof. 
     Next, as shown in  FIG. 8C , when the transparent display device  100  overlaps the external device  110 , the first touch input is based on a touch operation for drawing along the contour line of the external device  110  ( 803 ) and the second touch input is based on a touch operation for drawing along the contour line of the object ( 804 ). Here, information of sensing the second touch input ( 804 ) is displayed on the transparent display device  100 . 
     Accordingly, the image of the object displayed on the transparent display device  100  may include the information of sensing the second touch input ( 802 ) in  FIG. 8B , as shown in  FIG. 8C . The transparent display device  100  detects the coordinate information according to the first touch input and the second touch input and the relational information between the coordinate information in  FIG. 8C  and stores the detected information as described with reference to  FIG. 8B . Here, the transparent display device  100  stores the coordinate information and the relational information between the coordinate information detected in the process of  FIG. 8B  and the coordinate information and the relational information between the coordinate information detected in the process of  FIG. 8C  to be distinguished that the coordinated information and the relational information are detected from each other process. 
     As shown in  FIG. 8D , when the transparent display device  100  overlaps the external device  110 , the first touch input is based on a touch operation for drawing along the contour line of the external device  110  ( 805 ) and the second touch input is based on a touch operation for drawing along the contour line of the object ( 806 ). Here, the second touch input may further include a touch operation for filling inside the contour line of the object. Information of sensing the second touch input ( 806 ) is displayed on the transparent display device  100 . Accordingly, the image of the object displayed on the transparent display device  100  may include an image including the information of sensing the second touch input in the processes shown in  FIGS. 8B and 8C . 
     The transparent display device  100  detects and stores the coordinate information on the transparent display device  100  according to the first touch input and the second touch input in the process shown in  FIG. 8D  and the relational information between the coordinate information, as described with reference to  FIG. 8B . When storing the information, the transparent display device  100  stores the detected coordinate information and the relational information to be distinguished from the coordinate information and the relational information obtained in the processes shown in  FIGS. 8B and 8C . 
     As shown in  FIG. 8E , when the transparent display device  100  overlaps the external device  110 , the first touch input is based on a touch operation for drawing along the contour line of the external device  110  ( 807 ), and the second touch input is based on a touch operation for drawing along the contour line of the object ( 808 ). Here, the second touch input may further include a touch operation for filling inside the contour line of the object. Information of sensing the second touch input ( 808 ) is displayed on the transparent display device  100 . Accordingly, the image of the object displayed on the transparent display device  100  may be the image including all the information of sensing the second touch input in processes shown in  FIGS. 8B, 8C, and 8D . 
     The transparent display device  100  obtains coordinate information on the transparent display device  100  according to the first touch input ( 807 ) and the second touch input ( 808 ) in  FIG. 8E  and the relational information between the coordinate information, and stores the detected information. Here, the transparent display device  100  stores the detected coordinate information and the relational information obtained in the process of  FIG. 8E  to be distinguished from the coordinate information and the relational information obtained in the processes shown in  FIGS. 8B through 8D . 
     When the transparent display device  100  and the external device  110  overlap each other as shown in  FIG. 8F , the first touch input is based on a touch operation for drawing along the contour line of the external device  110  ( 809 ) and the second touch input is based on a touch operation for writing along a text “RABBIT” ( 810 ). Here, information of sensing the second touch input ( 810 ) is displayed on the transparent display device  100 . Accordingly, the image of the object displayed on the transparent display device  100  is an image including all the information of sensing the second touch inputs in the processes shown in  FIGS. 8B through 8E . The transparent display device  100  obtains coordinate information on the transparent display device  100  according to the first touch input and the second touch input in  FIG. 8F  and the relational information between the coordinate information, and stores the detected information as shown in  FIGS. 8B through 8E . 
     According to displaying information of sensing the second touch inputs in the processes shown in  FIGS. 8B through 8F  on the transparent display device  100 , the information of sensing the second touch inputs is displayed on the transparent display device  100  as shown in  FIG. 8G . As described above, by displaying the information of sensing the second touch inputs on the transparent display device  100  when the second touch input is received, a displaying location about the object, which would be transmitted from the external device  110 , may be determined in advance. 
     Also, the processes shown in  FIGS. 8B through 8F  may be performed after changing a location of the transparent display device  100  or moving the transparent display device  100  to arrange pieces of the object displayed on the external device  110 . Therefore, the transparent display device  100  may clearly distinguish the first touch input and the second touch input from each other in each screen. For example, after receiving the first touch input and the second touch input in  FIG. 8B , the transparent display device  100  changes its location or moves, and then, receives the first touch input and the second touch input according to the process of  FIG. 8C  to select the object displayed on the external device  110  as shown in  FIG. 8C . Therefore, the first and second touch inputs in the process of  FIG. 8B  and the first and second touch inputs in the process of  FIG. 8C  may be distinguished from each other via sensing of the location variation or the moving of the transparent display device  100 . 
       FIGS. 9A through 9C  are diagrams showing examples of screen for describing the first and second touch inputs. 
     Referring to  FIG. 9A , the transparent display device  100  and the external device  110  have the same size. Referring to  FIG. 9B , a first touch input operation is performed based on a menu  910  displayed on the transparent display device  100 , and a second touch input is based on a touch operation for setting a closed region with respect to a sun, a tap-based touch operation with respect to a cloud, and a touch operation for drawing a contour line of a flower. The closed region shown in  FIG. 9B  is not limited thereto. For example, the closed region may be set as various types of closed loops in the transparent display device  100 . 
       FIGS. 10A through 10D  are diagrams showing examples of the screens for describing a first touch input and a second touch input based on an augmented reality service. 
       FIG. 10A  shows a case where information about the external device  110  based on the augmented reality service is displayed adjacent to the external device  110  that is seen through the transparent display device  100 . The information about the external device  110  based on the augmented reality service may be provided from the external device  110 , another external device, or a server based on a physical locations between the transparent display device  100  and the external device  110 . 
     The information about the external device  110  based on the augmented reality service may be provided using an access point. When the transparent display device  100  and the external device  110  are located within a communication area of the same access point, physical locations of the transparent display device  100  and the external device  110  may be estimated by using an indoor sensor capable of estimating a physical location of a device such as a geomagnetic sensor, an acceleration sensor, a gyro sensor, and an altitude sensor mounted in the device. Thus, the information about the external device  110  based on the augmented reality service may be provided from the above described other external device or the server according to the estimated physical locations. 
     Otherwise, the transparent display device  100  receives or reads, from the external device  110 , information that is necessary for receiving information based on the augmented reality service about the external device  110  (for example, mark information for recognizing the external device  110 ) using short distance communication such as NFC, and then, collects and displays the information based on the augmented reality service about the external device  110  from the server or the above described other external device. 
     The information about the external device  110  seen through the transparent display device  100  based on the augmented reality service may include a name of the device, a name of the owner, and contents of the external device, which may be shared with other devices, as shown in  FIG. 10A , but is not limited thereto. 
     When displaying the information about the external device  110  based on the augmented reality service as shown in  FIG. 10A , the first touch input may be based on an operation of setting a touch-based closed region about the external device  110  as shown in  FIG. 10B . The touch-based closed region is not limited to the example shown in  FIG. 10B . 
     According to receipt of the first touch input, information about a shared folder may be displayed on the transparent display device  100  as shown in  FIG. 10C . The information about the shared folder may be information based on the augmented reality service, or information that is received from the external device  110  when the first touch input is transmitted to the external device  110 . Here, the screen displayed on the external device  110  may not display the information about the shared folder. 
     When the second touch input according to the operation of setting the touch-based closed region or tap-based touch operation on a desired folder is received based on the information about the shared folder displayed on the transparent display device  100  as shown in  FIG. 10C , available pictures may be displayed as shown in  FIG. 10D . The screen of the external device  110  may not display the available pictures shown in  FIG. 10D . 
     The transparent display device  100  may perform the second touch input operation by an operation of setting a touch-based closed region on a desired picture from among the available pictures shown in  FIG. 10D . 
     Meanwhile, in operation S 202  of  FIG. 2 , the transparent display device  100  requests the external device  110  for information about at least one selected object, based on the first and second touch inputs. A signal requesting the information about the object may include the coordinate information on the transparent display device  100  according to the first and second touch inputs and/or relational information between the coordinate information. 
     Otherwise, the signal requesting the information related to the object may include coordinate information on the external device  110  according to the first and second touch inputs, wherein the coordinate information is converted by using the coordinate information converting function of the transparent display device  100 , and/or relational information between the coordinate information. The coordinate information on the external device  110  according to the second touch input may be coordinate information of the object that is displayed on the external device  110 . 
     The signal requesting the information related to the object may further include a signal requesting relation information with the object. The signal requesting relation information with the object may include, for example, information for requesting a folder and objects included in the folder, when the object selected according to the second touch input is the folder. The objects included in the folder may be referred to as objects that are not displayed on the external device  110 . 
     The signal requesting the information related to the object may include coordinate information on the transparent display device  100  according to the first and second touch inputs, and screen size information of the transparent display device  100 . In this case, the external device  110  may detect coordinate information on the external device  110  according to the first and second inputs based on the information transmitted from the transparent display device  100  and the screen information of the external device  110 . The coordinate information on the external device  110  may be detected by the processes described with reference to  FIGS. 8B through 8F , but is not limited thereto. 
     The signal requesting the information related to the object may include various pieces of information that may be estimated by the examples of the first and second touch inputs described with reference to  FIGS. 3 through 10D . 
     In operation S 203 , the transparent display device  100  receives information related to the selected object from the external device  110 , and in operation S 204 , the transparent display device  100  displays the received information related to the object on the transparent display device  100 . 
     The information related to the object may include at least one other object having the same display type as that of the object selected by the second touch input. The other object has a different display location on the external device  110  from that of the selected object. That is, as shown in  FIG. 6B , when the second touch input is received based on the touch operation for writing the text P, the transparent display device  100  may receive all of the text Ps that are displayed at different locations on the external device  110  from the external device  110 , and displays the received text. 
     Here, the display locations of the received information on the transparent display device  100  may similarly correspond to the display locations on the external device  110 . If there are a plurality pieces of received information, the transparent display device  100  receives information about display coordinates on the external device  110 , detects information about display coordinates on the transparent display device  100  by using the screen size information of the transparent display device  100  and the display coordinate information transmitted from the external device  110 , and displays the plurality of objects by using the detected coordinate information. The coordinate information may be detected by the coordinate information converting operation that is described above. 
     However, the external device  110  may detect information about coordinates on the transparent display device  100  by using the screen size information of the transparent display device  100  and the information about the display coordinates of the plurality pieces of the object information on the external device  110 , and may transmit the detected coordinate information and the object information to the transparent display device  100 . Then, the transparent display device  100  may display the objects based on the received coordinate information. 
     In operation S 203 , the information about the selected object transmitted from the external device  110  may include information relating to the selected object. The information relating to the object may include information that is not displayed on the external device  110  (for example, information about objects included in a folder) as described above. 
     In operation S 204 , displaying the received information on the transparent display device  100  may include displaying the received information at similar locations as those of the external device  110  as shown in  FIGS. 6C, 7C, and 9C . However, when the second touch input is received as shown in  FIG. 10D , pictures Pic 1 , Pic 5 , and Pic 6 , which are the selected objects, are received. Thus, the transparent display device  100  may display the received pictures Pic 1 , Pic 5 , and Pic 6  sequentially or on locations based on the screen shown in  FIG. 10D . The received information may be stored in a clip board in the transparent display device  100 , or may be displayed on a clip board after generating the clip board. 
       FIG. 11  is a flowchart illustrating a method of displaying information in a transparent display device according to another exemplary embodiment. The method illustrated in  FIG. 11  includes an editing function. 
     In operation S 1101 , the transparent display device  100  receives a first touch input and a second touch input. The first and second touch inputs are the same as those described with reference to  FIGS. 2 through 10 . 
     In operation S 1102 , the transparent display device  100  requests the external device  110  for information related to an object based on the first and second touch inputs. The request for the information related to the object is the same as that described in operation S 201  of  FIG. 2 . 
     In operation S 1103 , the transparent display device  100  receives information corresponding to the request from the external device  110 . The information related to the object that is received is the same as that described in operation S 203 . 
     In operation S 1104 , the transparent display device  100  displays the received information the transparent display device  100 . 
     In operation S 1105 , the transparent display device  100  edits the received information that is displayed on the transparent display device  100  according to a user input. 
     That is, when the received object is displayed on the transparent display device  100  as shown in  FIG. 7C  and a touch-based user input for combining the objects ( 701  and  702 ) is received, the transparent display device  100  displays a screen on which the objects are combined as shown in  FIG. 7D . 
     The user inputs  701  and  702  may be received via various touch-based operations. For example, the user inputs  701  and  702  may be performed as various touch-based operations, for example, a touch-based operation for long-touching the object to be moved and dragging the object to a desired location of the object to be combined, a touch-based operation for long touching the object to be moved and long-touching the desired location of the object to be combined, a touch-based operation for setting a touch-based closed region on the object to be moved and long-touching the desired location of the object to be combined, or a touch-based operation for setting a touch-based closed region on the object to be moved, setting a touch-based closed region on the desired location of the object to be combined, and connecting the closed regions. 
     The editing operation in operation S 1105  is not limited to the combination of the objects as shown in  FIGS. 7C and 7D . The editing may include various edits on the object, such as change in the shape of the object or change in the content of the object, and an edit on the screen including the object. 
     The transparent display device  100  may perform the above editing operation based on an interaction with the external device  110 . Accordingly, the information displayed on the external device  110  may reflect the editing result in the transparent display device  100  in real-time. The editing result may be stored in the external device  110  only, in the transparent display device  100  only, or in both the devices  100  and  110 , according to the user input in the transparent display device  100 . 
       FIG. 12  is a flowchart illustrating a method of displaying information in a transparent display device according to another exemplary embodiment. In  FIG. 12 , the transparent display device  100  is flexible, and a front portion and a rear portion of the transparent display device  100  may be transformed or deformed according to a touch-based input. The external device  110  has a touch screen. 
     In operation S 1201 , a touch input for selecting an object displayed on the external device  110  that is seen through the transparent display device  100  is received. Here, the received touch input may correspond to the second touch input described with reference to  FIGS. 2 through 10 . 
     In operation S 1202 , front and rear surface portions of the transparent display device  100  to which the touch input is received are deformed to protrude toward the external device  110 . 
       FIGS. 13A and 13B  are side views showing a relation between the transparent display device  100  that is flexible and has the front and rear surface portions  1301  and  1302  that are deformed together according to the touch-based input, and the external device  110 . 
       FIG. 13A  is a side view showing the transparent display device  100  and the external device  110  overlapping each other before the touch input is received. 
       FIG. 13B  shows a case where the front and rear surface portions  1301  and  1302  of the transparent display device  100  are transformed together to touch a touch screen  1303  of the external device  110  according to the touch-based user input to the front surface portion  1301  of the transparent display device  100 . The rear surface portion  1302  of the transparent display device  100  may be configured as a constant voltage type so that the touch screen of the external device  110  may recognize a contact portion of the rear surface portion  1302  of the transparent display device  100  as a touch-based input; however, the present invention is not limited thereto. That is, the rear surface portion  1302  may be configured according to a touch sensing type of the touch screen  1303  in the external device  110 . 
     Meanwhile, in operation S 1203 , the transparent display device  100  receives information related to the selected object from the external device  110  based on the touch input due to the contact between the rear surface portion  1302  of the transparent display device  100  and the external device  110 . 
     In operation S 1204 , the transparent display device  100  displays the received information. 
       FIG. 14  is a flowchart illustrating a method of displaying information in a transparent display device  100  according to another exemplary embodiment.  FIG. 14  shows a case where the information related to the object displayed on the external device  110  and the screen size information are transmitted based on a local area wireless communication between the transparent display device  100  and the external device  110 . 
     In operation S 1401 , the transparent display device  100  receives the information related to the object displayed on the external device  110  and the screen size information of the external device  110  via the local area wireless network. The local area wireless communication may include NFC, Bluetooth communication, Wi-Fi direct communication and IR association communication, but is not limited thereto. 
     In operation S 1402 , the transparent display device  100  checks whether the transparent display device  100  overlaps the external device  110 . The checking in the operation S 1402  may including checking the intention of the user to display the object displayed on the external device  110  that is seen through the transparent display device  100  on the transparent display device  100  according to the touch input to the transparent display device  100 . The intention of the user may be interpreted as the intention to select an object to be displayed on the transparent display device  100 . 
     The checking operation may be performed by disposing a contact sensor on the rear surface portion of the transparent display device  100  or transmitting a sensing result sensed by a contact sensor disposed on a front surface portion of the external device  110  to the transparent display device  100  via the local area wireless communication, but is not limited thereto. 
     Also, in the operation S 1402 , the transparent display device  100  and the external device  110  may overlap so that the external device  110  may be included within the screen of the transparent display device  100  when the external device  110  is smaller as shown in  FIG. 3A , but is not limited thereto. If the transparent display device  100  is smaller than the external device  110  as shown in the example of  FIG. 4A , a part of the external device  110  may overlap the transparent display device  100 , but is not limited thereto. When the transparent display device  100  and the external device  110  have equal sizes as shown in  FIG. 9A , the overlapping surfaces of the transparent display device  100  and the external device  110  may be the same as each other. 
     In operation S 1402 , if it is determined that the transparent display device  100  and the external device  110  overlap each other, the transparent display device  100  displays the information related to the object displayed on the external device  110  by using the information transmitted via the local area wireless communication according to the user input in operation S 1403 . The user input in the operation S 1403  may include a request for displaying the object displayed on the external device  110  that is seen through the transparent display device  100 , but is not limited thereto. 
       FIG. 15  is a flowchart illustrating a method of displaying information in a transparent display device according to another exemplary embodiment.  FIG. 15  shows a case where information obtained by photographing the external device  110  using a camera function of the transparent display device  100  is displayed on the transparent display device  100  according to a user input. 
     In operation S 1501 , the transparent display device  100  photographs an object displayed on the external device  110  by using the camera function. 
     In operation S 1502 , the transparent display device  100  determines whether the transparent display device  100  and the external device  110  overlap each other. Determining whether the transparent display device  100  and the external device  110  overlap each other may be performed in the same manner as that of operation S 1402  described above. 
     In operation S 1503 , if it is determined that the transparent display device  100  and the external device  110  overlap each other, the transparent display device  100  displays the object displayed on the external device  110  that is photographed according to the user input. The user input may include a request for outputting the object displayed on the photographed external device  110 , but is not limited thereto. 
       FIG. 16  is a functional block diagram of the transparent display device  100  according to an exemplary embodiment. 
     Referring to  FIG. 16 , the transparent display device  100  may include a transparent display  1610 , a storage  1620 , a communication interface  1630 , a processor  1640 , and a sensor  1650 . However, the transparent display device  100  may further include additional components other than those shown in  FIG. 16 . For example, the transparent display device  100  may include an interface, such as a universal serial bus (USB) or a camera module. 
     The transparent display  1610  is configured so that the object displayed on a screen of the external device  110  may be seen through the transparent display  1610  and may be configured to receive a touch-based input. The transparent display unit  1610  may be formed in various types, for example, a transparent liquid crystal display (LCD) type, a transparent thin-film electroluminescent panel (TFEL) type, a transparent OLED type, or a projection type. Hereinafter, examples of the structure of the transparent display  1610  will be described below. 
     The transparent LCD type is a transparent display device formed by removing a backlight unit from a currently used LCD device and using a pair of polarization plates, an optical film, a transparent thin film transistor (TFT), and a transparent electrode. The transparent display device may be referred to as a transparent display. In case of the transparent LCD device, a transmittance is degraded due to the polarization plates or the optical film and optical efficiency is reduced since peripheral light is used instead of the backlight unit; however, a large size transparent display may be realized. 
     The transparent TFEL type is a transparent display device using an alternating current (AC) type inorganic thin film EL display (AC-TFEL) including a transparent electrode, an inorganic phosphor, and an insulating film. The AC-TFEL emits light when accelerated electrons pass through the inorganic phosphor to excite the phosphor. If the transparent display unit  1610  is the transparent TFEL type, the processor  1640  may adjust the electrons to be projected to an appropriate location to determine a location displaying the information. Since the inorganic phosphor and the insulating film are transparent, the transparent display may be easily obtained. 
     Otherwise, the transparent OLED type is a transparent display device using an OLED that emits light by itself. Since an organic emission layer is transparent, the OLED may serve as the transparent display device provided that both electrodes are realized as transparent electrodes. In the OLED, electrons and holes are injected from both sides of the organic emission layer to be combined in the organic emission layer and emit light. The transparent OLED device may display the information by injecting the electrons and holes to desired locations. 
       FIG. 17  is a diagram showing a detailed structure of the transparent display  1610  that is formed as the transparent OLED type. However, the transparent display  1610  is not limited to the example shown in  FIG. 17 . 
     Referring to  FIG. 17 , the transparent display  1610  includes a transparent substrate  1702 , a transparent transistor layer  1703 , a first transparent electrode  1704 , a transparent organic emission layer  1705 , a second transparent electrode  1706 , and a connection electrode  1707 . 
     The transparent substrate  1702  may be formed of a polymer material that is transparent such as plastic, or a glass material. The material forming the transparent substrate  1702  may be determined according to environment in which the transparent display device  100  is used. For example, the polymer material is light and flexible, and thus may be applied to a portable display device. The glass material may be applied to show windows or general windows. 
     The transparent transistor layer  1703  is a layer including a transistor that is fabricated by replacing opaque silicon used in a conventional TFT with an organic material such as transparent zinc oxide or titanium oxide. In the transparent transistor layer  1703 , a source, a gate, a drain, and various dielectric layers  1708  and  1709  are formed, and the connection electrode  1707  for electrically connecting the drain to the first transparent electrode  1704  may be formed. The transparent transistor layer  1703  includes a plurality of transparent transistors that are distributed throughout the entire display surface of the transparent display device  100 . The processor  1640  applies a control signal to the gate in each of the transistors in the transparent transistor layer  1703  to drive the corresponding transparent transistor and display information. 
     The first transparent electrode  1704  and the second transparent electrode  1706  are disposed at opposite sides to each other while the transparent organic emission layer  1705  is interposed. The first transparent electrode  1704 , the transparent organic emission layer  1705 , and the second transparent electrode  1706  form an organic light-emitting diode (OLED). 
     The transparent OLED may be classified as a passive matrix OLED (PMOLED) and an active matrix OLED (AMOLED) according to a driving method thereof. The PMOLED has a structure in which cross points between the first and second transparent electrodes  1704  and  1706  form pixels. However, in the AMOLED, a TFT is disposed to drive each of the pixels. 
     Each of the first and second transparent electrodes  1704  and  1706  includes a plurality of line electrodes, arranged perpendicularly to each other. For example, if the line electrodes of the first transparent electrode  1704  are arranged in a transverse direction, the line electrodes of the second transparent electrode  1706  are arranged in a longitudinal direction. Accordingly, there are a plurality of crossing areas formed between the first and second transparent electrodes  1704  and  1706 . The transparent transistor is connected to each of the crossing areas. 
     The processor  1640  generates a potential difference in each of the crossing areas by using the transparent transistor. The electrons and holes are induced to the transparent organic emission layer  1705  from the first and second electrodes  1704  and  1706  within the crossing area where the potential difference is generated, and then, combined with each other to emit light. On the other hand, the crossing area where the potential difference is not generated does not emit light, and accordingly, background image of the rear surface is seen as it is. 
     Indium tin oxide (ITO) may be used as the first and second transparent electrodes  1704  and  1706 . Otherwise, a newly developed material such as graphene may be used. Graphene is a material of a honeycomb-shaped plane structure in which carbon atoms are connected to each other and having a transparent property. Otherwise, the transparent organic emission layer  1705  may be formed of various materials. 
     In addition, as described above, the transparent display  1610  may be formed as the projection type, as well as the transparent LCD type, the transparent TFEL type, and the transparent OLED type. The projection type is a method of displaying an image by projecting the image to a transparent screen such as a head-up display. 
     Also, the transparent display  1610  may be a dual-touchable touch screen, or may be a touch screen, a front surface of which is only touchable. 
     The transparent display  1610  displays information including the object processed in the transparent display device  100 . The information may include information except for the object. The information except for the object may denote information that is displayed, but may not be selected by the user input. 
     The transparent display  1610  is formed as a transparent device, and a transparency of the transparent display  1610  may be adjusted by adjusting light transmittance of the transparent device or by adjusting RGB value of each pixel. 
     Also, the transparent display  1610  may have a structure in which an OLED and an LCD are combined. In the transparent display  1610 , the OLED may be located adjacent to a front surface input portion, and the LCD may be located adjacent to a rear surface input portion. In a case where the transparent display  1610  has the above combined structure, the transparent display  1610  maintains a transparent state such as the glass during power-off status, and when power is applied, the LCD blocks the light so that the transparent display  1610  becomes opaque. 
     The transparent display  1610  receives a touch input of the user through the front surface input unit. The screen displayed on the transparent display  1610  may include a user interface (UI) or a graphic user interface (GUI). Also, the transparent display  1610  may receive and display the information related to the object from the external device  110  according to the touch input (the first and second touch inputs) of the user on the object displayed on the external device  110  that is seen through the transparent display unit  1610 . 
     The storage  1620  stores at least one program that is configured to execute the information display method in the transparent display  1610 . The storage unit  1620  may include a non-volatile memory such as a high speed random access memory, a magnetic disk storage device, or a flash memory, or other non-volatile semiconductor memories. 
       FIG. 18  is a diagram illustrating software layers stored in the storage  1620  of the transparent display device  100  according to an exemplary embodiment. 
     Referring to  FIG. 18 , the software layer may include a storage module  1810 , a sensor and recognition module  1820 , a communication module  1830 , an input/output module  1860 , and a legend module  1870 , but is not limited thereto. 
     The storage module  1810  includes a system database  1811  that is a storage for storing general data such as address book and environmental information, and a touch mode data region  1812  for storing setting values for touch modes of the object that will be displayed on the transparent display  1610 . 
     The sensor recognition module  1820  includes a module  1821  for sensing a touch on the transparent display  1610 , and a module  1822  for classifying the input touch. The module  1822  for classifying the input touch may classify the touch input as a front input mode  1823  for transferring an input on the front surface input interface to an event processor X 11 , a rear input mode  1824  for transferring an input on a rear surface input interface to the event processor X 11 , and a dual mode  1825  for transferring a dual-touch input (both-touch input of the front surface input interface and the real surface input interface) to the event processor X 11 . However, the sensor recognition module  1820  may be configured by an input mode for only transferring the input on the front surface of the transparent display  1610  to the event processor X 11 . 
     The communication module  1830  may include a telephony module  1840  and a messaging module  1850 , but is not limited thereto. 
     The telephony module  1840  includes an information collection module  1842  for connecting a phone call, and a voice service module  1841  for transmitting voice over the Internet based on voice over Internet protocol (VoIP). 
     The messaging module  1850  includes an instant module  18 S 1  regarding conversation between users through an Internet connection, a module  1852  regarding short message service (SMS) text messages and multimedia messages, and a module  1853  for emailing. 
     The input/output module  1860  includes a UI &amp; graphic module  1861 , and a multimedia module  1865 . 
     The UI &amp; graphic module  1861  includes an X 11  module  1862  for receiving a touch input by a window manager, a module  1863  that outputs all objects seen by a user on a screen, and an evaluation module  1864  regarding a mode setting value stored for each object and a current touch input. 
     The multimedia module  1865  includes a moving picture reproducing module  1866 , a moving picture and still image capturing module  1867 , and a voice reproducing module  1868 . 
     The programs for executing the information display method according to the exemplary embodiments may be stored in the storage module  1871 . The storage module  1871  may store various applications. 
     As described above, the storage  1620  may store programs of various configurations, and is not limited to the example shown in  FIG. 18 . 
     The communication interface  1630  may communicate with at least one of the external device  110 , the server  120 , and the AP  130 . To perform communication, the communication interface  1630  may be configured to transmit/receive data via a wireless communication network such as wireless Internet, wireless Intranet, a wireless phone network, a wireless local area network (LAN), a Wi-Fi network, a Wi-Fi direct (WFD) network, a 3G network, a 4G Long Term Evolution (LTE) network, a Bluetooth network, an infrared data association (IrDA) network, a radio frequency identification (RFID) network, a ultra wideband (UWB) network, a Zigbee network, or a near field communication (NFC) network; however, the present invention is not limited thereto. In particular, the communication interface  1630  may include a global positioning system (GPS) module. 
     The processor  1640  may perform operations according to the above described exemplary embodiments by executing the programs stored in the storage  1620 . The processor  1640  receives a first touch input representing reference information with respect to the external device  110  that is seen through the transparent display  1610 , and a second touch input representing a selection on an object displayed on the external device  110 . The processor  1640  requests information related to the object to the external device  110  based on the first and second touch inputs received via the communication interface  1630 . When receiving the information related to the object from the external device  110  via the communication interface  1630 , the processor  1640  displays the received information on the transparent display  1610 . 
     Operations of the processor  1640  regarding the information display method according to the exemplary embodiments may be performed as described with reference to the flowcharts in  FIGS. 2, 11, 12, 14, 15 , and  FIG. 21  that will be described later. 
     The sensor  1650  senses a current status of the transparent display device  100  such as location of the transparent display device  100 , contact of the user on the transparent display device  100 , orientation of the transparent display device  100 , and acceleration or deceleration of the transparent display device  100  and generates a sensing signal for controlling operations of the transparent display device  100 . In particular, the sensor  1650  may generate a sensing signal regarding the location of the transparent display device  100  in order to receive information based on the augmented reality service described with reference to  FIGS. 10A through 10D . 
       FIG. 19  is a functional block diagram of the transparent display device  100  according to an exemplary embodiment. 
     Referring to  FIG. 19 , the transparent display device  100  may include a transparent display  1901 , a user input interface  1902 , a sensor  1903 , a camera  1904 , a storage  1905 , a communication interface  1906 , a port  1907 , an audio input interface  1908 , an audio signal processor  1909 , an audio output interface  1910 , a power supply  1911 , and a processor  1912 , but is not limited thereto. That is, the transparent display device  100  may include fewer components than those of  FIG. 19 , or may include additional components other than those of  FIG. 19 . 
     The transparent display  1901  may be referred to as a touch screen. The transparent display  1901  may display objects, and may receive a touch-based user input. The transparent display  1901  may receive the touch-based user input via at least one of a front surface and a rear surface of the transparent display  1901 . To do this, the transparent display  1901  includes at least one touch sensor. The touch sensor may recognize the user input based on (x, y) coordinates. The touch sensor may include a sensor for recognizing a direct-touch, or a sensor for recognizing a proximity-touch. 
     The user input may be generated according to a request of a user based on gestures of the user, or user&#39;s selection. The gesture of the user may be variously defined by combinations of the number of touches, touch patterns, touch area, and touch intensity. 
     As described above with reference to the transparent display  1610  of  FIG. 16 , the transparent display  1901  is formed as a transparent device, and a transparency of the transparent display  1901  may be adjusted by adjusting light transmittance of the transparent device or by adjusting RGB value of each pixel. Also, the transparent display  1901  may have a structure in which an OLED and an LCD are combined. In the transparent display  1901 , the OLED may be located adjacent to a front surface of the transparent display  1901 , and the LCD may be located adjacent to a rear surface of the transparent display  1901 . 
     The transparent display  1901  may display a screen respectively responding to a touch-based user input through at least one of the front and rear surfaces thereof, a user input based on the sensor  1903 , a user input via the camera  1904 , and a user input via the audio input interface  1908 . The screen displayed on the transparent display  1901  may include a UI or a GUI screen. 
     The transparent display  1901  may have a physical structure like the transparent display  1610  described with reference to  FIG. 16 . Two or more transparent display  1901  may be formed according to the type of the transparent display device  100 . 
     The user input interface  1902  generates input data (or control data) for controlling operations of the transparent display device  100  and a user input. The user input interface  1902  may include a keypad, a dome switch, a touch pad that is used instead of a mouse, a jog wheel, a jog switch, and a hardware (H/W) button. 
     The sensor  1903 , like the sensor  1650  shown in  FIG. 16 , senses a current status of the transparent display device  100  such as location of the transparent display device  100 , contact of the user on the transparent display device  100 , orientation of the transparent display device  100 , and acceleration or deceleration of the transparent display device  100  and generates a sensing signal for controlling operations of the transparent display device  100 . 
     The sensor  1903  may include a sensor except for the sensors for sensing the direct touch or the proximate touch described regarding the transparent display  1901 . For example, the sensor  1903  may include a proximity sensor. The proximity sensor is a sensor for detecting whether an object approaches a previously set defection surface or whether the external object is present nearby by using a force of an electromagnetic field or an infrared ray without an actual physical touch. Examples of the proximity sensor include a transparent photoelectric sensor, a direct reflective photoelectric sensor, a mirror reflective photoelectric sensor, a high frequency oscillation photoelectric sensor, a capacitive photoelectric sensor, a magnetic photoelectric sensor, an infrared photoelectric sensor, etc. 
     The camera  1904  processes an image frame such as a still image or a moving image obtained from an image sensor in a conference call mode or a photographing mode. The processed image frame may be displayed on the transparent display  1901 . The image frame processed by the camera  1904  may be stored in the storage  1905  or may be transmitted to another device through the communication interface  1906  or the port  1907 . The device receiving the transmitted image frame may include at least one of the external device  110 , the server  120 , and the AP  130 , but is not limited thereto. 
     The camera  1904  may also be configured to receive the user input to the front and rear surfaces of the transparent display  1901  or to photograph the object. The number of cameras  1904  may be two or more according to a structure of the transparent display device  100 . The camera  1904  may be used as an input apparatus that recognizes a user&#39;s spatial gesture. 
     The storage  1905  stores at least one program configured to be executed by the processor  1912 , which will be described later, and a resource. The at least one program includes a program that executes an information display method, an operating system (OS) program of the transparent display device  100 , applications set in the transparent display device  100 , and a program necessary for performing various functions (for example, communication function and display function) of the transparent display device  100 . 
     The resource includes information necessary for executing the above-described programs, user interface screen information for performing the information display method mentioned in embodiments of the present invention, and the user input information recognized by the first and second touch inputs. The user input information recognized as the first and second touch inputs may be set based on the examples described with reference to  FIGS. 3 through 10 , but is not limited thereto. 
     The storage  1905  may be configured to independently include a storage that stores at least one program necessary for performing various functions of the transparent display device  100  and an operating system program, and a storage that stores one or more programs, resources, and various applications that execute the information display method. 
     The storage  1905  may include at least one type of storage medium among a flash memory type, a hard disk type, a multimedia card micro type, and a card type memory (for example, an SD or XD memory), a read only memory (ROM), an electronically erasable programmable read-only memory (EEPROM), a programmable read only memory (PROM) magnetic memory, and an optical disk. 
     The communication interface  1906  may be configured to transmit data to and receive data from at least one of the external device  110 , a server ( 120 ), and AP ( 130 ) via a wireless communication network such as wireless Internet, wireless Intranet, a wireless phone network, a wireless local area network (LAN), a Wi-Fi network, a Wi-Fi direct (WFD) network, a 3G network, a 4G Long Term Evolution (LTE) network, a Bluetooth network, an infrared data association (IrDA) network, a radio frequency identification (RFID) network, a ultra wideband (UWB) network, a Zigbee network, or a near field communication (NFC) network, but is not limited thereto. 
     The communication interface  1906  may include at least one of a broadcasting reception module, a mobile communication module, a wireless Internet module, a wired Internet module, a short distance communication module, and a location information module but is not limited thereto. 
     The broadcasting reception module receives a broadcasting signal and/or broadcasting related information from an external broadcasting management server through a broadcasting channel. The broadcasting channel may include a satellite channel and a terrestrial channel. The mobile communication module transmits and receives a wireless signal to and from at least one of a base station, the external device  110 , and the server  120  over a mobile communication network. The wireless signal may include various types of data according to a voice call signal, a conference phone call, or transmission/reception of a text/multimedia message. The wireless Internet module is a module for a wireless Internet connection. The wired Internet module is a module for a wired Internet connection. 
     The short distance communication module is a module for short distance communication. Short distance communication technologies may use Bluetooth, RFID, IrDA, UWB, Zigbee, WFD, NFC, etc. Like the exemplary embodiment shown in  FIG. 14 , the information about the object displayed on the external device  110  and the screen size information may be received via the short distance communication module. For example, when using the NFC communication method and a distance between the external device  110  and the transparent display device  100  is within a radius of the short distance communication based on the NFC, the transparent display device  100  may read or receive the above information from the external device  110 . 
     The location information module is a module for identifying or obtaining the location of the transparent display device  100 . As an example, a GPS module may be used. The GPS module receives location information from a plurality of satellites. The location information may include coordinate information represented by latitude and longitude. 
     The port  1907  may transmit and receive data to and from the external device  110  by using a plug and play interface such as a USB port. The plug and play interface is a module that automatically detects and enables use of (i.e., play) if the external device  110  is plugged into the transparent display device  100 . The device is not limited to the external device  110 . 
     The audio input interface  1908  receives an input of an external sound signal in a call mode, a recording mode, or a voice recognition mode, etc. The audio input interface  1908  may be configured as, for example, a microphone. The audio input interface  1908  may be configured to include various noise removal algorithms for removing noise that occurs during the process of receiving the input of the external sound signal. 
     The sound signal input by using the audio input interface  1908  may be user&#39;s input representing a selection on the object displayed on the external device  110  that is seen through the transparent display unit  1901  according to an exemplary embodiment. The sound signal input by using the audio input interface  1908  may be stored in the storage  1905  or may be transmitted to the outside through the communication interface  1906  or the port  1907 . The outside may include the external device  110 , other external devices (not shown), the server  120 , and the AP  130 . 
     The audio signal processing unit  1909  provides an interface between the audio input interface  1908  and the processor  1912  and between the audio output interface  1910  and the processor  1912 . That is, the audio signal processing unit  1909  converts the sound signal received from the audio input interface  1908  into audio data that may be processed by the processor  1912  and transmits the audio data to the processor  1912 . The audio signal processing unit  1909  converts the audio data transmitted from the processor  1912  into an electrical sound signal and transmits the electrical sound signal to the audio output interface  1910 . 
     The audio output interface  1910  outputs the sound signal or the audio signal received from the audio signal processing unit  1909  in the call mode or an audio production mode. The audio signal output interface  1910  may be configured as a speaker. The audio input interface  1908  and the audio output interface  1910  may be integrally configured like a head set. 
     The transparent display  1901 , the user input interface  1902 , the sensor  1903 , the camera  1904 , and the audio input interface  1908  may be referred to as input apparatuses or input/output apparatuses according to a function of a user interface between the transparent display device  100  and the user. For example, in a case where the function of the user interface between the transparent display device  100  and the user includes a touch screen function, a sound recognition function, and a spatial gesture recognition function, the user input interface  1902 , the sensor  1903 , the camera  1904 , and the audio input interface  1908  may be referred to as the input apparatuses, and the transparent display  1901  may be referred to as the input/output apparatus. 
     The power supply  1911  supplies power to various elements of the transparent display device  100 . The power supply  1911  includes one or more power sources such as a battery and an alternating current (AC) power source. The transparent display device  100  may not include the power supply  1911  but may include a connection unit (not shown) that may be connected to an external power supply (not shown). 
     The processor  1912  may be referred to as one or more processors that control a general operation of the transparent display device  100 . Although the processor  1912  is implemented as a single chip in  FIG. 19 , the processor  1912  may be divided into a plurality of processors according to a function of the transparent display device  100 . 
     The processor  1912  may generally control the transparent display  1901 , the user input interface  1902 , the sensor  1903 , the camera  1904 , the storage  1905 , the communication interface  1906 , the port  1907 , the audio input interface  1908 , the audio signal processing unit  1909 , and the audio output interface  1910 . Thus, the processor  1912  may be referred to as a controller, a microprocessor, a digital signal processor, etc. 
     The processor  1912  may also provide user&#39;s input that is input through the transparent display  1901 , the user input interface  1902 , the sensor  1903 , the camera  1904 , and the audio input interface  1908  that correspond to input apparatuses and a user interface based on the transparent display  1901 . 
     The processor  1912  may execute at least one program related to the information display method according to the exemplary embodiments. The processor  1912  may execute the program by reading the program from the storage  1905  or downloading the program from an external apparatus such as an application providing server (not shown) or a market server (not shown) through the communication interface  1906 . 
     The processor  1912  may be understood to include an interface function unit interfacing between various functional modules and the processor  1912  of the transparent display device  100 . The operation of the processor  1912  related to the information display method according to the exemplary embodiments may be performed as shown in flowcharts of  FIGS. 2, 11, 12, 14, 15, and 21  that will be described later. 
       FIG. 20  is a flowchart illustrating operations of the external device  110  according to an exemplary embodiment. 
     In operation S 2001 , the external device  110  receives a request for information related to at least on object displayed on the external device  110  from the transparent display device  100 . The request for information may be transmitted via at least one of the direct communication between the devices, the communication via a server, and the communication via a repeater. 
     The request for information related to the object may be input based on the first touch input and the second touch input to the transparent display device  100 . The first touch input is a user input to the transparent display device  100  for representing the reference information about the external device  110  that is seen through the transparent display device  100 . The second touch input is a user input to the transparent display device  100  for selecting at least one object displayed on the external device  110  that is seen through the transparent display device  100 . 
     The request for information related to the object may include the displayed location information (coordinate information) of the selected object on the external device  110  as described in the above exemplary embodiments, the screen size of the transparent display device  100 , and the coordinate information of the first and second touch inputs on the transparent display device  100 , but is not limited thereto. 
     However, when the transparent display device  100  operates as the flowchart shown in  FIG. 21 , the request for information related to the object may be based on the touch input corresponding to the second touch input. 
     In operation S 2002 , the external device  110  selects an object in response to the received request for the information related to the object. For example, if the requested object is an icon, the external device  110  selects the icon of the requested object and the application program connected to the icon. If the requested object is a folder, the external device  110  selects the requested folder and files or data located at a lower layer of the folder. If the requested object is an object included in one screen, the external device  110  selects the object by using the coordinate information included in the received request. If the requested object is a plurality of objects included in one screen, the external device  110  respectively selects the plurality of objects by using the coordinate information of the object included in the received request. 
     In operation S 2003 , the external device  110  transmits information related to the selected object to the transparent display device  100 . The information related to the object is transmitted to the transparent display device  100  in the same manner as the request for the information is received, but is not limited thereto. For example, the request for the information may be received via the direct communication between the devices, and the information related to the object selected in response to the request may be transmitted to the transparent display device  100  via the repeater or the server. 
       FIG. 21  is a flowchart illustrating a method of displaying information on a transparent display device according to another exemplary embodiment.  FIG. 21  shows a case where the second touch input mentioned with reference to  FIG. 2  is used. 
     In operation S 2101 , the transparent display device  100  receives a touch input for selecting an object displayed on the external device  110  that is seen through the transparent display device  100 . Here, the touch input corresponds to the second touch input mentioned in  FIGS. 2 through 10 . The information about the external device  110  that is seen through the transparent display device  100  may be the same as that mentioned in  FIGS. 1 through 10 . 
     In operation S 2102 , the transparent display device  100  requests the external device  110  for information related to the object selected based on the touch input. A signal for requesting information related to the object selected based on the touch input transmitted to the external device  110  includes a signal for requesting information related to the object selected based on the second touch input mentioned in  FIGS. 2 through 10 . 
     In operation S 2103 , the transparent display device  100  receives information about the selected object from the external device  110 . The received information corresponds to the request signal in operation S 2102 , and may be the same as the information received in operation S 203  shown in  FIG. 2 . 
     In operation S 2104 , the transparent display device  100  displays the received information. The received information may be displayed in the same manner as that of operation S 204  shown in  FIG. 2 . 
     The flowchart shown in  FIG. 21  may be modified to include the operation S 1105  shown in  FIG. 11  so that the object displayed on the transparent display device  100  may be edited based on the interaction between the transparent display device  100  and the external device  110 . 
     The information display method according to exemplary embodiments may also be embodied as computer readable codes on a computer readable recording medium. The computer readable medium may be any recording apparatus capable of storing data that is read by a computer system, e.g., a read-only memory (ROM), a random access memory (RAM), a compact disc (CD)-ROM, a magnetic tape, a floppy disk, an optical data storage device, and so on. The computer readable medium may be distributed among computer systems that are interconnected through a network, and the present invention may be stored and implemented as computer readable code in the distributed system. 
     While the exemplary embodiments have been particularly shown and described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.