Patent Publication Number: US-11378807-B2

Title: Electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2019/010979, filed on Aug. 28, 2019, the contents of which are hereby incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     Embodiments of the disclosure relate to electronic devices. More specifically, embodiments of the present disclosure relate to a controller that interacts with electronic devices used in, e.g., virtual reality (VR), augmented reality (AR), or mixed reality (MR). 
     DESCRIPTION OF RELATED ART 
     Virtual reality (VR) refers to a special environment or situation generated by man-made technology using computer and other devices, which is similar but not exactly equal to the real world. 
     Augmented reality (AR) refers to the technology that makes a virtual object or information interwoven with the real world, making the virtual object or information perceived as if exists in reality. 
     Mixed reality (MR) or hybrid reality refers to combining of the real world with virtual objects or information, generating a new environment or new information. In particular, mixed reality refers to the experience that physical and virtual objects interact with each other in real time. 
     The virtual environment or situation in a sense of mixed reality stimulates the five senses of a user, allows the user to have a spatio-temporal experience similar to the one perceived from the real world, and thereby allows the user to freely cross the boundary between reality and imagination. Also, the user may not only get immersed in such an environment but also interact with objects implemented in the environment by manipulating or giving a command to the objects through an actual device. 
     Recently underway are vigorous research efforts for gear used in such industry sectors; particularly, head-mounted display (HMDs) and HMD-interacting controllers. HMD refers to a type of digital device that is worn on the user&#39;s head, as are glasses or helmets, to allow the user to view multimedia content, and controller means an assistant digital device that an HMD-wearing user holds in her hand to execute content provided from the HMD when experiencing augmented reality (AR) and virtual reality (VR). 
     By its nature, the controller is portable and is prone to hit other objects or escape off the user&#39;s hand when the HMD-wearing user moves her hand to manipulate content. To avoid such circumstances, the controller typically comes with a strap portion which may hold the controller in the user&#39;s hand. 
     However, it is not easy for the user to put the strap portion on her hand with the HMD worn on her head, with the result that the controller is uncomfortable to hold or manipulate. 
     Conventionally, a module for adjusting the tension of the strap portion is embedded in the controller. However, such module is bulky, forcing the controller to be made in larger size and volume and hence causing inconvenience in use of the controller. 
     SUMMARY 
     An object of the present disclosure is to provide an electronic device for use in virtual reality (VR), augmented reality (AR), or mixed reality (MR), which is capable of easily adjusting the tension of a strap portion provided with a controller upon using the electronic device. 
     Another object of the present disclosure is to provide an electronic device with a strap tension adjuster minimized in size and volume. 
     According to an embodiment of the present disclosure, an electronic device comprises a strap portion of which both ends are connected to a handle of the electronic device and a strap tension adjuster disposed inside the handle, wherein the strap tension adjuster includes a link button disposed to partially protrude to an outside of the handle and a first spring connected with one end of the strap portion, wherein when the strap portion turns from a first state in which the handle and the strap portion are positioned adjacent to each other to a second state in which the strap portion is positioned away from the handle, the strap portion remains in the second state and, when the link button is pressed, the strap portion turns back to the first state. 
     The strap tension adjuster may further include a first gear around which the first spring is wound, the first gear spinnable in a first direction. When the link button is pressed, the first gear is spinnable in a second direction opposite to the first direction. 
     The first gear may include first sawteeth with first slope surfaces inclined in the first direction. 
     The strap tension adjuster may further include a second gear coupled and unspinnably fastened to the link button. 
     The second gear may further include second sawteeth with second slope surfaces inclined in the second direction. The first sawteeth and the second sawteeth may be symmetrically positioned, so that the first slope surfaces face the second slope surfaces. 
     The second gear may include a receiving groove for receiving a portion of the link button. 
     The receiving groove may have openings formed in both ends thereof to allow the portion of the link button to move along a straight line inside the receiving groove. 
     The portion of the link button may include a first arm. 
     The first arm may be longer than the receiving groove. The first arm may be disposed to be slidable in the receiving groove. As the link button is pressed, the first arm may push the first gear away from the second gear. 
     The first spring may be a spiral spring. 
     The first spring may be disposed so that a central axis of the first spring is coaxial with a rotation axis of the first gear. 
     The strap tension adjuster may further include a second spring elastically supporting the first gear. The second spring may be disposed so that a central axis of the second spring is coaxial with a rotation axis of the first gear. 
     The second spring may be positioned inside the first gear. 
     The electronic device may further include a pin supporting the first gear and the second gear to be placed in a predetermined position inside the handle. The pin may be disposed inside the handle so that a central axis of the pin is coaxial with the rotation axis of the first gear. 
     The pin may pass through the first gear and the second gear along the rotation axis of the first gear. The second spring may be coupled with the pin. 
     One end, or both ends, of the pin may be fastened to an inner wall of the handle. 
     The electronic device may further include a connecting element connecting an end of the strap portion with the first spring. 
     Another end of the strap portion may be rotatably connected to the handle 
     According to embodiments of the present disclosure, the electronic device may easily adjust the tension between the strap frame and the controller by simply applying an external force to the strap frame, thus allowing the user to hold and use the controller in a comfortable manner. 
     According to embodiments of the disclosure, the controller includes the strap tension adjuster minimized in size and volume, allowing it to be made as compact as possible and used in a significantly convenient way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a concept view illustrating an example 5G network environment in which heterogeneous electronic devices are connected to a cloud network, according to an embodiment of the present disclosure; 
         FIG. 2  is a block diagram illustrating the structure of an eXtended Reality (XR) electronic device according to one embodiment of the present disclosure. 
         FIG. 3  is a perspective view of a VR electronic device according to one embodiment of the present disclosure. 
         FIG. 4  illustrates a situation in which the VR electronic device of  FIG. 3  is used. 
         FIG. 5  is a perspective view of an AR electronic device according to one embodiment of the present disclosure. 
         FIG. 6  is an exploded perspective view of a controller according to one embodiment of the present disclosure. 
         FIGS. 7 to 13  illustrate various display methods applicable to a display unit according to one embodiment of the present disclosure. 
         FIG. 14  is a perspective view illustrating a controller implementing an electronic device according to an embodiment of the present disclosure; 
         FIG. 15  is a perspective view illustrating a strap portion according to an embodiment of the present disclosure; 
         FIG. 16  is a view illustrating a strap tension adjuster positioned inside a controller according to an embodiment of the present disclosure; 
         FIG. 17  is a perspective view illustrating a strap tension adjuster according to an embodiment of the present disclosure; 
         FIG. 18  is an exploded perspective view illustrating a strap tension adjuster according to an embodiment of the present disclosure; 
         FIG. 19  is a view illustrating an inside of a controller handle according to an embodiment of the present disclosure; and 
         FIGS. 20 and 21  are views illustrating a state of using a controller according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In what follows, embodiments disclosed in this document will be described in detail with reference to appended drawings, where the same or similar constituent elements are given the same reference number irrespective of their drawing symbols, and repeated descriptions thereof will be omitted. 
     In describing an embodiment disclosed in the present specification, if a constituting element is said to be “connected” or “attached” to other constituting element, it should be understood that the former may be connected or attached directly to the other constituting element, but there may be a case in which another constituting element is present between the two constituting elements. 
     Also, in describing an embodiment disclosed in the present document, if it is determined that a detailed description of a related art incorporated herein unnecessarily obscure the gist of the embodiment, the detailed description thereof will be omitted. Also, it should be understood that the appended drawings are intended only to help understand embodiments disclosed in the present document and do not limit the technical principles and scope of the present disclosure; rather, it should be understood that the appended drawings include all of the modifications, equivalents or substitutes described by the technical principles and belonging to the technical scope of the present disclosure. 
     [5G Scenario] 
     The three main requirement areas in the 5G system are (1) enhanced Mobile Broadband (eMBB) area, (2) massive Machine Type Communication (mMTC) area, and (3) Ultra-Reliable and Low Latency Communication (URLLC) area. 
     Some use case may require a plurality of areas for optimization, but other use case may focus only one Key Performance Indicator (KPI). The 5G system supports various use cases in a flexible and reliable manner. 
     eMBB far surpasses the basic mobile Internet access, supports various interactive works, and covers media and entertainment applications in the cloud computing or augmented reality environment. Data is one of core driving elements of the 5G system, which is so abundant that for the first time, the voice-only service may be disappeared. In the 5G, voice is expected to be handled simply by an application program using a data connection provided by the communication system. Primary causes of increased volume of traffic are increase of content size and increase of the number of applications requiring a high data transfer rate. Streaming service (audio and video), interactive video, and mobile Internet connection will be more heavily used as more and more devices are connected to the Internet. These application programs require always-on connectivity to push real-time information and notifications to the user. Cloud-based storage and applications are growing rapidly in the mobile communication platforms, which may be applied to both of business and entertainment uses. And the cloud-based storage is a special use case that drives growth of uplink data transfer rate. The 5G is also used for cloud-based remote works and requires a much shorter end-to-end latency to ensure excellent user experience when a tactile interface is used. Entertainment, for example, cloud-based game and video streaming, is another core element that strengthens the requirement for mobile broadband capability. Entertainment is essential for smartphones and tablets in any place including a high mobility environment such as a train, car, and plane. Another use case is augmented reality for entertainment and information search. Here, augmented reality requires very low latency and instantaneous data transfer. 
     Also, one of highly expected 5G use cases is the function that connects embedded sensors seamlessly in every possible area, namely the use case based on mMTC. Up to 2020, the number of potential IoT devices is expected to reach 20.4 billion. Industrial IoT is one of key areas where the 5G performs a primary role to maintain infrastructure for smart city, asset tracking, smart utility, agriculture and security. 
     URLLC includes new services which may transform industry through ultra-reliable/ultra-low latency links, such as remote control of major infrastructure and self-driving cars. The level of reliability and latency are essential for smart grid control, industry automation, robotics, and drone control and coordination. 
     Next, a plurality of use cases will be described in more detail. 
     The 5G may complement Fiber-To-The-Home (FTTH) and cable-based broadband (or DOCSIS) as a means to provide a stream estimated to occupy hundreds of megabits per second up to gigabits per second. This fast speed is required not only for virtual reality and augmented reality but also for transferring video with a resolution more than 4K (6K, 8K or more). VR and AR applications almost always include immersive sports games. Specific application programs may require a special network configuration. For example, in the case of VR game, to minimize latency, game service providers may have to integrate a core server with the edge network service of the network operator. 
     Automobiles are expected to be a new important driving force for the 5G system together with various use cases of mobile communication for vehicles. For example, entertainment for passengers requires high capacity and high mobile broadband at the same time. This is so because users continue to expect a high-quality connection irrespective of their location and moving speed. Another use case in the automotive field is an augmented reality dashboard. The augmented reality dashboard overlays information, which is a perception result of an object in the dark and contains distance to the object and object motion, on what is seen through the front window. In a future, a wireless module enables communication among vehicles, information exchange between a vehicle and supporting infrastructure, and information exchange among a vehicle and other connected devices (for example, devices carried by a pedestrian). A safety system guides alternative courses of driving so that a driver may drive his or her vehicle more safely and to reduce the risk of accident. The next step will be a remotely driven or self-driven vehicle. This step requires highly reliable and highly fast communication between different self-driving vehicles and between a self-driving vehicle and infrastructure. In the future, it is expected that a self-driving vehicle takes care of all of the driving activities while a human driver focuses on dealing with an abnormal driving situation that the self-driving vehicle is unable to recognize. Technical requirements of a self-driving vehicle demand ultra-low latency and ultra-fast reliability up to the level that traffic safety may not be reached by human drivers. 
     The smart city and smart home, which are regarded as essential to realize a smart society, will be embedded into a high-density wireless sensor network. Distributed networks comprising intelligent sensors may identify conditions for cost-efficient and energy-efficient conditions for maintaining cities and homes. A similar configuration may be applied for each home. Temperature sensors, window and heating controllers, anti-theft alarm devices, and home appliances will be all connected wirelessly. Many of these sensors typified with a low data transfer rate, low power, and low cost. However, for example, real-time HD video may require specific types of devices for the purpose of surveillance. 
     As consumption and distribution of energy including heat or gas is being highly distributed, automated control of a distributed sensor network is required. A smart grid collects information and interconnect sensors by using digital information and communication technologies so that the distributed sensor network operates according to the collected information. Since the information may include behaviors of energy suppliers and consumers, the smart grid may help improving distribution of fuels such as electricity in terms of efficiency, reliability, economics, production sustainability, and automation. The smart grid may be regarded as a different type of sensor network with a low latency. 
     The health-care sector has many application programs that may benefit from mobile communication. A communication system may support telemedicine providing a clinical care from a distance. Telemedicine may help reduce barriers to distance and improve access to medical services that are not readily available in remote rural areas. It may also be used to save lives in critical medical and emergency situations. A wireless sensor network based on mobile communication may provide remote monitoring and sensors for parameters such as the heart rate and blood pressure. 
     Wireless and mobile communication are becoming increasingly important for industrial applications. Cable wiring requires high installation and maintenance costs. Therefore, replacement of cables with reconfigurable wireless links is an attractive opportunity for many industrial applications. However, to exploit the opportunity, the wireless connection is required to function with a latency similar to that in the cable connection, to be reliable and of large capacity, and to be managed in a simple manner Low latency and very low error probability are new requirements that lead to the introduction of the 5G system. 
     Logistics and freight tracking are important use cases of mobile communication, which require tracking of an inventory and packages from any place by using location-based information system. The use of logistics and freight tracking typically requires a low data rate but requires large-scale and reliable location information. 
     The present disclosure to be described below may be implemented by combining or modifying the respective embodiments to satisfy the aforementioned requirements of the 5G system. 
       FIG. 1  illustrates one embodiment of an AI device. 
     Referring to  FIG. 1 , in the AI system, at least one or more of an AI server  16 , robot  11 , self-driving vehicle  12 , XR device  13 , smartphone  14 , or home appliance  15  are connected to a cloud network  10 . Here, the robot  11 , self-driving vehicle  12 , XR device  13 , smartphone  14 , or home appliance  15  to which the AI technology has been applied may be referred to as an AI device ( 11  to  15 ). 
     The cloud network  10  may comprise part of the cloud computing infrastructure or refer to a network existing in the cloud computing infrastructure. Here, the cloud network  10  may be constructed by using the 3G network, 4G or Long Term Evolution (LTE) network, or 5G network. 
     In other words, individual devices ( 11  to  16 ) constituting the AI system may be connected to each other through the cloud network  10 . In particular, each individual device ( 11  to  16 ) may communicate with each other through the eNB but may communicate directly to each other without relying on the eNB. 
     The AI server  16  may include a server performing AI processing and a server performing computations on big data. 
     The AI server  16  may be connected to at least one or more of the robot  11 , self-driving vehicle  12 , XR device  13 , smartphone  14 , or home appliance  15 , which are AI devices constituting the AI system, through the cloud network  10  and may help at least part of AI processing conducted in the connected AI devices ( 11  to  15 ). 
     At this time, the AI server  16  may teach the artificial neural network according to a machine learning algorithm on behalf of the AI device ( 11  to  15 ), directly store the learning model, or transmit the learning model to the AI device ( 11  to  15 ). 
     At this time, the AI server  16  may receive input data from the AI device ( 11  to  15 ), infer a result value from the received input data by using the learning model, generate a response or control command based on the inferred result value, and transmit the generated response or control command to the AI device ( 11  to  15 ). 
     Similarly, the AI device ( 11  to  15 ) may infer a result value from the input data by employing the learning model directly and generate a response or control command based on the inferred result value. 
     &lt;AI+Robot&gt; 
     By employing the AI technology, the robot  11  may be implemented as a guide robot, transport robot, cleaning robot, wearable robot, entertainment robot, pet robot, or unmanned flying robot. 
     The robot  11  may include a robot control module for controlling its motion, where the robot control module may correspond to a software module or a chip which implements the software module in the form of a hardware device. 
     The robot  11  may obtain status information of the robot  11 , detect (recognize) the surroundings and objects, generate map data, determine a travel path and navigation plan, determine a response to user interaction, or determine motion by using sensor information obtained from various types of sensors. 
     Here, the robot  11  may use sensor information obtained from at least one or more sensors among lidar, radar, and camera to determine a travel path and navigation plan. 
     The robot  11  may perform the operations above by using a learning model built on at least one or more artificial neural networks. For example, the robot  11  may recognize the surroundings and objects by using the learning model and determine its motion by using the recognized surroundings or object information. Here, the learning model may be the one trained by the robot  11  itself or trained by an external device such as the AI server  16 . 
     At this time, the robot  11  may perform the operation by generating a result by employing the learning model directly but also perform the operation by transmitting sensor information to an external device such as the AI server  16  and receiving a result generated accordingly. 
     The robot  11  may determine a travel path and navigation plan by using at least one or more of object information detected from the map data and sensor information or object information obtained from an external device and navigate according to the determined travel path and navigation plan by controlling its locomotion platform. 
     Map data may include object identification information about various objects disposed in the space in which the robot  11  navigates. For example, the map data may include object identification information about static objects such as wall and doors and movable objects such as a flowerpot and a desk. And the object identification information may include the name, type, distance, location, and so on. 
     Also, the robot  11  may perform the operation or navigate the space by controlling its locomotion platform based on the control/interaction of the user. At this time, the robot  11  may obtain intention information of the interaction due to the user&#39;s motion or voice command and perform an operation by determining a response based on the obtained intention information. 
     &lt;AI+Autonomous Navigation&gt; 
     By employing the AI technology, the self-driving vehicle  12  may be implemented as a mobile robot, unmanned ground vehicle, or unmanned aerial vehicle. 
     The self-driving vehicle  12  may include an autonomous navigation module for controlling its autonomous navigation function, where the autonomous navigation control module may correspond to a software module or a chip which implements the software module in the form of a hardware device. The autonomous navigation control module may be installed inside the self-driving vehicle  12  as a constituting element thereof or may be installed outside the self-driving vehicle  12  as a separate hardware component. 
     The self-driving vehicle  12  may obtain status information of the self-driving vehicle  12 , detect (recognize) the surroundings and objects, generate map data, determine a travel path and navigation plan, or determine motion by using sensor information obtained from various types of sensors. 
     Like the robot  11 , the self-driving vehicle  12  may use sensor information obtained from at least one or more sensors among lidar, radar, and camera to determine a travel path and navigation plan. 
     In particular, the self-driving vehicle  12  may recognize an occluded area or an area extending over a predetermined distance or objects located across the area by collecting sensor information from external devices or receive recognized information directly from the external devices. 
     The self-driving vehicle  12  may perform the operations above by using a learning model built on at least one or more artificial neural networks. For example, the self-driving vehicle  12  may recognize the surroundings and objects by using the learning model and determine its navigation route by using the recognized surroundings or object information. Here, the learning model may be the one trained by the self-driving vehicle  12  itself or trained by an external device such as the AI server  16 . 
     At this time, the self-driving vehicle  12  may perform the operation by generating a result by employing the learning model directly but also perform the operation by transmitting sensor information to an external device such as the AI server  16  and receiving a result generated accordingly. 
     The self-driving vehicle  12  may determine a travel path and navigation plan by using at least one or more of object information detected from the map data and sensor information or object information obtained from an external device and navigate according to the determined travel path and navigation plan by controlling its driving platform. 
     Map data may include object identification information about various objects disposed in the space (for example, road) in which the self-driving vehicle  12  navigates. For example, the map data may include object identification information about static objects such as streetlights, rocks and buildings and movable objects such as vehicles and pedestrians. And the object identification information may include the name, type, distance, location, and so on. 
     Also, the self-driving vehicle  12  may perform the operation or navigate the space by controlling its driving platform based on the control/interaction of the user. At this time, the self-driving vehicle  12  may obtain intention information of the interaction due to the user&#39;s motion or voice command and perform an operation by determining a response based on the obtained intention information. 
     &lt;AI+XR&gt; 
     By employing the AI technology, the XR device  13  may be implemented as a Head-Mounted Display (HMD), Head-Up Display (HUD) installed at the vehicle, TV, mobile phone, smartphone, computer, wearable device, home appliance, digital signage, vehicle, robot with a fixed platform, or mobile robot. 
     The XR device  13  may obtain information about the surroundings or physical objects by generating position and attribute data about 3D points by analyzing 3D point cloud or image data acquired from various sensors or external devices and output objects in the form of XR objects by rendering the objects for display. 
     The XR device  13  may perform the operations above by using a learning model built on at least one or more artificial neural networks. For example, the XR device  13  may recognize physical objects from 3D point cloud or image data by using the learning model and provide information corresponding to the recognized physical objects. Here, the learning model may be the one trained by the XR device  13  itself or trained by an external device such as the AI server  16 . 
     At this time, the XR device  13  may perform the operation by generating a result by employing the learning model directly but also perform the operation by transmitting sensor information to an external device such as the AI server  16  and receiving a result generated accordingly. 
     &lt;AI+Robot+Autonomous Navigation&gt; 
     By employing the AI and autonomous navigation technologies, the robot  11  may be implemented as a guide robot, transport robot, cleaning robot, wearable robot, entertainment robot, pet robot, or unmanned flying robot. 
     The robot  11  employing the AI and autonomous navigation technologies may correspond to a robot itself having an autonomous navigation function or a robot  11  interacting with the self-driving vehicle  12 . 
     The robot  11  having the autonomous navigation function may correspond collectively to the devices which may move autonomously along a given path without control of the user or which may move by determining its path autonomously. 
     The robot  11  and the self-driving vehicle  12  having the autonomous navigation function may use a common sensing method to determine one or more of the travel path or navigation plan. For example, the robot  11  and the self-driving vehicle  12  having the autonomous navigation function may determine one or more of the travel path or navigation plan by using the information sensed through lidar, radar, and camera. 
     The robot  11  interacting with the self-driving vehicle  12 , which exists separately from the self-driving vehicle  12 , may be associated with the autonomous navigation function inside or outside the self-driving vehicle  12  or perform an operation associated with the user riding the self-driving vehicle  12 . 
     At this time, the robot  11  interacting with the self-driving vehicle  12  may obtain sensor information in place of the self-driving vehicle  12  and provide the sensed information to the self-driving vehicle  12 ; or may control or assist the autonomous navigation function of the self-driving vehicle  12  by obtaining sensor information, generating information of the surroundings or object information, and providing the generated information to the self-driving vehicle  12 . 
     Also, the robot  11  interacting with the self-driving vehicle  12  may control the function of the self-driving vehicle  12  by monitoring the user riding the self-driving vehicle  12  or through interaction with the user. For example, if it is determined that the driver is drowsy, the robot  11  may activate the autonomous navigation function of the self-driving vehicle  12  or assist the control of the driving platform of the self-driving vehicle  12 . Here, the function of the self-driving vehicle  12  controlled by the robot  12  may include not only the autonomous navigation function but also the navigation system installed inside the self-driving vehicle  12  or the function provided by the audio system of the self-driving vehicle  12 . 
     Also, the robot  11  interacting with the self-driving vehicle  12  may provide information to the self-driving vehicle  12  or assist functions of the self-driving vehicle  12  from the outside of the self-driving vehicle  12 . For example, the robot  11  may provide traffic information including traffic sign information to the self-driving vehicle  12  like a smart traffic light or may automatically connect an electric charger to the charging port by interacting with the self-driving vehicle  12  like an automatic electric charger of the electric vehicle. 
     &lt;AI+Robot+XR&gt; 
     By employing the AI technology, the robot  11  may be implemented as a guide robot, transport robot, cleaning robot, wearable robot, entertainment robot, pet robot, or unmanned flying robot. 
     The robot  11  employing the XR technology may correspond to a robot which acts as a control/interaction target in the XR image. In this case, the robot  11  may be distinguished from the XR device  13 , both of which may operate in conjunction with each other. 
     If the robot  11 , which acts as a control/interaction target in the XR image, obtains sensor information from the sensors including a camera, the robot  11  or XR device  13  may generate an XR image based on the sensor information, and the XR device  13  may output the generated XR image. And the robot  11  may operate based on the control signal received through the XR device  13  or based on the interaction with the user. 
     For example, the user may check the XR image corresponding to the viewpoint of the robot  11  associated remotely through an external device such as the XR device  13 , modify the navigation path of the robot  11  through interaction, control the operation or navigation of the robot  11 , or check the information of nearby objects. 
     &lt;AI+Autonomous Navigation+XR&gt; 
     By employing the AI and XR technologies, the self-driving vehicle  12  may be implemented as a mobile robot, unmanned ground vehicle, or unmanned aerial vehicle. 
     The self-driving vehicle  12  employing the XR technology may correspond to a self-driving vehicle having a means for providing XR images or a self-driving vehicle which acts as a control/interaction target in the XR image. In particular, the self-driving vehicle  12  which acts as a control/interaction target in the XR image may be distinguished from the XR device  13 , both of which may operate in conjunction with each other. 
     The self-driving vehicle  12  having a means for providing XR images may obtain sensor information from sensors including a camera and output XR images generated based on the sensor information obtained. For example, by displaying an XR image through HUD, the self-driving vehicle  12  may provide XR images corresponding to physical objects or image objects to the passenger. 
     At this time, if an XR object is output on the HUD, at least part of the XR object may be output so as to be overlapped with the physical object at which the passenger gazes. On the other hand, if an XR object is output on a display installed inside the self-driving vehicle  12 , at least part of the XR object may be output so as to be overlapped with an image object. For example, the self-driving vehicle  12  may output XR objects corresponding to the objects such as roads, other vehicles, traffic lights, traffic signs, bicycles, pedestrians, and buildings. 
     If the self-driving vehicle  12 , which acts as a control/interaction target in the XR image, obtains sensor information from the sensors including a camera, the self-driving vehicle  12  or XR device  13  may generate an XR image based on the sensor information, and the XR device  13  may output the generated XR image. And the self-driving vehicle  12  may operate based on the control signal received through an external device such as the XR device  13  or based on the interaction with the user. 
     [Extended Reality Technology] 
     eXtended Reality (XR) refers to all of Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR). The VR technology provides objects or backgrounds of the real world only in the form of CG images, AR technology provides virtual CG images overlaid on the physical object images, and MR technology employs computer graphics technology to mix and merge virtual objects with the real world. 
     MR technology is similar to AR technology in a sense that physical objects are displayed together with virtual objects. However, while virtual objects supplement physical objects in the AR, virtual and physical objects co-exist as equivalents in the MR. 
     The XR technology may be applied to Head-Mounted Display (HMD), Head-Up Display (HUD), mobile phone, tablet PC, laptop computer, desktop computer, TV, digital signage, and so on, where a device employing the XR technology may be called an XR device. 
     In what follows, an electronic device providing XR according to an embodiment of the present disclosure will be described. 
       FIG. 2  is a block diagram illustrating the structure of an XR electronic device  20  according to one embodiment of the present disclosure. 
     Referring to  FIG. 2 , the XR electronic device  20  may include a wireless communication unit  21 , input unit  22 , sensing unit  23 , output unit  24 , interface unit  25 , memory  26 , controller  27 , and power supply unit  28 . The constituting elements shown in  FIG. 2  are not essential for implementing the electronic device  20 , and therefore, the electronic device  20  described in this document may have more or fewer constituting elements than those listed above. 
     More specifically, among the constituting elements above, the wireless communication unit  21  may include one or more modules which enable wireless communication between the electronic device  20  and a wireless communication system, between the electronic device  20  and other electronic device, or between the electronic device  20  and an external server. Also, the wireless communication unit  21  may include one or more modules that connect the electronic device  20  to one or more networks. 
     The wireless communication unit  21  may include at least one of a broadcast receiving module, mobile communication module, wireless Internet module, short-range communication module, and location information module. 
     The input unit  22  may include a camera or image input unit for receiving an image signal, microphone or audio input unit for receiving an audio signal, and user input unit (for example, touch key) for receiving information from the user, and push key (for example, mechanical key). Voice data or image data collected by the input unit  22  may be analyzed and processed as a control command of the user. 
     The sensing unit  23  may include one or more sensors for sensing at least one of the surroundings of the electronic device  20  and user information. 
     For example, the sensing unit  23  may include at least one of a proximity sensor, illumination sensor, touch sensor, acceleration sensor, magnetic sensor, G-sensor, gyroscope sensor, motion sensor, RGB sensor, infrared (IR) sensor, finger scan sensor, ultrasonic sensor, optical sensor (for example, image capture means), microphone, battery gauge, environment sensor (for example, barometer, hygrometer, radiation detection sensor, heat detection sensor, and gas detection sensor), and chemical sensor (for example, electronic nose, health-care sensor, and biometric sensor). Meanwhile, the electronic device  20  disclosed in the present specification may utilize information collected from at least two or more sensors listed above. 
     The output unit  24  is intended to generate an output related to a visual, aural, or tactile stimulus and may include at least one of a display unit, sound output unit, haptic module, and optical output unit. The display unit may implement a touchscreen by forming a layered structure or being integrated with touch sensors. The touchscreen may not only function as a user input means for providing an input interface between the AR electronic device  20  and the user but also provide an output interface between the AR electronic device  20  and the user. 
     The interface unit  25  serves as a path to various types of external devices connected to the electronic device  20 . Through the interface unit  25 , the electronic device  20  may receive VR or AR content from an external device and perform interaction by exchanging various input signals, sensing signals, and data. 
     For example, the interface unit  25  may include at least one of a wired/wireless headset port, external charging port, wired/wireless data port, memory card port, port for connecting to a device equipped with an identification module, audio Input/Output (I/O) port, video I/O port, and earphone port. 
     Also, the memory  26  stores data supporting various functions of the electronic device  20 . The memory  26  may store a plurality of application programs (or applications) executed in the electronic device  20 ; and data and commands for operation of the electronic device  20 . Also, at least part of the application programs may be pre-installed at the electronic device  20  from the time of factory shipment for basic functions (for example, incoming and outgoing call function and message reception and transmission function) of the electronic device  20 . 
     The controller  27  usually controls the overall operation of the electronic device  20  in addition to the operation related to the application program. The controller  27  may process signals, data, and information input or output through the constituting elements described above. 
     Also, the controller  27  may provide relevant information or process a function for the user by executing an application program stored in the memory  26  and controlling at least part of the constituting elements. Furthermore, the controller  27  may combine and operate at least two or more constituting elements among those constituting elements included in the electronic device  20  to operate the application program. 
     Also, the controller  27  may detect the motion of the electronic device  20  or user by using a gyroscope sensor, g-sensor, or motion sensor included in the sensing unit  23 . Also, the controller  27  may detect an object approaching the vicinity of the electronic device  20  or user by using a proximity sensor, illumination sensor, magnetic sensor, infrared sensor, ultrasonic sensor, or light sensor included in the sensing unit  23 . Besides, the controller  27  may detect the motion of the user through sensors installed at the controller operating in conjunction with the electronic device  20 . 
     Also, the controller  27  may perform the operation (or function) of the electronic device  20  by using an application program stored in the memory  26 . 
     The power supply unit  28  receives external or internal power under the control of the controller  27  and supplies the power to each and every constituting element included in the electronic device  20 . The power supply unit  28  includes battery, which may be provided in a built-in or replaceable form. 
     At least part of the constituting elements described above may operate in conjunction with each other to implement the operation, control, or control method of the electronic device according to various embodiments described below. Also, the operation, control, or control method of the electronic device may be implemented on the electronic device by executing at least one application program stored in the memory  26 . 
     In what follows, the electronic device according to one embodiment of the present disclosure will be described with reference to an example where the electronic device is applied to a Head Mounted Display (HMD). However, embodiments of the electronic device according to the present disclosure may include a mobile phone, smartphone, laptop computer, digital broadcast terminal, Personal Digital Assistant (PDA), Portable Multimedia Player (PMP), navigation terminal, slate PC, tablet PC, ultrabook, and wearable device. Wearable devices may include smart watch and contact lens in addition to the HMD. 
       FIG. 3  is a perspective view of a VR electronic device according to one embodiment of the present disclosure, and  FIG. 4  illustrates a situation in which the VR electronic device of  FIG. 3  is used. 
     Referring to the figures, a VR electronic device may include a box-type electronic device  30  mounted on the head of the user and a controller  40  ( 40   a ,  40   b ) that the user may grip and manipulate. 
     The electronic device  30  includes a head unit  31  worn and supported on the head and a display unit  32  being combined with the head unit  31  and displaying a virtual image or video in front of the user&#39;s eyes. Although the figure shows that the head unit  31  and display unit  32  are made as separate units and combined together, the display unit  32  may also be formed being integrated into the head unit  31 . 
     The head unit  31  may assume a structure of enclosing the head of the user so as to disperse the weight of the display unit  32 . And to accommodate different head sizes of users, the head unit  31  may provide a band of variable length. 
     The display unit  32  includes a cover unit  32   a  combined with the head unit  31  and a display unit  32   b  containing a display panel. 
     The cover unit  32   a  is also called a goggle frame and may have the shape of a tub as a whole. The cover unit  32   a  has a space formed therein, and an opening is formed at the front surface of the cover unit, the position of which corresponds to the eyeballs of the user. 
     The display unit  32   b  is installed on the front surface frame of the cover unit  32   a  and disposed at the position corresponding to the eyes of the user to display screen information (image or video). The screen information output on the display unit  32   b  includes not only VR content but also external images collected through an image capture means such as a camera. 
     And VR content displayed on the display unit  32   b  may be the content stored in the electronic device  30  itself or the content stored in an external device  60 . For example, when the screen information is an image of the virtual world stored in the electronic device  30 , the electronic device  30  may perform image processing and rendering to process the image of the virtual world and display image information generated from the image processing and rendering through the display unit  32   b . On the other hand, in the case of a VR image stored in the external device  60 , the external device  60  performs image processing and rendering and transmits image information generated from the image processing and rendering to the electronic device  30 . Then the electronic device  30  may output 3D image information received from the external device  60  through the display unit  32   b.    
     The display unit  32   b  may include a display panel installed at the front of the opening of the cover unit  32   a , where the display panel may be an LCD or OLED panel. Similarly, the display unit  32   b  may be a display unit of a smartphone. In other words, the display unit  32   b  may have a specific structure in which a smartphone may be attached to or detached from the front of the cover unit  32   a.    
     And an image capture means and various types of sensors may be installed at the front of the display unit  32 . 
     The image capture means (for example, camera) is formed to capture (receive or input) the image of the front and may obtain a real world as seen by the user as an image. One image capture means may be installed at the center of the display unit  32   b , or two or more of them may be installed at symmetric positions. When a plurality of image capture means are installed, a stereoscopic image may be obtained. An image combining an external image obtained from an image capture means with a virtual image may be displayed through the display unit  32   b.    
     Various types of sensors may include a gyroscope sensor, motion sensor, or IR sensor. Various types of sensors will be described in more detail later. 
     At the rear of the display unit  32 , a facial pad  33  may be installed. The facial pad  33  is made of cushioned material and is fit around the eyes of the user, providing comfortable fit to the face of the user. And the facial pad  33  is made of a flexible material with a shape corresponding to the front contour of the human face and may be fit to the facial shape of a different user, thereby blocking external light from entering the eyes. 
     In addition to the above, the electronic device  30  may be equipped with a user input unit operated to receive a control command, sound output unit, and controller. Descriptions of the aforementioned units are the same as give previously and will be omitted. 
     Also, a VR electronic device may be equipped with a controller  40  ( 40   a ,  40   b ) for controlling the operation related to VR images displayed through the box-type electronic device  30  as a peripheral device. 
     The controller  40  is provided in a way that the user may easily grip the controller  40  by using his or her both hands, and the outer surface of the controller  40  may have a touchpad (or trackpad) or buttons for receiving the user input. 
     The controller  40  may be used to control the screen output on the display unit  32   b  in conjunction with the electronic device  30 . The controller  40  may include a grip unit that the user grips and a head unit extended from the grip unit and equipped with various sensors and a microprocessor. The grip unit may be shaped as a long vertical bar so that the user may easily grip the grip unit, and the head unit may be formed in a ring shape. 
     And the controller  40  may include an IR sensor, motion tracking sensor, microprocessor, and input unit. For example, IR sensor receives light emitted from a position tracking device  50  to be described later and tracks motion of the user. The motion tracking sensor may be formed as a single sensor suite integrating a 3-axis acceleration sensor, 3-axis gyroscope, and digital motion processor. 
     And the grip unit of the controller  40  may provide a user input unit. For example, the user input unit may include keys disposed inside the grip unit, touchpad (trackpad) equipped outside the grip unit, and trigger button. 
     Meanwhile, the controller  40  may perform a feedback operation corresponding to a signal received from the controller  27  of the electronic device  30 . For example, the controller  40  may deliver a feedback signal to the user in the form of vibration, sound, or light. 
     Also, by operating the controller  40 , the user may access an external environment image seen through the camera installed in the electronic device  30 . In other words, even in the middle of experiencing the virtual world, the user may immediately check the surrounding environment by operating the controller  40  without taking off the electronic device  30 . 
     Also, the VR electronic device may further include a position tracking device  50 . The position tracking device  50  detects the position of the electronic device  30  or controller  40  by applying a position tracking technique, called lighthouse system, and helps tracking the 360-degree motion of the user. 
     The position tacking system may be implemented by installing one or more position tracking device  50  ( 50   a ,  50   b ) in a closed, specific space. A plurality of position tracking devices  50  may be installed at such positions that maximize the span of location-aware space, for example, at positions facing each other in the diagonal direction. 
     The electronic device  30  or controller  40  may receive light emitted from LED or laser emitter included in the plurality of position tracking devices  50  and determine the accurate position of the user in a closed, specific space based on a correlation between the time and position at which the corresponding light is received. To this purpose, each of the position tracking devices  50  may include an IR lamp and 2-axis motor, through which a signal is exchanged with the electronic device  30  or controller  40 . 
     Also, the electronic device  30  may perform wired/wireless communication with an external device  60  (for example, PC, smartphone, or tablet PC). The electronic device  30  may receive images of the virtual world stored in the connected external device  60  and display the received image to the user. 
     Meanwhile, since the controller  40  and position tracking device  50  described above are not essential elements, they may be omitted in the embodiments of the present disclosure. For example, an input device installed in the electronic device  30  may replace the controller  40 , and position information may be determined by itself from various sensors installed in the electronic device  30 . 
       FIG. 5  is a perspective view of an AR electronic device according to one embodiment of the present disclosure. 
     As shown in  FIG. 5 , the electronic device according to one embodiment of the present disclosure may include a frame  100 , controller  200 , and display unit  300 . 
     The electronic device may be provided in the form of smart glasses. The glass-type electronic device may be shaped to be worn on the head of the user, for which the frame (case or housing)  100  may be used. The frame  100  may be made of a flexible material so that the user may wear the glass-type electronic device comfortably. 
     The frame  100  is supported on the head and provides a space in which various components are installed. As shown in the figure, electronic components such as the controller  200 , user input unit  130 , or sound output unit  140  may be installed in the frame  100 . Also, lens that covers at least one of the left and right eyes may be installed in the frame  100  in a detachable manner. 
     As shown in the figure, the frame  100  may have a shape of glasses worn on the face of the user; however, the present disclosure is not limited to the specific shape and may have a shape such as goggles worn in close contact with the user&#39;s face. 
     The frame  100  may include a front frame  110  having at least one opening and one pair of side frames  120  parallel to each other and being extended in a first direction (y), which are intersected by the front frame  110 . 
     The controller  200  is configured to control various electronic components installed in the electronic device. 
     The controller  200  may generate an image shown to the user or video comprising successive images. The controller  200  may include an image source panel that generates an image and a plurality of lenses that diffuse and converge light generated from the image source panel. 
     The controller  200  may be fixed to either of the two side frames  120 . For example, the controller  200  may be fixed in the inner or outer surface of one side frame  120  or embedded inside one of side frames  120 . Or the controller  200  may be fixed to the front frame  110  or provided separately from the electronic device. 
     The display unit  300  may be implemented in the form of a Head Mounted Display (HMD). HMD refers to a particular type of display device worn on the head and showing an image directly in front of eyes of the user. The display unit  300  may be disposed to correspond to at least one of left and right eyes so that images may be shown directly in front of the eye(s) of the user when the user wears the electronic device. The present figure illustrates a case where the display unit  300  is disposed at the position corresponding to the right eye of the user so that images may be shown before the right eye of the user. 
     The display unit  300  may be used so that an image generated by the controller  200  is shown to the user while the user visually recognizes the external environment. For example, the display unit  300  may project an image on the display area by using a prism. 
     And the display unit  300  may be formed to be transparent so that a projected image and a normal view (the visible part of the world as seen through the eyes of the user) in the front are shown at the same time. For example, the display unit  300  may be translucent and made of optical elements including glass. 
     And the display unit  300  may be fixed by being inserted into the opening included in the front frame  110  or may be fixed on the front surface  110  by being positioned on the rear surface of the opening (namely between the opening and the user&#39;s eye). Although the figure illustrates one example where the display unit  300  is fixed on the front surface  110  by being positioned on the rear surface of the rear surface, the display unit  300  may be disposed and fixed at various positions of the frame  100 . 
     As shown in  FIG. 5 , the electronic device may operate so that if the controller  200  projects light about an image onto one side of the display unit  300 , the light is emitted to the other side of the display unit, and the image generated by the controller  200  is shown to the user. 
     Accordingly, the user may see the image generated by the controller  200  while seeing the external environment simultaneously through the opening of the frame  100 . In other words, the image output through the display unit  300  may be seen by being overlapped with a normal view. By using the display characteristic described above, the electronic device may provide an AR experience which shows a virtual image overlapped with a real image or background as a single, interwoven image. 
       FIG. 6  is an exploded perspective view of a controller according to one embodiment of the present disclosure. 
     Referring to the figure, the controller  200  may include a first cover  207  and second cover  225  for protecting internal constituting elements and forming the external appearance of the controller  200 , where, inside the first  207  and second  225  covers, included are a driving unit  201 , image source panel  203 , Polarization Beam Splitter Filter (PBSF)  211 , mirror  209 , a plurality of lenses  213 ,  215 ,  217 ,  221 , Fly Eye Lens (FEL)  219 , Dichroic filter  227 , and Freeform prism Projection Lens (FPL)  223 . 
     The first  207  and second  225  covers provide a space in which the driving unit  201 , image source panel  203 , PBSF  211 , mirror  209 , a plurality of lenses  213 ,  215 ,  217 ,  221 , FEL  219 , and FPL may be installed, and the internal constituting elements are packaged and fixed to either of the side frames  120 . 
     The driving unit  201  may supply a driving signal that controls a video or an image displayed on the image source panel  203  and may be linked to a separate modular driving chip installed inside or outside the controller  200 . The driving unit  201  may be installed in the form of Flexible Printed Circuits Board (FPCB), which may be equipped with heatsink that dissipates heat generated during operation to the outside. 
     The image source panel  203  may generate an image according to a driving signal provided by the driving unit  201  and emit light according to the generated image. To this purpose, the image source panel  203  may use the Liquid Crystal Display (LCD) or Organic Light Emitting Diode (OLED) panel. 
     The PBSF  211  may separate light due to the image generated from the image source panel  203  or block or pass part of the light according to a rotation angle. Therefore, for example, if the image light emitted from the image source panel  203  is composed of P wave, which is horizontal light, and S wave, which is vertical light, the PBSF  211  may separate the P and S waves into different light paths or pass the image light of one polarization or block the image light of the other polarization. The PBSF  211  may be provided as a cube type or plate type in one embodiment. 
     The cube-type PBSF  211  may filter the image light composed of P and S waves and separate them into different light paths while the plate-type PBSF  211  may pass the image light of one of the P and S waves but block the image light of the other polarization. 
     The mirror  209  reflects the image light separated from polarization by the PBSF  211  to collect the polarized image light again and let the collected image light incident on a plurality of lenses  213 ,  215 ,  217 ,  221 . 
     The plurality of lenses  213 ,  215 ,  217 ,  221  may include convex and concave lenses and for example, may include I-type lenses and C-type lenses. The plurality of lenses  213 ,  215 ,  217 ,  221  repeat diffusion and convergence of image light incident on the lenses, thereby improving straightness of the image light rays. 
     The FEL  219  may receive the image light which has passed the plurality of lenses  213 ,  215 ,  217 ,  221  and emit the image light so as to improve illuminance uniformity and extend the area exhibiting uniform illuminance due to the image light. 
     The dichroic filter  227  may include a plurality of films or lenses and pass light of a specific range of wavelengths from the image light incoming from the FEL  219  but reflect light not belonging to the specific range of wavelengths, thereby adjusting saturation of color of the image light. The image light which has passed the dichroic filter  227  may pass through the FPL  223  and be emitted to the display unit  300 . 
     The display unit  300  may receive the image light emitted from the controller  200  and emit the incident image light to the direction in which the user&#39;s eyes are located. 
     Meanwhile, in addition to the constituting elements described above, the electronic device may include one or more image capture means (not shown). The image capture means, being disposed close to at least one of left and right eyes, may capture the image of the front area. Or the image capture means may be disposed so as to capture the image of the side/rear area. 
     Since the image capture means is disposed close to the eye, the image capture means may obtain the image of a real world seen by the user. The image capture means may be installed at the frame  100  or arranged in plural numbers to obtain stereoscopic images. 
     The electronic device may provide a user input unit  130  manipulated to receive control commands. The user input unit  130  may adopt various methods including a tactile manner in which the user operates the user input unit by sensing a tactile stimulus from a touch or push motion, gesture manner in which the user input unit recognizes the hand motion of the user without a direct touch thereon, or a manner in which the user input unit recognizes a voice command. The present figure illustrates a case where the user input unit  130  is installed at the frame  100 . 
     Also, the electronic device may be equipped with a microphone which receives a sound and converts the received sound to electrical voice data and a sound output unit  140  that outputs a sound. The sound output unit  140  may be configured to transfer a sound through an ordinary sound output scheme or bone conduction scheme. When the sound output unit  140  is configured to operate according to the bone conduction scheme, the sound output unit  140  is fit to the head when the user wears the electronic device and transmits sound by vibrating the skull. 
     In what follows, various forms of the display unit  300  and various methods for emitting incident image light rays will be described. 
       FIGS. 7 to 13  illustrate various display methods applicable to the display unit  300  according to one embodiment of the present disclosure. 
     More specifically,  FIG. 7  illustrates one embodiment of a prism-type optical element;  FIG. 8  illustrates one embodiment of a waveguide-type optical element;  FIGS. 9 and 10  illustrate one embodiment of a pin mirror-type optical element; and  FIG. 11  illustrates one embodiment of a surface reflection-type optical element. And  FIG. 12  illustrates one embodiment of a micro-LED type optical element, and  FIG. 13  illustrates one embodiment of a display unit used for contact lenses. 
     As shown in  FIG. 7 , the display unit  300 - 1  according to one embodiment of the present disclosure may use a prism-type optical element. 
     In one embodiment, as shown in  FIG. 7( a ) , a prism-type optical element may use a flat-type glass optical element where the surface  300   a  on which image light rays are incident and from which the image light rays are emitted is planar or as shown in  FIG. 7( b ) , may use a freeform glass optical element where the surface  300   b  from which the image light rays are emitted is formed by a curved surface without a fixed radius of curvature. 
     The flat-type glass optical element may receive the image light generated by the controller  200  through the flat side surface, reflect the received image light by using the total reflection mirror  300   a  installed inside and emit the reflected image light toward the user. Here, laser is used to form the total reflection mirror  300   a  installed inside the flat type glass optical element. 
     The freeform glass optical element is formed so that its thickness becomes thinner as it moves away from the surface on which light is incident, receives image light generated by the controller  200  through a side surface having a finite radius of curvature, totally reflects the received image light, and emits the reflected light toward the user. 
     As shown in  FIG. 8 , the display unit  300 - 2  according to another embodiment of the present disclosure may use a waveguide-type optical element or light guide optical element (LOE). 
     As one embodiment, the waveguide or light guide-type optical element may be implemented by using a segmented beam splitter-type glass optical element as shown in  FIG. 8( a ) , saw tooth prism-type glass optical element as shown in  FIG. 8( b ) , glass optical element having a diffractive optical element (DOE) as shown in  FIG. 8( c ) , glass optical element having a hologram optical element (HOE) as shown in  FIG. 8( d ) , glass optical element having a passive grating as shown in  FIG. 8( e ) , and glass optical element having an active grating as shown in  FIG. 8( f ) . 
     As shown in  FIG. 8( a ) , the segmented beam splitter-type glass optical element may have a total reflection mirror  301   a  where an optical image is incident and a segmented beam splitter  301   b  where an optical image is emitted. 
     Accordingly, the optical image generated by the controller  200  is totally reflected by the total reflection mirror  301   a  inside the glass optical element, and the totally reflected optical image is partially separated and emitted by the partial reflection mirror  301   b  and eventually perceived by the user while being guided along the longitudinal direction of the glass. 
     In the case of the saw tooth prism-type glass optical element as shown in  FIG. 8( b ) , the optical image generated by the controller  200  is incident on the side surface of the glass in the oblique direction and totally reflected into the inside of the glass, emitted to the outside of the glass by the saw tooth-shaped uneven structure  302  formed where the optical image is emitted, and eventually perceived by the user. 
     The glass optical element having a Diffractive Optical Element (DOE) as shown in  FIG. 8( c )  may have a first diffraction unit  303   a  on the surface of the part on which the optical image is incident and a second diffraction unit  303   b  on the surface of the part from which the optical image is emitted. The first and second diffraction units  303   a ,  303   b  may be provided in a way that a specific pattern is patterned on the surface of the glass or a separate diffraction film is attached thereon. 
     Accordingly, the optical image generated by the controller  200  is diffracted as it is incident through the first diffraction unit  303   a , guided along the longitudinal direction of the glass while being totally reflected, emitted through the second diffraction unit  303   b , and eventually perceived by the user. 
     The glass optical element having a Hologram Optical Element (HOE) as shown in  FIG. 8( d )  may have an out-coupler  304  inside the glass from which an optical image is emitted. Accordingly, the optical image is incoming from the controller  200  in the oblique direction through the side surface of the glass, guided along the longitudinal direction of the glass by being totally reflected, emitted by the out-coupler  304 , and eventually perceived by the user. The structure of the HOE may be modified gradually to be further divided into the structure having a passive grating and the structure having an active grating. 
     The glass optical element having a passive grating as shown in  FIG. 8( e )  may have an in-coupler  305   a  on the opposite surface of the glass surface on which the optical image is incident and an out-coupler  305   b  on the opposite surface of the glass surface from which the optical image is emitted. Here, the in-coupler  305   a  and the out-coupler  305   b  may be provided in the form of film having a passive grating. 
     Accordingly, the optical image incident on the glass surface at the light-incident side of the glass is totally reflected by the in-coupler  305   a  installed on the opposite surface, guided along the longitudinal direction of the glass, emitted through the opposite surface of the glass by the out-coupler  305   b , and eventually perceived by the user. 
     The glass optical element having an active grating as shown in  FIG. 8( f )  may have an in-coupler  306   a  formed as an active grating inside the glass through which an optical image is incoming and an out-coupler  306   b  formed as an active grating inside the glass from which the optical image is emitted. 
     Accordingly, the optical image incident on the glass is totally reflected by the in-coupler  306   a , guided in the longitudinal direction of the glass, emitted to the outside of the glass by the out-coupler  306   b , and eventually perceived by the user. 
     The display unit  300 - 3  according to another embodiment of the present disclosure may use a pin mirror-type optical element. 
     The pinhole effect is so called because the hole through which an object is seen is like the one made with the point of a pin and refers to the effect of making an object look more clearly as light is passed through a small hole. This effect results from the nature of light due to refraction of light, and the light passing through the pinhole deepens the depth of field (DOF), which makes the image formed on the retina more vivid. 
     In what follows, an embodiment for using a pin mirror-type optical element will be described with reference to  FIGS. 9 and 10 . 
     Referring to  FIG. 9( a ) , the pinhole mirror  310   a  may be provided on the path of incident light within the display unit  300 - 3  and reflect the incident light toward the user&#39;s eye. More specifically, the pinhole mirror  310   a  may be disposed between the front surface (outer surface) and the rear surface (inner surface) of the display unit  300 - 3 , and a method for manufacturing the pinhole mirror will be described again later. 
     The pinhole mirror  310   a  may be formed to be smaller than the pupil of the eye and to provide a deep depth of field. Therefore, even if the focal length for viewing a real world through the display unit  300 - 3  is changed, the user may still clearly see the real world by overlapping an augmented reality image provided by the controller  200  with the image of the real world. 
     And the display unit  300 - 3  may provide a path which guides the incident light to the pinhole mirror  310   a  through internal total reflection. 
     Referring to  FIG. 9( b ) , the pinhole mirror  310   b  may be provided on the surface  300   c  through which light is totally reflected in the display unit  300 - 3 . Here, the pinhole mirror  310   b  may have the characteristic of a prism that changes the path of external light according to the user&#39;s eyes. For example, the pinhole mirror  310   b  may be fabricated as film-type and attached to the display unit  300 - 3 , in which case the process for manufacturing the pinhole mirror is made easy. 
     The display unit  300 - 3  may guide the incident light incoming from the controller  200  through internal total reflection, the light incident by total reflection may be reflected by the pinhole mirror  310   b  installed on the surface on which external light is incident, and the reflected light may pass through the display unit  300 - 3  to reach the user&#39;s eyes. 
     Referring to  FIG. 9( c ) , the incident light illuminated by the controller  200  may be reflected by the pinhole mirror  310   c  directly without internal total reflection within the display unit  300 - 3  and reach the user&#39;s eyes. This structure is convenient for the manufacturing process in that augmented reality may be provided irrespective of the shape of the surface through which external light passes within the display unit  300 - 3 . 
     Referring to  FIG. 9( d ) , the light illuminated by the controller  200  may reach the user&#39;s eyes by being reflected within the display unit  300 - 3  by the pinhole mirror  310   d  installed on the surface  300   d  from which external light is emitted. The controller  200  is configured to illuminate light at the position separated from the surface of the display unit  300 - 3  in the direction of the rear surface and illuminate light toward the surface  300   d  from which external light is emitted within the display unit  300 - 3 . The present embodiment may be applied easily when thickness of the display unit  300 - 3  is not sufficient to accommodate the light illuminated by the controller  200 . Also, the present embodiment may be advantageous for manufacturing in that it may be applied irrespective of the surface shape of the display unit  300 - 3 , and the pinhole mirror  310   d  may be manufactured in a film shape. 
     Meanwhile, the pinhole mirror  310  may be provided in plural numbers in an array pattern. 
       FIG. 10  illustrates the shape of a pinhole mirror and structure of an array pattern according to one embodiment of the present disclosure. 
     Referring to the figure, the pinhole mirror  310  may be fabricated in a polygonal structure including a square or rectangular shape. Here, the length (diagonal length) of a longer axis of the pinhole mirror  310  may have a positive square root of the product of the focal length and wavelength of light illuminated in the display unit  300 - 3 . 
     A plurality of pinhole mirrors  310  are disposed in parallel, being separated from each other, to form an array pattern. The array pattern may form a line pattern or lattice pattern. 
       FIGS. 10( a ) and ( b )  illustrate the Flat Pin Mirror scheme, and  FIGS. 10( c ) and ( d )  illustrate the freeform Pin Mirror scheme. 
     When the pinhole mirror  310  is installed inside the display unit  300 - 3 , the first glass  300   e  and the second glass  300   f  are combined by an inclined surface  300   g  disposed being inclined toward the pupil of the eye, and a plurality of pinhole mirrors  310   e  are disposed on the inclined surface  300   g  by forming an array pattern. 
     Referring to  FIGS. 10( a ) and ( b ) , a plurality of pinhole mirrors  310   e  may be disposed side by side along one direction on the inclined surface  300   g  and continuously display the augmented reality provided by the controller  200  on the image of a real world seen through the display unit  300 - 3  even if the user moves the pupil of the eye. 
     And referring to  FIGS. 10( c ) and ( d ) , the plurality of pinhole mirrors  310   f  may form a radial array on the inclined surface  300   g  provided as a curved surface. 
     Since the plurality of pinhole mirrors  300   f  are disposed along the radial array, the pinhole mirror  310   f  at the edge in the figure is disposed at the highest position, and the pinhole mirror  310   f  in the middle thereof is disposed at the lowest position, the path of a beam emitted by the controller  200  may be matched to each pinhole mirror. 
     As described above, by disposing a plurality of pinhole arrays  310   f  along the radial array, the double image problem of augmented reality provided by the controller  200  due to the path difference of light may be resolved. 
     Similarly, lenses may be attached on the rear surface of the display unit  300 - 3  to compensate for the path difference of the light reflected from the plurality of pinhole mirrors  310   e  disposed side by side in a row. 
     The surface reflection-type optical element that may be applied to the display unit  300 - 4  according to another embodiment of the present disclosure may employ the freeform combiner method as shown in  FIG. 11( a ) , Flat HOE method as shown in  FIG. 11( b ) , and freeform HOE method as shown in  FIG. 11( c ) . 
     The surface reflection-type optical element based on the freeform combiner method as shown in  FIG. 11( a )  may use freeform combiner glass  300 , for which a plurality of flat surfaces having different incidence angles for an optical image are combined to form one glass with a curved surface as a whole to perform the role of a combiner. The freeform combiner glass  300  emits an optical image to the user by making incidence angle of the optical image differ in the respective areas. 
     The surface reflection-type optical element based on Flat HOE method as shown in  FIG. 11( b )  may have a hologram optical element (HOE)  311  coated or patterned on the surface of flat glass, where an optical image emitted by the controller  200  passes through the HOE  311 , reflects from the surface of the glass, again passes through the HOE  311 , and is eventually emitted to the user. 
     The surface reflection-type optical element based on the freeform HOE method as shown in  FIG. 11( c )  may have a HOE  313  coated or patterned on the surface of freeform glass, where the operating principles may be the same as described with reference to  FIG. 11( b ) . 
     In addition, a display unit  300 - 5  employing micro LED as shown in  FIG. 12  and a display unit  300 - 6  employing a contact lens as shown in  FIG. 13  may also be used. 
     Referring to  FIG. 12 , the optical element of the display unit  300 - 5  may include a Liquid Crystal on Silicon (LCoS) element, Liquid Crystal Display (LCD) element, Organic Light Emitting Diode (OLED) display element, and Digital Micromirror Device (DMD); and the optical element may further include a next-generation display element such as Micro LED and Quantum Dot (QD) LED. 
     The image data generated by the controller  200  to correspond to the augmented reality image is transmitted to the display unit  300 - 5  along a conductive input line  316 , and the display unit  300 - 5  may convert the image signal to light through a plurality of optical elements  314  (for example, microLED) and emits the converted light to the user&#39;s eye. 
     The plurality of optical elements  314  are disposed in a lattice structure (for example, 100×100) to form a display area  314   a . The user may see the augmented reality through the display area  314   a  within the display unit  300 - 5 . And the plurality of optical elements  314  may be disposed on a transparent substrate. 
     The image signal generated by the controller  200  is sent to an image split circuit  315  provided at one side of the display unit  300 - 5 ; the image split circuit  315  is divided into a plurality of branches, where the image signal is further sent to an optical element  314  disposed at each branch. At this time, the image split circuit  315  may be located outside the field of view of the user so as to minimize gaze interference. 
     Referring to  FIG. 13 , the display unit  300 - 5  may comprise a contact lens. A contact lens  300 - 5  on which augmented reality may be displayed is also called a smart contact lens. The smart contact lens  300 - 5  may have a plurality of optical elements  317  in a lattice structure at the center of the smart contact lens. 
     The smart contact lens  300 - 5  may include a solar cell  318   a , battery  318   b , controller  200 , antenna  318   c , and sensor  318   d  in addition to the optical element  317 . For example, the sensor  318   d  may check the blood sugar level in the tear, and the controller  200  may process the signal of the sensor  318   d  and display the blood sugar level in the form of augmented reality through the optical element  317  so that the user may check the blood sugar level in real-time. 
     As described above, the display unit  300  according to one embodiment of the present disclosure may be implemented by using one of the prism-type optical element, waveguide-type optical element, light guide optical element (LOE), pin mirror-type optical element, or surface reflection-type optical element. In addition to the above, an optical element that may be applied to the display unit  300  according to one embodiment of the present disclosure may include a retina scan method. 
     Hereinafter, according to the present disclosure, an electronic device may be implemented as a controller available to the user wearing an HMD as shown in  FIGS. 3, 4, and 14 . Referring to  FIGS. 3 and 4 , VR electronic device encompasses a head mounted display (HMD)-type electronic device  30  worn on the user&#39;s head and controller-type electronic device  40 ,  40   a , or  40   b  which is manipulated by the HMD-wearing user in her hand. 
     According to an embodiment, the controller  40 , as an implementation of the electronic device of the present disclosure, may be embodied as shown in  FIG. 14 .  FIG. 14  is a perspective view illustrating a controller implementing an electronic device according to an embodiment of the present disclosure. Hereinafter, electronic device denotes the controller  40  shown in  FIG. 14 , and the terms “electronic device” and “controller  40 ” may be interchangeably used. 
     According to an embodiment of the present disclosure, the controller  40  may control operations and interactions related to content or VR images or videos displayed on the HMD  30  used for AR and/or VR. 
     Referring to  FIG. 14 , according to an embodiment of the present disclosure, the controller  40  includes a handle  41  which may easily be gripped in the user&#39;s hand, a strap portion  400  wrapped around the user&#39;s hand, and a strap tension adjuster  410  provided inside the controller  40 . For example, a touchpad (or trackpad) or buttons for receiving the user&#39;s input are provided on an upper portion  42  of the handle of the controller  40 . 
     As described above, the handle  41  of the controller  40  may be referred to as a grip, and the upper portion  42  of the handle may be referred to as a head  42 . 
     Various sensors and a microprocessor extending from the handle  41  may be embedded in the head  42 . As shown in  FIGS. 14 to 21 , the handle  41  may be shaped as an elongated bar to allow the user to easily grip in her hand, and the head  42  may be shaped as a ring. 
     Two opposite ends of the strap portion  400  are connected to the handle  41 , and one (hereinafter, a ‘first end’) of the ends is connected with the strap tension adjuster  410  while the other (hereinafter, a ‘second end’) is rotatably connected with the handle  41 . The first end of the strap portion  400  is connected with the strap tension adjuster  410  via a connecting element  43 , which is described below in detail. 
     Referring to  FIG. 15 , the strap portion  400  includes a strap frame  401 , a cushion  402 , a hinge shaft  403 , a washer  404 , a spring washer  405 , a washer plate  406 , a nut  407 , and an E-ring  408 . The washer  404 , the spring washer  405 , the washer plate  406 , the nut  407 , and the E-ring  408  all may be fitted over the hinge shaft  403 . 
       FIG. 15  is a perspective view illustrating a strap portion according to an embodiment of the present disclosure. 
     Referring to  FIG. 15 , the strap frame  401  is a part wrapped around the user&#39;s hand. According to the present disclosure, the strap frame  401  may be formed of a metal or plastic with a predetermined strength. The cushion  402  is mounted on the inner surface of the strap frame  401  which directly contacts the user&#39;s hand, mitigating damage due to friction between the user&#39;s hand and the strap frame  401 . The cushion  402  may be formed of elastic rubber or a similar material. The hinge shaft  403  fastens the second end of the strap portion  400  to the handle  41  while allowing the strap portion  400  to rotate around the hinge shaft  403  from the handle  41 . The hinge shaft  403  passes through the handle  41  and connects to the strap portion  400 . By the washer  404  and the spring washer  405 , the strap portion  400  is prevented from damage due to friction with the handle  41  although rotating around the hinge shaft  403 . 
     The washer plate  406  is used to fasten the hinge shaft  403  to an inner wall of the handle  41 , and the nut  407  is coupled to the hinge shaft  403  to prevent the hinge shaft  403  from escaping off the washer plate  406 . The E-ring  408  prevents the nut  407  from loosening from the hinge shaft  403  as the hinge shaft  403  rotates. 
     The configuration in which the strap portion  400  rotates around the hinge shaft  403  is described below in greater detail. 
     Referring to  FIG. 16 , according to an embodiment, the strap tension adjuster is embedded inside the handle  41 , with a link button  411  partially protruding to the outside of the handle  41 . In other words, a button part  411   a  of the link button  411  projects to the outside of the handle  41 . An opening  44  is formed in the bottom of the handle  41  to pass a connecting element  43  therethrough to connect the second end of the strap portion  400  with the strap tension adjuster  410  embedded inside the handle  41 . 
       FIG. 16  is a view illustrating a strap tension adjuster  410  positioned inside a controller according to an embodiment of the present disclosure. 
     According to an embodiment of the present disclosure, the strap tension adjuster  410  is described below in greater detail with reference to  FIGS. 17 and 18 . According to an embodiment, the strap tension adjuster  410  includes a link button  411 , a first gear  413 , a first spring  415 , a second gear  416 , a second spring  419 , and a pin  420 . 
       FIG. 17  is a perspective view illustrating the strap tension adjuster according to an embodiment of the present disclosure.  FIG. 18  is an exploded perspective view illustrating the strap tension adjuster according to an embodiment of the present disclosure. 
     The link button  411  is configured to be pressed towards the inside of the handle  41  when the button part  411   a  of the link button  411  is pressed by the user in which case the first gear  413  is pushed away from the second gear  416  by a portion  412  of the link button  411 . The link button  411  includes a first arm  412  that pushes the first gear  413  away from the second gear  416  as shown in  FIGS. 17 and 18 . The first arm  412  contacts and connects with the first gear  413 . 
     The first gear  413  includes a body  413   a  around which the first spring  415  is wound and first sawteeth  414  and is configured to be spinnable in a first direction a 1  of  FIG. 18 . Each of the first sawteeth  414  has a first slope surface  414   a  inclined in the first direction a 1  and no slope surface formed in a second direction a 2  opposite to the first direction a 1 . 
     The second gear  416  includes second sawteeth  417  and is configured to be stopped from spinning in the first and second directions a 1  and a 2 . The second gear  416  may be configured to be unspinnably coupled with the link button  411 . For example, the second gear  416  may be unspinnably fastened to the inner wall of the handle  41 . In the case where the second gear  416  is configured to be unspinnably coupled with the link button  411 , since the second gear  416  has a receiving groove  418  for receiving a portion  412  of the link button  411  and the portion  412  of the link button  411  remains engaged to the receiving groove  418 , the second gear  416  is unable to spin in the first direction a 1  or second direction a 2 . 
     As shown in  FIGS. 17 and 18 , where the portion  412  of the link button  411  is formed as, e.g., the first arm  412 , the first arm  412  is formed to be longer than the receiving groove  418 . To enable the first arm  412  to push away the first gear  413  when the button part  411   a  is pressed by the user, the receiving groove  418  is configured to have openings in both ends thereof, and the first arm  412  placed in the receiving groove  418  moves straight along an xl axis. 
     Each of the second sawteeth  417  has a second slope surface  417   a  inclined in the second direction a 2  and no slope surface formed in the first direction a 1  opposite to the second direction a 2 . 
     Thus, the first sawteeth  414  and the second sawteeth  417  may be symmetrically arranged as shown in  FIGS. 17 and 18  and, when the first gear  413  is positioned adjacent to the second gear  416 , the first sawteeth  414  and the second sawteeth  417  may be engaged with each other. In other words, the first slope surface  414   a  and the second slope surface  417   a  are disposed to face, and come in frictional contact with, each other. 
     Thus, while being engaged with the second gear  416 , the first gear  413  may be spun around the xl axis only in the direction a 1  by the first slope surfaces  414   a  of the first sawteeth  414  and the second slope surfaces  417   a  of the second sawteeth  417 . 
     However, as the button part  411   a  is pressed by the user, the first arm  412  may be slid straight along the receiving groove  418 , pushing away the first gear  413  to disengage from the second gear  416 . As the first gear  413  and the second gear  416  are disengaged from each other, the first gear  413  is enabled to spin in the second direction a 2 . 
     The first spring  415  may be a spiral spring and be wound around the body  413   a  of the first gear  413 . For example, the first spring  415  may be wound around the first gear  413 , with its center coaxial with the rotation axis xl of the first gear  413 , and one end of the first spring  415  is fastened to the body  413   a  of the first gear  413 . The opposite end (hereinafter, a second end  415   a ) of the first spring  415  is connected with the connecting element  43 . 
     The first end of the strap portion  400  is indirectly connected with the opposite end  415   a  of the first spring  415  via the connecting element  43 . 
     According to an embodiment, the strap tension adjuster  410  may further include a second spring  419  that allows the first gear  413 , which has been pushed away from the second gear  416  by the user pressing the button part  411   a , to be engaged back with the second gear  416  as the user releases the button part  411   a.    
     For example, as shown in  FIGS. 17 and 18 , the second spring  419  elastically supports the first gear  413 , inside the first gear  413 , on the xl axis towards the outside of the handle  41 . The center of the second spring  419  is coaxial with the rotation axis of the first gear  413 . The second spring  419  is contracted when the first gear  413  is pushed away by the first arm  412  and is elastically restored while pushing the first gear  413  towards the outside of the handle  41  when the button part  411   a  is released. 
     The first gear  413  and the second gear  416  are fastened by the pin  420  in predetermined positions inside the handle  41 . The pin  420  penetrates the first gear  413  and the second gear  416  along the xl axis which is the center axis and rotation axis of the first gear  413  and the second gear  416 . One end, or two opposite ends, of the pin  420  are fastened to an inner wall fastening part  41   a  which is formed on an inner wall of the handle  41 . In this case, the second spring  419  and the pin  420 , in combination, may be placed inside the first gear  413 . 
     The operation of the controller  40  and the strap tension adjuster  410  according to the user&#39;s manipulation is described below with reference to  FIGS. 19, 20, and 21 . For ease of description, a state in which the controller  40  is not in use by the user and another in which the controller  40  is used by the user are described in order. 
       FIG. 19  is a view illustrating an inside of a handle of a controller according to an embodiment of the present disclosure.  FIGS. 20 and 21  are views illustrating an example of using the controller according to an embodiment of the present disclosure. 
     While not in use, the controller  40  need not be positioned to allow the user to grip the handle  41 , thus the strap portion  400  is assumed to be in a first state where it is closest to the handle  41 . 
     In the first state, the first spring  415  shown in  FIG. 19  remains mostly wound around the body  413   a  of the first gear  413  and, thus, the connecting element  43  connected to the second end  415   a  of the first spring  415  is mostly positioned inside the handle  41 . 
     To grip the handle  41 , the user sufficiently spaces the strap portion  400  away from the handle  41 , thereby securing a wide space between the strap portion  400  and the handle  41 . 
     In the second state where the strap portion  400  stays away from the handle  41 , the first end  401   a  of the strap portion  400  travels longer from the handle  41  than the second end of the strap portion  400  fastened to the handle  41 , so that the connecting element  43  connected with the first end  401   a  of the strap portion  400  is tensioned to pull the connecting element  43  and the second end  415   a  of the first spring. 
     In this case, since the first slope surfaces  414   a  formed in the first sawteeth  414  are slidable over the second slope surfaces  417   a  formed in the second sawteeth  417  although the first sawteeth  414  are engaged with the second sawteeth  417 , the first gear  413  connected with the first spring  415  may be spun in the first direction a 1 . 
     Therefore, the first gear  413  is spun in the first direction a 1  by the tension of the first spring  415  but not in the second direction a 2  by steady engagement between the first sawteeth  414  and the second sawteeth  417 . In other words, by the engagement between the first gear  413  and the second gear  416 , the first spring  415  is extended towards the opening  44  of the handle  41  and remains in the extending position. 
     The user may secure a wide space between the strap portion  400  and the handle  41  by spacing the first end  401   a  of the strap portion  400  away from the handle  41 . The user may put her left hand hl through the secured space and grip the handle  41  as shown in  FIG. 20 . 
     If the strap portion  400  remains spaced away from the handle  41  while the user holds the handle  41  in her left hand hl, the user&#39;s left hand hl does not come in tight contact with the handle  41 . The user may press the button part  411   a  of the link button  411 , tightening up the strap portion  400  on the user&#39;s left hand hl. 
     If the user presses the button part  411   a  of the link button  411  with her left hand, the first arm  412  of the link button  411  slides through the receiving groove  418  formed in the second gear  416 , pushing away the first gear  413 . As the first gear  413  is pushed away, the engagement between the first gear  413  and the second gear  416  is released, allowing the first gear  413  to spin in the second direction a 2 . 
     Since the tension on the connecting element  43  is released by the user, the first spring  415  is elastically restored so that the first gear  413  is pushed away from the second gear  416  by the first arm  412  to be enabled to spin in the second direction a 2 . Thus, the first gear  413  is spun in the second direction a 2  by the elastic restoring force of the first spring  415 . 
     If the strap portion  400  becomes tight enough to bring the user&#39;s left hand hl in tight contact with the handle  41 , the elastic restoration of the first spring  415  ends, and the first gear  413  stops spinning in the second direction a 2 . 
     As the strap portion  400  tightly holds the handle  41  in the user&#39;s left hand hl, the controller may be prevented from escaping off the user&#39;s hand, and a space may be secured between the handle  41  and the strap portion  400  by simple manipulation of the strap portion  400 . This way may significantly enhance the use convenience of the controller. 
     If the user shakes her hand with the strap portion  400  holding the handle  41  in the hand, the strap portion  400  may be freely rotated in a direction r 1  or r 2  around the hinge shaft  403 . In other words, as the second end of the strap portion  400  is fastened to the handle  41  to be freely rotatable in the direction r 1  or r 2  around the hinge shaft  403 , the user&#39;s hand motion is not disturbed by the strap portion  400 . 
     According to the present disclosure, the strap tension adjuster may be made compact by simplifying the components as compared with the prior art, thus contributing to reducing the overall size and volume of the controller  40 . 
     Particular embodiments or other embodiments of the present disclosure described above are not mutually exclusive to each other or distinguishable from each other. Individual structures or functions of particular embodiments or other embodiments of the present disclosure described above may be used in parallel therewith or in combination thereof. 
     For example, it means that structure A described with reference to a specific embodiment and/or figure and structure B described with reference to other embodiment and/or figure may be combined together. In other words, even if a combination of two different structures is not explicitly indicated, it should be understood that combination thereof is possible unless otherwise stated as impossible. 
     The detailed descriptions above should be regarded as being illustrative rather than restrictive in every aspect. The technical scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and all of the modifications that fall within an equivalent scope of the present disclosure belong to the technical scope of the present disclosure. 
     DESCRIPTION OF DENOTATIONS 
     
         
         
           
               10 : cloud network 
               20 : electronic device 
               400 : strap portion 
               410 : strap tension adjuster 
               411 : link button 
               413 : first gear 
               415 : first spring 
               416 : second gear 
               419 : second spring 
               420 : pin