Patent Publication Number: US-2022229490-A1

Title: Augmented reality device and method for detecting user&#39;s gaze

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a bypass continuation of International Application No. PCT/KR2022/000682 designating the United States, filed on Jan. 13, 2022, in the Korean Intellectual Property Office and claiming priority to Korean Patent Application No. 10-2021-0008942, filed on Jan. 21, 2021, Korean Patent Application No. 10-2021-0084155, filed on Jun. 28, 2021, and Korean Patent Application No. 10-2021-0128345, filed on Sep. 28, 2021, in the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein in their entireties. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to an augmented reality (AR) device and method for detecting a user&#39;s gaze, and more particularly, to an AR device for detecting a user&#39;s gaze and a method thereof by using a light emitter and a light receiver located in a support of the AR device. 
     BACKGROUND ART 
     Augmented reality (AR) is a technology that projects a virtual image onto a physical environment space of the real world or a real world object and displays the virtual image as a single image. While being worn on a user&#39;s face or head, an AR device allows the user to see a real scene and a virtual image through a glasses type device using a see-through display such as a waveguide in front of the user&#39;s eyes. As research on such an AR device is being actively conducted, various types of wearable devices have been released or are expected to be released. In the glasses type AR device of the related art, a camera is generally arranged on a rim portion surrounding a waveguide to track the user&#39;s gaze, which causes the rim portion of the AR device to be enlarged, and further, causes the user wearing the AR device to feel uncomfortable. 
     DESCRIPTION OF EMBODIMENTS 
     Technical Problem 
     Provided are an augmented reality (AR) device and a method capable of detecting a user&#39;s gaze by using a light reflector and a light receiver located in a support extending from a frame of the AR device. 
     Provided are an AR device and a method capable of detecting a user&#39;s gaze by using light reflected through a light reflector formed on a waveguide. 
     Provided are an AR device and a method capable of more accurately detecting a user&#39;s gaze by calculating a degree of bias of a support of the AR device based on a pattern formed on a light reflector. 
     Solution to Problem 
     According to an aspect of the disclosure, there is provided an augmented reality (AR) device including: a waveguide; a light reflector comprising a pattern; a support configured to fix the AR device to a user&#39;s face of the AR device; a light emitter and a light receiver installed on the support; and at least one processor configured to: control the light emitter to emit light toward the light reflector, identify the pattern based on the light received by the light receiver, and obtain gaze information of a user of the AR device based on the identified pattern, wherein the light emitted toward the light reflector is reflected by the light reflector and directed toward an eye of the user, and wherein the light received by the light receiver comprises light from the light directed toward the eye of the user being reflected by the eye of the user. 
     The support may include a temple extending from a frame around the waveguide to be positioned on an ear of the user; and a nose support extending from the frame and positioned on a nose of the user. 
     The light reflector may be coated on the waveguide. 
     The light reflector may be formed on the waveguide. 
     The at least one processor may be further configured to analyze the identified pattern and identify a degree of bias of the support with respect to the frame, the support extending from the frame. 
     The at least one processor may be further configured to: generate a mapping function for calculating a position of a gaze point of the user based on the degree of bias of the support with respect to the frame, and based on the mapping function and the degree of bias of the support with respect to the frame, obtain the gaze information of the user. 
     The at least one processor may be further configured to, based on the light received by the light receiver, obtain a position of one or more feature points corresponding to the eye of the user. 
     The at least one processor may be configured to input the position of the one or more feature points corresponding to the eye of the user and the degree of bias of the support with respect to the frame into the mapping function and calculate the position of the gaze point of the user. 
     The position of the one or more feature points may include a position of a pupil feature point of the eye of the user and a position of a glint feature point of the eye of the user. 
     The at least one processor may be further configured to: display a target point at a specific position on the waveguide in order to calibrate the mapping function, receive light reflected by the eye of the user looking at the displayed target point through the light receiver, and calibrate the mapping function based on the light reflected by the eye of the user looking at the displayed target point. 
     The at least one processor may be further configured to: based on the light reflected by the eye of the user looking at the displayed target point, identify the pattern of the light reflector, based on the identified pattern, identify the degree of bias of the support, and based on the light reflected by the eye of the user looking at the displayed target point, obtain a position of one or more feature points corresponding to the eye of the user looking at the displayed target point. 
     The at least one processor may be further configured to input a degree of bias of the temple and the position of the one or more feature points into the mapping function, and calibrate the mapping function so that a position value of the target point is output from the mapping function. 
     The light emitter may be an infrared light-emitting diode (IR LED), and the light receiver is an IR camera. 
     The light emitter may be an infrared (IR) scanner, and the light receiver is an IR detector. 
     The at least one processor may be further configured to: based on IR light obtained from the IR detector, obtain a position of one or more feature points corresponding to the eye of the user calibrated according to a degree of bias of the support with respect to the frame, and obtain the gaze information of the user based on the calibrated position of the one or more feature points corresponding to the eye of the user. 
     According to another aspect of the disclosure, there is provided a method, performed by an augmented reality (AR) device, of detecting a user&#39;s gaze, the method including: emitting, by a light emitter installed in a support of the AR device, light toward a light reflector comprising a pattern, the light emitted by the light emitter being directed toward an eye of a user wearing the AR device, receiving, by a light receiver installed on the support, the light reflected by the eye of the user, identifying the pattern based on the light received through the light receiver, and obtaining gaze information of the user based on the identified pattern. 
     The method may further include analyzing the identified pattern and identifying a degree of bias of the support with respect to the frame based on the identified pattern, wherein the support extends from the frame, wherein the obtaining of the gaze information may include determining a gaze direction of the user based on the degree of bias of the support with respect to the frame. 
     The method may further include generating a mapping function for calculating a position of a gaze point of the user based on the degree of bias of the support with respect to the frame, wherein the obtaining of the gaze information may include calculating the position of the gaze point of the user based on the mapping function and the degree of bias of the support with respect to the frame. 
     The method may further include, based on the light received by the light receiver, obtaining a position of one or more feature points corresponding to the eye of the user, wherein the obtaining of the gaze information comprises inputting the position of the one or more feature points corresponding to the eye of the user and the degree of bias of the support with respect to the frame into the mapping function and calculating the position of the gaze point of the user. 
     According to another aspect of the disclosure, there is provided a computer-readable recording medium having recorded thereon a program for executing a method including: emitting, by a light emitter installed in a support of the AR device, light toward a light reflector comprising a pattern, the light emitted by the light emitter being directed toward an eye of a user wearing the AR device; receiving, by a light receiver installed on the support, the light reflected by the eye of the user; identifying the pattern based on the light received through the light receiver; and obtaining gaze information of the user based on the identified pattern. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating an example in which an augmented reality (AR) device detects a user&#39;s gaze using a gaze detector located in a temple portion of the AR device, according to an example embodiment of the disclosure. 
         FIG. 2  is a diagram illustrating an example of an AR device according to an example embodiment of the disclosure. 
         FIG. 3  is a block diagram of an AR device according to an example embodiment of the disclosure. 
         FIG. 4  is a diagram illustrating an example of operations of a light emitter and a light receiver of an AR device, according to an example embodiment of the disclosure. 
         FIG. 5A  is a diagram illustrating an example of a light emitter that emits planar light, according to an example embodiment of the disclosure. 
         FIG. 5B  is a diagram illustrating an example of a light emitter that emits point light, according to an example embodiment of the disclosure. 
         FIG. 5C  is a diagram illustrating an example of a light emitter that emits line light, according to an example embodiment of the disclosure. 
         FIG. 6A  is a diagram illustrating an example in which a light emitter and a light receiver are arranged in a temple of an AR device, according to an example embodiment of the disclosure. 
         FIG. 6B  is a diagram illustrating an example in which a light emitter and a light receiver are arranged in a nose support of an AR device, according to an example embodiment of the disclosure. 
         FIG. 6C  is a diagram illustrating an example in which a light emitter and a light receiver are arranged in a temple and a nose support of an AR device, according to an example embodiment of the disclosure. 
         FIG. 6D  is a diagram illustrating an example in which a light emitter and a light receiver are arranged in a temple and a nose support of an AR device, according to an example embodiment of the disclosure. 
         FIG. 7A  is a diagram illustrating an example of a dot pattern formed on a light reflector of an AR device, according to an example embodiment of the disclosure. 
         FIG. 7B  is a diagram illustrating an example of a grid pattern formed on a light reflector of an AR device, according to an example embodiment of the disclosure. 
         FIG. 7C  is a diagram illustrating an example of a pattern in the form of a 2D marker, according to an example embodiment of the disclosure. 
         FIG. 7D  is a diagram illustrating an example of a light reflector that covers a part of a waveguide, according to an example embodiment of the disclosure. 
         FIG. 8A  is a diagram illustrating a light emission angle and a pattern before a temple of an AR device is biased, according to an example embodiment of the disclosure. 
         FIG. 8B  is a diagram illustrating a light emission angle and a pattern after a temple of an AR device, is biased according to an example embodiment of the disclosure. 
         FIG. 9  is a diagram illustrating an example of a pattern identified from an array of light received through a light receiver when a light emitter of an AR device is an infrared (IR) scanner, according to an example embodiment of the disclosure. 
         FIG. 10  is a diagram illustrating an example of an eye feature identified from an array of light received through a light receiver of the AR device when a light emitter of an AR device is an IR scanner, according to an example embodiment of the disclosure. 
         FIG. 11  is a diagram illustrating examples of functions used by an AR device to calculate a center of an eyeball and calculate a gaze point of a user, according to an example embodiment of the disclosure. 
         FIG. 12  is a flowchart of a method, performed by an AR device, of detecting a user&#39;s gaze, according to an example embodiment of the disclosure. 
     
    
    
     MODE OF DISCLOSURE 
     Throughout the disclosure, the expression “at least one of a, b or c” indicates only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof. 
     Hereinafter, embodiments of the disclosure will now be described in detail with reference to the accompanying drawings for one of skill in the art to be able to perform the disclosure without any difficulty. The disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments of the disclosure set forth herein. In order to clearly describe the disclosure, portions that are not relevant to the description of the disclosure are omitted, and similar reference numerals are assigned to similar elements throughout the present specification. 
     Throughout the specification, it will be understood that when an element is referred to as being “connected to” another element, it may be “directly connected to” the other element or be “electrically connected to” the other element through an intervening element. In addition, when an element is referred to as “including” a constituent element, other constituent elements may be further included not excluded unless there is any other particular mention on it. 
     The term ‘augmented reality (AR)’ herein denotes a technology that provides viewing of a virtual image on a physical environment space of the real world or viewing of a virtual image together with a real object. 
     In addition, the term ‘AR device’ denotes a device capable of creating ‘AR’, and includes not only AR glasses that are typically worn on a user&#39;s face but also includes head-mounted display (HMD) apparatuses and AR helmets that are worn on the user&#39;s head, etc. 
     Meanwhile, the term ‘real scene’ denotes a scene of the real world that the user sees through the AR device, and may include a real world object. In addition, the term ‘virtual image’ denotes an image generated by an optical engine, and may include both a static image and a dynamic image. The virtual image may be observed with a real scene, and may be an image representing information about a real object in the real scene, information about an operation of the AR device, a control menu, etc. 
     Accordingly, an AR device may be equipped with an optical engine to generate a virtual image including light generated by a light source, and a waveguide formed of a transparent material to guide the virtual image generated by the optical engine to the user&#39;s eyes and allow the user to see a scene of the real world together with the virtual image. In addition, as described above, the AR device needs to be able to allow the user to observe a scene of the real world, and thus, an optical element for redirecting the path of light that basically has straightness is required in order to guide the light generated by the optical engine to the user&#39; eyes through the waveguide. Here, the path of the light may be redirected by using reflection by, for example, a mirror, or by using diffraction by a diffractive element, for example, a diffractive optical element (DOE) or a holographic optical element (HOE), but the disclosure is not limited thereto. 
     Hereinafter, the disclosure will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a diagram illustrating an example in which an augmented reality (AR) device  1000  detects a user&#39;s gaze using a gaze detector  1500  located in a temple portion of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 1 , the AR device  1000  may detect the user&#39;s gaze by using a light emitter  1510  and a light receiver  1520 . The light emitter  1510  and the light receiver  1520  used to detect the user&#39;s gaze may be provided in, for example, the temple portion of the AR device  1000 , and the AR device  1000  may effectively identify user&#39;s eyes by using the light emitter  1510  and the light receiver  1520  provided in the temple portion. Infrared (IR) light may be emitted from the light emitter  1510  provided in the temple portion toward a waveguide of the AR device  1000 , reflected by a light reflector, and received from the user&#39;s eyes through the light receiver  1520  provided in the temple portion. Also, the AR device  1000  may obtain information about the user&#39;s eyes based on the received IR light, and detect a gaze direction of the user by using the obtained information about the eyes. 
     The AR device  1000  denotes a device capable of creating ‘AR’, and may include, for example, AR glasses that are worn on a user&#39;s face, but the disclosure is not limited thereto. For example, the AR device  1000  may include a head-mounted display (HMD) apparatus and an AR helmet that are worn on the user&#39;s head, etc. In this case, a gaze detector  1500  may be provided on an inner side part of the HMD apparatus facing the side of the user&#39;s eyes in the HMD apparatus or on an inner side part of the AR helmet facing the side of the user&#39;s eyes in the AR helmet. 
       FIG. 2  is a diagram illustrating an example of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 2 , the AR device  1000  may include a glasses-type body configured to be worn by a user as a glasses-type display device. 
     The glasses-type body may include a frame  110  and a support  190 . The support  190  may extend from the frame  110  and be used to seat the AR device  1000  on a user&#39;s head. The support  190  may include a temple  191  and a nose support  192 . The temple  191  may extend from the frame  110  and may be used to fix the AR device  1000  to the user&#39;s head on a side surface of the glasses-type body. The nose support  192  may extend from the frame  110  and may be used to seat the AR device  1000  on a user&#39;s nose, and may include, for example, a nose bridge and a nose pad, but the disclosure is not limited thereto. 
     Also, a waveguide  170  to which a light reflector  1400  is attached may be located on the frame  110 . The frame  110  may be formed to surround an outer circumferential surface of the waveguide  170 . The waveguide  170  may be configured to receive projected light in an input region and output at least part of the input light in an output region. The waveguide  170  may include a left eye waveguide  170 L and a right eye waveguide  170 R. 
     A left eye light reflector  1400 L and the left eye waveguide  170 L may be provided at positions corresponding to a user&#39;s left eye, and a right eye light reflector  1400 R and the right eye waveguide  170 R may be provided at positions corresponding to a user&#39;s right eye. For example, the left eye light reflector  1400 L may be attached to the left eye waveguide  170 L, or the right eye light reflector  1400 R may be attached to the right eye waveguide  170 R, but the disclosure is not limited thereto. In addition, for example, the left eye light reflector  1400 L may be coated on the inner side of the left eye waveguide  170 L to be attached to the left eye waveguide  170 L, or the right eye light reflector  1400 R may be coated on the inner side of the right eye waveguide  170 R to be attached to the right eye waveguide  170 R. 
     In addition, an optical engine  120  of a projector that projects display light including an image may include a left eye optical engine  120 L and a right eye optical engine  120 R. The eye optical engine  120 L and the right eye optical engine  120 R may be located on both sides of the AR device  1000 . Alternatively, one optical engine  120  may be included in a central portion around the nose support  192  of the AR device  1000 . Light emitted from the optical engine  120  may be displayed through the waveguide  170 . 
     The light emitter  1510  and the light receiver  1520  of the gaze detector  1500  may be provided on an inner side part of the support  190  of the AR device  1000 , which is a position between the support  190  and user&#39;s eyes. The light emitter  1510  and the light receiver  1520  may be provided to face the light reflector  1400  in the support  190  of the AR device  1000 . For example, the light emitter  1510  and the light receiver  1520  may be provided at positions spaced from the frame  110  by about 10 mm to 15 mm on the inner side of the temple  191  of the AR device  1000 , in order to respectively emit and receive IR light without being disturbed by user&#39;s hair, etc. 
       FIG. 3  is a block diagram of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 3 , the AR device  1000  according to an example embodiment of the disclosure may include a user inputter  1100 , a microphone  1200 , a display  1300 , a light reflector  1400 , a gaze detector  1500 , a communication interface  1600 , a storage  1700 , and a processor  1800 . Also, the gaze detector  1500  may include the light emitter  1510  and the light receiver  1520 . 
     The user inputter  1100  refers to a means by which a user inputs data for controlling the AR device  1000 . For example, the user inputter  1100  may include a key pad, a dome switch, a touch pad (e.g., a touch-type capacitive touch pad, a pressure-type resistive overlay touch pad, an infrared sensor-type touch pad, a surface acoustic wave conduction touch pad, an integration-type tension measurement touch pad, a piezoelectric effect-type touch pad), a jog wheel, a jog switch, but the disclosure is not limited thereto. 
     The microphone  1200  may receive an external audio signal, and process the received audio signal into electrical voice data. For example, the microphone  1200  may receive an audio signal from an external device or a speaker. The microphone  1200  may use various denoising algorithms for removing noise generated during a process of receiving the external audio signal. The microphone  1200  may receive a voice input of the user for controlling the AR device  1000 . 
     The display  1300  may display information processed by the AR device  1000 . For example, the display  1300  may display a user interface for capturing an image of surroundings of the AR device  1000 , and information related to a service provided based on the captured image of the surroundings of the AR device  1000 . 
     According to an example embodiment of the disclosure, the display  1300  may provide an AR image. The display  1300  according to an example embodiment of the disclosure may include the waveguide  170  and the optical engine  120 . The waveguide  170  may include a transparent material through which a partial region of a rear surface is visible when the user wears the AR device  1000 . The waveguide  1320  may be configured as a flat plate of a single layer or multi-layer structure including a transparent material through which light may be internally reflected and propagated. The waveguide  1320  may face an exit surface of the optical engine  120  to receive light of a virtual image projected from the optical engine  120 . Here, the transparent material is a material through which light is capable of passing, its transparency may not be 100%, and may have a certain color. According to an example embodiment of the disclosure, the waveguide  170  includes the transparent material, and thus the user may view not only a virtual object of the virtual image but also an external real scene, so that the waveguide  170  may be referred to as a see-through display. The display  1300  may output the virtual object of the virtual image through the waveguide  170 , thereby providing an AR image. When the AR device  1000  is a glasses type device, the display  1300  may include a left display and a right display. 
     The light reflector  1400  may reflect light emitted from the light emitter  1510  which will be described later. The light reflector  1400  and the waveguide  170  may be provided at positions facing the user&#39;s eyes, and may be attached to each other. For example, the light reflector  1400  may be coated on at least a partial region of the waveguide  170 . In addition, the light reflector  1400  may be attached to or coated on other elements included in the glasses type AR device  1000  in addition to the waveguide  170 , for example, a vision correcting lens for vision correction or a cover glass installed to protect the waveguide  170 . The light reflector  1400  may include a material capable of reflecting IR light emitted from the light emitter  1510 . The light reflector  1400  may be, for example, silver, gold, copper, ora material including one or more of these metals, but the disclosure is not limited thereto. Accordingly, the IR light emitted from the light emitter  1510  may be reflected by the light reflector  1400  and directed toward the user&#39;s eyes, and the IR light reflected back from the user&#39;s eyes may be reflected by the light reflector  1400  and directed toward the light receiver  1520 . 
     The light reflector  1400  may be coated on the waveguide  170  to have a certain pattern. The pattern formed on the light reflector  1400  may include, for example, a dot pattern, a line pattern, a grid pattern, a 2D marker, etc., but the disclosure is not limited thereto. In addition, the pattern formed on the light reflector  1400  may be formed on, for example, a part of the waveguide  170  at which the user&#39;s gaze is less frequently directed. The pattern formed on the light reflector  1400  may be formed on, for example, a part of the waveguide  170  that does not interfere with capturing or scanning the user&#39;s eyes. For example, the certain pattern may indicate a pattern formed by a part in which light emitted from the light emitter  1510  is reflected and a part in which the light is not reflected, in the light reflector  1400 . Because light emitted toward the part in which the light is not reflected, in the light reflector  1400  is not reflected by the light reflector  1400 , the light receiver  1520  does not receive the light emitted toward the part in which the light is not reflected. Accordingly, the pattern of the light reflector  1400  formed by the part in which light is reflected and the part in which the light is not reflected may be detected from the light received by the light receiver  1520 . In addition, when the light emitted from the light emitter  1510  is IR light, the certain pattern may include a material for reflecting the IR light, and the material for reflecting the IR light may not be visible to the user&#39;s eyes. Because most of a real world light or real scene observed by the user through the AR device  1000  includes visible light, the user may not be disturbed by the light reflector  1400  in which the certain pattern is formed, and may observe the real world light or real scene. 
     The gaze detector  1500  may include the light emitter  1510  that emits IR light for detecting the user&#39;s gaze and the light receiver  1520  that receives the IR light, and may detect data related to the user&#39;s gaze of the user who wears the AR device  1000 . 
     The light emitter  1510  of the gaze detector  1500  may emit the IR light toward the light reflector  1400  so that the IR light reflected by the light reflector  1400  may be directed toward the user&#39;s eyes. The light emitter  1510  may emit the IR light toward the light reflector  1400 , the emitted IR light may be reflected by the light reflector  1400 , and the reflected IR light may be directed toward the user&#39;s eyes. The light emitter  1510  may be provided at a position in the AR device  1000  where the IR light may be emitted toward the light reflector  1400 . The light emitter  1510  may be located on the support  190  of  FIG. 2  that supports the AR device  1000  on the user&#39;s face, for example, like the temple  191  and the nose support  192  of  FIG. 2 . 
     In addition, the IR light reflected from the user&#39;s eyes may be reflected by the light reflector  1400  and received by the light receiver  1520  of the gaze detector  1500 . The IR light directed toward the user&#39;s eyes may be reflected from the user&#39;s eyes, the IR light reflected from the user&#39;s eyes may be reflected by the light reflector  1400 , and the light receiver  1520  may receive the IR light reflected by the light reflector  1400 . The light receiver  1520  may be provided at a position in the AR device  1000  where the IR light reflected from the light reflector  1400  may be received. The light receiver  1520  may be located on the support  190  of  FIG. 2  that supports the AR device  1000  on the user&#39;s face, for example, like the temple  191  and the nose support  192  of  FIG. 2 . Also, for example, the nose support  192  of  FIG. 2  may include a nose bridge and a nose pad. In addition, the nose bridge and the nose pad may be integrally configured, but the disclosure is not limited thereto. 
     For example, the light emitter  1510  may be an IR light-emitting diode (LED) that emits IR light, and the light receiver  1520  may be an IR camera that captures IR light. In this case, the IR camera may capture the user&#39;s eyes using the IR light reflected by the light reflector  1400 . When the light emitter  1510  is the IR LED and the light receiver  1520  is the IR camera, the light emitter  1510  may emit IR light of planar light toward the light reflector  1400 , and the light receiver  1520  may receive the IR light of the planar light reflected from the light reflector  1400 . The planar light may be light emitted in a planar form, and the planar light emitted from the light emitter  1510  may be directed toward at least a part of the entire region of the light reflector  1400 . At least a part of the entire region of the light reflector  1400  may be set so that the planar light reflected from at least a part of the entire region of the light reflector  1400  may cover the user&#39;s eyes. 
     Alternatively, for example, the light emitter  1510  may be an IR scanner that emits IR light, and the light receiver  1520  may be an IR detector that detects IR light. In this case, the IR scanner may emit IR light so that the IR light for scanning the user&#39;s eyes is directed toward the user&#39;s eyes, and the IR detector may detect the IR light reflected from the user&#39;s eyes. When the light emitter  1510  is the IR scanner that emits IR light and the light receiver  1520  is the IR detector that detects IR light, the light emitter  1510  may emit line lights in the form of line, and the line lights emitted from the light emitter  1510  may be directed toward a part of the entire region of the light reflector  1400 . At least a part of the entire region of the light reflector  1400  may be set so that the line lights reflected from at least a part of the entire region of the light reflector  1400  may cover the user&#39;s eyes. When the light emitter  1510  is the IR scanner that emits IR light and the light receiver  1520  is the IR detector that detects IR light, the light emitter  1510  may emit point lights in the form of point, and the point lights emitted from the light emitter  1510  may be directed toward a part of the entire region of the light reflector  1400 . At least a part of the entire region of the light reflector  1400  may be set so that the point lights reflected from at least a part of the entire region of the light reflector  1400  may cover the user&#39;s eyes. 
     When the light emitter  1510  is the IR scanner and the light receiver  1520  is the IR detector, the light emitter  151  may emit IR light of the point light or the line light to the light reflector  1400 , and the light receiver  1520  may receive the IR light of the point light or the linear light reflected from the light reflector  1400 . In this case, the light emitter  1510  may sequentially emit IR light while moving a light emitting direction of the light emitter  1510  so that the IR light of the point light or the line light may cover a space where the user&#39;s eyes are located. Although the IR scanner generally includes the IR LED and a micro-electro mechanical systems (MEMS) mirror capable of controlling a direction of the IR light emitted from the IR LED and reflecting the IR light, hereinafter, the IR scanner, the IR LED and the MEMS mirror are collectively referred to as and described as an IR scanner. In addition, although the IR detector generally includes several photodiodes installed in a part where light detection is required, hereinafter, the IR detector and photodiodes are described as the IR detector. 
     When the AR device  1000  is a glasses type device, the light emitter  1510  and the light receiver  1520  may be provided on the temple  191  of the AR device  1000 . For example, referring to  FIG. 2 , the light emitter  1510  and the light receiver  1520  may be provided on an inner side part of the temple  191  of the AR device  1000 , which is a position between the temple  191  and user&#39;s eyes. For example, referring to  FIG. 2 , the light emitter  1510  and the light receiver  1520  may be provided at positions spaced from the frame  110  by about 10 mm to 15 mm on the inner side of the temple  191  of the AR device  1000  The light emitter  1510  and the light receiver  1520  may be provided to face the light reflector  1400  in the temple  191  of the AR device  1000 . 
     Also, for example, referring to  FIG. 2 , the light emitter  1510  and the light receiver  1520  may be provided on the nose support  192  of the AR device  1000 . The light emitter  1510  and the light receiver  1520  may be provided on an inner side part of the nose support  192  of the AR device  1000 , which is a position between the nose support  192  and the user&#39;s eyes. For example, referring to  FIG. 2 , the light emitter  1510  and the light receiver  1520  may be provided at positions spaced from the frame  110  by about 10 mm to 15 mm on an inner side of the nose support  192  of the AR device  1000 . The light emitter  1510  and the light receiver  1520  may be provided to face the light reflector  1400  in the nose support  192  of the AR device  1000 . 
     The gaze detector  1500  may provide data related to the gaze of the user&#39;s eyes to the processor  1800 , and the processor  1800  may obtain gaze information of the user based on the data related to the gaze of the user&#39;s eyes. The data related to the gaze of the user&#39;s eyes is data obtained by the gaze detector  1500 , and may include a type (e.g., point light, line light, or planar light) of IR light emitted from the light emitter  1510 , characteristics of the IR light emitted from the light emitter  1510 , data regarding an emission region of the IR light emitted from the light emitter  1510 , and data indicating the characteristics of the IR light received from the light receiver  1520 . Further, the gaze information of the user is information related to the user&#39;s gaze, may be generated by analyzing the data related to the gaze of the user&#39;s eyes, and may include information about, for example, a location of the user&#39;s pupil, a location of a pupil central point, a location of the user&#39;s iris, a center of the user&#39;s eyes, a location of glint feature point of the user&#39;s eyes, a gaze point of the user, a gaze direction of the user, etc. but the disclosure is not limited thereto. The gaze direction of the user may be, for example, a direction of eth user&#39;s gaze from the center of the user&#39;s eyes toward the gaze point at which the user gazes. For example, the gaze direction of the user may be represented by a vector value from the center of the user&#39;s left eye toward the gaze point and a vector value from the center of the user&#39;s right eye toward the gaze point, but the disclosure is not limited thereto. According to an example embodiment of the disclosure, the gaze detector  1500  may detect data related to the gaze of the user wearing the AR device  1000  at a previously determined time interval. 
     The communication interface  1600  may transmit/receive data for receiving a service related to the AR device  1000  to/from an external device and a server. 
     The storage  1700  may store a program to be executed by the processor  1800 , which will be described later, and may store data input to or output from the AR device  1000 . 
     The storage  1700  may include at least one of an internal memory or an external memory. The internal memory may include, for example, at least one of a volatile memory (e.g., dynamic RAM (DRAM), static RAM (SRAM), synchronous dynamic RAM (SDRAM), etc.), a non-volatile memory (e.g., one time programmable ROM (OTPROM), programmable ROM (PROM), erasable and programmable ROM (EPROM), electrically erasable and programmable ROM (EEPROM), mask ROM, flash ROM, etc.), hard disk drive (HDD), or solid state drive (SSD). According to an example embodiment of the disclosure, the processor  1800  may load a command or data received from at least one of the non-volatile memory or another element into the volatile memory and process the command or the data. Also, the processor  1800  may store data received or generated from another element in the non-volatile memory. The external memory may include, for example, at least one of compact flash (CF), secure digital (SD), micro secure digital (Micro-SD), mini secure digital (Mini-SD), extreme digital (xD), or memory stick. 
     Programs stored in the storage  1700  may be classified into a plurality of modules according to their functions. According to an example embodiment, each of the plurality of modules may include one or more computer readable codes, which may include, for example, a light irradiation code  1710 , a light reception code  1720 , an eye feature detection code  1730 , a pattern detection code  1740 , a bias determination code  1750 , a pupil position detection code  1760 , a gaze determination code  1770 , and a calibration code  1780 . For example, a memory may be included in the gaze detector  1500 , and, in this case, the light irradiation code  1710  and the light reception code  1720  may be stored as firmware in the memory included in the gaze detector  1500 . 
     The processor  1800  controls the overall operation of the AR device  1000 . For example, the processor  1800  may execute the programs stored in the storage  1700 , thereby generally controlling the user inputter  1100 , the microphone  1200 , the display  1300 , the light reflector  1400 , the gaze detector  1500 , the communication interface  1600 , the storage  1700 , etc. 
     The processor  1800  may execute the light irradiation code  1710 , the light reception code  1720 , the eye feature detection code  1730 , the pattern detection code  1740 , the bias determination code  1750 , the pupil position detection code  1760 , the gaze determination code  1770 , and the calibration code  1780  that are stored in the storage  1700 , thereby determining the gaze point of the user and the gaze direction. 
     According to an example embodiment of the disclosure, the AR device  1000  may include a plurality of processors  1800 , and the light irradiation code  1710 , the light reception code  1720 , the eye feature detection code  1730 , the pattern detection code  1740 , the bias determination code  1750 , the pupil position detection code  1760 , the gaze determination code  1770 , and the calibration code  1780  may be executed by the plurality of processors  1800 . 
     For example, some of the light irradiation code  1710 , the light reception code  1720 , the eye feature detection code  1730 , the pattern detection code  1740 , the bias determination code  1750 , the pupil position detection code  1760 , the gaze determination code  1770 , and the calibration code  1780  may be executed by a first processor, and the others of the light irradiation code  1710 , the light reception code  1720 , the eye feature detection code  1730 , the pattern detection code  1740 , the bias determination code  1750 , the pupil position detection code  1760 , the gaze determination code  1770 , and the calibration code  1780  may be executed by a second processor, but the disclosure is not limited thereto. 
     For example, the gaze detector  1500  may include another processor and a memory, and the other processor may execute the light irradiation code  1710  and the light reception code  1720  that are stored in the memory, and the processor  1800  may execute the eye feature detection code  1730 , the pattern detection code  1740 , the bias determination code  1750 , the pupil position detection code  1760 , the gaze determination code  1770 , and the calibration code  1780  that are stored in the storage  1700 . 
     The processor  1800  may execute the light irradiation code  1710  stored in the storage  1700  so that the light emitter  1510  may emit IR light toward the light reflector  1400 . The processor  1800  may control the light emitter  1510  by executing the light irradiation code  1710 , and the light emitter  1510  controlled by the processor  1800  may emit the IR light toward at least a partial region of the light reflector  1400  so that the IR light reflected by the light reflector  1400  may cover the user&#39;s eyes. 
     For example, when the light receiver  1520  is an IR camera, the light emitter  1510  may be an IR LED, and the processor  1800  may control the IR LED so that the IR light emitted from the IR LED may be reflected by the light reflector  1400  and irradiated to a region including the user&#39;s eyes, in order for the IR camera to capture the user&#39;s eyes. For example, in order to reflect the light emitted from the IR LED by using the light reflector  1400  and irradiate the light to the region including the user&#39;s eyes, the processor  1800  may control an irradiation direction of the IR light emitted from the IR LED, and apply power to the IR LED, thereby controlling emission of the IR light from the IR LED. 
     According to one example embodiment of the disclosure, the IR camera and the IR LED may be installed toward the light reflector  1400  of the AR device  1000  so that the IR camera may capture the entire region of the user&#39;s eyes, and the processor  1800  may control the IR LED installed toward the light reflector  1400  to emit the IR light. An example in which the irradiation direction of the IR light emitted from the IR LED is controlled will be described in more detail with reference to  FIG. 5A . 
     According to another example embodiment of the disclosure, when the light receiver  1520  is an IR detector, the light emitter  1510  may be an IR scanner, and the processor  1800  may control the IR scanner to scan the user&#39;s eyes by reflecting the IR light emitted from the IR scanner by using the light reflector  1400 , so that the IR detector may detect the user&#39;s eyes. For example, in order to scan the user&#39;s eyes by reflecting the light emitted from the IR scanner by using the light reflector  1400 , the processor  1800  may control an irradiation direction of the IR light emitted from the IR scanner, and apply power to the IR scanner, thereby controlling emission of the IR light from the IR scanner. An example in which the irradiation direction of the IR light emitted from the IR scanner is controlled will be described in more detail with reference to  FIGS. 5B and 5C . 
     The processor  1800  may execute the light reception code  1720  stored in the storage  1700  so that the light receiver  1520  may receive the light reflected by the light reflector  1400  from the user&#39;s eyes. The processor  1800  may control the light receiver  1520  by executing the light reception code  1720 , and the light receiver  1520  controlled by the processor  1800  may receive the light reflected by the light reflector  1400  from the user&#39;s eyes. 
     For example, when the light emitter  1510  is an IR LED, the light receiver  1520  may be an IR camera, and the processor  1800  may control the IR camera to capture the user&#39;s eyes through the light reflected by the light reflector  1400  from the user&#39;s eyes. 
     Alternatively, for example, when the light emitter  1510  is an IR scanner, the light receiver  1520  may be an IR detector, and the processor  1800  may control the IR detector to detect the IR light reflected by the light reflector  1400  from the user&#39;s eyes, so that the IR detector may detect the user&#39;s eyes. 
     The processor  1800  may execute the eye feature detection code  1730  stored in the storage  1700 , thereby detecting features related to the gaze of the user&#39;s eyes. For example, the processor  1800  may execute the eye feature detection code  1730 , thereby detecting a position of a pupil feature point of the user&#39;s eyes and a position of a glint feature point of the user&#39;s eyes. The pupil feature point may be, for example, a pupil central point, and the glint feature point of the eyes may be a part having brightness greater than or equal to a certain value in a detected eye region. The position of the pupil feature point and the position of the glint feature point of the eyes may be identified, for example, by a coordinate value indicating a position in a coordinate system of the light receiver  1520 . For example, the coordinate system of the light receiver  1520  may be a coordinate system of an IR camera or a coordinate system of the IR detector, and the coordinate value in the coordinate system of the light receiver  1520  may be a 2D coordinate value. 
     The processor  1800  may detect features related to the gaze of the eyes by analyzing the light received by the light receiver  1520 . For example, when the light receiver  1520  is an IR camera, the processor  1800  may identify the position of the pupil feature point and the position of the glint feature point of the eyes in an image captured by the IR camera. Alternatively, for example, when the light receiver  1520  is an IR detector, the processor  1800  may analyze the IR light detected by the IR detector, thereby identifying the position of the pupil feature point and the position of the glint feature point of the eyes. When the positions of the feature points are identified based on the IR light detected by the IR detector, the position of the pupil feature point and the position of the glint feature point may have values calibrated by reflecting the bias of the support  190 . The position of the pupil feature point and the position of the glint feature point calibrated by reflecting the bias of the support  190  will be described in more detail with reference to  FIG. 11 . 
     Also, the processor  1800  may analyze the light received by the light receiver  1520 , thereby obtaining a coordinate value indicating the position of the pupil feature point and a coordinate value indicating the position of the glint feature point of the eyes. For example, when the light receiver  1520  is an IR camera, the processor  1800  may obtain the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes from the coordinate system of the IR camera. The coordinate system of the IR camera may be used to indicate the position of the pupil feature point and the position of the glint feature point of the eyes, and, for example, coordinate values corresponding to pixels of an image captured by the IR camera on the coordinate system of the IR camera may be previously set. Also, based on a property (e.g., brightness) of IR light received through the IR camera, a coordinate value corresponding to a feature point of the eyes may be identified. 
     For example, when the light receiver  1520  is an IR camera, the processor  1800  may identify the position of the pupil central point in the image captured by the IR camera. The processor  1800  may identify the brightness of IR light received through an image sensor of the IR camera including a plurality of photodiodes, and identify at least one pixel that receives IR light indicating the pupil among the pixels of the image captured by the IR camera, thereby identifying the position of the pupil central point. For example, positions of the pixels in the image captured by an IR camera may be identified through the coordinate system of the IR camera, and the position of the pupil central point may have a coordinate value in the coordinate system of the IR camera, as a position value of at least one pixel corresponding to the pupil central point. 
     For example, the processor  1800  may identify a position of the brightest point in the image captured by the IR camera, in order to identify the glint feature point of the eyes. The processor  1800  may identify the brightness of the IR light received through the image sensor of the IR camera including the plurality of photodiodes, and may identify at least one pixel corresponding to bright IR light equal to or greater than a certain reference among the pixels of the image captured by the IR camera, thereby identifying the position of the glint feature point of the eyes. For example, the processor  1800  may identify the pixel corresponding to the brightest IR light among the pixels of the image captured by the IR camera, thereby identifying the position of the glint feature point of the eyes. For example, the positions of the pixels in the image captured by the IR camera may be identified through the coordinate system of the IR camera, and the position of the glint feature point of the eyes may have the coordinate value in the coordinate system of the IR camera, as a position value of the pixel corresponding to the glint feature point. 
     Alternatively, for example, when the light receiver  1520  is an IR detector, the processor  1800  may calculate the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes in the coordinate system of the IR detector. 
     When the light emitter  1510  is an IR scanner, the processor  1800  may control the IR scanner to sequentially irradiate a point light source ora line light source to cover a region where the user&#39;s eyes are located, and sequentially receive the light reflected from the user&#39;s eyes through the IR detector in order to scan the region where the user&#39;s eyes are located. In addition, the processor  1800  may analyze an array of light sequentially received through the IR detector, thereby identifying the pupil feature point and the glint feature point of the eyes. 
     The coordinate system of the IR detector may be used to indicate the position of the pupil feature point of the pupil and the position of the glint feature point of the eyes, and, for example, coordinate values corresponding to the lights in the array of lights sequentially received through the IR detector on the coordinate system of the IR detector may be previously set. For example, irradiation directions and irradiation times of lights emitted from the IR scanner may be determined according to an operation setting value of the IR scanner, and a light array may be formed from the lights emitted from the IR scanner. For example, based on the irradiation direction and irradiation time of the lights emitted from the IR scanner, and reception time of the lights received from the IR detector, coordinate values corresponding to the lights in the light array on the coordinate system of the IR detector may be identified. In addition, based on the property (e.g., brightness) of the lights in the array of lights sequentially received through the IR detector, light corresponding to the feature point of the eye and coordinate values of the light may be identified. 
     For example, the processor  1800  may identify lights having a brightness equal to or less than a certain value in the received light array, thereby identifying the position of the pupil feature point based on coordinate values corresponding to the identified lights on the coordinate system of the IR detector. 
     For example, the processor  1800  may identify light having a brightness equal to or greater than a certain value in the received light array, thereby identifying a coordinate value corresponding to the identified light on the coordinate system of the IR detector as the coordinate value of the glint feature point of the eyes. 
     Also, for example, when the light receiver  1520  is an IR detector, the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes may be values calibrated by reflecting the degree of bias of the support  190  of the AR device  1000 , which will be described below. In this case, the processor  1800  may calculate the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes calibrated by reflecting the degree of bias of the temple  191  of the AR device  1000  and/or the degree of bias of the nose support  192 . The calibrated coordinate values may be input to a mapping function which will be described below. 
     The processor  1800  may execute the pattern detection code  1740  stored in the storage  1700 , thereby detecting a pattern of the light reflector  1400 . The light reflector  1400  may be coated on one surface of the waveguide  170  of the AR device  1000  to have a certain pattern. The processor  1800  may receive the IR light reflected by the user&#39;s eyes and reflected by the light reflector  1400  through the light receiver  1520 , and identify a shape of the pattern based on the received IR light. The pattern formed on the light reflector  1400  may include, for example, a dot pattern, a line pattern, a grid pattern, a 2D marker, etc., but the disclosure is not limited thereto. An example of the pattern formed on the light reflector  1400  and identified by the pattern detection code  1740  will be described in more detail with reference to  FIGS. 7A to 7D . When the temple  191  is biased with respect to the frame  110 , the pattern identified by the pattern detection code  1740  may have a deformed shape. 
     For example, when the light receiver  1520  is an IR camera, the IR camera may capture the user&#39;s eyes based on the IR light reflected by the light reflector  1400 , and the processor  1800  may identify a pattern within an image obtained by capturing the user&#39;s eyes from the image. 
     For example, when the light receiver  1520  is an IR detector, the IR detector may sequentially receive IR lights reflected by the light reflector  1400 , and the processor  1800  may identify a part related to the pattern of the light reflector  1400  in an array of the sequentially received IR lights. 
     The processor  1800  may execute the bias determination code  1750  stored in the storage  1700 , thereby determining a degree to which the support  190  of the AR device  1000  is biased with respect to the frame  110 . The support  190  may include, for example, the temple  191  and the nose support  192 . When the user wears the AR device  1000 , the temple  191  may be widened or narrowed according to the size of the user&#39;s head and face. At this time, when the IR light is received after the support  190  is biased with respect to the frame  110 , the bias determination code  1750  may identify a pattern having a deformed shape from the received IR light. Also, the bias determination code  1750  may compare the pattern having the deformed shape with a non-deformed pattern, thereby estimating the degree of bias of the support  190 . For example, the bias determination code  1750  may compare the pattern having the deformed shape with the non-deformed pattern to identify degree of deformation of the pattern, and may determine degree of bias of the support  190  based on the degree of deformation of the pattern. Alternatively, the bias determination code  1750  may analyze only the pattern having the deformed shape without comparing the pattern having the deformed shape with the non-deformed pattern, thereby estimating the degree of bias of the support  190 . For example, when the pattern is a dot pattern, the bias determination code  1750  may identify a difference between intervals between points in the pattern having the deformed shape, thereby estimating the degree of bias of the support  190 . 
     For example, the degree of bias of the temple  191  may be expressed as a bias angle indicating a difference between a default angle of the temple  191  with respect to the frame  110  and an angle of the biased temple  191  with respect to the frame  110 , but the disclosure is not limited thereto. Also, for example, the degree of bias of the nose support  192  may be expressed as a bias angle indicating a difference between a default angle of the nose support  192  with respect to the frame  110  and an angle of the biased nose support  192  with respect to the frame  110 , but the disclosure is not limited thereto. 
     In the above, it has been described that the pattern detection code  1740  detects the deformation of the pattern formed on the light reflector  1400 , and the bias determination code  1750  analyzes the pattern having the deformed shape to estimate the degree of bias of the support  190 , but the disclosure is not limited thereto. 
     For example, a certain pattern may be formed on a part of the AR device  1000  that may reflect light emitted from the light emitter  1510  to direct the reflected light toward the light receiver  1520 . For example, the pattern may be formed on a partial region of the frame  110  of the AR device  1000  directed toward the light emitter  1510  and the light receiver  1520 . For example, the pattern may be formed by forming a certain curve in a partial region of the frame  110 . Alternatively, for example, the pattern may be formed by forming a material capable of reflecting light on a partial region of the frame  110 . In addition, the pattern may be attached to or coated on other elements included in the glasses type AR device  1000 , for example, a vision correcting lens for vision correction or a cover glass installed to protect a waveguide. 
     Alternatively, for example, the pattern may be formed on a partial region of the nose support  192  of the AR device  1000  directed toward the light emitter  1510  and the light receiver  1520 . For example, the pattern may be formed by forming a certain curve in a partial region of the nose support  192 . Alternatively, for example, the pattern may be formed by forming a material capable of reflecting light on a partial region of the nose support  192 . In this case, the light emitter  1510  and the light receiver  1520  are preferably located in the temple  191  of the AR device  1000 , but the disclosure is not limited thereto. 
     Alternatively, for example, the pattern may be formed in a partial region of the temple  191  of the AR device  1000  directed toward the light emitter  1510  and the light receiver  1520 . For example, the pattern may be formed by forming a certain curve in a partial region of the temple  191 . Alternatively, for example, the pattern may be formed by forming a material capable of reflecting light on a partial region of the temple  191 . In this case, the light emitter  1510  and the light receiver  1520  are preferably located on the nose support  192  of the AR device  1000 , but the disclosure is not limited thereto. 
     The processor  1800  may execute the pupil position detection code  1760  stored in the storage  1700 , thereby detecting a pupil position of the user&#39;s eyes. The pupil position detection code  1760  may identify the pupil position of the user&#39;s eyes based on the IR light reflected from the light reflector  1400 . 
     For example, when the light receiver  1520  is an IR camera, the pupil position detection code  1760  may identify the pupil position of the user&#39;s eyes within an image captured by the IR camera from the image. Alternatively, for example, when the light receiver  1520  is an IR detector, the pupil position detection code  1760  may analyze the IR light sequentially obtained by the IR detector, thereby calculating the pupil position of the user&#39;s eyes. 
     The pupil position detection code  1760  may identify the pupil central point of the user&#39;s eyes, thereby identifying the pupil position of the user&#39;s eyes. 
     The processor  1800  may execute the gaze determination code  1770  stored in the storage  1700 , thereby obtaining information about the user&#39;s gaze. The processor  1800  may execute the gaze determination code  1770 , thereby calculating a position of the center of the user&#39;s eyes. The center of the user&#39;s eyes may be the center of user&#39;s eyeballs. The processor  1800  may calculate the position of the center of the user&#39;s eyes, based on the pupil position of the user&#39;s eyes obtained by the pupil position detection code  1760  and the degree of bias of the support  190  obtained by the bias determination code  1750 . For example, the processor  1800  may calculate the position of the center of the user&#39;s eyes so that a value calculated based on a matrix for calibrating the degree of bias of the support  190 , a value indicating the position of the center of the user&#39;s eyes and a bias of axis of the image obtained by capturing the user&#39;s eyes can be a value of the pupil position of the user&#39;s eyes obtained by the pupil position detection code  1760 . For example, the center of the eye may be the center of the eyeball, and the position of the center of the user&#39;s eyes may have a 3D coordinate value in a coordinate system of a real space. 
     The processor  1800  may execute the gaze determination code  1770 , thereby calculating a position of the gaze point of the user. In order to calculate the position of the gaze point of the user, the processor  1800  may previously generate a mapping function for calculating the position of the gaze point from features of the user&#39;s eyes. The mapping function is a function for calculating the position of the gaze point of the user in consideration of features of the user&#39;s eyes and bias information of the support  190 , and may be generated during a calibration process of the calibration code  1780  which will be described below. For example, the position of the gaze point may have a 3D coordinate value in the coordinate system in the real space, but the disclosure is not limited thereto. For example, the position of the gaze point may have a coordinate value in the coordinate system of the waveguide  170 , but the disclosure is not limited thereto. 
     The processor  1800  may execute the gaze determination code  1770 , thereby calibrating the features related to the user&#39;s gaze obtained from the eye feature detection code  1730  based on the degree of bias obtained from the bias determination code  1750 . Also, the processor  1800  may apply the features related to the user&#39;s gaze calibrated based on the degree of bias to the mapping function, thereby calculating the position of the gaze point of the user. Also, a gaze direction of the user may be determined based on the position of the central point of the user&#39;s eyes and the gaze point of the user calculated by the gaze determination code  1770 . A method of obtaining the gaze direction of the user by using the gaze determination code  1770  will be described in more detail with reference to  FIG. 11 . 
     Alternatively, the processor  1800  may calculate the gaze point of the user without using the above-described mapping function. For example, when the light receiver  1520  is an IR camera, the gaze determination code  1770  may calculate the gaze direction of the user&#39;s eyes from the image obtained by capturing the user&#39;s eyes by using a certain algorithm. In this case, the obtained gaze direction may be a vector value indicating the gaze direction of the user&#39;s eyes in the camera coordinate system. The algorithm used to obtain the gaze direction of the user&#39;s eyes may be an algorithm for fitting a 3D eye model. The algorithm for fitting the 3D eye model may be an algorithm for obtaining a vector value indicating the gaze direction of the user by comparing an eye image corresponding to a reference vector value indicating the gaze direction of the user with an image captured by an IR camera In addition, the gaze determination code  1770  may convert the vector value indicating the gaze direction in the camera coordinate system into a vector value indicating the gaze direction in the coordinate system of the waveguide 170  by using the bias angle of the temple  191 . Thereafter, the gaze determination code  1770  may calculate an intersection point between a vector indicating the gaze direction in the coordinate system of the waveguide  170  and the waveguide  170 , thereby obtaining the gaze point of the user. 
     The processor  1800  may execute the calibration code  1780  stored in the storage  1700 , thereby calibrating the mapping function based on the bias angle of the support  190 . The processor  1800  may execute the calibration code  1780 , thereby calibrating the mapping function to obtain the gaze point of the user based on a previously set default bias angle and features of eyes. 
     For example, when the light receiver  1520  is an IR camera, the processor  1800  may display a target point for calibration through the waveguide 170 , and capture the user&#39;s eyes looking at the target point by using the IR camera. In addition, the processor  1800  may identify and analyze a pattern within the image obtained by capturing the user&#39;s eyes, thereby obtaining a bias angle of the support  190 . In addition, the processor  1800  may detect positions of the feature points related to the user&#39;s eyes from the image obtained by capturing the user&#39;s eyes, and input the positions of the feature points of the user&#39;s eyes and the bias angle of the support  190  into the mapping function. The processor  1800  may calibrate the mapping function so that a position value of the target point may be output from the mapping function to which the positions of the feature points of the user&#39;s eyes and the bias angle of the support  190  are input. 
     For example, when the light receiver  1520  is an IR detector, the processor  1800  may display the target point for calibration through the waveguide 170  and control the IR scanner to emit IR light for scanning the user&#39;s eyes looking at the target point. In addition, the processor  1800  may receive and analyze IR light reflected from the user&#39;s eyes through the IR detector, identify a pattern of the light reflector  1400 , and estimate the bias angle of the temple  191 . The processor  1800  may analyze the IR light based on the bias angle of the temple  191 , thereby identifying positions of the calibrated feature points of eyes. For example, when the processor  1800  estimates the positions of the feature points of eyes by using the IR scanner and the IR detector, because results of estimating the positions of the feature points of eyes are affected by an operating angle of the IR scanner, the positions of the feature points of eyes may be calibrated based on the bias of the support  190  by calculating a value obtained by subtracting the bias angle of the support  190  from the operating angle of the IR scanner. 
     In addition, the processor  1800  may input the positions of the calibrated feature points of the eyes into the mapping function, and calibrate the mapping function so that the position value of the target point may be output from the mapping function in which the calibrated positions of the feature points of the eyes are input. 
       FIG. 4  is a diagram illustrating an example of operations of the light emitter  1510  and the light receiver  1520  of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 4 , the light emitter  1510  may emit IR light toward the light reflector  1400 , and the emitted IR light may be reflected by the light reflector  1400  and directed toward user&#39;s eyes. In addition, the IR light directed toward the user&#39;s eyes may be reflected back by the user&#39;s eyes and directed toward the light reflector  1400 , and the IR light reflected by the user&#39;s eyes may be reflected back by the light reflector  1400  and directed toward the light receiver  1520 . Also, the light receiver  1520  may receive IR light reflected from the user&#39;s eyes by the light reflector  1400  and directed toward the light receiver  1520 . 
     In  FIG. 4 , for convenience of explanation, it has been described that the AR device  1000  which is a glasses type display device emits IR light toward the user&#39;s left eye and receives reflected IR light from the user&#39;s left eye, but the disclosure is not limited thereto. The AR device  1000  may emit IR light toward the user&#39;s right eye and receive the reflected IR light from the user&#39;s right eye in the same manner as shown in  FIG. 4 . 
       FIG. 5A  is a diagram illustrating an example of the light emitter  1510  that emits planar light according to an example embodiment of the disclosure. 
     Referring to  FIG. 5A , the light emitter  1510  of  FIG. 2  may be an IR LED, and the light receiver  1520  of  FIG. 2  may be an IR camera. In this case, the light emitter  1510  may emit IR light of the planar light toward the light reflector  1400 , and the emitted IR light may be reflected by the light reflector  1400  and directed toward a user&#39;s eye. For example, in order to reflect the light emitted from the IR LED by using the light reflector  1400  and irradiate the light to the region including the user&#39;s eye, the processor  1800  may control an irradiation direction of the IR light emitted from the IR LED, and apply power to the IR LED, thereby controlling emission of the IR light from the IR LED. In addition, the IR light of the planar light reflected by the light reflector  1400  may cover the entire user&#39;s eye. In this case, the light receiver  1520  may be an IR camera, and the IR camera may receive the IR light reflected by the user&#39;s eye, thereby capturing the user&#39;s eye. 
     For example, coordinate values corresponding to pixels of an image captured by the IR camera on the coordinate system of the IR camera may be previously set. In addition, the processor  1800  may identify a coordinate value corresponding to a feature point of the eye based on a property (e.g., brightness) of IR light received through the IR camera. For example, the processor  1800  may identify the brightness of IR light received through an image sensor of the IR camera including a plurality of photodiodes, and identify at least one pixel that receives IR light indicating the pupil among the pixels of the image captured by the IR camera, thereby identifying a coordinate value  51  corresponding to the pupil central point on the IR coordinate system. In this case, the IR light representing the pupil may be an IR light having a brightness lower than a certain value, but the disclosure is not limited thereto. 
     Also, for example, the processor  1800  may identify the brightness of the IR light received through the image sensor of the IR camera including the plurality of photodiodes, and may identify at least one pixel representing the glint feature point of the eye among the pixels of the image captured by the IR camera, thereby identifying a coordinate value  52  corresponding to a glint feature point on the IR coordinate system. In this case, the IR light representing the glint feature point of the eye may be an IR light having a brightness greater than a certain value, but the disclosure is not limited thereto. 
     According to an example embodiment of the disclosure, the light emitter  1510  may be an IR LED that emits blinking light, and in this case, the light reflector  1400  may be an IR event camera. The IR event camera may be an IR camera that is activated when a specific event occurs and automatically captures a subject. The IR event camera may be activated to automatically capture the user&#39;s eye, for example, when patterns of blinking light are different. 
       FIG. 5B  is a diagram illustrating an example of the light emitter  1510  that emits point light according to an example embodiment of the disclosure. 
     Referring to  FIG. 5B , the light emitter  1510  of  FIG. 2  may be an IR scanner, and the light receiver  1520  of  FIG. 2  may be an IR detector. In this case, the light emitter  1510  may emit IR light of a point light toward the light reflector  1400 , and the emitted IR light may be reflected by the light reflector  1400  and directed toward user&#39;s eye. In this case, the light emitter  1510  may sequentially emit IR lights of point light toward the light reflector  1400  while changing an emission direction to a vertical direction or a horizontal direction, and the sequentially emitted IR lights of point light may be reflected by the light reflector  1400  to cover the entire user&#39;s eye. For example, in order to reflect the IR lights of point light sequentially emitted from the IR scanner by using the light reflector  1400  and irradiate the IR lights of point light to a region including the user&#39;s eye, the processor  1800  may control irradiation directions of the IR lights emitted from the IR scanner. In this case, the light emitter  1510  may be a 2-dimensional (2D) scanner and the light receiver  1520  may be at least one photodiode. 
     For example, coordinate values corresponding to the IR lights in the array of lights sequentially received through the IR detector on the coordinate system of the IR detector may be previously set, and the processor  1800  may identify a coordinate value corresponding to a feature point of the eye based on properties (e.g., brightness) of the IR lights in the array of IR lights sequentially received through the IR detector. For example, the processor  1800  may identify coordinate values corresponding to IR lights having a brightness equal to or less than a certain value in the array of the received IR lights on the coordinate system of the IR detector, thereby identifying a coordinate value  53  corresponding to the pupil center point on the IR coordinate system. Also, for example, the processor  1800  may identify coordinate values corresponding to IR lights having a brightness equal to or less than a certain value in the array of the received IR lights on the coordinate system of the IR detector, thereby identifying a coordinate value  54  corresponding to the glint feature point of the eye on the IR coordinate system. 
       FIG. 5C  is a diagram illustrating an example of the light emitter  1510  that emits line light according to an example embodiment of the disclosure. 
     Referring to  FIG. 5C , the light emitter  1510  of  FIG. 2  may be an IR scanner, and the light receiver  1520  of  FIG. 2  may be an IR detector. In this case, the light emitter  1510  may emit IR light of line light toward the light reflector  1400 , and the emitted IR light may be reflected by the light reflector  1400  and directed toward user&#39;s eye. For example, in order to reflect the IR lights of line light sequentially emitted from the IR scanner by using the light reflector  1400  and irradiate the IR lights of point light to a region including the user&#39;s eye, the processor  1800  may control irradiation directions of the IR lights emitted from the IR scanner. In this case, the light emitter  1510  may sequentially emit IR lights of line light toward the light reflector  1400  while changing an emission direction, and the sequentially emitted IR lights of line light may be reflected by the light reflector  1400  to cover the entire user&#39;s eye. In this case, the light emitter  1510  may be a 1-dimensional (1D) scanner and the light receiver  1520  may be a photodiode array including a plurality of photodiodes. When the light receiver  1520  is the photodiode array, it is more preferable that the light receiver  1520  is provided in the temple  191 . For example, when horizontal line light is emitted from the light emitter  1510 , the light emitter  1510  may change the emission direction to a vertical direction to cover the region including the user&#39;s eye, and, when a vertical line light is emitted from the light emitter  1510 , the light emitter  1510  may change the emission direction to the horizontal direction. 
     For example, coordinate values corresponding to the IR lights in the array of lights sequentially received through the IR detector on the coordinate system of the IR detector may be previously set, and the processor  1800  may identify a coordinate value corresponding to a feature point of the eye based on properties (e.g., brightness) of the IR lights in the array of IR lights sequentially received through the IR detector. For example, the processor  1800  may identify line lights of IR light having a brightness greater than or equal to a certain value, and identify a photodiode corresponding to IR light having a brightness less than or equal to the certain value among a plurality of photodiodes that have received the line lights according to the respective line lights, thereby identifying a coordinate value  55  corresponding to the pupil center point on the IR coordinate system. In addition, for example, the processor  1800  may identify line lights of IR light having a brightness greater than or equal to a certain value, and identify a photodiode corresponding to IR light having a brightness less than or equal to the certain value among a plurality of photodiodes that have received the line lights according to the respective line lights, thereby identifying a coordinate value  56  corresponding to the glint feature point of the eye on the IR coordinate system. 
     In  FIGS. 5A to 5C , for convenience of description, an example in which the AR device  1000  which is the glasses type display device, emits IR light toward user&#39;s one eye has been described, but the disclosure is not limited thereto. The AR device  1000  may emit IR light toward the user&#39;s other eye in the same manner as illustrated in  FIGS. 5A to 5C . 
       FIG. 6A  is a diagram illustrating an example in which the light emitter  1510  and the light receiver  1520  are provided in the temple  191  of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 6A , the AR device  1000  of  FIG. 2  may be a glasses type device, and the light emitter  1510  and the light receiver  1520  may be provided on the temple  191  of the AR device  1000 . The light emitter  1510  and the light receiver  1520  may be provided on an inner side part of the temple  191  of the AR device  1000 , which is a position between the temple  191  and user&#39;s eyes. For example, the light emitter  1510  and the light receiver  1520  may be provided at positions spaced from a frame by about 10 mm to 15 mm on an inner side of the temple  191  of the AR device  1000  The light emitter  1510  and the light receiver  1520  may be provided to face the light reflector  1400  in the temple  191  of the AR device  1000 . 
       FIG. 6B  is a diagram illustrating an example in which the light emitter  1510  and the light receiver  1520  are provided in the nose support  192  of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 6B , the AR device  1000  of  FIG. 2  may be a glasses type device, and the light emitter  1510  and the light receiver  1520  may be provided on the nose support  192  of the AR device  1000 . The light emitter  1510  and the light receiver  1520  may be provided on an inner side part of the nose support  192  of the AR device  1000 , which is a position between the nose support  192  and user&#39;s eyes. The light emitter  1510  and the light receiver  1520  may be provided to face the light reflector  1400  in the nose support  192  of the AR device  1000 . 
       FIG. 6C  is a diagram illustrating an example in which the light emitter  1510  and the light receiver  1520  are provided in the temple  191  and the nose support  192  of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 6C , the AR device  1000  of  FIG. 2  may be a glasses type device, the light emitter  1510  may be provided on the temple  191  of the AR device  1000 , and the light receiver  1520  may be provided on the nose support  192  of the AR device  1000 . The light emitter  1510  may be provided on an inner side part of the temple  191  of the AR device  1000 , which is a position between the temple  191  and user&#39;s eyes. The light receiver  1520  may be provided on an inner side part of the nose support  192  of the AR device  1000 , which is a position between the nose support  192  and user&#39;s eyes. The light emitter  1510  and the light receiver  1520  may be provided to face the light reflector  1400  in the AR device  1000 . 
       FIG. 6D  is a diagram illustrating an example in which the light emitter  1510  and the light receiver  1520  are provided in the temple  191  and the nose support  192  of the AR device  1000  according to an example embodiment of the disclosure. 
     Referring to  FIG. 6D , the AR device  1000  of  FIG. 2  may be a glasses-type device, the light emitter  1510  may be provided on the nose support  192  of the AR device  1000 , and the light receiver  1520  may be provided on the temple  191  of the AR device  1000 . The light emitter  1510  may be provided on an inner side part of the nose support  192  of the AR device  1000 , which is a position between the nose support  192  and user&#39;s eyes. The light receiver  1520  may be provided on an inner side part of the temple  191  of the AR device  1000 , which is a position between the temple  191  and user&#39;s eyes. The light emitter  1510  and the light receiver  1520  may be provided to face the light reflector  1400  in the AR device  1000 . 
     In  FIGS. 6A to 6D , it has been described that one light emitter  1510  and one light receiver  1520  are provided in the AR device  1000 , but the disclosure is not limited thereto. For example, a plurality of light emitters  1510  may be provided in the AR device  1000 . In this case, the plurality of light emitters  1510  may be provided on the temple  191 , or the plurality of light emitters  1510  may be provided on the nose support  192 . Alternatively, the plurality of light emitters  1510  may be dividedly provided on the temple  191  and the nose support  192 . 
     Also, for example, the plurality of light receivers  1520  may be provided in the AR device  1000 . In this case, the plurality of light receivers  1520  may be provided on the temple  191 , or the plurality of light receivers  1520  may be provided on the nose support  192 . Alternatively, the plurality of light receivers  1520  may be dividedly provided on the temple  191  and the nose support  192 . 
     In  FIGS. 6A to 6D , for convenience of description, it has been described that the light emitter  1510  and the light receiver  1520  are provided in a left eye part of the AR device  1000 , which is the glasses type display device, but the disclosure is not limited thereto. In the AR device  1000 , the light emitter  1510  and the light receiver  1520  may be provided in a right eye part of the AR device  1000  in the same manner as illustrated in  FIGS. 6A to 6D . 
       FIG. 7A  is a diagram illustrating an example of a dot pattern formed on the light reflector  1400  of the AR device  1000  according to an example embodiment of the disclosure,  FIG. 7B  is a diagram illustrating an example of a grid pattern formed on the light reflector  1400  of the AR device  1000  according to an example embodiment of the disclosure,  FIG. 7C  is a diagram illustrating an example of a pattern in the form of a 2D marker according to an example embodiment of the disclosure, and  FIG. 7D  is a diagram illustrating an example of the light reflector  1400  that covers a part of the waveguide  170  according to an example embodiment of the disclosure. 
     Referring to  FIG. 7A , the dot-shaped pattern may be formed on the light reflector  1400  of the AR device  1000  of  FIG. 2 . Referring to  FIG. 7B , the grid-shaped pattern may be formed on the light reflector  1400  of the AR device  1000  of  FIG. 2 . According to an example embodiment, IR light may not be reflected from a part where the pattern is formed. At this time, because the dot-shaped pattern or the grid-shaped pattern is for detecting bias of a support or a temple of an AR device, it is preferable to have a regular shape. 
     Referring to  FIG. 7C , the pattern formed on a part of the light reflector  1400  of the AR device  1000  of  FIG. 2  at which the user&#39;s gaze is less frequently directed. The formed pattern may be, for example, a pattern in the form of the 2D marker, but the disclosure is not limited thereto. The pattern may be formed on, for example, a part of the light reflector  1400  that does not interfere with capturing or scanning the user&#39;s eyes. 
     Referring to  FIG. 7D , the light reflector  1400  may be formed on a part of the waveguide  170  of the AR device  1000  of  FIG. 2 . For example, the light reflector  1400  may not be located in a part of the waveguide  170  which has little relation to reflection of IR light. 
     For example, when the light receiver  1520  is an IR camera, the IR camera may capture the user&#39;s eyes based on the IR light reflected by the light reflector  1400 , and the IR light may not be reflected from the part where the pattern is formed. For example, a part of an image obtained by capturing the user&#39;s eyes in which the IR light is not reflected may be in black, and the processor  1800  may identify the black part in the image obtained by capturing the user&#39;s eyes, thereby identifying the pattern in the image. 
     For example, when the light receiver  1520  is an IR detector, the IR detector may sequentially receive IR lights reflected by the light reflector  1400 , and the IR light may not be reflected from the part where the pattern is formed. For example, the processor  1800  may identify a part of an IR light array formed by the sequentially received IR lights, from which the IR light is not reflected, thereby identifying the pattern of the light reflector  1400 . 
       FIG. 8A  is a diagram illustrating a light emission angle and a pattern before the temple  191  of the AR device  1000  is biased according to an example embodiment of the disclosure, and  FIG. 8B  is a diagram illustrating a light emission angle and a pattern after the temple  191  of the AR device  1000  is biased according to an example embodiment of the disclosure. 
     Referring to  FIG. 8A , in the glasses type AR device  1000  as shown in  FIG. 2 , before the temple  191  is biased, the light emitter  1510  may emit IR light toward the light reflector  1400  on which a point pattern is formed. According to an example embodiment, the light emitter  1510  may emit IR light toward the light reflector  1400  at a first light emission angle  80 , and a first pattern  82  may be identified by the AR device  1000  based on the IR light received by the light receiver  1520 . 
     In addition, referring to  FIG. 8B , in the glasses type AR device  1000  as shown in  FIG. 2 , after the temple  191  is biased, the light emitter  1510  may emit IR light toward the light reflector  1400  at a second light emission angle  90 , and a second pattern  92  may be identified by the AR device  1000  based on the IR light received by the light receiver  1520 . 
     As shown in  FIGS. 8A and 8B , the first pattern  82  and the second pattern  92  may include dots with different spaces from each other, and the AR device  1000  may compare the first pattern  82  and the second pattern  92 , thereby identifying degree of bias of the temple  191 . For example, a bias angle with respect to the first pattern  82  may be set to ‘0’, and a bias angle with respect to the second pattern  92  may be calculated based on differences in positions between points in the first pattern  82  and points in the second pattern  92 . For example, the bias angle with respect to the second pattern  92  may be a difference value between the first light emission angle  80  and the second light emission angle  90 . For example, when a pattern corresponding to the first light emission angle  80  is the first pattern  82  and a pattern corresponding to the first light emission angle  80  is the second pattern  92 , the processor  1800  may compare spaces of the dots in the first pattern  82  with the spaces of the dots in the second pattern  92 , thereby identifying difference values of the spaces of the dots in the second pattern  92  with respect to the spaces of the dots in the first pattern  82 , and may input the identified difference values into at least one function for calculating degree of bias of the temple  191 , thereby calculating the degree of bias of the temple  191  indicating a difference between the first light emission angle  80  corresponding to the first pattern  82  and the second light emission angle  90  corresponding to the second pattern  92 . 
     In addition, for example, when a pattern corresponding to the first light emission angle  80  is the first pattern  82  and a pattern corresponding to the first light emission angle  80  is the second pattern  92 , the processor  1800  may compare positions of the dots in the first pattern  82  with the positions of the dots in the second pattern  92 , thereby identifying difference values of the positions of the dots in the second pattern  92  with respect to the positions of the dots in the first pattern  82 , and may input the identified difference values into at least one function for calculating degree of bias of the temple  191 , thereby calculating the degree of bias of the temple  191  indicating a difference between the first light emission angle  80  corresponding to the first pattern  82  and the second light emission angle  90  corresponding to the second pattern  92 . 
     According to another example embodiment, the processor  1800  may identify the degree of bias of the temple  191  based on the second pattern  92  without comparing the first pattern  82  and the second pattern  92 . In this case, the processor  1800  may identify the difference values of the spaces of the dots in the second pattern  92 , and input the identified difference values into at least one function for calculating the degree of bias of the temple  191 , thereby calculating the degree of bias of the temple  191 . 
       FIG. 9  is a diagram illustrating an example of a pattern identified from an array of light received through the light receiver  1520  when a light emitter of the AR device  1000  is an IR scanner  1520 - 1  or  1520 - 2  according to an example embodiment of the disclosure. 
     Referring to  FIG. 9 , the IR scanner  1520 - 1  may represent an IR scanner before the support  190  of the glasses type AR device  1000  as shown in  FIG. 2  is biased. The IR scanner  1520 - 1  may sequentially emit IR light of point lint toward a region where user&#39;s eyes are located by using the light reflector  1400 , and the light receiver  1520  may receive a first light array  90 . 
     In addition, the IR scanner  1520 - 2  may represent the IR scanner after the support  190  of the AR device  1000  is biased. The IR scanner  1520 - 2  may sequentially emit IR light of point lint toward the region where user&#39;s eyes are located by using the light reflector  1400 , and the light receiver  1520  may receive a second light array  92 . 
     In the first light array  90  and the second light array  92 , positions and spaces of light signals corresponding to dot patterns of the light reflector  1400  may be different from each other, and the AR device  1000  may compare a part corresponding to the dot pattern of the light reflector  1400  in the first light array  90  and a part corresponding to the dot pattern of the light reflector  1400  in the second light array  92 . Also, the AR device  1000  may identify degree of bias of the support  190  of the AR device  1000  based on results of comparison. 
     For example, because IR light emitted toward the dot pattern is not reflected by the light reflector  1400 , light signal may not be received in parts  90 - 1 ,  90 - 2 ,  90 - 3 , and  90 - 4  of the first light array  90  corresponding to dot patterns and parts  92 - 1 ,  92 - 2 ,  92 - 3 , and  92 - 4  of the second light array  92  corresponding to dot patterns. The processor  1800  may identify parts of the first light array  90  from which no light signal is received, thereby identifying the parts  90 - 1 ,  90 - 2 ,  90 - 3 , and  90 - 4  of the first light array  90  corresponding to the dot patterns, and identifying coordinate values  90 - 5 ,  90 - 6 ,  90 - 7 , and  90 - 8  on a coordinate system of the IR scanner  1520 - 1  respectively indicating the parts  90 - 1 ,  90 - 2 ,  90 - 3 , and  90 - 4  corresponding to the dot patterns. Also, for example, the processor  1800  may identify parts of the second light array  92  from which no light signal is received, thereby identifying the parts  92 - 1 ,  92 - 2 ,  92 - 3 , and  92 - 4 of the second light array  92  corresponding to the dot patterns, and identifying coordinate values  92 - 5 ,  92 - 6 ,  92 - 7 , and  92 - 8  on a coordinate system of the IR scanner  1520 - 2  respectively indicating the parts  92 - 1 ,  92 - 2 ,  92 - 3 , and  92 - 4  corresponding to the dot patterns. 
     The processor  1800  may compare the coordinate values  90 - 5 ,  90 - 6 ,  90 - 7 , and  90 - 8  on the coordinate system of the IR scanner  1520 - 1  respectively indicating the parts  90 - 1 ,  90 - 2 ,  90 - 3 , and  90 - 4  of the first light array  90  corresponding to the dot patterns with the coordinate values  92 - 5 ,  92 - 6 ,  92 - 7 , and  92 - 8  on the coordinate system of the IR scanner  1520 - 2  respectively indicating the parts  92 - 1 ,  92 - 2 ,  92 - 3 , and  92 - 4  of the second light array  92  corresponding to the dot patterns, thereby identifying differences between the coordinate values  90 - 5 ,  90 - 6 ,  90 - 7 , and  90 - 8  and the coordinate values  92 - 5 ,  92 - 6 ,  92 - 7 , and  92 - 8 . For example, the processor  1800  may calculate the degree of bias of the support  190  of the AR device  1000 , based on a difference value between the coordinate value  90 - 5  and the coordinate value  92 - 5 , a difference value between the coordinate value  90 - 6  and the coordinate value  92 - 6 , a difference value between the coordinate value  90 - 7  and the coordinate value  92 - 7 , and a difference value between the coordinate value  90 - 8  and the coordinate value  92 - 8 . 
     In  FIG. 9 , for convenience of description, the IR scanner  1520 - 1  before the support  190  is biased and the IR scanner  1520 - 2  after the support  190  of the AR device  1000  is biased are illustrated separately in  FIG. 9 , in order to distinguish the IR scanner  1520 - 1  before the support  190  of the AR device  1000  is biased from the IR scanner  1520 - 2  after the support  190  of the AR device  1000  is biased. However, the IR scanner  1520 - 1  before the support  190  is biased and the IR scanner  1520 - 2  after the support  190  of the AR device  1000  may be a same IR scanner installed in the AR device  1000 . 
     In addition, in  FIG. 9 , for convenience of description, it has been described that one first light array  90  is used to identify the dot pattern using the IR scanner  1520 - 1  before the support  190  is biased, and one second light array  92  is used to identify the dot pattern using the IR scanner  1520 - 2  after the support  190  of the AR device  1000  is biased, but the disclosure is not limited thereto. A plurality of light arrays for covering the dot pattern may be used to identify the dot pattern using the IR scanner  1520 - 1  before the support  190  is biased, and a plurality of light arrays for covering the dot pattern may be used to identify the dot pattern using the IR scanner  1520 - 2  after the support  190  is biased. 
       FIG. 10  is a diagram illustrating an example of an eye feature identified from an array of light received through the light receiver  1520  when a light emitter of the AR device  1000  is the IR scanner  1520 - 1  or  1520 - 2  according to an example embodiment of the disclosure. 
     Referring to  FIG. 10 , the IR scanner  1520 - 1  before the support  190  of the glasses type AR device  1000  as shown in  FIG. 2  is biased may sequentially emit IR light of point lint toward a region where user&#39;s eyes are located by using the light reflector  1400 , and the light receiver  1520  may receive a third light array  100 . 
     In addition, after the support  190  of the AR device  1000  is biased, the IR scanner  1520 - 2  may sequentially emit IR light of point lint toward the region where user&#39;s eyes are located by using the light reflector  1400 , and the light receiver  1520  may receive a fourth light array  102 . 
     In the third light array  100  and the fourth light array  102 , positions and spaces of light signals corresponding to feature points of eyes may be different from each other. The AR device  1000  may calibrate positions of parts corresponding to the feature points of the eyes from the fourth light array  102  in consideration of a bias angle of the support  190 . 
     For example, the processor  1800  may identify parts  102 - 1  in the fourth light array  102  corresponding to the glint feature points of the eyes, based on brightness of lights in the fourth light array  102 , and identify coordinate values  102 - 2  on the coordinate system of the IR scanner indicating the parts  102 - 1  corresponding to the glint feature points of the eyes. Thereafter, the processor  1800  may calibrate the coordinate values  102 - 2  indicating the glint feature points of the eyes by using the bias angle calculated in  FIG. 9 . For example, the processor  1800  may multiply the coordinate values  102 - 2  representing the glint feature points of the eyes by a compensation matrix  18  of  FIG. 11  which will be described below, thereby obtaining calibrated coordinate values. 
     In  FIG. 10 , for convenience of description, the IR scanner  1520 - 1  before the support  190  is biased and the IR scanner  1520 - 2  after the support  190  of the AR device  1000  is biased are illustrated separately in  FIG. 10 , in order to distinguish the IR scanner  1520 - 1  before the support  190  of the AR device  1000  is biased from the IR scanner  1520 - 2  after the support  190  of the AR device  1000  is biased. However, the IR scanner  1520 - 1  before the support  190  is biased and the IR scanner  1520 - 2  after the support  190  of the AR device  1000  are the same IR scanners installed in the AR device  1000 . 
     In addition, in  FIG. 10 , for convenience of description, it has been described that third light array  100  is used to identify feature points of eyes using the IR scanner  1520 - 1  before the support  190  is biased, and one fourth light array  102  is used to identify feature points of eyes using the IR scanner  1520 - 2  after the support  190  of the AR device  1000  is biased, but the disclosure is not limited thereto. A plurality of light arrays for covering user&#39;s eyes may be used to identify feature points of eyes using the IR scanner  1520 - 1  before the support  190  is biased, and a plurality of light arrays for covering user&#39;s eyes may be used to identify feature points of eyes using the IR scanner  1520 - 2  after the support  190  is biased. 
       FIG. 11  is a diagram illustrating examples of functions used by the AR device  1000  to calculate a center of an eyeball and calculate a gaze point  16  of a user according to an example embodiment of the disclosure. 
     Equation 11 represents a relationship between a coordinate value  12  of a pupil center of the eye in a coordinate system of an IR camera and a coordinate value  13  in real space representing the center of the eyeball. In an example embodiment of the disclosure, the coordinate value  12  of the coordinate system of the IR camera may have a 2D coordinate value, and the coordinate value  13  of the real space may have a 2D coordinate value or a 3D coordinate value. 
     For example, when the coordinate value  13  representing the center of the eyeball is multiplied by a camera rotation matrix  20  and a scale factor and a value representing a bias in an image is added, the coordinate value  12  of the pupil center of the eye may be calculated. The camera rotation matrix  20  is a matrix that converts a coordinate value in real space into a coordinate value of a camera coordinate system in consideration of a position in which a camera is provided. The coordinate value  13  representing the center of the eyeball may be converted into the coordinate value of the coordinate system of the IR camera by multiplying the coordinate value  13  representing the center of the eyeball by the camera rotation matrix  20 , and the size of the converted coordinate value may be normalized by multiplying the converted coordinate value by a scale factor. In addition, by adding a value indicating the bias in the image to the normalized size of the coordinate value, a normalized 2D coordinate value may be corrected by reflecting the bias in the image so that the coordinate value  12  of the pupil center of the eye may be calculated. In addition, the value representing the bias in the image may be used to arrange a position of the eye in an image captured by the IR camera in a reference position. For example, the value representing the bias in the image may be a value for moving a center point of the eye in the captured image to a center point of the captured image, based on a difference between the center point of the image captured by the IR camera and the center point of the eye in the captured image. 
     In an example embodiment of the disclosure, the camera rotation matrix  20 , the scale factor and the value representing the bias in the image may be determined in consideration of, for example, a position in which an IR LED is provided, a position in which the IR camera is provided, a capturing direction of the IR camera, an angle of view of the IR camera, the image captured by the IR camera, information related to the human eye (e.g., eyeball size, pupil size, etc.), previously captured eye images, etc., and may be previously set in the AR device  1000  during manufacturing of the AR device  1000 . 
     In an example embodiment of the disclosure, the AR device  1000  may input the coordinate value  12  of the pupil center of the eye into Equation 11, thereby obtaining the coordinate value  13  representing the center of the eyeball. 
     Equation 15 may represent a relationship between values  17  representing feature points of the eye and the gaze point  16  of the user. For example, the feature points calibrated by reflecting a bias of the support  190  may be obtained by multiplying the values  17  representing the feature points of the eye by a compensation matrix  18 . In addition, a value  19  that is output by inputting a value obtained by multiplying the values  17  representing the feature points of the eye by the compensation matrix  18  into a mapping function F may be a coordinate value  16  representing the gaze point of the user. The compensation matrix  18  may be a matrix for compensating for degree of a bias of the support  190 . The compensation matrix  18  may be determined through comparison between images captured from the IR camera in a state in which the support  190  of the AR device  1000  of  FIG. 2  is not biased and images captured by the IR camera in a state in which the support  190  of the AR device  1000  is biased, and the compensation matrix  18  may be previously set in the AR device  1000  during manufacturing of the AR device  1000 . For example, the compensation matrix  18  may be determined so that the images captured from the IR camera in a state in which the support  190  is biased may be converted into the images captured by the IR camera in a state in which the support  190  is not biased, in consideration of the degree of the bias of the support  190 . However, the example in which the compensation matrix  18  is determined is not limited thereto. 
     For example, the compensation matrix  18  may be determined through comparison between information obtained from the images captured from the IR camera in a state in which the support  190  is not biased and information obtained from the images captured by the IR camera in a state in which the support  190  of the AR device  1000  is biased. Data obtained from an image may include, for example, a size of the image, a position of the eye in the image, a position of the pupil in the image, a position of a pattern in the image, etc., but the disclosure is not limited thereto. 
     Alternatively, for example, the compensation matrix  18  may be determined by comparing the images captured from the IR camera in a state in which the support  190  is not biased and the information obtained from the images captured by the IR camera in a state in which the support  190  of the AR device  1000  is biased. Alternatively, for example, the compensation matrix  18  may be determined by comparing the information obtained from the images captured from the IR camera in a state in which the support  190  is not biased and the images captured by the IR camera in a state in which the support  190  of the AR device  1000  is biased. 
     In addition, the mapping function F, which is a function for calculating the gaze point of the user from the feature points of the eye, may be determined such that the gaze point of the user is calculated from the reward matrix  18  and the feature points of the eye, and may be previously set in the AR device  1000  during manufacturing of the AR device  1000 . 
     The AR device  1000  may obtain the coordinate value  16  representing the gaze point of the user from positions of the feature points of the eye using Equation 15. 
       FIG. 12  is a flowchart of a method, performed by the AR device  1000  of  FIGS. 2 and 3 , of detecting a user&#39;s gaze according to an example embodiment of the disclosure. 
     In operation S 1200 , the AR device  1000  may emit IR light toward the light reflector  1400  through the light emitter  1510  installed on the support  190  extending from the frame  110  of the AR device  1000 . The AR device  1000  may emit the IR light toward at least a partial region of the light reflector  1400  so that the IR light reflected by the light reflector  1400  may cover user&#39;s eyes. 
     For example, when the light receiver  1520  is an IR camera, the light emitter  1510  may be an IR LED, and the AR device  1000  may control the IR LED so that the IR light emitted from the IR LED may be reflected by the light reflector  1400  and may cover the user&#39;s eyes, in order for the IR camera to capture the user&#39;s eyes. Alternatively, for example, when the light receiver  1520  is an IR detector, the light emitter  1510  may be an IR scanner, and the AR device  1000  may control the IR scanner to scan the user&#39;s eyes by reflecting the IR light emitted from the IR scanner by using the light reflector  1400 , so that the IR detector may detect the user&#39;s eyes. 
     In operation S 1205 , the AR device  1000  may receive the IR light reflected by the user&#39;s eye and reflected back by the light reflector  1400 , through the light receiver  1520  installed on the support  190  extending from the frame  110  of the AR device  1000 . 
     For example, when the light emitter  1510  is an IR LED, the light receiver  1520  may be an IR camera, and the AR device  1000  may control the IR camera to capture the user&#39;s eyes through the light reflected by the light reflector  1400  from the user&#39;s eyes. Alternatively, for example, when the light emitter  1510  is an IR scanner, the light receiver  1520  may be an IR detector, and the AR device  1000  may control the IR detector to detect the IR light reflected by the user&#39;s eye and reflected back by the light reflector  1400 , so that the IR detector may detect the user&#39;s eyes. 
     In operation S 1210 , the AR device  1000  may detect previously set features related to the gaze of the user&#39;s eyes based on the received IR light. For example, the AR device  1000  may detect a position of a pupil feature point of the user&#39;s eyes and a position of a glint feature point of the eyes. The pupil feature point may be, for example, a pupil central point, and the glint feature point of the eyes may be a part having brightness greater than or equal to a certain value in a detected eye region. The position of the pupil feature point and the position of the glint feature point of the eyes may be identified, for example, by a coordinate value indicating a position in a coordinate system of the light receiver  1520 . For example, the coordinate system of the light receiver  1520  may be a coordinate system of an IR camera or a coordinate system of the IR detector, and the coordinate value in the coordinate system of the light receiver  1520  may be a 2D coordinate value. 
     The AR device  1000  may detect previously set features related to the gaze of the eyes by analyzing the light received by the light receiver  1520 . For example, when the light receiver  1520  is an IR camera, the AR device  1000  may identify the position of the pupil feature point and the position of the glint feature point of the eyes in an image captured by the IR camera. Alternatively, for example, when the light receiver  1520  is an IR detector, the AR device  1000  may analyze the IR light detected by the IR detector, thereby identifying the position of the pupil feature point and the position of the glint feature point of the eyes. 
     In addition, the AR device  1000  may analyze the light received by the light receiver  1520 , thereby obtaining a coordinate value indicating the position of the pupil feature point and a coordinate value indicating the position of the glint feature point of the eyes. For example, when the light receiver  1520  is an IR camera, the AR device  1000  may obtain the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes from the coordinate system of the IR camera. For example, when the light receiver  1520  is an IR camera, the AR device  1000  may identify the position of the pupil central point in an image captured by the IR camera. For example, the position of the pupil central point may have a coordinate value in the coordinate system of the IR camera. 
     For example, the AR device  1000  may identify a position of the brightest point in the image captured by the IR camera, in order to identify the glint feature point of the eyes. The AR device  1000  may identify the brightness of the IR light received through an image sensor of the IR camera including a plurality of photodiodes, and may identify at least one pixel corresponding to bright IR light equal to or greater than a certain reference among pixels of the image captured by the IR camera, thereby identifying the position of the glint feature point of the eyes. For example, the AR device  1000  may identify the pixel corresponding to the brightest IR light among the pixels of the image captured by the IR camera, thereby identifying the position of the glint feature point of the eyes. For example, the position of the glint feature point of the eyes may have a coordinate value in the coordinate system of the IR camera. 
     Alternatively, for example, when the light receiver  1520  is an IR detector, the AR device  1000  may calculate the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes in the coordinate system of the IR detector. 
     When the light emitter  1510  is an IR scanner, the AR device  1000  may control the IR scanner to sequentially irradiate a point light source ora line light source to cover a region where the user&#39;s eyes are located, and sequentially receive the light reflected from the user&#39;s eyes through the IR detector in order to scan the region where the user&#39;s eyes are located. Also, the AR device  1000  may analyze an array of light sequentially received through the IR detector, thereby identifying the pupil feature point and the glint feature point of the eyes. For example, the AR device  1000  may identify light having a brightness equal to or greater than a certain value in the received light array, thereby identifying a coordinate of the glint feature point of the eyes. For example, the position of the glint feature point of the eyes may have a coordinate value in the coordinate system of the IR detector. 
     In operation S 1215 , the AR device  1000  may detect a pattern of the light reflector  1400  based on the received IR light. The light reflector  1400  may be coated on one surface of the waveguide  170  of the AR device  1000  to have a certain pattern. The AR device  1000  may receive the IR light reflected by the user&#39;s eyes and reflected by the light reflector  1400  through the light receiver  1520 , and identify a shape of the pattern based on the received IR light. The pattern formed on the light reflector  1400  may include, for example, a dot pattern, a line pattern, a grid pattern, a 2D marker, etc., but the disclosure is not limited thereto. When the temple  191  is biased with respect to the frame  110 , the pattern identified by the pattern detection code  1740  may have a deformed shape. 
     For example, when the light receiver  1520  is an IR camera, the IR camera may capture the user&#39;s eyes based on the IR light reflected by the light reflector  1400 , and the AR device  1000  may identify a pattern within an image obtained by capturing the user&#39;s eyes from the image. For example, when the light receiver  1520  is an IR detector, the IR detector may sequentially receive IR lights reflected by the light reflector  1400 , and the AR device  1000  may identify a part related to the pattern of the light reflector  1400  in an array of the sequentially received IR lights. 
     In operation S 1220 , the AR device  1000  may determine a degree to which the support  190  of the AR device  1000  is biased with respect to the frame  110 . When the IR light is received after the support  190  is biased with respect to the frame  110 , the AR device  1000  may identify a pattern having a deformed shape from the received IR light. Also, for example, as in  FIGS. 8A and 8B , the AR device  1000  may compare the pattern having the deformed shape with a non-deformed pattern, thereby estimating the degree of bias of the support  190 . For example, the degree of bias of the temple  191  may be expressed as a bias angle indicating a difference between a default angle of the temple  191  with respect to the frame  110  and an angle of the biased temple  191  with respect to the frame  110 , but the disclosure is not limited thereto. Also, for example, the degree of bias of the nose support  192  may be expressed as a bias angle indicating a difference between a default angle of the nose support  192  with respect to the frame  110  and an angle of the biased nose support  192  with respect to the frame  110 , but the disclosure is not limited thereto. 
     Also, for example, when the light receiver  1520  is an IR detector, the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes may be values calibrated by reflecting the degree of bias of the support  190  of the AR device  1000 . When the light receiver  1520  is an IR detector, for example, when the coordinate values  102 - 2  corresponding to the IR lights  102 - 1  corresponding to the feature points of the eyes in the light array  102  of  FIG. 10  are calculated, the degree of bias of the support  190  may be reflected. For example, the AR device  1000  may calibrate positions of the lights  102 - 1  corresponding to the feature points of the eyes in the light array  102  among the lights in the light array  102  received by the IR detector, by reflecting the degree of bias of the support  190 . The AR device  1000  may directly calculate the coordinate values  102  corresponding to the feature points of the eyes in the coordinate system of the IR detector, based on the calibrated positions of the lights  102 - 1  corresponding to the feature points of the eyes in the light array  102 . In this case, the AR device  1000  may calculate the coordinate value of the pupil feature point and the coordinate value of the glint feature point of the eyes calibrated by reflecting the degree of bias of the temple  191  of the AR device  1000  and/or the degree of bias of the nose support  192 . The calibrated coordinate values may be input to a mapping function. 
     In operation S 1225 , the AR device  1000  may identify the pupil position of the user&#39;s eyes based on the IR light reflected from the light reflector  1400 . For example, when the light receiver  1520  is an IR camera, the AR device  1000  may identify the pupil position of the user&#39;s eyes within an image captured by the IR camera from the image. Alternatively, for example, when the light receiver  1520  is an IR detector, the AR device  1000  may analyze the IR light sequentially obtained by the IR detector, thereby calculating the pupil position of the user&#39;s eyes. The AR device  1000  may identify the pupil central point of the user&#39;s eyes, thereby identifying the pupil position of the user&#39;s eyes. 
     In operation S 1230 , the AR device  1000  may obtain a gaze direction of the user. The AR device  1000  may calculate a position of the center of the user&#39;s eyes. The center of the user&#39;s eyes may be the center of user&#39;s eyeballs. The AR device  1000  may calculate the position of the center of the user&#39;s eyes, based on the pupil position of the user&#39;s eyes and the degree of bias of the support  190 . For example, the processor  1800  may calculate the position of the center of the user&#39;s eyes so that a value calculated based on a matrix for calibrating the degree of bias of the support  190 , a value indicating the position of the center of the user&#39;s eyes and a bias of axis of the image obtained by capturing the user&#39;s eyes can be a value of the pupil position of the user&#39;s eyes obtained by the pupil position detection code  1760 . For example, the center of the eye may be the center of the eyeball, and the position of the center of the user&#39;s eyes may have a 3D coordinate value in a coordinate system of a real space. 
     The AR device  1000  may calculate a position of the gaze point of the user. In order to calculate the position of the gaze point of the user, the AR device  1000  may previously generate a mapping function for calculating the position of the gaze point from features of the user&#39;s eyes. The mapping function is a function for calculating the position of the gaze point of the user in consideration of features of the user&#39;s eyes and bias information of the support  190 , and may be generated during a calibration process of the calibration code  1780 . For example, the position of the gaze point may have a 3D coordinate value in the coordinate system in the real space, but the disclosure is not limited thereto. For example, the position of the gaze point may have a coordinate value in the coordinate system of the waveguide  170 , but is not limited thereto. 
     The AR device  1000  may calibrate the features related to the user&#39;s gaze based on the degree of bias obtained from the bias determination code  1750 . Also, the AR device  1000  may apply the features related to the user&#39;s gaze calibrated based on the degree of bias to the mapping function, thereby calculating the position of the gaze point of the user. Also, a gaze direction of the user may be determined based on the position of the central point of the user&#39;s eyes and the gaze point of the user calculated by the gaze determination code  1770 . 
     Meanwhile, the AR device  1000  may calibrate the mapping function based on the bias angle of the support  190 . The AR device  1000  may calibrate the mapping function for obtaining the gaze point of the user based on a default bias angle and features of eyes. 
     For example, when the light receiver  1520  is an IR camera, the AR device  1000  may display a target point for calibration through the waveguide 170 , and capture the user&#39;s eyes looking at the target point by using the IR camera. In addition, the processor  1800  may identify and analyze a pattern within the image obtained by capturing the user&#39;s eyes, thereby obtaining a bias angle of the support  190 . In addition, the AR device  1000  may detect positions of the feature points related to the user&#39;s eyes from the image obtained by capturing the user&#39;s eyes, and input the positions of the feature points of the user&#39;s eyes and the bias angle of the support  190  into the mapping function. The AR device  1000  may calibrate the mapping function so that a position value of the target point may be output from the mapping function to which the positions of the feature points of the user&#39;s eyes and the bias angle of the support  190  are input. 
     For example, when the light receiver  1520  is an IR detector, the AR device  1000  may display the target point for calibration on the waveguide 170  and control the IR scanner to emit IR light for scanning the user&#39;s eyes looking at the target point. In addition, the AR device  1000  may receive and analyze IR light reflected from the user&#39;s eyes through the IR detector, identify a pattern of the light reflector  1400 , and estimate the bias angle of the temple  191 . The AR device  1000  analyze the IR light based on the bias angle of the temple  191 , thereby identifying positions of the calibrated feature points of eyes. For example, when the AR device  1000  estimates the positions of the feature points of eyes by using the IR scanner and the IR detector, because results of estimating the positions of the feature points of eyes are affected by an operating angle of the IR scanner, the positions of the feature points of eyes may be calibrated based on the bias of the support  190  by calculating a value obtained by subtracting the bias angle of the support  190  from the operating angle of the IR scanner. 
     In addition, the AR device  1000  may input the positions of the calibrated feature points of the eyes into the mapping function, and calibrate the mapping function so that the position value of the target point may be output from the mapping function in which the calibrated positions of the feature points of the eyes are input. 
     An example embodiment of the disclosure may be implemented as a recording medium including computer-readable instructions such as a computer-executable program module. According to an example embodiment, the computer-readable instructions may be computer codes, which are implemented as one or more computer-executable program modules. A computer-readable medium may be any available medium which is accessible by a computer, and may include a volatile or non-volatile medium and a removable or non-removable medium. Also, the computer-readable medium may include computer storage medium and communication medium. The computer storage media include both volatile and non-volatile, removable and non-removable media implemented in any method or technique for storing information such as computer readable instructions, data structures, program codes, program modules or other data. The communication medium may typically include computer-readable instructions, data structures, or other data of a modulated data signal such as program modules. 
     A computer-readable storage medium may be provided in a form of a non-transitory storage medium. Here, the term ‘non-transitory storage medium’ refers to a tangible device and does not include a signal (e.g., an electromagnetic wave), and does not distinguish between a case where data is stored in a storage medium semi-permanently and a case where data is stored temporarily. For example, the non-transitory storage medium may include a buffer in which data is temporarily stored. 
     According to an example embodiment of the disclosure, the method according to various embodiments of the disclosure disclosed herein may be included in a computer program product and provided. The computer program product may be traded between a seller and a purchaser as a commodity. The computer program product may be distributed in a form of a machine-readable storage medium (e.g., compact disk read only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) through an application store (e.g., PlayStore™) or directly between two user devices (e.g., smart phones). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) may be temporarily stored in a machine-readable storage medium such as a manufacturer&#39;s server, an application store&#39;s server, or a memory of a relay server. 
     In addition, in the specification, the term “unit” may be a hardware component such as a processor or a circuit, and/or a software component executed by a hardware component such as a processor. 
     Also, in the specification, the expression “include at least one of a, b or c” means “include only a”, “include only b”, “include only c”, “include a and b”, “include b and c”, “include a and c”, or “include a, b, and c”. 
     The above-described description of the disclosure is provided only for illustrative purposes, and those of skill in the art will understand that the disclosure may be easily modified into other detailed configurations without modifying technical aspects and essential features of the disclosure. Therefore, it should be understood that the above-described embodiments are exemplary in all respects and are not limited. For example, the elements described as single entities may be distributed in implementation, and similarly, the elements described as distributed may be combined in implementation. 
     The scope of the disclosure is not defined by the detailed description of the disclosure but by the following claims, and all modifications or alternatives derived from the scope and spirit of the claims and equivalents thereof fall within the scope of the disclosure.