Patent Publication Number: US-11647822-B2

Title: Diffuser and hair dryer having a diffuser

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2020-0044035, filed in Korea on Apr. 10, 2020, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a diffuser and a hair dryer including a diffuser. 
     2. Background 
     When removing moisture from wet hair or when styling hair, a hair dryer that discharges gas through a gas outlet may be used. In one example, the hair dryer may provide air or gas having certain characteristics desired by a user, such as a desired gas temperature, a desired gas speed, and a desired gas flow shape or area, through a diffuser. The diffuser may be coupled to a main body of the hair dryer to change the gas characteristics. Further, the diffuser may include a care device such as massage protrusions or bristles to manage scalp health and the like. 
     Korean Utility Model Application Publication No. 20-2011-0002484 discloses a diffuser provided in a hair dryer and having a massage protrusion to treat a user&#39;s scalp and hair. The diffuser may discharge air or gas while caring for a scalp or in facilitating hair styling. 
     A human head may be a curved surface. In order to provide effective care to the user, designing a diffuser in consideration of an efficient or ergonomic shape in consideration of a user&#39;s head becomes an important task in this technical field. 
     The above reference is incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
         FIG.  1    is a view showing a hair dryer according to an embodiment; 
         FIG.  2    is a view showing a diffuser separated from a hair dryer according to an embodiment; 
         FIG.  3    is a view showing an internal cross-section of the hair dryer shown in  FIG.  2   ; 
         FIG.  4    is a view showing a gas or air outlet in a hair dryer according to an embodiment; 
         FIG.  5    is a view showing a diffuser according to an embodiment; 
         FIG.  6    is a view showing an exploded view of a diffuser according to an embodiment; 
         FIG.  7    is a view showing an internal cross-section of a diffuser according to an embodiment; 
         FIG.  8    is a view showing a diffuser according to an embodiment when viewed from the front; 
         FIG.  9    is a view showing a first portion formed on a diffuser according to an embodiment viewed from the side; and 
         FIG.  10    is a view showing a second portion formed on a diffuser according to an embodiment viewed from the side. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS.  1 - 3   , the hair dryer  100  may include a main body  110 , a handle  180 , and a diffuser  200  as shown in  FIG.  1   . In addition, as shown in  FIG.  2   , the main body  110  may include a gas or air outlet  150  through which gas or air introduced from outside is discharged. 
     As shown in  FIG.  3   , the main body  110  may include a gas or air flow path  111  through which the introduced gas flows. The gas inside of the gas flow path  111  may be discharged through the gas outlet  150  to the outside. The main body  110  may have an extended shape along a front-rear direction and may have various cross-sectional shapes such as circular, elliptical, stadium, or polygonal shapes when viewed from the front. 
     In the present disclosure, front, rear, left, right, top, and bottom definitions may be made centering on the main body  110 . Referring to  FIG.  2   , the gas outlet  150  may be provided at a front side of the main body  110 , and the handle  180  may have a shape extending substantially downward from the main body  110 . 
     The gas flowing inside the main body  110  may be introduced through a gas inlet, which may be provided on the handle  180  (as shown in  FIG.  3   ) or alternatively on the main body  110  (for example, at a rear of the main body  110 ). As shown in  FIGS.  1  to  3   , when the gas inlet is provided on the handle  180 , the gas flow path  111  may extend from gas inlet formed in the handle  180  toward the gas outlet  150  of the main body  110 , or upward and frontward. The gas may be introduced or suctioned from the outside through the gas inlet, and the introduced gas may flow along the gas flow path  111  and be discharged to the outside through the gas outlet  150 . 
     The handle  180  may be a portion of the hair dryer  100  grabbed by a hand of a user, and may have a shape that improves grip convenience. The handle  180  may extend downward from the main body  110 , as illustrated in  FIGS.  1  to  3   , but embodiments disclosed herein are not limited to a downward handle  180 . The handle  180  may be integrally molded with the main body  110 , or separately manufactured from the main body  110  and later coupled to the main body  110 . 
     When the handle  180  is manufactured separately from the main body  110  and later coupled to the main body  110 , the handle  180  may be provided such that a longitudinal direction thereof with respect to the main body  110  is fixed or variable. For example, the handle  180  may have a hinge coupling portion or hinge structure, and may be coupled to the main body  110  such that the longitudinal direction of the handle  180  is changeable (e.g., foldable) relative to the main body  110  so as to make grasping and/or styling convenient. 
     The extending direction of the handle  180  may vary. However, for convenience of description below, the direction in which the handle  180  extends from the main body  110  will be described as a downward direction. 
     Referring to  FIG.  3   , the hair dryer  100  according to an embodiment may include a fan  119  capable of moving (e.g., suctioning and/or discharging) gas or air and adjusting a speed of the gas or air discharged through the gas outlet  150 . The fan  119  may be provided in the gas flow path  111  to blow the gas. The fan  119  may be provided inside the handle  180  (as illustrated) or alternatively inside of the main body  110  (e.g., a rear of the main body  110 ). 
     The fan  119  may be provided near or adjacent to the gas inlet. For example, when the gas inlet is provided in the handle  180 , the gas flow path  111  may extend from the gas inlet of the handle  180  to the gas outlet  150 , and the fan  119  may be provided in a portion of the gas flow path  111  located in the handle  180 . 
     A temperature adjuster  117  (e.g., a heater or cooler) may be provided inside of the main body  110  (or alternatively, the handle  180 ) to adjust a temperature of the discharged gas. The temperature adjuster  117  may be provided in various forms and may be provided at various positions. In  FIG.  2   , the temperature adjuster  117  is provided inside the main body  110 . 
     In addition, the temperature adjuster  117  may be provided in various types. The temperature adjuster  117  may use a heating scheme by providing current to a coil-shaped resistor to generate heat. However, the resistor of the temperature adjuster  117  may not necessarily be in the shape of the coil, and may be provided in various types, such as a thermoelement capable of heating the gas or adjusting the temperature of the gas. As another example, the temperature adjuster  117  may include a thermoelectric cooler (TEC) or Peltier device to provide cool air. 
     A method for operating the hair dryer  100  according to an embodiment of the present disclosure will be schematically described with respect to gas or air flow. 
     First, the user may manipulate or operate a power button provided on the main body  110  or the handle  180 . When the power button is turned on, the fan  119  may be operated, and gas may be introduced or suctioned into the hair dryer  100 . 
     The gas introduced through the gas inlet flows along the gas flow path  111  via the fan  119  toward the gas outlet  150 , and the gas is discharged through the gas outlet  150  to the user. In this process, a flow speed of the gas along the gas flow path  111  may be adjusted by the fan  119 , and a temperature of the gas flowing along the gas flow path  111  may be adjusted by the temperature adjuster  117 . 
     In one example, the hair dryer  100  according to an embodiment may include a controller  115 . The controller  115  may be connected not only to the fan  119 , the temperature adjuster  117 , the power button, and a manipulator or user interface to select a desired temperature or flow speed, but also to a light irradiator or light  260  ( FIG.  6   ), a proximity sensor  269  ( FIG.  6   ), a moisture measurement protrusion or sensor  312  ( FIG.  6   ), and the like, which may be provided on the diffuser  200  and to be described later. The controller  115  may control the above described components. 
     The controller  115  may be provided on one of the diffuser  200 , the main body  110 , or the handle  180 . Alternatively, a plurality of controllers  115  may be respectively arranged on all of the diffuser  200 , the main body  110 , and the handle  180 . As indicated in  FIG.  3   , the controller  115  may be provided on the main body  110  to be signally connected to the diffuser  200 , or, as indicated by the dotted lines in  FIG.  1   , a plurality of controllers  115  may be respectively arranged on the diffuser  200  and the main body  110 . 
     Adjusting operating states of the fan  119  and the temperature adjuster  117  may be performed by manipulation of the manipulator or user interface by the user or may be automatically performed based on an operation mode preset or predetermined in the controller  115 . In addition, when a distance to a target located in front of the diffuser  200  is identified to be equal to or less than a reference or predetermined distance through the proximity sensor  269  of the diffuser  200 , the controller  115  may control the light irradiator  260  of the diffuser  200  to irradiate light ( FIG.  6   ). 
     The controller  115  may identify an impedance of the target located in front of the diffuser  200  through the moisture measurement protrusion  312  of the diffuser  200 , and determine a moisture amount of the target through the impedance. As the moisture amount increases, the controller  115  may control the fan  119  such that the speed of the gas discharged through the gas outlet  150  increases, control the temperature adjuster  117  such that the gas temperature increases, or control the light irradiator  260  such that a light amount of the light irradiator  260  increases. 
     As shown in  FIG.  1  or  3   , the main body  110 , where the gas outlet  150  is provided, may have a cross-section in an approximately circular shape and may have a front-rear length that is longer than a left-right width or diameter of the cross-section. However, the cross-section shape of the main body  110  may be varied as needed. 
     The gas outlet  150  of the hair dryer  100  according to an embodiment of the present disclosure will be described in detail with reference to  FIG.  3   . At least a portion of the gas flow path  111  may be defined inside the main body  110 , and at least one side of the main body  110  may be opened or have an opening. For example, the main body  110  may extend in the front and rear direction, and a front surface thereof may be opened at a front end  112  ( FIG.  4   ). The front end  112  may be a wall or front rim defining a front opening. The front opening of the main body  110  may be in communication with the gas flow path  111 . The gas outlet  150  may be defined by an inner rim or surface of the front end  112 . The front opening of the main body  110  may correspond to an end of the gas flow path  111 , and the end of the gas flow path  111  may correspond to the gas outlet  150 . 
     Referring to  FIG.  4   , in one example, the gas outlet  150  may include a discharge base or disc  152 , which may be provided at the front opening of the main body  110 . The discharge base  152  may be concentric with or provided inside of the front end  112 . An outer edge of the discharge base  152  may be spaced apart from the front end  112  to define a side portion or opening  156  therebetween. The discharge base may have a center portion or opening  154 . Gas may be discharged through the side and center openings  154  and  156 , which may alternatively be referred to as outer and inner openings. The gas flowing along the gas flow path  111  may be simultaneously delivered to the center opening  154  and the side opening  156  to be discharged to the outside. 
     The center opening  154  and the side opening  156  may correspond to discharge holes through which the gas is discharged from the gas outlet  150 . The center opening  154  may be defined at a central side on the cross-section of the gas outlet  150 , and a cross-sectional shape thereof may be circular. However, embodiments disclosed herein are not limited to circular cross-sections, and a shape of the center opening  154  may be a polygonal shape such as a square as needed, and a size of a diameter, width, or cross-sectional area thereof may also be varied as needed. 
     The side opening  156  may surround the center opening  154 . For example, as shown in  FIG.  4   , the center opening  154  may be defined in a substantially circular shape at the center of the discharge base  152  and/or a center of the entire gas outlet  150 , and the side opening  156  may be an opening in a shape of a ring surrounding the discharge base  152 . The ring shape may have an extended shape and/or a closed curve shape. For example,  FIG.  4    discloses the side opening  156  having a circular ring shape. However, the ring shape of the side opening  156  may not necessarily be circular, and may be, for example, a polygonal ring shape such as a triangle or a square. 
     An optional guide cone  155  may be provided inside of the center opening  154  such that gas flows through a ring-shaped opening defined between, on the one hand, an inner side of the discharge base  152  defining the center opening  154 , and, on the other hand, an outer surface of the guide cone  155 . Details of the discharge base  152  and guide cone  155  will be described later. Like the shape of the side opening  156 , the shape of the portion of the center opening  154  outside of the guide cone  155  is not limited to a circular ring shape, and may be, for example, a polygonal ring shape such as a triangle or a square. 
     The center opening  154  and the side opening  156  may be in communication with a same portion of the gas flow path  111 . The center opening  154  may be concentric with the side opening  156 . 
     A cross-sectional area of the entirety of the discharged gas may correspond to a size of an entire cross-section formed by the front end  112 . However, the discharge base  152  may block a portion of the gas flowing through the gas outlet  150 . The discharged gas may be diffused while flowing through the side opening  156 , and a portion of the gas flow may be distributed toward a center of the cross-section where the gas is not discharged (i.e., toward the discharge base  152 ), and thus, the cross-sectional area of the discharge gas may be reduced. 
     Accordingly, the center opening  154  may be defined at a center of the side opening  156 , and the gas of the side opening  156  that is distributed toward the center of the discharge base  152  may be suppressed by gas discharged through the center opening  154 . The gas flowing through the center opening  154  may suppress the gas flowing through the side opening  156  and prevent the gas flowing through the side opening  156  from being distributed toward the center of the gas outlet  150 , so that it may be advantageous for the entire discharged gas to maintain an initial cross-sectional area thereof. 
     Gas flowing through the center and side openings  154  and  156  may have a large cross-sectional area, facilitating a drying process. For example, an entire volume of gas discharged through the center opening  154  and the side opening  156  may be sufficient to allow the user to dry a larger area. 
     Since the center opening  154  and the side opening  156  may be in communication with the same cross-sectional area of the gas flow path  111 , there may not necessarily be separate gas flow paths  111  for the center opening  154  and the side opening  156 . Thus, provided three-dimensional gas discharge to the user may be efficient. 
     The center opening  154  may be defined at a center of the discharge base  152 , and the side opening  156  may be defined between an outer circumferential surface of the discharge base  152  and the front end  112  of the main body  110 , which may be a wall or rim defining the front opening. 
     The discharge base  152  may be coupled to the front end  112  of the main body  110  and may have a same cross-sectional shape of the front opening, but embodiments disclosed herein are not be limited thereto and may be formed in various shapes or materials. For example, the discharge base  152  may be provided to be partially different from the shape of the front opening of the main body  110  to determine the shape of the side opening  156 , and may be molded with a material that is the same as or different from a material of the front end  112  or outer wall of the main body  110 . 
     The discharge base  152  may constitute an entirety or a portion of one surface (e.g., the front surface) of the main body  11 , so that the center opening  154  may be defined at the center of the discharge base  152 , and the side opening  156  may be defined between the outer circumferential surface of the discharge base  152  and the front end  112  of the main body  110 . 
     The discharge base  152  may be coupled to an opening of the main body  110  in various schemes, such as a scheme using a plurality of coupling ribs and/or may be integrally molded with the main body  110 . 
     In one example, as shown in  FIG.  4   , the discharge base  152  may be indented or recessed toward an interior of the main body  110  from the front end  112  such that a front rim of the front end  112  protrudes further forward than a front surface of the discharge base  152 . 
     Furthermore, a center of the front surface of the discharge base  152  may be indented or recessed toward the interior of the main body  110  such that the front surface of the discharge base  152  may form a curved or bent surface. Accordingly, the gas discharged through the center opening  154  may be discharged upstream or before the gas discharged through the side opening  156 . 
     When the gas discharged through the center opening  154  starts to be diffused prior to the gas discharged through the side opening  156 , the cross-sectional area of the gas discharged through the central opening  154  may be increased through diffusion, and may suppress a flow of the gas discharged through the side opening  156  toward a center. Further, a curvature of the curved surface of the front surface of the discharge base  152  may be variously set as necessary to prevent or reduce turbulence. 
     A guide cone  155  may be provided at a center of the center opening  154  to guide a flow of the gas discharged through the center opening  154 . The gas may be discharged between an inner surface of the center opening  154  and the guide cone  155 . 
       FIG.  4    illustrates the guide cone  155  provided at the center of the center opening  154 . As the guide cone  155  is provided, the gas flowing through the center opening  154  is discharged into a space between the inner surface of the center opening  154  and an outer surface of the guide cone  155 . 
     When the guide cone  155  is provided at the center of the center opening  154 , the gas may flow through an outer portion of the center opening  154 , which may be a ring-shaped discharge hole. The gas discharged through the center opening  154  may have a ring-shaped cross-section. 
     The gas discharged through the center opening  154  may contribute to suppressing a reduction of a cross-sectional area of the gas discharged through the side opening  156  by blocking some gas discharged through the side opening  156  from flowing toward inward toward a center in the flow process. In addition, the guide cone  155  may increase a level or speed at which the gas discharged through the center opening  154  diffuses outward. 
     When the cross-sectional area of the gas discharged through the center opening  154  is increased due to the guide cone  155 , the suppression of inward flow of gas discharged through the side opening  156  may be increased. 
     In one example, in the guide cone  155 , a rear end protruding toward the gas flow path  111  and a front end protruding in a discharge direction of the gas of the center opening  154  may respectively have conical shapes. The conical shape may mean a shape in which a cross-sectional area has a circular or elliptical shape, and where a diameter or width of the circle gradually decreases as a length increases. 
     However, in the conical shape, the circular shape of the cross-sectional area is not limited to perfect circles and may have, for example an ellipse or stadium shape. Furthermore, a reduction in the diameter may not necessarily be constant; for example, a diameter reduction rate may gradually increase or gradually decrease. 
     As the front end of the guide cone  155  protrudes in the conical shape, the gas discharged through the center opening  154  may be increasingly concentrated toward a rim of the center opening  154 . Thus, a flow of the gas discharged through the side opening  156  and flowing toward the center opening  154  may be further suppressed. 
     An outer circumferential surface of the guide cone  155  may have a shape or size corresponding to an inner circumferential surface of the center opening  154 , and a separation distance between the outer circumferential surface of the guide cone  155  and the inner circumferential surface of the center opening  154  may be varied as needed. Further, the guide cone  155  may be made of a material the same as or different from the material of the discharge base  152 , and a curvature of the outer surface thereof may be variously designed as needed. 
     In one example, the gas outlet  150  may further include a discharge guide ring. The discharge guide ring may be provided on the inner surface of the center opening  154  and protrude in the discharge direction of the gas discharged through the center opening  154  to guide the gas flow together with the guide cone  155 .  FIG.  4    illustrates that the guide cone  155  and the discharge guide ring may be arranged in the center opening  154 . 
     The discharge guide ring may have a ring shape extending along the rim of the center opening  154 , and may be integrally molded with the discharge base  152  or molded separately from the discharge base  152  to be later coupled to the inner circumferential surface of the center opening  154 . 
     The discharge guide ring may protrude outward or forward and rearward from the center opening  154  or the discharge base  152  and/or protrude based on the gas discharge direction. The flow of the gas through the center opening  154  may be concentrated between the guide cone  155  and the discharge guide ring by the guide cone  155  and the discharge guide ring protruding from the center opening  154 . A protruding end of the discharge guide ring may have a curved shape to facilitate the gas flow. A diameter of the discharge guide ring may be different for each portion, and a shape thereof may also be varied as needed. The front end  112  of the main body  110  may include a first coupling member  120  described later. 
     Referring to  FIGS.  5  and  6   , the diffuser  200  may be removably coupled to the main body  110  so that the gas discharged from the gas outlet  150  may be introduced into the diffuser  200  and to be discharged to the outside of the hair dryer  100 . The diffuser  200  may alternatively be referred to as a head or nozzle head. 
     The diffuser  200  may be coupled to the main body  110  such that a rear side thereof covers the gas outlet  150 , and the gas discharged from the gas outlet  150  may flow into the diffuser  200  through a gas inlet hole  215  defined at a rear side of the diffuser  200 . 
     The user may selectively use the diffuser  200  for scalp or hair management. For example, the user may use a diffuser  200  including a massage protrusion or bristle  310  and a light irradiator or light  260 , which will be described later, for scalp care. The user may also use the same diffuser  200  to dry hair, and a shape of the diffuser  200  may be configured such that a flow of a cross-sectional area of the gas is increased as needed in a hair drying step. 
     The rear side of the diffuser  200  may be coupled to the front end  112  of the main body  110 . A first coupling portion or member  120  ( FIG.  4   ) may be provided at the front end  112  of the main body  110 , and a second coupling portion or member  220  configured to be coupled to the first coupling portion  120  may be provided at the rear side of the diffuser  200 . 
     A coupling scheme between the diffuser  200  and the main body  110  may vary. The diffuser  200  may be coupled to the main body  110  in a scheme such as screw coupling, fitting coupling, magnetic coupling, or sliding coupling to receive the gas from the main body  110 . 
     An embodiment of the present disclosure may improve ease of use of the user as the diffuser  200  is provided to be removable from the main body  110 . For example, the user may remove the diffuser  200  when the user desires to use more concentrated gas discharged directly from the gas outlet  150  of the main body  110 . Further, the user may add the diffuser  200  to the main body  110  when the user wants a more diffused or dispersed flow of gas. 
     The diffuser  200  may include a diffusing case  210  and a discharge or diffuser cover  300 . The diffusing case  210  and a discharge cover  300  may form an exterior of the diffuser  200 . 
     The diffuser may have a curved bell shape or hat shape. An inner diameter of the diffuser  200  may increase in a forward direction. An internal cross-sectional area of the diffusing case  210  and discharge cover  300  increases from a rear side or end  212  to a front side or rim  211 . 
     Accordingly, gas delivered from the gas outlet  150  may be provided to the user in a state in which a flow cross-sectional area thereof is increased as the gas speed is reduced in the forward direction of the diffuser  200 . The user may use the diffuser  200  for natural drying, styling, etc. for hair. 
     The front side  211  of the diffusing case  210  may be opened to define an open front surface. An entirety or a portion of the front surface of the diffusing case  210  may define the open surface. The gas present inside the diffuser  200  may be discharged to the outside through the open surface of the diffusing case  210  and be provided to the user while being discharged forward through the front side  211 . 
     The open surface defined at the front side  211  of the diffusing case  210  may be exposed to the outside, or the discharge cover  300  may be provided to be coupled to the open surface. 
       FIG.  5    shows a state in which the discharge cover  300  is coupled to the open surface. The discharge cover  300  may include at least one gas discharge hole  305  defined therein through which the gas may be discharged. The discharge cover  300  may have a shape corresponding to the open surface of the diffusing case  210  and may be coupled to the diffusing case  210  to be located on or at the open surface. 
     A plurality of gas discharge holes  305  may be defined and may be spaced apart from each other in the front surface of the discharge cover  300 .  FIG.  5    shows a plurality of gas discharge holes  305  that are uniformly distributed and arranged in the front surface of the discharge cover  300 . In such an arrangement, gas may be discharged through an entirety of the front surface of the discharge cover  300 , and the user may receive gas that is discharged forward through the discharge cover  300  and more uniformly dispersed. 
     The discharge cover  300  may be provided such that an edge  302  located on the outermost side with respect to a radial direction of the diffuser  200  is in close contact with the diffusing case  210 . The diffusing case  210  may have a front circumferential portion or rim  236  surrounding the open surface in the front side  211 , and the edge  302  may have a shape corresponding to that of the front circumferential portion  236  and may be in contact with the front circumferential portion  236 . 
     The front circumferential portion  236  may have a first portion  237  and a second portion  238 . The first portion  237  and the second portion  238  may be arranged with different distances from the gas inlet hole  215  and/or rear side  212  of the diffusing case  210 . The edge  302  of the discharge cover  300  may be molded to correspond to shapes of the first portion  237  and the second portion  238  so as to be in close contact with the front circumferential portion  236  of the diffusing case  210 . 
     The first and second portions  237  and  238  may represent various curves or waves defined by an outer edge of the diffusing case  210 . The first portion  237  may be a hump or mountain and the second portion  238  may be a valley such the front circumferential portion  236  is further forward at the first portion  237  than at the second portion  238 . 
     The front circumferential portion  236  of the diffusing case  210  and the edge  302  of the discharge cover  300  may be designed to fit over or on a head of the user with an arbitrary curved surface while respectively having curvatures and having different lengths protruding forward along an outer circumferential direction of the diffuser  200 . Accordingly, a proximity or molding with the scalp or the hair of the user may be efficiently increased to minimize a space between the head of the user and the diffuser  200 , thereby increasing a heating, drying, or treating effect. An amount of gas discharged forward through the discharge cover  300  and/or an amount or intensity of light provided by the light irradiator  260  may be efficiently increased. 
     An ergonomic design is made through the front circumferential portion  236  of the diffusing case  210  and the edge  302  of the discharge cover  300 , which may be arranged to form curves when viewed from the side as described above and shown in the figures. In this case, the curvatures and the like of the front circumferential portion  236  and the edge  302  may be designed based on a standard head that is statistically determined. 
     For example, an embodiment of the present disclosure may define a R127 curvature design from a shape of the standard head, and design the shapes of the front circumferential portion  236  and the edge  302 , and an overall shape of the diffusing case  210  and discharge cover  300 , to correspond thereto. 
     In one example, a proximity or distance sensor  269  may be provided inside the diffusing case  210  to improve ease of use and efficiency of the diffuser  200 . An open region or hole  303  may be defined in the discharge cover  300  such that a distance measurement accuracy of the proximity sensor  269  for a target in front of the diffuser  200  (e.g., the hair or the scalp of the user) may be improved. The proximity sensor  269  may be implemented in various schemes such as pressure, ultrasound, infrared, laser, light, etc. to measure a distance to the target in front of the proximity sensor  269 , and a region of the discharge cover  300  in front of the proximity sensor  269  may be opened to define the open region  303 . 
     In one example,  FIG.  5    shows a discharge cover  300  having a plurality of massage protrusions or bristles  310 . The massage protrusions  310  may have a pillar shape protruding forward from the diffuser  200  and may press the scalp of the user to provide a massage effect. A cross-sectional shape, a protruding length, an arrangement form, and the like of the massage protrusions  310  may be variously determined in terms of a design. An embodiment of the present disclosure provides the user with scalp massage through the massage protrusions  310  while also providing the gas diffused through a front surface of the discharge cover  300  to the user, thereby providing the improved ease of use and facilitating scalp and hair care. 
     Referring to  FIGS.  6  and  7   , the diffuser  200  may include the diffusing case  210 , a guide frame  240 , the light irradiator  260 , a light diffusion frame  280 , and the discharge cover  300 . 
     A rear side  212  of the diffusing case  210  may be coupled with the main body  110 , and the open surface may be defined in the front side  211 . The inner diameter of the diffusing case  210  may increase from the rear side  212  to the front side  211  so that the gas exiting the main body  110  may be diffused and discharged to the outside. The gas discharged through the gas outlet  150  of the main body  110  may be provided to the user in a state in which the flow cross-sectional area thereof is increased as the gas is flowing in the diffusing case  210 . 
       FIGS.  6  and  7    show a diffusing case  210  in which the inner diameter thereof increases from the rear side  212  to the front side  211  and accordingly an outer diameter thereof increases in the same manner. The gas inlet hole  215  may be defined in the rear side  212  of the diffusing case  210 . When the diffusing case  210  is coupled to the main body  110 , the gas inlet hole  215  may be positioned to face, surround, or communicate with the gas outlet  150 . Further, the gas discharged from the gas outlet  150  may be introduced into the diffusing case  210  through the gas inlet hole  215 . 
     The gas inlet hole  215  may be located at a center of the rear side  212  of the diffusing case  210  when viewed from the rear, and a cross-sectional shape of the gas inlet hole  215  may correspond to that of the gas outlet  150 . For example, the gas inlet hole  215  may be defined to have an inner diameter larger than that of the side opening  156  of the gas outlet  150 , so that the gas discharged from the gas outlet  150  may be completely introduced into the diffusing case  210  through the gas inlet hole  215 . 
     The second coupling portion  220  coupled to the main body  110  may be provided on the rear side  212  of the diffusing case  210 . The diffusing case  210  may include a rear circumferential portion or body  217  surrounding the gas inlet hole  215  in the rear side  212 , and the second coupling portion  220  may be provided at a rear end or side of the rear circumferential portion  217  surrounding the gas inlet hole  215 . 
     The second coupling portion  220  may further include a coupling sleeve or flange  224 . The coupling sleeve  224  may extend rearward from the rear of the rear circumferential portion  217 . The coupling sleeve  224  may be provided to outwardly surround the front end  112  of the main body  110  when the diffuser  200  is coupled to the main body  110 . 
     The first coupling portion  120  may be provided at the front end  112  of the main body  110  and may have a first magnetic fastening portion  127  (e.g., a magnet of a first polarity or a metal) embedded inside the outer wall of the front end  112  or located inside the outer wall. The first coupling portion  120  may further include a power transmitter or transceiver (e.g., a wireless power transceiver that works through electromagnetic induction) provided on an outer surface or a front surface of the outer wall of the front end  112 . 
     The second coupling portion  220  may have a second magnetic fastening portion  227  (e.g., a magnet of a second polarity or a metal) embedded in the rear circumferential portion  217  or located inside the rear circumferential portion  217 . The second coupling portion  220  may further include a power receiver or transceiver (e.g., a wireless power transceiver that works through electromagnetic induction) provided on or at an inner surface or rear surface of the coupling sleeve  224 . 
     The first coupling portion  120  may be coupled to the second coupling portion  220 . At least one of the first magnetic fastening portion  127  and the second magnetic fastening portion  227  may include a magnetic force generator (e.g., a ferromagnetic material or an electric current) so that the first magnetic fastening portion  127  and the second magnetic fastening portion  227  may be magnetically coupled to each other. The magnetic coupling means a scheme of mutual coupling through a magnetic force generated from the magnetic force generator, which may be implemented as a magnet and/or an electromagnet. 
     The power transmitter may supply power to the power receiver, which may be aligned, in contact with, or in connection with the power receiver when the diffuser  200  is coupled to the main body  110 . The power receiver may be connected to components or devices of the diffuser  200  (e.g., the light irradiator  260 , the proximity sensor  269 , and the moisture measurement protrusion  312  described later) to supply power thereto. 
     The open surface surrounded by the front circumferential portion  236  may be defined in the front side  211  of the diffusing case  210 , and the gas inside the diffusing case  210  may be discharged forward through the diffuser  200  through the open surface in the front side  211 . 
     The guide frame  240  may be provided inside the diffusing case  210 . The guide frame  240  may guide the flow of the gas introduced through the gas inlet hole  215 . 
     The guide frame  240  may face the gas inlet hole  215  of the diffusing case  210 . The guide frame  240  may have a diffusion portion or base  241  at a center thereof, a first guide or ring  246  provided radially outward of the diffusion portion  241 , and a second guide or ring  251  provided radially outward of the first guide  246 . The guide frame  240  may include a guide connector or tab  253  extending along the radial direction of the diffuser  200  to connect the diffusion portion  241 , the first guide  246 , and the second guide  251  to each other. 
     The diffusion portion  241  of the guide frame  240  may face the gas inlet hole  215  to diffuse the gas introduced through the gas inlet hole  215  outward in the radial direction. The flow cross-sectional area of the gas introduced through the gas inlet hole  215  may be increased by the diffusion portion  241 . 
     A flow direction of the gas discharged from the center opening  154  may be changed by the diffusion portion  241 . The diffusion portion  241  may have a larger diameter than the center opening  154 , and diffuse the gas provided from the center opening  154  outward in the radial direction. 
     The first guide  246  may have a ring shape, and the diffusion portion  241  may be located at a center of the first guide  246 . The diffusion portion  241  may have a circular cross-section, and may be outwardly spaced apart from the diffusion portion  241  while being concentric with the diffusion portion  241  of the first guide  246 . 
     A first flow path or opening  258  may be provided between the first guide  246  and the diffusion portion  241 . The first guide  246  may be spaced apart from the diffusion portion  241  to define the first flow path  258  between the first guide  246  and the diffusion portion  241 . The gas diffused through the diffusion portion  241  may flow through the first flow path  258 . 
     The second guide  251  may have a ring shape corresponding to the ring shape of the first guide  246 , and the diffusion portion  241  and the first guide  246  may be located at a center of the second guide  251 . The second guide  251  may be concentric with the diffusion portion  241  and the first guide  246  and may be spaced apart from the first guide  246 . 
     An inner diameter of the first guide  246  may be larger than the diameter of the diffusion portion  241 , and an inner diameter of the second guide  251  may be larger than an outer diameter of the first guide  246 . Accordingly, the first flow path  258  may be defined between the diffusion portion  241  and the first guide  246 , and a second flow path or opening  259  may be defined between the first guide  246  and the second guide  251 . 
     The gas diffused by the diffusion portion  241  may flow through the first flow path  258  and the second flow path  259 . An outer diameter of the second flow path  259  may be larger than the diameter of the gas inlet hole  215 , so that the gas introduced through the gas inlet hole  215  may be diffused by the diffusion portion  241  and flow with a larger flow cross-section. 
     The light irradiator  260  may be located in front of the guide frame  240  and installed on a front surface of the guide frame  240 . The light irradiator  260  may have a plurality of light emitters  262  (e.g., light emitting diodes or LEDs) arranged on a circuit board  265 . The circuit board  265  may include a plurality of circuit boards separated from each other, and the plurality of boards of the circuit board  265  may have a size, shape and arrangement corresponding to that of the diffusion portion  241 , the first guide  246 , and the second guide  251  of the guide frame  240 . The circuit board  265  may not interfere with gas or air flowing through the first and second flow paths  258  and  259 . 
     The plurality of circuit boards  265  may respectively include a central board or base  266 , a first board or ring  267 , and a second board or ring  268 . The central board  266  may have a cross-sectional shape corresponding to the diffusion portion  241 . For example, the diffusion portion  241  may have the circular cross-section, and the central board  266  may have a circular cross-section in the same manner as the diffusion portion  241 . The central board  266  may be provided on or at a front surface of the diffusion portion  241  and may include a plurality of light emitters  262 . 
     The first board  267  may have a shape corresponding to the first guide  246 . For example, the first guide  246  may have a ring shape, and the first board  267  may have a ring shape in the same manner as the first guide  246 . The first board  267  be provided on or at a front surface of the first guide  246  and may include a plurality of light emitters  262 . 
     The second board  268  may have a shape corresponding to the second guide  251 . For example, the second guide  251  may have a ring shape, and the second board  268  may have a ring shape in the same manner as the second guide  251 . The second board  268  may be provided on or at a front surface of the second guide  251  and may include a plurality of light emitters  262 . 
     The central board  266 , the first board  267 , and the second board  268  may be arranged to be concentric like the diffusion portion  241 , first guide  246 , and second guide  251  of the guide frame  240 . The first board  267  may be outwardly or radially spaced apart from the central board  266 , and the second board  268  may be outwardly or radially spaced apart from the first board  267 . An inner diameter of the first board  267  may be larger than a diameter of the central board  266 , and an inner diameter of the second board  268  may be larger than an outer diameter of the first board  267 . Like the guide frame  240 , the first flow path  258  may be located between the central board  266  and the first board  267 , and the second flow path  259  may be located between the first board  267  and the second board  268 . 
     A position of the light irradiator  260  may be secured by a coupling between the light diffusion frame  280  and the guide frame  240 , which will be described later. Alternatively, the central board  266 , the first board  267 , and the second board  268  may be optionally coupled (e.g., adhered, welded, or pressed-fit) to front surfaces of the diffusion portion  241 , the first guide  246 , and the second guide  251 , respectively. The circuit board  265  may include optional tabs or connectors corresponding to the guide connectors  253  to connect the central board  266 , the first board  267 , and the second board  268  to each other. When such optional connectors are included, the optional connectors may be coupled to (e.g., adhered, welded, or pressed-fit) to the guide connectors  254  of the guide frame  140  and/or light diffusion connectors  288  of the light diffusion frame  280  described later. As another alternative, when such optional connectors are included, the circuit board  265  may be coupled to just one or two of the front surfaces of the diffusion portion  241 , the first guide  246 , and the second guide  251 . For example, the central board  266  may be secured to the diffusion portion  241 , while the first and second boards  267  and  268  merely contact and/or are merely positioned to align with the first guide  246 , and the second guide  251 , respectively. 
     The light irradiator  260  may irradiate light toward the front side  211  of the diffusing case  210  through the plurality of light emitters  262 . The light irradiated from the light irradiator  260  may be emitted toward a location ahead or forward of the diffuser  200  through the front side  211  of the diffusing case  210 . 
     For example, the light irradiated from the light irradiator  260  may pass through the open surface of the diffusing case  210  and through the gas discharge holes  305  of the discharge cover  300 , through the massage protrusion  310  of the discharge cover  300 , or, if the discharge cover  300  is made of a transparent or translucent material, through a main body or portion the discharge cover  300 . 
     As the light is irradiated forward from the diffuser  200 , the diffuser  200  may treat a user&#39;s hair or scalp care. The light irradiated from the light irradiator  260  may contribute to improving scalp and hair health while drying the user&#39;s scalp or hair or while providing heat to the user&#39;s scalp or hair. The wavelength of the light irradiated from the light emitter  262  may be predetermined or may be selected by the user. For example, red light (620-660 nm) may be used to prevent hair loss or increase blood flow to the scalp, or UV light (100-400 nm) may be used to sanitize the scalp or treat skin conditions such as scalp psoriasis. 
     The proximity sensor  269  may be provided on the circuit board  265  of the light irradiator  260 .  FIG.  6    shows a state in which the proximity sensor  269  is provided on the central board  266  of the light irradiator  260 . 
     The proximity sensor  269  may be provided at a center of the central board  266 . The proximity sensor  269  may be provided to measure a separation distance from the target positioned in front of the proximity sensor  269 . The controller  115  may be provided to control the light irradiator  260  based on the separation distance between the proximity sensor  269  and the target measured by the proximity sensor  269 . 
     For example, when the separation distance from the target measured by the proximity sensor  269  is equal to or less than a reference or predetermined distance, the controller  115  may control the light irradiator  260  such that the light irradiator  260  irradiates the light forward via the light emitters  262 . The reference distance may be predetermined in terms of a design or control. The light irradiator  260  may also be operated through a physical switch, which may be operated even when the separation distance measured by the proximity sensor  269  is equal to or less than the reference distance. As the proximity sensor  269  is used, the light irradiator  260  may be operated when the separation distance from the target in front of the diffuser  200  (i.e., the scalp or the hair of the user) is equal to or less than the reference distance, thereby improving ease of use and an operation efficiency. 
     The proximity sensor  269  may be provided in various types. For example, the proximity sensor  269  may be a pressure sensor that detects whether a pressing force is applied from the user&#39;s scalp or hair, or a photosensitive sensor that measures a level at which an amount of sensed light decreases as the separation distance from the scalp or the hair decreases. 
     In addition, the proximity sensor  269  may be an infrared (IR) sensor that measures an infrared ray transmitted from the target to measure the separation distance from the scalp or the hair. In this case, the proximity sensor  269  may be provided to irradiate the infrared ray forward. 
     The light diffusion frame  280  may be located in front of the light irradiator  260 . The light diffusion frame  280  may be installed on a front surface of the light irradiator  260  to forwardly cover the light emitters  262  of the light irradiator  260 . 
     The light diffusion frame  280  may include a central light diffusion portion or diffuser  282 , a first light diffusion portion or diffuser  284  and a second light diffusion portion or diffuser  286 . The light diffusion frame  280  may further include a light diffusion connector  288  to connect the central light diffusion portion  282 , the first light diffusion portion  284 , and the second light diffusion portion  286  to each other. 
     The central light diffusion portion  282  may have a cross-sectional shape corresponding to that of the central board  266 . For example, the central board  266  may have a circular cross-section, and the central light diffusion portion  282  may have a circular cross-section in the same manner as the central board  266  and may cover the front surface of the diffusion portion  241 . 
     The first light diffusion portion  284  may have a shape corresponding to the first board  267 . For example, the first board  267  may have the previously described ring shape, and the first light diffusion portion  284  may have a ring shape in the same manner as the first board  267  and may cover the front surface of the first board  267 . 
     The second light diffusion portion  286  may have a shape corresponding to the second board  268 . For example, the second board  268  may have the previously described ring shape, and the second light diffusion portion  286  may have a ring shape in the same manner as the second board  268  and may cover the front surface of the second board  268 . 
     The central light diffusion portion  282 , the first light diffusion portion  284 , and the second light diffusion portion  286  may be arranged to be concentric like the arrangement of the guide frame  240  and the light irradiator  260 . The first light diffusion portion  284  may be outwardly spaced apart from the central light diffusion portion  282 , and the second light diffusion portion  286  may be outwardly spaced apart from the first light diffusion portion  284  so as not to block a flow of discharged air or gas. 
     An inner diameter of the first light diffusion portion  284  may be larger than a diameter of the central light diffusion portion  282 , and an inner diameter of the second light diffusion portion  286  may be larger than an outer diameter of the first light diffusion portion  284 . Like the guide frame  240 , the first flow path  258  may be located between the central light diffusion portion  282  and the first light diffusion portion  284 , and the second flow path  259  may be located between the first light diffusion portion  284  and the second light diffusion portion  286 . 
     The diffuser  200  may be provided in a shape in which the first flow path  258  and the second flow path  259  are extended in the front and rear directions through the guide frame  240 , the light irradiator  260 , and the light diffusion frame  280 . The light diffusion connector  288  may be provided in a shape corresponding to the guide connector  253 . For example, the guide connector  253  and the light diffusion connector  288  may have an extended shape along the radial direction of the diffuser  200 . 
     The light diffusion connector  288  may be located in front of and aligned with the guide connector  253  so as not to block a flow of discharged air or gas. The light diffusion frame  280  may be fixed inside the diffusing case  210  as the light diffusion frame  280  is fastened to the guide connector  253 . 
     An embodiment of the present disclosure is advantageous in terms of a design and structurally stable in that, in a state in which the guide frame  240  is constituted by a plurality of components, the plurality of components may be able to be handled as a single component through the guide connector  253 . In addition, an embodiment of the present disclosure is advantageous in terms of the design and structurally stability in that, in a state in which the light diffusion frame  280  is constituted by a plurality of components, the plurality of components are able to be handled as a single component through the light diffusion connector  288 . 
     Furthermore, the light diffusion connector  288  of the light diffusion frame  280  may be coupled to the guide connector  253  of the guide frame  240 , so that all of the central light diffusion portion  282 , the first light diffusion portion  284 , and the second light diffusion portion  286  may be stably fixed and secure, which is advantageous in terms of coupling. 
     The light diffusion frame  280  may be made of a material through which light is transmitted (i.e., a transparent or translucent material, such as plastic or glass). The light irradiated from the light irradiator  260  may be scattered and diffused while passing through the light diffusion frame  280 . The light diffusion frame  280  may be provided in front of the light irradiator  260  so that the light irradiated from the light irradiator  260  may be provided to the user while being scattered and diffused and being uniformly dispersed in a larger area. 
     A treatment for the diffusion or the scattering of the light may be performed on a front surface or a rear surface of the light diffusion frame  280 . For example, etching may be performed or a pattern through laser processing and the like may be formed on a surface of the light diffusion frame  280 . 
     In one example, the central light diffusion portion  282  may shield the front surface of the central board  266 , and a portion of the central light diffusion portion  282  in front of the proximity sensor  269  may be opened or formed with a hole such that the measurement of the separation distance from the target in front of the diffuser  200  via the proximity sensor  269  may be convenient or undisturbed. When the proximity sensor  269  is provided at the center of the central board  266 , the central light diffusion portion  282  may have a hole defined at a center thereof (as shown in the figures) to expose the proximity sensor  269  forwardly and allow transmission of a signal to or from the proximity sensor  269 . 
     The discharge cover  300  may shield the open surface defined in the front side  211  of the diffusing case  210  in which the guide frame  240 , the light irradiator  260 , and the light diffusion frame  280  may be embedded. The plurality of gas discharge holes  305  may be defined in the discharge cover  300  so that gas may be discharged and the light may be irradiated forward. 
     The edge  302  of the discharge cover  300  may have a curvature configured to correspond to that of the front circumferential portion  236  of the diffusing case  210  when viewed from the side. A front surface of the discharge cover  300  may form a curved surface that is indented or recessed rearwards centerwardly so that the discharge cover  300  may have a shape corresponding to the head of the user, which may facilitate a massage effect through the massage protrusions  310  while providing the gas or air and the light to the user. 
     The plurality of massage protrusions  310  may each have a contact portion provided on a front surface or end thereof. The contact portions of the plurality of massage protrusions  310  may be configured such that a sense of touch with the scalp or the hair of the user may be improved and damage to the scalp and the hair may be minimized. For example, the contact portion may be made of an elastic or soft material such as silicon, rubber, or plastic. 
     The discharge cover  300  may also include at least one moisture measurement protrusion or sensor  312 , which may also serve as a massage protrusion  310 . The moisture measurement protrusion  312  may be provided to measure a moisture amount of the scalp or the hair of the user. A pair of moisture measurement protrusions  312  may be arranged to measure an impedance, such as a bioelectrical impedance through an electric field formed therebetween. 
     The moisture measurement protrusions  312  may be connected to the controller  115 . The controller  115  may determine the impedance using a voltage, a current, a resistance, and the like, which are identified through the moisture measurement protrusion  312 , and determine the moisture amount of the scalp or the hair of the user based on the determined impedance. The controller  115  may further control an operation of the fan  119 , the temperature adjuster  117 , or the light irradiator  260  based on the determined moisture amount. 
     For example, the controller  115  may control the fan  119  to increase a rotation speed (such that the speed of discharged gas increases) as the determined moisture amount of the scalp or the hair of the user increases. Alternatively or in addition thereto, the controller  115  may control the temperature adjuster  117  such that a temperature of the discharged gas increases and/or control the light irradiator  260  such that a light amount or intensity increases as the determined moisture amount of the scalp or the hair of the user increases. A light amount or intensity may be increased by increasing a number of light emitters  262  emitting light and/or increasing an intensity of light emitted by each light emitter  262 . 
     A pair of moisture measurement protrusions  312  may include a first moisture measurement protrusion  315  electrically having a first pole and a second moisture measurement protrusion  316  having a second pole opposite to the first pole. The controller  115  may determine the impedance and the moisture amount through the electric field formed between the first moisture measurement protrusion  315  and the second moisture measurement protrusion  316 . 
     A plurality of pairs of moisture measurement protrusions  312 , each of which includes the first moisture measurement protrusion  315  and the second moisture measurement protrusion  316 , may be arranged. One pair of moisture measurement protrusions  312  may be provided to be spaced apart from another pair of moisture measurement protrusions  312 , and different massage protrusions  310  may be positioned therebetween. 
     In one example, the open region  303  may be defined at a center of the discharge cover  300 . The proximity sensor  269  may be exposed forward through the hole defined in the light diffusion frame  280  and the open region  303  of the discharge cover  300 , and may measure the separation distance from the target in front of the diffuser  200 . A protection member (e.g., a transparent film or layer) that protects the proximity sensor  269  and allows the infrared ray or the like to pass straight therethrough may be provided in front of the proximity sensor  269  (e.g., in a center hole of the light diffusion frame or in the open region  303 ). 
     Referring to  FIG.  7   , the first coupling portion  120  of the main body  110  may include the first magnetic fastening portion  127 , and the second coupling portion  220  of the diffuser  200  may include the second magnetic fastening portion  227 . The diffuser  200  may be coupled to the front end  112  of the main body  110  through a magnetic coupling or interaction between the first magnetic fastening portion  127  and the second magnetic fastening portion  227 . The first coupling portion  120  may further include a hook fastener or loop, and the second coupling portion  220  may further include a hook configured to be fastened to the hook fastener so that a coupling stability between the diffuser  200  and the main body  110  may be enhanced. 
     Hereinafter, a flow of the gas discharged from the gas outlet  150  according to an embodiment of the present disclosure will be described with reference to  FIG.  7   . In the gas outlet  150 , the gas is discharged from the center opening  154  and the side opening  156 . The gas inlet hole  215  of the diffusing case  210  may have a diameter equal to or larger than that of the side opening  156  and face the gas outlet  150  so that the gas discharged from the center opening  154  and the side opening  156  may be introduced into the inlet hole  215 . 
     The guide frame  240  may be provided inside the diffusing case  210  to face the gas outlet  150 . The diffusion portion  241  of the guide frame  240  may be positioned to face the center opening  154  of the gas outlet  150 . 
     The gas discharged from the center opening  154  may flow toward the diffusion portion  241 . As the diffusion portion  241  has a diameter larger than that of the center opening  154 , the gas discharged from the center opening  154  may be diffused outward along the radial direction of the diffuser  200 . 
     The diffusion portion  241  may have a diffusion protrusion or cone  242  on a rear surface thereof facing the center opening  154 . The diffusion protrusion  242  may have a curvature such that a diameter thereof decreases in a rearward direction to protrude or point toward the gas outlet  160 . The diameter of the diffusion protrusion  242  may decrease toward a center, which may face the gas outlet  160 . A diffusion effect of the gas discharged from the center opening  154  may be improved by the diffusion protrusion  242 . 
     At least a portion of the gas discharged from the center opening  154  may flow along the first flow path  258  defined between the diffusion portion  241  and the first guide  246  in the guide frame  240  by the diffusion portion  241  and the diffusion protrusion  242 . In one example, the gas discharged from the side opening  156  may flow outward to surround the gas discharged from the center opening  154 , and the gas discharged from the side opening  156  may also diffuse outward along the radial direction of the diffuser  200  as the gas of the center opening  154  is diffused by the diffusion portion  241 . At least a portion of the gas discharged from the side opening  156  and at least a portion of the gas discharged from the center opening  154  may flow along the second flow path  259  defined between the first guide  246  and the second guide  251  in the guide frame  240 . 
     Despite a design feature where the inner diameter of the diffuser  200  may increase in a forward direction, the discharging of the gas through the center opening  154  and the side opening  156  in the forward direction while being maintained in a specific form may be effectively suppressed through the guide frame  240 . The diffuser  200  may allow the gas discharged from the center opening  154  and the side opening  156  to be effectively dispersed and diffused with a larger flow cross-sectional area while preventing the flow of the gas from being maintained in the specific form. 
     In one example, the light irradiator  260  and the light diffusion frame  280  may be arranged in front of the guide frame  240  inside the diffusing case  210 . The light irradiator  260  and the light diffusion frame  280  may be coupled with the guide frame  240  and may be handled as a single component, improving space utilization, convenience, security, and design. 
     The light irradiator  260  and the light diffusion frame  280  may define the first flow path  258  and the second flow path  259  together with the guide frame  240 . The flow of the gas formed by the guide frame  240  may be effectively maintained, and the gas may be discharged forward from the diffuser  200  through the light irradiator  260  and the light diffusion frame  280 . 
     In the light irradiator  260 , the first board  267  may be positioned to be forward or in front of the central board  266 , and the second board  268  may be positioned to be forward or in front of the first board  267 . The plurality of light emitters  262  arranged in the light irradiator  260  may be arranged to form a spherical or curved surface that is indented or recessed rearward. The plurality of light emitters  262  may be arranged in a form in which a distance from a center of the light irradiator  260  along the radial direction increases forwardly. Such arrangement of the light emitters  262  may correspond to the shape of the front surface of the discharge cover  300  indented rearward. The plurality of light emitters  262  arranged on the light irradiator  260  may be arranged to form the curved surface to correspond to the user&#39;s head having a curvature, so that a uniform amount of light may be provided to the user&#39;s scalp and hair. 
     Like the light irradiator  260 , the guide frame  240  may be provided such that the first guide  246  may be positioned ]forward or in front of the diffusion portion  241 , and the second guide  251  may be positioned forward or in front of the first guide  246 . The first board  267  provided on the front surface of the first guide  246  may be positioned forward or in front of the central board  266  provided at the front surface of the diffusion portion  241 , and the second board  268  provided at the front surface of the second guide  251  may be positioned forward or in front of the first board  267 . 
     Like the light irradiator  260 , in the light diffusion frame  280 , the first light diffusion portion  284  may be positioned forward or in front of the central light diffusion portion  282 , and the second light diffusion portion  286  may be positioned forward or in front of the first light diffusion portion  284 . A distance between the light diffusion frame  280  and the light irradiator  260  may be kept constant, and uniform dispersion and scattering of the light may be induced. In the guide frame  240 , as the second guide  251  may be positioned forward of the first guide  246  and the first guide  246  may be positioned forward of the diffusion portion  241 , a space in which the gas introduced from the gas inlet hole  215  is diffused in the radial direction may be secured, and the gas may be smoothly introduced into the first flow path  258  and the second flow path  259 . 
       FIG.  7    shows the guide frame  240 , the light irradiator  260 , and the light diffusion frame  280  protruding forward in a direction away from centers thereof. 
       FIG.  7    also shows a light blocking portion or shield  271  surrounding the proximity sensor  269 . The light blocking portion  271  may have a hollow cylindrical shape, but embodiments disclosed herein are not limited. The light blocking portion  271  may be provided to surround the proximity sensor  269  along a circumferential direction of the diffuser  200 , preventing a situation in which the light emitter  262  around the proximity sensor  269  affects a measurement the proximity sensor  269 . The proximity sensor  269  may be located inside the light blocking portion  271 . The light blocking portion  271  may have a shape extending from the central board  266  to the discharge cover  300 . 
     The light blocking portion  271  may be opened in a forward direction to prevent structural interference from occurring in a measurement of the separation distance between the diffuser  200  and the front target by the proximity sensor  269 . For example, when the proximity sensor  269  measures an infrared ray transmitted from the target, the light blocking portion  271  may have a front opening to allow the infrared ray transmitted from the target to be completely provided to the proximity sensor  269 . 
     The light blocking portion  271  may be provided to extend rearward from the discharge cover  300 , or may be formed integrally with the discharge cover  300  or integrally with the central board  266 . The light blocking portion  271  may be manufactured separately from the discharge cover  300  and the central board  266 , and may be later coupled to or combined with the discharge cover  300  and/or the central board  266 . 
     As described above, the hair dryer  100  may include the main body  110 , the handle  180 , and the diffuser  200 . The main body  110  may include the gas outlet  150  to discharge the gas introduced from the outside, and the handle  180  may extend from the main body  110 . 
     The diffuser  200  may be removably coupled to the main body  110  so that the gas discharged from the gas outlet  150  may flow into the diffuser  200 , and the gas introduced into the diffuser  200  may be discharged to the outside. 
     Referring to  FIG.  8   , the rear side  212  of the diffusing case  210  may be coupled to the main body  110 , and the gas discharged from the gas outlet  150  may be introduced into the diffusing case  210  through the gas inlet hole  215  defined in the rear side  212 . The open surface may be defined in the front side  211  so that the gas introduced into the diffusing case  210  may be discharged to the outside through the open surface. 
     The diffusing case  210  may include the front circumferential portion  236  surrounding the open surface. The front circumferential portion  236  may include the first portion  237  and the second portion  238 , and at least a portion of the first portion  237  may be positioned forwardly of the second portion  238 . 
     The diffusing case  210  may also be referred to as an outer shell, while the discharge cover  300  ( FIG.  5   ) may be referred to as an inner shell. The diffusing case  210  may be concave to define a cavity or recession. The discharge cover  300  may be similarly concave to define a cavity. The diffuser  200 , by the curvatures of the diffusing case  210  and discharge cover  300 , may have a curvature configured to surround at least a portion of a user&#39;s head. The internal devices of the diffuser  200  (i.e., the guide frame  250 , the light irradiator  260 , and the light diffusion frame  280 ) may also be concave in a same direction as the discharge case  210  and the discharge cover  300  such that centers of the guide frame  250 , the light irradiator  260 , and the light diffusion frame  280  are closer to the rear or gas inlet hole  215 , while outer edges are closer to a front or the discharge cover  300 . 
     Referring to  FIGS.  8  to  10   , in an embodiment of the present disclosure, the diffusing case  210  may include the front circumferential portion  236  at the front edge and defining the front opening, and the front circumferential portion  236  may include the first portion  237  and the second portion  238 . 
     The first portion  237  and the second portion  238  may be arranged forward of the gas inlet hole  215  with different distances to the gas inlet hole  215 . The front circumferential portion  236  may have a wave shape. For example, the first portion  237  may be positioned further forward than the second portion  238  such that the diffusing case  210  may have somewhat of a flower petal shape. The first portion  237  may be thought of as a hump or mountain, while the second portion  238  may be thought of as a valley. There may be a plurality of first and second portions  237  and  238  alternately arranged with each other along a circumferential direction to form a plurality of circumferential curves. 
       FIG.  8    shows the first portion  237  positioned forwardly of the second portion  238  and the second portion  238  positioned rearwardly of the first portion  237 . In the present disclosure, the first portion  237  and the second portion  238  of the front circumferential portion  236  may be distinguished and defined in a relative relationship therebetween. 
     The diffuser  200  may discharge the gas to the user while being positioned adjacent to the user&#39;s scalp and hair. However, the user&#39;s head is not flat. In a general body, the head may have an approximate spherical shape having a curvature. 
     The diffusing case  210  may provide the gas to the user through the front surface thereof corresponding to the open surface. A shape of the diffusing case  210  may be concave and curved to have a general semisphere or hollow cone shape, and an edge of the diffusing case  210  defining the front opening may be curved or have a wave structure. 
     With respect to an overall semisphere or hollow cone shape, when the diffusing case  210  is flat (e.g., like a plate), it may be difficult for an entirety of the diffusing case  210  to be in close contact with the user&#39;s head. For example, when a central side of the discharge case  210  is in close contact with or adjacent to the user&#39;s head, an outer edge of the discharge case  210  may be spaced apart from the user&#39;s scalp and hair. A distance between the central side of the discharge case  210  and the user&#39;s scalp may be greater than a distance between the outer edge of the discharge case  210  and the user&#39;s scalp. Less discharged gas may reach the user&#39;s head, and more gas discharged through the discharge case  210  may escape to the through a space between the outer edge of the discharge case  210  and the head of the user, reducing a care effect. Consequently, when the gas is discharged, a deviation in a separation distance from the scalp and the hair of the user may occur. Accordingly, an embodiment of the present disclosure may have a curved surface corresponding to a curvature of the user&#39;s head. 
     Even when the discharge cover  210  is provided to be curved, when the front circumferential portion  236  is not varied and has a more uniform shape in the same front-rear plane (which may be the case if the discharge case  210  were, for example, a perfect semisphere), there may be further disadvantages with respect to air flow. Accordingly, embodiments disclosed herein provide the front circumferential portion  236 , which may not be positioned on one front-rear plane and instead may be divided into the first portion  237  and the second portion  238  having protruding length or heights in the forward direction that are different from each other. 
     The position comparison between the first portion  237  and the second portion  238  as described above may be identified by comparing positions of a line formed by a front end of the first portion  237  and a line formed by a front end of the second portion  238  when viewed from the side. For example, when the diffuser  200  is viewed from the side as shown in  FIGS.  9  and  10   , a line formed by the front end of the first portion  237  may be positioned in front of a line formed by the front end of the second end  238 , and the line formed by the front end of the second portion  238  may be positioned behind the line formed by the front end of the first portion  237 . The first portion  237  and the second portion  238  may be formed at different positions in the front and rear direction for the open surface to easily form a curved surface that could cover, for example, a spherical surface. 
     As shown in  FIG.  8   , the second portion  238  may be positioned closer to a center of the discharge case  210  than a general or average circumference of the discharge case  210 , and the first portion  237  may be located farther from the center of when compared to the second portion  238 . 
     As described above, an embodiment of the present disclosure may allow the open surface to effectively form the curved surface and allow an entirety of the front circumferential portion  236  to be at a uniform or more uniform distance from the scalp of the user as the front circumferential portion  236  of the diffusing case  210  is not in a general circular shape when viewed from the front and is not in a general straight shape when viewed from the side. The front circumferential portion  236  may be constituted by a plurality of first portions  237  and a plurality of second portions  238 , and the first portion  237  and the second portion  238  may be alternately arranged along a circumference of the open surface. 
     As shown in  FIGS.  9  and  10   , when viewed from the side, the first portion  237  may be a convex portion and the second portion  238  may be a concave portion. The first portion  237  and the second portion  238  may be alternately arranged without a directionality in order to provide the same effect in any use direction of the user. In addition, the front circumferential portion  236  may correspond to a general sphere surface through the alternating shape as described above, so that the entirety of the front circumferential portion  236  may be in close contact with a spherical surface (e.g., a head). 
     The first portion  237  and the second portion  238  may extend along the circumference of the open surface while at least partially varying in a length forwardly extending from the gas inlet hole  215 . The first portion  237  and the second portion  238  may be arranged such that front ends of at least portions thereof form a curved surface when viewed from the side. The first portion  237  and the second portion  238  may have shapes capable of being in close contact with a sphere surface while lengths thereof extending forward from the gas inlet hole  215 , the rear side of the diffuser  200 , the main body  110 , etc. may be continuously changing. In one example, the first portion  237  and the second portion  238  may extend along the circumference of the open surface while respectively forming curvatures when viewed from the side. 
     As described above, the head of the body may have a surface corresponding to a sphere surface, and the first portion  237  and the second portion  238  may extend along a circumference of a front edge of the discharge case  210  defining the front open surface of the while respectively forming the curvatures to correspond to the sphere surface as described above. The first portion  237  and the second portion  238  may extend along the circumference of the open surface while the lines formed by the front ends of the first portion  237  and the second portion  238  respectively form curves when viewed from the side. The curvatures formed by the first portion  237  and the second portion  238  may not always be constant and may be variously determined in terms of design to correspond to the sphere surface. 
       FIGS.  9  and  10    show the first portion  237  and the second portion  238  respectively having predetermined curvatures and extending along the circumference of the discharge case  210 , according to an embodiment. In one example, the second portion  238  may have a concavely curved shape and may be provided such that a forwardly extended length thereof increases in a direction away from a center thereof. 
       FIG.  10    shows the second portion  238  according to an embodiment of the present disclosure. Referring to  FIG.  10   , the second portion  238  may have the concavely curved shape in the front and rear direction. However, the concavity may only be apparent when viewed from the side. When viewed from the front, the concavely curved second portion  238  may not appear to be indented or recessed into the diffusing case  210 . 
     A cross-section of the diffusing case  210  may be maintained in the circular shape when viewed from the front, and the second portion  238  may be not be indented inward toward a center of the diffusing case  210  when viewed from the front. The second portion  238  may be provided such that only the front-rear length and the line formed by the front end of the second portion  238  may be concavely curved to form the curve. 
     The shape characteristics of the first portion  237  or the second portion  238  may be derived three-dimensionally. It may be understood in  FIG.  8    that the second portion  238  is more indented or recessed toward a center of the cross-section of the diffusion case  210  than the first portion  237  due to perspective. A front edge of the second portion  238  merely forms a curve through a change in the extended front-rear length of the front end, and the second portion  238  may not be indented inward toward the center of the diffusion case  210  with respect to the first portion  237  on a specific plane viewed from the front. 
     In relation to the second portion  238 , when the user&#39;s head is regarded to have the sphere surface, due to three-dimensional characteristics, a user&#39;s head portion corresponding to the second portion  238  may protrude more than a portion corresponding to the first portion  237  even when the first portion  237  is in close contact with the user&#39;s head. 
     Accordingly, the second portion  238  may be more concavely curved than the first portion  237 . Not only the first portion  237  but also the second portion  238  may be in close contact with the user&#39;s head. This may be effective in drying hair, treating the scalp with light therapy, or performing the massage. 
     The first portion  237  may have a convexly curved shape and may be provided such that a forwardly extended length thereof increases in a direction toward a center thereof.  FIG.  9    shows the first portion  237  having the convexly curved shape in a forward direction according to an embodiment of the present disclosure. Each first portion  237  may be located between a pair of second portions  238 , and each second portion  238  may also be located between a pair of first portions  237 . 
     Like the second portion  238 , in the first portion  237 , the convexly curved shape may correspond to the shape of the front end of the first portion  237  viewed from the side. When viewed from the front, the convexly curved the first portion  237  may not protrude outwardly of the diffusing case  210 . Such characteristics of the first portion  237  and the second portion  238  may be identified through the shape of the diffusing case  210  in  FIGS.  9  and  10   . 
     In relation to the first portion  237 , when the user&#39;s head is regarded to have the sphere surface, due to three-dimensional characteristics, a portion of the user&#39;s head corresponding to the first portion  237  may be indented or recessed more than a portion corresponding to the second portion  238  even when the second portion  238  is in close contact with the user&#39;s head. The first and second portions  237  and  238  may be configured to mimic side curvatures or recesses of a natural human head. 
     The first portion  237  may be more convexly curved than the second portion  238 . Accordingly, the first portion  237  is able to be three-dimensionally attached to the user&#39;s head, which is regarded as the sphere surface. This may be effective in drying hair, treating a scalp with light therapy, or performing the massage. The first portion  237  may be provided such that a front-rear length thereof increases in a direction toward a center of the first portion  237  in a circumferential direction of the front circumferential portion  236  when viewed from the side, so that the first portion  237  may have the convex shape. The second portion  238  may be provided such that a front-rear length thereof decreases in a direction toward a center of the second portion  238  in the circumferential direction of the front circumferential portion  236  when viewed from the side, so that the second portion  238  may have the concave shape. 
     The first portion  237  and the second portion  238  may be arranged such that the curvatures thereof are constant and the front-rear lengths thereof vary along the circumference of the front circumferential portion  236 , or may be arranged such that the curvatures thereof vary along the circumference. 
       FIG.  8    shows that an overall shape of the diffuser case  210  may have a triangular shape when viewed from a front with rounded vertex portions and where the first portion  237  and the second portion  238  may have substantially triangular shapes. When viewed from a side in  FIGS.  9  and  10   , the first and second portions  237  and  238  may have substantially triangular shapes with rounded vertexes. 
       FIG.  9    shows that the first portion  237  with a central side located at the frontmost position may have a curved substantially triangular shape.  FIG.  10    shows that the concave shape of the second portion  238  with a central side located at the rearmost position may have a curved substantially triangular shape or form a curved triangular space or recess. 
     As described above, the first portion  237  and the second portion  238  in an embodiment of the present disclosure may have various shapes optimized for close contact with the user&#39;s head. 
     An embodiment of the present disclosure may further include the light irradiator  260  ( FIG.  6   ) provided inside the diffusing case  210  and irradiating light to the front side  211  of the diffusing case  210  through the open surface. 
     When the diffusing case  210  is defined in a flat shape, and when the light irradiator  260  irradiates the light toward the user&#39;s head, a portion of the front circumferential portion  236  may be in a close contact with or adjacent to the user&#39;s head, but a remaining portion thereof may be spaced apart from the user&#39;s head. Through such separation space, a portion of the light irradiated from the light irradiator  260  may not reach the user&#39;s head, thereby reducing the user&#39;s scalp and hair care effects. 
     However, as in an embodiment of the present disclosure, an entirety of the front circumferential portion  236  where the forwardly convex first portion  237  and the rearwardly concave second portion  238  are formed may be uniformly in close contact with or adjacent to the user&#39;s head. Therefore, light treatment to the user may be improved by minimizing a situation in which the light irradiated from the light irradiator  260  leaks to the outside and is lost. 
     In one example, referring to  FIG.  6   , the diffuser  200  may further include the discharge cover  300 . The discharge cover  300  may be coupled to the front side  211  of the diffusing case  210  to shield the open surface of the diffusing case  210 , and may include the gas discharge hole  305  through which the gas inside the diffusing case  210  is discharged to the outside. The gas transmitted from the main body  110  or the light irradiated from the light irradiator  260  may be supplied to the user&#39;s scalp and hair through the discharge cover  300 . 
     In one example, the discharge cover  300  may include the massage protrusion  310  that protrudes forward to press the target in front of the discharge cover  300 . The diffuser  200  may massage the user&#39;s scalp through the massage protrusion  310 . As the front circumferential portion  236  of the diffusing case  210  has the first portion  237  and the second portion  238 , a level of close contact between the discharge cover  300  and the user&#39;s head may be improved, and the massage effect may also be increased. 
     The discharge cover  300  may include the edge  302  having a curvature corresponding to the front circumferential portion  236  when viewed from the side and located inward of the front circumferential portion  236 . The entirety of the discharge cover  300  may be in close contact with the user&#39;s head with the edge  302  has a shape corresponding to the front circumferential portion  236  including the first portion  237  and the second portion  238 . 
     The discharge cover  300  may have a shape in which a front surface thereof directed in the front direction is indented or recessed rearwards centerwardly so as to form a concave cavity or curvature. When the discharge cover  300  is provided in the diffuser  200 , the discharge cover  300  may define the shape of the aforementioned open surface. 
     The discharge cover  300  may have an approximate spherical surface shape that is recessed rearwards. Further, as the edge  302  and the front surface of the discharge cover  300  and the front circumferential portion  236  of the diffusing case may be in close contact with a head through the formation of the first portion  237  and the second portion  238 , massage, light, and drying treatment may be improved. 
     This application is related to co-pending U.S. application Ser. Nos. 17/077,915 filed on Oct. 22, 2020, 17/077,917 filed on Oct. 22, 2020, 17/077,921 filed on Oct. 22, 2020, 17/077,922 filed on Oct. 22, 2020, 17/077,927 filed on Oct. 22, 2020, 17/077,929 filed on Oct. 22, 2020, 17/085,385 filed on Oct. 30, 2020, and 17/077,119 filed on Oct. 22, 2020, the entire contents of which are incorporated by reference herein. 
     Embodiments disclosed herein may provide a diffuser having an efficient shape corresponding to a user&#39;s head and a hair dryer including the same. Embodiments disclosed herein may provide a diffuser and a hair dryer including the same capable of effectively improving a user&#39;s scalp and hair care effect. 
     A diffuser may have a shape capable of effectively accessing user&#39;s scalp and hair and providing a care effect, and a hair dryer including the same. In a human body, a surface of a head corresponds to a curved surface having a curvature, not a plane. When a front end of the diffuser that provides gas, air, or a care effect to a user has a usual plain round structure, a distance between a portion of the diffuser and the user&#39;s head may be different from a distance between a remaining portion of the diffuser and the user&#39;s head. 
     For example, the remaining portion of the diffuser may be spaced apart from the user&#39;s head even when another portion (e.g., center portion) of the diffuser is in close contact with the user&#39;s head. Gas may leak through a region between the remaining portion of the diffuser and the user&#39;s head, a massage protrusion may be further from the scalp of the user, or light irradiated for the care effect may escape to an outside. 
     When the diffuser has a general circular structure that does not take the user&#39;s head into consideration, a light amount of an LED module for scalp care may be lost and the gas provided to the user may leak outside. Accordingly, embodiments disclosed herein may minimize loss of the LED light amount and air volume and effectively increase ease of use by applying a triangular shape structure to a diffusing case  210 . 
     The diffusing case may include three cut regions obtained by cutting a cone to form 120 degrees with a center of an axis. Each cut region may have a shape allowing an entirety of the cut region to be in close contact with a substantially spherical surface. 
     The diffuser may include a diffusing case having a rear side removably coupled to a main body of a hair dryer. Gas or air discharged from the main body may be introduced into the diffusing case through a gas or air inlet hole defined at the rear side. An open surface or front opening may be defined at a front side of the diffusing case such that the gas introduced into the diffusing case is discharged to an outside through the open surface, 
     The diffusing case may include a front circumferential portion surrounding the open surface. The front circumferential portion may include a first portion and a second portion. The first portion may be at least partially located forwardly of the second portion. 
     The first portion may include a plurality of first portions and the second portion may include a plurality of second portions. The plurality of first portions and the plurality of second portions may be alternately arranged with each other along a circumference of the open surface. The first portion and the second portion may extend along the circumference of the open surface, and a distance from a front end of each of the first portion and the second portion to the rear side may vary along at least a partial region of the front end. 
     In the front circumferential portion, the first portion and the second portion may extend along the circumference of the open surface while respectively having curvatures when viewed from the side. The second portion may have a concave curved shape in a rearward direction, and the distance from the front end of the second portion to the rear side may increase in a direction away from a center of the second portion. The first portion may have a convex curved shape in a forward direction, and the distance from the front end of the first portion to the rear side may increase in a direction toward a center of the first portion. 
     The diffuser may further include a light irradiator provided inside the diffusing case and irradiating light forwardly of the diffusing case through the open surface. The diffuser may further include a discharge cover coupled to the front side of the diffusing case to shield the open surface. The discharge cover may include a gas discharge hole defined therein to discharge the gas inside the diffusing case to the outside. 
     The discharge cover may include a massage protrusion protruding forward to press a target in front of the discharge cover. The discharge cover may include an edge having a curvature corresponding to the front circumferential portion when viewed from the side. The edge may be located inward of the front circumferential portion. The discharge cover may have a front surface directed in a forward direction having a shape of being indented or recessed rearwards in a direction toward a center of the front surface. 
     Embodiments disclosed herein may be implemented as a hair dryer comprising a main body including a gas or air outlet to discharge gas therethrough, a handle extending from the main body, and a diffuser removably coupled to the main body to introduce the gas discharged from the gas outlet therein and discharge the gas introduced therein to outside. The diffuser may include a diffusing case having a rear side removably coupled to the main body of the hair dryer. Gas discharged from the gas outlet may be introduced into the diffusing case through a gas inlet hole defined at the rear side. An open surface may be defined at a front side of the diffusing case such that the gas introduced into the diffusing case may be discharged to an outside through the open surface. 
     The diffusing case may include a front circumferential portion surrounding the open surface. The front circumferential portion may include a first portion and a second portion. The first portion may be at least partially located forwardly of the second portion. The first portion and the second portion may extend along a circumference of the open surface. A distance from a front end of each of the first portion and the second portion to the rear side may vary along at least a partial region of the front end. 
     In the front circumferential portion, the first portion and the second portion may extend along the circumference of the open surface while respectively having curvatures when viewed from the side. The second portion may have a concave curved shape in a rearward direction, and the distance from the front end of the second portion to the rear side may increase in a direction away from a center of the second portion. The first portion may have a convex curved shape in a forward direction, and the distance from the front end of the first portion to the rear side may increase in a direction toward a center of the first portion. 
     Embodiments disclosed herein may be implemented as a diffuser comprising a case having a rear side configured to be removably coupled to a hair dryer and a front edge, wherein the case may be formed to be concave to have a cavity recessed rearward from the front edge, and an inlet formed at the rear side and configured to communicate with an outlet of the hair dryer when the case is coupled to the hair dryer such that fluid discharged from the hair dryer flows through the inlet and forward toward the front edge. The front edge may have at least one first section that protrudes forward and at least one second section that may be recessed rearward. 
     The at least one first section may include a plurality of first sections and the at least one second section may include a plurality of second sections. The plurality of first and second sections may be alternately arranged in a circumferential direction of the front edge. Font-rear lengths of the first and second sections may be varied along the circumferential direction. The plurality of first and second sections may be curved and connected to each other to form a continuous wave pattern. 
     A distance from the rear side to the at least one first section may be greater than a distance from the rear side to the at least one second section. The at least one first section may be curved to have a convex curved shape in a forward direction. The at least one second section may be curved to have a concave curved shape in a forward direction. 
     A light may be provided inside the case and configured to emit light in a forward direction. A cover may be coupled to the front side of the case and including a discharge hole through which fluid inside the case may be discharged. The cover may include at least one protrusion protruding forward to press a target in front of the cover. The cover may include an edge having a curvature corresponding to the front edge of the case and provided to be radially inward of the front edge. The cover may have a front surface facing a forward direction and that may be recessed rearwards. 
     Embodiments disclosed herein may be implemented as a hair dryer comprising a main body including an outlet through which fluid may be discharged, a handle extending from the main body, and a diffuser. The diffuser may include a rear side removably coupled to the main body, an inlet formed at the rear side and configured to communicate with the outlet of the main body such that fluid discharged from the outlet may be introduced into the diffuser through the inlet, a front surface having at least one opening through which fluid introduced into the diffuser may be discharged to an outside, the front surface having a concave curvature to be recessed rearward, and a front edge. The front edge may be an outer edge of the front surface. The front edge may have at least one first section and at least one second section. The at least one first section may extend farther forward than the at least one second section. 
     Distances from front ends of each of the at least one first section and the at least one second section to the rear side may vary. The at least one first and second sections may be curved. 
     The at least one second section may have a concave curved shape in a forward direction, and the distance from the front end of the second section to the rear side may increase in a circumferential direction away from a circumferential center of the at least one second section. The at least one first section may have a convex curved shape in a forward direction, and the distance from the front end of the at least one first section to the rear side may increase in a circumferential direction toward a circumferential center of the first section. The front surface of the diffuser may include a plurality of bristles protruding in a forward direction. 
     Embodiments disclosed herein may be implemented as a diffuser for a hair dryer comprising an outer shell having a truncated cone shape such that a diameter increases from a rear to a front. A front edge may have a wave shape. A rear edge may define an inlet through which fluid is received. The outer shell may have a cross-sectional area configured to at least partially surround a human head and a curvature configured to at least partially conform to a curvature of a human head. The rear edge may be configured to be coupled to and removed from a hair dryer at an outlet of the hair dryer through which fluid may include discharged. 
     An inner shell may be configured to be secured to a front side of the outer shell. The inner shell may have at least one discharge hole through which fluid introduced into the inlet may be discharged. A front edge of the inner shell may have a wave shape. The inner shell may have a cross-sectional area configured to at least partially surround a human head and a curvature configured to at least partially conform to a curvature of the human head. At least one massage protrusion may protrude forward from the inner shell and be configured to massage the human head. 
     A guide frame may be provided between the outer and inner shells and have a plurality of openings to guide fluid introduced through the inlet toward the discharge hole. A center of the frame may be closer to the inlet than an outer edge of the frame. 
     A circuit board may be provided between the outer and inner shells and have a plurality of openings that align with the plurality of openings of the guide frame. A plurality of light emitting devices may be provided on the circuit board and face the inner shell. Light emitted from the plurality of light emitting devices may pass through the discharge hole. 
     The diffuser may have an efficient shape corresponding to the user&#39;s head and the hair dryer may include the same. Embodiments of the present disclosure may provide the diffuser and the hair dryer including the same capable of effectively improving the user&#39;s scalp and hair care effect. 
     Although a specific embodiment of the present disclosure has been illustrated and described above, those of ordinary skill in the art to which the present disclosure pertains will appreciate that various modifications are possible within the limits without departing from the technical spirit of the present disclosure provided by the following claims. 
     However, the present disclosure may be implemented in many different forms and is not limited to embodiments described herein. In addition, in order to clearly describe the present disclosure, components irrelevant to the description are omitted, and like reference numerals are assigned to similar components throughout the specification. 
     In this specification, duplicate descriptions of the same components are omitted. Further, in this specification, it will be understood that when a component is referred to as being “connected with” another component, the component may be directly connected with the other component or intervening components may also be present. In contrast, it will be understood that when a component is referred to as being “directly connected with” another component in this specification, there are no intervening components present. Further, the terminology used herein may be for the purpose of describing a specific embodiment only and is not intended to be limiting of the present disclosure. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     It will be further understood that the terms “comprises”, “comprising”, “includes”, and “including” specify the presence of the certain features, numbers, steps, operations, elements, and parts or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, and parts or combinations thereof. Further, the term ‘and/or’ includes a combination of a plurality of listed items or one of the plurality of listed items. In this specification, ‘A or B’ may include ‘A’, ‘B’, or ‘both A and B’. 
     It will be understood that when an element or layer is referred to as being “on” another element or layer, the element or layer can be directly on another element or layer or intervening elements or layers. In contrast, when an element is referred to as being “directly on” another element or layer, there are no intervening elements or layers present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     Spatially relative terms, such as “lower”, “upper” and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “lower” relative to other elements or features would then be oriented “upper” relative to the other elements or features. Thus, the exemplary term “lower” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments of the disclosure are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the disclosure. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the disclosure should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.