Patent Publication Number: US-9900500-B2

Title: Method and apparatus for auto-focusing of an photographing device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit under 35 U.S.C. § 119(a) of a Korean patent application filed on May 30, 2013 in the Korean Intellectual Property Office and assigned Serial number 10-2013-0061782, the entire disclosure of which is hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an auto-focusing method and apparatus of a photographing device. 
     BACKGROUND 
     As communication technologies have developed, electronic devices, for example, a portable terminal such as a smart phone, a tablet Personal Computer (PC), a smart camera, a digital camera, and the like, have become widely utilized. A portable terminal are utilized in a significantly wide field since the portable terminal is convenient to use and easy to carry. 
     Recently, a camera that provides a performance of high-definition and high-resolution has been contained in a portable terminal and thus, a user&#39;s desire for readily photographing a picture and/or a video has been increased. Accordingly, an auto-focusing system has been provided that automatically focuses on a subject without a special manipulation by a user of a camera or a camera application of a terminal. 
     Generally, an auto-focusing scheme supported in a photographing device includes an infrared auto-focusing scheme, a contrast detection auto-focusing scheme, or a phase difference detection auto-focusing scheme. When a significant amount of reflection occurs, such as reflection from a plane of glass, or when a distance to a subject is far, the infrared auto-focusing scheme is difficult to execute for focusing. The contrast detection auto-focusing scheme executes focusing based on a contrast of a portion of a subject and thus, the contrast detection auto-focusing is difficult to execute when a contrast does not exist in the subject. The phase difference detection auto-focusing scheme generates two images using a lens in a detection sensor and executes focusing using an interval between the images. The phase difference detection auto-focusing scheme has difficulty in executing focusing when light, such as sunlight or a reflected light, enters through a lens or when a subject is significantly small. Therefore, there is a need for a method of effectively executing focusing when a portable terminal equipped with a camera photographs a picture and/or a video. 
     The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure. 
     SUMMARY 
     Aspects of the present disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present disclosure is to provide a method and apparatus for auto-focusing of an electronic device. An embodiment of the present disclosure provides a method and apparatus for selecting focusing sensors optimized for an electronic device in a respective environment and/or situation by utilizing various sensors supported in an electronic device, and executing auto-focusing using the selected sensors. 
     Another aspect of the present disclosure is to provide an electronic device equipped with a camera. Another embodiment of the present disclosure provides a method and apparatus for accurately and promptly focusing on a subject using various sensors, i.e., more than one sensor, supported in an electronic device, as opposed to using a single sensor. 
     In accordance with an aspect of the present disclosure, an auto-focusing method of a electronic device is provided. The method includes collecting sensor information using a plurality of sensors of the electronic device when a camera is driven, determining at least one focusing sensor, from among the plurality of sensors, based on the collected sensor information, and focusing on a subject located in an image collected from the camera using the at least one determined focusing sensor. 
     In accordance with another aspect of the present disclosure, a photographing device is provided. The photographing device includes a camera unit configured to collect an image including a subject, a sensor unit configured to collect photographing environment information, and to collect a plurality of pieces of sensor information by processing the photographing environment information, when the camera unit is driven, and a controller configured to collect sensor information using the plurality of sensors, to determine at least one focusing sensor, from among the plurality of sensors, based on the collected sensor information, and to control focusing on a subject located in the image collected from the camera unit using the at least one determined focusing sensor. 
     In accordance with another aspect of the present disclosure, an electronic device equipped with a camera selects a set of optimized sensors from among various sensors supported in the electronic device based on a camera photographing mode and an ambient environment, and automatically focuses on a subject using the corresponding set of sensors. 
     In accordance with another aspect of the present disclosure, focusing on a desired subject is promptly and accurately executed in an environment where focusing is difficult, by utilizing sensors included in a terminal without separately changing a physical hardware. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating a configuration of an electronic device according to an embodiment of the present disclosure; 
         FIG. 2  is a flowchart illustrating an auto-focusing method of an electronic device according to an embodiment of the present disclosure; 
         FIG. 3  is a flowchart illustrating an auto-focusing method according to an embodiment of the present disclosure; 
         FIG. 4  is a flowchart illustrating an auto-focusing method of an electronic device according to an embodiment of the present disclosure; and 
         FIG. 5  illustrates diagrams for describing a candidate group of focusing sensors according to an embodiment of the present disclosure. 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures. 
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness. 
     The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents. 
     It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
     A method and apparatus according to the present disclosure may be applied to a portable terminal. It is apparent that the portable terminal may be a portable terminal, a smart phone, a tablet Personal Computer (PC), a hand-held PC, a Portable Multimedia Player (PMP), a Personal Digital Assistant (PDA), a camera, a portable electronic device, and any other similar and/or suitable electronic device. Hereinafter, descriptions will be provided by assuming that an auto-focusing method and apparatus of an electronic device according to the present disclosure is applied to a portable terminal. 
       FIG. 1  is a block diagram illustrating a configuration of an electronic device according to an embodiment of the present disclosure. 
     Referring to  FIG. 1 , an electronic device  100  according to the present disclosure is configured to include a display unit  110 , an input unit  120 , a communication unit  130 , an audio processing unit  140 , a camera unit  150 , a sensor unit  160 , a storage unit  170 , and a controller  180 . 
     The display unit  110  executes a function of outputting various function screens used for operating the electronic device  100 . The display unit  110  supports a function of visually providing a user with a menu, input data, function setting information, and other various information. The display unit  110  may be formed of a Liquid Crystal Display (LCD), an Organic Light Emitting Diodes (OLED), an Active Matrix Organic Light Emitting Diodes (AMOLED), or the like, however, the display unit  110  is not limited thereto and may be any other similar and/or suitable display device. 
     The display unit  110  may display a photographed image screen obtained through the camera unit  150  when the camera unit  150  is driven. The display unit  110  may display a User Interface (UI) for controlling a camera, together with the photographed image screen. For example, the display unit  110  may display a UI for photographing mode settings, including a shutter speed, an open/close state of an aperture, a white balance, an International Organization of Standardization (ISO) standard for sensitivity to light, application of a filter, and the like, a shutter menu, a picture/video mode switching menu, and a zooming in/out menu, together with the photographed image screen. Also, the display unit  110  of the present disclosure may display, on a photographed image screen, a focus mark that defines a focus area for executing focusing with respect to a photographed image, under a control of the controller  180 . 
     The input unit  120  senses a user input, and executes a function of transferring an input signal corresponding to the user input to the controller  180 . The input unit  120  may be configured to include any of the following elements which are not shown in  FIG. 1 , such as a key pad, a dome switch, a capacitive and/or resistive touch pad, a jog wheel, a jog switch, a finger mouse, a wheel, a hard key, and the like. Also, the input unit  120  may be configured to include any of the following elements which are not shown in  FIG. 1 , such as a touch sensor, a proximity sensor, an electromagnetic sensor, a pressure sensor, and the like. The input unit  120  may be provided as a virtual touch pad, when a touch panel of the electronic device  100  is provided in a form of a full touch screen and/or a partial touch screen. Also, when a touch panel is included in the display unit  110 , the display unit  110  may operate as the input unit  120 . In this case, an input signal for operating a terminal may be generated through the touch panel. 
     The input unit  120  according to the present disclosure may sense a user input for setting a photographing mode of the camera unit  150 , a user input for requesting focusing, and a user input for requesting beginning of photographing. 
     The communication unit  130  executes communication by transmitting and receiving a wireless signal to/from a location external to the communication unit  130 . The communication unit  130  according to the present disclosure may be configured to include a mobile communication module  131  and a Global Positioning Service (GPS) receiving module  132 , but the communication unit  130  is not limited thereto and may include any other similar and/or suitable communication module for wired and/or wireless communication. For example, the communication unit may be configured to further include a wireless Internet module for wireless Internet connection and a satellite communication module. 
     The mobile communication module  131  transmits and receives a wireless signal to/from a base station, a server, and the like. The wireless signal may include data provided in various forms as a voice call signal, a video call signal, and a text/multimedia message is transmitted and received. The GPS receiving module  132  receives a GPS satellite signal from a GPS satellite, and transfers the received GPS satellite signal to the controller  180 , under a control of the controller  180 . The controller  180  may calculate location information associated with a location where the terminal  100  is currently located, using a GPS satellite signal. 
     The audio processing unit  140  may be formed of a coder/decoder (codec), and the codec may be formed of a data codec, that processes packet data and the like, and an audio codec, that processes an audio signal such as a voice and the like. The audio processing unit  140  converts a digital audio signal into an analog audio signal through the audio codec and plays back the analog audio signal through a Speaker (SPK), and converts an analog audio signal input through a Microphone (MIC) into a digital audio signal through the audio codec. 
     In the present disclosure, the audio processing unit  140  supports a sensor function that collects and measures an ambient sound. For example, when the audio processing unit  140  collects an ambient audio signal through a MIC when the camera unit  150  is driven, the audio processing unit  140  may transfer the collected audio signal to the controller  180 . The controller  180  determines whether a voice signal exists among the collected audio signal, and when it is determined that a voice signal exists, the controller  180  may measure a direction and a distance to a subject corresponding to and/or generating the voice signal using a triangulation scheme. 
     The camera unit  150  is driven under a control of the controller  180 , and executes a function of collecting an image by photographing a subject. The camera unit  150  may be activated based on a signal generated from the input unit  120 , and may collect an image. The camera unit  150  may be configured to include at least one of the following elements, which are not shown in  FIG. 1 , such as a camera sensor, an image signal processor that converts an optical signal into an electric signal, a digital signal processor that executes image processing, such as scaling, removing noise, Red Green Blue (RGB) signal converting, or the like, of a video signal output from the image signal processor so as to display the video signal, and the like. Here, the camera sensor may be at least one of a Charge-Coupled Device (CCD) sensor, a Complementary Metal-Oxide Semiconductor (CMOS) sensor, or any other similar and/or suitable camera and/or image sensor. The camera unit  150  may be configured to include a first camera, which may be a front side camera, for photographing a picture in a self-mode, and a second camera, which may be a back side camera, for photographing a subject located in front of a user. The controller  180  may control the display unit  110  so as to display an image collected through the camera unit  150  as a preview image. 
     Also, as a request for execution of photographing is generated, the controller  180  photographs an image collected through the camera unit  150  at a point in time corresponding to the generation of the request for execution of photographing, and the camera unit  150  generates an image. The generated image may be temporarily and/or permanently stored in the storage unit  170 . The sensor unit  160  senses and collects information on a change in a user input and a change in an ambient environment, and executes a function of transferring the information to the controller  180 . In the present disclosure, the sensor unit  160  collects senor information associated with a change in a magnetic field, gravity, a pressure, a temperature, humidity, a quantity of light, a sound, and the like, so as to determine a current state of the electronic device  100 . 
     The sensor unit  160  may be configured to include various sensors that are not shown in  FIG. 1 , for example, a touch sensor that recognizes a touch input, a proximity sensor that senses a proximity of an external object or a user input instrument, a distance measuring sensor, an image sensor that collects an image, a motion recognition sensor that recognizes a motion and a movement in a three-Dimensional (3D) space, a direction sensor that senses a direction and the like, an acceleration sensor that detects a moving speed, and the like, and any other similar and/or suitable sensor. The electronic device  100  according to the present disclosure may not be limited by a configuration of the sensor unit  160 , and a MIC that collects an audio signal and/or a communication module may also execute a function of the sensor unit  160 . 
     Also, in the electronic device  100  according to the present disclosure, a sensing processing module  171  may detect feature information through collected sensor information, such as an eye pattern recognition algorithm that may recognize a direction at which a user gazes, a sound localization algorithm, a symbol recognition algorithm, a facial recognition algorithm, an edge detection algorithm, and the like. 
     The sensor unit  160  according to the present disclosure may be activated to collect ambient environment information and to transfer the collected information to the controller  180 , under a control of the controller  180 , when the camera unit  150  is driven. The controller  180  may determine at least one focusing sensor, or in other words, the controller  180  may select at least one sensor to be the at least one focusing sensor, based on sensor information and a photographing mode. 
     The storage unit  170  stores various data and the like generated in the electronic device  100 , in addition to an Operating System (OS) of the electronic device  100  and various applications, which may be referred to as apps. The data may include data generated from execution of an application, which may be referred to as an app, of the electronic device  100 , and all types of storable data that may be generated using a portable terminal and/or storable data that may be received from an outside source, for example, an external server, another portable terminal, a personal computer, or any other similar and/or suitable outside and/or external source. The storage unit  170  may store a user interface provided in the electronic device  100  and various setting information associated with processing functions of a portable terminal. In the storage unit  170 , programs and/or commands for the electronic device  100  may be stored. The controller  180  may execute the programs and/or commands stored in the storage unit  170 . 
     The storage unit  170  may include at least one type of storage medium, which may be a non-volatile computer readable storage medium, from among a flash memory type, a hard disk type, a multimedia card micro type, a card type of memory, for example, a Secure Digital (SD) memory, an xD memory, or the like, a Random Access Memory (RAM), a Static Random Access Memory (SRAM), a Read-Only Memory (ROM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a Programmable Read-Only Memory (PROM), a magnetic memory, a magnetic disk, an optical disk, or any other similar and/or suitable storage medium. 
     According to an embodiment of the present disclosure, the storage unit  170  may temporarily and/or permanently store an image collected through the camera unit  150 . Also, the storage unit  170  may temporarily and/or permanently store a picture and/or a video generated in response to a request for execution of photographing. The storage unit  170  may store information associated with a picture and/or information to be associated with the picture, for example, time information associated with a time where the picture is photographed, location information, information associated with a mode set for a camera when the picture is photographed, pixel information, and the like. 
     The storage unit  170  according to the present disclosure may be configured to include a plurality, i.e., more than one of the sensing processing module  171  that may detect feature information through collected sensor information, such as an eye pattern recognition algorithm that may recognize a direction in which a user gazes, a sound localization algorithm, a symbol recognition algorithm, a facial recognition algorithm, an edge detection algorithm, and the like. 
     The controller  180  controls general operations of the electronic device  100 , controls a signal flow among internal components of the electronic device  100 , and executes a function of processing data. The controller  180  may control supplying of power from a battery to internal components of the electronic device  100 . When power is supplied, the controller  180  controls a boot process of the electronic device  100 , and executes various application programs stored in a program area for executing a function of the electronic device  100 , based on settings of a user. 
     In the present disclosure, the controller  180  may be configured to include a sensor information collecting unit  181 , a sensor determining unit  182 , and a focusing unit  183 . 
     The sensor information collecting unit  181  is connected with the sensor unit  160 , the communication unit  130 , the audio processing unit  140 , the storage unit  170 , and the camera unit  150 , and may activate a plurality of sensors supported in a terminal, such as the electronic device  100 , when the camera unit  150  is driven, so as to collect sensor information of the sensors. It is preferable that the sensor information includes first sensor information that may be collected through the camera unit  150 , a MIC, the communication unit  130 , the sensor unit  160 , and the like, and second sensor information that may be collected through the sensing processing module  171  based on the collected first sensor information, such as face detection, voice detection, outline information, and the like. Here, the collected sensor information may be different based on a type of an electronic device and an ambient environment. 
     The sensor determining unit  182  may determine at least one auto-focusing sensor based on sensor information collected through the sensor information collecting unit  181  and a photographing mode. The auto-focusing sensor may include at least a direction measuring sensor that determines a direction of a subject and a distance measuring sensor that determines a distance to a subject. The sensor determining unit  182  may calculate an accuracy point of sensor information for each collected sensor and a weight associated with a photographing mode and may determine a sensor having the highest value to be an auto-focusing sensor, however, the present disclosure is not limited thereto and other similar and/or suitable methods of determining the auto-focusing sensor may be used. 
     The focusing unit  183  focuses on a subject by using a direction measuring sensor (not shown) and a distance measuring sensor (not shown) determined by the sensor determining unit  180 . For example, the focusing unit  183  may determine a direction in which the camera unit  150  aims, or in other words, a direction in which the camera unit  150  is pointed, using the distance measuring sensor, and may determine a direction of a subject based on the direction in which the camera  150  aims. The focusing unit  183  may set a Region Of Interest (ROI) for focusing on a direction of a subject. The focusing unit  183  may execute focusing by determining a distance from the set ROI to the subject, using the distance measuring sensor. 
     Hereinafter, detailed functions of the controller will be described with reference to  FIGS. 2 through 4 . 
     With the tendency of digital devices for convergence, there are many various modifications of a digital device to enumerate. The electronic device  100  may be configured by omitting or replacing predetermined components in the described configuration based on a type of the device provided. 
       FIG. 2  is a flowchart illustrating an auto-focusing method of an electronic device according to an embodiment of the present disclosure. 
     Referring to  FIG. 2 , the electronic device  100  detects a user input for driving a camera, such as the camera unit  150 , and/or driving a camera application in operation  210 . In operation  220 , the electronic device  100  activates, i.e. turns on, the camera unit  150 . In this process, the electronic device  100  may display a preview image collected through the camera unit  150  in the display unit  110 . In operation  230 , when the camera unit  150  is activated, the electronic device  100  collects a plurality of pieces of sensor information using a configuration supported in the electronic device  100  and sensing programs. Here, it is preferable that the sensor information includes sensor information collected through the camera unit  150 , a MIC, the communication unit  130 , the sensor unit  160 , and the like, and also includes sensor information collected through the sensing processing module  171  based on information collected through the components, such as face detection, voice detection, edge detection, for example, outline information, symbol recognition, direction recognition, location measurement, movement recognition, motion recognition, and the like. 
     For example, when the camera unit  150  is activated, the electronic device  100  may collect ambient luminance information, that is, information associated with a quantity of light, through a sensor that senses light, audio information collected through a MIC, location information of a terminal, and the like. Also, the electronic device  100  may collect sensor information needed for using an eye pattern recognition algorithm, a sound localization algorithm, a symbol recognition algorithm, a face recognition algorithm, an edge detection algorithm, and any other similar and/or suitable algorithm used by the electronic device  100 . 
     In operation  240 , the electronic device  100  analyzes the collected sensing information and calculates accuracies and weights of sensors, or in other words, calculates an accuracy point and a weight of each sensor. Here, the accuracy point indicates a numerical value calculated based on ambient environment information, and the weight indicates a numerical value assigned for each sensor based on a photographing mode of a photographing device. 
     For example, when a photographing environment is dark, an accuracy of sensor information collected through an image sensor may be low. Further, since the accuracy of the image sensor is low, there may be difficulty in collecting sensor information through a face recognition algorithm and an eye pattern recognition algorithm that uses image sensor information. In this case, the electronic device  100  may calculate accuracies and weights of other sensors, excluding sensors that use an image sensor, to be relatively higher. 
     In operation  250 , the electronic device  100  may determine at least one sensor for focusing, or, in other words, may determine at least one focusing sensor optimized for a photographing environment and a photographing mode based on accuracies and weights of sensors. Here, the at least one focusing sensors may include at least one of a direction measuring sensor (not shown) for measuring a direction of a subject and a distance measuring sensor (not shown). Here, the photographing mode may include a still image photographing mode, such as a picture photographing mode, and a video photographing mode. The direction measuring sensor and the distance measuring sensor may be different from each other or may be identical to each other, and this may not be limited thereto. 
     The photographing mode of the electronic device  100  may be a picture photographing mode as opposed to a video photographing mode, and an ambient environment and a weight of each sensor is different for each photographing mode and thus, sensors determined for measuring a sound and a direction for each photographing mode may be different from a video photographing mode. 
     For example, when a user photographs a video with an electronic device that is not equipped with a communication modem in an environment where it is dark and free of noise, the electronic device determines a stereo microphone sensor as a direction measuring sensor and also determines a stereo microphone sensor as a distance measuring sensor since a quantity of light is insufficient due to the dark environment and the lack of noise. In a case where the photographing mode of the camera is the video photographing mode and thus, there is a high probability that a subject generally exists in a direction from which a sound is heard, and thus, it may be construed to be a case in which a weight of a microphone sensor is calculated to be high in a photographing mode. 
     Here, the stereo microphone sensor may calculate a direction and a distance to the subject using a triangulation scheme. Also, when a user photographs a still image, for example, a picture, with an electronic device that is not equipped with a communication modem in an environment where it is dark and free of noise, the electronic device may determine a symbol recognition algorithm to be a distance measuring sensor. For example, in a video photographing mode, an image of a supplementary light that is shone may be included in an image and thus, there may be difficulty in using the supplementary light. However, in a still image, a subject desired to be photographed may be different from a subject that transfers a voice, and it may be possible that an electronic device shines a predetermined image pattern on the subject through the supplementary light. Therefore, in the sill image photographing mode, using the supplementary light is more useful for executing focusing and thus, in the still image photographing mode, a symbol recognition sensor may be selected to be a focusing sensor for measuring a distance and a stereo microphone sensor may be determined to be a focusing sensor for measuring a direction. An algorithm for measuring a distance to the subject using the symbol recognition sensor may measure a direction of the subject through a microphone sensor first, may set the corresponding direction to be an ROI, and may shine the supplementary light to the corresponding direction. Subsequently, the electronic device may be aware of a size of a symbol, and a size of the subject is inversely proportional to a distance between the electronic device and the subject and thus, the electronic device may measure the distance to the subject using the same. 
     In operation  260 , the electronic device  100  focuses on the subject using the at least one determined auto-focusing sensor, or in other words, the electronic device  100  executes focusing by measuring a distance to and a direction of a subject using the at least one determined sensor. Hereinafter, a focusing method will be described in detail with reference to  FIG. 3 . 
       FIG. 3  is a flowchart illustrating an auto-focusing method according to an embodiment of the present disclosure. 
     Referring to  FIG. 3 , the electronic device  100  determines a reference subject in an image collected through a camera, such as the camera unit  150 , in operation  310 . Here, the subject may be construed to be a target for which a decision associated with focusing is made, or in other words, the determined reference subject in an image may be used as a target corresponding to the auto-focusing method. For example, the electronic device  100  may use various decision algorithms to decide the reference subject. For example, the electronic device  100  may use an algorithm that extracts an outline of a subject using a grade of a brightness, a color, a chroma, and the like and a continuity of the grade. In this example, the subject may include a subject having a clear outline and a subject that does not have a clearly outstanding outline, such as a landscape. When the subject having a clear outline exists, the electronic device  100  may determine the subject having the clear outline to be the reference subject which is used as a reference for focusing. 
     Alternatively, the electronic device  100  may use an algorithm that calculates a similarity of a brightness, a color, a chroma, and the like, and extracts only an area having a similar characteristic to be a subject. Also, the electronic device  100  may detect a facial area from an image as a subject and may recognize the subject. The face detection operation may be executed together with an auto facial recognition function of a camera. When the electronic device  100  fails to recognize or extract a subject in an image, the electronic device  100  may determine a central area of the image to be the reference subject which is a target for which a decision associated with focusing is made. 
     In operation  320 , the electronic device  100  determines the subject to be the target for which a decision associated with focusing is made, and determines and/or measures a direction of the subject using the direction measuring sensor determined in operation  250  of  FIG. 2 . 
     For example, when the electronic device  100  is equipped with a stereo microphone, a direction and/or a distance to the subject may be determined based on a triangulation scheme using the sound localization algorithm. Alternatively, when the subject is a person and the person is equipped with a terminal including a communication device, the electronic device  100  may recognize location information of the terminal of the person corresponding to the subject, so as to determine a direction of the subject. 
     In operation  330 , the electronic device  100  sets an ROI for focusing, that is, the electronic device  100  sets a focusing area to a selected direction where the subject exists, when the direction of the subject is determined. Here, the electronic device  100  may output a focus mark indicating the set ROI on a predetermined position of a preview image. Here, the electronic device  100  executes graphics processing, with respect to a focus mark, differently based on whether focusing is completed, and outputs a state in which focusing is completed and a state in which focusing is incomplete to be distinguished. The ROI corresponds to an area that provides a reference for refocusing and an area that provides a reference for sensing a movement of a subject. 
     In operation  340 , the electronic device  100  may determine a distance from the ROI to the subject using the distance measuring sensor determined in operation  250  of  FIG. 2 , or in other words, the electronic device  100  may measure a distance to the subject using the distance measuring sensor, so as to complete an operation of focusing on the subject. 
     For example, the electronic device  100  may measure a time that it takes for an infrared light and/or an ultrasonic wave emitted from the electronic device  100  to return back through reflection from the subject, so as to determine the distance to the subject. Alternatively, when the subject is recognized through the facial recognition, the electronic device  100  may determine the distance to the subject based on a size of the subject in an image, a ratio of the subject to the image, and the like. Also, the electronic device  100  may measure the distance to the subject using a symbol recognition sensor. In this case, the electronic device  100  may measure a direction of the subject through a microphone sensor, may set the corresponding direction to be an ROI, and may shine a supplementary light in the corresponding direction. Subsequently, the electronic device  100  may be aware of a size of a symbol, and a size of the subject is inversely proportional to a distance between the electronic device  100  and the subject and thus, the electronic device  100  may measure the distance to the subject using the same. 
       FIG. 4  is a flowchart illustrating an auto-focusing method of an electronic device according to another embodiment of the present disclosure. 
     Referring to  FIG. 4 , in operation  410 , the camera unit  150  is driven according to a user input and/or a predetermined schedule and the electronic device  100  enters a picture photographing mode. The electronic device  100  according to the present disclosure may support a half-press shutter function. In this process, the electronic device  100  may display a preview image collected through the camera unit  150  in the display unit  110 . 
     In operation  420 , when the camera unit  150  is activated, the electronic device  100  collects a plurality of pieces of sensor information using a configuration supported in the electronic device  100  and sensing programs. Subsequently, the electronic device  100  analyzes the collected sensing information and calculates an accuracy point and a weight of each sensor. Here, the accuracy point indicates a numerical value calculated based on ambient environment information, and the weight indicates a numerical value assigned for each sensor based on a photographing mode of the electronic device  100 . 
     In operation  430 , the electronic device  100  may determine at least one focusing sensor optimized for a photographing environment and a photographing mode based on accuracy points and weights of sensors, or in other words, the electronic device  100  may determine at least one sensor for focusing based on sensor information. Here, the focusing sensors include at least a direction measuring sensor for measuring a direction of a subject and a distance measuring sensor. The direction measuring sensor and the distance measuring sensor may be different from each other and may be identical to each other, however, the present disclosure is not limited thereto. 
     In operation  440 , the electronic device  100  detects a first user input that requests execution of the half-press shutter function. Here, the first user input may be an input of pressing a shutter button or a half-pressing of the shutter button, as supported in the electronic device  100 , with a first pressure. In operation  450 , the electronic device  100  executes focusing by determining and/or measuring a direction and a distance to the subject using at least one determined sensor, which may be the determined focusing sensor, in response to the first user input. The electronic device  100  may output information associated with focusing to the display unit  110  as a preview image screen. When a focusing operation is completed, the electronic device  100  may be operated in a focusing lock state (AF Lock) while a user inputs a half-press shutter button. In this example, the user may determine whether focusing on the subject is executed, through a preview screen. 
     In operation  460 , the electronic device  100  may detect a second user input that requests photographing a picture. Here, the second user input may be an input of pressing a shutter button with a second pressure which is relatively greater than the first pressure. In operation  470 , the electronic device  100  executes photographing in order to photograph a picture of the subject in response to the second user input. 
       FIG. 5  illustrates diagrams for describing a candidate group of focusing sensors according to an embodiment of the present disclosure. 
     Referring to  FIG. 5 , an electronic device according to the present disclosure calculates an accuracy of a sensor based on a change of a photographing environment, assigns a weight based on a photographing mode, and supports a function of determining a focusing sensor based on a photographing environment, so as to select a sensor optimized for the photographing environment when a camera executes photographing. 
     For example, the diagram  501  is a table including accuracies of sensors for selecting a subject direction measuring sensor from among focusing sensors, and “a line” included in the table of  FIG. 5  may be construed to be an accuracy point of each sensor based on a photographing environment. The electronic device  100  may select, as a candidate group, sensors that are capable of measuring a direction from among sensors supported in the device. For example, a candidate group of direction measuring sensors may include an image sensor, a microphone, an eye recognition detection processing module, a facial recognition processing module, a communication module, and the like. The direction measuring sensors may collect sensor information based on a change of an environment, such as a change in illumination, ambient noise, and a communication signal. The electronic device  100  calculates a point based on sensor measurement accuracy, which is based on the collected sensor information. 
     For example, as illustrated in the diagram  501 , an eye pattern recognition algorithm and a facial recognition algorithm may be operated based on the information collected through the image sensor, and an accuracy of measured sensor information may be deteriorated based on a change in illumination, that is, when illumination is significantly high or low. That is, when ambient illumination is significantly high or low, the electronic device  100  sets an accuracy point of image sensor information to “0”, and when illumination is appropriate, the electronic device  100  sets an accuracy point of the image sensor to be the highest point. Also, when provided with a communication modem and a Global Positioning System (GPS) receiving module sensors that may not be affected by a change of illumination, the electronic device  100  may reflect them and may set the accuracy point to a constant value irrespective of a change of an environment. 
     Subsequently, the electronic device  100  calculates a weight value based on a photographing mode for each sensor. The weight value based on the photographing mode may indicate a value in an ideal environment, for example, a value in a case where photographing is executed in a state in which all of the sensors supported in a device are available for use. The electronic device  100  may select, as a direction measuring sensor, a sensor having the highest point obtained by multiplying an accuracy point and a weight value. 
     The electronic device  100  may select a focusing sensor using the following Equation 1.
 
MAX(point) i=1   n   =X   e   W   m   Equation 1
 
Here, X e  denotes an accuracy point of a sensor in a photographing environment, W m  denotes a weight value of a corresponding sensor based on a photographing mode, and n denotes a total number of sensors supported in an electronic device.
 
     For example, a diagram  502  is a table including accuracies of sensors for selecting a subject distance measuring sensor from among focusing sensors, and “a line” included in the table of  FIG. 5  may be construed to be an accuracy of each sensor based on a photographing environment. It may be recognized that a candidate group of distance measuring sensors and a candidate group of direction measuring sensors are determined to be different through comparing the diagram  501  and the diagram  502 . 
     For example, a gaze detection sensor may be appropriate for measuring a direction of a subject, whereas it may be inappropriate for measuring a distance. Conversely, a symbol recognition sensor may be appropriate for measuring a distance to a subject, whereas it may be inappropriate for measuring a direction of the subject. Therefore, a weight of each sensor in an algorithm for selecting distance measuring sensors may be configured to be different from a case of calculating a weight of a direction measuring sensor. As described in the diagram  501 , the electronic device  100  may calculate accuracies and weights of distance measuring sensors, and may select a sensor having the highest point obtained by multiplying an accuracy point and a weight value to be a distance measuring sensor. 
     A description will be made through a concrete example. When a terminal, such as the electronic device  100 , is operated in a video photographing mode, the terminal selects a communication modem as a direction measuring sensor, and selects an image sensor as a distance measuring sensor. For example, when a subject is equipped with a portable terminal including a communication device, such as the electronic device  100  including the communication unit  130 , a direction of photographing the subject may be sensed by recognizing a location of the portable terminal of the subject. Also, the terminal measures a signal of the portable terminal of the subject so as to sense a direction, and measures a distance using an image sensor since a quantity of light is sufficient and thus, a time for focusing may be reduced. Conversely, when the subject is not a person and/or does not have the portable terminal equipped with a communication device, the direction of the subject may be sensed by detecting a gaze of a person who executes photographing through an image sensor. Also, when the distance to the subject is far, the distance may be measured using a GPS receiving unit and MAP information associated with a neighboring area. 
     Conversely, when the terminal is operated in a picture photographing mode, a quantity of light is sufficient and thus, a communication modem and an image sensor may be determined to be focusing sensors in the same manner as the video photographing mode. When the subject is a person and is equipped with the portable terminal including the communication modem, the terminal senses a direction of the subject and sets an ROI in a preview mode, and calculates a distance to the subject using the image sensor at a point in time when a user half-presses a shutter button so as to focus on the subject. 
     As described above, according to the present disclosure, at least one focusing sensor is determined according to a photographing environment, a characteristic of a sensor, and a photographing mode, and focusing on a subject may be executed using the determined focusing sensors. That is, according to the present disclosure, focusing is executed by variously changing focusing sensors based on sensor information of sensors and thus, focusing on a desired subject may be promptly and accurately executed in an environment where focusing is difficult. 
     While the present disclosure has been described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.