Patent Publication Number: US-2021185160-A1

Title: Terminal device, terminal device control method, and memory medium

Description:
FIELD 
     The application concerned is related to a terminal device, a terminal device control method, and a memory medium. 
     BACKGROUND 
     Devices that are capable of performing wireless communication and that are configured to be easily portable (called mobile devices), such as multifunctional cellular phone terminals (smartphones) and tablet computers, are in widespread use. Generally, such mobile devices are equipped to perform communication of voice messages using the telephone function or using the Internet-based voice communication. In the following explanation, such functions of performing communication of voice messages are collectively referred to as the voice communication function. In the case of using the voice communication function in a mobile device, a touch-sensitive panel needs to be tapped for one or more times. Hence, for example, if a person is holding some other things in hands, a situation may often arise when the tapping operation is felt cumbersome. 
     For that reason, regarding smartphones, various operation methods have been proposed to activate predetermined functions in a contactless manner without performing the tapping operation. For example, in Patent Literature 1 is disclosed a configuration in which a plurality of sensors is used in combination and the device is operated in response to the actions and the utterances of the user. Moreover, in Patent Literature 2 is disclosed a configuration in which the operation mode of a mobile device is decided according to the orientation of the mobile device. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Application Laid-open No. 2017-215970 
     Patent Literature 2: Japanese Translation of PCT International Application Publication No. 2012-508530 
     SUMMARY 
     Technical Problem 
     However, in the conventional contactless operation methods, attention is not given to security. For example, when there is an incoming call based on the voice communication function in the mobile device of a user, there is a risk that the incoming call gets answered in response to a predetermined action performed by some other person present near the concerned user. 
     It is an objective of the application concerned to provide a terminal device, a terminal device control method, and a memory medium that enable contactless activation of the voice communication function only by a specific user. 
     Solution to Problem 
     For solving the problem described above, a terminal device according to one aspect of the present disclosure has a microphone; a communication unit that performs communication via a network; a first sensor that obtains depth information; a first face detecting unit that performs first-type face detection for detecting a face and distance to the face based on the depth information; and a processor, wherein when a communication program, which is meant for making the processor perform transmission and reception of messages including voice messages and which has a sound input mode for enabling collection of sounds using the microphone and transmission of voice messages based on the collected sounds, is executed, and when a message is received by the communication unit under control of the communication program being executed, the processor performs the first-type face detection using the first face detecting unit and controls turning ON and turning OFF the sound input mode according to result of the first-type face detection. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram that schematically illustrates an exemplary information processing system applicable in the application concerned. 
         FIG. 2  is a diagram illustrating an exemplary external appearance of a terminal device applicable in embodiments. 
         FIG. 3  is an exemplary flowchart for schematically explaining a sequence of operations performed for voice message transmission according to the existing technology. 
         FIG. 4A  is a diagram illustrating an example of the display on the display unit of a terminal device in which a message is received. 
         FIG. 4B  is a diagram of a screen displayed in the display unit for enabling voice message transmission. 
         FIG. 5  is an exemplary flowchart for schematically explaining a sequence of operations performed for voice message transmission according to a first embodiment. 
         FIG. 6  is an exemplary block diagram illustrating a hardware configuration of the terminal device applicable to the first embodiment. 
         FIG. 7  is a diagram illustrating a more detailed configuration example of a first sensor. 
         FIG. 8  is a diagram for explaining the principle of distance measurement implemented in the first sensor. 
         FIG. 9  is a diagram illustrating an example of depth information output by the first sensor according to the first embodiment. 
         FIG. 10  is an exemplary functional block diagram for explaining the functions of the terminal device according to the first embodiment. 
         FIG. 11  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to the first embodiment. 
         FIG. 12  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to a first modification example of the first embodiment. 
         FIG. 13  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to a second modification example of the first embodiment. 
         FIG. 14  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to a second embodiment. 
         FIG. 15A  is a diagram illustrating an example of a banner image that is displayed in the display unit in the display lock state. 
         FIG. 15B  is a diagram illustrating an example of a display lock release screen to be used for releasing the display lock according to face authentication. 
         FIG. 16  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to a first modification example of the second embodiment. 
         FIG. 17  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to a second modification example of the second embodiment. 
         FIG. 18  is a diagram that schematically illustrates an example of an information processing system that is applicable to a third embodiment and that is used in the case of implementing a push notification. 
         FIG. 19  is an exemplary functional block diagram for explaining the functions of a terminal device according to the third embodiment. 
         FIG. 20  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to the third embodiment. 
         FIG. 21  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to a first modification example of the third embodiment. 
         FIG. 22  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device according to a second modification example of the third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Preferred embodiments of the application concerned are described below in detail with reference to the accompanying drawings. In the embodiments described below, identical constituent elements are referred to by the same reference numerals, and their explanation is not given repeatedly. 
     First Embodiment 
     (Information processing system applicable in embodiments)  FIG. 1  is a diagram that schematically illustrates an exemplary information processing system applicable in the application concerned. With reference to  FIG. 1 , a plurality of terminal devices  1  is connected to a server  3  via a network  2  such as the Internet. Moreover, to the server  3 , a storage  4  is also connected that represents a high-capacity memory medium configured with a hard disk drive or a flash memory. 
     Each terminal device  1  is installed with application software  5  (hereinafter, referred to as an SNS application  5 ) that enables the use of, for example, an SNS (Social Networking Service) provided by the server  3 . The SNS provided by the server  3  is, for example, a service enabling transmission and reception of messages, including voice messages, among the terminal devices  1  via the network  2 . For example, the user of the terminal device  1  receives the SNS application  5 , which is stored in the storage  4 , from the server  3 ; installs it in the terminal device  1 ; and registers account information in the server  3 . With that, the user becomes able to use the SNS, which is provided by the server  3 , from the SNS application  5 . 
     The storage  4  can be used to store programs meant for implementing the functions (described later) of the embodiments and their modification examples according to the application concerned. For example, the user can access the server  3  using the terminal device  1 ; obtain the programs from the storage  4  via the server  3 ; and install the programs in the terminal device  1 . 
     The terminal device  1  is an information processing device configured to be small in size, light in weight, and easily portable. Examples of the terminal device  1  include a multifunctional cellular phone (smartphone) and a tablet computer. The following explanation is given under the assumption that the terminal device  1  is a smartphone. 
       FIG. 2  is a diagram illustrating an exemplary external appearance of the terminal device  1  applicable in embodiments. With reference to  FIG. 2 , the terminal device  1  includes a display unit  10 , a home button  11 , a microphone  12 , a speaker  13 , a first sensor  14 , and a second sensor  15 . The display unit  10  is a touch-sensitive panel in which, for example, a display device and an input device are configured in an integrated manner. Examples of the display device include an LCD (Liquid Crystal Display) and an organic EL (Electro-Luminescence) display. The input device outputs control signals according to the position at which it is touched. 
     The home button  11  is, for example, a button for receiving user operations meant for controlling the overall operations of the terminal device  1 . For example, when the display on the display unit  10  is locked thereby restricting the user operations with respect to the display unit  10 , the home button  11  can be operated to release the display lock. The microphone  12  collects, for example, the voice of the user and converts it into voice signals. The speaker  13  converts voice signals into a voice output. 
     As the first sensor  14 , for example, a ranging element is used. In the application concerned, as the first sensor  14 , a ToF (Time of Flight) sensor is used that performs ranging based on the difference between an illumination light, which is obtained by irradiation of a laser light, and the reflected light, which is obtained as reflection of the laser light from the ranging target. For example, the user holds the terminal device  1  in such a way that the side on which the first sensor  14  is installed is directed toward his or her face, and the distance (depth) to the parts of the face is measured by the first sensor  14 . Then, based on the depth information about the parts of the face as obtained by the first sensor  14  and based on preregistered depth information of the face, the terminal device  1  can perform face authentication of the user. 
     As the second sensor  15 , for example, an image sensor is used that performs imaging and obtains images. 
     In the information processing system, the user of each terminal device  1  can activate the SNS application  5  in the corresponding terminal device  1 , and communicate messages including voice messages with the terminal devices  1  of the other users. 
     (Voice Message Communication According to Existing Technology) 
     Prior to the explanation of a first embodiment, the communication performed according to the existing technology is explained in a schematic manner. The following explanation is given with the focus on the example of transmission and reception of voice messages between two terminal devices  1 . Herein, the two terminal devices  1  are referred to as a terminal device  1 (A) and a terminal device  1 (B); and the users of the terminal devices  1 (A) and  1 (B) are referred to as users A and B, respectively. 
       FIG. 3  is an exemplary flowchart for schematically explaining a sequence of operations performed for voice message transmission according to the existing technology. For example, the user A activates the SNS application  5  in the terminal device  1 (A) (Step S 1000 ). The user B, who has activated the SNS application  5  in the terminal device  1 (B) in an identical manner, sends a message having, for example, text data to the terminal device  1 (A). That message is received in the terminal device  1 (A) (Step S 1001 ). 
       FIG. 4A  is a diagram illustrating an example of the display on the display unit  10  of the terminal device  1 (A) in which the message is received. In the display of the display unit  10 , for example, the elapse of time is indicated from the top toward the bottom of the screen, and a message  20  that is received is displayed at the upper end of the screen. In the example illustrated in  FIG. 4A , a button  21  meant for voice message transmission is displayed at the lower end. 
     If the user A wishes to reply to the message, which is received at Step S 1001 , using a voice message; he or she operates (taps) the button  21 . In response to the operation of the button  21 , the terminal device  1 (A) switches the screen of the display unit  10  to a screen meant for voice message transmission.  FIG. 4B  is a diagram of a screen displayed in the display unit  10  for enabling voice message transmission. In the screen of the display unit  10 , a talk area  30  having a talk button  31  gets displayed. 
     When an operation (for example, tapping) of the talk button  31  is detected (Step S 1002 ), the terminal device  1 (A) starts audio recording of the sounds collected by the microphone  12  (Step S 1003 ). The audio recording is continuously performed while the talk button  31  is in the operated state. When it is detected that the talk button  31  is released from the operated state (Step S 1004 ), the terminal device  1 (A) ends the audio recording and sends the recorded contents to the terminal device  1 (B) (Step S 1005 ). 
     In this way, in the transmission of a voice message according to the existing technology, the talk button  31  is operated and, while the talk button  31  is in the operated state, the voice to be transmitted gets recorded. Thus, the user A who wishes to send a voice message happens to hold the terminal device  1  in one hand and operate the talk button  31  using the other hand. Hence, for example, when the user A is holding some other thing in one hand, the operation of the terminal device  1  becomes extremely cumbersome. 
     In the explanation given above, the audio recording is performed while the talk button  31  is in the operated state; and a voice message is sent that is recorded till the point of time of releasing the talk button  31  from the operated state. However, that is not the only possible example. Alternatively, it is also possible to think of a method in which a voice message is sent while the talk button  31  is still in the operated state. However, in that method too, the fact remains that the terminal device  1  is held in one hand and the talk button  31  is operated using the other hand. 
     (Voice Message Transmission According to First Embodiment) 
     Given below is the schematic explanation about the voice message transmission performed according to the first embodiment.  FIG. 5  is an exemplary flowchart for schematically explaining a sequence of operations performed for voice message transmission according to the first embodiment. In the following explanation, it is assumed that, for example, the user A makes the terminal device  1 (A) obtain an image of his or her face using the first sensor  14  and perform face authentication. The information about the authenticated face is stored in the terminal device  1 (A). 
     For example, the user A activates the SNS application  5  in the terminal device  1 (A) (Step S 1100 ). The user B, who has activated the SNS application  5  in the terminal device  1 (B) in an identical manner, sends a message having, for example, text data to the terminal device  1 (A). The message is received in the terminal device  1 (A) (Step S 1101 ). 
     Upon receiving the message, the terminal device  1 (A) turns the first sensor  14  toward his or her face and moves it closer to the face. Based on the face detection result obtained by the first sensor  14 , the terminal device  1 (A) determines whether or not the detected face is an already-authenticated face. If the detected face is determined to be an already-authenticated face (Step S 1102 ), the terminal device  1 (A) starts audio recording of the voice collected by the microphone  12  (Step S 1103 ). The audio recording is continuously performed until it is determined based on the detection result of the first sensor  14  that the face has moved away. When it is detected based on the detection result of the first sensor  14  that the face has moved away from the terminal device  1 (A) by a predetermined distance or more (Step S 1104 ), the terminal device  1 (A) ends the audio recording and sends the recorded contents to the terminal device  1 (B) (Step S 1105 ). 
     In this way, in the first embodiment, only by moving the face close to the terminal device  1 (A), a voice message can be set without having to perform any button operation in the terminal device  1 (A). Thus, in response to a message from the user B, the user A becomes able to easily send a voice message using only one hand. 
     In the explanation given above, audio recording is performed while the face is kept close to the terminal device  1 (A); and the recorded voice message is sent once the face is moved away from the terminal device  1 (A) by a predetermined distance or more. However, that is not the only possible case. Alternatively, it is also possible to think of a method in which a voice message is sent while the face is kept close to the terminal device  1 (A). In that case too, the fact remains that a voice message can be easily sent as a response using only one hand. 
     (More Detailed Explanation of First Embodiment) 
     Given below is the more detailed explanation of the first embodiment. 
     (Specific Configuration of Terminal Device According to First Embodiment) 
     Firstly, regarding the terminal device  1  according to the first embodiment, the specific explanation is given below.  FIG. 6  is an exemplary block diagram illustrating a hardware configuration of the terminal device  1  applicable to the first embodiment. With reference to  FIG. 6 , the terminal device  1  includes a CPU (Central Processing Unit)  1000 , a ROM (Read Only Memory)  1001 , a RAM (Random Access Memory)  1002 , an imaging unit  1003 , a ranging unit  1004 , a storage  1006 , an input device  1007 , a display control unit  1009 , a data I/F (interface)  1010 , a communication I/F  1011 , an audio I/F  1012 , and an orientation detecting unit  1013  that are connected to each other by a bus  1020 . Moreover, the terminal device  1  includes a power source unit  1060  that supplies power to the constituent elements of the terminal device  1 . 
     To the ranging unit  1004 , a light source unit  1005  is connected. The power supply unit  1060  supplies power to the ranging unit  1004  and the light source unit  1005  via switches  1061   a  and  1061   b , respectively. Moreover, the power supply unit  1060  supplies power to the imaging unit  1003  via a switch  1062 . The switches  1061   a ,  1061   b , and  1062  switch between the ON state and the OFF state under the control of, for example, the CPU  1000 . 
     The storage  1006  is a nonvolatile memory medium such as a flash memory or a hard disk drive. The CPU  1000  follows instructions written in the programs that are stored in the storage  1006  or the ROM  1001 , and controls the overall operations of the terminal device  1  while using the RAM  1002  as the work memory. 
     The input device  1007  outputs control signals according to user operations. The display control unit  1009  generates display signals, which are displayable by a display device  1008 , based on display control signals sent by the CPU  1000 . The input device  1007  and the display device  1008  are configured in an integrated manner and function as a touch-sensitive panel  1030 . 
     The data I/F  1010  is an interface for enabling the terminal device  1  to perform data communication with external devices. For example, USB (Universal Serial Bus) or Bluetooth (registered trademark) can be used as the data I/F  1010 . The communication I/F  1011  performs communication with the network  2 . To the audio I/F  1012  are connected the microphone  12  and the speaker  13 . The audio I/F  1012  performs AD (Analog to Digital) conversion of the analog sound signals that are based on the sounds collected by the microphone  12 , and output digital sound data. Moreover, the audio I/F  1012  performs DA (Digital to Analog) conversion of sound data received via the bus  1020  into analog sound signals, and sends it to the speaker  13 . 
     The orientation detecting unit  1013  detects the orientation of the terminal device  1 . For example, as the orientation detecting unit  1013 , it is possible to implement a 9-axis sensor including a gyro sensor (an angular velocity sensor), an acceleration sensor, and a geomagnetic sensor that individually perform detection along the three axes, namely, the x axis, the y axis, and the z axis. 
     The imaging unit  1003  corresponds to the second sensor  15  and includes: an image sensor that outputs image signals corresponding to the light with which it is irradiated; an optical system that guides the light from the photographic subject to the light receiving surface of the image sensor; and a processing unit that performs predetermined signal processing and predetermined image processing with respect to the image signals output from the image sensor. As the image sensor, it is possible to use a solid-state image sensing device (CIS: CMOS Image Sensor) in which a CMOS (Complementary Metal Oxide Semiconductor) is used. 
     The solid-state imaging device can be configured by forming an image sensor unit, in which pixels are arranged in an array-like manner, and a processing unit on a single semiconductor chip. Moreover, the solid-state imaging device can have a two-layer structure configured by bonding a layer in which an image sensor is formed and a layer in which a processing unit is formed. However, that is not the only possible case. Alternatively, the solid-state imaging device can have a three-layer structure configured by further bonding a layer in which a memory is formed to the layers in which an image sensor unit and a processing unit are formed. 
     The ranging unit  1004  and the light source unit  1005  constitute a ToF sensor representing the first sensor  14 . Although explained later in detail, the light source unit  1005  includes a light source of, for example, infrared light (IR). The ranging unit  1004  includes a light receiving element that receives the reflected light of the infrared light emitted from the light source unit  1005  onto the target, and includes a signal processing unit that generates point group information in which each point holds depth information based on the output of the light receiving element (distance information along the optical axis direction). 
       FIG. 7  is a diagram illustrating a more detailed configuration example of the first sensor  14 . In the first sensor  14 , the light source unit  1005  includes a light modulating unit  1050 , a VCSEL (Vertical Cavity-Surface Emitting Laser)  1051 , and a projector lens  1052 . The ranging unit  1004  includes a light receiving lens  1040 , a ToF sensor  1041 , a memory unit  1042 , a no-effect information generating unit  1043 , an arithmetic processing unit  1044 , and an output unit  1045 . 
     The light modulating unit  1050  sends the light output from the VCSEL  1051 , such as modulation signals to be used in performing modulation at high-frequency waves of about 10 MHz, to the VCSEL  1051 . Moreover, the light modulating unit  1050  sends timing signals, which indicate the timings of modulation of the light of the VCSEL  1051 , to the ToF sensor  1041  and the no-effect information generating unit  1043 . 
     According to the modulation signals sent by the light modulating unit  1050 , the VCSEL  1051  emits light while performing high-speed modulation of the light of the invisible area such as the infrared light; and emits the resultant light onto the target object for distance measurement by the first sensor  14 . In the first embodiment, the light source that emits light toward the target object is explained as the VCSEL  1051 . However, alternatively, it is possible to use some other light source such as a laser diode. 
     The projector lens  1052  is configured using a narrow-angle lens for adjusting the distribution of light, so that the light emitted from the VCSEL  1051  has the desired irradiation angle. 
     The light receiving lens  1040  is configured using a wide-angle lens that covers the light receiving range of the light received by the first sensor  14  for the purpose of distance measurement. The light receiving lens  1040  forms an image of the light, which is collected within the angle of field of the light receiving range, onto the sensor surface of the ToF sensor  1041 . 
     The ToF sensor  1041  is configured using light receiving elements (pixels) having sensitivity in the wavelength area of the light that is emitted from the VCSEL  1051 ; and receives the light, with which the light receiving lens  1040  has formed an image, using a plurality of light receiving elements arranged in an array-like manner on the sensor surface. For example, the ToF sensor  1041  includes the light receiving elements in about 180×240 number of arrays. The ToF sensor  1041  is disposed near the VCSEL  1051  and receives the light coming from the light receiving range including the irradiation range within which the light is emitted from the VCSEL  1051 . Then, the ToF sensor  1041  outputs RAW signals having the amount of light received by each light receiving element as the measured value. 
     The memory unit  1042  is used to store point group information that is built using the RAW signals output from the ToF sensor  1041 . For example, the memory unit  1042  can be used to store the latest point group information obtained when a change occurs in the light receiving range, or can be used to store, as background information, the point group information in the state in which no target object is present in the light receiving range. 
     The no-effect information generating unit  1043  eliminates, according to the timing signals received from the light modulating unit  1050 , the effect of the ambient light from the RAW signals received from the ToF sensor  1041 . As a result, the no-effect information generating unit  1043  generates point group information having only the reflected light component corresponding to the light emitted from the VCSEL  1051  as the measured value (hereinafter, called no-effect information); and sends the no-effect information to the arithmetic processing unit  1044 . Moreover, the no-effect information generating unit  1043  reads the background information stored in the memory unit  1042 ; obtains the difference between the background information and the point group information built using the RAW signals received from the ToF sensor  1041 ; and generates no-effect information confined to the target object in the light receiving range. 
     Regarding the arithmetic processing unit  1044 , every time the no-effect information is received from the no-effect information generating unit  1043 , the arithmetic processing unit  1044  performs the calculation for obtaining the distance to the target object from each point in the no-effect information; and sends depth signals, which represent the distances, to the output unit  1045 . Moreover, as may be necessary, the arithmetic processing unit  1044  can read the latest point group information stored in the memory unit  1042 , and obtain the distances to the target object using that point group information. 
     The output unit  1045  generates depth information, in which the distances to the photographic subject are lined up according to the arrangement of the light receiving elements, based on the depth signals received from the arithmetic processing unit  1044 ; and outputs the depth information to the bus  1020 . 
     Meanwhile, in the explanation given above, a VCSEL is used as the light source element in the light source unit  1005 . However, that is not the only possible case. Alternatively, for example, an LED (Light Emitting Diode) can be used as the light source element used in the light source unit  1005 . 
     Explained below with reference to  FIG. 8  is the principle of distance measurement implemented in the first sensor  14 . For example, the VCSEL  1051  emits illumination light toward the target object, and the ToF sensor  1041  receives the reflected light, which is obtained due to the reflection of the illumination light from the target object, with a delay of a time period ϕ from the emission timing of the illumination light according to the distance to the target object. At that time, in the ToF sensor  1041 , the reflected light is received by a light receiving unit A, which receives light at the same time interval as the time interval at which the VCSEL  1051  emits the illumination light, and by a light receiving unit B, which receives light at that same time interval but starting from the end of light reception by the light receiving unit A. Thus, an electric charge gets accumulated in the light receiving units A and B. 
     Based on the ratio of the electrical charge accumulated in the light receiving unit A and the electrical charge accumulated in the light receiving unit B, the time period ϕ taken till the reception of the reflected light can be obtained; and the distance to the target object can be calculated according to the speed of light. Such a ToF method for calculating the distance to the target object based on the ratio of the electrical charge is called an indirect ToF. 
     In contrast, the ToF method for calculating the distance to the target object based on the time difference between the illumination light and the reflected light is called a direct ToF. In the application concerned, either one of the indirect ToF and the direct ToF can be implemented. 
       FIG. 9  is a diagram illustrating an example of the depth information output by the first sensor  14  according to the first embodiment. In the example illustrated in  FIG. 9 , the depth information is expressed in the form of gradation by performing interpolation among the points. In  FIG. 9 , excluding the background, the portion having a darker shade (black shade) indicates a shorter distance, and the portion having a lighter shade (white shade) indicates a longer distance. 
     More particularly, regarding the face that is oriented sideways as illustrated in  FIG. 9 , it can be understood that a temporal region  50 , an outer edge  51   a  of the auricle of ear, and an earing  52  have the darkest shade and are at the shortest distance. Moreover, it can be understood that a jaw  53  has a lighter shade than the temporal region  50  and is farther than the temporal region  50 . Furthermore, it can be understood that hair  54  on the back of the head has the lightest shade and is farthest from among the other areas of the face. Moreover, it can be understood that, in the auricle of ear, the outer edge  51   a  and an inner portion  51   b  have different levels of darkness, and the inner portion  51   b  is farther than the outer edge  51   a.    
     In this way, based on the ranging result obtained by the first sensor  14 , it becomes possible to obtain the concavo-convex shape of the target object. 
       FIG. 10  is an exemplary functional block diagram for explaining the functions of the terminal device  1  according to the first embodiment. With reference to  FIG. 10 , the terminal device  1  includes an SNS application unit  100 , a detection/control unit  110 , an overall control unit  120 , a communication unit  121 , a display unit  122 , an input receiving unit  123 , an authenticating unit  124 , and a user information storing unit  125 . 
     Of those functions, the SNS application unit  100  corresponds to the SNS application  5  provided by the server  3 , and is configured in the terminal device  1  as a result of installing an installation program, which is obtained from the server  3 , in the terminal device  1 . The detection/control unit  110  performs operations according to the first embodiment, and is configured in the terminal device  1  as a result of installing an installation program, which is obtained from the server  3  or another server, in the terminal device  1 . However, that is not the only possible case. Alternatively, the installation program for configuring the detection/control unit  110  can be included in the installation program for configuring the SNS application unit  100 . 
     On the other hand, the overall control unit  120 , the communication unit  121 , the display unit  122 , the input receiving unit  123 , and the authenticating unit  124  are installed in advance in the terminal device  1 . The user information storing unit  125  is configured using, for example, a predetermined area of the storage  1006 . 
     The overall control unit  120  represents, for example, the OS (Operating System) that controls the overall operations of the terminal device  1 . The communication unit  121  controls the communication performed via the network  2 . The display unit  122  generates display control signals meant for performing display in the display device  1008 . The input receiving unit  123  receives user operations with respect to the input device  1007 . 
     The authenticating unit  124  authenticates the user of the terminal device  1  based on the user information stored in the user information storing unit  125 . The user information used by the authenticating unit  124  in performing user authentication contains: a user ID; a password; a PIN (Personal Identification Number) code; face information based on the depth information detected by a first face detecting unit  112  (described later); and a taken image detected by a second face detecting unit  114  (described later). 
     The SNS application unit  100  includes a UI (User Interface) unit  101 , a communication processing unit  102 , and a sound processing unit  103 . The UI unit  101  provides a user interface enabling the user to scan the terminal device  1 ; and is used to define the configuration of the display screens to be displayed in the display device  1008  by the display unit  122  and to define user operations performed with respect to the input device  1007  and received by the input receiving unit  123 . The communication processing unit  102  performs processing related to the communication in the concerned SNS. The sound processing unit  103  performs processing related to the transmission and reception of voice messages in the concerned SNS. 
     The detection/control unit  110  includes a ranging processing unit  111 , the first face detecting unit  112 , an imaging processing unit  113 , the second face detecting unit  114 , a movement estimating unit  115 , and an application control unit  116 . 
     The ranging processing unit  111  performs ranging using the first sensor  14 , that is, using the ranging unit  1004  and the light source unit  1005 ; and obtains depth information. The first face detecting unit  112  detects the face based on the depth information obtained by the ranging processing unit  111 . Moreover, the first face detecting unit  112  can compare a plurality of sets of depth information obtained in chronological order, and accordingly detect the movement of the face. 
     The imaging processing unit  113  performs imaging using the imaging unit  1003  and obtains a taken image. The second face detecting unit  114  detects the face based on the taken image obtained by the imaging processing unit  113 . Moreover, the second face detecting unit  114  can compare a plurality of taken images obtained in a chronological order, and accordingly detect the movement of the face. 
     The movement estimating unit  115  estimates the movement of the terminal device  1  based on the output of the orientation detecting unit  1013 . For example, when the user holds the terminal device  1  in hand and moves it, the movement estimating unit  115  can detect the movement according to the movement estimation result based on the output of the orientation detecting unit  1013 . 
     The application control unit  116  controls the operations of the SNS application unit  100  and obtains the state of the SNS application unit  100 . For example, based on the result of face detection performed by the first face detecting unit  112  and the second face detecting unit  114 , the application control unit  116  controls the operations of the SNS application unit  100 . 
     The programs that are written for implementing the operations of the SNS application unit  100  and the detection/control unit  110  in the terminal device  1  are stored in a downloadable manner in a computer (for example, the server  3 ) that is connected to the network  2  such as the Internet. Alternatively, the programs can be distributed via the network  2  such as the Internet. Still alternatively, the programs can be recorded as installable files or executable files in a computer-readable recording medium such as a CD (Compact Disk), a flexible disk (FD), or a DVD (Digital Versatile Disk). 
     Of those programs, the program written for configuring the SNS application unit  100  (i.e., the SNS application  5 ) has a modular configuration including the UI unit  101 , the communication processing unit  102 , and the sound processing unit  103 . The program written for configuring the detection/control unit  110  (i.e., a control program) has a modular configuration including the ranging processing unit  111 , the first face detecting unit  112 , the imaging processing unit  113 , the second face detecting unit  114 , and the application control unit  116 . As far as the actual hardware is concerned, the CPU  1000  reads the programs from a recording medium, such as the ROM  1001  or the storage  1006 , and executes the programs; so that the abovementioned constituent elements get loaded and generated in the main memory device such as the RAM  1002 . 
     Meanwhile, from among the functions included in the detection/control unit  110 , regarding the functions that are same as the preinstalled functions in the terminal device  1 , the preinstalled functions in the terminal device  1  can be used. For example, when the terminal device  1  has the preinstalled function of performing face authentication based on the depth information, that face authentication function can be used in the ranging processing unit  111  and the first face detecting unit  112 . 
     (Details of Operations According to First Embodiment) 
     Given below is the more detailed explanation about the operations performed in the terminal device  1  according to the first embodiment.  FIG. 11  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1  according to the first embodiment. At the start of the operations illustrated in the flowchart in  FIG. 11 , it is assumed that the switches  1061   a  and  1061   b  are in the OFF state. Hence, no power is supplied to the ranging unit  1004  and the light source unit  1005 , and their functions are disabled. In an identical manner, it is assumed that the switch  1062  is in the OFF state. Hence, no power is supplied to the imaging unit  1003 , and its functions are disabled. 
     At Step S 100 , the application control unit  116  obtains the state of the SNS application unit  100 , and determines whether or not the SNS application  5  is running. If the application control unit  116  determines that the SNS application  5  is not running (No at Step S 100 ), then the system control returns to Step S 100 . On the other hand, if the application control unit  116  determines that the SNS application  5  is running (Yes at Step S 100 ), then the system control proceeds to Step S 101 . 
     At Step S 101 , the application control unit  116  determines whether or not the voice input autodetection mode is turned ON in the settings. The voice input autodetection mode is an item set, for example, using a setting screen presented by the overall control unit  120 . When the voice input autodetection mode is turned ON, the autodetection function of the detection/control unit  110  with respect to a voice input gets enabled. If the application control unit  116  determines that the voice input autodetection mode is not turned ON in the settings (No at Step S 101 ), then the system control proceeds to Step S 120 . 
     At Step S 120 , the application control unit  116  instructs the SNS application unit  100  to maintain the operation mode for inputting messages to the normal character input mode. After the operation at Step S 120  is performed, the application control unit  116  ends the sequence of operations illustrated in the flowchart in  FIG. 11 . 
     Meanwhile, at Step S 101 , if the application control unit  116  determines that the voice input autodetection mode is turned ON in the settings (Yes at Step S 101 ), then the system control proceeds to Step S 102 . At Step S 102 , the application control unit  116  determines whether or not the SNS application unit  100  has received a message that is sent from another terminal device  1  using the corresponding SNS application  5 . In that case, the message can be a text message written by inputting characters, or a voice message given by inputting the voice. 
     If the application control unit  116  determines that the SNS application unit  100  has not received a message (No at Step S 102 ), then the system control returns to Step S 102 . On the other hand, if the application control unit  116  determines that the SNS application unit  100  has received a message (Yes at Step S 102 ), then the system control proceeds to Step S 103 . 
     At Step S 103 , the application control unit  116  turns ON the ranging unit  1004  and the light source unit  1005 . More particularly, the application control unit  116  instructs, for example, the overall control unit  120  to control the switches  1061   a  and  1061   b  in the ON state. As a result of switching ON the switches  1061   a  and  1061   b , power gets supplied to the ranging unit  1004  and the light source unit  1005 , and their functions are enabled. Once the functions of the ranging unit  1004  and the light source unit  1005  are enabled, the ranging processing unit  111  starts the ranging operation based on the depth information output from the ranging unit  1004 . 
     Subsequently, at Step S 104 , the application control unit  116  determines whether or not the terminal device  1  has been moved during a predetermined period of time since the point of time of reception of the message at Step S 102 . The application control unit  116  can determine about the movement of the terminal device  1  based on, for example, the output of the movement estimating unit  115 . 
     Herein, although the explanation is given about the case in which it is determined at Step S 104  about whether or not the terminal device  1  has been moved, that is not the only possible case. For example, at Step S 104 , the face can be detected based on the depth information obtained by the ranging processing unit  111 , and it can be determined whether or not the detected face has moved closer to the terminal device  1 . That implies obtaining the variation in the relative position between the terminal device  1  and the face representing the ranging target. 
     If the application control unit  116  determines at Step S 104  that the terminal device  1  has not been moved during the predetermined period of time (No at Step S 104 ), then the system control proceeds to Step S 112 . On the other hand, if the application control unit  116  determines at Step S 104  that the terminal device  1  has been moved during the predetermined period of time (Yes at Step S 104 ), then the system control proceeds to Step S 105 . 
     At Step S 105 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . Subsequently, at Step S 106 , based on the distance obtained at Step S 105 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. 
     If the application control unit  116  determines at Step S 106  that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 106 ), then the system control proceeds to Step S 112 . That is, in this case, it is possible to think that the user has no intention to perform a voice input and send a voice message. Hence, the subsequent operations related to voice message transmission are cancelled. 
     On the other hand, if the application control unit  116  determines at Step S 106  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 106 ), then the system control proceeds to Step S 107 . 
     Meanwhile, in  FIG. 11 , although it is illustrated that the operations at Steps S 105  and S 106  are over in only one iteration; in practice, the operations at Steps S 105  and S 106  are performed in a loop until the condition at Step S 106  is satisfied. 
     At Step S 107 , the application control unit  116  instructs the SNS application unit  100  to set the operation mode to the voice input mode (i.e., to turn ON the voice input mode). In response to the instruction, the SNS application unit  100  sets the operation mode to the voice input mode, and starts voice input processing using the sound processing unit  103  based on the sounds collected by the microphone  12 . 
     Then, at Step S 108 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which is obtained as a result of processing performed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 102 . 
     Subsequently, at Step S 109 , based on the face detection result obtained by the first face detecting unit  112 , the application control unit  116  determines whether or not the object (face) has moved away from the predetermined distance from the terminal device  1 . If the application control unit  116  determines that the object (face) has not moved away from the predetermined distance (No at Step S 109 ), then the system control returns to Step S 108 . 
     On the other hand, at Step S 109 , if the application control unit  116  determines that the object (face) has moved away from the predetermined distance (Yes at Step S 109 ), then the system control proceeds to Step S 110 . That is, in this case, it is possible to think that the user intends to discontinue or end the transmission of the voice message. At Step S 110 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to that instruction, the SNS application unit  100  ends the voice input processing performed by the sound processing unit  103 , and ends the voice message transmission performed by the communication processing unit  102 . 
     Subsequently, at Step S 111 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 110 . If the application control unit  116  determines that the next message is received (Yes at Step S 111 ), then the system control returns to Step S 104 . On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 111 ), then the system control proceeds to Step S 112 . 
     At Step S 112 , the application control unit  116  turns OFF the ranging unit  1004  and the light source unit  1005 . More particularly, the application control unit  116  instructs, for example, the overall control unit  120  to control the switches  1061   a  and  1061   b  in the OFF state. As a result of switching OFF the switches  1061   a  and  1061   b , the power supply from the power supply unit  1060  to the ranging unit  1004  and the light source unit  1005  is stopped, and their functions are disabled. 
     When the operation at Step S 112  is finished, the sequence of operations illustrated in the flowchart in  FIG. 11  is ended. 
     In this way, in the first embodiment, the SNS application unit  100  controls the operation of turning ON and turning OFF the voice input mode based on the distance between the terminal device  1  and the face. That eliminates the need for the user to perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. That is, the user becomes able to send a voice message in a contactless manner except for holding the terminal device  1 . 
     Moreover, in the first embodiment, the SNS application unit  100  controls the operation of turning ON and turning OFF the voice input mode based on the output of the ToF sensor  1041  for which infrared light is used as the light source. Hence, even in a dark environment such as in the night time, the control for turning ON and turning OFF the voice input mode can be performed. For example, in the case of performing that control using an image sensor such as a CIS, it is required to have the outside light of some brightness. Hence, such an image sensor is not suitable for use in a dark environment. 
     Furthermore, in the first embodiment, the distance to the face is measured at the time when a voice input is performed for sending a voice message. Hence, the sensitivity of the microphone  12  (the gain with respect to the output of the microphone  12 ) can be adjusted based on the distance to the face. That enables transmission of the voice message with an appropriate sound level. 
     First Modification Example of First Embodiment 
     Given below is the explanation of a first modification example of the first embodiment. In the first embodiment, the SNS application unit  100  controls the voice input mode based on the distance of the face from the terminal device  1 . In contrast, in the first modification example of the first embodiment, the SNS application unit  100  controls the voice input mode by detecting the movement of the mouth based on the depth information. 
     In the first modification example of the first embodiment, the configuration of the terminal device  1  as explained with reference to  FIGS. 6 to 10  according to the first embodiment can be implemented without modification. 
       FIG. 12  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1  according to the first modification example of the first embodiment. In  FIG. 12 , the operations identical to the operations illustrated in the flowchart in  FIG. 11  are referred to by the same step numbers, and their explanation is given in short. At the start of the operations illustrated in the flowchart in  FIG. 12 , it is assumed that the switches  1061   a  and  1061   b  are in the OFF state. In an identical manner, it is assumed that the switch  1062  is in the OFF state. Hence, no power is supplied to the imaging unit  1003 , and its functions are disabled. 
     In the flowchart illustrated in  FIG. 12 , the operations from Step S 100  to Step S 107  are identical to the operations performed from Step S 100  to Step S 107  illustrated in the flowchart in  FIG. 11 . That is, at Step S 100 , the application control unit  116  determines whether or not the SNS application  5  is running. If the application control unit  116  determines that the SNS application  5  is not running (No at Step S 100 ), then the system control returns to Step S 100 . On the other hand, if the application control unit  116  determines that the SNS application  5  is running (Yes at Step S 100 ), then the system control proceeds to Step S 101 . 
     At Step S 101 , the application control unit  116  determines whether or not the voice input autodetection mode is turned ON in the settings. If the application control unit  116  determines that the voice input autodetection mode is not turned ON in the settings (No at Step S 101 ), then the system control proceeds to Step S 120 . At Step S 120 , the application control unit  116  instructs the SNS application unit  100  to maintain the operation mode for inputting messages to the normal character input mode. That marks the end of the sequence of operations illustrated in the flowchart in  FIG. 12 . 
     Meanwhile, at Step S 101 , if the application control unit  116  determines that the voice input autodetection mode is turned ON in the settings (Yes at Step S 101 ), then the system control proceeds to Step S 102 . At Step S 102 , the application control unit  116  determines whether or not the SNS application unit  100  has received a message that is sent from another terminal device  1  using the corresponding SNS application  5 . If the application control unit  116  determines that the SNS application unit  100  has not received a message (No at Step S 102 ), then the system control returns to Step S 102 . 
     On the other hand, if the application control unit  116  determines that the SNS application unit  100  has received a message (Yes at Step S 102 ), then the system control proceeds to Step S 103 . At Step S 103 , the application control unit  116  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 104 , the application control unit  116  detects the movement of the terminal device  1  using a gyro and determines whether or not the terminal device  1  has been moved during a predetermined period of time since the point of time of reception of the message at Step S 102 . If the application control unit  116  determines that the terminal device  1  has not been moved (No at Step S 104 ), then the system control proceeds to Step S 205 . 
     On the other hand, if the application control unit  116  determines at Step S 104  that the terminal device  1  has been moved during the predetermined period of time (Yes at Step S 104 ), then the system control proceeds to Step S 105 . At Step S 105 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 106 , based on the distance obtained at Step S 105 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. In an identical manner to the explanation given with reference to  FIG. 11 ; in practice, the operations at Steps S 105  and S 106  are performed in a loop until the condition at Step S 106  is satisfied. 
     At Step S 106 , if the application control unit  116  determines that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 106 ), then the system control proceeds to Step S 205 , and the subsequent operations related to voice message transmission are canceled. 
     On the other hand, if the application control unit  116  determines at Step S 106  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 106 ), then the system control proceeds to Step S 107 . At Step S 107 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode. 
     Subsequently, at Step S 200 , the application control unit  116  instructs the first face detecting unit  112  to start detecting the movement of the mouth in the face using the face detection result that is based on the depth information. In response to the instruction, the first face detecting unit  112  compares a plurality of sets of depth information obtained in, for example, chronological order and detects the movement of the mouth. 
     Subsequently, at Step S 201 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which has been processed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 102 . 
     Then, at Step S 202 , based on the result of mouth movement detection started by the first face detecting unit  112  at Step S 200 , the application control unit  116  determines whether or not the movement of the mouth has stopped for a predetermined period of time. At Step S 202 , if the application control unit  116  determines that the movement of the mouth has not stopped for the predetermined period of time (No at Step S 202 ), then the system control returns to Step S 201 . On the other hand, if the application control unit  116  determines that the movement of the mouth has stopped for the predetermined period of time (Yes at Step S 202 ), then the system control proceeds to Step S 203 . 
     Meanwhile, in  FIG. 12 , although it is illustrated that the operations at Steps S 201  and S 202  are over in only one iteration; in practice, the operations at Steps S 201  and S 202  are performed in a loop until the condition at Step S 202  is satisfied. 
     The operations performed from Step S 203  onward are identical to the operations performed from Step S 110  onward illustrated in the flowchart in  FIG. 11  according to the first embodiment. That is, at Step S 203 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to the instruction, the SNS application unit  100  ends the voice input processing performed using the sound processing unit  103 , and ends the voice message transmission operation performed using the communication processing unit  102 . 
     Subsequently, at Step S 204 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 203 . If the application control unit  116  determines that the next message is received (Yes at Step S 203 ), then the system control returns to Step S 104 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 204 ), then the system control proceeds to Step S 205 . At Step S 205 , the application control unit  116  turns OFF the ranging unit  1004  and the light source unit  1005 . When the operation at Step S 205  is finished, the sequence of operations illustrated in the flowchart in  FIG. 11  is ended. 
     In this way, in the first modification example of the first embodiment, the control for turning OFF the voice input mode is performed according to the result of detecting the movement of the mouth based on the depth information. Hence, voice message transmission can be controlled with higher accuracy. 
     Moreover, in the first modification example of the first embodiment, in an identical manner to the first embodiment, the user need not perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. 
     Furthermore, in the first modification example of the first embodiment, in an identical manner to the first embodiment, the SNS application unit  100  controls the operation of turning ON and turning OFF the voice input mode based on the output of the ToF sensor  1041  for which infrared light is used as the light source. Hence, even in a dark environment such as in the night time, the control for turning ON and turning OFF the voice input mode can be performed. 
     Second Modification Example of First Embodiment 
     Given below is the explanation of a second modification example of the first embodiment. In the first modification example of the first embodiment, the SNS application unit  100  controls the voice input mode by detecting the movement of the mouth based on the depth information. In contrast, in the second modification example of the first embodiment, the SNS application unit  100  controls the voice input mode by detecting the movement of the mouth based on a taken image. 
     In the first modification example of the first embodiment, the configuration of the terminal device  1  as explained with reference to  FIGS. 6 to 10  according to the first embodiment can be implemented without modification. 
       FIG. 13  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1  according to the second modification example of the first embodiment. In  FIG. 13 , the operations identical to the operations illustrated in the flowchart in  FIG. 11  are referred to by the same step numbers, and their explanation is given in short. At the start of the operations illustrated in the flowchart in  FIG. 13 , it is assumed that the switches  1061   a  and  1061   b  are in the OFF state. In an identical manner, it is assumed that the switch  1062  is in the OFF state. Hence, no power is supplied to the imaging unit  1003 , and its functions are disabled. 
     In the flowchart illustrated in  FIG. 13 , the operations from Step S 100  to Step S 107  are identical to the operations performed from Step S 100  to Step S 107  illustrated in the flowchart in  FIG. 11 . That is, at Step S 100 , the application control unit  116  determines whether or not the SNS application  5  is running. If the application control unit  116  determines that the SNS application  5  is not running (No at Step S 100 ), then the system control returns to Step S 100 . On the other hand, if the application control unit  116  determines that the SNS application  5  is running (Yes at Step S 100 ), then the system control proceeds to Step S 101 . 
     At Step S 101 , the application control unit  116  determines whether or not the voice input autodetection mode is turned ON in the settings. If the application control unit  116  determines that the voice input autodetection mode is not turned ON in the settings (No at Step S 101 ), then the system control proceeds to Step S 120 . At Step S 120 , the application control unit  116  instructs the SNS application unit  100  to maintain the operation mode for inputting messages to the normal character input mode. That marks the end of the sequence of operations illustrated in the flowchart in  FIG. 13 . 
     Meanwhile, at Step S 101 , if the application control unit  116  determines that the voice input autodetection mode is turned ON in the settings (Yes at Step S 101 ), then the system control proceeds to Step S 102 . At Step S 102 , the application control unit  116  determines whether or not the SNS application unit  100  has received a message that is sent from another terminal device  1  using the corresponding SNS application  5 . If the application control unit  116  determines that the SNS application unit  100  has not received a message (No at Step S 102 ), then the system control returns to Step S 102 . 
     On the other hand, if the application control unit  116  determines that the SNS application unit  100  has received a message (Yes at Step S 102 ), then the system control proceeds to Step S 103 . At Step S 103 , the application control unit  116  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 104 , the application control unit  116  detects the movement of the terminal device  1  based on the output of the movement estimating unit  115  and determines whether or not the terminal device  1  has been moved during a predetermined period of time since the point of time of reception of the message at Step S 102 . If the application control unit  116  determines that the terminal device  1  has not been moved (No at Step S 104 ), then the system control proceeds to Step S 306 . 
     On the other hand, if the application control unit  116  determines at Step S 104  that the terminal device  1  has been moved during the predetermined period of time (Yes at Step S 104 ), then the system control proceeds to Step S 105 . At Step S 105 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 106 , based on the distance obtained at Step S 105 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. In an identical manner to the explanation given with reference to  FIG. 11 ; in practice, the operations at Steps S 105  and S 106  are performed in a loop until the condition at Step S 106  is satisfied. 
     At Step S 106 , if the application control unit  116  determines that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 106 ), then the system control proceeds to Step S 306 , and the subsequent operations related to voice message transmission are canceled. 
     On the other hand, if the application control unit  116  determines at Step S 106  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 106 ), then the system control proceeds to Step S 107 . At Step S 107 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode. 
     Subsequently, at Step S 300 , the application control unit  116  turns ON the functions of the imaging unit  1003 . More particularly, the application control unit  116  instructs, for example, the overall control unit  120  to start supplying power to the imaging unit  1003 . In response to the instruction, the overall control unit  120  turns ON the switch  1062  and starts the power supply from the power source unit  1060  to the imaging unit  1003 . As a result, the functions of the imaging unit  1003  are enabled, and the imaging processing unit  113  starts obtaining a taken image. 
     Then, at Step S 301 , the application control unit  116  instructs the second face detecting unit  114  to start detecting the movement of the mouth in the face using the face detection result that is based on the taken image. In response to the instruction, the second face detecting unit  114  compares a plurality of taken images obtained in, for example, chronological order and detects the movement of the mouth. 
     Subsequently, at Step S 302 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which is obtained as a result of processing performed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 102 . 
     Then, at Step S 303 , based on the result of mouth movement detection started by the second face detecting unit  114  at Step S 301 , the application control unit  116  determines whether or not the movement of the mouth has stopped for a predetermined period of time. At Step S 303 , if the application control unit  116  determines that the movement of the mouth has not stopped for the predetermined period of time (No at Step S 303 ), then the system control returns to Step S 302 . On the other hand, if the application control unit  116  determines that the movement of the mouth has stopped for the predetermined period of time (Yes at Step S 303 ), then the system control proceeds to Step S 304 . 
     Meanwhile, in  FIG. 13 , although it is illustrated that the operations at Steps S 302  and S 303  are over in only one iteration; in practice, the operations at Steps S 302  and S 303  are performed in a loop until the condition at Step S 303  is satisfied. 
     The operations performed from Step S 304  onward are identical to the operations performed from Step S 110  onward illustrated in the flowchart in  FIG. 11  according to the first embodiment. That is, at Step S 304 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to the instruction, the SNS application unit  100  ends the voice input processing performed using the sound processing unit  103 , and ends the voice message transmission operation performed using the communication processing unit  102 . 
     Subsequently, at Step S 304 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 304 . If the application control unit  116  determines that the next message is received (Yes at Step S 304 ), then the system control returns to Step S 104 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 305 ), then the system control proceeds to Step S 306 . At Step S 306 , the application control unit  116  turns OFF the imaging unit  1003 , the ranging unit  1004 , and the light source unit  1005 . More particularly, the application control unit  116  instructs, for example, the overall control unit  120  to stop the power supply to the imaging unit  1003 , the ranging unit  1004 , and the light source unit  1005 . In response to the instruction, the overall control unit  120  turns OFF the switches  1061   a ,  1061   b , and  1062 ; and thus stops the power supply to the imaging unit  1003 , the ranging unit  1004 , and the light source unit  1005 . 
     When the operation at Step S 306  is finished, the sequence of operations illustrated in the flowchart in  FIG. 13  is ended. 
     In this way, in the second modification example of the first embodiment, the control for turning OFF the voice input mode is performed according to the result of detecting the movement of the mouth based on the taken image. Herein, in contrast to the fact that the ToF sensor  1041  obtains the depth information consistently based on the point group information, the image sensor of the imaging unit  1003  can output taken images representing, for example, full-color images taken using R (red), G (green), and B (blue) colors. Hence, the movement of the mouth can be detected with higher accuracy. Thus, in the second modification example of the first embodiment, voice message transmission can be controlled with higher accuracy than in the first modification example of the first embodiment. 
     Moreover, in the second modification example of the first embodiment, in an identical manner to the first embodiment, the user need not perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. 
     Second Embodiment 
     Given below is the explanation of a second embodiment. In the second embodiment, when the SNS application  5  receives a message during the display lock applied by the OS (the overall control unit  120 ), face authentication is performed based on the depth information and the display lock is released. 
     Meanwhile, in the second embodiment, the configuration of the terminal device  1  as explained with reference to  FIGS. 6 to 10  according to the first embodiment can be implemented without modification. 
       FIG. 14  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1  according to the second embodiment. At the start of the operations illustrated in the flowchart in  FIG. 14 , it is assumed that the switches  1061   a ,  1061   b , and  1062  are in the OFF state. 
     Prior to the operations illustrated in the flowchart in  FIG. 14 ; in the terminal device  1 , it is assumed that the OS (the overall control unit  120 ) has locked the display of the display unit  10  so that, for example, there is a restriction on the operations that the input receiving unit  123  can receive from among the user operations performed using the input device  1007 . Moreover, in the display lock state, for example, only some of the functions of the SNS application  5  (for example, the communication processing unit  102 ) are activated and are implemented in the background. 
     At Step S 500 , the application control unit  116  determines whether or not the SNS application unit  100  has received a message that is sent from another terminal device  1  using the corresponding SNS application  5 . If the application control unit  116  determines that the SNS application unit  100  has not received a message (No at Step S 500 ), then the system control returns to Step S 500 . On the other hand, if the application control unit  116  determines that the SNS application unit  100  has received a message (Yes at Step S 500 ), then the system control proceeds to Step S 501 . 
     At that time, for example, the UI unit  101  of the SNS application unit  100  displays a banner image in the display unit  10  as an indication that a message has been received.  FIG. 15A  is a diagram illustrating an example of a banner image  16  that is displayed in the display unit  10  in the display lock state. In the example illustrated in  FIG. 15A , the banner image  16  including the brief of the received message is displayed in the upper end of the display unit  10 . In the existing technology, for example, when the banner image  16  is tapped (touched by a finger), a display lock release screen meant for inputting the information to release the display lock is displayed in the display unit  10 .  FIG. 15B  is a diagram illustrating an example of a display lock release screen  17  to be used for releasing the display lock according to face authentication. 
     At Step S 501 , the application control unit  116  determines whether or not the voice input autodetection mode is turned ON in the settings. If the application control unit  116  determines that the voice input autodetection mode is not turned ON in the settings (No at Step S 501 ), then the system control proceeds to Step S 520 . At Step S 520 , the application control unit  116  instructs the SNS application unit  100  to maintain the operation mode for inputting messages to the normal character input mode. That marks the end of the sequence of operations illustrated in the flowchart in  FIG. 14 . 
     On the other hand, if the application control unit  116  determines that the voice input autodetection mode is turned ON in the settings (Yes at Step S 501 ), then the system control proceeds to Step S 502 . At Step S 502 , the application control unit  116  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 503 , the application control unit  116  instructs the authenticating unit  124  to perform face authentication based on the depth information obtained by the first face detecting unit  112 . At that time, it is desirable that the application control unit  116  instructs the overall control unit  120  to display the display lock release screen  17  illustrated in  FIG. 15B , so as to prompt the user to carry out face authentication. 
     Then, at Step S 504 , the application control unit  116  determines whether or not the face authentication performed by the authenticating unit  124  was successful. If the application control unit  116  determines that the face authentication was not successful (No at Step S 504 ), then the sequence of operations illustrated in the flowchart in  FIG. 14  is ended. On the other hand, if the application control unit  116  determines that the face authentication was successful (Yes at Step S 504 ), then the system control proceeds to Step S 505 . At Step S 505 , the application control unit  116  instructs the overall control unit  120  to release the display lock. Subsequently, at Step S 506 , the application control unit  116  activates the main unit of the SNS application  5  (i.e., activates the entire SNS application unit  100  including the UI unit  101 , the communication processing unit  102 , and the sound processing unit  103 ). 
     The operations performed from Step S 507  onward are identical to the operations performed from Step S 104  onward illustrated in the flowchart in  FIG. 11  according to the first embodiment. That is, at Step S 507 , the application control unit  116  detects the movement of the terminal device  1  based on the output of the movement estimating unit  115  and determines whether or not the terminal device  1  has been moved during a predetermined period of time since the point of time of reception of the message at Step S 102 . If the application control unit  116  determines that the terminal device  1  has not been moved (No at Step S 507 ), then the system control proceeds to Step S 515 . 
     On the other hand, if the application control unit  116  determines that the terminal device  1  has been moved during the predetermined period of time (Yes at Step S 507 ), then the system control proceeds to Step S 508 . At Step S 508 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 509 , based on the distance obtained at Step S 508 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. Meanwhile, in  FIG. 14 , although it is illustrated that the operations at Steps S 508  and S 509  are over in only one iteration; in practice, the operations at Steps S 508  and S 509  are performed in a loop until the condition at Step S 509  is satisfied. 
     If the application control unit  116  determines at Step S 509  that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 509 ), then the system control proceeds to Step S 515 , and the subsequent operations related to voice message transmission are canceled. 
     On the other hand, if the application control unit  116  determines at Step S 509  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 509 ), then the system control proceeds to Step S 510 . At Step S 510 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode. Then, at Step S 511 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which is obtained as a result of processing performed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 500 . 
     Subsequently, at Step S 512 , the application control unit  116  determines whether or not the object (face) has moved away from the predetermined distance from the terminal device  1 . If the application control unit  116  determines that the object (face) has not moved away from the predetermined distance (No at Step S 512 ), then the system control returns to Step S 511 . On the other hand, if the application control unit  116  determines that the object (face) has not moved away from the predetermined distance (Yes at Step S 512 ), then the system control proceeds to Step S 513 . 
     Meanwhile, in  FIG. 14 , although it is illustrated that the operations at Steps S 511  and S 512  are over in only one iteration; in practice, the operations at Steps S 511  and S 512  are performed in a loop until the condition at Step S 512  is satisfied. 
     At Step S 513 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to that instruction, the SNS application unit  100  ends the voice input processing performed by the sound processing unit  103 , and ends the voice message transmission performed by the communication processing unit  102 . 
     Subsequently, at Step S 514 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 513 . If the application control unit  116  determines that the next message is received (Yes at Step S 513 ), then the system control returns to Step S 507 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 514 ), then the system control proceeds to Step S 515 . At Step S 515 , the application control unit  116  turns OFF the ranging unit  1004  and the light source unit  1005 . When the operation at Step S 515  is finished, the sequence of operations illustrated in the flowchart in  FIG. 14  is ended. 
     In this way, in the second embodiment, when a message is received by the SNS application  5  that runs in the background in the display lock state, the display lock is released by performing face authentication using the depth information, and the main unit of the SNS application  5  is activated. Thus, even if a message is received by the SNS application  5  in the display lock state, the user can still release the display lock and send a voice message using the SNS application  5 , for example, just by holding the terminal device  1  in one hand and performing face authentication, without having to perform the operation of tapping the touch-sensitive panel  1030  of the terminal device  1 . 
     At that time, face authentication is performed based on the output of the ToF sensor  1041  for which infrared light is used as the light source. Hence, even in a dark environment such as in the night time, when a message is received by the SNS application  5  in the display lock state, it becomes possible to release the display lock. Moreover, as far as turning ON or turning OFF the voice input mode by the SNS application unit  100  is concerned, since the control is performed based on the output of the ToF sensor  1041  for which infrared light is used as the light source, the ON/OFF control of the voice input mode can be performed even in a dark environment such as in the night time. 
     Furthermore, in the second embodiment, in an identical manner to the first embodiment, the SNS application unit  100  controls the operation of turning ON and turning OFF the voice input mode based on the distance between the terminal device  1  and the face. That eliminates the need for the user to perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. 
     Moreover, in the second embodiment, at the time of performing a voice input for sending a voice message, the distance to the face is measured. Hence, the sensitivity of the microphone  12  (the gain with respect to the output of the microphone  12 ) can be adjusted based on the distance to the face. That enables transmission of the voice message with an appropriate sound level. 
     First Modification Example of Second Embodiment 
     Given below is the explanation of a first modification example of the second embodiment. In the first modification example of the second embodiment, when a message is received by the SNS application  5  in the display lock state applied by the OS (the overall control unit  120 ), face authentication is performed based on the depth information and the display lock is released. In addition, in an identical manner to the first modification example of the first embodiment, the SNS application unit  100  controls the voice input mode by detecting the movement of the mouth based on the depth information. 
     In the first modification example of the second embodiment, the configuration of the terminal device  1  as explained with reference to  FIGS. 6 to 10  according to the first embodiment can be implemented without modification. 
       FIG. 16  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1  according to the first modification example of the second embodiment. In  FIG. 16 , the operations identical to the operations illustrated in the flowchart in  FIG. 14  are referred to by the same step numbers, and their explanation is given in short. At the start of the operations illustrated in the flowchart in  FIG. 16 , it is assumed that the switches  1061   a ,  1061   b , and  1062  are in the OFF state. 
     Prior to the operations illustrated in the flowchart in  FIG. 16 ; in the terminal device  1 , it is assumed that the OS (the overall control unit  120 ) has locked the display of the display unit  10 ; and, for example, some functions of the SNS application  5  are implemented in the background. 
     The operations performed from Step S 500  to Step S 510  are identical to the operations performed from Step S 500  to Step S 510  illustrated in the flowchart in  FIG. 14 . That is, at Step S 500 , the application control unit  116  determines whether or not the SNS application unit  100  has received a message that is sent from another terminal device  1  using the corresponding SNS application  5 . If the application control unit  116  determines that the SNS application unit  100  has not received a message (No at Step S 500 ), then the system control returns to Step S 500 . 
     On the other hand, if the application control unit  116  determines that the SNS application unit  100  has received a message (Yes at Step S 500 ), then the system control proceeds to Step S 501 . At that time, for example, the UI unit  101  of the SNS application unit  100  displays, as illustrated in  FIG. 15A , the banner image  16  in the display unit  10  as an indication that a message has been received. 
     At Step S 501 , the application control unit  116  determines whether or not the voice input autodetection mode is turned ON in the settings. If the application control unit  116  determines that the voice input autodetection mode is not turned ON in the settings (No at Step S 501 ), then the system control proceeds to Step S 520 . At Step S 520 , the application control unit  116  instructs the SNS application unit  100  to maintain the operation mode for inputting messages to the normal character input mode. That marks the end of the sequence of operations illustrated in the flowchart in  FIG. 16 . 
     On the other hand, if the application control unit  116  determines that the voice input autodetection mode is turned ON in the settings (Yes at Step S 501 ), then the system control proceeds to Step S 502 . At Step S 502 , the application control unit  116  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 503 , the application control unit  116  instructs the authenticating unit  124  to perform face authentication based on the depth information obtained by the first face detecting unit  112 . At that time, it is desirable that the application control unit  116  instructs the overall control unit  120  to display the display lock release screen  17  illustrated in  FIG. 15B , so as to prompt the user to carry out face authentication. 
     Then, at Step S 504 , the application control unit  116  determines whether or not the face authentication performed by the authenticating unit  124  was successful. If the application control unit  116  determines that the face authentication was not successful (No at Step S 504 ), then the sequence of operations illustrated in the flowchart in  FIG. 16  is ended. On the other hand, if the application control unit  116  determines that the face authentication was successful (Yes at Step S 504 ), then the system control proceeds to Step S 505 . At Step S 505 , the application control unit  116  instructs the overall control unit  120  to release the display lock. At Step S 505 , the application control unit  116  instructs the overall control unit  120  to release the display lock. Subsequently, at Step S 506 , the application control unit  116  activates the main unit of the SNS application  5 . 
     The operations performed from Step S 507  onward are identical to the operations performed from Step S 104  onward illustrated in the flowchart in  FIG. 12  according to the first modification example of the first embodiment. That is, at Step S 507 , the application control unit  116  detects the movement of the terminal device  1  based on the output of the movement estimating unit  115  and determines whether or not the terminal device  1  has been moved during a predetermined period of time since the point of time of reception of the message at Step S 500 . If the application control unit  116  determines that the terminal device  1  has not been moved (No at Step S 507 ), then the system control proceeds to Step S 535 . 
     On the other hand, if the application control unit  116  determines that the terminal device  1  has been moved during the predetermined period of time (Yes at Step S 507 ), then the system control proceeds to Step S 508 . At Step S 508 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 509 , based on the distance obtained at Step S 508 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period. In an identical manner to the explanation with reference to  FIG. 11 ; in practice, the operations at Steps S 508  and S 509  are performed in a loop until the condition at Step S 509  is satisfied. 
     If the application control unit  116  determines at Step S 509  that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 509 ), then the system control proceeds to Step S 535 , and the subsequent operations related to voice message transmission are canceled. 
     On the other hand, if the application control unit  116  determines at Step S 509  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 509 ), then the system control proceeds to Step S 510 . At Step S 510 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode. 
     Subsequently, at Step S 530 , the application control unit  116  instructs the first face detecting unit  112  to start detecting the movement of the mouth in the face using the face detection result that is based on the depth information. In response to the instruction, the first face detecting unit  112  compares a plurality of sets of depth information obtained in, for example, chronological order and detects the movement of the mouth. 
     Subsequently, at Step S 531 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which has been processed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 500 . 
     Then, at Step S 532 , based on the result of mouth movement detection started by the first face detecting unit  112  at Step S 530 , the application control unit  116  determines whether or not the movement of the mouth has stopped for a predetermined period of time. At Step S 532 , if the application control unit  116  determines that the movement of the mouth has not stopped for the predetermined period of time (No at Step S 532 ), then the system control returns to Step S 531 . On the other hand, if the application control unit  116  determines that the movement of the mouth has stopped for the predetermined period of time (Yes at Step S 532 ), then the system control proceeds to Step S 533 . 
     Meanwhile, in  FIG. 16 , although it is illustrated that the operations at Steps S 531  and S 532  are over in only one iteration; in practice, the operations at Steps S 532  and S 532  are performed in a loop until the condition at Step S 202  is satisfied. 
     The operations performed from Step S 533  onward are identical to the operations performed from Step S 110  onward illustrated in the flowchart in  FIG. 11  according to the first embodiment. That is, at Step S 533 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to the instruction, the SNS application unit  100  ends the voice input processing performed using the sound processing unit  103 , and ends the voice message transmission operation performed using the communication processing unit  102 . 
     Subsequently, at Step S 534 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 533 . If the application control unit  116  determines that the next message is received (Yes at Step S 533 ), then the system control returns to Step S 507 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 534 ), then the system control proceeds to Step S 535 . At Step S 535 , the application control unit  116  turns OFF the ranging unit  1004  and the light source unit  1005 . When the operation at Step S 535  is finished, the sequence of operations illustrated in the flowchart in  FIG. 16  is ended. 
     In this way, in the first modification example of the second embodiment, in an identical manner to the second embodiment, when a message is received by the SNS application  5  that runs in the background in the display lock state, the display lock is released by performing face authentication using the depth information, and the main unit of the SNS application  5  is activated. Thus, even if a message is received by the SNS application  5  in the display lock state, the user can still release the display lock and send a voice message using the SNS application  5 , for example, just by holding the terminal device  1  in one hand and performing face authentication, without having to perform the operation of tapping the touch-sensitive panel  1030  of the terminal device  1 . 
     Moreover, in the first modification example of the second embodiment, the control for turning OFF the voice input mode is performed according to the result of detecting the movement of the mouth based on the depth information. Hence, voice message transmission can be controlled with higher accuracy. 
     Furthermore, in the first modification example of the second embodiment, in an identical manner to the second embodiment, the user need not perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. 
     Moreover, in the first modification example of the second embodiment, in an identical manner to the second embodiment, as far as turning ON or turning OFF the voice input mode by the SNS application unit  100  is concerned, since the control is performed based on the output of the ToF sensor  1041  for which infrared light is used as the light source, the ON/OFF control of the voice input mode can be performed even in a dark environment such as in the night time. 
     Furthermore, in the first modification example of the second embodiment, in an identical manner to the second embodiment, the distance to the face is measured at the time when a voice input is performed for sending a voice message. Hence, the sensitivity of the microphone  12  (the gain with respect to the output of the microphone  12 ) can be adjusted based on the distance to the face. That enables transmission of the voice message with an appropriate sound level. 
     Second Modification Example of Second Embodiment 
     Given below is the explanation of a second modification example of the second embodiment. In the second modification example of the second embodiment, when a message is received by the SNS application  5  in the display lock state applied by the OS (the overall control unit  120 ), face authentication is performed based on the depth information and the display lock is released. In addition, in an identical manner to the second modification example of the first embodiment, the SNS application unit  100  controls the voice input mode by detecting the movement of the mouth based on a taken image. 
     In the second modification example of the second embodiment, the configuration of the terminal device  1  as explained with reference to  FIGS. 6 to 10  according to the first embodiment can be implemented without modification. 
       FIG. 17  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1  according to the second modification example of the second embodiment. In  FIG. 17 , the operations identical to the operations illustrated in the flowchart in  FIG. 14  are referred to by the same step numbers, and their explanation is given in short. At the start of the operations illustrated in the flowchart in  FIG. 17 , it is assumed that the switches  1061   a ,  1061   b , and  1062  are in the OFF state. 
     Prior to the operations illustrated in the flowchart in  FIG. 17 ; in the terminal device  1 , it is assumed that the OS (the overall control unit  120 ) has locked the display of the display unit  10 ; and, for example, some functions of the SNS application  5  are implemented in the background. 
     The operations performed from Step S 500  to Step S 510  are identical to the operations performed from Step S 500  to Step S 510  illustrated in the flowchart in  FIG. 14 . That is, at Step S 500 , the application control unit  116  determines whether or not the SNS application unit  100  has received a message that is sent from another terminal device  1  using the corresponding SNS application  5 . If the application control unit  116  determines that the SNS application unit  100  has not received a message (No at Step S 500 ), then the system control returns to Step S 500 . 
     On the other hand, if the application control unit  116  determines that the SNS application unit  100  has received a message (Yes at Step S 500 ), then the system control proceeds to Step S 501 . At that time, for example, the UI unit  101  of the SNS application unit  100  displays, as illustrated in  FIG. 15A , the banner image  16  in the display unit  10  as an indication that a message has been received. 
     At Step S 501 , the application control unit  116  determines whether or not the voice input autodetection mode is turned ON in the settings. If the application control unit  116  determines that the voice input autodetection mode is not turned ON in the settings (No at Step S 501 ), then the system control proceeds to Step S 520 . At Step S 520 , the application control unit  116  instructs the SNS application unit  100  to maintain the operation mode for inputting messages to the normal character input mode. That marks the end of the sequence of operations illustrated in the flowchart in  FIG. 16 . 
     On the other hand, if the application control unit  116  determines that the voice input autodetection mode is turned ON in the settings (Yes at Step S 501 ), then the system control proceeds to Step S 502 . At Step S 502 , the application control unit  116  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 503 , the application control unit  116  instructs the authenticating unit  124  to perform face authentication based on the depth information obtained by the first face detecting unit  112 . At that time, it is desirable that the application control unit  116  instructs the overall control unit  120  to display the display lock release screen  17  illustrated in  FIG. 15B , so as to prompt the user to carry out face authentication. 
     Then, at Step S 504 , the application control unit  116  determines whether or not the face authentication performed by the authenticating unit  124  was successful. If the application control unit  116  determines that the face authentication was not successful (No at Step S 504 ), then the sequence of operations illustrated in the flowchart in  FIG. 17  is ended. On the other hand, if the application control unit  116  determines that the face authentication was successful (Yes at Step S 504 ), then the system control proceeds to Step S 505 . At Step S 505 , the application control unit  116  instructs the overall control unit  120  to release the display lock. Subsequently, at Step S 506 , the application control unit  116  activates the main unit of the SNS application  5 . 
     The operations performed from Step S 507  onward are identical to the operations performed from Step S 104  onward illustrated in the flowchart in  FIG. 13  according to the second modification example of the first embodiment. That is, at Step S 507 , the application control unit  116  detects the movement of the terminal device  1  based on the output of the movement estimating unit  115  and determines whether or not the terminal device  1  has been moved during a predetermined period of time since the point of time of reception of the message at Step S 500 . If the application control unit  116  determines that the terminal device  1  has not been moved (No at Step S 507 ), then the system control proceeds to Step S 546 . 
     On the other hand, if the application control unit  116  determines that the terminal device  1  has been moved during the predetermined period of time (Yes at Step S 507 ), then the system control proceeds to Step S 508 . At Step S 508 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 509 , based on the distance obtained at Step S 508 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. In an identical manner to the explanation given with reference to  FIG. 13 ; in practice, the operations at Steps S 508  and S 509  are performed in a loop until the condition at Step S 509  is satisfied. 
     If the application control unit  116  determines at Step S 509  that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 509 ), then the system control proceeds to Step S 546 , and the subsequent operations related to voice message transmission are canceled. 
     On the other hand, if the application control unit  116  determines at Step S 509  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 509 ), then the system control proceeds to Step S 510 . At Step S 510 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode. 
     The operations performed from Step S 540  onward are identical to the operations performed from Step S 300  onward illustrated in the flowchart in  FIG. 13  according to the second modification example of the first embodiment. That is, at Step S 540 , the application control unit  116  turns ON the functions of the imaging unit  1003  and starts obtaining a taken image using the imaging processing unit  113 . Then, at Step S 541 , the application control unit  116  instructs the second face detecting unit  114  to start detecting the movement of the mouth in the face using the face detection result that is based on the taken image. 
     Subsequently, at Step S 542 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which is obtained as a result of processing performed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 102 . 
     Then, at Step S 543 , based on the result of mouth movement detection started by the second face detecting unit  114  at Step S 541 , the application control unit  116  determines whether or not the movement of the mouth has stopped for a predetermined period of time. At Step S 543 , if the application control unit  116  determines that the movement of the mouth has not stopped for the predetermined period of time (No at Step S 543 ), then the system control returns to Step S 542 . On the other hand, if the application control unit  116  determines that the movement of the mouth has stopped for the predetermined period of time (Yes at Step S 543 ), then the system control proceeds to Step S 544 . 
     Meanwhile, in an identical manner to the explanation given with reference to  FIG. 13 ; in practice, the operations at Steps S 542  and S 543  are performed in a loop until the condition at Step S 543  is satisfied. 
     At Step S 544 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to that instruction, the SNS application unit  100  ends the voice input processing performed by the sound processing unit  103 , and ends the voice message transmission performed by the communication processing unit  102 . 
     Subsequently, at Step S 544 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 544 . If the application control unit  116  determines that the next message is received (Yes at Step S 544 ), then the system control returns to Step S 507 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 545 ), then the system control proceeds to Step S 546 . At Step S 546 , the application control unit  116  turns OFF the imaging unit  1003 , the ranging unit  1004 , and the light source unit  1005 . When the operation at Step S 546  is finished, the sequence of operations illustrated in the flowchart in  FIG. 17  is ended. 
     In this way, in the second modification example of the second embodiment, in an identical manner to the second embodiment, when the SNS application  5 , which runs in the background in the display lock state, receives a message; the display lock is released by performing face authentication based on the depth information, and the main unit of the SNS application  5  is activated. Hence, even if a message is received by the SNS application  5  in the display lock state, the user can still release the display lock and send a voice message using the SNS application  5 , for example, just by holding the terminal device  1  in one hand and performing face authentication, without having to perform the operation of tapping the touch-sensitive panel  1030  of the terminal device  1 . 
     Moreover, in the second modification example of the second embodiment, the control for turning OFF the voice input mode is performed according to the result of detecting the movement of the mouth based on the taken image. Herein, in contrast to the fact that the ToF sensor  1041  obtains the depth information based on the point group information, the image sensor of the imaging unit  1003  can output taken images representing, for example, full-color images taken using RGB colors. Hence, the movement of the mouth can be detected with higher accuracy. Thus, in the second modification example of the second embodiment, voice message transmission can be controlled with higher accuracy than in the first modification example of the second embodiment. 
     Furthermore, in the second modification example of the second embodiment, in an identical manner to the second embodiment, the user need not perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. 
     Third Embodiment 
     Given below is the explanation of a third embodiment. In the third embodiment, the explanation is given about an example in which a notification about the reception of a message from another terminal device  1   a  is received by the SNS application  5  in the form of a push notification in the display lock state applied by the OS (the overall control unit  120 ).  FIG. 18  is a diagram that schematically illustrates an example of an information processing system that is applicable to the third embodiment and that is used in the case of implementing a push notification. With reference to  FIG. 18 , a plurality of terminal devices  1   a  is connected to an SNS system  3   a  via the network  2  such as the Internet. Moreover, a push notification server  6  that provides a known push notification service is connected to the network  2 . 
     (Configuration Applicable to Third Embodiment) 
     In the terminal devices  1   a , the hardware configuration explained with reference to  FIGS. 6 and 7  can be applied without modification. Each terminal device  1   a  has the SNS application  5  installed therein for using the SNS provided by the SNS system  3   a , and has a driver program  500  according to the third embodiment installed therein. The driver program  500  runs in coordination with the SNS application  5 , and controls the ranging unit  1004  in the terminal device  1   a  by mediating between the OS (Operating System) and the ranging unit  1004 . 
     The SNS system  3   a  includes an SNS server  300 , a storage  301 , a notification server  310 , and a message server  311 . The SNS server  300  has equivalent functions of the functions of the server  3 . For example, the SNS server  300  provides the service for enabling transmission and reception of messages including voice messages among the terminal devices  1   a  via the network  2 . The storage  301  corresponds to the storage  4  illustrated in  FIG. 1 . 
     The notification server  310  and the message server  311  represent the configuration for issuing push notifications. The message server  311  receives the messages that are sent by the SNS application  5  of each terminal device  1   a  to the SNS system  3   a . When the message server  311  receives a message, the notification server  310  instructs the push notification server  6  to issue a push notification for that message. 
     Regarding the existing push notifications, the schematic explanation is given with reference to the configuration illustrated in  FIG. 18 . A push notification is issued from the push notification server  6  to the devices (the terminal devices  1   a ) in which an application program corresponding to the push notification is installed. In the third embodiment, the SNS application  5  is assumed to be the application program corresponding to push notifications. When a user operation is performed to allow a push notification to the SNS application  5  installed in the concerned terminal device  1   a , the SNS application  5  sends identification information, which enables identification thereof, to the push notification server  6  at a predetermined timing such as at the time of activation of the terminal device  1   a  or the SNS application  5 ; and requests for a notification ID. 
     In response to the request, the push notification server  6  issues a notification ID unique to the concerned terminal device  1   a , stores the issued notification ID, and sends the notification ID along with the identification information of the SNS application to the sender of the notification ID request. The notification ID is identification information enabling the push notification server  6  to identify the SNS application  5  allowing the push notification and the terminal device  1   a  in which the concerned SNS application  5  is installed. When the OS (Operating System) of a device is iOS (registered trademark) provided by the Apple Inc. US, the notification ID represents the device token. 
     The SNS application  5  stores the obtained notification ID in the memory unit (for example, the RAM  1002 ) of the terminal device  1   a . Moreover, the SNS application  5  sends that notification ID to the provider of the SNS application  5  or to the SNS system  3   a  that is the provider of the message meant for issuing a push notification to the SNS application  5 . The SNS system  3   a  stores the notification ID in the notification server  310 . 
     In the SNS system  3   a , when a push notification is to be issued by the notification server  310  to, for example, a particular device; the notification server  310  sends the notification ID for that device to the push notification server  6 ; receives a message to be push-notified from the message server  311  and sends that message to the push notification server  6 ; and requests the push notification server  6  to issue a push notification. In response to that request, the push notification server  6  sends the notification ID and the message to the terminal device  1   a  that is identified by the notification ID. 
     When the terminal device  1  receives the notification ID and the message; if the SNS application  5  is running, the OS of that terminal device  1   a  detects the SNS application  5  corresponding to the notification ID, and the detected SNS application  5  displays the message according to a predetermined method. On the other hand, if the OS has locked the display of the display unit  10  and if the SNS application  5  is not running; then, for example, the OS displays the banner image  16  (see  FIG. 15A ), which indicates the reception of a message, in the display unit  10  in the locked state. 
       FIG. 19  is an exemplary functional block diagram for explaining the functions of the terminal device  1   a  according to the third embodiment. In the terminal device  1   a , a detection/control unit  110 ′ additionally includes an activation control unit  117  as compared to the detection/control unit  110  explained with reference to  FIG. 10 . The activation control unit  117  corresponds to the driver program  500  explained with reference to  FIG. 18 , and controls the operations of the ranging unit  1004  by mediating between the OS (Operating System) and the ranging unit  1004 . The activation control unit  117  can be formed in the terminal device  1   a  by installing, in the terminal device  1   a , a driver installation program that is either downloaded via the network  2  or recorded in a computer-readable recording medium such as a CD, an FD, or a DVD. 
     Meanwhile, in the third embodiment, regarding the hardware configuration of the terminal device  1   a , the configuration of the terminal device  1  explained with reference to  FIGS. 6 and 7  according to the first embodiment can be applied without modification. 
     (Details of Operations According to Third Embodiment) 
       FIG. 20  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1   a  according to the third embodiment. 
     At the start of the operations illustrated in the flowchart in  FIG. 20 , it is assumed that the switches  1061   a ,  1061   b , and  1062  are in the OFF state. Prior to the operations illustrated in the flowchart in  FIG. 20 ; in the terminal device  1   a , it is assumed that the OS (the overall control unit  120 ) has locked the display of the display unit  10 . Moreover, at that time, it is assumed that the SNS application  5  is not running even in the background. 
     At Step S 600 , the activation control unit  117  makes an inquiry to the overall control unit  120  about the presence or absence of a message reception notification in the form of a push notification. If the activation control unit  117  determines according to the result of the inquiry that there is no notification (No at Step S 600 ), then the system control returns to Step S 600 . On the other hand, if the activation control unit  117  determines according to the result of the inquiry that there is a notification (Yes at Step S 600 ), then the system control proceeds to Step S 601 . At that time, for example, the overall control unit  120  displays the banner image  16  (see  FIG. 15A ), which indicates that a message is received, in the display unit  10 . 
     At Step S 601 , the activation control unit  117  makes an inquiry to the overall control unit  120  about whether or not the voice input autodetection mode is turned ON in the settings. If the activation control unit  117  determines according to the result of the inquiry that the voice input autodetection mode is not turned ON in the settings (No at Step S 601 ), then the sequence of operations illustrated in  FIG. 20  is ended. 
     In that case, under the normal control of the overall control unit  120 , for example, as a result of tapping on the position of the banner image  16  displayed in the display unit  10 , the overall control unit  120  displays the display lock release screen in the display unit  10 . Then, in response to a predetermined display lock release operation, the overall control unit  120  activates the SNS application  5 . That enables transmission and reception of messages using the SNS application  5 . 
     On the other hand, if the activation control unit  117  determines according to the result of the inquiry that the voice input autodetection mode is turned ON in the settings (Yes at Step S 601 ), then the system control proceeds to Step S 602 . At Step S 602 , the activation control unit  117  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 603 , the activation control unit  117  requests the overall control unit  120  to ensure that the authenticating unit  124  performs face authentication based on the depth information obtained by the first face detecting unit  112 . In response to that request, the overall control unit  120  performs face authentication based on the depth information. At that time, the overall control unit  120  can display the display lock release screen  17  illustrated in  FIG. 15B  in the display unit  10 , so as to prompt the user to carry out face authentication. 
     Then, at Step S 604 , the activation control unit  117  makes an inquiry to the overall control unit  120  about whether or not the face authentication performed by the authenticating unit  124  was successful. If the activation control unit  117  determines according to the result of the inquiry that the authentication was not successful (No at Step S 604 ), then the sequence of operations illustrated in the flowchart in  FIG. 20  is ended. On the other hand, if the activation control unit  117  determines according to the result of the inquiry that the authentication was successful (Yes at Step S 604 ), then the system control proceeds to Step S 605 . 
     At Step S 605 , the activation control unit  117  requests the overall control unit  120  to release the display lock. In response to that request, the overall control unit  120  releases the display lock. Then, at Step S 606 , the activation control unit  117  activates the main unit of the SNS application  5 . The activation of the main unit of the SNS application  5  can be alternatively performed by the overall control unit  120 . 
     The operations performed from Step S 607  onward are identical to the operations performed from Step S 104  onward illustrated in the flowchart in  FIG. 11  according to the first embodiment. That is, at Step S 607 , the application control unit  116  detects the movement of the terminal device  1   a  based on the output of the movement estimating unit  115  and determines whether or not the terminal device  1  has been moved during a predetermined period of time since, for example, the point of time of reception of a message at Step S 600 . If the application control unit  116  determines that the terminal device  1   a  has not been moved (No at Step S 607 ), then the system control proceeds to Step S 615 . 
     On the other hand, if the application control unit  116  determines at Step S 607  that the terminal device  1   a  has been moved during the predetermined period of time (Yes at Step S 607 ), then the system control proceeds to Step S 608 . At Step S 608 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 609 , based on the distance obtained at Step S 608 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. Meanwhile, in  FIG. 20 , although it is illustrated that the operations at Steps S 608  and S 609  are over in only one iteration; in practice, the operations at Steps S 608  and S 609  are performed in a loop until the condition at Step S 609  is satisfied. 
     If the application control unit  116  determines at Step S 609  that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 609 ), then the system control proceeds to Step S 615  and the subsequent operations related to voice message transmission are cancelled. 
     On the other hand, if the application control unit  116  determines at Step S 609  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 609 ), then the system control proceeds to Step S 610 . At Step S 610 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode. Then, at Step S 611 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which is obtained as a result of processing performed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 600 . 
     Subsequently, at Step S 612 , based on the face detection result obtained by the first face detecting unit  112 , the application control unit  116  determines whether or not the object (face) has moved away from the predetermined distance from the terminal device  1   a . If the application control unit  116  determines that the object (face) has not moved away from the predetermined distance (No at Step S 612 ), then the system control returns to Step S 611 . On the other hand, at Step S 612 , if the application control unit  116  determines that the object (face) has moved away from the predetermined distance (Yes at Step S 612 ), then the system control proceeds to Step S 613 . 
     Meanwhile, in  FIG. 20 , although it is illustrated that the operations at Steps S 611  and S 612  are over in only one iteration; in practice, the operations at Steps S 611  and S 612  are performed in a loop until the condition at Step S 612  is satisfied. 
     At Step S 613 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to that instruction, the SNS application unit  100  ends the voice input processing performed by the sound processing unit  103 , and ends the voice message transmission performed by the communication processing unit  102 . 
     Subsequently, at Step S 614 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 613 . If the application control unit  116  determines that the next message is received (Yes at Step S 614 ), then the system control returns to Step S 607 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 614 ), then the system control proceeds to Step S 615 . At Step S 615 , the activation control unit  117  turns OFF the ranging unit  1004  and the light source unit  1005 . When the operation at Step S 615  is finished, the sequence of operations illustrated in the flowchart in  FIG. 20  is ended. 
     In this way, in the third embodiment, the ranging unit  1004  and the light source unit  1005  are turned ON in response to a push notification, and the face authentication is performed based on the depth information. Thus, even if a message sent from another terminal device  1   a  using the corresponding SNS application  5  is received in the display lock state, the user can still release the display lock and send a voice message using the SNS application  5 , for example, just by holding the terminal device  1   a  in one hand and performing face authentication, without having to perform the operation of tapping the touch-sensitive panel  1030  of the terminal device  1   a.    
     Moreover, in the third embodiment, in an identical manner to the first embodiment, the SNS application unit  100  controls the operation of turning ON and turning OFF the voice input mode based on the distance between the terminal device  1   a  and the face. That eliminates the need for the user to perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1   a  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1   a  in one hand and moving it closer to the face. 
     Furthermore, in the third embodiment, the distance to the face is measured at the time when a voice input is performed for sending a voice message. Hence, the sensitivity of the microphone  12  (the gain with respect to the output of the microphone  12 ) can be adjusted based on the distance to the face. That enables transmission of the voice message with an appropriate sound level. 
     First Modification Example of Third Embodiment 
     Given below is the explanation of a first modification example of the third embodiment. In the first modification example of the third embodiment, a notification about the reception of a message from another terminal device  1   a  is received by the SNS application  5  in the form of a push notification in the display lock state applied by the OS (the overall control unit  120 ). Along with that, in an identical manner to the first modification example of the first embodiment, the SNS application unit  100  controls the voice input mode by detecting the movement of the mouth based on the depth information. 
     Meanwhile, in the first modification example of the third embodiment; regarding the hardware configuration of the terminal device  1   a , the configuration of the terminal device  1  explained with reference to  FIGS. 6 and 7  according to the first embodiment can be applied without modification. 
       FIG. 21  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1   a  according to the first modification example of the third embodiment. 
     In  FIG. 21 , the operations identical to the operations illustrated in the flowchart in  FIG. 20  are referred to by the same step numbers, and their explanation is given in short. At the start of the operations illustrated in the flowchart in  FIG. 21 , it is assumed that the switches  1061   a ,  1061   b , and  1062  are in the OFF state. Moreover, in an identical manner to the flowchart illustrated in  FIG. 20 , prior to the operations illustrated in the flowchart in  FIG. 21 ; in the terminal device  1   a , it is assumed that the OS (the overall control unit  120 ) has locked the display of the display unit  10 . Moreover, at that time, it is assumed that the SNS application  5  is not running even in the background. 
     In  FIG. 21 , the operations from Step S 600  to Step S 606  are identical to the operations from Step S 600  to Step S 606  illustrated in the flowchart in  FIG. 20 . That is, at Step S 600 , the activation control unit  117  makes an inquiry to the overall control unit  120  about the presence or absence of a message reception notification in the form of a push notification. If the activation control unit  117  determines according to the result of the inquiry that there is no notification (No at Step S 600 ), then the system control returns to Step S 600 . On the other hand, if the activation control unit  117  determines according to the result of the inquiry that there is a notification (Yes at Step S 600 ), then the system control proceeds to Step S 601 . At that time, for example, the overall control unit  120  displays the banner image  16  (see  FIG. 15A ), which indicates that a message is received, in the display unit  10 . 
     At Step S 601 , the activation control unit  117  makes an inquiry to the overall control unit  120  about whether or not the voice input autodetection mode is turned ON in the settings. If the activation control unit  117  determines according to the result of the inquiry that the voice input autodetection mode is not turned ON in the settings (No at Step S 601 ), then the sequence of operations illustrated in  FIG. 20  is ended. 
     In that case, under the normal control of the overall control unit  120 , for example, as a result of tapping on the position of the banner image  16  displayed in the display unit  10 , the overall control unit  120  displays the display lock release screen in the display unit  10 . Then, in response to a predetermined display lock release operation, the overall control unit  120  activates the SNS application  5 . That enables transmission and reception of messages using the SNS application  5 . 
     On the other hand, if the activation control unit  117  determines according to the result of the inquiry that the voice input autodetection mode is turned ON in the settings (Yes at Step S 601 ), then the system control proceeds to Step S 602 . At Step S 602 , the activation control unit  117  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 603 , the activation control unit  117  requests the overall control unit  120  to ensure that the authenticating unit  124  performs face authentication based on the depth information obtained by the first face detecting unit  112 . In response to that request, the overall control unit  120  performs face authentication based on the depth information. 
     Then, at Step S 604 , the activation control unit  117  makes an inquiry to the overall control unit  120  about whether or not the face authentication performed by the authenticating unit  124  was successful. If the activation control unit  117  determines according to the result of the inquiry that the authentication was not successful (No at Step S 604 ), then the sequence of operations illustrated in the flowchart in  FIG. 20  is ended. On the other hand, if the activation control unit  117  determines according to the result of the inquiry that the authentication was successful (Yes at Step S 604 ), then the system control proceeds to Step S 605 . 
     At Step S 605 , the activation control unit  117  requests the overall control unit  120  to release the display lock. In response to that request, the overall control unit  120  releases the display lock. Then, at Step S 606 , the activation control unit  117  activates the main unit of the SNS application  5 . The activation of the main unit of the SNS application  5  can be alternatively performed by the overall control unit  120 . 
     The operations performed from Step S 607  onward are identical to the operations performed from Step S 104  onward illustrated in the flowchart in  FIG. 12  according to the first modification example of the first embodiment. That is, at Step S 607 , the application control unit  116  detects the movement of the terminal device  1  based on the output of the movement estimating unit  115  and determines whether or not the terminal device  1  has been moved during a predetermined period of time since the point of time of reception of the message at Step S 600 . If the application control unit  116  determines that the terminal device  1  has not been moved (No at Step S 607 ), then the system control proceeds to Step S 625 . 
     On the other hand, if the application control unit  116  determines that the terminal device  1  has been moved within the predetermined period of time (Yes at Step S 607 ), then the system control proceeds to Step S 608 . At Step S 608 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 609 , based on the distance obtained at Step S 608 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. In an identical manner to the explanation given with reference to  FIG. 11 ; in practice, the operations at Steps S 608  and S 609  are performed in a loop until the condition at Step S 609  is satisfied. 
     If the application control unit  116  determines at Step S 609  that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 609 ), then the system control proceeds to Step S 625  and the subsequent operations related to voice message transmission are cancelled. 
     On the other hand, if the application control unit  116  determines at Step S 609  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 609 ), then the system control proceeds to Step S 610 . At Step S 610 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode). 
     Then, at Step S 620 , the application control unit  116  instructs the first face detecting unit  112  to start detecting the movement of the mouth in the face using the face detection result that is based on the depth information. In response to the instruction, the first face detecting unit  112  compares a plurality of sets of depth information obtained in, for example, chronological order and detects the movement of the mouth. 
     Subsequently, at Step S 621 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which has been processed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 600 . 
     Then, at Step S 622 , based on the result of mouth movement detection started by the first face detecting unit  112  at Step S 620 , the application control unit  116  determines whether or not the movement of the mouth has stopped for a predetermined period of time. At Step S 622 , if the application control unit  116  determines that the movement of the mouth has not stopped for the predetermined period of time (No at Step S 622 ), then the system control returns to Step S 621 . On the other hand, if the application control unit  116  determines that the movement of the mouth has stopped for the predetermined period of time (Yes at Step S 622 ), then the system control proceeds to Step S 623 . 
     Meanwhile, in  FIG. 21 , although it is illustrated that the operations at Steps S 621  and S 622  are over in only one iteration; in practice, the operations at Steps S 621  and S 622  are performed in a loop until the condition at Step S 202  is satisfied. 
     The operations performed from Step S 623  onward are identical to the operations performed from Step S 110  onward illustrated in the flowchart in  FIG. 11  according to the first embodiment. That is, at Step S 623 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to the instruction, the SNS application unit  100  ends the voice input processing performed using the sound processing unit  103 , and ends the voice message transmission operation performed using the communication processing unit  102 . 
     Subsequently, at Step S 624 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 623 . If the application control unit  116  determines that the next message is received (Yes at Step S 623 ), then the system control returns to Step S 607 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 624 ), then the system control proceeds to Step S 625 . At Step S 625 , the application control unit  116  turns OFF the ranging unit  1004  and the light source unit  1005 . When the operation at Step S 625  is finished, the sequence of operations illustrated in the flowchart in  FIG. 21  is ended. 
     In this way, in the first modification example of the third embodiment, the ranging unit  1004  and the light source unit  1005  are turned ON in response to a push notification, and the face authentication is performed based on the depth information. Thus, even if a message sent from another terminal device  1   a  using the corresponding SNS application  5  is received in the display lock state, the user can still release the display lock and send a voice message using the SNS application  5 , for example, just by holding the terminal device  1   a  in one hand and performing face authentication, without having to perform the operation of tapping the touch-sensitive panel  1030  of the terminal device  1   a.    
     Moreover, in the first modification example of the third embodiment, the control for turning OFF the voice input mode is performed according to the result of detecting the movement of the mouth based on the depth information. Hence, voice message transmission can be controlled with higher accuracy. 
     Furthermore, in the first modification example of the third embodiment, in an identical manner to the second embodiment, the user need not perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. 
     Moreover, in the first modification example of the third embodiment, in an identical manner to the second embodiment, as far as turning ON or turning OFF the voice input mode by the SNS application unit  100  is concerned, since the control is performed based on the output of the ToF sensor  1041  for which infrared light is used as the light source, the ON/OFF control of the voice input mode can be performed even in a dark environment such as in the night time. 
     Furthermore, in the first modification example of the third embodiment, in an identical manner to the second embodiment, the distance to the face is measured at the time when a voice input is performed for sending a voice message. Hence, the sensitivity of the microphone  12  (the gain with respect to the output of the microphone  12 ) can be adjusted based on the distance to the face. That enables transmission of the voice message with an appropriate sound level. 
     Second Modification Example of Third Embodiment 
     Given below is the explanation of a second modification example of the third embodiment. In the first modification example of the third embodiment, a notification about the reception of a message from another terminal device  1   a  is received by the SNS application  5  in the form of a push notification in the display lock state applied by the OS (the overall control unit  120 ). Along with that, in an identical manner to the second modification example of the first embodiment, the SNS application unit  100  controls the voice input mode by detecting the movement of the mouth based on a taken image. 
     Meanwhile, in the second modification example of the third embodiment; regarding the hardware configuration of the terminal device  1   a , the configuration of the terminal device  1  explained with reference to  FIGS. 6 and 7  according to the first embodiment can be applied without modification. 
       FIG. 22  is an exemplary flowchart for explaining a voice message transmission operation performed in the terminal device  1   a  according to the second modification example of the third embodiment. 
     In  FIG. 22 , the operations identical to the operations illustrated in the flowchart in  FIG. 20  are referred to by the same step numbers, and their explanation is given in short. At the start of the operations illustrated in the flowchart in  FIG. 22 , it is assumed that the switches  1061   a ,  1061   b , and  1062  are in the OFF state. Moreover, in an identical manner to the flowchart illustrated in  FIG. 20 , prior to the operations illustrated in the flowchart in  FIG. 21 , in the terminal device  1   a , it is assumed that the OS (the overall control unit  120 ) has locked the display of the display unit  10 . Moreover, at that time, it is assumed that the SNS application  5  is not running even in the background. 
     In  FIG. 21 , the operations from Step S 600  to Step S 606  are identical to the operations from Step S 600  to Step S 606  illustrated in the flowchart in  FIG. 20 . That is, at Step S 600 , the activation control unit  117  makes an inquiry to the overall control unit  120  about the presence or absence of a message reception notification in the form of a push notification. If the activation control unit  117  determines according to the result of the inquiry that there is no notification (No at Step S 600 ), then the system control returns to Step S 600 . On the other hand, if the activation control unit  117  determines according to the result of the inquiry that there is a notification (Yes at Step S 600 ), then the system control proceeds to Step S 601 . At that time, for example, the overall control unit  120  displays the banner image  16  (see  FIG. 15A ), which indicates that a message is received, in the display unit  10 . 
     At Step S 601 , the activation control unit  117  makes an inquiry to the overall control unit  120  about whether or not the voice input autodetection mode is turned ON in the settings. If the activation control unit  117  determines according to the result of the inquiry that the voice input autodetection mode is not turned ON in the settings (No at Step S 601 ), then the sequence of operations illustrated in  FIG. 22  is ended. 
     In that case, under the normal control of the overall control unit  120 , for example, as a result of tapping on the position of the banner image  16  displayed in the display unit  10 , the overall control unit  120  displays the display lock release screen in the display unit  10 . Then, in response to a predetermined display lock release operation, the overall control unit  120  activates the SNS application  5 . That enables transmission and reception of messages using the SNS application  5 . 
     On the other hand, if the activation control unit  117  determines according to the result of the inquiry that the voice input autodetection mode is turned ON in the settings (Yes at Step S 601 ), then the system control proceeds to Step S 602 . At Step S 602 , the activation control unit  117  turns ON the ranging unit  1004  and the light source unit  1005 . 
     Subsequently, at Step S 603 , the activation control unit  117  requests the overall control unit  120  to ensure that the authenticating unit  124  performs face authentication based on the depth information obtained by the first face detecting unit  112 . In response to that request, the overall control unit  120  performs face authentication based on the depth information. 
     Then, at Step S 604 , the activation control unit  117  makes an inquiry to the overall control unit  120  about whether or not the face authentication performed by the authenticating unit  124  was successful. If the activation control unit  117  determines according to the result of the inquiry that the authentication was not successful (No at Step S 604 ), then the sequence of operations illustrated in the flowchart in  FIG. 22  is ended. On the other hand, if the activation control unit  117  determines according to the result of the inquiry that the authentication was successful (Yes at Step S 604 ), then the system control proceeds to Step S 605 . 
     At Step S 605 , the activation control unit  117  requests the overall control unit  120  to release the display lock. In response to that request, the overall control unit  120  releases the display lock. Then, at Step S 606 , the activation control unit  117  activates the main unit of the SNS application  5 . The activation of the main unit of the SNS application  5  can be alternatively performed by the overall control unit  120 . 
     The operations performed from Step S 607  onward are identical to the operations performed from Step S 104  onward illustrated in the flowchart in  FIG. 13  according to the second modification example of the first embodiment. That is, at Step S 607 , the application control unit  116  detects the movement of the terminal device  1   a  based on the output of the movement estimating unit  115  and determines whether or not the terminal device  1  has been moved during a predetermined period of time since, for example, the point of time of reception of a message at Step S 600 . If the application control unit  116  determines that the terminal device  1   a  has not been moved (No at Step S 607 ), then the system control proceeds to Step S 636 . 
     On the other hand, the application control unit  116  determines at Step S 607  that the terminal device  1   a  has been moved during the predetermined period of time (Yes at Step S 607 ), then the system control proceeds to Step S 608 . At Step S 608 , the application control unit  116  obtains the distance to the object (face) based on the face detection result obtained by the first face detecting unit  112 . 
     Subsequently, at Step S 609 , based on the distance obtained at Step S 608 , the application control unit  116  determines whether or not the object (face) has moved closer within a predetermined distance during a predetermined period of time. In an identical manner to the explanation given with reference to  FIG. 13 ; in practice, the operations at Steps S 608  and S 609  are performed in a loop until the condition at Step S 609  is satisfied. 
     If the application control unit  116  determines at Step S 609  that the object (face) has not moved closer within the predetermined distance during the predetermined period of time (No at Step S 609 ), then the system control proceeds to Step S 636  and the subsequent operations related to voice message transmission are cancelled. 
     On the other hand, if the application control unit  116  determines at Step S 609  that the object (face) has moved closer within the predetermined distance during the predetermined period of time (Yes at Step S 609 ), then the system control proceeds to Step S 610 . At Step S 610 , the application control unit  116  instructs the SNS application unit  100  to turn ON the voice input mode). 
     The operations performed from Step S 630  onward are identical to the operations performed from Step S 300  onward illustrated in the flowchart in  FIG. 13  according to the second modification example of the first embodiment. That is, at Step S 630 , the application control unit  116  turns ON the functions of the imaging unit  1003  and starts obtaining a taken image using the imaging processing unit  113 . Then, at Step S 631 , the application control unit  116  instructs the second face detecting unit  114  to start detecting the movement of the mouth in the face using the face detection result that is based on the taken image. 
     Subsequently, at Step S 632 , in the SNS application unit  100 , the communication processing unit  102  sends the voice data, which is obtained as a result of processing performed by the sound processing unit  103 , as a voice message to the sender of the message received at Step S 600 . 
     Then, at Step S 633 , based on the result of mouth movement detection started by the second face detecting unit  114  at Step S 631 , the application control unit  116  determines whether or not the movement of the mouth has stopped for a predetermined period of time. At Step S 633 , if the application control unit  116  determines that the movement of the mouth has not stopped for the predetermined period of time (No at Step S 633 ), then the system control returns to Step S 632 . On the other hand, if the application control unit  116  determines that the movement of the mouth has stopped for the predetermined period of time (Yes at Step S 633 ), then the system control proceeds to Step S 634 . 
     In an identical manner to the explanation given with reference to  FIG. 13 ; in practice, the operations at Steps S 632  and S 633  are performed in a loop until the condition at Step S 633  is satisfied. 
     At Step S 634 , the application control unit  116  instructs the SNS application unit  100  to end (turn OFF) the voice input mode. In response to that instruction, the SNS application unit  100  ends the voice input processing performed by the sound processing unit  103 , and ends the voice message transmission performed by the communication processing unit  102 . 
     Subsequently, at Step S 634 , the application control unit  116  determines whether or not the next message is received within a predetermined period of time since ending the voice input mode at Step S 634 . If the application control unit  116  determines that the next message is received (Yes at Step S 634 ), then the system control returns to Step S 607 . 
     On the other hand, if the application control unit  116  determines that the next message is not received within the predetermined period of time (No at Step S 635 ), then the system control proceeds to Step S 636 . At Step S 636 , the application control unit  116  turns OFF the imaging unit  1003 , the ranging unit  1004 , and the light source unit  1005 . When the operation at Step S 636  is finished, the sequence of operations illustrated in the flowchart in  FIG. 22  is ended. 
     In this way, in the second modification example of the third embodiment, the ranging unit  1004  and the light source unit  1005  are turned ON in response to a push notification, and the face authentication is performed based on the depth information. Thus, even if a message sent from another terminal device  1   a  using the corresponding SNS application  5  is received in the display lock state, the user can still release the display lock and send a voice message using the SNS application  5 , for example, just by holding the terminal device  1   a  in one hand and performing face authentication, without having to perform the operation of tapping the touch-sensitive panel  1030  of the terminal device  1   a.    
     Moreover, in the second modification example of the third embodiment, the control for turning OFF the voice input mode is performed according to the result of detecting the movement of the mouth based on the taken image. Herein, in contrast to the fact that the ToF sensor  1041  obtains the depth information based on the point group information, the image sensor of the imaging unit  1003  can output taken images representing, for example, full-color images taken using RGB colors. Hence, the movement of the mouth can be detected with higher accuracy. Thus, in the second modification example of the third embodiment, voice message transmission can be controlled with higher accuracy than in the first modification example of the third embodiment. 
     Furthermore, in the second modification example of the third embodiment, in an identical manner to the third embodiment, the user need not perform an operation such as tapping the touch-sensitive panel  1030  of the terminal device  1  in order to turn ON or turn OFF the voice input mode, and can send a voice message, for example, just by holding the terminal device  1  in one hand and moving it closer to the face. 
     Meanwhile, the effects described in the present written description are only explanatory and exemplary, and are not limited in scope. That is, it is also possible to achieve other effects. 
     Meanwhile, a configuration as explained below also falls within the technical scope of the application concerned. 
     (1) A terminal device comprising: 
     a microphone; 
     a communication unit that performs communication via a network; 
     a first sensor that obtains depth information; 
     a first face detecting unit that performs first-type face detection for detecting a face and distance to the face based on the depth information; and 
     a processor, wherein 
     when a communication program, which is meant for making the processor perform transmission and reception of messages including voice messages and which has a sound input mode for enabling collection of sounds using the microphone and transmission of voice messages based on the collected sounds, is executed, and when a message is received by the communication unit under control of the communication program being executed, 
     the processor performs the first-type face detection using the first face detecting unit and controls turning ON and turning OFF the sound input mode according to result of the first-type face detection. 
     (2) The terminal device according to (1), wherein, when the distance detected by the first face detecting unit is shorter than a predetermined distance, the processor performs control to turn ON the sound input mode.
 
(3) The terminal device according to (1) or (2), wherein, when the distance detected by the first face detecting unit is equal to or greater than a predetermined distance, the processor performs control to turn OFF the sound input mode.
 
(4) The terminal device according to any one of (1) to (3), further comprising a face authenticating unit that performs authentication based on the face detected by the first face detecting unit, wherein
 
     when the communication program is executed and when the message is received by the communication unit in a state in which the processor has applied display restriction on display in the terminal device, the processor performs face authentication using the face authenticating unit, and 
     when a face gets authenticated in the face authentication, the processor releases the display restriction. 
     (5) The terminal device according to any one of (1) to (4), wherein, when the message is received by the communication unit, the processor performs control to turn ON function of the first sensor.
 
(6) The terminal device according to any one to (1) to (5), further comprising a movement detecting unit that performs movement detection for detecting movement of the terminal device, wherein
 
     when a predetermined movement is detected in the movement detection performed by the movement detecting unit, the processor performs the first-type face detection using the first face detecting unit and performs control to turn ON and turn OFF the sound input mode according to result of the first-type face detection. 
     (7) The terminal device according to (1), further comprising: 
     a second sensor that obtains image information; and 
     a second face detecting unit that performs second-type face detection in which a face is detected based on the image information, wherein 
     when the distance detected by the first face detecting unit is shorter than a predetermined distance and when the sound input mode is turned ON, the processor performs the second-type face detection using the second face detecting unit and detects movement of mouth in a face, and 
     when the movement of mouth is not detected for a predetermined period of time, the processor performs control to turn OFF the sound input mode. 
     (8) The terminal device according to (1), wherein 
     when the distance detected by the first face detecting unit is shorter than a predetermined distance and when the sound input mode is turned ON, the processor detects movement of mouth in the face with respect to which the first face detecting unit performed the first-type face detection, and 
     when the movement of mouth is not detected for a predetermined period of time, the processor performs control to turn OFF the sound input mode. 
     (9) A terminal device control method comprising: 
     a depth information obtaining step that includes obtaining depth information using a first sensor; 
     a first face detection step that includes performing first-type face detection for detecting a face and distance to the face based on the depth information obtained in the depth information obtaining step; 
     an execution step that includes executing a communication program, which is meant for making a processor perform transmission and reception of messages including voice messages and which has a sound input mode for enabling collection of sounds using a microphone and transmission of voice messages based on the collected sounds; 
     a determination step that includes determining, by the processor, whether or not a message is received based on the communication program executed in the execution step; and 
     a control step that, when it is determined in the determination step that the message is received, includes
         performing the first-type face detection in the first face detection step, and   performing control, by the processor, to turn ON and turn OFF the sound input mode according to result of the first-type face detection.
 
(10) The terminal device control method according to (9), wherein, when the distance detected in the first face detection step is shorter than a predetermined distance, the control step includes performing control to turn ON the sound input mode.
 
(11) The terminal device control method according to (9) or (10), wherein, when the distance detected in the first face detection step is equal to or greater than a predetermined distance, the control step includes performing control to turn OFF the sound input mode.
 
(12) The terminal device control method according to any one of (9) to (11), further comprising a face authentication step that performs authentication based on the face detected in the first face detection step, wherein
       

     when the communication program is executed and when the message is received by a communication unit, which performs communication via a network, in a state in which the processor has applied display restriction on display in the terminal device, the control step includes performing face authentication in the face authentication step, and 
     when a face gets authenticated in the face authentication, the control step includes releasing the display restriction. 
     (13) The terminal device control method according to any one to (9) to (12), wherein, when the message is received by a communication unit that performs communication via a network, the control step includes performing control to turn ON function of the first sensor.
 
(14) The terminal device control method according to any one to (9) to (13), further comprising a movement detection step that includes performing movement detection for detecting movement of the terminal device, wherein
 
     when a predetermined movement is detected in the movement detection performed in the movement detection step, the control step includes performing the first-type face detection in the first face detection step and performing control to turn ON and turn OFF the sound input mode according to result of the first-type face detection. 
     (15) The terminal device control method according to (9), further comprising: 
     an image information obtaining step that includes obtaining image information using a second sensor; and 
     a second face detection step that includes performing second-type face detection in which a face is detected based on the image information obtained in the image information obtaining step, wherein 
     when the distance detected in the first face detection step is shorter than a predetermined distance and when the sound input mode is turned ON, the control step includes performing the second-type face detection in the second face detection step and detecting movement of mouth in a face, and 
     when the movement of mouth is not detected for a predetermined period of time, the control step includes performing control to turn OFF the sound input mode. 
     (16) The terminal device control method according to (9), wherein 
     when the distance detected in the first face detection step is shorter than a predetermined distance and when the sound input mode is turned ON, the control step includes detecting movement of mouth in face with respect to which the first-type face detection was performed in the first face detection step, and 
     when the movement of mouth is not detected for a predetermined period of time, the control step includes performing control to turn OFF the sound input mode. 
     (17) A computer-readable memory medium that is used to store a control program meant for making a processor execute: 
     a face detection step that includes performing face detection for detecting a face and distance to the face based on depth information obtained by a sensor; 
     an execution step that includes executing a communication program, which is meant for making the processor perform transmission and reception of messages including voice messages and which has, as an operation mode at time of being executed in the processor, a sound input mode enabling collection of sounds using a microphone and transmission of voice messages based on the collected sounds; 
     a determination step that includes determining whether or not a message is received based on the communication program executed in the execution step; and 
     a control step that, when it is determined in the determination step that the message is received, includes
         performing the face detection in the face detection step, and   performing control to turn ON and turn OFF the sound input mode according to result of the face detection.       

     REFERENCE SIGNS LIST 
     
         
           1  terminal device 
           2  network 
           3  server 
           5  SNS application 
           10  display unit 
           12  microphone 
           13  speaker 
           14  first sensor 
           15  second sensor 
           16  banner image 
           17  display lock release screen 
           100  SNS application unit 
           101  UI unit 
           102  communication processing unit 
           103  sound processing unit 
           110  detection/control unit 
           111  ranging processing unit 
           112  first face detecting unit 
           113  imaging processing unit 
           114  second face detecting unit 
           115  movement estimating unit 
           116  application control unit 
           117  activation control unit 
           120  overall control unit 
           124  authenticating unit 
           500  driver program 
           1003  imaging unit 
           1004  ranging unit 
           1005  light source unit 
           1013  orientation detecting unit 
           1041  ToF sensor 
           1051  VCSEL