Abstract:
An object of the present invention is to provide a portable electronic device which the user can comfortably use by suppressing temperature rise in the surface of the device caused by heat from a heat source. The object is achieved by a portable electronic device including: a first casing; a second casing disposed opposed to one of surfaces of the first casing and capable of changing a position relative to the first casing while maintaining a state where opposed surfaces are opposed; and a heat source disposed in the second casing. Surface of the second casing includes: a first region which is covered with the first casing in a first state where the first and the second casings are opposed and is exposed to the outside in a second state where the position relative to the first casing is changed and area of the opposed surfaces of the first and the second casings decreases from the first state; and a second region which is always exposed to the outside in both of the first and the second states. At least a part of the heat source is disposed in a position corresponding to the first region.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2009-248216, filed on Oct. 28, 2010, entitled “PORTABLE ELECTRONIC DEVICE”. The content of which is incorporated by reference herein in its entirety. 
         [0003]    2. Description of the Related Art 
         [0004]    Hitherto, as an apparatus for projecting an image onto a wall surface or a screen, there is a so-called projector. A mainstream projector is an apparatus of a so-called standing type to which power is supplied from a commercial power source and which is used in a state where it is fixed in a predetermined position. The projector of the standing type, in a fixed state, projects an image onto a wall surface or a screen in a fixed place. 
         [0005]    On the other hand, in recent years, a portable projector which is small and easy to carry is proposed as the projector. For example, Japanese Patent Application Publication Laid-open No. 2007-96542 (patent document 1) discloses a portable terminal with a projector function, having an upper cabinet, a lower cabinet, and a hinge connecting the upper and lower cabinets so as to be swingable, and in which a projector having a lens and a light source is mounted. 
         [0006]    The conventional projector of the standing type uses a light source of high luminance for projecting an image onto a large screen and, since an amount of heat generation from the light source is also large, is provided with a fan and a vent for improving heat dissipation efficiency. However, since a portable terminal with a projector function in recent years is constructed compactly, if a mechanism for dissipating heat generated by a light source of a projector is added, it is considered that the portable terminal becomes large. 
         [0007]    In the conventional portable terminal with the projector function, in the case of continuously using the projector, temperature rise near the light source has to be considered. In particular, in the case of a portable electronic device such as a cellular phone, since the skin of the user directly touches the surface of the terminal at the time of speech communication or operation, the user easily feels the temperature difference that the projector mounting position is warmer than the other part. There is consequently the possibility that the user of the cellular phone feels unpleasant. 
         [0008]    For example, in the patent document 1, as an example of the portable terminal with the projector function, examples of a folding type, a slider type, and a straight (candy bar) type are illustrated. In portable terminals of all of the types, a light emitting unit of a projector is provided at the front end near the receiver, but a mechanism for cooling it is not provided. Consequently, after use of the projector, the portion around the receiver becomes warm. When the user makes a telephone call by using the portable terminal, the user feels warm by his/her ear and may feel unpleasant during use. 
         [0009]    Considering a situation that the user carries the portable terminal of the patent document 1 after use of the projector, the portable terminals of all of the types have a structure that heat generated by the projector warms the surface of the portable terminal in a portable mode. Consequently, a temperature difference occurs between a part heated (for example, a part around the receiver) and the other part. Due to this, there is the possibility that the user feels unpleasant when he/she carries the portable terminal by hand or touches the portable terminal in order to make a telephone call with the portable terminal. 
       SUMMARY OF THE INVENTION 
       [0010]    According to an aspect of the present invention, a portable electronic device includes: a first casing; a second casing disposed opposed to one of surfaces of the first casing and capable of changing a position relative to the first casing while maintaining a state where opposed surfaces are opposed; and a heat source disposed in the second casing, wherein surface of the second casing includes: a first region which is covered with the first casing in a first state where the first and the second casings are opposed and is exposed to the outside in a second state where the position relative to the first casing is changed and area of the opposed surfaces of the first and the second casings decreases from the first state; and a second region which is always exposed to the outside in both of the first and the second states, and at least a part of the heat source is disposed in a position corresponding to the first region. 
         [0011]    The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a first state of a portable electronic device according to a first embodiment of the present invention; 
           [0013]      FIG. 2  is a perspective view of a second state of the portable electronic device illustrated in  FIG. 1 ; 
           [0014]      FIG. 3  is a perspective view of the portable electronic device in  FIG. 2  as seen from the rear face side; 
           [0015]      FIG. 4A  is a perspective view of an internal structure of a first casing of the portable electronic device illustrated in  FIG. 3 ; 
           [0016]      FIG. 4B  is a perspective view of an internal structure of a second casing of the portable electronic device illustrated in  FIG. 3 ; 
           [0017]      FIG. 5  is a block diagram of a schematic configuration of the portable electronic device according to the first embodiment of the present invention; 
           [0018]      FIG. 6  is a partially cutaway cross sectional view of the portable electronic device in  FIG. 2  as seen from a side thereof; 
           [0019]      FIG. 7  is a partially cutaway cross sectional view of the portable electronic device in  FIG. 1  as seen from a side thereof; 
           [0020]      FIG. 8  is a diagram illustrating an example of a message displayed to the user at the end of use of the projector; 
           [0021]      FIG. 9  is a perspective view of a portable electronic device according to a second embodiment of the present invention; and 
           [0022]      FIG. 10  is a perspective view of a portable electronic device according to a third embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    The present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. Constituent elements in the embodiments include those that can be easily assumed by those skilled in the art or that are substantially equivalent. In the following, a cellular phone will be taken as an example of the portable electronic device. The object to which the present invention is applied is not limited to a cellular phone. For example, the present invention can be applied to a Personal Handyphone System (PHS), a Personal Digital Assistant (PDA), a portable navigation system, a notebook-sized personal computer, a game device, and the like. 
         [0024]    First, the configuration of the appearance of a portable electronic device will be described.  FIG. 1  is a perspective view of a first state of a portable electronic device according to a first embodiment of the present invention.  FIG. 2  is a perspective view of a second state of the portable electronic device illustrated in  FIG. 1 .  FIG. 3  is a perspective view of the portable electronic device in  FIG. 2  as seen from the rear face side. 
         [0025]    A portable electronic device  10  is a cellular phone having a wireless communication function and has, as illustrated in  FIGS. 1 and 2 , first and second casings  10   a  and  10   b  each having an almost rectangular parallelepiped shape. Largest surfaces of the first and the second casings  10   a  and  10   b  are disposed so as to oppose each other. The sizes of the opposed surfaces of the first and the second casings  10   a  and  10   b  are almost the same. The portable electronic device  10  is a slider-type cellular phone obtained by assembling the first casing  10   a  slidably along the second casing  10   b  in the longitudinal direction of the opposed surfaces of the first and the second casings  10   a  and  10   b.    FIG. 1  illustrates the portable electronic device  10  in a first state which is a state where the first and the second casings  10   a  and  10   b  face each other, concretely, an overlapped region of the opposed surfaces (facing surfaces) of the first and the second casings  10   a  and  10   b  is the largest (that is, completely overlapped).  FIG. 2  illustrates the portable electronic device  10  in a second state in which relative positions of the second casing  10   b  to the first casing  10   a  are changed from the first state to the direction of blank arrow A and the overlapped area of opposed surfaces (facing surfaces) of the first and the second casings  10   a  and  10   b  is smaller than that in the first state. 
         [0026]    In the present embodiment, the region in the surface of the second casing  10   b,  which is covered with the first casing  10   a  in the first state and is exposed to the outside in the second state, that is, the region which is covered with (faces) the first casing  10   a  in the first state and which is not covered with (does not face) the first casing  10   a  in the second state will be called a first region in the second casing  10   b.  The region in the surface of the second casing  10   b,  which is always exposed to the outside in both the first and the second states, that is, the region which is not covered with the first casing  10   a  in both of the first and the second states will be called a second region in the second casing  10   b.  A region in the surface of the first casing  10   a,  which is not exposed in the first state but is exposed to the outside in the second state will be called a third region in the first casing  10   a . In the first embodiment, as illustrated in  FIG. 2 , operation keys  13  and a microphone  15  which will be described later are disposed in the third region. 
         [0027]    The first casing  10   a  has, in addition to the operation keys  13  and the microphone  15  for taking sound at the time of speech communication of the portable electronic device  10  as illustrated in  FIG. 2 , a portable telephone circuit board which plays main functions of a cellular phone and will be described later, a speaker  17 , a camera module  40 , a main antenna and the like. 
         [0028]    The second casing  10   b  has a display  12  illustrated in  FIGS. 1 and 2  as a display unit, and the face of the display  12  is included in the second region. On the display  12 , as a predetermined image, a standby image is displayed in a state where the portable electronic device  10  waits for reception or a menu image used for supporting an operation on the portable electronic device  10  is displayed. Below the display  12 , a direction and determination key  14  is disposed. Above the display  12 , a receiver  16  that generates sound at the time of speech communication of the portable electronic device  10  is provided. On the inside of the second casing  10   b , concretely, in a position corresponding to the first region, a projector  34  is disposed. 
         [0029]      FIG. 3  is a perspective view of the portable electronic device  10  of  FIG. 2  seen from the rear face side, that is, seen from the side opposite to the face on which the display  12  and the operation keys  13  are provided. The configuration provided on the rear face side of the portable electronic device  10  will be described below with reference to  FIG. 3 . First, as illustrated in  FIG. 3 , the projector  34  is disposed in a position corresponding to the first region in the second casing  10   b.  By disposing the projector  34  in the position corresponding to the first region in the second casing  10   b,  heat generated from the projector  34  as a heat source is conducted more to the first region than to the second region. That is, in the position corresponding to the first region, in the second casing  10   b,  generated heat is conducted to the first region more than to the second region. 
         [0030]    As illustrated in  FIG. 3 , slits  35  are formed in the first region in the second casing  10   b.  The slits  35  are vent holes connecting the inside of the second casing  10   b  to the outside of the casing and are openings for releasing air in the casing overheated by the heat generated from the heat source such as the light source of the projector  34  to the outside of the casing. Although the slits are provided as openings in the embodiment, as long as air can be released, any shape may be employed. For example, a number of holes or mesh-shaped openings may be provided. 
         [0031]    As illustrated in  FIG. 3 , on the rear face side of the first casing  10   a,  that is, on the side opposite to the face on which the operation keys  13  are disposed, the speaker  17  and the camera module  40  are disposed. 
         [0032]      FIG. 4A  is a perspective view of an internal structure example of the first casing  10   a  of the portable electronic device  10  in  FIG. 3 .  FIG. 4B  is a perspective view of an internal structure example of the second casing  10   b.  With reference to  FIGS. 4A and 4B , the layout in each of the above-described configurations of the portable electronic device  10  will be described below. As illustrated in  FIG. 4A , in the first casing  10   a,  the speaker  17 , a cellular phone circuit board  22   a,  a main antenna  26   a,  a camera module  40 , and the like are disposed. As described above, the image-taking lens that captures an image of the camera module  40  is exposed from the first casing  10   a  to the outside. 
         [0033]    As illustrated in  FIG. 4B , in the second casing  10   b , the projector  34  and a projector control board  22   b  are disposed on the side of the rear face (the face opposite to the face for displaying an image) of the display  12 . The projector  34  has a light emitting unit  34   a.  The light emitting unit  34   a  is exposed to the outside, that is, disposed in an opening formed in the second casing  10   b . The projector  34  projects an image by emitting light from the light emitting unit  34   a.    
         [0034]    Further, the portable electronic device  10  has, in the second casing  10   b,  a vibration motor  38  and a fan  38   a  coupled to the rotary shaft of the vibration motor  38 . The vibration motor  38  is an eccentric motor whose rotary shaft is provided with an eccentric weight, generates vibrations by making the rotary shaft provided with the eccentric weight rotate, and makes the second casing  10   b  vibrate. The vibration motor  38  is used at the time of notifying of an incoming call and can notify the user of an incoming call by vibrating the second casing  10   b  without outputting sound. 
         [0035]    The fan  38   a  is coupled to the rotary shaft of the vibration motor  38  and rotates when the vibration motor  38  runs. When the fan  38   a  rotates by the rotation of the vibration motor  38 , the flow of air is generated in the second casing  10   b.  By the generation of the flow of air by the fan  38   a,  the air in the second casing  10   b  and the outside air circulate via the slits  35 . By the circulation, the warmed air around the projector  34  can be discharged to the outside, and the projector  34  and its periphery can be cooled down. In a manner similar to the first embodiment, by disposing the fan  38   a  adjacent to the projector  34  to send the air blown from the fan  38   a  to the projector  34  or discharging the air around the projector  34  by the fan  38   a  to the outside, the projector  34  can be cooled efficiently. According to the first embodiment, only by adding the fan  38   a  to the tip of the existing vibration motor  38 , the function of cooling the projector  34  can be added. Consequently, the number of parts and mounting space which increases due to the addition of the cooling function can be reduced, and the device can be miniaturized. 
         [0036]    As illustrated in  FIG. 4B , a heat insulation sheet  39  is interposed between the surface (second region) of the display  12  and the projector  34 . By disposing the heat insulation sheet  39 , conduction of heat generated from the heat source such as the light source of the projector  34  to the surface on the side of the display  12  can be suppressed. As the heat insulation sheet, for example, a heat insulating material in a thin sheet shape made of mainly microballoon (closed pores) for an electronic device can be suitably used. 
         [0037]    By disposing the projector  34  on the side of the second casing  10   b  provided with the display  12 , even when the second casing  10   b  is set in the second state at the time of projecting an image, a projected image can be prevented from being blocked. By dispersing the heat generation sources, rise in temperature only in a part of the first casing  10   a  and/or the second casing  10   b , particularly, only in a part of the surface can be suppressed. For example, the projector  34  is provided on the side of the second casing  10   b  on which parts that do not generate heat so much like the display  12  of an LCD are mounted. The cellular phone circuit board  22   a,  a battery (not illustrated), and the like which do not generate heat as much as the projector  34  but can be heat generation sources are provided on the side of the first casing  10   a.  By providing the camera module  40  on the side of the first casing  10   a,  the camera module  40  can be disposed far from the heat generation of the projector  34 , and the number of connections between the circuit on the side of the display  12  and the circuit on the side of the operation keys  13  can be made small. 
         [0038]      FIG. 5  is a block diagram of a schematic configuration of the portable electronic device according to the first embodiment of the present invention. With reference to  FIG. 5 , the functional configuration of the portable electronic device  10  will be described below. As illustrated in  FIG. 5 , the portable electronic device  10  has a control unit  22 , a storing unit  24 , a transmitting and receiving unit  26 , an operation unit  28 , a sound processing unit  30 , a display unit  32 , the projector  34 , a temperature sensor  36 , the vibration motor  38 , and the like. 
         [0039]    The control unit  22  is a processing unit such as a central processing unit (CPU), a micro processor unit (MPU), or the like for controlling general operation of the portable electronic device  10  in a centralized manner. Specifically, the control unit  22  controls the operation of the transmitting and receiving unit  26 , the sound processing unit  30 , the display unit  32 , and the like so that various processes of the portable electronic device  10  are executed in proper procedure in accordance with operation of the operation unit  28  and software stored in the storing unit  24  of the portable electronic device  10 . The various processes of the portable electronic device  10  include, for example, verbal communication performed via a line switching network, creation and transmission/reception of an electronic mail, browsing of a Web (World Wide Web) site on the Internet, and the like. Operations of the transmitting and receiving unit  26 , the sound processing unit  30 , the display unit  32 , and the like include, for example, transmission/reception of signals by the transmitting and receiving unit  26 , input/output of voice by the sound processing unit  30 , and display of an image by the display unit  32 . 
         [0040]    Concretely, the control unit  22  executes processes on the basis of programs (for example, an operating system program, an application program, and the like) stored in the storing unit  24 . The control unit  22  sequentially reads instruction codes from the operating system program, the application program, or the like stored in the storing unit  24  and executes processes on the basis of instruction codes. Examples of the application program executed by the control unit  22  include an application program for driving the projector and controlling the rotation of a cooling fan using the vibration motor  38  which will be described later, an image reproduction application program for reproducing a still picture and a motion picture, and a game application program for operating various games. 
         [0041]    In the storing unit  24 , software and data used for the processes in the control unit  22 , for example, the application program that controls the driving of the projector  34 , the image reproduction application program that reproduces a still picture and a motion picture, and the application program for operating various games are stored. 
         [0042]    In the storing unit  24 , in addition to the above application programs, for example, voice data received by communication or downloaded, software used by the control unit  22  for control on the storing unit  24 , an address book that stores and manages telephone numbers, mail addresses, and the like of other parties of communication, a sound file of dial tone, ringtone, and the like, temporary data used in processes of software, and the like are also stored. Computer programs and temporary data used in processes of software are temporarily stored in a work area allocated in the storing unit  24  by the control unit  22 . The storing unit  24  is constructed by, for example, nonvolatile storing devices (a nonvolatile semiconductor memory such as a Read Only Memory (ROM), a hard disk drive, and the like), readable/writable storage devices (such as an Static Random Access Memory (SRAM) and Dynamic Random Access Memory (DRAM)), and the like. 
         [0043]    The transmitting and receiving unit  26  has the main antenna  26   a,  establishes a wireless signal line of the CDMA method or the like between itself and a base station via a channel assigned by the base station, and performs telephone communication and information communication with the base station. 
         [0044]    The operation unit  28  is constructed by, for example, the operation keys  13  to which various functions are assigned such as a power key, a telephone call key, numeric keys, character keys, direction keys, a determination key, and a transmission key, and the direction and determination key  14 . When the keys are operated by the user, a signal corresponding to the operation is generated. The generated signal is supplied as an instruction of the user to the control unit  22 . 
         [0045]    The sound processing unit  30  executes processes on a sound signal input from the microphone  15  and a sound signal output to the receiver  16 . Specifically, the sound processing unit  30  amplifies sound input from the microphone  15 , performs A/D conversion (Analog-to-Digital conversion) on the sound, also performs a signal process such as encoding, and outputs the resultant digital sound data to the control unit  22 . The sound processing unit  30  performs processes such as decoding, D/A conversion (Digital-to-Analog conversion), and amplification on the sound data supplied from the control unit  22  and outputs the resultant analog sound signal to the receiver  16 . 
         [0046]    The display unit  32  has a display panel (the above-described display  12  or the like) such as a liquid crystal display (LCD) or an organic electro-luminescence panel and displays a video image according to video data supplied from the control unit  22  and an image according to image data on the display panel. The display unit  32  may have, in addition to the display  12 , for example, a sub-display in a position which is exposed to the outside also in a state where the casing is closed. 
         [0047]    The projector  34  is an image projecting unit for projecting an image and, as described above, is disposed in a position corresponding to the first region in the second casing  10   b.  The portable electronic device  10  projects an image, that is, emits light which forms an image from the light emitting unit  34   a  of the projector  34 , thereby projecting an image onto a predetermined region (projection region) in a wall (not illustrated) surface, screen, or the like on the opposed face in the sliding direction (refer to the direction A in  FIG. 2 ) of the second casing  10   b.  The operation of the projector  34  is controlled by the control unit  22  so that various video images such as a movie or presentation data sent from the control unit  22  can be projected and displayed in the projection region. 
         [0048]    The projector  34  includes a light source and an optical system for switching whether light emitted from the light source is projected or not. As the projector  34 , for example, a projector using a halogen light, an Light Emitting Diode (LED) light source, or an Laser Diode (LD) light source as the light source and using an Liquid Crystal Display (LCD) or a Digital Micro-mirror Device (DMD) as the optical system can be employed. In this case, by disposing the optical systems in such a way that the optical systems covers the entire projection region and turning on/off the pixels of the optical systems in accordance with an image, the image can be projected to the entire projection region. As the projector  34 , a projector having a laser as a light source and an optical system including a switching device that switches whether light emitted from the light source is passed or not and a mirror for performing a raster-scan with the light passed through the switching device can also be employed. In this case, by scanning the entire projection region with light emitted from the light source while changing the angle of the light emitted from the laser by the mirror, an image can be projected to the projection region. 
         [0049]    The temperature sensor  36  is a detecting unit disposed in the projector  34  and detects the internal temperature. The vibration motor  38  is, as described above, an eccentric motor in which the fan  38   a  is connected to the tip of the rotary shaft. The vibration motor  38  makes the fan  38   a  attached to the tip of the rotary shaft rotate to circulate the air in the second casing  10   b,  thereby cooling the projector  34 . When the temperature detected by the temperature sensor  36  becomes equal to or higher than predetermined temperature, the control unit  22  runs the vibration motor  38  to rotate the fan  38   a.  Basically, the portable electronic device  10  in the first embodiment is constructed as described above. 
         [0050]    Referring now to  FIGS. 6 and 7 , the image displaying/projecting operation of the portable electronic device  10  in the first embodiment, concretely, a state during image projection by the projector  34  and a state after the image projection will be described.  FIG. 6  is a partially cutaway cross sectional view of the portable electronic device in  FIG. 2  as seen from a side thereof.  FIG. 7  is a partially cutaway cross sectional view of the portable electronic device in  FIG. 1  as seen from a side thereof. 
         [0051]    In the portable electronic device  10  according to the first embodiment, in the case of projecting an image by using the projector  34 , as illustrated in  FIG. 6 , the second casing  10   b  is made slide in the direction of the hollow arrow A along the first casing  10   a  to expose the first region corresponding to the position where the projector  34  is disposed to the outside. In this state, the control unit  22  of the portable electronic device  10  makes light emitted from the light emitting unit  34   a  of the projector  34  to project an image onto a wall face or a screen. As described above, at the time of projection, by setting the portable electronic device  10  in the second state, the first region to which heat generated from the light source of the projector  34  and the like is conducted can be set to a state where it does not face the first casing  10   a  and is exposed to the outside air. Consequently, the heat generated by the projector  34  can be released to the outside of the casing (the second casing  10   b ) with high heat dissipation effect, and temperature rise in the casing can be suppressed. Preferably, the portable electronic device  10  has a posture sensor that detects the positional relation between the first and the second casings  10   a  and  10   b,  and the control unit  22  allows projection of an image only in the case that the second state is detected on the basis of a detection result of the sensor. With the configuration, projection of an image not in a proper posture can be suppressed. 
         [0052]    Further, when the temperature sensor  36  in the projector  34  detects that the internal temperature becomes equal to or higher than the predetermined temperature, the control unit  22  of the portable electronic device  10  runs the vibration motor  38 . By running the vibration motor  38 , the fan  38   a  is rotated to send air, so that the air in the casing warmed by the heat generated by the projector  34  can be discharged from the slits  35 . By the operation, the projector  34  can be forcedly cooled. Cooling by the vibration motor  38  and the fan  38   a  in such a manner, even in the case of continuously using the projector  34  for long time, temperature rise can be suppressed with reliability. 
         [0053]    The portable electronic device  10  is of the slider type of making the second casing  10   b  slide in the longitudinal direction along the first casing  10   a,  and the projector  34  having the heat source is disposed in a position corresponding to the first region which is exposed to the outside when the second casing  10   b  slides. Consequently, also in the case of projecting an image in a state where the portable electronic device  10  is put on a stand, as illustrated in  FIG. 6 , the projector  34  is apart from the stand only by the thickness of the first casing  10   a,  and the first region to which heat of the projector  34  is mainly conducted is also apart from the stand. Therefore, the effect of heat dissipation by outside air can be expected and air can be circulated via the slits  35 . 
         [0054]    As described above, in the portable electronic device  10 , the heat insulation sheet  39  is disposed between the display  12  in the second casing  10   b  and the projector  34 , so that heat generated by the projector  34  can be prevented from being conducted to the surface on the side of the display  12 . Consequently, in addition to the effect of the heat dissipation from the first region and the cooling effect by the fan  38   a,  conduction of heat generated by the projector  34  to the surface on the side of the display  12  of the second casing  10   b  can be suppressed by the heat insulation effect of the heat insulation sheet  39 . As a result, heating of the second region in the second casing  10   b  can be suppressed. For example, even when the telephone rings during use of the projector and the user puts the receiver  16  on his/her ear, since the surface temperature difference is small, the user can talk over the telephone without feeling unpleasant. 
         [0055]    Now, the case where the user performs image projection by the projector  34  in the second state in which the second casing  10   b  is made slide in the direction of the hollow arrow A and is displaced and, after completion of the projection, the user carries the portable electronic device  10  (by putting it into a pocket or a bag, or by hand) will be described. In the case where the user carries the portable electronic device after completion of the projection of the projector  34 , basically, the relative positions of the first and the second casings  10   a  and  10   b  are returned to the first state as illustrated in  FIG. 7 . In this state, the projector  34  as the heat source is sandwiched between the first casing  10   a  and the display  12  of the second casing  10   b.  The first region is in a position opposed to the first casing  10   a.  Only by returning the second casing  10   b  to the first state after completion of the projection of the projector  34 , the user can carry the portable electronic device  10  without directly touching the first region heated by the projector  34  with a hand. Since the first region heated most by the use of the projector  34  can be prevented from being exposed, occurrence of the surface temperature difference of the portable electronic device  10  is suppressed. Even when the portable electronic device  10  is carried by a hand, the possibility that the user feels unpleasant can be reduced. 
         [0056]    In the portable electronic device  10  in the second state where the projector  34  is used, by heat dissipation to the outside air and forced cooling by the fan  38   a,  the temperature rise is suppressed in the second region in addition to the first region. Further, since the heat insulation sheet  39  is disposed between the projector  34  and the display  12 , conduction of heat from the projector  34  to the surface on the side of the display  12  is suppressed. Even immediately after projection of the projector  34 , temperature rise in the second region such as the side faces of the display  12  can be suppressed. As a result, the temperature difference between the second region in the second casing and the surface of the first casing can be reduced. 
         [0057]    Preferably, at the end of use of the projector  34 , the portable electronic device  10  projects, from the projector  34 , a message urging the user to set the portable electronic device into the first state.  FIG. 8  is a diagram illustrating an example of a message displayed to the user at the end of use of the projector. For example, preferably, at the end of projection of the projector  34 , the control unit  22  includes notification information such as “Please close the operation unit after use of the projector” in a projected image as illustrated in  FIG. 8 . By projecting the message, the user is alerted to carry the portable electronic device  10  which is set in the first state. It can reduce the possibility such that the user forgets to set the portable electronic device  10  into the first state after projection of the projector  34 , carries the device in the second state, touches the first region in the second casing  10   b  to which heat of the projector  34  is conducted, and feels unpleasant. Although the projected image including the notification information is projected, instead or in addition, the notification information may be displayed on the display  12  of the portable electronic device  10 . 
         [0058]    Preferably, the projector  34  is disposed with space from the substrate of the display  12  and the surface on the side of the display  12  of the second casing  10   b.  More preferably, the projector  34  is fixed to the face on the side of the first region of the second casing  10   b.  By disposing the projector  34  apart from the surface on the side of the display  12  of the second casing  10   b,  a structure that heat is not easily conducted to the surface on the side of the display  12  of the second casing  10   b  can be realized. 
         [0059]    For a member used for the first region in the second casing  10   b  or the peripheral part (exterior) of the projector  34 , by using a composite material of copper (Cu), aluminum (Al), and the like having excellent heat conductivity as the material of a radiator plate, the heat dissipation effect can be further enhanced. Further, by enlarging the surface area by attaching a patterned-indented fin to the surface of the radiator plate material, the heat dissipation effect can be further enhanced. 
         [0060]    Preferably, for example, the control unit  22  intermittently controls the rotation of the vibration motor  38  at timings of switching a projection image and, during cooling operation by running the vibration motor  38 , controls to interrupt the projecting operation. By the control, occurrence of blurring in an image projected can be suppressed. 
         [0061]    Preferably, the vibration motor  38  has a configuration that a one-way clutch is interposed between the rotary shaft and the eccentric weight. With the configuration, at the time of rotation in one direction, for example, a forward direction, the vibration motor can generate vibrations by rotating the eccentric weight. At the time of rotation in another direction, for example, in a reverse direction, the vibration motor can rotate only the fan  38   a  at the tip of the rotary shaft without rotating the eccentric weight. As described above, by employing the configuration including the one-way clutch, only the fan can be rotated. Without generating vibrations, cooling operation can be performed. 
         [0062]      FIG. 9  is a perspective view of a portable electronic device according to a second embodiment of the present invention. In the first embodiment, as illustrated in  FIG. 2 , an image is projected from the projector  34  in the second state where the second casing  10   b  slides in the longitudinal direction of the first casing  10   a  of the portable electronic device  10 . The present invention, however, is not limited to the portable electronic device of this type. For example, the second embodiment illustrated in  FIG. 9  relates to the case where a projector  134  is mounted on a cellular phone of a type in which a second casing  110   b  slides in the short-side direction of a first casing  110   a  of a portable electronic device  100 . In a second state illustrated in  FIG. 9 , an image may be projected from a light emitting unit  134   a  of the projector  134 . 
         [0063]    The configuration of the portable electronic device  100  is basically the same as that of the first embodiment but is different with respect to the point that the movement direction in which the relative position between the first and the second casings  110   a  and  110   b  changes is the short-side direction. The light emitting unit  134   a  of the projector  134  is provided near to the first region at the front end in the movement direction (the direction of hollow arrow B). 
         [0064]    Since the portable electronic device  100  is similar to the portable electronic device  10  of the first embodiment except for the above-described configuration, the description will not be repeated. 
         [0065]    Also in the type in which the second casing  110   b  slides in the short-side direction of the first casing  110   a  like in the portable electronic device  100 , by providing the projector  134  in a position corresponding to the first region where the projector  134  is exposed in the second state and faces the first casing  110   a  in the first state, in a posture (first state) where the user carries the device, the first region to which heat is conducted most can be prevented from being touched by the user. Thus, the possibility that the user feels unpleasant can be reduced. At the time of projecting an image by the projector  134 , heat generated from the projector  134  can be released from the first region exposed to the outside. Therefore, temperature rise in the casing can be suppressed. 
         [0066]    Also in the portable electronic device  100 , when the internal temperature detected by the temperature sensor  36  in the projector  134  becomes equal to or higher than predetermined temperature, by running the vibration motor  38  to rotate the fan  38   a  to discharge the air in the projector  134  from the slits  35 , the control unit  22  can forcedly cool the projector  134 . With the technique, the temperature rise in the casing can also be suppressed. 
         [0067]    Also in the portable electronic device  100 , by disposing a heat insulation sheet (not illustrated) between a display  112  of the second casing  110   b  and the projector  134 , conduction of heat generated by the projector  134  to the surface on the side of the display  112  can be suppressed. 
         [0068]      FIG. 10  is a perspective view of a portable electronic device according to a third embodiment of the present invention. In the third embodiment illustrated in  FIG. 10 , a first casing  210   a  and a second casing  210   b  of a portable electronic device  200  are supported swingably around a pivot point provided around a receiver  216  as a center. In  FIG. 10 , in a second state where the second casing  210   b  is turned by 90 degrees in the direction of hollow arrow C, an image is projected from a light emitting unit  234   a  of a projector  234  disposed in the first region exposed to the outside. Although not illustrated, in a second state where the second casing  210   b  is turned by 180 degrees in the direction of the hollow arrow C, a telephone call or image projection may be made. 
         [0069]    The configuration of the portable electronic device  200  is basically the same as that of the first and the second embodiments but is different with respect to the point that, as illustrated in  FIG. 10 , from a first state where the surfaces of the largest area of the first and the second casings  210   a  and  210   b  face each other, the relative position is changed by turning the second casing  210   b  in the direction of the hollow arrow C, thereby setting the device in a second state. Accordingly, the projector  234  is disposed in the first region of the second casing  210   b  exposed to the outside, and the light emitting unit  234   a  is provided near to the first region at the end. 
         [0070]    Since the portable electronic device  200  is similar to the portable electronic device  10  described in the first embodiment except for the above-described configuration, the description will not be repeated. 
         [0071]    Also in the type in which the second casing  210   b  is turned relative to the first casing  210   a  to be in the second state like in the portable electronic device  200 , by providing the projector  234  in a position corresponding to the first region where the projector  234  is exposed in the second state and faces the first casing  210   a  in the first state, in a posture (first state) where the user carries the device, the first region to which heat is conducted most can be prevented from being touched by the user. Thus, the possibility that the user feels unpleasant can be reduced. At the time of projecting an image by the projector  234 , heat generated from the projector  234  can be released from the first region exposed to the outside. Therefore, temperature rise in the casing can be suppressed. 
         [0072]    Also in the portable electronic device  200 , when the internal temperature detected by the temperature sensor  36  in the projector  234  becomes equal to or higher than predetermined temperature, by running the vibration motor  38  to rotate the fan  38   a  to discharge the air in the projector  234  from the slits  35 , the control unit  22  can forcedly cool the projector  234 . 
         [0073]    Also in the portable electronic device  200 , by disposing a heat insulation sheet (not illustrated) between a display  212  of the second casing  210   b  and the projector  234 , conduction of heat generated by the projector  234  to the surface on the side of the display  212  can be suppressed.