Patent Publication Number: US-2011076005-A1

Title: Portable electronic device having camera

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a portable electronic device having a camera. 
     2. Description of Related Art 
     In recent years, portable electronic devices, such as mobile phones with cameras have become more and more widely used. A typical camera used in the portable electronic device is equipped with a shutter, and an image sensor such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor, which is exposed automatically at a predetermined shutter speed. 
     A conventional camera adopts a mechanical shutter, which uses an arrangement of spring, cam and gear to control the speed of the shutter. However, the shutter has a complex structure and occupies a large amount of space in the camera. This may increase the size of the portable electronic device having the camera. 
     Therefore, a portable electronic device having a camera which can overcome the above-mentioned problems is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is a partially disassembled isometric view of a portable electronic device in which a camera and a liquid crystal shutter are implemented according to an exemplary embodiment. 
         FIG. 2  is a schematic, isometric view of the portable electronic device of  FIG. 1 . 
         FIG. 3  is a sectional view taken along line III-III, showing a plurality of structures of the camera and the liquid crystal shutter of  FIG. 1 . 
         FIG. 4  is a sectional view of the liquid crystal shutter of  FIG. 3 , in which a control circuit is further comprised. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments will now be described in detail below with reference to the drawings. 
     Referring to  FIGS. 1 and 2 , a portable electronic device  100  in accordance with an exemplary embodiment is provided. In this embodiment, the portable electronic device  100  is a mobile phone. It is noteworthy that the portable electronic device  100  can also be a MP3, a notebook computer, a personal digital assistant (PDA), etc. The portable electronic device  100  includes a front cover  110 , a back cover  120 , a camera  130  and a liquid crystal shutter  140  for the camera  130 . The front cover  110  is connected to the back cover  120 , thereby cooperatively forming a housing of the portable electronic device  100 . 
     The portable electronic device  100  further includes a main circuit board  112  received in the housing, and the main circuit board  112  is fixed to the front cover  110 . The main circuit board  112  is configured for controlling various functions of the mobile phone, including operations of the camera  130  and the liquid crystal shutter  140 . 
     The camera  130  is also received in the housing and fixed to the front cover  110 . The camera  130  is electrically connected to the main circuit board  112 , thereby is being controlled by the main circuit board  112  to capture images. Referring also to  FIG. 3 , the camera  130  includes a lens barrel  132 , a barrel holder  134 , an optical lens  136  received in the lens barrel  132 , and an image sensor  138  optically aligned with the optical lens  136 . The lens barrel  132  is partly received in the barrel holder  134  and is movable along an optical axis of the optical lens  136  relative to the barrel holder  134 . The image sensor  138  is fixed to the barrel holder  134 . The image sensor  138  can be a complementary metal-oxide semiconductor (CMOS) or a charge coupled device (CCD). It is to be understood that the number of the optical lens  136  can be more than one, as long as the images of objects can be focused on the image sensor  138 . 
     The back cover  120  has a through hole  122  defined therein. In this embodiment, the through hole  122  is rectangular. The through hole  122  is located facing the camera  130 . The lens barrel  132  is adjacent to the through hole  122  such that ambient light passing the through hole  122  can transmit through the optical lens  136  and then onto the image sensor  138 . The liquid crystal shutter  140  is positioned in the through hole  122  and fixed to the back cover  120 . In an alternative embodiment, the liquid crystal shutter  140  is fixed to the back cover  120  in a manner such that the side surface of the liquid crystal shutter  140  is adhered to an inner wall of the back cover  120  in the through hole  122 . The liquid crystal shutter  140  is used as a shutter structure of the camera  130 . In addition, the liquid crystal shutter  140  can prevent dust from entering the camera  130 . 
     Referring to  FIG. 4 , the liquid crystal shutter  140  includes a first polarizer  141 , a first light-pervious electrode  142 , a liquid crystal layer  143 , a second light-pervious electrode  144  and a second polarizer  145  sequentially stacked in an order from a position away from the camera  130  to a position closer to the camera  130 . In this embodiment, the first and second light-pervious electrodes  142  and  144  are plate electrodes covering the entire area of the liquid crystal shutter  140 . In this embodiment, each of the first and second light-pervious electrodes  142  and  144  includes a light-pervious plate and a light-pervious conductive film coated on the light-pervious plate. The light-pervious conductive film can be comprised of indium tin oxide. In an alternative embodiment, the liquid crystal layer  143  is a twisted-nematic type (TN type). The first polarizer  141  has a polarization axis perpendicular with that of the second polarizer  145 . 
     The liquid crystal shutter  140  further includes a control circuit  150 . The control circuit  150  is electrically connected to the first and second light-pervious electrodes  142  and  144  for controlling a voltage between the first and second light-pervious electrodes  142  and  144 . The control circuit  150  includes a voltage supply  152  and a switch  154  connected in series. The switch  154  is configured for switching on/off of the voltage supply  152 . Preferably, a voltage applied to the liquid crystal layer  143  between the first and second light-pervious electrodes  142  and  144  is larger than the saturation voltage of the liquid crystal layer  143 . The control circuit  150  can be integrated in the main circuit board  112 . In this case, a battery of the portable electronic device  100  can act as the voltage supply  152  of the liquid crystal shutter  140 . 
     When the switch  154  is in an on state, a voltage is applied between the first and second light-pervious electrodes  142  and  144 . Thus, orientations of the liquid crystal molecules of the liquid crystal layer  143  tend to become parallel with an electric field direction. When the voltage applied between the two electrodes  142  and  144  is larger than the saturation voltage of the liquid crystal layer  143 , orientations of the liquid crystal molecules of the liquid crystal layer  143  are parallel with that voltage, i.e. perpendicular with the first and second electrodes  142  and  144 . Light transmitting through the first polarizer  142  becomes linear polarized light. Then the linearly polarized light is transmitted through the liquid crystal layer  143  and keeps the polarization direction unchanged. Because the polarization axis of the second polarizer  145  is perpendicular with that of the first polarizer  141 , the light transmitting through the liquid crystal layer  143  is blocked by the second polarizer  145 . Here the liquid crystal shutter  140  is in a dark state. That is, the ambient light is blocked by the liquid crystal shutter  140 . 
     When the switch  154  is in an off state, no voltage is applied between the first and second light-pervious electrodes  142  and  144 , the liquid crystal layer  143  thereby returns to its original orientations of the liquid crystal molecules. It is known by those skilled in the art that TN type liquid crystal layer can cause a polarization direction of linearly polarized light to rotate 90°. Thus, a polarization direction of the light passing the first polarizer  141  is rotated 90° by the liquid crystal layer  143 . That is, the light passing the liquid crystal layer  143  has a polarization direction parallel with the polarization axis of the second polarizer  145 . Thus, the light can be transmitted through the second polarizer  145 , then passed through the optical lens  136  and finally onto the image sensor  138 . Here the liquid crystal shutter  140  is in a bright state. Therefore, the liquid crystal shutter  140  has a light switch function, thereby acting as a shutter structure. 
     It is noteworthy that the polarization axis of the first polarizer  141  can also be parallel with that of the second polarizer  145 . Accordingly, the light is blocked by the liquid crystal shutter when the switch is in an off state, and the light is passed through the liquid crystal shutter when the switch is in an on state. In addition, the liquid crystal layer  143  can be, other types of liquid crystal instead, such as a super twisted nematic (STN) type. Furthermore, the liquid crystal shutter  140  can also be fixed to the front cover  110 . Accordingly, the camera  130  is fixed to the back cover  120 . 
     The portable electronic device  100  of the exemplary embodiment includes a liquid crystal shutter  140  fixed to a cover of the portable electronic device  100 . Thus the liquid crystal shutter  140  does not occupy any space inside the camera  130 . In addition, the liquid crystal shutter  140  merely comprises a multi-layer structure and is replaced in lieu of a dust-proof window for the camera  130 . Therefore, the portable electronic device  100  comprising the liquid crystal shutter  140  has a simpler structure and a smaller size. 
     It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.