Abstract:
High data rate interconnections between foldable parts of a cellular telephone handset, such as the handset keypad and handset display portions, are made by free space optical data transmission between light emitting devices such as laser diodes or LEDs and photodiodes, without use of optical waveguides or cables between the foldable parts.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention pertains to the field of communications handsets such as are used for cellular telephony and more particularly relates to optical couplings between relatively movable portions of the handsets. 
         [0003]    2. State of the Prior Art 
         [0004]    Recently, mobile telephone handsets have evolved beyond mere telephones, and many now include a digital camera, a high resolution TV player, a video phone, a digital music player, and an internet browsing device. Mobile telephone manufacturers are currently designing a next generation (known as Generation 3.5 or Generation 4) of high performance telephone handsets. 
         [0005]    To make the handsets more compact and easier to carry, cellphone handsets have been designed with handset portions which are moveable relative to each other between a compact closed configuration and a deployed configuration. For example, the radio transmitter and receiver are housed in a cellphone body which also carries a keypad, while one or more display screens, and now a digital camera, are mounted on a display unit which is attached mechanically and electrically to the cellphone body. Two popular configurations include the flip open or clamshell style handset where the display unit is hinged to the cellphone body, and the slide style handset where the display portion slides linearly in relation to the cellphone body between a closed condition where the display portion entirely covers the keyboard of the body portion and an extended condition where the keyboard is exposed for access. 
         [0006]    Such two part cellphone handsets require a means for interconnecting the display screen or screens and the digital camera to the receiver, transmitter and other circuits in the cellphone body. In the past, this interconnection was made with electrically conductive wiring such as a coaxial cable or a ribbon cable. However, with increasing data transfer rates between the interconnected portions of the handset, the traditional electrical connections are proving inadequate. 
         [0007]    Ordinary electrical flexible cable may be vulnerable to EMI (electromagnetic interference noise) and/or the electronic cable can be inadequate for the data rates above 1 Gb/s which are required by the newer handsets. 
         [0008]    To meet this challenge many cellphone manufacturing companies are developing flexible optical cable for making the interconnection between the body and display portions as a replacement for the electrical cable. However, the requirements on the optical cable or fiber interconnection are very tight, particularly as to mechanical reliability under repeated flexing and bending (in terms of optical cable bending frequency and bending radius) and the thickness of the optical cable (thinner is better given the small dimensions of typical handsets). Moreover, mobile phone handsets must be cheap, so that economy of parts and cost of assembly are important. 
       SUMMARY OF THE INVENTION 
       [0009]    The aforementioned difficulties are addressed in the present invention by using free space optical transmission of data between the cellphone body and display units and eliminating the need for a cable connection between those elements. That is, optical data links are established without interconnecting waveguides, e.g. across free space or air gaps, between circuits of a communications handset and in particular between portions of the handset which are movable relatively to each other in foldable, collapsible or deployable handsets. 
         [0010]    According to this invention a communications handset of the type having first and second handset portions mutually displaceable between a closed condition and a deployed condition and having electronic circuits in each of the portions is improved by providing at least one light emitting device and at least one light detecting device on each of the handset portions. The emitting and detecting devices are connected to the circuits on their respective portions and are optically aligned across a free space in the closed condition and the deployed condition of the handset for providing optical transfer of data between the electronic circuits of the two handset portions. 
         [0011]    In one form of the invention the first handset portion is a body portion with a keypad and the second handset portion is a display portion hinged to the body portion for movement between the closed condition and the deployed condition. 
         [0012]    In another form of the invention the first handset portion is a body portion with a keypad and the second portion is a display portion linearly slidable relative to the body portion between the closed condition and the deployed condition. 
         [0013]    In one embodiment of the invention, a first light emitting device and a first light detecting device is provided on each of the portions in optical alignment for providing data transfer in the closed condition of the handset and a second light emitting device and a second light detecting device is provided on each of the portions in optical alignment for providing data transfer in the deployed condition of the handset. 
         [0014]    In another embodiment of the invention wherein the handset portions are hinged to each other, the light emitting devices and light detecting devices are optically aligned axially to the hinge. 
         [0015]    These and other features, improvement and advantages of the present invention will be better understood from the following detailed description in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0016]      FIG. 1  is a perspective view of a typical flip-open or clamshell type cellular telephone handset, shown in closed condition with the display portion folded over the main body portion of the unit; 
           [0017]      FIG. 2  is a perspective view of the handset of  FIG. 1  shown in open condition with the display portion deployed away from the main body portion of the unit; 
           [0018]      FIG. 2   a  is a schematic view illustrating the arrangement of the photo emitters and photo detectors in an open condition of the handset of  FIG. 2 ; 
           [0019]      FIG. 3  is a side schematic view of the closed handset of  FIG. 1  with an optical transmitter/receiver pair indicated by small rectangular boxes; 
           [0020]      FIG. 4  is a side schematic view as in  FIG. 3  but with the handset open as in  FIG. 2  and showing the optical transmitter/receiver pair aligned for data communication between the deployed display portion and the main body portion; 
           [0021]      FIG. 5  is a fragmentary close up view of the hinge joining the main body portion to the display portion of the handset unit of  FIG. 1 , illustrating another possible arrangements of two optical transmitter/receiver pairs aligned axially to the hinge; 
           [0022]      FIG. 6  is a top side perspective view of a slide-to-open type cellular telephone handset, shown in closed condition with the display portion retracted over the main body portion of the unit; 
           [0023]      FIG. 7  is a perspective view of the handset of  FIG. 6  shown in open condition with the display portion extended from the main body portion of the unit; 
           [0024]      FIG. 8  is a diagram illustrating one possible arrangement of optical transmitter/receiver pairs in the handset of  FIGS. 6 and 7 ; 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    With reference to the drawings in which like elements are indicated by like numerals,  FIG. 1  illustrates a typical flip-open or clamshell type cellular telephone handset generally designated by numeral  10  and which has a main body portion  12  and a display portion  14  joined to each other by a hinge  16 . The body portion  12  and display portion  14  have internal surfaces  12   a ,  14   a  respectively which are mutually opposing in the closed condition of the unit  10  shown in  FIG. 1 . When the handset  10  is deployed to its open condition seen in  FIG. 2  the internal surfaces  12   a ,  14   a  both face approximately towards the same direction, and in practice face towards the user or holder of the handset. 
         [0026]    In most communications handsets of this type the main body portion  12  contains and houses a radio transceiver which receives and transmits radio signals over the air, a battery for powering the various circuits and systems of the handset  10 , and a keypad  18 , among still other devices. The display portion  14  normally includes an LCD (liquid crystal display) screen  20  on the internal surface  14   a  and often a second smaller outer LCD screen  22  on an exterior surface  14   b . The exterior display  22  typically shows handset status, caller identification and other information while the handset  10  is closed. In many newer handsets, a still or video camera  24  is provided on the display portion  14 , which displays captured images on LCD  20  and is also connected to the radio transceiver and other circuits in the main body  12  so that the images can be sent to other handsets through the radio communications network or downloaded, e.g., to a computer. 
         [0027]    Both LCDs  20 ,  22  and the camera  24  on the display portion  14  require interconnection for data transfer to and from the circuits of the body portion  12 . According to this invention, this interconnection is provided at least in part by optical links without use of a physical connection or optical waveguide, such as across a free space or air gap, between one or more light emitter/detector pairs. 
         [0028]      FIG. 3  illustrates in schematic form a flip-open style handset  10  shown closed with display portion  14  folded over the body portion  12 . A first photo emitter/photo detector set  30  is mounted on interior surface  12   a  of body portion  12  and a second photo emitter/photo detector set  32  is mounted on the exterior surface  14   b  of the display portion  14 . In the closed condition of  FIG. 3 , the second emitter/detector set  32  faces away from body portion  12 , while the first emitter/detector set  30  faces up from body portion  12  towards display portion  14 . Also, in the closed condition of  FIG. 3  the second set  32  is laterally offset, to the left in  FIG. 3 , relative to the first set  30 . When the handset  10  is deployed to the open condition of  FIG. 4  by rotation of the display portion  14  about a hinge  16  relative to the body portion  12 , the first and second photo emitter/detector sets  30 / 32  come into optical alignment with each other, such that the photo emitter of one set is optically aligned with the photo detector of the other set. By deploying the display portion  14  the second emitter/detector set  32  swings through an arc of about 180 degrees from an upwardly facing position in  FIG. 3  to a downwardly facing position in  FIG. 4 , and also moves from its initial, inoperative offset position to an operative position overlying the first emitter/detector set  30 . The optical links are established between the photo emitter/detector pairs without need for flexible optical cable. 
         [0029]    The arrangement of the photo emitter/detector sets  30 ,  32  in the aligned operative position may be better understood from  FIG. 2   a . The first emitter/detector pair  30  includes photo emitter  30   a  and photo detector  30   b . The second emitter/detector pair  32  includes photo emitter  32   a  and photo detector  32   b . Photo emitter  30   a  is electrically driven by a driver integrated circuit  36  installed in body portion  12  for converting electronic data signals provided by electronic circuits in the body portion into optical signals which are then emitted by photo emitter  30   a  towards photo detector  32   b  of the overlying second emitter/detector set  32 , as suggested by arrow A. Photo detector  32   b  receives the optical signals from photo emitter  30   a  and converts them into electrical signals which are processed by receiver integrated circuit  42  installed in display portion  14 . The processed signals can then be supplied to LCD display  20 . Digital data signals from camera  24  are supplied to transmitter driver integrated circuit  40  which drives photo emitter  32   a . Photo emitter  32   a  on the display portion  14  converts the electrical drive signals from driver IC  40  into light signals encoded with data from camera  24  and emits the optical light signal towards photo detector  30   b  on the body portion  12 , as suggested by arrow B, where the received optical signal is converted back to an electrical signal by receiver integrated circuit  38 , which processes the signals and supplies them to the appropriate circuits in the body portion  12 . 
         [0030]    The photo emitter  30   a  and photo detector  32   b  form one photo emitter/detector pair, providing data transmission from the body portion  12  to the display portion  14 . Photo emitter  32   a  and photo detector  30   b  form a second photo emitter/detector pair, providing data transmission from the display portion  14  to the body portion  12 . The optical links provided by each photo emitter/detector pair can support high speed data transmission at rates in excess above 1 gigabit/second using currently available optoelectronic components. The photo emitters  30   a ,  32   a  may be either LEDs (light emitting diodes) or laser diodes such as VCSELs (vertical cavity surface emitting laser). Laser diodes are useful for higher data transmission bandwidths above 500 Mbs. The emitter and detector in each pair may be spaced apart from each other by a free space or air gap, which in most mobile telephone handsets  10  will not exceed 1 centimeter. It may be preferable to mount the photo emitter/receiver pairs spaced apart from each other on the handset  10  to minimize possible optical and electrical cross coupling and interference. 
         [0031]    The photo emitter/detectors may be installed in window openings provided in the housings of the body portion  12  and display portion  14 , and covered with plastic or other material chosen to be transparent or translucent to the optical wavelengths emitted by the photo detectors  30   a ,  32   a . The windows may be simple flat glass or plastic, or may include a lens of glass or plastic for condensing the optical data signal between emitter and detector. 
         [0032]      FIG. 5  illustrates an alternate arrangement of the photo emitter detector sets  30 ,  32  where the photo emitter/detector pairs are aligned axially along hinge  16 . The hinge  16  has a center knuckle  16   b  attached to display portion  14  and contained between side knuckles  16   a ,  16   c  attached to body portion  12 . The axis of hinge  16  lies transversely to the knuckles as suggested by line  16   x . Opening and closing of the display portion  14  relative to body portion  12  causes center knuckle  16   b  to rotate relative to side knuckles  16   a,b  about the hinge axis  16   x . Photo emitter  30   a  and photo detector  30   b  are mounted on axially opposite sides of side knuckle  16   c . Photo detector  32   b  is shown mounted on center knuckle  16   b  facing towards and in optical alignment with photo emitter  30   a , while photo emitter  32   a  is supported by any suitable means adjacent to side knuckle  16   c  facing towards and in optical alignment with photo detector  30   b . In this arrangement the photo emitters and photo detectors  30   a,b  and  32   a,b  are in continuous optical alignment in both the open and closed conditions of the handset  10 . It is understood that the photo emitters and photo detectors  30   a,b  and  32   a,b  in  FIG. 5  are connected to corresponding driver integrated circuits in a manner analogous to that explained above with respect to  FIG. 2   a . The spacing between the photo emitter and photo detector of each aligned pair  30 ,  32  may be very small or negligible, or the photo emitter/detector pair may even be in contact with each other, but nonetheless data transmission takes place by direct illumination of the photo detector by the photo emitter without any intervening optical conduit such as optical fiber. 
         [0033]      FIGS. 6 and 7  illustrate a typical slide-to-open cellular telephone handset  50 , which has a body portion  52  and a display portion  54 . In a closed condition of the handset  50  shown in  FIG. 6  the display portion  54  directly overlies and largely covers the body portion  52 . The handset  50  is deployed for use by linearly sliding the display portion  54  relative to the body portion along mutually facing interior surfaces of the portions  52 ,  54  along arrow L in  FIG. 7 . The display portion  54  slides to an extended position to partially expose an interior surface  56  of the body portion  52  on which is installed a keypad  58 . Display portion carries an LCD screen  60 , a video or still digital camera  62  and additional control buttons  58   b.    
         [0034]    As shown in  FIG. 8 , in the slide-to-open handset  50 , two sets  62 ,  64  of photo emitters and photo detectors are provided on inside surface  56  of the body portion  52  and one photo emitter/photo detector set  66  is provided on an opposing inside surface of display portion  54 . The photo emitter/photo detector set  66  overlies set  62  in the closed position of handset  50  and overlies set  64  in the open condition of handset  50 , as illustrated in  FIG. 8 . Set  62  includes photo emitter  62   a  and photo detector  62   b . Set  64  includes photo emitter  64   a  and photo detector  64   b . Set  66  includes photo emitter  66   a  and photo detector  66   b . Corresponding driver integrated circuits  68  and receiver integrated circuits  70  are provided for each of the photo emitters and photo detectors, as explained previously in connection with  FIGS. 2   a  through  4 . In the closed condition of handset  50 , data is transmitted from the display portion  54  to body portion  52  by photo emitter/detector pair  62   a , 66   b , and from display portion  54  to body portion by emitter/detector pair  66   a ,  62   b . In the open condition of handset  50 , data is transmitted from the body portion  52  to display portion  54  by photo emitter/detector pair  64   a , 66   b  and from display portion  54  to body portion by emitter/detector pair  66   a ,  64   b.    
         [0035]    In the arrangements described above the different free space optical interconnections can be supplemented with conventional hard wired connections for those circuits which do not require high bandwidth data rates. In particular, battery power may be supplied from the body portion to the display portion of the handset by means of conductive wires. 
         [0036]    While particular embodiments of the invention have been described and illustrated for purposes of clarity and explanation, it will be understood that many changes, modifications and substitutions will be apparent to those having only ordinary skill in the art without thereby departing from the scope and spirit of the invention which is defined by the following claims.