Abstract:
A rotatable connector comprises a plurality of optically conductive light rings adapted to mount to a first rotatable component; a plurality of light emitters for illuminating said light rings; a plurality of light detectors adapted to mount on a second rotatable component for detecting illumination of the photoconductive rings on the first rotatable component over a predetermined range of rotation.

Description:
BACKGROUND  
       [0001]     The present invention relates generally to connectors for electronic devices, such as mobile telephones and personal digital assistants, and more particularly to a rotating optical connector.  
         [0002]     Mobile telephones and personal digital assistants with housing components that rotate about an axis are known. Electrical connections between components in the rotating housing sections are conventionally made by means of a cable or wire passing through the rotating connector. This means of connection limits the amount of rotation because the cable or wire twists when the housing sections are rotated. Consequently, most conventional rotating connector designs limit rotation to approximately 180°. Therefore, there is a need for new rotating connectors that permit a full 360° of rotation in either direction.  
       SUMMARY  
       [0003]     The present invention provides a rotating connector that rotates 360° in either direction. The rotating connector can be used to connect electrical circuits contained in rotating housing sections. The rotating connector includes first and second optical couplers. A first optical coupler includes a plurality of light rings that can be selectively illuminated by light emitters. The second optical coupler includes a plurality of light detectors for detecting the illumination of the light rings. The light rings are made of an optically-conductive polymer that propagates light throughout the entire ring when illuminated by the light emitter.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is a frontal view of a mobile telephone constructed in accordance with the present invention with the top section of the housing in a closed position.  
         [0005]      FIG. 2  is a frontal view of a mobile telephone constructed in accordance with the present invention with the top section of the housing in an open position.  
         [0006]      FIG. 3  is a functional block diagram illustrating the main components of the mobile communication device.  
         [0007]      FIG. 4  illustrates an exemplary rotating connector for electrically connecting the first and second housing sections.  
         [0008]      FIG. 5  is a plan view of an optical coupler used in the rotating connector for bidirectional communication.  
         [0009]      FIG. 6  is a section view of the rotating connector.  
         [0010]      FIG. 7  is a plan view of an optical coupler.  
         [0011]      FIG. 8  is a plan view showing an optical coupler used in the rotating connector for unidirectional communication.  
         [0012]      FIG. 9  is a section view of a second embodiment of the rotating connector.  
         [0013]      FIG. 10  is section view of a third embodiment of the rotating connector.  
         [0014]      FIG. 11  illustrates an exemplary method of transmitting power through a rotating connector. 
     
    
     DETAILED DESCRIPTION  
       [0015]     Referring now to the drawings, an exemplary portable electronic device according to the present invention is shown. More particularly,  FIGS. 1 and 2  illustrate a mobile communication device, indicated generally by the numeral  100 , constructed in accordance with the present invention. Those skilled in the art will appreciate, however, that the present invention is in no way restricted to mobile communication devices and has general application in a wide range of portable electronic devices, including personal digital assistants, video and/or audio players, digital cameras, and video cameras.  
         [0016]     The mobile communication device  100  includes first and second housing sections  102  and  104 , respectively, which rotate relative to one another about a vertical axis. In a preferred embodiment, a full 360 degrees of rotation in either direction is permitted.  FIG. 1  shows the mobile telephone  100  when the first and second housing sections  102  and  104  are rotated to a closed position (0° rotation).  FIG. 2  shows the mobile communication device  100  when the housing sections  102  and  104  are rotated to an open position (180° rotation).  
         [0017]      FIG. 3  illustrates the functional elements of the mobile communication device  100 . A first circuit  110  is disposed in the first housing section  102 . A second circuit  130  is disposed in the second housing section  104 . Circuits  110  and  130  are operatively connected by means of a rotatable connector  200 . Circuit  110  may be powered by a battery. Circuit  130  may have a separate battery. Alternatively, power may be transferred between circuits  110  and  130 , as hereinafter described.  
         [0018]     Circuit  110  in housing section  102  includes a control circuit  112 , memory  114 , keypad  116 , transceiver  118 , audio circuit  120  and interface circuit  128 . The control circuit  112 , which may include a microprocessor controls the overall operation of the mobile communication device  100  according to program instructions stored in memory  114 . Memory  114  stores program instructions and data needed for operation. The keypad  116  is part of the user interface. In the exemplary embodiment, the keypad  116  is a standard phone keypad  116  that is actuated by the user to control the functions of the mobile communication device  100 . Keypad  116  is used when the housing section  104  is in the open position. Transceiver  118  enables communication with remote devices. Transceiver  118  may, for example, comprise a standard cellular transceiver and/or short-range wireless interface, such as a Bluetooth transceiver. Audio circuit  120  processes audio signals input via microphone  122  and output via speaker  124 . Microphone  122  converts acoustic signals to electrical audio signals. Speaker  124  converts electrical audio signals into acoustic signals. Interface circuit  128  interfaces circuit  110  with the rotating connector  200  to enable communication between circuits  110  and  130 .  
         [0019]     Circuit  130  in housing section  104  includes control circuit  132 , memory  134 , display  136 , joystick control  138 , one or more function keys  140 , and interface circuit  142 . Control circuit  132 , which may comprise a microprocessor, controls the display  136  and receives input from the joystick  138  and function keys  140 . Memory  134  stores program code and data used by the control circuit  132 . Interface circuit  142  interfaces circuit  130  with the rotating connector  200  to enable communication between circuits  110  and  130 .  
         [0020]     Display  136 , joystick  138 , and function keys  140  form part of the user interface. Display  136  displays information, such as menus, addresses, phone numbers, and other application data. Display  136  may comprise a liquid crystal display or touch screen display. The joystick control  138  and function keys  140  may be used to control the operation of the mobile communication device  100 . Joystick control  138  enables the user to navigate through menus presented on the display  136 , move a pointer on the display  136 , and to select menu items and other items presented on the display  136 . Function keys  140  may have functions assigned thereto that are activated or enabled by pressing a corresponding function key  140 . For example, in a default mode, the function keys  140  may be used to initiate and/or end a call. The particular functions assigned to function keys  140  may change depending on the operating mode.  
         [0021]      FIG. 4  illustrates one exemplary rotating connector  200 . Rotating connector  200  comprises first and second optical couplers  202 . In this particular embodiment, the optical couplers  202  are disposed in opposing face-to-face relationship and are centered on the axis of rotation of the housing sections  102  and  104 . The optical couplers  202  may be surrounded by a light shield  206 .  
         [0022]      FIGS. 5 and 6  illustrate an exemplary optical coupler  202  in more detail.  FIG. 5  shows the optical coupler  202  in plan view.  FIG. 6  shows a sectional view of the optical coupler  202 . The optical couplers  202  include a substrate  204  having a plurality of light channels  208  formed therein concentrically arranged about the axis of rotation. The substrate  204  is preferably electrically non-conductive. The bottom surface and side walls of the light channels  208  are coated with a reflective material. The light channels  208  are filled with an optically conductive polymer to form concentric light rings  210 . In the exemplary embodiment shown in  FIG. 5 , each light ring  210  has an associated light emitter  212  and light detector  214 . In the exemplary embodiment, the light emitters  212  and light detectors  214  are embedded in the light rings  210 , though embedding is not required. The electrical leads  216  for light emitters  212  and light detectors  214  pass through the substrate  204 . The light emitters  212 , such as light emitting diodes (LEDs), illuminate respective light rings  210 . An optical fiber may also be used as a light emitter  212 , where one end of the optical fiber is connected to an external light source, and the opposite end emits light into a respective light ring  210 . The light is conducted by the light ring  210  so that the entire light ring is illuminated. The light detectors  214 , such as photodiodes, in the opposing optical coupler  202  detect illumination of the light rings  210 . Alternatively, an optical fiber may be used to convey light to an external light detector  214 . Thus, digital signals can be optically transmitted between housing sections  102  and  104  by illuminating the light ring  210  in one optical coupler  202  in accordance with a digital sequence, and detecting the resulting illumination pattern with the light detectors  214  in the opposing optical coupler  202 .  
         [0023]     The optically conductive polymer propagates light around a light conducting ring  210  when the corresponding light emitter  212  is illuminated. Because the entire light ring  210  illuminates, the light detector  214  can detect the illumination at any angular position over a full 360 degrees of rotation. A prismatic film  215 , such as the Vikuiti Brightness Enhancing Films (BEF) manufactured by 3M, may be disposed over the light rings  210  to enhance the brightness of the light rings  210  when they are illuminated and to help distribute the light around the light ring  210 . The prismatic film  215  includes an array of prisms that concentrate light within a particular range of viewing angles. The prisms may extend concentrically around the light rings  210 . Alternatively, the prisms may extend radially. The prisms transmit light rays normal to the film  215 , but internally reflect oblique light rays. The oblique light rays are “recycled” by internally reflecting the light rays back towards the prismatic film  215  closer to normal so as to pass the light rays through the prismatic film  215 . The process of internal reflection and recycling concentrates light in a particular range of viewing angles. More than one layer of prismatic film  215  may be used with the prisms oriented in different directions.  
         [0024]      FIG. 7  illustrates the relative positions of the light emitters and detectors  212  and  214  when the optical couplers  202  are rotated 45 degrees relative to one another. The light emitters  212  and  214  for a first optical coupler  202  are shown in white. The light emitters  212  and light detectors  214  for the second optical coupler  202  are superimposed and shown in black. Due to the circular geometry of the optical couplers  202 , the light detectors  214  for the top optical conductors  202  remain aligned with the respective light rings  210  over 360 degrees of rotation. Thus, light detectors  214  are able to detect illumination of their corresponding light rings  210  at any angular position.  
         [0025]     Optical couplers  202  may be surface mounted on printed circuit boards containing circuits  110  and  130 , for example, using a ball grid array. Alternatively, the optical couplers  202  may be mounted to the housing sections  102  and  104  and connected to the printed circuit boards by means of a cable. Other mounting technologies may also be used.  
         [0026]     Because each light ring  210  corresponds to one communication channel, the optical couplers  202  are capable of half-duplex, bidirectional transmission of digital information between the housing sections  102  and  104 . Any given communication channel  208  can be used to transmit or receive at a given time. However, a single channel  208  cannot be used to transmit and receive simultaneously. In some embodiments, selected channels  208  may be used only for transmission, while other selected channels  208  may be used only for reception. The light rings  210  for the transmit-only channels  208  can omit the light detector  214 . Similarly, the receive-only channels  208  can omit the light rings  210  and emitters  212 .  
         [0027]     There may be some applications where bidirectional communication is not required.  FIG. 8  illustrates an exemplary embodiment for one-way communication. As shown in  FIG. 8 , the optical coupler  202  on the transmit side is simplified by eliminating the light detectors  214 . The optical coupler  202  for the transmit side includes the light rings  210  and light emitters  212  as previously described. On the receive side, the optical coupler  202  may comprises a light detector array  218  without light rings  210  or light emitters  212 .  
         [0028]     To avoid the necessity of a separate battery to power circuit  130 , one pair of light rings  210  may be replaced by a pair of electrically conductive rings to enable power transfer between circuits  110  and  130 . In this case, the electrically conductive ring pair may be electrically connected by brushes or roller contacts to maintain an electrical connection between the optical couplers  202  at all angles of rotation.  
         [0029]      FIG. 9  illustrates a second embodiment of the rotatable connector indicated generally the by numeral  300  that enables power to be transmitted. This embodiment is similar to the embodiment shown in  FIGS. 1-8 . Rotating connector  300  includes two optical couplers  302 . The optical couplers  302  each include a substrate  304  having a plurality of light channels  308  and light rings  310  as previously described. Each light ring  310  includes an associated light emitter  312  and light detector  314  with leads  316 . The optical couplers  302  can optically transmit and/or receive digital information as previously described.  
         [0030]     In the embodiment shown in  FIG. 9 , the polymer used to form the light rings  310  is not only optically conductive, but is also electrically conductive. An additional electrical lead  317  connects to the light rings. The light emitters  312  and light detectors  314  are electrically insulated from the light conducing rings  310 . A conductive sphere  320  is disposed between the light rings  310  to electrically connect the opposing light rings  310  in the optical couplers  302 . The facing surfaces of the light rings  310  may have a slightly concave shape to hold the conductive sphere  320  in place.  
         [0031]     In this embodiment, data can be transmitted electrically as well as optically. To transmit information, an electrical signal, e.g., voltage or current, is applied to the light ring  310  on the transmit side. The electrical signal is conducted from the light ring  310  on the transmit side, through the conductive sphere  320 , to the light ring  310  on the receive side. A Schmitt trigger may be used to detect the electrical signals on the receive side. Thus, each light ring  310  provides two communication channels: an optical channel and an electrical channel. In one exemplary embodiment, the optical channel may be used for high speed digital data. The electrical channel may be used to transfer power, ground or analog signals. Those skilled in the art will recognize that the electrical channel may also be used to transmit digital data.  
         [0032]      FIG. 10  illustrates another embodiment of the rotating connector indicated generally by the numeral  400 . In this embodiment, the rotating connector  400  includes two optical couplers  402 ; an inner coupler and an outer coupler. Each optical coupler  402  comprises a plurality of vertically-stacked light rings  410 . As in the first embodiment, each light conducting ring includes a light emitter  412  and a light detector  414  with leads  416 . The basic operation of the optical couplers  402  is the same as previously described. When a light-conducting ring  410  in one optical coupler  402  is illuminated, the light is detected by a corresponding light detector  414  in the opposing coupler  402 . As in the previous embodiment, this design allows light detection at any angular position over 360 degrees.  
         [0033]     In some applications, it may be desirable to know the angular position of the housing sections  102  and  104  relative to one another. For example, it may be desirable to know when the housing section  102  is in the closed position, open position, or some intermediate position. The following describes various ways to detect the degree of rotation in terms of the embodiment of  FIGS. 4-8 . However, it will be appreciated that these angle detection methods also apply to the other embodiments described herein.  
         [0034]     If the direction of rotation is not important, the degree of rotation from the closed position can be determined based on the output level of the light detector. The light transmitted around the light ring  210  will necessarily attenuate. The amount of attenuation is a function of the distance the light travels through the light ring  210 . Thus, the control circuits  112  and  132  may determine the amount of relative rotation by monitoring the output level of the light detector  214 . For example, based on the output level of the light detectors  214 , the control circuits  112  and/or  132  may be determine that the housing section  104  has been rotated 30° from the closed position. In this case, however, it is not known which direction the housing section  104  is rotated. If the direction of rotation is important, the light rings  210  may be manufactured with an optical gradient so that attenuation will vary depending on the direction of rotation.  
         [0035]     In another embodiment, one of the optical couplers  202  may include optical marks that can be detected by a separate optical detector that functions as a position sensor  126 . The optical marks may be applied to one of the light rings  210 . In this embodiment, the control circuit  112  can determine the angular position of the housing sections  102  and  104  by detecting and counting the optical marks when the housing sections  102  and  104  are rotated. Alternatively, position information may be encoded into the optical marks. For example, the optical marks could vary in width and or spacing so that the angular position can be determined from the pattern of the optical marks. As another example, unique optical marks similar to a bar code may be applied at fixed positions around the circumference of the optical coupler.  
         [0036]     If one of the light rings  210  is electrically conductive, the position sensor  126  may detect a change in an output voltage due to relative rotation of the housing sections  102  and  104 . An input voltage Vin may be applied at a fixed location on one light ring  210  and an output voltage Vout at a fixed locaton on the opposing light ring  210  may be measured. The light rings  210  act like a variable resistor so that the output voltage Vout will change responsive to relative rotation. If it is important to distinguish the direction of rotation, the light ring  210  may have a resistive gradient.  
         [0037]      FIG. 11  illustrates an alternate method of powering circuit  130  using a power supply in circuit  110  and connector  200 . If circuit  130  requires only a small amount of power, a high power LED  160  and photovoltaic cell  162  can be used to wirelessly transmit power from circuit  110  to circuit  130 . The light from the high power LED  160  may be transmitted through an optical fiber  164  passing through the center of the rotating connector  200  and directed onto the photovoltaic cell  152 , which converts the light energy to electrical energy to power circuit  130 .  
         [0038]     The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.