Abstract:
A lightwaveguide panel to be used with a a mobile telephone (MT) or personal digital assistant (PDA), the pannel comprises a first portion for lighting an LCD and/or a keyboard, and a second integral portion, said second portion including a first inclined surface for directing light from a source of light onto a light-reflecting acoustically responsive membrane, and a second inclined surface for directing light from said membrane onto a photo-detector.

Description:
FIELD OF THE INVENTION 
   The present invention relates to optical microphones and, in particular, to a light waveguide panel used in communication and other devices having displays and key-boards, such as mobile telephones (MT&#39;s), personal digital assistants (PDAs), and the like. The invention also relates to an assembly incorporating an optical microphone in such a light waveguide panel. 
   BACKGROUND OF THE INVENTION 
   Known communication and other devices, such as MTs, PDAs, and the like, use visual displays to relay information and keyboard panels as input and operating means. In these devices, both the visual displays and the key-board panels function as light waveguides, which constitute a major feature of their operation and construction. The devices allow the use of surrounding light and/or light produced by internal light sources to illuminate their displays and keyboard panels, thus enabling the reading and writing of input/output information. 
   In addition, these devices are intended to be utilized with the input of audio information (speech), using ordinary microphones. 
   DISCLOSURE OF THE INVENTION 
   It is therefore a broad object of the present invention to provide an optical microphone built into displays or keyboard panels mobile telephones (MTs), personal digital assistants (PDAs), and similar devices. 
   The invention therefore provides a light waveguide panel to be used with a mobile telephone (MT) or a personal digital assistant (PDA), the panel comprising a first transparent portion configured to be interposed between a light source and an LCD or keyboard for lighting the LCD and/or keyboard, and a second integral transparent portion, the second portion including a first inclined surface oriented for directing light from a source of light onto a light-reflecting acoustically responsive membrane, and a second inclined surface oriented for directing light from the membrane onto a photodetector. 
   The invention further provides an assembly for a mobile telephone (MT) or a personal digital assistant (PDA) having an LCD board and/or keyboard; a first light source for said LCD board and/or keyboard, and an optical microphone including a second light source, a light-reflecting, acoustically responsive membrane and a photodetector, the assembly comprising a light waveguide panel having a first transparent portion interposed between said first light source and said LCD board and/or keyboard for lighting the LCD and/or keyboard; and a second, integral, transparent portion disposed between the second light source and the light-reflecting membrane; the second, integral portion including a first surface for directing light from the second light source to the light-reflecting membrane, and a second surface for directing light reflected from the membrane onto the photodetector. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in connection with certain preferred embodiments with reference to the followin illustrative figures so that it may be more fully understood. With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
     In the Drawings: 
       FIG. 1  is a cross-sectional view of a portion of a mobile telephone (MT) device with its housing removed, exposing a light waveguide panel in accordance with a first embodiment of the present invention; 
       FIG. 2  is a plan view of the embodiment of  FIG. 1   
       FIG. 3  is a plan view of a second embodiment of the invention, similar to the panel of  FIG. 1 , additionally furnished with pressure-equalizing holes, and 
       FIGS. 4  to  13  are cross-sectional and plan views of further embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates, in cross-section, a portion of an MT without its housing in accordance with the present invention. Shown are an at least partly transparent light waveguide panel  2 ; a liquid crystal display (LCD) having a glass board  4 ; keyboard  6 ; electronic board  8  bearing light sources  10 , e.g., LEDs; a photodetector  12  and a source of light  14 . On the upper surface of panel  2  is mounted an acoustically responsive membrane  16 , affixed between a disc-shaped spacer  18  and a disc  20 . Membrane  16  is mounted in alignment with the source of light  14  and photodetector  12 . 
   A portion  22  of light waveguide panel  2 , between membrane  16 , source of light  14  and photodetector  12 , is configured to include a pyramidal cutout  24  surrounded by an annular, inclined surface  26  comprising lenses  28 ,  30  located adjacent to the source of light  14  and phtodetector  12 , respectively. The pyramidal surface of cutout  24  is advantageously coated with an opaque material  32  or, alternatively an opaque partition (not shown) may be inserted into pyramidal cutout  24  so as to prevent light from passing into portion  22  between the light waveguide walls, allowing it to pass only through lenses  28 ,  30 . Pyramidal cutout  24  may advantageously form holes  34  in the light waveguide portion under membrane  16 , so as to form a vertical air passage between the space below the membrane  16  and the atmosphere, for obvious reasons. Instead of holes  34  made in panel  2 , one or more horizontally directed holes or channels  36  may be made in spacer  18  and/or in portion  22  of the waveguide panel, as shown in FIG.  3 . 
   Referring now to  FIG. 4 , there is illustrated a modification of the light waveguide panel of  FIG. 1 , in which the light waveguide portion  22  is made without lenses  28 ,  30 . Instead, the inclined surface  26  or surfaces  26 ,  26 ′ are configured with an inclination angle calculated to direct light beams from the source of light  14  onto membrane  16 , and the reflected beams onto photodetector  12 . 
     FIG. 5  illustrates a further embodiment similar to that of  FIG. 4 , however, having lenses  40 ,  42 , respectively, affixed onto, or made integrally with, the source of light  14  and photodetector  12 . 
   Referring to  FIGS. 6 and 7 , in this embodiment the source of light  14  and photodetector  12  are disposed in spaced-apart relationship. Light reflected from the membrane  16  impinges on incline  44 , which, contrary to the previous embodiments, faces a direction opposite portion  22  so as to reflect the light along axis A of the panel to meet an additional inclined surface  46  reflecting the light in the direction of lens  36  of photodetector  12 . This configuration is useful in cases where stray radio frequency interference exists. In such cases, photodetector  12  should be placed adjacent to electronic processing circuits, while the other parts of the microphone, e.g. the light source  14  and membrane  16 , are of necessity located father away in consideration of the user&#39;s mouth. In order to achieve improved reflection of light, a second, inclined surface  48  may be provided parallel to and in spaced-apart relationship from surface  46 , forming an air gap between the two inclined surfaces for improving light reflection. 
   A yet further embodiment of the invention is illustrated in FIG.  8 . Accordingly, lenses  50 ,  52  are formed on one surface of the panel portion  22 , while the inclined surfaces  54 ,  56  are formed on its opposite surface. An opaque partition  58  is placed between the light source  14 , photodetector  12 , the two lenses  50 ,  52  and the two inclined surfaces  54 .  56 . 
     FIG. 9  depicts a modification of the embodiment of  FIG. 8 , in which, instead of partition  58 , a pyramidal cutout  24  is made between lenses  50 ,  52 , and the inclined surfaces  54 , 56  are much steeper. 
     FIGS. 10 and 11  illustrate a still further embodiment of the invention, in which the membrane  16  of the optical microphone is partly affixed on a section of the LCD display board  4 , and a half-disk-shaped insert  60  is placed on keyboard  6 . As is known, LCDs are usually made of glass, which is difficult and costly to work into a desired configuration. Thus insert  60  is mounted adjacent to the glass plate of the LCD display board  4 , and the membrane attached to spacer  18  is affixed on both the display board  4  and insert  60 , the edges of which abut each other along line  62  of  FIG. 11  Light directed onto and reflected from the membrane  16  passes through member  60  and the portion of display  4  located underneath the membrane. Obviously, the arrangement of  FIGS. 10 and 11  can be incorporated into anyone of the embodiments of the light waveguide panel shown in  FIGS. 3  to  9 . 
     FIG. 12  illustrates a further embodiment, similar to that of  FIGS. 10 and 11 , except for the construction of the microphone&#39;s membrane assembly. Here, the microphone membrane comprises glass display LCD board  4  coated with a light-reflecting substance, such as thin aluminium or gold layer  64  covering a portion  66  of the glass. 
   Naturally, the sensitivity of this type of membrane is relatively low, and such a construction requires the use of a high-power light source, such as that of a laser. 
   In the embodiment of  FIG. 13 , the spacer  18 , e.g., as shown in  FIG. 1 , is eliminated by the formation of a recess  68  in panel portion  22  below the membrane  16 , thereby effectively producing a raised annulus  70  acting as a spacer onto which membrane  16  is affixed. Obviously and conversely, the panel portion  22  may be formed with raised portions for mounting the membrane  16  is spaced relationship to the surface of the panel beneath it. 
   It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing discription, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.