Abstract:
An electric device includes a housing having an indicator window and a visual indicator adapted to emit a visible light signal through the indicator window for indicating a status of the device. The device also has at least one of the following components, which are operative within a first spectral range of light substantially covering red or infrared light: an IR transmitter for transmitting infrared light, an IR receiver for receiving infrared light, an electronic component sensitive to infrared light, or an optical detector susceptible of infrared or red light. The visible light signal is provided within a second spectral range, which substantially covers blue light and is outside the first spectral range.

Description:
TECHNICAL FIELD 
   The present invention relates to an electric apparatus having a housing, an indicator window in the housing, and visual indicator means adapted to emit a visible light signal through the indicator window for indicating a status of the apparatus, wherein the apparatus furthermore has at least one of the following components, which are operative within a first range of light essentially covering red or infrared light: an IR transmitter for transmitting infrared light, an IR receiver for receiving infrared light, an electronic component sensitive to infrared light, or an optical detector susceptible of infrared or red light, 
   BACKGROUND ART 
   A mobile or cellular telephone is a well-known example of an apparatus according to the above. Within the context of this document reference will consistently be made to a mobile telephone for any commercially available mobile communications network, such as GSM. However, the invention is not limited to merely a mobile telephone; other equally applicable examples of electric apparatuses are radio pagers lap-top computers, organizers and communicators (also known as personal digital assistants), i.e. portable telephone devices including a computer and application programs, such as a built-in calendar, Moreover, the term “mobile communications network” is meant to have the widest possible meaning, thereby including all types of cellular networks, satellite networks, wireless local area networks (LANs), etc. 
   Mobile telephones are generally provided with a visual indicator for indicating status information about the connectivity of the mobile telephone with respect to the mobile communications network. Moreover, a battery charge indicator in often provided for alerting a user of the telephone, when the remaining battery charge drops below a predetermined limit. W098/56152 discloses a mobile telephone having such status indicators. 
   One common approach is to provide the mobile telephone with a combined green and red indicator window mounted at the top of the telephone housing. A dual-color light emitting device, such as a red light emitting diode (LED) combined with a green LED, is mounted to a printed circuit board within the telephone housing. An optical light guide is arranged between the external indicator window and the internal light emitting device. The dual-color light emitting device may for instance be used according to the following: 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               Green light flashing at low 
               The mobile telephone is in 
             
             
                 
               frequency 
               contact with at least one base 
             
             
                 
                 
               transceiver station (BTS) 
             
             
                 
               No green light 
               No contact with any BTS 
             
             
                 
               Green light flashing at a 
               A message is available (such as 
             
             
                 
               higher frequency 
               SMS) 
             
             
                 
               Red flashing light 
               Low battery charge level 
             
             
                 
               Red continuous light 
               The battery is being recharged 
             
             
                 
                 
             
           
        
       
     
   
   Consequently, a green visual indicator is used for informing the user of whether the mobile telephone is in operative contact with the mobile communications network (so that, inter alia, the user is free to initiate an outgoing telephone call), or whether the mobile telephone has currently lost its operative contact with the mobile communications network. 
   Many mobile telephones and other portable communication apparatuses are provided with at least one component, which either operates with, or is sensitive to, infrared (IR) or visible red light. For instance, the mobile telephone may be equipped with an IR port for performing information interchange with external devices. Another example is an optical detector, which is adapted to detect when the surrounding light is weaker than a predetermined limit, and in response turn on e.g. the display or the keyboard illumination, so as to give the user a better opportunity of operating the telephone also in situations of darkness. Such an optical detector may alternatively be used as a proximity switch for detecting whether the user or an external object is located in proximity with the mobile telephone. Yet another example is various unprotected integrated circuits (ICs) or other semiconductor components, which have no protective coating and which may be damaged if exposed to infrared light. 
   SUMMARY 
   According to the invention, the following problem is identified, and a solution thereof is provided, as defined by the enclosed independent patent claims. 
   Whenever a mobile telephone or other electric apparatus comprises at least one component, which according to the above operates with or is sensitive to infrared or visible red light, there is also a risk that the light produced by the visual indicator(s) will contain infrared or visible red wavelengths, particularly if the visual indicator is adapted to generate for instance a red visual indicator signal. In such a case, the infrared or visible red wavelengths may accidentally leak or propagate to the above components and consequently affect the operative realibility thereof in an undesired and uncontrollable way. 
   The above problem is solved through the inventive understanding that visual user feedback may be given by providing a visual indicator, that is adapted to produce a visible light signal in a spectral range, which is clearly separated (in terms of wavelengths) from visible red and infrared light. More specifically, the visible light signal is given a blue color. 
   Other objects, features and advantages of the present invention will appear from the following disclosure of the preferred embodiments, from the attached drawings as well as from the dependent claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described in more detail, reference being made to the accompanying drawings, in which: 
       FIG. 1  is a schematic front view of an electric apparatus according to the invention, exemplified as a mobile telephone, 
       FIG. 2  is a schematic, enlarged plan view of a portion of the telephone shown in  FIG. 1 , 
       FIG. 3  is a schematic block diagram, illustrating a mobile telephone, a mobile communications network and an external device, with which the mobile telephone communicates over first and second wireless links, and 
       FIG. 4  shows some examples of an electric apparatus. 
   

   DETAILED DESCRIPTION 
   In all the drawings, similar or identical reference numerals have a similar or identical meaning and are therefore only described in detail with reference to the first drawing, in which they appear. 
   Some examples of an electric apparatus are shown in  FIG. 4 , which include a mobile telephone  400 , a laptop computer  410 , a personal digital assistant or organizer  420 , and a radio pager  430 . In FIG.  1  and  FIG. 2 , the features of the invention are described in connection with a mobile telephone  1 ; however, it will be understood to one of ordinary skill in this art that the features described therein are intended to be employed in any electric apparatus, such as those illustrated in FIG.  4 . Referring to  FIG. 1 , the telephone has a housing  10 , an antenna  2  mounted on top of the housing, a speaker  4 , volume adjustment controls  5 , an LCD display  6  and a keybpad  7 . The keypad  7  has a plurality of individual keys, such a YES button  12  and a NO button  13 , arrow keys  14 ,  15 , a clear key  1 G, numeric keys  17 (labeled “0” through “9”), a star key  18  and a hash key  19 . A status indicator window  3  is provided at the top portion of the housing  10  and is adapted to emit a visible status indication signal  23 . An IR port  20  is provided at the upper right side portion of the telephone housing  10  and is adapted to perform wireless information interchange with accessories or other external devices over an IR link. An optical detector  29  is provided to the left of the upper front portion of the housing  10 . The optical detector  29  is arranged to act as a proximity detector for determining the presence of an external object or user by detecting reflected IR light. Additionally or alternatively, the optical detector  29  may be used for providing automatic illumination of certain parts of the telephone, such as the display  6  and/or the keypad  7 , in situations of poor light. 
   A rechargeable battery  28  is mounted at the rear of the telephone housing  10  and is therefore not visible in the front view of FIG.  1 . Consequently, the battery  28  has only been indicated by way of a dashed arrow. A foldable flip  8  is movably mounted to the apparatus housing  10  by means of a hinge mechanism  11 . The flip  8  comprises a sound opening  9 , through which vocal sound is received from the user of the telephone and forwarded to an internal microphone (not shown in the drawing). 
   Referring for a moment to  FIG. 3 , an exemplifying real-life use of the mobile telephone  1  is illustrated. The user of the mobile telephone  1  has a mobile communications subscription at a mobile communications network operator  120 . The network operator  120  disposes of various mobile communications network equipment, including a plurality of base transceiver stations (BTS)  121 ,  122 ,  123 , which are connected to the network operator  120  through respective links  131 ,  132 ,  133 . The mobile telephone  1  accesses the mobile communications network  100  over a radio link  134  to the nearest base transceiver station  123 . The mobile communications network provided by the network operator  120  is a conventional cellular mobile communications network, such as GSM, which in turn is part of an international mobile communications network  100 , to which the network operator  120  is connected through a link  111 . In GSM, the wireless link  134  operates on either 900 MHz or 1800 MHz. 
   Furthermore, the mobile telephone  1  may establish, through the IR port  20 , a supplementary short-range IR link  135  for information interchange with telephone accessories or any other piece of external equipment, such as a laptop computer  140 , which is provided with a corresponding IR port and is available in proximity with the mobile telephone  1 , for instance within a distance of 0.5 m. In the preferred embodiment, the supplementary short-range IR link  135  is a standardized, serial infrared communications link according to IrDA (the Infrared Data Association), having its headquarters in Walnut Creek, Calif. USA. 
   Referring back to  FIG. 2 , a schematic plan view is shown of an upper internal portion of the telephone  1  according to the preferred embodiment. The status indicator window  3 , the IR port  20  and the optical detector  29  are all schematically indicated by dashed symbols. The telephone  1  comprises a printed circuit board  21 , upon which various circuits and components are provided, as will be described below. 
   One of these components is a transceiver device (not shown), which according to the preferred embodiment is a conventional dual-channel homodyne transmitter/receiver for use in a TDMA (Time Division Multiple Access) mobile communications network, such as the GSM network  100  of FIG.  3 . As is readily realized by the skilled person, the transceiver device comprises various radio circuitry, such as bandpass filters, amplifiers, local oscillators, mixers, lowpass filters, AD converters, digital filters, etc. However, since the present invention is not directed at the radio parts of the apparatus, which are responsible for providing the communication link to the mobile communications network, the internal structure of the transceiver device is not described herein. 
   The printed circuit board  21  also contains a controller  50  (CPU, DSP, programmable logic array, etc), as well as associated memory circuits, etc (not shown). Moreover, the printed circuit board  21  has a light emitting device  22  mounted thereon at its uppermost end (facing the antenna  2 ). A light guide  26  is connected at a first end to the status indicator window  3  and at a second end to the light emitting device  22 . 
   The light emitting device  22  of the preferred embodiment comprises a blue light emitting diode (LED), which is driven by logic circuitry not shown in FIG.  2 . The light emitted from the blue diode  22  is guided through the light guide  26  to the status indicator window  3  for the purpose of providing status information to the user, as will be described below. In the preferred embodiment of  FIG. 2 , the light emitting device  22  is implemented by a blue-color LED, which is commercially available under the model name CL-270HE from Citizen, 1-23-1, Kami-kurechi, Fujiyoshidashi, Yamanashi-ken 403-0001, Japan. This LED has a peak wavelength at about 470 nm. However, other blue wavelengths are possible, such as 430 nm. Alternatively, the device  22  may be implemented by any other commercially available light emitting component. 
   The status indicator window  3  is made from a material, which is made transparent to blue light but is essentially opaque to light of longer wavelengths, such as green, rod and infrared light. The choice of material for the window  3  is left to the skilled person, which is believed to be able to select a suitable material, for instance a plastics material, from the wide range of commercially available materials with spectral filtering characteristics. 
   As shown in  FIG. 2 , the printed circuit board  21  further comprises an IR transmitter/receiver  30 , which is mounted next to the IR port  20  and is arranged to provide aforesaid supplementary short-range IR link  135  to external devices. Assuming for a moment that the light emitting diode  22  was not adapted to produce blue light but light of longer wavelengths, such as green or red light, then there would be an apparent risk of leakage or propagation of spurious light from the light emitting diode  22  to the IR transmitter/receiver  30 , as indicated by an arrow  35  in FIG.  2 . Moreover, the infrared light emitted from the IR transmitter/receiver  30  could have propagated undesiredly through the status indicator window  3  (see arrow  36 ), had the window not been given a function for preventing other light than blue from escaping therethrough, as described above. 
   Similarily, if green or red light was emitted by the light emitting device  22  through the window  3 , as indicated by an arrow  33   a , such light could have propagated, through reflections at an external object  60 , back to the IR port  20 , as indicated by an arrow  33   b , thereby causing undesired interference with the IR transmitter/receiver  30 . Moreover, such green or red light could leak from the light emitting device  22  to an unprotected integrated circuit  40  and cause damage thereof, as indicated by an arrow  34 . Additionally, this light could continue to the optical detector  29  and cause undesired interference. 
   Remembering now that the light emitted from the light emitting device  22  and through the status indicator window  3  is indeed blue and is kept within a spectral range (involving wavelengths such as 430 nm or 470 nm), which is clearly separated from the spectral range of visible red ligth (starting at 750 nm) or infrared light (between about 750 nm and 1 mm), it is clear that the present invention will effectively prevent such undesired interference. 
   The blue light signal  23  emitted by the light emitting device  22  may be used in many different ways for providing useful status indication to the user of the mobile telephone  1 . For instance, the controller  50 , or any other logic device of the telephone  1 , may give the blue light signal  23  a flashing intensity for indicating that the mobile telephone  1  is in operative contact either with the mobile communications network  100  (over the radio link  134 ) or the external device  140  (over the supplementary short-range IR link  135 ). Moreover, the blue light signal  23  may be given a more rapidly flashing intensity, so as to indicate the availability of a message directed to the user and kept at the network operator  120 . Other frequencies of flashing intensity may be used for indicating e.g. a low remaining charge of the battery  28 , or that the battery  28  is currently being recharged. Additionally, the blue light signal  23  may be given a continuous intensity to indicate, for instance, that information is currently being exchanged over the radio link  134  or, alternatively, the IR link  135 . 
   The present invention has been described above with reference to a few embodiments. However, other embodiments than the ones explicitly described are equally possible within the scope of the invention, as defined by the appended independent patent claims. In particular, the invention is applicable to other electric devices than mobile telephones, such as lap-top computers, radio pagers, communicators (personal digital assistants) or organizers.