Patent Publication Number: US-2005128735-A1

Title: Head-mounted instruments

Description:
FIELD OF THE INVENTION  
      This invention relates to head-mounted instruments and particularly, but not exclusively, to head-mounted indirect ophthalmoscopes.  
     BACKGROUND TO THE INVENTION  
      A conventional head-mounted indirect ophthalmoscope comprises a headband a front region of which carries an ophthalmoscope unit and the rear of which has an adjustment knob for adjusting the effective size of the headband (e.g. by altering the tension in the headband) to suit the size of the wearer&#39;s head. The ophthalmoscope unit has a light source powered by a separate battery pack which can be mounted on the user&#39;s belt or a wall, or is alternatively powered by a wall-mounted mains electricity power supply. The ophthalmoscope unit also has image-receiving optics by which the user (e.g. doctor or optician) of the ophthalmoscope views a stereoscopic image of a patient&#39;s retina illuminated by the light from the light source.  
      In one known head-mounted indirect ophthalmoscope, the adjustment knob for adjusting the tension applied to the headband also serves to accommodate a battery pack, an arrangement which is cumbersome particularly since an electrical wire extends between the battery pack and the light source and this wire becomes twisted as the knob is rotated and can be placed under tension at the extremes of rotary movement of the knob. The invention was devised to provide a head-mounted indirect ophthalmoscope with an improved arrangement of electrical power supply to the light source of the ophthalmoscope unit.  
     SUMMARY OF THE INVENTION  
      According to the invention a head-mounted instrument comprises an electrically powered instrument unit, a headband for carrying the instrument unit at or adjacent the front of the wearer&#39;s head, the headband carrying adjustment means having a manually adjustable member for manually adjusting the effective size of the headband to suit the size of the wearer&#39;s head, the adjustment member being located at the rear of the user&#39;s head when the headband is worn, electric battery means for powering the instrument unit, the battery means being located or locatable on the headband such that the weight of the battery means is centred substantially at the centre of the rear of the user&#39;s head when the headband is worn, the battery means being supported or supportable on the headband other than through the intermediary of the adjustment member.  
      Supporting the battery means on the headband independently of the adjustment member has the advantage over the known instrument that the adjustment member is not encumbered by the battery means so movement of the adjustment member is not impeded by the weight or inertia of the battery means or by the need to maintain an electrical connection between the adjustment member and the instrument unit throughout the range of movement of the adjustment member. Moreover, where the battery means is detachable (or includes a detachable battery pack) for recharging, the separate functionality of the battery means and the adjustment member simplifies the detachable mounting of the battery means on the headband.  
      The adjustment member may be in the form of a manually rotatable knob projecting centrally from the rear of the headband, rotation of the knob altering the effective size of the headband, e.g. by altering the tension in the headband. The central positioning of the adjustment member enables the instrument to be used by a right or left-handed person.  
      A front surface of the battery means may be concave, to fit snugly against the back of a wearer&#39;s head.  
      The battery means may comprise a battery pack which is removable from the headband for recharging of the battery pack, and the battery pack may have two cell compartments disposed on respective sides of a central slot which accommodates the adjustment means. Instead of a single battery pack with a central slot, there may be two battery packs located or locatable on the headband on either side of the adjustment means, providing a symmetrical arrangement.  
      The battery means may further comprise a base unit onto which the battery pack can be removably fitted and which is permanently or semi-permanently attached to the headband, the base unit being electrically wired to the instrument unit. The base unit may have electrical contacts co-operating with contacts on the battery pack.  
      The battery pack is preferably chargeable either when mounted on the headband or when removed from the headband.  
      In order to charge the battery pack, the instrument may be complemented by an electrical charger capable of charging the battery pack when mounted on the headband as well as a spare battery pack, and the charger is preferably capable of undertaking these two charging functions simultaneously.  
      In the preferred embodiment the instrument unit is an ophthalmoscope unit and the instrument is an indirect ophthalmoscope. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A head-mounted indirect ophthalmoscope according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
       FIG. 1  is a perspective view of the ophthalmoscope;  
       FIG. 2  is a perspective view of the ophthalmoscope of  FIG. 1  with a battery pack removed;  
       FIG. 3  is a perspective view of the separated battery pack;  
       FIG. 4  is a perspective view of a charger for the ophthalmoscope; and  
       FIG. 5  is a perspective view of the ophthalmoscope of  FIG. 1  mounted in the charger of  FIG. 4 , without a spare battery pack. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 1 , the ophthalmoscope has a headband  1  the front region of which carries an ophthalmoscope unit  3  having a light source and optics for viewing an image of a patient&#39;s retina illuminated by the light source, the intensity of which is controllable by a control  2 . The tension in the headband  1  is adjusted by adjustment means including a rotatably adjustable knob  4  which projects centrally from the ophthalmoscope at the rear thereof. An upper loop  5  extends from one side of the headband to the other and, in use, extends over the top of the wearer&#39;s head. An adjusting knob  5   a  controls the effective length of the loop  5 .  
      To the rear of the headband is permanently attached a battery base unit  6  having slots  7  through which lengths of the headband  1  extend. Between the slots  7  the front surface  8  of the base unit  6  is concave, to fit snugly against the back of the wearer&#39;s head. An electrical wire  9  passes from the base unit  6  to the light control  2  and a line  9   a  continues to the ophthalmoscope unit  3 . The base unit  6  has an indicator light  10  displaying the extent of battery charge. A battery pack  11  is detachably fitted to the base unit  6 .  
      As best seen in  FIG. 2 , a central region of the base unit  6  has a battery pack release clip  12  adjacent a rearwardly projecting wall  13  which surrounds a drive shaft (not shown) for the adjustment knob  4 . The rear convex surface  14  of the base unit  6  has two spaced locating ramps  15  positioned just inwardly of two electrical contacts  16 .  
      It can be seen from  FIG. 3  that the battery pack  11  has two cell compartments  17  interconnected by a saddle  18  beneath which is a slot  19 . The front surface  20  of the battery pack  11  is concave and complements the convex rear surface  14  of the base unit  6 , and this concave surface  20  has two tapering recesses  22  adjacent two electrical contacts  23 . When the battery pack  11  is fitted to the base unit  6  the tapering ramps  15  slide into the tapering recesses  22  and the slot  19  accommodates the wall  13 . In its fitted position, the two contacts  16  respectively engage the two contacts  23  and the clip  12  engages a formation on the battery pack  11 . The symmetrical shape of the battery pack  11  ensures that its centre of gravity is disposed centrally at the rear of the wearer&#39;s head. The battery pack  11  can be removed from the base unit  6  by releasing the clip  12  and sliding the battery pack  11  away from the base unit, the centre of gravity of which is also disposed centrally at the rear of the wearer&#39;s head.  
       FIG. 4  shows a charger  25  for charging the battery pack  11 . The charger has an outer casing one side of which has a socket  26  to receive power at 12 volts a power supply unit. An upper part of the charger  25  has a slot  27  shaped to receive the battery pack  11  which is shown in position in the slot  27  in  FIG. 4 . It will be appreciated that the battery pack  11  illustrated in  FIG. 4  may be a spare battery pack, allowing one pack to be charged whilst another is in use on the ophthalmoscope. At the sides of the upper slot  27  the charger  25  has electrical contacts  28  ( FIG. 5 ) which engage the contacts  23  on the battery pack  11  when the latter is inserted in the slot  27 .  
      The lower portion of the charger  25  has a larger slot  29  with two ledges each provided with an electrical contact  30  ( FIG. 4 ). This larger slot  29  accommodates a base unit  6  with a battery pack  11  attached, enabling a battery pack  11  to be charged whilst still attached to the base unit ( FIG. 5 ). To achieve this the base unit  6  has two forwardly facing electrical contacts  32  one of which is visible in  FIG. 1 . These contacts  32  engage the pair of contacts  30  in the charger  25  when the charger is charging the battery pack  11  mounted in the ophthalmoscope. The charger  25  can simultaneously charge a spare battery pack  11  ( FIG. 4 ) and a battery pack  11  mounted in the ophthalmoscope, as shown in  FIG. 5 .  
      It will be appreciated that many variations may be made to the features of the described instrument without departing from the scope of the invention as defined in the claims. Furthermore, the battery means of claim  1  can be any arrangement of at least one battery supportable on the headband in the way required by claim  1  and able to power the instrument. Thus, for example, the battery means may comprise a single battery or a plurality of batteries. If the battery means comprises a plurality of batteries these may be contained in, or held together to form, one or more battery packs or may be directly attachable to the headband individually.