FIELD OF INVENTION 
   The present invention relates to a user interface for a computing device, and is particularly relevant to wearable computing devices. 
   PRIOR ART 
   The most conventional user interface for a computing device is a combination of a keyboard and a pointing device, such as a mouse. This is an extremely appropriate combination for use on a desktop, either for a desktop personal computer or for a notebook computer used on a desktop. For other types of device, other user interfaces are more attractive. For a personal digital assistant (PDA), keyboards are used but a pen-based interface with handwriting recognition is a popular alternative. Speech recognition is a further alternative user interface. However, in other user contexts, none of these conventional user interfaces are wholly satisfactory. One such environment is wearable computing, particularly where it is desired that the computing device is unobtrusive and does not inhibit normal user interaction. Another such environment is while the user is performing a complex task requiring use of his or her hands and perhaps also voice, and is using the computing device for reference or technical support (for example, in aircraft maintenance). It is desirable to provide user interfaces for computing devices which are advantageous over the conventional alternatives for non-standard user environments. 
   SUMMARY OF INVENTION 
   Accordingly, the invention provides wearable computing apparatus, comprising: a processor; a device for presenting information from the processor to a user; and a device for providing user input to the processor in response to the information presented to the user, wherein the device is adapted to be activated wholly or partly by a foot of the user. 
   It is known to provide foot controls for desktop computers—either by adaptation of a conventional mouse (as described in U.S. Pat. No. 5,886,685), or by provision of a mouse adapted to be moved by the foot and wired to the desktop computer (the “NoHands Mouse” produced by Hunter Digital of 11999 San Vicente Blvd., Suite 440, Los Angeles, Calif. 90049). Use of foot pedals is also well known in the context of conventional word processing (often to start or stop dictation machines). However, none of the prior art solutions is adapted to a wearable computer, as opposed to a desktop computer provided with a fixed arrangement of peripherals. 
   Preferably, the user input device is adapted to select an item from a displayed list, or a point or an area from a displayed area, or an item from an audible list. 
   It is particularly preferred for the user input device to comprise a foot mounted position sensor, whereby translation of the position sensor with respect to a reference unit (which may be worn by the user—for example, on a user&#39;s belt) is measured as relative motion by the processor. This can be translated into relative motion across a display (either in one or two dimensions—optionally, only an appropriate dimension of the position sensor translation is measured). Selection may be achieved by translation in another dimension (eg vertically) or by another means. Preferably, the position sensor is also an orientation sensor, in which case selection or any other predetermined action (button press) can be carried out by rotation of the foot control unit beyond a threshold value. 
   In a further aspect, the invention provides computing apparatus, comprising: a processor; a display for presenting information from the processor to a user; and a user input device comprising a foot mounted position and orientation sensor, wherein translation of the foot mounted position sensor causes translation of a selection device across the display and rotation of the foot mounted position sensor causes a predetermined operation to be carried out by the processor in respect of information indicated by the selection device. 


   
     DESCRIPTION OF DRAWINGS 
       FIG. 1  shows a schematic representation of a user wearing a computing apparatus in accordance with embodiments of the present invention; 
       FIG. 2  shows a schematic diagram of the main functional elements of the computing apparatus of  FIG. 1 ; 
       FIG. 3  indicates the methods of communication between a processor unit and a foot control unit for the computing device of  FIG. 1 ; 
       FIG. 4  indicates use of a foot control unit according to an embodiment of the invention to select from a one-dimensional list; 
       FIGS. 5A and 5B  indicates use of a foot control unit according to an embodiment of the invention to position a pointer within an area and select an item at the pointer position; and 
       FIG. 6  indicates a foot control unit according to a further embodiment of the invention. 
   


   DESCRIPTION OF PREFERRED EMBODIMENTS 
   Specific embodiments of the present invention will now be described by way of example. 
     FIG. 1  shows a stylised representation of a user wearing a wearable computing apparatus according to an embodiment of the invention, and  FIG. 2  shows the main functional elements of this apparatus. The processor  20  is contained within a processor unit  10 , in this case worn on the body of the user (for example, mounted on a belt). Also contained in the processor unit  10  are a memory  21  and a communications control unit  22 . Also contained within the processor unit  10 , but not shown, will be such circuitry as is necessary to control or interact with the other system elements (such circuitry may include, for example, a video driver for a display)—the skilled person will readily appreciate what circuitry would be necessary for each such system element. 
   The wearable computing apparatus also comprises two separate devices for presenting information to a user. One of these elements is eyeglass display unit  11 , comprising a communications unit  23  and a microdisplay  24 . A variety of types of microdisplays are known—generally these occupy only a small part of the user&#39;s visual field, but by means of appropriate optical elements provide displayed information which appears to be of larger size but further away from the user. Appropriate microdisplays are known, and are commercially available from, for example: Colorado Microdisplay Inc. of 2477 55 th  Street, Boulder, Colo., 80301 USA; Displaytech, Inc. of 2602 Clover Basin Drive, Longmont, Colo. 80503-7603 USA; Displaywear Inc. of 831A Bransten Road, San Carlos, Calif. 94070 USA; and Tekgear Inc. of 1-90 Market Avenue, Winnipeg, Manitoba R3B 0PS Canada. The other information presenting element is an earpiece unit  12  containing a communications unit  23  and a speaker unit  25 . Information can be provided to the user through the speaker unit  25  in the form of simulated speech created by appropriate software routines. Such speech synthesizers are known, examples including the following: Bell Labs Text to Speech Synthesis, provided by Lucent Technologies; and the Festival Speech Synthesis System of the University of Edinburgh. Speech synthesis would most logically be carried out at the main processor  20 , but with digital to analogue conversion at the speaker unit  25 . It will be understood that the eyeglass display unit  11  and the earpiece unit  12  will contain other components necessary to the normal function of such units: for example, the eyeglass display unit will typically contain a power source and a processor and may contain a video controller (if this is not present in the processor unit  12 ) and the earpiece unit  12  will typically contain a power source, a processor and a digital to analogue converter. 
   Different forms of communications units  22 , 23  can be employed in accordance with conventional or other approaches for connecting peripheral units with a main processor. A particularly appropriate approach for wearable computing apparatus is to use a short range wireless networking protocol such as Bluetooth (the Bluetooth specification is determined by the Bluetooth Special Interest Group). In this case, communications control unit  22  may be a Bluetooth master unit and communications units  23  may be Bluetooth slave units. 
   Foot control unit  13  and its interaction with the main processor  20  will now be described with reference to  FIGS. 2 and 3 . In a preferred embodiment, the foot control unit is an electromagnetic position sensor, such as those produced by Ascension Technology Corporation of PO Box 527, Burlington, Vt. 05402 USA (products such as Flock of Birds and Motion Star). Such products are typically used for motion tracking (for example, in recording movement of actors for subsequent animation). Sensor systems such as Flock of Birds operate by measuring position and orientation of one or more receiving antenna sensors with respect to a transmitting antenna, normally fixed in space. The transmitting antenna is driven by a pulsed DC signal. The receiving antenna measures the transmitted magnetic field pulse and the earth&#39;s magnetic field, with a microprocessor controlling transmitting and receiving elements and converting received signals into position and orientation inputs. An example of such a system is described in U.S. Pat. No. 4,945,305, which teaches a sensor adapted to return a position and orientation relative to a transmitter position. Numerous further such sensors, operating according to similar or different signalling regimes (such as AC electromagnetic and optical regimes) are available and could be employed for the present purpose by the person skilled in the art. The skilled person will appreciate from the above references how to acquire or construct such a sensor. Alternative forms of sensor (for example, an optical sensor adapted to determine navigation across an arbitrary surface by recognition of variation in the surface, as discussed in the applicants&#39; U.S. Pat. No. 5,578,813) can be employed in other embodiments of the invention—some such alternative embodiments are described further below. 
   When such DC-pulsed electromagnetic sensors are used for motion tracking, it is normal to fix the transmitting antenna in space. For embodiments of the present invention, there is no reason to do this as only relative motion is required (as is the case for a conventional tracking device such as a mouse) and it is effective to mount the transmitter unit  26  with the main processor  20 . A suitable alternative would be to mount the transmitter unit  26  on the user&#39;s other foot—in that way, motion would be completely under the user&#39;s control, and the proximity of transmitter unit  26  and receiving unit  27  could allow use of lower power signals, reducing power demand on the computing apparatus as a whole. A transmitting antenna of transmitter unit  26  provides a signal received by receiving antenna of receiving unit  27  of foot control unit  13 . A processor  28  of the foot control unit calculates the relative position and orientation of the receiving unit  27  relative to the transmitter unit  26  (or alternatively, simply collects data from the receiving unit  27  for subsequent calculation by the main processor  20 ) after compensation for the earth&#39;s magnetic field and returns relevant data to the main processor through communications unit  23 . The main processor  20  is therefore able to calculate change in relative position and orientation of the receiving unit  27  relative to the transmitter unit  26  over time, as a stream of signals from the transmitter unit  26  leads to receipt of a stream of position and orientation signals from the receiving unit. 
   While  FIG. 3  shows operation of such a foot control unit  13  with the user in a sitting position, there is no constraint on the user to adopt any particular position—a foot control unit  13  of this type could equally well be used with the user in a standing position. While it will generally be more convenient for the user to be able to place one or both feet on the ground when using such a foot control unit  13 , even this is not essential. 
   Relative motion determined from position signals can be used as a method of obtaining user input in essentially the same manner as for translational motion of a conventional mouse. For selection from a one-dimensional list (as may be required in a visual interface or an audible interface), only one dimension of position need be used to indicate the item to be selected—for example, foot motion left or right in a horizontal plane (x-axis), but not vertical motion (z-axis) or motion up and down (y-axis) in the horizontal plane (see  FIG. 4  for the case of a visual display—for an audible interface translational movement can cycle through a list of options in a similar manner). To select an item (rather than merely “point” to it) one of the other dimensions could be used—for example, a significant y-axis motion could indicate “selection” at that x-axis position. A further possibility is to use orientation information (as will be discussed below for two-dimensional selection) or to use a separate mechanism, such as a hand-activated button, for actual selection. 
   Two-dimensional selection can operate in very much the same manner as a conventional mouse (and would be the normal approach to use for a visual interface). In this case, motion of the foot anywhere in the horizontal plane would translate to motion in that plane in essentially the same manner as a conventional mouse. One possibility for selection may be to use the vertical dimension (lift the foot off the ground, or tap the toe or heel)—however, more positional accuracy may be provided by use of the orientation sensors, and detecting rotation of the foot (for example, an anticlockwise rotation of the foot by 30 degrees or more could indicate a right click and a similar clockwise rotation a left click for an equivalent mouse)—rotation about the toe is likely to lead to greater positional accuracy than rotation around the heel.  FIG. 5A  shows an example of translation of the user&#39;s foot to translate a pointing device and so indicate an item for selection, and  FIG. 5B  shows the act of selection by rotation of the user&#39;s foot. Further features of a conventional mouse in conventional operating systems, such as selecting an area, can be replicated in much the same way as for a conventional mouse by dragging the foot across the ground in a “left-clicked” or “right-clicked” foot position. A preferred use for movement in the z-direction is to allow repositioning of the foot without “dragging” the selection device (in the same manner as lifting and replacing a conventional mouse)—however, an issue associated with this is to ensure that the foot control unit “knows” when to restart translational motion of the pointing device. One approach would be disable translational motion of the pointing device when relative motion in the z-direction exceeds a predetermined value, and to re-enable the translational motion of the pointing device on a “click”—such as a rotation of the foot and hence the foot control unit above a threshold value. The user could then reposition his or her foot and rotate it to re-activate the tracking action—this allows the user to use the mouse in a preferred area of greatest sensitivity, or on a particularly suitable surface. 
   A foot control unit as described above can be used effectively in a range of otherwise difficult user contexts. If the computing apparatus is intended not to affect normal user movement and interaction, use of the foot (which plays no part in normal user interaction) can allow free use of normal person-to-person communication by means of voice, facial gesture or manual gesture. If the computing apparatus is to provide technical support for a user conducting an engineering task, use of the foot for user interface control allows the user full use of hands and senses where not occupied by the presentation of information to the user. 
   A “foot mouse” of the type described above operates according to relative motion between the foot control unit and a reference unit. The reference unit will be worn by the user for wearable computer apparatus, but may be retained on the desktop (as for a normal peripheral) or may be mounted within a notebook computer. A pointing and selecting device of this type may be advantageous not only for a wearable computing apparatus, but also for a conventional desktop computer. As a foot control unit of this type can be worn by, rather than simply operated by, a user&#39;s foot, there is greater potential for more rapid and natural use. 
   Embodiments of wearable computing apparatus in accordance with aspects of the invention can be achieved with alternative designs of “foot mouse”. Two such further embodiments, based on optical mouse technology and on accelerometer technology, are discussed below. 
   An embodiment using an optical mouse technology foot control unit is shown in  FIG. 6 , with reference also being made to  FIGS. 1 and 2 . The components of the wearable computer shown in  FIGS. 1 and 2  other than foot control unit  13  are essentially as described above, the one difference being that processor unit  10  does not serve as a reference for foot control unit  13 —signals received from the foot control unit are converted directly into display positions. 
     FIG. 6  shows the foot control unit itself mounted within a shoe  61 . A window  67  formed of synthetic diamond or similar robust and scratch-resistant material is provided in the shoe  61 . Behind the window is a sensor assembly  62 . 
   The sensor assembly  62  may comprise a sensor such as those available in the range of Optical Navigation products provided by Agilent Technologies, Inc—these products include complete sensor, lens and ASIC bundles suitable for integration into a foot control design of this type. The sensor comprises a light source  64  such as a laser or an LED, which illuminates the area of an underlying surface  66  through the window, the imaging element  65  of the sensor (for example, a 16×16 CMOS pixel grid) capturing the reflected image a large number of times per second and providing this to an integrated circuit  63 . The patterns provided by the texture of the surface  66  underneath the window can be sensed and their translation measured between images, this translation being converted into signals useful for translation of the cursor on the display. An exemplary sensor of this type optimised for cordless mouse applications is the ADNS-2030 of Agilent Technologies, Inc. 
   As before, a mechanism is required to provide a selection event at the foot control unit  13 . Simplest integration with existing optical mouse technology might be provided by use of an actual button press within the shoe (for example, activated by a user&#39;s toe). Alternatively, any of the mechanisms provided above for use with the relative position foot control unit could be used—particularly use of a second axis for selection from a one-dimensional list and foot rotation to indicate a left or right click. This could be done with appropriate programming either at the foot control unit  13  or at the processor unit  10  receiving the data stream from the foot control unit  13 . 
   An embodiment using an accelerometer foot control unit will now be described. The components of the wearable computer shown in  FIGS. 1 and 2  other than foot control unit  13  are again essentially as described above, the difference being as before that processor unit  10  does not serve as a reference for foot control unit  13 , with signals received from the foot control unit are converted directly into display positions. The sensor in the foot control unit is however not a relative position sensor but an accelerometer (use of accelerometers in computer mice is described in, for example, U.S. Pat. No. 4,787,051) or a gyroscopic sensor, such as that used in the Gyration Ultra Cordless Optical Mouse produced by Gyration, Inc. (for example, the Gyration MG1101), which allows motion of the foot control unit itself to be converted into a signal representative of the translation of the foot sensor itself. Such a foot control unit is closely analogous to the relative position sensor foot control unit described above—any of the mechanisms to provide a selection event suitable for use in the relative position sensor foot control unit are suitable for use with an accelerometer or gyroscopic foot control unit. 
   Where a foot control unit requires power, this could of course be provided by an appropriate battery. An alternative is for the foot control unit to be powered by the user, for example by a piezoelectric generator in the shoe (see N. S. Shenck, J. A. Paradiso, Energy scavenging with shoe-mounted piezoelectrics, IEEE Micro 21 (2001) 30-41). 
   Other foot control unit technologies could also be used. An XY stress detector mounted in a shoe could also be used to provide foot-controlled positional information. Microwave technology could be used instead of DC-pulsed electromagnetic sensor technology to achieve measurement of relative position. The skilled person will appreciate from the principles set out here which technologies will be appropriate to the intended purpose.
A wearable computing apparatus includes a processor; a device for presenting information from the processor to a user, and a device for providing user input to the processor in response to the information presented to the user. The device is adapted to be activated wholly or partly by a foot of the user.