1 Communication through head movements Juha Pieviläinen Alternative communication & access to information seminar 2003 Department of Computer Sciences University of Tampere

2 Software Content Tracking technologies Introduction Devices References Interaction style

3 Introduction ”Computer users who cannot use a conventional hand-operated computer mouse and/or keyboard, may use a head operated mouse or keyboard in order to control their computer and, by using an on-screen keyboard, to type information.” [5] A Head Operated Joystick – Experience with use, G. Evans and P. Blenkhorn, CSUN 99, available at

4 Introduction Navigating virtual environments and more often playing games require a way to control field of vision. Keyboards, mice and joysticks might do the job, but they really are NOT natural way to change ones field of vision, turning ones head is.

5 Tracking technologies mechanical magnetic sourceless, non-inertial optical acoustic (ultrasound) inertial

6 Technologies - mechanical DescriptionStrengthsWeaknesses Measure change in position by physically connecting the remote object to a point of reference with jointed linkages Accurate Low lag No line of sight or magnetic interference problems Good for tracking small volumes accurately Intuitive, due to tethering Subject to mechanical part wear-out [2] Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at

7 Technologies - magnetic DescriptionStrengthsWeaknesses Use sets of coils (in a transmitter) that are pulsed to produve magnetic fields. Magnetic sensors (in receiver) determine the strenght and angles of the fields. Pulsed magnetic field may be AC or DC Inexpencive Accurate No line of sight problems Good noise immunity Map whole body motion Large ranges – size of small room Ferromagnetic and/or metal conductive surfaces cause field distortion. Electromagnetic interference from radios. Accurace diminishes with distance High latencies due to filtering [2] Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at

8 Technologies – sourceless, non-inertial DescriptionStrengthsWeaknesses Use passive magnetic sensors, referenced to the earth’s magnetic field, to provide measurement of roll, pitch, and yaw, and as a derivative, angular acceleration and velocity Inexpensive Transmitter not necessary Portable Only 3 DOF Difficult to mark movement between magnetic hemispheres [2] Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at

9 Technologies - optical DescriptionStrengthsWeaknesses Use a variety of detectors, from ordinary video cameras to LEDs, to detect either ambient light or light emitted under control of the position tracker. Infrared light is often used to prevent interference with other activities High availability Can work over large area Fast No magnetic interference problems High accuracy Line of sight necessary Limited by intensity and coherence of light sources Weight Expensive [2] Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at

10 Technologies – acoustic (ultrasound) DescriptionStrengthsWeaknesses Use three microphones and three emitters to compute the distance between a source and receiver via triangulation. use ultrasonic frequencies (above 20 kHz) so that the emitters will not be heard Inexpensive No magnetic interference problems Lightweight Ultrasonic noise interference Low accuracy since speed of sound in air varies with environmental conditions Echoes cause reception of ”ghost” pulses Line of sight necessary [2] Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at

11 Technologies - intertial DescriptionStrengthsWeaknesses Use accelerometers and gyroscopes. Orientation of the object is computed by jointly intergrating the outputs of the rate gyros whose outputs are proportional to angular velocity about each axis. Changes in position can be computed by double intergrating the outputs of the accelerometers using their known orientation Unlimited range Fast No line of sight problems No magnetic interference problems Senses orientation directly Small size Low cost Only 3 DOF Drift No accurate for slow position changes [2] Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at

12 Technologies - Status MechanicalInertialAcoustic Military uses Situations when low cost system needed Poor static accuracy problems need to be solved Commercial products are available OpticalMagnetic Mature technology Military versions in-use Mature technology Military versions in-use Need accuracy improvement before implementation of HUD makes sense

13 Interaction style Absolute pointing vs. relative pointing similar to mousesimilar to joystick [5] A Head Operated Joystick – Experience with use, G. Evans and P. Blenkhorn, CSUN 99, available at require good head control skills less precise control needed

14 Devices – Tracker 2000 optical head tracker choice between mouse and joystick mode 8 directions different button types available, physical buttons, sip/puff straw or optical switch [1] 100 % Hands-free Computer Access – Madentec’s 2000 series, R. Marsden, P.Eng., Madentec Limited, available at

15 Devices – ADL-1 mechanical head tracker serial connection cost around 1200 $ [2] Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at

16 Devices – Smart-Nav optical head tracker replaces mouse price ranging between 129 to 299 $ [3] Eye Control Technologies, Inc. webpage at

17 Software – SymbolCreator at the moment on experimental status typing by selecting icons

18 Software – SoftType Text entry into all standard Windows applications Clicking done by dwell selection Different keyboard layouts available Word prediction [6] Origin Instruments Corporation webpage at

19 Software – SoftType [6] Origin Instruments Corporation webpage at A more simple layout for kids

20 Software – SoftType [6] Origin Instruments Corporation webpage at Qwerty Layout with integrated Dragger toolbar and Word Prediction.

21 References % Hands-free Computer Access – Madentec’s 2000 series, R. Marsden, P.Eng., Madentec Limited, available at 2.Review of Virtual Environment Interface Technology, C. Youngblut, R.E. Johnson, et al., Institute for Defence Analyses, available at ftp/publications/IDA-pdf/ 3.Eye Control Technologies, Inc. webpage at 4.Hands-free navigation in VR environments by teacking the head, S.B. Kang, CRL 97/1Technical Report Series, available at 5.A Head Operated Joystick – Experience with use, G. Evans and P. Blenkhorn, CSUN 99, available at 6.Origin Instruments Corporation webpage at

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