We propose and demonstrate a retractable 3d tracking device that can be attached to any surface (desk, clothing, or another wearable electronic device) for use as an input interface providing haptic feedback. The system is based on “optical hair module” idea proposed earlier in our research (see smart laser scanner) but instead of a laser, it relies on a physical link between a reference base and a graspable extremity, and thus is capable of haptic feedback. A two axis potentiometer forms the base and records azimuth and elevation of the retractable cord (we also tried with two-axis isometric force sensor), while a rotary encoder embedded on the mobile part continuously measures elongation, thus achieving precise 3D measurements in real time. We investigated pointing accuracy and pointing speed by fitting the parameters of Fitt’s law and steering law [], and compared the device performances with that of more traditional interfaces such as the mouse and trackpad. An interesting feature of this system for controlling a 2d cursor is the ability to swiftly (and smoothly) trade cursor speed for accuracy by simply modifying the length of the retractable cord. The system was also tried on a base-less configuration, where each extremity is hold in a different hand, thus providing fast or slow cursor displacement depending on which hand is performing the gesture.
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A rotary encoder, a motor vibrator, push buttons and a multi-colored LED was embedded on the case containing the retractable keychain spring. (Presently, the retractable cord and the signal wires run separately, but we plan to use a conductor cable that would have this double function.) While 3D data recorded by this device can be used for gesture recognition or virtual object manipulation in a CAD environment as with the smart laser scanner, this research brings many interesting issues of its own. We also plan to put a speaker and a microphone in the case, so that the device could be coupled with a mobile phone – that would never leave the pocket! – and used alternatively as a microphone, speaker and annotation device.
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