Studies on vision often involve
creating virtual stimuli. Images are displayed to viewers through
computer screens, rather than having the viewer encounter physical
objects. Using virtual stimuli (those created on a computer)
rather than physical objects greatly facilitates experimentation,
because an infinite number of stimuli can be created to very precise
specifications. Research on haptics (touch) suffers from the
inability to create virtual objects. Usually, stimuli for haptics
experiments are physical objects, which cannot span an infinite set and
are limited by manufacturing capabilities.
The PHANToM allows the creation of
virtual haptic and visual stimuli. The device has two arms; at
the end of each is a thimble. A participant places two of his
fingers, usually the thumb and index fingers of the right hand, into
the thimbles. The PHANToM now knows where those fingers are and
can exert force on the fingers. Most importantly, the PHANToM can
be programmed to exert force on the fingers contingent on where the
fingers are in space. For example, the PHANToM could be asked to
create a virtual sphere. It displays an image via a mirror of the
sphere, seen in 3D with shutter glasses. The PHANToM also no
longer allows the fingers to move into the space of the sphere.
The experience for the user is that he can both see and feel the
virtual sphere.
The PHANToM can be programmed in C/C++ to display visual and haptic stimuli with a wide variety of characteristics. Any visual stimulus creatable on another computer is creatable on the PHANToM. The haptic stimuli are constrained by the mechanics of the device, but can take on a wide range of shapes, sizes, and compliances. The visual and haptic stimuli do not have to agree, which has most notably been used in this lab for research on visual-haptic cue combination.
Our PHANToM is the 1.5 high force
premium PHANToM device made by SensAble Technologies. The PHANToM
arms are mounted below a mirror, on which the reflection from a CRT
monitor can be seen by the viewer.
