A Graphic to Tactile Interface
The following is an excerpt from the final report of a
Eye Institute research grant, which investigated the use of the VideoTact
as a tactile interface to Microsoft Windows.
Health and Human Services grant: SBIR 5-R44-EY08166-04
Development period: 4/19/94-6/30/96
Grant Title: "Haptic Display of Computer Graphics
for the Blind"
All of the following primary goals of the project have been met:
To help resolve the significant difference between the Windows display
monitor and the electrotactile array resolution, a combined approach was
Development of a durable high density array, and lightweight, portable,
low power drive electronics.
Effectively interfacing to the Windows system, and translating the cursor
and windowing events into appropriate electrotactile stimuli.
Enabling blind test subjects to efficiently navigate the Windows environment.
Effective methods of:
Avoiding stimulus accommodation (the tendency of the skin to grow used
to a static display).
Avoiding masking effects by presenting qualitatively distinct stimuli ("tactile
Compensating for area/intensity summation (the perceived increase in stimulus
magnitude as the number of active tactors increases).
Gray scaling the stimulus so that the perceptual quality attributes do
not change with the change in perceived intensity.
Efficiently processing and displaying bitmap graphics (as well as dynamic
video information from a video camera - for future use as a mobility aid).
While we plan to continue to develop the system, we have identified several
areas where further research is needed:
Generally, a tactor pixel position is determined by ratiometrically mapping
its screen position (based on zoom level) to the array, but child windows
(buttons and other controls) dominate parent windows in overlap conditions,
or in cases of coincident mapping.
Due to the possibility of multiple windows and/or window types being mapped
to the same tactor, especially in the outermost zoom level, the cursor
dimensions and tactile color dynamically change depending on the type of
Windows object the cursor overlies; this helps to indicate what the underlying
object is, as well as providing a form of "kinesthetic" feedback for mouse
or digitizer motion. A beep is generated when the cursor type changes;
this draws the user's attention to the corresponding tactile event.
Appropriately displaying Windows events so that they are most discriminable;
while we have achieved this to a large extent, it is clear that this area
can be improved.
Determining a greater number of "tactile color" regions in the stimulus
space. Four such primary regions, each mutually distinct and gray scaleable,
have been discovered so far, but we believe that this number could be greatly
expanded. The tactile colors are used to help avoid masking effects when
presenting one tactile object in the context of another.
Reduction in the cost and complexity of the system. With the knowledge
of the required stimulus range that we have gained from the Phase II research,
we believe that with further development the system could be dramatically
simplified and made affordable.
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