The AR Workbench: A Complete Co-located Reach-in Mirror-Based ...

7 Evaluation & Results
Marlon Richert, Master’s Thesis, Friday, 23 February, 2007
The final prototype of the workbench turned out reasonably well. It is now safe to
use, as it no longer has any glass parts, with a plastic sheet replacing the glass
mirror. During the middle of the day, with closed Venetian blinds, both real and
virtual objects are clearly visible with approximately equal brightness through the
glossy, shaded piece of plastic that serves as the mirror. The executions of the
wooden workbench and the special projection screen have a slight mismatch in
dimensions, however, with the screen being slightly wider than the workbench
allows for, leading to an unsuitably tight fit. Future versions of the workbench should
allow for a bit larger margin of error in production size. Additionally, due to a
miscommunication that led the carpenter to believe that the projection screen was
actually another mirror, he left out the support beams for it. In that light, it is
actually a boon of sorts that the workbench frame fits so tightly around the
projection screen frame or otherwise the projection screen would not even stay up
there at all. If you look closely, you can barely see this in Figure 23.
Figure 23 Backside of the workbench, showing the projection screen at the
top and the video projectors at the bottom. On the left side of the picture, you
can just make out the Polhemus ISOTRAK II.
Unfortunately, the current hardware setup has some shortcomings with respect to
some its envisioned usages, a result of some of the constraints that the
nonfunctional requirements impose on it. First, if we want to use the system to
stimulate the production of motor imagery in treating hemiplegia, having only one
receiver to track the motions of the arm is simply not enough. As mentioned in
chapter 1, the more spatially correct the observed movements, the stronger they
invoke motor imagery. Unfortunately, this is nearly impossible to provide anything
than merely the spatially correct movement of the hand with only one motion
tracker. For correctly recording and recreating the motions of the entire arm, at least
two additional trackers are necessary: one for the upper arm and one for the lower
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