Nice post again AlexP! You’re doing great work =)
Would this still have the issue of blocking blobs if fingers are next to eachother since the fingers are only being illuminated from one angle? The other downside that i’d miss is the ability to interpret finger pressure since that can be really important sometimes. Do you think this technique could overcome these obstacles? Like the other techniques, it seems there are definite limitations to this design still.
I think if we could modify the design to incorporate the benefits of the other techniques this would be great. FTIR’s pressure sensitivity, DI’s ability to track fiducials and laser’s ability to send bright output at small wavelengths would be great.
The blocking issue could be fixed by using more than one laser light source.
As is it the case with FTIR, from my experience, the finger pressure is also detectable by this design.
Here is how it works:
Since the laser plane of light is about 1mm thick and it is positioned right above the surface of the acrylic/glass, when the finger just barely touches it, it will hit just the tip of the finger which will register as a small IR light blob.
Here is the low finger pressure illustation (borrowed and modified J. Han’s diagram here):
Now, when you apply more pressure the larger part of the finger will be illuminated by the laser light plane, which will result in larger blobs.
Here is the high finger pressure illustation (borrowed and modified J. Han’s diagram here):
I think that fiducial tracking is also possible with this method.
One way that this could be done is by using some kind of selectively difused and transparent material that will light up when placed in the laser light plane (create kind of FTIR effect within the material). So using this method the fiducials will be the inverse of the ones that are comonly used.
Hope this will clarify some of the questions…
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