Self-Acquisition (Mobile), page-2

Hi @squeef

Good questions.

Away with fam atm so moby at this stage and not lot if time to delve into right now. Not overly concerned myself though.

This may assist as the original basis for the tech was born from corneal topography and obviously now moved into incorporating iris modality as well.

Link at bottom page.

Note the 3 general principles and explanations.

U can see under placido is where first Purkinje imaging comes in and then into scanning slit and sheimpflug photography starts discussing "triangulation" for light and imaging.

I suspect there is a combination of these methods (or others as well) to enure images r captured correctly.

Have to remember the corneal biometric component is based on Purkinje and the tear film merely mimicking the contour of the actual underlying cornea. The tear film changes ever so slightly each time due to Brownian motion so the tech is never actually looking for an exact match....hence "one time pin".

That is primarily why this tech is diff from most others...they all look for an "exact" match....making it potentially more open to hack and spoofing methods as static format.

Because one part of WBT tech is recognising constantly changing biometric components as part of the whole (inc. iris etc) then makes much more difficult to spoof.

I suggest the triangulation etc. prob come into calcs to assist with imaging....can't be any diff than current iris NIR pics in moby like Fujitsu. The eye is curved yet that tech takes a pic reflecting NIR into the eye....generally reducing corneal specular reflections (which WBT actually uses as a strength) to remove or reduce wot they call "artefacts" or noise I guess, from memory.

Hope helps a bit...will try mayb explain better how I see it anyway in a couple of days wen hm again.

Nice weekend all.

http://eyewiki.aao.org/Corneal_topography#Placido_Disc_Reflection_for_curvature_analysis