Ok, I’ve been searching the forum for hours and I still don’t understand why fiducials won’t work on a FTIR setup.
The way I see it (from a purely theoretical point of view, as I have no experience at all): Let’s suppose we are using a compliant surface; when we rest an object on the surface, the light escapes from the acrylic underneath the touching area, illuminating the object, and allowing the camera to see it from behind.

What am I missing here?

The fact that you need to apply pressure onto the surface in order to get the light out of the surface.
And when you do, the ficudals you stuck on the object will not be visible, since all that will hapen is that the surface releases light on the bottom side, where you pressed it.

Thanks for the quick reply.
About the pressure, I was under the impression that very little force was needed when using a compliant surface. In any case, the object could be made heavy enough, no?

I’m not sure I follow the second part of your reasoning. Do we agree that the light escapes from the top of the acrylic at first? Why doesn’t it bounce on the fiducial?
Hmmmm, maybe the problem is that the compliant surface attenuates the light too much before reaching the fiducial?

When trying to use the fiducials i printed for reactivision 1.4 with my FTIR setup nothing was visible to the camera, which i thought would be the out come.  I do not as yet have a good silicon compliant layer but will have shortly, so once i have made it i will do some tests with a fairly weighty wooden cube with fiducials stuck to the sides.  Although i dont think it will work as the blob created will be to bright to have any contrast on the fiducial.  The other way to do it would be to cast in silicon the fiducials so that the blobs created are in the shape of the fiducial. but rotating them would be sticky!

The problem if you are not using a compliant surface is that paper doesn’t trigger the FTIR effect, but I guess that if you make the object’s surface of a “compliant material” it would work; although silicon rubber doesn’t seem very appropriate, like you say. Am I right here?