You could do something similar with a much more low-tech implementation. What if you had a tray with gray lettering, then a clear (plastic?) layer with another set of gray lettering, and then a second clear layer with a set of black lettering. If the two clear layers were somewhat "bubbled" to create a separation between each layer, it would create a blur effect when viewed from anything but a direct angle, since the three sets of letters wouldn't line up. When you placed an item with enough weight on top, though, the clear layers would flatten and all of letters would line up, eliminating the blur effect.

Clever, but I think it should be the other way around: blurry when the glasses are in the tray and clear when they are on your face.

neato.

graefix, I thought that at first too but then I realized I think the point is that the glasses are litterally required to make the it clear...not to the viewer but on that tray.

i agree with graefix and posted that same comment on swissmiss when it first appeared.

It just seems logically backwards to me. the glasses should be required to make it clear to the viewer.

Neat! I might make a low tech one for my husband without the blurry/focus effect - just an eye chart in a dish.