So I made a cardboard-and-blutack prototype of the followspot reflex sight with heads-up display idea that I’ve been thinking of, with a very nice beamsplitter cube loaned from my makerspace friend. Too bad they’re quite expensive — might not be so practical to use one in the end (rather than a semi-silvered mirror), but they’re so nifty. #tinkering
@gbrnt not much under AU$50 for 25mm cube, but I just found some cheaper ones around $25 each (often they’re slightly out of spec for scientific use, but fine for hobby).
@aearil the answer seems to be basically no, as some back of the envelope maths told us you need the interface layer to be on the order of single microns thick, with consistency down another OOM. It’s cleanroom territory afaict.
@aearil I don’t believe so. It’s not based on simple refractive index change but frustrated total internal reflection and the evanescent wave. A wave hitting the transition at greater than critical angle will have its energy split between the TIR portion and a portion from the evanescent wave on the other side of the gap, dependent on the width of the gap section compared to the wavelength iirc
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