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QUOTE (Gofer @ 26 May 2007, 14:52) <{POST_SNAPBACK}>I can see where you're coming from John with the coherent fibre optic problem. I suppose mirrors (as in periscope) would be out of the question?
The problem with this approach would be that it would only be visible from a very narrow angle, i.e. from directly head-on. To project it onto a translucent surface at the signal face would require special optics to bring the beam to a focus at that point.

Although Rapid do come highly recommended (I dread to think how much stuff I have bought from them in recent years!), they do not currently stock 0402 sized LEDs in white ('nano' sized at Ngineering). Everything else but, unfortunately, otherwise I would be using them myself!
These do, however, seem the only way forward to a matrix display at present, as there are no other obvious ways of doing it in anything less than O Gauge (and I have looked into it many times over the years). In principle, a 7x5 matrix of these would work out at about 9mm by 4.5mm, assuming it were possible to arrange them virtually touching each other. This style of LED is rectangular (0402 means 40 thou by 20 thou), so you could make the array either tall and thin, or short and wide, depending which way round you placed them. Making the array with a fixed 'pixel' pitch horizontally and vertically would probably look a bit better, but would result in something a bit bigger than the minimum. Perhaps a combination of the two orientations might produce the optimum result. It is unfortunate that LED display manufacturers don't seem to see a large enough market for an integrated matrix display of this kind of size, because there are no technical reasons why they couldn't be produced. It's only a matter of packaging.
The kind of individual LEDs we are talking about here are really designed for surface mounting on PCBs, not for wiring, so attempts to do so are not for the faint-hearted!
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