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I suspect this was an easy way to test it without having to build a rotatable optical bench.

A practical device may be an array of light sources and telescopes on a rotating mount or a set of moveable mirrors that achieve the same effect.

If it is required, then in a real application you could just rotate the laser array instead.

I also wonder about the requirement for the letters to be made of reflective material.

Or rotate the telescopes

... which are radially symmetric.

I recognize the ambiguity, but was referring to the orientation of the telescope system to the target.