When multiple layers of storage material are coated with fluorescent material, they turn intervening laser beams into fluorescent light. This fluorescent light is immune to corruption from intervening layers and other lasers. More specifically, each base layer is marked with a pattern of "pits." When this layer is coated with fluorescent material, the pits gather a greater thickness of fluorescent stuff. The contrast between pit-thickness and layer-thickness of fluorescent material results in a unique reading of stored data.
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