US Patent 7255978 Multi-level optical structure and method of manufacture

A multi-level optical device includes a substrate having a baseline level. At least one feature is disposed at a level above the baseline level. At least one feature is disposed at a level below the baseline level, or in the feature above the baseline level is located at a distance apart from the feature below the baseline level. The distance has an accuracy inn the range of approximately ±0.05 μm to less than approximately ±1.0 μm.