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US 4,895,790 AGranted
High-efficiency, multilevel, diffractive optical elements
AssigneeMassachusetts Institute of Technology
InventorsGary J. Swanson, Wilfrid B. Veldkamp
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Abstract
The method utilizes high resolution lithography, mask aligning, and reactive ion etching. In particular, at least two binary amplitude masks are generated. A photoresist layer on an optical element substrate is exposed through the first mask and then etched. The process is then repeated for the second and subsequent masks to create a multistep configuration. The resulting optical element is highly efficient.
Claims14
Method for making high efficiency multilevel, diffractive, optical elements comprising:
- generating a plurality of binary amplitude masks including the multilevel information, the masks being configured to provide 2.sup.N levels where N is the number of masks;
- and
- utilizing the masks' information serially for serial etching of 2.sup.N levels into the optical element, the etching depths for the masks being related by a fixed ratio.
Method for making high efficiency multilevel, diffractive, optical elements comprising:
- generating a plurality of binary amplitude masks including the multilevel information by lithographic pattern generation, the masks configured to provide 2.sup.N levels where N is the number of masks;
- aligning a first one of the masks with respect to the optical element;
- coating the optical element with photoresist;
- exposing the photoresist through the aligned mask;
- developing the photoresist;
- etching the optical element;
- aligning the next one of the masks with respect to the pattern etched with the first of the masks;
- and
- repeating the coating, exposing, developing, etching, and aligning steps for each of the masks to produce 2.sup.N levels into the optical element.
6 more elements
Dependencies are inferred from the claim text.