US 8,300,233 B2 · Interferometric encoder systems

Abstract

A method for determining information about changes along a degree of freedom of an encoder scale includes directing a first beam and a second beam along different paths and combining the first and second beams to form an output beam, where the first and second beams are derived from a common source, the first and second beams have different frequencies, where the first beam contacts the encoder scale at a non-Littrow angle and the first beam diffracts from the encoder scale at least once; detecting an interference signal based on the output beam, the interference signal including a heterodyne phase related to an optical path difference between the first beam and the second beam; and determining information about a degree of freedom of the encoder scale based on the heterodyne phase.

Claims66

Dependent claims

A method for determining information about changes along a degree of freedom of an encoder scale, the method comprising:

deriving a first beam and a second beam from a common source, the first and second beams having difference frequencies;
directing the first beam and the second beam along different paths and combining the first and second beams to form an output beam, where the first beam contacts the encoder scale at a non-Littrow angle and the first beam diffracts from the encoder scale at least once;
detecting an interference signal based on the output beam, the interference signal comprising a heterodyne phase related to an optical path difference between the first beam and the second beam;
and
determining information about a degree of freedom of the encoder scale based on the heterodyne phase.

2 more elements

Dependencies are inferred from the claim text.

Interferometric encoder systems

Life of this patent

Interferometric encoder systems

Life of this patent

Abstract

Claims66