Patent Number: 7,088,441

Title: Method and apparatus for measuring wavelength changes in a high-resolution measurement system

Abstract: A method and apparatus for measuring a wavelength-related characteristic of a radiation source is provided. Two beams travel through substantially identical filters at different angles, which produces two different output signals that behave similarly with respect to power and/or temperature variations. In various embodiments, the two beams are filtered through two portions of a single filter. A diffraction grating may be mounted to the filter to split incident radiation into first and second beams. The beams thus travel through the filter at different angles, to produce two output signals that can be combined to compensate for common-mode errors as well as power variations. Extremely small size and high-resolution may be achieved. Single or multiple detectors may also be used. Filter temperature sensitivities may also be compensated based on a direct temperature measurement or based on outputs derived from two additional beams through filters with a different temperature dependency from the filters used for the first two beams. Alternatively, the angle at which a beam travels through a filter may be physically adjusted to compensate for temperature change.

Inventors: Nahum; Michael (Kirkland, WA), Tobiason; Joseph D. (Woodinville, WA), Atherton; Kim W. (Kirkland, WA)

Assignee: Mitutoyo Corporation

International Classification: G01J 1/42 (20060101)

Expiration Date: 8/08/02018