Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1991-03-01
1993-04-27
Turner, Samuel A.
Optics: measuring and testing
By polarized light examination
With light attenuation
356356, 356358, 250237G, G01B 1114, H01J 314
Patent
active
052067041
ABSTRACT:
A position measuring apparatus includes an optical instrument placed in a first plane, a first diffraction grid placed in a second plane, parallel to the first plane, a retro-reflecting element, a second diffraction grid, and an optical element, preferably placed in the first plane. The optical instrument splits a beam of light into at least two divergent partial beams which are diffracted by the first diffraction grid into parallel partial beams. The parallel partial beams are conducted through the retro-reflecting element and then impinge onto the second diffraction grid. The second diffraction grid diffracts the partial beams and causes them to interfere with each other at the optical element. A detection device measures a change (.DELTA.OPD) of path difference of the partial beams which is directly proportional to the change in distance between the first and second planes. This change (.DELTA.OPD) of the path difference can be detected by the detection device as a light-dark modulation at the optical element.
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Huber Walter
Spanner Erwin
Dr. Johannes Heidenhain GmbH
Pham Hoa
Turner Samuel A.
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