Patent ID: 6252669
Filing Date: 2001-06-26
Classification: G01B

Abstract:
An interferometric instrument for sensing a surface of a test object, comprising:a radiation producing unit for emitting a briefly coherent radiation;an arrangement for periodically changing a light path of a received beam component, the arrangement including at least two acousto-optical deflectors and a stationary reflecting element that receives the received beam component directly from the at least two acousto-optical deflectors, the stationary reflecting element being a grating;a first beam splitter for generating a first beam component and a second beam component in response to the briefly coherent radiation, the first beam component being aimed at the surface of the test object and the second beam component being aimed at the reflecting element;an interference element for causing the first beam component reflected from the surface of the test object and the second beam component reflected from the reflecting element to interfere with one another to produce an interfered radiation;a photodetector for receiving the interfered radiation; anda frequency shift arrangement for producing a frequency shift between the first beam component and the second beam component of the interfered radiation, the frequency shift arrangement being provided in at least one of an optical path of the first beam component and an optical path of the second beam component.