Apparatus and method for high-speed phase shifting for interferometric measurement systems

摘要

Described are a method and apparatus for high-speed phase shifting of an optical beam. A transparent plate having regions of different optical thickness is illuminated by an optical beam along a path of incidence that extends through the regions. The transparent plate can be moved or the optical beam can be steered to generate the path of incidence. The optical beam exiting the transparent plate has an instantaneous phase value according to the region in which the optical beam is incident. Advantageously, the phase values are repeatable and stable regardless of the location of incidence of the optical beam within the respective regions, and phase changes at high modulation rates are possible. The method and apparatus can be used to modulate a phase difference of a pair of coherent optical beams such as in an interferometric fringe projection system.

主权项

1. A method for modulating a phase difference of a pair of coherent optical beams, the method comprising:
providing a transparent plate having a pair of parallel surfaces, a first region having a first optical thickness and a second region having a second optical thickness, the first and second optical thicknesses being different from each other; illuminating the first region of the transparent plate with at least a first beam of a pair of coherent optical beams, wherein a phase difference of the pair of coherent optical beams has a first value; moving the transparent plate from a first position with respect to the first beam to a second position with respect to the first beam; and illuminating the second region of the transparent plate with at least the first beam, wherein the phase difference of the pair of coherent optical beams has a second value, the first and second values being different from each other.