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

Abstract

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.

Description

technical field [0001] The present invention relates generally to high-speed phase shifting of light beams and more particularly to high-speed phase shifting of interference fringe patterns for three-dimensional imaging systems. Background technique [0002] Precise non-contact three-dimensional (3D) metrology based on fringe interferometry has been developed for a range of industrial applications. Measurements are typically performed on large volumes at low data acquisition rates. For various applications such as medical and dental imaging, 3D imaging systems typically require high spatial resolution and short measurement duration. Furthermore, many systems are limited in size to enable use by operators such as technicians, doctors or dentists. An example of a compact 3D imaging system is described in PCT Patent Application No. PCT / US08 / 80940, which is hereby incorporated by reference. [0003] Conventional systems that address the above limitations are limited in speed ...

AI Technical Summary

Problems solved by technology

Both techniques rely on mechanical translation mechanisms capable of submicron positioning stability, and systems employing these techniques are limited in data acquisition speed due to translation mechanism settling time

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