Abstract
We describe a computer-controlled low-coherence interference microscope, based on a Linnik interferometer configuration that can rapidly and accurately map the shape of micro-machined surfaces exhibiting steps and discontinuities. The novel feature of the system is a fast, switchable achromatic phase-modulator operating on the geometric phase, using a pair of ferro-electric liquid crystal devices.
Highlights
Two new techniques based on low-coherence interferometry (LCI) have been developed recently
We describe a computer-controlled low-coherence interference microscope, based on a Linnik interferometer configuration that can rapidly and accurately map the shape of micro-machined surfaces exhibiting steps and discontinuities
The novel feature of the system is a fast, switchable achromatic phase-modulator operating on the geometric phase, using a pair of ferro-electric liquid crystal devices. 2004 Optical Society of America
Summary
Two new techniques based on low-coherence interferometry (LCI) have been developed recently. This phase shift is very nearly independent of the wavelength Such a GPM has the drawback that the time required to rotate the HWP from one angle to another is much longer than the time required to acquire the values of intensity at an array of points in the interference pattern with a CCD camera. This problem can be overcome by using retarding plates based on ferro-electric liquid crystal devices, whose principal axes can be switched through a known angle in a very short time [7]. With a proper choice of initial settings, the deviations of the actual phase shifts from their nominal values can be held to less than ±15° over the range of wavelengths from 490 nm to 650 nm [11]
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