Abstract: An interferometry system for monitoring changes in the position of an object, the system includes a spectrally broadband light source, a sensor module having an interferometer that direct portions of the light received from the source along separate paths. The system includes an intensity monitor having a detector configured to measure the intensity of additional light derived from the source and to produce a monitor output signal. The system includes an electronic processing module to process a sensor output signal based on the monitor output signal to account for intensity fluctuations in light output by the source, and determine information about the changes in the position of the object. The intensity monitor is configured to characterize the intensity fluctuations as a function of wavelength or intensity fluctuations that are spectrally correlated.

Abstract: An interferometry system for monitoring changes in the position of an object, the system includes a spectrally broadband light source, a sensor module having an interferometer that direct portions of the light received from the source along separate paths. The system includes an intensity monitor having a detector configured to measure the intensity of additional light derived from the source and to produce a monitor output signal. The system includes an electronic processing module to process a sensor output signal based on the monitor output signal to account for intensity fluctuations in light output by the source, and determine information about the changes in the position of the object. The intensity monitor is configured to characterize the intensity fluctuations as a function of wavelength or intensity fluctuations that are spectrally correlated.

Abstract: Apparatus and methods for adjusting the polarizations of the components of an input beam to reduce leakage caused by imperfections in an interferometer are disclosed. The apparatus includes an interferometer positioned to receive an input beam that includes two components having different frequencies and different polarizations, the interferometer including a polarizing beam splitter positioned to spatially separate the input beam into two intermediate beams, the first intermediate beam corresponding to the first component and the second intermediate beam corresponding to the second component, where imperfections in the interferometer cause leakage of one of the components into the intermediate beam corresponding to the other of the components. The apparatus further includes a polarization compensator that includes at least one retardation plate positioned to adjust the polarizations of the components of the input beam to reduce the leakage caused by the imperfections in the interferometer.