Low-coherence interferometry optical sensor using a single wedge polarization readout interferometer

A method, based on low-coherence interferometry, for measuring a physical quantity, the method comprising:

• providing a light system for generating a light intensity characterized by a coherence length;
• providing a sensing interferometer, having a sensor path length difference that is sensitive to the physical quantity such as to be modified by a variation of the physical quantity and that is larger than said coherence length;
• providing a polarization readout interferometer, having a readout path length difference and based on two-beam interferometer configuration, said polarization readout interferometer comprising an input polarizer for decomposing into two linear orthogonal polarization components a light, a single birefringent wedge in which are propagating at different speed said polarization components, an output polarizer for recombining after propagation in the wedge the polarization components and a focusing optic arrangement;
• providing, at a detection location, a photodetector;
• relaying the light intensity from the light system into the sensing interterometer, wherein said sensing interferometer generates a sensor light signal as a function of its sensor path length difference;
• relaying said sensor light signal, using said focusing optic arrangement, through the input polarizer, the birefringent wedge and the output polarizer and towards said output location and generating, at said detection location by recombination of said polarization components, a readout light signal as a function of said readout path length difference;
• detecting, with said photodetector, said readout light signal;
• and
• generating a photodetector signal corresoonding to the detected readout light signal, as a function of the readout path length difference for determining the physical quantity by analyzing the photodetector signal as a function of the readout path length difference.

A polarization interferometer, having a path length difference, for providing, upon receiving an input light, an output signal, the polarization interferometer comprising:

• an input polarizer for decomposing said input light into two linear orthogonal polarization components;
• a single birefringent wedge in which are propagating at different speeds said polarization components;
• an output polarizer for recombining, after propagation in the wedge, the polarization components;
• and
• a focusing optic arrangement for relaying the input light through the input polarizer, the single birefringent wedge and the output polarizer and towards an output location,
• whereby said interferometer, upon receiving said input light, provides, at the output location, said output signal as a function of the path length difference.

A method for minimizing a dispersion effect on a measurement of a physical quantity made using an interferogram produced by an low-coherence interferometry-based tandem interferometer optical system, the method comprising:

• selecting a first birefringent material sensitive to the physical quantity and having a first dispersion, and a second birefringent material different from said first birefringent material and having a second dispersion, a value of said first dispersion to be similar to a value of said second dispersion;
• providing a sensing component made of said first birefringent material;
• providing a birefringent wedge made of said second birefringent material;
• and
• producing said optical system having a sensing interferometer comprising said sensing component for providing a path length difference modifiable by a variation of said physical quantity, and a polarization readout interferometer optically coupled to said sensing interferometer and having a single one of said birefringent wedge, said polarization readout interferometer having a readout path length difference and being based on two-beam interferometer configuration, for providing a spatially distributed interferogram.