Optical sensor using low-coherence interferometry
AssigneeOpsens Inc.
InventorGaetan Duplain
Life of this patent
Estimating the term…
Abstract
The invention provides a method and a system for measuring a physical quantity by means of a tandem interferometer optical sensor system based on low-coherence interferometry. The system comprises a light system, a sensing interferometer and a polarization readout interferometer. The invention provides a polarization interferometer comprising a single birefringent wedge. The invention also provides for a dispersion-compensated optical sensor system. The invention also provides an interferometer sensitive to temperature that comprises a trajectory in a LiB3O5 crystal with an x-cut orientation.
Claims38
A tandem interferometer optical sensor system, based on low-coherence interferometry, for measuring a physical quantity, the system comprising:
- a light system generating a light intensity characterized by a coherence length;
- a sensing interferometer, having a sensor path length difference larger than said coherence length, for receiving the light intensity and generating a sensor light signal as a function of said sensor path length difference, wherein said sensor path length difference is modifiable by a variation of the physical quantity;
- and
- a polarization readout interferometer, having a readout path length difference and based on two-beam interferometer configuration, receiving the sensor light signal and generating, at an output location and as a function of said readout path length difference, a readout light signal, said polarization readout interferometer comprising an input polarizer for decomposing the sensor light signal into two linear orthogonal polarization components, a 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 received sensor light signal through the input polarizer, the birefringent wedge and the output polarizer and towards said output location, to thereby provide the readout light signal as a function of the readout path length difference.
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 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 interferometer, 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 corresponding photodetector signal as a function of the readout path length difference;
- and
- determining the physical quantity by analyzing the photodetector signal as a function of the readout path length difference.
An interferometer, sensitive to a temperature, the interferometer comprising:
- a LiB3O5 crystal with an x-cut orientation;
- and
- a path length difference that comprises a trajectory in said LiB3O5 crystal, whereby the path length difference is sensitive to the temperature such as to be modified by a variation of the temperature, to thereby provide a temperature-sensitive interferometer.
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.
Dependencies are inferred from the claim text.