Broadband interferometry and method for measurement range extension by using same
AssigneeAutomated Precision, Inc.
InventorsYongwoo Park, Shuai Sun, Kam Lau
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Abstract
A broadband interferometry for a measurement range extension beyond a coherence length of a light source is achieved through a local oscillation of the reference beam is replicated by a cavity multiplication or cascading optical delayed lines with a fiber optic cavity, and quantifiable optical properties including a wavelength group delay, a chromatic dispersion, a polarization mode dispersion and a model dispersion are inserted into the local oscillation of the reference beam to incrementally quantify the replicated copies of the local oscillation as the number of the delayed copies of the local oscillation increase for extension of a measurement rage to the target.
Claims27
A broadband interferometry device for a measurement range extension beyond a coherence length of a light source, comprising:
- a wavelength tunable laser as the light source outputting a coherent wavelength light;
- an interferometer including a reference arm and a measurement arm and disposed between the wavelength tunable laser and a target to be measured;
- a first beam splitter dividing the coherent wavelength light into a first portion of the reference arm and a second portion of the measurement arm;
- and
- a signal processing circuit including first and second photodiodes for photocurrent generation, a transimpedance amplifier for voltage conversion and an analog electrical differential amplifier for amplifying a difference between the first and second portions of the coherent wavelength light,
- wherein a local oscillation of the first portion of the coherent wavelength beam is replicated to generate a series of temporally delayed copies of the local oscillation, and quantifiable optical properties are inserted into the temporally delayed copies for incremental quantification as the number of the delayed copies of the local oscillation increase for extension of a measurement range to the target beyond the coherence length of the light source.
A broadband interferometry device for a measurement range extension beyond a coherence length of a light source, comprising:
- a wavelength tunable laser as the light source outputting a coherence wavelength beam;
- and
- an interferometer disposed between the wavelength tunable laser and a target to be measured and including a reference arm, a measurement arm and a device combining a reference beam and a measurement beam to produce a combined interference beam,
- wherein a local oscillation of the reference beam is replicated by a cavity multiplication or cascading optical delayed lines with a fiber optic cavity, and quantifiable optical properties including at least one of a wavelength group delay, a chromatic dispersion, a polarization mode dispersion and a modal dispersion are inserted into the local oscillation of the reference beam to incrementally quantify the replicated copies of the local oscillation as the number of the delayed copies of the local oscillation increase for extension of a measurement range to the target.
A method for extending an interferometric measurement range beyond a coherence length of a light source, comprising:
- directing a reference beam from a wavelength tunable laser to a reference interferometer arm and directing a measurement beam to be reflected by an object for measurement;
- multiplicating a cavity or optical delay lines of a local oscillation in a reference beam by MN (M being the number of interferometer arms and N being the number of cascaded couplers in the reference interferometer arm) to generate a series of temporally delayed copies of the local oscillation of the reference beam;
- inserting quantifiable optical properties to the local oscillation in the reference beam;
- detecting localized interference fringes using a photoreceiver followed by a signal digitizer after combining the local oscillation in the reference beam and the measurement beam;
- and
- analyzing the interference fringes for the measurement range extension.
Dependencies are inferred from the claim text.