Methods, systems and devices for estimating a parameter of interest in a borehole. The method may include generating information from an optical displacement device relating to relative motion between two or more reflective surfaces thereof that is indicative of the parameter of interest; and preventing changes in the information resulting from changes at the optical displacement device in at least one of i) temperature, or ii) pressure, by compensating for the changes. Compensating may include adjusting at least one light source generating an electromagnetic beam at least partly received by the optical displacement device responsive to information relating to a control optical displacement device at the optical displacement device. Compensating may include using an optical displacement device and configuring the optical displacement device such that a difference between a first variable gap and a second variable gap is substantially zero while the apparatus is subject to nominal conditions.

An interferometer measuring device is disclosed which includes a workpiece stage (10), a laser interferometer (20) and a measuring reflector (30) mounted on the workpiece stage. The measuring reflector (30) is comprised of a plurality of planar mirrors (31) that are joined together along a horizontal direction. The laser interferometer (20) includes a first interferometer (21) and a second interferometer (22). The first interferometer (21) and the second interferometer (22) are configured such that during a horizontal movement of the workpiece stage (10) with respect to the laser interferometer (20), when light beams emanated from the first interferometer (21) and the second interferometer (22) are incident on a transition section (32) defined by corresponding adjacent two of the planar mirrors (31), the light beam emanated from the first interferometer (21) is incident on one of the adjacent two planar mirrors (31) and the light beam emanated from the second interferometer (22) is incident on the other of the adjacent two planar mirrors (31). Additionally, the first interferometer (21) and the second interferometer (22) alternately provide positional information to the workpiece stage (10). A method for controlling such an interferometer measuring device is also disclosed. The interferometer measuring device and the method enable an extended horizontal measurement range for the workpiece stage (10) by using the plurality of planar mirrors (31) that are joined together as well as by alternating zero-reference updating of the two interferometers (21, 22).

A method for constructing a three-dimensional image of a sample includes producing electromagnetic radiation and directing the produced electromagnetic radiation such that it is incident on the sample at an oblique angle. The incident electromagnetic radiation is scanned in discrete increments to a plurality of discrete locations along a first direction, and at each discrete location, scanned along a second direction orthogonal to the first direction. The sample reflects a first portion of the incident electromagnetic radiation and absorbs a second portion of the incident electromagnetic radiation, and emits electromagnetic radiation responsive to the absorption. A plurality of cross-sectional images is produced from the reflected electromagnetic radiation and the emitted electromagnetic radiation, and each cross-sectional image is modified to compensate for the oblique angle. The modified cross-sectional images are then combined to create a three-dimensional image of the sample.

An apparatus and method are provided. In particular, at least one first electro-magnetic radiation may be provided to a sample and at least one second electro-magnetic radiation can be provided to a non-reflective reference. A frequency of the first and/or second radiations varies over time. An interference is detected between at least one third radiation associated with the first radiation and at least one fourth radiation associated with the second radiation. Alternatively, the first electro-magnetic radiation and/or second electro-magnetic radiation have a spectrum which changes over time. The spectrum may contain multiple frequencies at a particular time. In addition, it is possible to detect the interference signal between the third radiation and the fourth radiation in a first polarization state. Further, it may be preferable to detect a further interference signal between the third and fourth radiations in a second polarization state which is different from the first polarization state. The first and/or second electro-magnetic radiations may have a spectrum whose mean frequency changes substantially continuously over time at a tuning speed that is greater than 100 Tera Hertz per millisecond.

A method of air refractive index correction for an absolute long distance measurement adopting a two-color method based on a single wavelength and a synthetic wavelength is provided. Two lasers emit two laser beams with a constant single wavelength and a variable wavelength, respectively, to form a synthetic wavelength chain from large to small through a laser interferometric system. Each order of the synthetic wavelength chain is used to obtain a series of the estimate values of optical distance with gradually increasing accuracy. After optical distances corresponding to a minimum synthetic wavelength and a single wavelength are obtained simultaneously, the corrected absolute distance is achieved according to the principle of the two-color method for air refractive index correction. The method can realize full-path correction of air refractive index along the actual path of the distance measurement, and has low requirements on the measurement precision of environmental parameters such as temperature and pressure.

A method of processing data from a distributed fibre-optic interferometric sensor system for measuring a measurand, the system comprising multiple interferometric sensors. The method comprises interrogating two or more of the multiple interferometric sensors to record a raw measurement time series for each of the sensors. The method further comprises calculating a common reference time series as a measure of central tendency of the raw measurement time series from two or more reference sensors, the reference sensors being selected from the multiple interferometric sensors. Finally, the method comprises compensating at least one raw measurement time series from a measurement sensor selected from the multiple interferometric sensors with the common reference time series to produce a compensated measurement time series, the measurement sensor being configured to be sensitive to the measurand. The invention further relates to a distributed fibre-optic interferometric sensor system.

The optical coherence tomography includes a processor, wherein the processor is configured to: vectorize the Jones matrix and then convert the vectorized Jones matrix into an expanded matrix; calculate at least an eigenvalue and at least an eigenvector of the expanded matrix by performing an eigenvalue decomposition to the expanded matrix; and estimate the polarization characteristic of the subject by using at least an eigenvalue and at least an eigenvector of the Jones matrix acquired based on the at least eigenvalue and the at least eigenvector of the expanded matrix.

Systems and methods for performing optical coherence tomography (OCT) on a target using microcomb lasers in accordance with embodiments of the invention are illustrated. One embodiment includes an OCT system that includes a laser generator configured to generate a laser beam, and an optical amplifier configured to amplify the laser beam, a microresonator configured to receive the amplified laser beam and couple the received laser beam into the microresonator to generate a microcomb laser, a grating configured to filter the generated microcomb laser, an interferometer configured to split the generated microcomb laser into a sample arm and a reference arm, an OCT probe configured to generate tomograms of a target using the sample arm, and a spectrometer configured to obtain depth information from the interferogram and generate cross-sectional images of the target based on the obtained depth information.

An optical coherence tomography device includes an SS-OCT optical system which includes a wavelength swept optical source which sweeps an emission wavelength, an optical splitter which splits an interference signal light caused by interference between a measurement light and a reference light into a first interference signal light and a second interference signal light having a phase difference from the first interference signal light, a balance detector which includes a first detector configured to detect the first interference signal light and a second detector configured to detect the second interference signal light, and which processes detection signals from the first and second detectors to perform balance detection, and an optical member which is disposed between the optical splitter and one of the first detector and the second detector to generate a fixed pattern noise by one of the first interference signal light and the second interference signal light.

The present invention provides a novel simple, portable, compact and inexpensive approach for interferometric optical thickness measurements that can be easily incorporated into an existing microscope (or other imaging systems) with existing cameras. According to the invention, the interferometric device provides a substantially stable, easy to align common path interferometric geometry, while eliminating a need for controllably changing the optical path of the beam. To this end, the inexpensive and easy to align interferometric device of the invention is configured such that it applies the principles of the interferometric measurements to a sample beam only, being a single input into the interferometric device.