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 system for optical coherence tomography using multiple interferometers presented. The interferometry system includes a source configured to generate a variable wavelength light beam. A first splitter is configured to split the variable wavelength light beam to at least a first light beam and a second light beam. A first delay element is configured to delay the first light beam by a first time delay. A second delay element is configured to delay the second light beam by a second time delay, such that the delayed first light beam and the delayed second light beam are out of coherence with each other. A first interferometer is configured to receive the delayed first light beam as an input. A second interferometer is configured to receive the delayed second light beam as an input.

An interferometer system for measuring the displacement of a location of a test surface includes a reference arm comprising two reflective optical elements with optical power, a measurement arm comprising two reflective optical elements with optical power wherein one of the optical elements of the reference arm is one of the optical elements of the measurement arm. A housing can be provided in which the reflective optical elements are mounted, all such components made from a material having a low CTE. Further, spider support structures can be provided for positioning a reflective optical element within the housing, and/or for positioning a fiber optic device within the system. Light detecting elements can be installed on a side of a spider support structure facing the test surface and used to detect a tilt of the test surface which can be used to improve the accuracy of the displacement measurement.

A cat's-eye swept source laser designed for Optical Coherence Tomography (OCT) and spectroscopy, focusing on reducing relative intensity noise (RIN). It features a semiconductor gain chip and a cat's-eye configuration with an adjustable bandpass filter managed by an angle-control actuator, optimizing wavelength tuning and noise reduction. This efficient design can eliminate the need for a thermoelectric cooler, simplifying the system and reducing costs. The laser supports various imaging techniques, offering improved signal-to-noise ratios and high-resolution images.

A velocity-compensated frequency sweeping interferometer has a single measurement light producing device that produces a coherent light source consisting of a single light beam. The light producing device produces a scanning wavelength light beam. A primary beam splitter produces a first reference beam and a first measurement beam from said single light beam. The first reference beam travels a fixed path length to a primary reference reflector and the first measurement beam travels to and from a moveable reflective target over an unknown path length. A distance measurement interferometer is created by interfering the first reference beam with the first measurement beam. A return frequency measurement interferometer provides a measure of frequency of the return beam from the target which, when compared with the frequency of the outgoing beam, allows for velocity compensation of the target.

A multi-mode frequency sweeping interferometer has a single measurement light producing device configured to produce a coherent light source consisting of a single light beam. The single measurement light producing device transitions the single light beam between a fixed light beam and a scanning wavelength light beam. A primary beam splitter produces a first reference beam and a first measurement beam from said single light beam. The first reference beam is configured to travel a fixed path length to a primary reference reflector and the first measurement beam is configured to travel to and from a moveable reflective target over an unknown path length. A first interferometer is created by interfering the first reference beam with the first measurement beam and one or more optoelectronic devices may be configured to determine a measured distance to the movable reflective target.

Length metrology apparatuses and methods are disclosed for measuring both specular and non-specular surfaces with high accuracy and precision, and with suppressed phase induced distance errors. In one embodiment, a system includes a laser source exhibiting a first and second laser outputs with optical frequencies that are modulated linearly over large frequency ranges. The system further includes calibration and signal processing portions configured to determine a calibrated distance to at least one sample.

Methods are known for implementing general optical functions using wave splitters. However, these methods rely on these wave splitters having maximal extinction ratio, which is difficult to achieve in practice. The present invention provides methods for automatically adjusting wave splitters to provide maximal extinction ratio.

Some embodiments of the invention relate to a laser tracker for progressive tracking of a reflective target and for determining the distance to the target having a distance measuring unit, which is designed as an interferometer, for determining a distance change to the target by means of interferometry, a laser beam source for generating measuring radiation for the interferometer, a base, which defines a standing axis, a beam guiding unit for emitting the measuring radiation and for receiving at least a part of the measuring radiation reflected on the target, wherein the beam guiding unit is pivotable by a motor about the standing axis and an inclination axis, which is essentially orthogonal in relation to the standing axis, in relation to the base, and an angle measuring functionality for determining an alignment of the beam guiding unit in relation to the base.

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.