A method for obtaining the profile of the outer surface (22) of a medium (21) having a median plane (23) comprising the following steps: obtaining two time signals A and B (1002), for, at each instant, a same geometrical target on a readout line of the outer surface (22); determining at least one Doppler frequency (2001) associated with each time signal A and B; sampling each time signal A and B (2002) at a frequency greater than 2 times the Doppler frequency to obtain a payload signal; determining an envelope (2004) of the payload signal of each signal A and B; performing a relative combination between the envelopes of each signal A and B (3001) to obtain a monotonic and bijective function F; and determining the profile of the outer surface (3002) using a calibration of the function F.

Systems, devices and methods for measuring surface roughness and surface shape of an optical element using a dual-mode interferometer are disclosed. The devices implement optical filters, with a compact form, that allows measurement of both surface characteristics without rearranging the system components. One example interferometric system includes a laser light source and a low coherence light source that alternatively provide light to a collimator, followed by a polarizer, and a polarizing beam splitter. The system further includes two optical filters, a quarter waveplate, two objectives and a reference optical component. Each light source produces a set of interferograms, where one set of interferograms is used to measure the surface shape and another set of interferograms is used to measure the surface roughness of the optical component.

A laser measurement system for measuring up to 21 geometric errors, in which a six-degree-of-freedom geometric error simultaneous measurement unit and a beam-turning unit are mounted on either the clamping workpiece or the clamping tool, while an error-sensitive unit is mounted on the remaining one, the beam-turning unit has several switchable working postures and multi-component combinations in its installation state, it can split or turn the laser beam from the six-degree-of-freedom geometric error simultaneous measurement unit to the X, Y, and Z directions in a proper order, or the beam-turning unit can split or turn a beam from the error-sensitive unit to the six-degree-of-freedom geometric error simultaneous measurement unit. The present invention is of simple configuration and convenient operation. Up to 21 geometric errors of three mutual perpendicular linear motion guides are obtained by a single installation and step-by-step measurement.

Nonlinear interferometers include a nonlinear optical medium that is situated to produce a conjugate optical beam in response to a pump beam and a probe beam. The pump, probe, and conjugate beams propagate displaced from each other along a common optical path. One of the beams is selectively phase shifted, and the beams are then returned to the nonlinear medium, with the selectively phase shift beam phase shifted again. The nonlinear medium provides phase sensitive gain to at least one of the probe or conjugate beams, and the amplified beam is detected to provide an estimate of the phase shift.

The present invention discloses a processing method for laser heterodyne interferometric signal based on locking edge with high frequency digital signal. A reference signal and a measurement signal of heterodyne interferometer, after being processed by photodetector, signal amplifier, filtering circuit, voltage comparator and high frequency digital edge locking module, are transferred to pulse counting synchronized latching processing module, to obtain entire cycle interference fringe numbers and filling pulse numbers in one interference fringe cycle, of the reference signal and the measurement signal; the numbers are transferred to a computer to obtain displacement and speed of a measured object; usage of a high frequency digital pulse signal to lock the rising edge of laser heterodyne interferometric signal can improve the gradient of the rising edge of interference signal and eliminate wrong pulse caused by noises, and improve the accuracy and stability of the processing for the following signals.

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.

A digital measuring device implemented on a photonic integrated circuit, the digital measuring device including a tunable laser source implemented on the photonic integrated circuit configured to sweep over a frequency range to provide multi-wavelength light, a first waveguide structure implemented on the photonic integrated circuit configured to direct a first portion of light from the laser source at a moving object and receive light reflected from the moving object, a second waveguide structure implemented on the photonic integrated circuit configured to combine a second portion of light from the laser source with the light reflected from the moving object to produce a measurement beam, and a first detector implemented on the photonic integrated circuit configured to detect intensity values of the measurement beam to measure a distance between the digital measuring device and the moving object.

A measurement method for interferometrically measuring the shape of a surface (112) of a test object (114). A test wave (125-1, 125-2) directed at the test object has a wavefront that is at least partially adapted to the desired shape of the surface, and a reference wave (128-1, 128-2) directed at a reflective optical element (130-1, 130 2) has a propagation direction that deviates from the propagation direction of the test wave (125-1, 125-2) for each of two input waves by diffraction at a diffractive element (124). For each wavelength, the test wave is superimposed after interaction with the test object with the associated reference wave after the back-reflection at the first reflective optical element. The test and reference waves are diffracted again at the diffractive element for superposition. An interferogram produced by the superposition is captured in a capture plane (148-1, 148-2). The interferograms are jointly evaluated.

An optical device for sensing a surface profile of an object surface of an object by means of interferometric distance measurement, including a beam splitter for splitting a light beam of a light source into first and second sub-beams, a beam divider for dividing each sub-beam into a reference and a measuring beam, a mirror for reflecting the two reference beams, wherein each measuring beam is directed onto a measuring area on the object surface for reflection and after reflection is directed as object beam to the beam divider, each reference beam reflected by the mirror and directed as mirror beam to the beam divider, the object and mirror beams each interfere and are each fed as an evaluation beam to a detector unit for evaluation. Further include a light source for generating a monochromatic light beam, a detector unit, a signal evaluation unit and for determining the surface profile.

Improved optical coherence tomography systems and methods to measure thickness of the retina are presented. The systems may be compact, handheld, provide in-home monitoring, allow the patient to measure himself or herself, and be robust enough to be dropped while still measuring the retina reliably.