An interferometer apparatus which include two or more coupled fiber optic Michelson interferometers using fiber optic stretches which stretch two or more optical fibers wound around the perimeter of the optical fiber stretchers by the same amount is disclosed. Preferably a pair of reference and sample fiber optic stretches are utilized which run in a push-pull mode of operation. When one of the interferometers is a coherent light interferometer it can be used as a reference distance scale for all of the remaining low coherence light interferometer. A method for measuring a physical property of a device under test is also disclosed using the apparatus of the present invention.

A projection exposure tool for microlithography for imaging mask structures of an image-providing substrate onto a substrate to be structured includes a measuring apparatus configured to determine a relative position of measurement structures disposed on a surface of one of the substrates in relation to one another in at least one lateral direction with respect to the substrate surface and to thereby simultaneously measure a number of measurement structures disposed laterally offset in relation to one another.

A motion detector adapted to detect activity of extremely small scale organisms, such as micro-organisms, bacteria and fungi, and even of viruses and genetic material, such as DNA and RNA. The motion detector is capable of detecting nano-motion, that is, motion in the order of nanometers or less.

A bidirectional Littrow two-degree-of-freedom grating interference measurement device based on double gratings includes a transmission two-dimensional grating and a reflection two-dimensional grating. A dual-frequency laser emitted by a light source passes through the transmission two-dimensional grating with a specific grating pitch to form four beams in X direction and Y direction, the four beams are incident on the reflection two-dimensional grating at a Littrow angle, and the four beams diffracted by the reflection two-dimensional grating return to the transmission two-dimensional grating in an incidence direction along the same path; different orders of transmission light of the four beams of light in different directions may form stable interference signals carrying displacement information, and the stable interference signals are received by a detector.

A bidirectional Littrow two-degree-of-freedom grating interference measurement device based on double gratings includes a transmission two-dimensional grating and a reflection two-dimensional grating. A dual-frequency laser emitted by a light source passes through the transmission two-dimensional grating with a specific grating pitch to form four beams in X direction and Y direction, the four beams are incident on the reflection two-dimensional grating at a Littrow angle, and the four beams diffracted by the reflection two-dimensional grating return to the transmission two-dimensional grating in an incidence direction along the same path; different orders of transmission light of the four beams of light in different directions may form stable interference signals carrying displacement information, and the stable interference signals are received by a detector.

A three-dimensional measurement device includes: a light emitter; an optical system that splits an incident light, irradiates a measurement object with an object light and irradiates a reference plane with a reference light, and recombines the object and reference lights and emits a combined light; an imaging device that takes an image of a light emitted from the optical system; a storage device that stores transmission axis absolute angle data each obtained by a previous actual measurement of an absolute angle of a transmission axis of each polarizer; and a control device that calculates a phase difference between the reference and object lights based on luminance data of each pixel in luminance image data and the transmission axis absolute angle data of each polarizer corresponding to the pixel, and measures a height of the measurement object at the measurement position.

Compact and robust machine vision systems are provided herein. A machine vision system includes an optoelectronic system configured to emit measurement beams towards objects and a motion module configured to move the objects and/or components of the optoelectronic system. The machine vision system uses the relative motions to reduce degrees of freedom required to sample the objects to produce 3D images. The optoelectronic system includes a light source configured to emit a beam and sweep its frequency. The optoelectronic system includes primary interferometers configured to measure distances to points of an object and auxiliary interferometers configured with reference delays. The optoelectronic system includes electronic circuitry configured to interpret outputs of the interferometers into distance measurements by simpler computations in the time domain. The electronic circuitry is configured to measure frequency integrals of the interferometers and determine the distance measurements by comparing the measured frequency integrals.

A high-resolution phase detection method and system based on a plane grating laser interferometer. The method uses a dual-frequency interferometer to measure the displacement, and the measurement signal processing comprises an integral part and a decimal portion, a phase equation set of a displacement measurement signal is constructed according to a measurement optical path principle of a heterodyne plane grating laser interferometer; a non-linear equation set for which the unknowns are instantaneous phase, interval phase and signal amplitude is established; and the equation sets above are solved by using the least squares method, so as to realize phase discrimination, thereby realizing precise displacement measurement. The method can solve the problems in the traditional time measurement-based phase detection technology, such as low measurement accuracy, and failing to satisfy small measuring range measurement. The measurement method can be applied to systems such as precision manufacturing equipment and lithography machine.

The invention provides a method for calibration of an optical measurement system, which may be a heterodyne interferometer system, wherein a first optical axis and a second optical axis have a different optical path length, the method comprises: .sup.measuring a first measurement value along the first optical axis using a first measurement beam, .sup.measuring a second measurement value along the second optical axis using a second measurement beam, .sup.changing a wavelength of the first measurement beam and the second measurement beam, .sup.measuring a further first measurement value along the first optical axis using the first measurement beam with changed wavelength, measuring a further second measurement value along the second optical axis using the second measurement beam with changed wavelength, .sup.determining a cyclic error of the optical measurement system on the basis of the measured values, and .sup.storing a corrective value based on the cyclic error.

Provided herein is technology relating to analysis of images and particularly, but not exclusively, to methods and systems for determining the area and/or volume of a region of interest using optical coherence tomography data. Some embodiments provide for determining the area and/or volume of a lesion in retinal tissue using three-dimensional optical coherence tomography data and a two-dimensional optical coherence tomography fundus image.