The invention relates to a method for creating a two-dimensional interferogram with a Michelson-type free-beam interferometer, comprising an extended, partially spatially coherent light source and a two-dimensional light detector, wherein light from the light source is split by a beam splitter with a semitransparent beam splitter mirror into a sample light beam and a reference light beam and taken to a sample arm and a reference arm, wherein the sample light beam returning from a sample is directed by the beam splitter mirror onto the light detector, wherein the reference light beam emerging from the reference arm makes a predetermined angle greater than zero with the sample light beam on the light detector, and wherein the length of the reference arm is variable, where the reference light beam is directed by means of an odd number of reflections in each reflection plane in at least one reference arm section so that it is displaced laterally to itself and travels antiparallel through a light-deflecting element working by refraction or diffraction which is secured at the exit of the reference arm.

A data acquisition apparatus includes an illumination device, a first beam splitter, a measurement unit, and a photodetector. A measurement optical path and a reference optical path are positioned between the illumination device and the photodetector. In the first beam splitter, light traveling in a first direction and light traveling in a second direction are generated from incident light. The measurement optical path is positioned in the first direction, the reference optical path is positioned in the second direction, and the measurement unit is disposed on the measurement optical path. In the optical surface of the first beam splitter, an incident position of light emitted from the illumination device changes with time, and the angle formed by light propagating through the measurement optical path and the optical axis of the measurement optical path changes with change in the incident position.

A data acquisition apparatus includes an illumination device, a first beam splitter, a measurement unit, and a photodetector. A measurement optical path and a reference optical path are positioned between the illumination device and the photodetector. In the first beam splitter, light traveling in a first direction and light traveling in a second direction are generated from incident light. The measurement optical path is positioned in the first direction, the reference optical path is positioned in the second direction, and the measurement unit is disposed on the measurement optical path. In the optical surface of the first beam splitter, an incident position of light emitted from the illumination device changes with time, and the angle formed by light propagating through the measurement optical path and the optical axis of the measurement optical path changes with change in the incident position.

Systems and methods are provided for a digital holography range Doppler receiver. The subject system transmits outgoing electromagnetic radiation to a target, and provides a first reference local oscillator (LO) beam to a first detector and a second reference LO beam to a second detector, based on the outgoing electromagnetic radiation. The system receives reflected electromagnetic radiation from the target through a first optical receiver and a second optical receiver having a smaller diameter, and determines range and velocity of the target simultaneously using an interference with the second reference LO beam. The system applies time and frequency offsets to the first reference LO beam based on the measured range and velocity to align the first reference LO beam with the reflected electromagnetic radiation, and produces an image of the target using the first reference LO beam having the applied time and frequency offsets.

Method and system for determining separation distance between an object and a processing or measuring tool involve generating a measurement beam of low coherence optical radiation, leading the measurement beam towards the object and the reflected measurement beam towards an optical interferometric sensor assembly in a first direction of incidence, generating a reference beam of low coherence optical radiation, and leading the reference beam towards the optical interferometric sensor assembly in a second direction of incidence, superimposing the measurement and reference beams on a common region of incidence, detecting position of a pattern of interference fringes between the measurement and reference beams on the region of incidence, and determining difference in optical length between a measurement optical path and a reference optical path on position of the pattern of interference fringes along an illumination axis, indicative of a difference between (a) current separation distance between the processing or measuring tool and the object and (b) predetermined nominal separation distance.

The invention relates to a full-field OCT method for generating an imaging of an ocular fundus (31), in which short-coherent light (22) is emitted and split into an object beam path (25) and a reference beam path (24). The object beam path (25) is directed onto the ocular fundus (33). The reference beam path (24) and a portion of the object beam path (25) reflected by the ocular fundus (31) are directed onto an image sensor (32), such that an interference between the reference beam path (24) and the object beam path (25) occurs on the image sensor (32), wherein the reference beam path (24) impinges on the image sensor (32) at an angle deviating from the object beam path (25). Before impinging on the image sensor (32), the reference beam path (24) impinges on an optical correction element (27) in order to reduce a chromatic aberration within the reference beam path (24). Intensity information and phase information is determined from a capturing of the image sensor. A focus-adjusted image of the ocular fundus is calculated. The invention also relates to a system that is suitable for carrying out said method. Images of the ocular fundus can be captured without the beam path being previously adapted to the refractive power of the eye lens.

An apparatus and method for die defect detection are disclosed. The apparatus includes: a light source unit (10) for emitting light of at least two wavelengths; a beam splitter (40) for receiving the light emitted by the light source unit (10) and splitting it into a first portion and a second portion, the first portion of the light reflected by a die (60) surface under inspection and thereby forming a detection beam; a reference unit (70) for receiving the second portion of the light and processing it into a reference beam; and a detection unit (90) for receiving the detection beam and the reference beam. The reference beam crosses the detection beam at an angle and thus produces interference fringes on a sensing surface of the detection unit (90), based on which a defect parameter of the die (60) surface under inspection is determined. This apparatus is capable of measuring a die with improved accuracy and efficiency and is suitable for the measurement of large dies.

The invention relates to a free-beam interferometric method for illuminating a sequence of sectional areas in the interior of the light-scattering object. The method makes it possible for the user to select a larger image field and/or a higher image resolution than previously possible with the occurrence of self-interference of the specimen light from a scattering specimen.

The present disclosure discloses a dual-channel optical three-dimensional interference method based on underdetermined blind source separation, which blindly separates out, through interference data collected by a CCD camera, interference signals between surfaces of a slide under test, to solve interference signal parameters, including an interference signal amplitude-frequency and an interference signal phase-frequency. Based on a dual-channel optical three-dimensional Michelson-type interference experiment, estimation of a mixed matrix is obtained by a K-means clustering algorithm, and recovery of a source signal is achieved by a L1 norm shortest path method. It is finally achieved that laser wavenumber scanning can accurately and blindly separate out the interference signals of the four surfaces based on light intensity values collected by the CCD camera, to achieve the blind separation of the interference signals of the four surfaces.

Systems and methods for improved interferometric imaging are presented. One embodiment is a partial field frequency-domain interferometric imaging system in which a light beam is scanned in two directions across a sample and the light scattered from the object is collected using a spatially resolved detector. The light beam could illuminate a spot, a line or a two-dimensional area on the sample. Additional embodiments with applicability to partial field as well as other types of interferometric systems are also presented.