The present invention provides a reflective condensing interferometer for focusing on a preset focus. The reflective condensing interferometer includes a concave mirror set, a convex mirror, a light splitting element, and a reflecting element. The concave mirror set has first and second concave surface portions which are oppositely located on two sides of a central axis passing through the preset focus and are concave on a surface facing the central axis and the preset focus. Light is preset to be incident in parallel to the central axis in use. The convex mirror is disposed between the concave mirror set and the preset focus on the central axis, and is convex away from the preset focus. The light splitting element vertically intersects with the central axis between the convex mirror and the preset focus. The reflecting element is disposed between the light splitting element and the convex mirror.

An analysis apparatus includes an acquisition part that acquires a plurality of interference images based on a plurality of optical path lengths between the reference surface and the surface of the object to be measured from the interference measurement apparatus, a calculation part that calculates a sine wave component and a cosine wave component of an interference signal for each pixel in the plurality of interference images, respectively, an error detection part that detects an error between a first Lissajous figure constructed on the basis of the sine wave component and the cosine wave component for each pixel and an ideal second Lissajous figure, a correction part that corrects the sine wave component and the cosine wave component for each pixel on the basis of the error, and a geometry calculation part that calculates surface geometry of the object to be measured on the basis of the corrected sine wave component and cosine wave component is provided.

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.

A system is provided for measuring distance or displacement, comprising: first and second laser sources configured to provide first and second laser outputs; a beam combiner configured to receive and combine at least part of the first and second laser outputs into a combined laser output; a signal calibrator configured to receive at least part of the first laser output, the second laser output, or the combined laser output, and output a calibration signal; a plurality of optical paths, including a first optical path, a second optical path, the plurality of optical paths being configured to direct at least part of the combined beam onto an optical detector to produce an interference signal; and a signal processor configured to receive the interference signal and determine a pathlength difference between the first and second optical paths.

A method of measuring a particle density of particles includes emitting, by a laser, a laser beam directed to a mirror, redirecting the laser beam by the mirror with a predetermined periodic movement, and focusing the laser beam to a detection volume by an optical imaging device. The method further includes determining a self mixing interference signal of an optical wave within a laser cavity if the self mixing interference signal is generated by laser light of the laser beam reflected by at least one of the particles and suppressing a false self mixing interference signal for particle detection if the self mixing interference signal is caused by a disturbance in an optical path of the laser beam. The false self mixing signal caused by the disturbance in the optical path of the laser beam is suppressed in a defined range of angles of the mirror during the periodic movement.

An ophthalmological image processing apparatus includes an image obtaining portion for obtaining ophthalmological image data, which is captured by an imaging unit, of a subject eye, and an image processing portion for processing the ophthalmological image data. The image processing portion uses a first front image of the subject eye in a first depth region to correct a second front image of the subject eye captured in a second depth region which is different from the first depth region. The first front image and the second front image are constructed based on the ophthalmological image data. The ophthalmological image processing apparatus can reduce an artifact which is generated in an ophthalmological image.

An optical metrology device produces beams of light with varying wavelengths in a spectral range for measurement of a sample that is at least partially transparent to the spectral range. The light is obliquely incident on the sample, where a portion of the light is reflected off the top surface and a portion is transmitted through the sample and is reflected off the bottom surface. The incident light and/or reflected light is polarized and a phase modulator, such as a photoelastic modulator or electrooptic modulator, is adjusted based on the wavelengths in each beam of light to produce a same retardation of polarization for each beam of light. The reflected light that is received by a detector does not include light reflected from the bottom surface of the sample. A characteristic of a buried structure below the top surface of the sample is determined using the detected reflected light.

The methods disclosed herein include recording at near-vertical first and second measurement positions respective first and second interferograms of the photomask surface and defining a difference map as the difference between the first and second interferograms. Respective first and second normal forces on the photomask are also measured at the first and second measurement positions. The change in the normal force is used define a scaling factor, which is applied to the difference map to define a scaled difference map. A compensated flatness measurement with a reduced shape contribution due to gravity is obtained by subtracting the scaled difference map from the first interferogram. An interferometer-based flatness measurement system is also disclosed.

Disclosed is a method for measuring etch depth including the following steps: splitting a light beam into a first, and respectively second, incident beam directed towards a first, respectively second, area of a sample exposed to an etching treatment to form a first, and respectively second, reflected beam, recombining the first reflected beam and the second reflected beam to form an interferometric beam; detecting a first, and respectively second, interferometric intensity signal relative to a first, respectively second, polarisation component; calculating a lower envelope function and an upper envelope function of a differential polarimetric interferometry signal; determining an offset function and a normalisation function from the first lower envelope function and the first upper envelope function; and calculating a differential polarimetric interferometry function normalised locally at each time instant.

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.