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.

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.

Techniques for removing interferometry signal phase variations caused by distortion and other effects in a multi-layer stack include: providing an electronic processor sample interferometry data acquired for the stack using a low coherence imaging interferometry system; transforming, by the electronic processor, the sample interferometry data to a frequency domain; identifying a non-linear phase variation from the sample interferometry data in the frequency domain, in which the non-linear phase variation is a result of dispersion introduced into a measurement beam by the test sample; and removing the non-linear phase variation from the sample interferometry data thereby producing compensated interferometry data.

An interferometer measuring device is disclosed which includes a workpiece stage (10), a laser interferometer (20) and a measuring reflector (30) mounted on the workpiece stage. The measuring reflector (30) is comprised of a plurality of planar mirrors (31) that are joined together along a horizontal direction. The laser interferometer (20) includes a first interferometer (21) and a second interferometer (22). The first interferometer (21) and the second interferometer (22) are configured such that during a horizontal movement of the workpiece stage (10) with respect to the laser interferometer (20), when light beams emanated from the first interferometer (21) and the second interferometer (22) are incident on a transition section (32) defined by corresponding adjacent two of the planar mirrors (31), the light beam emanated from the first interferometer (21) is incident on one of the adjacent two planar mirrors (31) and the light beam emanated from the second interferometer (22) is incident on the other of the adjacent two planar mirrors (31). Additionally, the first interferometer (21) and the second interferometer (22) alternately provide positional information to the workpiece stage (10). A method for controlling such an interferometer measuring device is also disclosed. The interferometer measuring device and the method enable an extended horizontal measurement range for the workpiece stage (10) by using the plurality of planar mirrors (31) that are joined together as well as by alternating zero-reference updating of the two interferometers (21, 22).

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 method for constructing a three-dimensional image of a sample includes producing electromagnetic radiation and directing the produced electromagnetic radiation such that it is incident on the sample at an oblique angle. The incident electromagnetic radiation is scanned in discrete increments to a plurality of discrete locations along a first direction, and at each discrete location, scanned along a second direction orthogonal to the first direction. The sample reflects a first portion of the incident electromagnetic radiation and absorbs a second portion of the incident electromagnetic radiation, and emits electromagnetic radiation responsive to the absorption. A plurality of cross-sectional images is produced from the reflected electromagnetic radiation and the emitted electromagnetic radiation, and each cross-sectional image is modified to compensate for the oblique angle. The modified cross-sectional images are then combined to create a three-dimensional image of the sample.

Optical coherence tomography light sources can be non-linear and attempts to linearize them can lead to asynchrony between the light source and A-line scans and missampling in the scans causing signal noise. Accordingly, a system and methods are provided herein to detect missampling by obtaining a plurality of interferograms; providing at least two wavenumber reference signals at different wavenumbers, wherein the wavenumber reference signals comprise attenuated or enhanced portions of each of the plurality of interferograms; aligning each of the plurality of interferograms according to one of the at least two wavenumber reference signals; and for each of the plurality of interferograms, identifying an interferogram as missampled if another of the at least two reference signals does not align with a corresponding reference signal in a statistically significant number of the plurality of interferograms. An optical element, for example, an optical notch, may be used to generate the reference signals.

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.

An optical measurement device includes: a splitter to split light into measurement light and reference light; a switch interferometer to output first interference light obtained by causing two orthogonally polarized waves of the reference light to interfere with each other, second interference light obtained by causing two orthogonally polarized waves of reflected light from a target object of the measurement light to interfere with each other, and third interference light obtained by causing the reference light and the reflected light to interfere with each other; a photoelectric converter to convert the interference light into electric signals; a digital converter to perform A/D conversion on the electric signals; and a calculation processor to obtain an optical path-length difference between the two orthogonally polarized waves of each of the reference light and the reflected light, and an optical path-length difference between the reference light and the measurement light.

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.