Embodiments of systems and methods for measuring a surface topography of a semiconductor chip are disclosed. In an example, a method for measuring a surface topography of a semiconductor chip is disclosed. A plurality of interference signals each corresponding to a respective one of a plurality of positions on a surface of the semiconductor chip are received by at least one processor. The plurality of interference signals are transformed by the at least one processor into a plurality of spectrum signals each corresponding to the respective one of the positions on the surface of the semiconductor chip. The spectrum signals are classified by the at least one processor into a plurality of categories using a model. Each of the categories corresponds to a region having a same material on the surface of the semiconductor chip. A surface height offset between a surface baseline and at least one of the categories is determined by the at least one processor based, at least in part, on a calibration signal associated with the region corresponding to the at least one of the categories. The surface topography of the semiconductor chip is characterized by the at least one processor based, at least in part, on the surface height offset and the interference signals.

Apparatus and methods are described for calibrating an optical system that is used for measuring optical properties of a portion of a subjects body. During a calibration stage, a front surface of a calibration object (300) is illuminated, light reflected from a plurality of points on the calibration object (300) is detected, and intensities of the light reflected from the plurality of points on the calibration object (300) are measured. During a measurement stage, the portion of the subjects body is illuminated, and light reflected from the portion of the subjects body is detected. Measurements performed upon the light that was reflected from the portion of the subjects body are calibrated, using the measured intensities of the light reflected from the plurality of points on the calibration object (300). Other applications are also described.

An optical coherence tomography (OCT) measurement system for precision measurement of a translucent sample is provided. The system includes an optical coherence tomography (OCT) imaging system comprising a broadband light source, a reference path with reference path length, and sample path with a beam scanning assembly and an imaging lens assembly; a sample positioning assembly including an immersion bath for positioning the translucent sample within an immersion bath; a position assembly for locating the translucent sample within a field of view (FOV) of the OCT imaging system; an immersion lens assembly associated with the imaging lens assembly configured to eliminate an air to bath refractive interface between a distal surface of the OCT imaging lens including an immersion tip and a surface of the bath; a first set of calibration parameters that relate a position of a scanning beam at an imaging plane to drive signals of the scanning assembly; and a second set of calibration parameters for relating an optical path length or optical path length variation of the scanning beam at an imaging plane to the position of the scanning beam or to the drive signals of the scanning assembly.

Embodiments of systems for classifying interference signals are disclosed. In an example, a system for classifying interference signals includes an interferometer including a light source and a detector, and at least one processor. The interferometer is configured to provide a plurality of interference signals each corresponding to a respective one of a plurality of positions on a surface of a semiconductor chip. A spectrum of the light source is greater than a spectrum of white light. The at least one processor is configured to classify the interference signals into a plurality of categories using a model. Each of the categories corresponds to a region having a same material on the surface of the semiconductor chip.

The present inventive concept relates to an optical coherence tomography (OCT)-based intraoral scanner calibration device including: a light source; an optical coupler for splitting the path of light irradiated from the light source in first light and second light; a reference part for generating reference light from the first light split by the optical coupler; a sample part for generating measurement light from the second light split by the optical coupler; and a signal generator for generating an OCT image from the reference light and the measurement light.

An interferometer includes a first interferometer arm and a second interferometer arm. A first central beam, originating from a central image point of an image, passes through the first interferometer arm. A second central beam, originating from the central image point, passes through the second interferometer arm. The first central beam and the second central beam are superimposed and generate a k.sub.perpendicular=0 interference at a superposition point. A first light beam perpendicular to the first central beam, originating from an image point of the image, passes through the first interferometer arm. A second light beam perpendicular to the second central beam, originating from the image point, passes through the second interferometer arm. The first light beam and the second light beam overlap at the superposition point. At the superposition point, a wave vector component of the first light beam opposes a wave vector component of the second light beam.

A method for calibrating electromagnetic radiation-based three-dimensional imaging includes: obtaining (501) a calibration imaging result at least partly on the basis of electromagnetic waves received from a calibration artifact, forming (502) calibration data on the basis of the calibration imaging result and a known thickness profile of the calibration artifact, and correcting (503), with the aid of the calibration data, an imaging result obtained at least partly on the basis of electromagnetic waves received from a sample to be imaged. The calibration artifact includes layers, for example Langmuir-Blodgett films, having pre-determined thicknesses and stacked on each other so as to achieve the pre-determined thickness profile of the calibration artifact. A three-dimensional imaging system configured to carry out the method.

A compensation optical unit (30) for a measurement system (10) for determining a shape of an optical surface (12) of a test object (14) by interferometry generates a measuring wave (44), directed at the test object, with a wavefront that is at least partly adapted to a target shape of the optical surface from an input wave (18). The unit includes first (32) and second (34) optical elements disposed in a beam path of the input wave. The second optical element is a diffractive optical element configured to split the input wave into the measuring wave and a reference wave (42) following an interaction with the first optical element. At least 20% of a refractive power of the entire compensation optical unit is allotted to the first optical element, and this allotted refractive power has the same sign as the refractive power of the entire compensation optical unit.

Interferometric measurement signals are detected by a single optical interferometric interrogator for a length of a sensing light guide and an interferometric measurement data set corresponding to the interferometric measurement signals is generated. The interferometric measurement data set is transformed into a spectral domain to produce a transformed interferometric measurement data set. The transformed interferometric measurement data set is compared to a baseline interferometric data set to identify a time-varying signal corresponding to a time-varying disturbance. The baseline interferometric data set is representative of the sensing light guide not being subjected to the time-varying disturbance. A compensating signal is determined from the time-varying signal and used to compensate at least a portion of the interferometric measurement data set for the time-varying disturbance as part of producing a measurement of the parameter.

A method that corrects an error in positioning in a positioning mechanism by using a measurable length value measured by a laser interferometer and a measured value for spatial coordinates measured by the positioning mechanism. The method includes a measurement step in which a retroreflector affixed to a displacer is displaced to a plurality of measurement points, and the measured length value and the measured value at each of the measurement points is acquired; and a parameter calculation step in which a correction parameter is calculated based on the measured value, the measured length value, and the coordinates of a rotation center of the tracking-type laser interferometer. A first correction constant is applied to the measured length value for each measurement line, and a second correction constant different from the first correction constant is applied to the coordinates of the rotation center of the interferometer for each measurement line.