Generally, in accordance with the various illustrative embodiments disclosed herein, a heterodyne optical interferometer incorporates error correction elements to correct a cyclic error that may be present in an interferometric measurement. The cyclic error can be caused by various factors such as an imperfect polarization relationship between two wavelength components, deficiencies in optical propagation paths (such as light leakage), imperfect optical coatings, and/or imperfect components. The cyclic error, which typically manifests itself as erroneous displacement information characterized by a low velocity sinusoidal frequency component, can be reduced or eliminated by using birefringent optical elements and other optical elements to alter certain characteristics of one or both wavelength components and reduce light leakage components in one or more light propagation paths in the heterodyne optical interferometer.

A method for measuring the depth of the vapour cavity during an industrial machining process employs a high-energy beam. An optical measuring beam is directed towards the base of a vapour cavity. An optical coherence tomograph generates interference factors or other raw measurement data from reflections of the measurement beam. An evaluation device generates interference-suppressed measurement data, wherein raw measurement data that is generated at different times is processed together in the course of a mathematical operation. This operation can be a subtraction or a division. Slowly changing interference factors can thus be eliminated. An end value for the distance to the base of the vapour cavity is calculated from the interference-suppressed measurement data using a filter. As a result, the depth of the vapour cavity can be determined, in the knowledge of the distance at a part of the surface of the work piece that is not exposed to the high-energy beam.

What is proposed is a device (1) for optically measuring an object, comprising an interferometer (2) having a measurement arm (21), wherein the measurement arm (21) is provided for optically measuring the object, and comprising a focusing element (3) arranged within the measurement arm (21). According to the invention, the device (1) comprises a first retardation element (4) arranged within the measurement arm (21) and downstream of the focusing element (3), wherein the first retardation element (4) has a movable displacement element (42), by means of which the optical path length of the beam path of the measurement arm (21) is variable.

A rotation angle measuring device includes a light source for generating a first light beam with a first polarization direction and a second light beam with a second polarization direction; a first beam splitter for splitting the first light beam and the second light beam to generate a third light beam and a fourth light beam; an image sensor for sensing a first interference pattern generated by the first and second light beams passing through a first displacement measurement module, and sensing a second interference pattern generated by the third and fourth light beams passing through a second displacement measurement module; and a processing unit for calculating two displacement values at two different positions on a measured object according to the first and second interference patterns, in order to further calculate a rotation angle of the rotation angle measuring device relative to the measured object along a first axis.

A wear amount measuring apparatus includes a light source, a light transmission unit, a first and a second irradiation unit, a spectroscope and an analysis unit. The light transmission unit splits a low-coherence light from the light source into a first and a second low-coherence light. The first and the second irradiation units irradiate the first and the second low-coherence light to the component to receive reflected lights from the component. The light transmission unit transmits the reflected lights received by the first irradiation unit and the second irradiation unit to the spectroscope. The spectroscope configured to detect intensity distribution of the reflected lights from the first and the second irradiation unit. The analysis unit calculates a thickness difference between a thickness of the component at the first measuring point and that at the second measuring point by performing Fourier transform on the intensity distribution.

A displacement detecting device includes a first diffraction grating, a light source, a displacement detecting unit, and a light receiving unit. The displacement detecting unit includes a light flux dividing unit, a second diffraction grating, and a reference reflecting member. An incident angle of a first light flux to the first diffraction grating, a diffraction angle of the first diffraction grating, an incident angle of the first light flux to the second diffraction grating, and a diffraction angle of the second diffraction grating are angles at which a displacement amount in an optical path length of the first light flux from the light flux dividing unit to the first diffraction grating and a displacement amount in an optical path length of the first light flux from the first diffraction grating to the second diffraction grating become equal in a case where a measured member is displaced in a direction orthogonal to a measured surface.

An optical coherence tomography scanner for imaging an intraoral sample has a wavelength-tunable light source configured to generate scanning light having a range of wavelengths and a scanning probe having a scanning head. A light circulator is configured to direct the scanning light to a first sample arm having at least a first optical fiber for conveying light to the sample, to direct a sample signal, having scattered and reflected light from the sample, back from the first optical fiber, to a detector, and to direct a reference signal, having light reflected back along the first optical fiber from a partially reflective surface at the scanning head, to the detector. The detector forms a digital output signal indicative of interference of the combined sample and reference signals. A display is configured to form an image of sample features according to the digital output signal.

A space-division multiplexing optical coherence tomography apparatus and system is provided. In one embodiment, the system includes a light source, a reference arm, and a sample arm. The sample arm splits the sampling light into a plurality of sampling beams which may be scanned simultaneously onto a surface of a sample. An optical delay may be introduced into the sampling beams before scanning. A plurality of reflected light signals returned from the sample is collected. In one arrangement, the signals may be combined to produce a single reflected light signal. The reflected light signal(s) and a reference signal are combined to produce an interference signal comprising data representative of digitized images captured of the actual object. In one embodiment, a single sample arm may be used for scanning and collecting image data. A related method is also provided.

Apparatus and methods are described including a line spectrometer that receives a point of light. The line spectrometer includes a first optical element, and a second optical element configured to convert the point of light to a line of light and to direct the line of light toward the first optical element. The first optical element defines first and second surfaces, a distance between the first and second surface varying as a function of distance along the first optical element, the first optical element thereby being configured to generate first and second reflected lines of light that reflect respectively from the first and second surfaces. A detector array receives the first and second lines of light, and generates an interferogram in response thereto. A computer processor determines a spectrum of the point of light, by analyzing the interferogram. Other applications are also described.

The present invention provides a measurement apparatus for measuring a position of an object, comprising a reflecting portion provided on the object and having a surface on which reflectors configured to retroreflect light are arrayed, an optical system configured to cause first light to be incident on the surface, receive second light as reflected light of the first light, cause third light generated from the second light to be incident on the surface, and receive fourth light as reflected light of the third light, and a processor configured to determine the position of the object based on a detection result of the forth light, wherein the optical system is configured such that a displacement between optical paths of the first light and the second light is corrected by a displacement between optical paths of the third light and the fourth light.