Abstract: An interferometer and method for interferometric analysis are provided. The methodology includes generating first and second light beams from a light source, interacting the first light beam with an object under inspection, forming, from light emanating from the object under inspection in response to the interacting, an image of the light source on an image sensor, projecting the second light beam on the image on the image sensor, the combination of the light emanating from the object under inspection and the second light beam forming a collective image on the image sensor, applying a Fourier transform to the collective image formed on the image sensor, thereby forming a phase image, and isolating a wavefront map of the object under inspection from within the phase image.

Abstract: A pulsed laser system includes a modulator module configured to provide pulsed electrical signals and a plurality of solid-state seed sources coupled to the modulator module and configured to operate, responsive to the pulsed electrical signals, in a pulse mode. Each of the plurality of solid-state seed sources is tuned to a different frequency channel separated from any adjacent frequency channel by a frequency offset. The pulsed laser system also includes a combiner that combines outputs from each of the solid state seed sources into a single optical path and an optical doubler and demultiplexer coupled to the single optical path and providing each doubled seed frequency on a separate output path.

Abstract: A method for detecting shapes based on interferometric observation of an object surface subjected to narrow-band lighting. Movement of the interferometer (1) relative to the object surface (2) generates a measuring signal on a photo receiver, e.g., camera circuit (5), from which two extremely closely positioned signal frequencies (fo) and (fo+?f) are extracted. The phase difference between the two signal components is used for determining the distance and/or the change in distance. The method has a large unambiguousness range, making it possible to have a large depth measurement range, and can be used for workpieces having offset areas on the surface, wherein the measurement is not disturbed along the edges and the offset areas. The method also allows examining strongly inclined surfaces having a steep inclination such that that traditional methods based on evaluating interference lines cannot be used because of a high density of the interference lines.

Abstract: An image sensor 20A contains a photodiode array portion 21, a signal processor 22, a switching instruction part 23A and a control part 24A. Each switch SWn is provided between the corresponding photodiode PDn and the common output line L, and instructed to carry out the switching operation by the switching instruction part 23A so as to be closed, whereby the charges accumulated in the junction capacitance portion of the photodiode PDn are output to the common output line L. On the basis of the instruction from the switching instruction part 23A, the N switches SW1 to SWN carry out the switching operation so that the N switches SW1 to SWN are set to the close state in the different periods and the interval at which each switch SWn is set to the close state is equal to an integral multiple of a base period. As described above, the charge accumulation time of each of the N photodiodes PD1 to PDN is set to an integral multiple of the base period.

Abstract: A wavefront measuring apparatus for optical pickup includes: a beam splitting section; a wavefront shaping section; a beam combining section that generate interference light; an interference fringe image-acquiring section that acquires an interference fringe image including wavefront information of the light beam; and an analyzing section that analyzes a wavefront of the light beam on the basis of the interference fringe image. The analyzing section includes: an image processing section that performs a filtering process on the interference fringe image to eliminate a frequency component corresponding to the sub beam, so as to acquire the filtering-processed interference fringe image, and a wavefront analyzing section that analyzes a wavefront of the main beam on the basis of the filtering-processed interference fringe image.

Abstract: An optical characteristic measuring apparatus includes: a light source section which sweeps wavelengths of a first input light and a second input light respectively, frequencies of the first and second input lights being different from each other and polarized states of the first and second input lights being perpendicular to each other, and outputs the first and second input light; an interference section which inputs one branched light of the first and second input lights to a measuring object, makes output light from the measuring object interfere with other branched light of the first and second input lights, and outputs a plurality of interference lights; a plurality of light receiving sections which are respectively provided for the interference lights, receives the interference lights respectively, and outputs signals in accordance with optical powers of the interference lights respectively; and a low-pass filter for filtering the outputted signals.

Abstract: A method for detecting shapes based on interferometric observation of an object surface subjected to narrow-band lighting. Movement of the interferometer (1) relative to the object surface (2) generates a measuring signal on a photo receiver, e.g., camera circuit (5), from which two extremely closely positioned signal frequencies (fo) and (fo+?f) are extracted. The phase difference between the two signal components is used for determining the distance and/or the change in distance. The method has a large unambiguousness range, making it possible to have a large depth measurement range, and can be used for workpieces having offset areas on the surface, wherein the measurement is not disturbed along the edges and the offset areas. The method also allows examining strongly inclined surfaces having a steep inclination such that that traditional methods based on evaluating interference lines cannot be used because of a high density of the interference lines.

Abstract: A new and useful imaging concept is provided that is designed to improve the manner in which control information for an imaging optical system such as a lithographic imaging optical system can be generated. An imaging optical system comprises imaging optics defining a primary optical path along which a primary image is imaged, and a measurement optical path is established and includes at least part of the primary optical path. The imaging optical system is configured to obtain information from the measurement optical path for use in providing control information for the imaging optical system. Such a system is particularly useful for measuring the topography of a large region of the surface under investigation, like the entire instantaneous field of a wafer, instead being limited to a small patch or set of patches.

Abstract: An object of the present invention is to provide an electron microscope that employs a hologram of a diffraction pattern to reconstruct a microscopic image involving no imaging aberration due to image forming lenses, as well as a combined illumination lens used for such an electron microscope.

Abstract: A method for detecting shapes based on interferometric observation of an object surface subjected to narrow-band lighting. Movement of the interferometer (1) relative to the object surface (2) generates a measuring signal on a photo receiver, e.g., camera circuit (5), from which two extremely closely positioned signal frequencies (fo) and (fo+?f) are extracted. The phase difference between the two signal components is used for determining the distance and/or the change in distance. The method has a large unambiguousness range, making it possible to have a large depth measurement range, and can be used for workpieces having offset areas on the surface, wherein the measurement is not disturbed along the edges and the offset areas. The method also allows examining strongly inclined surfaces having a steep inclination such that that traditional methods based on evaluating interference lines cannot be used because of a high density of the interference lines.

Abstract: An optical tomographic imaging apparatus capable of obtaining a high resolution tomographic image rapidly. Light beams swept in wavelength intermittently and repeatedly within first and second wavelength ranges respectively are outputted simultaneously from a light source unit. If the wavelength of either one of the light beams is within a fifth wavelength range, the other light beam is not outputted. The first or second wavelength range includes at least a portion of the fifth wavelength range. Each light beam is split into measuring and reference beams by a coupler. Wavelengths of reflected beams from a measuring object when the measuring beams are irradiated on the object and the reference beams are divided by a WDM coupler. The reflected beams and reference beams are combined by an optical coupler, and each interference beam produced thereby is detected with respect to each light beam as an interference signal.

Abstract: A computer-implemented method, system, and computer program code are provided for characterizing an edge break, e.g., part features and/or geometric discontinuities that could give rise to edge sharpness, as may be encountered in a chamfer, bevel, fillet and other part features. The methodology enables to accurately and consistently determine in a manufacturing setting, for example, any applicable geometric parameter for characterizing the edge break.

Abstract: An interferometery system for making interferometric measurements of an object, the system including: a beam generation module which during operation delivers an output beam that includes a first beam at a first frequency and a second beam at a second frequency that is different from the first frequency, the first and second beams within the output beam being coextensive, the beam generation module including a beam conditioner which during operation introduces a sequence of different shifts in a selected parameter of each of the first and second beams, the selected parameter selected from a group consisting of phase and frequency; a detector assembly having a detector element; and an interferometer constructed to receive the output beam at least a part of which represents a first measurement beam at the first frequency and a second measurement beam at the second frequency, the interferometer further constructed to image both the first and second measurement beams onto a selected spot on the object to produce

Abstract: Systems and methods are described for faster processing of multiple spatially-heterodyned direct to digital holograms.

Abstract: An optical tomographic imaging apparatus capable of obtaining a high resolution tomographic image rapidly. Light beams swept in wavelength intermittently and repeatedly within first and second wavelength ranges respectively are outputted simultaneously from a light source unit. If the wavelength of either one of the light beams is within a fifth wavelength range, the other light beam is not outputted. The first or second wavelength range includes at least a portion of the fifth wavelength range. Each light beam is split into measuring and reference beams by a coupler. Wavelengths of reflected beams from a measuring object when the measuring beams are irradiated on the object and the reference beams are divided by a WDM coupler. The reflected beams and reference beams are combined by an optical coupler, and each interference beam produced thereby is detected with respect to each light beam as an interference signal.

Abstract: Preferred embodiments of the present invention are directed to systems for phase measurement which address the problem of phase noise using combinations of a number of strategies including, but not limited to, common-path interferometry, phase referencing, active stabilization and differential measurement. Embodiment are directed to optical devices for imaging small biological objects with light. These embodiments can be applied to the fields of, for example, cellular physiology and neuroscience. These preferred embodiments are based on principles of phase measurements and imaging technologies. The scientific motivation for using phase measurements and imaging technologies is derived from, for example, cellular biology at the sub-micron level which can include, without limitation, imaging origins of dysplasia, cellular communication, neuronal transmission and implementation of the genetic code.

Abstract: Systems and methods are described for recording multiple spatially-heterodyned direct to digital holograms in one digital image.

Abstract: An optical image measuring apparatus capable of speedily measuring a velocity distribution image of a moving matter.

Abstract: An improved confocal microscope system is provided which images sections of tissue utilizing heterodyne detection. The system has a synthesized light source for producing a single beam of light of multiple, different wavelengths using multiple laser sources. The beam from the synthesized light source is split into an imaging beam and a reference beam. The phase of the reference beam is then modulated, while confocal optics scan and focus the imaging beam below the surface of the tissue and collect from the tissue returned light of the imaging beam. The returned light of the imaging beam and the modulated reference beam are combined into a return beam, such that they spatially overlap and interact to produce heterodyne components. The return beam is detected by a photodetector which converts the amplitude of the return beam into electrical signals in accordance with the heterodyne components. The signals are demodulated and processed to produce an image of the tissue section on a display.

Abstract: A surface texture measuring instrument provided with a near-field measuring unit (30) including a near-field probe (33) that forms a near-field light at a tip end thereof when a laser beam is irradiated, a laser source (35) that generates the laser beam to be irradiated on the near-field probe (33), a detection element (38) that detects scattering effect of the near-field light generated when the near-field probe (33) is moved close to a workpiece (1), and an actuator (32) that displaces the near-field probe (33) and the workpiece (1) in a direction moving close to/away from each other, includes: a laser length-measuring unit (20) that measures a relative distance between a reference position and the workpiece (1) in the vicinity of the tip end of the near-field probe (33) or a relative distance between the reference position and the near-field probe (33).

Abstract: An apparatus, which includes a light source, a polarizing plate for converting the light beam to linearly polarized light, a half mirror for dividing the light beam into signal light and reference light and superimposing the signal light and the reference light on each other to produce interference light, a wavelength plate for converting the reference light to circularly polarized light, a frequency shifter for shifting a frequency of the reference light, a reference mirror which is moved by a piezoelectric element, a polarization beam splitter for extracting an S-polarized light component and a P-polarized light component from the interference light, CCDs for detecting the respective polarized light components and outputting detection signals, and portion for calculating a signal intensity of the interference light and a phase thereof based on the detection signals. An image of an object to be measured is formed based on a result obtained by calculation.

Abstract: The invention provides a novel method for absolute fringe order identification in multi-wavelength interferometry based on optimum selection of the wavelengths to be used. A theoretical model of the process is described which allows the process reliability to be quantified. The methodology produces a wavelength selection which is optimum with respect to the minimum number of wavelengths required to achieve a target dynamic measurement range. Conversely, the maximum dynamic range is produced from a given number of optimally selected wavelengths utilized in a sensor. The new concept introduced for optimum wavelength selection is scalable, i.e. from a three wavelength system to a four wavelength system, from four wavelengths to five, etc.

Abstract: Frequency-scanning interferometry is used for measuring test objects having multiple surface regions. The regions are distinguished and can be measured based on different measuring criteria. Interference data is gathered for the imageable portion of the test object from a plurality of interference patterns taken over substantially the same imageable portion at different measuring beam frequencies. The interference data is evaluated to determine topographical measures of associated points on the test object. The topographical measures are compared against a benchmark to distinguish between points on the test object that are within a first of the surface regions from points on a boundary separating the first surface region from one or more other surface regions of the imageable portion of the test object. The interference data of points within the first surface region are further evaluated to a higher accuracy.

Abstract: A method for optical tomography is adapted to measure a medium, and includes the following steps: (A) generating a two-frequency mutually correlated low-coherence beam, an optical path difference of the beam being smaller than a coherence length; (B) focusing the beam on different depth positions of the medium such that the beam becomes a signal beam after being reflected by the medium; and (C) analyzing the signal beam reflected by the medium using a signal processing unit that includes a lens and a pinhole located at a focal point of the lens so as to obtain a sectioning image of the medium.

Abstract: An apparatus for detecting the surface profile of a test object includes a light source, a beam splitter, a reflective component, a sensor, and a computing device. The light source emits a light beam. The beam splitter divides the light beam into reference and probing beams. The reference beam is reflected by the reflective component back to the beam splitter. The reflective component is configured so that components of the reflected reference beam travel at different optical path lengths to the beam splitter. The probing beam is reflected by the test object back to the beam splitter. The beam splitter combines the reflected reference and probing beams to result in a heterodyne light beam. The sensor converts the heterodyne light beam into a corresponding electrical signal. The computing device records the converted electrical signal. A method for detecting the surface profile of the test object is also disclosed.

Abstract: An optical image measuring apparatus capable of effectively obtaining a direct current component of a heterodyne signal which is composed of background light of interference light is provided.

Abstract: The invention is an apparatus and method for second harmonic optical coherence tomography of a sample comprising a laser coupled to an interferometer which has a reference arm and in a sample arm. A nonlinear crystal in the reference arm generates a second harmonic reference signal. The sample typically backscatters some second harmonic light into the sample arm. A broadband beam splitter optically coupled to the reference arm and sample arm combines the signals from the reference arm and sample arm into interference fringes and a dichroic beam splitter splits the interference fringes into a fundamental and second harmonic interference signal. A detector is optically coupled to the dichroic beam splitter detects interference fringes from which both an OCT and second harmonic OCT image can be constructed using a conventional data processor.

Abstract: Provided is an optical image measuring apparatus capable of easily changing a scanning interval of an object to be measured in a depth direction with high precision.

Abstract: A remote sensor capable of imaging vibrations at many simultaneous points using high-speed imaging cameras is disclosed. The preferred embodiment operates in heterodyne detection mode using a single camera to capture signals to recover multi-pixel vibrations. One alternative embodiment employs two cameras and homodyne optical I/Q detection. A second alternative embodiment uses a single camera and temporally phase shifted local oscillator to also carry out homodyne optical I/Q detection. The disclosed sensors are capable of scalability to large numbers of pixels and can capture vibration frequencies over a wide range.

Abstract: An apparatus operable to record a spatially low-frequency heterodyne hologram including spatially heterodyne fringes for Fourier analysis includes: a laser; a beamsplitter optically coupled to the laser; an object optically coupled to the beamsplitter; a focusing lens optically coupled to both the beamsplitter and the object; a digital recorder optically coupled to the focusing lens; and a computer that performs a Fourier transform, applies a digital filter, and performs an inverse Fourier transform.

Abstract: Systems and methods are described for spatial-heterodyne interferometry for transmission (SHIFT) measurements. A method includes digitally recording a spatially-heterodyned hologram including spatial heterodyne fringes for Fourier analysis using a reference beam, and an object beam that is transmitted through an object that is at least partially translucent; Fourier analyzing the digitally recorded spatially-heterodyned hologram, by shifting an original origin of the digitally recorded spatially-heterodyned hologram to sit on top of a spatial-heterodyne carrier frequency defined by an angle between the reference beam and the object beam, to define an analyzed image; digitally filtering the analyzed image to cut off signals around the original origin to define a result; and performing an inverse Fourier transform on the result.

Abstract: Systems and methods are described for reduction of reference hologram noise and reduction of Fourier space smearing, especially in the context of direct-to-digital holography (off-axis interferometry). A method of reducing reference hologram noise includes: recording a plurality of reference holograms; processing the plurality of reference holograms into a corresponding plurality of reference image waves; and transforming the corresponding plurality of reference image waves into a reduced noise reference image wave.

Abstract: A fundamental concept of the invention consists thus in the fact that temporally variable reference and object light bundles are generated for object detection, the bundles are superimposed at a light receiver and detected beam by beam and the penetration of the object by selected beams is determined in response to the temporal variability of the superimposed beams.

Abstract: An interferometric measuring method and device for measuring the shape of, or the distance to, surfaces are provided, in which light is generated, modulated with respect to its frequency, conducted to both an object surface and a reference surface, brought to interference, and conducted to a photodetector, and, to detect the particular distance, a phase of the photodetector signal is evaluated. A simple, rugged configuration, with the capability of taking a high-resolution measurements in the context of a large unambiguity range, is achieved in that the phase is considered in at least two different instants with the wavelengths that correspond on the basis of the frequency modulation, and the results are fed to the evaluation.

Abstract: Systems and methods are described for spatial-heterodyne interferometry for reflection and transmission (SHIRT) measurements. A method includes digitally recording a first spatially-heterodyned hologram using a first reference beam and a first object beam; digitally recording a second spatially-heterodyned hologram using a second reference beam and a second object beam; Fourier analyzing the digitally recorded first spatially-heterodyned hologram to define a first analyzed image; Fourier analyzing the digitally recorded second spatially-heterodyned hologram to define a second analyzed image; digitally filtering the first analyzed image to define a first result; and digitally filtering the second analyzed image to define a second result; performing a first inverse Fourier transform on the first result, and performing a second inverse Fourier transform on the second result.

Abstract: An interferometric measuring device for measuring the shape of a surface of an object having a radiation source which emits a short-coherent radiation, a beam splitter for forming an object beam which is directed via an object light path to the object, and a reference beam which is directed via a reference light path to a reflective reference plane, and having an image converter which picks up the radiation reflected back by the surface and the reference plane and brought to interference, and sends it to an analyzing device for determining a measuring result pertaining to the surface, the optical length of the object light path being changed relative to the optical length of the reference light path for analyzing the interference peak.

Abstract: The present invention relates to systems and methods of field-based light scattering spectroscopy. These systems and methods provide for the diagnosis of tissue by measuring the size and distribution of cellular characteristics. Field based measurements provide phase information resulting from the interaction of scatterers within the material and the incident wavefront. These measurements can be used to provide three dimensional images of tissue.

Abstract: An optical arrangement of the Michelson interferometer type having a measuring arm for measuring optical properties of at least two mutually spaced regions in an optically transparent and/or diffusive object. A reference arm has a path length variation unit which generates a periodic change in path length for the radiation in the reference arm. Arranged in the measuring arm upstream of the object is a detour unit. The detour unit imparts a detour which is larger than at least one second measuring beam into at least one measuring beam. The detour unit selects a detour to be equal to a distance between regions to be measured in the object. Using the optical arrangement the object is irradiated with the aid of a number of measuring beams corresponding to the number of regions. In each case two measuring beams have an optical path difference which corresponds to a geometrical distance between two regions.

Abstract: Interferometric method(s) and apparatus for accurately measuring aspherical surfaces and transmitted wavefronts, particularly of the type having relatively large diameters and departure employed in lithographic applications used in the fabrication of integrated circuits and the like. An interferometer, preferably of the Fizeau type, is provided with at least one aspherical reference surface that is positioned adjacent the test optic. The test optic can be either rotationally or non-rotationally symmetric, a reflecting aspherical test surface, or a refracting system that is illuminated by an aspherical wavefront or produces a transmitted aspherical wavefront. In any case, the departure of the test optic from its intended performance is ultimately determined. The aspherical reference surface is illuminated by an aspherical wavefront provided by upstream optics structured so that the incident aspherical wavefront propagates normal to the aspherical reference surface across its entire surface.

Abstract: Apparatus for eliminating sign uncertainty in a coherent phase generated carrier demodulator in a multi-channel sensor system has a downconverter array arranged to separate the in-phase component I and the quadrature phase component of the sensor output for each channel. A coordinate transformer uses the in-phase component and quadrature phase component to calculate an arctangent for the phase angle for each channel. A digital signal processor adds 180° to each arctangent calculation for which the tangent is a negative number.

Abstract: An apparatus for measuring the surface shape of the surface to be measured of an optical system to be measured includes a rotary stage holding the optical system to be measured thereon and rotatable about the optical axis of the optical system to be measured, a device for detecting the rotation azimuth of the rotary stage, an irradiating optical system for sequentially applying a coherent light beam to the plurality of measuring diameter positions of the surface to be measured of the optical system to be measured held on the rotary stage, a light receiving element for detecting the reflected light of the coherent light beam from the surface to be measured as an interference signal, and a calculating system for effecting the measurement of the surface shape of the surface to be measured on the basis of the result of the detection of the interference signal at each of the plurality of measuring diameter positions of the surface to be measured and the result of the detection by the rotation azimuth detecting dev

Abstract: A method of obtaining a spectrum in a Fourier transformation infrared spectrophotometer includes the following steps: sampling a set of data while a movable mirror of the Fourier transformation infrared spectrophotometer performs a reciprocal movement, wherein the set of data constitutes an interferogram; judging whether the interferogram is reliable or not by comparing the shape of the interferogram with a shape of another interferogram or shapes of other interferograms obtained through neighboring measurement of measurements; accumulating the data of interferograms that are judged to be reliable; and constituting an absorption spectrum using a Fourier transformation method based on the accumulated data. Since unreliable data are adequately avoided from the data accumulation, the reliability of the accumulated data is assured, and an accurate absorption spectrum can be obtained.

Abstract: Frequency-scanning interferometry is applied to common-path interferometers for measuring topographical features of test objects. A reference element located adjacent to a test object functions as both a beamsplitter and a reference surface. A first portion of a measuring beam reflects from the reference surface of the reference element as a reference beam, and a second portion of the measuring beam transmits through the reference element to and from a surface of the test object as an object beam. Both beams are conveyed along a common path to a detector that records a plurality of intensity variations produced by constructive and destructive interference between localized portions of the object and reference beams associated with different transverse coordinates on the test object surface.

Abstract: The invention relates to a method for detecting objects. To this end, temporally variable reference light beams and object light beams are generated. The beams are superimposed at a light receiver and detected beam-by-beam, and the penetration of the object by selected beams is determined in response to the temporal variability of the superimposed beams.

Abstract: In a phase interference detecting system with use of an interferometer, a height from a reference surface on a measurement surface is detected by receiving interference components of reflection lights from the reference surface and a measurement surface, which lights are divided from a laser beam and are modulated with a frequency being different therefrom, i.e., by irradiating only one laser beam. A light detector is constructed with a line type sensor for receiving the interference components of the reflection lights, and has a plurality of pixel groups for common use of a measurement surface and a plurality of pixel groups for exclusive use of a reference surface, which are provided at both thereof.

Abstract: Interferometer for measuring a phase difference between a reference beam (37) and an object beam (36′) transformed by an optical element (10), comprising light source means (2), an optical device (3) and detection means (4) in a detection plane (34). The optical device (3) comprises a first light conductor (30) having a first output surface (31) that generates an object beam (36) having a spherical wave front and a second light conductor (32) having a second output surface (33) that generates a reference beam (37) having a spherical wave front, directed onto the detection plane (34), wherein the set-up of the first light conductor (30) and the optical element (10) is such that the transformed object beam (36′) interferes with the reference beam (37) in the detection plane (34).

Abstract: A shape measuring apparatus is provided, which is capable of accurately measuring the shape of an observed surface of an object to be measured and which can be designed to be compact in size and light in weight. An optical reflected image from an observed surface of an object to be measured and an optical reflected image from a reference surface are interfered with each other to generate interference light. The interference light is dispersed into at least three beams, which are shifted in phase by respective predetermined phase shifting amounts. At least three interference fringe images are simultaneously captured by at least one image pickup device which is smaller in number than the interference fringe images.

Abstract: A method for interferometric measurement comprises emitting waves onto a reference surface (1) and onto a measured object (2), which each reflects a part of the emitted waves, and receiving both the reflected parts of the waves by the same receiver (4). In the receiver the parts of the waves generate a representation of the measured object (2) in the form of an interferogram, from which the form of the measured object (2) is determined. The emitted waves comprise waves of three well-defined wavelengths &ngr;1, &ngr;2 and &ngr;3, where &ngr;1≠&ngr;2≠&ngr;3, which wavelengths are chosen to substantially satisfy the mutual relation &ngr;1=(&ngr;2.&ngr;3)/(2.&ngr;3−&ngr;2) and generate an interferogram each in the receiver (4).

Abstract: Measurement of an internal structure of a sample is performed using interference of light within a short time. Through a first optical frequency comb generator 5 using a first signal having a frequency f1 and generating reference light having a sideband every interval of the frequency f1 and a second optical frequency comb generator 6 using a second signal having a frequency f2 and generating object light having a sideband every interval of the frequency f2, and sweeping of emission timing between the reference light and the object light, by changing a phase difference or frequency difference between the first signal and second signal, and detecting a change in light intensity of the interference light due to the interference, operation of detecting the interference position is made at a high speed.

Abstract: An interferometric measuring device for detecting the shape, roughness or distance of surfaces is described. The interferometric measuring device has a modulation interferometer in which two partial beams are formed, one of which is shifted in its light phase or light frequency with respect to the other by a modulation device. The surface is measured with a measuring probe which is connected to the modulation interferometer and in which a measuring beam and a reference beam are formed, and an interference pattern which is analyzed in a connected receiving unit is formed from the measuring beam and the reference beam.