113 results about "Heterodyne interferometer" patented technology

The present invention provides a multi-wavelength interference real-time absolute distance measurement device on the basis of femtosecond optical comb synchronization frequency locking. The multi-wavelength interference real-time absolute distance measurement device on the basis of femtosecond optical comb synchronization frequency locking comprises: a multi-wavelength generator on the basis of the femtosecond optical comb synchronization frequency locking configured to emit a plurality of high-frequency stable object wavelength lasers; a heterodyne interferometer configured to receive lasers outputted by the multi-wavelength generator after the femtosecond optical comb synchronization frequency locking, returning measurement light and reference light after generation of interference through the heterodyne interferometer being coupled in single mode fibers by lens focusing to form mixed multi-wavelength heterodyne interference signals; and a synchronization phase demodulation module configured to separate the mixed multi-wavelength heterodyne interference signals obtained by the heterodyne interferometer through wavelength demodulation to obtain interference signals corresponding to each wavelength and perform synchronization phase measurement processing of the interference signals corresponding to each wavelength to finally obtain an accurate absolute distance value. The multi-wavelength interference real-time absolute distance measurement device on the basis of femtosecond optical comb synchronization frequency locking is high in traceability of values, high in measurement precision, large in non-fuzziness measuring range, fast in update rate and easy to measurement on site in real time, and is applicable to the fields of the industrial production, the equipment manufacture and the large-size precision measurement.

The invention relates to a heterodyne interferometer measurement system for measuring displacement and a measuring method thereof. The measurement system comprises a workbench reflector set and a laser heterodyne interferometer; the workbench reflector set comprises a first plant reflector disposed on the lateral side of the workbench and parallel with an optical axis, and a second plant reflector having certain angle with the optical axis; and the laser heterodyne interferometer comprises a polarization slitting prism, a cube corner prism, a reference plane reflector having certain angle with the optical axis, and two quarter-wave plates. The measuring method comprises the following steps of: allowing a reference beam and a measuring beam generated by a laser passing through the polarization slitting prism to respectively enter a photoelectric conversion element after multiple reflections and transmissions, processing to obtain an optical path difference (OPD), and then obtaining Z-axis displacement Z of the workbench. The invention needs not to use the plane reflectors disposed at two sides of a projection objective lens, resulting in simple structure; and needs not to increase extra size of the projection objective lens at X-axis direction. The cost of the measurement system is reduced due to less number of the used plane reflectors.

A heterodyne interferometer includes a light source, an optical system, and a signal generator including at least two light-receiving elements that respectively output a first signal and a second signal. The signal generator generates a third signal and a fourth signal of which phases are respectively shifted by 90° from phases of the first signal and the second signal, generates a first periodic signal by adding a signal that is obtained by multiplying the first signal and the second signal to a signal that is obtained by multiplying the third signal and the fourth signal, and generates a second periodic signal by subtracting a signal that is obtained by multiplying the first signal and the fourth signal from a signal that is obtained by multiplying the second signal and the third signal.

A Pound-Drever-Hall frequency stabilizing system of a dual-cavity dual-frequency solid laser device comprises the dual-cavity dual-frequency solid laser device, two independent heterodyne interferometer systems, two frequency regulators and an F-P (Fabry-Perot) optical resonant cavity. The optical resonant cavity is used as frequency stabilizing reference, the two independent heterodyne interferometer systems are used for detection to obtain two channels of error signals, the two frequency regulators are driven, and two working frequencies of the dual-cavity dual-frequency solid laser device are simultaneously locked at two resonance frequencies of the F-P optical resonant cavity. The F-P optical resonant cavity is used as the frequency stabilizing reference, the two working frequencies of the dual-cavity dual-frequency solid laser device are stabilized simultaneously, the laser frequency stability is higher than 10<-10>, and the Pound-Drever-Hall frequency stabilizing system can be widely applied to fields of interferometry for absolute distances of synthesis waves, generation of THz waves and the like.

The invention discloses a double-shaft micro-electromechanical system (MEMS) scanning-based heterodyne interference system and a double-shaft MEMS scanning-based method, relates to a quick scanning-based laser heterodyne interferometer system and a quick scanning-based laser heterodyne interferometer method, and solves the problems that the operation wavelength of the conventional cross-polarization heterodyne interferometer technology is a visible light wave band and shaking errors are large. The scheme is that: 2 mu m polarization orthogonal laser is subjected to beam splitting by a beam splitter prism to form a transmitted beam and a reflected beam, wherein the reflected beam serving as a reference intermediate frequency signal is transmitted to a computer, S light in the transmission beam is reflected, P light is transmitted, passes through a one fourth wave plate, an MEMS oscillating mirror and an F-theta lens, passes through a to-be-tested sample cell, returns according to the original optical path and is mixed with the P light; and a mixed beam serving as a measurement intermediate frequency signal is sent to the computer, and is processed by the computer so as to obtain the physical quantity information of a to-be-tested sample. The system and the method are suitable for the detection field of infrared optical materials.

This invention discloses one interference signal test system based on double direction Mach interometer, which comprises distribution fiber sensor and signal test circuit, wherein, the sensor comprises first detector, second detector, light source and three couplers; the said interference signalphi(t) to first detector time t1 difference from second detector time t2+t3 to get vibration point O real position according to the time lag.

The invention discloses a nonlinear-error-free laser heterodyne interferometer system for angle measurement, wherein the nonlinear-error-free laser heterodyne interferometer system comprises a single-frequency laser source, an acousto-optical frequency shift unit, an optical interference device, a planar mirror which moves along with the movement of a measured member, and a phase detecting device, wherein the single-frequency laser source and the acousto-optical frequency shift unit can operate for generating an incident light beam which has no frequency aliasing and has certain frequency difference and is spatially separated. Under the function of the optical interference device, the incident light beam is reflected twice by the planar mirror. Finally the reflected incident light beam is input to the phase detecting device. The yaw angle of the measured member is determined by means of change amount of the phase difference. Between generation of a measuring light beam with certain frequency difference from the acousto-optical frequency shift unit and interference, the transmission paths are separated and are spatially independent. The nonlinear-error-free laser heterodyne interferometer system prevents a periodical nonlinear error which is caused by polarized light with two frequencies in the interference optical path, thereby effectively improving measurement accuracy. The nonlinear-error-free laser heterodyne interferometer system can be widely used for geometric quantity precise measurement in the fields of numerical control machine tools, military industry, spaceflight, etc.

The invention discloses a biaxial MEMS reflective galvanometer and F-Theta lens-based linear scanning system used for a laser heterodyne interferometer, which relates to a scanning system using an optical lens and solves the problems that the conventional optical scanning system has single applicable wavelength and cannot realize linear and uniform-speed scanning. The linear scanning system comprises a laser, a polarization beam splitter prism, a 1/4 wave plate, a biaxial MEMS reflective galvanometer, a triplet F-Theta lens set, a high reflection mirror and a photoelectric detector, wherein the biaxial MEMS reflective galvanometer is positioned at the position of a system focal length of the triplet F-Theta lens set. The biaxial MEMS reflective galvanometer and F-Theta lens-based linear scanning system used for the laser heterodyne interferometer is suitable for the scanning system of the laser heterodyne interferometer.

The invention discloses a common-path heterodyne interferometer based on the phase shift of a low-frequency-difference acousto-optic frequency shifter. The common-path heterodyne interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter comprises a light beam adjusting unit, a low-frequency-difference phase shifting unit, a light beam combining unit, a common-path interference unit and an area array detector unit. The light beam adjusting unit is used for adjusting output lasers of a laser device into two laser beams with identical powers. The low-frequency-difference phase shifting unit is used for adjusting the frequencies of the two laser beams obtained by the light beam adjusting unit to obtain two laser beams with the output difference frequency being a low difference frequency lower than 100 Hz. The light beam combining unit is used for carrying out beam combination on the two laser beams output by the low-frequency-difference phase shifting unit. The common-path interference unit is used for dividing the lasers combined by the light beam combining unit into common-path measuring light and reference light so as to generate interference. The area array detector unit is used for collecting the interference. According to the common-path heterodyne interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter, heterodyne interference phase shift of the acousto-optic frequency shifter is adopted to avoid that moving parts exist in the interferometer, the measurement accuracy is improved, the anti-interference performance is good, the anti-interference capacity is improved through the common path and the influences of the self-errors of a system light path are lowered through the common path.

The invention discloses a heterodyne point diffraction interferometer based on the phase shift of a low-frequency-difference acousto-optic frequency shifter. The heterodyne point diffraction interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter comprises a light beam adjusting unit, a low-frequency-difference phase shifting unit, a point diffraction unit and an area array detector unit. The light beam adjusting unit is used for adjusting output lasers of a laser device into two laser beams with identical powers. The low-frequency-difference phase shifting unit is used for adjusting the frequencies of the two laser beams obtained by the light beam adjusting unit to obtain two laser beams with the output difference frequency being a low difference frequency lower than 100 Hz. The point diffraction unit is used for dividing the lasers adjusted by the low-frequency-difference phase shifting unit into measuring light and reference light so as to generate interference. The area array detector unit is used for collecting the interference. According to the heterodyne point diffraction interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter, heterodyne interference phase shift of the acousto-optic frequency shifter is adopted to effectively avoid that moving parts exist in the interferometer, the measurement accuracy is improved, the anti-interference performance is good, the low-frequency-difference heterodyne interferometer and the area array detector unit carry out consecutive collection, more abundant information can be obtained, phase position can be solved precisely, and noise influences can be avoided.

A novel technique using an acousto-optic modulator (AOM) as part of a heterodyne interferometer which measures optical path differences between a test signal and a reference signal is disclosed. An array of distinct frequencies are used to drive the AOM, yielding a spatially dispersed array of frequency-shifted subaperture beams of the test signal which are interfered with the wavefront to be measured and then combined with the dispersed reference signal. The frequency shifting of the AOM allows a single detector to collect the beams for signal processing to determine a measurement of the wavefront.

A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X_R and measurement (or target) fiducial X_M are reflected back and are then detected by photodiodes. The measured phase changes Δφ_R and Δφ_m resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

In a wafer thickness measuring apparatus and a method thereof, detection values are obtained from a sample piece (for example, a wafer chip) at a plurality of measurement points thereon by first and second detectors for absolute measurement of distances, and at the same time, measurement values of the fluctuations, for relative measurement of distances, are obtained by the optical heterodyne interferometer, and those measurement values are memorized as a plurality of measurement data being related with those measurement values. When measuring the thickness of a wafer, the measurements are performed at measurement points on the wafer which has a front surface and a reverse surface in height lying within the height of the sample piece, on which such a correspondence is obtained, thereby obtaining the detection values of the first and second detectors. Searching conversely from those detection values by referring the correspondence data, the respective detection values are converted into the data of the relative fluctuations therefrom upon the basis of the thickness of the sample piece, thereby obtaining the relative amounts of fluctuation in positions (i.e., the distances) upon the basis of the thickness of the sample piece, respectively. Then, by conducting addition and/or subtraction of the fluctuation amount on the front surface and the reverse surface from the thickness of the sample piece as a reference, it is possible to calculate out the thickness of the wafer to be measured.

A high-precision heterodyne interferometer measures relative displacement by creating a thermally-insensitive system generally not subject to polarization leakage. By using first and second light beams separated by a small frequency difference (Deltaf), beams of light at the first frequency (f0) are reflected by co-axial mirrors, the first mirror of which has a central aperture through which the light is transmitted to and reflected by the second mirror. Prior to detection, the light beams from the two mirrors are combined with light of the second and slightly different frequency. The combined light beams are separated according to the light from the mirrors. The change in phase (Deltaphi) with respect to the two signals is proportional to the change in distance of Fiducial B by a factor of wavelength (lambda) divided by 4pi (DeltaL=lambdaDeltaphi1/(4pi)). In a second embodiment, a polarizing beam splitting system can be used.

The invention discloses a heterodyne interferometer based on the phase shift of a low-frequency-difference acousto-optic frequency shifter. The heterodyne interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter comprises a light beam adjusting unit, a low-frequency-difference phase shifting unit, a beam expanding unit, a light beam combining unit and an area array detector unit. The light beam adjusting unit is used for adjusting output lasers of a laser device into two laser beams. The low-frequency-difference phase shifting unit is used for adjusting the frequencies of the two laser beams obtained by the light beam adjusting unit to obtain two laser beams with the output difference frequency being a low difference frequency lower than 100 Hz. The beam expanding unit is used for expanding the diameters of the two laser beams output by the low-frequency-difference phase shifting unit to be equal to the size of a surface to be measured and using the expanded two laser beams as reference light and measuring light respectively. The light beam combining unit is used for enabling the measuring light returned from the surface to be measured and the reference light to be combined to generate interference. The area array detector unit is used for collecting the interference. According to the heterodyne interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter, heterodyne interference phase shift of the acousto-optic frequency shifter is adopted to effectively avoid that moving parts exist in the interferometer, the measurement accuracy is further improved, and the anti-interference performance is good.

The invention provides a two-channel Doppler heterodyne interferometer. The Doppler heterodyne interferometer aims at achieving the measurement of two central wavelength target spectral lines. The interferometer comprises an interferometer entrance pupil, a collimating system, a beam splitter prism, a blazed grating component, a stripe imaging system and a detector array. The core component of the beam splitter prism is a depolarization beam splitting film in a 50-to-50 half-reflective and half-transparent mode. The stripe imaging system comprises a front lens group and a back lens group, and a narrow-band filter switching device is arranged between the collimating system and the beam splitter prism. The blazed grating component includes that a first blazed grating, a second blazed grating, a third blazed grating and a fourth blazed grating are respectively arranged on a reflected light way. A Littrow angle is formed by the working face normals of the four blazed gratings and the corresponding incident optical axis, wherein, a working grating is formed by the first blazed grating and the third blazed grating, and another working grating is formed by the second blazed grating and the fourth blazed grating so that the interference of individual wavelength is achieved. The corresponding grating working surface center of the working grating forms an optical path difference of the interferometer along the difference between the distances of the center of the beam splitter prism.

The invention discloses an absolute distance dynamic measurement system based on a swept-frequency interferometer, and a measurement method of the absolute distance dynamic measurement system, and belongs to the field of absolute distance dynamic measurement. The invention aims at solving a problem that a conventional measurement system is low in measurement precision under the impact of vibration. The system comprises two parts, wherein one part is used for carrying out the FSI absolute distance measurement, and the other part is used for carrying out the real-time monitoring of a target displacement through employing an additional heterodyne interferometer which consists of a single frequency laser and an acoustic optical modulator, thereby eliminating the impact from a Doppler effect introduced by the change of an optical path of a measurement path. The method comprises the step: obtaining an absolute distance (shown in the description) through employing the signals detected by a first detector, a second detector and a balance detector in the measurement system. A signal obtained by the second detector is used for correcting an error caused by the instable modulation frequency of the acoustic optical modulator.

A laser heterodyne interferometer idle stroke error automatic compensator belongs to the technical field of laser measurement. A polaroid sheet and a laser length measuring instrument are arranged in sequence at a co-optical axis at one side of a polarization splitting prism opposite to a reference prism; the polaroid sheet is fixed at an electric rotary platform; the electric rotary platform, the laser length measuring instrument and an air refracting index measuring instrument are respectively connected with a control unit of the laser heterodyne interferometer by a control bus; a probe sensor of the air refracting index measuring instrument is arranged between the polarization splitting prism and a measurement prism. The compensator can effectively reduce effects by the idle stroke error on measurement results during real-time measurement.

A differential-phase polarization-sensitive optical coherence tomography system includes a polarized heterodyne interferometer for generating a reference beam to be reflected by a movable mirror unit, and a signal beam to be reflected by an imaging plane in a specimen. The interferometer further generates a first electrical signal output corresponding to first linear polarized waves of the reference and signal beams, and a second electrical signal output corresponding to second linear polarized waves of the reference and signal beams. A differential amplifier receives the first and second electrical signal outputs, and generates a differential signal output therefrom. A data acquisition unit is used to measure amplitudes of the first and second electrical signal outputs and the differential signal output. A computing unit computes the amplitudes measured by the data acquisition unit to determine a reflectivity, a phase retardation, and a fast axis angle of the imaging plane in the specimen.

The invention relates to the laser field, in particular to a method for realizing double-frequency output lasers. The method for realizing double-frequency output lasers comprises the following steps that: a first microchip laser and a second microchip laser are pumped by a pump light source, so as to ensure that the first microchip laser and the second microchip laser have optical thickness difference in cavity length, and furthermore, the range of the optical thickness difference is between 0 and 0.1 mm. The first microchip laser and the second microchip laser are a single whole through optical cement, gluing or deepened optical cement. Two single-longitudinal-mode output fundamental wave or frequency doubled laser output lasers with little difference in wavelength are formed through the pumping of the same pumping source, so as to obtain a microchip-type double-frequency laser which is used for double-frequency laser heterodyne interferometers and replaces the common double-frequency He-Ne laser. As the invention puts forward a novel method for realizing double-frequency output lasers, the double-frequency laser in small size can be obtained.

The invention discloses a method for detecting adhesion between spatial heterodyne interferometer gratings, which relates to the field of optical instruments. The method comprises the steps that: a heterodyne interferometer to be adhered is vertically placed on a transparent platform of an adhesion regulation mechanism; laser lights output by a laser are subjected to diffuse reflection of an integrating sphere to form a uniform surface light source and are incident to an alignment system to form parallel lights which are incident on the heterodyne interferometer to be adhered; interference fringes are formed on an exit end of the heterodyne interferometer to be adhered, wherein the interference fringes are received by a CCD after passing through an image system and are displayed on a computer in real time; fx interference fringes formed on the whole image surface width w1 of the CCD by a special wavelength light source lambda 0 after the special wavelength light source lambda 0 passes through an interference system are calculated; a photosensitive adhesive is uniformly coated on the heterodyne interferometer to be adhered, micro-adjustment is performed on oblique angles of alpha and beta of two arm gratings, and the interference fringes on the whole image surface of the CCD are read till f changes to fx to enable the two gratings to be positioned; and two adhered gratings are cured. The method for detecting adhesion between the spatial heterodyne interferometer gratings solves the technical problem of difficult accurate control over the grating oblique angle in the adhesion process of the spatial heterodyne interferometer. The error of the oblique angels of the two arm gratings can be controlled in 2.5 seconds.

The present invention relates to a scanning microscope using a heterodyne interferometer, which can be used for mapping or imaging complex optical parameters such as physical structures and material properties of a sample under test. The heterodyne interferometer is designed to provide in- and quadrature-phase interference signal which can be used for extracting the phase and amplitude change induced on the probe beam. The phase and the amplitude of the probe beam, which is reflected from or transmitted through the sample, are modified by the physical structures and material properties of the sample. Therefore, by scanning the probe beam, local variations of the phase and amplitude can be mapped, and, thereby, three-dimensional microscopic physical structures and material properties can be imaged by processing the phase and amplitude values.

Provided is a measuring apparatus that includes a heterodyne interferometer; a first detector configured to detect interference light between reference light and light to be detected, and output a measured signal; a second detector configured to detect interference light between the first and the second light, and output a reference signal; an oscillator configured to generate a standard signal having a frequency corresponding to a frequency shift amount; a first synchronization detector configured to perform synchronous detection of the measured signal and the standard signal; a second synchronization detector configured to perform synchronous detection of the reference signal and the standard signal; a first processing unit that determines a phase difference between the measured signal and the reference signal based on the outputs of the first synchronization detector and the second synchronization detector; and a second processing unit that determines the position of the object based on the phase difference.