92 results about "Phase shifting algorithm" patented technology

The invention provides a structured light three-dimensional surface shape perpendicular measuring method using a continuous scanning mode. When a measured objected is continuously scanned by an image surface of a structured light projector in the perpendicular direction, N frames (N>=3) N-step phase shift sinusoidal gratings are sequentially and cyclically imaged on the measured objected, a CCD camera synchronously obtains sinusoidal grating images subjected to object height modulation through a semi-transparent semi-reflective mirror in the same direction. Fourier transformation processing is conducted on the collected image set pixel by pixel along the time axis or the N-step phase shift algorithm is applied to continuous N frames (N>=3) phase shift sinusoidal grating images, so that distribution of modulation degrees of the sinusoidal grating images on the surface of the object is obtained. A three-dimensional surface shape of the object is rebuilt through a corresponding relation, which is obtained in advance through calibration, between the modulation degrees and the height. The continuous-scanning structured light three-dimensional surface shape perpendicular measuring method has the advantages of perpendicular measurement and three-dimensional surface shape high-precision measurement.

An optical system wave aberration calibration apparatus and a calibration method of using the apparatus to test an error relate to the optical measurement technology field. The current optical system can not evaluate whether the test error satisfies a detection precision requirement before detecting an optical element and the current optical system can not select an appropriate phase shifting algorithm to process collected data. The above problems can be solved by using the invention. The method comprises the following steps: a light splitting system emits two beams of common-optical-path orthogonal-line polarized lights and after being emitted by a polarization splitting prism, the polarized lights are coupled to a reference fiber through a coupling lens; two spherical waves diffracted by the reference fiber perform interference and an interferogram can be acquired; a photoelectric detector is used to collect the interferogram and to transmit to a computer; piezoelectric ceramics areused to carry out phase shifting and the photoelectric detector collects the interferogram several times; a thirteen step phase shifting algorithm is used to carry out data processing analysis so as to obtain the test error. By using the invention, ultrahigh precision testing of the optical system wave aberration can be realized.

The invention relates to a thin strip continuous casting billet surface defect sinusoidal grating phase shifting detection device and method. Sinusoidal grating projection and a spatial phase shifting algorithm are combined, strip steel surface defects are detected by combining defect profile measurement and height measurement, grating image gray scale distribution is directly converted to phase distribution, interference of oxide scales, water films and surface high temperature is effectively restrained, reliable and fast recognizing and positioning of surface defects of moving thin strip continuous casting billets in the high temperature state are achieved, three-dimensional shapes of the casting billet surface defects can be visually displayed, digitized assessment of the surface quality of the moving casting billets is achieved, and detection is stable, accurate and high in reliability. In addition, the thin strip continuous casting billet surface defect sinusoidal grating phase shifting detection device and method have an important meaning for improving the thin strip continuous casting billet surface defect detection automation degree, reducing production cost and improving production efficiency.

A method and apparatus for inspecting patterned transmissive substrates, such as photomasks, for unwanted particles and features occurring on the transmissive as well as pattern defects. A transmissive substrate is illuminated by a laser through an optical system comprised of a laser scanning system, individual transmitted and reflected light collection optics and detectors collect and generate signals representative of the light transmitted and reflected by the substrate. The defect identification of the substrate is performed using only those transmitted and reflected light signals, and other signals derived from them, such as greyscale representations and image features. Defect identification is performed using a pattern inspection algorithm by comparing image feature representations of the present substrate with an idealized representation thereof, and using an advanced phase shift algorithm that accounts for particular types of expected anomalies.

The invention discloses a phase defect detection system and method based on a short-phase dry-dynamic Twyman interferometer. The system comprises two parts including a short-phase dry polarization light source and a polarization Twyman interferometer. The method comprises the following steps: firstly, enabling a light beam emitted by a short-phase laser device to pass through a polaroid and a half-wave plate and enter a Michelson interference structure; emitting a pair of linearly polarized light with orthogonal polarization directions and coupling the pair of linearly polarized light into a polarization-maintaining optical fiber; taking the linearly polarized light as a light source of a main interferometer; then adjusting a PZT (Piezoelectric Transducer) to be matched with phase difference of an interference cavity of an interferometer main body part; compensating phase delay between reference light and testing light; finally, acquiring four interference figures with the phase shifting amount difference of pi/2 in sequence by utilizing a polarization camera; solving through a phase-shifting algorithm to obtain information of phase defects. The phase defect detection system and method, disclosed by the invention, have the advantages of large view field, high resolution ratio, good shock resistance and simplicity in operation and can be used for real-time and high-precision detection of the phase defects of an optical element.

The invention discloses a 3D morphology recovery method combining phase shift interference with vertical scanning interference, and the method comprises the steps: controlling piezoelectric ceramic microstep vertical scanning through an upper computer program, converting an interference pattern collected by each scanning step into a digital signal, and storing the digital signal in a computer; discriminating the position of the maximum light intensity of each pixel in the interference pattern as a zero optical path difference position corresponding to the pixel through employing the extremum method, recording the number of a frame where the zero optical path difference position is located, and preliminarily calculating the height information of morphology according to correlated formulas; extracting the phase information of interference fringes through employing a five-step phase shift method, combining with a preliminary calculation result, and precisely recovering the 3D morphology according to correlated formulas. The method solves a problem that the phase change between the adjacent pixels cannot exceed 2*phi in a phase shift algorithm, is high in measurement precision, is simple in algorithm and is high in practicality.

The invention discloses a method and a device for measuring three fields independently and synchronously in real time by using three-dimensional digital speckle pattern interferometry. The measurement device comprises three independent digital speckle pattern interferometric light paths. The method comprises the following steps of: synchronously acquiring three images of a measured object which is undeformed as reference images and three real-time images of the measured object which is deformed by using the three independent digital speckle pattern interferometric light paths, and subtracting the reference images from the corresponding real-time images to obtain three real-time speckle pattern interferometric fringe patterns; accurately acquiring a plurality of speckle pattern interferometric fringe patterns with equal phase shift, and extracting three phase images of the measured object which is deformed by using a phase shift algorithm; unpacking the three phase images by using a computer to further obtain three continuous phase unwrapping patterns; and calculating three-dimensional displacement components of the measured object by using the phase unwrapping patterns respectively. Three displacement sub-fields can be measured synchronously and independently in real time, and the method and the device are applied to dynamic problems as well as the accurate phase measurement of three-dimensional displacement sub-fields.

The invention discloses a fast phase unwrapping algorithm which is composed of four key parts including an N-step phase shifting algorithm, making Mask, solving the fringe grade and phase unwrapping.The fast phase unwrapping algorithm concretely comprises the steps: (1) the N-step phase shifting algorithm is applied to solve the wrapping phase; (2) N sinusoidal fringe patterns are utilized to make Mask; (3) the wrapping phase and the connected domain marking algorithm are utilized to solve the fringe grade; and (4) phase unwrapping is performed according to the fringe grade so as to obtain the absolute phase for three-dimensional reconstruction. According to the algorithm, phase solving and unwrapping can be performed by only projecting N sinusoidal phase shifting fringe patterns, and thephase recovery effect is equivalent to that of the conventional method and the algorithm has great advantage in computing speed so that the algorithm is suitable for the application field having therequirement of fast three-dimensional measurement.

The invention discloses a system and a method for real-time ultrasonic elastography displacement estimation. The method includes: firstly, pre-estimating to-be-processed two frames of radio-frequency signals by means of the two-dimensional matching algorithm to obtain a displacement field U(u,v), wherein displacement variation exists between the two frames of radio-frequency signals; secondly, setting a priori estimate tp which is equal to the axial displacement Ut(u) of the displacement field U(u,v); thirdly, keeping displacement of the two frames of radio-frequency signals within a 1/4 wavelength; and finally, calculating phase shift according to the priori estimate tp and the lateral placement Ut(v) of the displacement field U(u,v) to obtain the axial displacement field u(t). By means of the system and the method for real-time ultrasonic elastography displacement estimation, the problem of phase aliasing in traditional phase shifting algorithm is solved, and estimation precision is effectively improved on the premise of giving consideration to the arithmetic speed.

The invention discloses a software phase locking method applicable to single-phase and three-phase power systems and belongs to the technical field of grid synchronization. The design thought mainly comprises the following steps: determining a single-phase or three-phase phase-locked loop mode by virtue of a state of a control switch K, and enabling a single-phase voltage to generate two paths oforthogonal signals such as u alpha and u beta by virtue of a phase-shifting algorithm or enabling a three-phase voltage to generate the u alpha and u beta by adopting Clark coordinate transformation;enabling the u alpha and u beta to pass through a positive-sequence component extraction link and a complex band-pass filter so as to obtain a network voltage fundamental positive-sequence component;performing Park transformation to obtain u d and u q, feeding the difference of the u q and 0 into a PI controller to be regulated, adding the output quantity of the PI controller and a rated angularfrequency omega f of the power grid so as to obtain a starting phase angle by using an integrator, and obtaining the final phase angle from the starting phase angle by using a comparator and a selector. The phase locking method provided by the invention can be applicable to the single-phase and three-phase power systems, and the frequency and phase angle of the network voltage can be accurately tracked under asymmetric distorted network voltages.

The invention provides a loop radial shearing N-step phase-shift interferometer based on the polarization phase-shift principle. The loop radial shearing N-step phase-shift interferometer is composed of a polarization modulation system, a loop radial shearing system, an N-step phase-shift system and an imaging system. Measured wavefront generated after a measured light beam passes through a measured element enters the polarization modulation system and then is changed into linearly polarized light. The linearly polarized light enters the loop radial shearing system and then is divided into two beams of orthogonal linear polarized light in the horizontal polarization direction and the vertical polarization direction respectively, and the two beams of orthogonal linear polarized light pass through the N-step phase-shift system to form two beams of circular polarized light in the levorotation direction and the dextrorotation direction respectively. A rotation polarization analyzer achieves N-step phase shift. Finally, the imaging system collects N interference fringe diagrams, and then the phase-shift algorithm is adopted for analyzing the interference fringe diagrams to calculate the wavefront phase position of the reconstructed light beams. According to the loop radial shearing N-step phase-shift interferometer based on the polarization phase-shift principle, no reference mirrors are needed, a light path structure is simple, and anti-vibration capability is good; the N-step phase-shift technology is adopted for recovering the wavefront, and phase position extraction data processing speed and algorithm precision are improved.

The invention discloses a three-dimensional measurement method combining a two-step phase shift method with phase encoding. The three-dimensional measurement method is composed of three key parts including a two-step phase shift principle, a phase fusion method and a phase encoding principle. The method is advantaged in that compared with a traditional phase shift algorithm, the two-step phase shift algorithm can greatly reduce measurement errors and can be well used for actual measurement, the phase information of two wrapped phase diagrams is directly fused, and only one wrapped phase diagram needs to be subjected to phase unwrapping, so the error rate is reduced to a certain extent; compared with a method based on intensity coding, the phase coding method is insensitive to surface contrast, ambient light and camera noise, and has high robustness.

The invention discloses a phase nonlinear error compensation method in a surface structured light three-dimensional imaging technology. The method comprises the following steps that: a four-step phase shift algorithm is employed to obtain phase information, and the phase information is substituted into a ratio of second harmonic to first harmonic, and a higher harmonic component ratio containing a gamma value is obtained; a harmonic component is obtained according to discrete Fourier transform, the gamma value is generally between 0 and 3, the gamma value which is not equal to 1 is pre-coded into a fringe image, a modulated harmonic component is obtained, and the pre-modulated gamma value of each pixel in the fringe image projected by a projector is calculated; and the pre-modulated gamma value obtained by calculation and the reflectivity are loaded into a projection fringe algorithm of the projector, and a camera and projector gray value modeling and least square approximation technology are utilized to obtain the accurate gamma value of each pixel in the fringe image projected by the projector, and the original fringe image of the projector is corrected through the accurate gamma value. According to the method of the invention, the error of the image collected by a camera can be greatly reduced.

The invention relates to a sensitivity test system and method based on a wavelength phase shifting algorithm. Lasers emitted by a wavelength tuning laser are reflected back from a to-be-tested piece and a reference mirror in an optical path system and have interference, a CCD receives interference lasers returned from the to-be-tested piece and the reference mirror and records interference light intensity. The position of the reference mirror is adjusted by piezoelectric ceramic I according to hardware phase shifting principle, and surface form W1 of the to-be-tested piece is measured; surface form W2 of the to-be-tested piece is measured by changing wavelength according to the wavelength phase shifting algorithm. Interference cavity length when|W2-W1| is the minimum is determined. The position of the to-be-tested piece is adjusted by piezoelectric ceramic II, and the moving distance L of the piezoelectric ceramic II is recorded by a laser Doppler interferometer. Surface form W3 of the to-be-tested piece after the piezoelectric ceramic II moves for L is analyzed on the basis of the wavelength phase shifting algorithm, whether the difference between the surface forms W3 and W2 measured before and after adjustment of the piezoelectric ceramic II is consistent with the moving distance L of the piezoelectric ceramic II is analyzed, so that the wavelength phase shifting algorithm precision is obtained, and the purpose of calibration of measurement precision is achieved.

The invention discloses a microstructure rapid measurement method suitable for white light scanning interference, and the algorithm comprises the steps: controlling piezoelectric ceramics to carry out time sequence vertical scanning within a certain scanning length according to a micro step pitch through a software program of an upper computer, and collecting and storing one interferogram in a computer when each step is moved; carrying out adaptive median filtering processing on the stored time sequence interferogram; finding out the position of the maximum light intensity value of each pixel point in the time sequence interferogram by adopting a hypersymmetric search method, recording the frame number of the interferogram where the position is located, and preliminarily calculating the height information of the morphology according to a related formula; and extracting phase information of the interference fringes by using a seven-step phase shift algorithm, and unwrapping according to a related formula in combination with a preliminary calculation result to accurately recover the microstructure of the tested sample. The method solves the problems that noise singular point interference and adjacent pixel point phase change cannot exceed 2pi in a phase shift algorithm, effectively reduces the influence caused by scanning errors, and has the characteristics of high measurement precision, simple algorithm, high applicability and the like.

The invention discloses synthetic phase shifting digital holographic microscopy. A large quantity of low-resolution phase shifting holograms is synthesized to form a high-resolution phase shifting hologram through ingenious design of a synthetic phase shifting algorithm for solving a linear system of equations, then the high-resolution phase shifting hologram is subjected to inverse transformation, and a complex amplitude image with high resolution and signal-to-noise ratio is reproduced. Compared with traditional phase shifting digital holography, the synthetic phase shifting digital holographic microscopy can improve the holographic imaging resolution remarkably; compared with synthetic aperture digital holographic microscopy, the synthetic phase shifting digital holographic microscopy has the advantage that the high-resolution hologram can be acquired accurately without a splicing fusion process of multiple holograms.

The invention relates to an instantaneous phase-shifting secondary interference confocal measuring device and a method, belonging to the field of measurement of ultra-precise three-dimensional microstructure surface topography. The measuring device comprises a synchronous phase-shifting module, wherein three sides of the module are respectively provided with identical interference signal receivers, and each interference signal receiver comprises a collecting objective lens, a detection pinhole and a photodetector; the measuring device controls the three interference signal receivers to synchronously collect output signal under a first confocal measuring condition and a second confocal measuring condition, and the confocal micro-displacement measurement is completed by a three-step phase-shifting algorithm. The invention integrates the characteristics of phase-shifting secondary confocal technology and synchronous phase-shifting technology, realizes the ultra-precise high-speed dynamic measurement and has the advantages of strong anti-vibration capability and low phase-shifting error.

The invention discloses a modulation method for a cascaded PWM (pulse-width modulation) rectifier. The modulation method for the cascaded PWM rectifier comprises the following steps of: extracting the modulation signal of each H bridge unit in real time; calculating to obtain the carrier wave phase updating value of a cascading unit; updating the carrier wave phase; and taking the updated value as the practical carrier wave signal of the unit. Because each unit load of the cascaded PWM rectifier can not be completely consistent, each H bridge modulation model can not be completely consistent according to the power equivalence principle, and therefore, the corresponding switching subharmonic can not be offset when a traditional carrier wave phase-shifting algorithm is adopted. On the basis of the novel modulation algorithm adopted by the modulation method disclosed by the invention, influence on net side current due to inconsistent modulation signals can be effectively lowered, and primary harmonic and the WTHD (weighted total harmonic distortion) value of the net side current are lowered.

The invention discloses a moving object three-dimensional measurement method based on color fringe projection. The method comprises the steps: S1, establishing a fringe projection three-dimensional measurement system; S2, projecting the color stripes to the surface of the moving object by a projector, and generating deformed color stripes through the modulation effect of the surface of the movingobject; S3, synchronously collecting all deformed color stripes by a camera, and extracting sine stripes in a red channel and cosine stripes in a blue channel; S4, respectively calculating a truncation phase of the sine fringe and a truncation phase of the cosine fringe by using a three-step phase shift algorithm; S5, performing phase unwrapping on the sine fringe truncation phase and the cosine fringe truncation phase to obtain a sine fringe absolute phase and a cosine fringe absolute phase; S6, calculating the average phase of the sine fringe absolute phase and the cosine fringe absolute phase, and eliminating the phase error caused by the motion of the object; and S7, converting the average phase into height information, and reconstructing the three-dimensional shape of the moving object.

The invention discloses a double-wavelength time domain phase demodulation method based on equivalent wavelength pi/(2k) phase shift. According to the method, in the double-wavelength simultaneous phase-shifting interference detection, the extraction of an equivalent wavelength phase in a double-wavelength moire fringe is realized; phase shifting is carried out by taking pi/(2k) of the equivalentwavelength as a phase shifting stepping quantity, the moire fringe interference light intensity information is subjected to additive and multiplicative processing, a time domain phase-shifting interference processing method and a frequency spectrum gating technology are combined, and therefore an equivalent wavelength pi/(2k) phase-shifting interval interferogram is obtained; interferogram sequences with a pi/2 phase-shifting interval are extracted from the interferogram sequence at an interval of k frames o as to obtain an equivalent wavelength pi/2 phase-shifting interval interferogram; anda phase-shifting algorithm is utilized for processing, the extraction of the equivalent wavelength phase information of the moire fringe under the zero-carrier-frequency introduction condition is finally realized, so that the problem that a traditional moire fringe processing method in the dual-wavelength simultaneous phase-shifting interference is dependent on the space-domain carrier frequency can be solved.

The invention discloses a compact type collimating common optical path phase shifting digital holography imaging system and method. The system comprises a laser, a plane mirror, a microobjective, a pinhole, a collimating lens, a line polarizing film, an unpolarized splitting prism and a coating film reflector, and the coating film reflector is connected with piezoelectric ceramics; a picture sensor collectors a hologram, wherein the hologram is obtained by interference of object waves irradiated to objects and reference optical waves reflected by the coating film reflector, a two-dimensional rotation regulating frame with the unpolarized splitting prism is adjusted for adjusting the object light wave angle, the piezoelectric ceramic is controlled to achieve reference optical wave phase shifting, the hologram is analyzed and rebuilt through a phase shifting algorithm and a diffraction propagation method , and an imaging result is obtained. The system can adjust the two-dimensional rotation regulating frame by compactly arranging the coating film reflector driven by the piezoelectric ceramic and the unpolarized splitting prism, and the piezoelectric ceramic is controlled to obtain the holography, so that the imaging stability, practicability and reliability are effectively improved, and the system is simple and easy to obtain.

The invention discloses a mirror surface object three-dimensional measurement method based on sine pulse width modulation stripes. The measurement method comprises the following steps: firstly, generating sine pulse width modulation four-step phase shift diagrams of three frequencies by utilizing a computer; respectively projecting the four-step phase shift diagrams of each frequency to the surface of a measured mirror surface object; using an optical system for defocusing, and converting sine pulse width modulation stripes into standard sine stripes; after the standard sine stripes are projected to the surface of the measured mirror surface object, collecting the standard sine stripes by an imaging system, and obtaining a wrapping phase through a four-step phase shift algorithm; and finally, performing phase unwrapping on the wrapped phase, obtaining the height of the measured mirror surface by directly establishing the relation between the absolute phase and the height, and recovering the three-dimensional morphology. According to the invention, the non-linear problems of projection and the camera are eliminated, the measurement precision is improved, the calculation is simple, the control is flexible, the operation is simple and convenient, the robustness on the measurement of a mirror surface object is high, and the method has potential application prospect and practical value in precision measurement.