235 results about "Phase function" patented technology

A new way of mixing instrumental and digital means is described for the general field of wave front sensing. The present invention describes the use, the definition and the utility of digital operators, called digital wave front operators (DWFO) or digital lenses (DL), specifically designed for the digital processing of wave fronts defined in amplitude and phase. DWFO are of particular interest for correcting undesired wave front deformations induced by instrumental defects or experimental errors. DWFO may be defined using a mathematical model, e.g. a polynomial function, which involves coefficients. The present invention describes automated and semi-automated procedures for calibrating or adjusting the values of these coefficients. These procedures are based on the fitting of mathematical models on reference data extracted from specific regions of a wave front called reference areas, which are characterized by the fact that specimen contributions are a priori known in reference areas. For example, reference areas can be defined in regions where flat surfaces of a specimen produce a constant phase function. The present invention describes also how DWFO can be defined by extracting reference data along one-dimensional (1D) profiles. DWFO can also be defined in order to obtain a flattened representation of non-flat area of a specimen. Several DWFO or DL can be combined, possibly in addition with procedures for calculating numerically the propagation of wave fronts. A DWFO may also be defined experimentally, e.g. by calibration procedures using reference specimens. A method for generating a DWFO by filtering in the Fourier plane is also described. All wave front sensing techniques may benefit from the present invention. The case of a wave front sensor based on digital holography, e.g. a digital holographic microscope (DHM), is described in more details. The use of DWFO improves the performance, in particular speed and precision, and the ease of use of instruments for wave front sensing. The use of DWFO results in instrumental simplifications, costs reductions, and enlarged the field of applications. The present invention defines a new technique for imaging and metrology with a large field of applications in material and life sciences, for research and industrial applications.

What is disclosed is a system and method for determining arterial pulse transit time (PTT) for a subject. In one embodiment, time-series signals are received for each of a proximal and distal arterial site of a subject's body which represent blood volume changes in the microvascular tissue at each site. A proximal and distal analytic signal is obtained which has a first component being a waveform of the respective time-series signal and a second component being a transform of the respective waveform. A phase function is determined for the first and second components of each analytic signal. The phase function obtained for the proximal waveform is then subtracted from the phase function obtained for the distal waveform to get a phase difference. The phase difference is analyzed with the subject's heart rate to determine an arterial pulse wave transit time between the two proximal and distal sites.

We present a method and apparatus for local and superficial measurement of the optical properties of turbid media. The depth probed is on the order of 1 transport mean free path of the photon. The absorption coefficient, reduced scattering coefficient and the phase function parameter γ=(1−g₂)/(1−g₁) are optical parameters computed from a single measurement of the spatially resolved reflectance close to the source. Images of superficial structures of the medium can be obtained by performing multi-site measurements. An important application of this technique is the characterization of biological tissues, for example for medical diagnostic purposes. Measurements on biological tissues can be achieved using a probe of diameter less than 2 mm, and the average volume probed is on the order of 1 mm³. Separate images of absorption and tissue structure can be achieved with a resolution of approximately one transport mean free path of the considered tissue.

The invention relates to the filed of optical aspheric surface accurate measurement, in particular to a real-time partial zero compensation optical aspheric surface profile detection method. Current zero measurement method only can measure a dynamic range of several wavelengths so that the dynamic range of detection is small. The dynamic range of measurement in the invention is determined by three parts, consisting of a compensation lens, a phase function yGGH which corresponds to a computer generated hologram kinoform loaded by an LCSLM (Liquid Crystal Spatial light Modulator), and a residual phase function yRES. According to the real-time partial zero compensation optical aspheric surface profile detection method, a partial zero compensation technology is adopted, the LCSLM loaded with the computer generated hologram is served as a partial zero compensation element, and a convergent lens playing a role in compensation and an interference fringe analyzing technology are combined, therefore, the dynamic range of measurement is greatly improved, and detection to the profiles of the large aspheric surfaces can be implemented.

The invention relates to a method for generating three-dimensional imaging original echoed signals of chromatography synthetic aperture radars, which comprises the following steps: taking a three-dimensional image containing backward plural scattering coefficients of imaging area targets in a rectangular coordinate system OXYZ as the input, carrying out three dimensional fourier transform on the three-dimensional image and converting an image signal to a rectangular coordinate system wave-number domain; converting signals in Kx, Ky and Kz domains to be signals in Kw, Ku and Kv domains according to the method of converting the rectangular coordinate system to a spherical coordinate system; introducing imaging geometrical relationships among same imaging area of chromatography synthetic aperture radars by multiplying three dimensional filter function H2 (Kw, Ku and Kv); introducing a transmission signal form by the multiplication of a two-dimensional inverse Fourier transform function and a reference phase function; and at last, by W direction process and other operations, obtaining the three-dimensional imaging original echoed signals of chromatography synthetic aperture radars, which contains a carrier frequency. The method can be used for generating three-dimensional imaging original echoed signals of side-looking, downward-looking, forward-looking, backward-looking and downward side-looking chromatography synthetic aperture radars, and has high echo generating efficiency and easy realization of modularization.

The invention discloses an improved algorithm based on parameter estimation and compensation of a quadratic phase function, and belongs to the technical field of signal and information processing. Thealgorithm performs range walk correction on slow time-range frequency domain echo signal considering range walk and Doppler diffusion through Keystone transform, and then eliminates a coupling relation between the range frequency f and the slow time tn in a second-order phase item corresponding to the acceleration in a narrow-band condition; meanwhile, a folding factor corresponding to the blindspeed is searched, a folding factor compensation item is constructed to correct the range walk caused by the blind speed; then the target acceleration is estimated by using the quadratic phase function, and a second-order phase item corresponding to the acceleration is constructed to compensate Doppler diffusion of the echo signal; and finally, long-term phase-coherent accumulation is performed soas to realize high-speed weak target detection of bistatic radar. The method disclosed by the invention is high in operation speed, stable in performance and applicable to detection of weak targets with a low signal-to-noise ratio and difficultly estimated target parameters.

Methods and apparatus for imaging a phase or amplitude that characterizes a scattered field emanating from a physical medium. A local probe is stepped to a plurality of successive probe positions and illuminated with an illuminating beam, while a specified phase function is imposed on a reference beam relative to the illuminating beam. A field associated with the scattered field is superimposed with the reference beam and the detection of both yields a detected signal which is recorded as a function of probe position in order to obtain a hologram. The holograph is transformed, filtered, and retransformed to generate an image. Alternatively, the illuminating beam may directly illuminate successive positions of the physical medium.

To effectively reduce a measurement error in a parameter indicating two-dimensional spatial distribution of a state of polarization generated by variations in retardation of a birefringent prism pair due to a temperature change or other factors, while holding a variety of properties of an imaging polarimetry using the birefringent prism pair. By noting that reference phase functions φ₁(x, y) and φ₂(x, y) are obtained by solving an equation from each vibration component contained in an intensity distribution I(x, y), the reference phase functions φ₁(x, y) and φ₂(x, y) are calibrated concurrently with measurement of two-dimensional spatial distribution S₀(x, y), S₁(x, y), S₂(x, y), and S₃(x, y) of Stokes parameters.

The invention provides a method for measuring object deformation by time-domain multi-wavelength heterodyne speckle interference. The method combines a time-domain speckle interference measurement technology, a heterodyne interference measurement technology and a multi-wavelength measurement technology. Multi-wavelength is introduced for expanding measurement scope; heterodyne is introduced for ensuring measurement precision; and the time-domain technology can directly provide a phase function for a time-varying field. The method has the advantages of simplifying an object deformation detecting system, using two lasers with different central wavelengths, realizing multi-wavelength measurement and expanding the measurement scope.

A stray-light tolerant LIDAR measurement system. The system comprises an interferometer assembly having a continuous-wave laser source, a photodetection arrangement and optical components. The laser source comprises a laser-light-generating component, a downstream optical phase modulator and a control unit connected to the modulator to deliver a control signal corresponding to a pseudo-noise signal defined by a predetermined phase function. The interferometer assembly comprises an evaluation unit which is coupled to the interferometric photodetector assembly to detect the detector signals of same and to determine the presence and/or movement of particles and/or objects from the detector signals wherein, in the case of two wavelengths emitted from the laser light generating components, the detector signals are detected separately in two wavelength regions, and the phase function has a predetermined step-like time course and the evaluation unit scans the detector signals in synchrony with the timing of the steps of the phase function.

The invention relates to a fiber grating which can realize any target response, which belongs to fiber communication, optical sensor and other relative light signal processing fields. The product is a fiber grating of sampling structure realized with phase model scanning method; the period and phase function of the initial end of the fiber grating, As, Phi s (z) and A s (z) are period, phase function and apodization function of any given fiber grating initial end. And it can acquires distance Zk from the K ultraviolet exposure position to the sample fiber grating initial end and the amplitude Ak of refraction rate modulation leaded in at the Zk. The character of the invention is: its reflection spectrum has multi-channel type, and some special reflection peak in them has the demanded target reflection response, or has the character of target phase shift.

The invention belongs to the technical field of digital signal processing, in particular relates to a harmonic spectrum interpolation correction analysis method of a power network. The method provides the method for using the interpolation correction method to eliminate the phase change to further correct the spectrum through the analysis of the reasons of the spectrum leakage. The method utilizes the windowed interpolation spectrum analysis method to estimate the changing phase and utilizes the estimated result to construct a corresponding anti-phase function, the constructed anti-phase function is multiplied by a discrete sequence which is generated by Fourier inverse transformation in a time domain, and the multiplied discrete new sequence is carried out the Fourier transformation again, thereby achieving the spectrum correction effect. The analysis, the simulation and the experiment results can show that the method effectively improves the precision of the harmonic spectrum analysis of the power network during the non-synchronous sampling simultaneously when verifying the effectiveness of the method of the invention.

A variable near-null compensator for measuring aspheric surfaces by subaperture stitching includes a pair of counter-rotating CGH phase plates, each of the phase plates having a phase function including two terms Z5 and Z7 of Zernike polynomials. The phase plates are mounted on a pair of precision rotary center-through tables, wherein rotational axes of the pair of precision rotary center-through tables coincide with the optical axes of the phase plates. A figure metrology apparatus includes a wavefront interferometer, the test mirror mount, the near-null compensator and the mechanical adjustment components therefor. The optical axis of the near-null compensator coincides with the optical axis of the interferometer. A method for measuring aspheric surfaces by subaperture stitching includes the steps of mounting the test mirror, measuring the subapertures with the figure metrology apparatus, and finally processing the data by stitching.

A system and method for efficient phase error correction in range migration algorithm (RMA) for synthetic aperture radar (SAR) systems implemented by making proper shifts for each position dependent phase history so that phase correction can readily be performed using the aligned phase history data during batch processing. In its simplest form, the invention (44) is comprised of two main parts. First (60), alignment of the phase error profile is achieved by proper phase adjustment in the spatial (or image) domain using a quadratic phase function. Second (62), the common phase error can be corrected using autofocus algorithms. Two alternative embodiments of the invention are described. The first embodiment (44a) adds padded zeros to the range compressed data in order to avoid the wrap around effect introduced by the FFT (Fast Fourier Transform). This embodiment requires a third step (64): the target dependent signal support needs to be shifted back to the initial position after phase correction. The second embodiment (44b) uses the range compressed data without padded zeros. Instead, an aperture of greater length needs to be generated by the Stolt interpolation. In this embodiment, the third step (64) of shifting the signal support back can be eliminated.

A method for an automatic equalization of sound pressure levels in at least one listening location, where the sound pressure is generated by a first and at least a second loudspeaker, comprising supplying an audio signal of a programmable frequency to each loudspeaker, where the audio signal supplied to the second loudspeaker is phase-shifted by a programmable phase shift relative to the audio signal supplied to the first loudspeaker, and where the phase shifts of the audio signals supplied to the other loudspeakers thereby are initially zero or constant; measuring the sound pressure level at each listening location for different phase shifts and for different frequencies; providing a cost function dependent on the sound pressure level; and searching a frequency dependent optimal phase shift that yields an extremum of the cost function, thus obtaining a phase function representing the optimal phase shift as a function of frequency.

The invention belongs to the technical field of digital signal processing such as seismic exploration data processing and electronic signal processing, and particularly relates to a method for performing two-dimensional filtering to a digital signal. The method comprises the following steps: collecting data gathers of the digital seismic signal; performing Hilbert transformation to the data gathers of the digital seismic signal to obtain cosine phase function gathers and instantaneous envelope gathers of the digital seismic signal; conducting the two-dimensional filtering on the cosine phase function gathers; performing corresponding multiplication to the cosine phase function gathers after two-dimensional filtering and the instantaneous envelope gathers; and outputting the data gathers of the digital seismic signal after the noise, the interfering signal as well as the aliasing phenomenon are eliminated, so as to achieve the purpose of fidelity processing of the digital seismic signal.

The invention discloses a multi-angle forward scattering transmittance meter, which comprises a transmitting terminal, a receiving terminal and a control system, wherein the transmitting terminal comprises a modulation circuit and a light source transmitting unit; the receiving terminal comprises photoelectric conversion units and a signal processing circuit; the light source transmitting unit emits a light pulse with a fixed frequency; the emitted light is received by three photoelectric conversion units arranged in a forward scattering direction, and converted into an electric signal after being scattered by atmosphere under the action of the modulation circuit; a weak tested signal is detected through the signal processing circuit and the tested signal is collected through an A/D (alternating/direct) chip, and corresponding meteorological visibility can be calculated by an ARM (Advanced RISC (Reduced Instruction-Set Computer) Machines) embedded control system. According to the invention, different scattering phase factors correspond to different scattering phase functions so that the visibility precision is improved; a scattering signal is received by three scattering angles with 20, 35 and 50 degrees; the fault of a photoelectric detector is judged by comparison of three visibility values and the reliability of a visibility meter is improved.

The present invention discloses a multi-channel aerosol scattering absorption measuring instrument, comprising a light path device, a detection device and a gas path device. The light path device supplies three different wavelengths of laser entering the detection device in sequence; the detection device is provided with photoelectric detectors at multiple angles for measurement, so as to reduce the measurement error of aerosol scattering coefficient; the gas path device comprises a sample loading unit, a calibration unit and a sample discharging unit; and a light source from the light path device and a gas flow from the gas path device enter the photoacoustic cavity of the detection device respectively and are detected by a control unit. The aerosol scattering absorption measuring instrument of the present invention is characterized by multi-channel, multi-angular, full-scale and direct measurement of scattering phase function and absorption coefficient of aerosol particles, combines the function of synchronously acquiring the optical parameters of an aerosol (such as scattering coefficient, extinction coefficient, visibility, transmittance, single scattering albedo, etc.), and achieves the integrated on-line detection of different optical parameters of an aerosol with high automation degree and good stability.

A method processes an optical image. The method includes providing a measured magnitude of the Fourier transform of a two-dimensional complex transmission function. The method further includes providing an estimated phase term of the Fourier transform of the two-dimensional complex transmission function. The method further includes multiplying the measured magnitude and the estimated phase term to generate an estimated Fourier transform of the two-dimensional complex transmission function. The method further includes calculating an inverse Fourier transform of the estimated Fourier transform, wherein the inverse Fourier transform is a spatial function. The method further includes calculating an estimated two-dimensional complex transmission function by applying at least one constraint to the inverse Fourier transform.

The invention discloses a transformer winding operating state diagnosis method. The method includes following steps: collecting vibration signals of each testing point of a transformer winding; performing Fourier transformation to the vibration signals to obtain a vibration frequency response curve of the transformer winding; performing inverse Fourier transformation to obtain a free vibration signal of the transformer winding; decomposing the free vibration signal into a plurality of intrinsic mode function components; performing Hibert transformation to obtain Hibert transformation values of the intrinsic mode function components; constructing analytic functions corresponding to each intrinsic mode function component and corresponding Hibert transformation value, and calculating slope of a phase function corresponding to each analytic function, wherein the slopes are intrinsic frequencies of each order of the transformer winding; and judging the state of the transformer winding according to changing of the intrinsic frequencies. By the transformer winding operating state diagnosis method, the operating state of the transformer winding can be accurately and efficiently judged, problems can be found conveniently and timely to maintain a transformer.

The invention provides a Monte Carlo simulation method for underwater uplink laser communication. The Monte Carlo simulation method for underwater uplink laser communication comprises the steps that the initial coordinates of photons are determined, that is, the initial quantity of the photons is obtained, a Gaussian light source of laser is sampled, and an initial light source is generated; a next coordinate position is calculated according to the previous photon coordinate position,that is, a random free step length of photons is generated, an initial scattering angle is generated by a scattering phase function, a random azimuth angle is determined, and an initial transmission direction cosine of the photons is determined; and whether the photons are scattered in the next step is judgedaccording to different heights of the photons. According to the Monte Carlo simulation method for underwater uplink laser communication, scattering and weight attenuation of photons in the transmission process are simulated, the scattering positions and weights of the photons are further calculated and judged, the underwater communication condition is accurately simulated, and important guiding significance is provided for improving the quality and stability of underwater communication.