36 results about "Fourier phase" patented technology

An absolute optical encoder apparatus for measuring an absolute position comprises an optical disk or scale element (100) having both incremental and absolute code tracks formed thereon. In the embodiment, a photoemitter light source (110, 111) illuminates the tracks onto a CCD area array sensor (115, 116) such that an image is formed from a pixel matrix having of rows and columns. Two detector line rows (410, 420) of the pixel matrix are each read out from the portion of the matrix comprising the incremental and absolute code tracks respectively. Inaccurate mounting of the disk or scale element can cause fluctuations in the period of the code tracks resulting from the rotation of the disk or movement of the scale element. The mounting inaccuracies are compensated for either by matching the spatial frequency by dynamically changing row of detector line read from the incremental image of the code track or by altering the numerical value of the pattern period used in the Fourier phase algorithm. The absolute position is numerically calculated from the imaged code tracks.

An absolute optical encoder apparatus for measuring an absolute position comprises an optical disk or scale element (100) having both incremental and absolute code tracks formed thereon. In the embodiment, a photoemitter light source (110, 111) illuminates the tracks onto a CCD area array sensor (115, 116) such that an image is formed from a pixel matrix having of rows and columns. Two detector line rows (410, 420) of the pixel matrix are each read out from the portion of the matrix comprising the incremental and absolute code tracks respectively. Inaccurate mounting of the disk or scale element can cause fluctuations in the period of the code tracks resulting from the rotation of the disk or movement of the scale element. The mounting inaccuracies are compensated for either by matching the spatial frequency by dynamically changing row of detector line read from the incremental image of the code track or by altering the numerical value of the pattern period used in the Fourier phase algorithm. The absolute position is numerically calculated from the imaged code tracks.

Thin-film thickness and refractive index are measured using the Fourier amplitude of a broadband interferometric spectrum. Due to the smooth nature of the Fourier amplitude as a function of wavelength, as compared to the fast varying Fourier phase conventionally used to measure thickness, increased stability and repeatability of measurement are achieved. As a result, measurements of ultra-thin films with thickness below 100 nm are possible with reliable results.

The invention relates to a method and an apparatus for measuring the thickness of a transparent film by broad band interferometry, comprising the steps of preparing a correlogram of the film by an interferometer, applying a Fourier transformation to said correlogram to obtain a Fourier phase function, removing a linear component thereof, applying a second integral transformation to the remaining non-linear component to obtain an integral amplitude function of said non-linear component, identifying the peak location of said integral amplitude function and determining the thickness of the film as the double value of the abscissa at said peak location considering a refractive index of a film which is dependent on wavelength. The last two steps may be replaced by identifying the peak locations of said integral amplitude function and determining the thickness of the films as the double values of the abscissas at the peak locations.

The invention belongs to the technical field of image processing, and particularly provides an SAR image registration method based on straight lines and an FFT to mainly solve the problems that an existing technology is poor in registration effect and high in computing complexity. The method comprises the first step of inputting two SAR images and detecting the straight lines of the two images through a margin fitting method, the second step of carrying out statistics on the detected straight lines according to a slope difference histogram and calculating rotating parameters, the third step of carrying out the Fourier transform on a reference image and a rotated image to be registered to obtain a Fourier transform diagram, the fourth step of calculating horizontal movement parameters through the Fourier phase correlation method, and the fifth step of enabling the horizontally-moved and rotated image to be registered to coincide with the reference image and finishing the registration. The SAR image registration method has the advantages that the effect degree on the registration of the SAR images from noise is small, the registration result of the SAR images with abundant linear features is stable, the registration effect is better, speed is high, and the computing complexity is low, and the SAR image registration method can be used for pattern recognition, automatic navigation and computer vision and remote sensing image process.

Under one aspect, a phase contrast imaging system includes a coherent light source emitting a coherent beam directed toward a sample area; a lens arranged to collect at least part of the beam from the sample area; an element Fourier transforming the collected beam in a Fourier plane; a liquid crystal cell in the Fourier plane that transmits at least part of the transformed beam, wherein the cell includes liquid crystal molecules having a phase transition temperature, and wherein at temperatures exceeding the phase transition temperature, light transmitted through the liquid crystal molecules obtains a different phase than light transmitted through the liquid crystal molecules obtains at temperatures below the phase transition temperature; and an element inversely Fourier transforming the transmitted beam to provide an image. Part of the transformed beam has an intensity sufficient to heat a portion of the liquid crystal molecules above the phase transition temperature.

An assembly for converting a microscope into a phase contrast microscope includes a first optical Fourier element that Fourier transforms light from a coherent light source, a cell in the Fourier plane arranged to receive light from the first optical Fourier element, a second optical Fourier element arranged to receive light from the cell and inversely Fourier transform the received light to provide an image, an image sensor that detects the image and generates an electronic representation of the image, and an adaptor capable of coupling the first and second Fourier elements, the cell, and the image sensor to the microscope such that the first Fourier element Fourier transforms light collected by the microscope objective. The cell includes liquid crystal molecules having a phase transition temperature, wherein at temperatures exceeding the phase transition temperature, light transmitting through the liquid crystal molecules obtains a different phase than light transmitting through the liquid crystal molecules at temperatures below the phase transition temperature.

Certain aspects pertain to Fourier camera systems and methods. In one aspect, a Fourier camera comprises a first optical system, a second optical system, a variable aperture filter, and a light detector. The first optical system configured to receive illumination reflected from a curved sample surface. The variable aperture filter configured to move an aperture to a plurality of aperture locations in a Fourier plane, wherein the aperture filters light from the first optical system to the second optical system. The light detector configured to receive light from the second optical system, and configured to acquire a plurality of raw intensity images of the curved sample surface corresponding to the plurality of aperture locations, wherein the raw images are iteratively updated in overlapping regions in Fourier space to generate a focused, substantially uniform resolution image of the curved sample surface, and wherein the overlapping regions correspond to the plurality of aperture locations.

The invention relates to a method and an apparatus for measuring the thickness of a transparent film by broad band interferometry, comprising the steps of preparing a correlogram of the film by an interferometer, applying a Fourier transformation to said correlogram to obtain a Fourier phase function, removing a linear component thereof, applying a second integral transformation to the remaining non-linear component to obtain an integral amplitude function of said non-linear component, identifying the peak location of said integral amplitude function and determining the thickness of the film as the double value of the abscissa at said peak location considering a refractive index of a film which is dependent on wavelength. The last two steps may be replaced by identifying the peak locations of said integral amplitude function and determining the thickness of the films as the double values of the abscissas at the peak locations.

The invention discloses a Fourier phase recovery method and system based on a plug-and-play neural network. The Fourier phase recovery method based on the plug-and-play neural network comprises the steps of constructing a mathematical model of a Fourier phase recovery problem for the phase recovery problem; converting the mathematical model into a solvable non-convex optimization problem. The non-convex optimization problem is solved through an alternating direction descent multiplier algorithm, a denoising neural network trained in advance is added in the solving process to serve as a sub-module of the alternating direction descent multiplier algorithm, the denoising neural network plays a regularization constraint role on an iterative value of the alternating direction descent multiplieralgorithm, and finally a restored image is obtained. According to the method, the defects that an existing classical algorithm is sensitive to an initial value, poor in robustness and the like can beovercome, and a high-quality image can be recovered from low-signal-to-noise-ratio phase-free measurement.

Reference-free compensated imaging makes an estimation of the Fourier phase of a series of images of a target. The Fourier magnitude of the series of images is obtained by dividing the power spectral density of the series of images by an estimate of the power spectral density of atmospheric turbulence from a series of scene based wave front sensor (SBWFS) measurements of the target. A high-resolution image of the target is recovered from the Fourier phase and the Fourier magnitude.

Provided is a method for analyzing image slices. The method includes extracting first and second sub-slices from first and second image slices, respectively, and computing a shift between the first and second image slices based on the first and second sub-slices. The first and second sub-slices overlap.Also provided is a method for controlling a cursor on a screen. The method includes determining a shift between a first image slice and a second image slice and determining a displacement of the cursor on the screen based on the determined shift.

The invention discloses an improved phase recovery algorithm based on MSE selection, which includes the following steps: A1, taking random Fourier phase as input, obtaining the reconstruction result of the phase recovery algorithm, and calculating the Fourier amplitude and the reconstruction result The mean square error between the initial Fourier amplitudes of the target; A2. Repeat step A1 with multiple different random Fourier phases as input to obtain corresponding multiple reconstruction results and corresponding multiple mean square errors; A3 . Using the mean square error as an evaluation index of the quality of the reconstruction result, selecting the optimal reconstruction result from the plurality of reconstruction results as the final output, so as to realize the phase recovery of the target object. The invention can realize stable phase recovery.

The invention relates to a method for relay protection in the field of power systems. Disclosed is a method of synchronizing sampling current and voltage at both ends of a power system, using distributed parameter long-line equations, and realizing double-terminal fault location according to the method that the positive-sequence or negative-sequence voltages at both ends of the fault point are equal. The method includes the following main steps: the line protection device samples the secondary current of the current transformer and the secondary voltage of the voltage transformer on the side of the line to obtain the corresponding instantaneous values ​​of current and voltage, and obtains the three-phase current and the three-phase current on the side through the Fourier algorithm. The Fourier form of the phase voltage, and the phasor form of the current and voltage obtained by receiving the synchronous sampling of the opposite side protection through the optical fiber communication network and filtering and calculating, using the condition that the positive sequence voltage or negative sequence voltage on both sides of the fault point is equal, the protection is obtained. The distance from the installation to the reference point. The method is not affected by the power supply impedance and transition resistance of the line operation mode. Theory and practice have proved that the method can greatly improve the accuracy of fault location of transmission lines.

The present application discloses a novel sheared beam imaging system and target imaging acquisition method, wherein the novel sheared beam imaging system applies the Fourier phase extraction technology to the traditional sheared beam imaging technology, thereby removing the traditional The two steps of beam frequency shifting and fringe demodulation in the cut-beam imaging system become possible, and then realize the purpose of simplifying the structure of the cut-beam imaging system, improving the imaging signal-to-noise ratio and reducing the complexity of the image reconstruction algorithm, which greatly The performance of the shearing beam imaging system is improved and its engineering realization is facilitated.