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.

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.

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.

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.

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 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.