119 results about "Grating interferometer" patented technology

The present invention is directed to a heterodyne reflectometer system and method for obtaining highly accurate phase shift information from heterodyned optical signals, from which extremely accurate film depths can be calculated. A linearly polarized light comprised of two linearly polarized components that are orthogonal to each other, with split optical frequencies, is directed toward a film causing one of the optical polarization components to lag behind the other due to an increase in the optical path in the film for that component. A pair of detectors receives the beam reflected from the film layer and produces a measurement signal, and the beam prior to incidence on the film layer and generates a reference signal, respectively. The measurement signal and reference signal are analyzed by a phase detector for phase shift. The detected phase shift is then fed into a thickness calculator for film thickness results. A grating interferometer may be included with the heterodyne reflectometer system with a grating, which diffracts the reflected beam into zeroth- and first-order bands, which are then detected by separate detectors. A detector receives the zeroth-order beam and generates another measurement signal. Another detector receives the first-order beam and generates a grating signal. The measurement signal from the grating and reference signal may be analyzed by a phase detector for phase shift, which is related to the thickness of the film. Conversely, either measurement signal may be analyzed with the grating signal by a phase detector for detecting a grating phase shift. The refractive index for the film may be calculated from grating phase shift and the heterodyne phase shift. The updated refractive index is then used for calculating thickness.

Embodiments of methods and apparatus are disclosed for obtaining a phase-contrast digital radiographic imaging system and methods for same that can include an x-ray source for radiographic imaging; a beam shaping assembly including a collimator and a source grating, an x-ray grating interferometer including a phase grating, and an analyzer grating; and an x-ray detector, where a single arrangement of the beam shaping assembly, the x-ray grating interferometer and a position of the detector is configured to provide spectral information (e.g. at least two images obtained at different relative beam energies).

Phase sensitive X-ray imaging methods can provide substantially increased contrast over conventional absorption based imaging, and therefore new and otherwise inaccessible information. The use of gratings as optical elements in hard X-ray phase imaging overcomes some of the problems that have impaired the wider use of phase contrast in X-ray radiography and tomography. So far, to separate the phase information from other contributions detected with a grating interferometer, a phase-stepping approach has been considered, which implies the acquisition of multiple radiographic projections. Here,an innovative, highly sensitive X-ray tomographic phase contrast imaging approach is presented based on grating interferometry, which extracts the phase contrast signal without the need of phase stepping. Compared to the existing phase step approach, the main advantage of this new method dubbed 'reverse projection' is the significantly reduced delivered dose, without degradation of the image quality. The new technique sets the pre-requisites for future fast and low dose phase contrast imaging methods, fundamental for imaging biological specimens and in-vivo studies.

In accordance with the principles of the invention, a lamellar grating interferometer breaks the radiation down into its wavelength components. The two sets of teeth of the grating are moved relative to each other. The spectral output of the interferometer is focused on an array of detectors and data is stored for a large number of positions of the grating teeth. The collected data is then Fourier transformed to recover the spectrum of the radiation.

Embodiments of methods and apparatus are disclosed for obtaining a phase-contrast digital imaging system and methods for same that can include an x-ray source for radiographic imaging; a beam shaping assembly, an x-ray grating interferometer including a phase grating and an analyzer grating; and an x-ray detector; where the source grating, the phase grating, and the analyzer grating are detuned and a plurality of uncorrelated reference images are obtained for use in imaging processing with the detuned system.

The invention provides a two-degree-of-freedom heterodyne grating interferometer displacement measurement system and method. The system comprises a double-frequency laser device, a grating interferometer, a measuring grating, a receiver and a signal processing unit. The grating interferometer comprises a lateral displacement light splitting prism, a polarization light splitting prism, a 1/4 wave plate, a reflecting mirror and an optical fiber coupler. The method realizes displacement measurement based on grating diffraction, the optical Doppler effect and the optical-beat frequency principle. Laser of the double-frequency laser device is incident to the interferometer and the measuring grating and then optical signals are outputted to the signal processing unit. When the interferometer and the measuring grating perform two-degree-of-freedom linear relative movement, the system can output two linear displacements; the measurement system adopts Littrow incident conditions, a measurement target has large passive movement tolerance and two linear displacements can be measured simultaneously so that precision can reach the nanoscale and higher scale; and the measurement system has advantages of short light path, small size, compact structure, low weight and low requirement for the measuring grating and is suitable for two-degree-of-freedom high-precision long-stroke displacement measurement.

An x-ray CT system that generates tomographic phase contrast or dark field exposures, has at least one grating interferometer with three grating structures arranged in series in the radiation direction, with a modular design of the second and third grating structures. The distance between the first grating structure of the x-ray source and the second grating structure (fashioned as a phase grating) of the respective grating/detector modules is adapted, depending on the fan angle, corresponding to a period of the grating structure of the x-ray source projected onto the grating detector module at a respective fan angle (φ_i).

A high-optical-subdivision grating interferometer based on plane mirrors comprises a double-frequency orthogonal linear polarization laser light source, a polarization beam splitter, the first mirror, the second mirror, the third mirror, the fourth mirror, a first quarter wave plate, a second quarter wave plate, a scale grating, a data collection, processing and control unit and a double-frequency heterodyne interference photoelectric detection unit which is composed of a non-polarization beam splitter, a first analyzer placed on the orthogonal double-frequency linearly polarized light by 45 degrees, a first detector corresponding to the first analyzer, a second analyzer placed on the orthogonal double-frequency linearly polarized light by 45 degrees and a second detector corresponding to the second analyzer. The scale grating is designed into a high-density -1-level sub-high diffraction efficiency reflection type grating, measurement light beams are diffracted multiple times through the scale grating through the combination with the plane mirrors, and therefore the high optical subdivision fold can be obtained, and important application value in the field of increasing the grating interferometer resolution ratio and accuracy is achieved.

An x-ray CT system for x-ray phase contrast and/or x-ray dark field imaging has a grating interferometer that has a first grating structure that has a number of band-shaped x-ray emission maxima and minima arranged in parallel, the maxima and minima exhibiting a first grating period, a second band-shaped grating structure that produces, as a phase grating, a partial phase offset of x-ray radiation passing therethrough and that exhibits a second grating period, a third band-shaped grating structure with a third grating period with which relative phase shifts of adjacent x-rays and/or their scatter components are detected, and a device for value-based determination of the phase between adjacent x-rays and/or for value-based determination of the spatial intensity curve per detector element perpendicular to the bands of the grating structures. The third grating structure has a grating period that is larger by a factor of 2 to 5 than the grating period of the first grating structure.

A displacement detecting device has a diffraction grating, grating interferometers, and relative position information output sections. The grating interferometers have a light source, reflectors, a beam splitter, and light receiving sections. The reflectors reflect 1st-order diffracted lights diffracted by the diffraction grating, and cause the reflected 1st-order diffracted lights to be incident at a position substantially identical to the position at which the light from the light source is irradiated. Furthermore, the reflectors cause the 1st-order diffracted lights to be incident on the diffraction grating at an angle different to either the incidence angle of the light from the light source incident on the diffraction grating or the angle at which the 1st-order diffracted lights are transmitted through or reflected by the diffraction grating.

A self-adaptive common-light-path grating interferometer comprises grating rulers which relatively move, a cube-corner prism, a reflector, a transmitting and reflecting mirror, a position sensitive detector, a polarization beam splitter, a linear polarization light source, a PZT micrometric displacement driver, a data collecting and processing and controlling unit and a polarization phase shift interference photoelectric detection unit or a double-frequency heterodyne interference photoelectric detection unit, wherein the PZT micrometric displacement driver is used for driving the cube-corner prism, the reflector and the transmitting and reflecting mirror. The self-adaptive method based on the diffraction light spot position feedback control cube-corner prism or the reflector is adopted to guarantee the complete common light path character of the dynamic grating interferometer, light path influence caused by relative movement errors of the grating rulers is eliminated, and high precision and high resolution ratio are obtained.

The invention relates to a cross-polarization laser feedback grating interferometer of a phase modulation type, and a measurement method thereof. The measurement principle is based on the grating diffraction, optical Doppler effect, Lamb semi-classical theory and time-domain orthogonal demodulation principle. The orthogonally polarized light outputted by a birefringent dual-frequency helium-neon laser is perpendicularly incident to a polarization beam splitting prism and is divided into two linearly polarized light beams in different polarization directions. The two polarized light beams respectively pass through two different electrooptical modulators and then are respectively reflected by a reflector at a +/-1-order Littrow incidence angle to a reflection-type diffraction grating. The diffracted light returns to the laser cavity along the respective incident light, and performs self-mixing interference with the light in the cavity. The backward output light of the laser passes through a polarizer and then only the single-mode light is retained and accepted by a photodetector. An output signal of the photodetector is outputted to a data processing module for data processing, and the two-dimensional displacement of a target to be measured is obtained. The grating interferometer has the advantages of simple structure, large measuring range and high measurement resolution.

A lamellar grating interferometer is described, in which the light beams are collimated and focused onto the grating by means of mirror 9, which at the same time serves for collecting the light reflected from the grating. In this case, the light beam of a white light source 1 is first collimated by means of first lens 2, and subsequently passed through a sample cuvette 3. The transmitted light beam is subsequentlyy focused and coupled by another lens 2 into a fibre 17. The light to this fibre 17 is subsequentlyy directed towards a mirror 9, reflected from this mirror 9 onto a grating 11, which forms part of a lamellar grating interferometer which is realised by means of a micro electro mechanical device MEMS 7, which is mounted on a MEMS holder 6, as is the fibre 17. The light reflected from this grating 11 is reflected onto the same mirror 9, and focused and coupled by this same mirror 9 into a second multimode fibre 18, which is also fastened to the holder 6. The light guided by this second multimode fibre 18 is subsequently fed into a detection device 4.

The invention discloses a real-time correction method of a grating interferometer alignment error. A grating interferometer displacement measurement optical path, a pose deflection detection optical path, a photoelectric detection module, and an interferometer signal processing and error compensation module are comprised. The grating interferometer displacement measurement optical path is mainly composed of a laser light source, a grating, a non-polarizing beam splitter, a polarizing beam splitter and a quarter-wave plate. The pose deflection detection optical path is mainly composed of a semi-transparent and semi-reflective mirror and a focusing lens. The interferometer signal processing and error compensation module processes grating interferometer signal displacement demodulation and grating measurement error compensation. According to the invention, the symmetrical optical path and a four-quadrant detector are used to measure the deflection about the x, y, and z axes of an optical reading head with respect to the grating ruler's space pose; the real-time correction of the displacement measurement is realized through the error compensation model; finally the measurement accuracy of a grating interferometer is improved; and the method has the advantages of simple measurement and small error.

The invention relates to a cascade acoustic microstructure optical fiber long cycle grating interferometer which comprises a light source, a 3dB coupler, a microstructure optical fiber, two three-dimensional regulation frames, a signal generator, a piezoelectric ceramic chip, an acoustic amplifier, an acoustic damper, a spectrum analyzer, a connecting single-mode optical fiber and a lead, and belongs to the technical field of optical fiber induction. A sine electric signal is generated through the signal generator, acts on the piezoelectric ceramic chip, is converted into an acoustic signal, amplified through the acoustic amplifier and laterally loaded to the microstructure optical fiber to form an acoustic long cycle optical fiber grating, and then a Mach-Zehnder interference effect is formed through a high reverse film; and an induction optical fiber is corroded to generate an evanescent field and is arranged in an environment to be measured. In addition, a functional material is filled into the cladding air hole of the microstructure optical fiber, so that an electric field, a magnetic filed and the like can be measured and the induction sensitivity is further improved. The cascade acoustic microstructure optical fiber long cycle grating interferometer has the advantages that the structure is simple, the tunability is good, the sensitivity is high, and refractive index, temperature, the electric field, the magnetic field, gas concentration and other parameters can be induced.

The invention discloses a laser self-blending grating interferometer and a measuring method thereof. The grating interferometer comprises a laser device, a diffraction grating, a plane mirror, a photoelectric detector, an electrical signal processing system and a data collecting and analyzing system. The diffraction grating is arranged on an output laser path of the laser device, and the displacement direction of the diffraction grating is perpendicular to the output laser path of the laser device. Laser emitted by the laser device is vertically incident to the diffraction grating to form all levels of diffraction laser symmetrically distributed at the two sides of an incident laser path, the plane mirror is arranged on a laser path of a certain m level of diffraction laser to enable the m (m is not equal to zero) level of diffraction laser to be vertically incident to the plane mirror, return along an original laser path and then be incident to the diffraction grating again for secondary diffraction, secondary diffraction laser carries grating displacement information to return into a cavity of the laser device in the direction opposite to emergent laser of the laser device for self-blending interference. The grating interferometer has the advantages of being simple and compact in structure, low in cost and high in capacity of resisting interference, and automatically recognizing the displacement direction, and the laser feedback level does not need to be controlled.

A plane grating interferometer displacement measuring system comprises a single-frequency laser, beam splitters, acousto-optic modulators, a grating interferometer, a plane grating, a receiver, an electronic signal processing component, an optical fiber coupler and a frequency synthesizer, wherein the grating interferometer comprises a polarizing beam splitter, refractive element, a right-angle prism and a quarter-wave plate. The plane grating interferometer displacement measuring system realizes displacement measurement based on grating diffraction, an optical Doppler effect and an optical beat frequency principle. When the grating interferometer and the plane grating do linear relative motion with two degrees of freedom, the plane grating interferometer displacement measuring system canoutput two pieces of linear displacement. The plane grating interferometer displacement measuring system can realize sub-nanometer or higher resolution and precision, can measure two pieces of lineardisplacement simultaneously, has the advantages of high measurement precision and simple structure, and can improve the comprehensive performances of a workpiece bench when used as a lithography machine ultra-precision workpiece bench position measuring system.

A device and method of the present disclosure provides large field-of-view Talbot-Lau phase contrast CT systems up to very high X-ray energy. The device includes microperiodic gratings tilted at glancing incidence and tiled on a single substrate to provide the large field-of-view phase contrast CT system. The present disclosure is a simple, economical, and accurate method for combining multiple GAIs into a larger FOV system, capable of performing phase-contrast tomography (PC-CT) on large objects. The device and method can be applied to medical X-ray imaging, industrial non-destructive testing, and security screening.

A displacement measurement system of heterodyne grating interferometer, comprises a reading head, a measurement grating and an electronic signal processing component. Laser light emitted from the laser tube is collimated, passes through the first polarization spectroscope, and then emits two light beams with a vertical polarization direction and a vertical propagation direction; the two light beams pass through two acousto-optic modulators and respectively generate two first-order diffraction light beams with different frequencies, which are later divided into reference light and measurement light; two parallel reference light beams form a beat frequency electric signal with positive and negative first-order diffraction measurement light respectively after passing through a measurement signal photo-electric conversion unit; the beat frequency signals are transmitted to the electronic signal processing component for signal processing, thus the output of linear displacement in two directions is realized.

A two-degree-of-freedom heterodyne grating interferometer displacement measurement system comprises a double-frequency laser device, a grating interferometer, a measuring grating, a receiver and a signal processing unit, wherein the grating interferometer comprises a lateral displacement beam splitter prism, a polarization splitter prism, a referencing grating and a retraction component, and the measurement system achieves displacement measurement based on grating diffraction, an optical Doppler effect and an optical beat frequency principle. Laser of the double-frequency laser device is emitted to the grating interferometer and the measuring grating, and then optical signals are output to the receiver and then to the signal processing unit. When the grating interferometer and the measuring grating do two-degree-of-freedom linear relative motion, the system can output two pieces of linear displacement. According to the two-degree-of-freedom heterodyne grating interferometer displacement measurement system, a secondary diffraction principle is adopted to achieve four optical subdivisions, the sub-nanometer and even higher resolution ratio can be achieved, and the two pieces of the linear displacement can be measured simultaneously. The two-degree-of-freedom heterodyne grating interferometer displacement measurement system has the advantages of being insensitive to environment, high in measurement precision, light and the like, and is capable of improving the comprehensive performance of the workpiece table serving as a position measurement system for a photoetching machine ultraprecise workpiece table,.