144 results about "Shearing interferometer" patented technology

An interferometer scans the sample surface laterally with respect to the optical axis of the interferometric objective. The objective is tilted, so that the sample surface is placed at an angle with respect to the maximum coherence plane of the instrument. By moving the sample stage laterally, at an angle, through a point at a set distance from the objective on the objective's optical axis, rather than vertically along the optical axis, different parts of the object intersect the maximum coherence plane at different times as the surface passes through the coherence plane, the precise time depending on the profile of the surface. When the OPD of a point on the object's surface is greater than the coherence length of the light source, the intensity of light reflected from this point does not produce interference fringes. Therefore, the intensity registered by the detector is approximately constant. However, when the object point enters the zone of coherence, the interference effects modulate the intensity the same way as in a regular VSI procedure. As the object moves along the scanning direction, it also has a relative vertical speed with respect to the objective because of the tilt of the objective's optical axis with respect to the scanning plane; therefore, the lateral scanning motion produces an OPD variation as the vertical scan in a conventional system. As a result, light intensity data are acquired continuously as the test surface is scanned, thus elimination the need for stitching multiple sub-sets of data.

Beam shear can be reduced in an interferometric system by conditioning an input beam prior to directing the input beam to an interferometer. Accordingly, apparatus and methods for conditioning an interferometer input beam are disclosed.

The invention relates to the field of shaped pulse measurement, in particular to a spectrum shearing interferometer suitable for measuring shaped pulses. A plane grating, a first concave face reflecting mirror, a double-slit baffle, a first reflecting mirror and a second reflecting mirror are used for forming a special 4f zero dispersion compressor, the distance between the plane grating, the first reflecting mirror and the second reflecting mirror and the first concave face reflecting mirror is equal to the focal length of the first concave face reflecting mirror in the 4f zero dispersion compressor, the mode that the 4f zero dispersion compressor is added with the double-slit baffle is used for acquiring two quasi monochromatic long pulses, the two quasi monochromatic long pulses and a pulse to be measured are made to be in sum frequency. According to the mode, a shearing amount omega and the band width delta omega of an auxiliary pulse segment participating in sum frequency can be prevented from varying along with the change of the characteristics of the pulses to be measured, the shearing amount omega can be changed conveniently to measure the same pulse, the corresponding phase difference of each frequency of the pulse can be solved independently, and therefore the shaped pulses with various characteristics can be measured accurately.

The invention relates to a projection objective lens wave aberration detection device and method. Light emitted by a light source is uniformly radiated on a projection objective lens object plane, a scatter plate and a needle hole are installed on a masking stage, the needle hole is arranged on an object plane of a projection objective lens, the field of view is selected through the movement of the masking stage, a shearing grating is arranged on an image plane of the projection objective lens, the shearing grating is installed on a wafer stage together with a detector, the phase shifting function is realized through the transverse precise movement of the grating by the wafer stage, and simultaneously each frame of a shearing interference figure in the phase shifting process is recorded by utilizing the detector. Two-dimensional shearing is realized by utilizing the two-dimensional grating, the phase shifting function is integrated into the shearing interference instrument, and the high-precise measurement of the projection objective lens wave aberration is realized by adopting the characteristics of the phase space vector.

A system for calibrating a spatial light modulator array includes an illumination system and a spatial light modulator array that reflects or transmits light from the illumination system. A projection optical system images the spatial light modulator array onto an image plane. A shearing interferometer creates an interference pattern in the image plane. A controller controls modulation of elements of the spatial light modulator array. The shearing interferometer includes a diffraction grating, a prism, a folding mirror or any other arrangement for generating shear. The shearing interferometer can be a stretching shearing interferometer, a lateral shearing interferometer, or a rotational shearing interferometer. The shearing interferometer may include a diffraction grating with a pitch corresponding to a shear of the light by an integer number of elements. The projection optics resolves each element of the spatial light modulator array in the image plane. The controller can modulate alternate columns of elements of the spatial light modulator array.

A phase shift transverse shear interferometer consists of a first polarizer, an input parallel plate, a second polarizer, a third polarizer, a first shear plate, a second shear plate, an output parallel plate, a quarter wave plate, a detecting deflection machine, a CCD camera and a computer, the phase shift transverse shear interferometer is an equal optical path interference optical system, the shear quantity can be continuously adjusted, which is very applicable to the wavefront measurement of the short interference length, and satisfies the wavefront measurement of the different light beam bore and the measurement precision.

The invention discloses a Ronchi shearing interferometer based phase extraction method. A Ronchi shearing interferometer structure used in the Ronchi shearing interferometer based phase extraction method comprises a light source, a focusing lens, a scattering optical element, one-dimensional diffraction grating plates, a measured optical system platform, chessboard gratings, a two-dimensional photoelectric sensor and a computer. The one-dimensional diffraction grating plates and the chessboard gratings are arranged on an object plane and an image plane of the measured optical system and the phase is calculated due to collection of 9 interferometric fringe patterns with the shifting interval to be a quarter of pi to eliminate influences to the phase extraction accuracy from multi-level diffraction light in Ronchi shearing interference. The Ronchi shearing interferometer based phase extraction method has the advantages of eliminating the influences of diffraction items in higher levels other than the levels 0, 1 and minus 1, reducing the phase extraction system error in wave aberration detection and improving the wave aberration detection accuracy of the optical system.

A system for calibrating a spatial light modulator array includes an illumination system and a spatial light modulator array that reflects or transmits light from the illumination system. A projection optical system images the spatial light modulator array onto an image plane. A shearing interferometer creates an interference pattern in the image plane. A controller controls modulation of elements of the spatial light modulator array. The shearing interferometer includes a diffraction grating, a prism, a folding mirror or any other arrangement for generating shear. The shearing interferometer can be a stretching shearing interferometer, a lateral shearing interferometer, or a rotational shearing interferometer. The shearing interferometer may include a diffraction grating with a pitch corresponding to a shear of the light by an integer number of elements. The projection optics resolves each element of the spatial light modulator array in the image plane. The controller can modulate alternate columns of elements of the spatial light modulator array.

A lateral-shear interferometer utilizes two relatively thick glass plates bonded together in a single block with a tilted air gap between opposing inner surfaces. The thickness of the glass plates is selected to be sufficiently large to separate the output beams from the light reflected from the top and bottom surfaces of the block, thereby eliminating the need for antireflection coatings. The shear interferometer is combined with an external mirror mounted on a tilt stage actuated by a computer-controlled tilt actuator to perform phase-shifting interferometric analysis in conventional manner.

A device for detecting system wave aberration of a photoetchingprojection objective comprises a light source, an illuminating system, a pinhole space filter, a beamsplitter, a to-be-detected projection objective, a spherical reflector, a two-dimensional grating, a space filter and an image sensor. According to the device, a level selection window is taken as the space filter, so that noise is reduced, the measuring accuracy is improved, and the defect of limitation of Talbot distance to the image sensor position is overcome. The spherical reflector is added to a light path, can be used for detection of system wave aberration of an immersedprojection objective and can also be used for detection of system wave aberration of a non-immersedprojection objective; full-field system wave aberration of the projection objective can be detected, and wave aberration represented by 36 Zernike coefficients is obtained; and with adoption of a light path structure of a shearing interferometer, the device has the advantages of high detecting accuracy, good repeatability and the like.

Disclosed are a digital phase-shifting lateral shearing interferometer and an optical system wave aberration measurement method. The interferometer is composed of a light source, a small-hole mask, a first spatial light modulator, a second spatial light modulator, a two-dimensional photoelectric detector and a computer. The first spatial light modulator is arranged as a grating by computer programming to serve as a shearing light splitter, the second spatial light modulator is arranged as a double-window mask to serve as a filter for filtering high-order diffraction light at zero order and more than two orders, and only diffraction light at +1 order and -1 order takes part in interference. The problem that the high-order diffraction light takes part in interference is solved, the interferometer has the advantage that changeable shearing direction and adjustable shearing rate can be realized without replacing or rotating any device.

The invention relates to a wave-front measuring instrument of a collimation deflection beam and a measuring method thereof, relating to the wave-front measurement of a collimation deflection beam in the optical field. The measuring instrument comprises a beam deviation device and a hearing interference light path, wherein the beam deviation device comprises a reflector and an electric combined platform controlled by a computer. The measuring method comprises the following steps: using a stripe generated by a collimation laser through the measuring instrument as a reference stripe chart; setting the action parameter of the combined platform by the computer according to the deflection angle of a beam to be measured; controlling the reflector to rotate and translate to change the propagation direction of the beam into a direction perpendicular to the translation direction of the combined platform; measuring a distorted stripe chart; and calculating the wave-front distribution of the deflected beam at an incidence hole according to a stripe-processing algorithm. By adding a device capable of changing the propagation direction of the deflected beam on a basis of a radial shearing interferometer in the quadrilateral structure, the invention can conveniently and rapidly measure the wave-front distribution of the collimation deflection beam and solve the problem that the traditional instrument can not directly measure the wave-front distribution of the collimation deflection beam.

A scuffing detection method for a lateral shearing interferometer is provided. The lateral shearing interferometer to be scuffed is coated evenly with photosensitive glues and is vertically put on a high precision optical plate of a precision adjusting platform. The laser light output by a laser forms into even parallel light on the lateral shearing interferometer to be scuffed. Interference fringes formed on the send out end of the lateral shearing interferometer to be scuffed are received by a digital camera and are displayed in real time on a computer. The CCD pixel number M0 of the digital camera occupied by N0 interference fringes is calculated. Two prisms are moved slightly to read CCD pixel number M of the digital camera occupied by N0 interference fringes. When the CCD pixel number M becomes to be M0, the two prisms are set not to move. The two scuffed prisms are solidified. The invention solves a technical problem in background technology that the lateral shearing amount of the lateral shearing interferometer is hard to be precisely controlled. The error of the lateral shearing amount of the invention can be controlled within 1%.

A wavefront measurement system includes a source of electromagnetic radiation. An imaging system directs the electromagnetic radiation at an object plane that it uniformly illuminates. A first grating is positioned in the object plane to condition the radiation entering the input of a projection optic. A projection optical system projects an image of the first grating onto the focal plane. A second grating is positioned at the focal plane that receives a diffracted image of the source to form a shearing interferometer. A CCD detector receives the image of the first grating through the projection optical system and the second grating that forms a fringe pattern if there are aberrations in the projection optical system. Phaseshift readout of fringe pattern can be accomplished by stepping the first grating in a lateral direction and reading each frame with the CCD detector. The first grating includes a plurality of reflecting lines each formed by a plurality of reflecting dots. The first grating has a pitch that is ½ times the magnification of the projection system times the pitch of the second grating for achromatic operation.

A wavefront measurement system includes a source of electromagnetic radiation. An illumination system delivers the electromagnetic radiation to an object plane. A source of a diffraction pattern is in the object plane. A projection optical system projects the diffraction pattern onto an image plane, which includes a mechanism (e.g., a shearing grating) to introduce the lateral shear. A detector is located optically conjugate with the pupil of the projection optical system, and receives an instant fringe pattern, resulting from the interference between sheared wavefronts, from the image plane. The diffraction pattern is dynamically scanned across a pupil of the projection optical system, and the resulting time-integrated interferogram obtained from the detector is used to measure the wavefront aberration across the entire pupil.

The invention provides a small-sized radial shearing interferometer based on the four-step phase-shifting theory, comprising a polarizer (P1), a polarizing beam splitter (PBS), a beam reducer or expander system, a quarter-wave (QW) plate, a binary micro-polarizer array and a photosensor CCD (Charge-Coupled Device) camera, wherein the beam reducer or expander system comprises a first lens (L1) with the focus f1, a second lens (L2) with the focus f2 (f1 is not equal to f2), a first reflector (M1) and a second reflector (M2). According to the interferometer, an aberrated beam enters the small-sized radial shearing interferometer to form a pair of beams which are arranged on the same optical axis and have polarization directions vertical to each other and beam sizes reduced and expanded according to the same proportion, and the pair of beams are projected on the photosensitive surface of the CCD camera to form a single-frame interferogram after passing through a four-step phase shifter which comprises the quarter-wave plate (QW) and the binary micro-polarizer array. The small-sized radial shearing interferometer based on the four-step phase-shifting theory does not need a fully-flattened reference mirror, can be used in the field of wavefront sensing application such as adaptive optics, and can effectively suppress environmental disturbance due to the adoption of a complete common path structure, and has low environment requirements and stable interferogram.

A neutron imaging system detects both the phase shift and absorption of neutrons passing through an object. The neutron imaging system is based on either of two different neutron wavefront sensor techniques: 2-D shearing interferometry and Hartmann wavefront sensing. Both approaches measure an entire two-dimensional neutron complex field, including its amplitude and phase. Each measures the full-field, two-dimensional phase gradients and, concomitantly, the two-dimensional amplitude mapping, requiring only a single measurement.

A wavefront measurement system includes a source of electromagnetic radiation. An imaging system directs the electromagnetic radiation at an object plane that it uniformly illuminates. A first grating is positioned in the object plane to condition the radiation entering the input of a projection optic. A projection optical system projects an image of the first grating onto the focal plane. A second grating is positioned at the focal plane that receives a diffracted image of the object plane to form a shearing interferometer. A CCD detector receives the image of the pupil of the projection optical system through the projection optical system and the second grating that forms a fringe pattern if there are aberrations in the projection optical system. Phaseshift readout of fringe pattern can be accomplished by stepping the first grating in a lateral direction and reading each frame with the CCD detector.

A method and apparatus for using a dual-beam interferometer to test surface flatness is provided. The interferometer directs two beams focused at distinct points on a testing surface, such as the surface of a magnetic recording disc. An offset distance “d” between the two beams is provided on the target surface. In the present invention, the separation distance “d” is adjustable. The feature of adjustable separation distance in the interferometer allows the interferometer to meet the different spatial frequency requirements of various applications. In operation, first and second reflected beams are returned to an intensity beam splitter, where they are split and then recombined into two new beams of substantially equal intensity. The second of the two new light beams is constructed by the interference of half intensity of the first and half intensity of second beams, and is sent to a photodiode. The photodiode generates signals in response to the changing interference fringes caused as a result of the modulation of the optical path length difference between the original first and second beams. A local height difference on the reflective surface is calculated relative to the separation distance “d”.

An online detection method for magnetoelasticity performance of thin-ferromagnetic-film, which belongs to the field of engineering materials, structure deformation, and mechanical test. The device implementing the method of the invention comprises a thin-ferromagnetic-film non-uniform stress measuring light path and a film hysteresis loop measuring light path, wherein, the film non-uniform stress measuring light path comprises a laser, a beam expander, a grating, a lens, a filter screen, and a CCD camera; and the film hysteresis loop measuring light path comprises a laser, a beam expander, a polarizer, an analyzer, and a photodetector. The method of the invention comprises the steps of measuring non-uniform curvature of the thin-ferromagnetic-film surface by shearing interferometer to obtain the non-uniform stress in film, and measuring the hysteresis loop of the film by using magnetooptic Kerr effect of the thin-ferromagnetic-film surface. The method can simultaneously online measure the non-uniform stress and the hysteresis loop of thin-ferromagnetic-film, so as to provide experimental basis for the research on magnetoelasticity coupling behavior of the thin-ferromagnetic-film.