79 results about "Point diffraction interferometer" patented technology

The invention discloses a polarized point diffraction interferometry system for test of low-reflectivity optical spherical surfaces. As the reflectivity of the optical spherical surface is low in the actual polishing process, a high-precision interference test system needs to have the function of adjusting visibility of fringes to obtain the ideal visibility of interference fringes. The invention solves the problem of realizing adjusting the visibility of interference fringes while ensuring the test precision of the spherical surface. The invention is technically characterized by establishing the polarized point diffraction interferometer system capable of realizing adjusting the visibility of interference fringes by introducing a polarization optical element to adjust the polarization states of light beams based on a point diffraction interferometer system capable of realizing high-precision test; and putting forward corresponding structure design and system error correction methods by analyzing the function characteristics of each element in the interferometer system to realize high-precision test of the spherical surfaces. The invention provides a feasible method for high-precision test of the low-reflectivity optical spherical surfaces.

The invention discloses a device and a method for aligning a pinhole of a point-diffraction interferometer, belonging to the technical field of optical precise debugging, namely a device and a method for aligning the pinhole of the point-diffraction interferometer provided to realize real-time monitoring of precise aligning and aligning states of a focusing spot and a diffraction pinhole in the point-diffraction interferometer. The device comprises a laser device, a laser beam expander, a first dispersion prism, a half-wave plate, a second dispersion prism, a third dispersion prism, a quarter-wave plate, a focus lens, a pinhole plate, a three-dimensional scanning and micro-adjusting mechanism, a first laser power meter, a second laser powder meter, a third laser power meter, a position detector and a computer. According to the device and the method disclosed by the invention, the aligning speed is increased; the pinhole aligning state is quickly aligned again when being monitored; power change of the laser device is detected by a sole laser power meter in the invention and the aligning state is reflected by a ratio of the laser power instead of an absolute value so that error judgment on the aligning state of the pinhole caused by laser power change is overcome.

The invention provides a point diffraction interferometer and comprises a light source module, a mask which can produce an ideal spherical wave, an optical diffraction component which can produce multi-level sub-diffraction light, an image sensor and an optical component. The measured optical component is arranged between the mask and the optical diffraction component and the diffraction light of some levels can permeate the optical component completely, wherein, the diffraction light of a certain level can permeate the optical component partly while being diffracted partly; the diffraction light of some levels can permeate the optical component completely, wherein, the diffraction light of a certain level can be diffracted or the optical component consists of a plurality of windows and a plurality of small holes; diffraction light of some levels can selectively permeate the window, however, the non-diffracted light can be diffracted through the small hole on the optical component. The point diffraction interferometer of the invention conducts measurement through a plurality of interference graphs which are produced at the same time and the sampling frequency is improved, moreover, the design and operation of the whole system is simplified and the motion error of a phase-shift component can be avoided.

The invention provides a high-numerical-aperture optical fiber point diffraction interference device used for three-coordinate measurement and a method thereof, and relates to optical measurement. Light emitted by a laser device is divided into transmission light and reflected light via a polarized beam splitting prism. Point diffraction spherical wave front W2 is generated at a sub-wavelength aperture optical fiber emergent end by transmission light, and point diffraction spherical wave front W1 is generated at the sub-wavelength aperture optical fiber emergent end by reflected light after being reflected by a moving reflecting mirror. A CCD detector acquires W1 and W2 interference fringes, and three-dimensional coordinate measurement of a measured object is realized via multi-step phase-shifting and a double iteration algorithm of an L-M algorithm. A problem in the prior art that high-numerical-aperture and high-energy diffraction spherical wave front is difficult to realize simultaneously by a point diffraction interferometer used for three-coordinate measurement is solved. The beneficial effects are that probes of two sub-wavelength aperture optical fibers act as measuring probe heads, the high-brightness and high-numerical-aperture point diffraction spherical wave front is acquired, the requirement of light sensitivity is reduced and measurement range of an optical fiber point diffraction interference system used for three-coordinate measurement is enlarged.

The interferometer includes the optical part and the data acquisition, process and control parts. The optical part includes the laser, the convergent lens, the lens soaked by the solid coated with super resolving power mask arranged in optical axis in sequence along the traveling direction of the laser beam. The part to be measured is positioned above the optical axis and the image lens is in lower part. The data acquisition, process and control parts include the CCD camera, the computer and the displacement controller. The key technique in the invention is the lens soaked by the soild and the mask with supper resolving power. Thus, the smaller pinhole can be obtained as the ideal light source with spherical wave. The position and size of the pinhole are adjustable, providing high transmittance of light and low requirement for the quality of the light beam.

The invention provides a detection device and method for small hole calibration, wherein light emitted by a laser is divided into two paths of light after passing through a filter hole, a condenser lens, a spatial filter, a beam expanding lens, a lambda/2 wave plate, a lambda/4 wave plate and a semi-transmitting semi-reflecting mirror; the first path of light is reflected by a reflector after passing through an attenuation plate and a beam splitter, and the reflected light is further reflected by the beam splitter to a first small hole so that diffracted spherical wave is produced by the first small hole and then is transmitted through the beam splitter; the second path of light passing through the semi-transmitting semi-reflecting mirror is reflected by the reflector to irradiate a second small hole; the diffracted spherical wave produced by the second small hole is reflected by the beam splitter before forming interference with the diffracted spherical wave produced by the first small hole; interference fringes pass through the condenser lens and then are collected by an optical detector; and finally, the errors of the diffracted spherical waves produced by three small holes areobtained through predetermined replacement operations. The detection device and the detection method provided in the invention are capable of improving the measurement accuracy of a point-diffractioninterferometer and reducing the processing cost of a high-accuracy small hole.

The invention discloses a device and a method for detecting reference spherical wave deviation in a visible point diffraction interferometer and belongs to the field of reference spherical wave ultra-high precision detection methods. The limitation of a Hartmann wavefront sensor on wavefront micro-deviation detection is overcome so that the wavefront high-precision detection can be realized. A light path comprises an incidence convergent light wave, a grating, a small pore plate with three circular holes along an orthogonal direction and a charge coupled device. The output end of the charge coupled device is connected to a computer. After being diffracted through the grating, the incidence convergent light wave is divided into a plurality of diffraction orders; +/-1 order of diffraction light respectively passes through two small holes; after the light is diffracted by the small holes, approximately ideal spherical waves are generated; two spherical waves are subjected to shear interference; an interference image is recorded on a CCD (Charge Coupled Device) detector; and after the interference image is collected, the diffraction wavefront deviation can be obtained. According to the device and method disclosed by the invention, the diffraction wavefront high-precision detection is realized by performing the shear interface of the spherical waves generated through double-hole diffraction in a visible light band.

A wavelength turning phase-shift point-diffraction interference measuring device and a method thereof belong to the field of surface profile measuring devices and methods for optical elements based on phase-shift point-diffraction interferometers. The device comprises a tunable laser light source module, a point-diffraction interference module and a control system; the tunable laser light source module comprises a tunable laser, a first spectroscope, a second spectroscope, a wavemeter and a dynamometer; the point-diffraction interference module comprises a beam adjusting mirror assembly, a needle hole plate, an interferometer imaging mirror assembly and a CCD (Charge Coupled Device) camera; the control system comprises a tunable laser control module, a CCD camera collection control module and a main-control computer. The device can realize phase shift and accomplish phase-shift point-diffraction interference measurement by using a wavelength-tunable laser, does not adopt a piezoceramic phase shifter PZT (Piezoe-lectric Transducer) or utilize a piezoceramic moving pyramid reflecting mirror or other mechanical moving components for phase shift, overcomes the technical problems that a mechanical phase shift device is high in manufacturing difficulty and high in cost, and stress deformation errors is caused by dead weight of a mechanical phase-shift device.

The invention relates to a method used for improving measuring accuracy of a point-diffraction interferometer, and belongs to the test field of point-diffraction interferometers. The method comprises the following steps of: placing a gathering lens and a foraminule plate on a same optical axis, enabling a parallel light source to gather through the gathering lens, and exit through the foraminule plate; enabling part of rays to form testing light, enabling the other part of rays to be used as reference light, and enabling the testing light and the reference light to share a light path on an ocular circle position of an imaging lens of a camera; and marking the light intensity maximum value of ocular circle on the ocular circle position of the imaging lens as A, placing an attenuation piece for which A point is taken as a centre and the transmissibility is gradually improved, wherein the attenuation piece is used for adjusting the light intensity distribution of an ocular circle light beam of the imaging lens, and the image intensities of the centre and an edge interference fringe are consistent. The method provided by the invention has the advantages that the design and structure are simple, the cost is cheap, the processing and manufacturing are easy, the problem that the rim light intensity of the point-diffraction interferometer is dropped so as to cause analog-digital conversion digit reduction is solved with lower cost, and the measuring accuracy of the point-diffraction interferometer is improved.

The invention discloses a heterodyne point diffraction interferometer based on the phase shift of a low-frequency-difference acousto-optic frequency shifter. The heterodyne point diffraction interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter comprises a light beam adjusting unit, a low-frequency-difference phase shifting unit, a point diffraction unit and an area array detector unit. The light beam adjusting unit is used for adjusting output lasers of a laser device into two laser beams with identical powers. The low-frequency-difference phase shifting unit is used for adjusting the frequencies of the two laser beams obtained by the light beam adjusting unit to obtain two laser beams with the output difference frequency being a low difference frequency lower than 100 Hz. The point diffraction unit is used for dividing the lasers adjusted by the low-frequency-difference phase shifting unit into measuring light and reference light so as to generate interference. The area array detector unit is used for collecting the interference. According to the heterodyne point diffraction interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter, heterodyne interference phase shift of the acousto-optic frequency shifter is adopted to effectively avoid that moving parts exist in the interferometer, the measurement accuracy is improved, the anti-interference performance is good, the low-frequency-difference heterodyne interferometer and the area array detector unit carry out consecutive collection, more abundant information can be obtained, phase position can be solved precisely, and noise influences can be avoided.

The invention discloses a device and method for measuring the curvature radius of a spherical mirror based on a pinhole type point diffraction interferometer. Double quantitative defocusing is realized through sequentially inserting two parallel flat plates with different thicknesses in an interfering cavity of the pinhole type point diffraction interferometer. When the parallel flat plates are not placed in a test optical path, wavefront data W0 are obtained through phase shifting measurement. After the two parallel flat plates with different thicknesses are respectively placed in the test optical path, two different wavefronts W1 and W2 are obtained through phase shifting measurement, and the calculating formula of the curvature radius of the spherical mirror is derived through the difference between the defocusing coefficients of the W1 and the W0, the difference between the defocusing coefficients of the W2 and the W0 and a Gaussian imaging formula. When the non-contact type measurement method is adopted, the damage of the surface of the spherical mirror is avoided, a feasible method is provided for the non-destructive measurement of the curvature radius of the spherical mirror with a large numerical aperture. Meanwhile, the method is suitable for the surface shape test of the spherical mirror with the large numerical aperture.

The invention relates to a common-optical path polarization point diffraction phase-shift interference wavefront sensor, which comprises a polaroid, a first double refraction lens, a second double refraction lens, a phase-shift interference system, a CCD (Charge Coupled Device) sensor and a computer, as well as a polarization PDI (Point-diffraction Interferometer) mask plate provided with a needle hole and additionally arranged at a confocal plane of the first and second double refraction lenses, wherein a linearly polarized light beam to be detected is divided into two beams by the first double refraction lens, E light is converged at the needle hole of the polarization PDI mask plate to be subjected to small hole diffraction so as to serve as reference light, and O light passes through the polarization PDI mask plate nearly without decrement to serve as testing light; the reference light and the testing light pass through the phase shift interference system to form a four-frame time or space phase shift interference figure; streak contrast gradient is adjusted through rotating the polaroid; and then a phase shift algorithm is adopted to re-establish a phase position of a wavefront to be detected. According to the invention, the wavefront sensor adopts a common-optical path, dispenses with special reference light, is strong in system stability and adjustable in streak contrast gradient, and is suitable for high-precision detection for dynamic and static stage of various wavefront phase positions.

The invention discloses a system and a method for accurately calibrating an optical path of a point diffraction interferometer based on image information. The system comprises spectroscopic prisms, abeam expanding collimation system, a diffraction orifice plate, a wave-front sensor, lenses, an optical power meter, three-dimensional precision electronically controlled translation stage and driverthereof, a CCD1 (charge-coupled device), and a computer. The method comprises the following steps of: analyzing and obtaining a mathematical relationship between an alignment error and a diffraction wave-front deviation by using the Rayleigh-Sommerfeld diffraction theory; designing an accurate optical path calibration system according to requirements to obtain a spot-hole alignment image and lightintensity before and after the diffraction orifice plate; then analyzing and measuring alignment deviation information through an image processing algorithm to establish a mathematical model betweenthe measurement quantity and the control quantity; and finally, achieving accurate calibration according to a system implementation principle. According to the system and the method for accurately calibrating the optical path of the point diffraction interferometer based on the image information, the precise alignment of the diffraction holes and the spot in the visual environment is realized, andthe influence of the alignment deviation on the detection precision of the point diffraction interferometer to some extent is eliminated. The system and the method have characteristics of high precision and high efficiency, and reduce the damage of the laser to the vision of operators during experimental operation.

Disclosed herein is a point-diffraction interferometer which can inspect a surface quality of an optical system for extreme ultraviolet lithography using a high-order harmonic X-ray source with excellent coherence, and an apparatus and method for generating a high-order harmonic X-ray. The present invention uses a high-order harmonic X-ray beam as a coherence light source, thus remarkably reducing the size of an apparatus for generating a light source to approximately 1/100 of a device using a light source generated in a conventional synchrotron. Further, the present invention simplifies the construction of an interferometer by employing a thin foil in which a pinhole is formed through a drilling technique using high power femtosecond laser, thus increasing the industrial utility of the interferometer.

The present invention is related with the two-channel point-diffraction interferometer for testing the optical systems or optical elements. The two-channel point-diffraction interferometer comprising a laser source inducing a linearly polarized laser beam which is divided by a beam splitter to a working channel and to a reference channel whereas the one half of light as working channel is directed from the first collimator to the working collimator by a first single-mode optical fibre to keep polarization of light unchanged, and another half of light as reference channel is directed from the second collimator to the reference collimator by a second single-mode optical fibre to keep polarization of light unchanged.

The invention discloses a full visual field low frequency heterodyne point diffraction interferometer. An acousto-optic frequency shifter is adopted to shift phase by heterodyne interference so that moving members of the interferometer are avoided, and measurement accuracy is further increased. The interferometer has good anti-interference performance, reduced development difficulty and cost, and compared with mechanical drive, the interferometer has more obvious advantages. Two optical fibers are used to respectively generate measuring light and reference light instead of part of emitting light; the interferometer combines the advantages that optical fiber point diffraction light is easy to access and flexible to adjust; compared with typical optical fiber point diffraction interferometer system, the measurement value aperture diameter range is increased. Besides, beam combination of point diffraction measurement light and reference light is realized by gluing angle ground fiber tips with light splitting plain films, wherein the beam combination is realized through outer sides of the semi-transparent and semi-reflection plain films, interference of diffraction opening edges on wave front of convergence light spots is avoided. The interferometer is easy to operate and has low cost.

The invention provides a method for leveling the end surface of a probe of a three-coordinate measuring device based on the point diffraction interferometer, and relates to the technical field of measurement. The method for adjusting zero position of the probe based on the wave surface symmetry is adopted. The method comprises the following steps of: acquiring the initial wave surface data by a detector; rotating the probe by 180 degree, and panning the probe to acquire the wave surface again; making the difference with the initial wave surface data after rotating the wave surface data by 180degree; panning the probe to the middle position, which is the zero position of the probe, between the initial position and the position in which the difference is the minimum value, and adjusting thetilt angle of the probe and obtaining the wave surface data; and fitting the wave surface by using the Zernike polynomial fitting method to obtain a x-y direction tilt term coefficient, and adjustingthe angle to which the coefficient is the maximum value to achieve leveling the end surface of the probe. According to the method for leveling the end surface of the probe of the three-coordinate measuring device based on the point diffraction interferometer, the technical problem of the measurement accuracy is affected in the prior art because the end face of the probe is difficult to level withrespect to the detecting surface. The beneficial effect of the invention is as follows: the state of the end face of the probe is determined, and the requirements for solving a measurement model is satisfied, so that the reconstruction result of the three-dimensional coordinate is more accurate and can be obtained more quickly.