Abstract: Conical surfaces (and other complex surface shapes) can be interferometrically characterized using a locally spherical measurement wavefront (e.g., spherical and aspherical wavefronts). In particular, complex surface shapes are measured relative to a measurement point datum. This is achieved by varying the radius of curvature of a virtual surface corresponding to a theoretical test surface that would reflect a measurement wavefront to produce a constant optical path length difference (e.g., zero OPD) between the measurement and reference wavefronts.

Abstract: A method of processing an optical element comprises providing an interferometer optics; arranging a calibrating substrate in a beam of measuring light emitted by the interferometer optics; superimposing measuring light having traversed the first and second surfaces of the calibrating substrate with reference light, and taking a first interferometric measurement of the superimposed measuring light and reference light; arranging the aspherical surface of the optical element in the beam of measuring light emitted by the interferometer optics, while the calibrating substrate is not arranged in the beam of measuring light; superimposing measuring light having interacted with the aspherical surface and the reference light, and taking a second interferometric measurement of the superimposed measuring light and reference light; determining deviations of the aspherical surface from a target shape thereof in dependence of the first and second measurements; and machining the aspherical surface of the optical element.

Abstract: A phase shifting wavefront superimposition method in which the intensities of superimposition patterns of object wavefront and reference wavefronts produced successively in time with respective phase shifts by predefinable phase steps are registered for a respective predefinable location and, from the registered intensities, an object-induced phase difference between object wavefront and reference wavefront is determined for the respective location. Phase step errors in the successively produced superimposition patterns are determined by means of a spatial superimposition pattern evaluation and taken into account correctively in the determination of the object-induced phase difference. The method is used for example, in wavefront measurement of optical imaging systems by means of phase shifting interferometry for the purpose of highly accurate determination of imaging errors.

Abstract: An optical field sensing system and an associated method are provided that are tolerant of scintillation. The system includes a wavefront sensor that measures gradients across a wavefront at a first resolution defined by the subapertures of the wavefront sensor. The system also includes an intensity sensor that measures the intensity across the wavefront at a higher resolution. The system further includes a wavefront processor that determines respective phases across the wavefront. In addition to the gradients and the intensity measurements, the wavefront processor may determine the respective phases based also upon the noise affiliated with the measurements. In this regard, the wavefront processor may determine the respective phases across the wavefront at least partially based upon the gradients as adjusted by weights that are based upon the intensity measured by the intensity sensor and are influenced by evidence of scintillation.

Abstract: A method and apparatus for performing optical microscopy in one to three dimensions employs a spectral self-interference fluorescent microscopy technique that includes providing at least one fluorescent microscopy sample, at least one objective lens, and at least one reflecting surface. The fluorescent sample is disposed between the objective lens and the reflecting surface, the distance from the sample to the reflecting surface being several to several tens times an excitation wavelength. Excitation light causes the fluorescent sample to emit light, at least a portion of which is reflected by the reflecting surface. The objective lens collects the reflected light and the light emitted directly by the fluorescent sample. The direct and reflected light interfere causing spectral oscillations in the emission spectrum. The periodicity and the peak wavelengths of the emission spectrum are spectroscopically analyzed to determine the optical path length between the fluorescent sample and the reflecting surface.

Abstract: A laser beam is irradiated onto a moving object, and scattered light reflected from the moving object is split into two beams, which are then received through respective spatial filters that are 90° out of phase with each other, thereby providing two signals. The signals are processed to determine the movement direction of the moving object.

Abstract: There is provided an interferometer for measuring a surface shape of an optical element using interference, including a reference wave-front generating unit for generating a reference wave front for measuring the surface shape, which is provided in a target optical path, and includes an Alvarez lens.

Abstract: An interferometry method includes: imaging test light reflected from at least a first portion of a test surface to interfere with reference light on a camera and form an interference pattern, wherein the imaging defines a depth of focus for the light reflected from the test surface, and wherein the test light and reference light are derived from a common source; varying an optical path length difference between the test light and reference light over a range larger than the depth of focus, wherein the optical path length difference corresponds to a difference between a first optical path between the common source and the camera for the test light and a second optical path between the common source and the camera for the reference light; and maintaining the first portion of the test surface within the depth of focus as the optical path length difference is varied.

Abstract: A method disclosed in this specification is an aberration measuring method in which a light flux converged by a condensing optical system is made incident on a optical system to be measured, the light flux that has passed through the optical system to be measured is reflected by a reflecting optical system having a center of curvature at a light convergence point on a light emergence side of the optical system to be measured is made incident on the optical system to be measure again, and wavefront aberration of the optical system to be measured is detected as interference fringes using the light flux that has passed through the optical system to be measured again. Measurement is carried out while changing the numerical aperture of the optical system to be measured to a numerical aperture larger than a numerical aperture in the actual use, thereby realizing highly precise measurement of the wavefront aberration all over the effective numerical aperture of the optical system to be measured.

Abstract: An integrated interferometric and intensity based microscopic inspection system inspects semiconductor samples. A switchable illumination module provides illumination switchable between interferometric inspection and intensity based microscopic inspection modes. Complex field information is generated from interference image signals received at a sensor. Intensity based signals are used to perform the microscopic inspection. The system includes at least one illumination source for generating an illumination beam and an integrated interferometric microscope module for splitting the illumination beam into a test beam directed to the semiconductor sample and a reference beam directed to a tilted reference mirror. The beams are combined to generate an interference image at an image sensor. The tilted reference mirror is tilted with respect to the reference beam that is incident on the mirror to thereby generate fringes in the interference image.

Abstract: An interferometric system including: an interferometer that directs a measurement beam at an object point to produce a return measurement beam, focuses the return measurement beam to an image point in an image plane, and mixes the return measurement beam with a reference beam at the image point to form a mixed beam; a beam combining layer located at the image plane which is responsive to the mixed beam and produces an optical beam therefrom, wherein the layer comprises a thin film with an array of transmissive openings formed therein and further comprises a fluorescent material associated with each of the openings of the array of openings; a detector that is responsive to the optical beam from the beam combining layer; and an imaging system that directs the optical beam from the beam combining layer onto the detector.

Abstract: In a speckle interferometer apparatus 2, an optical member mounting device 10 mounted with optical members including a pair of luminous flux outputting devices 9a, 9b, 9c, 9d is disposed on the object side of a main unit of an imaging device 3 while being separated from the imaging device 3. A light-transmitting area 14 is formed between the pair of luminous flux outputting devices 9a, 9b, 9c, 9d so as to transmit therethrough interference light from an object surface.

Abstract: Iterative algorithm methods and systems for slope or gradient-type data is presented for wavefront zonal estimation of regular and irregular pupil shapes. The methods and systems bears universal wavefront estimation matrices that are directly applicable to any pupil shape without the need to set up new matrices. The algorithm consists in first extending the sampling pupil to a larger regular square shape and second extrapolating the sampled slope data outside of the sampling pupil employing Gerchberg-type iterations. Unbiased least-squares wavefront estimation is then performed in the square domain. Results show that the RMS deviation error of the estimated wavefront from the original wavefront can be less than ?/150 after about twelve iterations and less than ?/100 (both for ? equal 632.8 nm) within as few as five iterations.

Abstract: A method of extracting a tomographic image of a layer within a body by optical coherence tomography, involves capturing three images, namely a non-interference background image, a first interference-fringe image of said layer, and a second interference-fringe image phase-shifted relative to the first interference-fringe image. The tomographic image is obtained by mathematically combining the three captured images. In a preferred embodiment random noise is removed by averaging and inter-layer effects are removed by applying a compensation function. This system is then used to extract the 2D cross-sectional images encoded in a multiple-layer information carrier.

Abstract: A method including: generating a sequence of phase-shifted interferometry images of an object surface relative to a reference surface; and calculating an unequally weighted average of the phase-shifted interferometry images to produce a final image. The final image can be useful as a lateral metrology image. The method may further include calculating a surface topography image from the sequence of phase-shifted interferometry images. Embodiments further include apparatus related to the method.

Abstract: A method of manufacturing an optical element having an optical surface of a target shape includes performing an interferometric test using an interferometer optics, wherein the interferometer optics includes a hologram that deflects a beam of measuring light by a substantial angle or that displaces an axis of symmetry of measuring light emerging from the hologram with respect to an axis of symmetry of measuring light incident on the hologram.

Abstract: A frequency-scanning interferometer is modified to include a diffuse reference surface. An illuminating system produces an expanding measuring beam, portions of which reflect from a test object surface and the diffuse reference surface on converging paths to an imaging system. Interference patterns between overlapping images of the object and reference surfaces are generated at a plurality of frequencies for measuring the object surface with respect to the reference surface.

Abstract: A system for inspecting specimens such as semiconductor wafers is provided. The system provides scanning of dual-sided specimens using a diffraction grating that widens and passes nth order (n>0) wave fronts to the specimen surface and a reflective surface for each channel of the light beam. Two channels and two reflective surfaces are preferably employed, and the wavefronts are combined using a second diffraction grating and passed to a camera system having a desired aspect ratio. The system preferably comprises a damping arrangement which filters unwanted acoustic and seismic vibration, including an optics arrangement which scans a first portion of the specimen and a translation or rotation arrangement for translating or rotating the specimen to a position where the optics arrangement can scan the remaining portion(s) of the specimen. The system further includes means for stitching scans together, providing for smaller and less expensive optical elements.

Abstract: A method for qualifying and/or manufacturing an optical surface includes: arranging a first substrate having a first surface and a second surface opposite the first surface in a beam path of a first incident beam with the first surface facing towards the first incident beam, and taking an interferometric measurement of the second surface; arranging the first substrate in the beam path of the first incident beam with the second surface facing towards the first incident beam, and taking an interferometric measurement of the second surface; arranging a third surface of a second substrate in a beam path of a second incident beam, and taking an interferometric measurement of the third surface; arranging the third surface of the second substrate and the first substrate in the beam path of the second incident beam, and taking an interferometric measurement of the third surface.

Abstract: An interferometric measuring method and device for measuring the shape of, or the distance to, surfaces are provided, in which light is generated, modulated with respect to its frequency, conducted to both an object surface and a reference surface, brought to interference, and conducted to a photodetector, and, to detect the particular distance, a phase of the photodetector signal is evaluated. A simple, rugged configuration, with the capability of taking a high-resolution measurements in the context of a large unambiguity range, is achieved in that the phase is considered in at least two different instants with the wavelengths that correspond on the basis of the frequency modulation, and the results are fed to the evaluation.

Abstract: A wavefront measuring system and method for detecting phase aberrations in wavefronts that are reflected from, transmitted through or internally reflected within objects sought to be measured, e.g., optical systems, the human eye, etc. includes placing a reticle in the path of a return beam from the object, and placing a detector at a diffraction pattern self-imaging plane relative to the reticle. The diffraction pattern is analyzed and results in a model of the wavefront phase characteristics. A set of known polynomials is fitted to the wavefront phase gradient to obtain polynomial coefficients that describe aberrations in the object or within the wavefront source being measured.

Abstract: An interferometry method including: i) forming an optical interference image by combining different portions of an optical wave front reflected from a pair of surfaces; ii) recording an interference signal at different locations of the optical interference image in response to varying the relative position of the two surfaces over a range of positions; iii) transforming the interference signal for at least one of the locations to produce a spectrum having a peak at a spectral coordinate corresponding to the variation in the relative position of the two surfaces over a range of positions; iv) identifying the spectral coordinate of the peak; and v) for each location, extracting the spectral phase of the interference signal at the coordinate of the peak. For example, the method may further include, for each of the different locations, determining a surface profile of one of the surfaces based on the spectral phase of the interference signal at each of the multiple locations.

Abstract: Conical surfaces (and other complex surface shapes) can be interferometrically characterized using a locally spherical measurement wavefront (e.g., spherical and aspherical wavefronts). In particular, complex surface shapes are measured relative to a measurement point datum. This is achieved by varying the radius of curvature of a virtual surface corresponding to a theoretical test surface that would reflect a measurement wavefront to produce a constant optical path length difference (e.g., zero OPD) between the measurement and reference wavefronts.

Abstract: A wavefront measurement system has a source of electromagnetic radiation. An imaging system focuses the electromagnetic radiation at an object plane. A first grating is positioned in the object plane and has a plurality of rulings with randomized height. A stage moves the first grating parallel to the rulings. A projection optical system projects an image of the first grating onto an image plane. A second grating is at the image plane. A detector behind the second grating receives a fringe pattern produced by the second grating.

Abstract: A projection exposure apparatus includes an exposure light source, an illumination system for illuminating a pattern, formed on a first object, with light from the exposure light source, a projection optical system for projecting a pattern, as illuminated with the light, onto a second object, and an interferometer for use in measurement of an optical characteristic of the projection optical system, wherein the interferometer is operable to perform the measurement by use of light from the exposure light source.

Abstract: In a method for determining wavefront aberrations for the characterization of imaging characteristics in an optical imaging system, the measurement results from two different measurement methods, which are carried out at successive times, are combined. In this case, at least some of the aberration parameters which are determined in the previous first measurement method are used as a given precondition for determining aberration parameters with the aid of the second measurement method, and are assessed accordingly. This results in a hybrid method, in which the strength of at least two measurement methods are used in a combined form, and specific weaknesses of any one method can be avoided.

Abstract: In certain aspects, the invention features scanning interferometry systems and methods that can scan an optical measurement surface over distances greater than a depth of focus of imaging optics in the interferometry system, while keeping an optical measurement surface in focus (i.e., maintaining an image of the optical measurement surface coincident with the detector). The optical measurement surface refers to a theoretical test surface in the path of test light in the interferometer that would reflect the test light to produce an optical path length difference (OPD) between it and reference light that is equal to a constant across a detector.

Abstract: A control system is provided for controlling the shape of a flexible electromagnetic radiation structure. The control system includes a plurality of actuators and a plurality of computational elements. Each of the plurality of actuators is coupled to a portion of the radiation structure and can be selectively actuated by the plurality of computational elements. Thus, the plurality of actuators and the plurality of computational elements provide control of the flexible electromagnetic radiation structure shape. In one embodiment, each of the plurality of computational elements controls one section of the flexible electromagnetic radiation structure. Thus each of the plurality of computational elements receives controls the one or more of the plurality of actuator within its section. Together, the plurality of computational elements provide a distributed control network for the radiation structure.

Abstract: An interferometer system comprises a reference surface, a support for an object providing an object surface, a radiation source for emitting radiation of an adjustable frequency onto the reference surface and the object surface, a position-sensitive radiation detector, a controller for adjusting a plurality of different frequencies of the radiation emitted by the radiation source, and an integrator for averaging the interference patterns superposed on the radiation detector at different frequencies. Moreover, there is provided a method for recording an interferogram, a method for providing an object with a target surface as well as a method for manufacturing an object with a target surface.

Abstract: A method is described that involves tracking a fringe line disturbance that has breached its field of reference. The method also involves translating each pixel location of the tracked fringe line disturbance to an x,y,zs data point. x and y represent a position on the plane of an interferometer's sample stage. zs represents the height of a sample above the x,y position. The sample is placed upon the sample stage of an inteferometer so as to create the fringe line disturbance. The fringe line disturbance is observed on the interferometer's detector.

Abstract: A system for characterizing an aspheric surface with respect to an expected shape thereof, comprising a light source to emit light of desirable properties. A ferrofluid deformable mirror apparatus has a reflective surface being controllably deformable. The reflective surface is shaped as a function of the expected shape so as to reflect light in a known path toward a detector. Optical elements project light from the light source onto the aspheric surface such that light is reflected along an expected path if the aspheric surface has the expected shape. Light is reflected from the aspheric surface along an actual path. The optical elements project light on the reflective surface of the ferrofluid deformable apparatus such that light is reflected along the known path. A detector receives light reflected along at least one of the actual path and the known path to obtain an interference pattern as a function of the expected path.

Abstract: Methods for determining an appropriate tuning rate for interferometry systems employing phase-shifting interferometry are disclosed.

Abstract: A Fizeau interferometer apparatus is used for both low and high interference measurement. When irradiating a reference surface and a sample with a low coherent luminous flux, a path-matching passage divides the low coherent luminous flux into first and second paths, while the optical path length difference between the respective luminous fluxes passed through the two paths equals twice the optical distance between the reference surface and the sample. When irradiating the reference surface and the sample with a high coherent luminous flux, the luminous flux is made incident on the sample side of the path-matching passage at a position coaxial with the low coherent luminous flux.

Abstract: A conventional phase shifting interferometer that is used for measuring distances (e.g., in the micron range) typically provides two orthogonal, or quadrature, signals. The output signals typically include an offset that introduces a related measurement error unless it is compensated or eliminated. A standard way for eliminating offsets is to generate and/or process additional signals that are phase shifted by 180 degrees, or other known amounts. In contrast, the present invention provides a signal indicative of the offset contribution to a detector signal in an interferometer by varying the wavelength of radiation from the illumination source of the interferometer during the time that the offset determining signal is acquired or integrated by that detector. The method can be conveniently implemented with each signal detection channel of an interferometer, for a variety of interferometer designs.

Abstract: In a phase unwrapping method for fringe image analysis, when storing newly calculated numeric data into a storage list, the new numeric data is initially compared with numeric data of a representative rank within each rank block in the storage list, whereby the rank block to store the data is chosen. Subsequently, the new numeric data is compared with each of respective numeric data within thus chosen rank block, so as to determine a rank at which the new numeric data is to be stored, and then is stored into the storage list. Along with the storing of numeric data, rank data is updated.

Abstract: An interferometric measuring device includes a reference arm having a reference surface and a measuring arm having lighting optics for deflecting measuring light onto a measuring surface of an object to be measured, and having an image recorder connected to an analyzing device. A rapid, simple measurement with a rugged design of the measuring device may be achieved by configuring the lighting optics as a light guide body insertable into a cavity in the object to be measured, having a peripheral, radially symmetrical effective reflex surface directed radially or obliquely outward, and also including at least one deflector surface deflecting the measuring light onto same.

Abstract: A method for accurately synthesizing a full-aperture data map from a series of overlapped sub-aperture data maps. In addition to conventional alignment uncertainties, a generalized compensation framework corrects a variety of errors, including compensators that are independent in each sub-aperture. Another class of compensators (interlocked) include coefficients that are the same across all the sub-apertures. A constrained least-squares optimization routine maximizes data consistency in sub-aperture overlap regions. The stitching algorithm includes constraints representative of the accuracies of the hardware to ensure that the results are within meaningful bounds. The constraints also enable the computation of estimates of uncertainties in the final results. The method therefore automatically calibrates the system, provides a full-aperture surface map, and an estimate of residual uncertainties.

Abstract: A deformation measuring method using electronic speckle pattern interferometry comprises the steps of subtracting an average intensity from the intensity in a time domain at each point of a speckle pattern image so as to compute the cosine component of intensity; subjecting the cosine component to Hilbert transform in a temporal domain so as to compute the sine component of intensity; determining the arctangent of the ratio between thus computed sine and cosine components so as to determine an object phase; carrying out an unwrapping operation; and outputting three-dimensional deformation distribution data in a displayable mode.

Abstract: A method and a device for interferential microscopic imaging of an object which comprises sending a light beam in each of the arms of a two-wave interferometer, one of the arms comprising the object to be analyzed. The phase is subjected to a sinusoidal modulation to a frequency f. The signal modulation results from mechanical oscillation of an assembly of elements of the interferometer. The interference signal (S) is integrated during the phase variation via a multichannel sensor. A computer enables to record the integrated interference signal obtained during each period fraction 1/n and to calculate, subsequently, the image of the object. The invention is potentially useful for characterizing thin layers, for controlling components in microelectronics, for reading data stored in volume (3D) and objects unstable in time; in biology and in vivo studies.

Abstract: An interferometry method including: i) forming an optical interference image by combining different portions of an optical wave front reflected from multiple surfaces; ii) recording an interference signal at different locations of the optical interference image in response to varying a property of the optical wave front that causes pairs of the multiple surfaces that have different optical path separations to contribute differently to the interference signal; iii) transforming the interference signal for at least one of the locations to produce a spectrum having a peak at a spectral coordinate corresponding to each pair of the multiple surfaces; and iv) identifying the spectral coordinate of the peak corresponding to a selected pair of the multiple surfaces.

Abstract: A point source module is provided, comprising: a Shack cube comprising a beam splitter cube with an attached spherical reference surface defining a reference arm; a test arm that is associated with transmission of optical radiation from a source to a sample; a point source of optical radiation whose emissions traverse both the reference arm and the test arm; and a detector associated with a surface of the beam splitter cube and receiving optical radiation from both the reference arm and the test arm and comprising a detector arm, an objective lens associated with the test arm, or both. Further, a method of aligning the point source module is provided, along with a method of using the point source microscope is provided. The apparatus and methods provide a compact, robust device and technique for measuring or locating optical or mechanical datum of parts that are being manufactured or assembled.

Abstract: In a method and apparatus for detecting small periodic wave patterns in technical surfaces, monochromatic coherent primary light is directed onto a workpiece surface approximately at right angles to the expected periodic wave patterns, and at an angle of incidence that grazes the workpiece surface, creating a diffraction image of the waved surface structure in the secondary-light beam. The occurrence of two intensity maxima immediately indicates the presence of a periodic wave pattern, whose period is evaluated through inverse proportionality from the spacing of neighboring intensity maxima, while the depth of the wave troughs is determined from the intensity of neighboring intensity maxima and from the period. The intensity distribution in the diffraction image in the secondary-beam path is subjected to an autocorrelation, and both the period and the depth of the wave pattern can be calculated from the autocorrelation function.

Abstract: To measure a convex mirror, a reference beam and a measurement beam are both provided through a single optical fiber. A positive auxiliary lens is placed in the system to give a converging wavefront onto the convex mirror under test. A measurement is taken that includes the aberrations of the convex mirror as well as the errors due to two transmissions through the positive auxiliary lens. A second measurement provides the information to eliminate this error. A negative lens can also be measured in a similar way. Again, there are two measurement set-ups. A reference beam is provided from a first optical fiber and a measurement beam is provided from a second optical fiber. A positive auxiliary lens is placed in the system to provide a converging wavefront from the reference beam onto the negative lens under test. The measurement beam is combined with the reference wavefront and is analyzed by standard methods.

Abstract: A method and system for measuring optical characteristics of a sub-component within a composite optical system is disclosed. In one embodiment, the present invention generates an optical response from a composite optical system. The present embodiment then separates an optical response of a sub-component from the optical response of the composite optical system. The present embodiment then determines the optical characteristics of the sub-component by utilizing at least one portion of the optical response of the sub-component.

Abstract: An apparatus and a method are provided which allow two opposite plane surfaces of a body to be interferometrically measured simultaneously using light from a single light source. From a parallel light beam (P) produced by a light source (1) partial light beams (A, B) having positive and negative diffraction angles are produced using a beam splitter (8) in the form of a diffraction grating. The partial light beams strike the respective surfaces (90, 91) of the body (9) to be measured and are reflected thereat. The reflected partial light beams (A, B) are interfered with the throughgoing partial light beam (P) having an order of diffraction of zero and the thus produced interference patterns are digitized and subtracted from each other, whereby the parallelism of both surfaces (90, 91) of the body can be determined.

Abstract: An expanding measuring beam is inserted into a cavity of a frequency-scanning interferometer. The expanding measuring beam encounters non-specular (diffuse) reference and object surfaces so that the reflected light can be imaged with an imaging system of reduced dimension. The compact interferometer is adaptable to a variety of applications. For example, the compact interferometer can be incorporated into a sensor of a multi-stage measuring instrument or into a handheld imager.

Abstract: The invention features methods and systems in which wavelength-tune PSI data is analyzed in the frequency domain to produce spectrally separated frequency peaks each corresponding to a particular pair of surfaces in an interferometric cavity defined by multiple pairs of surfaces. Each frequency peak provides optical path length information about a corresponding pair of surfaces in the cavity. As a result, the interferometric data from such cavities provides simultaneous information about multiple surfaces.

Abstract: A method and apparatus to linearize the phase shifts produced by the wavelength-varying driving mechanism of an interferometer used in phase shift interferometry for the measurement of multiple reflective surfaces first calibrates a sequence of physical values used as the input to the driving mechanism to produce a known linear or a known constant phase shift increment between any two adjacent interferograms. The calibration process, in essence, involves the determination of the sequence of physical values, such as the voltage change with respect to the time, through the process of iteration. This sequence then is used as an input to the phase shift driving mechanism for ongoing operation of the system, thereby compensating for non-linear characteristics of the system.

Abstract: The method is used for the interferometric measurement, in particular for the interferometric absolute measurement, of non-rotationally symmetric wavefront errors on a specimen. The specimen can in this case be brought into a plurality of rotational positions, at least one measurement result being determined in each of the rotational positions. A mathematical evaluation of all measurement results is carried out in conclusion. The measurement is carried out in at least two measurement series (M, N). The measurement results (M1 . . . Mm, N1 . . . Nn) of each of the measurement series (M, N) are respectively determined in mutually equidistant rotational positions of the specimen. Each of the measurement series (M, N) comprises a specific number m, n of measurements. The individual numbers m, n are natural and mutually coprime numbers.

Abstract: A wavefront measuring apparatus and a wavefront measuring method are capable of performing optical measurement on a test optical system, including an immersion optical system, with comparable ease of handling to that of the conventional measuring method using a concave member, and substantially independently of reflection that may occur at the surface closest to the test optical system among the surfaces of an optical member for reflecting light exiting from the test optical system. The wavefront measuring apparatus has a light source, a reference light path in which a reference member for producing reference light is disposed, and a test light path in which the test optical system is disposed. A plano-convex optical member with a wall thickness approximately equal to the radius of curvature of a convex surface thereof is disposed in the test light path in such a manner that a plane surface thereof faces toward the test optical system.