Abstract: A method for designing a diffractive optic includes identifying an initial performance metric for the diffractive optic, the diffractive optic including a substrate. A test cell is selected from an array of cells on the substrate. A height of the test cell is changed by a predetermined height unit. Images are computed at a plurality of discrete wavelengths or using a continuous spectrum using diffraction-based propagation through at least a portion of the array of cells. A wavelength metric is determined for each of the images. The wavelength metrics for each of the images is consolidated into a perturbed performance metric. The perturbed performance metric is compared to the initial performance metric and the method identifies whether the perturbed performance metric is an improvement over the initial performance metric.

Abstract: Systems, methods and devices are implemented for optical imaging. In one embodiment of the present disclosure, an optical imaging apparatus utilizes a laser-based coherent light source, and an optical device to pass grated light along an illumination direction from the laser-based coherent light source toward an object. Additionally, an illumination modulator is provided for changing angles at which the light, moving toward the object plane, reaches the object plane, and the light reaches the object plane at different angles. Further, the apparatus can include circuitry to process image-based data in response to and based on the light reaching the object plane at different angles for a user-viewable image of an object in proximity of the object plane.

Abstract: The invention relates to a lithography system comprising an optical column, a moveable target carrier for displacing a target such as a wafer, and a differential interferometer module, wherein the interferometer module is adapted for emitting three reference beams towards a first mirror and three measurement beams towards a second mirror for determining a displacement between said first and second mirror. In a preferred embodiment the same module is adapted for measuring a relative rotation around two perpendicular axes as well. The present invention further relates to an interferometer module and method for measuring such a displacement and rotations.

Abstract: A method of aligning at least two wave shaping elements, a method of measuring a deviation of an optical surface from a target shape and a measuring apparatus for interferometrically measuring a deviation of an optical surface from a target shape.

Abstract: Methods and systems for measuring a surface of an object are provided, wherein portions of the surface of the object are interferometrically measured and data representing a shape of the surface of the object are obtained by stitching the measurement data corresponding to each portion together. For measuring the individual portions of the surface of the object a variable light shaping member is utilized preferably constructed by arranging two diffraction gratings in a beam path of measuring light and appropriately displacing the two diffraction gratings relative to each other depending on a target shape of a particular portion of the surface of the object.

Abstract: An imaging apparatus includes a diffraction grating configured to produce an interference pattern by diffracting diverging light from a light source, an absorption grating configured to block part of the interference pattern, a detector configured to detect light transmitted through the absorption grating, and a moving unit configured to move the diffraction grating and the absorption grating. The moving unit causes relative movement of the interference pattern and the absorption grating by moving the diffraction grating and the absorption grating such that the diffraction grating and the absorption grating are not moved relative to each other.

Abstract: A method comprises determining a first processing center position to calculate a wavefront aberration of an optical system, determining a second processing center position to calculate a wavefront aberration, correcting the first processing center position in a first direction using the second processing center position in the first direction and correcting the second processing center position in a second direction using the first processing center position in the second direction.

Abstract: A circular common-path point diffraction interference wavefront sensor includes an optical matching system, a beam-splitter, a first reflection mirror, a second reflection mirror, a first Fourier lens, a second Fourier lens, a charge-coupled device (CCD) detector, a computer system, and a two-pinhole mask having a reference pinhole and a testing window and placed at a confocal plane of the first Fourier lens and the second Fourier lens. A testing beam is divided into two beams through the beam-splitter. One beam makes the pinhole diffraction by the reference pinhole, thereby producing the approximately ideal plane wave as the reference wave. Another beam passes through the testing window almost without any attenuation as the signal wave. The spatially linear carrier frequency is introduced by adjusting the tilt angle of the beam-splitter. The present invention is adapted for all kinds of dynamic and static detection field of wavefront phase.

Abstract: The general field of the invention is that of optical devices designed for measuring anemometer parameters such as speed and temperature, the device being mounted on an aircraft and comprising an optical emission module illuminating the outside air, an optical reception module capable of receiving the light scattered by the air molecules, optical means forming a reference path and computing means connected to the reception module. The optical reception module comprises optical mixing means for mixing a portion of the beam originating from the reference path and a portion of the scattered light beam. The optical emission and reception means are arranged so that the reception device collects the light originating from the Brillouin-Mandel'shtam scattering.

Abstract: Embodiments of the present invention relate to a surface wave enabled darkfield aperture structure comprising an aperture layer, a aperture in the aperture layer and a plurality of grooves around the aperture. The aperture layer has a first and second surface. The plurality of grooves is in the first surface. A surface wave propagates along at least the first surface. The plurality of grooves is configured to generate a darkfield at the aperture by modifying the surface wave to cancel out direct transmission of a uniform incident light field received by the aperture.

Abstract: Systems and methods are provided for measuring aberration in a lithographic apparatus. A radiation beam is modulated using an array of individually controllable elements, and the modulated beam is projected using a projection system. A pattern is provided on the array of individually controllable elements to modulate the radiation beam, and the pattern comprises a repeating structure that is formed from a plurality of features that are dimensioned such that first order diffraction of the radiation beam substantially fills the pupil of the projection system. A sensor detects the projected radiation and measures interference in the radiation projected by the projection system. Aberration in the detected radiation beam is then measured.

Abstract: A measurement apparatus which measures spatial coherence in an illuminated plane illuminated by an illumination system, comprises a measurement mask which has at least three pinholes and is arranged on the illuminated plane, a detector configured to detect an interference pattern formed by lights from the at least three pinholes, and a calculator configured to calculate the spatial coherence in the illuminated plane based on a Fourier spectrum obtained by Fourier-transforming the interference pattern detected by the detector.

Abstract: The penetration depth of surface acoustic wave scales with wavelength. To measure thinner films using impulse stimulated thermal scattering (ISTS) it is advantageous to reduce the measurement wavelength to on the order of 1 micron. One way to reduce the measurement wavelength is to employ a high numerical aperture lens to converge an excitation and probe laser beam in an optical system at wider angles. While doing this, the increased optical/mechanical tolerances can be reduced by fine-tuning the phase between an excitation laser pattern and a probe laser pattern by adjusting either a neutral-density filter or matching plate for a particular wavelength. Blocking unwanted diffraction order beams generated by the optical system with a specialized design beam block plate is needed to retain the long wavelength capability.

Abstract: An imaging interferometer includes optics defining an interferometric cavity, in which the optics include a first beam-splitting optic positioned to separate an input beam into a test beam and a reference beam, a second beam-splitting optic positioned to transmit the test beam to the test surface, receive the test beam back from the test surface, and thereafter recombine the test beam with the reference beam, and a third optic positioned to direct the reference beam from the first optic to the second optic. The interferometric cavity defines a virtual reference surface positioned along a path for the reference beam between the second and third optics. The interferometer also includes an imaging channel positioned to receive the recombined test and reference beams, where the imaging channel includes an imaging detector, and at least one imaging element configured to image the test surface and the virtual reference surface onto the detector.

Abstract: Disclosed is an interference objective lens unit, comprising: an objective lens; a beam splitter that splits the light transmitted through the objective lens into a reference optical path in which a reference mirror is provided and a measuring optical path in which the measuring object is placed, and that superposes the split lights to output interference light; a first holder that holds the objective lens and that is formed by material having a first linear expansion coefficient; and a second holder that holds the reference mirror and that is formed by material having a second linear expansion coefficient different from the first linear expansion coefficient, wherein when a usage environment temperature changes, a difference in the linear expansion coefficients between the first holder and the second holder corrects an optical path difference between the reference optical path and the measuring optical path.

Abstract: An optical wavefront sensor comprising a light manipulation device; a detector for detecting light signals having been subjected to the light manipulation device; and a controller coupled to the manipulation device, the controller controlling the manipulation device to function as a lenslet array, each lenslet of the array focussing an incident portion of a wavefront onto the detector. The controller may also control the distance between the detector and the manipulation device. The spatial resolution of Shack-Hartmann sensors can be increased by digital scanning the wavefront with the manipulation device. The wavefront sensing can be dynamic adaptive by setting of parameters of the manipulation device.

Abstract: A method of aligning at least two wave shaping elements, a method of measuring a deviation of an optical surface from a target shape and a measuring apparatus for interferometrically measuring a deviation of an optical surface from a target shape.

Abstract: A multilayer optical device includes an arrangement, on a substrate, of a first layer, a second layer, and a space therebetween. The second layer is a thin-film. The arrangement of the first and second layers and the space therebetween produces transmitted, reflected, or dispersed spectrally modified electromagnetic energy from electromagnetic energy incident upon the arrangement. An optical function of the device is dependent at least in part on interference effects. An optical detector system includes a similar multilayer optical device. The space within the device is in fluid communication with structures for receiving a fluid such that the device operates in a first or second mode depending on absence or presence of the fluid within the space. The system includes a detector for receiving the modified electromagnetic energy, and a controller in fluid communication with the space that establishes the absence or presence of the fluid in the space.

Abstract: A method and apparatus for spatially resolved wavefront measurement on a test specimen, a method and apparatus for spatially resolved scattered light determination, a diffraction structure support and a coherent structure support therefor, and also an objective or other radiation exposure device manufactured using such a method, and an associated manufacturing method. An embodiment involves carrying out, for the wavefront measurement, a first shearing measuring operation, which includes a plurality of individual measurements with at least two first shearing directions and spatially resolved detection of shearing interferograms generated, and an analogous second shearing measuring operation with at least one second shearing direction, the at least one second shearing direction being non-parallel to at least one first shearing direction. From the shearing interferograms detected, it is possible e.g.

Abstract: An observation device 1 comprises a light source unit 10, a biaxial scanning system 20, a wavefront modulation unit 30, an optical branching unit 40, a light detection unit 50, a wavefront detection unit 60, a control unit 70, and the like. The wavefront modulation unit 30 presents a compensating phase pattern for compensating for an aberration of input light and a branching phase pattern for splitting the input light into first and second beams. The wavefront detection unit 60 receives inputted light and detects a wavefront of the inputted light. The compensating phase pattern for compensating for the wavefront aberration is feedback-controlled in loop processing that includes the detection of a wavefront distortion of the light by the wavefront detection unit 60, the adjustment of the phase pattern by the control unit 70 according to the result of detection, and the presentation of the phase pattern by the wavefront modulation unit 30.

Abstract: A label-free interferometric biosensor is disclosed which is based on the self-mixing optical interferometer. Inside the biosensor, an incoming beam is divided into two beam portions which pass through a channel and bio materials, respectively. Interference of the portions is realized by the self-mixing effect and used to detect existence of an analyte, such as DNA or protein molecules. The label-free biosensor is compact and can be made on a chip using the semiconductor technology. It is also convenient to use due to moderate alignment requirement. Furthermore, an array of the interferometers fabricated on a chip enables high-throughput and highly parallel measurements.

Abstract: A device for the optical measurement of an optical system, in particular an optical imaging system, is provided. The device includes at least one test optics component arranged on an object side or an image side of the optical system. An immersion fluid is adjacent to at least one of the test optics components. A container for use in this device, a microlithography projection exposure machine equipped with this device, and a method which can be carried out with the aid of this device are also provided. The device and method provide for optical measurement of microlithography projection objectives with high numerical apertures by using wavefront detection with shearing or point diffraction interferometry, or a Moiré measuring technique.

Abstract: A method for measuring a saturated photorefractive index and a recording time constant to correct the precision includes measuring the diffraction efficiency as a function of time for both phase matching and phase mismatching. The saturated photorefractive index and the recording time constant are verified by substitution into a theoretical formula derived from the Coupled Wave Theory. Thus, the method allows a precise determination of the dynamic range of volume holographic memories and thus their storage capacities. The same procedure can also apply to photopolymers.

Abstract: A differential interference contrast (DIC) determination device and method utilizes an illumination source, a layer having a pair of two apertures that receive illumination from the illumination source, and a photodetector to receive Young's interference from the illumination passing through the pair of two apertures. In addition, a surface wave assisted optofluidic microscope and method utilize an illumination source, a fluid channel having a layer with at least one aperture as a surface, and a photodetector that receives a signal based on the illumination passing through the aperture. The layer is corrugated (e.g., via fabrication) and parameters of the corrugation optimize the signal received on the photodetector.

Abstract: Methods and compositions are provided for detecting biomolecular interactions. The use of labels is not required and the methods can be performed in a high-throughput manner. The invention also provides optical devices useful as narrow band filters.

Abstract: Optical element having an optical surface, which optical surface is adapted to a non-spherical target shape, such that a long wave variation of the actual shape of the optical surface with respect to the target shape is limited to a maximum value of 0.2 nm, wherein the long wave variation includes only oscillations having a spatial wavelength equal to or larger than a minimum spatial wavelength of 10 mm.

Abstract: An adjustable two-dimensional lamellar grating system including a lamellar grating and a movable mirror disposed substantially parallel to one another, and an interferometer using the adjustable lamellar grating system. In one example, the lamellar grating includes a dielectric wafer having a dielectric wafer having a plurality of periodically spaced recesses formed therein, wherein the dielectric wafer has higher reflectivity at its surface facing the movable mirror than at a second opposing surface. In one example, the system also includes a mechanism for moving the mirror relative to the dielectric wafer.

Abstract: A non-periodic reflection beamsplitter or reflector for use in an interferometer. The interferometer employs non-periodic reflectors or a non-periodic beamsplitter in order to produce interference patterns to analyze. The non-periodic reflectors or beamsplitters may be concentrically arranged reflectors having equal area. The beamsplitter consists of two adjacent non-periodic structures having complementary reflection and transmission patterns.

Abstract: Light from the first and second different wavelength light sources is combined and supplied to a director that directs zeroth order light to a reference surface and other order, generally first order diffracted light to on a location of the sample surface which is dependent upon wavelength. Light reflected by the sample and reference surfaces interfere. A characteristic of a sample surface is determined from interference light of the first wavelength. Interference light of the second wavelength is used to enable phase-locking by adjusting the path length difference by moving the reference surface or changing the refractive index of a path portion to compensate for phase variation due to environmental effects. Non-mechanical scanning is used to scan the sample surface by using a variable wavelength source and a director providing different first order diffraction angles for different wavelengths or an acousto-optical device that provides a variable pitch acoustic diffraction grating.

Abstract: In certain aspects, disclosed methods include directing test light reflected from an object to form an image of the object on a detector, where the object includes a diffractive structure. The test light at the detector includes both specularly and non-specularly reflected light from the diffractive structure, and the diffractive structure is under-resolved in the image. The method further includes directing reference light to interfere with the test light at the detector where the reference and test light being derived from a common source, varying an optical path length difference between the test and reference light, acquiring an interference signal from the detector while varying the optical path length difference, and determining information about the diffractive structure based on the interference signal and on predetermined information derived from a mathematical model of light reflection from a model diffractive structure.

Abstract: Systems, devices, methods, and computer-readable media relating to terahertz radiation detection are disclosed. A method of detecting terahertz radiation may include transmitting a reference beam and a signal beam through a common-path interferometer. The method may further include transmitting a terahertz beam through a target object. Furthermore, the method may include causing the signal beam and the terahertz beam to simultaneously propagate through an electro-optical element within the common-path interferometer after transmitting the terahertz beam through the target object to induce a phase delay between the signal beam and the reference beam. In addition, the method may include calculating the phase delay and calculating an amplitude of an electric field of the terahertz beam from the phase delay.

Abstract: Various embodiments of the present invention are directed to systems and methods for obtaining images of objects with higher resolution than the diffraction limit. In one aspect, a method for collecting evanescent waves scattered from an object comprises electronically configuring a reconfigurable device to operate as a grating for one or more lattice periods using a computing device. Propagating waves scattered from the object pass through the reconfigurable device and a portion of evanescent waves scattered from the object are projected into the far field of the object. The method includes detecting propagating waves and detecting the portion of evanescent waves projected into the far field for each lattice period using an imaging system.

Abstract: An interferometric tracking device is disclosed. A first grating is optically coupled to a second grading such that the second grating is rotationally offset from the first grating. Imaging optics are adapted to image light passing through the first and second gratings onto a focal plane array. A plurality of wedge plates are optically disposed between the imaging optics and the second grating, such that the wedge plates generate a plurality of spots on the FPA when light from a point source is incident upon the first grating.

Abstract: An improved condition testing system and method integrated into microelectronic circuits includes a structure including a semiconductor material with a target portion and a second portion for determining the presence and nature of various external (e.g. magnetic field, microwave, bioelectric or incident radiation) or internal stresses (e.g. binary circuit-state or analog signal recognition) or conditions acting upon the material. The target portion has a first feature when at least one of the following occurs: an external force is received by the second portion of the structure and an internal condition occurs in the target portion. The system and method further has a test grating determined and shaped and located to produce a first optical interference pattern when the target portion and the grating are exposed to non-invasive illumination and when the target portion has the first feature.

Abstract: The present invention is related with the optical instrument such as interferometer for testing the optical systems and samples whereas the optical instrument comprises the laser (1) for generating the laser beam which passes the beam expander (2), beam-splitter (23) dividing the laser beam to a working light beam and reference light beam, focusing objectives (3, 7), flat glass plate (4) with one side coated by thin metal highly reflecting coating with the pattern including a pinhole, computer (12), CCD camera (13), tested part or optical system (6). In addition the optical instrument comprises at least two flat mirrors (24, 25), observation objective and at least one stop (20) placed between the beam-splitter (23), flat mirrors (24, 25) and/or focusing objective (7).

Abstract: An improved beaconless adaptive optics system and process. A target is illuminated with a high energy laser beam of a directed energy laser. Wave front measurements are made of high energy laser beam reflections from the target. These wave front measurements are analyzed by a high speed processor to determine both high frequency phase components and low frequency phase components in the wave front data. (Applicants' experiments have shown that there is a direct correlation between beam spot size on the target and the phase variance of the reflected laser beam. The correlation is: the greater the phase variance the smaller the beam spot size.) Applicants have developed a technique for providing special control algorithms that provide very high speed control of the elements of a deformable mirror using this phase variance as a feedback parameter. Applicants have also developed algorithms to correct a limited number of Zernike modes associated with the wave front control.

Abstract: Scatterometry for measuring overlay. A second set of superimposed gratings are superposed over a first set of superimposed gratings. The second set of gratings have a different periodicity from the first set of gratings or a different orientation. Consequently the first order diffraction pattern from the second set of superimposed gratings can be distinguished from the first order diffraction pattern from the first set of superimposed gratings.

Abstract: A device for the optical measurement of an optical system which, in a useful operating mode, receives useful radiation on a useful radiation entrance side and emits it on a useful radiation exit side. The device includes a measurement radiation source, by which at least one exit-side element, which emits measurement radiation to the optical system, can be positioned on the useful radiation exit side of the optical system, and a detector, by which at least one entrance-side element, which receives measurement radiation coming from the optical system, can be positioned on the useful radiation entrance side of the optical system. The measurement radiation source includes a source-side measurement structure mask for positioning on the useful radiation exit side and/or the detector includes a detector-side measurement structure mask for positioning on the useful radiation entrance side.

Abstract: Disclosed are compact optical interferometer array, miniature optical interferometer array, and miniature optical interferometer. The interferometer arrays contain a spatial phase modulator array and a detector array. They are used for conducting multiple measurements. The miniature interferometer has only one component—a spatial phase modulator. Without passing through any focus lens, beam portions coming out of the modulator spread and merge together by themselves. Size of the miniature interferometer can reach subwavelength or even nanoscale. The interferometer array and miniature interferometer find applications in miniature spectrometer, color filter, display, adjustable subwavelength grating, etc.

Abstract: A measuring apparatus includes a pinhole mask, located on an object plane of an optical system to be measured, and having a plurality of pinholes for generating a spherical wave from a measuring light beam, and a diffraction grating for splitting the measuring light beam that has passed the pinhole mask and the optical system, in which Lg=m·Pg2/? is met, where Pg is a grating pitch of the diffraction grating, ? is a wavelength of the measuring light beam, m is an integer other than zero, and Lg is a distance between the diffraction grating and an image plane of the optical system. The measuring apparatus detects an interferogram formed by interference between a plurality of the measuring light beams split by the diffraction grating. The plurality of measuring light beams includes an aberration of the optical system.

Abstract: Systems and methods for providing trigger signals in an optical interrogator, wherein multiple triggers are generated within each period of a varying reference signal, and wherein the triggers are evenly spaced according to the wavenumber of the reference signal. In one embodiment, an optical frequency domain reflectometry system provides a laser beam to a reference interferometer to produce a reference signal. This signal is passed through a 4×4 optical coupler which splits the signal into a first signal and a second signal that is 90 degrees out of phase with the first signal. These signals are converted to electrical signals, and a trigger unit generates triggers at points at which the two electrical signals have zero-crossings, and at which the magnitudes of the signals are equal. The resulting triggers remain evenly spaced within the period of the reference signals, even when the period is changed.

Abstract: An image processing system includes a wavefront coding element that codes a wavefront forming an optical image, a detector for converting the optical image to a data stream and an image processor for processing the data stream with a reduced set filter kernel to reverse effects of wavefront coding and generate a final image. The reduced set filter kernel may include a reduced set distributive filter kernel. An image processing method includes wavefront coding a wavefront that forms an optical image, converting the optical image to a data stream, and processing the data stream with a reduced set filter kernel to reverse effects of wavefront coding and generate a final image. The processing consists of processing the image, for each pixel, with filter tap logic consisting of a shifter.

Abstract: Apparatus, techniques and systems for implementing an optical interferometer to measure surfaces, including mapping of instantaneous curvature or in-plane and out-of-plane displacement field gradients of a sample surface based on obtaining and processing four optical interferograms from a common optical reflected beam from the sample surface that are relatively separated in phase by ?/2.

Abstract: This invention provides a compact delay-line interferometer that can be used in Differential Phase Shift Keying (DPSK) and Differential Quardratic Phase Shift Keying (DQPSK) demodulators. The delay-line interferometer is based on polarization components including beam shifter, beam splitter and wave plates. The realized demodulators can be used as either discrete components or integrated with balanced detectors. Time delay generated in the interferometer can be controlled with a phase shifter, using either thermal, piezoelectric, mechanical of electrical means. This application claims priority to US Provisional Patent Application Ser. No. 61/238,687, filed Sep. 1, 2009, titled “Polarization Based Interferometer.” This application also claims priority to US Provisional Patent Application Ser. No. 61/295,766, filed Jan. 18, 2010, titled “Delay-Line-Interferometer for Integration with Balanced Receivers.

Abstract: A differential interference contrast (DIC) determination device and method utilizes an illumination source, a layer having a pair of two apertures that receive illumination from the illumination source, and a photodetector to receive Young's interference from the illumination passing through the pair of two apertures. In addition, a surface wave assisted optofluidic microscope and method utilize an illumination source, a fluid channel having a layer with at least one aperture as a surface, and a photodetector that receives a signal based on the illumination passing through the aperture. The layer is corrugated (e.g., via fabrication) and parameters of the corrugation optimize the signal received on the photodetector.

Abstract: Methods for measuring expansion of a test sample. One method includes establishing a diffraction slit between two blades, with the position of at least one of the blades being dependent upon the length of a test sample of material. As the temperature of the sample changes, the width of the slit changes. Light is projected through the slit onto a target and an diffraction pattern is measured. Changes in the light diffraction pattern correspond to the thermal expansion of the sample. Another method includes establishing a diffraction slit between two blades, with the position of at least one of the blades being dependent upon a length along a test sample of material. As a load is applied to the test sample, the width of the slit changes. Changes in the light diffraction pattern correspond to Young's Modulus for the sample.

Abstract: An optical telescope system, method of actively, adaptively providing optical control to an array of articulated mirrors in a sparse aperture in the optical telescope system and a computer program product therefor. Array apertures are selected sequentially for imaging. Each aperture is temporally modulating at a unique/different frequency and, simultaneously, focal plane images are detected for each array aperture with known and separable temporal dependencies. The images are processed for the current set of said focal plane images to detect an image wavefront. The feeding back wavefront errors are fed back to aperture actuators for controlling the array.

Abstract: A method of wavefront (100) analysis including applying a transform to the wavefront, applying a plurality of different phase changes (110, 112, 114) to the transformed wavefront (108), obtaining a plurality of intensity maps (130, 132, 134) wherein the plurality of different phase changes are applied to region of the transformed wavefront, corresponding to a shape of the light source.

Abstract: A method is provided for the electronic scanning of the intensity distribution of an optical interference pattern by means of a linear image sensor, wherein the interference pattern is produced by overlapping two temporally partly coherent beams striking at an arbitrarily predefined angle ? in relation to one another and is provided with an interference strip having a carrier frequency greater than the scanning frequency, and amplitude modulation that can be varied slowly in relation to the pixel width, wherein at least one optical grating is disposed in the beam path of at least one of two incident beams and the image sensor is disposed in the diffraction image of the grating(s) such that, at the site of the image sensor, the beams interfere, and the beams enclose an angle ? at the site of the image sensor, the angle being smaller than ?.

Abstract: A measurement apparatus includes a first mask that is arranged on an object plane of a target optical system, and has a window that transmits measurement light, a second mask that has a reflection surface for reducing coherence of the measurement light, and a diffraction grating configured to split the measurement light that has been reflected on the second mask, has passed the first mask and the target optical system, wherein a distance Lg between the diffraction grating and an image plane of the target optical system satisfies Lg=m·Pg2/? where Pg is a grating pitch of the diffraction grating, ? is a wavelength of the measurement light, and m is an integer except for 0.