A method for analyzing the wavefront effect of an optical system includes: illuminating a measurement mask (110, 310) with illumination light, producing an interferogram in a specified plane using a diffraction grating (150) from a wavefront from the illuminated measurement mask and traveling through the optical system; and capturing the interferogram with a detector (170). Different angular distributions of the illumination light incident on the measurement mask are produced via a mirror arrangement of independently settable mirror elements. A plurality of interferograms are captured in a plurality of measurement steps, wherein these measurement steps differ respectively in angular distribution of the illumination light that is incident on the measurement mask. A matching wavefront deviation portion in the measurement results obtained respectively in the measurement steps is ascertained to determine the respective system wavefront deviations of the optical system for the pupil regions illuminated respectively in the individual measurement steps.

Projection objective wave-front aberration detecting device and a detecting method thereof, wherein the projection objective wave-front aberration detecting device comprises a light source and illuminating system, an object plane grating, an object plane displacement stage, a measured projection objective, an image plane grating, a two-dimensional photoelectric sensor, an image plane displacement stage and a control processing unit. According to the invention, by controlling the length of the object plane grating line, or the periodic structure of the object plane grating perpendicular to the shearing diffraction direction, or the object plane grating to adopt a sinusoidal grating, or the image plane grating to adopt an amplitude-phase hybrid grating, the complexity of an interference field is reduced, and the wave-front aberration detection speed and precision are improved, and the precision and speed of in-situ wave-front aberration detection can be improved.

A method for adjusting a measuring device having an interferometer unit with an optical axis, an optical distance measuring device with a measuring axis and a support slide that is moveable along a slide axis. The measuring axis is first aligned parallel to the slide axis. An adjustment body with a first spherical reflection and/or diffraction surface and a retro reflector at the back side is arranged at the support slide. It is brought into a first confocal position, in which a first center point of the first spherical reflection/diffraction surface coincides with the focus of the spherical wavefront that is emitted from the interferometer unit. The retro reflector defines a vertex that is located close to the first center point, such that the measuring axis of the distance measuring device extends close to the focus of the emitted spherical wavefront. In doing so, Abbe-faults can be reduced or eliminated.

Embodiments described herein provide a method for cleaning contamination from sensors in a lithography tool without requiring recalibrating the lithography tool. More particularly, embodiments described herein teach cleaning the sensors using hydrogen radicals for a short period while the performance drifting is still above the drift tolerance. After a cleaning process described herein, the lithography tool can resume production without recalibration.

A measurement apparatus includes a filter changing a light amount of an irradiation light, a lens irradiating a surface of a material with the irradiation light, a stage changing a focus position of the irradiation light in a depth direction of the material, an interfering light extractor causing the irradiation light to interfere with reflected light from the material, a detector detecting an intensity of interfering light obtained by interference between the irradiation light and the reflected light, and a controller calculating a height of the surface of the material based on the detected intensity of interfering light while changing a relative focus position of the irradiation light with respect to the material at a given measurement point of the surface of the material. The controller controls the filter or light source based on the detected intensity of interfering light to change the light amount of the irradiation light.

A two-dimensional diffraction grating for a phase-stepping measurement system for determining an aberration map for a projection system comprises a substrate provided with a square array of through-apertures, wherein the diffraction grating is self-supporting. It will be appreciated that for a substrate provided with a square array of through-apertures to be self-supporting at least some substrate material is provided between each through-aperture and the adjacent through apertures. A method of designing a two-dimensional diffraction grating for a phase-stepping measurement system for determining an aberration map for a projection system comprises: selecting a general geometry for the two-dimensional diffraction grating, the general geometry having at least one parameter; and selecting values for the least one parameter that result in a grating efficiency map for the two-dimensional diffraction grating so as to control the contributions to a first harmonic of a phase stepping signal.

A method, device and electronic apparatus for estimating physical parameters are disclosed. The method includes: reading a Newton's rings fringe pattern obtained by performing an interferometric measurement on a unit to be measured; obtaining the number and length of first-direction signals of the Newton's rings fringe pattern; performing, for each of the first-direction signals, a discrete chirp Fourier transform (DCFT) on the first-direction signal based on each first chirp rate parameter within a range of the length of first-direction signals, to obtain a first magnitude spectrum of an intensity distribution signal in a DCFT domain; determining a first chirp rate parameter and a first frequency parameter corresponding to a first magnitude peak value based on the first magnitude spectrum; and estimating the physical parameters involved in the interferometric measurement at least according to the first chirp rate parameter and first frequency parameter corresponding to the first magnitude peak value. In this way, the physical parameters involved in the interferometric measurement can be estimated with high accuracy and stably.

A method for determining the inversion state of a soft contact lens (1), comprising imaging a soft contact lens having a convex surface (2, 3) and a concave surface (3, 2), a lens center and a lens edge (5) surrounding said soft contact lens (1), the method comprising using an optical coherence tomography system to obtain at least one sectional image of at least a part of the contact lens (1) comprising the lens edge (5), determining a cross-sectional edge geometry of the contact lens (1) extending from the lens edge (5) towards the lens center of the contact lens in the sectional image, the cross-sectional edge geometry corresponding to the convex and concave surface boundaries of the contact lens (1) in the sectional image, selecting a parameter defining the cross-sectional edge geometry of the contact lens (1) imaged and comparing the parameter defining the cross-sectional edge geometry of the contact lens (1) with a predetermined parameter defining a cross-sectional edge geometry of a non-inverted contact lens to determine whether said contact lens (1) is inverted.

Method for determining the refractive index (n) of a material of a contact lens, in particular of a soft contact lens, the contact lens (1) having a first surface and a second surface defining a lens geometry there between, by measuring the wavefront issued by the contact lens (1) with a wavefront sensor (4), obtaining data of the geometry of at least one section of the contact lens (1) with an optical coherence tomography system (3) and communicating the geometry of the at least one section of the contact lens (1) from the optical coherence tomography system (3) to an analyzer, particularly a computer, and determining the refractive index (n) of the material of the contact lens from the geometry of the at least one section of the contact lens and from the wavefront issued by the contact lens (1).

A light source capable of spectral modulation is modulated conventionally to produce a correlogram at the test surface position of an SCI interferometer. The mean wavelength of the light source is changed to obtain multiple corresponding phase-shifted correlograms that can be processed by applying conventional multiple-wavelength interferometric analysis to determine physical attributes of the test surface. One simple way to achieve this result is by splitting the light beam produced by the source into at least three simultaneous beams passed through filters with corresponding different mean-wavelength transmission bands. Because the correlograms are produced simultaneously, they can be used to practice instantaneous phase-shifting interferometry using conventional analysis algorithms.