The wavefront measurement device performs: generating a first pupil function at a reference wavelength based on input data of a wavefront aberration; calculating a first image plane amplitude at a reference wavelength based on the first pupil function; generating a second pupil function at a multi-wavelength region; calculating a second image plane amplitude at the multi-wavelength region based on the second pupil function; correcting a measured point spread function using the first and second image plane amplitudes; applying a constraint condition using the corrected point spread function to the first image plane amplitude to correct the first image plane amplitude; generating a third pupil function based on the corrected first image plane amplitude; and calculating a wavefront aberration on a pupil plane based on the third pupil function.

System and method for monitoring of performance of a mirror array of a digital scanner with a use of light, illuminating the mirror array at grazing (off-axis) incidence, and an optical imaging system that includes a lateral shearing interferometer (operated in either static or a phase-shifting condition) during and without interrupting the process of exposure of the workpiece with the digital scanner, to either simply identify problematic pixels for further troubleshooting or measure the exact magnitude of the deformation of a mirror element of the mirror array.

Methods and systems for calculating a reflectance value of a reflective coating on a curved surface of an optical element include calculating the reflectance value by taking a series of photon count measurements of an extended radiation source over a range of values of emitted radiation reflected from the curved surface into a detector. A combination of the measurements and a known value of accepted or conforming reflectance for the reflective coating is used to calculate the reflectance value of the reflective coating on the curved surface.

A method of testing an optical network with a device, the method comprising transmitting a light pulse in a first direction from a light source of the device through the optical network toward an optical reflector, wherein the light pulse travels through the optical network in the first direction, is reflected by the reflector, and travels though the optical network in a second direction opposite the first direction after being reflected by the reflector; measuring a power level of the light pulse after the light pulse travels through the optical network in the second direction; determining a total loss of the light pulse in both the first direction and the second direction; and determining a loss of the optical network by subtracting a loss of the light pulse in the second direction only from the determined total loss of the light pulse.

A method for restoring an illumination system installed in an EUV apparatus is provided.

Disclosed are a method and an apparatus for inspection of workpieces and products having curved and, in particular, spherical surfaces. The method is based on scanning inspected objects with a narrow probing beam of electromagnetic radiation and concurrently measuring the radiation scattered on the surface. The method and apparatus improve the detectability of features and imperfections on inspected surfaces by providing invariable parameters and conditions of scanning, robust mechanical stability of scanning systems, high positioning accuracy of the probing electromagnetic beam and efficient collection of the scattered radiation. The apparatus allows surface defect classification, determining defect dimensions and convenient automation of inspection.

A method and a device for characterizing the surface shape of an optical element. In the method, in at least one interferogram measurement carried out by an interferometric test arrangement, a test wave reflected at the optical element is caused to be superimposed with a reference wave not reflected at the optical element. In this case, the figure of the optical element is determined on the basis of at least two interferogram measurements using electromagnetic radiation having in each case linear input polarization or in each case circular input polarization, wherein the input polarizations for the two interferogram measurements differ from one another.

A method of determining a status of a floating roof of a storage tank using a radar level gauge system arranged above the floating roof, the radar level gauge system being controllable to selectively evaluate reflected energy traveling towards the radar level gauge system in each propagation direction of a plurality of different propagation directions, the method comprising the steps of: radiating, by the radar level gauge system, an electromagnetic transmit signal towards the floating roof; receiving, by the radar level gauge system, an electromagnetic reflection signal resulting from reflection of the transmit signal at the floating roof; selectively evaluating, by the radar level gauge system based on the reflection signal, reflected energy traveling from the floating roof towards the radar level gauge system in each propagation direction of the plurality of different propagation directions; and determining the status of the floating roof based on the selective evaluation.

Methods and systems for determining optical properties for light transmitted mediums are provided. One method includes acquiring one or more measured values indicative of a reflectance for a material, acquiring one or more measured values indicative of a transmittance for the material, and determining a set of calculated values for an index of refraction coefficient and an extinction coefficient from the one or more measured values indicative of reflectance and transmittance, respectively. The method includes identifying a calculated value from the set of calculated values for the index of refraction coefficient and a calculated value from the set of calculated values for the extinction coefficient that are within a threshold determined by the difference between the one or more measured values indicative of the reflectance or transmittance and a predicted reflectance or transmittance, respectively. The method includes determining a reflectance and transmittance for the material using the calculated values.

A wavefront based characterization of surfaces based on reflections. An intraocular lens surface measurement system includes a light source configured to emit light that is reflected off an optical surface of an intraocular lens. A wavefront sensor is configured to receive the light that is reflected off the optical surface of the intraocular lens. A processor is configured to determine one or more characteristics of the optical surface of the intraocular lens based on a wavefront of the reflected light that is received by the wavefront sensor.