Abstract: The present invention relates to an imaging apparatus and comprises input and output polarisers, a first polarising beam splitter and at least one additional polarising beam splitter, a light sensitive detector and focussing means arranged on an axis. The input polariser resolves incident light into a single linear polarisation state. The first polarising beam splitter receives light from the input polarises, and resolves it into equal magnitude orthogonally polarised rays which are mutually spaced and have a path difference therebetween. The or each additional polarising beam splitter is arranged to receive light from the first polarising beam splitter. The transmission axis of the output polariser is parallel to or perpendicular to the transmission axis of the input polarises to resolve the orthogonally polarised light rays having past through the or each additional polarising beam splitter into the same or perpendicular polarisation state as light resolved by the, first polariser.

Abstract: A method and apparatus for characterizing an object with a wavefront from the object is disclosed. In one embodiment, the apparatus includes: a reticle positioned in a path of the wavefront, the reticle comprising two superimposed linear grating patterns; at least one light detector positioned relative to the reticle to receive a self-image diffraction pattern of the reticle produced by the wavefront; and at least one processor receiving signals from the light detector representative of the self-image diffraction pattern and deriving derivatives associated therewith, the processor using the derivatives to characterize said object.

Abstract: Apparatus and methods for in situ and ex situ measurements of spatial profiles of the modulus of the complex amplitude and intensity of flare generated by an optical system. The in situ and ex situ measurements comprise interferometric and non-interferometric measurements that use an array of diffraction sites simultaneously located in an object plane of the optical system to increase signals related to measured properties of flare in a conjugate image plane. The diffraction sites generate diffracted beams with randomized relative phases. In general, the interferometric profile measurements employ phase-shifting point-diffraction interferometry to generate a topographical interference signal and the non-interferometric measurements are based on flare related signals other than topographic interference signals.

Abstract: An instrument for measuring dimensional changes in materials, such as ultra-low thermal expansion materials, contains an optically balanced measuring loop. Both an object beam and a loop beam propagate around the measuring loop. The object beam encounters both opposite side surfaces of the test object and the loop beam encounters remaining components of the measuring loop in common with the object beam. The object and loop beams can be separately compared to reference beams for producing heterodyne signal beams.

Abstract: An apparatus and to a method of monitoring an interferometer, comprising the steps of: coupling a first optical signal into the interferometer and into a wavelength reference element, detecting a first resulting interference signal being a result of interference of parts of the first optical signal in the interferometer, detecting a resulting reference signal of the wavelength reference element, the resulting reference signal being a result of interaction of the first optical signal with the wavelength reference element, and comparing the first resulting interference signal with the resulting reference signal to detect a drift of the interferometer, if any.

Abstract: A method for classifying defects of an object includes irradiating lights having different polarizations onto the object to create an inspection spot on the object, collecting scattered lights generated by the irradiated lights scattering from the inspection spot, and classifying defects of the object by type of defect by analyzing the scattered lights. An apparatus for classifying defects of an object includes light creating means emitting lights having different polarizations to create an inspection spot on the object, and a detecting member for collecting scattered lights that are created from the lights scattering from the inspection spot, wherein the scattered lights are analyzed and classified in accordance with defects positioned on the inspection spot of the object.

Abstract: A spectroscopy system is provided which operates in the vacuum ultraviolet spectrum. More particularly, a system utilizing reflectometry techniques in the vacuum ultraviolet spectrum is provided for use in metrology applications. To ensure accurate and repeatable measurement, the environment of the optical path is controlled to limit absorption effects of gases that may be present in the optical path. To account for absorption effects that may still occur, the length of the optical path is minimized. To further account for absorption effects, the reflectance data may be referenced to a relative standard. Referencing is particularly advantageous in the VUV reflectometer due to the low available photon flux and the sensitivity of recorded data to the composition of the gaseous medium contained with the optical path. Thus, errors that may be introduced by changes in the controlled environment may be reduced.

Abstract: A laser tracking interferometer directs a laser beam to a retroreflector serving as an object to be measured to sense a displacement of the retroreflector using interference with a laser beam back reflected from the retroreflector. The laser tracking interferometer includes: a reference sphere; a carriage that rotates about a center of the reference sphere; a laser interferometer; a displacement gage for providing a displacement signal corresponding to a relative displacement between the reference sphere and the displacement gage; a data processing apparatus for computing a displacement of the retroreflector; a position sensitive detector for providing a position signal corresponding to deviation of a laser beam; and a controller for controlling rotation of the carriage based on the position signal so that the amount of deviation becomes zero.

Abstract: Generating a multispectral or hyperspectral image of an image source with an optical system having an adjustable, wavenumber-dependent point spread function, by collecting panchromatic images of the image source, each of which corresponds to a selected point spread function and includes a measured intensity data set corresponding to a range of wavelengths, transforming the panchromatic images into the spatial frequency domain by using a Fourier transform, solving a matrix equation at each spatial frequency, in which a vector of the transformed panchromatic images is equal to the product of a predetermined matrix of discrete weighting coefficients and a vector representing a wavenumber content of the image source at each spatial frequency, resulting in a determined wavenumber content of the image source in the spatial frequency domain, and inverse transforming the determined wavenumber content of the image source from the spatial frequency domain into the image domain, resulting in the multispectral or hypersp