The present invention relates to an arrangement and to a method for wavefront analysis comprising a radiation source (8) that emits an electromagnetic wavefront of electromagnetic radiation (1) to be analyzed; a spatially resolving detector unit (4, 4a, 4b, 4c) for detecting the electromagnetic wavefront; and an electronic evaluation unit (5, 7) connected to the detector unit (4, 4a, 4b, 4c). The at least one beam guidance unit (3) for guiding the electromagnetic radiation (1), that is only diffractive and/or reflective, has at least one opening (3a, 3b, 3c) and the detector unit (4, 4a, 4b, 4c) is arranged behind the at least one opening (3a, 3b, 3c) of the beam guidance unit (3) in the direction of propagation of the electromagnetic radiation (1) for detecting a diffraction pattern of the electromagnetic radiation (1) diffracted at the at least one opening (3a, 3b, 3c).

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.

A metrology apparatus (302) includes a higher harmonic generation (HHG) radiation source for generating (310) EUV radiation. Operation of the HHG source is monitored using a wavefront sensor (420) which comprises an aperture array (424, 702) and an image sensor (426). A grating (706) disperses the radiation passing through each aperture so that the image detector captures positions and intensities of higher diffraction orders for different spectral components and different locations across the beam. In this way, the wavefront sensor can be arranged to measure a wavefront tilt for multiple harmonics at each location in said array. In one embodiment, the apertures are divided into two subsets (A) and (B), the gratings (706) of each subset having a different direction of dispersion. The spectrally resolved wavefront information (430) is used in feedback control (432) to stabilize operation of the HGG source, and/or to improve accuracy of metrology results.

Observing a disturbance of a wavefront of reference light received from a target and generating a wavefront in a conjugate relationship with the wavefront by use of a driving optical system. Generating a plurality of control signals on a basis of a plurality of Zernike coefficients calculated as a Zernike polynomial which approximates the wavefront disturbance in order to respectively drive a plurality of deformable mirrors included in the driving optical system. Providing an adaptive optical system which can optically compensate a wavefront disturbance derived from an atmospheric fluctuation even in a case of radiating laser light to a target moving at a high speed.

A wavefront sensor measures the phase distribution of a beam of light perpendicular to its axis of propagation. The Shack-Hartmann (S-H) wavefront sensor is based on segmentation of the incident light beam into small, spatially distributed, parts. Each of these parts is then incident on a lens, and the deviation of the focal spot from the lens optical axis is measured in two dimensions, usually by a camera or detector array. An array of lenses is used to characterize the wavefront of the entire beam.

The present invention provides a free space optical communication system that uses orthogonal modes of aberration in a laser beam as means for encoding the information. The system comprises a transmission station which transmits the user defined information in terms of the amplitudes of certain orthogonal aberration modes present in the transmitted beam. The beam then travels through free space before it reaches the receiving station. The receiving station comprises a high speed wavefront sensor of light beams. The wavefront sensor measures the amplitudes of various orthogonal aberration modes present in the incident beam at different instants of time. The amplitudes of the orthogonal modes at a certain regular time interval are then used to extract the user information.

A wavefront sensor includes a mask and a sensor utilized to capture a diffraction pattern generated by light incident to the mask. A reference image is captured in response to a plane wavefront incident on the mask, and another measurement image is captured in response to a distorted wavefront incident on the mask. The distorted wavefront is reconstructed based on differences between the reference image and the measurement image.

An optical apparatus is comprising an optical imaging arrangement generating either an image of the original object field or the field of the original sample at the pupil plane which consist of both amplitude and phase information. The apparatus is further comprising a digital adaptive optics arrangement with a wave front sensor and a computing unit, which is adapted to generate at least one orthogonally translated digital copy of the original sample object field at the spatial Fourier or pupil plane and to analytically calculate a wave front error based on the phase difference between the original sample wave front and its digital copy or copies.

A metrology apparatus (302) includes a higher harmonic generation (HHG) radiation source for generating (310) EUV radiation. Operation of the HHG source is monitored using a wavefront sensor (420) which comprises an aperture array (424, 702) and an image sensor (426). A grating (706) disperses the radiation passing through each aperture so that the image detector captures positions and intensities of higher diffraction orders for different spectral components and different locations across the beam. In this way, the wavefront sensor can be arranged to measure a wavefront tilt for multiple harmonics at each location in said array. In one embodiment, the apertures are divided into two subsets (A) and (B), the gratings (706) of each subset having a different direction of dispersion. The spectrally resolved wavefront information (430) is used in feedback control (432) to stabilize operation of the HGG source, and/or to improve accuracy of metrology results.

A computer-aided image correction method for images with at least spatially partially coherent light requiring only a phase-modulated image as input. It does not reconstruct the phases on the image sensor, but rather assumes that they should ideally all be the same. With this assumption, the invention formulates a constraint and an update rule. The result of the iteration is an amplitude distribution of the lightwave field, which could have been measured directly if aberrations in the form of wavefront distortions had not contributed to the actual image acquisition. Further, a device that can, using the image correction method, be used as an adaptive optic for imaging instruments.