Abstract:
Method and systems are presented for analysing a wavefront using a spectral wavefront analyser to extract optical phase and spectral information at a two dimensional array of sampling points across the wavefront, wherein the relative phase information between the sampling points is maintained. Methods and systems are also presented for measuring an eye by reflecting a wavefront of an eye and measuring the wavefront at a plurality of angles to provide a map of the off-axis relative wavefront curvature and aberration of the eye. The phase accuracy between wavelengths and sample points over a beam aperture offered by these methods and systems have a number of ocular applications including corneal and anterior eye tomography, high resolution retinal imaging, and wavefront analysis as a function of probe beam incident angle for determining myopia progression and for designing and testing lenses for correcting myopia.
Abstract:
Interferometry-based methods and apparatus are presented for analysing one or more wavefronts from a sample, in which the sample wavefronts are interfered with two or more reference wavefronts to produce two or more interferograms in a sufficiently short time period for the interferograms to be captured in a single exposure of an image capture device such as a CCD array. Each interferogram has a unique carrier frequency dependent on the angle between a respective pair of sample and reference wavefronts. In certain embodiments multiple sample and/or reference wavefronts are generated using scanning mirrors, while in other embodiments utilising multi-wavelength beams multiple sample and/or reference wavefronts are generated with wavelength dispersive elements. The methods and apparatus are suitable for measuring aberrations at one or more positions on the retina of an eye.
Abstract:
Interferometry-based methods and apparatus are presented for analyzing one or more wavefronts from a sample, in which the sample wavefronts are interfered with two or more reference wavefronts to produce two or more interferograms in a sufficiently short time period for the interferograms to be captured in a single exposure of an image capture device such as a CCD array. Each interferogram has a unique carrier frequency dependent on the angle between a respective pair of sample and reference wavefronts. In certain embodiments multiple sample and/or reference wavefronts are generated using scanning mirrors, while in other embodiments utilizing multi-wavelength beams multiple sample and/or reference wavefronts are generated with wavelength dispersive elements. The methods and apparatus are suitable for measuring aberrations at one or more positions on the retina of an eye.
Abstract:
An apparatus and method is disclosed for accurate, real time monitoring of the wavefront curvature of a coherent laser beam. Knowing the curvature, it can be quickly determined whether the laser beam is collimated, or focusing (converging), or de-focusing (diverging). The apparatus includes a lateral interferometer for forming an interference pattern of the laser beam to be diagnosed. The interference pattern is imaged to a spatial light modulator (SLM), whose output is a coherent laser beam having an image of the interference pattern impressed on it. The SLM output is focused to obtain the far-field diffraction pattern. A video camera, such as CCD, monitors the far-field diffraction pattern, and provides an electrical output indicative of the shape of the far-field pattern. Specifically, the far-field pattern comprises a central lobe and side lobes, whose relative positions are indicative of the radius of curvature of the beam. The video camera's electrical output may be provided to a computer which analyzes the data to determine the wavefront curvature of the laser beam.
Abstract:
There is provided a wavefront measuring method for obtaining wavefront information of an optical system. The method including: irradiating the optical system with a light beam; allowing the light beam passed via the optical system to come into a diffraction grating having periodicity in a first direction; and obtaining the wavefront information based on an interference fringe formed by light beams generated from the diffraction grating. The diffraction grating including: first portions which allow light to pass therethrough; and second portions which shield light, each of the second portions being provided between two of the first portions. A ratio between a width of one of the first portions in the first direction and a width of one of the second portions in the first direction is changed in the first direction, the one of the first portions and the one of the second portions being adjacent to each other.
Abstract:
Method of characterizing a light beam (FL) comprising the steps consisting in: a) disposing the input ends (EE1-EE11) of N>3 optical fibres (F01-F011) on the path of said light beam, in such a way that a respective portion of said beam is coupled and propagates in each optical fibre and is emitted from its output end (ES1-ES11) so as to form a respective secondary beam; b) introducing an angular spectral dispersion into said secondary beams by means of at least one dispersive element (RD); c) propagating the dispersed secondary beams in such a way that they overlap to form an interferogram; d) acquiring an image of said interferogram; and e) extracting from said image of said interferogram an item of information relating to the spatial variation of the phase of said light beam at a plurality of wavelengths. Device for the implementation of such a method.
Abstract:
Un système optique du type interferometre à cisaillage propre à recevoir un faisceau de lumière monochromatique (FI) définit, sur le trajet dudit faisceau, au moins deux zones optiquement conjuguées l'une de l'autre, l'une dite plan d'analyse (PA), et l'autre dite plan de partition (PP). Trois dioptres principaux (M1,M2,M3), au moins partiellement réfléchissants, situés au voisinage du plan de partition, ou d'une image de celui-ci renvoient trois faisceaux d'axes non colinéaires, qui interfèrent. On y ajoute des moyens d'observation (PDV) de l'image interférométrique, existant dans au moins une zone dite plan d'observation, voisine d'un plan de référence confondu avec le plan de partition (PP) ou conjugué de celui-ci (P0). Cette observation montre des figures d'interférences qui contiennent des informations sur les défauts de phase du faisceau à analyser.