Importance

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Abstract

The invention relates to an optical device (2) for characterising a diffraction grating (14) which is formed by first and second interferometric diffractive sensors (4, 6) which are integral, spaced apart from each other at a determined first distance, and each comprise a reading grating (10a, 10b) and at least one light intensity detector, these first and second sensors providing respectively first and second electrical signals which, during a relative displacement (.DELTA.x) between the device and the diffraction grating, vary as a function of the spatial frequency of this grating in first and second regions of the latter, which regions are located respectively opposite two reading gratings and each receive light supplied by at least one light source. In particular, the first and second electrical signals define first and second phases of the first and second sensors. Furthermore, the device comprises means for measuring a difference between the phases of the first and second signals and means (24) for measuring the accumulation of this difference during a displacement of the device along the grating. The invention also relates to optical devices for determining the spatial frequency of a grating of a type similar to the above-mentioned device. The invention likewise relates to methods of producing diffraction gratings using a device of the above-mentioned type.

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First Claim