A novel method for measurement of angular displacement in one or two dimensions for arbitrarily shaped objects is presented. The method is based on Fourier transforming the scattered field from a single laser beam that illuminates the target. The angular distribution of the light field at the target is linearly mapped onto an array image sensor placed in the Fourier plane. Measuring this displacement facilitates the determination of the angular displacement. It is demonstrated both theoretically and experimentally that the angular displacement sensor is insensitive to object shape, target distance and any longitudinal or transverse movement of the target, if the image sensor is placed in the Fourier plane. A straightforward procedure to place the image sensor in the Fourier plane is presented here. Theoretically and experimentally, it is shown that the method has a resolution of 0.3 mdeg for small angular displacements, and methods for further improvement in resolution are discussed. No special surface treatment is required for surfaces having irregularities of the order of or larger than the wavelength of the incident light. It is shown that this is the case for most surfaces of practical interest. Furthermore, it is shown that robust, non-contact optical systems for industrial applications can be produced. Une nouvelle methode est presentee pour mesurer les deplacements angulaires d'objets de forme arbitraire dans une ou deux dimensions. La methode est basee sur une transformation de Fourier du champ diffuse d'un seul faisceau laser qui illumine l'objet. La distribution angulaire du champ sur l'objet est transformee de facon lineaire sur un capteur d'images place dans le plan de Fourier. Mesurer ce deplacement facilite la determination du deplacement angulaire. Il est demontre de facon theorique et experimentale que le deplacement angulaire n'est pas sensible la forme de l'objet, ni a la distance de l'objet, ni a un deplacement longitudinal ou transverse de l'objet, si le capteur est place dans le plan de Fourier. Une maniere facile de placer le capteur dans le plan de Fourier est presentee ici. De facon theorique et experimentale, il est demontre que la methode a une resolution de 0.3 mdeg pour petits deplacements angulaires, et des methodes pour ameliorer cette resolution sont proposees. Aucun traitement special de la surface n'est necessaire pour des surfaces ayant des irregularites de l'ordre de la longeur d'onde de la lumiere utilisee. Il est demontre que ceci est le cas pour la plupart des surfaces d'interet pratique. De plus, il est demontre que des systemes optiques non-contact robustes pour applications industrielles peuvent etre produites.
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