Publications by authors named "Olivier Acher"

We describe a new type of spectropolarimeter in which light is separated to simultaneously measure six spectra carrying polarimetric information on a 2D CMOS camera. The polarization separation along one of the camera axes was obtained using a novel prism, and the spectral dispersion along the other camera axis was obtained using an imaging spectrometer. An ideal version of the six-fold separating prism is first described, in which polarimetric separation is performed along the canonical polarization states used to define the Stokes vector, and it can be explained without any math.

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Investigations of the in-plane positioning capabilities of microscopes using machine-readable encoded patterned scales are presented. The scales have patterns that contain absolute position information, and adequate software accurately determines the in-plane position from the scale images captured by the microscope camera. This makes in-plane positioning experiments simple and fast.

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In this paper we propose a new strategy towards simultaneous co- and cross-polarized measurements of Raman spectra in a confocal microscope. One of the advantages of this strategy is that it is immune to polarization-dependent efficiency of diffraction gratings. It is shown via linear angle-resolved and circular polarization measurements that the accuracy of these snapshot polarization measurements on solid and liquid samples are in good agreement with available models and data.

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An absolute encoder based on vision system nanoGPS OxyO was developed by HORIBA France. This encoder provides three types of position information, namely, two inplane co-ordinates and inplane angular orientation. This paper focuses on the characterization of its angular performance.

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In this paper, we show that it is possible to build a polarization splitter from a pair of commercially available geometrical phase lenses. This optical component splits an incoming beam into two circularly polarized beams, with a separation angle that can be varied by a simple translation or rotation adjustment. Our experiments show that excellent polarization separation is obtained with separation angles ranging from nearly zero up to 120mrad, and for wavelengths ranging from 532nm up to 780nm.

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The prediction and the engineering of the electromagnetic properties of metamaterials are increasingly important issues. Recently, several approaches have been proposed to compute these properties through appropriate averages of local fields within the unit cell. In particular, we proposed a Field Summation method that has been used successfully to determine either analytically or numerically the effective properties of different composites and metamaterials.

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We show that conventional paper can be cut using a 1W laser diode, provided the cutting lines are first traced using a proper ink. The ink should absorb the laser light, and penetrate deep into the paper. An "invisible ink" that is transparent in the visible range and absorbing in the infrared has been successfully tested.

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