In situ calibration of a Michelson type, speckle-shearing interferometer: Wobbling mirror effect

In situ calibration of piezoelectric transducers in a phase stepping, Michelson type, speckle-shearing interferometer can be affected by mirror wobbling introduced by the transducers. When this happens, a modulation of the curves employed for calibration can be readily detected in imaging systems with large apertures. A calibration method that takes into account the modulation of these curves is, therefore, essential to insure the required regularity of the phase steps. A computer model of speckle-shearing interferometry is used to deal with piezoelectric non-linearities and mirror wobbling in the interferometer, and to show how the calibration curves are affected when both phenomena are present. Computer simulated and experimental results validate the calibration technique advanced here.     

UV-vis absorption spectroscopy and multivariate analysis as a method to discriminate tequila

Based on the UV-vis absorption spectra of commercially bottled tequilas, and with the aid of multivariate analysis, it is proved that different brands of white tequila can be identified from such spectra, and that 100% agave and mixed tequilas can be discriminated as well. Our study was done with 60 tequilas, 58 of them purchased at liquor stores in various Mexican cities, and two directly acquired from a distillery. All the tequilas were of the "white" type, that is, no aged spirits were considered. For the purposes of discrimination and quality control of tequilas, the spectroscopic method that we present here offers an attractive alternative to the traditional methods, like gas chromatography, which is expensive and time-consuming.     

Annular phase-only mask for high focal depth

We present an annularly distributed phase-only mask that generates an axial irradiance distribution identical to the point spread function of the Dowski-Cathey lens [Appl. Opt. 34, 1859 (1995)]. This apodizer has an ambiguity function with a bow-tie effect, and consequently its axial modulation transfer function varies slowly with spherical aberration.