Person:
Sánchez Brea, Luis Miguel

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First Name
Luis Miguel
Last Name
Sánchez Brea
URI
https://hdl.handle.net/20.500.14352/75070
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Óptica
Area
Optica
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2002 - 20093
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Author: Bernabeu Martínez, Eusebio × Has files: false ×

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Now showing 1 - 3 of 3
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    On the standard deviation in charge-coupled device cameras: A variogram-based technique for nonuniform images
    (Journal of Electronic Imaging, 2002) Sánchez Brea, Luis Miguel; Bernabeu Martínez, Eusebio
    When estimating the standard deviation of a magnitude with spatial dependence, it is necessary to carry out several measurements at every location where the magnitude is estimated. However, in image applications the standard deviation is commonly measured by means of only one high-uniform image. This procedure tends to increase the standard deviation due to spatial nonuniformity of the image. In this work we propose a new technique based on the variogram, which is a function that measures the spatial correlation of the image, that can be employed to accurately estimate the standard deviation of nonuniform images obtained by charge-coupled device cameras.
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    Optoelectronic device for the measurement of the absolute linear position in the micrometric displacement range
    (Materials, Devices, and Applications, 2005) Morlanes Calvo, Tomás; Peña, José Luis de la; Sánchez Brea, Luis Miguel; Alonso Fernández, José; Crespo Vázquez, Daniel; Saez Landete, José; Bernabeu Martínez, Eusebio; Badenes, Goncal; Abbott, Derek; Serpenguzel, Ali
    In this work, an optoelectronic device that provides the absolute position of a measurement element with respect to a pattern scale upon switch-on is presented. That means that there is not a need to perform any kind of transversal displacement after the startup of the system. The optoelectronic device is based on the process of light propagation passing through a slit. A light source with a definite size guarantees the relation of distances between the different elements that constitute our system and allows getting a particular optical intensity profile that can be measured by an electronic post-processing device providing the absolute location of the system with a resolution of 1 micron. The accuracy of this measuring device is restricted to the same limitations of any incremental position optical encoder.
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    Talbot effect with aberrated beams
    (Modeling Aspects in Optical Metrology II, 2009) Torcal Milla, Francisco José; Sánchez Brea, Luis Miguel; Bernabeu Martínez, Eusebio; Bosse, Harald; Bodermann, Bernd; Silver, Richard M.
    Diffraction gratings are one of the most used elements in optics and even in other fields of science. They are used also like part of measurement devices in scientific and industrial applications. As it is well known, self-imaging effect appears when a diffraction grating is illuminated with a coherent beam, such as a plane wave. This effect has been analyzed in depth and its behavior is well known under ideal grating and illumination conditions. Usually, the illumination beam is not perfectly collimated but presents a certain degree of aberration. The motivation of this work is to try to explain the behavior of the self-images of an ideal amplitude grating when it is illuminated by a non-perfect beam, that is, an aberrated beam. The known of this effect can help to understand how much the aberration of the light beam affects to the diffraction pattern, and more in depth, to the self-imaging phenomenon. The results presented in this work can be very useful in metrology applications, since sometimes the contrast obtained experimentally does not correspond to the theoretical predictions, usually due to aberrations in the light beam. For this, we have used a formalism based in the Rayleigh-Sommerfeld approach. We have modeled the aberrations by using the Zernike polynomials. On the other hand, we have considered all kinds of aberrations, spherical, coma, tilt, astigmatism, etc. As it is expected the contrast of the self-images decrease when the order of them increases and also when the aberration degree increase. In some cases, contrast inversion is also produced for high aberrations.