Sánchez Brea, Luis Miguel

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First Name
Luis Miguel
Last Name
Sánchez Brea
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
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Now showing 1 - 4 of 4
  • Publication
    Optoelectronic device for the measurement of the absolute linear position in the micrometric displacement range
    (Society of Photo-Optical Instrumentation Engineers (SPIE), 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.
  • Publication
    Talbot effect with aberrated beams
    (The International Society for Optical Engineering (SPIE), 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.
  • Publication
    In-line detection and evaluation of surface defects on thin metallic wires
    (The International Society for Optical Engineering (SPIE), 2001) Martínez Antón, Juan Carlos; Siegmann, Philip; Sánchez Brea, Luis Miguel; Gómez Pedrero, José Antonio; Canabal Boutureira, Héctor; Bernabeu Martínez, Eusebio; Hoefling, Roland; Jueptner, Werner P. O.; Kujawinska, Malgorzata
    We have developed a prototype for in-line detection of surface defects in metallic wires, specially for scratches. A simple geometrical relationship between surface topography and conical reflection, permits to correlate the defects with intensity patterns in a simple way. The presented apparatus consists basically in a grating-divided laser beam incident on angular equidistant points. A CCD and an associated optics capture the information of the whole wire perimeter at once. Analytic rudiments are provided in agreement with the experimental results.
  • Publication
    On the standard deviation in charge-coupled device cameras: A variogram-based technique for nonuniform images
    (IS&T- The Society for Imaging Science and Technology, 2002-04) 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.