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
    Correlation technique for the compensation of diffraction widening of optical reference signals
    (Optical Society of America, 2009-09-01) Saez Landete, José; Alonso Fernández, José; Sánchez Brea, Luis Miguel; Morlanes Calvo, Tomás; Bernabeu Martínez, Eusebio
    Two-grating measurement systems are routinely employed for high-resolution measurements of angular and linear displacement. Usually, these systems incorporate zero reference codes (ZRCs) to obtain a zero reference signal (ZRS), which is used as a stage-homing signal. This signal provides absolute information of the position to the otherwise relative information provided by the two-grating incremental subsystems. A zero reference signal is commonly obtained illuminating the superposition of two identical pseudorandom codes and registering the transmitted light by means of a photodiode. To increase the resolution of the system, a reduction of the grating period and the ZRC widths is required. Due to this reduction, the diffractive effects produce a widening of the ZRS and, in turn, a loss of the measuring accuracy. In this work, we propose a method to narrow the distorted signal obtained with a Lau-based encoder, reinstating the accuracy of the ZRS. The method consists of the inclusion of a correlation mask on the detector. A theoretical model to design the mask has been developed, and experimental results have been obtained that validate the proposed technique.
  • Publication
    Invariant grating pseudoimaging using polychromatic light and a finite extension source
    (The Optical Society Of America, 2008-04-01) Sánchez Brea, Luis Miguel; Saez Landete, José; Alonso Fernández, José; Bernabeu Martínez, Eusebio
    The Talbot effect is a well studied phenomenon by which grating pseudoimages appear at certain periodic distances when monochromatic light is used. Recently, numerical simulations have shown a new phenomenon; when a polychromatic light beam is used in a double grating system, the intensity of the pseudoimages presents a transverse-profile that remains unaffected over a wide range of propagation distances. This effect can be used to increase the tolerances of gratings based optical devices, such as displacement measurement systems, interferometers, and spectrometers. The pseudoimages formation with a polychromatic and finite extension light source is analytically and experimentally demonstrated. Relatively simple analytical expressions for the intensity and the contrast allow us to predict when pseudoimages present a constant contrast and when they disappear. Furthermore, we experimentally obtain the pseudoimages using the proposed configuration, corroborating the theoretical predictions.
  • Publication
    Quasicontinuous pseudoimages in sinusoidal grating imaging using an extended light source
    (Elsevier Science BV, 2004-06-01) Sánchez Brea, Luis Miguel; Alonso Fernández, José; Bernabeu Martínez, Eusebio
    When a polychromatic light illuminates a grating, an achromatic and continuous self-imaging regime is produced, what means that Talbot planes are eliminated. In this work, we investigate the existence of this continuous regime for generalized grating imaging. We have found that amplitude gratings with sinusoidal profiles may form, under monochromatic and partially coherent illumination, pseudoimages whose contrast or modulation present a smooth dependence on the gap between the two gratings.