Person:
Quiroga Mellado, Juan Antonio

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First Name
Juan Antonio
Last Name
Quiroga Mellado
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Óptica
Area
Optica
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Search Results

Now showing 1 - 6 of 6
  • Publication
    Wavefront measurement by solving the irradiance transport equation for multifocal systems
    (Spie-Soc Photo-Optical Instrumentation Engineers, 2001-12) Quiroga Mellado, Juan Antonio; Gómez Pedrero, José Antonio; Martínez Antón, Juan Carlos
    A method for sensing wavefronts is presented. The method is based on the resolution of the irradiance transport equation, which relates the irradiance distribution and the shape of the wavefront of a light beam propagating along a given direction. The method presents no restrictions in the locations of the measurement planes and incorporates an improved procedure to geometrically correct the acquired images to take into account the effect of ray deflection in the propagation of the irradiance distributions. With the proposed technique, we measure the wavefront at the exit pupil of a progressive addition lens and find good agreement with an alternative deflectometric method.
  • Publication
    Recent advances in automatic demodulation of single fringe patterns
    (Springer Verlag Berlin, 2006) Quiroga Mellado, Juan Antonio; Crespo Vázquez, Daniel; Gómez Pedrero, José Antonio; Martínez Antón, Juan Carlos
  • Publication
    Optical method for the surface topographic characterization of Fresnel lenses
    (SPIE--The International Society for Optical Engineering, 2011) Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio; Alonso Fernández, José; Quiroga Mellado, Juan Antonio
    Fresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices. As applications are more exigent this characterization is of increasing importance. We present a technique to characterize the surface topography of optical surfaces. It is especially well adapted to Fresnel lenses where abrupt surface slopes are usually difficult to handle in conventional techniques. The method is based on a new photometric strategy able to codify the height information in terms of optical absorption in a liquid. A detailed topographic map is simple to acquire by capturing images of the surface. Some experimental results are presented. A single pixel height resolution of similar to 0.1 mu m is achieved for a height range of similar to 50 mu m. A surface slope analysis is also made achieving a resolution of similar to +/- 0.15 degrees.
  • Publication
    Structured light-based NDT techniques of interest in the aerospace industry
    (The British Institute of Non-Destructive Testing, 2003-04) Quiroga Mellado, Juan Antonio; Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio
    Structured light techniques (Moiré, projected fringes and other pattern projection techniques) have been used for many years in the aerospace and other industries for external defect location and characterization, 3D shape, deformation measurements and the like. The application of digital image processing methods to the images generated by these techniques has made possible the realization of fast and automatic systems for quantitative NDT measurements. This work is divided in two parts. First, the principal approaches to structured light-based NDT are reviewed, presenting the basis, performance characteristics as well as their expected ranges and resolutions. The second part concentrates on the digital image processing techniques of interest in the field of structured light-based NDT. As the images produced by these techniques are often in the form of phase-modulated fringe patterns, the branch of image processing that deal with this kind of images is denominated fringe pattern processing. Among the many existing fringe pattern processing techniques, the paper will concentrate on the phase-shifting methods (spatial and temporal) and the regularization and natural demodulation methods. It will be shown how when acquisition time is not critical, and several phase-shifted images can be acquired, phase-shifting techniques are well-suited for phase demodulation. Related with these techniques is the so-called phase unwrapping problem that will be discussed. Finally, fringe pattern processing techniques are discussed which can be applied in cases when acquisition time or the optical set-up only allows the use of one fringe pattern. In this case the problem of demodulating the phase is ill-posed from a mathematical point of view and special techniques as regularization and the so-called natural demodulation are needed.
  • Publication
    Automatic demodulation of single-image fringe patterns with application in the evaluation of external defects in aeronautical surfaces by shadow-moire
    (VDI-VDE - Verlag GMBH, 2004) Quiroga Mellado, Juan Antonio; Crespo Vázquez, Daniel; Fournier, N.; Martínez Antón, Juan Carlos
    Automatic demodulation of single-image fringe patterns is of great importance in research areas were it is difficult to apply standard phase evaluation techniques such as phase sampling or Fourier transform methods. In this work we will present recent advances in the automatic demodulation of single-image fringe patterns. In particular we have used two methods for the demodulation process: the regularized phase tracker (RPT) and the isotropic quadrature transform (IQT). For a reliable and automatic demodulation of real fringe patterns by means of the RPT and the IQT techniques we have developed strategies for fringe pattern normalization, modulo 2π fringe orientation computation and adaptive processing, which all together configure a reliable and fast demodulation scheme. We have applied these techniques in the evaluation of external defects in aeronautical surfaces by the shadow moire technique and for this purpose a software package has been developed that works together with an in-line inspection system for indentation assessment designed by the company NDT-Expert. Experimental results of the system will be shown and performance will be discussed.
  • Publication
    Detection of microbumps in aeronautic surfaces by means of an elastical Moire system
    (SPIE--The International Society for Optical Engineering., 2001) Quiroga Mellado, Juan Antonio; Martínez Antón, Juan Carlos; Canabal Boutureira, Héctor; Bernabeu Martínez, Eusebio; Álvaro Labajo, M.; Cortés Testillano, V.
    We provide a simple solution for the particular problem of the in-service inspection of aeronautic surfaces in order to detect bumps that otherwise it is made visually and usually less reliably. Bumps and other surface defects can be a symptom of a more serious internal damage. We have extended the use of the well know shadow Moire technique to be implemented in convex curved surfaces. The use of flexible Ronchi grating allows its adaptation to a convex general surface. The effect is the contrast enhancement of only the small defects sweeping-off other misleading height profile fringes. The result obtained are quite satisfactory compared to the use of flat reference gratings. The experimental set- up consists of a plastic foil with a printed Ronchi grating stretched between three points which adapts to nay cylindrical or conical convex surface independently of the relative grating-surface orientation. Static quantification of defects profiles is also possible by means of with an attached CCD camera. Visual detectability of local surface structures lye in the range of approximately 30 micrometers in depth.