Person: Alonso Fernández, José
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First Name
José
Last Name
Alonso Fernández
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Department
Óptica
Area
Optica
Identifiers
5 results
Search Results
Now showing 1 - 5 of 5
Item Optical method for the surface topographic characterization of Fresnel lenses(Optical Fabrication, Testing and Metrology IV, 2011) Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio; Alonso Fernández, José; Quiroga Mellado, Juan AntonioFresnel 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.Item 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, AliIn 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.Item Laser beam deflectometry based on a subpixel resolution algorithm(Optical Engineering, 2001) Canabal Boutureira, Héctor Alfonso; Alonso Fernández, José; Bernabéu Martínez, EusebioA deflectometric method for the characterization of optical systems is presented. It is based on the use of a CCD camera and a subpixel resolution algorithm for the measurement of the deflection of a laser beam that propagates through the system. To obtain accurate results, three different algorithms for measuring the position of the deflected beam are tested and compared. Based on this comparison, an algorithm based on the calculation of the phase of the fast Fourier transform (FFT) is selected, and an accuracy of 0.024 pixels is obtained on the determination of the beam position in our setup. Using an XY scanning stage, the proposed method is completely automated and applied for the characterization of ophthalmic lenses. In this application, the gradients of the wavefront refracted by the lens are measured directly, and from them, the thickness and the local power of the lens are computed.Item Optical autofocus for high resolution laser photoplotting(Photonic Materials, Devices, and Applications, 2005) Alonso Fernández, José; Crespo Vázquez, Daniel; Jiménez Castillo, Isidoro; Bernabéu Martínez, Eusebio; Badenes, Goncal; Abbott, Derek; Serpenguzel, AliAn all optical autofocus has been designed and tested for tight line width control in a high NA laser photoplotter system. The laser system is based in a GaN semiconductor laser with power 30 mW and wavelength 405 nm. The advantage of using this laser, despite the relatively long wavenlength, is compactness and easy for high frequency modulation. The autofocus system is based in a secondary 635 nm GaAlAs laser without need for wavelength, neither power stabilization. The two beams are delivered coaxially through the focusing lens by means of a dichroic beamsplitter. Focusing lens need no correction for chromatic aberration, as this is compensed by appropriate autofocus beam divergence. After reflection in the sample, the autofocus beam is separated from the returning writing beam and then guided to a collimation sensor, in which defocus of about 1/20 of the Rayleigh range of the writing beam can be detected and compensated by an analogue PID electronic control. Stable linewidth within 5% is achieved with different numerical aperture focusing lenses.Item Improvements in laser beam characterization with a CCD-based setup(Photonics in Measurement, 2004) Quiroga Mellado, Juan Antonio; González Moreno, Ricardo; Alonso Fernández, José; Bernabeu Martínez, EusebioCCD-based setups are widely extended in commercial beam profilers. In many beam-profiling applications the high sensitivity of CCD-camera makes necessary the attenuation of the beam. It can affect the beam profile and cause lost of information in regions of low irradiance. In this work we analyze the combined influence of noise and masking in the beam characterization, particularly in the measurement of second order moments. We also apply an extended intensity range imaging technique to improve the quality of the information obtained by a generic instrument. It is achieved merging several images with different sensitivities which are obtained with different integration times.