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 Experimental measurements of generalized grating images(Applied Optics, 2002) Crespo Vázquez, Daniel; Alonso Fernández, José; Bernabeu Martínez, EusebioThe term generalized grating imaging is used to describe the process of image formation of a grating using only another grating as imaging system. The moiré and the Lau effects could be regarded as particular cases of such a process. Here we deal with the less-studied case of images formed at finite distances from the gratings, using an extended monochromatic light source. Some experimental results are shown for the images obtained in this last case, and they are compared with theoretical predictions.Item Generalized grating imaging using an extended monochromatic light source(Journal of the Optical Society of America A-Optics Image Science And Vision, 2000) Crespo Vázquez, Daniel; Alonso Fernández, José; Bernabeu Martínez, EusebioIt is a well-known fact that one grating can act as an imaging element for another grating when the first is illuminated with an extended monochromatic light source. The conditions for image formation in such a system are studied when the finite size and position of the broad light source are considered. From the presented analysis, expressions for the location and the depth of focus of such images can be derived.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 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 Reflection optical encoders as three-grating moiré systems(Applied Optics, 2000) Crespo Vázquez, Daniel; Alonso Fernández, José; Bernabeu Martínez, EusebioReflection optical encoders are studied as three-grating moiré systems. An analysis is made of the differences that may appear between it and the standard case in which an optical encoder is regarded as a two-grating system.