<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0185-1101</journal-id>
<journal-title><![CDATA[Revista mexicana de astronomía y astrofísica]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. mex. astron. astrofis]]></abbrev-journal-title>
<issn>0185-1101</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional Autónoma de México, Instituto de Astronomía]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0185-11012010000100013</article-id>
<title-group>
<article-title xml:lang="es"><![CDATA[Amplitude fluctuations in curvature sensing: comparison of two schemes]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Voitsekhovich]]></surname>
<given-names><![CDATA[V. V.]]></given-names>
</name>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Orlov]]></surname>
<given-names><![CDATA[V. G.]]></given-names>
</name>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Astronomía ]]></institution>
<addr-line><![CDATA[México D. F.]]></addr-line>
<country>Mexico</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>04</month>
<year>2010</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>04</month>
<year>2010</year>
</pub-date>
<volume>46</volume>
<numero>1</numero>
<fpage>145</fpage>
<lpage>152</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0185-11012010000100013&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0185-11012010000100013&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0185-11012010000100013&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="es"><p><![CDATA[Se investiga la influencia de las fluctuaciones en amplitud sobre la calidad de la reconstrución de fases en la medición de la curvatura. Se comparan los dos esquemas: el que emplea dos imágenes simétricas fuera de foco (esquema de Roddier) y el que emplea una sola (esquema de Hickson). Se demuestra que la precisión de la reconstrucción de fases con el esquema de Hickson se ve fuertemente afectada por fluctuaciones en amplitud incluso leves, mientras que el esquema de Roddier funciona bien incluso con grandes fluctuaciones en amplitud.]]></p></abstract>
<abstract abstract-type="short" xml:lang="en"><p><![CDATA[The influence of amplitude fluctuations on the quality of phase reconstruction in curvature sensing is investigated. Two curvature schemes are compared: one with two symmetrically-defocused images (Roddier scheme) and one with a single defocused image (Hickson scheme). It is shown that the accuracy of phase reconfluctuations, while the Roddier scheme works well under quite strong amplitude o struction with the Hickson scheme is strongly affected even by low-level amplitude fluctuations.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[instrumentation: adaptive optics]]></kwd>
<kwd lng="en"><![CDATA[techniques: high angular resolution]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <p align="center"><font face="verdana" size="4"><b>Amplitude fluctuations in curvature sensing: comparison of two schemes</b></font></p>     <p align="center"><font face="verdana" size="2">&nbsp;</font></p>     <p align="center"><font face="verdana" size="2"><b>V. V. Voitsekhovich<sup>1</sup> and V. G. Orlov<sup>1</sup></b></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><i><sup>1</sup>&nbsp;Instituto de Astronom&iacute;a, Universidad Nacional Aut&oacute;noma de M&eacute;xico, Apdo. Postal 70&#150;264, 04510 M&eacute;xico, D. F., Mexico. (<a href="mailto:orlov@astroscu.unam.mx">orlov@astroscu.unam.mx</a>, <a href="mailto:voisteko@astroscu.unam.mx">voisteko@astroscu.unam.mx</a>).</i></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2">Received 2009 March 30    <br>   Accepted 2010 January 14</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>RESUMEN</b></font></p>     ]]></body>
<body><![CDATA[<p align="justify"><font face="verdana" size="2">Se investiga la influencia de las fluctuaciones en amplitud sobre la calidad de la reconstruci&oacute;n de fases en la medici&oacute;n de la curvatura. Se comparan los dos esquemas: el que emplea dos im&aacute;genes sim&eacute;tricas fuera de foco (esquema de Roddier) y el que emplea una sola (esquema de Hickson). Se demuestra que la precisi&oacute;n de la reconstrucci&oacute;n de fases con el esquema de Hickson se ve fuertemente afectada por fluctuaciones en amplitud incluso leves, mientras que el esquema de Roddier funciona bien incluso con grandes fluctuaciones en amplitud.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>ABSTRACT</b></font></p>     <p align="justify"><font face="verdana" size="2">The influence of amplitude fluctuations on the quality of phase reconstruction in curvature sensing is investigated. Two curvature schemes are compared: one with two symmetrically&#150;defocused images (Roddier scheme) and one with a single defocused image (Hickson scheme).  It is shown that the accuracy of phase reconfluctuations, while the Roddier scheme works well under quite strong amplitude o struction with the Hickson scheme is strongly affected even by low&#150;level amplitude fluctuations.</font></p>     <p align="justify"><font face="verdana" size="2"><b><i>Key Words: </i></b>instrumentation:  adaptive optics &#151; techniques:  high angular resolution.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><a href="/pdf/rmaa/v46n1/v46n1a13.pdf" target="_blank">DESCARGAR ART&Iacute;CULO EN FORMATO PDF</a></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>ACKNOWLEDGMENTS</b></font></p>     <p align="justify"><font face="verdana" size="2">This work was supported by Direcci&oacute;n General de Asuntos del Personal Acad&eacute;mico (Universidad Nacional Aut&oacute;noma de M&eacute;xico) under projects IN107906&#150;2 and IN113308 (PAPIIT).</font></p>     ]]></body>
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