Author
Octavio Cardona-Nunez
Bio: Octavio Cardona-Nunez is an academic researcher from National Institute of Astrophysics, Optics and Electronics. The author has contributed to research in topics: Conic section & Conic constant. The author has an hindex of 7, co-authored 15 publications receiving 157 citations.
Topics: Conic section, Conic constant, Curvature, Ronchi test, Toroid
Papers
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TL;DR: A common mathematical model is established for the Ronchi and Hartmann tests and for interpretation of the Ronchigrams as level curves of the components of the transversal aberrations.
Abstract: A common mathematical model is established for the Ronchi and Hartmann tests and for interpretation of the Ronchigrams as level curves of the components of the transversal aberrations. With the same point of view, a Hartmanngram is regarded as two 90° crossed null Ronchi gratings. A simple and direct method is also developed for calculating Ronchigrams for the cases of centered and off-axis conic sections with the point light source at any location.
37 citations
TL;DR: This method is based on the method of continuum least squares to obtain the vertex’s curvature and conic Constant of the fitted conic on-axis, given the curvature at the vertex and the conic constant of the parent conic from where the authors want the section and the size of that section.
Abstract: To help in the fabrication of off-axis conic sections, we present a method to approximate this off-axis section by an on-axis conic centered on the portion desired. This method is based on the method of continuum least squares to obtain the vertex’s curvature and conic constant of the fitted conic on-axis, given the curvature at the vertex and the conic constant of the parent conic from where we want the section and the size of that section. Simple analytic expressions for the curvature and conic constant are derived in terms of the parameters of the off-axis section.
26 citations
TL;DR: Assuming the Ronchi and the Hartmann tests to be null tests, it was able to design special screens for each test that produce aligned straight fringes and a square array for the observed patterns.
Abstract: Assuming the Ronchi and the Hartmann tests to be null tests, we were able to design special screens for each test that produce aligned straight fringes and a square array for the observed patterns. It also became clear that the screen filter and observing planes for both tests can be interchanged.
22 citations
TL;DR: Using a technique that was previously developed for measuring the radius of curvature of spherical surfaces, an alternative method for testing cylindrical as well as toric lenses is presented.
Abstract: Using a technique that was previously developed for measuring the radius of curvature of spherical surfaces, an alternative method for testing cylindrical as well as toric lenses is presented. The basic equipment required is a nodal bench and a low power He–Ne laser.
17 citations
TL;DR: A method of measuring the profile along one diameter of a conic surface is presented and useful mathematical relations are derived that can be used for comparing theoretical and real values of the sagitta of the surface.
Abstract: A method of measuring the profile along one diameter of a conic surface is presented. Using some well-known formulas for the conic sections, useful mathematical relations are derived that, together with a simple experimental setup can be used for comparing theoretical and real values of the sagitta of the surface.
14 citations
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TL;DR: A method for null-testing fast convex aspheric optical surfaces is presented, using a cylindrical screen with a set of lines drawn on it in such a way that its image, which is formed by reflection on a perfect surface, yields a perfect square grid.
Abstract: A method for null-testing fast convex aspheric optical surfaces is presented The method consists of using a cylindrical screen with a set of lines drawn on it in such a way that its image, which is formed by reflection on a perfect surface, yields a perfect square grid Departures from this geometry are due to imperfections of the surface, allowing one to know if the surface is close to the design shape Tests conducted with a full hemisphere and with the parabolic surface of a lens show the feasibility of the method Numerical simulations show that it is possible to detect surface departures as small as 5 microm
94 citations
Journal Article•
TL;DR: In this paper, a method is described by which these patterns can be easily calculated for any required case; and series of typical patterns are shown together with actual interferograms for comparison.
Abstract: In order to obtain a rapid estimate of the quality of a lens by observing its behaviour in the interferometer, it is necessary for the observer to be familiar with the characteristic patterns of the various primary aberrations under various conditions of adjustment. A method is described by which these patterns can be easily calculated for any required case; and series of typical patterns are shown together with actual interferograms for comparison.
51 citations
TL;DR: The feasibility of using null screens for testing the segments of a parabolic segmented telescope mirror for the Large Millimeter Telescope (LMT) is analyzed and an algorithm for designing the null screen forTesting the off-axis segments of conic surfaces is described.
Abstract: The feasibility of using null screens for testing the segments of a
parabolic segmented telescope mirror for the Large Millimeter Telescope
(LMT) is analyzed. An algorithm for designing the null screen
for testing the off-axis segments of conic surfaces is
described. Actual screen designs for the different classes of
segments of the LMT are presented. The sensitivity of the test and
the required accuracies for the fabrication and positioning of the
screen are analyzed. A measuring accuracy of ∼12 µm in
surface sagitta is within the reach of the technique.
42 citations
TL;DR: This work uses trapezoidal integration to analyze the new patterns, since it does not have the smoothing drawback at the edges of the wave front in the Ronchi test.
Abstract: We use a square grid in the Ronchi test. This grid allows processing of both the X and the Y directions when calculating optical path difference. We use trapezoidal integration to analyze the new patterns, since it does not have the smoothing drawback at the edges of the wave front.
38 citations
TL;DR: A common mathematical model is established for the Ronchi and Hartmann tests and for interpretation of the Ronchigrams as level curves of the components of the transversal aberrations.
Abstract: A common mathematical model is established for the Ronchi and Hartmann tests and for interpretation of the Ronchigrams as level curves of the components of the transversal aberrations. With the same point of view, a Hartmanngram is regarded as two 90° crossed null Ronchi gratings. A simple and direct method is also developed for calculating Ronchigrams for the cases of centered and off-axis conic sections with the point light source at any location.
37 citations