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Proceedings Paper

Tactile sensor for aspheric measurements; Technical Digest
Author(s): Rene Schoene; Johann Zaenkert; Tobias Hanning
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Paper Abstract

The LINOS Photonics company has developed a new tactile sensor to measure aspheric surfaces. The sensing device drives along spherical coordinates and the measuring data of a level curve is obtained by the rotation of the lens. The complete asphere of the lens is reconstructed by a number of such level curves. All data is given in a spherical coordinate system. The company provides a software to determine the error between the actual surface and a reference asphere with respect to a cartesian coordinate system. But the algorithm depends on the strong assumption that the peak of the reconstructed asphere is equal to the rotational point of the measuring instrument. Our algorithm expands the existing method. We minimize the distance of the reference asphere to the measuring points in a cartesian coordinate system. To do this, we calculate the optimal rotation and translation of the reference asphere to the measured points. This defines a non-linear optimization problem, which is solved with algorithm of Levenberg and Marquardt. Furthermore, we are able to calculate the Jacobi matrix with respect to the rotation center. The output of the proposed algorithms contains the maximal deviation for each measuring point in z-direction and the variance of the error. Additionally, we determine a pseudo tangential deviation between the reference and the actual geometry by a secant method. Altogether the new algorithm enables us to deliver comparable results for the asphere measuring problem.

Paper Details

Date Published: 2 May 2005
PDF: 4 pages
Proc. SPIE 10315, Optifab 2005: Technical Digest, 103150P (2 May 2005); doi: 10.1117/12.612040
Show Author Affiliations
Rene Schoene, Univ. of Passau (Germany)
Johann Zaenkert, LINOS Photonics GmbH & Co. KG (Germany)
Tobias Hanning, Univ. of Passau (Germany)


Published in SPIE Proceedings Vol. 10315:
Optifab 2005: Technical Digest
Robert E. Fischer; Masahide Katsuki; Matthias Pfaff; Kathleen A. Richardson, Editor(s)

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