Advanced techniques for measuring primary mirrors for astronomical telescopes.

Persistent Link:
http://hdl.handle.net/10150/186389
Title:
Advanced techniques for measuring primary mirrors for astronomical telescopes.
Author:
Burge, James Howard
Issue Date:
1993
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The optical measurement of primary mirrors for astronomical telescopes has become increasingly challenging for two reasons. The mirrors, in addition to being larger, are faster and more aspheric in order to shorten the length of the telescope, and the required accuracy of the optical surfaces is more stringent. This dissertation presents improved methods for measuring these mirrors in the laboratory to the required accuracy. The wire test and the scanning pentaprism test, which measure surface slope errors, were designed and run under computer control. The wire test was used to measure the conic constant of a 3.5-m f/1.75 primary mirror to an accuracy of ±0.003 and the scanning pentaprism test measured the conic constant of a 1.8-m f/1 primary to ±0.003. Improvements in these tests were identified that could increase the accuracy significantly. Interferometric optical testing with null correctors is widely used for measuring aspheric surfaces to high accuracy. A system-level analysis of the null test is given. The test is optimized for wavefront accuracy, imaging distortion, and measurement noise from ghost reflections and diffraction. The optical design and analysis of null correctors, including designs for testing 6.5-m f/1.25 and 8.4-m f/1.14 primary mirrors are given. Several new null corrector designs and a method for performing tolerance analysis using structure functions are given. An error in the null corrector, if not detected, would cause the primary mirror to be polished to the wrong shape. (The primary mirrors for the Hubble Space Telescope and the European New Technology Telescope were misshapen because of faulty null correctors.) A new test of null correctors is presented that uses a computer-generated hologram (CGH) to synthesize a perfect primary mirror. When the CGH is measured through the null corrector, it appears as a perfect primary mirror. Apparent surface errors in this measurement can be attributed to errors in the null corrector. A complete error analysis of this test is given. This method has been proven on null correctors for 3.5-m primary mirrors, where it measured errors as small as 5.1 nm rms and confirmed the conic constants to ±0.000078.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic.; Optics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Optical Sciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Angel, J. Roger P.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleAdvanced techniques for measuring primary mirrors for astronomical telescopes.en_US
dc.creatorBurge, James Howarden_US
dc.contributor.authorBurge, James Howarden_US
dc.date.issued1993en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe optical measurement of primary mirrors for astronomical telescopes has become increasingly challenging for two reasons. The mirrors, in addition to being larger, are faster and more aspheric in order to shorten the length of the telescope, and the required accuracy of the optical surfaces is more stringent. This dissertation presents improved methods for measuring these mirrors in the laboratory to the required accuracy. The wire test and the scanning pentaprism test, which measure surface slope errors, were designed and run under computer control. The wire test was used to measure the conic constant of a 3.5-m f/1.75 primary mirror to an accuracy of ±0.003 and the scanning pentaprism test measured the conic constant of a 1.8-m f/1 primary to ±0.003. Improvements in these tests were identified that could increase the accuracy significantly. Interferometric optical testing with null correctors is widely used for measuring aspheric surfaces to high accuracy. A system-level analysis of the null test is given. The test is optimized for wavefront accuracy, imaging distortion, and measurement noise from ghost reflections and diffraction. The optical design and analysis of null correctors, including designs for testing 6.5-m f/1.25 and 8.4-m f/1.14 primary mirrors are given. Several new null corrector designs and a method for performing tolerance analysis using structure functions are given. An error in the null corrector, if not detected, would cause the primary mirror to be polished to the wrong shape. (The primary mirrors for the Hubble Space Telescope and the European New Technology Telescope were misshapen because of faulty null correctors.) A new test of null correctors is presented that uses a computer-generated hologram (CGH) to synthesize a perfect primary mirror. When the CGH is measured through the null corrector, it appears as a perfect primary mirror. Apparent surface errors in this measurement can be attributed to errors in the null corrector. A complete error analysis of this test is given. This method has been proven on null correctors for 3.5-m primary mirrors, where it measured errors as small as 5.1 nm rms and confirmed the conic constants to ±0.000078.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academic.en_US
dc.subjectOptics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineOptical Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairAngel, J. Roger P.en_US
dc.contributor.committeememberMartin, Hubert IIIen_US
dc.contributor.committeememberShack, Rolanden_US
dc.contributor.committeememberGreivenkamp, Johnen_US
dc.identifier.proquest9408466en_US
dc.identifier.oclc720410770en_US
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