Title: Aperture alignment in autocollimator-based deflectometric profilometers

Abstract

During the last ten years, deflectometric profilometers have become indispensable tools for the precision form measurement of optical surfaces. They have proven to be especially suitable for characterizing beam-shaping optical surfaces for x-ray beamline applications at synchrotrons and free electron lasers. Deflectometric profilometers use surface slope (angle) to assess topography and utilize commercial autocollimators for the contactless slope measurement. To this purpose, the autocollimator beam is deflected by a movable optical square (or pentaprism) towards the surface where a co-moving aperture limits and defines the beam footprint. In this paper, we focus on the precise and reproducible alignment of the aperture relative to the autocollimator's optical axis. Its alignment needs to be maintained while it is scanned across the surface under test. The reproducibility of the autocollimator's measuring conditions during calibration and during its use in the profilometer is of crucial importance to providing precise and traceable angle metrology. In the first part of the paper, we present the aperture alignment procedure developed at the Advanced Light Source, Lawrence Berkeley National Laboratory, USA, for the use of their deflectometric profilometers. In the second part, we investigate the topic further by providing extensive ray tracing simulations and calibrations of a commercialmore » autocollimator performed at the Physikalisch-Technische Bundesanstalt, Germany, for evaluating the effects of the positioning of the aperture on the autocollimator's angle response. The investigations which we performed are crucial for reaching fundamental metrological limits in deflectometric profilometry.« less

Authors:

Geckeler, R. D.  ^[1];

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Artemiev, N. A. ^[2]; Barber, S. K. ^[2]; Just, A. ^[1]; Lacey, I. ^[2]; Kranz, O. ^[1]; Smith, B. V. ^[3]; Yashchuk, V. V. ^[2]

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+ Show Author Affiliations

1. Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Publication Date:

Tue May 24 00:00:00 EDT 2016

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1530235

Alternate Identifier(s):

OSTI ID: 1254335

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Review of Scientific Instruments

Additional Journal Information:

Journal Volume: 87; Journal Issue: 5; Journal ID: ISSN 0034-6748

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

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