A new Aperture Centring Device (ACenD) for precisely positioning small apertures with respect to the autocollimator’s optics has been developed. With the new device, differences in the angle response of autocollimators between the calibration at a laboratory and their subsequent application in the slope measuring profilers are significantly minimized. Evaluation of the device with a circular aperture size of d=2.5 mm was carried out in different laboratories. It was verified that the ACenD is capable of achieving a reproducible aperture alignment < 0.1 mm. The device is a substantial aid for the operation of slope measuring profilometers and enables the measurable, documentable, and transferable positioning of apertures that did not exist before.
An angle metrology project (SIB58 Angles) addressing the challenging issues related to performance of autocollimators in slope measuring profilers run for three years and was completed recently with cooperation of a wide range of partners. Outcomes of the project which are for interest to the X-ray optics community are presented; new aperture centring device (ACenD) for the accurate centring of a beam-limiting aperture in front of an autocollimator (with a positional accuracy of ±0.1 mm), performance of autocollimators with varying distances to reflector at small apertures, developed guides for calibration of autocollimators and reference angle encoders, first 2D calibration of autocollimators, new devices and novel methods for traceable generation and measurement of angles at nanoradian precision.
A portable device has been developed in TUBITAK UME to calibrate high precision autocollimators with nanoradian precision. The device can operate in the range of ±4500" which is far enough for the calibration of the available autocollimators and can generate ultra-small angles in measurement steps of 0.0005" (2.5 nrad). Description of the device with the performance tests using the calibrated precise autocollimators and novel methods will be reported. The test results indicate that the device is a good candidate for application to on-site/in-situ calibration of autocollimators with expanded uncertainties of 0.01" (50 nrad) particularly those used in slope measuring profilers.
The requirements on the quality of ultra-precise X-ray optical components for application in the Synchrotron Radiation
(SR) community are increasing continually and strongly depend on the quality of the metrology devices available to
measure such optics. To meet the upcoming accuracy goal of 50 nrad rms for slope measuring profilers, a dedicated
project, SIB58 Angles, consisting of 16 worldwide partners and supported by the European Metrology Research
Programme (EMRP) was started in Sep 2013. The project covers investigations on autocollimators under extremely
challenging measuring conditions, ray-tracing models, 2D autocollimator calibration (for the first time worldwide),
determination of error sources in angle encoders providing traceability by ‘sub-division of 2π rad’ with nrad uncertainty,
angle generation by 'ratio of two lengths' in nrad level, and on the development of portable precise Small Angle
Generators (SAGs) for regular in-situ checks of autocollimators’ performance. Highlights from the project will be
reported in the paper and the community of metrology for X-Ray and EUV Optics will be informed about its progress
and the latest work in angle metrology.
Measurement uncertainty is an important topic for traceable measurements. Nevertheless not many literatures on the uncertainty of flatness measurements have been reported. In this paper, we report on this issue according to the Guide to the Expression fo Uncertainty in Measurements (GUM). First stability of the reference optical flat used in Fizeau interferometer is discussed analytically, numerically, and experimentally. Then other uncertainty sources in actual measurements are investigated. As a result the uncertainty of flatness measurement of a large aperture flatness interferometer made by National Metrology Institute of Japan is 1/77 wavelength.
Conference Committee Involvement (5)
Advances in Metrology for X-Ray and EUV Optics IX
24 August 2020 | Online Only, California, United States
Advances in Metrology for X-Ray and EUV Optics VIII
11 August 2019 | San Diego, California, United States
Advances in Metrology for X-Ray and EUV Optics VII
6 August 2017 | San Diego, California, United States
Advances in Metrology for X-Ray and EUV Optics VI
29 August 2016 | San Diego, California, United States
Advances in Metrology for X-Ray and EUV Optics V
18 August 2014 | San Diego, California, United States