Automated suppression of errors in LTP-II slope measurements with x-ray optics

Ali, Zulfiqar; Artemiev, Nikolay A.; Cummings, Curtis L.; Domning, Edward E.; Kelez, Nicholas; McKinney, Wayne R.; Merthe, Daniel J.; Morrison, Greg; Smith, Brian V.; Yashchuk, Valeriy V.

doi:10.1117/12.894061

Cited by 21 publications

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“…The measurement procedure used is the same as discussed in Ref. 19 The expected surface figure distortion of the HOMS-3 single crystal silicon substrate (with an assumed Young's modulus of 131 GPa and a density of 2.3 g/cm 3 ) due to gravity is of the same order of magnitude as the specified residual surface slope error. Therefore for the slope measurements, the mirror was installed oriented face up on two supports (a cylinder and a ball) displaced symmetrically about the substrate's geometrical center.…”

Section: Surface Metrology In the Slope Domainmentioning

confidence: 94%

“…19 The rms measurement error for a single run is found to be about 80 err   nrad. The estimated rms error of the resulting measurements is about 40-60 nrad.…”

Section: Averaging Of Ltp and Dltp Measurementsmentioning

confidence: 99%

“…The substrate under measurement is placed on an automated rotating, flipping, and aligning (ARFA) system. 19 With the ARFA system, high precision slope measurements with significant suppression of instrumental errors due to systematic effects, set-up drifts, and random noise become possible. 15,17,19,20 The substrate was measured along one central tangential trace of 440 mm.…”

Section: Surface Metrology In the Slope Domainmentioning

confidence: 99%

“…Flipping of the SUT between the LTP runs was performed with an automated rotating, flipping, and aligning (ARFA) system, 19 when the LTP was at rest. After each reset of the SUT with the ARFA system, we checked the preservation of the correct tangential and sagittal position of the next scanning trace.…”

Section: Ltp-ii Measurementmentioning

confidence: 99%

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Cross comparison of surface slope and height optical metrology with a super-polished plane Si mirror

et al. 2012

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We report on a cross-comparison of low-spatial-frequency surface slope and height metrology with a super-polished flat X-ray mirror Si substrate fabricated for the Stanford Linear Accelerator Center Linac Coherent Light Source hard X-ray mirror system HOMS-3. The substrate with overall dimensions of 450 × 30 × 50 mm 3 was specified to have a radius of curvature between 150 km and 195 km with a residual (after subtraction of the best-fit cylinder) slope variation on the level of 0.1 µrad rms, when measured in the tangential direction over a clear aperture of 380 × 5 mm 2 . Surface slope metrology with an accuracy of better than 60 nrad rms was performed with an upgraded long trace profiler LTP-II and an auto-collimator-based developmental LTP (DLTP). The instruments are available at Advanced Light Source optical metrology laboratory. Surface figure in the height domain was characterized at the Lawrence Livermore National Laboratory X-ray science and technology group with a large field-of-view ZYGO TM (12 in) interferometer. The error of the interferometric measurement is estimated to be approximately 0.5 nm rms. We describe in detail the experimental methods and techniques that achieved state-of-the-art metrology with the super-high quality optic under test. We also discuss the relation between surface slope and height metrology and the principle problems of their cross-comparison. We show that with some precautions cross comparison can be made reliably, providing supplemental information on surface figure quality.

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Section: Surface Metrology In the Slope Domainmentioning

confidence: 94%

“…19 The rms measurement error for a single run is found to be about 80 err   nrad. The estimated rms error of the resulting measurements is about 40-60 nrad.…”

Section: Averaging Of Ltp and Dltp Measurementsmentioning

confidence: 99%

Section: Surface Metrology In the Slope Domainmentioning

confidence: 99%

Section: Ltp-ii Measurementmentioning

confidence: 99%

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Cross comparison of surface slope and height optical metrology with a super-polished plane Si mirror

et al. 2012

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“…Because of these advantages, deflectometry has turned out to be especially suitable for characterising beam-shaping optical surfaces for x-ray beamline applications at the modern synchrotrons and Free Electron Lasers (FEL), e.g. [1][2][3][4][5][6][7][8]. Due to their large size (up to 1.5 m length), aspherical, rotationally asymmetric shape, and extremely stringent demands on their form accuracy (< 1 nm peak-to-valley in form, < 50 nrad root-mean-squared in slope [9,10,11]), they pose equally stringent demands on the quality, alignment, and characterisation of the components of deflectometric devices used for their measurement.…”

Section: Introductionmentioning

confidence: 99%

Aperture alignment in autocollimator-based deflectometric profilometers

Geckeler

Artemiev

Barber

et al. 2016

Review of Scientific Instruments

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Abstract. During the last ten years, deflectometric profilometers have become indispensible tools for the precision form measurement of optical surfaces. They have proven to be especially suitable for characterising 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 utilise 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 use with their deflectometric profilometers. In the second part, we investigate the topic further by providing extensive ray tracing simulations and calibrations of a commercial 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.Keywords: Deflectometry, profilometry, x-ray optics, synchrotron metrology, autocollimator, alignment, calibration, surface slope metrology 1 This research was performed while N. A. Artemiev was at

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High precision tilt stage as a key element to a universal test mirror for characterization and calibration of slope measuring instruments

Yashchuk

Artemiev

Centers

et al. 2016

Review of Scientific Instruments

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The ultimate performance of surface slope metrology instrumentation, such as long trace profilers and autocollimator based deflectometers, is limited by systematic errors that are increased when the entire angular range is used for metrology of significantly curved optics. At the ALS X-Ray Optics Laboratory, in collaboration with the HZB/BESSY-II and PTB (Germany) metrology teams, we are working on a calibration method for deflectometers, based on a concept of a universal test mirror (UTM) [Proc. SPIE 6704, 67040A (2007)]. Potentially, the UTM method provides high performance calibration, and accounts for peculiarities of the optics under test (e.g., slope distribution) and the experimental arrangement (e.g., the distance between the sensor and the optic under test). At the same time, the UTM calibration method is inherently universal, applicable to a variety of optics and experimental arrangements. In this work we present the results of tests with a key component of the UTM system, a custom high precision tilt stage, which has been recently developed in collaboration with Physik Instrumente, a Author to whom correspondence should be addressed. Electronic mail: VVYashchuk@lbl.gov. 2GmbH. The tests have demonstrated high performance of the stage and its capability (after additional calibration) to provide angular calibration of surface slope measuring profilers over the entire instrumental dynamic range with absolute accuracy better than 30 nrad. The details of the stage design and tests are presented. We also discuss the foundation of the UTM method and calibration algorithm, as well as the possible design of a full scale UTM system.

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Automated suppression of errors in LTP-II slope measurements with x-ray optics

Cited by 21 publications

References 0 publications

Cross comparison of surface slope and height optical metrology with a super-polished plane Si mirror

Cross comparison of surface slope and height optical metrology with a super-polished plane Si mirror

Aperture alignment in autocollimator-based deflectometric profilometers

High precision tilt stage as a key element to a universal test mirror for characterization and calibration of slope measuring instruments

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