Transfer of autocollimator calibration for use with scanning gantry profilometers for accurate determination of surface slope and curvature of state-of-the-art x-ray mirrors
Ian LaceyKevan AndersonJeff DickertRalf D. GeckelerA. JustFrank SiewertBrian V. SmithValeriy V. Yashchuk
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X-ray optics, desired for beamlines at free-electron-laser and diffraction-limited-storage-ring x-ray light sources, must have almost perfect surfaces, capable of delivering light to experiments without significant degradation of brightness and coherence. To accurately characterize such optics at an optical metrology lab, two basic types of surface slope profilometers are used: the long trace profilers (LTPs) and nanometer optical measuring (NOM) like angular deflectometers, based on electronic autocollimator (AC) ELCOMAT-3000. The inherent systematic errors of the instrument's optical sensors set the principle limit to their measuring performance. Where autocollimator of a NOM-like profiler may be calibrated at a unique dedicated facility, this is for a particular configuration of distance, aperture size, and angular range that does not always match the exact use in a scanning measurement with the profiler. Here we discuss the developed methodology, experimental set-up, and numerical methods of transferring the calibration of one reference AC to the scanning AC of the Optical Surface Measuring System (OSMS), recently brought to operation at the ALS Xray Optics Laboratory. We show that precision calibration of the OSMS performed in three steps, allows us to provide high confidence and accuracy low-spatial-frequency metrology and not 'print into' measurements the inherent systematic error of tool in use. With the examples of the OSMS measurements with a state-of-the-art x-ray aspherical mirror, available from one of the most advanced vendors of X-ray optics, we demonstrate the high efficacy of the developed calibration procedure. The results of our work are important for obtaining high reliability data, needed for sophisticated numerical simulations of beamline performance and optimization of beamline usage of the optics. This work was supported by the U. S. Department of Energy under contract number DE-AC02-05CH11231.Road roughness is gaining increasing importance as an indicator of road condition, both in terms of road pavement performance, and as a major determinant of road user costs. This need to measure roughness has brought a plethora of instruments on the market. The International Road Roughness Experiment (IRRE) covered two categories of instruments - profilometers, which measure the longitudinal elevation profile of the road and converts this into a roughness index, and response type road roughness measuring systems (RTRRMS's), which integrate readings of the device into an instrument specific numeric. The analyses demonstrated a good correlation between the RTRRMS's, and between the RTRRMS's and profilometer records, and showed that they could all be calibrated to a single roughness scale without compromising their accuracy.
International Roughness Index
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This study concentrates on obtaining profiles of rough terrain suitable for vehicle dynamics simulations in a cost–effective manner. Commercially available inertial profilometers are unable to profile the terrains of interest due to their severe roughness. A mechanical profilometer is developed and evaluated by profiling obstacles with known profiles, as well as rough 3-D test track profiles. A good correlation between the profiled and actual terrains is achieved. Realistic three-dimensional (3-D) terrain models are generated from the terrain profiles. The Displacement Spectral Densities (DSDs) of the profiled terrains are found to contain discrete peaks; a straight line fit would not be an accurate estimation for the specific rough terrains. Comparisons between the terrains defined in the International Roughness Index (IRI) and the present study indicate that the roughness index of the terrains profiled with the mechanical profilometer is significantly higher than the terrains normally profiled by inertial profilometers.
International Roughness Index
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Anodizing
Interference microscopy
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The influence of surface roughness on performance of machinery parts and assessment principle of surface roughness were summarized. Several surface roughness measurement methods were described. Attentions were paid to surface roughness measurement by profilometer.
Surface Metrology
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Digital Holographic Microscopes (DHM) allows the capture of all the information necessary to provide 3D phase measurements with a nanometer vertical resolution in a single image acquisition. DHM images provide measurements of the surface topography which can be used for surface analysis, roughness measurements for example. In this paper we present roughness measurements on micro-balls of different sizes for which numerical procedures are applied for form factor and waviness removal. DHM thus permits quantitative measurements of the roughness on a 2 dimensional area allowing enlarged information compared to common profilometers. Mean roughness of 5 to 30 nm are measured and compared to values obtained by a profilometer.
Waviness
Digital Holographic Microscopy
Digital holography
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Abstract The paper presents an analysis of influence of ambient temperature changes on the values of parameters in topography measurements with the use of different profilometry techniques. In order to check this, a series of measurements was performed. Two multiprofilometry instruments were used - a contact profilometer, further equipped with an interferometric transducer, and an optical one with a confocal probe. Measurements were performed on first-class flat interferometric glass and on an A-type roughness standard - under different conditions, with simultaneous registration of differences in ambient temperature values. These values were either intentionally changed or the temperature variations were the result of air conditioning control. The performed research showed that - despite the asperities on the surface being really small - there is a relationship between changes of temperature and the results obtained from the measured surface, which in some cases can be seriously distorted.
Texture (cosmology)
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Abstract Studies of surface finish have shown the desirability of relating profilometer roughness readings to actual peak-to-valley distances of the type that a micrometer measures. Approximate multiplying factors for converting profilometer readings into peak-to-valley roughness have been obtained from taper sections of a variety of abrasive-finished steel surfaces with profilometer roughness in the range of 1 to 100 microinches rms. For cylindrical ground surfaces, the factor can be taken as about 4½; for other types of fixed-abrasive finishes, as 6 or 7; and for loose-abrasive-lapped surfaces, as 10. These are mean values and individual factors may deviate by as much as one third of the mean value. The factors quoted give values for “predominant peak” roughness; they should be doubled to obtain “deepest maximum” roughness, this being a second way of describing the peak-to-valley roughness. No evidence was found of any increase in the factor for a given type of finish with a decrease in the profilometer roughness, even for the finest surfaces studied.
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The performance of mechanical seals was influenced significantly by surface roughness.On the MMU-2 friction and wear test machine and the LI-3 type stylus profilometer,three stationary rings with different surface roughness were tested.The law of characteristic roughness change of seal faces with different primary surface roughness was studied during the running-in,and was compared with the law of profile arithmetic average deviation roughness change of surface.The research results show that the roughness of the surface changes from different to consistent.The results provide a basis for the exact designing seal-face roughness of mechanical seals and the reasonable selecting manufacturing method of seal faces by characteristic roughness.
Stylus
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Characterization of surface roughness remains today a crucial problem, in particular in the fields of optics and mechanics. Many techniques [1] have been developed in this aim, and involve scatterometers or profilometers. However the measured roughness values may strongly vary from one technique to another, and it becomes necessary to normalize the statistical parameters that describe surface defects. In this paper we present experimental results obtained from 3 techniques that are Angle-Resolved light Scattering measurements (ARS), mechanical profilometer (Talystep) and Atomic Force Microscope (AFM). Moreover, a theoretical tool is provided for a detailed investigation of the apparatus functions relative to the light scattering and Talystep techniques.
Characterization
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Instrumental techniques available for measuring the roughness of optical surfaces include mechanical profilometers and optical heterodyne profilometers, both of which yield surface profiles, and total integrated and angle-resolved scattering, from which roughness values can be derived using appropriate theoretical relations. These methods are used to measure the roughness of a set of roughness standards made by polishing ground Zerodur surfaces for progressively longer times. The measured roughnesses are compared, and the reasons for the differences are discussed.
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