Displacement-free stereoscopic phase measuring deflectometry based on phase difference minimization.

In this paper, we propose a phase difference minimization algorithm to measure the specular surface shape in a displacement-free stereoscopic phase measuring deflectometry (PMD) system. The presented system is capable of solving the height-normal ambiguity appearing in a PMD system without moving any system component. Both the surface normal and the absolute height are simultaneously obtained by implementing phase difference minimization between the phase distributions in the LCD screen and the camera image plane. In particular, phase difference minimization is performed by using a second order polynomial fitting iteration method. Bi-cubic sub-pixel interpolation combined with 2D Fourier integration is used to reconstruct the surface. Finally, the performance of the proposed stereoscopic PMD system is verified by measuring the surface shapes of different mirrors and performing repeatability tests.

Deflectometry encoding the measured angle in a time-dependent intensity signal.

We propose a new concept of a deflectometer, aimed to provide high accuracy measurements with high sampling rate and low noise, as required by state-of-the-art slope-measuring profilometers, like Long Trace Profilometers or Nanometer Optics Measuring instruments. For this purpose, we introduce certain modifications to the usual working principle of autocollimators so that the measured angle is not given by the displacement of the pattern captured by a CCD, but by the harmonic contents of the time-modulated intensity signal acquired by a photodiode. By doing this, the signal can be sampled not by just a few thousand pixels but by millions of samples/s.

Characterization, optimization and surface physics aspects of in situ plasma mirror cleaning.

Although the graphitic carbon contamination of synchrotron beamline optics has been an obvious problem for several decades, the basic mechanisms underlying the contamination process as well as the cleaning/remediation strategies are not understood and the corresponding cleaning procedures are still under development. In this study an analysis of remediation strategies all based on in situ low-pressure RF plasma cleaning approaches is reported, including a quantitative determination of the optimum process parameters and their influence on the chemistry as well as the morphology of optical test surfaces. It appears that optimum results are obtained for a specific pressure range as well as for specific combinations of the plasma feedstock gases, the latter depending on the chemical aspects of the optical surfaces to be cleaned.

Lateral packing of mineral crystals in bone collagen fibrils.

Combined small-angle x-ray scattering and transmission electron microscopy studies of intramuscular fish bone (shad and herring) indicate that the lateral packing of nanoscale calcium-phosphate crystals in collagen fibrils can be represented by irregular stacks of platelet-shaped crystals, intercalated with organic layers of collagen molecules. The scattering intensity distribution in this system can be described by a modified Zernike-Prins model, taking preferred orientation effects into account. Using the model, the diffuse fan-shaped small-angle x-ray scattering intensity profile, dominating the equatorial region of the scattering pattern, could be quantitatively analyzed as a function of the degree of mineralization. The mineral platelets were found to be very thin (1.5 nm approximately 2.0 nm), having a narrow thickness distribution. The thickness of the organic layers between adjacent mineral platelets within a stack is more broadly distributed with the average value varying from 6 nm to 10 nm, depending on the extent of mineralization. The two-dimensional analytical scheme also leads to quantitative information about the preferred orientation of mineral stacks and the average height of crystals along the crystallographic c axis.

Perforated layer structures in liquid crystalline rod-coil block copolymers.

We report a novel observation of the tetragonal perforated layer structures in a series of rod-coil liquid crystalline block copolymers (BCPs), poly(styrene-block-(2,5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PS-b-PMPCS). PMPCS forms rigid rods while PS forms the coil block. Differential scanning calorimetry (DSC), polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and transmission electron microscopy (TEM) techniques were used to investigate these rod-coil molecules, and a perforated layer structure was observed at f(PMPCS) approximately 0.37 in relatively low molecular weight (M(w)) samples and approximately 0.5 in high M(w) PS-b-PMPCS. This substantial phase boundary shift was attributed to the rod-coil nature of the BCP. The perforation obeys a tetragonal instead of hexagonal symmetry. The "onset" of perforation was also observed in real space in sample PS(272)-b-PMPCS(93) (f(PMPCS) approximately 0.52), in which few PS chains punctuate PMPCS layers. A slight increase in f(PS), by blending with PS homopolymer, led to a dramatic change in the BCP morphology, and uniform tetragonal perforations were observed at f(PMPCS) approximately 0.48.

Reversible de-intercalation and intercalation induced by polymer crystallization and melting in a poly(ethylene oxide)/organoclay nanocomposite.

Semicrystalline polymer/layered silicate nanocomposites were prepared by solution blending of a low molecular weight poly(ethylene oxide) (PEO) with an organically modified montmorillonite, Cloisite 10A (C10A). The intercalation morphology was studied by temperature-dependent synchrotron wide-angle X-ray diffraction (WAXD). Unlike PEO homopolymers, significant secondary crystallization was observed in the PEO/C10A nanocomposites. Reversible de-intercalation and intercalation processes were detected during secondary crystallization and subsequent melting of secondary crystals. On the basis of two-dimensional WAXD results on oriented samples, an interphase layer between the silicate primary particles and PEO lamellar crystals was proposed. Secondary PEO crystallization in the interphase regions was inferred to be the primary driving force for polymer chains to diffuse out of the silicate gallery. This study provided a useful method to investigate polymer diffusion in nanoconfined spaces, which can be controlled by PEO secondary crystallization and melting outside the silicate gallery.