This PDF file contains the front matter associated with SPIE Proceedings Volume 10750, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

In this paper we will discuss theoretical modeling of laser scattering from complex and large objects. We will describe the main features of scattering cross-section calculation of randomly rough objects, some of its uses and the basis for its validity with different calculation examples. The computation of scattering cross-sections is performed in four steps, mathematical description of the surface, description of electromagnetic and statistical parameters associated with elementary facets representing the object surface, calculation and summation of the backscattered cross-sections from the different elementary facets. Thereby the coherent and incoherent scattering cross-sections of the object are obtained. With this numerical method we can compute resolved and unresolved cross-sections.

We describe our approach for the modeling of space objects on the basis of 3-D designs supplemented with surface material assignments and their associated electro-optical properties. Challenges with this approach include incorporating Bi-directional Reflectance Distribution Function (BRDF) models that are both representative and robust over a range of wavelengths. In view of the small angles subtended by most space objects observed at a distance, any limitations of the applicability of BRDFs measured with much larger laboratory fields of view need to be assessed. In addition, any observational effects associated with partial coherence under conditions addressed by the van Cittert-Zernike theorem require investigation. More comparisons of predictions and observations are needed to guide these developments.

Other than water, pure bulk liquids and solids are rarely encountered in the environment, but more commonly exist as layers on various substrates, e.g. concrete, metals, glass, etc. Unlike gas-phase transmission spectra, condensed-phase reflectance spectra depend not only on absorption, but also on the material’s refraction and reflection at interfaces. Providing reference spectra to account for the plethora of morphological conditions (e.g. substrate, layer thickness, particle or droplet size) that may be encountered under different scenarios is a daunting challenge. An alternative approach is to derive the complex optical constants, n and k, which can be used to model the optical phenomena in media and at interfaces, minimizing the need for a vast number of laboratory measurements. The current status of obtaining such optical constants for both solids and liquids is briefly summarized.

In the 1950s H.C. van de Hulst heuristically developed a simple formula, called anomalous diffraction approximation (ADA), which closely represents the extinction efficiency derived from Mie theory for spherical dielectric particles in certain limits. The method is computationally fast and can be applied to non-spherical particle shapes, thus it is very useful. The formula works best for large size parameters (proportional to radius over wavelength) and for the refractive index ratio of the particle to background close to one. Because of its usefulness, work has continued to develop this approach for a variety of particle shapes and a greater range of size parameter and refractive index. In this paper a more rigorous foundation is used that begins with the scalar Helmholtz equation and leads to the ADA formulas with appropriate approximations for both dielectric and conducting particles. By relaxing some of the approximations and accounting for the polarizability response of the particle to the applied field, an improved-ADA formula is derived. It more accurately predicts the extinction and absorption efficiencies over the full range of the particle size parameter and for real part of refractive index ratios from just less than one up to 2.5 and for the imaginary part much less than 1.

The bidirectional reflectance distribution function (BRDF) describes material reflectance by relating incident irradiance to scattered radiance. One popular class of BRDF models is the microfacet model, which assumes geometric optics but is more readily applicable to remote sensing. One drawback of this geometric optics model is the need for a cross section conversion term, which diverges at grazing angles. This problem is only partially addressed by adding a geometric attenuation term to conserve energy, while still neglecting wave optics effects. Based on previous work comparing microfacet and wave optics models, Butler proposed to replace the geometric attenuation and cross-section conversion terms with a theoretical approximation, the closed-form polarization factor, Q. Analysis presented both at Optics and Photonics by Butler in 2017 and SPIE Defense and Commercial Sensing (DCS) by Ewing in 2018 show this modification to be effective for both high density (but low fidelity) data, and low density (but high fidelity) data, particularly at grazing angles, but that analysis only examined unpolarized data. In this work, the theoretical modification is analyzed using high fidelity, low density, in-plane polarimetric oblique and grazing angle BRDF data. These polarimetric data are fit to the novel version of the microfacet model for each polarization separately, using the polarization factor Q, and the error in the fits are compared to the unpolarized fits that were presented at SPIE DCS. These results suggest incorporating the polarization factor to improve the quality of fit consistently for materials, including substantial improvement at grazing angles.

The morphology, size, and media surrounding a solid material can all influence its optical properties, such as scattering, absorption, and reflection of light. While it is possible to measure the optical properties of hundreds of individual surface or particle configurations, it is impractical. Conversely, knowledge of the bulk optical constants n and k of a pure solid facilitates computation of arbitrarily sized particles, shapes, surrounding media, etc. As we describe here, single-angle reflectance spectroscopy is one such method used to obtain the bulk optical constants of solids. In particular, solid crystalline materials typically have responses in the mid- and far-infrared arising from phenomena such as lattice (phonon) vibrations as well as stretching or bending vibrations, among others. These vibrational modes in the mid- and far-infrared often present unique experimental challenges as the wavelength of light across such a wide spectral range varies greatly and can dimensionally approach the magnitude of specimens and even optical apertures used to limit the illumination area. Here we describe challenges and solutions, with an emphasis on optical instrumentation and far-infrared spectra, related to measuring realistic-sized mineralogical samples (down to ca. 2 mm) where sample purity, exposed surface area, cost, and rarity can all play important roles in obtaining the optical constants n and k.

We report on recent progress in the development of our focal plane imaging system for the detection and characterization of small fabrication errors in diffraction gratings. The instrument uses a purpose-designed high dynamic range imaging method in conjunction with a low-cost digital camera to acquire images with a dynamic range that can now exceed eight orders of magnitude. The sensitivity and utility of the instrument is demonstrated with measurements of three different diffraction gratings. Avenues for further possible improvements of the instrument are discussed.

Speckle-based techniques have noteworthy applications in the field of material science, surface characterization, determining mechanical displacements, biological activity in diffuse layer, imaging through turbid layer etc. The passage of coherent light through a diffuse layer generates a random speckle pattern, which have the inherent feature of carrying information associated with the diffuse layer. Dynamic laser speckle associated with the displacements of scattering surface has prominent impacts in the study of biological activity inside the diffuse layer. Investigations are progressing in the direction of exploring the dynamical properties associated with speckled speckles and its applications in imaging and characterization scenarios. In this work, we theoretically and experimentally study the dynamical properties of speckles through a static scattering layer using intensity correlation. The displacement (transverse or angular) produced in the concealed scatterer generates the dynamic speckle pattern which is observed through a second static diffuser. We expect to find applications of this investigation into the tracking objects hidden in the diffuse layer, measuring biological activity in diffuse layer, displacement measurements, etc.

In the semiconductor manufacturing, the control of Chemical-Mechanical Planarization (CMP) process time for Shallow Trench Isolation (STI) is important. A wafer under- or over-polishing causes leakage and short-circuits making the chips defective. The CMP process control by interferometry is one of the most used systems to monitor the polishing time. In some cases, the interferometry process control is not possible because the wafer patterns cause some unwanted effects such as scattering, diffraction, and absorption. Consequently the signal is affected. In this paper, we apply a theoretical and experimental approach on the light reflected from different STI stacks in order to interpret the observed optical phenomenon. The experimental study is done to get close to the light measurement conditions within the manufacturing environment. With this experiment, we evidence that the trench pattern inside memory zones is responsible for the diffraction effect on the signal. In a production environment, this pattern results in a lower measured intensity when the size of memory area increases. Besides, numerical calculations are performed based on differential method in order to predict the diffracted intensity, which depends on the chip design parameters and the incident wavelengths tuning. By using STI models, this method helps to determine the wavelengths with the highest reflected intensity.

A technique is introduced to extend traditional polarized-light microscopy to obtain quantitative c-axis orien- tation images of reflective non-cubic crystal grains such as a titanium. The technique is based on multiple generalized illumination and detection states in a laser polarimeter and a physical model mapping resulting im- age irradiance to crystal orientation, and is demonstrated by comparing relative-orientation images with EBSD orientation maps of a Ti-6Al-4V sample. The new technique is shown to be somewhat more tolerant than EBSD to mechanically-induced surface roughness and deformation, although grain contrast for a Ti-7Al sample was be only weakly correlated with roughness as measured by an AFM.

The Operational Landsat Imager (OLI) stray light performance was tested in 2010 in Ball’s stray light test facility. After the launch of OLI in 2013, measurements of on-orbit stray light performance confirmed the excellent pre-launch results. Ball is currently building OLI-2 for launch in 2020 and stray light testing was performed on the instrument in March 2018. This paper compares these measurements to OLI stray light test results and shows how they provide high confidence that OLI-2 will also provide excellent on-orbit stray light performance. Stray light performance of the two near identical builds is quite similar. This demonstrates the consistency of the assembly process and the repeatability of the testing performed in the Ball stray light test facility.

Proper care of aging books in libraries requires nondestructive diagnostic techniques for measuring the condition of the paper. Optical techniques offer nondestructive capability. For this reason, both spectral reflection and visible bidirectional reflectance distribution function measurements (BRDF) are examined. Both new and aged Whatman paper are measured. Spectral measurements are sensitive to changes in the location and width of spectral features in the paper. This can be indicative of paper degradation. BRDF measurements show changes in the paper fiber structure such as broken fibers. Fiber scatter cross sections are modeled using an improved anomalous diffraction approximation and Kubelka- Munk equations.

Absolute diffuse reflectance measurements may be carried out by means of both integrating sphere and goniometer- based methods. At the National Research Council of Canada, the scale of absolute diffuse spectral reflectance is currently realized in the UV/VIS/NIR range using the modified Sharp-Little integrating sphere method. To ex- tend the wavelength range and improve instrument performance, a new absolute reflectometer facility is presently being constructed. The new system features a monochromator-based tunable light source, interchangeable detector systems (PMT, Si, and extended InGaAs) and a custom polytetrafluoroethylene integrating sphere. Aspects of the sphere aimed at mitigating the effects of sphere asymmetry and sample recess will be discussed. Data characterizing the wavelength scale, bandpass, and linearity of the new system will also be presented.

The Spectralon is one of the best materials for the calibration of spectral measurements. Normally, the Spectralon must be illuminated and measured at right angle, but, this is not always possible, particularly for outdoor measurements where we cannot control the Sun position. A Spectralon plate has a BRDF (Bidirectional Reflectance Distribution Function), which is not completely flat as a perfect Lambertian surface and this affects the calibration. Furthermore, when illuminated or observed at angles, the Spectralon polarizes the light and it can also create reddening effects in some conditions. Moreover, several sensors (most of the spectrometers) are sensitive to the polarization and are prone to create reading artefacts. First, this paper presents a calibration procedure adapted to these situations; it takes into account the polarization and the Spectralon BRDF. Second, this paper presents also a Spectralon BRDF model that is required to calculate its reflectance at the encountered angular conditions. This BRDF model is an algorithm framework (based on curve fitting methods) that was deduced from the analysis of thousands Spectralon measurements done with various illumination, viewing and polarization angles. The model is decomposed into several sub-models for the various encountered scattering types (backscattering and deep, forward and sub-surface scatterings), plus models for the polarization contrast and reddening.

Camera calibration is fundamental for camera based measurement processes. While photogrammetric calibration models are widely established, the more sophisticated approach, describing an independent ray for every pixel, still requires thorough investigation to achieve its full potential. Such a Generic-Camera-Calibration or so called Vision-Ray-Calibration (VRC) compensates the effects of lens distortions more precisely than other techniques and can calibrate various lenses. Our current efforts are to improve calibration algorithms for VRC and find geometrically optimal calibration procedures. As a step towards this goal we present a metric to compare calibration results and therefore the necessary procedure to ensure that the coordinate systems of the calibrations are similar. With this new metric it is easier to investigate VRC procedures.

Raman measurements were carried out on Ho³⁺ doped Lithium Niobate crystals. When the excitation wavelength of 532nm is used, in addition of expected Raman modes, forbidden bands are detected, while when exciting with 785nm, “classical” Raman spectrum was recorded with expected modes according to Raman selection rules. Additional lines are attributed to emission lines of Ho doped crystals. We detect, within a very good resolution, in the same Stokes spectrum, the transitions between the electronic states, and the vibrational states as well. We report on the analysis of these data as function of Ho-content, for different polarizations and wavelengths, of the incident laser beam.

The application of X-ray reflectivity (XRR) and X-ray scattering (XRS) technique for studying thin film surfaces is discussed. A simple method to evaluate thin film mass density accurately from the XRR distribution has been given, named XRR-DE method. According to the measured mass density, optical constant of thin film could be calculated, which is very important for evaluating the surface roughness of thin film from XRS distribution. The first-order perturbation theory (FOPT), one of the XRS methods, is extensively validated for smooth surfaces and can extract power spectral density (PSD) function of the surface roughness directly and uniquely from measured scattering distribution. The conditions of applicability of FOPT have also been discussed. While the three Al₂O₃ thin films were deposited by Atomic layer deposition (ALD), Au thin film was evaporated by electron beam coating. The density of the Al₂O₃ thin films evaluated by XRR-DE method is 3.25g/cm³, 3.227 g/cm³, and 3.224 g/cm³. The density difference is less than 1%, and the results are in good agreement with the reported data. However, as an amorphous film, its density is much smaller than that of the sapphire single crystal (3.965g/cm³). The density of Au film evaluated by XRR-DE method is 17.05g/cm³. The scattering indicatrix for different thin films were measured, and one-dimensional PSD functions and effective RMS roughness were calculated by FOPT, which coincide well with the measurements of atomic force microscopy (AFM). The results demonstrated that FOPT is valid for measuring the surface roughness of thin films. Specifically, calculating optical constants from the experimentally measured mass densities by XRR-DE of the studied thin films could improve the measurement accuracy.

The intellectualized system of Jones-Mueller-matrix mapping of the optically thin (attenuation coefficient τ≤ 0,1 ) blood plasma films with intellectualized analysis (based on the Decision tree method), for differentiating such samples to "norma" and "fibroadenoma" proposed for the first time. Proposed method of intellectual analysis are classical method for the linear data classification with the "teacher" and the means of decision support. Using the statistical analysis, statistical moments for every coordinate distributions were obtained and they are as diagnostic features in the database. The obtained results has a “high” authenticity in terms of evidence-based medicine.

The Jones matrix mapping of blood plasma films was considered in this paper. The statistical analysis (statistical moments of the 1st - 4th orders) of the obtained elements was carried out. To increase the accuracy and reliability of the diagnosis, the number of informative indicators was increased due to the correlation analysis. which increased the number of inputs to 8. The differentiation of nosologies was based on the rules of fuzzy logic.

Experimental investigations of the effects of colouring of a beam traversing a light-scattering medium is presented. It is shown that the result of colouring of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. Spectral investigation of the effects of colouring has been carried out using a solution of liquid crystal in a polymer matrix. The amplitude ratio of the non-scattered and the singly forward scattered interfering components significantly affects the colour intensity. It has further been established that the spectral content of the illuminating beam strongly influences the colour of the resulting radiation.

Paper contains results of investigation the elasticity of erythrocytes in the flow by the temporal chaotization of the field of scattered radiation scattered by erythrocytes in dependence on the flow rate in a glass flat capillary. To test the reliability of the results, a test sample - erythrocytes in hypertonic solution - was used. Hypertonic solution leads to a decrease in the elasticity of the erythrocyte membrane. To quantify the chaos, the Lyapunov's maximal index of fluctuations of the intensity of the field of scattered coherent optical radiation was used.

Paper contains results of modeling of nanosized gratings and muscle tissue with different optical parameters. Nanogratings and muscle tissue modeling with calculations of scattered radiation characteristics were conducted in COMSOL Multiphysics environment. Dependencies of coefficients of transmission and reflection on angle of incidence for visible frequency range are also demonstrated.

Additive manufacturing has already found broad acceptance in rapid prototyping of machinery and is an emerging technology in many other fields such as radio frequency (RF) engineering, where the advantages of the so-called 3D printing technology overcome limitations of established processes and allow entirely new designs. The ability to create almost arbitrary shapes with high precision has proven very useful for antenna design, for example. Using conductive and dielectric ink, RF transmission lines can be 3D printed directly on uneven surfaces. As for RF structures geometrical dimensions are crucial for the resulting RF properties such as impedance, a technique to measure the distance between the printing nozzle and the substrate is necessary. This turns out to be a challenging task since a small spot size is required and transparent (dielectric) as well as reflective (conductor) materials must be detected while maintaining a mechanically flexible and robust system. We propose a distance measurement system based on coherent optical frequency domain reflectometry to accurately measure this distance. The proposed miniaturized coupling optic uses a gradient-index (GRIN) lens with a diameter of less than 3 mm, can be integrated into a printing head easily and is compatible to standard single-mode fibers. In first experiments, we have achieved very promising results that show a good agreement with (destructive) microscopic measurements. Reflective and transparent surfaces can be detected with μm-accuracy.

Diffraction fields many times can generate a focusing region, we describe the focusing region associated with symmetric transmittances, analyzing its associated phase function. We show that some generic features, it can be obtained from a differential equation for a focusing geometry, which is obtained through angular representation for diffraction fields, the diffraction field presents a new focusing region whose geometry and spatial evolution can be described with the analysis of the phase singularities avoiding the integral diffraction calculation.