A window function is used to represent the variation in the intensity of the radiation in a light beam. Windowing effects are factored into computations of the angular distribution of light scattered by a sinusoidal surface. These effects, as well as those of harmonics and noise, are shown for the angular distributions computed from simulated profiles. The integrated power in each diffraction peak computed for perfect sinusoids, measured profiles, and simulated profiles with different window functions is compared to that of a measured angular distribution.

A set of O-50 grade beryllium mirrors, removed from the polishing process at regular intervals, were subjected to a study of the wavelength dependence of scatter in the visible to infra-red. Analysis of these scatter measurements showed that the roughness calculated from the scatter measurements exhibited a parabolic wavelength dependence. The slope of the calculated roughness as a function of (lambda) ^1/2 (the parabolic slope) was taken as a measure of this anomalous scatter wavelength dependence. Mirrors with significant surface pitting were found to have the largest parabolic slopes; while unpitted beryllium mirrors, exhibited similar, though still significant parabolic slopes, indicating that the wavelength scaled as expected. Scatter measurements made on two key beryllium mirrors partially coated with a thin aluminum film further confirmed that surface pitting and intrinsic optical properties of beryllium both contributed to anomalous scatter.

A rigorous one-dimensional integral solution has been utilized to bring up some ideas about possible ways for detecting isolated surface defects by means of angle resolved scattering. Our preliminary results indicate that a suitable combination of polarization and different incidence angles can be useful. Numerical examples are given both for modelled defects and real defects measured with a Talystep profilometer.

Light distribution in a standard scintillation camera is a complex process. The photons come across many different optical materials and many types of specular and rough optical surfaces. Complexity is further added to the model when the spatial and angular sensitivities of the detection components--the photomultipliers--are considered. To be able to correctly predict the PSF of a gamma camera, we developed a Monte-Carlo ray-tracing model which was subsequently compared to data measured on an existing gamma camera head (PRISM 3000 from Picker International Inc.). The experimental configuration was first replicated: geometry, optical properties of the crystal, light guide, photomultiplier tube window and photocathode, index matching fluid and gamma ray energy. Several other parameters, such as back mirror reflectivity and border reflectivity, were the optimized. Finally an a posteriori modelization of the scattered refracted and reflected fields at the rough interface between the crystal and the light guide was obtained by fitting simulation results to experimental data.

One of the most common assumptions for recovering object features in computer vision and rendering objects in computer graphics is that the radiance distribution of diffuse reflection from materials is Lambertian. We propose a reflectance model for diffuse reflection from smooth inhomogeneous dielectric surfaces that is empirically shown to be significantly more accurate than the Lambertian model. The resulting reflected diffuse radiance distribution has a simple mathematical form. The proposed model for diffuse reflection utilizes results of radiative transfer theory for subsurface multiple scattering. For an optically smooth surface boundary this subsurface intensity distribution becomes altered by Fresnel attenuation and Snell refraction making it become significantly non-Lambertian. The reflectance model derived in this paper accurately predicts the dependence of diffuse reflection from smooth dielectric surfaces on viewing angle, always falling off to zero as viewing approaches grazing. This model also accurately shows that diffuse reflection falls off faster than predicted by Lambert's law as a function of angle of incidence, particularly as angle of incidence approaches close to 90 degree(s). We present diffuse reflection effects near occluding contours of dielectric objects that are strikingly deviant from Lambertian behavior, and yet are precisely explained by our diffuse reflection model. An additional feature of our diffuse reflection model is that is predicts the diffuse albedo purely in terms of the physical parameters of a smooth dielectric surface, allowing rigorous derivation of the relative brightness of specular and diffuse reflection.

In this paper, we present a numerical study of optical waves scattered by rough surfaces. The calculations are based on the use of plane-wave expansions to describe the reflected and transmitted fields on the surface (also known as the Rayleigh hypothesis). This theory is applied to one-dimensional randomly rough dielectric surfaces, by using a random grating numerical generation. Two methods are recalled for the straightforward numerical implementation of the theory: the Point-Matching Method (PMM) and the Fourier Series Method (FSM). Examples of results for a metallic and a dielectric surface, obtained with the latter method, are in good agreement with calculations by an exact numerical method. It is reported that the FSM has a wider domain of validity but that the PMM has a faster computation time.

An Ocean Lidar system was developed for measuring the optical parameters of the sea water. In our system, the FOV of the receive is changed to obtain the different sea water optical parameters. The attenuation coefficient c equals 0.32 m-1, absorption a equals 0.07 m-1 with Sechhi Disc Depth (SDD) 13 m and c equals 0.31 m-1, a equals 0.06 m-1 with SDD equals 14 m are obtained in situ separately.

Several cleaning methods suitable for cleaning small, low scatter samples in the laboratory are compared. In the present work, these cleaning methods were evaluated for other materials including uncoated fused silica, aluminum oxide and tantalum oxide coated fused silica, molybdenum, and gallium arsenide. The strip cleaners provide outstanding cleaning with drag wiping performing. In addition, results show that the durable surfaces can withstand repeated cleaning cycles. Gallium arsenide is a fragile material which does not stand up well to strip cleaning or solvent swabbing.

An instrument capable of measuring and mapping hydrocarbon contamination densities as low as 3 milligrams/square foot has been developed for use in pre-bonding inspection of spacecraft components. The instrument makes use of the 3.4 micrometer absorption band present in hydrocarbons. Measurements above, one, and below the band are made to compensate for effects due to variations in substrate roughness. The instrument, dubbed 'SurfMap- IR^TM, has been tested on substrates of aluminum and steel.

This paper presents several types of surface optical property data provided directly and derived from an extended capability directional reflectometer. These data are required in a variety of scientific and industrial fields of research, development and testing including tailored coating development, support of remote sensing, ground truth investigations, thermal analysis, prediction of vehicle signatures, quality control of coatings and surfaces, and studies of geologic and biological sample study. A comparison of the commonly used experimental methods is provided. An explanation and documentation of the reasons for the inadequacy of IR diffuse gold integrating sphere directional reflectometers for most of the extended capability tasks is presented. Examples of data taken with an extended capability directional reflectometer are given. Progress on the development of fully automated, computer controlled hemi-ellipsoidal hemispherical directional reflectometers using a state-of-the-art FT-IR is noted. The sample measurement time from measurement start to printed results for the automated instrument will be less than 10% of the time required for the manual reflectometer.

A unique broadband scatterometer has been designed, built and tested for NASA Goddard. One use of the instrument will be to accurately measure the BRDF of calibration standards used by shuttle astronauts in experiments to measure atmospheric ozone. BRDF accuracy is better than 1% except for angles of incidence and scatter greater than 80 degrees. The source employs a high intensity xenon arc and programmable monochromator that allows measurements to be made anywhere from 0.23 to 0.9 micrometers over adjustable bandwidths as small as four nanometers. The goniometer allows out-of-plane measurements to be made in either transmission or reflection from horizontal samples.

This paper reviews the recent completion of an instrument capable of laser radar simulation and measurements of the monostatic bidirectional reflection from coherent polarized radiation with the target in the far-field of the illumination and the detector in the far-field of the target. This instrument can provide as low as 10^-6 steradians^-1 sensitivity for 10.6 micrometers and also account for optical phenomena such as speckle, polarization effect and the opposition effect.

A wavelength scanning, total integrated scattering instrument has been constructed for backward and forward light scattering studies in the 400 - 1000 nm wavelength range. In both modes calibration can be made with two references, one diffuse and one specular. The two types of calibration give similar results in reflectance mode, but in transmittance mode, some discrepancies were noted. Correctly positioned apertures suppress stray light from the source. A detailed study has been made on the effects of this arrangement when low level scattering samples are studied. Small amounts of scattering from the source optics can be erroneously registered as originating from the sample. This stray light can have a dramatic impact on the determination and interpretation of scattering from low scattering multilayer samples. It is shown that a diffuse reflectance spectrum of a thermally oxidized silicon wafer, where the stray light has not been considered, would be interpreted as due to correlated interface roughness. When the stray light was blocked the spectra implied uncorrelated interface roughness. It is recommended to combine reflectance and transmittance measurements of scattered light to ensure correct interpretation.

An approach is presented which allows the development of an in-process fiber optic stray light sensor and adapted real-time signal processing procedures for quality control of polished optical glass surfaces. The power of this new method is illustrated by presenting an instructive example in great detail.

The roughness of a number of uncoated glass substrates with different surface quality as well as surfaces of fluoride films is investigated by various characterization techniques. The influence of bandwidth limitation and the dependence on the examined sample area become obvious. The results obtained from the different measuring methods are shown to complement each other appropriately.

This paper presents the surface roughness characteristics obtained from three different instruments: a mechanical stylus profilometer, a split-beam detection optical profilometer, and an interference microscope. Experimental data for both molded and coated plastic reflector surfaces using different measuring techniques are reviewed and the deficiencies in relating the various methods are clearly illustrated.

In this paper we study the effects of depolarization and scattering from a rough surface over a large range of wavelengths, additional measurements are reported that have been made on a very rough black anodized aluminum sample.

After recalling rough surfaces modelling and theoretical study of light scattering from such surfaces, we present in this paper an experimental set-up to measure backscattered light with a very high angular selectivity. The device is then tested for various samples such as white diffusers, ground metallic surfaces and eventually silver mirrors. When the surface is diffusive, very accurate results can be easily obtained. For surfaces with a specular peak, stray scattering from the surrounding can make the measurement very difficult. However, even in that extreme case, we have been able to investigate into the inverse problem thanks to the angular selectivity and have found quite a reasonable value for the correlation length.

The visual aspect of products meant for the general public is becoming an equally important criterium for their commercial success as their technical qualities and their cost. In most cases, the aesthetic quality of products is visually assessed by experienced people whose judgement is considered as a reference.This procedure has two major disadvantages: i) This visual estimation is entirely related to individual sensitivity and cannot be quantified. Only a comparative analysis is possible and requires a sufficient range of reference samples which are indispensable for this evaluation. ii) This visual evaluation concerns the global evaluation of the appearance and cannot dissociate with entire precision the roles of different parametres such as the color, the luminosity, the form and the shine of the surface. .. It is therefore rather difficult to point out possible modifications that could be brought to the process of fabrication in order to improve the aesthetic quality of the products. To be freed from the restrictions of visual inspection, the industrial world tries to endow itself with systematic procedures and instruments for physical measurement that evaluate the visual aspect of the surfaces. The study that we propose here belongs to this field of research, and applies more particularly to the measuring of the brightness of plastic pieces the surface of which presents an undulation of less than a millimetre deep (skin profile). In the first part of this study, we shallpropose a systematic analysis of visual aspect which four different and independant criteria defines. We shall explain why traditional methods for the measurement of scattering cannot be applied to such wavy surfaces. The material BRDF (Bidirectionnal Reflection Distribution Function) must be estimated from the analysis of their roughness by the means of established scattering models, such as that of Beckmann and Spizzichino. Secondly we shall introduce the procedure that we have developed in order to analyze the visual aspect of plastic samples, through confocal microscopy and image processing. A low magnification analysis allows one to measure the skin contours of the surfaces and to infer the local surface orientation which determines the exact values of the incidence and observation angles. A second analysis, with high magnification and an adequate image processing software, enables the extraction of the microroughness responsible for the scattering, and one can then evaluate the scattering properties of the material. Finally,the combination of the properties of scattering and of the local orientation of the surface allows the prediction of the degree of visibility of the skin profile of the surface. The statistical distribution of the measured parametres is also taken into account.

In support of Strategic Defense Initiative Organization objectives to develop optical quality chemical vapor deposition (CVD) diamond windows, the infrared optical scatter characteristics of thin, polished, free-standing CVD and natural type IIa diamond films were measured at room temperature and 500 degree(s)C. The CVD diamond scatter characteristics are compared with those of the natural type IIa diamond of similar thickness at identical temperature. The diamond samples were about 10 to 30 mm in size and 250 to 500 micrometers in thickness. The diamond samples were provided by various manufacturers and laboratories both in the United States and abroad.

A logical approach to investigating materials that scatter non-topographically is to coat them with a thin layer that scatters only topographically (i.e., a layer that wavelength scales) so that the two scatter sources can be separated. This technique has been used to study scatter from beryllium mirrors using layers of aluminum and gold. In the course of these investigations it was learned that many aluminum surfaces do not wavelength scale (no information was available on gold). This was discovered fairly late in the study and caused a lot of extra expense and frustration. This paper presents wavelength scaling data from the uv to the mid-IR for several materials. The intention is to provide guidance for future studies of this nature.

The Stokes/Mueller approach provides complete characterization of sample induced polarization changes to both specular and scattered light that is reflected or transmitted from optical components. Ellipsometry is a subset of this more complete approach to polarization analysis. In this paper, Mueller matrices of several samples are found and compared to the matrix of ideal elements. Samples include optical mirrors that scatter both topographically and non-topographically, waveplates, and optical windows.

Angle resolved scattering from bulk fused silica substrates has been measured at .442 micrometers and .633 micrometers . The angle dependent scatter pattern and wavelength dependence are compared to Rayleigh scatter theory. The measured bulk scatter data is applied to the measurement of fused silica substrate total scatter and the resulting measurement limitations imposed by bulk scatter.

The results of past BRDF round robin comparisons precipitated the establishment of ASTM committee E12.09 on Optical Techniques and the promulgation of the standard E1392, `Standard Practice for Angle Resolved Optical Scatter Measurements on Specular or Diffuse Surfaces.' A recent 10.6 micrometers BRDF round robin tested the utility of this standard practice document. The master sample set included two IR diffuse surfaces, two metal mirrors, one glass mirror and an IR grating. The in-plane BRDF was measured for 10 degree(s) angle-of- incidence, s polarized light at ten optical scatter facilities in the United States. These measurement results are compared.

Measured optical properties of large absorbing arbitrarily shaped particulates are compared to calculated optical properties of smooth homogeneous spheres. The particulates examined are spherical carbon particles with rough surface structure and oil shale. The results of measurements of phase functions of single particles at (lambda) equals 514.5 nm and hemispherical reflectance from 450 to 1959 nm are used in an inverse two-flux model to calculate the average albedo of a single particle. For carbon particles, ideal spheres show a higher forward scatter contribution than measured properties of rough spheres. Two types of oil shale particles with different optical properties but similar size and surface structure are investigated. Particle albedo and phase functions are compared, and the error of measuring the phase function at one wavelength is investigated. Results are also compared to isotropic scattering particles.

A new instrument has been developed that takes hundreds of thousands of points of scattered light data at 0.1 degree(s) resolution over a three dimensional segment of the hemisphere. The data can be acquired and displayed in 0.5 to 20 seconds depending on the amount of data desired. The instrument is the size of a 'shoe box' and provides solid state operation. With the instrument's high resolution three dimensional capability, well-defined three dimensional interference patterns, speckle, and diffraction can be seen in near-real-time. Much of these patterns are out of the plane of incidence and sometimes add significantly to the scatter, and may allow a scattering surface to be characterized through methods not available before. The high speed capability makes this instrument ideal for scattered light measurements to be used for high resolution surface defect quality control on high volume assembly lines.

We report on the design and fabrication of an all-silicon test pattern that is very useful for assessing the performance of all types of profiling instruments. We present examples of results obtained from applying this method to various kinds of profiling instruments, including a WYKO TOPO 3D system, Micromap Promap 512 profilers, a ZYGO Maxim 3D system, and scanning probe AFM systems. We also present the results from a measurement of the BRDF of the step with a TMA CASI scatterometer to show the utility of the step as a potential calibration standard for scattered light measuring instruments.