We experimentally tested the operator formalism of radiative transfer on the response of an instrument to partially coherent wavefield produced by radiation emitted by distant and extended blackbody sources. The predictions of the formalism are found to agree well with the experiments. Phase space parameters are identified that characterize a measurement as well as indicating when the formalism will be useful, when we are not in the regime of geometrical optics or plane wave diffraction.
At every conference since 1995 we have reported on work in- progress to find a consistent formalism connecting the radiance concept with measurement of radiance, even under conditions where wave effects are important. In such circumstances, classical radiometry no longer provides an adequate description. In this conference we report on measurements of radiance that are well modeled by our theory, but would not be adequately described by classical radiometry.
For some stray light applications, it may be advantageous to use a black applique rather than a conventional black coating. Appliques consist of a free-standing sheet of black material and an adhesive or other means for attaching the applique to a substrate. In this paper the optical scatter in the visible and infrared of black appliques from Battelle, Dupont, Edmund Scientific, Energy Science Laboratory, Inc. (ESLI), Rippey and Rodel is reported and compared to Martin Black. The Rippey and Rodel appliques are sold as polishing cloths for the semiconductor industry, whereas the ESLI applique was originally developed as a low sputter yield coating. The Battelle applique consists of a carbon loaded polyurethane film with a surface which is heat molded into a micro-grooved pattern. The ESLI applique consists of high aspect ratio fibers mounted in an adhesive base and was the blackest applique of all those investigated. For an incidence angle of 10 degrees, a scattering angle of 45 degrees and a wavelength of 632.8 nm, the BRDF of the best ESLI applique was 3 multiplied by 10-4, compared to 1 multiplied by 10-3 for the best Battelle applique, 1.5 multiplied by 10-3 for a representative Martin Black sample and 1.8 multiplied by 10-3 for the Edmund applique. The Battelle applique is quasi-diffuse due to its surface microstructure, with a higher BRDF (2-5 multiplied by 10-3) at scatter angles less than 15 degrees For a wavelength of 10.6 micrometer, an incidence angle of 7.5 degrees and a scatter angle of 45 degrees, the BRDF of the ESLI coating (1 multiplied by 10-3) was slightly higher than Martin Black (8 multiplied by 10 -4), with the Battelle applique exhibiting strong dependences on scatter angle and groove orientation. In the 2 - 14 micrometer spectral range, the directional hemispherical reflectance of the ESLI coating at a 20 degree incidence angle is below 0.45% and only weakly dependent on incidence angle to 60 degrees. In- plane and cross-plane BRDF measurements at 3.39 micrometer are reported on a 'biased' ESLI coating which is designed for use at near grazing incidence. In-plane BRDF measurements at wavelengths of 0.6328 and 10.6 micrometer are reported for most of the appliques studied.
Diamond grown with chemical vapor deposition (CVD) processes is currently being considered for use as a long wave infrared (LWIR) dome material for advanced missiles. In order to assess diamond's suitability for this application, a complete understanding of the optical properties of CVD diamond is needed. This includes a determination of the relative amount of bulk and surface scattering, and a measurement of the absorption in thick CVD diamond films. In this paper, we present scattering data for visible (0.633 micrometers ) and infrared (10.6 micrometers ) wavelengths from optically smooth thick diamond films. Scattering data from the aluminized front and back surfaces of the films is also reported. These measurements, together with first order scattering theory, provide a means for determining the component of scattered radiation which is due to bulk scattering. The bulk absorption is also estimated from a detailed energy balance using reflectance, transmittance and scattering measurements.
A thermochemical polishing technique (using low carbon steel at 700 degree(s)C to 900 degree(s)C) was employed to reduce the roughness on the surface of diamond films from 20,000-40,000 angstroms rms to 30-45 angstroms rms. These polycrystalline films were grown by filament assisted chemical vapor deposition (FACVD) onto (100) oriented silicon substrates. SEM micrographs reveal etch pits in the films, and these limit the final polish which can be achieved. This paper show that the hot iron technique polishes a (111) oriented film, which is the hardest direction for abrasive polishing. Preliminary studies indicate that for chemical polishing there is no large difference between the polishing rates of diamond as a function of orientation.
Nonimaging optics can be used to reduce systematic measurement errors associated with diffuse reflectance measurement instrumentation. An analysis of measurement errors related to a sample's scattering characteristics, a detector's field-of-view and the reflectometer's geometry is presented. Recent designs for hemi-ellipsoid and integrating sphere reflectometers, incorporating nonimaging optics, are reviewed.
A status report is presented on the obstacles and current research related to using CVD diamond as an optical material. Problems discussed include properties of CVD carbon deposits, including structure, thermal conductivity and oxidation resistance, which are relevant to the optical uses of diamond; absorption coefficient measurements on CVD diamond in the visible and IR; and a review of various aspects of the synthesis of CVD diamond, including the growth of transparent and translucent diamond, efforts to grow diamond at low substrate temperatures, and approches to reducing the optical scatter of as grown polycrystalline diamond films and windows. Particular attention is given to techniques for reducing optical scatter which involve modifying materials morphologies during the growth process by controlling nucleation density, renucleaton frequency, and/or the orientation of crystal faces at film surfaces; techniques for postdeposition polishing of the surface of CVD diamond films and windows; and optical applications for CVD diamond.
Polycrystalline diamond films have been synthesized in an oxygen-acetylene flame (15-20 tm thick and in a filament-assisted CYD reactor (10-60 p. m thick). The quality of the diamond was measured with a Raman microprobe optical and electron microscopes an FTIR and a UV-Vis-NIR spectrophotometer. The hemispherical transmittance and reflectance of several films was measured in the UV visible and infrared with integrating spheres. The transmittance and reflectance was found to depend on which surface of the film faces the spectrophotometer''s beam this result can be explained by total internal reflection effects and the different roughness scales of the film''s two surfaces. Preliminary results on the polishing of several FACVD films using a heated steel disk a rhenium filament and a hydrogen environment are discussed. An Auger depth profile of the steel disk shows graphite at the surface of the disk iron carbide in the bulk and a depletion of carbon in the bulk near the surface. The films'' surface roughness before and after polishing was measured with a profiometer and local roughness averages of A have been achieved. Results of optical scatter measurements made on films before and after polishing are presented. 1.