The present galvanometer mirrors may be manufactured by four different methods: (1) polishing of bare beryllium, (2) electroless plating of Ni, (3) polishing or single diamond-point of electroplated Ni, and (4) thin-film epoxy replication. The IR reflectivity of beryllium in the 3-14 microns range is sufficiently high to obviate additional mirror coatings, while electroless Ni and epoxy-replicated mirrors require a subsequent coating to achieve the requisite reflectivities. Nevertheless, there are galvanometer configurations that do not lend themselves to polishing. Replication is the lowest-cost mirror-fabrication method.

Beryllium mirrors, approximately 19.8 cm x 8.8 cm in size, were designed, procured, and evaluated. The mirrors are off-axis rectangular segments of an f/1 paraboloid. These segments, which are the primary mirrors in a Cassegrainian telescope design, are lightweighted and incorporate a stress-free mounting technique which minimizes post-assembly alignment. Upon delivery, the mirrors were characterized to determine their compliance with the figure, scatter, reflectance, and dimensional specifications.

Design characteristics which influence the cost and producibility of near-net-shape blanks for light-weight beryllium optics discussed. Producibility factors include cell geometry and mountings. Design rules are presented for defining the size, shape and arrangement of light-weighting cells. Particular emphasis is given to the size of web intersections. The use of internal versus external mountings is evaluated with respect to cost and producibility. Overall optic cost is reviewed with respect to the impact of blank fabrication requirements on the optic design, the design and fabrication of tooling, and the fabrication of the optic blank. Standards are proposed for specific mirror blank characteristics. These standards are presented as a starting point for discussion.

A program to fabricate a large, optically fast, aspheric lightweight Be mirror has demonstrated state-of-the-art technology. The mirror blank was fabricated as a 1.0-m diameter, f/0.58 ellipse, directly from IP-70 grade powder, using near-net-shape HIPing as well as a patented tooling approach that produced a closed back, honeycomb-cored mirror weighing less than 18 kg. Details of the mirror design and of the assembly for HIPing are given. The blank was HIPed, leached and machined to final shape with all design goals met; as-HIPed, the blank was within +/- 0.5-mm in all dimensions, and the radius of curvature was within 0.2 percent of target. The mirror was loose-abrasive ground using plunge grinding with a full-size tool, then rough polished using a full-size flexible pitch lap. In-process metrology used a special swing-arm profilometer with demonstrated accuracy and repeatability below one micron.

The lessons learned in recent fabrication of beryllium mirrors could have a significant impact on how beryllium optics of the future are produced. This paper provides an overview of the latest techniques for beryllium optics fabrication and a comparison of the results achieved. Specific technical ureas discussed include: new beryllium powders, results of consolidation, beryllium material property improvements, modified machining procedures, thermal stabilization, single point turning, burnishing techniques, replica faceplates, support structure bonding, mirror superpolishing, and new optical testing techniques.

This paper addresses technology advances in the replication of Be optics to optical figure requirements. The replication effort discussed has achieved a specific net, aspheric optical figure within several waves (6328 A) peak-to-valley, combined with replication cross sections and features as thin as 0.020 inch, to tolerances of less than 0.005 inch. The replication is performed in a HIP consolidation process. Currently, the process has been applied to fabrication of developmental quantities of nonimaging, small optical components including plano, spherical and aspheric configurations. The process discussed is applicable to cost-effective high volume production of small Be optical and nonoptical components, and the principles employed may be effective in reducing costs for large Be optics in low volumes.

In this study we have examined the polishability of bare beryllium as it relates to processing for the fabrication of a mirror substrate. Our work has shown that annealing treatments can produce microporosity in the beryllium by a mechanism known as Thermally Induced Porosity (TIP). When the porous material is polished, the achievable scatter is degraded. TIP response is sensitive to the processing history of the material and the effect can vary from minimal to substantial. We have also demonstrated a scatter screening test which can indicate the sensitivity of a given lot of material to TIP.

A statistical-design-of-experiments approach is here adopted to investigate the process sensitivity of an evaporative Be-coating technique as a function of its process parameters: deposition rate, substrate temperature, and run time. A total of 18 coating runs was used to produce Be coatings on Al, Si, fused silica, and Be substrates, and these were then characterized by SEM, IR spectrophotometry, stylus profilometry, and weight gain. On the basis of the results obtained, a functional relationship is developed between quality-related characteristics and evaporation-process parameters; the process sensitivity for each response is then ascertained by calculating the gradient of each such characteristic relative to all three process parameters.

Several advanced, lightweight, robust, broadband-diffuse absorptive baffle materials are available for sensor-system designers. These materials technologies are shown to be scaleable, and to possess target-survivable performance; they include sputter-deposited Be on cold-rolled Be ingot sheet material or Be foam, plasma-sprayed Be, plasma-sprayed B-on-Be, and CVD B4C on graphite. An account is also given of the Optics Manufacturing Operations Development and Integration Laboratory Advanced Optical Baffle Program.

Baffle materials have been fabricated by laying down thick, fine grained Be coatings using magnetron sputtering on formable Be ingot sheet material. Six different coating process variations were used. Three different bias voltage settings (-200 V, -50 V and no bias) were applied to either water cooled or thermally isolated substrates. A 20 percent solution of HF acid in ethanol was used to etch the Be coatings in order to increase light absorption. SEM revealed significant variations in surface morphology of the etched coatings. Acid etching increased the number of light traps in the surface, particularly those below one micrometer in feature size, thus increasing light absorption in the visible region. Specular reflectance measurements from 400 nm to 50 microns revealed that thick coatings laid down with a -50 V bias and etched for one minute produced diffuse, light absorbing baffle surfaces with reflectivities of less that 5 percent, out to 40 microns.

Because of the unique properties of beryllium (Be) and the advantages of single point turning, a development program has been instituted to single point turn beryllium as a means to produce optics. Initial effort to diamond turn beryllium resulted in less than desirable results and development efforts were directed at finding a more suitable tool material. Both single and polycrystalline tool materials were evaluated and cubic boron nitride (CBN) was found to produce the better results. Tool wear has been the primary limitation in precision machining beryllium and advances have allowed a two order-of-magnitude reduction in this problem. After considerable efforts, results with CBN appear to be approaching a limit, and diamond, as tool material, was re-evaluated with promising results. A development program is now under way to determine if diamond may be used to machine larger and more complex beryllium parts.

Fine grained, sputter-deposited Be coatings with thicknesses up to 290 microns have been laid down on six coupons of various substrate materials including S-200 grade beryllium, SiC and Ti6Al4V alloy. Each coated substrate was subsequently polished to a very low surface roughness (less than 5 A rms) finish by one of two different polishing techniques. Bidirectional reflectance distribution function (BRDF) measurements were taken at 632.8 nm and at 10.6 microns. BRDF values at 10.6 microns were measured as low as 9 x 10 exp -7/sr at 10-deg off-specular. Calculated power spectrum density curves showed remarkably little or no anomalous scatter except for one coating laid down with no substrate bias and an uncooled substrate. The measured reflectances of the polished Be coatings at 10.6 microns is about 5 percent below that for the gold reference surface (i.e., about 94 percent of absolute reflectance).

In the presence of such extreme radiation as that encountered in SDI beam-weapons scenario, the Ni plating on Be telescopic mirror substrates will blister badly enough to severely degrade optical performance. Attention has accordingly been given to a bare-Be polished surface which can withstand irradiation through its high specific heat, high thermal conductivity, and low atomic number. Technologies pertinent to the production of such mirrors are here discussed for the case of an off-axis, f/2.0, all-Be telescope mirror for a diffraction-limited intersatellite laser-communication system.

This report will describe the status of an effort to catalog the refractive index, absorption, reflectance and transmittance of selected IR transmitting materials over the wavelength range from 1 to 1000 microns, and at temperatures from 300 to about 2 K. Data are presented for LiF, CaF2, BaF2, KBr, and TlBr, as well as for KRS-5 (TlBr-I) and KRS-6 (TlBr-Cl). A cryooptical measurements facility at NASA-Goddard, which has been used to generate some of the cataloged data, is also described.

Hostile environments created by short wavelength electromagnetic radiation (UV, X-ray and gamma-radiation) or from particle fluxes (alpha-particles, beta-particles, protons, and neutrons), can produce discoloration within optical glasses. The associated loss in transmission is detrimental to the performance of any optical system and must be eliminated or reduced to a manageable level. For applications within these hostile environments, radiation-stabilized optical glasses have been developed. To optimize system performance, optical glasses which have been stabilized for applications within the particular radiation environment must be selected. If the environment is a mixture of radiation fields, compromises are called for.

Dichromated gelatin layers facilitate the design and fabrication of holographic optical elements of high optical quality and diffraction efficiency. The research efforts are aimed at the development and evaluation of layer deposition techniques for the manufacturing of large format holograms in dichromated gelatin. The emphasis is placed on the realization of DCG films that exhibit low scattering losses and high modulation capacity. Such properties ensure the attainment of the desired diffraction efficiency, bandwidth and operation in the IR. These objectives are achieved by means of precise control of the thickness and of the hardness of the holographic film while maintaining the capability to modify the refractive index modulation over a wide range. The diffraction efficiency is a non-linear function of the grating strength, i.e. of the layer thickness, of the geometry, of the reconstruction wavelength and of the refractive index modulation. For a given geometry and constant layer thickness, it is the index of refraction modulation that determines the IR shift in the operating wavelength of the hologram. The desired film thickness of 10 tm is achieved by means of nozzle deposition and exhibits a thickness variation of ±1 um over the 1 m2 aperture. The high capacity for index of refraction variation is realized by means of precise control of the flow velocity and of the water evaporation rate during the drying of the film. The exposure duration, the development process and the subsequent thermal after-treatment of the film facilitate the attainment of the desired modulation characteristics for JR operation.

At the International Lens Design Conference (ILDC) in Monterey, California, one of the design problems posed was to create a `non-lens' (a lens which did nothing) to within the diffraction limit of any ray which passed through the system, but which used exactly 100 mm of glass. The lens has an entrance and exit aperture which are separated by 250 mm, the aperture of which is to be made as large as possible, such that any ray which enters the first hole and exits the second does so as it would have if the lens were removed to within the diffraction limit (<0.07 waves RMS wavefront error.) In short, use 100 mm of glass and do nothing to the light which goes through it. The author, along with several colleagues at the design conference who also work primarily in the long-wave infrared (LWIR) waveband, reposed the problem in terms of IR materials and wavelengths. The design problem was studied in the IR. Instead of glass, Germanium (n equals 4.00) was used, and instead of designing for the visible diffraction limit of 0.588 micrometers , a diffraction limit at 10 micrometers was used. This paper documents the results of that study, with particular attention paid to the differences between the visible and IR solutions. By no means have all of the solutions to the problem been found, but the higher index and much higher diffraction limit result in some fascinating solutions.

In this paper, an attempt is made to study the heat capacity of MOS field-effect devices of optical materials under strong magnetic field using ternary compounds and nonlinear optical samples as examples of optical materials. The magneto-heat capacity of ternary materials is formulated in MOSFET by considering the fourth order in effective mass theory and taking into account the inter-actions of the conduction, heavy-hole, light-hole, and the split-off bands, respectively. The same capacity in nonlinear optical materials has also been formulated for the present case on the basis of newly-derived, generalized, 2-D carrier energy spectra by incorporating the anisotropic crystal potential and the Hamiltonian together with the anisotropies of the effective electron mass and the spin-orbit splitting parameter of the valence band for both the weak and strong electric field limits. The authors studied the surface electric field and the magnetic field dependences of the magneto heat capacity in n-channel inversion layers of the said materials taking n-Hg1-XCdXTe and CdGeAs2 as examples for both the limits. It is found that the magneto-heat capacity increases with magnetic field and surface field for both the limits in various types of oscillatory manners for all the cases. The theoretical results are in quantitative agreement with the experimental observation as reported elsewhere. In addition, the corresponding results of the magneto heat capacity for relatively wide-gap optical materials have been obtained from generalized expressions under certain limiting conditions.

Structural, electrical and infrared optical properties of screen printed vanadium oxide thick films have been studied for the first time. It is seen that the original starting material, in the form of V2O3, undergoes a global transformation to its next higher oxide V2O5 during firing. This has been confirmed through DTA and XRD. The crystalline morphology of the transformed V2O5 seems to improve as a function of firing temperature in the range of 400-600 C. The associated screen printed resistors have temperature coefficient of resistance in the range of -37,000 to -17,000 ppm per K over a temperature range of -65 to +155 C and thermistor constant equal to 2000 K, which are independent of firing temperature. It is observed that both electrical resistivity and infrared emissivity decreases with increase of firing temperature, attaining values of 1.12 x 100 ohm cm for electrical resistivity and 82 percent for IR emissivity at a 550 C firing.

A novel coating has been developed for the 120-230 nm wavelength VUV region which yields significantly higher reflectivity over selectable bandwidths and can be used to fabricate high-performance narrowband reflection filters; the spectral properties of such filters are greatly enhanced through their use in tandem. The coating uses a combination of high and low refractive index dielectric pairs. The proper choice of high-low ratio reduces the effects of VUV absorption for high refractive index films whose extinction coefficient is much higher than for a low-index material.

An overview of the optical transmittance and reflectance characteristics of selected metal sulfide thin-film coatings obtained on glass substrates by chemical bath deposition is presented. The focus is on their application as solar control coatings, solar absorber coatings, decorative coatings, and as an imaging medium. Coatings of PbS-CuxS, Bi2S3- CuxS, SnS-CuxS, and ZnS-CuxS offer a range of solar control characteristics. Depending on the thickness of the individual films, solar absorptance of approximately equals 90% has been observed for SnS-CuxS and ZnS-CuxS thin films. Pleasant shades of colors observed in reflected daylight due to the thin film interference in these films together with the ease with which chemically deposited coatings can be obtained on cylindrical or planar substrates suggest the use of these films as decorative coatings. An application of these films as a photographic medium is possible based on the photo-accelerated chemical deposition of PbS and Bi2S3 thin films by which a specularly reflective image is obtained.

Spectral measurements of dielectric multilayer coatings that are exposed to vacuum or high humidity indicate that ion-plate coatings are very stable and capable of retaining their spectral characteristics within the recording's linewidth, unlike conventional electron beam-deposited coatings. The deposition of dense, dielectric thin films improves the durability and survivability of optical coatings in hostile environments. Reactive low-voltage ion plating is identified as the most versatile deposition process, with the least problematic upscaling.

Effective antireflection coating designs for infrared windows are developed for the 3-5 micron and 8-12 micron bands. Dual band performance with these designs are optimized with computer aided techniques. A simple scheme to improve their oblique incidence performance is examined. Potential use of these designs in practical coatings without the use of radioactive materials is also discussed.

A design technique for multi-level binary optic structures that exhibit very low broadband reflectivity at oblique incidence is developed. The multi-level binary grating structures are equivalent to multi-layer thin film antireflection coating systems synthesized by the step-down inhomogeneous film technique. The design is shown to produce reflectivity of less than a few percentage points over a broadband optical spectra and over a wide range of the angles of incidence for unpolarized light. Designs for minimum reflection for unpolarized light are obtained for a two, three, and four-level binary system over a specified light wavelength range and angle of incidence. It is shown that three or four level systems are sufficient to produce very low reflectivity. It is also shown that the grating spacing does not have to be less than half the light wavelength to achieve this low broadband reflectivity.

Multilayer stacks of optical filters for spaceborne electrooptical imaging employ a staggered edge filter and a matching antireflection stack, in order to achieve the requisite passband characteristics and eliminate unwanted sideband transmission throughout the optical range. After discussing the general principles of staggered-reflector configurations and their use in the reduction of sideband transmission, attention is given to the spectral properties of the filters designed and their stability against anticipated variations in temperature and angles of incidence.

Aerospace sensing enables the remote optical measurement and investigation of important atmospheric, biological, and geological processes whose understanding is important to the continuing health of planet Earth. The meaningful scientific interpretation of these remote measurements requires an improvement to our absolute radiometric calibration capability that, in turn, necessitates deeper knowledge of optical stability of materials used for such calibration procedures. This paper describes a framework to pursue studies of the effects of various space environment factors, together with the influences on those effects of prior processing history of the optical materials. Initial observations about the optical behavior of diffuse reflectance candidate materials in simulated space environment tests are also summarized, together with plans for further study, analysis, and evaluation.

This report summarizes cost adjustment factors for beryllium (Be, S200) and titanium (Ti, 6Al-4V) that were derived relative to aluminum (Al, 7075-T6). Aluminum is traditionally the material upon which many of the Cost Analysis Office, Missile Division cost estimating relationships (CERs) are based. The adjustment factors address both research and development and production (Q > 100) quantities. In addition, the factors derived include optical elements, normal structure, and structure with special requirements for minimal microcreep, such as sensor assembly parts and supporting components. Since booster cost per payload pound is an even larger factor in total missile launch costs than was initially presumed, the primary cost driver for all materials compared was the missiles' booster cost per payload pound for both R&D and production quantities. Al and Ti are 1.5 and 2.4 times more dense, respectively, than Be, and the cost to lift the heavier materials results in greater booster expense. In addition, Al and Ti must be 2.1 and 2.8, respectively, times the weight of a Be component to provide equivalent stiffness, based on the example component addressed in the report. These factors also increase booster costs. After review of the relative factors cited above, especially the lower costs for Be when stiffness and booster costs are taken into consideration, affordability becomes an important issue. When this study was initiated, both government and contractor engineers said that Be was the material to be used as a last resort because of its prohibitive cost and extreme toxicity. Although the initial price of Be may lead one to believe that any Be product would be extremely expensive, the total cost of Be used for space applications is actually competitive with or less costly than either Al or Ti. Also, the Be toxicity problem has turned out to be a non-issue for purchasers of finished Be components since no machining or grinding operations are required on the finished components. Several new costing techniques are developed which provide quantitative measures of the cost of material stiffness, costs related to payload weight, and costs associated with the relative temperature stability of different materials. In addition, use is made of the Design/Cost Trade Model developed by Applied Research, Inc., to determine the booster cost differential relative to changes in payload weight, and a mirror fabrication cost model, developed by OCA Applied Optics, was used for mirror costing. This report is a summary of an extensive study done by the U.S. Army Strategic Defense Command, Huntsville, Alabama.