Identifying injuries, deformities, and diseases by non-invasive instrumental means has been a major innovation in medicine. Diagnostic and imaging medical devices have revolutionized diagnosis and surgery, providing more efficient way to identify injuries and diseased or damaged tissues. In this paper, identification of different animal tissues using a miniature near-infrared (NIR) spectrometer will be demonstrated. Each tissue type contains different amounts of moisture and proteins, and by using this miniature spectrometer, a miniature fiber-optic probe and chemometrics; the ability to recognize tissues spectral differences is established.
Identifying injuries, deformities, and diseases by non-invasive instrumental means has been a major innovation in medicine. Diagnostic and imaging medical devices have revolutionized diagnosis and surgery, providing more efficient way to identify injuries and diseased or damaged tissues. In this paper, identification of different animal tissues using a miniature near-infrared (NIR) spectrometer will be demonstrated. Each tissue type contains different amounts of moisture and proteins, and by using this miniature spectrometer, a miniature fiber-optic probe and chemometrics; the ability to recognize tissues spectral differences is established.
Ion beam figuring provides a highly deterministic method for the final precision figuring of optical components with advantages over conventional methods. The process involves bombarding a component with a stable beam of accelerated particles that selectively removes material from the surface. Figure corrections are achieved by rastering the fixed-current beam across the workpiece at appropriate, time-varying yelocities. Unlike conventional methods, ion figuring is a noncontact technique and thus avoids such problems as edge rolloff effects, tool wear, and force loading of the workpiece. This work is directed toward the development of the precision ion machining system at NASA's Marshall Space Flight Center. This system is designed for processing small (≈ 10-cm diam) optical components. Initial experiments were successful in figuring 8-cm-diam fused silica and chemical-vapor-deposited SiC samples. The experiments, procedures, and results of figuring the sample workpieces to shallow spherical, parabolic (concave and convex), and non-axially-symmetric shapes are discussed. Several difficulties and limitations encountered with the current system are discussed. The use of a 1-cm aperture for making finer corrections on optical components is also reported.
A demonstration x-ray optic has been produced by diamond turning and replication techniques that could revolutionize the fabrication of advanced mirror assemblies. The prototype optic was developed as part of the Advanced X-Ray Astrophysics Facility, Spectrographic project. The initial part of the project was aimed at developing and testing the replication technique so that it could potentially be used for the production of the entire mirror array comprised of up to 50 individual mirror shells.
Cylindrical (hyperbolic-parabolic Wolter I) mirrors have been electroformed from nickel over an electroless nickel-phosphorous (NiP) plated aluminum mandrel in support of the NASA AXAF-S x-ray spectrometer program. The electroless nickel was diamond turned and polished to achieve a surface finish of 10 angstroms rms or better. Gold was then plated on the nickel alloy after an electrochemical passivation step. Next a heavy layer of pure nickel was plated one millimeter thick with computer controlled stress at zero using a commercial PID program to form the actual mirror. This shell was removed from the NiP alloy coated mandrel by cryogenic cooling and contraction of the aluminum to release the mirror. It is required that the gold not adhere well to the NiP but all other plated coatings must exhibit good adherence. Four mirrors were fabricated from two mandrels prepared by this method. Two mirrors were made from each mandrel. Electrolytically deposited gold was used on three parts and vacuum deposited gold (1500 angstroms) on the fourth. The mandrel surface finish was about 10 angstroms rms at the time of plating in each case. The area of each part is 0.7 square meters (7.5 square feet).
An important step in the fabrication of an optical component involves the imparting of a precise contour on the optic, which can be expensive and time consuming. Ion beam figuring is the imparting of a contour on an optical component by removing material through the impingement of a broad beam of accelerated neutral particles, and provides a highly deterministic method for the final precision figuring (or correcting) of optical components with advantages over conventional methods. The high predictability allows the possibility of single step figuring, resulting in significant time and cost savings. And unlike grinding, polishing and lapping, ion figuring is non-contacting and so avoids several problems including: edge roll off effects, tool wear, and loading of the work piece. It has previously been demonstrated that ion figuring is effective for the correcting of large optical components. These implementations typically use the process for final figure correction on meter class optical components. The work discussed here is the development of the Precision Ion Machining System (PIMS) at NASA's Marshall Space Flight Center, designed for the processing of smaller (less than 10 cm diameter) optics. Initial experiments using a Kaufman type ion source to figure 8 cm diameter fused silica and silicon carbide samples were successful. Experiments involved correcting flat samples and imparting spherical and aspherical contours.
A demonstration x-ray optic has been produced by diamond turning and replication techniques that could revolutionize the fabrication of advanced mirror assemblies. The prototype optic was developed as part of the Advanced X-ray Astrophysics Facility, Spectrographic project. The initial part of the project was aimed at developing and testing the replication technique so that it could potentially be used for the production of the entire mirror array comprised of up to 50 individual mirror shells.
Ion figuring of optical components is a relatively new technology that can alleviate some of the problems associated with traditional contact polishing. Because the technique is noncontacting, edge distortions and rib structure print through do not occur. This investigation was aimed at determining the effect of ion figuring on surface roughness of previously polished or ductile ground ceramic optical samples. This is the first step in research directed toward the combination of a prefinishing process (ductile grinding or polishing) with ion figuring to produce finished ceramic mirrors. Multiple, chemical vapor deposited silicon carbide (CVD SiC) samples were polished or ductile ground to specular or near-specular roughness. These samples were then characterized to determine topographic surface information. The surface evaluation consisted of stylus profilometry, interferometry, and optical and scanning electron microscopy. The surfaces were then ion machined to depths from 0 to 5 μm. The finished surfaces were characterized to evaluate the effects of the ion-machining process with respect to the previous processing methods and the preexisting subsurface damage. This study provides some of the information required to effectively utilize a combined ductile grinding or polishing with ion machining as a procedure for figuring optical components.
A novel adaptive optical system is being developed at NASA's Marshall Space Flight Center (MSFC). The system is based on the idea of integrating the wave front sensor into the mirror of a segmented system. This approach provides a self contained, adaptive optic which can accurately measure and correct for the localized tilt of the incoming wave front. The mirror components contain the sensing elements, the actuators and potentially some of the reconstruction processing. These segments have a hexagonal shape and will be used to form a segmented, adaptive optic, mirror. The potential mission for this type of mirror is in the form of the primary of a 12 meter class beam expander to direct laser energy through the atmosphere. This energy can then be utilized to power orbital transfer vehicles, charge depleted batteries on satellites during solar eclipse or other future space missions.
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