A brief review of the properties of isotropic materials is presented (especially as it pertains to the adhesives), some techniques are discussed to minimize the size of adhesive models and the results are applied to a family of sample problems to explain the discrepancy between the apparent behavior of adhesives and the anticipated (or published) behavior. Suggestions are offered to designers to assist them in realizing the 'published behavior' in addition to the analysis suggestions for the engineer.
Analytical techniques for estimating the axial contact stress in a single element lens mechanically clamped near its rim have previously been described. In this paper, we present a progress report on an ongoing investigation of the effects upon this stress of changing the interface type, the geometric parameters and dimensions of the design or the materials used. The sensitivity of the design of temperature changes also is discussed. From the trends shown here, the optomechanical engineer can predict approximately what consequences might be expected if various parameters are changed during the design phase.
A kinematic whiffle tree type mount for a 60 inch Pyrex spherical mirror that is figured on both sides was designed and built at the Optical Sciences Center. Interferometric testing of the optic was performed in two orientations and these results were then compared with the results of finite element analyses. This comparison was facilitated by the use of computer program PCFRINGE and PHASE. The results of the comparison indicates that analytic predictions, based on the methodology presented herein, will accurately predict the performance of kinematic mirror mount configurations.
We describe an approach for mounting the approximately 0.8 m diameter optical elements in a refractive corrector for the Multiple Mirror Telescope (MMT). The optical elements are mounted on discrete pads of RTV rubber to an Invar/carbon steel cell. Following the conversion of the MMT to use a single 6.5 m primary mirror, the corrector will provide up to a 1 degree(s) diameter field-of-view for multi-object spectroscopy with optical fibers or for wide- field imaging.
This paper describes a novel packaging design for a lithium niobate Mach-Zehnder interferometric modulator. The modulator is mounted to the bottom of a miniature carrier using elastic supports to minimize transmission of bending, random vibration and shock loads. Optical fibers are threaded from the modulator ends to the outside world via tubular feed- throughs located to allow for thermal expansion of the carrier without inducing stress on the fibers. An electric current board is attached to the carrier, and wire bonds from the board to the modulator provide the required voltages. The total package envelope is less than 0.41 in3 in volume. A major design goal was to achieve a hermetically sealed package, using all-metallic seals wherever possible. The package cover is resistance-seam-welded over the carrier top. However, as an intermediate step in the development process, the optical fibers are sealed with epoxy at the feed-through locations, rather than with solder seals to metallized fibers, which would provide a true hermetic seal. The paper provides supporting analysis performed to demonstrate the effectiveness of the design, including the epoxy seals, as well as experimental test results which validate the design.
A procedure to maximize the fundamental frequency of optical structures is presented. The optimization method uses the finite element stresses due to the mechanical loading and the free-vibration mode shapes to determine design coefficients for the elements. Design coefficients are used to modify an initial design following an iterative procedure. This method of optimal structural design, referred to here as the Maximum Stiffness Design (MSD), is demonstrated by increasing the fundamental frequency of a support structure for a beam collapser and a telescope. Furthermore, the optimization technique is used to develop optimum contour shapes for single arch and double arch mirrors. A sixteen inch diameter solid mirror blank with a four inch diameter central hole and a 48 inch optical surface radius of curvature is optimized for maximum fundamental frequency, minimum weight, and minimum rms surface error for both single arch and double arch configurations.
Automated optimum design techniques based on nonlinear programming methods can be applied to the design of large, lightweight mirrors. Requirements of general purpose finite element programs with optimization capabilities, and specific design issues related to optics are presented. Examples lightweight mirror designs illustrate the benefit of optimization tools.
A finite element program such as NASTRAN provides displacements and rotations at grid points only. When ray tracing on a deformed surface, it is necessary to accurately determine the displacement and slope at all ray intersections which seldom occur at grid points. This paper describes a general purpose post-processing program to accurately interpolate over a model, using element shape functions. The user may specify a choice of linear interpolation or cubic interpolation for plate and shell models.
This paper is a compilation of process and design information to aid engineers in the creation of components suited for the electroforming manufacturing process. It should be used as a 'rule of thumb' to aid in the initial layout phase for designing electroformed parts. Production cost saving design features for various optical and structural components will be discussed; e.g., mirrors and coldshields. Many components may be manufactured by electroforming, including metal optics such as searchlight mirrors, and precision structural components like coldshields. All are manufactured by a similar process but key differences require tailored manufacturing planning. This paper will discuss these design and manufacturing differences. For example, high quantity, low cost, production parts can utilize reusable steel mandrels if the component design meets certain shape requirements.
TAUVEX (Tel Aviv Ultra Violet EXplorer) is an astronomical telescope designed and built by EL-OP in conjunction with the Tel Aviv University Wise Observatory, for space research. It will be launched on the SRG satellite in 1995 as a part of the SODART X-Ray telescope. The thermal design has to cope with the extreme space environmental conditions caused by the solar heat flux and deep space, the satellite low power consumption requirement and the temperature restrictions of the various optical elements combined with surface finish requirements dictated by the stray light demands. In this paper we summarize the TAUVEX design considerations and the analysis which leads to the final thermal design.
Specifications for future airborne tactical electro-optical systems often call for very large, unobstructed horizontal scan angles. This requirement poses unique challenges for the mechanical design of the gimbal system. This paper describes the design and testing of a two- axis gimbal which incorporates a modular sector bearing system, a limited-angle direct-drive torque motor, and a lightweight, high-accuracy position transducer to provide an unobstructed optical aperture of more than five inches through a horizontal scan angle of +/- 90 degree(s), while allowing more than +/- 50 degree(s) of elevation travel.
This paper describes the mechanical support developed by AMOS for the collimator that is used to perform some optical tests of the military satellite HELIOS. This support is computer controlled, class 100 clean environment compatible and can be used in high vacuum (10-6 mbar). Because of the specifications, static and dynamic analyses using finite element (FEM) method were necessary during the design phase. The final support is about 1 m high, 2.5 m long and 1.5 m across for a weight of about 1000 kg. It is able to rotate the collimator optical axis around a point with amplitudes of +/- 2.1 degree(s) and +/- 1.1 degree(s) in the vertical and horizontal planes respectively with a resolution of 1' and a repeatability of 2'.
This paper describes a five-degree-of-freedom mount developed by AMOS to perform the integration of the large aspheric mirror into the mechanical structure of the military satellite HELIOS. This mirror mount is computer controlled, class 100 clean environment compatible and can be used in rough vacuum (10-1 mbar). Because of the specifications, dynamic analyses using finite element (FEM) method were necessary during the design phase. The final mirror mount is about 1.5 m high, 1.7 m long and 1.1 m across for a weight of about 700 kg. It is able to rotate the mirror around its vertex with amplitudes of +/- 1 degree(s) around the horizontal and vertical axes with resolution and repeatability better than 2'.
An investigation of the effects of elastic hysteresis on certain ball bearing/plate configurations used in optics mounting (when subjected to rolling-sliding friction forces) has been performed. The energy losses attributable to surface friction breakaway coefficients were measured. The elastic strain work in the ball and plate material has been proven to be the primary cause of the inherent, measurable energy loss of hysteresis. This paper compares the hysteresis work loss of different ball bearing sizes and materials when interacting with tungsten carbide plate. In addition, the Dahl friction force (i.e., the friction force required to move a ball within the linear region of the static friction curve) is demonstrated and measured. Ball materials of stainless steel, ceramic, and tungsten carbide were subjected to laboratory testing with results indicating that the forces of rolling and/or sliding friction are influenced by, and dependent upon the ball size and material used in the ball bearing support mount. Also, a methodology for performing calculations of the rolling friction breakaway forces extending beyond the Dahl friction regime (at the transition point of static to dynamic) is demonstrated.
When machine vision utilizing pattern recognition for precise position measurement is used, special emphasis on spatial filtering, stability, and repeatability of the optical image is required. The opposing requirements of a large field of view, which provides for rapid searching, and a high magnification, which provides for higher accuracy, can be mutually exclusive when the image detector is a small CCD array with a finite pixel size. A video microscope for machine vision is described whose key design requirements were appropriate resolution, low cost, a given small space of predetermined shape, two fixed and precise magnifications to be achieved with given object-to-image distances, illumination evenness of 5% or better, and having both dark and bright field illumination.
Positioning and maintaining alignment of the corrective optics for the Space Telescope is the objective of the COSTAR Optical Benches. The fixed and deployable Optical Benches are graphite/epoxy structures to achieve the alignment requirements. The optical benches are comprised of various cross section tubes and flat panels. Layups are designed to meet specific material properties, one of which is near zero CTE. Precision CTE measurements are necessary to ensure mission success. Eastman Kodak performed all developmental and acceptance CTE testing of the COSTAR optical benches. The apparatus used to perform the precision CTE measurements is described. Three test sets were used. A laser based, single coupon test and a multiple coupon LVDT based system performed the coupon tests. A proprietary Universal Tube Tester was used to measure the CTE of 80' rhomboid cross section tubes for flight use. Uncertainties of 0. 02 ppm/ degree(s)F were achieved. Typical COSTAR test results are discussed, including graphical data for all three test configurations.
This paper describes the application of a two-frequency heterodyne interferometry in the micro-displacement measurement, and discusses the optomechanical design of the displacement measuring apparatus with high precision, long measuring range, high moving sensitivity, and high stability. The measuring uncertainty of this apparatus is +/- 7 X 10-3 micrometers within a 5 X 104 micrometers measuring range. This apparatus is mainly used in testing and calibrating linear displacement sensors.
Several optomechanical tasks for the Los Alamos National Laboratory's (LANL) Free- Electron Laser (FEL) were set by the envisioned project goals as early as 1988. Unfortunately, the FEL project has been set aside due to funding constraints. The tasks reported on here required extensive modeling for final adaptability into the FEL environment. The systems to be described are best identified as (1) a Brewster attenuation device, (2) an optical mode relay lens system, (3) a spectral harmonics band-filtering system, (4) a 25-nm micropulse spectrometer system, (5) a 12.5-nm micropulse spectrometer system, (6) a 0.6-nm micropulse spectrometer system, and (7) a reflective mode profile rotator. The Brewster attenuation device was successfully used inside the FEL resonator. The optical mode relay lens system, spectral harmonics band filtering system, and reflective mode profile rotator were completed but never used. The 25-nm micropulse spectrometer was optically and mechanically completed, but the detector electronics were never finished. The 12.5- and 0.6-nm micropulse spectrometers were never assembled, due to hardware that was common to the 25-nm system.