A 6.5 inch diameter hyper-hemispherical silicon dome was developed on IRAD for an infrared countermeasures aircraft self-protection system. Having passed operational level environmental testing and many hours of flight performance, a prototype dome was subjected to MIL test requirements in simulated crash safety testing at the manufacturer's facility. Although the dome cracked during shock testing, it remained intact preserving aircraft integrity and actually passing safety requirements. This paper describes design requirements, stress analyses of the dome and its mounting, and test results including a forensic cause of failure study of the dome. The results add insight to the margins of safety normally applied to the stress analyses of brittle optical materials and examine actual cause of failure in the prototype part.

Several approaches have been used to calculate a closed-form solution for the athermal bond thickness for mounting optical elements. All of the previously developed closed-form solutions use the assumption that the bondline is thin with respect to the width of the bond in the axial direction. While this assumption is mathematically convenient, it is not empirically or theoretically supported. To compensate for the inaccuracies of these closed-form solutions, recent research using test data and finite element analysis has centered on generating empirically determined correction factors that are applied to the closed-form solutions for a zero-stress bond. In this paper an alternative closed-form solution that incorporates the bond aspect ratio is presented. The values generated from this formula are compared to the empirical results of a finite element analysis (FEA) study. An example case is used to compare the results provided by the different methods for calculating the ideal bond thickness.

This paper offers guidance to design engineers on the safe mounting of optical mirrors using elastomeric adhesives. Elastomeric adhesives are attractive because they isolate mirrors from the strains and deflections of the structural attachments in the instrument: The elastomers provide an effective buffer between them. Unfortunately the elastomers also couple the mirrors to mounts of, usually, differing thermal expansion properties. The design of the adhesive bond joints must balance the stiffness of the mirrors, the properties of the elastomers and the differences in CTE between the mirrors and their mounts. The engineer is guided, by this paper, in the design of the elastomeric adhesive bond.

NASA's planned Kepler mission uses a space-born Schmidt telescope to search for Earth-size and smaller planets around distant stars using differential photometry. This paper reports the successful design, analysis and implementation of suspending a large actively cooled (-90C) focal plane array with associated electronics inside the warm (0C) Kepler photometer. Since a Schmidt Telescope requires the focal plane to be in the middle of the telescope, it must be suspended while obscuring only a small portion of the incoming light. The Kepler focal plane is comprised of 21 individual science CCD modules and 4 guidance sensor modules covering an area that is roughly 1200 square centimeters in a telescope with a 0.95m aperture. The Kepler system requires the detector data to be digitized near the focal plane, so a detector electronics box is also suspended behind the CCD array. A total of 65 kilograms is supported by the spider structure inside the telescope and must remain stable through environments and during on-orbit operations. Key to the performance of the system is a stiff, light-weight composite structure that supports the focal plane and electronics above the primary mirror. This spider structure is used to align the focal plane with respect to the primary mirror in the system, and is intentionally over-constrained after alignment. Techniques used to align the focal plane to the optical system are discussed and predicted alignment performance and stability are reported.

An edge-backlight unit (EBLU) is applied to as the light device to provide uniform light of liquid crystal display (LCD). Generally, cathode cold fluorescent lamp (CCFL) is utilized to be the light source of BLU. With the advantages like long life, no mercury containing and good endurance of heavy impact, the light emitting diode (LED) is well known as a viable device for solid state lighting. To achieve the market requirement of the thin-film liquid crystal display (LCD) and the green-level product, the LED is replaced the CCFL used in monitor to make display thinner, lighter, no Hg containing. In this paper, the integrated LED luminance-uniform device with right angle microprism structure is proposed that it can make the point-like light to distribute propagating-light line pattern successfully. To optimize the distributions and sizes of microprisms, our designed LED-linear device can achieve an optical efficiency more than 85%, and its light output area is 2.5 times the input light source. Therefore, the LED luminous device with microprsims not only can decrease the LED to save the space, but also enhance the luminous efficiency. In future, an integrated LED luminance-uniform device could make displays thinner and brighter for light guide plate (LGP) applications.

A general overview of adhesive bonding for optical elements addresses all the relevant parameters and properties. An extensive listing of references is associated with many of the critical topics. Technical literature addressing optical bonding has been difficult to find. This paper has conducted a search to aid engineers trying to solve these bonding problems. The user must first look at his/her options for fastening the optical element. Next, he/she must consider all the parameters that influence its cure, performance and survival. If an adhesive represents a good solution, the type of adhesive must be selected. Throughout this selection process, it is important to maintain priorities on critical parameters. Compromises must always be made and assigning priority levels will aid in making these decisions. Future work will establish a selection matrix weighing relevant factors in making the adhesive selection more logical.

Although silicone technology has existed for over 5 decades, this unique material continues to find usage in new applications. Its unique chemical and physical characteristics allow its usage as fuel resistant gaskets, biologically compatible for us in medical devices in the body, coatings for Atomic Oxygen protection in space, and for interocular lenses for cataract disease. This paper will examine various silicones as effective encapsulants and lenses for High Brightness LEDs (HB LEDs). Physical and optical characteristics will be tested to determine which materials may prove to be the best.

CFRP (carbon fiber reinforced plastic) is an attractive material for fabrication of optical systems. The stiffness-to-weight ratio of CFRP is high, the coefficient of thermal expansion is low, the structure thermalizes rapidly, and many of the structural properties can be tailored to the application. We have used CFRP and CFRP-aluminum sandwich panels extensively in the structures of astronomical, optical telescopes up to 1.5m diameter aperture. In designing the optical structures, we have chosen some key fabrication techniques with CFRP that take advantage of the mechanical properties. This paper discusses the design and fabrication of 2 major telescope projects. The 1m ULTRA telescope has both the optics and the OTA fabricated from CFRP. This telescope has been recently installed at the SDSU Mt. Laguna Observatory near San Diego. A 1.4m telescope for the Naval Research Lab is being designed and fabricated at CMA. The optics, OTA, and the mount are all being fabricated using CFRP composites. The result is a lightweight structure which can be moved or deployed as necessary.

The use of composite materials in the fabrication of optical telescope mirrors offers many advantages over conventional methods, including lightweight, portability and the potential for lower manufacturing costs. In the construction of the substrate for these mirrors, sandwich construction offers the advantage of even lower weight and higher stiffness. Generally, an aluminum or Nomex honeycomb core is used in composite applications requiring sandwich construction. However, the use of a composite core offers the potential for increased stiffness and strength, low thermal distortion compatible with that of the facesheets, the absence of galvanic corrosion and the ability to readily modify the core properties. In order to design, analyze and optimize these mirrors, knowledge of the mechanical properties of the core is essential. In this paper, the mechanical properties of a composite triangular cell core (often referred to as isogrid) are determined using finite element analysis of a representative unit cell. The core studied offers many advantages over conventional cores including increased thermal and dimensional stability, as well as low weight. Results are provided for the engineering elastic moduli of cores made of high stiffness composite material as a function of the ply layup and cell size. Finally, in order to illustrate the use of these properties in a typical application, a 1.4-m diameter composite mirror is analyzed using the finite element method, and the resulting stiffness and natural frequencies are presented.

Presented is a poster presentation relating to the final assembly and testing of the Ultra Lightweight Telescope for Research in Astronomy, ULTRA [1]. The program is a 3-year Major Research Instrumentation (MRI) program funded by NSF. Objectives are to demonstrate carbon fiber reinforced plastic (CFRP) composite mirrors for ground-based optical telescopes. Presented will be final assembly of the telescope including the unique features of the system including the 27 kg primary mirror, hexapod secondary mirror control, motorized iris for the primary mirror cover. Also presented are results of the optical testing of the 0.4m mirrors used as developmental optics in the program.

Ball Aerospace and Technologies Corp. (BATC) is developing a Fine Steering Mirror (FSM) for the James Webb Space Telescope (JWST). This high reliability FSM is designed to provide line-of-sight steering in two orthogonal axes as part of the Aft Optical System (AOS) of a large telescope that operates at the L2 Lagrange point. This paper presents the mechanical design of the mechanism which satisfies stringent requirements for operation in vacuum and cryogenic environments. Also given is a status of the flight hardware development and early results of cryogenic testing.

An active tangent link system was developed to provide transverse support for large thin meniscus mirrors. The support system uses six tangent links to control position and distribute compensating force to the mirror. Each of the six tangent links utilizes an electromechanical actuator and an imbedded lever system working through a load cell and flexure. The lever system reduces the stiffness, strength and force resolution requirements of the electromechanical actuator and allows more compact packaging. Although all six actuators are essentially identical, three of them are operated quasi statically, and are only used to position the optic. The other three are actively operated to produce an optimal and repeatable distribution of the transverse load. This repeatable load distribution allows for a more effective application of a look up table and reduces the demands on the active optics system. A control system was developed to manage the quasi static force equilibrium servo loop using a control matrix that computes the displacements needed to correct any force imbalance with good convergence and stability. This system was successfully retrofitted to the 4.3 meter diameter, 100 mm thick SOAR primary mirror to allow for more expeditious convergence of the mirror figure control system. This system is also intended for use as the transverse support system for the LSST 3.4 meter diameter thin meniscus secondary mirror.

A multi-axis passive isolation system was designed for dual mode operation to minimize pointing error due to spacecraft dynamic disturbances and to minimize payload response due to launch loads for the Mars terminal as part of the Mars Laser Communications Demonstration Project. Numerical optimization techniques using MSC/Nastran finite element software were utilized to explore isolator design configurations using a lower bound frequency constraint of 20 Hz subject to performance and mounting constraints. Response functions were developed that included the frequency spread of the six isolator modes and the rigid-body line-of-sight error due to translational and angular base disturbances that served as merit functions and/or constrained quantities during optimization. The performance of the resulting isolator configurations based on single and six degree-of-freedom isolator models are discussed.

Optomechanics is defined as the science or engineering of maintaining the proper shapes and positions of the functional elements in an optical system. At the optomechanical interface, manufacturing tolerances affect the shape and position of the surface in a lens system. Even very small variations will cause extra aberrations which degrade the optical performance of a lens system. The traditional approach to the optomechanical tolerance design is a top-down process. The optical designers typically designate the critical to quality parameters, such as tolerances of tilts, decenters, and locations of optical elements. A significant drawback of this top-down process is that the tolerances determined by optical designers do not take the real manufacturing and assembly process into consideration. As a result, some tolerances are too tight for the manufacturing, and the yield rate of the production is difficult to improve. The objective of this study is to develop a surface based optomechanical tolerance model that calculates the variation of the critical to quality parameters for a lens system. The distribution of these parameters can be treated as inputs to the optical design. Therefore, the optical performance will be predictable than the top-down approach, and the manufacturability of the optical system can be improved.

A central aspect in the design of the Mars lasercom terminal was limiting the line-of-sight jitter of the optical payload due to translational and angular dynamic excitation from the host spacecraft. Line-of-sight jitter analyses were performed on the Mars terminal payload that accounted for the passive and active stabilization systems, the elastic response of the payload, and the detailed elastic characteristics of the isolator. The line-of- jitter was significantly impacted by the coupling between the local dynamic response of the isolator main spring and the payload structure. Critical modes of the payload are identified and the impact of the isolator main spring surge mode is discussed along with mitigation strategies using models correlated to vibration test data.

Many aspects must be considered in the design of telescope enclosures. One critical aspect is the floor sensitivity to movement. The floor moves due to floor-foundation interaction, floor-wall interaction, soil-floor interaction, and internal enclosure loads. This paper presents the details of the design of an environmental enclosure floor having minimum rotation due internal laboratory equipment loads, which can have a significant effect on the deformation of the floor. Floor analysis is presented by finite element methods. An example of a floor design is presented in the context of a future Navy Prototype Optical Interferometer (NPOI) environmental enclosure.

This paper discusses analytical equations and finite-element models for thermal stresses and deformations caused by continuous edge, three-point and face elastomeric bonds. Analytical equations for the athermalized edge bond thickness are derived where possible and verified by finite-element solutions. The comparison shows that simple analytical solutions provide good estimates for thermal stresses and deformations. Advantages and disadvantages of different types of bonds are discussed.

The Navy Prototype Optical Interferometer (NPOI) in Flagstaff, Arizona, makes use of separate smaller telescopes spaced along a Y-array and used simultaneously to simulate an equivalent single large telescope. Each telescope is mounted on a massive reinforced concrete pier tied to bedrock. The mass of the pier dampens most, but not all, of the unwanted vibration in the required spectrum. The quality and resolution of a stellar image depends on minimizing movement of the mirrors due to vibration. The main source of pier vibration is due to the soil-pier interaction. Surrounding environmental and man-made vibration propagates through the soil as body and surface waves, and forces the pier to move. In this paper, a novel concept based on a sleeve/air gap system to isolate the soil from the pier is used to minimize the vibration input to the telescope. An example of the concept is presented with respect to the future implementation of a 1.4-m diameter composite telescope at the Navy Prototype Optical Interferometer.

Vibration effects can be a maj or limiter in the performance of optical instruments used for guidance, control, surveillance and observation. The author has recently developed software that takes the physical prescription data for the optical system, calculates the influence coefficients between all the elements in the system and the system's image and then prepares a NASTRAN finite element model ofthe optical imaging behavior. This model can be added to the elastic model ofthe optical instrument and NASTRAN can then calculate all the motions ofthe image on the detector. This paper describes the use of the Ivory Optomechanical Modeling Tools in analyzing optical instruments in vibration environments and uses a recent FUR project as a practical example oftheir utility.

A novel high-resolution x-ray powder diffractometer has been designed and commissioned at the bending magnet beamline 11-BM at the Advanced Photon Source (APS), Argonne National Laboratory (ANL). This state-of-the-art instrument is designed to meet challenging mechanical and optical specifications for producing high-quality powder diffraction data with high throughput. The 2600 mm (H) X 2100 mm (L) X 1700 mm (W) diffractometer consists of five subassemblies: a customized two-circle goniometer with a 3-D adjustable supporting base; a twelve-channel high-resolution crystal analyzer system with an array of precision x-ray slits; a manipulator system for a twelve scintillator x-ray detectors; a 4-D sample manipulator with cryo-cooling capability; and a robot-based sample exchange automation system. The mechanical design of the diffractometer as well as the test results of its positioning performance are presented in this paper.

A novel ultra-high-vacuum (UHV)-compatible x-ray monochromator has been designed and commissioned at the undulator beamline 8-ID-I at the Advanced Photon Source (APS) for x-ray photon correlation spectroscopy applications. To meet the challenging stability and x-ray optical requirements, the monochromator integrates two new precision angular positioning mechanisms into its crystal optics motion control system: An overconstrained weak-link mechanism that enables the positioning of an assembly of two crystals to achieve the same performance as a single channel-cut crystal, the so called "artificial channel-cut crystal"; A ceramic motor driven in-vacuum sine-bar mechanism for the double crystal combined pitch motion. The mechanical design of the monochromator, as well as the test results of its positioning performance are presented in this paper.

Harmonic drive transmissions (HDTs) are compact, low-backlash, high-ratio, high-resolution rotary motion transmissions. One application to benefit from these attributes is the revolute joint robot. Engineers at the Advanced Photon Source (APS) are investigating the use of this type of robot for the positioning of an x-ray detector; understanding the properties of the robot components is crucial to modeling positioner behavior. The robot bearing elements had been investigated previously, leaving the transmission as the missing component. While the benefits of HDTs are well known, the disadvantages, including fluctuating dissipation characteristics and nonlinear stiffness, are not understood as well. These characteristics can contribute uncontrolled dynamics to the overall robot performance. A dynamometer has been constructed at the APS to experimentally measure the HDT's response. Empirical torque and position data were recorded for multiple transmission load cases and input conditions. In turn, a computer model of the dynamometer HDT system was constructed to approximate the observed response.

The Advanced Technology Solar Telescope (ATST) has a 4.24m off-axis primary mirror designed to deliver diffraction-limited images of the sun. Its baseline secondary mirror (M2) design uses a 0.65m diameter Silicon Carbide mirror mounted kinematically by a bi-pod flexure mechanism at three equally spaced locations. Unlike other common telescopes, the ATST M2 is to be exposed to a significant solar heat loading. A thermal management system will be developed to accommodate the solar loading and minimize "mirror seeing effect" by controlling the temperature difference between the M2 optical surface and the ambient air at the site. Thermo-elastic analyses for steady state thermal behaviors of the ATST secondary mirror was performed using finite element analysis by I-DEAS^TM and PCFRINGE^TM for the optical analysis. We examined extensive heat transfer simulation cases and their results are discussed. The goal of this study is to evaluate the optical performances of M2 using thermal models and mechanical models. Thermal responses from the models enable us to manipulate time dependent thermal loadings to synthesize the operational environment for the design and development of TMS.

Space-based surveillance sensors are covered by a shroud to protect the delicate optics from adverse environments (aerothermal heating and contamination) during hypersonic flight through the atmosphere. Once the sensor payload reaches a safe altitude, the shroud is deployed and then sensor operation begins. When the pyrotechnic actuators are fired to deploy the shroud or nosecone, large and microscopic particles are dislodged. The source of these particles is the charred thermal protection insulation material on outer surface of the shroud, and particulate contaminants deposited on the inside surface of shroud and on sensor components during assembly process. These dislodged particles can end up within the sensor field of view (FOV), and remain there for extended periods of time, with the duration depending on the air density and vehicle velocity. These undesirable particles within the sensor FOV can degrade infrared sensor performance in several ways. These particles can cause obscuration, scattering and produce spurious thermal signature, thus making it difficult to image the objects of interest. This paper presents the aeromodeling techniques used to estimate the number and size of particles, and the duration these particles can stay within the sensor FOV. This information can then be used to predict the resulting degradation in sensor performance.

All-elastic motorized flexure stages have been developed for critical metrology applications where X-Y runout of the motion must be less than 300 nm over a 10 mm stroke. The design was adapted from a highly stable flat-blade flexure stage that was manually driven and used in several instruments where long term stability of adjustments were important. The adaptations included a motor-driven miniature ball screw, a Z axis position sensor repeatable to 10 microns and elastic strain relief between the ball nut and the driven table. In-situ testing of the actuators demonstrated that they met or exceeded all specifications for their performance.

We present the optomechanical design of a polarimeter to be used with the SCUBA-2 camera at the James-Clerk-Maxwell Telescope. The polarimeter, built to study polarized sub-millimeter radiations, has a clear aperture of 269 mm and is composed of three optical elements: a calibration polarizer, a half wave plate rotating at a speed of up to5 Hz, and an analyzer polarizer. All three elements can be placed in and out of the beam, depending on the telescope's observation mode.

The Laser MegaJoule (LMJ) final optics assembly: - performs the frequency conversion (from 1053nm to 351nm), - focuses 4 laser beams, - addresses any point of the focal volume. This paper introduces recent studies concerning the new optomechanical design of this system. The following topics are presented: - the new optical frame design - the 3 axis movement system - the interface between the optical Line Replaceable Unit (LRU) and the structure (TTT system) - the principal optic LRU presentation.

The use of uncooled infrared (IR) imaging technology in Thermal Weapon Sight (TWS) systems produces a unique tool that perfectly fulfills the all-weather, day-and-night vision demands in modern battlefields by significantly increasing the effectiveness and survivability of a dismounted soldier. The main advantage of IR imaging is that no illumination is required; therefore, observation can be accomplished in a passive mode. It is particularly well adapted for target detection even through smoke, dust, fog, haze, and other battlefield obscurants. In collaboration with the Defense Research and Development Canada (DRDC Valcartier), INO engineering team developed, produced, and tested a rugged thermal weapon sight. An infrared channel provides for human detection at 800m and recognition at 200m. Technical system requirements included very low overall weight as well as the need to be field-deployable and user-friendly in harsh conditions. This paper describes the optomechanical design and focuses on the catadioptric-based system integration. The system requirements forced the optomechanical engineers to minimize weight while maintaining a sufficient level of rigidity in order to keep the tight optical tolerances. The optical system's main features are: a precision manual focus, a watertight vibration insulated front lens, a bolometer and two gold coated aluminum mirrors. Finite element analyses using ANSYS were performed to validate the subsystems performance. Some of the finite element computations were validated using different laboratory setups.

A new macromolecular crystallographic facility developed by The General Medicine and Cancer Institutes Collaborative Access Team (GM/CA-CAT) at the Advanced Photon Source (APS) is a part of the Biosciences Division (BIO), Argonne National Laboratory (ANL). The facility consists of three beamlines: two lines based on the first "hard" dual canted undulators and one bending magnet beamline [1]. Several compact collimator systems have been developed for the purpose of background reduction in macromolecular crystallography experiments. The apparatus consists of a tube collimator, pinhole and kinematics mount. This paper will present a series of compact collimator designs and crystallographic applications based on experimental requirements [2]. We also describe the magnet-based kinematic mounting structures [3] developed as a collimator holder.

MTS (MIRI telescope simulator) is the Spanish contribution to the JWST Project. MTS is a part of the Optical Ground Support Equipment (OGSE) for the Assembly Integration and Verification (AIV) and Calibration phase of the MIRI instrument at the RAL (Rutherford Appleton Laboratory) facilities. Briefly, MTS main objetive consists on delivering a diffraction-limited test beam, including the obscuration and mask pattern, to the MIRI instrument that reproduces the output beam of the JWST in environmental conditions similar to those corresponding to the flight. In this work, the current status of the project is reported on. Mainly, after a description of the whole instrument and the optomechanical performances required, the paper will be focused on the current status of the purchase and characterization of certain critical elements belonging to the different subsystems. The first step has been the verification of the thermoelastic behaviour of its structure, employing a mass prototype. Both extensometer measurements and optical measurements with alignment mirror cubes have been carried out during a thermal vacuum test of this MTS prototype. The correlation of the measurements, optically and mechanically, will provide a better knowledge of the structure behavior and will be used to define the integration process.

This paper presents recent studies on the mechanical support system of Laser MegaJoule large dimension optical components. The dimensions of these optical components and their orientation resulted in considerable distortions due to gravity. An original and very simple method based on an isostatic mounting together with industrial springs located on the edges of the component is presented. Springs are used to compensate for gravity distortion. This system provides improved support performance at very low cost (for example, PV less than 0.5μm for a 610mm * 430mm * 80mm silicate optic at 45° from the vertical). The support systems are optimized with IDEAS finite element analysis software and validated with experimental measurements.

The inability of an optical spherometer to measure large curvature radii in optical convex surfaces is well known. This is because the movement of the optical component or the instrument cannot be physically carried out since this would involve crossing each other. This study proposes the opto-mechanical design of a spherometer that will have a source light, a beam splitter, and a liquid lens composed of a plane surface and a transparent elastic membrane with a liquid medium between them. By changing the volume of the liquid the shape of the membrane and the thickness of the lens will change. The present study offers a paraxial analysis of the relationships obtained to measure the curvature radius together with its uncertainty as a function of changes in the volume. The study also presents the work range of the instrument. The instrument is focused on the vertex of the surface and on the center of curvature with aid an intensity detector.

There are a total of one hundred seventy precision flat mirrors within the optical array at the Navy Prototype Optical Interferometer (NPOI). During the build phase each mirror center is positioned in space relative to a primary fiducial. Prior to nightly astronomy observations each mirror train, up to six trains containing ten mirrors each, are checked and finely adjusted if necessary. The facilitation of diverse science programs and expanding capabilities at the NPOI require reconfigurations of optical mounts. As part of this process, alignment of the reconfigured optical train is performed. Similar tools and techniques are in use for each of these three processes. A light emitting diode (LED), mounted on a motorized target arm is strategically attached to each mirror's mount for viewing the mirror's center point. A focusable precision alignment telescope mounted in a precision v-block assembly is employed as the basic alignment tool. The human eye is the detector. In this paper, we describe the current tools and techniques used at the NPOI to achieve the requisite alignment tolerances and validations during the build, operations, and reconfiguration phases. We also discuss the development of alignment tolerances, the deficiencies of the current tools and techniques, issues with digital imaging and centroiding, and efforts to enhance, quantify, and validate the alignments.

Reconfigurations of the original optical mounts are required to facilitate the expanding capabilities and diverse science programs at the Navy Prototype Optical Interferometer. The mounts of current interest are tangent-arm gimbaled mounts located in vacuum chambers, remotely controlled, and precisely aligned through a narrow range of motion. In order to achieve the desired large changes in pathway reflections, the articulated range of the mount was increased from 4 to 45 degrees in elevation and from 4 to 90 degrees in azimuth. This increase was achieved on the elevation axis by fashioning and attaching a worm gear device, and a direct-drive type mechanism was used on the azimuth axis. The original alignment resolution and stability were preserved by retaining the high precision tangent-arm actuators. In this paper, we present the design modifications that achieved the form, fit, and function required for remote-controlled reconfiguration and alignment. The mechanical modifications, modes of operation, test results, and reconfigurations are described in detail.

Engineering specifications for O-ring seal surfaces are well documented. However, when seal surfaces are located on asymmetrically loaded vacuum end-plates, consideration must be given not only to surface finish and flatness, but also to load-induced deflections. When deflections are significant, O-ring compression can relax and potentially cause vacuum leaks. Large vacuum systems, such as the 9000 cubic foot system at the Navy Prototype Optical Interferometer (NPOI), cannot afford costly vacuum leaks due to improper end-plate design. The NPOI employs vacuum end-plates that serve both as structural members, and as vacuum system entrance and exit ports for stellar light. These ports consist of vacuum components attached directly to the end-plate via static O-ring sealing techniques. Optical geometry dictates off-center port locations, which create asymmetric end-plate loading. This paper details the behavior of a 22 inch diameter, multi-port, end-plate for the NPOI Fast Delay Line subsystem. In depth CAD modeling and finite element analysis techniques were used to determine load-induced stress distributions and deflections in the end-plate. After several design iterations, an end-plate design was substantiated that maintains vacuum seal integrity under loading, exhibits a conservative factor of safety, and is readily manufacturable.