A parametric design study of light weight mirror shapes with various support conditions was performed utilizing the finite element program NASTRAN. Improvements in the mirror performance were made based on the following design criteria: (1) minimization of the optical surface wavefront variations, (2) minimization of the self-weight directly related to cost of manufacturing, and (3) optimal location of support points. A pre-processor to automatically generate a finite element model for each mirror geometry was developed in order to obtain the structural deformations systematically. Additionally, a post-processor, which prepares an input data file for FRINGE (an optical computer code) was developed for generating the optical deflections that lead to the surface wavefront variations. Procedures and modeling techniques to achieve the optimum (the lightest and stiffest mirror shape due to self-weight) are addressed.

There is a need for reliable mirrors which are both light-weight and stiff. However very little documentation exists that compare different types of light weight mirrors. This lead to this parametric study to compare different mirror types, namely, contoured back mirrors, symmetric sandwich mirrors, and open back mirrors. This paper examines each mirror type as compared in each of several categories: 1) Self weight induced deflection, which is a product of stiffness and weight, for mirrors mounted on their backs and of equivalent thickness. 2) Efficiency of mirrors which are of equivalent weight, where efficiency is a function of self weight induced deflection and mirror thickness. 3) Fabrication constraints including ease of manufacture, ease of mounting, mirror thickness, and quilting or print-through of the mirror face plate. The results obtained in these categories can be used to design light-weight mirrors with greater confidence in preferred mirror type.

New demands on the performance of light-weight optical systems have led to the design and development of light-weight foam core mirrors for various applications. Foam core mirrors offer the advantage of additional weight savings without sacrificing optical performance. The design of a foam core mirror is complex and the optical performance depends largely upon the various mechanical design parameters. Although the elastic modulus, E, of the core material is important, the optical performance of light-weight mirrors is highly sensitive to the core shear modulus, G. Therefore, to effectively design a light-weight foam core mirror, the value of G for the core material must be established with a high level of confidence. This paper addresses the theoretical analysis and test method utilized to accurately determine the shear modulus for cellular foam materials and illustrates the significance of G as a parameter in the design of light-weight mirrors.

Litton/Itek Optical Systems has been the leader in the development of deformable mirrors for use in high quality optical systems since 1973. The monolithic piezoelectric mirror (MPM) which was introduced in 1974, has been the quality product against which all other visible wavelength compensators have been compared. The stacked actuator deformable mirror (SADM) , first delivered in 1980, set new performance standards for infrared systems. These devices continue to maintain high quality large stroke performance in the field. In 1981 Itek began the development of a new concept in deformable mirrors, the low voltage electrodistortive mirror (LVEM) . Itek teamed with Bell Aerospace in 1984 to develop a cooled silicon electrodisplacive mirror (CSEM) technology. The CSEM development emphasized extending the LVEM technology to high energy laser systems applications by incorporating a silicon multiport pin-fin heat exchanger into the mirror structure. Recently, in 1988 Itek has begun developing a cost efficient cooled mirror technology compatible with moderate flux levels and quantity production. The LVEM uncooled technology has matured and represents the current state-of-the-art in deformable mirror performance. Upon its maturity, the CSEM technology will provide both high performance and cost efficient cooled deformable mirrors for the needs of the high energy laser community.

A wide variety of deformable mirror structures have been studied for wavefront correction since the advent of adaptive optics nearly two decades ago. These structures generally fall into two categories: 1) segmented facesheet and 2) continuous facesheet. In addition there are two methods of correction: 1) zonal control and 2) modal control. The basic mirror types are discussed and analyzed in terms of wavefront correction capabilities. Curve fitting characteristics are explained in terms of the optical influence function and mirror meshing functions. Basic design equations and finite element models are developed for the overall system including mirror component parts such as actuators, facesheet, basal structure, and electronic drivers.

With the advent of "smart structures", a new generation of microactuators and microsensors are required to perform the sensing and micromanipulation functions on micrometer dimensions. Litton/Itek Optical Systems has pioneered the development of precision displacement actuators fabricated from the electroceramic lead-magnesium-niobate (PMN) for the past decade. Both conventional tape cast and advanced photolithographic techniques have been utilized to extend the PMN electroceramic technology to the realm of the microactuator. The microactuators have been fabricated in small sizes, batch processed, and deposited onto PMN substrates. The actuators have produced unsurpassed displacement resolution, set-point accuracy, and dynamic response. More specifically, PMN is a unique point-of-departure material which exhibits negligible hysteresis, a low coefficient of thermal expansion, low power dissipation, and large electrostrains, all important parameters for precision displacement transducers.

This paper describes the application of finite element analysis to calculate the dynamic response of a xerographic laser printer write head known as a "raster output scanner" (ROS). Steady and transient dynamic loading conditions are applied to a structural model of the ROS component support casting which has mathematical relationships accounting for the opto-mechanical interaction of 14 laser spot conditioning lenses and mirrors with the mounting structure. The output of the these relationships describe the dynamic response of the laser spot at the photoconductor surface. The response amplitude is then compared to a motion specification to determine if perceptible defects in xerographic prints will occur.

Recent advances in the technology of silicon micro-fabrication, building upon the fabrication technologies of microelectronics, have led to a capability for the fabrication of micromechanical components and devices that can be incorporated on a silicon chip, along with electronic components. Early products using this technology are already on the market. They use passive mechanical structures, such as diaphragms for pressure transducers or cantilever beams for accelerometers. During the summer of 1988, a rotating electrostatic micromotor was fabricated and operated, and it is now expected that sensors with active micromechanical components will be developed. This technology offers the possibility of fabricating complex mechanical systems at extremely low cost, and it could lead to a major new industry.

A description is given of the design, fabrication and analysis of an electrostatically-driven microactuator in which a planetary-motion rotor rolls inside a cylindrically shaped stator cavity. The design has four primary advantages: (1) the motor geometry and the rolling motion enable very small gaps which are accurate and stable, and across which electrostatic forces act, leading to high forces on the rotor, (2) relative motion is achieved by rolling rather than sliding, thus obviating the concern over internal friction, (3) higher output torques can be traded for lower rotor speeds, due to immediate planetary reduction, and (4) the power output should be higher than for systems constructed using two-dimensional silicon fabrication approaches, since wobble motor lengths are not limited by such fabrication methods. The stator segment recruitment logic can range from simple, open-loop stepping to full servo-controlled commutation using rotor position sensors. Two-dimensional analytical and finite-element simulations which estimate motor torque generated by electrostatic fields have been used to determine the influence of: (1) rotor and stator radii, (2) stator segment angular width and position with respect to the contact point, (3) stator segment voltage(s), and (4) dielectric properties and dimensions (e.g., insulator thickness on rotor) of motor materials. Dynamic models of motor behavior are also under development. A number of eccentric-motion micro motors, constructed via different fabrication techniques, have been operated. Electro-discharge machining (EDM) is the fabrication method of choice for the prototypes presently used for experimental studies. Typical rotor diameters for the EDM motor are about 500 microns, with lengths of 5,000 microns. Motor operation has been achieved with commutation rates in excess of 120,000 RPM.

Integrated polysilicon mechanisms have received considerable attention in recent literature as a common technology to fabricate microdynamics systems [1],[2],[3],[4],[5]. Inherent in that attention is the recognition that these structures will operate at considerable speeds for reasonably long periods. To date however, little is known about the dynamic properties- most notably the friction and wear, of the structural materials used to fabricate such micromechanical structures. Furthermore, a critical need in the continued development of silicon-based micromechanical systems are forms of actuation which are compatible with both the materials and processing technology of silicon microelectronics. Actuation would ideally be powered and controlled electrically to fully exploit the potential of integrated, micro electromechanical systems. We describe a series of experiments, in situ measurements and theoretical models designed to provide estimates of the coefficients of friction and the nature of wear in integrated polysilicon micromechanisms. In addition, a method for the measurement of residual stress, Young's modulus, and fatigue in thin films under tension using surface micromachined electric microactuators is presented. Among the features of this technique is a suspended rotor, linear electrostatic actuator and the availability of a continuously varying load, providing the potential for performing dynamic studies. The force generated by an electric microactuator is used to produce mechanical deformations in the material of interest. The design, fabrication, and experimental results on a specific device for the study of BTDA-ODA/MPDA polyimide films are discussed.

X-ray masks are micromechanical structures. They are best fabricated from thin films of low atomic number materials with built-in tensile strain. Optimized low pressure chemical vapor deposited polysilicon films have the desired characteristics for excellent x-ray masks. They also offer many other application opportunities as stencil masks and optical filters. Deep x-ray lithography has been developed in Germany. Concepts in very thick photoresist processing are fundamentally involved in this procedure. The end result: nearly three-dimensional metal structures will be very beneficial to future micro-structure fabrication.

There has been a growth of interest in fluid transport in very small structures. The basis for this interest derives from the application of micromachining technology to problems in fluidics. Several aspects of this problem are reviewed and discussed including some of our recent research on this topic. The problems discussed may be separated into those dealing with biological systems and those that explore the applicability of the macroscopic Navier-Stokes equations to very small planar channels. In the work conducted at the University of Pennsylvania, an experimental investigation of fluid flow in extremely small channels was conducted. Three devices have been constructed with channels of rectangular cross-section ranging in area from 7200 to 80 square microns. It was found that in the relatively large flow channels that the experimental observations were in rough agreement with the predictions from the Navier-Stokes equations. However, in the smallest of the chan-nels, there was a significant deviation from the Navier-Stokes predictions.

The Boeing Infrared Sensor (BIRS) calibration facility represents a major capital investment by the Boeing Company in optical and infrared technology. It was designed and built for the calibration and test of large aperture LWIR sensors and seekers, as well as for other emerging technological requirements. Calibration is done with either a fixed or scanning beam which has been radiometrically characterized. Presently, the system is configured for endoatmospheric c ibration with a highly uniform background field which can be set com ensurate with expected sensor ission background levels. During calibration, the sensor under test resides in an environmental chamber which simulates mission ambient conditions.

An environmentally sealed, densely packaged optical assembly utilizing an all-aluminum alloy primary optical train has been developed as part of the Infrared Calibrated Airborne Spatial Measurement System (IR CASMS) for deployment in the retractable turret of a C-130 aircraft. The primary optical train, consisting of a Kennedy scanner with a rotating pentagon prism, a Ritchey-Chretien telescope, and a clamshell-type relay assembly, is aligned on a common optical bench that is hard-mounted to the aircraft turret using kinematic mounting techniques. The single-point diamond-machined mirrors and mounts, utilizing a bolt-together design to permit mirror maintenance and eliminate potting instabilities, make use of integrally machined mounting pads and datums that permit alignment by means of an autocollimating alignment telescope. Remotely actuated miniature precision mechanisms for focusing the telescope, changing optical bandpass filters, and presenting field-filling blackbody energy to the 120 element HgCdTe detector array have been designed for optimum packaging efficiency. Two calibrated blackbodies, one thermoelectrically cooled, the other employing an etched-foil heater, are isolated from the desiccated optical environment in a sealed, heat-rejecting plenum and are coupled to the primary optical train by means of zinc selenide relay lenses. This paper presents a functional description of the IR CASMS optical assembly and discusses the construction and alignment details of the optical train, blackbodies, mechanisms, and environmental enclosure.

The increasing demand for the light-weight elastic manipulator requires the accurate means of measuring end-point deflection and slope of each link due to its flexibility. The end-effector position and orientation of an elastic robot depends on both link tip deflection and slope in addition to the joint angles. In other words, for an accurate control of end-effector position and orientation, the link tip deflection and slope should be measured using any sensory devices. The proposed system uses a laser beam to measure two-dimensional deflection and slope angle and can be utilized for static and dynamic correction of robot end-effector position using the appropriate control schemes.

Optical fibers are popular devices for measuring a variety of physical phenomena; pressure, temperature, magnetic flux, etc. Analysis of optical fiber sensors has been limited to the classical Lame' solution for conditions of plane strain. Finite element analysis can remove the plane strain limitation and allows the evaluation of realistic sensor configurations. This paper dis-cusses the application of analog techniques to the modeling of wave propagation in a single mode quartz fiber using a finite element code. The results are compared to published data for pressure and temperature sensors.

The hardware and software of COD area image measuring system and CCD high precision laser alignment system are described in this essay.

A new fabrication technique for nonaxissymmetric aspheric glass lenses is developed. In a laser printer, a combination lens system consisting of spherical lenses and a long cylindrical lens is used for the F-e conversion system. However, the conventional F-e lens system has a large aberration characteristic In its wide beam scanning. Aberration-free characteristics can be achieved using a nonaxissymmetric aspheric surface on a normal toroidal lens. This configuration results in a surface similar to a toroidal figure, but with the short radius gradually varied along the main axis. However, this type of nonaxissymmetric lens is difficult to produce with the conventiona lapping method. To overcome this problem, a new numerically controlled aspheric surface generator is constructed. Pairs of glass blanks are set around a turntable that rotates continuously at about 4 rpm. The surfaces of the blanks are machined with a grinding wheel, while the grinding spindle swings to generate the short radius of a basic toroidal figure. Furthermore, the grinding depth is dynamically controlled by actuating the turntable position through linkage with the rotation angle of the turntable. With this figure-generating principle, pairs of lenses with arbitrary surfaces can be machined at the same time. A 115 mm x 16 mm modified toroidal lens with an aspheric length of 80 Am is machined. Machining time for a lens is 45 minutes, and a figure accuracy of ± 0. 2 P.M and a surface roughness of 0.05 (Lm Rmax are achieved.

An efficient method for calculating optimum dimensions of Cassegrain telescope baffles will be dis-cussed. The baffles are designed to prevent light which has bypassed the optical system or which is outside the field of view from reaching the final image plane. It is also desired to minimize the baffle size to maximize the effective aperture. Graphical methods have been used, but they are time consuming and have limited accuracy. Previous analytical techniques have been cumbersome and difficult to implement. The new technique presented here is an iterative algorithm suitable for implementation on a small computer. The authors have written such a program and have found it to give fast, reliable design information.

The optical hardware design and methods of alignment for the GOES (Geostationary Operational Environmental Satellite) imaging instrument are discussed. The instrument is a multi-channel space-borne meteorological system. Included will be the results of a tolerance and sensitivity analysis for the optics and their adjustment mechanisms. A brief summary of the sequence of system alignment steps taken to achieve the final configuration of the instrument will conclude the discussion.

The optical alignment hardware and methods now in use for the GOES (Geostationary Operational Enviromental Satellite) Sounder optics are described. The alignment mechanisms and their mechanical and optical sensitivities are included. The alignment methods discussion includes a description of the prealignment testing and the optical measurements used for final instrument coregistration.

This paper describes the test equipment required for precise IR and visible channel microradian alignments for geosynchronous orbiting meteorological instruments. The test equipment design criteria, design, function and use are explained in detail. Wave front error measurements, vibration isolation, thermal compensation and stress free mounting configurations are described.

The Small Displacement Transducer (SDT) was developed by General Research Corporation (GRC) for the Defense Nuclear Agency (DNA) to assist in the development of advanced materials. The ideal material for many applications has a small coefficient of thermal expansion and a large modulus of elasticity. These properties make a structure using these materials insensitive to thermal loads from solar radiation or from intense pulsed nuclear radiation.

We outline a proposed precision experiment in fundamental physics, emphasizing the engineering requirements in the construction of the equipment. The objective of the experiment is to detect a predicted finite range gravitational force commonly called the "Fifth Force". Its execution involves measuring the earth's gravitational field vector at a large number of precisely located points (to 0.1 mm) around a closed surface. We will explain the basic idea behind the design and its advantages over previous experiments and state the accuracy requirements of various components. We will also describe two conceptual designs of the position and motion-control device.

The paper discusses the design considerations made on a 'scanning earth sensor' in order to avoid the possible failure of the system due to resonance induced by the vibrations generated during the launch and by the vibrations existing on the spacecraft structure. The most severely affected part of the sensor is its scan mechanism. The scan mechanism consists of a scan mirror and an angle encoder which are fixed on a torsional flexture. The oscillating frequency of the mechanism is made use of, in the necessary attitude determination and control process of the satellite. The transverse frequencies of the flexture are brought to a safe range by adjusting the tension on the flexture which in turn, eliminates the encoder-reference errors. An experimental set up is established in which a reflective sensor is used to measure this frequency which yields the tension on the flexture. This methodology for measurement of frequency and tension is successfully realized and the sensor is qualified in the necessary vibration test requirements of the mission.

Moller-Wedel has developed a very high accuracy angle measuring instrument. The angular resolution of the instrument exceeds 0.005 arcsec (-25 nano-radians). The repeatibility and absolute accuracy are in the 50 nano-radian range. The measuring range is at least 300 arcsec (-1.5 millirad). The instrument utilizes a linear CCD array with patented processessing techniques to determine the position of the return collimator image. The image is produced by an optimized optical system which projects a slit illuminated by light emitting diodes. High accuracy and stability also require thermal compensation in the opto-mechanic design of the instrument.

An existing mirror drive used in the Belgian Leopard 1 sight has been modified to accomodate a multiple optical output (visible + laser + Thermal Imaging System). The weight/size problem has been solved by using very lightweighted mirror substrates. One design which has been developped with the aid of the Finite Element Mode-ling uses MCA' metal matrix composite because of its high specific stiffness, and moderate machining cost compared to Zerodur and beryllium. Constraints analysis, material choice, design, manufacturing, integration and tests are complete. Laboratory, environment and field trials have shown good results.

This paper reports on the design, construction, and implementation of a new chopping secondary mirror system for the Kuiper Airborne Observatory. This observatory facility maintains a 0.91 m diameter telescope in a modified C-141 aircraft at the NASA Ames Research Center. This telescope is routinely used at stratospheric altitudes for astronomical observations at infrared and submillimeter wavelengths that are inaccessible from the ground.

An advanced flexural concept has been developed which allows a large angular mirror deflection of +/- 10 degrees in output beam space and position sensing accuracies approaching t6 microradians. A resolution of approximately 1 in 100,000 is possible with this design and the test sensors. Optical systems require precision pointing and positioning mirrors for various applications, i.e. beam alignment and communications. To date, mirrors with two degrees of large angle rotational freedom are of the gimbaled or flexural type. The advanced flexural system decreases overall mirror inertia; this quality also decreases drive motor size and lessens the complexity of the mirror system. Two prominent problems arise in current flexural designs; limited angular displacement and mirror pumping ( i.e. mirror motion perpindicular to the face of the mirror ). The advanced flexure system addresses these conditions. Mirror positional accuracy is another key component of active mirror systems. Spherical edge sensing with inductive sensors offers very high resolutions in 2 axes of rotation not possible previously with these devices.

This paper describes a precision subminiature three-axis translation stage used in the GOES Sounder to provide positional adjustment of twelve cooled infrared detectors. Four separate translation stages and detectors are packaged into a detector mechanism which has an overall size of 0.850 X 1.230 X 0.600 inches. Each translation stage is capable of +0.015 inch motion in the X and Y axes and +0.050/-0.025 inch motion in the Z axis with a sensitivity of 0.0002 inches. The function of the detector translation stage allows real time detector signal peaking during Sounder alignment. The translation stage operates in a cryogenic environment under a 10-6 torr vacuum.

The Geostationary Operational Environmental Satellite (GOES) Telescope is designed to be passively temperature compensated so that focus requirements will be met over a broad range of temperatures. Concerns over the effects of temperature gradients on the optical performance of the telescope and the repeatability of the "pointing error" of the telescope spawned the need for a detailed thermal/optical test. The telescope temperature compensation system, the thermal environment in which it must work and the test setup used to measure optical performance under varying temperature conditions are discussed in this paper.

The GOES Telescope utilizes a flexure mounting system for the secondary mirror to minimize thermally induced distortions of the secondary mirror. The detailed design is presented along with a discussion of the microradian pointing requirements and how they were achieved. The methodology used to dynamically tune the flexure/secondary mirror assembly to minimize structural interactions will also be discussed.

Conical scanning of a laser beam can be effectively used to measure the pointing offset of that laser beam from a point-reflective target such as a retro-reflector. The conical scan measurement method codes the lower frequency pointing error onto a carrier at the frequency of the conical motion. It then reduces the time varying, measured reflected beam intensity by a phase sensitive demodulation technique. Previous analyses of the conical scan measurement method have assumed a laser beam shape that is Gaussian. In practice the laser beam is often not Gaussian, leaving open the question of how well this method works for realistic beams. The present report describes a beam shape independent analysis of the conical scan laser pointing offset measurement process. A formulation is given that represents the process as an infinite series of differential operators acting on the beam shape function. This series is found to be rapidly convergent for unimodal beam shapes and small scan' radii.

This paper describes a new class of instruments that can reliably produce and control small motions. The instrument is intrinsically stiff, stable, athermal and adaptable to very harsh environments. Although the principles may be scaled for large motions, their current application is optimized for the optical wavelength range, a micron to an angstrom or smaller. The paper also describes the "calibrated elasticity" principles used in the development of the instruments.