A description is presented of the degradations in optical performance which result when optical components are exposed to intense CW or pulse laser beams. The intensities which cause either catastrophic or non catastrophic failure are discussed. Finally, some remedies to minimize performance degradation and maximize component life are given.
Many complex optical and electro-optical systems are currently operating in the space environment, and other more sophisticated systems are being planned for future development and operation. Assurance of the survivability of these systems is typically provided by ground-based testing, simulating those aspects of the space environment considered most serious. Such testing, however, has not prevented occasional anomalous behavior and unexplained failures from occurring. To properly explain the degradation mechanisms affecting these systems and to obtain the engineering and testing data necessary for the development of improved systems requires that in situ testing in the space environment be accomplished. The Long Duration Exposure Facility (LDEF) can provide this capability. Several of the experiments being developed for the first LDEF mission will seek to determine the effects of the space environment on components which will form the key elements of future electro-optical systems, and a considerable number of related experiments have been proposed. The engineering and scientific community is encouraged to become aware of this activity and to participate in the planning and experiment development for future LDEF missions.
Identification of erosion mechanisms in optical materials and the controlling material properties are almost non-existent. This review attempts to provide a general view of many aspects of the characterization of optical materials exposed to a rain environment at high subsonic to supersonic velocities based on rather fragmented and still incomplete evaluations. A small number of materials, representative of a broad range of material behavior and type, is examined in some depth to demonstrate the uniqueness of the damage produced by multiple water drop impacts in relation to more conventional material evaluation procedures. The ultimate objective of an erosion mechanism investigation for optical materials is to find ways to extend the incubation period for erosion damage in order to reduce optical degradation through the growth of internal fracture networks and/or erosion pits. Acceptable levels of performance may be achieved for a specific material or class of materials by a basic and carefully planned materials-oriented program and through a cooperative effort between materials development and rain erosion assessment programs.
The performance of airborne infrared systems is affected by limitations on weight, size, cost and the available aperture as well as by aerodynamic heating, rain erosion, icing, atmospheric turbulence and poor visibility. Their impact on the design and choice of materials for thermal imagers and seekers is discussed.
The behavior in space environment of evaporated Al uncoated and coated with reactively deposited silicon oxide (SiOx), electron beam evaporated SiO2 and A1203 and Al and Ag coated with double layers of Al203 + SiOx is compared metallized metallized Teflon and Kapton, anodized Al (Alzak), and white paints. Flight data from three calorimetric experiments and one reflectometer flown in different orbital environments are compared with laboratory test data. The results demonstrate that evaporated thin films are extremely versatile and stable coatings for space applications. Through the use of control samples studied in different laboratory tests and monitored for up to 12,000 hours of solar exposure in different orbits, a classification of orbital severity and an estimate of laboratory simulation accuracy is obtained.
This paper is a brief overview of the effects of radiation on transparent optical components. The results of extensive measurements on ten commonly used optical glasses are reviewed and related to the performance of optical systems in radiation environments. Physical models and formula which describe the response of these materials to radiation are discussed. Simplified test procedures that will adequately parameterize the growth and bleaching of radiation darkening are outlined. Radioluminescence efficiency in glass is discussed.
The unique and demanding requirements on mirrors for use in synchrotron radiation beams are discussed in the light of recent experience with current mirror technology. The crucial role played by optical scattering from real mirror surfaces is discussed along with scattering and roughness measurement results on available mirrors. Mirror-cooling requirements and implications are reviewed. The prospects for future mirrors with smoother substrates, larger sizes, greater stability against spontaneous or thermally generated distor-tions, and more complex optical figures are discussed as well.
When an optical receiver is to operate underwater and detect a signal from a point optical source located at altitude above the water, unusual design constraints are imposed by the underwater environment. The effect of the propagation medium on a deeply submerged optical receiver is examined. Design features are optimized for background limited operation. Important and useful relationships are developed comparing the aperture area and optical filter bandwidths achieveable in telecentric and conventional optical designs. It is shown that telecentric optical configurations can provide improved system performance if the receiver field-of-view must be larger than ± 32 degrees.
ERDA, through its Division of Solar Energy is directing and funding a competitive(preliminary design proposal for a 10 MWe pilot power plant of the solar thermal central receiver type. The plant is expected to be operational in 1980 and is to be located near Barstow, CA. Sandia Laboratories in its capacity as technical manager of the project has performed technical evaluations and comparisons of the several subsystem designs supplied by the competing contractors. Predicted performance parameters for the optical subsystems are presented. These data were obtained by the application of a Monte Carlo ray trace program prepared by the authors. A short description of the program is included.
The Shiva laser system is part of a new 20 terawatt laser facility at Lawrence Livermore Laboratory.. The system contains more than $5,000,000 worth of optics. This paper discusses the various optical components, typical-component quantities and specification, and the problem of laser damage to components.
The performance of large laser systems for laser fusion is limited by self-induced damage to optical components, arising from the interaction of the intense light with the optical materials in the laser system. In the design of the beam transport optics, due consideration must be given to high intensity effects, including self-focusing, surface damage, and internal reflection focusing. The constraints imposed on the design of optical components by these considerations are discussed.
The plan for the development of commercial inertial confinement fusion (ICE) power plants is discussed, emphasizing the utilization of the unique features of laser fusion to arrive at conceptual designs for reactors and optical systems which minimize the need for advanced materials and techniques requiring expensive test facilities. A conceptual design for a liquid lithium fall reactor is described which successfully deals with the hostile x-ray and neutron environment and promises to last the 30 year plant lifetime. Schemes for protecting the final focusing optics are described which are both compatible with this reactor system, and show promise of surviving a full year in order to minimize costly downtime. Damage mechanisms and protection techniques are discussed, and a recommendation is made for a high f-number metal mirror final focusing system.
The optical design of a large CO2 laser for research into inertial confinement fusion is dominated by a number of physical constraints. These con-straints are described and the consequences and solutions by which the design objectives can be met are discussed.
In addition to the usual optical aberrations, high energy laser systems can experience beam degradation from effects that are usually ignored in conventional optical systems. Much of this degradation is the result of thermally generated component distortion or density variations in the gaseous environment. We will discuss some simple models for these distortions and present the results of computer calculations which demonstrate their effect on a beam propagated through a typical optical train.
Real high energy laser systems are rife with sources of phase (and amplitude) distortions that usually tend to degrade the far field irradiance distribution. Recent advances in deformable mirror design, beam sampling devices and concept implementation technology may make it possible to perform on line phase compensation. However, there are limits to the performance capabilities which are mostly a result of the spatial and/or temporal characteristics of the phase aberrations. Nonetheless, it might be possible to significantly improve the performance of high power laser systems by utilizing the adaptive optics technology that is available today. This paper will address some of that technology.
Predictions of optical performance for spinning cryogenic infrared sensors that operate in changing thermal and structural dynamic environments requires performing analyses involving several technologies. Although the individual thermal, structural and optical analyses are not unique, the interfacing of these analyses is unique in the optical industry. This interfacing is an important problem in performing cost-effective system analyses that often require several design/analysis iterations. We have addressed this problem by writing interface codes in order to automate the data transfer among the separate analyses. Several design/analysis iterations were performed using the T/S/O process until the design met optical performance and other requirements across the wide temperature range. The design and trade-off process for the cryogenic spinning sensor (which contains materials with different coefficients of thermal expansion) is discussed. This paper shows how the T/S/O process has been used to design a sensor that is nearly athermal across a wide temperature range.
As the conveyor belt stopped the checker picked up an item, and passed it over a slot on the counter and in that instant the register displayed the name of the item and a price. The customer had just experienced in operation Sperry Univac's AccuScanTM Grocery Checkout System. The supermarket checkout system is designed to read and decode those mysterious bars and stripes appearing in ever increasing numbers on grocery, drug and other supermarket products. A low power Helium Neon continuous wave laser with beam expander optics and a Photo-multiplier comprise the scanner, the heart of the AccuScanTM System. The scanner provides the video signals used by the AccuScanTM System to decode the symbol. The Laser/Photomultiplier optical and scanning system will be described in detail with attention to the adverse operating characteristics in which the system must operate, and the problems encountered in designing the system and AccuScan'sTM solutions. This is a performance history of installed systems and actual environmental solutions which must be found in order to scan in the supermarket environment at a cost effective price.
Shock, vibration, and large ambient temperature excursions changed the optical packaging of a Hard Copy Display from routine to challenging. This rugged, precise facsimile was designed or a military application, utilizing a CRT imaged 1:1 onto a wet processed film. The requirement that the equipment meet MIL-E-16400 necessitated such machine specifications as: less than 10 percent jitter of a 1.2 mil spot over a 48-inch path length in a 1/2 g vibration field, while holding ±0.001 inch depth of focus over a temperature range of 1000 F. The initial design reflected a ruggedized version of an office-environment piece of similar equipment, but analysis revealed that it could not survive the shock forces, that the rack temperature would have to be closely controlled, and that severe constraints were put on the CRT specifications. The final design concept makes use of several unusual techniques to meet all specifications. Certain major structural components are made of aramid fiber/epoxy composite, the folding mirrors are mounted on flexures, and the CRT is mounted in a form-fitting housing. The layout geometry balances thermal expansions of components tending to increase the optical path against thermal expansion of components tending to decrease the optical path, while utilizing the dimensional invariance of the aramid/epoxy composite structure. Certain problems arising in the implementation of this design are discussed, along with their solutions. The equipment has been functioning satisfactorily in the field for 3 years.
AR coatings for potential window materials (ZnS and GaAs) were developed. Emphasis was placed on developing AR coatings with rain erosion resistance. Rain erosion resistance of two-layer AR coatings (NdF3/ZnSe, LaF1/ZnSe, and ThF4/ZnSe) on small ZnS substrates was demonstrated. When exposed to a simulaÃ¢â€šÂ¬ed one inch per hour rainfall at 470 mph for 20 minutes, the coatings remained intact with about 10 percent loss in transmittance. The same coatings on GaAs were severely degraded by the rain erosion test. The surface finish of the substrate appeared to be an important factor for rain erosion resistance. Coatings on substrates that satisfied the scratch-dig specification of 60-40 exhibited superior rain erosion resitance.