Though the exact origins of active and adaptive optics are unknown, recent history can be traced by the development of components. Earnest development of active and adaptive optical components began in the early 1970s with two areas of emphasis: (1) compensated imaging and (2) laser beam propagation. Typical for defense driven research and development programs, much of the evolutionary successes and pitfalls will forever remain undisclosed. Recent declassification of adaptive optics technology including laser guide star use has opened the way for exploitation by astronomers and others of the component development. It is the sole purpose of this paper to show those that would be users that the technology is mature.

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. The segmented mirror technology features independently activated mirror elements controlled in the piston, tip, and tilt modes. The continuous facesheet designs use discrete electroceramic or electrostatic displacement actuators arranged in either an axial or bimorph position to bend the 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. The continuous facesheet deformable mirror is used as a model to develop basic design equations which are used for parametric trades.

A computerized closed loop wavefront control system has been developed by Hughes Danbury Optical Systems (HDOS) in support of the Advanced Beam Control System (ABCS) Program. This system uses a 97 channel Litton Itek Optical Systems deformable mirror (DM) to provide accurate wavefront control. The continuous facesheet mirror has a 63 mm aperture and drivers which address each of the 97 low voltage electrostrictive actuators independently. Performance has been thoroughly tested to ensure meeting the system requirements. Facesheet stroke is 4 (mu) when actuated in piston, and 2.7 (mu) for a singularly driven actuator; test results indicate linear surface displacement as a function of input voltage throughout this stroke region. Hysteresis is less than 1.5% of the total stroke and an actuator's coupling to its nearest neighbor is approximately 10%. Single actuator bandwidth is virtually flat out to 1 kHz. Performance data is presented. The computerized wavefront control system is capable of accurately measuring the output wavefront and generating commands to produce the desired shape. Closed loop control has been demonstrated to produce various mirror surfaces with an accuracy of 0.020 (mu) rms. Data is presented showing the control capability.

Segmented Adaptive Optic Mirrors have been developed, fabricated, and demonstrated in real time atmospheric compensation systems. Until recently, most Segmented Adaptive Optic Mirrors have been designed for single wavelength applications and have not required more than 1.5 (mu) of surface motion since absolute phasing of the surface is not required for very narrow bandwidth compensation. Requirements for astronomical and imaging systems have required the design and fabrication of long stroke (6 - 10 (mu) ) segmented mirrors capable of absolute phasing of the segments, optical response from 0.4 to 3.5 (mu) and bandwidths above 2.5 KHz.

Laserdot has been working on adaptive optics systems for over 15 years. The first applications were about laser beam control. This has led to the first kind of deformable mirrors we use for the correction and dithering of the wavefront. These mirrors may be cooled depending on the laser beam power. Lately, with the participation of different European institutions, this knowledge has been applied to astronomical imaging. The `Come On' project showed how interesting such a technique is. `Come On Plus,' the project to be carried out, will certainly improve these first results. At the same time, jointly with Francois Roddier and for astronomical purposes too, Laserdot has achieved some bimorph mirrors which are to be used with a curvature sensor. This paper aims to oversee the mechanical components which have been designed for these different studies.

The National Solar Observatory is constructing a continuous-face-plate mirror with 61 actuators. The mirror, which has a clear aperture of 218 mm, features a detachable face plate and replaceable actuators that are servoed to maintain a position measured by capacitors which are within the actuators themselves. The actuators are 20-mm diameter and are placed on 32-mm centers. Each has a range of 6.4 microns for a voltage swing of +/- 175 volts. The servos have a bandwidth of 1 KHz (-3 db). In order to couple the face plate to the actuators, each actuator has a rare-earth magnet on its end that attracts a steel button cemented to the 3-mm-thick glass faceplate. The mirror is a contender for those systems needing a relatively large adaptive mirror with relatively few actuators, for example, to replace the secondary mirror of a Cassegrain telescope. At Sacramento Peak the mirror will be used with the 76-cm aperture Vacuum Tower Telescope to observe small details on the sun.

This technical paper describes a new unique form of deformable mirror that was engineered, designed, and built at Hughes Danbury Optical Systems. This paper discusses the current state of the art, the requirements, configuration, and special features such as the choice of materials for the mirror, interchangeable actuators, cooling technique and fabrication details.

We have developed a zonal deformable mirror that controls the wavefront of a high average power visible laser beam used for isotope separation. The mirror corrects greater than five waves of astigmatism, power, or random second order aberrations to 1/20 wave rms. Sufficient resolution is achieved to correct third order aberrations as well. A monolithic glass substrate with dimensions 77 mm X 121 mm X 10 mm is used in this design. Twenty-five actuator attachment members are incorporated into the shape of the back side of the substrate. Piezoelectric translators (PZTs) attached in a rectangular array deform the continuous substrate to the proper conjugate shape. The PZTs are attached through flexures designed to be compressionally stiff and laterally soft. In this way the intended PZT displacement is transmitted efficiently to the substrate while isolating both the mirror and the PZTs from undesirable lateral loads. Mirror parameters were determined from elastic mechanical beam approximations. Finite element analysis was used to verify performance prior to prototyping. A Hartmann sensor controls the mirror in a closed loop adaptive system. The system description is covered in a companion paper. This paper describes the mirror design and presents performance data.

Active mirror components have permitted the realization of adaptive optical systems that improve astronomical seeing and can benefit optical communication. Future progress in adaptive optical systems will accelerate as compact, fast, and simple phase-compensating devices become available. We describe the development of a new form of membrane mirror array that, when wire-addressed or optically-addressed, becomes a key element in conventional or unconventional adaptive optical systems.

The deformable mirror is the single most expensive component in atmospheric correction systems of 100 actuators or less. An innovative design for a membrane mirror is proposed as a cost effective alternative to conventional deformable mirrors. The mirror features a high voltage (250v) bias on the mirror surface, which eliminates many of the disadvantages of past membrane mirror designs. The High Bias Membrane Mirror provides a rugged, reliable, inexpensive unit suitable for low power, low density wavefront correction systems. As such it is ideal for compensated imaging systems for surveillance and astronomy, which may require only partial compensation.

We present recent results of our investigations into the feasibility of a wavefront corrector for adaptive optics, using nematic liquid crystal material. In particular, we are aiming at a small, flexible adaptive optics module, to be located at the focal plane of existing and new-generation telescopes in order to improve imaging quality. We address some of the specific problems investigated, concerning the theoretical behavior of the LC corrector, its comparison with other state-of-the-art wavefront correctors, modal and zonal, the speed and slew rate of the actuators, and a real-time capacitive servo loop scheme controlling the actuator retardance.

The LAMP program which represents a major milestone in the development of the technology to make very large aperture optical systems is described. The program integrates automated optical fabrication and test techniques with real time wavefront sensors, computers, and software, and advanced control theory. The program demonstrates that mirrors greater than 10 m can be made in segments and be capable of actively correcting wavefront errors.

The stress polishing technique is a powerful tool for fabrication of off-axis mirror profiles. The inherent smoothness that can be achieved from polishing spheres can now be applied to asymmetric profiles. This smoothness combined with the need for the mirror to be thin and flexible can be coupled to active mounting systems which readily correct low order shapes to produce a near ideal system. This technique will allow the fabrication of complete off-axis telescopes within the same basic cost range as on-axis systems, if not for less. The strength of this statement comes from the fact that both the primary and secondary mirror can be fabricated and mounted using the same techniques, affording less stringent global profile requirements during fabrication. The components are literally bent into final shape with minimal high spacial residual error in the telescope, making the system function at optimum.

A silver mirror process is described which can provide mirrors with excellent environmental durability. The stresses which can develop in dielectric protective or enhancement layers are discussed, and an estimate of the coating stress induced by an active component is obtained. It is speculated that as state-of-the-art coatings approach bulk optical properties, the mechanical properties, especially the yield strength, may also approach bulk values; if this happens, the possibility exists that coatings will craze on a typical active surface.

A hardware demonstration of segmented mirror systems for adaptive optics is described. The basis of the phased array mirror extendible large aperture (PAMELATM) concept is that large adaptive mirrors can be fabricated from many small segments by utilizing edge-sensors, which measure the piston error between segments. We have investigated the interaction between the piston and tilt control loops which direct the motion of individual segments. The segment tilt, which is set by a wavefront-sensor-based control loop, directly affects the piston error between segments; therefore, the segment piston control loop must be able to perform corrections much faster than the rate at which the tilt corrections are being performed. In this experiment, we have one fully actuated segment with a wavefront sensor measuring the error in the wavefront gradient. An adjacent segment is driven in piston to produce the piston error signal. We measure and present the bandwidth trade-offs between the two control loops and predict how this will affect the performance of larger systems. This interactive control loop methodology has an advantage over normal adaptive optics systems in that the computationally intensive wavefront reconstruction process can be removed due to the direct measurement of both the tilt and the piston errors.

The final surface figure error correction of a 1.3 m ULETM frit-bonded, ultra- lightweight, off-axis primary mirror petal was successfully completed using the ion figuring process. The petal was a concave aspheric optical element. Ion figuring is an optical fabrication method that provides highly controlled error correction of previously polished surfaces using a directed, inert and neutralized ion beam to physically sputter material from the optic surface. The surface figure error of the petal following conventional polishing was 5.02 (lambda) p-v, 0.62 (lambda) rms, and was improved to 0.17 (lambda) p-v, 0.015 (lambda) rms in four process (test-ion figure) iterations ((lambda) equals 632.8 nm). A multi-iteration process sequence was selected to address the various surface figure error volume and spatial frequency components and involved applying three different beam removal functions. The benefits of ion figuring a complex shaped optic using multiple figuring-testing iterations were clearly demonstrated.

Fine-steering mirrors (FSM) are being used in a greater variety of optical systems than ever before. The performance requirements for these systems vary just as widely. It is important for optical system designers, space-based-observation instrument principal investigators, astronomers, tactical weapons seeker designers, and others to understand the capabilities of FSM. It is also necessary for us to be able to specify FSM performance and environments in a manner that effectively communicates system needs to the component manufacturers. If the specification is initially incomplete, major disruption to the program can occur when requirements are understood. This paper introduces the critical and secondary performance and environmental parameters that make up an FSM specification. Also discussed are situations when the various parameters become important.

The transitional response of filters such as the Bessel can be realized in closed loop servo systems without dependence on pole zero cancellation or step command shaping. This paper presents the theory by example of a straightforward design method for emulating a Bessel step response in a closed loop servo system. Design methods presented here are applicable for adapting most polynomial filter equations.

A space-based optical communications experiment, developed at Lincoln Laboratory, requires a fast steering mirror as part of its spatial pointing, tracking and acquisition system. The High Bandwidth Steering Mirror version C (HBSM-C), has been designed, built and tested. This device steers a small-aperture mirror of 6 mm about two axes, through an operating range of 25 milliradian and a small-signal closed-loop bandwidth up to 2 kHz. The HBSM-C has endured a rigorous space-qualification test program with no special caging mechanism needed during high-level random vibration of 19 g rms. A description of the functional requirements, design and assembly, and analytical methods used is presented. Key results from performance and environmental testing are shown.

The gimbaled flat steering mirrors commonly used for pointing the outgoing line-of-sight of optical systems can also be driven to stabilize the line-of-sight, effectively isolating it from vehicle base motion. The stabilization equations provide the relative rates of the gimbal angles as functions of the angular velocity of the base. These equations are of use in feed-forward stabilization systems. Two algorithmic methods of deriving the stabilization equations are presented. These methods are distinguished from others by their use of a kinematic reference frame that is attached to the line-of-sight. The first method is completely general and can be applied to any system. The second is limited to systems of a specific configuration, but allows direct generation of uncoupled stabilization equations. Analysis of an aerial photography system is presented as an example.

The European Space Organization (ESO) requested Physik Instrumente (PI) to develop a system to compensate for atmospherically induced image jitter in astronomical telescopes. The product, designated S-380 by PI, is a sophisticated adaptive optic system using closed loop piezoelectric actuators and momentum compensation to significantly improve telescope resolution during long integrations by correcting for image jitter in real time. Optimizing the design of this system involved solving several interdependent problems, including: (1) selection of the motion system, (2) arrangement of the pivot points and actuators, (3) momentum compensation, and (4) selection of the sensor system. This paper presents the trade-offs leading to final design of the S-380 system, some supporting technical analysis and ongoing efforts at PI to provide fast tilting platforms for larger mirrors.

The performance of fast steering mirrors is frequently limited by the presence of mechanical resonances. This paper studies the addition of damping material to the rotor or mirror of a galvanometer-based fast steering mirror in order to reduce the effects of these resonances. Both analytical and experimental efforts document the relative effectiveness of rotor versus mirror damping as a function of mirror size. The results indicate that the addition of damping material can result in a reduction in step response time.

Presently, there is a new generation of fine-steering mirrors (FSM) being developed using magnetic suspension. They possess the high bandwidth and line-of-sight stabilization characteristics desirable from an FSM, and eliminate the singlepoint failure concern of the flexure suspension system. These devices, while also providing active focus and collimation control, introduce an interesting servo control problem. Misalignments between the center-of-gravity (CG), actuator, and sensor operating axes present nontrivial balancing requirements. This paper discusses a technique developed by Ball Aerospace Systems Group (BASG) to establish servo control of a magnetically suspended FSM (MSFSM). The process is dependant on the mirror's mass property matrix and two unknown coordinate transformations. The first is a CG-to-actuator (decoupling) transformation defined by statically balancing the actuator forces. The second is a sensor-to-CG transformation characterized by injecting noise into the system and compensating for off-axis cross coupling. Using this technique, BASG has developed a 5-inch MSFSM having 600 hertz closed 1oop bandwidth in the pointing axes and 50 hertz in the suspension axes.

The development of the Integrated Beam Control Demonstration (IBCD) brassboard for the Advanced Beam Control System (ABCS) program requires high speed large angle steering mirrors for internal laser beam control. These mirrors, which use large dynamic range voice- coil actuators and position sensor for steering and precision pointing, must be able to steer through a significant fraction of a radian in two axes and operate at a high bandwidth. Hughes Danbury Optical Systems, Inc., has successfully designed, fabricated, and tested these large angle fast steering mirrors. This paper presents some of the measurement data acquired during the recently concluded performance testing.

The fundamental element in the design, manufacture, and operation of active and adaptive optical components is the actuator. This technology has prime influence on the bandwidth, weight, and overall system accuracy. Various actuator types are commercially available which have a broad range of capabilities in terms of stroke, frequency response, hysteresis, set-point accuracy, resolution, force, power dissipation, and just plain physical size and weight. Several different types of actuator technologies are reviewed with emphasis placed upon their basic properties, design fundamentals, key parameters, and response characteristics.

Low voltage ferroelectric microdisplacement actuators are excellent candidates for use in zonal correction deformable mirrors (DMs) used in adaptive optical systems. Selection/specification is a critical process, however, since the device's electro-mechanical performance largely determines the mirror performance, and its electrical load characteristics strongly influence the cost of drive electronics. Several commercially available low voltage actuator devices were tested to establish a database for new DM designs. Both quasi-static and dynamic response characteristics were investigated. Test results are presented and conclusions are drawn concerning the merits of each device for typical deformable mirror applications.

Huge magnetoelastic interactions in the rare earths Tb, Dy, and Sm provide the basis of a technically important class of magnetostrictive materials with saturation strains, 10-3 < (Delta) l/l < 10-2. Rare earth elements, oxides, intermetallic compounds, and rapidly quenched amorphous metals all exhibit large magnetostrictions. Of particular importance here are the binary hexagonal TbxDy1-x alloys, which produce extremely high magnetostrictions at cryogenic temperatures, and the pseudobinary cubic TbxDy1-xFe2 compounds, which exhibit huge strains at room temperature and above. For the highly magnetostrictive room temperature materials, specific features which dominate the magnetostrictive behavior are: (1) large magnetic moments (approximately equals 1 T), (2) large magnetostriction anisotropy, (lambda) 111 >> (lambda) 100, and (3) changes in the magnetic easy axes from <100> (low magnetostrictive) to <111> (giant magnetostrictive) with temperature. Magnetostrictions > 10-3 are found as high as 150 degree(s)C in Tb.27Dy.73Fe2 and 250 degree(s)C in TbFe2.

Ni-Ti shape memory actuators respond to temperature changes with a shape change. Therefore, they are sensors and actuators. They combine large motion, rather high forces and small size, thus providing high work output. They usually consist of only a single piece of metal, e.g., a helical spring, and do not require sophisticated mechanical systems. They often fit into tight spaces in given designs, where other thermal actuators, like thermostatic bimetals or wax actuators, would require a major redesign of the product. In flow-control or oil pressure control valves, for example, helical springs can be placed in the fluid path, without restricting the flow. Thus, they provide fast response to changes in temperature. Shape memory actuators have been used successfully in the areas of thermal compensation, thermal actuation, and thermal protection.

High output paraffin (HOP) thermal actuators are used as linear motors in spacecraft mechanical systems. Heat energy to drive the devices is provided by either environmental temperature changes or electrically powered resistance heaters. Mechanical work is obtained from the 15% expansion of paraffin that occurs during the solid-to-liquid phase change. This paper describes the design and characterization of an HOP positioning actuator prototype (HPAP); an HOP actuator configured to provide accurate, high force positioning for adaptive systems such as space structures and optics. The HPAP provides a maximum 150 lbf over a displacement of 0.1 in. when powered with 20 W at 28 V ac or dc. Parameters critical to use in adaptive systems are characterized including dynamic response vs. load and power input, set-point accuracy, and accuracy vs. actuator velocity. With 10 watts of cooling available through conduction, calculated HPAP response time against a 100 lbf load is 7.9, 21, and 150 seconds for step changes of 10, 100, and 1000 micrometers respectively. Measurement of the set- point accuracy was limited by the accuracy of the position measuring equipment (+/- .03 micrometers ). Test results indicate that HOP thermal actuators are appropriate for utilization in adaptive systems requiring high displacement, accurate positioning within a control bandwidth of 0.5 Hz or less.

A linear amplifier and a pulsed amplifier used for driving electroceramic actuators have different design requirements. Noncapacitive loads place other constraints on amplifier design. Linear driver amplifier design considerations for electroceramic actuator operation include low quiescent power dissipation, virtually no crossover distortion, and the capability of high peak output current for wide bandwidth performance with high capacitive devices. The design and discussion presented in this paper provides a basis for and realization of this type of driver amplifier.

The possibility of using a single piezoelectric element simultaneously as both a structural actuator and collocated sensor is investigated. The coupled actuator and sensor equations for an arbitrary elastic structure with piezoelectric elements are developed using an assumed modes energy method. Examination of these equations suggests a simple implementation of collocated strain or strain rate sensing using a voltage driven piezoelectric element. The properties of such a collocated strain or strain rate sensor are presented. The general equations are applied to the case of a cantilevered beam with surface mounted piezoceramics. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with a single piezoelectric element used for collocated strain rate feedback.

Lead magnesium niobate (PMN) has many attractive features for precision submicron control. At room temperature hysteresis is less than 1%, thermal expansion is less than 1 ppm/ degree(s)C, and the sensitivity is 375 ppm strain at 600 V/mm. There has been recent interest in using PMN actuators in applications near 0 degree(s)C, which is near the Curie temperature of the PMN material. An investigation was conducted to obtain data on PMN:BA strain response and hysteresis at lower temperatures. Results of these experiments which were conducted to characterize the longitudinal and transverse field-induced strains at temperatures between -7 degree(s)C to 24 degree(s)C are provided for SELECT multilayer actuators and electroceramic plates. Measurements were made at 1 Hz both at constant maximum field (600 V/mm) as well as constant maximum strain (300 ppm for longitudinal; 140 ppm for transverse). Data shows that hysteresis and strain sensitivity to field increase monotonically as the temperature is decreased throughout the test range. Transverse strain is shown to track the longitudinal strain closely, within a simple scale factor. A comparison is made between constant field and constant strain hysteresis for both the longitudinal and transverse cases. Finally, data is presented which shows a factor of four reduction in hysteresis using passive charge control.

We put forth the proposition that multipupil imaging systems can be brought to zero absolute phase in real time, using information in the existent real-scene images. This proposition inverts the usual logic that says `phase the pupils to improve resolution;' we use the magnitude of higher image spatial frequencies to determine the proper phase relationship for the pupils. Defining the spatial frequency region above the single pupil cutoff but below the multipupil cut off as the phasing band, we demonstrate three real-scene sensing approaches that allow us to maximize the energy in the phasing band, at which point the interpupil piston error is zero. A simple two pupil experiment is used in these proof-of-principle demonstrations.

One of the most significant limitations to conventional atmospheric compensation systems is their very restricted field of view (FOV), generally equal to an isoplanatic patch size. A wavefront sensing and compensation concept is proposed that should allow the FOV to be increased in size by factors of ten or more. The kernel of the idea is to use wavefront measurements in several (approximately equals 9) directions separated by 100 - 200 (mu) rad to deduce an estimate of the three dimensional optical path difference (OPD) distribution in the atmosphere. The algorithms are roughly based on those used for medical tomographic imaging. Preliminary analysis indicates that from 9 measurement directions it is possible to estimate the OPD contributions from approximately six altitude layers. Once this 3-D OPD distribution is calculated, it may be used to deconvolve wide FOV short exposure images (i.e., wide FOV speckle holography) or it may be used to derive the drive signals for a suite of deformable mirrors that are conjugate to their respective altitude slices. Initial indications are that the FOV may be increased to 500 (mu) rad for a 3.5 m telescope operating at 0.8 micrometers . Further, since the OPD contribution in each layer is smaller than the full atmosphere, the requirements on the system performance are somewhat relaxed.

A temporal carrier frequency shearing interferometer was designed and fabricated for Kaman Aerospace to support the Space Shuttle based Wavefront Control Experiment (WCE). This platform and the intended experiments placed many constraints (weight, size, power, sensitivity, etc.) on the sensor design process. The sensor resulting from this design meets all requirements by using a rotating crossed log spiral grating and PMT detectors to achieve both a large tilt range and high precision. A measurement dynamic range of 1340:1 is obtained at 3875 wavefronts per second and the sensor is shot noise limited over 5 decades of signal.

This paper describes a system capable of real-time wavefront reconstruction for a 512 subaperture shearing interferometer. The system was designed to interface with a 1536 channel (512 segment) deformable mirror for atmospheric compensation using an artificial beacon. The phase gradients were measured using a shearing interferometer operating at two distinct shear lengths with quantum limited performance at 200 photons per subaperture. A 128 node parallel processor performed a sparse matrix multiply to reconstruct the phasefront in real time. The matrix truncation technique used allowed 90% of the elements to be removed with only minor penalty in wavefront accuracy.

The Multiple Aperture Real Time Image Normalization Instrument (MARTINI) is an astronomical adaptive optics system for visible imaging and spectroscopic feedthrough at the 4.2-m William Herschel Telescope on La Palma. It consists of a six-subaperture, tip-tilt-piston, segmented mirror device and uses 4r(0) aperture-matching to provide optimum slope removal in zones large enough for operation in the visible and with reference objects fainter than V = 13 exp m. This limit is achieved by optimizing the use of reference light, by analyzing the information from a photon counting wavefront sensor using a non-flaming (i.e., irregular sampling) infinite impulse response filter for estimation and prediction of the wavefront slopes. The value of this approach is discussed along with its extension to higher-order correction schemes. Experimental evidence supporting the theoretical basis of the MARTINI system is also presented. The astronomical potential of such an approach, and the drawbacks, are outlined.

Wavefront sensing is a very powerful technique whose capability in the field of diffraction- limited imaging through turbulence has been demonstrated. The ultimate performance of a Hartmann-Shack wavefront sensor is analyzed and used to define a detector choice strategy.

We report recent experimental verification of an new method to determine atmospheric phase directly from focused images of starlight. An artificial neural network is used to infer the phase from two images of a star, one at the exact focus and another intentionally out of focus. We applied the network to images of Vega obtained on the 1.5 m telescope at Starfire Optical Range (SOR), Kirtland Air Force Base, Albuquerque, New Mexico. Neural network predictions agree well with phase reconstructions using a conventional Hartmann wavefront sensor. The network approach offers a simple, inexpensive way to implement adaptive optics on astronomical telescopes in the near term.

Photodetector arrays and architectures for optical processing, including acousto-optical (AO) signal processing applications such as spectrum analysis, for which the demands on photodetector arrays are substantially greater than for typical image sensing applications, are discussed. Critical parameters of AO photodetector arrays such as high dynamic range, high sensitivity, high speed, and low crosstalk are noted. The current status of and future needs for detector arrays for AO signal processing are presented. Nonconventional detector structures and concepts that have potential for future AO optical signal processing use are noted.

Piezoelectrics have been around for decades as acoustic or sensing components. In the last few years, however, they have seen increasing use as means to provide motion and control in the micron realm, well below the resolution level of mechanical or electromechanical devices. Their high hysteresis (15 - 20%), however, was a problem in some systems, and this led to the development of electrostrictive materials, which reduced that hysteresis by an order of magnitude, but at a cost of other parameters. The purpose of this paper is to compare the properties of each of them, without favoring one or the other.

High force, high strain, wide bandwidth linear actuators are now available driven by the new class of `giant' magnetostrictive material called Terfenol-D. Performance data are reported which allow evaluation of several actuator designs. Strokes over 100 (mu) , clamped forces to 1700 N, and a frequency range of dc to over 3 KHz are available from small actuators. Fundamental principles of linear actuator design based on Terfenol-D drive are discussed, along with Terfenol-D characteristics which can be altered to affect actuator performance. Terfenol-D piezomagnetic constants which adapt to external variables, along with the self sensing capabilities of Terfenol-D actuators, will allow development of advanced control capabilities, or smart actuators.

Abstract not available.

The purpose of our study is the development of the hardware and the software of a fast- response Hartmann sensor (HS), providing real-time measurements of the WF local tilts, expanding the WF in terms of the 19 low order Cernike polynomials, and estimation of the temporal and spatial WF statistics.

This paper deals with application of adaptive optical systems (AOS) in the atmosphere. The optical systems are related to solutions to the following problems: (1) transfer of optical image or contrast; (2) provision of conservation of initial qualities of optical radiation during propagation through the atmosphere; and (3) energy transfer in the atmosphere with the use of laser beams. We discuss the subject beginning with the fact that, at present, all the traditional modern opto-electronic systems, operating in the atmosphere, cannot practically realize their potential efficiency. And here one of the cardinal means for providing efficient operation of optical systems in the atmosphere is the use of systems, algorithms, and elements of adaptive optics. When describing modern atmospheric adaptive optical systems, special attention should be paid the following distorting factors of the atmosphere: refraction in atmospheric layers (along extended paths), atmospheric turbulence, molecular absorption resulting in thermal blooming high power radiation. The goal of our analysis is to determine the limiting capabilities when using adaptive optical systems. As a measure of correction quality we utilize the relative increase of the Strehl parameter or energy criterion.