Showing papers on "Adaptive optics published in 1979"
01 Nov 1979
TL;DR: The mathematics of the technique, which implies extraction of a wavefront θ(f) at one spatial plane based on the intensity p(x) in a conjugate plane, and computer simulations are shown.
Abstract: Adaptive optics with controllable delay in a matrix of regions focuses the image of an object upon a detector array in an image plane that provides a signal set representative of the radiant energy incident upon a matrix of locations in the image plane An image signal processor processes this signal set to provide a wavefront error signal representative of the estimated wavefront phase distortion of the radiant energy incident upon the detector array A control system responds to this wavefront error signal to effect alteration of the phase delay introduced by the adaptive optics to reduce the phase distortion of radiant energy incident upon the detector array
178 citations
TL;DR: Continuous-wave phase-conjugate wavefront generation via real-time holography in Bi12 SiO20 crystals is presented and applications include real- time imaging through phase-disturbing media, optical processing, and interferometry.
Abstract: Continuous-wave phase-conjugate wavefront generation via real-time holography in Bi12 SiO20 crystals is presented. The efficiency of the device is analyzed in terms of wavefront reflectivity. Electro-optic configurations allowing gain in the reflected wave intensity are considered. Applications include real-time imaging through phase-disturbing media, optical processing, and interferometry.
146 citations
TL;DR: Arrays of corner reflectors behave similarly to nonlinear optical phase conjugators in correcting phase distortions in imaging systems and a preliminary analysis of these properties is presented.
Abstract: Arrays of corner reflectors behave similarly to nonlinear optical phase conjugators in correcting phase distortions in imaging systems. An experimental demonstration and a preliminary analysis of these properties are presented.
64 citations
TL;DR: It is shown theoretically and experimentally that with large gain this configuration ignores amplitude fluctuations and unambiguously estimates phase at high speed over a dynamic range of multiple-pi radians.
Abstract: A simple closed-loop system for estimating optical phase, called an interference phase loop, is presented. In this system the output intensity from an elementary interferometric phase sensor (e.g., Zernike phase contrast, homodyne, heterodyne, polarization, or shearing interferometer) is detected and used to drive a phase modulator in the path of the wavefront being measured. It is shown theoretically and experimentally that with large gain this configuration ignores amplitude fluctuations and unambiguously estimates phase at high speed over a dynamic range of multiple-pi radians. When self-interference (e.g., Zernike phase contrast) is employed, monochromatic light is not required.
30 citations
TL;DR: In this article, the authors describe a recently developed shearing interferometer that is designed for general purpose laboratory use, including a description of the instrument characteristics and principle of operation as well as a comparison of measured and theoretical accuracy limits.
Abstract: The fundamental measurement required for proof of quality of an optical system is the shape of its transmitted wavefront. A knowledge of wavefront error and the transmission characteristics of an optical system allow calculation (at the measurement wavelength) of all commonly used quality factors such as optical transfer function, point spread function, Strehi ratio, etc. This paper describes a recently developed shearing interferometer that is designed for general purpose laboratory use. Included is a description of the instrument characteristics and principle of operation as well as a comparison of measured and theoretical accuracy limits.
22 citations
Patent•
30 Aug 1979
TL;DR: In this paper, a method of mitigating 2πN phase ambiguity in an adaptive optics control system is disclosed wherein the radiation sensed by a detector within a feedback loop is passed through an aperture having a variable diameter.
Abstract: A method of mitigating 2πN phase ambiguity in an adaptive optics control system is disclosed wherein the radiation sensed by a detector within a feedback loop is passed through an aperture having a variable diameter. The turn-on of the adaptive optics control system is initiated with the aperture in an open position to transmit radiation from all actuator zones onto the detector resulting in a convergence free of the 2πN phase ambiguity. The diameter of the aperture is then reduced slowly compared to the bandwidth of the control system to converge to a near diffraction limited output beam at the aperture.
17 citations
11 Jul 1979
TL;DR: The Integrated Imaging Irradiance (I3) Sensor (U.S.Patent #4,141,652) incorporates several novel features which overcome these difficulties, resulting in an AC Hartmann-type sensor that has demonstrated optimum performance with relaxed engineering requirements as mentioned in this paper.
Abstract: At present, two wavefront sensor concepts are being developed which drive the deformable mirror in real-time phase conjugate adaptive optical systems. Analyses show that the Hartmann-type sensor and the shearing interferometer can both approach optimum theoretical performance, and, in fact, shearing interferometer sensors have been built which demonstrate this capability. Until now, however, the optimum Hartmann-type sensor has not been built because proposed implementations do not take advantage of AC detection required for long wave application, and because the simple Hartmann sensor poses severe engineering problems of system alignment. The Integrated Imaging Irradiance (I3) Sensor (U.S.Patent #4,141,652) incorporates several novel features which overcome these difficulties, resulting in an AC Hartmann-type sensor that has demonstrated optimum performance with relaxed engineering requirements.
14 citations
TL;DR: In this paper, the interferometer described in this paper combines a number of principles known for a long time in a system of unusual versatility, including classical interferometry for visual or photographic evaluation of apertures up to 150 mm diameter, to programmed scan heterodyne interferometers with fringe counting and to time and space-resolved subfringe measurement with better than 10 nm resolution.
Abstract: The interferometer described in this article combines a number of principles known for a long time in a system of unusual versatility. The operation modes range from classical interferometry for visual or photographic evaluation of apertures up to 150 mm diameter, to programmed scan heterodyne interferometry with fringe counting and to time- and space-resolved subfringe measurement with better than 10 nm resolution. The instrument is primarily intended as a diagnostic tool in adaptive optics to monitor the deformable corrector mirror during operation.
10 citations
01 Mar 1979
TL;DR: In this paper, a review of high-powered laser power transmission systems for a satellite power system is presented, where the relationship between power output and waste heat, the laser efficiency and costs, as well as mass-to-power ratios for various laser power transmissions systems (LPTS) are analyzed.
Abstract: High-powered lasers projected for application to a satellite power system are reviewed. The chemical laser, combining an oxidizer and fuel to produce a high-density chemical reaction, is considered, as is the gasdynamic type. The electric-discharge laser (EDL) in which a high-temperature, high-pressure gas is expanded through a supersonic nozzle, is described, noting that the most recent models use the fast-flow N/sub 2/-CO/sub 2/ technique, with an electron beam controlling the discharge. Beam shaping is examined in relation to energy propagation, together with a discussion of the principal factors affecting the propagation of high-powered laser beams. Refractors/mirrors as well as adaptive optics for correcting errors resulting from vibration, flexure, and initial fabrication are taken into account. The relationship between power output and waste heat, the laser efficiency and costs, as well as mass-to-power ratios for various laser power transmission systems (LPTS) are analyzed. It is concluded that the development of an LPTS able to handle the satellite power appears technologically feasible using scaling and phased-array techniques.
4 citations
11 Jul 1979
TL;DR: In this article, a method for dynamically deforming a thin mirror to correct the phase aberration function for defocus and astigmatism is presented, where three piezo-electric actuators attached to the back edges and parallel to the front surface of the mirror induce edge moments that bend the mirror to its desired shape for correction of the aberrated wavefront.
Abstract: A new method for dynamically deforming a thin mirror to correct the phase aberration function for defocus and astigmatism is presented. Three piezo-electric type actuators attached to the back edges and parallel to the front surface of the mirror induce edge moments that bend the mirror to its desired shape for correction of the aberrated wave-front. A three-actuator deformable water-cooled mirror breadboard has been designed and built. Major features, design constraints, and performance expectations of the deformable mirror design are described.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
4 citations
19 Dec 1979
TL;DR: In this article, the authors reported the results of calculations on the wavelength sensitivity of the irradiance of a laser beam due to the combined effects of diffraction and atmospheric turbulence, for propagation through the earth's atmosphere to an orbiting satellite.
Abstract: This paper reports the results of calculations on the wavelength sensitivity of the irradiance of a laser beam due to the combined effects of diffraction and atmospheric turbulence, for propagation through the earth's atmosphere to an orbiting satellite. In particular, the issue of the optimum wavelength selection which minimizes the effective beam spread is determined for the following effects: wavelength, from 0.5 μm to 10 μm; long time turbulence; short time turbulence (perfect tilt correction); non-isoplanaticity, since the satellite is in motion; perfect higher order corrections, various zenith angles; and large aperture diameters. The new results differ from the results of previous studies in several aspects. First, the transmitter is located on a mountain as opposed to sea level to reduce the effects of atmospheric turbulence and extinction. Numerical evaluations are presented of the mean-square tilt angular pointing error for non-isoplanatic effects for both zenith and off-zenith angles. The resulting mean-square pointing error scales very closely to the -2.11 power of aperture diameter, and -1.75 power of the cosine of the zenith angle for a lead angle of 52 microradians, based on the profile of Barletti, et al. The results, for 3 to 4 meter diameter apertures, indicate that the minimum beam spread is always in the infrared, for all zenith angles. In the infrared, the beam spread angle can be decreased by 50% with tilt correction, with the spread at 10.6 μm wavelength smaller than that for 3.8 μm, although the beam spread angle is relatively insensitive to the infrared wavelength. Still smaller beam spreads can be achieved at the short wavelength end of the infrared spectrum only by using higher order adaptive optics to compensate for atmospheric turbulence; while the longer wavelengths can benefit from still larger diameters without the necessity for the use of higher order turbulence corrections.
01 May 1979
TL;DR: The feasibility of mechanizing an adaptive array of independent laser oscillators for generation of a high power coherent output was experimentally investigated in this article, where a phase lock demonstration formed the basis for the design and fabrication of the high power, watercooled, control mirror subsequently installed in the NASA LeRC high power laser.
Abstract: The feasibility of mechanizing an adaptive array of independent laser oscillators for generation of a high power coherent output was experimentally investigated. Tests were structured to evaluate component/system requirements for delivery of energy to a low-earth orbit satellite. Initial experiments addressed the control issues of phase locking unstable resonators at low power levels. A successful phase lock demonstration formed the basis for the design and fabrication of the high power, water-cooled, control mirror subsequently installed in the NASA LeRC high power laser. Tests were performed to characterize the operational limits of the laser system and included quantitative assessment of the frequency stability, noise sources, and optical properties of the beam.
11 Jul 1979
TL;DR: In this paper, the operation of a nine-zone multidither adaptive optics system is described and closed-loop control system data show the interaction of dither frequency spacing with achievable system bandwidth.
Abstract: Described is the operation of a nine-zone multidither adaptive optics system. Closed-loop control system data show the interaction of dither frequency spacing with achievable system bandwidth. Performance predictions for a 69-zone system are presented.
01 Jan 1979
TL;DR: In this paper, the optimal estimation and control methods for high energy laser adaptive optics systems are described, and three system types are examined: active multidither (AMD), phase conjugate (PC), and Beam Cleanup (BC).
Abstract: : Optimal estimation and control methods for high energy laser adaptive optics systems are described. Three system types are examined: Active Multidither (AMD), Phase Conjugate (PC), and Beam Cleanup (BC). Sources of phasefront distortion considered include: atmospheric turbulence, backscatter speckle, base vibration, and mirror thermal distortion. Kalman-type digital algorithms for phasefront aberration estimation are developed and evaluated through computer simulation; performance comparisons with classical estimation approaches are provided. Optimal feedback-feedforward controllers are designed for the active system components; performance comparisons with classical designs and sensivitiy studies related to disturbance model mismatches and active component bandwidth are presented. Results of integrated estimation and control simulations are evaluated. Areas for further refinement of the adaptive optics approaches and potential system implementations are recommended.
11 Jul 1979
TL;DR: In this paper, a multi-actuator deformable mirror and control system is described that will cancel laser wavefront phase errors caused by the quasi-static aberrations occurring in large aperture metal mirror optics.
Abstract: A multi-actuator deformable mirror and control system is described that will cancel laser wavefront phase errors caused by the quasi-static aberrations occurring in large aperture metal mirror optics. The design of the differential ball screw driven mirror, its characterization and system performance are detailed. By using a sequential dither focus irradiance sensing/optimization algorithm, the system is shown to be able to correct wavefront aberrations of up to 4 waves p-p at 10.6 µm.
TL;DR: In this article, the authors proposed an algorithm for the optimization of the process of focusing a light beam by the conditional gradient method, which is identical with the familiar phase conjugation algorithm.
Abstract: Nonlinear distortions of light beams traveling under thermal self-interaction conditions can be compensated by an algorithm for the control of the initial beam profile. In the linear case the proposed algorithm for the optimization of the process of focusing of a light beam by the conditional gradient method is identical with the familiar phase conjugation algorithm. This analogy is used to investigate a number of problems relating to the efficiency of phase-conjugate adaptive optical systems.
TL;DR: Experimental results are presented on the performance of an IR multidither adaptive-optics system with rotating, extended targets with openloop discriminants, target speckle-noise spectra, and closed-loop beam quality obtained as functions of target and system parameters.
Abstract: Experimental results are presented on the performance of an IR multidither adaptive-optics system with rotating, extended targets. A nine-zone deformable mirror with superimposed dithers was employed at 10.6 μm with spherical metallic targets of varying roughness and diameter. The results presented include open-loop discriminants, target speckle-noise spectra, and closed-loop beam quality obtained as functions of tarparameters. Experimental results are interpreted using a simplified model for the adaptive-get and system optics system and target.
TL;DR: In this article, the importance of the degradations introduced by atmospheric turbulence is shown, and it is shown that it is necessary to correct the first orders of the turbulence, by an active optics system.
Abstract: After a reminder of the expression of the optical efficiency in heterodyne detection. The importance of the degradations introduced by atmospheric turbulence is shown. The expression of the efficiency when correlations are performed, proves that it is necessary to correct the first orders of the turbulence, by an active optics system.
01 Jan 1979
TL;DR: In this article, a simple algebraic model for a continuous-wave laser beam delivered on target with spreading due to both random and deterministic phase aberrations is presented, where the authors show that sometimes conventional adpative optics concepts can produce counter-intuitive and very disappointing results when applied to thermal blooming.
Abstract: : This paper presents a simple algebraic model for a continuous-wave laser beam delivered on target with spreading due to both random and deterministic phase aberrations. The number of deterministic Zernike mode phase aberrations included in sufficient to give a realistic representation for thermal blooming. The aberrations modeled generally include those applied by an adaptive optics system to compensate the naturally occurring ones. For the random phase aberrations, compensation is a linear process the net result of which is a simple scaling down. By contrast, the thermal-blooming aberrations are complicated nonlinear functions of the applied compensations. Consequently, for this case, the interaction of applied and natural aberrations must be modeled in detail. The model shows that sometimes conventional adpative optics concepts can produce counter-intuitive and very disappointing results when applied to thermal blooming. However, the analysis suggests novel remedies that will tend to optimize the corrections made, thus better realizing the full potential of adaptive optics. (Author)
03 May 1979
TL;DR: In this paper, a method for evaluating the optical performance of optical systems consisting of large, flexible, actively controlled mirrors in the presence of thermal and dynamic disturbances is described, where the computer simulation described is divided into four major blocks: optics, thermal, structures, and dynamics.
Abstract: This paper describes a method for evaluating the optical performance of optical systems consisting of large, flexible, actively controlled mirrors in the presence of thermal and dynamic disturbances. The computer simulation described here is divided into four major blocks: optics, thermal, structures, and dynamics. The control aspects are included in the various models used in each block. The output of the simulation is a dynamic point-spread function from which real-time or average quantities such as the line-of-sight error, Strehl ratio, and power in a certain area are calculated. As an example, a two-mirror system that expands a high-power collimated beam and focuses it on a distant plane is considered. The effects of heating of the mirrors are simulated and results on the point-spread function and associated quantities are presented.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, a simple but reasonably accurate model of the entire adaptive optics (AO) loop is proposed to evaluate AO concepts for the correction of nonlinear atmospheric phenomena occurring in high energy laser beam propagation and to perform AO system trade offs.
Abstract: To evaluate adaptive optics (AO) concepts for the correction of nonlinear atmospheric phenomena occurring in high energy laser beam propagation and to perform AO system trade offs, a simple, but reasonably accurate, model of the entire AO loop is required. Heretofore, no such model existed which takes into account the temporal response of the atmosphere and yet is simple enough to permit extensive system tradeoffs. We have developed such a model. Optimum thermal blooming correction dictates that the atmospheric response time must be accounted for properly, especially for strong blooming strength. Experimental verification of the above model was carried out using an argon-ion laser with an iodine blooming cell and a closed AO loop to provide corrections for tilt, focus, and astigmatism. Reasonable agreement between theory and experimental data was achieved.
01 Jan 1979
11 Jul 1979
TL;DR: In this paper, an adaptive optical component for thermal blooming compensation is used for modeling atmospheric path lengths of several kilometers within a laboratory setup where the total path length is limited to a few meters.
Abstract: An instrumentation system has been designed for the evaluation of thermal blooming compensation. The purpose is to investigate the maximization of 10.6 μm CO2 laser radiation in the target plane through maximization of the return 3-5 μm radiation from the laser induced "hot spot" by using a pinhole sensor and a slow dither algorithm. The adaptive optical component to be used in the evaluation is a three-actuator modal deformable mirror supplied to the USAF by Perkin-Elmer Corporation. This paper deals primarily with the design of a thermal blooming cell that will be used for modeling atmospheric path lengths of several kilometers within a laboratory setup where the total path length is limited to a few meters. The theory required to perform the scaling is currently available in the literature. We present it in a format designed to aid the optical engineer, whose primary concern is the evaluation of an adaptive optical system for thermal blooming compensation. The interplay of the many parameters that may be varied is illustrated in graphical form to facilitate choices. As an example, we included our design for a one-meter cell to be incorporated in the slow dither experiment.
01 Sep 1979
TL;DR: In this paper, the phase retrieval problem consists of the wave aberration function of an optical system from intensity measurements made in the image plane, and an adaptive optical system may then be corrected for the aberration to yield improved performance.
Abstract: : The phase retrieval problem consists of the wave aberration function of an optical system from intensity measurements made in the image plane. An adaptive optical system may then be corrected for the aberration to yield improved performance. Several algorithms for performing phase retrieval are discussed and the results of computer simulations are presented. The sensitivity of the algorithms with respect to type and magnitude of aberrations, image plane detector dimensions and noise levels, non-monochromaticity of incident radiation and the structured target objects is investigated. Results demonstrate the practicality of phase retrieval.
21 Sep 1979
TL;DR: A non-coherent vector-matrix multiplication system (using a linear LED input array, a covariance matrix mask and a linear photodiode detector array) is described, modified to perform complex multiplications and to be an iterative optical processor (I0P) to solve the adaptive phased array radar processing problem.
Abstract: A non-coherent vector-matrix multiplication system (using a linear LED input array, a covariance matrix mask and a linear photodiode detector array) is described. The system has been modified to perform complex multiplications and by feedback to be an iterative optical processor (I0P) to solve the adaptive phased array radar processing problem.