Papers by Sergio Restaino
Adaptive optics performance model for optical interferometry
Applied Optics, 2007
High-QE fast-readout wavefront sensor with analog phase reconstruction
Proceedings of SPIE, Sep 11, 1998
ABSTRACT The contradiction inherent in high temporal bandwidth adaptive optics wavefront sensing ... more ABSTRACT The contradiction inherent in high temporal bandwidth adaptive optics wavefront sensing at low-light-levels (LLL) has driven many researchers to consider the use of high bandwidth high quantum efficiency (QE) CCD cameras with the lowest possible readout noise levels. Unfortunately, the performance of these relatively expensive and low production volume devices in the photon counting regime is inevitably limited by readout noise, no matter how arbitrarily close to zero that specification may be reduced. Our alternative approach is to optically couple a new and relatively inexpensive Ultra Blue Gen III image intensifier to an also relatively inexpensive high bandwidth CCD camera with only moderate QE and high rad noise. The result is a high bandwidth broad spectral response image intensifier with a gain of 55,000 at 560 nm. Use of an appropriately selected lenslet array together with coupling optics generates 16 X 16 Shack-Hartmann type subapertures on the image intensifier photocathode, which is imaged onto the fast CCD camera. An integral A/D converter in the camera sends the image data pixel by pixel to a computer data acquisition system for analysis, storage and display. Timing signals are used to decode which pixel is being rad out and the wavefront is calculated in an analog fashion using a least square fit to both x and y tilt data for all wavefront sensor subapertures. Finally, we present system level performance comparisons of these new concept wavefront sensors versus the more standard low noise CCD camera based designs in the low-light-level limit.
Unclassified Unclassified Unclassified UL 30 Xiaolei Zhang (202) 404-2389 We describe the motivat... more Unclassified Unclassified Unclassified UL 30 Xiaolei Zhang (202) 404-2389 We describe the motivations for and the conceptual design of the second-generation back-end beam combiner and fringe tracker for the Navy Prototype Optical Interferometer. The new back end is expected to result in much-improved data quality and sensitivity compared to the existing back end. It will also enable the observations of geostationary satellites in the visible and near infrared regions of the spectrum.
Review of Scientific Instruments, 2005
We present an adaptive optics (AO) system for the control of geometrical fluctuations in a laser ... more We present an adaptive optics (AO) system for the control of geometrical fluctuations in a laser beam based on the interferometric detection of phase front. By comparison with the usual Shack–Hartmann and phase diversity based AO systems, we show that this technique is of particular interest when high sensitivity and high bandpass are required for correction of small perturbations like, for instance, the control of the input laser beam of gravitational waves interferometric detectors.
Sandia National Laboratory has constructed segmented Micro-Electro-Mechanical deformable mirrors ... more Sandia National Laboratory has constructed segmented Micro-Electro-Mechanical deformable mirrors that are under investigation for their suitability in experimental Adaptive Optics systems for the Naval Research Laboratory. These mirrors are fabricated in a hexagonal array and can been constructed with flat surfaces, or with optical power allowing each mirror to bring its subaperture of light to a focus similar to a Shack-Hartman array. Each mirror can use the tip, tilt and piston function to move the focused spots to the reference location, and the measurement of the applied voltage can be used directly to power a similar flat MEMS deformable mirror. Unlike the Shack-Hartman array, this wavefront sensor can detect large magnitude aberrations up to and beyond where the focused spots overlap, due to the ability to dither each focused spot. Previous publications reported on this novel new technique and the electrical specifications, while this paper reports on experiments and analysis ...
Developing a portable NRL fast frame rate seeing monitor
SPIE Proceedings, 2004
The Naval Prototype Optical Interferometer (NPOI) is a long-baseline, multi-station interferomete... more The Naval Prototype Optical Interferometer (NPOI) is a long-baseline, multi-station interferometer whose collection apertures can be relocated to provide flexible baseline lengths. While NPOI has the longest baseline at optical wavelengths in the world, the sensitivity of the interferometer is limited by the size of the individual collection apertures which are currently 0.5 meters in diameter. NPOI is currently upgrading its collection apertures to 1.4 meter diameter light weight telescopes to increase the sensitivity. At its location on the Anderson Mesa in Arizona, the chosen diameter of the telescope apertures is much larger than the average r 0 of the site. As a result, adaptive optics must be used to correct for the wavefront aberrations. Several adaptive optics system configurations are suitable to provide the required wavefront correction, but it is highly desirable to have the adaptive optics systems as a component of the telescopes. This is being accomplished by designing the telescopes so that the adaptive optics system resides in the base of each telescope allowing a truly reconfigurable array. Thus evaluating and characterizing the performance of the adaptive optics systems is a critical component of identifying the desired adaptive optics system to support the move to larger aperture telescopes. This paper outlines a modular, electro-optical testbed that has been constructed for characterizing candidate adaptive optics systems for use at NPOI. The testbed makes use of innovative technologies to characterize the spatial and temporal performance of an adaptive optics system. Spatial performance is evaluated using a spatial light modulator liquid crystal device while temporal response is evaluated with a fast steering mirror that is used in series with the liquid crystal device. We report on the capabilities of the testbed and on the initial characterization of a low cost portable adaptive optics system.
Springer Proceedings in Physics
2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat. No.03TH8666)
Our program for the upgrade of the Naval Prototype Optical Interferometer with large telescopes a... more Our program for the upgrade of the Naval Prototype Optical Interferometer with large telescopes and adaptive optics has produced a test-bed for the in system evaluation and testing of our MEMs adaptive optics components and system performances. We have already reported in recent publications the basic characteristics of the test-bed. In order to improve the capabilities of such laboratory set-up
The development of sensors that are compact, lighter weight, and adaptive is critical for the suc... more The development of sensors that are compact, lighter weight, and adaptive is critical for the success of future military initiatives. Space-based systems need the flexibility of a wide FOV for surveillance while simultaneously maintaining high-resolution for threat identification and tracking from a single, nonmechanical imaging system. In order to meet these stringent requirements, the military needs revolutionary alternatives to conventional imaging systems. We will present recent progress in active optical (aka nonmechanical) zoom for space applications. Active optical zoom uses multiple active optics elements to change the magnification of the imaging system. In order to optically vary the magnification of an imaging system, continuous mechanical zoom systems require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of elements. By incorporating active elements into the optical design, we have designed, demo...
In order to optically vary the magnification of an imaging system, continuous mechanical zoom len... more In order to optically vary the magnification of an imaging system, continuous mechanical zoom lenses require multiple optical elements and use fine mechanical motion to precisely adjust the separations between groups of lenses. By incorporating active elements into the optical design, imaging systems that are capable of variable optical magnification with no macroscopic moving parts are possible. Changing the effective focal length and magnification of an imaging system can be accomplished by positioning two or more active optics in an optical design. In this application, the active optics (deformable mirrors) serve as variable focal-length lenses and steering mirrors making an active optical zoom system that can zoom in on off-axis points on the image and therefore track objects in the field of view of the system. We will present results from a bench top system.
Journal of the Optical Society of America A, 2011
A wealth of experimental data has shown that atmospheric turbulence can be anisotropic; in this c... more A wealth of experimental data has shown that atmospheric turbulence can be anisotropic; in this case, a Kolmogorov spectrum does not describe well the atmospheric turbulence statistics. In this paper, we show a quantitative analysis of anisotropic turbulence by using a non-Kolmogorov power spectrum with an anisotropic coefficient. The spectrum we use does not include the inner and outer scales, it is valid only inside the inertial subrange, and it has a power-law slope that can be different from a Kolmogorov one. Using this power spectrum, in the weak turbulence condition, we analyze the impact of the power-law variations α on the long-term beam spread and scintillation index for several anisotropic coefficient values ς. We consider only horizontal propagation across the turbulence cells, assuming circular symmetry is maintained on the orthogonal plane to the propagation direction. We conclude that the anisotropic coefficient influences both the long-term beam spread and the scintillation index by the factor ς 2−α .
Low Cost Adaptive Optics System
ABSTRACT Overall system; Wavefront sensing; Wavefront reconstruction; Wavefront correction; An op... more ABSTRACT Overall system; Wavefront sensing; Wavefront reconstruction; Wavefront correction; An optical system layout; Results; Present status
Optics Letters, 2004
Phase diversity is a phase-retrieval algorithm that uses a pair of intensity images taken symmetr... more Phase diversity is a phase-retrieval algorithm that uses a pair of intensity images taken symmetrically about the wave front to be determined. If these images are taken about the system input pupil this is equivalent to a curvature-sensing algorithm. Traditionally a defocus aberration kernel is used to produce the phase-diverse data. We present a generalization of this method to allow the use of other functions as the diversity kernel. We discuss the necessary and sufficient conditions that such a function must satisfy for use in a null wave-front sensor. Computer simulations were used to validate these results.
Wide-field-of-view foveated imaging system using a liquid crystal spatial light modulator
Proceedings of …, 2002
Wide-field-of-view foveated imaging system using a liquid crystal spatial light modulator. [Proce... more Wide-field-of-view foveated imaging system using a liquid crystal spatial light modulator. [Proceedings of SPIE 4715, 58 (2002)]. David V. Wick, Ty Martinez, Jeffrey T. Baker, Don M. Payne, Bradley R. Stone, Sergio R. Restaino. Abstract. ...
Applied optics, Sep 20, 1995
We describe a binary approach to adaptive wave-front correction, especially suitable for narrow b... more We describe a binary approach to adaptive wave-front correction, especially suitable for narrow band applications, which would be simpler than conventional adaptive technology. Appropriate parts of the aberrant wave front are phase retarded by half a wavelength to ensure that none of the image-forming rays add together destructively. Simulations for monochromatic light show that the residual wave-front errors, in the absence of other errors, would result in Strehl ratios of~ 40% with diffraction-limited widths at visible wavelengths. ...
Liquid crystal active optics correction for large space based optical systems
<title>New University of Puerto Rico/Air Force Research Laboratory initiative in adaptive optics interferometry</title>
Astronomical Interferometry, 1998
ABSTRACT The University of Puerto Rico, Mayaguez, in conjunction with the Deep Space Surveillance... more ABSTRACT The University of Puerto Rico, Mayaguez, in conjunction with the Deep Space Surveillance Branch (DEBS) of the USAF Research Laboratory (AFRL) Phillips Site (PL) in Albuquerque, NM is initialing an Adaptive Optics (AO) Interferometry program. The program will begin with four projects. We currently have funding for a three element optical interferometer, described in this paper, using Technology developed at DEBS, for a new wavefront sensor and a Liquid Crystal (LC) wavefront compensator being presented at this meeting&#39;(1-9) .and a Low Light Level Fringe Tracker (LLLFT)(1,6-11,16-24) Michelson: Interferometer. We are also developing a program to put a similarly configured inexpensive two-element interferometer test-bed in orbit. The interferometer would have optical elements on a 10-meter boom It will use Aperture Synthesis by rotation and motion of the elements along the booms. The third project under development would incorporate the initial 3-element interferometer into a larger array with the additional collaboration of New Mexico Tech and New Mexico State University at a 10,600&#39; site near Socorro, NM. As part of the ground based interferometry effort we are trying to develop inexpensive meter class telescopes. The 0.75meter telescopes we are building for our small interferometer will serve as prototypes and system test-beds. The telescopes will be robotic, remotely operable, essentially self-orienting and portable. We hope to produce such systems for commercial distribution for approximately $250K each. All of the ground-based interferometric systems will be configured for remote operation and independent use of sub-arrays while upgrades and repairs are underway. The major thrust of the UPR effort will be to develop inexpensive interferometers for diverse applications with the law light level capabilities and the LC adaptive optics developed at the Phillips Site. Particular applications will be for high-resolution astronomy and satellite imaging. The adaptive optics will be such that they can be placed on the individual telescopes and are nor part of the interferometer. They will then serve as templates for AO systems of general interest. As an additional part of all of these projects we will try to develop the use of optical fibers for several applications. We would like to couple the telescopes with fiber if we can develop an efficient way to couple the output signal from the telescope to the fibers, In addition we hope to use fiber stretchers for optical path compensation to replace expensive conventional optical delay lines.
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Papers by Sergio Restaino