Wide-field Fizeau imaging telescope: experimental results

Kendrick, Richard L.; Aubrun, Jean-Noel; Bell, Ray; Benson, Robert S.; Benson, Larry; Brace, David; Breakwell, J. V.; Burriesci, Larry; Byler, E.; Camp, John; Cross, Gene; Cuneo, Peter; Dean, P. D.; Digumerthi, Ramji; Duncan, A. L.; Farley, J. M.; Green, Andrew; Hamilton, H H; Herman, Bruce J.; Lauraitis, Kris; Leon, Erich de; Lorell, Kenneth R.; Martin, R.; Matosian, Ken; Muench, Tom; Ni, Mel; Palmer, Alice; Roseman, Dennis; Russell, Sheldon M.; Schweiger, Paul F.; Sigler, Rob; Smith, John A.; Stone, Richard E.; Stubbs, David; Swietek, Gregg; Thatcher, John; Tischhauser, Chris W.; Wong, Harvey; Zarifis, Vassilis; Gleichman, Kurt W.; Paxman, Rick

doi:10.1364/ao.45.004235

Cited by 50 publications

(19 citation statements)

References 9 publications

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“…The life-cycle plan had proposed Fizeau-type additive beam combining, sometimes known as Bracewell nulling, which is used effectively in the IR to study small moons in our solar system and search for exosolar planetary systems in distant solar systems. Unlike a single-aperture imaging system, interferometric beam analysis from two (or more; Kendrick et al 2006) collection apertures allows an instantaneous differential measurement to be made concerning the fringe visibility of a -beam pattern‖ (Korotkov et al 2006;Tucker et al 2008). This allows both better spatial resolution and polarimetric precision to be achieved simultaneously, with spatial resolution being improved sometimes by 2L/D at about 10 for a relatively small baseline separation L of two apertures of D diameter separated by 2D between centers.…”

Section: Final 15 Years Of Study To Evaluate Coherent Array Imagersmentioning

confidence: 99%

A Novel Passive Millimeter Imager for Broad-Area Search - Final Report on Project PL09-NPMI-PD07 (PNNL-55180)

Tedeschi¹,

Bernacki²,

Kelly³

et al. 2011

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SummaryThis report describes research and development efforts toward a novel passive millimeter-wave (mmwave) electromagnetic imaging device for broad-area search. It addresses the technical challenge of detecting anomalies that occupy a small fraction of a pixel. The purpose of the imager is to pinpoint suspicious locations for cuing subsequent higher-resolution imaging. The technical basis for the approach is to exploit thermal and polarization anomalies that distinguish man-made features from natural features. The scale of applicability ranges from several meters to hundreds of kilometers.This project began by building two research-grade passive mm-wave polarimeters for studying anomalies in ambient scene thermal emissions. The first system consisted of a full polarimeter to take single-channel imaging data using a 2D elevation and azimuthal steerable scanner. It was conservatively designed as a balanced Dicke switching radiometer to obtain reliable phenomenological data from the field. It was later adapted into a differential unbalanced Dicke radiometer that performed comparative radiance and polarimetry measurements between two closely aligned but slightly different views of a common scene. This differential radiometer afforded new insights into the small but real polarimetric changes that complex scenes can display as a result of man-made disturbances or, from reflective or angular materials that reflect/scatter efficiently the cold overhead skyshine into the field-of-view (FOV) of a down-looking imaging radiometer. The results were surprisingly devoid of scene clutter from natural scattering and reflective surfaces, presumably because of the random raking, fractal-like textures of natural surfaces. In contrast, surfaces or materials disturbed by non-random actions, such as human foot traffic over grass, produced notable radiometric anomalies. Subsequently, we designed and built a larger differential imager using a two-aperture binocular system to give better angular resolution. This system worked remarkably well and has provided surprisingly crisp differential scene data that appears to substantiate an important thesis of this proposed work: that differential thermal imagery using a large baseline offset between two imaging telescopes could generate sub-Rayleigh limit spatial resolution of small anisotropies induced into their emitted or scattered radiation. Demonstrated capabilities during the project include: We were able to provide a complete and sensitive Stokes analysis of the mm-wave radiation. All radiation has two vector quantities that completely describe the amplitude and phase of the E-and B-fields, and the changes of these field quantities can be quantified as a four-component vector known as the Stokes vector. Rapid analysis of this vector (I, Q, U, V) can be made with full polarimeters, and we carried out this work near to the theoretical radiometric sensitivities predicted by classical formulae. From an analysis of the Stokes vectors for sundry different materials and scenarios of observa...

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Section: Final 15 Years Of Study To Evaluate Coherent Array Imagersmentioning

confidence: 99%

A Novel Passive Millimeter Imager for Broad-Area Search - Final Report on Project PL09-NPMI-PD07 (PNNL-55180)

Tedeschi¹,

Bernacki²,

Kelly³

et al. 2011

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“…Background H IGH resolution space-based optical imaging systems require large apertures to achieve high angular resolution. To ameliorate the problem of increased mass and volume associated with traditional monolithic telescopes, a design involving a nine-telescope array (U.S. patent 5 905 591) has been built and demonstrated in a testbed known as "Star-9" [1]. The telescope design involves inexpensive and easy to produce all-spherical optics.…”

Section: Introductionmentioning

confidence: 99%

The Control System of a Distributed Aperture Imaging Testbed

Aubrun

Bishop

et al. 2010

IEEE Trans. Contr. Syst. Technol.

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Star-9 is an experimental demonstration of distributed-aperture imaging built at the Lockheed Martin Advanced Technology Center. White light from a scene generator enters an array of nine telescopes and is combined at a focused image plane. Relative aberrations from each telescope are regulated by a control system using phase diversity and active relay mirrors. A Weiner filter is applied to the image, and the resulting angular resolution and image quality are nearly diffraction-limited with the diameter of the array. The control system takes estimates from the phase diversity algorithm and uses them to command mirrors to adjust tip, tilt, and piston in each telescope. Each active mirror has inductive position sensors for local position control. The mirrors are actuated by picomotors and inchworm motors. In addition to tip/tilt/piston errors, the control system is equipped to correct for pupil geometry and rotation errors, and to perform field of regard steering. In this paper, we present details on the control system's local sensing, control law synthesis, and precision actuation methodology. We also describe the incorporation of phase diversity and automated phasing algorithms with the control system and give performance results.Index Terms-Active optics control system, distributed aperture, Fizeau imaging system, multiple telescope array, phased array telescope.

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“…This exit pupil then passes through a small aperture telescope and a fine-resolution image of the object is formed onto a detector array in the focal plane. Much of the work associated with distributed aperture imaging systems has been in the context of imaging with passive illumination; researchers have demonstrated the ability to perform diffraction limited imaging with such a system [1]. In this paper we consider an active, distributed aperture system that uses flood-illumination of the object with a pulsed laser.…”

Section: Introductionmentioning

confidence: 99%

Distributed aperture active imaging

Marron

Kendrick

2007

SPIE Proceedings

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With a distributed aperture imaging system, one creates a large imaging aperture by combining the light from a series of distributed telescopes. In doing this, one can construct a fine-resolution imaging system with reduced volume. In this paper we present work on distributed aperture, active imaging systems that use coherent detection and digital image formation. In such a system, the image formation process incorporates digital correction of optical and atmospheric phase errors. Here we discuss the principles underlying this method and present results from laboratory experiments and field experiments performed over a 0.5 km outdoor test range.

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Wide-field Fizeau imaging telescope: experimental results

Cited by 50 publications

References 9 publications

A Novel Passive Millimeter Imager for Broad-Area Search - Final Report on Project PL09-NPMI-PD07 (PNNL-55180)

A Novel Passive Millimeter Imager for Broad-Area Search - Final Report on Project PL09-NPMI-PD07 (PNNL-55180)

The Control System of a Distributed Aperture Imaging Testbed

Distributed aperture active imaging

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