The Navy Precision Optical Interferometer is an astronomical optical interferometer operating near Flagstaff, Arizona. A
joint program between the United States Naval Observatory, the Naval Research Laboratory and Lowell Observatory, it
has historically been involved in space imagery and astrometry. More recent work has pushed for the addition of more
baselines. It is currently capable of co-phasing 6 elements, so the commissioning of additional baselines requires ease of
use and reconfigurability. At the time of this publication, a seventh station has been added and the final commissioning
work on an eighth and ninth station are being completed. These last two stations will increase the longest baseline to 435
meters. This paper discusses the work to date on adding these stations and provides details on increased capabilities.
The turbulent effects from the Earth’s atmosphere degrade the performance of any optical
system within it. There have been numerous studies in the effects of atmospheric turbulence
on an imaging system that is pointed vertically to the sky looking at distant objects and the
seeing conditions associated with it. We investigate the calculation of the seeing conditions
with an imaging system pointed horizontally in terrestrial and maritime environments. We
have acquired video data of different horizontal paths in the infrared wavelengths and
performed data analysis that will be the basis of new characterizations and modeling of
horizontal path atmospheric turbulence.
Adaptive Optics (AO) is an ensemble of techniques that aims at the remedial of the deleterious effects that the Earth's
turbulent atmosphere induces on both imagery and signal gathering in real time. It has been over four decades since the
first AO system was developed and tested. During this time important technological advances have changed profoundly
the way that we think and develop AO systems. The use of Micro-Electro-Mechanical-Systems (MEMS) devices and
Liquid Crystal Devices (LCD) has revolutionized these technologies making possible to go from very expensive, very
large and power consuming systems to very compact and inexpensive systems. These changes have rendered AO
systems useful and applicable in other fields ranging from medical imaging to industry. In this paper we will review the
research efforts at the Naval research Laboratory (NRL) to develop AO systems based on both MEMs and LCD in order
to produce more compact and light weight AO systems.
The Naval Research Laboratory has developed a method for simulating atmospheric turbulence and a testbed that simulates its aberrations using a liquid crystal (LC) spatial light modulator (SLM). This testbed allows the simulation of so-called atmospheric seeing conditions ranging from very poor to very good and different algorithms may be easily employed on the device for comparison. Many models for simulating turbulence often neglect temporal transitions along with different seeing conditions. Using the statistically independent set of Karhunen-Loeve polynomials in conjunction with Kolmogorov statistics in this approach provides a spatial and temporal model for simulating turbulence. An added benefit to using an LC SLM is its low cost; and multiple devices can be used to simulate multiple layers of turbulence in a laboratory environment. Current testing using multiple LC SLMs is under investigation at the Naval Research Laboratory.
The observation of satellites at geostationary earth orbits (GEO) from the ground presents some formidable
technical and scientific challenges. In recent years, several approaches have been proposed and some have
undergone field tests. The Naval Research Laboratory has pioneered the use of the Michelson-style sparse
aperture interferometers for this problem by using the Naval Prototype Optical Interferometer (NPOI).
Other groups have proposed the use of Intensity Interferometry to solve this problem. It is in this
framework that we are addressing the issue of comparing Signal-to-Noise-Ratio (SNR) expressions and
numerical simulations for various approaches in order to establish which is the most suitable technique for
ground based observations. In this paper we present a comparison of SNR simulations for a Michelson
Interferometer, an Intensity Interferometer and a filled aperture telescope. We present the basic background
of the two interferometric techniques and the standard SNR expressions for the three approaches. We
review the parameters of the simulations discussing the limitations and we will present the results.
The Naval Prototype Optical Interferometer (NPOI) is the longest baseline at visible wavelengths interferometer in the
world. The astronomical capabilities of such an instrument are being exploited and recent results will be presented. NPOI
is also the largest optical telescope belonging to the US Department of Defense with a maximum baseline of 435 meter
has a resolution that is approximately 181 times the resolution attainable by the Hubble Space Telescope (HST) and 118
times the resolution attainable by the Advanced Electro-Optical System (AEOS). It is also the only optical interferometer
capable of recombining up to six apertures simultaneously. The NPOI is a sparse aperture and its sensitivity is limited by
the size of the unit aperture, currently that size is 0.5 meters. In order to increase the overall sensitivity of the instrument
a program was started to manufacture larger, 1.4 meter, ultra-light telescopes. The lightness of the telescopes
requirement is due to the fact that telescopes have to be easily transportable in order to reconfigure the array. For this
reason a program was started three years ago to investigate the feasibility of manufacturing Carbon Fiber Reinforced
Polymer (CFRP) telescopes, including the optics. Furthermore, since the unit apertures are now much larger than r0 there
is a need to compensate the aperture with adaptive optics (AO). Since the need for mobility of the telescopes, compact
AO systems, based on Micro-Electro-Mechanical-Systems (MEMS), have been developed. This paper will present the
status of our adaptive optics system and some of the results attained so far with it.
The use of Spatial Light Modulators (SLM), Liquid Crystal Devices for atmospheric turbulence simulation in
optical system has increased in the recent years. These devices allow the development of test-beds that can be
used to simulate, analyze and improve optical components or systems in a controlled laboratory environment
before further implementation on the eld. Most research has been performed at visible wavelengths with
the use of a vast array of atmospheric turbulence simulation algorithms. We present preliminary work on an
atmospheric simulation test bed which uses an algorithm developed at NRL with a transmissive high denition
Liquid Crystal Device SLMs for applications in the short-wavelength infrared, with the main focus of interested
at 1550nm. Preliminary results are shown for the application to a high denition re
ective Liquid Crystal Device
SLM for the same wavelength.
For the past decade our group has been involved in the development and test of small
portable Adaptive Optics (AO) systems based on MEMs Deformable Mirrors (DM)
technology. The main trust of this activity was toward what is usually referred as vertical
propagation of the light that is the common situation for astronomical applications.
However, in the past couple of years our efforts have been towards the correction of
horizontal path imagery. In this regime the atmospheric turbulence presents different
types of problems such to make the development of AO systems much more demanding.
Once again one of the starting points for us is the development of a test bed where AO
components and algorithms can be tested under well controlled conditions.
Adaptive optics (AO) systems are well demonstrated in the literature with both laboratory and real-world systems being
developed. Some of these systems have employed MEMS deformable mirrors as their active corrective element. More
recent work in AO for astronomical applications has focused on providing correction in more than one conjugate plane.
Additionally, horizontal path AO systems are exploring correction in multiple conjugate planes. This provides
challenges for a laboratory system as the aberrations need to be generated and corrected in more than one plane in the
optical system. Our work with compact AO systems employing MEMS technology in addition to liquid crystal spatial
light modulator (SLM) driven aberration generators has been scaled up to a two conjugate plane testbed. Using two
SLM based aberration generators and two separate wavefront sensors, the system can apply correction with two MEMS
deformable mirrors. The challenges in such a system are to properly match non-identical components and weight the
correction algorithm for correcting in two planes. This paper demonstrates preliminary results and analysis with this
system with wavefront data and residual error measurements.
The Naval Prototype Optical Interferometer (NPOI) is the longest baseline interferometer operating at visible
wavelengths in the world. The astronomical capabilities of such an instrument are being exploited and recent results will
be presented. NPOI is also the largest optical telescope belonging to the US Department of Defense with a maximum
baseline of 435 meter has a resolution that is approximately 181 times the resolution attainable by the Hubble Space
Telescope (HST) and 118 times the resolution attainable by the Advanced Electro-Optical System (AEOS). It is also the
only optical interferometer capable of recombining up to six apertures simultaneously. The NPOI is a sparse aperture and
its sensitivity is limited by the size of the unit aperture, currently that size is 0.5 meters. In order to increase the overall
sensitivity of the instrument a program was started to manufacture larger, 1.4 meter, ultra-light telescopes. The lightness
of the telescopes requirement is due to the fact that telescopes have to be easily transportable in order to reconfigure the
array. For this reason a program was started three years ago to investigate the feasibility of manufacturing Carbon Fiber
Reinforced Polymer (CFRP) telescopes, including the optics. Furthermore, since the unit apertures are now much larger
than r0 there is a need to compensate the aperture with adaptive optics (AO). Since the need for mobility of the
telescopes, compact AO systems, based on Micro-Electro-Mechanical-Systems (MEMS), have been developed. This
paper will present the status of our adaptive optics system and some of the results attained so far with it.
We report a tentative interferometric detection of an earth-orbiting artificial satellite using optical interferometry. We
targeted four geosynchronous communications satellites with the Navy Prototype Optical Interferometer (NPOI) near
Flagstaff, AZ, and obtained interferometric fringes on one of them, DIRECTV-9S. We used an east-west 15.9-meter
baseline of the NPOI and took data in 16 spectral channels covering the 500-850 nm wavelength range. Observations
took place during the "glint season" of 28 February to 3 March 2008, when the geometry of the solar panel arrays and the
Sun's position creates glints as bright as 2nd magnitude of a few minutes' duration each night. We detected fringes on
the satellite at approximately the 2 σ level on 1 March at magnitude 4.5. Subsequent analysis shows that the fringe
amplitudes are consistent with a size scale of 2 meters (50 nanoradians at geosynchronous orbit) in an east-west
direction. This detection shows that interferometric detection of satellites at visual wavelengths is possible, and suggests
that a multi-baseline interferometer array tailored to the angular size and brightness of geosynchronous satellites could
lead to images of these satellites.
The Naval Research Laboratory has developed a new method for generating atmospheric turbulence and a testbed that
simulates its aberrations far more inexpensively and with greater fidelity using a Liquid Crystal (LC) Spatial Light
Modulator (SLM) than many other methods. This system allows the simulation of atmospheric seeing conditions ranging
from very poor to very good and different algorithms may be easily employed on the device for comparison. These
simulations can be dynamically generated and modified very quickly and easily. In addition, many models for simulating
turbulence often neglect temporal transitions along with different seeing conditions. Using the statistically independent
set of Karhunen-Loeve polynomials in conjunction with Kolmogorov statistics in this model provides an accurate spatial
and temporal model for simulating turbulence. An added benefit to using a LC SLM is its low cost; and multiple devices
can be used to simulate multiple layers of turbulence in a laboratory environment. Current testing with using multiple LC
SLMs is under investigation at the Naval Research Laboratory and the Naval Postgraduate School.
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 we have started an upgrade that aims at developing a Multi Conjugate Adaptive
Optics (MCA) test-bed. This test bed is based on the use of multiple Liquid Crystal Spatial Light
Modulators (LCSLMs) for producing different phase screens at different spatial locations within the
set-up. Details of this new set-up are presented in another paper in these proceedings. This paper
specifically deals with the analytic portion of the MCAO test-bed.
Adaptive optics systems have advanced considerably over the past decade and have become common tools
for optical engineers. The most recent advances in adaptive optics technology have lead to significant
reductions in the cost of most of the key components. Most significantly, the cost of deformable elements
and wavefront sensor components have dropped to the point where multiple deformable mirrors and Shack-
Hartmann array based wavefront sensor cameras can be included in a single system. Matched with the
appropriate hardware and software, formidable systems can be operating in nearly any sized research
laboratory. The significant advancement of MEMS deformable mirrors has made them very popular for use
as the active corrective element in multi-conjugate adaptive optics systems so that, in particular for
astronomical applications, this allows correction in more than one plane. The NRL compact AO system and
atmospheric simulation systems has now been expanded to support Multi Conjugate Adaptive Optics
(MCAO), taking advantage of using the liquid crystal spatial light modulator (SLM) driven aberration
generators in two conjugate planes that are well separated spatially. Thus, by using two SLM based
aberration generators and two separate wavefront sensors, the system can measure and apply wavefront
correction with two MEMS deformable mirrors. This paper describes the multi-conjugate adaptive optics
system and the testing and calibration of the system and demonstrates preliminary results with this system.
The Naval Prototype Optical Interferometer (NPOI) is the longest baseline at visible
wavelengths interferometer in the world. The astronomical capabilities of such an
instrument are being exploited and recent results will be presented. NPOI is also the
largest optical telescope belonging to the US Department of Defense with a maximum
baseline of 435 meter has a resolution that is approximately 181 times the resolution
attainable by the Hubble Space Telescope (HST) and 118 times the resolution attainable
by the Advanced Electro-Optical System (AEOS). It is also the only optical
interferometer capable of recombining up to six apertures simultaneously. The NPOI is a
sparse aperture and its sensitivity is limited by the size of the unit aperture, currently that
size is 0.5 meters. In order to increase the overall sensitivity of the instrument a program
was started to manufacture larger, 1.4 meter, ultra-light telescopes. The lightness of the
telescopes requirement is due to the fact that telescopes have to be easily transportable in
order to reconfigure the array. For this reason a program was started three years ago to
investigate the feasibility of manufacturing Carbon Fiber Reinforced Polymer (CFRP)
telescopes, including the optics. Furthermore, since the unit apertures are now much
larger than r0 there is a need to compensate the aperture with adaptive optics (AO). Since
the need for mobility of the telescopes, compact AO systems, based on Micro-Electro-
Mechanical-Systems (MEMS), have been developed. This paper will present the status of
our adaptive optics system and some of the results attained so far with it.
Infrared imaging has typically relied on quantum well and quantum dot focal plane arrays which
inherently have a narrow spectral response. In order to detect 'color' information within the
infrared spectrum, several detectors are used with a filtering scheme to sample different
wavelengths and the data is post-processed to yield multi-spectral images. Using the 320 x 256
pixel quantum dot-in-a-well (DWELL) infrared focal plane arrays developed by the University
of New Mexico's Center for High Technology Materials offers numerous advantages including
wide spectral response (1 μm to 30 μm +) and response tunability. The latter of these allows
multi-spectral imaging without switchable filters. A simple external bias voltage is applied to
tune spectral response on a pixel by pixel basis. This presentation outlines the work to date and
future work to be accomplished on this project to implement tunable color imaging capabilities
in several wavelengths throughout the infrared spectrum using the DWELL structure. Precision
radiometry, similar to astronomical photometry using a charge coupled device, will be realized in
addition to color imaging capabilities, requiring a full characterization of noise processes and
techniques for noise reduction in this novel device.
The Naval Research Laboratory (NRL) has been conducting research
in novel portable adaptive optics systems for many years. These systems
are tested exhaustively in a laboratory environment before being migrated
to field experiments on astronomical telescopes. As part of the laboratory
testing, an atmosphere simulator hardware testbed has been developed to
provide a realization of atmospheric turbulence based on Kolmogorov
statistics. In this testbed, a high-pixel count liquid crystal spatial light
modulator induces the atmospheric turbulence through a series of
computer calculated phase maps. User controls allow a wide range of
telescope apertures and seeing conditions to be explored for testing the
adaptive optics system. This paper explains and reports on the use of this
dynamic and expandable system in characterizing the performance and
optimization parameters of the adaptive optics systems at NRL.
The Naval Research Laboratory (NRL) has been exploring Carbon Fiber Reinforced
Polymer (CFRP) material for telescope construction, including all support structures and
optics, resulting in over an order of magnitude reduction in weight over traditional steel
and glass telescopes. This has allowed the exploration of novel micro-positioning motors
for telescope pointing. A typical inertial drive telescope pointing system relies on the
large mass of the optics and telescope assembly. A prototype 0.4 meter telescope has
been developed with a total mass less than 8 kilograms necessitating the investigation of
non-traditional drive systems. This paper reports on many of the prototype 0.4 meter
telescope specifications, including optics, structure and drive hardware. Initial testing is
of the open-loop drive system is also reported.
The Naval Research Laboratory (NRL) has been exploring the use of meter class telescopes using Carbon Fiber Reinforced Polymer (CFRP) material for support structure and optics, resulting in over an order of magnitude reduction in weight over traditional steel and glass telescopes. In conjunction with Composite Mirror Applications (CMA), for the past three years this program has proceeded from conceptual phase to prototype development. In this paper we will review the various stages of this program. We will also present the status of our 0.4 meter and 1.4 meter telescopes. Experimental results from these developments and testing will be shown.
The Naval Research Laboratory (NRL) has been conducting research
in novel portable adaptive optics systems for many years. These systems
are tested exhaustively in a laboratory environment before being migrated
to field experiments on astronomical telescopes. As part of the laboratory
testing, an atmosphere simulator hardware testbed has been developed to
provide a realization of atmospheric turbulence based on Kolmogorov
statistics. In this testbed, a high-pixel count liquid crystal spatial light
modulator induces the atmospheric turbulence through a series of
computer calculated phase maps. User controls allow a wide range of
telescope apertures and seeing conditions to be explored for testing the
adaptive optics system. This paper explains and reports on the use of this
dynamic and expandable system in characterizing the performance and
optimization parameters of the adaptive optics systems at NRL.
An all reflective Shack Hartmann style wavefront sensor has been developed using a Sandia National
Laboratory segmented Micro-Electro-Mechanical (MEM) deformable mirror. This wavefront sensor is
presently being explored for use with adaptive optics systems at the Naval Prototype Optical Interferometer
and other experimental adaptive systems within the Naval Research Laboratory. The 61 MEM mirror
segments are constructed in a hexagonal array and each segment can be constructed with either flat or
optically powered surfaces. The later allows each mirror segment to bring its subaperture of light to a focus
on an imaging array, creating an array of spots similar to a Shack Hartmann. Each mirror segment has tip,
tilt and piston functionality to control the position of the focused spot such that measurement of the applied
voltage can be used to drive a deformable mirror. As the system is reflective and each segment is
controllable, this wavefront sensor avoids the light loss associated with refractive optics and has larger
dynamic range than traditional Shack Hartmann wavefront sensors. 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 of the open-loop performance, including repeatability
and linearity measurements. The suitability of using the MEM deformable mirror as a high dynamic range
reflective wavefront sensor will be discussed and compared to current wavefront sensors and future work
will be discussed.
The Naval Prototype Optical Interferometer (NPOI) is the longest baseline at visible wavelengths interferometer in the world. The astronomical capabilities of such an instrument are being exploited and recent results will be presented. NPOI is also the largest optical telescope belonging to the US Department of Defense with a maximum baseline of 435 meter has a resolution that is approximately 181 times the resolution attainable by the Hubble Space Telescope (HST) and 118 times the resolution attainable by the Advanced Electro-Optical System (AEOS). It is also the only optical interferometer capable of recombining up to six apertures simultaneously. The NPOI is a sparse aperture and its sensitivity is limited by the size of the unit aperture, currently that size is 0.5 meters. In order to increase the overall sensitivity of the instrument a program was started to manufacture larger, 1.4 meter, ultra-light telescopes. The lightness of the telescopes requirement is due to the fact that telescopes have to be easily transportable in order to reconfigure the array. For this reason a program was started three years ago to investigate the feasibility of manufacturing Carbon Fiber Reinforced Polymer (CFRP) telescopes, including the optics. Furthermore, since the unit apertures are now much larger than r0 there is a need to compensate the aperture with adaptive optics (AO). Since the need for mobility of the telescopes, compact AO systems, based on Micro-Electro-Mechanical-Systems (MEMS), have been developed. This paper will present the status of our adaptive optics system and some of the results attained so far with it.
Sandia National Laboratory has constructed several segmented MEMS 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 desired 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. This paper reports on experiments and analysis of the open-loop performance, including repeatability measurements.
Many electro optical devices are now available for compensating atmospheric distortions in optical systems. To support the characterization of these devices in a consistent fashion a common testbed that physically simulates these atmospheric aberrations is required. This paper reports on a system that realizes seeing conditions ranging from very poor to excellent and feeds these wavefronts to the compensation device under test. The testbed provides quantitative characterization of the system under test and evaluates residual wavefront error.
Deployment costs of large aperture systems in space or near-space are directly related to the weight of the system. In
order to minimize the weight of conventional primary mirrors and simultaneously achieve an agile system that is capable
of a wider field-of-view (FOV) and true optical zoom without macroscopic moving parts, we are proposing a
revolutionary alternative to conventional zoom systems where moving lenses/mirrors and gimbals are replaced with
lightweight carbon fiber reinforced polymer (CFRP) variable radius-of-curvature mirrors (VRMs) and MEMS
deformable mirrors (DMs). CFRP and MEMS DMs can provide a variable effective focal length, generating the
flexibility in system magnification that is normally accomplished with mechanical motion. By adjusting the actuation of
the CFRP VRM and MEMS DM in concert, the focal lengths of these adjustable elements, and thus the magnification of
the whole system, can be changed without macroscopic moving parts on a millisecond time scale. In addition, adding
optical tilt and higher order aberration correction will allow us to image off-axis, providing additional flexibility.
Sandia National Laboratories, the Naval Research Laboratory, Narrascape, Inc., and Composite Mirror Applications,
Inc. are at the forefront of active optics research, leading the development of active systems for foveated imaging, active
optical zoom, phase diversity, and actively enhanced multi-spectral imaging. Integrating active elements into an
imaging system can simultaneously reduce the size and weight of the system, while increasing capability and flexibility.
In this paper, we present recent progress in developing active optical (aka nonmechanical) zoom and MEMS based
foveated imaging for active imaging with a focus on the operationally responsive space application.
Many devices are now being used in Adaptive Optics Systems for compensating atmospheric
distortions. We have developed a testbed that simulates atmospheric aberrations using a Liquid
Crystal Spatial Light Modulator and the speed in which they vary may be controlled. This system
allows the simulation of seeing conditions ranging from very poor to very good and these aberrations
to be compensated by a second device. This second device may be a deformable mirror in
conjunction with an Adaptive Optics System. Using these two devices simultaneously provides a
well-defined quantitative characterization of the system and residual wavefront error using Point
Spread Function and interferometric techniques.
Sandia National Laboratory has constructed several segmented MEMS
deformable mirrors that are under investigation for their suitability in Adaptive Optics
systems for the Naval Research Laboratory. These mirrors are constructed in a
hexagonal array and have 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 desired reference location, and the measurement of the applied voltage can be
used directly to power a similar flat MEMS deformable mirror. This paper reports on the
suitability of this reflective wavefront sensor for closed-loop Adaptive Optics
applications.
The use of adaptive and active optics (AO) is enabling the construction and test of flexible optical systems with
performances unprecedented. This flourishing of technical advances is also due to the availability of new technologies
that are much lower in cost, much easier to implement and use. Among these new technologies the use of Micro-Electro-
Machined (MEM) mirrors is one of the primary sources of innovation. Several groups are actively working in bringing to
fruition AO systems based on MEMs technologies and at the same time several groups are working to improve the
MEMs technology and tailor it more and more towards various aspects of the AO problems. This technology is
especially interesting to the Navy Prototype Optical Interferometer (NPOI) upgrade. In this field several AO systems
have to be constructed and operated. It is of the outmost importance that each system has a less complex and costly
approach than classical AO systems.
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, demonstrated, and patented imaging systems that are capable of variable optical magnification with no macroscopic moving parts.
The portability of meter-class telescopes has been limited by the weight of the mirror, tube assembly and the mount required to provide pointing and tracking. The novel lightweight carbon fiber reinforced polymer telescopes being developed for array population at the Naval Prototype Optical Interferometer are orders of magnitude lighter than traditional telescopes. When combined with a lightweight carbon fiber mount, these telescopes will be easily transportable from one telescope station to another to change the interferometer baseline. The mount for a lightweight telescope is currently under development at Composite Mirror Applications, Inc. This paper reports on the design constraints of the mount, the scalability to larger aperture telescopes and the integration of sensors to measure the performance characteristics of this system during operation.
This paper reports on the measurement and reconstruction using two algorithms of an Adaptive Tilt Mirror's (ATM) reflected wavefront using a Shack-Hartmann (SH) based wavefront sensor. The ATM consists of a deformable mirror mounted onto a fast steering mirror platform. Reconstruction of the wavefront was performed using Finite Difference and Finite Element reconstruction algorithms for comparison. The SH wavefront sensor with high frame-rate readout camera and the two types of software reconstructors provide a visualization of the ATM's surface while being moved physically on the fast steering mirror platform at a rate of 30 Hz.
Adaptive optics systems are commonly added onto conventional astronomical telescopes to improve the wavefront quality in the presence of atmospheric turbulence. Recent successes in the development of carbon fiber reinforced polymer telescopes have significantly reduced the weight of meter class telescopes making them portable, however, most adaptive optics systems continue to be constructed on large optical benches. The Navy Prototype Optical Interferometer is developing several 1.4 m portable telescope with internal wavefront correction. As part of this upgrade, a prototype 0.4 m aperture telescope has been constructed and a light weight, compact adaptive optics system is being developed. We present in this paper the design of an adaptive optics system for the lightweight telescope. The key to this system is the incorporation of a compact wavefront correction device and a novel collimation optic within the base of the telescope.
A 0.4 meter lightweight telescope has been developed as a prototype for a future 1.4 meter telescope to be implemented at the Naval Prototype Optical Interferometer (NPOI). Using carbon fiber construction for all components, including optics, an order of magnitude reduction in weight is easily obtainable, with the estimated weight of the 1.4 meter telescope being less than 300 pounds. However, lightweight composite materials traditionally offer certain drawbacks, such as different material behavior and vibration characteristics from conventional materials and difficulty in obtaining optical surface quality. This paper describes the characterization of the mechanical properties of the advanced materials used in the construction of these telescopes and includes measurements of the optical figure obtained with carbon fiber construction.
In this paper we present results using a compact, portable adaptive optics system. Such compact systems are possible thanks to the use of new technologies based on Micro-Electro-Machined deformable mirrors and liquid crystals devices among other possible technologies. In the paper we will illustrate our experience with such devices; we will address the pros and cons of such approach, some experimental results and new trends for future tests.
In most adaptive optics systems, there are two elements that control wavefront correction. These are a tip/tilt platform and a deformable mirror. The tip/tilt platform can correct the lower order aberrations like piston, tip and tilt. The deformable mirror can correct the higher order aberrations like defocus, astigmatism, etc. By mounting the deformable mirror onto the tip/tilt platform, one corrective element is now used in the system, rather than two. This is made possible by the use of a lightweight MEMS deformable mirror, as traditional deformable mirrors tend to be quite large and bulky. Other advantages are that there is less overall optics and a simpler alignment process needed with this configuration.
An optical testbed has been developed for the comparative analysis of wavefront sensors based on a modified Mach Zender interferometer design. This system provides simultaneous measurements of the wavefront sensors on the same camera by using a common aberrator. The initial application for this testbed was to evaluate a Shack-Hartmann and Phase Diversity wavefront sensors referenced to a Mach-Zender interferometer. This testbed has the added benefit of being able to train the deformable mirror against the spatial light modulator and evaluate its ability to compensate the spatial light modulator. In the paper we present some results from the wavefront sensors along with preliminary results from the wavefront corrective elements in the optical testbed.
In this paper we present some preliminary results of an ultra-light weight telescope manufactured entirely with Carbon Fiber Reinforced Polymer (CFRP), including the optics, coupled with a light weight Adaptive Optics (AO) system. This research has many scopes, ranging from long baseline interferometry to laser communications. In this paper we will examine some of the mechanical properties of the telescope and describe the testing that the system is undergoing.
The use of adaptive and active optics (AO) is enabling the construction and test of flexible optical systems with performances unprecedented. This flourishing of technical advances is also due to the availability of new technologies that are much lower in cost, much easier to implement and use. Among these new technologies the use of Micro-Electro-Machined (MEM) mirrors is one of the primary sources of innovation. Several groups are actively working in bringing to fruition AO systems based on MEMs technologies and at the same time several groups are working to improve the MEMs technology and tailor it more and more towards various aspects of the AO problems. In this paper we will presents an overview of MEMs adaptive optics problems. We will especially focus on our experience in this field and discuss results from our AO system. We will discuss pros and cons on the use of MEM for adaptive optics and elaborate on our experience on field-testing of these devices. This paper will also briefly discuss the broader use of adaptive optics in fields other than atmospheric compensation.
KEYWORDS: Microelectromechanical systems, Mirrors, Analog electronics, Adaptive optics, Deformable mirrors, Control systems, Manufacturing, Commercial off the shelf technology, Actuators, Electronics
The use of Micro-Electro-Machined (MEM) devices as deformable mirrors (DM) for active and adaptive optics is increasing dramatically. Such increases are due to both the cost and simplicity of use of these devices. Our experience with MEM DMs has been positive, however the controlling protocols of these devices presents some issues. Based on our experience and needs we decided to design a generic controller based on a fast communication protocol. These requirements have pushed us to design a system around a USB 2.0 protocol. In this paper we present our architectural design for such controller. We present also experimental data and analysis on the performance of the controller. We describe the pros and cons of such approach versus other techniques. We will address how general such architecture is and how portable is to other systems.
In most adaptive optics systems, there are two elements that control wavefront correction, a fast steering mirror that corrects tip and tilt and a deformable element that corrects higher order aberrations. By mounting the deformable element onto the tip/tilt platform, complete wavefront compensation is now possible at one location in an optical system. The advantage of mounting a lightweight Micro Electro-Machined (MEM) deformable mirror on a tip/tilt stage is both fewer optical components and a simpler alignment process. The impact on the frequency stability of the of the MEM device on the tip/tilt platform is approximately 5% of the driving frequency.
Adaptive optics techniques have been demonstrated in both laboratory and field tests, with a great level of scientific satisfaction, especially in astronomical and surveillance communities. Such successes have sparked the interest for these techniques in other fields, like biomedical imaging and industrial applications. However, to decrease complexity and costs, both very important issues for applications other than astronomical and surveillance, new technologies have to be brought to fruition. MEMS are becoming a very important player in this arena. We describe a portable adaptive optics (AO) system based on a MEM device that has been tested in both laboratory and field experiments. Results of these tests are discussed. Capabilities and shortcomings of this technology are discussed. A look at future applications and trends is given.
In this paper, we summarize progress in free space laser propagation research at the U.S. Naval Research Laboratory, specifically in the context of propagating and detecting signals through the atmosphere in a maritime environment. Transmission through the atmosphere over large bodies of water presents different challenges than transmission through the atmosphere over land. Our paper reports some of these findings as well as progress in our collaborative efforts to mitigate turbulence to enhance our data links.
An optical testbed has been developed for the comparative analysis of wavefront sensors based on a modified Mach Zender interferometer design. This system provides simultaneous measurements of the wavefront sensors on the same camera by using a common aberrator. The initial application for this testbed was to evaluate a Shack-Hartmann and Phase Diversity wavefront sensors referenced to a Mach-Zender interferometer. In the current configuration of the testbed, aberrations are controlled using a liquid crystal spatial light modulator, and corrected using a deformable mirror. This testbed has the added benefit of being able to train the deformable mirror against the spatial light modulator and evaluate its ability to compensate the spatial light modulator. In the paper we present results from the wavefront sensors in the optical testbed.
Modern microprocessors are rapidly reaching performance levels that make them suitable for wavefront sensing and correction. This has the combined advantage of reducing system costs and a smaller footprint for the control system. These reductions have provided adaptive optics system designers with the capability of producing small form factor and low power system compared to just a few years ago. In recent work on the NRL portable adaptive optics system, our group has investigated implementing alternative computer peripherals for deformable and tip/tilt mirror control to support the low power low cost approach. This paper reports on characterization of several computer peripherals for use within adaptive optics systems with a focus on minimizing size, weight, cost and power consumption.
Adaptive optics techniques have been proved in both laboratory and field tests to the satisfaction especially of the astronomical and surveillance communities. Such success have sparked interests in other fields, however, to increase efficiency and lower costs new technologies have to be brought to fruition. MEMs are becoming a very important player in this arena. In this paper we describe a portable adaptive optics (AO) system that has been tested in both laboratory and field experiments. Results of these tests will be discussed. Capabilities and shortcomings of this technology will be discussed. A look at future applications and trends will be given.
In most adaptive optics systems, there are two elements that control wavefront correction. These are a tip/tilt platform and a deformable mirror. The tip/tilt platform can correct the lower order aberrations like piston, tip and tilt. The deformable mirror can correct the higher order aberrations like defocus, coma, spherical, etc. Currently in this method, two conjugate planes must be created by the two elements. It is also a necessity that these two conjugate planes be identical. This requires more optics and a more complicated alignment process. In this project a deformable mirror is mounted onto a tip/tilt platform resulting in the two correction elements having the same conjugate plane, automatically. This is made possible by the use of a lightweight deformable mirror, as traditional deformable mirrors tend to be quite large and bulky. Results of this experimental project will be presented.
Adaptive optics techniques have been proved in both laboratory and field tests to the satisfaction especially of the astronomical and surveillance communities. Such success have sparked interests in other fields, however, to increase efficiency and lower costs new technologies have to be brought to fruition. MEMs are becoming a very important player in this arena. In this paper we describe a portable adaptive optics (AO) system that has been tested in both laboratory and field experiments. Results of these tests will be discussed. Capabilities and shortcomings of this technology will be discussed. A look at future applications and trends will be given.
Adaptive optics techniques have been proved in both laboratory and field tests to the satisfaction especially of the astronomical and surveillance communities. Such success have sparked interests in other fields, however, to increase efficiency and lower costs new technologies have to be brought to fruition. MEMs are becoming a very important player in this arena. In this paper we describe a portable adaptive optics (AO) system that has been tested in both laboratory and field experiments. Results of these tests will be discussed. Capabilities and shortcomings of this technology will be discussed. A look at future applications and trends will be given.
The idea of using liquid crystal devices as an adaptive optics component has been proposed by several authors. In recent years a vigorous research effort has been carried out, and it is still flourishing, in several countries. Mainly the research and experimental work has been concentrated in the USA, U.K. and Russia. There are several reasons why liquid crystals may represent a valid alternative to the traditional deformable mirror technology that has been used for the past two decades or so. The main attractiveness of LC resides in the cost. Current deformable mirror technology has a range of price going from $2K to $15K per channel. LC technology promises to be at least a couple of orders of magnitude cheaper. Other reasons are connected with reliability, low power consumption and with a huge technological momentum based on a wide variety of industrial applications. In this paper we present some preliminary characterizations of a new, large format device. Such devices have the potential for extremely high-resolution wave-front control due to the over 10,000 corrective elements. The characterization of the device, so far, consists of measurements of the overall optical quality and of the phase control relationship
The cost of adaptive optics technology is dominated by the cost of current deformable mirror technology which has a range of price going from $2K to $15K per channel. Liquid crystal technology promises to be at least a couple of orders of magnitude cheaper. Liquid crystals offer other advantages such as reliability, low power consumption and with a huge technological momentum based on a wide variety of industrial applications. In this paper we present some preliminary characterizations of a new, large format liquid crystal device. Such devices have the potential for extremely high-resolution wave-front control due to the over 10,000 corrective elements.
The idea of using liquid crystal devices as an adaptive optics component has been proposed by several authors. In recent years a vigorous research effort has been carried out, and it is still flourishing, in several countries. Mainly the research and experimental work has been concentrated in the USA, U.K. and Russia. There are several reasons why liquid crystals may represent a valid alternative to the traditional deformable mirror technology that has been used for the past two decades or so. The main attractiveness of LC resides in the cost. Current deformable mirror technology has a range of price going from $2K to $15K per channel. LC technology promises to be at least a couple of orders of magnitude cheaper. Other reasons are connected with reliability, low power consumption and with a huge technological momentum based on a wide variety of industrial applications. In this paper we present some preliminary characterizations of a new, large format device. Such devices have the potential for extremely high-resolution wave-front control due to the over 10,000 corrective elements. The characterization of the device, so far, consists of measurements of the overall optical quality and of the phase control relationship.
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