With continued advances in cylindrical optics manufacturing capability, interferometric testing of such optics is difficult.
This is due to the lack of a well characterized cylindrical reference surface. In this paper, the Random Fiber Test (RFT)
is used to experimentally quantify the quality of fiber surface as a cylindrical reference. The basic idea of the experiment
is to take measurements at different rotations about, and translations along the fiber axis. From these measurements the
quality of the fiber surface in both directions can be determined.
A method of absolute testing of a cylindrical wavefront is presented. The method is a merging of the random ball test method with the fiber optic reference test. The random ball test assumes a large number of interferograms of a good quality sphere with errors that are statistically distributed such that the average of the errors goes to zero. The fiber optic reference test utilizes a specially processed optical fiber to provide a high quality reference wave from an incident line focus from the cylindrical wave under test. A simulation and preliminary experiment results are presented which indicate that this method can significantly reduce the effects of fiber surface errors, yielding more accurate cylindrical wave measurements.
Applications for Cylindrical and near-cylindrical surfaces are ever-increasing. However, fabrication of high quality
cylindrical surfaces is limited by the difficulty of accurate and affordable metrology. Absolute testing of such surfaces
represents a challenge to the optical testing community as cylindrical reference wavefronts are difficult to produce. In
this paper, preliminary results for a new method of absolute testing of cylindrical wavefronts are presented. The method
is based on the merging of the random ball test method with the fiber optic reference test. The random ball test assumes a
large number of interferograms of a good quality sphere with errors that are statistically distributed such that the average
of the errors goes to zero. The fiber optic reference test utilizes a specially processed optical fiber to provide a clean
high quality reference wave from an incident line focus from the cylindrical wave under test. By taking measurements at
different rotation and translations of the fiber, an analogous procedure can be employed to determine the quality of the
converging cylindrical wavefront with high accuracy. This paper presents and discusses the results of recent tests of this
method using a null optic formed by a COTS cylindrical lens and a free-form polished corrector element.
In support of improved gamma-ray detectors for astrophysics and observations of Terrestrial Gamma-ray Flashes (TGFs), we have designed a new approach for the collection and detection of optical photons from scintillators such as Sodium Iodide and Lanthanum Bromide using a light concentrator coupled to an Avalanche photodiode (APD). The APD has many advantages over traditional photomultiplier tubes such as their low power consumption, their compact size, their durability, and their very high quantum efficiency. The difficulty in using these devices in gamma-ray astronomy has been coupling their relatively small active area to the large scintillators necessary for gamma-ray science. Our solution is to use an acrylic Compound Parabolic Concentrator (CPC) to match the large output area of the scintillation crystal to the smaller photodiode. These non-imaging light concentrators exceed the light concentration of focused optics and are light and inexpensive to produce. We present our results from the analysis and testing of such a system including gains in light collecting efficiency, energy resolution of nuclear decay lines, as well as our design for a new, fast TGF detector.
The Geospace Dynamics Observatory (GDO) mission observes the near-Earth region in space called Geospace with
unprecedented resolution, scale and sensitivity. At a distance of 60 Earth Radii (Re) in a near-polar circular orbit and a
~27-day period, GDO images the earth’s full disk with (1) a three-channel far ultraviolet imager, (2) an extreme
ultraviolet imager of the plasmasphere, and (3) a spectrometer in the near to far ultraviolet range that probes any portion
of the disk and simultaneously observes the limb.
The exceptional capabilities of the GDO mission include (1) unprecedented improvement in signal to noise for globalscale
imaging of Earth’s space environment that enable changes in the Earth’s space environment to be resolved with
orders of magnitude higher in temporal and spatial resolution compared to existing data and other approaches, and (2)
unrivaled capability for resolving the temporal evolution, over many days, in local time or latitude with a continuous
view of Earth’s global-scale evolution while simultaneously capturing the changes at scales smaller than are possible
with other methods.
This combination of new capabilities is a proven path to major scientific advances and discoveries. The GDO mission (1)
has the first full disk imagery of the density and composition variability that exist during disturbed “storm” periods and
the circulation systems of the upper atmosphere, (2) is able to image the ionosphere on a global and long time scale
basis, (3) is able to probe the mechanisms that control the evolution of planetary atmospheres, and (4) is able to test our
understanding of how the Earth is connected to the Sun.
This paper explores the optical and technical aspects of the GDO mission and the implementation strategy. Additionally,
the case will be made that GDO addresses a significant portion of the priority mission science articulated in the recent
Solar and Space Physics Decadal Survey.1
A new, economical, lenslet-array-based imaging sensor design is proposed, simulated, and analyzed. In this investigation a bare lenslet array model is first developed in Code V®. The results show that, as expected, intolerable optical cross-talk is present in this simple system. This problem has been addressed in previous systems via the inclusion of a physical image separation layer. The alternative system proposed here to alleviate crosstalk involves the introduction of both polarizers and spectral filters. As a consequence this simple system design also provides spectro-polarimetric resolution. Simulations were developed in order to analyze the system performance of two designs. The simulation results were analyzed in terms of a measure of signal-to-noise ratio (SNR) and in terms of an en-squared energy that includes all subimages. The results show that a design employing only a few spectral filters suppresses crosstalk for objects of small angular extent but does not suppress crosstalk to a tolerable level for 2π steradian illumination, as evidenced by SNR less than one. However, the inclusion of more spectral filters results in a spectro-polarimetric thin imager design that suppresses crosstalk and provides finer spectral resolution without the inclusion of a signal separation layer.
The Marshall Grazing Incidence X-ray Spectrograph (MaGIXS) is a proposed sounding rocket experiment designed to observe
spatially resolved soft X-ray spectra of the solar corona for the first time. The instrument is a purely grazing-incidence
design, consisting of aWolter Type-1 sector telescope and a slit spectrograph. The telescope mirror is a monolithic Zerodur
mirror with both the parabolic and hyperbolic surfaces. The spectrograph comprises a pair of paraboloid mirrors acting as
a collimator and reimaging mirror, and a planar varied-line-space grating, with reflective surfaces operate at a graze angle
of 2 degrees. This produces a flat spectrum on a detector covering a wavelength range of 6-24Å (0.5-1.2 keV). The design
achieves 20 mÅ spectral resolution (10 mÅ /pixel) and 5 arcsec spatial resolution (2.5 arcsec / pixel) over an 8-arcminute
long slit. The spectrograph is currently being fabricated as a laboratory prototype. A flight candidate telescope mirror is
also under development.
We use the two-dimensional Chebyshev polynomials as the basis for decomposition of test data over rectangular apertures, particularly for anamorphic optics. This includes simple optics such as cylindrical lenses and mirrors as well as complex optics, such as aspheric cylindrical optics. The new basis set is strictly orthogonal over rectangles of arbitrary aspect ratio and they correspond well with the aberrations of systems containing such type of optics. An example is given that applies the new basis set to study the surface figure error of a cylindrical Schmidt corrector plate. It is not only an excellent fitting basis but also can be used to flag misalignment errors that are critical to fabrication.
JWST optical component in-process optical testing and cryogenic requirement compliance certification, verification &
validation is probably the most difficult metrology job of our generation in astronomical optics. But, the challenge has
been met: by the hard work of dozens of optical metrologists; the development and qualification of multiple custom test
setups; and several new inventions, including 4D PhaseCam and Leica Absolute Distance Meter. This paper summarizes
the metrology tools, test setups and processes used to characterize the JWST optical components.
We report initial results on designing and manufacturing a Schmidt-like corrector plate for a commercial off-the-shelf cylindrical lens, eliminating the cylindrical equivalent of its spherical aberration. The corrector is made by figuring the correction profile onto a precision glass window, which is subsequently aligned to the cylindrical lens. We have successfully fabricated the first plate and applied it in an interferometric test of a near-cylinder optic. The interferometric data from before and after applying the corrector demonstrates that the modified optic produces a cylindrical test wavefront with <1λ P-V of residual error at 632.8 nm, a >25× reduction compared to the uncorrected case.
The standalone, portable Terahertz (THz) Imaging Profiler Array (TIPA) based on an Offner Relay design has been
constructed as a THz beam profiler and multispectral imager. It integrates a solid-state detector technology (Schottky
Diodes) that can be configured in an array to cover the frequency range from 0.60 to 0.90 THz. The reconfigurable 16
element Schottky diode detector array is utilized along with imaging and scanning mirror modules and system control
hardware and software to produce high spatial or temporal beam profiles of THz beams. Images of THz source profiles
are presented along with THz images of relevant targets. Potential applications are discussed.
Active modelocking of multiple polariton lasers mediated by real time sensing offers novel capabilities for
optically based sensing. We outline a strategy based in part on short range polariton-polariton interactions
and in part on an actively managed external optical field coherent with each of the individual polariton lasers.
This actively managed coherent optical field is required to establish long range coherence between multiple
spatially distinct polariton lasers. Polariton lasers offer nonlinear behavior at excitation levels of a few quanta
of the optical field, time constants of picoseconds or less, and optical wavelength dimensions of individual
lasers. Achievement of useful long range, hundreds of meters, polariton based optical sensing appears
useful, but to require active cohering of arrays of polariton lasers. Continuous metrology and active control of
the system coherence offer unique opportunities for sensing approaching quantum limited operation. We
consider strategies and capabilities of sensing systems based on such arrays of spatially distinct, but
collectively coherent, polariton lasers. Significant advances in a number of technical areas over decades
appear needed to achieve such systems.
Quantifying the results for a multi-conjugate adaptive optics (MCAO) system is more complex than a
traditional adaptive optics (AO) system. The complexity of analyzing a MCAO system stems from using
multiple deformable mirrors (DMs) and quantifying the influence functions at the wavefront sensor (WFS).
In this paper, analysis tools are developed to quantify MCAO performance. Influence functions from two
deformable mirrors are propagated to a WFS using CODEV to simulate an MCAO design comparable to
the Dunn Solar Telescope (DST). Using MATLAB, the propagated influence functions are mapped to the
appropriate field positions, and reconstructor matrices are built using the mapped influence functions. Next,
a correctability analysis was performed using theoretical random phase screens. The developed tools are
versatile and useful as a system design tool and in a laboratory setting.
A mathematical approach for the third order solution for a general zoom lens design is proposed. The design starts with a
first-order layout. Lens elements with the proper refracting power are placed at the proper distances to meet the physical
constraints of the intended lens system. For the third-order design stage, a matrix notation called "Aberration
Polynomial," which clarifies the linearity of the transformation from a normal thin group configuration to a general thin
group configuration by pupil shift and conjugate shift theory is implemented.
The purpose of the method is correcting low-order aberrations during the preliminary design of zoom lenses. The goal is
to mathematically reduce to zero the four aberration coefficients of the third-order (spherical aberration, coma,
astigmatism, and distortion) rather than searching for a minimum by commercial design software. Once this theory is
proven and accepted, it becomes possible to determine how many groups are needed for a particular optical system. The
method of aberration polynomials establishes the number of groups needed to correct a given number of aberrations at a
given number of zoom positions. Furthermore, it provides the shape or bending of the elements, from where it will be
possible to continue to optimize with standard methods.
The goal of an imaging sensor with nearly constant response, constant image quality, with a focal plane array of pixels
whose overlap can be scaled, that can still provide a nearly hemispherical field-of-view has been demonstrated. The
topic of this paper is the optical design of just such a sensor. A flow down of these performance constraints to hardware
specifications is bounded by information theory, diffraction theory, plus practical matters that constrain the overlap of
focal plane arrays.
A set of performance goals for a sensor are the ability to observe features ≤25 μr features in size within a 45° scene
using >1 G pixels.
There is a continuous demand for larger, lighter, and higher quality telescopes. Over the past several decades, we have
seen the evolution from launchable 2 meter-class telescopes (such as Hubble), to today's demand for deployable 6
meter-class telescopes (such as JWST), to tomorrow's need for up to 150 meter-class telescopes. As the apertures
continue to grow, it will become much more difficult and expensive to launch assembled telescope structures. To
address this issue, we are seeing the emergence of new novel structural concepts, such as inflatable structures and
membrane optics. While these structural concepts do show promise, it is very difficult to achieve and maintain high
surface figure quality. Another potential solution to develop large space telescopes is to move the fabrication facility
into space and launch the raw materials.
In this paper we present initial in-space manufacturing concepts to enable the development of large telescopes. This
includes novel approaches for the fabrication of the optical elements. We will also discuss potential optical designs for
large space telescopes and describe their relation to the fabrication methods. These concepts are being developed to
meet the demanding requirements of DARPA's LASSO (Large Aperture Space Surveillance Optic) program which
currently requires a 150 meter optical aperture with a 16.6 degree field of view.
The Buchdahl dispersion model provides a rapidly converging polynomial form for describing the dispersion of refractive materials. Via this model, the dispersion of a material over the waveband of concern can be accurately characterized by a simple polynomial form, often out to only the second order. In this paper, the Buchdahl model is applied to hybrid refractive-diffractive achromats for both 3-5μm (MWIR) band and 8-12μm (LWIR) band. For each waveband, Buchdahl dispersion coefficients of IR materials and the diffractive optical element (DOE) are defined by optimally choosing the Buchdahl chromatic coordinate and best-fitting the Buchdahl model to the dispersion of materials and the DOE. The principles for selecting 1 to 2 IR materials combined with a DOE to produce hybrids achromatized at 3 and 4 wavelengths are discussed. A series of thin lens predesign examples are presented.
Approximately 5 billion dollars in US revenue was lost in 2003 due to open area fires. In addition many lives are lost annually. Early detection of open area fires is typically performed by manned observatories, random reporting and aerial surveillance. Optical IR flame detectors have been developed previously. They typically have experienced high false alarms and low flame detection sensitivity due to interference from solar and other causes. Recently a combination of IR detectors has been used in a two or three color mode to reduce false alarms from solar, or background sources. A combination of ultra-violet C (UVC) and near infra-red (NIR) detectors has also been developed recently for flame discrimination. Relatively solar-blind basic detectors are now available but typically detect at only a few tens of meters at ~ 1 square meter fuel flame. We quantify the range and solar issues for IR and visible detectors and qualitatively define UV sensor requirements in terms of the mode of operation, collection area issues and flame signal output by combustion photochemistry. We describe innovative flame signal collection optics for multiple wavelengths using UV and IR as low false alarm detection of open area fires at long range (8-10 km/m2) in daylight (or darkness). A circular array detector and UV-IR reflective and refractive devices including cylindrical or toroidal lens elements for the IR are described. The dispersion in a refractive cylindrical IR lens characterizes the fire and allows a stationary line or circle generator to locate the direction and different flame IR “colors” from a wide FOV. The line generator will produce spots along the line corresponding to the fire which can be discriminated with a linear detector. We demonstrate prototype autonomous sensors with RF digital reporting from various sites.
The design & tolerancing of an optical testing system (OTS) presents a unique set of challenges not generally encountered during the typical optical design process. The authors have spent the past six years developing and using a series of optical systems designed to measure the surface figure & radius-of-curvature of various ultra-lightweight mirrors at 30 K. These mirrors were part of a technology development program to support NASA’s James Webb Space Telescope (JWST). The design of these systems required consideration of the following: (i) potentially large figure errors in the test mirror (due to gravity sag & cryo-distortion), (ii) cryo-shrinkage of the aperture and radius-of-curvature, (iii) figure changes due to the use of mirror actuators, and (iv) vibration between the OTS & the test mirror. In addition, an exhaustive tolerancing process was required for each system in order to reach a set of alignment tolerances that were achievable using the equipment available and within the test environment. The authors found many aspects of the OTS design process to be significantly different from the norm; at the same time, however, viewing the process as a typical optical design problem often-times brought clarification. This paper will describe both the differences and the similarities observed between the design of an OTS as opposed to a traditional imaging system.
The 1.4-meter semi-rigid, beryllium Advanced Mirror System Demonstrator (AMSD) mirror completed initial cryogenic testing at Marshall’s X-ray Calibration Facility (XRCF) in August of 2003. Results of this testing show the mirror to have very low cryogenic surface deformation and possess exceptional figure stability. Additionally, the mirror substrate exhibits virtually no change in surface figure over the James Webb Space Telescope (JWST) operational temperature range of 30 to 62 Kelvin. The lightweighted, semi-rigid mirror architecture approach demonstrated here is a precursor to the mirror technology being applied to the JWST observatory. Testing at ambient and cryogenic temperatures included the radius of curvature actuation system and the rigid body displacement system. These two systems incorporated the use of 4 actuators to allow the mirror to change piston, tilt, and radius of curvature. Presented here are the results of the figure change, alignment change, and radius change as a function of temperature. Also shown will be the actuator influence functions at both ambient and cryogenic temperatures.
The successful augmentation of NASA's X-Ray Cryogenic Facility (XRCF) at the Marshall Space Flight Center (MSFC) to an optical metrology testing facility for the Sub-scale Beryllium Mirror Demonstrator (SBMD) and NGST Mirror Sub-scale Demonstrator (NMSD) programs required significant modifications and enhancements to achieve reliable data. In addition to building and integrating both a helium shroud and a rugged, stable platform to support a wavefront sensor, a custom sensor suite was assembled and integrated to meet the test requirements. The metrology suite consisted of a high-resolution Shack-Hartmann sensor, a point diffraction interferometer, a point spread function camera, and a radius of curvature measuring device.
The evolution from the SBMD and NMSD tests to the Advanced Mirror System Demonstrator (AMSD) program is less dramatic in some ways, such as the reutilization of the existing helium shroud and sensor support structure. However, significant modifications were required to meet the AMSD program's more stringent test requirements and conditions resulting in a substantial overhaul of the sensor suite and test plan. This paper will discuss the instrumentation changes made for AMSD, including the interferometer selection and null optics. The error budget for the tests will be presented using modeling and experimental data. We will show how the facility is ready to meet the test requirements.
The successful augmentation of NASA's X-Ray Cryogenic Facility (XRCF) at the Marshall Space Flight Center (MSFC) to an optical metrology testing facility for the Sub-scale Beryllium Mirror Development (SBMD) and NGST Mirror Sub-scale Development (NMSD) programs required significant modifications and enhancements to achieve useful and meaningful data. In addition to building and integrating both a helium shroud and a rugged and stable platform to support a custom sensor suite, the sensor suite was assembled and integrated to meet the performance requirements for the program. The subsequent evolution from NMSD and SBMD testing to the Advanced Mirror System Demonstrator (AMSD) program is less dramatic in some ways, such as the reutilization of the existing helium shroud and sensor support structure. However, significant modifications were required to meet the AMSD program's more stringent test requirements and conditions resulting in a substantial overhaul of the sensor suite and test plan. This overview paper will discuss the instrumentation changes made for AMSD, including the interferometer selection, null optics, and radius of curvature measurement method. The error budgeting process will be presented, and the overall test plan developed to successfully carry out the tests will be discussed.
An Optical Testing System (OTS) has been developed to measure the figure and radius of curvature of Next Generation Space Telescope (NGST) developmental mirrors in a vacuum, cryogenic environment using the X-Ray Calibration Facility (XRCF) at Marshall Space Flight Center (MSFC). The OTS consists of a WaveScope Shack-Hartmann sensor from Adaptive Optics Associates as the main instrument and a Leica Disto Pro distance measurement instrument. Testing is done at the center of curvature of the test mirror and at a wavelength of 632.8 nm. The error in the figure measurement is <EQ(lambda) /13 peak-to-valley (PV). The error in radius of curvature is less than 5 mm. The OTS has been used to test the Subscale Beryllium Mirror Demonstrator (SBMD), a 0.532-m diameter spherical mirror with a radius of curvature of 20 m. SBMD characterization consisted of three separate cryogenic tests at or near 35 K. The first two determined the cryogenic changes in the mirror surface and their repeatability. The last followed cryo-figuring of the mirror. This paper will describe the results of these tests. Figure results will include full aperture results as well as an analysis of the mid-spatial frequency error results. The results indicate that the SBMD performed well in these tests with respect to the requirements of (lambda) /4 PV (full aperture), (lambda) /10 PV (mid-spatial, 1-10 cm), and +/- 0.1 m for radius of curvature after cryo-figuring.
The design analysis and preliminary testing of a prototype AFOCL is described. The AFOCL is an active optical component composed of solid state lead lanthanum-modified zirconate titanate (PLZT) ferroelectric ceramic with patterned indium tin oxide (ITO) transparent surface electrodes that modulate the refractive index of the PLZT to function as an electro- optic lens. The AFOCL was developed to perform optical re- alignment and wavefront correction to enhance the performance of Ultra-Lightweight Structures and Space Observatories. The AFOCL would be an active optical component within a larger optical system. Information from a wavefront sensor would be processed to provide input to the AFOCL to drive the sense4d wavefront tot he desired shape and location. While offering variable and rapid focusing capability similar to liquid crystal based spatial light modulators, the AFOCL offers some potential advantages because it is a solid-stat, stationary, low-mass, rugged, and thin optical element that can produce wavefront quality comparable to the solid refractive lens it replaces. The AFOCL acts as a positive or negative lens by producing a parabolic phase-shift in the PLZT material through the application of a controlled voltage potential across the ITO electrodes. To demonstrate the technology, a 4 mm diameter lens was fabricated to produce 5-waves of optical power operating at 2.051 micrometers wavelength. Optical metrology was performed on the device to measure focal length, optical quality, and efficiency for a variety of test configurations. Preliminary data was analyzed and compared to idealized performance available from computer-based models of the AFOCL.
NASA is intent on exploiting the unique perspective of space-based remote optical instruments to observe and study largescale environmental processes. Emphasis on smaller and more affordable missions continues to force the remote sensing instruments to find innovative ways to reduce the size, weight, and cost of the sensor package. This is a challenge because many of the proposed instruments incorporate a high quality meter-class telescope that can be a significant driver of total instrument costs. While various methods for telescope weight reduction have been achieved, many of the current approaches rely on exotic materials and specialized manufacturing techniques that limit availability or substantially increase costs. A competitive lightweight telescope technology that is especially well suited to space-based coherent Doppler wind lidar has been developed through a collaborative effort involving NASA Marshall Space Flight Center (MSFC) through the Global Hydrology and Climate Center (GHCC) and the University of Alabama in Huntsville (UAH) at the Center for Applied Optics (CAO). The new lightweight optics using metal alloy shells and surfaces (LOMASS) fabrication approach is suitable for high quality metal mirrors and meter-class telescopes. Compared to alternative materials and fabrication methods the new approach promises to reduce the areal density of a meter-class telescope to less than 15-kg/m2; deliver a minimum ?/1O-RMS surface optical quality; while using commercial materials and equipment to lower procurement costs. The final optical figure and finish is put into the mirrors through conventional diamond turning and polishing techniques. This approach is especially advantageous for a coherent lidar instrument because the reduced telescope weight permits the rotation of the telescope to scan the beam without requiring heavy wedges or additional large mirrors. Ongoing investigations and preliminary results show promise for the LOMASS approach to be successful in demonstrating a novel alternative approach to fabricating lightweight mirrors with performance parameters comparable with the Space Readiness Coherent Lidar Experiment (SPARCLE). Development and process characterization is continuing with the design and fabrication of mirrors for a 25-cm telescope suitable for a lidar instrument.
Over the past 7 years, NASA Marshall Space Flight Center (MSFC) through the Global Hydrology and Climate Center (GHCC) has been working; in collaboration with the University of Alabama in Huntsville (UAH) Center for Applied Optics (CAO), and others; towards demonstrating a solid state coherent Doppler lidar instrument for space-based global measurement of atmospheric winds. The Space Readiness Coherent Lidar Experiment (SPARCLE) was selected by NASA's New Millennium Program to demonstrate the feasibility and technology readiness of space-based coherent wind lidar. The CAO was responsible for the design, development, integration, and testing of the SPARCLE optical system. Operating at 2-micron wavelength, SPARCLE system performance is dominated by the optical quality of the transmitter/receiver optical system. The stringent optical performance requirements coupled with the demanding physical and environmental constraints of a space-based instrument necessitate extensive characterization of the telescope optical performance that is critical to predicting the lidar system efficiency and operation in space. Individual components have been measured prior to assembly and compared to the designed specifications. Based on the individual components, the telescope design was optimized to produce a suitable telescope. Once the telescope is completed, it will be tested and evaluated and the data shall be used to anchor computer based models of the optical system. Commercial optical modeling codes were used to evaluate the performance of the telescope under a variety of anticipated on-orbit environments and will eventually be compared to environmental tests conducted in the course of qualifying the telescope for flight. Detailed analysis using the "as built" data will help to reduce uncertainties within the lidar system model and will increase the accuracy of the lidar performance predictions.
A small rugged interferometer was required for measuring the depletion zones generated in a protein crystal growth experiment. The exploration for an optimum solution yielded an instrument that uses solid optical design techniques, where air is removed from the optical path and replaced with 'solid air' or glass. The interferometer is a Mach-Zehnder configuration with the reference and test arms separated as orthogonal polarization states with a polarization beam splitting cube (PBSC), then recombined by another PBSC, maintaining the orthogonality of the reference and test beam polarizations. An off-the-shelf liquid crystal variable phase plate was sufficient to produce the necessary 2(pi) phase shift. The device was built and tested and shoed excellent performance. The spatial resolution of the interferometer is limited only by the 0.011mm pixels at the 5 by 5 mm detector and the imager is operating at telecentric 1:1 conjugates. Phase resolution, using the Hariharan 5-step algorithm, is measured to be better than (lambda) /50. In this paper, calibration test results are presented and future upgrades are outlined.
The SPAce Readiness Coherent Lidar Experiment (SPARCLE) is the first demonstration of a coherent Doppler wind lidar in space. Coherent lidars can accurately measure the wind velocity by extracting the Doppler frequency shift in the back-scattered signal from the atmosphere through optical heterodyne (coherent) detection. Coherent detection is therefore highly sensitive to aberrations in the signal phase front, and to relative alignment between the signal and the local oscillator beams. The telescope and scanning optics consist of an off-axis Mersenne telescope followed by a rotating wedge of silicon and a window of fused silica. The wedge is in very close proximity to the experiment window, and is essentially in contact with the scanner motor/encoder system. The can environment temperature is nominally 20 degrees Celsius, the window ranges from -20 degrees Celsius to 0 degrees Celsius, and the scanner motor/encoder system alone could generate temperatures as high as 35 degrees Celsius. This thermal environment, coupled with the relatively large sensitivity of silicon's refractie index to temperature, has required careful thermal design and compensation techniques. This paper discusses the optical issues of these thermal effects and a variety of methods used to ameliorate them.
The results of a design study for the development of an eye- safe (near-infrared wavelength), compact, multichannel optical interconnect system appropriate for integration with electronics and to be used for short distance communication are discussed. There are potential advantages to using optical interconnects instead of current hardwire interconnections for data transmission over short distances. This technology also has potential applications to data transmission for computing applications. This design study focused on the development of an optical interconnect module to function much like a conventional data cable. The module must be rugged, small, easily integrated into current data transfer, and must have the potential to be produced in volume and at lost cost. The desired system level performance of the optical interconnects was evaluated and design specifications were determined for the optical design. Trade studies involving current technologies were performed to determine suitable hardware configurations. These requirements pointed toward the application of microfabrication technology and micro-optics in order to accomplish the design goals. A pseudo-monolithic silicon-based optical system has been proposed involving diffractive and microrefractive optics along with integrated sensors and emitters. The device emphasizes the use of existing technologies gathered from different disciplines and integrated into one system.
The results of a comprehensive design study for the development of a compact infrared zoom lens suitable for use in guided munitions are discussed. The continuously variable zoom of the lens offers significant operational performance benefits to weapon systems using fixed or switchable FOV optics. Two practical zoom lens systems were designed that showed potential to meet typical guided munitions system requirements by utilizing in the first system conventional surfaces and a combination of conventional and diffractive surfaces in the second system. Significant weight savings, enhanced optical performance, and excellent athermalization over conventional lenses were realized. The optical performance over the entire 4:1 zoom range and 5-20 degrees field-of-view is near-diffraction limit while maintaining a constant F-number.
A method of understanding the behavior of multiple coaxial Bessel beams is presented. An attempt to develop a way to modify the longitudinal behavior of Bessel beams is discussed by analogy to a multiple plane wave interference pattern. It is shown, both with theory and numerical simulation, that the summation of several coherent Bessel beams of differing convergence will alter the performance of the propagating beam in a predicable manner.
Solid optics is a design strategy which has no air spaces throughout the entire optical path and therefore produces extremely rugged optical systems. In an ideal solid system, lens elements, refractive or diffractive, beam splitters, sources, detectors, and any other optical elements are cemented together to form a single rigid assembly. The resulting system, essentially a solid block of glass, is impervious to misalignment. Certain systems such as analogue optical computers, for example, are ideally suited to the advantages of solid optical design schemes. A solid correlator system is presented and a designer's wish list is discussed.
Gains in micro-optic technology may provide enhanced performance for IR sensing applications. The benefits in noise reduction and increase in signal-to-noise ratio on the detector arrays can off-set the increased cost of adding micro-lens structures to the detector assemblies. Additionally, new manufacturing techniques make it feasible to make micro-lens structures on the same substrate as the detector elements. One of the advantages of this technology growth is the shifting of alignment to the fabrication stage instead of the filter assembly stage. Important considerations include: fill factor, diffraction efficiency, optical and electronic crosstalk, optical power, and optical bandwidth.
In this paper some practical observations related to the fabrication of multifocal IOLs are presented from the viewpoint of a diffractive optics design and fabrication group whose experience lies mostly outside the area of ophthalmic optics.
A lens configuration called the limiting lens has been studied which describes the highest power, shortest focal length system for a given cylindrical volume. We consider here the classification and study of lenses which are constrained to fit into small packages in terms of how close the configurations come to the limiting lens.
This paper describes a method by which designs for high power lenses and lenses constrained to very short spaces can be evaluated or started. First the fundamentally highest power refractive lens is presented. Then the paraxial properties of this lens are fully described followed by a brief third order analysis. 1.