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Conference on current developments in Lens design and optical engineering II

作者： Mouroulis, P Shea, JJ Thomas, DA CALTECH Jet Propuls Lab Pasadena CA 91109 USA

ISBN: (纸本)0819441554

We present a design and tolerancing approach that permits the achievement of a high degree of spatial and spectral uniformity of response from a pushbroom imaging spectrometer. Such uniformity of response is crucial for the extraction of accurate spectroscopic information from remotely sensed data. The spectrometer system example comprises two independent spectrometer modules covering the 400-2500 nm range, separated through a dichroic mirror. The relative merits of alternative approaches are briefly reviewed before concentrating on the problem of building a flight-worthy system that can approximate its design performance. The tolerancing approach requires simultaneous monitoring of many parameters, and specifically: overall image quality, spectral distortion, spectral MTF variation with field, spatial distortion, spatial MTF variation with wavelength, and slit magnification to within a small fraction of a pixel. It is shown that the wavefront error alone or even supplemented by distortion figures is insufficient for characterizing a system with high response uniformity. Tolerance values on the components and their positioning are primarily guided by the need to achieve the same magnification between the two spectrometer modules, as well as by the interferometric alignment method.

关键词： Tolerancing Spectrometers Short wave infrared radiation Beam splitters Mirrors Modulation transfer functions Distortion Image quality Point spread functions Wavefronts

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Scintillation bit error rate reduction for free space optical communications systems

Scintillation bit error rate reduction for free space optica...

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Conference on current developments in Lens design and optical engineering II

作者： Mayhew, LM Willebrand, H Kube, E LightPointe Commun Inc Boulder CO 80301 USA

ISBN: (纸本)0819441554

Although relatively unaffected by rain and snow, free space infrared laser optical communication systems are affected by fog and atmospheric turbulence. We have calculated the signal loss from scintillation to predict bit error rates by varying the amount of scintillation, the link distance, and system details. Increasing the number of transmitters and the effective area was predicted to improve scintillation in earlier work in this field.(1) We found that increasing both the number of transmitters and the effective receiver area greatly improved the signal loss caused by scintillation and thus, the bit error rate. For example, under high scintillation (Cn(2) = 10(-13) M,213), the four transmitter/receiver system at a link distance of 1 kin should experience a bit error rate of better than 10(-10) for a 4.0 dB loss. Under the same conditions, an identical system with only one transmitter and receiver should experience a bit error rate of 10(-1.5) (0.032 bits per second) for the same 4.0 dB loss. Increasing just the number of transmitters or the number of receivers improved the signal, but increasing both improved the signal even more than expected. In general, single beam systems should be limited to link distances less than about 600 m.

关键词： scintillation laser communications infrared bit error rate link budget

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2W reliable operation in 50 μm-wide InGaAsP/InGaP/AlGaAs (λ=810 nm) SQW diode lasers with tensile-strained InGaP barriers

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ELECTRONICS LETTERS 2001年第21期37卷 1289-1290页

作者： Yamanaka, F Wada, M Kuniyasu, T Ohgoh, T Fukunaga, T Hayakawa, T Fuji Photo Film Co Ltd Miyanodai Technol Dev Ctr Kanagawa 2588538 Japan

A new InGaAsP/InGaP/AlGaAs (lambda = 810 nm) laser with tensile-strained InGaP barriers, broad waveguide structure and current blocking region near the facet is reported. 2 W continuous wave operation over 2000 h from... 详细信息

关键词： continuous wave operation Semiconductor lasers Chemical vapour deposition 2 W InGaAsP/InGaP/AlGaAs SQW diode lasers optical waveguides aluminium compounds optical fabrication iii-V semiconductors InGaP barriers indium compounds MOCVD gallium compounds gallium arsenide tensile-strained InGaP barriers design of specific laser systems optical fabrication, surface grinding waveguide lasers Laser beam interactions and properties Lasing action in semiconductors tensile-strained barriers single quantum well laser laser beams InGaAsP/InGaP/AlGaAs laser aperture quantum well lasers InGaAsP-InGaP-AlGaAs laser reliability optical waveguides and couplers reliable operation Maintenance and reliability Reliability current blocking region 2000 h Laser beam characteristics and interactions engineering materials InGaP Surface treatment and coating techniques facet broad waveguide structure 50 mum Optoelectronics manufacturing 810 nm

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Chemical Imaging System: current status and challenges

Chemical Imaging System: Current status and challenges

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Conference on Algorithms for Multispectral, Hyperspectral, and Ultraspectral Imagery VII

作者： Ifarraguerri, A Jensen, JO USA SBCCOM Edgewood Chem Biol Ctr AMSSB RRT DP Aberdeen Proving Ground MD 21010 USA

ISBN: (纸本)0819440760

The Chemical Imaging System (CIS) is a small, high-speed long-wave infrared (8 - 12 mum) imaging spectrometer which is currently under development by the United States Army. The fielded system will operate at 360 scans per second with a large format focal-plane-array. The CIS, which is currently at the exploratory development stage, is scheduled for transition to engineering development in 2005. currently, the CIS uses the TurboFT FTS in conjunction with a 16-pixel direct-wired HgCdTe detector array. The TurboFT spectrometer provides high-speed operation in a small, lightweight package. In parallel to the hardware developments an algorithm and software development effort is underway to address some unique features of the CIS. The TurboFT-based system requires a non-uniform sampling Fourier transform algorithm in order to preserve signal fidelity. Also, the availability of multiple pixels can be exploited in order to improve the interference suppression capabilities of the system by allowing the detection and identification algorithm to adapt its parameters to the changing background. Due to the enormous amount of data generated, the signal processing must proceed at very high rate. High-speed computers operating with a parallel architecture are required to process the data in real time. This paper describes the current CIS "bread box" system. It includes some field measurement results followed by a discussion of the issues and challenges associated with meeting the design goals set for the program.

关键词： Chemical Imaging System imaging spectrometer TurboFT vapor detection

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Tomographic characterization of grain-size correlations in polycrystalline Al-Sn

Tomographic characterization of grain-size correlations in p...

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developments in X-Ray Tomography iii

作者： Krill iii, C.E. Döbrich, K. Michels, D. Michels, A. C., Rau T., Weitkamp A., Snigirev R., Birringer FR 7.3 Technische Physik Universität des Saarlandes Geb. 43B D-66041 Saarbrücken Germany

The inadequacies of current analytical models for grain growth are thought to arise in part from their mean-field nature: they ignore the presence of correlations in the sizes of neighboring grains induced by the process of grain growth itself. Although grain-size correlations have been identified in microstructures generated by computer simulations of grain growth, no comparable evidence has been obtained from real samples - primarily because of the experimental difficulties associated with evaluating this inherently three-dimensional property. Using absorption-contrast x-ray microtomography, we have attempted to characterize the network of grain boundaries in polycrystalline samples of Al doped with up to 3 at.% Sn. In principle, since the tin atoms segregate to the grain boundaries, it should be possible to determine the size and relative position of each grain from a three-dimensional reconstruction of the Sn distribution, from which the desired correlation function could be calculated directly. However, the grain boundaries in Al-Sn are not uniformly decorated with tin, which presents a formidable challenge to quantifying the microstructural properties of such samples. Significant progress toward overcoming this problem has been achieved by applying a constrained phase-field grain-growth algorithm to an approximate microstructure gleaned from the tomographic contrast data.

关键词： Computerized tomography

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Implementation of battlespace agents for network-centric electronic warfare

Implementation of battlespace agents for network-centric ele...

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Battlespace Digitization and Network-Centric Warfare

作者： Sciortino J.C., Jr. Smith iii, J.F. Kamgar-Parsi, B. Franciose, R. Naval Research Laboratory 4555 Overlook Ave. SW Washington DC 20375 United States

In the Network-Centric Warfare (NCW) paradigm, battlespace agents autonomously perform selected tasks delegated by actors/shooters and decision-makers including controlling sensors. Network-Centric electronic warfare (NCEW) is the form of electronic combat used in NCW. Focus is placed on a network of interconnected, adapting systems that are capable of making choices about how to survive and achieve their design goals in a dynamic environment. The battlespace entities: agents, actor/shooters, sensors, and decision-makers are tied together through the information and sensor grids. The grids carry a flood of data and information among the entities that can be used to increase the tempo of operations. This flood will overwhelm human actors and decision-makers. To avoid this, it will be necessary to take advantage of developments in artificial intelligence (AI) and complexity theory in the form of complex adaptive systems (CAS). AI will allow autonomous sensor control, data collection, and data interpretation. The information grid itself may be controlled by battlespace agents that rely on AI to perform their functions. These agents can be used in hostile environments that require rapid reaction-response loops where it would be dangerous to send a human actor or decision-maker. Collectively these battlespace entities form a CAS which is composed of many adaptive autonomous agents coexisting in the battlespace and competing or cooperating to achieve their goals.

关键词： Electronic warfare

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Lithographic performance results for a new 50 kV electron-beam mask writer

Lithographic performance results for a new 50 kV electron-be...

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20th Annual BACUS Symposium on Photomask Technology

作者： Chakarian, V. Bylciw, S. Sauer, C. Trost, D. Zywno, M. Teitzel, R. Raymond iii, F. Abboud, F. Etec Systems Inc. Applied Materials Company 26460 Corporate Avenue Hayward CA 94545 United States

current pattern generation tool designs will be inadequate to meet the advanced requirements for next-generation masks, particularly at the 100 nm node. Etec Systems, Inc. has developed a complete raster-based patterning solution to provide improved resolution, critical dimension (CD) uniformity, positional accuracy, and throughput. This solution meets the challenges of the 130-nm device generation with extendibility to at least 100 nm devices. Our complete patterning solution includes an electron-beam (e-beam) pattern generation system and a new 50 kV process. The e-beam system includes a column with 50 kV accelerating voltage and a new graybeam writing technique. To accomplish this technique, a pulse-width modulated blanking system, per-pixel deflection, retrograde scanning, and multiphase and multipass writing are used. This combination of features results in markedly improved lithographic performance and enables the use of conventional high-contrast resists for faster process implementation. Additional significant innovations of this pattern generation system include a novel stage design, an integrated automated material handling system (AMHS), on-board diagnostics, and improved environmental/thermal management. We believe this comprehensive patterning solution offers the best combination of benefits to the user in terms of versatility and extendibility.

关键词： Masks

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Positioning accuracy of primary mirror actuators for large aperture space based optical instruments

Positioning accuracy of primary mirror actuators for large a...

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Conference on current developments in Lens design and optical Systems engineering

作者： Hatheway, AE Alson E Hatheway Inc Pasadena CA 91101 USA

ISBN: (纸本)0819437387

This paper describes the Rubicon(tm) actuator, discusses its test data and derives from the data the actuator's accuracy function based upon the observed accuracy of long and short stroke motion commands. The accuracy is described in terms of the rms positioning error (in nanometers) for moves of a given size, regardless of position in the stroke.

关键词： actuator nanometer space instruments accuracy move error

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Opto-mechanical design of primary mirror assembly for free gyro stabilized seeker

Opto-mechanical design of primary mirror assembly for free g...

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Conference on current developments in Lens design and optical Systems engineering

作者： Perona, BJ Yarbrough, C Prill, S Raytheon Missile Syst Co Tucson AZ 85710 USA

ISBN: (纸本)0819437387

In Free Gyroscopic Stabilized Seekers, the Primary Minor has the multiple functions of a magnetic rotor, the primary rotating mass and the primary reflector for the optical train. The introduction of rare-earth magnetic alloys to this class of seeker has provided increased flexibility in materials selection, opto-mechanical design and cost of manufacture. Along with superior magnetic properties, the rare-earth alloy Neodymium-Iron-Boron (NdFeB) comes with the undesirable properties of anisotropic CTE, high susceptibility to corrosion and manufacturing challenges. This paper discusses the opto-mechanical design, structural and optical modeling and analysis of a primary mirror assembly utilizing an NdFeB insert with centrifugal, linear acceleration and thermal loading as well as the optical test results, qualification testing of long-term figure stability and validation of the mechanical/magnetic/optical design model.

关键词： opto-mechanical design gyroscope rare-earth magnet

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Minimizing gravity sag of a large mirror with an inverted Hindle-mount

Minimizing gravity sag of a large mirror with an inverted Hi...

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Conference on current developments in Lens design and optical Systems engineering

作者： Robinson, DW NASA Goddard Space Flight Ctr Greenbelt MD 20771 USA

ISBN: (纸本)0819437387

A method of minimizing the optical distortion from gravity sag on a suspended large autocollimating flat mirror has been devised. This method consists of an inverted nine-point Hindle-Mount. A conventional Hindle-Mount is located underneath a sky-viewing mirror and is primarily under compression loads from the weight of the mirror. It is not suitable for the situation where the mirror is viewing the ground, since a mirror would tend to fall out of the mount when in an inverted position. The inverted Hindle-Mount design consists of bonded joints on the backside of the mirror that allow the mirror to be held or suspended above an object to be viewed. This ability is useful in optical setups such as a calibration test where a flat mirror is located above a telescope so that the telescope may view a known optic.

关键词： Hindle mount optical mounting techniques bonding epoxy cell

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