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This PDF file contains the front matter associated with SPIE Proceedings Volume 7680, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
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L-3 Communications CyTerra Corporation has developed a high throughput universal explosive detection system
(PassPort) to automatically screen the passengers in airports without requiring them to remove their shoes. The technical
approach is based on the patented energetic material detection (EMD) technology. By analyzing the results of sample
heating with an infrared camera, one can distinguish the deflagration or decomposition of an energetic material from
other clutters such as flammables and general background substances. This becomes the basis of a universal explosive
detection system that does not require a library and is capable of detecting trace levels of explosives with a low false
alarm rate. The PassPort is a simple turnstile type device and integrates a non-intrusive aerodynamic sampling scheme
that has been shown capable of detecting trace levels of explosives on shoes. A detailed description of the detection
theory and the automated sampling techniques, as well as the field test results, will be presented.
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The paper presents a spoof detection technique employing multi-spectral and multi-polarization imaging for a
contactless fingerprint-capture system. While multispectral imaging has been proven to enable spoof detection for
contact fingerprint imagers, these imagers typically rely on frustrated total internal reflection that requires a planar
fingerprint, achieved by contact. The multispectral imaging method is based primarily on the difference in the spectral
absorption profile between a real finger and a fake one. This paper will describe the expansion of this capability using
blue and red light with contactless imaging in conjunction with polarization. This new method uses images at various
rotated linear polarizations (each image representing a different value of specular and diffuse components), which are
used to create the feature vectors representing the spectral and polarization diversity. The software extracts complex
wavelet transforms (CWT) and FFT features from the images and builds a supervised learning method to train Support
Vector Machine (SVM) classifiers. Experimental data was collected from a diversity of human fingers and silicon based
phantoms molded from the corresponding humans. Fake and actual fingerprints were collected using individuals with a
large diversity in skin tone, age, and finger dimensions. Our initial results, with an accuracy rate of at least 83%, are
promising and imply that using the polarization diversity can enhance the spoof detection performance.
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This paper reports the development and initial testing of a field-portable sensor for monitoring hydrogen peroxide (H2O2)
and water (H2O) vapor concentrations during building decontamination after accidental or purposeful exposure to
hazardous biological materials. During decontamination, a sterilization system fills ambient air with water and peroxide
vapor to near-saturation. The peroxide concentration typically exceeds several hundred ppm for tens of minutes, and
subsequently diminishes below 1 ppm. The H2O2/ H2O sensor is an adaptation of a portable gas-sensing platform based
on Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology. By capitalizing on its spectral resolution, the
TDLAS analyzer isolates H2O2 and H2O spectral lines to measure both vapors using a single laser source. It offers a
combination of sensitivity, specificity, fast response, dynamic range, linearity, ease of operation and calibration,
ruggedness, and portability not available in alternative H2O2 detectors. The H2O2 range is approximately 0- 5,000 ppm.
The autonomous and rugged instrument provides real-time data. It has been tested in a closed-loop liquid/vapor
equilibrium apparatus and by comparison against electrochemical sensors.
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Near infrared (NIR) spectroscopy can provide inexpensive, rapid and contact-free chemical content measurements for
on-line, hand-held and laboratory applications. Traditionally multiwavelength NIR analyzers are based on incandescent
lamp light sources with rotating filter wheels, even though designs relying on lamp technology and moving parts mean
larger size, require frequent maintenance and eventually limit measurement speed of the system. Today, optical power
and available wavelength range of LEDs enable their use in chemical content analyzers. In this publication, a paper
moisture meter with high speed LED techniques is presented. A prototype developed at VTT utilizes an extended
InGaAs detector to measure diffuse reflection at four NIR wavelengths ranging from 1.2 to 2.1 μm. Source LED currents
are amplitude modulated with fixed sinusoidal frequencies. Optical signals at each wavelength are demodulated from the
detector signal using real-time digital lock-in detection method on an FPGA. Moisture content is calculated and
displayed on the embedded platform. The design allows very high speed operation, where the result is updated every 1
ms. Performance of the prototype system was studied by measuring a set of known sealed paper samples. Paper moisture
measurement accuracy was 0.14, repeatability 0.01 and 2σ noise 0.04 moisture percent. Laboratory tests showed that
channel crosstalk after detection is below background noise level. The measured signal-to-noise ratios per channel were
70 - 85 dB when all LEDs were on. The overall performance equals the level of incandescent lamp based on-line
moisture meters currently in use in paper mill and process automation. The developed system forms a good basis also for
other content measurements.
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VTT Technical Research Centre of Finland has developed a new low cost hand-held staring hyperspectral imager for
applications previously blocked by high cost of the instrumentation. The system is compatible with standard video and
microscope lenses. The instrument can record 2D spatial images at several wavelength bands simultaneously. The
concept of the hyperspectral imager has been published in SPIE Proc. 7474. The prototype fits in an envelope of 100
mm x 60 mm x 40 mm and its weight is ca. 300 g. The benefits of the new device compared to Acousto-Optic Tunable
filter (AOTF) or Liquid Crystal Tunable Filter (LCTF) devices are small size and weight, speed of wavelength tuning,
high optical throughput, independence of polarization state of incoming light and capability to record three wavelengths
simultaneously. The operational wavelength range with Silicon-based CCD or CMOS sensors is 200 - 1100 nm and
spectral resolution is 2 - 10 nm @ FWHM. Similar IR imagers can be built using InGaAs, InSb or MCT imaging
sensors. The spatial resolution of the prototype is 480 x 750 pixels. It contains control system and memory for the image
data acquisition. It operates either autonomously recording hyperspectral data cubes continuously or controlled by a
laptop computer. The prototype was configured as a hyperspectral microscope for the spectral range 400 - 700 nm. The
design of the hyperspectral imager, characterization results and sample measurement results are presented.
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This paper reports instrument characterization measurements, which were recently arranged to provide comparative
information on different hyperspectral chemical imaging systems. Three different instruments were studied covering
both tunable filter and push-broom techniques: The first instrument MatrixNIRTM is based on a LCTF tunable filter and
InGaAs camera and covers wavelengths from 1000 to 1700 nm. The second one SisuCHEMATM is based on push-broom
technology and MCT camera operating from 1000 to 2500 nm. The third system is an instrument prototype from VTT
Technical Research Centre of Finland exploiting high speed Fabry-Perot interferometer and MCT camera, currently
calibrated from 1260 to 2500 nm. The characterization procedure was designed to study instrumental noise, signal-to-noise
ratio, linearity and spectral as well as spatial resolution. Finally, a pharmaceutical tablet sample was measured with
each instrument to demonstrate speed of measurement in a typical application. In spite of differences in wavelength
ranges and camera technologies used, the results provide interesting information on relative instrumental advantages and
disadvantages, which may be useful for selecting appropriate instrumentation for defined applications. Further, an
additional aim of this study is to compare the high speed Fabry-Perot imaging technology under development against the
established chemical imaging techniques available on the market today.
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Near-infrared (NIR) spectroscopy is a widely used method for material identification for laboratory and industrial
applications. While standard spectrometers only allow measurements at one sampling point at a time, NIR Spectral
Imaging techniques can measure, in real-time, both the size and shape of an object as well as identify the material the
object is made of.
The online classification and sorting of recovered paper with NIR Spectral Imaging (SI) is used with success in the paper
recycling industry throughout Europe. Recently, the globalisation of the recycling material streams caused that water-based
flexographic-printed newspapers mainly from UK and Italy appear also in central Europe. These flexo-printed
newspapers are not sufficiently de-inkable with the standard de-inking process originally developed for offset-printed
paper. This de-inking process removes the ink from recovered paper and is the fundamental processing step in paper
recycling. Thus, flexo-printed newspapers are a growing problem for recycling as they reduce the quality of the produced
paper if their amount exceeds a certain limit of the recovered paper.
This paper describes the chemometric model development using an NIR LCTF based hyperspectral imaging system for
the detection of flexographic printing inks. The achieved accuracy with the LCTF based system is above 95%.
Subsequently the model was transferred to an industrial spectrograph based sorting prototype evaluating the application
with an instrumentation that is suitable for the recycling industry. Again an accuracy of over 95% on the object level was
achieved for a sorting test including the physical sorting of the objects using an array of pneumatic nozzles.
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Diffuse reflectance near infrared hyperspectral imaging is an important analytical tool for a wide variety of industries,
including agriculture, consumer products, chemical and pharmaceutical development and production. Using this
technique as a method for the standoff detection of explosive particles is presented and discussed. The detection of the
particles is based on the diffuse reflectance of light from the particle in the near infrared wavelength range where CH,
NH, OH vibrational overtones and combination bands are prominent.
The imaging system is a NIR focal plane array camera with a tunable OPO laser system as the illumination source. The
OPO is programmed to scan over a wide spectral range in the NIR and the camera is synchronized to record the light
reflected from the target for each wavelength. The spectral resolution of this system is significantly higher than that of
hyperspectral systems that incorporate filters or dispersive elements. The data acquisition is very fast and the entire
hyperspectral cube can be collected in seconds. A comparison of data collected with the OPO system to data obtained
with a broadband light source with LCTF filters is presented.
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An uncooled linear array of 66 infrared elements has been designed, simulated, and fabricated using MEMS
techniques. CMOS compatible poly-Silicon thermoelectric materials are utilized. Numerical simulations optimize the
geometry and physical parameters for the thermopile materials. The pixel dimensions are 2.0 mm x 0.45 mm with 0.5
mm pitch. Excellent performance has been obtained in Nitrogen environment: D* = 1.2 x 108 cm √Hz/W; ι = 31 ms; and
cross talk of <15%. Measured performance is comparable to, and in some respects exceeds, the performance of
thermopile linear arrays based on Bi and Sb materials. The arrays are packaged for integration with an existing
dispersive infrared spectrometer.
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We examine the problem of simultaneous drive and capacitance sensing, on a microelectromechanical systems (MEMS)
device, where the drive is a bipolar AC waveform. The attention of this paper is particularly focused on wavelength
calibration of the microspectrometer, a MEMS micromachined Fabry Perot filter monolithically integrated with a
photodetector. However, this work is also very pertinent to other bipolar AC driven MEMS devices, which presently use
separate measurement MEMS structures. To avoid charging effects, the microspectrometer must be driven by an
AC waveform and, the only option for capacitance measurement is to do so simultaneously, on the same terminals, as
the drive waveform is applied. We propose a novel differential capacitive sensing circuit to determine the centre
wavelength of the MEMS-based micro-spectrometer, allowing closed-loop control of the microspectrometer's centre
wavelength. Automatic calibration can be realized with the addition of a known light source.
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A novel technology has been developed which enables high-brightness, broadband light output from the VUV to the IR
spectral regions. A focused laser is used to sustain a high-pressure xenon discharge inside a bulb, creating a smaller,
hotter discharge than can be obtained by using an electrically-driven discharge. This allows for continuous output down
to 120 nm wavelength and into the infrared. Application areas include hyperspectral imaging, standoff detection,
surveillance, bioanalytical instrumentation, microscopy, and materials studies. Laser-driven optical discharges were first
investigated over 30 years ago, providing the initial technical understanding of such discharges. However it took the
convergence of two separate elements - the availability of low-cost, high-efficiency CW diode lasers; and a market need
for high-brightness, broadband light source - to provide the impetus for further development in this area. Using near-IR
CW diode lasers at power levels from 15 W to over 2000 W, we have generated high-pressure xenon discharges having
temperatures as high as 10,000 C. The optical brightness of these discharges can be over an order of magnitude higher
than those obtainable from the brightest xenon arc lamps, and can be several orders of magnitude brighter than
deuterium lamps. Results from modeling of these discharges as well as experimental measurements will be presented.
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Commercially available quantum cascade semiconductor materials continue to mature. When integrated into external
cavity quantum cascade laser (ECqcL™) geometries, these laser systems are now providing near-continuous coverage
throughout the entire 3 - 13 μm regime. Such coverage enables molecular detection systems to enjoy high sensitivity
and selectivity. Individual lasers have been demonstrated to provide > 320 wavenumbers of tuning. Wide tuning ranges
have also been demonstrated at wavelengths in the 3 - 4 μm regime. In addition, phase continuous (mode-hop-free)
tuning allows for extremely high resolution spectroscopy to be performed throughout the mid-IR. Daylight Solutions
will review the most up-to-date results regarding wavelength coverage, tuning range and power levels achieved from
ECqcL™ systems. Daylight will also provide recent results in sensitivity and coverage from their multi-species Swept
Sensor™ and photoacoustic detection platforms.
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A spectral sensing method with sufficient sensitivity to detect vapors of low vapor-pressure compounds such as
explosives would have great promise for defense and security applications. An opportunity is Intracavity Laser
Absorption Spectroscopy (ICLAS) at IR wavelengths. Our approach is based on multi-mode external-cavity quantum
cascade lasers and a scanning Fabry-Perot spectrometer to analyze the laser mode spectrum in the presence of a narrow
band intracavity absorber. This paper presents results of numerical solution of laser rate equations that support
feasibility of kilometer effective active-cavity path lengths and sensitivity to concentrations of 10 ppb. This is
comparable to the saturated vapor pressure of TNT. System design considerations and first experimental results are
presented at 10 and 70 μm wavelengths.
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Electron Spin Resonance, also referred to as electron paramagnetic resonance (ESR / EPR), is the only direct method for
measuring free radicals, reactive molecules with unpaired electrons that cause the oxidative breakdown of oils, food
products, and also play a role in the biochemistry of disease. We discuss a recently developed miniature, high sensitivity
ESR spectrometer called Micro-ESRTM. The technology promises to revolutionize the accessibility of ESR spectroscopy
for industrial and scientific users.
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We developed a spectrometer for signals at single photon levels in the near infrared (NIR) region based on a tunable up-conversion
detector. This detector uses a 5-cm periodically poled lithium niobate (PPLN) waveguide to convert NIR
photons to a shorter wavelength that are then detected by a silicon avalanche photodiode. The sensitivity of this
spectrometer is -126 dBm, which is three orders-of-magnitude higher than any commercial optical spectrum analyzer in
this wavelength range. Additionally, we use two PPLN waveguides to implement a polarization-independent up-conversion
spectrometer, and use it to study a fiber-based quantum communication system.
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Advances in hardware have miniaturized the emissions spectrometer and associated optics, rendering them easily
deployed in the field. Such systems are also suitable for vehicle mounting, and can provide high quality data and
concentration information in minutes. Advances in software have accompanied this hardware evolution, enabling the
development of portable point-and-click OP-FTIR systems that weigh less than 16 lbs. These systems are ideal for first-responders,
military, law enforcement, forensics, and screening applications using optical remote sensing (ORS)
methodologies. With canned methods and interchangeable detectors, the new generation of OP-FTIR technology is
coupled to the latest forward reference-type model software to provide point-and-click technology. These software
models have been established for some time. However, refined user-friendly models that use active, passive, and solar
occultation methodologies now allow the user to quickly field-screen and quantify plumes, fence-lines, and combustion
incident scenarios in high-temporal-resolution. Synthetic background generation is now redundant as the models use
highly accurate instrument line shape (ILS) convolutions and several other parameters, in conjunction with radiative
transfer model databases to model a single calibration spectrum to collected sample spectra. Data retrievals are
performed directly on single beam spectra using non-linear classical least squares (NLCLS). Typically, the Hitran line
database is used to generate the initial calibration spectrum contained within the software.
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Emerging chemical threats to homeland security challenge the specificity of sensor-based chemical detectors. As the
number of chemicals to detect increases, the false alarm rates of these sensor-based systems tend to increase and the
usefulness of the detector in real world situations declines. The infrared (IR) absorption spectrum of a material is a
physical constant and highly specific for the molecule of interest. For many years, IR spectra have been used by chemists
to identify unknowns based on comparison with spectra of known materials and to determine the presence of chemical
functional groups through spectral interpretation. IR spectroscopy is well suited for the identification of broad-based
chemical threats. This discussion shall concern the conceptual development of a hand held IR spectroscopy system for
the identification of chemical vapor threats. The discussion shall focus on design tradeoffs where miniaturization is of
paramount importance. Quantitative IR absorption spectra of threat compounds were used to model absorption line
strengths at moderate spectral resolutions. IDLH detection limits targets, acquisition time, etendué, and signal-to-noise
parameters guided the concept design and pathlength of a long path gas cell used in conjunction with a hand held FT-IR
spectrometer.
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OPTRA is developing a high speed resonant Fourier transform infrared (HSR-FTIR) spectrometer for surface
contaminant measurements via time resolved thermal luminescence. This system incorporates a multipass reciprocating
interferometer and a resonant mirror structure to accomplish the scanning. The configuration and associated reduced
physical stroke length requirement for a given spectral resolution allows for the use of high speed resonant actuators
such as piezo stacks. Because the spectral range is limited only by the spectral transmission and reflection properties of
the components, this system can be made as broadband as a typical FTIR spectrometer system. For this application, the
system will be designed for the 700 - 1400 cm-1 spectral range with 8 cm-1 spectral resolution.
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This paper presents the statistical formulation of misalignments of optical components. As a case study, sensitivity
analysis is performed to evaluate the optical performance of an assembled Fourier Transform (FT) microspectrometer.
Precision alignment of optical components is a critical factor to achieve high sensitive measurement. Positional and
angular misalignments of optical components are propagated and accumulated from one part to another as the beam is
delivered. Optical paths are modeled as kinematic variables of a linked chain, and its propagation is calculated using
forward kinematics with homogeneous transform matrices. This approach not only formulates the deviation of beam
paths as traditional optics do, but also accommodates statistical variables to represent the mean and variance of
kinematic errors. With the assumption of Gaussian distribution of the errors, the statistical equation was linearly
propagated. The beam deviation was further combined with a light coupling model at the detector to evaluate the
degradation of optical. Its prototype and experimental results were also reported.
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Miniaturized spectrometers covering spectral regions from UV to thermal IR are of interest for several applications. For
these purposes VTT has for many years been developing tuneable MEMS-based and more recently piezo-actuated
Fabry-Perot Interferometers (FPIs). Lately several inventions have been made to enter new wavelengths in the VIS range
and enlarge apertures of MEMS devices and also extending the wavelength range of piezo-actuated FPIs. In this paper
the background and the latest FPI technologies at VTT are reviewed and new results on components and system level
demonstrators are presented. The two FPI technologies are compared from performance and application point of view.
Finally insight is given to the further development of next generation devices.
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We present a recently developed miniature scanning Fourier-Transform spectrometer (ARCspectro ANIR), which is
based on a lamellar grating interferometer and uses a micro-mechanical actuator. The small dimensions of the
interferometer (35 mm x 35 mm x 65 mm) and its low weight makes this device a truly portable Fourier-Transform
spectrometer. Two different versions of this new spectrometer are presented: one version uses an InGaAs photodiode
(0.9μm to 2.6 μm) and the other a MCT detector (2 to 4.5 μm). Their performances are discussed and also illustrated
with measurement and application examples.
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This paper reports on a CMOS-Compatible Linear Variable Optical Filter (LVOF) visible micro-spectrometer. The
CMOS-compatible post process for fabrication of the LVOF has been used for integration of the LVOF with a CMOS
chip containing a 128-element photodiode array and readout circuitry. Fabrication of LVOF involves a process for
fabrication of very small taper angles, ranging from 0.001° to 0.1°, in SiO2. These layers can be fabricated flexibly in a resist layer by just one lithography step and a subsequent reflow process. The 3D pattern of the resist structures is
subsequently transferred into SiO2 by appropriate etching. Complete LVOF fabrication involves CMOS-compatible
deposition of a lower dielectric mirror using a stack of dielectrics on the wafer, tapered layer formation and deposition of
the top dielectric mirror. The LVOF has been optimized for 580 nm - 720 nm spectral operating range and has also been
mounted on a CCD camera for characterization. The design of LVOF micro-spectrometer, the fabrication and
characterization results are presented.
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The design and optical performance of a small-footprint, low-power, turnkey, Point-And-Stare hyperspectral analyzer,
capable of fully automated field deployment in remote and harsh environments, is described. The unit is packaged for
outdoor operation in an IP56 protected air-conditioned enclosure and includes a mechanically ruggedized fully reflective,
aberration-corrected hyperspectral VNIR (400-1000 nm) spectrometer with a board-level detector optimized for point
and stare operation, an on-board computer capable of full system data-acquisition and control, and a fully functioning
internal hyperspectral calibration system for in-situ system spectral calibration and verification. Performance data on the
unit under extremes of real-time survey operation and high spatial and high spectral resolution will be discussed.
Hyperspectral acquisition including full parameter tracking is achieved by the addition of a fiber-optic based
downwelling spectral channel for solar illumination tracking during hyperspectral acquisition and the use of other
sensors for spatial and directional tracking to pinpoint view location. The system is mounted on a Pan-And-Tilt device,
automatically controlled from the analyzer's on-board computer, making the HyperspecTM particularly adaptable for base
security, border protection and remote deployments. A hyperspectral macro library has been developed to control
hyperspectral image acquisition, system calibration and scene location control. The software allows the system to be
operated in a fully automatic mode or under direct operator control through a GigE interface.
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The miniaturized IR spectrometer discussed in this paper is comprised of: slit, planar imaging diffraction grating and
Thermo-Electric (TE) detector array, which is fabricated using CMOS compatible MEMS technology. The resolving
power is maximized by spacing the TE elements at an as narrow as possible pitch, which is limited by processing
constraints. The large aspect ratio of the TE elements implies a large cross-sectional area between adjacent elements
within the array and results in a relatively large lateral heat exchange between micromachined elements by thermal
diffusion. This thermal cross-talk is about 10% in case of a gap spacing of 10 μm between elements. Therefore, the
detector array should be packaged (and operated) in vacuum in order to reduce the cross-talk due to the air conduction
through the gap. Thin film packaging is a solution to achieve an operating air pressure at1.3 mBar, which reduces the
cross-talk to 0.4%. An absorber based on an optical interference filter design is also designed and fabricated as an IC
compatible post-process on top the detector array. The combination of the use of CMOS compatible materials and
processing with high absorbance in 1.5 - 5 μm wavelength range makes a complete on-chip microspectrometer possible.
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