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.

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.

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.

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.

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.

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.

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 MatrixNIR^TM is based on a LCTF tunable filter and InGaAs camera and covers wavelengths from 1000 to 1700 nm. The second one SisuCHEMA^TM 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.

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.

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.

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.

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.

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.

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.

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.

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-ESR^TM. The technology promises to revolutionize the accessibility of ESR spectroscopy for industrial and scientific users.

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.

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.

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.

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.

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.

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.

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.

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.

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 Hyperspec^TM 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.

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.