This PDF file contains the front matter associated with SPIE Proceedings Volume 8368, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Making a lens design working in automotive environment is a real challenge. Both optical and mechanical designer must work together to prevent problems during operation. The increasing trend to use vision sensors in transportation is driven both by legislation and consumer demands for higher safety and better driving experiences. With the demand, many new material and design techniques have been developed increasing the lens designer toolbox. This paper reviews the design constraints of the automotive and aerospace environment and how modern material, tools and approaches can be used to fulfill it. We discussed a particular trade-off between the uses of plastic and glass optical component. We also discussed the impact of vision system which is outside or inside the vehicle regarding design trades and performances within the environmental constraints.

Fiber optic sensors offer many advantages over electrical sensors for use in harsh environments. One advantage over distributed electrical sensors is the elimination of the need to route electrical power and wiring to the sensors, which, in general, improves safety and reduces power consumption. Another advantage is that the optical sensors are immune to electromagnetic interference that may be caused by radio frequency signals used for communications. Another benefit of using an optical approach for impact detectors is the implicit immunity from false detections that may otherwise be caused by unrelated mechanical shock or vibration events. Previous studies have documented the characteristics of the Optical Debris Impact Sensor (ODIS). With the ODIS, the impacts are inferred by detecting the brief triboluminescent optical pulses generated by the abrupt charge separation within a phosphor that is caused by the particle impacts. The main limitations of the ODIS are the small detection area and the limited sensitivity. This paper describes a method for extending the ODIS to accomplish broad area detection on a surface with potentially higher sensitivity. The sensing element is comprised of a stack of planar optical waveguides with phosphor-coated strips. The geometry of the design ensures optical pulses are automatically captured by the waveguides and routed to a fiber optic cable that transports the signal to a remote high-speed photodetector. Background light levels in the vicinity of the detector are filtered out by the tailored frequency response of the photodetector.

A new design of a fiber optic sensor using Palladium as a sensitive layer is presented. In this new configuration, a transducer layer is deposited on a multimode fiber (without the optical cladding). The transducer layer is a multilayer stack based on a silver, a silica and a Pd layer. The spectral modulation of the light transmitted by the fiber allows to detect hydrogen. The sensor is only sensitive to the Transverse Magnetic polarized light and the Transverse Electric polarized light can be used as a reference signal. The multilayer thickness defines the sensor performance. The Silica thickness tunes the resonant wavelength, whereas the silver and Pd thickness determines the sensor sensitivity. We present some results obtained for different multilayer Pd configurations.

For many hydrogen related applications it is preferred to use optical hydrogen sensors above electrical systems. Optical sensors reduce the risk of ignition by spark formation and are less sensitive to electrical interference. Currently palladium and palladium alloys are used for most hydrogen sensors since they are well known for their hydrogen dissociation and absorption properties at relatively low temperatures. The disadvantages of palladium in sensors are the low optical response upon hydrogen loading, the cross sensitivity for oxygen and carbon, the limited detection range and the formation of micro-cracks after some hydrogen absorption/desorption cycles. In contrast to Pd, we find that the use of magnesium or rear earth bases metal-hydrides in optical hydrogen sensors allow tuning of the detection levels over a broad pressure range, while maintaining a high optical response. We demonstrate a stable detection layer for detecting hydrogen below 10% of the lower explosion limit in an oxygen rich environment. This detection layer is deposited at the bare end of a glass fiber as a micro-mirror and is covered with a thin layer of palladium. The palladium layer promotes the hydrogen uptake at room temperature and acts as a hydrogen selective membrane. To protect the sensor for a long time in air a final layer of a hydrophobic fluorine based coating is applied. Such a sensor can be used for example as safety detector in automotive applications. We find that this type of fiber optic hydrogen sensor is also suitable for hydrogen detection in liquids. As example we demonstrate a sensor for detecting a broad range of concentrations in transformer oil. Such a sensor can signal a warning when sparks inside a high voltage power transformer decompose the transformer oil over a long period.

In this paper we explore Fluorescence Technology as applied to the design and development of O₂ sensors that can be used for aerospace application and discuss the various test and measurement techniques used to estimate the O₂ gas concentration. Jet fuel comprised of heavier hydrocarbon components is much less volatile, than jet fuel having a flash point of approximately 37° C and JP-4 having a flash point of approximately -17° C. In contrast, straight-run gasoline has a flash point of approximately -40°C. The flash point is the minimum temperature where a liquid fuel can generate enough vapor to form a flammable mixture with air. If the temperature is below the flash point there isn't enough fuel evaporating to form a flammable fuel-air mixture. Since jet fuel and gasoline have similar flammable concentration limits, gasoline must produce much more vapor at a given temperature to have such a low flash point; hence gasoline is much more volatile than jet fuel. We compare the various intensity based approaches and contrast them with the frequency domain techniques that measure phase to extract fluorescent lifetimes. An innovate compact measurement system using the frequency heterodyning cross correlation technique that can be used for various applications is described in detail while the benefits are explored together with some test data collected. The various inerting fuel tank requirements are explained.

This paper describes the 1st successful Plastic Optical Fiber (POF) cable and Glass Optical Fiber (GOF) hydrogen detection sensor systems developed for the Boeing Evolved Expandable Lunch Vehicle (EELV) Delta IV Launch Vehicle harsh environment of engine section. H₂ sensors are necessary to monitor the possible leak of rocket prior launch to avoid explosion, which can be highly dangerous. Due to harsh environment of launch vehicle, we developed the first combination of 100 m POF and glass fiber H₂ sensors. The hydrogen sensor consisted of optrodes distributed at multiple locations along a fiber optic cable-based network. These hydrogen sensors were used on the Common Booster Core (CBC) of Delta IV had to perform in temperatures between -18° C and +60° C. The hydrogen sensor sensitive chemistry was fully reversible and had demonstrated a response to hydrogen gas in the range of 0% to 10% with a resolution of 0.1 % and a response time of 5 seconds measured at a gas flow rate of 1 cc/mm. The optical signature of the optrode in the visible spectrum varied proportionally to the local hydrogen gas concentration. To qualify the POF and fiber optic cables, performed detail investigation for attenuation loss, thermal, humidity, temperature, vibration and accelerate testing for life expectancy. Extensive networking using LabView were carried out for lab and actual field demonstrations.

Structural Health Monitoring (SHM) has been identified as an area of significant potential for advanced aircraft maintenance programs that ensure continued airworthiness, enhanced operational safety and reduced life cycle cost. Several sensors and sensory systems have been developed for the implementation of such health monitoring capability. Among a wide range of developed technologies, fiber optic sensor technology, in particular fiber Bragg grating based emerged as one of the most promising for aircraft structural applications. This paper is set to explore the suitability of using a new Fiber Bragg Grating sensor (FBG) system developed for operation in two modes, low and high speed sensing modes, respectively. The suitability of the system for potential use in aircraft load monitoring and damage detection applications has been demonstrated. Results from FBG sensor system were in good agreement with results from conventional resistive strain gauges, validating this capability for load monitoring. For damage detection, the FBG sensor system was able to detect acoustic waves generated 52 inches (1.32 m) away. The initial results, obtained in a full stale experimentation, demonstrate the potential of using FBG sensors for both load monitoring and damage detection in aircraft environment.

Installation of fiber optic communication systems on aircraft is very challenging, particularly in military fighters requiring tight confinement. The issues to be addressed include developing an installation approach compatible with maintenance and through-life support whilst having affordable upfront costs. This applies both to the passive harness components (cable and connectors) and to active transceivers. In this paper we discuss the challenges for cable, connector, and transceiver installations and the system implications for civil and military platforms. This paper further demonstrates how an innovative approach to sub-system testing can help to de-risk technology by simulating installation environments in the laboratory and verifying through-life performance. Furthermore, testing of fiber optic cable in the laboratory with prototype components, representative cable lengths, routing and number of connector breaks, and even harness abuse is elaborated upon. A technique was devised using the BAE Systems Optical System and Component Assessment Rig (OSCAR) to evaluate through life operation. This report also shows prototype testing for typical fiber optic harnesses (during build) and the environmental conditions faced on aerospace platforms. Transceiver installation options (integrated onto processor boards, use of daughter PCBs, active connectors and active cables) are discussed and sub-system test setups are described. Results show how test data is used to assess subsystems: passive components have been tested over the -55 °C to +125 °C temperature range and active components over the -40 °C to +80 °C region. In addition, Gigabit Ethernet data is shown operating over the representative hardware with the results tabulated and shown in this paper. The implications for anticipated aircraft installations are summarized.

Fiber optic hydrophones are useful for a variety of underwater monitoring applications, as they offer high sensitivity, signal-to-noise ratio and multiplexing ability for marine acoustics and offer longer term reliability than conventional electronic hydrophones. The frequency response of packaged fibers depends strongly on the material and mechanical parameters of the sensor design. Two fiber bragg-grating (FBG)-based hydrophones are described and their frequency response is measured. One consists of a diaphragm-linked FBG, and another is a polymer coated FBG. While the diaphragm-linked FBG has predictable resonances, resonance features on the simpler coated FBG hydrophone are observed as well.

The Dual Optical Embedded Dust Sensor (DOEDS) is designed for the sensitive, accurate detection of particles for preventive health monitoring of the AGT1500 engine and M1 Abrams/Ground Combat Vehicles (GCVs). DOEDS is a real-time sensor that uses an innovative combination of optical particle sensing technologies and mechanical packaging in a rugged, compact and non-intrusive optical design. The optical sensor, implementing both a single particle sensor and a mass sensor, can operate in harsh environments (up to 400°F) to meet the particle size, size distribution, mass concentration, and response time criteria. The sensor may be flush- or inline-mounted in multiple engine locations and environments.

A miniature fiber-optic chemical sensor system allowing for simultaneous detection of gas concentrations and physical parameters is described, fabricated and tested. The design is focused on minimizing influence of the sensor onto the system under test, therefore employing very thin and pliable fiber probes. Microfabrication of the sensor structure is described and a suitable interrogation setup is introduced. Measurements of O₂ and CO₂ concentrations are presented and discussed. Applications in continuous medical monitoring and necessary design and operating parameters are described.

We present in this paper a novel implementation of a wearable see through display including a diffractive exit pupil expander element. The optical system is a pupil forming system which integrates also a diffractive beam combiner.

The use of bio-fuels and fuel blends, specially in automotive industry, has been increasing substantially in recent years due to market prices and trends on sustainable development policies. Different spectral analysis techniques for quality control, production, purity, and counterfeit detection have been reported as non-invasive, fast, and price accessible. Raman spectra from three different commercial binary E10 fuel-ethanol blends has been obtained by using a low-cost Fourier-Transform Raman spectrometer (FT-Raman). Qualitative comparison between the commercial fuel blends and a laboratory-prepared fuel blend have been performed. The characteristic Raman lines from some additives contained in the commercial gasoline have been also observed. The spectral information is presented in the range of 0 cm^-1 to 3500 cm^-1 with a resolution of 1.66 cm^-1. These Raman spectra shows reduced frequency deviation (less than 0.4 cm^-1 when compared to standard Raman spectra from cyclohexane and toluene without compensation for instrumental response). Higher resolution values are possible, since the greater optical path lengths of the FT-Raman are achievable before the instrumental physical effects appear. The robust and highly flexible FT-Raman prototype proposed for the spectral analysis, consisting mainly of a Michelson interferometer and a self-designed photon counter, is able to deliver high resolution and precise Raman spectra with no additional complex hardware or software control. The mechanical and thermal disturbances affecting the FT-Raman system are mathematically compensated by extracting the optical path information from the generated interference pattern of a λ=632.8 nm Helium-Neon laser (HeNe laser), which is used at the spectrum evaluation.

Structural Health Monitoring (SHM) is a sought after concept that is expected to advance military maintenance programs, increase platform operational safety and reduce its life cycle cost. Such concept is further considered to constitute a major building block of any Integrated Health Management (IHM) capability. Since 65% to 80% of military assets' Life Cycle Cost (LCC) is devoted to operations and support (O&S), the aerospace industry and military sectors continue to look for opportunities to exploit SHM systems, capability and tools. Over the past several years, countless SHM concepts and technologies have emerged. Among those, fiber optic based systems were identified of significant potential. This paper introduces the elements of an SHM system and investigates key issues impeding the commercial implementation of fiber optic based SHM capability. In particular, this paper presents an experimental study of short gauge, intrinsic, spectrometric-based in-fiber Bragg grating sensors, for potential use as a component of an SHM system. Fiber optic Bragg grating sensors are evaluated against resistance strain gauges for strain monitoring, sensitivity, accuracy, reliability, and fatigue durability. Strain field disturbance is also investigated by "embedding" the sensors under a photoelastic coating in order to illustrate sensor intrusiveness in an embedded configuration.

Security, defense and sensing applications often require routing of optical fibers through constrained spaces. Fibers or fiber cables must frequently be tightly matched or mounted onto structures having arbitrary shapes or forms, which inevitably leads to requirement for tight fiber bends. In such case macro bend loss presents one of the major concerns and limitations in practical applicability of optical fibers. Fibers with high bend tolerance are therefore required in such environments. To date, significant works relating to the understanding and improvement of bend-loss sensitivity have been carried on for single-mode fibers and fiber systems. However, in security and defense applications, robust connectivity and installation reliability issues often favor multimode fiber systems.

Space-based optical communications using satellites in low earth orbit (LEO) and Geo synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. Building high speed communications network using optical links in space has proven to be an extremely complicated task and many such schemes were tried without success in the past. However in the last few years, there has been impressive progress made to bring the concept of space based laser systems for inter-satellite communications to fruition in civilian and government-non classified projects. Laser Communications High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. Also discussed are the laser based optical inter-satellite communication equipment which enables large capacity communication, and the advantage of their systems. Laser-based communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity.

The paper proposes the development and verification of a hardware and software tool that will be able to evaluate and optimize sensorized aerospace structures is proposed. The tool will be extension of an existing suite of structural health monitoring (SHM) and diagnostic prognostic system (DPS). The goal of the extended SHM-DPS is to apply multi-scale nonlinear physics-based finite element analyses to the "as-is" structural configuration to determine residual strength, remaining service life, and future inspection intervals and procedures. Information from a distributed system of sensors will be used to determine the "as-is' state of the structure versus the "as-designed" target. The proposed approach will enable active monitoring of aerospace structural component performance and realization of DPS-based maintenance. Software enhancements will incorporate information from a sensor system that is distributed over an aerospace structural component. In the case of the proposed project, the component will be a stiffened composite fuselage panel. Two stiffened panels is instrumented with wireless sensors; the second with an optimized sensor network. It is shown that the sensor system output will be routed and integrated into a nonlinear multi-scale physics-based finite element analysis (FEA) tool to determine the panel's residual strength, remaining service life, and future inspection interval. The FEA will utilize the GENOA progressive failure analysis software suite, which is applicable to metallic and advanced composites.

We report on cooperative research program between Army Research Laboratory (ARL), Night Vision and Electronic Sensors Directorate (NVESD), and University of Maryland (UMD). The program aims to develop advanced on-the-fly atmospheric image processing techniques based on local information fusion from a single or multiple monochrome and color live video streams captured by imaging sensors in combat or reconnaissance situations. Local information fusion can be based on various local metrics including local image quality, local image-area motion, spatio-temporal characteristics of image content, etc. Tools developed in this program are used to identify and fuse critical information to enhance target identification and situational understanding in conditions of severe atmospheric turbulence.

Depth mapping or depth sensing has become a popular field, applied not only to automotive sensing for collision avoidance (radar) but also to gesture sensing for gaming and virtual interfaces (optical). Popular gesture sensing devices such as the Kinect from Microsoft's Xbox gaming device produce a full absolute depth map, which is in most cases not adapted to the task on hand (relative gesture sensing). We propose in this paper a new gesture sensing technique through structured IR illumination to provide a relative depth mapping rather than an absolute one, and this reducing the requirements on computing power and therefore enabling this technology for wearable computing such as see through display.

The polarization state of light provides valuable information about scenes that cannot be obtained directly from intensity or spectral images. Polarized light reflected from scenes has been found to be useful and can reveal contrasts that do not appear in classical intensity images and find many applications in remote sensing, biomedical imaging, or industrial control. Cost, size, and technological complexity of polarimetric imagers depend on the number of polarimetric parameters they measure. In this context, a key issue is to evaluate the added value of each measured polarimetric parameter in order to optimize the compromise between complexity and efficiency of these systems. In target detection applications, the relevant criterion for quantifying the performance of an imaging configuration is contrast (or discrimination ability). Analysis of the contrast and its optimization in polarimetric images have been investigated in the radar and optics communities. We investigate in the paper how the polarisation imaging can be applied in automotive vision based sensor. This study present various type of polarisation sensitive optical system. Detection of small and low-contrast objects has been found to be improved with the help of this kind of optical system.

Electro-optic sensors made of lasers or photodetectors assemblies can be associated with a window interface. In order to use these sensors in an avionics application, this interface has to be set on the periphery of the aircraft. This creates constraints on both the position/access of the associated electronics circuit card and the aircraft fuselage. Using an optical fiber to guide the light signal to a sensor being situated inside the aircraft where electronics circuit cards are deployed is an obvious solution that can be readily available. Fiber collimators that adapt to circular TO-can type window sensors do exist. However, they are bulky, add weight to the sensor and necessitate regular maintenance of the optical interface since both the sensor window and the collimator end-face are unprotected against contamination. Such maintenance can be complex since the access to the electronics circuit card, where the sensor is sitting, is usually difficult. This interface alignment can also be affected by vibrations and mechanical shocks, thus impacting sensor performances. As a solution to this problem, we propose a highly-hermetic feedthrough fiber pigtailed circular TO-can package. The optical element to optical fiber interface being set inside the hermetic package, there is no risk of contamination and thus, such a component does not require any maintenance. The footprint of these sensors being identical to their window counterparts, they offer drop-in replacement opportunities. Moreover, we have validated such packaged electro-optic sensors can be made to operate between -55 to 115°C, sustain 250 temperature cycles, 1500G mechanical shocks, 20Grms random vibrations without any performance degradations. Their water content is much smaller than the 0.5% limit set by MIL-STD-883, Method 1018. They have also been verified to offer a fiber pigtail strain relief resistance over 400g. Depending on the electronics elements inside these sensors, they can be made to have a MTBF over 50 000h at 100°C.

A fiber optic data system can be designed and constructed with many options for active components and for passive system elements. With regard to the passive interconnection system components, each application may have a different list of fiber/cable, connectors, ruggedization materials and other components. The selection of these items should be made keeping in mind the specific particular requirements of the system, from the standpoint of environmental and mechanical requirements and from the standpoint of the users who will be installing, maintaining and possibly repairing the system sometime in the future. The paper will review various alternatives available for selection of components, discussing options for different scenarios of required optical performance. Considerations of component selection with regard to capabilities of the installers/maintenance and repair people who will be responsible for the success of the system will also be discussed. A fiber optic system is not necessarily more difficult to install and maintain, but it is different from electrical systems and as long as proper component selection and training are implemented, the fiber optic system should be durable and successful.

We propose a new non destructive optical method for the determination of the shear modulus G of solid materials. The shear modulus is determined by measuring the twisted angle θ as a response of the material sample, depending on an applied force. The measuring of this twisted angle is obtained by using an adapted polarimetric sensor. The effective measurements of rigidity modulus G for different materials were experimentally achieved, we obtained respectively 1.4464.10¹⁰ N/m², 0.99417.10⁹ N/m² and 1.0395.10¹¹ N/m² for Aluminum, PMMA and Steel. The study has demonstrated the effective usefulness of our method for evaluating the rigidity modulus. A good agreement between the theoretical and experimental results was achieved. This study permit to design and elaborate a new type of optical torque sensor for electrical power assisted steering system.

Harsh environment avionics applications require operating temperature ranges that can extend to, and exceed -50 to 115°C. For obvious maintenance, management and cost arguments, product lifetimes as long as 20 years are also sought. This leads to mandatory long-term hermeticity that cannot be obtained with epoxy or silicone sealing; but only with glass seal or metal solder or brazing. A hermetic design can indirectly result in the required RF shielding of the component. For fiber-optics products, these specifications need to be compatible with the smallest possible size, weight and power consumption. The products also need to offer the best possible high-speed performances added to the known EMI immunity in the transmission lines. Fiber-optics transceivers with data rates per fiber channel up to 10Gbps are now starting to be offered on the market for avionics applications. Some of them are being developed by companies involved in the "normal environment" telecommunications market that are trying to ruggedize their products packaging in order to diversify their customer base. Another approach, for which we will present detailed results, is to go back to the drawing boards and design a new product that is adapted to proven MIL-PRF-38534 high-reliability packaging assembly methods. These methods will lead to the introduction of additional requirements at the components level; such as long-term high-temperature resistance for the fiber-optic cables. We will compare both approaches and demonstrate the latter, associated with the redesign, is the preferable one. The performance of the fiber-optic transceiver we have developed, in terms of qualification tests such as temperature cycling, constant acceleration, hermeticity, residual gaz analysis, operation under random vibration and mechanical shocks and accelerated lifetime tests will be presented. The tests are still under way, but so far, we have observed no performance degradation of such a product after more than 1050 hours of operation at 95°C.

This research effort is to demonstrate a remote sensing method using optical fibers with a Fourier Transform Infrared (FTIR) interferometer as an evanescent wave spectroscopic technique. In addition to the usual advantages of optical fiber sensors, such as small size and weight, optical fibers can be embedded in aircraft structures in locations where humidity and corrosion can accumulate but cannot be directly observed. A fiber-optic-FTIR experimental setup, including several samples of field corroded materials, has been assembled to spectrally detect Aluminum Hydroxide [Al(OH)₃] which is one of the major components of aluminum corrosion. Absorption spectra of Al(OH)₃ have been collected using an Attenuated Total Reflection (ATR) crystal as a reference spectral signature. The absorption spectra of samples from a simulated corrosion process and from the field corroded structures have been collected and compared with the reference Al(OH)₃ spectra. Chalcogenide optical fibers are used for remote sensing purposes to detect corrosion. Two distinctive absorption peaks, attributable to aluminum hydroxide, are noticed from the simulated corrosion and from the field corroded structures.

High Power LED is poised to replace traditional lighting sources such as Fluorescent, HID, Halogen and conventional incandescent bulbs in many applications. Due to the solid state compact nature of the light source it is inherently rugged and reliable and has been the favored lighting source for most indoor and outdoor applications including many hazardous locations that impact, and safety environments including mining, bridge, Aerospace, Automotive . In order to accelerate this transition many enhancements and advances are taking place to improve on the reliability, and thermal performance of these devices. This paper explores the various improvements and advances made in the packaging of LEDs to enhance their performance