We review two different techniques for visualization and processing of three-dimensional (3D) objects based on passive and active optical sensing. First, we describe the basis of a passive-sensing technique based on integral imaging. Also, we show that it is possible to improve the depth of field of this method by using amplitude-modulated microlens arrays. Second, we describe an active-sensing technique based on digital holography. Finally, we apply both techniques to de-velop 3D image processing applications. In particular, we design two different 3D pattern recognition techniques. Both of them are based in storing the 3D data in two-dimensional (2D) form. In this way, it is possible to recognize 3D objects by performing 2D correlations or applying neural network techniques. Experimental results are presented.
In this paper, we present a novel technique for automated remote optical ID tag recognition and verification. The design of distortion-invariant ID tags aims to achieve a correct object authentication even if the ID tag is detected and captured at different distances (i.e. scale variance) or from different views (i.e. rotation variance). Information included in the ID tag is encrypted in order to increase security. We use a fully phase encoded primary pattern and keys by spatial phase multiplexing. This encryption technique is compared with the amplitude-based encoding used in previous works. Experimental results and analysis are presented.
This paper analyzes the security of amplitude encoding for double random phase encryption. We describe several types of attack. The system is found to be resistant to brute-force attacks but vulnerable to chosen and known plaintext attacks.
One of the main challenges in integral imaging is to overcome the limited depth of field. Although it is widely assumed that such limitation is mainly imposed by diffraction due to lenslet imaging, we show that the most restricting factor is the pixelated structure of the sensor (CCD). In this context, we take profit from these sensor constraints and demonstrate that by proper binary amplitude modulation of the pickup microlenses, the depth of field can be substantially improved with no deterioration of lateral resolution.
We address the problem of defining degrees of coherence for
partially polarized Gaussian light. Some previously published
approaches provide efficient solutions to this problem, but we
will show on simple examples that they do not clearly separate
partial polarization and partial coherence effects. We thus
introduce intrinsic degrees of coherence, which characterize
partial coherence independently of the choice of coordinate
systems and of the partial polarization state of each field. The
larger of these degrees has a clear physical meaning since it
corresponds to the largest scalar degree of coherence that can
be obtained after propagating the light waves through polarization
modulators and perfect polarizers. Another interesting physical
interpretation is obtained by relating the intrinsic degrees of
coherence to the Shannon entropy, which is a classic measure of
the "disorder" of a physical phenomenon.
We propose a statistical approach to detect a three-dimensional object using digital holography. The proposed algorithm uses the statistical properties of the speckle noise to find a probabilistic model for the likelihood function of the presence of the three-dimensional object in the scene. Phase shifting holography is used to generate the optical hologram of the 3D object and inverse Fresnel diffraction is used to reconstruct the 3D object. The complex wave generated from the inverse Fresnel integral is used as an input to the proposed algorithm. We show that the reconstructed 3D scene can be modeled as an object buried in a background complex Gaussian noise and the object is multiplied by a complex Gaussian noise. Analytical analysis and simulations show that the proposed technique is able detect the three dimensional coordinates of the distorted target object.
Security applications of sensors in a networking environment has a
strong demand of sensor authentication and secure data transmission
due to the possibility of man-in-the-middle and address spoofing
attacks. Therefore a secure sensor system should fulfil the three
standard requirements of cryptography, namely data integrity,
authentication and non-repudiation. This paper is intended to
present the unique sensor development by AIM, the so called SecVGA,
which is a high performance, monochrome (B/W) CMOS active pixel
image sensor. The device is capable of capturing still and motion
images with a resolution of 800x600 active pixels and converting the
image into a digital data stream. The distinguishing feature of this development in comparison to standard imaging sensors is the on-chip cryptographic engine which provides the sensor authentication, based on a one-way challenge/response protocol. The implemented protocol results in the exchange of a session-key which will secure the following video data transmission. This is achieved by calculating a cryptographic checksum derived from a stateful hash value of the complete image frame. Every sensor contains an EEPROM memory cell for the non-volatile storage of a unique identifier. The imager is
programmable via a two-wire I2C compatible interface which controls the integration time, the active window size of the pixel array, the frame rate and various operating modes including the authentication procedure.
Face verification/recognition is a tough challenge in comparison to
identification based on other biometrics such as iris, or fingerprints. Yet, due to its unobtrusive nature, the face is naturally suitable for security related applications. Face verification process relies on feature extraction from face images. Current schemes are either geometric-based or template-based. In the latter, the face image is statistically analysed to obtain a set of feature vectors that best describe it. Performance of a face verification system is affected by image variations due to illumination, pose, occlusion, expressions and scale. This paper extends our recent work on face verification for constrained platforms, where the feature vector of a face image is the coefficients in the wavelet transformed LL-subbands at depth 3 or more. It was demonstrated that the wavelet-only feature vector scheme has a comparable performance to sophisticated state-of-the-art when
tested on two benchmark databases (ORL, and BANCA). The significance of those results stem from the fact that the size of the k-th LL- subband is 1/4k of the original image size. Here, we investigate the use of wavelet coefficients in various subbands at level 3 or 4 using various wavelet filters. We shall compare the performance of the wavelet-based scheme for different filters at different subbands with a number of state-of-the-art face verification/recognition schemes on two benchmark databases, namely ORL and the control section of BANCA. We shall demonstrate that our schemes have comparable performance to (or outperform) the best performing other schemes.
Advances in digital image processing, the advents of multimedia computing, and the availability of affordable high quality digital cameras have led to increased demand for digital images/videos. There has been a fast growth in the number of information systems that benefit from digital imaging techniques and present many tough challenges. In this paper e are concerned with applications for which image quality is a critical requirement. The fields of medicine, remote sensing, real time surveillance, and image-based automatic fingerprint/face identification systems are all but few examples of such applications. Medical care is increasingly dependent on imaging for diagnostics, surgery, and education. It is estimated that medium size hospitals in the US generate terabytes of MRI images and X-Ray images are generated to be stored in very large databases which are frequently accessed and searched for research and training. On the other hand, the rise of international terrorism and the growth of identity theft have added urgency to the development of new efficient biometric-based person verification/authentication systems. In future, such systems can provide an additional layer of security for online transactions or for real-time surveillance.
The present trend of increasing functionality onboard unmanned vehicles is made possible by rapid advances in high-performance computers (HPCs). An HPC is characterized by very high computational capability (100s of billions of operations per second) contained in lightweight, rugged, low-power packages. HPCs are critical to the processing of sensor data onboard these vehicles. Operations such as radar image formation, target tracking, target recognition, signal intelligence signature collection and analysis, electro-optic image compression, and onboard data exploitation are provided by these machines. The net effect of an HPC is to minimize communication bandwidth requirements and maximize mission flexibility. This paper focuses on new and emerging technologies in the HPC market. Emerging capabilities include new lightweight, low-power computing systems: multi-mission computing (using a common computer to support several sensors); onboard data exploitation; and large image data storage capacities. These new capabilities will enable an entirely new generation of deployed capabilities at reduced cost. New software tools and architectures available to unmanned vehicle developers will enable them to rapidly develop optimum solutions with maximum productivity and return on investment. These new technologies effectively open the trade space for unmanned vehicle designers.
The wars in Iraq and Afghanistan have shown the importance of sensor and robotic technology as a force multiplier and a tool for moving soldiers out of harms way. Situations on the ground make soldiers easy targets for snipers and suicide bombers. Sensors and robotics technology reduces risk to soldiers and other personnel at checkpoints, in access areas and on convoy routes. Early user involvement in innovative and aggressive acquisition and development strategies are the key to moving sensor and robotic and associated technology into the hands of the user, the soldier on the ground. This paper discusses activity associated with rapid development of the robotics, sensors and our field experience with robotics in Iraq and Afghanistan.
This research is part of a broader effort to develop a supervisory control system for small robot navigation. Previous research and development focused on a "one-touch, point-and-go" navigation control system using visual homing. In the current research, we have begun to investigate visual tracking methods to extend supervisory control to tasks involving tracking and pursuit of a moving object. Ground-to-ground tracking of arbitrary targets in natural and damaged environments is challenging. Automatic tracking is expected to fail due to line-of-sight obstruction, lighting gradients, rapid changes in perspective and orientation, etc. In supervisory control, the automatic tracker needs able to alert the operator when it is at risk of losing track or when it may have already lost track, and do so with a low false alarm rate. The focus of the current research is on detecting tracking failure during pursuit. We are attempting to develop approaches to detecting failure that can integrate different low-level tracking algorithms. In this paper, we demonstrate stereo vision methods for pursuit tracking and examine several indicators of track loss in field experiments with a variety of moving targets in natural environment.
Currently, multiple humans are needed to operate a single uninhabited aerial vehicle (UAV). In the near future, combat techniques will involve single operators controlling multiple uninhabited ground and air vehicles. This situation creates both technological hurdles as well as interaction design challenges that must be addressed to support future fighters. In particular, the system will need to negotiate with the operator about proper task delegation, keeping the operator appropriately apprised of autonomous actions. This in turn implies that the system must know what the user is doing, what needs to be done in the present situation, and the comparative strengths for of the human and the system in each task. Towards building such systems, we are working on an Intelligent Control Framework (ICF) that provides a layer of intelligence to support future warfighters in complex task environments. The present paper presents the Adjustable Autonomy Module (AAM) in ICF. The AAM encapsulates some capabilities for user plan recognition, situation reasoning, and authority delegation control. The AAM has the knowledge necessary to support operator-system dialogue about autonomy changes, and it also provides the system with the ability to act on this knowledge. Combined with careful interaction design, planning and plan-execution capabilities, the AAM enables future design and development of effective human-robot teams.
Sandia National Laboratories has developed a mesoscale wheeled hopping vehicle (WHV) to overcome the longstanding problems of mobility and power in small scale unmanned vehicles. The system provides mobility in situations such as negotiating obstacles in the vertical dimension and rough terrain that are prohibitive for other small ground base vehicles.
We illustrate an approach for planning UAV sensing actions in urban or constrained domains. We plan and optimize a collection strategy for a target of interest using Design Sheet, a numeric/symbolic algebraic constraint propagation package. Once a set of sensing plans have been developed, we use a probabilistic roadmap planning algorithm to plan a route for a fixed wing UAV through urban terrain to collect that information. This planner has several novel features to improve performance for urban domains.
UAVs are a key element of the U. S. Army's vision for Force Transformation, and are expected to be employed in large numbers per FCS Unit of Action (UoA). This necessitates a multi-UAV level of autonomous collaboration behavior capability that meets RSTA and other mission needs of FCS UoAs. Autonomous Collaborative Mission Systems (ACMS) is an extensible architecture and behavior planning / collaborative approach to achieve this level of capability. The architecture is modular and the modules may be run in different locations/platforms to accommodate the constraints of available hardware, processing resources and mission needs. The modules and uniform interfaces provide a consistent and platform-independent baseline mission collaboration mechanism and signaling protocol across different platforms. Further, the modular design allows flexible and convenient extension to new autonomous collaborative behaviors to the ACMS through: adding new behavioral templates in the Mission Planner component; adding new components in appropriate ACMS modules to provide new mission specific functionality; adding or modifying constraints or parameters to the existing components, or any combination of these. We describe the ACMS architecture, its main features on extensibility, and updates on current spiral development status and future plans for simulations in this report.
Seacoast Science develops chemical sensors that use polymer-coated micromachined capacitors to measure the dielectric permittivity of an array of selectively absorbing materials. We present recent results demonstrating the sensor technology's capability to detect components in explosives and toxic industrial chemicals. These target chemicals are detected with functionalized polymers or network materials, chosen for their ability to adsorb chemicals. When exposed to vapors or gases, the permittivity of these sorbent materials changes depending on the strength of the vapor-sorbent interaction. Sensor arrays made of ten microcapacitors on a single chip have been previously shown to detect vapors of organic compounds (chemical warfare agents, industrial solvents, fuels) and inorganic gases (SO2, CO2, NO2). Two silicon microcapacitor structures were used, one with parallel electrode plates and the other with interdigitated "finger-like" electrodes. The parallel-plates were approximately 300 μm wide and separated by 750 nm. The interdigitated electrodes were approximately 400 μm long and were elevated above the substrate to provide faster vapor access. Eight to sixteen of these capacitors are fabricated on chips that are 5 x 2 mm and are packaged in less than 50 cm3 with supporting electronics and batteries, all weighing less than 500 grams. The capacitors can be individually coated with different materials creating a small electronic nose that produces different selectivity patterns in response to different chemicals. The resulting system's compact size, low-power consumption and low manufacturing costs make the technology ideal for integration into various systems for numerous applications.
In an unattended, implanted or mobile ground sensor scenario, the microcantilever platform is well suited: sensor power consumption has been demonstrated at the nanowatt level and, as a microelectromechanical system, the platform is inherently compact. In addition, the remarkable sensitivity, low cost, scalability, durability and versatility of microcantilever sensors make this technology among the most promising solutions for unattended ground sensing of chemical and biological agents, as well as explosives. Nevada Nanotech Systems, Inc (NNTS) is developing a microcantilever- based detection system that will measure trace concentrations of explosives, toxic chemicals, and biological agents in air. A baseline sensor unit that includes the sensor array, electronics, power supply and air handling has been designed and preliminary demonstrations of the microcantilever platform have been conducted. The envisioned device would measure about two cubic inches, run on a small watch battery and cost a few hundred dollars. Finally, the NNTS microcantilever sensor has potential as a multifunctional transducer for enhancing detection and discrimination. Recent test results using this platform will be discussed.
The Army is currently developing acoustic overwatch sensor systems that will provide extended range surveillance, detection, and identification for force protection and tactical security on the battlefield. A network of such sensors remotely deployed in conjunction with a central processing node (or gateway) will provide early warning and assessment of enemy threats, near real-time situational awareness to commanders, and may reduce potential hazards to the soldier. In contrast, the current detection of chemical/biological (CB) agents expelled into a battlefield environment is limited to the response of chemical sensors that must be located within close proximity to the CB agent. Since chemical sensors detect hazardous agents through contact, the sensor range to an airburst is the key-limiting factor in identifying a potential CB weapon attack. The associated sensor reporting latencies must be minimized to give sufficient preparation time to field commanders, who must assess if an attack is about to occur, has occurred, or if occurred, the type of agent that soldiers might be exposed to. The long-range propagation of acoustic blast waves from heavy artillery blasts, which are typical in a battlefield environment, introduces a feature for using acoustics and other disparate sensor technologies for the early detection and identification of CB threats. Employing disparate sensor technologies implies that warning of a potential CB attack can be provided to the solider more rapidly and from a safer distance when compared to that which conventional methods allow. This capability facilitates the necessity of classifying the types of rounds that have burst in a specified region in order to give both warning and provide identification of CB agents found in the area.
In this paper, feature extraction methods based on the discrete wavelet transform (DWT) and multiresolution analysis facilitate the development of a robust classification algorithm that affords reliable discrimination between conventional and simulated chemical/biological artillery rounds using acoustic signals produced during detonation. Distinct characteristics arise within the different airburst signatures because high explosive warheads emphasize concussive and shrapnel effects, while chemical/biological warheads are designed to disperse their contents over large areas, therefore employing a slower burning, less intense explosive to mix and spread their contents. The ensuing blast waves are readily characterized by variations in the corresponding peak pressure and rise time of the blast, differences in the ratio of positive pressure amplitude to the negative amplitude, and variations in the overall duration of the resulting waveform. We show that, highly reliable discrimination (> 98%) between conventional and potentially chemical/biological artillery is achieved at ranges exceeding 3km. A feedforward neural network classifier, trained on a feature space derived from the distribution of wavelet coefficients found within different levels of the multiresolution decomposition yields.
Seismic detection systems for homeland security applications are an important additional layer to perimeter and border protection and other security systems. General Sensing Systems has been developing low mass, low cost, highly sensitive geophones. These geophones are being incorporated within a seismic cable. This article reports on
the concept of a seismic sensitive cable and seismic sensitive ribbon design. Unlike existing seismic cables with sensitivity distributed along their lengths, the GSS new cable and ribbon possesses high sensitivity distributed in several points along the cable/ribbon with spacing of about 8-12 to 100 meters between geophones. This cable/ribbon is highly suitable for design and installation in extended perimeter protection systems. It allows the use of a mechanical cable layer for high speed installation. We show that any installation mistakes in using the GSS seismic sensitive cable/ribbon have low impact on output seismic signal value and detection range of security systems.
The advent of network coding promises to change many aspects of networking. Network coding moves away from the classical approach of networking, which treats networks as akin to physical transportation systems. We overview some of the main features of network coding that are most relevant to wireless networks. In particular, we discuss the fact that random distributed network coding is asymptotically optimal for wireless networks with and without packet erasures. These results are extremely general and allow packet loss correlation, such as may occur in fading wireless channels. The coded network lends itself, for multicast connections, to a cost optimization which not only outperforms traditional routing tree-based approaches, but also lends itself to a distributed implementation and to a dynamic implementation when changing conditions, such as mobility, arise. We illustrate the performance of such optimization methods for energy efficiency in wireless networks and propose some new directions for research in the area.
In the recent years, there has been a lot of research on sensor networks and their applications. In particular for monitoring large and potentially hostile areas these networks have proven to be very useful. The technique of land-based sensor networks can be extrapolated to sensing buoys at sea or in harbors. This is a novel and intriguing addition to existing maritime monitoring systems. At TNO, much research effort has gone into developing sensor networks. In this paper, the TNOdes sensor network is presented. Its practical employability is demonstrated in a surveillance application deploying 50 nodes. The system is capable of tracking persons in a field, as would be the situation around a military compound. A camera-system is triggered by the sensors and zooms into the detected moving objects. It is described how this system could be modified to create a wireless buoys network. Typical applications of a wireless (and potentially mobile) buoy network are bay-area surveillance, mine detection, identification and ship protection.
A common problem in modern military communication networks is node discovery. In order to form a robust and efficient network each node needs to notify the network of its existence and, where security policies allow, to report its location. Furthermore, the process of fast and covert new node identification and recognition can help prevent friendly fire incidents. Once a network is established, new nodes often need to join the existing network, and they need a way to do this without compromising their own security, or the security of the network that they are joining. In addition, an established network requires a method of discovering the existence of another disjoint network that has migrated into communication range, so that a cross-link can be established between the networks in order to form a larger network. This process of nodes "discovering" each other is called node discovery, and this provides a capability that has many applications. A good node discovery scheme for military communication related applications has a number of properties including: fast and reliable network entry, covertness, secure and jam proof signaling, and range extension compared to the primary communications link itself. For the purposes of this paper the mechanism that provides node discovery will be called the Discovery Waveform. The Discovery Waveform has many applications such as terminal discovery for wireless communications, node discovery for establishing networking, and seemingly unrelated applications such as bursting time critical data.
Contraves Space AG is currently developing the OPTEL family of optical terminals for free-space optical communications. The optical terminals within the OPTEL family have been designed so as to be able to position Contraves Space for future opportunities open to this technology. These opportunities range from commercial optical satellite crosslinks between geostationary (GEO) satellites, deep space optical links between planetary probes and the Earth, as well as optical links between airborne platforms (either between the airborne platforms or between a platform and GEO satellite). This paper will present an overview of the space based and airborne system architectures that the Contraves Space family of OPTEL terminals have been designed to support, provide a description and performance summary of each OPTEL terminal and the key technologies that have been developed.
We report on the design, fabrication and characterization of 1550 nm electroabsorption modulators based on InGaAs/InAlAs coupled quantum wells grown on InP substrate by MBE. Large and small single modulators and modulator arrays have been fabricated on a wafer scale with an optimized device fabrication technology. The modulator size, shape, contact arrangements, and the array configurations have been varied to achieve suitable device performance for different retro-reflective free-space optical communication links. The device electrical and optical properties have been characterized by I-V, photoluminescence, absorption, transmittance and reflectance measurements. Modulators exhibit contrast ratios of 2:1 at a 3V driving bias and contrast ratios of 2:1 over a 30 nm bandwidth at 6V. A maximum contrast ratio of 4:1 is obtained at a 12 V driving voltage.
This paper reports the development of novel retroreflectors for use in free-space optical communication systems. It will be important for the retroreflectors to have a very wide field of view to make such systems practicable and affordable. Corner cube retroreflectors present a practical means of meeting the requirement for a wide field of view, but require use of materials with very high refractive index. Practical measurements on initial samples of high index corner cubes have shown encouraging optical performance. The measured results approximately confirm predictions of the variation of reflection efficiency with the angle of incidence. Retroreflectors based on graded-index, spherical (GRIN-sphere) lenses potentially offer an alternative with valuable technical advantages over the use of high-index corner cubes, if such lenses can be fabricated with a suitable combination of optical quality, size and relative aperture. The key property of GRIN-sphere lenses is that they can in principle suppress the most problematic feature of sphere lenses, that is, their strong spherical aberration. Predictions for practical graded-index sphere lens structures show valuable potential for improvement compared to uniform sphere lenses, including diffraction limited optical performance over significant fractions of the lens aperture.
Retro-reflective optical communication was investigated in field trials set up in urban and maritime environments. A 1550 nm laser transceiver with an output power ranging from 1 mW to 2 W and liquid crystal polarisation modulators in conjunction with corner cube reflectors were used in different experimental arrangements. The emphasis in this work was on system performance issues in tactical application such as the effects of platform vibrations and beam distortion induced by the atmospheric turbulence. In particular, the conditions for counteraction of communication interrupts, caused by line of sight jitter, using a dynamic tip-tilt mirror in the laser transceiver were tested. We report on the results from field trials wherein these issues have been addressed.
Security in optical communications has been recently a concern due primarily of the vast amount and the sensitivity of information that a single fiber carries. It is generally accepted that data security is encrypted by the end-user and that the optical network is not easy to tap as it was with wired networks. However, the sophistication of eavesdroppers has increased and if an optical link is accessed, then the encryption code of data can be broken with the use of supercomputers. In addition to data eavesdropping, eavesdroppers may access the link for malicious attacks, or for transmitting erroneous data by mimicking a source. Therefore, it is important that the receiver has the means and intelligence to recognize the signature of the source and the optical channel so that when the link is tapped, the receiver recognizes it and it alerts the network management or it triggers a data rerouting process. In fact, an optical channel, including source, fiber and optical components, has its own optical parameters that constitute a signature. These parameters are the result of linear and non-linear phenomena that affect the quality characteristics of the optical signal and which can not be mimicked. Therefore, the understanding of optical parameters that define the optical channel signature is very critical. In this paper we provide an analysis of the factors affecting the signal quality and thus they constitute the signature of the optical channel, we model the optical channel and demonstrate via simulations that small parametric variation affect the signature of the channel. As a result, monitoring the signal parameters leads to source and channel authentication whereas detecting the parametric variability of channel deducts channel degradation or tapping.