Showing papers in "Optical Engineering in 2011"
TL;DR: This tutorial discusses compressed sensing in the context of optical imaging devices, emphasizing the practical hurdles related to building such devices and offering suggestions for overcoming these hurdles.
Abstract: The emerging field of compressed sensing has potentially powerful implications for the design of optical imaging devices In particular, compressed sensing theory suggests that one can recover a scene at a higher resolution than is dictated by the pitch of the focal plane array This rather remarkable result comes with some important caveats however, especially when practical issues associated with physical implementation are taken into account This tutorial discusses compressed sensing in the context of optical imaging devices, emphasizing the practical hurdles related to building such devices, and offering suggestions for overcoming these hurdles Examples and analysis specifically related to infrared imaging highlight the challenges associated with large format focal plane arrays and how these challenges can be mitigated using compressed sensing ideas
249 citations
TL;DR: A review of the history and current status of ion exchanged glass waveguide technology is given in this article, where an overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applica- tions are discussed.
Abstract: We review the history and current status of ion exchanged glass waveguide technology. The background of ion exchange in glass and key developments in the first years of research are briefly described. An overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applica- tions are discussed. Ion exchanged waveguide technology has served as an available platform for studies of general waveguide properties, in- tegrated optics structures and devices, as well as applications. It is also a commercial fabrication technology for both passive and active wave- guide components. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
246 citations
TL;DR: In this article, the use of liquid crystals in different photonic components: optical filters and switches, beam-steering devices, spatial light modulators, integrated devices based on optical waveguiding, lasers, and optical nonlinear components are discussed.
Abstract: Liquid crystals are nowadays widely used in all types of display applications. However their unique electro-optic properties also make them a suitable material for nondisplay applications. We will focus on the use of liquid crystals in different photonic components: optical filters and switches, beam-steering devices, spatial light modulators, integrated devices based on optical waveguiding, lasers, and optical nonlinear components. Both the basic operating principles as well as the recent state-of-the art are discussed.
215 citations
TL;DR: A new driver-monitoring method considering both driver drowsiness and distraction, and a novel eye state-detection algorithm that combines appearance features obtained using PCA and LDA, with statistical features such as the sparseness and kurtosis of the histogram from the horizontal edge of the eye.
Abstract: Most driver-monitoring systems have attempted to detect either driver drowsiness or distraction, although both factors should be considered for accident prevention. Therefore, we propose a new driver-monitoring method considering both factors. We make the following contributions. First, if the driver is looking ahead, drowsiness detection is performed; otherwise, distraction detection is performed. Thus, the computational cost and eye-detection error can be reduced. Second, we propose a new eye-detection algorithm that combines adaptive boosting, adaptive template matching, and blob detection with eye validation, thereby reducing the eye-detection error and processing time significantly, which is hardly achievable using a single method. Third, to enhance eye-detection accuracy, eye validation is applied after initial eye detection, using a support vector machine based on appearance features obtained by principal component analysis (PCA) and linear discriminant analysis (LDA). Fourth, we propose a novel eye state-detection algorithm that combines appearance features obtained using PCA and LDA, with statistical features such as the sparseness and kurtosis of the histogram from the horizontal edge image of the eye. Experimental results showed that the detection accuracies of the eye region and eye states were 99 and 97%, respectively. Both driver drowsiness and distraction were detected with a success rate of 98%.
118 citations
TL;DR: A novel mul- timodal image fusion scheme based on the joint sparsity model which is derived from the distributed compressed sensing, which demonstrates the effectiveness of the proposed method in terms of visual effect and quantitative fusion evaluation indexes.
Abstract: Image fusion combines multiple images of the same scene into a single image which is suitable for human perception and practical applications. Different images of the same scene can be viewed as an ensemble of intercorrelated images. This paper proposes a novel mul- timodal image fusion scheme based on the joint sparsity model which is derived from the distributed compressed sensing. First, the source images are jointly sparsely represented as common and innovation components using an over-complete dictionary. Second, the common and innovations sparse coefficients are combined as the jointly sparse coeffi- cients of the fused image. Finally, the fused result is reconstructed from the obtained sparse coefficients. Furthermore, the proposed method is compared with some popular image fusion methods, such as multiscale transform-based methods and simultaneous orthogonal matching pursuit- based method. The experimental results demonstrate the effectiveness of the proposed method in terms of visual effect and quantitative fusion evaluation indexes. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
111 citations
TL;DR: A bird's-eye view of the main and recent proposals of switches based on the thermo-optic effect is reported and their performances compared.
Abstract: All-optical networking can be the sole approach to provide the huge bandwidth required for future networks The essential elements in such an optical network are optical switches A number of options have been proposed in order to implement them efficiently We focus on thermo-optical switches First, the physical principles of the thermo-optic effect are briefly introduced A description of the most common technologies used for the fabrication of thermo-optic switches is provided along with the values of thermo-optic coefficient for a number of materials The main steps useful in order to design thermo-optical switches are also briefly introduced Finally, a bird's-eye view of the main and recent proposals of switches based on the thermo-optic effect is reported and their performances compared
93 citations
TL;DR: Two approaches based on nonsequential projection angle sequences allowing a convenient postacquisition balance of temporal and spatial resolution are proposed and applied with cold neutron imaging of water desorption from originally saturated particles during natural air-drying experiments and with x-ray tomography of a polymer blend heated during imaging.
Abstract: Modern computed tomography (CT) equipment allowing fast 3-D imaging also makes it possible to monitor dynamic processes by 4-D imaging. Because the acquisition time of various 3-D-CT systems is still in the range of at least milliseconds or even hours, depending on the detector system and the source, the balance of the desired temporal and spatial resolution must be adjusted. Furthermore, motion artifacts will occur, especially at high spatial resolution and longer measuring times. We propose two approaches based on nonsequential projection angle sequences allowing a convenient postacquisition balance of temporal and spatial resolution. Both strategies are compatible with existing instruments, needing only a simple reprograming of the angle list used for projection acquisition and care with the projection order list. Both approaches will reduce the impact of artifacts due to motion. The strategies are applied and validated with cold neutron imaging of water desorption from originally saturated particles during natural air-drying experiments and with x-ray tomography of a polymer blend heated during imaging.
81 citations
TL;DR: A new method of display and detail enhancement for high dynamic range infrared images is presented that effectively maps the raw acquired infrared image to 8-bit domain based on the same architecture of bilateral filter and dynamic range partitioning approach.
Abstract: Dynamic range reduction and detail enhancement are two important issues for effectively displaying high-dynamic-range images acquired by thermal camera systems. They must be performed in such a way that the high dynamic range image signal output from sensors is compressed in a pleasing manner for display on lower dynamic range monitors without reducing the perceptibility of small details. In this paper, a new method of display and detail enhancement for high dynamic range infrared images is presented. This method effectively maps the raw acquired infrared image to 8-bit domain based on the same architecture of bilateral filter and dynamic range partitioning approach. It includes three main steps: First, a bilateral filter is applied to separate the input image into the base component and detail component. Second, refine the base and detail layer using an adaptive Gaussian filter to avoid unwanted artifacts. Then the base layer is projected to the display range and the detail layer is enhanced using an adaptive gain control approach. Finally, the two parts are recombined and quantized to 8-bit domain. The strength of the proposed method lies in its ability to avoid unwanted artifacts and adaptability in different scenarios. Its great performance is validated by the experimental results tested with two real infrared imagers.
78 citations
TL;DR: An advanced geometric camera technique which employs a frontal image concept and a hyper-precise control point detection scheme with digital image correlation is presented and Simulation and real results have successfully demonstrated the superior of the proposed technique.
Abstract: In many machine vision applications, a crucial step is to accurately determine the relation between the image of the object and its physical dimension by performing a calibra- tion process. Over time, various calibration techniques have been developed. Nevertheless, the existing methods cannot satisfy the ever-increasing demands for higher accuracy per- formance. In this letter, an advanced geometric camera cali- bration technique which employs a frontal image concept and a hyper-precise control point detection scheme with digital image correlation is presented. Simulation and real experi- mental results have successfully demonstrated the superior of the proposed technique. C 2011 Society of Photo-Optical Instrumen-
74 citations
TL;DR: The metrics, imagery data bases, and sensors associated with Ai/ATR performance are reviewed and possible technical approaches that could enable new advancements in military-relevant performance are suggested.
Abstract: Aided and automatic target recognition (Ai/ATR) capability is
a critical technology needed by the military services for modern combat.
However, the current level of performance that is available is largely deficient
compared to the requirements. This is largely due to the difficulty
of acquiring targets in realistic environments but has also been due to
the difficulty in getting new concepts from, for example, the academic
community, due to limitations for distribution of classified data. The difficulty
of the performance required has limited the fulfillment of the promise
that is so anticipated by the war fighter. We review the metrics, imagery
data bases, and sensors associated with Ai/ATR performance and suggest
possible technical approaches that could enable new advancements
in military-relevant performance.
71 citations
TL;DR: The generation of sinusoidal fringe patterns is studied by properly defocusing binary ones, which permits the use of an arbitrary exposure time, which provides the potential to adapt the exposure time automatically.
Abstract: Automatically adapting the camera exposure time is crucial for industrial applications where minimum human intervention is usually desirable. However, it is very challenging to realize such a capability for a conventional fringe projection system where only a finite increment of the exposure time is allowed due to its digital fringe generation nature. We study the generation of sinusoidal fringe patterns by properly defocusing binary ones, which permits the use of an arbitrary exposure time. This provides the potential to adapt the exposure time automatically. We present the principle of an automatic exposure technique and show some experimental results.
TL;DR: In this article, the authors demonstrate the suppression of the bulk generation- recombination current in nBn devices based on an InAsSb active layer (AL) and a AlSbAs barrier layer (BL).
Abstract: We demonstrate the suppression of the bulk generation- recombination current in nBn devices based on an InAsSb active layer (AL) and a AlSbAs barrier layer (BL). This leads to much lower dark cur- rents than in conventional InAsSb photodiodes operating at the same temperature. When the BL is p-type, very high doping must be used in the AL (nBpn + ). This results in a significant shortening of the device cut- off wavelength due to the Moss-Burstein effect. For an n-type BL, low AL doping can be used (nBnn), yielding a cutoff wavelength of ∼4.1 μm and a dark current close to ∼3 × 10 −7 A/cm 2 at 150 K. Such a device with a4 -μm-thick AL will exhibit a quantum efficiency (QE) of 70% and background-limited performance operation up to 160 K at f/3. We have madenBnnfocalplane arraydetectors(FPAs)with a 320 ×256 formatand a 1.3-μm-thick AL. These FPAs have a 35% QE and a noise equivalent temperature difference of 16 mK at 150 K and f/3. The high performance of our nBnn detectors is closely related to the high quality of the molecular beam epitaxy grown InAsSb AL material. On the basis of the temperature dependence of the diffusion limited dark current, we estimate a minority carrier lifetime of ∼670 ns. C 2011 Society of Photo-Optical Instrumentation Engineers
TL;DR: This paper proposes a novel representation and recognition approach to bimodal biometrics and shows that the approach is not only novel but also simple and computationally efficient.
Abstract: It has been demonstrated that multibiometrics can produce higher accuracy than single biometrics. This is mainly because the use of multiple biometric traits of the subject enables more information to be used for identification or verification. In this paper, we focus on bimodal biometrics and propose a novel representation and recognition approach to bimodal biometrics. This approach first denotes the biometric trait sam- ple by a complex vector. Then, it represents the test sample through the training samples and classifies the test sample as follows: let the test sample be expressed as a linear combination of all the training samples each being a complex vector. The proposed approach obtains the solu- tion by solving a linear system. After evaluating the effect, in representing the test sample of each class, the approach classifies the test sample into the class that makes the greatest effect. The approach proposed is not only novel but also simple and computationally efficient. A large num- ber of experiments show that our method can obtain promising results. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.3554740)
TL;DR: Experimental results show that the proposed method achieves robust vein pattern extraction and provides a lower equal error rate in finger-vein recognition.
Abstract: Finger-vein recognition uses the finger-vein pattern extracted from the captured vein images to identify individuals. However, the captured vein images contain irregular shading and noise. To extract effective vein pattern from these unclear images, this paper proposes a novel vein pattern extraction approach by running the region growing operator on the different seeds. As the proposed method emphasizes continuity and symmetry of valleys in the cross-sectional profile, it can extract the robust finger-vein patterns and be against irregular shading and noise. Experimental results show that the proposed method achieves robust vein pattern extraction and provides a lower equal error rate in finger-vein recognition.
TL;DR: In this article, the authors evaluated the performance of concentrating photovoltaic (CPV) modules using optical properties (transmittance, refractive index, reflectance, and absorptance) of PMMA, soda-lime glass, borosilicate glass, and quartz refractors.
Abstract: Concentrating photovoltaic (CPV) technology has recently gained interest based on its scalability and expected low levelized cost of electricity. The reliability of encapsulation materials used in CPV systems, however, is not well established. For example, the present qualification test for CPV modules includes only real-time ultraviolet (UV) exposure, i.e., methods for accelerated UV testing have not yet been developed. To better define the stress inherent to CPV systems, the UV and infrared spectra transmitted through representative optical systems were evaluated. Measurements of optical components are used to assess expected optical performance and quantify damaging optical exposure. Optical properties (transmittance, refractive index, reflectance, and absorptance) of candidate materials (including PMMA, soda-lime glass, borosilicate glass, and quartz refractors), components (including Ag- and Al-enabled reflectors), and encapsulants (including EVA, ionomer, PDMS, PPMS, polyolefin, and PVB) were identified. The activation spectrum was calculated for the representative optical systems using an assumed action spectrum to compare the expected damaging dose of UV radiation delivered to the cell encapsulation. The dose and flux analysis identifies the significance of IR relative to UV exposure for CPV systems. Because UV light is typically more highly attenuated, the UV dose within the encapsulation may not greatly exceed the unconcentrated global solar condition, but the thermal load scales nearly directly with the geometric concentration. Relative to a previous analysis for crystalline silicon cell technology, the analysis here is performed for III-V multijunction technology. Novel aspects here also include additional materials (such as TPU encapsulation) and additional components (transmission through silicone on glass lenses, antireflective coatings, and the front glass used with reflective systems, as well as reflection off of the cell).
TL;DR: This paper presents stereo vision-based vehicle detection approach on the road using a road feature and disparity histogram, and verifies the vehicles using a depth map and gray image to improve the performance.
Abstract: This paper presents stereo vision-based vehicle detection approach on the road using a road feature and disparity histogram. It is not easy to detect only vehicles robustly on the road in various traffic situations, for example, a nonflat road or a multiple-obstacle situation. This paper focuses on the improvement of vehicle detection performance in various real traffic situations. The approach consists of three steps, namely obstacle localization, obstacle segmentation, and vehicle verification. First, we extract a road feature from v-disparity maps binarized using the most frequent values in each row and column, and adopt the extracted road feature as an obstacle criterion in column detection. However, many obstacles still coexist in each localized obstacle area. Thus, we divide the localized obstacle area into multiple obstacles using a disparity histogram and remerge the divided obstacles using four criteria parameters, namely the obstacle size, distance, and angle between the divided obstacles, and the difference of disparity values. Finally, we verify the vehicles using a depth map and gray image to improve the performance. We verify the performance of our proposed method by conducting experiments in various real traffic situations. The average recall rate of vehicle detection is 95.5%.
TL;DR: This work proposes the use of high-resolution digital displays as active calibration targets to obtain more accurate calibration results for all types of cameras, and finds markedly lower reprojection errors when using active targets.
Abstract: Traditionally, most camera calibrations rely on a planar target with well-known marks. However, the localization error of the marks in the image is a source of inaccuracy. We propose the use of high-resolution digital displays as active calibration targets to obtain more accurate calibration results for all types of cameras. The display shows a series of coded patterns to generate correspondences between world points and image points. This has several advantages. No special calibration hardware is necessary because suitable displays are practically ubiquitious. The method is fully automatic, and no identification of marks is necessary. For a coding scheme based on phase shifting, the localization accuracy is approximately independent of the camera's focus settings. Most importantly, higher accuracy can be achieved compared to passive targets, such as printed checkerboards. A rigorous evaluation is performed to substantiate this claim. Our active target method is compared to standard calibrations using a checkerboard target. We perform camera, calibrations with different combinations of displays, cameras, and lenses, as well as with simulated images and find markedly lower reprojection errors when using active targets. For example, in a stereo reconstruction task, the accuracy of a system calibrated with an active target is five times better.
TL;DR: A novel algorithm for generating a full parallax 3D computer generated hologram (CGH) with occlusion effect is presented, which is an important property of 3D perception, but has often been neglected in most CGH related works.
Abstract: Computational holography becomes highly complicated and demanding when it is employed to produce real three-dimensional (3D) images. Here we present a novel algorithm for generating a full parallax 3D computer generated hologram (CGH) with occlusion effect, which is an important property of 3D perception, but has often been neglected in most CGH related works. The ray casting technique is introduced to handle the occlusion issue. Horizontally and vertically distributed rays are projected from each hologram sample to the 3D objects to obtain the complex amplitude distribution. The proposed algorithm has no restriction on-or approximation to-the 3D objects, and it can produce reconstructed images with correct shading effect and no visible artifacts. An optical experiment is performed to validate our approach, using a phase-only spatial light modulator to optically reconstruct a 3D scene. The experimental result confirmed that the CGHs produced by our algorithm can successfully reconstruct 3D images with full parallax and occlusion effect.
TL;DR: A novel optical asymmetric cryptosystem based on a phase-truncated Fourier transform with two decryption keys independent of each other, referred to as universal key and special key, respectively, is proposed.
Abstract: We propose a novel optical asymmetric cryptosystem based on a phase-truncated Fourier transform. Two decryption keys independent of each other are generated. They are referred to as universal key and special key, respectively. Each of them can be used for decryption independently in absence of the other. The universal key is applicable to decrypt any ciphertext encoded by the same encryption key, but with poor legibility. On the contrary, the special key is adequate for legible decryption, but only valid for one ciphertext corresponding to the specified plaintext. A set of simulation results show the interesting performance of two types of decryption keys.
TL;DR: A new finger recognition method based on the score-level fusion of finger veins, fingerprints, and finger geometry features is proposed; its performance is better than the conventional Z-score normalization method and the equal error rate was lower than those of the other methods.
Abstract: Multimodal biometrics provides high recognition accuracy and population coverage by using various biometric features. A single finger contains finger veins, fingerprints, and finger geometry features; by using multimodal biometrics, information on these multiple features can be simultaneously obtained in a short time and their fusion can outperform the use of a single feature. This paper proposes a new finger recognition method based on the score-level fusion of finger veins, fingerprints, and finger geometry features. This research is novel in the following four ways. First, the performances of the finger-vein and fingerprint recognition are improved by using a method based on a local derivative pattern. Second, the accuracy of the finger geometry recognition is greatly increased by combining a Fourier descriptor with principal component analysis. Third, a fuzzy score normalization method is introduced; its performance is better than the conventional Z-score normalization method. Fourth, finger-vein, fingerprint, and finger geometry recognitions are combined by using three support vector machines and a weighted SUM rule. Experimental results showed that the equal error rate of the proposed method was 0.254%, which was lower than those of the other methods.
Journal Article•
TL;DR: A fiber-optic localized surface plasmon (FO LSPR) sensor was fabricated by gold nanoparticles (Au NPs) immobilized on the end-face of an optical fiber as mentioned in this paper.
Abstract: A fiber-optic localized surface plasmon (FO LSPR) sensor was fabricated by gold nanoparticles (Au NPs) immobilized on the end-face of an optical fiber. When Au NPs were formed on the end-face of an optical fiber by chemical reaction, Au NPs aggregation occurred and the Au NPs were immobilized in various forms such as monomers, dimers, trimers, etc. The component ratio of the Au NPs on the end-face of the fabricated FO LSPR sensor was slightly changed whenever the sensors were fabricated in the same condition. Including this phenomenon, the FO LSPR sensor was fabricated with high sensitivity by controlling the density of Au NPs. Also, the fabricated sensors were measured for the resonance intensity for the different optical systems and analyzed for the effect on sensitivity. Finally, for application as a biosensor, the sensor was used for detecting the antibody-antigen reaction of interferon-gamma.
TL;DR: Using a standard stereo-photogrammetry approach, as well as a simple, yet powerful structured light projection concept based on a slide-projector, this work demonstrates an acquisition rate of more than 700 dense and accurate 3D measurements per second.
Abstract: The field of image-based shape measurements using structured illumination has been an active research area for several decades now. A lot of different methods are widely used e.g. for industrial inspection, surveillance as well as multimedia purposes. Usually, short measurement times and high correspondence accuracy are mutually exclusive properties, due to the limitations of the used projection technology. Using a standard stereo-photogrammetry approach, as well as a simple, yet powerful structured light projection concept based on a slide-projector, we demonstrate an acquisition rate of more than 700 dense and accurate 3D measurements per second.
TL;DR: In this paper, the design and performance of a pump-limited, 600 W, singlemode, single-frequency TFL amplifier chain are discussed. But the authors do not consider the effect of stimulated Brillouin scattering (SBS).
Abstract: Thulium-doped fiber lasers (TFLs) emitting retina-safe 2-μm wavelengths offer substantial power-scaling advantages over ytterbium-doped fiber lasers for narrow linewidth, single-mode operation. This article reviews the design and performance of a pump-limited, 600 W, single-mode, single-frequency TFL amplifier chain that balances thermal limitations against those arising from stimulated Brillouin scattering (SBS). A simple analysis of thermal and SBS limits is anchored with measurements on kilowatt class Tm and Yb fiber lasers to highlight the scaling advantage of Tm for narrow linewidth operation. We also report recent results on active phase-locking of a TFL amplifier to an optical reference as a precursor to further parallel scaling via coherent beam combining.
TL;DR: A surveillance video system, which detects various posture-based events and uses adapted Vander-Lugt correlator and JTC techniques to make decisions on the identity of a patient and his three-dimensional positions in order to overcome the problem of crowd environment.
Abstract: Home automation is being implemented into more and more domiciles of the elderly and disabled in order to maintain their independence and safety. For that purpose, we propose and validate a surveillance video system, which detects various posture-based events. One of the novel points of this system is to use adapted Vander-Lugt correlator (VLC) and joint-transfer correlator (JTC) techniques to make decisions on the identity of a patient and his three-dimensional (3-D) positions in order to overcome the problem of crowd environment. We propose a fuzzy logic technique to get decisions on the subject's behavior. Our system is focused on the goals of accuracy, convenience, and cost, which in addition does not require any devices attached to the subject. The system permits one to study and model subject responses to behavioral change intervention because several levels of alarm can be incorporated according different situations considered. Our algorithm performs a fast 3-D recovery of the subject's head position by locating eyes within the face image and involves a model-based prediction and optical correlation techniques to guide the tracking procedure. The object detection is based on (hue, saturation, value) color space. The system also involves an adapted fuzzy logic control algorithm to make a decision based on information given to the system. Furthermore, the principles described here are applicable to a very wide range of situations and robust enough to be implementable in ongoing experiments.
TL;DR: A robust detection and tracking method that can detect and track ship targets in cluttered forward looking infrared image sequences and the histogram back-projection technique is applied to the mean shift procedure for real-time application.
Abstract: This paper proposes a robust detection and tracking method that can detect and track ship targets in cluttered forward looking infrared image sequences. The proposed method includes two major steps, tar- get detection and target tracking. Because the target's imaging size will be scaled-up gradually along with the imaging distance being reduced, the target's imaging process is analyzed in detail and the target's imag- ing size is estimated in real-time. Based on the estimation of the target's imaging size, the targets with different imaging sizes can be treated as small targets by image scaling operation and detected successfully us- ing the improved multilevel filter and iterative segmentation technique. In the tracking stage, the histogram back-projection technique, which has little effect on the movement of the camera, is applied to the mean shift procedure for real-time application. Extensive experiments demonstrate the utility and the performance of the proposed approach. C
TL;DR: This system can segment leaves from images of live plants with arbitrary image conditions, and classify them against sketched leaf shapes or real leaves, and estimate the three-dimensional information of leaves which is not only useful for leaf segmentation but is also beneficial for further 3-D shape recovery.
Abstract: In this paper, we incorporate a set of sophisticated algorithms to implement a leaf segmentation and classification system. This system inherits the advantages of these algorithms while eliminating the difficulties each algorithm faced. Our system can segment leaves from images of live plants with arbitrary image conditions, and classify them against sketched leaf shapes or real leaves. This system can also estimate the three-dimensional (3-D) information of leaves which is not only useful for leaf segmentation but is also beneficial for further 3-D shape recovery. Although our system requires more than one image to reconstruct the 3-D structure of the scene, it has been designed so that only a few images with close viewpoints are sufficient to achieve the task, thus the system is still flexible and easy to use in image acquisition. For leaf classification, we adopt the normalized centroid-contour distance as our classification feature and employ a circular-shift comparing scheme to measure leaf similarity so that the system has the advantage of being invariant to leaf translation, rotation and scaling. We have conducted a series of experiments on many leaf images and the results are encouraging. The leaves can be well segmented and the classification results are also acceptable.
TL;DR: In this paper, a theoretical study of free-standing phase transmission gratings for high-resolution extreme ultraviolet (EUV) and soft x-ray spectroscopy was performed. And the authors used rigorous coupled wave analysis methods to optimize the grating design parameters and discuss features of segmented grating arrays.
Abstract: We report on a theoretical study of free-standing phase transmission gratings for high-resolution extreme ultraviolet (EUV) and soft x-ray spectroscopy and investigate their properties. Designed for wavelengths between about 2 and 40 nm, the devices may provide a first order diffraction efficiency beyond 30%. We use rigorous coupled wave analysis methods in order to optimize the grating design parameters and discuss features of segmented grating arrays. Elemental, as well as compound, materials such as Be, Mo, LiF, and poly-(methylmethacrylate) are considered with respect to their potential and practical limitations in terms of feasibility and sensitivity to radiation damage. Simulations are performed for several samples on the radiation produced by a table-top EUV plasma source and applications to astrophysical problems are considered.
TL;DR: In this article, the authors discuss the proliferation of uncooled IR detectors in commercial and military markets, which are widely used in firefighting, surveillance, industrial process monitoring, machine vision, and medical applications.
Abstract: Significant progress has been made over the past decade on uncooled focal plane array technologies and production capabilities. The detector pixel dimensions have continually decreased with an increase in pixel performance making large format, high-density array products affordable. In turn, this has resulted in the proliferation of uncooled IR detectors in commercial and military markets. Presently, uncooled detectors are widely used in firefighting, surveillance, industrial process monitoring, machine vision, and medical applications. Within the military arena, uncooled detectors are ubiquitous in Army soldier systems such as weapon sights, driver's viewers, and helmet-mounted sights. Uncooled detectors are also employed in airborne and ground surveillance sensors including unmanned aerial vehicles and robot vehicles.
TL;DR: In this article, a time-resolved microscope system that enables the study of the sequence of events and individual processes involved during the entire timeline from the initial energy deposition to the final state of the material, typically associated with the formation of a crater on the surface.
Abstract: The dynamics of material response following initial localized energy deposition by the laser pulse on the material's surface is still largely unknown. We describe a time-resolved microscope system that enables the study of the sequence of events and the individual processes involved during the entire timeline from the initial energy deposition to the final state of the material, typically associated with the formation of a crater on the surface. To best capture individual aspects of the damage timeline, this system can be configured to multiple imaging arrangements, such as multiview image acquisition at a single time point, multi-image acquisition at different time points of the same event, and tailored sensitivity to various aspects of the process. As a case example, we present results obtained with this system during laser-induced damage on the exit surface of fused silica.