KEYWORDS: Image segmentation, Signal attenuation, Sun, Cameras, Detection and tracking algorithms, Airborne remote sensing, Image processing algorithms and systems, Image processing, Light, RGB color model
Several new techniques are introduced to the component-based vehicle detection in the aerial imagery. The shape-independent
tricolour attenuation model based on the spectral power density difference between the regions lighted by
direct sunlight and/or diffuse skylight is used to identify cast shadows. The simple linear iterative clustering (SLIC)
performs local clustering for superpixels, which were merged by a statistical region merging (SRM) method based on the
independent bounded difference inequality theorem. The car body parts were found with Support Vector Machine based
on the radiometric and geometric features of the segmented regions. All the algorithms used in this approach require
minimum human intervention, providing a robust detection.
In the aerial images of 11.2 cm/pixel resolution the car components that can be seen are only large parts of the car such
as car bodies, windshields, doors and shadows. Furthermore, these components are distorted by low spatial resolution,
low color contrast, specular reflection and viewpoint variation. We use the mean shift procedure for robust segmentation
of the car parts in the geometric and color joint space. This approach is robust, efficient, repeatable and independent of
the threshold parameters. We introduce a hierarchical segmentation algorithm with three consecutive mean-shift
procedures. Each is designed with a specific bandwidth to segment a specific car part, whose size is estimated a priori,
and is followed by a support vector machine in order to detect this car part, based on the color features and the
geometrical moment based features. The procedure starts with the largest car parts, which are then removed from the
segmented region lists after the detection to avoid over-segmentation of large regions with the mean-shift using smaller
bandwidth values. Finally we detect and count the cars in the image by combining the detected car parts according to the
spatial relations. Experiment results show a good performance.
We propose a feature-based approach for vehicle detection in aerial imagery with 11.2 cm/pixel resolution.
The approach is free of all constraints related to the vehicles appearance. The scale-invariant feature
transform (SIFT) is used to extract keypoints in the image. The local structure in the neighbouring of the
SIFT keypoints is described by 128 gradient orientation based features. A Support Vector Machine is used
to create a model which is able to predict if the SIFT keypoints belong to or not to car structures in the
image. The collection of SIFT keypoints with car label are clustered in the geometric space into subsets and
each subset is associated to one car. This clustering is based on the Affinity Propagation algorithm
modified to take into account specific spatial constraint related to geometry of cars at the given resolution.
Optical responses of a modulation doped lattice-matched InGaAs/InAlAs single quantum well structure
grown by gas source molecular beam epitaxy were characterized by photoreflectance PR at various
temperatures and depths. Two features corresponding to the ground state transition coming from the
SQW and the band gap transition generated from the buffer layer are observed in the PR spectra and
agree with those calculated theoretically. The optical transitions were perturbed by the energy shifts of
the electronic states due to Stark effect induced by the doped result. The values of the Varshni
coefficients of InGaAs/InAlAs were obtained from the relation between the exciton transition energy
and the temperature. The built-in electric field could be determined and located from a series of PR
spectra by sequential etching processes. The results suggest that a built-in electric field exists at the
buffer/substrate interface.
Thermal management has the important influence in quantum effect of light emitting diodes (LED)
based on printed circuit board (PCB). In the industrial processing, the quality of the thermal
dissipation is decided by the gumming technique between the PCB and aluminum plate. Because it
transfers the heat from electric device to the aluminum plate, which completely removes the heat. In
this study, a superior method, alumina thin films, soldered the LED lamps to enhance the heat transfer.
The films were fabricated onto 1070 aluminum alloy substrate by plasma spraying, vacuum sputtering
and electric plating technologies. The dielectric coatings were characterized by several subsequent
analyses, especially the measurement of thermal resistance. The X-Ray diffraction (XRD) diagram
analysis reveals that alumina phases were successfully grown on the individual substrate. Compared to
alumina coating fabricated by plasma spraying and electric plating technologies, vacuum sputtering
creates low sheet resistivity, high hardness, high critical load, and good thermal conduction of 119
W/m-K.
The production of CuInGaSe2 (CIGS) solar cell is based on vacuum processes, which requires a high manufacturing
temperature and high cost. Our result show a simple method has been developed to prepare the silica substrates of CIGS
solar cell. It's synthesized by sol-gel process from tetraethylorthosilicate (TEOS), methanol (CH3OH) and pure water (both ion-exchange and distillation) in the presence of ammonia as catalyst. The preparation procedure was elaborated as
the flexible sequence to control chemical composition and properties of the particles in sol-gel-derived silica substrate.
The morphology, particle size, and size distribution of CIGS substrate were characterized with dynamic light scattering
(DLS) and atomic force microscopy (AFM). The results of AFM morphology and statistic evidence we find an easy way,
non-vacuum and low temperature processes, to successfully prepare the CIGS solar cell substrates with surface roughness below 3 nm. It is powerful the advance study in low cost solar cell.
We have successfully demonstrated a holographic memory in a single LiNbO3 crystal with two simultaneous
but individual readout channels. A special scheduled exposure model is derived to obtain equal diffraction
efficiency of each hologram in this memory. The simultaneous readout technique is achieved in a hybrid-multiplexed
memory using angular multiplexing and the polarization multiplexing. Polarization multiplexing
offers the mechanism of simultaneous readout for two individual orthogonally polarized images. In each
angular position of the holographic memory, these two orthogonally polarized images can be reconstructed
simultaneously and each of them can be viewed independently. After our proposed scheduled exposure,
experimental result of diffraction efficiency in each hologram becomes equal and the result is consistent with
our prediction.
An important issue in developing applications for photopolymers in holography is the effect of diffraction efficiency on recording properties although acrylamide derivative monomers had been widely used in polyvinylalcohol-based film. Now it is possible to create these samples with a fine particle sizes choice than was previously available. We exploit these recent advances in photopolymer processing to systematically evaluate how the diffraction efficiency of a photopolymer depends on its surface silica particle size. In this paper illustrate that sample diffraction efficiencies higher than 85 % can be reached and the effective thickness used to record the hologram is around 1.0 mm.
We have developed the design method for planar holographic Bragg reflectors by layer-peeling algorithm. We have modified the layer-peeling algorithm to synthesize planar holographic Bragg reflectors. We use iterative layer-peeling algorithm with fabrication constraints to solve the difficulties of fabricating the negative parts of apodization and shorten the length in planar holographic Bragg reflectors. The novel designs for the passband WDM filter that we have demonstrated is easier to manufacture.
In this paper, we have developed the design method for planar holographic Bragg reflectors by layer-peeling algorithm. Layer-peeling algorithm is known as an efficient tool for synthesizing fiber Bragg grating which is one-dimension gating. We have modified the layer-peeling algorithm that can synthesize planar holographic Bragg reflectors. In order to solve the difficulty of fabricating the negative parts of apodization in planar holographic Bragg reflectors, we use iterative layer-peeling algorithm with fabrication constraints. The designed planar holographic Bragg reflector with 1
lob is 5.7 mm long, containing no phase shift. The stopband isolation is −30 dB. The bandwidth utilization factor is 68%. The dispersion is 91 ps/nm in the 0.54 nm passband at −1 dB. The group delay ripple is below 0.6 ps. The novel designs for the passband WDM filter that we have demonstrated is easier to manufacture.
We propose the iterative layer-peeling algorithm (LPA) and the genetic algorithm (GA) to numerically optimize the fiber Bragg grating (FBG) design. Fabrication constraints are introduced in the design, such that the designed FBGs satisfy the spectral specifications and are easy to fabricate. The powerful numerical optimization permits removing the phase shifts in the FBGs, so that the gratings can be fabricated with conventional high quality holographic phase masks, without need for custom made phase masks. We introduce the inverse LPA, which is faster than the conventional transfer matrix method by two orders of magnitude for analysis of the FBGs. The synthesis of the FBG using the LPA and the analysis of the FBG using the inverse LPA can be iterated in a loop, which allows applying the constraints in both grating and spectrum spaces. The impact of the applied constraints and the convergence are analyzed. The GA is powerful for achieving the global optimum with a higher probability than that of the iterative algorithm and simulated annealing. Our GA is enhanced by a new Fourier series-based real-valued encoding to provide high degrees of freedom, and a rank-based fitness function. The new GA enables us to remove phase shifts in the gratings. All the designed WDM band-pass gratings with minimum dispersion are fabricated using the holographic phase mask without phase shifts. The experimental gratings with dispersion of ± 33 ps/nm in the 0.33 nm flat-top passband will be shown.
We here present an efficient analysis method for fiber Bragg grating, called inverse layer-peeling algorithm, which is originated from the layer-peeling algorithm. The layer-peeling algorithm is known as an efficient method for synthesizing fiber Bragg grating. The profile of grating can be reconstructed accurately from its strongly complex reflection spectrum with this algorithm. We found that this method also has the ability for analyzing fiber Bragg grating by inversing its synthesis procedures. With comparing the current analysis method, the inverse layer-peeling algorithm provides accuracy results and is faster by two orders of magnitude than the transfer matrix method.
In this paper, we have developed the synthesized method for volume Hologram grating by layer-peeling algorithm. Layer-peeling algorithm is known as an efficient tool for synthesizing fiber Bragg grating which is one-dimension grating without absorption. By taking account for attenuation and angles of incident wave, we have modified the layer-peeling algorithm that can synthesize volume Hologram grating in lithium niobate crystal.
We here present a new method for synthesizing the fiber Bragg grating. This method, which we name as reborn Born method, is originated from the first order Born approximation. It provides more accurate results for synthesizing strong fiber Bragg grating. It is more accurate than layer-peeling algorithm with synthesizing uniform grating. The comparison shows that the reborn Born method enables to synthesize the gratings that layer-peeling algorithm fails to calculate.
An optical security holographic memory encrypted by a random phase key and decrypted by a holographic key (a holographic optical element; HOE) is presented and demonstrated. The security hologram is based on protecting the access to the memory from the unauthorized users by encoding the reference waves. The holographic decryption key is fabricated by storing the wavefront information of the set of reference beams. Each addressed reference beam is stored in the HOE through holographic multiplexing technique. The decryption process is achieved by using the reconstruction reference beam to access the secure data. This security hologram system is suitable for practical application since the decryption key can be controlled copied. As to our best knowledge, this is the first experimental impementation to replace a random phase mask key.
We propose a volume-holographic filter to perform 3D object filtering. Theoretical analysis and the corresponding experiment of the shifting tolerance of the volume-holographic filter are demonstrated. We find that the shifting selectivity is different for different shifting directions, which include laterally horizontal, laterally vertical, and longitudinal directions. The simulation results show that the shifting selectivity depends on the scale of the object and the distance between obejct and the holographic filters.
We have studied the characteristic of the angular multiplexing with spherical reference wave in volume holographic storage. Through the theoretical analysis and the corresponding experimental observation, the angular sensitivity is almost independent of the distances between the point source and the hologram. Accordingly, an all- optical angular sensing system have been proposed and demonstrated.
Here we propose our study in the temporal and spatial uniformity of a phase conjugate wave generated from photorefractive self-pumped phase conjugators. The phase perturbation of the conjugate wave is caused by the thermal effect in the crystals. We find that beam size and intensity is the key parameters for controlling the uniformity.
Using the self-pumped phase conjugation with a photorefractive BaTiO3 crystal, we propose a device which changes the flow direction of signals. Two beams of light involve in the device and signals are transferred between them. They share the total-internal-reflection (TIR) loop in the crystal. The transferred pattern can be a positive replica of the original pattern or a negative replica of it.
We propose here a simple way to synthesize a shift, rotation and limited size correlation filter, making use of the idea of synthetic discriminant functions (SDF). The SDF is synthesized by superimposing four 2nd order circular harmonics of a training reference pattern in 4 different sizes. Computer simulation experiments have shown that the filter is indeed shift, fully rotation and limited size invariant over a size range from 1 to 1.75. The invariant range can be increased if more training patterns are used.
The system consists of two mutually orthogonal linearly polarized laser beams carrying the Fourier spectra of a reference pattern and an input pattern into a photorefractive crystal, respectively. The image of every reference pattern in the input would appear at the output plane regardless of whether it is moving or not. However, a still non-reference pattern presented at the input plane would not show up at the output plane. Therefore stationary noise pattern never shows up in the output plane.
A scheme capable of demonstrating shift- and rotational-invariant associative memory is presented. The scheme can be implemented both digitally and optically. In optical implementation, we use one holographic spatial frequency filter and one ordinary hologram of the reference pattern. A BaTiO3 crystal is also employed in the experiment. In the digital implementation of the scheme, in addition to the rotational invariance it is shift invariant too. However, the optical implementation exhibits shift invariance only when the BaTiO3 crystal is sufficiently large.
A method of performing shift- and rotational-invariant associative memory is proposed. The method can be implemented both optically and digitally with computers. The method is detailed and some results of the digital implementation are presented. The experimental results show that the original reference pattern is recovered by partial inputs in any orientation. If the input is not the original reference pattern or a partial version of it, the results produced by this method are unidentifiable.
A simple way to synthesize a shift, fully rotational and limited size invariant composite matched spatial filter for a coherent optical correlator is proposed. We use circular harmonic components of the same order of a reference pattern in different sizes as the training images instead of using the whole reference pattern in different orientations and different sizes as is reported by other workers. This saves much labor and time in the synthesis of the filter. In this article, we have synthesized a simple filter containing four second order circular harmonic components of the alphabetic letter `E' in four relative sizes 1, 1.17, 1.33, and 1.5. Results of computer simulation have shown that this filter is shift, fully rotational and limited size invariant over the size range from 1 to 1.5. Computer simulation has also shown that this filter possesses discriminating ability.
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