This paper presents the signalprocessing method of laser images used for detection of small collinear obstacles in helicopter airborne applications. It is very difficult, if not almost impossible, for a regular passi...
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ISBN:
(纸本)0780331435
This paper presents the signalprocessing method of laser images used for detection of small collinear obstacles in helicopter airborne applications. It is very difficult, if not almost impossible, for a regular passive imaging sensor based on CCD detectors to detect such small, remote objects. It was proved in the literature that the fusion of range and intensity data is needed for such a task. The paper presents a new and improved algorithm for real time imageprocessing which enable detection of small tiny objects from sparse data, from a fast moving platform.
An image compression scheme based on wavelet transform (WT) and human visual properties Is presented. The design of the scheme is aimed to develop an image coding technique, mainly, for natural images, of high perform...
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ISBN:
(纸本)7505338900
An image compression scheme based on wavelet transform (WT) and human visual properties Is presented. The design of the scheme is aimed to develop an image coding technique, mainly, for natural images, of high performance which means high compression ratio and good reconstruction qualify in both objective measure and subjective visual effects. The technique should also be easy implementable so that it can be readily put into practical use. To fulfill these requirements, WT is chosen to be the first basis of the technique. It is well recognized that WT by its very nature is superior in image coding to those transforms traditionally used for image coding. Then a type of quantizer designed based on a human visual property, known as contrast-masking, is used for quantization of the subimages at various resolution levels. With fine adjustment of parameters for different resolution levels, this quantizer lends good reconstruction quality of images. A combined coding scheme with high coding gain, consisting of a modified RLC followed by Huffman coding, is invented in accordance with the properties of the quantized subimages. Finally, some experiment reslts with the 'Lena'' and ''Girl'' images are given.
This paper discusses the many and varied design considerations of a 2-D digital subband filter bank implementation for orthogonal sampling structures, which enables the derivation of only two subbands rather than the ...
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ISBN:
(纸本)7505338900
This paper discusses the many and varied design considerations of a 2-D digital subband filter bank implementation for orthogonal sampling structures, which enables the derivation of only two subbands rather than the usual four. In particular, the design trade-off and overall performance of a Quadrature Mirror Filter pair, in combination with a 2-D diagonal prefilter is explored and the ensuing problems of avoiding and compensating for aliasing within the subbands, as well as for the signal reconstruction process at the decoder are highlighted.
The denial of effective communications by enemy forces during hostile military operations has been a primary concern for military commanders since the inception of radio communications on the battlefield before World ...
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The denial of effective communications by enemy forces during hostile military operations has been a primary concern for military commanders since the inception of radio communications on the battlefield before World War ii. Since then, the electromagnetic environment has been in a constant state of evolution toward more sophisticated jam-resistant and convert forms of modulation. For example, exotic modulation techniques employing spread spectrum (SS) signaling are routinely used by our adversaries to provide their communication links an advantage over US and Allied jammers. More recently, these same spread spectrum modulation techniques are being refined to provide convert, low probability-of-intercept (LPI) features to the unintended interceptor. The thrust of this paper focuses on developments in the theory and algorithms for detection, characterization, and exploitation of advanced waveforms using new mathematical signalprocessing tools introduced within the past decade. Specifically, quadratic time-frequency signal representations, wavelet transforms, and cyclostationary signalprocessing are introduced. This overview demonstrates the importance of these advanced techniques in a clear and concise manner. applications and future research activities are described in this significant area that is gaining much attention in a variety of technical fields.
Intelligent identification of background and foreground in video scenes is used to gain compression. This is implemented as a two layer object model in a software-only video compressor with a bit rate range from less ...
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ISBN:
(纸本)0780332598
Intelligent identification of background and foreground in video scenes is used to gain compression. This is implemented as a two layer object model in a software-only video compressor with a bit rate range from less than 10 Kbps up to to 1.2 Mbps. Quadtree decomposition on an error metric between the input and transmitted images directs the coder towards a foreground layer of active image fragments. A rate buffering system limits the bandwidth by transmitting only the foreground blocks which most improve the image and are above some error threshold. A high fidelity background layer is identified and communicated to the decoder, which can be used to redraw background fragments as foreground objects move across them. Blocks can be coded by various methods, such as fractal transforms or truncated DCTs. This system can be implemented in RISC processors without the need for dedicated hardware. It is suitable for low bit rate applications with slowly varying backgrounds, such as personal video communications over packet networks, or closed circuit TV surveillance using fixed or wireless links.
An innovative perspective to analyze the quality of Digital Elevation Models (DEM) it is here presented. It is based on the fractal Brownian model which is suitable for the description of natural surfaces. Application...
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ISBN:
(纸本)0819423599
An innovative perspective to analyze the quality of Digital Elevation Models (DEM) it is here presented. It is based on the fractal Brownian model which is suitable for the description of natural surfaces. applications to across-track interferometric Synthetic Aperture Radar (SAR) DEM and classical photogrammetric DEM is here accomplished showing the viability and usefulness of the proposed method.
Current hyperspectral imaging cameras are typically limited in throughput either by a slit or other optical geometries requiring small solid angle instantaneous fields of view. The High Etendue Imaging Fourier Transfo...
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ISBN:
(纸本)081942207X
Current hyperspectral imaging cameras are typically limited in throughput either by a slit or other optical geometries requiring small solid angle instantaneous fields of view. The High Etendue Imaging Fourier Transform Spectrometer (HEIFTS) optical design is a new optical geometry for the production of spectral autocorrelation fringe modulation over an image plane defined by a large CCD array. A throughput advantage approaching several hundred appears realizable, with an accompanying increase in signal to noise proportional to ''root N.'' The simple optical implementation of this design will be discussed along with initial experimental results.
We study the problem of choosing an image based optimal wavelet basis with compact support for image data compression and provide a general algorithm for computing the optimal wavelet basis. We parameterize the mother...
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We study the problem of choosing an image based optimal wavelet basis with compact support for image data compression and provide a general algorithm for computing the optimal wavelet basis. We parameterize the mother wavelet and scaling function of wavelet systems through a set of real coefficients of the relevant quadrature mirror filter (QMF) banks. We further introduce decomposition entropy as an information measure to describe the distance between a given digital image and its projection into the subspace spanned by the wavelet basis. The optimal basis for the given image is obtained through minimizing this information measure. The resulting subspace is used for image analysis and synthesis. Experiments show improved compression ratios due to the application of the optimal wavelet basis and demonstrate the potential applications of our methodology in image compression. This method is also useful for constructing efficient wavelet based image coding systems.
A new experimental method for vibration modal analysis based on all-optical photorefractive processing is presented. The method utilizes an optical lock-in approach to measure phase variations in light scattered from ...
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ISBN:
(纸本)0819422371
A new experimental method for vibration modal analysis based on all-optical photorefractive processing is presented. The method utilizes an optical lock-in approach to measure phase variations in light scattered from optically rough, continuously vibrating surfaces. In this four-wave mixing technique, all-optical processing refers to mixing the object beam containing the frequency modulation due to vibration with a single frequency modulated pump beam in the photorefractive medium that processes the modulated signals. This allows for simple detection of the conjugate wavefront image at a CCD. The conjugate intensity is shown to be a function of the first-order ordinary Bessel function and linearly dependent on the vibration displacement induced phase delta, for delta = 4 pi xi/lambda << 1 where xi is the vibration displacement and lambda is the source wavelength. Furthermore, the results demonstrate the unique capabilities of the optical lock-in vibration detection technique to measure vibration signals with very narrow bandwidth (< 1 Hz) and high displacement sensitivity (sub-Angstrom). This narrow bandwidth detection can be achieved over a wide frequency range from the photorefractive response limit to the reciprocal of the photoinduced carrier recombination time. The technique is applied to determine the modal characteristics of a rigidly clamped circular disc from 10 kHz to 100 kHz.
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