Efficient SAR Raw Data Compression in Frequency Domain

SAR raw data compression is necessary to reduce huge amounts of SAR data for a memory on board a satellite, space shuttle or aircraft and for later downlink to a ground station. In view of interferometric and polarimetric applications for SAR data, it becomes more and more important to pay attention to phase errors caused by data compression. Herein, a detailed comparison of block adaptive quantization in time domain (BAQ) and in frequency domain (FFT-BAQ) is given. Inclusion of raw data compression in the processing chain allows an efficient use of the FFT-BAQ and makes implementation for on-board data compression feasible. The FFT-BAQ outperforms the BAQ in terms of signal-to-quantization noise ratio and phase error and allows a direct decimation of the oversampled data equivalent to FIR-filtering in time domain. Impacts on interferometric phase and coherency are also given

Fluorescence Blinking and Photobleaching of Single Terrylenediimide Molecules Studied with a Confocal Microscope

Single terrylenediimide molecules diluted in a 20-nm-thick polyvinylbutyral polymer film were localized and observed by scanning confocal fluorescence microscopy. A modular and compact confocal microscope and the high optical stability of the molecules allowed a repeated imaging and observation over >5 h at room temperature. Most of the molecules showed several “on-off-on” transitions (blinking) on a time scale from seconds to hours, before permanent bleaching occurred. We determined that >1.5 × 10^7 fluorescence photons are emitted from the most-stable molecules before the final bleaching step occurs. Despite the “on-off-on” transitions, however, the overall change in fluorescence intensity, either integrated over each image of a time series or summed for several individual molecules, resembled an exponential-like decay, familiar from measurements of many-molecule ensembles. We also observed the polarization of the fluorescence from single molecules during excitation with circular polarized light. From these measurements, possible rotations of the molecular dipoles were studied. Over a span of 5 h, the polarization angle in most cases did not change by >15-20°. This may explain the slow and small intensity changes but excludes molecular rotation as a reason for the blinking behavior

Using quality measures for quality improvement: The perspective of hospital staff

Research objective: This study examines the perspectives of a range of key hospital staff on the use, importance, scientific background, availability of data, feasibility of data collection, cost benefit aspects and availability of professional personnel for measurement of quality indicators among Iranian hospitals. The study aims to facilitate the use of quality indicators to improve quality of care in hospitals. Study design: A cross-sectional study was conducted over the period 2009 to 2010. Staff at Iranian hospitals completed a self-administered questionnaire eliciting their views on organizational, clinical process, and outcome (clinical effectiveness, patient safety and patient centeredness) indicators. Population studied: 93 hospital frontline staff including hospital/nursing managers, medical doctors, nurses, and quality improvement/medical records officers in 48 general and specialized hospitals in Iran. Principal findings: On average, only 69% of respondents reported using quality indicators in practice at their affiliated hospitals. Respondents varied significantly in their reported use of organizational, clinical process and outcome quality indicators. Overall, clinical process and effectiveness indicators were reported to be least used. The reported use of indicators corresponded with their perceived level of importance. Quality indicators were reported to be used among clinical staff significantly more than among managerial staff. In total, 74% of the respondents reported to use obligatory indicators, while this was 68% for voluntary indicators (p<0.05). Conclusions: There is a general awareness of the importance and usability of quality indicators among hospital staff in Iran, but their use is currently mostly directed towards external accountability purposes. To increase the formative use of quality indicators, creation of a common culture and feeling of shared ownership, alongside an increased uptake of clinical process and effectiveness indicators is needed to support internal quality improvement processes at hospital level

Wavelet based ScanSAR Image Compression Minimizing Block Effects

ScanSAR images are important products of modern spaceborne SAR systems. A wide swath is covered during one single data take. Usual processing of ScanSAR images with a high number of looks not only reduces speckle but also leads to data compression. However, the amount of data can be further reduced, if an appropriate ScanSAR data compression is applied. In our paper, we propose a new wavelet based compression technique, which adapts to the ac energy distribution in ScanSAR images and minimizes artifacts due to compression. Special attention is paid to reduce block effects. Our technique is tested on ScanSAR data of RADARSAT and the SIR-C space shuttle mission. Compressing the SIR-C ScanSAR scene of Chickasha/Oklahoma, USA with factor 1:8, we achieve an improvement in the overall signal-to-distorsion-noise ratio (SDNR) from 29.7 dB to 48.03 dB

Adaptive SAR Image Compression in Wavelet Domain

Synthetic Aperture Radar (SAR) provides valuable information for the remote sensing community. Polarimetry and interferometry are most important applications. They require amplitude and phase information of complex SAR data. Here, we propose a flexible phase preserving algorithm (FLECS) to compress these complex SAR data. Flexibility allows adjustment of compression ratio to the application's requirements. Adaptability of the algorithm ensures a signal-to-distortion-noise ratio and a phase error, which is nearly independent from image contents. The algorithm uses wavelet transform for energy packing and linear quantization for lossy compression in transform domain. In case of separately performed phase compression vector quantization is applied

On-Board SAR Processing - ScanSAR Data Compression

This work gives reasons for using the selected algorithm for ScanSAR image compression. The algorithm is descibed in detail together with experimental results of our detailed study. Results in terms of signal-to-distorsion-noise ratios (SDNR) and phase errors (standard deviation) are compared to results gained upon stripmap SAR images

On-board SAR Processing - Data Compression Performance - Modelling and Simulation

This documentation describes both work packages, perfomance modelling and performance simulation, due to the high interaction between both. The studies of prior workpackages are extended to compression of polarimetric and interferometric data sets. Phase errors are carefully studied. BAQ is suggested for SAR raw data compression. However, if data compression and processing can be fused, the FFT-BAQ is a good solution. For SAR image compression an approach in wavelet domain is preferred

Leaky waveguide modes along the edge of a dielectric wedge

International audienceIt is shown experimentally that a Gaussian beam focused from within a finite wedge onto its edge at an angle of total reflection excites a leaky waveguide mode propagating along the edge. This newly described phenomenon is interpreted in terms of waveguide modes of a tapered dielectric slab of a mode index, which is known to decrease with slab thickness. This decrease in the refractive index leads to a gradual refraction of the incident beam parallel to the edge. A numerical simulation of a focused Gaussian beam incident on a finite dielectric wedge gives a full account of this phenomeno

Rastersondentechniken - Einsatz magnetischer Rastersondentechniken in der praeventiven Qualitaetsicherung. Teilprojekt: Magneto-Optisches Nahfeldmikroskop Abschlussbericht

It is suggested to use the tetrahedral tip as a probe for magneto-optic near field microscopy in order to characterise by near-field optical means the local distribution of metals in magnetic storage media and to measure the local distribution of the magnetic field in magnetic write heads. Advantages of the tetrahedral tip as compared to other optical near field probes are expected from its high resolving power, the selective contrast for different materials and the favorable polarisation properties. The main result consists of the realisation of a force distance control of the tetrahedral tip on the basis of quartz tuning forks and its implementation in a combined SNOM/AFM mode. Although no magneto-optical applications could be demonstrated the force distance control is considered as an important prerequisite for this aim. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(79,35) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman