Search results for "Pixel"
showing 10 items of 421 documents
Objective improvement of the visual quality of ion microscope images
2013
The need to operate with low ion beam fluences implies the images obtained using ion microscope (IM) are often grainy and have poor visual quality compared to what can be obtained using e.g. confocal microscopy. This results from the Poissonian distribution of counts in pixels. Here we report work on some different approaches for objectively improving the visual quality of IM images. In this work we present (i) dramatic improvement in the visual image quality of off-axis and direct-scanning transmission ion microscopy (STIM) images by suppression of zero-pixels; (ii) denoising of PIXE images using wavelet filtering and (iii) use of the feature preserving characteristics of wavelet filtering…
Selective Change Driven Vision Sensor With Continuous-Time Logarithmic Photoreceptor and Winner-Take-All Circuit for Pixel Selection
2015
The objective of Selective Change Driven (SCD) Vision is to capture and process those scene pixels that have the greatest impact in the motion estimation task. The implemented SCD Vision sensor delivers the pixels ordered according to the illumination change undergone by each pixel, from the last time each pixel was read-out. This ordering strategy is especially interesting for motion detection algorithms, since it allows for a reduction in data bandwidth requirements without decreasing accuracy. The speed of the obtained pixel flow allows movement detection and tracking at a speed several orders of magnitude higher than conventional vision systems. To accomplish these objectives, the senso…
Spatial analysis of the homogeneity of the land surface temperature in three Spanish test sites
2015
Calibration and validation cal/val are key activities to test the data quality acquired from satellite-based instruments, as well as to report the accuracy of derived products such as the land surface temperature LST. Calibration of thermal infrared TIR data and validation of LST products at low spatial resolution requires the identification of large and homogeneous areas, which is a difficult task. In this work, spatial and temporal homogeneity of LST was analysed over three Spanish regions: the agricultural area of Barrax, Donana National Park, and Cabo de Gata Natural Park. For this purpose, very high spatial resolution approximately 3 m imagery acquired with the Airborne Hyperspectral S…
Water‐vapour retrieval from Meteosat 8/SEVIRI observations
2007
This paper aims to propose operational algorithms to retrieve the total atmospheric water vapour content (W) using the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on-board Meteosat 8. MODTRAN3.5 was used to obtain simulated data in the thermal infrared channels IR10.8 and IR12.0, in order to determine the numerical values of the coefficients of the algorithms. The algorithm proposed for land pixels takes into account the SEVIRI observation geometry and the radiometric temperatures obtained in the split-window channels at two different times during a day and requires a minimum difference of 10 K in terms of temperature between the two situations. Comprehensive error analyses gave …
Methodology for the retrieval of vegetation chlorophyll fluorescence from space in the frame of the flex mission preparatory
2016
FLEX (FLuorescence EXperiment) is a candidate mission for the European Space Agency (ESA) Earth Explorer program. The main objective of the mission is the measurement the chlorophyll fluorescence signal emitted by vegetation at the red and far-red spectral regions (roughly 630-770 nm). The current FLEX mission design includes different instruments intended to provide the appropriate characterization of those atmospheric and surface parameters necessary for the retrieval and interpretation of the fluorescence signal. The complete processing chain for the derivation of fluorescence and reflectance products from the radiance data acquired by the different instruments included in the FLEX paylo…
On the Advantages of Asynchronous Pixel Reading and Processing for High-Speed Motion Estimation
2008
Biological visual systems are becoming an interesting source for the improvement of artificial visual systems. A biologically inspired read-out and pixel processing strategy is presented. This read-out mechanism is based on Selective pixel Change-Driven (SCD) processing. Pixels are individually processed and read-out instead of the classical approach where the read-out and processing is based on complete frames. Changing pixels are read-out and processed at short time intervals. The simulated experiments show that the response delay using this strategy is several orders of magnitude lower than current cameras while still keeping the same, or even tighter, bandwidth requirements.
A methodology for obtaining the crop temperature from NOAA-9 AVHRR data
1991
Abstract In this paper a methodology for obtaining the crop temperature from NOAA-9 AVHRR data has been developed, which is based on a theoretical model that permits interpreting the remote sensing temperature measurement in heterogeneous and rough surfaces. This procedure determines the crop temperature by evaluating prsviously: (1) the temperature difference between crop and ground, (2) the atmospheric and emissivity corrections, (3) the ground and vegetation emissi-vities in the AVHRR bands 4 (10-3-11-3 μm) and 5 (11 -5-12-5 μm), and (4) the proportion of ground in each pixel. We have applied this method to obtain a map of orange-tree temperatures for the Valencian region and satisfactor…
A Comparative Study on Feature Selection for Retinal Vessel Segmentation Using FABC
2009
This paper presents a comparative study on five feature selection heuristics applied to a retinal image database called DRIVE. Features are chosen from a feature vector (encoding local information, but as well information from structures and shapes available in the image) constructed for each pixel in the field of view (FOV) of the image. After selecting the most discriminatory features, an AdaBoost classifier is applied for training. The results of classifications are used to compare the effectiveness of the five feature selection methods.
Unsupervised recognition of retinal vascular junction points.
2014
Landmark points in retinal images can be used to create a graph representation to understand and to diagnose not only different pathologies of the eye, but also a variety of more general diseases. Aim of this paper is the description of a non-supervised methodology to distinguish between bifurcations and crossings of the retinal vessels, which can be used in differentiating between arteries and veins. A thinned representation of the binarized image, is used to identify pixels with three or more neighbors. Junction points are classified into bifurcations or crossovers according to their geometrical and topological properties. The proposed approach is successfully compared with the state-of-t…
Improving SIFT-based descriptors stability to rotations
2010
Image descriptors are widely adopted structures to match image features. SIFT-based descriptors are collections of gradient orientation histograms computed on different feature regions, commonly divided by using a regular Cartesian grid or a log-polar grid. In order to achieve rotation invariance, feature patches have to be generally rotated in the direction of the dominant gradient orientation. In this paper we present a modification of the GLOH descriptor, a SIFT-based descriptor based on a log-polar grid, which avoids to rotate the feature patch before computing the descriptor since predefined discrete orientations can be easily derived by shifting the descriptor vector. The proposed des…