An application of speckle photography techniques to unsteady gas flow measurements is presented. The instrumentation developed for the analysis of double-exposure photographs by digital signal processing is described....
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An application of speckle photography techniques to unsteady gas flow measurements is presented. The instrumentation developed for the analysis of double-exposure photographs by digital signal processing is described. It is shown that 2-D velocity fields can be measured even when the flow is not perfectly 2-D. Accuracy and limitations of these techniques are discussed.
The statistical behavior of images is inherently nonstationary. Unfortunately, most image processing algorithms assume stationary image models. Spatially adaptive algorithms have been developed which take into account...
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The statistical behavior of images is inherently nonstationary. Unfortunately, most image processing algorithms assume stationary image models. Spatially adaptive algorithms have been developed which take into account local image statistics. In this paper we derive radiometric and geometric transforms which generate nearly stationary (block stationary) images in the first and second moments. We show that true stationarity is impossible to realize. The aim of these transformations is to enhance the performance of nonadaptive processing techniques, in particular data compression.
Multispectral middle IR (8–13- μ m) data were acquired with an aircraft scanner over Utah. Because these digital image data were dominated by temperature, all six channels were highly correlated. Extensive processin...
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Multispectral middle IR (8–13- μ m) data were acquired with an aircraft scanner over Utah. Because these digital image data were dominated by temperature, all six channels were highly correlated. Extensive processing was required to allow geologic photointerpretation based on subtle variations in spectral emittance between rock types. After preliminary processing, ratio images were produced and color ratio composites created from these. Sensor calibration and an atmospheric model allowed determination of surface brightness, temperature, emittance, and color composite emittance images. The best separation of major rock types was achieved with a principal component transformation, followed by a Gaussian stretch, followed by an inverse transformation to the original axes.
This paper discusses the use of moiré techniques to enhance optically the generation ofbinary images in automatic visual inspection systems. Techniques for enhancing the illumination ofout-of-plane features or hi...
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This paper discusses the use of moiré techniques to enhance optically the generation ofbinary images in automatic visual inspection systems. Techniques for enhancing the illumination ofout-of-plane features or highlighting areas of missing or misaligned parts on an assembly wereinvestigated. The applications of these techniques to a practical inspection problem weredemonstrated.
Various criteria have been considered for image quality measure. Some of these involve subjective human visual evaluation, while others rely on statistical techniques. In this paper, a cross-spectrum error criterion i...
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Various criteria have been considered for image quality measure. Some of these involve subjective human visual evaluation, while others rely on statistical techniques. In this paper, a cross-spectrum error criterion is considered as a distortion measure for undersampled band-limited images. The effect of undersampling, aliasing on the perfect image, is demonstrated by manipulation in the frequency domain. Subjective comparison of the digital simulation results and the appropriate calculated spectral error indicate that the latter is a useful quantity for the analysis of distortion present in undersampled images. Relevance of our analysis to spatial filtering experiments and the mean square error is also discussed.
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