Human visual processing of orientation in broad stimuli.

Recently our lab has shown that with broadband stimuli (either visual noise or natural scenes), performance for detecting oriented content is worst at horizontal, best at the obliques, and intermediate at vertical orientations--an anisotropy (termed the horizontal effect ) quite different from the well-known oblique effect (worst performance obliques) obtained with simple line or grating stimuli. This horizontal effect can be explained by a proposed anisotropic normalization model that operates at the level of striate cortex by implementing the known numerical biases of striate neurons preferring different orientations as well as the strength of those responses from neurons tuned to similar orientations and spatial frequencies (with that strength being dependent on the spatial relationships between different scales and orientations present in the stimuli). To assess how the proposed striate normalization mechanism might operate when the visual system is presented with broadband stimuli containing different amounts of spatial frequency and orientation content, two suprathreshold matching experiments were conducted. Additionally, to provide an estimate of how broadband stimuli might modulate the weights of the proposed model, a series of neural response simulations were carried out on different types of broadband natural scene imagery. The stimuli for the psychophysical experiments were generated by making broadband isotropic visual noise patterns and filtering their amplitude spectra to contain a test increment across a specified range of orientations and spatial frequencies. The extent of the test increment\u27s orientation and frequency bandwidth was systematically varied. A standard psychophysical matching paradigm was used to assess the perceived strength of the oriented structure in a test pattern relative to the oriented structure in a comparison pattern. The results yielded the traditional oblique effect when a fairly small range of orientations and high spatial frequencies were incremented and the horizontal effect was observed for broadband increments of about 20 degrees and 1-octave in frequency and larger. A blend of the two anisotropies was observed at intermediate increment bandwidth. The results of the psychophysical experiments were discussed in the context of the proposed striate normalization model with added insight from the results of the neural response simulations

Vision Sensors and Edge Detection

Vision Sensors and Edge Detection book reflects a selection of recent developments within the area of vision sensors and edge detection. There are two sections in this book. The first section presents vision sensors with applications to panoramic vision sensors, wireless vision sensors, and automated vision sensor inspection, and the second one shows image processing techniques, such as, image measurements, image transformations, filtering, and parallel computing

Color and Dynamic Visual Signals Fusion

U tezi su predstavljene robusne, računski efikasne, metode za sjedinjavanje slika, video sekvenci i objektivne mere (algoritmi) za automatsku procenu uspešnosti sjedinjavanja slika i video sekvenci. Razvijeni algoritmi daju bolje rezultate nego postojeći i pri tome pogodni su za rad u realnom vremenu. U istraživanju uzet je u obzir i šum koji se javlja u realnom sistemu i predloženi su načini za njegovo prigušenje u samom procesu sjedinjavanja. Istraživanje je obuhvatilo i sprovođenje subjektivnih testova za procenu uspešnosti sjedinjavanja, kako bi se izvršilo podešavanje parametara metoda za sjedinjavanje i mera za procenu uspešnosti sjedinjavanja.The thesis presents robust, computer efficient, image and video sequencе fusion and objective measurements (algorithms) for automatically evaluating the success of image and video sequencе fusion. Developed algorithms provide better results than existing methods and they are suitable for real-time operation. The study also took into account the noise that occurs in the real systems, and proposed ways for its suppressing in the process of fusion. The survey also included the implementation of subjective tests to assess the success of the fusion, in order to make adjustments to the fusion parameters and measures for assessing the success of the fusion