Estimating vanishing points using visual spatial frequencies of textures on planar surfaces

2003 ◽  
Author(s):  
H. Fujiwara ◽  
Zhong Zhang
Keyword(s):  
Vanishing Points ◽  
Planar Surfaces ◽  
Visual Spatial ◽  
Spatial Frequencies

Natural scenes have matched amplitude-modulated sounds that systematically influence visual scanning

2012 ◽  
Vol 25 (0) ◽  
pp. 121
Author(s):  
Marcia Grabowecky ◽  
Aleksandra Sherman ◽  
Satoru Suzuki
Keyword(s):  
Eye Movements ◽  
Spatial Frequency ◽  
Memory Task ◽  
High Spatial Frequency ◽  
Visual Object ◽  
Natural Scenes ◽  
Scale Invariant ◽  
Visual Coding ◽  
Visual Spatial ◽  
Spatial Frequencies

We have previously demonstrated a linear perceptual relationship between auditory amplitude-modulation (AM) rate and visual spatial-frequency using gabors as the visual stimuli. Can this frequency-based auditory–visual association influence perception of natural scenes? Participants consistently matched specific auditory AM rates to diverse visual scenes (nature, urban, and indoor). A correlation analysis indicated that higher subjective density ratings were associated with faster AM-rate matches. Furthermore, both the density ratings and AM-rate matches were relatively scale invariant, suggesting that the underlying crossmodal association is between visual coding of object-based density and auditory coding of AM rate. Based on these results, we hypothesized that concurrently presented fast (7 Hz) or slow (2 Hz) AM-rates might influence how visual attention is allocated to dense or sparse regions within a scene. We tested this hypothesis by monitoring eye movements while participants examined scenes for a subsequent memory task. To determine whether fast or slow sounds guided eye movements to specific spatial frequencies, we computed the maximum contrast energy at each fixation across 12 spatial frequency bands ranging from 0.06–10.16 cycles/degree. We found that the fast sound significantly guided eye movements toward regions of high spatial frequency, whereas the slow sound guided eye movements away from regions of high spatial frequency. This suggests that faster sounds may promote a local scene scanning strategy, acting as a ‘filter’ to individuate objects within dense regions. Our results suggest that auditory AM rate and visual object density are crossmodally associated, and that this association can modulate visual inspection of scenes.

Multisensory Integration Is Modulated by Auditory Sound Frequency and Visual Spatial Frequency

2019 ◽  
Vol 32 (7) ◽  
pp. 589-611
Author(s):  
Jessica J. Green ◽  
Allison M. Pierce ◽  
Spencer L. Mac Adams
Keyword(s):  
Spatial Frequency ◽  
Frequency Spectrum ◽  
Visual Information ◽  
Sound Frequency ◽  
Audiovisual Speech ◽  
Low Level ◽  
Speech Stimuli ◽  
Visual Spatial ◽  
Spatial Frequencies ◽  
Stimulus Features

Abstract Accurate integration of auditory and visual information is essential for our ability to communicate with others. Previous studies have shown that the temporal discrepancies over which audiovisual speech stimuli will be integrated into a coherent percept are much wider than those typically observed for simple stimuli like beeps and flashes of light. However, our sensitivity to the low-level features of simple stimuli is not constant. We hypothesized that part of the enhanced integration of audiovisual speech may be due to it consisting predominantly of the sound frequencies and visual spatial frequencies that humans are most sensitive to. Here, we examined integration behaviors for pure tones across the sound frequency spectrum and visual gratings across the spatial frequency spectrum to examine how these low-level features modulate integration. The temporal window of integration was modulated by both sound frequency and visual spatial frequency, with the widest integration window occurring when both stimuli fell within their respective peak sensitivity ranges. These results suggest that part of the increased tolerance for temporal asynchrony typically observed for audiovisual speech may be due to the differential integration of low-level stimulus features that are dominant within complex audiovisual speech.

scholarly journals Transformation from local image contrast to location-independent numerosity tuning in human extrastriate cortex

2021 ◽  
Author(s):  
Jacob M Paul ◽  
Martijn van Ackooij ◽  
Tuomas C ten Cate ◽  
Benjamin M Harvey
Keyword(s):  
Visual Cortex ◽  
Spatial Frequency ◽  
Computational Modelling ◽  
Occipital Cortex ◽  
Extrastriate Cortex ◽  
Visual Responses ◽  
Fourier Decomposition ◽  
Visual Spatial ◽  
Spatial Frequencies ◽  
Item Size

Many animals use visual numerosity, the number of items in a group, to guide behavior. Neurons in human association cortices show numerosity-tuned responses, decreasing amplitude with distance from a specific numerosity. How are such responses derived from early visual responses? Recent studies show aggregate response amplitudes in human early visual cortex monotonically increase with numerosity, regardless of object size and spacing. This is surprising because numerosity is typically considered a high-level visual or cognitive feature. Here we first use computational modelling of 7T fMRI data to show these monotonic responses originate at the stimulus's retinotopic location in primary visual cortex (V1). Given this location, we then ask whether these monotonic responses can be better described by V1's established response properties. We characterize the Fourier decomposition (into contrast at specific orientations and spatial frequencies) of laboratory numerosity stimuli. This demonstrates that aggregate Fourier power (at all orientations and spatial frequencies) nonlinearly follows numerosity with little effect of item size, spacing or shape: it is proportional to numerosity at a fixed contrast. This nonlinear relationship lets us distinguish predictions of responses to Fourier power and numerosity. Monotonic responses are better predicted by Fourier power, later tuned responses are better predicted by numerosity. Tuned responses emerge after lateral occipital cortex and are independent of retinotopic location. We propose that numerosity's straightforward perception and neural responses reflect its straightforward estimation from early visual spatial frequency domain image representations. Our numerical vision may have built on behaviorally beneficial analysis of spatial frequency in simpler animals.

scholarly journals Sound-driven enhancement of vision: disentangling detection-level from decision-level contributions

2013 ◽  
Vol 109 (4) ◽  
pp. 1065-1077 ◽  
Author(s):  
Alexis Pérez-Bellido ◽  
Salvador Soto-Faraco ◽  
Joan López-Moliner
Keyword(s):  
Visual Processing ◽  
Response Selection ◽  
Reaction Times ◽  
Order Effects ◽  
Detection Level ◽  
Decision Level ◽  
Visual Spatial ◽  
Spatial Frequencies ◽  
Psychophysical Analysis ◽  
Stimulus Features

Cross-modal enhancement can be mediated both by higher-order effects due to attention and decision making and by detection-level stimulus-driven interactions. However, the contribution of each of these sources to behavioral improvements has not been conclusively determined and quantified separately. Here, we apply psychophysical analysis based on Piéron functions in order to separate stimulus-dependent changes from those accounted by decision-level contributions. Participants performed a simple visual speeded detection task on Gabor patches of different spatial frequencies and contrast values, presented with and without accompanying sounds. On one hand, we identified an additive cross-modal improvement in mean reaction times across all types of visual stimuli that would be well explained by interactions not strictly based on stimulus-driven modulations (e.g., due to reduction of temporal uncertainty and motor times). On the other hand, we singled out an audio-visual benefit that strongly depended on stimulus features such as frequency and contrast. This particular enhancement was selective to low-visual spatial frequency stimuli, optimized for magnocellular sensitivity. We therefore conclude that interactions at detection stages and at decisional processes in response selection that contribute to audio-visual enhancement can be separated online and express on partly different aspects of visual processing.

scholarly journals Glyph guessing for ‘oo’ and ‘ee’: spatial frequency information in sound symbolic matching for ancient and unfamiliar scripts

2017 ◽  
Vol 4 (9) ◽  
pp. 170882 ◽  
Author(s):  
Nora Turoman ◽  
Suzy J. Styles
Keyword(s):  
Spatial Frequency ◽  
Historical Time ◽  
Adult Readers ◽  
Visual Spatial ◽  
Internet Users ◽  
Spatial Frequencies ◽  
The Difference ◽  
Diverse Groups ◽  
Geographical Space ◽  
Larger Sample

In three experiments, we asked whether diverse scripts contain interpretable information about the speech sounds they represent. When presented with a pair of unfamiliar letters, adult readers correctly guess which is /i/ (the ‘ee’ sound in ‘feet’), and which is /u/ (the ‘oo’ sound in ‘shoe’) at rates higher than expected by chance, as shown in a large sample of Singaporean university students (Experiment 1) and replicated in a larger sample of international Internet users (Experiment 2). To uncover what properties of the letters contribute to different scripts' ‘guessability,’ we analysed the visual spatial frequencies in each letter (Experiment 3). We predicted that the lower spectral frequencies in the formants of the vowel /u/ would pattern with lower spatial frequencies in the corresponding letters. Instead, we found that across all spatial frequencies, the letter with more black/white cycles (i.e. more ink) was more likely to be guessed as /u/, and the larger the difference between the glyphs in a pair, the higher the script's guessability. We propose that diverse groups of humans across historical time and geographical space tend to employ similar iconic strategies for representing speech in visual form, and provide norms for letter pairs from 56 diverse scripts.

scholarly journals Amplitude-modulated auditory stimuli influence selection of visual spatial frequencies

2013 ◽  
Vol 13 (3) ◽  
pp. 6-6 ◽  
Author(s):  
E. Orchard-Mills ◽  
E. Van der Burg ◽  
D. Alais
Keyword(s):  
Auditory Stimuli ◽  
Visual Spatial ◽  
Spatial Frequencies ◽  
Selection Of

The Imaging of Crystal Structures and Crystal Defects

1978 ◽  
Vol 36 (3) ◽  
pp. 207-217
Author(s):  
J.M. Cowley
Keyword(s):  
Electron Microscope ◽  
Crystal Structures ◽  
Phase Contrast ◽  
Crystal Defects ◽  
Atom Density ◽  
Lack Of Information ◽  
Spatial Frequencies

The problem of "understandinq" electron microscope imaqes becomes more acute as the resolution is improved. The naive interpretation of an imaqe as representinq the projection of an atom density becomes less and less appropriate. We are increasinqly forced to face the complexities of coherent imaqinq of what are essentially phase objects. Most electron microscopists are now aware that, for very thin weakly scatterinq objects such as thin unstained bioloqical specimens, hiqh resolution imaqes are best obtained near the optimum defocus, as prescribed by Scherzer, where the phase contrast imaqe qives a qood representation of the projected potential, apart from a lack of information on the lower spatial frequencies. But phase contrast imaqinq is never simple except in idealized limitinq cases.

X-Ray Replication of Submicrometer Linewidth Patterns

1977 ◽  
Vol 35 ◽  
pp. 136-137
Author(s):  
Henry I. Smith ◽  
D.C. Flanders
Keyword(s):  
Electron Beam Lithography ◽  
Cross Sectional ◽  
X Ray ◽  
Electron Backscattering ◽  
Spatial Frequencies ◽  
Cross Sectional Profile ◽  
Carbon Foils ◽  
Sectional Profile ◽  
And Control ◽  
Soft Radiation

Scanning electron beam lithography has been used for a number of years to write submicrometer linewidth patterns in radiation sensitive films (resist films) on substrates. On semi-infinite substrates, electron backscattering severely limits the exposure latitude and control of cross-sectional profile for patterns having fundamental spatial frequencies below about 4000 Å(l),Recently, STEM'S have been used to write patterns with linewidths below 100 Å. To avoid the detrimental effects of electron backscattering however, the substrates had to be carbon foils about 100 Å thick (2,3). X-ray lithography using the very soft radiation in the range 10 - 50 Å avoids the problem of backscattering and thus permits one to replicate on semi-infinite substrates patterns with linewidths of the order of 1000 Å and less, and in addition provides means for controlling cross-sectional profiles. X-radiation in the range 4-10 Å on the other hand is appropriate for replicating patterns in the linewidth range above about 3000 Å, and thus is most appropriate for microelectronic applications (4 - 6).

A simple way for producing holographic filters suitable for image improvement

1978 ◽  
Vol 36 (1) ◽  
pp. 226-227
Author(s):  
K.-H. Herrmann ◽  
E. Reuber ◽  
P. Schiske
Keyword(s):  
Transfer Functions ◽  
Diffraction Order ◽  
Lateral Position ◽  
Simple Method ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Wiener Filters ◽  
Image Improvement ◽  
Optical Reconstruction ◽  
Set Up

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.

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