An Additional Dimension to Grating Perception

Perception ◽  
1978 ◽  
Vol 7 (6) ◽  
pp. 707-715
Author(s):  
Christopher W Tyler
Keyword(s):  
Visual Acuity ◽  
Spatial Frequency ◽  
Modulation Frequency ◽  
Two Dimensional ◽  
Sinusoidal Modulation ◽  
Additional Dimension ◽  
Harmonic Components ◽  
Perceptual Mechanism

Visual acuity ( A) for a two-dimensional multiplicative sinusoidal contrast grid (sinusoidal chessboard) was measured as a function of spatial frequency (ω) of modulation in one of the dimensions. The reduction in acuity as frequency was increased was well described by the equation: A = −2 πkω + c, where k and c are constants. At suprathreshold contrasts, the frequency of modulation appeared to be doubled relative to the underlying modulation frequency. This doubling is not related to the frequency of the harmonic components of the chessboard, but suggests the existence of a perceptual mechanism sensitive to areas of sinusoidal modulation which are seen at twice the frequency of the variation in contrast.

The Dependence of Monocular Rivalry on Spatial Frequency

Perception ◽  
1973 ◽  
Vol 2 (2) ◽  
pp. 127-133 ◽  
Author(s):  
J Atkinson ◽  
F W Campbell ◽  
A Fiorentini ◽  
L Maffei
Keyword(s):  
Spatial Frequency ◽  
Sine Wave ◽  
Ambiguous Figures ◽  
Alternation Rate ◽  
Higher Harmonics ◽  
Square Wave ◽  
Sharp Edges ◽  
Harmonic Components ◽  
Sine Wave Gratings

The effect of change in spatial frequency on the alternation rate of two crossed gratings was measured. The rate was found to decrease with increase in spatial frequency, but to change only little with contrast. Low alternation rate was observed for crossed square-wave gratings compared to crossed sine-wave gratings; here the rate of rivalry is largely dependent upon the presence or absence of the first three harmonic components rather than the higher harmonics which contribute to the sharp edges of the square wave. The results are compared with those for some ambiguous figures.

Temporal-Discontinuity Detection with Contrast-Modulated Gratings

Perception ◽  
1995 ◽  
Vol 24 (11) ◽  
pp. 1257-1264
Author(s):  
Shigeru Ichihara ◽  
Kenji Susami
Keyword(s):  
Spatial Frequency ◽  
Modulation Frequency ◽  
Sinusoidal Grating ◽  
Local Contrast ◽  
Staircase Method ◽  
Low Contrast ◽  
Discontinuity Detection ◽  
Temporal Discontinuity ◽  
Sinusoidal Gratings ◽  
The Subject

Three experiments on temporal-discontinuity detection were carried out. In experiment 1, temporal-discontinuity thresholds were measured for sinusoidal gratings by the use of the double-staircase method. A sinusoidal grating was presented twice successively. The subject judged whether or not an interval was present. The temporal-discontinuity threshold increased as the spatial frequency of the grating increased, but decreased as the contrast of the grating increased. In experiment 2, contrast-modulated gratings were used instead of the sinusoidal grating. The temporal-discontinuity threshold increased as the carrier frequency increased, and the threshold for each contrast-modulated grating was similar to that for the no-modulation (sinusoidal) grating whose contrast was the same as the maximum local contrast of the contrast-modulated grating. In experiment 3, temporal-discontinuity thresholds were measured for low-contrast (3%) sinusoidal gratings. The thresholds were very low, even for such low-contrast gratings. These results suggest that the low-spatial-frequency channels are not involved in detecting the modulation frequency of the contrast-modulated grating. Rather, the local contrast seems to be the determinant of the detection of the contrast-modulated grating itself.

Applicability of Wordnet Architecture in Lexical Borrowing Studies

2020 ◽  
Author(s):  
Ewa Geller ◽  
Michał Gajek ◽  
Agata Reibach ◽  
Zuzanna Łapa
Keyword(s):  
Broad Spectrum ◽  
Two Dimensional ◽  
Lexical Borrowing ◽  
Source Language ◽  
Additional Dimension ◽  
Macrostructure Organization ◽  
Lexical Relations

Abstract The aim of the paper is to present a new, wordnet-based method of studying lexical borrowing. In contrast to the two-dimensional (micro- and macrostructure) organization of traditional dictionaries, describing each unit in isolation, wordnets introduce an additional dimension of inter-word relations in the entire lexicon. The ability to connect wordnets cross-linguistically allows in turn for juxtaposing, comparing, and visualizing a broad spectrum of lexical relations between loanwords within the recipient language and their cognates in the source language for which the term cross-linguistic mapping has been used. The method was applied to a wordnet-based, yet differently structured network of Polish loanwords in Yiddish. This allowed to supplement the traditional typology of transferred words by introducing the notion of ‘rootedness’, that is the degree of their interconnectedness in the source and recipient systems. This in turn has provided a promising means for distinguishing inherited from acquired vocabulary.

The Image Watermarking against Shearing Based on Dopplerlet Transformation

2011 ◽  
Vol 181-182 ◽  
pp. 276-280
Author(s):  
Ming Hui Deng ◽  
Wen Zhe Li ◽  
Qi Chen Li
Keyword(s):  
Spatial Frequency ◽  
Dimensional Space ◽  
Image Watermarking ◽  
Time Windows ◽  
Geometric Distortion ◽  
Frequency Change ◽  
Two Dimensional ◽  
Frequency Distributions ◽  
Chirp Signals ◽  
Wigner Transformation

In this paper, a robust image watermarking method in two-dimensional space/spatial-frequency distributions domain is proposed which is robust against geometric distortion. This watermarking is detected by a linear frequency change. The dopplerlet transformation is used to detect the watermark. The chirp signals are used as watermarks and this type of signals is resistant to all stationary filtering methods and exhibits geometrical symmetry. In the two-dimensional Radon-Wigner transformation domain, the chirp signals used as watermarks change only its position in space/spatial-frequency distribution, after applying linear geometrical attack, such as scale rotation and cropping. But the two-dimensional Radon-Wigner transformation needs too much difficult computing. So the image is put into a series of 1D signal by choosing scalable local time windows. The watermark embedded in the dopplerlet transformation domain. The watermark thus generated is invisible and performs well in StirMark test and is robust to geometrical attacks. Compared with other watermarking algorithms, this algorithm is more robust, especially against geometric distortion, while having excellent frequency properties.

Measuring Frog Visual Acuity by a Novel Method

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 65-65
Author(s):  
A-C Aho
Keyword(s):  
Visual Acuity ◽  
Spatial Frequency ◽  
Rana Temporaria ◽  
Leopard Frog ◽  
Retinal Cell ◽  
Common Frog ◽  
Optomotor Response ◽  
Leopard Frogs ◽  
Grating Pattern ◽  
The Common

The sensory capabilities of animals have usually been measured either by lengthy conditioned discrimination procedures, or by using some specific unconditioned reflex. Amphibian visual acuity has previously been measured only by the latter type of method. Birukow's (1937 Zeitschrift für Vergleichende Physiologie25 92 – 142) optomotor response experiments on the common frog ( Rana temporaria) yielded an acuity of 4.3 cycles deg−1, which is surprisingly high in the sense that the retinal cell mosaics would suggest a substantially lower acuity. I have used a new method of measuring acuity based on the frog's prey-catching behaviour, a behaviour that has proved very useful for investigations of amphibian vision. Leopard frogs ( R. pipiens) were presented with a stimulus screen where two patches of identical black/white vertical grating were seen through two small horizontal oval windows (left and right) in a large screen displaying a horizontal grating pattern. The windows were of ‘mealworm’ size (18 mm long and 7 mm high, with the frog positioned 220 mm from the screen). One of the two vertical gratings was drifting in the window. If resolved, the movement triggered prey-catching behaviour in the frog: orienting, jumping towards the target, and even snapping. The spatial frequency of the two vertical gratings was varied, while the horizontal pattern of the screen was kept constant throughout the experiment. Orienting or jumping towards the moving grating was taken as an indication that the frog was able to resolve the spatial frequency in question. This method yielded a visual acuity of 2.8 cycles deg−1, which is in good agreement with the eye optics and the retinal grain of frogs (very similar for the common frog and the leopard frog). The method in itself implies that this is a ‘functional’ acuity value.

scholarly journals Two-Dimensional Spatial Frequency Content and Confusions among Dot Matrix Characters

1979 ◽  
Vol 23 (1) ◽  
pp. 384-388
Author(s):  
Michael E. Maddox
Keyword(s):  
Spatial Frequency ◽  
Similarity Measure ◽  
Similarity Measures ◽  
Final Analysis ◽  
Second Phase ◽  
Two Dimensional ◽  
Two Phase ◽  
Frequency Spectra ◽  
Character Size ◽  
Point Fast Fourier Transform

A two-phase study was conducted which related the confusions among dot matrix characters to the two-dimensional spatial frequency similarity of these characters. During the first phase of the study, subjects were shown single alphanumeric characters from four different dot matrix fonts and five matrix size/character sub-tense combinations. Data from this phase of the research were analyzed in terms of both correctness and character confusion frequencies. The second phase of the study consisted of digitizing and analyzing all characters from two of the fonts used in the first phase. The fonts chosen represent the most and least confusable of the four, based on the performance data obtained. These characters were scanned photometrically using a computer-controlled X-Y stage and subjected to a 512 × 512 point fast Fourier transform (FFT). The Fourier coefficients were correlated for all possible character pairs within each font-matrix/character size cell. These correlations provided an objective similarity measure among characters based upon their 2-D spatial frequency spectra. In addition to the spatial frequency similarity measure, a simple digital Phi coefficient was calculated for each character pair. The final analysis performed in this study was the correlation of observed performance (confusions) with objective similarity measures (2-D spectra and Phi coefficients).

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