The Detection of Interocular Phase Differences

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 272-272
Author(s):  
M J Morgan
Keyword(s):  
Temporal Frequency ◽  
Random Noise ◽  
Broad Band ◽  
Vertical Axis ◽  
Phase Lag ◽  
Depth Effect ◽  
Television Receiver ◽  
Frequency Components ◽  
Pulfrich Effect ◽  
Motion Detectors

When dynamic visual noise such as the ‘snow’ on a detuned television receiver is viewed with a temporal delay between the two eyes, the noise appears to rotate in depth around a vertical axis [Ross, 1974 Nature (London)248 363 – 364; Morgan and Tyler, 1995 Proceedings of the Royal Society of London, Series B262 371 – 376]. Random noise evidently contains a wide spread of spatiotemporal Fourier components, including those for horizontal motion, which may cause a Pulfrich effect when there is an interocular delay. To investigate the temporal-frequency components necessary for the effect, a display was designed containing only a single temporal frequency. Spatially broad-band grey-level noise was flickered, such that each pixel of the noise was sinusoidally modulated over time. An interocular delay was introduced as a phase lag of the flicker in one eye. This produced a rotating depth effect. The threshold for detecting the phase shift was about 5° of phase angle, irrespective of temporal frequency, except for frequencies greater than ∼20 Hz, when the depth effect was no longer seen. Tests of several models of the phase-lag detection are described, including the possibility that there are dichoptic motion detectors also tuned to stereodisparity.

An adaptive Reichardt detector model of motion adaptation in insects and mammals

1997 ◽  
Vol 14 (4) ◽  
pp. 741-749 ◽  
Author(s):  
Colin W.G. Clifford ◽  
Michael R. Ibbotson ◽  
Keith Langley
Keyword(s):  
Dynamic Range ◽  
Frequency Tuning ◽  
Temporal Frequency ◽  
Optic Tract ◽  
Intrinsic Property ◽  
Wide Field ◽  
Motion Adaptation ◽  
Motion Sensitivity ◽  
Differential Motion ◽  
Motion Detectors

AbstractThere are marked similarities in the adaptation to motion observed in wide-field directional neurons found in the mammalian nucleus of the optic tract and cells in the insect lobula plate. However, while the form and time scale of adaptation is comparable in the two systems, there is a difference in the directional properties of the effect. A model based on the Reichardt detector is proposed to describe adaptation in mammals and insects, with only minor modifications required to account for the differences in directionality. Temporal-frequency response functions of the neurons and the model are shifted laterally and compressed by motion adaptation. The lateral shift enhances dynamic range and differential motion sensitivity. The compression is not caused by fatigue, but is an intrinsic property of the adaptive process resulting from interdependence of temporal-frequency tuning and gain in the temporal filters of the motion detectors.

scholarly journals Frequency estimators with high resistance to interference from image frequency components

2018 ◽  
Vol 12 (2) ◽  
pp. 147-158 ◽  
Author(s):  
Wei Zhou ◽  
Liqun Gan ◽  
Hong Xiao ◽  
Yi Zhang ◽  
Haitao Xu ◽  
...  
Keyword(s):  
Mean Squared Error ◽  
Frequency Estimation ◽  
Geometric Mean ◽  
Random Noise ◽  
Estimation Algorithm ◽  
Side Lobe ◽  
Sine Wave ◽  
Practical Engineering ◽  
Frequency Components ◽  
Image Frequency

This paper presents an improved frequency estimation algorithm based on the interpolated discrete Fourier transform. High-accurate frequency estimation can be achieved by taking the geometric mean of two independent estimates, which are derived from the real parts of the two largest spectral bins and the imaginary parts, respectively. In situations where only a small number of sine wave cycles are observed, the ability of the algorithm to cancel interference from image frequency components results in improvements in accuracy. The residual errors of the proposed algorithm have been theoretically analyzed with maximum side-lobe decaying windows, since the windows have simple and uniform analytical expression of interpolation algorithm. The performance of the proposed algorithm was investigated using both Hanning and three-term maximum side-lobe decaying windows. A comparative analysis of systematic errors and noise sensitivity was performed between the new algorithm and traditional algorithms. Both the root mean squared error and the probability density of the errors were investigated under noisy conditions. Simulation results demonstrated that the new algorithm is not only highly resistant to interference from image components but is also resistant to the effects of random noise. The results presented in the paper are useful for identifying the best choice of algorithm in practical engineering applications.

A Robustness Watermarking Algorithm for Digital Color Image Print-Scan Process

2013 ◽  
Vol 333-335 ◽  
pp. 992-997
Author(s):  
Yun Lu Ge ◽  
Hui Han ◽  
Xiao Dong Sun ◽  
Sheng Pin Wang ◽  
Sheng Yun Ji
Keyword(s):  
Color Image ◽  
Random Noise ◽  
Color Space ◽  
Low Frequency ◽  
New Method ◽  
Color Spaces ◽  
Image Watermark ◽  
Color Space Conversion ◽  
Frequency Components ◽  
Orthogonal Transform

Most of watermarking algorithms are for digital grey image, which are not robust against the attacks of print-scan process, and the embedded information capacity is small. To solve these problem, a new method based on DWT transform and Walsh orthogonal transform for the print-scan process of digital color image was proposed. The method chosed the color spaces conversion from RGB to CIEL*a*b* for digital color image. The low frequency components of the DWT transform image was embed the watermark. The results show that the correlation of watermark is improved using Walsh orthogonal transform, the watermark extraction rate is high and image watermark is distinct and readable after print-scan process. And this method is robust against the various attacks of the print-scan process, such as color space conversion, image halftone, D/A conversion, A/D conversion, scaling, rotation, cropping, skew, and random noise signals.

Direction-Selective Neurons in the Optokinetic System With Long-Lasting After-Responses

2002 ◽  
Vol 88 (5) ◽  
pp. 2224-2231 ◽  
Author(s):  
Nicholas S. C. Price ◽  
Michael R. Ibbotson
Keyword(s):  
Temporal Frequency ◽  
Optic Tract ◽  
Movement Control ◽  
Oscillatory Behavior ◽  
Head Movements ◽  
Functional Roles ◽  
Preferred Direction ◽  
Spatial Frequencies ◽  
Pretectal Nucleus ◽  
Motion Detectors

We describe the responses during and after motion of slow cells, which are a class of direction-selective neurons in the pretectal nucleus of the optic tract (NOT) of the wallaby. Neurons in the NOT respond to optic flow generated by head movements and drive compensatory optokinetic eye movements. Motion in the preferred direction produces increased firing rates in the cells, whereas motion in the opposite direction inhibits their high spontaneous activities. Neurons were stimulated with moving spatial sinusoidal gratings through a range of temporal and spatial frequencies. The slow cells were maximally stimulated at temporal frequencies <1 Hz and spatial frequencies of 0.13–1 cpd. During motion, the responses oscillate at the fundamental temporal frequency of the grating but not at higher-order harmonics. There is prolonged excitation after preferred direction motion and prolonged inhibition after anti-preferred direction motion, which are referred to as same-sign after-responses (SSARs). This is the first time that the response properties of neurons with SSARs have been reported and modeled in detail for neurons in the NOT. Slow cell responses during and after motion are modeled using an array of Reichardt-type motion detectors that include band-pass temporal prefilters. The oscillatory behavior during motion and the SSARs can be simulated accurately with the model by manipulating time constants associated with temporal filtering in the prefilters and motion detectors. The SSARs of slow cells are compared with those of previously described direction-selective neurons, which usually show transient inhibition or excitation after preferred or anti-preferred direction motion, respectively. Possible functional roles for slow cells are discussed in the context of eye movement control.

scholarly journals Apparent Motion and the Pulfrich Effect

Perception ◽  
1975 ◽  
Vol 4 (1) ◽  
pp. 3-18 ◽  
Author(s):  
Michael J Morgan ◽  
Peter Thompson
Keyword(s):  
Apparent Motion ◽  
Target Position ◽  
Moving Object ◽  
Continuous Motion ◽  
Depth Effect ◽  
Pairing Effect ◽  
Moving Stimuli ◽  
Pulfrich Effect

The Pulfrich pendulum effect, obtained by viewing a moving object with a filter over one eye, was examined with target stimuli in apparent, rather than continuous, motion. The filter-induced depth effect persisted until a certain degree of intermittency in the presentations of the target was reached, and then it broke down. The degree of intermittency that could be tolerated before the depth effect broke down increased with the density of the filter. It could be argued that the filter determined a shift in the pairing of successive inputs to the eyes, such that the target position in the unfiltered eye was fused with the preceding target position in the filtered eye. However, it appears that the shifted-pairing effect cannot account for the depth impression seen when the target intermittency is less than about 30 ms. Below this value of intermittency a filter can produce a depth effect even when the delay it introduces is small in comparison to the intermittency of the input. The depth effect seen with intermittencies less than 30 ms appears to be of the same magnitude as that obtained with stimuli in continuous motion. It is concluded that a filter can cause two different kinds of depth shift with apparently moving stimuli.

Role of the color-opponent and broad-band channels in vision

1990 ◽  
Vol 5 (04) ◽  
pp. 321-346 ◽  
Author(s):  
Peter H. Schiller ◽  
Nikos K. Logothetis ◽  
Eliot R. Charles
Keyword(s):  
Spatial Frequency ◽  
Temporal Frequency ◽  
Broad Band ◽  
High Spatial Frequency ◽  
Brightness Perception ◽  
Rods And Cones ◽  
Form Vision ◽  
Temporal Domain ◽  
Frequency Domains

AbstractThe functions of the primate color-opponent and broad-band channels were assessed by examining the visual capacities of rhesus monkeys following selective lesions of parvocellular and magnocellular lateral geniculate nucleus, which respectively relay these two channels to the cortex. Parvocellular lesions impaired color vision, high spatial-frequency form vision, and fine stereopsis. Magnocellular lesions impaired high temporal- frequency flicker and motion perception but produced no deficits in stereopsis. Low spatial-frequency form vision, stereopsis, and brightness perception were unaffected by either lesion. Much as the rods and cones of the retina can be thought of as extending the range of vision in the intensity domain, we propose that the color-opponent channel extends visual capacities in the wavelength and spatial-frequency domains whereas the broad-band channel extends them in the temporal domain.

Experimental and Numerical Study of the Depth Effect on the First Order and Slowly Varying Motions of a Floating Body in Bichromatic Waves

2010 ◽  
Author(s):  
Joa˜o Pessoa ◽  
Nuno Fonseca ◽  
C. Guedes Soares
Keyword(s):  
Numerical Study ◽  
Vertical Cylinder ◽  
Vertical Axis ◽  
Second Order ◽  
The Body ◽  
Floating Body ◽  
Harmonic Waves ◽  
Depth Effect ◽  
Drift Motion ◽  
First Order

The paper presents an experimental and numerical investigation on the motions of a floating body of simple geometry subjected to harmonic and bi-harmonic waves. The experiments were carried out in three different water depths representing shallow and deep water. The body is axis-symmetric about the vertical axis, like a vertical cylinder with a rounded bottom, and it is kept in place with a soft mooring system. The experimental results include the first order motion responses, the steady drift motion offset in regular waves and the slowly varying motions due to second order interaction in bi-harmonic waves. The hydrodynamic problem is solved numerically with a second order boundary element method. The results show a good agreement of the numerical calculations with the experiments.

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