Visual Acuity and Spatio-Spatial Frequency Doubling in Sinusoidal Chessboards

1975 ◽  
Author(s):  
C. William Tyler
Keyword(s):  
Visual Acuity ◽  
Spatial Frequency ◽  
Frequency Doubling

Observations on Spatial-Frequency Doubling

Perception ◽  
1974 ◽  
Vol 3 (1) ◽  
pp. 81-86 ◽  
Author(s):  
C W Tyler
Keyword(s):  
Spatial Frequency ◽  
Transient Response ◽  
Frequency Doubling ◽  
Amacrine Cells ◽  
Distortion Model ◽  
Detection Model ◽  
Disparity Detection

The involvement of disparity detectors in the perception of spatial-frequency doubling in a flickering grating was tested by viewing the grating horizontally. Frequency doubling was unimpaired, and must therefore occur independently of disparity detection. A distortion model of frequency doubling was compared with a flicker-detection model, in predicting the appearance of nonsinusoidal gratings. The results support the flicker-detection model but not the distortion model. Physiological considerations suggest that spatial-frequency doubling may be mediated by the transient response of the amacrine cells in the retina.

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.

Insights for mfVEPs from perimetry using large spatial frequency-doubling and near frequency-doubling stimuli in glaucoma

2020 ◽  
Vol 141 (1) ◽  
pp. 45-55
Author(s):  
Siti Nurliyana Abdullah ◽  
Gordon F. Sanderson ◽  
Mohd Aziz Husni ◽  
Ted Maddess
Keyword(s):  
Spatial Frequency ◽  
Frequency Doubling

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.

scholarly journals Visual acuity of budgerigars for moving targets

Biology Open ◽  
2021 ◽  
Author(s):  
Sandra Chaib ◽  
Juliane Gaviraghi Mussoi ◽  
Olle Lind ◽  
Almut Kelber
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Spatial Frequency ◽  
Detection Threshold ◽  
Moving Targets ◽  
Resolution Limit ◽  
Food Items ◽  
Visual Spatial ◽  
Behavioural Tests ◽  
Circular Target

For a bird, it is often vital to visually detect food items, predators, or individuals from the same flock, i.e. moving stimuli of various shapes. Yet, behavioural tests of visual spatial acuity traditionally use stationary gratings as stimuli. We have behaviourally tested the ability of budgerigars (Melopsittacus undulatus) to detect a black circular target, moving semi-randomly at 1.69 degrees second−1 against a brighter background. We found a detection threshold of 0.107±0.007 degrees of the visual field for target size corresponding to a resolution of a grating with a spatial frequency of 4.68 cycles degree−1. This detection threshold is lower than the resolution limit for gratings but similar to the threshold for stationary single objects of the same shape. We conclude that the target acuity of budgerigars for moving single targets, just as for stationary single targets, is lower than their acuity for gratings.

Deposition of Cr Atoms Using Switching-Detuning Light Mask for Direct Atom Lithography

2019 ◽  
Vol 15 (6) ◽  
pp. 626-630
Author(s):  
Li Zhu ◽  
Xiao Deng ◽  
Jie Liu ◽  
Xinbin Cheng ◽  
Tongbao Li
Keyword(s):  
Spatial Frequency ◽  
Deposition Time ◽  
Frequency Doubling ◽  
Deposition Process ◽  
Atom Beam ◽  
High Uniformity ◽  
Dipole Force ◽  
Scaling Down ◽  
Pitch Distance ◽  
Atom Lithography

Background: As progress on the nanofabrication has made semiconductor developed rapidly, there is an increasing need in precise pitch standards to calibrate the structure of devices at nanoscale. Nano-gratings fabricated by atom lithography are unique and suitable to act as precise pitch standard because its pitch distance is directly traceable to a natural constant. As the scaling down of nano-devices, it is very challenging to double the spatial frequency of nano-grating while keeping the self-traceability in atom lithography. Methods: In this study, the switching-detuning light mask is utilized for Cr atom lithography. During a single deposition process, the standing wave frequency is switching from positive detuning to negative detuning alternatively. Results: Nano-gratings fabricated using switching-detuning light mask is successfully replicated with double spatial frequency and self-traceability. Non-uniformity between neighboring Cr lines shows up with a corrected pitch of 107.15 Conclusion: Non-uniformity is mainly caused by the dipole force discrepancy between positive and negative detuning light mask. Therefore, to increase the high uniformity of nano-gratings, the deposition time of negative detuning should be at least twice as the positive detuning. On the other hand, to reduce the pitch uncertainty, it is necessary to reduce the distance between the atom beam and reflection mirror as close as possible. These two significant optimization designs are promising to increase the spatial frequency doubling performance with high uniformity and accuracy.

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