Anisotropy in Oriented-Line-Target Detection at High and Low Luminance Contrast

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 38-38 ◽  
Author(s):  
L M Doherty ◽  
D H Foster
Keyword(s):  
Target Detection ◽  
Line Segment ◽  
Visual Angle ◽  
Detection Threshold ◽  
Luminance Contrast ◽  
High Luminance ◽  
Line Segments ◽  
Low Luminance ◽  
Line Target ◽  
Oriented Line

Observers can detect a uniquely oriented line segment (‘target’) in a background field of uniformly oriented line segments (‘nontargets’) even if viewing time is brief. When the lines have high luminance contrast, the variation of orientation increment threshold with nontarget orientation is periodic, generally with a period of about 90° although smaller periods have been found. Do the orientation-sensitive mechanisms giving rise to periodicities function only at high contrast? This question was addressed in a line-target detection experiment. Twenty white line segments of length 1 deg visual angle were presented in a circular field of diameter 20 deg visual angle. Nontarget orientations were in the range 0°, 5°, …, 175°, and the difference between nontarget and target orientations was varied adaptively. Stimulus displays lasting 40 ms were followed by a blank interstimulus interval lasting 60 ms and then a random-line mask. A view-tunnel provided a grey background of luminance 35 cd m−2 and stimulus contrast was 0.1, 0.3, 0.5, 0.7, or 0.9 log unit above the observer's luminance detection threshold for one line segment. When contrast was 0.1 log unit above this threshold, performance was near chance level. As contrast increased from 0.3 to 0.9 log unit above luminance detection threshold, performance improved and orientation increment thresholds decreased, showing that early orientation-processing is most effective at high luminance contrast. Nonetheless, periodicities were found in all conditions where performance was better than chance which suggests that the orientation-sensitive mechanisms associated with periodicities operate at both high and low luminance contrast.

Resolution of binocular rivalry: Perceptual misbinding of color

2006 ◽  
Vol 23 (3-4) ◽  
pp. 561-566 ◽  
Author(s):  
SANG WOOK HONG ◽  
STEVEN K. SHEVELL
Keyword(s):  
Binocular Rivalry ◽  
Luminance Contrast ◽  
Binding Problem ◽  
High Luminance ◽  
Binding Process ◽  
Neural Representations ◽  
Low Luminance ◽  
Neural Binding ◽  
The Right

Is neural binding of color and form required for perception of a unified colored object? Individual cells selectively tuned to both color and orientation are proposed to moot the binding problem. This study reveals perceptual misbinding of color, thereby revealing separate neural representations of color and form followed by a subsequent binding process. Low luminance-contrast, rivalrous chromatic gratings were presented dichoptically. Each grating had alternating chromatic and gray stripes (e.g., red/gray in the left eye, green/gray in the right eye). Observers viewed the two rivalrous, 2 cpd gratings for 1 min. The duration of exclusive visibility was measured for four percepts: left-eye stimulus, right-eye stimulus, fusion of the two colors, or a two-color grating (e.g. a red/green grating). The percept of a two-color grating (misbinding) was observed with Michelson luminance contrast in the grating up to 20%. In general, for a given level of luminance contrast either misbinding (low luminance contrast) or color mixture (high luminance contrast) was observed, but not both of them. The perceived two-color gratings show that two rivalrous chromaticities are both represented neurally when color and form are combined to give a unified percept. “Resolution” of competing chromatic signals from the two eyes is not restricted to color dominance and color mixture. The transition from misbinding to color mixture by increasing luminance contrast shows that luminance edges have an important role in correct localization of color.

scholarly journals Different latencies of edge detection cause the fluttering-heart illusion

2021 ◽  
Author(s):  
Masahiro Suzuki ◽  
Kazuhisa Yanaka
Keyword(s):  
Edge Detection ◽  
Luminance Contrast ◽  
Second Order ◽  
High Luminance ◽  
First Order ◽  
Low Luminance

AbstractWe studied the mechanism causing the fluttering-heart illusion in which the motion of an inner figure appears unsynchronized compared with that of the outer figure surrounding it although the motion of both figures is objectively synchronized in reality. Experiment 1 examined the effect of edges’ luminance contrasts. The illusion was measured under conditions where the luminance contrasts of the outer and inner figures’ edges were varied. The results indicated that the illusion occurred when the outer figure’s edge had a high luminance contrast and the inner figure’s edge had a low luminance contrast and that the illusion was reversed when the outer figure’s edge had a low luminance contrast and the inner figure’s edge had a high luminance contrast. Experiment 2 examined the effect of the first- and second-order edges. The illusion was measured under conditions where the first- and second-order edges coexisted or only the first-order edges existed. The results indicated that the illusion occurred when the outer figure had the first-order edge and the inner figure had the second-order edge, and that the illusion was reversed when the outer figure had the second-order edge and the inner figure had the first-order edge. These findings supported the hypothesis that the different latencies of edge detection cause the fluttering-heart illusion.

Effect of Luminance Contrast on the Motion Aftereffect

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 191-191
Author(s):  
M Ishihara
Keyword(s):  
Spatial Frequency ◽  
Motion Aftereffect ◽  
Luminance Contrast ◽  
Sinusoidal Grating ◽  
Channel Activity ◽  
High Luminance ◽  
Frequency Condition ◽  
Parvocellular Pathway ◽  
Low Luminance ◽  
Transient Channel

The effects of luminance contrast and spatial frequency in the transient channel were investigated by making use of the motion aftereffect (MAE) caused by adaptation to a drifting sinusoidal grating. Two experiments were performed. The PSE of the velocity was measured as an index of the MAE. The adapting grating was made to drift at a velocity of 2.28 deg s−1 and its spatial frequency was 0.8, 1.6, or 3.2 cycles deg−1. In the first experiment, the MAE caused by a luminance contrast grating or an equiluminous chromatic grating was measured. In the second experiment, luminance contrast gratings were used to measure the effect of the contrast differences between adapting and test gratings. The largest MAE was observed when a low-luminance-contrast grating or an equiluminous chromatic grating was presented as test stimulus after adaptation to a high-luminance-contrast grating in the low-spatial-frequency condition. Generally, the MAE increased with increasing adapting contrast and with decreasing test contrast or spatial frequency. Little MAE was observed at high test contrasts. The results may be explained by assuming that activity in the sustained channel (or parvocellular pathway) inhibits activity in the transient channel (or magnocellular pathway) owing to the domination of sustained channel activity when the test is a static high-luminance-contrast grating providing much information about position and form.

Less is more: Simple stimuli provoke more variable search strategies.

2020 ◽  
Author(s):  
Anna Nowakowska ◽  
Alasdair D F Clarke ◽  
Jessica Christie ◽  
Josephine Reuther ◽  
Amelia R. Hunt
Keyword(s):  
Line Segment ◽  
Search Strategies ◽  
Complex Objects ◽  
Search Behaviour ◽  
Line Segments ◽  
Surface Level ◽  
Efficient Search ◽  
Less Is More ◽  
Dramatic Shift

We measured the efficiency of 30 participants as they searched through simple line segment stimuli and through a set of complex icons. We observed a dramatic shift from highly variable, and mostly inefficient, strategies with the line segments, to uniformly efficient search behaviour with the icons. These results demonstrate that changing what may initially appear to be irrelevant, surface-level details of the task can lead to large changes in measured behaviour, and that visual primitives are not always representative of more complex objects.

Explanation for Neon Color Effect in Achromatic Line Segments on Chromatic Inducers Based on the Multiple Interpretation Hypothesis

2005 ◽  
Vol 101 (1) ◽  
pp. 267-282
Author(s):  
Seiyu Sohmiya
Keyword(s):  
Visual System ◽  
Line Segment ◽  
Color Contrast ◽  
Achromatic Color ◽  
Line Segments ◽  
Color Effect ◽  
Complementary Color ◽  
Multiple Interpretation ◽  
Color Induction ◽  
Simultaneous Color Contrast

In van Tuijl's neon configurations, an achromatic line segment on a blue inducer produces yellowish illusory color in the illusory area. This illusion has been explained based on the idea of the complementary color induced by the blue inducer. However, it is proposed here that this illusion can be also explained by introducing the assumption that the visual system unconsciously interprets an achromatic color as information that is constituted by transparent and nontransparent colors. If this explanation is correct, not only this illusion, but also the simultaneous color contrast illusion can be explained without using the idea of the complementary color induction.

ALPHA-REGULAR STICK UNKNOTS

2012 ◽  
Vol 21 (06) ◽  
pp. 1250059 ◽  
Author(s):  
CHRISTOPHER FRAYER ◽  
CHRISTOPHER SCHAFHAUSER
Keyword(s):  
Line Segment ◽  
Line Segments

Suppose Pn is a regular n-gon in ℝ2. An embedding f : Pn ↪ ℝ3 is called an α-regular stick knot provided the image of each side of Pn under f is a line segment of length 1 and any two consecutive line segments meet at an angle of α. The main result of this paper proves the existence of α-regular stick unknots for odd n ≥ 7 with α in the range [Formula: see text]. All knots constructed will have trivial knot type, and we will show that any non-trivial α-regular stick knot must have [Formula: see text].

A Duplicate Chinese Document Image Retrieval System Based on Line Segment Feature in Character Image Block

2011 ◽  
pp. 14-23
Author(s):  
Yung-Kuan Chan ◽  
Tung-Shou Chen ◽  
Yu-An Ho
Keyword(s):  
Image Retrieval ◽  
Line Segment ◽  
Document Image ◽  
Experimental Results ◽  
Document Images ◽  
Rapid Progress ◽  
Image Block ◽  
Line Segments ◽  
Image Retrieval System ◽  
On Line

With the rapid progress of digital image technology, the management of duplicate document images is also emphasized widely. As a result, this paper suggests a duplicate Chinese document image retrieval (DCDIR) system, which uses the ratio of the number of black pixels to that of white pixels on the scanned line segments in a character image block as the feature of the character image block. Experimental results indicate that the system can indeed effectively and quickly retrieve the desired duplicate Chinese document image from a database.

scholarly journals Offshore Platform Extraction Using RadarSat-2 SAR Imagery: A Two-Parameter CFAR Method Based on Maximum Entropy

Entropy ◽  
2019 ◽  
Vol 21 (6) ◽  
pp. 556 ◽  
Author(s):  
Qi Wang ◽  
Jing Zhang ◽  
Fenzhen Su
Keyword(s):  
False Alarm ◽  
Maximum Entropy ◽  
Target Detection ◽  
Detection Threshold ◽  
River Estuary ◽  
Offshore Platform ◽  
Accuracy Evaluation ◽  
Oil And Gas Development ◽  
Offshore Oil ◽  
Two Parameter

The ability to determine the number and location of offshore platforms is of great significance for offshore oil spill monitoring and offshore oil and gas development. Considering the problem that the detection threshold parameters of the two-parameter constant false alarm rate (CFAR) algorithm require manual and repeated adjustment of the during the extraction of offshore platform targets, this paper proposes a two-parameter CFAR target detection method based on maximum entropy based on information entropy theory. First, a series of threshold parameters are obtained using the two-parameter CFAR algorithm for target detection. Then, according to the maximum entropy principle, the optimal threshold is estimated to obtain the target detection results of the possible offshore platform. Finally, the neighborhood analysis method is used to eliminate false alarm targets such as ships, and the final target of the offshore platform is obtained. In this study, we conducted offshore platform extraction experiments and an accuracy evaluation using data from the Pearl River Estuary Basin of the South China Sea. The results show that the proposed method for platform extraction achieves an accuracy rate of 97.5% and obtains the ideal offshore platform distribution information. Thus, the proposed method can objectively obtain the optimal target detection threshold parameters, greatly reduce the influence of subjective parameter setting on the extraction results during the target detection process and effectively extract offshore platform targets.

Subjective and pupil responses to discomfort glare from small, high-luminance light sources

2018 ◽  
Vol 51 (4) ◽  
pp. 592-611 ◽  
Author(s):  
Y Tyukhova ◽  
CE Waters
Keyword(s):  
Pupil Size ◽  
Rating Scale ◽  
Light Sources ◽  
Background Luminance ◽  
High Luminance ◽  
Low Luminance ◽  
Point Rating Scale ◽  
Main Effect ◽  
Discomfort Glare ◽  
Relative Change

This study examined human subjective and pupil responses to small, high-luminance light sources seen against low-luminance backgrounds. Subjective judgements of glare using a seven-point rating scale and the change in pupil diameters following exposure to glare of 47 subjects were measured during evaluation of 36 conditions comprising three glare source luminances (20,000; 205,000; 750,000 cd/m2), two source positions (0°, 10°), two source sizes (10−5, 10−4 sr) and three background luminances (0.03; 0.3; 1 cd/m2). Data analysis suggests that the relative pupil size is correlated with subjective responses to discomfort glare to some extent (r = 0.659). Analysis of variance of relative pupil size measurements demonstrates a significant main effect of the background luminance suggesting that when the background luminance decreases, the relative pupil size increases. Relative pupil size shows the same trend as the relative change in illuminance at the eyes and the discomfort glare perception.

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