scholarly journals Accessing depth-resolved high spatial frequency content from the optical coherence tomography signal

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sergey Alexandrov ◽  
Anand Arangath ◽  
Yi Zhou ◽  
Mary Murphy ◽  
Niamh Duffy ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Spatial Frequency ◽  
Structural Changes ◽  
High Spatial Frequency ◽  
Optical Coherence ◽  
Frequency Content ◽  
Structural Alterations ◽  
Spatial Frequencies ◽  
Internal Structures ◽  
Optical Coherence Tomography Signal

AbstractOptical coherence tomography (OCT) is a rapidly evolving technology with a broad range of applications, including biomedical imaging and diagnosis. Conventional intensity-based OCT provides depth-resolved imaging with a typical resolution and sensitivity to structural alterations of about 5–10 microns. It would be desirable for functional biological imaging to detect smaller features in tissues due to the nature of pathological processes. In this article, we perform the analysis of the spatial frequency content of the OCT signal based on scattering theory. We demonstrate that the OCT signal, even at limited spectral bandwidth, contains information about high spatial frequencies present in the object which relates to the small, sub-wavelength size structures. Experimental single frame imaging of phantoms with well-known sub-micron internal structures confirms the theory. Examples of visualization of the nanoscale structural changes within mesenchymal stem cells (MSC), which are invisible using conventional OCT, are also shown. Presented results provide a theoretical and experimental basis for the extraction of high spatial frequency information to substantially improve the sensitivity of OCT to structural alterations at clinically relevant depths.

scholarly journals Hybrid motion illusions as examples of perceptual conflict

2021 ◽  
Vol 2 ◽  
Author(s):  
Arthur Shapiro
Keyword(s):  
Spatial Frequency ◽  
Spatial Scales ◽  
High Spatial Frequency ◽  
Natural World ◽  
Fine Scale ◽  
Frequency Content ◽  
Coarse Scale ◽  
Trade Offs ◽  
Spatial Frequencies ◽  
Contrast Information

Shapiro and Hedjar (2019) proposed a shift in the definition of illusion, from ‘differences between perception and reality’ to ‘conflicts between possible constructions of reality’. This paper builds on this idea by presenting a series of motion hybrid images that juxtapose fine scale contrast (high spatial frequency content) with coarse scale contrast-generated motion (low spatial frequency content). As is the case for static hybrid images, under normal viewing conditions the fine scale contrast determines the perception of motion hybrid images; however, if the motion hybrid image is blurred or viewed from a distance, the perception is determined by the coarse scale contrast. The fine scale contrast therefore masks the perception of motion (and sometimes depth) produced by the coarser scale contrast. Since the unblurred movies contain both fine and coarse scale contrast information, but the blurred movies contain only coarse scale contrast information, cells in the brain that respond to low spatial frequencies should respond equally to both blurred and unblurred movies. Since people undoubtedly differ in the optics of their eyes and most likely in the neural processes that resolve conflict across scales, the paper suggests that motion hybrid images illustrate trade-offs between spatial scales that are important for understanding individual differences in perceptions of the natural world.

scholarly journals Effects of Spatial Frequency Filtering Choices on the Perception of Filtered Images

Vision ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 29
Author(s):  
Sabrina Perfetto ◽  
John Wilder ◽  
Dirk B. Walther
Keyword(s):  
Spatial Frequency ◽  
Behavioral Outcomes ◽  
High Spatial Frequency ◽  
Frequency Content ◽  
Frequency Filtering ◽  
Image Content ◽  
Specific Choice ◽  
Spatial Frequencies ◽  
Spatial Frequency Filtering ◽  
Frequency Components

The early visual system is composed of spatial frequency-tuned channels that break an image into its individual frequency components. Therefore, researchers commonly filter images for spatial frequencies to arrive at conclusions about the differential importance of high versus and low spatial frequency image content. Here, we show how simple decisions about the filtering of the images, and how they are displayed on the screen, can result in drastically different behavioral outcomes. We show that jointly normalizing the contrast of the stimuli is critical in order to draw accurate conclusions about the influence of the different spatial frequencies, as images of the real world naturally have higher contrast energy at low than high spatial frequencies. Furthermore, the specific choice of filter shape can result in contradictory results about whether high or low spatial frequencies are more useful for understanding image content. Finally, we show that the manner in which the high spatial frequency content is displayed on the screen influences how recognizable an image is. Previous findings that make claims about the visual system’s use of certain spatial frequency bands should be revisited, especially if their methods sections do not make clear what filtering choices were made.

Depth Interpolation with Sparse Disparity Cues

Perception ◽  
1989 ◽  
Vol 18 (1) ◽  
pp. 39-54 ◽  
Author(s):  
Sofia M Würger ◽  
Michael S Landy
Keyword(s):  
Spatial Frequency ◽  
Narrow Band ◽  
High Spatial Frequency ◽  
Linear Interpolation ◽  
Uniform Field ◽  
Frequency Content ◽  
Apparent Contrast ◽  
Spatial Frequencies ◽  
Basic Stimulus ◽  
Filtered Noise

The interpolation of stereoscopic depth given only sparse disparity information was investigated. The basic stimulus was a rectangle with zero disparity at one edge, and 20 or 30 min visual angle disparity at the other. The depth assigned to the ambiguous intervening locations was measured by means of a small briefly-flashed binocular comparison spot. For a stimulus consisting of a uniform rectangle presented on a background of random dots with zero disparity, interpolated depth was greater for a high mean contrast between rectangle and background than for a low mean contrast. Relative to a linear interpolation between the edges, a larger difference in edge disparity resulted in poorer depth interpolation. Depth interpolation based on rivalrous information was examined by filling the stimulus rectangle with narrow-band filtered noise which was uncorrelated between the two eyes. Four different passbands which were matched in apparent contrast were investigated. The results demonstrate that the rivalrous low-spatial-frequency content was resistant to interpolation; rivalrous high spatial frequencies did not interfere with depth interpolation. High-spatial-frequency stimuli yielded a percept similar to the uniform-field condition, whereas low-spatial-frequency stimuli lay in a depth plane near or even behind the background. In the latter case a transparent plane was perceived which was linearly interpolated between the two edges, and which floated above the rivalrous noise.

On the Variety of Percepts Associated with Dichoptic Viewing of Dissimilar Monocular Stimuli

Perception ◽  
1992 ◽  
Vol 21 (1) ◽  
pp. 47-62 ◽  
Author(s):  
Yuede Yang ◽  
David Rose ◽  
Randolph Blake
Keyword(s):  
Spatial Frequency ◽  
High Spatial Frequency ◽  
Frequency Difference ◽  
The Other ◽  
Frequency Content ◽  
High Transparency ◽  
Frequency Information ◽  
Dichoptic Viewing ◽  
Spatial Frequencies ◽  
Over Time

Upon dichoptic viewing of dissimilar patterns, several distinct perceptual states may be experienced over time. One state is exclusive monocular dominance, wherein the view of only one eye is seen in its entirety for some period of time. Another state is characterized by a mosaic-like collage consisting of portions of the view of each eye. Two other states involve simultaneous perception of both monocular images in their entirety. In one of these states, the two monocular stimuli appear to be superimposed without depth (a phenomenon we shall term ‘superimposition’). In the other state, the two monocular stimuli appear to be located at different depth planes (which we shall term ‘transparency’). This paper documents the stimulus conditions favoring these various perceptual states. Exclusive monocular dominance occurs most often when the two eyes view dissimilar patterns with the same spatial-frequency content, particularly when both patterns consist of low spatial frequencies. Superimposition also occurs most often when the two eyes view the same spatial frequencies, but predominantly when those spatial frequencies are high. Transparency is favored when the spatial-frequency difference between the eyes is great, particularly when the view of one eye consists of high spatial-frequency information.

scholarly journals Choroidal vessel density in unilateral hyperopic amblyopia using en-face optical coherence tomography

2020 ◽  
Author(s):  
Syunsuke Araki ◽  
Atsushi Miki ◽  
Katsutoshi Goto ◽  
Tsutomu Yamashita ◽  
Tsuyoshi Yoneda ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Normal Control ◽  
Structural Changes ◽  
Vascular Density ◽  
Optical Coherence ◽  
Swept Source ◽  
3 Dimensional ◽  
Face Images ◽  
En Face ◽  
Normal Controls

Abstract Background Structural changes of the choroid, such as choroidal thickening, have been indicated in amblyopic eyes with hyperopic anisometropia as compared to fellow or healthy eyes. The purpose of the present study was to investigate choroidal vascular density (CVD) in children with unilateral hyperopic amblyopia.Methods This study included 88 eyes of 44 patients with unilateral amblyopia due to hyperopic anisometropia with or without strabismus and 29 eyes of 29 age-matched normal controls. The CVD of Haller's layer was quantified from en-face images constructed by 3-dimensional swept-source optical coherence tomography images flattened relative to Bruch's membrane. The analysis area was a 3×3-mm square of macula after magnification correction. Relationships between CVD and other parameters [best-corrected visual acuity (BCVA), refractive error and subfoveal choroidal thickness (SFCT)] were investigated, and CVDs were compared between amblyopic, fellow, and normal control eyes.Results Mean CVD was 59.11 ± 0.66% in amblyopic eyes, 59.23 ± 0.81% in fellow eyes, and 59.29 ± 0.74% in normal control eyes. CVD showed a significant positive relationship with SFCT (p=0.004), but no relationships with other parameters. No significant differences in CVD were evident among amblyopic, fellow, and normal control eyes after adjusting for SFCT (p=0.502).Conclusions CVD was unrelated to BCVA, and CVD did not differ significantly among amblyopic, fellow and normal control eyes. These results suggest that the local CVD of Haller's layer is unaffected in unilateral hyperopic amblyopic eyes.

Sign in / Sign up

Export Citation Format

Share Document