Go to the NASA Homepage
 
Search >
Click to Search
Human Systems Integration Division homepageHuman Systems Integration Division homepage Organization pageOrganization page Technical Areas pageTechnical Areas page Outreach and Publications pageOutreach and Publications page Contact pageContact page
Human Systems Integration Division Homepage
Outreach & Publications Sidebar Header
Go to the Outreach & Publications pageGo to the Outreach & Publications page
Go to Awards pageGo to Awards page
Go to News pageGo to News page
Go to Factsheets pageGo to Factsheets page
Go to Multimedia pageGo to Multimedia page
Go to Human Factors 101 pageGo to Human Factors 101 page
What is Human System Integration? Website
Publication Header
Visual Sensitivity To Spatially Sampled Modulation In Human Observers  (1991)
Abstract Header
Thresholds were measured for detecting spatial luminance modulation in regular lattices of visually discrete dots. Thresholds for modulation of a lattice are generally higher than the corresponding threshold for modulation of a continuous field, and the size of the threshold elevation, which depends on the spacing of the lattice elements, can be as large as a one log unit. The largest threshold elevations are seen when the sample spacing is 12 minutes of arc or greater. These results are similar to those observed by Burr et al.
(1985) [Vision Res. 25, 717-727], who proposed an explanation based on a compressive point non-linearity. Although their explanation is not consistent with the present data, the results may be explained in terms of nonlinear saturation of a spatially opponent stage early in the visual pathway. Theories based on response compression cannot explain the further observation that the threshold elevations due to spatial sampling are also dependent on modulation frequency: the greatest elevations occur with higher modulation frequencies. The idea that this is due to masking of the modulation frequency by the spatial frequencies in the sampling lattice is considered.
Private Investigators Header
Authors Header
Groups Header
Keywords Header
Human, Modulation, Observers, Sampled, Sensitivity, Spatially, Visual
References Header
Vision Res., 31, 895-905.
Download Header
Adobe PDF Icon  Mulligan_samp300.pdf (Download Acrobat Reader Click to download Adobe Acrabat Reader)
  (797KB) (application/pdf)
Go to the First Gov Homepage
Go to the NASA - National Aeronautics and Space Administration Homepage
Curator: Phil So
NASA Official: Alonso Vera
Last Updated: August 15, 2019