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D.G. Johnson, J. Beer, R.D. Glickman, F. Hudson; An Interactive Model of Viewer Thresholds Perturbed by Coherent and Incoherent Point Glare Sources . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1223.
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© ARVO (1962-2015); The Authors (2016-present)
It is useful to model aspects of visual performance prior to actual psychophysical experimentation in order to define the most important test parameters. An important application of such modeling is the prediction of disability glare effects from lasers, which are increasingly common in everyday life and can disrupt tasks such as aviation and driving. A unique property of the laser is its coherent emission, which causes the distinctive "laser speckle" effect. The contribution of speckle to glare disability is not well understood, and the present investigation was made to study coherent glare sources, and to account for speckle in a predictive model.
A LabView–based model incorporating the Vos glare function was developed to predict the equivalent background luminance throughout the visual field as a function of the eccentricity, range, and irradiance of a glare source. In addition to the conventional parameters utilized in the Vos function, an additional term, coherence length (L), was incorporated to represent source coherence and thereby serve as a metric of speckle. L is conventionally defined as 2/(nΔ), where is the center wavelength of the source, n is the refractive index of the propagating medium, and Δ is the source’s spectral width
All parameters used in the model, including the coherence of the glare source, can be changed by the user to evaluate their effects on the visual threshold of a simulated grating stimulus. The coherence length of a laser source appears to be an important factor determining glare disability, relative to conventional non–coherent sources.
This interactive model has been used to evaluate the glare disability associated with laser and non–laser sources. It can be applied to hazard evaluations in real world scenarios such as driving, in which the visibility of traffic signs may be obscured by glare. These predictions will be tested against psychophysical experiments with human observers.
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