The Effects of Scattered Light from Optical Components on Visual Function
Technical Report,12 Nov 2013,31 Jan 2016
Engility Corporation JBSA Fort Sam Houston United States
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Contrast acuity and contrast sensitivity were measured in twelve subjects without and with eight different optical materials OM positioned in front of their right eye. The measurements were taken without and with light from a glare source present. The OM consisted of four haze standards with percent haze H between approximately 1 and 20 and four reflective LEP with percent haze between 1 and 5. In addition to H, clarity, light scatter log s at scatter angles between 7-10 deg and the amount of scatter at angles from 1-70 deg bi-directional transmission distribution function or BTDF were measured. The scatter metrics, H, log s, and cumulative scatter beyond specific angles from the BTDF were plotted against changes in contrast acuity and contrast sensitivity between no OM baseline and OM viewing conditions with and without glare, which included measured change in visual performance between the Glare and No Glare conditions for each OM. The general effect of glare was to reduce acuity and contrast sensitivity. For the haze standards, H was an excellent predictor of the performance declines with glare. For the LEP, H was determined not a good predictor, where scatter metrics derived from the BTDF were found to be the best predictors of the performance losses with glare. The latter finding suggests measurement of the BTDF of reflective LEP provides important information about scatter effects on visual function that the traditional scatter measure of haze does not perform to provide an accurate metric.