Oliver J.W.,Air Force Research Lab |
Stolarski D.J.,TASC Incorporated |
Stolarski D.J.,TASC Inc |
Noojin G.D.,TASC Incorporated |
And 10 more authors.
Journal of Biomedical Optics | Year: 2010
A series of experiments are conducted in vivo using Yucatan mini-pigs (Sus scrofa domestica) to determine thermal damage thresholds to the skin from 1940-nm continuous-wave thulium fiber laser irradiation. Experiments employ exposure durations from 10 ms to 10 s and beam diameters of approximately 4.8 to 18 mm. Thermal imagery data provide a time-dependent surface temperature response from the laser. A damage endpoint of minimally visible effect is employed to determine threshold for damage at 1 and 24 h postexposure. Predicted thermal response and damage thresholds are compared with a numerical model of optical-thermal interaction. Results are compared with current exposure limits for laser safety. It is concluded that exposure limits should be based on data representative of large-beam exposures, where effects of radial diffusion are minimized for longer-duration damage thresholds. © 2010 Society of Photo-Optical Instrumentation Engineers.
Foutch B.K.,Air Force Research Lab |
Stringham J.M.,TASC Corporation |
Lakshminarayanan V.,University of Waterloo |
Lakshminarayanan V.,University of Michigan
Journal of Modern Optics | Year: 2011
There are three variables involved in modeling measurement errors - type, severity, and selectivity. Whereas clinicians typically utilize a graphical technique to grade color deficiencies based on D-15 panel tests, Vingrys and King-Smith developed a quantitative scoring technique for panel color tests, which models all three factors by utilizing an overall moment of inertia for color difference vectors (CDVs) calculated in 1976 CIELUV space. We propose a least squares analysis via linear regression of the errors (ΔU, ΔV) according to the following equation: ΔV=mΔU, where m=slope of best-fit line determined by linear regression. Error type is determined by the angular proximity of the best-fit line to known confusion axes representing protan, deutan, tritan or unspecified color defects. The severity is the sum of the CDV lengths of all errors made, and the selectivity is determined by the adjusted variance of the least squares fit. We determined normative threshold values for type, severity and selectivity by inspecting 142 cap arrangements with tentative diagnoses. We then analyzed 49 standard D-15 cap arrangements of subjects with definitive diagnoses to determine the sensitivity and specificity of our method to defect types. The results were then compared with those of Vingrys and King-Smith. Our linear regression technique provides an improved assessment of error arrangements that represent subtle unspecified color defects. However, our model appears too sensitive to atypical repositioning errors made when the majority of errors lie along known confusions. Used in conjunction with previous quantitative methods, linear regression by least squares proves a useful tool in the classification of errors of D-15 color panel tests. © 2011 Copyright Taylor and Francis Group, LLC.