Laser-protective technologies and their impact on low-light level visual performance

摘要

Abstract: Laser eye protection (fixed wavelength) can be grouped into three broad categories: adsorptive (dyes, phosphate glass), interference (dielectric, holographic and rugate), or hybrid (i.e., absorptive and interference, interference and interference, etc.). The approaches differ markedly in design complexity, cost, and their impact on visual performance. The challenge is to achieve a balance between complexity and cost while minimizing the impact on visual performance. The data to be discussed are resolution thresholds set by five observers with a corrected or uncorrected acuity of 20/20. The observer modulates the spatial frequency of a sinusoidal grating while grating contrast is fixed at 5, 10, 20, 40 and 80%. The first study quantifies visual performance from low photopic (10 ftL) down through low scotopic light levels (5E-5 ftL). The data show a sharp drop in acuity as ambient light level drops from 1 to .001 ftL (roughly equivalent to a quarter moon). The second study measures visual acuity over the same range of light levels while the observer wears: (1) multi line absorptive laser eye protection, (2) hybrid laser eye protection, and (3) neutral density equivalents. The results demonstrate that once the data is normalized for spectral compatibility and scotopic transmittance there are no significant differences between the filters. A third study assesses the loss in visual performance as scotopic transmittance is reduced from 40 to 30 to 20%. The implications for filter requirements and design will be discussed.!10