A PRELIMINARY STUDY OF THE EFFECTS OF MUTIPLE-PULSE LASER EXPOSURES ON VISUAL THRESHOLDS

Leon McLin

Abstract

PURPOSE. To compare the threshold for a spot target superimposed on an extended laser source for three conditions with the same average power and to evaluate whether reciprocity holds. For pulsed light exposures ranging from 1-150 ms, the total energy of a flash (intensity × duration) determines its brightness or adaptation potential. However, below 1 ms, there are little data supporting this reciprocal relationship of intensity and duration. METHOD. Six subjects completed a method-of-adjustment task to determine the increment threshold for the presence of a 0.23ş white test spot superimposed on a 0.61ş laser beam. A 532 nm laser (Coherent Verdi Nd:VAO4) beam was steered with an acoustic-optical modulator to produce 10-µs pulses and 1 ms pulses at 10-Hz. In addition, the effect of a continuous wave (CW) laser exposure with the same average power was determined. The design was repeated-measures with a single repeated-factor: laser condition.

RESULTS. Increment thresholds measured during 10-µs pulse laser exposures and CW laser exposures were roughly 3 times greater than those measured during 1-ms pulses (p<0.001). Thresholds for 10-µs pulses were statistically equal to thresholds for CW laser exposures. Therefore, somewhat surprisingly, a reciprocal relationship was not demonstrated.

CONCLUSIONS. More pulse-durations and pulse-repetition-frequencies must be studied before generality of reciprocity failure is more fully understood.

Details

Year: 2001

Program Number: Poster 137

Author Affiliation: Air Force Research Laboratory

Co-Authors: Fred Previc, Peter Smith, William Kosnik, Norman Barsalou

Co-Author Affiliation: Logicon/TASC, Logicon/TASC, Logicon/TASC, Jackson Foundation

Room: Exhibit Hall C