Study Of Laser Speckle-homogeneity And It's Application On Protective-measurement

Objective: Laser beam is labile to be changed with many reasons result in maldistribution of its energy. But well-distributed laser radiation in practical application is often needed , so it brings how to average the energy of laser beam. The purpose of this study was introduced a method to average the laser energy based on speckle interferometry and evaluate the effect of it to the optical density-measurement of laser goggles.Methods: A pulsed Nd: YAG laser of wavelenth 532nm, repeated frequency of 1 Hz and 5mm of laser beam diameter was used in the experiment. After a single-mode (TEM₀₀) or multimode (TEM₀₂) laser beam was dispersed, added a ground glass-phase plates or spackle-phase shifter in the optical path, measured and analysed the homogenization of laser spot energy at various distance. Then measured goggles-optical density in the same optical path and studied effect of laser speckle-homogeneity on protective-measurement.Result: (1) Ground glass-phase plates can be used in the near-field of strict symmetrical energy because leveling effect of which was better than spackle-phase shifter. And the latter should be used in the far-field. (2) The standard deviation of transmittance was cut down if only we added the homogeneity-equipment in the optical path. Sometimes it can enhance one order of magnitude. (3) Measured value of goggles-optical density was changed regulary when laser beam was dispersed. The degree of stability of measurement was improved and the measured value had a little discrepancy if the homogeneity-equipment was used.