Transmission of a Gaussian scanning beam through circular, square, and slit apertures: Part II. Experimental results for transmission through a circular aperture.

To perform an analysis of the hazards associated with scanned laser radiation to determine compliance with either federal or user standards, it is usually necessary to determine the amount of energy entering a specified aperture. A mathematical model has recently been developed that may simplify the hazard analysis. Experimental data and the mathematical model were compared for stationary and scanning Gaussian laser beams transmitted through a stationary 7-mm-diameter circular aperture, representing the dilated pupil of the human eye. Data were obtained for three values of laser beam diameter. The data and the mathematical model were found to agree within the estimated experimental error when the laser beam was concentric with the aperture, the situation typically encountered in compliance measurements. For two of the three laser beam diameters studied, as the eccentricity of the laser beam with respect to the center of the aperture was increased, the difference between the data and the mathematical model was found to increase. At the higher degrees of eccentricity, the percentage errors were shown to be highly sensitive to the errors in the determination of relative position.