Studies of Resolution in a Bragg Imaging System

This paper presents the results of experiment and theory concerning the resolution capabilities of a Bragg diffracting system which uses a cylindrically convergent laser beam for imaging objects which scatter sound. The derived theory predicts that thin wires, oriented parallel to the convergence line of the light beam and separated by one wire diameter, will just be resolved if the wire diameter is equal to (Λ/2)/sinαm, where Λ is the sound wavelength and αm is the semiangle of the light convergence. For wire orientation at right angles to this direction, the resolution is of quite a different character. The predicted wire diameter is then (Λ/2)/sinθm, where θm is half the angle subtending the light beam in the direction perpendicular to the wire axes. Copper wires as small as 10 sound wavelengths in diameter could be experimentally resolved in our system when the wires were oriented parallel to the convergence line of the light beam. When oriented at right angles, wires as small as 23 of a sound wavelen...