An Optical Apparatus for Very-Small-Angle Light Scattering - Design, Analysis, and Performance

Copyright © 1976, American Telephone and Telegraph Company. Printed in U.S.A. An Optical Apparatus for Very-Small-Angle Light Scattering--Design, Analysis and Performance By J. B. LASTOVKA ( M a n u s c r i p t received A p r i l 4, 1976) We describe an optical apparatus designed and built to extend conventional light-scattering measurements to the very-small-angle regime. The present instrument covers the angular range 0.003° ^ 0 ^ 0.15° with an instrumental resolution ( H W H M ) of 0.00045° (1.6 arc seconds), and exhibits an exceptionally low stray-light background. The theoretical and practical considerations important in achieving this performance are analyzed in detail. Besides its primary purpose of studying long-wavelength (0.01 cm to 1 cm) thermally driven fluctuations, the present type of apparatus should also prove quite useful in other areas where long-wavelength perturbations must be probed, such as, (i) holographic and optical memory imaging, (it) surface roughness testing, and (Hi) index of refraction profiling.