The averaged intensity distribution of the diffraction spectrum of light transmitted by a superimposed ultrasonic wave and diffuser is investigated in the far field. The diffuser plate makes each spectral component broaden owing to its random nature. The intensity at an observation plane is represented as a summation of each component of the diffraction spectrum. A measure to distinguish the zeroth-order spectral component from the first-order component is given under the assumption that the diffuser obeys Gaussian statistics. It is suggested theoretically and experimentally that the roughness parameter of the diffuser can be obtained from the measurement of the ratio between the peak intensities of the zeroth- and first-order spectra. The advantage of using an ultrasonic wave is that its wavelength can be utilized as a marker for the determination of the roughness parameter.
© 1979 Optical Society of America
Yoshihiro Ohtsuka and Yoh Imai, "Diffraction spectrum of light transmitted by a superimposed ultrasonic wave and diffuser," J. Opt. Soc. Am. 69, 963-968 (1979)