The Autocorrelation Function of the Speckle Intensity Fluctuation Integrated Spatially by a Detecting Aperture of Finite Size

Note: Simultaneous measurement of transverse speed and axial velocity from a single optical beam

A method is introduced for simultaneously measuring transverse speed and axial velocity using a single optical beam and a standard photon Doppler velocimetry (PDV) sensing architecture. This result is of particular interest given the recent, widespread use of PDV and the fact that optical velocimetry has thus far been limited to measuring motion in one dimension per probe. Further, this result demonstrates that both axial velocity data and transverse speed data (at least qualitative) may be obtained entirely through signal analysis; not requiring hardware modification. This result is immediately relevant to analyses of existing PDV data and to future efforts in high-speed optical velocimetry.

Reproduction of sound from old wax phonograph cylinders using the laser-beam reflection method

A laser-beam reflection method was developed to reproduce the sound from old wax phonograph cylinders. Since this optical method is noncontacting and nondestructive, the sound even from repaired wax cylinders can be reproduced. In principle, the method is based on geometrical optics. However, the reflection phenomenon from the grooves of a wax cylinder does not exactly obey the law of geometrical optics because of the finite width of the illuminating beam. Severe problems concerning the properties of the reproduced sounds were found in developing the optical method; they were solved fairly well from quantitative investigations of the reproduced sound. As a result, the laser-beam reflection method is practical and powerful enough to reproduce the sound from all kinds of old wax cylinder.

Blood flow observed by time-varying laser speckle

The temporal statistics of laser speckle from vascular tissues on skin surface have been measured. Based on a temporal spectral analysis of the speckle signal, a new method of monitoring skin blood flow is proposed.