326
4 Speckle-Optical Methods and Devices for Studying …
Fig. 4.3 Experimental scheme for the study of intensity fluctuations spectra of dynamic specklefield during longitudinal shift of the diffuser and alteration of conditions of observation and
illumination. Reprinted from [2] with permission
lens with the focal distance f = 4.5 cm and the width of waist W 0 = 20 μm at a set
divergence degree.
Rotation of the disk led to the change of the speckle-field formed by coherent
radiation from this diffuser. There were performed registration and transformation
of intensity fluctuations of dynamic speckle-field into electrical signal through a field
diaphragm using PMT 79 (photomultiplier tube) at a distance R from the diffuser.
Then the electrical signal was processed with the spectrum analyzer SK4-72.
1. Changes of the distance between the diffuser and the photoreceiver zi = const.
The distance between the illuminator and the rotating diffusely transmitting disk is
registered, and longitudinal shift of the object under study is made as a result of
changes of distance R. The photoreceiver is fixed to the shifted object. In this case,
decorrelation velocity and changes of spectral harmonics value are conditioned by
the growth of sizes of speckles according to
x i (R) =
λR
π W (z i )
for different values z i , such as z i = 60, 120, 180, 240 μm, and growth of values of
diffraction parameter σ (R) calculated from (4.22).
The change of the amplitudes of the first spectral harmonics A 1 (R) of intensity
fluctuation spectra of dynamic speckle-field at fixed values z i is presented in Fig. 4.4.
4 Speckle-Optical Methods and Devices for Studying …
Fig. 4.3 Experimental scheme for the study of intensity fluctuations spectra of dynamic specklefield during longitudinal shift of the diffuser and alteration of conditions of observation and
illumination. Reprinted from [2] with permission
lens with the focal distance f = 4.5 cm and the width of waist W 0 = 20 μm at a set
divergence degree.
Rotation of the disk led to the change of the speckle-field formed by coherent
radiation from this diffuser. There were performed registration and transformation
of intensity fluctuations of dynamic speckle-field into electrical signal through a field
diaphragm using PMT 79 (photomultiplier tube) at a distance R from the diffuser.
Then the electrical signal was processed with the spectrum analyzer SK4-72.
1. Changes of the distance between the diffuser and the photoreceiver zi = const.
The distance between the illuminator and the rotating diffusely transmitting disk is
registered, and longitudinal shift of the object under study is made as a result of
changes of distance R. The photoreceiver is fixed to the shifted object. In this case,
decorrelation velocity and changes of spectral harmonics value are conditioned by
the growth of sizes of speckles according to
x i (R) =
λR
π W (z i )
for different values z i , such as z i = 60, 120, 180, 240 μm, and growth of values of
diffraction parameter σ (R) calculated from (4.22).
The change of the amplitudes of the first spectral harmonics A 1 (R) of intensity
fluctuation spectra of dynamic speckle-field at fixed values z i is presented in Fig. 4.4.