330
4 Speckle-Optical Methods and Devices for Studying …
region, then W = λzπ W 0 and in this case approximation of illumination with a
spherical wave is applicable [16].
In its turn, longitudinal shift of the object under study leads to changes of speckle
sizes x(z) in observation plane due to (4.28).
Dependence of medium speckle sizes x i (z) under longitudinal shift for some
fixed distances R from rotating diffuser to the observation field is presented in Fig. 4.8.
In this figure, the straight line is drawn at level δ = 140 μm and corresponds to the
size of diaphragm of photoelectric sensor in observation field.
The results of the conducted measurements of the amplitudes of the first spectral harmonics A 1 (z) of spectra of intensity fluctuation of dynamic speckle-field for
fixed values R are presented in Fig. 4.9. The change of longitudinal shift can be
determined according to the changes of the amplitude A 1 (z) in the area of monotony
of any dependence represented in Fig. 4.9. A device (Fig. 4.10) was developed for
determining linear longitudinal shifts of the surface.
Fig. 4.8 Dependence of average speckle size x on the longitudinal shift z i for R = const: 1—R
= 30 mm; 2—R = 50 mm; 3—R = 70 mm; 4—R = 100 mm. Reprinted from [2] with permission
Fig. 4.9 Dependence of the amplitude A 1 of the first spectral harmonic at measuring the distance
in the longitudinal direction for fixed R: 1—R = 30 mm; 2—R = 50 mm; 3—R = 70 mm; 4—R =
100 mm. Reprinted from [2] with permission
4 Speckle-Optical Methods and Devices for Studying …
region, then W = λzπ W 0 and in this case approximation of illumination with a
spherical wave is applicable [16].
In its turn, longitudinal shift of the object under study leads to changes of speckle
sizes x(z) in observation plane due to (4.28).
Dependence of medium speckle sizes x i (z) under longitudinal shift for some
fixed distances R from rotating diffuser to the observation field is presented in Fig. 4.8.
In this figure, the straight line is drawn at level δ = 140 μm and corresponds to the
size of diaphragm of photoelectric sensor in observation field.
The results of the conducted measurements of the amplitudes of the first spectral harmonics A 1 (z) of spectra of intensity fluctuation of dynamic speckle-field for
fixed values R are presented in Fig. 4.9. The change of longitudinal shift can be
determined according to the changes of the amplitude A 1 (z) in the area of monotony
of any dependence represented in Fig. 4.9. A device (Fig. 4.10) was developed for
determining linear longitudinal shifts of the surface.
Fig. 4.8 Dependence of average speckle size x on the longitudinal shift z i for R = const: 1—R
= 30 mm; 2—R = 50 mm; 3—R = 70 mm; 4—R = 100 mm. Reprinted from [2] with permission
Fig. 4.9 Dependence of the amplitude A 1 of the first spectral harmonic at measuring the distance
in the longitudinal direction for fixed R: 1—R = 30 mm; 2—R = 50 mm; 3—R = 70 mm; 4—R =
100 mm. Reprinted from [2] with permission