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5 Laser Specklometer, Speckle-Optical Diagnostics and Laser …
today. Recently, the speckle-optical methods for measurement of real-time velocities
and shifts have been developed intensively. This is determined by the combination of
traditional organization of optical methods such as contactlessness, remoteness, high
accuracy with the possibility of determination of movement parameters and coordinates of the object, which scatter the light significantly. If the object is stationary,
then the observed speckle-structure is stationary too. The speckle-image detects
pulsations of light spots (speckles) intensity, so called boiling, during oscillations of
the object as a whole or during time alterations of its microrelief. As dynamics of
these processes is connected with dynamics of the object, then certain judgments can
be made about the character of movement or about alteration of the rough surface
itself while studying frequency characteristics of intensity fluctuations in observation plane. If skin is considered as a rough surface, which suffers applied shock of
muscle contractions, sanguimotions, etc., then abnormalities can be detected in the
processes mentioned above according to features of intensity fluctuation spectra and
can be connected with certain diseases.
The development of this direction is undoubtedly connected with studying nature
and statistical characteristics of speckle-fields, which were investigated by a number
of authors [2–8]. But this question was considered in detail only for the case
when light is scattered on one surface. Along with this, in experimental practices,
especially in the medical–biological one there are cases when light has to pass
through one more scattering medium before the object or after it. The question of
twice scattered radiation application in speckle-optics and in particular in speckleinterferometry requires more detailed studying. Consideration of statistical characteristics of dynamic speckles formed twice by scattered light is of theoretical interest
as the field amplitude will have non-Gaussian statistics in this case.
During illumination of multilayer-structured skin, a dynamic speckle-structure is
formed as a result of a coherent composition of many elementary waves scattered
on moving particles, which are cells of dermis, epidermis, etc., which form fetal
integument and blood cells, primarily erythrocytes.
For simple macroscopic homogenous systems, modeling of coherent dispersion
has shown that average velocity of particle movement is proportional to fluctuation
frequency [9]. But adequate models, which describe light dispersion from complex
systems such as biological tissues in vivo [10, 11], have not been created yet.
In biological experiments while using speckle-optics, continuous mobility of
objects under consideration must be mentioned, in particular, possible alteration of
their microstructure that leads to speckle decorrelation. When speckle-interferometry
is to be used, then a practical test of method independence is needed in every particular case. Useful information about the process dynamics can also be obtained during
time-changing speckle-fields, which are of great interest today.
The distinctive feature of the study of many medical–biological preparations is
their small sizes, and that requires the application of magnifying optics. Besides,
being an integral part of many speckle methods, the optical system plays an important
role in forming of speckle-fields and speckle-interferograms. Though its impact on
contrast, size of speckles, etc., was studied in a number of works, questions such as
5 Laser Specklometer, Speckle-Optical Diagnostics and Laser …
today. Recently, the speckle-optical methods for measurement of real-time velocities
and shifts have been developed intensively. This is determined by the combination of
traditional organization of optical methods such as contactlessness, remoteness, high
accuracy with the possibility of determination of movement parameters and coordinates of the object, which scatter the light significantly. If the object is stationary,
then the observed speckle-structure is stationary too. The speckle-image detects
pulsations of light spots (speckles) intensity, so called boiling, during oscillations of
the object as a whole or during time alterations of its microrelief. As dynamics of
these processes is connected with dynamics of the object, then certain judgments can
be made about the character of movement or about alteration of the rough surface
itself while studying frequency characteristics of intensity fluctuations in observation plane. If skin is considered as a rough surface, which suffers applied shock of
muscle contractions, sanguimotions, etc., then abnormalities can be detected in the
processes mentioned above according to features of intensity fluctuation spectra and
can be connected with certain diseases.
The development of this direction is undoubtedly connected with studying nature
and statistical characteristics of speckle-fields, which were investigated by a number
of authors [2–8]. But this question was considered in detail only for the case
when light is scattered on one surface. Along with this, in experimental practices,
especially in the medical–biological one there are cases when light has to pass
through one more scattering medium before the object or after it. The question of
twice scattered radiation application in speckle-optics and in particular in speckleinterferometry requires more detailed studying. Consideration of statistical characteristics of dynamic speckles formed twice by scattered light is of theoretical interest
as the field amplitude will have non-Gaussian statistics in this case.
During illumination of multilayer-structured skin, a dynamic speckle-structure is
formed as a result of a coherent composition of many elementary waves scattered
on moving particles, which are cells of dermis, epidermis, etc., which form fetal
integument and blood cells, primarily erythrocytes.
For simple macroscopic homogenous systems, modeling of coherent dispersion
has shown that average velocity of particle movement is proportional to fluctuation
frequency [9]. But adequate models, which describe light dispersion from complex
systems such as biological tissues in vivo [10, 11], have not been created yet.
In biological experiments while using speckle-optics, continuous mobility of
objects under consideration must be mentioned, in particular, possible alteration of
their microstructure that leads to speckle decorrelation. When speckle-interferometry
is to be used, then a practical test of method independence is needed in every particular case. Useful information about the process dynamics can also be obtained during
time-changing speckle-fields, which are of great interest today.
The distinctive feature of the study of many medical–biological preparations is
their small sizes, and that requires the application of magnifying optics. Besides,
being an integral part of many speckle methods, the optical system plays an important
role in forming of speckle-fields and speckle-interferograms. Though its impact on
contrast, size of speckles, etc., was studied in a number of works, questions such as