378
5 Laser Specklometer, Speckle-Optical Diagnostics and Laser …
minimal time of frequency meter). Using it, we can study separate small muscle
areas by measuring velocity of their contraction.
While conducting this study, the dependence of velocity of muscle contraction on
time was studied. The obtained results agree with the calculations of velocities due
to implicit data. Duration of a single contraction is 200–300 ms, and about 40 ms of
them goes to the process of active contraction. Maximal velocity of contraction is
about 3 times higher than the velocity of relaxation, and it is developed during 20–25
ms. The increase of the external load leads to approximately proportional decrease
of contraction velocity. The offered technique can be applied not only for studying
muscle contraction, but for studying the movement of other diffusive objects.
5.2 Study of Deformations of Epithelial Tissues Using
the Speckle-Photography Method
Majority of the data of electromyographic study give the possibility to estimate
functioning of motor units or the whole muscle. Meanwhile, not only study of a local
area, but also the detailed study of a huge surface of a tissue of a living organism
participated in the process of muscle contraction, i.e., deformation fields, is of interest.
Such an approach would give the possibility to obtain additional information about
the activity of the muscle system of an organism along with the data of the already
existing electromyographic methods.
Non-contact methods of speckle-photography exist in coherent optics for determining deformation fields and are successfully used in technical physics. Two images
of the object in the initial and the excited states are registered on a photomaterial
for determining transverse shifts. The images are covered with a spotted structure
or speckles in coherent laser light. They obtained in such a way photography or
specklogram is enough to determine the shift field. A posterior processing in the
system of coherent information processing using spatial filtering gives the possibility to determine the areas of equal shifts or to determine shift at each point of the
object [31].
A leg of a frog was used as a research object, in which contraction is characterized by very heterogeneous deformations. Preliminary test has shown that the
exposure time must not exceed 1 ms. He–Ne laser usually used in such tests is not
so powerful to provide registration of the speckle-pattern on films with a resolution
of 100 lines/mm and higher in such a period of time. That is why a pulsed He–Ne
laser was constructed as a radiation source with energy in free-running mode up to
0.8 J. The radiation expanded with a telescopic system was directed onto the object,
which was photographed with a standard photocamera “Zenit” with magnification
close to unit. Laser radiation was synchronized with the excitation of the object.
The first exposure was conducted when the tissue rested, then it was stimulated,
and the pulse delayed relative to the stimulating pulse launched the laser for the
second time (time of delay is 10:200 ms). After such a twofold exposure, the photofilm
5 Laser Specklometer, Speckle-Optical Diagnostics and Laser …
minimal time of frequency meter). Using it, we can study separate small muscle
areas by measuring velocity of their contraction.
While conducting this study, the dependence of velocity of muscle contraction on
time was studied. The obtained results agree with the calculations of velocities due
to implicit data. Duration of a single contraction is 200–300 ms, and about 40 ms of
them goes to the process of active contraction. Maximal velocity of contraction is
about 3 times higher than the velocity of relaxation, and it is developed during 20–25
ms. The increase of the external load leads to approximately proportional decrease
of contraction velocity. The offered technique can be applied not only for studying
muscle contraction, but for studying the movement of other diffusive objects.
5.2 Study of Deformations of Epithelial Tissues Using
the Speckle-Photography Method
Majority of the data of electromyographic study give the possibility to estimate
functioning of motor units or the whole muscle. Meanwhile, not only study of a local
area, but also the detailed study of a huge surface of a tissue of a living organism
participated in the process of muscle contraction, i.e., deformation fields, is of interest.
Such an approach would give the possibility to obtain additional information about
the activity of the muscle system of an organism along with the data of the already
existing electromyographic methods.
Non-contact methods of speckle-photography exist in coherent optics for determining deformation fields and are successfully used in technical physics. Two images
of the object in the initial and the excited states are registered on a photomaterial
for determining transverse shifts. The images are covered with a spotted structure
or speckles in coherent laser light. They obtained in such a way photography or
specklogram is enough to determine the shift field. A posterior processing in the
system of coherent information processing using spatial filtering gives the possibility to determine the areas of equal shifts or to determine shift at each point of the
object [31].
A leg of a frog was used as a research object, in which contraction is characterized by very heterogeneous deformations. Preliminary test has shown that the
exposure time must not exceed 1 ms. He–Ne laser usually used in such tests is not
so powerful to provide registration of the speckle-pattern on films with a resolution
of 100 lines/mm and higher in such a period of time. That is why a pulsed He–Ne
laser was constructed as a radiation source with energy in free-running mode up to
0.8 J. The radiation expanded with a telescopic system was directed onto the object,
which was photographed with a standard photocamera “Zenit” with magnification
close to unit. Laser radiation was synchronized with the excitation of the object.
The first exposure was conducted when the tissue rested, then it was stimulated,
and the pulse delayed relative to the stimulating pulse launched the laser for the
second time (time of delay is 10:200 ms). After such a twofold exposure, the photofilm