3.2 Holographic Interferometry Using Generation Regime …
229
3.2.2 Holographic Recording of Muscle Stress of Hand
in Radiation of Pulsed Ruby Laser with Double
Monopulse
The study of living objects using holographic methods is impossible in continuous
gas laser radiation due to high mobility of the objects under study. In this case, pulsed
laser gives great possibilities for holographic research of shifts and deformations of
human skin, which makes it possible to record an interferogram in short periods of
time. It also helped to eliminate firm fixing of the object under study.
The two-pulsed holographic interferometry is one of the most effective methods
to obtain information about the dynamics of fast processes, deformations of movable
diffuse objects. The implementation of paired pulse laser sources with the pulse duration of 10–100 ns and the regulated interval between them from 100 to 700 μs enables
to increase significantly the number of tasks solved with the holography methods.
The regulation of the interval of radiation pulse sequence is mostly determined by
the optical shutter used [121–152].
In those cases when accurate synchronization (microsecond unit order) is needed,
step connection of laser Q-code is necessary. In the works [128, 129], stress on the
electrooptical shutter (EOS) of the laser was measured twice to obtain paired pulses of
the laser. Each pulse was generated after corresponding stress release. Approximate
equality of amplitudes of generated laser pulses can be reached through selecting
the step amplitude. Time interval between the steps determines the interval between
the monopulses. The main disadvantage of this method is that the laser resonator
transforms stepwise into supraliminal state, and that is why time of development of
a giant pulse is little (≈100 ns). Besides, highly qualitative sorting elements should
be used in the resonator to obtain sufficient radiation coherence.
One of the most effective ways of generation of giant pulses with identical
monofrequent spectrum and regulated interval of the sequence is the injection of
monofrequent laser with quasi-stationary pulse of millisecond duration generation.
In this case, the pulse transformation interval is determined by the duration of inoculating radiation and naturally by the pump pulse of the driven laser [132, 133,
142–150]. But the technical implementation of this method is rather difficult, and
the laser itself becomes rather cumbersome.
A combined shutter is usually used in the laser to obtain the regime of generation
of paired pulses generation when OES stabilizes the moment of appearance of the
giant pulse, and the antireflective filter provides a narrow generation spectrum. In the
work [133], the control circuit of OES was suggested and investigated, the principle
of operation of which is analogous to that of the combined shutter. In this case,
the scheme of positive electrooptical feedback (PEOF) functions as an antireflective
filter. Thereafter, the inclusion mode providing the effective generation spectrum
narrowing and stabilization of moments of giant pulse appearance are fulfilled with
the same OES. In our case, the combined shutter is used in the laser. The stress is
gradually released from the OES to generate the paired pulses.
The optical scheme of the resonator of the optical laser is presented in Fig. 3.26.
229
3.2.2 Holographic Recording of Muscle Stress of Hand
in Radiation of Pulsed Ruby Laser with Double
Monopulse
The study of living objects using holographic methods is impossible in continuous
gas laser radiation due to high mobility of the objects under study. In this case, pulsed
laser gives great possibilities for holographic research of shifts and deformations of
human skin, which makes it possible to record an interferogram in short periods of
time. It also helped to eliminate firm fixing of the object under study.
The two-pulsed holographic interferometry is one of the most effective methods
to obtain information about the dynamics of fast processes, deformations of movable
diffuse objects. The implementation of paired pulse laser sources with the pulse duration of 10–100 ns and the regulated interval between them from 100 to 700 μs enables
to increase significantly the number of tasks solved with the holography methods.
The regulation of the interval of radiation pulse sequence is mostly determined by
the optical shutter used [121–152].
In those cases when accurate synchronization (microsecond unit order) is needed,
step connection of laser Q-code is necessary. In the works [128, 129], stress on the
electrooptical shutter (EOS) of the laser was measured twice to obtain paired pulses of
the laser. Each pulse was generated after corresponding stress release. Approximate
equality of amplitudes of generated laser pulses can be reached through selecting
the step amplitude. Time interval between the steps determines the interval between
the monopulses. The main disadvantage of this method is that the laser resonator
transforms stepwise into supraliminal state, and that is why time of development of
a giant pulse is little (≈100 ns). Besides, highly qualitative sorting elements should
be used in the resonator to obtain sufficient radiation coherence.
One of the most effective ways of generation of giant pulses with identical
monofrequent spectrum and regulated interval of the sequence is the injection of
monofrequent laser with quasi-stationary pulse of millisecond duration generation.
In this case, the pulse transformation interval is determined by the duration of inoculating radiation and naturally by the pump pulse of the driven laser [132, 133,
142–150]. But the technical implementation of this method is rather difficult, and
the laser itself becomes rather cumbersome.
A combined shutter is usually used in the laser to obtain the regime of generation
of paired pulses generation when OES stabilizes the moment of appearance of the
giant pulse, and the antireflective filter provides a narrow generation spectrum. In the
work [133], the control circuit of OES was suggested and investigated, the principle
of operation of which is analogous to that of the combined shutter. In this case,
the scheme of positive electrooptical feedback (PEOF) functions as an antireflective
filter. Thereafter, the inclusion mode providing the effective generation spectrum
narrowing and stabilization of moments of giant pulse appearance are fulfilled with
the same OES. In our case, the combined shutter is used in the laser. The stress is
gradually released from the OES to generate the paired pulses.
The optical scheme of the resonator of the optical laser is presented in Fig. 3.26.