190
3 Holographic Interferometry for Studying …
The ability of the holographic method to preserve and further reconstruct the wave
front recorded by the hologram makes it possible to realize two generation regimes
of dye lasers radiation in the studies of surface reliefs [28, 29, 31].
The holographic relief surface contouring in generation regime of one reconstructed wavelength of dye laser radiation.
During the experiment, it was ascertained that the quality of the hologram recorded
separately in dye laser radiation with the wavelengths of 590, 596.5 and 585 nm
stayed almost the same. In its turn, it made it possible using the double-exposure
method to record two wave fronts with different wavelengths, the interval between
which can be smoothly changed in the limits of 0.01–30 nm on one type of dye,
in radiation of one laser consequently on one hologram. While reconstructing the
wave front according to such a hologram, we will obtain the relief surface contours
according to the work [69]. And as the distance between the neighboring contour
lines is definitely connected with interval between wavelengths used in hologram
recording, then the change of this generation interval from 0.01 to 30 nm leads to the
depth distance change from 1 cm to 6 μm. It is obvious that quick change of the dye
will allow extending the limits of wavelength generation reconstruction and, thus,
increasing the minimal resolution along the depth between the neighboring contour
relief lines. In this case, the possibility of holographic recording will be limited by
the spectral sensitivity of the photomaterial to wavelengths of the radiation recording
the hologram and its resolution. Such a hologram recording has few differences from
recording using the immersion method [93]. The difference is only that in one case in
the interval between the exposures the wavelength changes, and in another one—the
refractive index of liquid or gas. A common disadvantage of both types of recording
is that they are suitable only while studying the relief of static surfaces.
The holographic contouring of surface relief in multi-long-wave converting regime
of dye laser radiation generation [22, 30, 31].
Making holograms of surface relief in colliding beams using multifrequency
regime of 6G rhodamine laser generation was conducted on the set-up, the optical
scheme of which is presented in Fig. 3.1.
As it was shown in Sect. 3.1.1, introduction of 6G-rhodamine laser with laser
pump of Fabry–Perot interferometer, particularly, with the base of 100 μm into the
resonator gave the possibility to obtain simultaneous generation of four wavelengths.
Thus, by changing the free dispersion region of the interferometer the multi-longwave generation regime can be implemented. This regime is especially important
during holographic study of relief of a surface changing in time. In this case, the
width of the lines determines narrowing (definition) of the surface relief contours,
and the interval between the generation lines specifies the distance due to the depth,
which corresponds to the neighboring contour lines. The duration of the generation
pulse regulates the dynamics of fast processes. The most typical surfaces: a sphere, a
cylinder, a wedge and some surface areas of turbine bucket model, were the objects of
the study. The hologram recording was conducted in 6G rhodamine laser radiation,
the generation spectrum of which consisted of four lines splitted by the interval of 1.8
nm. In this case in the plane of the hologram during the exposure, four interference
structures with spatial frequency of about 5000 lines/mm emerge, which appear as
3 Holographic Interferometry for Studying …
The ability of the holographic method to preserve and further reconstruct the wave
front recorded by the hologram makes it possible to realize two generation regimes
of dye lasers radiation in the studies of surface reliefs [28, 29, 31].
The holographic relief surface contouring in generation regime of one reconstructed wavelength of dye laser radiation.
During the experiment, it was ascertained that the quality of the hologram recorded
separately in dye laser radiation with the wavelengths of 590, 596.5 and 585 nm
stayed almost the same. In its turn, it made it possible using the double-exposure
method to record two wave fronts with different wavelengths, the interval between
which can be smoothly changed in the limits of 0.01–30 nm on one type of dye,
in radiation of one laser consequently on one hologram. While reconstructing the
wave front according to such a hologram, we will obtain the relief surface contours
according to the work [69]. And as the distance between the neighboring contour
lines is definitely connected with interval between wavelengths used in hologram
recording, then the change of this generation interval from 0.01 to 30 nm leads to the
depth distance change from 1 cm to 6 μm. It is obvious that quick change of the dye
will allow extending the limits of wavelength generation reconstruction and, thus,
increasing the minimal resolution along the depth between the neighboring contour
relief lines. In this case, the possibility of holographic recording will be limited by
the spectral sensitivity of the photomaterial to wavelengths of the radiation recording
the hologram and its resolution. Such a hologram recording has few differences from
recording using the immersion method [93]. The difference is only that in one case in
the interval between the exposures the wavelength changes, and in another one—the
refractive index of liquid or gas. A common disadvantage of both types of recording
is that they are suitable only while studying the relief of static surfaces.
The holographic contouring of surface relief in multi-long-wave converting regime
of dye laser radiation generation [22, 30, 31].
Making holograms of surface relief in colliding beams using multifrequency
regime of 6G rhodamine laser generation was conducted on the set-up, the optical
scheme of which is presented in Fig. 3.1.
As it was shown in Sect. 3.1.1, introduction of 6G-rhodamine laser with laser
pump of Fabry–Perot interferometer, particularly, with the base of 100 μm into the
resonator gave the possibility to obtain simultaneous generation of four wavelengths.
Thus, by changing the free dispersion region of the interferometer the multi-longwave generation regime can be implemented. This regime is especially important
during holographic study of relief of a surface changing in time. In this case, the
width of the lines determines narrowing (definition) of the surface relief contours,
and the interval between the generation lines specifies the distance due to the depth,
which corresponds to the neighboring contour lines. The duration of the generation
pulse regulates the dynamics of fast processes. The most typical surfaces: a sphere, a
cylinder, a wedge and some surface areas of turbine bucket model, were the objects of
the study. The hologram recording was conducted in 6G rhodamine laser radiation,
the generation spectrum of which consisted of four lines splitted by the interval of 1.8
nm. In this case in the plane of the hologram during the exposure, four interference
structures with spatial frequency of about 5000 lines/mm emerge, which appear as