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3 Holographic Interferometry for Studying …
3.3.9 Recording on Photothermoplastic Carriers
The principle of operation of the laser-holographic complex is presented in
Sect. 3.3.2. The registering medium should satisfy hologram recording and meet
the following requirements:
1. provide recording of high-quality holograms with a low signal-noise coefficient
and high contrast that is necessary for further automatic data processing;
2. this hologram shout come back to the place of the image at the interferometry
accuracy;
3. the registering materials should give static repetition at least within the limits of
one series.
Photothermoplastic (PTP) carriers are relatively new registering material, which
allows recording holograms and interferograms with processing intervals of 2–3 s.
And they do not need “wet” processing that is typical for argentiferous materials.
We will remind how the PTP-material works. Before the exposure the PTP-material
is sensitized giving a high voltage of about 5–15 kV on corona-forming electrode
located before the PTP-layer. As a result of ionization, the PTP-layer is discharged.
During the exposure, the PTP-layer is discharged under the light depending on the
illumination.
In order to develop a latent image, it is necessary to warm up the thermoplastic to
the fluid state when the surface deformation of the thermoplastic layer occurs under
electrostatic forces, which is determined by the charge remained on it. To fix the
image, it is enough to cool the PTP-layer 5–10 °C. If the PTP-layer is warmed up
to the temperature, which is higher than the fluidity temperature, the surface relief
will become even and the image will be erased. There are PTP-materials on solid
transparent substrate (quartz, glass) or on Mylar. The glass PTP endures up to hundred
recording-erasing cycles, but with some quality losses. Both film- and matrix PTP
are processed in the place of exposure, and that is why the problem of hologram
return with interference accuracy is absent. In the experiments matrix, PTP-material
on glass support was used.
The possibility of hologram and interferogram registration with the pulse laser
was tested on a photothermoplastic carrier as well as on high-resolution photoplates.
In the last case, the hologram size can be rather large—30 × 40 cm
2 . Due to this fact,
it is possible to observe from three directions, and to determine the space shift vector,
in this case, a system of (3.62) is composed and solved. It is advisable to use spherical
reference waves for recording and reconstruction of such a hologram. To fulfill this,
microdiaphragm lenses should be used instead of the telescopic systems 12, 13. It
is possible to use one objective, through which both reference and reconstructing
beams will pass under a small angle.
The holograms were recorded in convergent beams in carrier frequency of about
1000 lines/mm that corresponded to the angle between the reference and the object
beams of about 40°. The monopulse laser energy was 0.5 J. The pulse duration
was 40 ns, and the pulse interval was 400 μs. During the study, the holographic
3 Holographic Interferometry for Studying …
3.3.9 Recording on Photothermoplastic Carriers
The principle of operation of the laser-holographic complex is presented in
Sect. 3.3.2. The registering medium should satisfy hologram recording and meet
the following requirements:
1. provide recording of high-quality holograms with a low signal-noise coefficient
and high contrast that is necessary for further automatic data processing;
2. this hologram shout come back to the place of the image at the interferometry
accuracy;
3. the registering materials should give static repetition at least within the limits of
one series.
Photothermoplastic (PTP) carriers are relatively new registering material, which
allows recording holograms and interferograms with processing intervals of 2–3 s.
And they do not need “wet” processing that is typical for argentiferous materials.
We will remind how the PTP-material works. Before the exposure the PTP-material
is sensitized giving a high voltage of about 5–15 kV on corona-forming electrode
located before the PTP-layer. As a result of ionization, the PTP-layer is discharged.
During the exposure, the PTP-layer is discharged under the light depending on the
illumination.
In order to develop a latent image, it is necessary to warm up the thermoplastic to
the fluid state when the surface deformation of the thermoplastic layer occurs under
electrostatic forces, which is determined by the charge remained on it. To fix the
image, it is enough to cool the PTP-layer 5–10 °C. If the PTP-layer is warmed up
to the temperature, which is higher than the fluidity temperature, the surface relief
will become even and the image will be erased. There are PTP-materials on solid
transparent substrate (quartz, glass) or on Mylar. The glass PTP endures up to hundred
recording-erasing cycles, but with some quality losses. Both film- and matrix PTP
are processed in the place of exposure, and that is why the problem of hologram
return with interference accuracy is absent. In the experiments matrix, PTP-material
on glass support was used.
The possibility of hologram and interferogram registration with the pulse laser
was tested on a photothermoplastic carrier as well as on high-resolution photoplates.
In the last case, the hologram size can be rather large—30 × 40 cm
2 . Due to this fact,
it is possible to observe from three directions, and to determine the space shift vector,
in this case, a system of (3.62) is composed and solved. It is advisable to use spherical
reference waves for recording and reconstruction of such a hologram. To fulfill this,
microdiaphragm lenses should be used instead of the telescopic systems 12, 13. It
is possible to use one objective, through which both reference and reconstructing
beams will pass under a small angle.
The holograms were recorded in convergent beams in carrier frequency of about
1000 lines/mm that corresponded to the angle between the reference and the object
beams of about 40°. The monopulse laser energy was 0.5 J. The pulse duration
was 40 ns, and the pulse interval was 400 μs. During the study, the holographic