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3 Holographic Interferometry for Studying …
1.3.2. The beam splitter 2 serves for splitting radiation from the laser 1 into illuminating and reference beams, for input of reconstructing beams from the
continuous He–Ne laser 17, and for adjustment of schemes with the continuous laser 17. The transmission coefficients of the beam splitter should be
about 95% and the reflection coefficients—of about 5%. Interference pattern
should not be observed at the wavelengths λ 1 = 694.3 nm and λ 2 = 632.8
nm in the transmitted and reflected beams. It is recommended to produce a
beam splitter in the form of a plane-parallel plate, on the edge of which an
antireflective coating should be put (for λ = 694.3 nm). The coating should
be laser-resistant. And the wavefront distortions in the reflected and the transmitted beams for λ 1 and λ 2 at the diameter of 10 mm should not exceed 0.1λ
for λ = 632.8 nm. The beam splitter 2 should have two smooth adjustment
spins (in the plane of the drawing and in the perpendicular plane), light sensitivity—2
and also parallel shift in the drawing plane along the direction of
the beam generated by the laser 17, the sensitivity is 0.01 mm.
1.3.3. The lens 3 should provide even illumination of the surface of the object
under study of 50 × 60 cm
2 . Laser damage resistance should be observed. A
negative lens should be used as an objective.
1.3.4. The mirrors 4, 5, 10 should provide the required direction of the recording
and the reconstructing beams. The reflecting surface should be frontal, and
the reflection coefficient should be maximal for λ 1 and λ 2 . The mirrors 4,
5, 10 should be capable of angle adjustments in two mutually perpendicular
planes.
1.3.5. The electrooptical device 6 should provide the rotation at 90° of the polarization plane of the transmitted linear-polarized radiation with λ 1 = 694.8
nm under voltage and not change the polarization state in its absence. KDP
crystal, Pockels or Kerr cell can be used as such a device.
1.3.6. The beam splitter 7 should provide formation of two spatially separated reference beams. The ratio between transmission and reflection coefficients of the
beam splitter should be chosen according to the conditions of equality of
intensities of the reference beams in the plane of the light-sensitive layer
of the reversible carrier 14. There should be no interference structures
in the reference beams. The covering should be laser-resistant. The beam
splitter 7 should have the possibility of angle adjustments in two mutually
perpendicular planes.
1.3.7. The polarizers 9 and 9
are to be in crossed state during hologram recording
and in parallel (or remote) during reconstruction. There should be no shifts
and inclinations, which pass through the beam polarizers when λ 1 is replaced
by λ 2 . When the polarizers turn or move away, change of distortions of the
wave front should not exceed 0.05 λ. If it is impossible, then the plate λ/2
11 and λ/4 19 should be used and the polarizers are to be crossed.
1.3.8. The mirror 10 with the piezoelectric element 8 should provide phase modulation of the reference beam. To do this the piezoelectric element 8 should
provide harmonic oscillations of the mirror 10 in the direction, which is
perpendicular to its surface with the amplitude of 2 μm and the frequency
3 Holographic Interferometry for Studying …
1.3.2. The beam splitter 2 serves for splitting radiation from the laser 1 into illuminating and reference beams, for input of reconstructing beams from the
continuous He–Ne laser 17, and for adjustment of schemes with the continuous laser 17. The transmission coefficients of the beam splitter should be
about 95% and the reflection coefficients—of about 5%. Interference pattern
should not be observed at the wavelengths λ 1 = 694.3 nm and λ 2 = 632.8
nm in the transmitted and reflected beams. It is recommended to produce a
beam splitter in the form of a plane-parallel plate, on the edge of which an
antireflective coating should be put (for λ = 694.3 nm). The coating should
be laser-resistant. And the wavefront distortions in the reflected and the transmitted beams for λ 1 and λ 2 at the diameter of 10 mm should not exceed 0.1λ
for λ = 632.8 nm. The beam splitter 2 should have two smooth adjustment
spins (in the plane of the drawing and in the perpendicular plane), light sensitivity—2
and also parallel shift in the drawing plane along the direction of
the beam generated by the laser 17, the sensitivity is 0.01 mm.
1.3.3. The lens 3 should provide even illumination of the surface of the object
under study of 50 × 60 cm
2 . Laser damage resistance should be observed. A
negative lens should be used as an objective.
1.3.4. The mirrors 4, 5, 10 should provide the required direction of the recording
and the reconstructing beams. The reflecting surface should be frontal, and
the reflection coefficient should be maximal for λ 1 and λ 2 . The mirrors 4,
5, 10 should be capable of angle adjustments in two mutually perpendicular
planes.
1.3.5. The electrooptical device 6 should provide the rotation at 90° of the polarization plane of the transmitted linear-polarized radiation with λ 1 = 694.8
nm under voltage and not change the polarization state in its absence. KDP
crystal, Pockels or Kerr cell can be used as such a device.
1.3.6. The beam splitter 7 should provide formation of two spatially separated reference beams. The ratio between transmission and reflection coefficients of the
beam splitter should be chosen according to the conditions of equality of
intensities of the reference beams in the plane of the light-sensitive layer
of the reversible carrier 14. There should be no interference structures
in the reference beams. The covering should be laser-resistant. The beam
splitter 7 should have the possibility of angle adjustments in two mutually
perpendicular planes.
1.3.7. The polarizers 9 and 9
are to be in crossed state during hologram recording
and in parallel (or remote) during reconstruction. There should be no shifts
and inclinations, which pass through the beam polarizers when λ 1 is replaced
by λ 2 . When the polarizers turn or move away, change of distortions of the
wave front should not exceed 0.05 λ. If it is impossible, then the plate λ/2
11 and λ/4 19 should be used and the polarizers are to be crossed.
1.3.8. The mirror 10 with the piezoelectric element 8 should provide phase modulation of the reference beam. To do this the piezoelectric element 8 should
provide harmonic oscillations of the mirror 10 in the direction, which is
perpendicular to its surface with the amplitude of 2 μm and the frequency