Scientific and technological problems,
such as liquid and gas flow propagation, production of high
purity medicine, heat and mass transfer, high accuracy temperature
and pressure measurements, blood testing in medical treatment
as well as non-destructive testing in machinery and microelectronics,
can be successfully solved by holographic and optical technique.
Holography is a unique optical technique
that has a number of advantages as compared to conventional
photography. With holography, both the amplitude and phase
are stored in a photosensitive recorder called a hologram.
Since the hologram records all the information contained
in a wave front from the object, the reconstructed images
by means of holography are truly three-dimensional and extremely
The hologram making consists of the recording
an interference pattern of the light scattered by an object
and reference wave from the same source on a high-resolution
light-sensitive material. To visualize an object image,
it is necessary to illuminate the hologram by the reference
beam. The light incident on the hologram will diffract on
the recorded pattern as on a diffraction grating. An observer
can see through the hologram a 3-D image of the object in
the same place as it was during the recording.
The method known as holographic interferometry
is based on the comparison between the wave front of the
initial state of the object from a hologram and that propagating
from the object at the current moment (real-time holographic
interferometry) or on the comparison between the two wave
fronts from the object recorded on the same hologram in
its different states (double-exposure holographic interferometry).
Such a comparison gives one very accurate data on the optical
and mechanical properties of the object under investigation.
There is also another method called time-average holographic
interferometry. Time-average holography produces a hologram
which is made while an object is driven in resonance. A
visual image of the vibration pattern is obtained. The major
advantage over the conventional interferometry methods is
the possibility of studying and testing transparent and
reflective light-diffusing objects.
1.2. Experimental techniques.
We have designed several devices for scientific
and industrial application: Holographic camera REGINA for
space research, Holographic microscope, Holographic camera
for non-destructive testing of the outside surface of the
spacecraft windows. The REGINA holographic camera with a
photothermoplastic recorder and a TV-system can be mounted
either on a table or directly on the set-up which is used
to study the processes one has to test. The placing is arbitrary
(vertical, horizontal, etc.)
The camera contains a He-Ne laser with
the output power of nearly 2 mW, optical elements, a power
supply and a hologram recorder. A remote control board is
connected to the camera with a cable.
The investigations of the object can be
made in 2 regimes:
1. Real-time holographic interferometry.
The hologram of an object is recorded on
a photothermoplastic. Then one analyzes the interference
pattern of object wave and the wave reconstructed from the
hologram. The quantitative variation of the refractive index
can be calculated with a computer, into which a signal from
the TV-camera is fed. The temporal changes in the interference
fringes can be recorded on a video-tape.
2.Double-exposure holographi interferometry.
An initial state of the object is recorded
on a hologram. Then, after a certain time the second exposure
REGINA holographic Camera is a compact optical device that
permits visual observation and investigation of physical
and chemical processes in liquids and gases, non-destructive
testing, and different types of hologram production.
have tested holographic interferometry with a holographic
camera in the following fields:
Physical chemistry (crystal growth and dissolution).
Camera was used for the first time on board a space laboratory
to investigate crystal dissolution processes.
gravity is much reduced in space, the rate at which the
dissolved material is removed is decreased because convection
currents are practically nil. This results in an increased
concentration gradient in the near surface layers, and an
overall retardation of the dissolution rate.
holographic interferometry can be successfully employed
to visualize the distribution of the materials in the solution
in terms of the refractive index variations. In this method,
the hologram records the difference between the two states
of the object (Solution) at definite time intervals, i.e.
the change in the refractive index in the cell interior
is recorded as a function of time. When the wavefront is
reconstructed, we get an interference pattern which can
be interpreted by conventional methods to determine the
quantitative changes in the refractive index and then the
Biomedical research (blood testing, electrophoretic analysis)
and cytological studies.
interferometry is successfully used in investigations of
alive cells. A REGINA camera with a special microscope unit
allows to examine plant cells, bacteria, etc. and to measure
the water transport in plant cells and respiration of plants.
To examine directly the plants cells, we use a special microscope
system. The hologram is fixed on a photothermoplastic material.
The reconstructed image is transmitted by a TV camera to
an IBM PC for processing. The object is studied in real
time. The experimental plants are placed in a special valve.
They are kept there for some time without water. Then the
hologram is recorded and after that the water is given to
the plant. The interference pattern begins to change. Looking
at the changes of the fringes on the display, one can observe
the water transport in the plant.
in electrophoresis experiments.
successful use of the holographic camera in space flights
has extended the range of applicability of holography for
studying the dynamics of physical and chemical processes
under reduced-gravity conditions. Two holograms of isotachophoresis
were recorded with the REGINA Hologram Camera designed especially
for the purpose. The experiment was motivated by the problem
of producing highly pure biological drugs.The electrophoretic
technique is more precise, powerful and convenient. Among
the various methods of purification, separation, and analysis
used for in biology. This method is extremely effective
in the separation of biological preparations on the level
of protein molecules, subcellular particles, and cells.
Although the available electrophoretic apparatus and the
methods for controlling the separation are highly advanced,
they do not allow visual monitoring of the process dynamics.
A precise understanding of the changes which occur in the
course of electrophoresis is required for developing methods
and apparatus for making pure preparation.
electrophoresis uses staining, which is quite suitable for
a preliminary analysis but must be abandoned when a preparation
is produced in a pure form.
alternative method is to control electrophoresis by holographic
interferometry. This method allows observation of the separation
of unstained preparation, and makes it possible to determine
the changes in the refractive index of the solution as a
function of the changing concentration of the fraction being
separated. Finite-fringe holographic interferometry has
been used in experiments. A hologram permits reconstruction
of the isotachophoresis of a preparation.
of free convection in a closed space by real-time holographic
using the holographic interferometry method with hologram
REGINA Camera was used in investigations of a free convection
jet in real time in a closed space filled with various liquids.
The optical layout is the same as in the previous section.
A closed liquid gate with a small point-heater at the bottom
was placed in the camera and the hologram of the initial
state of the liquid (without heating) was recorded.
applying voltage to the electric heather which is placed
at the bottom of the gate one can view the kinetics of the
Aero- and hydrodynamics (flow visualization, speed measurements,
turbulence research, vibration convection analysis, shock
wave propagation diagnostics, etc.)
REGINA camera is also effective for non-destructive testing
in industry. For example, we have used it for testing units
and parts of precision tools, products in microelectronic
industry, optical fibers, optical components, etc.
Non-destructive testing of artificial heart valves (AHV).
many people have cardiovascular diseases. For some of them
the only chance to stay alive is a surgical implantation
of an artificial heart valve (AHV).
patients's life directly depends on the quality of the AHV.
AHV must open and close for several million cycles during
the 20 year operation. Thus, the quality control during
the manufacturing and testing of the final products is the
main guarantee of reliability of the subsequent operation
of valves. Therefore, testing operations make up over 40%
of all production operations. With the help of modern effective
testing methods we can make AHV more reliable and durable.
Quantitative and qualitative testing of the mechanical properties
of AHV and also testing of their hydrodynamic parameters
can be made by REGINA. We have designed methods for testing
AHV under dynamical loads. The deformation of "EMIKS" AHV
was explored. We also use hydrodynamic testing of AHV parameters
in a special device which simulates the conditions under
which the heart can work normally. We also have a special
device for visualization of liquid flows which travel through
the valve and for measurement of the velocity distribution
of the flows.
Non-destructive holographic testing of quality of metallization
in the holes of electronic boards.
are many methods of testing defects of the holes in boards.
All of them take a lot of time. This method allows to speed
up this procedure and to obtain better results than by conventional
methods.Also we can see what type of defect is in the hole.
is quite simple.The board is illuminated by spherical coherent
laser waves.With the help of a diode and TV camera the distribution
intensity is registered. When the hole is illuminated by
the laser beam, one can see the diffraction picture on the
monitor. It looks like a set of circular zones. The analysis
of the picture gives the possibility of estimation of the
quality of the metallized surface of the holes.
hologram is a record from which one can obtain information
about the geometry and optical properties of the object
and the quality of the surface. Diffraction pattern contains
a central maximum with 5 or 6 circles. This picture allows
to estimate the diffraction on the holes and also the type
of metallisation defect.
analysis shows that the test hole has a symmetrical pattern.
Defective holes have asymmetrical ones, also there are some
differences in the distribution of illuminated and dark
zones. Some circles can be absent in defective holes.
experiments were supported theoretically. The results of
investigations are in good agreement. Special testing devices
can be created on this basis.
Camera REGINA is an ideal device for teaching students of
any specialty; it provides a vivid idea and practical skills
for those studying mechanics, physics, hydroaerodynamics,
chemistry, physical optics; illustrates and provides the
possibility to carry out laboratory work in molecular physics
(studying of gas processes, physical characteristics of
liquids, gases and solid bodies); assists in studying mechanics,
physical oscillations, strength and plastically theory;
visualizes gas and liquid flows and provides the idea of
turbulence; is of great use in acoustics.
the physical optics REGINA allows to study geometrical optics
(properties of optical elements); light diffraction and
interference, coherence of emission; gives the idea of holography,
holographic interferometry and optical processing of information.
elements and holographic cameras were tested and used at
the Zero-gravity conditions in space flights and under the
severe loading at the underwater measurements. It tolerates
chocks up to 50 g, strong vibrations and changes of temperature
in wide range. "REGINA" camera is new word in the optical
instrumentation. It allows to apply the sophisticated technology
developed in specially protected and very expensive environment
for everyday use in the simplest laboratory and industrial
State Electronics Division Executive Secretary
Phisico-Technical Institute Russian Academy of Science
Politekhnicheskaya, St. Petersburg 194021, Russia