As they gradually take their place in the
international market economy context, the central and eastern European
countries (CEEC) and the New Independent States (NIS) of the former
Soviet Union are confronted with the constraints of competitiveness.
This entails having to comply with European rules and standards,
particularly by using, in industry, measuring instruments which
are as precise as those in the West. But the market cost of such
equipment is relatively high, so high in fact that it constitutes
a barrier to its purchase. Three SMEs, therefore, namely Lasertex
(Poland), EKMO R&D (Belarus) and SSIA (Ukraine) decided to throw
themselves into the fray and to produce what they could not afford
to buy: a laser interferometer, namely an instrument of very high
precision used to check the machining of industrial parts. Supported
by the European scientific and technical cooperation programme known
as INCO-COPERNICUS, the specific task of which is to support research
in these countries, the LIMI project, of which these three partners
were the driving force, has been developed in cooperation with Chalmers
University of Technology in Göteborg (Sweden) and the National
Institute for Materials Physics in Rome (Italy).
Precision to the micron level
In order to work, an interferometer of this type uses an initial
source producing two laser beams which are polarised orthogonally.
Thanks to this optical polarisation, the two beams can follow two
different paths; one will serve for reference, the other for measurement.
When the two beams are recombined, they form an interfering image.
This interfering signal depends on the wavelength of the ray used.
This device makes it possible to perform measurements on axes of
up to 30 metres, and with a very high degree of precision (the latter
depending on the wavelength of the luminous source), to the order
of a submicron.(1).
What was the problem to be solved? "In industrial conditions,
the length of the laser beam wave is subject to vibrations and thermal
effects due to the influence of the environment, such as temperature,
humidity or pressure", explains Janusz Rzepka, of Lasertex
Co. Ltd, the Polish team. "So we had to concentrate our efforts
on developing a stabilisation system for the frequency of the laser
beam within the interferometer itself, the main constraint being
how to eliminate some elements which were too costly."
Maximum performance for minimum size
The central element of the system is a ferro?electric liquid crystal
cell. This acts as a fast optical polarisation switch, capable of
moving from one beam to the other extremely rapidly (with an exceptional
frequency of 4 KHz), making it possible to eliminate disturbances
from mechanical vibrations electronically. The development of this
cell was a great challenge and constitutes the core of the project.
It was carried out by EKMO R&D, the National Institute for Materials
Physics in Rome and Chalmers University at Göteborg in Sweden.
The cell has the same functions as other systems already available,
but can be manufactured at a much lower cost. "What is more,
it is very small, measuring 13´17´2 mm, making it possible
to obtain a compact and robust element", specifies Janusz Rzepka.
The interferometer was built by the Lasertex company in close collaboration
with the State Scientific Industrial Association (SSIA) of Kharkov
in Ukraine. It consists of three parts: the liquid crystal cell,
the laser head (14.5 cm long) and the measuring unit. The latter
is fixed to the laser head and contains the optical elements (polarisers,
lenses, photodetector, etc.) and the electronic measuring instruments.
The data are then transmitted directly to an electronic unit which
calibrates them according to values such as the air temperature,
pressure and humidity recorded by detectors placed on the object
"This is a working prototype, successful for several reasons",
says Peter Härtwich, the scientific officer responsible for
the project at the Research Directorate-General. "Firstly,
the new interferometer has all the measuring qualities of its competitors.
In addition, its miniaturisation makes it the most compact and robust
instrument of this type in the world. It is marketed by the three
eastern European partners (Lasertex, SSIA and EKMO R&D) and
a patent has been filed by Lasertex".
As proof that the device really will be capable of being exported
to both eastern and western European countries, the company was
quick to sell some interferometers to Polish and German industry.
This project is thus a precursor of the arrival of eastern industrialists
on the world market. It gave rise to the closest kind of cooperation
between the different partners, with each of them drawing on their
fields of expertise and excellence in order to make this collaboration
the most fruitful possible.
(1) A micron = a millionth
of a metre.
Laser Interferometer for High Quality Manufacturing Industry
Chalmers University of Technology
Department of Physics - Liquid Cristal Group
Fax : +46 - 31 772 34 36
E-mail : email@example.com
- Chalmers University of Technology, Göteborg, Sweden
- Lasertex Co Ltd, Wroclaw (Warsaw), Poland
- EKMO R&D, Minsk, Belarus
State Scientific Industrial Association of Metrology (SSIA),
- Istituto Nazionale di Fisica delle Materia (INFM), Rome,
address for high resolution photos:
The interferometer, consisting of its laser
head, measuring unit and, in the centre, the liquid crystal cell.