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When competition rhymes with precision

A very high precision instrument used to check the machining of industrial parts, the laser interferometer developed in the context of the LIMI project is the most compact - and also the most robust - currently on the market.

Three SMEs located in Poland, Belarus and Ukraine are at the origin of this research project. Supported by the INCO-Copernicus programme, they are working together with two Swedish and Italian research centres. The aim is to develop a laser interferometer. This ultra-precise measuring instrument for the machine tool industry had, up to now, been unaffordable in central and eastern Europe. The project has resulted in an innovatory and accessible system which opens up the path to exports and new markets for industrialists in these countries.


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 measured.

"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 (LIMI)



Tomasz Matuszczyk
Chalmers University of Technology
Department of Physics - Liquid Cristal Group
Göteborg, Suède
Fax : +46 - 31 772 34 36
E-mail :

- Chalmers University of Technology, Göteborg, Sweden (coordinator)
- Lasertex Co Ltd, Wroclaw (Warsaw), Poland
- EKMO R&D, Minsk, Belarus
State Scientific Industrial Association of Metrology (SSIA), Kharkov, Ukraine
- Istituto Nazionale di Fisica delle Materia (INFM), Rome, Italy

Web address for high resolution photos:

The interferometer, consisting of its laser head, measuring unit and, in the centre, the liquid crystal cell.