Holographic technique helps in testing and research.
Holographic techniques, that can record both the phase and amplitude of the light reflected by an object, can be used to generate a true, three-dimensional image. Holograms were originally demonstrated by Dennis Gabor in the late 1940s, but significant interest and application of holography did not occur until the 1960s when a convenient source of radiation, in the form of the laser, became available.
During the past three decades, several types of interferometric holography have been demonstrated, еасh having advantages of specific devices for measurements. The technique has been used in applications that include the inspection of aircraft components, the measurement of shrinkage in concrete structures, etc. In each case, a holographic interferometer can show dimensional changes that are difficult to detect with the help of other kinds of techniques. Several types of holographic devices are used for research and quality control, the holograms being produced by a number of different method.
One can describe holography as a powerful tool that will remain the research laboratory in the years to come. Increased processing capabilities of computers in addition to the availability of compact low-cost lasers will significantly broaden the range of applications for holographic technique. Continued progress in each of these areas will lead to wider use of holography for quality control and other applications.
Notes:
Interferometric – интерферометрический
Shrinkage – сокращение, сжатие
Concrete – бетон
Ex.10 Translate the sentences, paying attention to the Absolute Participle Construction and its place in a sentence.
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There are different types of engines, all of them representing the means by which it is possible to utilize the tremendous amount of energy, stored in water, coal, oil, wood and other fuels.
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A d. c. motor being installed, the r. p. m. can be controlled automatically.
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Different molecules have different speeds, the average speed of all molecules remaining the same as long as the temperature is constant.
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One scientist after another have tried cooling some gas to absolute zero, their attempts coming to nothing.
Ex.11 Translate the text. Find the Participles and Absolute Participle Constructions.
THE LASER TODAY AND TOMORROW
The laser has become a multipurpose tool. It has caused a real revolution in technology.
Atoms emit rays of different length, which prevents the forming of an intense beam of light. The laser forces its atoms to emit rays having the same length and traveling in the same direction. The result is a narrow, extremely intense beam of light that spreads out very little and is therefore able to travel very great distances.
The most common laser is the helium-neon laser in the laser tube, containing 10. per cent helium gas and 90 per cent neon gas. At the end of the tube there is a mirror, and at the other end there is a partial mirror.2 The electrons get energy from a power supply3 and become "excited", giving off energy as light. This light is reflected by the mirror at one end of the tube. It can only escape through the partial mirror at the other end of the tube.
The first laser was built in 1960. Since then scientists have developed several types of the laser which make use of luminescent crystals, luminescent glass, a mixture of various gases and finally semiconductors.
Having been developed at Lebedev Institute of Physics in 1962, semiconductor quantum generators occupy a special place among the optical generators. While the size of the ruby crystal laser comes to tens of centimetres and that of the gas generator is about a metre long, the semiconductor laser is a few tens of a millimetre long, the density of its radiation being hundreds of thousands of times greater than that of the best ruby laser.
But the most interesting thing about the semiconductor laser is that it is able to transform electrical energy directly into light wave energy. With an efficiency approaching 100 per cent as compared to a maximum of about 1 per cent of other types, the semiconductor laser opens up new possibilities of producing extremely economical sources of light.
But it is in the field of communication that the laser will find its most extensive application in future. Scientists foresee the day when a single laser beam will be employed to carry simultaneously millions of telephone conversations or a thousand of television programmes. It will serve for fast communications across continents, under the sea, between the Earth and spaceships and between men traveling in space.
The potential importance of these applications continues to stimulate new development in the laser field.
Notes:
1. the laser – слово лазер состоит из начальных букв фразы, описывающей функцию прибора: Light Amplification by Stimulated Emission of Radiation – усиление света в результате вынужденного излучения.
2. partial mirror – полупрозрачное стекло.
3. power supply – источник питания