Indeed, sensor systems that use interferometry are bulky as they are associated with a number of optical elements and the complexity grows substantially and imposes stringent mechanical requirements because the alignment is critical. However, severe drawbacks are associated with their practical use, especially when several measurement points are considered or the installation must be performed in open spaces. These interferometric techniques are considered to have high performance and generally well-suited, and reliable for metrological applications. Among the classic interferometric techniques 1 like Moiré interferometery 3, 4, holographic interferometry 5, 6, laser doppler vibrometery 7, speckle interferometry 8, 9 for vibration monitoring, Michelson interferometer 10 is the most popularly adopted apparatus by scientists and engineers. These optical techniques combined with advanced computers, frame grabbers and image processing algorithms make them handy for most of the industrial applications. Numerous traditional interferometers 1 are now in use for the mission of common man from research laboratories to flying satellites. Several techniques that use optical interference for the measurement of displacements and vibrations have been developed 2. Measurements of displacement and vibration have been an area of interest in many engineering problems using these two phenomena. Daniel Malacara 1 in his book detailed these phenomena, their differences, advantages and disadvantages and various instruments that are made for physical measurements. However, the two phenomena are so different and are so adequately explained in many text books. The diffraction pattern seen on any observation screen is really another interference pattern. In reality, there is no difference between the interference and diffraction pattern. The most striking examples are the interference and diffraction patterns often seen every day in experiments with light. When the laser beam is used for measurement applications, the spatial profile of the laser beam exhibiting particular distribution patterns and propagation properties in space and time are much more important. Controlling the profile of a laser beam in space and time is an important research challenge in optical technology. The formation of a spectrum by a diffraction grating used in a spectroscopeĪiry's disc seen when a star is viewed in an astronomical telescopeĬoloured patterns seen when a sliver of mica or a piece of stressed plastic is viewed between crossed polarisers (sometimes also seen when a CD case reflects light from a clear blue sky at a particular angle).Lasers are predominantly used as diagnostic tools or as energy sources in scientific research exploration. Newton's rings seen when a convex lens is placed on a piece of flat glass If you look through the fabric of an umbrella at a distant street light you will see a diffraction pattern consisting of an array of bright squares this is also formed by interference. Both of these result from the interference of light reflected from two (almost) parallel surfaces separated by a distance comparable with the wavelength of light. Another similar example is the coloured reflection you see from the objective lenses of binoculars. In everyday life I would say the most commonly experienced example is the coloured patterns you see when oil spreads on water.
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