Key Words: Double beam interferometry, multiple-beam interferometry, interference, metrology, optical testing, optical measurements, Eclipse
Definition:Double beam interferometry is an analytical technique based on the principle that converging light waves will combine either constructively or destructively to produce a new wave with characteristic patterns of light and fringes that provide information on the source waves and the surfaces from which they are reflected
TECHNOLOGY:
When two light waves (or any other form of EM radiation) collide, the peaks and valleys of each wave combine on a point-by-point basis to either mutually reinforce or cancel each other. The resulting wave band will possess a succession of alternately bright and dark interference fringes that will vary in size, number and pattern depending on the differences in path length travelled by each wave.
The function of optical systems for double beam interferometry is then to allow observation of these interference patterns appearing in the wedge space formed by two surfaces. Their basic set-up comprises a high resolution microscope and an interferometer with a highly coherent light source such as a monochromatic laser. This allows for the generation of crisp interferograms, capable of resolving minute differences in surface details (down to the nanometre scale). Regardless of application, however, advanced software is required with any interferometer for the accurate analysis of fringe patterns, which can become increasingly complex depending on the subject material.
APPLICATIONS:
The interferograms produced by modern instruments can provide rich information on the character of surface microstructures, including roughness, shape and waviness in a non-destructive manner. As such, the technique is a fundamental tool employed by metrologists in a variety of precision manufacturing industries including the production and engineering of semiconductors, optics, MEMS and microelectronics. The technique is also well suited for the analysis of metals, composites, minerals and is therefore commonly used for both research and quality control purposes in metallurgical and geologic studies.
MICROSCOPE CONFIGURATION:
Supported by NIS Elements software, Nikon's Eclipse LV 150 series and LV 100D of microscopes offer a range of configurations suitable for double beam interferometry.
SYSTEM SOLUTION:
Please consult with your local Nikon representative.