ABSTRACT
This chapter presents interferometry and holography for quantitative measurements of refraction index and density. In monochromatic interferometry, it is well known that the classical interference pattern is represented by a succession of dark and bright red fringes. In general, interference fringes can be localized if they are observed at a precise location in space or unlocalized if they are observed in the space area where the beams overlap. Among the most used interferometers with separated beams, it is worth mentioning the Michelson interferometer. On the screen, a unique black fringe is obtained because the reflexions produced by the two beams on the beam splitter plate generate a shift of a half period for one of the beams. The test section is crossed by one of the beams and the test section windows are compensated by two identical plates located in the path of the other beam.
