This work shows the measurement of the refraction index of a glass plate using a Point Diffraction Interferometer (PDI). The plate of the PDI has a micro-hole and transmittance of less than 10%. The experimental setup consists in a He-Ne laser illuminating a spatial filter, a collimated beam is produced by an achromatic lens, and close to the focal point of a second lens (focusing lens), the plate of the Point Diffraction Interferometer is located. When the laser light pass through the plate of the PDI, it is generated an interference reference pattern, called Ir, which is recorded. As a second step, a glass plate with unknown index refraction is introduced between the focusing lens and the plate of the PDI, obtaining a new modified interference pattern, called It. We use the geometrical of figure of interference fringe for analysis of the interferograms. Value of the refraction index of the glass plate, nt, can be derived, with the previous knowledge of the glass plate thickness. Some experimental results will be shown.
Using the analogy of the double-slit experiment developed by Young and using interferometric technique
developed by Chalmers, we built an interferometric arrangement that can analyze local defects of an optical
surface. With a reflective spatial light modulator (RSLM) controlled by a PC, two apertures are open each
time, and the apertures became as secondary light sources, producing interference pattern for specific zones
for the surface under test. The interference pattern is observed, and storage into a computer by using a CCD
camera. Finally the results are compared with the results obtained using a Fizeau commercial interferometer.