Point diffraction interferometer for measurement of the refraction index of a glass plate

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 I_r, 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 I_t. We use the geometrical of figure of interference fringe for analysis of the interferograms. Value of the refraction index of the glass plate, n_t, can be derived, with the previous knowledge of the glass plate thickness. Some experimental results will be shown. (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.