A new method for measuring simultaneously the thickness and the refractive index of a transparent plate is proposed. The method is based on a simple, variable lateral-shear, wavelength-scanning interferometer. To achieve highly accurate measurements of both refractive index <i>n</i> and thickness <i>d</i> we use several means to determine these two quantities. We finely tune a distributed-feedback diode laser light source to introduce a phase shift into the detected signal, whereas we make the sample rotate to produce variable lateral shearing. Phase shifting permits precise determination of the optical thickness, <i>nd</i>, whereas refractive index <i>n</i> is obtained from the retrieved phase of the overall interference signal for all incidence angles.
© 2003 Optical Society of America
(120.2650) Instrumentation, measurement, and metrology : Fringe analysis
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(220.4840) Optical design and fabrication : Testing
Giuseppe Coppola, Pietro Ferraro, Mario Iodice, and Sergio De Nicola, "Method for Measuring the Refractive Index and the Thickness of Transparent Plates with a Lateral-Shear, Wavelength-Scanning Interferometer," Appl. Opt. 42, 3882-3887 (2003)