It is shown that Fizeau interferometry provides an accurate optical method to measure the refractive index and wedge angle of transparent plates used as optical components in different experiments. A near IR external cavity diode laser having spectral resolution up to 10-7 has been employed to measure the refractive index of the test plates by introducing amplitude modulation technique in the detection system of our phase shifting Fizeau interferometry. Detection of spatial fringes has been performed to find out the wedge angles of the plates by using a He-Ne laser along with the CCD-image sensor. © 2002 Elsevier Science Ltd. All rights reserved.