Line-Field Swept-Source Interferometer for Simultaneous Measurement of Thickness and Refractive Index Distribution

We present a novel method for simultaneous measurement of the thickness and refractive index distribution of a transparent specimen by a line-field swept-source interferometer. In this study, by illuminating with the line-field beam instead of the point-focused beam, multiple interferences along the line-field distribution are measured simultaneously by using a combination of a novel swept source of 800-nm central region and a Si-based 1024-pixel charge-coupled device (CCD) detector. When the transparent specimen has an uneven thickness or nonuniform refractive index, the whole distribution of these two parameters can be also simultaneously measured over the illuminated region with a one-step comparison process. Using four types of transparent specimens, the thickness and refractive index distribution of each sample and a group sample paired with two specimens are accurately measured during the single wavelength scanning time of 27 ms by using the swept source with a 36-Hz sweeping rate and the CCD detector with a 36-kHz line rate.