Measuring distance and thickness simultaneously is important in biological, medical,\nelectronic, and various industries. Herein, we propose a method for simultaneously measuring the\ndisplacement and thickness of transparent materials using a pulsed terahertz wave. For this technique,\na beam splitter was used to design the optical path such that the terahertz wave would incident\nthe specimen vertically to achieve centimeter measurement range and micrometer resolution.\nThe measured terahertz waveform carries peak time information reflected from the upper and\nlower surfaces of the sample, and the thickness can be calculated using the time difference between\nthe first and second reflected peaks. The displacement can also be calculated using peak time difference\nwhen the sample moves from the initial position to the changed position. For validation, an experimental\ntest was performed using aluminum, acrylic, and glass plates. The results confirmed a measurement\nrange of 1 cm with an error of less than 23 microm, and the thickness error was less than 8 microm.
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