Use of CCD arrays versus PSD detectors in an optical triangulation-based microtopographer

For some years we are studying the problem of the non invasive topographic characterization of rough surfaces of interest in the industrial world. We based our system on a simple and robust discreet triangulation procedure. The topographic information is obtained from the horizontal shift incurred by the bright spot created, by an oblique collimated light beam, on a surface when it is displaced vertically. A laser beam is focused onto a small, diffraction limited, spot on the surface and is made to scan it over the desired region. The sample is placed on XY high accuracy step motion table to perform the scanning of the sample areas of interest. At each sampled point the bright spot formed on the surface is perpendicularly imaged onto a photo-sensitive detection system and its position obtained. The horizontal spot's position shift regarding some reference is calculated. This shift is proportional to the vertical distance (height) between the surface and a reference plane. Obtained the surface's heights matrice the tridimensional reproduction of surface's can be performed and statistical characterization parameters calculated. Between the electronic spot's detection systems that can be used, in this communication we will present details about the characteristics and performance of the use of CCD's linescan (Fairchild 143A) cameras in comparison with the use of the so called PSD's (SiTek 1L10).