We present the measurement and graphical representation of spatial differential values of the surface roughness factor for various steel samples. The measurements were made by a newly developed optoelectronic sensor system comprising a light emitting diode (LED) and two phototransistors. The light beam from the LED illuminated an area of 1 mm2 on the metallic surface. The reflected light and scattered light were captured by two different photo detectors. The sample surface was scanned using a computer numerical control (CNC) machine. The photocurrent signals acquired at each point on the surface were digitized, and a parameter was calculated to correspond to the degree of roughness of the surface at the given point. The measured roughness factor is compared with the readings of a standard instrument, and the instrument was calibrated to display the measurements in micrometers. The measured values processed by a personal computer provided a three-dimensional (3-D) mapping of the surface texture.
The present work reports the design and implementation of an optical-sensor based virtual instrument for visualizing and estimating the degree of corrosion of metal surfaces exposed to atmosphere. A platform carrying the specimen plates was driven by a stepper motor assembly horizontally in XY directions. An opto-electronic transmitter-receiver unit was fixed vertically very close to the platform so that the sample surfaces may be scanned by a light beam. The reflected and scattered optical signals from each point in the scanned area were acquired by the sensor module. A parameter incorporating the relative values of these signals proved to be a fairly reliable measure of the surface texture, which in turn consistently represented the degree of corrosion. These signals interfaced with a personal computer enabled 3D visualization of the magnitude of the corrosion level of the surface and 2D mapping of the surface corrosion.