On-line defect detection of aluminum coating using fiber optic sensor

Abstract

Aluminum metallization using the sprayed coating for exhaust mild steel (MS) pipes of tractors is a standard practice for avoiding rusting. Patches of thin metal coats are prone to rusting and are thus considered as defects in the surface coating. This paper reports a novel configuration of the fiber optic sensor for on-line checking the aluminum metallization uniformity and hence for defect detection. An optimally chosen high bright 440 nm BLUE LED (light-emitting diode) launches light into a transmitting fiber inclined at the angle of 60° to the surface under inspection placed adequately. The reflected light is transported by a receiving fiber to a blue enhanced photo detector. The metallization thickness on the coated surface results in visually observable variation in the gray shades. The coated pipe is spirally inspected by a combination of linear and rotary motions. The sensor output is the signal conditioned and monitored with RISHUBH DAS. Experimental results show the good repeatability in the defect detection and coating non-uniformity measurement.

Theoretical and experimental investigation into the influence factors for range gated reconstruction

“…Reflected intensity strongly depends on the characteristics of the target surface [20]. Although Lambertian target (ideal diffuse surface) is commonly assumed due to its simplicity, target reflection is in fact far more complicated, and BRDF concept is normally used to describe that.…”

Measuring the Radial Position of Defects within Optical Fibers Using Skew Rays

“…A few techniques have been proposed over the years. One known technique [5] operates by visually analyzing the diffracted light when external surface illumination is used. Since this involves a point-by-point inspection, it is impractical for long lengths of fibers.…”