Growing quality and cost reduction demands in the actual industry require efforts in many fields of the production process. On-line dimensional control of 100% of the production, including surface defect detection, is becoming a key factor for the competitiveness of the modern industries, being a very important factor for systematic homogeneous inspection, customer claims reduction, fast process feedback, process knowledge improvement and drastic start-up times reduction, among others. Conoscopic Holography has proven to be an accurate, robust, versatile and reliable technology for off-line and on-line dimensional inspection. This paper shows the actual developments at University of Oviedo for one of the Conoscopic Holography based sensors, the Long-Standoff Conoline. This sensor has the particularity of obtaining a distance profile of a target while working at a long distance, keeping an outstanding relation between resolution and stand-off. Typical values are 0.1 mm resolution at 700 mm distance. Using this sensor and the appropriate software, surface defects (scratches, pores, lacks of material, form defects, adherences), can be reliably obtained from a long distance in a great variety of materials and surface configurations. Examples are shown of the effectiveness of the solution: (1) A system for on-line cracks inspection in steel continuous casting is currently working at Aceralia LDA steelmaking factory in Asturias (Spain), being able to detect cracks in hot steel (above 800°C) with scale present from 1200 mm standoff. (2) Using the same configuration, very small scratches or form defects in finished steel can also be detected, being independent of the surface orientation or form. Finally, current developments to improve integration of the system, operation speed, robustness are presented, together with suggested fields of application.
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