The ability to classify materials based on color or visual appearance creates a quality-control limitation in many manufacturing sectors, including the sorting of materials such as wood veneer and marble. When sorting is performed manually, it is subjective and prone to error. To automate the task, Asiris Vision Technologies (San Sebastián, Spain; www.asinistech.com) has developed Clastone, a technology that the company says can reproduce human behavior in color-classification tasks. In real time and using a neural network, it can identify classification criteria such as color, texture, and position of visual faults and can locate anomalous colors representative of faults in certain materials.
Traditional sorting technologies may rely on lasers and CCD cameras or matching technologies may be used; these are easy to use and can be very accurate but are unsatisfactory or not feasible on heterogeneous materials. To overcome the limitations, Asiris has developed the AVT-2000, the first inspection system for the marble industry that automates all the quality-control tasks and shade classification. Its vision system can inspect marble tiles ranging from 150 × 300 to 650 × 650 mm. The color module uses a Camera Link camera from TVI Vision (Helsinki, Finland; www.tvivision.com), custom fluorescent illumination with feedback control loop, and a frame grabber from Bitflow (Woburn, MA, USA; www.bitflow.com). A shade module allows automatic classification on the basis of user-defined shades; the fault module detects surface and edge defects; and a geometric module performs geometric analysis of color images.
