Introduction Laser‐based inspection systems originated in the late 1960s to automate the inspection task. Applied primarily to defect detection in flat, homogeneous products, these systems gained widespread use in the 1970s and through the 1980s. The bright, coherent light source provided the means to capture a range of defect optical effects including absorption, reflectivity, transmissivity, distortion and scattering. Unfortunately, early laser systems employed extremely inefficient light collection techniques. Much of the defects' optical information was lost. Fifteen to 20 years on, almost all commercial laser systems continue to employ this technology.
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