On-line submicron profile measurements from safe distances with conoscopic holography: feasibility and potential problems

On-line noncontact surface inspection with high precision is still an open problem. Usual methods are, in general, not applicable in hostile environments or not adequate for on-line measurement, as they are either slow in nature or need to work from very short, unsafe distances, providing small depths of field and apertures. The ongoing work toward the development of a noncontact optical profile measuring sensor that could be used for submicron measurements in on-line applications is presented here. Our approach is based on conoscopic holography and triangulation, and uses a very simple method for removing speckle noise, which is key for obtaining high precisions from safe distances (several centimeters). (C) 2008 Society of Photo-Optical Instrumentation Engineers.