Metrology for laser-structured microdevices by CCD-camera based vision systems

Recent developments in the area of micromachining and mircofabrication are accelerating commercial awareness of microstructures. Product applications ranging from automotive and medical devices to industrial, chemical and consumer products show the necessity of adequate fabrication methods for microstructures. These fabrication methods include high resolution measurement technologies. Images of the machined area, recorded via videography by a CCD-camera based computer vision system are evaluated to obtain the two dimensions (x and y) of the microstructured devices. Height measurement (z) is performed by automatically focussing on two different levels of the workpiece. The achieved accuracy of the measurement data is evaluated. During structuring of microdevices an autofocus system is used to control the removal process by laser radiation to obtain the desired geometry. The mathematical algorithms used by the vision system to guide the focus of the CCD-camera are discussed. The designed measurement system is tested by microstructuring of hard metals and ceramics with short pulse (ns, ps) laser radiation.