Localization of a workpiece position and orientation by means of off axis photodiodes

For applications that require precision with a resolution of few micrometers, determining the exact position of the workpiece relative to the processing laser beam in the XY-plane is a challenge that is currently solved only through time-consuming and complex to integrate, as well as expensive measurement systems. Here, we address the challenge of automatically determining the position and orientation of a workpiece in the ultrashort pulse laser machine with no movement of the workpiece and no impairment of the processing optic. Our approach involves the evaluation of spatially resolved secondary process emissions while the laser passes over the surface - either during the processing or in a separate measurement step with fluence below the ablation threshold. The measurement does not affect the duration of the processing, as it happens in parallel to it. Here, we thoroughly examine the secondary emission-based position detection of a Philips Metamorpha project workpiece. We divide the process in two steps: a coarse and a fine position detection and achieve a precision of up to 2.4 μm. Moreover, we develop an automation algorithm and implemented it in the FPGA of our edge-device, which enables the analysis of the data while it is being collected with a temporal resolution of 10 μs.