22 ANALYTICAL AND LABORATORY EQUIPMENT
TESTING at INDUSTRIAL-SCALE SPEED
Doris Knauer reveals the results of some innovative microscopic testing research
F
or the first time ever, scientists from the Fraunhofer Institute for
Production Technology have succeeded in achieving 100% microscopic testing in the industrial environment. A piezo-
based drive system from PI was decisive for this success. Te new high-throughput
process from IPT now allows microscoping of large-surface objects within seconds. Conventional high- magnification image recording of boards and microwell plates, for example, is often very time consuming and therefore 100% testing is not possible, which makes random testing the only alternative. Te new process will be particularly beneficial to the biotech and electronics fields.
Te idea of the scientists was that during image recording, the stage moves the object continuously at a constant velocity in contrast to the conventional ‘stop-and-go’ method. In addition, they combined the time-optimised scanning process with real-time data handling and image-processing steps. Even CPU-intensive tasks such as the stitching processes run almost without any delay. Individual images can be merged seamlessly into the overall image even while measuring is in progress. Of course, the scientists admit that this is mainly due to the processing power of the system and the sophisticated software, but the hardware used also contributes to this. It needs to adjust the focus accordingly during continuous scanning.
100% microscopic tests are now possible in the industrial environment
www.scientistlive.com (Image courtesy of Fraunhofer IPT)
Fast autofocusing Te surface topology exceeds the depth of focus of a microscopic objective, irrespective of whether this is due to unevenness of injection-moulded plastic microwell plates or the different heights of the components on the board, or tilting of the entire wafer during the manufacturing of electronics. It is only possible to focus sharply on the surface when the focus is adjusted in a range of around 300 µm. A real-time autofocus function is therefore necessary for 3D image recording; it must be adjusted dynamically in the direction of the optical axis with high precision. Tis task is performed by a Pifoc piezo-based objective scanner from PI. With a travel range of up to 500 µm, it is well suited to autofocus applications and, when taking accuracy and
The Pifoc objective scanner makes precision positioning possible even over comparatively large travel ranges to 100 or even 400 µm
dynamics into account, is far superior to stepper motors. Te Pifoc Z drives are designed to be very small and stiff. Te response times are short and, thanks to stable guiding, precision positioning is possible even over large travel ranges. Te zero-play and high-precision flexure guide ensure high focus stability. Piezo systems stand for accuracy, but here they demonstrate another strong point. Te repeatability and settling time of less than 10ms are important. Te drive prevents the object from going out of focus at high scanning speeds. In conjunction with direct metrology, capacitive sensors and digital controllers, the Pifoc achieves the highest linearity at a maximum deviation of 0.06 %. Te capacitive sensors measure the mechanical part in motion directly and without physical contact. Neither friction nor hysteresis interferes with the measurement. Te position of the objective can be matched accurately to the image.
For more information ✔ at
www.scientistlive.com/eurolab
Doris Knauer is with PI.
www.pi.ws
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