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Automation and Microscopy: Faster Test & Measurement, Surface Metrology – Piezo Speed is Enabler for 100% Testing

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Fast nano-focus drives speed up high-throughput microscopy systems: Large-surface objects can be examined within seconds. For the first time ever, 100-percent microscopic tests are now possible in the industrial environment. (Image: Fraunhofer IPT)
Fast nano-focus drives speed up high-throughput microscopy systems: Large-surface objects can be examined within seconds. For the first time ever, 100-percent microscopic tests are now possible in the industrial environment. (Image: Fraunhofer IPT)

Everybody who commutes by car is familiar with the concept: constant velocity gets you faster to your destination than stop-and-go traffic. This well-known principle from the macro-world is now employed in the nano-world by scientists from the Fraunhofer Institute for Production Technology IPT in Aachen, Germany.

Their solution speeds up microscopic testing of large-surface objects, such as well plates, and enables 100% testing for the first time. A fast nano-focus device based on a piezo-ceramic actuator embedded in a flexure guided lens positioning mechanism from PI (Physik Instrumente) is one of the driving forces for this success.

FraunhoferMicroscopy_YouTube

The technique pays big dividends in bio-technology and pharmaceutical applications because it now allows the complete and thorough examination of micro well plates in just seconds. Conventional motion and image analysis processes at high magnification were too slow to achieve 100-percent testing, and randomized testing was the only alternative. What works well for bio-technology is also useful in semiconductor metrology and material science applications.

A P-725 Piezo-driven Nano-Focus Scanner for Microscope Objective Lenses shown with a compact digital controller: Significantly faster response, higher reliability and service life than motorized Z stages. This model provides 400um closed loop travel and can be used in upright and inverted microscopes. (Image: PI)
A P-725 Piezo-driven Nano-Focus Scanner for Microscope Objective Lenses shown with a compact digital controller: Significantly faster response, higher reliability and service life than motorized Z stages. This model provides 400um closed loop travel and can be used in upright and inverted microscopes. (Image: PI)

 

PIFOC ® microscopy lens scanners work in upright and inverted microscopes. (Image: PI)
PIFOC ® microscopy lens scanners work in upright and inverted microscopes. (Image: PI)

 

Step and settle response of a P-726 high stiffness nano-focus device for large objectives. (Image: PI)
Step and settle response of a P-726 high stiffness nano-focus device for large objectives. (Image: PI)

The new approach by the scientists at the IPT keeps the XY scanning stage moving the object to be tested at constant velocity during the image recording process. However, because of the relatively large variations in the surface topology (caused by precision limitations of injection-molded plastic micro well plates), a static fixed microscope objective cannot be used. The height variations would considerably exceed the depth of focus and lead to blurry, useless images.

Assembly view of a PI PIFOC nano-focus device shown with thread-adapter inserts, objective and Quick-lock tool. (Image: PI)
Assembly view of a PI PIFOC nano-focus device shown with thread-adapter inserts, objective and Quick-lock tool. (Image: PI)

As a countermeasure, a fast focus drive with an adjustment range of 400 µm and nanometer precision is employed. A real-time autofocus function is necessary for three-dimensional image recording; the focus must be adjusted dynamically in the direction of the optical axis with high precision. This is where the piezo-driven microscope lens scanner comes into play.

Video: Overview - piezo drives in microscopy applications
Video: Overview – Piezo Drives in Microscopy Applications

Combined with the latest software and hardware for fast data handling and image-processing this precision micro-mechanical device now allows for complex tasks, such as stitching processes, to run virtually in real-time. Individual images can be merged seamlessly into the overall image even while measuring is in progress.

Ingredients for the modular high-speed microscope (Image: Fraunhofer IPT)
Ingredients for the modular high-speed microscope (Image: Fraunhofer IPT)

Piezo mechanic drives can respond with a position change within milliseconds of a drive voltage change with precision in the nanometer range or even below.  The process is very repeatable, ensuring that the microscope object stays in focus all the time even during high scanning speeds.

 

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About PI

PI (Physik Instrumente) is a leading manufacturer of precision motion control equipment, piezo motors, air bearing stages and hexapod parallel-kinematics for semiconductor applications, photonics, bio-nano-technology and medical engineering. PI has been developing and manufacturing standard & custom precision products with piezoceramic and electromagnetic drives for 4 decades. The company has been ISO 9001 certified since 1994 and provides innovative, high-quality solutions for OEM and research. PI is present worldwide with fifteen subsidiaries, R&D / engineering on 3 continents and total staff of more than 1,000.

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