Hexapod Parallel Kinematics Update

There are many new developments for parallel kinematic multiaxis positioners.   The video below explains some of the differences between serial and parallel kinematics.

Other articles on hexapod applications can be found here.

See you at the Pathology Visions Conference

Digital pathology and telepathology are new weapons in fighting disease.  Its enablers are the Internet and microscopy automation.  At the Pathology Visions Conference in San Diego next week, we will be discussing key aspects of fast focus automation in particular.  Here's the abstract:

Advances in high-throughput, high-reliability focus automation for digital pathology

Scott Jordan
Director, NanoAutomation Technologies
PI (Physik Instrumente) L.P.

Broad adoption of digital pathology depends upon reliable and repeatable slide digitization.  In turn, repeatable/reliable whole slide imaging depends upon the ability to quickly find, hold and track focus. We discuss recent advances in piezoelectric focusing mechanisms and associated metrology of relevance to the community.

High-speed, high reliability focus optimization plays an important role in digital pathology by enabling faster capture of more repeatable images, by maintaining crisp focus during slide scanning motions, and by enabling real-time tracking over the acquisition intervals required by some emerging microscopy techniques. These attributes make focus automation a key variable in diagnostic concurrence.

Of the mechanical approaches available, piezo-actuator driven focus mechanisms combined with through-optic laser sensors offer the high-speed and high reliability required for meeting emerging demands. Piezo actuator driven mechanisms provide sub-millisecond response and can keep pace with throughput-driven methodologies.  Thus they can improve process economics in digital pathology as they have in applications like gene sequencing, semiconductor lithography and interferometric metrology.

Here we review:

  • Four types of piezo actuators
  • Reliability and speed capability of piezo actuator driven focus mechanisms
  • Focus detection technologies often used with piezo mechanisms
  • Examples of piezo deployment for high speed focus in other industries
  • Key metrics for evaluating and selecting focusing technologies
Read more articles on piezo motion devices

New Technology Enables Focusing from Afar

When most people hear the word "piezo" in the context of motion control, they understandably think of the classical piezoelectric stack actuator, composed of hundreds of thin layers of specialized ceramic interleaved with electrodes and sintered together.  When a voltage is applied, the stack expands.  Expansion is limited to about 1% of the stack length-- thus, a 100 mm long stack provide about 100 microns of travel.  Clever, frictionless lever amplifiers can be fabricated (usually using sophisticated wire electric discharge machining) to provide magnified travel.  In this way a compact piezo stage can provide hundreds of microns of travel.

This basic approach has served the microscopy industry well over our many years of manufacturing our popular PIFOC™ objective positioners, specialized linear motion devices optimized to tuck unobtrusively into a turret assembly while providing fast and straight axial positioning of the objective.  However, microscopes' dimensional constraints limit the amount of lever amplification such devices can incorporate.  400 microns has traditionally been the limit for PIFOCs in our catalog.

Until now.  Over the past several years, we've engineered new piezo technologies which provide much longer travels.  Rather than rely on the simple expansion and contraction of the ceramic element, our various piezomotors utilize either ultrasonic linear actuation or various approaches to walking actuation.  Each piezomotor principle has its inherent strengths for target applications but all provide theoretically unlimited travel, fieldless operation, high stiffness and holding force, nanoscale position-hold stability over long periods, and compact size.
N-725 PIFOC® is the first piezo-objective
drive with integrated NEXACT®
Piezo Linear Motor, combining
smooth motion, long travel ranges
and fast response with extreme position stability

Our NEXACT® motors, part of our PiezoWalk® family of ceramic motors, are an excellent example of all the above, plus sub-nanometer resolution.  Their small size and impressive force makes them ideal for long-travel objective positioning, and they are at the heart of our new N-725 NEXACT PIFOC Objective Positioner.  Offering a full 1 mm of travel, this unique mechanism offers high speed and maintenance-free operation.  Its long travel helps accommodate varying substrates and easy load/unload operations, making it ideal for automation applications.  And now it is available in systems integrating the Motion X FocusTrac™Autofocus Sensor for especially responsive and crisp autofocus actuation.

N-725 tracking focus of
a disk spinning at 300 RPM
Meanwhile, autofocus is now a capability which spans almost all PI motion device and controller combinations.  Ease-of-use, stability, speed, applications flexibility and reliable focus capture from extreme out-of-focus conditions were notable design targets accomplished with all configurations.  Systems integrating N-725 meet all these criteria over the full 1mm range of the device.  Its sophisticated, all-digital E-861 Controller/Driver offers USB and RS-232 connectivity together with TTL utility and trigger lines and a joystick port.  And, as a PI General Command Set device, it is supported by a wealth of proven software development tools and the leading microscopy suites.

Fast, automatic focus capture
from 900 microns out of focus!
A special capability is Fast Focus & Freeze (F3), PI's exclusive ability to capture and track the focal plane and then bumplessly switch to nanoscale-stable position-hold, with the ability to precisely position the objective with respect to the focal plane using the device's integrated position sensor.  This is an invaluable capability for high-throughput automated Z sectioning and other quantitative studies where the focal plane serves as a datum plane.  With N-725, F3means the initial condition can be up to 1 mm out of focus.

Count the enablers: unprecedented travel, easy integration, high responsiveness, fast actuation, robust focus-capture and tracking, and Fast Focus & Freeze.  N-725 is a revolutionary addition to the microscopist's toolkit.