High-precision vertical positioning

From multiphoton fluorescence microscopy to wafer inspection, vertical positioning systems with large travel range, high dynamics and precision are required in numerous applications in microscopy and industry. With the new V-308 voice coil PIFOC, PI now offers a magnetic direct drive-based solution that unites all these requirements.

Two different objective holders as well as a set of adapter rings for different diameter objectives.
Two different objective holders as well as a set of adapter rings for different diameter objectives.

The core element of the V-308 PIFOC is a single axis slider with high-precision lateral crossed roller guides placed on the base body. The slider is driven by a centred PIMag voice coil motor, which was specifically developed for high dynamics. The 7 mm large travel range can be limited upwards and downwards with adjustable hard stops by the user. Acceleration is up to 8 m/s², the maximum velocity 200 mm/s. This results in step-and-settle times of below 15 ms for 100 and 250 nm step sizes at ±15 nm error band. Therefore, a very fast positioning of the focusing unit, very fast data acquisition, and high productivity can be achieved. The high-resolution optical PIOne linear encoder is used to achieve the high precision requested. A minimum incremental motion of 10 nm and a bidirectional repeatability of 25 nm (at 100 nm travel) can be realized.

Vertical positioning systems are required in numerous applications in microscopy and industry.
Vertical positioning systems are required in numerous applications in microscopy and industry.

Magnetic weight force compensation

A special feature of the new V-308 PIFOC is the magnetic weight force compensation. This ensures a levitation of the slider and mounted load without power supply and it so prevents an uncontrolled crash in case of a power failure or when switching off the controller. For a flexible use of the axis – when switching the objective, for example – the user can adjust the counteracting force and compensate an overall load (objective and holder) of up to 1 kg. Because of this, the axis acts as a horizontal axis even when being used vertically. With dimensions of 87x77x30 mm, the drive is very compact. An adapter plate ensures mounting on an optical bench or plate, with a metric or imperial hole pattern. Two different objective holders (for vertical or horizontal mounting) as well as a set of adapter rings for different diameter objectives, up to size M32x0.75, are available. As a standard, the V-308 PIFOC is offered with the specially developed C-414 controller. Alternatively, the axis can be operated with ACS controllers with built-in EtherCAT functionality. Users can actively control servo control parameters (“gain scheduling”), which in addition with other ACS features such as ServoBoost, can further enhance the performance.