Using Autofocus Systems to Achieve Accurate Focusing over Long Timespans

Topics Covered

Introduction to Autofcous Systems
nPFocus Series Piezo Stages
Key Features of nPFocus Series Piezo Stages
About nPoint | nanopositioning and motion control

Introduction to Autofocus Systems

Autofocus systems are designed for maintaining accurate focus over prolonged periods of time, automating image acquisition and scanning objects.

The combination of autofocus systems and piezo stages can generate high-speed and high-precision images even under varying environmental conditions. It is possible to integrate autofocus systems into traditional microscopes in different configurations as well as into commercial inspection equipment and custom optical assemblies.

nPFocus Series Piezo Stages

Sample drift or loss of focus over periods of time is caused by several factors, including external mechanical vibrations and thermal drift in the microscope. Loss of focus will also be the result of changes in the sample thickness during positioning or scanning. These issues can be addressed by autofocus systems by allowing a sample to remain in focus over extended periods of time irrespective of changes in sample or external conditions.

Piezo stages enable nearly real-time focus even when the sample is in motion. The speed of the piezo stages can be 10X times greater than other common focusing systems. Closed-loop nanopositioning systems are capable of providing nanoscale precision, stability, and repeatability. The autofocus system couples to the microscope or optical assembly, which measures and transmits signals to the nPoint controller.

On receipt of the signals, the stage is moved, thereby positioning the optic to focus at the location of interest. With continuous increase in throughput and decrease in size of features, the capability of integrating autofocus systems and piezo stages is increasingly becoming crucial for applications demanding nanometer precision. A combination of an nPFocus piezo stage and focal point autofocus system is depicted in Figure 1.

Figure 1. nPFocus piezo stage with Focal Point autofocus system

Key Features of nPFocus Series Piezo Stages

The nPFocus Series piezo stages are engineered for applications demanding speed and accuracy. With a travel range of up to 1000µm and sub-nanometer resolution, they can be adapted to a range of microscope objectives. They can be used with upright or inverted microscopes. An nPFocus piezo stage is illustrated in Figure 2.

Figure 2. nPFocus piezo stage


The combination of autofocus systems and piezo stages can be used in the following applications:

  • Vibration isolation
  • Tracking
  • Super resolution microscopy
  • Surface topography
  • Semiconductor inspection
  • Process control
  • Micro-scale machine vision
  • Laser processing
  • High speed inspection
  • Biological imaging

About nPoint | nanopositioning and motion control

nPoint, Inc. specializes in piezo actuator driven flexure stages available in one, two or three axes of motion. Our ultra-precision motion control scanners and controllers provide users with the highest level of performance available in the marketplace.

With design and production facilities located in Middleton, WI and distribution channels throughout the world, nPoint provides each of our customers the same outstanding service regardless of the application.

Our product lines include standard products consisting of upgrade kits for your AFM and stand alone research instruments, a growing list of OEM applications and custom design for your unique research application. Let nPoint be your complete nanopositioning solution provider.

This information has been sourced, reviewed and adapted from materials provided by nPoint | nanopositioning and motion control.

For more information on this source, please visit nPoint | nanopositioning and motion control.

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