In collaboration with an engineering undergraduate project, we have developed a flexible, low-cost system for maintaining image focus during time-lapse and video microscopy (where focus drift over time can be problematic). The system uses a software-controlled stepper motor to maintain focus in a closed-loop feedback arrangement using an image analysis approach to quantify the amount of detail in the image. The focusing attachment is not microscope specific and can be assembled from inexpensive, readily available components.

The composite video on the left demonstrates the system in use. The video shows a screen capture from the camera attached to the microscope (top right), external views of the focusing motor rig (top left), and a plot of the focus metric over time (bottom). When the image is manually moved out of focus the software quickly returns the image to focus via the motor attachment.

Full blueprints for the mechanical components can be downloaded here.

For more information, contact Darren M Wells or Andy French.

An accompanying paper is available: