Fast, high-precision autofocus on a motorised microscope: Automating blood sample imaging on the OpenFlexure...

Area of Science:

• Biomedical Engineering
• Microscopy
• Parasitology

Background:

• The OpenFlexure Microscope offers automated image acquisition for research and healthcare.
• Accurate autofocus is crucial for high-magnification imaging of malaria parasites due to a shallow depth of field.
• Existing systems require precise autofocus for reliable malaria diagnosis in low-resource settings.

Purpose of the Study:

• To develop and evaluate accurate autofocus methods for the OpenFlexure Microscope.
• To ensure reliable, focused image acquisition for malaria diagnosis.
• To assess autofocus performance considering system limitations like backlash and drift.

Main Methods:

• Implementing and testing autofocus algorithms to identify the focal plane.
• Developing procedures for acquiring image stacks with consistent focus.
• Introducing and evaluating a method to verify autofocus success during image acquisition.
• Analyzing speed, reliability, and precision of autofocus methods.

Main Results:

• Successful identification of focal planes and acquisition of focused image stacks.
• Demonstrated autofocus verification method enhances reliability.
• Evaluation of autofocus methods' speed, precision, and reliability under system constraints.

Conclusions:

• The developed autofocus methods are effective for the OpenFlexure Microscope.
• Reliable autofocus is achievable despite system backlash and drift.
• The system shows potential for supporting malaria diagnosis in resource-limited environments.