High-accuracy differential autofocus system with an electrically tunable lens.

Area of Science:

• Optical microscopy
• Biophotonics
• Instrumentation

Background:

• Accurate focusing is critical for high-resolution microscopy.
• Existing autofocus systems face limitations in speed and precision.
• Differential detection methods offer potential for enhanced autofocus performance.

Purpose of the Study:

• To develop a high-speed, ultra-sensitive autofocus system for microscopy.
• To implement an electrically tunable lens (ETL) for differential detection in autofocus.
• To improve signal-to-noise ratio by minimizing optical interference.

Main Methods:

• Utilized an electrically tunable lens (ETL) for dynamic focal length adjustment.
• Implemented differential detection at speeds below 300 Hz.
• Employed pupil segmentation to prevent interference between outgoing and incoming beams.
• Achieved focus drift accuracy better than 1/22 focal depth (~20 nm with a 100x objective).

Main Results:

• Demonstrated selective locking onto desired focal layers.
• Enabled high-speed differential operations near the focal plane.
• Significantly improved signal-to-noise ratio through pupil segmentation.
• Attained sub-20 nm focus drift accuracy, showcasing ultra-sensitivity.

Conclusions:

• The proposed quasi-confocal microscopy autofocus system offers a novel and effective solution.
• The integration of ETL and pupil segmentation enhances autofocus performance.
• This system provides a new implementation pathway for advanced microscopy techniques.