All-optical microscope autofocus based on an electrically tunable lens and a totally internally reflected IR laser

Area of Science:

• Microscopy and Imaging Technologies
• Optical Physics
• Biomedical Engineering

Background:

• High-resolution microscopy requires precise focus stabilization over extended periods.
• Conventional autofocus systems rely on mechanical components like piezoelectric stages or objective actuators.
• Existing methods for focus detection include image analysis and infrared light intensity measurement.

Purpose of the Study:

• To develop a novel, all-optical autofocus system for microscopes.
• To enable rapid and precise focus stabilization without mechanical movement.
• To provide a cost-effective alternative to existing autofocus technologies.

Main Methods:

• Implementation of an electrically tunable lens for focus adjustment.
• Utilizing a totally internally reflected infrared probe beam for defocus detection.
• Development of a feedback loop based on the lateral position of the infrared laser on a quadrant photodetector.
• Addressing combined contributions from mechanical defocus and tunable lens deformation.

Main Results:

• Achieved focus stabilization at rates up to hundreds of Hertz.
• Demonstrated autofocus capability without any mechanical movement of the microscope stage or objective.
• The system exclusively uses reflective optics.
• Significant cost reduction compared to comparable piezo-based actuators.

Conclusions:

• The proposed all-optical autofocus system offers high-speed, precise, and non-mechanical focus stabilization.
• This technology is suitable for long-term, high-resolution microscopic imaging.
• The system presents a more affordable and efficient solution for advanced microscopy applications.