Doppler optical coherence tomography with a micro-electro-mechanical membrane mirror for high-speed dynamic focus...

Area of Science:

• Biomedical Engineering
• Optical Imaging
• Microelectromechanical Systems

Background:

• Doppler optical coherence tomography (DOCT) systems require precise control of optical beam focus for axial scanning.
• Dynamic focus adjustment is crucial for improving imaging resolution and Doppler shift estimation accuracy.

Purpose of the Study:

• To develop and evaluate an electrostatically actuated elliptical microelectromechanical system (MEMS) membrane mirror for dynamic focus adjustment in DOCT.
• To assess the impact of the MEMS mirror on imaging performance, including resolution and Doppler shift estimation precision.

Main Methods:

• An elliptical MEMS membrane mirror was designed and electrostatically actuated at 8 kHz.
• The mirror's optical characteristics, including numerical aperture and spot size, were maintained over a 1mm imaging depth in water.
• Imaging performance was evaluated using gel samples with microspheres and a flow phantom.

Main Results:

• The MEMS mirror successfully adjusted optical beam focus and tracked axial scanning for the DOCT system.
• Constant numerical aperture (approx. 0.13) and spot size (approx. 6.7 microm) were maintained over the imaging depth.
• Improved imaging performance was observed in resolving microspheres and enhanced Doppler shift estimation precision in the flow phantom.

Conclusions:

• The developed MEMS membrane mirror effectively enhances DOCT imaging performance.
• The mirror's small form factor (1.4 mm x 1 mm) facilitates integration into endoscopic systems for in vivo applications.
• This technology holds promise for advancing in vivo endoscopic DOCT imaging.