A fully automated calibration method for an optical see-through head-mounted operating microscope with variable zoom...

Area of Science:

• Medical Imaging
• Augmented Reality
• Image-Guided Therapy

Background:

• Head-mounted displays (HMDs) are crucial for augmented reality (AR) in image-guided therapy (IGT).
• Accurate calibration between displays and patient coordinates is essential for AR visualization systems.
• Calibrating optical see-through devices, especially those with complex optics like operating microscopes, is challenging due to varying focus and zoom.

Purpose of the Study:

• To present a fully automatic calibration method for the Varioscope M5 AR operating binocular.
• To ensure precise alignment of AR visualizations across all zoom and focus settings.
• To evaluate the accuracy and latency of the developed automatic calibration system.

Main Methods:

• Developed a novel automatic calibration method utilizing a specialized calibration pattern.
• Employed a linear guide system driven by a stepping motor for precise adjustments.
• Integrated custom calibration software for automated process execution.

Main Results:

• Achieved an overlay error of 0.14-0.91 mm in the calibration plane, less than 1% of the field of view.
• Measured maximum spatial displacement due to dynamic latency between 1.1-2.8 mm.
• Determined a disparity between true objects and computed overlays representing a latency of 0.1 seconds.

Conclusions:

• The presented automatic calibration method is accurate and time-efficient for clinical applications.
• This method meets the requirements for standard use of optical see-through AR systems in healthcare.
• The system provides reliable AR visualization crucial for advanced image-guided therapy.