High-accuracy calibration method for an underwater one-mirror galvanometric laser scanner

Area of Science:

• Robotics
• Optical Engineering
• Oceanography

Background:

• Accurate 3D perception is crucial for autonomous underwater robots operating in deep-sea environments.
• Traditional underwater laser scanners face challenges in achieving high calibration accuracy due to installation errors and light refraction.
• Existing methods struggle to compensate for these factors, limiting precise underwater measurements.

Purpose of the Study:

• To propose a high-accuracy calibration method for underwater laser scanners that is independent of installation errors and accounts for refraction.
• To develop a novel approach for calibrating the light-plane cluster in underwater measurement scenarios.
• To enhance the 3D perception capabilities of underwater equipment for autonomous operations.

Main Methods:

• A land-based, installation-error-independent model was developed to calculate the galvanometer shaft axis and light-plane cluster poses using three light planes.
• A 3D model was created to simulate the refractive behavior of the light-plane cluster underwater.
• A partition-based method was proposed for calibrating the underwater light-plane cluster, improving accuracy in submerged conditions.

Main Results:

• The proposed land-based model demonstrated a 2x improvement in calibration accuracy compared to traditional installation-error-dependent models.
• The developed underwater laser scanner achieved measurement accuracies of 11.98 µm in air and 12.75 µm underwater for a standard sphere.
• Measurements in air and underwater conditions showed good agreement, validating the method's effectiveness.

Conclusions:

• The proposed calibration method significantly enhances the accuracy of underwater laser scanners by addressing installation errors and refraction.
• This advancement is vital for improving the 3D perception and autonomous operation of underwater robots.
• The validated high accuracy of the method paves the way for more reliable deep-sea exploration and operations.