Superlarge depth range 3D measurement based on dual-focal optimization strategy

Area of Science:

• Optical Metrology
• 3D Measurement Technologies

Background:

• Fringe projection profilometry (FPP) is a key high-accuracy 3D measurement technique.
• Binary defocusing methods enhance FPP speed but limit measurement depth to isolated regions.
• Existing optimizations primarily extend the front of these limited depth ranges.

Purpose of the Study:

• To develop a novel strategy for expanding the measurement depth range in FPP.
• To overcome the limitations of isolated depth ranges in traditional binary defocusing systems.
• To achieve a super-large and continuous measurement depth range.

Main Methods:

• Proposed a dual-focal optimization strategy using a cylindrical lens group.
• Simultaneously adjusted projector focal lengths in meridian and sagittal planes.
• Optimized focal lengths based on light field distribution properties to expand the proper defocusing region.

Main Results:

• Successfully created a larger, continuous proper defocusing region.
• Increased the measurement depth range from two isolated ranges (120 mm and 650 mm) to a single range of 950 mm.
• Acquired improved measurement results over the expanded depth range.

Conclusions:

• The dual-focal optimization strategy effectively overcomes the depth limitations of traditional FPP binary defocusing methods.
• This approach enables a super-large and continuous measurement depth range.
• The method offers enhanced performance for high-accuracy 3D measurements across a wider range.