High-frequency color-encoded fringe-projection profilometry based on geometry constraint for large depth range.

Area of Science:

• Optical Metrology
• 3D Imaging
• Computer Vision

Background:

• Fringe projection profilometry (FPP) is a key 3D measurement technique.
• Geometry-constraint methods in FPP face limitations in measurement depth range with high-frequency patterns.
• Candidate point selection reliability decreases with reduced depth range.

Purpose of the Study:

• To extend the measurement depth range in high-frequency fringe projection profilometry.
• To develop a novel color-encoded fringe projection method for reliable point selection.
• To enable accurate 3D measurements over extended depth ranges.

Main Methods:

• Color encoding of projected fringe patterns using the hue-saturation-intensity (HSI) color space.
• Direct wrapped phase retrieval using the intensity component.
• Introduction of complementary-hue for correct corresponding point selection.
• Mathematical analysis of color crosstalk effects on phase and color code identification.

Main Results:

• The new method allows reliable candidate point selection with up to six candidate points.
• Phase calculation is independent of color crosstalk.
• Color crosstalk has minimal impact on color code identification.
• High accuracy 3D measurements achieved over a large depth range.

Conclusions:

• The developed color-encoded FPP method significantly extends the measurement depth range.
• The technique ensures high accuracy and reliability, even for isolated objects.
• Utilizes only two high-frequency color-encoded fringe patterns for efficient measurement.