Multi-color Surface Inspection via Wavelength-multiplexed Phase-shifting

The patent combines multiple phase-shifted spatial light intensity patterns into a single captured image by illuminating the surface with multiple wavelength regimes simultaneously. Each wavelength regime corresponds to a different phase shift, allowing the system to capture all phase information in one shot rather than requiring multiple sequential acquisitions. This merging of temporal sequences into a spatial multiplexing scheme resolves the contradiction by eliminating the time delay between acquisitions while maintaining the precision benefits of phase-shifting interferometry.

The patent transitions from temporal dimension (multiple sequential images taken at different times) to spatial dimension (multiple phase-shifted patterns encoded in different wavelength regimes captured simultaneously). By using wavelength-multiplexed illumination where each color channel represents a different phase shift, the system encodes what would traditionally require time separation into spatially distinguishable channels, thereby capturing all phase information in a single instantaneous capture.

The patent merges multiple phase-shifted measurements into a single captured image by using simultaneous multi-wavelength illumination. All phase-shifted spatial light intensity patterns are projected at the same moment across different wavelength regimes, and the camera captures them all in one exposure. This eliminates the temporal separation that causes orientation variations in sequential acquisitions, thereby maintaining measurement precision while improving reliability through consistent spatial relationships.

The patent adapts the traditional static phase-shifting approach (which assumes fixed spatial relationships) to a dynamic environment by making the illumination adaptive across wavelength regimes. Instead of requiring the entire system to be static, the system dynamically assigns different phase shifts to different wavelengths and captures them simultaneously, allowing the measurement to remain valid even when the object or camera moves during the capture process.

The patent uses wavelength as an additional dimension to encode phase information, transitioning from a single spatial channel to multiple spectral channels. By projecting phase-shifted patterns at different wavelengths simultaneously and capturing them with a color camera, the system creates spectral-multiplexed measurements that are insensitive to spatial misalignment. This allows precise surface inspection of moving objects without requiring fixed spatial relationships between the illumination source, camera, and surface.

The patent changes the illumination parameter from monochromatic to multi-wavelength, where each wavelength regime carries a different phase shift. This parameter change allows the system to encode multiple measurements in parallel across the spectral domain, making the inspection process adaptable to moving surfaces while maintaining measurement precision through wavelength-based differentiation rather than temporal sequencing.

The patent makes the single camera serve multiple functions by using its color sensing capability to detect multiple wavelength regimes simultaneously. Instead of requiring separate monochrome cameras for each phase shift, the system uses a standard color camera to capture all phase-encoded wavelength information in one shot. This multi-functionality approach reduces the number of required sensors while maintaining the time efficiency of single-shot acquisition.

The patent uses periodic phase-shifting patterns encoded in different wavelength regimes, where each color channel undergoes a cyclic phase variation. By synchronizing the illumination patterns across wavelengths and capturing them simultaneously, the system leverages the periodic nature of the phase shifts to extract surface information from the combined signal, reducing acquisition time while managing system complexity through coordinated temporal-spectral modulation.