Dynamic 3D Scanner Using Variable-Frequency Stripe Pattern
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Solution Overview
Problem
Existing dynamic 3D scanning methods face challenges with calculation efficiency and stability, especially when scanning moving objects, due to the need for coding frames and synchronization delays between cameras and projectors.
Innovation Solution
A method using a variable-frequency stripe pattern projected onto a spatial object, which allows for 3D image reconstruction in a single frame without the need for coding frames, enhancing accuracy and reducing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional coding frames and multiple projection patterns are used for 3D scanning, then measurement precision is improved, but productivity deteriorates due to multiple projections and synchronization delays
Solution Approach 1:
The patent segments the phase information encoding into multiple frequency components within a single projected pattern. By projecting one pattern containing multiple frequencies simultaneously, the system avoids multiple sequential projections while still enabling precise phase measurement through frequency-domain analysis, thus resolving the contradiction between precision and speed
Solution Approach 2:
The patent employs periodic phase-shifted patterns with different frequencies projected in a single frame. The use of periodic functions (sinusoidal patterns) with varying frequencies allows the system to encode multiple phases of information simultaneously, achieving high measurement precision without requiring multiple sequential projections, thereby improving scanning productivity
2Measurement precision
If multiple projection patterns are used for accurate phase unwrapping, then measurement precision is improved, but loss of time increases due to sequential projection requirements
Solution Approach 1:
The patent transforms the problem from temporal dimension (multiple patterns projected sequentially in time) to frequency dimension (multiple frequencies encoded in one spatial pattern). By using frequency multiplication, the system achieves the same phase unwrapping information that would require multiple time-sequential projections, but instead encodes it all in a single projected pattern, eliminating time loss while maintaining precision
3Measurement precision
If synchronized camera-projector system is used for dynamic scanning, then measurement precision is maintained, but device complexity increases due to synchronization requirements
Solution Approach 1:
The patent makes the system self-synchronized by encoding temporal information into the spatial frequency structure of a single projected pattern. The camera captures this single pattern without requiring external synchronization signals with the projector, as all phase information is contained within the spatial frequencies of one static pattern. This eliminates complex synchronization hardware and control systems while maintaining measurement precision
4Measurement precision
If coding frames are used for 3D reconstruction, then measurement precision is improved, but productivity deteriorates due to additional processing steps
Solution Approach 1:
The patent merges the functions of multiple coding frames into a single projected pattern by superimposing multiple frequency components. This single pattern performs the work of multiple separate coding frames, eliminating the need for sequential projection and processing of multiple frames, thus improving processing efficiency while maintaining the precision benefits of coded structured light
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method improves the accuracy and robustness of 3D image reconstruction, especially for moving objects, while reducing computational resources and eliminating synchronization delays.
Implementation Method 1
acquiring an image using a projector to project coded structured light onto a surface of an object to be measured
Implementation Method 2
using a camera to collect a structured light image modulated by the surface of the object
Implementation Method 3
the stripe pattern is a variable-frequency pattern formed with the usage of a periodic function, and the stripe pattern is arranged such that the width/height of its stripes corresponds to an oscillation period si of eight pixels or its multiples
Data Source
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AI summary
A method for dynamic 3D scanning of a spatial object comprising the following steps: projecting (101) a stripe pattern (4) onto a spatial object (5) by a projector (2) of a dynamic 3D scanner (1), wherein the stripe pattern (4) is a variable-frequency pattern formed with the usage of a periodic function, and the stripe pattern (4) is arranged such that the width/height of its stripes corresponds to an oscillation period si of eight pixels or its multiples, where a maximum value of the oscillation period si is limited to a maximum value of the resolution of the projector (2), wherein i = (0,1, ...,n); the stripes form a sequence S of said oscillation periods si, wherein at most three of consecutive oscillation periods si may have the same value, wherein i = (0,1, ..., n); the sum of the oscillation periods si forming the sequence S must be equal to or greater than the maximum value of the resolution of the projector (2), wherein i = (0,1, ...,n); and the method comprises further the steps of capturing (102) by a camera (3) of the dynamic 3D scanner (1) a frame of the spatial object (5) with the stripe pattern (4) onto its surface, generating (103) a map of the probability of qualifying pixels for a reconstruction of a 3D image of the spatial object (5) from the captured frame, thresholding (104) the map of the probability of qualifying pixels for a reconstruction of a 3D image of the spatial object (5) to obtain (105) a shadow mask comprising pixels excluded from the reconstruction of a 3D image of the spatial object (5), correlating (106) the captured frame with the shadow mask to obtain (107) a frame comprising the spatial object (5) with the stripe pattern (4) onto its surface with blanked out pixels excluded from the reconstruction of a 3D image of the spatial object (5), generating (109) a map of the imaginary component of a signal with a variable frequency and a map of the real component of a signal with a variable frequency from the frame comprising the spatial object (5) with the stripe pattern (4) onto its surface with blanked out pixels excluded from said reconstruction, generating (110) a wrapped phase map with a variable frequency from the map of the imaginary component of a signal with a variable frequency and the map of the real component of a signal with a variable frequency, generating (116) a pixel map with data comprising assigned oscillation period numbers and a map of probability values of assigning oscillation period numbers from the wrapped phase map with a variable frequency, filtering out (117) from the pixel map with data comprising assigned oscillation period number areas having on the map of probability values of assigning the oscillation period numbers a value ≤ 0.99, reconstructing (118) the filtered out areas from the pixel map, generating (119) an unwrapped phase map with a variable frequency from the wrapped phase map with a variable frequency and the pixel map with reconstructed (118) filtered out areas, transforming (120) the unwrapped phase map with a variable frequency into an unwrapped phase map with a constant frequency so as to obtain a uniform oscillation period over the entire frequency domain of the unwrapped phase map, reconstructing (121) a 3D image of the spatial object based on the unwrapped phase map with a constant frequency.