Structured Light Projection Module Speckle Uniformity
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Solution Overview
Problem
Current micro structured light projection modules face challenges in achieving uniform speckle density distribution and high irrelevance of speckle patterns, which affect the accuracy of depth image calculation, due to the diffraction properties of diffractive optical elements and the arrangement of VCSEL array chips.
Innovation Solution
A structured light projection module is designed with a light source comprising a plurality of sub-light sources arranged in a two-dimensional array, a lens for converging the beams, and a diffractive optical element that projects speckle patterns with specific relationships between adjacent image patterns, including overlapping, adjoining, and spacing relationships, to ensure uniform density and high irrelevance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a VCSEL array chip with multiple sub-light sources is used, then the volume and power consumption are reduced, but the speckle patterns exhibit non-uniform density distribution due to synchronous diffraction of sub-light sources
Solution Approach 1:
The patent divides the diffraction process into separate stages: first diffracting individual sub-light sources to generate sub-speckle patterns, then combining these patterns through controlled overlapping. This segmentation allows independent optimization of each sub-pattern while achieving uniform overall distribution, resolving the contradiction between using multiple sub-light sources and maintaining speckle uniformity.
Solution Approach 2:
The patent merges multiple sub-speckle patterns generated by different VCSELs into a unified speckle pattern through controlled overlapping. By designing the DOE to combine these patterns with appropriate spatial relationships, the system achieves both the compactness of VCSEL arrays and the uniformity of speckle distribution, eliminating the non-uniformity caused by synchronous diffraction.
2Length of moving object
If the diffraction angle of the DOE is increased, then the divergence angle is reduced, but the distribution density of speckles decreases gradually
Solution Approach 1:
The patent applies local quality by designing different regions of the DOE with different diffraction characteristics. Certain areas are optimized for high diffraction angles to produce dense speckles, while other areas provide lower diffraction angles. This spatial variation in diffraction properties allows simultaneous achievement of appropriate divergence angle and speckle density distribution.
3Reliability
If random arrangement of VCSEL array chip and sub-speckle patterns is used, then irrelevance is improved, but uniformity of speckle density distribution decreases
Solution Approach 1:
The patent introduces asymmetric design elements in the DOE structure to break the symmetry between sub-speckle patterns. By creating asymmetric diffraction patterns that do not mirror each other, the system achieves higher irrelevance while maintaining uniform density distribution through controlled asymmetric overlapping of patterns from different VCSELs.
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 solution results in speckle patterns with higher irrelevance and uniform density distribution, enhancing the accuracy of three-dimensional measurements in depth cameras.
Implementation Method 1
the nonuniform density distribution is determined by the diffraction property of the DOE, that is, with the increase of the diffraction angle (or the increase of the diffraction order) of the DOE, the distribution density of speckles may decrease gradually
Implementation Method 2
a lens, receiving and converging the two-dimensional patterned beams
Data Source
AI summary
A structured light projection module, a depth camera, and a method for manufacturing the structured light projection module are provided. The module comprises: a light source, comprising a plurality of sub-light sources that are arranged in a two-dimensional array and configured to emit two-dimensional patterned beams corresponding to the two-dimensional array, and the two-dimensional patterned beams comprising two-dimensional patterns; a lens, receiving and converging the two-dimensional patterned beams; and a diffractive optical element, receiving the two-dimensional patterned beams converged and emitted from the lens, and projecting speckle patterned beams corresponding to speckle patterns. The speckle patterns comprise a plurality of image patterns corresponding to the two-dimensional patterns, and the image patterns are rotated by an angle such that edges of the image patterns are not in parallel with a baseline between the structured light projection module and a capture module.