Hermitian Symmetric Coded Light Pattern for Depth Sensing
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Solution Overview
Problem
Existing active sensing technologies face issues with accuracy due to patterns causing 'ghost images' and eye safety concerns, and complex patterns are expensive to manufacture, affecting the reliability and cost-effectiveness of 3D reconstruction.
Innovation Solution
A hermitian symmetric coded light pattern is generated using a diffractive optical element (DOE) with a tessellated binary codebook pattern that satisfies specific codeword constraints, eliminating ghost images and reducing the intensity of the zero-order beam, thereby improving accuracy and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex pattern is used to provide adequate depth estimation resolution, then measurement precision is improved, but manufacturing cost increases due to expensive multi-stage, multi-mask photolithographic process
Solution Approach 1:
The patent applies asymmetry by using a hermitian symmetric pattern (which has specific symmetry properties) rather than a completely symmetric or asymmetric pattern. This symmetry constraint simplifies the manufacturing process while maintaining the ability to provide adequate depth estimation resolution. The hermitian symmetry allows the pattern to be manufactured using a single-mask photolithographic process, reducing manufacturing complexity and cost compared to multi-stage processes required for arbitrary complex patterns.
2Device complexity
If a conventional pattern is used for active sensing, then device complexity is simple, but ghost images are generated causing interference during depth sensing
Solution Approach 1:
The patent uses hermitian symmetric patterns which have specific symmetry properties that eliminate ghost images while maintaining relatively simple device complexity. The symmetry constraints on the pattern design prevent the formation of ghost images that would otherwise interfere with depth sensing, thereby improving reliability without significantly increasing device complexity.
3Ease of manufacture
If a conventional pattern is used for active sensing, then manufacturing cost is low, but a large zero-order beam is created causing eye safety issues
Solution Approach 1:
The hermitian symmetric pattern design inherently reduces the intensity of the zero-order beam compared to conventional patterns. This reduction in zero-order beam intensity mitigates eye safety issues while maintaining manufacturing cost-effectiveness. The symmetry constraints guide the light distribution in a way that disperses energy more evenly, preventing concentration in the zero-order beam.
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 hermitian symmetric pattern enhances depth sensing accuracy, reduces ghost images, and lowers manufacturing costs by using a single-mask photolithographic process, making it suitable for structured light systems.
Implementation Method 1
a diffractive optical element (DOE) with a tessellated binary codebook pattern
Data Source
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AI summary
A method includes identifying one or more codewords of a bit sequence that fail to satisfy at least one codeword constraint. The method also includes removing the one or more codewords from the bit sequence to generate a punctured bit sequence. The method further includes determining whether the punctured bit sequence is symmetric. The method includes, in response to determining that the punctured bit sequence is symmetric, generating a hermitian symmetric codebook primitive based at least in part on the punctured bit sequence, where the hermitian symmetric codebook primitive is useable to form a diffractive optical element (DOE) of a structured light depth sensing system.