Diffractive Optical Elements for Structured Light Intensity Control
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Solution Overview
Problem
Existing diffractive optical elements (DOEs) struggle with manufacturing process variations and design approximations, leading to significant differences between desired and actual intensity profiles in structured light patterns, which affects the accuracy of surface characterization and depth sensing.
Innovation Solution
A two-dimensional DOE with different periods in orthogonal dimensions is used to generate an aggregated one-dimensional multi-spot pattern, where densely packed small spots overlap to form larger spots with a desired intensity profile, reducing the impact of manufacturing errors and design inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a DOE with small feature size periodic optical structures is used to generate the desired illumination pattern, then the intensity profile can be controlled, but manufacturing process variations and design approximations cause large differences between desired and actual intensity profiles
Solution Approach 1:
The patent divides the optical system into multiple DOEs, where each DOE generates a subset of the desired spots. By segmenting the spot generation across multiple elements, the system reduces the sensitivity of each individual DOE to manufacturing variations, as errors in one DOE affect only a portion of the total pattern rather than the entire intensity profile.
Solution Approach 2:
The patent combines the output patterns from multiple DOEs to form the final illumination pattern. By merging the spot patterns from multiple elements, the system achieves the desired overall intensity profile while benefiting from the statistical averaging effect that reduces the impact of individual manufacturing variations.
2Ease of manufacture
If arbitrary phase profiles are fabricated using semiconductor fabrication or molding processes, then the desired illumination pattern can be generated, but process variations and defects lead to significant deviations from the desired intensity profile
Solution Approach 1:
The patent segments the spot generation function across multiple DOEs, allowing each element to be fabricated with standard processes while maintaining overall pattern accuracy. This segmentation enables the use of mature fabrication techniques without requiring ultra-precise manufacturing for each individual DOE.
Solution Approach 2:
The patent changes the design parameters by using multiple DOEs with different phase profiles rather than a single DOE with complex phase variations. This parameter change allows the system to achieve the desired intensity profile through the combination of simpler, more manufacturable individual elements.
3Ease of manufacture
If design approximations are used in DOE design, then fabrication becomes more feasible, but the actual intensity profile deviates significantly from the desired profile
Solution Approach 1:
The patent merges the output patterns from multiple DOEs, each designed with acceptable approximations, to achieve the desired overall intensity profile. The combination of multiple patterns with minor deviations results in a final pattern that closely matches the target, as errors tend to average out across the merged patterns.
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
This approach allows for the generation of structured light patterns with high tolerance to manufacturing variations and design approximations, resulting in a desired intensity profile while maintaining a higher yield and lower production costs, thus improving the accuracy and reliability of surface characterization and depth sensing applications.
Implementation Method 1
A two-dimensional diffractive optical element (DOE) with different periods in two orthogonal directions may be used to generate an aggregated one-dimensional (1-D) multi-spot pattern
Implementation Method 2
The plurality of densely packed 1-D multi-spot patterns may at least partially overlap with each other at a target plane such that the aggregated light pattern also appears to be a 1-D multi-spot pattern
Data Source
AI summary
Disclosed herein are techniques for structured light pattern generation. A method for generating a one-dimensional structured light pattern in a first direction and with a desired intensity pattern includes generating a plurality of one-dimensional light patterns using a two-dimensional diffractive optical element with different periods in two orthogonal directions, and combining the plurality of one-dimensional light patterns to form the one-dimensional structured light pattern with the desired intensity pattern. Each of the one-dimensional light patterns includes a one-dimensional light pattern in the first direction. The plurality of one-dimensional light patterns is distributed in a second direction different from the first direction. A separation angle between each pair of adjacent one-dimensional light patterns of the plurality of one-dimensional light patterns in the second direction and with respect to the two-dimensional diffractive optical element is less than a threshold value.