Optical Phased Array Asymmetry for Main and Grating Lobe Detection
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Solution Overview
Problem
Existing optical systems face challenges in distinguishing between main and grating lobes in optical phased arrays, leading to confusion in LiDAR scenes and loss of light due to grating lobe back-reflections, which can confound the detection process.
Innovation Solution
Implementing optical phased arrays with asymmetric element factors in both transmit and receive apertures, allowing for differential sensitivity to specific regions of the field-of-view, enabling the differentiation between main and grating lobes by comparing detected events across apertures with different far-field angular intensity patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If optical phased arrays use symmetric element factors, then the system is simpler to manufacture and operate, but the ability to distinguish between main and grating lobes deteriorates
Solution Approach 1:
The patent applies asymmetry by using asymmetric element factors in the optical phased array configuration. Specifically, the element factors are designed to be asymmetric functions of the spatial frequency variable u, which creates differential sensitivity to different regions of the field-of-view. This asymmetric design enables the system to distinguish between main lobes and grating lobes by comparing detected events across multiple apertures with different far-field angular intensity patterns, thereby resolving the contradiction between manufacturing simplicity and detection precision.
2Measurement precision
If optical phased arrays use asymmetric element factors, then the detection precision improves, but the device complexity increases
Solution Approach 1:
The patent segments the detection system into multiple receive apertures, each with a specific optical phased array configured according to different element factors. This segmentation allows the system to distribute the complexity across multiple independent units, each handling specific portions of the field-of-view. By comparing events across these segmented apertures, the system achieves enhanced detection precision while managing device complexity through modular architecture.
Solution Approach 2:
The patent implements local quality by assigning different element factors to different receive apertures, creating differential sensitivity across specific regions of the field-of-view. Each aperture is optimized for detecting particular angular regions, allowing the system to achieve high detection precision in each local region while maintaining overall system manageability through localized optimization rather than uniform complexity throughout the entire system.
3Ease of operation
If optical systems use conventional phased arrays, then the system is simpler to operate, but light collection efficiency deteriorates due to grating lobe back-reflections
Solution Approach 1:
The patent converts the harmful grating lobe back-reflections into beneficial detection opportunities. By using asymmetric element factors and multiple receive apertures with different far-field angular intensity patterns, the system can distinguish between main lobe signals and grating lobe signals. The grating lobes, which would normally cause confusion and energy loss, are instead utilized to provide additional spatial information that enhances detection capability when properly processed across the multiple apertures.
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
Enhances light collection efficiency, increases usable field-of-view, and reduces ambiguity errors by effectively distinguishing between main and grating lobes, thereby improving detection accuracy and resolution in LiDAR systems.
Implementation Method 1
a plurality of grating elements arranged along the waveguide according to an element factor associated with the respective OPA
Implementation Method 2
Steering about a first axis perpendicular to the linear distribution can be provided by changing the relative phase shifts in phase shifters feeding each of the emitter elements
Data Source
AI summary
An apparatus comprises: at least one transmit aperture configured to provide an optical beam having a far-field angular intensity pattern comprising first and second lobes at first and second angular positions; and a plurality of receive apertures configured to receive optical beams, each receive aperture comprising a respective optical phased array (OPA) formed by a plurality of antenna elements, where each antenna element comprises: a waveguide coupled to a phase shifter, and a plurality of grating elements arranged along the waveguide according to an element factor; wherein the element factors associated with at least two different OPAs of respective receive apertures correspond to different respective far-field angular intensity patterns that at least partially overlap; wherein the far-field angular intensity pattern of the at least one transmit aperture at least partially overlaps with the far-field angular intensity patterns of the at least two different OPAs of respective receive apertures.