FMCW Lidar Beam Steering Using Rotating Polygon Mirror
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Solution Overview
Problem
Current lidar systems for autonomous vehicles face a trade-off between performance and cost, with high-performance systems being expensive and requiring multiple units to achieve a 360-degree field of view, which is impractical due to the cost and bulkiness of two-dimensional Galvo mirror systems.
Innovation Solution
A Frequency-Modulated Continuous Wave (FMCW) lidar system with a beam steering or scanning arrangement that provides approximately 360-degree horizontal and 20-degree vertical scanning, allowing for fewer lidar units to achieve a comparable scanning field of view without significant movement of electrical components, using a splitter and circulator arrangement to generate multiple channels from a single source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple lidar units are used to achieve 360-degree field of view, then the scanning coverage is improved, but the cost and system complexity increase
Solution Approach 1:
The patent combines multiple scanning functions (horizontal and vertical) into a single lidar unit by integrating a rotating polygon mirror with multiple reflective facets. This allows one lidar unit to perform the work of multiple units, achieving 360-degree horizontal coverage and vertical scanning capabilities simultaneously, thereby reducing the total number of required lidar units and associated system complexity
Solution Approach 2:
The single lidar unit is designed with multi-functional capabilities through the polygon mirror assembly, enabling it to scan across the entire horizontal field of view and vertical angles. The polygon mirror with its multiple facets allows the single unit to perform both horizontal rotation scanning and vertical elevation scanning, making it a universal scanning solution that replaces multiple specialized lidar units
2Measurement precision
If two-dimensional Galvo mirror systems are used for scanning, then the scanning precision is improved, but the cost and bulkiness increase
Solution Approach 1:
The patent replaces the complex two-dimensional Galvo mirror mechanical system with a rotating polygon mirror mechanism. Instead of using two separate galvanometer mirrors for horizontal and vertical scanning, the invention uses a single rotating polygon mirror with multiple facets that can be rotated to different angular positions. This substitution maintains scanning precision while significantly reducing mechanical complexity, cost, and bulkiness of the system
Solution Approach 2:
The patent introduces dynamic rotation of the polygon mirror assembly to achieve both horizontal and vertical scanning. By rotating the entire polygon mirror to different angular positions around the vertical axis, the system dynamically changes the horizontal field of view. Simultaneously, the individual facets of the polygon mirror provide vertical scanning angles. This dynamic mechanism replaces static or separately-controlled Galvo mirror systems with a more integrated and compact solution
3Ease of manufacture
If a single lidar unit is used, then the cost is reduced, but the scanning field of view is limited
Solution Approach 1:
The patent extends the scanning capability from a single plane to three-dimensional space by utilizing the polygon mirror's geometry. The polygon mirror has multiple facets arranged in a specific geometric pattern, allowing the single lidar unit to scan not only horizontally by rotating the entire assembly but also vertically by utilizing the angular arrangement of the facets. This dimensional extension enables a single unit to cover the same field of view that would otherwise require multiple units positioned at different locations
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 configuration reduces the number of lidar units needed, lowers costs, and maintains performance by enabling efficient long-range detection with a simplified scanning mechanism similar to Time-of-Flight systems.
Implementation Method 1
a beam steering arrangement configured to scan the light beam up to a first range in a first directional field of view and to scan the light beam up to a second range in a second directional field of view that is perpendicular to the first directional field of view
Data Source
AI summary
According to one aspect, a coherent lidar system such as a Frequency-Modulated Continuous Wave (FMCW) lidar system may be provided with a beam steering or scanning arrangement which provides three-dimensional scanning. By providing a beam steering or scanning arrangement which provides an approximately 360 degree range of horizontal scanning, and an approximately twenty degree range of vertical scanning, an FMCW lidar system may achieve a scanning field of view that is similar to that of Time-of-Flight (TOF) lidar systems. A FMCW lidar system with three-dimensional scanning may enable fewer FMCW lidar systems to be used to provide a desired overall scanning field of view, and also achieve a comparable overall scanning field of view as a TOF lidar system substantially without issues such as the significant movement of electrical components.