360° Scanning LiDAR Head With Risley Prism for Range Accuracy
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Solution Overview
Problem
Monostatic LIDAR sensors face challenges with anomalous range calculations due to scattering and limited dynamic range, especially in applications requiring a 360° field of view, high resolution, and fast frame rates, which are exacerbated by scattering and attenuation of return beams at close and distant ranges.
Innovation Solution
A high-speed 360° scanning LIDAR head utilizing a Risley prism pair assembly with independently rotating angled and reflecting elements, minimizing back-scattering and enhancing dynamic range through a compact design that allows for rapid rotational rates without data and power transmission mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If monostatic LIDAR sensors are used with co-aligned launch and return beams, then the structure is simple and mirror size is small, but scattering of the launch beam is detected at the detector leading to anomalous range calculations
Solution Approach 1:
An optical chopper is introduced as an intermediary component between the launch beam source and the detector. The chopper modulates the launch beam in a time-varying pattern before it reaches the target, and the detector uses this modulation information to distinguish the return beam from scattered light. This mediator enables the system to maintain the simple monostatic structure while eliminating the harmful effect of scattered light detection.
2Measurement precision
If the detector has extremely high dynamic range to detect distant return beams, then the range measurement capability is improved, but the device complexity and cost increase
Solution Approach 1:
The optical chopper applies periodic modulation to the launch beam, creating a time-varying signal pattern. The detector synchronizes with this periodic modulation to identify and measure only the modulated return beam components. This periodic action enables the detector to operate at lower dynamic range by filtering out unmodulated scattered light and background noise, thus reducing the complexity requirements.
3Adaptability or versatility
If optical scanner is used to achieve 360 degree field of view with high resolution, then the scanning coverage is improved, but the device complexity and size increase
Solution Approach 1:
The optical scanning system is segmented into multiple independent scanning mirrors, each responsible for a specific angular sector. Instead of using a single large complex scanner, the system divides the 360-degree field of view into multiple segments that can be scanned by smaller, simpler mirror assemblies. This segmentation reduces the size and complexity of each individual component while achieving the overall wide coverage through coordinated operation.
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 provides a compact, high-speed scanning LIDAR with a 360° field of view, achieving accurate range measurements across a wide dynamic range and fast frame rates, reducing scattering interference and enabling efficient operation in challenging environments.
Implementation Method 1
A high-speed 360° scanning LIDAR head utilizing a Risley prism pair assembly
Implementation Method 2
independently rotating angled and reflecting elements
Implementation Method 3
LIght Detection And Ranging (LIDAR) which measures the time of flight (TOF) of a collimated optical launch beam
Data Source
Figure 1
Figure 2
Figure 2a~3(c)
AI summary
A head for directing radiated energy from a source to a coordinate in a field of view defined by at least one of azimuth and elevation, comprises an angled element and a planar reflecting element. The angled element rotates about a first axis and redirects the beam, the redirection of the angled element differing in at least one of direction and extent as it is rotated. The reflecting surface rotates about a second axis parallel to the first. An axis normal to the surface extends at an angle to the second axis. The reflecting surface receives the redirected beam at a point thereon and reflects it in a direction within the FOV. A rotator may be positioned between the source and the angled element to support and independently rotate the angled element and the reflecting surface about the first and second axes without impeding the energy.