Fiber Tip Reimaging in Scanning LiDAR for Signal Coupling
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Solution Overview
Problem
Traditional LIDAR systems suffer from significant signal degradation due to decentering at the fiber tip caused by fast scanning mirror rotation, leading to reduced measurement range and increased power requirements, especially in frequency-modulated systems.
Innovation Solution
The fiber tip is re-imaged onto the center of rotation of the scanning mirror, minimizing decenter errors and using nondegenerate laser sources with wavelength division multiplexing techniques to enhance measurement range and reduce optical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fast scanning mirror rotational velocity is increased to increase frame rate, then productivity is improved, but the target signal strength deteriorates due to misalignment at the fiber tip
Solution Approach 1:
Instead of moving the fiber tip with the scanning mirror to maintain alignment, the patent inverts the approach by keeping the fiber tip stationary at the center of rotation and using a fixed scanning mirror. This eliminates the misalignment problem while maintaining high scanning speeds, as the beam path is stabilized rather than the detector position.
Solution Approach 2:
The patent introduces a beam combining optics system that acts as an intermediary between the scanning mirror and the fiber tip. This intermediary system ensures that the returned light from the fast scanning mirror is properly directed to the stationary fiber tip, maintaining coupling efficiency even at high scanning velocities.
2Measurement precision
If a single mode fiber with small core diameter is used to improve measurement precision, then measurement precision is improved, but the system becomes more sensitive to misalignment
Solution Approach 1:
The patent eliminates the need to move the fiber tip by inverting the traditional scanning approach. The fiber tip remains stationary at the center of rotation, eliminating alignment sensitivity issues while maintaining the use of single mode fibers for precise range measurements through coherent detection.
3Measurement precision
If phase drift is induced into the scanning to improve gaze characteristics, then measurement precision is improved, but the system complexity increases
Solution Approach 1:
Instead of inducing phase drift into the scanning motion to improve gaze characteristics, the patent inverts the approach by using a stationary fiber tip at the center of rotation with a fixed scanning mirror. This eliminates the need for complex phase drift compensation while maintaining or improving measurement precision through stable optical coupling.
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 improves signal coupling efficiency, increases measurement range, and reduces system size by eliminating the need for a second scanning mirror, while enabling simultaneous range and velocity measurements with immunity to crosstalk.
Implementation Method 1
an optic, such as re-imaging lens 512, is provided between the optical fiber and the first scanning mirror 506, and the re-imaging lens 512 is configured to focus the laser beam emitted from the optical fiber 502 on or close to the center of rotation 516
Implementation Method 2
This lens collimates the divergent laser beam which is subsequently reflected by the second scanning mirror 508 toward the scene 510
Implementation Method 3
using nondegenerate laser sources with wavelength division multiplexing techniques to enhance measurement range and reduce optical losses
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A light detection and ranging (LIDAR) system 500 is provided that includes first and second optical scanning mirrors 506, 508 to steer a laser beam emitted from the tip of an optical fiber 504 to scan a scene 510, and collect light incident upon any objects in the scene that is returned to the fiber tip 504. The LIDAR system 500 further includes a re-imaging lens 512 located between the optical fiber and scanning mirror 506, and an optic 514 located between the scanning mirror and the scene. The re-imaging lens 512 focuses the laser beam emitted from the optical fiber 504 on or close to the first scanning mirror's center of rotation and thereby re-image the fiber tip at or close to the center of rotation, from which the laser beam is reflected as a divergent laser beam. And the optic is configured to collimate or focus the divergent laser beam from the first scanning mirror 506 that is launched toward the scene 510. The first and second scanning mirrors 506, 508 rotate along orthogonal axes to steer the laser beam across the scene 510 according to a scanning pattern. In some examples, the first scanning mirror 506 is rotatable with a faster angular velocity than the second scanning mirror 508 to scan the scene 510 according to a scanning pattern. In some examples, the optic is a collimator 514 which may alternatively be located between the second scanning mirror 508 and the scene 510. In other examples, the collimator 514 may be replaced with a focus lens configured to focus the divergent laser beam from the scanning mirror to produce a focused laser beam.