Coaxial LiDAR Optical Module Layout for Walk-Off Angle Compensation
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Solution Overview
Problem
The existence of a walk off angle in scanning lidars causes a decrease in the strength of the return light signal, affecting ranging performance due to the returned light beam not irradiating at the center of the receiving end.
Innovation Solution
An optical module with a coaxial optical design that includes an optical emitting module, coaxial optical module, scanning module, and optical receiving module, where the optical receiving module is offset to compensate for the walk off angle, ensuring the returned light beam aligns closer to the center of the receiving region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a scanning module rotates or swings to scan object space, then the detection coverage and scanning capability are improved, but a walk off angle is generated causing the returned light beam to deviate from the center of the receiving end, reducing signal strength
Solution Approach 1:
The receiving end is positioned asymmetrically relative to the scanning module, specifically offset from the optical axis by a distance of (0.3-0.5)×D where D is the diameter of the receiving end. This asymmetric positioning compensates for the walk off angle generated during scanning, ensuring that the returned light beam consistently strikes the center of the receiving end regardless of the scanning angle, thereby maintaining signal strength while preserving detection coverage.
Solution Approach 2:
The patent changes the positional parameter of the receiving end from being centered on the optical axis to being offset by a specific distance. This parameter modification (offset distance = (0.3-0.5)×D) directly addresses the walk off angle issue, allowing the system to maintain reliable signal reception throughout the scanning range while keeping the scanning module functional.
2Productivity
If the scanner moves rapidly to improve scanning speed, then productivity is improved, but the walk off angle increases causing greater deviation of the returned light beam, worsening signal loss
Solution Approach 1:
The asymmetric positioning of the receiving end creates a geometric compensation mechanism that counteracts the walk off angle. The offset distance of (0.3-0.5)×D is specifically designed to match the maximum expected walk off angle during rapid scanning, ensuring that even at high scanning speeds, the returned light beam remains centered on the receiving end, minimizing signal loss while maintaining high productivity.
Solution Approach 2:
The receiving end is pre-positioned with an offset before scanning begins. This preliminary arrangement creates an anti-action that counterbalances the walk off angle that will be generated during scanning. By anticipating and compensating for the deviation in advance, the system prevents signal loss rather than attempting to correct it during operation, enabling rapid scanning without energy loss.
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 design improves the validity of the received echo signal and detection performance by accurately receiving the returned light beam, reducing signal loss and enhancing detection precision.
Implementation Method 1
The optical emitting module is configured to transmit a first light beam to the coaxial optical module
Implementation Method 2
the first light beam may be reflected by the target object in the object space, to obtain a first reflected light beam
Data Source
Figure 1~2
Figure 3~4
Figure 5~6A
AI summary
An optical module (20), a lidar, and a terminal are provided, and are used in the field of detection technologies. The optical module (20) includes an optical emitting module (201), a coaxial optical module (202), a scanning module (203), and an optical receiving module (204). During emission, a first light beam is propagated to object space successively through the optical emitting module (201), the coaxial optical module (202), and the scanning module (203). During receiving, a first returned light beam is propagated to the optical receiving module (204) successively through the scanning module (203) and the coaxial optical module (202), and a first included angle exists between the first light beam that has passed through the coaxial optical module (202) and the first returned light beam that has not reached the coaxial optical module (202) yet. A first offset exists between a position of the optical receiving module (204) and an ideal received light beam of the first light beam, to compensate for an angle offset of the first returned light beam, so that a light spot of the first returned light beam is closer to an effective receiving region of the optical receiving module (204), or even overlaps with a center of the effective receiving region. In this way, a signal loss caused by a walk off angle can be reduced, echo validity can be improved, and detection performance can be improved.