Lidar Scan Mirror Cover Geometry for Low-Loss Wide-Angle Scanning
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Solution Overview
Problem
LIDAR scanner transmitting devices face limitations in achieving large scanning angle ranges due to the limited deflection angle of MEMS mirrors and the introduction of Fresnel losses and unwanted reflections when using cover elements like flat plates or gradient index lenses.
Innovation Solution
A transmitting device with a scanning mirror protected by a monocentric hemispherical shell cover element, where the laser beams are pre-collimated before passing through the cover, ensuring minimal Fresnel losses and no unwanted reflections by aligning the beam axis with the center of curvature of the hemispherical shell, maintaining beam collimation and integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flat plate cover element is used to protect the MEMS mirror, then the mirror is protected, but Fresnel losses and unwanted reflections occur
Solution Approach 1:
The patent applies a hemispherical cover element instead of a flat plate. The hemispherical shape is centered at the MEMS mirror's pivot point, creating a curved optical path that eliminates Fresnel losses and unwanted reflections while maintaining mirror protection. This curvature transformation resolves the contradiction between protection and optical loss.
2Adaptability or versatility
If multiple MEMS mirrors are used to achieve larger scanning angle range, then the scanning angle increases, but device complexity and synchronization requirements increase
Solution Approach 1:
The patent changes the optical parameters by introducing a hemispherical cover element that modifies the optical path. This allows a single MEMS mirror to achieve effective larger scanning coverage by eliminating optical losses that previously limited the scanning angle, avoiding the need for multiple mirrors and their associated synchronization complexity.
3Adaptability or versatility
If the laser beam is directed at the cover element at different angles, then multiple scan angle areas are covered, but the cover element influences each beam differently causing optical losses
Solution Approach 1:
The hemispherical cover element creates a geometry where laser beams traveling at different angles to cover multiple scan areas all pass through the cover at optimal angles, eliminating differential Fresnel losses. The spherical curvature ensures uniform optical performance across the entire scanning range.
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 allows for larger scanning angle ranges with reduced optical losses and reflections, enhancing the performance and compactness of LIDAR scanners while maintaining beam quality and reducing manufacturing complexity and costs.
Implementation Method 1
All other beams of the laser beam S 1 ,..., S n (more accurately, one should speak of a laser beam bundle) are inevitably refracted at the interfaces
Implementation Method 2
A pre-collimated laser beam S 3 coming from the emitting device 1 is completely collimated by passing twice through the hemispherical shell HK
Implementation Method 3
the hemispherical shell HK acting as a diverging lens. The unavoidable optical effect of the hemispherical shell HK is compensated according to the invention by directing the laser beam S 1 ,..., S n from the emission device 1 onto the cover element 4 in a pre-collimated state
Implementation Method 4
A laser beam striking the cover element—this may also apply to multiple laser beams directed at the scanning mirror, and to each of the laser beams after reflection from the scanning mirror—consequently experiences Fresnel losses depending on the angle of incidence on the flat plate
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
The invention relates to a transmitting device, containing an emitting device (1) and a scanning mirror (2), which can be deflected about the center point (MP) of the scanning mirror and which is arranged within a housing (3) having a transparent cover element (4). The cover element (4) is formed, at least in an outcoupling region (4.2), by a portion of a monocentric hemisphere shell (HK) having a curvature center point (K) and is arranged covering the scanning mirror (2) in such a way that the curvature center point (K) and the center point (MP) of the scanning mirror (2) coincide.