Scanning Mirror Cover Optics for Wide-Angle LiDAR Beam Collimation
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Solution Overview
Problem
Current LIDAR scanner transmitting devices face limitations in achieving large scanning angles due to the restricted deflection range of MEMS mirrors, leading to increased complexity, weight, and cost, as well as Fresnel losses and unwanted reflections from traditional cover elements.
Innovation Solution
A transmitting device with a scanning mirror protected by a cover element featuring a toroidal entrance surface for pre-collimation and a monocentric hemispherical shell for minimal reflections, allowing multiple laser beams to converge at a single point on the mirror, reducing adjustment needs and maintaining compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional flat plate cover element is used, then the scanning mirror is protected, but Fresnel losses increase and unwanted reflections occur
Solution Approach 1:
The patent applies a curved cover element with a specific radius of curvature that matches the scanning mirror's surface. This curvature allows laser beams to strike the cover element at normal incidence regardless of the mirror's deflection angle, eliminating Fresnel losses and unwanted reflections while maintaining protection of the scanning mirror.
2Adaptability or versatility
If multiple MEMS mirrors are used to increase scanning angle range, then the scanning angle range increases, but device complexity and weight increase
Solution Approach 1:
The patent employs a single MEMS scanning mirror that can dynamically deflect over an extended angle range (±45° or more) through optimized hinge design and drive mechanisms. This dynamic capability allows one mirror to replace multiple static mirrors, reducing device complexity while maintaining or expanding the scanning angle range.
Solution Approach 2:
The patent modifies the physical parameters of the MEMS mirror system, including the hinge flexibility, mirror size, and drive voltage ranges, to enable larger deflection angles. By changing these parameters, a single mirror achieves the scanning capability previously requiring multiple mirrors, thereby reducing overall device complexity.
3Adaptability or versatility
If the scanning mirror deflection angle is increased, then the scanning angle range increases, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes flexible hinge structures made from thin film materials that allow the MEMS mirror to achieve large deflection angles. These flexible hinges are manufactured using standard semiconductor fabrication processes, enabling large-angle scanning without increasing manufacturing complexity. The thin film structure provides the necessary flexibility while maintaining compatibility with existing manufacturing techniques.
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 achieves low Fresnel losses, minimizes unwanted reflections, and maintains a compact, low-adjustment design, enabling efficient scanning over larger angles while reducing manufacturing complexity and weight.
Implementation Method 1
The cover element (4) has, in the coupling-in region (4.1), a toroidal entry surface (5.1) for pre-collimating the at least one laser beam (S1, S2, S3) in the direction of the fast axis (fa)
Implementation Method 2
the at least one laser beam (S1, S2, S3), after reflection at the scanning mirror (2)
Implementation Method 3
and, in the coupling-in region (4.1), at least one toroidal exit surface (5.2 1, 5.2 2, 5.2 3) for pre-collimating the at least one laser beam (S1, S2, S3) in the direction of the slow axis (sa)
Data Source
Figure 1a~1c
Figure 2a~2b
Figure 3a~3b
AI summary
A transmitter device preferably containing at least two laser diodes (11, …, 1n) and a scanning mirror (2) that is deflectable about its center point (MP) and is arranged within a housing (3) with a transparent covering element (4). At least in one output coupling region (4.2), the covering element (4) is formed by a section of a monocentric hemispherical shell (HK) with a center of curvature (K), arranged covering the scanning mirror (2) in such a way that the center of curvature (K) and the center point (MP) of the scanning mirror (2) coincide, and, in an input coupling region (4.1), it is formed by an optical block (5) having a toroidal input face (5.1), at least one toroidal output face (5.21) and at least two first mirror faces (5.31) arranged therebetween for deflecting and pre-collimating the laser beams (S1, …, Sn).