LiDAR Coupler Microlens Layout for Numerical Aperture Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LiDAR devices face challenges in achieving high coupling efficiency for light reflected from objects due to mismatches in numerical apertures between waveguide-to-free-space couplers and collimating optical systems, leading to signal-to-noise ratio (SNR) issues and reduced accuracy in distance measurements.
Innovation Solution
The implementation of microlenses with tailored numerical apertures and configurations to match and transform angular light energy distributions, reducing the mismatch between couplers and collimating optics, thereby improving coupling efficiency and SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If collimating optics with an exactly flat object field are used to position waveguide-to-free-space couplers precisely in the focal plane, then coupling efficiency is improved, but the device becomes large, heavy and expensive
Solution Approach 1:
An array of microlenses is introduced as an intermediary optical element between the waveguide-to-free-space couplers and the collimating optics. The microlenses perform preliminary focusing and angular transformation of the light beams, enabling the use of simpler, lighter collimating optics while maintaining precise coupling efficiency. The microlenses act as a mediator that bridges the gap between the planar coupler array and the curved focal field required by simple collimating optics.
2Measurement precision
If microlenses with increased numerical aperture are added to improve coupling efficiency, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The optical system is segmented into distinct functional modules: the waveguide-to-free-space couplers, the array of microlenses with tailored numerical apertures, and the collimating optics. Each segment performs a specific optical function, allowing for independent optimization and simplification. The microlenses are arranged in a regular array pattern, which simplifies manufacturing and alignment while achieving the desired angular transformation and numerical aperture matching.
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
Enhances the fraction of light coupled into waveguides, resulting in improved signal-to-noise ratio and accuracy of distance measurements, without increasing size, weight, or cost of the collimating optics.
Implementation Method 1
Each microlens has, on a side pointing towards the couplers, a coupler-side numerical aperture, and on a side pointing towards the collimating optical system a collimator-side numerical aperture that is greater than the coupler-side numerical aperture
Implementation Method 2
Each microlens is associated with one of the couplers and forms a real or virtual image of the associated coupler
Data Source
Figure 1~4
Figure 5~6
Figure 7~8
AI summary
A LiDAR device (14) for scanning measurement of a distance to an object (12) comprises a photonic integrated circuit (52) with a plurality of optical waveguides (38) and a plurality of couplers 40). Each coupler (40) emits light guided in the optical waveguide (38) into free space and/or couples light propagating in free space into the optical waveguide (38). A collimating optical system (44) collimates light beams emitted by the couplers (40) and/or focuses collimated light beams. Microlenses (54; 54a, 54b) form real or virtual images of associated couplers (40), said images being arranged in an object field (56) of the collimating optical system (44). The collimating optical system (44) has a collimator numerical aperture which is greater than each of the coupler numerical apertures. Each microlens (54; 54a, 54b) has a collimator-side numerical aperture that is greater than its coupler-side numerical aperture. In this manner, insertion losses caused by NA mismatch are reduced.