Stray Light Filter Structures for LiDAR Detector Arrays
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Solution Overview
Problem
LiDAR systems employing sensitive silicon photomultiplier (SiPM) arrays face limitations in detection performance due to degradation of signal-to-noise ratio caused by stray light, despite the use of narrow-band spectral filters and black-painted baffles, which are not always sufficient in attenuating unwanted light.
Innovation Solution
The implementation of stray light filter structures, including micro lens arrays with pinhole arrays and bandpass optical filters, as well as slit filters, to further attenuate stray light and optimize the optical path, reducing the transmitter laser power required and overall system power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If narrow-band spectral filters and black-painted baffles are used to reduce stray light, then stray light attenuation is improved, but detection performance is still degraded due to insufficient attenuation
Solution Approach 1:
The optical path is divided into multiple segments with dedicated stray light filters at different locations. Each filter (aspherical lens, pinhole array, microlens array) addresses stray light from specific sources or angles, providing comprehensive attenuation that single filters cannot achieve
Solution Approach 2:
Aspherical lens elements are introduced as intermediary components between the transmitter and detector arrays. These lenses refract and redirect stray light away from the detectors while allowing return light to pass through, acting as mediators that separate useful light from harmful stray light
2Length of moving object
If high transmitter laser power is used to detect objects at long distance, then detection distance is improved, but power consumption increases
Solution Approach 1:
The patent converts the harmful effect of stray light into a beneficial filtering mechanism. By strategically placing filters and optical elements, stray light paths are redirected and concentrated into specific regions away from the detectors, while return light paths remain unaffected. This transforms the problematic stray light into a controllable optical element that enhances rather than degrades performance
Solution Approach 2:
The optical system parameters are optimized to maximize return light collection efficiency. The aspherical lens curvature, pinhole array geometry, and microlens focal lengths are specifically designed to match the optical characteristics of the transmitter and detector arrays, improving the signal strength without increasing transmitter power
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
These filter structures effectively reduce stray light, enhancing the signal-to-noise ratio and enabling LiDAR systems to detect objects at longer distances with reduced power consumption, thereby improving detection performance.
Implementation Method 1
an aspherical lens positioned in the return optical path between the collection lens and the detector array to reduce stray light scattering
Implementation Method 2
a microlens array positioned in the return optical path between the pinhole array and the detector array
Implementation Method 3
bandpass optical filters, as well as slit filters
Data Source
AI summary
Embodiments of the present disclosure provide stray light filter structures in light detection and ranging (LiDAR) systems to attenuate stray light and reduce unwanted scattering. In some embodiments, a micro lens array is used together with a pinhole array to block stray light in the optical path just prior to the photodetector. In some embodiments, a bandpass optical filter is used in the optical path prior to the microlens array. In other embodiments, a slit filter is used further upstream in the optical path to block unwanted stray light and allow returning signal light to pass to imaging optics that provide a returning signal light image at a photodetector. In some embodiments, the imaging optics include a collimating lens and a focusing lens. In some embodiments, an optical bandpass filter is positioned on the optical path between the collimating lens and the focusing lens to reject light that is outside of a an expected wavelength range for returning signal light. These and other embodiments and details are further disclosed herein.