Lidar Receiver Non-Circular Spatial Filter Ambient Light Suppression
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Solution Overview
Problem
Lidar systems face challenges in effectively distinguishing between backscattered light pulses from objects at various distances due to the dynamic range of signal strength and the presence of ambient light, which can lead to reduced accuracy and increased complexity in detecting weak signals from distant objects.
Innovation Solution
A receiver module with a non-circular light-transmissive mask is used to spatially filter light, allowing transmission of light pulses at a range of incidence angles while suppressing ambient light, and a sensitive photodetector is employed to enhance detection capabilities, particularly for weak signals from distant objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circular spatial filter is used to block ambient light, then ambient light suppression is improved, but light transmission from distant objects at various incidence angles is blocked
Solution Approach 1:
The patent applies asymmetry by replacing the conventional circular spatial filter with a non-circular aperture having an aspect ratio greater than 1:1. This asymmetric shape is specifically oriented to match the elliptical projection of the laser beam on the target, allowing the aperture to transmit backscattered light from distant objects while suppressing ambient light from other directions. The asymmetric geometry resolves the contradiction by selectively transmitting desired signals while blocking harmful ambient light.
Solution Approach 2:
The patent applies local quality by creating a spatially varying transmission profile through the non-circular aperture. The aperture's specific shape and orientation provide different transmission characteristics for light coming from different directions and locations. This local differentiation in transmission quality allows the system to preferentially transmit backscattered light from the laser target while blocking ambient light from other sources, resolving the contradiction between ambient light suppression and signal transmission.
2Use of energy by moving object
If the collection lens aperture is increased to collect more light from distant objects, then signal strength is improved, but ambient light collection is also increased
Solution Approach 1:
The patent applies the intermediary principle by introducing a non-circular spatial filter aperture between the collection lens and the detector. This intermediary component selectively transmits light based on its spatial characteristics, allowing the collection lens to maintain a large aperture for efficient light gathering while the aperture filter removes ambient light before it reaches the detector. The spatial filter acts as a mediator that preserves signal collection efficiency while eliminating harmful ambient light interference.
Solution Approach 2:
The patent applies local quality by using the non-circular aperture to create directionally selective transmission. The aperture's specific shape and orientation provide different transmission qualities for light from different directions, allowing the system to collect light efficiently from the laser target direction while suppressing ambient light from other directions. This local differentiation resolves the contradiction between maximizing light collection and minimizing ambient light interference.
3Object-affected harmful factors
If a smaller aperture is used to reduce ambient light, then ambient light suppression is improved, but signal strength from distant objects is reduced
Solution Approach 1:
The patent applies asymmetry by using a non-circular aperture with aspect ratio > 1:1 that is elongated in the direction of laser beam scanning. This asymmetric shape allows the aperture to maintain a larger effective area for transmitting backscattered signal light while presenting a smaller profile for blocking ambient light from perpendicular directions. The asymmetric geometry enables the system to suppress ambient light effectively without sacrificing signal strength from distant objects.
Solution Approach 2:
The patent applies dimensionality change by transitioning from a circular (isotropic) aperture to a non-circular (anisotropic) aperture with different dimensions in different directions. The elongated shape in the scanning direction versus the compressed shape in the perpendicular direction creates different transmission characteristics along different axes. This dimensional differentiation allows the aperture to transmit signal light efficiently while blocking ambient light, resolving the contradiction between ambient light suppression and signal strength preservation.
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 configuration improves the signal-to-background ratio, reduces dynamic range, and minimizes range aliasing, enabling more accurate detection of light pulses from a range of distances while effectively suppressing ambient light, thereby enhancing the overall performance of lidar systems.
Implementation Method 1
a collection lens for collecting light from a scene to form an image of the light
Implementation Method 2
a mask for spatially filtering the light imaged by the collection lens to at least partly transmit a light pulse backscattered from an object in the scene
Implementation Method 3
a photodetector for detecting the light pulse collected by the lens and transmitted by the mask
Data Source
AI summary
A receiver module for a lidar system includes a collection lens for collecting light from a scene to form an image of the light. The receiver module also includes a mask for spatially filtering the light imaged by the collection lens to at least partly transmit a light pulse backscattered from an object in the scene. The mask is opaque apart from at least one non-circular light-transmissive region. Each non-circular light-transmissive region has orthogonal length and width. The length exceeds the width and is sufficient to transmit light incident on the collection lens at a range of incidence angles in a first angular dimension. The receiver module also includes a photodetector for detecting the light pulse collected by the lens and transmitted by the mask.