LiDAR Polarization Filtering for Ambient Light Rejection
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Solution Overview
Problem
LiDAR systems face interference from ambient light and false detection of light pulses from other vehicles using similar technology, leading to inaccurate object distance calculations and system malfunctions.
Innovation Solution
A detecting system that uses polarized light pulses and a linear polarizer to filter out unpolarized and differently polarized light, maintaining signal integrity and reducing noise by ensuring only polarized light at a predefined angle reaches the detector, with the ability to adjust polarization angles to differentiate between reflected and direct light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an optical filter is used to filter ambient light, then the interference from ambient light is reduced, but light having the same wavelength as the laser pulse cannot be filtered, causing false detection from other LiDAR systems
Solution Approach 1:
The patent changes the polarization state parameter of light to differentiate between desired and undesired light sources. By emitting polarized light pulses and using polarizing filters, the system can distinguish between reflected light from targets and direct light from other LiDAR systems based on their different polarization states, resolving the false detection problem while maintaining ambient light rejection
Solution Approach 2:
The patent introduces polarization state as an intermediary property to mediate between the laser light and the detector. By incorporating polarizing filters and using polarized light, the system creates an additional discrimination layer that allows the detector to differentiate between reflected light (which maintains or changes polarization) and direct light from other vehicles (which has different polarization characteristics)
2Measurement precision
If the detector readout time slot is synchronized with the pulse time slot, then the detector can capture the reflected pulse, but the back section of the reflected pulse is not read within the capturing time slot, requiring a second readout
Solution Approach 1:
The patent employs periodic pulsed operation where the light source emits periodic light pulses and the detector performs synchronized periodic readouts. By timing the detector readout to coincide with the expected arrival of reflected pulses from distant objects, the system captures the relevant light signal while minimizing the need for extended readout periods, as the pulsed nature creates predictable periodic detection windows
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
Improves the signal-to-noise ratio and accuracy of distance calculations by effectively blocking ambient and interfering light, reducing false detections and enhancing the system's ability to distinguish between reflected and direct light pulses.
Implementation Method 1
at least one linear polarizer configured for polarizing light at the polarization angle and being so disposed with respect to the detector such that the light reaching the detector passes through the linear polarizer and is polarized at the polarization angle
Implementation Method 2
a light source configured to emit light pulses towards a distant object, the light pulses being polarized at a predefined polarization angle
Implementation Method 3
a detector configured to detect at least a portion of the light pulses reflected from the distant objects
Data Source
AI summary
A detecting system is provided for detecting distant objects. The system includes a light source configured to emit light pulses towards a distant object, the light pulses are being polarized at a predefined polarization angle; a detector configured to detect at least a portion of the light pulses reflected from the distant objects; and at least one linear polarizer configured for polarizing light at the polarization angle and being so disposed with respect to the detector such that the light reaching the detector passes through the linear polarizer and is polarized at the polarization angle.