Laser Vehicle Speed Detection with Time-Delayed Beat Interference
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Solution Overview
Problem
Existing speed detection systems for vehicles, such as pitot tubes and LIDAR sensors, are susceptible to environmental conditions and particle scattering, leading to reduced performance in determining speed, especially at mid-elevations where fewer airborne particles are present.
Innovation Solution
A laser-based speed detection system that utilizes a time-delayed interference method to measure beat frequencies from backscatter light, combining it with a reference light to enhance accuracy and performance by using redundant paths for increased reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a LIDAR sensor is used to detect airspeed by comparing laser beam frequency to backscatter frequency, then speed detection capability is provided, but measurement precision deteriorates in environments with fewer airborne particles such as at mid-elevations
Solution Approach 1:
The backscatter light is divided into multiple portions (first portion and second portion) that are processed through different paths. One path measures beat frequency directly while the other introduces a time delay before measuring beat frequency. This segmentation allows the system to use multiple measurement results to determine speed, improving precision in environments with fewer particles where single measurements may be insufficient.
Solution Approach 2:
The system measures a first beat frequency from the first portion of backscatter light and a second beat frequency from the second portion after time delay. By comparing these multiple measurements and using feedback from both paths, the system can determine speed more accurately even when particle concentrations are low, as the redundant measurements provide corrective information.
2Reliability
If a pitot tube is used to detect vehicle speed by protruding into the airflow, then speed detection is enabled, but reliability deteriorates due to susceptibility to environmental conditions such as bird strikes, insect strikes, and ice formation
Solution Approach 1:
The patent replaces the mechanical pitot tube system with an optical LIDAR-based speed detection system. Instead of using a physical sensor that protrudes into the airflow and is vulnerable to environmental damage, the system uses laser beams to measure the Doppler shift of backscatter light from airborne particles, enabling non-contact speed measurement that is immune to bird strikes, insect strikes, and ice formation.
3Measurement precision
If multiple measurement paths are used to improve measurement precision, then accuracy in determining speed increases, but device complexity increases
Solution Approach 1:
The patent combines multiple measurement approaches within a unified LIDAR system. Both the direct beat frequency measurement path and the time-delayed beat frequency measurement path operate within the same optical system, sharing common components such as the laser beam source and detector. This merging allows the system to achieve improved measurement precision through multiple paths while minimizing the increase in overall device complexity.
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
The system provides enhanced accuracy and reliability in determining vehicle speed by utilizing beat frequency differences and redundant paths, improving performance across varying particle concentrations.
Implementation Method 1
A backscatter light generated in response to transmitting a laser beam into an atmosphere
Implementation Method 2
A first beat frequency from interfering a first portion of the backscatter light with a reference light derived from the laser beam
Implementation Method 3
A first beat frequency from interfering a first portion of the backscatter light with a reference light
Implementation Method 4
A time delay is introduced to a second portion of the backscatter light to form a time delayed backscatter light. A second beat frequency from interfering the time delayed backscatter light with the reference light is measured. The second beat frequency is time delayed from the first beat frequency
Data Source
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AI summary
A method, apparatus, and system detect a speed of a vehicle. A backscatter light generated in response to transmitting a laser beam into an atmosphere during movement of the vehicle is received. A first beat frequency from interfering a first portion of the backscatter light with a reference light derived from the laser beam is measured. A time delay is introduced to a second portion of the backscatter light to form a time delayed backscatter light. A second beat frequency from interfering the time delayed backscatter light with the reference light is measured. The second beat frequency is time delayed from the first beat frequency. A difference between the first beat frequency and the second beat frequency is determined. The speed of the vehicle using the difference between the first beat frequency and the second beat frequency is determined.