Optical Chirped Range Detection Using Dual-Chirp Doppler Correction
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Solution Overview
Problem
Doppler frequency shifts due to object motion significantly affect optical chirp range measurements, leading to errors in range detection and object identification in LIDAR systems.
Innovation Solution
A method and apparatus that utilize a combination of up and down chirped transmitted optical signals to determine a matched pair of ranges, calculating a Doppler effect by combining these ranges, and employing a processor to correct for Doppler shifts in LIDAR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If object motion is present during optical chirp range measurement, then range detection can still be performed, but Doppler frequency shifts cause errors in range detection and object identification
Solution Approach 1:
The patent transmits both up-chirp signals (frequency increasing with time) and down-chirp signals (frequency decreasing with time) instead of only up-chirp signals. By inverting the chirp direction, the Doppler frequency shift effects are reversed, allowing the system to differentiate between range-induced frequency shifts and motion-induced Doppler shifts through comparison of the two signal types.
Solution Approach 2:
The patent changes the chirp parameter (frequency modulation direction) to create two distinct measurement modes: up-chirp and down-chirp. By varying this parameter and comparing results from both modes, the system can identify and correct Doppler-induced errors while maintaining accurate range detection even when objects are in motion.
2Measurement precision
If up-chirp and down-chirp signals are transmitted to correct Doppler effects, then detection accuracy improves, but device complexity increases due to additional signal processing requirements
Solution Approach 1:
The patent combines up-chirp and down-chirp transmission within a unified LIDAR system architecture. By merging these two signal types and processing them through integrated algorithms that compare frequency differences, the system achieves Doppler correction without requiring entirely separate measurement systems, thereby limiting the increase in complexity.
Solution Approach 2:
The patent creates a complementary copy of the up-chirp signal in the form of a down-chirp signal with inverted frequency modulation. This copied signal serves as a reference for comparing Doppler effects, allowing the system to identify and correct errors through differential analysis without adding excessive processing burden.
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
Accurately compensates for Doppler effects, improving range detection precision and object identification by reducing errors caused by object motion.
Implementation Method 1
motion of an object, to which range is being detected using an optical chirp, noticeably affects such applications due to Doppler frequency shifts
Data Source
AI summary
Techniques for Doppler correction of chirped optical range detection include obtaining a first set of ranges based on corresponding frequency differences between a return optical signal and a first chirped transmitted optical signal with an up chirp that increases frequency with time. A second set of ranges is obtained based on corresponding frequency differences between a return optical signal and a second chirped transmitted optical signal with a down chirp. A matrix of values for a cost function is determined, one value for each pair of ranges that includes one in the first set and one in the second set. A matched pair of one range in the first set and a corresponding one range in the second set is determined based on the matrix. A Doppler effect on range is determined based on combining the matched pair of ranges. A device is operated based on the Doppler effect.