Pulse Laser Ranging with Time-Domain Waveform Matching
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Solution Overview
Problem
The triggering threshold of time digital converter systems in pulse laser ranging varies with echo signal amplitude, causing significant fluctuations in triggering time and complicating low-and-medium frequency phase type ranging methods.
Innovation Solution
A pulse laser ranging system employing a time domain waveform matching technique, incorporating a hardware setup with an FPGA, optical collimation, and ADC sampling, along with a software algorithm for waveform analysis and interpolation, to stabilize the triggering threshold and improve time resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed threshold value is used for laser echo time determination, then the circuit structure is simple, but time drift error cannot be overcome
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the threshold value based on the amplitude of the laser echo signal. Instead of using a fixed threshold, the system calculates an adaptive threshold that changes with signal characteristics, thereby eliminating time drift error while maintaining reasonable circuit complexity. This is achieved through real-time analysis of signal amplitude and corresponding threshold adjustment.
2Measurement precision
If constant fraction discrimination method or CR-high-pass discrimination method is used to eliminate time drift error, then measurement precision is improved, but circuit structure becomes complicated and difficult to implement
Solution Approach 1:
The patent replaces complex analog circuit implementations with digital signal processing methods. Instead of using complicated constant fraction discrimination circuits or CR-high-pass filter circuits, the invention uses digital algorithms to achieve the same time drift error elimination function. This substitution of digital processing for analog circuitry simplifies the overall system while maintaining high measurement precision.
3Device complexity
If error compensation method with multiple fixed threshold values is used, then circuit structure is simple and easy to implement, but determination and fitting of error compensation curve increases complexity of the ranging method
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing threshold values in a lookup table before actual ranging operations. Instead of performing complex curve determination and fitting during the ranging process, the system pre-processes the threshold calibration data and stores it for rapid retrieval during measurement. This eliminates the need for real-time curve fitting while maintaining simplicity in circuit structure and reducing operational 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
This approach achieves a time resolution finer than 50ps and enhances the signal-to-noise ratio, overcoming triggering time fluctuations and increasing test frequency, while simplifying the system complexity.
Implementation Method 1
the photoelectric conversion system converts the optical echo signal into an electric echo signal
Implementation Method 2
measuring the TOF (time of flight) of the pulsed laser and then obtaining the distance from the target to a ranging device
Data Source
Figure 1
AI summary
Provided are a pulse laser ranging system and method employing a time domain waveform matching technique. The system comprises a software part and a hardware part. The hardware part comprises an optical collimation system, an FPGA, a filter, a photoelectric conversion system, an analog amplifier circuit, a laser transmitter, a signal combination system, an ADC sampling system and a narrow pulse laser transmitting circuit. When transmitting a control signal to control laser transmission, the FPGA sends a time reference pulse to the signal combination system. The signal combination system integrates the time reference pulse with a fixed amplitude analog echo signal to form an echo signal with a time reference. The echo signal with a time reference is quantified into a digital detection signal in the ADC sampling system. The digital detection signal is sent to the FPGA to undergo data analysis. The software part is used to perform time domain waveform matching analysis to obtain a ranging result. The ranging result is output by the FPGA.