Phase-Based Laser Ranging With Adaptive Filtering And Segmented FFT
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Solution Overview
Problem
Existing phase-based laser ranging methods face challenges such as noise interference, limited computation capacity, and accuracy issues due to hardware constraints, leading to low output rates and significant errors, especially when measuring high-speed objects or long distances.
Innovation Solution
A high-accuracy, fast phase-based laser ranging method that employs adaptive filtering, all-phase fast Fourier transform, and Kalman filtering to improve signal-to-noise ratio, reduce phase errors, and enhance computation efficiency, allowing for faster and more stable distance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Fourier transform is performed on sampled data, then phase demodulation can be achieved, but spectrum leakage occurs when array length is not an integer power of 2, reducing measurement accuracy
Solution Approach 1:
The patent applies segmentation by dividing the sampled data into multiple segments and performing Fourier transform on each segment separately. This allows the use of power-of-2 array lengths for each segment while processing longer overall data sequences, avoiding spectrum leakage without requiring the entire dataset to be a power of 2. The segmented approach maintains measurement precision while simplifying the processing requirements.
2Measurement precision
If sampling length is increased to improve measurement accuracy, then more complete phase information can be obtained, but computation time increases and flash memory may overflow on single-chip microcontrollers
Solution Approach 1:
The patent segments the long sampling data into smaller chunks that can be processed individually within the memory constraints of single-chip microcontrollers. Each segment is processed separately using FFT, and results are combined to achieve accurate distance measurement over the full sampling period. This approach enables processing of effectively unlimited sampling lengths while avoiding memory overflow and reducing computation time per processing cycle.
Solution Approach 2:
The patent performs preliminary actions by pre-processing the segmented data and preparing it for FFT computation before actual distance calculation. This includes organizing data into power-of-2 sized blocks and pre-computing any necessary transformation matrices, which optimizes the subsequent processing steps and reduces overall computation time on resource-constrained microcontrollers.
3Measurement precision
If phase demodulation accuracy is continuously improved by adding sampling bits and signal operation bits, then measurement precision increases, but hardware processing capacity is exceeded and output speed decreases
Solution Approach 1:
The patent segments the high-precision phase demodulation process into multiple smaller computational steps that can be executed efficiently on existing hardware. By processing data in segments and using optimized algorithms for each segment, the system achieves high phase resolution accuracy without requiring excessive processing power or memory, thus maintaining high output speed while improving measurement precision.
4Measurement precision
If noise filtering is applied to improve signal quality, then signal-to-noise ratio increases, but computation time and processing complexity increase
Solution Approach 1:
The patent applies noise filtering in a segmented manner, processing each data block independently rather than filtering the entire dataset at once. This reduces the computational complexity of the filtering operation while maintaining effective noise reduction and signal-to-noise ratio improvement. The segmented filtering approach can be efficiently implemented on single-chip microcontrollers without excessive processing overhead.
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 method significantly improves signal-to-noise ratio, reduces phase errors, and increases data output speed by 20 times, achieving high-accuracy and stability in distance measurements.
Implementation Method 1
transmitting a laser signal f1(t) to a to-be-measured object through a laser diode, and receiving an echo signal f2(t) through an avalanche photo diode (APD)
Data Source
AI summary
The present disclosure provides a high-accuracy, fast, and phase-based laser ranging method. The method includes: S1, obtaining an eigen signal and an avalanche photon diode (APD) echo signal whose phases are different and frequencies are the same; S2, performing, through an adaptive filtering method, denoising on an initial signal, to obtain two denoised signals; S3, separately performing data splitting, reconstitution, and all-phase fast Fourier transform on the denoised signals, to obtain a frequency-phase spectral line of the eigen signal and a frequency-phase spectral line of the APD echo signal; S4, separately traversing maximum phase values of the frequency-phase spectral line of the eigen signal and the frequency-phase spectral line of the APD echo signal, to obtain a phase difference Δφ; S5, converting the phase difference Δφ into a distance; S6, performing signal mean filtering processing, and S7, performing Kalman filtering processing.