采样频率和激光脉宽对全波形激光雷达测距精度的影响

全波形激光雷达测距精度，又称测距重复精度或测距标准差，受激光器出光稳定性、激光脉宽、探测器响应时间抖动、电路噪声、波形形态、波形采样频率和波形处理算法等因素影响。理论分析了不同采样频率和不同脉宽对全波形激光雷达测距精度的影响，并采集不同的采样频率(1.25、2.5、5 GHz)和不同脉宽(1、2、3、···、10 ns)条件下的波形数据，经滤波、插值、波形提取等预处理后，利用线性高斯拟合、加权线性高斯拟合、迭代加权线性高斯拟合、期望最大化算法、和Levenberg Marquardt算法共5种算法计算测距值并统计测距精度。实验结果表明，EM算法获得的测距精度相比其他4种算法受到波形畸变的影响最小；加权线性高斯拟合算法获得的测距精度受采样频率变化的影响最小；相同波形幅值条件下，实际脉宽增加2.47倍，利用EM算法获得的测距精度从0.97 mm下降至1.18 mm，因此增加脉宽会降低测距精度；在光脉宽为4 ns的情况下，5 GHz采样频率数据在EM算法获得的测距精度分别为2.5 GHz、1.25 GHz采样频率数据的测距精度的1.71倍和3.07倍，而当2.5 GHz和1.25 GHz采样频率数据分别插值2倍和4倍至5 GHz后，仅为1.17倍和1.29倍，因此提高采样频率能够提高测距精度，而对低采样频率数据进行插值能够获得接近高采样频率数据的测距精度。

Influence of sampling frequency and laser pulse width on ranging accuracy of full-waveform LiDAR

The ranging accuracy of full-waveform LiDAR, also known as ranging repetition accuracy or ranging standard deviation, is affected by laser output light stability, laser pulse width, detector response time jitter, circuit noise, waveform shape, waveform sampling frequency, waveform processing algorithm and so on. The effects of different sampling frequencies and pulse widths of full-waveform LiDAR on ranging accuracy were analyzed theoretically. The waveform data under different sampling frequency (1.25, 2.5, 5 GHz) and pulse width (1, 2, 3,···, 10 ns) were collected and preprocessed by filtering, interpolation and waveform extraction. Linear Gaussian fitting, weighted linear Gaussian fitting, iterative weighted linear Gaussian fitting, expectation maximization algorithm and Levenberg Marquardt algorithm were used to calculate the ranging value and the ranging accuracy. The experimental results show that the ranging accuracy obtained by EM algorithm is least affected by waveform distortion compared with the other four algorithms, and that the ranging accuracy obtained by weighted linear Gaussian fitting algorithm is least affected by the change of sampling frequency. Under the condition of the same waveform amplitude, the actual pulse width increases 2.47 times, and the ranging accuracy obtained by EM algorithm is reduced from 0.97 mm to 1.18 mm, so increasing the pulse width will reduce the ranging accuracy. When the optical pulse width is 4 ns, the ranging accuracy of 5 GHz sampling frequency data obtained by EM algorithm is 1.71 and 3.07 times of that of 2.5 GHz and 1.25 GHz sampling frequency data, respectively, while when 2.5 GHz and 1.25 GHz data are interpolated 2 times and 4 times to 5 GHz, they are only 1.17 times and 1.29 times, so increasing the sampling frequency can improve the ranging accuracy. On the other hand, the ranging accuracy close to the high sampling frequency data can be obtained by interpolating the low sampling frequency data.