高速相位式激光测距数字鉴相方法仿真与实现

High speed digital phase-difference measuring methods simulation and implementation in phase-shift laser range finder

为实现高速、高精度相位式激光测距鉴相,根据数字相关法、数字同步解调法、频域数字鉴相法和全相位FFT法的鉴相原理,基于仿真考察了在白噪声、频率偏移等因素影响下的鉴相性能。仿真结果证明,在高速测量下(500 kHz),全相位FFT法优于其他方法。为应用于高精度相位式激光测距原理样机,设计全相位FFT法的FPGA信号处理方案,利用傅里叶变换共轭对称性从而实现了高速实时鉴相。实验数据表明:在500 kHz测距速率下,信噪比为40 dB,频率偏移0.01时,鉴相精度为0.09°;调制频率为100 MHz时,测距精度为0.38 mm。因此,全相位FFT鉴相法适用于高速、高精度相位差测量,提出的实现方案具有实际意义。

In order to implement digital phase-difference measurement in phase-shift laser range finder with high measuring speed and high accuracy measurement performances under the influence of white noise or frequency deviation and so on were analyzed based on simulation which is in accordance to the principles of digital correlation method,frequency domain digital measuring method,digital synchronous method and all-phase FFT method.The simulation results indicate that with high measuring speed,all-phase FFT method is better than others.The implementation scheme of all-phase FFT in FPGA was designed for the sake of development of high accuracy laser range finder prototype,and high-speed real-time measurement was realized using conjugation symmetry of DFT.Experimental data show that the accuracy of all-phase FFT is 0.09°（0.38 mm at 100 MHz modulation frequency） with 500 kHz measuring speed,under the condition of SNR 40 dB and introduced frequency deviation 0.01.Consequently,all-phase FFT method is applicable to high speed and high accuracy phase-difference measurement,and the way to implement phase-difference measuring unit is feasible.