应用于脉冲展宽激光测距系统的自动增益控制

Automatic Gain Control for Pulse-Broadened Laser-Ranging System

在脉冲法激光测距系统中,由于电光/光电转换、目标物的位置及反射率变化,回波脉冲的幅值和脉宽通常会发生改变,导致直接使用固定阈值法时测距系统会产生较大的误差。虽然自动增益控制系统可以减少该误差,但当前大部分自动增益控制都是通过峰值保持电路测量回波脉冲的峰值,存在保持峰值衰减、不稳定、响应速度慢等问题。为此,本研究使用250 MHz高速模数转换模块采集回波脉冲的峰值,并在现场可编程逻辑门阵列内实现峰值保持与清零。与带有峰值保持电路的自动增益控制系统相比,该系统具有电路简单、电压峰值不会衰减、响应速度更快等优点。实验结果表明:设计的带有改进型自动增益控制的激光测距系统可以有效地把回波幅值控制在较小范围内(0.76~1.44 V),从而减小测量误差。

In pulsed laser-ranging systems,the amplitude and pulse width of the echo pulse typically vary owing to the electrooptical/photoelectric conversion process and the changes in the target position or reflectivity,which results in significant errors when the fixed threshold method is used directly.Although an automatic gain control(AGC)system can minimize the error,most AGCs measure the peak value through the peak holding circuit,which causes problems such as peak holding attenuation,instability,and slow response speed.Therefore,a 250-MHz-high-speed analog-to-digital conversion module is used in this study to obtain the peak value of the echo pulse and achieve peak retention and zeroing in the field programmable logic gate array.Compared with the AGC system with a peak-holding circuit,the system has a simplified circuit,no attenuation of voltage peak,and a faster response.The experimental results show that the designed laser ranging system can effectively control the amplitude of the echo pulse within a narrow range(0.76‒1.44 V)to reduce measurement errors.