Laser radar technology has been developed rapidly since the advent of laser. Among various laser radars, the three-dimensional (3D) imaging lidar has been of great concern. The traditional 3D imaging radar based on direct detection mode has two main ways: The first method is to use a single pulse of high peak power for time-of-flight ranging. This method requires a laser capable of producing pulsed laser with high peak power and narrow pulse width, which is expensive and difficult to manufacture and cannot be miniaturized. The second approach is to use time-correlated single-photon counting techniques. Although this method can work with low peak power laser pulses, it requires a long pixel dwell time to establish the distribution of photoelectrons, which seriously reduces the imaging speed.
In order to overcome the above problems, the research team led by Chen Weibiao from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, carried out the research of 3D imaging lidar based on high-speed pseudo-random code modulation and photon counting, and verified it in outdoor environment. Related research results are published in Chinese Optics Letters, Volume 14, No. 11, 2016 (Y. F. Zhang, et al., Three-dimensional imaging lidar system based on high speed pseudorandom modulation and photon counting).
The principle of the 3D imaging lidar based on high-speed pseudo-random code modulation and photon counting is as follows: Pseudo-random codes have sharp autocorrelation value and very low cross-correlation value, so the position of pseudo-random codes can be extracted from noise by correlation operation. The target distance can be obtained by calculating the time between the transmitting and receiving of the modulated laser. In this method, low power emission and single photon reception are adopted. Both the peak power requirement of the laser and the pixel dwell time are reduced. The advantages of low peak power and high imaging speed make it possible to reduce the size and power consumption of the system without sacrificing the imaging speed.
The results of the outdoor imaging with the target distance of 1.2 km are reported in this paper, and high-quality 3D images are obtained. Prof. Chen Weibiao believes that the advantages of high sensitivity and high imaging speed the technology possesses make it suitable for long-distance three-dimensional imaging and detection, such that the technology has a great development potential.
Further work is to achieve system miniaturization and low power consumption and to enhance SNR in the high noise level conditions.
为克服上述方法存在的问题，中国科学院上海光学精密机械研究所的陈卫标研究员课题组开展了基于高速伪随机码调制和单光子计数的激光三维成像雷达技术的研究，并完成了室外环境下的验证实验。相关研究成果发表在Chinese Optics Letters 2016年第11期上（Y. F. Zhang, et al., Three-dimensional imaging lidar system based on high speed pseudorandom modulation and photon counting）。