Abstract
The decoherence in coherent lidar becomes serious with the increase in distance. A small laser spot can suppress the decoherence of the echo light from noncooperation targets. However, it is very difficult to keep a small light spot over a long distance. In this paper, a pulsed coherent lidar with high sensitivity at the few-photon level was demonstrated. A phase plate was used to modulate the wavefront of the laser to achieve 100 m focusing which reduced the decoherence effect. Based on coherent detection and time-of-flight (TOF) measurements, long-distance laser ranging and imaging on all days was realized. A signal classification and superposition method was used to extract the echo signal submerged in noise. The system was experimentally demonstrated by ranging different noncooperation targets within 105.0 m. The measurement rate was 10 k/s, and the measurement uncertainty was 1.48 cm. In addition, laser imaging was realized at ~50.0 m. The system was simple and portable as well as eye safe, and it may offer new application possibilities in automated vehicle lidar.
Highlights
Laser detection and ranging has been widely used in topographic mapping, ocean detection, unmanned driving and other fields due to its advantages of high transmission efficiency, small size, and high resolution [1–3]
Ranging and imaging lidar of tens of kilometers has been realized based on a single-photon detector, which is one of the most sensitive optical detection techniques [4–9]
Coherent detection can effectively suppress the influence of background light by interfering with the received signal with a local oscillator, making it one of the most sensitive optical detection techniques [10,11]
Summary
Laser detection and ranging (lidar) has been widely used in topographic mapping, ocean detection, unmanned driving and other fields due to its advantages of high transmission efficiency, small size, and high resolution [1–3]. Coherent detection can effectively suppress the influence of background light by interfering with the received signal with a local oscillator, making it one of the most sensitive optical detection techniques [10,11]. It is widely used in Doppler lidar, coherent laser communication and other fields [12–21]. The laser spot of the lidar is usually larger than 20 mm in diameter while the distance is longer than 100.0 m [6,9]. A phase plate was used to modulate the wavefront of the laser to achieve 100 m focusing so that the light spot was kept at approximately 10.0 mm in diameter, which reduced the decoherence effect. The system was eye safe, portable and exhibited excellent anti-interference performance, which provides a new technology in automated vehicle lidar and site investigation
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