Abstract
This paper presents the implementation of a pulse-type LAser Detection And Ranging (LADAR) system based on heterodyne detection for long-range measurement. A pulse-type LADAR based on an intensity direct-detection is certainly simple and mature, but it requires a high peak-power laser and a low-noise avalanche photodiode for long-range measurement, which restricts the scope of the application due to the weight, power consumption, and cost of the laser and the photodetector. In this work, heterodyne detection using a PIN photodiode is implemented to increase receiver sensitivity instead of using a low-noise avalanche photodiode. An optical phase-locked loop is adopted to generate an optical local oscillator signal for heterodyne detection. The proposed heterodyne detection scheme achieves a minimum detectable signal level of -52.6 dBm at a bandwidth of 1.2 GHz, and it is adopted in a pulse-type LADAR system for long-range measurement. The pulse-type LADAR system can measure a distance of 2.77 km at a repetition rate of 40 kHz, and it demonstrates great advantages for realizing real-time 3D imaging for long-range measurement with a high frame rate.
Highlights
LAser Detection And Ranging (LADAR) is a remote sensing technique in which a laser is used to measure the distance to an illuminated target
Implementation of a pulse-type laser detection and ranging system based on heterodyne detection for long-range measurement with high repetition rate
In the coherent detection scheme based on frequency-modulated continuouswave (FMCW) technology, the echo signal is mixed with an optical local oscillator signal to produce a beat-note signal, and the frequency of the beat-note signal corresponds to the distance to an illuminated target
Summary
LAser Detection And Ranging (LADAR) is a remote sensing technique in which a laser is used to measure the distance to an illuminated target. In the coherent detection scheme based on FMCW technology, the echo signal is mixed with an optical local oscillator signal to produce a beat-note signal, and the frequency of the beat-note signal corresponds to the distance to an illuminated target.. Despite its obvious practical advantages, FMCW technology requires a laser source with a highly linear optical frequency sweep to avoid distortion of the range profile caused by nonlinearity of the optical frequency sweep.. Despite its obvious practical advantages, FMCW technology requires a laser source with a highly linear optical frequency sweep to avoid distortion of the range profile caused by nonlinearity of the optical frequency sweep.10 It is not suitable for a LADAR system requiring a high repetition rate and longrange measurement. A pulse-type LADAR system based on heterodyne detection is proposed for long-range high-speed measurement. It was experimentally verified that the proposed pulse-type LADAR system is suitable for long-range measurement with a high repetition rate
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