﻿ 同步扫描水下激光成像的工作范围
 舰船科学技术  2018, Vol. 40 Issue (6): 113-116 PDF

Working scope of synchronous scanning underwater laser imaging system
HE Da-hua
Huazhong Institute of Electro-Optics, Wuhan National Laboratory for Optoelectronics, Wuhan 430223, China
Abstract: Synchronous scanning is one of the effective methods to eliminate backscattering of water in underwater laser imaging application. Synchronous scanning underwater laser imaging system can get a two-dimensional image by scanning laser beam transversely together with the platform moving forward. In this paper, constraints of laser power, sensitivity of the detector, target lambertian reflectivity, target distance, attenuation coefficient of water, velocity of the platform, speed of revolution, transverse FOV, image resolution etc are established. When these constraints are met, synchronous scanning underwater laser imaging system can get two-dimentional images without distortion.
Key words: synchronous scanning     underwater laser imaging     working scope     backscattering     image distortion
0 引 言

2 同步扫描图像形成过程

 图 1 同步扫描水下激光成像系统原理图 Fig. 1 Schematic diagram of sychronous scanning underwater laser imaging system

 图 2 激光扫描图像采样点的时序关系 Fig. 2 Temporal sequence of sampling points in laser scanning image

3 同步扫描水下激光成像的工作范围

3.1 系统参数约束关系的定量分析

 ${P_r} = \frac{{{P_0} \cdot \rho \cdot A}}{{\pi \cdot {R^2}}}{e^{ - 2cR}}{\text{。}}$

${P_0}$ =1 W， $\rho$ =0.05，A= $2.0 \times {10^{ - 3}}{{\rm m}^2}$ ，有

 ${P_r} = 3.2 \times {10^{ - 5}} \cdot \frac{{{e^{ - 2cR}}}}{{{R^2}}}{\text{。}}$ (1)

${P_r}$ 为激光回波功率，不同光电倍增管的阈值灵敏度 ${P_T}$ 有一定差异，在此取 ${P_T}$ =10-9W，把光电倍增管看作功率器件，其输出与激光回波的瞬时功率成正比，与激光束的横向扫描速度无关，因此要保证光电倍增管能探测到信号，只要满足回波功率大于其阈值灵敏度即可，因此有 ${P_r} > {10^{ - 9}}$ ，故

 $\frac{{{e^{ - 2cR}}}}{{{R^2}}} > 3.1 \times {10^{ - 5}}{\text{。}}$ (2)

 $R > 2{\text{。}}$ (3)

 $a = \frac{{70 \cdot \pi \cdot R}}{{180 \cdot N}},b = \frac{V}{{4 \cdot S}}{\text{。}}$

 $N \cdot V = 4.9 \cdot S \cdot R{\text{。}}$ (4)

 $V < 0.29R{\text{。}}$ (5)

 $0.1 < V < 3{\text{。}}$ (6)

3.2 系统参数约束关系图谱

N=1 024，c取0.1，0.2，0.5时的约束关系图谱如下：

 图 3 系统参数约束关系图谱（N=1 024） Fig. 3 Constraint relation map between system parameters (N=1 024)

c=0.1，0.2，0.5分别代入式（2），可分别得R<21.2 m，R<13.0 m和R<6.5 m，它决定了系统探测距离上限，在图中分别为线段FG、线段EH和线段CI。线段AB最小探测距离限制条件，对应R=2。线段AG和线段DF分别为载体速度的下限和上限，对应V=0.1和V=3。线段BD是由式（5）决定的扫描电机最大转速限制条件。c=0.1时，系统的工作范围为区域ABDFGAc=0.2时，系统的工作范围为区域ABDEHAc=0.5时，系统的工作范围为区域ABCIA

 $S = \frac{{N \cdot V}}{{4.9 \cdot R}}$

 图 4 系统参数约束关系图谱（N=3 072） Fig. 4 Constraint relation map between system parameters (N=3 072)

 $V < 0.1R{\text{。}}$ (7)

4 结 语

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