水下动态参数的测试是特种武器、 两栖武器、 水下专用武器性能考核的必备环节, 而水下运动体的速度信息是评价水下武器性能的重要指标之一。 针对现有的水下高速目标参数测试系统中存在的成本高、 安装调试复杂、 设备体积庞大等问题, 提出一种以激光光幕为有效区域水上、 水下分体式, 实时、 非接触的测速方法。 通过分析Lambert-Beer定律和体散射函数等数学原理, 确定了水下光谱传输规律综合考虑性价比获得最佳峰值波长; 将1m的圆柱体作为散射体模拟光在水中的散射情况, 追迹空间区域内的光线总数为1×10⁵, 获得位于传播方向上1, 3, 5和7 m处的接收面上辐照度的光能量分布, 从而获取系统激光光源的最佳峰值功率。 以此为依据, 采用定距测时原理和一维原向反射技术, 由峰值波长为532 nm的半导体光纤耦合绿光激光器、 光纤耦合式鲍威尔棱镜防水扩束器、 一维原向反射器等构建光学系统。 激光光源、 光电转换部分和信号调理部分位于水上, 激光光幕和原向反射器位于水下, 通过光纤束完成两路光信号的发射和反射光的回收。 发射端光纤一端与光源耦合, 另外一端与鲍威尔棱镜耦合置于水下形成扇形光幕。 接收端光纤一端均布于鲍威尔棱镜出口, 另一端与PIN型光电传感器耦合。 设计齿形一维原向反射器并完成加工制造, 光线将沿着入射光方向原向返回, 另外一维方向则仍为镜面反射, 将接收系统置于发射点垂直光面内附近即可接收大部分光能量, 解决了现有原向发射器因水介质折射率不同于空气而导致原向反射特性消失的问题。 实验采用波长为(532±5) nm绿光激光器, 功率稳定性<1%, 光学噪声< 0.5%, 准直后耦合至长度为2 m的单模光纤再经过鲍威尔棱镜展宽为60°扇形一字线光幕, 扩束模块封装采用尼龙防水材料, 接收光纤均布于光源周围形成环形光纤束, 光纤另外一端均匀排列与PIN光敏二极管直接耦合。 光敏二极管前加中心波长为532 nm的光学滤光片, FWHM=(3±1) nm, 透过率为70%。 PIN型光敏二极管有效尺寸为5.0 mm×5.0 mm。 采用多档可调的光电信号调理电路以适应不同尺寸的测试对象。 该系统进行了不同目标速度参数测试实验, 以钢弩为发射装置, 信号经过光纤回收、 信号调理, 采集至计算机处理获得波形及区间内平均速度, 两激光光幕之间的距离为定值300 mm, 波形峰值作为计时时刻。 成功获取了较高信噪比的波形信号和目标速度值。 利用水下运动体模型与模拟结果进行比较得到其绝对误差。 实验结果表明: 本方法结构简单、 重复性好, 可实现有效区域达到1 m×1 m, 最小可测目标尺寸为5 mm, 理论测速上限可达1 000 m·s^-1, 实验数据通过与理论经验公式结果比对表明, 系统测试精度可达0.2%。

Dynamic parameter measurement is the essential of performance for special weapons, such as amphibious and underwater special weapons. The information about velocity of moving target underwater is one of the important factors for evaluating underwater weapons performance. There are many disadvantages of the traditional connect measurement method, for example, aluminum foil target and comb target have poor reliability, small effective area and low repeatability in an underwater environment. At the same time, the methods of Doppler and sonar are very expensive. In order to solve these problems, we propose a real-time and non-contact method to obtain weapon velocity parameters based on the split-type reflective and with laser screen as effective area. The law of underwater spectral transmission is determined by analyzing the law of Lambert-Beer and the function of body scattering and other mathematical principles. The optimal laser peak wavelength was obtained. A 1 m-diameter cylinder was created as a scatterer to simulate the scattering of in water. The total number of traced space rays was 1×10⁵. And the light energy of the irradiance at the receiving surface located at 1, 3, 5, and 7 m was obtained. So the optimal peak power of the system laser source was obtained also. On the basis of this, the optical system adopted principle of determining the distance measuring time principle and the one-dimensional retro-reflective technology, which consisted of 532 nm, fiber-coupled semiconductor lase,fiber-coupled laser beam expander used Powell lens and retro-reflector. The laser emission part and the signal processing part were located on the water, and the effective area of the laser screen was located under the water. The laser was emitted and the signal was recovered by the optical fiber. One end of the transmitting optical fiber was coupled with the light source, and the other end of the optical fiber was coupled with the Powell lens to form a fan-shaped light screen under water. One end of the receiving optical fiber was distributed at Powell prism exit, and the other end was coupled with the PIN-type photoelectric sensor. One-dimensional tooth-shaped retro-reflector was designed and manufactured, the light would be returned along the original direction, and the other dimensional direction would observe the principle of specular reflection. The receiving system was placed near the vertical point of the emission point in order to collect most of the reflected light. The problem of the current reflector was solved, that is to say, reflection characteristic disappeared, because the refractive index of the water was different from the air. The experiment adopted a laser with a wavelength of (532±5) nm, power stability <1%, optical noise <0.5%. After it was collimated, the laser was coupled to a single-mode fiber with a length of 2 m, then was widened to a 60° fan sharp laser screen by a Powell lens. The beam expander module used nylon as the waterproof material, and the receiving optical fiber was uniformly distributed around the light source to form an annular fiber bundle, and the other end of the optical fiber was evenly arranged and directly coupled with the PIN photodiode. In front of the photodiode, a center wavelength 532 nm optical filter was added, FWHM = (3±1) nm and the transmittance was 70%. The effective size of the PIN photodiode was 5.0 mm×5.0 mm. Adopted multiple adjustable optical signal conditioning circuits to adapt to different sizes of targets. The system performed different velocity of targets measurement. The steel file was used as a launching device. The signal was collected through fiber; then processed by conditioning circuit, finally, transmitted to the computer. The waveform and the average velocity were obtained. The distance between the two laser screens was a constant value of 300 mm, and the peak value of the waveform was used as a timing moment. The higher SNR waveform signals were acquired successfully. That system has been tested for different target speed parameters, and the waveform signal and the target speed value of higher signal-to-noise ratio have been successfully obtained. The experiments of different target were set up, and the signal waveform with high signal-to-noise ratio was successfully obtained. The absolute error was obtained by comparing the underwater moving target model with the simulation results. The experimental results showed that the proposed method can achieve the test requirements of 1 m×1 m in effective area, the minimum measurable target size of 5 mm. The accuracy of system was more than 0.2%, though compared with the results of initial velocity measurement and empirical formula.