Velocity Measurement of a Highspeed Underwater Projectile With Laser Barriers

To improve the precision of velocity measurements for high-speed underwater projectiles and meet the requirements for device terminal alarms, a method for identifying and measuring high-speed underwater projectiles with a large-area laser barrier was proposed. The absorption of laser transmission underwater and the relationship between scattering and suspended particles were simulated and analyzed. An optical system consisting of a waterproof modulated laser transceiver probe, multifiber transmission and a retroreflector was designed to decrease the large optical energy dissipation. The laser beam was expanded to form a triangular barrier with a Powell prism. The fiber array surrounding the prism receives the reflected laser light from the retroreflector. The other end of the optical fiber is coupled to a PIN-PD detector through a narrowband filter. The output electric signal is then processed by an amplifier, demodulator and low-pass filter. The shortcomings of traditional split-type and multielement optical structures in water were effectively overcome by this compact integrated probe structure, and the effective area was expanded to 2 m ×2 m. The velocity of high-speed underwater steel balls and lead blocks, the simulated projectiles, was acquired accurately to verify the feasibility of velocity measurement for high-speed underwater projectiles with laser barriers.