Underwater optical ranging: A hybrid LIDAR-RADAR approach

A hybrid LIDAR-RADAR system is applied to optical ranging in order to achieve centimeter-type range accuracy over the distance of meters with high range resolution. The experiment is performed for NIR 830 nm, red 660 nm, green 532 nm using photomultiplier tube, interference filter, RF demodulator. An optical wavelength in the NIR region helps to protect the system against the effects of changing turbidity levels of water because NIR wavelengths absorb quickly in clean water without being affected by scattering, the components that make total attenuation. The modulation frequency of 66 MHz for NIR wavelength allowed a theoretical maximum range measurement of 1.71 m within the unambiguous range, which drops to 1.61 cm at 70 Mhz. A scheme involving chaotic modulation techniques (CLIDAR) will be studied in future.