USA As Represented by Secretary of the Navy

Stephen B Doyle

Lee E Estes

An attenuation meter is provided for use in a water environment. In operation, a transmitter of the meter transmits a laser pulse focused to a size at a predetermined range. A receiver of the meter images a focused spot to minimize unwanted light back scattering and avoid diffractive spreading within the back scattering region. Filtering the angular region can further reject scattered light. The filtered light is received, measured and processed by a oscilloscope as pulse averages. The meter also includes a photodetector to measure a diffuse attenuation coefficient. The output voltage of the photodetector is measured and processed by the oscilloscope that produces an average voltage over a preset number of pulses. A controller best fits voltage to time dependence to produce the diffuse attenuation coefficient. Only the shape of the receiver time dependence is required to provide the diffuse attenuation coefficient measurement.

Optical attenuation coefficient meter

A system is provided for detection of surface glints on a water surface. A laser of the system produces a nearly horizontal or vertical linearly polarized laser light pulse. Lens of the system form an afocal imaging system with lateral magnification and longitudinal magnification that projects an image of the laser light at a pulse location onto the water surface. A portion of the laser light is focused onto a high speed detector. The output of the high speed detector is connected to a digitizer to provide system synchronization and to monitor the laser light. A glint image of the pulse location is detected by a broad band detector. The electrical output of the detector is input to the digitizer where the output is digitized. The output of the digitizer is then sent to a computer where the output is stored and analyzed.

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Wakefield, RI, United States of America

Stephen B Doyle