[Show abstract][Hide abstract] ABSTRACT: A method is described for modeling the effects of spatial apertures on optical sensor systems. The method consists of defining a set of basis functions that is obtained by partitioning the aperture image plane into a series of rectangular regions and replacing the field in each rectangular subregion with an orthogonal function series approximation. Each orthogonal function has a finite extent that is matched to the aperture image. The individual functions are propagated by application of the Fresnel approximation of the Rayleigh-Sommerfeld diffraction formula to other ranges, and the resultant functions are shown to be valid basis functions for defining a field at any other range. The technique is applied to a scattering problem using complex Fourier series.
Journal of the Optical Society of America A 08/2006; 23(7):1626-30. DOI:10.1364/JOSAA.23.001626 · 1.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The linear mechanism for optical-to-acoustic energy conversion is explored for optoacoustic communication from an in-air platform or surface vessel to a submerged vessel such as a submarine or unmanned undersea vehicle. The communication range that can be achieved is addressed. A number of conventional signals used in underwater acoustic telemetry applications are shown to be capable of being generated experimentally through the linear optoacoustic regime conversion process. These results are in agreement with simulation based on current theoretical models. A number of practical issues concerning linear optoacoustic communication are addressed that lead to a formulation of a linear-regime optoacoustic communication scheme. The use of oblique laser beam incidence at the air-water interface to obtain considerable in-air range from the laser source to the in-water receiver is addressed. Also, the effect of oblique incidence on in-water range is examined. Next, the optimum and suboptimum linear optoacoustic sound-generation techniques for selecting the optical wavelength and signaling frequency for optimizing in-water range are addressed and discussed. Optoacoustic communication techniques employing M-ary frequency shift keying and multifrequency shift keying are then compared with regard to communication parameters such as bandwidth, data rate, range coverage, and number of lasers employed.
[Show abstract][Hide abstract] ABSTRACT: Propagation through the ocean's surface at shallow angles with a laser has been successfully demonstrated experimentally in the ocean. A 6-mJ multipulse laser at a depth of 1.5 m in water with an attenuation coefficient of approximately 3.3 m(-1) was easily detected 600 m away on a sunlit day at an angle of 1 degree to the ocean's surface. The measured efficiency was 3.6 x 10(-2) (J/J)/sr (joules received per receiver steradian per joule transmitted). Statistical ray trace analysis and physical tank modeling produced equivalent efficiencies.