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Abstract
Long-range optical imaging applications are typically hindered by atmospheric turbulence. The effect of turbulence on an imaging system can manifest itself as an image blur effect usually quantified by the phase distortions present in the system. The blurring effect can be understood on the basis of the measured strength of atmospheric optical turbulence along the propagation path and its impacts on phase perturbation statistics within the imaging system. One method for obtaining these measurements is by the use of a dynamically ranged Rayleigh beacon system that exploits strategically varied beacon ranges along the propagation path, effectively obtaining estimates of the aberrations affecting an optical imaging system. We developed a method for extracting tomographic turbulence strength estimations from a dynamically ranged Rayleigh beacon system that uses a Shack–Hartmann sensor as the phase measurement device. The foundation for extracting tomographic information from strategically range-varied beacon measurements obtained in rapid sequence is presented along with modeled example cases for typical turbulence scenarios. Additionally, the processing algorithm was used to simulate identification of isolated strong turbulence layers. We present the chosen processing algorithm’s foundation and provide discussion of the utility of this algorithm as an atmospheric turbulence profiling methodology.
Highlights
Long-range optical imaging applications are typically hindered by atmospheric turbulence
A dynamically ranged Rayleigh beacon system is a modification of a traditional Rayleigh beacon system design to allow for the originating location of the backscattered field to change in the range from the collecting aperture of the telescope
This paper presents an approach for extracting localized turbulence strength information based on the methodology employed by a dynamically ranged Rayleigh beacon; the associated data exploitation algorithm that has been developed and investigated can accurately produce tomographic refractive index structure parameter strength profiles
Summary
Long-range optical imaging applications are typically hindered by atmospheric turbulence. This type of measurement and response has been proposed to increase the effective range of a laser weapon system through sequential compensation iterations within a slowly changing or nearly static atmosphere This proposes a laser beam projection system with a near-field phase retrieval method for delivering more power to a target at an extended range.[4] These works have provided inspirational aspects influencing the design concept of a dynamically ranged Rayleigh beacon system[1]; each individual method presents differences that influence that way the collected data is analyzed to produce estimates of the strength of the refractive index structure parameter, associated turbulence-related metrics, or near-real-time phase correction. The dynamically ranged beacon system utilizes a series of direct measurements of the wavefront present in the system’s pupil as the input to producing a profile estimate of the turbulence strength This is inherently different from methods where associated measurements are made, such as C2T, and inferred relations are used to get back to an index of refraction structure parameter estimate. The data processing algorithm for constructing a turbulence strength profile, the basis for the algorithm’s formulation, and the results from modeled scenarios are presented in this paper
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