A device is described for generating true-time delays optically for microwave signals used in beam steering and beam shaping in phased-array antennas. The device can be adapted to provide delays from picoseconds to nanoseconds. A single, compact unit should provide parallel delays for more than 64 independent antenna elements with a greater than 6-bit resolution. The time delays are produced by multiple reflections in a mirror configuration with continuous refocusing. A single spatial light modulator selects independent optical path lengths for each of the parallel antenna elements. Amplitude control for beam shaping can be integrated into the device. The unit can be made rugged for harsh environments by use of solid-block construction. The operation of the true-time delay device is described, along with the overall system configuration. Preliminary experimental data are given.

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. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Practical stellar interferometry for space domain awareness is challenged by the relative motions of orbital objects and telescope arrays that require array phasing using guide stars. An orbital object’s image sensitivity to the location and brightness of the guide star is problematic, possibly resulting in a degraded resolution or loss of image content when both objects fall within the interferometer’s field of view. We characterized an orbital object’s visibility using visibility contrast to noise ratios ( C N R Δ v ) as a performance metric for orbital object image quality. Experimental validations included orbital object visibility measurements for dual binary pinholes that were scaled in size and brightness individually to match expected interferometer data collection scenarios. We show agreement in C N R Δ v results, indicating resolvable orbital object signals during periods of collection when signal contributions from both the orbital object and guide star are present. Expanding presented results to imaging interferometers, we discuss how dual object imaging could degrade performance under the scenarios examined.

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What is believed to be a novel holographic optical encoding scheme has been developed to enhance the performance of laser sensors designed for the measurement of wavelength and angular trajectory. A prototype holographic imaging diffractometer has been created to reconstruct holographic cueing patterns superimposed in the focal plane of wide-angle scene imagery. Based on experimental pattern metric measurements at the focal plane, a theoretical model is used to compute the laser source wavelength and its apparent propagation direction within the sensor's field of view. The benefits of incorporating holographic enhancements within an imager-based sensor architecture are discussed.

This effort desciibes the fabrication and testing of binary-phase Fourier gratings designed to generate an incoherent anay of output source points with nonuniform user-defined intensities, symmetric about the zeroth order. Like Dammann fanout gratings, these binary-phase Fourier gratings employ only two phase levels to generate a defined output array. Unlike Dammann fanout gratings, these gratings generate an array of nonunifom, userdefined intensities when projected into the far-field regime. The paper describes the process of design, fabrication, and testing for two different version of the binary-phase grating; one designed for a 12 pm wavelength, referred to as the Long-Wavelength Infimed (LWIR) grating, and one designed for a 5 pm wavelength, referred to as the Mid-Wavelength Infked Grating (MWIR).

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