The Navy Precision Optical Interferometer (NPOI) has two purposes: wide angle precise astrometry and high-resolution imaging, both at visible wavelengths. It operates with up to six 12-cm diameter apertures simultaneously, with baseline lengths (distances between array elements) from 16 m to 79 m, and disperses the combined light into 16 spectral channels. It has been operational since first fringes were found in 1994; six-beam operations began in 2001. The NPOI is undergoing upgrades in numerous areas: control system and data acquisition improvements, a second beam combiner, additional array stations for both longer and shorter baselines, and supplemental delay lines to improve sky coverage for the longer baselines. Future possibilities include the installation of four fixed 1.8 m telescopes as well as up to six moveable lightweight 1.4 m telescopes. Observing programs, including programs led by outside investigators, cover a broad range of stellar astrophysics as well as observations of geostationary satellites.

Recent work at the U.S. Naval Research Laboratory studied atmospheric turbulence on dynamic links with the goal of developing an optical anemometer and turbulence characterization system for unmanned aerial vehicle (UAV) applications. Providing information on the degree of atmospheric turbulence, as well as wind information and scintillation, in a low size, weight and power (SWaP) system is key for the design of a system that is also capable of adapting quickly to changes in atmospheric conditions. The envisioned system consists of a bi-static dynamic link between a transmitter (Tx) and a receiver (Rx), relying on a small UAV. In a dynamic link, the propagation distance between the Tx/Rx changes rapidly. Due to SWaP constraints, a monostatic system is challenging for such configurations, so we explored a system in which the Tx/Rx is co-located on a mobile platform (UAV), which has a mounted retroreflector. Beam divergence control is key in such a system, both for finding the UAV (increased beam divergence at the Tx) and for signal optimization at the Rx. This led us to the concept of using adaptive/active elements to control the divergence at the Tx but also to the implementation of an adaptive/active retroreflector in which the return beam divergence can be controlled in order to optimize the signal at the Rx. This paper presents the design, fabrication and characterization of a low SWaP adaptive retroreflector.

In this paper we present a status report of our liquid crystal (LC) adaptive optics program. Liquid crystal have been proposed to be used for adaptive optics components by several authors. We are actively pursuing a two prong approach, on one side we have built a closed loop test bed based on a 127 element nematic LC device; on the other side we are actively involved in research on the ferroelectric side of the LC devices. In this paper we present preliminary results from our testbed. The essential elements of this testbed are a Shack-Hartman based wavefront sensors with an analog reconstructor, and the 127 nematic elements from Meadowlark Optics. Some of the basic experimental parameters will be reviewed, and result will be discussed. Furthermore we will present the status of our activity in the field of ferroelectric LC. Several prototypes are under testing to establish their capabilities as AO components.

We present the combined use of large aperture adaptive lens with large optical power modulation with a multi actuator adaptive lens. The Multi-actuator Adaptive Lens (M-AL) can correct up to the 4th radial order of Zernike polynomials, without any obstructions (electrodes and actuators) placed inside its clear aperture. We demonstrated that the use of both lenses together can lead to better image quality and to the correction of aberrations of adaptive optics optical systems.

We present here results using two novel active optic elements, an electro-static membrane mirror, and a dual frequency nematic liquid crystal. These devices have the advantage of low cost, low power consumption, and compact size. Possible applications of the devices are astronomical adaptive optics, laser beam control, laser cavity mode control, and real time holography. Field experiments were performed on the Air Force Research Laboratory 3.6 meter telescope on Maui, Hawaii.

Many electro optical devices are now available for compensating atmospheric distortions in optical systems. To support the characterization of these devices in a consistent fashion a common testbed that physically simulates these atmospheric aberrations is required. This paper reports on a system that realizes seeing conditions ranging from very poor to excellent and feeds these wavefronts to the compensation device under test. The testbed provides quantitative characterization of the system under test and evaluates residual wavefront error.