Freddie Santiago

Characterization of the lightweight telescope developed for the NPOI

A 0.4 meter lightweight telescope has been developed as a prototype for a future 1.4 meter telescope to be implemented at the Naval Prototype Optical Interferometer (NPOI). Using carbon fiber construction for all components, including optics, an order of magnitude reduction in weight is easily obtainable, with the estimated weight of the 1.4 meter telescope being less than 300 pounds. However, lightweight composite materials traditionally offer certain drawbacks, such as different material behavior and vibration characteristics from conventional materials and difficulty in obtaining optical surface quality. This paper describes the characterization of the mechanical properties of the advanced materials used in the construction of these telescopes and includes measurements of the optical figure obtained with carbon fiber construction.

Low altitude horizontal scintillation measurements of atmospheric turbulence over the sea: Experimental results

We present the current status and developments of a horizontal beam path laser propagation experiment over the sea performed off the coast of Puerto Rico. Atmospheric turbulence effects have been measured by a Shack-Hartmann wavefront sensor with a Dalsa CCD camera and by a scintillometer from Optical Scientific, Inc* (OSI). We present preliminary scintillation measurements for an approximate period of two days from the two optical systems during the month of July 2005, also suggestions for improvement in the software, data acquisition protocol and hardware are presented.

Marine environment optical propagation measurements

We describe the status and initial results of a long term campaign to measure the effects of atmospheric turbulence upon a horizontally directed laser beam, whose altitude above the sea surface is 2 metres. The measurements are made with a video rate Shack-Hartmann wavefront sensor. Currently the source-receiver distance is 110 metres and additional sites have been identified to extend this single pass geometry to around 1 km. To date we have sampled over 70 hours of data, from December 2003 to April 2004. The preliminary scintillation power spectra and phase structure functions have been determined for some of the data sets, which we present here.

Comparing horizontal path C2n measurements over 0.6 km in the tropical littoral environment and in the desert

We have measured the optical turbulence structure parameter, C2n, in two extremely different locations: the first being the littoral region on the southwest coast of Puerto Rico. The second location is over the dry desert in central New Mexico. In both cases, the horizontal beam paths are approximately 0.6 km long, within 2 meters of the local surface (Puerto Rico) and varying between 2 to 100 meters (New Mexico). We present our findings from the two datasets.

Horizontal path propagation measurements over the sea

We report on the current status of a horizontal path length laser propagation campaign that is being performed over the sea, just off the coast of Puerto Rico. The effects of atmospheric turbulence in a tranquil marine environment have been measured with a video rate Shack--Hartmann wavefront sensor. The small perturbations in the wavefront phase and the degree of scintillation are presently being determined in a single pass from source to receiver, over a trial distance of 110 meters. Additional sites have been identified which allow for single pass measurements up to approximately 1 kilometer. Over 70 hours of data have been sampled to date, between December 2003 and April 2004.

High quality adaptive optics zoom with adaptive lenses

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.

UV-cured polymer optics

Although many optical-quality glass materials are available for use in optical systems, the range of polymeric materials is limited. Polymeric materials have some advantages over glass when it comes to large-scale manufacturing and production. In smaller scale systems, they offer a reduction in weight when compared to glass counterparts. This is especially important when designing optical systems meant to be carried by hand. We aimed to expand the availability of polymeric materials by exploring both crown-like and flint-like polymers. In addition, rapid and facile production was also a goal. By using UV-cured thiolene-based polymers, we were able to produce optical materials within seconds. This enabled the rapid screening of a variety of polymers from which we down-selected to produce optical flats and lenses. We will discuss problems with production and mitigation strategies in using UV-cured polymers for optical components. Using UV-cured polymers present a different set of problems than traditional injection-molded polymers, and these issues are discussed in detail. Using these produced optics, we integrated them into a modified direct view optical system, with the end goal being the development of drop-in replacements for glass components. This optical production strategy shows promise for use in lab-scale systems, where low-cost methods and flexibility are of paramount importance.

Measuring a deformable mirror's surface while under physical vibrations

This paper reports on the measurement and reconstruction using two algorithms of an Adaptive Tilt Mirrors (ATM) reflected wavefront using a Shack-Hartmann (SH) based wavefront sensor. The ATM consists of a deformable mirror mounted onto a fast steering mirror platform. Reconstruction of the wavefront was performed using Finite Difference and Finite Element reconstruction algorithms for comparison. The SH wavefront sensor with high frame-rate readout camera and the two types of software reconstructors provide a visualization of the ATMs surface while being moved physically on the fast steering mirror platform at a rate of 30 Hz.